U.S. patent application number 12/913943 was filed with the patent office on 2011-05-26 for absorption refrigeration cycles; apparatus; and, methods.
Invention is credited to CALVIN WOHLERT.
Application Number | 20110120157 12/913943 |
Document ID | / |
Family ID | 43922528 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110120157 |
Kind Code |
A1 |
WOHLERT; CALVIN |
May 26, 2011 |
ABSORPTION REFRIGERATION CYCLES; APPARATUS; AND, METHODS
Abstract
The present disclosure relates to improvements in refrigeration
cycles. This disclosure relates to preferred processing of solution
from absorber arrangements of absorption refrigeration cycles, to
separate out refrigerant liquid. Examples are provided. A variety
of equipment configurations, techniques, and processes are
disclosed, as examples.
Inventors: |
WOHLERT; CALVIN;
(Centennial, CO) |
Family ID: |
43922528 |
Appl. No.: |
12/913943 |
Filed: |
October 28, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61280105 |
Oct 30, 2009 |
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Current U.S.
Class: |
62/101 ;
62/476 |
Current CPC
Class: |
F25B 15/02 20130101;
Y02A 30/27 20180101; F25B 15/14 20130101; Y02B 30/62 20130101; Y02A
30/277 20180101 |
Class at
Publication: |
62/101 ;
62/476 |
International
Class: |
F25B 15/00 20060101
F25B015/00 |
Claims
1. A process of conducting an absorption refrigeration cycle; the
process comprising steps of: (a) processing dilute solution into
concentrated solute solution and refrigerant liquid without a step
of vaporizing and condensing refrigerant contained in the dilute
solution; (b) directing at least a portion the refrigerant liquid
into a first evaporator arrangement to vaporize at least a portion
of the refrigerant; (c) directing the concentrated solute solution
into an absorber arrangement; and, (d) directing vaporized
refrigerant from an evaporator arrangement into an absorber
arrangement, for absorption of the refrigerant into concentrated
solute solution therein.
2. A process according to claim 1 wherein: (a) the step of
processing dilute solution comprises applied electric field
processing.
3. A process according to claim 2 wherein: (a) the step of
processing dilute solution comprises at least one of
electrodialysis; electrodeionization; capacitive deionization; and,
membrane capacitive deionization.
4. A process according to claim 1 wherein: (a) the step of
processing dilute solution comprises membrane-based processing.
5. A process according to claim 4 wherein: (a) the step of
processing dilute solution comprises reverse osmosis
processing.
6. A process of conducting an absorption refrigeration cycle in
accord claim 1 wherein: (a) the step of directing the refrigerant
liquid, from the step of processing, comprises directing the
refrigerant liquid into the first evaporator arrangement without
further dilution of the refrigerant liquid.
7. A process according to claim 6 wherein: (a) the step of
directing the concentrated solution into an absorption arrangement
comprises directing concentrated solution from a membrane-based
processing step into an absorber arrangement without further
concentration.
8. A process according to claim 1 wherein: (a) the step of
directing vaporized refrigerant comprises directing the refrigerant
into the absorber arrangement into which the concentrated solute
solution is directed.
9. A process according to claim 8 wherein: (a) the step of
directing concentrated solute solution into an absorber arrangement
comprises directing concentrated solute solution, from the step of
processing dilute solution, into the absorber arrangement into
which the vaporized refrigerant is directed.
10. A process according to claim 9 wherein: (a) not all of the
concentrated solute solution, from the step of processing dilute
solution, is directed into the absorber arrangement in which the
vaporized refrigerant is directed.
11. A process according to claim 1 wherein: (a) the step of
processing dilute solution comprises a combination of
membrane-based processing and applied electric field
processing.
12. An absorption refrigeration cycle comprising: (a) at least a
first absorber arrangement configured to absorb refrigerant gas,
from a first evaporator arrangement, into a solution to provide a
dilute solution; (b) a least a first evaporator arrangement
configured to receive refrigerant liquid and to process at least a
portion of the refrigerant liquid into refrigerant gas; and, (c) a
non-vaporizing solution processing unit system configured to
process dilute solution into: strong solution; and, refrigerant
liquid, at least a portion of which refrigerant liquid is for
direction to the first evaporator arrangement.
13. An absorption refrigeration cycle according to claim 12
wherein: (a) the non-vaporizing solution processing unit system
comprises at least an applied electric field processing unit
system.
14. An absorption refrigeration cycle according to claim 12
wherein: (a) the non-vaporizing solution processing unit system
comprises at a membrane-based solution processing unit system.
15. An absorption refrigeration cycle according to claim 14
wherein: (a) the membrane-based solution processing unit system
includes at least one reverse osmosis unit having: a high pressure
side inlet; a high pressure side outlet; a low pressure side inlet;
and, a low pressure side outlet.
16. An absorption refrigeration cycle according to claim 12
wherein: (a) the first absorber arrangement is configured to absorb
refrigerant gas into strong solution, to provide dilute
solution.
17. An absorption refrigeration cycle according to claim 12
wherein: (a) the non-vaporizing solution processing unit system is
configured to process the dilute solution from the absorber
arrangement into: the strong solution; and, a refrigerant liquid
for direction to the first evaporator.
18. An absorption refrigeration cycle according claim 12 wherein:
(a) the non-vaporizing solution processing unit system includes
both an applied electric field solution processing unit system and
a membrane-based processing unit system.
19. A process of conducting an absorption refrigeration cycle; the
process comprising steps of: (a) processing dilute solution into
concentrated solute solution and refrigerant liquid by at least one
of membrane-based processing and applied electric field processing;
(b) directing at least a portion the refrigerant liquid into a
first evaporator arrangement to vaporize at least a portion of the
refrigerant; (c) directing the concentrated solute solution into an
absorber arrangement; and, (d) directing vaporized refrigerant from
an evaporator arrangement into an absorber arrangement, for
absorption of the refrigerant into concentrated solute solution
therein.
20. An absorption refrigeration cycle comprising: (a) at least a
first absorber arrangement configured to absorb refrigerant gas,
from a first evaporator arrangement, into a solution to provide a
dilute solution; (b) a least a first evaporator arrangement
configured to receive refrigerant liquid and to process at least a
portion of the refrigerant liquid into refrigerant gas; and, (c) a
processing unit system configured to process dilute solution into:
strong solution; and, refrigerant liquid, at least a portion of
which refrigerant liquid is for direction to the first evaporator
arrangement; the solution processing unit system comprising at
least one of: a membrane-based processing unit system; and, an
applied electric field processing unit system.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application includes, with edits, the disclosure
of U.S. provisional application 61/280,105, filed Oct. 30, 2009.
The complete disclosure of U.S. provisional application 61/280,105
is incorporated herein by reference. Also, a claim of priority is
made to U.S. application 61/280,105 to the extent appropriate.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to refrigeration cycles
generally, in which heat is transferred from a heat source to a
heat sink. More specifically, the disclosure relates to absorption
refrigeration cycles, in which at least one absorber arrangement is
used in the refrigeration cycle, for absorbing refrigerant vapor
into absorption (strong) solution to generate dilute solution. The
techniques particularly relate to processing dilute solution into:
(a) strong solution, for example for operation of the absorber
arrangement; and, (b) recovered refrigerant liquid, for example for
operation of an evaporator, preferably without using a step of
vaporizing (boiling) the refrigerant to recover it from the dilute
solution, i.e. without conducting a phase change of the
refrigerant, for recovery from the dilute solution. General
techniques described herein for processing of dilute solution into
strong solution (and recovery of refrigerant liquid from the dilute
solution) include membrane-based processing, in which a membrane
with preferential permeability with respect to one of a solvent or
solute is used. An example membrane-based processing by reverse
osmosis processing is described. Other processing techniques that
can be applied either separately or in conjunction with
membrane-based processing include applied electric field processing
such as, for example: electrodialysis, electrodeionization,
capacitive deionization and membrane capacitive deionization.
BACKGROUND
[0003] Refrigeration cycles are used in a wide variety of
applications including: air conditioning; liquid cooling
applications; refrigeration; and, heat pumps. These have been
applied in a wide variety of industrial and manufacturing
applications, as well as environmental cooling and/or heating
operations.
[0004] In general, a refrigeration cycle can be used as a cooling
device, a heating device, or both. If a relatively low temperature
source of heat energy is desired to be kept below ambient
conditions as the intended outcome, typically the process will be
referenced as a cooling cycle. If a relatively high temperature
heat sink is desired to be kept above ambient, the cycle will
typically be referenced as a heat pump cycle. Thus, a refrigeration
cycle can be used for cooling and/or heating (the later sometimes
referred to as heat pumping).
[0005] Many refrigeration cycles are of a type commonly referred to
as absorption refrigeration cycles. In general terms, in an
absorption cycle, refrigerant is absorbed into a solution, to
generate a dilute solution. In a desorber (generator) the
refrigerant in released (recovered) from the solution, leaving
strong solution behind. The strong solution is directed into an
absorber arrangement, in which heat is removed and in which
refrigerant, transferred from an evaporator arrangement, is
absorbed.
[0006] In general, improvements in refrigerant cycles are desired,
for cost effective and efficient energy use. Herein, improvements
are described, which at least in part relate to: techniques of
generating strong solutions for absorber arrangement operation;
and, recovery of refrigerant liquid for use in evaporator
arrangement operation of an absorption refrigeration cycle.
SUMMARY
[0007] According to the present disclosure, techniques are provided
for modification of practices and equipment concerning
refrigeration cycles. Of particular concern, are absorption
refrigeration cycles; a general characteristic of which is that
within the cycle a vapor (gas) phase refrigerant is absorbed into
an absorber solution, to generate a dilute solution; and,
refrigerant is recovered from the dilute solution, for use in the
refrigeration cycle.
[0008] In general terms, techniques according to the disclosure are
applicable to provide for recovery of the refrigerant from the
dilute solution, with re-generation of the dilute solution into a
concentrated solution (for example for use in an absorber
arrangement operation) whereby the refrigerant is efficiently
recovered, for example in some applications without vaporizing the
refrigerant from the dilute solution and then recondensing; i.e.
without a phase change conducted to recover refrigerant from dilute
solution. In general, then, certain techniques according to the
present disclosure involve absorption refrigeration cycles operated
with application of non-vaporizing (i.e. non-phase change)
techniques for recovery of refrigerant from dilute solution. A wide
variety of such techniques can be applied, including ones now known
or later developed. Examples characterized herein for this purpose
include membrane-based processing; and/or applied electric field
processing.
[0009] In general terms, "membrane-based processing" is solution
processing used to regenerate dilute solution into concentrated
solution, whereby the refrigerant is recovered, typically without
vaporizing the refrigerant from the dilute solution and
recondensing, via membrane-based separation. An example
membrane-based processing technique described herein as applicable
for such a recovery of the refrigerant from the dilute solution, is
reverse osmosis processing. By the term "reverse osmosis
processing" as used herein, what is meant is processing that
involves passing solvent through a reverse osmosis membrane
arrangement, to provide: on one (low pressure) side of the reverse
osmosis membrane, a relatively purified (reduced solute) solvent;
and, on the other (high pressure) side of the membrane, a solution
relatively concentrated in solute.
[0010] The reverse osmosis membrane unit system and processing can
be conducted in a variety of manners, with the variety of specific
equipment configurations. Techniques described in U.S. application
Ser. No. 12/455,998, filed Jun. 9, 2009; and, U.S. provisional
application 61/131,947, filed Jun. 13, 2008, each of which is
incorporated herein by reference, can be applied. Within the
present disclosure, some specific example arrangements are
characterized.
[0011] Other forms of membrane-based processing that can be applied
in overall systems and processing techniques according to the
present disclosure include ones in which the membrane is selected
for passing of solute.
[0012] Other refrigerant recovery techniques usable in accord with
the present invention include applied electric field processing.
There may also be non-vaporizing, i.e. non-phase change. Herein the
term "applied electric field processing" is meant to refer to any
solution processing technique in which the solution is passed
through a cell or system of cells, across which an electric field
is applied. Under the influence of the applied electric field,
selected solute migration can occur, with the equipment configured
to provide for a net result of: a reduced solute solution; and, in
many instances, recovery of the solute inclusion into a
concentrated solute solution or composition. Examples of applied
electric field processing usable with techniques according to the
present disclosure include: electrodialysis; electrodeionization;
capacitive deionization; and, membrane capacitive deionization,
although any variety of techniques now known or later developed can
be used.
[0013] Various types of non-vaporizing (non-phase change) solution
processing techniques for recovery of refrigerant and generation of
concentrated solution can be used independently or together, with
systems, arrangements and techniques according to the present
disclosure. Multiple stages or cascading effects can be used, to
accomplish relatively pure solvent (refrigerant) recovery and/or
generation of the relatively strong concentrated solute
solution.
[0014] It is noted that in some systems and processes according to
the present disclosure, solution processing can be conducted with a
number of different specific types of non-vaporizing (i.e.
non-phase change) solution processing, in the same system. For
example, reverse osmosis techniques can be applied in the same
system in which applied electric field processing is also used. In
accord with terminology used herein, such a system can be
characterized as comprising a "reverse osmosis membrane (unit)
system" or by similar terms; or, alternatively, as a "applied
electric field processing (unit) system" or by similar terms, or by
both terms.
[0015] It is also noted that many of the techniques described
herein can be applied, to advantage, in processing or processing
systems in which then is also some vaporization of refrigerant
during recovery.
[0016] There is no requirement that all specific equipment
configurations, materials, and processing steps characterized
herein, be used in all practices in accord with the general
principles of the present disclosure. Variations are possible, as
will be understood from the following descriptions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic depiction of a prior art vapor
compression refrigeration cycle, or vapor compression cycle.
[0018] FIG. 2 is a schematic depiction of a prior art absorption
refrigeration cycle or absorption cycle.
[0019] FIG. 3 is a schematic depiction of an improved absorption
cycle in accord with techniques of the present disclosure; the
cycle of FIG. 3 usable as an example absorption osmosis
refrigeration cycle and/or an example absorption applied electric
field processing refrigeration cycle.
[0020] FIG. 3A is a schematic depiction of a first example reverse
osmosis (membrane) unit system and process usable in the cycle of
FIG. 3, to recover a refrigerant liquid for evaporator
operation.
[0021] FIG. 3B is a schematic depiction of a second, alternate,
example reverse osmosis (membrane) unit system and process usable
in the cycle of FIG. 3, to recover refrigerant for evaporator
operation.
[0022] FIG. 4 is a schematic depiction of a first alternate
absorption refrigeration cycle, to the one of FIG. 3, using
techniques according to the present disclosure.
[0023] FIG. 5 is a schematic depiction of a second alternate
absorption refrigeration cycle using techniques according to the
present disclosure.
[0024] FIG. 6 is a schematic depiction of a third alternate
absorption refrigeration cycle using techniques according to the
present disclosure.
[0025] FIG. 7 is a schematic depiction of an example of applied
electric field processing system.
DETAILED DESCRIPTION
I. Further Regarding Prior Art Refrigeration Cycles
A. Prior Art Vapor Compression Cycles--Generally
[0026] In FIG. 1, a prior art vapor basic compression cycle is
depicted, schematically, at 1. Referring to FIG. 1, at 3 a
refrigerant compressor is depicted schematically. In general, the
refrigerant compressor 3 is operated to compress refrigerant (in a
vapor or gas phase) transferred thereto via conduit or line 4, to
generate a compressed refrigerant (vapor or gas) in conduit or line
5. Conduit or line 4 will generally be referred to as a low
pressure refrigerant vapor (or gas) conduit or line; and, line 5 as
a high pressure refrigerant vapor (or gas) conduit or line. In a
typical process, heat will have been imparted to the refrigerant,
during the process of compression in the compressor 3, so the
refrigerant vapor (gas) in conduit or line 5 will typically be
relatively hot by comparison to the refrigerant vapor (or gas) in
conduit or line 4. Also, the increased pressure allows for
condensing of refrigerant vapor at an increased temperature (and
vice versa on the low pressure side of the system).
[0027] It is noted that herein, in connection with refrigeration
cycles, phase changes of refrigerant between a gas phase and a
liquid phase are characterized. In general, the terms "vapor"
and/or "vapor phase" are used herein interchangeably with the terms
"gas" and/or "gas phase," to characterize the refrigerant when it
is in the gas or vapor phase. Similarly, the terms "boiling" and
"vaporizing" are meant to be used interchangeably. The terms
"conduit" and "line" are also meant to be used interchangeably.
[0028] Relatively high pressure refrigerant (vapor or gas) from
line 5 is directed to a condenser arrangement or system 7. In the
condenser arrangement or system 7, the refrigerant (vapor or gas)
is condensed to a pressurized refrigerant liquid. The pressurized
refrigerant liquid is shown leaving the condenser arrangement at
line 8. During operation of the condenser arrangement 7, heat
(energy) is removed from the refrigerant (vapor or gas) and is
transferred out of the system. In general, this heat transfer out
is indicated by arrows 9. It is noted that the heat can be expelled
as heat to the environment, for example in operation of a typical
air conditioner, or it can be captured in another material, and be
applied in a selected manner. In FIG. 1, line 9x is meant to
indicate introduction of a heat sink to the condenser arrangement
7, for example air or liquid, to which heat, given off during the
condensation of the refrigerant, is transferred. Of course, the
heat sink can be the environment.
[0029] The pressurized refrigerant liquid of line 8, from the
condenser 7, is shown in the refrigeration cycle 1, as directed
into an expansion system or device 10, in which the pressure is
reduced. The reduced pressure refrigerant liquid from the expansion
(or pressure reduction) system 10 is shown then directed through
line 12 into evaporator arrangement or system 13 via a distribution
system or other arrangement.
