Investigation of Waste Biogas Flame Stability Under Oxygen or Hydrogen-Enriched Conditions

Abstract

Increasing production rates of the biomethane lead to increased generation of waste biogases. These gases should be utilized on-site to avoid pollutant emissions to the atmosphere. This study presents a flexible swirl burner (~100 kW) with an adiabatic chamber capable of burning unstable composition waste biogases. The main combustion parameters and chemiluminescence emission spectrums were examined by burning waste biogases containing from 5 to 30 vol% of CH4 in CO2 under air, O2-enriched atmosphere, or with the addition of hydrogen. The tested burner ensured stable combustion of waste biogases with CH4 content not less than 20 vol%. The addition of up to 5 vol% of H2 expanded flammability limits, and stable combustion of the mixtures with CH4 content of 15 vol% was achieved. The burner flexibility to work under O2-enriched air conditions showed more promising results, and the flammability limit was expanded up to 5 vol% of CH4 in CO2. However, the combustion under O2-enriched conditions led to increased NOx emissions (up to 1100 ppm). Besides, based on chemiluminescence emission spectrums, a linear correlation between the spectral intensity ratio of OH* and CH* (IOH*/ICH*) and CH4 content in CO2 was presented, which predicts blow-off limits burning waste biogases under different H2 or O2 enrichments.