Characterization of biogas-hydrogen premixed flames using Bunsen burner

• Published in: International journal of hydrogen energy Vol. 39; no. 25; pp. 13292 - 13299
• Main Authors: Zhen, H.S., Leung, C.W., Cheung, C.S., Huang, Z.H.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 22.08.2014; Elsevier
• Subjects: Alternative fuels. Production and utilization; Applied sciences; Biogas; Biogas-H2 fuel; Carbon dioxide; Carbon monoxide; CO emission; Combustion; Energy; Equivalence ratio; Exact sciences and technology; Flame stability; Flame stabiltiy; Fuels; Hydrogen; Laminar; Laminar burnig velocity; Premixed flames; Biogas-H2 fuel; Flame stabiltiy; CO emission; Laminar burnig velocity; Characterization; Biogas-H; Hydrogen; fuel; Premixed flame; Biogas
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2014.06.126

Experimental study is conducted to clarify the effects of hydrogen addition to biogas and hydrogen fraction in the biogas-H2 mixture on the stability, thermal and emission characteristics of biogas-H2-air premixed flames using a 9 mm-ID-tube Bunsen burner. Variation in biogas composition is allowed to range from BG60 (60%CH4–40%CO2), down to BG50 (50%CH4–50%CO2) and to BG40 (40%CH4–60%CO2). For each biogas, the fraction of hydrogen in the biogas-H2 mixture is varied from 10% to 50%. The results show that upon hydrogen addition and increasing hydrogen fraction in the fuel mixture, there are corresponding changes in flame stability, laminar burning velocity, flame tip temperature and CO pollutant emission. Under the tested conditions of 400 ≤ Re ≤ 800 and 0.8 ≤ Ф ≤ 1.2, the otherwise incombustible biogas-air mixture becomes flammable upon hydrogen addition and the threshold value of hydrogen fraction for occurrence of stable flames increases with the increase in the CO2 concentration of biogas. Overall, the flame stability is best at rich equivalence ratio of Ф = 1.2. The laminar burning velocity of the biogas-H2-air mixture is found to be higher than pure biogas due to addition of hydrogen, and it monotonically increases at higher hydrogen fraction. Further, a shift in equivalence ratio for peak laminar burning velocity from stoichiometric Ф = 1.0 to Ф = 1.2 is observed. The results also show a monotonic increase in flame temperature and a monotonic decrease in CO emission at higher hydrogen fraction. The more efficient oxidation of CO into CO2 reveals that more complete combustion is induced by hydrogen addition. •Biogas of various compositions with hydrogen addition was considered.•Biogas-air flame stability was improved by hydrogen addition.•Flame temperature was enhanced by hydrogen addition.•Laminar burning velocity was increased by hydrogen addition.•CO emission was reduced by hydrogen addition.