[0030] In the evaporator arrangement 13, heat is transferred to the
refrigerant liquid, vaporizing (evaporating) some (or all) of the
refrigerant liquid. The vaporized refrigerant is shown leaving the
evaporator arrangement 13 at line 15, which via line 4 is directed
back into the refrigerant compressor 3, for compression.
[0031] The heat transfer which occurs in the evaporator system 13
cools the material from which the heat is transferred. For example,
if the heat transferred into the evaporator 13 is from a hot air
source, the result will be a cooling of the air; which is typical
of an air conditioning cycle. Of course, other relatively hot
materials (for example liquid or gas) can be directed into the
evaporator 13, for transfer of heat to the refrigerant with the
result being a cooled liquid or gas (and a vaporized refrigerant).
Still referring to FIG. 1, the hot material transferred into the
evaporator system 13, is shown generally at lines 16. Removal of
the cooled material is shown at 17.
[0032] A wide of variety of equipment configurations, conduit
configurations, pump configurations, etc. can be used. No specific
combination of equipment is meant to be indicated, other than for
providing general operation.
[0033] In the general terms used herein, the refrigeration cycle 1,
for example, could be an air conditioning cycle, if the system is
operated to provide cool air to an environment from the evaporator
13 via output 17. The refrigeration cycle 1 would be characterized
as a heat pump, since it is operated is to provide heated air to an
environment, via the condenser 7 and output 9.
[0034] A typical present-day, state-of-the-art water cooled vapor
compressor refrigeration cycle, operating at the Air Conditioning,
Heating and Refrigeration Institute, (AHRI), standard full load
conditions of 85.degree. F. (29.4.degree. C.) condenser water
entering temperature and 44.degree. F. (6.7.degree. C.), leaving
chilled water temperature, is capable of producing 1 ton (12,000
Btu/hr, or 3.517 kW) of cooling capacity for between 0.58 and 0.62
kW/ton of energy input (0.165 to 0.171 kW of input per kW of
output). Reference to 85.degree. F. (29.4.degree. C.) condenser
water, would be the temperature of the condenser water for
operation of condenser arrangement 7; and, the reference to
44.degree. F. (6.7.degree. C.) chilled water temperature, is
referring to cooling output from evaporator arrangement 13, shown
at line 17 in a typical water chilling application.
[0035] Above it was noted that some or all of the refrigerant
liquid may be vaporized in the evaporator arrangement 13. There is
no specific requirement that all of the refrigerant liquid be
vaporized in the evaporator arrangement. The extent, to which
vaporization occurs in the evaporator arrangement, will typically
turn on the type of evaporator arrangement used.
[0036] In the refrigeration industry today there are three commonly
used evaporator configurations. These are: "flooded", "Direct
Expansion (DX)", and "liquid overfeed". Under normal operating
circumstances, heat is transferred to the evaporator heat
exchanger; this heat transforming the refrigerant through a phase
change from a liquid into a gaseous state. In the flooded and
direct expansion configurations liquid is fed into the evaporator
and evaporated (gaseous) refrigerant is removed from the evaporator
system. In these configurations the mass of liquid added to the
evaporator in steady state steady flow conditions is equal to the
mass of gaseous refrigerant removed from the evaporator. The
flooded and direct expansion system these systems are designed with
the intent of only removing a gaseous refrigerant from the
evaporator arrangement.
[0037] A liquid overfeed evaporator arrangement is designed such
that a liquid refrigerant is fed into the evaporator and a mixture
of both: a) un-evaporated refrigerant liquid; and, b) evaporated
gaseous refrigerant, is removed from the evaporator. Thus, in the
case of the liquid overfeed arrangement the entirety of the
refrigerant entering the evaporator is not evaporated prior to
leaving the evaporator.
[0038] In a flooded evaporator arrangement, a separate vessel is
typically provided which serves to gravity feed liquid refrigerant
into the coil while vaporized gaseous refrigerant is bubbled out of
the evaporator.
[0039] Herein, in both the prior art systems and the improved
systems characterized, the evaporator arrangement depicted may be
of the type which completely vaporizes refrigerant liquid, or which
only partially vaporizes the refrigerant liquid. Either can be used
with techniques as described herein.
B. Prior Art Absorption Refrigeration Cycles--Generally
[0040] Attention is now directed to FIG. 2, in which a prior art
basic absorption refrigeration cycle is indicated generally at 30.
Referring to FIG. 2, refrigerant (gas or vapor) is shown at line 31
directed into condenser arrangement 32. The condenser arrangement
32 of system 30 can be analogous to, and be operated analogously
to, condenser arrangement 7, FIG. 1. Heat output from the condenser
32 is shown at lines 33, and comprises heat rejection to the
environment or captured in a sink for use. A heat sink (gas or
liquid) input for this is shown at 33x.
[0041] Condensed refrigerant is shown leaving the condenser 32 via
line 35. Line 35 is typically pressurized, as will be understood
from the remaining parts of this description. At 36, the
pressurized, condensed, refrigerant (liquid) of line 35 is depicted
passed through an expansion or pressure reduction device to reduce
pressure, with line 37 comprising a reduced pressure refrigerant
line or distribution device directed into evaporator arrangement or
system 39. In the evaporator arrangement or system 39, some (or
all) of the refrigerant is evaporated, with the resulting gas
(vapor) phase refrigerant shown removed from evaporator arrangement
or system 39 at line 40. Evaporator arrangement or system 39 can be
analogous to evaporator 13, FIG. 1, with heat transfer (input) into
the evaporator 39 shown at lines 41. Again, for example, the heat
input at lines 41 can be from hot air, for example if the
absorption cycle 30 is operated as an air conditioner. It can also
be a transfer of heat from another heat source. The cooled material
(air, water, etc.) from evaporator system 39 is shown at line
42.
[0042] The low pressure refrigerant vapor of line 40 is shown being
directed into absorber arrangement or system 45. Within the
absorber arrangement or system 45, the refrigerant is absorbed into
solution indicated generally in sump 46. The solution is typically
characterized as an "absorption solution," "absorber solution" or
by related terms and can comprise a variety of materials.
Typically, the absorber solution, before absorption of the
refrigerant therein, is a solute/solvent solution typically
referred to as "strong," i.e. relatively concentrated in solute. By
the term "relatively" concentrated, in this context, reference is
meant by comparison to after refrigerant absorption. In general
terms, the solute provides for relatively low solvent vapor
pressure to the solution, in this instance by comparison to the
solvent without the solute therein.
[0043] The absorber solution, once diluted by the absorbed
refrigerant, as shown at sump 46, is sometimes referenced as
"dilute solution." The dilute solution is shown leaving the
absorber at line 48. It is directed into pump 50, by which it is
pressurized, the resulting pressurized dilute solution line being
indicated generally at 51. The pressurized dilute solution of line
51 is directed into a desorber (or generator) arrangement or system
55. In general, the desorber arrangement 55 is operated with a
thermal (i.e. energy) input indicated generally at 56, which will
serve to boil off the refrigerant, generating a pressurized
refrigerant vapor phase in line 58; and, regenerating the dilute
solution into a strong solution. The refrigerant vapor phase
generated in the desorber 55 is shown directed to line 31, a
refrigerant vapor inlet line to the condenser system 32.
[0044] In general, then, a characteristic of an absorption cycle 30
of the prior art characterized herein in connection with FIG. 2, is
that in an absorber arrangement refrigerant is absorbed into an
absorption solution, to create a dilute solution; and, the
refrigerant is recovered from the dilute solution by vaporizing the
refrigerant out of solution.
[0045] Within the desorber (generator) system 55, as a result of
removal of refrigerant gas (vapor), strong solution or strong
absorbent solution is re-generated, shown being removed from
desorber system 55 at line 59. This solution is depicted directed
from through a pressure reducer 60, and into a reduced pressure
strong solution line 61, which typically includes strong (i.e.
concentrated) solution or absorber solution. This line is directed
into absorber arrangement or system 45.
[0046] Referring to the example absorber arrangement 45 depicted,
the strong, solution from line 61 is shown directed therein via
optional sprayer arrangement 62, which will distribute the strong,
solution through the absorber arrangement 45. The strong solution
is also shown absorbing the refrigerant, to generate dilute
solution in sump 46. As the refrigerant vapor is absorbed into the
absorber solution, energy will be released. This energy will tend
to produce heating of the absorber solution. To keep the vapor
pressure of the absorber solution low it is desirable to keep the
absorber solution temperature low. To do this, heat is typically
removed from the absorber solution. One way to accomplish this heat
removal is to transfer this heat into an absorber heat transfer
loop such as is shown at 65. Referring to FIG. 2, the example
absorber arrangement 45 depicted includes therein optional packing
45x to facilitate heat transfer, and refrigerant absorption, by
increasing surface area.
[0047] The absorber heat transfer loop 65 is shown transferring
heated material via line 66, for example heat from absorber
arrangement 45 having been absorbed by another gas or liquid (heat
sink) into a heat transfer arrangement 70. Heat removed via the
heat transfer arrangement 70 is shown at lines 71. The (relatively)
cooled circulation fluid is shown leaving the heat transfer unit 70
via line 72, by which it is directed back into the absorber 45 via
heat transfer loop 65.
[0048] Prior art absorption cycles are predominately thermally
driven (also known as heat driven) cycles with only a relatively
small amount (in relation to the amount of thermal energy required)
of mechanical energy need to operate the pumping components of the
cycle. For the depicted cycle 30, the absorption cycle thermal
energy input at 56 can be derived from a variety of sources. Common
examples include natural gas, fuel oil, steam or hot water.
Absorption refrigeration cycles are typically rated in terms of
their Coefficient Of Performance, or COP for short, where COP is
the ratio of the cooling energy produced divided by the input
energy required to drive the cycle. In typical water chilling
applications, a single stage water cooled absorption refrigerant
cycle operating an AHRI standard full load conditions is capable of
producing one ton (3.517 kW) of cooling capacity for approximately
10,000-12,000 Btu/hr of energy input rate. This equates to a COP
range of 0.83 to 1.0.
[0049] Still referring to FIG. 2, attention is directed to optional
heat exchanger 73. Heat exchanger 73 is configured and positioned
to transfer some of the heat from line 55 into line 51. Such a heat
exchanger, sometimes characterized as a "GAX" or generator absorber
arrangement, can be used in association with a generator or
desorber 55.
[0050] It is noted that both of the cycles 1 and 30, are depicted
schematically. A wide variety of equipment configurations are
possible, for the various evaporator arrangements, condenser
arrangements, absorber arrangements, desorber arrangements, heat
transfer arrangements as well as for the lines, pumps, compressors,
and expansion or pressure reduction devices. There is not meant to
be any specific mechanical configuration for the components, or
operation of them, implied by the descriptions.
C. Typical Traditional Approaches to Improving Refrigeration
Cycles
[0051] Since their inception, the basic cycles described above
(vapor compression and absorption) have been improved upon in terms
of operational efficiency through various alterations or
enhancements to the basic cycles. Enhancements such as in
development of various heat recovery mechanisms, multi-staging,
intercoolers, and overall improvements in efficiency of individual
components of the cycles have been made. However, the fundamental
principles of the cycles have remained unchanged to a great extent.
At present, these cycles are typically considered the most
cost-effective and efficient refrigeration cycles available. While
other refrigeration cycles exist, for example thermal acoustic and
thermal electric, vapor compression cycles and absorption cycles
are, at present, the most commonly used refrigeration cycles.
II. Improved Absorption Cycles--Generally
[0052] In a typical, traditional, absorption cycle, FIG. 2,
separation of the refrigerant liquid out of the absorption solution
(see desorber 55, FIG. 2) is a distillation or boiling process.
That is, sufficient energy is put in to vaporize (phase change)
refrigerant liquid in the dilute solution to a gaseous state, to
separate it from the dilute solution; with the remaining solution
after refrigerant desorption being increased in solute
concentration (to a concentrated or strong solution). In general,
substantial energy input to a desorber or generator is needed, for
separation of the refrigerant (by boiling i.e. phase change) from
the dilute solution to occur.
[0053] According to the present disclosure, an alternative is
provided: (a) to using thermal energy input to a desorber system to
produce a phase change of the refrigerant for reconcentrating the
absorbent solution from a dilute (weak) solution to a more
concentrated solution; and, (b) to separate the refrigerant from
the dilute solution as a vapor phase. In some examples, reverse
osmosis processing is applied, which allows avoidance of a
relatively energy inefficient step of converting the refrigerant to
the gas phase during refrigerant recovery from the dilute
solution.
[0054] In more general terms, non-vaporizing solution processing is
used with assemblies and systems and techniques according to the
present disclosure for processing of solution in the alternative to
installation of vaporizing processes. The terms "non-vaporizing
solution processing," "non-phase change solution processing" and
variants thereof as used herein, are meant to refer to any solution
processing technique, now known or later developed, in which
refrigerant is recovered from dilute solution, without a phase
change in the refrigerant occurring. This also generally leads to
concentrated solution regeneration.
[0055] Examples of currently available and usable non-vaporizing
solution processing techniques (i.e. non-phase change solution
processing) usable with systems, arrangements and techniques
according to the present disclosure, include membrane-based
processing and applied electric field processing. These techniques,
characterized more specifically below, can be applied independently
or together in a system to accomplish system processing. Also, each
term is not meant to be exclusive of the other.
[0056] As used herein in this context, the terms "membrane-based
processing", "membrane-based solution processing" and variants
thereof, are meant to refer to processing in which a membrane or
membrane arrangement is provided, with preferential transfer of
material across the membrane used facilitate solution processing.
Reverse osmosis processing is an example of membrane-based
processing, in which a reverse osmosis membrane arrangement is
provided, so that the solvent from a solution on one side will tend
to pass through the membrane in a manner increasing concentration
in solute on one side and providing for increased amounts of
reduced solute solvent on the other.
[0057] In general, the term "applied electric field processing" and
variants thereof, as used herein, is meant to refer to forms of
non-vaporizing solution processing (i.e. non-phase change solution
processing) in which the electric field is applied to the solution
in a manner facilitating preferred migration of solute or selected
solute materials. This can be used, for example to drive solute
materials out of the solution, generating a reduced solute
solution. This technique can also be used to recover the solute, to
facilitate generation of a concentrated solute solution. Examples
of applied electric field processing referenced specifically
herein, include electrodialysis processing, electrodeionization
processing, capacitive deionization processing and membrane
capacitive deionization.
[0058] In some processes, more than one type of a non-vaporizing
processing can be applied to accomplish desired solution
processing. For example, it may be desirable to process dilute
solution from an absorption refrigeration cycle, via the applied
electric field processing, when the solution is most concentrated
in solute. Then, after initial applied electric field processing,
one can use reverse osmosis processing techniques to further
process the solution, into purified solvent. A use for this type of
processing can be when the solute concentration is so high that an
undesirable level of pressure, or number of stages, is needed to be
applied to the solution to accomplish effective reverse osmosis
processing.
[0059] When the system is one in which both "membrane-based
processing" and "applied electric field processing" is used, the
system or process can be characterized as comprising
"membrane-based processing" and/or as comprising "applied electric
field processing" and by variants thereof.
[0060] In general, because a non-vaporizing processing is used in
the present disclosure to reconcentrate the absorption solution,
the energy and process of boiling off a refrigerant to get it out
of the absorbent liquid is no longer required. In addition, because
the separation of the refrigerant from the absorption solution is
not accomplished via a boiling off process, with the presently
described techniques, a condenser arrangement is not required to
condense the refrigerant vapor and reject energy from this portion
of the cycle.
[0061] As an example, pressurizing and conveying a liquid, as is
the case in the example presently described systems when reverse
osmosis processing is the membrane-based processing used, is less
energy intensive that pressurizing (compressing) and conveying a
gas, as would be used in a vapor compression or refrigeration
cycle. This is in part because liquids are less compressible than
gases, and therefore less work (energy) is needed to raise the
pressure of a liquid than would be required for an equivalent mass
of the same gas. Indeed, in a gas compression process, much of the
work required to compress the gas is converted into heat rather
than into the increased energy state of the compressed gas. The
heat of compression is a byproduct of the overall gas compression
process, and is commonly viewed as an expression of the
inefficiencies of the process. For example, in a standard zero psig
(1 bar) to 100 psig (7.9 bar) air compressor, approximately 80% of
the energy input into the compressor ultimately gets lost as heat,
rather than producing actual compressed air.
[0062] A typical operating concentration of absorbent solutions
required to effectively operate a refrigeration cooling cycle such
as the absorption cycle of FIG. 2, with standard AHRI full load
conditions, would present calculated (or predicted) osmotic
pressures on the order of 8,000 to 12,000 psig (552 to 827 bar),
depending on the solution used, the solution operating temperature,
and membrane effectiveness. Currently available reverse osmosis
membrane units on the market are typically capable of operation
only up to a maximum operating pressure of about 690 psig (48.6
bar), i.e. on the order of a magnitude less pressure than would be
required for an absorption osmosis refrigeration cycle. Therefore,
with currently available reverse osmosis membrane technology, a
cascading type reverse osmosis membrane unit system, for example as
described in U.S. patent application Ser. No. 12/455,998 filed Jun.
9, 2009; and, in U.S. provisional application 60/131,947, filed
Jun. 13, 2008, will often be used. Examples are described and
depicted herein.
[0063] Again, and as will be discussed further below, alternate
non-vaporizing solution processing as an alternate to, or in
addition to, reverse osmosis processing, can be used. Here,
advantages will result when the specific non-vaporizing solution
processing technique is energy efficient, relative to the
techniques that involve vaporization, etc. For example, when the
non-vaporizing processing is applied electric field processing,
efficiencies will result when the amount of applied electric field
(and energy associated with generation and maintenance thereof) is
less than the alternate system demands in the presence of a
vaporization, etc.
