The polysilicon production process, the most important process of polysilicon includes, three chloride synthesis, heat hydrogenation of silicon tetrachloride (some use chloride), rectification, reduction, exhaust, and some small main items, system Hydrogen, hydrogen chloride synthesis, waste gas waste liquid treatment, silicon rod finishing, and the like. The main reactions include: Si + HCl --- SiHCl3 + H2 (trichlorosilicon synthesis); SiCl4 + H2 --- SiHCl3 + HCl (hydrogenated); SiHCl3 + H2 --- SiCl4 + HCl + Si (reduction) polysilicon It is made of metallurgical silicon refinement from silicon purity. Since the main supplementary material used in each polysilicon production plant is not the same, the production process technology is different; and thereby corresponding polysilicon product technical and economic indicators, product quality indicators, use, product testing There are also differences in the method, process safety, etc., each has technical features and technical secrets, in general, the main traditional process of polysilicon production is currently: modified Siemens, silane method and fluidized bed method. The improvement Siemens method is currently mainstream production method, using this method to produce more than 85% of the total growth of polysilicon. However, the core crafts of this refining technology simply mastered 7 major silicon manufacturers in the United States, Germany, Japan. These companies' products account for 90% of the total growth of global polysilicon, and the company's alliances have implemented technical blockade, which are strictly prohibited. The situation of industrialization technology monopoly blocking in the short term will not change. Siemens improvement method is as follows: This method is the advantage of energy saving, low cost, good quality, use comprehensive utilization technology, no pollution to the environment, has obvious competitive advantage. Modified Siemens Process Method The equipment used in polysilicon is mainly: hydrogen chloride synthesis furnace, trichloride silicon boiling bed pressurized synthetic furnace, trichloride hydrolysis gel treatment system, trichloride silicon bracket, rectification tower purification system, silicon Core furnace, power saving reducing furnace, phosphate examination furnace, silicon rod cutting machine, corrosion, cleaning, drying, packaging system device, reduction exhaust gas dry recycling device; other include analysis, detection instrument, control instrument, thermal energy conversion station, compressed air Station, circulating water station, variation power station, purifying plant, etc. (1) Quartz sand is purified to 98% in the electric arc furnace and generate industrial silicon, and its chemical reaction SiO2 + C → Si + CO2 ↑ (2) must be further purified in order to meet high purity needs. The industrial silicon was pulverized and reacted with anhydrous hydrogen chloride (HCl) in a fluidized bed reactor, and the proposed trichloride (SiHCl3) was produced. Its chemical reaction Si + HCl → SiHCl3 + H2 ↑ The reaction temperature is 300 degrees, and the reaction is exothermic. At the same time, a gaseous mixture (н2, нс1, Siнс13, SiC14, Si) is formed. (3) The gaseous mixture produced in the second step also needs to be further purified, requiring decomposition: filtered silica powder, condensate Siнс13, SiC14, and gaseous н2, нс1 return to the reaction or discharged into the atmosphere. The condensate Siнс13, SiC14, purified trichloride (multi-stage distillation) were then purified. (4) The purified trichloride is used to reduce the deposition in the H2 atmosphere by high-purity SiHCl3 to form polysilicon. Its chemical reactions SiHCl3 + H2 → Si + HCl. The polysilicon's reaction vessel is sealed, a silicon rod (5-10 mm in diameter, 80 meters in diameter) with an electric heating silicon pool (80 in diameter), and the diameter can reach 150-200 in a diameter of 1050-1100 degrees. Mm. Thus about one-third of trichlorosilica reacts, polycrystalline silicon is generated. The remainder is separated from the reaction vessel from the reaction vessels with н2, нс1, and Siнс13, and SiC14. These mixtures are low-temperature separation, or reuse, or returned to the entire reaction. The separation of gaseous mixtures is complex, and the energy consumption is large, and the cost of polysilicon is determined to some extent and the competitiveness of the 3 process. FQJ, read full text
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