U.S. patent application number 16/516954 was filed with the patent office on 2020-01-09 for solid-oxide fuel cell systems.
The applicant listed for this patent is CUMMINS ENTERPRISE LLC. Invention is credited to Matthew Joseph ALINGER, Irfan Saif HUSSAINI, Andrew Philip SHAPIRO.
Application Number | 20200014046 16/516954 |
Document ID | / |
Family ID | 52349936 |
Filed Date | 2020-01-09 |
United States Patent
Application |
20200014046 |
Kind Code |
A1 |
HUSSAINI; Irfan Saif ; et
al. |
January 9, 2020 |
SOLID-OXIDE FUEL CELL SYSTEMS
Abstract
The present application provides combined cycle fuel cell
systems that include a fuel cell, such as a solid-oxide fuel cell
(SOFC), comprising an anode that generates a tail gas and a cathode
that generates cathode exhaust. The system or plant may include
adding fuel, such as processed or refined tail gas, to the inlet
air stream of a reformer to heat the reformer. The system or plant
may include removing water from the tail gas and recycling the
removed water into an inlet fuel stream. The inlet air stream may
be the cathode exhaust stream of the fuel cell, and the inlet fuel
stream may be input hydrocarbon fuel that is directed to the
reformer to produce hydrogen-rich reformate. The system or plant
may direct some of the processed or refined tail gas to a bottoming
cycle.
Inventors: |
HUSSAINI; Irfan Saif;
(Glenville, NY) ; ALINGER; Matthew Joseph;
(Delmar, NY) ; SHAPIRO; Andrew Philip;
(Schenectady, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CUMMINS ENTERPRISE LLC |
Indianapolis |
IN |
US |
|
|
Family ID: |
52349936 |
Appl. No.: |
16/516954 |
Filed: |
July 19, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14145088 |
Dec 31, 2013 |
10361444 |
|
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16516954 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02E 60/563 20130101;
H01M 8/04067 20130101; H01M 2250/407 20130101; H01M 2008/1293
20130101; Y02E 60/50 20130101; H01M 8/04089 20130101; H01M 8/0618
20130101; H01M 8/0637 20130101; Y02E 60/566 20130101; H01M 8/04291
20130101; H01M 8/04097 20130101; H01M 8/04164 20130101; H01M 8/0662
20130101 |
International
Class: |
H01M 8/0612 20060101
H01M008/0612; H01M 8/04119 20060101 H01M008/04119; H01M 8/0637
20060101 H01M008/0637; H01M 8/0662 20060101 H01M008/0662; H01M
8/04007 20060101 H01M008/04007; H01M 8/04089 20060101
H01M008/04089; H01M 8/04291 20060101 H01M008/04291 |
Claims
1.-15. (canceled)
16. A combined cycle fuel cell system comprising: a solid-oxide
fuel cell comprising an a cathode configured to generate a cathode
exhaust, and an anode configured to generate a tail gas; a
reforming system configured to convert at least a portion of a
mixture of input hydrocarbon fuel and input steam into a
hydrogen-rich reformate, and to output the hydrogen-rich reformate
to the anode of the fuel cell; and a bottoming cycle, wherein the
tail gas is prevented from being input into the anode and cathode
of the fuel cell, wherein a first portion of the tail gas is
directed to the bottoming cycle to drive the bottoming cycle, and
wherein the reforming system is heated to facilitate conversion of
the input hydrocarbon fuel and the input steam into the
hydrogen-rich reformate by directing through the reforming system
at least a portion of heated cathode exhaust that is formed by
combusting a second portion of the tail gas in the cathode
exhaust.
17. The system of claim 16, wherein a portion of the cathode
exhaust is mixed with at least one of the input hydrocarbon fuel
and the hydrogen-rich reformate upstream of the fuel cell.
18. The system of claim 16, wherein the system includes a water
separator configured to remove water from the cathode exhaust, the
water removed from the cathode exhaust being directed to the
reforming system as steam to form at least a portion of the input
steam.
19. The system of claim 16, wherein the solid-oxide fuel cell
receives input air, and wherein the heated cathode exhaust output
from the reforming system is used to heat the input air via a heat
exchanger.
20. The system of claim 16, wherein the bottoming cycle comprises a
combustion engine and the first portion of the residual tail gas
drives the combustion engine.
21. A combined cycle fuel cell system comprising: a solid-oxide
fuel cell comprising an a cathode configured to generate a cathode
exhaust, and an anode configured to generate a tail gas; a
reforming system configured to convert at least a portion of a
mixture of input hydrocarbon fuel and input steam into a
hydrogen-rich reformate, and to output the hydrogen-rich reformate
to the anode of the fuel cell; and a bottoming cycle, wherein the
tail gas is prevented from being input into the anode and cathode
of the fuel cell, wherein a first portion of the tail gas is
directed to the bottoming cycle to drive the bottoming cycle,
wherein the reforming system is heated to facilitate conversion of
the input hydrocarbon fuel and the input steam into the
hydrogen-rich reformate by directing through the reforming system
at least a portion of heated cathode exhaust that is formed by
combusting a second portion of the tail gas in the cathode exhaust,
and wherein the system includes a boiler configured to receive
water removed from the tail gas by a water separator and produce
the input stream, at least a portion of a cathode exhaust stream
output by the reforming system is directed to the boiler to heat
the water removed from the tail gas by the water separator to
produce the input steam, and at least a portion of the cathode
exhaust system output by the reforming system and directed to the
boiler passes through multiple heat exchangers positioned upstream
of the boiler.
22. The system of claim 21, wherein a portion of the cathode
exhaust is mixed with at least one of the input hydrocarbon fuel
and the hydrogen-rich reformate upstream of the fuel cell.
23. The system of claim 21, wherein the system includes a water
separator configured to remove water from the cathode exhaust, the
water removed from the cathode exhaust being directed to the
reforming system as steam to form at least a portion of the input
steam.
24. The system of claim 21, wherein the solid-oxide fuel cell
receives input air, and wherein the heated cathode exhaust output
from the reforming system is used to heat the input air via a heat
exchanger.
25. The system of claim 21, wherein the bottoming cycle comprises a
combustion engine and the first portion of the residual tail gas
drives the combustion engine.
Description
BACKGROUND
[0001] This disclosure relates generally to combined cycle fuel
cell systems, and more particularly to high-efficiency solid-oxide
fuel cell (SOFC) systems that achieve higher fuel cell conversion
efficiencies than that achievable using conventional combined cycle
systems.
