Experimental analysis of the effects of hydrogen addition on methane combustion, Sci ...
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INTERNATIONAL JOURNAL OF ENERGY RESEARCH
Int. J. Energy Res. 2012; 36:
643 647
–
Published online 7 February 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/er.1822
Experimental analysis of the effects of hydrogen
addition on methane combustion
Mustafa
˙
lbas
1,
,y
and
˙
lker Yılmaz
2
-
1
Faculty of Technology, Department of Energy Systems Engineering, Gazi University, 06500, Ankara, Turkey
2
College of Aviation, Department of Airframe and Powerplant, Erciyes University, 38039, Kayseri, Turkey
SUMMARY
This paper presents gas emissions from turbulent chemical flow inside a model combustor, for different blending
ratios of hydrogen–methane composite fuels. Gas emissions such as CO and O
2
from the combustion reaction were
obtained using a gas analyzer. NOx emissions were measured with a NOx analyzer. The previously obtained flame
temperature distributions were also presented. As the amount of hydrogen in the mixture increases, more hydrogen
is involved in the combustion reaction, and more heat is released, and the higher temperature levels are resulted.
The results have shown that the combustion efficiency increases and CO emission decreases when the hydrogen
content is increased in blending fuel. It is also shown that the hydrogen–methane blending fuels are efficiently used
without any important modification in the natural gas burner. Copyright
r
2011 John Wiley & Sons, Ltd.
KEY WORDS
hydrogen; hydrogen–methane blending fuel; emission measurements; model combustor
Correspondence
*Mustafa
˙
lba
-
, Faculty of Technology, Department of Energy systems Engineering, Gazi University, 06500, Ankara, Turkey.
y
E-mail: ilbas@gazi.edu.tr
Received 25 August 2010; Revised 11 November 2010; Accepted 27 December 2010
1. INTRODUCTION
from a swirl-stabilized combustor under unconfined
flame conditions in methane–air premixed flames.
Earlier studies showed that adding a small amount of
hydrogen into natural gas could improve the combus-
tion and reduce the exhaust emissions [5–10].
Hydrogen blending effects on flame structure and
NO emission behavior have been numerically investi-
gated by Park et al. [11] using detailed chemistry in
methane–air counterflow diffusion flames. A compu-
tational study to investigate the effects of hydrogen
addition on methane–air flames at different conditions
has been performed in the study of Chen [12]. Zhao
et al. [13] have studied experimentally the effects of
hydrogen on methane combustion characteristics in a
quartz reactor. They measured gas emissions at the
exit of the reactor. Zhang et al. [14] have performed
an experimental research to study hydrogen-assisted
catalytic combustion of hydrocarbon in a microtube.
Their experimental results showed that the added
hydrogen acts as an assistant for ignition and expands
the range for methane steady burn. Experimental work
has been conducted on a hydrogen–diesel dual fuel
engine by Saravanan and Nagarajan [15]. The above
literature review reveals an inadequate understanding
of emission distribution by fuelled hydrogen–methane
blending in flame region. Besides this, gas emissions
from different hydrogen–methane blending in flame
Energy is essential to human welfare and quality of
life. However, energy production and consumption
generate significant environmental problems that can
have serious consequences and even put at risk the
long-term sustainability of the planet’s ecosystems [1].
The world energy demand is increasing more rapidly
due to increasing population of the world and techno-
logical advances. Most of the world energy demand is
supplied by fossil fuels (coal, oil and gas). However,
these fossil fuels have limited sources. Scientists and
researchers around the world are currently working
hard to find new sources of energy for the future.
Much research has been carried out over the past
years on emissions from hydrocarbon combustion
process. Experimental studies on the combustion of
hydrogen–methane blending fuel are less than hydro-
carbon fuel combustion in combustion literature.
Medwell et al. [2] reported the measurements in
turbulent non-premixed CH
4
/H
2
jet flames issuing into
a heated and highly diluted co-flow. A laboratory-scale
burner has been used by Derudi et al. [3] to investigate
the sustainability of mild combustion with the coke
oven gas, an industrial byproduct mainly constituted by
methane and hydrogen (CH
4
/H
2
40/60% by volume).
Kim et al. [4] investigated the effect of hydrogen addition
643
Copyright
r
2011 John Wiley & Sons, Ltd.
M.
