针对磷酸铁锂前驱体磷酸铁生产过程中副产物磷酸镁铵难以利用的问题，提出了一种通过焙烧制备含钙镁等中微量元素磷肥（聚磷酸镁铵）的新思路，在焙烧温度为250~550 ℃、焙烧时间为0.5~3.0 h的条件下，开展了磷酸镁铵制备聚磷酸镁铵的工艺及机理研究，并通过热重-傅里叶红外（TG-IR）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）、氮气物理吸附仪、激光粒度仪对样品的晶型、焙烧过程中的样品质量变化及气相产物、形貌、比表面积和孔隙率及颗粒粒径分布进行了表征，揭示了反应过程机理。实验结果表明，在一定范围内，提高焙烧温度和延长焙烧时间都能促进磷酸盐的聚合及提高脱氮率，基于产物中磷形态分布和脱氮率等指标得出焙烧的优选焙烧温度为350 ℃、焙烧时间为2 h时，在此条件下所得聚磷酸镁铵中磷的聚合度分布为1~3，聚合率达到45.28%，脱氮率达到79.90%。得到的聚磷酸镁铵相比原样磷酸镁铵，有效钙、有效镁及水溶磷和有效磷等养分指标均有30%以上的提升，可作为一种新型的含钙镁等中微量元素的磷肥。

A new approach was proposed to prepare phosphate fertilizers（magnesium ammonium polyphosphate） containing trace elements such as calcium and magnesium through calcination，in response to the problem of difficult utilization of by-product magnesium ammonium phosphate in the production process of lithium iron phosphate（precursor of iron phosphate）.The process and mechanism of preparing magnesium ammonium polyphosphate from magnesium ammonium phosphate were studied under the conditions of calcination temperature of 250~550 ℃ and calcination time of 0.5~3.0 h.The crystal structure，sample quality change during calcination，gas phase products，morphology，specific surface area，porosity，and particle size of the samples were analyzed by thermogravimetric Fourier transform infrared（TG-IR），X-ray diffraction（XRD），scanning electron microscopy（SEM），nitrogen physical adsorption analyzer，and laser particle size analyzer.The diameter distribution was characterized，revealing the mechanism of the reaction process.The experimental results showed that within a certain range，increasing the calcination temperature and prolonging the calcination time could promote the polymerization of phosphate and improve the denitrification rate.Based on the distribution of phosphorus forms and denitrification rate in the product，the optimal calcination temperature was 350 ℃ and the calcination time was 2 h.Under these conditions，the polymerization degree distribution of phosphorus in magnesium ammonium polyphosphate obtained was 1~3，the polymerization rate reached 45.28%，and the denitrification rate reached 79.90%.The obtained magnesium ammonium polyphosphate showed an improvement of over 30% in nutrient indicators such as available calcium，available magnesium，water-soluble phosphorus，and available phosphorus compared to the original magnesium ammonium phosphate.It could be used as a new type of phosphorus fertilizer containing trace elements such as calcium and magnesium.