U.S. patent application number 13/050189 was filed with the patent office on 2011-09-29 for systems and methods for generating power and chilling using unutilized heat.
This patent application is currently assigned to EXXONMOBIL RESEARCH AND ENGINEERING COMPANY. Invention is credited to Bhupender S. MINHAS, Tahmid I. MIZAN, Sufang ZHAO.
Application Number | 20110232305 13/050189 |
Document ID | / |
Family ID | 44170482 |
Filed Date | 2011-09-29 |
United States Patent
Application |
20110232305 |
Kind Code |
A1 |
MINHAS; Bhupender S. ; et
al. |
September 29, 2011 |
SYSTEMS AND METHODS FOR GENERATING POWER AND CHILLING USING
UNUTILIZED HEAT
Abstract
The present application provides a sorption system for
generating power and chilling that includes at least one absorber
to absorb a working fluid in a liquid sorbent, a pump in fluid
communication with the absorber to yield a feed of pressurized
liquid sorbent and absorbed working fluid, a heat source to heat
the feed of pressurized liquid sorbent and absorbed working fluid
to yield a feed of working fluid at a supercritical state, a
generator in fluid communication with the feed of working fluid at
a supercritical state to yield power and a feed of working fluid in
an at least partially condensed state, and an evaporator in fluid
communication with the feed of working fluid in the at least
partially condensed state to yield chilling and uncondensed working
fluid. Additional systems and method for the generating power and
chilling are provided.
Inventors: |
MINHAS; Bhupender S.;
(Bridgewater, NJ) ; MIZAN; Tahmid I.;
(Bridgewater, NJ) ; ZHAO; Sufang; (Vienna,
VA) |
Assignee: |
EXXONMOBIL RESEARCH AND ENGINEERING
COMPANY
Annandale
NJ
|
Family ID: |
44170482 |
Appl. No.: |
13/050189 |
Filed: |
March 17, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61317966 |
Mar 26, 2010 |
|
|
|
Current U.S.
Class: |
62/79 ;
62/238.3 |
Current CPC
Class: |
F25B 2309/061 20130101;
F25B 17/083 20130101; Y02A 30/27 20180101; Y02A 30/277 20180101;
F25B 15/02 20130101; Y02A 30/276 20180101; Y02B 30/62 20130101 |
Class at
Publication: |
62/79 ;
62/238.3 |
International
Class: |
F25B 29/00 20060101
F25B029/00; F25B 27/02 20060101 F25B027/02 |
Claims
1. A sorption system for generating power and chilling, comprising:
(a) a first vessel containing a sorbent material in fluid
communication with a working fluid and operatively connected to a
heat source to yield a feed of working fluid at a supercritical
state; (b) a generator in fluid communication with the feed of
working fluid at supercritical state to yield power and a feed of
working fluid in an at least partially condensed state; and (c) an
evaporator in fluid communication with the feed of working fluid in
the at least partially condensed state to yield chilling and a feed
of uncondensed working fluid.
2. The sorption system of claim 1, wherein the sorbent material is
selected from zeolites, metal organic frameworks (MOFs), zeolitic
imidazolate frameworks (ZIFs), silicagel, adsorbing polymers,
carbon, and activated carbon, and combinations thereof.
3. The sorption system of claim 2, wherein the sorbent material is
a zeolite.
4. The sorption system of claim 1, wherein the working fluid is
selected from carbon dioxide, methane, ethane, propane, butane,
ammonia and chlorofluorocarbons.
5. The sorption system of claim 4, wherein the working fluid is
carbon dioxide.
6. The sorption system of claim 1, wherein the heat source is an
unutilized heat source.
7. The sorption system of claim 1, wherein the generator is a
turboexpander.
8. The sorption system of claim 1, further comprising: a second
vessel containing sorbent material in fluid communication with the
working fluid and operatively connected to a heat source to yield a
second feed of working fluid at a supercritical state.
9. The sorption system of claim 8, wherein each of the first vessel
and the second vessel has a sorption mode and a desorption mode,
wherein in the desorption mode the working fluid is released from
the sorbent material in response to the heat source, and wherein in
the sorption mode, the working fluid is sorbed by the sorbent
material, wherein when the first vessel is operating in the
adsorption mode, the second vessel is operating in the desorption
mode and, wherein when the first vessel is operating in the
desorption mode, the second vessel is operating in the sorption
mode.
10. A process for generating power and chilling comprising:
adsorbing a working fluid onto a sorbent material; heating the
sorbent material to desorb the working fluid from the sorbent
material at a supercritical state; directing the desorbed fluid to
drive a generator to generate power and to at least partially
condense the desorbed working fluid; and evaporating the at least
partially condensed desorbed fluid to yield chilling and a feed of
uncondensed working fluid.
11. The process of claim 10, wherein the sorbent material is
selected from zeolites, metal organic frameworks (MOFs), zeolitic
imidazolate frameworks (ZIFs), silicagel, adsorbing polymers,
carbon, and activated carbon, and combinations thereof.
12. The process of claim 11, wherein the sorbent material is a
zeolite.
13. The process of claim 10, wherein the working fluid is selected
from carbon dioxide, methane, ethane, propane, butane, ammonia and
chlorofluorocarbons.
14. The process of claim 13, wherein the working fluid is carbon
dioxide.
15. The process of claim 14, wherein the heating is provided by
unutilized heat from one of a refining operation and chemical
processing operation.
16. The process of claim 15, wherein the unutilized heat is at a
temperature of 450.degree. F. or lower.
17. A sorption system for generating power and chilling,
comprising: (a) an absorber to absorb a working fluid in a liquid
sorbent; (b) a pump in fluid communication with the absorber to
yield a feed of pressurized liquid sorbent and absorbed working
fluid; (c) a heat source to heat the feed of pressurized liquid
sorbent and absorbed working fluid to yield a feed of working fluid
at a supercritical state; (d) a generator in fluid communication
with the feed of working fluid at a supercritical state to yield
power and a feed of working fluid in an at least partially
condensed state; and (e) an evaporator in fluid communication with
the feed of working fluid in the at least partially condensed state
to yield chilling and uncondensed working fluid.
18. The sorption system of claim 17, wherein the working fluid is
selected from carbon dioxide, methane, ethane, propane, butane,
ammonia and chlorofluorocarbons.
19. The sorption system of claim 18, wherein the working fluid is
carbon dioxide.
20. The sorption system of claim 17, wherein the evaporator is in
fluid communication with the absorber.
21. The sorption system of claim 17, wherein the heat source is an
unutilized heat source.
22. The sorption system of claim 21, wherein the heat source
includes a vapor generator.
23. The sorption system of claim 22, further comprising a cooler in
fluid communication with the vapor generator.
24. The sorption system of claim 23, wherein the cooler includes
cooling water.
25. The sorption system of claim 22, wherein the vapor generator is
a rectification column.
26. The sorption system of claim 17, wherein the generator is a
turboexpander.
27. A process for generating power and chilling comprising:
absorbing a working fluid into a liquid sorbent to yield a liquid
sorbent and absorbed working fluid; pressurizing the liquid sorbent
and absorbed working fluid to increased pressure; heating the
pressurized liquid sorbent and absorbed working fluid to desorb the
working fluid from the sorbent material in a supercritical state;
directing the desorbed working fluid to drive a generator to
generate power and to at least partially condense the desorbed
working fluid; and evaporating the at least partially condensed
desorbed working fluid to yield chilling and uncondensed working
fluid.
