烧碱氟硅酸钠法制冰晶石联产白炭黑工艺研究

Research on production process of cryolite and by-product silica white by sodium hydroxide-sodium fluosilicate method

研究了烧碱氟硅酸钠法生产冰晶石并联产优质白炭黑的工艺条件,确定了烧碱分解氟硅酸钠生产白炭黑的影响因素。用低浓度的烧碱(循环生产过程中用母液)在一定条件下与氟硅酸钠反应,得到白炭黑软膏和氟化钠溶液。白炭黑软膏经洗涤干燥后得白炭黑产品;氟化钠溶液经二次过滤后打入储槽备合成用。将一定浓度的氢氧化钠溶液预热到100℃,加入计算量的氢氧化铝,搅拌反应直至溶液澄清,即得铝酸钠溶液。将氟化钠溶液和铝酸钠溶液按照一定的比例加入到合成槽,控制一定的合成温度,反应结束后过滤即得冰晶石产品。采用此方法合成的冰晶石与氨水氨解氟硅酸钠法生产的冰晶石相比流动性好、质量合格、适合电解铝启槽用,具有良好的市场前景,并且具有废水可以循环利用、环境污染少的特点。

Production process of producing cryolite and by-producing high-quality silica white with sodium hydroxide-sodium fluosilicate （NaOH-Na2SiF6） method was researched and factors influencing the process that NaOH decomposing Na2SiF6 to produce silica white were confirmed.NaOH （mother liquid will be used in the real production cycle） with low concentration reacted with Na2SiF6 at a certain condition and silica paste as well as sodium fluoride solution was then obtained.Silica paste was washed and dried to prepare silica white product and sodium fluoride solution was pumped into storage tank for further synthesis after secondary filtration.NaOH solution at a certain concentration preheated to 100 ℃,and then add aluminium hydroxide with calculated amount.Stirring the solution till it turned to clear and sodium aluminate solution will be prepared.Adding sodium fluoride solution and sodium aluminate solution in definite proportion into a synthetic tank,controlling temperature and cryolite product will be finally obtained through filtration after completion of the reaction.Cryolite product produced by this method had better fluidity,acceptable quality,and suitable for start-up of aluminum electrolysis comparing with that produced by ammonia-sodium fluosilicate method.Therefore,it has good market prospect.Moreover,wastewater can be recycled and it has less environmental pollution.