[0002] Fuel cells are electrochemical energy conversion devices
that have demonstrated a potential for relatively high efficiency
and low pollution in power generation. A fuel cell generally
provides a direct current (dc) which may be converted to
alternating current (ac) via for example, an inverter. The dc or ac
voltage can be used to power motors, lights, communication
equipment and any number of electrical devices and systems. Fuel
cells may operate in stationary, semi-stationary, or portable
applications. Certain fuel cells, such as solid oxide fuel cells
(SOFCs), may operate in large-scale power systems that provide
electricity to satisfy industrial and municipal needs. Others may
be useful for smaller portable applications such as for example,
powering cars.
[0003] A fuel cell produces electricity by electrochemically
combining a fuel and an oxidant across an ionic conducting layer.
This ionic conducting layer, also labeled the electrolyte of the
fuel cell, may be a liquid or solid. Common types of fuel cells
include phosphoric acid (PAFC), molten carbonate (MCFC), proton
exchange membrane (PEMFC), and solid oxide (SOFC), all generally
named after their electrolytes. In practice, fuel cells are
typically amassed in electrical series in an assembly of fuel cells
to produce power at useful voltages or currents.
[0004] In general, components of a fuel cell include the
electrolyte and two electrodes. The reactions that produce
electricity generally take place at the electrodes where a catalyst
is typically disposed to speed the reactions. The electrodes may be
constructed as channels, porous layers, and the like, to increase
the surface area for the chemical reactions to occur. The
electrolyte carries electrically charged particles from one
electrode to the other and is otherwise substantially impermeable
to both fuel and oxidant.
[0005] Typically, the fuel cell converts hydrogen (fuel) and oxygen
(oxidant) into water (byproduct) to produce electricity. The
byproduct water may exit the fuel cell as steam in high-temperature
operations. This discharged steam (and other hot exhaust
components) may be utilized in turbines and other applications to
generate additional electricity or power, providing increased
efficiency of power generation. If air is employed as the oxidant,
the nitrogen in the air is substantially inert and typically passes
through the fuel cell. Hydrogen fuel may be provided via local
reforming (e.g., on-site steam reforming) or remote reforming of
carbon-based feedstocks, such as reforming of the more readily
available natural gas and other hydrocarbon fuels and feedstocks.
Examples of hydrocarbon fuels include, but are not limited to,
natural gas, methane, ethane, propane, methanol, and other
hydrocarbons.
[0006] Present day examples of combined cycle fuel cell systems
routinely achieve at least 50% conversion efficiency. The
efficiency of combined cycle fuel cell systems in converting
hydrocarbon fuel into electrical energy is limited by loss
mechanisms within the system that produce or lose heat and by
losses of the fuel cell due to partial utilization of fuel. Typical
or common attempts to improve performance or efficiency of combined
cycle fuel cell systems at low fuel utilization have involved fuel
and/or air-recycling. Fuel recycling in combined cycle fuel cell
systems, however, requires large reformers and large high
temperature blowers that are costly and technically challenging.
Similarly, air recycling in combined cycle fuel cell systems
requires high-temperature blowers that are not cost-effective.
[0007] In view of the foregoing, there is a need to provide
cost-reduction techniques that increase the plant efficiency of
combined cycle fuel cell systems through increased fuel cell
efficiency that eliminate the need of fuel and/or air recycling
that requires costly high temperature blowers and, potentially,
heat exchangers.
BRIEF DESCRIPTION
[0008] In one aspect, a first exemplary embodiment of a combined
cycle fuel cell system is disclosed. The system may include a
solid-oxide fuel cell fuel cell, a reforming system, a water
separator, a bottoming cycle, and/or a residual tail gas pathway.
The solid-oxide fuel cell fuel cell may include an anode configured
to generate a tail gas, and a cathode configured to generate a
cathode exhaust stream. The reforming system may be configured to
receive and output at least a portion of the cathode exhaust stream
and convert at least a portion of a mixture of input hydrocarbon
fuel and input steam into a hydrogen-rich reformate. The
hydrogen-rich reformate may be utilized by the anode of the fuel
cell. The water separator may be configured to the receive the tail
gas of the fuel cell and remove water from the tail gas to form
residual tail gas. The water removed from the tail gas may be
directed to the reforming system as steam to form at least a
portion of the input steam. The bottoming cycle may include a
combustion engine. The residual tail gas pathway may be configured
to divert a first portion of the residual tail gas to the bottom
cycle to drive the bottom cycle, and to divert a second portion of
the residual tail gas to the cathode exhaust stream.
[0009] In another aspect, a second exemplary embodiment of a
combined cycle fuel cell system is disclosed. The system may
include a solid-oxide fuel cell, a reforming system, and/or a
bottoming cycle. The solid-oxide fuel cell may include a cathode
configured to generate a cathode exhaust, and an anode configured
to generate a tail gas. The reforming system may be configured to
convert at least a portion of a mixture of input hydrocarbon fuel
and input steam into a hydrogen-rich reformate, and to output the
hydrogen-rich reformate to the anode of the fuel cell. The system
may be configured such that the tail gas is prevented from being
input into the anode and cathode of the fuel cell. The system may
be configured to direct a first portion of the tail gas to the
bottoming cycle to drive the bottoming cycle. The reforming system
may be heated to facilitate conversion of the input hydrocarbon
fuel and the input steam into the hydrogen-rich reformate by
directing through the reforming system at least a portion of heated
cathode exhaust that is formed by combusting a second portion of
the tail gas in the cathode exhaust.
DRAWINGS
[0010] The foregoing and other features, aspects and advantages of
this disclosure will become apparent from the following detailed
description of the various aspects of the disclosure taken in
conjunction with the accompanying drawings, wherein:
[0011] FIG. 1 is a diagram illustrating a combined cycle power
plant or system that employs a solid-oxide fuel cell (SOFC) running
on reformed fuel (e.g., hydrogen-rich reformate) according to one
embodiment of the disclosure; and
[0012] FIG. 2 is a diagram illustrating a combined cycle power
plant or system that employs a solid-oxide fuel cell (SOFC) and a
partial oxidation reformer according to another embodiment of the
disclosure.
