溶析结晶法分离盐硝的研究

Separation of Sodium Sulfate and Sodium Chloride from Brines by Solventing-out Process

测定了不同温度下氯化钠、硫酸钠及其混盐在水-甲醇溶液中的饱和溶解度,发现温度对混盐溶液中氯化钠和硫酸钠的溶解度影响不大,而溶剂比(甲醇:水)对其影响显著.提出了溶析结晶法分离盐硝的新工艺.新工艺将混盐饱和溶液与经过浓缩的混盐原料液相混合,加入甲醇将硫酸钠析出.然后蒸出甲醇和水,析出氯化钠,并得到氯化钠和硫酸钠混盐饱和溶液,循环使用.实验表明,在温度为20～30℃,甲醇:水质量比为0.364的条件下,硫酸钠的一次循环收率为50.2%,纯度为98.7%,氯化钠的一次循环收率为60.1%,纯度为97.6%.

The solubility of NaCl and Na2SO4 in the aqueous methanol solution of pure or mixed salt was determined respectively at different temperature. It was found that temperature has little influence but the solvent mass ratio (CH3OH:H2O) has great influence on the solubility of NaCl or Na2SO4 in the mixed salt aqueous methanol solution. A new separation process of NaCl and Na2SO4 from brines by using the 搒olventing-out?method was proposed and examined. In this process, the saturated solution of NaCl and Na2SO4 was first mixed with the concentrated brines, and then Na2SO4 was selectively crystallized from the aqueous solution by the addition of methanol. After methanol and water were separated from the solution by distillation and evaporation respectively, NaCl crystallized and the mixed salt saturated solution of NaCl and Na2SO4 was obtained which may be used cyclically. Experimental results show that the purity of Na2SO4 and NaCl prepared is 98.7% and 97.6% respectively and their yields can be over 50% and 60% respectively by one turn under the conditions of the solvent mass ratio of methanol to water 0.364 and temperature 20~30℃.