| Wet Flue Gas Desulfurization(WFGD)is the most widely used desulfurization control technology in coal-fired power plants.Among them,the desulfurization tower is the core equipment in the WFGD system.The state of gas-liquid two-phase flow in the tower directly affects the desulfurization efficiency,demisting efficiency,pressure loss,and gas-liquid mass transfer and other parameters in the tower.However,in the actual operation of conventional desulfurization towers,there are problems such as uneven distribution of internal flue gas flow field,high operating costs,low demisting efficiency of the demister,low slurry utilization,and "gypsum rain",pollution caused by slurry entrainment.Therefore,in order to meet the demand of ultra-low emission of coal-fired power plants and improve the performance of the desulfurization towers of WFGD system,the following studies have been conducted on the many problems that exist in the desulfurization towersFirstly,CFD technique is introduced to simulate the thermal field of the desulfurization tower equipped with 3 kinds of turbulator for different porosities and diameters of turbulence unit.The mechanism of turbulator operation is revealed through the analysis on the variation of velocity,temperature and pressure distribution with porosity and turbulence unit diameter.The results show that the installation of turbulator can significantly improve the uniformity of flue gas flow field of the desulfurization tower with the standard variance of cross sectional velocity being below 1.0,thus effectively prolonging the residence time of slurry and improving the probability of gas-liquid contact and utilization of slurry in the absorption region.Taking into consideration the distribution of the flow field,the mixing degree of gas-liquid and the loss of energy,the best performance of the turbulator can be obtained with a porosity being at 50%and a turbulence unit diameter 1.2m.Secondly,the flow field in the desulfurization tower was optimized,The influence of two factors that the design conditions(inlet flue arrangement of the desulfurization tower,tower body diameter-height ratio ?)and operating conditions(spray cone angle ? and flue gas waste heat recovery and utilization)on the flow field in the tower were explored.Among them,for the inlet duct layouts,this paper first proposed a tangential multi-inlet flue arrangement.The research results show that when the flue arrangement with 1200 tangential circular entrance and radius of tangential circle R=3.5m is used,the flow field uniformity in the tower has been significantly improved.The distribution of flue gas velocity in the tower mostly concentrated in the optimal range of 3.5-5.6m/s.The residence time of the slurry in the tower is increased from 1.36s to 2.77s.The temperature distribution at the inlet and in the tower is more uniform.Comprehensive consideration is given to energy loss and mass transfer between the two phases.When the Diameter-Height ratio ? of desulfurization tower is 13:24,the effect is the best When the spray cone angle ? is 135°,the slurry residence time reaches a peak value.Comprehensive consideration is taken to reduce the pressure loss in the tower and extend the residence time of the slurry.The best effect is achieved when the spray cone angle ? is 120°.After the waste heat of the flue gas is recovered,the uniformity of the temperature distribution in the tower can be effectively improved.Finally,in order to explore the demisting characteristics of the mist eliminator in the desulfurization tower.The CFD software was used to simulate the flow field in the two-dimensional single flow channel of mist eliminator.The simulation results were compared with the experimental data.Optimal turbulence model suitable for simulating mist eliminator working conditions was selected.Error analysis of the steady-unsteady flow simulation was completed;The comparative study was conducted on the folded plate mist eliminator with double liquid groove and Arc-plate mist eliminator with barb.According to the results of the study,five kinds of demister optimization schemes were designed.The efficiency of demisting and pressure loss were comprehensively considered.Finally,a new mist eliminator with double-liquid groove and three-channel was optimized.The results showed that the mist eliminator performance has been significantly improved. |
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