A method for mechanochemical carbon sequestration of solid feedstocks

Abstract

The present invention relates to a method for the mechanochemical sequestration or capture of carbon from CO2 in solid feedstocks, wherein the method comprises wetting and deagglomeration before carbon sequestration. The invention further relates to an apparatus suitable for the mechanochemical sequestration of carbon dioxide in solid feedstocks and uses thereof.

Description

A METHOD FOR MECHANOCHEMICAL CARBON SEQUESTRATION OF SOLID FEEDSTOCKSField of the invention

[0001] The present invention relates to a method for the mechanochemical sequestration or capture of carbon from CO2 in solid feedstocks. The invention further relates to an apparatus suitable for the mechanochemical sequestration of carbon dioxide in solid feedstocks and uses thereof.Background art

[0002] Anthropogenic emissions have increased carbon dioxide concentrations in the atmosphere to at least 30% more than Pre-Industrial Era levels. Moreover, it is estimated that future global carbon dioxide emissions will increase from about 7.4 GcC (billions of tons of atmospheric carbon) per year, which was the level in 1997, to 26 GtC per year by 2100. The adverse environmental impact linked with increased carbon dioxide emissions has resulted in more stringent environmental standards regarding emissions of pollutants into the atmosphere.

[0003] The management of carbon dioxide emissions can be achieved by: increasing the efficiency of energy conversion, using low-carbon or carbon-free energy sources, as well as the capture and sequestration of carbon dioxide emissions. The sequestration of carbon dioxide, remains the preferred method for tackling antecedent carbon dioxide emissions.

[0004] Mineral carbonation is a sequestration process in which minerals, such as olivine and serpentine, or calcium-rich minerals, react with carbon dioxide to form geologically stable mineral carbonates. These processes mimic the naturally occurring weathering of rocks.

[0005] The mineral carbonation approach has several inherent advantages, including a vast natural abundance of raw materials and the permanent and benign storage of CO2 in solid form. The primary drawback to mineral carbonation has been the reaction kinetics, because these naturally occurring processes happen slowly over geological timeframes instead of industrial time scales. Previous studies have suspended minerals in aqueous carriers, because such systems have been shown to have faster kinetics than direct carbonation. The mineral aqueous mineral carbonation step involves the leaching of magnesium, calcium or another suitable metal or combination of metals and the subsequent reaction with dissolved hydrogen carbonate. A disadvantage of aqueous methods is that the resulting aqueous product or slurry needs to be used on-site to avoid expensive and energy-inefficient transportation or evaporation.

[0006] Sequestration employing solids has been achieved by crushing magnesium-rich minerals to a fine particle size to promote surface reactions that are known to control most mineral dissolution reactions. Such processes have been hampered by extensive comminution of the raw materials, high partial pressures and long reaction times, all of which render the process energy intensive. Other studies have also reported that preheating the serpentine minerals to about 650 °C and above 50 bars of pressure significantly increases their carbonation reactivity, probably due to dehydroxylation, increase in the surface area and destabilization of the crystal structure. However, this pre-treatment isvery energy intensive, requiring more than 200 kWh / ton of serpentine.

[0007] The main commercially available carbonation solutions are either autoclaves relying on high temperature and pressure combinations, or so-called curing chambers designed to cure CC>2-absorbing concrete admixtures after casting. Typically these are not capable of continuous reaction.

[0008] Hence, there remains a need to develop a streamlined, low-temperature and energy-efficient process which can capture carbon dioxide into CC>2-related functional groups across a wide variety of raw materials and which is performed on economically viable timeframes.

[0009] US2008277319A1 discloses a method for the sequestration and transformation of carbon dioxide generated by anthropogenic sources. The method comprises the steps of size-selecting mineral particles and combining it with water to form a slurry which is then reacted with carbon dioxide.

[0010] W02021087606A1 discloses ball milling methods for mechanochemical CO2 sequestration in mineral feedstocks.

[0011] It is an object of the present invention to provide an improved process for sequestering carbon dioxide into solid feedstocks.

[0012] It is a further object of the present invention to provide a process for sequestering carbon dioxide into solid feedstocks which is energy efficient and can preferably be operated as a continuous process.

[0013] It is a further object of the present invention to provide an apparatus suitable for the sequestration of carbon dioxide in solid feedstocks.Summary of the invention

[0014] The present inventors have found that the sequestration of CO2 can be achieved in a highly- efficient manner for a large variety of feedstocks when considering such factors as energy consumption, carbon sequestration capacity, and reactor throughput capacity, if a mechanochemical sequestration method is applied wherein the feedstock is wetted and deagglomerated prior to the carbon sequestration step. The methods can be optimally performed by submitting an agitated bed of deagglomerated and wetted feedstock to carbon sequestration in a different apparatus than where the feedstock was deagglomerated. By separating the high-energy consumption deagglomeration from the carbon sequestration, long residence times in the carbon sequestration apparatus can be applied while low-energy consumption carbon sequestration can still be achieved. In particular, the inventors have found that when a mechanochemical CO2 sequestration wherein moisture control, deagglomeration and carbon sequestration is performed as described herein, an efficient method is obtained which provides consistent results, throughput and CO2 sequestration performance, thereby greatly enhancing process reliability and efficiency. Additionally, it was found that the method can conveniently be coupled to existing flue gas streams, such as fossil fuel flue gas combustion streams or cement kiln flue gas, allowing point-source emissions to be captured without capital- and energy-intensive stand-alone capture processes. The method results not only in a reduction of CO2 concentration but also in SOXand / or NOXreduction, thereby providing further environmental benefits.

[0015] Hence, in a first aspect, the present invention provides a method for carbon sequestration comprising the steps of: i) providing a solid feedstock; ii) providing a carbon-rich gas comprising at least 0.5 vol% CO2; iii) wetting the solid feedstock to obtain a wetted solid feedstock having a moisture content of at least 3 wt.%; iv) deagglomerating the wetted solid feedstock; v) contacting the deagglomerated wetted solid feedstock with the carbon-rich gas to obtain CC>2-enriched material.

[0016] The method is preferably operated in continuous mode.

[0017] Preferably, step (iv) is performed in a first apparatus, and step (v) is performed in a second apparatus, the first apparatus being distinct from the second apparatus.

[0018] Step (v) preferably comprises contacting an agitated bed of the deagglomerated wetted solid feedstock with the carbon-rich gas. The agitated bed is preferably achieved by a mechanical agitation operation (as opposed to a fluidized bed wherein agitation is caused by gas flow).

[0019] In another aspect, the invention provides a production facility for the sequestration of carbon in a solid feedstock thereby producing solid CC>2-enriched material, said production facility comprising a first apparatus which is a deagglomeration apparatus placed upstream of a second apparatus which is suitable for contacting a solid material with a carbon-rich gas comprising at least 0.5 vol% CO2

[0020] In another aspect of the invention there is provided a combustion plant (such as a fossil fuel combustion, wood pellet combustion, biomass combustion or municipal waste combustion plant) or a cement plant comprising a production facility as described herein wherein a gas inlet of the second apparatus is fluidly coupled to a flue gas outlet of the combustion area of the combustion plant or the calciner of a cement plant. Thus, the combustion plant or cement plant and the second reactor are connected such that flue-gas from combustion or calcining can be provided to the reactor.

[0021] In a further aspect there is provided the use of a production facility as described herein for carbon sequestration. In a further aspect there is provided the use of a production facility as described herein for the CO2-enrichment of a solid feedstock. In a further aspect there is provided the use of a production facility as described herein for the removal of CO2 from a carbon-rich gas, such as a flue gas as described herein.Brief description of the figures

[0022] The present invention will now be described in more detail with reference to specific embodiments of the invention, given only by way of illustration, and with reference to the accompanyingdrawings.

[0023] Figures 1 (a) and 1 (b) are schematic representations of a process according to the invention. The dotted lines illustrate different options for wetting the solid feedstock. In figure 1 (b) deagglomeration is performed while contacting a carbon-rich gas.

[0024] Figures 2(a) and 2(b) are schematic representations of a process according to the invention wherein an additional deagglomeration step after carbon sequestration takes place. In figure 2(b) deagglomeration is performed while contacting a carbon-rich gas while figure 2(c) illustrates that CO2 can be contacted with the feedstock before and / or during agglomeration. Figure 2(d) illustrates optional CO2 contacting before and / or during agglomeration but with water added during CO2 contacting.

[0025] Figures 3(a), 3(b) and 3(c) are schematic representations of a process according to the invention wherein a size-reduction step takes place before wetting and deagglomeration. In figure 2(b) size-reduction is performed while contacting a carbon-rich gas while in figure 3(c) an additional deagglomeration step after carbon sequestration takes place. It will be understood by the skilled person that since the various embodiments of the present invention can be combined, it is explicitly envisaged that the embodiments of figures 2(a)-2(d) can be combined with the embodiments of Figures 3(a)-3(c).

[0026] Figures 4-6 show a preferred embodiment of a rotary shaft-drive agitator as described herein, which is a screw 10 for conveying solid material along a longitudinal axis A of a hollow housing of a reactor (not shown). The screw 10 comprises a longitudinal shaft 100 extending along the longitudinal axis A and a helical flighting 101 mounted to the longitudinal shaft 100. The longitudinal shaft 100 is supported at each end by respective bearings (not shown) and may be rotated using any method known in the art.

