The situation and its development trend. At the same time, the relevant situation of Baosteel was introduced, especially the research results on the reuse of refractories after use were reported.

　　The performance of recycled products can approach or reach the level of new products, and some can even reach the level of high-quality refractory materials.

　　 At present, our country consumes about 8 million tons of refractory materials every year, and the amount of refractory materials discarded after use exceeds 3 million tons. If these used refractories are sorted, sorted and treated with special processes, high-value refractory raw materials can be obtained. These processed recycled materials can not only produce high-quality unshaped refractory materials, but also regenerate high-quality shaped products. Some of them can be used as metallurgical auxiliary materials, such as slag splash protection materials, slag-forming agents, etc., and can also be used in Used in construction, cement and agriculture. This not only saves the country's mineral resources and energy, but also reduces environmental pollution and greatly reduces the cost of refractory materials. Therefore, it is very meaningful to study the reuse of refractories after use.

1 Foreign recycling status and development trends Many foreign countries, especially developed countries, attach great importance to the recycling of discarded refractory materials, and the development is also very fast, so the recycling rate of refractory materials is generally relatively high, such as steel The factory has reached more than 80%. Some companies cooperate with universities and research institutions to conduct in-depth research on the reuse of waste refractory materials.

　　 In some places, companies specializing in the recycling and reprocessing of used refractories have been established, and the used refractories are developing in the direction of being fully utilized, and some companies are also developing in the direction of zero emission of refractory materials.

The refractories used in the Japanese steel industry are mainly used as slag-forming agents or slag regulators, and can also be used as substitutes for molding sand; 50% of the castable AI2O3-Si2-C (ASC) for the iron trough has been reused, mainly Using aggregates for making iron ditch amorphous refractories; using post-magnesia-chrome bricks as fillers for eccentric bottom taps, the pouring rate is 98% higher than that of Tiantian Shouxin Baoshan Iron and Steel Co., Ltd. Technology Center Shanghai 201900 98%; A-MA pouring The recycled materials are used as repair materials and gunning materials, and can also be processed into refractory bricks. Nippon Steel has also developed a production method of using scrap to produce shrouds for continuous casting; Kashima Iron and Steel has successfully researched the reuse process of the skateboard. They used the method of pouring and restoring the castable and the ring inlay method to make the skateboard after repairing. The service life is the same as the new skateboard.

　　 Japan's Zhiduo Steel Plant uses waste bricks as the main raw material to develop ramming materials around the bottom of the ladle, ladle castables and shaped products. For example, unburned magnesia bricks are used in the molten pool of the electric furnace produced with 85% recycled materials and 15% of new materials, magnesia-carbon bricks used in the slag line of electric furnaces produced with 90% of recycled materials and 10% of virgin materials, and all used The RH bottom produced from recycled materials is fired into magnesia chrome bricks, etc. The performance of recycled bricks is shown in Table 1, and its use effect is basically the same as that of original bricks (new bricks). The recycling rate of refractory materials used by Zhiduo Steel Plant in Japan has reached Table 1 The performance items of new bricks and recycled bricks in Zhiduo Steel Plant in Japan have shown porosity/% volume density compressive strength/MPa erosion rate U/(times) recycled brick original brick 1) When used in the slag line of an electric furnace.

The 　　 ball discarded refractory material business has invented many technologies to recycle most of the discarded refractory materials from industries such as glass, steel, chemical industry, waste incineration, etc., and has also developed an optimal recycling and demolition method. The recycling rate of refractory materials used in French glass kilns. In 1993, the company developed a method for recycling refractory materials used in various furnaces, tundishes, ingot molds and ladle linings in the steel industry. Direct injection into the furnace to protect the furnace wall.

　　 American steel mills produce 1 million tons of discarded refractory materials every year. Almost all of them were buried in the past, with only a small amount being recycled. 1998 Meitian Trustworthy: Male, born in 1956, master's degree, professor-level senior engineer.

