萤石与浓硫酸反应制备氢氟酸动力学研究

Study on the Preparation Kinetics of Hydrofluoric Acid Using Fluorite and Concentrated Sulfuric Acid

为解决采用伴生型萤石代替单一型萤石生产氢氟酸的技术难题,揭示了伴生型萤石与浓硫酸的反应机制及动力学规律。研究在不同液固摩尔比和温度条件下单一型萤石和伴生型萤石与浓硫酸反应生成氟化氢的转化率。结果表明,单一型萤石产酸的最佳液固摩尔比和温度分别为1.25∶1和200℃,转化率为97.5%;伴生型萤石为1.50∶1和200℃,转化率为84.5%。单一型萤石产酸反应符合界面化学反应控制模型,而伴生型萤石产酸反应符合固相产物层内扩散控制模型。扫描电镜(SEM)结果表明,伴生型萤石与浓硫酸反应时存在严重的团聚现象并形成致密的硫酸钙钝化层,阻碍了浓硫酸与未反应萤石内核的接触。本试验为伴生型萤石与浓硫酸反应生产无水氢氟酸提供了科学依据。

The reaction mechanism and kinetic law of utilizing associated fluorite in conjunction with concentrated sulfuric acid were elucidated to address the technical challenge of hydrofluoric acid production.At different liquid-solid molar ratios and temperatures,the conversion rate of single fluorite and associated fluorite when reacting with concentrated sulfuric acid to produce hydrofluoric acid was investigated.The optimal conditions for single fluorite were a liquid-solid molar ratio of 1.25∶1 at 200℃,and the conversion rate was 97.5%,while,a liquid-solid molar ratio of 1.50∶1 and 200℃were found as the optimized conditions for the associated fluorite,and the conversion rate was 84.5%.The reaction between single fluorite and concentrated sulfuric acid followed the interfacial chemical reaction control model,whereas the reaction between associated fluorite and concentrated sulfuric acid followed the diffusion control model.In addition,the SEM tests showed a serious agglomeration phenomenon,a dense passivation layer of calcium sulfate was formed during the reaction between associated fluorite and concentrated sulfuric acid,impeding the contact between unreacted core and sulfuric acids.This study therefore provides scientific foundation on producing anhydrous hydrofluoric acid using associated fluorite.