热法制备含磷钾中微量元素肥料的实验研究

我国大部分土壤缺乏中微量元素,影响作物健康生长和农产品品质.热法制备肥料具有可利用中低品位磷矿,磷、钙、镁、硅等植物有益元素经高温活化养分有效性高的优点,但其工艺存在热能消耗较大的问题.本文研究SiO2/P2O5、MgO/P2O5、CaO/P2O5(mol)对体系熔融特性温度的影响,通过正交优选确定熔点为1273℃的配方PF-1.在此基础上,研究硼、锰、钾、铁元素对P2O5-CaO-MgO-SiO2体系熔点的影响,得到各营养元素的合适添加量为硼3％～5％,锰2％～4％,钾4％～8％,铁2％ ～ 5％.结合制肥需求,以磷矿、白云石、钾长石和硼镁矿等矿物原料配成矿物配方PF-2,熔点降为1045℃,降低了228℃,在增加肥料产品营养元素多样性的同时,达到了节能降耗的目的.考察热法制备肥料工艺中各养分转化率的变化规律,研究表明,延长焙烧时间可显著提高钾和铁元素的转化率;提高焙烧温度可促进各营养元素的有效转化;在熔融水淬条件下各元 素转化率普遍较焙烧法高,尤其是磷.

Experimental study on thermal process of preparing phosphorus potassium fertilizers containing medium and trace elements

Due to the lack of trace elements in most soils in China, the healthy growth of crops and the quality of agricultural products are adversely affected. The thermal process of fertilizer preparation has the advantage of using medium and low grade phosphate ore and high effectiveness of nutrients by high temperature activation of beneficial elements such as phosphorus, calcium, magnesium and silicon, while the energy consumption of the process is high. In this study, the effect of mole ratio of SiO2/P2O5, MgO/P2O5, CaO/P2O5 on the melting characteristic temperature of the system was firstly investigated, and the formulation PF-1 with a melting point of 1273oC was determined by orthogonal selection. Then the effect of elements such as boron, manganese, potassium, iron etc. on the melting point of P2O5-CaO-MgO-SiO2 system was studied. The results showed that the appropriate addition of nutrients were 3~5% boron, 2~4% manganese, 4~8% potassium, and 2~5% iron, respectively. Taking into account fertilizer requirements, the mineral formulation PF-2 was designed with minerals such as phosphorus ore, dolomite, potash feldspar and boron magnesium ore, and its melting point was lowered to 1045oC, comparing with PF-1, the melting point lowered 228 oC, energy saved and abundant nutrient elements contained in the final product. The corresponding conversion rates of the nutrients under different thermal preparation conditions were examined. It is found that the extension of calcination roasting time can significantly improve the conversion rate of potassium and iron, and the increase of roasting temperature also can promote the effective transformation of various nutrients. Besides, the corresponding conversion rates of each element under the condition of melting water quenching is generally higher than that of roasting method, especially phosphorus.