Co 2 capture device using cavitation

Abstract

The present invention relates to methods for capturing carbon dioxide that employ a series of linked chemical process steps and unique heat-recovery and heat-transfer methods which together provide a low energy penalty. The methods include recovery of heat from carbon capture components, i.e., internal heat recovery, and recovery of heat from an external source, e.g., from power generation facility flue gas.

Description

CO2 CAPTURE DEVICE USING CAVITATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 63 / 551,945, filed February 9, 2024, hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The invention relates generally to the reduction of carbon dioxide in the atmosphere and, more particularly, to the capture and sequestration of carbon dioxide.BACKGROUND

[0003] Gases that trap heat in the atmosphere are called greenhouse gases. The concentration of greenhouse gases in the atmosphere has been rapidly increasing in recent years. Climate scientists have established a correlation between greenhouse gas concentrations in the atmosphere and the earth’s temperatures. Over the last century, the rate at which greenhouse gases are emitted into the atmosphere has increased. A concomitant rise in the rate at which average temperatures have increased has also been observed.

[0004] CO2 is the most abundant greenhouse gas, and its rate of production and release into the atmosphere is increasing annually. Reducing CO2 emissions into the atmosphere can help mitigate global warming and climate change, however, reducing CO2 emissions at the global level has proved difficult. For example, the Paris Agreement is an international treaty on climate change whose goal is to reduce greenhouse gas emissions and keep the rise in mean global temperature to below 2 °C. In 2015, the European Union and 194 countries initially ratified or acceded to the Paris Agreement. Within two years, the United States ceased participation in the Paris Agreement, contending that the agreement put the United States at a permanent disadvantage.

[0005] Another option for reducing atmospheric CO2 concentrations involves the capture of CO2 and subsequent sequestration in solid form. Several technologies are available to capture CO2 from large CCh-emitters like fossil fuel power plants. Chemical absorption capture technologies use CCE-absorbing chemicals, including various amines and basic species. Chemical looping combustion (CLC) uses the concept of preventing CO2 dilution with flue gases by avoiding the direct contact between flue and combustion air. In CLC processes, oxygen required for combustion of fuel is supplied in the form of metal oxide in solid phaseinstead of gaseous oxygen. Enzyme based separation techniques remove CO2 from gas mixtures by harnessing naturally occurring reactions of CO2 in living organism. In one example, the enzyme carbonic anhydrase is used to convert CO2 into bicarbonate. Although these processes have been shown to be capable of capturing CO2, many existing process suffer from various shortcomings, including low capacity, low selectivity, and high separation costs. There exists a need in the industry for an efficient and robust carbon capture system that addresses these shortcomings.SUMMARY

[0006] The present inventor has devised a method for capturing CO2 that addresses the issues discussed above. The solution resides in the use of a single reaction unit in which a carbon capture reaction and a carbon conversion reaction are performed. The use of a single reaction unit reduces complexity and reduces process costs in comparison to other carbon capture systems. The single reaction unit efficiently drives the conversion of starting materials to the desired products with product yields that are significantly higher than existing carbon capture methods. The single reaction unit method employs an agitation device that not only mixes components but also helps drive capture and conversion reactions to completion. Gasliquid and solid-liquid mass transport barriers are overcome using a triphasic reaction mixture in combination with a high shear rate agitator.

