Aalborg Universitet
Control and experimental characterization of a methanol reformer for a 350W high temperature polymer electrolyte membrane fuel cell system
Andreasen, Søren Juhl; Kær, Søren Knudsen; Jensen, Hans-Christian Becker; Sahlin, Simon Lennart
Publication date:
2011
Document Version
Accepted author manuscript, peer reviewed version Link to publication from Aalborg University
Citation for published version (APA):
Andreasen, S. J., Kær, S. K., Jensen, H-C. B., & Sahlin, S. L. (2011). Control and experimental characterization of a methanol reformer for a 350W high temperature polymer electrolyte membrane fuel cell system. Poster presented at Hydrogen and Fuel Cells Conference 2011, Xcaret, Mexico.
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Control and experimental characterization of a methanol reformer for a 350W Control and experimental characterization of a methanol reformer for a 350W p
high temperature polymer electrolyte membrane fuel cell system high temperature polymer electrolyte membrane fuel cell system g p p y y y
Sø J hl A d * Sø K d K H Ch i ti B k J d Si L t S hli
Søren Juhl Andreasen*, Søren Knudsen Kær, Hans-Christian Becker-Jensen and Simon Lennart Sahlin ø , ø ,
Department of Energy Technology Aalborg University Pontoppidanstræde 101 9220 Aalborg East Denmark Department of Energy Technology, Aalborg University, Pontoppidanstræde 101, 9220 Aalborg East, Denmark p gy gy g y pp g
Introd ction Steam reforming of methanol for a HTPEM f el cell stack Conclusions Introduction Steam reforming of methanol for a HTPEM fuel cell stack g Conclusions
High temperature polymer The experimental system consists of a membrane fuel pump for pumping the 60% (vol ) methanol/ The experimental setup developed is able to High temperature polymer
l t l t b (HTPEM)
The experimental system consists of a membrane fuel pump for pumping the 60% (vol.) methanol/
40% ( l ) d i i d t i t Th i t i iti ll t t h h ti
The experimental setup developed is able to
d d il d f h
electrolyte membrane(HTPEM) 40% (vol.) deionised water mixture. The mixture initially enters an evaporator where heating, conduct detailed measurements of the fuel cells offer many evaporation and superheating is carried out, primarily by the hot fuel cell cathode exhaust air duringy performance of the methanol reformer system.
advantages due to their
p p g , p y y g
normal operation and electrical heaters during start-up The evaporated fuel mixture afterwards performance of the methanol reformer system.
This can provide vital information of the critical advantages due to their
i d ti t
normal operation, and electrical heaters during start-up. The evaporated fuel mixture afterwards
t th th l f h it i f d i t h d i h t i i l CO CO
This can provide vital information of the critical
ti t f h t i l di
increased operating tempera- enters the methanol reformer, where it is reformed into a hydrogen rich gas containing also CO, CO2 operating parameters of such a system, including tures comparedp to similar water and unconverted methanol. The heat required for the steam reforming process is transferred the transient behavior of the different state Nafion-based membrane tech-
q g p
by burning the exhaust fuel cell anode gas in an integrated burner inside the methanol reformer The variable that all play an important role in Nafion based membrane tech
nologies that rely on the
by burning the exhaust fuel cell anode gas in an integrated burner inside the methanol reformer. The
schematics of the experimental setup can be seen in figure 3 variable that all play an important role in predicting the usable hydrogen output by the nologies, that rely on the
d i bili i f li id
schematics of the experimental setup can be seen in figure 3. predicting the usable hydrogen output by the
conductive abilities of liquid Fuel tank Pump Air Burner oxidant system, and just as important; the content of
water. The polybenzimidazole
y j p
different pollutants including CO and residual
tank MFC
T
water. The polybenzimidazole T
(PBI) membranes are different pollutants, including CO and residual
unconverted methanol Such results and models
H t T T T
(PBI) membranes are i ll it d f f
unconverted methanol. Such results, and models
bl t di t thi b h i i t t h
Heater
especially suited for reformer Air P able to predict this behavior are important when
Evaporator
P
systems,y , where highg CO MFC Evaporator P T designing control strategies. The gas
tolerance is required This designing control strategies. The gas
concentrations measured during the tests can by
T P
T T
tolerance is required. This enables the use fuels based on
concentrations measured during the tests can by i fi 7 b l
MeOH+H2O steam 1
G l i T
T T
enables the use fuels based on seen in figure 7, below.
