Technical field
The present invention is generally concerned with the
art of generating electrical energy by means of fuel
cells. More specifically, it relates to a fuel cell
system comprising a fuel cell stack, an evaporator for
evaporating a mixture of methanol and water to be fed
through a catalytic reformer for producing portions of
free hydrogen, the fuel cell stack being composed of a
number of proton exchange membrane fuel cells each
featuring electrodes in form of an anode and a cathode
for delivering an electric current, the reaction of free
hydrogen into ionic form with contact to the anode being
proportional to the flow of electric current between the
electrodes .
Background of the invention
Electrochemically, a fuel cell converts a raw fuel into
electrical energy and heat and will continue the
production as long as raw fuel is being continuously
supplied.
The basic conversion technology of fuel cells is well
known for at least a century but has come into a
renaissance with the latest development and demands for
fuel saving and environmental friendly technology.
Additionally fuel cell technology is advantageous for
electrical supply on mobile or remote platforms and for
backup solutions .
Briefly explained, using the protone exchange membrane
technology, a fuel cell needs a supply of hydrogen to be
passed along a first electrode, forming the anode, and a
supply of oxygen, typically taken directly as
atmospheric air, to be passed along a second electrode,
forming the cathode. Arranged between the electrodes is
an ion-conducting layer, typically a polymer film
comprising platine and phosphoric acid. Supplying the
hydrogen and oxygen, generates an electrical voltage
between the electrodes and a current will be able to
flow between the electrodes and supply an attached
electrical consumer. Corresponding to the draw of
current, a number of hydrogen and oxygen molecules will
react, and later when combined in the exhaust the
hydrogen ions and oxygen will form water as the end
product. Additionally the system will generate heat.
Since the necessary oxygen supply is achieved by taking
in sufficient amounts of oxygen containing atmospheric
air, the overall need for utilizing a fuel cell is to
form a steady and sufficient supply of hydrogen.
Supplying hydrogen can possibly be from pressurized
cylinders, small or large, but the distribution and
storage is critical since hydrogen is a highly explosive
gas. Pressurizing hydrogen is quite energy consuming and
even in pressurized form hydrogen takes up relatively
much space. A better solution is to generate hydrogen
directly on the spot by conversion of more stable forms
of fuel into a synthetic gas containing high amounts of
hydrogen, hereafter called a syngas.
Appreciated is the process of using methanol for
producing the hydrogen containing syngas for the obvious
advantages when it comes to distribution. The technology
describe both low and high temperature fuel cell stacks
where a temperature of 120 degrees celcius is the
temperature for which the split between the technologies
is commonly understood. More specifically a low
temperature system commonly works in the temperature
area around 70 degrees Celcius and the high temperature
system at around 160 degrees Celcius. However, for both
technologies apply that the process requires a reformer,
for processing the fuel and supplying a syngas
containing free hydrogen. The fuel processed is methanol
in an aquatic solution, herafter referenced as liquid
fuel. In a first stage, a heater evaporates the liquid
fuel and the gas is forwarded to the reformer. The
reformer includes a catalyst including copper, which in
addition to heat converts the liquid fuel into a syngas
mainly consisting of hydrogen with a relatively large
content of carbon dioxide and a small content of water
mist and carbon monoxide. The syngas is directly useable
as a fuel supply for supplying the fuel cell.
For an effective operation of the reformer, the state of
art suggests the reformer to be arranged as an upright
standing entity, such that the incoming gas cannot
escape without interaction with the reformer catalyst
and be reformed to the appreciated syngas. This design
manner is though a challenge when the wish is to build a
fuel cell system that is more compact and preferably is
designed as an exchangeable rack unit with the obvious
advantages .
Thus, there is a need for an improvement of the design
of the reformer in order to achieve a more compact
design. There is also a need for an improved design of
the reformer, which in a more reliable way secures that
the full amount of supplied gas mixture, delivered by
the evaporator, is reformed into syngas.
