Study On The System Energy Integration Of Reaction And Separation Process

Energy consumption accounts for a large proportion in the multi-component distillation system. Especially the energy consumption of low-temperature distillation accounts for 50%-70% separation cost. Therefore, the energy saving methods should not only design the reasonable distillation temperature and pressure, but also take into account the distillation column condenser and reboiler matched with the heat exchanger network. In the actual chemical processes, part of streams need to be heated and the other part of streams need to be cooled, when the production processing condition determined. How to effectively organize hot and cold streams and solve the heat exchange problems, that are important issues of improving the whole process and equipment.Reaction and separation process is the core of chemical equipment. Its structure directly affects the entire device. It is singificant to study the theory and methods of reaction and separation system energy integration. The system of reaction and separation process of exothermic reaction can be achieved the effect of energy integration by the process design. In this paper, the interaction of reaction and separation system between process parameters are studied. According to the energy coupling and matching rules of reaction-separation process and Temperature-Enthalpy graph, it presents a gradual optimization strategy in system energy integration of reaction and separation process. Make a study on the EGBE and EGEA reaction and separation process by the computer simulation which is based on the software of Aspen Plus. Details are as follows.(1) Design the production process of EGBE and EGEA by Aspen Plus.Select NRTL equation. Calculate minimum number of stage and minimum reflux ratio by DSTWU column. Determine number of actual stages and actual reflux ratio. Set basis operating parameters of simulation.(2) According to Temperature-Enthalpy graph, continuously change parameters and operating conditions of hot and cold streams. Optimize heat exchanger network. Present a gradual optimization strategy in system energy integration of reaction and separation process.Make distillation and heat exchanger networks got heat integration. The strategy is divided into the following three steps:i. Draw cold composite curve, hot composite curve and grand composite curve. According to the conditions, set initial operating parameters with the simulation of Aspen Plus. Draw cold composite curve, hot composite curve and grand composite curve on the Temperature-Enthalpy graph.ii. Systems analysis of energy integration. Change the positon of composite curve. Increase heat temperature of heat streams or lower cold temperature of cold streams to make heat and cold streams having a better matching. Reduce the extra hot and cold utility consumption.iii. Process optimization. According to the changed temperature to design the new operating pressure of process. Constantly change the process parameters to achieve the purpose of energy integration. Repeat these steps until the system energy consumption of public works will not reduce. Then the optimal operating conditions are the system operating parameters.(3) Make a study on the EGBE and EGEA reaction and separation process to prove the reaction-separation system integration strategy is useful. Set initial operating parameters with the simulation of Aspen Plus. Study the effects of reaction feed mole ratio and reaction conversion rate on the total heat. Total system heat consumption is minimum when feed molar ratio is 1:1, the conversion rate is 90%. Draw cold composite curve, hot composite curve and grand composite curve. Analysis of the grand composite curve with the strategy. Distillation column operating pressure is variable. Study the influence of different pressures on the public works. Derive the optimal operating parameters when total system heat consumption is minimum. Through the adjustment of process conditions, the EGBE Public works energy consumption reduce from 156.3kW to 101.4kW, which is more than one-third of energy consumption. The EGEA Public works energy consumption reduce from 102.7kW to 94.5kW. These examples show that the gradual optimization strategy is very effective. Improve energy efficiency of the system. Get the purpose of the distillation column matched with the heat exchanger network. Prove that it is effective to solve reaction-separation system emergy integration problems with the gradual optimization strategy in system energy integration of reaction and separation process. Provide an effective method to solve the complex energy integration problems of reaction-separation system.