[0007] Some aspects of the disclosure are directed to a method for capturing CO2 and storing the CO2 in the form of a mineral carbonate. In some aspects, the method comprises combining a gas stream comprising CO2, a stream comprising Mg(OH)2, and a stream comprising CaCh to provide a combined stream; feeding the combined stream through an agitating device; forming CaCOa and MgCh in the combined stream; collecting an agitating device effluent stream comprising the CaCOa and MgCh; and recovering the CaCOa from the effluent stream. In some aspects, the Mg(OH)2 is in solid form. In some aspects, the solid Mg(OH)2 has an average particle size ranging from 1 pm to 10 pm. In some aspects, the solid Mg(OH)2 has an average particle size that is any one of, less than, greater than, or in between 1 pm, 2 pm, 3 pm, 4 pm, 5 pm, 6 pm, 7 pm, 8 pm, 9 pm, and 10 pm, or any range derivable therein. In some aspects, the solid Mg(OH)2 has an average particle size of about 4 pm. In some aspects, the Mg(OH)2 is in an aqueous solution. In some aspects, the Mg(OH)2 further comprises MgCh. In some aspects, the MgCh is in solid form. In some aspects, the MgCh is in an aqueous solution. In some aspects, the combined stream comprises three phases, solid, liquid, and gas. In some aspects, the combined stream is in the form of a slurry. In some aspects,the slurry is an aqueous comprises solids and dissolved salts. In some aspects, agitating the combined stream comprises feeding the combined stream through an agitating device selected from the group consisting of a flow-through cavitation device, a horizontal mixer, a spiral mixer, a planetary drive mixer, a paddle mixer, a vortex mixer, an ultrasonic mixer, a rotating tank agitator, a shaker, and a homogenizer. In some aspects, the agitating device adds heat to the combined stream, and the heat promotes a reaction that forms the CaCOa and MgCh. In a flow-through cavitation device, a fluid flows through the device and a spinning rotor creates numerous bubbles in the fluid that quickly collapse. The rapid formation and collapse of bubbles creates pressurized shock waves, shear forces, and localized heating. The shockwaves, shear forces and heating can accelerate the reaction of reactants in the fluid. A flow-through cavitation device can be controlled by varying rotor rotation rate. The cavitation device interior exhibits little to no temperature gradients, and little to no scaling or fouling of the rotor and other components is observed. A flow-through cavitation device provides efficient mixing, increased reaction rates, and improved product yields. In some aspects, a flow-through cavitation device is used to increase the rate of conversion of Mg(0H)2, CaCh, and CO2 into CaCOa and MgCh. In some aspects, a plurality of agitating devices are used. Agitating devices can be used in parallel to simultaneously process multiple combined streams, or in series to increase the conversion of carbon capture and conversion reactions. In some aspects, a combination of different agitating devices can be used. The different agitating devices can be used in series or parallel. In some aspects, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more agitating devices can be arranged to process one or more combined streams. In some aspects, a plurality of agitating devices can be arranged in a series / parallel arrangement where each of two or more agitating devices can be arranged in parallel, and each parallel path can include one or more agitating devices in series. In some aspects, the combined stream within the agitating device is at a temperature ranging from 20 °C to 55 °C. The combined stream within the agitating device may be at a temperature that is any one of, less than, greater than, or between 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55 °C, or any range derivable therein.

[0008] In some aspects, an agitating device effluent stream comprises both MgCh in solution and solid CaCCh, and the solid CaCCh is separated from the solution-phase MgCh by filtration. In some aspects, the agitating device effluent stream comprises water. In some aspects, a concentration of MgCh in the agitating device effluent stream ranges from 5% to 25%, by weight. In some aspects, the concentration of MgCh in the agitating device effluentstream is any one of, less than, greater than, or in between 5 %, 6 %, 7% , 8 %, 9 %, 10 %, 11 %, 12 %, 13 %, 14 %, 15 %, 16 %, 17 %, 18 %, 19 %, 20 %, 21 %, 22 %, 23 %, 24 %, and 25 % by weight, or any range derivable therein. In some aspects, a concentration of MgCh in the agitating device effluent stream is about 15% by weight. In some aspects, the concentration of MgCh in the agitating device effluent stream is measured as the ratio of mass of MgCh to mass of the agitating device effluent stream. In some aspects, the agitating device effluent stream comprises substantially no CaCh. In some aspects, the agitating device effluent stream comprises substantially no Mg(OH)2. In some aspects, the CO2 from the gas stream is sequestered in the form of precipitated calcium carbonate (PCC). In some aspects, the PCC has a purity that is greater than or equal to 99%. In some aspects, the agitating device effluent stream is fed to an uptake reactor. The use of a post-agitation uptake reactor allows for further carbonation of remaining, unreacted intermediates such that the reaction to final calcium carbonate product is driven to completion. In some aspects, the agitating device effluent stream is fed to de-aeration tank. In some aspects, some gases dissolved in the effluent stream are removed in the de-aeration tank. In some aspects, the effluent stream in the de-aeration tank is at atmospheric pressure. In some aspects, the effluent stream in the de-aeration tank is at a pressure that is less than atmospheric pressure. Reducing pressure of the effluent stream in the de-aeration tank promotes the removal of gases dissolved in the effluent stream.