[0064] In general, an absorption cycle improved according to the
represent disclosure, if optimally configured, can be substantially
more efficient than a vapor compression refrigeration cycle or a
traditional absorption refrigeration cycle. This will be apparent
from the following descriptions.
III. An Example Improved Absorption Cycle, FIG. 3
[0065] Attention is now directed to FIG. 3, in which an improved
absorption refrigeration cycle is indicated generally at 80. The
improved absorption refrigeration cycle 80 may be referred to
herein as an "absorption osmosis refrigeration cycle" or by similar
terms, when the system is configured to include a reverse osmosis
membrane unit system, and a reverse osmosis processing step, in the
cycle.
[0066] Referring to FIG. 3, the absorption cycle 80 is similar to
absorption cycle 30, FIG. 2, except for the absences of: the
desorber (generator) 55; and, the condenser 32. Instead, conversion
of the dilute solution line from the absorber arrangement into: (a)
a strong solution line for use in an absorber arrangement loop;
and, (b) a refrigerant liquid line for use in an evaporator
arrangement, is provided by non-vaporizing solution processing; for
example a reverse osmosis processing, using a reverse osmosis
(membrane) unit system. In FIG. 3, a non-vaporizing solution
processing unit system for this purpose is indicated generally (and
schematically) at 82. The non-vaporizing solution processing system
82 can, for example, be a reverse osmosis processing unit system as
discussed below, or an alternate system, as also discussed
below.
[0067] In general terms, a characteristic of an improved absorption
refrigeration cycle in accord with the present disclosure, is that
a desorber (generator) operated to process the dilute solution
into: (a) vapor phrase refrigerant line; and, (b) a strong solution
line, that is operated by conducting a phase change on the
refrigerant (typically liquid to gas) to affect the separation is
not used. Rather, the dilute solution is processed into: (a) a
concentrated or strong solution; and, (b) liquid phase refrigerant,
by using non-vaporizing solution processing techniques, such as
membrane-based techniques (for example reverse osmosis) and/or
applied electric field techniques (such as electrodialysis;
electrodeionization; capacitive deionization; and, membrane
capacitive deionization). These techniques do not involve a phase
change for the refrigerant, in connection with the solution
processing (refrigerant recovery and solution
re-concentration).
[0068] Referring to FIG. 3, dilute solution (containing
refrigerant) from an absorber arrangement 83 is shown in line 84
being directed into the non-vaporizing solution processing unit
system 82. Line 84, in general terms, comprises a solution to be
processed by the non-vaporizing solution processing unit system 82.
At line 85, a concentrated solution out from the non-vaporizing
solution processing unit system 82 is shown. At line 86, a purified
solvent line (liquid refrigerant line) out from the non-vaporizing
processing unit system 82 is shown. Because the solvent comprises
the refrigerant, then, line 86 can be characterized as a
refrigerant liquid line 87. When the concentrated solution line out
85 comprises strong solution for the absorber arrangement 83, line
85 can be referred to as the strong solution line 88.
[0069] It is noted that in parent U.S. provisional application
61/280,105, the non-vaporizing processing unit system 82 was
specifically referred to as a "reverse osmosis membrane unit
system", since a specific example non-vaporizing solution
processing technique that was described therein, to avoid
vaporization processing, was reverse osmosis unit processing,
generally in accord with U.S. application Ser. No. 12/455,998.
[0070] In other aspects, cycle 80 is analogous to cycle 30. Thus,
refrigerant liquid 87 is directed into (a first) evaporator
arrangement 90, which can be analogous to evaporator 39. Heat
transfer to the refrigerant liquid in the evaporator arrangement 90
is provided by heat input at lines 91, which for example can be
heat provided by a hot gas (for example air) or a liquid. This will
provide a cooling effect on the air or liquid involved, shown
leaving the evaporator arrangement 90 at 92. At line 95
refrigerant, at least a portion of which is now refrigerant gas
(vapor), is shown removed from the evaporator arrangement 90 and
directed to (a first) absorber arrangement 83. At 96, dilute
solution within the absorber arrangement 83 is shown, resulting
from absorbing the refrigerant vapor into liquid of a strong
solution (absorption solution), in the example from line 88 fed
into the absorber arrangement 83. This generates the dilute
solution of line 84.
[0071] Also, analogous to the cycle 30, FIG. 2, strong solution 88,
FIG. 3 is shown directed into the absorber arrangement 83, in the
example via optional spray arrangement 97. Heat transfer from the
absorption solution occurs, within the absorber arrangement 83,
into absorber cooling loop 99. Absorption solution, diluted with
refrigerant, is shown in sump 96. Within absorber arrangement 83 is
depicted optional packing 83x, to increase surface area for
absorption.
[0072] Absorber heat transfer loop 99 is shown transferring fluid
from absorber arrangement 83 to heat recovery or transfer unit 100.
Heat (energy) recovered or rejected from the unit 100 is shown
taken off at lines 101. While this is a heat rejection from the
system 80, it can be captured and used if desired. At line 103
fluid from the absorber heat transfer loop 99 is shown directed
back into the absorber arrangement 83, as a sink for heat transfer
from the absorbing solution in the absorber arrangement 83.
[0073] Again, then, in general system 80 is analogous to system 30,
except for removal of: a desorber (generator) 55 that separates
refrigerant by phase change; a condenser 32 that converts the vapor
phase refrigerant from the desorber to a liquid phase; and, the use
of the non-vaporizing solution processing unit system 82, for
example configured to include: a membrane-based processing unit
system such as reverse osmosis (membrane) unit system, another type
of non-vaporizing solution processing system (such as applied
electric field processing unit system), or both.
[0074] A variety of configurations of equipment can be used for the
non-vaporizing processing unit system 82. For example, when the
system 82 is a reverse osmosis (membrane) unit system, if
available, a single reverse osmosis membrane unit could be used for
the reverse osmosis membrane unit system 82, with: (a) solution to
be processed directed in via line 84; (b) selected liquid
(refrigerant) transferred across the reverse osmosis membrane
arrangement and thus separated, shown removed via line 86; and, (c)
concentrated high pressure side outlet (concentrated or strong
solution) shown removed via line 85. However, in general, for
efficient operation of an absorbent refrigerant cycle, with one
reverse osmosis unit, a sufficiently high pressure would be
required (across the membrane arrangement) that typical
conventionally (currently) available reverse osmosis membranes
would not be adequate. As a result, when currently available
membrane technology and techniques, for reverse osmosis processing
is used in membrane-based processing unit system 82, it will
typically comprise a cascading reverse osmosis membrane unit
system, applying principles in general accord with those described
in U.S. patent application Ser. No. 12/455,998 filed Jun. 9, 2009;
and, U.S. provisional application 61/131,947, filed Jun. 13, 2008,
each of which is incorporated herein by reference, in its
entirety.
[0075] Of course as discussed above, unit system 82 can be a
non-vaporizing solution processing unit system which uses an
alternate to membrane-based separation/purification technologies.
For example, it can include equipment and techniques for applied
electric field processing, in which an applied electric field is
used to provide force for transfer of solute providing for a more
dilute solution (leading to recovery of refrigerant) and a more
concentrated solution in solute (leading to concentrated solution
recovery). Example techniques for this, referenced below, include
electrodialysis, electrodeionization capacitive deionization, and
membrane capacitive deionization techniques.
[0076] It is also noted that the processing unit system 82 can
comprise multiple step systems involving more than one
non-vaporizing solution processing technique.
IV. Examples of Usable Reverse Osmosis Processing (and Reverse
Osmosis (Membrane) Unit System)
A. A First Example--FIG. 3A
[0077] An example usable reverse osmosis (membrane) unit system for
a reverse osmosis (membrane) unit system (i.e. non-vaporizing
solution processing unit system 82) is indicated generally at FIG.
3A. It is noted that many variations are possible, using,
generally, the principles described in U.S. patent application Ser.
No. 12/455,998 filed Jun. 9, 2009; and, U.S. provisional
application 61/131,947, filed Jun. 13, 2008.
[0078] Attention is now directed to FIG. 3A, in which a
membrane-based processing unit system in the form of a reverse
osmosis (membrane) unit system is used for system 82. System 82
than can generally correspond to FIG. 13, of U.S. application Ser.
No. 12/455,998. Referring to FIG. 3A, dilute solution input is
shown at 84, in this example comprising absorbed refrigerant in
strong solution (i.e. a dilute solution) from sump 96 of the
(first) absorber arrangement 83, FIG. 3. At 85, concentrated
solution output from system 82 is shown. This can be used as strong
solution (absorption solution) directed into the absorber
arrangement 83 via line 88, FIG. 3.
[0079] At 86, FIG. 3A, purified (reduced solute) solvent from
reverse osmosis unit system (comprising a non-vaporizing processing
unit system 82) is shown leaving the system 82. The liquid in line
86 could comprise, for example, recovered refrigerant liquid to be
directed into evaporator arrangement 90, FIG. 3.
[0080] For the particular reverse osmosis membrane unit system used
as system 82 depicted in FIG. 3A, a particular type of component
used in the system comprises a modified reverse osmosis (membrane)
unit. Such units, as described as in U.S. application Ser. No.
12/455,998, generally comprise a system in which: a reverse osmosis
membrane arrangement is positioned to define a high pressure side
and a low pressure side; and, the unit is provided with: a high
pressure side liquid flow inlet; a high pressure side liquid flow
outlet; a low pressure side liquid flow inlet; and, a low pressure
liquid flow outlet. This is a modification from traditional reverse
osmosis (membrane) unit systems commercially available, which are
typically provided with only: a high pressure side inlet, a high
pressure side outlet, and, a low pressure side outlet. In general,
such systems can be generated with currently available reverse
osmosis membrane technology, if the components included within the
housing are appropriately configured.
[0081] Referring to FIG. 3A, the example system 82 depicted is
generally as follows: dilute solution input at 84, is directed
through reverse osmosis (RO) pump 100 to provide a pressurized
solution in liquid line 101. At A is depicted a reverse osmosis
unit, comprising a reverse osmosis membrane arrangement 105, with a
high pressure side 105x and low pressure side 105y. The solution
84, pressurized by pump 100 is shown directed into reverse osmosis
unit A via low pressure side inlet line 106. Reverse osmosis unit A
has a low pressure side outlet indicated generally at 107. Within
the reverse osmosis unit 105, a solution directed into high
pressure side inlet 108 is concentrated by passage of solvent
across the membrane arrangement 105 into side 105y. At 109, a high
pressure side concentrate outlet line is shown from unit 105. At
110 a pressure reduction device is shown so that the pressure of
the concentrated solution outlet can be reduced; concentrated
solution out from system 82, being shown via line 85. The pressure
reduction device 110 can be of any number of configurations and can
be used to generate mechanical or electrical power.
[0082] Low pressure side outlet line 107 from unit A is shown
directed into reverse osmosis unit B, which comprises a reverse
osmosis membrane arrangement 115 defining a high pressure side 115x
and a low pressure side 115y. Low pressure side inlet line 116 for
unit B comprises a low pressure side outlet from unit A via line
107. It is noted that at joint 118, the liquid in line 107 is
split, with a portion directed via line 119 into reverse osmosis
pump 120, to create a pressurized line 121 directed to joint
122.
[0083] At 124 a low pressure side outlet line from reverse osmosis
membrane unit B is shown. This is directed as a low pressure side
inlet line to reverse osmosis unit C.
[0084] Reverse osmosis unit C comprises a reverse osmosis membrane
arrangement 130 with a high pressure side 130x and a low pressure
side 130y. Reverse osmosis unit C has: a high pressure side liquid
inlet line 131; a high pressure side liquid outlet line 132; a low
pressure side liquid inlet line 124; and, a low pressure side
liquid outlet line 133.
[0085] Low pressure side outlet flow from line 133 is directed to
joint 135 where it is split into: (a) a line 136, directed to
reverse osmosis unit D as a low pressure side inlet; and, (b) line
137, directed to reverse osmosis unit pump 138 and into pressurized
line 139. Flow in line 139 is directed to joint 196, referenced
below.
[0086] Reverse osmosis unit D comprises reverse osmosis membrane
arrangement 140 with a high pressure side 140x and a low pressure
side 140y. The unit D has: a low pressure side outlet line 141; a
high pressure side inlet line 142; and, a high pressure side outlet
line 143, in addition to the low pressure side inlet line 136.
[0087] The low pressure side outlet line 141 from reverse osmosis
unit D (which represents a reduced solute solvent or purified
solvent line from unit D) is shown directed to reverse osmosis unit
E. Reverse osmosis unit E comprises a reverse osmosis membrane
arrangement 150 defining a high pressure side 150x and a low
pressure side 150y. The unit E has: a low pressure side inlet line
151, which receives liquid from line 141; a low pressure side
outlet line 152; a high pressure side inlet line 153; and, a high
pressure side outlet line 154. In general, line 152 comprises a
reduced solute solvent or purified solvent outlet line from unit E.
Line 152 is directed to joint 156, where it is split into line 157
and line 158. Line 157 is directed as a low pressure side inlet
line to reverse osmosis unit F.
[0088] Reverse osmosis unit F comprises a reverse osmosis membrane
arrangement 160 having a high pressure side 160x; and, a low
pressure side 160y. In addition to low pressure side inlet line
157, reverse osmosis unit F is operated with: a low pressure side
outlet line 161; a high pressure side inlet line 162, and a high
pressure side outlet line 163. Low pressure side outlet line 161
can be viewed as a reduced solute solvent or purified solvent
outlet line from reverse osmosis unit F. This line 161 is directed,
in the example shown, as a low pressure side inlet line 166 for
reverse osmosis unit G.
[0089] Reverse osmosis unit G comprises a reverse osmosis membrane
arrangement 170 having a high pressure side 170x and a low pressure
side 170y. Reverse osmosis unit G is operated with: low pressure
side inlet line 166; low pressure side outlet line 171; high
pressure side inlet line 172; and, high pressure side outlet line
173.
[0090] The low pressure side outlet line 171 generally represents a
reduced solute solvent or purified solvent line from reverse
osmosis unit G. As shown, line 171 is directed via reverse osmosis
pump 175 into line 176, a high pressure side inlet line for reverse
osmosis unit H.
[0091] Reverse osmosis unit H has a reverse osmosis membrane
arrangement 180 defining a high pressure side 180x and a low
pressure side 180y. Reverse osmosis unit H can be viewed as final
"polishing" reverse osmosis unit system, for purifying the solvent
(refrigerant) of system 82. A low pressure side outlet line from
reverse osmosis unit H is shown at 181. When used in connection
with the overall system of FIG. 3, line 181 reflects a purified
refrigerant liquid line, to be directed to the evaporator
arrangement 90 via line 86, FIG. 3.
[0092] Reverse osmosis unit H, FIG. 3A, also has a high pressure
side outlet line indicated at 182. Line 182 carries solute
(concentrated as a result of the operation of the reverse osmosis
unit H) in high pressure side solvent. In the system of FIG. 3A, it
is shown directed through pressure reducer 183 and into high
pressure side inlet line 172 for operation of reverse osmosis unit
G. Within reverse osmosis unit G, the high pressure side liquid is
further concentrated in the solute, as a result of the movement of
solvent across membrane 170, with line 173 being an increased
concentration line in solute relative to the concentration of
solute in line 172. At joint 190, a portion of liquid from line 152
(directed into line 158, from joint 156) is shown after
pressurization of reverse osmosis unit pump 191 being directed via
line 192 to join with the liquid in line 173. This mixed liquid
solution is directed as a high pressure side inlet via line 162
into reverse osmosis unit F. At 163, the high pressure side outlet
from reverse osmosis unit F, which is concentrated in solute
relative the concentration in line 162, is shown directed into the
high pressure side inlet 153 for reverse osmosis unit E. At 154, a
high pressure side outlet, which is concentrated in solute relative
to line 153, is shown directed to joint 196. At joint 196, the
liquid from line 154 is joined with liquid from line 139 and is
directed to high pressure side inlet line 142 for reverse osmosis
unit D. At line 143 a high pressure side concentrate out line from
reverse osmosis unit D is shown, concentrated in solute relative to
line 142, being taken off unit D and being directed as a high
pressure side inlet line 131 to reverse osmosis unit C.
[0093] At line 132, high pressure side concentrate (concentrated in
solute relative to line 131) is shown being removed from reverse
osmosis unit C and directed to joint 122, where it is joined with
liquid in line 121 and directed to high pressure side inlet line
198 to reverse osmosis unit B. At 199, a high pressure side outlet
line from reverse osmosis unit B is shown. High pressure side
outlet line 199 would be concentrated in solute, relative to the
concentration in inlet 198. Line 199 is shown in FIG. 3A directed
to reverse osmosis pump 200 and then into high pressure side inlet
line 108 for reverse osmosis unit A. High pressure side outlet line
109, which would be concentrated in solute relative to line 108, is
then shown directed to pressure reducer 110 and taken from
non-vaporizing processing unit system 82 as a concentrated solution
in solute, via line 85. This would, then, comprise strong solution
in line 85, FIG. 3, for operation of the absorber arrangement
83.
[0094] In general, then, when the non-vaporizing solution
processing unit system 82 uses reverse osmosis processing, the
system 82 operates to take a solution in line 84 and process it
into two outlet solutions: (a) a concentrated solute solution, line
85; and, (b) a reduced solute, relatively purified solvent, line
86.
[0095] In the overall context of the absorption refrigeration cycle
of FIG. 3, dilute solution at line 84 is processed into a recovered
refrigerant liquid line 86 and a concentrated or strong solution
line 85, without the need for a step involving either: a desorber
(generator) 55 to convert refrigerant to a vapor (gas) phase for
separation, FIG. 2; or a condenser 32, FIG. 2, to convert the
refrigerant back to a liquid phase, for direction to the evaporator
arrangement 90, of FIG. 3.
