Note: Descriptions are shown in the official language in which they were submitted.
INTERNAL STEAM DELIVERY SYSTEM
FIELD OF THE INVENTION
[0001] The embodiments of the present invention generally relate to solid
oxide
electrolyzer (SOEC) mechanical systems and internal steam delivery therefor.
BACKGROUND OF THE INVENTION
[0002] Electrochemical devices, such as fuel cells, can convert energy stored
in fuels to
electrical energy with high efficiencies. In a fuel cell system, such as a
solid oxide fuel cell
(SOFC) system, an oxidizing flow is passed through the cathode side of the
fuel cell while a
fuel conduit flow is passed through the anode side of the fuel cell. The
oxidizing flow is
typically air, while the fuel flow can be a hydrocarbon fuel, such as methane,
natural gas,
liquefied petroleum gas (LPG)/propane, ethanol, or methanol. The fuel cell
enables the
transport of negatively charged oxygen ions from the cathode flow stream to
the anode flow
stream, where the ion combines with either free hydrogen or hydrogen in a
hydrocarbon
molecule to form water vapor and/or with carbon monoxide to form carbon
dioxide. The
excess electrons from the negatively charged ion are routed back to the
cathode side of the
fuel cell through an electrical circuit completed between anode and cathode,
resulting in an
electrical current flow through the circuit. A fuel cell system may include
multiple hot boxes,
each of which may generate electricity. A hotbox may include a fuel conduit
stream that
provides oxidizing fuel to one or more fuel stacks, where the fuel is oxidized
during
electricity generation.
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[0003] SOFCs may be operated as an electrolyzer in order to produce hydrogen
and
oxygen, referred to as solid oxide electrolyzer cells (SOEC). SOECs are
located in a hotbox.
In SOFC mode, oxide ions are transported from the cathode side (air) to the
anode side (fuel)
and the driving force is the chemical gradient of partial pressure of oxygen
across the
electrolyte. In SOEC mode, a positive potential is applied to the air side of
the cell and the
oxide ions are now transported from the steam side to the air side. Since the
cathode and
anode are reversed between SOFC and SOEC (i.e., SOFC cathode is SOEC anode,
and SOFC
anode is SOEC cathode), the SOFC cathode (SOEC anode) may be referred to as
the air
electrode, and the SOFC anode (SOEC cathode) may be referred to as the steam
electrode.
[0004] During SOEC mode, water in the fuel stream is reduced (H20 + 2e402- +
H2) to
form H2 gas and 02- ions, 02- ions are transported through the solid
electrolyte, and then
oxidized on the air side (02- to 02) to produce molecular oxygen. Since the
open circuit
voltage for a SOFC operating with air and wet fuel (hydrogen, reformed natural
gas) is on the
order of 0.9 to IV (depending on water content), the positive voltage applied
to the air side
electrode in SOEC mode raises the cell voltage up to typical operating
voltages of 1.1 to 1.45
V.
SUMMARY OF THE INVENTION
[0005] The embodiments of the present invention are directed to various steam
use and
safety systems that substantially obviate one or more problems due to
limitations and
disadvantages of the related art.
[0006] The embodiments of the present invention the relate to an internal
steam delivery
system that includes a system comprising a mass flow controller to control the
liquid water
flowrate into a circulation heater, wherein measurement and control is
performed with liquid
water prior to steam conversion.
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[0007] Additional features and advantages of the invention will be set forth
in the
description which follows, and in part will be apparent from the description,
or may be
learned by practice of the invention. The objectives and other advantages of
the invention
will be realized and attained by the structure particularly pointed out in the
written
description and claims hereof as well as the appended drawings.
[0008] It is to be understood that both the foregoing general description and
the following
detailed description are exemplary and explanatory and are intended to provide
further
explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The accompanying drawings, which are included to provide a further
understanding
of the invention and are incorporated in and constitute a part of this
specification, illustrate
embodiments of the invention and together with the description serve to
explain the
principles of the invention.
[0010] FIG. 1 is an SOEC system process flow diagram according to an example
embodiment of the present invention.
[0011] FIG. 2 is an SOEC system process flow diagram according to another
example
embodiment of the present invention.
[0012] FIG. 3 is an SOEC system process flow diagram according to another
example
embodiment of the present invention.
[0013] FIG. 4 is an SOEC system process flow diagram according to another
example
embodiment of the present invention.
[0014] FIG. 5 illustrates a circulation heater according to an example
embodiment of the
invention.
