Note: Descriptions are shown in the official language in which they were submitted.
CA 02477723 2004-09-08
-l'
SYSTEM AND METHOD FOR CONTROLLING THE OPERATION OF A
FUEL PROCESSING SYSTEM
Field of the Invention
The present invention relates generally to fuel processing systems, and more
particularly to a control system that automates the operation of a fuel
processing
system.
Background and Summary of the Invention
Fuel processors are used to produce hydrogen gas from a feedstock. In recent
years, more and more research is being conducted to develop a commercially
practicable fuel processor. For example, one goal is to couple a fuel
processor with a
fuel cell stack to provide a fuel processing system that may be used as an
alternative,
or supplement, to conventional energy systems.
An important step to achieving a fuel processor for commercial applications,
and especially for smaller scale consumer applications, is a control system
that
automates at least a substantial portion of the operation of the fuel
processing system.
In laboratory environments where the fuel processing system is not being used
continuously or left unattended for prolonged periods of time, a manually
operated
system may be acceptable. Should a problem arise, trained technicians will be
on
hand. However, in commercial applications, such as in households, vehicles and
the
like where the consumer will generally not be trained in the operation and
design of
the fuel processing system, the operation of the system must be automated.
Even
when the fuel processing system is functioning properly, consumers will
neither have
the technical knowledge, nor the desire, to manually control the operation of
the
system.
Therefore, there is a need for a control system adapted to automate the
operation of a fuel processor, such as a fuel processor forming a portion of a
fuel
processing system including a fuel cell stack. The present invention provides
such a
CA 02477723 2007-11-01
control system and a method for monitoring and/or controlling the operation of
a fuel
processing system.
In accordance with an illustrative embodiment of the invention, there is
provided an
automated fuel processing system with a malfunction-detecting control system.
The
automated fuel processing system includes a feed assembly, a fuel processor, a
heating
assembly, a fuel cell stack, and a control system. The feed assembly is
adapted to deliver at
least one feed stream to the fuel processor, which is adapted to produce
hydrogen gas
therefrom. The fuel processor has at least one hydrogen-producing region
adapted to receive
the at least one feed stream and to produce a resultant stream containing at
least substantially
pure hydrogen gas therefrom. The heating assembly is adapted to receive at
least one fuel
stream and to combust the fuel stream to heat the fuel processor to an
elevated temperature.
The fuel cell stack is adapted to receive an oxidant and at least a portion of
the resultant
stream and to produce an electric current therefrom. The fuel processing
system is normally
adapted to operate in a hydrogen-producing operating state in which the fuel
processor is
maintained at an elevated temperature and pressure suitable for producing the
resultant
stream, the at least one fuel stream is delivered to the heating assembly, the
at least one feed
stream is delivered to the hydrogen-producing region, and the at least a
portion of the
resultant stream is delivered to the fuel cell stack. The control system is
adapted to monitor
the operation of the fuel processing system to detect malfunctions therein.
The control
system is adapted to transition the fuel processing system between at least
the hydrogen-
producing operating state, a standby state, in which the fuel processor is
maintained at the
elevated temperature and pressure but no more than a nominal amount of the
resultant stream
is delivered to the fuel cell stack, and an off state, in which the fuel
processing system is
depressurized and cooled. Upon detection of a malfunction when the fuel
processing system
is operating in the hydrogen-producing state, the control system is adapted to
automatically
stop delivery of the at least a portion of the resultant stream to the fuet
cell stack. Upon
detection of the malfunction, the control system is further adapted to
selectively transition the
fuel processing system to either the off state or the standby state.
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In accordance with another illustrative embodiment of the invention, there is
provided
an automated fuel processing system with a malfunction-detecting control
system. The
automated fuel processing system includes a feed assembly, a fuel processor, a
heating
assembly, a fuel cell stack, and a control system. The feed assembly is
adapted to deliver at
least one feed stream to the fuel processor, which is adapted to produce
hydrogen gas
therefrom. The fuel processor has at least one hydrogen-producing region
adapted to receive
the at least one feed stream and to produce a resultant stream containing at
least substantially
pure hydrogen gas therefrom. The heating assembly is adapted to receive at
least one fuel
stream and to combust the fuel stream to heat the fuel processor to an
elevated temperature.
The fuel cell stack is adapted to receive an oxidant and at least a portion of
the resultant
stream and to produce an electric current therefrom. The fuel processing
system is normally
adapted to operate in a hydrogen-producing operating state in which the fuel
processor is
maintained at an elevated temperature and pressure suitable for producing the
resultant
stream, the at least one fuel stream is delivered to the heating assembly, the
at least one feed
stream is delivered to the hydrogen-producing region, and the at least a
portion of the
resultant stream is delivered to the fuel cell stack. The control system is
adapted to monitor
the operation of the fuel processing system to detect malfunctions therein.
Upon detection of
a malfunction when the fuel processing system is operating in the hydrogen-
producing state,
the control system is adapted to automatically stop delivery of the at least a
portion of the
resultant stream to the fuel cell stack. Upon detection of the malfunction and
responsive to
receipt of a reset signal, the control system is adapted to transition the
fuel processing system
to a standby state, in which the fuel processor is maintained at the elevated
temperature and
pressure but no more than a nominal amount of the resultant stream is
delivered to the fuel
cell stack.
In accordance with another illustrative embodiment of the invention, there is
provided
an automated fuel processing system with a malfunction-detecting control
system. The
automated fuel processing system includes a feed assembly, a fuel processor, a
heating
assembly, a fuel cell stack, and a control system. The feed assembly is
adapted to deliver at
least one feed stream to the fuel processor, which is adapted to produce
hydrogen gas
therefrom. The fuel processor has at least one hydrogen-producing region
adapted to receive
the at least one feed stream and to produce a resultant stream containing at
least substantially
pure hydrogen gas therefrom. The heating assembly is adapted to receive at
least one fuel
-1B-
CA 02477723 2007-11-01
stream and to combust the fuel stream to heat the fuel processor to an
elevated temperature.
