基于变压精馏分离乙酸乙酯/正己烷共沸体系两塔的温差，利用Aspen Plus软件，以年度总成本最小为目标函数，对部分及完全热集成变压精馏工艺进行了稳态模拟及优化。在此基础上，利用Aspen Dynamics软件开发了多种控制结构，通过引入不同进料流量及组成的扰动测试控制结构的有效性。结果表明，完全热集成变压精馏工艺比部分热集成变压精馏工艺的经济性稍好。动态响应结果表明，部分热集成变压精馏工艺的压力?补偿温度控制结构可有效处理不同程度的干扰，能有效提高控制结构对干扰的响应速度，缩短达到新稳态的时间，保证乙酸乙酯和正己烷产品纯度在99.9wt%之上；而完全热集成变压精馏工艺的组分?温度串级控制结构仅能处理较小的组分和流量干扰，实现稳健控制，无法处理较大的干扰。综合比较两种工艺的经济性和可控性，认为部分热集成变压精馏工艺分离乙酸乙酯/正己烷共沸体系优于完全热集成变压精馏工艺。
The azeotropic composition of ethyl-acetate/n-hexane azeotropic system dramatically shifts with pressure. Therefore, this system can be effectively separated by pressure-swing distillation (PSD). In order to save the total annual cost (TAC) and energy, the partially and fully heat-integrated pressure-swing distillation (HIPSD) between condenser and reboiler of two columns were used in this process. The simulation and optimization of different heat-integrated PSD processes were carried out by using Aspen Plus software. The results showed that the energy cost, equipment cost and TAC of the fully HIPSD process had further reductions of 12.24%, 4.38% and 8.60% compared with partially HIPSD process. On the basis of the best optimal process, feed flowrate and composition disturbances with several different degrees were introduced to test the dynamic characteristics of different control structures for partial and fully HIPSD processes by Aspen Dynamics. For partially HIPSD process, three kinds of control structure including basic control structure, proportional control structure and pressure-compensated temperature control structure were developed to test the effectiveness of control structures. The results of the dynamic response showed that the pressure-compensated temperature control structure could handle the feed flowrate and composition disturbances with different degrees and effectively maintain the purity of ethyl acetate and n-hexane products at 99.9wt%. For fully HIPSD process, the composition/temperature cascade control structure could effectively handle the small disturbances (±5% and ±10%) and achieve robust control, but this control structure cannot effectively maintain the product purity of 99.90wt% and realize robust control when subject to ±20% feed and composition disturbances. Compared with the partially HIPSD mode, the fully HIPSD mode could handle much smaller feed flow rate and composition disturbances despite of a little economic benefit. Therefore, the selection of energy-saving modes for the separation process should weigh economy against controllability.
参考文献
[1] 程能林. 溶剂手册[M]. 第5版. 北京: 化学工业出版社, 2015.
[2] 白鹏，朱良伟，李晓峰，等. 正己烷和乙酸乙酯间歇共沸精馏分离共沸剂的研究[J]. 石油化工. 2006, 35(01): 37-41.
[3] 杨金杯，余美琼，郑志功，等. 热集成变压精馏分离乙酸乙酯与乙醇工艺及模拟[J]. 山东大学学报(工学版). 2013(01): 109-114.
[4] Susial P S A R E. Vapor Pressure and VLE Data Measurements on Ethyl Acetate/Ethanol Binary System at 0.1, 0.5, and 0.7 MPa[J]. Journal of Chemical Engineering of Japan. 2011, 44(3): 155-163.
[5] 黄丽红，韩淑萃. 萃取精馏分离乙酸乙酯和正己烷的过程模拟[J]. 广东化工. 2012, 39(11): 64-65.
[6] 杨文东，袁慎峰，陈志荣，等. 乙酸乙酯—正己烷萃取精馏过程的模拟计算[J]. 计算机与应用化学. 2012, 29(8): 955-958.
[7] 叶青，肖国栋. 共沸精馏分离正已烷和乙酸乙酯的模拟研究[J]. 常州大学学报(自然科学版). 2010, 22(02): 31-33.
[8] 吕利平，李航，李兵，等. 变压精馏分离乙酸乙酯-正己烷共沸物的动态特性[J]. 高校化学工程学报. 2018, 32(02): 478-486.
[9] Lü L, Zhu L, Liu H, et al. Comparison of continuous homogenous azeotropic and pressure-swing distillation for a minimum azeotropic system ethyl acetate/n-hexane separation[J]. Chinese Journal of Chemical Engineering. 2018, 26(10): 2023-2033.
[10] Luo B, Feng H, Sun D, et al. Control of fully heat-integrated pressure swing distillation for separating isobutyl alcohol and isobutyl acetate[J]. Chemical Engineering and Processing: Process Intensification. 2016, 110: 9-20.
[11] Zhang Z, Zhang Q, Li G, et al. Design and control of methyl acetate-methanol separation via heat-integrated pressure-swing distillation[J]. Chinese Journal of Chemical Engineering. 2016, 24(11): 1584-1599.
[12] Zhu Z, Wang L, Ma Y, et al. Separating an azeotropic mixture of toluene and ethanol via heat integration pressure swing distillation[J]. Computers & Chemical Engineering. 2015, 76: 137-149.
[13] Wang Y, Zhang Z, Zhang H, et al. Control of Heat Integrated Pressure-Swing-Distillation Process for Separating Azeotropic Mixture of Tetrahydrofuran and Methanol[J]. Industrial & Engineering Chemistry Research. 2015, 54(5): 1646-1655.
[14] Luyben W L. Design and Control of a Fully Heat-Integrated Pressure-Swing Azeotropic Distillation System[J].
[15] Luyben W L. Control of a triple-column pressure-swing distillation process[J]. Separation and Purification Technology. 2017, 174: 232-244.
[16] Zhu Z, Xu D, Jia H, et al. Heat Integration and Control of a Triple-Column Pressure-Swing Distillation Process[J]. Industrial & Engineering Chemistry Research. 2017, 56(8): 2150-2167.
[17] Luyben W L. Comparison of extractive distillation and pressure-swing distillation for acetone/chloroform separation[J]. Computers & Chemical Engineering. 2013, 50: 1-7.
[18] Wang Y, Zhang Z, Xu D, et al. Design and control of pressure-swing distillation for azeotropes with different types of boiling behavior at different pressures[J]. Journal of Process Control. 2016, 42: 59-76.
[19] Luyben W L. Distillation Design and Control Using Aspen Simulation[G]. John Wiley & Sons, 2006.
[20] Zhang Z, Zhang Q, Li G, et al. Design and control of methyl acetate-methanol separation via heat-integrated pressure-swing distillation[J]. Chinese Journal of Chemical Engineering. 2016, 24(11): 1584-1599.
[21] Zhang Q, Peng J, Zhang K. Separation of an azeotropic mixture of dimethyl carbonate and methanol via partial heat integration pressure swing distillation[J]. Asia-Pacific Journal of Chemical Engineering. 2017, 12(1): 50-64.
[22] Cao Y, Li M, Wang Y, et al. Effect of feed temperature on economics and controllability of pressure-swing distillation for separating binary azeotrope[J]. Chemical Engineering and Processing: Process Intensification. 2016, 110: 160-171.
