Proceedings of theInternational Conference on Power Engineering-09(ICOPE-09) November 16-20, 2009, Kobe, Japan

Heat and Reaction Characteristics of Multistage Alcoholic-Fuel Reformer(2nd Report: Velocity and Radical Chemiluminescence Measurements)
Yasuhiro RAI1, Kazuya TATSUMI1,2, Keisuke KUWABARA1 and Kazuyoshi NAKABE1,2
1. Dept. of Mech. Eng. and Sci., Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan
2. Adv. Research Inst. Fluid Sci. and Eng., Kyoto University

ABSTRACTThe present study discusses the heat and reaction characteristics of the multistage
alcoholic-fuel reformer. Gas temperatures, exhaust gas components and radical chemiluminescence intensities
were monitored in the reformer. In the single-stage case, temperature level inside the reactor and decomposition
ratio of CH3OH, , were decreased with an increase in equivalence ratio, ≥. In contrast, higher  resulted
in lower OH-radical chemiluminescence intensity inside the reactor. In the double-stage case that a portion of the
air was supplied to the secondary port, a slight increase in the H 2 concentration was observed, and an excessive
increase of local temperature was avoided. These results show the double-stage air supply is effective to control
the temperature distribution and avoid an undesired hot-spot in the reformer without causing a significant change
in the components of the product gas.
Keywords: Compact fuel reformer, Hydrogen production, Multistage reactor, Temperature measurement,
Chemiluminescence intensity measurement
1. INTRODUCTION
Hydrogen, which is called one of the most promisingenergy sources, can be used for highly efficient energy
systems such as fuel cells and hydrogen engines. Althoughlarge-scale industrial process of hydrogen production has
been established in chemical plants, time is required until theinfrastructures of hydrogen distributions and storages are
introduced into the society. Meanwhile, on-site hydrogenproduction is essential for future distributed power supplying
systems. A multistage compact fuel reformer, which iscomposed of multiple ports for step-by-step supply ofreactants, air, and water vapor, was applied to producehydrogen from alcoholic fuels and examined in terms of heatand reaction characteristics. Reactants were supplied partiallyto the reformer from several ports in order to perform
effective and quick control of local heat balance andtemperature inside the reformer, which is believed to result in
the enhancement of reforming effectiveness and the
reduction of undesired exhausts such as soot or CO [1-5].
In this paper, results of a prototype multistage tube
type reformer are reported. Methanol was used as fuel inthe both previous and present experiments [5]. Alcoholic
fuel is relatively easy to transport and store since it ischemically stable and is in liquid phase under normal
temperature and pressure. It is, therefore, considered to besuitable for compact energy supply systems with an output
of several kilo watts [6]. No catalyst was applied to thereformer in the studies. It is reported that the thermal
condition of the reformer greatly affects the reforming
performance in either case: with and without catalyst [7, 8].
Therefore, as the initial step of evaluating the multistage
reformer, the experiment was conducted without insertingthe catalyst to discern the degree of effects of multiplying
the reaction stages from those of the catalyst characteristics.
Reforming gas temperatures, exhaust gas components,
and radical chemiluminescence intensities were monitored in
the reformer. OH-radical chemiluminescence is measured to② Fuel injection port ④ Stainless tube bundle⑤ Thermocouples③ Baffle plate① Primary air port

Evaporator

Reactor⑥ Electric heater⑦ Second-stage air port

15mm
100mm

200mm
130mm

65mm 50mm

r
28mm

e

O

xi

ⅱ

ⅲ

ⅳ

ⅴ

ⅵ

ⅶ

ⅷ

ⅸ

Fig. 1. Schematic view of the reformer (evaporator &reactor).

