Characterization of the combustion of the mixtures biogas-syngas at high strain rates

Abstract

Applying gasification on the residue generated by the biogas process would increase flexibility and efficiency of waste treatment plants while leading to a simultaneous production of biogas and syngas. Existing electricity conversion systems at biogas and gasification plants are usually designed to operate with a single bio-fuel (biogas/syngas). It is, hence, necessary to identify the combustion characteristics of these blended fuels in order to implement them efficiently in the existing systems.The aim of this work is to characterize the structure and emission of mixtures of biogas and syngas in counter-flow flame configuration at laminar regime. Particular attention is paid to the chemical effects of CO2 contained in the biogas and radiative heat losses of the flame. Several compositions of biogas and syngas have been considered in the fuel mixture.The results show that the flame properties are very sensitive to fuel composition. An increase in the volume of methane in the biogas or hydrogen in the syngas improves the Low Heat Value (LHV) of the fuel. Moreover, the addition of a volume of syngas exceeding half of that of biogas allows a reduction of harmful emissions while maintaining a constant level of operating temperature. At the flame front, the NO species is found to be governed by thermal route whereas it is generally produced by prompt path before and after the flame front. In addition, the chemical effect of CO2 reduces the maxima of temperature and emission. This effect remains constant in the syngas mixtures while it is very sensitive to biogas composition where it decreases with the amount of CH4 in biogas.