Process and system for in process tailings (IPT) mineral carbonation

Abstract

Embodiments herein generally relate to a process and system for in process tailings (IPT) mineral carbonation utilizing accelerated mineral carbon sequestration in finely ground ultramafic rock. In at least one example, the method comprises sparging a stream of compressed carbon dioxide (CO2) containing gas to form sparged carbon dioxide; mixing and reacting (i) the sparged carbon dioxide (CO2), with (ii) an ultramafic mineral slurry formed of a mix of a comminuted ultramafic rock and water; and forming a carbonated mineral slurry, comprising water mixed with a carbonate mineral, which permanently or temporarily stores the carbon dioxide (CO2).

Description

TITLE: PROCESS AND SYSTEM FOR IN PROCESS TAILINGS (IPT) MINERAL CARBONATIONCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] The present invention claims priority to, and the benefit of, United States Provisional Patent Application No. 63 / 557,054 filed on February 23, 2024 (“METHOD AND SYSTEMS FOR IN PROCESS TAILING (IPT) MINERAL CARBONATION”), the entire contents which are incorporated herein by reference.FIELD

[0002] Various examples are described herein that generally relate to carbon capture, carbon sequestration and carbon storage using mineral carbonation, and in particular, to a process and system for in process tailings (IPT) mineral carbonation utilizing accelerated mineral carbon sequestration in finely ground ultramafic rock.BACKGROUND

[0003] Carbon capture technology is increasingly used to combat the effects of climate change.Passive mineral carbonation is an example method for carbon capture that has been studied for decades. This is a natural process where ultramafic rock passively reacts with CO2 in the atmosphere to form carbonate minerals to store CO2. Passive mineral carbonation techniques are, however, slow. In contrast, existing forms of active mineral carbonation use autoclave processes, which occur at elevated temperatures and pressures, and consequently, demand high operational and capital cost.SUMMARY OF VARIOUS EMBODIMENTS

[0004] In at least one broad aspect, there is provided a process for mineral carbonation, comprising: sparging a stream of compressed carbon dioxide (CO2) containing gas to form sparged CO2; mixing and reacting (i) the sparged carbon dioxide (CO2), with (ii) an ultramafic mineral slurry comprising comminuted ultramafic rock; and forming a carbonated mineral slurry which stores the CO2.

[0005] In some examples, the ultramafic rock contains a brucite mineral.

[0006] In some examples, the mineral carbonate is a magnesium carbonate.

[0007] In some examples, the magnesium carbonate is a nesquehonite mineral.

[0008] In some examples, the ultramafic rock is comminuted to have a particle size of less than 2 millimeters, and preferably less than 200 pm or less than 20 pm.

[0009] In some examples, the ultramafic mineral slurry has a solid density of greater than 5%.

[0010] In some examples, the sparged carbon dioxide increases the acidity of the water in the slurry to a pH below 9, and preferably between 7 to 8.5.

[0011] In some examples, the process further comprises ceasing exposure of the slurry to sparged CO2, which allows the slurry pH to naturally buffer back to basic conditions to encourage the natural precipitation of carbonate minerals.

[0012] In some examples, the comminuted ultramafic rock has been removed from minerals comprising pentlandite, heazlewoodite, awaruite, cobaitpentlandite, magnetite, chrome spinel, as well as platinum group metals including platinum, palladium, rhodium, osmium or iridium.

[0013] In some examples, the process is performed after or before a mineral concentration processes.

[0014] In some examples, the process further comprises recirculating, concentrating and recompressing unreacted carbon dioxide (CO2).

[0015] In some examples, the process is performed as either a batch or continuous process.

[0016] In some examples, the sparging is performed on gas with a purity of at least 5% CO2 , and more preferably, at least 95% CO2.

[0017] In some examples, the method is performed ex-situ.

[0018] In some examples, the bubble size has a diameter of less than 2 mm, or less than 1 mm.

[0019] In some examples, the mixing is performed at ambient temperature and ambient atmospheric pressure.

[0020] In another broad aspect, there is provided a system for mineral carbonation, comprising: at least one receptacle for mixing and reacting (i) sparged carbon dioxide (CO2), with (ii) an ultramafic mineral slurry; and at least one sparging unit fluidically coupled to the receptacle for sparging a stream of compressed CO2 to form the sparged CO2.

[0021] In some examples, the system comprises one or more baffles inside of the tank preventing the formation of a vortex during mixing, and otherwise keeping the slurry well mixed and the solids suspended.

[0022] In some examples, the system further comprises a recirculation system, for recirculating unreacted CO2 in a headspace portion of the tank.

[0023] In some examples, the at least one tank comprises an agitator for mixing.

[0024] Other features and advantages of the present application will become apparent from the following detailed description taken together with the accompanying drawings. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the application, are given by way of illustration only, since various changes and modifications within the spirit and scope of the application will become apparent to those skilled in the art from this detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] For a better understanding of the various embodiments described herein, and to show more clearly how these various embodiments may be carried into effect, reference will be made, by way of example, to the accompanying drawings which show at least one example embodiment, and which are now described. The drawings are not intended to limit the scope of the teachings described herein.

[0026] FIG. 1 A is a simplified block diagram for a process for in process tailings (IPT) mineral carbonation.

[0027] FIG. IB is an example application for integrating the system for IPT mineral carbonation into a metallurgical flowsheet.

[0028] FIG. 1C is another example application for integrating the system for IPT mineral carbonation into the metallurgical flowsheet.

[0029] FIG. 2 illustrates an example system for IPT mineral carbonation.

[0030] FIG. 3 illustrates another example system for IPT mineral carbonation, which includes a recirculation subsystem.

[0031] FIG. 4 illustrates still another example system for IPT mineral carbonation, which includes the use of multiple carbonation tanks.

[0032] FIG. 5 is a process flow for an example method for IPT mineral carbonation.

[0033] FIGs. 6A - 6C show various plots illustrating the variable pH effects resulting from injecting sparged carbon dioxide (CO2) into the processed slurry, wherein the data is acquired from batch testing.

[0034] FIG. 7 shows various plots illustrating the carbon sequestration potential of the IPT mineral carbonation process, as well as the overall pH of the processed slurry, wherein the data is acquired from a continuous process.

[0035] FIG. 8 shows an example system for automated IPT mineral carbonation.

[0036] Further aspects and features of the example embodiments described herein will appear from the following description taken together with the accompanying drawings.DESCRIPTION OF VARIOUS EMBODIMENTS

[0037] Disclosed examples relate to a process and system for in process tailings (IPT) mineral carbonation utilizing accelerated mineral carbon sequestration in finely ground ultramafic rock.I. DEFINITIONS

[0038] Any term or expression not expressly defined herein shall have its commonly accepted definition understood by a person skilled in the art. As used herein, the following terms have the following meanings.