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DETAILED DESCRIPTION OF THE INVENTION
[0015] The various embodiments will be described in detail with reference to
the
accompanying drawings. Wherever possible, the same reference numbers will be
used
throughout the drawings to refer to the same or like parts. References made to
particular
examples and implementations are for illustrative purposes, and are not
intended to limit the
scope of the embodiments of the invention or the claims.
[0016] Values and ranges can be expressed herein as from "about" one
particular value,
and/or to "about" another particular value. When such a range is expressed,
examples
include from the one particular value and/or to the other particular value.
Similarly, when
values are expressed as approximations, by use of the antecedent "about" or
"substantially" it
will be understood that the particular value forms another aspect. In some
embodiments, a
value of "about X" may include values of +/- 1% X or +/- 5% X. It will be
further
understood that the endpoints of each of the ranges are significant both in
relation to the other
endpoint, and independently of the other endpoint. The values and ranges
provide examples,
but the embodiments of the invention are not so limited.
[0017] It will be apparent to those skilled in the art that various
modifications and
variations can be made to the present disclosure without departing from the
spirit and scope
of the disclosure. Since modifications combinations, sub-combinations and
variations of the
disclosed embodiments incorporating the spirit and substance of the disclosure
may occur to
persons skilled in the art, the disclosure should be construed to include
everything within the
scope of the appended claims and their equivalents.
[0018] In various embodiments of the present embodiments, steam can be
recycled in the
SOEC system.
[0019] FIG. 1 is an SOEC system 100 according to an example embodiment of the
present
invention.
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Date regue/Date received 2023-05-30
[0020] As illustrated in FIG. 1, SOEC system 100 includes air conduit 105, air
blower 106,
recycle steam inlet I 1 1, hotbox 150, optional hydrogen conduit 130, enriched
air conduit 125,
steam and hydrogen product outlet 120, splitter 160, steam recycle blower 170,
external
steam conduit 210, input hydrogen conduit 225, deionized water conduit 205,
heater 206, and
mass flow controller 207.
[0021] According to an example configuration and operation, steam input at
external steam
conduit 210 can have a temperature of between about 100 C and 110 C (e.g.,
105 C) and a
pressure of about 1 psig. In the various embodiments, steam may be input to
the SOEC
system 100 from an external source or may be generated locally. In some
embodiments,
multiple steam inlets may be configured to receive external and/or local
steam, respectively.
Alternatively, or additionally, water, such as deionized water conduit 205,
may be input to the
SOEC system 100 and heated by heater 206 (e.g., vaporized).
[0022] Air input (e.g., ambient air) at air conduit 105 may be ambient
temperature, perhaps
between about ¨ 20 C and + 45 C, at the local atmospheric pressure. Air from
air conduit
105 is received at air blower 106, and air output by air blower 106 will be a
slightly higher
temperature than ambient due to the heat of compression. For example, the
temperature of
air output by air blower 106 may be about 30 C at 1.0 psig as compared to 20 C
ambient air
temperature.
[0023] Hydrogen from optional hydrogen conduit 130 may only be required for
startup and
transients when hydrogen is not being otherwise produced by SOEC system 100.
For
example, there is no longer a need for a separate hydrogen feed stream or
hydrogen recycle
steam at steady state. Pressure for this hydrogen stream is a design option
determined at the
time of site construction, and may be between about 5 psig and 3000 psig. The
temperature
is likely to be near ambient, as it is likely to be coming from storage.
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[0024] Air input at air conduit 105 and hydrogen input at optional hydrogen
conduit 130 are
input to hotbox 150. In turn, hotbox 150 outputs steam and hydrogen product H2-
H20-G at
steam and hydrogen product outlet 120 of hotbox 150, where G stands for Gross.
Hotbox
output H2-H20-G may have a temperature between about 100 C and 180 C (e.g.,
130 C), a
pressure of between about 0.1 and 0.5 psig.
[0025] In addition, hotbox output H2-H20-G is input to splitter 160 and is
split into a steam
recycle stream RECH2OLP, where LP stands for low pressure, and a net product
H2-H20-N,
where N stands for Net (e.g., output for commercial use or storage). Here, net
product H2-
H20-N may have a temperature between about 100 C and 180 C (e.g., 130 C), a
pressure of
between about 0.1 psig and 0.5 psig. Steam recycle stream RECH2OLP may have a
temperature of between about 100 C and 180 C (e.g., 130 C), a pressure of
between about
0.1 psig and 0.5 psig. Hotbox 150 may further output enriched air at enriched
air conduit 125
that may have a temperature of between about 120 C and 300 C, at essentially
local
atmospheric pressure (e.g., less than 0.5 psig or less than 0.05 psig).
