U.S. patent application number 13/349378 was filed with the patent office on 2012-11-15 for vapor absorption system.
This patent application is currently assigned to Caitin, Inc.. Invention is credited to Thomas P. Gielda, Jayden D. Harman.
Application Number | 20120285661 13/349378 |
Document ID | / |
Family ID | 46507449 |
Filed Date | 2012-11-15 |
United States Patent
Application |
20120285661 |
Kind Code |
A1 |
Gielda; Thomas P. ; et
al. |
November 15, 2012 |
VAPOR ABSORPTION SYSTEM
Abstract
Provided herein is a vapor absorption system, adapted to receive
a vapor comprising a vacuum pump having an operating liquid, where
the vapor is received by an operating liquid and condensed therein
to provide condensed liquid mixed with the operating liquid.
Inventors: |
Gielda; Thomas P.; (Saint
Joseph, MO) ; Harman; Jayden D.; (San Rafael,
CA) |
Assignee: |
Caitin, Inc.
Fremont
CA
|
Family ID: |
46507449 |
Appl. No.: |
13/349378 |
Filed: |
January 12, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61433165 |
Jan 14, 2011 |
|
|
|
61443705 |
Feb 16, 2011 |
|
|
|
Current U.S.
Class: |
165/104.13 ;
165/104.27 |
Current CPC
Class: |
F25B 2341/0015 20130101;
F25B 41/00 20130101; Y10T 137/0318 20150401; Y10T 137/6416
20150401 |
Class at
Publication: |
165/104.13 ;
165/104.27 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Claims
1. A heat transfer system comprising an evacuation chamber adapted
to receive a first liquid, at least one venturi vacuum pump
associated with the evacuation chamber to cause, in use, the
pressure within the evacuation chamber to be reduced to promote
vaporization of liquid in the chamber and to thereby cause cooling,
and a first heat exchanger having a fluid pathway for a heat
exchange fluid to pass through the first heat exchanger and being
associated with the evacuation chamber to provide heat to the first
liquid in the chamber to support the vaporization and thereby to
cool the heat exchange fluid.
2. A heat transfer system as claimed at claim 1 wherein vapor from
the vaporization of the first liquid is received and condensed
within a flow stream of a second liquid which passes through the at
least one venturi vacuum pump to cause the reduced pressure.
3. A heat transfer system as claimed in claim 2 wherein the flow
stream of the second liquid passes through a second heat exchange
system after exiting the venturi vacuum to thereby cool the second
liquid.
4. A heat transfer system as claimed in claim 3 wherein the second
liquid is returned to the inlet of the venturi vacuum pump in
cyclic manner.
5. A heat transfer system as claimed in claim 4 wherein the first
liquid and the second liquid are of the same substance and
evacuation chamber and venturi vacuum pump form a closed system.
Description
CROSS-REFERENCE
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/433,165 filed Jan. 14, 2011, and U.S.
Provisional Application No. 61/443,705, filed Feb. 16, 2011, which
applications are entirely incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a system and method for
absorption of a vapor into a liquid. The system has many
applications but is particularly useful for distillation of a
liquid mixture such as water with impurities. It also has
application as a heat transfer system. However, the system is not
limited to these two applications.
[0003] Absorption, in chemistry, is a physical or chemical
phenomenon or a process in which atoms, molecules, or ions enter
some bulk phase by being taken up by the volume. In this
application we are particularly concerned about the absorption of a
vapor into a liquid.
[0004] Usual vapor absorption techniques have specific
applications. They are usually relatively slow process unless some
chemical reaction is occurring. Because of this, absorption
processes have relatively limited application. However, the present
invention has identified a method of obtaining a much faster rate
of absorption where chemical interaction is not involved, with the
result that vapor absorption systems may be used in applications
where they were never previously considered, or at least not
considered viable.
[0005] Following on from the new vapor absorption system which is
disclosed herein, there are disclosed new and improved distillation
systems and heat transfer system, making use of the vapor abortion
system.
[0006] Distillation is of course, a well known process. It is used
often where traditional filtration techniques have not been
effective at purifying a liquid mixture. Conventional distillation
requires the application of heat energy to cause the production of
a vapor which is then passed through a condenser to condense the
vapor back to a liquid for use. While conventional distillation is
generally effective at purifying liquids such as water, the energy
cost is substantial and often uneconomic. Improvements to the
process have increased efficiency significantly, but the process
has remained too expensive for purification of water for general
use.
[0007] Efforts to improve the efficiency of the distillation
process have included attempts at operation at reduced pressure. It
is well known that vaporization of liquid occurs more rapidly when
the pressure is reduced. However, such systems have had limited
success due to difficulty and expense associated with an evacuating
system in conjunction with the evaporation and condensing
subsystems. An example of one attempt is that disclosed in U.S.
Pat. No. 3,864,215 (Arnold). The system of that disclosure utilizes
the low pressure region of a venturi to provide the reduced
pressure. It was particularly applicable to a marine environment
but retained some complexity in that it still incorporated a
condenser.
[0008] Heat transfer systems are also well known. Air-conditioning
and refrigeration systems form subsets of this broad category. It
is well known that conventional heat exchange systems use very
substantial amounts of energy in order to transfer energy. The use
of new vapor absorption systems substantially improves the
efficiency or C.O.P. (co-efficient of performance) of a heat
transfer system.
