The invention relates generally to the capture of carbon dioxide from the atmosphere and/or from point sources (e.g., power plants, chemical plants, natural gas fields, oil fields, industrial sites).
Due to the combustion of fossil fuels, the atmospheric concentration of carbon dioxide has steadily risen from ˜280 ppm to over 380 ppm in the last 200 years. Concern about anthropogenic climate change has generated research into technologies that limit the CO2 emissions from the combustion of fossil fuels and into technologies that remove CO2 directly from the atmosphere.
A process for capturing carbon dioxide from the atmosphere and/or from carbon dioxide point sources (e.g., power plants, chemical plants, natural gas fields, oil fields, industrial sites) is described. The process may involve reacting an alkaline solution with carbon dioxide.
In one aspect, a process for capturing carbon dioxide is provided. The process comprises providing water and processing the water to generate acidic solution species and alkaline solution. The process further comprises neutralizing the acidic solution, and capturing carbon dioxide from a source of carbon dioxide with the alkaline solution.
In one aspect, a process for capturing carbon dioxide and generating chlorine gas and hydrogen gas is provided. The process comprises providing water and processing the water to generate sodium hydroxide, chlorine gas, and hydrogen gas. The process further comprises capturing carbon dioxide from a source of carbon dioxide by reacting the carbon dioxide with the sodium hydroxide to form sodium bicarbonate and/or disodium carbonate.
In one aspect, a process for capturing carbon dioxide is provided. The process comprises providing a salt solution and processing the salt solution to generate a metal hydroxide and an acidic solution. The process further comprises capturing carbon dioxide from a source of carbon dioxide by reacting the carbon dioxide with the metal hydroxide to form a metal bicarbonate and/or metal carbonate.
In one aspect, a process for capturing carbon dioxide is provided. The process comprises providing water and adding ash obtained from a source of biomass to the water to form alkaline solution. The process further comprises capturing carbon dioxide from a source of carbon dioxide by with the alkaline solution.
Other aspects, embodiments, and features of the invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. The accompanying figures are schematic and are not intended to be drawn to scale. For purposes of clarity, not every component is labeled in every figure. Nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention.
Processes for capturing carbon dioxide are described. The carbon dioxide may be captured from the atmosphere and/or from the waste stream of a carbon dioxide point source (e.g., power plants, chemical plants, natural gas fields, oil fields, industrial sites, etc.). The processes can involve capturing carbon dioxide using alkaline solutions (e.g., NaOH). In some processes, the carbon dioxide may react with the alkaline solution to form a product (e.g., NaHCO3). As described further below, the alkaline solution may be made a number of different ways. In some of the processes, products produced during processing may be used to add value beyond carbon dioxide capture, as described further below.
It should be understood that the schematic processes shown in the figures are provided as examples though other processes are also within the scope of the present invention. The term “acidic species” refers to dissolved species (e.g., ions) that contribute to the acidity of a solution. The term “alkaline species” refers to dissolved species (e.g., ions) that contribute to the alkalinity of a solution.
Step 10 involves formation of an alkaline solution. Step 20 involves capturing carbon dioxide from the atmosphere and/or from the waste stream of a carbon dioxide point source. For example, the carbon dioxide may be captured by reacting it with the alkaline species in the solution produced in Step 10 and/or dissolving it in the alkaline solution produced in step 10. Step 30 (
In some embodiments, step 10 (as shown in
In some embodiments, it may be preferable for the body (or source) of water to be large to provide a sufficient supply of water for the process. For example, the body of water may be an ocean, a sea, a lake, or a river. Water may be supplied from the body of water to a plant where the additional processing steps are performed.
In some embodiments, step 30 (
NaCl+H2O+CO2→NaHCO3+½Cl2+½H2
The embodiments illustrated in
Na++Cl−+H2O→Na++OH−+½Cl2+½H2
The embodiments illustrated in
It should be understood that though the above description relates to Cl2 and H2, other suitable gases and corresponding acids may also be used in processes of the invention. In some embodiments (
CH3COO−+Na++H2O→CH3COOH+NaOH
The final step of the embodiments illustrated in
Ultimately, the embodiments depicted in
CO2+R-M+H2O→MHCO3+R—H
In other embodiments, step 10 of
In some embodiments, as indicated by
Na2SO4+2H2O→2NaOH+H2SO4
It should be understood that in any of the above reactions, sodium may be replaced with another suitable cation such as potassium.
