Experimental evaluation of thermal radiation and soot concentration rates for syngas flames in lean condition and oxygen enhanced combustion

Abstract

The combustion process is a major source of energy for future decades. However, this process negatively impacts the environment with the emission of particulate matter into the atmosphere, known as soot. Therefore, it is desirable that more sustainable and efficient combustion processes are researched. For this reason, the use of biomass gasification has been studied, resulting in a fuel known as syngas, largely composed of hydrogen and carbon monoxide. This gas can reduce emissions as it is derived from biomass. Another way to reduce emissions is using syngas in lean conditions. In this context, the present work aims to present the experimental study of the correlation of a synthetic syngas as fuel produced with a hydrogen and carbon monoxide mixture, and the technique of enriching the air with oxygen in lean conditions using a diffuse flame. A test bench was developed to evaluate the presence of soot and the emission of thermal radiation in the flame, with oxygen-enriched air and equivalence ratios in lean conditions. It was noted that the use of oxygen-enhanced combustion increases the formation of soot and thermal radiation. The highest concentration of soot occurs in an equivalence ratio of 1, for a mixture with 41% hydrogen and 23% oxygen. It reaches more than 3.5 parts per million of soot, more than double the amount of soot when compared with 21% of oxygen in the same conditions. The best results for the mean radiation of the flame occur in the equivalence ratio of 0.9, where values higher than 120 kW/m2 are achieved with 21.7% of oxygen and 33.7% of hydrogen. In addition, the fuel with a higher percentage of CO induces less soot formation and lower emissions of thermal radiation at the beginning of the flame.

Keywords

• Synthetic syngas
• Lean combustion
• Biomass gasification