˙
lba
-
and
˙
. Yılmaz
Effects of hydrogen addition on methane combustion
region have not been investigated using an industrial
natural gas burner, so do this study. Hence, present
study is intended to investigate experimentally emis-
sion distributions using observed data in flame region.
Air pollution effects of hydrocarbon combustion
have been accelerating the utilization of hydrogen as
an alternative fuel. From the environmental point of
view, the advantage of hydrogen combustion is that it
does not produce the greenhouse gas CO
2
and various
other pollutants including CO.
In our previous studies [5–9], the distributions of
gas emissions including NO, CO and CO
2
were not
obtained and not presented at different radial distance
and along the axis of model combustor. This paper is
the first study of the authors taken data in flame region
and inside of the combustor. The aim of this study is to
determine emission distributions from the combustion
of hydrogen–methane composite fuel in the model
combustor. This paper is the part of an ongoing work.
And so the temperature distributions obtained earlier
were also presented [7].
having different hydrogen percentage are presented
and discussed in this section. Two different hydro-
gen–methane blending fuels including 70% CH
4
-30%
H
2
(called M70H30) and 30% CH
4
-70% H
2
(M30H70)
were used in the study. All performed measurements
were made under atmospheric and standard air inlet
temperature in clean combustion technologies research
lab at Erciyes University, Kayseri, Turkey.
All taken data by measurement tools used in this
experimental study is subject to small errors. During
the experiments, the error in the values of the NO
emission is
3 ppm and, errors in the values of the CO
and CO
2
are
7
0.12%, respectively.
The error in the measurements of temperatures during
the experiments may be estimated by considering the
error in the type of thermocouple used. Such an error
for type R of thermocouple is
7
3.81C. The error in the
values of the volumetric fuel flow is
7
0.128Nm
3
h
1
.
An error analysis for the derivated quantities, such as
thermal power, combustion efficiency, excess air ratio,
is performed. The error analysis results indicate that
the uncertainty is the range of 3–8%. It is clear that
from the above arguments, the errors in the measure-
ments and the derived quantities do not significantly
influence the final results.
The measured radial CO emission distributions for
M70H30, 40 kW thermal power and 70% of excess air
ratio were shown at different axial distances in Figure 2.
Maximum CO emission was measured at the centre
of the combustor for all axial distances while it is
decreasing towards the combustor wall. With decreasing
temperature of gas emission, CO emissions decrease
along the radius of the combustor. Increasing the hydro-
gen content in blending fuel has resulted in significant
increase in flame temperature, leading to fast chemical
conversion of CO to CO
2
through CO oxidation.
Figure 3 gives the influence of fuel type on CO emis-
sions at 70% of excess air ratio in hydrogen–methane
blending fuels. As can be seen from this figure, CO
emission level of 30% CH
4
-70% H
2
is less than that of
70% CH
4
-30% H
2
because of higher hydrogen content
fuel. Also it is shown from this figure that CO emission
decreases gradually towards exit of the combustor.
The effect of varying the fuel type on the NOx
emissions from experiments carried out using 70%
CH
4
-30% H
2
and 30% CH
4
-70% H
2
was presented
in 40 kW thermal power in Figure 4. When using
M70H30 as fuel, the NOx emissions were measured in
the range of 30–40 ppm and 45–70 ppm at the centre of
the combustor in 40 kW of thermal power, respec-
tively. As expected, NOx emission increases with the
increase of hydrogen amount in the fuel mixture due to
more energy addition to the fired system.
CO and CO
2
emission distributions for 40 kW
thermal power and 20% excess air ratio were plotted at
different percentage of hydrogen in Figure 5. As seen
from this figure, the CO emission decreases with
increasing the hydrogen percentage because of less
3.5 ppm and
7
7
2. DESCRIPTION OF THE
EXPERIMENTAL PROCEDURE
The combustor used in this study included a conical
entry and a vertical stainless steel combustion chamber,
which is a cylindrical enclosure of 250mm radius and
1400mm length. Two reactant streams emerge from two
separate coaxial jets producing a swirling diffusion
flame. The fuel is injected from the central jet, whereas
the combustion air enters from the outer annular jet.
Gas sampling for the measurement of local mean O
2
,
CO and NOx concentrations was achieved using a
stainless steel water-cooled, water-quenched probe [5].
The measurement instrumentation included an
electrochemical oxygen measuring cell for O
2
measure-
ments, infrared gas analyzer for CO (Siemens Ultramat
23) and a chemiluminescent analyzer (Teledyne Model
200EHIEM) for NOx measurements. The flame tem-
peratures at different locations of the combustion
chamber were measured with R-type thermocouples
that located at different axial distance.
