Methods for carbon credit generation and engineered production of carbonate minerals

Abstract

Systems, devices and methods for sequestering carbon dioxide through the production of carbonate minerals from divalent metal oxide bearing material are described herein. A method includes adding the divalent metal oxide bearing material into a carbonation reactor along with water and carbon dioxide, and operating the carbonation reactor under conditions to convert the divalent metal oxides into a carbonate minerals. To generate a carbon credit, energy used by the process and the mass of mineralized carbon entering and exiting the process may be monitored and reported to an issuer of carbon credits.

Description

METHODS FOR CARBON CREDIT GENERATION AND ENGINEERED PRODUCTION OF CARBONATE MINERALSTECHNICAL FIELD

[0001] The following relates generally to systems, devices and methods for sequestering carbon through the production of carbonate minerals and carbon credit generation associated therewith.BACKGROUND

[0002] Carbon Dioxide (CO2) is a key greenhouse gas. It is known to trap heat in the Earth’s atmosphere, thus contributing to global warming. It is estimated that human activities have raised the amount of CO2in the atmosphere by approximately 50% since the industrial revolution. Various human activities contribute to the release of atmospheric CO2, including large-scale fossil fuel power plants, industrial activities, transportation, urban development and deforestation.

[0003] As CO2emissions outpace the ability of the Earth’s flora to absorb CO2, the concentration of CO2in the atmosphere will continue to rise. As such, methods for reducing the concentration of CO2in the atmosphere are desirable. Methods may include both engineered carbon management systems and natural carbon management systems. Engineered carbon management systems use technology to directly reduce atmospheric CO2by concentrating and confining it in forms other than in the atmosphere while natural carbon management systems use natural cycles, like photosynthesis, to reduce atmospheric CO2levels.

[0004] One approach for the reduction of CO2in the atmosphere is through the process of carbon sequestration. Carbon sequestration is the long-term storage of carbon, and typically refers to capture and storage of carbon that would otherwise be released into the atmosphere. One form of carbon sequestration involves storing carbon in carbonate minerals. Divalent metals are known to be capable of bonding with carbonate ions to form carbonate minerals, and so divalent metals can be used in carbon sequestration methods.

[0005] Carbonate minerals are the largest natural reservoir of CO2. Each year, more than 300 million tonnes of atmospheric CO2are sequestered through a reaction called mineral carbonation, where oxides of divalent metals bind with CO2to form stable carbonateminerals. The rate at which mineral carbonation occurs can be accelerated through the use of engineered processes, which enable a rapid realization of a mineral’s carbonation potential which would otherwise occur on geologic timescales. Carbonation potential is the total chemical capacity of a unit of material to mineralize CO2, and its calculation can be determined using the modified Steiner equation. Engineered mineral carbonation is often considered as a basis for both carbon management technologies, where mineral oxides are used as sorbents to bind with CO2either temporarily (carbon capture) or for more than 100 years (carbon storage). A key advantage of mineralized CO2is that there is minimal risk of future leakage back into the atmosphere.

[0006] Typical mineral oxide sorbent-based carbon capture technologies first transform the oxide mineral into a carbonate mineral and second calcining the carbonate mineral to produce both a pure stream of CO2and a regenerated oxide mineral for subsequent carbonation. An example of this is calcium looping carbon capture technology. Calcium looping technologies first carbonate calcium oxide, a divalent metal oxide bearing material (DMOBM), to form carbonate minerals using CO2contained in a mixed gas, such as flue gas, and then calcines the formed calcium carbonate to produce a stream of high purity CO2and regenerate calcium oxide. Calcination is a process where solid minerals are heated to the point where they thermally decompose, in this case releasing CO2that is chemically bound to the calcium. The system operates in a loop between the calcination and carbonation step.

[0007] Figure 1 illustrates typical carbon capture technologies which employ mineralization and calcination. The produced high purity stream of CO2is suitable for pipeline transport to an underground storage facility but requires access and infrastructure to connect the CO2source to the underground storage facility. Figure 2 is a schematic diagram depicting a chemical process involved with calcium looping for direct air capture.

[0008] While the CO2contained in the carbonate minerals formed in the carbonation step of an oxide mineral looping technology could store CO2in the long term and avoid calcination, there would be no net carbon benefit because of the typical production route for the oxide minerals generates significant greenhouse gas emissions.