28. The process of claim 27, wherein the working fluid is selected
from carbon dioxide, methane, ethane, propane, butane, ammonia and
chlorofluorocarbons.
29. The process of claim 28, wherein the working fluid is carbon
dioxide.
30. The process of claim 27, wherein the heating is provided by
unutilized heat from one of a refining operation and chemical
processing operation.
31. The process of claim 27, wherein the unutilized heat is at a
temperature of 450.degree. F. or lower.
32. The process of claim 27, wherein the generator is a
turboexpander.
33. A sorption system for generating power, comprising: (a) a first
vessel in fluid communication with a working fluid and a liquid
sorbent material, wherein the working fluid is adsorbed in the
liquid sorbent in the first vessel to yield a feed of liquid
sorbent with an adsorbed working fluid; (b) a heat source in fluid
communication with the feed of liquid sorbent with the adsorbed
working fluid and a heat source, wherein the heat source disengages
the liquid sorbent from the adsorbed working fluid to create a feed
of working fluid at a supercritical state and a feed of liquid
sorbent; (c) a first generator in fluid communication with the feed
of working fluid at supercritical state to yield power and a feed
of working fluid in an at least partially condensed state in fluid
communication with the first vessel; and (d) a second generator in
fluid communication with the feed of liquid sorbent to yield power
and a feed of liquid sorbent in fluid communication with the first
vessel.
34. The sorption system according to claim 33, wherein the first
generator is a turbo expander.
35. The sorption system according to claim 33, wherein the second
generator is a twin screw expander.
36. The sorption system of claim 33, wherein the heat source is an
unutilized heat source.
37. The sorption system of claim 36, wherein the heat source
includes a vapor generator.
38. The sorption system of claim 33, wherein the working fluid is
selected from carbon dioxide, methane, ethane, propane, butane,
ammonia and chlorofluorocarbons.
39. A process for generating power, comprising: absorbing a working
fluid into a liquid sorbent to yield a liquid sorbent and absorbed
working fluid; pressurizing the liquid sorbent and absorbed working
fluid to increased pressure; heating the pressurized liquid sorbent
and absorbed working fluid to desorb the working fluid from the
liquid sorbent in a supercritical state; directing the desorbed
working fluid to drive a first generator to generate power and to
at least partially condense the desorbed working fluid; and
directing the liquid sorbent to drive a second generator to
generate power.
40. The process of claim 39, wherein the working fluid is selected
from carbon dioxide, methane, ethane, propane, butane, ammonia and
chlorofluorocarbons.
41. The process of claim 40, wherein the working fluid is carbon
dioxide.
42. The process of claim 39, wherein the heating is provided by
unutilized heat from one of a refining operation and chemical
processing operation.
43. The process of claim 42, wherein the unutilized heat is at a
temperature of 450.degree. F. or lower.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application relates and claims priority to U.S.
Provisional Patent Application No. 61/317,966 entitled "Systems and
Methods for Generating Power and Chilling Using Unutilized Heat",
filed on Mar. 26, 2010.
FIELD OF THE INVENTION
[0002] The present application relates to systems and methods
employing sorbent materials to generate power and chilling using
unutilized heat. In particular, the present invention relates to a
system and method for the simultaneous generation of power and
chilling utilizing waste heat.
BACKGROUND OF THE INVENTION
[0003] Petroleum refining and petrochemical processing operations
are energy intensive. It is often necessary to conduct these
operations at high temperatures using high temperature heat sources
including, but not limited to, steam. After the steam or other hot
streams have performed the intended functions, there remains
unutilized energy. Refineries and petrochemical facilities
typically utilize only 70% of the input energy and a large amount
of energy loss occurs at lower temperatures, 450.degree. F. or
below. There is a strong need to recapture or utilize this energy.
Potential uses of this energy include production of electric power,
shaft power, or chilling of process streams. However, the cost of
equipment to capture this heat can be a disincentive because of the
low efficiencies of waste heat capture devices when the source of
heat is at or below 450.degree. F. Electric power, shaft power, and
chilling can be effectively utilized in refineries and
petrochemical processes to increase the overall efficiency of the
facility.
[0004] In an effort to increase efficiency, it is desirable to
recover and utilize unutilized heat. One method described in U.S.
Pat. No. 5,823,003 to Rosser et al. attempts to make use of waste
heat and apply such heat to an adsorbent material in order to
release an adsorbed gas at a higher pressure, which in turn can be
used in a refrigeration cycle that contains an expansion valve.
U.S. Pat. No. 5,823,003 describes the use of a zeolite-water
combination for a sorption refrigeration system.
[0005] Current methods to obtain refrigeration from sorbent
materials in chemical process applications have their limitations.
Often the sorbent materials and gases employed in sorption systems
require processing equipment that is expensive to maintain, operate
under vacuum, have a refrigeration temperature above water freezing
point (32 F), unreliable, and requires a large allocation of space.
Such limitations often render the recovery of unutilized heat
economically unsustainable.
[0006] Accordingly, there remains a need to make unutilized heat
recovery efforts more cost-effective by providing the opportunity
to utilize lower (less than 450.degree. F.) grades of unutilized
heat and to reduce equipment and space requirements of the process.
There also remains a need to provide other uses, besides
refrigeration, of the fluid released from unutilized heat-charged
sorbent materials.
SUMMARY OF THE INVENTION
[0007] One embodiment of the present application provides a
sorption system for generating power and chilling including a first
vessel containing a sorbent material in fluid communication with a
working fluid and operatively connected to a heat source to yield a
feed of working fluid at a supercritical state, a generator in
fluid communication with the feed of working fluid at supercritical
state to yield power and a feed of working fluid in an at least
partially condensed state, and an evaporator in fluid communication
with the feed of working fluid in the at least partially condensed
state to yield chilling and a feed of uncondensed working fluid. In
one embodiment, the heat source is an unutilized heat source.
[0008] The present application also provides a process for
generating power and chilling including adsorbing a working fluid
onto a sorbent material, heating the sorbent material to desorb the
working fluid from the sorbent material at a supercritical state,
directing the desorbed fluid to drive a generator to generate power
and to at least partially condense the desorbed working fluid, and
evaporating the at least partially condensed desorbed fluid to
yield chilling and a feed of uncondensed working fluid. In one
embodiment, the heating is provided by unutilized heat from one of
a refining operation and chemical processing operation.
[0009] The present application also provides a sorption system for
generating both power and chilling that includes an absorber to
absorb a working fluid in a liquid sorbent, a pump in fluid
communication with the absorber to yield a feed of pressurized
liquid sorbent and absorbed working fluid, a heat source to heat
the feed of pressurized liquid sorbent and absorbed working fluid
to yield a feed of working fluid at a supercritical state, a
generator in fluid communication with the feed of working fluid at
a supercritical state to yield power and a feed of working fluid in
an at least partially condensed state, and an evaporator in fluid
communication with the feed of working fluid in the at least
partially condensed state to yield chilling and uncondensed working
fluid. The heat source may be an unutilized heat source.
[0010] The present application also provides a process for
generating both power and chilling that includes absorbing a
working fluid into a liquid sorbent to yield a liquid sorbent and
absorbed working fluid, pressurizing the liquid sorbent and
absorbed working fluid to increased pressure, heating the
pressurized liquid sorbent and absorbed working fluid to desorb the
working fluid from the sorbent material in a supercritical state,
directing the desorbed working fluid to drive a generator to
generate power and to at least partially condense the desorbed
working fluid, and evaporating the at least partially condensed
desorbed working fluid to yield chilling and uncondensed working
fluid. In one embodiment, the heating is provided by unutilized
heat from one of a refining operation and chemical processing
operation.
