基于膜分离器的NH_3-H_2O-LiBr吸收式制冷系统的研究分析
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摘要
氨-水-溴化锂(NH_3-H_2O-LiBr)三元吸收式制冷系统中溴化锂的存在有利于发生过程的进行,降低循环精馏热,但阻碍了吸收氨的传质过程,对吸收性能不利。对此本文提出基于膜分离器的氨-水-溴化锂吸收式制冷循环,可将溴化锂从进入吸收器的溶液中分离出来,进而改善吸收性能。并进行了在膜分离器中分离溴化锂的实验,实验结果表明NH_3-H_2O-LiBr三元溶液在膜分离器中两次循环后分离效率达98%。基于实验中的分离效率,利用Aspen Plus模拟器,进一步模拟分析了基于膜分离器的氨-水-溴化锂吸收式制冷系统,并计算其性能系数(COP)。结果表明,与普通三元循环相比,基于膜分离器的新型循环的能耗较低,性能系数可提高近10%。当发生温度从60℃升高到120℃时,循环的发生器热负荷逐渐降低,COP逐渐增大,最大达0.5869,较普通循环高6%,此时溴化锂质量分数变化范围为0～30%。
The existence of lithium bromide can significantly improve the process of generation and reduce energy consumption of rectification. But it has negative effect on the absorption process of ammonia. Therefore, the new cycle of NH_3-H_2O-LiBr absorption refrigeration system based on membraneseparator was proposed to separate lithium bromide from the solution stream entering absorber and improve absorption performance. And the experiment for separating lithium bromide in the membraneseparator was carried out. The results showed that the separation efficiency of lithium bromide can reach98% after twice solution cycle in membrane separator. Based on the separation efficiency of experiments,the Aspen Plus monitor process was used for further simulating and analyzing the NH_3-H_2O-LiBrabsorption refrigeration system with membrane separator. Simulation results indicated that due to theapplication of membrane separator, the energy consumption of new cycle based on membrane separatorwas lower than the normal absorption system and the COP can be improved nearly 10%. When generatortemperature increased from 60℃ to 120℃, the generator heat load decreased and the COP of absorption cycle increased with the highest value of 0.5869 at the mass fraction of lithium bromide ranging from 0—30%.
The existence of lithium bromide can significantly improve the process of generation and reduce energy consumption of rectification. But it has negative effect on the absorption process of ammonia. Therefore, the new cycle of NH_3-H_2O-LiBr absorption refrigeration system based on membraneseparator was proposed to separate lithium bromide from the solution stream entering absorber and improve absorption performance. And the experiment for separating lithium bromide in the membraneseparator was carried out. The results showed that the separation efficiency of lithium bromide can reach98% after twice solution cycle in membrane separator. Based on the separation efficiency of experiments,the Aspen Plus monitor process was used for further simulating and analyzing the NH_3-H_2O-LiBrabsorption refrigeration system with membrane separator. Simulation results indicated that due to theapplication of membrane separator, the energy consumption of new cycle based on membrane separatorwas lower than the normal absorption system and the COP can be improved nearly 10%. When generatortemperature increased from 60℃ to 120℃, the generator heat load decreased and the COP of absorption cycle increased with the highest value of 0.5869 at the mass fraction of lithium bromide ranging from 0—30%.
引文
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[16] LIANG Yuanyuan, LI Shuhong, YUE Xiaoyang, et al. Analysis ofNH3-H2O-LiBr absorption refrigeration integrated with anelectrodialysis device[J]. Applied Thermal Engineering, 2017,115:134-140.
[17]林子雄,鄢烈祥,李骁淳,等.基于流程模拟器和列队竞争算法的精馏操作优化[J].化工进展, 2013, 32(1):54-58.LIN Zixiong, YAN Liexiang, LI Xiaochun, et al. Distillationprocess operation optimization based on process simulator and theline-up competition algorithm[J]. Chemical Industry andEngineering Progress, 2013, 32(1):54-58.
