The Numerical Simulation And Optimization For The Internal Design In The Desulfurization Spray Tower

SO₂ and NOx emissions from coal-fired flue have a serious impact on human health,industrial-agricultural production and construction environment.With the increasingly stringent SO₂ emission standards and the development of domestic desulfurization technology,limestone wet flue gas desulfurization has been widely used as a desulfurization technology with stable operation,high desulfurization efficiency and low operation cost.Based on the Fluent software platform,the numerical simulation of the internal design of the desulfurization spray tower for a 1000MW unit in a power plant is carried out in this paper.In this paper,the RNG k-?model is used to simulate the gas turbulence model in the tower,and the DPM model is used to track the droplet movement in the tower by combining the structured grid with the unstructured grid.Based on the double film theory,the SO₂ absorption model was written and the UDF interface was imported;Simple algorithm was used to simulate the velocity field,pressure field,droplet concentration field,and SO₂ concentration field under different design parameters and operating parameters of each part of the model.The influence of the tower resistance characteristics and SO₂ removal efficiency was mainly explored.According tothe actual situation,the speed and desulfurization efficiencyof each section optimized in the tower,were compared with pilot plants,and the following conclusions were drawn:?1?By studying the empty tower smoke flow field without spray droplets,it can be found that the greater the distance between spray layer spacing,demister spacing,and the distance between the last layer of spray layer and the first layer of demister,the better the uniformity of velocity within the tower and the lowest pressure drop.And when the shower spacing is 2.20 m,the pressure drop of the absorption section is269 Pa;When the demister spacing is 3.20 m,the pressure drop at the outlet of the first demister to the absorption tower is 1118.5 Pa;When the distance between the last layer of spray layer and the first layer of demister is 3.20 m,the pressure drop at the outlet of the last layer of spray layer to the demister is 1019 Pa.?2?When the spraying layer four-layer nozzles are all in operation,the number of nozzles does not affect the distribution uniformity of droplet concentration and the velocity uniformity of the gas in the section of the tower.However,with the increase of nozzle number,the pressure drop of the absorption section increases and the desulfurization efficiency increases.When the 1,2 spray layers on the number of nozzles are 58,68,78,88,98,3,4 layers are 138,148,158,168,178,the absorption section pressure drop:841 Pa,888 Pa,942 Pa,1007 Pa,1051 Pa,desulfurization efficiency is 90%,94%,96.5%,98.3%,98.8%.?3?Considering spray layer three operation and one standby mode,and selecting three different layers of sprinkler layer,the distribution uniformity of droplet concentration in the tower is good,and the uniformity of smoke velocity is better.When the operating layers are 1,2,and 4,the pressure drop in the absorption section of the tower is the smallest,which is 785 Pa,and the desulfurization efficiency is88%.When the operation layers are 2,3,and 4,the desulfurization efficiency in the tower is the highest,which is 94.8%,the pressure drop is 952 Pa.?4?When the spray speeds of 1 and 3 layer are 2.52 m/s,3.52 m/s,4.52 m/s,5.52m/s,6.52 m/s and 1.35 m/s,2.35 m/s,3.35 m/s,4.35 m/s,5.35 m/s,the uniformity of droplet concentration distribution in each section of the tower is better,and the airflow speed is not affected by the spray speed.The pressure drop decreased with the increase of the spray droplet velocity,which were 731 Pa?714 Pa?714 Pa?707Pa?707 Pa,respectively.The desulfurization efficiency increased with the increase of the spray rate:62.6%,82.6%,87.5%,92.5%,and 94.5%,respectively.In practical projects,the spray flow rate should be appropriately increased to reduce the flue gas resistance and increase the desulfurization efficiency in the tower.?5?The tower structural device was optimized to set the spray layer spacing,demister spacing,final layer spray layer and first layer demister spacing to 2.20 m,3.20 m,and 3.20 m,respectively,and set diversion board at the outlet of the desulfurization tower.Set 162 nozzles on the 1 and 2 spray layers,and 188 nozzles on the 3 and 4 spray layers.The numerical simulation of the velocity field inside the tower is performed when the spray layer and the nozzle fully opened.The results showed that the critical section speed values are close to the measured values of the power plant,and the dispersion is small,which can meet various engineering indexes and is conducive to the stable operation of the desulfurization system.The optimized desulfurization efficiency is 99.6%,which is slightly higher than the actual measured value of the power plant after operation,the error rate is 0.49%.This confirms that this topic has a certain practical significance.