[0009] For example, most mineral oxides are produced from the calcination of naturally occurring carbonate minerals, a proven and low-cost technology. The calcination (at 700- 1000°C) of limestone (naturally occurring Calcium carbonate) to produce 1 tonne of Calcium oxide inevitably releases at least 0.96 tonnes of C02from the limestone and additional CO2is emitted from the production of heat that enables the calcination, leading to typical embodied carbon footprint of 1.1 tonnes CO2per tonne of Calcium oxide. Embodied carbonfootprint is the magnitude of greenhouse gas emissions emitted to the atmosphere for the production of one unit of material. Embodied carbon footprint can be determined using standardized methods such as ISO 14064. The maximum amount of CO2that 1 tonne of Calcium oxide can bind with is 0.96 tonnes, meaning that the Calcium oxide must be regenerated (or looped) in a capture system to achieve a negative carbon balance. A negative carbon balance represents a net reduction in carbon from the atmosphere. The inclusion of looping requires additional capital cost, operating cost, energy demand compared to a system which uses only a carbonation step. It will be appreciated that a method of mineral carbonation technology that avoids the need for “looping” is desired.

[0010] To avoid the need for looping within a mineral oxide-based carbon management technology, one unit of the DMOBM used in the technology must have an embodied carbon footprint less than its carbonation potential of the same unit. For example, 1 tonne of DMOBM with a carbonation potential of 0.75 tonnes of CO2and an embodied carbon footprint of 0.15 tonnes of CO2equivalent can realize a carbon benefit of 0.6 tonnes of CO2.

[0011] A key aspect of carbon management systems is the proof of their impact on atmospheric carbon levels. Typically, an organization independent of the operation of carbon management system, such as a governmental body or carbon market registry, verifies the magnitude of impact on atmospheric carbon dioxide levels and issues carbon credits to the operator, generating the potential of a monetary benefit to the operator of the carbon management system. The issuance of carbon credits is an essential component of carbon management systems because it enables the operator to monetize their activities, a key incentive for reducing emissions of carbon dioxide in the atmosphere.

[0012] To generate a carbon credit it is necessary to precisely measure the carbon balance of a carbon management system, including its inputs and outputs, over its life cycle. For many types of carbon management systems, the measurement of carbon balance has a high level of uncertainty limiting the potential of the carbon management system to be utilized.

[0013] There have been various carbon management systems developed. Such methods are generally expensive and / or inefficient and / or have high levels of uncertainty, and, in any event, levels of CO2continue to rise. New systems, devices and methods for generating carbon credits, and thereby reducing atmospheric CO2, are needed.SUMMARY OF THE INVENTION

[0014] In one broad aspect of the invention, there is provided a method for realizing a net carbon emission reduction by sequestering carbon dioxide in carbonate materials by converting a low embodied carbon material containing divalent metals into carbonate mineral containing materials, the method comprising: obtaining divalent metal oxide bearing material with an embodied carbon footprint less than its carbon potential; combining said divalent metal oxide bearing material and carbon dioxide in an engineered reactor under conditions which enable the conversion of oxide minerals into carbonate minerals; and operating the carbonation reactor under conditions to convert the divalent metal oxides into carbonate minerals.

[0015] In one broad aspect of the invention, there is provided a method for sequestering carbon dioxide in carbonate materials by converting a feedstock containing divalent metals into carbonate materials, comprising: converting the feedstock into a divalent metal oxide bearing material; combining divalent metal oxide bearing material and carbon dioxide in a reactor under conditions which enable the conversion of oxide minerals into carbonate minerals; and operating the carbonation reactor under conditions to convert the divalent metal oxide bearing material into a carbonate material.

[0016] In another aspect of the invention, there is provided a method for sequestering carbon dioxide in carbonate materials by converting a feedstock containing divalent metals into carbonate materials, wherein the feedstock is a magnesium bearing feedstock, and the divalent metal oxide bearing material is made up mostly of magnesium, calcium, or a mixture of calcium and magnesium.

[0017] In another aspect of the invention, there is provided one or more of the above methods, wherein the carbon dioxide is obtained from direct air capture.

[0018] In another aspect of the invention, there is provided one or more of the above methods, wherein the carbonation reactor is operated for between 1 and 10 hours.

[0019] In another aspect of the invention, there is provided one or more of the above methods, wherein the carbonation reactor is operated for 2 hours.

[0020] In another aspect of the invention, there is provided one or more of the above methods, wherein the reactor is operated at a temperature between 10°C and 30°C.

[0021] In another aspect of the invention, there is provided one or more of the above methods, wherein the carbonation reactor is operated at a temperature of 20°C.

[0022] In another aspect of the invention, there is provided one or more of the above methods, wherein the composition of divalent metal oxide bearing material is between 2% solid and 8% solid.

[0023] In another aspect of the invention, there is provided one or more of the above methods, wherein the composition of the divalent metal oxide bearing material is 5% solid.

[0024] In another aspect of the invention, there is provided one or more of the above methods, wherein the pressure of carbon dioxide supplied to the carbonation reactor is between 70 and 90 psi.

[0025] In another aspect of the invention, there is provided one or more of the above methods, wherein the pressure of carbon dioxide supplied to the carbonation reactor is 80 psi.

[0026] In another aspect of the invention, there is provided one or more of the above methods, wherein sensors may be utilized to determine the net change in mineralized carbon to enable the generation of a carbon credit.

