U.S. patent application number 13/292381 was filed with the patent office on 2012-05-17 for adsorption chilling for compressing and transporting gases.
This patent application is currently assigned to EXXONMOBIL RESEARCH AND ENGINEERING COMPANY. Invention is credited to Ian A. CODY, Bhupender S. MINHAS.
Application Number | 20120118004 13/292381 |
Document ID | / |
Family ID | 45092396 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120118004 |
Kind Code |
A1 |
MINHAS; Bhupender S. ; et
al. |
May 17, 2012 |
ADSORPTION CHILLING FOR COMPRESSING AND TRANSPORTING GASES
Abstract
A gas transport system including a conduit (e.g., a pipeline)
containing a feed of a gas at a first temperature and first
pressure, a source of a refrigerant from an adsorption system in
thermal communication with the conduit to cool the feed of gas to a
reduced temperature, and at least one compressor to receive the
cooled feed of gas and increase the amount of cooled feed of gas to
a second pressure, in which the second pressure is greater than the
first pressure.
Inventors: |
MINHAS; Bhupender S.;
(Bridgewater, NJ) ; CODY; Ian A.; (Adelaide,
AU) |
Assignee: |
EXXONMOBIL RESEARCH AND ENGINEERING
COMPANY
Annandale
NJ
|
Family ID: |
45092396 |
Appl. No.: |
13/292381 |
Filed: |
November 9, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61413122 |
Nov 12, 2010 |
|
|
|
Current U.S.
Class: |
62/476 |
Current CPC
Class: |
F17C 2260/04 20130101;
F17C 2227/0157 20130101; F17C 5/06 20130101; Y02C 20/40 20200801;
F17C 2225/035 20130101; F17C 2225/0123 20130101; F17C 2223/033
20130101; F17C 9/00 20130101; F17C 2227/0339 20130101; F17C
2227/039 20130101; F17C 2223/0123 20130101; F17C 2221/013 20130101;
Y02C 10/00 20130101; F17C 2270/0155 20130101 |
Class at
Publication: |
62/476 |
International
Class: |
F25B 15/00 20060101
F25B015/00 |
Claims
1. A gas transport system comprising: (a) a conduit containing a
feed of a gas at a first temperature and first pressure; (b) a
source of a refrigerant from an adsorption system in thermal
communication with the conduit to cool the feed of gas to a reduced
temperature; and (c) at least one compressor to receive the cooled
feed of gas and increase the amount of cooled feed of gas to a
second pressure, wherein the second pressure is greater than the
first pressure.
2. The gas transport system of claim 1, wherein the adsorption
system includes, (i) an adsorbent capable of adsorbing the
refrigerant and in fluid communication with the refrigerant; (ii) a
heating source to heat the adsorbent and desorb the refrigerant
therefrom; and (iii) an expansion valve to receive a supply of the
refrigerant that has been desorbed from the adsorbent.
3. The gas transport system of claim 2, wherein the adsorption
system further includes a cooling source to cool the adsorbent and
adsorb the refrigerant.
4. The gas transport system of claim 1, wherein the gas is a
greenhouse gas.
5. The gas transport system of claim 4, wherein the greenhouse gas
is carbon dioxide.
6. The gas transport system of claim 4, further comprising a
subterranean outlet to receive and sequester the greenhouse
gas.
7. The gas transport system of claim 6, wherein the subterranean
outlet to receive and sequester the greenhouse gas includes a
hydrocarbon deposit.
8. The gas transport system of claim 5, wherein the feed of the
carbon dioxide is obtained, at least in part, from an exhaust
gas.
9. The gas transport system of claim 8, further comprising a
pre-transport adsorption system to selectively adsorb carbon
dioxide from the exhaust gas to obtain upon desorption the feed of
the carbon dioxide at the first temperature and first pressure.
10. The gas transport system of claim 5, wherein the refrigerant is
carbon dioxide.
