Research On The Optimal Design Of A SCR-denox System And Its Application For A300MW Coal-fired Power Plant

With the implementation of Emission standard of air pollutants for thermal powerplants, the outdated NOx combustion technologies cannot have satisfied the criterion,which is emission concentration≤100mg/m3, in China. Therefore acceleratingdevelopments and applications of DeNOx-technology is one of the most importantmeasures in reducing NOx emission. Because of the rationality of SCR-DeNOx system,nowadays, SCR-DeNOx technology has been widespread used in large coal-fired powerplant.The paper takes a SCR-DeNOx system for a300MW coal-fired power plant asstudy objects. The author puts forward an optimal structure design by using numericalsimulation and sets up a1:10model to have the flow field model test. Finally, the writercompletes debugging and heating-state adjustment test on the scene.By using the optimal design—arrange a set of linear type guide plate in theentrance of the SCR system and a set of fold-line type guide plate in the exit; put a setof line-arc type of guide plate in the bend of upstream and downstream of AIG and theentrance of rectifier grille respectively, the experiment results, under the BMCRcircumstances, showed that the flue gas velocity numerical simulation deviations at theupstream and downstream of AIG, the entrance of the first catalyst, and the exit of thesystem are:9.2%,9.8%,11.9%and10.7%, the results of using the model are:10.2%,9.7%,12.4%and13.0%, they are all under the criterion which is not over15%. Thenumerical simulation NH3/NOx molar ratio at entrance of the first catalyst is3.6%, andthe model test result is3.8%which are under10%. The numerical simulation degree ofgas entering the entrance of the first catalyst is8.6°satisfies the control standard--±10°. The pressure drop of numerical simulation is708Pa and model test result is730Pa,which are under800Pa in the fact. The field of velocity, concentration and pressure arealmost the same in both numerical simulation and model test, which means the resultsof numerical simulation are credible and using this method to optimize SCR-NOxsystem is reasonable and feasible.After debugging and heating-state adjustment test, when the concentration of NOxis under100mg/m3, the deviation of the concentration of NOx of two systems are8.5%and9.2%which can do with the criterion≤10%. The optimized system works well in theactual operation, the emission of NOx is less than100mg/m3, it can run continuously for168hours at full capacity with the ratio of DeNox is more than80%and emission rate ofammonia is less than2.5mg/m3.The research results of this paper using in the actual could meet the nationalstandard, as the same time, the research method and results of this paper can provide reference to optimize SCR-DeNOx systems in the future.