U.S. patent application number 15/389617 was filed with the patent office on 2018-04-26 for reformer with bypass for internal fuel cell reforming.
This patent application is currently assigned to LG Fuel Cell Systems, Inc.. The applicant listed for this patent is LG Fuel Cell Systems, Inc.. Invention is credited to Robert Cunningham, Eric Dean, Michael Jennings.
Application Number | 20180115002 15/389617 |
Document ID | / |
Family ID | 61970517 |
Filed Date | 2018-04-26 |
United States Patent
Application |
20180115002 |
Kind Code |
A1 |
Cunningham; Robert ; et
al. |
April 26, 2018 |
Reformer With Bypass For Internal Fuel Cell Reforming
Abstract
A fuel cell system having a fuel cell stack, comprising an anode
portion and a cathode portion, a source of hydrocarbon fuel, and a
reformer unit having one or more cold-side, reforming passages, a
fuel supply conduit, a reformate exhaust conduit, one or more
hot-side channels, a cathode exhaust conduit, a cathode inlet
conduit, one or more bypass channels having non-reforming passages
for fuel to bypass the cold-side channels, and a flow controller
for controlling the flowrate in the bypass channels, and methods
for operating the same, is provided.
Inventors: |
Cunningham; Robert; (Derby,
GB) ; Dean; Eric; (Derby, GB) ; Jennings;
Michael; (Derbyshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG Fuel Cell Systems, Inc. |
North Canton |
OH |
US |
|
|
Assignee: |
LG Fuel Cell Systems, Inc.
North Canton
OH
|
Family ID: |
61970517 |
Appl. No.: |
15/389617 |
Filed: |
December 23, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15333255 |
Oct 25, 2016 |
|
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15389617 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01B 2203/1047 20130101;
H01M 8/04007 20130101; C01B 2203/0833 20130101; C01B 2203/0838
20130101; B01J 2219/00117 20130101; B01J 2219/00103 20130101; B01J
2219/00164 20130101; C01B 2203/1064 20130101; C01B 3/384 20130101;
B01J 12/007 20130101; B01J 19/0013 20130101; C01B 2203/066
20130101; H01M 8/04089 20130101; B01J 7/00 20130101; C01B 2203/067
20130101; H01M 8/04753 20130101; B01J 2219/00076 20130101; B01J
2219/2479 20130101; B01J 19/248 20130101; H01M 8/0662 20130101;
B01J 2219/2462 20130101; C01B 2203/0233 20130101; C01B 2203/1235
20130101; C01B 2203/1241 20130101; H01M 8/04201 20130101; B01J
2219/00087 20130101; H01M 8/0618 20130101; C01B 2203/1082
20130101 |
International
Class: |
H01M 8/0612 20060101
H01M008/0612; H01M 8/04089 20060101 H01M008/04089; H01M 8/04746
20060101 H01M008/04746; H01M 8/04082 20060101 H01M008/04082; H01M
8/0662 20060101 H01M008/0662; H01M 8/04007 20060101
H01M008/04007 |
Claims
1. In a fuel cell system comprising: a source of a hydrocarbon
fuel; a reformer for receiving the hydrocarbon fuel and converting
the hydrocarbon fuel to reformate; and a fuel cell stack having an
anode inlet for receiving a mixture of the reformate and the
hydrocarbon fuel, a method of controlling the volumetric ratio of
the reformate and hydrocarbon fuel in the mixture comprising:
providing a flow path for fuel to bypass the reformer; controlling
the flow rate of fuel within the flow path; and combining the fuel
flowing through the bypass flow path with the reformate.
2. The method of claim 1 further comprising: removing higher
hydrocarbons from the hydrocarbon fuel
3. The method of claim 1 further comprising: heating the fuel
bypassing the reformer prior to combining the fuel.
4. The method of claim 3, wherein the heating results from a
transfer of heat from a cathode exhaust gas.
5. The method of claim 1, wherein at least a portion of the fuel
comprises an anode exhaust gas.
6. In a fuel cell system configured for internal reforming of a
hydrocarbon fuel in the fuel cell stack, a method of operation
comprising: supplying a hydrocarbon fuel to the system; feeding a
portion of the hydrocarbon fuel to a reformer to thereby convert
the fuel to reformate; bypassing a second portion of the
hydrocarbon fuel around the reformer; combining the bypassed
hydrocarbon fuel with the reformate at a selected feed rate;
supplying the combined reformate and hydrocarbon fuel to an anode
inlet of the fuel cell stack; and controlling the volumetric ratio
of the combined reformate and hydrocarbon fuel supplied to the
anode inlet of the fuel cell stack by selecting the feed rate of
the bypassed hydrocarbon fuel.
7. The method of claim 6 further comprising heating the reformate
and the bypassed fuel by transferring heat from a gas supplied from
a cathode exhaust of the fuel cell stack.
8. The method of claim 7 further comprising coating at least a
portion of the surfaces exposed to the bypassed fuel with a ceramic
material to thereby inhibit carbon formation on the coated
surfaces.
9. A fuel cell system comprising: a fuel cell stack configured for
internal reforming of a hydrocarbon fuel, said fuel cell stack
comprising: an anode portion in fluid communication with an anode
inlet and an anode exhaust; a cathode portion in fluid
communication with a cathode inlet and a cathode exhaust; a source
of hydrocarbon fuel; a reformer unit for converting hydrocarbon
fuel to reformate, said reformer unit comprising: one or more
cold-side channels for providing a reforming passage for fuel
through said reformer unit; a fuel supply conduit in fluid
communication with said fuel source and said cold-side channels; a
reformate exhaust conduit in fluid communication with said
cold-side channels and said anode inlet; one or more hot-side
channels for providing a passage for a cathode exhaust gas through
said reforming unit, said hot-side channels being in sufficient
proximity to said cold-side channels to effect heat transfer
between the fluids flowing through the respective channels; a
cathode exhaust conduit in fluid communication with said cathode
exhaust and said hot-side channels; a cathode inlet conduit in
fluid communication with said hot-side channels and said cathode
inlet; one or more bypass channels for providing a non-reforming
passage for fuel through said reformer unit, said bypass channels
being in fluid communication with said fuel supply conduit and said
reformate exhaust conduit to thereby combine the non-reformed fuel
with the reformate; and a flow controller for controlling the flow
rate of fuel flowing through said bypass channels.
