Systems, devices and methods of using mineral waste for carbon capture

Abstract

Systems and methods of producing magnesium carbonate from a mineral waste stream are described herein. The methods include receiving and contacting a mineral waste stream having a solid fraction having magnesium and a carbon dioxide stream at a reactor unit. Carbon dioxide present in the carbon dioxide stream dissolves in the liquid fraction of the mineral waste stream to produce a carbonic acid solution that leaches the magnesium from the mineral grains of the solid fraction. The methods also include directing at least a portion of the solid fraction of the pulp from the reactor unit to a cavitation unit to undergo cavitation, the cavitation inhibiting the formation of a passivation layer on the mineral grains of the solid fraction. After undergoing cavitation, a reactor product stream is directed to a separator unit to separate a liquid fraction therefrom into an aqueous phase stream comprising magnesium carbonate.

Description

Title: SYSTEMS, DEVICES AND METHODS OF USING MINERAL WASTE FOR CARBON CAPTURECross-Reference

[0001] The present application claims priority to United States Provisional Patent Application No. 63 / 472,077 entitled “Systems, Devices and Methods of Using Mineral Waste for Carbon Capture” filed on June 9, 2023, the entire contents of which are hereby incorporated herein by reference for all purposes.Technical Field

[0002] The embodiments disclosed herein relate to systems, devices and methods of processing mineral waste, and, in particular to systems, devices and methods of producing magnesium carbonates from mineral waste.Background

[0003] Carbon dioxide is a greenhouse gas commonly present in industrial emissions. Unfortunately, each year, human activities release more carbon dioxide into the atmosphere than natural processes can remove, causing the amount of carbon dioxide in the atmosphere to increase.

[0004] One approach to reduce the amount of carbon dioxide present in the atmosphere is to sequester it in solid form. Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide.

[0005] In addition to the above, there are various waste residues, such as mineral waste in mining or waste concrete, that are accumulated and not utilized for industrial processing. More specifically, waste generated through mining in the form of overburden and coal processing in the form of rejects and tailings has been defined as mineral waste.

[0006] Others have previously tried to develop technologies for sequestering carbon dioxide in mineral waste, however, these processes are inefficient, expensive and difficult to implement.

[0007] Accordingly, there is a need for new systems, devices and methods of using mineral waste for carbon capture.Summary

[0008] In accordance with a broad aspect, a method of producing magnesium carbonate from a mineral waste stream is described herein. The method includes: receiving, in a reactor unit, a mineral waste stream and a carbon dioxide stream, the mineral waste stream being a pulp having a liquid fraction and a solid fraction, the solid fraction comprising mineral grains having magnesium; contacting the mineral waste stream and the carbon dioxide stream in the reactor unit, carbon dioxide present in the carbon dioxide stream dissolving in the liquid fraction of the mineral waste stream to produce a carbonic acid solution that leaches the magnesium from the mineral grains of the solid fraction; directing at least a portion of the solid fraction of the pulp from the reactor unit to a cavitation unit to undergo cavitation, the cavitation inhibiting the formation of a passivation layer on the mineral grains of the solid fraction; after undergoing the cavitation, re-directing at least a portion of the solid fraction back to the reactor unit; directing at least a portion of the solid fraction of the pulp and the liquid fraction of the pulp as a carbonate stream from the reactor unit to a separator unit to separate the solid fraction into a solid phase stream and the liquid fraction into an aqueous phase stream, the aqueous phase stream comprising the magnesium carbonates; and precipitating the aqueous phase stream to produce the magnesium carbonates.

[0009] In at least one embodiment, the cavitation unit performs hydrodynamic cavitation.

[0010] In at least one embodiment, the hydrodynamic cavitation includes directing the at least a portion of the solid fraction of the pulp from the reactor unit through a venturi.

[0011] In at least one embodiment, the cavitation unit performs ultrasonic cavitation.

[0012] In at least one embodiment, the reactor unit is maintained at an ambient temperature.

[0013] In at least one embodiment, the carbon dioxide stream is received from an industrial process.

[0014] In at least one embodiment, the carbon dioxide stream is atmospheric air.

[0015] In at least one embodiment, the method further comprises: monitoring a first quantity of carbon dioxide within the carbon dioxide stream and a second quantity of carbon dioxide within precipitate stream; and determining a carbon credit based on a volume of carbon dioxide being sequestered in the magnesium carbonates, the volume of carbon dioxide being sequestered in the magnesium carbonates being a difference between the second quantity of carbon dioxide within precipitate stream and the first quantity of carbon dioxide within the carbon dioxide stream.

[0016] In at least one embodiment, the directing at least a portion of the solid fraction of the pulp from the reactor unit to a cavitation unit to undergo cavitation includes continuously recirculating the at least a portion of the solid fraction of the pulp for a period of time.

