Simulation And Optimization Of Ethylene Bulk Polymerization Process Using Polymer Plus

Polyethylene(PE) is one of the most widely used polyolefin resin products. UnipolTM PE process is the domestic largest production process, playing an important role in the production of PE in our country.In view of the large number of UnipolTM PE production lines, Polymer plus software was used in our work to establish the simulation model of UnipolTM PE process.Applying of the simulation model, the process operation and condensing model(CM) of UnipolTM PE process were researched. Line-up competition algorithm(LCA) was applied for optimizing the main operating parameters which affects the production. Thus, we could increase capacity under the current technological conditions, optimize operation, reduce the cost of operation, remove operation bottleneck, and improve enterprise economic benefit and comprehensive competitiveness.Therefore, the work and the conclusion of our paper are as follows:(?) The model of UnipolTM PE process in Polymer plus had beed established. Based on the analysis and summary of UnipolTM PE process, the component identification and the process model were established by Polymer plus software.On the basis of relevant literature, physical method and its parameters used in the modeling were selected. Thirteen elementary reactions which focus on the grade choosing 1-butene as comonomer were selected to describe the process of ethylene polymerization kinetics.At the same time, ethylene polymerization kinetics model of one active site model and three active sites model in the catalyst were respectively determined. So did its kinetic parameters.(?) To test the accuracy of our model established in Polymer plus above, the simulation results and the data from industrial production were contrasted.Then, the following researches were conducted through the model:(1) Effect of the heat exchanger,s outlet temperature on the production process.(2) Effect of the catalyst feeding situation on the production process.(3) Effect of hydrogen and ethylene molar ratio on PE formula weight and melt index(MI).(4) Effect of 1-butene and ethylene molar ratio on PE density.(5) Application of related empirical formula, fitting out of the nexus of melt index and 1-butene and ethylene molar ratio.The research contents above can provide a reference for industrial practical operation.(?) Model established in Polymer plus above was used to study the condensing model operation of UnipolTM PE process. While maintaining the feed temperature and pressure constant, the established model was applied to study the following:(1) relations between isopentane content in the circulating gas and dew point.(2) relations between isopentane content in the circulating gas and the liquid content in the feed stream.(3) relations between isopentane content in the circulating gas and heat exchanger energy consumption.(4) relations between isopentane content in the recycling gas and and product yield.(5) The effect of isopentane feeding position on production. Through the above study, the following conclusions are obtained:(1) the dew point of circulating gas rising with the increasing of isopentane content. In order to ensure normal operation of UnipolTM PE process, isopentane content should be controlled below 11.5 %.(2) Production increases with the temperature of the heat exchanger decreasing. But the effect is not significant.(3) The energy consumption of the heat exchanger is mainly related to the outlet temperature, having no direct relationship with the content of isopentane.(4) Under the condition of ensuring the process in normal running, the production rising with the increasing of isopentane content.(5) Comprehensive analysis of product yield and influence on the stability, optimization of the process is not recommended to take the isopentane feed position in consideration.(?) Data transmission platform was established between the process simulation software Polymer Plus and mathematical software MATLAB. LCA optimization algorithm was applied for optimizing the main operating parameters which affects the production. Under the current technological conditions,the maximum production of the condensing model operation of UnipolTM PE process is 15927.55 kg/hr, increased by 94.2% than the original process yield.At the same time, a set of optimized operation parameters are obtained, as following:(1) isopentane content in the circulating gas is 0.0672.(2) Outlet temperature of the heat exchanger is 313.95 K.(3) Reactor feed temperature is 313.15 K.(4) Feed rate of the catalyst is 3.56 kg/hr.These optimized operation parameters can provide theoretical guidance for the optimization of process operation and upgrading the operating parameters.