Study On Preparation Of Special Silicon-Steel Magnesium Oxide

Magnesia, which is mainly used for the production of refractory materials and metal magnesium and etc, is an important inorganic chemical. In addition, it also applies in rubber, plastics, fuel, regent, medicine, livestock feed additive and so on. Although our country is rich in magnesite reserves, their grade is lower and the MgO content of magnesia obtained after calcinations of magnesite is only 90%~92%. In view of developing trend, magnesia tends towards high- purity and speciality products. Therefore, it is urgent how to improve the addition value of magnesia. Magnesia should be prepared in the form of serial, functional and fine products so as to meet the requirements of market and improve commercial benefits of magnesia industry.In this paper, light-burned magnesia was slaked and carbonated to afford magnesium bicarbonate liquor, Fe and Ca of which were removed by activated carbon. The purified liquor was then pyrolyzed to obtain basic magnesium carbonate, which was calcined to result in silicon-steel magnesium oxide. The effects of carbonization time on chemical composition concentrations of leaching liquor and solid-liquid ratio on the leaching rates of magnesium and iron were discussed. The impacts of adsorption temperature and time on the adsorption reaction of Fe and the regeneration of used activated carbon by hydrochloric acid were also investigated, respectively. We also gave an insight into the effects of pyrolytic temperature, time and temperature rise rate on the particle size and appearance of final magnesia product. To measure the boron content in magnesia, the most absorption wavelength of boron had been determined. Based on experiments, the suitable procssing parameters were obtained, i.e. solid-to-liquid ratio of carbonation, 20g/L;carbonation time, 60min;when 5g of activated carbon was regenerated with 20mL of (1+1) hydrochloric acid at 20℃, it can be reused after desiccation;500mL of carbonization leaching liquor was treated with 10g activated carbon at 20℃ for 80min;pyrolysis at 100℃ with slow temperature rise rate for 20min;calcination temperature, 950℃;the most absorption wavelength of boron, 540nm. The content of MgO in magnesium oxide has reached 99.5%, and those of impurity CaO and Fe are less than 0.09% and 0.05%, grains less than 5μ reach to 72.3%, and the dispersivity of the product is good. Adding boric acid into the purified leaching solution of carbonization with 0.022g/L~2.3054g/L and adjusting its pH value to 9-10, the boron content in the obtained magnesia is between 30~1000ppm which meet the requirement of boron content for silicon-steel magnesia.