[0009] In some aspects, a method for capturing CO2 further comprises generating Mg(OH)2 from a MgCh-containing material. In some aspects, the method comprises heating a MgCh-containing material in the presence of water to form HC1 and Mg(OH)2. In some aspects, the water is in the form of steam. In some aspects, the water is in the form of liquid water. In some aspects, the MgCh-containing material is a hydrate of MgCh. In some aspects, the hydrate of MgCh has the formula (I)MgCh nH2O (I) where n is from 1 to 12. In some aspects, Mg(OH)2 generated from a MgCh-containing material is used as an input for CO2 sequestration. In some aspects, Mg(OH)2 generated from a MgCh-containing material is combined with a gas stream comprising CO2 and with an aqueous stream comprising CaCh to provide a combined stream that is then agitated to form MgCh and CaCCh.

[0010] In some aspects a solution comprising MgCh or an aqueous stream comprising MgCh is de-watered to provide a MgCh-containing material. In some aspects, de-watering theaqueous solution of magnesium chloride comprises removing at least a portion of water from the aqueous stream comprising MgCh using a boiler / evaporator to provide a concentrated solution of magnesium chloride. The boiler / evaporator generates steam, in some aspects. In some aspects, heat is recovered from steam generated by the boiler / evaporator. In some aspects, the method further comprises the step of removing additional water from the aqueous stream comprising MgCh using a spray dryer. In some aspects, at least a portion of the heat used by the boiler / evaporator is recovered heat. In some aspects, a MgCh-containing material obtained by de-watering is recycled. In some embodiments, a MgCh-containing material obtained by de-watering is heated in the presence of water to form HC1 and Mg(0H)2. In some aspects, Mg(0H)2 derived from a MgCh-containing material is used as in input for CO2 sequestration. In some aspects, an input for CO2 sequestration is at least one of a gas stream comprising CO2, an aqueous stream comprising Mg(0H)2, and an aqueous stream comprising CaCh.

[0011] The ability to recover heat from areas with surplus heat and use the energy from that heat, whether it be in the same form or a different form, in a different heat-absorptive part of the carbon capture process reduces the need from heat or energy from a power production facility. This thermodynamic coupling between various components of the carbon capture process provides a means by which the energy penalty can be reduced. Heat recovery from sources within the carbon capture process (internal) and from un-used or waste heat from the power production facility reduces the need from heat or energy from a power production facility.

[0012] It is specifically contemplated that any limitation discussed with respect to one embodiment of the invention may apply to any other embodiment of the invention. Furthermore, any composition of the invention may be used in any method of the invention, and any method of the invention may be used to produce or to utilize any composition of the invention.

[0013] Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a block diagram of a carbon dioxide sequestration process according to some embodiments of the present invention.

[0015] FIG. 2 is a process flow diagram of a carbon sequestration process according to some embodiments of the present invention.DETAILED DESCRIPTION

[0016] The present invention relates to methods for capturing carbon dioxide and permanently sequestering carbon dioxide in the form of a mineral carbonate.

[0017] As used herein, the term de-watering signifies removing water from a solution or mixture that contains water. In some aspects, de-watering is performed to completion, such that substantially all water is removed. In some aspects, de-watering is not performed to completion, such that some water remains in the original, water-containing solution or mixture.

[0018] As used herein, the terms “carbonates” or “carbonate products” are generally defined as mineral components containing the carbonate group, [CCh]2'. Thus, the terms encompass both carbonate / bicarbonate mixtures and species containing solely the carbonate ion. The terms “bicarbonates” and “bicarbonate products” are generally defined as mineral components containing the bicarbonate group, [HCCh]1’. Thus, the terms encompass both carbonate / bicarbonate mixtures and species containing solely the bicarbonate ion.

[0019] As used herein “Ca / Mg” signifies either Ca alone, Mg alone or a mixture of both Ca and Mg. The ratio of Ca to Mg may range from 0:100 to 100:0, including, e.g., 1:99, 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10, 95:5, and 99:1. The symbols “Ca / Mg”, “MgxCa(i-x)” and “CaxMg(i-x)” are synonymous. The phrases “Group II” and “Group 2” are used interchangeably. A hydrate of magnesium chloride refers to any hydrate, including but not limited to hydrates that have 2, 4, 6, 8, or 12 equivalents of water per equivalent of magnesium chloride. Based on the context, the abbreviation “MW” either means molecular weight or megawatts. The abbreviation “PFD” is process flow diagram. The abbreviation “Q” is heat (or heat duty), and heat is a type of energy. This does not include any other types of energy.

