The manufacture of magnesia introduced the process defect of refired magnesite

At present, the total production of heavy-burned magnesia in China is 4 million to 4.5 million tons per year. Following the industry habits, sintered magnesia can be roughly divided into heavy fired magnesia, medium-grade magnesia, high-purity magnesia.

Until the 1980 s, in the 30 years of time, the production of sintered magnesite is mainly composed of the anshan iron and steel in magnesite, successively with 25 cubic meters, 32 cubic meters, 40 cubic metres, 47 cubic meters and 55 m cubic meters of shaft kiln and coke as fuel, with massive magnesite stone as raw material, adopt step calcination and artificial discharging produces 92% of the dead burned magnesite, content of MgO style for the steelmaking furnace bricks for raw material.

The disadvantage of this process is that the ore utilization rate is low and the fine grain ore cannot be used. High content of impurities, the ash content in coke will cause pollution to magnesia, so that the content of SiO2 and Al2O3 in magnesia increases, and the content of MgO can only be guaranteed at 92%. The continuous operation is poor, the thermal decomposition of large magnesite ore produces small particles that stick to the kiln wall, and the materials in the kiln are prone to "lump", which results in the frequent change of the material flow and thermal system in the kiln, leading to the failure of mechanized operation. The density of magnesite is low, and the magnesite is decomposed in the pre-tropical zone in the kiln, releasing CO2 and turning into light-fired MgO. However, the MgCO3 "mother salt illusion" still exists, which is not favorable for further densification of magnesite. The volume density of sintered magnesite is only between 3.0g and 3.1g per cubic centimeter. Serious environmental pollution, magnesite decomposition of a large number of CO2 and combustion flue gas mixed with fine coke particles and light burning dust fly out of the kiln, environmental pollution, high temperature flue gas treatment is difficult.

At present, China's reburned magnesia is still calcined with secondary and tertiary ores in solid fuel shaft kilns. The content of MgO of magnesia is 90%~92%, and the volume density is above 3.10 grams per cubic centimeter. Refired magnesia is the main raw material for the production of ordinary magnesia-fired bricks and amorphous refractories. The annual output of Liaoning province is estimated at 2.5 million tons. Because can use 3 class mine, the product price is low and have the market, at present hard eliminate.