Slagging agent for separating silicon slag during polysilicon medium smelting and its application method

Abstract

The invention belongs to the field of medium smelting of polycrystalline silicon, and specifically relates to a slag-forming agent convenient for silicon slag separation in the medium smelting of polycrystalline silicon, and an application method thereof. The slag-forming agent is formed by mixing the following raw materials: 50%-80% of SiO2, 10%-35% of CaO and 5%-15% of CaCl2. The application method comprises the steps of (1) adding a silicon material into a graphite crucible and heating the silicon material by using a medium-frequency induction furnace until the silicon material is completely melted into a silicon liquid; (2) adding the slag-forming agent into a mixer according to the components of the raw materials and mixing the above materials uniformly; (3) adding well-mixed slag-forming agent into the silicon liquid, keeping a temperature and carrying out the medium smelting; (4) pouring out generated residues after the medium smelting is finished; and (5) repeating the steps (3)-(4) for 2-4 times, cooling the silicon liquid for solidification after the medium smelting is finished, and measuring the boron content by ICP-MS. The slag-forming agent can improve a silicon slag separation effect, reduce viscosity of the slag during the slag silicon separation, increase recovery rate and reduce cost.

Description

technical field [0001] The invention belongs to the field of polysilicon medium smelting, and in particular relates to a slagging agent which facilitates the separation of silicon slag during polysilicon medium smelting and its application method. Background technique [0002] In today's world, the energy crisis and the pressure of environmental pollution coexist, and people urgently need clean, safe and sustainable new energy. As an energy source that meets such requirements, solar energy has always been the goal pursued by people. The earliest use of solar energy is the utilization of its thermal effect, but it is difficult to fully meet the needs of modern society. Until the discovery of the semiconductor photoelectric effect and the manufacture of solar cells, people found new ways to use solar energy. Silicon is the most ideal raw material for solar cells. The impurities in it mainly include metal impurities such as Fe, Al, and Ca and non-metallic impurities such as B...

AI Technical Summary

Problems solved by technology

[0004] In the existing medium smelting process, the low borosilicate calcium slagging agent requires a temperature above 1600°C to separate the silicon slag, and the refining temperature needs to be above 1900°C. The higher the temperature, the greater the loss of silicic acid and the lower the recovery rate. , It is difficult to separate silicon slag below 1600 °C, not only the recovery rate is low, but also a large amount of unseparated slag agent is mixed in the final silicon ingot, which reduces the yield of silicon material