Brown corundum production process
Bauxite ore shipped from outside is mainly composed of hard bauxite monohydrate, which contains a large amount of water and is first pretreated with raw materials. Pretreatment involves sintering the ore with low sulphur coal to remove most of the water until the ore still contains water of crystallisation. The dewatered ore pile is manually screened to remove impurities due to the presence of some large pieces. After screening, the ore is crushed into small pieces by a jaw crusher and then the ore, iron filings and coal are mixed in a certain ratio according to the production requirements, the coal used being low sulphur anthracite. In general the mixing ratio of ore, iron filings and coal is 10:0.7:0.4. The mixed raw material is transported to the smelting furnace via a belt for smelting. As coal burning does not allow the temperature to reach the required production temperature, three graphite electrodes are installed in the smelting furnace to bring it up to the required smelting temperature.
The smelting is sintered at 2000°C for 5-6.5 hours and the temperature in the smelting furnace can be monitored through the monitoring room during smelting. The smelted molten prize is cooled in a cooling vessel. After cooling, the low-silica iron sinks to the bottom of the vessel, while the upper part is the product required for production, i.e. brown corundum. Water is added to the cooling vessel to speed up the cold water, and a hot water cooling pond is built next to the vessel for efficient recycling of water resources. The freshly discharged brown corundum is crushed into smaller pieces by a jaw crusher and then crushed into smaller particles by rollers or ball mills etc. The crushed particles are sieved according to the international or customer required particle size standards and then packed in the warehouse according to the customer's required packaging and awaiting sale.
The whole process can be expressed as follows:
① dehydration pretreatment of bauxite;
② mixing bauxite, iron filings, anthracite, in proportion;
③ preparing graphite electrode (generating high temperature and high pressure arc);
④ adding raw materials into the electric arc furnace;
⑤ dumping out brown corundum after several hours of high temperature smelting;
⑥ separating the low silica iron from brown corundum at the bottom after cooling;
⑦ crushing the large brown corundum into products with required particle size