Description of the invention
The overall object of the present invention is to
provide a fuel cell system with a more compact reformer
design, which in addition provides a better way secures
that the full amount of supplied gas mixture is reformed
into syngas.
Investigations has shown, that in the upright design of
the prior art reformer, the gas will flow in the passage
with the lowest resistance. This will typically be along
the vertical walls of the reformer entity. The catalyst,
being carbon pellets with a copper adding will tend to
pack in the entity, which even more will direct the gas
flow to the channels at the vertical wall and lower the
effect of the reformer. The volume of the catalyst will
further depend on the temperature and the oxidation
level of the catalyst. Thus, even topping off the volume
of the catalyst in the reformer will not secure that the
reformer is filled with catalyst to a level where the
process of reforming the liquid fuel into syngas is
achieved optimally.
The object of the present invention is according to the
invention achieved by adding the technical features of
the reformer in the fuel cell system as explained in
claim 1.
More specifically the fuel cell system comprises a fuel
cell stack, a catalytic reformer, filled with a
catalyst, having an inlet for receiving a flow of gas
and an outlet for delivering a syngas to the fuel cell
stack, an evaporator for evaporating a mixture of
methanol and water to be fed through the catalytic
reformer for producing portions of free hydrogen, the
fuel cell stack being composed of a number of proton
exchange membrane fuel cells each featuring electrodes
in form of an anode and a cathode for delivering an
electric current, the reaction of free hydrogen into
ionic form with contact to the anode being proportional
to the flow of electric current between the electrodes
where the reformer is comprising at least two chambers
for containing the catalyst, the chambers each having an
inlet for receiving the flow of gas and an outlet for
passing the flow of gas to the succeeding chamber or the
outlet of the reformer
In an embodiment, the chambers are provided by
separating the entity into chambers by insertion of
walls. This has the effect as to direct the gas through
the reformer and secure that the flow of gas is exposed
to the catalyst and reformed into syngas. Achieved is
that the path through the reformer is made longer
avoiding the gas to find a shortcut through the
reformer .
In an embodiment, at least one opening in the wall is
provided between the chambers to serve as a pathway for
the flow of gas. The wall will direct the flow of gas
and the opening will secure that the flow of gas is
following the intended path through the system. Since
openings can be made both in the top and bottom of the
reformer separation walls the gas flow can be directed
in the up or the down going direction within the
reformer and thus less space is taken up and it is
secured that the gas is sufficiently exposed to the
reformer catalyst and reformed into syngas.
In a further embodiment, the openings are provided by
limiting the extension of the walls within the reformer
module. More specifically, the walls for separation is
arranged protruding down from the top of the entity or
protruding up from the bottom of the entity.
For prolonging the path for the flow of gas through the
reformer module, the walls for providing chambers of the
reformer are such shaped as to form an up and down zig
zagging path. The effect achieved is to provide a
prolonged path for the flow of gas through the system
and a better exposure to the catalyst. A further effect
is reached as to direct the flow of gas away from the
walls and into the mid of the catalyst material thereby
providing a better exposure to the catalyst. The overall
result is a better reformation of fuel into syngas.
Additionally, in an embodiment separation walls that
separate the flow of gas into two or more parallel paths
are inserted into the path and improve the exposure of
the gas to the catalyst and the production of hydrogen
rich syngas. The separation walls further serve as
heating elements .
In a further embodiment, the walls are shaped in such a
way that the channel is directly vertical. This has the
effect of providing a long path for the flow of gas. The
vertical orientation of the channel will further help
the flow of gas to follow a path that leads into the mid
of the catalyst material.
In a further embodiment, the walls are shaped in such a
way that the channel is not orientated directly
vertical. It has to be understood that the prolonging of
the channel will need that directly vertical sections of
the reformer are interconnected by not directly vertical
orientated transportation sections. Further, the effect
of not directly vertical orientated sections of the
channel will be as to lead the flow of gas into the mid
of the catalyst material.