4
1
Gas sample point T
e.g. liquid alcohols. This workg q H2 CO CO2 H2O MeOH Catalyst B 80 x 106 4
presents the control strategies H2,CO,CO2,H2O,MeOH 2 Catalyst
bed Burner
presents the control strategies
of a methanol refoermer for a 70 5
H2 [%]
CO2 [%]
Fuel Cell Stack 2 bed
of a methanol refoermer for a
350W HTPEM FC t Th
CO [ppm]
TOC [ppm]
350W HTPEM FC system. The 33 60 4
H2 B rner f el
system examined is the H2 Burner fuel on [%] n [ppm]
system examined is the Air
Serenergy H3-350 Mobile Fuel/Reformate gas T Gas sample point centratio 50 3 entratiojn
Serenergy H3-350 Mobile Air
B tt Ch i t t d ol. Conc . Conce
Gas sample point Burner fuel
Fuel/Reformate gas
Battery Charger, an integrated
40
Vo
2
Vol.
system, which is shown iny , T
figure 1 B h t 30 1
figure 1. Burner exhaust 30 1
(from bottom of reformer) Figure 3: The different gas/liquid flow paths of the reformer system, also with visible temperature, pressure and gas sample points.(from bottom of reformer)
In order to examine the performance of the system a series of primary input variables are defined
g g q p y , p , p g p p
0 2000 4000 6000 8000 10000 12000
20
Time [s]
0 2000 4000 6000 8000 10000 120000
In order to examine the performance of the system a series of primary input variables are defined,
d t f diff t t diti fi d d i d th i t Th
Figure 7: Gas concentrations of the presented test series. The hydrogen CO2 and CO measurements shown are based on a gas
and a set of different measurement conditions are fixed and imposed on the running system. The hydrogen, CO2 and CO measurements shown are based on a gas sample where all liquid has been condensed i e dry gas measurement
input variables for the system in the presented measurement data are: methanol/water pump flow, sample where all liquid has been condensed, i.e. dry gas measurement.
Whereas TOC shows the methanol content of the wet gas sample.
input variables for the system in the presented measurement data are: methanol/water pump flow,
reformer operating temperature evaporator heating air flow and temperature and burner hydrogen The resulting output gas of the reformer show a
Whereas TOC shows the methanol content of the wet gas sample.
reformer operating temperature, evaporator heating air flow and temperature, and burner hydrogen
fl Th lti t t fl d t ti f th t b i fi The resulting output gas of the reformer show a
h d t t f d 72% i i
flow. The resulting temperatures, flows, and gas concentrations of the system can be seen in figure hydrogen content of around 72%, increasing
4,5 and 7., slightly with increasing temperature. An importants g y c eas g e pe a u e po a
contaminant in the gas is CO which even in contaminant in the gas is CO, which, even in HTPEM f l ll ff t th f It i
Figure 1: The Serenergy H3 350 Mobile
400
MFC Air Evaporator [L/min]
MFC Air Burner [L/min]
400
FC exit Air
Evap pipe HTPEM fuel cell affect the performance. It is seen
Figure 1: The Serenergy H3-350 Mobile
Battery Charger; an integrated 350W 350
MFC Air Burner [L/min]
MFC H2 Burner [L/min]
Pump flow [mL/hr]
350
Evap pipe Reformate output Burner exhaust FC A d it
that the CO content varies between 1-2000 ppm
Battery Charger; an integrated 350W HTPEM fuel cell system fuelled through a
350 FC Anode exit
Burner temperature Reformer temperature
I d h i h
pp to as high as 20000 ppm in the presented
y g
methanol reformer [www.serenergy.dk]. 300 300 Burner/Reformer setpoint
In order to characterize the to as high as 20000 ppm in the presented
measurements These are all within acceptable
performance of the methanol measurements. These are all within acceptable
f h BASF P2100 HTPEM f l ll
250
mL/hr]
250
o C]
performance of the methanol
reformer in the FC system the /min , m 200 o rature [ 200 ranges for the BASF P2100 HTPEM fuel cells
reformer in the FC system, the
f d l i t d Flow [L/ Temper used in the Serenergy H3-350, but depend much
reformer module is separated used in the Serenergy H3 350, but depend much
on the reformer temperature and can easily
150
F
150
from the fuel cell stack, to on the reformer temperature, and can easily
d bl it f t if t l f th t i
100 100
,
enable more precise measure- 100 double quite fast if proper control of the system is
enable more precise measure-
ments of the reformer itself 50 50 not prioritized and taken into consideration. The
ments of the reformer itself, p
same is valid for the unconverted methanol
disconnecting the influence 0 same is valid for the unconverted methanol,
which affect on fuel cell lifetime is still unclear
0 2000 4000 6000 8000 10000 12000
0
Time [s] 00 2000 4000 Time [s]6000 8000 10000 12000
Figure 5: The operating temperatures of the methanol reformer system
g
and limitations imposed by the Figure 4: The different gas/liquid flows of the system during the test which affect on fuel cell lifetime is still unclear.
i
Figure 5: The operating temperatures of the methanol reformer system, including some controller set points
and limitations imposed by the
fuel cell stack Examining ex series.
including some controller set points.
