硫磺还原分解磷石膏制硫化钙过程磷、氟杂质迁移规律研究

Study on transfer laws of phosphorus and fluorine impurities during producing calcium sulfide through sulfur reduction decomposition of phosphogypsum

硫磺还原分解磷石膏制硫酸联产低碳钙基材料是实现磷石膏规模化消纳和循环经济利用的有力途径。明晰磷、氟这两种关键杂质在磷石膏分解过程中的迁移转化规律对调控硫磺还原分解磷石膏反应有重要作用。首先对磷石膏的性质及组成做了全面解析,确定了磷、氟杂质在磷石膏中的存在形式,通过热力学软件模拟计算揭示了这两种杂质在反应前后的物相转变。利用纯石膏探讨了影响硫磺分解磷石膏制硫化钙的关键因素,在优化条件下,探讨了不同含量的磷、氟杂质在分解过程中的迁移变化。研究结果表明:当温度为800℃、反应时间为2.0 h、硫磺物质的量分数为40%时,硫酸钙的分解率达98%以上。在该条件下,磷杂质主要以难溶性磷的形式存在于固相产物中,且部分共晶磷会释放出来以难溶性磷的形式存在;氟则主要以难溶性氟的形式存在,并且有少部分进入气相产物中。该研究结果可为磷石膏循环经济利用提供一定的理论指导。

The reduction and decomposition to produce sulfuric acid and low-carbon calcium-based materials is a powerful way to realize the large-scale disposal and circular utilization of phosphogypsum.Clarifying the migration and transformation rules of phosphorus and fluorine,two key impurities in the decomposition process of phosphogypsum,plays an important role in regulating the reaction of sulfur reduction and decomposition of phosphogypsum.This article firstly provided a comprehensive analysis of the properties and composition of phosphogypsum,identifying the forms in which impurities such as phosphorus and fluorine exist within it.By using thermodynamic software to simulate calculations,the phase transformations of these two impurities before and after the reaction were revealed.Utilizing pure gypsum,the key factors affecting the decomposition of phosphogypsum to produce calcium sulfide were explored.Under optimized conditions,the migration and changes of different amounts of phosphorus and fluorine impurities during the decomposition process were investigated.The research results showed that when the temperature was 800℃,the reaction time was 2 h,and the molar fraction of sulfur was 40%,the decomposition rate of phosphogypsum could reach more than 98%.Under this condition,phosphorus impurities mainly existed in the solid phase products in the form of insoluble phosphorus,and some eutectic phosphorus would be released and existed in the form of insoluble phosphorus.The fluorine mainly existed in the form of insoluble fluorine,and a small part entered the gas phase products.The research results of this paper could provide certain theoretical guidance for the recycling economy utilization of phosphogypsum.