提出一种以日云石和菱镁石的混合矿物为原料、以铝粉为还原剂的具空热还原炼镁,然后利用镁还原后的残渣制取氢氧化铝的工艺和技术,并进行实验研究.结果表明:以煅烧后的白云石和菱镁石混合矿物为原料的真空金属热还原炼镁,在还原温度为1 200℃、还原时间为2h、铝粉过量系数为5％的条件下,镁的还原率可达89％以上,还原渣主要物相为CaO·2Al2O3,还原渣中Al2O3的含量为67％左右；该炼镁还原渣经碳酸钠和氢氧化钠的混合碱液浸出后,Al2O3的浸出率达到85％,浸出Al2O3后渣的主要成分为CaCO3;浸出液中的Al2O3以可溶解的铝酸钠存在于浸出液中,后经碳分分解制得氢氧化铝,氢氧化铝的白度达到97％.%The experiments of a new method of producing magnesium and aluminum hydroxide as by-product using dolomite and magnesite as materials and aluminum powder as reductant were studied. The results show that when magnesium is produced by vacuum aluminothermic reduction using the mixture of calcined dolomite and calcined magnesite as materials, the reduction ratio of Mg can be over 89% under the conditions of reduction temperature 1 200 "C, reduction time 2 h, and the excess coefficient of reductant 5%. The main phase of the reduction slag is CaO2Al2O3 aQd the content of alumina is about 67%. The A12O3 leaching rate of reduction slag reaches 85% when the reduction slag is leached with a mixture of sodium hydroxide and sodium carbonate. The main phase of leaching slag is CaCO3. The Al2O3 enters into the leaching solution with soluble sodium aluminate. Aluminum hydroxide with whiteness of over 97% can be obtained after carbonation precipitation.
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