U.S. patent application number 13/509044 was filed with the patent office on 2013-03-14 for refrigerant storage in secondary loop refrigeration systems.
This patent application is currently assigned to E.I. DU PONT DE NEMOURS AND COMPANY. The applicant listed for this patent is Mark Brandon Shiflett, Akimichi Yokozeki. Invention is credited to Mark Brandon Shiflett, Akimichi Yokozeki.
Application Number | 20130061612 13/509044 |
Document ID | / |
Family ID | 43992374 |
Filed Date | 2013-03-14 |
United States Patent
Application |
20130061612 |
Kind Code |
A1 |
Shiflett; Mark Brandon ; et
al. |
March 14, 2013 |
REFRIGERANT STORAGE IN SECONDARY LOOP REFRIGERATION SYSTEMS
Abstract
A process and system for storing and recovering a secondary
refrigerant such as carbon dioxide in a secondary loop
refrigeration system after a shutdown of the primary refrigeration
system using ionic liquids is described. The process eliminates the
release of the secondary refrigerant into the environment and the
need to recharge the secondary loop after a shutdown of the primary
refrigeration system.
Inventors: |
Shiflett; Mark Brandon;
(Wilmington, DE) ; Yokozeki; Akimichi;
(Wilmington, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shiflett; Mark Brandon
Yokozeki; Akimichi |
Wilmington
Wilmington |
DE
DE |
US
US |
|
|
Assignee: |
E.I. DU PONT DE NEMOURS AND
COMPANY
Wilmington
DE
|
Family ID: |
43992374 |
Appl. No.: |
13/509044 |
Filed: |
November 10, 2010 |
PCT Filed: |
November 10, 2010 |
PCT NO: |
PCT/US2010/056227 |
371 Date: |
May 10, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61260369 |
Nov 11, 2009 |
|
|
|
Current U.S.
Class: |
62/77 ;
62/498 |
Current CPC
Class: |
F25B 45/00 20130101;
F25D 17/02 20130101; F25B 25/005 20130101; F25B 2500/27 20130101;
F25B 1/00 20130101; F25B 2309/06 20130101; C09K 5/047 20130101 |
Class at
Publication: |
62/77 ;
62/498 |
International
Class: |
F25B 45/00 20060101
F25B045/00; F25B 1/00 20060101 F25B001/00 |
Claims
1. In a secondary loop refrigeration system that comprises a
primary refrigeration loop containing a primary refrigerant, a
secondary refrigeration loop containing a secondary refrigerant,
and a heat exchanger contacted by both the primary and secondary
refrigeration loops, a method of storing secondary refrigerant,
comprising (a) flowing at least a portion of the secondary
refrigerant from the secondary loop to an auxiliary container; and
(b) absorbing at least a portion of the flowed secondary
refrigerant with an ionic liquid in the auxiliary container to form
a mixture thereof.
2. A method according to claim 1 further comprising a step of
separating the second refrigerant from an ionic liquid, and flowing
the separated secondary refrigerant from the auxiliary container
back into the secondary loop.
3. A method according to claim 1 wherein separating the secondary
refrigerant from an ionic liquid comprises heating the mixture of
the ionic liquid and absorbed secondary refrigerant.
4. A method according to claim 1 further comprising a step of
compressing the primary refrigerant.
5. A method according to claim 1 further comprising a step of
absorbing the prim ref in an ionic liquid.
6. A method according to claim 1 wherein the secondary refrigerant
comprises carbon dioxide.
7. A method according to claim 1 wherein an ionic liquid comprises
a cation selected from the group consisting of cations represented
by the structures of the following formulae: ##STR00003## wherein:
A) R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.12
and R.sup.13 are independently selected from the group consisting
of: (vii) H, (viii) halogen, (ix) --CH.sub.3, --C.sub.2H.sub.5, or
C.sub.3 to C.sub.25 straight-chain, branched or cyclic alkane or
alkene, optionally substituted with at least one member selected
from the group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (x)
--CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.25
straight-chain, branched or cyclic alkane or alkene comprising one
to three heteroatoms selected from the group consisting of O, N, Si
and S, and optionally substituted with at least one member selected
from the group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH;
(xi) C.sub.6 to C.sub.20 unsubstituted aryl, or C.sub.3 to C.sub.25
unsubstituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
(xii) C.sub.6 to C.sub.25 substituted aryl, or C.sub.3 to C.sub.25
substituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and wherein said substituted aryl or substituted heteroaryl has one
to three substituents independently selected from the group
consisting of: (A) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to
C.sub.25 straight-chain, branched or cyclic alkane or alkene,
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, (B) OH, (C)
NH.sub.2, and (D) SH; and (vii)
--(CH.sub.2).sub.nSi(CH.sub.2).sub.mCH.sub.3,
--(CH.sub.2).sub.nSi(CH.sub.3).sub.3,
--(CH.sub.2).sub.nOSi(CH.sub.3).sub.m, where n is independently 1-4
and m is independently 0-4; B) R.sup.7, R.sup.8, R.sup.9, and
R.sup.10 are independently selected from the group consisting of:
(viii) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.25
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (ix) --CH.sub.3,
--C.sub.2H.sub.5, or C.sub.3 to C.sub.25 straight-chain, branched
or cyclic alkane or alkene comprising one to three heteroatoms
selected from the group consisting of O, N, Si and S, and
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (x) C.sub.6
to C.sub.25 unsubstituted aryl, or C.sub.3 to C.sub.25
unsubstituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and C.sub.6 to C.sub.25 substituted aryl, or C.sub.3 to C.sub.25
substituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and wherein said substituted aryl or substituted heteroaryl has one
to three substituents independently selected from the group
consisting of: (E) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to
C.sub.25 straight-chain, branched or cyclic alkane or alkene,
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, (F) OH, (G)
NH.sub.2, and (H) SH; and (xi)
--(CH.sub.2).sub.nSi(CH.sub.2).sub.mCH.sub.3,
--(CH.sub.2).sub.nSi(CH.sub.3).sub.3,
--(CH.sub.2).sub.nOSi(CH.sub.3).sub.m, where n is independently 1-4
and m is independently 0-4; and C) optionally at least two of
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7,
R.sup.8, R.sup.9, and R.sup.10 can together form a cyclic or
bicyclic alkanyl or alkenyl group.
8. A method according to claim 1 wherein an ionic liquid comprises
an anion selected from one or more members of the group consisting
of: [CH.sub.3CO.sub.2].sup.-, [HSO.sub.4].sup.-,
[CH.sub.3OSO.sub.3].sup.-, [C.sub.2H.sub.5OSO.sub.3].sup.-,
[AlCl.sub.4].sup.-, [CO.sub.3].sup.2-, [HCO.sub.3].sup.-,
[NO.sub.2].sup.-, [NO.sub.3].sup.-, [SO.sub.4].sup.2-,
[PO.sub.3].sup.3-, [HPO.sub.3].sup.2-, [H.sub.2PO.sub.3].sup.1-,
[PO.sub.4].sup.3-, [HPO.sub.4].sup.2-, [H.sub.2PO.sub.4].sup.-,
[HSO.sub.3].sup.-, [CuCl.sub.2].sup.-, Cl.sup.-, Br.sup.-, I.sup.-,
SCN.sup.-, carborates optionally substituted with alkyl or
substituted alkyl; carboranes optionally substituted with
alkylamine, substituted alkylamine, alkyl or substituted alkyl; and
a fluorinated anion.
9. A method according to claim 1 wherein an ionic liquid comprises
a cation selected from one or more members of the group consisting
of pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium,
pyrazolium, thiazolium, oxazolium, triazolium, phosphonium,
ammonium, benzyltrimethylammonium, choline, dimethylimidazolium,
guanidinium, phosphonium choline, tetramethylammonium, and
tetramethylphosphonium.
