U.S. patent application number 12/062269 was filed with the patent office on 2008-10-09 for electrochemical methods to generate hydrogen and sequester carbon dioxide.
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 | 20080245672 12/062269 |
Document ID | / |
Family ID | 39825998 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080245672 |
Kind Code |
A1 |
Little; C. Deane ; et
al. |
October 9, 2008 |
ELECTROCHEMICAL METHODS TO GENERATE HYDROGEN AND SEQUESTER CARBON
DIOXIDE
Abstract
A carbon dioxide negative method of manufacturing renewable
hydrogen and trapping carbon dioxide from the air or gas streams is
described. Direct current renewable electricity is provided to a
water electrolysis apparatus with sufficient voltage to generate
hydrogen and hydroxide ions at the cathode, and protons and oxygen
at the anode. These products are separated and sequestered and the
base is used to trap carbon dioxide from the air or gas streams as
bicarbonate or carbonate salts. These carbonate salts, hydrogen,
and trapped carbon dioxide in turn can be combined in a variety of
chemical and electrochemical processes to create valuable
carbon-based materials made from atmospheric carbon dioxide. The
net effect of all processes is the generation of renewable hydrogen
from water and a reduction of carbon dioxide in the atmosphere or
in gas destined to enter the atmosphere.
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.: |
12/062269 |
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: |
205/555 ;
205/343 |
Current CPC
Class: |
C25B 15/02 20130101;
C25B 1/04 20130101; Y02E 60/36 20130101; H01M 8/0656 20130101; C25B
15/08 20130101; Y02P 20/133 20151101; Y02E 50/30 20130101; Y02E
60/50 20130101; H01M 16/003 20130101 |
Class at
Publication: |
205/555 ;
205/343 |
International
Class: |
C25B 1/04 20060101
C25B001/04; C25B 1/00 20060101 C25B001/00 |
Claims
1. A method of generating renewable hydrogen and sequestering
gaseous carbon dioxide comprising: a) supplying a direct current
from an electrical source at a predetermined voltage to a water
electrolysis unit having at least one water electrolysis cell
including an aqueous electrolyte substantially free of chloride
ions and an anode region adapted to generate oxygen gas and protons
separated from a cathode region adapted to generate hydrogen gas
and hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte; b) producing oxygen gas
and protons at the anode region, wherein the protons are present in
the form of an acid; c) producing hydrogen gas and hydroxide ions
at the cathode, wherein the hydroxide ions are present in the form
of a base; d) collecting the hydrogen gas product; e) collecting
the oxygen gas product; f) removing some or all of the acid from
the anode region; g) removing some or all of the base from the
cathode region; and h) contacting the hydroxide ions in the base
with a source of gaseous carbon dioxide to sequester carbon dioxide
in solution as bicarbonate or carbonate or a mixture thereof.
2. The method according to claim 1, wherein the source of gaseous
carbon dioxide is atmospheric carbon dioxide.
3. The method according to claim 1, wherein the source of gaseous
carbon dioxide is a gas stream.
4. The method according to claim 1, further comprising isolating
bicarbonate or carbonate from the solution.
5. The method according to claim 4, wherein isolating bicarbonate
or carbonate from the solution comprises precipitating bicarbonate
or carbonate from the solution.
6. The method according to claim 4, further comprising the step of
concentrating the solution.
7. The method according to claim 1, further comprising chilling the
solution to a temperature ranging from about 0.degree. C. to about
10.degree. C. to precipitate carbonate or bicarbonate from the
solution.
8. The method according to claim 1, further comprising adding a
salt comprising calcium ions to isolate calcium carbonate from the
solution.
9. The method according to claim 1, further comprising adding a
salt comprising magnesium ions to isolate magnesium carbonate from
the solution.
10. The method according to claim 1, further comprising spraying
the solution to precipitate carbonate or bicarbonate from the
solution.
11. The method according to claim 1, further comprising applying to
the water electrolysis cell a counter-current flow adapted to
introduce concentrated electrolyte into a central feed chamber
separated by semi-permeable membranes from the anode and cathode
regions, such that the direction of flow of the electrolyte is
opposite to the direction of flow of acid and base produced at the
anode and cathode regions.
12. The method according to claim 1, further comprising maintaining
a separate anode and cathode region by providing at least one ion
selective membrane positioned between the anode region and the
cathode region of the electrolysis cell.
13. The method according to claim 1, further comprising maintaining
a separate anode and cathode region by providing at least one
non-selective, semi-permeable membrane positioned between the anode
region and the cathode region of the electrolysis cell.
14. The method according to claim 1, further comprising
continuously supplying fresh electrolyte to the electrolysis
cell.
15. The method according to claim 1, further comprising supplying
fresh electrolyte to the electrolysis cell in a batch-wise
manner.
16. The method according to claim 1, further comprising maintaining
a pH difference between the anode region and the cathode region of
at least 6 pH units.
17. The method according to claim 1, wherein the electricity
supplied from the source ranges from about 1.2 to about 10.0
volts.
18. The method according to claim 1, wherein the voltage supplied
from the energy source is at least 1.2 volts.
19. The method according to claim 1, wherein a pH of the base
produced at the cathode region ranges from about pH=8 to about
pH=14.
20. The method according to claim 1, further comprising applying
positive pressure to the electrolysis cell to remove the acid from
the anode region and the base from the cathode region.
21. The method according to claim 1, further comprising applying a
gravity feed to the electrolysis cell to remove the acid from the
anode region and the base from the cathode region.
22. The method according to claim 1, further comprising
continuously pumping acid from the anode region to an acid storage
region and the base from the cathode region to a base storage
region.
23. The method according to claim 1, wherein the electrical source
is a renewable energy source.
24. The method according to claim 23, further comprising recycling
the hydrogen gas to the renewable energy source to be utilized as a
fuel.
25. The method according to claim 23, wherein the renewable energy
source is a fuel cell powered by renewable hydrogen, a synthetic
fuel, biomass, or biofuel.
26. The method according to claim 23, wherein the renewable energy
source is any one of a wind turbine, solar cell, hydroelectric
generator, biofuel, geothermal, or oceanic.
27. The method according to claim 1, further comprising recycling
the hydrogen gas to generate renewable electricity.
28. The method according to claim 1, further comprising recycling
the hydrogen gas and the oxygen gas to regenerate water and
electricity supplied to the electrolysis unit.
29. The method according to claim 1, wherein the source does not
consume fossil based fuels.
30. The method according to claim 1, wherein the electrical source
is a nuclear generator.
31. The method according to claim 1, wherein the aqueous
electrolyte comprises an alkali salt substantially free of chloride
ions.
32. The method according to claim 1, wherein the aqueous
electrolyte comprises a sodium salt substantially free of chloride
ions.
33. The method according to claim 1, wherein the aqueous
electrolyte is selected from the group consisting of sodium
sulfate, potassium sulfate, calcium sulfate, magnesium sulfate,
sodium nitrate, potassium nitrate, sodium bicarbonate, sodium
carbonate, potassium bicarbonate, potassium carbonate, calcium
carbonate, and magnesium carbonate.
34. The method according to claim 1, wherein the electrolyte is
saturated in solution.
35. The method according to claim 1, further comprising maintaining
a saturated electrolyte solution.
36. The method according to claim 1, wherein the aqueous
electrolyte is sodium sulfate or potassium sulfate.
37. The method according to claim 1, further comprising
regenerating electrolyte supplied to the electrolysis unit by
reacting the acid removed from the anode region of the electrolysis
cell with sodium chloride to produce hydrochloric acid and the
original electrolyte salt.
38. The method according to claim 1, further comprising collecting
and concentrating the base.
39. A base produced according to the method of claim 1.
40. A building material comprising carbonate produced according to
the method of claim 1, wherein the building material is any one of
a dry wall product, filled polyvinyl chloride, tile, grout,
synthetic stone, filled resin, or an adhesive.
41. The method according to claim 1, further comprising contacting
the acid produced at the anode region with a mineral compound to
form a carbon dioxide sequestering material.
42. The method according to claim 42, wherein the mineral compound
is any one of talc, clay mineral sepiolite, clay minerals,
serpentine, asbestos, or mining byproducts.
43. The method according to claim 1, further comprising contacting
the acid produced at the anode region with the gaseous carbon
dioxide in an electrochemical cell to produce reduced carbon
compounds having a general formula of CmHxO.sub.2n, wherein m an
integer between 1 and 6, x is an integer between 0 and 24, and n is
an integer between 0 and 6.
44. The method according to claim 43, wherein the reduced carbon
compound is any one of formic acid, oxalic acid, formaldehyde, or
methanol.
45. The method according to claim 1, further comprising chemically
reducing carbon dioxide by reacting hydrogen gas produced by the
system with carbon dioxide trapped by the system to produce carbon
monoxide, a precursor for other synthetic processes.
46. The method according to claim 1, wherein an amount of carbon
dioxide sequestered is greater than an amount of carbon dioxide
generated by the electrical source.
47. The method according to claim 1, wherein a difference of at
least 6 pH units is maintained between the anode region and cathode
region by supplying electrolyte utilizing bi-direction flow.
48. The method according to claim 1, wherein a difference of at
least 6 pH units is maintained between the anode region and cathode
region utilizing convection currents generated by rising hydrogen
gas in the cathode region and rising oxygen gas in the anode
region.
49. The method according to claim 1 further comprising
concentrating cations from the electrolyte and delivering the
cations to the cathode region.
50. The method according to claim 1 further comprising
concentrating anions from the electrolyte and delivering the anions
to the anode region.
51. A process of producing renewable hydrogen from water and
bicarbonate from gaseous carbon dioxide comprising: supplying a
direct current from an electrical source at a predetermined voltage
to a water electrolysis unit having at least one electrolysis cell
including an aqueous electrolyte substantially free of chloride
ions and an anode region adapted to generate oxygen gas and protons
separated from a cathode region adapted to generate hydrogen gas
and hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte; producing hydrogen gas
and hydroxide ions at the cathode region; removing some or all of
the base comprising hydroxide ions from the cathode region of the
electrolysis cell; and contacting the hydroxide ions with gaseous
carbon dioxide to produce a solution comprising bicarbonate,
carbonate or a mixture thereof; and isolating bicarbonate from the
solution.
52. A process of producing renewable hydrogen from water and
carbonate from gaseous carbon dioxide comprising: supplying a
direct current from an electrical source at a predetermined voltage
to a water electrolysis unit having at least one electrolysis cell
including an aqueous electrolyte substantially free of chloride
ions and an anode region adapted to generate oxygen gas and protons
separated from a cathode region adapted to generate hydrogen gas
and hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte; producing hydrogen gas
and a base comprising hydroxide ions at the cathode region;
removing some or all of the base comprising hydroxide ions from the
cathode region; contacting the hydroxide ions with gaseous carbon
dioxide to produce a solution comprising bicarbonate, carbonate, or
a mixture thereof; and isolating carbonate from the solution.
