U.S. patent application number 12/062374 was filed with the patent office on 2008-10-09 for renewable energy system for hydrogen production and carbon dioxide capture.
This patent application is currently assigned to NEW SKY ENERGY, INC.. Invention is credited to Timothy C. Heffernan, Joseph V. Kosmoski, C. Deane Little, C. Gordon Little.
Application Number | 20080245660 12/062374 |
Document ID | / |
Family ID | 39825998 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080245660 |
Kind Code |
A1 |
Little; C. Deane ; et
al. |
October 9, 2008 |
RENEWABLE ENERGY SYSTEM FOR HYDROGEN PRODUCTION AND CARBON DIOXIDE
CAPTURE
Abstract
The present invention is an integrated system for the production
of hydrogen and the removal of carbon dioxide from the air or gas
streams. The integrated system includes an energy source for
generating electrical energy and a water source coupled to the
energy source. The water source includes ionic electrolytes. The
energy source supplies energy to the water source to electrolyze
water to produce hydrogen gas, oxygen gas, acid and base. The
carbon dioxide reacts with the base. In some embodiments, the
energy source is a renewable energy source. The integrated system
produces substantially no carbon dioxide and when combined with a
renewable energy source, produces clean hydrogen fuel and reduces
atmospheric carbon dioxide, resulting in carbon dioxide negative
energy and manufacturing strategies.
Inventors: |
Little; C. Deane; (Boulder,
CO) ; Heffernan; Timothy C.; (Indianapolis, IN)
; Kosmoski; Joseph V.; (Wildomar, CA) ; Little; C.
Gordon; (Boulder, CO) |
Correspondence
Address: |
FAEGRE & BENSON LLP;PATENT DOCKETING
2200 WELLS FARGO CENTER, 90 SOUTH SEVENTH STREET
MINNEAPOLIS
MN
55402-3901
US
|
Assignee: |
NEW SKY ENERGY, INC.
Boulder
CO
|
Family ID: |
39825998 |
Appl. No.: |
12/062374 |
Filed: |
April 3, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60921598 |
Apr 3, 2007 |
|
|
|
Current U.S.
Class: |
204/242 |
Current CPC
Class: |
Y02E 60/36 20130101;
C25B 1/04 20130101; Y02E 60/50 20130101; H01M 8/0656 20130101; Y02E
50/30 20130101; H01M 16/003 20130101; C25B 15/08 20130101; Y02P
20/133 20151101; C25B 15/02 20130101 |
Class at
Publication: |
204/242 |
International
Class: |
C25B 1/00 20060101
C25B001/00 |
Claims
1. An integrated system for the production of hydrogen and the
removal of carbon dioxide comprising: an energy source for
generating electrical energy; and a water source coupled to the
energy source, wherein the water source comprises ionic
electrolytes, and wherein the energy source supplies energy to the
water source to electrolyze water to produce oxygen gas, hydrogen
gas, acid and base; wherein carbon dioxide reacts with the base;
and wherein the integrated system produces substantially no carbon
dioxide.
2. The integrated system of claim 1, wherein the energy source is a
renewable energy source.
3. The integrated system of claim 2, wherein the hydrogen is used
to generate renewable electricity to replace or supplement the
renewable energy source.
4. The integrated system of claim 2, wherein the renewable energy
source is one of wind, solar, hydroelectric, geothermal, oceanic,
wave or tidal.
5. The integrated system of claim 1, wherein the energy source is
one of biomass and biofuel.
6. The integrated system of claim 1, wherein the carbon dioxide is
captured from one of the atmosphere and a gas stream.
7. The integrated system of claim 1, wherein the carbon dioxide is
converted to a value-added product.
8. The integrated system of claim 7, wherein the value-added
product is one of methane, methanol, formic acid, urea,
formaldehyde, carbon monoxide, formamide, acetone, acetic acid,
supercritical carbon dioxide, limestone, acetaldehyde, ethylene
glycol, ethanol, a bicarbonate salt or a carbonate salt.
9. The integrated system of claim 7, wherein the value-added
product is one of a building material, a plastic, a polymer, a
resin, a fabric, a fertilizer, antifreeze, a lubricant, a buffer, a
pesticide, a fiber, a foam, a film, paint, a carbon dioxide neutral
fuel, a solvent, a stored source of carbon dioxide, a paving
material, a filler for plastics, agricultural lime, baking soda or
baking powder.
10. The integrated system of claim 1, wherein the hydrogen is sent
to the energy source.
11. A system for producing value-added products, including
renewable hydrogen, and removing carbon dioxide comprising: a water
electrolysis process for producing hydrogen gas and a hydroxide
base at a cathode and oxygen gas and acid at an anode; and an
energy source for supplying an electrical input to the water
electrolysis process; wherein the hydrogen gas is collected and
supplements the energy source; wherein the base removes atmospheric
carbon dioxide; and wherein the system removes more atmospheric
carbon dioxide than it produces.
12. The system of claim 11, wherein the energy source is a
renewable energy source.
13. The system of claim 12, wherein the renewable energy source is
one of wind, solar, hydroelectric, geothermal, oceanic, wave or
tidal.
14. The system of claim 11, wherein the carbon dioxide is captured
by reaction with the hydroxide base and is converted to at least
one of carbonate salt or bicarbonate salt.
15. The system of claim 11, wherein the value-added product is one
of a building material, a plastic, a polymer, a resin, a fabric, a
fertilizer, antifreeze, a lubricant, a buffer, a pesticide, a
fiber, a foam, a film, paint, a carbon dioxide neutral fuel, a
solvent, a stored source of carbon dioxide, a paving material, a
filler for plastics, agricultural lime, baking soda or baking
powder.