fuel cell stack. Examining ex-
l i l th f t The set of measurements conducted starts out with an initial heating of the system and fuel flow of
clusively the reformer system g y
300 mL/hr where the reformer temperature is settled at 260oC and 270oC in order to evaluate the
Future Work
will also enable the mapping of 300 mL/hr, where the reformer temperature is settled at 260 C and 270 C in order to evaluate the
gas output at this operating point After this the fuel flow is shortly set to 400 mL/hr in order to test
Future Work
will also enable the mapping of
the evaporator independently gas output at this operating point. After this, the fuel flow is shortly set to 400 mL/hr in order to test the evaporator independently
f th f l ll th d h t the effect this operation has on the unconverted methanol in the outlet reformate gas. Afterwards The further work with the presented experimental
of the fuel cell cathode exhaust p g
the temperature is changed to 280oC, where the gas composition is evaluated at 200, 300 an 400 The further work with the presented experimental setup include a detailed analysis of system air, and the capabilities of the the temperature is changed to 280 C, where the gas composition is evaluated at 200, 300 an 400
mL/hr During the last of the examined fuel flows the system was unable to remain at the desired setup include a detailed analysis of system
ti id tif i th d l
, p
burner supplying heat for the mL/hr. During the last of the examined fuel flows, the system was unable to remain at the desired
t t d t hi h h t i t th d li d b th 4 5 L/ i h d hi h operating range, identifying the upper and lower burner supplying heat for the
reforming process The temperature due to higher heat requirements than delivered by the 4,5 L/min hydrogen, which was bounds of operation. This is important in order to reforming process. The used throughout the tests. During the presented tests some of the system states were kept p p
structure the start-up and shut-down scheduling
motivation for this analysis is g g p y p
constant in order to minimize their interference with the captured results The tests shown were structure the start up and shut down scheduling of the system Such an analysis would e g be y
the characterization of the constant in order to minimize their interference with the captured results. The tests shown were
i il d t lid t th t t l t t f th f t t Th f of the system. Such an analysis would e.g. be
the characterization of the
reformer system both transient primarily used to validate the system control strategy of the reformer temperature. The reformer able to identify the minimum fuel pump flow, reformer system, both transient
d t d t t i d t temperature control is carried out as a cascade PID control, as shown in figure 6. y p p
which depends on the available heat transferred
and steady-state in order to p , g which depends on the available heat transferred
from the fuel cell exhaust air to the evaporator
properly know the limitations of from the fuel cell exhaust air to the evaporator.
F th l i f t i t t
p p y
the system and enable the Further more an analysis of transient system
the system and enable the
d l t f ffi i t t l capabilities will be conducted to develop
development of efficient control capab es be co duc ed o de e op
simulation models that can be used in designing
algorithms, to suit the different simulation models that can be used in designing
ti l t t l t t ith t t
g ,
application demands that such optimal system control structures with respect to
application demands that such
systems are used in A picture e.g. load change speed, system efficiency, low
systems are used in. A picture
f h i l i
g g p , y y,
and CO content Being able to make online
of the experimental setup is and CO content. Being able to make online
predictions of the important system states is
shown in figure 2. predictions of the important system states is
d i h lif i f h
shown in figure 2.
expected to increase the lifetime of such system,
Figure 6: The reformer temperature is controlled by two control loop in a cascade control structure the inner loop controlling the burner temperature
if combined with advanced control strategies.
Figure 6: The reformer temperature is controlled by two control loop in a cascade control structure, the inner loop controlling the burner temperature, which is has a faster dynamic characteristic than the reformer temperature, which in the outer loop is controlled by slowly adjusting the burner Reformer/Burner
Evaporator heater y p , p y y j g if combined with advanced control strategies.
temperature.
Th i t ti f f l ll t k d th f
The reformer temperature is affected by many disturbances, the burner temperature, the fuel flow, The integration of fuel cell stack and the reformer The reformer temperature is affected by many disturbances, the burner temperature, the fuel flow,
the methanol conversion process and multiple heat losses in the system In order to control this will play an important role in the next phase of the the methanol conversion process and multiple heat losses in the system. In order to control this
t t th d t l t t h i d t t t t t ith biliti p y p p
system testing and is also required for evaluating temperature, the cascade control strategy was chosen in order to test a strategy with capabilities
Pump system testing, and is also required for evaluating
the validity and relevance of the developed of improving the speed and precision at which the reformer temperature could be controlled. As
Evaporator Pump
the validity and relevance of the developed
p g p p p
seen in figure 5 the burner set point and the actual burner temperature act fast once step is
F l t k
Evaporator
controllers. It is expected that different control seen in figure 5, the burner set point, and the actual burner temperature act fast once step is
imposed on the reformer set point temperat re The air flo to the b rner is adj sted to meet the
Fuel tank Control system p
approaches should be matched to the particular imposed on the reformer set point temperature. The air flow to the burner is adjusted to meet the
Fi 2 A i t l t f th approaches should be matched to the particular
application and its requirements burner set point temperature. Meanwhile the slower acting reformer temperature controller
Figure 2: An experimental setup of the
methanol reformer including evaporator p p g p application and its requirements.
adjusts the burner set point to finally enable control of the reformer temperature
methanol reformer including evaporator.
adjusts the burner set point to finally enable control of the reformer temperature.