10. The system of claim 9, wherein said bypass channels is in
sufficient proximity to said hot-side channels to effect heat
transfer between the fluids flowing through the respective
channel.
11. The system of claim 9, wherein said bypass channels is in
sufficient proximity to said cathode inlet conduit to effect heat
transfer between the fluids flowing through the respective
channel.
12. The system of claim 11, wherein said bypass channel is a line
which passes through said cathode inlet conduit, wherein said
amount of heat transferred from the fluid in the cathode inlet
conduit to the non-reformed fuel in the bypass channel is
determined at least in part by the length of the bypass channel
line disposed in the cathode inlet conduit.
13. The system of claim 9, wherein said bypass channel is lined
with a ceramic coating to inhibit carbon formation.
14. The system of claim 9, further comprising a higher hydrocarbon
reduction unit.
15. The system of claim 9, further comprising a combustor.
16. The system of claim 9, wherein the reformer unit is a steam
reformer.
17. The system of claim 16, wherein said reformer unit comprises a
catalyst containing at least one Group VIII metal.
18. The system of claim 17, wherein the at least one Group VIII
metal comprises 0.1 to 40 wt % of said catalyst.
19. The system of claim 17, wherein said catalyst further comprises
one or more promoter elements selected from a group containing
elements from Groups IIa-VIIa, elements Groups Ib-Vb, lanthanide
series, and actinide series.
20. The system of claim 17, wherein said promoter element comprises
0.01 to 10 wt % of the catalyst.
Description
RELATED APPLICATIONS
[0001] This Application is a continuation of U.S. patent
application Ser. No. 15/333,255, titled "Steam Reformer Bypass Line
and Flow Controller," filed Oct. 25, 2016, which is herein
incorporated by reference in its entirety for all purposes.
FIELD
[0002] This disclosure generally relates to fuel cells. More
specifically, this disclosure is related to systems and methods
which may support internally-reforming fuel cells.
BACKGROUND
[0003] A fuel cell is an electrochemical system in which a fuel
(such as hydrogen) is reacted with an oxidant (such as oxygen) at
high temperature to generate electricity. One type of fuel cell is
the solid oxide fuel cell (SOFC). The basic components of a SOFC
may include an anode, a cathode, a solid electrolyte, and an
interconnect. The fuel may be supplied to the anode, and the
oxidant may be supplied to the cathode of the fuel cell. At the
cathode, electrons ionize the oxidant. The electrolyte comprises a
material that allows the ionized oxidant to pass through to the
anode while simultaneously being impervious to the fluid fuel and
oxidant. At the anode, the fuel is combined with the ionized
oxidant in an electrochemical reaction that releases electrons to
be conducted back to the cathode through the interconnect.
Additional heat, generated from ohmic losses within the fuel cell
components, is removed from the fuel cell by either the anode or
cathode flow stream or is radiated to the environment.
[0004] A SOFC may be structured, e.g., as a segment-in-series or
in-plane series arrangement of individual cells. The oxidant is
typically introduced at one end of the series of cells and flows
over the remaining cells until reaching the cathode exhaust outlet.
Each fuel cell transfers a portion of the ohmic heat into the
oxidant thereby raising its temperature, and forming a temperature
gradient which increases from the oxidant inlet to the exhaust. In
turn, this temperature gradient reduces the differential
temperature between the fuel cell components and the oxidant,
thereby reducing the heat transferred between the two.
Consequently, a temperature gradient may also develop in the fuel
cell which increases from the oxidant inlet to the oxidant exhaust.
This temperature gradient may reduce fuel cell performance, reduce
life, or cause thermal stresses across the cells that may cause
material degradation or failure of the fuel cell components.
[0005] The anode of a SOFC may be a mixed cermet comprising nickel
and zirconia (such as, e.g., yttria stabilized zirconia (YSZ)) or
nickel and ceria (such as, e.g., gadolinia dope ceria (GDC)).
Nickel, and other materials, may function not only to support the
chemical reaction between the fuel and the ionized oxidant but may
have catalytic properties which allow the anode to reform a
hydrocarbon fuel within the fuel cell. One method of reforming the
hydrocarbon fuel is steam reforming of methane (CH.sub.4), an
endothermic reaction:
CH.sub.4+H.sub.20.fwdarw.CO+3H.sub.2.DELTA.H.degree.=206.2
kJ/mole
[0006] The heat necessary for reforming methane could be supplied
directly from the ohmic heat generated from the fuel cells, with
the reforming reaction either taking place in a separate reformer
unit, or directly within the fuel cell stack. This direct heat
transfer may help cool the stack and reduce thermal stresses.
However, in-stack reforming introduces several technical
challenges. Unreformed methane must be supplied in the correct
amount to avoid excessively cooling of the fuel cell and in the
correct manner to avoid localized cooling. Additionally,
hydrocarbon fuels have a propensity to form carbon, particularly
when a significant amount of reforming is performed:
C.sub.xH.sub.2x+2.fwdarw.C+(x+1)H.sub.2
Carbon formation can cause fouling and degradation of fuel cell
components through anode delamination, metal dusting and other
failure mechanisms.
[0007] Consequently, supplying a mixture of a reformate that has
been generated external to the fuel cell and unreformed fuel to the
anode may provide better a balance for system performance and
durability than supplying the stack with either reformate or
unreformed fuel alone. However, the ratio of reformed and
unreformed fuel must be precisely controlled. If the ratio is too
high, the large temperature gradient across the fuel stack will
remain. If it is too low, carbon formation becomes more likely
leading to reduced life.