[0017] In accordance with a broad aspect, a system for producing magnesium carbonate from a mineral waste stream is described herein. The system includes a reactor unit being configured to: receive a mineral waste stream and a carbon dioxide stream, the mineral waste stream being a pulp having a liquid fraction and a solid fraction, the solid fraction comprising mineral grains having magnesium; provide for the mineral waste stream to contact the carbon dioxide stream, carbon dioxide present in the carbon dioxide stream dissolving in the liquid fraction of the mineral waste stream to produce a carbonic acid solution that leaches the magnesium from the mineral grains of the solid fraction; direct at least a portion of the solid fraction of the pulp to a cavitation unit to undergo cavitation, the cavitation inhibiting the formation of a passivation layer on the mineral grains of the solid fraction; receive, after undergoing the cavitation at least a portion of the solid fraction from the cavitation unit; and direct at least a portion of the solid fraction of the pulp and the liquid fraction of the pulp as a carbonate stream to a separator unit. The system also includes the separator unit being configured to separate the solid fraction into a solid phase stream and the liquid fraction into an aqueous phase stream,the aqueous phase stream comprising the magnesium carbonates; and a precipitation unit being configured to precipitate the aqueous phase stream to produce the magnesium carbonates.

[0018] In at least one embodiment, the cavitation unit performs hydrodynamic cavitation.

[0019] In at least one embodiment, the cavitation unit includes a venturi and the at least a portion of the solid fraction of the pulp from the reactor unit is directed through the venturi.

[0020] In at least one embodiment, the cavitation unit performs ultrasonic cavitation.

[0021] In at least one embodiment, the reactor unit is maintained at an ambient temperature.

[0022] In at least one embodiment, the carbon dioxide stream is received from an industrial process.

[0023] In at least one embodiment, the carbon dioxide stream is atmospheric air.

[0024] In at least one embodiment, the system includes a computing unit configured to: monitor a first quantity of carbon dioxide within the carbon dioxide stream and a second quantity of carbon dioxide within precipitate stream; and determine a carbon credit based on a volume of carbon dioxide being sequestered in the magnesium carbonates, the volume of carbon dioxide being sequestered in the magnesium carbonates being a difference between the second quantity of carbon dioxide within precipitate stream and the first quantity of carbon dioxide within the carbon dioxide stream.

[0025] In at least one embodiment, the reactor unit is further configured to continuously recirculate the at least a portion of the solid fraction of the pulp to the cavitation unit for a period of time.

[0026] Other aspects and features will become apparent to those ordinarily skilled in the art, upon review of the following description of some exemplary embodiments.Brief Description of the Drawings

[0027] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification. In the drawings:

[0028] FIG. 1 is a block diagram of system of using mineral waste for carbon capture, according to at least one embodiment described herein.

[0029] FIG. 2 is a block diagram of method of using mineral waste for carbon capture, according to at least one embodiment described herein.

[0030] FIG. 3 is a tests diagram showing details of cavitation tests performed on a system according to at least one embodiment described herein.Detailed Description

[0031] Various apparatuses, systems and methods will be described below to provide an example of each claimed embodiment. No embodiment described below limits any claimed embodiment and any claimed embodiment may cover apparatuses, systems and methods that differ from those described below. The claimed embodiments are not limited to apparatuses, systems and methods having all of the features of any one apparatus, system or method described below or to features common to multiple or all of the apparatuses, systems and methods described below.

[0032] It should be understood that the term “mineral waste” as used herein may include but is not limited to alkaline earth metal containing mineral waste and may contain alkaline earth metals and alkaline earth metal containing rocks, including but not limited to magnesium (Mg). For example, the alkaline earth metal containing mineral waste may include serpentine or serpentinite. Optionally, the alkaline earth metal containing material may include alkaline earth metal containing rocks such as sandstone, granite, anorthosite, basalt, serpentinite, peridotite, serpentinized peridotite, ophiolitic rocks, mafic and ultramafic rocks (containing Mg and Fe minerals), rocks containing more than 10% of pyroxene and peridot, or a combination thereof. Optionally, the alkaline earth metal containing material may also include a phyllosilicate. Further optionally, the alkaline earth metal containing material may include alkaline earth metal containing minerals such ascalcium silicate, magnesium silicate, feldspar, plagioclase feldspar (andesine), peridot (olivine sand), pyroxene (enstatite olivine sand), olivine, serpentine (as in mineral family containing antigorite, chrysotile, lizardite), wollastonite, calcium oxide (CaO), magnesium oxide or periclase (MgO), brucite (Mg(OH)2), mafic and ultramafic minerals (containing Mg and Fe), or a combination thereof.