53. A method of producing renewable hydrogen and carbon dioxide
neutral or carbon dioxide negative acid comprising: a) supplying a
direct current from a renewable electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte; b) producing oxygen gas and protons at the cathode
region, wherein the protons are present in the form of an acid; c)
removing some or all of the acid from anode region; d) collecting
the acid in a reservoir; and e) concentrating the acid.
54. The method according to claim 53, wherein a pH of the cathode
region ranges from about pH=0 to about pH=5.
55. The method according to claim 53, wherein the acid is sulfuric
acid.
56. A method of producing renewable hydrogen and a carbon dioxide
neutral or carbon dioxide negative base comprising: a) supplying a
renewable electric current from a source to a water electrolysis
unit having at least one electrolysis cell including an aqueous
electrolyte substantially free of chloride ions and an anode region
adapted to generate oxygen gas and protons separated from a cathode
region adapted to generate hydrogen gas and hydroxide ions, wherein
the anode and the cathode regions are electrically connected by the
electrolyte; b) producing hydrogen gas and hydroxide ions at the
cathode region, wherein the hydroxide ions are present in the form
of a base; c) removing some or all of the base from the cathode
region; d) collecting the base in a reservoir; and e) concentrating
the base.
57. The method according to claim 56, wherein a pH of the base
region ranges from about pH=8 to about pH=14.
58. The method according to claim 56, wherein the base is sodium or
potassium hydroxide.
59. A method of generating and maintaining separate regions of
concentrated hydronium ions and concentrated hydroxide ions
comprising: a) contacting a cathode region including at least one
cathode adapted to generate hydrogen gas and hydroxide ions and an
anode region including at least one anode adapted to generate
oxygen gas and hydronium with an aqueous electrolyte; b) applying a
DC voltage between 1.2 and 10 volts to the anode and cathode; c)
removing the hydrogen gas and hydroxide ions from the cathode
region; and d) removing the oxygen gas and hydronium ions from the
anode region.
60. The method of claim 60, further comprising the step of
supplying the cathode and anode regions with fresh electrolyte
utilizing bi-directional flow.
61. The method of claim 60 further comprising the step of creating
convection currents within the anode and the cathode regions.
62. The method of claim 60, further comprising the step of
separating the anode and the cathode region with a porous glass
frit.
63. A method of generating renewable hydrogen and producing a
carbon dioxide sequestering compound comprising the steps of: a)
supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, the anode and
the cathode regions electrically connected by the electrolyte; b)
producing oxygen gas and protons at the anode region, wherein the
protons are present in the form of an acid; c) removing some or all
of the acid from the anode region; d) concentrating the acid,
wherein the acid has a pH ranging from about pH=0 to about pH=5;
and e) contacting the acid with a material that when exposed to a
strong acid is converted to a carbon dioxide sequestering
solution.
64. The method according to claim 63, wherein the material is any
one of a mineral clay sepiolite, serpentine, talc, asbestos, or a
mining byproduct.
65. The method according to claim 63, wherein the acid is sulfuric
acid.
66. The method according to claim 63, further comprising the step
of adding base to the carbon dioxide sequestering solution.
67. The method according to claim 63, further comprising the step
of contacting the carbon dioxide sequestering solution with a
source of gaseous carbon dioxide.
68. The method according to claim 67, further comprising the step
of precipitating and processing magnesium salts from the carbon
dioxide sequestering solution.
69. A method of generating renewable hydrogen and producing
pressurized carbon dioxide gas from atmospheric or gas stream
carbon dioxide comprising: a) supplying a direct current from an
electrical source at a predetermined voltage to a water
electrolysis unit having at least one electrolysis cell including
an aqueous electrolyte substantially free of chloride ions and an
anode region adapted to generate oxygen gas and protons separated
from a cathode region adapted to generate hydrogen gas and
hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte; b) producing oxygen gas
and protons at the anode region, wherein the protons are present in
the form of an acid; c) producing hydrogen gas and hydroxide ions
at the cathode, wherein the hydroxide ions are present in the form
of a base; d) removing some or all of the acid from the anode
region; e) removing some or all of the base from the cathode
region; f) contacting the base comprising hydroxide ions with
gaseous carbon dioxide to produce a solution comprising
bicarbonate, carbonate, or a mixture thereof; g) contacting the
solution with acid produced at the anode region of the cell to
produce carbon dioxide gas under pressure; and h) collecting the
pressurized carbon dioxide gas.
70. The method according to claim 69, further comprising producing
super critical carbon dioxide from the collected pressurized carbon
dioxide gas.
71. A method of generating renewable hydrogen and producing urea
fertilizer, the method comprising the steps of: a) supplying an
electric current from an electrical source at a predetermined
voltage to a water electrolysis unit having at least one
electrolysis cell including an aqueous electrolyte substantially
free of chloride ions and an anode region adapted to generate
oxygen gas and protons separated from a cathode region adapted to
generate hydrogen gas and hydroxide ions, wherein the anode and the
cathode regions are electrically connected by the electrolyte; b)
producing oxygen gas and protons at the anode region, wherein the
protons are present in the form of an acid; c) producing hydrogen
gas and hydroxide ions at the cathode region, wherein the hydroxide
ions are present in the form of a base; d) removing some or all of
the acid from the anode region; e) removing some or all of the base
from the cathode region; f) contacting the base with a gaseous
source of carbon dioxide to produce a feedstock comprising
bicarbonate or carbonate or a mixture thereof; g) contacting the
acid produced at the anode region with the feedstock to produce
carbon dioxide gas; and h) contacting the carbon dioxide gas with a
source of anhydrous ammonia under pressure to produce urea.
72. A method of generating renewable hydrogen and producing urea
fertilizer, the method comprising the steps of: a) supplying an
electric current from an electrical source at a predetermined
voltage to a water electrolysis unit having at least one
electrolysis cell including an aqueous electrolyte substantially
free of chloride ions and an anode region adapted to generate
oxygen gas and protons separated from a cathode region adapted to
generate hydrogen gas and hydroxide ions, wherein the anode and the
cathode regions are electrically connected by the electrolyte; b)
producing oxygen gas and protons at the anode region, wherein the
protons are present in the form of an acid; c) producing hydrogen
gas and hydroxide ions at the cathode region, wherein the hydroxide
ions are present in the form of a base; d) removing some or all of
the acid from the anode region; e) removing some or all of the base
from the cathode region; f) contacting the base with a gaseous
source of carbon dioxide to produce a feedstock comprising
bicarbonate or carbonate or a mixture thereof; g) contacting the
acid produced at the anode region with the feedstock to produce
carbon dioxide gas; and h) reacting the carbon dioxide gas and
hydrogen produced at the cathode with nitrogen gas in an
electrochemical process to produce urea.
73. A method of generating renewable hydrogen and producing carbon
dioxide neutral or carbon dioxide negative agricultural lime
comprising the steps of: a) supplying a direct current from a
renewable or nuclear electrical source at a predetermined voltage
to a water electrolysis unit having at least one electrolysis cell
including an aqueous electrolyte substantially free of chloride
ions and an anode region adapted to generate oxygen gas and protons
separated from a cathode region adapted to generate hydrogen gas
and hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte; b) producing oxygen gas
and protons at the anode region, wherein the protons are present in
the form of an acid; c) producing hydrogen gas and hydroxide ions
at the cathode, wherein the hydroxide ions are present in the form
of a base; d) removing some or all of the acid from the anode
region; e) removing some or all of the base from the cathode
region; f) contacting the base having a pH of greater than about
pH=10 with gaseous carbon dioxide to produce a carbonate enriched
feedstock; g) contacting the feedstock with an aqueous composition
comprising calcium ions; and h) precipitating calcium carbonate
from the feedstock to produce agricultural lime.
74. A method of generating renewable hydrogen and producing carbon
dioxide neutral or carbon dioxide negative quick lime comprising:
a) supplying a direct current from a renewable or nuclear
electrical source at a predetermined voltage to a water
electrolysis unit having at least one electrolysis cell including
an aqueous electrolyte substantially free of chloride ions and an
anode region adapted to generate oxygen gas and protons separated
from a cathode region adapted to generate hydrogen gas and
hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte; b) producing oxygen gas
and protons at the anode region, wherein the protons are present in
the form of an acid; c) producing hydrogen gas and hydroxide ions
at the cathode region, wherein the hydroxide ions are present in
the form of a base; d) removing some or all of the acid from the
anode region; e) removing some or all of the base from the cathode
region; f) contacting the base having a pH of greater than about
pH=10 with gaseous carbon dioxide to produce a carbonate enriched
feedstock; g) contacting the carbonate enriched feedstock with an
aqueous solution comprising calcium ions to generate calcium
carbonate; h) applying heat to the calcium carbonate to produce
quick lime.
75. The method according to claim 74, wherein carbon dioxide
released from applying heat to the calcium carbonate is contacted
with base to regenerate the carbonate feedstock.
76. The method according to claim 74, wherein carbon dioxide
released from applying heat to the calcium carbonate is sequestered
and pressurized for use as supercritical carbon dioxide.
77. A method of generating renewable hydrogen and producing carbon
monoxide from atmospheric or gas stream carbon dioxide comprising:
a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte; b) producing oxygen gas and protons at the anode
region, wherein the protons are present in the form of an acid; c)
producing hydrogen gas and hydroxide ions at the cathode region,
wherein the hydroxide ions are present in the form of a base; d)
removing some or all of the acid from the anode region; e) removing
some or all of the base from the cathode region; f) contacting the
base with gaseous carbon dioxide to produce a solution comprising
bicarbonate or carbonate or a mixture thereof; g) contacting the
solution with acid produced in the anode region of the cell to
produce carbon dioxide gas under pressure; h) collecting the
pressurized carbon dioxide gas; and i) reducing a portion of the
carbon dioxide gas with a portion of the hydrogen gas generated at
the cathode to produce carbon monoxide.
78. A method of generating renewable hydrogen and producing formic
acid from atmospheric or gas stream carbon dioxide comprising: a)
supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte; b) producing oxygen gas and protons at the anode
region, wherein the protons are present in the form of an acid; c)
producing hydrogen gas and hydroxide ions at the cathode region,
wherein the hydroxide ions are present in the form of a base; d)
removing some or all of the acid from the anode region; e) removing
some or all of the base from the cathode region; f) contacting the
base with a gaseous carbon dioxide to produce a solution comprising
bicarbonate or carbonate or a mixture thereof; g) contacting the
solution with acid produced in the anode region of the cell to
produce carbon dioxide gas under pressure; h) collecting the
pressurized carbon dioxide gas; i) reducing a portion of the carbon
dioxide gas with a portion of hydrogen gas generated at the cathode
to produce carbon monoxide; and j) reacting a portion of the carbon
monoxide with methanol in the presence of the base produced at the
cathode having a pH of at least 10 to produce methyl formate; and
k) hydrolyzing the methyl formate to produce formic acid.