SUMMARY OF THE INVENTION
[0009] The invention resides in a vapor absorption system adapted
to receive a vapor comprising a vacuum pump having an operating
liquid wherein the vapor is received by an operating liquid and
condensed therein to provide condensed liquid mixed with the
operating liquid.
[0010] According to a preferred feature of the invention, the
absorption of vapor within the system is effective to cause
production of more vapor.
[0011] According to a preferred feature of the invention, the
vacuum pump is a venturi vacuum pump and the operating liquid is a
liquid which passes through the venturi vacuum pump to produce a
vacuum operative on the vapor.
[0012] According to a preferred feature of the invention, a first
heat exchange means is provided to support the production of
vapor.
[0013] According to a preferred feature of the invention, a second
heat exchanger is provided to expel heat from the operating liquid
after it has passed through the venturi vacuum pump.
[0014] According to a preferred feature of the invention, the
operating liquid is passed through the first heat exchanger to pass
heat from the operating liquid to the first heat exchanger.
[0015] According to a preferred feature of the invention, condensed
liquid derived from the vapor is removed for use.
[0016] According to the preferred embodiment, the system is a
distillation system.
[0017] According to the preferred embodiment, the system is a heat
transfer system.
[0018] According to the preferred embodiment, the operating liquid
is circulated through the system.
[0019] According to a further aspect, the invention resides in a
distillation system comprising an evacuation chamber adapted to
receive a liquid mixture to be distilled, the evacuation chamber
having a space above the liquid mixture filled with a gas, and a
vacuum pump associated with the evacuation chamber and adapted in
use to provide a reduced pressure within the gas to cause
vaporization of the liquid mixture and wherein a primary liquid is
passed in association with the gas in the evacuation chamber to
receive and condense the vapor.
[0020] According to a preferred feature of the invention, at least
a portion of the primary water is circulated through the vacuum
pump.
[0021] According to a preferred feature of the invention, a first
heat exchange means is provided to enable latent heat of
vaporization to be received by the liquid mixture to support the
vaporization of the liquid mixture.
[0022] According to a preferred feature of the invention, the first
heat exchange means comprises features associated with the wall of
the evacuation chamber to promote the receipt of the latent heat of
vaporization from the surroundings.
[0023] According to a preferred feature of the invention, the first
heat exchange means comprises a first heat exchange means
associated with the evacuation chamber through which heat exchange
fluid passes to surrender the latent heat of vaporization to the
liquid mixture, the latent heat of vaporization being received by
the heat exchange fluid from a source remote from the first heat
exchanger.
[0024] According to the preferred embodiment, the vacuum pump is a
venturi pump in use having a fluid flow through the venturi pump to
provide a reduced pressure at a venturi throat section.
[0025] According to the preferred embodiment, the venturi pump has
a venturi throat section configured to receive the gas from the
evacuation chamber and the fluid flow is the primary liquid so that
the venturi pump is operative to cause the reduced pressure of the
gas in the evacuation chamber by receiving the gas into the primary
liquid.
[0026] According to the preferred embodiment, porting is associated
with the venturi the pump, the porting being adapted to convey gas
to the venturi pump.
[0027] According to the preferred embodiment, heat within the
primary water exiting the venturi pump is removed by means of a
second heat exchange means.
[0028] According to the preferred embodiment, the second heat
exchange means is associated with a pathway for the primary liquid
which passes through ground to surrender heat to the ground.
[0029] According to the preferred embodiment, a liquid mixture
control system to control the entry and exit of liquid mixture from
the evacuation chamber.
[0030] According to the preferred embodiment, the liquid mixture to
be distilled is water and the primary is a liquid immiscible with
water.
[0031] According to the preferred embodiment, the primary liquid is
oil.
[0032] According to a further aspect, the invention resides in a
method of distillation of a liquid mixture using an evacuation
chamber comprising vaporizing the liquid mixture by reducing the
pressure within the evacuation chamber by means of a vacuum pump,
to provide a distillation vapor and receiving and condensing the
distillation vapor within a primary liquid passing in association
with the distillation vapor.
[0033] According to a preferred feature of the invention, the
vacuum pump is a venturi vacuum pump having a venturi throat
section and the primary liquid passes through the venturi vacuum
pump to provide a reduced pressure in the venturi throat region and
distillation vapor is drawn into the venturi through porting at the
venturi throat region and received and condensed by the primary
liquid.
[0034] According to a preferred feature of the invention, at least
a portion of the primary water is circulated.
[0035] According to a preferred feature of the invention, at least
a portion of the primary water is circulated by being received from
a holding tank and being returned to a holding tank after passing
through the vacuum pump.
[0036] According to a preferred feature of the invention, a first
heat exchange means is provided to enable latent heat of
vaporization to be received by the liquid mixture to support the
vaporization of the liquid mixture.
[0037] According to a preferred embodiment, the first heat exchange
means comprises features associated with the wall of the evacuation
chamber to promote the receipt of the latent heat of vaporization
from the surroundings.
[0038] According to a preferred embodiment, the first heat exchange
means comprises a first heat exchanger associated with the
evacuation chamber through which heat exchange fluid passes to
surrender the latent heat of vaporization to the liquid mixture,
the latent heat of vaporization being received by the heat exchange
fluid from a source remote from the first heat exchanger.
[0039] According to a preferred embodiment, heat within the primary
water exiting the venturi pump is removed by means of a second heat
exchange means.