Thermal power values for each experiment were
calculated using reading volumetric flow from flow-
meter (Tecfluid Mod. 6001/Fe). Details regarding the
experiment system and its equipments are reported in
References [5–7]. Schematic diagram of experimental
setup used is given in Figure 1.
3. EXPERIMENTAL RESULTS AND
DISCUSSION
The gas emission distributions such as CO, NOx and
temperature levels of hydrogen–methane blending fuels
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Int. J. Energy Res. 2012; 36:
643 47 ©
–
6
201 John Wiley & Sons, Ltd.
1
DOI: 10.1002/er
M.
˙
lba
-
and
˙
. Yılmaz
Effects of hydrogen addition on methane combustion
Figure 1.
Schematic diagram of experimental setup [6,7].
250
300
250
70%CH4-30%H2
30%CH4-70%H2
y=0.2m
y=0.56m
y=1.36m
200
200
150
150
100
100
50
50
0
0
0
200
400
600
800
1000
1200
1400
0
25
50
75
100
Axial distance [mm]
Radial distance [mm]
Figure 3.
CO emissions measured at different fuel composi-
tions (r
5
0 m, 8.6% O
2
,40kW).
Figure 2.
Radial CO distributions at different axial locations
(M70H30, 40 kW).
hydrogen in the blending fuel. Hydrogen addition to
methane allows the combustor to be operated with lean
mixtures that reduce CO and CO
2
emissions. Also,
lean mixtures provide complete combustion process,
decreasing carbon monoxide emission. The lean
burning conditions give possibilities for very low CO
Int. J. Energy Res. 2012; 36:643
–
647 © 2011 John Wiley & Sons, Ltd.
645
DOI: 10.1002/er
M.
˙
lba
-
and
˙
. Yılmaz
Effects of hydrogen addition on methane combustion
emissions. Similar trend for CO
2
emission can be seen
from the same figure.
Figure 6 depicts the effect of the fuel type on tem-
perature levels along axial distance at the centre of the
combustor in 40 kW of the thermal power. It is seen
that the temperature levels increase as the hydrogen
content increases in the blending fuel. Temperature
levels decrease gradually towards the combustor exit
and reaches minimum value at the combustor exit.
Hydrogen addition to methane also has the potential
of reducing NOx emissions without the limitations
found in other NOx reduction methods. As hydrogen
addition causes large flame stability limit, allowing for
leaner combustion (up to equivalance ratio of 3:2).
In addition to flame stability, hydrogen addition creates
a more consistent fuel composition.
Figure 7 shows how the flame temperature dis-
tributions from the hydrogen–methane blending fuel
combustion are affected by variations in the thermal
power by changing from 40 to 60 kW in the model
combustor. As expected, the higher thermal power
gives relatively higher temperature level in the com-
bustor exit. It is clear that from that figure, the flame
temperature of the hydrogen–methane blending fuels
decreases with increasing the axial distance and sub-
sequently reach the lowest value in the exit of the
combustor.
The combustion efficiency of hydrogen combustion is
very high (near 100%), due to superior combustion char-
acteristics of hydrogen. Hence, the combustion efficiency
of hydrocarbon fuel is relatively low compared hydrogen
combustion. The combustion efficiency may be defined as
theratioofreactedfueltofuelbeforereaction[16].
The effect of hydrogen addition on the combustion
efficiency is also calculated in this study. Depending on
1800
M70H30
M30H70
1600
100
1400
90
70%CH4-30%H2
30%CH4-70%H2
1200
80
1000
70
60
800
50
600
40
400
30
200
20
10
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0
0
200
400
600
800
1000
1200
1400
Distance [m]
Axial distance [mm]
Figure 6.
The effect of fuel type on the temperature levels [7].
Figure 4.
NOx emissions measured at different fuel composi-
tions (r
5
0 m, 8.6% O
2
,40kW).
1800
40 KW
60 KW
1600
14
12
11
CO
CO
2
1400
12
10
1200
9
10
8
1000
7
8
800
6
6
5
600
4
4
400
3
2
2
200
1
0
0
0
30
70
100
0
0.2
0.4
0.6
0.8
1
1.2
1.4
% Hydrogen
Distance [m]
Figure 5.
CO and CO
2
emissions for different percentage of
hydrogen [7].