DETAILED DESCRIPTION
[0013] Each embodiment presented below facilitates the explanation
of certain aspects of the disclosure, and should not be interpreted
as limiting the scope of the disclosure. Moreover, approximating
language, as used herein throughout the specification and claims,
may be applied to modify any quantitative representation that could
permissibly vary without resulting in a change in the basic
function to which it is related. Accordingly, a value modified by a
term or terms, such as "about," is not limited to the precise value
specified. In some instances, the approximating language may
correspond to the precision of an instrument for measuring the
value. When introducing elements of various embodiments, the
articles "a," "an," "the," and "said" are intended to mean that
there are one or more of the elements. The terms "comprising,"
"including," and "having" are intended to be inclusive and mean
that there may be additional elements other than the listed
elements. As used herein, the terms "may" and "may be" indicate a
possibility of an occurrence within a set of circumstances; a
possession of a specified property, characteristic or function;
and/or qualify another verb by expressing one or more of an
ability, capability, or possibility associated with the qualified
verb. Accordingly, usage of "may" and "may be" indicates that a
modified term is apparently appropriate, capable, or suitable for
an indicated capacity, function, or usage, while taking into
account that in some circumstances, the modified term may sometimes
not be appropriate, capable, or suitable. Any examples of operating
parameters are not exclusive of other parameters of the disclosed
embodiments. Components, aspects, features, configurations,
arrangements, uses and the like described, illustrated or otherwise
disclosed herein with respect to any particular embodiment may
similarly be applied to any other embodiment disclosed herein.
[0014] The embodiments described herein with reference to the
figures (and variations thereof) advantageously provide increased
plant efficiencies, as compared to prior plant embodiments, of at
least about 50%, and potentially within the range of about 50% to
about 65%, and potentially preferably within the within the range
of about 55% to about 65%, while enabling or providing steam
reforming without employing fuel and/or air recycle loops. Thereby,
advantages provided by the features described herein include
without limitation, include the lack of fuel and/or air cycle
loops, minimizing temperature difference across the fuel cell
(e.g., an SOFC stack), and relatively high system efficiency at a
relatively low fuel utilization rate.
[0015] Other embodiments of the present disclosure are also
contemplated, as noted in the discussion. While the illustrated
exemplary embodiments of the disclosure are shown and discussed
with reference to solid-oxide fuel cells, the principles described
herein may be applied to comparable fuel-cell technologies (as is
known in the art). Further, a vast variety of waste heat and/or
fuel recovery cycles and methods for integrating those cycles are
also possible using the principles described herein and are hereby
contemplated by this disclosure.
[0016] FIG. 1 is a simplified diagram illustrating an exemplary
combined cycle power plant or fuel cell system 10 according to the
present disclosure that employs a solid-oxide fuel cell (SOFC) 26
running on reformed fuel without recirculation, as explained
further below. More specifically, as shown in FIG. 1, inlet fuel 12
from a fuel source is input into the plant or system 10. The input
fuel 12 may be obtained, provided, manufactured, refined or
otherwise input into the plant or system 10. The input fuel 12 may
be any fuel effective in power generation via the fuel cell 26 of
the plant or system 10. In some embodiments, the input fuel 12 may
be a hydrocarbon fuel or a mixture of hydrocarbon fuels. In some
such embodiments, the input fuel 12 may be substantially CH4 (e.g.,
natural gas or methane).
[0017] As shown in FIG. 1, the input fuel 12 may be translated
along a first pathway 14 into or to one or more fuel pre-heater 18.
In some embodiments, the pathways or passageways of the plant or
system 10, including the first pathway 14, may be pipes or other
conduits in which the input fuel 12 and other liquids and/or gases
flow there through. In some embodiments, the plant or system 10 may
include one or more fuel blower 16 effective in pressurizing or
otherwise translating a particular amount or rate of the input fuel
12 to the fuel pre-heater 18 along the first pathway 14 (and
potentially through other pathways or aspects of the plant or
system 10 that are positioned or arranged downstream of the fuel
blower 16). In some embodiments however, the fuel blower 16 may not
be utilized. For example, the source or origin of the input fuel 12
may include, define or include a sufficient pressure or flow rate
such that a sufficient rate or amount of input fuel 12 is fed or
translated into the plant or system 10 (e.g., to the fuel
pre-heater 18 and aspects or components downstream thereof). The
fuel blower 16 may therefore be dependent upon the natural or
source conditions (e.g., flow rate) of the input fuel 12 and/or the
requirements or operating parameters of the plant or system 10
(e.g., the supply pressure of the input fuel 12).
[0018] At or after the fuel pre-heater 18, input water 20 may be
added to or mixed with the input fuel 12. For example, as shown in
FIG. 1 water 20 may be mixed with, or added to, the input fuel 12
at the fuel pre-heater 18. In some embodiments, water 20 may be
mixed with, or added to, the input fuel 12 after (i.e., downstream
of) the fuel pre-heater 18 along a second pathway 22. The water 20
mixed with the input fuel 12 at or after the fuel pre-heater 18 may
be steam (i.e., at or above about 100 degrees Celsius). As
discussed further below, the water 20 (e.g., steam) added to the
input fuel 12 may be (or at least include) removed water 28 that
was removed or separated from the anode exhaust or tail gas 24 of
the fuel cell 26 of the plant or system 10. In some embodiments,
the entirety of the water 20 added to the input fuel 12 may be the
water 28 that was removed or separated from the anode exhaust or
tail gas 24 of the fuel cell 26. The ratio of input fuel 12 and
water 20 (e.g., steam) (when added to the input fuel 12) may vary
depending upon desired operating parameter of the plant or system
10 (e.g., desired output load). In some embodiments, the mole
fraction of the mixture of input fuel 12 and added water 20 (e.g.,
steam) may be about two-thirds water 20 (e.g., steam) and one-third
input fuel 12 (e.g., CH4).
[0019] The fuel pre-heater 18 may be configured to receive the
input fuel 12 from the first pathway 14, as shown in FIG. 1. As
discussed above, the fuel pre-heater 18 may also be configured to
receive water 20 (e.g., steam) and, potentially, mix the input
water 20 and input fuel 12. The fuel pre-heater 18 may be any fuel
pre-heater effective in heating the input fuel 12 (and,
potentially, the added water 20). The amount of heat applied to the
input fuel 12 (or, potentially, the water 20 and input fuel 14
mixture) by the fuel pre-heater 18 may vary depending upon desired
operating parameters of the plant or system 10 (e.g., desired
output load). In some embodiments, the fuel pre-heater 18 may be
configured to heat the input fuel 12 (or, potentially, the water 20
and input fuel 14 mixture) to at least about 500 degrees Celsius.