[0096] In general terms, a reverse osmosis membrane unit system, as
depicted in FIG. 3A, can be characterized as including a first,
final, dilute solvent outlet-generating reverse osmosis unit (unit
H); a first, final, concentrate outlet-generating reverse osmosis
unit (unit A); and, an intermediate reverse osmosis (membrane)
(unit) system comprising at least one reverse osmosis unit, in this
instance comprising units B, C, D, E, F and G. Further, unit B can
be characterized as a final, concentrate flow direction (or first
solvent or dilute solvent flow direction) reverse osmosis unit of
the intermediate reverse osmosis (membrane) (unit) system; and,
unit G can be characterized as a first, concentrate flow direction
or final solvent (or dilute solvent) flow direction reverse osmosis
(membrane) unit, of the intermediate reverse osmosis (membrane)
(unit) system.
[0097] Further, although not required in all applications of the
techniques described herein, the reverse osmosis system, FIG. 3A
can be characterized as a process conducted such that: [0098] (a)
concentrate from the first, final, solvent outlet-generating
reverse osmosis unit is directed into the intermediate reverse
osmosis membrane unit system, as part of a feed stream thereto;
[0099] (b) reduced-solute solvent from the intermediate reverse
osmosis membrane unit system is directed to the first, final,
solvent outlet-generating reverse osmosis unit as part of an inlet
feed stream thereto; [0100] (c) concentrate from the intermediate
reverse osmosis membrane unit system is directed into the first,
final, concentrate outlet-generating reverse osmosis unit as part
of an inlet feed stream thereto; [0101] (d) each reverse osmosis
unit in the intermediate reverse osmosis membrane unit system is
conducted with both a high pressure side inlet feed and a low
pressure inlet feed; [0102] (e) each reverse osmosis unit in the
intermediate reverse osmosis membrane unit system provides a high
pressure concentrate outlet and a low pressure side outlet; and,
[0103] (f) the dilute solution to be processed is directed into at
least one of: the first, final, solvent outlet-generating reverse
osmosis unit; the intermediate reverse osmosis membrane unit
system; and, the first, final, concentrate outlet-generating
reverse osmosis membrane unit.
[0104] Of course a wide variety of equipment configurations can be
used for the reverse osmosis processing and the RO unit system. The
examples depicted, are meant to indicate generally the principle
that the processing of a dilute solution, from an absorber
arrangement in a absorption refrigeration cycle, can be conducted
by reverse osmosis processing, to process the dilute solution into:
liquid refrigerant; and, strong or concentrated solution for an
absorber arrangement, without an energy intensive step of
processing the dilute solution through vaporizing the refrigerant.
Providing the refrigerant via separation in liquid form, also
avoids the need for the condenser step.
B. A Hypothetical Example (Using the Systems of FIGS. 3 and 3A) as
Described in U.S. Provisional 61/280,105
[0105] This engineered example is provided to illustrate an example
application of the invention and to illustrate the advantages of
this method compared to the existing conventional, prior art,
methods. The example is based on the systems of FIGS. 3 and 3A. It
is described as a cooling cycle.
[0106] For this example, assume an aqueous lithium bromide (LiBr)
absorbent solution, used in an absorption refrigeration process in
which the refrigerant is water. A LiBr solution was chosen for this
example because at present it is a commonly used solution for
absorption cycle based chillers and air conditioning equipment
operating at standard AHRI conditions.
[0107] For this example, assume that the cycle is operating at
standard full load AHRI conditions with an 85.degree. F.
(29.4.degree. C.) condenser water entering temperature (line 104,
FIG. 3) and a 44.degree. F. (6.7.degree. C.) chilled water leaving
temperature (line 92, FIG. 3) with a flow rate of 3.0 gpm/ton
(gallons per minute per ton, or 3.23 liters/minute per kW of
cooling output) for the condenser water and 2.4 gpm/ton (2.58
liters/minute per kW of cooling output) for the chilled water. This
example is based on a 958.5 ton (3370.9 kW of cooling) equivalent
capacity water-cooled chiller producing chilled water.
[0108] For this example it is assumed that the absorbent solution
is being processed at a fixed temperature of 90.degree. F.
(32.2.degree. C.) through all stages in the RO (reverse osmosis)
process FIG. 3A and the pressure drop in various ones of the
conduits carrying solution, will be negligible. It has also been
assumed that: partially bypassed (in dilute solution flow
direction) RO (reverse osmosis) units B, D and F will have a
solution flow related pressure drop of 7.5 feet of water column
(168 mmHg) on both the high pressure and low pressure sides of the
membrane arrangements; and, non-bypassed RO units, units A, C, E
and G will have a solution flow related pressure drop of 15 feet of
water column (336 mmHg) on both the high pressure and low pressure
sides of the membrane arrangements. Reverse osmosis unit H is
assumed to have a solution flow related pressure drop of 15 feet of
water column (336 mmHg) on the high pressure side of the membrane
and a negligible pressure drop on the low pressure (water) side of
the membrane.
[0109] For reverse osmosis units A, C, E and G, a unit such as the
ITT PCI membrane B1 tubular membrane arrangement available from
Membrane Specialists, Hamilton, Ohio 45015 can be used, modified as
necessary to have a low pressure side inlet with appropriate
structural modification for high pressure side flow and low
pressure side isolation. For units B, D, and F, similar reverse
osmosis units can be used, again modified as necessary to have a
low pressure side inlet and with appropriate structural
modification for high pressure side flow and low pressure side flow
isolation. For reverse osmosis unit H, a reverse osmosis unit such
as the TFC.RTM. SS (single-stage) spiral wound membrane unit
available from Koch Membrane Systems, Inc., Wilmington, Mass. 01887
can be used, without modification.
[0110] It is also assumed that the efficiency of each pump is 87%
and that each motor is 92.5% efficient. Each pressure letdown
device is assumed to be a turbine style power regenerative device
which will be used to assist in the pressurization function that is
being provided by each pressurization pump. It is assumed that the
efficiency for each pressure letdown device is 77% effectiveness at
converting the available pressure differential and flow rate into
usable power. The example also assumes a driving differential
pressure across the membrane arrangement in each reverse osmosis
(RO) unit at a level which is 20% higher than the difference in
osmotic pressures that would be ideally required for the two
solutions exiting the high and low pressure sides of the RO unit.
This extra pressure is typical of conventional RO systems as a
means of providing moderate permeate flux rates and to also
overcome the concentration gradients which will inherently exist in
the solutions near the membrane wall. This engineered example is
described assuming a steady state, steady flow condition. In this
example all concentrations are presented as % by weight.
[0111] The dilute (aqueous LiBr) absorbent solution to be processed
enters the (example reverse osmosis membrane unit) system 82 via
conduit 84 at a concentration of 54.0% LiBr. The re-concentrated,
or desorbed, solution which leaves the reverse osmosis membrane
unit system via conduit 85 in system 82 of FIG. 3A is fed into the
absorber 83 shown in FIG. 3 at a concentration of 55.75% LiBr. The
approximate vapor pressure of the LiBr solutions being fed into,
and out of, the absorber arrangement 83, FIG. 3, at an operating
temperature of 90.degree. F. (32.2.degree. C.), are 5.1 (line 88)
and 7.5 (line 84) mmHg (millimeter mercury) absolute, respectively.
This represents an equivalent refrigerant vapor pressure of
35.degree. F. (1.67.degree. C.) and 45.degree. F. (7.22.degree.
C.), respectively which would be sufficient to produce 44.degree.
F. (6.67.degree. C.) chilled water, in line 92, FIG. 3, in this
example. In the absorber arrangement 83, the refrigerant vapor, in
this case water vapor, is absorbed. This creates a dilute solution
(in sump 96) from the strong solution (line 88) that is fed into
the absorber arrangement 83. The dilute solution is then removed
from the absorber arrangement 83, at 84, and is passed via conduit
84, FIG. 3A into the (reverse osmosis membrane) unit system 82 for
the desorption (separation) process.
[0112] The flow rate of vapor from the evaporator arrangement 90 to
the absorber arrangement 83, FIG. 3, via line 95 is 187.3 #/min
(84.96 kg/min) which corresponds to the flow rate of liquid
refrigerant that is fed into the evaporator arrangement 90, via
conduit 89, from conduit 86 of the reverse osmosis membrane unit
system 82, FIG. 3A. At an average evaporator temperature of
40.degree. F. (4.44.degree. C.) and using water as a refrigerant
which enters the evaporator arrangement at 90.degree. F.
(32.2.degree. C.), the water (refrigerant) has an enthalpy change
from 90.degree. F. (32.2.degree. C.) liquid to 40.degree. F.
(4.44.degree. C.) liquid, of 50 Btu/# (British thermal units/pound)
27.8 kcal/kg). At 187.3 #/min (84.96 kg/min) approximately 46.87
tons (164.8 kW) of cooling is lost in flash to cool the refrigerant
liquid from 90.degree. F. (32.2.degree. C.) to 40.degree. F.
(4.44.degree. C.) in the evaporator arrangement 90. The remaining
heat energy absorbed in the evaporator arrangement 90 is used to
change from a liquid to a slightly superheated refrigerant gas and
serves as the useful cooling provided by the overall refrigeration
cycle 80, FIG. 3. The heat uptake in the evaporator at these
conditions would be 958.5 tons (3370.9 kW) of cooling.
[0113] The solution in conduit 84, FIG. 3A, is pressurized by pump
100 from an entering pressure in conduit 84 of 0.0967 Pounds per
Square Inch Absolute (PSIA) (666.7 Pa) to a pressure of 41.1 PSIA
(2.834 bar) at a flow rate of 5,967 pounds per minute (#/min)
(2706.6 kg/min) of solution in line 101. The solution comprises
3222 #/min (1461.5 kg/min) of solute (LiBr) and 2745 #/min (1245.1
kg/min) of solvent (water) and has a calculated osmotic pressure of
8578 PSIA (591.43 bar). The shaft power required of pump 100 at the
assumed efficiencies would be 20 break horsepower (BHP) (14.91
kW).
[0114] The solution is conducted via conduit 106 to the low
pressure side inlet of reverse osmosis unit A. A flux of the water
solvent will permeate through the membrane of reverse osmosis unit
A, causing a reduction in the solution concentration on the low
pressure side 105y of the reverse osmosis unit A as it travels
through that reverse osmosis unit A and exits via conduit 107. In
this example the solution leaving reverse osmosis unit A via
conduit 107 is receiving 3109 #/min (1410.2 kg/min) of permeated
water as it is processed in reverse osmosis unit A. At the same
time solution on the high pressure side 105x of reverse osmosis
unit A that entered via conduit 108 is being concentrated by the
removal of the same amount (3109 #/min (1410.2 kg/min)) of
permeated water before exiting via conduit 109. The pressure in
conduit 107 is reduced from that in conduit 101 by the 15 feet
water column (336 mmHg) of flow related pressure drop associated
with this reverse osmosis membrane unit A.
[0115] The solution exiting reverse osmosis unit A via conduit 107,
now 35.5% LiBr by weight, is conveyed at a rate of 9076 #/min
(4116.8 kg/min) and has a calculated osmotic pressure of 4288 PSIA
(295.6 bar).
[0116] The flow in conduit 107 is directed to joint 118, where it
is split into conduit 119 and conduit 116. Conduit 119 is part of a
bypass line comprising conduits 119 and 121; and, pump 120. 78% of
the total flow in conduit 107 is directed into conduit 119 while
the remaining 22% of the flow from conduit 107 is directed into
the, conduit 116. The flow in conduit 119 is directed to the high
pressure side 115x of reverse osmosis unit B, from joint 122 and
conduit 198, via pump 120 and conduit 121. The flow in conduit 116
is directed into a low pressure side 115y of the reverse osmosis
unit B where it is further processed.
[0117] A flux of the water solvent will permeate through the
membrane arrangement 115 of reverse osmosis unit B causing a
reduction in the solution concentration on the low pressure side
115y of the reverse osmosis B unit as it travels through that
reverse osmosis unit B and exits via conduit 124.
[0118] In this example, the solution leaving reverse osmosis unit B
via conduit 124 is receiving 187.3 #/min (84.96 kg/min) of
permeated water as it is processed in reverse osmosis unit B. At
the same time, solution on the high pressure side 115x of reverse
osmosis unit B that entered via conduit 198 is being concentrated
by the removal of the same amount (187.3 #/min (84.96 kg/min)) of
permeated water before exiting via conduit 199. The pressure in
conduit 124 is reduced from that in conduit 116 by the 7.5 feet
water column (168 mmHg) of flow related pressure drop associated
with reverse osmosis membrane unit B. Because, in this example, the
permeate flux rate through the partially bypassed reverse osmosis
units B, D, and F is significantly less than the flux through the
other non-bypassed, reverse osmosis units A, C, E, and G the
physical surface area of these reverse osmosis units (B, D and F)
is anticipated to be smaller than the physical surface area of the
non-bypassed reverse osmosis units (A, C, E and G) and therefore
the flow related pressure drop in the partially bypassed units (B,
D, E) is estimated to be half of that expected in the non-bypassed
units (A, C, E and G) as an approximation.
[0119] The solution exiting reverse osmosis unit B via conduit 124,
now 32.46% LiBr by weight, is conveyed at a rate of 2184 #/min
(990.6 kg/min) and has a calculated osmotic pressure of 3779 PSIA
(260.6 bar).
[0120] The solution is then conducted via conduit 124 to the low
pressure side 130y inlet of reverse osmosis unit C. A flux of the
water solvent will permeate through the membrane 130 of reverse
osmosis unit C, causing a reduction in the solution concentration
on the low pressure side 130y of reverse osmosis unit C, as it
travels through that reverse osmosis unit C and exits via conduit
133. In this example, the solution leaving reverse osmosis unit C
via conduit 133 is receiving 709 #/min (321.6 kg/min) of permeated
water as it is processed in reverse osmosis unit C. At the same
time solution on the high pressure side 130x of reverse osmosis
unit C that entered via conduit 131 is concentrated by the removal
of the same amount (709 #/min (321.6 kg/min)) of permeated water
before exiting via conduit 132. The pressure in conduit 133 is
reduced, from that in conduit 124, by the 15 feet water column (336
mmHg) of flow related pressure drop associated with reverse osmosis
membrane unit C.
[0121] The solution exiting reverse osmosis unit C via conduit 133,
now 24.5% LiBr by weight, is conveyed at a rate of 2893 #/min
(1312.2 kg/min) and has a calculated osmotic pressure of 2611 PSIA
(180.0 bar).
[0122] The flow in conduit 133 is directed to joint 135, where it
is split into a first conduit 137 and a second conduit 136. The
first conduit 137 is part of a bypass line comprising conduits 137
and 139, and pump 138. 68% of the total flow in conduit 133 is
directed into conduit 137 while the remaining 32% of the flow from
conduit 133 is directed into the second conduit 136. The flow in
conduit 137 is directed to the high pressure side joint 196 via
pump 138. The flow in conduit 136 is directed into the low pressure
side inlet of reverse osmosis unit D where it is further
processed.
[0123] A flux of the water solvent will permeate through the
membrane arrangement 140 of reverse osmosis unit D, causing a
reduction in the solution concentration on the low pressure side
140y of the reverse osmosis unit D as it travels through reverse
osmosis unit D and exits via conduit 141. In this example, the
solution leaving reverse osmosis unit D via conduit 141 is
receiving 187.3 #/min (84.96 kg/min) of permeated water as it is
processed in reverse osmosis unit D. At the same time, solution on
a high pressure side 140x of reverse osmosis unit D that entered
via conduit 142 is concentrated by the removal of the same amount
(187.3 #/min (84.96 kg/min)) of permeated water before exiting via
conduit 143. The pressure in conduit 141 is reduced from that in
conduit 136 by the 7.5 feet water column (168 mmHg) of flow related
pressure drop associated with this membrane unit.
[0124] The solution exiting reverse osmosis unit D via conduit 141
is now 20.38% LiBr by weight, is conveyed at a rate of 1113 #/min
(504.8 kg/min), and has a calculated osmotic pressure of 2082 PSIA
(143.5 bar).
[0125] The solution is then conducted via conduit 141 to a low
pressure inlet 151, for low pressure side 150y of reverse osmosis
unit E. A flux of the water solvent will permeate through the
membrane arrangement 150 of reverse osmosis unit E, causing a
reduction in the solution concentration on the low pressure side
150y of reverse osmosis unit E as it travels through that unit E
and exits via conduit 152. In this example the solution leaving
reverse osmosis unit E via conduit 152 is receiving 507 #/min (230
kg/min) of permeated water as it is processed in reverse osmosis
unit E. At the same time solution on the high pressure side 150x of
reverse osmosis unit E that entered via conduit 153 is concentrated
by the removal of the same amount (507 #/min (230 kg/min)) of
permeated water before exiting via conduit 154. The pressure in
conduit 152 is reduced from that in conduit 141 by the 15 feet
water column (336 mmHg) of flow related pressure drop associated
with this membrane unit.
[0126] The solution exiting reverse osmosis unit E via conduit 152,
now 14.0% LiBr by weight, is conveyed at a rate of 1620 #/min
(734.8 kg/min) and has a calculated osmotic pressure of 1345 PSIA
(92.7 bar).
[0127] The flow in conduit 152 directed to joint 156 is split into
conduit 158 and conduit 157. Conduit 158 is part of a bypass line
comprising conduits 158 and 192, and pump 191. 80% of the total
flow in conduit 152 is directed into conduit 158 while the
remaining 20% of the flow from conduit 152 is directed into the
second conduit 157. The flow in conduit 158 is directed to the high
pressure side joint 190 via pump 191. The flow in conduit 157 is
directed into the low pressure side 160y of the reverse osmosis
unit F where it is further processed.