[0040] According to a preferred embodiment, second heat exchange
means is associated with a pathway for the primary liquid which
passes through ground or cold water to surrender heat to the ground
or cold water, respectively.
[0041] According to a preferred embodiment, the primary liquid is
oil and the liquid mixture is a mixture of water and other
substance or substances.
[0042] According to a further aspect, the invention resides in a
heat transfer system comprising an evacuation chamber adapted to
receive a first liquid, at least one venturi vacuum pump associated
with the evacuation chamber to cause, in use, the pressure within
the evacuation chamber to be reduced to promote vaporization of
liquid in the chamber and to thereby cause cooling, and a first
heat exchanger having a fluid pathway for a heat exchange fluid to
pass through the first heat exchanger and being associated with the
evacuation chamber to provide heat to the first liquid in the
chamber to support the vaporization and thereby to cool the heat
exchange fluid.
[0043] According to a preferred feature of the invention, vapor
from the vaporization of the first liquid is received and condensed
within a flow stream of a second liquid which passes through the at
least one venturi vacuum pump to cause the reduced pressure.
[0044] According to a preferred feature of the invention, the flow
stream of the second liquid passes through a second heat exchange
system after exiting the venturi vacuum to thereby cool the second
liquid.
[0045] According to a preferred feature of the invention, the
second liquid is returned to the inlet of the venturi vacuum pump
in cyclic manner.
[0046] According to a preferred feature of the invention, the first
liquid and the second liquid are of the same substance and
evacuation chamber and venturi vacuum pump form a closed
system.
[0047] The invention will be more fully understood in the light of
the following description of several preferred embodiments.
INCORPORATION BY REFERENCE
[0048] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent, or patent
application was specifically and individually indicated to be
incorporated by reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized, and the accompanying drawings of which:
[0050] FIG. 1 is a diagrammatic representation of a distillation
system according to the first embodiment;
[0051] FIG. 2 is a diagrammatic representation of a distillation
system according to the second embodiment;
[0052] FIG. 3 is a diagrammatic representation of a distillation
system according to the third embodiment;
[0053] FIG. 4 is a diagrammatic representation of a distillation
system according to the fourth embodiment;
[0054] FIG. 5 is a diagrammatic representation of a distillation
system according to the fifth embodiment; and
[0055] FIG. 6 is a diagrammatic representation of a heat exchange
system according to the sixth embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0056] One element of the vapor absorption systems disclosed herein
is a system which places a vapor under a vacuum by use of a vacuum
pump having an operating liquid wherein the vapor is received by
the operating liquid and condensed therein to provide condensed
liquid mixed with the operating liquid. The system therefore is
limited to a system whereby the vapor condenses when being absorbed
by the operating liquid, rather than an alternative such as being
dissolved as a gas. The system is particularly applicable where the
system is incorporated in a continuous process and in particular
where the absorption of vapor is operative to cause the production
of new vapor. The system is most easily provided by use of a
venturi vacuum pump and the operating liquid is the liquid which
passes through the venturi to produce a vacuum. The venturi thereby
produces a vacuum which draws the vapor into the operating liquid,
where it condenses. Typical vapors may be water vapor, or methanol.
Many others are suitable. In some instances the operating liquid is
of the same substance as the vapor. Distillations systems are
described below where the operating liquid is water and the vapor
is water vapor. In other instances, the operating liquid and the
vapor may be different substances. One embodiment described uses
oil as the operating liquid and water as the vapor, while another
uses water as the operating liquid and methanol as the vapor.
[0057] An important aspect of the system is that ongoing
vaporization can occur, that is, the process can be continuous.
Indeed, the use of the vacuum pump enables the vapor to be
replenished because the vapor pressure is reduced as the vapor is
absorbed. For a distillation system, the distilled product may be
withdrawn from the system for use. In contrast, a heat transfer
system is a closed system and nothing (or almost nothing) need be
withdrawn or added. Generally, the system will operate on a
recycling basis, where the operating liquid recycles through the
system. But there are configurations where that need not be the
case.
[0058] For the vapor absorption system described to be effective,
they require a vacuum pump of high efficiency. An improved venturi
vacuum pump is disclosed in a corresponding application by the same
inventors and based on the same basic application. The rest of this
discussion assumes use of a venturi vacuum pump according to that
disclosure and therefore that disclosure is hereby incorporated by
reference. The features of the vapor absorption system of the
invention are best appreciated by a discussion with reference to
the specific embodiments.
[0059] The first embodiment of the invention is directed to a
distillation system which incorporates an evacuation chamber and an
evacuation pump. The embodiment is described with reference to FIG.
1.
[0060] The distillation system 11 according to the first embodiment
comprises an evacuation chamber 14 adapted to receive a quantity of
liquid to be distilled. For the purposes of this description, the
embodiment will be described with reference to the distillation of
water, referred to herein as secondary water, such as contaminated
water or ground water which is too polluted or mineralized for
direct use, but reference will be made later in the description to
the distillation of other mixtures including liquid mixtures. The
evacuation chamber 14 is adapted to be evacuated to a reasonably
high level (preferably less than 3 kPa) by one or more evacuation
pumps 16 and therefore is constructed accordingly. The actual
design of the evacuation chamber is not critical to the invention,
and will depend significantly upon the circumstances of the
installation. Those skilled in the art will be able to identify the
appropriate design criteria. Typically, an evacuation chamber may
comprise a substantially cylindrical vessel with the axis of the
cylinder 21 being oriented substantially vertically. The ends 23,
25 may be strengthened by being of convex or concave profile. But
other configurations such as substantially spherical chambers are
conceivable.
