Numerical Analysis of Performance of Cyclone-Tube Demister Based on Orthogonal Design

Facing the increasingly strict requirements of industrial flue gas emission in China, this paper designed a new type of cyclone-tube demister to overcome the low removal efficiency of fine droplets that particle size less than 20 μm by wave-plate demister. The flow of flue gas in the cyclone tube demister was numerically simulated by using Euler-Lagrangian method, using rigid spherical water drops instead of fog drops. And the RNG k-ε model and DPM model were used for the alternating coupling calculation of continuous phase and discrete phase. The performance changes of the cyclone-tube demister under different flow velocities were studied. Based on the simulation experiment of orthogonal design, the influence of the structural parameters of the cyclone-tube demister on the demisting performance was studied. The simulation results of basic structure cyclone-tube demister show that, under the flow rate of 3~7 m/s, the removal efficiency of droplets with diameter greater than 20 μm is more than 99%; the removal efficiency of droplets with a diameter of 10~20 μm is above 86.5%; the removal efficiency of droplets with a diameter of 2~10 μm is above 51.3%; when the pressure drop is 61.4~321.3 Pa, it can significantly improve the removal efficiency of fine droplets. By analyzing the results of orthogonal simulation test, it is found that the increase of a and the decrease of d are beneficial to improve the removal efficiency of droplets. With the increase of a, d and H, the pressure drop of flue gas flowing through the demister will be increased. The optimum structure with demister efficiency of 2~10 μm as index is d=100 mm, H=2000 mm, a=900°, the optimum structure with demister efficiency of 10~20 μm as index is d=100 mm, H=1600 mm, a=900°, the optimum structure with the pressure drop as index d=100 mm, H=2400 mm, a=540° are obtained. The cyclone-tube demister proposed in this study can significantly improve the removal efficiency of fine droplets, which is of great significance to the ultra clean emissions of coal-fired power plants.