Study On NO_x Control Proiect On130MW Power Plant Boiler

This article describes the SNCR/SCR hybrid denitrification project on a130MW (420t/h) pulverized coal power plant. Effective engineering solutions for engineering problems were provided in this study by in-depth analysis. The results can provide guidance and reference to small and medium sized boiler DeNOx renovation project.Firstly, the selective non-catalytic reduction/selective catalytic reduction (SNCR/SCR) hybrid technology for flue gas denitrification programs on a420t/h coal-fired boiler was described in this article. The numerical simulation of the DeNOx rehabilitation programs was also studied with CFD software. Then, debugging and test results showed that SNCR denitrification efficiency was only10%-15%and the highest SCR denitrification efficiency was only47%. Beside, ammonia slip was also higher than design value. Thus, the overall denitrification effect couldn’t meet the design value of the performance guarantee when the project was completed.To solve the problem of SCR low denitrification efficiency, an independent supplement ammonia SCR spray guns rehabilitation method was designed based on testing and analysis. After the spray guns were installed, the concentration of NOx and NH3distribution were measured in the SCR catalyst outlet using the mesh method. Test results showed that NOx emissions were reduced from165mg/Nm3to101mg/Nm3, the NH3concentration distribution deviation was reduced, and the distribution uniformity was improved. The average ammonia slip was decreased from7.1ppm to3.1ppm.To solve the problem of SNCR low denitrification efficiency, the cause was found by testing and analyzing the boiler furnace flue parameters. Firstly, an additive MMT was added in urea to solve the inhibition of SNCR reaction caused by high CO concentration and then improve SNCR efficiency. Pilot-scale experiments were studied on a tube furnace using simulated flue gas, which achieved good test results. NO removal efficiency increased to41.6%after adding MMT when the reaction temperature was900℃and CO content was800ppm. However, when MMT additive was used in the actual boiler, SNCR efficiency was increased by only11.4%and SNCR denitrification efficiency has not yet reached the design value (40%).Finally, a system improvement was conducted by changing the original central pulverized coal system into a half bunker type milling system with exhaust gas as the conveyance medium. After the transformation, SNCR efficiency was increased to43.4%, exceeding the design value (40%). The total NOx emissions was decreased to83mg/Nm3, the (SNCR/SCR) hybrid denitrification efficiency was58%, and the ammonia slip was1.7ppm. The results fully meet the requirements of environmental emissions and the performance guarantee.