[0061] The evacuation chamber 14 is provided with an inlet 31 and a
drain or outlet 33. In the first embodiment, a first valve 35 is
associated with the inlet 31 to allow secondary water to enter the
chamber upon demand. A second valve 37 is associated with the drain
33 to enable concentrated solution to be flushed from the chamber
14 at the end of a batch process. The evacuation chamber 14 is also
provided with access means to enable maintenance of the interior of
the chamber 14. The access means may be provided by a removable
panel (not shown) or by removal of one of the ends 23 or 25. This
access may be used to remove scale and other solid material which
may be deposited from the secondary water.
[0062] The evacuation pump 16 is arranged to extract vapor from the
upper portion of the chamber 14. In the first embodiment, the
evacuation pump 16 is a venturi pump, and as is discussed below, a
venturi pump is particularly suitable for use in relation to the
invention. The venturi pump 40 comprises a venturi inlet 41, a
venturi outlet 43 and a narrowed venturi throat section 45
intermediate the venturi inlet 41 and the venturi outlet 43. In the
first embodiment, a port 47 connects the low pressure venturi
throat section 45 of the venturi pump 16 with the evacuation
chamber 14.
[0063] In operation, the venturi pump 16 evacuates the evacuation
chamber to a pressure below that of the vapor pressure of the
secondary water in the evacuation chamber 14. As a result the
secondary water is caused to boil at a relatively low temperature
that can be close to normal room temperature. This effect is of
course well known and is regularly demonstrated in secondary school
science classrooms. In such experiments, the venturi pump is
typically connected to a tap or valve of the mains water supply and
the water passing through the venturi pump causing the reduced
pressure is disposed to waste. In the present invention, it is
recognized that the water being expelled from the venturi pump
comprises not just the water that enters the venturi inlet 41 but
also water from the vapor that is withdrawn from the evacuation
tank through the port 47. Such vapor condenses almost immediately
upon entering the water stream flowing through the venturi throat
section 45. The first embodiment is therefore provided with a
receiving tank 50 having a tank inlet 51 connected by piping 52 to
the venturi outlet 43. A recirculation outlet 53 is provided
proximate the base of the receiving tank 50 which supplies primary
water (purified water) to a recirculation pump 55 which pumps
primary water to the venturi pump 40. The recirculation pump 55 is
selected to be of the size and type suitable to feed the venturi
pump 40 at the required pressure and flow rate. A water take off
port 57 is provided either as a separate outlet from the receiving
tank 50 or as a port from the piping 52 or otherwise to withdraw
water from the receiving tank 50 for use. The rate of withdrawal is
controlled to prevent the receiving tank from being emptied. To
this extent, the receiving tank can act as well as a storage tank
or alternatively storage means may be provided separately.
[0064] In operation, it can be seen that water is pumped from the
receiving tank 50 by the recirculation pump 55 to the venturi pump
16 and then returned to the receiving tank 50. In the process,
water is received into the stream from the water vapor extracted
from the evacuation tank 14. As is discussed below, it is possible
to achieve a take-up rate of about 1 part of water from the
evacuation tank to approximately 30 parts of water pumped through
the venturi pump 16. The system can therefore be sized according to
the volume of water to be withdrawn from the receiving tank 50.
[0065] It is to be appreciated that an apparatus according to the
first embodiment has removed the need for a conventional condenser
system within the distillation system. A condenser system has
typically been seen as an essential part of a distillation process
but in the first embodiment, the condensation takes place
inherently in the venturi pump 16. This has significant advantages
which are discussed later.
[0066] While the distillation system described does not require the
secondary water to be raised to a high temperature, it is to be
appreciated that the boiling process nonetheless requires the input
of heat energy to provide the latent heat of vaporization. The
advantage of the system is that while the energy must be provided,
because the evaporation system can be arranged to operate at or
near an ambient or normal temperature, a low grade heat source may
be used. For small units, the evacuation tank 14 may be configured
to withdraw sufficient energy from the atmosphere. In the first
embodiment, the cylindrical wall of the evacuation chamber 14 has a
corrugated profile to increase the surface area and thereby
facilitate the removal of heat from the atmosphere. In a further
adaptation, the external surface of the evacuation chamber is
painted black to promote the absorption of heat from the external
environment.
[0067] The temperature required in the secondary water depends
significantly upon the performance of the vacuum pump and in
particular the vacuum level achieved. At the same time, it is to be
appreciated that as the pressure, is reduced a greater volume of
vapor will be caused to boil off. In addition, it has been found by
testing and modeling that good performance of the venturi system
requires that the there be a significant, difference between the
temperature of primary water and the secondary water. The primary
water should be at least 15.degree. C. cooler than the secondary
water. Preferably, the primary water should be cooler than the
secondary water by 20.degree. C. or more.
[0068] It is desirable that the temperature of the secondary water
is in the vicinity of at least 40.degree. C. or more and therefore,
this embodiment can be suitable for a situation where the
surroundings can provide the latent heat energy from the
surroundings.