In some embodiments, the fuel pre-heater 18 may be configured to
heat the input fuel 12 (or, potentially, the water 20 and input
fuel 14 mixture) to at least about 700 degrees Celsius.
[0020] In some embodiments, the fuel pre-heater 18 may be a
recuperator or heat exchanger. As shown in FIG. 1, the fuel
pre-heater 18 may utilize at least a portion of the anode exhaust
or tail gas 24 of the fuel cell 26 of the plant or system 10 to
heat the input fuel 12 (and, potentially, the added water 20). The
fuel pre-heater 18 may be configured to maintain the tail gas 24
and input fuel 12 (and, potentially, the added water 20) separate
and distinct from one another. For example, the fuel pre-heater 18
may utilize the hot tail gas 24 to heat the relatively cooler input
fuel 12 (or, potentially, the water 20 and input fuel 14 mixture)
via conduction and/or convection without mixing the tail gas and
input fuel 12 (or the water 20 and input fuel 14 mixture). Along
with the fuel pre-heater 18, the other components or aspects of the
plant or system 10 may configured to maintain the tail gas 24 and
input fuel 12 (and, potentially, the added water 20) separate and
distinct from one another, as shown in FIG. 1. In this way, plant
or system 10 may be configured such that the anode exhaust or tail
gas 24 is prevented from mixing with the input fuel 12 (and,
potentially, the added water 20). Stated differently, the plant or
system 10 may be void of a fuel recycle loop in which the anode
exhaust or tail gas 24 of the fuel cell 26 of the plant or system
10 is mixed with the input fuel 12 and utilized by the fuel cell 26
(e.g., the anode thereof).
[0021] As shown in FIG. 1, after the input fuel 12 (or,
potentially, the water 20 and input fuel 14 mixture) is heated via
the fuel pre-heater 18, the mixture of water 20 (e.g., steam) and
input fuel 14 (e.g., CH4) may travel along the second pathway 22 to
one or more reformer 30. The reformer 30 may be configured to
convert at least a portion of the mixture of the heated input fuel
12 and added water 20 (e.g., stream) into a hydrogen-rich reformate
33 or syngas mixture of hydrogen and one or more byproduct. The
hydrogen-rich reformate 33 or syngas exiting or output by the
reformer 30 may be cooler than the mixture of water 20 and inlet
fuel 14 entering or input to reformer 30. The hydrogen-rich
reformate 33 from the reformer 30 may be output along a third
pathway 32. The reformer 30 may be any reformer effective in
producing a hydrogen-rich reformate 33 from the mixture of water 20
and input fuel 14. In some embodiments, the reformer 30 may be a
steam reformer which is configured to react the steam 20 at high
temperature with the input fuel 12. In some such embodiments, the
reformer 30 may be a methane reformer. In some embodiments the
reformer 30 may be heated to relatively high temperatures (e.g., at
least about 500 degree Celsius) and configured to react the steam
20 with the input fuel 12 in the presence of a metal-based catalyst
(e.g., nickel) to yield a hydrogen-rich reformate 33 of hydrogen
and one or more byproduct, such as carbon monoxide. In some
embodiments, byproducts of the hydrogen-rich reformate 33 (i.e.,
other than hydrogen (H2)) may include carbon monoxide (CO) and
carbon dioxide (CO2). As explained further below, the reformer 30
may be heated to facilitate the reforming process from burning the
tail gas 24 of the fuel cell 26 in the cathode exhaust stream of
the fuel cell 26 and passing the heated resultant through the
reformer 30.
[0022] In some embodiments, such as the exemplary plant or system
10 embodiment shown in FIG. 1, the reformer 30 may convert only a
portion or fraction of the mixture of water 20 (e.g., steam) and
input fuel 14 (e.g., CH4) into the hydrogen-rich reformate 33
(i.e., H2 and one or more byproduct). In such embodiments, the
byproducts of the hydrogen-rich reformate 33 may include
non-utilized water 20 and non-utilized fuel 12 in addition to any
other potential byproducts formed by the reformer 30 (e.g., CO and
CO2).
[0023] The reformer 30 may be configured to utilize or use at least
a portion of the anode exhaust or tail gas 24 given off by the fuel
cell 12 to promote the reforming reaction (as explained further
below). For example, as shown in FIG. 1 at least a fraction of the
anode exhaust stream or tail gas 24 of the fuel cell 12 may be
combusted burned, ignited or otherwise reacted within the cathode
exhaust stream 34 of the fuel cell 12 of the plant or system 10 to
produce heat (i.e., heat recovery of the cathode exhaust stream
34). The heat may then be utilized by the reformer 30 (i.e., the
reformer is heated) to promote the reforming reaction.
[0024] As shown in FIG. 1, the hydrogen-rich reformate 33 output by
the reformer 30 may travel along the third pathway 32 to the inlet
of fuel cell 26 of the plant or system 10. For example, the
hydrogen-rich reformate 33 may be output to the inlet of an anode
of the fuel cell 26. As shown in FIG. 1, the fuel cell 26 may be
positioned remote from, or adjacent to, the reformer 30 (i.e., the
reformer 30 may be external to the fuel cell 26). For example, the
fuel cell 26 may be provided within a housing, and the reformer 30
may be positioned exterior to the housing of the fuel cell 26 as
shown in FIG. 1. Stated differently, the reformer 30 may be
positioned external or remote from a housing of the fuel cell 26 as
shown in FIG. 1.
[0025] The fuel cell 26 may be configured to produce electricity,
such as direct current, from the hydrogen-rich reformate 33 output
by the reformer 30 and input air 70. The fuel cell 26 may convert
the chemical energy of the hydrogen-rich reformate 33 into
electricity through a chemical reaction with oxygen or another
oxidizing agent. In some embodiments the fuel cell 26 may include
an anode (negative side), a cathode (positive side) and an
electrolyte that allows charges to move between the two sides of
the fuel cell 26. Electrons may be drawn from the anode to the
cathode through an external circuit, producing direct current
electricity.
