基于离心力场-移动床协同强化机制的气固两相分离特性

In modern refinery and natural gas transport, a vast amount of high temperature dusty gas has to be purified. Single traditional gas cleanup technique generally has disadvantages such as low efficiency, high energy consumption and complicated operation, etc. The centrifugal force separation fails to capture the dusts smaller than 10 microns, while the traditional filtration has to meet frequent blowback because of the micropore congestions in the filter cake. In this project, a compact dedust scheme coupling the centrifugal force field with the dynamic filter cake is proposed. It is anticipated that the secondary flow at the top area of centrifugal force field and the precessing vortex core (PVC) can be controlled. On the other hand, a self-cleaning mechanism is obtained by employing the low-velocity moving particles as the filtering medium. Thus a new gas-solid separation scheme with high efficiency and low energy loss is proposed wherein multi-separation mechanisms are cooperative intensified. This project is planned to investigate the separation mechanism on both macro (energy loss, separation effect) and micro (local dust distribution, local residence time, local velocity distributions) scales through large cold model experiment, CFD simulation and theory analysis. It is anticipated to determine the relationship of the physical property, the operating condition and the structural parameters; to found the model of the dust-capture of centrifugal force/dynamic filtering cake, the quantitative criterion of the self-cleaning; to analyze/control the individual contribution of the centrifugal force/dynamic filtering cake. Then a universal flow-separation model for the proposed coupling scheme can be given. It can be used to provide new methods and theoretical basis for future engineering optimal design purpose.

石油化工、煤化工等过程需要处理大量高温含尘气体。单一气体净化方式存在效率低、能耗高、操作复杂等缺陷。离心分离对10微米以下颗粒物分离能力有限，传统过滤方式则因滤饼易堵塞需频繁反吹。本项目将离心力场和大颗粒移动床拦截两种分离机制耦合在同一装备中；可有效抑制离心力场内二次流和旋进涡核的不利影响；同时将低速运动的颗粒作为过滤介质，使滤饼具有“自清洁”能力，并实现大颗粒连续再生，形成一种高效低阻、实现多重分离机制协同强化的气固两相分离装备的新构型。采用大型冷模实验、理论分析和数值模拟相结合的方法，从宏观层面（阻力损失、分离效果）和微观层面（局部粉尘分布、两相流场-停留时间分布）两个尺度探索物性参数、操作参数、结构参数之间的耦合关系，建立离心力场和动态滤饼粉尘捕集模型；获得动态滤饼自清洁“能力”的定量判据；分解、调控两种机制对分离效果的“贡献”；建立耦合分离模型；为装备优化设计提供新方法和理论依据。

能源、化工过程产生的大量高温含尘烟气的低能耗高效净化已成为制约其发展的技术“瓶颈”。鉴于离心分离对10微米以下颗粒物分离能力有限，传统过滤方式则因滤饼易堵塞需频繁反吹，本项目提出了一种将离心力场和移动床拦截两种分离机制耦合于一体的新型气固分离技术及装备，其能耗（压降）明显低于传统旋风分离器，是一种高效低阻的新型分离装备构型。通过流场测试，考察了几何结构及内置移动床的设置对削弱二次流、顶涡流、旋进涡核的影响；获得了设备内部静压及三维速度场的分布，揭示了设备内部流场结构的耦合分布规律，并提出了结构优化的建议。通过分析压降-时间响应曲线，确定了不同物性粉尘的最小临界捕集颗粒流率。获得了耦合装备自清洁效应的机理性认识，即自清洁效应分为外自清洁效应和内自清洁效应两部分。外自清洁效应源于旋风壳体内强旋流的剪切作用；内自清洁效应则一方面来源于捕集颗粒下行摩擦颗粒床内网面，另一方面则是由捕集颗粒的横向速度梯度造成的剪切机制贡献。分解-量化了耦合装备中两种分离机制——离心分离和移动床动态滤饼分离的“贡献分率”。确定了物性参数、操作参数、结构参数与压降、效率之间的定量关系。建立了压降、分离效率的计算模型；可为工程设计、操作提供参考。基于对上述原型装备的深入分析和整体优化，形成了一种新型旋风-环形百叶窗式颗粒床耦合分离装备。克服了原型装备中“自清洁效应与捕集效率是一对矛盾”的固有缺陷；在显著提高除尘效率的同时降低了能耗，使传统旋风分离器的分离极限粒径由10微米大幅降低到5微米，能耗降低50%以上，为进一步工业应用奠定了坚实的基础。