Technical description

The first step in aluminum smelting is to produce alumina. In the process of producing alumina by sintering method, the first step is to sinter the raw materials prepared from bauxite, lime, alkali and other raw materials into mature materials. The sintering process is carried out in a rotary kiln, with a firing temperature of around 1300 ℃. The final process of producing alumina is to roast aluminum hydroxide into alumina, which is currently generally done using a rotary kiln with a roasting temperature of 1200-1250 ℃ (the reaction temperature in this article refers to the temperature of the kiln gas used for heating the material being 200-300 ℃ higher than it) In the production of metallic aluminum using aluminum oxide as raw material through molten salt electrolysis, as well as in electric furnace steelmaking and certain metallurgical and chemical production processes, carbon products such as anode paste (or carbon blocks), electrode paste, electrodes (rods), anode plates, etc. are required. In the production of carbon products, raw materials such as petroleum coke, metallurgical coke, delayed coke, asphalt coke, and smokeless coal need to be calcined at 1100-1300 ℃ under oxygen free conditions to remove moisture and volatile matter, make the structure denser, increase the true density, enhance thermal stability, oxidation resistance, mechanical strength, conductivity, and thermal conductivity. This process can be completed in a rotary kiln. Due to the combustion of volatile components, the exhaust gas temperature is extremely high, and waste heat boilers are generally used to recover heat In the process of aluminum electrolysis, fluorite materials such as cryolite (Na3AIF6), aluminum fluoride (AIF3), and sodium fluoride (NaF) are also required as fluxes. The production of fluoride salts first uses sulfuric acid and fluorite (CaF2) as raw materials to produce hydrogen fluoride, which is also carried out in rotary kilns - internal or external hot kilns. Drying of various fluoride salt products and slag gypsum is also done using a rotary kiln In addition, a large amount of waste residue from alumina production, namely red mud, is mainly used for the production of red mud cement. Therefore, sintering alumina plants often have a larger scale red mud cement plant attached, which also uses rotary kilns Red mud is a solid waste residue generated during the production of alumina, which appears red due to its high content of iron oxide. Its comprehensive utilization has attracted great attention from countries around the world.