[0011] In accordance with another aspect of the present invention,
a sorption system for generating power is disclosed. The sorption
system includes a first vessel in fluid communication with a
working fluid and a liquid sorbent material such that the working
fluid is adsorbed in the liquid sorbent in the first vessel to
yield a feed of liquid sorbent with an adsorbed working fluid. The
working fluid is selected from carbon dioxide, methane, ethane,
propane, butane, ammonia and chlorofluorocarbons. The feed of
liquid sorbent with an adsorbed working fluid is fed to a heat
source. The heat source may be an unutilized heat source which
includes a vapor generator. The heat source disengages the liquid
sorbent from the adsorbed working fluid to create a feed of working
fluid at a supercritical state and a feed of liquid sorbent. A
first generator is in fluid communication with the feed of working
fluid at supercritical state to yield power and a feed of working
fluid in an at least partially condensed state which is in fluid
communication with the first vessel. The first generator may be
turbo expander. A second generator is in fluid communication with
the feed of liquid sorbent to yield power and a feed of liquid
sorbent in fluid communication with the first vessel. The second
generator may be a twin screw expander.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will now be described in conjunction with the
accompanying drawings in which:
[0013] FIG. 1 is a schematic of a sorption system for the
generation of chilling in accordance with an aspect of the present
invention.
[0014] FIG. 2 is a Mollier Diagram annotated to show four points
that correspond to four stages of the sorption system described in
FIG. 1.
[0015] FIG. 3 is a Mollier Diagram annotated to show alternative
process points based on the use of waste heat to achieve a
temperature of about 450.degree. F. and alternative process points
based on the use of higher sorbing pressures for use in connection
with the generation of chilling.
[0016] FIG. 4 is a schematic of an adsorption system for the
generation of power and/or chilling in accordance with an
embodiment of the present application.
[0017] FIG. 5 is a schematic of an absorption system for the
generation of power and/or chilling in accordance with an
embodiment of the present application.
[0018] FIG. 6 is a schematic of an absorption system for the
generation of power in accordance with an embodiment of the present
application.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present application will now be described in greater
detail in connection with the figures and the following terms.
[0020] As used herein, the term "sorbent material" refers to a
material that reversibly binds a working fluid. Sorbent materials
include, but are not limited to, absorbents and adsorbents.
[0021] As used herein, the term "working fluid" refers to a liquid
or gas that can reversibly bind to the sorbent material.
[0022] As used herein, the term "generator" refers to a turbine,
shaft or other mechanism driven by a working fluid (e.g., a working
fluid pressurized by an absorption or adsorption system) to
generate power or work.
[0023] As used herein, the term "vessel" refers to a container
suitable for containing a sorbent material and a working fluid
under suitable conditions to permit sorption (e.g., absorption or
adsorption) and/or desorption.
[0024] As used herein, the term "waste heat," "unutilized heat" or
"unutilized heat source" refers to the residual or remaining heat
source (e.g., steam) following the processing operation after the
heat source has been used for its primary purpose in the refining
or petrochemical processing operation. Unutilized heat is also
referred to as waste heat. The unutilized heat or unutilized heat
source refers to a heat source that is no longer of any use in
refining and/or petrochemical processing operations and would
traditionally be discarded. The unutilized heat can be provided as
an unutilized heat stream. For example, but not limitation,
unutilized heat can include steam that was employed in a heat
exchanger used in petroleum and petrochemical processing, and is of
no value to current processes and is being discarded.
[0025] As used herein, the term "pump" refers to a physical device
that assists in transporting fluids and/or pressurizing fluids to
an increased pressure.
[0026] As used herein, the term "efficiency" in context of the
present invention is defined as the power plus chilling generated
over the heat input.
[0027] As used herein, the term "twin screw expander" in the
context of the present invention is defined as a device driven by
high pressure liquid or mixed phase sorbent liquid to generate
power or shaft work.
[0028] For purposes of illustration and not limitation, a zeolite
13X/CO.sub.2 adsorption system 100 is provided, as depicted
schematically in FIG. 1. A Mollier Diagram for carbon dioxide at
various temperatures and pressures for this embodiment is shown in
FIGS. 2 and 3 for reference. In this embodiment, two vessels 111
and 112 are maintained in an adsorption mode and a desorption mode,
respectively. When one vessel is in the adsorption mode, the other
vessel is in the desorption mode and vice versa. In this example,
the sorbent material is zeolite 13X and the working fluid is
CO.sub.2. For the vessel in the adsorption mode, carbon dioxide is
adsorbed by the zeolite 13X at a pressure of about 140 psi and a
temperature of about 95.degree. F. These conditions are denoted in
FIG. 2 as Stage 1.
[0029] After adsorption is complete, the adsorbent bed is isolated
(e.g., by operating the relevant valve (e.g., valve 141 for vessel
111 or valve 142 for vessel 112)) and heated using unutilized heat
from a petroleum refining or chemical process. The adsorption mode
can last for several seconds (e.g., 10 seconds) to several minutes.
The duration of the adsorption mode varies based upon the adsorbent
material and fluid selected. Unutilized heat 121 or 122 is applied
to the vessel in order to desorb the carbon dioxide, thus
initiating the desorption mode. Using the unutilized heat, the
vessel is heated to about 212.degree. F. in this particular
embodiment. A pressurized stream is generated due to desorption of
CO.sub.2 from the 13X sorbent material as the adsorbent bed heats
to 212.degree. F. In response to operation of a back pressure
regulator valve (e.g., valve 113 for vessel 111 or valve 114 for
vessel 112), high pressure CO.sub.2 is released from the vessel to
pressure damper or cooler 115 at a preset pressure (e.g.,
.about.1400 psig), which is denoted in FIG. 2 as stage 2. The
temperature of the CO.sub.2 is approximately 212.degree. F.
[0030] The pressurized CO.sub.2 stream is cooled in the pressure
damper/cooler 115 to approximately 110.degree. F., which is denoted
as stage 3 in FIG. 2. As a result, the pressure of the cooled
CO.sub.2 stream in the line 131 is approximately 1380 psi and the
temperature is approximately 110.degree. F. The cooled working
fluid stream is subsequently expanded adiabatically using an
expansion valve 116 to about 140 psi and -40.degree. F., which is
denoted as stage 4 in FIG. 2. The expansion valve 116 may be a flow
restrictor or a needle valve to restrict but not stop flow. This
cooled stream 132 can be used as a high quality refrigeration load
for many different applications within refineries or similar
facilities where unutilized heat is readily available. For example,
the refrigerated CO.sub.2 can be directed to a heat exchanger 118
to chill process streams within refineries and chemical plants.
[0031] After performing the refrigeration operation within the
exchanger 118, the carbon dioxide of this representative embodiment
can have a temperature of about 60.degree. F. to 100.degree. F. and
a pressure of about 140 psi. The carbon dioxide working fluid 133
is then recycled back to one of the vessels for use in a subsequent
adsorption mode.
[0032] The CO.sub.2/zeolite 13X system has a pressure index of
greater than 3.5. The pressure index is determined in accordance
with the procedure set forth below.