[0008] Additionally, assemblies for controlling the flow rate of a
fluid typically include needle valves or other types of valves and
orifice plates. Some adjustable orifice plates comprise rotating
plates wherein each plate defines an opening. The alignment of
plate openings determines the effective flow area of the orifice.
However, these solutions are not suitable for the high temperature
and pressure conditions of an operating fuel cell and are prone to
leakage.
[0009] There remains a need for precise control of the ratio of
reformed and unreformed fuels delivered to a fuel cell stack to
ensure that the proper amount of reforming occurs internally to the
fuel cell. Additionally, there remains a need for systems and
methods to achieve this precise control.
[0010] In accordance with some embodiments of the present
disclosure, a reformer with a bypass is provided. The bypass may
contain a flow controller that restricts the bypass flow. The flow
controller may be adjustable to control the flow rate of the fluid
through the bypass, thereby enabling precise control of the ratio
of reformate and unreformed fuels supplied to the fuel cell stack.
This design permits some of the disclosed embodiments to
accommodate a wide range of in-stack reforming fuel cell designs
and minimizes the risk for carbon formation.
[0011] In accordance with some embodiments of the present
disclosure, effective and adjustable means are provided that
control the fluid flow rate within a reformer bypass in a high
temperature and pressure environment.
[0012] In accordance with some embodiments of the present
disclosure, a reformer unit is provided. The reformer unit may have
a reforming section, a heat exchanging section, and a bypass
section. The reforming section may reform a hydrocarbon-containing
fuel, and have an inlet in fluid communication with a source of
hydrocarbon fuel and an outlet in fluid communication with an anode
inlet of a fuel cell stack. The heat exchanging section may heat a
fluid flowing in the reforming section, in the bypass section, or
both, and may have an inlet in fluid communication with an exhaust
of a cathode of a fuel cell stack, and an outlet adapted for fluid
communication with an inlet of a cathode of a fuel cell stack. The
heat exchanging section is in thermal communication with said
reforming section (or said bypass section or both) to effect heat
transfer between the fluids flowing in each section. The bypass
section provides a flow path for the hydrocarbon-containing fuel
around the reforming section, and has an inlet in fluid
communication with the reforming section inlet, an outlet in fluid
communication with the reforming section outlet, and a variable
orifice flow controller positioned in the bypassing flow path.
[0013] In accordance with some embodiments of the present
disclosure, a variable orifice flow controller for controlling the
flow of a high temperature, high pressure, or both fluid is
provided. The flow controller may comprise an upstream connector, a
downstream connector and an interconnector. The upstream connector
may have cylindrical tubular portion defining a conduit in fluid
communication with a flow path of high temperature fluid and a
frusto-conical portion defining a plurality of conduits in fluid
communication with the conduit. The downstream connector may define
a frusto-conical cavity for receiving the frusto-conical portion of
said upstream connector and a plurality of conduits in fluid
communication with said cavity. The interconnector may provide a
fluid-tight connection when the frusto-conical portion of the
upstream connector is received within the cavity defined by said
downstream connector. The amount of fluid communication between the
plurality of conduits defined by the downstream and upstream
connectors is selected by the radial alignment between the upstream
and downstream connectors when in a gastight connection.
[0014] In accordance with some embodiments of the present
disclosure a variable orifice flow controller for controlling the
flow of a high temperature, high pressure, or both gas is provided.
The flow controller may comprise an upstream connector, a
downstream connector, a disc, and an interconnector. The upstream
connector may have cylindrical tubular portion defining a conduit
in fluid communication with a flow path of high temperature fluid
and a frusto-conical portion defining a plurality of conduits in
fluid communication with the conduit. The downstream connector may
define a frusto-conical cavity for receiving the frusto-conical
portion of said upstream connector and a conduit in fluid
communication with the cavity. The disc may define a plurality of
conduits and may be adjacent to a face of the frusto-conical
portion of said upstream connector in a selected radial alignment
such that the plurality of conduits defined by the disc are in
fluid communication with the plurality of conduits defined by the
frusto-conical portion of the upstream connector and the conduit
define by the downstream connector. The interconnector may provide
a fluid-tight connection when the frusto-conical portion of the
upstream connector is received within the cavity defined by said
downstream connector. The amount of fluid communication between the
plurality of conduits define by the disc and the plurality of
conduits defined by the frusto-conical portion of said upstream
connector is selected by the radial alignment of the conduits when
in a gastight connection.
[0015] In accordance with some embodiments of the present
disclosure, a reformer unit for a fuel cell is presented. The
reformer unit may comprise a reforming section, a heat exchanging
section, and a bypass plenum. The reforming section reforms a
hydrocarbon-containing fuel and has an inlet in fluid communication
with a source of hydrocarbon-containing fuel and an outlet plenum
in fluid communication with an anode inlet of a fuel cell stack.
The heat exchanging section heats a fluid flowing in the reforming
section, the bypass plenum, or both. The heat exchanging section
has an inlet in fluid communication with the exhaust of a cathode
and an outlet adapted for fluid communication with an inlet of
cathode of the fuel cell stack. The heat exchanging section is in
thermal communication with the reforming section and the bypass
plenum to effect a heat transfer. The bypass plenum provides a flow
path for the hydrocarbon-containing fuel to bypass the reforming
section and has an inlet in fluid communication with the reforming
section inlet, an outlet in fluid communication with the reforming
section outlet plenum and a flow restrictor in the flowpath between
the outlet of the bypass plenum and the outlet plenum of the
reforming section.