The fuel cell stack is adapted to receive an oxidant and at least a portion of
the resultant
stream and to produce an electric current therefrom. The fuel processing
system is normally
adapted to operate in a hydrogen-producing operating state in which the fuel
processor is
maintained at an elevated temperature and pressure suitable for producing the
resultant
stream, the at least one fuel stream is delivered to the heating assembly, the
at least one feed
stream is delivered to the hydrogen-producing region, and the at least a
portion of the
resultant stream is delivered to the fuel cell stack. The control system is
adapted to monitor
the operation of the fuel processing system to detect malfunctions therein.
Upon detection of
a malfunction when the fuel processing system is operating in the hydrogen-
producing state,
the control system is adapted to automatically stop delivery of the at least a
portion of the
resultant stream to the fuel cell stack. Upon detection of the malfunction,
the control system
is further adapted to stop delivery of at least one fuel stream to the heating
assembly and stop
delivery of the at least one feed stream to the fuel processor.
-1C-
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Many other features of the present invention will become manifest to
those versed in the art upon making reference to the detailed description
which follows
and the accompanying sheets of drawings in which preferred embodiments
incorporating
the principles of this invention are disclosed as illustrative examples only.
Brief Description of the Drawinas
Fig. 1 is a schematic view of a fuel processing system according to the
present invention, including a fuel processing assembly and a fuel r,ell
stack.
Fig. 2 is a schematic view showing components of the fuel processor
of Fig. 1.
Fig. 3 is a schematic view showing the controller and the feed
assembly of Fig. 2.
Fig. 4 is a schematic view showing the controller and the hydrogen-
producing region of Fig. 2.
Fig. 5 is a schematic view showing an embodiment of the hydrogen-
producing region of Fig. 2 including a preheating assembly.
Fig. 6 is a schematic view showing another embodiment of the
preheating assembly of Fig. 5.
Fig. 7 is a schematic view showing the controller and the separation
region of Fig. 2.
Fig. 8 is a schematic view showing the controller, polishing region and
the output assembly of Fig. 2.
Fig. 9 is a schematic view showing the controller and the combustion
region of Fig. 2.
Fig. 10 is a front elevation view of a user interface for a controller for
the fuel processor of Fig. 1.
Fig. 11 is a flow chart illustrating the relationships between the
automated operating states of the fuel processing system of Fig. 1.
Fig. 12 is a flow chart illustrating the relationships between the
subroutines executable by the controller of Fig. 1.
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CA 02477723 2004-09-08
Detailed Description and Best Mode of the Invention
A fuel processing system is shown in Fig. 1 and generally indicated at
10. As shown, system 10 includes a fuel processing assembly 12 and a fuel cell
stack
14. Fuel processing assembly 12 includes a fuel processor 16 that produces
hydrogen
gas from a feed stream 20, which typically comprises an alcohol or
hydrocarbon, and
which may include water. Fuel processing assembly 12 further includes a feed
assembly 18 that delivers feed stream 20 to fuel processor 16. Examples of
suitable
feedstocks include alcohols, such as methanol, ethanol, ethylene glycol and
propylene
glycol, and hydrocarbons, such as methane, propane and transportation fuels,
such as
gasoline, diesel and jet fuel. It is within the scope of the present invention
that any
other suitable feedstock may be used, as is known in the art.
Fuel processor 16 converts the feedstock into hydrogen gas, at least a
significant portion of which is typically delivered to fuel cell stack 14.
Stack 14 uses
the hydrogen gas to produce an electric current that may be used to meet the
electrical
load supplied by an associated electrical device 22, such as a vehicle, boat,
generator,
household, etc. It should be understood that device 22 is schematically
illustrated in
the Figures and is meant to represent one or more devices adapted to receive
electric
current from the fuel processing system responsive to an applied electric
load.
Fuel cell stack 14 includes one or more fuel cells adapted to produce
an electric current from the hydrogen gas produced by the fuel processor. An
example of a suitable fuel cell is a proton exchange membrane (PEM) fuel cell,
in
which hydrogen gas is catalytically dissociated in the fuel cell's anode
chamber into a
pair of protons and electrons. The liberated protons are drawn through an
electrolytic
membrane into the fuel cell's cathode chamber. The electrons cannot pass
through
the membrane and instead must travel through an external circuit to reach the
cathode
chamber. The net flow of electrons from the anode to the cathode chambers
produces
an electric current, which can be used to meet the electrical load being
applied by
device 22. In the cathode chamber, the protons and electrons react with oxygen
to
fonn water and heat. Other types of fuel cells may be used in stack 14, such
as
alkaline fuel cells.
Also shown in Fig. 1 is a control system 26 with a controller 28 that is
adapted to automate the operation of fuel processing assembly 12, and in some
embodiments, the entire fuel processing system 10. Unlike conventional fuel
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CA 02477723 2004-09-08
processing systems, which are manually operated and require a trained
technician to
be available should the system malfunction or require adjustment, the
performance of
system 10 is regulated and automatically adjusted responsive to changes in
operating
parameters detected by control system 26. As discussed in more detail
subsequently,
control system 26 includes controller 28, which is preferably software
operating on a
processor. However, it is within the scope of the present invention that
controller 28
may be otherwise implemented, such as with one or more digital and/or analog
circuits, or the combination of the two.
Control system 26 further includes a plurality of sensor assemblies in
communication with controller 28 and adapted to monitor selected operating
parameters of the fuel processing system. Responsive to input signals from the
sensor
assemblies, user conunands from a user-input device, and/or programmed
subroutines
and command sequences, the controller regulates the operation of the fuel
processing
system. More specifically, controller 28 communicates with a control-signal
receiving portion of the desired region or element of the fuel processing
system by
sending command signals thereto directing a particular response. For example,
controller 28 may send control signals to pumps to control the speed of the
pumps, to
valve assemblies to control the relative flowrate therethrough, to pressure
regulators
to control the pressure of the conduit or vessel regulated thereby, etc.
