Numerical Simulation of the Influence of CO2 on the Combustion Characteristics and NOX of Biogas

• Published in: Frontiers in energy research Vol. 9
• Main Authors: Ma, Jinshuang, Qi, Chuanjia, Luo, Siyi, Zuo, Zongliang
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 06.01.2022
• Subjects: biogas; CO2 concentration; combustion characteristics; NOX; simulation
• ISSN: 2296-598X; 2296-598X
• DOI: 10.3389/fenrg.2021.811037

The existence of inert gases such as N 2 and CO 2 in biogas will reduce the proportion of combustible components in syngas and affect the combustion and NO X formation characteristics. In this study, ANSYS CHEMKIN-PRO software combined with GRI-MECH 3.0 mechanism was used to numerically simulate the effects of different CO 2 concentrations (CO 2 volume ratio in biogas is 0–41.6%) on flame combustion temperature, flame propagation speed and nitrogen oxide formation of complex biogas with low calorific value. The results showed that when the combustion reaches the chemical equilibrium, the flame combustion temperature and flame propagation speed decrease with the increase of CO 2 concentration, and the flame propagation speed decreases even more slowly. Meanwhile, the molar fraction of NO at chemical equilibrium decreases with the increase of CO 2 concentration and the decrease is decreasing, which indicates that the effect of CO 2 concentration in biogas on NO is simpler. While the molar fraction of NO 2 does not change regularly with the change of CO 2 concentration, the effect of CO 2 concentration in biogas on NO 2 is complicated. The highest molar fraction of NO 2 was found at chemical equilibrium when the CO 2 concentration was 33.6%, when the target was a typical low calorific value biogas.