[0128] A flux of the water solvent will permeate through the
membrane arrangement 160 of reverse osmosis unit F, causing a
reduction in the solution concentration on the low pressure side
160y of the reverse osmosis unit F as it travels through that unit
F and exits via conduit 161. In this example the solution leaving
reverse osmosis F via conduit 161 is receiving 187.3 #/min (84.96
kg/min) of permeated water as it is processed in the reverse
osmosis unit F. At the same time, solution on the high pressure
side 160x of reverse osmosis unit F that entered via conduit 162 is
concentrated by the removal of same amount (187.3 #/min (84.96
kg/min)) of permeated water before exiting via conduit 163. The
pressure in conduit 161 is reduced from that in conduit 157 by the
7.5 feet water column (168 mmHg) from flow related pressure drop
associated with this membrane unit.
[0129] The solution exiting reverse osmosis unit F via conduit 161,
now 8.87% LiBr by weight, is conveyed at a rate of 511 #/min (231.8
kg/min) and has a calculated osmotic pressure of 813 PSIA (56.1
bar).
[0130] The solution is then conducted via conduit 161 to the low
pressure side inlet 166 of reverse osmosis unit G. A flux of the
water solvent will permeate through the membrane arrangement 170 of
reverse osmosis unit G causing a reduction in the solution
concentration on the low pressure side 170y of the unit G as it
travels through that unit G and exits via conduit 171. In this
example, the solution leaving reverse osmosis unit G, via conduit
171, is receiving 403 #/min (182.8 kg/min) of permeated water as it
is processed in reverse osmosis unit G. At the same time, solution
on the high pressure side 170x of reverse osmosis unit G that
entered via conduit 172 is concentrated by the removal of the same
amount (403 #/min (182.8 kg/min)) of permeated water before exiting
via conduit 173. The pressure in conduit 171 is reduced from that
in conduit 161 by the 15 feet water column (336 mmHg) from flow
related pressure drop associated with reverse osmosis membrane unit
G.
[0131] The solution exiting reverse osmosis unit G via conduit 171,
now 4.96% LiBr by weight, is conveyed at a rate of 915 #/min (415
kg/min) and has a calculated osmotic pressure of 439 PSIA (30.27
bar).
[0132] The flow in conduit 171 is directed to reverse osmosis unit
H, a first, final, reverse osmosis unit in the reverse osmosis
membrane unit system 82, via pump 175 and conduit 176. The flow in
conduit 171 exits reverse osmosis unit G at a pressure of 5.4 PSIA
(0.3723 bar) and is pressurized via pump 175 to a pressure of 685.7
PSIA (47.3 bar) in conduit 176. The calculated power input required
at pump 175 is 50 BHP. The pressurized solution in conduit 176
flows into the high pressure side 180x inlet of reverse osmosis
unit H where it is further processed. A flux of the water solvent
will permeate through the membrane arrangement 180 of reverse
osmosis unit H causing an increase in the solution concentration on
the high pressure side 180x of the unit H as it travels through
that unit H and exits via conduit 182.
[0133] The flux of permeate water through the membrane arrangement
180 of reverse osmosis unit H is collected on the low pressure side
180y of the membrane 180 and is conveyed out of the reverse osmosis
unit H via conduit 181. It is directed to the evaporator
arrangement 90, FIG. 3, via conduit 86 and 87. The permeate leaving
reverse osmosis unit H via conduit 181 serves as the refrigerant
liquid in the overall refrigerating cycle 80, FIG. 3.
[0134] In this example, the refrigerant liquid leaving reverse
osmosis unit H via conduit 181 is conveyed at a rate of 187.3 #/min
(84.96 kg/min) and a pressure of 6.5 PSIA (0.4482 bar) and is
assumed to be pure water at this point in the process cycle. The
solution exiting reverse osmosis unit H via conduit 182 is
increased in concentration from that in conduit 176 through the
removal of permeate from the solution in the reverse osmosis
membrane unit H. The concentration of the solution in conduit 182
is 6.24% LiBr and has a calculated osmotic pressure of 558 PSIA
(38.5 bar). The pressure in conduit 182 is reduced from that in
conduit 176 by the 15 feet water column (336 mmHg) from flow
related pressure drop associated with this membrane unit. The
solution in conduit 182 is conveyed into optional pressure reducing
device 183 where a pressure reduction could be provided if needed.
In this example the flows on the system were balanced such that the
use of this pressure reduction device 183 is optional. In this
example, the pressure drop across unit 183 was calculated to be 2
feet of water column (44.79 mmHg). Therefore, the pressure of the
solution in conduit 172 is calculated to be 678 PSIA (46.75
bar).
[0135] The solution in conduit 172 is conveyed to the high pressure
side 170x of reverse osmosis unit G where it is further
concentrated to 14% LiBr upon exiting into conduit 173. The average
calculated osmotic pressure on the high pressure side 170x of the
membrane arrangement 170 of reverse osmosis unit G is 951.5 PSIA
(65.6 bar). The calculated pressure in conduit 173 is 672 PSIA
(46.33 bar). The average calculated osmotic pressure of the
solution on the low pressure side 170y of the membrane arrangement
170 of reverse osmosis unit G is 626 PSIA (43.16 bar). Thus, the
difference in calculated average osmotic pressure between the
solutions on the high pressure side 170x and the low pressure side
170y of the reverse osmosis membrane arrangement 170 of reverse
osmosis unit G is 325.5 PSIA (22.44 bar). The actual pressure
difference between the high pressure side 170x and the low pressure
side 170y is 667 PSI (45.99 bar), on average, in this calculated
example. Thus, a flux of permeate water is able to pass through the
reverse osmosis membrane arrangement 170 from the high pressure
side 170x to the low pressure side 170y. The maximum difference in
osmotic pressure, on the more concentrated flow end of the reverse
osmosis membrane unit G is between the flows entering via conduit
166 and exiting via conduit 173. The difference in osmotic
pressures at this point is calculated to be 532 PSI (36.68 bar),
which is less than the average actual operating pressure
differential and thus a flux of permeate through membrane
arrangement 170 can be achieved.
[0136] The solution in conduit 173 is conveyed at a rate of 324
#/min (147 kg/min) to joint 190 where it is combined with flow of
equal LiBr concentration from conduit 192. The combined flow from
joint 190 is conveyed at a rate of 1620 #/min (734.8 kg/min) into
conduit 162 which serves to feed the solution to the high pressure
inlet side 160x of reverse osmosis unit F for further processing.
The pump 191 pressurizes the flow from conduit 158 such that it is
able to feed into joint 190 at the desired flow rate. The
calculated power input required at pump 191 is 68 BHP.
[0137] Reverse osmosis unit F further concentrates the solution
flowing on the high pressure side 160x of the membrane arrangement
160 from a concentration of 14% in conduit 162 to a concentration
of 15.83% in conduit 163. The maximum difference in osmotic
pressure, seen by the reverse osmosis unit F, is on the more dilute
end between the solutions contained in conduits 162 and 161. The
calculated difference in osmotic pressure between these solutions
is 532 PSI (36.68 bar). The actual operating pressure difference
between these two solutions upon entering and exiting reverse
osmosis unit F at this end of the reverse osmosis unit F is 660.8
PSI (45.56 bar), thus a net flux of permeate through the membrane
arrangement 160 of unit F can be established.
[0138] The solution in conduit 163 is conveyed at a flow rate of
1433 #/min (650 kg/min) to the high pressure side inlet 153 reverse
osmosis unit E, where it is further concentrated to 24.5% LiBr,
upon exiting into conduit 154 which corresponds to a calculated
osmotic pressure of 2611 PSIA (180.02 bar). The calculated pressure
in conduit 154 is 663 PSIA (45.71 bar) at a solution flow rate of
926 #/min (420 kg/min). The maximum difference in osmotic pressure
seen by the reverse osmosis unit E is on the more concentrated end
between the solutions contained in conduits 154 and 151. The
calculated difference in osmotic pressure between these solutions
is 529 PSI (36.47 bar). The actual operating pressure difference
between these two solutions upon entering and exiting reverse
osmosis unit E, at this end of the unit E, is 611.3 PSI (42.15
bar). Thus a flux of permeate water is able to pass through the
reverse osmosis membrane arrangement 150 of unit E from the high
pressure side 150x to the low pressure side 150y.
[0139] The solution in conduit 154 is conveyed to at a rate of 926
#/min (420 kg/min) to joint 196 where it is combined with flow of
equal LiBr concentration from conduit 139. The combined flow from
joint 196 is conveyed at a rate of 2893 #/min (1312.2 kg/min) into
conduit 142, which serves to feed the solution to the high pressure
side 140x of reverse osmosis unit D for further processing. The
pump 138 pressurizes the flow from conduit 137 such that it is able
to feed into joint 196 at the desired flow rate. The calculated
power input required at pump 138 is 101 BHP. Reverse osmosis unit D
further concentrates the flow of solution on the high pressure side
140x, of the membrane arrangement 140, from a concentration of
24.5% in conduit 142 to a concentration of 26.2% in conduit 143.
The maximum difference in osmotic pressure seen by the reverse
osmosis unit D is on the more dilute end between the solutions
contained in conduits 142 and 141. The calculated difference in
osmotic pressure between these solutions is 529 PSI (36.47 bar).
The actual operating pressure difference between these two
solutions upon entering and exiting unit D, at this end of the RO
unit D, is 641.3 PSI (44.21 bar). Thus a net flux of permeate
through the membrane arrangement 140 of unit D can be
established.
[0140] The solution in conduit 131 is conveyed at a flow rate of
2706 #/min (1227.4 kg/min) to the high pressure side 130x of
reverse osmosis unit C, where it is further concentrated to 35.5%
LiBr upon exiting into conduit 132, which corresponds to a
calculated osmotic pressure of 4288 PSIA (295.65 bar). The
calculated pressure in conduit 132 is 653.2 PSIA (45.04 bar) at a
solution flow rate of 1997 #/min (905.8 kg/min). The maximum
difference in osmotic pressure seen by the reverse osmosis unit C
is on the more concentrated end between the solutions contained in
conduits 132 and 124. The calculated difference in osmotic pressure
between these solutions is 509 PSI (35.09 bar). The actual
operating pressure difference between these two solutions upon
entering and exiting unit C at this end of unit C is 621.8 PSI
(42.87 bar). Thus, a flux of permeate water is able to pass through
the reverse osmosis membrane arrangement 130 of unit C from the
high pressure side 130x to the low pressure side 130y.
[0141] The solution in conduit 132 is conveyed to joint 122 where
it is combined with flow of equal LiBr concentration from conduit
121. The combined flow from joint 122 is conveyed at a rate of 9076
#/min (4116.8 kg/min) into conduit 198 which serves to feed the
solution to the high pressure side 115x of reverse osmosis unit B
for further processing. The pump 120 pressurizes the flow from
conduit 119 such that it is able to feed into joint 122 at the
desired flow rate. The calculated power input required at pump 120
is 350 BHP. Reverse osmosis unit B further concentrates the flow of
solution on the high pressure side 115x of the membrane arrangement
115 from a concentration of 35.5% in conduit 198 to a concentration
of 36.25% in conduit 199. The maximum difference in osmotic
pressure seen by the reverse osmosis unit B is on the more dilute
end between the solutions contained in conduits 198 and 124. The
calculated difference in osmotic pressure between these solutions
is 509 PSI (34.54 bar). The actual operating pressure difference
between these two solutions upon entering and exiting unit B at
this end of the unit B is 617.1 PSI (42.548 bar). Thus, a net flux
of permeate through the membrane arrangement of unit B can be
established.
[0142] The solution in conduit 199 is conveyed at a flow rate of
8889 #/min (4032 kg/min) to the high pressure side 105x of reverse
osmosis unit A via pump 200. Upon leaving the unit A, liquid on the
high pressure side 105x of the reverse osmosis membrane arrangement
105, has been further concentrated to 55.75% LiBr upon exiting into
conduit 109 which corresponds to a calculated osmotic pressure of
9146 PSIA (630.59 bar). Pump 200 serves to increase the pressure of
the solution as it is conveyed from conduit 199 into conduit 108.
Pump 200 increases the pressure from 645.3 PSIA (44.492 bar) in
conduit 199 to a pressure of 737 PSIA (50.81 bar) in conduit 108.
The calculated pumping power required for pump 200 is 66 BHP. The
maximum difference in osmotic pressure seen by the reverse osmosis
unit A is on the more concentrated end between the solutions
contained in conduits 109 and 101. The calculated difference in
osmotic pressure between these solutions is 568 PSI (39.16 bar).
The actual operating pressure difference between these two
solutions upon entering and exiting unit A at this end of the unit
A is 689.4 PSI (47.53 bar). Thus a flux of permeate water is able
to pass through the reverse osmosis membrane arrangement 105 of
unit A from the high pressure side 105x to the low pressure side
105y.
[0143] The solution in conduit 109 is then conveyed to a pressure
reduction device 110. This device reduces a solution flow of 7466
#/min (3386.5 kg/min) from a pressure of 730 PSIA (50.332 bar) to 9
PSIA (0.6205 bar), and would produce a shaft power output of 225
BHP which could be used to offset some of the power consumption of
the other pumps in the system 82.
[0144] In general, the flow of solution increases in concentration
along the high pressure side path from conduit 176 through unit H,
into conduit 182, through pressure reduction device 183, into
conduit 172, and then through the high pressure sides for units G,
F, E, D, and B, pump 200, and then through unit A; while,
conversely, the flow of solution from conduit 101 generally
decreases in concentration following the low pressure side path of
unit A through units B, C, D, E, F, and G, then prior to entering
the first final reverse osmosis membrane unit H in the membrane
unit system 82 with the various joints, bypasses, and
pressurization changes as previously described herein. Herein such
a process is referenced as a cascading reverse osmosis process,
although the number of RO units can be varied.
[0145] The results of this engineered example indicate a total net
power input requirement of 654 shaft BHP via reverse osmosis pumps
100, 175, 191, 138, 120 and 200, and a total power generated via
pressure letdown device 110 of 225 shaft BHP, for a net total
system power input requirement of 429 shaft BHP. Using the assumed
electrical motor efficiencies of 92.5%, this equates to a total
power input requirement of 346 kW to produce 958.5 tons (3370.9 kW)
of cooling which represents a system full load efficiency of 0.36
kW/ton (0.10236 kW of energy input/kW of cooling produced).
[0146] In comparison, a present state of the art vapor compression
water cooled centrifugal chiller operates in the range of
approximately 0.60 kW/ton (0.1706 kW of energy input/kW of cooling
produced) under these same stated operating conditions. This
example indicates that the absorption osmosis refrigeration cycle
80, FIG. 3, has the potential to operate using 40% less energy than
a present state of the art vapor compression refrigeration cycle.
In this example if one were to assume that this chiller were to
operate as a base loaded machine operating at full load under these
conditions for 6500 hours per year the electrical consumption
savings would be approximately 1,495,260 kWh per year. If this
electrical energy were to be purchased for $0.085/kWh that would
equate to an annual operating cost savings of $127,097. Additional
calculations of other configurations of the (reverse osmosis
membrane unit) system 82 indicate that by adding more membrane
stages, the system 82 has the ability to produce a cycle that
operates with an even lower overall energy consumption per ton
(3.517 kW) of cooling than was demonstrated in the example
presented here.
[0147] A further comparison could be made to a present state of the
art water cooled absorption cycle operating as a chiller under the
same stated conditions. Because the prior art absorption cycles are
predominately thermally driven (also known as heat driven) cycles a
comparison to the reverse osmosis absorption cycle is not as
direct. As stated above, a typical present day single stage
absorption chiller operates with a cooling Coefficient Of
Performance (or COP) in the range of 0.83 to 1.0, where COP is the
ratio of the cooling energy produced divided by the input energy
required to drive the cycle. This example indicates that the
absorption osmosis refrigeration cycle 80, FIG. 3, has the
potential to operate at an energy input rate of 346 kW to produce
958.5 tons (3370.9 kW) of cooling. This equates to an operational
COP of 9.74 which is approximately a 10 times greater efficiency
than standard water cooled absorption cycle as described herein.
Although the energy efficiency of the standard absorption cycle is
poor, sources of thermal energy are typically less expensive than
electrical or mechanically driven sources of energy input. This
explains why the standard, thermally driven, absorption cycle is
still in common use for certain applications where abundant
relatively high temperature waste heat is readily available. The
comparison against the vapor compression cycle is more appropriate
due to its similarity in terms of being driven from mechanical work
(primarily electric motor driven), rather than being predominately
thermal or heat driven as is the case in the standard absorption
cycle. A standard absorption cycle could be driven with
electrically generated heat, however the very poor efficiency and
the relatively high price of electricity makes this concept
impractical especially given the fact that a vapor compression
cycle is less expensive in terms of initial equipment cost and is
significantly more energy efficient than the standard absorption
cycle.
[0148] If the energy savings potential of this cycle 80 were to be
achieved in many applications on a wide scale, the impact on the
world's electrical consumption for cooling could be notably
improved over the present state of the art vapor compression
refrigeration cycles. In addition, because the example described
application uses water as a refrigerant many of the environmental
and safety concerns associated with other commonly used
refrigerants such as ozone depletion, global warming potential,
flammability, or toxicity are avoided.
C. Some Comments Updating the Hypothetical Example of Section IV.
B.