[0016] In accordance with some embodiments of the present
disclosure, a flow restrictor for restricting the flow of a high
temperature fluid through an orifice providing fluid communication
between two plenums is provided. The flow restrictor may comprise a
connector mounted to a wall of a first plenum, a fitting, an
elongated flow restricting member, and an internally threaded
sealing nut. The connector comprises a first portion defining a
cylindrical cavity having a threaded portion and a second portion
which defines a frusto-cylindrical cavity in communication with the
cylindrical cavity. The fitting comprises a frusto-conical end
portion that is positioned within the frusto-conical cavity and
defines an axial slot. The elongated flow restricting member
comprises a cylindrical threaded portion positioned and threadably
engaged with the cylindrical cavity, a portion extending from one
end of said cylindrical portion into the axial slot and a tapered
portion extending from the other end of the cylindrical portion
through the orifice. The axial alignment of the tapered portion and
the orifice is selectable by rotating the flow restricting member
relative to the connector. The internally threaded sealing nut
engages an external threaded portion of the connector and provides
a fluid-tight seal between the fitting and the connector.
[0017] In accordance with some embodiments of the present
disclosure, a reforming unit for a fuel cell system is provided.
The reforming unit may comprise a reforming section, a heat
exchanging section and a bypass plenum. The reforming section
reforms a hydrocarbon containing fuel. The heat exchanging section
effects a heat transfer between a fluid flowing therethrough and
the fluid flowing through the reforming section, the bypass plenum,
or both. The bypass plenum provides a flowpath for the
hydrocarbon-containing fuel to bypass the reforming section. The
bypass plenum may comprise a flow restrictor in the outlet of the
bypass plenum to control the amount of fluid communication between
the outlet of the bypass plenum and the outlet of the reforming
section.
[0018] In accordance with some embodiments of the present
disclosure, a method of controlling the volumetric ratio of a
reformate and a hydrocarbon fuel in a mixture is provided. The
method may be applied to a fuel cell system comprising a source of
hydrocarbon fuel, a reformer and a fuel cell stack. The reformer
may be configured for receiving the hydrocarbon fuel and converting
the hydrocarbon fuel to a reformate. The fuel cell stack may have
an anode inlet for receiving a mixture of the reformate and the
hydrocarbon fuel. The method may comprise providing a flow path for
fuel to bypass the reformer, controlling the flow rate of fuel
within the flow path, and combining the fuel flowing through the
bypass flow path with the reformate.
[0019] In accordance with some embodiments of the present
disclosure, a method of operating a fuel cell is provided. The fuel
cell system may be configured for internal reforming of a
hydrocarbon fuel in the fuel cell stack. The method may comprise
supplying a hydrocarbon fuel to a reformer to thereby convert the
fuel to reformate, bypassing a second portion of the hydrocarbon
fuel around the reformer, combining the bypassed hydrocarbon fuel
with the reformate at a selected feed rate, supplying the combined
reformate and hydrocarbon fuel to an anode inlet of the fuel cell
stack, and controlling the volumetric ratio of the combined
reformate and hydrocarbon fuel supplied to the anode inlet of the
fuel cell stack by selecting the feed rate of the bypassed
hydrocarbon fuel.
[0020] In accordance with some embodiments of the present
disclosure, a fuel cell system is provided. The fuel cell system
may comprise a fuel cell stack, a source of hydrocarbon fuel and a
reformer unit. The fuel cell stack may be configured for internal
reforming of a hydrocarbon fuel, and may comprise an anode portion
in fluid communication with an anode inlet and an anode exhaust,
and a cathode portion in fluid communication with a cathode inlet
and a cathode exhaust. The reformer unit may convert hydrocarbon
fuel to a reformate, and may comprise one or more cold-side
channels, a fuel supply conduit, a reformate exhaust conduit, one
or more hot-side channels, a cathode exhaust conduit, a cathode
inlet conduit, one or more bypass channels, and a flow controller.
The one or more cold-side channels may provide a reforming passage
for fuel through the reformer unit. The fuel supply conduit may be
in fluid communication with the fuel source and the cold-side
channels. The one or more hot-side channels may provide a passage
for a cathode exhaust gas to pass through the reforming unit and
may be in sufficient proximity to the cold-side channels to effect
a heat transfer between the fluids flowing through the respective
channels. The cathode exhaust conduit may be in fluid communication
with the cathode exhaust and the hot-side channels. The cathode
inlet conduit may be in fluid communication with the hot-side
channels and the cathode inlet. The one or more bypass channels may
provide a non-reforming passage for fuel through the reformer unit
and may be in fluid communication the fuel supply conduit and the
reformate exhaust conduit to thereby combined the non-reformed fuel
with the reformate. The flow controller may control the flow rate
of the fuel flowing through said bypass channels.
[0021] These and many other advantages of the present subject
matter will be readily apparent to one skilled in the art to which
the disclosure pertains from a perusal of the claims, the appended
drawings, and the following detail description of the
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a system diagram of a fuel cell system with a
reformer having a bypass in accordance with some embodiments of the
present disclosure.
[0023] FIGS. 2A and 2B are perspective views of a reformer having a
bypass in accordance with some embodiments of the present
disclosure.
[0024] FIG. 3 provides two perspective views of a flow controller
in accordance with some embodiments of the present disclosure.
[0025] FIG. 4 provides two cross-section views of the flow
controller of FIG. 3 in accordance with some embodiments of the
present disclosure.
[0026] FIG. 5 illustrates a perspective view of the assembled flow
controller of FIG. 3 in accordance with some embodiments of the
present disclosure.
[0027] FIG. 6 illustrates a disassembled, perspective view of a
flow controller in accordance with some embodiments of the present
disclosure.
[0028] FIG. 7 illustrates an assembled, perspective view of the
flow controller of FIG. 6 in accordance with some embodiments of
the present disclosure.
[0029] FIG. 8 illustrates two perspective views of a reformer unit
having a bypass plenum in accordance with some embodiments of the
present disclosure.
[0030] FIG. 9 illustrates the inlet plenum of a reformer unit
having a bypass plenum in accordance with some embodiments of the
present disclosure.
[0031] FIG. 10 illustrates a close-up view of a bypass plenum in
accordance with some embodiments of the present disclosure.
[0032] FIG. 11 illustrates exploded and assembled cross-sectional
views of a flow restrictor in accordance with some embodiments of
the present disclosure.
[0033] FIG. 12 provides a close-up view and a cross-sectional view
of the outlet of a bypass plenum in accordance with some
embodiments of the present disclosure.
[0034] Referring to the drawings, some aspects of non-limiting
examples of a fuel cell system in accordance with an embodiment of
the present disclosure are schematically depicted. In the drawings,
various features, components and interrelationships between aspects
of an embodiment of the present disclosure are depicted. However,
the present disclosure is not limited to the particular embodiments
presented and the components, features and interrelationships as
illustrated in the drawings and described herein.
DETAILED DESCRIPTION
[0035] The objectives and advantages of the claimed subject matter
will become apparent from the following detailed description of the
preferred embodiments thereof in connection with the accompanying
drawings, in which like reference numerals denote like
elements.
[0036] A system diagram of a fuel cell system 100 configured for
internal reforming of a hydrocarbon fuel having a bypass in
accordance with some embodiments of the present disclosure is
illustrated in FIG. 1. The system 100 comprises a fuel cell stack
102, a source of hydrocarbon fuel 116, a reformer unit 118, and an
oxidant source 150. The fuel cell stack 102 comprises an anode
portion 104 in fluid communication with an anode inlet 106 and an
anode exhaust 108, and a cathode portion 110 in fluid communication
with a cathode inlet 112 and a cathode exhaust 114. The fuel cell
stack 102 may be of any fuel cell design, and is preferably a
SOFC.
[0037] The source of hydrocarbon fuel 116 may provide any type of
hydrocarbon fuel, such as, e.g., methane or natural gas, to the
fuel cell system 100. The source of oxidant 150 may provide air or
other oxidant to the fuel cell system 100.
[0038] The reformer unit 118 converts hydrocarbon fuel from the
source of hydrocarbon fuel 116 into a reformate and comprises one
or more cold-side channels 120, a fuel supply conduit 122, a
reformate exhaust conduit 124, one or more hot-side channels 126, a
cathode exhaust conduit 128, a cathode inlet conduit 130, one or
more bypass channels 132, and a flow controller 134. In a preferred
embodiment the reformer unit 118 is a steam reformer.
[0039] The cold-side channels 120 provide reforming passages that
reform the fuel supplied from the source of hydrocarbon fuel 116
into a reformate. The cold-side channels 120 may be referred to as
a reforming section. The reforming passages may contain a catalyst
comprising at least one Group VIII metal, and preferably one Group
VIII noble metal, such as, e.g., platinum, palladium, rhodium,
iridium or a combination thereof. A catalyst comprising rhodium and
platinum are preferred. The catalyst may contain active metals in
any suitable amount that achieves the desired amount of hydrocarbon
conversion. For example, the active catalyst metals may comprise
0.1 to 40 wt % of the catalyst. In some embodiments, the active
catalyst metals may comprise 0.5 to 25 wt % of the catalyst. In
some embodiments, the active catalyst metals may comprise 0.5 to 15
wt % of the catalyst.
[0040] In some embodiments, the catalyst may contain one or more
promoter elements to improve the catalyst activity, durability,
suppress carbon formation, or any combination of these or other
improvements. The promoter elements may include, but are not
limited to, elements from Groups IIa-VIIa, Groups Ib-Vb, lanthanide
and actinide series elements, or any combination thereof. Promoters
such as magnesia, ceria, and baria may suppress carbon formation.
The promoter elements may be present in any amount ranging, from
0.01 to 10 wt % of the catalyst. In some embodiments, the promoter
elements may be present in amount ranging from 0.01 to 5 wt % of
the catalyst. The embodiments of the present disclosure are not so
limited and may contain any amount of active metal, promoter
elements, or both in ranges outside of those expressly listed.
[0041] The catalyst may be supported on a carrier comprising a
refractory oxide such as, e.g., silica, alumina, titania, zirconia,
tungsten oxides, and mixtures thereof, although the disclosure is
not limited to refractory oxides. In some embodiments, the carrier
may comprise a mixed refractory oxide compound comprising at least
two cations. The catalyst active and promoter elements may be
deposited on the carrier by any of a number of techniques. The
catalyst may be deposited by impregnation onto the carrier, e.g.,
by contacting the carrier materials with a solution of the catalyst
followed by drying and calcining the structure. The catalyst may be
coated onto the plates of a heat exchanger or on inserts placed
into the cold-side channels 120. Catalyst pellets of a suitable
size and shape may also be placed in the cold-side channel 120.
However, the embodiments of the present disclosure are not so
limited, and any means of incorporating the catalyst into the
cold-side channels 120 may be used, such as, e.g., using a porous
support structure.
[0042] The cold-side channels 120 are in fluid communication with
the source of hydrocarbon fuel 116 via a fuel supply conduit 122
that functions to transport the hydrocarbon fuel from the source of
the hydrocarbon fuel 116 to the cold-side channels 120 of the
reformer unit 118.
[0043] In accordance with some embodiments, the fuel cell system
100 may further comprise a higher hydrocarbon reduction unit 148
which is in fluid communication with both the source of hydrocarbon
fuel 116 and the fuel supply conduit 122. The higher hydrocarbon
reduction unit 148 may be used upstream of the reformer unit 118 to
reduce the level of higher hydrocarbons fed to the reformer unit
118 cold-side channels 120 and the bypass channel 132. By reducing
the level of higher hydrocarbons fed to the reformer unit 118, the
higher hydrocarbon reduction unit 148 inhibits carbon formation
within the fuel cell system 100.
[0044] As the hydrocarbon fuel passes through the reforming
passages of the cold-side channels 120 it is at least partially
reformed to reformate or syngas (a mixture containing hydrogen and
carbon monoxide). This reformate flows into the reformate exhaust
conduit 124, which may also be referred to as an outlet plenum,
that is in fluid communication with both the cold-side channels 120
and the anode inlet 106. Prior to reaching the anode inlet 106, the
reformate in the reformate exhaust conduit 124 may reach a junction
at which the reformate may be combined and mixed with the flow of
an unreformed hydrocarbon fuel flowing through the bypass channel
132. The unreformed hydrocarbon fuel flowing through the bypass
channel 132 may flow through a heat exchanger 142, which may be
referred to a second heat exchanging section. The heat exchanger
142 transfers heat from the cathode exhaust into the unreformed
fuel. In some embodiments, the heat exchanger may be located
upstream from the hot-side channels 126 rather than downstream as
depicted in FIG. 1. In some embodiments, the hot fluid flowing
through heat exchanger 142 may be some fluid other than the cathode
exhaust, such as, e.g., the anode exhaust, gasses from a
anode-exhaust recycling combustor (such as combustor 146), or other
source.
[0045] Reformer Unit 118 also comprises one or more hot-side
channels 126, which may referred to as a heat exchange section. The
hot-side channels 126 provide a passage for a cathode exhaust gas
to flow through the reforming unit 118. These channels 126 may be
arranged in a sufficiently close proximity and orientation to the
cold-side channels 120 in order to effect the transfer of heat
between fluids flowing in the hot-side channels 126 and the
cold-side channels 120. The fluid flows in these channels maybe
oriented for parallel flow, counter flow, cross flow, or any other
heat exchanger configuration. Regardless of the proximity of the
heat exchange section to the reforming section, both components are
arranged to be in thermal communication with one another.
[0046] The hot-side channels 126 of reformer unit 118 are in fluid
communication with the cathode exhaust 114 via the cathode exhaust
conduit 128. Additionally, the hot-side channels 126 may be in
fluid communication with the cathode inlet 112 via the cathode
inlet conduit 130. In accordance with some embodiments, the cathode
exhaust in the cathode inlet conduit 130 is supplied to the suction
side of a cathode ejector 140. The oxidant source 150 may provide
the motive energy which operates the cathode ejector 140. The
cathode exhaust and oxidant may flow through the cold-side channels
of a heat exchanger 144 prior to being supplied to the cathode
inlet 112. The hot-side channels of heat exchanger 144 may provide
passage ways for a combustor 146 exhaust gas flow or other hot
fluid which transfers heat into the combined cathode
exhaust-oxidant flow supplied to the cathode inlet 112.
[0047] The reformer unit 118 comprises one or more bypass channels
132, which may be referred to as a bypass section for providing a
bypassing flow path, that provide a non-reforming passage for
hydrocarbon fuel to flow through the reformer unit 118. The bypass
channel 132 is in fluid communication with the fuel supply conduit
122 and the reformate exhaust conduit 124. The unreformed
hydrocarbon fuel from the bypass channel 132 may be combined and
mixed with the reformed fuel flowing through the reformate exhaust
conduit 124. The bypass channel 132 may be a line comprising a
ceramic coating in order to inhibit metal-catalyzed carbon
formation.
[0048] In accordance with some embodiments of the present
disclosure, perspective views of a reformer having a bypass are
illustrated in FIG. 2A and FIG. 2B. A portion the reformer unit 118
is illustrated as having a bypass channel 132. The bypass channel
132 may be a line (such as, e.g., piping, hose, or similar
component) connected proximate to and in fluid communication with
the fuel supply conduit 122. As shown in FIG. 2B, the bypass
channel 132 line may pass through the cathode inlet conduit 130
prior to merging with the reformate exhaust conduit 124. The
cathode inlet conduit 130 may also be considered an exhaust duct
through which the cathode exhaust is removed from the reforming
unit 118. In some embodiments, the passage of the bypass channel
132 line through the cathode inlet conduit 130 will effect a heat
transfer between the two fluids flowing in their respective
sections. This arrangement may provide the function of heat
exchanger 142, although the embodiments of the present disclosure
are not so limited. The amount of heat transferred between the
cathode exhaust in the cathode inlet conduit 130 and the unreformed
fuel in the bypass channel 132 line may be effected by varying the
length of the bypass channel 132 line in the cathode inlet conduit
130.
[0049] In some embodiments, the one or more bypass channels 132 may
be integrated with the structure of the cold-side channels 120 and
the hot-side channels 126 such that the channels 132 are in
sufficient proximity to the hot-side channel 126 effect a heat
transfer. In some embodiments, the one or more bypass channels 132
may be the equivalent of un-catalyzed cold-side channels 120.
[0050] The reformer unit 118 may further comprise a flow controller
134, which may be referred to as a variable orifice flow
controller, in the bypass channel 132. The flow controller 134 may
be an interchangeable flow orifice. The flow controller restricts
the flow of the unreformed hydrocarbon fuel by reducing the
effective area of the bypass channel 132. Controlling the flow rate
of the unreformed hydrocarbon fuel flowing in the bypass channel
132 allows the precise control of the ratio of reformate to
unreformed fuel mixture supplied to the anode 104.
[0051] In accordance with some embodiments of the present
disclosure, the fuel cell system 100 may further comprise one or
more anode exhaust recycle lines. For example, a portion of the
anode exhaust may be drawn into an anode ejector 138. The motive
force for the anode ejector 138 may be the source of hydrocarbon
fuel 116, which may be pressurized by any conventional means. The
recycled anode exhaust may then be combined with the source of
hydrocarbon fuel 116 supplied to the reformer unit 118.
[0052] Another portion of the anode exhaust may be drawn into an
auxiliary ejector 136. The auxiliary ejector 136 may be supplied by
the oxidant source 150. The combined oxidant--anode exhaust mixture
may then flow to a combustor 146 that supplies a combustion product
to the hot-side channels of heat exchanger 144. This combustion
product may then be vented to the environment at 152. Other systems
may be supplied with these combustion products or other portions of
the anode exhaust, e.g., to power a turbine which may pressure
various flows in the fuel cell.
[0053] In accordance with some embodiments of present disclosure, a
variable orifice flow controller 300 is provided, which may be flow
controller 134 as described above. One embodiment of the flow
controller 300 is illustrated in FIG. 3 to FIG. 5. FIG. 3
illustrates two perspective views of a disassembled flow controller
300. The flow controller 300 comprises an upstream connector 302, a
downstream connector 310, and an interconnector 316.
[0054] The upstream connector 302 may have a cylindrical tubular
portion which defines a conduit 304 that is in fluid communication
with a bypass flow path designed to receive a fluid flowing through
the bypass flow path. Other geometric configurations may be
suitable for the conduit 304. The upstream connector 302 may
further comprise frusto-conical portion 306 which defines a
plurality of conduits 308. The plurality of conduits are in fluid
communication with conduit 304.
[0055] The downstream connector 310 may define a frusto-conical
cavity 312 configure to receive the frusto-conical portion 306 of
the upstream connector 302. The downstream connector 310 may
further define a plurality of conduits 314 in fluid communication
with the cavity 312. Additionally, the conduits 314 are in fluid
communication with the reformate exhaust conduit and the anode
inlet.
[0056] The plurality of conduits 308 and 314 may each be opposing,
arcuate conduits, although other geometric designs may be used, and
each conduit 308 may form an opposing pair with a conduit 314.
[0057] The interconnector 316 may be a connection fitting designed
to provide a fluid-tight connection after the frusto-conical
portion 306 is received within the frusto-conical cavity 312. The
interconnector 316 may comprise a plurality of internal threads
(not shown) which engage a plurality of threads (not shown) on the
downstream connector 310. By tightening the interconnector 316 onto
the downstream connector, the fluid-tight connection may be
achieved. The fluid-tight connection may be gastight, wherein the
gas refers to the gas flowing through flow controller 300 or the
gas surrounding the flow controller 300, such as, e.g., the
atmosphere, or may refer to liquids. The interconnector 316 may be
a hose nut.
[0058] The amount of fluid communication between the plurality of
conduits 308 and 314, which may be considered the same as the flow
rate through the bypass line, may be selected by the radial
alignment between the upstream and downstream connectors 302 and
310, respectively. As shown in FIG. 4, the conduits 308 and 314 may
be aligned to provide the maximum flow rate achievable for a give
flow controller 300 design, or the conduits 308 and 314,
respectively, may be intentionally misaligned in order to reduce
the effective flow area of the flow controller 300, thereby
reducing the overall flow rate of the fluid in the bypass
conduit.
[0059] The flow controller 300 may further comprise an alignment
tab 318 affixed to the upstream connector 302 and a plurality of
alignment notches 320 on the downstream connector 310. The
alignment tab 318 and notches 320 function together to prevent the
rotation of the upstream connector 302 around its long axis
relative to the downstream connector 310, thereby maintaining the
desired alignment and, therefore, flow rate. In some embodiments
the alignment of the conduits 308 and 314 is maintained by
compression fit rather than, or in addition to, the use of the
alignment tab 318 and notches 320.
[0060] A perspective view of the assembled flow controller 300 is
shown in FIG. 5.
[0061] The flow controller 300 illustrated in FIGS. 3-5 is designed
for applications in which other designs would fail due to the high
temperature, high pressure, or both high temperature and pressure
of those applications. These high temperatures may be caused by the
recycled anode exhaust which may be supplied to the fuel cell
system reforming unit. Additional heat may be provided by a cathode
exhaust gas (or other high temperature gas) heat exchanger which
may be located upstream of the flow controller 300. For example,
flow controller 300 may be able to maintain a fluid-tight
connection at temperatures of at least 650 degrees Celsius, 700
degrees Celsius, 800 degrees Celsius, 850 degrees Celsius, 900
degrees Celsius, or 950 degrees Celsius.
[0062] A flow controller 600 in accordance with some embodiments of
the present disclosure is illustrated in FIG. 6 and FIG. 7. FIG. 6
illustrates the exploded, unassembled perspective view of the
controller 600. An assembled, perspective view of controller 600
may be seen in FIG. 7. This flow controller may function in a
manner similar to the controller 300 as described, and may contain
components performing like functions. In the embodiment illustrated
in FIG. 6 and FIG. 7, the downstream connector (not shown) may, or
may not, define a plurality of conduits. The flow controller 600
may comprise a disc 622 that defines a plurality of conduits 624.
In accordance with some embodiments, the alignment of the plurality
of conduits 308 and 624 will determine the amount of fluid
communication in bypass line. An alignment tab 618 may be affixed
to the disc 622 and may be aligned with one of a plurality of
notches 620 on the upstream connector 302. When the upstream and
downstream connectors are in a fluid-tight connection, the
alignment tab 618 and open of the plurality of notches 620 operate
to prevent rotation of the disc 622 relative to the upstream
connector, and, therefore, maintain the amount of fluid
communication between the plurality of conduits 308 and 624. The
flow controller may further comprise a retaining element 626, such
as, e.g., a screw, which retains the disc 622 adjacent to a face
628 of the frusto-conical portion 306 of the upstream connector
302.
[0063] The flow controller 600 illustrated in FIGS. 6-7 is designed
for applications in which other designs would fail due to the high
temperature, high pressure, or both high temperature and pressure
of those applications. These high temperatures may be caused by the
recycled anode exhaust which may be supplied to the fuel cell
system reforming unit. Additional heat may be provided by a cathode
exhaust gas (or other high temperature gas) heat exchanger which
may be located upstream of the flow controller 300. For example,
flow controller 600 may be able to maintain a fluid-tight
connection at temperatures of at least 650 degrees Celsius, 700
degrees Celsius, 800 degrees Celsius, 850 degrees Celsius, 900
degrees Celsius, or 950 degrees Celsius.
