System and method for removing carbon dioxide from an atmosphere and global thermostat using the same

Abstract

A system for removing carbon dioxide from an atmosphere to reduce global warming including an air extraction system that collects carbon dioxide from the atmosphere through a medium and removes carbon dioxide from the medium; a sequestration system that isolates the removed carbon dioxide to a location for at least one of storage and generation of a renewable carbon fuel; and one or more power supplying units that supply heat to the air extraction system to remove the carbon dioxide from the medium, at least one of the one or more power supplying units being a fossil fuel plant.

Claims

1. A system capable of directly removing CO.sub.2 from a planet's atmosphere by extracting and collecting carbon dioxide from the atmosphere, such that when a plurality of other such systems strategically placed across the globe, and coordinated so as to collectively function for extracting CO.sub.2 from the atmosphere is capable of reducing the ambient concentration of CO.sub.2 in the planet's atmosphere from what it may otherwise be, the plurality of systems being in locations geographically dispersed around the planet with each capable of removing carbon dioxide from the planet's atmosphere by extracting and collecting carbon dioxide from the atmosphere, each system comprises an air contactor, wherein the air contactor comprises an amine absorbent on a solid surface, the amine being capable of absorbing carbon dioxide from the atmosphere, and of being regenerated by having the carbon dioxide removed therefrom using process heat steam; a regenerator wherein the amine absorbent of the air contactor is regenerated; a fluid flow connector extending from the regenerator to a source of low temperature steam, at a temperature of less than about 120 C., the source of process heat steam being the steam exhaust from a steam-operated electric generator, the steam for operating the steam-operated electric generator being heated from a primary process using a primary energy source, for extracting and collecting carbon dioxide from the sorbent medium and regenerating the sorbent medium; and a location for at least one of storage and generation of a renewable carbon fuel, so that the plurality of systems together can effectively extract carbon dioxide from the atmosphere in an economically efficient manner.

2. The system of claim 1, wherein the primary energy source for each system is selected from the group of primary energy sources consisting of: fossil fuel, geothermal, nuclear, solar, biomass and other renewable energy sources and exothermic chemical processes whose use can result in a supply of process heat.

3. The system of claim 1, wherein process heat is obtained from a primary energy source selected from the group of energy sources consisting of: fossil fuel, geothermal, nuclear, solar, biomass and other renewable energy sources and exothermic chemical processes, the use of which can result in a supply of process heat.

4. The system of claim 1, including a collection system that isolates the removed carbon dioxide to a location for at least one of sequestration, storage and generation of a renewable carbon fuel or a non-fuel product such as fertilizer and construction materials.

5. The system of claim 4, wherein the medium is a porous solid.

6. The system of claim 4, wherein the air extraction system collects carbon dioxide and the collection system isolates the removed carbon dioxide using the heat supplied by the energy source.

7. The system of claim 1, wherein the solid surface is moveable in a substantially continuous path during the steps of removing carbon dioxide from the air and removing carbon dioxide from the medium.

8. The systems of claim 1 wherein each of the plurality of systems further comprises: a sequestration system that removes the carbon dioxide from the collector chamber and isolates the removed carbon dioxide to a location for at least one of sequestration, storage and generation of a renewable carbon fuel or non-fuel products such as fertilizers and construction materials.

9. The systems of claim 8 wherein the process heat steam is provided at a temperature of less than 100 C.

10. A worldwide system for directly removing carbon dioxide from the atmosphere to at least reduce the rate of increase of carbon dioxide in the atmosphere of the Earth, comprising a plurality of individual systems located around the planet, each of which is capable of reducing the amount of carbon dioxide in the planet's atmosphere by extracting carbon dioxide from the atmosphere, each individual system comprises an air contactor comprising an amine supported on a solid substrate and capable of absorbing CO.sub.2, the amine being supported on a solid surface; so as to be exposed to the open air; a regenerator for the CO.sub.2-containing air contactor; a source of process heat steam and a flow connector for passing the process heat steam at a temperature of less than about 120 C. from the source of process heat to the regenerator for capturing carbon dioxide from, and regenerating, the medium, and a fluid flow connector to pass the CO.sub.2 from the regenerator to a storage location, so that the plurality of systems together can effectively extract carbon dioxide from the atmosphere at a rate that at least reduces the rate at which carbon dioxide concentration is increasing in the atmosphere.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Various exemplary embodiments of this invention will be described in detail, with reference to the following figures, wherein:

(2) FIG. 1 is a generalized block diagram of a system for removing carbon dioxide from an atmosphere according to an exemplary embodiment of the present invention;

(3) FIG. 2 is a block diagram of a system for removing carbon dioxide from an atmosphere according to an exemplary embodiment of the present invention;

(4) FIG. 3 is a block diagram of an air extraction system according to an exemplary embodiment of the present invention; and