[0039] “Active Mineral Carbonation” refers to a process whereby the ultramafic rock interacts with CO2 in a concentrated gas stream in an engineered manner.

[0040] “Ambient Pressure” refers to an air pressure within the range of approximately 95 kPa to 105 kPa (0.95 atm to 1.05 atm). This range includes, but is not limited to, standard atmospheric pressure at sea level, commonly defined as 101.3 kPa (1 atm; 760 mmHg).

[0041] “Ambient Temperature” refers to a temperature within the range of approximately 20°C to 25°C (293 K to 298 K; 68°F to 77°F) under typical indoor conditions.

[0042] “Injection Time” is the total time CO2 is sparged into a tank containing ultramafic mineral slurry, during batch processing. The injection time typically defines the amount of time of CO2 sparging to allow the contents inside the tank to reach a target pH level. In some cases, the inj ection time refers to at least the amount of time of continuous CO2 sparging (by one or more spargers fluidically coupled to a tank) for the pH inside the tank to reach the target pH level (e.g., below 8 pH). The injection time may include either: (i) time of continuous sparging, or (ii) cumulative time of periods of non-continuous sparging.

[0043] "Memory" refers to a non-transitory tangible computer-readable medium for storing information in a format readable by a processor, and / or instructions readable by a processor to implement an algorithm. The term "memory" includes a plurality of physically discrete, operatively connected devices despite use of the term in the singular. Non-limiting types of memory include solid- state, optical, and magnetic computer readable media. Memory may be non-volatile or volatile. Instructions stored by a memory may be based on a plurality of programming languages known in the art, with non-limiting examples including the C, C++, Python ™, MATLAB ™, and Java ™ programming languages.

[0044] “Mineral carbonation” refers to a process whereby Ca, Fe and Mg in ultramafic / mafic minerals react with CO2 to form stable carbonates and permanently or temporarily sequester CO2 geologically. In some cases, it can occur naturally in the presence of CO2.

[0045] “Passive Mineral Carbonation” refers to a natural process where the ultramafic rock interacts with CO2 in the atmosphere.

[0046] "Processor" refers to one or more electronic devices that is / are capable of reading and executing instructions stored on a memory to perform operations on data, which may be stored on amemory or provided in a data signal. The term "processor" includes a plurality of physically discrete, operatively connected devices despite use of the term in the singular. Non-limiting examples of processors include devices referred to as microprocessors, microcontrollers, central processing units (CPU), and digital signal processors. It is understood herein that the processor performing a function comprises the processor executing instructions stored on a memory.

[0047] “Residence Time” is the average time that content (i.e., an ultramafic mineral slurry) resides within a tank, in a continuous feed process, before being conveyed out of the tank.

[0048] “Ultramafic Rock” or “Ultramafic Ore” is defined as rocks having MgO (magnesium oxide) and SiO? (silicon dioxide (silica)), and in some cases, (i) greater than 10% or greater than 18% of MgO (magnesium oxide), and (ii) less than 50% or less than 45% of SiO? (silicon dioxide (silica)) and which may or may not contain the mineral brucite.II. GENERAL OVERVIEW

[0049] As explained below, the disclosed process enables storing carbon dioxide (CO2) by actively reacting the CO2 with minerals to form mineral carbonates. The IPT carbonation process represents an active and controlled form of mineral carbonation that accelerates natural mineral carbonation reactions beyond the passive pick up rate.

[0050] In at least one example, tailings from a mineral concentrator (e.g., generated by mining or milling processes) are treated and conditioned with a concentrated source of CO2 in a controlled process. The CO2 is sparged into a tailings slurry that includes ultramafic rock that has been ground to have a fine size distribution. The sparged CO2 reacts, inside one or more carbonation tanks, with the ground minerals, in the tailings slurry, to form mineral carbonates, which in turn, results in permanent or temporary storage of the CO2. In some examples, the carbonation tanks are configured such that unreacted CO2, in the tank head space, is recompressed and recirculated to maximize CO2 storage efficiency, which is the fraction of CO2 injected that is stored as a solid carbonate.

[0051] If the mineral carbonation storage process is applied after mineral concentration, an appreciated advantage of the disclosed process is that it can be used to sequester CO2 geologically in the mineral concentrator tailings while the tailings are still in the processing circuit, rather than afterthey have been finally deposited (e.g., in a tailings management facility) which minimizes operating and material handling costs.

[0052] Reference is now made to FIG. 1A, which shows an example block diagram for a system 150 used in process tailings (IPT) mineral carbonation, in accordance with disclosed examples.

[0053] As shown, the IPT carbonation system 150 receives two feed inputs: (i) a feed of concentrated CO2 102; and (ii) a feed of ultramafic mineral slurry 104.

[0054] The feed of concentrated CO2 102 is obtained, for example, from an industrial source of carbon dioxide, which has been compressed and concentrated for use with system 150. In some examples, if the CO2 feed is not already concentrated, then it is initially compressed and concentrated before feeding into system 150. As provided herein, the concentrated CO2 is also initially sparged into the ultramafic mineral slurry.

[0055] The ultramafic mineral slurry 104 comprises a slurry of comminuted ultramafic mineral rock or ore, that is combined with water. The ultramafic mineral rock is comminuted to reduce its size, and then mixed and combined with the water to form the slurry.

[0056] The use of ultramafic rock is important because it has been appreciated that, when mixed with the CO2, it contains minerals which are reactive with the CO2 and thereby allows for sequestration of large quantities of CO2. In at least one example, the ultramafic rock contains the mineral brucite, which has been found to be highly reactive with CO2.

[0057] Additionally, as noted, the ultramafic mineral rock is comminuted to reduce its size and produce finely ground rock. The finely ground rock has a larger surface area, which maximizes CO2 exposure to mineral surfaces and promotes faster and more complete reactions. In some examples, the ultramafic rock is comminuted to have a particle size of less than 2 millimeters, and more preferably, less than 200 micrometers or less than 20 micrometers. It is then combined with a liquid to be a slurry with a solids density in a range of preferably greater than 5%.

[0058] In at least one example, the ultramafic mineral slurry 104 is obtained from thickened mine tailings generated during the metallurgical process (FIG. 1C). During the metallurgical process, the ultramafic rock is ground to extract valuable minerals. In this manner, the ultramafic rock is already finely ground when the carbonation process is performed. The operating costs of the carbonationprocess are therefore low because the process is treating material that is already being handled, and after the valuable minerals have been extracted.