79. A method of generating renewable hydrogen and producing formic
acid from atmospheric or gas stream carbon dioxide comprising: a)
supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte; b) producing oxygen gas and protons at the anode
region, wherein the protons are present in the form of an acid; c)
producing hydrogen gas and hydroxide ions at the cathode region,
wherein the hydroxide ions are present in the form of a base; d)
removing some or all of the acid from the anode region; e) removing
some or all of the base from the cathode region; f) contacting the
base having a with gaseous carbon dioxide to produce a solution
comprising cesium bicarbonate; and g) electrolyzing cesium
bicarbonate to form formic acid.
80. A method of generating renewable hydrogen and producing formic
acid from atmospheric or gas stream carbon dioxide comprising: a)
supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte; b) producing oxygen gas and protons at the anode
region, wherein the protons are present in the form of an acid; c)
producing hydrogen gas and hydroxide ions at the cathode region,
wherein the hydroxide ions are present in the form of a base; d)
removing some or all of the acid from the anode region; e) removing
some or all of the base from the cathode region; f) contacting the
base with gaseous carbon dioxide to produce a solution comprising
bicarbonate or carbonate or a mixture thereof; and g) hydrogenating
the bicarbonate in the presence of a catalyst to produce formic
acid.
Description
BENEFIT CLAIM
[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
applications entitled RENEWABLE ENERGY SYSTEM FOR HYDROGEN
PRODUCTION AND CARBON DIOXIDE CAPTURE, filed on the same day and
assigned Ser. No. ______, and 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. ______, both of which are herein incorporated by reference
in their entirety.
TECHNICAL FIELD
[0003] The present invention relates to carbon dioxide capture and
sequestration and generation of renewable hydrogen. More
specifically, the present invention relates to the use of water
electrolysis to generate renewable hydrogen and compounds used to
capture and sequester carbon dioxide from the atmosphere or gas
streams.
BACKGROUND
[0004] Removing carbon dioxide from the atmosphere requires a very
large energy input to overcome the entropic energies associated
with isolating and concentrating a diffuse gas. Current strategies
for sequestering carbon dioxide from the atmosphere or for
producing renewable hydrogen are either inefficient, cost
prohibitive, or produce toxic by-products such as chlorine. To
lower global carbon dioxide levels and reduce new carbon dioxide
emissions, it is critical to develop economically feasible
processes to remove vast quantities of carbon dioxide from the
atmosphere or gas streams by capturing and sequestering it in a
stable form, or by converting it to valuable commodity products.
The production of carbon free renewable fuels is also a critical
goal in the fight against global warming.
SUMMARY
[0005] According to some embodiments, the present invention is an
electrochemical method of generating hydrogen and sequestering
carbon dioxide from a gaseous source. A direct current is supplied
from an electrical source at a predetermined voltage to a water
electrolysis unit including at least one electrolysis cell
including an aqueous electrolyte substantially free of chloride
ions. The electrolysis cell includes an anode region separated,
either passively or actively, from a cathode region. The anode and
cathode regions of the electrolysis cell are electrically connected
by the electrolyte. Hydrogen and base are generated at the cathode
region and are individually isolated as products or reagents for
down stream processes. Oxygen and acid are produced at the anode
region and are individually isolated as products or reagents for
down stream processes. The hydroxide ions present in the base are
further reacted with a gaseous source of carbon dioxide to
sequester carbon dioxide in solution as carbonate, bicarbonate, or
mixtures thereof.
[0006] According to other embodiments, the present invention is an
electrochemical method of producing hydrogen gas from water and
bicarbonate from carbon dioxide trapped from the air or a gas
stream. Direct current electricity is supplied to a water
electrolysis cell having an anode region adapted to generate oxygen
and protons and a cathode region adapted to generate hydrogen and
hydroxide ions. The anode and cathode regions are electrically
connected by the electrolyte. The hydroxide ions are removed from
the cathode region and contacted with gaseous carbon dioxide from
the atmosphere or gas stream to produce a solution of bicarbonate,
carbonate, or mixtures thereof. The solution is further processed
to isolate bicarbonate.
[0007] According to some embodiments the present invention is an
electrochemical method of producing hydrogen gas from water and
carbonate from the atmosphere or a gas stream. Direct current
electricity is supplied to a water electrolysis cell having an
anode region adapted to generate oxygen and protons and a cathode
region adapted to generate hydrogen and hydroxide ions. The anode
and cathode regions are electrically connected by the electrolyte.
The hydroxide ions are removed from the cathode region and
contacted with gaseous carbon dioxide from the atmosphere or gas
stream to produce a solution of bicarbonate, carbonate, or mixtures
thereof. The solution is further processed to isolate
carbonate.
[0008] According to some embodiments, the present invention is an
electrochemical method of producing hydrogen gas and a carbon
dioxide neutral or carbon dioxide negative hydroxide base.
Renewable or nuclear direct current electricity is supplied to an
electrolysis cell having an anode region adapted to generate oxygen
and protons and a cathode region adapted to generate hydrogen and
hydroxide ions. The anode and cathode regions are electrically
connected by the electrolyte. Some or all of the hydroxide ions are
removed from the cathode region in the form of a base. The base
solution is further processed to concentrate and purify the base,
which has been manufactured without any significant carbon dioxide
production.
[0009] According to still other embodiments, the present invention
is an electrochemical method of producing hydrogen gas and a carbon
dioxide neutral or carbon dioxide negative acid. Renewable or
nuclear direct current electricity is supplied to a water
electrolysis cell having an anode region adapted to generate oxygen
and protons and a cathode region adapted to generate hydrogen and
hydroxide ions. The anode and cathode regions are electrically
connected by the electrolyte. Some or all of the protons are
removed from the anode region in the form of an acid. The acid
solution is further processed to concentrate and purify the acid,
which has been manufactured without net carbon dioxide
emissions.
[0010] According to various other embodiments, the present
invention is a method of generating and maintaining separate
regions of acid and base in an electrolysis chamber. Water
electrolysis is used to generate protons and oxygen at the anode
region while also generating hydroxide ions and hydrogen at the
cathode region. Active and passive barriers are used to prevent
recombination of the acid and base thereby maximizing the pH
gradient between the two regions. The individual products are
collected and isolated.
[0011] According to further embodiments, the present invention is
an electrochemical method of preparing hydrogen and carbon dioxide
sequestering compounds from minerals. Water electrolysis is used to
generate protons and oxygen at the anode region while also
generating hydroxide ions and hydrogen at the cathode region. The
protons are present in the form of an acid and some or all of the
acid is removed from the anode region. The acid is processed and
then contacted with certain minerals that when activated form
carbon dioxide sequestering compounds. These compounds are further
reacted with a gaseous source of carbon dioxide to capture or
sequester carbon dioxide from the gaseous source.
[0012] According to yet other embodiments, the present invention is
a method of producing pressurized carbon dioxide. Water
electrolysis is used to generate protons and oxygen at the anode
region while also generating hydroxide ions and hydrogen at the
cathode region. All products are individually collected. The
hydroxide ions, processed as a base, are reacted with carbon
dioxide-containing gas from the atmosphere or gas stream, resulting
in a solution of carbonate or bicarbonate or a mixture thereof. The
protons, processed as acid, are reacted with the carbonate or
bicarbonate to release carbon dioxide in an enclosed environment to
produce pressurized carbon dioxide. According to yet further
embodiments, the pressurized carbon dioxide can be heated and
pressurized to produce super critical carbon dioxide.
[0013] According to still other embodiments, the present invention
is an electrochemical method of producing carbon dioxide neutral
urea. Water electrolysis is used to generate protons and oxygen at
the anode region while also generating hydroxide ions and hydrogen
at the cathode region. Each of these products are collected and
processed as reagents. Hydrogen and carbon dioxide are reacted with
a source of nitrogen to produce urea.
[0014] According to still other embodiments, the present invention
is an electrochemical method of producing hydrogen and carbon
dioxide negative agricultural lime. Water electrolysis is used to
generate protons and oxygen at the anode region while also
generating hydroxide ions and hydrogen at the cathode region. Each
of these products are collected and processed as reagents. The
hydroxide ions, processed as a base, are reacted with carbon
dioxide containing gas from the atmosphere or gas stream to produce
a solution of carbonate. The carbonate solution is further
processed with a source of calcium ions to produce CaCO3,
agricultural lime.
[0015] According to yet other embodiments, the present invention is
an electrochemical method of producing hydrogen and carbon dioxide
neutral quick lime. Water electrolysis is used to generate protons
and oxygen at the anode region while also generating hydroxide ions
and hydrogen at the cathode region. Each of these products is
collected and processed as reagents. The hydroxide ions, processed
as a base, are reacted with carbon dioxide containing gas from the
atmosphere or gas stream to produce a solution of carbonate. The
carbonate solution is further processed with a source of calcium
ions to produce calcium carbonate. The calcium carbonate is then
heated to produce quick lime.
[0016] According to still other embodiments, the present invention
is an electrochemical method of producing hydrogen and carbon
monoxide from atmospheric carbon dioxide. Water electrolysis is
used to generate protons and oxygen at the anode region while also
generating hydroxide ions and hydrogen at the cathode region. These
products are collected and processed as reagents. The hydroxide
ions, processed as a base, are reacted with carbon dioxide
containing gas from the atmosphere or gas stream to produce a
solution of carbonate and bicarbonate or a mixture thereof. The
solution is further reacted with protons, processed as acid, to
release carbon dioxide in a controlled reaction environment. The
carbon dioxide is further reacted with hydrogen produced by the
water electrolysis process to form carbon monoxide.
[0017] According to yet other embodiments the present invention is
an electrochemical method of producing formic acid from the air or
a gas stream. Water electrolysis is used to generate protons and
oxygen at the anode region while also generating hydroxide ions and
hydrogen at the cathode region. These products are collected and
processed as reagents. The hydroxide ions, processed as a base, are
reacted with carbon dioxide containing gas from the atmosphere or
gas stream to produce a solution of carbonate and bicarbonate or a
mixture thereof. The solution is further reacted with the protons,
processed as acid, to release carbon dioxide in an enclosed or
controlled reaction environment. The carbon dioxide is further
reacted with reagents produced by the electrolysis and methanol to
form formic acid.
[0018] 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
[0019] FIG. 1 is a schematic diagram of an integrated water
electrolysis system according to various embodiments of the present
invention.
[0020] FIGS. 2-5 are schematic diagrams of a water electrolysis
cell according to various embodiments of the present invention.
[0021] FIGS. 6A and 6B are schematic diagrams of water electrolysis
cells according to other embodiments of the present invention.