10. A method according to claim 1 wherein an ionic liquid comprises
an anion selected from one or more members of the group consisting
of aminoacetate, ascorbate, benzoate, catecholate, citrate,
dimethylphosphate, formate, fumarate, gallate, glycolate,
glyoxylate, iminodiacetate, isobutyrate, kojate, lactate,
levulinate, oxalate, pivalate, propionate, pyruvate, salicylate,
succinamate, succinate, tiglate, tetrafluoroborate,
tetrafluoroethanesulfonate, tropolonate, [CH.sub.3CO.sub.2].sup.-,
[HSO.sub.4].sup.-, [CH.sub.3OSO.sub.3].sup.-,
[C.sub.2H.sub.5OSO.sub.3].sup.-, [AlCl.sub.4].sup.-,
[CO.sub.3].sup.2-, [HCO.sub.3].sup.-, [NO.sub.2].sup.-,
[NO.sub.3].sup.-, [SO.sub.4].sup.2-, [PO.sub.4].sup.3-,
[HPO.sub.4].sup.2-, [H.sub.2PO.sub.4].sup.-, [HSO.sub.3].sup.-,
[CuCl.sub.2].sup.-, Cl.sup.-, Br.sup.-, I.sup.-, SCN.sup.-,
[BF.sub.4].sup.-, [PF.sub.6].sup.-, [SbF.sub.6].sup.-,
[CF.sub.3SO.sub.3].sup.-, [HCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.3HFCCF.sub.2SO.sub.3].sup.-, [HCClFCF.sub.2SO.sub.3].sup.-,
[(CF.sub.3SO.sub.2).sub.2N].sup.-,
[(CF.sub.3CF.sub.2SO.sub.2).sub.2N].sup.-,
[(CF.sub.3SO.sub.2).sub.3C].sup.-, [CF.sub.3CO.sub.2].sup.-,
[CF.sub.3OCFHCF.sub.2SO.sub.3].sup.-,
[CF.sub.3CF.sub.2OCFHCF.sub.2SO.sub.3].sup.-,
[CF.sub.3CFHOCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.2HCF.sub.2OCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.2ICF.sub.2OCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.3CF.sub.2OCF.sub.2CF.sub.2SO.sub.3].sup.-,
[(CF.sub.2HCF.sub.2SO.sub.2).sub.2N]_,
[(CF.sub.3CFHCF.sub.2SO.sub.2).sub.2N].sup.-, F.sup.-, and anions
represented by the structure of the following formula: ##STR00004##
wherein R.sup.11 is selected from the group consisting of: (v)
--CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.10
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (vi) --CH.sub.3,
--C.sub.2H.sub.5, or C.sub.3 to C.sub.10 straight-chain, branched
or cyclic alkane or alkene comprising one to three heteroatoms
selected from the group consisting of O, N, Si and S, and
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (vii)
C.sub.6 to C.sub.10 unsubstituted aryl, or C.sub.3 to C.sub.10
unsubstituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and (viii) C.sub.6 to C.sub.10 substituted aryl, or C.sub.3 to
C.sub.10 substituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and wherein said substituted aryl or substituted heteroaryl has one
to three substituents independently selected from the group
consisting of: (A) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to
C.sub.10 straight-chain, branched or cyclic alkane or alkene,
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, (B) OH, (C)
NH.sub.2, and (D) SH.
11. A method according to claim 1 wherein an ionic liquid is
selected from the group consisting of 1-butyl-3-methylimidazolium
hexafluorophosphate [bmim][PF.sub.6], 1-butyl-3-methylimidazolium
tetrafluoroborate [bmim][BF.sub.4], 1-hexyl-3-methylimidazolium
bistrifluoromethylsulfonylimide [hmim][Tf.sub.2N], and
1-butyl-3-methylimidazolium acetate [bmim][acetate].
12. An apparatus for adjusting the temperature of an object, medium
or space, comprising: (a) a primary refrigeration module that
comprises a primary refrigeration loop containing a primary
refrigerant, a condenser and an expansion valve; (b) a secondary
refrigeration module that comprises a secondary refrigeration loop
containing a secondary refrigerant, and an evaporator; (c) and a
heat exchanger contacted by both the primary and secondary
refrigeration loops; and (d) an auxiliary container in fluid
communication with the secondary refrigeration loop through a flow
interrupter, said auxiliary container containing at least one ionic
liquid; wherein the condenser is located in proximity to an object,
medium or space to be heated, or the evaporator is located in
proximity to an object, medium or space to be cooled.
13. An apparatus according to claim 12 wherein the condenser is
located in proximity to an object, medium or space to be
heated.
14. An apparatus according to claim 12 wherein the evaporator is
located in proximity to an object, medium or space to be
cooled.
15. An apparatus according to claim 12 further comprising a
compressor to compress the primary refrigerant.
16. An apparatus according to claim 12 further comprising an
absorber to absorb the primary refrigerant in an ionic liquid.
17. An apparatus according to claim 12 further comprising a heat
source in thermal contact with the auxiliary container.
18. An apparatus according to claim 12 wherein the flow interrupter
comprises a valve.
19. An apparatus according to claim 18 wherein the valve comprises
a pressure relief valve.
20. An apparatus according to claim 12 wherein the secondary
refrigerant comprises carbon dioxide.
21. An apparatus according to claim 12 wherein an ionic liquid
comprises a cation selected from the group consisting of cations
represented by the structures of the following formulae:
##STR00005## wherein: A) R.sup.1, R.sup.2, R.sup.3, R.sup.4,
R.sup.5, R.sup.6, R.sup.12 and R.sup.13 are independently selected
from the group consisting of: (xiii) H, (xiv) halogen, (xv)
--CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.25
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (xvi) --CH.sub.3,
--C.sub.2H.sub.5, or C.sub.3 to C.sub.25 straight-chain, branched
or cyclic alkane or alkene comprising one to three heteroatoms
selected from the group consisting of O, N, Si and S, and
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (xvii)
C.sub.6 to C.sub.20 unsubstituted aryl, or C.sub.3 to C.sub.25
unsubstituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
(xviii) C.sub.6 to C.sub.25 substituted aryl, or C.sub.3 to
C.sub.25 substituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and wherein said substituted aryl or substituted heteroaryl has one
to three substituents independently selected from the group
consisting of: (A) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to CM
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, (B) OH, (C)
NH.sub.2, and (D) SH; and (vii)
--(CH.sub.2).sub.nSi(CH.sub.2).sub.mCH.sub.3,
--(CH.sub.2).sub.nSi(CH.sub.3).sub.3,
--(CH.sub.2).sub.nOSi(CH.sub.3).sub.m, where n is independently 1-4
and m is independently 0-4; B) R.sup.7, R.sup.8, R.sup.9, and
R.sup.10 are independently selected from the group consisting of:
(viii) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.25
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (ix) --CH.sub.3,
--C.sub.2H.sub.5, or C.sub.3 to C.sub.25 straight-chain, branched
or cyclic alkane or alkene comprising one to three heteroatoms
selected from the group consisting of O, N, Si and S, and
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (x) C.sub.6
to C.sub.25 unsubstituted aryl, or C.sub.3 to C.sub.25
unsubstituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and C.sub.6 to C.sub.25 substituted aryl, or C.sub.3 to C.sub.25
substituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and wherein said substituted aryl or substituted heteroaryl has one
to three substituents independently selected from the group
consisting of: (E) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to
C.sub.25 straight-chain, branched or cyclic alkane or alkene,
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, (F) OH, (G)
NH.sub.2, and (H) SH; and (xi)
--(CH.sub.2).sub.nSi(CH.sub.2).sub.mCH.sub.3,
--(CH.sub.2).sub.nSi(CH.sub.3).sub.3,
--(CH.sub.2).sub.nOSi(CH.sub.3).sub.m, where n is independently 1-4
and m is independently 0-4; and C) optionally at least two of
R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8,
R.sup.9, and R.sup.10 can together form a cyclic or bicyclic
alkanyl or alkenyl group.