[0059] Continuing with reference to FIG. 1A, as explained in further detail herein - after receiving the input feeds, the IPT carbonation system 150 agitates and reacts the concentrated and sparged CO2 with the ultramafic mineral slurry, in one or more sealed tank vessels. The result is the formation of mineral carbonates which store the CO2, and which are mixed with the water to form an output slurry 106 containing mineral carbonate. The output slurry may then be transported to a tailings management facility, e.g., for permanent or temporary storage of CO2.

[0060] A unique feature of the disclosed IPT carbonation process, is that it can be used to sequester larger volumes of carbon dioxide, in a given time period, as compared to passive mineral carbonation processes. In particular, the process is able to sequester larger volumes of carbon dioxide in less and shorter time periods compared to passive carbonation processes.

[0061] As well, compared to other forms of active mineral carbonation, the disclosed process can be performed at atmospheric temperature and pressure, without adding any reagents. This is contrasted to many conventional active mineral carbonation processes that rely on the use of autoclave processes, which occur at elevated temperatures and pressures, and consequently, demand high operational and capital cost. The high capital and operating costs make these conventional processes prohibitive. Accordingly, by performing the process at atmospheric temperatures and pressures without reagents, the overall operating and capital costs of the process are lowered.

[0062] In view of the foregoing, disclosed embodiments allow for large scale accelerated CO2 storage in mineral forms as an ex-situ process, i.e., occurs above the ground. The disclosed process is differentiated from in-si tu carbonation technologies which inject CO2 and often water at depths underground before material handling.III. EXAMPLE SYSTEM FOR IPT CARBONATION

[0063] Reference is now made to FIG. 2, which illustrates an example system 150a for IPT mineral carbonation. The system 150a is an example configuration for the system 150 in FIG. 1 A.

[0064] As shown, the system 150a includes a carbonation tank 202 (or other receptacle). In at least one example, tank 202 comprises a sealed vessel. The tank 202 is used for mixing: (i) the concentrated CO2 stream 102; and (ii) the ultramafic mineral slurry 104, which are both fed into tank 202.

[0065] Tank 202 itself includes an agitator 204, disposed therein, which is used for mixing the feeds. In some examples, agitator 204 is actuated by an actuator mechanism 206 (e.g., a motor or the like), attached to an agitator shaft 204a.

[0066] Tank 202 can also include one or more baffles 210. Baffles 210 may be located, for instance, along the outer perimeter of the tank volume. In some examples, baffles 210 are used for preventing the formation of a vortex during mixing, and otherwise keeping the slurry well mixed and the solids suspended.

[0067] The IPT carbonation system 150a also includes a sparging unit 208. The sparging unit 208 is fluidically coupled to the tank 202, e.g., a bottom or side portion of tank 202. The coupling between sparging unit 208 and tank 202 may be direct, or in-direct. In some examples, the system 150a can include more than one sparging unit 208, e.g., each receiving a separate feed of concentrated CO2 (which may come from a common source).

[0068] In operation, sparging unit 208 receives the concentrated feed of CO2 gas 102, and operates to convert (e.g., transform) the gas stream into small bubbles 102’ (also referenced herein as a sparged input feed or stream 102’). The small bubbles 102’ rise through the ultramafic mineral slurry 104, inside tank 202. As described below, the sparged CO2 102’ dissolves into the water and is used to form aqueous carbonate species when reacting with the ultramafic mineral slurry.

[0069] As provided in greater detail below, an effect of sparging CO2 into the slurry is to lower the pH of the mixture. This allows for mineral carbonation without the use of reagents, and while maintaining the sealed tank 202 at room ambient temperature conditions (e.g., approximately 20°C ~ 25°C) and normal atmospheric ambient pressure (e.g., approximately 101.3 kPA ~ 1 atm).

[0070] In at least one example, the sparging unit 208 is configured to produce CO2 bubbles with a small diameter. This is because as the bubble diameter decreases, the surface area-to-volume ratio of the bubble increases. In turn, this facilitates the quicker dissolution of the sparged CO2 gas in the mineral slurry. The quicker dissolution is a result of various factors including increased gas-liquidcontact, longer residence time in the slurry (i.e., lower buoyancy) among other factors. In some examples, the sparging unit generates ultra-fine bubbles (e.g., less than 2.0 mm in diameter), or microfine bubbles (e.g., less than 1.0 mm in diameter).

[0071] To that end, the sparging unit 208 may be a cavitation-tube sparging system designed based on the principle of hydrodynamic cavitation, to produce ultra-fine bubbles. In other examples, the sparging unit 208 is a jetting style sparger that produces micro-fine bubbles.

[0072] In at least one example, the sparging is performed on gas with a purity at least 5% CO2, and more preferably, of at least 95% CO2.

[0073] Continuing with reference to FIG. 2, the amount of CO2 sequestered as a result of the process in IPT carbonation system 150 may be monitored using a monitoring system 250. More particularly, the amount of CO2 that is stored is quantified by means of a carbon balance around the process. The total carbon content of material is assayed on a sample taken from an intake pipe 250a, and assayed again on a sample taken from an outtake pipe 250b to calculate the amount of CO2 stored.IV. MINERAL CARBONATION REACTION INSIDE IPT CARBONATION SYSTEM

[0074] With continued reference to FIG. 2, the following is a discussion of the mineral carbonation reaction that occurs within the tank 202 using an example case where the ultramafic mineral slurry 104 includes a brucite mineral.

[0075] As exemplified, tank 202 receives a feed of ultramafic mineral slurry 104 that includes the brucite mineral Mg(OH)2, (s), which is mixed with water (H2O) to form the slurry. The brucite mineral initially dissolves in water in accordance with Formula (1):

[0076] The sparged CO2 reacts with the water, inside tank 202, in accordance with Formula (2) which acidifies the water and promotes the dissolution of ultramafic minerals such as brucite. Notethat depending on the pH, the dissolved carbonate species may be in the form of CO32” HCCh’ or H2CO3 and that this reaction is generalized:

[0077] The mineral carbonation reaction then occurs in accordance with Formula (3), to form a solid magnesium carbonate mineral, one of which may be the nesquehonite mineral (MgC02■ 3H2OS), which is a hydrated magnesium carbonate:

[0078] Accordingly, an output slurry 106 is formed comprising precipitated solid magnesium carbonate minerals (MgC02■ 3H2O(S)) mixed with water as well as some dissolved and unprecipitated magnesium carbonate minerals.

[0079] It has been appreciated that mineral carbonation occurs rapidly in hydroxides (e.g., brucite) and slowly in silicates (e.g., olivine, serpentine). Previous attempts at using mineral carbonation processes that focus on the use silicates, require reagents, high pressures and temperatures, and / or expensive equipment such as autoclaves. The disclosed process avoids these high-cost features by prioritizing storage primarily in the mineral brucite.

