Life Cycle Assessment Based On MTO Process Simulation And Research On Heat Exchanger Optimization Simulation

Ethylene propylene(referred to as diene)is an important industrial raw material and an important guarantee for a stable economy.The large-scale production of dienes also brings various environmental problems.With the "double carbon" and new energy policies proposed in recent years,the industry has paid more and more attention to various environmental indicators.In this paper,the methanol-to-olefins(MTO)process is taken as the research object,and the environmental impact assessment of the whole process is carried out by means of chemical simulation technology and life cycle assessment method;in order to improve the energy recovery efficiency,the shell-and-tube heat exchanger is improved,and it is verified and calculated by fluid simulation technology.First,a rigorous process simulation of the MTO process was carried out based on a large number of literature data.In the high-temperature reaction stage,a fluidized bed reactor is simulated through a combination of multiple reactors,with accurate reaction kinetics to ensure the accuracy of product distribution,and the heat recovery is optimized through the heat exchange network;in the pre-separation section,the reaction product is impurities are removed and pressurized to provide separation conditions for the subsequent stage;in the cryogenic separation stage,the diene is purified using the pre-depropanization separation sequence,and a cascade refrigeration cycle is simulated at the same time.Through simulation optimization,the input and output list of the whole process material and energy consumption was obtained,which laid a solid foundation for the environmental impact assessment of the MTO process.Then,according to the process simulation data,the environmental impact assessment research of the whole MTO process is carried out based on the life cycle assessment theory.This paper uses the Ecoinvent3.0 database and uses the Re Ci Pe2016 method to evaluate the MTO process.Using this evaluation method,a preliminary evaluation result is obtained through comparative analysis of each process stage,and then a separate evaluation and analysis is performed on each process stage to identify key processes and obtain important environmental impact categories and key impact factors.Finally,in order to improve the heat transfer efficiency of the inter-stream heat exchanger and reduce the kinetic energy loss of the shell-side fluid of the heat exchanger,this paper adds a rotating impeller to the shell side of the traditional shell-and-tube heat exchanger.Through the finite element fluid simulation calculation,it is found that,The rotating device not only improves the heat transfer efficiency,but also reduces the loss of fluid kinetic energy,which significantly improves the heat transfer performance of the heat exchanger.This paper summarizes the evaluation data through process simulation,and uses life cycle assessment tools to evaluate the entire process.The results show that the raw material demand in the reaction stage and the energy demand in the cryogenic separation stage account for a large proportion of the impact on the environment;through finite element fluid simulation the improved shell-and-tube heat exchanger is calculated,and it is found that it can improve the heat exchange efficiency and further reduce the original energy consumption of the process in the future.