Process Simulation Of Coal-based Methyl Methacrylate Production System

The production of methyl methacrylate(MMA)attracted great attentions in recent years.Various reaction routes have been developed,wherein the coal-based one has been extensively studied.In 2008,researchers at Institute of Process Engineering,Chinese Academy of Sciences proposed a new process to produce MMA with lower cost.In order to promote the industrial application of the new technology,it is necessary to provide comprehensive information of process and system optimization.In this work,simulation method was established for the coal-based production route for MMA synthesis.Consequently,all basic data of the process flow,material and energy balances,unit operating parameters and the optimum operating conditions were obtained.Finally,the impact of each reaction unit on the environment was quantitatively analyzed by the green degree evaluation method,which provides a theoretical basis for the industrialization of the technology.The main contents and conclusions of this thesis are as the following:1)The flow diagram of MMA synthesis process was designed based on the physical properties of the intermediates and final products,and the results of lab scale demonstration equipment;the UNIQUAC was selected for the calculation of thermodynamic properties.Specifically,RStioc,Radfrac,Heater,Flash,Extract were employed to simulate the equipment,such as reactor,distillation column,heat exchanger,flash tank,extraction tower,respectively.Then,the calculation model of the whole process of coal-based MMA technology was obtained;2)The production process of MMA is simulated and analyzed by Aspen Plus simulation software.The operation parameters and separation schemes of the key equipment were analyzed and optimized towards the purity,yield and energy consumption of the intermediates and target product by using the sensitivity analysis tool.It was found that the operation temperature of the condenser and the operation pressure of the flash tank are the key factors of the yield of propionaldehyde.The optimal operation conditions are condensor at 20 ℃ and the flash tank at 200 kPa.Aiming at the purity of methacrylaldehyde and the content of water in the reaction system,the energy consumption of recovering MAL firstly process was reduced by 42.8%compared with the process of recovering the catalyst.By analyzing of extraction and separation efficiency of n-hexane and toluene,it was found that the extraction process suitable for the purification of methacrylic acid is toluene extraction,and the recovery rate of methacrylic acid is 6%higher than that of n-hexane extraction.As for the comparing process specification and energy consumption,it was found that the bi-solvent extraction separation is the optimal separation process for purifying methyl methacrylate,and the energy consumption is reduced by 15.1%and 34.9%compared with the single solvent extraction process for water and n-hexane,respectively.3)The influence of coal-based MMA production process on the environment was analyzed quantitatively by using the green degree evaluation method.The green degree value of the four reaction units of MMA synthesis process were obtained based on the simulation results,which were-35.56 gd/h,879.05 gd/h,-20.14 gd/h,168.51 gd/h,respectively.The analysis showed that the hydroformylation reaction unit was the least green unit.And the approach to improve the green degree of such a process is to develop a novel process of propionaldehyde separation with a lower energy consumption.