温石棉尾矿酸法焙烧产物提取氧化镁的研究

Extracting MgO from Roasted Product of Chrysotile Tailings with Sulfuric Acid and Ammonium Sulfate

针对温石棉尾矿中提取MgO助剂消耗高、经济成本高等问题,采用浓硫酸和硫酸铵为混合酸性反应助剂,通过焙烧工艺提取温石棉尾矿中的MgO。优化工艺参数为:助剂中硫酸的摩尔比为80%;助剂(以SO_4^(2-)计)与石棉尾矿(以MgO计)的摩尔比为1.2:1;焙烧温度为350℃;保温时间为90 min,MgO的浸出率可达到83%~85%。适当增大酸性助剂中硫酸的摩尔比、助剂与温石棉尾矿物料比和温度可增大MgO提取率,而延长保温时间的效果不明显。TG-DSC与XRD分析表明,酸法焙烧温石棉尾矿反应过程主要分为3个阶段:第1阶段(136~253℃)纤蛇纹石与硫酸铵和硫酸反应生成中间产物(NH_4)_2Mg(SO_4)_2;第2阶段(253~324℃)残余的纤蛇纹石与(NH_4)_2Mg(SO_4)_2反应生成(NH_4)_2Mg_2(SO_4)_3;第3阶段(324~400℃)(NH_4)_2Mg_2(SO_4)_3分解,最终生成MgSO_4。

In order to solve the problem of high consumption of reaction promoter and high energy economic cost of extraction magnesium from chrysotile tailings, roasting experiments of chrysotile tailings with sulfuric acid and ammonium sulfate have been operated to extract MgO from chrysotile tailings. The results showed that the optimized parameters are as follows： sulfuric acid molar percentage in additive is 80%, additive-tailings molar ratio 1.2：1, roasting temperature 350℃ and holding time 90 min. The extraction rate of MgO reached 83%～85% at optimum process conditions. Moreover, the MgO extraction rate increases with the molar percentage of sulfuric acid, the molar ratio of additive to tailings and the roasting temperature increasing appropriately, while the effect of holding time is not apparent. The results of TG-DSC and XRD show that the roasting progress can mainly be divided into three stages. The first stage（136 ～ 253 ℃）： the mid-products（NH4）2Mg（SO4）2 was generated by the reaction of chrysotile tailings, sulfuric acid and ammonium sulfate. The second stage（253 ～ 324 ℃）： the（NH4）2Mg2（SO4）3 was formed by the reaction of the rest chrysotile tailings and（NH4）2Mg（SO4）2. The third stage（324 ～ 400 ℃）： the MgSO4 was generated by the decompositions of（NH4）2Mg2（SO4）3.