[0026] Steam recycle stream RECH2OLP is input to steam recycle blower 170. The
resulting
recycled steam REC-STM may have a temperature of between about 100 C and 180
C (e.g.,
140 C), a pressure between about 0.5 and 1.5 psig (e.g., about 1 psig), and is
input into
hotbox 150 at recycle steam inlet 111. Additional steam or heat can be
supplied to recycle
steam inlet 111 by a further steam recycle outlet (not shown), which captures
air exhaust heat
(e.g., ¨280 C) of hotbox 150. In some embodiments, there may be no recycled
hydrogen
feed included with the recycled steam.
[0027] As can be understood from FIG. 1, incoming steam temperature at
external steam
conduit 210 (e.g., 105 C) may be low compared with a SOEC configuration with
internal
steam generation. A plurality of recycle loops can be configured to SOEC
systems using
both internal steam generation from a recycle steam outlet (not shown) and
external steam
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Date regue/Date received 2023-05-30
generation from steam conduit 210. In other words, recycle steam inlet 111 is
configured to
receive steam from external steam conduit 210 and/or recycle steam.
[0028] SOEC system 100 utilizes external steam conduit 210 as well as heated
deionized
water conduit 205. Deionized water of deionized water conduit 205 can be
heated by heater
206. Mass flow controller 207 is located upstream from one or more heaters 206
and is
configured to control the liquid water flowrate into the one or more heaters.
The mass flow
of steam exiting the one or more heaters 206 is equal to the mass flow of
liquid water
entering the one or more heaters 206. Hydrogen is supplied by input hydrogen
conduit 225.
Each of external steam 210, input hydrogen conduit 225, and heated deionized
water conduit
205 are supplied on the recycle loop downstream from steam recycle blower 170,
as shown in
FIG. 1. The resulting hydrogen and steam product is input at recycle steam
inlet ill.
[0029] Mass flow controller 207 may be achieved by one or more devices such as
a
proportional (or flow) valve and a water flow meter as separate devices or an
integrated
device.
[0030] FIG. 2 is an SOEC system 200 process flow diagram according to another
example
embodiment of the present invention. The components of SOEC system 200 are
similar to
the components of SOEC system 100, as described in connection with FIG. 1, and
the
differences between systems 200 and 100 will now be described.
[0031] In the example embodiment, SOEC system 200 does not require use of
input steam
conduit as well as the recycle loop by not utilizing splitter 160 and steam
recycle blower 170,
and their downstream. Instead, SOEC system 200 generates internal steam by
heating
deionized water of deionized water conduit 305 that is received at water inlet
310. Steam
outlet by recycle steam outlet 121 is further heated by vaporizer 320 and
mixed with
hydrogen of input hydrogen conduit 325. The resulting hydrogen and steam
product is input
at recycle steam inlet 111, as shown in FIG. 2.
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[0032] FIG. 3 is an SOEC system 300 process flow diagram according to another
example
embodiment of the present invention. The components of SOEC system 300 are
similar to
the components of SOEC system 100, as described in connection with FIG. 1, and
the
differences between systems 300 and 100 will now be described.
[0033] In the example embodiment, SOEC system 300 does not require use of an
input
steam conduit as well as the recycle loop by not utilizing splitter 160 and
steam recycle
blower 170, and their downstream. Instead, SOEC system 300 generates internal
steam by
heating deionized water of deionized water conduit 405 that is received at
water inlet 410.
Steam outlet by recycle steam outlet 121 is further heated by vaporizer 420
and mixed with
hydrogen of input hydrogen conduit 425. In some configurations, a demister
(not shown) is
included at the output of vaporizer 420. In some configurations, excess steam
can be vented
to enriched air conduit 125. The resulting hydrogen and steam product is input
at recycle
steam inlet 1 1 1, as shown in FIG. 3.
[0034] FIG. 4 is an SOEC system 400 process flow diagram according to yet
another
example embodiment of the present invention. The components of SOEC system 400
are
similar to the components of SOEC system 100, as described in connection with
FIG. 1, and
the differences between systems 400 and 100 will now be described.
[0035] In the example embodiment, SOEC system 400 does not require use of an
input
steam conduit as well as the recycle loop by not utilizing splitter 160 and
steam recycle
blower 170, and their downstream. Instead, SOEC system 400 generates internal
steam by
heating deionized water of deionized water conduit 505 that is received at
water inlet 510.
Steam outlet by recycle steam outlet 121 is regulated by water monitor system
520 (e.g., level
transducer float type). Steam released and optionally heated and demisted by
water
monitoring system 520 is mixed with hydrogen of input hydrogen conduit 525.
The resulting
hydrogen and steam product is input at recycle steam inlet 1 1 1, as shown in
FIG. 4.