[0027] Figure 4 shows in a perspective view a rotary shaft-driven agitator as described herein, which is a screw. The helical flighting 101 is formed by a series of blades, each blade being defined as a section of the helical flighting related to one complete helix turn (as shown in figure 6). The helical flighting may be made from one continuous metal sheet wound into multiple blades, or may be made from distinct blades or parts of blades which are joined e.g. by welding. Furthermore, the helical flighting 101 comprises at least one blade having a plurality of openings 102 extending through the blade. The plurality of openings 102 may be arranged symmetrically around the longitudinal axis A, preferably the plurality of openings 102 are provide at the same radial distance in the radial direction R from the longitudinal axis A. As shown in figure 6, the plurality of openings 102 may be identical. The screw 10 further comprises agitation means formed by a plurality of agitation elements 103 extending between the blades of the helical flighting 101 to substantially form a single, double or triple agitation helix H or a part thereof. Preferable the pitch of the agitation helix H is at least ten times the pitch of the helical flighting 101 .

[0028] Figure 5 shows a side view of the screw shown in Figure 4.

[0029] Figure 6 shows a front view of the screw shown in Figure 4.

[0030] Figures 7-9 show a preferred second apparatus 1000 for the preparation of CC>2-enriched material. The second apparatus 1000 has a hollow housing 1 , 1 1 and a screw 10 as shown in figures4-6 mounted in the hollow housing 1 , 11. The screw 10 is supported at each end by respective bearings (not shown) and may be rotated using a drive unit 2 connected to one end of the screw, imparting rotational movement to facilitate material transport. A motor 3 is connected to the drive unit, providing the necessary power for the rotational movement of the screw shaft. A variable speed control mechanism may be integrated into the motor for adjusting the rotational speed to control the conveying rate (not shown).

[0031] Figure 7 shows in a perspective view a second apparatus according to an embodiment of the invention. The second apparatus 1000 further comprises a gas inlet 12 forming a first passage through the wall of the housing 1 , 11 , a solid material inlet 13 forming a second passage through the wall of the housing 11 and a solid material outlet 14 forming a third passage through the wall of the housing 1 , 1 1. Notwithstanding the in- and outlets, the housing 1 , 11 is configured to be substantially airtight. The second apparatus 1000 may further comprise a material chute 4, wherein the material chute 4 is connected to the material outlet 14 such that solid material can be removed from the reactor through solid material outlet 14. The screw 10 is configured to convey solid feedstock from the solid material inlet 13 to the solid material outlet 14 while the gas comprising at least 0.5 vol% CO2 is present in, preferably flowing through the hollow housing 1 , 11.

[0032] Figure 8 shows a side view of the second apparatus shown in Figure 7.

[0033] Figure 9 shows a front view of the second apparatus shown in Figure 7 wherein part of housing was omitted to expose the screw positioned inside the reactor.Description of embodiments

[0034] The expression “comprise” and variations thereof, such as, “comprises” and “comprising” as used herein should be construed in an open, inclusive sense, meaning that the embodiment described includes the recited features, but that it does not exclude the presence of other features, as long as they do not render the embodiment unworkable.

[0035] The expressions “one embodiment”, “a particular embodiment”, “an embodiment” etc. as used herein should be construed to mean that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of such expressions in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. For example, certain features of the disclosure which are described herein in the context of separate embodiments are also explicitly envisaged in combination in a single embodiment.

[0036] The singular forms “a,” “an,” and “the” as used herein should be construed to include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its broadest sense, that is as meaning “and / or” unless the content clearly dictatesotherwise.

[0037] Whenever reference is made throughout this document to a compound which is a salt, this should be construed to include the anhydrous form as well as any solvates (in particular hydrates) of this compound, unless explicitly defined otherwise.

[0038] As used herein, the expression “wt.%” when used in the context of an ionic compound refers to the amount of the compound inclusive of its counterion(s).

[0039] The term “CC>2-enriched material” is used herein to refer to the solid feedstock after being contacted with the carbon-rich gas in step (v). Depending on the feedstock, the physical and / or chemical mechanism underlying the CO2 sequestration may be different. For example, in case the feedstock comprises a mineral the CO2 will typically be converted to carbonates (also referred to as carbonation). In case the feedstock comprises elemental carbon (such as graphite) the CO2 will typically be bonded to the carbon in the form of various functional groups including carboxylates, epoxides, carbonyl groups, etc.

[0040] In accordance with the invention, the BET surface area as referred to herein is determined at a temperature of 77K using a sample mass of 0.1 -0.5g. The BET surface area as referred to herein is determined using nitrogen. A preferred analysis method to determine the BET surface area comprises heating samples to 400 °C for a desorption cycle prior to surface area analysis. A suitable and thus preferred analysis apparatus for determining the BET surface area is a Micromeritics Gemini VII 2390 Surface Analyzer preferably equipped with a Micromeritics FlowPrep 060 flowing-gas degassing unit.

[0041] TGA as used herein refers to Thermogravimetric Analysis, a technique known to the person skilled in the art. A preferred TGA setup to determine the CO2 content of the feedstocks and carbonated materials in the context of the present invention is a Setaram TAG 16 TGA / DSC dual chamber balance employing a 0.1-2 mg sample. In accordance with the invention, the TGA is performed under an inert atmosphere, such as nitrogen or argon.

[0042] In accordance with the invention, unless specified otherwise, the particle size distribution characteristics referred to herein such as D10, D50 and D90 as well as the specific surface area (unless explicitly mentioned to be BET surface area) are determined by measuring with a laser light scattering particle size analyzer utilizing the Mie theory of light scattering, such as the Brookhaven laser particle sizer, Model Microbrook 2000LD or another instrument of equal or better sensitivity and reporting the data using a volume equivalent sphere model. As is known to the skilled person, the D50 is the mass median diameter, i.e. the diameter at which 50% of a sample’s mass is comprised of smaller particles. Similarly, the D10 and D90 represent the diameter at which 10 or 90% of a sample’s mass is comprised of smaller particles.

[0043] The Total Carbon (TC) content referred to herein is preferably determined in accordance with the method described on Soil Sampling and Methods of Analysis, 2nd Ed., CRC Press (2008), p. 244 and further, incorporated herein by reference. The Total Carbon (TC) content is always expressed herein as wt.% based on the total weight of the composition being measured. For example, in case the total carbon content of the solid feedstock is referred to, it is based on the total weight of the solidfeedstock, in case the total carbon content of the CO2 enriched material is referred to, it is based on the total weight of the CC>2-enriched material.

[0044] The moisture content of the solid materials referred to herein (e.g. the solid feedstock provided in step (i) of the method, and the wetted CC>2-enriched material obtained in step (iv)) refers to the moisture content determined by oven-drying the material at 150 °C until constant weight and comparing the initial weight with the dry weight.

[0045] For the purposes of the present disclosure, ideal gas law is assumed such that the mol% of a gas is considered as equal to the vol%.

[0046] In the context of the present invention, reference may be made to the solid material comprised in the second apparatus during operation as “the wetted solid feedstock”. The skilled person will understand that the solid material in the reactor converts from "wetted solid feedstock” to “CC>2-enriched material” as the reaction progresses and that reference to “the solid feedstock” once step (v) has been initiated should be interpreted as referring to the material regardless of its actual stage of conversion to CC>2-enriched material, unless specified otherwise.Process description

[0047] In a first aspect, the present invention provides a process for the preparation of CC>2-enriched material comprising: i) providing a solid feedstock; ii) providing a carbon-rich gas comprising at least 0.5 vol% CO2; iii) wetting the solid feedstock to obtain a wetted solid feedstock having a moisture content of at least 3 wt.%; iv) deagglomerating the wetted solid feedstock, optionally while contacting the carbon-rich gas; v) contacting the deagglomerated wetted solid feedstock with the carbon-rich gas.

[0048] Step (v) of the method results in CC>2-enriched material. In some embodiments of the invention, the method is provided wherein at least step (v), preferably steps (iii)-(v) are performed in continuous mode. The term continuous is to be interpreted as a process in which the production of the CC>2-enriched material is performed continuously by continuous carbon sequestration in step (v). The continuous process thus continuously outputs CC>2-enriched material over a given period of time. Preferably, steps (iii) and (iv) are also performed continuously, such that the process continuously wet, deagglomerates, and sequesters carbon over a given period of time. This is in contrast to batch processing wherein there is no continuous output of CC>2-enriched material but rather a discrete portion (“batch”) which is treated for a time until the complete batch is fully processed all at once. Even if at least step (v), preferably steps (iii)-(v) are performed in continuous mode, some other steps may still be performed in batch mode. For example, the solid feedstock of step (i) may be stored in a silo and continuously fed to the wetting of step (iii) and submitted to steps (iii)-(v) in a continuous manner. Alternatively, a discrete portion of solid feedstock can be provided all at once, after which it is submitted to steps (iii)-(v) in a continuous manner such that CC>2-enriched material is continuously recovered over a given period of time until thediscrete portion of feedstock is spent. A hybrid of these two forms can also be envisaged, wherein discrete portions of solid feedstock are continuously fed (according to a regular or irregular pattern) into step (iii). In all of these described cases, step (v) is considered to be continuous since the output of CC>2-enriched material is continuous over a given period of time. Preferably, steps (iv) and (v) are also continuously performed. In any case, a buffer storage, like a buffer silo, may still be employed to absorb differences in processing capacity of steps (iii), (iv) and (v). In some embodiments of the invention, the method is operated such that CC>2-enriched material is continuously recovered over a period of at least 1 minute, preferably at least 10 minutes, more preferably at least 30 minutes. In preferred embodiments of the invention, the method is operated such that the CC>2-enriched material is continuously recovered over a period of at least 1 hour, preferably at least 4 hours, more preferably at least 8 hours.

[0049] As with any chemical process, the appropriate reaction parameters such as residence time, temperature, pressure, etc. during step (v) are highly dependent on the extent of CC>2-sequestration desired and can routinely be determined by sampling material on a regular basis and monitoring reaction progress e.g. via Total Carbon determination as explained herein.

