废弃镁-铬耐火材料中镁的浸出动力学

Leaching kinetics of magnesium from spent magnesia-chromium refractories

本研究采用SEM-EDS和BSE对废弃镁-铬耐火材料浸出前后的微观特性进行了检测,通过浸出动力学试验研究了浸出条件对镁浸出的影响,采用统计和作图法对镁的浸出过程进行了动力学分析。结果表明,原料中不同物相之间嵌布关系复杂,浸出渣为铬铁尖晶石且颗粒中存在各种孔洞和裂纹。升高温度、增加盐酸浓度和液固比可以加快镁的浸出速度,从而促进整个浸出过程,其中温度的促进作用最强。最终确定废弃镁-铬耐火材料中镁的浸出过程符合渐进转化模型,其控制步骤为化学反应,表观活化能为69.11 kJ/mol,动力学方程为:X/(1-X)=4.898×10^(8)×CHCl0.7982×(L/S)0.7407×e-8312/T×t0.9276。

In this study,the microscopic properties of spent magnesia-chromium refractories before and after leaching were detected by SEM-EDS and BSE.In addition,the influence of conditions on magnesium leaching was studied by leaching kinetics test,and the kinetics of the leaching process was analyzed by statistical and graphical methods.The results indicate that the relationship between different phases in raw material is complicated that the leaching residue is chromite spinel,and the particles have various holes and cracks.Increasing temperature,hydrochloric acid concentration and liquid-solid ratio can accelerate leaching velocity of magnesium,thereby promoting the whole leaching process,and the promotion effect of temperature is the most significant.The process of leaching magnesium from spent magnesiachromium refractories conforms to the progressive-conversion model with chemical reaction being the rate-controlling step,in which the corresponding apparent activation energy was 69.11 kJ/mol,and its kinetic equation can be expressed as follows:X/(1−X)=4.898×10^(8)×CHCl 0.7982×(L/S)0.7407×e−8312/T×t0.9276.