[0026] In some embodiments, the fuel cell 26 may be a solid oxide
fuel cell (SOFC), as shown in FIG. 1, which includes a solid oxide
or ceramic electrolyte. In some such embodiments, the anode may use
oxygen ions that diffuse through the electrolyte to oxidize the
hydrogen-rich reformate 33 output by the reformer 30. The oxidation
reaction between the oxygen ions and the hydrogen of the
hydrogen-rich reformate 33 output by the reformer 30 may produce
heat, water and electricity. The electrolyte of the fuel cell 26
may be a dense layer of ceramic that conducts oxygen ions. The
anode of the fuel cell 26 may produce an anode exhaust stream or
tail gas 24. In some embodiments, the anode exhaust stream or tail
gas 24 may include hydrogen and CO. In some embodiments, the anode
exhaust stream or tail gas 24 may include water, hydrogen,
CO.sub.2, CO and/or CH.sub.4. The cathode of the fuel cell 26 may
be a porous layer on the electrolyte where oxygen reduction takes
place. The cathode may produce a cathode exhaust stream 34. The
cathode exhaust stream 34 may substantially include N.sub.2. As
mentioned above, a portion of the tail gas 24 may be combusted in
the cathode exhaust stream 34 to heat the cathode exhaust stream 34
and, thereby, heat the reformer 30 (as the heated cathode exhaust
stream 34 is directed to the reformer 30). As described further
below, the heated cathode exhaust stream 34 may also be used to
heat the input air 70 of the fuel cell 26 via at least one heat
exchanger 80.
[0027] As shown in FIG. 1, in some embodiments the tail gas 24 of
the fuel cell 26 may be directed along a fourth pathway 36 to the
fuel pre-heater 18. The tail gas 24 may be relatively hot, such as
at least about 850 degrees Celsius. As described above, the fuel
pre-heater 18 may recuperate the relatively hot tail gas 24 to heat
the inlet fuel 12 (or a mixture of inlet water 20 and inlet fuel
12). Further, as also discussed above, the fourth pathway 36 and
the fuel pre-heater 18 (as well as other components or aspects of
the plant or system 10, potentially), may substantially prevent the
tail gas 24 from mixing with the inlet fuel 12 (or a mixture of
inlet water 20 and inlet fuel 12) or otherwise from entering or
being input into the fuel cell 26 (e.g., to the anode or cathode
thereof).
[0028] Upon exiting the fuel pre-heater 18, the plant or system 10
may direct the tail gas 24, such as through the use of a fifth
passageway 38, to an inlet of an air pre-heater 40 as shown in FIG.
1. Like the fuel pre-heater 18, the air pre-heater 40 may be a
recuperator or heat exchanger. As shown in FIG. 1, the air
pre-heater 40 may utilize the anode exhaust or tail gas 24 of the
fuel cell 26 of the plant or system 10 to heat input air 70. The
air pre-heater 40 may be configured to maintain the tail gas 24 and
input air 70 separate and distinct from one another. For example,
the fuel pre-heater 18 may utilize the hot tail gas 24 to heat the
relatively cooler input air 70 via conduction and/or convention
without mixing the tail gas and input air 70.
[0029] As shown in FIG. 1 the plant or system 10 may include a
water separator or condenser 44 configured to remove water (H2O)
from the tail gas 24. For example, as shown in the exemplary
illustrative embodiment of FIG. 1, the plant or system 10 may
include a sixth passageway 42 that directs the tail gas 24 from the
output of the air pre-heater 40 to the input of the water separator
or condenser 44. The water separator or condenser 44 may be any
mechanism or configuration that is effective in removing H2O from
the tail gas 24. In embodiments wherein the tail gas 24 is above
the boiling point of the water in the tail gas 24, the plant may
include a condenser 44 to condenser and remove the water from the
tail gas 24 as removed liquid water 28. In some embodiments, at
least a portion of the removed water 28 separated from the tail gas
24 via the water separator 44 may be the input water 20 that was
added to the input fuel 12 prior to the reformer 30 and or fuel
cell 26. The water separator or condenser 44 may remove
substantially all or only a portion of the water contained within
the tail gas 24. For example, in some embodiments the plant or
system 10 may be configured such that the water separator or
condenser 44 removed at least about 75 percent of the water
contained within the tail gas 24. As another example, the plant or
system 10 may be configured such that the water separator or
condenser 44 removed at least about 95 percent of the water
contained within the tail gas 24.
[0030] The water separator or condenser 44 may output (i.e.,
provide downstream) residual tail gas 46 that contains less water
therein as compared to the un-treated tail gas 24 input (i.e., that
is upstream) to the separator or condenser 44. The residual tail
gas 46 may be directed along a seventh or residual tail gas pathway
48 that diverts, splits or otherwise separates the residual tail
gas 46 into two or more portions, as shown in FIG. 1. With
reference to FIG. 1, the plant or system 10 may be configured to
divert a first portion 50 of the residual tail gas 46 and a second
portion 52 of the residual tail gas 46. The respective amounts or
proportions of the first and second portions 50, 52 of the residual
tail gas 46 may vary depending upon scale, desired operating
parameters, and the like. In some embodiments, the first portion 50
may contain the majority (i.e., over 50%) of the residual tail gas
46. In some such embodiments, the first portion 50 may contain at
least 75% of the residual tail gas 46. In some other embodiments,
the second portion 52 may contain the majority (i.e., over 50%) of
the residual tail gas 46.
[0031] As shown in FIG. 1, the first portion 50 of the residual
tail gas 46 may be input to at least one bottoming cycle 54, such
as via a passageway. The bottoming cycle 54 may be configured to
utilize the residual tail gas 46 to produce an additional
electrical energy in addition to the fuel cell 26. In some
embodiments, the residual tail gas 46 may drive a combustor of a
combustion engine of the bottoming cycle 54. The combustion engine
may be utilized in conjunction with a generator or like mechanism
to produce additional electricity. In some embodiments, the
combustion engine of the bottoming cycle may be a reciprocating
engine, Rankine cycle, Brayton cycle, and/or sterling cycle. In
some embodiments the reciprocating engine may be a reciprocating
4-stroke, reciprocating 2-stroke, opposed piston 2-stroke and/or
gas turbine. According to another embodiment, heat from the
bottoming cycle 54 exhaust may be transferred to the first tail gas
portion 50 via a return path to further boost the production of
electrical power provided by the bottoming cycle 54. In some
embodiments the system or plant 10 may include a CO2 separation
mechanism configured to remove CO2 from the first portion 50 of the
residual tail gas 46 prior to the input of the bottoming cycle 54,
such as the input of a combustion engine.