[0050] The carbon-rich gas of step (ii) of the method described herein may be any gas stream comprising significant amounts of CO2. It will be understood by the skilled person that the composition of the gas may change as the reaction progresses but that continuous replenishment may be provided by e.g. a continuous flow of fresh gas through step (v) (and optionally step (iv) of the method). Coupled with a continuous supply of solid feedstock, this allows the method to operate in continuous mode. In view of the CO2 sequestration happening throughout the process, the gas will have a lower CO2 concentration after step (v) of the method compared to the gas entering step (v) of the method respectively.

[0051] In embodiments of the method described herein the carbon-rich gas provided in step (ii) comprises a combustion flue gas, in particular a flue gas from fossil fuel combustion, wood pellet combustion, biomass combustion or municipal waste combustion. Fossil fuel combustion may be coal, petroleum coke, petroleum, natural gas, shale oil, bitumens, tar sand oil, or heavy oils combustion, or any combination thereof. The combustion flue gas may optionally have been treated to reduce the water content, the SO2 content, and / or the NOx content. In embodiments of the method described herein, the carbon-rich gas provided in step (ii) comprises a cement kiln flue gas. Typically cement kiln flue gas will comprise a fossil fuel combustion flue gas as cement kilns are typically heated by fossil fuel combustion, typically additionally enriched with CO2 originating from the limestone calcination happening inside the cement kiln for the purpose of cement manufacturing. The cement kiln flue gas may optionally have been treated to reduce the water content, the SO2 content, and / or the NOx content.

[0052] The CO2 concentration in the carbon-rich gas provided in step (ii) is preferably at least 1 vol%, preferably at least 2 vol%, more preferably at least 3 vol%. Typical CO2 concentrations for combustion flue gas and cement kiln flue gas are in the range of 1-20 vol%, such as 2-15 vol% or 2-5 vol% or 5-15 vol%, such that it is preferred that the carbon-rich gas provided in step (ii) has a CO2 concentration in the range of 1-20 vol%, such as 2-15 vol% or 2-5 vol% or 5-15 vol%. In alternative embodiments of the invention, the carbon-rich gas provided in step (ii) comprises at least 80 vol% CO2, preferably at least95 vol% CO2.

[0053] The deagglomeration step (iv) may be performed while contacting a carbon-rich gas comprising at least 0.5 vol% CO2, such as a carbon-rich gas as described herein in the context of step (ii). The carbon-rich gas used in step (iv) can be partially or completely recovered and used in step (v). For process balancing, other carbon-rich gas streams may be mixed before the carbon-rich gas recovered from step (iv) is used in step (v). Thus, in some embodiments of the invention wherein step (iv) is performed while contacting a carbon-rich gas comprising at least 0.5 vol% CO2, step (ii) comprises recovering at least part of the carbon-rich gas used in deagglomeration step (iv) and providing it to form at least part of the carbon-rich gas which is used in step (v), optionally after a step of adjusting the humidity of the gas. In such embodiments, the first carbon-rich gas provided in step (ii) of the method described herein is thus first used in step (iv) of the method and subsequently used in step (v) of the method.

[0054] In preferred embodiments of the method described herein, step (ii) comprises providing hot combustion flue gas or cement kiln flue gas with a temperature of more than 120 °C, preferably more than 150 °C, preferably more than 190 °C, and cooling the hot flue gas. The cooling can be effected by any cooling means known to the skilled person, including a heat-exchanger (e.g. with ambient air or coolant), passive cooling, and / or jacket cooling. With passive cooling is meant that the piping transporting the flue gas allows for sufficient heat-exchange with ambient air to cool the hot flue gas. In practice this can be achieved by e.g. increasing piping length, decreasing piping diameter, not insulating the piping etc. Jacket cooling may comprise running a coolant fluid through a jacket placed around the piping transporting the flue gas. The coolant fluid used in the heat-exchanger or the jacket may be any known coolant, including regular water, or a coolant having a freezing point of less than -5 °C, preferably less than -10°C, (typically an aqueous coolant comprising one or more glycols and one or more anticorrosion agents). The cooling is preferably effected by a heat-exchanger and / or jacket cooling. The cooling is preferably performed to a temperature of below 120 °C, preferably below 100 °C, preferably below 90 °C, more preferably below 80 °C, most preferably below 70 °C. After the cooling it may be desirable to perform a further step wherein the cooled flue gas is submitted to a liquid-gas separation step (e.g. using a dehumidifier, demisting pad, or similar equipment) to remove water droplets and / or decrease the moisture content of the cooled flue gas, or to perform a humidification step (depending on the humidity of the flue gas source and the composition of other gases mixed to prepare the carbon- rich gas). In some embodiments of the invention step (ii) comprises providing hot combustion flue gas or cement kiln flue gas with a temperature of more than 120 °C, and cooling the hot flue gas to a temperature of below 100 °C, wherein the cooled flue gas is submitted to a gas-liquid separation step, the liquid being collected and used for wetting the solid feedstock in step (iii), preferably by spraying on the first CC>2-enriched material. In any scenario it is preferred that the temperature of the gas fed employed in step (v) is at least 1 °C above the dew point inside the apparatus wherein step (v) is performed, preferably within 1-20 °C above the dew point, such that the moisture content of the solid phase can more easily be controlled.

[0055] In case the carbon-rich gas provided in step (ii) comprises a combustion flue gas or cement kilnflue gas, it is preferred that the apparatus wherein step (v) is performed comprises a gas inlet which is fluidly connected to a combustion flue gas outlet of a combustion plant. In some embodiments, step (ii) comprises combustion of a fuel as described herein elsewhere, thereby obtaining a hot combustion flue gas with a temperature of more than 120 °C, preferably more than 150 °C, preferably more than 190 °C. In case the carbon-rich gas provided in step (ii) comprises a cement kiln flue gas, it is preferred that the apparatus wherein step (v) is performed comprises a gas inlet which is fluidly connected to a cement kiln flue gas outlet of a cement plant. In some embodiments, step (ii) comprises calcining limestone, thereby obtaining a hot flue gas with a temperature of more than 120 °C, preferably more than 150 °C, preferably more than 190 °C.

[0056] Step (iii) and step (iv) of the method of the present invention may be performed sequentially or simultaneously. Step (iii) and step (iv) of the method of the present invention are advantageously performed simultaneously, for example by wetting the solid feedstock while it is being subjected to a deagglomeration operation.

[0057] As will be clear from the present description, step (v) is a substantially dry process. While the present inventors have found that moisture control of the solid phase provides unique advantages, step (v) is not performed on an aqueous solution or slurry. The present inventors have found that this greatly improves energy efficiency (as no water has to be removed afterwards) and imparts unique properties on the resulting mechanochemically carbonated solid feedstocks, yielding materials which are substantially different from e.g. aqueous carbonation materials.

[0058] The common assumption when working with flue gas for carbon sequestration with regard to moisture control is that the flue gas temperature should be kept above the dew point (preventing condensation). The present inventors have surprisingly found that it is the moisture content of the solid feedstock which is decisive for the overall efficiency of the operations.

[0059] The moisture content of the wetted solid feedstock is expressed in wt.% and determined by total weight of the wetted solid feedstock. The moisture content of the wetted solid feedstock is preferably more than 2 wt.%, preferably more than 5 wt.%, more preferably more than 10 wt.% The present inventors have surprisingly found that the moisture content of the wetted solid feedstock is preferably less than 35 wt.%, preferably less than 27 wt.%, most preferably less than 20 wt.%, since above these levels reduced efficiencies are observed, in particular in case the CO2-enrichment of step (v) is a process wherein no significant size reduction occurs, as is described herein elsewhere. Depending on the feedstock, above this moisture content, a tendency to convert to a slurry may also be observed. The moisture content of the deagglomerated wetted solid feedstock at the start of step (v) is preferably the same as specified herein for the wetted solid feedstock.

[0060] The step (iii) of wetting the solid feedstock may be performed by any means known to the skilled person. Preferably, step (iii) comprises spraying an aqueous composition, such as water, on the solid feedstock; and / or step (iii) comprises contacting the solid feedstock with a humid gas such that it can increase the moisture content of the solid feedstock when it is contacted therewith. This humid gas may be a carbon-rich gas as is described in the context of step (ii). It is highly preferred that step (iii) comprises spraying an aqueous composition, such as water, onto the solid feedstock. The presentinventors have found that such surface wetting is advantageous for the CO2 sequestration efficiency. However even if the solid feedstock is wetted by spraying in step (iii), if dry gas is used for step (v), the solid feedstock may dry out quickly, such that additional moisture control steps are necessary to maintain the moisture content of the solid phase during step (v) at or above the second moisture content. To reduce or eliminate the need for such additional moisture control steps, it is preferred that next to spraying water in step (iii), the humidity of the carbon-rich gas employed in step (v) is controlled such that moisture content of the wetted CC>2-enriched material during step (v) remains at or above the moisture content of the deagglomerated wetted solid feedstock at the start of step (v). In all of the embodiments described herein, it is preferred that the carbon-rich gas has a relative humidity (RH) of at least 50%, preferably at least 70 %, more preferably at least 85 %, such as about 100 %.

[0061] According to the invention the wetting of step (iii) results in an increase of moisture content of the solid feedstock, preferably an increase in moisture content of at least 2 wt.%, preferably at least 5 wt.%. Thus, the moisture content of the wetted solid feedstock obtained in step (iii) is higher than the moisture content of the solid feedstock provided in step (ii), preferably at least 2 wt.% higher, more preferably at least 5 wt.% higher.

[0062] Suitable deagglomeration operations for use in step (iv) include grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), shaking, blending, pulverizing, powderizing, crushing, crumbling, a fluidized bed or ultrasonication.