(5) FIG. 4 is a map illustrating a global thermostat according to an exemplary embodiment of the present invention;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(6) FIG. 1 is a generalized block diagram of a system, generally designated by reference number 1, for removing carbon dioxide from an atmosphere according to an exemplary embodiment of the present invention. The system 1 includes an air extraction system 40 and a sequestration system 50. The air extraction system 40 preferably incorporates any known or later-discovered CO.sub.2 extraction method, including methods which use a medium to absorb and/or bind CO.sub.2 from the atmospheric air by exposing the medium to chemical, electrical and/or physical interaction with the CO.sub.2 in the captured air. The medium may be liquid, gaseous or solid, or a combination of liquid, gaseous and solid substances, where in the case of solids, the substance is preferably porous. The medium is preferably recyclable so that after the CO.sub.2 is captured by the medium and separated from the medium for sequestration, the medium can be reused for absorption/binding of additional CO.sub.2. However, in other embodiments the medium may be sequestered along with the captured CO.sub.2. As shown in FIG. 1, the separation of the CO.sub.2 from the medium, as well as other processes such as the absorption/binding of CO.sub.2 and the sequestration of the CO.sub.2 performed by the sequestration system 50, may be made more efficient by the addition of heat to the air extraction system 40. In the present invention, the heat is process heat generated by a fossil fuel power plant, to be described in further detail below. The term process heat as used herein refers to the lower temperature heat remaining after the higher temperature heat has been used to generate electricity. More generally, the term process heat refers to any low temperature heat remaining after a primary process or that is added by the process itself, such as, for example, exothermic carbonation reactions in which carbon dioxide is stored as a mineral.

(7) FIG. 2 is a block diagram of a system, generally designated by reference number 2, for removing carbon dioxide from an atmosphere according to an exemplary embodiment of the present invention. The system 2 includes a fossil fuel power plant 30, an air extraction system 42 and a sequestration system 50. Each of these components of the system 2 are explained in detail below.

(8) The fossil fuel power plant 30 may be any known or later discovered facility that relies on the burning of fossil fuels, such as, for example, coal, fuel oil, natural gas and oil shale, for the generation of electricity. The thermal energy produced by the fossil fuel power plant 30 is used to produce electricity and the residual thermal energy (i.e., process heat) may be used to drive the air extraction system 42 and/or the sequestration system 50. For example, the process heat from the fossil fuel power plant 30 may be used to improve the efficiency of chemical and/or physical reactions used in the air extraction system 42 to absorb CO.sub.2 from the air and/or to drive on the CO.sub.2 from the medium.

(9) The residual heat provided by the fossil fuel power plant 30 may be supplemented by energy generated by a supplemental energy source. For example, the supplemental energy source may be a waste incineration plant or a renewable energy source, such as, for example, solar, nuclear, biomass, and geothermal energy sources, which provides additional thermal energy to drive the air extraction system 42 and/or the sequestration system 50. Process heat from the supplemental energy source may also be used to drive the air extraction system 42 and/or the sequestration system 50.

(10) FIG. 3 is a block diagram of the air extractor system 42 useable with the system 2 according to an exemplary embodiment of the present invention. The air extractor system 42 includes an air contactor 41, a causticizer 43, a slaker 45, a calciner 47 and a capture unit 49. The air contactor 41 may use a sorbent material to selectively capture CO.sub.2 from the air, and may be composed of any known or later-discovered contactor structures, such as, for example, large convection towers, open, stagnant pools, and packed scrubbing towers. In the present embodiment, the sorbent material may be sodium hydroxide (NaOH), which readily absorbs CO.sub.2 from the air. It should be appreciated that other known or future-discovered capture methods may be used, such as, for example, chemical absorption, physical and chemical adsorption, low-temperature distillation, gas-separation membranes, mineralization/biomineralization and vegetation. As a further example, as known in the art, aqueous amine solutions or amine enriched solid sorbents may be used to absorb CO.sub.2. Preferably, the sorbent material is regenerated and the capture method requires less than about 100-120 C. heat to regenerate the sorbent material.

(11) In this embodiment, at the air contactor 41, CO.sub.2 may be absorbed into an NaOH solution forming sodium carbonate (Na.sub.2CO.sub.3). Of course, other known or future-developed absorbers may also be used as an alternative or in addition to an NaOH solution. The generated Na.sub.2CO.sub.3 is then sent to the causticizer 43, where the NaOH is regenerated by addition of lime (CaO) in a batch process. The resulting CaCO.sub.3 solid is sent to the calciner 47 where it is heated in a kiln to regenerate the CaO, driving off the CO.sub.2 in a process known as calcination. The regenerated CaO is then sent through the slaker 45, which produces slaked lime Ca(OH).sub.2 for use in the causticizer 43.

