Advances in smelting technology of high purity silicon powder
The process of high purity silicon powder chemical vapor deposition furnace relies on fine design, comprehensive utilization of heat energy and expansion of equipment, thus increasing the output of single furnace and significantly reducing the power consumption. Through computer simulation calculation, the distribution of feed inlet is optimized, and various intake nozzles are designed to meet the requirements of uniform distribution of temperature field, flow field and material concentration in reduction furnace. Under the condition of reducing power consumption and material consumption, it is more favorable to grow products with smooth surface and uniform and compact diameter.
Cold hydrogenation is widely used in the efficient recovery of high purity silicon powder byproducts. In domestic manufacturing enterprises, cold hydrogenation process is used to treat by-products almost without exception. In the past three years, the total cold hydrogenation capacity of such production enterprises has reached 31.45 million tons per year, the larger hydrogenation capacity of a single unit has reached 150,000 tons per year, and the power consumption is about 0.5 kWh/kg -trichloroethylene, which is more than 70% lower than thermal hydrogenation.
Comprehensive utilization of by-products. In the process of high purity silicon powder, the by-product is returned to the system after purification. In most companies, by-products silicon dioxide and silicon tetrachloride are disproportionated in the presence of a catalyst to produce silicon dioxide, which is purified and returned to the system for use. HCl is sent to synthesis or directly to cold hydrogenation. Through this measure, the consumption of raw materials has been greatly reduced.
The product quality was improved and the energy consumption was greatly reduced through the development and application of the effective sieve-plate binding filler for purification of high purity silicon powder by adsorption and pressure distillation and the coupling process of purification. The steam consumption of a typical enterprise has been reduced from 200 tons/ton in 2009 to less than 30 tons/ton at present, and the steam consumption has been reduced by over 70%. The pressure coupled purification process also cancels or reduces the consumption of circulating water at the top of the tower by 45% ~ 70%.
Safety and environmental protection. The production of such products was once considered a "highly polluting" industry, resulting from silicon tetrachloride, a by-product of the production of high-purity silicon powder. Silicon tetrachloride can be used as the raw material of polycrystalline silicon, which can be converted into silicon tetrachloride at low cost through hydrogenation process and returned to the system for use. It can also be used to produce high-tech products. These are effective means to reduce production costs. In recent years, domestic enterprises have upgraded technology, strengthened management, and environmental protection departments have standardized online monitoring. People's awareness of environmental protection has gradually increased.
It is a simple and clear standard to judge whether an enterprise can survive in the case of no revolutionary breakthrough in high purity silicon powder technology. The domestic smelting technology is also constantly developing and improving.