[0080] An important aspect of the disclosed carbonation reaction is the use of the sparged CO2 stream 102’ . The sparged CO2 stream 102’ causes the water inside the tank 202 to turn acidic. In some examples, the water is acidified with a pH in a range of less than 9, and approximately between 5 to 8.5 and in some cases, between 7 to 8.5. This pH change allows for rapid carbonation because elements such as Mg, Ca, Fe - in the ultramafic mineral slurry - dissolve into the water as metal cations. The dissolved metals cations react with aqueous carbonate species and precipitate as solid carbonate minerals to permanently fix the CO2 into a new carbonate mineral (e.g., nesquehonite mineral). In at least one example, the sparging is used to reduce the pH of the slurry solution to be less than 8.5.

[0081] When the ultramafic rock or ore leaves the tank 202, it is no longer exposed to the CO2 sparging. The result is that the slurry pH naturally buffers back to basic conditions, which occurs without the addition of reagents. The effect of this pH “rebound” is to cause the further natural precipitation of carbonate minerals, e.g., into the nesquehonite mineral, or otherwise, solid iron, calcium or magnesium carbonate minerals which may or may not be hydrated. This is because, as pHrebounds (increases), the solubility of carbonate minerals decreases, promoting their natural precipitation. An appreciated advantage is that the natural buffering of pH continues to occur even after storage of the output slurry, e.g., in a tailings management facility.V. IPT CARBONATION SYSTEM WITH CO2RECIRCULATION

[0082] Reference is now made to FIG. 3, which illustrates another example system 150b for IPT carbonation. The system 150b is another example configuration for the system 150 in FIG. 1 A.

[0083] The system 150b is generally analogous to the system 150a (FIG. 1). However, in the exemplified case, the system is further designed to capture unreacted CO2 in the headspace 302 of the tank vessel 202. This captured unreacted CO2 is recompressed, and fed back into the tank 202 to maximize the use of CO2.

[0084] More generally, during the reaction process, unreacted CO2 is introduced through the sparging unit 208 and may enter into the headspace 302 of the tank 202. The CO2 gas in the headspace 302 can be recompressed and recirculated back into the tank 202, via a recirculation subsystem 306. This is performed to maximize the utilization of the CO2 and conversion to carbonates, as well as to prevent CO2 emissions.

[0085] The recirculation subsystem 306 can include one or more pumps 306a (e.g., centrifugal pumps), which are fluidically coupled to one or more conduits disposed within the tank 202. Because the tank 202 is a sealed vessel, the pump 306a can pump out (e.g., via negative pressure) the CO2 in the headspace 302, and channel the CO2 304 to a re-compressor unit 306b. The re-compressor unit 306b recompresses the CO2 to provide a compressed stream of CO2 306. In some examples, the recompressor unit 306b can include various knock-out drums, compressor units and a wet receiver(s) to purify the recycled stream.

[0086] Recirculation subsystem 306 can also include a combiner unit 306c, which combines the re-circulated and compressed CO2 stream 306, with a new compressed CO2 stream 102 that requires storage. The combined and compressed CO2 stream 308 is then fed back into the tank 202, via the sparging unit 208.VI. IPT CARBONATION SYSTEM USING MULTIPLE TANKS

[0087] Reference is now made to FIG. 4, which illustrates still another example system 150c for IPT carbonation. The system 150c is yet another example configuration for the system 150 in FIG. 1A.

[0088] The system 150c is generally analogous to the system 150b (FIG. 3), with the exception that the system includes multiple tanks 202. In some examples, system 150c is used where there is a large volume of CO2 requiring storage. In these cases, the mineral carbonation reactions occur in multiple tanks 202, operating in parallel. While three tanks 202a - 202c are exemplified in FIG. 4, the system 150c can include any number of tanks 202.

[0089] System 150c can include a tank distributor 402, which is used to distribute the input feed of ultramafic mineral slurry 104 as between the plurality of tanks 202a - 202c. Within each tank, the slurry is processed, and the output slurry 106 is then combined and conveyed downstream.

[0090] As exemplified, a single or common re-circulation subsystem 306 can be provided, as between the multiple tanks 202a - 202c. In other examples, a separate re-circulation subsystem 306 is provided for each tank 202, or a subset of tanks 202. In still other examples, the system 150c may not necessarily include the re-circulation subsystem 306. The re-circulation subsystem 306 may also be provided for some tanks, and not others.

[0091] In other examples, the tanks may also be operated in series. For example, the slurry is transferred sequentially between the sealed tanks 202 (e.g., via gravity) for processing using, for example, a series of upcomers.VII. EXAMPLE PROCESS

[0092] The following is a description of example processes for IPT carbonation.(i.) General Process.

[0093] FIG. 5 exemplifies a process 500 for IPT carbonation using ultramafic mineral rock.

[0094] At 502, the ultramafic mineral slurry 104 is produced and fed into tank 202. The ultramafic slurry may be formed by taking ultramafic rock (e.g., including ultramafic ore), which is then commuted into smaller particles (e.g., via milling). The commuted ultramafic rock is then mixed with water to output an ultramafic slurry.

[0095] In some examples, the ultramafic rock is sourced from a mine. In some other examples, as described further on with respect to FIG. 1C, the ultramafic rock is subject to upstream processing (e.g., in a mineral concentrator 154c), prior to producing the mineral slurry for processing. For example, the ultramafic slurry may be produced as an intermediate tailings in a metallurgical flowsheet, and the IPT process may also be integrated at an intermediate point in the flowsheet.

[0096] In at least one example, the ultramafic rock particles are commuted to have a particle size (P80) diameter of 2,000 pm or less, 200 pm or less, 20 pm or less or 2 pm or less. As noted above, the commutation may be the result of upstream processing, such as during a mineral concentrator process. Without limitation to theory, the use of finer particle sizes results in greater CO2 sequestration. This is because the finely ground rock has a larger surface area, which maximizes CO2 exposure to mineral surfaces and promotes faster and more complete reactions. The particle size (P80) may be determined using a Malvern™ Panalytical™ particle size analyzer (e.g., Malvern™ Mastersizer™ 3000) which uses laser diffraction or through standard sieve analysis.

[0097] In at least one example, the percent of solids in the ultramafic mineral slurry, expressed as a percentage of the total mass charge slurry (g), may be in a range of 1% to 60%. In some examples, the percent of solids in the slurry is greater than 5%, greater than 10%, greater than 20%, or greater than 30%. In at least one example, the percent of solids in the mineral slurry is in a range of 30% to 60%.