16. The system of claim 11, wherein the hydrogen is used as fuel or
chemical feedstock.
17. An integrated system for capturing and converting carbon
dioxide to a value-added product, the integrated system comprising:
a renewable energy source for generating energy; and a water
electrolysis apparatus, wherein the energy from the renewable
energy source is supplied to the water electrolysis apparatus to
produce hydrogen, oxygen, a base and an acid and wherein the
hydrogen, the oxygen, the base and the acid are separately
sequestered; wherein the atmosphere has an initial concentration of
carbon dioxide prior to supplying energy from the renewable energy
source to the water electrolysis apparatus; wherein after supplying
energy from the renewable energy source to the water electrolysis
apparatus, the base produced reacts with the carbon dioxide from
the atmosphere such that the atmosphere has a resulting
concentration of carbon dioxide less than the initial concentration
of carbon dioxide; and wherein the carbon dioxide is converted to a
value-added product.
18. The integrated system of claim 17, wherein the renewable energy
source is one of wind, solar, hydroelectric, geothermal, oceanic,
wave or tidal.
19. The integrated system of claim 17, wherein the value-added
product is one of carbonate salt or bicarbonate salt.
20. The integrated system of claim 19, wherein the acid is used to
liberate the carbonate or bicarbonate as carbon dioxide for storage
or for conversion to the value-added product.
21. The integrated system of claim 17, wherein the value-added
product is one of methane, methanol, formic acid, urea,
formaldehyde, carbon monoxide, formamide, acetone, acetic acid,
supercritical carbon dioxide, limestone, acetaldehyde, ethylene
glycol, or ethanol.
22. The integrated system of claim 17, wherein the oxygen and
hydrogen are transported to and used at a fuel cell.
24. The integrated system of claim 17, wherein the hydrogen is
transported to the renewable energy source.
24. A system for recovering carbon dioxide comprising: a water
electrolysis apparatus having an anode and a cathode, wherein the
water electrolysis apparatus produces oxygen and aqueous acid at
the anode and produces hydrogen and aqueous base at the cathode;
and a renewable energy source coupled to the water electrolysis
apparatus for providing energy to the water electrolysis apparatus;
wherein the aqueous base produced by the water electrolysis
apparatus is used to capture carbon dioxide; wherein the system
captures more carbon dioxide than the system produces; and wherein
the system produces less than about 100 mg of chlorine per liter of
electrolyte.
25. The system of claim 24, wherein the system produces less than
about 10 mg of chlorine per liter of electrolyte.
26. The system of claim 25, wherein the system produces less than
about 1 mg of chlorine per liter of electrolyte.
27. The system of claim 24, wherein the carbon dioxide is converted
to a value-added product.
28. The system of claim 27, wherein the value-added product is one
of carbonate salt and bicarbonate salt.
30. The system of claim 27, wherein the value-added product is one
of methane, methanol, formic acid, urea, formaldehyde, carbon
monoxide, formamide, acetone, acetic acid, supercritical carbon
dioxide, limestone, acetaldehyde, ethylene glycol, or ethanol.
31. The system of claim 27, wherein the value-added product is one
of a building material, a plastic, a polymer, a resin, a fabric, a
fertilizer, antifreeze, a lubricant, a buffer, a pesticide, a
fiber, a foam, a film, paint, a carbon dioxide neutral fuel, a
solvent, a stored source of carbon dioxide, a paving material, a
filler for plastics, agricultural lime, baking soda or baking
powder.
32. The system of claim 24, wherein the renewable energy source is
one of wind, solar, hydroelectric, geothermal, oceanic, wave or
tidal.
33. The system of claim 24, wherein the carbon dioxide is captured
from one of the atmosphere or a gas stream.
34. The system of claim 33, wherein the system captures carbon
dioxide from a gas stream, wherein the gas stream is one of a flue
gas, fermenter gas effluent, air, biogas, landfill methane or
carbon dioxide contaminated natural gas.
35. The system of claim 24, wherein the energy source is one of
biomass or biofuel.
36. An integrated water electrolysis system for the production of
hydrogen, oxygen, acid and base comprising: an aqueous electrolyte
solution; an electrical source; an anode and anode reaction region
comprising hydronium ions, wherein an operational concentration of
the hydronium ions is between about 100 and about 10,000,000 times
higher than an initial concentration of the hydronium ions; and a
cathode and cathode reaction region comprising hydroxide ions,
wherein an operational concentration of the hydroxide ions is
between about 100 and about 10,000,000 times higher than an initial
concentration of the hydroxide ions; wherein carbon dioxide reacts
with the hydroxide ions to form carbonate or bicarbonate; and
wherein the integrated water electrolysis system produces
substantially no carbon dioxide.
37. The system of claim 36, wherein the electrolyte solution
comprises sodium or potassium sulfate at a sulfate concentration of
greater than about 0.1 molar.
38. The system of claim 36, wherein the base produced is one of
sodium hydroxide or potassium hydroxide.
39. The system of claim 38, wherein the integrated water
electrolysis system produces greater than about 40 grams of sodium
hydroxide or potassium hydroxide for every kilogram of
hydrogen.
40. The system of claim 36, wherein the acid produced is sulfuric
acid.
41. The system of claim 40, wherein the integrated water
electrolysis system produces greater than about 49 grams of
sulfuric acid for every kilogram of hydrogen.
42. The system of claim 36, and further comprising a hydrogen fuel
cell, wherein the hydrogen is sent to a hydrogen fuel cell to
provide direct current electricity to the integrated water
electrolysis system.
43. The system of claim 36, wherein the integrated water
electrolysis system removes more carbon dioxide from the atmosphere
or a gas stream than it produces.