11. The gas transport system of claim 1, wherein the heat source
includes a supply of heating fluid in thermal communication with
the feed of gas exiting the compressor to heat the heating fluid,
wherein the feed of gas exiting the compressor is at a second
temperature, the second temperature greater than the reduced
temperature.
12. The gas transport system of claim 1, wherein the adsorbent is
selected from zeolites, zeolitic imidazolate frameworks (ZIFs),
Metal-Organic Frameworks (MOFs), and any combination thereof.
13. The gas transport system of claim 1, wherein a series of at
least two compressors are provided to pressurize the feed of gas to
an increased pressure.
14. The gas transport system of claim 13, wherein the refrigerant
is introduced downstream of a first compressor and upstream of a
second compressor to cool the feed of gas prior to entering the
second compressor.
15. A method of transporting a gas comprising: (a) providing a
conduit containing a feed of a gas at a first temperature and first
pressure; (b) directing a source of a refrigerant from an
adsorption system to the conduit to thermally communicate with the
conduit and cool the feed of gas to a reduced temperature; and (c)
introducing the cooled feed of gas to at least one compressor to
increase the amount of cooled feed of gas to a second pressure,
wherein the second pressure is greater than the first pressure.
16. The method of transporting a gas of claim 15, wherein the
adsorption system includes (i) an adsorbent capable of adsorbing
the refrigerant and in fluid communication with the refrigerant;
(ii) a heating source to heat the adsorbent and desorb the
refrigerant therefrom; and (iii) an expansion valve to receive a
supply of the refrigerant that has been desorbed from the
adsorbent.
17. The method of transporting a gas of claim 16, wherein the
adsorption system further includes a cooling source to cool the
adsorbent and adsorb the refrigerant.
18. The method of transporting a gas of claim 15, wherein the gas
is a greenhouse gas.
19. The method of transporting a gas of claim 18, wherein the
greenhouse gas is carbon dioxide.
20. The method of transporting a gas of claim 18, further
comprising introducing the greenhouse gas at the second pressure to
a subterranean outlet to receive and sequester the supply of the
greenhouse gas.
21. The method of transporting a gas of claim 20, wherein the
subterranean outlet to receive and sequester the supply of the
greenhouse gas includes a hydrocarbon deposit.
22. The method of transporting a gas of claim 19, wherein the feed
of the carbon dioxide is obtained, at least in part, from an
exhaust gas.
23. The method of transporting a gas of claim 22, further
comprising selectively adsorbing carbon dioxide from the exhaust
gas in an adsorption system to obtain upon desorption the feed of
the carbon dioxide at the first temperature and first pressure.
24. The method of transporting a gas of claim 19, wherein the
refrigerant is carbon dioxide.
25. The method of transporting a gas of claim 15, wherein the heat
source includes a supply of heating fluid in thermal communication
with the feed of gas exiting the compressor to heat the heating
fluid, wherein the feed of gas exiting the compressor is at a
second temperature, the second temperature greater than the reduced
temperature.
26. The method of transporting a gas of claim 15, wherein the
adsorbent is selected from zeolites, zeolitic imidazolate
frameworks (ZIFs), Metal-Organic Frameworks (MOFs), and any
combination thereof.
27. The method of transporting a gas of claim 15, wherein a series
of at least two compressors are provided to obtain the pressurized
source of gas.
28. The method of transporting a gas of claim 27, wherein the
refrigerant is introduced downstream of a first compressor and
upstream of a second compressor to cool the feed of gas prior to
entering the second compressor.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application relates and claims priority to U.S.
Provisional Patent Application No. 61/413,122, filed on Nov. 12,
2010.
FIELD
[0002] The present invention relates to methods and systems of
employing an adsorption process to cool a gas in the process of
being compressed or transported. These methods and systems are
particularly applicable to greenhouse gas sequestration efforts,
such as for use in carbon dioxide sequestration.
BACKGROUND
[0003] Gas is transported in a variety of ways for a variety of
needs. For example, natural gas often must be transported a great
distance from a source to substations and/or consumers.