[0033] Alternatively, higher temperature heat can be applied to
desorb more working fluid molecules from the adsorption bed. As
shown in FIG. 3, and for purposes of illustration and not
limitation, stage 2 is now stage 2A, in which a higher-temperature
unutilized heat source is used to heat the bed to 450.degree. F.,
instead of 212.degree. F. The pressurized stream is to be cooled to
110.degree. F. before expansion. It, therefore, will require a much
higher amount of cooling media at stage 2. The efficiency of this
alternative system based on a 450.degree. F. heat source, using the
selection of zeolite 13X and carbon dioxide, will be significantly
different as it requires higher level of heating and cooling. It is
understood, however, that a selection of sorbent material and fluid
based on a higher level heat pressure index can produce a sorption
system that is better suited for a higher quality of heat.
[0034] For purposes of the above discussion, each vessel can be a
shell in tube-type configuration with adsorbents in the tube. The
vessel can have an inner diameter of about 5 ft and contains tubes
having a length of about 20 ft. Other suitable vessels can be used.
Furthermore, exchanges other than shell-in-tube heat exchanges can
be selected based on ordinary skill in the art.
[0035] This example is provided for illustrative purposes; other
sorbent materials and fluids can be used in the place of, or in
addition to, zeolite 13X and CO.sub.2. Additional details of
similar adsorption systems are disclosed in U.S. patent application
Ser. No. 12/603,243 entitled, "System Using Unutilized Heat for
Cooling and/or Power Generation," which is incorporated by
reference in its entirety herein.
[0036] In accordance with one aspect of the present application, an
adsorption system for generating power and chilling is provided.
The adsorption system includes a first vessel containing a sorbent
material in fluid communication with a working fluid and
operatively connected to a heat source to yield a feed of working
fluid at a supercritical state, a generator in fluid communication
with the feed of working fluid at supercritical state to yield
power and a feed of working fluid in an at least partially
condensed state, and an evaporator in fluid communication with the
feed of working fluid in the at least partially condensed state to
yield chilling and a feed of uncondensed working fluid. In one
embodiment, the heat source is an unutilized heat source or stream.
For example, the unutilized heat source is from a chemical
processing or petrochemical refining operation.
[0037] The system can also include a second vessel containing
sorbent material in fluid communication with the working fluid and
operatively connected to a heat source to yield a second feed of
working fluid at a supercritical state. Each of the first vessel
and the second vessel has a sorption mode and a desorption mode,
wherein in the desorption mode the working fluid is released from
the sorbent material in response to the heat source, and wherein in
the sorption mode, the working fluid is sorbed by the sorbent
material, wherein when the first vessel is operating in the
adsorption mode, the second vessel is operating in the desorption
mode and, wherein when the first vessel is operating in the
desorption mode, the second vessel is operating in the adsorption
mode.
[0038] For the purpose of illustration and not limitation, an
adsorption system 400 in accordance with one aspect of the present
application is illustrated in FIG. 4. The adsorption system 400
includes a first vessel 411, a second vessel 412, a generator 413,
and an evaporator 414 for which cooling is desired. The first and
second vessel 411 and 412 can be a shell-in-tube type configuration
with the sorbent material in the tubes. For example, the first and
second vessels can have an inner diameter of about 5 feet and
contain tubes having a length of about 20 feet. Other vessel sizes
are considered to be well within the scope of the present
application. Furthermore, the present application is not limited to
shell-in-tube heat exchangers, other exchangers and other vessels
can be selected based on ordinary skill in the art and are
considered to be well within the scope of the present application
including but not limited to the use of sorbent beds, structured
adsorbents, and hollow fiber adsorbents.
[0039] An unutilized heat stream 431 passes through the first
vessel 411. Unutilized heat contained in the stream 431 passes
through the walls of the line containing the stream into the first
vessel 411. An unutilized heat stream 432 passes through the second
vessel 412. Unutilized heat contained in the stream 432 passes
through the walls of the line containing the stream into the second
vessel 412. The unutilized heat streams 431 and 432 can supply from
the same unutilized heat source or separate unutilized heat
sources. Alternatively or additionally, vessels 411 and 412 can
also be adapted to receive a feed of cooling media to regenerate
the adsorbents housed therein.
[0040] A valve assembly 441 is interposed between the first vessel
411 and the generator 413. In this embodiment, the valve assembly
441 functions as a back pressure regulator which permits the
working fluid to escape from the first vessel 411 at a
predetermined or pre-set pressure. The predetermined or pre-set
pressure can range, for example, from about 500 psig to about 3000
psig, which is dependent upon the amount of sorbent material
contained in the vessel and the temperature of the unutilized heat
stream. A second valve assembly 442 is interposed between the
second vessel 412 and the generator 413. Like the first valve
assembly 441, the second valve assembly 442 functions as a back
pressure regulator, which permits the working fluid in the second
vessel to escape from the second vessel 412 at a pre-set
pressure.
[0041] In operation, the first vessel 411 is in fluid communication
with a feed of working fluid 421 fed to the first vessel at
pressure .about.100 psia and temperature .about.100 F. A control
valve 451 controls the flow of working fluid to the first vessel
411. Similarly, the second vessel 412 is in fluid communication
with a feed of working fluid 421 fed to the second vessel at
pressure 100 psia and temperature 100 F. A control valve 452
controls the flow of fluid to the second vessel 412. When the
working fluid 421 is fed to the first vessel 411, the working fluid
is adsorbed onto a sorbent material contained in the first vessel
411. Similarly, when the working fluid is fed to the second vessel
412, the working fluid is adsorbed onto the sorbent material
contained in the second vessel 412.
[0042] In one embodiment, the first and second vessels 411 and 412
operate in tandem. The working fluid 421 flows into the first
vessel 411 when the valve 451 is open. The valve 451 remains open
until equilibrium is established within the first vessel 411. The
adsorption mode can last for several seconds (e.g., .about.10
seconds) to several minutes. The duration of the adsorption mode
varies based upon the adsorbent material and fluid selected. The
unutilized heat stream 431 passes through the first vessel 411 such
that the sorbent material and the working fluid are heated, which
results in the desorption of the working fluid from the sorbent
material. This increases the pressure of the working fluid
contained in the first vessel 411. Once the pre-set pressure is
reached, the working fluid is released from the first vessel 411
via the valve assembly 441, to yield a feed of working fluid at a
super-critical state 422 at pressure .about.1600 psia and
temperature .about.255 F.
[0043] The feed of working fluid at a supercritical state 422 is
used to run to the generator 413 to generate power. The generator
is run using a turbine, a turboexpander or any other suitable
device to create shaft work to be able to run the generator for
power. It is also contemplated that the generator may also be used
to drive rotating equipment such as pumps or compressors to perform
work on a process stream. Additionally, the device yields a feed of
working fluid in an at least partially condensed state 423 at a
pressure about 100 psia and temperature -58 F. In one embodiment,
the feed of working fluid at supercritical state 422 passes through
the generator to either generate electricity or perform work by
driving a shaft or other suitable mechanism. In accordance with an
aspect of the present invention, the amount of power generated is
0.95 mega watts (MW) based on 60,000 lb/hr CO.sub.2 flow rate. It
is contemplated that the amount of power generated may vary based
upon the system components.
