Foam flotation method capable of separating silicon powder and carbon silicon powder

Abstract

The invention relates to technology for the powder separation of silicon and carborundum in mortar produced in a silicon chip wire sawing process in the field of solar photovoltaic, in particular to a foam flotation method for separating silicon from carborundum. The foam flotation method for separting silicon power and carborundum powder comprises the following steps of: adding a finishing agent into mortar produced in a silicon chip wire sawing process according to a principle of 100 to 1,000 weight portions of mortar and 100 to 1,000 weight portions of finishing agent; and stirring the mortar and the finishing agent uniformly, allowing the mixture to settle in three layers, and collecting the upper layer of carborundum and the lower layer of silicon power respectively, wherein the middle layer is a liquid layer. The finishing agent is prepared by mixing a solvent and surface modifier according to a principle of 99 to 70 percent of solvent and 1 to 30 percent of surface modifier. The content of the residual carborundum of the collected silicon powder is less than 0.5 volume percent and the content of the residual silicon in the mortar is less than 10 volume percent.

Description

technical field [0001] The invention relates to a powder separation technology for silicon and silicon carbide in mortar produced by a silicon wafer wire sawing process in the field of solar photovoltaics, in particular to the separation of silicon and silicon carbide by using a foam flotation method. technical background [0002] Various silicon wafers, including polycrystalline silicon and monocrystalline silicon solar cells, and silicon wafers used in the microelectronics industry, are generally produced by cutting with wire saws and silicon carbide abrasive slurry, hereinafter referred to as mortar. The thickness of the silicon wafer is generally 0.22mm, and there is still a development trend of further thinning at present. The width of the wire saw kerf is generally 0.18-0.30mm, which means that about 20-60% of the high-purity silicon material becomes sawdust and enters the slurry. Its extraction and recovery is equivalent to opening up a new source of high-purity silic...

AI Technical Summary

Problems solved by technology

The reagents such as tribromomethane required for liquid phase gravity flotation are very expensive and toxic; most of the silicon powder chips produced in the process of polysilicon wire sawing are micron to submicron, and according to general experience, liquid phase gravity flotation will be very difficult

Therefore, this technology is not ideal even as an intermediate step in the extraction of high-purity silicon

[0007]In general, there are no production and application reports on the recovery of high-purity silicon from silicon crystal wire saw abrasive slurry at home and abroad; the number of related technology patents is also very small. It shows that none of them can provide high-purity silicon recovery technology that can be implemented in production, and even basically cannot provide reference for it.