It should be understood that the sensor assemblies, control-signal
receiving devices, and communication pathways described herein may be of any
suitable construction known in the art. The sensor assemblies may include any
suitable sensor for the operating parameter being monitored. For example, flow
rates
may be monitored with any suitable flow meter, pressures may be monitored with
any
suitable pressure-sensing or pressure-regulating device, etc. The assemblies
may also,
but do not necessarily include a transducer in communication with the
controller. The
communication pathways may be of any suitable form known in the art, including
radio frequency, wired electrical signals, wireless signals, optical signals,
etc.
In the Figures, communication pathways are schematically illustrated
as single- or double-headed arrows. An arrow terminating at controller 28
schematically represents an input signal, such as the value of a measured
operating
parameter, being communicated to controller 28. An arrow extending from
controller
28 schematically represents a control signal sent by controller 28 to direct a
4
CA 02477723 2004-09-08
-5-
responsive action from the device at which the arrow terminates. For example,
in Fig.
2, dual-headed pathways 62 schematically illustrate that controller 28 not
only sends
command signals to corresponding receivers in fuel processor 16 and feed
assembly
18 to provide a determined responsive action, but also receives inputs from
sensor
assemblies contained within the fuel processor and feed assembly.
In Fig. 2, an embodiment of a fuel processing system 10 according to the
present invention is shown in more detail. As discussed, assembly 12 is shown
schematically as an example of a suitable fuel processor and feed assembly,
and other
fuel processors and feed assemblies may be used without departing from the
spirit and
scope of the present invention. To provide a framework for discussing the
interaction
of control system 26 with the fuel processing system shown in Fig. 2, the
principal
regions of fuel processing assembly will be briefly discussed in the following
description, followed by a more detailed description of each region with an
emphasis
on how the elements in the region interact with the control system of the
present
invention.
As discussed, fuel processing assembly 12 includes a fuel processor 16 and a
feed assembly 18. Feed assembly 18 delivers feed stream 20 to a hydrogen-
producing
region 34 of fuel processor 16. Hydrogen-producing region 34 produces hydrogen
gas from feed stream 20 through any suitable mechanism. Suitable mechanisms
include steam reforming of an alcohol or hydrocarbon vapor, partial oxidation
of a
hydrocarbon or alcohol vapor, a combination of partial oxidation and steam
reforming
a hydrocarbon or an alcohol vapor, pyrolysis of a hydrocarbon or alcohol
vapor, or
autothermal reforming of an alcohol or hydrocarbon. Examples of suitable steam
reformers are disclosed in U.S. Patent 6,221,117 issued April 24, 2001. When
hydrogren-producing region 34 operates by steam reforming, feed stream 20 will
typically include steam and an alcohol or hydrocarbon vapor. When region 34
operates by pyrolysis or partial oxidation, stream 20 will not include a water
component.
CA 02477723 2004-09-08
-5A-
From hydrogen-producing region 34, a resultant stream 36 delivers the
hydrogen-containing fluid to a separation region 38. When hydrogen-producing
region 34 is a stream reforming region, stream 36 may be referred to as a
reformate
stream. In separation region 38, the stream is divided into a product stream
40 and a
CA 02477723 2004-09-08
byproduct stream 42. Product stream 40 includes at least a substantial portion
of
hydrogen gas and preferably contains less than determined minimum
concentrations
of compositions that would damage or interfere with the intended use of the
product
stream. Ideally, stream 40 is free from such compositions, however, it is
sufficient
that any potentially interfering or damaging compositions are present in
concentrations that are not high enough to impair or interfere with the
intended use of
stream 40. For example, when the product stream is to be delivered to fuel
cell stack
14 (either directly, or after being stored for a selected period of time), the
stream
should be at least substantially free of carbon monoxide. However, the stream
may
1o contain water without damaging fuel cell stack 14 or the production of an
electric
current therein.
Sometimes, it may be desirable to pass product stream 40 through a
polishing region 44 in whi dh the concentration of undesirable compositions is
reduced
or removed. It should be understood that polishing region 44 is not essential
to all
embodiments of the invention. For example, separation region 38 may result in
product stream 40 being sufficiently free of undesired compositions for the
intended
use of the product stTeam.
From polishing region 44, the product stream is delivered to an output
assembly 50 from which the stream leaves the fuel processor 16 and is
delivered to a
suitable destination or storage device. For example, the product hydrogen may
be
delivered to fuel cell stack 14 via stream 52 to produce an electric current
therefrom.
Some or all of the produced hydrogen may altematively be delivered via stream
54 to
a storage device 56. Examples of suitable devices include storage tanks,
carbon
absorbents such as carbon nanotubes, and hydride beds, although any other
suitable
device for storing hydrogen gas may be used and is within the scope of the
present
invention.
At least portions of fuel processor 16 typically operate at an elevated
temperature. For example, hydrogen-producing region 34 typically operates at
an
elevated temperature, and separation region 38 may operate at an elevated
temperature. When an elevated temperature is desired, fuel processor 16 may
further
include a combustion region 60 or other suitable region for generating
sufficient heat
to maintain the fuel processor within selected temperature ranges.
6
CA 02477723 2004-09-08
Also shown in Fig. 2 is a user interface 58. User interface 58 enables
users to communicate with controller 28, such as by inputting user inputs,
and/or by
receiving information displayed by the controller.
As shown in Fig. 2, controller 28 communicates, via one- or two-way
communication pathways 62, with some or all of the regions of the fuel
processing
assembly described above. It should be understood that it is not required that
controller 28 communicate with each of the regions of the fuel processing
assembly
shown in Fig. 2, and that controller 28 may also communicate with regions
other than
those shown in Fig. 2. To illustrate this point, no communication pathways 62
have
been shown communicating with polishing region 44. However, it is within the
scope
of the present invention that system 26 may include one or more pathways
communicating with this portion of the fuel processing system.