(a) Baffle plate(b) Tube bundle
Fig. 2. Elements of the reformer.

evaluate the occurrence of the gas reaction. Flowcharacteristic inside the reactor was evaluated by LDV
measurement inside the acrylic pipe of the same dimensions
as the reformer. The effects of equivalence ratio and reactant
flow rate on the reforming characteristics are discussed,
mainly focusing on the partial oxidation reaction (POR).
2. EXPERIMENTAL SETUP
Figure 1 illustrates the schematic and cross-sectionalviews of the reformer. As shown in the figure, the reformer

r

Air
flow

O

2 . 32

1 . 62

1 . 96Bx

x / D = 1 . 25

was composed of two parts, i.e., the evaporator and reactor.
The evaporator was made of a galvanized steel pipewith inner diameter and length of 28mm and 200mm,
respectively. A fuel supply port was located at the sidesurface of the evaporator, on which an injector with electric
valve was mounted. An electrical rectangular signal wassent from a function generator (Yokogawa; WE500,
WE7281) to this injector to control the valve opening.
Therefore, flow rate of the fuel jet was controlled byadjusting the frequency and duty ratio of the signal to acertain value. An air supply port was set at the upstream
end of the evaporator. Air supplied to this port was provided
from a compressor, and the flow rate was controlled byrotameter and valve (Kofloc; RK1250). In the upstream anddownstream areas adjacent to the fuel supply port, electricband heaters (Sakaguchi E.H. Voc.; BH3430) were wrappedaround the evaporator pipe. This heater, powered by a
voltage slider (Yamabishi; V-130-3), raised the temperatureof the evaporator wall up to specified °C. Thus, the fuelwhich is injected from the fuel supply port, impinged on the
inner wall of the evaporator, and was vaporized there. The
vaporized fuel mixing with the air flowing from the
upstream air supply port, was then supplied to the reactor
through a baffle plate.
As shown in Fig. 1, this baffle plate was locatedbetween the evaporator and reactor. Multiple holes were
drilled in the 12mm-thick stainless disk. The configurationof the holes is shown in Fig. 2(a), i.e., a 5.5mm-hole was
located at the center of the disk and six holes with 2mm
diameter surrounded the center one. This multi-hole baffle
plate was expected to enhance the mixing between thevaporized fuel and air, and to prevent backfire from thereactor to the evaporator.
The reactor was made of a stainless steel pipe 28mm
in diameter and 500mm in length. In the areas of70≤x≤110mm and 120≤x≤160mm, bundles of 19 stainlesstubes (each tube inner diameter = 4mm, length = 40mm;
see Fig. 2(b)) were inserted in the reactor. These tube
bundles were expected to enhance the reaction efficiency
and also maintain a stable reaction under high equivalence
ratio by increasing the heat transfer at the tube walls. Band
heaters (Watlow; MB01E1AB3005) were attached to thepipe sidewall at each location identical to where the tube
bundles were inserted. These heaters were powered by a
voltage slider in the same way as those in the evaporator,
and the pipe wall was preheated before the experimentstarted.
Several loading ports were applied to the sidewalls of
the evaporator and reactor at the locations shown in Fig. 1.
Probes for temperature measurement made of K typethermocouples were inserted into the pipe through these
ports. This probe was a two-hole ceramic tube (tube outer
diameter = 3mm) having the weld spot of the thermocouple
wires exposed at the tip. To protect the exposed parts of thethermocouples from the flame and reactive gas, and also toprevent any catalysis effects, the thermocouples were
coated by silica-particles generated by burning the town gas
into which Hexamethyldisiloxane was mixed. The signals
from the thermocouples were recorded by a personal
computer through a digital multi-thermometer (Keyence;
NR-1000). The sampling rate and accuracy of thetemperature measurement was 1s and ±1°C, respectively.
Additional air was also supplied through these ports
to the reactor operated in the way of multistage reforming.
The end of the air-feed tube was located at the central axis

φ 28
A

A'
B'

Stainlesstube bundle

Baffleplate

Fig. 3. Cross-sectional
measurement points.
50

ReactorCoolant
water flow

view
14

Windowglass
Coolant
unit

of
5

the
30

LDV

velocity

10

PhotomultiplierPlanoconvex lenses
Band pass filter

Fig. 4 Cross-sectional view of the optical measurement
probe.

