Experimental Study On Concentration Distribution And Numerical Simulation Of Flow Field In Multiple-Spout FGD Tower

China is one of the most serious countries of SO2 pollution and coal combustion accounts for more than 90% SO2 emission in China. Flue gas desulfurization (FGD) is the most efficient and important technology to control acid rain and SO2 pollution. FGD can be classified as wet, semi-dry and dry methods.In the semi-dry flue gas desulfurization system, the circulating rate and concentration of particles in the desulfurizing tower greatly influence desulfurization performance of the system, efficiency of the desulfurizer, resistance of the process and economical efficiency of the system. In this paper, a multiple-spout FGD experimental apparatus was set up. The internal gas-solid flow characteristics of the tower were investigated. Effects of entrance air velocity, entrance particle concentration, tower height on internal velocity distribution, circulating rate of particles and particle concentration were studied. The experimental results showed that air velocity increased instantaneously along with tower height and then decreased gradually and large pressure loss was observed at the position where velocity intensely changed. Effect of tower height, which was ranged from 0 to 100 mm, on pressure loss was slight. Resistance concentrated in Venturi accelerating part. Particle concentration increased greatly, and the internal circulating rate of the 2nd stage reached 4, while 1~2 for the 1st stage. The ratio of the upper particle concentration to that of the lower stage was about 2. Thus the lower stage particle concentration was less than the upper stage. The low particle concentration of the lower stage cooperated with the fast evaporation of slurry and the high particle concentration of the upper stage provided more efficient reaction surface, which utilized the internal circulation with high efficiency. It was also found that the internal particle concentration and circulating rate increased with the increase of entrance particle concentration, but the system resistance also increased.By numerical simulation of the flow field inside the tower with FLUENT, the velocity field, pressure distribution, axial velocity distribution and velocity distribution of different section were obtained. Both the exit angle and entrance angle of Venturi accelerating part were optimized. The resistance loss of Venturi accelerating part with the angle of 30°, 45°and 60°was calculated. By comparison between simulation and experimental results, the computational results agreed well with those of experiment, which proofed that numerical simulation could be applied to FGD tower design.