[0063] Step (iv) is performed in a first apparatus, which is a deagglomeration apparatus, for example an apparatus equipped with means to achieve grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), shaking, blending, pulverizing, powderizing, crushing, crumbling, a fluidized bed or ultrasonication. In preferred embodiments of the invention, wherein steps (iii) and (iv) are performed simultaneously, the wetting of step (iii) also takes place in the first apparatus. This can for example be achieved by equipping a deagglomeration apparatus with one or more means to provide an aqueous composition such as water to the solid feedstock, such as one or more spray nozzles. Thus, the first apparatus preferably comprises deagglomeration means and wetting means, wherein the deagglomeration means preferably comprises means to achieve grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), shaking, blending, pulverizing, powderizing, crushing, crumbling, a fluidized bed or ultrasonication and wherein the wetting means preferably comprises one or more means to provide an aqueous composition such as water to the solid feedstock, such as one or more spray nozzles. The first apparatus preferably comprises one or more rotary shaft-driven agitation means, such as a screw (preferably a shaftless screw, or a screw wherein the helical flighting is attached to the outer surface of a screw shaft), a plough mixer, a ribbon mixer or a paddle mixer (e.g. a pug-mill), preferably a ribbon mixer or paddle mixer.

[0064] It is highly preferred that step (iv) is performed in a first apparatus, and step (v) is performed in a second apparatus, the first apparatus being distinct from the second apparatus. The present inventors have found that the energy input requirement for achieving effective carbon sequestration is much lower than the energy input requirement for achieving deagglomeration. Thus, by performing both operationsin separate apparatus, a much more energy efficient process can be obtained.

[0065] Step (v) of the method preferably comprises contacting an agitated bed of the deagglomerated wetted solid feedstock with the carbon-rich gas. An agitated bed may be achieved by any means known to the skilled person, including agitation by gas flow, mechanical means, sonication, magnetic means, etc. However, the present inventors have found that preferably step (v) comprises subjecting the deagglomerated wetted solid feedstock to a mechanical agitation operation while contacting the carbon- rich gas. Mechanical agitation may be achieved for example by rotating a rotary drum containing the feedstock, or operating mechanical agitation means in contact with the feedstock. Examples of mechanical agitation means are lifting flights mounted in the interior of a rotary drum (e.g. attached to the housing of a rotary drum), milling media (such as inert balls or beads) inside a rotary drum, static paddles mounted inside a rotary drum, a rotary shaft-driven agitation apparatus positioned within the reactor housing (e.g. a screw or a mixer). Preferred rotary shaft-driven agitation apparatus are a plough mixer, a ribbon mixer or a paddle mixer, more preferably a plough mixer or a paddle mixer. Thus, it is preferred that the second apparatus comprises mechanical agitation means configured for contacting solid material during operation such that an agitated bed of solid material is created inside the second apparatus during operation. In particularly preferred embodiments the second apparatus comprises one or more rotary shaft-driven agitation means in contact with the feedstock and step (v) comprises operating at least one of the one or more the rotary shaft driven agitation means. The present inventors have found that high-energy agitation means such as a fluidized bed (which requires a lot of compressor power) are not required to achieve efficient carbonation and a simple mechanically agitated bed suffices. Thus, at any point during step (v) of the method, the gas velocity inside the reactor is lower than the minimum fluidization velocity for the solid feedstock, preferably lower than 80% of the minimum fluidization velocity for the solid feedstock. By using a distinct apparatus from the deagglomeration apparatus the present invention can accommodate the high energy requirement of deagglomeration while keeping the overall process energy consumption low.

[0066] As will be understood from the above, in highly preferred embodiments of the invention the first and second apparatus comprise one or more rotary shaft-driven agitation means in contact with the feedstock, and step (iv) comprises operating at least one of the one or more rotary shaft driven agitation means of the first apparatus at a first speed, and step (v) comprises operating at least one of the one or more the rotary shaft driven agitation means of the second apparatus at a second speed, the first speed being higher than the second speed. Advantageously, the method is operated in continuous mode as explained herein before, and the method comprises simultaneously operating step (iv) and step (v), wherein step (iv) comprises operating at least one of the one or more rotary shaft driven agitation means of the first apparatus at a first speed, and step (v) comprises operating at least one of the one or more the rotary shaft driven agitation means of the second apparatus at a second speed, the first speed being higher than the second speed. In such embodiments the method preferably comprises continuously feeding wetted deagglomerated feedstock from the first apparatus to the second apparatus, optionally via a buffer storage such as a buffer silo. The ratio of the first speed to the second speed is preferably at least 2:1 , such as at least 3:1 . The second speed is preferably at most 350 rpm, preferably no more than 300 rpm. Preferably the one or more rotary shaft driven agitationmeans of the first apparatus comprises a ribbon mixer and step (iv) comprises operating the ribbon mixer at the first speed.

[0067] In preferred embodiments, the rotary shaft-driven agitation means of the second apparatus is rotated at a speed which produces an agitated feedstock bed reaching a height which is at least 15% higher, preferably at least 25% higher than the height of the feedstock bed when there is no rotation, the height of the bed being determined approximately in the centre of the surface of the powder bed and wherein the height of the bed when there is no rotation and the height of the agitated feedstock bed are determined on the same quantity of feedstock loaded in the agitation apparatus.

[0068] As explained before, the second apparatus preferably comprises one or more rotary shaft- driven agitation means in contact with the feedstock. The one or more rotary shaft driven agitation means of the second apparatus preferably comprises a screw (preferably a shaftless screw, or a screw wherein the helical flighting is attached to the outer surface of a screw shaft), a plough mixer, a ribbon mixer or a paddle mixer. Step (v) preferably comprises operating the screw (preferably a shaftless screw, or a screw wherein the helical flighting is attached to the outer surface of a screw shaft), plough mixer, a ribbon mixer or paddle mixer at the second speed. It is highly preferable that the one or more rotary shaft driven agitation means of the second apparatus comprises a screw wherein the helical flighting is attached to the outer surface of a screw shaft, or a shaftless screw. Such apparatus comprising a screw wherein the helical flighting is attached to the outer surface of a screw shaft or a shaftless screw are known to the skilled person for conveying solid materials up a slope. The present inventors have found that they can advantageously be used to produce a mildly agitated bed which allows efficient carbon sequestration to occur.

[0069] As will be understood by the skilled person a shaftless screw is a rotary shaft-driven agitation means because a rotary shaft is still used to rotate the screw, even though the shaft does not extend axially along with the flighting. The screw may be single flight or double flight. The screw may have a constant pitch or a variable pitch. The screw may have a tapered flight. The screw may further comprise paddles mounted on the shaft between the flighting. It is highly preferred that the screw comprises agitation means protruding from the surface of the helical flighting and one or more gas flow passages radially positioned between the first axis and the outer radius of the screw. The present inventors have found that such screws provide an optimized agitated bed and solid-gas interaction providing further improved carbon sequestration efficiency. The agitation means can comprise cut and folded flights. Preferably the agitation means comprise one or more lifting bars connecting two adjacent blades of the helical flighting. It is preferred that two adjacent blades of the helical flighting are connected to each other by two or more lifting bars and / or that a majority, of the blades are connected to two adjacent blades by one or more lifting bars. The lifting bars may be closed or comprise one or more openings. The lifting bars are preferably positioned substantially perpendicularto the helical flighting. It is preferred that if the screw comprises helical flighting attached to the outer surface of a screw shaft (as opposed to a shaftless screw), the one or more gas flow passages are formed by one or more openings extending through a blade of the helical flighting.

[0070] The first and / or second apparatus are preferably placed approximately horizontally. Theorientation of the apparatus is determined as being horizontally when the shaft of the one or more rotary shaft driven agitation means is placed horizontally. In case of a shaftless screw, there is typically a piece of shaft supporting the screw which is placed along the screw axis for connecting the screw with the motor.

[0071] The second apparatus preferably comprises a substantially airtight housing. In case the second apparatus comprises one or more rotary shaft-driven agitation means, this is positioned within said housing. The second apparatus preferably further comprises a solid feedstock inlet and a gas inlet. The solid feedstock inlet and the gas inlet each form a passage through the airtight housing for feeding the solid feedstock and the carbon-rich gas to the inside of the airtight housing. The solid feedstock inlet is preferably a substantially airtight solid feedstock inlet, such as a rotary valve, a trickle valve, butterfly valve, check valve, gate valve, globe valve, ball valve, preferably a rotary valve, or a trickle valve, highly preferably a rotary valve. If an airtight solid feedstock inlet is used, the apparatus comprises at least one gas inlet distinct from the solid feedstock inlet. By employing an airtight solid feedstock inlet continuous feeding of the solid feedstock to the reactor is enabled with minimal air entrainment such that optimal, continuous operation of the reactor can be achieved. Using a substantially air-tight solid feedstock inlet also allows the solid-feedstock provided in step (i) to be stored under a regular air atmosphere until it is fed to the reactor in step (iii), for example simply using a hopper coupled to the reactor. This allows workers to easily supply additional solid feedstock (e.g. by filling the hopper) without risk of exposure to the carbon-rich gas. Alternatively, the solid feedstock inlet and gas inlet may be the same inlet, which can be advantageous in case the solid feedstock is small enough for the particles to be entrained in the gas stream. The second apparatus also has at least one outlet suitable for removing solid material from the second apparatus. Said outlet is typically placed at the opposite side as the solid feedstock inlet. Said at least one outlet is distinct from the solid feedstock inlet and the gas inlet and should be suitable for removing solid material from the second apparatus (and may also be referred to herein as “solid material outlet”). Preferably the second apparatus comprises at least one solid material outlet which is substantially air-tight, for example using a valve as is described herein elsewhere for the solid feedstock inlet. In this case, a distinct gas outlet forming a passage through the wall of the airtight housing is necessary in case step (v) is to take place under an induced flow of gas as described herein elsewhere. Such setups are advantageous because by separating the solids outlet from the gas outlet they allow control over the gas composition in further stages of the process, for example if the solid material is exposed to another carbon sequestration step or a drying step wherein a gas having a different temperature, humidity and / or CO2 content is used. Alternatively, a solid material outlet may be provided which performs a dual function of solid material outlet and gas outlet, such that the CO2- enriched material and the (depleted) carbon-rich gas are removed from the reactor through the same outlet and later separated. In such a case, the solid feedstock and gas outlet may simply be an opening in the housing at a position where CC>2-enriched material can fall out of the apparatus under the influence of gravity, through the opening into a container or into a further carbon sequestration apparatus or a dryer placed in series with the second apparatus. The (depleted) carbon-rich gas may then be amongst others used in the further carbon sequestration apparatus, recirculated to the reactor it was recovered from or removed from the process, such as by venting to the atmosphere after anoptional dedusting step. The further carbon sequestration apparatus preferably has the features of the second apparatus described herein, with the provisio that an airtight solids inlet and a distinct solids and gas inlet are not necessary if the gas obtained from the second apparatus is fed to the further carbon sequestration apparatus. If the container is reversibly closable or disconnectable from the second apparatus, for example using a closable flow regulator, the container can be periodically emptied while the second apparatus can stay in continuous operation.