Turning now to Figs. 3-10, a more detailed discussion of the
components of fuel processing system 10 is provided, including examples of
operating parameters that may be monitored by the control system and command
signals that may be sent responsive thereto.
In Fig. 3, an illustrative embodiment of feed assembly 18 is shown in
more detail. As shown, assembly 18 includes a pump assembly 70 that includes
one
or more pumps 72 adapted to draw flows 74 and 76 from a feedstock supply 78
and a
water supply 80. When the feedstock is miscible in water, the feedstock and
water
may be mixed to form a composite feed stream 20, as shown in solid lines in
Fig. 3. It
is within the scope of the present invention, however, that the streams may be
separately delivered to fuel processor 16, as shown in dashed lines in Fig. 3.
It is also
within the scope of the present invention that water supply 80 and feedstock
supply 78
include fluid connections to sources extemal feed assembly 18. As discussed
previously, some embodiments of system 10 utilize a hydrogen-producing
mechanism
that does not require water. In these embodiments, feed assembly 18 will not
need to
include a water supply.
As shown in Fig. 3, controller 28 communicates with stream 20 to
monitor and/or regulate the flowrate and pressure in the stream. When the
flows are
separately drawn from their respective supplies, pump assembly 70 preferably
includes flow controls adapted to regulate the relative flow rate of each
component of
the feed stream responsive to inputs from controller 28. Preferably,
controller 28 also
7
CA 02477723 2004-09-08
receives inputs from pump assembly 70, such as the speed of each pump in pump
assembly 70 and the flowrate of fluid in feed stream(s) 20.
Controller 28 may also receive inputs regarding the level of fluid in
each supply 78 and 80. If the level drops below a selected level, the
controller may
direct additional fluid to be added to the supply, such as from an exteraal
source (not
shown). If no additional fluid is available and the level drops below
determined
minimum levels, then the controller may take the appropriate programmed
response,
such as executing the control system's shutdown subroutine and alerting the
user of
the problem, or fault, via user interface 58. As discussed in more detail
subsequently,
1 o when the controller determines that an operating parameter of the fuel
processing
system exceeds a determined threshold value or range of values, it will
automatically
actuate a shutdown subroutine to prevent damage to the fuel processing system.
By monitoring process parameters such as those discussed above,
controller 28 may compare the measured values to expected, or stored, values
to
determine if the fuel processing system is operating properly. Similarly, the
measured
values may be used by the controller to determine if other elements of the
fuel
processing system are within acceptable operating conditions. For example, if
the
measured flowrate (conununicated via pathway 62 and measured, for example, by
any
suitable flow meter) in stream(s) 20 does not correspond with the expected
flowrate,
as determined by controller 28 (such as based on progranuned data, the
measured
pump speed, etc.), then the controller may automatically execute its shutdown
subroutine or signal the user that the system requires servicing or
maintenance of
pump assembly 70.
In Fig. 4, feed stream 20 is delivered to hydrogen-producing region 34.
Region 34 includes suitable catalysts or other structure for the implemented
mechanism by which hydrogen gas is to be produced from stream 20. For example,
when region 34 produces hydrogen by steam reforming, it will contain one or
more
reforming catalyst beds 82 in which the feed stream is at least substantially
converted
into hydrogen gas and carbon dioxide. A byproduct of this reaction is carbon
3o monoxide, which in concentrations of even a few parts per million may
permanently
damage a PEM fuel cell stack. When the feedstock is methanol, the primary
reaction
is
CH3OH + H20 = 3H-, + CO2
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As discussed, the reaction in hydrogen-producing region 34 is typically
conducted at elevated temperatures. For example, steam reforming of methanol
is
preferably conducted at a temperature above approximately 250 C, and steam
reforming of most other alcohols and hydrocarbons is preferably conducted at
temperatures above approximately 600 C. To ensure that region 34 is
maintained
above a determined minimum temperature, and more preferably within determined
temperature ranges, controller 28 monitors the temperature of region 34. In
the
context of a steam reformer and other temperature-dependent catalyzed
reactions, it is
preferable that controller 28 monitors the temperature of the catalyst bed at
one or
1o more locations within or adjacent the catalyst bed to ensure that the bed
is within
determined temperature ranges. Should the temperature be approaching or below
a
detennined threshold value, controller 28 may cause the temperature to be
raised,
such as by sending additional fuel to combustion region 60. Controller 28 may
also
monitor the pressure in region 34, via a suitable pressure sensor or pressure
regulator,
to maintain the pressure in the region within selected limits.
It is within the scope of the present invention that controller 28 may be
adapted to direct more than one type of command signal responsive to detected
values
of an operating variable. For example, controller 28 may be programmed to
automatically try to achieve and maintain, via command signals, a determined
value
of an operating parameter, such as the temperature in hydrogen-producing
region 34,
the pressure in separation region 38, etc. This level of automation may be
referred to
as a first level of control, in which the controller maintains a particular
operating
parameter at or near a desired value. Typically, this value will be bounded by
threshold values that establish determined minimum and/or maximum values.
Should
the measured value of the operating parameter approach or exceed one of the
threshold values, controller 28 may send command signals other than those used
in
the first level of control described above. For example, the controller may
execute its
shutdown subroutine to transition the fuel processing system to its idle or
off
operating state.
When the performance of the mechanism utilized in the hydrogen-
producing region is temperature dependent, processor 16 will typically include
a
mechanism for selectively heating the hydrogen-producing device. The reforming
catalyst bed described above is an example of such a temperature-dependent
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CA 02477723 2004-09-08
mechanism. For example, it is preferable that bed 82 be preheated to at least
250 C
when steam reforming methanol, and at least 600 C when steam reforming other
alcohols and hydrocarbons.
