METHODS TO REDUCE NOX FORMATION DURING GAS COMBUSTION IN BOILERS

Abstract

A study of reduction of nitrogen oxides emissions using various methods and their combinations on operational typical steam and water heating boilers of Ukraine during combustion gas fuels was conducted. The experimental research of the power steam TGMP-314 boiler showed that when volume thermal stress of the firebox was reduced to qv » 0.09 MW/m3 (55 % of the nominal power), and the flue gas recirculation factor r = 17 %, the nitrogen oxides emissions were reduced by 75 % and they almost meet the requirements of the IED directive. This measure to reduce emissions of nitrogen oxides is also possible for other types of boilers, and it is advisable to implement for those combustion plants with an excess capacity of about 40–50 % and which have exhausted their factory-designated resource. On the water heating boiler KVGM-180, equipped with standard gas recirculation smoke exhauster, the research was conducted with aim to reduce of NOx emissions at combustion natural gas with recirculation of flue gases into the blowing air. NOx emissions were reduced by 67% to European standards, and the concentration of carbon monoxide in flue gases was below СО≤100 mg/Nm3 (at 3% O2) by a recirculation factor was of about r = 30%. The standard burners in the KVGM-180 boiler are two flow of air and can be considered a type of staged combustion burners. That is, in this case, a combination of the staged combustion burners and flue gas recirculation into blowing air was used. The research of combustion a methane and carbon dioxide mixture in the ratio of CH4 (76 %) and CO2 (24 %) (biogas) with regard to reduce the formation and emissions of nitrogen oxides in the DKVR-6.5-13 steam boiler was conducted. The obtained level of NOx in the flue gases is within the range of 63–76 mg/Nm3 (at 3 % O2), which fully complies with the EU standards for the operation of CP from 1 MW on natural gas and other gas fuels. Bibl. 34, Fig. 3, Tab. 1.