[0098] At 504, a stream of concentrated carbon dioxide (CO2) 102 is sparged to form a spargedCO2 stream 102’. This is exemplified in FIG. 2, showing the input feed 102 of concentrated CO2 being sparged by the sparging unit 208 as sparged feed 102’. The feed of concentrated CO2 may be produced using any method known in the art (e.g., any CO2 compressor).

[0099] As explained previously, in at least one example, the sparged CO2 has a bubble diameter of less than 2.0 mm, or less than 1.0 mm. As known in the art, the smaller bubble diametersincrease the surface area-to-volume ratio of the bubbles. In turn this facilitates the quicker dissolution of the sparged CO2 gas in the mineral slurry.

[0100] In at least one example, the volume percent of the injected gas which comprises CO2 is in a range of approximately 1% to 100%. In some examples, the volume of the gas comprising CO2 is 50% or above, 60% or above, 70% or above, 80% or above, 90% or above or 100%.

[0101] In some examples, the IPT carbonation process is designed using an average ratio of approximately 10 - 100 kg CO2 per tonne of dry tailings, and preferably approximately 32 kg CO2 per tonne of dry tailings. This ratio may allow achieving a desired pH for the mixture.

[0102] At 506, mixing occurs within the sealed tank 202 between the sparged CO2 102’ and the ultramafic mineral slurry 104. In at least one example, the mixture is agitated at a rate of between 100 RPM and 1,500 RPM to ensure proper mixing. The mixing occurs within the sealed tank 202 at approximately atmospheric ambient pressure (i.e., 101.3 kPa absolute), and standard ambient temperature (e.g., 20°C to 25°C).

[0103] In some examples, the sparged CChis injected, and the mixing continues to occur, until the pH of the slurry is below a pH of “9”, and preferably, below a pH of “8.5” or “8”. In some examples, the sparged CCh is injected until the pH is in a range of “5” to “8”, or “7” to “8”, and preferably close to a pH of “8”.

[0104] As indicated above, the effect of this pH change is that elements such as Mg, Ca, Fe - in the ultramafic mineral slurry - dissolve into the water as metal cations. The dissolved metals cations react with aqueous carbonate species and precipitate as solid carbonate minerals to temporarily or permanently fix the CO2 into a new carbonate mineral.

[0105] In some examples, the pH of the mixture is monitored using a pH meter (e.g., disposed inside the tank 202 and in contact with the mixture). The flow rate of the sparged CO2 is then manually or automatically adjusted to control the pH level of the mixture to the target pH level or range.

[0106] At 508, once the desired pH level is achieved, the mixture is removed from exposure to the CO2 sparging. In an example batch process, this can occur by deactivating the CO2 sparging, or otherwise slowing down the injection sparging flow rate into the tank. This allows for the natural rebounding of the pH level to alkaline levels in the output slurry 106. As noted above, this enables forthe further natural precipitation of carbonate minerals, e.g., into the nesquehonite mineral, or otherwise, solid iron, calcium or magnesium carbonate minerals which may or may not be hydrated.

[0107] In some examples, rather than activating or deactivating sparging at 504 and 508, the sparging unit 208 may be simply coupled and decoupled from the tank 202.

[0108] At 510, the output carbonated mineral slurry may be stored (e.g., in a tailings management facility). In some examples, the process of natural precipitation of carbonate minerals further continues during storage.

[0109] In other cases, where the process is integrated as an intermediate point in a flowsheet, the output slurry may not be immediately stored at 510, but rather, may be conveyed downstream for further processing (e.g., to a mineral concentrator).(ii.) Automated Process.

[0110] In some examples, the process 500 is automated or partially automated. This may be facilitated using an automated IPT carbonation system 800, as shown in FIG. 8.

[0111] As shown therein, the system can include a processor 802 coupled (e.g., via a computer data bus) to a memory 804, a pH meter 806 and a CO2 flow rate control unit 808. The CO2 flow rate control unit 808 can be any unit operable to control the flow rate of compressed CO2 into the tank 202 (e.g., an electronically controlled valve).

[0112] In some examples, which are not explicitly illustrated, the processor 802 is also coupled to the sparging unit 208 to activate or deactivate the sparging unit electronics. Processor 802 can also couple to any other component exemplified in FIGs. 2 - 4.

[0113] In these examples, with reference to method 500 - at 504, the processor 802 can automatically activate the control unit 808 and / or sparging unit 208 to allow for CO2 sparging into the tank 202. At 506, during the mixing, the processor 802 can further monitor a digital output received from the pH meter 806, which may be located inside the tank 202 and in contact with the mixture. In an example batch process, the processor 802 can then vary the CO2 flow rate, via control unit 808, such as to decrease the pH to the desired target pH level. Once the processor 802 detects that pH has reached the target level, then at 508, in a batch process, the processor 502 can automatically deactivate the sparging unit 208 and / or control unit 808.(iii.) Continuous or Batch Processing.

[0114] Process 500 (FIG. 5) can be applied as either a batch process or a continuous process. In a continuous process, new ultramafic slurry is continuously introduced and removed from the tank 202. In these examples, CO2 is continuously sparged into the tank as new slurry is being introduced therein.

[0115] In at least one example, the continuous process operates as follows: (i) the tank(s) 202 are initially filled with ultramafic slurry 104 at act 502, (ii) the sparging is activated at act 504, and the pH is monitored while mixing occurs (at act 506) to determine when the pH reaches the target level (e.g., below 8 pH), (iii) at this point, the ultramafic slurry is removed and conveyed downstream and a continuous replacement feed is added to the tank while maintaining the pH at a relatively constant level while output feed is removed. The pH may be maintained constant by either adjusting: (a) the input continuous feed rate of ultramafic slurry 104 into the tank, as well as the output feed rate out of the tank (i.e., adjusting the residence time), or (b) adjusting the injection rate of CO2 sparged into the tank. The pH monitoring, and adjustments to the feed rate or injection rate may be manual or automatic. If automated, it may be automated using the system exemplified in FIG. 8.VIII. EXAMPLE APPLICATIONS OF IPT CARBONATION SYSTEM

[0116] The following is a discussion of various example applications of the IPT carbonation system 150 and process, disclosed herein. In general, the IPT carbonation system 150 can be used in modular fashion, in different areas of the metallurgical flowsheet.

[0117] In some examples, the disclosed process is applied to ultramafic rock that does not contain metals that are mined such that the carbonation process is applied only for the purposes of CO2 storage and not in conjunction with the extraction of mineral concentrates. This is shown for example in FIG. IB. As shown, the ultramafic ore 152b is sourced from a mine 150b. It may then undergo processing in a mill 154b to produce the ultramafic mineral slurry 104 used for IPT processing. The IPT carbonation system 150 is then applied to produce the output mineral carbonated slurry 106. This slurry is then subject to storage 156b, e.g., at a tailings management facility.

