Siemens France Silicon Tetrachloride Exhaust Gas Treatment Process Of Exploration

At present, the main production process of high-purity silicon is Siemens process. Silicon tetrachloride as the largest by-product during Siemens process is a strongly corrosive chemical substance. It high-purity silicon is produced while 8t¹0t silicon tetrachloride would be made in domestic Siemens process. Domestic silicon industries have not yet fully grasp silicon tetrachloride hydrogenation technology, so silicon tetrachloride is difficult to recovery and return to the process. Mostly silicon industries poured the silicon tetrachloride on the open space around the plant or even into the river, and caused seriously environment pollution. With the rapid expansion of domestic polycrystalline silicon industry recently, the recovery process of the silicon tetrachloride will be the bottleneck. In this background, the process of preparation of silicon by zinc reacting with silicon tetrachloride were studied. Two different raw materials which are zinc tablets and zinc ingots were used. The impacts that the technology factors, which are reaction temperature, the reaction time on constant temperature and nitrogen flow rate, on the morphologies and the yield of silicon-products were studied. The morphologies of silicon products were analysed by SEM. Summary of the main contents are as follows:(1) Experimental conditions are as follows: The range of reaction temperature is from 750℃to 1050℃; The distance between the left hole of the furnace and the boat center ranges from 5cm to 15cm; Nitrogen flow rate ranges from 0.031/min to 0.061/min; The reaction time ranges from 0.5h to 3.0h; The heating temperature of SiCl₄ is 50℃.(2) The studies show that whether zinc tablets or zinc ingots used as the raw materials the macroscopical morphologies of silicon-products mainly includes granule-shape, needle-shape and twisted irregular rod-shape and shell-like form.(3) The studies show that the reaction temperature and the reaction time on constant temperature are important factors to the morphologies of silicon-products. The affect of the flow of nitrogen on the morphology of the product is not obvious. The influence that the factors work on the collective rate of the silicon products in the reactor boat mostly shows a similar change rules which is increasing at first and then decline. While, the collective rate which is used zinc ingot as raw materials is higher than that used zinc tablets as raw materials.(4) The studies show that the SEM morphologies of silicon products are various. Granular silicon is made from a number of irregular polyhedron and small spherical particles; Needle silicon contains cylindrical shape, Qinceng stone shape and sandwich shape; Twisted irregular rod shape silicon contains four morphologies such as pinecone shape, cylindrical shape.