本课题研究了硫酸和硫酸钾配成的硫酸氢钾同磷酸氢钙的复分解反应的动力学行为和用氯化钾、硫酸和肥料级磷酸氢钙为原料生产磷酸二氢钾的工艺。 用硫酸和硫酸钾进行了磷酸氢钙的分解反应实验，通过对加入硫酸盐和分解率一时间关系的分析，发现无论硫酸根／钙离子的比例如何，均有反应前期速度快，后期反应速度慢，因此表明“可透性的固态膜”的出现是必然的。固态膜的形成主要由硫酸的过量所引起，当硫酸超过理论量的30％出现反应不完全的现象，说明与湿法磷酸相似的有硫酸根过量的限定。克服固态膜对白肥分解的影响是提高磷得率的关键；白肥同硫酸氢钾的反应，在前期转化快，在1～1.5小时可以达到80％，后期的反应速度逐渐下降，但尚可继续进行。 分解率主要取决于反应的时间和硫酸用量。提高反应时间和反应温度可提高分解率。在反应前期，50℃的分解速度大于70℃的分解速度，60℃的分解速度最大。在反应后期，在50-70℃温度范围内，温度越高则分解率越大，反应也越快。 通过对不同粒径的白肥在不同温度下反应的研究，认为小颗粒白肥反应速度大于大颗粒。其中白肥和硫酸氢钾的复分解液固反应是扩散控制反应，并得出了反应的动力学方程。动力学模型是：四川大学工程硕士学位论文 通过对该模型的实验探讨认为磷酸氢钙粒子不是理论意义的球形，可能具有从表面到内部的细孔。用时间的负2.2次方校正后的方程表示，随着反应的进行，形成的固态膜越来越厚，即扩散的阻力越来越大。 工艺研究证明，用复分解反应来合成磷酸二氢钾是可行的;适宜的工艺条件是:硫酸的用量按与钙离子的比1:1~1.05，磷与钾的比1:1，反应的固液比用加入水的量控制在1:3一4，反应温度70一85℃;合成过程中钾的损失主要与白肥中的含氟量有关，磷的损失与体系中的硫酸用量、反应时间和液固比有关。过程主要参数同湿法磷酸的生产相似，故可以部分借用湿法磷酸浸取过程的研究结论。 在制造磷酸二氢钾的过程中，根据K:P和S:Ca的比例，用甲醇沉淀时游离酸以磷酸形式萃取在甲醇中，硫酸根与钾离子沉淀出硫酸钾，调节产品中的硫酸钾和磷酸二氢钾组成比例，从而调节产品中的磷钾比。由此可以制造出不同磷钾比的复合肥。关键词:磷酸氢钙、氯化钾、磷酸二氢钾、工艺研究 ＞＞＞＞下为英文版＞＞
This paper analyzes the kinetic behavior in the reaction of CaHPO4 and KHSO4 (mixed by H2SO4 and K2SO4), and the process of producing KH2PO4 with KC1、 H2SO4 with fertilizer CaHPO4 as the raw material.In this research, a reaction of H2SO4 with K2SO4 is carried out to decompose CaHPO4. Through the analyzing of the relation between sulfate used and decomposition time, we find for all the reaction, the reaction rate is fast at the beginning, but slow down following the reaction time, no matter how large the ratio of SO42- and Ca2+. So it shows that a transparent solid-state membrane occurs and the passivation of plain fertilizer is mainly caused by the overdose of H2SO4. The amount of used SO42- takes big effect on the passivation. When the amount of H2SO4 acid is excess for 30%, the reaction will be stopped uncompleted, that indicates that there is a limitation of overdose SO42- the same as for wet H3PO4 acid process. The key point to gain more phosphorus is to overcome the passivation of plain fertilizer. For the reaction of plain fertilizer and KHSO4, in the beginning of the reaction, transforms quickly, from 1 to 1.5 hour it could be transformed to 80%, after this period, in the end of the reaction, the speed of reaction will decrease, but still continues. The decomposition rate mainly depends on the time of reaction and the amount of used H2SO4.The result of the research indicates increasing the time and the temperature of the reaction can raise the decomposition rate. In the beginning of the reaction, the decomposing speed under 50℃ is faster than under 70℃, under 60℃ thedecomposing speed is the fastest. But in the end of the reaction, during the range of 50-70℃,the decomposition rate will increase as the increasing of temperature and speed of the reaction.Through the research the reaction of two kinds of particle sizes under different temperature, we consider the reaction speed of small particle plain fertilizer is faster than the big ones.The liquid-solid multiple-decomposition reaction of plain fertilizer and KHSO4 is a diffusion controlled reaction and its kinetic model can be written as follows:In this model, we do not consider the CaHPO4 particles spherical theoretically and believe that there are fine holes between their surface and interior. When fitting the - 2.2 power of the time into the equation, it is find that as the time goes on, the reaction is more and more difficult to complete, the reason is the resistance of the diffusion increases with the time.The process study of producing KH2PO4 finds that it is feasible to use the multiple-decomposition reaction to produce KH2PO4. The suitable operating conditions are:The amount of H2SO4 based on the ratio to Ca2+ 1:1-1.05 The ratio of phosphorus and potassium: 1:1 The solid -liquid ratio: 1:3-4 The reaction temperature: 70-85℃The lose of potassium is mainly related to the content of fluorine in the plain fertilizer, the lose of phosphorus is related to the amount of used H2SQ4 acid, reaction time and solid-liquid ratio in the system. The main parameters in the process are similar with that of wet H3PO4 acid process, so we can borrow part of the research conclusions from wet H3PO4 acid process.During the process of producing KH2PO4, based on the ratio of K:P and S:Ca, methanol is used to separate out K2SO4 as precipitate and leave H3PO4 inthe methanol in free acid type. By adjusting the ratio of K2SO4 and KH2PO4 in the product, P-K ratio in the product can be adjusted. In this way we can produce composition fertilizers with different P-K ratio.