Dolomite ore is first calcined (or fused) to obtain magnesia-calcium raw materials (such as dolomite sand/magnesia dolomite sand, magnesia-calcium sand, magnesia-calcium iron sand), and then prepared into various dolomite refractory materials. In addition to the advantages of high refractoriness, slag erosion resistance and thermal shock resistance, CaO can absorb non-metallic inclusions such as S, P, Al2O3, SiO2 in molten steel, and also has the function of purifying molten steel. Therefore, it is widely used in stainless steel refining furnaces; in addition, because dolomite bricks contain a large amount of free CaO, they can easily react with C2S in cement kiln materials to form C3S and produce stable kiln shells, so they are suitable for use in cement rotary kilns. Bring it.
Dolomite bricks are made of dolomite sand that is calcined from natural dolomite. Dolomite brick contains w (CaO) ≥ 40%, w (MgO) ≥ 35%, and also contains a small amount of SiO2, Al2O3, Fe2O3 and other impurities. If the mass ratio of CaO to MgO in the brick is less than 1.39, it is called magnesia dolomite brick.
Magnesia-calcium bricks include two types: one is a magnesia-calcium brick produced with synthetic magnesia-calcium sand as the main raw material; the other is a magnesia-calcium brick produced with dolomite sand (or magnesia dolomite sand) and magnesia as the main raw material , Also known as magnesia dolomite brick.
Refractory material that uses sintered dolomite sand, magnesia sand and/or graphite of different particle sizes as the main raw materials and can be used directly without firing. It has energy saving, good thermal shock stability, simple production process, and good slag resistance. .
Dolomite is also used to prepare a variety of magnesium-calcium amorphous refractories, such as electric furnace bottom ramming material, tundish coating material, ladle gunning material, converter gunning material, RH furnace gunning material, artesian hot filling material, etc. Refractory materials. Among them, the most used magnesia-calcium-iron dry ramming material for the bottom of the electric furnace is prepared from iron-containing magnesia-dolomite synthetic sand (magnesia-calcium iron sand) as the raw material. The use effect is good, such as Shanghai Baosteel 150tUHP The bottom life of the electric furnace reaches 1087 times; the bottom life of the 90t UHP electric furnace of Wuyang Iron and Steel Company is also more than 1500 times.
At present, dolomite is mainly used to synthesize magnesia-calcium refractories in refractories. In order to expand the application of dolomite resources in refractories, research has been done on the use of natural dolomite ore to synthesize calcium aluminate cement containing magnesia-aluminum spinel. Calcium aluminate cement (CMA) containing microcrystalline magnesia-aluminum spinel is a new type of binder for refractory materials. Its CaO content is reduced and contains magnesia-aluminum spinel. Compared with ordinary aluminate cement, it has more It has excellent high temperature volume stability, thermal shock resistance and slag erosion resistance.
In the field of cement industry, due to some reasons, some enterprises in our country still use magnesia-chrome bricks in the firing zone and transition zone of cement rotary kilns, while dolomite bricks have excellent high temperature resistance, kiln-hanging skin and resistance to alkaline substances. It can be used in the burning zone and transition zone of cement kiln to replace magnesia-chromium refractory bricks. At present, only a few manufacturers in my country use imported dolomite bricks in cement rotary kilns. Dolomite bricks are used in the burning zone of cement rotary kilns in my country. There is a lot of room for development. However, dolomite refractories are difficult to sinter. At the same time, refractories using dolomite sand as raw materials can easily absorb water and hydrate to form hydroxides during storage and repeated use, resulting in volume expansion, resulting in rupture and pulverization of the product. Acute weaknesses limit the application and development of dolomite refractories.
Therefore, in the future, we will increase research in this area to increase the application of dolomite resources in refractory materials, which can save relatively small reserves of magnesite. Use dolomite to develop new refractory materials, such as new aluminate cement, calcium hexaaluminate-spinel lightweight refractories, etc.
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