A kind of regeneration method of waste silicon carbide-silicon nitride refractory brick and its application

Abstract

The invention discloses a regeneration method of waste silicon carbide-silicon nitride refractory brick and applications thereof. The method comprises following schemes: (1) grinding waste silicon carbide-silicon nitride refractory bricks, adding a retting solution, carrying out retting, allowing the solution to stand still, filtering the solution, washing, and drying; (2) after grinding, adding ammonium chloride, heating, keeping the temperature, extracting the slag by water, washing by water, and drying; (3) after grinding, adding ammonium chloride and water, heating, keeping the temperature, filtering, soaking dry slag in water, filtering, washing by water, and drying; (4) after grinding, adding ammonium chloride, adopting supercritical ammonia-ethanol-methanol extraction, and carrying out separation; and (5) after grinding, adding ammonium chloride, adopting supercritical carbon dioxide extraction, performing separation, extracting silicon carbide-silicon nitride by water, filtering, washing by water, and drying. The product is used to produce refractory bricks. The content of SiC and Si3N4 in regenerated powder is high. The reaction conditions are mild and the method is suitable for industrial production.

Description

technical field [0001] The invention relates to a regeneration method and its application, in particular to a regeneration method of waste silicon carbide-silicon nitride refractory bricks and its application. Background technique [0002] At present, the aluminum smelting enterprises of electrolytic aluminum in my country have built a production capacity of 43.698 million tons, and the operating production capacity has reached 36.739 million tons. The electrolysis temperature of the large-scale aluminum electrolytic prebaking tank is between 950 and 970 ° C, and about 50 kg of cryolite, aluminum fluoride, magnesium fluoride and other electrolytes are consumed for each ton of aluminum produced. Due to thermal effects, chemical effects, mechanical erosion, Due to the molten salt reaction and chemical reaction caused by the action of electricity, the penetration of sodium and electrolyte, etc., the cathode carbon block in the aluminum electrolytic cell will be damaged after a ...

AI Technical Summary

Problems solved by technology

However, there are a series of technical defects in this method: first, it takes too long and the processing capacity is limited, and the water immersion time reaches 2 to 3 days at a time, and multiple rounds of water immersion, block selection, and water immersion are required; , objectively consumes a lot of water, because the fluoride salt it contains is only slightly soluble in water, and the maximum solubility of sodium fluoride in pure water is only 3.6-5g / 100mL water; pollution, and the cyanide in it has not been safely treated; fourth, the process is complicated; fifth, the energy consumption of the treatment is high, and it needs to be ground into powder with super hardness silicon carbide emery material, and the general grinding body is not competent The grinding function of this superhard material needs to be dried and calcined in a high-temperature electric furnace at 1700-1900°C; Sixth, the product has high content of impurities such as fluorine and aluminum and low value, and calcination in a high-temperature electric furnace at 1700-1900°C is not enough Volatile most of the impurities in it, but it will decompose the silicon carbide and silicon nitride in it, even the highly stable silicon nitride will sublimate and decompose at the melting point of 1900°C

[0006] Although the current SiC-Si 3 N 4 Refractory bricks are expensive, SiC, Si 3 N 4 The market value of the material is high, but due to the lack of effective recycling technology at home and abroad, a large number of waste silicon carbide-silicon nitride refractory bricks in the electrolytic aluminum industry are discarded, landfilled or stockpiled, or sent to high-temperature kilns as waste. Oxidation treatment, only part of the large waste silicon carbide-silicon nitride refractory bricks are used to replace genuine refractory bricks as refractory and wear-resistant materials for industrial kilns, and a small amount is directly crushed to replace genuine abrasives and mixed into the market