44. The system of claim 36, wherein the carbonate or bicarbonate is
converted to at least one of the group consisting of: methane,
methanol, formic acid, urea, formaldehyde, carbon monoxide,
formamide, acetone, acetic acid, supercritical carbon dioxide,
limestone, acetaldehyde, ethylene glycol, or ethanol.
45. The system of claim 36, wherein the carbonate or bicarbonate is
converted to one of a building material, a plastic, a polymer, a
resin, a fabric, a fertilizer, antifreeze, a lubricant, a buffer, a
pesticide, a fiber, a foam, a film, paint, a carbon based fuel, a
solvent, a stored source of carbon dioxide, a paving material, a
filler for plastics, agricultural lime, baking soda or baking
powder.
Description
[0001] This application claims the benefit under 35 U.S.C. 119(e)
of U.S. Provisional Patent Application No. 60/921,598, filed on
Apr. 3, 2007, entitled A NOVEL ELECTROCHEMICAL METHOD FOR REMOVING
CARBON DIOXIDE FROM GAS STREAMS AND SIMULTANEOUSLY GENERATING
HYDROGEN GAS, which is herein incorporated by reference in its
entirety.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] This application is related to co-owned and co-pending
application entitled ELECTROCHEMICAL APPARATUS TO GENERATE HYDROGEN
AND SEQUESTER CARBON DIOXIDE, filed on the same day and assigned
Ser. No. ______ and to co-owned and co-pending application entitled
ELECTROCHEMICAL METHODS TO GENERATE HYDROGEN AND SEQUESTER CARBON
DIOXIDE, filed on the same day and assigned Ser. No. ______, both
of which are herein incorporated by reference in their
entirety.
FIELD OF THE INVENTION
[0003] The present invention relates to the fields of renewable
hydrogen production and carbon dioxide capture and sequestration.
More specifically, the present invention relates to an integrated
system that uses renewable energy in combination with water
electrolysis to generate renewable hydrogen and capture and
sequester carbon dioxide.
BACKGROUND OF THE INVENTION
[0004] The electrochemical cleavage of water has traditionally been
viewed as a method of producing hydrogen and oxygen gas. In
traditional alkaline water electrolysis, two molecules of hydroxide
base are produced and consumed for every molecule of hydrogen
generated. One common method of producing hydroxide base uses the
chloralkali process in which sodium chloride, rather than water, is
electrolyzed. While effective, the chloralkali method generates
abundant chlorine, a toxic by-product, and generates several tons
of carbon dioxide pollution per ton of manufactured base when
powered with electricity generated from fossil fuels.
SUMMARY OF THE INVENTION
[0005] In one aspect, the present invention is an integrated system
for the production of hydrogen and the removal of carbon dioxide
including an energy source and a water source. The energy source
generates electrical energy. The water source is coupled to the
energy source and includes ionic electrolytes. The energy source
supplies energy to the water source to electrolyze water to produce
oxygen gas, hydrogen gas, acid and base. The carbon dioxide reacts
with the base. The integrated system produces substantially no
carbon dioxide.
[0006] In another aspect, the present invention is a system for
producing value-added products and removing carbon dioxide
including a water electrolysis process and an energy source. The
water electrolysis process produces hydrogen gas and a hydroxide
base. The energy source supplies an electrical input to the water
electrolysis process. The hydrogen gas is collected and supplements
the energy source and the base removes atmospheric carbon dioxide.
The system removes more atmospheric carbon dioxide than it
produces.
[0007] In yet another aspect, the present invention is an
integrated system for capturing and converting carbon dioxide to a
value-added product. The integrated system includes a renewable
energy source for generating electricity and a water electrolysis
apparatus. The energy from the renewable energy source is supplied
to the water electrolysis apparatus to produce hydrogen, oxygen, a
base and an acid, which are sequestered. The atmosphere has an
initial concentration of carbon dioxide prior to supplying energy
from the renewable energy source to the water electrolysis
apparatus. After supplying energy from the renewable energy source
to the water electrolysis apparatus, the base produced reacts with
the carbon dioxide from the atmosphere such that the atmosphere has
a resulting concentration of carbon dioxide less than the initial
concentration of carbon dioxide. The carbon dioxide is then
converted to a value-added product.
[0008] In still another aspect, the present invention is a system
for recovering carbon dioxide including a water electrolysis
apparatus having an anode and a cathode and a renewable energy
source coupled to the water electrolysis apparatus for providing
electrical energy to the water electrolysis apparatus. The water
electrolysis apparatus produces oxygen and aqueous acid at the
anode and produces hydrogen and aqueous base at the cathode. The
aqueous base produced by the water electrolysis apparatus is used
to capture carbon dioxide. The system captures more carbon dioxide
than the system produces and produces less than about 100 mg of
chlorine per liter of electrolyte.
[0009] In another aspect, the present invention is an integrated
water electrolysis system for the production of hydrogen, oxygen,
acid and base. The system includes an aqueous electrolyte solution,
an electrical source, an anode and anode region and a cathode and
cathode region. The anode and anode reaction region generate
between about 100 and about 10,000,000 times more hydronium ions
than are initially present in the electrolyte solution and the
cathode and cathode reaction region generate between about 100 and
about 10,000,000 times more hydroxide ions than are initially
present in the electrolyte solution. The carbon dioxide reacts with
the hydroxide ions to form carbonate or bicarbonate. The integrated
electrolysis system produces substantially no carbon dioxide.
[0010] These and other aspects, processes and features of the
invention will become more fully apparent when the following
detailed description is read with the accompanying figures and
examples. However, both the foregoing summary of the invention and
the following detailed description of it represent one potential
embodiment, and are not restrictive of the invention or other
alternate embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic diagram of an integrated water
electrolysis system, according to one embodiment.