Furthermore, it is often necessary or beneficial to compress a gas
for transportation or subsequent treatment. For example, during
carbon capture and sequestration efforts, gases must be compressed
and transported by pipeline or conduit to a remote location. This
is particularly relevant in refineries and the like since carbon
sequestration could play a significant role in helping to reduce
CO.sub.2 emission from the use of fossil fuels. To achieve this
high pressure, it often may be necessary to use a multi-stage
compression technique, as compressors have a limited compression
ratio. Furthermore, although the use of multi-stage compressors can
adequately increase the pressure of CO.sub.2, this process can also
increase the temperature of CO.sub.2 to unacceptable levels. If the
temperature at intermediate compression stages can be reduced, it
can significantly increase the moles of CO.sub.2 being compressed
by the next stage, thus increasing the efficiency of the
process.
[0004] Accordingly, there remains a need to cool gas streams that
are transported with the aid of compressors. Preferably, the
cooling can be provided with little to no operating costs and can
take advantage of resources provided by the conduit or pipeline
itself.
SUMMARY
[0005] According to one aspect of the present application, a gas
transport system is provided. The gas transport system includes a
conduit (e.g., a pipeline) containing a feed of a gas at a first
temperature and first pressure, a source of a refrigerant from an
adsorption system in thermal communication with the conduit to cool
the feed of gas to a reduced temperature, and at least one
compressor to receive the cooled feed of gas and increase the
cooled feed of gas to a second pressure, in which the second
pressure is greater than the first pressure.
[0006] According to another aspect of the present application, a
method of transporting a gas is provided. The method of
transporting the gas includes providing a conduit containing a feed
of a gas at a first temperature and first pressure, directing a
source of a refrigerant from an adsorption system to the conduit to
thermally communicate with the conduit and cool the feed of gas to
a reduced temperature, and introducing the cooled feed of gas to at
least one compressor to increase the cooled feed of gas to a second
pressure, in which the second pressure is greater than the first
pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic representation of a multi-stage
compression system for carbon dioxide sequestration, along with
possible points in which inter-stage adsorption chilling can be
applied to cool the compressed gas and improve compressor
performance downstream.
[0008] FIG. 2 is a schematic representation of the multi-stage
compression system of FIG. 1, in which an adsorption system
refrigerant is used to cool the transported gas via a heat
exchanger.
DETAILED DESCRIPTION
Definitions
[0009] As used herein, the term "fluid" refers to a liquid or gas
that can reversibly bind to the adsorbent, in a chemical or
physical sense. Because the fluid is generally directed to an
expansion valve, or other apparatus to provide a cooled fluid
stream, the term "refrigerant" can generally be used
interchangeably with the term "fluid."
[0010] As used herein, the term "vessel" refers to an enclosed
container suitable for containing an absorbent and a fluid under
suitable conditions to permit adsorption and desorption.
[0011] As used herein, an "exhaust gas" includes any gas that is
emitted from a process (e.g. an industrial process) or combustion
operation.
[0012] As used herein, the term "flue gas" refers to a gas that is
emitted from combustion operation and which is directly or
indirectly emitted to the atmosphere (e.g., via a flue, stack, pipe
or other conduit). A flue gas includes gases emitted from furnaces,
boilers, ovens and combustion operations associated with
petrochemical refining or chemical processing operations. Flue gas
is also intended to include turbine exhausts.
[0013] As used herein, the term "unutilized heat" or "unutilized
heat source" refers to the residual or remaining heat source (e.g.,
steam) remaining 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 any use in the
refining and/or petrochemical processing operation and would
traditionally be discarded. The unutilized heat can be provided as
a 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. Flue gases
are an effective waste heat source.
[0014] As used herein, the term "pump" refers to a device to assist
in transporting fluids from one place to another.
[0015] According to one aspect of the present application, a gas
transport system is provided. The gas transport system includes a
conduit containing a feed of a gas at a first temperature and first
pressure, a source of a refrigerant from an adsorption system in
thermal communication with the conduit to cool the feed of gas to a
reduced temperature, and at least one compressor to receive the
cooled feed of gas and increase the cooled feed of gas to a second
pressure, in which the second pressure is greater than the first
pressure.