[0044] The feed of working fluid in an at least partially condensed
state 423 is fed to an evaporator 414 to provide chilling and a
feed of uncondensed working fluid. The uncondensed working fluid
421 is then to be reintroduced to the first or second vessel. In an
exemplary embodiment the working fluid in an at least partially
condensed state 423 is processed through an evaporator to generate
chilling by using the latent heat of vaporization as well as
sensible heat of the working fluid, although other suitable vessels
to create chilling can be utilized. The chilling generated can be
used in many refinery processes. For example, the chilling can be
used in a heat exchanger to cool a process stream for refining or
petrochemical processing operations. In such an arrangement, the
unutilized heat, which normally would be lost, is recaptured and
used to perform cooling of another process stream. For example,
chilling can be used to cool water to provide cooling water to an
overhead condenser in a distillation tower. Chilling can be used to
recover gas molecules from a fuel stream. The chilling can also be
used in cooling the air intake of a gas turbine generator to
improve power output.
[0045] The present application is not intended to be limited for
use in process streams in refining and petrochemical processing
applications. It is contemplated that the heat exchanger can be
used in connection with a building cooling system located in one of
the buildings located at the facility such that the unutilized heat
can be used to cool one or more of the buildings. It is also
contemplated that the system can be used in connection with air
conditioning using exhaust heat from automobiles.
[0046] If tandem processing is desired through the second vessel,
the valve 451 is closed such that after the passing through the
evaporator 414, the working fluid at a pressure close to 100 psia
and temperature .about.100 F, is fed to the second vessel through
open control valve 452. The valve 452 remains open until
equilibrium is established within the second vessel 412. As
mentioned above, the adsorption mode can last for several seconds
(e.g., .about.10 seconds) to several minutes. The duration of the
adsorption mode varies based upon the adsorbent material and fluid
selected. The unutilized heat stream 432 passes through the second
vessel 412 such that the sorbent material and the working fluid are
heated, which results in the desorption of the working fluid from
the sorbent material. This increases the pressure of the working
fluid contained in the second vessel 412. Once the pre-set pressure
is reached, the working fluid is released from the second vessel
412 via valve assembly 442, to yield a feed of working fluid at a
supercritical state 422. The working fluid passes through the
system, as described above. After passing through the evaporator
414, the working fluid is returned to the first vessel 411.
[0047] In this manner, the first and second vessels 411 and 412 are
operated in tandem such that one is operating in an adsorption mode
when the other is operating in a desorption mode and vice versa.
With such an arrangement, the first and second vessels 411 and 412
operate to provide a continuous supply of working fluid to the
generator 413.
[0048] In one embodiment of this application, the working fluid is
selected from carbon dioxide, methane, ethane, propane, butane,
ammonia and chlorofluorocarbons (e.g., Freon.TM.), other
refrigerants, or other suitable fluids. The sorbent material is
selected from zeolites, metal organic frameworks (MOFs), zeolitic
imidazolate frameworks (ZIFs), ionic liquids, silicagel, adsorbing
polymers, carbon, and activated carbon, and combinations thereof.
In one embodiment the working fluid is carbon dioxide and/or the
sorbent material is a zeolite. In one embodiment the working fluid
is carbon dioxide and the zeolite is a zeolite X, preferably a
zeolite 13X.
[0049] The present application also provides an adsorption process
for generating both power and chilling. The process includes
adsorbing a working fluid onto a sorbent material, heating the
sorbent material to desorb the working fluid from the sorbent
material at a supercritical state, directing the desorbed fluid to
drive a generator to generate power or do shaft work and to at
least partially condense the desorbed working fluid, and
evaporating the at least partially condensed desorbed fluid to
yield chilling and a feed of uncondensed working fluid. The process
can use any of the features described above for the adsorption
system. In one embodiment, the heating is provided by unutilized
heat from one of a refining operation and chemical processing
operation. For example, the unutilized heat can be at a temperature
of 450 F or lower.
[0050] It is of note that the adsorption system and process
described herein do not require the use of a pump or additional
components to facilitate movement of the working fluid through the
system.
[0051] In accordance with the present invention, it has been
discovered that the generation of power and chilling simultaneously
is a more efficient and economical use of waste heat available in
refineries compared to the generation of chilling or power alone.
It is desirable to simultaneously integrate power and chilling
generation using waste heat within refinery and petro-chemical
plants (e.g. in a distillation column, chilling can be used to
lower the overhead temperature to improve throughput and power can
be used to pump feed to the distillation column reboiler). The
integration of recovered waste heat back in to refinery and
petrochemical processes improves the efficiency of the individual
process and the facility as a whole reducing the need to consume
additional fuel. This may result in a reduction of carbon dioxide
emissions.
[0052] The table below compares generation of power and chilling
together with power or chilling alone. The examples are based on
the use of a CO.sub.2-Zeolite 13X combination. The
adsorber/desorber bed is a shell and tube design with sorbent
material packed inside the tube. This comparison is based on same
amount of gas flow 60,000 lb/hr CO2. The equipment size of
adsorber/desorber beds is related with thermal swing time of the
process. Each adsorber/desorber vessel may have an inner diameter
of about 5 ft and contains tubes having a length of about 20 ft.
The process scheme illustrated in FIG. 1 can be used for the
chilling only case. To generate both power and chilling, the
process scheme illustrated in FIG. 4 can be utilized. To generate
power only, the process scheme is similar to FIG. 4 without the
evaporator.
TABLE-US-00001 Waste Inlet Outlet Inlet Outlet Heat Chilling Power
Efficiency Pressure Pressure Temp Temp. MW.sub.TH MW.sub.C MW.sub.E
% (psia) (psia) (F.) (F.) Chilling 6.45 1.38 0 21.4 1600 100 112
-58 Only Power 6.45 0.0 0.95 14.7 1600 100 255 -58 Only Chilling +
6.45 0.73 0.95 26.0 1600 100 255 -58 Power
[0053] In accordance with another aspect of the present
application, an absorption system for generating power and chilling
is provided. The absorption system includes an absorber to absorb a
working fluid in a liquid sorbent, a pump in fluid communication
with the absorber to yield a feed of pressurized liquid sorbent and
absorbed working fluid, a heat source to heat the feed of
pressurized liquid sorbent and absorbed working fluid to yield a
feed of working fluid at a supercritical state, a generator in
fluid communication with the feed of working fluid at a
supercritical state to yield power and a feed of working fluid in
an at least partially condensed state, and an evaporator in fluid
communication with the feed of working fluid in the at least
partially condensed state to yield chilling and uncondensed working
fluid.
[0054] For the purpose of illustration and not limitation, an
absorption system 500 in accordance with one aspect of the present
application is illustrated in FIG. 5. The absorption system 500
includes an absorber 511, a pump 512, a vapor generator 513, a
generator 514, an evaporator 515, a cooler 516 and a cooler
517.
[0055] In operation, the absorber 511 is in fluid communication
with a working fluid 521 fed to the absorber at a first pressure
(.about.560 psia) and a first temperature (.about.100 F) and a
liquid sorbent 522. In the absorber 511, the working fluid 521 is
absorbed in the liquid sorbent 522 to yield a liquid sorbent with
an absorbed working fluid 523. The absorber 511 can be an
absorption column or any other suitable vessel. During absorption
there is heat generated in the absorber that can be removed from
the absorber using cooling water, or any other suitable means, to
maintain the absorber at a temperature favorable for absorbing the
working fluid.
[0056] The pump 512 pumps the liquid sorbent with an absorbed fluid
523 from the absorber to a higher pressure to yield a feed of
pressurized liquid sorbent and absorbed working fluid 524. The
pressurized liquid sorbent and absorbed working fluid 524 is at a
higher pressure (.about.1400 psia) and a second temperature
(.about.104 F), generally greater than (100 F). The present
invention is not intended to be limited to the specified pressures
and temperatures; rather, other temperatures and pressures are
considered to be well within the scope of the present invention
provided such temperatures and pressures are suitable for the
pressurized liquid sorbent and absorbed working fluid.