[0069] In some locations, secondary water is available that is
already at or above the desired operating temperature of the
secondary water. In these circumstances, the latent heat may be
provided simply by having a controlled, continuous flow of
secondary water through the evacuation chamber at a rate somewhat
above the rate of evaporation of vapor. This arrangement has the
added advantage that the level of concentration of the salts in the
secondary chamber is kept at a stable level which is not
substantially higher than that of the incoming secondary water.
This will significantly reduce the build-up of salt deposits in the
evacuation chamber and therefore reduce the maintenance
requirements of the chamber. For this latter reason, continuous
flow of the secondary water will be preferred even where the
secondary water is too cool, and additional heating must be added,
as in the second embodiment. In a sophisticated adaptation, a
feedback control system is incorporated to regulate the flow of
secondary water through the evacuation chamber to control the
temperature and/or the salt concentration to desired levels.
[0070] It will also be appreciated that the latent heat energy
contained within the water vapor will be added to the water flowing
through the venturi pump 16 at the time the water vapor condenses
into the flow stream. As discussed below, it is desirable that the
temperature of the primary water flowing into the venturi is
significantly below that of the secondary water, and in the
embodiment, the temperature is kept around 12.degree. C. In the
first embodiment, this heat energy is transferred to the receiving
tank where it is dispersed to the environment. If the receiving
tank also serves as a storage tank with a relatively large volume,
the temperature rise will be minor and easily dispersed. There are
many locations where this means of disposing of the heat will be
suitable. In other locations, it is practicable to disperse the
heat into the ground by passing outlet pipes through the ground
before the water is passed to storage. Other means of cooling will
be apparent to those skilled in the art where appropriate
circumstances apply.
[0071] A second embodiment takes cognizance of the energy flow that
is required and is adapted to facilitate those flows. The second
embodiment is described with reference to FIG. 2. The second
embodiment is substantially identical to the first embodiment, and
therefore, in the drawings, like features are denoted with like
numerals.
[0072] The second embodiment differs from the first embodiment by
the inclusion of a evaporation heat exchanger 60 positioned to be
within the secondary water in the evaporation chamber 14, or
otherwise associated with the evaporation chamber 14 to allow heat
flow from the evaporation heat exchanger 60 to the secondary water.
The evaporation heat exchanger 60 is provided with an exchanger
inlet 61 and an exchanger outlet 63. The exchanger inlet 61 is
supplied with exchanger fluid from a low grade heat source.
Examples of suitable heat sources are a solar heated pond, or water
heated from a geothermal source. The exchanger fluid exits through
the exchanger outlet 63 and returned to the heat source for
reheating. The rate of flow may be maintained to control the heat
input to the secondary water, or alternatively, the heat input to
the exchange fluid may be controlled at the heat source.
[0073] It is to be appreciated that the effectiveness of the
distillation system according to the embodiments depends upon the
effectiveness of the venturi in reducing pressure and drawing vapor
away. A conventional venturi is not efficient and therefore venturi
vacuum pumps are generally in use for other purposes with limited
application and only where efficiency is not of primary concern. It
would not be cost effective for the present applications. However,
an improved venturi is disclosed in Australian Provisional Patent
Application Serial No. 2010901506, filed Apr. 9, 2010 ("LOW
PRESSURE DISTILLATION SYSTEM"), which is entirely incorporated
herein by reference. The performance of this new venturi is a
substantial improvement over the performance of a conventional
venturi rendering the present invention economically viable.
[0074] Certain embodiments of the improved venturi comprise a
chamber having an inlet tube, an outlet tube and a vacuum port.
Such units therefore can be readily used in the first and second
embodiments. Other embodiments of the improved venturi do not have
a chamber and draw the gas or vapor directly from its surroundings.
Therefore a third embodiment of a distillation system is disclosed
which is adapted to incorporate a venturi as described. The third
embodiment is described with reference to FIG. 3. The third
embodiment is substantially similar to the first embodiment and so,
in the drawings, like numerals are used to denote like
features.
[0075] The difference between the third embodiment and the first
embodiment is that the venturi is placed inside the evacuation
chamber 14 proximate the upper end 23, rather than being outside
the evacuation chamber 14 and connected to the evacuation chamber
by port 47. In other respects the third embodiment is identical to
that of the first embodiment and will not be described further.
[0076] In a further adaptation of the third embodiment, a
filtration means is provided at the vapor entry into the venturi to
remove any liquid droplets and return them to the secondary water,
thereby avoiding contamination of the primary water. This water is
not returned to the venturi and therefore the heat rise due to
release of latent heat upon the absorption and condensation of the
vapor does not affect the operation of the venturi.
[0077] While development of the improved vacuum pumps is in its
infancy and many parameters of the configuration will vary the
performance, it is believed that there may be a maximum optimal
size for larger applications. If that is so, it is possible to
operate a plurality of venturis in parallel to remove a higher
volume of vapor. The invention is therefore scalable from small
domestic units to large systems suitable for reticulated supplies
of cities.
[0078] It will be appreciated that the second embodiment may be
modified in a manner similar to the adaptation of the third
embodiment.
