氧化铝赋存形式对低钙烧结熟料矿相转化的影响

Effect of alumina existing formation on mineralogical transformation of sintered clinker with low lime dosage

采用石灰烧结法处理低品位含铝资源提取氧化铝,研究在n(CaO)/n(Al_2O_3)为1、烧结温度为1350℃条件下,氧化铝以a-氧化铝、莫来石和钙铝黄长石赋存形式的物料与石灰烧结后熟料矿相、晶体稳定性和在碳酸钠溶液中氧化铝浸出性能。结果表明:以α-氧化铝为原料时,Ca_(12)Al_(14)O_(33)优先生成,并进一步结合Al_2O_3转化成CaAl_2O_4。熟料矿相为CaAl_2O_4、Ca_(12)Al_(14)O_(33)、γ-Ca_2SiO_4和β-Ca_2SiO_4,CaAl_2O_4和Ca_(12)Al_(14)O_(33)晶胞体积较大,在碳酸钠溶液中,晶体稳定性较差,氧化铝的浸出率为91.60%;以莫来石或钙铝黄长石为原料时,Ca^(2+)逐步取代晶格中Si^(4+)位置并与Al^(3+)结合生成铝酸钙,分离出的Si^(4+)与CaO生成Ca_2SiO_4,而Ca_(12)Al_(14)O_(33)或Ca_3Al_2O_6的生成造成CaO不足,导致部分Ca_2Al_2SiO_7不能被转化,熟料矿相为CaAl_2O_4、Ca_(12)Al_(14)O_(33)、γ-Ca_2SiO_4、β-Ca_2SiO_4和Ca_2Al_2SiO_7,CaAl_2O_4和Ca_(12)Al_(14)O_(33)晶胞体积较小,与碳酸钠反应时活性稍差,氧化铝的浸出率低于80%。

The mineral phases,crystal stability and alumina leaching property in sodium carbonate of sintered clinker were studied using α-alumina,mullite and gehlenite as alumina-existing materials when the molar ratio of CaO to Al2O3is 1 at 1350℃ by extracting alumina from the low-grade alumina containing resources by the lime sintering method.The results show that Ca（12）Al（14）O（33） generates firstly,then it reacts with Al2O3 to form CaAl2O4.The sintered clinker is comprised of CaAl2O4,Ca（12）Al（14）O（33）,γ-Ca2SiO4 and β-Ca2SiO4 when using α-alumina as material.The unit cell volume of CaAl2O4 and Ca（12）Al（14）O（33） are larger with poor crystal stability in sodium carbonate solution,and the alumina leaching rate is 91.60%.Ca^（2＋） replaces the lattice position of Si^（4＋） and reacts with Al^（3＋） to form calcium aluminates,and then,the separated Si^（4＋） reacts with CaO to form calcium silicates.The formation of Ca12Al14O33 or Ca3Al2O6 causes the shortage of CaO,resulting in that Ca2Al2SiO7 can not be transformed completely.The mineral phases are CaAl2O4,Ca（12）Al（14）O（33）,γ-Ca2SiO4,β-Ca2SiO4 and Ca2Al2SiO7 when using mullite or gehlenite as alumina-containing materials.The unit cell volumes of CaAl2O4 and Ca（12）Al（14）O（33） are smaller with good crystal stability in sodium carbonate solution,and the alumina leaching rate is lower than 80%.