[0057] The feed of pressurized liquid sorbent and absorbed working
fluid 524 is heated using a heat source which can include a vapor
generator 513, e.g., a rectification column or any other suitable
vessel. The heat source 531 can pass through the vapor generator,
to disengage the working fluid from the liquid absorbent to yield a
feed of working fluid at a supercritical state 525 and the liquid
sorbent 527, which is fed to a cooler 516 before the liquid sorbent
522 is returned to the absorber 511. The cooler 516 can be in fluid
communication with the vapor generator and can include cooling
water. The feed of working fluid at a supercritical state 525 from
the vapor generator 513 is passed through a cooler 517 to reduce
the temperature from .about.275 F to .about.60 F. The pressure
remains at .about.1400 psia. Other temperatures and pressures are
considered to be well within the scope of the present invention.
The unutilized heat stream or source 531 can be operatively
connected to the vapor generator 513 such that unutilized heat from
the unutilized heat source can be transferred to the liquid sorbent
with an absorbed fluid contained within the vapor generator.
[0058] The feed of working fluid at a supercritical state 525 is
used to run to a generator 514 to generate power. The generator can
be a turbine, a turboexpander or any other suitable device to
generate power or work. A working fluid is selected such that the
generator yields a feed of working fluid in an at least partially
condensed state 526 at a pressure about .about.560 psia and a
temperature .about.43 F less than 100 F. The present invention is
not intended to be limited to the pressures and temperatures stated
herein; rather, other temperatures and pressures are considered to
be well within the scope of the present invention provided such
temperatures and pressures yield the partially condensed state 526.
In one embodiment, the feed of working fluid at supercritical state
525 passes through the generator to either generate power or
perform work by driving a shaft or other suitable mechanism. If
implemented at a refinery, the power generated can be supplied to
the power grid for refinery use or for supplying a third party. The
amount of power generated by the system in accordance with the
present invention may vary based upon the design of the system and
the selected components. For example, the system may generate
.about.32 kilo watts (KW) of power based on 45,000 lb/hr mixture of
CO.sub.2 and amyl acetate (stream 525). The molar concentration of
amyl acetate in 525 is 3%. It is contemplated that the system may
generate amounts in excess of 32 KW based upon the system design
and other constraints.
[0059] The working fluid in an at least partially condensed state
526 is fed to an evaporator 515 to yield chilling and uncondensed
working fluid 521 to be fed to the absorber 511. The evaporator 515
can be in fluid communication with the absorber 511. In an
exemplary embodiment the working fluid in an at least partially
condensed state 526 is processed through an evaporator 515 to
generate chilling by using the latent heat of vaporization of the
working fluid, although other suitable vessels to create chilling
can be utilized. The chilling generated can be used in many
refinery processes. For example, the chilling can be used in a heat
exchanger to cool a process stream for refining or petrochemical
processing operations. In such an arrangement, the unutilized heat,
which normally would be lost, is recaptured and used to perform
cooling of another process stream. Chilling can be used to cool
water to provide cooling water to an overhead condenser in a
distillation tower. Chilling can also be used to recover gas
molecules from a fuel stream. The chilling can also be used in
cooling the air intake of a gas turbine generator to improve power
output.
[0060] In accordance with another aspect of the present
application, an absorption system for generating power is provided.
Power is generated using both gas phase expansion and liquid phase
expansion. The absorption system includes an absorber to absorb a
working fluid in a liquid sorbent, a pump in fluid communication
with the absorber to yield a feed of pressurized liquid sorbent and
absorbed working fluid, a heat source to heat the feed of
pressurized liquid sorbent and absorbed working fluid to yield a
feed of working fluid at a supercritical state, at least one
generator.
[0061] For the purpose of illustration and not limitation, an
absorption system 600 in accordance with one aspect of the present
application is illustrated in FIG. 6. The absorption system 600
includes an absorber 611, a pump 612, a vapor generator 613,
generators 614 and 615, a cooler 616 and a cooler 617.
[0062] In operation, the absorber 611 is in fluid communication
with a working fluid 621 fed to the absorber at a first pressure
(.about.600 psia) and a first temperature (.about.127 F) and a
liquid sorbent 622. In the absorber 611, the working fluid 621 is
absorbed in the liquid sorbent 622 to yield a liquid sorbent with
an absorbed working fluid 623. The absorber 611 can be an
absorption column or any other suitable vessel. During absorption
there is heat generated in the absorber that can be removed from
the absorber using cooling water, or any other suitable means, to
maintain the absorber at a temperature favorable for absorbing the
working fluid.
[0063] The pump 612 pumps the liquid sorbent with an absorbed fluid
623 from the absorber to a higher pressure to yield a feed of
pressurized liquid sorbent and absorbed working fluid 624. The
pressurized liquid sorbent and absorbed working fluid 624 is at a
higher pressure (.about.1200 psia) and a second temperature
(.about.102 F). The present invention is not intended to be limited
to the specified pressures and temperatures; rather, other
temperatures and pressures are considered to be well within the
scope of the present invention provided such temperatures and
pressures are suitable for the pressurized liquid sorbent and
absorbed working fluid.
[0064] The feed of pressurized liquid sorbent and absorbed working
fluid 624 is heated using a heat source which can include a vapor
generator 613, e.g., a rectification column or any other suitable
vessel. The heat source 631 can pass through the vapor generator,
to disengage the working fluid from the liquid absorbent to yield a
feed of working fluid at a supercritical state 625 and the liquid
sorbent 627, which is fed to a cooler 616 and then to a generator
615 before the liquid sorbent 622 is returned to the absorber 611.
The generator 615 is suitable for use in liquid phase expansion to
generate. The generator 615 may be a twin screw expander, but other
power generating assemblies are considered to be well within the
scope of the present invention. The cooler 616 can be in fluid
communication with the vapor generator 613 and can include cooling
water. The feed of working fluid at a supercritical state 625 is at
a pressure (.about.1200 psia) and a temperature (.about.450 F).
Other temperatures and pressures are considered to be well within
the scope of the present invention. The unutilized heat stream or
source 631 can be operatively connected to the vapor generator 613
such that unutilized heat from the unutilized heat source can be
transferred to the liquid sorbent with an absorbed fluid contained
within the vapor generator.
[0065] The feed of working fluid at a supercritical state 625 is
used to run to a generator 614 to generate power. The generator 614
can be a turbine, a turboexpander or any other suitable device to
generate power or work. A working fluid is selected such that the
generator yields a feed of working fluid 626 at a pressure about
.about.600 psia and a temperature .about.398 F. The present
invention is not intended to be limited to the pressures and
temperatures stated herein; rather, other temperatures and
pressures are considered to be well within the scope of the present
invention.
[0066] The working fluid 626 is fed to a cooler 617. The reduced
temperature working fluid 621 from the cooler 617 is then fed back
to the absorber 611.
[0067] While described, solely for the sake of convenience, largely
in the context of a refining and petrochemical operation, the
present application is not intended to be limited thereto. It is
contemplated that, for example, the heat exchanger can be used in
connection with a building cooling system located in one of the
buildings located at the facility such that the unutilized heat can
be used to cool one or more of the buildings.
[0068] Thus the absorption system generates power and chilling by
recovering unutilized heat from an unutilized heat stream or
source. The unutilized heat source can be used heat from a heat
exchanger, or other process area of a chemical processing plant or
petrochemical refining plant.
