低品位高硫铝土矿静态焙烧脱硫及溶出性能

Desulfurization and digestion performance of low grade highsulfur bauxite by static roasting

以低品位高硫铝土矿为原料,通过静态焙烧-活化溶出技术路线,解决脱硫同时兼顾溶出性能。采取XRD,SEM和Materials Studio等手段,分析焙烧脱硫-活化溶出过程中氧化铝及一水硬铝石晶体转变,得出焙烧矿最佳溶出条件,对比分析原矿与焙烧矿溶出动力学。研究结果表明:焙烧促使一水铝石晶体减小,氧化铝晶体变大、结晶更加完整;当静态焙烧温度为600℃和时间为180 s时,焙烧后铝土矿中硫质量分数为0.29%,脱硫率为75.83%;在600℃焙烧90 s时,矿石最佳溶出条件为溶出温度280℃、溶出时间70 min、苛碱质量浓度为245 g/L、CaO添加质量分数10%,此时氧化铝相对溶出率为94.8%;正交实验结果表明影响氧化铝溶出率的主次因素排序为温度、CaO添加质量分数、时间、苛碱质量浓度;原矿与焙烧矿在溶出过程中其表观活化能分别为48.89 kJ/mol和63.99 kJ/mol,氧化铝溶出主要受内扩散控制;焙烧矿和原矿在特定溶出条件下氧化铝相对溶出率(y)与溶出温度(T)之间的关系分别为:y=u(T)=-372.59+2.80053T-0.00406T^2和y=u(T)=-563.42+4.32469T-0.00714T^2,以焙烧矿经验公式作为参数优化依据,在285℃时氧化铝溶出率为95.63%。

Using low-grade bauxite with high sulfur as a material,the static roasting-activating and digestion technical route were adopted to solve the problem of desulfurization and digestion simultaneously.The digestion performance of roasting ore and crystal transition of alumina were systematically investigated using XRD,SEM and Materials Studio methods.The digestion kinetics of the raw ore and the roasting ore were compared for the digestion performance.The results show that the roasting promotes the reduction of the crystal diaspore and the crystal of Al2O3 is more complete.When the static roasting temperature is 600℃ and the time is 180 s,the desulfurization ratio is 75.83%,and the sulfur mass fraction in the bauxite is 0.29%.The best digestion condition of the roasted ore is 280℃,the digestion time is 70 min,the caustic mass concentration is 245 g/L,the mass fraction of CaO is 10%,and the relative digestion ratio of the alumina is 94.8%.The orthogonal experiment resulits show that the primary and secondary factors about the digestion ratio of the alumina are the temperature,CaO mass fraction,time and caustic mass concentration.The apparent activation energy of raw ore and roasting ore are 48.89 kJ/mol and 64.24 k J/mol,respectively,which is controlled by internal diffusion.The relationship between the relative digestion ratio(y)of alumina and temperature(T)of roasting ore and raw ore under specific digestion conditions are y=u(T)=-372.59+2.80053 T-0.00406 T2 and y=u(T)=-563.42+4.32469 T-0.00714 T2.Taking the empirical formula of roasting ore as the basis of parameter optimization,the digestion ratio of alumina can be95.63% at 285℃.