[0012] FIG. 2 is a schematic view of a water electrolysis device of
the integrated water electrolysis system of FIG. 1, according to
one embodiment.
[0013] FIG. 3 is a schematic view of an alternative embodiment of
the water electrolysis device of FIG. 2, according to one
embodiment.
[0014] FIG. 4 is a schematic view of an alternative embodiment of
the water electrolysis device of FIG. 2, according to one
embodiment.
[0015] FIG. 5 is a schematic diagram of value-added products that
may be processed from the integrated water electrolysis system of
FIG. 1.
[0016] FIG. 6 is a schematic diagram of a water electrolysis
apparatus of the integrated water electrolysis system of FIG.
1.
[0017] While the invention is amenable to various modifications and
alternative forms, some embodiments have been shown by way of
example in the drawings and are described in detail below. As
alluded to above, the intention, however, is not to limit the
invention by those examples. On the contrary, the invention is
intended to cover all modifications, equivalents, and
alternatives.
DETAILED DESCRIPTION
[0018] FIG. 1 shows a schematic diagram of an integrated water
electrolysis system 10 for generating renewable hydrogen and
capturing carbon dioxide (CO.sub.2), according to one embodiment.
The integrated water electrolysis system 10 includes an electrical
energy source 12, a renewable energy source 14, an electrolysis
cell 16 including a cathode region 18 and a cathode 18a, an anode
region 20 and anode 20a, an aqueous electrolyte source 22 housing
an aqueous electrolyte solution 22a, a hydrogen collection and
storage reservoir 24, an oxygen collection and storage reservoir
26, a base collection and storage reservoir 28, an acid collection
and storage reservoir 30, a first carbon dioxide capture apparatus
32 connected to the base collection and storage reservoir 28, a
second carbon dioxide capture apparatus 34 connected indirectly to
the acid collection and storage reservoir 30, a carbon dioxide
product system 36 and a fuel cell 38. The integrated water
electrolysis system 10 and its components produce hydrogen, oxygen,
acid and base through water electrolysis, followed by subsequent
processing of one or more of these products to capture carbon
dioxide as carbonate salt, bicarbonate salt or mineral carbonates.
Using the base produced by the integrated water electrolysis system
10 to capture carbon dioxide, renewable hydrogen is generated as a
carbon dioxide negative rather than carbon dioxide neutral fuel and
can be used as a large-scale application for reducing global carbon
dioxide pollution. When combined with renewable or non-carbon
dioxide producing energy sources, the integrated water electrolysis
system 10 creates carbon dioxide negative energy strategies for
producing clean hydrogen fuel and reducing carbon dioxide. The
phrase "carbon dioxide negative" refers to the net overall
reduction of carbon dioxide in the atmosphere or a gas stream.
Thus, in stating that the integrated water electrolysis system 10
is carbon dioxide negative, it is meant that the integrated water
electrolysis system 10 removes substantially more carbon dioxide
than it produces. In addition, unlike traditional methods of
manufacturing hydroxide base, no substantial carbon dioxide or
chlorine gas is produced.
[0019] The electrical energy source 12 is a direct current (DC)
electrical source and is coupled to the renewable energy source 14.
The electrical energy source 12 and the renewable energy source 14
supply electricity to the electrolysis cell 16. The DC electricity
is used at a predetermined and sufficient voltage to electrolyze
water in the electrolysis cell 16 to charge the cathode region 18
and anode region 20 to power the electrolysis cell 16.
[0020] The renewable energy source 14 may be any renewable form of
energy, such as wind, solar, hydroelectric, geothermal, oceanic,
wave, tidal and fuel cells using renewable hydrogen. These
renewable energy sources do not generate carbon dioxide. For
example, wind acting upon a wind turbine can be used to generate
direct current electricity. Other energy sources that may generate
carbon dioxide may also be used to provide energy to the electrical
energy source including biofuel, biomass, coal, methane and the
like. According to one embodiment, nuclear energy may also be used
to provide energy to the integrated water electrolysis system
10.
[0021] When powered by renewable energy, the integrated water
electrolysis system 10 operates in an overall carbon dioxide
negative fashion, removing net carbon dioxide from the air or gas
streams and converting it to a variety of value-added products.
Nuclear energy is an alternate source of electricity, and also
allows carbon dioxide negative operation. Electricity from fossil
fuel burning is another alternative, but does not currently allow
carbon dioxide negative operation. With improvements in efficiency
of the apparatus or the process of electricity generation, fossil
fuel electricity would also allow a carbon dioxide negative
operation of the apparatus.
[0022] In one embodiment, the energy generated by the renewable
energy source 14 may be used to supplement the electrical energy
source 12. In an alternative embodiment, the energy generated by
the electrical energy source 12 may be used to supplement the
renewable energy source 14. Excess electricity can be stored in a
battery, converted by an inverter to alternating current for usage
by the grid, or converted to hydrogen as an energy storage
medium.
[0023] The electrical energy source 12 and the renewable energy
source 14 supply a sufficient amount of electricity to initiate
water electrolysis and electrolyze the aqueous electrolyte solution
at the electrolysis cell 16. In one embodiment, a minimal voltage
greater than about 1.2 V is applied to the electrolysis cell 16 to
initiate and maintain electrolysis. According to other embodiments,
the predetermined voltage supplied to the electrolysis cell 16
ranges from about 1.2 volts to about 10.0 volts. Application of a
higher voltage can increase the rate of the reaction, with a
penalty in energy efficiency.