22. An apparatus according to claim 12 wherein an ionic liquid
comprises an anion selected from one or more members of the group
consisting of: [CH.sub.3CO.sub.2].sup.-, [HSO.sub.4].sup.-,
[CH.sub.3OSO.sub.3].sup.-, [C.sub.2H.sub.5OSO.sub.3].sup.-,
[AlCl.sub.4].sup.-, [CO.sub.3].sup.2-, [HCO.sub.3].sup.-,
[NO.sub.2].sup.-, [NO.sub.3].sup.-, [SO.sub.4].sup.2-,
[PO.sub.3].sup.3-, [HPO.sub.3].sup.2-, [H.sub.2PO.sub.3].sup.1-,
[PO.sub.4].sup.3-, [HPO.sub.4].sup.2-, [H.sub.2PO.sub.4].sup.-,
[HSO.sub.3].sup.-, [CuCl.sub.2].sup.-, Cl.sup.-, Br.sup.-, I.sup.-,
SCN.sup.-, carborates optionally substituted with alkyl or
substituted alkyl; carboranes optionally substituted with
alkylamine, substituted alkylamine, alkyl or substituted alkyl; and
a fluorinated anion.
23. An apparatus according to claim 12 wherein an ionic liquid
comprises a cation selected from one or more members of the group
consisting of pyridinium, pyridazinium, pyrimidinium, pyrazinium,
imidazolium, pyrazolium, thiazolium, oxazolium, triazolium,
phosphonium, ammonium, benzyltrimethylammonium, choline,
dimethylimidazolium, guanidinium, phosphonium choline,
tetramethylammonium, and tetramethylphosphonium.
24. An apparatus according to claim 12 wherein an ionic liquid
comprises an anion selected from one or more members of the group
consisting of aminoacetate, ascorbate, benzoate, catecholate,
citrate, dimethylphosphate, formate, fumarate, gallate, glycolate,
glyoxylate, iminodiacetate, isobutyrate, kojate, lactate,
levulinate, oxalate, pivalate, propionate, pyruvate, salicylate,
succinamate, succinate, tiglate, tetrafluoroborate,
tetrafluoroethanesulfonate, tropolonate, [CH.sub.3CO.sub.2].sup.-,
[HSO.sub.4].sup.-, [CH.sub.3OSO.sub.3].sup.-,
[C.sub.2H.sub.5OSO.sub.3].sup.-, [AlCl.sub.4].sup.-,
[CO.sub.3].sup.2-, [HCO.sub.3].sup.-, [NO.sub.2].sup.-,
[NO.sub.3].sup.-, [SO.sub.4].sup.2-, [PO.sub.4].sup.3-,
[HPO.sub.4].sup.2-, [H.sub.2PO.sub.4].sup.-, [HSO.sub.3].sup.-,
[CUCl.sub.2].sup.-, Cl.sup.-, Br.sup.-, I.sup.-, SCN.sup.-,
[BF.sub.4].sup.-, [PF.sub.6].sup.-, [SbF.sub.6].sup.-,
[CF.sub.3SO.sub.3].sup.-, [HCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.3HFCCF.sub.2SO.sub.3].sup.-, [HCClFCF.sub.2SO.sub.3].sup.-,
[(CF.sub.3SO.sub.2).sub.2N].sup.-,
[(CF.sub.3CF.sub.2SO.sub.2).sub.2N].sup.-,
[(CF.sub.3SO.sub.2).sub.3C].sup.-, [CF.sub.3CO.sub.2].sup.-,
[CF.sub.3OCPHCF.sub.2SO.sub.3].sup.-,
[CF.sub.3CF.sub.2OCFHCF.sub.2SO.sub.3].sup.-,
[CF.sub.3CFHOCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.2HCF.sub.2OCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.2ICF.sub.2OCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.3CF.sub.2OCF.sub.2CF.sub.2SO.sub.3].sup.-,
[(CF.sub.2HCF.sub.2SO.sub.2).sub.2N].sub.-,
[(CF.sub.3CFHCF.sub.2SO.sub.2).sub.2N].sup.-, F.sup.-, and anions
represented by the structure of the following formula: ##STR00006##
wherein R.sup.11 is selected from the group consisting of: (ix)
--CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.10
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (x) --CH.sub.3,
--C.sub.2H.sub.5, or C.sub.3 to C.sub.10 straight-chain, branched
or cyclic alkane or alkene comprising one to three heteroatoms
selected from the group consisting of O, N, Si and S, and
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; (xi) C.sub.6
to C.sub.10 unsubstituted aryl, or C.sub.3 to C.sub.10
unsubstituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and (xii) C.sub.6 to C.sub.10 substituted aryl, or C.sub.3 to
C.sub.10 substituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and wherein said substituted aryl or substituted heteroaryl has one
to three substituents independently selected from the group
consisting of: (A) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to
C.sub.10 straight-chain, branched or cyclic alkane or alkene,
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, (B) OH, (C)
NH.sub.2, and (D) SH.
25. An apparatus according to claim 12 wherein an ionic liquid is
selected from the group consisting of 1-butyl-3-methylimidazolium
is hexafluorophosphate [bmim][PF.sub.6],
1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF.sub.4],
1-hexyl-3-methylimidazolium bistrifluoromethylsulfonylimide
[hmim][Tf.sub.2N], and 1-butyl-3-methylimidazolium acetate
[bmim][acetate].
Description
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) from, and claims the benefit of, U.S. Provisional
Application No. 61/260,369, filed Nov. 11, 2009, which is by this
reference incorporated in its entirety as a part hereof for all
purposes.
TECHNICAL FIELD
[0002] This invention relates to the field of refrigeration
systems. More specifically, the invention relates to a process and
system for storing a secondary refrigerant such as carbon dioxide
in a secondary loop refrigeration system using ionic liquids.
BACKGROUND
[0003] Secondary loop refrigeration systems have found widespread
use in supermarkets and storage warehouses. This type of
refrigeration system incorporates a primary refrigeration system
and a secondary loop. The primary refrigeration system is often a
traditional direct expansion design that uses a phase change
refrigerant and a compressor to circulate a primary refrigerant.
The secondary loop contains a nontoxic and nonflammable refrigerant
such as carbon dioxide or propylene glycol. A heat exchanger is
used to transfer energy between the primary refrigerant and the
refrigerant in the secondary loop. In use, the primary
refrigeration system is typically restricted to an isolated
location, e.g. a machine room or roof top, and the secondary loop
runs through the storage compartments for storing refrigerated
goods, e.g. supermarket display cases. Secondary loop refrigeration
systems offer many advantages over conventional refrigeration
systems, one of the most important being a significant improvement
in energy efficiency. Additionally, secondary loop refrigeration
systems are more compact, operate with a small charge of
refrigerant, and minimize the effects of refrigerant leakage.
[0004] Carbon dioxide is widely used as the secondary refrigerant
in the secondary loop of these refrigeration systems. A problem
arises when there is a shutdown of the primary refrigeration
system, e.g. due to a loss of electrical power. The secondary
refrigerant in the secondary loop increases in pressure, which can
lead to very high pressures, such that the secondary refrigerant
may need to be vented to prevent rupture of the secondary loop.
Typically, a safety relief device is used in these systems so that
when the pressure reaches the set point of the relief device, the
device opens to the atmosphere, releasing the secondary
refrigerant. The loss of the secondary refrigerant requires the
system to be recharged when operation is restarted in order for the
secondary loop to function properly.
[0005] Ionic liquids are known to absorb refrigerants such as
carbon dioxide, and have been used to remove carbon dioxide from
gas mixtures. For example, Moriya (US 2007/0084344) describes a gas
collection method for selectively absorbing a gas, such as carbon
dioxide, from a gas mixture using an ionic liquid. Additionally,
Tonkovich (US 2009/0071335) describes methods for separating
methane and carbon dioxide from a gas mixture using an ionic
liquid. However, ionic liquids have not been used as storage media
for a secondary refrigerant such as carbon dioxide in secondary
loop refrigeration systems.
[0006] Therefore, the need still exits for a method to store and
recover carbon dioxide in a secondary loop refrigeration system
after a shutdown of the primary refrigeration system.
SUMMARY
[0007] This invention solves the stated problem by providing a
method and apparatus for storing and recovering a secondary
refrigerant, such as carbon dioxide, in a secondary loop
refrigeration system using ionic liquids.
