On the Combustion of Hydrogen-Rich Gaseous Fuels with Low Calorific Value in a Porous Burner

Abstract

The main aim of this work is to investigate the combustion of hydrogen-rich gaseous fuels with a low calorific value in a porous burner, in particular, to study the effects of the composition of the fuel on flame stability and pollutant emissions. To this end, a range of low calorific value fuel gaseous mixtures of CH 4, H 2, CO 2, CO, and N 2 have been prepared in such a way that the constant pressure adiabatic flame temperature for all reacting mixtures was kept constant. In this study, the equivalence ratio was also kept constant. For comparison purposes, the combustion of pure methane in the same porous burner has also been studied. The results indicated that, for this burner design, the macroscopic flame shape of the fuel mixtures remains approximately the same as compared to pure methane but the former flames move further upstream from the burner exit. This is caused by the increase of the laminar flame speed as the H 2 content in the mixtures increases. As a result, the stability limits of the fuel mixture increase and the stability range enlarges. It was also observed that, for the Wobbe Index varying from 5 to 44 MJ/Nm 3, it is possible to burn stably at ≈260 kW/m 2, which reveals the fuel interchangeability potential of the present burner design. Because the flame moves further upstream, the enrichment with H 2 decreases the radiation efficiency. The pollutant emission indexes decreased significantly with the use of H 2 -enriched mixtures. For all fuel mixtures, the maximum emission index of CO and NO x was 0.75 and 0.09 g/kg, respectively.