Simulation Research On Reactive Distillation For Boron Removal In Polysilicon Production By Modified Siemens Process

Currently, Modified Siemens Process is widely used in our country to producepolysilicon. Purification of raw material trichlorosilane which is used for reduction isthe key process. Boron impurities are difficult to remove for the specificationof chlorosilanes, which usually need multi-stage distillation to separate that leads tolow distillation product yield. As a result, high energy consumption used for boronremoval make it hard to reduce the cost of production.To settle this problem, after analyzing the cause and the existing technologies,reactive distillation for boron removal technology directed at TCS refining materialand cold hydrogenation material was proposed. Aspen plus was used in the simulationstudy. A new multilayer wire gauze packing PACTU-800was developedfor chlorosilane system. The main work and results are as follows:1、Established reactive distillation for boron removal technology of TCS refiningmaterial. The result shows at300kPa, TCS was purified to a maximum limit, numberof theoretical plate was132and the reflux ratio was3.1.At the same time, molar flowof boron compounds reduced from10-5kmol/hr to10-7kmol/hr.2、 Established reactive distillation for boron removal technology of coldhydrogenation material. The influence of equilibrium constant to boron removal effectwas discussed from the point of view of Modified Simens Process optimization,which is important for the reactants selection in the further study. The result showsthat the boron content can be reduced2orders of magnitude which can be used toproduce solar-grade silicon. Energy consumption can be reduced30%approximately.3、The multilayer wire gauze packing PACTU-800was developed and tested.Fluid mechanics performance test shows that when the sprinkle density was0~40m~3/(m~2·h) and gas velocity was0~3.5m/s, the curves had a very concentrateddistribution when F<1.5, pressure drop were below1.48mbar/m which is higher thanMellapak250Y. Mass transfer performance test shows that the HETP of PACTU-800was310mm at different sprinkle densities, the efficiency was high.