Carbonation apparatus and carbonation system

Abstract

A carbonation apparatus (1) for carbonating a carbonatable raw material. The apparatus comprising a carbonation chamber (3), a slurry inlet (4), a gas inlet (7), a gas outlet (5), and a rotor arrangement (2). The carbonation apparatus (1) further comprising a rotor housing (10) having a plurality of vanes (8) and a central opening (9) for accommodating a portion of the rotor arrangement (2). The gas inlet (7) is positioned such that gas is introduced into the central opening (9) and upon rotation of the rotor arrangement (2), slurry and gas are agitated from the central opening (9) towards the rotor housing vanes (8) facilitating dissolution of gas into the aqueous phase of the slurry.

Description

CARBONATION APPARATUS AND CARBONATION SYSTEMTECHNICAL FIELD

[0001] The present invention relates to an apparatus for carbonating a raw material. The invention further relates to a carbonation system comprising one or more apparatuses for carbonating a raw material.BACKGROUND

[0002] The production of cement and concrete is linked to high CO2 emissions. The major part of the CO2 emissions are related to the cement clinker production, where high energy demands are required to calcine cement raw materials into the cement clinker. During the calcination, limestone is decarbonized and releases CO2. For now, there are no environmentally friendlier alternative raw materials which can be used instead of limestone.

[0003] One way of reducing the carbon footprint of cements and concrete products is to carbonate or re-carbonate (some of) the components in the final concrete such that the overall released CO2 is lower.

[0004] Another way of reducing the carbon footprint is to reduce the amount of cement clinker in the cement and concrete product by replacing the clinker with Supplementary Cementitious Materials (SCM). Known SCMs used today comprise fly ashes, blast furnace slags, and calcined clays. Additionally, there is an ongoing interest in utilizing and recycled concrete waste which upon activation may be utilized as an SCM in cements.

[0005] One way of activating recycled concrete is by griding the recycled concrete waste into Recycled Concrete Fines (RCF) and to carbonate the RCF. Carbonated RCF as an SCM is advantageous in that they allow for recycling and reuse of a valuable product, in combination with sequestration of CO2 while at the same time contributing with cementitious properties to the concrete.

[0006] Other SCM’s such as slags may also be carbonized to provide a negative carbon footprint in the final cement or concrete.

[0007] Disclosure of a dry and semi-dry process for carbonating RCF may be found in EP3744700 Bl where the RCF is grinded in a carbonizing atmosphere (carbogrinding) and subsequently fluidized in a fluidized bed with a gas comprising CO2.

[0008] A disclosure of a wet carbonation process may be found in EP3914651 Al where a carbonate slurry is prepared and introduced into a revolving drum together with a carbonatable material.

[0009] Another carbonation method can be found in WO 2022 / 178258 Al where a SCM material is manufactured by a wet carbonation process where a slurry is carbonated in a mixing tank during agitation and addition of CO2.

[0010] A challenge in the current wet carbonation processes is to provide an efficient and / or fast carbonization of the carbonatable material. One specific challenge is to provide a high gas-hold up ratio such that CO2 is readily available for efficient dissolution in liquid to form carbonic acid and thereby carbonate the carbonatable material. This may be achieved by vigorous stirring which requires high energy demand especially for viscous slurries, or slurries with a high solid to liquid ration.

[0011] Another challenge is to provide sufficiently distributed gas bubbles, preferably as small bubbles. The small bubbles allow for larger surface area of gas in the liquid. However, small nozzles for providing small bubbles tend to plug in environments with slurries and thus require more frequent shutdowns and cleaning operations.

[0012] It is therefore advantageous to provide a wet carbonation system in which the carbonization is achieved in a more efficient way.SUMMARY

[0013] With this background, it is therefore an object of the present invention to provide a carbonation apparatus for carbonating a raw material, the carbonation apparatus comprising:

[0014] a carbonation chamber configured to receive and accommodate a slurry;

[0015] a slurry inlet fluidly connected to the carbonation chamber;

[0016] a gas inlet configured to provide a CCE-containing gas into the carbonation chamber;

[0017] optionally a gas outlet fluidly connected to the carbonation chamber and configured to remove excess gas from the carbonation chamber;

[0018] a rotor arrangement positioned at least partially in the carbonation chamber and being rotatable with respect to the carbonation chamber;

[0019] a rotor housing comprising a plurality of vanes being spaced apart from each other and positioned along a periphery of the rotor housing to define a central opening within the rotor housing for accommodating the rotor arrangement;

[0020] wherein the gas inlet is positioned such that at least some of the CO2- containing gas is introduced into the central opening of rotor housing wherein, during intended use of the carbonation vessel, the rotor arrangement rotates relative to the rotor housing, and the slurry and the provided CCh-containing gas is agitated towards the rotor housing vanes whereby the gas bubbles upon impact with the vanes are broken into smaller bubbles.