In an embodiment, the walls are shaped in such a way
that sections of the channel are directly vertical,
optionally with not directly vertical sections. A s it
has to be understood the embodiment will serve to lead
the flow of gas to the mid of the channel in order to
expose the flow of gas to the catalyst and reform larger
amounts of evaporated gas into syngas.
In an embodiment, the walls are shaped in such a way
that the channel follows a path which is angled away
from a straight horizontal or vertical orientation. Thus
the path will direct the flow of gas towards the mid of
the channel and the gas will be more exposed to the
catalyst .
Further, the walls can be forming straight lines or they
can be curved or geometrically shaped.
More explicitly, an appreciated embodiment of the
channel will feature walls that are shaped in such a way
that the flow of gas is redirected towards the mid of
the channel or chamber securing that the flow of gas is
exposed as much as possible to the catalyst.
In a further embodiment the walls are comprising
protruding walls for maximizing the travel of the gas
flow from inlet to outlet of the reformer entity. The
application of protruding walls will avoid the building
of a shunt path, secure that the flow of gas will be
exposed to the catalyst, and enhance the process of
reforming the fuel into syngas.
In another embodiment, the walls comprise protruding
elements in form of noses for redirecting the gas flow
away from the walls of the chambers. Since the flow of
gas will be guided away from the walls and towards the
mid of the catalyst material, it is secured that the gas
is exposed to the catalyst and enhancing the process of
reforming the fuel into syngas.
The reformer housing, as explained uses heat and a
catalyst to reform the atomized methanol into a hydrogen
rich syngas. The housing including all the described
walls are thus serving as heating elements transferring
thermal energy into the process.
The explained embodiments can be taken alone or as
appreciated be combined with the overall object of
featuring a reformer where the flow of gas is exposed as
much as possible to the catalyst, whereby producing a
syngas with a very limited if any content of nonreformed
gas. By facilitating a high quality of reformed
syngas, the operation of the fuel cell stack will be
more reliable and efficient.
Especially appreciated is an embodiment of the system
where the components form modules that fit together into
a system in a modular way. The reformer module can
advantageously be formed out of one piece of material,
preferably aluminum, which on one side is having the
cavity of the reformer with the explained pathways
provided by the walls forming the channels and on the
other side is equipped with heat absorbing/ transporting
fins for taking up thermal energy from the other side.
The thermal energy to be absorbed for providing
evaporation of the liquid fuel can be supplied from the
exhaust of the waste gas burner. Especially appreciated
is if the exhaust from the waste gas burner is forwarded
fully or partly along the fins of the evaporator module
in order to achieve a better efficacy of the system. It
has to be understood that the modules can be physically
made using various methods of production, as e.g. diecasting
or by carving out the channels of the modules in
a machining process.
The reformer module can as explained, preferably be made
of aluminum, but the use of other thermal heat
conducting materials can be foreseen, such as alloys of
iron, stainless steel, magnesium as well as ceramic
materials .
Description of the drawing:
Embodiments of the invention will be described with
reference to the accompanying drawing, in which:
Fig. 1 , shows an illustration of a fuel cell system,
Fig. 2 , shows an illustration of an reformer module for
reforming atomized liquid fuel into syngas,
Fig. 1 , of the drawing shows a fuel cell system 1
comprising a fuel cell stack 2 , a number of supporting
modules for supplying the fuel cell stack 2 with a
modified fuel enabling the fuel cell stack 2 to produce
a steady flow of electrical current. The exceed gas
supplied to the fuel cell stack 2 but not being
converted into electrical current, is fed to the waste
gas burner 3 . The exhaust gas is under normal operating
conditions in the temperature area of 500 degrees
Celsius and the energy content is recycled for preparing
the syngas for fueling the fuel cell stack 2 . More
detailed, the exhaust is forwarded through the heat
exchanger module 4 , which takes up the heat from the
exhaust and transfer the heat to the neighboring module
in the stack here being the evaporator module 5 .