[0033] The mineral waste may be issued from various industrial wastes or residues such as slag, cement waste, mining processing waste and mineral processing waste, which are available without the need to be mined from geological formations. Optionally, the slag may include steelmaking slag, steelmaking worn MgO brick or a combination thereof. Optionally, the cement waste may include rotary kiln dust (CKD, LKD), waste cement, waste concrete, construction and demolition waste, concrete with aggregates, concrete brick, concrete, red brick or a combination thereof. Optionally, the mining and mineral processing waste may include phyllosilicate mining residue, chrysotile mining residue, serpentine (as in the rock matrix containing the ore) or a combination thereof.

[0034] In at least one aspect, the systems, devices and methods described herein may be used for chemically sequestering carbon dioxide from a carbon dioxide containing gas by producing alkaline earth metal carbonates. The carbon dioxide containing gas may be issued from industrial emissions and have various carbon dioxide concentrations according to the industrial process from which the emissions are derived. The carbon dioxide containing gas may also be atmospheric air.

[0035] In at least one aspect, there is provided a process for carbon dioxide chemical sequestration from industrial emissions that contain carbon dioxide by producing magnesium carbonates.

[0036] Turning now to FIG. 1 , shown therein is a block diagram of a system 10 of using mineral waste for capturing carbon.

[0037] At a first stage of the system 10, a mineral waste feed stream 101 and a carbon dioxide feed stream 102 are received at a reactor unit 100.

[0038] As described above, mineral waste feed stream 101 may be issued from various industrial wastes or residues such as slag, cement waste, mining processing waste and mineral processing waste, which are available without the need to be mined from geological formations. In at least one embodiment, mineral waste feed stream 101 comprises Mg and / or Ca and / or Si. In at least one embodiment, mineral waste feed stream 101 comprises between about 2 wt% and about 15 wt% solid, mixed with water. In at least one embodiment, a non-magnetic fraction mineral waste feed stream 101 comprises between about 2 wt% and about 15 wt% solid, mixed with water. In at least one embodiment, the solids of the mineral waste stream 101 have a particle size in a range of about 50 microns to about 150 microns.

[0039] In at least one embodiment, mineral waste feed stream 101 is received at reactor unit 100 as a pulp, where, in a prior step, metal ions present in a solid fraction of the mineral waste feed stream 101 are dissolved. In at least one embodiment, dissolution (i.e. of alkaline earth group metal ions) occurs in reactor 100. Mineral waste feed stream 101 may be at atmospheric pressure and temperature (e.g., at or about room temperature, 20 degrees C). After mineral waste feed stream 101 enters reactor 100, reactor 100 may be pressurized and / or heated and / or cooled and / or the liquid therein may be recirculated. In at least one embodiment, reactor 100 has a temperature in a range of about 10 degrees C and about 275 degrees C. In at least one embodiment, reactor 100 has pressure in a range of about 1 atm and about 60 atm. In at least one embodiment, a flow rate of mineral waste feed stream 101 may be dependent on a flow rate of mineral waste stream 158, which can be dependent on mill throughput. In at least one embodiment, the flow rate of mineral waste feed stream 101 may be in a range of about 5,000 tonne per day to about 20,000 tonne per day, optionally having and solids content in a range of about 2 wt% to about 15 wt%).

[0040] In some embodiments, reactor unit 100 may also be provided with a water stream 104. Water stream 104 may be utilized to dilute one of mineral waste feed stream 101 and carbon dioxide stream 102, or both.

[0041] Also referring to FIG. 1 , system 10 includes a carbon dioxide feed stream 102. Carbon dioxide feed stream 102 is gaseous and comprises carbon dioxide. As noted above, carbon dioxide feed stream 102 may be issued from industrial emissions and have various carbon dioxide concentrations, according to the industrial process from which the emissions are derived. The carbon dioxide feed stream 102 may also be atmospheric air.

[0042] Accordingly reactor unit 100 includes a gas inlet for receiving the carbon dioxide feed stream 102 and a liquid inlet for receiving the mineral waste feed stream 101.

[0043] In reactor unit 100, carbon dioxide feed stream 102 contacts mineral waste feed stream 101. In reactor 100, carbon dioxide from carbon dioxide feed stream 102 dissolves in the liquid fraction of mineral waste feed stream 101 and forms a carbonic acid solution therein. The carbonic acid solution then provides for the dissolution of the Mg in solution.

