Research On Energy Saving And High Efficiency Production Process Of High-purity Trichlorosilane

In the semiconductor industry,chlorosilane is an important raw material ofproducing polysilicon.Even if the raw material contains trace amounts ofimpurities,they will eventually affect the quality of the polysilicon products.Impuritiesmainly include metal chlorides and boron trichloride (boron acts as a kind of positivecharge dopant in the silicon), arsenic trichloride, phosphorus trichloride（phosphorusacts as a kind of negative charge dopant in silicon), etc.The difficulty of refining chlorosilane technology lies in the small difference ofthe boiling point of impurities and chlorosilane.It is difficult to remove the impuritiesby traditional distillation method, and the number of rectifying columns are high(usually5or more columns), production quality is unstable, the cost of equipmentinvestment is high, the volume is huge and it needs high energy consumption.Forthese problems, this paper used the chemical process simulation software Aspen Plusand Pro/II and applied heat pump rectification,dividing wall column distillation anddividing wall column using different pressure thermally coupled distillationtechnologies to simulate trichlorosilane purification process.And using the adsorptionmethod to remove boron from trichlorosilane was did in this paper.The main research work and results are as follows:(1) Refining trichlorosilane with heat pump distillation model was designedusing Aspen Plus.Compared the two types of heat pump distillation, one model usedthe vapor from the top as heat pump medium and the other model used the liquid fromthe bottom as heat pump medium.The results showed that the latter was better. Themodel using the liquid from the bottom as heat pump medium was optimized.Compression ratio of compressor was1.72and1.48respectively, the power ofcompressor was48.63kW, outlet pressure of throttle valve was227kPa, load ofauxiliary cooler was-49.96kW. Compared with conventional distillation，energy costsaving was about82%.(2) Refining trichlorosilane with dividing wall column model was designed usingPro/II. Compared with conventional distillation(Direct Sequence), energy saving was27.8%. A kind of partition collection redistributor which liquid flow rate can beadjusted was designed.It fully used static equipment,which can adjust both sides of the liquid flow rate easily and flexibly. Finally three-towers dividing wall usingdifferent pressure thermally coupled distillation technology process model wasdesigned. The pressures of three towers were200kPa,500kPa and800kPa.Comparedwith three-towers dividing wall column process, energy saving was about66.4%.(3) Macroporous ion exchange resins were acted as adsorbent for remove boron.Compare the adsorption effect with the resins A, B, C, D and E under the sameadsorption condition. Results showed that absorption effect of the macroporousweakly basic anion resins is better, the absorption effect of B is the best.The bestadsorption conditions were as follows: the adsorption time was6min, dryingtemperature of the resin was70℃, the adsorption temperature was20℃.