低品位钼精矿石灰焙烧-酸浸提取钼

Extraction of molybdenum from low grade molybdenum concentrates by calcium-based roasting and acid leaching process

采用XRD和TG-DSC分析研究低品位钼精矿石灰氧化焙烧过程的反应机理,确定石灰法焙烧-酸浸提钼工艺的优化参数。热重分析表明:石灰法焙烧主要发生Ca(OH)2的分解、MoS2的氧化、MoO2的再氧化及钼酸盐的生成等反应,焙烧过程主要产生MoO2、MoO3、CaMoO4、CaSO4等物相。XRD分析表明:当温度高于600℃、反应时间大于90 min时,焙砂中低价态钼的衍射峰完全消失,此时焙砂主要物相为CaMoO4和CaSO4,辉钼矿被充分氧化;石灰焙烧适宜的条件为Ca(OH)2与钼精矿质量比1:1、焙烧温度650℃、焙烧时间90 min,焙烧过程硫的保留率可达91.49%。钼焙砂酸浸适宜的浸出温度为90℃、浸出时间为2 h、H2SO4浓度为70 g/L、液固比为5:1,此时钼浸出率可达99.12%,CaMoO4被完全溶出。

The mechanism of chemical reactions was studied on the oxidation of low grade molybdenum concentrate with addition of calcium oxide by the methods of XRD and TG-DSC, and the optimum conditions of calcium-based roasting and acid leaching were determined. The result of TG-DSC shows that the reactions are composed mainly of decomposition of Ca（OH）2, oxidization of MoS2, re-oxidization of MoO2 and the formation of molybdate. The products are MOO2, MOO3, CaMoO4 and CaSO4 in the process of oxidation roasting. The XRD result shows that the diffractions of low valence state molybdenum can not disappear completely until roasting temperature exceeds 600℃ and roasting time is longer than 90 min. The main phases are CaMoO4 and CaSO4 in molybdenum calcine, and the molybdenite can be oxidized completely. The retaining ratio of sulfur can reach 91.49% under the conditions of mass ratio of Ca（OH）2 to molybdenum concentrate 1：1, roasting temperature 650 ℃ and roasting time 90min. The test shows that the leaching rate of molybedenum can reach 99.12% under the suitable conditions of leaching temperature 90℃, leaching time 2 h, sulfuric acid 70 g/L, the ratio of liquid to solid 5：1.