利用氟硅酸与电石灰制备四氟化硅工艺研究

为加快磷肥副产氟资源的综合利用,同时解决电石灰堆放占用大量土地、污染水资源等问题,采用磷肥副产氟硅酸与电石灰反应制备四氟化硅同时副产氟化钙,制备出高附加值、高品质的氟化物。重点研究了氯化钙与氟硅酸的配料比、反应温度、氯化钙溶液浓度、母液循环等因素对氟硅酸钙收率的影响,同时也分析了氟硅酸钙热解温度对四氟化硅产品质量的影响。研究结果表明,在氯化钙溶液浓缩至质量分数为60%、反应温度为55 ℃、氯化钙与氟硅酸质量比为2∶1条件下,氟硅酸钙的单批收率可达到86%;氟硅酸钙在350 ℃静态分解1 h,分解率达到99%,所得四氟化硅产品质量符合硅烷制备和无水氟化氢制备对原料的要求,所得副产物氟化钙产品质量满足行业标准（YB/T 5217—2019《萤石》）的要求。该方法氟、硅资源能够充分利用,且工艺简单、便于操作、易于工业化生产,为磷肥副产氟硅酸的综合利用提供了一定的指导方向。

Study on preparation process of silicon tetrafluoride from fluosilicic acid and electric lime

In order to speed up the comprehensive utilization of fluorine resource,by-product of phosphate fertilizer and solve the problems of large land occupation and water pollution caused by the stacking of electric lime.Silicon tetrafluoride was prepared by the reaction of fluorosilicic acid,by-product of phosphate fertilizer,and electric lime to prepare fluoride and by-product of calcium fluoride with high added value and high quality.The effect of the proportioning ratio of calcium chloride to fluorosilicic acid,reaction temperature,calcium chloride solution concentration and mother liquor circulation on the yield of calcium fluorosilicate were studied.At the same time,the effect of calcium fluorosilicate pyrolysis temperature on the quality of silicon tetrafluoride products were also analyzed.The results showed that calcium chloride was concentrated to 60%,and the single batch yield of calcium fluorosilicate could reach 86% at temperature of 55 ℃ and the ratio of calcium chloride to fluorosilicic acid of 2∶1.Calcium fluorosilicate was statically decomposed at 350 ℃ for 1 h,the decomposition rate reached 99%,and the the quality of as-prepared silicon tetrafluoride products met the requirements of preparation of silane and anhy-drous hydrogen fluoride,and the quality of the by-product calcium fluoride met the requirements of the industry standard（YB/T 5217—2019 Fluorite）.The fluorine and silicon resources could be fully utilized in the process research,and the process was simple,easy to operate,and easy to industrialized production,which provided certain guidance for the comprehensive utilization of phosphate fertilizer by-product fluorosilicic acid.