Other embodiments (e.g., as shown in
Step 20 involves capturing CO2 using the alkaline solution produced in step 10. In some embodiments, CO2 may be reacted with alkaline species through a spray tower. In some embodiments, step 20 involves adding the alkaline or basic solution (e.g., NaOH) produced in step 10 directly to a body of water (e.g., the ocean). In these embodiments, the process will increase the concentration of hydroxide ions and cations (e.g., in the form of NaOH) relative to the concentration of hydrogen ions and anions (e.g., in the form of HCl) in the body of water. In such an embodiment, the process will have increased the alkalinity of the body of water. The removal of anions from a body of water increases the alkalinity of the body of water because alkalinity is defined as the concentration difference between cations and anions:
Alkalinity=2[Ca2+]+[K+]+2[Mg2+]+[Na]−[Cl−]−2[SO42−]
The small excess charge of the cations over anions is mainly balanced by the concentrations of carbonate and bicarbonate ions. Increasing the alkalinity of the body of water causes a shift in the dissolved inorganic carbon (DIC) partitioning to balance the increase in positive conservative charge. That partitioning shift decreases the concentration of CO2(aq), which is the fraction of DIC that is able to interact directly with the CO2(g) in the atmosphere. As a result of decreasing the CO2(aq) fraction of DIC, the surface water becomes under-saturated in CO2(aq) and additional CO2(g) dissolves from the atmosphere into the body of water. The quantity of additional atmospheric CO2(g) that dissolves into the body of water is related to the increase in alkalinity. Therefore, in one embodiment of this invention, the removal and neutralization (step 30,
In this manner, processes of the invention effectively accelerate the natural CO2(g) uptake process of a body of water (e.g., an ocean). Additionally, the processes can enable mankind to better control the pH of bodies of water (e.g., an ocean). Currently, the uptake of anthropogenic CO2 causes the pH of bodies of water to drop. Removal and neutralization (step 30,
The embodiment of this invention illustrated in
In some embodiments, step 20 involves reacting the alkaline solution (e.g., sodium hydroxide or other suitable alkaline solution) with carbon dioxide from the atmosphere to produce a reaction product (e.g., sodium bicarbonate and/or disodium carbonate, or other suitable compound). In processes of the invention, the reaction product is not used to re-generate the alkaline species which are used to capture carbon dioxide. That is, the reaction product is used for other purposes than re-generating alkaline species used to capture carbon dioxide. As described further below, the reaction product may be disposed of and/or to otherwise further processed. For example, the reaction product may be disposed of by introducing the product into a suitable body of water (e.g., the ocean) or land-based environment (e.g., landfill, mine)
One representative reaction in which carbon dioxide reacts with alkaline species produced in step 10 is:
NaOH+CO2→NaHCO3
For example, to facilitate the reaction, a pool of highly concentrated sodium hydroxide (NaOH) may be collected. The pool may be exposed to the atmosphere causing the reaction to occur. In some processes, the sodium hydroxide (or other suitable compound) may be sold and shipped to a carbon dioxide point source (e.g., power plants, chemical plants, natural gas fields, oil fields, industrial sites, etc.). The waste stream produced by the carbon dioxide point source may be reacted with a concentrated pool of sodium hydroxide to cause the reaction to occur. The reaction of sodium hydroxide with carbon dioxide, thus, reduces the concentration of carbon dioxide in the atmosphere or in the waste stream of a carbon dioxide from a point source. The sodium bicarbonate and/or disodium carbonate that is formed from the reaction of the sodium hydroxide with the carbon dioxide may be added to the body of water, or otherwise collected and disposed.
The various embodiments illustrated in
½H2+¼O2→½H2O
In some embodiments (
½H2+½Cl2HCl
In some of these embodiments, the chlorine gas and hydrogen gas formed in step 10 may be combined in a fuel cell or a hydrogen gas turbine that produces either HCl(g) or HCl(aq) and electricity that can be harnessed for use in other processing steps or otherwise utilized. The application of the HCl fuel cell will likely be a valuable element of the process because the electricity produced in the fuel cell may substantially decrease of the operational costs.
The HCl produced in reaction by the combination of Cl2 and H2 can be removed for further processing (e.g., step 30,
In some cases, step 30 of
A variety of reactions may be used to safely dispose of the acid. The reactions may involve the dissolution of minerals by the acid to neutralize the acid and/or combine a chloride ion with a conservative cation. In some embodiments, the acid is disposed of in an exothermic reaction. For example, HCl may be disposed by reacting it with any suitable mineral and/or rock that neutralizes it and/or matches the chloride ions with conservative cations. For example, a silicate mineral or rock may be used to neutralize the HCl according to the following general reaction:
HCl+(silicate mineral/rock)→(chloride salts)+(silica rich mineral/rock)+H2O
A specific example of the acid neutralization illustrated in step 30 of
Mg2SiO4+4HCl→2MgCl2+SiO2+2H2O
It should be understood that step 30 of
In some embodiments of the invention, the acid is disposed of by reacting with rocks and/or minerals (e.g., silicate rocks and/or minerals) in a reaction vessel. In such embodiments, the rocks and/or minerals are transported to the reaction vessel. In some cases, the rocks and/or minerals may be processed to form smaller rocks and/or minerals. Once in the reaction vessel, the rocks and/or minerals are combined with the acid, and the dissolution of the rocks and/or minerals neutralizes the acid.