An example of a suitable mechanism for heating the reforming
catalyst, or any other hydrogen-producing device requiring an elevated
temperature, is
a preheating assembly 90, such as shown in Fig. 5. As shown, assembly 90
includes a
pump assembly 92 that draws a fuel stream 94 from a fuel supply 96 and
combusts
this stream to heat bed 82 or other hydrogen-producing device, as
schematically
illustrated in dashed lines at 100. Supply 96 may be located external fuel
processing
1o assembly 12. When fuel supply 96 is adapted to deliver a compressed gaseous
fuel,
pump assembly 92 is not required, and the fuel stream may be delivered
directly to an
igniter 98, such as schematically illustrated at 101. Igniter 98 is shown in
Fig. 5 and
is meant to include any suitable mechanism for igniting fuel stream 94. This
includes
a glow plug or resistance element, spark plug, pilot light, or other suitable
hot surface,
flame or spark to ignite the fuel. Another example of a suitable igniter 98 is
a
combustion catalyst.
Preheating assembly 90 may utilize any suitable fuel. Examples of
suitable fuels include propane, natural gas, and transportation fuels. Another
example
of a suitable fuel is hydrogen gas, such as hydrogen gas previously produced
by fuel
processor 16. In fact, controller 28 may direct a portion of the product
hydrogen
stream to be recycled to preheating assembly 90 through a suitable conduit
(not
shown) when the temperature in the hydrogen-producing region approaches or
falls
below a desired minimum temperature. When the byproduct stream contains
sufficient hydrogen gas or other combustible material, it too may serve as a
fuel
source for preheating assembly 90 or combustion region 60.
As shown, controller 28 communicates with fuel supply 96 and pump
assembly 92, such as previously described in connection with feedstock supply
78 and
pump assembly 70. Controller 28 also communicates with igniter 98. This
communication is preferably two-way communication so that controller 28 can
not
only selectively activate and deactivate the igniter, but also monitor the
igniter to
detect a lack of ignition, such as within a determined time period after a
control signal
is sent to activate the igniter, or an unintentional flameout. In either
situation, the
controller may trigger the shutdown subroutine. Controller 28 may, for
example,
CA 02477723 2004-09-08
automatically attempt to reactuate the igniter, and then trigger the shutdown
subroutine should the relight attempt fail. Preferably, actuating the shutdown
subroutine also causes controller 28 to send a command signal to stop pump
assembly
92 and the flow of fuel from supply 96.
Another embodiment of a preheating assembly is shown in Fig. 6 and
generally indicated at 102. Instead of providing heat to hydrogen-producing
region
34 through the use of a combustible fuel, assembly 102 utilizes a heater 104,
such as a
resistance heater that receives an electric current from a power source 106.
Examples
of power source 106 include fuel cell stack 14, a battery bank storing current
from
fuel cell stack 14, an external source of electric current, and a battery bank
independent of fuel cell stack 14. Controller 28 sends control signals to
heater 104 to
selectively activate, deactivate and control the heat output of the heater,
responsive to
inputs from sensors in region 34 and/or preprogrammed conunands stored in
controller 28.
Heating, such as in the above preheating assemblies or in the
subsequently described combustion region, may also be accomplished through the
use
of an external heat source. An example of this is through heat exchange with
the
combustion output from an external combustion source. Another example is
through
heat exchange with an output stream from a boiler or furnace.
Resultant stream 36 from region 34 is passed to separation region 38,
as shown in Fig. 7. In region 38, stream 36 is divided into product stream 40
and
byproduct stream 42. One suitable method for partitioning stream 36 is through
the
use of a hydrogen-selective membrane, which preferably isolates at least a
substantial
portion of the hydrogen gas, while limiting or preventing the inclusion of
undesirable
compositions. In Fig. 7 a membrane assembly 84 is shown and includes at least
one
hydrogen-selective membrane 86. Examples of suitable membranes are membranes
formed from palladium or palladium alloys. Other suitable hydrogen-separation
devices that may be used include absorbent beds, catalytic reactors, and
selective
oxidation. Examples of suitable absorbent beds include zeolite and carbon
beds, and
3o an example of a suitable catalytic reactor includes a water-gas-shift
reactor.
As shown, controller 28 communicates with separation region 38 to
monitor such process parameters as the temperature and/or pressure within
membrane
assembly 84 or any other hydrogen-separation device being used therein.
Controller
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CA 02477723 2004-09-08
28 may also monitor the temperature and/or pressure of product and byproduct
streams 40 and 42. In membrane-based separation systems, the flow of hydrogen
gas
through the membrane is typically driven by maintaining a pressure
differential
between the opposed sides of the membrane(s). Therefore, controller 28 may
monitor
and regulate this pressure responsive to the inputs from sensors on both sides
of the
membrane. Examples of suitable pressures are a pressure of approximately 30
psig or
more on the hydrogen-production side of the membrane and a pressure of
approximately 5 psig or less on the product side of the membrane. However, the
pressure on the product side of the membrane(s) may be greater than 5 psig if
the
1o pressure on the hydrogen-producing side of the membrane(s) is sufficiently
elevated.
Preferably, the product side of the membrane is maintained as close to ambient
pressure as possible, while being maintained above the minimum detennined
pressure
for the fuel cell stack or other end destination for the product stream. These
desired
threshold values, similar to the other controlled thresholds discussed herein,
are stored
by controller 28, such as in a memory device 88, and more preferably in a
nonvolatile
portion of a memory device. Memory device 88 is shown schematically in Fig. 8
only, but it should be understood that device 88 may be included with any
embodiment of control system 26 described herein.
In some embodiments of fuel processor 16, product stream 40 may still
contain more than an acceptable concentration of some compositions. Therefore,
it
may be desirable for fuel processor 16 to include a polishing region 44, such
as shown
in Fig. 8. Polishing region 44 includes any suitable structure for removing or
reducing the concentration of selected compositions in stream 40. For example,
when
the product stream is intended for use in a PEM fuel cell stack or other
device that
will be damaged if the stream contains more than determined concentrations of
carbon
monoxide or carbon dioxide, it may be desirable to include at least one
methanation
catalyst bed 110. Bed 110 converts carbon monoxide and carbon dioxide into
methane and water, both of which will not damage a PEM fuel cell stack.