[0022] FIG. 7 is a schematic diagram of value-added products that
may be processed from the integrated electrolysis system of FIG.
1.
[0023] FIG. 8 is a schematic diagram of a water electrolysis unit
according to an embodiment of the present invention.
[0024] 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
[0025] FIG. 1 is a schematic diagram of an integrated electrolysis
system 10 according to various embodiments of the present
invention. As shown in FIG. 1, the integrated electrolysis system
10 includes an electrical energy source 12, an electrolysis unit 16
including a cathode 18 and an anode 20, an aqueous electrolyte
source 22, a hydrogen collection and storage reservoir 24, an
oxygen collection and storage reservoir 26, a base collection and
storage reservoir 28, and an acid collection and storage reservoir
30. Additionally, according to various embodiments, the integrated
electrolysis system includes a first carbon dioxide capture
apparatus 32 connected to the base collection and storage reservoir
28, a second carbon dioxide capture apparatus 34 connected to the
acid collection and storage reservoir 30, and a hydrogen/oxygen
fuel cell 38.
[0026] The integrated electrolysis system 10 is used to produce
hydrogen, oxygen, acid, and base through water electrolysis,
followed by subsequent processing of one or more of these products
to capture and sequester carbon dioxide. Base produced by the
integrated electrolysis system 10 is used to capture and sequester
carbon dioxide. Additionally, the integrated electrolysis system 10
produces renewable hydrogen as a carbon dioxide neutral fuel. The
renewable hydrogen produced by the system 10 can be used as a
large-scale application for reducing global carbon dioxide
pollution, a significant factor in global warming. When combined
with renewable or non-carbon dioxide producing energy sources, the
integrated water electrolysis system 10 creates carbon dioxide
negative energy strategies for reducing the amount of carbon
dioxide in the atmosphere and for producing clean, renewable
hydrogen fuel. In addition, unlike traditional methods of
manufacturing hydroxide base, such as the chloralkali electrolysis
method, no substantial carbon dioxide or chlorine gas is
produced.
[0027] Many carbon based products can be manufactured from carbon
dioxide trapped by the integrated system 10. Commercial products
manufactured from carbon dioxide trapped by the integrated
electrolysis system 10 are carbon dioxide negative, resulting in an
overall net decrease in atmospheric carbon dioxide as gaseous
carbon dioxide is converted to 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.
[0028] As shown in FIG. 1, the integrated water electrolysis system
includes at least one water electrolysis cell 16. Electrolysis
cells are well known to those of skill in the art. According to
various embodiments, an electrolysis cell includes a cathode 18
located within a cathode region 42, an anode 20 located within
anode region 44, and an aqueous electrolyte 22a. Water is reduced
at the cathode and oxidized at the anode. The electrolyte is
responsible for charge transfer and the movement of ions within the
electrolysis cell.
[0029] According to various embodiments of the present invention,
the water electrolysis unit 16 includes a separate cathode region
42 and a separate anode region 44. In some embodiments, ion
selective membranes may be used to maintain separate anode and
cathode regions 42 and 44. In other embodiments, a porous glass
frit, filter, or other non-selective barrier is used to maintain
separate cathode and anode regions 42 and 44.
[0030] The cathode region 42 and the anode region 44 are
electrically connected by an aqueous electrolyte solution 22a
supplied from the electrolyte source 22. The aqueous electrolyte
solution 22a may include electrolyte solution, such as sodium,
potassium, calcium, or magnesium sulfate, nitrate, or carbonate.
According to various embodiments, the aqueous electrolyte includes
an alkali salt. The alkali salt is substantially free of chloride
and 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, potassium carbonate, calcium carbonate, and
magnesium carbonate. According to other embodiments, the aqueous
electrolyte solution can include sea water and/or sea salt.
[0031] According to one exemplary embodiment of the present
invention, the aqueous electrolyte solution 22a 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. After filtering, the
resultant solution is pumped into the electrolysis unit 16 using a
pump or gravity feed. In one embodiment, the aqueous electrolyte
solution 22a contains substantially no chloride such that the
electrolysis unit 16 and/or integrated electrolysis system 10
produce essentially no chlorine gas. In one embodiment, the
electrolysis reaction within the water electrolysis unit 16 and/or
integrated electrolysis system 10 produces less than about 100
parts per million (ppm) of chlorine, particularly less than about
10 ppm of chlorine, and more particularly less than about 1 ppm of
chlorine.
[0032] The concentration of the aqueous electrolyte solution 22a
can vary depending on the demands of the electrolysis cell and the
overall system 10. The electrolyte concentration may vary with
changes in the temperature, pH, and/or the selected electrolyte
salt. According to one embodiment, the concentration of the aqueous
electrolyte solution 22a is approximately 1M. According to another
embodiment a saturated aqueous electrolyte solution 22a is
maintained within the electrolysis cell.
[0033] FIG. 2 shows a schematic diagram of a water electrolysis
cell with a single permeable membrane. The water electrolysis cell
includes parallel cathode and anode chambers that contain closely
spaced electrodes separated by a semi-permeable membrane. This
configuration maintains high electrical conductivity while
minimizing loss of acid and base to recombination within the water
electrolysis cell.
[0034] Fresh aqueous electrolyte solution flows in the same
direction in both the cathode and anode chambers, gradually
becoming more basic in the cathode chamber and more acidic in the
anode chamber. Alternatively, fresh aqueous electrolyte solution
may be introduced through one of the cathode chamber and anode
chamber. In this case, selective ion flow across an anion or cation
specific membrane would ensure production of a highly pure acid or
base, respectively. This water electrolysis cell can be operated in
parallel or counter-current flow modes. Counter-current flow
minimizes chemical gradients formed across the semi-permeable
membrane 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 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,
instead producing no higher than a 7-unit pH gradient between
either strong acid and neutral electrolyte, or strong base and
neutral electrolyte.
[0035] FIG. 3 shows a schematic diagram of a water electrolysis
cell with two semi-permeable membranes. The water electrolysis cell
is a parallel or counter-current flow three-chamber water
electrolysis cell. A narrow central feed reservoir (such as
electrolyte source) of fresh aqueous electrolyte solution is
introduced between a first semi-permeable membrane and a second
semi-permeable membrane that separate the cathode chamber and anode
chamber. As illustrated in counter current mode, concentrated
aqueous electrolyte solution enters the central feed reservoir at a
first end of the water electrolytic cell and concentrated base and
acid exit the cathode chamber and the anode chamber, respectively.
At a second end of the water electrolytic cell, dilute base and
acid enter the cathode chamber and the anode chamber, and water or
dilute aqueous electrolyte solution exits the central feed
reservoir. This counter-current design reduces salt contamination
of base and acid produced and minimizes the chemical gradients
formed across the permeable membranes. In some embodiments, the
design may also be used to desalinate salt water.
[0036] In practice, the cathode chamber in FIG. 3 is initially
filled with dilute base, and the anode chamber is filled with
dilute acid, maintaining electrical conductivity between the
electrodes. Cations flow from the central feed reservoir through
the first semi-permeable membrane closest to the cathode chamber,
combining with hydroxide ions formed at the cathode chamber to
generate concentrated hydroxide base. Anions flow from the
electrolyte solution source through the second semi-permeable
membrane to the anode chamber, combining with protons formed at the
anode chamber to produce concentrated acid. The semi-permeable
membranes 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 counter-current
flow between the central feed reservoir and the cathode chamber and
anode chamber on either side. The counter-current flow system
minimizes chemical gradients across the membranes, because high
concentrations of base and acid exit the cathode chamber and anode
chamber opposite highly concentrated fresh electrolyte entering the
central feed reservoir. In parallel flow mode certain design
advantages are also realized.
[0037] 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 aligned in a
closely spaced parallel configuration. Semi-permeable or ion
selective membranes are optionally included between the inner pair
of electrodes. The membranes 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.
[0038] According to some embodiments, the aqueous electrolyte
solution 22a may undergo additional processing prior to entering
the anode and cathode regions of the cell. FIG. 5 is a schematic
diagram of a water electrolysis cell 116 configured to process the
aqueous electrolyte solution 148 prior to its introduction into the
electrolysis cell 116. As shown in FIG. 5, the electrolysis cell
116 includes an electrolysis chamber 152 including a cathode 118
located within a cathode region 142 and an anode 120 located within
an anode region 144. The electrolysis chambers 152 is fluidly
coupled to an electrolyte source 122. According to various
embodiments, the electrolysis cell 116 also includes a cathode
electrolyte preparation electrode 156 and an anode electrolyte
preparation electrode 158.
[0039] As shown in FIG. 5, the electrolyte preparation electrodes
156 and 158 are located within the aqueous electrolyte flow path
from the electrolyte source 122 to the electrolysis chamber 152.
According to various embodiments, a voltage is applied to the
electrolyte preparation electrodes 156 and 158 that is less than
the minimal theoretical voltage required for water electrolysis.
According to some embodiments, the applied voltage is less than
about 1.2V. When a potential is applied to the preparation
electrodes 156 and 158 the preparation electrodes 156 and 158 act
like charged poles, attracting the ions of the opposite charge.
According to some embodiments, the electrolyte preparation cathodes
156 attracts cations and repel anions. Similarly, the electrolyte
preparation anodes 158 attracts anions and repel cations. This
process presorts the ions present in the electrolyte solution 148
prior to its introduction into the electrolysis chamber 152.
[0040] Referring again to FIG. 1, a direct current is supplied to
the water electrolysis unit 16 from the electrical energy source 12
to electrolyze the aqueous electrolyte solution to produce
hydrogen, oxygen, acid, and base. According to some embodiments, as
shown in FIG. 1, a renewable energy source can be coupled to the
electrical energy source to supply energy to the integrated system.
Exemplary renewable energy sources include, but are not limited to,
the following: wind, solar, hydroelectric, oceanic, tidal,
geothermal, and fuel cells using renewable hydrogen. These
renewable energy sources do not generate carbon dioxide. 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
system 10. According to yet further embodiments, a renewable energy
source that generates substantially no carbon dioxide may be
coupled with a conventional energy source to supplement and/or
off-set the amount of energy supplied to the electrical energy
source from the conventional energy source.
[0041] According to one embodiment, the direct current is supplied
to the electrolysis unit 16 at a predetermined voltage sufficient
to initiate water electrolysis within the electrolysis cell 16.
According to one embodiment, the predetermined voltage supplied to
the electrolysis cell is at least 1.2 volts. According to other
embodiments, the predetermined voltage supplied to the cell ranges
from about 1.2 volts to about 10.0 volts. The result of the
electrolysis reaction within the cell 16 is the formation of
protons and oxygen gas at the anode region, and hydroxide ions and
hydrogen gas at the cathode region. The protons combine with anions
present in the electrolyte solution to form acid. Similarly, the
hydroxide ions combine with cations present in the electrolyte
solution to form base.
