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Chemical &
Biological
Engineering.
Experimental Analysis of the Stability parameters of Biogas-Hydrogen fuel blend
Ajulo, Tobiloba [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
Blo
w o
ut
vel
oci
ty (
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
Blo
w o
ut
vel
oci
ty (
m/s
)
Hydrogen concentration (%)
H2-CH4 mixture H2-CO2 mixture
150
200
250
300
350
400
5 10 15 20 25 30 35 40
Lif
t-off
vel
oci
ty (
m/s
)
Diluent concentration (%)
CO2-H2 mixture CH4-H2 mixture
5
10
15
20
25
30
35
100 300 500 700 900 1100
Lif
t-off
hei
gh
t (m
m)
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