The liquid fuel, a mixture of methanol and water, is
processed into a syngas consisting of free hydrogen for
use in the fuel cell stack 2 . In the evaporator module
5 , the fuel is atomized and evaporated into the twophase
stage of the liquid fuel. Further, the evaporated
gas is forwarded to the catalytic reformer module 6 that
reforms the evaporated gas into a syngas consisting
largely of free hydrogen. The catalytic reformer module
6 includes a catalyst including copper, which in
addition to heat converts the evaporated liquid fuel
into the syngas directly usable by the fuel cell stack
2 . The exhaust heat of the fuel cell stack 2 and the
waste gas burner 3 is led through channels in the
evaporator module 5 and catalytic reformer module 6 . The
temperature demand in the catalytic reformer 6 is
highest, so thus the catalytic reformer module 6 is
arranged directly behind the waste gas burner 3 . At a
later stage of the exhaust channel the evaporator module
5 takes up the heat from the exhaust in order to
evaporate the liquid fuel into gas.
Fig. 2 , shows an illustration of the reformer module 6
including the reformer 7 . The reformer module is shown
in an upright position where the orientation in the
working system is angled ninety degrees
counterclockwise. In other words, the reference sign no.
6 is pointing to the top of the system.
The system orientation in the working system state of
the art systems is in an upright position, where the gas
will flow up from the bottom to the top and be exposed
to the volume of catalyst in the reformer container. A s
explained the drawback is that the system takes up much
space in the vertical direction and that the flow of gas
is as such not sufficiently exposed to the catalyst and
reformed into syngas. The insufficient quality of syngas
influences the overall performance of the fuel cell
system in a negative way.
The reformer module 6 as pictured in fig. 2 , includes a
reformer 7 including a container 8 with an inlet 9 for
supplying an atomized and evaporated liquid fuel to be
reformed into syngas by the catalyst 10 in the container
8 . Further there is an outlet 11 for taking out the
syngas. Because of the view angle of fig. 2 , the outlet
is not visible but reference is made to the position.
The syngas is directly forwarded to the fuel cell stack
2 .
The reformer module 6 and container 8 , is as can be seen
from fig. 1 , formed as an elongated cube. The view in
fig. 2 , thus pictures the inner wall structure of the
reformer 7 . A characteristics of the reformer is that
the path from inlet 9 to outlet 11 goes up and down and
as such the path is prolonged for achieving a long
travel of the gas flow in order to expose the supplied
liquid, atomized or evaporated gas to the catalyst 10.
For the separation of the container 8 into chambers,
walls 12 are inserted. The walls 12 are in the present
embodiment going out either from the top or the bottom
of the container 8 , but could have the full length and
be supplied with penetrations between the chambers. The
penetrations could be made at specific points that would
force the gas flow to follow a specific path that helps
the gas flow to be more exposed to the catalyst 10 in
the container 8 . Further separation walls 13 can be
inserted to separate the flow of gas into separate
streams within the container. The walls 12 and
separation walls 13, further serve as heating elements
for heating the catalyst 10 and the supplied gas to a
temperature where the reaction into syngas can take
place. The walls 12 and separation walls 13 are in the
present embodiment showed orientated directly vertical .
However, the orientation of the walls can be in all
directions and the walls 12 and separation walls 13 can
have a shape that are not straight but could be bended
or formed in another suitable pattern as e.g. forming a
worm or a labyrinth form. The walls 12 or separation
walls 13 could also be equipped with protruding walls
14, which will enhance the transfer of thermal energy in
form of heat to the catalyst 10 or gas. Further the
protruding walls 14 will help to prolong the travel of
the flow of gas and thus provide a larger extend of
exposure to the catalyst. This will provide a better
quality of the syngas and a better overall system
performance. Further the protruding walls 14 can form a
nose 15 that serve to direct the stream of gas away from
the walls and into the mid of the path, where the stream
of gas will be more exposed to the catalyst. The nose 15
can take form starting with a straight vertical line
followed by an angled line or vice versa. A nose can
also be formed by two angled lines or shaped in another
way that intends to direct the stream of gas away from
the walls. More examples of noses 15 are shown in fig.