[0079] In an adaptation of the first, second or third embodiments,
where a continuous stream of cold water is available, this stream
can be fed directly to the venturi as the primary water. This may
be the case for a supply of water for a town or city. Water being
supplied to consumers may be broken into several smaller streams
and passed through a plurality of venturi vacuum pumps associated
with one or more evacuation chambers. While the
condensation/absorption process will heat the water as discussed,
this will not usually be a problem, particularly in cold
environments where it may even be an advantage. In such
installations the water is often gravity fed, which removes the
need for a pump to pressurize the primary water entering the
venturi. If a low cost energy source is available to provide the
latent heat, the operating cost will be very low. The capital cost
will also be modest. Without recirculation, the amount of water
collected will only be small, around 5% to 8% of the primary water
presented, but there are many water authorities that would pleased
to obtain that level of increase in useable water at relatively
very low operating and capital cost. Of course the productivity may
be increased by introducing some recirculation. This could be
achieved by having a holding pond above the elevation of the
distillation system from which the primary water is supplied and a
certain proportion of the flow can be pumped into the holding pond.
This would all a water authority considerable flexibility. When
rain water is plentiful, no recirculation is required and a
percentage increase in supply is provided at minimal operating
cost. When supply is moderate, still adequate but less than needed
to keep the storage systems full, some recirculation can be
provided to maintain the storage system close to capacity. As
rainfall supply becomes low, so the storage supply is being
drained, recirculation can be increased to a more significant level
to slow the fall of storage levels but not to stop it. If a drought
occurs and storage levels become critical, recirculation can be
increased so that the distillation system provides almost the full
demand. Even where low-grade energy is only available to a limited
extent, the distillation cost will still be competitive with
alternative drought relief measures. It is worth noting that in
many places, times of drought risk coincide with time of high solar
energy availability (summer), so with an appropriate designed solar
energy system, modest energy cost will be available. In a normal
year, additional costs for pimping may be easily amortized and
offset against the times no pumping is required to maintain a very
economic water supply.
[0080] It can be seen that a distillation system according to the
embodiments described so far wherein a vacuum pump reduces the
pressure in an evacuation chamber causing secondary water therein
to boil and wherein the water vapor resulting is received directly
into primary water associated with the vacuum pump has advantages.
Due to direct removal of the water vapor into primary water, no
separate condensation unit is required. As well, the boiling occurs
at a temperature that is considerably lower than at normal
pressure, which means that the hazards are reduced significantly.
Also, as previously discussed, the heat required can be provided
from a low grade source at considerably reduced expense. Especially
for larger installations, the capital cost as well as the
maintenance and running costs will be considerably reduced over
those of competing technologies.
[0081] While the application has been discussed with respect to
water containing contaminants, pollution of dissolved salts, or to
mixtures such as water and heavy metals or water and sewage, the
systems described can be readily adapted to a much wider range of
mixtures including mixtures of liquids. Its use for the
distillation of ethanol from an ethanol water mixture is most
advantageous. Typically, when ethanol is obtained from crops such
as tapioca or corn, the processing results in a liquid mixture that
contains approximately 20% alcohol to 80% water. Conventionally,
this mixture is distilled at high temperature in a process that
requires considerable high grade energy and this affects the cost
of production. However, use of the distillation process as
described herein enables the high grade energy to be replaced by
low grade energy. In addition, the distillation process works in
reverse from the normal distillation process described for sea
water. Because the ethanol-water mixture is an azeotrope, the
secondary mixture in the evacuation chamber which starts at about
20% alcohol will be concentrated by the distillation process
towards the azeotropic concentration of approximately 96% ethanol.
The evacuation boiling process results in a certain amount of the
ethanol being evaporated as well as the water. This evaporated
ethanol is taken up by the primary water in the venturi and
therefore is not lost. While the ethanol concentration in the
primary water will be relatively low, the primary water can then be
utilized at an earlier stage of the production process so that the
ethanol will once again end up being distilled. Thus there is no
loss of product but a substantial reduction in energy costs is
achieved. Where, alcohol is required at a higher level of purity
than the azeotropic concentration, existing production techniques
can be used or adapted to raise the concentration further. It will
be appreciated that there are many other distillation processes
that can benefit from the application of the embodiments to those
processes.
[0082] The process so far has been described with reference to
distillation, but as mentioned before the vapor absorption process
has an effect that has other applications. In order to provide a
better understanding of the invention, a summary of the principles
of operation are given below.
[0083] 1. The salt water in the tank H1 is boiled off at extremely
low pressure. The low pressure is generated via the venturi effect
from the fresh water flow through the venturi C2. Pressures less
than 3 kPa are desirable and have been generated in testing. This
will allow the water to boil off at temperatures between
30-65.degree. C.
[0084] 2. As the water boils away from the salt water mixture
energy must be added to the system. Note if water is vaporized at a
rate of 1 ml/sec, 2.4 kW of power must be supplied to provide the
latent heat. Any available heat source may be used but low cost
power such as solar power or waste heat is preferred.
[0085] 3. The process is enabled by the low pressures generated by
the fresh water flow because of the efficient design of the
venturis used. The pressure within the evaporation tank H1 can
reach below 3 kPa. In addition, the fresh water flow should be cool
at approximately 10-20.degree. C. The temperature differential is
key to sustaining the boiling process. A temperature differential
of at least 20.degree. C. and preferably higher is desirable. If
the temperature of the fresh water flow stream approaches the
temperature of salt water in the tank, the fresh water flow
cavitates, greatly reducing the efficiency of the cycle.