of the reactor, and two holes were drilled at the sidewall of
the tube tip, from which the air was injected to the reactor
in the radial direction.
Gas sampling for gas component analysis was
conducted by inserting a gas sampling probe into one of theloading ports. The probe was made of stainless tube 3mm indiameter. The position of the tip end was set at the reactor
centerline, and the gas was collected with this probe
through a 0.3mm nozzle by connecting the tube to a
vacuum-collecting chamber. The collected gas was thensupplied to a gas chromatograph (Shimadzu; GC-8A)
through a filtering chamber packed with silica gel, by
which water and unburned methanol were removed fromthe gas. A component detector on the basis of TCD(Thermal Conductivity Detector) method was applied to thegas chromatography. The column (Shinwa chem.;
Shincarbon ST) mounted in the chromatograph oven wascalibrated for H2, N2, O2, CO, and CO2 gases. Ar gas wasused as the carrier gas.
Measurements
using
LDV
(LaserDoppler
Velocimetry) were also conducted to evaluate the velocity
field in the reactor. In this case, a test section different fromthat used in the aforementioned experiment accompanying
reactions and temperature measurements was applied. An
acrylic pipe of the same size as the reactor shown in Fig. 3
was made by which an optical measurement from the
sidewall was available. This pipe was attached to the same
evaporator and baffle plate shown in Fig. 2. The air with theflow rate equal to the total volume of the air and fuelsupplied to the evaporator in the reaction experiment wasprovided to the upstream end of the evaporator. In the
upstream of the evaporator, a particle generator (TSI; six-jet
atomizer 9306) was attached and tracing particles of oil mist
(DEHS: Di-Ethyl-Hexyl-Sebacate C26H50O4, nominal
diameter = 1m) was mixed in the air. In the optical systemof the LDV, the laser produced by an argon-ion laser system(Spectra Physics; model 2017L-AR) having a wavelength of
514.5nm was used together with a beam splitter coupled witha Bragg cell to detect backward flows. The Doppler burst
signals from the back-scattering light of the particles wererecorded and analyzed by a signal processor (DANTEC;BSA F50), which was linked to and controlled by a personal
computer.

For evaluating the reforming reaction activeness, an
optical probe, shown in Fig. 4, was designed to measure
OH-radical chemiluminescence intensity. This probe wascomposed of an optical window, two plano-convex lenses, anarrow band pass filter (Edmund optics; CW = 334nm,
FWHM = 10nm) and a photomultiplier (Hamamatsu;
H5783-03). The optical window and each lens were madeof thermal quartz glass so that OH-radicalchemiluminescence light which is in ultraviolet band canpenetrate through with little attenuation. The focal point ofobservation can be adjusted by changing the distance
between two lenses ranging from 30mm to 50mm. To avoid
excess heat conduction from the reactor to the optical probe,
water cooling module was attached to this probe.
Micro-current
amplification andcurrent-to-voltage
conversion were conducted to detect weak optical signals
with the photomultiplier and record them by PC via A/Dconverter.
The procedure applied in the reaction experiment is
described in the following. The evaporator and reactor
pipes were first heated by the electric band heaters so thatthe temperatures measured at the locations of x/D=−5.0,
upstream of the baffle plate rear surface, and x/D=4.11
reached 200°C and 600°C, respectively. Then, the heaters
attached to the reactor were turned off and the fuel and air
were supplied to the reformer. Note that the heaters of theevaporator continued to be powered during the experimentand the temperature inside the evaporator was kept at about
200°C.
3. EXPERIMENTAL CONDITIONSAs described above, experiment was carried out withsingle-stage and double-stage reformers.
Table 1 shows the conditions of the experiment of thesingle-stage reformer. In this case, the fuel and air wereboth supplied to the reactor from the evaporator through thebaffle plate, which means that no air was injected from the
sidewall of the reactor in this case. Qair and Qfuel are thevolume flow rates of the air and fuel fed to the evaporator,
respectively. Note that Qfuel represents the volume flow rateof the fuel in liquid form. 1 is the equivalence ratio basedon the complete oxidative reaction. The stoichiometric ratioof the POR, therefore, is 1=3. qe is the output power of theelectric heater attached to the evaporator. As shown in Table
1, Qfuel was changed under four conditions, and for each
Qfuel, Qair was varied in the range of equivalence ratios,
3.0≤1≤7.0.
In Table 2, the conditions of the experiment carriedout for the double-stage reformer is shown. In this case,additional air was fed to the reactor at the location between
the two tube bundles, x/D=4.11. The experiment was
conducted under three conditions of Qfuel. In regard to each
Qfuel, air was supplied to the evaporator and reactor at themass flow rates of Qair1 and Qair2, respectively. The total
amount of air provided to the reactor, Qtotal=Qair1+Qair2, waskept constant in each Qfuel case, and the ratio of Qair2 to Qair1(=Qair2/Qair1) was changed. Therefore, the equivalence
ratio at the first stage, to which fuel and air were supplied
from the baffle plate, was varied in the range of 4.5≤1≤7.0.
Note that the total equivalence ratio of the whole reformer,
total, calculated from the values of Qtotal and Qfuel, was kept
at 4.0.
4. RESULTS AND DISCUSSION
Before moving on to the discussion, several parameters

