盐析结晶法制取硝酸钾研究

Study on preparing potassium nitrate by saltingout crystallization

硝酸铵与氯化钾复分解反应生产硝酸钾与氯化铵工艺，硝酸钾结晶率比较低，一般为45％-55％。为提高硝酸钾结晶率，研究了采用添加盐析剂的盐析结品法制取硝酸钾新工艺，通过盐析剂的盐析作用，硝酸钾与氯化铵在溶液中的有效浓度提高，从而使更多硝酸钾与氯化铵结晶析出，盐析剂始终在母液中循环并发生盐析作用。试验表明，盐析结晶法制取硝酸钾工艺可以使硝酸钾结晶率提高到80％。盐析结晶法制取硝酸钾最佯工艺条件：盐析剂添加量为硝酸钾量的40％（物质的量分数），硝酸钾结晶溶液质量分数50％～55％，硝酸钾冷却结晶终点温度为25℃，氯化铵溶液蒸发质量分数70％，氯化铵结晶终点温度55—65℃。

The double decomposition for the production of KNO3 and NH4Cl from NH4NO3 and KCl is the main method in China. In this process,the crystallization rate of KNO3 is lower, in general, it is between 45% - 55% , the recycling amount of the mother liquor is larger,the energy consumption is higher and the product cost is high. In order to improve the crystallization rate of KNO3, the new process for the production of KNO3 by salting - out crystallization method is studied e. i. through adding the salting - out agent, the effective concentration of KNO3 and NH4 Cl in the solution can be increased. Thus,the more amount of KNO3 and NH4 Cl will be crystallized and salted out. The salting- out agent is consistently recycled in the mother liquor. The tests show that this process can improve the crystallization rate of KNO3 up to 80%. The optimum process conditions are as follows ： the adding amount of salting - out agent is the 40% of the amount of KNO3 （ mass ）, the concentration of KNO3 solution is 50% -55% （mass） ,the end - point temperature of crystalline of KNO3 is 25 ℃ ,the concentration of NH4 Cl solution is 70% （ mass ） and the end - point temperature of crystalline of NH4 Cl is 55 - 65℃.