2 .
For the understanding of the system, the system
components are build as modules that can be fixed
together by conventional screws and bolts . Pathways for
e.g. exhaust gas are forwarded from module to module in
order to take out as much thermal energy as possible and
get a high efficacy of the system. Thus the modules can
be joined using gaskets in-between as can be seen in
fig. 1 between the evaporator module 5 and reformer
module 6 .
The modules can be made by machining of a bar of
material but could also be provided by die-casting,
extrusion, sintering etc. In the present embodiment, the
evaporator module is provided using a bar of aluminum
and carving out the channels for the reformer on a first
side of the bar. The other side of the bar is provided
with fins for taking up thermal energy from the burner
exhaust .
Provided by the invention is an enhanced catalytic
reformer for a fuel cell system, which enables a compact
design of the reformer for integration into a flat, rack
mountable system. With the new design, the challenges
with state of the art catalytic reformer systems has
been dealt with, and provided is a container for the
catalyst that in a sophisticated way serves to provide a
specific path through the system, which secures that the
flow of gas is exposed as much as possible to the
catalyst and reformed into syngas.

Claims :
1 . A fuel cell system comprising:
- a fuel cell stack
- a catalytic reformer, filled with a catalyst,
having an inlet for receiving a flow of gas and an
outlet for delivering a syngas to the fuel cell stack,
- an evaporator for evaporating a mixture of methanol
and water to be fed through the catalytic reformer for
producing portions of free hydrogen,
- the fuel cell stack being composed of a number of
proton exchange membrane fuel cells each featuring
electrodes in form of an anode and a cathode for
delivering an electric current, the reaction of free
hydrogen into ionic form with contact to the anode
being proportional to the flow of electric current
between the electrodes
C h a r a c t e r i z e d in,
that the reformer is comprising at least two chambers
for containing the catalyst, the chambers each having an
inlet for receiving the flow of gas and an outlet for
passing the flow of gas to the succeeding chamber or the
outlet of the reformer
2 . A system according to claim 1 ,
C h a r a c t e r i z e d in,
that the chambers are provided by separating the entity
into chambers by insertion of walls
3 . A system according to claim 2 ,
C h a r a c t e r i z e d in,
that at least one opening in the wall is provided
between the chambers to serve as a pathway for the flow
of gas.
4 . A system according to claim 2 ,
C h a r a c t e r i z e d in,
that the walls for separation is arranged protruding
down from the top of the entity or protruding up from
the bottom of the entity
5 . A system according to claim 2 ,
C h a r a c t e r i z e d in,
that chambers are provided as an up and down zig-zagging
path .
6 . A system according to claim 2 ,
C h a r a c t e r i z e d in,
that separation walls that separate the flow of gas into
two or more parallel paths are inserted into the path.
7 . A system according to claim 2 ,
C h a r a c t e r i z e d in,
that the walls are shaped in such a way that sections of
the channel is directly vertical, optionally with not
directly vertical sections.
8 . A system according to claim 2 ,
C h a r a c t e r i z e d in,
that the walls are shaped in such a way that the channel
follows a path which is angled away from a straight
horizontal or vertical orientation.
9 . A system according to claim 2 ,
C h a r a c t e r i z e d in,
that the walls are shaped forming straight lines or as
curved or geometrically shaped lines.
10. A system according to claim 2 ,
C h a r a c t e r i z e d in,
that the walls are shaped in such a way that the flow of
gas is redirected towards mid of the chamber
11. A system according to claims 2 - 10,
C h a r a c t e r i z e d in,
that the walls are comprising protruding walls for
maximizing the travel of the gas flow from inlet to
outlet of the reformer entity.
12. A system according to claims 2 - 11,
C h a r a c t e r i z e d in,
that the walls are comprising protruding elements in
form of noses for redirecting the gas flow away from the
walls of the chambers.
13. A system according to claims 2 - 12,
C h a r a c t e r i z e d in,
that the walls serve as heating elements for heating the
gas to be reformed.