Anthracite-carbon is a type of neutral refractory that can withstand high temperatures. It's made using anthracite raw materials, and then binder. It is highly stable at high temperature and resists corrosion by acid, alkali slags, salts and organic solvents. It can easily be oxidized.
Microporous carbon blocks with an average diameter of less than 0.5mm have been developed to improve the shortcomings in ordinary carbon bricks, such as their poor oxidation, corrosion and permeability. This new type is suitable for use in high temperature applications. The main raw material for this type of product is electric calcined alumina. It's then mixed with a small quantity of graphite and silicon powder. Medium-temperature pitches are used as a binder.
It is possible to control the alumina level of anthracite by using dry processes. This allows for good slag forming properties in blast-furnaces. The brick has a high thermal shock and wear resistance. Its abrasion-resistance is also better than clay bricks.
Burned pitch impregnated magnesite is a special type of carbon refractory, designed for use in industries such as metallurgical steelmaking or other industries that operate at temperatures exceeding 2000 deg C. These bricks are often found at the bottom of blast furnaces and hearths in metallurgical plants.
One of the reasons for their high-temperature strength is that they have a very low slag reduction coefficient. The high level of carbon in the brick also prevents slag constituents from chemically altering the dicalcium silicate bond, which maintains the high hot strength of the brick. It is also important that the carbon refractory be resistant to slag spalling. This is the phenomenon where the brick hot face cracks and falls away due to a reaction with slag constituents.
During the manufacturing process of carbon bricks, it is necessary to prevent their oxidation at high temperatures. To do so, the anthracite used as raw material must be calcined to eliminate volatile components and sulfur content, then added with metallurgical coke and medium-temperature pitch as the binding agent. In order to avoid the carbon oxidizing in high temperatures, the raw materials and bricks are sintered, held and fired under a reduced atmosphere.
Carbon bricks can be found in many metallurgical applications, including the bottom and hearth of blast furnaces, the pickling bath in electroplating, the dissolving tanks in papermaking, the reaction and storage tanks in chemical industries, and the autoclaves in petrochemical industries. In addition, they are also used in aluminum electrolyzer. This is the most popular type of refractory in metallurgy. It has many advantages, such as a small thermal expansion coefficient, high temperature resistance and a good resistance to acid, alkali, salt and organic solvents. Moreover, it is easy to form a dense structure with excellent corrosion resistance. It is the ideal material for metallurgical products, such as pickling tanks and plating tubs in the electroplating and papermaking industries.
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