[0027] In another broad aspect of the invention, there is provided a method of generating a carbon credit through mineral carbonation using mineral waste, the method comprising: contacting divalent metal-bearing mineral waste or a material derived from mineral waste with a carbon dioxide-bearing fluid in an engineered reactor; continuously monitoring the mass flow of carbonate minerals in a feed stream entering the engineered reactor and monitoring the mass flow of carbonate minerals in effluent exiting the engineered reactor; and reporting the cradle-to-grave life cycle greenhouse gas emissions attributed to the reaction that occurs within the engineered reactor to an issuer of carbon credits. “Mineral waste” refers to byproducts of mining and mineral concentration processes, may be solid, liquid or airborne, and may include, without limitation, waste rock, tailings, steel slag, kiln dust, red mud, residues, and overburden.

[0028] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the divalent metal bearing mineral waste is a slurry.

[0029] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the divalent metal bearing mineral waste is a powder.

[0030] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the divalent metal bearing mineral waste is a liquid.

[0031] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the feed stream is completed using laser induced breakdown spectroscopy.

[0032] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the feed stream is completed using Raman spectroscopy analysis.

[0033] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the feed stream is completed using inductively coupled plasma optical emissions spectroscopy.

[0034] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the feed stream is completed using fourier transform infrared analysis.

[0035] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the feed stream is completed using volumetric calcimetry.

[0036] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the feed stream is completed using fluorescence spectroscopy.

[0037] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the effluent stream is completed using laser induced breakdown spectroscopy.

[0038] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the effluent stream is completed using Raman spectroscopy analysis.

[0039] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the effluent stream is completed using combustion infrared detection.

[0040] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the effluent stream is completed using inductively couple plasma optical emissions spectroscopy.

[0041] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the effluent stream is completed using fourier transform infrared analysis.

[0042] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the effluent stream is completed using volumetric calcimetry.

[0043] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein quantification of carbonate minerals contained in the effluent stream is completed using fluorescence spectroscopy.

[0044] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the carbon dioxide-bearing fluid is a post combustion flue gas.

[0045] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the carbon dioxide-bearing fluid is a flue gas from cement production.

[0046] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the carbon dioxide-bearing fluid is a greater than 95% purity carbon dioxide gas concentrated by carbon dioxide capture.

[0047] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the carbon dioxide-bearing fluid is a biogas from anaerobic digestion.

[0048] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the carbon dioxide-bearing fluid is a liquified carbon dioxide.

[0049] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the mineral waste is historic mine tailings.

[0050] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the mineral waste is operating mine tailings.

[0051] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the mineral waste is steel slag.

[0052] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the mineral waste is cement kiln dust.

[0053] In another aspect of the invention, there is provided the above method of generating a carbon credit, wherein the mineral waste is red mud.BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Embodiments will now be described by way of example only with reference to the appended drawings wherein:

[0055] Figure 1 is a schematic prior art diagram depicting a typical arrangement for fluegas mineralization using calcium looping;

[0056] Figure 2 is a schematic prior art diagram depicting main processes involved with calcium looping for direct air capture;

[0057] Figure 3 is a generalized block flow diagram of a process of the invention;

[0058] Figure 4 shows the components of data reported to issuers of carbon credits;

[0059] Figure 5 is a generalized block flow diagram showing a process of the invention;

[0060] Figure 6 is a generalized block flow diagram showing a process of the invention;

[0061] Figure 7 is a schematic diagram showing the conversion of a feedstock to DMOBM, and subsequent conversion of DMOBM into a carbonate material;

[0062] Figure 8 is a schematic diagram showing the carbonation process of an embodiment of the invention;

[0063] Figure 9 is a schematic diagram depicting measurements for determining carbon credits;

[0064] Figure 10 is a generalized block flow diagram showing a process of the invention;

[0065] Figure 11 is a piping and instrumentation diagram showing the carbonation reaction setup of Example 3; and

[0066] Figure 12 shows an embodiment of the carbonation reaction setup of Example 3.DETAILED DESCRIPTION OF THE INVENTION

[0067] In one embodiment of the invention, the invention disclosed herein describes a method of generating a carbon credit by producing carbonate minerals using a material containing divalent metal oxides and directly measuring the net gain in mineralized carbon. An embodiment of the invention is the production of carbonate minerals of divalent metal bearing mineral waste for the generation of carbon credits.