Figure 7.
The effect of thermal power on the temperature
distributions [7].
646
Int. J. Energy Res. 2012; 36:
643 47 ©
–
6
201 John Wiley & Sons, Ltd.
1
DOI: 10.1002/er
M.
˙
lba
-
and
˙
. Yılmaz
Effects of hydrogen addition on methane combustion
this calculation it is shown that increasing the amount
of hydrogen in the composite fuel causes considerable
increase in the combustion efficiency.
swirling flames. International Journal of Hydrogen
Energy 2009; 34:1063–1073.
5. Ilbas M, Yilmaz I. Investigation of combustion of
hydrogen-methane blending hybrid fuel, Research
Project Report, The Scientific and Technological
Research Council of Turkey, Turkey, January 2008.
6. Yilmaz I. Numerical and experimental investigation
of hydrogen-methane combustion in a model
combustor, Ph.D. Thesis, Erciyes University, 2006
(in Turkish).
7. Yilmaz I, Ilbas M. An experimental study on
hydrogen-methane mixtured fuels. International
Communications in Heat and Mass Transfer 2008;
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8. Ilbas M, Yilmaz I, Veziroglu TN, Kaplan Y.
Hydrogen as burner fuel: modelling of hydrogen-
hydrocarbon composite fuel combustion and NOx
formation in a small burner. International Journal of
Energy Research 2005; 29:973–990.
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hydrogen and hydrogen–hydrocarbon composite
fuel combustion and NOx emission characteristics
in a model combustor. International Journal of
Hydrogen Energy 2005; 30:1139–1147.
10. Choudhuri RA, Gollahalli SR. Combustion charac-
teristics of hydrogen-hydrocarbon hybrid fuels.
International Journal of Hydrogen Energy 2000;
25:451–462.
11. Park JS, Kim JS, Keel S, Cho HC, Noh DS, Kim TK.
Hydrogen utilization as a fuel: hydrogen-blending
effects in flame structure and NO emission behaviour
of CH
4
–air flame. International Journal of Energy
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12. Chen Z. Effects of hydrogen addition on the propaga-
tion of spherical methane/air flames: a computational
study. International Journal of Hydrogen Energy 2009;
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13. Zhao K, Cui D, Xu T, Zhou Q, Hui S, Hu H. Effects
of hydrogen addition on methane combustion. Fuel
Processing Technology 2008; 89:1142–1147.
14. Zhang Y, Zhou Zhou J, Yanga W, Liua M. Effects of
hydrogen addition on methane catalytic combustion
in a microtube. International Journal of Hydrogen
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15. Saravanan N, Nagarajan G. An experimental
investigation on manifold-injected hydrogen as a
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4. CONCLUSION
Experiments were carried out using two different
hydrogen–methane blending fuels (so-called M70H30,
M30H70) in this study. Gas emissions such as CO and
NOx were measured with gas analyzers. The flame
temperatures obtained in the earlier study [7] at different
axial positions of the combustor were also presented.
Blending hydrogen with methane causes consider-
able reduction in temperature levels and thus NO
emissions compared with pure hydrogen combustion.
The results shown that the temperature level increases
and CO emission decreases when the hydrogen content
is increased in blending fuel.
The combustion of hydrogen–methane blending fuel
gives less CO emissions since C/H ratio reduces in
blending fuel. The results obtained are consistent with
previous experimental studies.
The reduction in CO emission (a typical toxic emis-
sion) results in considerable increase in combustion effi-
ciency. It is shown that the hydrogen–methane blending
fuels are efficiently used without any important modi-
fication in the natural gas burner. It is also shown that
hydrogen–methane blending fuels at different blending
ratios can be combusted and used in a model combustor.
ACKNOWLEDGEMENTS
This study was supported by the Scientific and
Technological Research Council of Turkey (TUBI-
TAK), Turkey under Project Number: 105M037. The
authors thank the TUBITAK for the support. This
paper has been presented in the 4th International
Exergy, Energy and Environment Symposium, 19–23
April 2009, UAE and selected for publication in IJER.
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bulent non-premixed jet flames in a heated and diluted
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of industrial hydrogen-containing byproducts.
Industrial and Engineering Chemistry Research
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4. Kim HS, Arghode VK, Gupta AK. Flame charac-
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Int. J. Energy Res. 2012; 36:643
–
647 © 2011 John Wiley & Sons, Ltd.
647
DOI: 10.1002/er
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