[0008] In one embodiment, this invention provides, in a secondary
loop refrigeration system that comprises a primary refrigeration
loop containing a primary refrigerant, a secondary refrigeration
loop containing a secondary refrigerant, and a heat exchanger
contacted by both the primary and secondary refrigeration loops, a
method of storing secondary refrigerant, comprising (a) flowing at
least a portion of the secondary refrigerant from the secondary
loop to an auxiliary container; and (b) absorbing at least a
portion of the flowed secondary refrigerant with an ionic liquid in
the auxiliary container to form a mixture thereof.
[0009] In another embodiment, this invention provides an apparatus
for adjusting the temperature of an object, medium or space,
comprising (a) a primary refrigeration module that comprises a
primary refrigeration loop containing a primary refrigerant, a
condenser and an expansion valve; (b) a secondary refrigeration
module that comprises a secondary refrigeration loop containing a
secondary refrigerant, and an evaporator; (c) and a heat exchanger
contacted by both the primary and secondary refrigeration loops;
and (d) an auxiliary container in fluid communication with the
secondary refrigeration loop through a flow interrupter, said
auxiliary container containing at least one ionic liquid; wherein
the condenser is located in proximity to an object, medium or space
to be heated, or the evaporator is located in proximity to an
object, medium or space to be cooled.
[0010] In a further embodiment, this invention provides a process
for storing carbon dioxide in a secondary loop refrigeration system
comprising the steps of (a) providing a secondary loop
refrigeration system comprising a secondary loop containing carbon
dioxide; (b) releasing the carbon dioxide from the secondary loop;
and (c) contacting the carbon dioxide released from the secondary
loop with at least one ionic liquid, whereby at least a portion of
the carbon dioxide is absorbed by the ionic liquid.
[0011] In yet another embodiment, this invention provides a
refrigeration system comprising (a) an object, space or medium to
be cooled; (b) a primary refrigeration system containing a primary
refrigerant, said primary refrigeration system comprising a
compressor, a condenser, and an expansion valve; (c) a second
refrigeration loop containing carbon dioxide; (d) an evaporator in
open communication with the second refrigeration loop for
transferring heat from said object, space or medium to the carbon
dioxide; (e) a heat exchanger for transferring heat from the carbon
dioxide in the second refrigeration loop to said primary
refrigerant in the primary refrigeration system; and (f) an
expansion tank in fluid communication with the second refrigeration
loop through a flow interrupter, said expansion tank containing at
least one ionic liquid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic drawing of an exemplary secondary loop
refrigeration system for use with the process disclosed herein.
[0013] FIG. 2 is a layout of the components of a vapor compression
cycle.
[0014] FIG. 3 is a layout of the components of an absorption
cycle.
DETAILED DESCRIPTION
[0015] As used above and throughout the description of the
invention, the following terms, unless otherwise indicated, shall
be defined as follows:
[0016] The term "secondary loop refrigeration system" refers to a
refrigeration system in which a thermal energy transfer medium
contained in a secondary loop is used to transport thermal energy
from a heat source to a primary refrigeration system.
[0017] The term "secondary loop" refers to the path over which the
thermal energy transfer medium travels while it is being cycled
between the heat source and the primary refrigeration system.
[0018] The term "secondary refrigerant" refers to the thermal
energy transfer medium in the secondary loop.
[0019] The term "primary refrigeration system" refers to the part
of a secondary loop refrigeration system where heat is transferred
to an object, medium or space, such as the external environment, by
way of a compressor or an absorber/generator system.
[0020] The term "primary refrigerant" refers to the thermal energy
transfer medium in the primary refrigeration system.
[0021] The term "ionic liquid" refers to an organic salt that is
fluid at or below about 100.degree. C.
[0022] The term "refrigerant" refers to a fluidic substance such as
a fluorocarbon (FC), hydrofluorocarbon (HFC), chlorofluorocarbon
(CFC), hydrochlorofluorocarbon (HCFC), or ammonia, alkanes,
alkenes, aromatics, carbon dioxide, or other gas such as hydrogen,
oxygen, nitrogen, and argon that may be used as a thermal energy
transfer medium. A refrigerant, when it changes phase from liquid
to vapor (evaporates), removes heat from the surroundings; and when
it changes phase from vapor to liquid (condenses), it adds heat to
the surroundings. Although the term refrigerant may carry the
connotation of a substance used only for cooling, the term is used
herein in the generic sense of a thermal energy transfer medium
that is applicable for use in a method, apparatus or system that
may be used for heating or cooling.
[0023] Disclosed herein are a method and apparatus for storing and
recovering a secondary refrigerant, such as carbon dioxide, in a
secondary loop refrigeration system using one or more ionic liquids
to absorb the secondary refrigerant. The inventions hereof may be
used in situations where, for example, there is a shutdown of the
primary refrigeration system. The methods and apparatus hereof
eliminate the release of a secondary refrigerant into the
environment and the need to recharge the secondary loop after a
shutdown of the primary refrigeration system. Secondary loop
refrigeration systems find utility in refrigeration applications
such as supermarket display cases and warehouse storage
containers.
Secondary Loop Refrigeration Systems
[0024] Secondary loop refrigeration systems are well known in the
art [see for example, U.S. Pat. Nos. 5,524,442 and 5,819,549 (each
of which is by this reference incorporated in its entirety as a
part hereof for all purposes)]. Briefly, a secondary loop
refrigeration system comprises a primary refrigeration system and a
secondary loop. The primary refrigeration system is a traditional
direct expansion design that uses a phase change refrigerant and a
compressor, or an absorber/generator system, to circulate the
refrigerant.
[0025] Any suitable phase change refrigerant may be used as the
primary refrigerant. Examples of suitable primary refrigerants
include without limitation ammonia, fluorocarbons such as
tetrafluoromethane (Freon 14), fluoroform (Freon 23), and
hexafluoroethane (Freon 116); hydrofluorocarbons such as
difluoromethane (HFC-32), 1,1-difluoroethane,
1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane
(HFC-134a), 1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane
(HFC-152a), fluoroethane (HFC-161), pentafluoroethane (HFC-125),
1,1,1,3,3-pentafluoropropane (HFC-245fa), and
1,1,1,3,3-pentafluorobutane (HFC-365mfc); fluoro-olefins such as
2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf); and mixtures
thereof.
[0026] The primary refrigeration system is typically contained in
an isolated location, e.g. a machine room or roof top, when the
system is used for cooling and it is desired to reject heat to the
atmosphere. In other embodiments, however, the system may be used
for heating, and the condenser is located in proximity to an
object, medium or space to be heated. The secondary loop contains a
secondary refrigerant, which is frequently carbon dioxide. Other
suitable secondary refrigerants, however, include nitrogen, argon,
helium, ammonia, perfluoroalkanes, ethylene glycols, and
hydrofluoroethers. When the system is used for cooling, such as
when the secondary loop runs through a storage compartment for
storing refrigerated goods (e.g. a supermarket display case), the
evaporator is located in proximity to an object, medium or space to
be cooled.
[0027] In operation of the cooling embodiment, heat energy from a
food storage compartment is transferred to the secondary
refrigerant in the secondary loop by way of an evaporator
containing refrigeration coils. The heat transfer to the secondary
refrigerant may be facilitated by the use of fans, which circulate
the air in the storage compartment. The secondary refrigerant is
circulated in the secondary loop to a heat exchanger by a
circulating pump. In the heat exchanger, the thermal energy from
the secondary refrigerant is transferred to the primary refrigerant
contained in the primary refrigeration system. The cooled secondary
refrigerant is returned to the storage compartment by way of the
secondary loop. The warmed primary refrigerant is circulated
through a compressor, or an absorber/generator system, to a
condenser where the primary refrigerant is liquefied and cooled. By
this process, the thermal energy is extracted from the primary
refrigerant and rejected into the environment. The primary
refrigerant is then expanded through an expansion valve and
returned to the heat exchanger.