[0044] In at least one embodiment, the aqueous slurry in reaction 100 may be agitated to enhance contact between the carbon dioxide containing gas and the alkaline earth metal containing material. The agitation may be ensured by a mechanical agitator such as a propeller. In at least one embodiment, it may be desirable to have an agitation speed that is in the turbulent mixing regime. This regime may be determined experimentally, but for many impeller designs desirable conditions can be obtained if the speed selected is greater than 10,000*viscosity / (Density*DA2). It should be understood that the exact mixing speed selected will depend upon the specifics of the implementation, and that the methodologies to determine this range are documented in the public domain. It should be understood that the agitation step is not limited to a mechanical agitation and may include various known and suitable agitation techniques, such as but not limited to fluidization agitation.

[0045] In at least one embodiment, reactor unit 100 may be operated at ambient temperature and / or near ambient pressure.

[0046] It should be understood that, within reactor 100, as the Mg dissolves into the carbonic acid solution, Mg closest to the surface of the mineral grains (e.g.,serpentine) of the mineral waste feed stream is depleted from the mineral grains at a rate that is higher than that of silica from the mineral grains. Because of this, silica may form a silica layer (i.e., a passivation layer) on the mineral grains. As this occurs, in some instances, carbonates may also form on the surface of mineral grains, thereby creating a carbonate passivation layer. In either case, an undesired surface reaction results in a layer forming on the mineral grains that reduces the mass transfer rate from the mineral grains to the carbonic action liquid.

[0047] In response to this, system 10 includes a cavitation unit 110. Cavitation unit 110 receives a reactor product stream 106 from reactor unit 100. Within the cavitation unit 110, reactor product stream 106 undergoes cavitation.

[0048] In at least one embodiment, the cavitation may be hydrodynamic cavitation. For example, in this embodiment, hydrodynamic cavitation can be performed by passing reactor product stream 106 through a constricted channel at a specific flow velocity or by mechanical rotation of an object through reactor product stream 106.

[0049] In at least one embodiment, the cavitation may be ultrasonic cavitation. For example, in this embodiment, ultrasonic cavitation may be performed by applying ultrasonic waves (e.g., radio waves) to the liquid.

[0050] In at least one embodiment, the cavitation may be hydrodynamic cavitation generated from forcing the slurry through a venturi. In venturi or similar linear flow restriction, cavitation occurs when the flow rate attained is sufficient to lower the local pressure within the throat of the device to the saturated vapor pressure of the liquid. Initiation of cavitation occurs when there is an initial transition from a single-phase flow to a two-phase bubbly flow, and as flow rate increases, an increasingly complex flow field develops. These flow fields are typically highly turbulent; larger gas filled vapor structures form, grow, and trigger vortex breakup. Discrete cavities can undergo oscillatory growth, coalescence, and breakup before finally collapsing as they are transported into higher pressure regions.

[0051] In at least one embodiment, the fluid of reactor product stream 106 has virtually no residence time in cavitation unit 110. Rather, reactor product stream 106 is acontinuously recirculating stream that returns to the reactor 100 as return stream 108. In at least one embodiment, a combined residence time of the fluid within reactor 100 and cavitation unit 110 is in about 36 hours.

[0052] Generally, as hydrogen ions from the CO2 / H2O of the fluid received at reactor 100 diffuse to the surface of mineral grains to the reactive metals in the mineral, the hydrogen ion react to release divalent metal ions. As the reaction products then diffuse away from the particle surface, they can leave behind a silica rich layer on the surface of the mineral grains. This so-called “passivating layer” is detrimental to the reaction process as it serves as a barrier to further interaction of the undissolved metals within the mineral and the hydrogen ions. Additionally, local conditions may result in the precipitation of silica or carbonates on the surface of the mineral grain that may also result in passivating layers.

[0053] Cavitation occurs when vapor bubbles form in low pressure regions of a liquid, and then are rapidly collapsed by returning them to a higher pressure environment. When these vapor bubbles collapse, micro-jets are generated, striking particle surfaces, and causing erosion of the surface of the particle. In the case of the minerals noted above, this erosion breaks the passivating layer and thereby enables greater extraction of alkaline earth ions.

[0054] In at least one embodiment, cavitation aims to destroy and / or exfoliate the Mg depleted silica matrix (i.e. passivating layer) on the surface of the minerals as it develops. As discussed in more detail below, in some cases, it may be advantageous to leach the Mg in the reactor until the passivating layer becomes rate limiting and then circulate through the cavitation unit 110 while leaching.

[0055] In at least one embodiment, system 10 may include an additive feed stream 107 for adding one or more additives to reactor unit 100. For example, in at least one embodiment, it may be desirable to leach Mg and / or Ca from the mineral waste feed stream 101 using a strong acid, such as but not limited to sulfuric acid, hydrochloric acid, an organic acid or any other appropriate acid. In such a case, CO2 could be introduced in the precipitation unit 140 along with a base such as but not limited to NaOH. In thisexample, there may be intermediate steps introduced into the system 10 to produce nickel products and they may not be based on ion exchange / resins capture.

