磷酸二氢钾结晶过程特性研究

采用梅特勒-托利多在线结晶工作站系统地研究了磷酸二氢钾的溶解度、超溶解度、红外特性以及冷却结晶过程的影响因素。结果表明，磷酸二氢钾的介稳区在低温区较宽，高温区较窄，且在40.1 ℃下具有最宽的介稳区；磷酸二氢钾在红外光谱上具有较好的朗伯-比尔特性，其特征峰波数分布在2 152 cm-1和1 082 cm-1处；降温速率越大，其介稳区宽度也随之增大；搅拌速率越高，其介稳区宽度反而降低；pH=4.0时，结晶效果最好，粒度分布也最为均匀，晶体颗粒粒径大；Fe3+的含量增大，将会导致磷酸二氢钾的介稳区变宽，并且其含量越大，颗粒越不均匀，粒度分布较宽，因此应严格控制生产工艺中Fe3+的质量分数≤0.001%；SO42-含量的增大，会使介稳区变窄，将会导致工业上结晶不易控制，因此也需严格控制生产工艺中SO42-的含量。

Study on characteristics of crystallization process of potassium dihydrogen phosphate

Solubility，super solubility，infrared characteristics，and the influencing factors in cooling crystallization process were systematically studied through the METTLER TOLEDO online crystallization workstation.Results showed that the potas-sium dihydrogen phosphate′s metastable zone was wide in a low temperature region，and was narrow in a high temperature zone，and in 40.1 ℃ it had the widest metastable zone.Potassium dihydrogen phosphate in IR spectra had a good Beer Lambertcharacteristic.The characteristic peak wavelength was distributed within 2 152 cm-1 and 1 082 cm-1.And the cooling rate was higher，the metastable zone width increased.The stirring rate was higher，the metastable zone width decreased.When pH was 4.0，the crystallization effect was the best，the particle size distribution was the most uniform，and crystal particle size reached maximum.Increasing Fe3+ content，will lead to KH2PO4 metastable zone width increase，and the more the Fe3+ content，the more uneven the size is and the wider the distribution is，so it should strictly control the production process of the Fe3+ mass fraction less than 0.001%. Increasing SO42- content，will narrow the metastable zone，lead to industrial crystallization that is not easy to control，therefore it needs to strictly control the content of SO42- in the production process.