[0021] Because of the position of the gas inlet, the gas is broken into smaller bubbles, the surface area pr volume of gas is increased, providing a larger gas-liquid boundary layer. The buoyancy of the smaller particles is additionally lowered enhancing the residence time of the bubbles in the slurry. These benefits together with agitation from the rotor arrangement ensure that the gas bubbles comprising CO2 are well distributed in the slurry and are readily available for being dissolved following the reaction:CO2(g) - CO2(aq)

[0022] Preferably, the majority of the CO2 containing gas is provided to the central opening. More preferably, all the CCh-containing gas is provided to the central opening.

[0023] As the dissolved CO2 in the form of carbonic acid is spend for the carbonation reaction, new CO2 will be dissolved almost immediately since it is well distributed and readily available.

[0024] The raw material may also be referred to as a carbonatable material.Preferred materials include metal oxide bearing materials. Typically, the raw material comprises alkaline rocks, such as alkaline silicates or alkaline oxides which are carbonated into carbonates. Preferably, the raw material comprises calcium or magnesium compounds which are carbonated into calcium carbonateor magnesium carbonate. The raw material may be a SCM-precursor, which in a carbonated state has cementitious properties when mixed into a concrete or cement product. The raw material may be concrete fines, steel slag, air cooled slag, by-pass dust, or other material having cementitious properties before and / or after carbonation. The carbonatable material may in particular be Basic Oxygen Furnace Slag (BOFS).

[0025] The carbonation vessel may have any suitable shape suitable for a mixing tank, such as a substantial cylindrical shape, a frustoconical shape or a combination thereof. In one or more embodiments, the carbonation chamber is substantially gas tight. This may be achieved by having a carbonation chamber, which is substantially enclosed, but having the required inlets and outlets for providing and removing slurry and gas to the carbonation chamber.

[0026] The carbonation apparatus may have a central axis which preferably is oriented in a substantially vertical direction. The rotor arrangement is preferably located near the central axis and / or coaxial with the central axis.

[0027] In one or more embodiments, the rotor arrangement may comprise a rotor shaft having an elongated shape and having a first end located towards the bottom of the carbonation chamber and a second end located outside the carbonation chamber. Preferably, the second end is located above the carbonation apparatus. A drive assembly may be coupled to the second end of the shaft such that the shaft may rotate with respect to the carbonation apparatus. The drive assembly may be an electric motor. In one or more embodiments, the rotor arrangement is configured to rotate with tip speeds of around 5 m / s to 8 m / s, preferably 6 m / s to 8 m / s, such as 7 m / s. This ensures that the bubbles are efficiently decreased in size. The tip speed may be larger or smaller than 5 m / s.

[0028] The first impeller may be located towards the first end of the shaft, i.e. it is located in a portion of the shaft located further towards the first end than the second end. During operation of the carbonation apparatus, the first impeller should be located below a liquid level of the carbonation apparatus.

[0029] Preferably, the first impeller is located in or near the first end of the shaft. The first impeller may comprise a number of blades or vanes located around the periphery of the shaft and extending from the periphery away from the center of the rotor shaft, preferably in a substantially radial direction from the shaft. The bladesor vanes may be substantially parallel to the central axis or inclined with respect to the central axis.

[0030] The gas outlet is preferably located in an upper portion of the carbonation vessel such that slurry do not enter the gas outlet during operation. The gas outlet is an optional feature which may be required if a low concentration of CO2 is provided or if the CO2 containing gas is provided in excess amounts.

[0031] In one or more embodiments, the rotor arrangement comprises a second impeller attached to the rotor shaft. The second impeller may be located above the first impeller. The second impeller is preferably located outside of the rotor housing.

[0032] The purpose of the second impeller is mainly to assist the first impeller in agitating the slurry. In this way, the first impeller can be configured in design to reduce bubble size, where the second impeller can be configured to provide optimal agitation in the carbonation apparatus. The second impeller is only an optional feature and may be provided for larger carbonation apparatuses or for particularly dense slurries.

[0033] In one or more embodiments, the second impeller is located in the middle third of the rotor shaft.

[0034] The carbonation apparatus may be configured with an intended liquid level optimal for the carbonation process. A length T may be defined from the bottom of the shaft to the intended liquid level. The second impeller may be located on the shaft at a position between 0.2T to 0.8T, preferably 0.3T to 0.7T, more preferably between 0.4T to 0.6T, such as around 0.5T.