[0056] The main product stream from reactor unit 100 is carbonate stream 112. Carbonate stream 112 includes precipitable carbonates. In some implementations, the carbonate stream 112 is a carbonate-loaded slurry that is provided to a first separation unit 120.

[0057] Separation unit 120 separates the carbonate stream 112 into a an aqueous phase stream 122 and a solid phase stream 124. The aqueous phase 122 includes the precipitable carbonates.

[0058] In at least one embodiment, separation unit 120 may be a filter press. In at least one embodiment, separation unit 120 may be a centrifuge. Therein, the liquid fraction, loaded with Mg, is pumped to nickel recovery unit 130. The solid fraction, mainly comprising silica (S iC>2), is filtered and removed from the separator unit 120 as solid phase stream 124. In at least one embodiment, at least a portion of the solid phase stream 124, being silica rich, may be used to form a silica product, optionally through the addition of further processing steps, such as but not limited to exposing solid phase stream 124 to other acids to purify the silica.

[0059] As noted above, at least part of the aqueous phase stream 122 includes the precipitable carbonates and is supplied to the nickel recovery unit 130. In at least one embodiment, in nickel recovery unit 130, nickel present in aqueous phase stream 122 will be adsorbed selectively, for example onto a solid substrate, and then, optionally, be eluted and purified to another usable material (such as but not limited to nickel sulphate).

[0060] In at least one embodiment, the aqueous stream 132 is released from nickel recovery unit 130 and supplied to a precipitation unit 140. At least a portion of the precipitable carbonates within the aqueous stream 132 are precipitated therein into alkaline earth metal carbonates. More specifically, in the precipitation unit 140, the precipitation of magnesium into magnesium carbonate occurs. In the precipitation unit, for example, the solution received from aqueous stream 132 may be slightly heated to accelerate the precipitation reaction.

[0061] The alkaline earth metal carbonates are produced as a precipitation slurry that is released from the precipitation unit 140 as precipitate slurry stream 142. In at least one embodiment, precipitation unit 140 has an atmospheric pressure. In at least one embodiment, precipitation unit 140 has a temperature in a range of about 30 degrees C to about 70 degrees C. In at least one embodiment, aqueous stream 132 has a residence time in the precipitation unit 140 of less than about 36 hours.

[0062] Second separator unit 150 receives the precipitate slurry stream 142 and separates the solids from the liquids therein to form the precipitate stream 152, which includes the magnesium carbonates. More specifically, the solid fraction produced by the precipitation reaction, mainly composed of magnesium carbonate (MgCO3), is filtered in second separator unit 150.

[0063] In at least one embodiment, at least a portion of the precipitate stream 152 produced by the aforementioned separation may be recycled as recycle stream 154 to the reactor unit 100. For example, from precipitate stream 152 could be recycled as recycle stream 154 to lower new water withdrawals and have a second chance at recovering any ions that did not precipitate. Solid carbonate stream 156 is the product of system 10.

[0064] It should be understood that the mineral waste feed stream 101 that includes the alkaline earth metals may be formed prior to being supplied to the reactor unit 100, for example but the optional units shown in FIG. 1. For example, in an optional step,

[0065] In at least one embodiment, system 10 may include one or more pretreatment units for pre-processing mineral waste feed stream 101. For example, system 10 may include crushing and / or grinding a mineral waste stream 158 comprising alkaline earth metals to enhance the available surface area for contact with the carbon dioxide containing gas and favor carbonation of the alkaline earth metal. In at least one embodiment, crushing and / or grinding the mineral waste stream 158 is performed in a grinding unit 160.

[0066] In at least one embodiment, crushing and / or grinding the mineral waste stream 158 is performed before a thermal pre-treating step. In this embodiment, a ground mineral waste stream 162 is provided to a pre-treatment unit 170 where dehydroxylation may be favored to occur. In at least one embodiment, this step is primarily for serpentine minerals. Other minerals may not need this step as there may be nothing to dehydroxylize. In at least one embodiment, pre-treatment unit 170 may have a temperature in a range of about 600 degrees C to about 750 degrees C. In at least one embodiment, pre-treatment unit 170 may have a residence time in a range of about 10 minutes to about 90 minutes.

[0067] Thermally pre-treating the alkaline earth containing material may help to at least partially remove undesirable water therefrom. During the thermal pre-treatment, water may be vaporized and the crystalline structure of the alkaline earth metal containing material may be changed into a more chemically active structure, allowing better dissolution of the alkaline earth metal in aqueous phase.

[0068] Ground mineral waste having been thermally treated in pre-treatment unit 170 leaves the pre-treatment unit 170 as a treated mineral waste stream 172. Treated mineral waste stream 172 may be supplied to a magnetic separation unit 180 to remove magnetic materials therefrom, such as but not limited to iron (Fe) containing materials, such as but not limited to iron oxide (FesCM and / or Fe2Os).