[0024] The aqueous electrolyte solution housed in the aqueous
electrolyte source 22 includes a concentrated aqueous electrolyte
solution, such as a sodium, potassium, calcium, or magnesium
sulfate, nitrate, or carbonate solution. According to various
embodiments, the aqueous electrolyte includes an alkali salt. The
alkali salt is a salt of the groups 1(IA) or 2(IIA) of the periodic
table. Exemplary electrolytes suitable for use with the present
invention include, but are not limited to, the following: sodium
sulfate, potassium sulfate, calcium sulfate, magnesium sulfate,
sodium nitrate, potassium nitrate, sodium bicarbonate, sodium
carbonate, potassium bicarbonate, or potassium carbonate. Other
suitable electrolyte solutions include sea water and aqueous sea
salt solutions. In one embodiment, the aqueous electrolyte solution
contains substantially no chloride such that the electrolysis cell
16 and/or integrated water electrolysis system 10, produce
essentially no chlorine gas. In one embodiment, the integrated
water electrolysis system 10 produces less than about 100
milligrams of chlorine per liter of electrolyte, particularly less
than about 10 milligrams of chlorine per liter of electrolyte, and
more particularly less than about 1 milligrams of chlorine per
liter of electrolyte.
[0025] According to one exemplary embodiment of the present
invention, the aqueous electrolyte solution is a saturated solution
of sodium sulfate prepared by adding an excess of sodium sulfate to
about 1000 liters of clean distilled water placed in a 1200 liter
electrolyte processing and storage reservoir. The solution is
maintained at about 30 degrees Celsius (.degree. C.) while being
mechanically mixed overnight. The resultant solution is filtered
and then pumped into the electrolysis cell 16 using a pump or
gravity feed.
[0026] The electrical energy supplied to the aqueous electrolyte
solution in the electrolytic cell 16 causes electrochemical
cleavage of the water to produce hydrogen, oxygen, base and acid.
The hydrogen and base are generated at the cathode region 18 and
oxygen and acid are generated at the anode region 20. The rising
gases within the solution cause dynamic fluid convection, which is
optimized by the electrolysis design. The convection flow of
electrolyte within the cathode region 18 and anode region 20
minimizes the recombination of the newly generated base and acid
typically experienced by traditional electrolysis cells. This
allows each of the concentration of base and acid within the
cathode region 18 and anode region 20 to increase to between about
100 and about 10,000,000 fold or more relative to its initial
concentrations. Particularly, each of the concentration of base and
acid within the cathode region 18 and anode region 20 increases to
between about 10,000 and about 10,000,000 fold or more relative to
its initial concentrations. More particularly, each of the
concentration of base and acid within the cathode region 18 and
anode region 20 increases to between about 100,000 and about
10,000,000 fold or more relative to its initial concentrations.
Even more particularly, each of the concentration of base and acid
within the cathode region 18 and anode region 20 increases to
between about 1,000,000 and about 10,000,000 fold or more relative
to its initial concentrations. Thus, in an aqueous electrolyte
source 22 producing hydroxide base and hydronium acid, the
concentration of hydroxide ions at the cathode region 18 is
increased by more than one hundred fold and the concentration of
hydronium ions at the anode region 20 is increased by more than one
hundred fold. The integrated water electrolysis system 10 is thus
capable of producing up to about 40 kilograms of sodium hydroxide
or a molar equivalent amount of potassium hydroxide for every
kilogram of hydrogen. In addition, according to some embodiments,
the integrated water electrolysis system 10 is capable of producing
up to about 49 kilograms of sulfuric acid for every kilogram of
hydrogen.
[0027] Once concentrations of base and acid reach a minimal
increase of one hundred fold relative to their initial electrolyte
concentration, resulting in a pH difference between the cathode
region 18 and anode region 20 of about four or more, fresh
electrolyte is pumped from the aqueous electrolyte source 22 to the
cathode region 18 and anode region 20. To equilibrate the volume of
liquid in the cathode region 18 and anode region 20, resultant base
and acid is removed from the cathode region 18 and anode region 20,
respectively. Batchwise or continuous flow addition of electrolyte
may be used to optimize production and operating conditions.
[0028] In one embodiment the fresh electrolyte is routed through a
configuration of pipes, which branches into a "T" formation, just
prior to entering the cathode region 18 and anode region 20. The
current between the cathode region 18 and anode region 20 is
conducted though the branched area of the electrolyte "T"
configuration. The dynamic flow of the fresh electrolyte is in
opposing directions as it enters the two electrolysis reaction
regions. The electrolyte supply flow rate is adjusted to overcome
ion migration due to the applied electric field, thereby
eliminating recombination or mixing of contents from the anode and
cathode reaction regions. The electrolyte supply flow rate can also
be adjusted to increase, decrease or maintain the concentrations of
the acid and base produced in their respective reaction
regions.
[0029] FIG. 2 shows a schematic diagram of the electrolysis cell
16. Generally, the electrolysis cell 16 may be any apparatus that
subjects an aqueous solution to an electric field of sufficient
strength to reduce water at the cathode region 18 and oxidize water
at the anode region 20. In one embodiment, the electrolysis cell 16
is a water electrolysis cell that converts aqueous electrolyte
solution from the aqueous electrolyte source 22 to hydrogen,
oxygen, base and acid. The water electrolysis cell 16 includes a
parallel cathode 18a and anode 20a that contain closely spaced
electrodes separated by a semi-permeable membrane 40. The
semi-permeable membrane 40 reduces liquid mixing within the water
electrolysis cell 16 but allows ion flow between the cathode 18a
and anode 20a. This configuration maintains high electrical
conductivity while minimizing loss of acid and base to
recombination within the water electrolysis cell 16. Anion or
cation specific membranes are used to limit salt contamination of
the acid or base produced.