[0149] Since the patent Provisional submittal it has been found
that it is appropriate for a correction factor to be applied to the
calculation of osmotic pressure. This correction factor is
appropriately applied when working with highly active ions (such as
lithium) or when working with non-dilute solutions. Under these
conditions, the solution can behave in a non-ideal manner and
produce actual osmotic pressures which deviate from values
calculated using traditional uncorrected methods. To account for
this, a factor is applied to the calculation of osmotic pressure
which is known as the Osmotic Coefficient. This Osmotic Coefficient
is a function of temperature, concentration, and the ionic strength
(or the solute activity coefficient). The values expressed in the
preceding Hypothetical Example, from U.S. Ser. No. 61/280,105, were
made without correcting for this Osmotic Coefficient.
V. A Modified Application of the Techniques Described in Connection
with FIGS. 3 and 3A; FIG. 3B
A. Use of a Second Example Reverse Osmosis Unit System--FIG. 3B
[0150] In the previous description, an example absorption osmosis
refrigeration cycle 80, FIG. 3, was described. In the system, a
membrane-based processing unit system for non-vaporizing solution
processing system 82, in particular a reverse osmosis membrane unit
system, was described as used, in place of a traditional desorber
(55), FIG. 2, and condenser 32, FIG. 2, to process dilute solution
from the absorber arrangement 83 into: a strong solution for the
absorber loop; and, a refrigerant liquid for the evaporator
arrangement 90. It was described that the (example reverse osmosis
membrane unit) system 82 can be a variety of systems with
advantages being derived from the lack of a step of separating
refrigerant, from the dilute solution, by conversion to vapor
(gas), with a concomitant input of energy. Indeed, the processing
of the dilute solution in the (reverse osmosis membrane unit)
system 82 is conducted by using a reverse osmosis process.
[0151] Herein above, it was explained that a wide variety of
processes involving reverse osmosis practices can be applied. An
example was described in connection with FIG. 3A. Here a cascading
reverse osmosis membrane system was described as an example system
82, in which the dilute solution from the absorber 83, FIG. 3, was
directed, initially, into a low pressure side of a first, final,
reverse osmosis membrane unit A.
[0152] Alternate reverse osmosis membrane unit systems can be used.
Indeed, in some systems the dilute solution from the absorber
arrangement 83 can be directed into the high pressure side of a
first reverse osmosis membrane unit system. An example of this is
provided in this section.
[0153] Referring to FIG. 3B, a reverse osmosis membrane unit system
82', usable as system 82, FIG. 3, for processing dilute solution
from line 84, in refrigeration cycle 80, is shown. Referring to
FIG. 3B, dilute solution input to system 82' is shown at line 84
with: (a) strong solution output from system 82' shown at line 85,
and (b) refrigerant liquid output from system 82' shown at line
86.
[0154] Referring to FIG. 3B, for the example system 82' depicted,
dilute solution 84 is directed into pump 300, and then into
pressurized line 301, which serves as a high pressure side inlet
line for reverse osmosis unit L. Reverse osmosis unit L comprises a
reverse osmosis membrane arrangement 305 having a high pressure
side 305x and a low pressure side 305y.
[0155] A high pressure side outlet from unit L is shown at 306,
comprising concentrated or strong solution directed through
pressure reduction device 307 into line 85.
[0156] Low pressure side outlet from reverse osmosis unit L is
shown at 310 being directed through pump 311 into line 312 which
serves as a low pressure side inlet for reverse osmosis unit M.
[0157] Reverse osmosis unit M comprises a reverse osmosis membrane
arrangement 315 having a high pressure side 315x and a low pressure
side 315y. Low pressure side outlet from reverse osmosis unit M is
shown at line 316 being directed to joint 317. At joint 317, the
low pressure side outlet flow from unit M is split into lines 318,
319. Line 319 is directed through pump 320 into line 321.
[0158] Line 318, serves as a low pressure side inlet line for
reverse osmosis unit N.
[0159] Reverse osmosis unit N comprises a reverse osmosis membrane
arrangement 325 having a high pressure side 325x and a low pressure
side 325y. Low pressure side outlet from reverse osmosis unit N is
shown at line 326 directed to reverse osmosis unit O as a low
pressure side inlet.
[0160] In general, reverse osmosis unit O comprises a reverse
osmosis membrane arrangement 335 having a high pressure side 335x
and a low pressure side 335y. Low pressure side outlet flow from
reverse osmosis unit O is shown at line 337 being directed to joint
338 where it is separated at lines 339, 340. Line 340 is directed
through pump 341 into line 342.
[0161] Line 339 operates as a low pressure side inlet line for
reverse osmosis unit P. Reverse osmosis unit P comprises a reverse
osmosis membrane arrangement 345 having a high pressure side 345x
and a low pressure side 345y. A low pressure side outlet flow from
reverse osmosis unit P is shown at line 347, which serves as a low
pressure side inlet line for reverse osmosis unit Q.
[0162] In general, reverse osmosis unit Q comprises a reverse
osmosis membrane arrangement 355 defining a high pressure side 355x
and a low pressure 355y. Low pressure side outlet flow from reverse
osmosis unit Q is shown at line 356 directed to pump 357 and into
line 358, which serves as a high pressure side inlet line for
reverse osmosis unit R.
[0163] Reverse osmosis unit R comprises a reverse osmosis membrane
arrangement 365 defining a high pressure side 365x and a low
pressure side 365y. Permeate on the low pressure side 365y
comprises purified solvent, i.e. refrigerant liquid, is shown
leaving the reverse osmosis unit R at low pressure side outlet 366,
to exit the system 82' and enter the refrigerator cycle 80 at
refrigerant liquid line 86.
[0164] A high pressure side outlet line from reverse osmosis unit R
is shown at 368 directed to optional pressure let-down device 369
to be directed into line 370 which operates as a high pressure side
inlet line to reverse osmosis unit Q.
[0165] A high pressure outlet line from reverse osmosis unit Q is
shown at line 371 where it is directed to joint 372 and is combined
with liquid in line 342. The combined liquid enters line 373, a
high pressure side inlet line for reverse osmosis unit P.
[0166] The high pressure side outlet from reverse osmosis unit P is
shown at line 375 being directed as a high pressure side inlet for
reverse osmosis unit O.
[0167] A high pressure side outlet from reverse osmosis O is shown
at line 378 being conveyed to joint 379 where it is joined with
liquid from line 321 and directed into line 380.
[0168] Line 380 serves as a high pressure side inlet line from
reverse osmosis unit N. A high pressure side outlet line from
reverse osmosis unit N is shown at line 381 being directed into
reverse osmosis pump 382, and then into a higher pressurized line
383 which serves as a high pressure side inlet line to reverse
osmosis unit M.
[0169] A high pressure side outlet flow from reverse osmosis unit M
is shown at line 385 being directed to optional pressure let-down
device 386 and then into line 387 which serves as a low pressure
side inlet line to reverse osmosis unit L.
[0170] It is noted that the reverse osmosis membrane unit system
82', FIG. 3B, can also be characterized as having: first, final,
concentrate-generating reverse osmosis unit L; a first, final,
purified solvent dilute solution-generating reverse osmosis unit R;
and, an intermediate reverse osmosis membrane unit system
comprising units M, N, O, P, and Q. Further unit M can be
characterized as a final, concentrate flow direction, or first
dilute purified solvent flow direction, reverse osmosis unit of the
intermediate reverse osmosis membrane unit system; and, unit Q can
be characterized as the final solvent or dilute solution flow
direction, or first concentrate flow direction, reverse osmosis
membrane unit of the intermediate reverse osmosis membrane unit
system. Further, the processing conducted by this reverse osmosis
membrane unit system 82', FIG. 3B, can be generally as
characterized above.
B. A Hypothetical Example using the Reverse Osmosis Unit System of
FIG. 3B, with the Absorption Osmosis Refrigeration Cycle of FIG.
3
[0171] FIG. 3B presents a schematic view of another embodiment of a
cascading RO membrane system that could be used as system 82, FIG.
3, to separate the refrigerant liquid from the dilute absorbent
solution. In this configuration the dilute solution leaving the
absorber arrangement 83, FIG. 3 in conduit 84 is pressurized and
conveyed via pump 300, FIG. 3B, to the high pressure inlet of the
reverse osmosis membrane unit L via conduit 301. The pressure of
the solution on the adjacent side to membrane arrangement is such
that a flux of solvent is transported through the membrane 305 of
unit L from the side of high pressure 305x to the side of lower
pressure 305y, thereby re-concentrating the solution from conduit
301 as it passes through unit L, and exits into conduit 306. The
now diluted solution on the low pressure side 305y of the reverse
osmosis membrane unit L exits unit L via conduit 310. In this
scenario the flow in conduit 310 follows a similar processing path
as described for FIG. 3A. However in contrast to FIG. 3A there is a
first processing of dilute solution from the absorber arrangement
83 of FIG. 3A, via first entering the high pressure side of a
reverse osmosis membrane unit.
[0172] The re-concentrated solution in conduit 306 then passes
through a pressure let down device 307 where additional power may
be generated as the solution moves into conduit 85. The solution in
conduit 85 is then transferred back to the inlet side of the
absorber arrangement 83, as is generically depicted in FIG. 3.
[0173] It is noted that the number, and arrangement of, the
membrane unit systems both in: FIG. 3A; and, FIG. 3B, is
representative of example possibilities only. Both the number of,
and the configuration of, the various stages of the reverse osmosis
units can be arranged in a variety of configurations. What has been
depicted here is merely intended to illustrate that multiple
configurations for the RO Membrane Unit System 82 depicted in FIG.
3 are possible.
[0174] The arrangement depicted in FIG. 3B can be useful as a means
of isolating the solute, or solute solution, from the remainder of
the RO unit system. Because only solvent is passed through the RO
membrane of unit L, the solvent solute mixture on the low pressure
side of unit L, and the rest of the system for that matter, could
consist of different solute than is present on the high pressure
side of unit L which includes the absorber side of the system. This
configuration could be used for a number of reasons. Reasons could
be that the solution used in the absorber could possess properties,
such as low pH or high corrosivity, which would require the use of
a relatively expensive RO membrane unit system. By using the
configuration of FIG. 3B an alternative solute could be used for
the remainder of the system whereby RO membrane units of relative
lower cost as compared to unit L could be deployed on the lower
pressure side of RO membrane unit L in the system due to the
ability of this system to use a less demanding solute solution at
the lower concentration ranges that would be seen on the remainder
of the system.
VI. Solvents, Solutes, and Solutions
[0175] There are a multitude of solvent, solute, and ultimate
solution variations capable of being used in an absorption
refrigeration cycle or system of the present disclosure with any of
a variety of non-vaporizing solution processing techniques. Some
examples of potential solutes include: potassium chloride,
potassium bromide, potassium fluoride, sodium chloride, sodium
bromide, sodium iodide, lithium chloride, lithium bromide, sodium
sulphide, sodium formate, calcium chloride, calcium bromide,
magnesium chloride, calcium hydrogen malate, sodium tetradecanoate,
sodium phosphate, ammonium bicarbonate, disodium orthophosphate,
propylene glycol, ethylene glycol, dimethylacetamide (DMAC) and
mixtures thereof, although alternatives are possible. In practice
any solute which disassociates into a solution with have the effect
of lowering the vapor pressure of that solution while at the same
time raising an osmotic pressure of the solution. Solutes could be
used individually or in various combinations to produce the desired
results. Mixtures of solutes could be used to produce many useful
properties of the solution such as: reduced corrosivity, lowered
propensity towards solute precipitation out of solution, viscosity,
thermal conductivity, pH adjustment of the solution to a more
desirable level, and/or reduced solution cost.
[0176] Some examples of potential solvents that could be used in
the system of the present disclosure include: water, ammonia,
various alcohols, refrigerant R-134a and mixtures thereof, although
alternatives are possible. Solvents can be used individually or in
various combinations to produce the desired results. Solute
mixtures can be used to produce desired properties or operating
conditions. For example, one could use a water/ethanol mixture or
ammonia as a refrigerant in the cycle which would have a lower
temperature freezing point than pure water, and thus could be used
in applications where sub-freezing (<32.degree. F. or
<0.degree. C.) temperatures are expected.
[0177] Further a mixture of solutes and a mixture of solvents can
be in the present invention. One example of this could be
illustrated by the use of a combination of water, ethanol,
propylene glycol, and sodium iodide.
VII. Some Example Alternate Cycles, FIGS. 4-6
[0178] The general principles characterized above can be applied in
a variety of alternately configured systems. Alternate
configurations can be used for each (or both) of: the
non-vaporizing solution processing based unit or system 82; and,
remaining features of the absorption osmosis refrigeration cycle
80, FIG. 3. Examples are provided herein, in FIGS. 4-6. These
figures are illustrative that a wide variety of alternate
configurations are possible.
A. A First Alternate Refrigeration Cycle, FIG. 4
[0179] Reference numeral 400, FIG. 4, depicts a first alternate
refrigeration cycle. The cycle 400 has some features in common with
cycle 80, FIG. 3, as follows. From non-vaporizing solution
processing unit system 82, a refrigerant line (i.e. purified
solvent line) 86 is shown. The line 86 includes liquid directed to
refrigerant liquid line 87 for (first) evaporator arrangement 90,
in this instance after passage through (optional) expansion or
pressure reduction device 401 as flow from line 402. Heat input to
the evaporator arrangement 90, to vaporize some or the entire
refrigerant, is shown at arrows 91 with a cooled air or liquid
output shown at 92.
[0180] Within the evaporator arrangement 90, at least a portion of
the refrigerant liquid is vaporized, with refrigerant gas (vapor)
shown leaving evaporator arrangement 90 at line 95, by which it is
directed into (first) absorber arrangement 83. In absorber
arrangement 83, the refrigerant vapor is absorbed into strong
solution, resulting in dilute solution in sump 96. Dilute solution
outlet flow from sump 96 is shown at line 403 which, in part,
provides liquid at line 84, as dilute solution input to the reverse
osmosis membrane unit system 82. In the particular example depicted
in FIG. 4, reverse osmosis pump 405 is depicted receiving liquid
from line 84. In some instances, the pump 405 would be considered
part of the non-vaporizing solution processing unit system 82; see
for example analogous pump 100, FIG. 3A.
[0181] Referring again to FIG. 4, at joint 410, a portion of the
liquid refrigerant from line 86 is shown directed into a line 411,
through expansion or pressure reduction device 412, and into a
coolant line 413 for absorber arrangement 83. (It is also noted
that absorber arrangement 83 is depicted with packing 83x).
[0182] Output from line 413, from absorber 83, comprising heated
material in line 413, is shown at line 415, analogous to FIG. 3.
This line, comprising heated (typically at least partially
vaporized) refrigerant, is now shown being directed to a second
absorber arrangement 420, with packing 420x, where it is absorbed
into strong solution, resulting in the dilute solution shown in
sump 421. The dilute solution from absorber arrangement 420 is
shown being directed via line 425 to joint 426 where it is combined
with the dilute solution output from absorber arrangement 83, to
form the dilute solution line 84 directed to the (reverse osmosis
membrane unit) non-vaporizing solution processing system 82.
[0183] It is noted that, together, first absorber arrangement 83
and second absorber arrangement 420 can be considered an "absorber
arrangement" for the system 400, in general accord with
characterizations described herein.
[0184] Strong or concentrated solution outlet from the
non-vaporizing solution processing system 82 is shown at line 85.
It is depicted directed through pressure reduction device 430 and
into line 431. It is noted that an analogous pressure reduction
device 430 in previous characterizations, was described as a
portion of the (reverse osmosis membrane unit) non-vaporizing
solution processing system 82, and it could be included as such
here; see for example unit 110, FIG. 3A.
[0185] The strong solution is directed to joint 432 where it is
split into lines 433 and 434. Line 433 is directed into (first)
absorber arrangement 83, and in particular to sprayer 435. Line 434
is directed into a absorber arrangement 420 and in particular to
sprayer 436. Within absorber 420, the strong solution is directed
into proximity with cooling loop 440, to heat material in the
cooling loop.
[0186] Fluid inlet to cooling loop 440 is shown entering the
absorber 420 at line 445. Heated outlet from loop 440 is shown
leaving absorber 420 and line 446. Pump 447 is depicted to
facilitate operation of the loop 440.
[0187] In general, the system 400 of FIG. 4 shows that heat
recovered in the absorber arrangement 83 in a refrigeration cycle
similar to that depicted in FIG. 3, can be absorbed by refrigerant
liquid directed into absorber arrangement 420, for increasing
refrigeration cycle efficiency. It is noted that a variety of
alternate equipment configurations pump and pressure let down
configurations and line configurations can be used. Further, no
specific structural feature with respect to such equipment as the
absorber arrangement or the evaporator arrangement in meant.
C. The Example System of FIG. 5
[0188] In FIG. 5 a second alternate variation is depicted, in
absorption osmosis refrigeration cycle 500. Again, many features
are analogous to ones described in connection with FIGS. 3 and
4.
[0189] Referring to FIG. 5, within system 500 is provided a (for
example membrane-based) non-vaporizing solution processing unit
system 82, for example a reverse osmosis membrane unit system.
Purified solvent (refrigerant) outlet flow from system 82 is shown
in line 86 as eventually directed as refrigerant liquid inlet line
87 for (first) evaporator arrangement 90 after passage (with flow
from line 502) through pressure let-down or expansion, or pressure
reduction, device 501.
[0190] Within in the evaporator arrangement 90, the refrigerant
liquid is at least partially converted to a vapor (gas) phase,
leaving the evaporator arrangement 90 at line 95. Heat input for
the evaporator arrangement 90 is shown at lines 91. Cooled gas or
liquid output from evaporator arrangement 90 is shown at line
92.
[0191] The refrigerant gas (vapor) in line 95 is shown directed
into (first) absorber arrangement 83, where it is absorbed by
strong solution to generate dilute solution, shown in sump 96.