　　 The Ministry of Energy, the Ministry of Industry and Technology and steel producers jointly formulated a three-year plan to extend the service life of refractory materials and recycle waste refractory materials. The government's support and cooperation between manufacturers, users and research institutions have strengthened research on the reuse of refractory materials after use. The application range of recycled refractory materials is desulfurization agent, slag modifier (slag forming agent), splashing slag furnace protection additive, raw material of calcium aluminate cement, refractory concrete aggregate, paving material, ceramic raw material, raw material for glass industry, roof Granular materials, abrasives and soil modifiers used in construction, or made into refractory products of original materials. The United States has conducted research on the use of dolomite bricks as a soil conditioner and slagging agent, and good results have been achieved. Today, the amount of waste refractories in the United States has been reduced a lot.

　　2 The status and development trend of domestic refractory recycling. In recent years, with the implementation of environmental protection policies, the competition in the refractory market has intensified, and the reuse of refractory materials after use has gradually received attention. Some companies have used after-use refractories to varying degrees. According to Xiao Jie, some steel mills put the used magnesia carbon bricks on the converter and electric furnace lining to reduce the consumption of refractory materials; some used magnesia carbon bricks are processed into pellets as electric furnace filling materials; especially some When the refractory plant produces magnesia-carbon bricks and aluminum-carbon bricks, a small amount of used magnesia-carbon bricks and continuous cast aluminum-carbon materials are added to reduce costs. This kind of rough utilization not only reduces the performance and use effect of the product, but also fails to play the role of that part of the refractory after use, and more of the refractory after use is still discarded. However, most of the AZS bricks used in glass kilns are recycled by refractory plants, and some are made into various bulk refractory materials, and some are used as raw materials for skateboards. The economic and social benefits are relatively significant. In short, the domestic recycling rate of refractory materials after use is very low, even if the part is used, it is at the cost of lowering the quality of the product. Therefore, the social benefit is very low.

　　 3 Baosteel's refractory recycling situation 3.1 Current situation Baosteel Co., Ltd. produces about 60,000 tons of post-use refractories every year. The trend of these waste refractories has three aspects: discard. Some clay bricks, high alumina bricks and aluminum-magnesia-carbon bricks are discarded as garbage.

　　Recycled by the waste recycling station of the Development Corporation and the refractory material production plant. After they are recycled, they manually pick out the useable waste refractory materials from the waste pile, knock out the residual steel, residual iron, residue and permeable metamorphic layer on the surface, and stack them according to the material classification. Then, they are processed into granules or powders of a certain size, some are sold at a very low price, and some are mixed into refractory products in a small proportion. Because there is no finishing, it is added in the original state, so the performance of the product is reduced. If some magnesia carbon brick production plants add 5% to 20% of waste magnesia carbon bricks when producing magnesia carbon bricks, even this will significantly reduce the performance of magnesia carbon bricks.

　　 The steel plant directly recycles and reuses itself. If the back slide is used as a tundish impact plate, some furnace lining bricks are used as permanent lining bricks for new furnaces after they are removed. However, Baosteel's post-use refractory recycling rate is very low.

　　 3.2 Research situation Baosteel's scientific research personnel conducted preliminary experimental research on the used magnesia carbon bricks. The results show that the performance of recycled magnesia-carbon bricks produced by using more than 80% of the used magnesia-carbon bricks is close to the A-level of the magnesia-carbon brick ferrous metallurgical industry standard (see Table 2 for the results), which is significantly better than that of Japanese recycled magnesia-carbon bricks. The level of magnesia carbon bricks.

　　 Table 2 Performance items of recycled magnesia-carbon bricks w (waste bricks) compressive strength/apparent porosity/bulk density high temperature flexural strength/MIPa Note: 1 and 2 = bricks developed by Baosteel 3 bricks developed by Japan.

The taphole filler of the electric furnace developed with the used magnesia carbon brick as the raw material has a self-opening rate of more than 95%, which is equivalent to the forsterite filler; The converter large-surface hot repair material and splashing slag material have been studied, and good results have been achieved; the magnesium-carbon castable developed using the used carbon-containing refractory material as the raw material, the results are shown in Table 3. From Table 3, we can see that, The castable developed by Baosteel has a low water addition, and its performance is equal to or better than that of Veitsch-Radex in Austria and magnesium-carbon castable in Japan. Because the life of Japanese magnesia-carbon castables used in LF slag line is twice that of high-quality corundum-MA(M) castables, the use of carbon-containing refractories after use is expected to be developed in Table 3 for carbon-containing castables. The performance items of magnesium-carbon castables add water/% volume density Bayi.

