Preparation Technology Research Of Highly Active Magnesia Using Magnesite From Sichuan-Tibet Region

Magnesium series products are important inorganic chemical materials of modern industry. Because of its large specific surface area, high surface activity, strong adsorption ability, the active magnesia is extensively used in many fields including catalyst industry, bio-medicine, rubber synthesis, etc. With high grade magnesite collected from Sichuan-Tibet region as raw material, three methods including calcination method, hydration method and carbonization method were used to prepare magnesia with different activity in this dissertation. The advantages and disadvantages of the three methods were compared. This study has a great significance on the comprehensive utilization of magnesite from Sichuan-Tibet region.Through orthogonal experimental, the calcinating technology was used to prepare light-burned magnesia with iodine adsorption value of105.5mg/g, CAA value of18.5s and specific surface area of34.86m2/g was obtained and magnesite decomposition rate is98.8%under the optimal condition:calcination temperature being700℃, calcination time being3h, heating rate being15℃/min and particle size being smaller than74μm. The quality of light-burned magnesia exceeds the standards of industrial first-grade active magnesia (activity-80).The hydration method was used to prepare highly active magnesia with the light-burned magnesia as raw material. The hydration rate of light-burned magnesia could reach94%under the optimal condition: hydration time being1h, hydration temperature being70℃and mass concentration being20g/L. The highly active magnesia was obtained by calcinating magnesium hydroxide at500℃for3h, whose iodine adsorption value being180.6mg/g, CAA value being8.5s and specific surface area being55.60m2/g. The quality exceeds the standards of industrial first-grade active magnesia (activity-180).The carbonization method was used to prepare highly active magnesia with the light-burned magnesia as raw material. Heavy magnesium water was obtained under following condition:carbonization temperature being40℃, carbonization time being50min and mass concentration being5g/L. The basic magnesium carbonate with a molecular formula4MgCO3·Mg(OH)2·4H2O was obtained by the pyrolysis of heavy magnesium water. Highly active magnesia was prepared by calcinating basic magnesium carbonate at600℃for2h, whose iodine adsorption value being190.5mg/g, CAA value being7.2s and specific surface area being79.47m2/g. The quality exceeds the standards of industrial first-grade active magnesia (activity-180).