[0068] In one embodiment, a sample can be taken at two points: as a powder feeding the mixing tank or as a slurry feeding the carbonation reactor. Different sample weight ratios may be used. In one embodiment, the sample weight ratio is 1 kg / t MgO. A sub-sample for analysis may be prepared using a riffle splitter. Different amounts may be used, but in one embodiment, 100 g for analysis may be prepared using the riffle splitter. For slurry sampling, a composite sample can be prepared using an online slurry sampler, and then the sample filtered and dried out for density and carbon analysis. A sample batch carbonation preparation record showing the types of data that may be recorded is provided below:Table 1 : batch carbonatation preparation record

[0069] For the carbonated material inorganic carbon content assessment, the sample can be taken at two points: as a powder in the final carbonated material after drying and homogenization steps or as a slurry during the discharge of the reactor. Different sample weight ratios may be used. In one embodiment, the sample weight ratio is 1 kg / t carbonated material. A sub-sample for analysis may be prepared using a riffle splitter. Different amounts may be used, but in one embodiment, 100 g for analysis may be prepared using the riffle splitter. For the slurry sampling, a composite sample can be prepared using an online slurry sampler, and then the sample filtered and dried out for density and carbon analysis. A sample batch carbonated material production record showing the types of data that may be recorded is provided below:Table 2: batch carbonated material production record

[0070] For a continuous monitoring of the process, an on-line transmitter for density and flow may be installed upstream of an online slurry sampler. The same configuration for the inlet and the outlet of the carbonatation process will provide information needed for the netmineralized C02assessment. Different sample weight ratios may be used. In one embodiment, the sample weight ratio is 1 kg / t. A sub-sample for analysis may be prepared using a riffle splitter. Different amounts may be used, but in one embodiment, 100 g for analysis may be prepared using the riffle splitter. A composite sample can be prepared using an online slurry sampler and then the sample filtered and dried out for density check and carbon analysis. Online monitoring will provide real time mass flow kg / h.

[0071] A sample continuous net mineralization assessment record showing the types of data that may be recorded is provided below:Table 3: continuous net mineralization assessment record

[0072] It will be appreciated that different techniques and equipment may be used to obtain some of the measurements and data described herein. By way of example, for the inorganic carbon analysis, the combustion analysis for sulfur and carbon determination method may be used (LECO furnace SC 832). For the real-time density monitoring, an ultrasonic on-line sensor may be used. For the real-time flow monitoring, an on-line flowmeter may be used (Magflow meter or ultrasonic doppler probe can be used. For the online sampling, an automatic programmable pipe auto-sampler may be used (launder box sampler or in-line stream cutter could be used).

[0073] By way of example, the following equipment could be used to obtain some of the measurements and data described herein:LECO carbon & sulfur analyzer model: SC832Example for an on-line density monitoring meter: Slurry Density Meter (ECO) - RhosonicsExample for an on-line flowmeter: Magnetic Flow Meter for Slurry Applications | Emerson USExample of a combined sensor for flow and density monitoring: OPTIMASS 7010 For advanced applications and process control | KROHNE GroupExample of on-line slurry sampler: Linear Samplers - Slurry & Solids - Heath & Sherwood (heathandsherwood64.com)

[0074] An end to-end description of an embodiment of the invention is provided below, with reference to Figure 5.

[0075] Referring to reference 1 in Figure 5, the inorganic carbon content and flow rate of a feed stream of Material (mineral waste or derived from mineral waste) containing divalent metals is determined before entering a reactor. Alternatively the mass fraction of carbonate mineral phases are determined. Various inorganic carbon measurement technologies may be used.

[0076] Referring to reference 2 in Figure 5, in a reactor, CO2bearing fluid in is combined with material (mineral waste or derived from mineral waste) containing divalent metals.Optionally, water may be added to the same reactor. The reactor may be a fluid bed, closed stirred reactor, autoclave, or column.

[0077] Referring to reference 3 in Figure 5, the combination is mixed and the reactor is operated under conditions under which mineral carbonates are formed.

[0078] Referring to reference 4 in Figure 5, the combined material is discharged from the reactor.

[0079] Referring to reference 5 in Figure 5, both the inorganic carbon content and flow rate of an effluent stream of Material (mineral waste or derived from mineral waste) containing carbonate minerals is determined. Alternatively, the inorganic carbon content of minerals is determined in the reactor (before discharge). Alternatively, the mass fraction of carbonate mineral phases are determined in the reactor (before discharge). Various inorganic carbon measurement technologies used are listed in the proposed claims.

[0080] Referring to reference 6 in Figure 5, the data from steps 1 and 5 are combined with the cradle-to-grave life cycle emissions attributed to the reaction that occurred in reference 3 in a report that is submitted to an issuer of carbon credits.Example 1

[0081] A bulk carbonation test and results are discussed below.

