Mortar recovery technique for cutting single-crystal and polycrystalline silicon wire

Abstract

The present invention relates to a technique of recovering mortar used in the wire cutting of monocrystalline silicon or polycrystalline silicon. Silicon is an important material for solar batteries, semiconductors, liquid crystal displays, etc. A silicon rod is cut into silicon wafers by the wire cutting technique, and in the process, a wire-cutting machine needs to be added with cutting liquid mortar, which is mainly composed of liquid phase polyethylene glycol and solid phase silicon carbide powder. When the wire-cutting machine cuts the silicon rod, the solid particles in the mortar are changed into waste mortar as the silicon carbide grinds the silicon rod and a steel wire. If the waste mortar is discharged directly, environment is polluted, and the raw material is wasted. The present invention adopts the mortar-recovering technique to recover the waste mortar, so that the waste mortar can be reused and the discharging of the three wastes can be reduced, so while reducing production cost, the mortar-recovering technique can protect environment. The technique of recovering mortar used in the wire cutting includes the following flow: waste mortar dope, one-step membrane filtration and PEG liquid; waste mortar dope, one-step membrane filtration, cleaning, powder drying, powder classification and SiC powder.

Description

technical field [0001] The invention relates to a technology for recovering mortar used for wire cutting of single crystal and polycrystalline silicon. Silicon is an important material used in solar cells, semiconductors, liquid crystal displays, and more. The application process of silicon materials in the solar energy manufacturing industry is: silicon raw materials→silicon ingots→silicon rods→silicon wafers→polycrystalline silicon cells→solar cell components and application systems; among them, the silicon rods are cut into silicon wafers. The wire cutting machine adds cutting fluid, that is, new mortar, and then discharges the waste mortar, thus, the problem of recycling and reusing the waste mortar is raised. technical background [0002] 1. Description of the composition of the new mortar, the composition of the new mortar and the waste mortar is shown in Table 1: [0003] Polyethylene Glycol, abbreviated as PEG. Molecular formula: HO(CH 2 CH 2 O)nH, the larger n,...

AI Technical Summary

Problems solved by technology

[0027] ① During the treatment process, only the waste mortar is physically separated, the solid-liquid two phases are not separated, and the recovered product is still black thick mortar;

[0028] ② There are still 10% to 20% solid impurities and tiny particles attached to the surface of SiC particles and suspended in PEG in the system that cannot be completely removed, and these impurities that have not been completely removed will continue to accumulate in the system with the increase in the number of cutting , after a period of time, the quality and efficiency of its recycled products used for silicon slicing have dropped significantly;

[0031] ①Using multi-stage filtration technology for solid-liquid separation, the process is complicated and the efficiency is low;

[0033] ③ The PEG liquid obtained after solid-liquid separation requires a water removal process, which consumes a lot of energy and may also cause changes in the molecular structure of PEG;

[0034] ④ Use water separation technology to classify SiC particles, which has low efficiency and large floor space;

[0035] ⑤ Classify SiC particles first and then chemically treat SiC particles, so that the normal distribution of the final SiC particle size will be shifted again, affecting the effect of silicon slicing

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