[0016] According to one embodiment, the conduit contains a feed of
a greenhouse gas, such as carbon dioxide. Particularly in those
embodiments in which the gas is a greenhouse gas, the system can
further include a subterranean outlet to receive and sequester the
greenhouse gas. The subterranean outlet can further include a
hydrocarbon deposit. In addition to sequestering the greenhouse
gas, introducing the greenhouse gas to the subterranean outlet can
also aid in the extraction of the hydrocarbon deposit.
[0017] The gas, particularly for example, a greenhouse gas such as
carbon dioxide, can be obtained, at least in part, from an exhaust
gas (e.g., a flue gas), including exhaust gases from petrochemical
refining operations. In one embodiment, a pre-transport adsorption
system is provided that selectively adsorbs the carbon dioxide from
the exhaust gas to selectively adsorb carbon dioxide from the
exhaust gas to obtain the feed to the gas transport system. Further
details of this method are described in co pending U.S. patent
application Ser. No. ______, which claims priority to U.S.
Provisional Patent Application No. 61/413,111 filed on Nov. 12,
2010, entitled "Recovery of Greenhouse Gas and Pressurization for
Transport", which is hereby incorporated by reference in its
entirety.
[0018] In one embodiment, the adsorption system includes an
adsorbent capable of adsorbing the refrigerant and in fluid
communication with the refrigerant, a heating source to heat the
adsorbent and desorb the refrigerant therefrom, and an expansion
valve to receive a supply of the refrigerant that has been desorbed
from the adsorbent. In a preferred embodiment, the adsorption
system further includes a cooling source to cool the adsorbent and
adsorb the refrigerant. The adsorbents used in the adsorption
system can be selected from, for example, zeolites, zeolitic
imidazolate frameworks (ZIFs), Metal-Organic Frameworks (MOFs), and
any combination thereof.
[0019] In certain embodiments, the adsorption system makes use of
the existing gas pipeline infrastructure to achieve additional
efficiencies. For example, when the gas to be transported is carbon
dioxide, the refrigerant can also be carbon dioxide. Thus, a supply
of refrigerant for the adsorption system can be readily obtained
from the pipeline itself. In an alternative embodiment, the heat
source includes a supply of heating fluid in thermal communication
with the feed of gas exiting the compressor to heat the heating
fluid. The heating fluid is heated since the feed of gas exiting
the compressor is at higher temperature, thereby also lowering the
temperature of the gas in the conduit.
[0020] In one embodiment, a series of at least two compressors are
provided to obtain the pressurized source of greenhouse gas. The
refrigerant can be introduced to the gas downstream of a first
compressor and upstream of a second compressor so as to exchange
heat with the gas exiting the first compressor and cool the gas
prior to entering the second compressor.
[0021] Another aspect of the present application provides a method
of transporting a gas. The method includes providing at least one
pipeline containing a supply of a gas, obtaining a source of a
refrigerant from an adsorption system, introducing the refrigerant
to the supply of gas, and introducing at least a portion of the
supply of the gas to at least one compressor to obtain a
pressurized source of gas.
[0022] The method will be understood from, and described in further
detail with the description of the system.
[0023] Generally, and solely for exemplary purposes of
illustration, an adsorption chilling system is described that
include adsorbents (e.g., MOF/ZIFs/Zeolites) that adsorb a
refrigerant (e.g., CO.sub.2) at lower temperature (T2) and lower
pressure (P2). The adsorbent bed is heated to release adsorbed
working fluid (i.e., the refrigerant) in a contained vessel. The
heat used can be, for example, heat from compressed CO.sub.2,
exhaust of turbines being used for compressors or some other waste
heat. Alternatively, a dedicated steam source can be employed to
provide heat to drive the desorption stroke. Desorption increases
the pressure of the released working fluid to P1 (>P2). The
pressurized working fluid is introduced to an expansion valve for
adiabatic expansion to pressure P2 and to reduce temperature to T3.