[0020] As used herein, the term “sequestration” is used to refer generally to techniques or practices whose partial or whole effect is to remove CO2 from point emissions sources and to store that CO2 in some form so as to prevent its return to the atmosphere. Use of this termdoes not exclude any form of the described embodiments from being considered “sequestration” techniques. The terms “capture” and “sequestration” are used interchangeably.

[0021] The use of the word “a” or “an,” when used in conjunction with the term “comprising” in the claims and / or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0022] Throughout this application, the term “about” is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

[0023] The terms “comprise,” “have” and “include” are open-ended linking verbs. Any forms or tenses of one or more of these verbs, such as “comprises,” “comprising,” “has,” “having,” “includes” and “including,” are also open-ended. For example, any method that “comprises,” “has” or “includes” one or more steps is not limited to possessing only those one or more steps and also covers other unlisted steps.

[0024] The above definitions supersede any conflicting definition in any of the reference that is incorporated by reference herein. The fact that certain terms are defined, however, should not be considered as indicative that any term that is undefined is indefinite. Rather, all terms used are believed to describe the invention in terms such that one of ordinary skill can appreciate the scope and practice the present invention.

[0025] The present disclosure generally relates to processes for sequestration of carbon dioxide in the form of calcium carbonate by capture of carbon dioxide, conversion into calcium carbonate, and disposal, storage, and / or sale of the calcium carbonate. The processes described herein provide useful technologies for cost-effective, energy-efficient, and environmentally carbon capture and conversion. The sequestration of carbon dioxide in solid form and subsequent disposal, sale, or storage in repositories is a technology that is useful for reducing carbon dioxide emissions to the atmosphere and contributing to the fight against climate change and global warming. The methods disclosed herein allow for the production of high purity CaCOa, known as Precipitated Calcium Carbonate, a high-end commodity cousin of limestone that is used, for example, in paper for its white-purity, as well as in plastics as a filler.

[0026] The methods disclosed herein relate to the capture and conversion of carbon dioxide in the form of a mineral carbonate. The source of carbon dioxide may be any carbon dioxide source, including atmospheric carbon dioxide. The carbon dioxide may be substantially pure carbon dioxide or comprise multiple components that include carbon dioxide and one ormore additional gases and / or other substances such as ash and other particulates. The carbon dioxide may be, for example, anthropogenic, or originating from human activity. In some embodiments, the carbon dioxide may be obtained from a waste gas stream, such as a flue gas from an electricity production plant, a cement production facility, a chemical processing plant, a steel production facility, or other industrial plant that produces carbon dioxide as a byproduct.

[0027] Industrial waste gas streams can contain carbon dioxide as the primary non-air derived component, and can contain additional components such as nitrogen oxides (NOx), sulfur oxides (SOx), and one or more additional gases. Additional gases and other components may include dust particles, for example, from calcining and combustion processes, mercury and other heavy metals, and carbon monoxide. Additional components in the gas stream may also include particulate matter such as fly ash, dusts, and metals including vanadium, thallium, strontium, selenium, molybdenum, mercury, manganese, lead, cobalt, chromium, cadmium, beryllium, boron, and arsenic; halides like hydrogen fluoride and hydrogen chloride; and organics such as un-combusted hydrocarbons. In some aspects, gaseous waste streams that can be treated to remove carbon dioxide can include carbon dioxide in amounts of 10 ppm to 1,000,000 ppm. For example, gaseous waste streams that include about 10 ppm to about 200,000 ppm, including about 1000 ppm to about 200,000 ppm, about 2000 ppm to about 200,000 ppm, about 3000 ppm to about 200,000 ppm, about 4000 ppm to about 200,000 ppm, about 5000 ppm to about 200,000 ppm, about 6000 ppm to about 200,000 ppm, about 7000 ppm to about 200,000 ppm, about 8000 ppm to about 200,000 ppm, about 9000 ppm to about 200,000 ppm, and about 10,000 ppm to about 200,000 ppm, or any amount between 10 ppm and 1,000,000 ppm can be treated to remove carbon dioxide using the methods disclosed herein.

