Study on extracting alumina from coal ashes in the coal-fired power plant

Utilize sintering method to extract alumina from coal ashes. The effects of sintering flux categories, sintering flux cooperation, sintering flux dosage, temperature and time on the leaching ratio of alumina from coal ashes was studied. The results show that sodium hydroxide can extract the most alumina from coal ashes than natronite and lime at lower temperature, and the leaching ratio of alumina is higher when sintered coal ashes with the mixture of sodium hydroxide and lime, and proper quantities lime can accelerate sodium hydroxide to leach the alumina from coal ashes. The factors of sintering process such as alkali ratio, calcium ratio, sintering temperature, sintering time have great impact on the leaching ratio of alumina in coal ashes. These influencing factors was investigated by orthogonal experiment. The influence order from big to small of above four factors is calcium ratio, sintering time, alkali ratio, sintering temperatures. When alkali ratio is 2:1, calcium ratio is 0.5:1.0, sintering temperatures is 700C and sintering time is 30 min, the leaching ratio of alumina reached to 76.20% in coal ashes.