[0072] It is highly preferred that there is an induced flow of the carbon-rich gas through the second apparatus during step (v). Such induced flow may be caused by mechanical means, such as a fan or compressor.

[0073] The second apparatus is preferably configured to move the feedstock from an inlet-side of the apparatus to an outlet-side of the apparatus. Since during operation, an agitated bed of solid material exists in the second apparatus, the apparatus is preferably configured to move the particles comprised in the agitated bed from an inlet-side of the apparatus to an outlet-side of the apparatus. The skilled person will understand that during normal operation, wherein the apparatus is continuously fed with solid feedstock, the agitated bed in the apparatus is constantly present, but the individual particles comprised in the bed will move from the inlet to the outlet of the apparatus in accordance with their average residence time in the apparatus.

[0074] In embodiments of the method described herein, in order to stimulate carbon sequestration, step (v) is performed at a temperature of less than 120 °C, preferably less than 100 °C, preferably less than 90 °C, more preferably less than 85 °C. In preferred embodiments of the invention, step (v) is performed at a temperature of at least 30 °C, preferably at least 35 °C, preferably at least 38 °C. In particularly preferred embodiments step (v) is performed at a temperature within the range of 30-85 °C, preferably 30-70 °C, most preferably 40-70 °C, such as 50-60°C. These temperatures allow improved carbon sequestration efficiencies to be achieved, in particular in case a slag as described herein is used as a solid feedstock. In preferred embodiments of the invention, no active heating is applied and any increase in temperature is attributed to the temperature of the incoming gas, friction resulting from the size reduction operation or to exothermic reactions taking place during the mechanochemical carbon sequestration. The temperature is preferably determined on the solid material during processing. In some embodiments, active cooling is applied during step (v), for example by providing a cooling jacket around the housing of the apparatus wherein step (v) is performed. The coolant fluid used in the jacket may be any known coolant, including regular water, or a coolant having a freezing point of less than -5 °C, preferably less than -10°C, (typically an aqueous coolant comprising one or more glycols and one or more anticorrosion agents). In all embodiments of the invention it is preferred that the carbon-rich gas has a temperature within the range of 30-85 °C, preferably 30-70 °C, most preferably 40-70 °C, such as 50-60°C when it is contacted with the deagglomerated wetted solid feedstock in step (v).

[0075] The low temperature requirement of the present process means that no fossil fuels are required, and electric heating means (or low caloric value green fuel sources) can realistically be used to supply heat in case the temperature of the gas feed is insufficient to reach the desired temperature. In thisway, fossil fuels can be avoided throughout the whole production chain.

[0076] The present inventors have also found that due to the high volumes of gas (typically flue gas) being employed for CO2-enrichment, moisture content of the solid feedstock, even if controlled, tends to evolve towards undesirable levels for the CO2-enrichment of step (v). A too low moisture content in step (v) results in decreased carbon sequestration efficiencies. Hence, it is preferred that the deagglomerated wetted solid feedstock is maintained at a moisture content equal to or higher than the moisture content at the start of step (v), throughout the further CO2-enrichment treatment of step (v). For the purposes of the present disclosure, to maintain at a target moisture content includes such situations where the solid feedstock deviates from the target moisture content, such deviation is detected or calculated, and corrected. In general, maintaining a certain moisture content throughout a process step should be interpreted to mean that the moisture content is within the desired range during at least 50% of the duration of the step, preferably at least 80% of the duration of the step, in particular throughout the complete duration of the step.

[0077] To maintain the deagglomerated wetted solid feedstock at a moisture content equal to or higher than the second moisture content throughout the CO2-enrichment treatment of step (v) may be performed by (re)wetting the solid phase by spraying an aqueous composition such as water, or by humidifying the carbon-rich gas which contacts the solid feedstock. As will be understood by the skilled person based on the present disclosure, in some preferred embodiments the method of the invention is provided wherein step (iii) comprises spraying an aqueous composition, such as water, on the solid feedstock to obtain wetted solid feedstock, and step (v) comprises maintaining the deagglomerated wetted solid feedstock at a moisture content equal to or higher than the moisture content at the start of step (v) throughout the CO2-enrichment treatment of step (v). The moisture content can be maintained at a moisture content equal to or higher than the moisture content at the start of step (v) throughout the CO2-enrichment treatment of step (v) for example by spraying the solid material one or more times throughout step (v) with an aqueous composition, such as water and / or by humidifying the gas contacting the deagglomerated wetted solid feedstock. Thus, in some embodiments of the invention step (iii) comprises spraying an aqueous composition, such as water, on the solid feedstock, and step (v) comprises spraying an aqueous composition, such as water, on the deagglomerated wetted solid feedstock. Humidification of a gas stream is within the routine capabilities of the skilled person and may be performed by any means, such as bubbling or sparging the gas through an aqueous composition (e.g. water), membrane-driven water-to-gas humidification, mixing the gas stream with water vapor, etc. As will be understood from the above, it is preferred that the surface of the solid material is kept substantially wetted throughout step (v).

[0078] In general, step (v) can be performed at atmospheric pressure, below atmospheric pressure or above atmospheric pressure. Hence, in some embodiments step (v) is performed at a pressure of more than about 150 kPa (e.g., at least 151.988 kPa), preferably more than about 300 kPa (e.g., at least 303.975 kPa). In alternative embodiments of the invention step (v) is performed at a pressure below atmospheric pressure, such as a pressure of less than around 100 kPa (e.g. less than 101.325 kPa), such as less than 50 kPa or less than 10 kPa. In any case, the pressure preferably does not exceed1013 kPa during step (v), preferably the pressure does not exceed 1013 kPa at any point during the method for carbon sequestration described herein. The present inventors have found that such pressures are not required for the present methods, thereby resulting in significant energy savings compared to high-pressure carbonation methods. In all embodiments of the present invention, but in particular those wherein step (v) is performed at a pressure below atmospheric pressure (such as a pressure of less than around 100 kPa (e.g. less than 101 .325 kPa)), it is preferred that reactor is such that the % of false air during step (v) is less than 30%, preferably less than 15%, preferably less than 5%.

[0079] In preferred embodiments of the invention, the ratio of the D50 of the deagglomerated wetted solid feedstock obtained in step (iv) to the D50 of the solid feedstock provided in step (i), is within the range of 0.8-2, preferably within the range of 0.8-1 .7, most preferably within the range of 0.9-1 .5.

[0080] It is highly preferred that step (v) does not result in significant size reduction. However the inventors have found that some agglomeration may take place. In preferred embodiments of the invention, the ratio of the D50 of the deagglomerated wetted solid feedstock obtained in step (iv) to the D50 of the CC>2-enriched material obtained in step (v), is less than 1 .2, preferably less than 1 .1 .

[0081] The method described herein preferably comprises a further step: (vi) deagglomerating the CC>2-enriched material obtained in step (v), optionally after one or more further CO2-enrichment steps wherein the solid material is contacted with a carbon-rich gas comprising at least 0.5 vol% CO2. The preferred embodiments described herein relating to the gas composition, temperature, pressure, duration, etc. of step (v) are also applicable to the optional one or more further CO2-enrichment steps.

[0082] Step (vi) may be performed using the same apparatus as used in step (iv), referred to herein elsewhere as the first apparatus. However, step (vi) is preferably performed using a third apparatus distinct from the deagglomeration apparatus used in step (iv), i.e. distinct from the first apparatus. In preferred embodiments of the invention, the ratio of the D50 of the deagglomerated wetted solid feedstock obtained in step (iv) to the D50 of the deagglomerated CC>2-enriched material obtained in step (vi), is within the range of 0.8-1 .5, preferably within the range of 0.8-1 .2, most preferably within the range of 0.9-1 .2.

