Combustion analysis of an equimolar mixture of methane and syngas in a surface-stabilized combustion burner for household appliances

• Combustion of methane–syngas were studied in a ceramic surface-stabilized combustion burner.
• The present study evaluates a high hydrogen content syngas.
• The overall flame structure was visualized with OH chemiluminescence.
• Radiation efficiencies were obtained from a radiometer measurements methodology.
• This type of burner exhibits a great potential for interchangeable use of gas fuels.

The primary objective of this work is to study the combustion of an equimolar mixture of methane and syngas (CH4–SG) in a ceramic surface-stabilized combustion burner. We examine the effects of the fuel composition, the air-to-fuel ratio and the thermal input on the flame stability, the radiation efficiency and the pollutant emissions (CO and NOx). In this study, we evaluate a syngas with a high hydrogen content that is similar to those obtained by coal gasification (50–60% H2) using Sasol/Lurgi gasification technology and biomass gasification, for example. To determine the effect of the air-to-fuel ratio (λ), the burner performance is analyzed at λ = 1.4 and λ = 1.1. Some studies have reported optimal operating conditions for λ = 1.4, whereas for hydrocarbons, the proximity to stoichiometric conditions at the λ = 1.1 air-to-fuel ratio produces the highest possible laminar burning velocity and flame temperature. The thermal inputs evaluated in this study correspond to three values (1.0, 1.8, and 2.5 kW) found in household appliances and for cooking appliances in particular. The results for this experimental burner design indicate that the macroscopic flame shape for an equimolar CH4–SG mixture is approximately the same as that for CH4. Moreover, the pollutant concentrations in the flue gas are generally below 85 ppm for CO and 15 ppm for NOx. However, the thermal input and the air-to-fuel ratio significantly affect the flame structure, the radiation efficiency and the pollutant emissions.