[0042] The continuous production of acid and base during water
electrolysis results in a pH difference between the cathode region
42 and the anode region 44 of the electrolysis cell 16. According
to one embodiment, the difference in pH between the cathode region
42 and the anode region 44 is at least 4 pH units. According to
other embodiments, the difference in pH between the cathode region
42 and the anode region 44 is at least 8 pH units. The difference
in pH between the cathode regions and anode regions 42 and 44 can
be maintained by preventing the catholyte formed in the cathode
region 42 and the anolyte formed in the anode region 44 from
combining.
[0043] FIG. 6A is a schematic diagram of an electrolysis cell 216A
according to one embodiment of the present invention. FIG. 6B is a
schematic diagram of another electrolysis cell 216B according to
another embodiment of the present invention. Each of the cells 216A
and 216B as shown in FIGS. 6A and 6B are configured to maintain a
separate cathode region 242A, 242B and a separate anode region
244A, 244B within the electrolysis cell 216A, 216B using fluid
dynamics. Additionally, according to further embodiments, the cells
216A, 216B are configured to maintain a pH difference between the
cathode region 242A, 242B and the cathode region 244A, 244B of at
least 4 pH units and more particularly, of at least 6 pH units.
[0044] In one embodiment, as shown in FIG. 6A, the electrochemical
cell 216A has a "T" configuration. The "T" shaped cell 216A
includes an elongated vertical portion 260A branching
bi-directionally into a horizontal portion 262. A continuous supply
of fresh electrolyte flows up through the elongated portion of the
"T" shaped shell, indicated by the arrows, from the electrolyte
source 222A. Once the electrolyte has reached the horizontal
portion 260A of the "T" shaped cell 216A, the electrolyte then
flows in opposite directions towards closely spaced cathode and
anode regions 242A and 242B. According to various embodiments, the
bi-directional flow rate of the electrolyte through the cell 216A
is greater than the rate of ion migration due to the applied
electric field and diffusion. Thus, the contents of the cathode and
the anode regions 242A and 244A cannot recombine, and the pH
difference between the anode and the cathode regions 242A and 244A
can be maintained.
[0045] In another embodiment, as shown in FIG. 6B, convective
currents within the cathode and anode regions 242B and 244B assist
in maintaining a pH difference between the cathode region 242B and
the anode region 244B of the electrolysis cell 216B. As shown in
FIG. 6B, hydrogen gas is formed at the cathode 218B and rises in
the form of bubbles in the electrolyte solution. The rising bubbles
create convective currents in the cathode region 242B. Similarly,
oxygen produced at the anode 220B rises in the form of bubbles,
creating convective currents in the anode region 244B.
Additionally, the electrolysis cell 216B includes a constricted
pathway 264 fluidly coupling the cathode and anode regions 242B and
244B. The convective currents in the cathode and the anode regions
242B and 244B in combination with the constricted fluid pathway 264
between the cathode and anode regions 242B and 244B assist in
maintaining a pH difference between the cathode and anode regions
242B and 244B of at least 4 pH units and, more particularly, of at
least 6 pH units. In further embodiments, an electrolysis cell
combining the features of the electrolysis cell shown in FIG. 6A
and the features of the electrolysis cell shown in FIG. 6B can be
utilized.
[0046] Once concentrations of base and acid reach a minimum
increase of one hundred fold relative to their initial electrolyte
concentration, the base and acid are removed from the cathode
region and anode region of the electrolysis cell. According to some
embodiments, the base and the acid are capable of achieving an
increase of over about 100,000 times their initial electrolyte
concentration. According to one embodiment, the base and the acid
formed at the cathode and anode regions are pumped to their
respective collection and storage reservoirs in the integrated
system 10. According to another embodiment, positive pressure may
be applied to remove the base and acid from the cathode and anode
regions. According to yet another embodiment, the base and acid may
be removed from their respective cell regions via gravity feed.
Fresh electrolyte is then delivered from the aqueous electrolyte
source to equilibrate the volume of liquid in the cathode region
and the anode region. According to one embodiment, the removal of
acid and base and introduction of fresh electrolyte may be
accomplished by a batch-wise process. According to another
embodiment, the removal of base and acid and the introduction of
fresh electrolyte may be accomplished by a continuous process,
creating a continuous flow electrolysis system.
[0047] According to some embodiments, the electrolyte flow rate can
be adjusted to overcome undesirable ion migration, eliminating
acid-base recombination and/or mixing of the electrolyte from the
cathode and anode regions. According to other embodiments, the
electrolyte flow rate can be adjusted to increase, decrease and/or
maintain the concentrations of the base and acid produced in their
respective regions of the electrolysis cell 16.
[0048] 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 18 or anode 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 regions are designed to direct this flow up
and out of the cathode 18 and anode 20 and into adjacent integrated
areas. The hydrogen, base, oxygen and acid are physically diverted
for collection in the hydrogen sequestration tank 24, the base
sequestration tank 28, the oxygen sequestration tank 26 and the
acid collection and storage reservoir 30, respectively.
[0049] The hydrogen and oxygen are collected in the hydrogen
collection and storage reservoir 24 and the oxygen collection and
storage reservoir 26, respectively. In some embodiments the
hydrogen and oxygen are used to supplement the electrical energy
source 12 when used as a fuel in a furnace, fuel cell 38, or engine
to provide direct current electricity for electrolysis. The
hydrogen and/or oxygen may also be used to react with other
products of the integrated electrolysis system 10 to create
value-added products. Finally, the hydrogen and/or oxygen may be
removed from the integrated electrolysis system 10 as a product to
be sold or used locally as a fuel or chemical feedstock.
[0050] The acid produced by the electrolysis unit 16 is routed to
the acid collection and storage reservoir 30. According to one
embodiment the pH of the acid ranges from about pH=0 to about pH=5.
The acid can be processed and removed from the system for sale as a
commodity. The acid may also be used to prepare certain
mineral-based carbon dioxide sequestering compounds, which are then
used to capture carbon dioxide from the atmosphere or gas streams.
The acid may also be used as a chemical reagent by the integrated
system to create other value added products. In one embodiment, the
carbonate and bicarbonate salts are isolated after reacting the
base with carbon dioxide. The acid can then release the carbon
dioxide from the carbonate or bicarbonate salts in a controlled
manner to further process the released carbon dioxide to produce
value-added products. These products may include, but are not
limited to: carbon monoxide, formic acid, urea, super-critical
carbon dioxide, pressurized carbon dioxide, liquid carbon dioxide
or solid carbon dioxide.
[0051] The base generated by the electrolysis unit 16 is sent to
the base collection and storage reservoir 28 and is sold or used as
a carbon dioxide neutral commodity or chemically reacted with
carbon dioxide gas to form carbonate or bicarbonate. In one
embodiment a pH of the base produced in the cathode region of the
cell can range from about pH=8 to about pH=14. When used to capture
carbon dioxide, the carbon dioxide is captured as carbonate,
bicarbonate, or mixtures thereof. 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.
[0052] The reaction of the base with the carbon dioxide can be
passive, relying only on natural gas-water mixing. An example of a
passive reaction includes an open-air treatment pond filled with
aqueous base, or a lined bed of hydroxide crystals. The reaction of
the base with carbon dioxide is spontaneous and can be enhanced by
increased concentrations of base or 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 into air or a
gas stream containing carbon dioxide. In another example, carbon
dioxide is actively removed by bubbling or forcing the gas stream
through a column or reservoir of base generated by the electrolysis
cell 16. Combinations of active and passive carbon dioxide trapping
systems are also envisioned.
[0053] In some embodiments of the present invention, sodium
bicarbonate and sodium carbonate are be formed by the integrated
water electrolysis system 10. Sodium bicarbonate and sodium
carbonate may be formed within the integrated electrolysis system
10. Alternately, base may be removed from the integrated
electrolysis system 10 and transported to another site to capture
carbon dioxide from the atmosphere or a gas stream using the
passive or active techniques previously described. By using the
base and/or acid to capture carbon dioxide from the atmosphere or a
gas stream, the overall integrated electrolysis system 10
sequesters substantially more carbon dioxide than it creates,
resulting in a net negative carbon dioxide footprint.
[0054] FIG. 7 illustrates value-added products that may be
processed from the carbon dioxide captured using the base and/or
acid produced by the integrated electrolysis system 10. The
integrated 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 or electrochemical reduction or reaction of
carbon dioxide 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.
These value added chemical building blocks can be sold as commodity
chemicals or used to produce a second class of value-added
products, including polymers, fabrics, urea and various building
materials. These value-added end products are then removed from the
integrated 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, reducing the cost of renewable hydrogen
production and creating a carbon dioxide negative energy strategy
with potentially dramatic impacts on global warming.
[0055] The center circle of FIG. 7 depicts exemplary products that
can be produced from the reaction of hydroxide base with carbon
dioxide, or (in the case of carbon monoxide) by chemical reduction
of captured carbon dioxide. 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 a variety of carbon-based monomers that serve as building
blocks for larger molecules. In many cases, the hydrogen, oxygen,
acid and base generated by the electrolysis unit 16 can be used for
this secondary processing. The carbon based building blocks can
also be further processed within the integrated electrolysis system
10 to make many valuable carbon based products. Some examples of
these are illustrated in the outer ring of FIG. 7.
[0056] According to one embodiment of the present invention, an
aqueous electrolyte solution is electrolyzed in a water
electrolysis cell to produce hydroxide ions in the cathode region.
The hydroxide ions are present in the form of a base such as sodium
or potassium hydroxide. Next the hydroxide ions in the base are
contacted with a source of gaseous carbon dioxide by any one of the
methods as described above to sequester the carbon dioxide in
solution as bicarbonate, carbonate, or mixtures thereof.
[0057] Bicarbonate and/or carbonate can be isolated from the
solution to produce a bicarbonate salt, a carbonate salt, or a
mixture there of. This can be accomplished by a variety of
techniques. For example, the pH of the solution can be maintained
between 8 or 9 to favor bicarbonate formation or maintained higher
than pH 11 to favor carbonate formation. Double displacement
reactions may be used to isolate different forms of carbonate or
bicarbonate. More specifically, sodium carbonate is reacted with
calcium chloride to form calcium carbonate, which easily
precipitates from solution. Similarly, magnesium salt can also be
used to convert sodium salts of bicarbonate or carbonate to less
soluble magnesium salts. The calcium carbonate and magnesium
carbonate can be purified and used or sold. Other processing
methods for the isolation of bicarbonate and carbonate include
concentration, precipitation, heating, cooling, solar evaporating,
vacuum evaporating, wind evaporating and crystallizing.
