考虑塔压变量优化的精馏塔间热集成
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摘要
塔压是改变塔内温度分布的关键参数。传统设计一般先固定塔压,然后再搜寻可能的热集成,未考虑精馏与换热过程的同步优化。以塔压为关键耦合变量优化塔间的热集成,首先给出筛选热集成物流的启发式规则,然后借助流程模拟数据建立塔压与待选物流温度的约束关系,最后以年度总费用为目标函数建立了考虑塔压参数作为变量的热集成优化模型,并利用GAMS软件求解。以某炼化企业40 kt·a~(-1)干气制乙苯的精馏系统为研究背景,将塔压与物流温度关系线性化。案例研究表明:苯塔和乙苯塔的压力分别为1.5和0.82 MPa时,对应最优的热集成方案,其年度总费用为9310000 CNY·a~(-1),热集成的经济效益约为39890000 CNY·a~(-1)。本研究揭示了塔压作为耦合变量对热集成的影响及作用机制,即塔压越高并非热集成效果越好,应考虑热集成系统中不同换热过程的相互影响和制约。
Pressure is a key parameter in controlling temperature distribution inside columns. Traditional column design usually fixes pressure first, and then possible heat integration opportunities are searched without considering simultaneous optimization of distillation and heat exchange. In this paper, column pressure was regarded as a key coupling variable in heat integration. Heuristic rules for screening streams of heat integration were first presented, and then the constraints between pressure and stream temperature were built using simulation data. Finally, annual cost as the objective function was expressed in the heat integration optimization model considering pressure as a variable, and GAMS was used to solve the problem. A distillation system which can produce 40 kt·a~(-1) of ethylbenzene from dry gas was taken as a case study from petrochemical industry, and the relationship between pressure and temperature was linearly fitted. The case study shows that the optimal pressures of the benzene and ethylbenzene columns are 1.5 MPa and 0.82 MPa, respectively. The total annual cost in the optimal heat integration scheme is 9.31 million CNY·a~(-1), and its economic benefits is about 39.89 million CNY·a~(-1). This study shows the effect and mechanism of pressure as a coupling variable on heat integration. Higher pressure does not result in better heat integration, and mutual effects/restraints should be considered in different heat exchanger processes of heat integrated systems.
Pressure is a key parameter in controlling temperature distribution inside columns. Traditional column design usually fixes pressure first, and then possible heat integration opportunities are searched without considering simultaneous optimization of distillation and heat exchange. In this paper, column pressure was regarded as a key coupling variable in heat integration. Heuristic rules for screening streams of heat integration were first presented, and then the constraints between pressure and stream temperature were built using simulation data. Finally, annual cost as the objective function was expressed in the heat integration optimization model considering pressure as a variable, and GAMS was used to solve the problem. A distillation system which can produce 40 kt·a~(-1) of ethylbenzene from dry gas was taken as a case study from petrochemical industry, and the relationship between pressure and temperature was linearly fitted. The case study shows that the optimal pressures of the benzene and ethylbenzene columns are 1.5 MPa and 0.82 MPa, respectively. The total annual cost in the optimal heat integration scheme is 9.31 million CNY·a~(-1), and its economic benefits is about 39.89 million CNY·a~(-1). This study shows the effect and mechanism of pressure as a coupling variable on heat integration. Higher pressure does not result in better heat integration, and mutual effects/restraints should be considered in different heat exchanger processes of heat integrated systems.
引文
[1]KANG Li-xia(康丽霞),JIANG Nan(姜楠),XIA Ming-xing(夏明星),et al.Parallel genetic algorithm for design of HEN based on Open MP system(基于Open MP的并行GA加速求解换热网络设计)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2016,30(2):431-438.
[2]WEI Ying(魏颖),FENG Xiao(冯霄).Research and progress on heat integrated complex system synthesis(塔系热集成问题的研究及进展)[J].Petroleum&Chemical Energy Conservation(石油和化工节能),2007(5):3-5.
[3]ZHAN Shi-hui(湛世辉),WANG Yu-fei(王彧斐),FENG Xiao(冯霄).Heat integration of columns in styrene plant(苯乙烯装置塔系热集成)[J].Chemical Industry and Engineering Progress(化工进展),2015,34(6):1564-1568.
[4]LI Chun-yan(李春妍),ZHANG Lü-hong(张吕鸿),PAN Xu-ming(潘旭明).Application of differential pressure thermally coupled distillation technology in high-purity pentane(差压热集成技术在高纯戊烷生产中的应用)[J].Acta Petrolei Sinica(Petroleum Processing Section)(石油学报(石油加工)),2011,27(2):308-312.
[5]Aly S.Heuristic approach for the synthesis of heat integrated distillation sequences[J].International Journal of Energy Research,1997,21(14):1297-1304.
[6]WANG Xu(汪旭),FENG Xiao(冯霄).Heat integration of distillation system based on simulation analysis and heuristic approach(基于模拟分析技术和启发式方法的精馏塔系热集成)[J].Journal of North China Electric Power University(华北电力大学学报),2010,37(1):87-91.
[7]QIAN Xin-hua(钱新华),SUN Xiao-jing(孙晓静),WANG Ke-feng(王克峰),et al.Energy integration based on simulation analysis and stochastic search(基于模拟分析技术和随机搜索算法的化工过程能量集成方法研究)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2007,21(2):322-327.
[8]SUN Yan-ze(孙艳泽),FENG Xiao(冯霄).Heat integration of equipments with different operating conditions(具有不同操作工况的装置的热集成)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2007,21(5):843-848.
