Investigation of NOx reburning inside a porous burner

Abstract

NOx Re burning is an attractive approach for the reduction of emission from existing combustion systems. The process involves partial oxidation of the re burning fuel under fuel-rich conditions as well as reaction between hydrocarbon radicals and nitric oxide and subsequent conversion of the intermediate nitrogenous species. This study investigates the re burning characteristics of NOX inside a porous burner. Porous burners are quite effective in stabilising flames at wide range of operating conditions (from very lean to rich) and are classified as low pollutants emitting burners. An experimental porous burner was designed and manufactured for this purpose The burner is instrumented for measuring temperature and pollutant emissions. Porous burner consists of a mixing chamber, heat exchanger and porous bed Premixed air and fuel is fed through the mixing chamber, wherein NOX and other diluents such as nitrogen and carbon dioxide can be added to the mixture. The premixed mixture is ignited at a downstream position and the flame stabilises inside the porous bed very dose to the top of the heat exchanger. The effects of equivalence ratios, flow velocities and input NOX concentration on flame stabilisation, NOX reburning efficiency and temperature profiles along the burner are investigated It was found that up to 92% reburning of NOX is achievable when operating at moderately rich conditions. It was also found that NOX levels in the inlet gas mixture could affect the reburning efficiency. Results also show that the maximum convergence efficiency correlate with input NOX concentration as weH as the flow vdocity and this maximum is almost independent of equivalence ratio.