[0069] In at least one embodiment, prior to entering reactor unit 100, a quantity of carbon dioxide within carbon dioxide stream 102 can be quantified. In at least one embodiment, the quantity of carbon dioxide within carbon dioxide stream 102 may be measured using a mass flow meter on an outlet of a carbon dioxide storage tank.

[0070] In at least one embodiment, after exiting the precipitation unit 140, a quantity of carbon dioxide within precipitate stream 142 can be quantified. After precipitation and solid separation, the solids can be analyzed using, for example, x-ray diffraction to determine the fraction of solid that is a carbonate phase (for example, 99%). The solid could then be weighed (for example, 1 tonne). These combined results could be used to provide the quantity of MgCOs (following the earlier example, the quantitywould be 990 kg of MgCOs), which can be multiplied by the molar ratio of MgCOs to CO2 to give the quantity of CO2 (following the earlier example, the quantity would be 518kg of CO2)

[0071] In at least one embodiment, system 10 may include one or more computing units (not shown) configured to receive carbon dioxide quantification information from and to perform continuous monitoring thereof.

[0072] In at least one embodiment, the one or more computing units may be configured to receive energy use information from one or more of the units described within system 10 and to perform continuous monitoring thereof.

[0073] In at least one embodiment, the one or more computing units may be configured to receive quantity information regarding the addition of one or more additives to the system 10 and to perform continuous monitoring thereof.Examples

[0074] The following paragraphs outline tests that were performed to assess cavitation in systems according to at least one embodiment described herein. Tables 1 and 2 below summarize the test conditions and results, respectively, of the tests.

[0075] Table 1 : Carbonation Assisted by Cavitation Tests Conditions SummaryTest ID T1 T2 T3 T6 T7 T8 T9 T10 T11 T12 T13HP (700- 30)HP HP ( + 1 stHP 700- (650- Carbo (650- 30) 30) 30) Carbo + 1 st Carbo 80PSI + + 1 st Carbo + + US 80PSI + 2nd Carbo / US C „ar .boIUlS_i+ 1 st + carbo US GlassSet-up Hielsher Only carbo + us carbo Carbo Carbo glass 2nd Carbo Carbo reactor + 2nd reactor + 3rd (US) + + 2nd carbo Carbo 3rd carbo Carbo (US)Steel SteelComp 1 Comp Comp Comp Comp Comp Com ial S p Comp 1 Comp 1Mater lag SlagTM 1 TM 1 TM 1 TM 1 TM recentes recentes 1 TM 1 TM TM TMUS 19.4 No 20 No No No 20 No 20 No 20 T reatment (Hz) % solid 15 15 15 13 13 1 1 3 3 3 3Retention 1.5 1.5 1.5 1.5 1.5 3.0 3.0 6.0 6.0 1 .5 + 2 X 1 .5 + 2 X Time (h) 3 3 CO220 20 20 20 20 Atm Atm Atm Atm 80PSI / Atm 80PSI / Atm pressure (PSI)temperature(C)Initial pH 9.6 9.6 9.6 8.3 9.7 9.8 9.8 9.6 9.6 10.0Final pH 7.5 6.5 6.5 6.2 5.9 5.9 6.1 6.2 6.2 5.1 28 59 54 46 59 223 159 42 31 52residues (pm)

[0076] Table 2: Carbonation Assisted by Cavitation Tests Results Summary

[0077] FIG. 3 is a tests diagram showing details of the tests.Tests T1, T2 and T3

[0078] The objective of tests T1 , T2, and T3 was to investigate the impact of ultrasound on the mineral carbonation process and its effectiveness in enhancing CO2 sequestration in serpentine ore. Test T1 was performed in the cavitation reactor, test T2 served as a reference and was conducted in a 1 -L Parr pressure reactor, and test T3 involved pre-treating the material with ultrasound before carbonation. The key metrics for assessing carbonation efficiency were the extraction of magnesium into solution and the total carbon content in the residues. In all three tests, magnesium extraction was around 6-7%, and there was no significant change in total carbon content in the residues, indicating no substantial improvement in CO2 sequestration yield due to ultrasound. However, ultrasound did significantly affect the particle size distribution, particularly in testT 1 , where the material was treated for 2 hours.

[0079] The following limitations were observed during the operation of the cavitation reactor:

[0080] Due to the energy released by the ultrasound, the temperature of the pulp in the reactor (test T1 ) reached 38°C after 45 minutes. The increase in the pulp temperature is linked to the energy supplied by the ultrasound, and since the reactor was not designed to operate in batch mode but in continuous mode, it was not possible to maintain an ambient temperature during the duration of the tests, even with the cooling system.

