流化结晶法磷回收工艺的动力学机理研究及数值模拟

Phosphorus recovery from wastewater becomes significant due to the increasingly growth of phosphorus demand and the shortage of phosphate rock. As a primary technique, struvite fluidized crystallization has been applied in practical conditions other than experimental studies. However, the reactor design and operation remains unclear because of the uncertainties of the dynamics and hydrodynamics in the crystallization. In this project, experiments and modeling are coupled aim to explore the crucial operational parameters during the pellets evolution. Kinetic mechanisms, such as nucleation, growth, aggregation and breakage, as well as their functions will be clarified and deduced. Based on the description of flow behavior via computational fluid dynamics, a numerical model which couples the thermodynamics, kinetics and hydrodynamics is established, and subsequently, the effects of reactor geometry and operational parameters with respect to phosphorus removal and characteristics of struvite pellets harvested can be figured out. In terms of studying the kinetics and hydrodynamics, a method on the basis of numerical simulation is proposed. The implementation of this project will provide a theoretical principle in reactor designs and operational parameters optimizations in fluidized crystallization. Moreover, the results will also be of great scientific significance and practical value in phosphorus recovery from wastewater.

随着磷需求的增长及磷矿资源的日益短缺，从废水中回收磷资源意义重大。鸟粪石流化结晶法作为代表性技术，近年已从实验室研究走向实际应用。然而，结晶动力学机理及水力学作用的不确定性是影响反应器设计及运行的关键科学问题和技术瓶颈。本项目拟采用实验与数值模拟相结合的方式，揭示鸟粪石流化结晶过程中重要操作参数对产品颗粒演化的影响规律；阐明鸟粪石流化结晶过程中成核、晶体生长、团聚及破碎动力学机理并推导相应表达式；通过计算流体力学软件模拟流化结晶反应器流场，并以此为基础，建立耦合热力学、动力学及水力学的鸟粪石流化结晶数值模型，探明反应器构型及运行参数对除磷性能及回收产品性质的影响。本项目针对结晶动力学与水力学，提出以数值模拟为核心的研究方法，研究成果有望为流化结晶反应器的设计及工艺参数的优化提供理论基础，在污水磷回收技术方面具有重要的科学意义和应用价值。

随着磷需求的增长及磷矿资源的日益短缺，从废水中回收磷资源意义重大。本项目采用实验与数值模拟相结合的方式，揭示了鸟粪石流化结晶过程中重要操作参数对产品颗粒演化的影响规律，推导了鸟粪石结晶过程中成核、晶体生长动力学表达式，建立了耦合热力学、动力学及水力学的鸟粪石流化结晶数值模型，探明了反应器构型及运行参数对除磷性能及回收产品性质的影响。主要研究结果如下：.1.明确了流化床内鸟粪石的颗粒化进程为晶体凝聚、絮团致密化、团聚式颗粒生长和包层式颗粒生长四个阶段。.2.拟合了鸟粪石成核与晶体生长动力学表达式，所得的动力学表达式能较好地预测实验过程中物料浓度和pH的变化情况，对最终产品粒度的预测也与实验结果相近。.3.建立了鸟粪石结晶数值模型。所建立的模型具备良好的模拟精度，模拟结果很好地再现了试验现象，同时形象地展示了操作参数的影响情况。.4.优化了流化床反应器的外型与组件。结果表明：一段式流化床具有最佳的的颗粒分级效果、适宜的造粒水力条件，配以分层进水组件，可创造颗粒适宜的流化条件，促进产品的颗粒化。. 综上所述，本项目结果可为流化结晶反应器的设计及工艺参数的优化提供理论基础，在污水磷回收技术方面具有一定的应用价值。