[0083] In some embodiments of the invention, step (v) comprises contacting the feedstock with a catalyst, preferably a metal oxide catalyst, such as a transition metal oxide catalyst. Examples of suitable catalysts are selected from the group consisting of iron oxides, cobalt oxides, ruthenium oxides, titanium oxides, nickel oxides, aluminium oxides and combinations thereof. The catalyst may be provided as a pure oxide or as a mineral comprising the oxide, for example the aluminium oxides may be provided in the form of a zeolite. The catalyst should be suitable for increasing the CO2 sequestration of the feedstock. In some embodiments the catalyst is selected from metal oxides for which the ratio TCcatTCo is more than 1 .01 , preferably more than 1 .05 wherein TCcat is the increase the total carbon content of a feedstock when a CO2 sequestration capacity test is performed, wherein a 10 gram sample of solid feedstock is loaded into a pressure cell with 500 grams of stainless steel balls (diameter 12 mm) coated with the catalyst, followed by pressurization of the cell to 1 MPa, and rotation of the pressurized cell at 5000 RPM for 48 hours, wherein the test is performed at an ambient temperature of 20°C andno heating or cooling is applied, and wherein TCo is the increase the total carbon content of a feedstock when a CO2 sequestration capacity test is performed, wherein a 10 gram sample of solid feedstock is loaded into a pressure cell with 500 grams of uncoated stainless steel balls (diameter 12 mm), followed by pressurization of the cell to 1 MPa, and rotation of the pressurized cell at 5000 RPM for 48 hours, wherein the test is performed at an ambient temperature of 20°C and no heating or cooling is applied.

[0084] The catalyst may for example be mixed with the solid feedstock, or immobilised on an inner surface of the second apparatus employed in step (v). The catalyst may also be immobilized on a porous support or bed which is fixed in the apparatus of step (v) in a way such that it allows contact with the solid feedstock.

[0085] The carbon sequestration methods described herein are preferably performed without employing a strong acid, preferably without employing any further oxidizing agent other than the gas provided in step (ii).

[0086] In accordance with preferred embodiments of the invention, the total power consumption represented by steps (iii)-(v) is less than 60 Wh per kg of CC>2-enriched material obtained in step (v), preferably less than 40 Wh, more preferably less than 30 Wh.

[0087] The method of the present invention preferably comprises a further step (vii) of drying the CO2- enriched material recovered in step (v), optionally after one or more further CO2-enrichment steps wherein the solid material is contacted with a carbon-rich gas comprising at least 0.5 vol% CO2, or of drying the deagglomerated material obtained in step (vi). The preferred embodiments described herein relating to the gas composition, temperature, pressure, duration, etc. of step (v) are also applicable to the optional one or more further CO2-enrichment steps. This avoids agglomeration / lumping of the material upon long-term storage. The deagglomeration of step (vi) may be performed before, during or after the drying of step (vii). Drying may be performed by any means known to the skilled person. Drying preferably comprises drying the CC>2-enriched material recovered in step (v) or step (vi) to a moisture content of less than 8 wt.% (by total weight of the dried CC>2-enriched material), preferably less than 5 wt.% (by total weight of the dried CC>2-enriched material), more preferably less than 2 wt.% (by total weight of the dried CC>2-enriched material). Drying is preferably performed by contacting the CO2- enriched material with a drying gas stream (preferably a continuous flow of a drying gas stream) having a temperature of less than 400 °C, preferably less than 300 °C, preferably less than 250 °C and preferably having a relative humidity (RH) of less than 50%, preferably less than 30%, most preferably less than 10%. By keeping the temperature of the drying gas below the values mentioned above, loss of the sequestered CO2 from the CC>2-enriched material is avoided. The drying may be performed inside the same apparatus as step (v) or in a distinct apparatus. For example, the drying may be performed inside the same apparatus as step (v) by changing the humidity of the gas stream after completion of the CO2-enrichment of step (v) which is especially advantageous if the method is not operated in continuous mode. For example, the drying may be performed inside the same apparatus as step (v), by introducing a drying gas stream having a reduced humidity and / or an increased temperature at a point inside the reactor between the solids feedstock inlet and the solid material outlet, which isespecially advantageous if the method is operated in continuous mode.

[0088] As is common in the art, the (depleted) carbon-rich gas after having been submitted to the carbon sequestration process described herein will typically be vented to the atmosphere, optionally after one or more treatments which preferably includes dedusting (e.g. using a baghouse or cartridge collector). Typically, in case an industrial flue gas is used, the (depleted) carbon-rich gas after having been submitted to the carbon sequestration process described herein will be fed to the emission stack of the industrial site.Properties of the solid feedstock and of the obtained CO2-enriched material

[0089] The method of the present invention is not particularly limited with regard to the feedstock used. In order to achieve significant carbon sequestration, it is preferred that the solid feedstock provided in step (i) is a material which exhibits an increase in CO2 content of at least 1 %, preferably of at least 4% when submitted to a CO2 sequestration capacity test wherein a 10 gram sample of solid feedstock is loaded into a pressure cell with 500 grams of stainless steel balls (diameter 12 mm) coated with titanium dioxide, followed by pressurization of the cell to 1 MPa, and rotation of the pressurized cell at 5000 RPM for 48 hours, wherein the test is performed at an ambient temperature of 20°C and no heating or cooling is applied, wherein the CO2 content is determined as mass loss above 400°C measured by TGA employing a temperature trajectory wherein the temperature was increased from room temperature to 800°C at a rate of 10 °C / min and then decreased to room temperature at a rate of 10 °C / min or that the solid feedstock provided in step (i) is a material which exhibits an increase in total carbon content of at least 1 %, preferably of at least 4% when submitted to a CO2 sequestration capacity test wherein a 10 gram sample of solid feedstock is loaded into a pressure cell with 500 grams of stainless steel balls (diameter 12 mm) coated with titanium dioxide, followed by pressurization of the cell to 1 MPa, and rotation of the pressurized cell at 5000 RPM for 48 hours, wherein the test is performed at an ambient temperature of 20°C and no heating or cooling is applied.

[0090] In preferred embodiments of the invention, the solid feedstock provided in step (i) comprises a mineral and / or elemental carbon. In some preferred embodiments, the feedstock comprises a carbonatable material preferably the feedstock comprises at least 0.1 wt.% (by total weight of the feedstock) carbonatable material, preferably at least 0.5 wt.% (by total weight of the feedstock) carbonatable material, most preferably at least 2 wt.% (by total weight of the feedstock) carbonatable material. The carbonatable material is preferably selected from calcium oxides, calcium hydroxides, magnesium oxides, magnesium hydroxides, calcium silicates, magnesium silicates, and combinations thereof.

[0091] The solid feedstock is typically a particulate or granulate material, such as a powder, preferably having the particle size distribution as described herein elsewhere. In some embodiments the solid feedstock provided in step (i) comprises one or more of coal combustion products (in particular fly ash or bottom ash), graphene, graphite, clay, shale, silicate minerals, glass (in particular soda-lime glass or borosilicate glass), iron or steel-making slags, wood, limestone, calcite, amosite, brucite, naturalpozzolan, volcanic rock, biochar, pyroxenes, hydrous magnesium silicates, talc, serpentines, serpentinite, peridotite, olivine, borosilicate glass, volcanic ash, perlite, pumice, obsidian, scoria, tuffs (e.g. rhyolite tuffs, dacite tuffs, basaltic tuffs, trachytic tuffs, phonolitic tuffs, digenetic lithoid tuffs), andesite, clinoptiololite, heulandite, augite, apatite, titanite, biotite, hauynite, nosean, sodalite, magnetite, muscovite, chabazite, analcite, hematite, cristobalite, tripoli, kaolinite, illite, mica, hornblende, mordenite, andesites, basalt, diatomite, tripoli, cherts, dolomite, forsterite, monticellite, wollastonite, diopside, enstatite, lizardite, potassium and sodium feldspars, antigorite, chrysotile, opaline shales, hydraulic cement, slaked lime, concrete, mafic or ultramafic mining tailings and zeolites, preferably selected from serpentinite, peridotite, basalt, volcanic rock, perlite, zeolites, soda-lime glass, bottom ash, coal fly ash, oil fly ash, coal fly ash, subbituminous coal fly ash, anthracite coal fly ash, bituminous coal fly ash, blast furnace (BF) slag (such as air-cooled blast furnace (ACBF) slag or water cooled blast furnace slag), granulating blast furnace (GBF) slag, basic oxygen furnace (BOF) slag, ladle furnace basic slag (LS), electric arc furnace (EAF) flag, and mafic or ultramafic mining tails. The furnace slags may be from ferrous metal production, non-ferrous metal production or phosphorous production, preferably from ferrous metal production. Most preferred are the slag feedstocks recited herein. In preferred embodiments of the present invention, the feedstock is not pre-treated with acid.

[0092] In preferred embodiments of the invention, the method described herein is provided wherein the solid feedstock provided in step (i), has one, two, three or four, preferably four of the following characteristics:• a D10 within the range of 0.005 to 3 pm;• a D50 within the range of 0.1 to 100 pm, preferably within the range of 0.1 to 40 pm, more preferably within the range of 1-40 pm, most preferably within the range of 5-40 pm;• a D90 within the range of 0.5 to 300 pm;• a BET surface area within the range of 0.1 to 10000 m2 / g, preferably within the range of 0.5-2000 m2 / g.

[0093] In all embodiments of the present invention it is preferred that the D90 of the solid feedstock provided in step (i) is as specified above, since this is the most important size characteristic influencing overall performance.

[0094] The deagglomerated and wetted solid feedstock preferably complies with the same particle size and surface area characteristics. In other words, the deagglomerated and wetted solid feedstock recovered in step (iv) preferably has one, two, three or four, preferably four of the following characteristics:• a D10 within the range of 0.005 to 3 pm; a D50 within the range of 0.1 to 100 pm, preferably within the range of 0.1 to 40 pm, more preferably within the range of 1-40 pm, most preferably within the range of 5-40pm;• a D90 within the range of 0.5 to 300 pm;• a BET surface area within the range of 0.1 to 10000 m2 / g, preferably within the range of 0.5-2000 m2 / g.