Table 1. Flow rate conditions in singe-stage case.
3
Qfuel [cm /s]
qe [W]
case
1
ss_f1
0.066
112
3.0, 3.5, 4.0, 4.5,
ss_f2
0.092
151
5.0, 5.5, 6.0, 6.5,
ss_f3
0.122
201
7.0
ss_f4
0.145
270
Table 2. Flow rate conditions in double-stage case.
3
Qfuel [cm /s]casetotal
1
ds_f1
0.066
(4.0),
ds_f2
0.092
4.0
4.5, 5.0, 5.5,
6.0, 6.5, 7.0
ds_f4
0.145

 =Qair2/Qair1(0.0),
0.125,0.25,0.375,
0.50, 0.625, 0.75

qe [W]
112
151
270

used for evaluating the performance of reformer are
introduced here.
In the present study, the quantity of the consumed
methanol cannot be measured directly due to the propertiesof the column applied to the gas chromatograph and the silica
gel chamber, which collects water and unreacted methanol.
Therefore, these quantities were estimated from theconcentrations of the other gases included in the exhaust gas.
Since the summation of the concentrations of H2, N2,
O2, CO and CO2 in the exhaust gas was 100±2%, the major
components of the gas was expected to be these five species
plus water and unreacted methanol that were collected by thesilica gel chamber. When paying attention on the carbon
atoms, the components possessing carbon atoms among the
products were found to be CO, CO2 and unreacted methanol.
Therefore, the quantity of the reacted methanol can becalculated using the concentrations of CO and CO2 in theexhaust gas. Therefore, the methanol conversion ratio, , isdefined as follows:

M CH 3OH , consumed
M CH 3OH , supplied
YCO  YCO2
YN 2





M CO  M CO2
M CH 3OH , supplied

(1)

M N2
M CH 3OH , supplied

where MX is the molar flow rate of the X component in theexhaust gas, and YX is the X’s concentration.
To evaluate the production efficiency of eachcomponent, the production rate of component X against 1molof methanol supplied, X, is defined as follows:X MXM fuel, supplied(YX / YN 2 ) M N 2(2)

M fuel, supplied

In calculating the production rate of H2O, H2O, it is assumed
that all hydrogen atoms originated from the reacted methanol
are used in producing H2 and H2O. Thus, H2O can beobtained by the following equation:
 H O  2   H
2

(3)
2

4.1 Single-stage reformer
Figure 5 shows the streamwise temperature
distributions along the centerline of the reactor in cases
ss_f1~ss_f4. In Fig. 5(a), the temperature at x/D=4.11 takes1=4.0,