[0069] The absorption system includes a liquid sorbent or a mixture
of liquid sorbents and a working fluid or a mixture of working
fluids.
[0070] In various embodiments, various combinations of liquid
sorbents and working fluids are considered to be within the scope
of the present application. It should be noted that a combination
that is suitable for application with a higher temperature
unutilized heat stream may not be applicable for a lower
temperature unutilized heat stream.
[0071] The liquid sorbent in the absorption system has an average
heat of sorption (Q) between about 2 kcal/mole and about 25
kcal/mole, or more preferably between about 3 kcal/mole and about
10 kcal/mole.
[0072] In one embodiment of the present application, the working
fluid is a gas and is selected from carbon dioxide, methane,
ethane, propane, butane, ammonia, chlorofluorocarbons (e.g.,
Freon.TM.), other refrigerants, or other suitable fluids. The
liquid sorbent is selected from water, ethylene glycols,
Triethylene glycol, polyethylene glycol, polyethylene glycol
dimethyl ether, N-methyl-2-pyrrolidone, dimethylsulfoxide,
potassium carbonate, amyl acetate, acetone, pyridine, ethyl
alcohol, methyl alcohol, acetic acid, isobutyl acetate, acetic
anhydride, ionic liquids, etc., or other suitable liquids and
combinations thereof. In one embodiment, the working fluid is
carbon dioxide and/or the liquid sorbent is N-methyl-2-pyrrolidone
and ionic liquids.
[0073] In accordance with another aspect of the present
application, a process for generating power and chilling is
provided. The process includes absorbing a working fluid into a
liquid sorbent to yield a liquid sorbent and absorbed working
fluid, pressurizing the liquid sorbent and absorbed working fluid
to increased pressure, heating the pressurized liquid sorbent and
absorbed working fluid to desorb the working fluid from the sorbent
material in a supercritical state, directing the desorbed working
fluid to drive a generator to generate power and to at least
partially condense the desorbed working fluid, and evaporating the
at least partially condensed desorbed working fluid to yield
chilling and uncondensed working fluid. The process can use any of
the features described above for the absorption system. In one
embodiment, the heating is provided by unutilized heat from one of
a refining operation and chemical processing operation. For
example, the unutilized heat is at a temperature of 450.degree. F.
or lower.
Pressure Index
[0074] Embodiments of the present application employ a "pressure
index" that can be determined at various desorbing temperatures,
which is used to determine suitable combinations of a sorbent
material and a working fluid. These combinations are especially
adaptable to be used in the sorption process disclosed herein,
since they collectively maximize pressurization of working fluid
(.DELTA.P) from available energy sources, which are often, but not
necessarily, low grade heat sources primarily intended to be used
for some other specific purpose (e.g., waste heat).
[0075] The pressure index is determined by the following method.
One hundred (100) grams of sorbent material are placed in a 1 liter
vessel designed to be isolated from associated equipment with
existing valves on both ends of the vessel. The vessel also has
indicators to measure the inside pressure and temperature. The
vessel is flushed and filled with a pure fluid (e.g., CO.sub.2) at
one atmospheric pressure. The sorbent material adsorbs fluid and
the sorbent may heat up. The vessel is equilibrated at 298 K
(77.degree. F.) and 1 atmospheric pressure, this sorbing pressure
being defined as P.sub.I=1.0. The vessel is heated to a
pre-selected desorbing temperature (e.g., 348 K i.e. 167.degree.
F.). When the vessel and sorbent material reach the pre-selected
desorbing temperature, the internal vessel pressure is measured to
determine P.sub.F. The pressure index is defined as the ratio of
P.sub.F to P.sub.I.
[0076] As noted above, embodiments of the present application make
use of a lower temperature of unutilized heat. In order to select a
sorbent material/fluid combination that is preferred for use with
low level heat (e.g., sorption systems that utilize low grade
unutilized heat), it is often desirable or necessary to ascertain
at least the low level heat pressure index, as determined above. A
pressure index of at least 1.5 is generally appropriate for use in
low level unutilized heat applications. Nevertheless, other
embodiments of the present application can use high level heat
sources. Thus in these embodiments, it is desirable to select a
high level heat pressure index. In such cases, combinations of
sorbent material and working fluid can have a pressure index as low
as 1.2.
Sorbent Materials
[0077] As noted above, and as used in this application, the term
"sorbent material" refers to a material that reversibly binds the
working fluid. Sorbent materials include, but are not limited to,
absorbents and adsorbents.
[0078] Absorbent materials that can be used in embodiments of the
present application include, but are not limited to, water,
glycols, amyl acetate, acetone, pyridine, ethyl alcohol, methyl
alcohol, acetic acid, isobutyl acetate, acetic anhydride, ionic
liquids, etc.
[0079] Adsorbent materials that can be used in embodiments of the
present application include, but are not limited to, metal-organic
framework-based (MOF-based) sorbents, zeolitic imidazole framework
(ZIF) sorbent materials, zeolites and carbon.
[0080] MOF-based sorbents include, but are not limited to,
MOF-based sorbents with a plurality of metal, metal oxide, metal
cluster or metal oxide cluster building units. As disclosed in
International Published Application No. WO 2007/111738, which is
hereby incorporated by reference, the metal can be selected from
the transition metals in the periodic table, and beryllium.
Exemplary metals include zinc (Zn), cadmium (Cd), mercury (Hg),
beryllium (Be) and copper (Cu). The metal building units can be
linked by organic compounds to form a porous structure, where the
organic compounds for linking the adjacent metal building units can
include 1,3,5-benzenetribenzoate (BTB); 1,4-benzenedicarboxylate
(BDC); cyclobutyl 1,4-benzenedicarboxylate (CB BDC); 2-amino 1,4
benzenedicarboxylate (H2N BDC); tetrahydropyrene 2,7-dicarboxylate
(HPDC); terphenyl dicarboxylate (TPDC); 2,6 naphthalene
dicarboxylate (2,6-NDC); pyrene 2,7-dicarboxylate (PDC); biphenyl
dicarboxylate (BDC); or any dicarboxylate having phenyl
compounds.
[0081] Specific materials MOF-based sorbent materials include:
MOF-177, a material having a general formula of
Zn.sub.4O(1,3,5-benzenetribenzoate).sub.2; MOF-5, also known as
IRMOF-I, a material having a general formula of
Zn.sub.4O(1,4-benzenedicarboxylate).sub.3; IRMOF-6, a material
having a general formula of Zn.sub.4O(cyclobutyl
1,4-benzenedicarboxylate); IRMOF-3, a material having a general
formula of Zn.sub.4O(2-amino 1,4 benzenedicarboxylate).sub.3; and
IRMOF-11, a material having a general formula of
Zn.sub.4O(terphenyl dicarboxylate).sub.3, or
Zn.sub.4O(tetrahydropyrene 2,7-dicarboxylate).sub.3; IRMOF-8, a
material having a general formula of Zn.sub.4O(2,6 naphthalene
dicarboxylate).sub.3; and Cu-BTC MOF, a material having a general
formula of C.sub.18H.sub.6Cu.sub.3O.sub.12 (copper
benzene-1,3,5-tricarboxylate).
[0082] Exemplary zeolitic imidazole framework (ZIF) sorbent
materials include, but are not limited to, ZIF-68, ZIF-60, ZIF-70,
ZIF-95, ZIF-100 developed at the University of California at Los
Angeles and generally discussed in Nature 453, 207-211 (8 May
2008), hereby incorporated by reference in its entirety.