[0082] The carbonation test was subject to the following conditions:1 . 30 kg of MgO (744 moles) (Baymag 30HP)2. 570 I of tap water3. Slurry density = 5% solid4. Slurry temperature at the beginning = 18.7 C5. Reaction time = 240 minutes6. Reaction pressure = 5 psig under CO2 atmosphere

[0083] The test results may be summarized as follows.1 . 20.9 kg of CO2were injected into the reactor, (475 moles)2. Based on the stochiometric ratio, (475 / 744) 63.8% of the reaction was completed.3. The slurry density after 240 minutes = 22% of solid for a final weight of 132 kg4. An increase of 4.4 times the initial weight suggests the formation of a carbonate with an important hydration level, Mg(CO3)2 . 5H2O seems to be the right molecule after 240 minutes.5. Inorganic carbon analysis of the final product 7.92% C indicates that the injected CO2is converted to a carbonate form (need to be characterized).6. The slurry temperature after 240 minutes = 22.9 C

[0084] The figure below shows a change of C content after 180 minutes of reaction, suggesting a change of the carbonate molecule. Hydromagnesite to lansfordite respectively: Mg5(CC>3)4(OH)2. 4H2O to MgCC>3.5H2O with a carbon content of 2.6% to 6.9%. inorg C %

[0085] The picture below represents the formation of solid (carbonates) during the reaction. The increase of weight seems to be proportional to the CO2 consumption, because the flowrate was slightly reduced during the test to keep the 5 psig.

[0086] The figure below shows a constant pressure into a closed reactor for a steady flowrate of CO2 (not monitored), indicating a dissolution and / or chemical reaction with the MgO slurry. pressure psig62100 50 100 150 200 250 300Time (min)

[0087] The figure below shows the magnesium in solution during the reaction, the low concentration of dissolved Magnesium, 230 mg / l, for all the experiment, indicates a Mg++ reaction with the carbonic acid (dissolved CO2) in a real time. For those conditions, the loss of magnesium in the filtrate is not significant, 0.6% of the total magnesium weight.Mg dissolved (mg / l)250

[0088] The high and steady pH for all the experiment presented in the figure below indicate that the dissolved CO2 reacts in real time with the MgO slurry because of an excess of CO2 should decrease the pH, carbonic acid pH is 4.6. This also means that no loss of CO2 is expected in the filtrate. pH1211.51110.510£ 9.598.587.570 50 100 150 200 250 300Time (min)

[0089] The experimental set up needs some improvement to record more data during the test. A mass flowmeter for the CO2 addition may help to understand and to optimize the kinetic of the chemical reaction.

[0090] A better methodology for the carbonates characterization is required, in addition to the total carbon analysis (LECO). It may be important to know the type of carbonate that is produced for a better mass balance and efficiency assessment.

[0091] The data analysis for this experiment shows that at low pressure and low temperature, the reaction seems to be driven by the MgO dissolution.

[0092] Increasing the magnesium dissolution will aim to reduce the reaction time by increasing the flowrate of CO2 for the same pressure and temperature.

[0093] For these conditions, 240 minutes seem to be not enough since 63.8% of the MgO was used based on the amount of CO2 added.

[0094] The analyses of the liquid phase during the test indicate that neither Mg nor CO2 are in excess and could be lost.

[0095] The volume inside the reactor was the same for all the experiment (46.5%)

[0096] The viscosity was the same for all the experiment, the current required to run the agitator was stable all along the reaction, starting at 1.73 amp. and finishing at 1.74 amp.

[0097] In another embodiment, the invention disclosed herein describes a method of sequestering carbon by carbonation of divalent metal oxide bearing material (DMOBM) into carbonate materials. An embodiment of the invention is the conversion of alkaline earth metal bearing material into carbonate minerals for the generation of carbon credits. Such an embodiment may entail using low embodied carbon source material and then storing the carbonates in a way that protects them from likely decomposition in 100 year timescales.

[0098] Figure 6 is a generalized block flow diagram representing the general process of conversion of DMOBM into a carbonate mineral. As shown in Figure 6, DMOBM, CO2 and water (H2O) are reacted together in a carbonation reactor. It will be appreciated that different types of reactors may be used including, for example, a closed, agitated reactor, packed bed reactor, circulating fluidized bed reactor, or adsorption tower. The end product is a carbonate mineral. In the present example depicted in Figure 6, the end product is a solid liquid mixture bearing in carbonate minerals and potentially containing unreacted oxides, hydroxides or mineral salts formed due to interactions with impurities present in impure CO2sources, though it will be appreciated that other carbonate mineral materials may be produced as an end product. The desired result of the method is the sequestration of carbon into a carbonate mineral, thus reducing atmospheric CO2emissions.

[0099] The key inputs for this process are low embodied carbon divalent metals in a reactive form, and CO2. It will be appreciated that divalent metals can be obtained from a variety of sources, including, without limitation, various raw materials or waste materials. By way of example only, historic asbestos tailings could be processed to extract magnesium oxide. Such magnesium oxide could then be used as the DMOBM input in the reaction generally, as shown in Figure 6, and could be reacted with CO2 and H2O to form magnesium carbonate.

