三水铝石矿低温焙烧脱碳脱水与溶出性能

Dehydration,Decarburization and Digestion Performance of Gibbsitic Bauxite by Low-Temperature Roasting

对三水铝石矿进行低温焙烧预处理,利用XRF,XRD和SEM等检测手段系统研究了焙烧温度、焙烧时间对三水铝石矿脱水脱碳与焙烧矿氧化铝溶出性能的影响及其作用机理.结果表明:焙烧后矿石质量大幅减少,矿石表面有明显的裂纹,呈片层状结构;三水铝石相减少,并逐渐向一水软铝石转变,同时针铁矿转变为赤铁矿;当焙烧温度为400℃,焙烧时间为30 min时,矿石中结晶水的质量分数为7.54%,脱水率为62.52%,碳的质量分数低至0.11%,脱碳率为85.73%;焙烧矿在溶出温度145℃、溶出时间30 min、循环母液苛性碱的质量浓度为170 g/L时,氧化铝实际溶出率为81.51%,高于原矿的氧化铝溶出率.焙烧矿溶出动力学结果表明氧化铝溶出过程中主要受内扩散控制,表观活化能为42.71 kJ/mol.

The gibbsite bauxite pretreated by low-temperature roasting,the effects of roasting temperature and time on the dehydration and decarbonization of gibbsite ore and the digestion performance of calcined alumina were systematically studied by means of XRF,XRD and SEM.The results show that the ore quality greatly reduces after roasting and the obvious cracks are observed on the ore surface with lamellar structures.The gibbsite phase decreases and gradually changes to the boehmite,while the goethite changes to the hematite.When the roasting temperature is 400℃and the roasting time is 30 min,the mass fraction of crystal water in the ore is 7.54%,the dehydration ratio is 62.52%,the mass fraction of carbon is down to 0.11%,and the decarbonization ratio is 85.73%.When the digestion temperature of calcined ore is 145℃,the digestion time is 30 min,the mass concentration of circulating mother liquor caustic soda is 170 g/L,and the actual digestion ratio of alumina is 81.51%,which is higher than that of the raw ore.The digestion kinetics results of calcined ore show that the digestion process of alumina is mainly controlled by internal diffusion,and the apparent activation energy is 42.71 kJ/mol.