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In the 1990s, magnesia chrome spinel brick manufacturers not only have a strong ability to hang the kiln skin, but also have a series of performance advantages in alkali resistance, sulfur melt and clinker liquid phase erosion, thermal shock resistance and mechanical stress caused by kiln body deformation, and thermal load resistance, which make it become the mainstream of alkaline brick technology development in the world. Among them, magnesia chrome spinel brick is used in cement firing zone and upper transition zone, which has the advantages of high fire resistance, good elastic structure and good resistance to thermodynamic corrosion, which can replace magnesium chromium brick and general basic brick. Magnesia iron spinel brick and magnesia manganese spinel brick are commonly known as active spinel brick. Magnesia iron spinel brick is a new variety appeared in the late 1990s, which has high fire resistance and strong oxidation resistance. Compared with dolomite brick and magnesium chromium brick, this kind of spinel brick has higher loading and unloading and thermochemical properties. The refractoriness of magnesia manganese spinel refractory brick is higher than that of magnesium iron spinel, the activity of manganese ion is higher, and the corrosion resistance of alkali, chlorine and sulfur is stronger.

At present, the main products of basic refractories used in large precalciner kilns (kilns with a daily output of more than 5000 tons) include magnesia spinel bricks, magnesia chrome bricks, dolomite bricks and magnesia zirconia bricks, while in China, magnesia spinel bricks and magnesia chrome bricks are the main products.

Magnesia spinel brick

Magnesia spinel refractory brick is usually made by mixing, molding and firing the raw materials of pre synthesized spinel and magnesia. Another method is to add alumina into magnesia to synthesize spinel during firing. Spinel brick made by one method is widely used in the market. This kind of brick has good thermal shock stability and high resistance to thermochemical erosion, which is mainly used in transition zone.

Price of magnesia chrome brick

Magnesia spinel brick reacts with cement clinker, which is easy to form low melting point minerals. Therefore, the brick is easy to melt when it contacts with the cement raw material and the liquid phase volume increases. Moreover, the amount of liquid phase penetrating into the brick increases, and the brick is prone to structural spalling. In addition, MgO spinel brick in transition zone, especially at the fulcrum, is subject to great mechanical stress, which also causes great damage to the brick.

The top of the furnace is made of refractory materials. The top of the furnace, also known as the furnace cover, is of circular arch shape and can be moved. The outer ring is a water jacket type steel structure. In the smelting process, the furnace top (especially the central part of the furnace top, around the electrode hole and dust removal hole) is in a high temperature state for a long time. Affected by the sudden change of temperature, it is affected by the chemical erosion of furnace gas and slag making powder, the radiation of electrode arc light and the erosion of smoke and dust. The dust accumulation on the furnace top also produces pressure and hinders effective heat dissipation. The furnace top is also affected by mechanical vibration when it is lifted and rotated The working strip is very bad, which is the weak link of the whole furnace lining. Therefore, the furnace life of magnesia chrome brick furnace refers to the service life of the furnace top. Because of the single electrode structure of DC EAF, there is no hot spot area. In addition, the water cooling zone at the top of the furnace is expanded, so the refractory materials used in the furnace are improved obviously. After the 1980s, with the expansion of the capacity of the EAF and the increase of the unit power, the working conditions at the top of the furnace become more severe, and the refractories used are also changed.

The traditional refractory material for furnace top is silica brick. The thermal shock resistance of silica brick is poor in low temperature range, and it is not suitable for the sudden change of temperature, and it is impossible to greatly improve the fire resistance due to the limitation of raw materials. Therefore, the flow of silicon brick droplet at high temperature not only reduces the basicity of slag, but also affects the refining effect and the life of furnace body seriously. In addition, the smelting temperature is increased and the smelting cycle is shortened by using oil injection and oxygen blowing, which makes the silica brick unable to meet the needs of smelting. Although some measures such as adding a small amount of oxychrome or asphalt impregnation into silica brick have been taken, but the effect is not obvious. As a result, high alumina brick, alkaline brick or corresponding refractory castable or ramming material are gradually used to build furnace top. The protective layer can effectively reduce the unit consumption of refractory, but the energy consumption is relatively increased.

The bottom of the furnace is made up of refractory materials, the bottom of the furnace and the bank slope, which is the gathering place for charging and molten steel. The bottom refractory materials are in direct contact with molten steel and slag, and are mainly subjected to chemical erosion and erosion, as well as by the covering and rapid cooling of furnace charge. When the furnace bottom lining reacts with the slag of fused magnesia chrome brick to form a metamorphic layer, it will become loose due to the reduction of the Mao dietong fraction during the reduction period, which is often caused by the invasion of molten steel. It is required that the masonry or knotting lining in this part should have strong overall performance, strict prevention of molten steel penetration, good high temperature performance, sufficient strength, corrosion resistance, erosion resistance, good thermal shock resistance and thermal shock resistance The product is stable and can be sintered well in the process of use.