| During the actual operation of the wet flue gas desulfurization system,there are problems such as low utilization rate of atomized slurry and secondary pollution caused by the entrained atomized slurry,which will affect the economic and environmental protective operation of the desulfurization system.In this paper,a 300 MW wet flue gas desulfurization system was treated as research object,and the numerical simulation method wass used to analyze the problems such as flue gas flow characteristics,gas-liquid contact process,droplet movement characteristics,atomization entrainment phenomenon,gas-liquid separation process.The main research contents include:Firstly,based on the FLUENT platform,the coupling calculation model of flue gas flow and the slurry spray process in spray tower was established.The influence of the slurry spray on the flue gas flow characteristics was analyzed.On this basis,the droplet distribution in the tower?the escape rate of droplets with different particle sizes and the concentration and particle size distribution of slurry at different regions and heights were analyzed and studied under 100% load.The influence of unit load on the entrainment characteristics of the desulfurization slurry was further obtained.Secondly,the coupling effect between gas flow,droplet and liquid film in mist eliminator channel was analyzed from the three aspects of the inertial separation of droplets,the collision and breakup of droplets and the formation and separation of liquid film.The corresponding calculation methods and equations were put forward afterwards which will lay the foundation for subsequent numerical calculations.Thirdly,the Euler-Lagrange approach was adopted to establish the gas-liquid two-phase flow in baffle demister of the wet flue gas desulfurization system.Three-dimensional numerical simulation was established to investigate the particle motion and trapping characteristics which were calculated under various inlet gas velocities and plate spacing,then the effects of collision between droplets,the breakup of droplets caused by gas flow and the interaction between droplets and wall film on separation efficiency were analyzed respectively.The simulated results showed that inlet gas velocity and droplet size are the main factors that affecting separation efficiency.The small size droplets have strong followability to the main gas flow,while the movement of large size droplets was mainly dominated by inertia.In addition,the overall demisting efficiency was increased when the collision of droplets was considered.The effects of droplet breakup on separation efficiency was minimal,and the model that considers the interaction between the droplet and the wall film can more accurately describe the secondary entrainment that occurs during the separation process.Finally,the main influencing factors of defogging efficiency and pressure drop of different plate type single-stage mist eliminators were analyzed.On this basis of single-stage mist eliminator,the influence of different plate type combination methods on the actual operating performance of the two-stage defogger was further analyzed. |
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