Alkaline refractories:What it is & Where it’s Used

  • Time:Aug 25, 2023
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Alkaline refractories are mainly composed of magnesia and calcium oxide, and magnesia bricks are commonly used. Magnesia bricks containing more than 80% to 85% of magnesium oxide have good resistance to alkaline slag and iron slag, and their refractoriness is higher than that of clay bricks and silica bricks. Mainly used in open hearth furnace, oxygen blowing converter, electric furnace, non-ferrous metal smelting equipment and some high temperature equipment.

【1】 Application of Alkaline Refractories

  1. Steelmaking industry: Alkaline refractories find extensive use in steelmaking processes such as steel ladles, converters, and electric arc furnaces. They line the inner walls of these equipment to withstand high temperatures, basic slag, and chemical reactions with molten metal.

  2. Cement industry: In cement kilns, rotary kilns, and other high-temperature zones within cement production plants, alkaline refractories are utilized due to their ability to resist the corrosive effects of alkaline compounds present in cement raw materials and fuels.

  3. Lime and dolomite industry: Alkaline refractories are employed in lime kilns and dolomite converters for the production of lime and dolomite. They withstand the high temperatures and alkaline conditions involved in the calcination process.

  4. Non-ferrous metallurgy: Alkaline refractories are utilized in non-ferrous metal smelting and refining processes. They are used in equipment like copper converters, aluminum electrolysis cells, and nickel flash smelting furnaces, where they exhibit resistance to corrosion from alkaline slags and molten metals.

  5. Glass industry: Alkaline refractories find application in glass melting furnaces and regenerators. They provide resistance to the corrosive effects of alkaline compounds present in glass batch materials and help maintain the structural integrity of the furnace lining.

  6. Petrochemical industry: In petrochemical plants, alkaline refractories are used in various units such as fluid catalytic cracking (FCC) units, hydrogen reformers, and pyrolysis furnaces. They resist the corrosive effects of alkaline substances and high-temperature environments encountered in these processes.

  7. Waste incineration: Alkaline refractories are employed in waste incinerators, where they withstand the high temperatures and alkaline conditions resulting from the combustion of waste materialsmore

【2】 The main components of alkaline refractories

  The main components of basic refractories are magnesium oxide and calcium oxide, of which the magnesium oxide content is usually greater than 70%, and the calcium oxide content is between 20% and 30%. In addition, in order to improve the melting performance of basic refractory materials, a certain amount of flux will be added, such as kaolin, silicate, etc.

  In addition, in order to reduce production costs and improve product performance, basic refractory materials can also be mixed with some other materials, such as lightweight aggregate, alumina, aluminum silicate, etc. These materials can improve the physical and chemical properties of basic refractory materials, and enhance their refractory performance and mechanical strength.

  It should be noted that the composition and proportion of basic refractory materials vary according to the manufacturing process and application. In the process of production and application, it is necessary to select the appropriate raw materials and proportioning scheme according to the specific process requirements and use environment to ensure that the quality and performance of the product meet the standard requirementsmore


【3】 Alkaline refractory production process

  1. Raw material preparation

  First, raw materials such as magnesia and alumina are mixed evenly in a certain proportion, and then processed into granules (such as pressing balls or extruding) to make them have certain plasticity and formability. Commonly used auxiliary additives include polysilicate (such as talc), calcium carbonate, red mud, etc.

  2. Molding treatment

  The pretreated raw materials are formed into refractory blanks of different shapes and specifications by pressing, extruding, casting, etc. Among them, the extrusion method is a common molding method, that is, the pretreated material is filled into the injection machine, and the material is extruded by high pressure to form a rod-shaped green body with a diameter of about 25mm to 75mm.

  3. Drying treatment

  The molded green body is dried by natural air or hot air to remove part of the water and improve the strength. In this step, it is necessary to pay attention to controlling the drying temperature and time to avoid problems such as cracks or deformation.

  4. Sintering treatment

  The dried green body is put into a resistance furnace and sintered at a high temperature (usually 1600°C to 1800°C) to make its internal structure form crystals and enhance its fire resistance and mechanical strength. In addition, the alkali corrosion resistance of the material can be further improved by adding a small amount of additives such as calcium fluoride and magnesium fluoride during the sintering process.

  5. Subsequent processing

  Cutting, grinding, polishing and other subsequent processing are carried out on the sintered material to meet different use environments and requirements. Among them, it is also necessary to carry out quality inspection and quality control on the materials to ensure that the products meet the refractory industry standards and customer requirementsmore

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