[0095] Since the CO2-enrichment treatment of step (v) preferably takes place without significant size reduction (maintaining an agitated bed without significant size reduction, as explained herein before), the CC>2-enriched material recovered in step (v) or step (vi) preferably complies with the same particle size and surface area characteristics. In other words, the CC>2-enriched material recovered in step (v) or step (vi) preferably has one, two, three or four, preferably four of the following characteristics:• a D10 within the range of 0.005 to 3 pm;• a D50 within the range of 0.1 to 100 pm, preferably within the range of 0.1 to 40 pm, more preferably within the range of 1 -40 pm, most preferably within the range of 5-40 pm;• a D90 within the range of 0.5 to 300 pm;• a BET surface area within the range of 0.1 to 10000 m2 / g, preferably within the range of 0.5-2000 m2 / g.

[0096] As explained before, for some materials which are prone to agglomeration during step (v), an additional deagglomeration step (vi) may be employed. If a deagglomeration step (vi) is employed, the CC>2-enriched material recovered in step (vi) preferably complies with the particle size and surface area characteristics specified above.

[0097] In some embodiments of the invention, step (i) comprises preconditioning a solid feedstock precursor by contacting it with a carbon-rich gas comprising at least 0.5 vol% CO2 (e.g. the carbon-rich gas of step (ii)) and / or size-reducing a solid feedstock precursor. The preconditioned and / or size- reduced material is then provided as the solid feedstock of step (i). Preconditioning of the solid feedstock precursor may be performed without simultaneously effecting a size-reduction of the feedstock. For example, the feedstock precursor can be stored with a continuous flow of the gas, the feedstock precursor can be stored in a gas-tight container in the presence of the gas, or the solid feedstock precursor can be subjected to mild agitation which does not result in a significant sizereduction of the solid feedstock precursor, for example in a Continuously Stirred Tank Reactor (CSTR). Preconditioning of the solid feedstock precursor may also be performed simultaneously with sizereducing the solid feedstock precursor by subjecting the solid feedstock precursor to a size-reduction operation while contacting it with the carbon-rich gas. The solid feedstock precursor may also be subjected to distinct preconditioning and size-reduction operations. Size-reduction of the solid feedstock precursor may be performed by subjecting the solid feedstock precursor, optionally while contacting the carbon-rich gas, to grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), shaking, blending, pulverizing, powderizing, crushing, crumbling, a fluidized bed or ultrasonication, preferably grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), or ultrasonication. Preferably size-reduction of the solid feedstock precursor is performed milling or crushing, preferably ball milling, roller milling, basket milling, hammer milling, rotor-stator milling, pin milling, jet milling and / or rod milling, preferably ball milling or roller milling, most preferably roller milling. Preferably size-reduction of the solid feedstock precursor is performed while the solid feedstock precursor contacts the carbon- rich gas. In preferred embodiments of the present invention, the solid feedstock precursor which is fed to the size-reduction operation in order to provide the solid feedstock of step (i) has a D95 before the size- reduction which is less than 20 mm, preferably less than 15 mm, more preferably less than 10 mm, most preferably less than 4 mm. For example, the D95 may be in the range of 3-7 mm. In some embodiments of the invention, the D95 before the size-reduction is in the range of 1-20 mm, preferably in the range of 2-15 mm, more preferably in the range of 3-10 mm such as 3-7 mm. The D95 described in this paragraph concerns the mass-based D95 determined by sieve analysis.

[0098] Without wishing to be bound by any theory, the present inventors believe that the sequestration methods of the invention when applied to materials such as graphite, allow platelet-like morphology to be maintained. This is observed by platelet thickness being maintained. Hence, in embodiments of the invention (in particular those embodiments where the feedstock of step (i) comprises or is graphite), the CC>2-enriched material recovered in step (v) or step (vi) has a platelet morphology and has a platelet thickness of more than 10 nm, preferably more than 20 nm, more preferably more than 50 nm. The platelet thickness as referred to herein is preferably determined by calculating the average platelet thickness determined by Transmission Electron Microscopy on all particles for which the platelet thickness can be determined in a random field of view of 25x25 micron recorded from a random sample of a homogenized batch of material.

[0099] The method of the invention is preferably performed such that the ratio of the CO2 content of the CC>2-enriched material recovered in step (v) or step (vi) to the CO2 content of the solid feedstock of step (i) is at least 1 .2:1 , preferably at least 1 .5:1 , preferably at least 3:1 , more preferably at least 10:1 , wherein the CO2 content is determined as mass loss above 400°C measured by TGA employing a temperature trajectory wherein the temperature was increased from room temperature to 800°C at a rate of 10 °C / min and then decreased to room temperature at a rate of 10 °C / min. Similarly, the method of the invention, in particular in case the feedstock is selected from non-carbonaceous materials such as the minerals, slags and glass described herein earlier, is preferably performed such that the ratio of the total carbon content of the second CC>2-enriched material recovered in step (v) or step (vi) to the total carbon content of the solid feedstock of step (i) is at least 1.05:1 , preferably at least 1.1 :1 , more preferably at least 1 .2:1 .A production facility for the sequestration of carbon and the production of CO2-enriched material

[0100] In another aspect, the invention provides a production facility for the sequestration of carbon in a solid feedstock thereby producing solid CC>2-enriched material, said production facility comprising a first apparatus which is a deagglomeration apparatus placed upstream of a second apparatus which is suitable for contacting a solid material with a carbon-rich gas comprising at least 0.5 vol% CO2 Theproduction facility is preferably configured for performing a process as described herein. The production facility is adapted to feed solid material from the first apparatus to the second apparatus, for example by having conveying means connecting a solid material outlet of the first apparatus with a solid material inlet of the second apparatus. The placement of the first apparatus upstream of the second apparatus should be interpreted as the placement such that during operation of the production facility, the solid feedstock is treated in the first apparatus before it is treated in the second apparatus.

[0101] The production facility preferably comprises wetting means. Said wetting means preferably comprise at least one aqueous composition (preferably water) dosing means, such as a spraying nozzle. The wetting means are configured for wetting solid material upstream of the deagglomeration apparatus and / or in the deagglomeration apparatus. Placement of wetting means upstream of the deagglomeration apparatus should be interpreted as the placement such that during operation of the production facility, the solid feedstock is wetted by the wetting means before it is deagglomerated in the deagglomeration apparatus.

[0102] The second apparatus preferably comprises a mechanical agitation means provided for creating an agitated bed of solid feedstock inside the apparatus during operation, as described herein before in the context of the method of the invention. The first apparatus and the second apparatus each preferably comprise one or more rotary shaft-driven agitation means configured to be in contact with the feedstock during use. Preferably the one or more rotary shaft driven agitation means comprises a screw (preferably a shaftless screw, or a screw wherein the helical flighting is attached to the outer surface of a screw shaft), a plough mixer, a ribbon mixer or a paddle mixer, as has been described herein before.

[0103] The second apparatus preferably comprises a substantially airtight housing. In case the second apparatus comprises a mechanical agitation means as described herein (such as one or more rotary shaft-driven agitation means), the mechanical agitation means is positioned within the housing. The second apparatus preferably further comprises a solid feedstock inlet and a gas inlet. The solid feedstock inlet and the gas inlet each form a passage through the airtight housing for feeding the solid feedstock and the carbon-rich gas to the inside of the airtight housing. The solid feedstock inlet is preferably a substantially airtight solid feedstock inlet, such as a rotary valve, a trickle valve, butterfly valve, check valve, gate valve, globe valve, ball valve, preferably a rotary valve, or a trickle valve, highly preferably a rotary valve. The second apparatus also comprises an outlet which is distinct from the solid feedstock inlet and the gas inlet and should be suitable for removing solid material from the reactor (and may also be referred to herein as “solid material outlet”). The outlet may also be substantially air-tight, for example using a valve as is described herein elsewhere for the solid feedstock inlet. In this case, a distinct gas outlet is necessary in case step (v) of the method is to take place under an induced flow of gas as described herein elsewhere. Alternatively, the solid material outlet may be provided for the dual function of solid material outlet and gas outlet, such that the CC>2-enriched material and the (depleted) carbon-rich gas can be removed from the reactor through the same outlet.

[0104] The one or more shaft-driven agitation means of the first and / or second apparatus are preferably placed substantially horizontally. The one or more shaft-driven agitation means of the firstapparatus are configured to rotate at a different rotational speed than the one or more shaft-driven agitation means of the second apparatus. The production facility is preferably configured to rotate at least one of the one or more rotary shaft driven agitation means of the first at a first speed and at least one of the one or more the rotary shaft driven agitation means of the second apparatus at a second speed, the first speed being higher than the second speed.

[0105] In some embodiments, the production facility further comprises a size-reduction apparatus placed upstream of the first apparatus. The size-reduction apparatus preferably comprises a housing, the housing comprising a solid feedstock inlet for introducing the solid feedstock into the size-reduction apparatus, and a gas inlet for introducing a gas stream into the size-reduction apparatus. The sizereduction apparatus preferably further comprises a size-selection means, preferably placed inside the housing, wherein the size-selection means is in fluid communication with the size-reduction apparatus and comprises an outlet for removing solid material entrained in the gas stream from the size-reduction apparatus, wherein the size-selection means is configured to separate material from the size-reduction apparatus into at least a first portion and a second portion, the first portion having a different average particle size than the second portion, and configured to feed the first portion to the outlet and to return the second portion to the size-reduction apparatus. The size-selection apparatus is preferably an air classifier or a sieve (such as a vibrating screen). The size-reduction apparatus is preferably a crusher or a mill, such as a ball mill, roller mill, basket mill, hammer mill, rotor-stator mill, pin mill, jet mill and / or rod mill, preferably ball mill or roller mill. The size-reduction apparatus is configured for reducing the particle size of solid material. The zone of the size-reduction apparatus where size-reduction occurs is in fluid communication with the gas inlet. The solid feedstock inlet and the gas inlet may be the same (allowing for example, a gas stream carrying solid feedstock to be used).