[0100] Although magnesium oxide is one potential DMOBM, it will be appreciated that any divalent metal in a reactive form could be used as the DMOBM in this invention, and that the resultant carbonate would vary according to the DMOBM used. In other embodiments, the divalent metal may be a divalent metal which is a part of the alkaline earth metal group. As another example of a DMOBM input, a calcium and magnesium bearing slurry generated during the processing of various types of ores could be used as a DMOBM input. Other DMOBM sources could include various mined materials. Other DMOBM sources could include calcium or Magnesium silicate bearing ores such as serpentine, wollastonite, or waste streams generated by mining and mineral processing operations, for example tailings from Nickel, Lithium, or Gold mining operations. The DMOBM may be in various forms, including powder form or slurry form.

[0101] Figure 7 is a schematic diagram showing the conversion of a feedstock to a DMOBM, and subsequent conversion of the DMOBM into a carbonate material. It shows a more detailed view of the full process to produce a DMOBM from a feedstock. Circuit A details one specific example of a process used to convert a feedstock into magnesium oxide powder. It will be appreciated that the steps and methods of Circuit A of Figure 7 would depend on the type of feedstock used and the form of DMOBM desired. However, Circuit B - the conversion of DMOBM to a carbonate material - would be the same regardless of the DMOBM used. In the example shown, the resulting carbonate material is magnesium carbonate, because the DMOBM used as an input for Circuit B was magnesium oxide powder. The carbonation reaction can be perform “directly” or “indirectly”. A direct route uses a crushed or ground ore or waste for carbonation without removing non-Calcium / Magnesium elements. A preferred embodiment is an indirect route were an ore or mineral waste is processed to isolate calcium / magnesium oxides prior to carbonation.Example 2

[0102] Figure 10 depicts the process generally of an embodiment of the invention from start to finish. Reference 1 of Figure 10 shows that a divalent metal oxide bearing material with an embodied carbon footprint less than its carbonation potential is sourced.

[0103] In reference 2 of Figure 10, in a reactor CO2bearing fluid in is combined with material (mineral waste or derived from mineral waste) containing divalent metals. Optionally water is added to the same reactor. The reactor may be a fluid bed, closed stirred reactor, autoclave, or column, though it will be appreciated that other reactors may be used as well.

[0104] Referring to reference 3 of Figure 10, the reactor is operated under conditions under which mineral carbonates are formed. Optionally hydrodynamic cavitation is used to accelerate the conversion of solid divalent metal oxide bearing material into mineral carbonates.

[0105] Referring to reference 4 of Figure 10, the combined material is discharged from the reactor.

[0106] Referring to reference 5 of Figure 10, the formed carbonate minerals may be landfilled. Alternatively, the carbonate minerals may be mixed with concrete, for example, though it will be appreciated that the carbonate minerals may be disposed of or managed in other ways as well.Example 3

[0107] Below is a description of an example in which the object was to set up a continuous reaction circuit enabling the carbonation of magnesium oxide (MgO) into magnesium carbonate (MgCO3) in a 50L glass reactor. This setup is depicted in the piping and instrumentation diagram in Figure 11 and photograph in Figure 12.

[0108] Equipment and reagents used were as follows:• 50-liter reactor• 200-liter conical polypropylene tank with mechanical agitator• Heating system for the reactor• Peristaltic pumps (Model: 77602-00, MasterFlex)• 220-liter barrels. pH probe (Model: InPro 3250i / SG / 120, Mettler Toledo)• Conductivity probe (Model: InPro 7100i / 12 / 120 / 4435, Mettler Toledo)• CO2pressure regulator (Model: RFG-320-H, Profax)• CO2flowmeters (GFM Mass flow meter 0-5 L / min and 0-100 L / min, Models: GFM17 and GM47, Aalborg)• CO2cylinder• MgO Baymag 30 HP• CO2weighing scale• Digital pressure gauge (Pressure gauge Digi-max, Model: FB16, Cecomp). Flexible PVC tubing (ID 3 / 8" and OD 1 / 2"). Flexible PVC tubing (ID 1 / 32" and OD 1 / 16")• Rubber stoppers• Water transfer pump for the jacket (Model: RLMPFVK115, Red Lion)• Beer carbonation stone Taidda 1 / 4"• PVC rod (12 inches, 1 / 2" diameter) for reactor inlet• PVC rod (20 inches, 1 / 2" diameter) for reactor outlet

[0109] The reagents were prepared as follows:1 . Weigh the required amount of MgO based on the desired %s / L.2. Fill the 200L tank with water and add the weighed MgO.3. Turn on the tank agitator and mix for 15 minutes until a homogeneous solution is obtained.4. Start the thermostatic bath and set the required system temperature.5. Turn on the agitator in the 50L reactor at 230 RPM.6. Connect the 200L tank outlet hose to the 50L reactor slurry inlet through pump PP-1 .7. Open valve M1 and start pump PP-1 at 400 RPM.8. Once the reactor is filled to 45L with slurry, stop pump PP-1 .

