Anhydrous treatment process for polycrystalline silicon slurry

Abstract

The invention relates to an anhydrous treatment process for polycrystalline silicon slurry. The process comprises the following steps of (1) carrying out solid-liquid-gas separation on upstream polycrystalline silicon slurry to obtain a liquid, gas A and a solid A, treating the liquid and the gas A, and collecting to obtain a liquid A; (2) heating and stirring the solid A by steam to obtain a dried solid product and silicon tetrachloride and part of trichlorosilane which exist in a gas manner, treating the silicon tetrachloride and part of trichlorosilane existing in a gas form, and collectingto obtain a liquid B; (3) heating the dried solid product through a pyrolyzing furnace to obtain solid wastes and high-boiling residues in a gaseous form, and carrying out catalytic cracking on the high-boiling residues in the gaseous form to obtain gas B and a liquid C; (4) allowing the solid wastes to pass through a gas locking tank, a cooling screw and a solid bin in sequence and discharging the solid wastes to a packaging and delivery unit, and (5) separating the liquid A, the liquid B, the liquid C and the gas B to obtain silicon tetrachloride and trichlorosilane products, residual high-boiling residues and part of solid B. The process has high utilization efficiency, and the anhydration is realized.

Description

technical field [0001] The invention relates to the field of polysilicon production, in particular to a polysilicon slag anhydrous treatment process. Background technique [0002] Polycrystalline silicon slag slurry is usually a mixture slurry obtained after rectification, mainly composed of chlorosilane, high boilers, aluminum trichloride and a small amount of silicon powder. Polysilicon slurry is an inevitable by-product in polysilicon production. Because it is highly harmful to the environment and chlorosilanes and high boilers have certain recovery value, the recycling of polysilicon slurry is very important to the entire polysilicon production process. significance. [0003] The traditional polysilicon slurry treatment process is: the slurry is sent to the dryer, and the silicon tetrachloride and a small amount of trichlorosilane are separated by the dryer, and the treated slurry is pumped into the hydrolysis tank by the screw pump for hydrolysis . But this process e...

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Problems solved by technology

But this process exists: (1) In order to ensure the normal use of the screw pump, the moisture content of the dried residue is about 20%, the recovery rate of silicon tetrachloride is generally about 80%, and the recovery of chlorosilane is not complete; (2) The high boiling matter in the drying process and a small amount of chlorosilane remain in the solid residue, which is directly sent to the hydrolysis unit, resulting in a waste of resources; (3) there are many residual residues after drying, which requires a large amount of water for hydrolysis, and the water consumption is high; (4) The waste gas and liquid produced by hydrolysis need to be separated treatment, the process path is long; (5) the hydrolysis system needs to add lime milk solution, and the hydrolysis reaction generates silica, which is easy to block the pipeline; (6) the dried and recovered chlorosilane contains a small amount of silicon powder, which cannot be directly used

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