螯合剂对湿法磷酸制备磷酸二氢钾结晶过程影响

The effect of chelating agents on the crystallization process of potassium dihydrogen phosphate prepared by wet-process phosphoric acid

湿法磷酸生产成本低,但杂质含量高,以湿法磷酸为原料制得的磷酸二氢钾(KDP)产品质量低。研究利用中和法,以杂质含量高的工业湿法磷酸为原料,制备柱状大颗粒磷酸二氢钾晶体。研究了螯合剂用量、降温速率和搅拌速率对磷酸二氢钾结晶过程的影响,考察了磷酸二氢钾的质量分数、收率、结晶速率和晶体形貌等指标,并进行了母液循环实验。研究结果表明:螯合剂能有效消除杂质离子对结晶过程的抑制作用。结晶的最适宜工艺条件为螯合剂用量0.70%、搅拌速率100 r·min^(-1)、降温速率0.1℃·min^(-1)。在此条件下得到的磷酸二氢钾晶体外观为柱状大颗粒,质量分数99.91%,平均粒度1.38 mm,结晶速率0.128 g·min^(-1),达到肥料级磷酸二氢钾优等品标准(HG/T 2321—2016);其中磷的单次收率49.86%。母液循环生产的磷酸二氢钾晶体质量分数、晶型和收率等指标全部达标。

The production cost of wet process phosphoric acid is low,but the impurity content is high,and the quality of potassium dihydrogen phosphate(KDP)product prepared from wet process phosphoric acid is low.The preparation of large columnar potassium dihydrogen phosphate crystal by neutralization method was studied,using industrial wet process phosphoric acid with high impurity content as raw material.The effects of the amount of chelating agent,cooling rate and stirring rate on the crystallization process of potassium dihydrogen phosphate were studied.The purity,yield,crystallization rate and crystal morphology of potassium dihydrogen phosphate were investigated.And the mother liquor circulation experiment was carried out.The results show that the chelating agent can effectively eliminate the inhibition of impurity ions on the crystallization process.The optimum crystallization conditions were as follows:the amount of chelating agent was 0.70%,the stirring rate was 100 r·min^(-1),and the cooling rate was 0.1℃·min^(-1).Under this condition,the crystal appearance of potassium dihydrogen phosphate obtained is columnar large particles,with purity of 99.91%,average particle size of 1.38 mm,and crystallization rate of 0.128 g·min^(-1),reaching the fertilizer grade potassium dihydrogen phosphate superior product standard(HG/T 2321—2016);the single yield of phosphorus is 49.86%.The crystal purity,crystal form,yield and other indicators of potassium dihydrogen phosphate produced by mother liquor recycling are all up to standard.