Dilute solution is shown leaving the absorber through line 503, to
be directed as a dilute solution into (membrane-based processing)
non-vaporizing solution processing system 82. In the example
depicted, reverse osmosis pump 505 is depicted. Pump 505 could also
be considered a portion of system 82, see for example pump 100,
FIG. 3A.
[0192] Referring to joint 510, a portion of the dilute solution
outlet from the system 82, via line 86, is shown directed via line
511 through pressure let-down or expansion device 512 and into a
coolant line 513 within (first) absorber arrangement 83. Here the
refrigerant absorbs heat and is at least partially converted to a
vapor. The refrigerant (typically gas) outlet from absorber cooling
circuit 514 comprising line 513, is shown at line 515. It is noted
that to facilitate increased surface area (and refrigerant
absorption) within absorber arrangement 83, packing 83x is
depicted.
[0193] Refrigerant (at least partially gas or vapor) in line 515 is
now directed to absorber arrangement 420, with packing 420x. Here
it is absorbed into "extra" strong solution in absorber arrangement
420, forming dilute solution in sump 421. Dilute solution outlet
flow from absorber arrangement 420 is shown at line 520, being
directed to (for example reverse osmosis membrane unit arrangement)
non-vaporizing solution processing unit system 82b. Within FIG. 5,
reverse osmosis pump 521 is depicted. Pump 521 could be considered
part of the arrangement 82b.
[0194] A diluted solution from (example reverse osmosis membrane)
non-vaporizing solution processing unit system 82b is shown at line
525 being directed into (reverse osmosis membrane unit)
non-vaporizing solution processing system 82.
[0195] Strong (concentrated) solution outlet flow from system 82 is
shown at line 85 being directed through pressure let-down device
530 into line 531 where it is directed to joint 532. Here the
strong solution is split, a portion being directed via line 533 as
strong solution inlet flow to absorber arrangement 83, in the
example depicted via sprayer 535. Also, from joint 532 a portion of
strong solution is directed via line 540 into membrane-based
processing unit system 82b, where it will receive permeate
refrigerant from the absorber solution circuit of second absorber
arrangement 420.
[0196] Extra concentrated or strong solution outlet from the
membrane-unit processing unit system 82b is shown being directed
via line 550 to pressure let-down or reduction device 551. This
will generate in line 552 an "extra" strong solution, relative to
the solution of line 533, for direction into absorber arrangement
420. In the example depicted, the extra strong solution is directed
to sprayer 556.
[0197] Associated with absorber 420 is a heat transfer loop 440
that receives heat from the refrigerant absorption process in
absorber 420. To facilitate refrigerant absorption packing 420x is
provided.
[0198] Fluid input to loop 440 is shown at line 445, with heated
fluid outlet being shown at line 446, and circulation being
facilitated by pump 447.
[0199] In general, FIG. 5 depicts the principles of FIG. 4,
relating to using energy output from one absorber to further
evaporate refrigerant, for outflow direction in a second absorber
arrangement, in combination with using a staged reverse osmosis
membrane unit system, to generate a concentrated solution for
operation of one absorber arrangement and an extra concentrated
solution for operation of another. This example then demonstrates
how selected principles characterized can be used to even a greater
advantage in some instances.
[0200] It is noted that absorber arrangement 83 and absorber
arrangement 420 can be, in accord with the terminology used herein,
collectively referred to as an absorber arrangement. Further, it is
noted that processing unit system 82 and processing unit system
82b, can be, in accord with terminology used herein, collectively
referred to as a non-vaporizing solution processing (unit)
system.
[0201] It is noted that a wide variety of specific equipment
configurations and types, pump and pressure let down devices and
types, and conduits (lines) types and configurations can be used.
Further locations selected equipment is a variable of choice for a
preferred efficiency, and in some instances alternate numbers or
locations of specific equipment such as pumps, pressure let down
devices, etc. is possible.
D. A Third Alternate Example System, FIG. 6
[0202] In FIG. 6, yet another example alternative configuration of
equipment is depicted, for an advantageous refrigeration cycle.
Referring to FIG. 6, refrigeration cycle 600 is generally depicted.
Attention is directed to non-vaporizing solution processing (unit)
system 82. From system 82, a process solvent (refrigerant) outlet
line is shown at line 86 being directed in part to a liquid
refrigerant line 87 for (first) evaporator arrangement 90. It is
noted that before being transferred into evaporator arrangement 90,
the liquid of line 87 depicted is passed, via line 602, through
pressure reduction device 401.
[0203] In evaporator arrangement 90, at least a portion of the
refrigerant liquid is vaporized. From evaporator arrangement 90,
vaporized (gaseous) refrigerant is shown leaving via line 95. Heat
input to the evaporator arrangement 90, to cause vaporization of
the refrigerant, is shown at line 91; with cooled fluid (gas or
liquid) outlet from evaporator arrangement 90 being shown at line
92.
[0204] The refrigerant vapor of line 95 is shown being directed
into (first) absorber arrangement 83, where it is absorbed into a
strong solution, to form diluted solution shown in sump 96. From
absorber arrangement 83, the resulting dilute solution outlet is
shown at line 403 being directed into the (for example
membrane-based) non-vaporizing solution processing unit system 82,
in this example through a depicted pump 405. It is noted that the
pump 405 could be a reverse osmosis pump considered a portion of
the reverse osmosis membrane unit system, see pump 100, FIG.
3A.
[0205] Attention is now directed to joint 410, at which a portion
of the liquid refrigerant from line 86, i.e. from the
non-vaporizing solution processing (unit) system 82, is shown
directed via line 411 and through expansion device or pressure let
down device 412, into loop 413. Heat is transferred into the
refrigerant in loop 413, within the absorber arrangement 83,
including packing 83x, with the outlet line at 415 from absorber
arrangement 83 comprising a refrigerant (gas or at least partially
vaporized) outlet line. The vapor from line 415 is directed into
absorber arrangement 420 with packing 420x, where it is combined
with the extra strong solution in absorber arrangement 420 to
provide a diluted extra strong solution or strong solution at 610.
This strong solution is shown directed from absorber arrangement
420 via line 611 as a strong solution inlet to absorber arrangement
83; in the example depicted by sprayer 612.
[0206] Absorber arrangement 83 is depicted with optional packing
83x to facilitate absorption by increasing the surface area of the
absorptive solution in absorber arrangement 83.
[0207] Referring again to membrane-based processing unit system 82,
strong solution outlet from system 82 is shown at line 85 directed
to joint 620. Here a portion of the concentrated solution or strong
solution from system 82 is shown directed via line 630 as input to
(for example membrane-based) non-vaporizing solution processing
unit system 82b. Extra concentrated outlet flow from (for example
reverse osmosis membrane) non-vaporizing unit system 82b is shown
directed via line 640, through pressure reduction device 641, into
line 652, as extra strong solution inlet to an absorber arrangement
420. In the example depicted, the inlet is shown provided by
sprayer 636.
[0208] Diluted solution outflow from system 82b is shown directed
via line 655 into (for example reverse osmosis) non-vaporizing
solution processing (unit) system 82 for further processing.
[0209] A portion of the liquid in line 85, comprising concentrate
solution from system 82 is shown being directed via line 656,
through pressure reduction device 657 into line 658, a liquid flow
inlet line to reverse osmosis membrane unit system 82b, for further
processing.
[0210] Referring now to absorber arrangement 420, attention is
directed to loop 440, which contains fluid (liquid or gas) heated
within the absorber 420. Optional packing 420x facilitates
increased surface area of the absorbent solution in absorber
arrangement 420.
[0211] Fluid inlet to loop 440 is shown at line 445, with heated
fluid outlet shown at 446. Circulation is facilitated by pump
447.
[0212] It is noted that system 82 and system 82b can be considered,
together, to be a non-vaporizing solution processing (unit) system
82c. Also, absorber arrangement 83 and absorber arrangement 420 can
be, in accord with terminology used herein, collectively referenced
as an "absorber arrangement."
[0213] The variation of FIG. 6 depicts how the principles of FIGS.
4 and 5 can be used together, along with directing extra strong
solution to series through a first absorber arrangement and then
into a second absorber arrangement, with step wise solution, for
efficient operation.
[0214] Again it is noted that a variety of options from the
specific equipment configuration and line configurations of FIG. 6
can be used. Equipment can be alternately located and in some
instances pump and pressure let down device use is optional.
VIII. Some Alternate Solution Processing Techniques, to Reverse
Osmosis Processing
A. General
[0215] As indicated above, in general refrigeration cycle systems,
equipment and techniques according to the present disclosure use
"non-vaporizing solution processing" for processing of the solution
into a more purified solution stream (for refrigerant recovery
and/or a more concentrated solution stream for strong solution
regeneration). Reverse osmosis processing was discussed above, as
an example of a membrane-based solution processing for application
in such systems. However, membrane-based processing need not be
limited to reverse osmosis processing, and the term is meant to
include within its scope any processing in which a membrane or
membrane arrangement unit is used to facilitate the processing, as
an alternative to refrigerant vaporization and recondensation.
[0216] Also, as noted above, alternate non-vaporizing (i.e.
non-phase change) solution processing techniques can be used, other
than mere "membrane-based solution processing" as the term was used
herein above. An example type of a non-vaporizing solution
processing technique characterized above, was applied electric
field processing. Again, the term "applied electric field
processing" is meant to refer to any solution processing system, in
which the solution is subjected to an applied electric field, which
facilitates migration of solute or selected solute material, to
effect generation of a reduced solute solvent (i.e. purified
solvent). Examples of applied electric field processing techniques
include: electrodialysis; electrodeionization; capacitive
deionization; and, membrane capacitive deionization. However, the
term "applied electric field processing" is meant to not be limited
to any particular type of technique or set of techniques, and is
not meant to be limited to currently used or known techniques. It
is noted that some applied electric field techniques may also be
membrane-based solution processing techniques, but this is not a
requirement.
[0217] It is also noted that certain of the reverse osmosis
pump/pressure letdown configurations, may be avoided, when an
applied electric field is used to provide the motivating force for
solution processing, rather than pressure differential. This may be
advantageous in some systems. It is noted that the equipment
configurations described, will be modified potentially to avoid
certain pumps in the system, if applied electric field processing
is used as an alternate to some or all membrane-based
processing.
[0218] Reverse osmosis functions by separating water from the ions
and other contaminates in the solution to be process via
pressurizing the entire fluid volume. Applied electric field
processing functions by moving the ions in the solution via an
applied electric field in combination with ion selective membranes.
Thus, the work is being done on moving the ions themselves rather
than pressurizing the entire feed stream may be a more efficient
means of purifying the solution as part of the overall
refrigeration cycle.
[0219] For an example of desirable application of the applied
electric field processing, consider that in some instances, in
which lithium bromide (LiBr) is used as the solute, osmotic
pressures at relatively high concentrations of lithium bromide may
be higher than practical for a reverse osmosis processing system,
or at high concentration lithium bromide (LiBr) crystallization may
limit the ability to use a reverse osmosis processing system. These
factors could inhibit functionality, increase efficiency or
increase cost of a reverse osmosis processing only system to an
undesirable level. However, with electrodialysis techniques, higher
concentrated lithium bromide solutions can be processed, at least
in a stage of the processing where relatively high concentration
solutions (LiBr) are involved. As the LiBr concentration is
reduced, in a cascading system, one can switch to a reverse osmosis
processing technique, for further processing.
[0220] It is noted that applied electric field processing can be
used in any of the non-vaporizing solution processing stages,
units, or systems previously described, in connection with the
figures, whether used alone or in conjunction with membrane-based
processing.
B. Electrodialysis Techniques
[0221] Electrodialysis (ED) it a process whereby salt ions are
separated from a feed solution through the use of ion-exchange
membranes and an applied electric field. The applied electric field
is typically direct current. The electric field is applied across
what is known as an electrodialysis stack. The stack is typically
multiple alternating layers of charged or ion selective membranes.
As the solution to be processed enters the stack it travels in
parallel to the membranes that comprise the electrodialysis stack
and perpendicular to the applied electric field. Both negatively
and positively charged ions will exist in the feed solution. The
negatively charged ions or anions will be attracted towards the
positive side of the applied electric field (which contains a
anode), while at the same time the positively charged ions or
cations will be attracted towards the negative side of the applied
electric field (which contains a cathode). This attraction will
cause a migration of the positively charged ions and the negatively
charged ions in opposite directions from each other, thus creating
an electric current. These ions will then pass through an ion
charge selective membrane. On one side of the feed stream the
positive ions will migrate through the negatively charged selective
membrane into a concentrated ion stream, while at the same time the
negative ions will migrate through a positively charged selective
membrane on the opposite side of the feed stream. As the ions
continue to move through the concentrated ion stream towards the
anode or cathode they will encounter an alternatively selective
membrane. This alternatively selective membrane will be positively
charged on the concentrated stream side containing the separated
cations and negatively charged on the concentrated stream side
containing the separated anions thus repulsing the likely charged
ions away from this second membrane an inhibiting further ion
progress in the direction of the applied electric field.
[0222] In the case of a Lithium Bromide solution the Lithium ions
will be positively charged and will migrate towards the cathode and
the Bromide ions will be negatively charged and will migrate
towards the anode.
[0223] An example applied electric field processing
(electrodialysis processing) system is shown in FIG. 7. Here the
lines 701 represent positively charged ion selective membranes and
lines 702 represent the negatively charged ion selective membranes.
That is, at least selected positive ions do not readily pass
through membrane 701, and at least selected negative ions do not
readily pass through membrane 702. There may be many streams to be
purified (reduced in ion concentration) which are illustrated here
as input streams 705, and the streams which are correspondingly to
be increased in selected ion concentration are shown here as
streams 706. The reduced-solute solvent product (off) streams are
shown at 707, and the concentrated off-streams are shown at 708. In
an example, near the anode (710) and cathode (711) there may be
some electrolysis of water into H.sub.2 and O.sub.2. Near the anode
710 the hydrogen forms H+ ions which may pair with the negative
(for example Bromide) ions to form a hydrogen bromide salt which,
when in solution, forms hydrobromic acid (a low pH solution), while
near the cathode 711 the OH- ions will form and pair to balance
charge with the positive (for example Li+ ions) to produce, for
example, a Lithium Hydroxide solution which is a basic
solution.
[0224] In general terms, the designator "X.sup.+" indicates a
cationic solute species, for example Li+ or Na+. The term "Y.sup.-"
designates a anionic solute species, for example Cl.sup.- or
Br.sup.-. The term "Z.sup.-z" indicates another solute species, for
example SO.sub.2.sup.-2.
[0225] The schematic indicates preferential passage of various
solute species through certain membranes over others, to generate
the identified flow lines out from the system, from various
introductory liquids into the system.
[0226] Numerous companies produce materials usable for ion exchange
(or ion selective) membranes. These include: Lenntech BV,
Rotterdamseweg 402, M2629 HH Delft, Netherlands; Dow Chemical
Company, 2030 Dow Center, Midland, Mich. 48674; and, General
Electric Co., 3135 Easton Turnpike, Fairfield, Conn.
06828-0001.
C. Electrodeionization Techniques
[0227] Electrodeionization (EDI) is similar to ED in regards to the
applied electric field via an anode and cathode and with regards to
the positively and negatively charged ion selective membrane
arrangements, although arrangements can vary. The primary
difference between these two technologies is the use of a an ion
exchange resin. In EDI the purifying compartment (or flow streams)
and sometimes the concentrating compartments (or flow streams)
contain an ion exchange resin. In traditional deionization
processes the stream to be processed is passed through an ion
exchange resin which preferentially binds to undesirable ions in
the water and replaces them less harmful ions. As this process
occurs the resin becomes saturated with the ions being removed from
the feed stream and depleted of its replacement "exchange" ions.
Once this occurs the resin need to be regenerated to flush out the
undesirable ions. This is typically done with acid and caustic
solutions. In the EDI system the OH- ions that form produce the
caustic action necessary to continuously regenerate the ion
exchange resin, while at the same time the H+ ions that from under
the influence of the anode will produce an acidic solution that
also regenerates the resin on a continuous basis.
D. Capacitive Deionization
[0228] Capacitive deionization (CDI), sometimes called
electrosorption desalination, is a technology for desalination and
water treatment in which salts and minerals are removed from water
by applying an electric field between two porous (often, carbon)
electrodes, similar to electric double-layer capacitors.
Counterions are stored in the electrical double layers which form
at the solution/matrix interface inside the porous electrodes, with
the ions of positive charge (cations) stored in the negatively
charged electrode, and vice-versa for the anions, which are stored
in the positively biased electrode (anode).
[0229] The electrodes used in CDI are typically prepared from
porous carbon particles with internal areas for ion adsorption in
the order of 1000 m2 per gram, but other materials are also
possible, such as carbon nanotubes and nanofibers. The two
oppositely placed (planar) electrodes are separated by a thin open
structured "spacer", or flow channel, through which the water
flows. Upon applying an electrical potential difference between the
two electrodes of the order of 0.8-1.5 V, anions are adsorbed in
the anode and cations into the cathode, thereby producing a
(partially) ion-depleted product stream. After the ion adsorption
capacity of the electrodes has been reached, the applied voltage
difference can be reduced to zero and a small product stream
concentrated ions is obtained in the ion release-step. In this way,
for example, an inflowing stream of brackish water is split into a
partially deionized stream and a more concentrated brine.
E. Membrane Capacitive Deionization
[0230] Membrane capacitive deionization (MCDI), sometimes called
"flow-through capacitor technology", is a modification of CDI by
inserting an anion-exchange membrane in front of the anode, and a
cation exchange membrane in front of the cathode. In this way, the
ions of equal charge sign as the electrode, the so-called co-ions
(e.g., the anions in the cathode) are inhibited from leaving the
electrode region. This co-ion-expulsion-effect, which at low
voltages negatively influences the salt adsorption rate and removal
capacity in CDI, is absent in MCDI. Another advantage of MCDI is
that during ion release, it is possible to use a reversed voltage
which leads to a faster and more complete rejection of the
counterions back into the flow channel.