1=6.0,1=7.01=5.0oTemperature, T [ C]

1=3.0,800

tube bundles

tube bundles

600
400
200
2 4 6 8 10 12 14 16 18oTemperature, T [ C]

0 2 4 6 8 10 12 14 16 18

x/D(a) case ss_f1

x/D(b) case ss_f2

tube bundles

tube bundles

800
600
400
200

2 4 6 8 10 12 14 16 18

2 4 6 8 10 12 14 16 18

x/Dx/D(c) case ss_f3(d) case ss_f4
Fig. 5. Streamwise temperature distributions along reactor
centerline (case ss_f1~f4).
0.5

x/D = 2.32

x/D = 4.11

x/D = 5.89

400

400

400

r/D

0.4
0.3
0.2
0.1
0.0
200

600 200

600 200

600oTemperature, T [ C]
Fig. 6. Radial temperature distributions in the reactor at
x/D=2.32, 4.11 and 5.89 (case ss_f2, 1=5.0).
0.5
x/D =1.25

x/D =1.62

x/D =1.96

x/D =2.32

r/D

0.4
0.3
0.2
0.1
0.0 0

1

2

3

0

1

2

3

0

1

2

3

0

(a) cross section A-A'

1

2

3

U [m/s]0.5
x/D =1.25

x/D =1.62

x/D =1.96

x/D =2.32

0.4

r/D

its maximum value in the case of 1=3.0 and the maximum
temperature decreases as 1 increases. The same trend fortemperature distribution can be seen in the other locations orin the other fuel flow rate cases. This is due to the fact thatwhen 1 becomes small, the oxygen supply rate to themethanol increases that results in promotion of theexothermic reaction of oxidation and increase of thetemperature of the reforming gas.
The streamwise temperature distributions show thesimilar characteristic in all cases, i.e., a maximum peak oftemperature is obtained at the location of x/D=4.11 and thetemperature level falls down in the downstream region.
Therefore, it is presumed that most of the exothermic
reactions take place at the area of stainless tube bundles.
Cross-sectional temperature distributions were alsomeasured by traversing the thermocouple probe in radial
direction. Figure 6 shows the results obtained in case ss_f2 of1=5.0. The streamwise locations of measurement were
x/D=2.32, 4.11 and 5.89 that correspond to the inlet of thefirst tube bundle, the middle point between two tube bundles,
and the outlet of the second tube bundle, respectively. Figure
7 shows the spanwise distributions of the streamwise velocity
at x/D=1.25, 1.62, 1.96 and 2.32, located in the area between
the baffle plate and the first stainless tube bundle, obtainedby the LDV measurements. Figure 7(a) and (b) shows theresults of the plane crossing the center and surrounding holesof the baffle plate ((a) cross-section A-A’; see Fig. 3), and theplane crossing the middle of the surrounding holes ((b)
cross-section B-B’), respectively.
In Fig. 6, at the position of x/D=2.32, corresponding to
the inlet of the first tube bundle, the minimum peak of thetemperature is observed at the centerline, and higher
temperature near the sidewall. In Fig. 7(a), two peaks of U
are observed at the locations of r/D=0 and 2.85. In Fig. 7(b),a maximum peak is obtained at r/D=0. These peak locations
correspond to the areas in the downstream of the center andsurrounding jets. Since the center nozzle has a larger
diameter than the surrounding ones, a jet of large flow rate
is issued through the center nozzle. The lower temperature
obtained at the centerline is, therefore, attributed to thiscenter jet blowing the premixed fuel gas produced from theevaporator. On the contrary, the reactor wall temperature isincreased by the heat generated in the downstream of thereactor. The gas near the wall is, hence, heated and a higher
temperature is obtained compared with the gas near thecenterline.
As shown in Fig. 7(a), the surrounding jets convect inthe downstream, and their velocity decreases as x/Dincreases. Near sidewall, flow with negative velocity isobserved in Fig. 7(b). These results indicate that a flow of
three-dimensional structure was generated in thedownstream area of the baffle plate, and a circulation canbe generated near the sidewalls due to the interaction
between the center jet and surrounding jets. Consequently,
most of the premixed fuel gas enters the inlet of the firsttube bundle in the area near the reactor centerline.
On the other hand, at the outlet of the tube bundles,
i.e., x/D=4.11 and 5.89 shown in Fig. 6, the temperaturetakes a maximum peak at the reformer centerline anddecreases along the radical direction. The temperature
increase obtained between x/D=2.32 and x/D=4.11 implies
that the reaction mainly starts not in the area between thebaffle plate and the first tube bundle, but inside the firsttube bundle. Furthermore, since the maximum peaks of U at
x/D=2.32 and T at x/D=4.11 are located at the centerline,

