Study On Process Intensification Of Methanol To Dimethyl Ether Production By Reactive Distillation

Dimethyl ether is one of the simplest ethers,which is one of the promising environmental energy substitutes.Reactive distillation is an effective method for the production of dimethyl ether.In this paper,the preparation of dimethyl ether by methanol reactive distillation method is studied,and a variety of separation methods are proposed for the separation of methanol and water generated in this process.The study to this process is mainly conducted in terms of its optimization and control through simulation.Firstly,the multi steady states of reactive distillation are analyzed by bifurcation analysis.Based on the multi steady states,a dynamic process intensification technique for reactive distillation is proposed and applied to the system.Under the unsteady operation,the conversion rate of the unsteady operation process is higher than that of the steady operation process,and the heat load of the reboiler is lower.Moreover,the unsteady operation process of reactive distillation is dynamic optimized taking the reboiler heat load and the conversion rate as the objective function.The optimization results show that the optimal assignment is 1.1 h high yield operation period and 0.1 h low yield operation period.Compared with the single steady state operation,the conversion rate of the optimized process is increased by 5.98%,and the heat load of reboiler is reduced by 7.74 k W.Secondly,based on the dynamic process intensification of reactive distillation,three different methanol water separation schemes are compared including traditional distillation scheme,the double effect distillation scheme,and the pervaporation separation scheme.The double effect distillation scheme realizes the complete thermal integration between the condenser of the first effect distillation column and the reboiler of the second effect distillation column.For the reactive distillation coupled with membrane separation scheme,the methanol water pervaporation membrane separation module was programmed by Aspen Custom Modeler software.Then taking the annual total cost as the optimization objective,the sequential iterative algorithm was used to optimize the operation parameters of the three schemes and the annual total cost and total energy consumption are chosen to evaluate these three schemes.The results show that reactive distillation coupled with membrane separation scheme has the most economic benefit and its total annual cost is reduced by 32.5% compared with the conventional distillation scheme.Finally,dynamic controllability of the three schemes is studied.Several dynamic control structures for each scheme are designed and compared.The comparative study shows that the reactive distillation coupled with membrane separation scheme performs well in terms of dynamic controllability.Through the above research,the economic and dynamic characteristics of dimethyl ether prepared by methanol reactive distillation were evaluated in all aspects,and the process configuration with both economy and controllability was obtained,which provides technical guidance for the industrial application of dimethyl ether prepared by methanol reactive distillation.