[0081] It was not possible to achieve a pressure higher than 20 psi during the tests, as it required too much energy for the probe to operate above 20 psi, and the system would automatically shut down.Tests T4 to T7

[0082] The goal of tests T4 to T7 was to evaluate whether sonication could destroy the passivation layer that forms on the surface of the ore during the carbonation of thermally treated samples. These tests sought to determine if sonication could disrupt the silicate passivation layer that develops during carbonation, thereby exposing fresh surfaces for further CO2 leaching.

[0083] Tests T4 and T5 were conducted to produce thermally treated and carbonated residues. Compl TM material was first thermally treated at 650°C for 45 minutes and then carbonated in a pressure reactor at 20 psi. The residues from tests T4 and T5 were then blended and divided into two sub-samples for further testing in T6 and T7.

[0084] In test T6, the material was treated with ultrasound for 15 minutes to break down the passivation layer, while in test T7 the material was not treated. In both tests, the magnesium extraction yield and total carbon content in the residues were equivalent, with 5% magnesium extraction and a total carbon content of 0.11 % in the residues. Therefore, these tests did not demonstrate a positive impact of ultrasound on removing the passivation layer from material obtained after thermal treatment.Tests T8 and T9

[0085] The objective of tests T8 and T9 was to evaluate the effect of ultrasound on the carbonation of recent steel slags. A literature review revealed that cavitation positively influences steel slag carbonation by enhancing the yield of calcium carbonate. In these tests, carbonation and sonication were conducted simultaneously over a period of 3 hours in a jacketed vessel reactor. Test T8 was performed without sonication, whereas test T9 included sonication. The results showed a modest improvement in calcium conversion with ultrasound, with 6% conversion in T8 (without ultrasound) and 9% in T9 (with ultrasound). However, these results are significantly lower than those reported by Santos et al. (2012), who observed calcium conversion rates of 30% without ultrasound and 49% with ultrasound. This discrepancy can be attributed to the different chemical and mineralogical characteristics of the materials used. In this study, the material contained 28.5% CaO and 37.5% Fe2O3, whereas Santos et al. (2012) used material with 56.7% CaO and only 0.17% Fe.Tests T10 and T11

[0086] The literature review highlighted that for sonication to have a real impact on the structure of the material, it is generally recommended to subject the material to be carbonated to long residence times. Tests T1 to T7 underwent relatively short durations of sonication (between 15 and 120 minutes) and did not show any significant difference in magnesium conversion between cases with and without sonication.

[0087] In the tests T10 and T11 , the reaction was carried out for a duration of 6 hours. During these 6 hours, test T11 was subjected to ultrasound, while test T10 served as the reference test without ultrasound. However, it was not possible to measure a significant impact of sonication on magnesium extraction, even with a long retention times (6h), with a magnesium extraction of approximately 9% in both cases.Tests T12 and T13

[0088] In test T13, the Compl TM material underwent thermal treatment at 700°C for 30 minutes, followed by a carbonation step using CO2 at 80 psi. The pulp was thenfiltered, and the residues underwent two additional carbonation stages, assisted by sonication, during which CO2 was bubbled through the pulp. Each stage was conducted at a pulp density of 15% for a duration of 3 hours. Test T12 serves as the reference test, following the same protocol but without sonication treatment.

[0089] The aim of these tests was to evaluate the effectiveness of cavitation- assisted carbonation at higher pulp densities to enhance the impact of cavitation on the material being treated. In the cavitation-assisted test T13, the extraction of magnesium was 25.8%, slightly higher than T12, which was conducted without ultrasound and achieved a magnesium extraction of 24.1 %. Therefore, increasing the pulp density of the solution led to a slight improvement in the extraction of Mg but does not justify the additional energy input required by sonication.

[0090] Table 3 provides the objectives, conditions and conclusions of the carbonation assisted by cavitation tests described above.

[0091] Table 3: Objectives, Conditions and Conclusions of the Carbonation Assisted by Cavitation Tests.

[0092] While the applicant's teachings described herein are in conjunction with various embodiments for illustrative purposes, it is not intended that the applicant's teachings be limited to such embodiments as the embodiments described herein are intended to be examples. On the contrary, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, and equivalents, without departing from the embodiments described herein, the general scope of which is defined in the appended claims.