Polishing
region 44 may also include another hydrogen-producing device 112, such as
another
reforming catalyst bed, to convert any unreacted feedstock into hydrogen gas.
In such
an embodiment, it is preferable that the second reforming catalyst bed is
upstream
from the methanation catalyst bed so as not to reintroduce carbon dioxide or
carbon
monoxide downstream of the methanation catalyst bed.
12
CA 02477723 2004-09-08
The product hydrogen stream, now generally indicated at 46, is next
passed to an output assembly 50 and thereafter expelled from the fuel
processor. As
shown in Fig. 8, output assembly 50 includes a valve assembly 114 including
one or
more valves that are controlled responsive to command signals from controller
28. It
should be understood that valve assembly 114 may include a single valve
adapted to
distribute the flow between two or more output streams, or it may include a
plurality
of valves, each directing flow into a different output stream. For example,
streams 52
and 54 are shown in Fig. 8 adapted to deliver a selected portion of product
stream 46
to fuel cell stack 14 and storage device 56. Each stream may contain anywhere
from
lo 0-100% of stream 46, depending upon the control signals sent by controller
28. For
example, if there is suitable electrical or thermal load being applied to
stack 14 by an
associated device, such as device 22, then all of the product stream may be
sent to the
fuel cell stack. On the other hand, if there is insufficient load being
applied to stack
14 to require the entirety of stream 46, then some or all of the stream may be
otherwise disposed of, such as being sent to storage device 56. It should be
understood that processor 16 may include additional conduits providing
additional
destinations for product hydrogen stream 46. For example, a selected portion
of the
stream may be sent to combustion region 60 or preheating assembly 90 to be
used as a
fuel source, or it may be transported to a hydrogen-consuming device other
than stack
14 or device 56.
Output assembly 50 preferably includes a vent stream 55 through
which valve assembly 114 may selectively send some or all of the hydrogen
stream,
responsive to control signals from controller 28. For example, during startup
and
shutdown sequences of the fuel processor, when the produced hydrogen stream
may
contain impurities or for other reasons be undesirable as a feed to stack 14,
vent
stream 55 may be used to dispose of any flow delivered to the output assembly.
Stream 55 may exhaust the stream to the atmosphere, deliver the stream to a
combustion unit, or dispose of the stream in any other suitable manner.
Controller 28
may also direct, via command signs to valve assembly 114, all flow to stream
55
3o during the idle, or standby, operating states of the fuel processor, where
only minimal
flow is typically received and when no hydrogen gas is demanded by stack 14.
As shown in Fig. 8, controller 28 not only directs the operation of
valve assembly 114, but also receives inputs indicative of such parameters as
the
13
CA 02477723 2004-09-08
pressure, temperature and/or flowrate in streams 52, 54 and 55. These inputs
may be
used, for example, to ensure that valve assembly 114 is operating properly and
to
regulate the pressure in stream 52 going to fuel cell stack 14 to ensure that
the
pressure is not lower than a determined minimum pressure. In systems where it
is
preferable that the pressure of stream 52 be as low as possible, controller 28
may also
selectively control a pressure regulator to reduce the pressure if it is above
a
determined value.
In Fig. 8, dashed communication pathways 62' are shown to
demonstrate schematically that control system 26 may also enable one- or two-
way
communication between controller 28 and fuel cell stack 14, storage device 56
or any
other destination for the product hydrogen streams. For example, responsive to
inputs
representative of the load being applied to stack 14 from device 22,
controller 28 may
regulate the rate at which hydrogen is sent to stack 14. Responsive to this
input from
stack 14, controller 28 may also regulate the rate at which hydrogen gas is
produced
by processor 16 by controlling the rate at which feedstock is delivered to the
fuel
processor by the feed assembly. For example, if there is little or no load
being applied
to stack 14 and system 10 is not adapted to store or otherwise utilize
hydrogen gas,
then controller 28 may automatically regulate the rate of hydrogen production
responsive to the applied load.
In Fig. 9, an embodiment of combustion region 60 is shown in more
detail. As shown, region 60 includes a pump assembly 120 that includes at
least one
pump adapted to draw a stream 122 of a combustible fuel from a supply 124.
Combustion fuel supply 124 may be a compressed gaseous fuel, in which case
pump
assembly 120 is not required. Similar to the above-described preheating
assembly 90,
any suitable igniter 126 may be used to ignite the fuel and thereby generate
heat to
maintain the fuel processor within determined temperature ranges. Responsive
to
inputs, such as from a temperature sensor in hydrogen-producing region 34,
controller
28 regulates the rate at which fuel is drawn from supply 124 to thereby
control the
temperature of the processor. The examples of igniters and suitable fuels
discussed
above with respect to preheating assembly 90 are also applicable to combustion
region 60, as well as the operating parameters that may be monitored and
selectively
regulated by control system 26.
14
CA 02477723 2004-09-08
Although the operation of the fuel processing system is preferably at
least substantially automated by control system 26, it may still be desirable
for the
fuel processing system to include a user interface, such as interface 58 shown
in Fig.
10. Interface 58 includes a display region 130 through which infonnation is
conveyed
to the user by controller 28. Typically, the displayed information is
indicative of the
operating state of the fuel processor, as will be described in more detail
subsequently.
Also, if the controller detects a malfunction and actuates the shutdown
subroutine,
display region 130 may include a notification of the fault, including the
detected
malfunction. The messages or other information displayed to the user are
typically
stored in the controller's nonvolatile portion of its memory device 88, and
are
automatically displayed by controller 28 responsive to triggering events
detected by
the control system. Display region 130 may also include displays of operating
parameters detected by the control system, such as selected flowrates,
temperatures
and pressures, supply levels, etc.