0.3
0.2
0.1
0.0 0

1

2

3

0

1

2

3

0

1

2

(b) cross section B-B'

3

0

1

2

3

U [m/s]Fig. 7. Cross-sectional distributions of the streamwise
velocity in the downstream area of the baffle plate (identicalflow condition with case ss_f1, 1=5.0).

CH3OH + M → CH3+OH HR,D=386.0kJ/mol(3)

Held and Dryer [9] proposed that this reaction predominates,
accounting for 75% to 90% of the total decomposition
reaction of methanol. Since this reaction is endothermic
reaction, it is presumed that OH-radical produced throughthis reaction is sensitive to the gas temperature. As mentioned
before, gas temperature increases in accordance with thedecrease of equivalence ratio . Namely, the increase of 
resulted in the decrease of exothermic heat per volume,
which caused smaller methanol decomposition ratio andlower OH-radical luminescence.
Figure 9 shows the relation between the concentrationsof components in the exhaust gas and equivalence ratio, 1.
The concentration of O2 is less than 0.2% in all cases
indicating that the supplied O2 were totally consumed in thereaction. The concentration of H2 increases as 1 increases in
the region of 1<5.0. However, in 1>5.0, YH2 is almost
constant or, in some cases, slightly decreases as 1 increases.
The aforementioned gas concentrations are the values
directly obtained from the gas component analysis of theexhaust gas. Therefore, effects of unburnt methanol andwater removed from the gas are not sufficiently considered.
In the following discussion, the trends of parameters  andX described in Eqs. (1) and (2) are discussed.
Figure 10 shows how 1 affects the conversion ratio of
methanol, .  decreases linearly as 1 increases. When 1 issmall, larger reaction heat is released due to the increase of
the supplied O2 rate. The temperature inside the reactor,
therefore, increases as described in Fig. 5, and thedecomposition and fully-oxidation reactions of methanol
become more active. On the contrary, under larger 1conditions, the air flow rate is reduced, which incurs afuel-rich condition in the reactions including POR and larger
heat loss at the reactor wall.
The production ratio, X, is shown in Fig. 11. In theregion of 1<5.0, H2 slightly increases as 1 increases, anddecreases in the region of 1>5.0. Hence, the maximum
production ratio of H2 is obtained approximately under thecondition of 4.0<1<5.0. When 1 is small, a large
conversion ratio, , is obtained as shown in Fig. 10. However,oxidization of H2 to H2O also becomes active due to the high80

1=3.0Concentration Y [%]Voltage [V]

0.20
0.15
0.10

1=4.00.05
0.00

1=5.0
0

100

200

300

400

500

60

YO2

YCO

YCO2

YN2

20

0

600

YH2

40

Time [s]

3

4

5

6



7

Fig. 8. OH-radical
Fig. 9. Relation between gas
chemiluminescence intensity for concentration and equivalence
the cases of equivalence ratios ratio (case ss_f4).
=3.0, 4.0 and 5.0.
1.4
1.0

