潍坊地区地下卤水中硫酸根和钙、镁离子脱除技术与应用研究

Removal Technology and Application of Sulfate,Calcium and Magnesium Ions from Underground Brine in Weifang Area

纯碱生产需要消耗大量氯化钠,直接利用丰富的高盐度地下海水资源,可有效降低生产成本。但高浓度地下海水中硫酸根和钙、镁离子浓度较高,必须脱除才能用于生产。文章以地下卤水为原料,通过分步沉淀法实现了卤水中的硫酸根和钙、镁离子的脱除。实验结果表明,向反应体系中加入聚丙烯酰胺作为助沉剂,能够有效地提高硫酸钙的沉降速度。在生产性实验中,通过向反应体系中引入二氧化碳废气,节省了沉淀剂量,获得了精制盐水以及高附加值的副产品硫酸钙、碳酸钙和氢氧化镁。文章提出的生产工艺可使碱业生产节省工业原盐1/3左右,使制碱所需精盐水中钙、镁等离子含量接近于零,硫酸根低于5 g/L,Cl-含量达到314 g/L以上,达到优质纯碱生产所需水平,副产品硫酸钙和碳酸钙纯度均达到96%以上,有害微量元素含量远低于食品添加剂标准要求。高盐度地下海水资源的高值化综合利用不仅能够有效节约生产成本,增加产值,而且能降低碳排放,保护了环境。

Soda ash plants use large amounts of industrial salt on a daily basis,so their production costs would be considerably reduced if sodium chloride could be partly substituted by underground brine.However,underground brine requires pretreatment due its high sulfate,calcium and magnesium ion contents.This article described a new process for removing these chemicals from brine by fractional precipitation.The experimental results show that adding polyacrylamide to the reaction system as sedimentation aid can effectively improve the sedimentation rate of calcium sulfate.In a pilot experiment,the process was modified by injecting carbon dioxide into the reaction system to reduce the amount of precipitant required,which allowed the manufacture of refined brine as well as the high value byproducts calcium sulfate,calcium carbonate,and magnesium hydroxide.This process reduced the amount of industrial salt required by approximately one third and produced high-quality refined brine that had extremely low calcium and magnesium ion contents as well as magnesium and calcium ion contents of almost zero,<5 g/L of sulfate ions,and>314 g/L of chloride ions.Furthermore,its byproducts contained>96%calcium sulfate and calcium carbonate and levels of harmful trace elements that were below the permissive standard for food additives in China.The comprehensive utilization of underground brine has the advantages of not only reducing the cost of production and increasing the output value of soda ash but also reducing carbon emissions and protecting the environment.