萃余酸制备工业级磷酸一铵的工艺研究

发布时间：2018-03-18 02:18

  本文选题：萃余酸　切入点：工业级磷酸一铵　出处：《武汉工程大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着能源成本的不断上升,使用耗能更低的湿法磷酸代替热法磷酸已经成为一种趋势。但是湿法磷酸含有很多的杂质,因此,目前世界上很多国家都在研究如何净化湿法磷酸,而且溶剂萃取法是目前唯一工业化应用的。溶剂萃取法净化湿法磷酸不可避免的会产生副产物萃余酸,如何合理的利用净化后产生的大量萃余酸便成为磷化企业发展的重点方向之一。利用萃余酸生产肥料磷铵的价值有限,用萃余酸生产工业级磷酸一铵可以更好的提高萃余酸的经济价值。本论文的主要研究内容包括三个部分：首先是研究了萃余酸进行氨化反应时萃余酸中各个离子的沉淀情况并使用试剂磷酸模拟萃余酸进行金属离子掺杂实验,研究金属离子杂质浓度对磷酸一铵产品质量的影响。其次通过考察工业级磷酸一铵的溶解度及介稳区宽度,晶体悬浮密度和过饱和度,估算磷酸一铵的结晶热,对工业级磷酸一铵的结晶过程进行了研究。最后优化了以萃余酸为原料制备工业磷酸一铵的工艺,并考察不同因素对磷酸一铵品质和收率的影响,得到最佳工艺条件。主要得出了以下结论：1.萃余酸氨化浆料中的MgO、Fe2O3、Al2O3、SO42杂质的析出率随pH增大而增大。Fe2O3、Al2O3在pH达到4的时候的析出率分别为99.73%和99.16%,MgO在pH4.5时析出率为91.24%,pH为5时析出率为98.12%。SO42-在pH为4.5时也有66.83%的析出率。萃余酸中含有Mg2+、Fe3+、Al3+这3种金属杂质都会影响所得的工业级磷酸一铵产品的品质,主要表现为降低其N含量。其中Mg2+杂质含量最多,影响也最大,在用萃余酸生产工业级磷酸一铵时应控制Mg2+含量少于3%。2.工业级磷酸一铵在水中的溶解度是温度的函数,随着温度的升高而升高,溶解度随着温度变化明显,在工业提纯或者生产时,磷酸一铵的结晶可以用冷却结晶来实现。在水溶液中,磷酸一铵介稳区的宽度随着温度升高而逐渐变窄,35-60℃时的介稳区宽度在10℃～15.7℃。晶体的收率随着磷酸一铵结晶时间的增长而增大,但是到了40min以后晶体收率保持稳定,结晶时间一般都控制在40min以内即可。3.制备工业级磷酸一铵的最优工艺为：稀释比为1.75,第一次中和反应终点pH为3.5,反应温度70℃,静置时间为3.5h。第二次中和反应终点pH为4.5,反应温度60℃,静置时间为3h。浓缩的相对密度为1.37,结晶温度40℃,结晶时间40min。在最优的工艺下,磷酸一铵收率为32.32%,产品纯度为98.79%,符合工业级磷酸一铵标准。
[Abstract]:With the increasing of energy cost, it has become a trend to replace thermal phosphoric acid with wet-process phosphoric acid with lower energy consumption. However, wet phosphoric acid contains a lot of impurities, so many countries in the world are studying how to purify wet-process phosphoric acid. Moreover, solvent extraction is the only industrial application at present. The purification of wet phosphoric acid by solvent extraction will inevitably produce the by-product leucic acid. How to make rational use of a large amount of extracted acid after purification has become one of the key directions in the development of phosphating enterprises, and the value of producing ammonium phosphate from fertilizer by extracting residual acid is limited. The economic value of industrial grade ammonium phosphate can be improved by the production of industrial ammonium phosphate. The main research contents of this thesis include three parts: firstly, we study each ion in the extraction residue acid when it is ammoniated. And the experiment of metal ion doping using reagent phosphoric acid to simulate the extraction of residual acid was carried out. The influence of metal ion impurity concentration on the quality of monoammonium phosphate product was studied. Secondly, the crystallization heat of ammonium phosphate was estimated by investigating the solubility, the width of metastable zone, the suspension density and supersaturation of crystal. The crystallization process of industrial grade monoammonium phosphate was studied. Finally, the process of preparing industrial ammonium phosphate from residual acid was optimized, and the effects of different factors on the quality and yield of ammonium monophosphate were investigated. The main conclusions are as follows: 1. The precipitation rate of MgO- Fe2O3Al2O3SO42 impurities in the ammoniated slurry is increased with the increase of pH value. The precipitation rate of Fe2O3Al2O3Al2O3 at pH 4 is 99.73% and 99.16mg-MgO in pH4.5 is 91.24g / h, respectively. The precipitation rate of Fe2O3Al _ 2O _ 3 is 99.73% and 99.16mg / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 4 / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 4 slurry. The precipitation rate at 5:00 is 98.12%. So _ 42- there is also 66.83% precipitation rate at pH 4.5.The presence of Mg2 Fe _ 3O _ 3 Al _ 3 in the residual acid will affect the quality of the industrial grade ammonium phosphate. The main performance is to reduce its N content. The impurity content of Mg2 is the most, and the influence is also the biggest. The content of Mg2 should be controlled less than 3.2. the solubility of industrial grade ammonium phosphate in water is a function of temperature. With the increase of temperature, the solubility changes obviously. In industrial purification or production, the crystallization of monoammonium phosphate can be achieved by cooling crystallization. The width of the metastable zone of monoammonium phosphate becomes narrower and narrower at 35-60 鈩，

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