[0028] In some aspects, the methods disclosed herein are performed at a temperature range of between about 30 °C to about 100 °C. In some aspects, the step of feeding the combined stream through an agitating device is performed at a temperature range of between about 30 °C. to about 100 °C. The methods disclosed herein can be performed at a temperature that is any one of, less than, greater than, between, or any range thereof of 30 °C, 31 °C, 32 °C, 33 °C, 34 °C, 35 °C, 36 °C, 37 °C, 38 °C, 39 °C, 40 °C, 41 °C, 42 °C, 43 °C, 44 °C, 45 °C, 46 °C, 47 °C, 48 °C, 49 °C, 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C, 60 °C, 61 °C, 62 °C, 63 °C, 64 °C, 65 °C, 66 °C, 67 °C, 68 °C, 69 °C, 70 °C, 71 °C, 72 °C, 73 °C, 74 °C, 75 °C, 76 °C, 77 °C, 78 °C, 79 °C, 80 °C, 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, 86°C, 87 °C, 88 °C, 89 °C, 90 °C, 91 °C, 92 °C, 93 °C, 94 °C, 95 °C, 96 °C, 97 °C, 98 °C, 99 °C, and 100 °C. In some aspects, the agitating device serves as a reactor in which both decarbonation and precipitation take place. By employing an agitating device as a reactor, chemical intermediates can be instantly reacted. The short reaction times observed using an agitating device as a reactor is a marked improvement over the longer periods of time associated with conventional processes in which intermediate concentration increases to respective solubility limits are rate-limiting and limit overall process duration. By including all reactants in a combined stream, low reaction rates associated with low solubility of intermediates is averted, thereby decreasing the residence time of intermediates and increasing the overall process rate.

[0029] In some aspects, the combined stream comprises a liquid:gas ratio ranging from 1:1 to 10:1. The combined stream can be provided at a liquid:gas ratio that is any one of, less than, greater than, between, or any range thereof of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, and 10:1.

[0030] A magnesium-containing material of the present disclosure may be, for example, a mineral selected from the group consisting of dolomite, magnesite, brucite, carnallite, talc, olivine, hydromagnesite, forsterite, pyrope, spessartine, grossular, andradite, uvarovite, hydrogrossular, norbergite, chondrodite, humite, clinohumite, datolite, titanite, chloritoid, lawsonite, axinite, ilvaite, epidote, zoisite, tanzanite, clinozoisite, allanite, dollaseite, vesuvianite, paopgoite, tourmaline, osumilite, cordierite, sekaninaite, eudialyte, milarite, enstatite, pigeonite, diopside, hedenbergite, augite, proxferroite, wollastonite, pectolite, anthophyllite, cummingtonite, tremolite, actinolite, hornblende, glaucophane, arfvedsonite, antigorite, chrysotile, lizardite, illite, montmorillonite, chlorite, vermiculite, sepiolite, palygorskite, biotite, phlogopite, margarite, glauconite, oligoclase, andesine, labradorite, bytownite, anorthite, cancrinite, hauyne, lazurite, erionite, chabazite, heulandite, stilbite, scolecite, mordenite, and clinoenstatite. A magnesium-containing material can be used as a source for magnesium salts, including but not limited to magnesium chloride, magnesium hydroxide, and magnesium oxide. In some aspects, a magnesium-containing material is treated with acid to aid in the breakdown and / or dissolution of the magnesium-containing material. In some aspects, hydrochloric acid (HC1, aq.) is used to treat a magnesium-containing material in order to obtain one or more magnesium salts. In some aspects, acid and a magnesium- containing material can be allowed to react without mechanical agitation or abrasion of solids. In some aspects, acid and magnesium-containing material can be subjected to mechanicalagitation and / or abrasion of solids. In some aspects, contacting a magnesium-containing material with acid is performed at ambient temperature. In some aspects, contacting a magnesium-containing material with acid is performed at greater-than-ambient temperature. In some aspects, the step of contacting a magnesium-containing material with acid is performed at ambient pressure. In some aspects, the step of contacting a magnesium-containing material with acid is performed at greater-than-ambient pressure. Liquid can be added to a mixture of acid and magnesium-containing material in order to increase contact between the acid and magnesium-containing material. In some aspects, contacting of the magnesium-containing material with acid allows the acid to react with the magnesium-containing material and leach salts from the magnesium-containing material into a brine or slurry. The brine or slurry can be recovered, and this brine or slurry contains magnesium salts from the magnesium-containing material. The magnesium salts present in a brine or slurry can be in solution, in solid form, or a combination of solution and undissolved solid. The magnesium salts present in a brine or slurry can be recovered using one of a variety of methods known to those of skill in the art. A brine or slurry containing leached salts can be transferred to a settling tank. Solids within the brine or slurry can be allowed to settle at the bottom of the settling tank. Alternatively, filters can be employed to remove solids from the brine or slurry. The brine or slurry can be transferred to an evaporation pond where liquid in the brine or slurry is allowed to evaporate. Solar energy and / or naturally-occurring wind can be harnessed to increase the rate of evaporation. In some aspects, no energy is provided to the evaporation pond to increase the rate of evaporation. In some aspects, non-renewable energy is not used to increase the rate of evaporation.

