| Nitrogen oxides(NOx),one of the major atmospheric pollutants,is not only one of the main culprits for acid rain and photochemical smog,but also one of the main reasons for the formation of smog weather.Therefore,how to effectively reduce the emission of nitrogen oxides is increasingly emphasized.As the main source of nitrogen oxides,coal-fired thermal power plants must bear the brunt of effective reduction of nitrogen oxide emissions.Selective catalytic reduction(SCR)technology is the most commonly used technology in the denitration section of thermal power plants in the world today.This article first introduced the equipment parameters,layout methods and reaction principles of the SCR denitration system in coal-fired power plants.At the same time,it introduced the development of domestic and foreign denitration technologies and the latest status,taking a 660 MW coal-fired unit SCR device as the research object,intercepting the coal of the unit.The flue gas channel segment of the outlet of the device and the inlet of the air preheater,and the SCR denitrification system containing the deflector group,the spray grid,the rectification grid,and the catalyst layer are modeled and analyzed,and the geometric model and the grid are established using GAMBIT.The division,using FLUENT software,respectively,numerical simulation analysis,the presence of the deflector in the flue,the conditions under different boiler load conditions,the best reaction temperature,the best ammonia mole imports to obtain the corresponding velocity field,The characteristics of nitrogen oxide concentration distribution,ammonia concentration distribution,and pressure distribution,and indirectly assess the effect of denitrification.The result is as follows:The target fluid is the cross-section fluid pressure and velocity distribution at 0.3m upstream of AIG,and the velocity,concentration,and pressure distribution of the firststage catalyst inlet cross section.Under the condition of installing the deflector,it is found that the fluid is compared with the case of installing the deflector.The speed deviation is reduced from 25.4% to 12.8% upstream of AIG 0.3m,the pressure deviation is reduced from 8.2% to 5.6% upstream of AIG,the inlet pressure of the first layer of the catalyst is reduced from 8.5% to 5.7%,the fluid at the inlet velocity of the catalyst The standard deviation was reduced from 12.3% to 4.21%,and it was found that increasing the concentration of the deflector has a better improvement in improving the concentration distribution.After the SCR denitration system was optimized based on the BMCR operating parameters,the numerical simulation method was used to study 75% THA,50% THA,and 40% THA.The results were found at 75% THA,50% THA,and 40% THA.The AIG upstream cross-section velocity deviations for the three conditions were 13.2%,12.8%,and 12.5%,respectively,and the first-tier catalyst inlet velocity deviations were 3.4%,3.78%,and 3.63%,respectively.The pressure loss from the horizontal flue gas inlet to the first layer of catalyst was 75.833 pa,63.33 pa,and 49.3 pa.The pressure deviation at the entrance to the first layer of the catalyst was 5.8%,5.3%,and 5.4%,respectively.It shows that even if the load of the unit of the SCR denitration system of the coal-fired unit changes,the system can still meet the requirements for uniform distribution of the flow fields.The best reaction temperature and the optimal reaction NH3/NO molar ratio,the chemical reaction was added after the numerical simulation,the denitration efficiency and the exit NH3 escape concentration as the target parameters,the optimal reaction temperature was 395 °C,the best import NH3 / The molar ratio of NO was controlled to 0.95,and the efficiency of the denitration reaction reached a maximum of 91.3%. |
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