【作者】 刘义明；

【导师】 朱家骅；

【作者基本信息】 四川大学 ， 化学工程， 2007， 硕士

【摘要】 从目前工业上磷铵装置的运行情况看，存在着料浆结垢严重，工艺流程长，尾气难处理，低品位热源利用困难，污染严重等薄弱环节。从节能、降耗、减排的角度出发，有必要开发一种流程短，排污环节少，能耗低的新工艺流程。磷酸氨化是一个受气膜传质控制的瞬间快速气液反应，根据双膜理论，反应发生在气液相界面，总反应速率取决于气膜中NH₃的传质速率。而提高传质速率，可从增大两相接触面积和传质系数着手。流化床造粒是一个成粒、混合、干燥于一身的集成造粒过程，具有流—固两相接触面积大，相对运动速度高的特点。采用流化床进行磷酸氨化既可获较大的传热、传质速率，还可实现反应—干燥同步完成。过热蒸汽作流化和干燥介质，不仅可通过冷凝的方法回收和利用其潜热使之能耗大幅下降，且无尾气处理的问题。本文结合过热蒸汽干燥、流化床造粒以及磷铵生产的各自特性，提出采用过热蒸汽流化床一步法制备磷铵的集成工艺。从磷酸氨化料浆结晶、氨的逸出和固体磷铵的热稳定性出发，结合流化床内颗粒和气相主体传热传质机理，对流化床内颗粒表面的磷酸氨化反应和干燥成粒机理进行了理论分析。根据实验目的和条件，拟定了实验工艺流程，对相关的主体设备和仪表进行了设计和选型，完成了装置的安装和调试。在理论分析的基础上，进行了过热蒸汽流化床反应干燥一步法制备MAP的试验探索工作。初步探讨了：（1）过热蒸汽流化床制备磷酸铵的稳定操作条件；（2）流化床进料NH₃／H₃PO₄摩尔比对产品N／P₂O₅质量比和NH₃损失率的影响；（3）流化颗粒产品包裹量和反应时间的关系，以考察产品颗粒能否长大；（4）流化床内操作温度对产品N／P₂O₅质量比的影响。实验结果表明：压力为70kPa、温度为100～130℃、进料NH₃／H₃PO₄摩尔比为1.1～1.8操作条件下，流化床内磷酸氨化—干燥过程可稳定操作。用玻璃珠为晶种，成功地在过热蒸汽流化床内制备出以磷酸一铵（MAP）为主的磷铵产品；在操作温度为100～130℃时，流化床进料NH₃／H₃PO₄摩尔比对产品N／P₂O₅质量比的影响不显著，产品N／P₂O₅质量比接近于纯净MAP的N／P₂O₅质量比0.198，说明该工艺过程无需氨过量；流化颗粒表面包裹的产品量随流化反应时间增加而增加，说明磷酸氨化反应能在颗粒表面连续进行，产品包裹在颗粒表面使其不断长大；随着流化床内操作温度升高，产品N／P₂O₅质量比的有所减小。本文通过理论分析和实验较深入地对过热蒸汽流化床反应干燥一步法制备磷铵集成新工艺的基本规律进行了探讨，所得结果为进一步的研究及过程开发提供了一定的依据。更多还原

【Abstract】 According to the actual running condition of ammonium phosphate plants,problems such as serious scaling of ammonium phosphate slurry, long process flow,being difficult to treat waste gas, the difficulty of utilizing low-grade heat resources,serious pollution are existed. From the point view of energy saving, loweringconsumption, and reduction, a new process flow with short flow, low consume, littlepollution discharge, will be developed.The ammoniation of phosphoric acid is an instantaneous fast gas-liquid reactioncontrolled by gas-film mass transfer. According to the bi-film theory, the reactionoccurs at the gas liquid film, the total rate of reaction lies upon NH₃ mass transferratio in gas film. Therefore, in order to improve mass transfer ratio, we can increase thegas-liquid contact area and mass transfer coefficient.Fluidized-bed granulation is a process integration of particle formation, mixingand drying. It has the characteristics of larger gas-solid interfacial area and highrelative velocity, larger heat and mass transfer velocity was obtained ammoniationhappening in the fluidized bed, and reaction and drying can be finished at the sametime.Act as medium of fluidizing and drying, latent heat of superheated steam can berecovered and utilized by condensing, energy consumption was greatly decreased, and there was not the problem of tail gas treatmentAccording to the characteristics of fluidized bed, superheated steam drying, andphosphoric acid ammonization reaction, an integrated one-step-process technologyproducing granular ammonium phosphate employed a superheated steam fluidizedbed was suggested.Starting from crystallization of ammoniated phosphoric acid slurry, escape ofammonia, thermal stability of solid ammonium phosphate, according to heat andmass transfer mechanism of particles and gas-phase in fluidized bed, theory analysisof ammoniating reaction、drying and particle formation of surface of solid particle influidized bed was done. According to the experiment purpose and conditions, anexperimental process flow was suggested the design and calculation of the mainequipment and instruments of process flow was done. And installation anddebugging of equipment was done.Basing on theoretical analysis of ammonification, drying and particle formationin fluidized bed, experiment was done in the superheated steam fluidized bed toprepare MAP by reaction and drying. The following question was investigated in theexperiment. （1）Steady operational conditions of preparing ammonium phosphate inthe superheated steam fluidized bed was investigated, （2） the product mass ratio of Nto P₂O₅ and loss rate of NH₃ was affected by the feed mole ratio molar ratio of NH₃ toH₃PO₄, （3） the growth rate of fluidized particle diameter was investigated in order toinvestigate if product particles growing or not., （4） the effect of operationtemperature in fluidized bed on product mass ratio of N to P₂O₅ was investigatedThe experimental results indicate that: the feeding molar ratio of NH₃ to H₃PO₄does not have an obvious effect on the mass ratio of N to P₂O₅, and the product massratio of N to P₂O₅ is approximately equal to 0.198 of purity MAP when operatingtemperature is from 100℃to 130℃, there did not need excessive ammonia in theprocess. The product weight packed on the surface of fluidized particle increasedwith increasing reaction time, and the size of the particle increase continuously. Theproduct mass ratio of N to P₂O₅ decreases with rising of operating temperature in thefluidized bed. The basic rules of new integrated technology for preparing ammoniumphosphate by reacting and drying in one step in the superheated steam fluidized bed,the results were the basis for further research and development.更多还原