| To recover the high value organic materials from the industrial effluent which contains acetonitrile and isopropanol,the separation for acetonitrile-isopropanol-water ternary azeotropic mixture by special distillation processes(extractive distillation,reactive-pressure-swing distillation and reactive-extractive distillation)are developed in this subject.The steady-state simulation of the proposed distillation processes is carried out using Aspen Plus,and the improved energy-saving processes on basic of conventional distillation process are developed.In this work,the pressure-relative volatility curves are used to find the optimal operating pressure of columns,and the suitable entrainer can be obtained by the solvent ratio-relative volatility curves.The energy saving technologies of heat-integrated,intermediate reboiler and heat pump are applied to reduce energy consumption of processes.The T-H diagram is developed to find the optimal process which has the best energy-saving performance.An analysis from the aspects of energy,exergy,economic and environment is conducted to evaluate the performance of the design’s processes.For the extractive distillation process,the mixture of acetonitrileisopropanol-water is separated by triple-column extractive distillation process using ethylene glycol as entrainer.Meanwhile,the energy-saving technologies of heat-integrated and intermediate reboiler are carried out to recover waste heat so that the energy consumption of proposed process can be saved adequately.The results present that the extractive distillation process combination heat-integrated and intermediate reboiler has greater energy saving potential than the conventional extractive distillation process.The best benefits process can save 36.24% total annual cost saving compared with those of the conventional extractive distillation process.In the reactive-pressure-swing distillation process,the component water could be removed firstly since it reacts with ethylene oxide in the reactive distillation column.The remainder acetonitrile-isopropanol binary mixture is separated by pressure-swing distillation process.The energy-saving technologies of heat-integrated and heat pump are used to recover waste heat and reduce the overall energy requirement of proposed processes.The result presents that the optimal reactive-pressure-swing distillation process can save 37.25% total annual cost compared with the optimal conventional extractive distillation process.In the process of reactive-extractive distillation process,the ethylene oxide reacts with water to form ethylene glycol,which can be used as an excellent extractant for separating acetonitrile-isopropanol mixture during the extractive distillation process so that the cost reduced.The process of heat-integrated and intermediate reboiler energy-saving design is developed to achieve the energy consumption reduced.Compared with the optimal conventional extractive distillation process,the optimal reactive-extractive distillation process can achieve 41.02% total annual cost reduce.The results show that the reactive-extractive distillation process has the excellent energy-saving performance.With the comparison of optimal conventional extractive distillation process and the reactive-pressureswing distillation process,it has the greatest economic benefits,and is the best design scheme for the separation of acetonitrile-isopropanol-water mixture. |
