【作者】 张丽；

【导师】 张宝林；

【作者基本信息】 郑州大学 ， 化学工艺， 2003， 硕士

【摘要】 酸分解磷矿法是目前主要的磷肥生产工艺，普通过磷酸钙又是其中的主要产品之一。本课题从解决过磷酸钙生产中一直以来存在的堆置熟化期长，产品易结块的不利情况出发，对目前一种较为广泛推广的适宜于各种磷矿和工艺过程的工业技术——添加活化疏松剂法进行研究，找出其对硫酸分解磷矿反应过程的作用。 活化疏松剂APA（Activator and Porous Agent，简称APA）是一种以表面活性剂为主的有机-无机复合物。从表面活性剂的性质出发，实验先研究了活化疏松剂对硫酸钙结晶过程的影响。结果发现，活化疏松剂的加入改变了硫酸钙晶体的晶习，使之从细小的针状变为较粗大的棱柱状晶体。活化疏松剂对酸矿反应的影响，是通过考察酸浓度和操作温度对磷矿转化率的影响来考察的。在酸浓度对转化率的影响实验中发现，活化疏松剂对反应的控制步骤并无决定性影响，在酸浓度为30％-40％时，添加活化剂与空白条件下磷矿的转化率并无太大的变化，随着酸浓度的增加，活化剂对提高磷矿转化率的效果越来越明显。这说明反应在低浓度时，液固比大，硫酸钙对酸矿反应的阻碍作用小，APA在传质过程中发挥不了特殊作用。当硫酸浓度在45％～60％范围内逐渐增加，反应速度加快，硫酸钙结晶形成的包裹膜对传质的阻碍作用也逐渐增大。当APA存在时，生成的硫酸钙结晶在APA的作用下晶习发生改变，在磷矿颗粒表面生成的薄膜可透性增强致使磷矿的转化率提高。由操作温度对转化率的影响实验中，温度升高，磷矿的转化率增加，加入APA的反应转化率提高得更明显。这说明结晶过程是酸解磷矿反应的重要过程，APA对结晶过程的影响较大，从而显著的影响了整个酸解磷矿过程。对实验现象进行比较发现，加入APA后反应的最高温度比空白条件下的高且鲜肥所需的固化时间短。反应产物经24小时后取样时最明显的区别是空白条件下得到的反应产物较硬，浓度在大于60％时还有些粘，而加了APA的反应物料干燥、疏松。 对反应第二阶段，以粒径不变的收缩未反应芯模型为基础建立数学模型。假设在反应进行到t₀时刻时的未反应芯半径为R₀，此时刻包裹在未反应芯表面的固态膜称为固态膜1，并设液相反应物在该膜中的有效扩散系数为D_eff1(扩散系数为k_1S。将此时刻之后的反应近似看成定态过程，此时刻之后形成的固态膜称为固态膜2，它介于固态膜1与未反应芯之间，设液相反应物在其中的有效扩散系数为D_eff1。则对于该过程，液相反应物游离酸A通过固态膜1的扩散速率与通过固态膜2的扩散速率及未反应芯表面上的化学反应速率都相等，并且等于整个反应过程的宏观反应速率。最后郑州大学硕士学位论文推出酸解磷矿反应第二阶段的数学模型:吞材，kc，l/夕。 f天。丫f无、f从，丫天。、l+I一曰—l+I一加l一一. 又R。)又k，，)戈DeffZ)戈R。)（3一14）叽一" 一 将实验分析数据代入并进行了假设，得到硫酸分解磷矿反应第二阶段的反应动力学的数学经验模型:3石对，户，a，f，。刁—11一十一eM月户aR:‘。戈Itxc一x。（l一二。）蚤、甘，（5一8）丫口少I一ta 一 由计算结果可知，在相同反应时间下，添加活化剂的反应中的扩散系数比空白样中的大，即扩散过程中的阻力比空白的小，这从数学模型中说明活化疏松剂对固态膜的性状有影响。从计算数据来看，水浴锅温度为341K时，常数项数据波动较大，因此对扩散系数的表达式的假设及对模型的简化过程还存在一定的误差，还需进一步完善。 结合化学反应的阿累尼乌斯方程，由试验数据拟合建立了由反应时间、熟化温度和活化能表达的动力学方程: 20703空白:万=79.166e“T·In（t）+BI（5一12）添加ApA:Z=7 1 0.092e塑些 R丁·In（t）+BZ（5一13） 该反应活化能是以转化率为反应速率求出的，为反应的表观活化能。由拟合结果可知，空白反应中的表观活化能和频率因子比添加APA的小，而这两项反映了反应速率常数的大小。由结果知，添加活化剂的反应的反应速率常数大于空白反应的，说明活化剂的加入降低了反应过程中的扩散阻力，从而使反应速度加快，磷矿转化率提高。 该模型在硫酸浓度为63%，硫酸温度为353K，搅拌速度为300rpm，lh成t<24h，0.128⁽Rs簇 0.154^，341K蕊T(353K条件下对实验结果的拟合情况较好，模型终值残差小于5%。不足之处在于在动力学方程中没有对酸浓度及磷矿粒径等影响因素进行研究，对于温度的影响还需做大量实验给予确定。此外，模型中的常数项B还需进一步确定其影响因素。 结晶过程是酸法磷肥生产中重要的过程之一。结晶的形状和大小在很大程度上决定着工艺流程、设备配置和生产的经济性，实际生产中工艺条件的控制都是围绕如何获得粗大、均匀的晶体进行的，用酸分解磷矿以制取过磷酸钙、萃取磷酸及其它含磷 郑州大学硕士学位论文产品都与硫酸钙结晶有直接联系。实验可知，活化疏松剂能够改变硫酸钙等晶体的晶习，因此，本课题不仅可?更多还原

