Simulation And Optimization Of Coal-based Mixed C₄ Hydrocarbon Separation Proccess

In recent years, the coal to olefins technology has developed very quickly and there are more and more corresponding plants put into operation. Meanwhile, the main by-products, mixed C4 hydrocarbons, have a considerable capacity. A better comprehensive utilization scheme of these resources according to their component is of great significance for the overall economic benefits of the coal to olefins projects.Based on Aspen Plus platform, combining with Matlab in the chemical calculation, the separation process of the coal-based Mixed C4 hydrocarbons was simulated and optimized in order to obtain high purity butenes. Due to the composition characteristics of the coal-based mixed C4 hydrocarbons, the separation process was divided into thee operating units, respectively butadiene hydrogenation unit, MTBE unit and butylene enrichment unit. According to the material system characteristics in each unit, EOS method based on PR model and EOS+y method based on NRTL-RK model were selected to complete the thermodynamic calculation. In the simulation process of each unit, different target variables were selected to analyze and optimize each unit operation. The optimized process parameters were obtained. In MTBE unit, a one-dimensional pseudo-homogeneous model of etherification reaction in tubular fixed-bed reactor was established. The model was calculated by the Runge-Kutta method with Matlab and the characteristics of etherification reaction distillation process were analyzed though this. In butene enrichment unit, the NRTL model parameters of C4-NMP systems were verified, which was obtained from early experimental datas. And the effect of the NMP solvent on the relative volatility of C4 hydrocarbons was analyzed. Though the simulation of the whole process,99.8% butene components (mass concentration) were acquired.Sulzer Mellapak structured 250Y type packing was selected as the distillation packing of extractive distillation column and solvent recovery column. The column diameters, maximum capacity factor and other parameters were obtained though sizing and rating for the ratification process. Applying Aspen Energy Analyzer, the optimal heat integration scheme of the whole separation process was designed via pinch technology. Thus important related parameters were obtained, such as capital cost, operating cost, total annual cost and the minimum utilities consumption(QH,mm,Qc,min).