[0058] According to various embodiments, solid bicarbonate and/or
carbonate can be used in the production of a wide range of building
materials. For example bicarbonate and/or carbonate can be used as
fillers in the manufacture of plastics, elastomers, adhesives, and
other polymer based materials. According to various other
embodiments, the solid bicarbonate and/or carbonate can be used in
the production of mortar, cement, plaster, tile, grout, wall board,
synthetic stone, and the like. Finally, solid sodium bicarbonate
can purified and sold as baking soda.
[0059] According to various embodiments of the present invention,
base produced at the cathode region of the electrolysis cell can be
utilized to produce carbon dioxide neutral or carbon dioxide
negative agricultural lime and quick lime. For example, a sodium
sulfate solution is electrolyzed in a water electrolysis cell to
form sodium hydroxide in the cathode region. The base is
concentrated such that it reaches a pH of at least pH=10 and then
is contacted with a gaseous source of carbon dioxide to favor
production of a sodium carbonate enriched feedstock. The
carbonate-enriched feedstock is then mixed with a calcium chloride
solution. Solid calcium carbonate precipitates from the feedstock
to produce agricultural lime. According to further embodiments,
heat may be applied to the solid calcium carbonate, produced
according to the method described above to produce carbon dioxide
neutral quick lime, or, if the carbon dioxide released is captured
again, carbon dioxide negative quick lime.
[0060] According to another embodiment of the present invention,
acid generated in the anode region of the electrolysis cell can be
utilized to produce a carbon dioxide sequestering material. Water
in an aqueous electrolyte solution is electrolyzed in an
electrolysis cell to produce strong acid at the anode region of the
cell. At least some or all of the acid is removed from the anode
region and collected and stored in an acid collection and storage
reservoir. According to one embodiment, the acid is concentrated
either within the anode region of the cell or in the acid
collection and storage reservoir such that the resulting pH of the
acid ranges from about pH=0 to about pH=5. According to a further
embodiment, the acid is concentrated such that it has a pH of about
pH=1. The acid is then reacted with a material that when exposed to
a strong acid is converted to a carbon dioxide sequestering
material. Exemplary materials that can be converted to a carbon
dioxide sequestering material by reaction with a strong acid
include, but are not limited to, the following: certain mineral
clays, sepiolite, serpentine, talc, asbestos, and various mining
byproducts such as asbestos mining waste. According to one
exemplary embodiment, serpentine can be dissolved in sulfuric acid
procuring a solution of magnesium sulfate while precipitating
silicon dioxide as sand. Addition of sodium hydroxide creates a
mixture of magnesium sulfate and magnesium hydroxide. The process
also converts toxic asbestos and asbestos waste into non-toxic
carbon dioxide binding materials. Subsequent exposure of the
magnesium solution to carbon dioxide from the atmosphere or a gas
steam results in the formation of either magnesium carbonate or
magnesite, both of which form precipitates. These precipitates are
well-suited for production of construction blocks. According to
further embodiments of the present invention, the carbon dioxide
sequestering material may be further reacted with strong acid to
release carbon dioxide gas under controlled conditions. The carbon
dioxide released from the carbon dioxide sequestering materials may
be captured and stored for further processing.
[0061] According to various other embodiments, base produced in the
cathode region and acid produced in the anode region of the
electrolysis cell can be used to produce concentrated or
pressurized carbon dioxide gas in a controlled reaction. For
example, water in an aqueous electrolyte solution is electrolyzed
to produce base at the cathode region and acid at the anode region.
Some or all of the base is removed from the cathode region and
collected and stored in the base collection and storage reservoir.
Some or all of the acid is removed from the anode region and is
collected and stored in the acid collection and storage reservoir.
The hydroxide ions present in the base are reacted with a gaseous
source of carbon dioxide to produce a solution including
bicarbonate, carbonate, or mixtures thereof. The acid is reacted
with the carbonate containing solution in an enclosed container to
produce highly concentrated and pressurized carbon dioxide.
Alternately the carbon dioxide can be released into a pipe or flow
system for transport to another site. In other embodiments, the
carbon dioxide may be further concentrated and/or purified.
[0062] According to other further embodiments, the carbon dioxide
produced according to the method above can be converted to urea.
Urea is a commonly used in the agricultural industry as a
fertilizer as it is rich with nitrogen. According to various
embodiments, the carbon dioxide is contacted with a source of
anhydrous ammonia under pressure to produce urea. According to
other embodiments, hydrogen produced at the cathode and carbon
dioxide produced according to the various methods described above
are reacted with nitrogen gas in an electrochemical process to
produce urea.
[0063] In other embodiments, the carbon dioxide gas can be
converted to useful products such as super critical carbon dioxide.
Pressurized carbon dioxide gas can be adjusted to a critical
temperature and a critical pressure to produce super critical
carbon dioxide. Super critical carbon dioxide is widely used in the
food processing and fragrance industries to extract caffeine from
coffee or tea, essential oils from seeds or plant materials, or to
manufacture dry ice. Recent advances have also shown super critical
carbon dioxide to be a valuable reagent or solvent in the synthetic
organic chemistry.
[0064] In other embodiments of the present invention, the carbon
dioxide produced according to the methods described above can be
converted to carbon monoxide, an essential building block in much
of synthetic organic chemistry. Several well known chemical
pathways are used industrially to convert carbon dioxide to carbon
monoxide. In one such embodiment, the Reverse Water Gas Shift
reaction utilizes hydrogen produced at the cathode to reduce carbon
dioxide into carbon monoxide and water.
[0065] Carbon monoxide has many applications in bulk chemicals
manufacturing. For example, aldehydes are produced by the
hydroformylation reaction of alkenes, carbon monoxide, and hydrogen
gas. Hydroformylation can be coupled to the Shell Higher Olefin
Process to give precursors to detergents. Additionally, methanol
can be produced by the hydrogenation of carbon monoxide. Finally in
the Monsanto process, methanol and carbon monoxide react in the
presence of a homogeneous rhodium catalyst and HI to give acetic
acid. Any chemical pathway that converts carbon dioxide to carbon
monoxide may be applied to carbon dioxide sequestered and released
from products of the aforementioned water electrolysis/carbon
dioxide capture technology described in this patent application.
When manufactured from atmospheric carbon dioxide such products are
carbon dioxide negative.
[0066] According to yet other embodiments of the present invention,
formate and formic acid may be produced from the products of the
water electrolysis reaction, described herein. For example, base
produced at the cathode can be reacted with a gaseous source of
carbon dioxide to produce a solution containing bicarbonate,
carbonate, or mixtures thereof. The carbonate containing solution
can be reacted with acid from the anode to release carbon dioxide
under controlled conditions. Hydrogen gas produced by the water
electrolysis reaction and methanol are added stepwise to yield
formic acid. In another embodiment, a 1M cesium bicarbonate,
processed from carbon dioxide sequestered in a basic solution can
be electrolyzed using palladium catalysts to produce formic acid in
high yield and Faradaic efficiency. In another method, the
carbonate or bicarbonate is reacted with acid formed at the anode
to release carbon dioxide in a controlled process. Hydrogen
produced by water electrolysis and methanol are then added step
wise to yield formic acid. Any chemical pathway that produces
formate or formic acid using products from the aforementioned water
electrolysis/carbon dioxide capture technology is contemplated by
these embodiments.
[0067] According to various other embodiments of the present
invention, the electrolysis products produced according to the
methods described above can be used to produce methanol. Many metal
oxide, zinc and zirconium catalysts are known to reduce carbon
dioxide to methanol. In one such embodiment, carbon dioxide trapped
from the atmosphere or a gas stream using base generated by water
electrolysis is released in a controlled environment using acid
also produced from the electrolysis process. The carbon dioxide and
hydrogen produced by water is released in a controlled environment
using acid also produced from the electrolysis process. The carbon
dioxide and hydrogen produced by water electrolysis are combined
and reacted over a nickel catalyst to produce methanol. In another
embodiment, the Fischer-Tropsch reaction is conducted over copper
or palladium to preferentially yield methanol. Any chemical pathway
that produces methanol using products from the present water
electrolysis and carbon dioxide capture technology is a potential
pathway.
EXAMPLES
[0068] 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
[0069] A water electrolysis unit, shown in FIG. 8, 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.
[0070] 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.
[0071] 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.
[0072] 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 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
[0073] 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. This system created a water
electrolysis device that produced concentrated base inside the tube
and concentrated acid outside the tube.
[0074] 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.
[0075] 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.
Alternatively, a renewable energy source such as wind, solar,
hydroelectric, geothermal or biomass energy could be used to power
the device.
[0076] 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 electrodes such as nickel, platinum, carbon or
stainless steel are best suited to the technology applications
envisioned.
[0077] 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.
Embodiments
[0078] Embodiment 1, is a method of generating renewable hydrogen
and sequestering gaseous carbon dioxide comprising:
[0079] a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one water electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte;
[0080] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0081] c) producing hydrogen gas and hydroxide ions at the cathode,
wherein the hydroxide ions are present in the form of a base;
[0082] d) collecting the hydrogen gas product;
[0083] e) collecting the oxygen gas product;
[0084] f) removing some or all of the acid from the anode
region;
[0085] g) removing some or all of the base from the cathode region;
and
[0086] h) contacting the hydroxide ions in the base with a source
of gaseous carbon dioxide to sequester carbon dioxide in solution
as bicarbonate or carbonate or a mixture thereof.
[0087] A base produced according to the method of embodiment 1.
[0088] A building material comprising bicarbonate or carbonate
produced according to the method of embodiment 1, wherein the
building material is any one of a dry wall product, filled
polyvinyl chloride, tile, grout, synthetic stone, filled resin, or
an adhesive.
[0089] The method according to embodiment 1, further comprising
contacting the acid produced at the anode region with a mineral
compound to form a carbon dioxide sequestering material.
[0090] The method according to embodiment 1, further comprising
contacting the acid produced at the anode region with a mineral
compound to form a carbon dioxide sequestering material, wherein
the mineral compound is any one of talc, clay mineral sepiolite,
clay minerals, serpentine, asbestos, or mining byproducts.
[0091] The method according to embodiment 1, further comprising
contacting the acid, hydrogen or other products produced by the
processes described above with the gaseous carbon dioxide in an
electrochemical cell to produce reduced carbon compounds having a
general formula of CmHxO.sub.2n, wherein m an integer between 1 and
6, x is an integer between 0 and 24, and n is an integer between 0
and 6.
[0092] The method according to embodiment 1, further comprising
contacting the acid produced at the anode region with the gaseous
carbon dioxide in an electrochemical cell to produce reduced carbon
compound, wherein the reduced carbon compound is any one of formic
acid, oxalic acid, formaldehyde, or methanol.
[0093] The method according to embodiment 1, further comprising
chemically reducing carbon dioxide by reacting hydrogen gas
produced by the system with carbon dioxide trapped by the system to
produce carbon monoxide, a precursor for other synthetic
processes.
[0094] The method according to embodiment 1, further comprising
reacting the carbon dioxide gas and hydrogen produced at the
cathode with nitrogen gas in an electrochemical process to produce
urea.