In other embodiments, the acid is neutralized through reaction with and/or dissolution of rocks and/or minerals in-situ (i.e., rocks and/or minerals in their natural location). In such processes, the acidic solution may be injected into or sprayed onto the rock and/or mineral (e.g., basaltic, ultramafic rock and/or mineral formations). In such processes, the acid can be neutralized when it contacts the rock and/or mineral formation, while flowing through and/or across the rock and/or mineral formation. The seepage flow may be engineered such that that time scale of acid flow through the rock and/or mineral formation would be slow relative to the timescale of the rock and/or mineral dissolution. If the timescales are appropriately engineered, then the acid will be largely neutralized when the dissolution products reach a body of water (e.g., the ocean).
In some embodiments, the acid is disposed of in an exothermic reaction and also generates additional useful energy. These embodiments, for example, may involve reacting the acid (e.g., HCl) with any suitable mineral or rock that contains reduced iron (Fe, Fe+, or Fe2+). The purpose of using reduced iron containing minerals and/or rocks is that the oxidation of the iron can be used to generate useful energy. For example, mafic and ultramafic rock, basalt, and certain iron ore all contain reduced iron. The acid (e.g., HCl) solution can dissolve these minerals in reactions similar to the following dissolution reaction of HCl and olivine:
(Mg,Fe)2SiO4+4HCl→2(Mg,Fe)Cl2+SiO2+2H2O
During the dissolution process, the following reaction will sometimes occur as the Fe2+ is oxidized to Fe3+ by the formation of H2(g):
Fe2SiO4+6HCl→2FeCl3+SiO2+2H2O+H2
That reaction results in the production of H2. In reactions similar to dissolution of olivine, it may be difficult to predict how much of the iron silicate will react with HCl to form FeCl2 and how much of it will react with HCl to form FeCl3. It is believed, however, that a subset of the Fe2+ will be oxidized to Fe3+ and that H2 will form when Fe2+ is oxidized. The hydrogen gas that is generated can be used to generate electricity, or it can be sold on the open market. There is a wide variety of minerals that could be used for this process step (e.g., mafic and ultramafic rock, basalt, and/or iron ores) including those that contain reduced iron for the purpose of disposing of the acid and oxidizing the reduced iron.
In some embodiments, the fraction of the Fe2+ that is not oxidized during the dissolution reaction described above can be used in a fuel-cell to generate electricity by oxidizing the FeCl2 to FeCl3. Generally, the dissolution of any rock containing reduced iron with an acid will produce a solution of reduced iron cations, the anion from the acid, and H2O. As an example, the dissolution of any rock containing reduced iron by HCl will produce some FeCl2. Additionally, as described above, a portion of the Fe2+ will be oxidized to Fe3+, and when the Fe2+ is oxidized, then the H+ in solution will be reduced to H2(g). As noted above, the portion of the Fe2+ that is not oxidized to Fe3+ forms FeCl2. That FeCl2 can be reacted with additional HCl and O2 in a fuel-cell to fully oxidize the remaining Fe2+ to Fe3+. The overall fuel-cell reaction is described by the following net reaction:
4FeCl2+4HCl+O2→4FeCl3+2H2O
The electrical energy generated from the oxidation of FeCl2 to FeCl3 can either be sold or used to run the process by producing more acid from seawater. The useful energy generated during the dissolution of minerals containing reduced iron can be used in other steps in the process.
In a different embodiment, a FeCl2—O2 fuel cell could be used that produce ferric hydroxide (Fe(OH)3) as a product.
As noted above, step 30 of
Using the mafic olivine mineral fayalite (i.e., Fe2SiO4) as an example, Fe2SiO4 is converted into FeCl3, SiO2, and H2O during the reaction with HCl (i.e., the acid) and Cl2 (i.e., the halogen gas). Depending somewhat on the conditions of the reaction, any hydrogen production from the dissolution of the ferrous minerals would also react exothermically with Cl2 (i.e., the halogen gas) forming HCl (i.e., the acid) and further dissolving the rocks/minerals.