As shown in Fig. 10, interface 58 may also include a user input device
132 through which a user may send commands to the controller. For example, the
user may manually input commands to cause controller 28 to startup the fuel
processor, shutdown the fuel processor, immediately stop operation of the fuel
processor, transition to an idle, or standby, state, etc.
It is within the scope of the present invention that input device 132
may be used to change the determined values utilized by controller 28 to
determine
whether the current operating state of the fuel processor needs to be
adjusted.
However, it may be desirable for some or all of the determined values to be
protected
from being changed by a user, or at least prevented from being changed by an
unauthorized user, such as one that does not previously enter a passcode or
other
authorizing command to the controller.
A user alert device 134 is also shown in Fig. 10 and may be used to
signal to a user that a malfunction or fault condition is detected. Device 134
may
include any suitable mechanism for attracting a user's attention, such as by
emitting
visual or audible signals. Also shown in Fig. 10 is a reset 136, which enables
a user
to cause the controller to restart the fuel processing system, such as after a
fault is
detected.
CA 02477723 2004-09-08
-16- '
As discussed, control system 28 automates the operation of fuel processing
assembly 12, and preferably automates the operation of the entire fuel
processing
system. In the preceding discussion, illustrative components, or regions of
fuel
processors and fuel processing systems according to the present invention were
described. Also discussed were the interaction of control system 26 with these
components, including examples of the operating parameters that may be
monitored
by controller 28, as well as the control signals that controller 28 may use to
regulate
the operation of the fuel processing system. It should be understood that any
desired
threshold values may be used. For example, controller 28 may be programmed to
utilize the specific operating parameters required for the feedstock, hydrogen-
producing mechanism, separation mechanism and product-stream destination
implemented in a particular embodiment of the fuel processing system. As a
specific
example, control system 26 may be programmed to automate fuel processing
system
10 according to any or all of the values of operating parameters described in
U.S.
Patent 6,221,117 issued April 24, 2001. Of course, other values may be used as
well.
Controller 28 preferaby is programmed to automatically switch between and
maintain defined operating states according to preprogrammed subroutines
responsive
to user inputs (such as to startup or shutdown the fuel processing system)
and/or
inputs from the operating parameters (such as the detection of a malfunction
or
operating parameter exceeding a defined threshold value for which automated
correction is not effective or preprogrammed).
To illustrate how control system 26 may automate the operation of a fuel
processing assembly and/or system, the following discussion and Figs. 11 and
12 are
provided. ln Fig. 11, examples of possible operating states and the
relationships
therebetween are schematically illustrated. As the following discussion
demonstrates,
the operating states may be achieved with only a few command signals from the
controller 28 since most of the fuel processing system is a passive system
that requires
an input stream to trigger a result. For example, once hydrogen-producing
region 34
CA 02477723 2004-09-08
-16A-
reaches at least a minimum acceptable operating temperature, it automatically
produces hydrogen gas when feed stream 20 is delivered thereto. Similarly,
separation region 38 and polishing region 44 automatically separate and
polish,
CA 02477723 2004-09-08
respectively, any stream delivered thereto, and fuel cell stack 14
automatically
produces an electric current when a hydrogen stream is delivered thereto.
In Fig. 11, four illustrative operating states are shown, namely, off
state 140, running state 142, standby state 144, and faulted state 146. Off
state 140
corresponds to when there is no feedstock being delivered to fuel processor
16, no
heat being generated in combustion region 60 or preheating assembly 90, and
the fuel
processor is depressurized. The fuel processing system is not operating and
has no
input or output streams.
Running state 142 corresponds to the state where the fuel processor is
lo receiving a flow of feedstock and producing hydrogen therefrom. The product
hydrogen stream is expelled from output assembly 50 and sent to fuel cell
stack 14 or
another destination. In the running state, combustion region 60 typically will
also be
used either intermittently or continuously to maintain the temperature with
the fuel
processor within determined threshold values, and preferably at or near a
selected
operating value between these threshold values.
Standby state 144 corresponds to when the fuel processor is
transitioning between its off and running states. In this state, the
controller achieves
and maintains determined operating temperatures and pressures within the fuel
processor, but typically little, if any, product stream will be delivered to
fuel cell stack
14 or storage device 56. Instead, any product stream reaching output assembly
50
will typically be combusted for heat, exhausted as waste gas, or otherwise
disposed
of. Standby state 144 may also be thought of as an idle state because the fuel
processing system is primed to produce hydrogen and/or electric current, but
none is
required or being generated in more than a nominal amount, such as would be
required to operate the fuel processing system.
From off state 140, controller 28 automatically directs the fuel
processor to achieve its standby operating state responsive to an input
signal, such as
a user input from interface 58, a load being applied to fuel cell stack 14, a
timed input
signal from controller 28 itself, etc. If standby state 144 is successfully
achieved,
controller 28 may either be programmed to direct system 10 to attain its
running state,
namely, by starting the flow of feedstock to fuel processor 16, or to await
the input of
a signal to trigger the transition to running state 142.
17
CA 02477723 2004-09-08
In either running state 142 or standby state 144, the detection of a
malfunction will cause controller 28 to automatically transition to faulted
state 146.
Faulted state 146 corresponds to when the controller detects a malfunction,
such as an
operating parameter exceeding a detennined threshold value. When this occurs,
the
controller preferably actuates user alert 134 to notify the user that there is
a problem
detected in the fuel processing system. Controller 28 also stops the flows of
fuel and
feedstock within the system, such as by directing the pump assemblies to stop
drawing from their corresponding supplies. Similarly, controller 28 may direct
any
product stream within the fuel processor to be utilized through stream 55,
thereby
io preventing any potentially contaminated stream from reaching fuel cell
stack 14 or
storage device 56. The igniters may also be deactivated.
From faulted state 146, the controller will either direct the transition to
off state 140, such as if no reset signal is received, or will attempt to
transition back to
standby state 144. If an input directing the controller to shutdown the fuel
processing
system is received while in the running state, controller 28 will preferably
transition
first to the standby state to safely stop the production of hydrogen, and then
to the off
state.