[0095] The method according to embodiment 1, further comprising the
steps of contacting the acid produced at the anode region with the
carbonate/bicarbonate solution to produce carbon dioxide gas and
contacting the carbon dioxide gas with a source of anhydrous
ammonia under pressure to produce urea.
[0096] Embodiment 2 is a process of generating renewable hydrogen
and producing bicarbonate comprising:
[0097] a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte;
[0098] b) producing hydrogen gas and hydroxide ions at the cathode
region;
[0099] c) removing some or all of the base comprising hydroxide
ions from the cathode region of the electrolysis cell; and
[0100] d) contacting the hydroxide ions with gaseous carbon dioxide
to produce a solution comprising bicarbonate, carbonate or a
mixture thereof; and
[0101] e) isolating bicarbonate from the solution.
[0102] Embodiment 3 is a process of generating renewable hydrogen
and producing carbonate comprising:
[0103] a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte;
[0104] b) producing hydrogen gas and a base comprising hydroxide
ions at the cathode region;
[0105] c) removing some or all of the base comprising hydroxide
ions from the cathode region;
[0106] d) contacting the hydroxide ions with gaseous carbon dioxide
to produce a solution comprising bicarbonate, carbonate, or a
mixture thereof; and
[0107] e) isolating carbonate from the solution.
[0108] Embodiment 4 is a method of generating renewable hydrogen
and producing carbon dioxide neutral or carbon dioxide negative
acid comprising:
[0109] a) supplying a direct current from a renewable electrical
source at a predetermined voltage to a water electrolysis unit
having at least one electrolysis cell including an aqueous
electrolyte substantially free of chloride ions and an anode region
adapted to generate oxygen gas and protons separated from a cathode
region adapted to generate hydrogen gas and hydroxide ions, wherein
the anode and the cathode regions are electrically connected by the
electrolyte;
[0110] b) producing oxygen gas and protons at the cathode region,
wherein the protons are present in the form of an acid;
[0111] c) removing some or all of the acid from anode region;
[0112] d) collecting the acid in a reservoir; and
[0113] c) concentrating the acid.
[0114] Embodiment 5 is a method of generating renewable hydrogen
and producing carbon dioxide negative or carbon dioxide neutral
base comprising:
[0115] a) supplying a direct current from a renewable electrical
source at a predetermined voltage to a water electrolysis unit
having at least one electrolysis cell including an aqueous
electrolyte substantially free of chloride ions and an anode region
adapted to generate oxygen gas and protons separated from a cathode
region adapted to generate hydrogen gas and hydroxide ions, wherein
the anode and the cathode regions are electrically connected by the
electrolyte;
[0116] b) producing hydrogen gas and hydroxide ions at the cathode
region, wherein the hydroxide ions are present in the form of a
base;
[0117] c) removing some or all of the base from the cathode
region;
[0118] d) collecting the base in a reservoir; and
[0119] e) concentrating the base.
[0120] Embodiment 6 is a method of generating and maintaining
separate regions of concentrated hydronium ions and concentrated
hydroxide ions comprising:
[0121] a) contacting a cathode region including at least one
cathode adapted to generate hydrogen gas and hydroxide ions and an
anode region including at least one anode adapted to generate
oxygen gas and hydronium with an aqueous electrolyte;
[0122] b) applying a DC voltage between 1.2 and 10 volts to the
anode and cathode;
[0123] c) removing the hydrogen gas and hydroxide ions from the
cathode region; and
[0124] d) removing the oxygen gas and hydronium ions from the anode
region.
[0125] The method of embodiment 6 further comprising the step of
supplying the cathode and anode regions with fresh electrolyte
utilizing bi-directional flow.
[0126] The method of embodiment 6 further comprising the step of
creating convection currents within the anode and the cathode
regions.
[0127] Embodiment 7 is a method of generating renewable hydrogen
and producing a carbon dioxide sequestering compound comprising the
steps of:
[0128] a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, the anode and
the cathode regions electrically connected by the electrolyte;
[0129] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0130] c) removing some or all of the acid from the anode
region;
[0131] d) concentrating the acid, wherein the acid has a pH ranging
from about pH=0 to about pH=5; and
[0132] e) contacting the acid with a material that when exposed to
a strong acid is converted to a carbon dioxide sequestering
solution.
[0133] The method according to embodiment 7, wherein the material
is any one of a mineral clay sepiolite, serpentine, talc, asbestos,
or a mining byproduct.
[0134] The method according to embodiment 7, further comprising the
step of adding base to the carbon dioxide sequestering
solution.
[0135] The method according to embodiment 7, further comprising the
step of contacting the carbon dioxide sequestering solution with a
source of gaseous carbon dioxide.
[0136] The method according to embodiment 7, further comprising the
step of precipitating and processing magnesium salts from the
carbon dioxide sequestering solution.
[0137] Embodiment 8 is a method of generating renewable hydrogen
and producing pressurized carbon dioxide gas comprising:
[0138] a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte;
[0139] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0140] c) producing hydrogen gas and hydroxide ions at the cathode,
wherein the hydroxide ions are present in the form of a base;
[0141] d) removing some or all of the acid from the anode
region;
[0142] e) removing some or all of the base from the cathode
region;
[0143] f) contacting the base comprising hydroxide ions with
gaseous carbon dioxide to produce a solution comprising
bicarbonate, carbonate, or a mixture thereof;
[0144] g) contacting the solution with acid produced at the anode
region of the cell in an enclosed chamber to produce carbon dioxide
gas under pressure; and
[0145] h) collecting the pressurized carbon dioxide gas.
[0146] The method according to embodiment 8, further comprising
producing super critical carbon dioxide from the collected
pressurized carbon dioxide gas.
[0147] Embodiment 9 is a method of generating renewable hydrogen
and producing carbon dioxide negative urea fertilizer, the method
comprising the steps of:
[0148] a) supplying a direct current from a renewable or nuclear
electrical source at a predetermined voltage to a water
electrolysis unit having at least one electrolysis cell including
an aqueous electrolyte substantially free of chloride ions and an
anode region adapted to generate oxygen gas and protons separated
from a cathode region adapted to generate hydrogen gas and
hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte;
[0149] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0150] c) producing hydrogen gas and hydroxide ions at the cathode
region, wherein the hydroxide ions are present in the form of a
base;
[0151] d) removing some or all of the acid from the anode
region;
[0152] e) removing some or all of the base from the cathode
region;
[0153] f) contacting the base having with a gaseous source of
carbon dioxide to produce a feedstock comprising bicarbonate or
carbonate or a mixture thereof;
[0154] g) contacting the acid produced at the anode region with the
feedstock to produce carbon dioxide gas; and
[0155] h) contacting the carbon dioxide gas with a source of
anhydrous ammonia under pressure to produce urea.
[0156] Embodiment 10 is a method of generating renewable hydrogen
and producing carbon dioxide negative urea fertilizer, the method
comprising the steps of:
[0157] a) supplying a direct current from a renewable or nuclear
electrical source at a predetermined voltage to a water
electrolysis unit having at least one electrolysis cell including
an aqueous electrolyte substantially free of chloride ions and an
anode region adapted to generate oxygen gas and protons separated
from a cathode region adapted to generate hydrogen gas and
hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte;
[0158] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0159] c) producing hydrogen gas and hydroxide ions at the cathode
region, wherein the hydroxide ions are present in the form of a
base;
[0160] d) removing some or all of the acid from the anode
region;
[0161] e) removing some or all of the base from the cathode
region;
[0162] f) contacting the base having with a gaseous source of
carbon dioxide to produce a feedstock comprising bicarbonate or
carbonate or a mixture thereof;
[0163] g) contacting the acid produced at the anode region with the
feedstock to produce carbon dioxide gas; and
[0164] h) reacting the carbon dioxide gas and hydrogen produced at
the cathode with nitrogen gas in an electrochemical process to
produce urea.
[0165] Embodiment 11 is a method of generating renewable hydrogen
and producing carbon dioxide negative agricultural lime comprising
the steps of:
[0166] a) supplying a direct current from a renewable or nuclear
electrical source at a predetermined voltage to a water
electrolysis unit having at least one electrolysis cell including
an aqueous electrolyte substantially free of chloride ions and an
anode region adapted to generate oxygen gas and protons separated
from a cathode region adapted to generate hydrogen gas and
hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte;
[0167] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0168] c) producing hydrogen gas and hydroxide ions at the cathode,
wherein the hydroxide ions are present in the form of a base;
[0169] d) removing some or all of the acid from the anode
region;
[0170] e) removing some or all of the base from the cathode
region;
[0171] f) contacting the base having a pH of greater than about
pH=10 with gaseous carbon dioxide to produce a carbonate enriched
feedstock;
[0172] g) contacting the feedstock with an aqueous composition
comprising calcium ions; and
[0173] h) precipitating calcium carbonate from the feedstock to
produce agricultural lime.
[0174] Embodiment 12 is a method of generating renewable hydrogen
and producing carbon dioxide neutral quick lime comprising:
[0175] a) supplying a direct current from a renewable or nuclear
electrical source at a predetermined voltage to a water
electrolysis unit having at least one electrolysis cell including
an aqueous electrolyte substantially free of chloride ions and an
anode region adapted to generate oxygen gas and protons separated
from a cathode region adapted to generate hydrogen gas and
hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte;
[0176] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0177] c) producing hydrogen gas and hydroxide ions at the cathode
region, wherein the hydroxide ions are present in the form of a
base;
[0178] d) removing some or all of the acid from the anode
region;
[0179] e) removing some or all of the base from the cathode
region;
[0180] f) contacting the base having a pH of greater than about
pH=10 with gaseous carbon dioxide to produce a carbonate enriched
feedstock;
[0181] g) contacting the carbonate enriched feedstock with an
aqueous solution comprising calcium ions to generate calcium
carbonate;
[0182] h) applying heat to the calcium carbonate to produce quick
lime.
[0183] The method according to embodiment 12, wherein carbon
dioxide released from applying heat to the calcium carbonate is
contacted with base to regenerate the carbonate feedstock.
[0184] The method according to embodiment 12, wherein carbon
dioxide released from applying heat to the calcium carbonate is
sequestered and pressurized for use as supercritical carbon
dioxide.