Chilled working fluid (i.e., refrigerant) can be used to chill
compressed gas, such as greenhouse gas like CO.sub.2, at one (or
more) of the intermediate stages of CO.sub.2 compression.
[0024] For purposes of illustration, and not limitation, an
exemplary multi-stage compression system (100) for carbon dioxide
sequestration is shown in FIG. 1. A feed of carbon dioxide (10) is
provided. This feed can be obtained, for example, from an
industrial flue gas based on the techniques disclosed in co pending
U.S. patent application Ser. No. ______, which claims priority to
U.S. Provisional Patent Application No. 61/413,111, which is,
hereby incorporated by reference in its entirety. This feed is
directed, via a conduit (e.g., pipeline (15)) to a series of
compressors (20, 30, 40) which yield successively higher-pressure
carbon dioxide (e.g., to a few thousand psi) for eventual
sequestration, for example, in a subterranean deposit. After each
compression stage, however, the temperature of the gas is
increased, which in turn, reduces the amount of molecules that can
be compressed by the next compressor. Accordingly, interstage
adsorption chilling can be provided via, for example, heat
exchangers (not shown), such as air fin heat exchangers, at
locations 25 and 35.
[0025] As shown in FIG. 2, an adsorption bed (110) is provided,
that contains tubes packed with adsorbents (e.g.,
MPFs/MOFs/ZIFs/Zeolites/Carbon). The adsorption bed is adapted to
receive either a feed of heat (e.g., steam) (120) or cold water
(130). During an adsorption stroke, the adsorption bed is provided
with a feed of cold water and the adsorbents adsorb refrigerant
(e.g., CO.sub.2). The cold water supply is valved off, and a feed
of heat is then fed to the adsorption bed to heat the adsorbent bed
to release adsorbed refrigerant. The present invention is not
intended to be limited to the use of packed tubes; rather, other
beds and arrangements are well within the scope of the present
invention provided such arrangements are capable of receiving
either a feed of heat or cold water.
[0026] During the desorption stroke, the temperature of the
desorbed refrigerant is increased. The pressurized refrigerant is
introduced to a heat exchanger (140) to reduce the temperature of
the refrigerant. After exiting the heat exchanger, the refrigerant
(145) is introduced to an expansion valve (150) to provide a cold
refrigerant stream that can be applied, via a heat exchanger (160),
for interstage cooling of a multi-stage compression carbon dioxide
system in which carbon dioxide is transported at high pressure for
eventual sequestration and/or to enhance downhole crude oil
recovery (see FIG. 1).
[0027] The adsorption system shown in FIG. 2 is equipped with a
second adsorption bed (170), also adapted to receive a feed of
either heat (180) or cold water (190). Having two adsorption beds
in parallel allows one adsorption bed to be regenerated (adsorption
stroke) while the other adsorption bed is in the desorption
stroke.
[0028] As shown in FIG. 2, adsorption chilling which has no moving
parts can be used for inter-stage cooling of compressed CO.sub.2.
FIG. 2, for purposes of simplicity, shows only one intermediate
stage for cooling, however, adsorption chilling could be used after
each intermediate stage for cooling the compressed CO.sub.2. In
certain embodiments, the adsorption chilling process can be
employed without use of a pump.
Gases Being Transported
[0029] The systems and methods of the presently disclosed subject
matter can be used to cool any gas that is being transported (e.g.,
in a pipeline). For example, gases being transported in a pipeline
are often compressed via one or more compressors. As compressors
have a limited compression ratio, a typical gas pipeline employs
multiple compressors. The multi-stage compression compresses the
gas to, for example, several thousand psi. Compressors increase the
pressure of the gas (e.g., CO.sub.2), but in this process, it also
increases the temperature of the gas. If the temperature of the gas
at an intermediate stage can be reduced, it can significantly
increase the amount of moles of gas being compressed by the next
stage compressor.