1.2
1.0

0.6

0.8

H2
CO

H2O
CO2

6





0.8



the reaction is expected to occur in this area.
In the present study, chemiluminescence intensity wasmeasured by the optical probe, as explained in the previous
section, for three conditions of single-stage case (equivalence
ratios 1=3.0, 4.0 and 5.0). Measurement points were
x/D=2.32, 4.11 and 5.89, all of which were situated on thecentral axis of the reactor. Among these positions, signal wasstrong enough to detect by the photomultiplier only at
x/D=4.11. Figure 8 shows the time histories of observed
voltage intensity for each equivalence ratio, 1=3.0, 4.0 and
5.0. In this figure, the corresponding OH-radicalchemiluminescence intensity is shown, monitored for 600
seconds after the temperature inside the reactor became
steady state. A maximum value of voltage was recorded forequivalence ratio 1=3.0 at x/D=4.11. 1=3.0 indicates the
stoichiometric mixture of POR and the minimum
equivalence ratio in the present study. For 1=4.0, lower
voltage was observed compared to 1=3.0 at the same
position. For 1=5.0, voltage output was too small to beobserved. Therefore, lower equivalence ratio resulted instronger luminescence intensity among these 1 conditions.
This can be explained by the following reaction [9]:

0.6
0.4
0.4
0.2
0.0

0.2
3

4

5

6



Fig. 10. Methanol conversion
ratio (case ss_f4).

7

0.0

3

4

5

7

Fig. 11. Mole production rates(case ss_f4).

temperature which leads the concentration of H2 to decrease
as shown in Fig. 9. On the contrary, under larger 1 condition,
the conversion ratio of methanol becomes small. Thus, a
trade-off matter exists between  and YH2. This is believed tobe the reason why the maximum peak of H2 is obtained at
4.0<1<5.0
To integrate all the results obtained through thetemperature, velocity and chemiluminescence measurements,
it is presumed that the reforming reactions start in the firststainless tube bundle, and the most of the reactions take place
upstream of the end of the second tube bundle. Furthermore,
the temperature takes its maximum value at the centerline of
the reactor, which means intensive reaction takes place at thecenter region of the reactor.
Based on these results mentioned above, it is effective
to supply the secondary air at the position of x/D=4.11, where
the primary important reforming reaction seems active.
4.2 Double-stage Reformer
Figure 12 shows the streamwise distributions of thetemperature along the reactor centerline obtained in thecases of double-stage reformer. The results of case ss_f4 of1=4.0 are included in the figure for comparison. The
parameter  is defined as the ratio of the air flow rate
supplied to the second and first stages.
At x/D=4.11, the temperature decreases as  increases.
In the downstream area (x/D6), on the contrary, thetemperature increases as  increases. Since the total amountof air supplied to the reactor in cases ds_f1, ds_f2 and ds_f4
was fixed at the constant value corresponding to case ss_f4,
an increase of  implies the increases of 1 and air flow rate
supplied to the second stage. In the double-stage reformer,
the air and fuel were supplied to the first stage in the same
way as in the single-stage case, and a common reaction
characteristic was expected to take place. The gas
temperature was, therefore, reduced under larger 1condition due to the fuel rich condition obtained in the firststage of the reactor as mentioned in the previous section.

oTemperature, T [ C]case ss_f4, 1=4.0
case ds_f4, 1=5.0,  =0.375
case ds_f4, 1=6.0,  =0.50
case ds_f4, 1=7.0,  =0.75

800
600
400

tube bundles

200
0

2

4

6

8

10

12

14

16

18

x/D
Fig. 12. Streamwise temperature distributions (comparison ofcases ss_f4 and ds_f4, total=4.0).
H2

1.4

CO

Single-stage

1.2

H2O

CO2



1.0

temperature level for practical use were obtained by thereformer.
2. A better performance was obtained under the conditionsof 1=4.5~5.0 than under the stoichiometric value ofpartial oxidation, 1=3, in the present reformer.
3. An optical measurement in the reformer was conductedandthecorrelation
betweenOH-radicalchemiluminescence intensity and the gas temperature
condition was confirmed.
4. A maximum peak existed in the H2 production rate persupplied fuel in relation with 1. This is due to thetrade-off between the methanol conversion ratio, , andH2 concentration.
5. In the double-stage case, temperature control of thereformer was possible without deteriorating the reforming
efficiency. Moreover, in some cases, increase of the H2
production rate by 10% was obtained in this casecompared with the singe-stage case.

