Chemical & Biological Engineering. Experimental Analysis of the Stability parameters of Biogas-Hydrogen fuel blend Ajulo, Tobiloba Abiodun [email protected] Supervisor 2014 Dr.Yajue Wu Overview Rapid diminution in the primary sources of global energy - fossil fuels (coal, oil, gas), increase in energy costs and environmental anxieties inspires the quest for a cleaner, sustainable and renewable fuel sources like Biogas and hydrogen. Biogas possesses inferior combustion characteristics: low heating value, low burning velocity, narrow flammability and flame stability as compared to fossil fuels. Hydrogen possesses a faster burning velocity, higher heating value, broader flammability limit but poses safety, storage and cost concerns. The study of their combined combustion behaviour is vital before general acceptance as an alternate energy source in the energy industry. Objective To examine the stability parameters (lift-off and blow-out) of Biogas-hydrogen fuel blend using a 2mm internal diameter burner. Results (a) (b) (c) Fig 2.0 Some instantaneous flame images (a) Pure hydrogen at increasing flow rate (b) and (c) Hydrogen-Methane and Hydrogen-Carbon dioxide at 20, 40, 60 L/min H2 respectively. Experimental procedures Flame images were immediately captured using a high speed digital camera Variation in pressure and flow rates of pure hydrogen until lift-off is achieved Variation in fuel flow rates and pressures until flame lift-off and blow-out is reached Flow rates of methane / carbon-dioxide was varied separately with fixed flow rates of hydrogen at (20, 40, 60) L/min Fig 3.0 Plot of experimental blowout velocity against concentrations of (a) methane and carbon-dioxide (b) hydrogen. Fig 4.0 Comparison of lift-off height of pure hydrogen, Fig 5.0 Comparison of lift-off velocity Hydrogen–methane hydrogen-methane, hydrogen-carbon dioxide mixture. and Hydrogen-carbon dioxide flames. Conclusions • Increasing hydrogen flow rates causes an increase in jet velocity and flame lift-off height. Also, an attached and lifted flame profile was produced depending on varying flow rates of the fuel blend as shown in Fig 2.0. • Flame blow-out velocity decreases with increasing concentration of diluents in the fuel blend and increases with increasing hydrogen concentration as shown in Fig 3.0, further affirming findings of Wu et al. (2007). • Lift-off heights of pure H2, H2-CH4 and H2-CO2 flames increases with increasing jet velocity and hydrogen flow rate as shown in Fig 4.0, supporting reports by Broadwell et al. (1984); Wu et al. (2007); Lawn, (2008). • Flame lift-off velocity decreases with increasing methane concentration, while reverse is the case for increasing carbon-dioxide concentration as shown in Fig 5.0. References 1. Broadwell, J.E., Dahm, W.J.A., Mungal, G. (1984) Blowout of turbulent diffusion flame, 303-310 2. Lawn, C.J. (2008) Lifted flames on fuel jets in co- flowing air. 1-30 3. Wu, Y., Al-Rahbi, I.S., Lu, Y., Khalghatgi, G.T. (2007). The stability of turbulent hydrogen jet flames with carbon dioxide and propane addition, 1840-1848 100 200 300 400 500 5 15 25 35 45 Blow out velocity (m/s) Diluent concentration (%) CO2-H2 mixture CH4-H2 mixture 150 200 250 300 350 400 450 50 55 60 65 70 75 80 85 90 95 Blow out velocity (m/s) Hydrogen concentration (%) H2-CH4 mixture H2-CO2 mixture 150 200 250 300 350 400 5 10 15 20 25 30 35 40 Lift-off velocity (m/s) Diluent concentration (%) CO2-H2 mixture CH4-H2 mixture 5 10 15 20 25 30 35 100 300 500 700 900 1100 Lift-off height (mm) Jet velocity (m/s) H2-CH4 lift off at 60l/min H2-CH4 lift off at 40l/min H2-CH4 lift off at 20l/min H2-CO2 lift off at 60l/min Pure H2