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.