(12) The capture unit 49 captures the CO.sub.2 driven off at the calciner 47 using any know or later-discovered CO.sub.2 capturing method that is effective in the low concentrations in which CO.sub.2 is present hi the atmosphere and that needs only low temperature heat for regeneration. For example, the capture unit 49 may use an amine based capture system, such as the system described in U.S. Pat. No. 6,547,854, incorporated herein by reference. The capture unit 49 may also compress the captured CO.sub.2 to liquid form so that the CO.sub.2 may be more easily sequestered.

(13) The sequestration system 50 may use any known or future-discovered carbon storing technique, such as, for example, injection into geologic formations or mineral sequestration. In the case of injection, the captured CO.sub.2 may be sequestered in geologic formations such as, for example, oil and gas reservoirs, unmineable coal seams and deep saline reservoirs. In this regard, in many cases, injection of CO.sub.2 into a geologic formation may enhance the recovery of hydrocarbons, providing the value-added byproducts that can offset the cost of CO.sub.2 capture and sequestration. For example, injection of CO.sub.2 into an oil or natural gas reservoir pushes out the product in a process known as enhanced it recovery. The captured CO.sub.2 may be sequestered underground, and according to at least one embodiment of the invention at a remote site upwind from the other components of the system 2 so that any leakage from the site is re-captured by the system 2.

(14) In regards to mineral sequestration, CO.sub.2 may be sequestered by a carbonation reaction with calcium and magnesium silicates, which occur naturally as mineral deposits. For example, as shown in reactions (1) and (2) below, CO.sub.2 may be reacted with forsterite and serpentine, which produces solid calcium and magnesium carbonates in an exothermic reaction.
Mg.sub.2SiO.sub.4+CO.sub.2=MgCO.sub.3+SiO.sub.2+95 kJ/mole(1)
Mg.sub.3Si.sub.2O.sub.5(OH).sub.4+CO.sub.2=MgCO.sub.3+SiO.sub.2+H.sub.2O+64 kJ/mole(2)

(15) Both of these reactions are favored at low temperatures. In this regard, both the air capture and air sequestration processes described herein may use electricity and/or thermal energy generate by the fossil fuel power plant 30 to drive the necessary reactions power the appropriate system components. In an exemplary embodiment of the present invention, a high temperature carrier may be heated up to a temperature in a range of about 400 C. to about 500 C. to generate steam to run a generator for electricity, and the lower temperature steam that exits from the electrical generating turbines can be used to drive off the CO.sub.2 and regenerate the sorbent (e.g., NaOH). The temperature of the high temperature heat, the generated electricity and the temperature of the lower temperature process heat remaining after electricity production can be adjusted to produce the mix of electricity production and CO.sub.2 removal that is considered optimal for a given application. In addition, in exemplary embodiments, still lower temperature process heat that emerges out of the capture and sequestration steps may be used to cool equipment used in these steps.

(16) One or more systems for removing carbon dioxide from an atmosphere may be used as part of a global thermostat according to an exemplary embodiment of the present invention. By regulating the amount of carbon dioxide in the atmosphere and hence the greenhouse effect caused by carbon dioxide and other gas emissions, the system described herein may be used to alter the global average temperature. According to at least one exemplary embodiment of the present invention, several carbon dioxide capture and sequestration systems may be located at different locations across the globe so that operation of the multiple systems may be used to alter the CO.sub.2 concentration in the atmosphere and thus change the greenhouse gas hearing of the planet. Locations may be chosen so as to have the most effect on areas such as large industrial centers and highly populated cities, or natural point sources of CO.sub.2 each of which could create locally higher concentrations of CO.sub.2 that would enable more cost efficient capture. For example, as shown in FIG. 4, multiple systems 1 may be scattered across the globe, and international cooperation, including, for example, international funding and agreements, may be used to regulate the construction and control of the systems 1. In this regard, greenhouse gases concentration can be changed to alter the average global temperature of the planet to avoid cooling and warming periods, which can be destructive to human and ecological systems. During the past history of our planet, for example, there have been many periods of glaciation and rapid temperature swings that have caused destruction and even mass extinctions. Such temperature swings in the future could be a direct cause of massive damage and destabilization of human society from conflicts resulting from potential diminished resources. The global thermostat described herein may be the key to preventing such disasters in the decades to come.

(17) Preferably, the air extraction system 42 and the sequestration system 50 are located at a facility that is separate from the fossil fuel power plant 30. Thus, the overall system 2 functions to remove from the atmosphere carbon dioxide produced by sources other than the fossil fuel power plant 30. It should also be appreciated that in an embodiment of the invention, the air extraction system 42 and the sequestration system 50 may be used to remove the equivalent amount of CO.sub.2 generated by the fossil fuel power plant, so that the entire facility may be considered carbon neutral. Also, removing CO2 from the atmosphere, rather than directly from the flue gases, is advantageous in that it avoids the pollutants in the flue gases that would poison the adsorbent and otherwise negatively effect costs and operations.

(18) While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.