Magnesium chromium brick manufacturers utilization value for steel

Many countries, especially developed countries, attach great importance to the reuse of waste refractory materials, and the reuse rate is generally relatively high, with some steel mills reaching over 80%. In this regard, Kouben started early and the technology is relatively mature. The reuse rate of refractory materials used by Japan's Zhiduo Steel Plant has reached 50% to 100%. In Japan's steel industry, waste refractory materials are mainly used as substitutes for slag making mixtures and molding sand. Some steel mills mainly use waste bricks as raw materials and have developed ramming materials for the bottom and periphery of the ladle, ladle pouring materials, and shaping products. For example, unburned magnesia bricks are used in the melting pool of electric furnaces produced with 85% recycled materials and 15% new materials, magnesia carbon bricks are used in the slag line of electric furnaces produced with 90% recycled materials and 10% new materials, and RH bottom fired magnesia chromium bricks are all produced with recycled materials. Kurasaki Corporation has developed immersion nozzle bricks using waste corundum graphite products as raw materials; Kashima Steel Company has developed a secondary utilization process for skateboard bricks.

The waste refractory materials from the iron ditch are all reused, mainly used as aggregates for Al₂O₃ - SiC-C castables. The United States uses waste refractory materials in desulfurization agents, slag modifiers (slag forming agents), slag splashing furnace protection additives, raw materials for calcium aluminate cement, refractory concrete aggregates, paving materials, ceramic raw materials, raw materials for the glass industry, granular materials for roof construction, abrasives, and soil modifiers. Its research on using tlzx stone bricks as soil conditioners and slagging agents has also achieved good results. Valoref, a French company specializing in the global business of waste refractory materials, has invented many technologies and furnace dismantling methods for recycling most of the waste refractory materials from industries such as glass, steel, chemicals, and waste incineration. This has enabled the recycling rate of refractory materials used in French glass kilns to reach 60% in 1997.

In China, the utilization rate of waste refractory materials is not high, but there has been significant development in recent years, Usually, waste refractory materials are used for metallurgy Auxiliary raw materials for the industry. Waste refractory bricks and amorphous refractory materials, including MgO-C bricks, are commonly used for hot repair of furnace linings, casting agents for casting holes, or as raw materials for manufacturing new MgO-C bricks. Waste Al₂O₃ - C bricks can also be used as raw materials for manufacturing sliding plate bricks, immersion nozzle bricks, and protective sleeves. Waste refractory materials used for secondary utilization and repair include: Al₂O₃ - ZrO₂ - SiO₂ bricks, large bricks for glass furnaces, oxygen converters MgO-C bricks for electric arc steelmaking furnaces, steel ladles, magnesium chromium bricks for electric furnaces, etc. Baosteel has conducted research on the reuse of refractory materials containing silicon carbide and carbon, from magnesia carbon bricks used in ladle and converter to lining bricks used in high-speed iron water channels and mixer cars, and has achieved preliminary good results. Typical products include recycled magnesia carbon bricks, ASC based castables, etc.

1. Magnesium aluminum spinel refractory material

Broadly speaking, spinel refers to minerals belonging to spinel group. Its general chemical formula is AO·B₂O₃ or AB₂O₄, where a is a positive divalent ion and B is a positive trivalent ion. According to the chemical composition of positive trivalent ions, it can be divided into aluminum spinel, chromium spinel and iron spinel. Generally, people are used to abbreviate magnesium aluminum spinel (MgAl₂O₄) as spinel.

The international standard definition of magnesia alumina spinel refractories is that the mass fraction of magnesia and magnesia in the spinel composition is not less than 20%. The chemical formula of magnesium aluminum spinel is MgAl₂O₄ (abbreviated as MA), with magnesium oxide accounting for 28.3% and aluminum oxide accounting for 71.7%. Generally, according to the theoretical chemical composition of the spinel, aluminum rich spinel, i.e. alumina solid solution spinel, will be formed on the side with high Al₂O₃ content, and magnesium rich spinel, i.e. periclase spinel coexisting spinel, will be formed on the side with high MgO content. As shown in Figure 1, spinel is a compound in the MgO Al₂O₃ binary system, and its melting point is 2135 ℃. There are two low eutectic melts formed in the MgO al ɑ o ɑ system, which exist in the spinel periclase binary system and the spinel corundum binary system respectively. The chemical compositions of the two low eutectic melts are 77/23 and 11/89 respectively, and their low eutectic temperatures are 2050 ℃ and 1925 ℃ respectively. It can be seen from Figure 1 that the solubility of periclase in magnesium aluminum spinel can reach 10wt% at high temperatures, The solubility of corundum in magnesia alumina spinel is higher. According to the above description, the spinel refractory composed of MgO and Al₂O₃ is undoubtedly highly refractory. In addition, the main advantage of spinel compared with dolomite brick and magnesia chrome brick is that it has strong corrosion resistance to reducing atmosphere, free SO₂/SO₃ and free K ₂O/Na₂O. at the same time, magnesia alumina spinel also has excellent thermal shock stability and wear resistance, and magnesia alumina spinel has high melting point, low thermal expansion coefficient and high hardness, which makes magnesia alumina spinel an indispensable part of refractories.