[0030] Accordingly, one embodiment of the presently disclosed
subject matter employs an adsorption process to provide inter-stage
cooling of a gas that is in the process of being transported. In
other words, in certain embodiments, the cooling from an adsorption
process is applied downstream from one compressor, but upstream
from a second compressor to, among other things, increase the
amount of gas that can be processed by the second compressor.
[0031] While not necessarily limited thereto, the systems and
methods of the presently disclosed subject matter are particularly
useful to cool greenhouse gases that are in the process of being
transported for purposes of sequestration. Alternatively, or
additionally, the greenhouse gases that are being transported can
be deposited in subterranean natural resource reserves to aid in
the extraction of oil, for example, or natural gas.
[0032] A person of ordinary skill in the art can determine
procedures for the sequestration of greenhouse gases (e.g., carbon
dioxide), once the greenhouse gas is transported to a proper
location. Furthermore, sequestration details can be found, for
example, in U.S. Pat. Nos. 7,726,402, and 7,282,189, each of which
hereby incorporated by reference. Further details regarding
techniques for depositing gases downhole to aid in the recovery of
crude oil and/or natural gas can be found, for example, in U.S.
Published Application No. 2007/0215350, hereby also incorporated by
reference.
[0033] Accordingly, an adsorption process can be used to cool, for
example, carbon dioxide, methane, nitrous oxides, ozone,
chlorofluorocarbons, and other greenhouse gases for which
sequestration is desirable. In a preferred embodiment, the gas that
is being transported is carbon dioxide.
Adsorbents
[0034] Adsorbents that can be used in embodiments of the present
invention include, but are not limited to, metal-organic
framework-based (MOF-based) sorbents, zeolitic imidazole framework
(ZIF) sorbent materials, zeolites and carbon.
[0035] MOF-based adsorbents include, but are not limited to,
MOF-based adsorbents 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), and
beryllium (Be). 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.
[0036] Specific materials MOF-based adsorbent 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; and IRMOF-8, a
material having a general formula of Zn.sub.4O(2,6 naphthalene
dicarboxylate).sub.3.
[0037] 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.
[0038] 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.
[0039] 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).
[0040] 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.68TMA.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).
[0041] 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.
[0042] Synthetic zeolite adsorbent 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 13 X product.
Fluids/Refrigerants
[0043] Non-limiting examples of fluids that can be used in
accordance with the present application include, but are not
limited to, carbon dioxide, methane, ethane, propane, butane,
ammonia and freon. As noted above, certain embodiments make use of
the gas that is being transported. For example, when carbon dioxide
is being transported for sequestration, carbon dioxide can also be
used as the fluid (i.e. refrigerant) in the adsorption process to
provide, for example, inter-stage cooling.
Selection of Sorbent Materials and Fluids/Refrigerants
[0044] As disclosed in U.S. Published Application No. 2010/0132359,
hereby incorporated by reference, a "pressure index" can be
determined at various desorbing temperatures and can be used to
select the sorbent material and refrigerant (i.e., the adsorption
system working fluid). 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 inside pressure and
temperature. The vessel is flushed and filled with 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 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). 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.
[0045] Certain embodiments of the present application make use of
lower temperature, unutilized heat (also referred to as waste
heat). In order to select a sorbent material/fluid combination that
can be used with, for example, relatively low grade waste heat,
adsorbents and refrigerants can be selected with minimum pressure
indexes, as defined above. In one embodiment the adsorbent and
refrigerant are selected such that the pressure index is at least
1.2, or at least 1.5, or at least 3, or at least 4, or at least
6.
[0046] While not limited thereto, U.S. Published Application No.
2010/0132359 discloses details regarding an embodiment in which
carbon dioxide is used as a working fluid and Zeolite 13 X is used
as the adsorbent. Other appropriate adsorbents can be selected
based on, for example, the working fluid (refrigerant) employed and
the heat available to drive the desorption stroke.
[0047] The present invention 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.
[0048] It is further to be understood that all values are
approximate, and are provided for description.
[0049] 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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