上流式反应器多相流动、混合和对流扩散不均匀特性及调控

Combining numerical simulation with experimental data, the characteristics of flow, mixing and convective diffusion are studied in up-flow reactors both on the scale of particle and reactor size experimentally and numerically to reduce local coking and temperature jump in up-flow reactors for residue hydro-treating. On the scale of particle size, the deposition and expanded processes of particles are simulated by lattice Boltzmann method (LBM), and we use level set method to simulate the flow, mix and convective diffusion processes of the gas and liquid fluids. The mechanism that the bubbles behaviors influence the flow, mixing and convective diffusion processes is got and the corresponding mechanism models are built up. On the scale of reactors, the flow, mixing and convective diffusion processes in reactors are simulated by Euler model while coupling the results of particles scale. Combining the experiments, we design some new inner components and build up the integral mathematical models of flow, mixing and convective diffusion processes in the up-flow reactors while exploring the allocation mechanisms between scales of particles and reactors and adding into the random factors in the multi-phase system. After the non-uniform characteristics on multiphase flow, mixing and convective diffusion are got, finally we can lay a foundation to solve the industry problems in the up-flow reactors.

为了减少渣油加氢工艺上流式反应器内局部结焦和飞温现象，本项目以数值模拟为主、结合实验，在颗粒尺度上和反应器尺度上研究气泡与颗粒对上流式反应器内多相流动、混合和对流扩散不均匀性分布的影响规律。采用格子玻尔兹曼方法（LBM）模拟颗粒沉积和膨胀过程，采用Level set方法模拟多孔介质内气液体系两相流型和对流扩散过程，获得颗粒尺度上气泡和颗粒特性对气液体系流动和对流扩散的影响机理。采用反应器尺度多相流欧拉模型模拟上流式反应器内流动、混合和对流扩散过程，将颗粒尺度模拟结果耦合到欧拉模型中。同时设计可调控气泡分布的内构件，结合上流式反应器内流动和对流扩散实验，充分考虑体系的随机性因素，探索颗粒尺度和反应器尺度参数之间的调配机制，建立起完整的上流式反应器流动、混合和对流扩散整体模型，获得反应器内流动、混合和对流扩散的不均匀分布特性，为解决上流式反应器的工业问题奠定科学基础。

针对上流式反应器内由于轴向与径向流动、混合和对流扩散过程的不均匀性，所引发的床层局部结焦和热点问题，利用实验、理论分析和计算机模拟方法，掌握了上流式反应器多相流动、混合和传质特性。首先建立了大密度比二维相场两相流模型（PF-LB），采用双向和单向插值相结合的方式描述大曲率边界，几何方法实现接触角滞后策略，利用自适应加快计算速度；且在完全LBM框架下建立了大密度两相流流动和传质模型（PF-CST-LB）；将两相PF-LB模型拓展到三相。结合LBM和fluent，数值模拟耦合可调控气泡特性内构件的上流式反应器内流动、混合和对流扩散过程，获得上流式反应器压降、相含率和液相扩散系数不均匀分布规律，结合实验，据此设计气液再分布器内构件，形成一套上流式反应器多过程的强化和调控体系。