The Distribution And Optimization Of Flow Field In An Ammonia Wet Desulfurization Tower For Sintering Flue Gas By Numerical Simulation Method

Sintering process is the main source of SO2in iron and steel industry, andcontroling the emission of SO2from sintering flue gas has become a inevitable choicefor China’s environmental protection and the sustainable development of iron and steelmetallurgy industry. Ammonia wet flue gas desulfurization (WFGD) technology hasbeen widely used now, but the phenomenon of "ammonia escape" is very serious,especially for the single tower. Based on operations of the large-scale sintering flue gasammonia desulfurization tower, the problems of desulfurization was analyzed, andnumerical simulation researches of gas-liquid two-phase flow field for differentoperation parameters and geometric structures in tower were carried out in detailed byCFD, and the simulation results were compared with the actual operational data tovalidate the authenticity.The simulation optimization results of desulfurization tower operation parametersshowed: The higher spray was suitable for large-scale spray absorption tower. Thespray angle should be90°or120°overall considering the effect of liquid film, heattransfer and resistance in tower. The fluctuation of flue gas inlet velocity had a biggerinfluence on the flow field in tower. Under steady state simulation system and withoutconsidering the droplets evaporation, the change of the flue gas inlet temperature hadno influence on the uniformity of flow field distribution and the loss of pressure intower, and the higher the flue gas inlet temperature was, the faster the temperaturedecreased. Increasing the liquid-gas ratio could contribute to the heat transfer andimprove desulfurization efficiency, but it would get the poor flow field uniformity andincrease resistance, in the case of meeting the requirement of environmental protection,it was advisable to choose the liquid-gas ratio5~7L/m3for this desulfurization system.The simulation optimization results of desulfurization tower geometric structuresshowed: Compared with the single entrance tower, the double entrance tower hadadvantages of flow field distribution and heat transfer, while the tangential doubleentrance could avoid the phenomenon that the local airflow was too dense whichcaused by two strands fumes hedge under the straight double entrance. For alarge-scale spray absorption tower, the change of the entrance angle had little influenceon the uniformity of flow field distribution and the loss of pressure in tower, but theincline entrance could avoid the condition that the spray seriflux entered into the entrance when the liquid level was abnormal fluctuated, and it was recommended thatthe entrance angle should take around10°in engineering design for a large-scale sprayabsorption tower. The breadth of plate above the entrance region should be0.5m~1.0m because the plate could not only prevent the spray seriflux from entering theentrance but also be advantageous to the uniformity of flow field distribution, while acertain angle could be taken into consideration to setup the plate. The flow guidedevice which was simple in structure, easy to operate and ladder-shaped in the entranceregion could improve the uniformity of the flow field distribution, and contribute to themass and heat transfer. The flow field under the way of the entrance-exit in the sameside and the top-side outlet would be more reasonable.