[2] IBRAHIM O M, BARNET S M, BALAMURU V G. Improving theperformance of ammonia-water absorption cycles using saltadditives and membranes[J]. ASHRAE Transactions, 1997, 103(1):439-443.
[3] FOOTE H W. Equilibrium in the system ammonia-water-ammonium thiocyanate[J]. Journal of the American ChemicalSociety, 1921, 43(5):1031-1038.
[4] DAVIS R O E, OLMSTEAD L B, LANDSURM F O J. Vaporpressure of lithium nitrate ammonia system[J]. Journal of theAmerican Chemical Society, 1921, 43(7):1575-1580.
[5] AHLBY L, HODGETT D, RADERMACHER R. NH3/H2O-LiBr asworking fluid for the compression/absorption cycle[J]. InternationalJournal of Refrigeration, 1993, 16(4):265-273.
[6] PETERS R, GREB O, KORINTH C, et al. Vapor-liquid equilibriain the system NH3+H2O+LiBr. 1. Measurements at T=303~423Kand P=0.1~1.5MPa[J]. J. Chem. Eng. Data, 1995, 40:769-774.
[7] WU Tiehui, WU Yuyuan, YU Zhiqiang, et al. Experimentalinvestigation on an ammonia-water-lithium bromide absorptionrefrigeration system without solution pump[J]. Energy Conversionand Management, 2011, 52:2314-2319.
[8] STEIU Simona, SALAVERA Daniel, BRUNO Joan Carles, et al. Abasis for the development of new ammonia–water–sodiumhydroxide absorption chillers[J]. International Journal ofRefrigeration, 2009, 32:577-587.
[9] ORTIZ J M, SOTOCA J A, EXPOSITO E, et al. Brackish waterdesalination by electrodialysis:batch recirculation operationmodeling[J]. Journal of Membrane Science, 2005, 252:65-75.
[10] MOHAMMADI T, KAVIANI A. Water shortage and seawaterdesalination by electrodialysis[J]. Desalination, 2003, 158:267-270.
[11]陈霞,蒋晨啸,汪耀明,等.反向电渗析(RED)在新能源及环境保护应用中的研究进展[J].化工学报, 2017, 69(1):1-12.CHEN Xia, JIANG Chenxiao, WANG Yaoming, et al. Advances inreverse electrodialysis and its applications on renewable energy&environment protection[J]. CIESC Journal, 2017, 69(1):1-12.
[12]时钧,袁权,高从堦.膜技术手册[M].北京:化学工业出版社,2001:438-442.SHI Jun, YUAN Quan, GAO Congjie. Membrane technologyhandbook[M].Beijing:Chemical Industry Press, 2001:438-442.
[13]张维润.电渗析工程学[M].北京:科学出版社, 1995:247-270.ZHANG Weirun. Electrodialysis engineering[M]. Beijing:SciencePress, 1995:247-270.
[14]曹连城,吴文珊.电渗析极限电流的测定及与水型水温的关系[J].湖北化工学报, 1999, 16(3):1-4.CAO Liancheng, WU Wenshan. Determination of ultimate currentof electrodialysis and its relationship with water temperature[J].Hubei Chemical Industry, 1999, 16(3):1-4.
[15] MANSOURI R, BOUKHOLDA I, BOUROUIS M, et al. Modelingand testing the performance of a commercial ammonia/waterabsorption chiller using Aspen-Plus platform[J]. Energy, 2015,93:2374-2383.
[16] LIANG Yuanyuan, LI Shuhong, YUE Xiaoyang, et al. Analysis ofNH3-H2O-LiBr absorption refrigeration integrated with anelectrodialysis device[J]. Applied Thermal Engineering, 2017,115:134-140.
[17]林子雄,鄢烈祥,李骁淳,等.基于流程模拟器和列队竞争算法的精馏操作优化[J].化工进展, 2013, 32(1):54-58.LIN Zixiong, YAN Liexiang, LI Xiaochun, et al. Distillationprocess operation optimization based on process simulator and theline-up competition algorithm[J]. Chemical Industry andEngineering Progress, 2013, 32(1):54-58.