[0110] The start of the procedure followed is as set out below:1 . Open the CO2flow control valve (FC1) and set the inlet flow rate as needed.2. Start a timer.3. Every 5 minutes, record the following parameters:• CO2cylinder mass• CO2inlet flow rate• Internal reactor temperature• Reactor outlet temperature• Outlet pH and conductivity4. Continuously monitor the following parameters to maintain experimental consistency:• Thermostatic bath temperature• Internal reactor pressure• CO2outlet flow rate5. When the outlet pH reaches neutrality (pH 7-7.5):• Take a 100 mL sample.• Connect the 50L reactor outlet hose to a 200L barrel.• Connect the 200L tank outlet hose to the 50L reactor inlet and start pump PP-1 at 90 RPM for a flow rate of 1 .5 L / min.• Note the time when the circuit becomes continuous.

[0111] The end of the procedure is as follows:1 . Take a final 100 mL slurry sample from the outlet.2. When the entire slurry from the tank has transferred to the reactor, close the CO2cylinder valve and stop the timer.3. Stop pump PP-1.4. When the reactor level drops below 40L, stop pump PP-2.5. Collect the remaining slurry from the reactor in a bucket, then transfer it to a barrel.6. Open valve M2 and drain the reactor content into containers, then transfer to the final slurry barrel.7. Allow the slurry to decant, then use a diaphragm pump to transfer the filtrate to another barrel.8. Dry the MgCO3in aluminum trays at 200°C for a minimum of 3 days.

[0112] The analysis of the procedure is as follows:1 . Filter the collected samples under vacuum.2. Recover the filtrate, acidify to pH < 2 with ACS-grade HNO3, and analyze Mg2+concentration.3. Recover the cake, dry it at 105°C for 24 hours, and analyze the carbon content using LECO.4. Weigh the dried MgCO3from the 200°C ovens and calculate the mass yield.

[0113] Information regarding CO2flowmeter correction factor relating to the procedure is as follows:

[0114] The results were as follows:These tests were performed with a concentration of 1% s / L, corresponding to 2 kg of MgO in 200 L of slurry.• Test 1 (Closed Loop): o Reaction Time: 90 min o Carbon Content: 11.03% o Final pH: 7.34 o Mg2+Concentration: 4780 ppmDetailed results for Test 1 are set out below:• Test 2 (Continuous): o Reaction Time: 60 min o Carbon Content: 10.53% o Final pH: 7.68 o Mg2+Concentration: 2488 ppmDetailed results for Test 2 are set out below:

[0115] The conclusion of the above-described example was that the obtained carbon content values of 11.03% and 10.53% demonstrate that CO2can be successfully sequestered using MgO. Further process optimization may reduce reaction times and better characterize the resulting product.

[0116] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the examples described herein. Also, the description is not to be considered as limiting the scope of the examples described herein.

[0117] It will be appreciated that the examples used herein are for illustrative purposes only. Different terminology can be used without departing from the principles expressed herein. For instance, components and modules can be added, deleted, modified or arranged with differing connections without departing from these principles.

[0118] Although the above principles have been described with reference to certain specific examples, various modifications thereof will be apparent to those skilled in the art as outlined in the appended claims.

Claims

Claims:1 . A method for sequestering carbon dioxide in carbonate materials by converting a feedstock containing divalent metals into carbonate materials, the method comprising: a) converting the feedstock into a divalent metal oxide bearing material; b) combining divalent metal oxide bearing material and carbon dioxide in a reactor under conditions which enable the conversion of oxide materials into carbonate materials; and c) operating the carbonation reactor under conditions to convert the divalent metal oxide bearing material into a carbonate material.

2. The method of claim 1 , wherein the feedstock is a magnesium bearing feedstock, and the divalent metal oxide bearing material is one of magnesium or calcium, or is a mixture of magnesium and calcium.

3. The method of claim 1 or 2, wherein the carbon dioxide is obtained from direct air capture.

4. The method of any one of claims 1 to 3, wherein the carbonation reactor is operated for between 1 and 10 hours.

5. The method of claim 4, wherein the carbonation reactor is operated for 2 hours.

6. The method of any one of claims 1 to 5, wherein the reactor is operated at a temperature between 10°C and 30°C.

7. The method of claim 6, wherein the carbonation reactor is operated at a temperature of 20°C.

8. The method of any one of claims 1 to 7, wherein the composition of divalent metal oxide bearing material is between 2% solid and 8% solid.

9. The method of claim 8, wherein the composition of the divalent metal oxide bearing material is 5% solid.

10. The method of any one of claims 1 to 9, wherein the pressure of carbon dioxide supplied to the carbonation reactor is between 70 and 90 psi.11 . The method of claim 10, wherein the pressure of carbon dioxide supplied to the carbonation reactor is 80 psi.