It should be understood that processes of the invention may include variation to those described above that would be recognized by those of ordinary skill in the art.
Processes of the invention can have a number of advantages. One benefit is that the process removes carbon dioxide from the atmosphere which leads to a number of environmental advantages. Another benefit of the process is that some of the steps (e.g., the formation of HCl in a fuel cell) produce useful energy that can be used in other aspects of the process. The energy may be generated, for example, from hydrogen production during the dissolution of reduced minerals (e.g., minerals comprising iron), electricity production through a fuel cell (e.g., FeCl2—HCl—O2; FeCl2—O2), or heat generated during the dissolution of silicate rocks and minerals. Because the energy cost is a large component of the total cost for most conventional CO2 capture and storage technologies, the low energy cost of the process represents a valuable technological advancement. An additional benefit of the process is the co-production of valuable chemicals with alkaline or basic solutions, which are used to capture CO2. For example, the embodiments illustrated in
The following examples are meant to be illustrative and are not limiting in any way.
The following diagrams illustrate examples of processes according to embodiments of the invention. Diagram A shows carbon dioxide capture and acid disposal. Calcium has been used to represent any metal found in silicate rocks. Diagram B shows a process with steps to recover energy through the oxidation of silicate rocks. Iron has been used to represent any metal found in silicate rocks that can be oxidized (e.g., iron and manganese). The chemistry for the process in Diagram B is shown below the figure.
Na++Cl−+H2O→Na++OH−+½Cl2+½H2
½Cl2+½H2→HCl
NaOH+CO2→NaHCO3
In step 2, a portion of the Fe2SiO6 will react with HCl to form FeCl3 (reaction 2a), while another portion of the Fe2SiO6 will react with HCl to form FeCl2 (reaction 2b). For the purposes of this example, we assume that ⅓ of the mineral will react to form FeCl3 while the other ⅔ will react to form FeCl2.
HCl+⅙Fe2SiO4→⅓FeCl3+⅙SiO2+⅓H2O+⅙H2 Reaction 2a
¼Fe2SiO4+HCl→½FeCl2+¼SiO2+½H2O Reaction 2b
In step 2, the Fe2SiO4 was reacted with HCl to form either H2 or FeCl2. As a result, step 3 employs two separate fuel cells to recover energy by oxidizing both the H2 and FeCl2 separately.
⅙H2+ 1/12O2→⅙H2O Reaction 3a
NOTE: When FeCl2 is run in a fuel-cell, the reaction requires the presence of an additional ½ a mole of HCl for each mole of NaOH originally produced.
½NaCl+½H2O→½HCl+½NaOH
½NaOH+½CO2→½NaHCO3
½FeCl2+½HCl+⅛O2→½FeCl3+¼H2O Reaction(s) 3b
The following diagram illustrates an example of a process according to an embodiment of the invention. In this process silicate rocks and minerals are oxidized using chlorine gas.
Na++Cl−+H2O→Na++OH−+½Cl2+½H2
2/6Cl2+ 2/6H2→ 4/6HCl
NaOH+CO2→NaHCO3
4/6HCl+⅙Fe2SiO4+⅙Cl2→ 2/6FeCl3+⅙SiO2+ 2/6H2O Reaction 2a
The additional ⅙H2 unit produced in step 1a and not employed to form HCl in step 1b is oxidized with O2 for form ⅙H2O and recover some electrical work.
⅙H2+ 1/12O2→⅙H2O Reaction 3a
1/12O2+NaCl+½H2O+CO2+⅙Fe2SiO4→NaHCO3+⅓FeCl3+⅙SiO2 Net reaction
Having thus described several aspects and embodiments of this invention, it is to be appreciated various alterations, modifications and improvements will readily occur to those skilled in the art. Such alterations, modifications and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
This application is continuation U.S. patent application Ser. No. 12/226,632, filed Oct. 23, 2008, which is a National Stage Application of PCT/US2007/010032, filed Apr. 26, 2007 which claims priority to U.S. Provisional Patent Application Ser. No. 60/795,419, filed Apr. 27, 2006 and U.S. Provisional Patent Application Ser. No. 60/844,472, filed Sep. 14, 2006, the disclosures of which are incorporated herein by reference.
This invention was made with government support under Grant No. NNG05GN50G, awarded by National Aeronautics and Space Administration. The United States Government has certain rights in the invention.
Number | Date | Country | |
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60795419 | Apr 2006 | US | |
60844472 | Sep 2006 | US |
Number | Date | Country | |
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Parent | 12226632 | Sep 2009 | US |
Child | 13004101 | US |