[0028] The primary refrigerant may be routed to the condenser by
either a vapor compression cycle or an absorption cycle. Vapor
compression and absorption cycles, and systems in which they are
run, are described in Application Guide for Absorption
Cooling/Refrigeration Using Recovered Heat [Dorgan et al (American
Society of Heating, Refrigeration and Air Conditioning Engineers,
Inc., 1995, Atlanta, Ga., Chapter 5)]. A schematic diagram for a
system in which a simple vapor compression cycle is run is shown in
FIG. 2. The system is composed of condenser and evaporator units
with an expansion valve, and a vapor compressor that is capable of
mechanically increasing the pressure of a refrigerant vapor. A
schematic diagram for a simple absorption cycle is shown in FIG. 3.
The system is composed of condenser and evaporator units with an
expansion valve similar to an ordinary vapor compression cycle
shown in FIG. 2, but an absorber-generator solution circuit
replaces the compressor. The circuit may be composed of an
absorber, a generator, a heat exchanger, a pressure control device
(A) and a pump for circulating the solution. In some embodiments,
the heat released by the absorber upon the absorption of the
refrigerant by the absorbent may be used to heat a mixture of
refrigerant and absorbent in the generator to separate the
refrigerant in vapor form from the absorbent. In various
embodiments, the absorbent can be any ionic liquid.
[0029] This invention thus involves an apparatus for adjusting the
temperature of an object, medium or space wherein the refrigerant
is routed to the condenser by either a vapor compression cycle or
an absorption cycle, as described herein, to cool or heat an object
(for example a conduit or a container), a medium (for example a
fluid such as air or water) or a space. The apparatus may thus be
composed of a mechanical compressor, a condenser and evaporator
units with an expansion valve; or it may include components such as
an absorber-generator solution circuit (which by the outflow and
inflow of heat increases the pressure of refrigerant vapor as a
compressor does mechanically) where the circuit may be composed of
an absorber, a generator, a heat exchanger, a pressure control
device and a pump for circulating the solution.
[0030] Vapor compression and absorption systems are further
described in US 2006/0197053 and US2007/0019708, each of which is
by this reference incorporated in its entirety as a part hereof for
all purposes.
[0031] An apparatus of this invention may be deployed for use in,
or fabricated or operated as, a refrigerator, a freezer, an ice
machine, an air conditioner, an industrial cooling system, a heater
or heat pump. Each of these instruments may be situated in a
residential, commercial or industrial setting, or may be
incorporated into a mobilized device such as a car, truck, bus,
train, airplane, or other device for transportation, or may be
incorporated into a piece of equipment such as a medical
instrument.
Ionic Liquids
[0032] Ionic liquids suitable for use as disclosed herein can, in
principle, be any ionic liquid that absorbs a secondary refrigerant
such as carbon dioxide; however, ionic liquids that have minimal
absorption of the refrigerant will be less effective. Ideally,
ionic liquids having high absorption of the selected refrigerant
are desired for efficient use as described herein. Additionally,
mixtures of two or more ionic liquids may be used.
[0033] Many ionic liquids are formed by reacting a
nitrogen-containing heterocyclic ring, preferably a heteroaromatic
ring, with an alkylating agent (for example, an alkyl halide) to
form a quaternary ammonium salt, and performing ion exchange or
other suitable reactions with various Lewis acids or their
conjugate bases to form the ionic liquid. Examples of suitable
heteroaromatic rings include substituted pyridines, imidazole,
substituted imidazole, pyrrole and substituted pyrroles. These
rings can be alkylated with virtually any straight, branched or
cyclic C.sub.1-20 alkyl group, but preferably, the alkyl groups are
C.sub.1-16 groups. Various triarylphosphines, thioethers and cyclic
and non-cyclic quaternary ammonium salts may also be used for this
purpose. Ionic liquids suitable for use herein may also be
synthesized by salt metathesis, by an acid-base neutralization
reaction or by quaternizing a selected nitrogen-containing
compound; or they may be obtained commercially from several
companies such as Merck (Darmstadt, Germany), BASF (Mount Olive,
N.J.), Fluka Chemical Corp. (Milwaukee, Wis.), and Sigma-Aldrich
(St. Louis, Mo.).
[0034] Representative examples of ionic liquids suitable for use
herein are included among those that are described in sources such
as J. Chem. Tech. Biotechnol., 68:351-356 (1997); Chem. Ind.,
68:249-263 (1996); J. Phys. Condensed Matter, 5: (supp
34B):B99-B106 (1993); Chemical and Engineering News, Mar. 30, 1998,
32-37; J. Mater. Chem., 8:2627-2636 (1998); Chem. Rev.,
99:2071-2084 (1999); and US 2008/0028777 (which is by this
reference incorporated in its entirety as a part hereof for all
purposes), and references cited therein. In one embodiment, a
library, i.e. a combinatorial library, of ionic liquids may be
prepared, for example, by preparing various alkyl derivatives of a
quaternary ammonium cation, and varying the associated anions. The
acidity of the ionic liquids can be adjusted by varying the molar
equivalents and type and combinations of Lewis acids.
[0035] Ionic liquids suitable for use herein comprise an anion and
a cation. In various different embodiments, the cation is selected
from the group consisting of cations represented by the structures
of the following formulae:
##STR00001##
wherein:
[0036] a) R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6,
R.sup.12 and R.sup.13 are independently selected from the group
consisting of: [0037] (i) H, [0038] (ii) halogen, [0039] (iii)
--CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.25
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; [0040] (iv)
--CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.25
straight-chain, branched or cyclic alkane or alkene comprising one
to three heteroatoms selected from the group consisting of O, N, Si
and S, and optionally substituted with at least one member selected
from the group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH;
[0041] (v) C.sub.6 to C.sub.20 unsubstituted aryl, or C.sub.3 to
C.sub.25 unsubstituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
[0042] (vi) C.sub.6 to C.sub.25 substituted aryl, or C.sub.3 to
C.sub.25 substituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and wherein said substituted aryl or substituted heteroaryl has one
to three substituents independently selected from the group
consisting of: [0043] (A) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3
to C.sub.25 straight-chain, branched or cyclic alkane or alkene,
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, [0044] (B)
OH, [0045] (C) NH.sub.2, and [0046] (D) SH; and [0047] (vii)
--(CH.sub.2).sub.nSi(CH.sub.2).sub.mCH.sub.3,
--(CH.sub.2).sub.nSi(CH.sub.3).sub.3,
--(CH.sub.2).sub.nOSi(CH.sub.3).sub.m, where n is independently 1-4
and m is independently 0-4;
[0048] b) R.sup.7, R.sup.8, R.sup.9, and R.sup.10 are independently
selected from the group consisting of: [0049] (viii) --CH.sub.3,
--C.sub.2H.sub.5, or C.sub.3 to C.sub.25 straight-chain, branched
or cyclic alkane or alkene, optionally substituted with at least
one member selected from the group consisting of Cl, Br, F, I, OH,
NH.sub.2 and SH; [0050] (ix) --CH.sub.3, --C.sub.2H.sub.5, or
C.sub.3 to C.sub.25 straight-chain, branched or cyclic alkane or
alkene comprising one to three heteroatoms selected from the group
consisting of O, N, Si and S, and optionally substituted with at
least one member selected from the group consisting of Cl, Br, F,
I, OH, NH.sub.2 and SH; [0051] (x) C.sub.6 to C.sub.25
unsubstituted aryl, or C.sub.3 to C.sub.25 unsubstituted heteroaryl
having one to three heteroatoms independently selected from the
group consisting of O, N, Si and S; and C.sub.6 to C.sub.25
substituted aryl, or C.sub.3 to C.sub.25 substituted heteroaryl
having one to three heteroatoms independently selected from the
group consisting of O, N, Si and S; and wherein said substituted
aryl or substituted heteroaryl has one to three substituents
independently selected from the group consisting of: [0052] (E)
--CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.25
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, [0053] (F) OH,
[0054] (G) NH.sub.2, and [0055] (H) SH; and [0056] (xi)
--(CH.sub.2).sub.nSi(CH.sub.2).sub.mCH.sub.3,
--(CH.sub.2).sub.nSi(CH.sub.3).sub.3,
--(CH.sub.2).sub.nOSi(CH.sub.3).sub.m, where n is independently 1-4
and m is independently 0-4;
[0057] c) optionally at least two of R.sup.1, R.sup.2, R.sup.3,
R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, and R.sup.10
can together form a cyclic or bicyclic alkanyl or alkenyl group
[0058] In one embodiment, the ionic liquid comprises an anion
selected from one or more members of the group consisting of:
[CH.sub.3CO.sub.2].sup.-, [HSO.sub.4].sup.-,
[CH.sub.3OSO.sub.3].sup.-, [C.sub.2H.sub.5OSO.sub.3].sup.-,
[AlCl.sub.4].sup.-, [CO.sub.3].sup.2-, [HCO.sub.3].sup.-,
[NO.sub.2].sup.-, [NO.sub.3].sup.-, [SO.sub.4].sup.2-,
[PO.sub.3].sup.3-, [HPO.sub.3].sup.2-, [H.sub.2PO.sub.3].sup.1-,
[PO.sub.4].sup.3-, [HPO.sub.4].sup.2-, [H.sub.2PO.sub.4].sup.-,
[HSO.sub.3].sup.-, [CuCl.sub.2].sup.-, Cl.sup.-, Br.sup.-, I.sup.-,
SCN.sup.-, carborates optionally substituted with alkyl or
substituted alkyl; carboranes optionally substituted with
alkylamine, substituted alkylamine, alkyl or substituted alkyl; and
a fluorinated anion.