0.8
0.6
0.4
0.2
0.0

0.0

0.2

0.4

0.6

0.8


Fig. 13. Relation between  and X (case ds_f4).

On the other hand, as indicated in Fig. 10, larger
amount of unreacted methanol enters the second stage inassociation with the increase of 1. In combination with theadditional air injected to the second stage, a more active
reaction, therefore, takes place in the downstream. This isbelieved to be the main reason why a higher temperature is
obtained in case ds_f4 in the downstream area.
Figure 13 illustrates how  affects X. The results ofthe single-stage case are included in the figure forcomparison. In case ds_f4, a slight increase of H2 isobserved as  increases in the area of 0.2≤≤0.6, and the
maximum difference between the results in cases ss_f4 andds_f4 is approximately 10%. This implies that the
production ratio of H2 is not largely affected by increasing
the reformer stage from single- to double-stage; at least theperformance of double-stage case is not inferior to that of
the single-stage case in the present study.
Although a noticeable improvement was not achieved,in terms of the reaction efficiency, by introducing the
double-stage reforming, the results obtained in Figs. 12 and13 indicate the possibility of controlling the temperature of
the reformer by multiplying the reaction stages without
incurring a serious deterioration of the reforming efficiency.
This is important since the reformer can be protected fromthermal fatigue by applying an appropriate gas supply ratio
and preventing the generation of a significant increase of
local temperature.
5. CONCLUSIONSIn the present article, single- and double-stage
methanol fuel reformer was experimentally evaluatedparticularly on the basis of the thermal and reaction
characteristics. The major conclusions obtained are listed in
the following.
1. A multistage reformer consisting of evaporator andreactor was fabricated and operated under the conditionsof varying the equivalence ratio, 1, in the range of
3.017.0. Hydrogen production and a suitable

6. REFERENCES
1. A. L. Dicks, Hydrogen Generation from Natural Gas for
the Fuel Cell Systems of Tomorrow, J. Power Sources,
61 (1996), pp. 113-124.
2. H. Marsh and D. Thingarajan, AIChE Ammonia Safety
Symposium, (1992).
3. M. Dunster and J. Korchnak, Production of Synthesis gas
from Hydrocarbonaceous Feedstock, Eur Patent No.
303438, (1989).
4. T. Calcott and T. Deague, US Patent No. 4 042 344，
(1977).
5. K. Tatsumi, K. Kuwabara, Y. Rai and K. Nakabe, Heat
andReaction
CharacteristicsofMultistage
Alcoholic-Fuel Reformer, Proc. 18th Int’l Symp.
Transport Phenomena (ISTP-18), (2007), pp. 847-854.
6. J. Larminie and A. Dickes, Fuel Cell Systems Explained,
John Wiley & Sons Inc. (2003).
7. B. Li, S. Kado and Y. Mukainakano, Temperature Profile
of Catalyst Bed during Oxidative Steam Reforming of
Methane over Pt-Ni Bimetallic Catalysts, Applied
Catalysis A, General 304 (2006), pp. 62-71.
8. C. Pan, R. He and Q. Li, Integration of High Temperature
PEM Fuel Cells with a Methanol Reformer, J. Power
Sources, 145 (2005), pp. 392-398.
9. T. J. Held and F. L. Dryer, A Comprehensive Mechanism for
Methanol Oxidation, Int’l J. Chemical Kinetics, 30 (1998),
pp. 805-830.
ACKNOWLEDGEMENT
This work is partially supported by the Mazda
foundation, General Sekiyu K. K. research foundation, andJapan Society for the Promotion of Science. The authors
would like to gratefully acknowledge their support.