[0083] Zeolite adsorbent materials include, but are not limited to,
aluminosilicates that are represented by the formula
M.sub.2/nO.Al.sub.2O.sub.3.ySiO.sub.2.wH.sub.2O, where y is 2 or
greater, M is the charge balancing cation, such as sodium,
potassium, magnesium and calcium, N is the cation valence, and w
represents the moles of water contained in the zeolitic voids.
Examples of zeolites that can be included in the methods and
systems of the present application include natural and synthetic
zeolites.
[0084] Natural zeolites include, but are not limited to, chabazite
(CAS Registry No. 12251-32-0; typical formula
Ca.sub.2[(AlO.sub.2).sub.4(SiO.sub.2).sub.8].13H.sub.2O), mordenite
(CAS Registry No. 12173-98-7; typical formula
Na.sub.8[(AlO.sub.2).sub.8(SiO.sub.2).sub.40].24H.sub.2O), erionite
(CAS Registry No. 12150-42-8; typical formula (Ca, Mg, Na.sub.2,
K.sub.2).sub.4.5[(AlO.sub.2).sub.9(SiO.sub.2).sub.27].27H.sub.2O),
faujasite (CAS Registry No. 12173-28-3, typical formula (Ca, Mg,
Na.sub.2,
K.sub.2).sub.29.5[(AlO.sub.2).sub.59(SiO.sub.2).sub.133].235H.s-
ub.2O), clinoptilolite (CAS Registry No. 12321-85-6, typical
formula Na.sub.6[(AlO.sub.2).sub.6(SiO.sub.2).sub.30].24H.sub.2O)
and phillipsite (typical formula: (0.5Ca, Na,
K).sub.3[(AlO.sub.2).sub.3(SiO.sub.2).sub.5].6H.sub.2O).
[0085] Synthetic zeolites include, but are not limited to, zeolite
A (typical formula:
Na.sub.12[(AlO.sub.2).sub.12(SiO.sub.2).sub.12].27H.sub.2O),
zeolite X (CAS Registry No. 68989-23-1; typical formula:
Na.sub.86[AlO.sub.2).sub.86(SiO.sub.2).sub.106].264H.sub.2O),
zeolite Y (typical formula:
Na.sub.56[(AlO.sub.2).sub.56(SiO.sub.2).sub.136].250H.sub.2O),
zeolite L (typical formula:
K.sub.9[(AlO.sub.2).sub.9(SiO.sub.2).sub.27].22H.sub.2O), zeolite
omega (typical formula:
Na.sub.6.8TMA.sub.1.6[AlO.sub.2).sub.8(SiO.sub.2).sub.28].21H.sub.2O,
where TMA is tetramethylammonium) and ZSM-5 (typical formula: (Na,
TPA).sub.3[(AlO.sub.2).sub.3(SiO.sub.2).sub.93].16H.sub.2O, where
TPA is tetrapropylammonium).
[0086] Zeolites that can be used in the embodiments of the present
application also include the zeolites disclosed in the Encyclopedia
of Chemical Technology by Kirk-Othmer, Volume 16, Fourth Edition,
under the heading "Molecular Sieves," which is hereby incorporated
by reference in its entirety.
[0087] Synthetic zeolite sorbent materials are commercially
available, such as under the Sylosiv.RTM. brand from W.R. Grace and
Co. (Columbia, Md.) and from Chengdu Beyond Chemical (Sichuan, P.R.
China). For example, Sylosiv.RTM. A10 is one commercially available
zeolite 13X product.
Working Fluids
[0088] As noted above, the term fluid refers to a liquid or gas
that reversibly binds to the sorbent material. Non-limiting
examples of fluids that can be used in accordance with the present
application include carbon dioxide, methane, ethane, propane,
butane, ammonia, chlorofluorocarbons (e.g., Freon.TM.), and other
suitable fluids and refrigerants. In certain particular
embodiments, any suitable fluid or refrigerant satisfying the
above-described pressure index can be used.
Selection of Sorbent Materials and Fluids
[0089] In accordance with another aspect of the invention, a method
is provided for selecting a sorbent material and a working fluid
for use in combination in an unutilized-heat sorbent system within
a chemical processing or petrochemical refining operation. The
method generally includes identifying a sorbent that meets the
pressure index criterion of at least 1.5. In one embodiment, the
sorbent material and the working fluid for use in combination are
selected if the measured internal pressure within the secured
chamber is at least two times, or at least three times, or at least
four times, or at least six times, or at least eight times the
sorbing pressure. The sorption system can be used to generate power
and chilling. The above-described method is not applicable to
absorption systems.
Heat of Sorption
[0090] Preferably, the sorbent material and fluid couple has an
average heat of sorption (Q) from about 2 kcal/mole to about 25
kcal/mole, and more preferably from about 4 kcal/mole to about 10
kcal/mole for heat sources up to 450.degree. F. The heat of
sorption should be between 2 kcal/mole to about 40 kcal/mole if a
higher temperature heat source (e.g., greater than 450.degree. F.
and up to 1700.degree. F.) is available. The sorbent material
should also have a high capacity for the working fluid.
Uses of Sorbent Systems of the Present Application
[0091] The adsorbent systems of the present application can be used
in various applications provided the setting allows for the
presence of a vessel that contains a sorbent material, a supply of
working fluid, a heat supply and means to effectively direct the
desorbed fluid to a generator to generate power and a evaporator to
provide chilling. For example, the desorbed gas can be directed to
a turboexpander to provide power.
[0092] The absorbent systems and methods of the present application
can be used in various applications provided the setting allows for
the presence of a absorber for absorbing a working fluid in a
liquid sorbent and a vapor generator for desorbing the working
fluid from the liquid sorbent, a supply of working fluid, a heat
supply and a pump, and means to effectively direct the desorbed
fluid to a generator to generate power and a evaporator to provide
chilling thereto.
[0093] Possible applications for sorption systems of the present
application include residential (for generating air conditioning in
the summer and a heat pump in the winter), vehicular (where the
on-board air conditioning utilizes exhaust heat) and industrial
(refining and chemical plants).
[0094] In one embodiment of the present application, the sorbent
system or method is used within a chemical or petrochemical plant,
and the desorbed fluid is used to generate power and to provide
chilling to aid in other process areas, particularly areas that
rely on temperature differences to separate components of a
mixture. For example, the chilling can be used to recover liquefied
petroleum gas (LPG, C.sup.3+) from flue gases going up a stack, or
the chilling can be used to operate condensers to improve the
effectiveness of vacuum distillation columns, particularly in the
summer months.
[0095] By proper selection of the sorbent material and working
fluid, the sorbent system or method can make effective use of lower
grade heat than previously provided by sorption systems in the
prior art. For example, in one embodiment of the present
application, the heat supply is "unutilized heat" which has a
temperature of from about 70.degree. C. (158 F) to about
300.degree. C. (572 F), more preferably from about 90.degree. C.
(194 F) to about 180.degree. C. (356 F).
[0096] The present application is not to be limited in scope by the
specific embodiments described herein. Indeed, various
modifications of the invention in addition to those described
herein will become apparent to those skilled in the art from the
foregoing description and the accompanying figures. Such
modifications are intended to fall within the scope of the appended
claims.
[0097] It is further to be understood that all values are
approximate, and are provided for description.
[0098] Patents, patent applications, publications, product
descriptions, and protocols are cited throughout this application,
the disclosures of each of which is incorporated herein by
reference in its entirety for all purposes.
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