[0030] Fresh aqueous electrolyte solution flows in the same
direction in both the cathode 18a and anode 20a, gradually becoming
more basic in the cathode region 18 and more acidic in the anode
region 20. Alternatively, fresh aqueous electrolyte solution may be
introduced through one of the cathode 18a and anode 20a. In this
case, selective ion flow across an anion or cation specific
membrane 40 would ensure production of a highly pure acid or base,
respectively. The water electrolysis cell 16 can be operated in
parallel or counter-current flow modes. Counter-current flow
minimizes chemical gradients formed across the semi-permeable
membrane 40 and may reduce the energy required to create such
gradients and produce highly concentrated acid and base. In a
counter-current system, the highest concentrations of hydronium and
hydroxide ions and their counter-ions are never located directly
across the semi-permeable membrane 40 from one another, but instead
reach maximum strength opposite incoming fresh aqueous electrolyte
solution in the counter-cell. This design avoids the need to create
a 13-14-unit pH gradients across the semi-permeable membrane 40,
instead producing no higher than a 7-unit pH gradient between
either strong acid and neutral electrolyte, or strong base and
neutral electrolyte. Parallel current flow also has certain energy
and design advantages.
[0031] FIG. 3 shows a schematic diagram of an alternative water
electrolysis cell 16A. Water electrolysis cell 16A is a counter or
parallel current flow three-chamber water electrolysis cell. A
narrow central feed reservoir (such as electrolyte source 22) of
fresh aqueous electrolyte solution is introduced between a first
semi-permeable membrane 42 and a second semi-permeable membrane 44
that separate the cathode 18a and anode 20a. In a counter-current
flow configuration, concentrated aqueous electrolyte solution
enters the central feed reservoir at a first end of the water
electrolytic cell 16A and concentrated base and acid exit the
cathode 18a and the anode 20a, respectively. At a second end of the
water electrolysis cell 16A, dilute base and acid enter the cathode
18a and the anode 20a, and water or dilute aqueous electrolyte
solution exits the central feed reservoir. This design reduces salt
contamination of base and acid produced and minimizes the chemical
gradients formed across the permeable membranes 42 and 44. In some
embodiments, the design may also be used to desalinate salt or
seawater and produce hydrogen, oxygen, acid and base.
[0032] In practice, the cathode 18a is initially filled with dilute
base, and the anode 20a is filled with dilute acid, maintaining
electrical conductivity between the electrodes. Cations flow from
the central feed reservoir through the first semi-permeable
membrane 42 closest to the cathode 18a, combining with hydroxide
ions formed at the cathode 18a to generate concentrated hydroxide
base. Anions flow from the electrolyte solution source 22 through
the second semi-permeable membrane 44 to the anode 20a, combining
with protons formed at the anode 20a to produce concentrated acid.
The semi-permeable membranes 42, 44 may be ion-selective (anion- or
cation-specific) membranes, or may be passive barriers minimizing
fluid flow, allowing passage of anions or cations in either
direction. Regardless of membrane selectivity, such a 3-cell system
can operate with parallel flow in all cells, or with countercurrent
flow between the central feed reservoir and the cathode 18a and
anode 20a on either side. The counter-current flow system minimizes
chemical gradients across the membranes, because high
concentrations of base and acid exit the cathode 18a and anode 20a
opposite highly concentrated fresh electrolyte entering the central
feed reservoir.
[0033] FIG. 4 is a schematic diagram of a stacked water
electrolysis cell according to some embodiments of the present
invention. The stacked porous electrodes may be used in some
embodiments to maximize acid and base production. According to one
embodiment, as shown in FIG. 4, the water electrolysis cell
includes two or more porous anode-cathode pairs 18a, 20a aligned in
a closely spaced parallel configuration. Semi-permeable or ion
selective membrane(s) 52 are optionally included between the inner
pair of electrodes. The membrane(s) 52 function to contain a narrow
electrolyte feed reservoir located between the inner pair of porous
anodes or cathodes. Fresh electrolyte flows from the reservoir
outward, contacting the first pair of electrodes, where water
oxidation occurs at the anode and water reduction occurs at the
cathode. Thus, as water passes through each pair of electrodes it
becomes increasingly acidic or basic. In one embodiment, the
electrodes may consist of fine mesh screens, porous micro or
nanosphere materials or thin plates with numerous flow channels
penetrating the electrode. Varying DC voltages in the range of
about 1.2 to about 10 Volts are supplied to these electrode pairs
to maximize the production of acid in the anode chamber and base in
the cathode chamber.
[0034] Referring back to FIG. 1, after water in the aqueous
electrolyte solution has been electrolyzed to produce hydrogen,
oxygen, base and acid, the products are sequestered and collected.
The gases are routed from the cathode region 18 or anode region 20
to storage or flow systems designed to collect such gases. The low
density of the gases relative to the aqueous electrolyte solution
causes the gases to rise. The reaction conditions and structures
are designed to direct this flow up and out of the cathode region
18 and anode region 20 and into adjacent integrated areas. The
hydrogen, base, oxygen and acid are physically diverted for
collection in the hydrogen collection and storage reservoir 24, the
base collection and storage reservoir 28, the oxygen collection and
storage reservoir 26 and the acid collection and storage reservoir
30, respectively.
[0035] The hydrogen and oxygen collected in the hydrogen collection
and storage reservoir 24 and the oxygen collection and storage
reservoir 26, respectively, may be used to generate electricity to
power the integrated water electrolysis system 10, to supplement
the electrical energy source 12 or to power a fuel cell (such as
the fuel cell 38), furnace or engine to provide direct current
electricity for water electrolysis. The hydrogen and/or oxygen may
also be used to react with other products of the integrated water
electrolysis system 10 to create more value-added products.