[0031] Carbon that is sequestered from a gas stream comprising carbon dioxide, reduction of a greenhouse gas emission, or any other type of carbon-neutral or carbon-negative activity associated with using the methods disclosed herein can be used to obtain an environmental credit, such as a carbon credit. Carbon credits are incentives that are issued to reduce greenhouse gas emissions by capping total annual emissions and letting the market assign a monetary value to a tradable unit.

[0032] In some aspects, the methods disclosed herein involve a multi-phasic mixture that includes liquid, solid, and gaseous components. Reactions including the multi-phase mixtures can be performed in a high temperature and high-pressure reactor which can be equipped with multiple ports for introducing solids, liquids, and / or gases and recovering solid- , liquid-, and / or gas-phase components. Concentration of gas-phase components can bedetermined using a gas chromatograph, for example. The identities and amounts of dissolved metals and potential organic constituents in an aqueous-phase can be determined using Ion Chromatography (“IC”), Nuclear Magnetic Resonance (“NMR”), and / or Inductively Coupled Plasma - Atomic Emission Spectroscopy (“ICP-AES”) analyses, for example. Carbonate content in a solid can be determined using Thermogravimetric Analysis (“TGA”), for example. Solid component pore and particle sizes can be determined using BET Pore Size Analysis and Laser Diffraction Particle Size Analysis, respectively.

[0033] Heat that is generated outside of the carbon capture process can be harnessed. In some aspects, a carbon capture system can be coupled to a power plant in order to reduce the carbon footprint of the power plant. Waste heat generated by power plants is typically released to the environment in the form of steam and other gases. This un-used waste heat can be exploited by tying it to a carbon capture system. As described herein, a carbon capture system can make use of external, co-generated heat in order to reduce energy input requirements. The net result of linking un-used waste heat allows for a carbon capture process that radically reduces the amount of net-heat required by the overall process.

[0034] In some aspects, the carbon capture process involves harvesting CO2 from a CCE-emission source, such as from flue gas of a power generation facility. In some aspects, heat is harvested from the CCE-emission source flue gas. Traditionally, flue gas from a power generation facility is released into the atmosphere. The flue gas includes water in the form of water vapor or steam, and additional gases. This waste flue gas can be harnessed in order to recover heat. The recovered heat can then be used to generate electricity, power a compressor, generate steam, and / or increase the temperature of steam. The steam may be generated, in part, from heat recovered during different segments of the carbon capture process, may be recovered from a power plant, or may be a combination derived from different sources.

[0035] The process disclosed herein comprises the steps of (a) combining a gas stream comprising CO2, an aqueous stream comprising Mg(OH)2, and an aqueous stream comprising CaCh to provide a combined stream, (b) feeding the combined stream through an agitating device, (c) forming CaCOa and MgCh in the combined stream, (d) collecting an agitating device effluent stream comprising the CaCOa and MgCh, and (e) recovering the CaCOa from the effluent stream. The agitating device effluent stream can be passed through a decarbonation-uptake reactor, for example, in a bubble column, prior to recovering the CaCOa from the effluent stream. In conventional Ca / Mg-based carbon capture methods, the purity of calcium carbonate is reduced by the presence of residual and trace magnesium. The use of apo st- agitation uptake reactor allows for further carbonation of remaining, unreacted intermediates such that the reaction to final calcium carbonate product is driven to completion. This reduces residual carbonated magnesium intermediates, and increases the conversion and ultimate purity of the calcium carbonate product. This also decreases the amount of residual, unreacted calcium chloride from the agitating device effluent stream, thereby providing a higher-purity, reduced-calcium aqueous magnesium chloride solution. In some aspects, a second post-agitation reactor is used. A second post-agitation uptake reactor can be used to further carbonation of remaining, unreacted intermediates such that the reaction to final calcium carbonate product is driven to completion.