[0118] FIG. 1C shows another example application of the IPT carbonation system 150. In this example, the system 150 is integrated after the tailing thickening 160c, and before discharging of thetailings, e.g., to the tailings management facility. In particular, in this example, the IPT carbonation process 158b is integrated with a nickel concentrator processes 154c, which recovers metals into concentrate products (in other cases, any other concentrator is used). As shown, a dilute ultramafic mineral slurry 156c is produced after the mineral concentration. The dilute slurry 156c is then subject to a tailings thickener 160c to produce the ultramafic mineral slurry 104. This example accordingly illustrates how the IPT carbonation system and process 150 is used as a continuous process as part of a metallurgical flow sheet.

[0119] Another example application for the IPT carbonation system 150 is to apply the same process and reaction mechanism ahead of nickel recovery processes (i.e., flotation process), such that it can improve the nickel recovery.

[0120] While the above discussion assumes an example case where the IPT process is applied with a nickel concentrator process - in other examples, the IPT process can be used in any other flowsheet with any other desired mineral concentrator process. More generally, the disclosed process and system may be applied before mineral concentration processes such as but not limited to comminution, flotation or magnetic separation such that the carbonation process results in an improvement in the recovery of a valuable mineral that contains one or more of nickel, cobalt, iron, chromium, platinum, palladium, rhodium, osmium or iridium. In some examples, the minerals also include pentlandite, heazlewoodite, awaruite, cobaitpentlandite, magnetite, chrome spinel, as well as platinum group metals including platinum, palladium, rhodium, osmium or iridium.IX. EXAMPLE TEST RESULTS

[0121] The following discussion relates to various example experimental tests conducted. The experimental tests confirm the effect of a number of key process parameters on CO2 sequestration, including: (i) pH level; (ii) particle size; (iii) percent solids; and (iv) percent carbon dioxide (CO2).

[0122] The metrics in the experimental test results are defined as follows:Agitation Rate: Rotational speed of the agitator 204 located in tank 202, expressed in units of rotation per minute (RPM).Cell Size: The volume of the tank 202, expressed in units of liters (L).- Continuous or Batch: In a continuous process, materials are fed into the system continuously, and products are simultaneously removed, allowing for ongoing operation without interruption. In contrast, a batch process involves processing materials in discrete, separate cycles, where a fixed quantity is treated before a new batch begins.- Gas CO2 Volume Percentage: Percent of carbon dioxide in the input sparged feed 102’, into tank 202, expressed as a percentage of the total volume (vol.) of gas comprising the sparged feed.- Gas Flow Rate: The rate of gas comprising the input sparged feed 102’, into the tank 202, expressed in units of liters per minute (LPM). This is measured using a flow meter.- Injection Time: The total time duration which the input sparged feed 102’ is injected into the tank 202, expressed in minutes (min) or hours (h).- kg CO2 / 1 Tailings: Represents the amount of carbon dioxide (CO2) sequestered or reacted per metric tonne of tailings. It quantifies how effectively mine tailings or other mineral residues capture and store CO2 during the disclosed mineral carbonation process. In disclosed experimental results, unless stated otherwise, the kg CO2 / t Tailings was measured thirty (30) days after carbonation (e.g., after the sparging was completed). During this period, the sample sits to allow dissolved carbonates to precipitate into solids.- Mass Charge: Represents the amount of mineral feedstock (i.e., the ultramafic mineral slurry 104) used in the experimental test, expressed in units of grams (g).- Particle Size: The size of comminuted ultramafic mineral rock particles in the ultramafic mineral slurry 104, which is fed into the IPT carbonation process. The particle size is expressed as P80, which is the particle size at which 80% of the material (by mass) is below a given size. The measurements are expressed in units of micrometers (pm) as a function of particle diameter assuming a spherical particle model. The particle size was determined using a Malvern™ Panalytical™ particle size analyzer (e.g., Malvern™ Mastersizer™ 3000) which uses laser diffraction to measure particle size.- Percent (%) Brucite in Sample: The percentage of the ultramafic mineral slurry 104 composed of brucite mineral. The percentage of Brucite in the sample is determined using a QEMSCAN™ mineralogy analysis and procedure- Percent (%) C of Feed Solids: Refers to the percentage of carbon (C) present in the solid feed material (i.e., the ultramafic mineral slurry 104) before processing via the IPT carbonation process. It indicates the carbon content as a proportion of the total mass charge of the solid feed. This is important because this is the baseline carbon content of the rock and this value is used to quantify how much CO2 was sequestered. The percent carbon is determined using a LECO carbon / sulfur analysis, as known in the art. A LECO Carbon Analyzer was used to measure the total carbon content of the sample based on an infrared (IR) absorption detector.- Percent (%) C of Product Solids: Refers to the percentage of carbon (C) present in the solid material after processing via the IPT carbonation process. It indicates how much carbon has been retained, removed, or transformed compared to the initial % C of feed solids. The percent carbon is determined using a LECO carbon / sulfur analysis, as known in the art. A LECO Carbon Analyzer was used to measure the total carbon content of the sample based on an infrared (IR) absorption detector.- Percent (%) C Increase: Refers to the percentage increase in carbon (C) content in the solid product compared to the feed solids after the mineral carbonation process. It quantifies how much additional carbon (typically from CO2 sequestration) has been incorporated into the solid phase. This is determined in accordance with the following equation:% C of Product Solids — $ C of Feed SolidsC Increase (%) = - - X 100$ C of Feed Solids- Percent (%) Solids: Refers to the proportion of solid material in a slurry, expressed as a percentage of the total weight of the mixture. This is determined by obtaining the weight of the slurry, then filtering out the solids, drying them and measuring their weight as a fraction of the mass of slurry.- Pressure: Pressure inside of the tank 202 when sealed, expressed relative to absolute pressure in units of kilopascals (kPa). In conducted experiment tests, the pressure was at 101.3 kPa, which is normal atmospheric pressure at sea level (i.e., 1 atm). This is measured using a pressure gauge.- Stream: Refers to the specific flow of material within a system, categorized based on particle size and composition. “Slimes” are ultra-fine particles, typically smaller than 20 pm (P80).“Combined tailings” comprise a mix of coarse and fine particles, whereby coarse particles have a P80 of approximately 115 pm.- Temperature: The temperature inside the tank 202 when sealed, expressed in units of Kelvin (K). In various conducted experimental tests, the temperature was approximately 298 K (i.e., approximately 25°C), which is considered to be standard laboratory room temperature.