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[0036] In the various embodiments, such as systems 100, 200, 300, 400, the
SOECs utilize
steam as a media input for the electrochemical process. When steam is not
readily available,
steam is generated from site-supplied water, such as deionized water. Use of
water to
generate steam has advantages. For example, controlling the mass flow of
liquid water is
simpler and more cost effective than controlling the mass flow of its high
temperature
gaseous form as steam.
[0037] For example, the steam flowrate into the electrolyzer is controlled by
varying the
liquid water mass flow into one or more heaters, such as a circulation heater.
In the various
configurations, heater power, temperatures, and/or pressure is balanced to
ensure that the
liquid water is changing state at a calculated rate (e.g., constant rate) and
that the mass flow
of steam exiting the one or more heaters is equal to the mass flow of liquid
water entering the
one or more heaters.
[0038] In known systems, adjustable control of steam flow requires costly and
large
components to accurately measure and control the steam flow. Scaling deposits
in the steam
can contaminate and cause premature failure of the steam measurement and
control devices.
Traditional steam boilers require water level, temperature, and pressure
control. Heating
elements in direct contact with the liquid water can quickly overheat and fail
if the liquid
level is not properly maintained. Boilers with heating elements in direct
contact with the
liquid water fail over time due to scaling build up on the heating elements.
[0039] In the various embodiments, flow control systems, devices, and methods
are
provided. The system uses mass flow controller (e.g., 207) to control the
liquid water
flowrate into one or more heaters (e.g., a circulation heater). As measurement
and control is
done with liquid water prior to steam conversion, there are no costly
measurement or control
devices downstream that may be contaminated with scaling deposits. Energy into
the heating
elements of the heaters and outlet temperature and pressure exiting the
circulation heater are
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monitored and controlled to balance the system resulting in equal mass
entering and exiting
the one or more heaters.
100401 Preferably, the embodiments use a circulation heater instead of a
traditional water
boiler. Circulation heaters make use of an intermediary medium such as
aluminum or brass
to dissipate and transfer heat to the process media embedded in an isolated
flow path. This
enables the embodiments to run "dry" with no water present and to be pre-
heated to operating
temperature without generating steam. This type of heating prevents heater
element burnout
that occurs in traditional boilers that are operated without water initially
present. Because the
water/steam is not in direct contact with the heating elements, they are not
at risk of failure
from scaling deposit build up.
100411 FIG. 5 illustrates a circulation heater 500 according to an example
embodiment of
the invention. Additional circulation heater or other heater configurations
are feasible, such
as single heating tube as well as multi-heating tubes configured in series
and/or in parallel.
[0042] Controlling the mass flow of liquid water is simpler and more cost
effective than
controlling it in high temperature gaseous form as steam. Accordingly, the
embodiments
reduce complexity and cost and eliminate known failure risks associated with
traditional
boiler designs.
[0043] In each of the various embodiments described herein, one or more
detectors can be
used to detect a safety event. For example, one or more pressure detectors and
one or more
thermal detectors can be used. One or more pressure detectors can be placed
along input
hydrogen conduits (e.g., 225, 325, 425, 525) to detect under pressure (e.g.,
under 5 PSI) and
excess pressure. If a pressure detector is tripped, the system (i.e., hotbox
150) is shutdown.
Additionally, one or more thermal detectors can be placed within the cabinet
of the hotbox to
detect excess heat (e.g., over 230 C). Cabinet ventilation is provided and
maintained by
Date regue/Date received 2023-05-30
enriched air blower 126, for example. If a thermal detector is tripped, the
system (i.e., hotbox
150) is shutdown.
[0044] The SOEC system (e.g., 100, 200, 300, 400) ceases receiving hydrogen
when the
SOEC system is operating at steady state or upon detection of a safety event.
Additionally,
the stack of electrolyzer cells in hotbox 150 can be configured to receive
hydrogen when the
SOEC system is in startup, shutdown, or when the SOEC system is not producing
hydrogen
or not producing enough hydrogen.
[0045] To operate an SOEC there are mechanical systems and components required
to
provide water, air, and start-up fuel. Safety systems also protect the system
against fire and
other damage to the surroundings and people in proximity. Operating the SOEC
with
required safety systems prevents harm and hazards due to leaking hydrogen
and/or other
failures. Other SOEC systems may include hazardous location devices, or double
containment of fuel components.
[0046] It will be apparent to those skilled in the art that various
modifications and
variations can be made in the internal steam delivery system of the present
invention without
departing from the spirit or scope of the invention. Thus, it is intended that
the present
invention cover the modifications and variations of this invention provided
they come within
the scope of the appended claims and their equivalents.
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