The effect of adding CO2 to the axis of natural gas combustion flames on CO and NOx concentrations in the combustion chamber

Abstract

The paper presents the results of experiments on the effect of carbon dioxide addition during natural gas air combustion on the concentrations of CO and NOx in the combustion chamber. Numerical simulations were also performed using the Chemkin-Pro program. Within the presented experiments, an innovative method of introducing carbon dioxide through the central nozzle of a kinetic burner was tested. This technique allows CO2 to be fed directly into the high-temperature zone, thus not hindering the mixing of the fuel with the oxidizer. The tests were carried out for excess combustion air ratio of λ=1.1, 1.15 and 1.2, respectively, during adding of CO2 to 15 vol.% of oxidizing mixture (air + carbon dioxide).From combustion gas analyses made at a distance of 740mm from the burner outlet in the furnace axis and 20 and 40 mm from the axis, it was found that combustion chamber CO concentrations depended on the amount of introduced CO2, the distribution of CO2 in the combustion chamber cross-section associated with the CO2 addition method and the excess air ratio. The highest CO concentrations were only noted in the combustion chamber axis with a considerable fraction of added CO2. Based on the computations and experiments it has been confirmed that diluting combustion has with CO2 results in a reduction of NOx concentrations.