[0086] 4. Fresh water vapor is entrained into the fresh water flow
at the venturi. Since the fresh water flow is much colder than the
water vapor, the water vapor immediately goes back into solution,
releasing significant heat.
[0087] 5. The fresh water stream at C3 is now significantly warmer
than and must be cooled. This may be accomplished by any
appropriate means available at the location, such as pumping the
water underground.
[0088] 6. Since the cycle boils the salt water at much lower
temperature, a heat source of lower quality (temperature) may be
used. It is believed that solar energy may be used in many
locations to maintain the temperature of the salt water in the
vicinity of 50.degree. C.
[0089] 7. Since we are using a lower quality heat source, the
energy input into the system from man-made sources is greatly
reduced, thereby increasing the efficiency of the system.
[0090] The requirement to have the primary water entering the
venturi vacuum to be at a temperature significantly lower than the
water in the evacuation chamber provides a significant limitation
to the system in certain applications. However, it has been found
that the primary liquid can be vegetable or other oil or other
immiscible chemicals or an oil-water mix. In this case the oil can
be at ambient temperature and does not need to be cooled to a
temperature below that of the sea water mixture in the evaporation
chamber. Therefore, a fourth embodiment is described with reference
to FIG. 4 which benefits from this advantage. The fourth embodiment
is similar to the second embodiment and so, in the drawings like
numerals are used to depict like features.
[0091] The significant difference between the fourth embodiment and
the second embodiment, and indeed the first embodiment also, is
that an oil is used as the primary liquid which is passed through
the venturi vacuum pump 16 rather than water. As the oil travels
through the venturi vacuum pump 16 it reduces pressure in the salt
water mixture in the evaporation chamber 14, and causes the
reservoir water to boil and vaporize in the manner as previously
disclosed with reference to the first and second embodiments.
Instead of being recycled directly, the resulting primary mixture
of oil and condensed water is passed to a separator inlet 73 of
separation means 71. The separation means 71 may take the form of a
settling tank or a cyclone or other device adapted to separate the
secondary water and oil. The oil is removed from the settling means
71 at oil outlet 75 and recirculated while the distilled water is
drawn off from water outlet 77. The primary mixture of oil and
condensed water is still heated from the latent heat when the water
condenses, but it is no longer essential to drop the temperature
below that of the water mixture in the evacuation tank. Therefore a
conventional heat exchanger 81 is provided which can remove the
heat of the heated oil to ambient surroundings, lowering the
temperature to only a little above ambient. With oil, the venturi
will still perform satisfactorily at this temperature. After
leaving the heat exchanger 51 the oil is either returned to
receiving tank 50 or indeed may be returned directly to the inlet
of the venturi vacuum pump. If used, the receiving tank 50 may only
be a holding tank with no cooling function at all, although in
certain applications further cooling may still be desirable.
[0092] It can be seen that the use of oil or the like expands the
applications of the invention.
[0093] The use of oil or similar as the primary liquid as in the
fourth embodiment allows a further adaptation which has a major
impact of the viability of the distillation system of the invention
for many applications. A fifth embodiment now describes that
adaptation with reference to FIG. 5. The fifth embodiment is very
similar to the fourth embodiment, and so, in the drawings, like
numerals are used to depict like features.
[0094] The fifth embodiment differs from the fourth embodiment by
routing the primary mixture of oil and condensed water which exits
from the venturi vacuum pump 16 to the inlet 61 of the evaporation
heat exchanger 60 associated with the evaporation chamber 14. When
the fluid exits from the evaporation heat exchanger 60 at outlet 62
it passes to the separation means 71 where the water and oil are
separated, as in the fourth embodiment.
[0095] The advantage of the fifth embodiment is that a substantial
portion of the latent heat required for vaporization in the
evacuation chamber is supplied by the latent heat returned to the
oil/water mixture when the water condenses. Fundamentally, the
latent heat required for vaporization is equal to the latent heat
returned to oil/water mixture when the vapor condenses. The
effectiveness will depend upon the extent to which the latent heat
can be extracted by the evaporation heat exchanger 60. With a high
efficiency heat exchanger, a small temperature difference can
sustain extraction of a substantial percentage of the latent
heat.
[0096] It is not possible to extract all energy from the oil/water
mixture and therefore a supplementary heat exchanger 65 having an
inlet 67 and an outlet 69 is provided to receive energy from a
suitable source to provide the additional energy not taken from the
evaporation heat exchanger. However, with appropriate selection of
an oil and an appropriate design of the venturi vacuum pump the
percentage of energy required to be provided by the secondary heat
exchanger 65 will be relatively small, so that the overall
efficiency of the system is high. In operation, the equilibrium of
the system can be controlled by the extent of energy input from the
supplementary heat exchanger 65. This can be controlled by
adjusting the temperature of the fluid passing through the
supplementary heat exchanger 65 as well as the flow rate of that
fluid. Crucially, the effectiveness of system will depend upon the
extent that the performance of the venturi will be maintained where
the temperature of the primary liquid is above the temperature of
the liquid being evaporated. With the first three embodiments, the
performance deteriorates drastically so that operation of the
system collapses. But as discussed, where oil is used the venturi
performance continues. Choice of primary liquid will therefore be
an important criteria when the system is used for the distillation
of other liquids.
[0097] Up until this point of the description, a system has been
described wherein a liquid is distilled by generating a substantial
vacuum. To support the process, except for the fifth embodiment,
significant amounts of energy must be transferred into the liquid
to be distilled in order to supply the latent heat of vaporization.