Finally, the hydrogen and/or oxygen may be removed from the
integrated water electrolysis system 10 as products to be sold or
used as fuels or chemical feedstocks. Because the hydrogen produced
with the integrated water electrolysis system 10 is generated
through a carbon dioxide neutral or carbon dioxide negative
process, the hydrogen offers a clean source of fuel.
[0036] The base generated by the water electrolysis cell 16 is sent
to the base collection and storage reservoir 28 and is sold or used
as a carbon dioxide neutral, highly purified commodity or
chemically reacted with carbon dioxide gas to form carbonate or
bicarbonate. When used to capture carbon dioxide, the carbon
dioxide is captured as carbonate salt or bicarbonate salt. The
carbon dioxide may be captured by reacting, sequestering, removing,
transforming or chemically modifying gaseous carbon dioxide in the
atmosphere or a gas stream. The gas stream may be flue gas,
fermenter gas effluent, air, biogas, landfill methane, or any
carbon dioxide-contaminated natural gas source. The carbonate salts
may subsequently be processed to generate a variety of carbon-based
products. For example, the carbonate salts may be concentrated,
purified, enriched, chemically reacted, diverted, transformed,
converted, evaporated, crystallized, precipitated, compressed,
stored or isolated.
[0037] The reaction of the base with the carbon dioxide can be
passive, without any physical effort to promote air-water-solid
mixing. An example of a passive reaction includes an open-air
reservoir filled with the base, or a solution containing the base,
or a layer of solid hydroxide base exposed to the air or a gas
stream. This reaction is spontaneous and can be driven by increased
concentrations of base and carbon dioxide. The reaction can also
proceed by active mechanisms involving the base or carbon dioxide.
An example of an active reaction includes actively spraying,
nebulizing, or dripping a basic solution in the presence of the
carbon dioxide. In another example, carbon dioxide is actively
reacted with the base by bubbling or forcing the gas stream through
a column or reservoir of base generated by the water electrolysis
cell 16. Combinations of active and passive carbon dioxide trapping
systems are also envisioned. In both cases, sodium bicarbonate and
sodium carbonate are formed by the integrated water electrolysis
system 10. These reactions may take place within the integrated
water electrolysis system 10 or may be removed from the integrated
water electrolysis system 10 and transported to another site for
capturing carbon dioxide from the atmosphere or a gas stream using
the passive or active techniques previously described.
[0038] The acid produced by the water electrolysis cell 16 is
routed to the acid collection and storage reservoir 30. The acid
can be processed and removed from the system for sale as a
commodity. The acid may be used to prepare certain mineral based
carbon dioxide sequestering compounds, which are then used to
capture carbon dioxide from the atmosphere or gas stream. The acid
may also be used by the integrated system as a chemical reagent to
create other value added products. The acid can be used to release
the carbon dioxide from the carbonate or bicarbonate salts in a
controlled manner to further process the released carbon dioxide
into value-added products. These products may include, but are not
limited to: carbon monoxide, formic acid, methanol, super-critical
carbon dioxide, pressurized carbon dioxide, liquid carbon dioxide
or solid carbon dioxide (dry ice).
[0039] When operated with renewable energy, the system produces
base and/or acid that may be used to capture carbon dioxide from
the atmosphere or a gas stream. In this mode, the overall
integrated water electrolysis system 10 sequesters substantially
more carbon dioxide than the integrated water electrolysis system
10 creates, resulting in a net negative carbon dioxide footprint.
Any significant carbon dioxide trapping makes all of the products
produced by the system carbon dioxide negative, particularly those
carbon products synthesized or produced from atmospheric carbon
dioxide.
[0040] FIG. 5 illustrates value-added products that may be
processed from the carbon dioxide captured using the base and/or
acid produced by the integrated water electrolysis system 10. The
integrated water electrolysis system 10 processes the value-added
products from the center of the diagram outward. As previously
mentioned, base generated from water electrolysis is reacted with
carbon dioxide to produce carbonate and bicarbonate salts. The
carbonate and bicarbonate salts can in turn be converted to carbon
monoxide by chemical reduction or reaction with hydrogen. The
combination of carbon monoxide and hydrogen is Syngas, a critical
cornerstone of synthetic organic chemistry. Through additional
processing of these central products, a number of chemical building
blocks, such as methane, urea, ethylene glycol, acetaldehyde,
formaldehyde, limestone, acetic acid, methanol, formic acid,
acetone and formamide can be formed. The value added chemical
building blocks can be removed from the integrated water
electrolysis system 10 for sale as products or remain in the
integrated system for further processing to a second class of
value-added products. These value-added end products are then
removed from the integrated water electrolysis system 10 and sold,
resulting in profitable conversion of carbon dioxide into carbon
dioxide negative products. Simultaneous production of renewable
hydrogen is subsidized by sale of these carbon products, creating a
carbon dioxide negative energy strategy with potentially dramatic
impacts on global warming.
[0041] The center circle of FIG. 5 depicts primary products that
can be produced from the reaction of hydroxide base with carbon
dioxide, or (in the case of carbon monoxide) by reaction of
captured carbon dioxide with hydrogen. These chemical compounds
include carbon dioxide, carbon monoxide, carbonate and bicarbonate,
all of which can be easily inter-converted. They can be further
processed to create standard chemical building blocks. In many
cases, the hydrogen, oxygen, acid and base generated by the water
electrolysis cell 16 can be used for this secondary processing. The
building blocks can also be further processed within the integrated
water electrolysis system 10 to make many valuable carbon based
products, exemplary embodiments of which are shown in FIG. 5.
