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A method for preparing porous silicon carbide by recycling waste silicon slurry from silicon wafer cutting

A technology for cutting porous silicon carbide and silicon wafers, applied in the direction of silicon carbide, carbide, etc., can solve the problems of complex process, long production cycle, and large amount of alkali reagent

Active Publication Date: 2018-07-03
江苏美科太阳能科技股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Many methods for recovering silicon carbide have been disclosed in the prior art. For example, patent CN102399620A discloses a method for recovering silicon carbide components from crystalline silicon cutting waste mortar. It is obtained by alkaline washing after melting and separation, resulting in a large amount of alkaline reagents. Patent CN102659111A discloses a method for recovering silicon and silicon carbide in silicon chip cutting waste mortar. Viscosity reducers and dispersants are added to separate by electrophoresis, resulting in a large amount of wastewater treatment , and there are problems such as complex process, large process conditions, and long production cycle, but there are few reports on direct recycling to prepare high-quality porous silicon carbide, which is not suitable for loading as a carrier

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0023] Weigh 50 kg of waste silicon slurry (containing 21 kg of silicon carbide, 4 kg of silicon, and 15 kg of polyethylene glycol) to obtain 27 kg of solid phase by pressure filtration at 0.5Mpa; mix 27 kg of solid phase with 14 kg of pH Mix 0.1 sulfuric acid aqueous solution, treat at 60°C for 8 hours, control the speed at 150r / min, and centrifuge for 50 minutes to obtain 26.7 kg of solid; put 26.7 kg of solid into the reaction tube, and feed nitrogen with a concentration of 2.5% tetrachloromethane mass percent , the nitrogen flow rate is 1 L / h per gram of solid, and react at 800°C for 8 hours to obtain 20.85 kg of porous silicon carbide.

[0024] The BET specific surface area of ​​porous silicon carbide measured by nitrogen physical adsorption method is 38m 2 / g, the pore volume is 0.09m by X-ray fluorescence spectrometry analysis 2 / g.

Embodiment 2

[0026] Weigh 50 kilograms of waste silicon slurry (containing 21 kilograms of silicon carbide, 4 kilograms of silicon, and 15 kilograms of polyethylene glycol), control the speed at 500 r / min, and centrifuge for 20 minutes to obtain 27 kilograms of solid phase; mix 27 kilograms of solid phase with 30 Mix a kilogram of sulfuric acid aqueous solution with a pH of 0.3, treat it at 80°C for 2 hours, and separate it by pressure filtration under a pressure of 0.8Mpa to obtain 26.3 kilograms of solid; put 26.3 kilograms of solid into a reaction tube, and feed chloroform with a concentration of 2% by mass Nitrogen gas, the flow rate of nitrogen gas per gram of solid is 2 L / h, react at 1400°C for 5 hours, and obtain 20.94 kg of porous silicon carbide.

[0027] The BET surface area of ​​porous silicon carbide measured by nitrogen physical adsorption method is 40m 2 / g, the pore volume analyzed by X-ray fluorescence spectrum is 0.11m 2 / g.

Embodiment 3

[0029] Weigh 50 kg of waste silicon slurry (containing 21 kg of silicon carbide, 4 kg of silicon, and 15 kg of polyethylene glycol) and filter under a pressure of 0.6Mpa to obtain 27 kg of solid phase; mix 27 kg of solid with 40 kg of pH 2 Nitric acid aqueous solution was mixed, treated at 70°C for 8 hours, and 26.5 kilograms of solids were separated by pressure filtration at a pressure of 1.5 MPa; 26.5 kilograms of solids were put into a reaction tube, and helium gas with a mass percentage concentration of 2.5% of dichloromethane was introduced, The helium flow rate was 3 L / h per gram of solid, and the reaction was carried out at 900°C for 8 hours to obtain 20.85 kg of porous silicon carbide.

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Abstract

The invention relates to a method for preparing porous silicon carbide by recovering waste silicon slurry produced after silicon chip cutting. The method comprises steps as follows: (1) the waste silicon slurry is subjected to solid-liquid separation, and a solid phase and a liquid phase are obtained through separation; (2) the solid phase is mixed with an inorganic acid water solution with the pH value being 0.1-2.0, solid-liquid separation is performed after acid treatment, and solids and liquids are separated; (3) inert gas containing chlorine substances is introduced to the solids and are sufficiently contacted with the solids, and porous silicon carbide is obtained through a reaction. With the adoption of the method, the technological process and the production cycle are short, the recovery rate is up to 98.5%, the obtained porous silicon carbide has higher surface area and pore volume and can be used as a carrier to be applied to the fields such as ammonia synthesis, p-hydroxy benzaldehyde hydrogenation, hydrogenation of nitrile compounds, dehydrogenation of alkane, arene oxidation and the like, so that resource waste and environment pollution are reduced, and the value of byproducts is increased.

Description

technical field [0001] The invention relates to a method for preparing porous silicon carbide by recycling waste silicon slurry from silicon wafer cutting, and belongs to the technical field of recyclable resource utilization. Background technique [0002] Multi-wire cutting of silicon wafers is one of the important processes in the production of crystalline silicon by solar energy enterprises. The silicon carbide and polyethylene glycol used in the multi-wire cutting process become mixed waste slurry after one use. Each ton of waste slurry contains about 0.20-0.45 tons of silicon carbide and 0.23- 0.55 tons, silicon powder 0.03-0.10 tons, black luster greater than 80% APHA, heavy metal content, suspended solids, ash and other indicators all exceed the standard, if not recycled, not only will seriously consume limited resources and energy, but also have a negative impact on the environment cause serious pollution. [0003] As we all know, silicon carbide has the advantages...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B32/97
CPCC01P2006/12C01P2006/14
Inventor 王禄宝刘明权梅森翟彩虹
Owner 江苏美科太阳能科技股份有限公司