[0036] Upon precipitation of the CaCOa product, an essentially pure, aqueous MgCh solution remains. Various methods may be used to separate the solid CaCOa from the aqueous MgCh solution. In one example, solid and solution are separated by passive-hydrostatic pressure, i.e., natural draining with hydrostatic -head pressure filtration. In some aspects, the agitating device effluent stream is passed through a de-aeration vessel in which the carbon dioxide-depleted effluent stream is allowed time to separate. The agitating device effluent stream residence time within the de-aeration vessel can range from 5 seconds to 10 minutes, for example. The agitating device effluent stream residence time within the de-aeration vessel can be any one of, less than, greater than, between, or any range thereof of 5 seconds, 10 seconds, 15 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, and 10 minutes. Carbon dioxide uptake, conversion into intermediate magnesium carbonate, magnesium bicarbonate, and / or magnesium sesquicarbonate (Mg(OH)HCO3), and subsequent conversion into a precipitated calcium carbonate (PCC) product occur rapidly within the agitating device. Dissolution of Mg(OH)2 from solid form is accelerated by agitation within the agitation device, and reaction between hydroxide ion and carbon dioxide removes hydroxide ion from solution, which further aids in and increases the rate of Mg(OH)2 dissolution. The methods disclosed herein that employ an agitating device can provide a carbon dioxide capture of greater than 80%, and up to 99%, based upon the starting carbon dioxide concentration in the gas stream comprising carbon dioxide.

[0037] The magnesium chloride solution can be de-watered to regenerate solid magnesium chloride, or a hydrate thereof. In an exemplary de-watering process, waste heat recovered from a flue gas stream may be used to drive the removal of water. In some aspects,a two-step de-watering process is employed whereby at least a portion of water from the magnesium chloride solution is removed in a first step using a boiler / evaporator, and at least a portion of remaining water is removed in a second step using a spray-dryer. The boiler / evaporator may be employed to remove at least a portion of water in the magnesium chloride solution to produce an intermediate fluid. This intermediate fluid may then be transferred to a spray-dryer that heats the intermediate fluid. The intermediate fluid may be flashed under pressure during which water / steam is separated as a vapor, and crystals of magnesium chloride hydrate. The regenerated magnesium chloride hydrate can then be transferred to a magnesium chloride decomposition reactor for subsequent reaction with water to provide magnesium hydroxide.EXAMPLES

[0038] The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

[0039] FIG. 1 is a diagram depicting a carbon capture process 100 as disclosed herein. At step 110, a gas stream comprising CO2, an aqueous stream comprising Mg(OH)2, and an aqueous stream comprising CaCh are joined to provide a combined stream. In some aspects, the combined stream is a three-phase stream comprising solid, liquid, and gaseous components. At step 120, the combined stream is fed through an agitating device. In the agitating device, reactants CO2, Mg(OH)2, and CaCh in the combined stream are converted into products CaCCh and MgCh. At step 130, an effluent stream from the agitating device is collected. The effluent stream comprises CaCOa and MgCh products, and can additional include unreacted starting materials (CO2, Mg(OH)2, and CaCh) and intermediates. At step 140, the effluent stream is fed to a post- agitation decarbonation-uptake reactor. In the decarbonation-uptake reactor, unreacted intermediates can react to form the desired CaCOa and MgCh products, thereby pushing the decarbonation process further towards completion and increasing product yield. At step 150, CaCOa is recovered from the effluent stream by separating the solid CaCOa from the liquid phase that includes MgCh in solution. At step 160, the effluent stream from whichCaCOa has been removed is de-watered to provide a MgCh-containing material. At step 170, the MgCh-containing material is reacted with water to form Mg(OH)2 and HC1. At step 180, the Mg(OH)2 is recycled and provided as an input stream to the agitating device.