[0032] As discussed above, as shown in the exemplary illustrative
embodiment of FIG. 1 the second portion 52 of the residual tail gas
46 may be added to the cathode exhaust stream 34 of the fuel cell
12 of the plant or system 10. In some embodiments the second
portion 52 of the residual tail gas 46 may be added to the cathode
exhaust stream 34 of the fuel cell 12 upstream of the reformer 30.
In some embodiments the second portion 52 of the residual tail gas
46 may be combusted burned, ignited or otherwise reacted within the
cathode exhaust stream 34 of the fuel cell 12 of the plant or
system 10 to produce heat (i.e., heat recovery of the cathode
exhaust stream 34). For example, an eighth passageway 58 may direct
the second portion 52 of the residual tail gas 46 to a combustion
point 56 along the cathode exhaust stream 34 located downstream of
the fuel cell 26 and upstream of the at least one heat exchanger 80
and, potentially, the reformer 30. In some embodiments, the cathode
exhaust stream 34 may substantially include N.sub.2. The combustion
point 56 of the second portion 52 of the residual tail gas 46 in
the cathode exhaust stream 34 downstream of the fuel cell 26 and
upstream of at least one of the at least one heat exchanger 80 and
reformer 30 may include any arrangement or configuration effective
in combusting the second portion 52 of the residual tail gas 46 in
the cathode exhaust stream 34. In some embodiments, the temperature
of the cathode exhaust stream 34 may be sufficient to ignite or
burn the second portion 52 of the residual tail gas 46. In some
embodiments, the plant or system 10 may include an ignition
mechanism for burning the second portion 52 of the residual tail
gas 46 in the cathode exhaust stream 34.
[0033] In some embodiments, the heat from the combustion of the
second portion 52 of the residual tail gas 46 may be directed to
the reformer 30 (i.e., the reformer is heated) to promote the
reforming reaction of the mixture of input water 20 and input fuel
12. In this way, the tail gas 24 of the fuel cell 26 may be
utilized as a catalyst for reforming (e.g., steam reforming) the
input fuel 12 into the hydrogen-rich reformate 33. In some
embodiments inputting the second portion 52 of the residual tail
gas 46 to the cathode exhaust stream 34 upstream of the at least
one heat exchanger 80 allows the residual tail gas 46 to be
recuperated without adding the residual tail gas 46 (i.e., fuel or
combustion products) to the inlet of the cathode of the fuel cell
26.
[0034] As shown in FIG. 1, in some alternative embodiments the
second portion 52 of the residual tail gas 46 may be added to the
cathode exhaust stream 34 of the fuel cell 12 downstream of the
reformer 30 and upstream of the at least one heat exchanger 80. In
some such embodiments, the second portion 52 of the residual tail
gas 46 may be added both upstream and downstream of the reformer
30. In some embodiments the second portion 52 of the residual tail
gas 46 may be combusted burned, ignited or otherwise reacted within
the cathode exhaust stream 34 of the fuel cell 12 of the plant or
system 10 to produce heat (i.e., heat recovery of the cathode
exhaust stream 34). For example, an alternative eighth passageway
58' may direct the second portion 52 of the residual tail gas 46 to
a combustion point 56' along the cathode exhaust stream 34 located
downstream of the fuel cell 26 and reformer 30, and upstream of the
at least one heat exchanger 80. The combustion point 56' of the
second portion 52 of the residual tail gas 46 in the cathode
exhaust stream 34 downstream of the fuel cell 26 and reformer 30,
and upstream of the at least one heat exchanger 80, may include any
arrangement or configuration effective in combusting the second
portion 52 of the residual tail gas 46 in the cathode exhaust
stream 34. In some embodiments, the temperature of the cathode
exhaust stream 34 may be sufficient to ignite or burn the second
portion 52 of the residual tail gas 46. In some embodiments, the
plant or system 10 may include an ignition or oxidation mechanism
for burning the second portion 52 of the residual tail gas 46 in
the cathode exhaust stream 34.
[0035] In some embodiments the plant or system 10 may include input
air 70, as shown in FIG. 1. The input air 70 may be fed to the fuel
cell 26, such as to the cathode of the fuel cell 26. In some
embodiments, the plant or system 10 may include one or more air
blower 72 effective in pressurizing or otherwise translating a
particular amount or rate of the input air 70 along a ninth pathway
74 (and potentially through other pathways or aspects of the plant
or system 10 that are positioned or arranged downstream of the air
blower 72). Operating parameters of the air blower 72 may be
dependent upon the requirements or operating parameters of the
plant or system 10 (e.g., energy output). In some embodiments, the
air blower 72 may be configured to output the air 70 and increase
the pressure of the input air 72 (e.g., within the output ninth
passageway 74) to at least about 2 atmospheres. As shown in FIG. 1
and described above, the input air 72 may be directed to the air
pre-heater 40. The air pre-heater 40 may utilize the tail gas 36 to
heat the input air 70 downstream of the blowers 72. In some
embodiments, the input air 72 may be heated by the air pre-heater
40 (via the tail gas 36) to at least about 100 degrees Celsius.
[0036] In some embodiments, as shown in FIG. 1, the plant or system
10 may include one or more air-to-air heat exchanger 80 configured
to recuperate the heat of the cathode exhaust stream 34 to heat the
input air 70. In some embodiments, as shown in the exemplary
illustrative embodiments shown in FIG. 1 the at least one
air-to-air heat exchanger 80 may be positioned immediately
downstream of the air pre-heater 40. A passageway 76 may extend
between the outlet of the air pre-heater 40 and the at least one
heat exchanger 82 to direct the pre-heated input air 70 to the at
least one heat exchanger 80. In some embodiments, the at least one
air-to-air heat exchanger 80 (and cathode exhaust stream 34) may be
configured to heat the input air 70 to at least about 500 degrees
Celsius. In some embodiments, the at least one air-to-air heat
exchanger 80 (and cathode exhaust stream 34) may be configured to
heat the input air 70 to at least about 700 degrees Celsius. In
some embodiments, the at least one air-to-air heat exchanger 80
(and cathode exhaust stream 34) may be a single or unitary
air-to-air heat exchanger.