F. Some General Observations
[0231] Applied Electric Filed Processing can be used in place of,
or in concert with, membrane-based processing such as reverse
osmosis processing. For example, in some instances the use of
applied electric field processing may be a preferred technology
where the salt solution is strongest, from the absorber, and
reverse osmosis or a cascading reverse osmosis arrangement could be
used where concentrations of the solution are lower. In some
systems the opposite may be preferred.
IX. Some Additional Comments
A. High Charge Density Solid Electrolyte or Polyelectrolyte
Membrane
[0232] It is possible that one could use a solid electrolyte
membrane, polyelectrolyte membrane, or a nano-structured solid
polymer membrane to serve as a separation membrane as a method of
accomplishing the desired solution processing. Such a membrane of
can be obtained from Dais Analytic Corporation, 11552 Prosperous
Drive, Odessa, Fla. 33556.
[0233] This type of membrane could be used to process high
concentration ionic solutions in a manner that utilizes a
vaporization step between the purified solvent side surface of the
membrane and another surface where the permeate could be condensed
upon, and collected from.
B. Battery Regeneration
[0234] If an applied electric field processing technique is
utilized there would likely be a separation of ionic species by
ionic electric charge. These separated streams of concentrated
ionic charge (electrolytes) could then be re-introduced to each
other via a "reverse" applied electric field processing step,
whereby electric power could be generated and therefore recovered.
Reversed Electro Dialysis (RED) or Flow Batteries are examples of
just such a process.
[0235] This recovered electrical energy can be utilized to offset
the power consumption of other portions of the cycle thereby
reducing the overall net energy requirement of the cycle.
[0236] It is further recognized that the separated ionic species
electrolytes could be generated and collected into storage vessels
and then recombined through an electrical energy generating process
at a later time as a means of managing electrical power consumption
profiles over time.
C. Concentrated Brine Storage
[0237] Because the useful cooling in the refrigeration cycle is
being provided in part by the introduction of a strong solution
into the absorber where that strong solution is then diluted via
the absorption of refrigerant vapor that is received from the
evaporator; it is recognized that a user of this cycle could
produce and store a strong solution and store that strong solution
for later use as a means of either providing an emergency backup
reserve of cooling in the event of a loss of primary power, or
could use the stored strong solution to produce cooling with a
significantly reduced power consumption requirement during specific
time periods as a means of managing electrical power consumption
profiles over time.
D. Characterization of Techniques and Systems that have Some Level
of Refrigerant Vaporization/Recondensation During Solution
Processing
[0238] Herein above, preferred techniques are characterized for
"non-vaporizing" or "non-phase change" systems, with respect to
refrigerant recovery. That is, the techniques are characterized as
usable in processes and techniques in which recovery of the
refrigerant from the dilute solution is conducted without a phase
change, i.e. without a vaporization/recondensation of the
refrigerant. Numerous techniques applicable to accomplish this were
described.
[0239] It is noted that many of the techniques of the present
disclosure can be applied in systems in which there is at least
some form or some amount of refrigerant vaporization also
occurring, during processing of dilute solution to recover
refrigerant liquid. For example, a membrane-based technique can be
applied in which there is some vaporization. Indeed, in Section IX.
A. above, the type of membrane characterized has been described as
including a form of vaporization step between layers of the
membrane.
[0240] In general, techniques according to the present disclosure,
can be applied in a process of conducting an absorption
refrigeration cycle, or in an absorption refrigeration cycle, in
which dilute solution is processed into concentrated solute
solution and refrigerant liquid with: a membrane-based solution
processing step and equipment, and/or an applied electric field
processing or step, without regard to whether there is also a step
of vaporizing and condensing refrigerant; with additional steps of
directing at least a portion of the refrigerant liquid into a first
evaporator arrangement to vaporize at least a portion of the
refrigerant; directing the concentrated solute solution into an
absorber arrangement; and, directing vaporized refrigeration from
the evaporator arrangement into an absorber arrangement, for
absorption of the refrigerant concentrated solute solution therein.
Indeed, an absorption refrigeration cycle can be provided which
includes: at least a first absorber arrangement configured to
absorb refrigerant gas, from a first evaporator arrangement, into a
solution to provide a dilute solution; at least a first evaporator
arrangement configured to receive refrigerant liquid and to process
at least a portion of the refrigerant into refrigerant gas; and, a
solution processing unit system configured to process dilute
solution into: strong solution; and, refrigerant liquid, at least a
portion of which refrigerant liquid is for direction to the first
evaporator arrangement, and wherein the solution processing unit
system, includes at least: a membrane-based processing unit system;
an applied electric field processing unit system; and/or both,
without regard to whether there is also a step of vaporizing done,
i.e. without regard to whether the solution processing system is
completely "non-vaporizing" or "non-phase change."
[0241] In general, the particular combination of technique chosen,
for a given system will turn on availability of energy and energy
costs, as well as the characteristics of the solution.
X. Summary of General Principles and Techniques
[0242] According to the present disclosure, techniques, methods,
and equipment usable for absorption refrigeration cycle processing,
are described. The techniques can be applied in a wide variety of
absorption refrigerant cycles, as indicated generally above.
However, a typical characteristic of many absorption refrigeration
cycle in which techniques according to the present disclosure are
used, is that solution from an absorber arrangement, comprising
dilute absorptive solution (typically a strong solute/solvent
combination or strong solution, having absorbed therein
refrigerant) is processed to recover the refrigerant without
vaporizing (boiling) refrigerant, i.e. without phase charge.
Typically, this is accomplished by processing of the dilute
absorptive or absorber solution by non-vaporizing (or non-phase
change) solution processing.
[0243] Herein, two general types of solution processing are
described. These types are "membrane-based processing" and "applied
electric field processing." The terms are not meant, however, to be
fully mutually exclusive. For example, some "membrane-based
solution processing" may also be "applied electric field
processing." Also, when a system is characterized as "comprising
membrane-based solution processing", it is not meant to indicate
that the system does not also include "applied electric field
processing" whether that "applied electric field processing" is
also membrane-based processing. Further, if the system or technique
is characterized as "comprising applied electric field processing"
it is not meant that the system does not include "membrane-based
processing" whether that "membrane-based processing" involves an
applied electric field.
[0244] The term " membrane-based processing" and variants thereof,
as used herein, is meant to refer to any non solution processing in
which a membrane is used to provide for selective transfer of
solute/solvent, as part of a processing to generate a more dilute
(i.e. purified) solvent and a more concentrated (in solute)
solution. The term "applied electric field solution processing" is
used to refer to any non solution processing in which an applied
electric field is used to facilitate solute or selected solute
removal from solution, to facilitate a recovery of refrigerant
and/or concentrated solution.
[0245] It is noted that in techniques according to the present
disclosure, various forms of solution processing can be used in the
same system or process.
[0246] An example membrane-based processing technique referenced
herein is "reverse osmosis processing." The term "reverse osmosis
processing" as used herein in this context, is meant to be a broad,
non-equipment specific and non-configuration specific term, that
indicates processing by using a reverse osmosis membrane
arrangement to pass a selected solvent or solvent system through
the membrane arrangement, from a high pressure side to a low
pressure side, while concentrating solute at the high pressure
side. This can be used to recover refrigerant as a purified
solvent, and to re-generate a diluted solution into a concentrated
solute solution (i.e. absorber solution).
[0247] The term "applied electric field processing" as used herein
in the context is meant to be broad, non-equipment specific and
non-configuration specific term that indicates processing by using
equipment in which an applied electric field is used to generate a
motivating force for transfer of a solute or selected solute
material from a solution. Some examples of "applied electric field
processing", includes electrodialysis; electrodeionization;
capacitive deionization; and, membrane capacitive deionization
techniques, each of which can be applied in systems according to
the present disclosure.
[0248] In many typical applications of the techniques described
herein, the "membrane-based processing" and/or "applied electric
field processing" techniques applied will be non-vaporizing or
non-phase change solution processing, i.e. conducted without
vaporization of refrigerant (in follow-up with condensation) for
refrigerant recovery. Indeed, in typical applications, the entire
solution processing system and steps involved (for refrigerant
liquid recovery) will be a "non-vaporizing solution processing
system" although alternatives are possible.
[0249] Typically, then, the refrigeration cycle is operated to lead
to recovery of the refrigerant in liquid form, without requiring
the refrigerant to be boiled (vaporized) out of the dilute
solution, and then condensed for recovery in liquid form. Thus,
equipment in a typical prior art absorption cycle for conducting
these steps can be avoided to advantage.
[0250] Although alternatives are possible, in many typical
absorption refrigeration cycles according to the present
disclosure, then, the following are included:
[0251] a) at least a first absorber arrangement configured to
absorb refrigerant vapor into strong solution, providing a dilute
solution;
[0252] b) at least a first evaporator arrangement configured to
receive at least a portion of the refrigerant liquid and to process
at least a portion of the refrigerant liquid into a refrigerant
gas; and,
[0253] c) a non-vaporizing processing unit system configured to
process the dilute solution into: strong solution for direction to
an absorber arrangement (with or without further processing); and,
a refrigerant liquid, at least a portion of which is for use in the
refrigeration cycle (with our without further processing).
[0254] The "non-vaporizing" processing unit system can be a
membrane-based processing system, an applied electric field
processing system, an alternate processing system, or a system
using a combination of such techniques, as characterized herein. An
example membrane-based processing system and technique
characterized as usable, is a reverse osmosis processing. Examples
of applied electric field processes comprise: electrodialysis;
electrodeionization; capacitive deionization; and, membrane
capacitive deionization. It is again noted that the terms "applied
electric field processing" and "membrane-based processing" are not
meant to be necessarily exclusive.
[0255] Herein, when it is said that the strong solution is directed
into an absorber arrangement (with or without further processing),
reference is meant to alternatives such as suggested by the
examples of FIGS. 3 and 4-6. In FIG. 3, for example, the specific
configuration depicted shows strong solution at line 85 from a
non-vaporizing solution processing unit system being shown directed
directly into absorber arrangement 83, i.e. without further
processing. A similar characterization applies for FIG. 4, although
at joint 432 the dilute solution is split into two lines, one for
each of two absorber arrangements, or portions of an overall
absorber arrangement. In FIG. 5, from joint 532 a portion of strong
solution from processing unit system 82 is directed into absorber
arrangement 83. However, another portion via line 540 is directed
to processing unit system 82b for further processing. On the other
hand, strong solution at line 550 from processing unit system 82b
is directed into unit 420 without further processing.
[0256] Finally, in the example of FIG. 6, strong solution at line
85 from processing unit system 82 is split at joint 620, with a
portion directed in line 630 for further processing at processing
unit system 82b before being directed via line 640 and ultimately
line 652 into absorber arrangement 420. Further, additional
processing can be characterized as occurring within unit 420 before
the solution via line 611 is directed into absorber arrangement
83.
[0257] The term "reverse osmosis processing" is used herein, is
also meant to be general, and non-specific, with respect to
particular equipment configurations. One or more membrane
arrangements can be used and varied configurations (including a
variety of membrane arrangements, pump arrangements, line
arrangements, pressure let-down devices, etc.) can be used. The
term "reverse osmosis processing," in general, is merely meant to
indicate a processing step in which a separation is conducted by
use of a reverse osmosis membrane arrangement with a pressure
differential thereacross.
[0258] Typically, a reverse osmosis (membrane) unit system includes
at least one (and typically a plurality) reverse osmosis membrane
unit having: a high pressure side inlet; a high pressure side
outlet; a low pressure side inlet; and, a low pressure side outlet.
However, the system may also include at least one reverse osmosis
membrane unit having: a high pressure side inlet; a high pressure
side outlet; a low pressure side outlet; and, no low pressure side
inlet. Many systems will include at least one of each.
[0259] In general terms, for the reverse osmosis (membrane) unit
system and reverse osmosis processing, equipment, techniques and
methods described generally in U.S. application Ser. No.
12/455,998, filed Jun. 9, 2009 and U.S. provisional 61/131,947,
filed Jun. 13, 2008, each of which is incorporated herein by
reference, can be used.
[0260] When such techniques are applied, although alternatives are
possible, typically the reverse osmosis processing comprises steps
of:
[0261] (a) providing a cascading reverse osmosis system including
at least: [0262] (i) a first, final, solvent outlet-generating
reverse osmosis unit; [0263] (ii) a first, final, concentrate
outlet-generating reverse osmosis unit; and, [0264] (iii) an
intermediate reverse osmosis (membrane) unit system comprising at
least one reverse osmosis unit; and,
[0265] (b) operating the reverse osmosis system to process the
dilute solution such that: [0266] (i) concentrate from the first,
final, solvent outlet-generating reverse osmosis unit is directed
into the intermediate reverse osmosis membrane unit system, as part
of a feed stream thereto; [0267] (ii) reduced-solute solvent from
the intermediate reverse osmosis membrane unit system is directed
into the first, final, solvent outlet-generating reverse osmosis
unit as part of an inlet feed stream thereto; [0268] (iii)
concentrate from the intermediate reverse osmosis membrane unit
system is directed into a first, final, concentrate
outlet-generating reverse osmosis unit as part of an inlet feed
stream thereto; [0269] (iv) each reverse osmosis unit in the
intermediate reverse osmosis membrane unit system is conducted with
both a high pressure side inlet feed and a low pressure side inlet
feed; [0270] (v) each reverse osmosis unit of the intermediate
reverse osmosis membrane unit system provides a high pressure side
concentrate outlet and a low pressure side outlet; and, [0271] (vi)
the dilute solution to be processed is directed to at least one of
the: first, final, solvent outlet-generating reverse osmosis unit;
the intermediate reverse osmosis (membrane) unit system; or, the
first, final, concentrate outlet-generating reverse osmosis
unit.
[0272] In some instances, portions of the above can be avoided.
[0273] Examples of such arrangements are described herein in
connection with FIGS. 3A, and 3B. For the reverse osmosis unit
system characterized in FIG. 3A: the first, final, solvent
outlet-generating reverse osmosis unit is unit H; the intermediate
reverse osmosis membrane unit system comprises reverse osmosis
units G, F, E, D, C, and B; and, the first, final, concentrate
outlet-generating reverse osmosis unit is unit A. In the example of
FIG. 3B, the first, final, solvent outlet-generating reverse
osmosis unit is unit R; the intermediate reverse osmosis membrane
unit system comprises units Q, P, O, N, and M; and, the first,
final, concentrate outlet-generating reverse osmosis unit is unit
L.
[0274] It is noted that with respect to the system depicted in FIG.
3A, reverse osmosis unit B will sometimes be referred to as the
final, concentrate flow direction, reverse osmosis unit, for the
intermediate reverse osmosis membrane system comprising units B, C,
D, E, F and G; and, unit G will sometimes be referred to as the
final, dilute solution flow direction reverse osmosis unit of the
intermediate reverse osmosis membrane unit system comprising units
B, C, D, E, F and G. In an alternate statement, unit B can be
characterized as the first dilute solution flow direction reverse
osmosis membrane unit of the intermediate reverse osmosis membrane
unit system comprising units B, C, D, E, F and G; and, unit G can
be characterized as the first, concentrate, flow direction reverse
osmosis unit of the intermediate reverse osmosis membrane unit
system comprising units B, C, D, E, F and G.
[0275] With respect to FIG. 3B, reverse osmosis unit M can be
characterized as the final, concentrate, flow direction unit (or
first, dilute solution, flow direction unit) of the reverse osmosis
membrane unit system comprising units M, N, O, P and Q; and,
reverse osmosis unit Q can be characterized as the final, dilute
solution flow direction unit (or first, concentrate, flow direction
unit) of the intermediate reverse osmosis membrane unit system
comprising unit M, N, O, P and Q.
[0276] It is expected that in a typical process, each reverse
osmosis unit in the intermediate reverse osmosis membrane unit
system will be operated with solute concentration in the high
pressure side inlet feed thereto to be within 20% of the solute
concentration in the low pressure side inlet feed thereto,
typically within 15% and often within 10%, although alternatives
are possible.
[0277] In the general terms characterized herein, then, a process
for conducting an absorption refrigeration cycle is provided. The
process includes steps for processing a dilute solution into a
concentrated solution and refrigerant liquid, without a step of
vaporizing and condensing the refrigerant. The step of processing
typically comprises directing dilute solution to a reverse osmosis
unit of reverse osmosis unit system for reverse osmosis
processing.
[0278] In a typical step of conducting an absorption refrigeration
cycle, refrigerant liquid is directed to a (first) evaporator
arrangement; concentrated solution (absorber solution) is directed
into an absorber arrangement; and, vaporized refrigerant from a
(first) evaporator arrangement is directed into an absorber
arrangement to generate dilute solution, upon absorption by a
concentrated solution in the absorber arrangement.
[0279] As indicated above, many of the techniques described herein
can be applied in systems in which the solution processing, of the
dilute solution into refrigerant liquid and strong solution, is
conducted with some vaporization of refrigerant liquid; i.e. in
which the processing is not "non-vaporizing" or "non-phase change",
as the terms used herein. Some such systems can still
advantageously include (comprise) membrane-based processing and/or
applied electric field processing techniques as described.
[0280] A variety of system configurations, processing techniques,
refrigerants, solvents, and solutions can be applied. In the
example description provided, the dilute solution comprises an
aqueous solution of lithium bromide, and the refrigerant comprises
water.
[0281] It is noted that principles according to the present
disclosure can be provided in a wide variety of systems, and there
is no requirement that a process technique or system include each
of the features characterized herein, in order to obtain some
benefit according the present disclosure.
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