It should be understood that controller 28 may be programmed to
include other operating states than those shown in Fig. 11. For example, there
may be
more than one running state, such as to correspond to different rates of
hydrogen
production. Similarly, there may be separate startup and standby operating
states.
Controller 28 transitions between the operating states by executing
various programmed subroutines, each of which directs the controller to
automatically
send input signals required to achieve a selected result. Illustrative
examples of
suitable subroutines are shown in Fig. 12 and include preheat 150, pressurize
152,
standby 154, online 156 and shutdown 158 and off 160.
In preheat subroutine 150, controller 28 sends command signals
required to begin heating the fuel processor to its desired operating
temperature range.
Typically, this subroutine includes directing combustion region 60 to begin
heating
the fuel processor. It may also include directing preheating assembly 90 or
102 to
begin heating hydrogen-producing region 34 to at least a minimum temperature
required to effectively produce a product stream with an acceptable
composition.
Both of these heat-producing units will typically continue to be used during
the
18
CA 02477723 2004-09-08
subsequent pressurize subroutine 152, then the preheating assembly will
generally be
deactivated (by turning off the igniter and/or stopping the flow of fuel, or
by
deactivating the heater). The combustion region will typically continue to
operate
during all but the shutdown and off subroutines, although the relative rate of
operation
may be regulated by controller 28, such as by controlling the rate at which
fuel is
delivered to the igniter.
Once the hydrogen-producing region has achieved a selected threshold
temperature, which is monitored and detected by a sensor assembly in
conununication
with controller 28, controller 28 executes pressurize subroutine 152. In
pressurize
1o subroutine 152, feed stream 20 is-introduced into the fuel processor (by
controller 28
actuating pump assembly 70) to begin the production of hydrogen and thereby
pressurize the fuel processor. Once the fuel processor reaches a selected
operating
pressure, the controller executes standby subroutine 154. When standby
subroutine
154 is executed, controller 28 deactivates the preheating assembly, and the
controller
regulates the flow of feed stream 20 to produce a sufficient flow in product
stream 52
and/or byproduct stream 42 to provide fuel for combustion region 60.
When there is a demand for hydrogen product stream, such as when a
load is applied to fuel cell stack 14, the online subroutine is executed. In
this
subroutine, the controller increases the flow rate of feed stream 20, thereby
increasing
the rate at which hydrogen is produced, and as a result current is produced in
stack 14.
Valve assembly 114 is also actuated by a suitable command signal to direct
hydrogen
to fuel cell stack 14. Assembly 114 may optionally be actuated in the
pressurize
subroutine to send a hydrogen stream to stack 14 so that stack 14 may produce
current
to power the operation of system 10.
Should a malfunction be detected by controller 28, controller 28 will
automatically execute its shutdown, or fault, subroutine. The shutdown
subroutine
may also be executed responsive to a user input signal or programmed signal
directing
shutdown of the fuel processing system. In this subroutine, the controller
stops the
flow of feed stream 20, as well as the flow of fuel to combustion region 60
and
preheating assembly 90.
If a command, such as the user actuating reset 136, is not received,
controller 28 will next execute its off subroutine. In this subroutine, the
controller
deactivates any activated heater or igniter and begins depressurizing the fuel
19
CA 02477723 2004-09-08
processor. Finally, when the fuel processing system is safely depressurized
and all
flows have stopped, the valves in assembly 114 are closed and the shutdown of
the
fuel processing system is complete.
It should be understood that the above operating states and subroutines
have been presented to provide an example of how the invented control system
automates the operation of fuel processing system 10. The examples provided
above
should not be construed in a limiting sense, as many variations of the
subroutines,
operating states and commands executed therein are possible and are within the
scope
of the present invention. For example, when fuel processing system 10 includes
a
1o storage device 56 adapted to store a supply of hydrogen gas, this stored
supply may be
sent to fuel cell stack 14 in the preheat subroutine to produce current to
power the
operation of the fuel processing system.
The automation of fuel processing system 10 enables it to be used in
households, vehicles and other commercial applications where the system is
used by
individuals that are not trained in the operation of fuel processing systems.
It also
enables use in environments where technicians, or even other individuals, are
not
normally present, such as in microwave relay stations, unmanned transmitters
or
monitoring equipment, etc. Control system 26 also enables the fuel processing
system
to be implemented in commercial devices where it is impracticable for an
individual
to be constantly monitoring the operation of the system. For example,
implementation of fuel processing systems in vehicles and boats requires that
the user
does not have to continuously monitor and be ready to adjust the operation of
the fuel
processing system. Instead, the user is able to rely upon the control system
to regulate
the operation of the fuel processing system, with the user only requiring
notification if
the system encounters operating parameters and/or conditions outside of the
control
system's range of automated responses.
It should be understood that the above examples are meant to illustrate
possible applications of such an automated fuel processing system, without
precluding
other applications or requiring that a fuel processing system according to the
present
invention necessarily be adapted to be used in all of the exemplary scenarios.
Furthermore, in the preceding paragraphs, control system 26 has been described
controlling various portions of the fuel processing assembly. It is within the
scope of
the present invention that the system may be implemented without including
every
CA 02477723 2004-09-08
aspect of the control system described above. Similarly, system 26 may be
adapted
(i.e. programmed) to monitor operating parameters not discussed herein and may
send
command signals other than those provided in the preoeding examples.
While the invention has been disclosed in its preferred fom, the
specific embodiments thereof as disclosed and illustrated herein are not to be
considered in a limiting sense as numerous variations are possible. Applicants
regard
the subject matter of the invention to include all novel and non-obvious
combinations
and subcombinations of the various elements, features, functions and/or
properties
disclosed herein. No single feature, function, element or property of the
disclosed
i o embodiments is essential to all embodiments. The following claims define
certain
combinations and subcombinations that are regarded as novel and non-obvious.
21