[0042] The commercial products manufactured from carbon dioxide
trapped by the integrated water electrolysis system 10 represent
carbon dioxide negative commodities, with the integrated water
electrolysis system 10 producing an overall net decrease in gaseous
carbon dioxide while creating value-added carbon products. Sale of
these products may dramatically subsidize renewable hydrogen
production, making clean hydrogen an inexpensive by-product of an
industrial process focused on converting atmospheric carbon dioxide
into valuable carbon-based products.
EXAMPLES
[0043] The present invention is more particularly described in the
following examples that are intended as illustrations only, since
numerous modifications and variations within the scope of the
present invention will be apparent to those skilled in the art.
Unless otherwise noted, all parts, percentages, and ratios reported
in the following examples are on a weight basis, and all reagents
used in the examples were commercially obtained, or may be
synthesized by conventional techniques.
Example 1
[0044] A water electrolysis cell, shown in FIG. 6, was constructed
to demonstrate the feasibility of generating concentrated acid and
base for carbon dioxide trapping. It consisted of a vertical
central electrolyte feed tube about 2.5 centimeters (cm) in
diameter, connected near its base to upward slanting anode and
cathode tubes attached opposite one another. Wire, screen or flat,
linear electrodes consisting of nickel, stainless steel or platinum
were placed in the anode and cathode tubes near their points of
attachment to the central tube. A concentrated, chloride-free
electrolyte solution of aqueous sodium sulfate was introduced to
the system via the central feed tube, creating an electrically
conductive cell in which water was oxidized at the anode and
reduced at the cathode. A small 15-watt solar panel was used to
provide renewable electricity to the system.
[0045] When a DC current from the solar panel was applied to the
system, hydrogen and hydroxide base were produced rapidly at the
cathode while oxygen and acid formed at the anode. Hydrogen and
oxygen gas flowed up the cathode and anode tubes, respectively, and
were collected at the top. Acid and base accumulating in the anode
and cathode tubes were collected via stopcock valves. Fresh
electrolyte introduced to the central feed tube forced acid and
base up the anode and cathode tubes, preventing them from
recombining within the system. Within a few minutes of operation,
the electrolyte in the anode cell had reached a pH of about 2, and
in the cathode cell a pH of about 12, a differential of 10 pH
units. Unlike the traditional chloralkali process for manufacturing
hydroxide base, this renewable method of base production generated
no chlorine or carbon dioxide. Sulfuric acid, a high demand
commodity chemical, was produced instead of chlorine.
[0046] Base produced in the cathode cell began to trap atmospheric
carbon dioxide immediately, a process that was greatly enhanced by
maximizing air-water exposure. This was achieved by bubbling air or
gas through the basic solution or by spraying base through a column
of air or carbon dioxide containing gas.
[0047] A passive trapping approach also demonstrated clear carbon
dioxide capture from the air. A small amount (20 g) of crystalline
NaOH was spread in a thin layer on a glass plate exposed to the
air. Over the first few days the hygroscopic NaOH absorbed
significant water vapor from the air, becoming a soggy mass of
crystals. During the course of the next two weeks these crystals
gradually dried up and became opaque white in color, a visible
change from the initial translucent NaOH crystals. The white
crystals were a combination of sodium bicarbonate and sodium
carbonate, formed from atmospheric carbon dioxide. Addition of an
acid, vinegar, to these crystals resulted in vigorous bubbling as
carbon dioxide was released back to the air.
Example 2
[0048] A second example used a 1-inch diameter glass tube sealed at
the bottom with a porous glass frit. The frit allowed fluid and ion
exchange between the inside and outside of the glass tube, creating
an inner anode or cathode cell. Flat nickel or platinum electrodes
were placed on opposite sides of the glass frit and attached to a
15 W DC photovoltaic panel or DC power supply. This system created
a water electrolysis device that produced concentrated base inside
the tube and concentrated acid outside the tube.
[0049] Depending on mode of operation, a pH differential of over 11
was quickly generated in this system; an acid-base concentration
gradient of over 20 billion fold. The electrolyte inside the tube
reached a pH of about 13, while across the frit, less than 1/4 inch
away, the electrolyte pH reached about 1.6. Vigorous production of
hydrogen and oxygen were also observed.
Example 3
[0050] A third example included a two-chamber flow-through system
constructed from machined plastic. A peristaltic pump was used to
circulate electrolyte solution into the anode and cathode chambers,
which were physically separated by a semi-permeable membrane or
filter. Variable width plastic spacers were used to vary the gaps
between the electrodes and the membrane. A nickel-copper alloy was
initially used as electrode material. Hydrogen and oxygen were
collected at valves at the top of the device, and acid and base
were continually circulated past the electrodes until sufficient
concentrations were reached. A variable output DC power source was
used to generate voltages sufficient to electrolyze water.
[0051] pH differentials of over about 10 units were quickly
achieved and maintained in this system. The nickel-copper
electrodes proved susceptible to corrosion at certain voltages.
Corrosion-resistant nickel, platinum, alloy or stainless steel
electrodes would be more suitable for use in the reactive
environments created within the water electrolysis system.
[0052] Overall, these experiments clearly demonstrate that water
electrolysis can be used in an integrated strategy to produce
renewable hydrogen and trap carbon dioxide from the air or gas
streams. Given that renewable hydrogen produced by water
electrolysis is already promoted as a clean alternative to fossil
fuels, this combined renewable hydrogen/carbon dioxide capture
technology represents a significant advance in reducing global
carbon dioxide emissions. Unlike other carbon dioxide capture
technologies, no chlorine or carbon dioxide are produced by this
renewable process.
[0053] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *