硝酸磷肥生产新工艺研究

结合中国中品位磷矿特点，提出一条新的制备优级品硝酸磷肥的工艺路线。重点解决了工艺中存在的两个关键问题，即酸解液的过滤和钙离子的去除。针对过滤环节选用磷石膏作为助滤剂来提高酸解液的过滤强度；针对除钙环节，采用两次除钙工艺，首先通过冷冻结晶的方法除掉大部分钙离子，再添加少量硫酸达到产品所需的除钙率。以湖北某磷矿为原料，对该工艺进行了系统研究。在硝酸用量为105%、硝酸质量分数为55％、结晶时间为 4 h、结晶终点温度为0 ℃的工艺条件下，一次除钙率达到73.17%，再加入硫酸进行二次除钙，除钙率达到85.25%，制得符合GB/T 10510-2007《硝酸磷肥、硝酸磷钾肥》的优级品硝酸磷肥。

Study on new production technology of nitrophosphate fertilizer

Considering the features of the mid-grade phosphate rocks in China，a new technology for producing the high-grade nitrophosphate fertilizer was presented.Two key problems have been solved，i.e.the filtration of acidolysis solution and calcium ions removing.The filtration intensity was accelerated by selecting phosphogypsum as a filter aid. The technology of two times removal of calcium was applied.Most of calcium ions were removed by the freezing crystallization at first.A further removal of calcium ions was carried out by adding only a small amount of sulfuric acid to insure the product can reach the national standards.The technology was systematically studied by using the phosphate rock from Hubei Province as raw material.And the optimal conditions were: nitric acid amount of 105%，nitric acid mass fraction of 55%，crystallization time of 4 h，and final temperature of 0 ℃.Under these conditions，73.17% of first calcium removing rate was reached.The second calcium removing rate was 85.25% by adding sulfuric acid.The prepared product accorded with the top grade nitrophosphate fertilizer stipulated in Nitrophosphate Fertilizer and Nitric Phosphate Potassium Fertilizer，GB/T 10510-2007.