[0059] In one embodiment, the ionic liquid comprises a cation
selected from one or more members of the group consisting of
pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium,
pyrazolium, thiazolium, oxazolium, triazolium, phosphonium,
ammonium, benzyltrimethylammonium, choline, dim ethylimidazolium,
guanidinium, phosphonium choline, tetramethylammonium, and
tetramethylphosphonium.
[0060] In another embodiment, the ionic liquid comprises an anion
selected from one or more members of the group consisting of
aminoacetate, ascorbate, benzoate, catecholate, citrate,
dimethylphosphate, formate, fumarate, gallate, glycolate,
glyoxylate, iminodiacetate, isobutyrate, kojate, lactate,
levulinate, oxalate, pivalate, propionate, pyruvate, salicylate,
succinamate, succinate, tiglate, tetrafluoroborate,
tetrafluoroethanesulfonate, tropolonate, [CH.sub.3CO.sub.2].sup.-,
[HSO.sub.4].sup.-, [CH.sub.3OSO.sub.3].sup.-,
[C.sub.2H.sub.5OSO.sub.3].sup.-, [AlCl.sub.4].sup.-,
[CO.sub.3].sup.2-, [HCO.sub.3].sup.-, [NO.sub.2].sup.-,
[NO.sub.3].sup.-, [SO.sub.4].sup.2-, [PO.sub.4].sup.3-,
[HPO.sub.4].sup.2-, [H.sub.2PO.sub.4].sup.-, [HSO.sub.3].sup.-,
[CuCl.sub.2].sup.-, Cl.sup.-, Br.sup.-, I.sup.-, SCN.sup.-,
[BF.sub.4].sup.-, [PF.sub.6].sup.-, [SbF.sub.6].sup.-,
[CF.sub.3SO.sub.3].sup.-, [HCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.3HFCCF.sub.2SO.sub.3].sup.-, [HCClFCF.sub.2SO.sub.3].sup.-,
[(CF.sub.3SO.sub.2).sub.2N].sup.-,
[(CF.sub.3CF.sub.2SO.sub.2).sub.2N].sup.-,
[(CF.sub.3SO.sub.2).sub.3C].sup.-, [CF.sub.3CO.sub.2].sup.-,
[CF.sub.3OCFHCF.sub.2SO.sub.3].sup.-,
[CF.sub.3CF.sub.2OCFHCF.sub.2SO.sub.3].sup.-,
[CF.sub.3CFHOCF.sub.2CF.sub.2SO.sub.3].sup.-,
[CF.sub.2HCF.sub.2OCF.sub.2CF.sub.2SO.sub.3].sub.-,
[CF.sub.21CF.sub.2OCF.sub.2CF.sub.2SO.sub.3],
[CF.sub.3CF.sub.2OCF.sub.2CF.sub.2SO.sub.3].sup.-,
[(CF.sub.2HCF.sub.2SO.sub.2).sub.2N]_,
[(CF.sub.3CFHCF.sub.2SO.sub.2).sub.2N].sup.-, F.sup.-, and anions
represented by the structure of the following formula:
##STR00002##
[0061] wherein R.sup.11 is selected from the group consisting of:
[0062] (i) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.10
straight-chain, branched or cyclic alkane or alkene, optionally
substituted with at least one member selected from the group
consisting of Cl, Br, F, I, OH, NH.sub.2 and SH; [0063] (ii)
--CH.sub.3, --C.sub.2H.sub.5, or C.sub.3 to C.sub.10
straight-chain, branched or cyclic alkane or alkene comprising one
to three heteroatoms selected from the group consisting of O, N, Si
and S, and optionally substituted with at least one member selected
from the group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH;
[0064] (iii) C.sub.6 to C.sub.10 unsubstituted aryl, or C.sub.3 to
C.sub.10 unsubstituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and [0065] (iv) C.sub.6 to C.sub.10 substituted aryl, or C.sub.3 to
C.sub.10 substituted heteroaryl having one to three heteroatoms
independently selected from the group consisting of O, N, Si and S;
and wherein said substituted aryl or substituted heteroaryl has one
to three substituents independently selected from the group
consisting of: [0066] (A) --CH.sub.3, --C.sub.2H.sub.5, or C.sub.3
to C.sub.10 straight-chain, branched or cyclic alkane or alkene,
optionally substituted with at least one member selected from the
group consisting of Cl, Br, F, I, OH, NH.sub.2 and SH, [0067] (B)
OH, [0068] (C) NH.sub.2, and [0069] (D) SH.
[0070] In one embodiment, the ionic liquid is selected from the
group consisting of 1-butyl-3-methylimidazolium hexafluorophosphate
[bmim][PF.sub.6], 1-butyl-3-methylimidazolium tetrafluoroborate
[bmim][BF.sub.4], 1-hexyl-3-methylimidazolium
bistrifluoromethylsulfonylimide [hmim][Tf.sub.2N], and
1-butyl-3-methylimidazolium acetate [bmim][acetate].
Method and Apparatus for Storing Secondary Refrigerant in a
Secondary Loop Refrigeration System
[0071] The method disclosed herein for storing a secondary
refrigerant in a secondary loop refrigeration system comprises the
following steps. The first step is providing a secondary loop
refrigeration system, as described above. When there is a shutdown
of the primary refrigeration system, e.g. due to a loss of
electrical power, the secondary refrigerant is released from the
secondary loop and contacted with at least one ionic liquid, as
described above, whereby at least a portion of the secondary
refrigerant is absorbed by the ionic liquid. The portion of the
secondary refrigerant absorbed is sufficient to relieve the
pressure in the secondary loop. The amount of ionic liquid needed
will depend on the amount of secondary refrigerant contained in the
secondary loop and the absorption capability of the ionic liquid
used. When operation of the primary refrigeration system resumes;
the absorbed secondary refrigerant may be released from the ionic
liquid back into the secondary loop. The secondary refrigerant can
be released from the ionic liquid most conveniently by heating the
ionic liquid containing the secondary refrigerant.
[0072] The inventions hereof can be better understood by reference
to FIG. 1., which shows a schematic drawing of an exemplary
secondary loop refrigeration system in cooling mode that may be
used to practice the method disclosed herein. The secondary loop
refrigeration system illustrated in FIG. 1 is suitable for use, for
example, in a supermarket or grocery store. Similar systems may be
useful for other applications, e.g. storage warehouses.
[0073] Referring to FIG. 1, the secondary loop containing the
secondary refrigerant is depicted by dashed arrows and runs through
an evaporator 10 in a refrigerated display case 90 (an example of a
storage compartment for storing refrigerated goods), which is
located in the interior of the store 100. The evaporator is in open
communication with the secondary loop for transferring heat from
the display case to the secondary refrigerant. In FIG. 1, the
primary refrigeration system is depicted by solid arrows and
comprises a compressor 30, a condenser 40, and an expansion valve
50. The heat exchanger 20 serves to transfer heat energy from the
secondary refrigerant in the secondary loop to the primary
refrigerant in the primary refrigeration system, as described
above.
