Investigation On The Energy Saving Of Polysilicon Reducing Exhaust Recovery And Distillation Process

In recent years,with the rapid growth of the China's GDP and energy consumption,haze weather is getting worse too.Photovoltaic power generation is an important clean energy and can help reduce smog,so it has attracted the great attention of the Chinese government.Polysilicon is the core of photovoltaic materials.In this paper,the process of reducing exhaust recovery and distillation of modified siemens method was simulated by the Aspen Plus software.The energy consumption and energy saving methods were discussed to lower the cost of polysilicon production and promote the development of photovoltaic industry.Firstly,the NRTL model was found to be suitable for simulation of the vapor liquid equilibrium experiment data in reference of SiHCl3-SiCl4 system.The main operating parameters of reducing exhaust recovery and distillation process during poly silicon manufacture were simulated via the NRTL model.The simulation data,were very near to the actual industry data and showed the fitness of the NRTL model.At the same time,rectifying column T4 and T5 were found to be the "bottle neck" of the system by energy consumption analysis,which taking up about 50%of the total energy consumption.Secondly,the double-effect distillation process was proposed to reduce the high energy consumption of rectifying column T4 and T5.The operating parameters and energy consumption of the double-effect distillation process were optimized with the Aspen Plus simulation.Compared the direct separation sequence with backed energy integration(DQB)with energy consumption of the conventional distillation process,it could save 2,930,500 yuan of operating cost per year and reduce the energy consumption by 47.37%.The energy saving was very apparent.Finally,the heat exchanger network of the conventional process and the double-effect process were optimized by pinch point technology.The optimal data of the conventional process showed that the total energy consumption dropped 17.31%from 26748.82 kW to 22117.9 kW,and the operating cost could save 3.020,000 yuan per year.The optimal network of reducing exhaust recovery and double-effect distillation process reduced the total energy consumption by 16.6%from 20714.11 kW to 17276.5 kW,and saved operation cost 2,240,700 yuan per year.Compared with the 26748.82 kW of the unimproved conventional process,the optimization reduced the total energy consumption by 35.4%and saved operation cost 6,177,000 yuan per year.The results indicated that the energy saving of the new optimal process was extremely obvious and feasible.It is benefit for the promotion of the reducing exhaust recovery and distillation process in the polysilicon manufacture.