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.

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: 
       
         
           
           
               
               
           
         
         wherein: 
         A) R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 12  and R 13  are independently selected from the group consisting of:
 (vii) H, 
 (viii) halogen, 
 (ix) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (x) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (xi) C 6  to C 20  unsubstituted aryl, or C 3  to C 25  unsubstituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; 
 (xii) C 6  to C 25  substituted aryl, or C 3  to C 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 3 , —C 2 H 5 , or C 3  to C 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 2  and SH, 
 (B) OH, 
 (C) NH 2 , and 
 (D) SH; and 
 
 (vii) —(CH 2 ) n Si(CH 2 ) m CH 3 , —(CH 2 ) n Si(CH 3 ) 3 , —(CH 2 ) n OSi(CH 3 ) m , where n is independently 1-4 and m is independently 0-4; 
 
         B) R 7 , R 8 , R 9 , and R 10  are independently selected from the group consisting of:
 (viii) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (ix) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (x) C 6  to C 25  unsubstituted aryl, or C 3  to C 25  unsubstituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; and C 6  to C 25  substituted aryl, or C 3  to C 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 3 , —C 2 H 5 , or C 3  to C 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 2  and SH, 
 (F) OH, 
 (G) NH 2 , and 
 (H) SH; and 
 
 (xi) —(CH 2 ) n Si(CH 2 ) m CH 3 , —(CH 2 ) n Si(CH 3 ) 3 , —(CH 2 ) n OSi(CH 3 ) m , where n is independently 1-4 and m is independently 0-4; and 
 
         C) optionally at least two of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 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 3 CO 2 ] − , [HSO 4 ] − , [CH 3 OSO 3 ] − , [C 2 H 5 OSO 3 ] − , [AlCl 4 ] − , [CO 3 ] 2− , [HCO 3 ] − , [NO 2 ] − , [NO 3 ] − , [SO 4 ] 2− , [PO 3 ] 3− , [HPO 3 ] 2− , [H 2 PO 3 ] 1− , [PO 4 ] 3− , [HPO 4 ] 2− , [H 2 PO 4 ] − , [HSO 3 ] − , [CuCl 2 ] − , Cl − , Br − , I − , SCN − , 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 3 CO 2 ] − , [HSO 4 ] − , [CH 3 OSO 3 ] − , [C 2 H 5 OSO 3 ] − , [AlCl 4 ] − , [CO 3 ] 2− , [HCO 3 ] − , [NO 2 ] − , [NO 3 ] − , [SO 4 ] 2− , [PO 4 ] 3− , [HPO 4 ] 2− , [H 2 PO 4 ] − , [HSO 3 ] − , [CuCl 2 ] − , Cl − , Br − , I − , SCN − , [BF 4 ] − , [PF 6 ] − , [SbF 6 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [(CF 3 CF 2 SO 2 ) 2 N] − , [(CF 3 SO 2 ) 3 C] − , [CF 3 CO 2 ] − , [CF 3 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CFHOCF 2 CF 2 SO 3 ] − , [CF 2 HCF 2 OCF 2 CF 2 SO 3 ] − , [CF 2 ICF 2 OCF 2 CF 2 SO 3 ] − , [CF 3 CF 2 OCF 2 CF 2 SO 3 ] − , [(CF 2 HCF 2 SO 2 ) 2 N]_, [(CF 3 CFHCF 2 SO 2 ) 2 N] − , F − , and anions represented by the structure of the following formula: 
       
         
           
           
               
               
           
         
         wherein R 11  is selected from the group consisting of:
 (v) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (vi) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (vii) C 6  to C 10  unsubstituted aryl, or C 3  to C 10  unsubstituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; and 
 (viii) C 6  to C 10  substituted aryl, or C 3  to C 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 3 , —C 2 H 5 , or C 3  to C 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 2  and SH, 
 (B) OH, 
 (C) NH 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 6 ], 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF 4 ], 1-hexyl-3-methylimidazolium bistrifluoromethylsulfonylimide [hmim][Tf 2 N], 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: 
       
         
           
           
               