Claims

ClaimsWhat is claimed is:

1. A method of producing magnesium carbonate from a mineral waste stream, the method comprising: receiving, in a reactor unit, a mineral waste stream and a carbon dioxide stream, the mineral waste stream being a pulp having a liquid fraction and a solid fraction, the solid fraction comprising mineral grains having magnesium; contacting the mineral waste stream and the carbon dioxide stream in the reactor unit, carbon dioxide present in the carbon dioxide stream dissolving in the liquid fraction of the mineral waste stream to produce a carbonic acid solution that leaches the magnesium from the mineral grains of the solid fraction; directing at least a portion of the solid fraction of the pulp from the reactor unit to a cavitation unit to undergo cavitation, the cavitation inhibiting the formation of a passivation layer on the mineral grains of the solid fraction; after undergoing the cavitation, re-directing at least a portion of the solid fraction back to the reactor unit; directing at least a portion of the solid fraction of the pulp and the liquid fraction of the pulp as a carbonate stream from the reactor unit to a separator unit to separate the solid fraction into a solid phase stream and the liquid fraction into an aqueous phase stream, the aqueous phase stream comprising the magnesium carbonates; and precipitating the aqueous phase stream to produce the magnesium carbonates.

2. The method of claim 1 , wherein the cavitation unit performs hydrodynamic cavitation.

3. The method of claim 2, wherein the hydrodynamic cavitation includes directing the at least a portion of the solid fraction of the pulp from the reactor unit through a venturi.

4. The method of claim 1 , wherein the cavitation unit performs ultrasonic cavitation.

5. The method of any one of claims 1 to 4, wherein the reactor unit is maintained at an ambient temperature.

6. The method of any one of claims 1 to 5, wherein the carbon dioxide stream is received from an industrial process.

7. The method of any one of claims 1 to 5, wherein the carbon dioxide stream is atmospheric air.

8. The method of any one of claims 1 to 7 further comprising: monitoring a first quantity of carbon dioxide within the carbon dioxide stream and a second quantity of carbon dioxide within precipitate stream; and determining a carbon credit based on a volume of carbon dioxide being sequestered in the magnesium carbonates, the volume of carbon dioxide being sequestered in the magnesium carbonates being a difference between the second quantity of carbon dioxide within precipitate stream and the first quantity of carbon dioxide within the carbon dioxide stream.

9. The method of any one of claims 1 to 8, wherein the directing at least a portion of the solid fraction of the pulp from the reactor unit to a cavitation unit to undergo cavitation includes continuously recirculating the at least a portion of the solid fraction of the pulp for a period of time.

10. A system for producing magnesium carbonate from a mineral waste stream, the system comprising: a reactor unit being configured to: receive a mineral waste stream and a carbon dioxide stream, the mineral waste stream being a pulp having a liquid fraction and a solid fraction, the solid fraction comprising mineral grains having magnesium; provide for the mineral waste stream to contact the carbon dioxide stream, carbon dioxide present in the carbon dioxide stream dissolving in the liquid fractionof the mineral waste stream to produce a carbonic acid solution that leaches the magnesium from the mineral grains of the solid fraction; direct at least a portion of the solid fraction of the pulp to a cavitation unit to undergo cavitation, the cavitation inhibiting the formation of a passivation layer on the mineral grains of the solid fraction; receive, after undergoing the cavitation at least a portion of the solid fraction from the cavitation unit; and direct at least a portion of the solid fraction of the pulp and the liquid fraction of the pulp as a carbonate stream to a separator unit; the separator unit being configured to separate the solid fraction into a solid phase stream and the liquid fraction into an aqueous phase stream, the aqueous phase stream comprising the magnesium carbonates; and a precipitation unit being configured to precipitate the aqueous phase stream to produce the magnesium carbonates.

11. The system of claim 10, wherein the cavitation unit performs hydrodynamic cavitation.

12. The system of claim 11 , wherein the cavitation unit includes a venturi and the at least a portion of the solid fraction of the pulp from the reactor unit is directed through the venturi.

13. The system of claim 10, wherein the cavitation unit performs ultrasonic cavitation.

14. The system of any one of claims 10 to 13, wherein the reactor unit is maintained at an ambient temperature.

15. The system of any one of claims 10 to 14, wherein the carbon dioxide stream is received from an industrial process.

16. The system of any one of claims 10 to 14, wherein the carbon dioxide stream is atmospheric air.

17. The system of any one of claims 10 to 16 further comprising:a computing unit configured to: monitor a first quantity of carbon dioxide within the carbon dioxide stream and a second quantity of carbon dioxide within precipitate stream; and determine a carbon credit based on a volume of carbon dioxide being sequestered in the magnesium carbonates, the volume of carbon dioxide being sequestered in the magnesium carbonates being a difference between the second quantity of carbon dioxide within precipitate stream and the first quantity of carbon dioxide within the carbon dioxide stream.

18. The system of any one of claims 10 to 17, wherein the reactor unit is further configured to continuously recirculate the at least a portion of the solid fraction of the pulp to the cavitation unit for a period of time.

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