Optimization And Thermodynamic Analysis Of Product Separation System Of Catalytic Pyrolysis Process For Maximizing Yields Of Propylene And Ethylene

With the increasing market demand for propylene,traditional steam cracking process of producing propylene has become unable to meet the current needs of the Chinese market.As a result,Catalytic Pyrolysis Process becomes to serve as a very effective way to improve the situation of the light olefins market supply.However,this situation has led to some problems to absorption –stabilization system,such as substandard product and high energy consumption.In order to solve these problems,a new products separation process is proposed in this paper to reduce the energy consumption and increase the energy efficiency.In this paper,based on refinery plant product data,the suthor used Aspen Plus to simulate the absorption – stabilization and gas fraction system.After the simulation process accomplished,the author compared the simulation results with the practical data to assure the accuracy of the simulation.Then the author calculated the energy consumption and exergy loss to pinpoint the equipment which is under poor operating situation.The simulation results can give guide to put forward a novel process to reduce energy consumption.In order to put forward a novel separation process,this paper investigated the different methods of separating each components in the feed stream.According to the simulation results,it consumed less energy to use absorption-desorption method to separate C2 from C₃ with mixed C₄ as the supplementary absorbent.As to the separation between C₃ and C₄,distillation can result in less energy consumption.Finally,using mixed C₄ to absorb oil component is an efficient way to reduce energy consumption.Based on the research results,this paper put forward an improved process to separate the products of FCC unit.There are two absorption-desorption systems in the new process.The first one is operated under 0.5MPa,and it is used to absorb the oil component from the feed stream.The second one is used to separate C2 and C₃ using mixed C₄ as supplementary absorbent.Besides,because propane is less usefull,the dethanizer is omitted in the new process.The LPG will be directly injected into propylene refining tower to produce pure propylene.According to the simulation results,the new process can result in 11.55% reduction of cooling load,17.51% reduction in heating load and 10.08% in total energy consumption.In addition,the exergy loss is reduced by 17.74% compared with base process.In a word,simulation result shows that the improved process performs excellently in reducing energy consumption and increasing the efficiency compared with the base process.