氟硅酸钙法制氟化氢联产偏硅酸钠新工艺研究

New technology of copreparing fluorine hydride and sodium metasilicate by hydrofluosilicic acid method

研究了以湿法磷酸和磷肥工业副产的氟硅酸为原料制取氟化氢联产偏硅酸钠的新工艺。实验原理:氟硅酸与石灰石反应得到含有氟化钙和二氧化硅固体成分的混合料浆,将混合料浆继续与氢氧化钠溶液反应(二氧化硅与氢氧化钠反应)生成偏硅酸钠,离心分离得到液体偏硅酸钠,剩余固体(氟化钙)与浓硫酸反应可生成氟化氢气体。工艺条件:氟硅酸与石灰石物质的量比为1∶3,反应温度为70～80℃,反应时间为2 h。在此条件下,石灰石的反应率可达93%,氟化钙的收率可达95%以上。但是偏硅酸钠的生产率较低,需进一步研究来提高反应率。

A new manufacturing technology of fluorine hydride and sodium metasilicate with wet-process phosphoric acid and hydrofluosilicic acid by-produced from phosphate fertilizer industry as raw materials was studied. Experiment principle： hydrofluosilicic acid and limestone reacted to prepare slurry mixture,which contained solid calcium fluoride and sihca,then the slurry mixture sequentially reacted with NaOH solution （ i. e. silica react with NaOH ） to prepare sodium metasilicate, liquid sodium metasilicate could be prepared by centrifugal separation, and remained solid reacted with concentrated sulfuric acid to obtain fluorine hydride gas. Results indicated that when the amount-of-substance ratio of hydrofluosilicic acid to lime- stone was 1 ： 3, reaction temperature was at 70 - 80 ℃, and stirring reaction lasted 2 h, the reaction efficiency of limestone could be as high as 93% and the yield of calcium fluoride could achieved above 95%. But sodium metasilieate productivity was low because of low reaction rate of active silica and NaOH solution, so further research should be carried out.