[0123] The experimental setup was similar to that exemplified in FIG. 2. With the exception of Example 5 (Continuous Processing), all batch results were obtained using a general aquarium sparging unit that generated bubble sizes that were, on average, less than 1 mm ~ 2 mm in diameter. The IPT carbonation process was generally designed using an average ratio of 32 kg CO2 per tonne of dry tailings. In each of the experiments, the CO2 was sparged until the pH level dropped to approximately below a pH of “8”.(i.) Example 1 - pH Levels

[0124] Experimental test results were conducted to evaluate the effect of decreased pH, resulting from CO2 sparging, on the mineral carbonation process. Table 1, below, summarize the process parameters used in a laboratory batch test.Table 1 - Process Parameters for pH Testing

[0125] FIGs. 6A and 6B show plots 600a, 600b that exemplify the effect of the change of pH in the processed slurry, as a result of: (i) exposing the processed slurry to CO2 sparging, in region 602, and then, (ii) ceasing exposure of the slurry to CO2 sparging, in region 604.

[0126] As shown in plot 600b, the pH of the slurry decreases during CO2 sparging in the region 602. More particularly, the slurry pH decreases from its natural alkalinity (~10) to ~7.2 due to 6.5 h of CO2 injection. Mg carbonates are formed and exist both dissolved in solution (plot line 610a), as well as existing as solid particles (plot line 610b).

[0127] After the cut-off mark 606, when the slurry is no longer exposed to CO2 sparging in region 604, the pH of the slurry increased and rebounded (i.e., the pH increased from 7.2 to 8.1).

[0128] In region 604, after the slurry is not exposed to CO2 sparging, the increase in pH facilitates further precipitation of the dissolved carbonates, i.e., carbonate precipitation. This is shown by the decreasing plot line 610a (i.e., a decreased percentage of carbonates dissolved in solution), and the increasing plot line 610b (i.e., an increased percentage of precipitated carbonates). This precipitation is encouraged by the slurry pH “rebounding” to more alkaline levels.

[0129] Accordingly, FIGs. 6A - 6B confirm the effect of performing mineral carbonation at room temperature and normal atmospheric pressure without using reagents by: (i) initially, reducing pH levels to below a pH of 9 via CO2 sparging, and (ii) subsequently, allowing the slurry pH to rebound to more alkaline levels to facilitate carbon participation.

[0130] FIG. 6C (plot 600c) and Table 2 summarize the data with respect to CO2 sequestering as a result of the conducted batch test.Table 2 - CO2 Sequestration Data for pH Testing(ii.) Example 2 - Particle Size

[0131] Experimental tests were also performed on different process streams in the flowsheet using different particle sizes for solids processed for the IPT carbonation process.

[0132] As shown in Table 3, tests were performed with two different sample ultramafic rock types which had an initial brucite content percentage of 3.5% and 1.5%. Each of these samples was then subject to different flowsheets, which involved various metal concentrator processes. These flowsheets produced intermediate tailings comprising solids with different particle sizes which were used for testing, as shown in Table 3 below.

[0133] More broadly, the experiments were conducted using three types of process flow streams: (i) two deslime cyclone overflow streams (COFI and COF2). These streams result from tailings from upstream desliming processes, e.g., used in mineral recovery from ultramafic rock containing the brucite. These streams were able to produce tailings with finer solids of less than 20 pm (P80); and (ii) a rougher non-magnetic tailings was also used, which refers to the waste material from the rougher magnetic recovery stage of mineral processing, specifically after a combination offlotation and magnetic separation processing for ultramafic rock containing the brucite. These rougher tailings produced coarser solids with a particle size of around 100 pm (P80).

[0134] It will be understood that these flowsheets provide only examples for processes for producing ultramafic rock with smaller particle sizes. In other cases, small particle sizes are produced through any other suitable metallurgical flowsheet process or method.

[0135] At a general level, the data confirms that samples with higher brucite content sequestered more CO2 than did samples with lower brucite content.

[0136] More particularly, the data confirms that particle size has an effect on the process, and that finer particle sizes result in greater CO2 sequestration. For each of the samples tested, the finer sample, which had a P80 particle size of less than 20 pm sequestered more carbon dioxide than coarser samples with a particle size of approximately 100 pm. In some cases, to achieve the finer particles, the IPT process is accordingly applied on final tailing streams, where the particle size distribution of the sample being carbonated is the finest.

[0137] Tables 4a - 4c further clarify the experimental parameters used for obtaining data for batches A - F in Table 3.Table 4a - Effect of Particle Size on CO2 Sequestration (Experimental Details Per Batch)Table 4b - Effect of Particle Size on CO2 Sequestration (Experimental Details Per Batch)Table 4c - Effect of Particle Size on CO2 Sequestration (Experimental Details Per Batch)(iii.) Example 3 - Pulp Density

[0138] The disclosed method of IPT carbonation may be operated at a wide range of pulp densities (% solids). Experimental tests were conducted to confirm the functionality of the technology at high, moderate, and low pulp density. The limiting factor for the process on the high end of % solids is the viscosity of the slurry, where too high of solids loading may in some cases result in a thick fluid that does not respond well to carbonation.

[0139] As exemplified in Tables 5 - 6, below, the experimental tests confirm that the IPT carbonation process is most effective between 5% to 40% solids, sequestering between 7.7-62 kg CO2 / t tailings. Above 40% solids, the tailings are believed to have rheological properties that may behave with high viscosity. It is believed, however, that the IPT carbonation process may function onother ore body's tailings that behave more favourably at >40% solids (less viscous), depending on the orebody's rheological properties.

[0140] Table 5, below, exemplifies CO2 storage results at a range of % solids between 5%- 40% for test batches A to E.Table 5 - High Level Overview of Effect of Tailing Pulp Density on CO2 Concentration in Tailings

[0141] Tables 6a - 6c provide additional details on the test parameters for each batch.Table 6a - Effect of Tailing Pulp Density on CO2 Concentration in Tailings (Experimental Details Per Batch)Table 6b - Effect of Tailing Pulp Density on CO2 Concentration in Tailings (Experimental Details Per Batch)Table 6c - Effect of Tailing Pulp Density on CO2 Concentration in Tailings (Experimental Details Per Batch)(iv.) Example 4 - CO2 Gas Strength

[0142] Experimental tests confirm that the method of IPT carbonation is effective between 1% to 100% CO2 gas strength, which allows sequestering between approximately 7.7 - 62 kg CCh / t tailings using the disclosed test conditions. Testing revealed that the method did not perform effectively at atmospheric concentrations of CO2 (0.04 % CO2), resulting in only 1.5 kg CO2 / t tailings stored after 50 hours of injection. While CO2 can be sequestered as low as 1% CO2, the method performs more effectively using gas strengths >=50% CO2.