[0185] Embodiment 13 is a method of generating renewable hydrogen
and producing carbon dioxide neutral or carbon dioxide negative
carbon monoxide comprising:
[0186] a) supplying a direct current from a renewable or nuclear
electrical source at a predetermined voltage to a water
electrolysis unit having at least one electrolysis cell including
an aqueous electrolyte substantially free of chloride ions and an
anode region adapted to generate oxygen gas and protons separated
from a cathode region adapted to generate hydrogen gas and
hydroxide ions, wherein the anode and the cathode regions are
electrically connected by the electrolyte;
[0187] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0188] c) producing hydrogen gas and hydroxide ions at the cathode
region, wherein the hydroxide ions are present in the form of a
base;
[0189] d) removing some or all of the acid from the anode
region;
[0190] e) removing some or all of the base from the cathode
region;
[0191] f) contacting the base with gaseous carbon dioxide to
produce a solution comprising bicarbonate or carbonate or a mixture
thereof;
[0192] g) contacting the solution with acid produced in the anode
region of the cell to produce carbon dioxide gas under
pressure;
[0193] h) collecting the pressurized carbon dioxide gas; and
[0194] i) reducing a portion of the carbon dioxide gas with a
portion of the hydrogen gas generated at the cathode to produce
carbon monoxide.
[0195] Embodiment 14 is a method of generating renewable hydrogen
and producing formic acid comprising:
[0196] a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte;
[0197] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0198] c) producing hydrogen gas and hydroxide ions at the cathode
region, wherein the hydroxide ions are present in the form of a
base;
[0199] d) removing some or all of the acid from the anode
region;
[0200] e) removing some or all of the base from the cathode
region;
[0201] f) contacting the base with a gaseous carbon dioxide to
produce a solution comprising bicarbonate or carbonate or a mixture
thereof;
[0202] g) contacting the solution with acid produced in the anode
region of the cell to produce carbon dioxide gas under
pressure;
[0203] h) collecting the pressurized carbon dioxide gas;
[0204] i) reducing a portion of the carbon dioxide gas with a
portion of hydrogen gas generated at the cathode to produce carbon
monoxide;
[0205] j) reacting a portion of the carbon monoxide with methanol
in the presence of the base produced at the cathode having a pH
ranging of at least 10 to produce methyl formate; and
[0206] k) hydrolyzing the methyl formate to produce formic
acid.
[0207] Embodiment 15, is a method of generating renewable hydrogen
and producing formic acid comprising:
[0208] a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte;
[0209] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0210] c) producing hydrogen gas and hydroxide ions at the cathode
region, wherein the hydroxide ions are present in the form of a
base;
[0211] d) removing some or all of the acid from the anode
region;
[0212] e) removing some or all of the base from the cathode
region;
[0213] f) contacting the base having a with gaseous carbon dioxide
to produce a solution comprising cesium bicarbonate; and
[0214] g) electrolyzing cesium bicarbonate to form formic acid.
[0215] Embodiment 16 is a method of generating renewable hydrogen
and producing formic acid comprising:
[0216] a) supplying a direct current from an electrical source at a
predetermined voltage to a water electrolysis unit having at least
one electrolysis cell including an aqueous electrolyte
substantially free of chloride ions and an anode region adapted to
generate oxygen gas and protons separated from a cathode region
adapted to generate hydrogen gas and hydroxide ions, wherein the
anode and the cathode regions are electrically connected by the
electrolyte;
[0217] b) producing oxygen gas and protons at the anode region,
wherein the protons are present in the form of an acid;
[0218] c) producing hydrogen gas and hydroxide ions at the cathode
region, wherein the hydroxide ions are present in the form of a
base;
[0219] d) removing some or all of the acid from the anode
region;
[0220] e) removing some or all of the base from the cathode
region;
[0221] f) contacting the base having a with gaseous carbon dioxide
to produce a solution comprising bicarbonate or carbonate or a
mixture thereof; and
[0222] g) hydrogenating the bicarbonate in the presence of a
catalyst to produce formic acid.
[0223] The method according to any one of embodiments 1-16, wherein
the source of gaseous carbon dioxide is atmospheric carbon
dioxide.
[0224] The method according to any one of embodiments 1-16, wherein
the source of gaseous carbon dioxide is a gas stream.
[0225] The method according to any one of embodiments 1-16, wherein
an amount of carbon dioxide sequestered is greater than an amount
of carbon dioxide generated by the electrical source.
[0226] The method according to any one of embodiments 1-16, further
comprising applying to the water electrolysis cell a
counter-current flow adapted to introduce concentrated electrolyte
into a central feed chamber separated by semi-permeable membranes
from the anode and cathode regions, such that the direction of flow
of the electrolyte is opposite to the direction of flow of acid and
base produced at the anode and cathode regions.
[0227] The method according to any one of embodiments 1-16, further
comprising maintaining a separate anode and cathode region by
providing at least one ion selective membrane positioned between
the anode region and the cathode region of the electrolysis
cell.
[0228] The method according to any one of embodiments 1-16, further
comprising maintaining a separate anode and cathode region by
providing at least one non-selective, semi-permeable membrane
positioned between the anode region and the cathode region of the
electrolysis cell.
[0229] The method according to any one of embodiments 1-16, further
comprising continuously supplying fresh electrolyte to the
electrolysis cell.
[0230] The method according to any one of embodiments 1-16, further
comprising supplying fresh electrolyte to the electrolysis cell in
a batch-wise manner.
[0231] The method according to any one of embodiments 1-16, further
comprising maintaining a pH difference between the anode region and
the cathode region of at least 6 pH units.
[0232] The method according to any one of embodiments 1-16, wherein
the pH of the anode region ranges from about pH=0 to about
pH=5.
[0233] The method according to any one of embodiments 1-16, wherein
the pH of the cathode region ranges from about pH=8 to about
pH=14.
[0234] The method according to any one of embodiments 1-16, wherein
the electricity supplied from the source ranges from about 1.2 to
about 10.0 volts.
[0235] The method according to any one of embodiments 1-16, wherein
the voltage supplied from the energy source is at least 1.2
volts.
[0236] The method according to any one of embodiments 1-16, wherein
a pH of the base produced at the cathode region ranges from about
pH=8 to about pH=14.
[0237] The method according to any one of embodiments 1-16, further
comprising applying positive pressure to the electrolysis cell to
remove the acid from the anode region and the base from the cathode
region.
[0238] The method according to any one of embodiments 1-16, further
comprising applying a gravity feed to the electrolysis cell to
remove the acid from the anode region and the base from the cathode
region.
[0239] The method according to any one of embodiments 1-16, further
comprising continuously pumping acid from the anode region to an
acid storage region and the base from the cathode region to a base
storage region.
[0240] The method according to any one of embodiments 1-16, wherein
the electrical source is a renewable energy source.
[0241] The method according to any one of embodiments 1-16, further
comprising recycling the hydrogen gas to a renewable energy source
to be utilized as a fuel.
[0242] The method according to any one of embodiments 1-16, further
comprising recycling the hydrogen gas to a renewable energy source
to be utilized as a fuel wherein the renewable energy source is a
fuel cell powered by renewable hydrogen, a synthetic fuel, biomass,
or biofuel.
[0243] The method according to any one of embodiments 1-16, further
comprising supplying renewable energy from a renewable energy
source to the electrical energy source wherein the renewable energy
source is any one of a wind turbine, solar cell, hydroelectric
generator, biofuel, geothermal, or oceanic.
[0244] The method according to any one of embodiments 1-16, further
comprising recycling the hydrogen gas to generate renewable
electricity.
[0245] The method according to any one of embodiments 1-16, further
comprising recycling the hydrogen gas and the oxygen gas to
regenerate water and electricity supplied to the electrolysis
unit.
[0246] The method according to any one of embodiments 1-16, wherein
the electrical energy source does not consume fossil based
fuels.
[0247] The method according to any one of embodiments 1-16, wherein
the electrical energy source is a nuclear generator.
[0248] The method according to any one of embodiments 1-16, wherein
the aqueous electrolyte comprises an alkali salt substantially free
of chloride ions.
[0249] The method according to any one of embodiments 1-16, wherein
the aqueous electrolyte comprises a sodium salt substantially free
of chloride ions.
[0250] The method according to any one of embodiments 1-16, wherein
the aqueous electrolyte is selected from the group consisting of
sodium sulfate, potassium sulfate, calcium sulfate, magnesium
sulfate, sodium nitrate, potassium nitrate, sodium bicarbonate,
sodium carbonate, potassium bicarbonate, potassium carbonate,
calcium carbonate, and magnesium carbonate.
[0251] The method according to any one of embodiments 1-16, wherein
the aqueous electrolyte comprises sea water and/or sea salt.
[0252] The method according to any one of embodiments 1-16, wherein
the electrolyte is saturated in solution.
[0253] The method according to any one of embodiments 1-16, further
comprising maintaining a saturated electrolyte solution.
[0254] The method according to any one of embodiments 1-16, wherein
the aqueous electrolyte is sodium sulfate or potassium sulfate.
[0255] The method according to any one of embodiments 1-16, further
comprising isolating bicarbonate or carbonate from the
solution.
[0256] The method according to any one of embodiments 1-16, further
comprising isolating bicarbonate or carbonate from the solution by
precipitating bicarbonate or carbonate from the solution.
[0257] The method according to any one of embodiments 1-16, further
comprising the step of concentrating the solution.
[0258] The method according to any one of embodiments 1-16, further
comprising chilling the solution to a temperature ranging from
about 0.degree. C. to about 10.degree. C. to precipitate carbonate
or bicarbonate from the solution.
[0259] The method according to any one of embodiments 1-16, further
comprising adding a salt comprising calcium ions to isolate calcium
carbonate from the solution.
[0260] The method according to any one of embodiments 1-16, further
comprising adding a salt comprising magnesium ions to isolate
magnesium carbonate from the solution.
[0261] The method according to any one of embodiments 1-16, further
comprising spraying the solution to precipitate carbonate or
bicarbonate from the solution.
[0262] The method according to any one of embodiments 1-16, further
comprising regenerating electrolyte supplied to the electrolysis
unit by reacting the acid removed from the anode region of the
electrolysis cell with sodium chloride to produce hydrochloric acid
and the original electrolyte salt.
[0263] The method according to any one of embodiments 1-16, further
comprising collecting and concentrating the base.
[0264] The method according to any one of embodiments 1-16, wherein
the acid is sulfuric acid.
[0265] The method according to any one of embodiments 1-16, wherein
the base is sodium hydroxide.
[0266] The method according to any one of embodiments 1-16, wherein
a difference of at least 6 pH units is maintained between the anode
region and cathode region by supplying electrolyte utilizing
bi-direction flow.
[0267] The method according to any one of embodiments 1-16, wherein
a difference of at least 6 pH units is maintained between the anode
region and cathode region utilizing convection currents generated
by rising hydrogen gas in the cathode region and rising oxygen gas
in the anode region.
[0268] The method according to any one of embodiments 1-16 further
comprising concentrating cations from the electrolyte and
delivering the cations the cathode region.
[0269] The method according to any one of embodiments 1-16 further
comprising concentrating anions from the electrolyte and delivering
the anions the anode region.
[0270] The method according to any one of embodiments 1-16, further
comprising the step of separating the anode and the cathode region
with a porous glass frit.
[0271] 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.
* * * * *