[0064] In accordance with some embodiments of the present
disclosure, a reformer unit 800 having a bypass plenum is
illustrated in FIGS. 8-10 and FIG. 12. FIG. 8 illustrates two
perspective views of the reformer unit 800. FIG. 9 is a close-up of
the reforming section inlet 808. FIG. 10 is a close-up view of the
bypass plenum 802. FIG. 11 illustrate a flow restrictor. FIG. 12
illustrates two perspective views, one being a cross section of the
other, of the reforming section outlet plenum 812 and the bypass
plenum 802 outlet 810.
[0065] The reformer unit 800 may comprise a reforming section 804
and a heat exchanging section 816 which may be the cold-side
channels and hot-side channels, respectively, as described above.
The reformer unit 800 may further comprise a bypass plenum 802
having an inlet 806, an outlet 810, and a flow restrictor 814. The
inlet 806 may be in fluid communication with the reforming section
inlet 808 and be configured to receive a portion of the unreformed
hydrocarbon-fuel, anode-exhaust mixture flowing thereto. The outlet
810 is in fluid communication with the reforming section outlet
plenum 812 such that the bypass plenum 802 and reforming section
804 flow paths may converge prior to being supplied to the anode.
The flow restrictor 814 may be disposed in a flow path between the
outlet 810 of the bypass plenum 802 and the outlet plenum 812 of
the reforming section 804.
[0066] The heat exchanging section 816 of the reformer unit 800 may
be configured to be in thermal communication with the bypass plenum
802. For example, the bypass plenum may share or have one or more
walls in contact with the heat exchange section 816. This will
effect a heat exchange between the cathode exhaust, or other hot
fluid, flowing through the heat exchanging section 816 to provide
thermal energy to the bypass flow prior to that flow being merged
with the reformed fuel from the reforming section 804. In some
embodiments, the flow of cathode exhaust or other hot fluid in the
heat exchange section 816 may be configured to exchange heat with
the fluid in the bypass plenum 802 prior to exchanging heat with
fluid in the reforming section 804. In other embodiments, the flow
of cathode exhaust or other hot fluid in the heat exchange section
816 may be configured to exchange heat with the fluid in the
reforming section 804 prior to exchanging heat with fluid in the
bypass plenum 802. The first occurring heat transfer may also be
referred to as an upstream thermal communication. Whether the heat
exchange between the fluid in the heat exchange section 816 occurs
first with the bypass plenum 802 or the reforming section 804 may
be controlled by, e.g., selecting the direction of flow of the
cathode exhaust or other hot fluid.
[0067] As shown in FIG. 12, the outlet 810 of the bypass plenum 802
may define an orifice 818 providing fluid communication between the
bypass plenum 802 and the outlet plenum 812 of the reforming
section 804. The flow restrictor 814 may comprise an elongated
member 822 (also referred to as a flow restricting member or an
elongated flow restricting member) which extends into the orifice
to reduce its cross-sectional area and restrict the fluid flowing
there through.
[0068] Alternate views of the flow restrictor 814 are provided in
FIG. 11. The flow restrictor 814 may comprise a connector 820 and
the flow restricting member 822. The connector 820 may be mounted
to the reformer unit 800 on a wall of the bypass plenum 802.
[0069] The flow restricting member 822 may be elongated and
removably carried by the connector 820. The member 822 extends
through the orifice 818, thereby reducing its effective
cross-sectional area. The flow rate of the fluid flowing between
the bypass plenum 802 and the outlet plenum 812 of the reforming
section 804 is selected by sizing the flow restricting member 822
relative to the orifice 818. The flow restricting member 822 may be
cylindrical. In some embodiments the flow restricting member 822
may have an oval or rectangular cross-section or may be conical or
other suitable shape. The elongated member 822 may have a threaded
portion (not shown) for engaging the connector 820.
[0070] In some embodiments, the flow restricting member 822 may
have a taper cross-section. The flow rate between the bypass plenum
802 and the outlet plenum, 812 may be determined by the sizing of
the member 822 and the orifice 818 and by the axial alignment
between the two. This axial alignment may be set by rotating a
threadably engaged member 822 within a threaded (not shown)
connector 820.
[0071] The connector 820 may have a first portion defining a
cylindrical cavity having a threaded portion for engaging the
elongated member 822, and may further have a second portion which
may define a frusto-cylindrical cavity in communication with the
cylindrical cavity. This cavity may accept a fitting 824 having a
frusto-cylindrical portion defining an axial slot. The elongated
member 822 may further comprise a portion which extends into this
axial slot, thereby preventing rotation of the elongated member 822
while the fitting is installed. In some embodiments, rotation of
the elongated member may be prevented when the nut 826 operably
engages connector 820 to provide a fluid-tight seal.
[0072] The flow restrictor 814 may further comprise an internally
threaded sealing nut 826 which may engage external threading on the
connector 820, thereby providing a fluid-tight seal between the
fitting 826 and the connector 820 when nut 826 is tightened on
connector 820. Additionally, fitting 824 may be engaged by the nut
826 to prevent leakage of system fluid around member 822.
[0073] The flow restrictor 814 illustrated in FIGS. 8 and 10-12 is
designed for applications in which other designs would fail due to
the high temperature and pressure of those applications. These high
temperatures may be caused by the recycled anode exhaust which may
be supplied to the fuel cell system reforming unit. Additional heat
may be provided by a cathode exhaust gas (or other high temperature
gas) heat exchanging section 816. For example, flow restrictor 814
may be able to maintain a fluid-tight connection at temperatures of
at least 650 degrees Celsius, 700 degrees Celsius, 800 degrees
Celsius, 850 degrees Celsius, 900 degrees Celsius, or 950 degrees
Celsius.
[0074] While preferred embodiments of the present subject matter
have been described, it is to be understood that the embodiments
described are illustrative only and that the scope of the subject
matter is to be defined solely by the appended claims when accorded
a full range of equivalence, many variations and modifications
naturally occurring to those of skill in the art from a perusal
hereof.
* * * * *