Method for extracting regenerated carbon-containing fused magnesia from waste magnesia carbon bricks

Abstract

The invention provides a method for extracting regenerated carbon-containing fused magnesia from waste magnesia carbon bricks, which comprises the following steps: 1, removing impurities on the surface layers of the waste bricks; 2, placing the waste bricks in a kiln, heating the waste bricks by using external fuel to 800 to 1,000 DEG C, combusting graphite in the materials, blowing 80 to 180 mm of air, raising the temperature to 1350 to 1400 DEG C, and forming decarburized layers on the surfaces of the materials; 3, continuing to blow air for 30 to 90 minutes, cooling down to 600 to 650 DEG C, keeping the temperature for 300 to 600 minutes, and oxidizing bonding agent in the materials; 4, cooling, moving out of the kiln and removing the decarburized layers; and 5, crushing, rolling, screening and obtaining a final product. In the invention, according to a principle that phenolic resin is oxidized at above 460 DEG C and loses bonding strength, false particles are removed. The product burnt by the method has high purity and the same performance as original fused magnesia, and retains the graphite with high utilization value; and the graphite is coated on the outer layer of the fused magnesia, fills the air pores in the fused magnesia particles, improves the volume density (g / m<3>) of the particles, and improves anti- etching performance.

Description

technical field [0001] The invention relates to a method for recycling waste magnesia-carbon bricks, in particular to a method for extracting and regenerating carbon-containing fused magnesia by using waste magnesia-carbon bricks as raw materials. Background technique [0002] The refractory materials used in the converter lining or ladle slag line of steelmaking plants at home and abroad are mainly magnesia-carbon bricks, which are made of fused magnesia, phosphorus flake graphite and additives with resin bonding machines. It is used in thermal furnaces and will be dismantled when a certain service life is reached. With the vigorous development of the steel industry, my country's steel output has increased year by year, and nearly one million tons of waste magnesia carbon bricks have been dismantled every year. Such an astonishing amount is discarded, which not only pollutes the environment, but also wastes resources. How to develop and utilize it? Experts and scholars enga...

AI Technical Summary

Problems solved by technology

[0005] Remove impurities on the surface of waste bricks - crushing - soaking in water - calcining - mixed grinding - sieving - leaving the factory, this method uses the principle of graphite oxidation at a high temperature above 800 ° C, and the graphite, binder and additives in the used magnesia carbon bricks All the materials are oxidized, so that the coarse, medium and fine particles in the original brick are completely separated, and the fused magnesia is restored. Although this method has a good separation effect, it burns the graphite with high utilization value and expensive additives. , become harmful impurities after oxidation, which will directly affect the performance of fused magnesia

[0006] Non-burning method: This method draws on part of the process flow of the burning loss method. It does not go through high-temperature calcination and retains valuable graphite. However, because it has not been fired, the binder has not been oxidized, and the bonding strength still exists, so the separation The effect is very poor, there are a lot of false particles, the so-called false particles are coarse, medium and fine particles are still wrapped together without separation

Although graphite is retained, the existence of false particles is very harmful to the product and will affect the bulk density of the product g / cm 3 and apparent porosity, significantly reducing service life

As we all know, magnesia carbon bricks are used in converter lining and ladle slag line. The grade of fused magnesia used in the bricks is very high. 3 , the pores have strict requirements, if the grade is lowered, the service life will be reduced, if the recycled fused magnesia is used to replace the original fused magnesia, the performance index of the original material must be met, the above treatment method, the former has too many impurities Large, accounting for about 3-4%, the latter has too many fake particles, accounting for about 15-20%, and impurities accounting for about 1-2%. These two methods also have a common disadvantage, that is, the problem that foreign impurities cannot be removed.

During the use of magnesia carbon bricks, molten slag will penetrate into the brick, and steel slag adheres to the surface of the brick. No matter what extraction method is used, the first step must be to remove the sundries on the surface of the brick, using manual knocking and mechanical cutting Because of the irregular shape of magnesia carbon bricks after use, the surface debris is very hard. For example, there are almost debris on the five sides of electric furnace ladle bricks. It is very difficult to remove them, and more or less there will be residues There are residues, which will bring in impurities, which will inevitably affect the performance of fused magnesia

Therefore, it cannot replace the original fused magnesia at all. As for the various drawbacks of the above extraction methods, the extracted product can only be infiltrated or downgraded in a small amount. If it is downgraded, its value is the same as that of the original Compared with raw materials, the added value is very low. Such a huge resource of waste magnesia carbon bricks has not been fully utilized. How to develop at a high level is imminent.

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