| The diameter of packing tower in the carbon dioxide capture system of coal-fired power plant is more than ten meters as the CO2 capacity reaches one million tons.Uneven distribution of gas-liquid phase which was caused by amplification effect,resulting in a decline of product quality and increase energy consumption. In order to reduce or eliminate the amplification effect, simulation studies of the gas-liquid flow characteristic in the packed tower was carried out from the following two aspects. The first one was ascending the technology of the gas inlet distribution. The other one was analyzing and optimizing the regularity of the gas-liquid distribution on the surface of packing.Computational fluid dynamics software FLUENT was used to simulate the flow field of Two-Line Vane Gas Distributor. The unevenness of gas distribution and the pressure drop was used as the evaluation criterion. The field of velocity, pressure field,turbulent kinetic energy and turbulent dissipation rate distribution was analyzed. The result showed that the gas flow of the first blade passage and distributor’s extremity was relatively small. A certain number of vortex existed on the certain plane and cover plate of the distributor. Most gas flow upward along the column wall after gas distributor. So the distribution was not uniformity. Because of the air friction and the velocity gradient, the pressure drop and turbulent dissipation of gas mainly concentrated on the blade and cover plate of the distributor.In order to reduce the gas unevenness and improve the property of the distributor,the optimization of physical structure was started which including the blade number N,the blade angle α, the blade radius R and the blade height H. Simulation results showed that the performance of distributor reached to the best when N=14, α=12°, R=500mm,H=3500mm.In order to explore the regularities of gas-liquid distribution on the surface of packing, structure packing was simplified to the tablet and corrugated board. Interface tracking VOF method was used to explore the stability of falling film flow on the impact of the some factors, such as wall structure, corrugated plate angle, liquid velocity and gaseous phase. Some results showed as follows. Relative to the plate,liquid membrane was easy to break as the peaks and troughs alternating on the surface of the corrugated plate. With the increasing of flow velocity, the liquid film thickness increased and the wall shear stress decreased. While the mass transfer could be strengthened by increasing the flow velocity, it was not always beneficial for some larger size corrugated plate. The whole change trending of the wall shear force was inversely proportional with the slope angle when it equals 0°、30°、45°、60°. When the angle of corrugated plate was large, the adhesion of liquid film on the wall was strong and also not easy to be flooded under the same fluid velocity. The disturbance on the surface of liquid membrane was enlarged after the gas got into the computing area.More severe interface turbulent could be happened on the corrugated plate under low gas velocity. On this occasion, the continuous liquid film were also more prone to rupture and resulted in entrainment. |
PDF Full Text Request