一水硬铝石赤泥钙化转型过程的实验研究

Experimental Study on Calcification Process of Diaspore Bayer Red Mud

针对拜耳法生产氧化铝过程中排放的高碱性赤泥无法大规模处理这一世界性难题,提出了钙化-碳化法处理赤泥新工艺.首先将赤泥进行钙化转型,脱去其中的碱;再将转型后的钙化赤泥与CO_2反应,回收赤泥中的氧化铝.并考察了温度、钙硅比及液固比等重要条件对赤泥钙化转型过程的影响.实验表明,一水硬铝石赤泥适宜的钙化条件为:温度160℃,钙硅物质的量比2. 5∶1,液固比3∶1.钙化转型后,赤泥中的w(Na_2O)由6. 70%降至0. 35%. XRD分析表明,赤泥经钙化转型后原先含碱的物相消失,钙化过程产生的主要物相为水化石榴石.

Large scale utilization of high alkalinity red mud generated in Bayer process is becoming a worldwide problem.Aiming at this problem,a novel calcification-carbonation process is proposed.Firstly,red mud was treated with lime,where the silicon phase is converted into hydrogarnet and alkali is removed.Then,calcification residue is decomposed by CO 2 and alumina is recovered.The effect of calcification temperature,Ca-Si molar ratio,and liquid-solid ratio on alkali content in calcification process were investigated.The results indicate that the w(Na 2O)in red mud reduces from 6.70%to 0.35%at reaction temperature of 160℃,Ca-Si molar ratio of 2.5∶1,liquid-solid ratio of 3∶1.Moreover,the XRD results show that diffraction peak of the alkali in red mud disappears after the calcification transformation,and hydrogarnet is the main phase.