[0037] As also shown in FIG. 1, the plant or system 10 may include
multiple air-to-air heat exchangers coupled in series, such as a
first low temperature heat exchanger 82 and a second high
temperature heat exchanger 84. Each of the first low temperature
heat exchanger 82 and second high temperature heat exchanger 84 may
utilize the relatively hot cathode exhaust stream 34 to heat the
input air 70. As shown in FIG. 1, the second high temperature heat
exchanger 84 may be positioned upstream of the first low
temperature heat exchanger 82 in the direction of the flow of the
input air 70 and downstream in the direction of the flow of the
cathode exhaust 34. In this way, the second high temperature heat
exchanger 84 may operate at a higher temperature as compared to the
first low temperature heat exchanger 82. In some embodiments, the
first low temperature heat exchanger 82 and the second high
temperature heat exchanger 84 may be made of differing materials,
such as the components thereof effective in transferring heat
between the cathode exhaust stream 34 and the input air 70. In some
embodiments, the second high temperature heat exchanger 84 may be
configured to more efficiently transfer heat from the cathode
exhaust 34 to the input air 70 as compared to the first low
temperature heat exchanger 82.
[0038] The input air 70 heated by the at least one heat exchanger
80 may be output to an inlet of the fuel cell 26. For example, a
passageway 86 may extend between the outlet of the at least one
heat exchanger 80 to the cathode inlet of the fuel cell 26. In some
embodiments the input air 70 heated by the at least one heat
exchanger 80 may be mixed with the inlet fuel 12 upstream of the
fuel cell 26. The heated input air 70 may be effective, at least in
part, to heat the fuel cell 26 such that the fuel cell can
efficiently operate. For example, the fuel cell 26 may be a SOFC
fuel cell and the heated input air 70 may be effective, at least in
part (e.g., along with the heated inlet fuel 12), to heat the SOFC
fuel cell to at least about 500 degrees Celsius. In some
embodiments, the fuel cell 26 may be a SOFC fuel cell and the
heated input air 70 may be effective, at least in part (e.g., along
with the heated inlet fuel 12), to heat the SOFC fuel cell to at
least about 800 degrees Celsius.
[0039] The cathode exhaust stream 34 may exit the fuel cell 26 and
be directed to the combustion point 56, as described above and
shown in FIG. 1. As also discussed above, the resulting heated
composition may be directed to and through the reformer 30 to
facilitate the reforming of the inlet fuel 12 into the
hydrogen-rich reformate 33 utilized by the fuel cell 26. While the
cathode exhaust stream 34 may lose heat to the reformer, the
cathode exhaust stream 34 exiting the reformer 30 may still be
relatively hot. For example, the cathode exhaust stream 34 exiting
the reformer 30 may be relatively hotter than the heated input air
70 output by the air pre-heater 40. As such, in some embodiments
the cathode exhaust stream 34 exiting the reformer 30 may be
directed to the at least one heat exchanger 80 to heat the heated
input air 70 output by the air pre-heater 40 before entering the
fuel cell 26. In this way, the heat provided by burning the second
portion 52 of the tail gas 24 of the fuel cell 26 to heat the
reformer 30 may be recuperated to heat the input air 70.
[0040] In some embodiments, the cathode exhaust stream 34 exiting
the reformer 30 may be at least about 800 degrees Celsius. In some
embodiments, the cathode exhaust stream 34 exiting the reformer 30
may be at least about 850 degrees Celsius. As shown in FIG. 1, the
plant or system 10 may include a tenth passageway 88 that directs
the cathode exhaust stream 34 output by the reformer 30 to the
input of the at least one heat exchanger 80. For example, the tenth
passageway 88 may direct the cathode exhaust stream 34 output by
the reformer 30 to the input of the high temperature heat exchanger
84. From the high temperature heat exchanger 84, the cathode
exhaust stream 34 may be directed or flow to the low temperature
heat exchanger 82.
[0041] In some alternative embodiments the plant or system 10 may
be configured to direct at least a portion 87 of the cathode
exhaust stream 34 to the inlet fuel 12. As shown in FIG. 1, at
least a portion 87 of the cathode exhaust stream 34 may be added to
the inlet fuel 12 upstream of the fuel cell 26. As also shown in
FIG. 1, at least a portion 87 of the cathode exhaust stream 34 may
be added to the inlet fuel 12 upstream of the fuel cell 26 and
downstream of the reformer 30 (e.g., when the fuel cell 26 and the
reformer 30 are remote from one another). In some embodiments (see
FIG. 2, for example), at least a portion 87 of the cathode exhaust
stream 34 may be added to the inlet fuel 12 into or upstream of
both the reformer 30 and the fuel cell 26 (or within the reformer
30), as shown in FIG. 1.
[0042] As shown in FIG. 1, the plant or system 10 may be configured
to direct the cathode exhaust stream 34 to a boiler 92. For
example, an eleventh passageway 90 may direct the cathode exhaust
stream 34 output by the at least one heat exchanger 80 to the input
of the boiler 92. In some embodiments, the cathode exhaust stream
34 output by the at least one heat exchanger 80 may be at least
about 100 degrees Celsius. The cathode exhaust stream 34 output by
the at least one heat exchanger 80 may thereby be utilized by the
boiler 92 to heat input liquid water to create steam 20. In some
embodiments the steam created by the boiler 92 may be the input
steam (or water) 20 that is mixed with the input fuel 12 and
ultimately input in to the reformer 30 to from the hydrogen-rich
reformate 33. After being utilized by the boiler 92 to form input
steam or water 20, the cathode exhaust stream 34 output by the
boiler 2 may be vented 94 to the atmosphere or otherwise removed
from the plant or system 10.
[0043] In some embodiments, the water heated and boiled by the
boiler 92 may be at least in part the removed water 28 from the
anode exhaust stream or tail gas 24. For example, at least a
portion of the removed water 28 from the anode exhaust stream or
tail gas 24 via the water separator or condenser 44 may be directed
to an inlet of the boiler 92. As shown in FIG. 1, in some
embodiments the water 28 removed or separated from the anode
exhaust stream or tail gas 24 may be split or portioned such that a
first portion is directed to the boiler 92 and the remaining
portion is drained or otherwise removed from the plant or system
10. For example, as show in FIG. 1 the plant or system 10 may
include a twelfth passageway 98 for directing a first portion of
the water 28 outlet of the separator or condenser 44 to the boiler
92, and a thirteenth passageway 96 for directing a second portion
of the water 28 outlet of the separator or condenser 44 to the
atmosphere or otherwise remote of the plant or system 10.
