Research On Off-gas Recycling Process In The Polysilicon Production

In the 21st century,with the development of solar energy and other clean energy technologies,the polysilicon that was used for producing solar cells has been developed rapidly.There are 70%-80%polysilicon was produced by modified Siemens technology.There are some useful components in the TCS that was vented from the CVD workshop.It is very important to reuse these components through multiple condensing,separation and reuse.Therefore,it is very important to reduce the energy consumption of the reduction exhaust recovery system in the production of polysilicon.Based on the production equipment of a domestic polycrystalline silicon production enterprise,taking absorption tower of off-gas recovery system as the research object,choosing chlorosilane as absorbent,hydrogen as the purpose product,the production of reduction exhaust recovery system is studied.Chemical process simulation software PRO?,NRTL and the Rad Frac method were adopted to simulate the changing about the composition of absorbing liquid,the temperature of the feeding liquid and the operating pressure.If the hydrogen chloride that in the hydrogen absorption rate can reach 99.0%the impurity content in hydrogen at the top of absorber and hydrogen chloride absorption rate is the best and the operation cost is the lowest as well.Now the ratio of TCS and STC is 7:3,the absorption liquid temperature is-40°C,the absorption pressure is 1600 KPa.There is one absorption tower in the simulation process,the other process parameters of the process flow with the flow stream input,the process is simple,the operation is convenient and the result is reliable.The article also adopted software analysis method,taking the production data as the basis and achieving the purpose of reducing the energy consumption of the system through optimizing the low-pressure condensation and separation process and reducing brine chiller power consumption.At last,the paper introduces the energy saving measures of the desorption tower,carries on the feasibility transformation and increases the heat energy recycling through using the heat-exchange system integrate concept.The feeding temperature of desorption tower can be improved 68°C,and this can reduce the chlorosilane temperature that from the tower kettle to the water heat exchanger.The energy consumption is decreased by 4908.5 kW h^-1,and the steam consumption of desorption tower is reduced by 3841.86 kW h^-1,and the water heat exchanger is reduced by3841.36 kW h^-1.Therefore,through simulation and modified,the desorption system energy saving effect is very obviously,it not only can decrease the power consumption for off-gas recovery process but also can enhance the competitive for the enterprise.