[0074] In the event of a shutdown of the primary refrigeration
system, pressure in the secondary loop increases. This pressure
increase may be sensed by a pressure sensor 70 in fluid
communication with the secondary loop. When the pressure in the
secondary loop exceeds a predetermined value, a flow interrupter,
for example a valve such as a pressure relief valve 80 depicted in
FIG. 1, is opened, thereby releasing the secondary refrigerant from
the secondary loop. The released secondary refrigerant enters an
expansion tank 60, which is in fluid communication with the
secondary loop, where it is contacted with at least one ionic
liquid contained in the tank, whereby at least a portion of the
released secondary refrigerant is absorbed by the ionic liquid.
When operation of the primary refrigeration system resumes, the
absorbed secondary refrigerant may be released from the ionic
liquid back into the secondary loop by heating the ionic liquid
using a heat source 65, such as an electrical heating element, a
natural gas or oil fueled heat source, that is in thermal contact
with the expansion tank.
EXAMPLES
[0075] This invention is further defined in the following examples.
It should be understood that these examples, while indicating
preferred embodiments of the invention, are given by way of
illustration only. From the above discussion and these examples,
the essential characteristics of this invention can be ascertained,
and without departing from the spirit and scope thereof, various
changes and modifications of the invention can be made to adapt it
to various uses and conditions.
[0076] The meaning of abbreviations used is as follows: "min" means
minute(s), "hr" means hour(s), "mL" means milliliter(s), ".mu.L"
means microliter(s), "g" means gram(s), "mg" means milligram(s),
".mu.g" means microgram(s), "Pa" means pascal(s), "kPa" means
kilopascal(s), and "MPa" means megapascal(s).
Materials
[0077] 1-Butyl-3-methylimidazolium hexafluorophosphate
[bmim][PF.sub.6] (Lot No. 1055432, Filling Code 31304010),
1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF.sub.4] (Lot
No. 1080045, Filling Code 11304079), and
1-butyl-3-methylimidazolium acetate [bmim][Ac] (Lot No. S25803,
Filling Code 444041302) were purchased from Fluka Chemika (Buchs,
Switzerland) with a purity of >96%, >97%, >95%
respectively. The 1-hexyl-3-methylimidazolium
bis(trifluoromethylsulfonyflimide [hmim][Tf.sub.2N] (Lot EQ500831
632) was purchased from EMD Chemicals, Inc. (Gibbstown, N.J.) with
a purity of >99%. Coleman grade CO.sub.2 was obtained from MG
Industries (Malvern, Pa.), with a minimum purity of 99.99%. A
molecular sieve trap was installed to remove trace amounts of water
from the CO.sub.2.
Example 1
Solubility of Carbon Dioxide in 1-Butyl-3-Methylimidazolium
Hexafluorophosphate
[0078] This example illustrates the solubility of carbon dioxide in
1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF.sub.6] at
temperatures of 283.15.degree. K, 298.15.degree. K, 323.15.degree.
K, and 348.15.degree. K.
[0079] The gas solubility measurements were made using a
gravimetric microbalance (IGA-003 Multicomponent Analyzer, Hiden
Isochema Ltd., Warrington WAS 7TN UK). The IGA design integrates
precise computer-control and measurement of weight change, pressure
and temperature to enable fully automatic and reproducible
determination of gas absorption isotherms and isobars. The
microbalance consists of an electrobalance with sample and
counterweight components inside a stainless steel pressure-vessel.
The balance has a weigh range of 0-100 mg with a resolution of 0.1
.mu.g. An enhanced pressure stainless steel (SS316LN) reactor
capable of operation to 2.0 MPa and 773.15.degree. K was installed.
Approximately 60 mg of the [bmim][PF.sub.6] ionic liquid sample was
added to the sample container and the reactor was sealed. The
sample was dried and degassed by first pulling a course vacuum on
the sample with a diaphragm pump (model MVP055-3, Pfeiffer Vacuum
Inc., Nashua, N.H.) and then fully evacuating the reactor to
10.sup.-9 M Pa with a turbopump (model TSH-071, Pfeiffer Vacuum
Inc.). While under deep vacuum, the sample was heated to
348.15.degree. K for 10 hr with an external water jacket connected
to a remote-controlled constant-temperature bath (Ministat, model
cc-S3, Huber-USA, Northport, N.Y.). A mixture of 30% ethylene
glycol and 70% water by volume was used as the recirculating fluid
with a temperature range from 278.15 to 363.15.degree. K. The
sample mass slowly decreased as residual water and gases were
removed. Once the mass had stabilized for at least 60 min, the
sample dry mass was recorded. The percent weight loss for the ionic
liquid was about 1-3%. This weight loss can be attributed to the
loss of residual water.
[0080] The IGA-003 can operate in both dynamic and static modes.
All absorption measurements were performed in static mode. Static
mode operation introduces gas into the top of the balance away from
the sample, and both the admittance and exhaust valves control the
set-point pressure. The sample temperature was measured with a type
K thermocouple with an accuracy of .+-.0.1.degree. K. The
thermocouple was located inside the reactor next to the sample
container. The water jacket maintained the set-point temperature
automatically to within an accuracy of .+-.0.1.degree. K. Four
isotherms (at 283.15, 298.15, 323.15, and 348.15.degree. K) were
measured beginning with 283.15.degree. K. Once the desired
temperature was achieved and stabilized, the admittance and exhaust
valves automatically opened and closed to adjust the pressure to
the first set-point. Pressures from 10.sup.-10 to 10.sup.-2 MPa
were measured using a capacitance manometer (model PKR25, Pfeiffer
Vacuum Inc.), and pressures from 10.sup.-2 to 2.0 MPa were measured
using a piezo-resistive strain gauge (model PDCR4010, Druck, New
Faifield, Conn.). The reactor pressure set-point was maintained to
within .+-.0.4 to 0.8 kPa. The pressure ramp rate was set at 20
kPa/min and the temperature ramp rate was set at 1.degree. K/min.
The upper pressure limit of the stainless steel reactor was 2.0
MPa, and several isobars up to 2.0 MPa (0.01, 0.05, 0.1, 0.4, 0.7,
1.0, 1.3, 1.5, and 2.0 MPa) were measured. To ensure sufficient
time for gas-liquid equilibrium, the ionic liquid sample was
maintained at set-point for a minimum of 3 hr with a maximum
time-out of 20 hr.
[0081] The IGA method exploits the relaxation behavior following
pressure and temperature changes to simultaneously evaluate the
time-dependent absorption and asymptotic uptake. The real-time
processor was used to determine the end-point for each isotherm.
The percent relaxation used as an end point for the real-time
analysis was 99 percent. The minimum weight change for real-time
analysis was set at 1 .mu.g, the acceptable average deviation of
the model from the acquired data was set at 7 .mu.g, and the target
interval for weight acquisition was set at a typical value of 1
.mu.g. The temperature variation during an isotherm was maintained
less than 0.1.mu..degree. K/min.
[0082] The solubility data for carbon dioxide in [bmim][PF.sub.6]
is given in Table 1. The results demonstrate that the ionic liquid
[bmim][PF.sub.6] absorbs significant quantities of carbon dioxide
at various temperatures and pressures and that the absorbed carbon
dioxide can be released by increasing the temperature of the ionic
liquid. These results suggest that the ionic liquid
[bmim][PF.sub.6] could be used as a storage medium for carbon
dioxide in a secondary loop refrigeration system.
