海洋工况下流化床内颗粒聚团行为及传热特性研究

The growing world demand for fossil fuels combined with the declining trend in discovering new giant onshore fields are increasingly driving the petroleum industry sector to develop and monetize oil and gas fields in off-shore areas. .Amidst the technologies currently in deployment in the context of offshore activities, traditional onshore fluidized bed reactors has been applied to the floating production storage and offloading (FPSO) and marine waste heat recovery system due to its excellent heat transfer and reaction property. The study of traditional onshore fluidized reactors has received considerable attention in the past three decades and these studies provide detailed theories on the particle aggregation behaviors and its influence on heat transfer characteristics. However, these theories cannot be applied to the offshore fluidized bed reactors due to the influence of complex marine environment. Therefore, clarification of particle aggregation behaviors and its influence on heat transfer characteristics in the offshore fluidized bed reactors is very necessary for the improvement of its efficiency, safety and reliability..In this study, the particle aggregation behaviors in the offshore fluidized bed reactors will be investigated by means of electrical capacitance volume tomography system and LBM-DEM (Lattice boltzmnn method-Discrete Element Method) coupling model in the Non-inertial frame of reference. The electrical capacitance volume tomography system is consists of multi-layer electrodes array sensor, multiplexer, data acquisition device and image reconstruction computer. A six degree of freedom experimental platform is built to simulate the actual working conditions of the offshore fluidized bed reactor. Moreover, the dynamic particle aggregation behaviors in the offshore fluidized bed reactors is also numerically simulated by means of the coupling of the lattice-Boltzmann method with the smoothed profile method which provides a coupling scheme between continuum fluid dynamics and rigid-body dynamics through a smoothed profile of the fluid-particle interface. Based on the experimental and simulation results, influence of the complex marine environment on the dynamic particle aggregation behaviors such as formation, movement and crushing will be discussed quantitatively. Finally, the dynamic feature change of particle aggregation behaviors and its potential effect on the heat transfer characteristics in the offshore fluidized bed reactors is discussed. Furthermore, an effective prediction model of the heat transfer characteristics in the offshore fluidized bed reactors is proposed. And the prediction accuracy will be evaluated by heat transfer experiments quantitatively..From this study, the particle aggregation behaviors in the offshore fluidized bed reactors will be clarified. And a more comprehensive understanding and effective prediction approach of the heat transfer characteristics in the offshore fluidized bed reactors will be provided.

海洋环境下流化床内颗粒聚团行为及其传热特性定量表征和预测是新一代海上流化床设计开发和安全运行亟待解决的核心问题。本项目以阐明海洋工况下流化床内颗粒聚团行为及其传热特性为研究目标，利用直接三维电容层析成像技术和基于格子玻尔兹曼方法的离散颗粒运动仿真模型，实现海洋工况下流化床内气固两相流动-传热过程的可视化测量和数值解析。旨在通过系统地实验和数值仿真研究，从床体运动引起的气固相间相互作用及附加惯性力场变化出发，阐明海洋工况下流化床床体运动对床内颗粒聚团行为及其导致的动态非均匀结构的影响机制及影响规律，提出海洋工况下颗粒聚团行为的量化表征模型，揭示颗粒团聚行为变化对传热过程的影响机理，并结合颗粒聚团更新理论建立海洋工况下的流化床机理性传热模型，提出能够反映海洋环境影响的流化床床层与传热表面间传热系数的预测模型，为海洋工况下流化床传热运行事故的预防及应对策略的制定提供理论及数据支撑。

随着世界各国对海洋资源开发、利用的不断深入和扩大，传统陆上多相反应器开始越来越多的出现在海洋工程设备当中。流化床作为一种具有高反应效率以及热传导效率的化学反应装置，逐渐开始在海上浮式生产储卸装置、船用尾气处理及热交换系统等海洋工程设备中得到了应用。但在风、浪、流等海洋环境载荷的影响下，流化床内的气固两相流体将会受到附加惯性力的作用，其流动特性将会出现外力场作用下的不稳定现象，并引起诸多危害，如导致传热部件的热疲劳，床内局部热点、飞温甚至烟灰沉积着火等。因此，研究海洋工况下的床内气固两相流动及传热特性对海上流化床反应器的设计、优化及安全分析具有重要的意义和价值。. 本项目针对海洋工况下流化床内气固两相流动-传热特性这一研究对象，通过系统地实验和数值仿真研究，阐明了环境载荷作用下流化床内颗粒聚团动态行为特性及其对床层传热过程的影响机制。项目从床体运动引起的气固相间相互作用及附加惯性力场变化出发，对流化床内颗粒聚团行为进行了可视化测量和数值模拟，分析了海洋工况下流化床床体运动对床内颗粒聚团的形成-演化-破碎行为及其引起的动态非均匀结构特性的影响规律及影响机制，提出了能够反映环境载荷影响的颗粒聚团行为特征参数量化表征模型；其次，建立了海洋工况下流化床内气固两相流流动-传热过程耦合机制模型，实现了非惯性系下流化床内传热过程的快速数值模拟，给出了海洋工况下颗粒聚团行为变化对传热过程的影响规律和影响机理；同时，结合颗粒聚团更新理论建立了海洋工况下的流化床机理性传热模型，提出了能够反映海洋环境载荷影响的流化床床层与传热表面间传热系数的预测模型。. 本项目研究成果可提高对环境载荷激励下流化床内气固两相流动-传热特性及其影响机制的认识，改善海上流化床的工作可靠性和效率，并为海洋工况下流化床局部热点、飞温及烟灰沉积着火等运行事故的预防及其应对策略的制定提供理论基础及数据支撑。