[9]LI Yu-gang(李玉刚),LI Chun-xin(李春欣),ZHANG Wei(张伟),et al.Heat integration of separation process for mixture with wide boiling-range(宽沸程物系分离过程的热集成)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2008,22(1):34-37.
[10]WU Meng-bing(吴孟兵).Heat integration distillation process in the application of pentane plant(热集成精馏工艺在戊烷装置中的应用)[J].Chemical Engineering&Equipment(化学工程与装备),2016(1):17-19.
[11]HAN Zhen(韩祯),LI Hong-da(李宏达),GAO Xin(高鑫),et al.Process simulation of separation of isopropylacetate-isopropanol mixture by pressure swing distillation with heat integration(乙酸异丙酯-异丙醇物系的热集成变压精馏分离模拟)[J].Petrochemical Technology(石油化工),2015,44(6):663-668.
[12]Andrecovich M J,Westerberg A W.An MILP formulation for heat integrated distillation sequence synthesis[J].AICh E Journal,1985,31(9):1461-1474.
[13]WANG Ke-feng(王克峰),YIN Hong-chao(尹洪超),YAO Ping-jing(姚平经),et al.Simultaneous optimization for separation system and heat exchanger network using genetic algorithm and neural network(分离系统与换热网络同步优化方法的改进神经元网络-遗传算法)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),1997,11(3):294-299.
[14]Lei Y,Qi X,Zhang B J,et al.Simultaneous optimization of the complex fractionator and heat exchanger network considering the constraints of variable heat removals in delayed coking units[J].Industrial&Engineering Chemistry Research,2014,53(33):13073-13086.
[15]Yee T F,Grossmann I E.Simultaneous optimization models for heat integration-II.Heat exchanger network synthesis[J].Computers&Chemical Engineering,1990,14(10):1165-1184.
[2]WEI Ying(魏颖),FENG Xiao(冯霄).Research and progress on heat integrated complex system synthesis(塔系热集成问题的研究及进展)[J].Petroleum&Chemical Energy Conservation(石油和化工节能),2007(5):3-5.
[3]ZHAN Shi-hui(湛世辉),WANG Yu-fei(王彧斐),FENG Xiao(冯霄).Heat integration of columns in styrene plant(苯乙烯装置塔系热集成)[J].Chemical Industry and Engineering Progress(化工进展),2015,34(6):1564-1568.
[4]LI Chun-yan(李春妍),ZHANG Lü-hong(张吕鸿),PAN Xu-ming(潘旭明).Application of differential pressure thermally coupled distillation technology in high-purity pentane(差压热集成技术在高纯戊烷生产中的应用)[J].Acta Petrolei Sinica(Petroleum Processing Section)(石油学报(石油加工)),2011,27(2):308-312.
[5]Aly S.Heuristic approach for the synthesis of heat integrated distillation sequences[J].International Journal of Energy Research,1997,21(14):1297-1304.
[6]WANG Xu(汪旭),FENG Xiao(冯霄).Heat integration of distillation system based on simulation analysis and heuristic approach(基于模拟分析技术和启发式方法的精馏塔系热集成)[J].Journal of North China Electric Power University(华北电力大学学报),2010,37(1):87-91.
[7]QIAN Xin-hua(钱新华),SUN Xiao-jing(孙晓静),WANG Ke-feng(王克峰),et al.Energy integration based on simulation analysis and stochastic search(基于模拟分析技术和随机搜索算法的化工过程能量集成方法研究)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2007,21(2):322-327.
[8]SUN Yan-ze(孙艳泽),FENG Xiao(冯霄).Heat integration of equipments with different operating conditions(具有不同操作工况的装置的热集成)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2007,21(5):843-848.
[9]LI Yu-gang(李玉刚),LI Chun-xin(李春欣),ZHANG Wei(张伟),et al.Heat integration of separation process for mixture with wide boiling-range(宽沸程物系分离过程的热集成)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2008,22(1):34-37.
[10]WU Meng-bing(吴孟兵).Heat integration distillation process in the application of pentane plant(热集成精馏工艺在戊烷装置中的应用)[J].Chemical Engineering&Equipment(化学工程与装备),2016(1):17-19.
[11]HAN Zhen(韩祯),LI Hong-da(李宏达),GAO Xin(高鑫),et al.Process simulation of separation of isopropylacetate-isopropanol mixture by pressure swing distillation with heat integration(乙酸异丙酯-异丙醇物系的热集成变压精馏分离模拟)[J].Petrochemical Technology(石油化工),2015,44(6):663-668.
[12]Andrecovich M J,Westerberg A W.An MILP formulation for heat integrated distillation sequence synthesis[J].AICh E Journal,1985,31(9):1461-1474.
[13]WANG Ke-feng(王克峰),YIN Hong-chao(尹洪超),YAO Ping-jing(姚平经),et al.Simultaneous optimization for separation system and heat exchanger network using genetic algorithm and neural network(分离系统与换热网络同步优化方法的改进神经元网络-遗传算法)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),1997,11(3):294-299.
[14]Lei Y,Qi X,Zhang B J,et al.Simultaneous optimization of the complex fractionator and heat exchanger network considering the constraints of variable heat removals in delayed coking units[J].Industrial&Engineering Chemistry Research,2014,53(33):13073-13086.
[15]Yee T F,Grossmann I E.Simultaneous optimization models for heat integration-II.Heat exchanger network synthesis[J].Computers&Chemical Engineering,1990,14(10):1165-1184.