System for recycling silicon powder in polycrystalline silicon reduction tail gas and method thereof

Abstract

The invention discloses a system for recycling silicon powder in polycrystalline silicon reduction tail gas and a method thereof, the recycling system comprises a main filter and a residual liquid filter which are connected in sequence, a silicon powder outlet of the residual liquid filter is connected with a nitriding furnace, and an outlet of the nitriding furnace is connected with a grinder. Through cooperative filtering of the main filter and the residual liquid filter, the solid content of drying liquid in the residual liquid filter is increased, drying energy consumption can be reduced,and the drying effect can be enhanced. Compared with an existing silicon slag recovery method, the method has the advantages that the separated silicon powder basically has no silane residue on the surface, is high in activity, can be directly fed into a nitriding furnace to be used for manufacturing silicon nitride powder, and is high in recycling value. The method is low in energy consumption and good in drying effect, the silicon powder discharged out of the filter is high in activity and can be directly recycled, meanwhile, the silicon powder with low value is changed into a silicon nitride product with higher additional value, and the economic value of polycrystalline silicon reduction reaction byproducts is increased.

Description

technical field [0001] The invention relates to the technical field of polysilicon production, in particular to a system and method for recycling silicon powder in polysilicon reduction tail gas. Background technique [0002] Polysilicon is a key raw material used in integrated circuits and photovoltaic power generation, and is a necessary raw material for the country's new energy development. In the current era of increasing shortage of fossil energy, the rise of new energy has become an inevitable trend. [0003] In the polysilicon production process in my country, 90% of the polysilicon production enterprises adopt the improved Siemens method polysilicon production process for polysilicon production, and at the same time use the CDI device (that is, the tail gas dry recovery device) to treat the tail gas generated by the reduction device (that is, the reduction tail gas) For recycling. Specifically, the hydrogen and chlorosilane in the reduction tail gas are separated an...

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Problems solved by technology

[0004] In the improved Siemens method, in the process of reducing trichlorosilane with hydrogen, because the temperature, proportion and the amount of dichlorodihydrosilane carried by trichlorosilane are not well controlled, fine silicon powder (with a particle size between 3μm) is entrained in the reduction tail gas, and the reduction tail gas containing fine silicon powder is recovered through the exhaust gas of the CDI device, and the fine silicon powder enters the chlorosilane liquid. If the fine silicon brought into the CDI device through the tail gas after the reduction production cannot be effectively removed The fine silicon powder brought in will cause the tower and pump of the CDI device to be blocked and worn, resulting in equipment damage or system shutdown, and will affect the downstream process. recycle it

The existing operation method is to directly put the chlorosilane liquid containing fine silicon powder into the jacketed heating tank for steam heating to dry the silicon slag. There are often silane residues, which affects the recycling of silicon powder

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