12. The method of any one of claims 1 to 11 , wherein sensors may be utilized to determine the net change in mineralized carbon to enable the generation of a carbon credit.

13. A method of generating a carbon credit through mineral carbonation using mineral waste, the method comprising: a) contacting divalent metal-bearing mineral waste or a material derived from mineral waste with a carbon dioxide-bearing fluid in an engineered reactor; b) continuously monitoring the mass flow of carbonate minerals in a feed stream entering the engineered reactor and monitoring the mass flow of carbonate minerals in effluent exiting the engineered reactor; and c) reporting the cradle-to-grave life cycle greenhouse gas emissions attributed to the reaction that occurs within the engineered reactor to an issuer of carbon credits.

14. The method of claim 13, wherein the divalent metal bearing mineral waste is a slurry.

15. The method of claim 13, wherein the divalent metal bearing mineral waste is a powder.

16. The method of claim 13, wherein the divalent metal bearing mineral waste is a liquid.

17. The method of claim 13, wherein quantification of carbonate minerals contained in the feed stream is completed using laser induced breakdown spectroscopy.

18. The method of claim 13, wherein quantification of carbonate minerals contained in the feed stream is completed using Raman spectroscopy analysis.

19. The method of claim 13, wherein quantification of carbonate minerals contained in the feed stream is completed using inductively coupled plasma optical emissions spectroscopy.

20. The method of claim 13, wherein quantification of carbonate minerals contained in the feed stream is completed using fourier transform infrared analysis.

21. The method of claim 13, wherein quantification of carbonate minerals contained in the feed stream is completed using volumetric calcimetry.

22. The method of claim 13, wherein quantification of carbonate minerals contained in the feed stream is completed using fluorescence spectroscopy.

23. The method of claim 13, wherein quantification of carbonate minerals contained in the effluent stream is completed using laser induced breakdown spectroscopy.

24. The method of claim 13, wherein quantification of carbonate minerals contained in the effluent stream is completed using Raman spectroscopy analysis.

25. The method of claim 13, wherein quantification of carbonate minerals contained in the effluent stream is completed using combustion infrared detection.

26. The method of claim 13, wherein quantification of carbonate minerals contained in the effluent stream is completed using inductively couple plasma optical emissions spectroscopy.

27. The method of claim 13, wherein quantification of carbonate minerals contained in the effluent stream is completed using fourier transform infrared analysis.

28. The method of claim 13, wherein quantification of carbonate minerals contained in the effluent stream is completed using volumetric calcimetry.

29. The method of claim 13, wherein quantification of carbonate minerals contained in the effluent stream is completed using fluorescence spectroscopy.

30. The method of claim 13, wherein the carbon dioxide-bearing fluid is a post combustion flue gas.31 . The method of claim 13, wherein the carbon dioxide-bearing fluid is a flue gas from cement production.

32. The method of claim 13, wherein the carbon dioxide-bearing fluid is a greater than 95% purity carbon dioxide gas concentrated by carbon dioxide capture.

33. The method of claim 13, wherein the carbon dioxide-bearing fluid is a biogas from anaerobic digestion.

34. The method of claim 13, wherein the carbon dioxide- bearing fluid is a liquified carbon dioxide.

35. The method of claim 13, wherein the mineral waste is historic mine tailings.

36. The method of claim 13, wherein the mineral waste is operating mine tailings.

37. The method of claim 13, wherein the mineral waste is steel slag.

38. The method of claim 13, wherein the mineral waste is cement kiln dust.

39. The method of claim 13, wherein the mineral waste is red mud.

40. A method for realizing a net carbon emission reduction by sequestering carbon dioxide in carbonate materials by converting a low embodied carbon material containing divalent metals into carbonate mineral containing materials, the method comprising: a) obtaining divalent metal oxide bearing material with an embodied carbon footprint less than its carbonation potential; b) combining said divalent metal oxide bearing material and carbon dioxide in an engineered reactor under conditions which enable the conversion of oxide minerals into carbonate minerals; and c) operating the carbonation reactor under conditions to convert the divalent metal oxides into carbonate minerals.41 . The method of claim 40, wherein the divalent metal oxide bearing material is a slurry.

42. The method of claim 40, wherein the divalent metal oxide bearing material is a powder.

43. The method of claim 40, wherein the divalent metal oxide bearing material is a liquid.

44. The method of claim 40, wherein the divalent metal oxide bearing material is historic mine tailings.

45. The method of claim 40, wherein the divalent metal oxide bearing material is operating mine tailings.

46. The method of claim 40, wherein the divalent metal oxide bearing material is steel slag.

47. The method of claim 40, wherein the divalent metal oxide bearing material is cement kiln dust.

48. The method of claim 40, wherein the divalent metal oxide bearing material is red mud.

Images