[0044] The embodiments described herein advantageously have
achieved overall fuel utilization greater or higher than 65% by
adding fuel (e.g., residual tail gas 46) to the inlet air stream
(e.g., to the cathode exhaust stream 34) of the reformer 30 and
removing water from the tail gas 24 and recycling the removed water
20 into the fuel inlet stream 12. In some embodiments the
advantageous fuel utilization is achieved by adding air (e.g., the
cathode exhaust stream 34) to the fuel stream (e.g., the
hydrogen-rich reformate 33 output by the reformer 30) and removing
water from the tail gas 24 and recycling the removed water 20 into
the fuel inlet stream 12.
[0045] A second exemplary illustrative embodiment of a combined
cycle system or plant for power generation is shown in FIG. 2 and
referenced generally by reference numeral 110. The exemplary system
or plant 110 is similar to the exemplary system or plant 10
described above and shown in FIG. 1 and therefore like reference
numerals preceded by the numeral "1" are used to indicate like
elements. The description above with respect to the system or plant
10, including description regarding alternative embodiments (i.e.,
modifications, variations or the like), equally applies to system
or plant 110 (and any alternative embodiments thereof).
[0046] As shown in FIG. 1, a difference between the exemplary
system or plant 110 of FIG. 2 from the exemplary system or plant 10
of FIG. 1 includes the configuration, arrangement and/or
orientation of the reformer 130 and fuel cell 126. As shown in FIG.
1, the reformer 130 may be positioned within, or internal to, the
fuel cell 126. For example, the fuel cell 126 may be provided
within a housing, and the reformer 130 may be positioned within the
confines of the housing of the fuel cell 126, as shown in FIG. 1.
Stated differently, the reformer or the reforming process of the
input fuel 12 may take place within the fuel cell 126 itself, as
opposed to taking place exterior to the fuel cell 126 and the
hydrogen-rich reformate 33 resulting therefrom being input to the
fuel cell 126. In some embodiments, the reformer 130 may include at
least one component or aspect of the fuel cell 126. In some
embodiments, the reformer 130 may include or utilize the anode of
the fuel cell 126 and the steam reforming process may take place at
the anode of the fuel cell 126. In some embodiments, the reformer
130 and/or reforming process is inside an SOFC stack of the fuel
cell 126.
[0047] In some embodiments, the reformer 130 may be a partial
oxidation reformer 130. In some such embodiments, the system 110
may be configured to introduce or mix at least a portion of air (or
other source of oxygen) with the mixture of input fuel 112 and
water 120 being input to the reformer 130 (or introduced into the
input fuel 112, or fuel 112 and water 120 mixture, within the
reformer 130). For example, as shown in FIG. 2, a portion 189 of
the input air 170 output by the at least one heat exchanger 180
(i.e., heated by the at least one heat exchanger 180) may be
introduced into the input fuel 112 (or fuel 112 and water 120
mixture) upstream of the reformer 130 or within the reformer 130.
In some embodiments, the air or oxygen source mixed with the input
fuel 112 (or fuel 112 and water 120 mixture) within, or upstream
of, the reformer 130 (e.g., the input air 170 output by the by the
at least one heat exchanger 180) may be output within the
hydrogen-rich reformate 133, and, eventually, within the tail gas
124 of the fuel cell 126.
[0048] In some alternative embodiments, the portion 189 of the
input air 170 mixed with the input fuel 112 (or fuel 112 and water
120 mixture) within, or upstream of, the reformer 130 may be a
portion 187 of the cathode exhaust 134. In some alternative
embodiments, the portion 189 of the input air 170 mixed with the
input fuel 112 (or fuel 112 and water 120 mixture) within, or
upstream of, the reformer 130 may be the input air 170 upstream of
the at least one heat exchanger 180. In some alternative
embodiments, the portion 189 of the input air 170 mixed with the
input fuel 112 (or fuel 112 and water 120 mixture) within, or
upstream of, the reformer 130 may be the input air 170 upstream of
the air pre-heater 140. In some alternative embodiments, the air
189 mixed with the input fuel 112 (or fuel 112 and water 120
mixture) within, or upstream of, the reformer 130 may be air
obtained from a source external to the system (i.e., not fed from
another component of the system 110).
[0049] It is to be understood that the above description is
intended to be illustrative, and not restrictive. Numerous changes
and modifications may be made herein by one of ordinary skill in
the art without departing from the general spirit and scope of the
invention as defined by the following claims and the equivalents
thereof. For example, the above-described embodiments (and/or
aspects thereof) may be used in combination with each other. In
addition, many modifications may be made to adapt a particular
situation or material to the teachings of the various embodiments
without departing from their scope. While the dimensions and types
of materials described herein are intended to define the parameters
of the various embodiments, they are by no means limiting and are
merely exemplary. Many other embodiments will be apparent to those
of skill in the art upon reviewing the above description. The scope
of the various embodiments should, therefore, be determined with
reference to the appended claims, along with the full scope of
equivalents to which such claims are entitled. In the appended
claims, the terms "including" and "in which" are used as the
plain-English equivalents of the respective terms "comprising" and
"wherein." Moreover, in the following claims, the terms "first,"
"second," and "third," etc. are used merely as labels, and are not
intended to impose numerical requirements on their objects. Also,
the term "operably" in conjunction with terms such as coupled,
connected, joined, sealed or the like is used herein to refer to
both connections resulting from separate, distinct components being
directly or indirectly coupled and components being integrally
formed (i.e., one-piece, integral or monolithic). Further, the
limitations of the following claims are not written in
means-plus-function format and are not intended to be interpreted
based on 35 U.S.C. .sctn. 112, sixth paragraph, unless and until
such claim limitations expressly use the phrase "means for"
followed by a statement of function void of further structure. It
is to be understood that not necessarily all such objects or
advantages described above may be achieved in accordance with any
particular embodiment. Thus, for example, those skilled in the art
will recognize that the systems and techniques described herein may
be embodied or carried out in a manner that achieves or optimizes
one advantage or group of advantages as taught herein without
necessarily achieving other objects or advantages as may be taught
or suggested herein.
[0050] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the disclosure
may include only some of the described embodiments. Accordingly,
the invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
[0051] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
* * * * *