| Wet flue gas desulfurization technology,which is widely applied in coal-fired power plant,will increase the number of droplets in flue gas,and this will finally increase the emission of PM2.5 and cause gypsum rain.In order to solve this problem,coal-fired power plants are equipped with demisters,which can decrease the number of droplets.Demisting efficiency of baffle plate demister which is widely applied for big droplets is high,but the demisting efficiency for small droplets is low.To solve this problem,a new kind of demister,vortex demister is proposed in this paper.Demisting efficiency of vortex demister for small droplets is high because of vortex.In this paper,vortex demister and baffle plate demister are studied by numerical simulation,and the results are compared.And some experiments are done in this paper to show the validity of the simulation.So how do plate spacing,length of baffle,baffle angle and length of gap influence the performance of vortex demister are studied at last.The main contents of this paper include four parts:(1)Vortex demister was studied by numerical simulation.Gas phase field was studied by Euler's method,and the motion of droplets was studied by Lagrange method.Fluent was used to simulate the motion of gas in demister,and the motion of droplets was got by a computer program,which was compiled by VB language.When simulating the motion of droplets,collision between droplets was considered.Direct simulation Monte Carlo method was used,so we judged whether two droplets collide according to probability.And when two droplets collide,hard sphere model was used,so the process of collision was ignored.After collision,two droplets became one droplet.In the simulation,secondary droplets were ignored,and temperature didn't change.(2)To show the validity of the simulation,the experimental platform was set up.Demisting efficiency and droplets separation efficiency of different sizes of vortex demister and baffle plate demister were got in experiment,and they were contrasted with simulation results.The results show that for vortex demister,demisting efficiency got by simulation is bigger than result got in experiment,and the difference is 3-4.8%,and for baffle plate demister,the biggest difference is 2.8%.On the whole,the simulation result of baffle plate demister can fit experimental result better than it of vortex demister.When the velocity is 3m/s and 4m/s,separation efficiency of different sizes of vortex demister got in experiment is bigger than that got in simulation,and for baffle plate demister,the simulation result can fit experimental result well The simulation results can agree well with experiment results on the whole,so the accuracy of the simulation results is verified.(3)Vortex demister was studied by numerical simulation.According to velocity contour and streamlines of vortex demister,there are vortexes behind baffles,and the flow field is complicated.According to distribution of discrete droplet of vortex demister,most of droplets are captured in the first half of demister,and only a few droplets can escape.Baffle plate demister was also studied for comparison.According to simulation results,demisting efficiency and pressure drop of vortex demister are higher than that of baffle plate demister.Comparing the results of vortex demister to the results of baffle plate demister,it can be found that the removal efficiency of small droplets of vortex demister is higher than that of baffle plate demister.For example,the removal efficiency of droplets whose diameter is 10?m of vortex demister is 17.8-28.2%higher than that of baffle plate demister.(4)By changing the structural parameters of the vortex demister,such as plate spacing,length of baffle,baffle angle and length of gap,demisting efficiency,pressure drop and separation efficiency of different sizes showed different rules.When plate spacing decreases from 35mm to 25mm,the demisting efficiency of vortex demister,pressure drop and separation efficiency of different sizes will increase.When the baffle angle increases from 46° to 56°,the demisting efficiency will increase.But when the angle increases from 56° to 66°,the demisting efficiency change little.The pressure drop and separation efficiency of different sizes will also increase with angle increasing.When length of baffle increases from 15mm to 21mm,the demisting efficiency,pressure drop and separation efficiency of droplets will increase.When gap's length increases from 8mm to 12mm,the demisting efficiency and pressure drop will increase little.And though the separation efficiency of droplets changes little,it will increase with the length of gap increasing on the whole. |
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