　　24h apparent porosity/% compressive strength/MPa bulk density Bayi.

　　3h apparent porosity/compressive strength/MPa Note: 4=developed by Baosteel, 5=developed by Veitsch-Radex, Austria, 6=developed by Japan.

　　 has very good development prospects.

　　 Baosteel has long conducted research on post-use magnesia-chrome bricks, which are added to the gunning material for RH furnaces in a certain proportion, showing a good use effect. Recently, the pre-research on recycled magnesia chrome bricks has been carried out. With more than 70% of the waste bricks, regenerated magnesia chrome bricks with w(MgO)=60% and sand (23)=18% have been developed. After 180°24 dagger treatment The bulk density, apparent porosity, and compressive strength are 3.12g-cm-3, 13%, and 64MPa, respectively; the bulk density, apparent porosity, and compressive strength after 1750 buried carbon treatment are 3.14g°cm-3. , 17.7%, 48MPa. It can be seen that recycled magnesia-chrome bricks have good performance and are expected to have application prospects in non-critical parts of cement kilns and RH furnaces.

　　 The preliminary research on the regeneration of refractory materials such as aluminum-magnesium-carbon ladle bricks and iron ditch materials has been carried out. The performance of the recycled aluminum-magnesium-carbon bricks developed with more than 90% of the waste bricks is: w(Al23)=69%, w(MgO)=14%, w(C)=8.5%, and the volume density is 3.01g°cm3 , The apparent porosity is 8.7%, and the compressive strength is 44MPa. The performance of ASC refractories recycled from discarded iron ditch materials is shown in Table 4. Its performance is close to or reaches the level of new products, especially the performance of recycled ASC bricks is better. The ASC bricks currently used by Baosteel’s torpedo vehicles have yet to undergo application research. Take Table 4 to use waste iron ditch material to regenerate ASC-based refractory performance items. Bulk density of castable ramming material/(Dtm3) low temperature thermal sensible porosity/% Compressive strength after treatment/MPa flexural strength/MPa 3h bulk density/ (.3) Significant porosity of buried charcoal treatment z% Compressive strength of buried charcoal treatment/MPa Purposes for tapping trench cover, torpedo cart tapping trench, ladle ladle torpedo cart, mixing furnace, blast furnace made of back trench material The ramming materials and castables used in the repair of the iron casting plant and small blast furnaces are expected to produce good results and are worthy of application research and promotion.

The author has conducted research on the production of shelf silica bricks for kilns using waste silica bricks as raw materials. The use of waste silica bricks is 90%, and the properties of recycled silica bricks are as follows: compressive strength 62MPa, apparent porosity 16%, true specific gravity 2.30g -cm-3, load softening temperature T.6=1620T4=1670°C. It can be seen that the brick has good performance, and the shelf brick has also achieved good results after use. Waste silica bricks can also be used as raw materials for siliceous thermal insulation boards, fire mud and lightweight silica bricks. Since these raw materials have completed the crystalline transformation, they can be made into unfired products or low-temperature fired products.

　　4 Conclusion At present, the recycling rate of refractory materials in our country is not high. Even if they are reused, they are basically simple incorporation and are not combined with advanced recycling technologies, so there is no obvious economic and social benefits.

The experimental research results show that high-quality refractory bricks, castables, ramming materials, repair materials, slag splashing materials, tap fillers, drainage sand and slag-forming agents can be made into high-quality refractory bricks with a high proportion of after-use refractories. Value products, and the performance of these products can approach or reach the level of the original product, and some can exceed the level of the original product.

　　 Countries all over the world have fully realized that used refractories are cheap renewable resources, which can significantly improve the economic and social benefits of enterprises, and the recycling of used refractories is also a contribution to environmental protection. Therefore, in the near future, high value-added, high-quality recycled products produced from used refractories as raw materials will develop rapidly, and the reuse rate of used refractories will increase rapidly, and there will be a trend towards zero emissions.