TABLE-US-00001 TABLE 1 Solubility of Carbon Dioxide in
[bmim][PF.sub.6] Temperature Pressure CO.sub.2 (.degree. K) (MPa)
(mass %) 283.05 0.05009 0.24 283.05 0.10018 0.46 283.55 0.39956
1.72 283.75 0.69959 2.97 283.65 0.99996 4.22 283.05 1.99975 8.35
298.05 0.05015 0.14 298.05 0.10020 0.29 298.15 0.39963 1.19 298.15
0.70000 2.07 298.05 0.99941 2.95 298.05 1.29990 3.80 298.05 1.49942
4.41 298.05 1.99919 5.80 323.25 0.01020 0.03 323.15 0.05026 0.09
323.15 0.10020 0.19 323.25 0.39961 0.76 323.15 0.70004 1.29 323.15
0.99979 1.81 323.15 1.30023 2.34 323.25 1.50027 2.70 323.25 1.99978
3.56 348.05 0.05008 0.04 348.05 0.10003 0.11 348.05 0.39969 0.51
348.05 0.70001 0.89 348.25 1.99951 2.45
Example 2
Solubility of Carbon Dioxide in 1-Butyl-3-methylimidazolium
Tetrafluoroborate
[0083] This example illustrates the solubility of carbon dioxide in
1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF.sub.4] at
temperatures of 283.15.degree. K, 298.15.degree. K, 323.15.degree.
K, and 348.15.degree. K.
[0084] The method and the apparatus used to make the solubility
measurements were the same as described in Example 1. The results
of the solubility measurements are given in Table 2. The results
demonstrate that the ionic liquid [bmim][BF.sub.4] absorbs
significant quantities of carbon dioxide at various temperatures
and pressures and that the absorbed carbon dioxide can be released
by increasing the temperature of the ionic liquid. These results
suggest that the ionic liquid [bmim][BF.sub.4] could be used as a
storage medium for carbon dioxide in a secondary loop refrigeration
system.
TABLE-US-00002 TABLE 2 Solubility of Carbon Dioxide in
[bmim][BF.sub.4] Temperature Pressure CO.sub.2 (.degree. K) (MPa)
(mass %) 282.75 0.01017 0.04 282.95 0.05015 0.24 283.05 0.10010
0.46 283.05 0.40010 1.88 283.25 0.69962 3.25 283.05 0.99967 4.64
283.05 1.30019 5.93 283.15 1.50006 6.79 283.05 2.00019 8.97 298.15
0.05002 0.19 298.05 0.10013 0.36 298.15 0.39956 1.42 298.15 0.70022
2.45 297.95 0.99967 3.46 298.15 1.30022 4.44 297.95 1.50008 5.09
298.05 2.00020 6.66 323.25 0.01015 0.06 323.15 0.05011 0.13 323.15
0.10014 0.23 323.15 0.39970 0.88 323.15 0.69962 1.49 323.15 1.00020
2.09 323.15 1.29965 2.69 323.15 1.50011 3.07 323.15 2.00000 4.02
348.15 0.01020 0.04 348.15 0.05013 0.07 348.05 0.10018 0.15 348.05
0.40018 0.60 348.15 0.69956 1.01 347.95 1.00027 1.43 348.15 1.30000
1.83 348.15 1.50024 2.11 348.05 1.99990 2.77
Example 3
Solubility of Carbon Dioxide in 1-Hexyl-3-methylimidazolium
bis(trifluoromethylsulfonyl)imide
[0085] This example illustrates the solubility of carbon dioxide in
1-hexyl-3-methylimidazolium bistrifluoromethylsulfonylimide
[hmim][Tf.sub.2N] at temperatures of 283.15.degree. K,
298.15.degree. K, 323.15.degree. K, and 348.15.degree. K.
[0086] The method and the apparatus used to make the solubility
measurements were the same as described in Example 1. The results
of the solubility measurements are given in Table 3. The results
demonstrate that the ionic liquid [hmim][Tf.sub.2N] absorbs
significant quantities of carbon dioxide at various temperatures
and pressures and that the absorbed carbon dioxide can be released
by increasing the temperature of the ionic liquid. These results
suggest that the ionic liquid [hmim][Tf.sub.2N] could be used as a
storage medium for carbon dioxide in a secondary loop refrigeration
system.
TABLE-US-00003 TABLE 3 Solubility of Carbon Dioxide in [hmim][Tf2N]
Temperature Pressure CO.sub.2 (.degree. K) (MPa) (mass %) 283.04
0.0103 0.08 283.08 0.0499 0.27 283.09 0.1000 0.51 283.17 0.3994
1.93 283.23 0.7003 3.39 283.10 0.9996 4.87 283.12 1.2993 6.35
283.08 1.4996 7.29 283.08 2.0002 9.79 298.25 0.0105 0.07 298.17
0.0504 0.20 298.11 0.1004 0.38 298.25 0.3993 1.38 298.08 0.7003
2.41 298.22 1.0004 3.43 298.24 1.2997 4.42 298.14 1.4993 5.06
323.12 0.0104 0.02 323.09 0.0504 0.10 323.12 0.1000 0.20 323.16
0.3999 0.85 323.13 0.6994 1.49 323.00 0.9995 2.15 323.08 1.3002
2.80 323.09 1.4994 3.19 323.12 1.9998 4.23 348.13 0.0105 0.04
348.11 0.0502 0.08 348.09 0.1002 0.18 348.14 0.4002 0.64 348.09
0.6995 1.10 348.20 1.0002 1.57 348.09 1.3003 1.99 348.18 1.5004
2.28 348.15 1.9994 2.97
Example 4
Solubility of Carbon Dioxide in 1-Butyl-3-methylimidazolium
Acetate
[0087] This example illustrates the solubility of carbon dioxide in
1-butyl-3-methylimidazolium acetate [bmim][acetate] at temperatures
of 283.15.degree. K, 298.15.degree. K, 323.15.degree. K, and
348.15.degree. K.
[0088] The method and the apparatus used to make the solubility
measurements were the same as described in Example 1. The results
of the solubility measurements are given in Table 4. The results
demonstrate that the ionic liquid [bmim][acetate] absorbs
significant quantities of carbon dioxide at various temperatures
and pressures and that the absorbed carbon dioxide can be released
by increasing the temperature of the ionic liquid. These results
suggest that the ionic liquid [bmim][acetate] could be used as a
storage medium for carbon dioxide in a secondary loop refrigeration
system.
TABLE-US-00004 TABLE 4 Solubility of Carbon Dioxide in
[bmim][acetate] Temperature Pressure CO.sub.2 (.degree. K) (MPa)
(mass %) 283.16 0.0103 1.73 283.10 0.0503 4.64 283.06 0.1001 7.07
283.14 0.3993 9.84 283.09 0.7000 11.70 283.09 0.9993 13.33 283.08
1.3016 14.85 282.99 1.4999 15.69 283.06 1.9999 17.93 298.09 0.0102
4.12 298.04 0.0503 6.91 298.18 0.1003 7.76 298.10 0.3994 9.61
298.13 0.7001 10.79 298.14 0.9996 11.83 298.25 1.3002 12.78 298.14
1.5000 13.39 298.13 1.9994 14.92 323.09 0.0104 2.61 323.11 0.0504
4.52 323.06 0.1004 5.38 323.11 0.3995 7.26 323.15 0.7003 8.27
323.05 1.0001 9.08 323.09 1.3002 9.75 323.08 1.4995 10.15 323.20
1.9993 11.13 348.09 0.0104 1.47 348.07 0.0505 3.19 348.15 0.1000
4.07 348.09 0.4002 6.04 348.12 0.6994 6.88 348.10 1.0003 7.51
348.12 1.2994 7.98 348.13 1.4997 8.21 348.18 1.9993 8.91
[0089] The term "invention" as used herein is a non-limiting term,
and is not intended to refer to any single embodiment of the
various inventions hereof to the exclusion of others, but
encompasses all possible embodiments as described in the
specification and the claims.
[0090] In this specification, unless explicitly stated otherwise or
indicated to the contrary by the context of usage, where an
embodiment of the subject matter to hereof is stated or described
as comprising, including, containing, having, being composed of or
being constituted by or of certain features or elements, one or
more features or elements in addition to those explicitly stated or
described may be present in the embodiment. An alternative
embodiment of the subject matter hereof, however, may be stated or
described as consisting essentially of certain features or
elements, in which embodiment features or elements that would
materially alter the principle of operation or the distinguishing
characteristics of the embodiment are not present therein. A
further alternative embodiment of the subject matter hereof may be
stated or described as consisting of certain features or elements,
in which embodiment, or in insubstantial variations thereof, only
the features or elements specifically stated or described are
present.
* * * * *