Research On Efficient Purification Of Chlorosilane And Energy-saving Optimization In Polysilicon Production

Improved Siemens Process is one of the most important processes of polysilicon production in China,which is widely related to chlorosilane distillation operation.Due to the requirement of high purity polysilicon products,the content of impurities in raw material chlorosilane must be very low.Meanwhile,the impurities such as boron and phosphorus in chlorosilane have different existing forms,the conventional distillation method is difficult to meet the requirement.This is also the reason for high reflux ratio and high energy consumption in the chlorosilane distillation process.In view of this problem,based on the existing technologies,this paper put forward a new high efficiency and energy-saving technology to purify TCS.Combined with the features of chlorosilane separation system,this paper uses simulation software Aspen Plus to simulate chlorosilane distillation process.A new porous packing is developed in industrial application research,and the efficient different pressure thermally coupled distillation technology which is suitable for large-scale production is purposed too.This energy consumption is nearly 50%lower than that of the original technology.The main research and results are as follow:(1)The study of new porous distillation packing in industrial applicationThrough the comparison of BX type monolayer nonporous wire packing with porous packing in the industrial operational test,this paper investigates the porous packing separation effect in removing boron and phosphorus.The result shows that,when the gas-phase F factor<1.3,the new type of porous distillation packing pressure drop is lower;when the gas phase factor F>1.9,the new type of porous distillation packing pressure drop is higher,when the F factor is under 1.6,mass transfer efficiency is highest.The content of boron in the porous distillation tower is similar in the BX of type tower,while the phosphorus content is slightly lower,which shows that the separation effect of porous packing is slightly better than the effect of BX packing.The BX tower best reflux quantity is about 1 m~3/h,and the porous packing tower is about 0.85 m~3/h.In another word,when the same separation effect is achieved,the operating cost of the new type of porous packing tower is 10.63%lower than BX tower.(2)The highly efficient different pressure thermally coupled distillation technology which is suitable for large-scale industrial production is developedBased on the simulation and optimized for the different pressure thermally coupled distillation tower with the professional chemical process simulation software,a highly efficient different pressure thermally coupled distillation technology which is suitable for large-scale industrial production is developed.Finally,this technology combining the chlorosilane distillation of large-scale technology and advanced automatic control program is applied in large-scale polysilicon production.This technology can meet the requirements of polysilicon product quality,and the consumption can be decreased by 47.7%which have a remarkable effect.