[0143] Table 7 exemplifies the results at different CO2 gas strengths ranging between 0% to100%.Table 7 - Effect of Varying CO2 Strength

[0144] Tables 8a - 8c provide additional details on the test parameters used for each of batch.Table 8a - Effect of Varying CO2 Strength (Experimental Details Per Batch)Table 8b - Effect of Varying CO2 Strength (Experimental Details Per Batch)Table 8c - Effect of Varying CO2 Strength (Experimental Details Per Batch)(v.) Example 5 - Continuous Processing

[0145] Experimental results were also applied in a pilot test using a continuous process in which new ultramafic slurry was continuously introduced and removed from a tank 202. In these examples, CO2 was being continuously sparged into the tank 202 as new slurry was being introduced therein.

[0146] In this example test, the tank 202 included three sparging units 208. Each of the spargers generated bubble sizes that were, on average, less than 2 mm in diameter.

[0147] Plot 700a (FIG. 7) demonstrates that a continuous feed of fresh tailings into the process, and discharge of carbonated tailings, results in a stable slurry pH, referred to as “steady-state operation”. The carbonated tailings are sampled in duplicate, assayed immediately and after 1 week, allowing observing the change in carbon assay from complete precipitation.

[0148] Plot 700b (FIG. 7) exemplifies the increase in carbon assay between an unreacted mineral slurry feed, and a carbonated discharge slurry, which demonstrates the extent of CO2 storage resulting from the carbonation reaction. In this example, an increase of 0.88% carbon is observed, representing 32 kg CO2 stored / 1 tailings.

[0149] The process parameters for obtaining the data in FIG. 7 is summarized in Table 9, below. Table 10 shows the data results illustrated in plot 700b.Table 9 - Experimental Parameters for Continuous FeedTable 10 - Experimental Data for Continuous Feed ProcessX. INTERPRETATION

[0150] Various systems or methods have been described to provide an example of an embodiment of the claimed subject matter. No embodiment described limits any claimed subject matter and any claimed subject matter may cover methods or systems that differ from those described below. The claimed subject matter is not limited to systems or methods having all of the features of any one system or method described below or to features common to multiple or all of the apparatuses or methods described below. It is possible that a system or method described is not an embodiment that is recited in any claimed subject matter. Any subject matter disclosed in a system or method described that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such subject matter by its disclosure in this document.

[0151] Furthermore, it will be appreciated that 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 embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and componentshave not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limiting the scope of the embodiments described herein.

[0152] It should also be noted that the terms “coupled” or “coupling” as used herein can have several different meanings depending in the context in which these terms are used. For example, the terms coupled or coupling may be used to indicate that an element or device can electrically, optically, or wirelessly send data to another element or device as well as receive data from another element or device. As used herein, two or more components are said to be “coupled”, or “connected” where the parts are joined or operate together either directly or indirectly (i.e., through one or more intermediate components), so long as a link occurs. As used herein and in the claims, two or more parts are said to be “directly coupled”, or “directly connected”, where the parts are joined or operate together without intervening intermediate components.

[0153] It should be noted that terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree may also be construed as including a deviation of the modified term if this deviation would not negate the meaning of the term it modifies. In some examples, these terms may mean ±5%, ±10% or ±50%.

[0154] Furthermore, any recitation of numerical ranges by endpoints herein includes all numbers and fractions subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.90, 4, and 5). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term "about" which means a variation of up to a certain amount of the number to which reference is being made if the end result is not significantly changed.

[0155] The present invention has been described here by way of example only, while numerous specific details are set forth herein in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that these embodiments may, in some cases, 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 description of the embodiments. Various modification and variations may be made to these exemplary embodiments without departing from the spirit and scope of the invention, which is limited only by the appended claims.

Claims

CLAIMS:

1. A process for mineral carbonation, comprising: sparging a stream of compressed carbon dioxide (CO2) containing gas to form sparged CO2; mixing and reacting (i) the sparged carbon dioxide (CO2), with (ii) an ultramafic mineral slurry comprising comminuted ultramafic rock; and forming a carbonated mineral slurry which stores the CO2.

2. The process of claim 1, wherein the ultramafic rock contains a brucite mineral.

3. The process of claim 2, wherein the mineral carbonate is a magnesium carbonate.

4. The process of claim 3, wherein the magnesium carbonate is a nesquehonite mineral.

5. The process of any one of claims 1 to 4, wherein the ultramafic rock is comminuted to have a particle size of less than 2 millimeters, and preferably less than 200 pm or less than 20 pm.

6. The process of any one of claims 1 to 5, wherein the ultramafic mineral slurry has a solid density of greater than 5%.

7. The process of any one of claims 1 to 6, wherein the sparged carbon dioxide increases the acidity of the water in the slurry to a pH below 9, and preferably between 7 to 8.5.

8. The process of any one of claims 1 to 7, further comprising ceasing exposure of the slurry to sparged CO2, which allows the slurry pH to naturally buffer back to basic conditions to encourage the natural precipitation of carbonate minerals.

9. The process of any one of claims 1 to 8, wherein the comminuted ultramafic rock has been removed from minerals comprising pentlandite, heazlewoodite, awaruite, cobaitpentlandite, magnetite, chrome spinel, as well as platinum group metals including platinum, palladium, rhodium, osmium or iridium.

10. The process of any one of claims 1 to 9, wherein the process is performed after or before a mineral concentration processes.

11. The process of any one of claims 1 to 10, further comprising recirculating, concentrating and recompressing unreacted carbon dioxide (CO2).

12. The process of any one of claims 1 to 11, performed as either a batch or continuous process.

13. The process of any one of claims 1 to 12, wherein the sparging is performed on gas with a purity of at least 5% CO2 , and more preferably, at least 95% CO2.

14. The process of any one of claims 1 to 13, wherein the method is performed ex-situ.

15. The process of any one of claims 1 to 14, wherein the bubble size has a diameter of less than2 mm, or less than 1 mm.

16. The process of any one of claims 1 to 15, wherein the mixing is performed at ambient temperature and ambient atmospheric pressure.

17. A system for carrying out the process of any one of claims 1 to 16, comprising: at least one receptacle for mixing and reacting (i) the sparged carbon dioxide (CO2), with (ii) the ultramafic mineral slurry; and at least one sparging unit fluidically coupled to the receptacle for sparging the stream of compressed CO2 to form the sparged CO2.

18. The system of claim 17, further comprising one or more baffles inside of the tank preventing the formation of a vortex during mixing, and otherwise keeping the slurry well mixed and the solids suspended.

19. The system of claims 17 or 18, further comprising a recirculation system, for recirculating unreacted CO2 in a headspace portion of the tank.

20. The system of any one of claims 17 to 19, wherein the at least one tank comprises an agitator for mixing.

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