Refining and purifying method for industrial silicon

Abstract

The invention discloses a refining and purifying method for industrial silicon. The method comprises the following steps: in a vacuum electric arc furnace, using an industrial silicon rod as a consumable negative pole and a conductive crucible as a positive pole, wherein the conductive crucible contains refining slags; after striking the arc for the electric arc furnace under high-temperature and vacuum conditions, the industrial silicon rod is gradually smelted and dropped to a positive pole crucible from the lower end of the consumable negative pole, and gas impurities and volatile impurities in industrial silicon molten drops are volatilized and diffused and are vacuumized out of the furnace by virtue of a vacuumizing device; after the industrial silicon molten drops drop into the positive pole crucible, nonvolatile impurities enter into the refining slags by slag-gold reaction and element exchange; and when the industrial silicon negative pole is molten, the refining slags are removed to obtain the refined and purified industrial silicon. According to the scheme, a high purification effect is achieved. 5-7N purity polycrystalline silicon can be obtained by way of purification.

Description

technical field [0001] The invention relates to the technical field of metallurgical industry, in particular to an industrial silicon refining and purification method. Background technique [0002] In qualified silicon substrates for silicon photovoltaic cells, in addition to C and O impurities, the content of B, P, Fe, Ca, Ti, V, Al, Na and other impurities should be less than 1.0×10 -6 , the concentration of other impurities should be lower than 1.0×10 -9 , Polysilicon of this purity is called solar grade silicon. Purity requirements for solar-grade silicon: First, the total content of impurities should be as low as possible, generally not higher than 100ppm; second, from the perspective of single impurities, Ti, V, B, P, etc. have the greatest impact, and the content must be lower than 1ppm. The purity of industrial silicon is about 95%-99%, and its impurities are mainly non-metallic impurities C, B, P and metal impurities Fe, Al, Ca, etc. If it is used as a solar phot...

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Problems solved by technology

[0003] Existing refining and purification processes, such as Elkem process, ARTIST process, Carbothermicmeth process, HEM process, Kawasaki Steel process, improved Siemens method-closed-loop SiHCl 3 Hydrogen reduction method, iodine chemical vapor transmission purification method under normal pressure, zinc reduction method, etc., the process is complicated, the purification effect is unstable, the cost is high, the energy consumption is high, and the pollution is serious

The existing vacuum consumable arc refining can volatilize and remove the gas and some volatile impurity elements in the raw material, but it is difficult to remove the difficult volatile impurity elements Fe, Al, etc.; the existing industrial silicon vacuum distillation refining metal can make the industrial The content of Ca element in silicon is significantly reduced, and it can remove phosphorus from industrial silicon by vacuum distillation, but it has no obvious effect on other difficult-to-volatile impurity elements

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