Defects in application of coal lining of submerged arc furnace

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Defects in application of coal lining of submerged arc furnaceIn the traditional lining research and construction of submerged arc furnace, pre-baked carbon b

Defects in application of coal lining of submerged arc furnace

In the traditional lining research and construction of submerged arc furnace, pre-baked carbon bricks or self-baked carbon bricks are used as the building materials for the high-temperature part of the furnace, and the cracks between carbon bricks are filled with cold ramming paste or warm ramming paste in the process of furnace building. Cold ramming paste is a kind of carbon-carbon composite material made of electrically calcined coal, graphite and modified binder, which is mainly used to fill gaps between carbon bricks in lining of aluminum electrolytic cell, submerged arc furnace, calcium carbide furnace and other industrial submerged arc furnace, and can be used without preheating during construction. However, the furnace building process has high requirements for operation. After the completion of furnace building, roasting is required before it can be put into use. In the process of roasting, due to the difference of paste shrinkage rate between carbon bricks and filled carbon bricks, each filled carbon brick may have a gap in the process of roasting, which is easy to cause carbon bricks floating. And the carbon brick and the gap will participate in the reduction reaction through the alloy carburizing and molten iron scour, making the gap become larger, the molten iron is easy to burn through the furnace shell at the iron outlet and the joint, resulting in forced furnace shutdown renovation, resulting in huge economic losses

1.1 Prebaked charcoal brick building process Prebaked charcoal brick is usually made of anthracite, petroleum coke and bitumen coke calcined at 1250℃ at normal temperature as aggregate, and coal bitumen as binder. It is mixed and squeezed in a certain proportion to make green charcoal brick.Before putting into use, the green carbon bricks are roasted in the internal reducing atmosphere of the roaster at a certain heating rate (generally the roasting temperature is not more than 1200 ℃C), and the stable geometric shape is formed after roasting, which is mainly used for lining construction of mineral furnace and electric furnace. Pre-baked charcoal bricks are used to build refractory lining and fill 40~50 blocks with electrode paste, hot ramming paste or cold ramming paste Mm gap, because the softening temperature of cold pounding paste is high, it is more sensitive to temperature change, and it needs preheating before use before construction, and because of the volatilization of toxic gases such as asphalt, the construction environment is more harsh, often the phenomenon of brick joint pounding is not solid. In addition, only the interseam paste is roasted during the heating of the furnace lining, and the interseam paste is adsorbed on the pre-baked carbon block during the roasting process. Because of the difference in shrinkage between the interseam paste and the pre-baked carbon brick, the interseam strength of the pre-baked carbon brick is the lowest, and it is also the part of the furnace lining that is most easily eroded by molten iron. After put into production, because the Raw material calcination and roasting temperature of pre-baked carbon brick is lower than the use temperature, residual volume shrinkage will occur during use. With the discharge of volatiles, the gap increases, and the metal liquid is easy to gradually penetrate through the gap. 1.2 self baking carbon brick lining technology of self baking carbon brick with pre-baked carbon brick is roughly same, adopt after high temperature calcined anthracite calcination temperature about 1750 ℃ or so) to aggregate, according to certain proportion to join coal asphalt binder and additives such as under a certain temperature evenly kneading, extrusion molding of carbon brick without roasting in advance can masonry furnace bottom and furnace lining, carbon brick gaps in between The gap between carbon bricks and carbon bricks as well as between carbon bricks and furnace wall shall be filled with low temperature seam paste and furnace lining structure. The roasting of self-baked carbon brick is different from that of pre-baked carbon brick, which is roasted layer by layer from top to bottom in reducing atmosphere by using oven technology and heat generated in the production process. The material of the self-baked carbon brick and the seam paste are similar, and the roasting starts at the same time under the same conditions. Therefore, the plastic deformation of the carbon brick in the roasting process can make up for the cracks generated during the furnace building, and eventually gradually graphitize to form a dense carbon lining with strong integrity, and complete the transformation from carbon to graphite with the increase of temperature.