氟石膏是氢氟酸生产过程中的副产品,为了变废为宝,利用硫磺为还原剂,采用两段法分解氟石膏制备硫酸和高纯氧化钙。一段反应为硫磺气化后氧化氟石膏生成硫化钙与二氧化硫,二段反应为一段反应生成的硫化钙与氟石膏高温反应生成氧化钙与二氧化硫,生成的氧化钙可用来中和废酸,也可进一步纯化后售卖,二氧化硫可用来制酸。此方法不但能实现硫、钙资源在厂区的内循环,而且能降低硫酸成本。通过热力学分析和一、二段不同反应温度及二段不同原料配比验证得到最佳反应条件为：一段反应温度为800 ℃、保温2 h;二段反应温度为1 100 ℃、保温1.5 h,反应物硫化钙与硫酸钙物质的量比为1.2:3。一段反应得到的硫化钙质量分数为83.51%,二段反应得到的氧化钙纯度为85.38%,并可进一步提纯到99.87%。硫酸生产成本估算为117.9元/t,远低于硫酸市场价格,具有较大的市场前景。

The fluorine gypsum is a by-product in the production of hydrofluoric acid.In order to turn waste into treasure,sulfuric acid and high-purity calcium oxide were prepared by using two-stage method with sulfur as reducing agent.The fluorine gypsum was reduced by sulfur vapor in the first stage,the generated CaS and fluorine gypsum reacted in the second stage,and the final products high purity CaO and SO₂ were obtained.The prepared CaO can be used to neutralize the waste acid or for sale after purification.The prepared SO₂ can be used to produce sulfuric acid.The process can not only realize the internal circulation of sulfur and calcium in factory,but also reduce the cost of sulfuric acid.The optimal reaction condition was obtained through thermodynamic analysis and verify test which contained various temperatures in the first stage and second stage and different raw materials ratio in second stage.The results were as follows: the reaction temperatures of the first stage and second stage were 800 ℃ and 1 100 ℃ respectively,the holding times of the first stage and second stage were 2 h and 1.5 h respectively,n（CaS）:n（CaSO₄）=1.2:3 in second stage.The CaS mass fraction after the first stage was 83.51%.The purity of CaO after the second stage was 85.38% and can be further purified to 99.87%.The production cost of sulfuric acid is estimated at 117.9 yuan/t,which is lower than the market price of sulfuric acid and has a great market prospect.