[0040] The carbon capture process employs a compact assembly of vessels and pumps that achieves 80-99% CO2 reduction. The carbon capture process disclosed herein combines decarbonation and precipitation reactions together and uses a single reactor to capture CO2 and convert it into a storable or saleable mineral calcium carbonate product of high purity.

Claims

CLAIMS1. A method for capturing CO2 from a gas stream and sequestering the CO2 in the form of a mineral carbonate comprising:(a) combining a gas stream comprising CO2, a stream comprising CaCh, and a stream comprising Mg(0H)2 to provide a combined stream;(b) feeding the combined stream through an agitating device;(c) forming CaCOa and MgCh in the combined stream;(d) collecting an agitating device effluent stream comprising the CaCOa and MgCh; and(e) recovering the CaCOa from the effluent stream.

2. The method of claim 1, wherein the Mg(0H)2 is in solid form.

3. The method of claim 2, wherein the solid Mg(0H)2 has an average particle size ranging from 1 pm to 10 pm.

4. The method of claim 2, wherein the solid Mg(OH)2 has an average particle size of about 4 pm.

5. The method of claim 1, wherein the Mg(OH)2 is in an aqueous solution.

6. The method of claim 1, wherein the stream comprising Mg(OH)2 further comprises MgCh.

7. The method of claim 6, wherein the MgCh is in solid form.

8. The method of claim 6, wherein the MgCh is in an aqueous solution.

9. The method of claim 1, wherein a concentration of MgCh in the agitating device effluent stream ranges from 5% to 25%, by weight.

10. The method of claim 9, wherein a concentration of MgCh in the agitating device effluent stream is about 15% by weight.

11. The method of claim 1, wherein the agitating device effluent stream comprises substantially no CaCh.

12. The method of claim 1, wherein the agitating device effluent stream comprises substantially no Mg(0H)2.

13. The method of claim 1, further comprising feeding the agitating device effluent stream to a de-aeration tank.

14. The method of claim 13, wherein the agitating device effluent stream within the deaeration tank is at atmospheric pressure.

15. The method of claim 1, wherein the combined stream within the agitating device is at a temperature ranging from 20 °C to 55 °C.

16. The method of claim 1, wherein agitating the combined stream comprises feeding the combined stream through a flow-through cavitation device.

17. The method of claim 16, wherein the flow-through cavitation device generates areas of low pressure in the combined stream that collapse and generate pressure waves through the combined stream.

18. The method of claim 17, wherein repeated generation and collapse of low pressure areas promotes a reaction that forms the CaCOa and MgCh.

19. The method of claim 1, wherein the CaCOa in step (c) is in solid form.

20. The method of claim 1, wherein the MgCh in step (c) is in solution.

21. The method of claim 20, wherein the solution of MgCh is an aqueous solution.

22. The method of claim 1, wherein recovering the CaCOa from the effluent stream comprises separating the precipitated CaCOa from the agitating device effluent stream comprising MgCh in solution by filtration.

23. The method of claim 1, wherein the CO2 from the gas stream is sequestered in the form of precipitated calcium carbonate (PCC).

24. The method of claim 23, wherein the PCC has a purity that is greater than or equal to 99%.

25. The method of claim 1, further comprising heating a MgCh-containing material in the presence of water to form HC1 and Mg(OH)2.

26. The method of claim 25, wherein the water is in the form of steam.

27. The method of claim 25, wherein the MgCh-containing material is a hydrate of MgCh.

28. The method of claim 27, wherein the hydrate of MgCh has the formula (I)MgCl2nH2O (I) where n is from 1 to 12.

29. The method of claim 1, wherein the Mg(OH)2of step (a) is the Mg(OH)2of claim 25.

30. The method of claim 21 , further comprising de-watering the aqueous solution of MgCl2to provide a MgCh-containing material.

31. The method of claim 30, wherein the MgCh-containing material is recycled.

32. The method of claim 31, wherein the recycled MgCh-containing material is heated in the presence of water to form HC1 and Mg(OH)2.

33. The method of claim 32, wherein the Mg(OH)2derived from the recycled MgCh- containing material is the recycled Mg(OH)2of claim 1.

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