High-efficiency combustion of natural gas with 21–30% oxygen-enriched air

This investigation was aimed at studying the influence of 21–30% oxygen concentration on the heating rate, emissions, temperature distributions, and fuel (natural gas) consumption in the heating and furnace-temperature fixing tests. Increase in the oxygen concentration led to a more rapid heating rate and lesser fuel consumption due to lower levels of the inert gas (N2). When the oxygen concentration was increased from 21% to 30%, the heating rate was increased by 53.6% in the heating test and the fuel consumption was reduced by 26.1% in the furnace-temperature fixing test. Higher oxygen concentrations yielded higher flame temperature; hence, the NOx emission increased with increasing oxygen concentration. However, the increase of NOx emission in the furnace-temperature fixing test was less than that in the heating test. Moreover, the NOx emission was more sensitive to the excess oxygen at higher oxygen levels. The CO2 concentration in the flue gas increased linearly with the oxygen concentration. Additionally, the temperature distributions became progressively nonuniform with increasing oxygen concentration because the convective heat transfer coefficient was altered.