NaCl溶液体系中钙镁杂质分步脱除工艺研究  

Study on the step-by-step removal process of calcium and magnesium impurities in NaCl solution

作　　者：陈志鹏 易美桂[1] CHEN Zhipeng;YI Meigui(School of Chemical Engineering,Sichuan University,Chengdu 610065,China)

机构地区：[1]四川大学化学工程学院,四川成都610065

出　　处：《应用化工》2025年第2期265-270,276,共7页Applied Chemical Industry

基　　金：国家自然基金项目(52274410);省级项目2019CDPZH-1熔盐氯化废渣的资源化利用-高纯碱式碳酸镁制备工艺研究(00307053A2029)。

摘　　要：为了实现熔盐氯化废渣的资源化高值利用,以熔盐氯化法制备海绵钛产生的工艺盐水为原料,研究NaCl溶液体系中钙、镁分步脱除,制备高纯氧化镁工艺,探讨NaCl溶液体系中镁沉淀产物的物相转化规律。结果表明,NaCl溶液延缓了含镁无定形物向三水碳酸镁转变,加快了三水碳酸镁向碱式碳酸镁转变,缩短了三水碳酸镁在溶液中的稳定存在时间,不利于体系中钙离子的脱除,因此,先常温除钙,再高温沉镁。较优的工艺条件为:(1)除钙过程反应时间为3.0 h、Na_(2)CO_(3)添加量为钙总摩尔量的6.7倍;(2)沉镁过程反应时间为1.0 h、Na_(2)CO_(3)添加量为一次滤液中镁摩尔量的1.3倍。制得的MgO纯度为99.2%,CaO含量为0.53%,满足《工业轻质氧化镁》(HG/T 573—2012)中I类优等品指标要求,脱除钙、镁后的NaCl母液达到回用标准。该除钙沉镁工艺实现了工艺盐水中镁及NaCl资源化利用。The process of preparing high-purity magnesium oxide by stepwise removal of calcium and magnesium from NaCl solution was studied using the brine produced by the molten salt chlorination method to prepare sponge titanium as raw material.The phase transformation law of magnesium precipitation products in NaCl solution was explored,and the step-by-step precipitation process route of calcium and magnesium was analyzed based on thermodynamic calculations.The influence of reaction time and Na_(2)CO_(3)addition amount on the process of calcium removal at room temperature and magnesium precipitation at high temperature was investigated.The results show that NaCl solution can delay the transformation of amorphous substances to trihydrate magnesium carbonate,accelerate the transformation of trihydrate magnesium carbonate to alkaline magnesium carbonate,shorten the stable existence time of trihydrate magnesium carbonate in the solution,and have adverse effects on the room temperature calcium removal process.The optimal step-by-step precipitation route is to first remove calcium at room temperature and then precipitate magnesium at high temperature.The optimal reaction time for calcium removal is 3.0 h,the amount of Na_(2)CO_(3)is 6.7 times the total molar amount of calcium,the reaction time for magnesium precipitation is 1.0 h,and the amount of Na_(2)CO_(3)added is 1.3 times the molar amount of magnesium in a single filtrate.Under these conditions,the purity of MgO produced is 99.2%,and the CaO content is 0.53%,meeting the requirements of Class I superior product indicators in the industrial light magnesium oxide standard(HG/T 573—2012).The mother liquor after calcium and magnesium removal meets the reuse requirements.Simultaneously achieving the resource utilization of magnesium and NaCl in process brine.

关 键 词：熔盐氯化 NACL 分步沉淀 氧化镁 

分 类 号：TQ132.2[化学工程—无机化工]