Providing this heat at reasonable cost is a key factor to the
commercial viability of the distillations systems that have been
described. But, of course, the transfer of heat is frequently an
object in its own right. It is the basis of all air conditioning
and refrigeration systems. Therefore a sixth embodiment of the
invention is described. This system is used as a heat transfer
system although it is only a minor adaptation of the fourth
embodiment. The embodiment of the heat transfer system is now
described with reference to FIG. 6 and the distillation system of
the second embodiment. As shown in FIG. 6, the heat transfer system
111 comprises an evacuation chamber 112 adapted to hold a body of a
refrigerating liquid 114. One or more high performance venturi
vacuum pumps 116 are associated with the chamber 112 by connection
means 118 to reduce the pressure within the evacuation chamber 112
to cause boiling of the refrigerating liquid 114 and thereby
vaporization. The vapor derived is drawn off by the venturi vacuum
pump through the connection means 118 in a manner similar to that
of the embodiments of the distillation system previously described.
As in the second embodiment of the distillation system, a first
heat exchanger 120 is associated with the evacuation chamber 112 to
provide relatively warm fluid to the heat exchanger 120 to supply
the heat which is surrendered to the refrigerating liquid 114 to
provide the latent heat of vaporization. In the process, the heat
exchange fluid is cooled and this cooled fluid can be circulated to
a remote heat exchanger, for air conditioning, refrigeration or the
like.
[0098] While the principle of operation is the same as for the
distillation system, certain details differ because the object is
not to draw off a purified liquid but to transfer heat. The system
is therefore configured to recycle the liquid that is evaporated
back to the evaporation chamber. The liquid in the evaporation
chamber is therefore a refrigerant and certain co-fluids have been
found to be particularly suitable, amongst them acetone/water
methanol/water and linoleic acid/methanol. For the remainder of the
discussion of this embodiment, the use of water/methanol will be
discussed. In that case, the refrigerating liquid is methanol and
the primary liquid is water. Optionally, a supply of water is
stored in container 122. Water from the container 122 is pumped by
pump 124 at a relatively low pressure in the order of 200 kPa to
the venturi vacuum pump 116. The reduced pressure generated by the
venturi as the primary water flows through it causes methanol in
the evaporation container to boil and the vapor to be conveyed to
the venturi where it is absorbed into the primary water and
condenses to liquid almost instantaneously. Again, latent heat is
released into the water/methanol mixture causing the temperature of
the mixture to rise. The water/methanol mixture exits the venturi
and is conveyed to a separating means 126. At the separating means
126, the methanol is separated from the water and then drawn off.
At this time, the water and methanol are at raised temperature.
After being removed from the separating means 126, water is passed
to a primary loop heat exchanger 128 to release heat to the
environment. As the temperature of the water does not need to be
reduced below ambient, a simple heat exchanger will suffice. As
well, the methanol is heated and preferably this also passes
through a methanol heat exchanger 130 before being returned to the
evaporation chamber 112. As an alternative to the provision of a
primary loop heat exchanger and a methanol heat exchanger, a single
heat exchanger may be provided before the separating means to cool
the water/methanol mixture. While this arrangement is preferable
because of the use of a single heat exchanger, it may introduce
problems with certain fluid mixtures. In either case, there will be
applications where the heat energy is used for heating purposes by
appropriate use of the heat exchanger. A valve means 132 between
the methanol heat exchanger and the evaporation chamber 112 (or
separating means 126 and evaporation chamber 112 if there is no
methanol heat exchanger) controls the return of methanol to the
evaporation chamber 112.
[0099] Just as with existing heat transfer systems the many
adaptations are possible, so it is with the present embodiment. The
lessons of existing heat exchange systems will remain applicable to
the present embodiment. In certain adaptations, a primary liquid
and secondary liquid are of the same substance and evacuation
chamber and venturi vacuum pump form a closed system.
[0100] A heat transfer system comprising an evacuation chamber
adapted to receive a first liquid, at least one venturi vacuum pump
associated with the evacuation 5 chamber to cause, in use, the
pressure within the evacuation chamber to be reduced to promote
vaporization of liquid in the chamber, and a first heat exchanger
having a fluid pathway for a heat exchange fluid to pass through
the first heat exchanger and being associated with the evacuation
chamber to provide heat to the first liquid in the chamber to
support the vaporization and 10 thereby to cool the heat exchange
fluid.
[0101] It will be recognized that many modification and adaptations
may be made to the embodiments described while remaining within the
scope of the invention. It is to be understood that all such
modifications and adaptations are to be considered as being within
the scope of the inventions described.
[0102] Throughout the specification and claims, unless the context
requires otherwise, the word "comprise" or variations such as
"comprises" or "comprising", will be understood to imply the
inclusion of a stated integer or group of integers but not the
exclusion of any other integer or group of integers.
[0103] While preferred embodiments of the present invention have
been shown and described herein, it will be obvious to those
skilled in the art that such embodiments are provided by way of
example only. Numerous variations, changes, and substitutions will
now occur to those skilled in the art without departing from the
invention. It should be understood that various alternatives to the
embodiments of the invention described herein may be employed in
practicing the invention. It is intended that the following claims
define the scope of the invention and that methods and structures
within the scope of these claims and their equivalents be covered
thereby.
* * * * *