               
           
         
         wherein: 
         A) R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 12  and R 13  are independently selected from the group consisting of:
 (xiii) H, 
 (xiv) halogen, 
 (xv) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (xvi) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (xvii) C 6  to C 20  unsubstituted aryl, or C 3  to C 25  unsubstituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; 
 (xviii) C 6  to C 25  substituted aryl, or C 3  to C 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 3 , —C 2 H 5 , or C 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 2  and SH, 
 (B) OH, 
 (C) NH 2 , and 
 (D) SH; and 
 
 (vii) —(CH 2 ) n Si(CH 2 ) m CH 3 , —(CH 2 ) n Si(CH 3 ) 3 , —(CH 2 ) n OSi(CH 3 ) m , where n is independently 1-4 and m is independently 0-4; 
 
         B) R 7 , R 8 , R 9 , and R 10  are independently selected from the group consisting of:
 (viii) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (ix) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (x) C 6  to C 25  unsubstituted aryl, or C 3  to C 25  unsubstituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; and C 6  to C 25  substituted aryl, or C 3  to C 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 3 , —C 2 H 5 , or C 3  to C 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 2  and SH, 
 (F) OH, 
 (G) NH 2 , and 
 (H) SH; and 
 
 (xi) —(CH 2 ) n Si(CH 2 ) m CH 3 , —(CH 2 ) n Si(CH 3 ) 3 , —(CH 2 ) n OSi(CH 3 ) m , where n is independently 1-4 and m is independently 0-4; and 
 
         C) optionally at least two of R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 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 3 CO 2 ] − , [HSO 4 ] − , [CH 3 OSO 3 ] − , [C 2 H 5 OSO 3 ] − , [AlCl 4 ] − , [CO 3 ] 2− , [HCO 3 ] − , [NO 2 ] − , [NO 3 ] − , [SO 4 ] 2− , [PO 3 ] 3− , [HPO 3 ] 2− , [H 2 PO 3 ] 1− , [PO 4 ] 3− , [HPO 4 ] 2− , [H 2 PO 4 ] − , [HSO 3 ] − , [CuCl 2 ] − , Cl − , Br − , I − , SCN − , 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 3 CO 2 ] − , [HSO 4 ] − , [CH 3 OSO 3 ] − , [C 2 H 5 OSO 3 ] − , [AlCl 4 ] − , [CO 3 ] 2− , [HCO 3 ] − , [NO 2 ] − , [NO 3 ] − , [SO 4 ] 2− , [PO 4 ] 3− , [HPO 4 ] 2− , [H 2 PO 4 ] − , [HSO 3 ] − , [CUCl 2 ] − , Cl − , Br − , I − , SCN − , [BF 4 ] − , [PF 6 ] − , [SbF 6 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [(CF 3 CF 2 SO 2 ) 2 N] − , [(CF 3 SO 2 ) 3 C] − , [CF 3 CO 2 ] − , [CF 3 OCPHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CFHOCF 2 CF 2 SO 3 ] − , [CF 2 HCF 2 OCF 2 CF 2 SO 3 ] − , [CF 2 ICF 2 OCF 2 CF 2 SO 3 ] − , [CF 3 CF 2 OCF 2 CF 2 SO 3 ] − , [(CF 2 HCF 2 SO 2 ) 2 N] − , [(CF 3 CFHCF 2 SO 2 ) 2 N] − , F − , and anions represented by the structure of the following formula: 
       
         
           
           
               
               
           
         
         wherein R 11  is selected from the group consisting of:
 (ix) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (x) —CH 3 , —C 2 H 5 , or C 3  to C 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 2  and SH; 
 (xi) C 6  to C 10  unsubstituted aryl, or C 3  to C 10  unsubstituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; and 
 (xii) C 6  to C 10  substituted aryl, or C 3  to C 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 3 , —C 2 H 5 , or C 3  to C 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 2  and SH, 
 (B) OH, 
 (C) NH 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 6 ], 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF 4 ], 1-hexyl-3-methylimidazolium bistrifluoromethylsulfonylimide [hmim][Tf 2 N], and 1-butyl-3-methylimidazolium acetate [bmim][acetate].