Combustion of hydrogen rich gaseous fuels with low calorific value in a porous burner placed in a confined heated environment

The main purpose of this work is to investigate the combustion of gaseous fuels with low calorific value in a porous burner placed in a confined heated environment, established by a laboratory-scale furnace, with temperature-controlled, isothermal walls. The study examines the effect of the composition of the fuel mixtures and of the furnace temperature on flame stability and pollutant emissions. Mixtures of CH4, H2 and CO diluted with CO2 and N2 were used as low calorific value fuels. The composition of the fuel mixtures was tailored such that the constant pressure adiabatic flame temperature at the equivalence ratio 0.5 remained at 1207 °C while the lower calorific values varied from 4.5 MJ/kg to 50 MJ/kg. The present results reveal that the upper stability limit was reduced by about 15% as compared with that in open environment. However, in both environments was observed that the hydrogen concentration in the fuel mixture enlarges the burner stability range. For methane concentrations in the fuel mixture higher than 40%, the stability limits do not vary appreciably. The pollutant emissions were measured in both open and confined environments. As the furnace temperature increases the CO and HC emission indexes decrease significantly.

► Combustion of gaseous fuels with low calorific value in a porous burner placed in a furnace.
► Effect of the fuel mixture composition and furnace temperature on flame stability and pollutant emissions.
► Presence of hydrogen in the fuel mixture enlarges the burner stability range.
► CO and HC emission indexes decrease significantly with the increase in furnace temperature.