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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-CO2 lift off at 60l/min

Pure H2