Study On Preparation Process Of Silicon-steel Magnesium Oxide With Carbonization Method

Magnesium oxide is a kind of important inorganic chemical materials, which is widely used in chemical industry, medicine, food adding, refractory materials, rubber industry, electronics and aviation, etc. Although magnesium resources are rich in our country, the high grade sources get less and less due to a long-term exploitation and primary products exporting. In view of developing of magnesium oxide in recent years, the products tend to high purification and fine. Therefore, it has important significance to improve the preparation of magnesium oxide process and reasonablely develop low grade sources for preparing high purity magnesia products.This study is involved in the preparation process of silicon-steel magnesium oxide with carbonization method. The main preparation processes of magnesium oxide using light-burned magnesia as raw materials by carbonization method are as follows. Frist, light-burned magnesia was hydrated and carbonated to obtain magnesium bicarbonate liquor.Then impurities Fe and Ca in magnesium bicarbonate liquor were covered by using a complex method. After that, the treated liquid was pyrolyzed to obtain basic magnesium carbonate which was calcined to get magnesia. The effects of hydration recation time and solid-liquid ratio on the component concentrations of magnesium bicarbonate liquor were discussed. The effects of reaction time and solid-liquid ratio of carbonization on the component concentrations of magnesium bicarbonate liquor were also investigated. Meanwhile the impacts of complexing agent addition and composite complexing agent addition on the removing impurities Fe and Ca were also investigated, respectively. We also gave an insight into the effects of pyrolytic temperature, pyrolytic pressure and adding additives on the particle size and deposition rate of magnesium bicarbonate liquor. Baesd on the above mentioned researches, the suitable processing conditions were obtained. The obtained results indicate that the preferred solid-liquid ratio and reaction time of hydration are80g/l and60min, while the favorable solid-liquid ratio and reaction time of carbonization are20g/l and60min. In the process of impurities removing,10ml triethanolamine(1:1) as a complexing agent was added into200ml magnesium bicarbonate liquid to cover impurities Fe, and then the treated liquid was pyrolyzed at90℃for20min to afford basic magnesium carbonate which was calcined to obtained final magnesia with99.3wt.% MgO,0.31wt.%CaO and0.042wt.%Fe2O3. Meanwhile, when using citric acid and oxalic acid as a composite complexing agent, MgO content of the final product magnesia obtained is more than98.2wt.%. CaO content0.24wt.%and Fe2O3content0.030wt.%under the condition of200ml magnesium bicarbonate liquid with adding1g citric acid and2g oxalic acid. Under the above preferred conditions, the grain size of the final product magnesia is mainly around3-4μm which meets the requirement of quality standard for silicon-steel magnesia. When pyrolizing the treated liquid at65℃for20min at low pressure, the magnesium prepicitation rate of magnesium bicarbonate liquor can reach the level of atmospheric. However, the main grain size of the final magnesia ranges from20to40um which can’t meet the quality requirement of silicon-steel magnesia.