【Abstract】 Single superphosphate is an old phosphoric fertilizer . But its process also have some difficult problems which have not been solved for long time , such as the longer stacking and curing time ,badly caking produces. So far , there is a new technology named adding activator and porous agent(abbreviated as APA) process widely applyed in China . Started from settling the disadvantages in the process , the subject research the activator and porous agent ’s influence on the acid-rock reactionAPA is a compound in which surface active agent is the main ingredient. According to some special properties of surface active agent , we observed and studied APA’s influence on CaSO4’s crystal form with the electronic microscope. The results indicate that APA is propitious to improve CaSCVs crystal form , and to get coarse and regular crystal. Through series acid-rock reaction experiments ,we can get the conclusion that APA can change the CaSCVs crystal form ,and lead to the coating layer around the unreacted phosphate ore grains loose and pervious ,and then make the resistance of the next reaction decreased and the percent conversion of the phosphate ore increased .Unreacted-core shrinking model can be used as physical model of the second stage of the reaction .We assumed that the radium of unreacted core was RO at to,and at this time the coating layor around the unreacted core was called as coating- I ,in which the expansion factor of liquor reactant was assumed as Kis.The reaction after to seemed as stationary state process. And the coating growing in this process was called as coating- II in which the effective expansion factor of liquor reactant was assumed as Deff2 According to the character of stationary state process, we can get the mathematic model of the second stage:On the basis of mathematic model and experimental data , the empirical equation can be derived:from the calculation results , we can get the conclusion that the expansion factor of liquor reactant in the reaction of adding APA is larger than that in the check, which means that adding APA can reduce the resistance force of coating layor so that the reaction speed is increased .During the derivation , some hypothesis and model simplifications were made . The equation still have some deficiencies to describe the process .So it need to be improved further .Combining the empirical equation with the Arrhenius equation , a rate equation for the digestion process was fitted to experimental results as follows:The results show that in the reaction of adding APA the reaction rate constant is larger than that in the check , which indicate that APA can increase the coating layer’s perviousness and make the reaction speed up.The reaction temperature is varied from 341 to 353K,the initial mean particle size 0.128to 0.154mm,and the initial sulphuric acid concentration is 63%, the stirrer speed 300rpm.Under such conditions , the equation is fitting well with the experimental data .The results indicated that the error between calculation and actual value is no more than 5%.Acid-rock reaction is the major technology of phosphoric fertilizer , and the crystallization is usually involved .So the study of the APA’s influence on the reaction not only supply assurance for the industrial implement of the no stacking and curing time technology (or called as adding APA process )in single superphosphate process, but also can infer some reference to adding APA in other acid-rock reaction.更多还原