Simulation And Optimization Of Methanol Distillation System

Methanol is a kind of common and large consumption organic product. It's not only the basic material and essential solvent to compose multiple organic products, but also becoming the trend to be a new kind of fuel in the world that the petroleum resource is decreasing day by day. In this background, the domestic methanol production capacity is expanding dramatically. Generally the crude methanol cannot meet the operation requirement so methanol distillation is needed. The energy consumption of methanol distillation process is 20% of the whole methanol producing energy consumption. So, it has more valuable significance to research the methanol distillation process system to reduce the energy consumption during the methanol distillation process by properly design and optimize the system and increase the yield and quality of the methanol products.Existing methanol 4-tower distillation process mainly includes pre-distillation column, pressurize distillation column, normal pressure distillation column and recovery column. This methanol distillation system is called double effect distillation:the steam from top of pressurize column goes into condenser/vaporizer, effectively utilizes the temperature difference of the top of the pressurize distillation column and the bottom of the normal pressure distillation column, so as to provide heat source to the bottom of normal pressure distillation column while also condenses the steam on the top of the pressurize distillation column.With utilizing of ASPEN PLUS, this paper strictly simulates and analyzes the methanol 4-column distillation system design condition. This paper chooses RadFrac unit operation model as distillation column model and improved Wilson and improved PSRK combined property method to simulate the system, through comparative analysis. Based on the high matching of the simulation result and design condition data, simulate and analyze the existing distillation system. The analyzing discoveries that the energy consumption is still huge with the existing double effect distillation by the pressurizer column and normal pressure column, meanwhile the whole distillation system requires large amount of water and discharges a lot of waste water. In order to use energy and resource reasonably and also reduce the cost of production, the paper utilize sensitivity analysis and parameter optimization, etc function of ASPEN PLUS to simulate and analyze the problem of the existing process, finds out the key to save energy and provide 3 energy saving optimizing solution:(1) Increase pressurize distillation column side stream to send to normal pressure distillation column as feed, (2) Circulate part of the waste water at bottom of the normal pressure distillation column and recovery column, (3) Utilize pressurize distillation column and pre-distillation column double effect rectification. Through simulating and calculating, the improved new process can save 24.57% public engineering amount of heat,26.84% public engineering cooling capacity,55.55% industrial water and decrease the waste water treatment by 54.89%, with the precondition to guarantee the methanol product quality and output.The unit operation model and property method selected in the paper is accurate and reliable to simulate the methanol distillation system, so the optimizing solution in this paper can contribute theory evidence for improving and new process development in terms of energy, water saving and decrease waste water discharge for methanol commercial production.