Abstract:

In order to study the separation performance of a two-stage combined demister, the performance of the two-stage swirling, combined and two-stage baffle demisters was analyzed. Numerical simulation method was used to analyze the difference of the internal flow field in demisters. By setting up an experimental platform, high-speed photography technology was used combined with the flow field distribution of the demisters to analyze the internal movement behavior of the droplets in the demisters, then the experimental research on the separation performance of the demisters was carried out from the aspects of pressure drop loss, separation efficiency and outlet droplets size. The results showed that the droplets are trapped in the baffle mainly by impacting the blades, sliding along the edge of the blades in the swirling plates, and then moving toward the wall at an angle close to the inclination angle of the blades to form a liquid film. As the inlet section gas velocity increases, the pressure drop of the three demisters gradually increases, the difference increases continuously, and the pressure drop of the two-stage swirling demister is the highest. When the inlet section gas velocity is lower than 5.7m/s, the separation efficiency of the two-stage swirling and combined demisters are close to 100%, and the median particle size of the droplets at the outlet of the combined demister is always lower than that in the inlet droplets, the particle size is smaller than the other two types of demister, so the separation ability for small particle size droplets is remarkable. When the liquid phase flow rate is gradually increased from 6.2m³/h to 13.7m³/h, the separation efficiency of the three demisters decreases, and the two-stage swirling demister has the strongest adaptability under high gas velocity and liquid flow. At the same time, the median particle size of the droplets of the three demisters outlets showed a downward trend, and the median particle size of the droplets at the outlet of the combined demister was still at the lowest level.

Key words: gas-liquid flow, combined demister, high-speed photography, particle size distribution, separation performance

摘要：

为研究两级组合式除雾器的分离性能，对两级旋流式、组合式、两级折流式3种除雾器进行性能分析。通过数值模拟方法分析除雾器内部流场差异，通过搭建实验平台，利用高速摄影技术并结合除雾器流场分布分析液滴在除雾器内部运动行为，进而从压降损失、分离效率、出口液滴粒径等方面开展除雾器分离性能的实验研究。结果表明：液滴在折流板内主要靠撞击叶片累积形成液膜而被捕集，在旋流板内沿叶片边缘滑动，以接近叶片倾角角度向壁面运动形成液膜被捕集；随入口截面速度增加，3种除雾器压降均逐渐增大，差值不断增加，两级旋流式除雾器压降最高；当入口截面速度低于5.7m/s时，两级旋流式、组合式除雾器分离效率均接近100%，同时组合式除雾器出口液滴中位粒径始终低于入口液滴中位粒径，并小于其余两种形式除雾器，对小粒径液滴分离能力显著；当液相流量从6.2m³/h逐步增加至13.7m³/h，3种形式的除雾器分离效率随液相流量增加呈下降趋势，其中两级旋流式除雾器在高气速、高液相流量下适应性最强，同时3种除雾器出口液滴中位粒径总体呈现下降趋势，其中组合式除雾器出口液滴中位粒径仍居于最低水平。

关键词: 气液两相流, 组合式除雾器, 高速摄影, 粒度分布, 分离性能