[0106] The gas inlet ofthe size-reduction apparatus and / or ofthe second apparatus is preferably fluidly connected to a combustion flue gas outlet of a combustion plant or a cement kiln.

[0107] The production facility is adapted to feed solid material from the size-reduction apparatus to the first apparatus, for example by having conveying means connecting a solid material outlet of the sizereduction apparatus with a solid material inlet of the first apparatus. The placement ofthe size-reduction apparatus upstream of the first apparatus should be interpreted as the placement such that during operation of the production facility, the solid feedstock is treated in the size-reduction apparatus before it is treated in the first apparatus.

[0108] If a size-reduction apparatus is used, the wetting means are configured forwetting solid material downstream of the size-reduction apparatus. Thus, the wetting means are placed between the sizereduction apparatus and the first apparatus and / or in the first apparatus. This means that during operation of the production facility, the solid feedstock is treated in the size-reduction apparatus before it is wetted by the wetting means.

[0109] In some embodiments of the invention there is provided a production facility as described herein and a gas source comprising a gas comprising at least 0.5 vol% CO2, wherein the gas source is fluidly connected to a gas inlet of the second apparatus. The gas source is preferably a flue gas source. In some embodiments the gas source is a flue gas outlet of a combustion plant (such as a fossil fuelcombustion, wood pellet combustion, biomass combustion or municipal waste combustion plant) or a cement plant, as described herein earlier.

[0110] As will be understood from the above, in preferred embodiments of the invention there is provided a production facility for the sequestration of carbon in a solid feedstock thereby producing solid CC>2-enriched material, said production facility comprising-a first apparatus which is a deagglomeration apparatus configured for receiving and deagglomerating a solid feedstock;-wetting means configured for wetting the solid feedstock before it is fed to the deagglomeration apparatus and / or configured for wetting the solid feedstock in the deagglomeration apparatus;-a second apparatus which configured for receiving deagglomerated wetted solid feedstock from the deagglomeration apparatus and contacting said deagglomerated wetted solid feedstock with a carbon- rich gas comprising at least 0.5 vol% CO2The production facility preferably comprises a size-reduction apparatus configured for receiving solid feedstock, reducing the size of the solid feedstock and feeding the resulting size-reduced solid feedstock to the deagglomeration apparatus.The preferred embodiments described in earlier paragraphs, for example relating to the first, second and size-reduction apparatus, are equally applicable to the production facility of this paragraph.

[0111] In another aspect of the invention there is provided a combustion plant (such as a fossil fuel combustion, wood pellet combustion, biomass combustion or municipal waste combustion plant) or a cement plant comprising a production facility as described herein wherein a gas inlet of the second apparatus is fluidly coupled to a flue gas outlet of the combustion area of the combustion plant or the calciner of a cement plant. Thus, the combustion plant or cement plant and the second reactor are connected such that flue-gas from combustion or calcining can be provided to the reactor.

[0112] In a further aspect there is provided the use of a production facility as described herein for carbon sequestration. In a further aspect there is provided the use of a production facility as described herein for the CO2-enrichment of a solid feedstock. In a further aspect there is provided the use of a production facility as described herein for the removal of CO2 from a carbon-rich gas, such as a flue gas as described herein.

[0113] Preferably the uses described herein comprise contacting a solid feedstock as described herein with a carbon-rich gas as described herein inside the reactor.List of reference signs1. Housing2. Drive Unit3. Motor4. Outlet10. Screw11. Housing12. Gas Inlet13. Material Inlet14. Material Outlet100. Screw Shaft101. Helical Flighting102. Opening in the Flighting103. Agitation Element1000. Second apparatusA. Longitudinal axisH. Triple HelixR. Radial direction

Claims

Claims1 . A method for carbon sequestration comprising the steps of: i) providing a solid feedstock; ii) providing a carbon-rich gas comprising at least 0.5 vol% CO2; iii) wetting the solid feedstock to obtain a wetted solid feedstock having a moisture content of at least 3 wt.%; iv) deagglomerating the wetted solid feedstock; v) contacting the deagglomerated wetted solid feedstock with the carbon-rich gas to obtain CC>2-enriched material, wherein step (iv) is performed in a first apparatus, and step (v) is performed in a second apparatus, the first apparatus being distinct from the second apparatus, wherein step (v) comprises contacting an agitated bed of the deagglomerated wetted solid feedstock with the carbon-rich gas, wherein the moisture content is determined by oven-drying the material at 150 °C until constant weight and comparing the initial weight with the dry weight.

2. The method of claim 1 wherein the carbon-rich gas comprises a combustion flue gas or a cement kiln flue gas.

3. The method of claim 1 or 2 wherein step (v) comprises subjecting the deagglomerated wetted solid feedstock to a mechanical agitation operation while contacting the carbon-rich gas.

4. The method of claim 3 wherein the first and second apparatus comprise one or more rotary shaft-driven agitation means in contact with the feedstock, and wherein step (iv) comprises operating at least one of the one or more rotary shaft driven agitation means of the first apparatus at a first speed, and step (v) comprises operating at least one of the one or more the rotary shaft driven agitation means of the second apparatus at a second speed, the first speed being higher than the second speed.

5. The method of claim 4 wherein the one or more rotary shaft driven agitation means of the second apparatus comprises a screw (preferably a shaftless screw, or a screw wherein the helical flighting is attached to the outer surface of a screw shaft), a plough mixer, a ribbon mixer or a paddle mixer and step (v) comprises operating the screw (preferably a shaftless screw, or a screw wherein the helical flighting is attached to the outer surface of a screw shaft), plough mixer, ribbon mixer or paddle mixer at the second speed.

6. The method of any one of claims 2-5 wherein the second apparatus comprises a substantially airtight housing, a solid feedstock inlet forming a passage through the wall of the housing, a gas inlet forming a passage through the wall of the housing and a solid material outlet forming a passage through the wall of the housing, wherein there is an induced flow of the carbon-rich gasthrough the second apparatus during step (v) and wherein the second apparatus is configured to move the feedstock from an inlet-side of the apparatus to an outlet-side of the apparatus.

7. The method of any one of the previous claims wherein steps (iii) and (iv) are performed simultaneously.

8. The method of any one of the previous claims, wherein step (iii) comprises spraying water onto the solid feedstock.

9. The method of any one of the previous claims wherein the moisture content of the wetted solid feedstock is more than 5 wt.%, preferably more than 10 wt.% and wherein the moisture content of the wetted solid feedstock is less than 35 wt.%, preferably less than 27 wt.%.

10. The method of any one of the previous claims wherein the solid feedstock provided in step (i), has one, two, three or four, preferably four of the following characteristics:• a D10 within the range of 0.005 to 3 pm;• a D50 within the range of 0.1 to 100 pm, preferably within the range of 0.1 to 40 pm, more preferably within the range of 1-40 pm, most preferably within the range of 5-40 pm;• a D90 within the range of 0.5 to 300 pm;• a BET surface area within the range of 0.1 to 10000 m2 / g, preferably within the range of 0.5-2000 m2 / g.11 . The method of any one of the previous claims wherein step (v) is performed at a temperature of less than 120 °C, preferably less than 100 °C, preferably less than 90 °C, more preferably less than 85 °C and a pressure of less than 1013 kPa.

12. The method of any one of the previous claims comprising a further step (vi) deagglomerating the CC>2-enriched material obtained in step (v), optionally after one or more further CO2-enrichment steps wherein the solid material is contacted with a carbon-rich gas comprising at least 0.5 vol% CO2.

13. The method of any one of the previous claims wherein step (i) comprises size-reducing a solid feedstock precursor while contacting a carbon-rich gas comprising at least 0.5 vol% CO2.

14. A production facility for performing the method of any one of claims 1-13, said production facility comprising-a first apparatus which is a deagglomeration apparatus configured for receiving anddeagglomerating a solid feedstock;-wetting means configured for wetting the solid feedstock before it is fed to the deagglomeration apparatus and / or configured for wetting the solid feedstock in the deagglomeration apparatus;-a second apparatus which configured for receiving deagglomerated wetted solid feedstock from the deagglomeration apparatus and contacting said deagglomerated wetted solid feedstock with a carbon-rich gas comprising at least 0.5 vol% CO215. The production facility of claim 14, comprising a size-reduction apparatus configured for receiving solid feedstock, reducing the size of the solid feedstock and feeding the resulting size-reduced solid feedstock to the deagglomeration apparatus.

16. The production facility of claim 14 or 15 wherein the second apparatus comprises a mechanical agitation means provided for creating an agitated bed of solid feedstock inside the apparatus during operation.

17. The production facility of any one of claims 14-16 wherein the second apparatus comprises a substantially airtight housing, a solid feedstock inlet, a gas inlet and an outlet which is distinct from the solid feedstock inlet and the gas inlet, and wherein the gas inlet of the second apparatus is fluidly connected to a combustion flue gas outlet of a combustion plant or a cement kiln.

18. The production facility of any one of claims 14-17 comprising a size-reduction apparatus configured for receiving solid feedstock, reducing the size of the solid feedstock and feeding the resulting size-reduced solid feedstock to the deagglomeration apparatus, wherein the sizereduction apparatus comprises a housing, the housing comprising a solid feedstock inlet for introducing the solid feedstock into the size-reduction apparatus, and a gas inlet for introducing a gas stream into the size-reduction apparatus and wherein the gas inlet of the size-reduction apparatus is fluidly connected to a combustion flue gas outlet of a combustion plant or a cement kiln.

19. The production facility of any one of claims 14-17 wherein the second apparatus is configured for contacting the deagglomerated wetted solid feedstock with a combustion plant flue gas or a cement kiln flue gas.

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