[0035] Alternatively, a height H may be defined from the carbonation chamber to the first impeller. If the carbonation apparatus is not provided with an intended liquid level, the position of the second impeller on the shaft may be made based on the height H. The second impeller may be located on the shaft at a position between 0.2H to 0.8H, preferably 0.3Hto 0.7H, more preferably between 0.4Hto 0.6H, such as around 0.5H.

[0036] An additional portion of the rotor shaft may extend outside the carbonation apparatus for support and / or connection with the driving means, but this additional portion is not considered for the location of the impellers.

[0037] The second impeller may be similar to the first impeller and comprise a number of blades or vanes located around the periphery of the shaft and extending from the periphery away from the center of the rotor shaft, preferably in a substantially radial direction from the shaft. The vanes or blades may be parallel to or inclined with respect to the central axis. In a preferred embodiment, the first impeller is different from the second impeller.

[0038] In one or more embodiments, the second impeller is a Rushton turbine type of impeller, i.e. having a horizontal plate comprising a number of vertically arranged blades along its periphery.

[0039] In a preferred embodiment, the second impeller comprising a vane part having a first end and second end, the first end and second end being attached to the shaft at different heights and with an angular offset. Preferably, the second impeller comprises a plurality of vane parts, in particular 2, 3, 4, 5, 6, 7, or 8 vane parts. The angular offset may be dependent on the number of vane parts and may be between 20° to 180°, such as 120° to 40°, preferably between 60° to 90°.

[0040] In a preferred embodiment of the second impeller, the vane part having a first vane portion extending from the shaft in a first direction and having a first vane surface being inclined with respect to the shaft axis, and a second vane portion extending in a second direction different from the first direction, the second vane portion having a second vane surface being inclined with respect to the shaft axis, the first vane portion and second vane portion being connected by an intermediate vane portion.

[0041] Preferably, the first vane portion is near the first end and the second vane portion is near the second end.

[0042] Preferably, at least one of the first vane portion or the second vane portion extends in a radial direction from the shaft. In one embodiment, both the first vane portion and the second vane portion extend in a radial direction from the shaft. Alternatively, the first vane portion and / or the second vane portion may extend in a direction inclined with a radial direction from the shaft. The inclination of the first vane portion and / or the second vane portion may be between 5° to 45°, such as 10° to 40°, such as 15°-35°, such as 20°-30°, such as 25°.

[0043] In a preferred embodiment, the intermediate vane portion has a vane surface parallel to the shaft axis.

[0044] In one or more embodiments, the rotor shaft is hollow and configured for having a CCh-containing gas flowing therethrough. The rotor shaft may be configured to receive the gas through the second end of the rotor shaft and for providing the gas to the first end where it may flow out of the rotor shaft through one or more openings. The second end is preferably located outside of the carbonation chamber and fluidly connected to a source of a CCh-containing gas.

[0045] The first impeller may be configured with one or more openings, configured to allow the CCh-containing gas to flow from the shaft and into the central opening of the rotor housing.

[0046] In one or more embodiments, the carbonation apparatus comprises one or more gas inlets. The one or more gas inlets are configured to provide a CO2- containing gas into or near the central opening in the rotor housing. The one or more gas inlets may in particular be located in a lower portion carbonation chamber such as on a bottom surface of the carbonation apparatus or on a bottom surface of the rotor housing.

[0047] In one or more embodiments, the CCh-containing gas may be provided both through the rotor shaft and through one or more gas inlets.

[0048] In one or more embodiments, the slurry may be provided to the carbonation chamber near the first impeller and / or the rotor housing, and the CCh-containing gas may be provided to the slurry prior to entering the carbonation chamber. Additional CCh-containing gas may be provided to the slurry in the carbonation chamber through the gas inlet.

[0049] The first impeller may comprise any number of blades such as six blades, eight blades, twelve blades, sixteen blades or any other number of blades. The first impeller may be sized for positioning within the central opening of the rotor housing.

[0050] The first impeller and the blades of the first impeller may have a number of different shapes. In one or more embodiments, the first impeller as a substantial half spherical shape. The first impeller may have a horizontal plate, preferably circular, and a number of blades attached to the bottom side of the horizontal plate. The blades being arranged on lines from the center of the horizontal plate towards the periphery of the horizontal plate. The blades may be arranged perpendicular to the horizontal plate or with an acute angle with respect to the horizontal plate.

[0051] In one or more embodiments, the blades may be curved or substantially straight blades.

[0052] Particular designs apply to the first impeller when a CO2-cotaining gas is provided through the shaft and the first impeller. In one or more embodiments, the first impeller comprises an impeller body having a plurality of outer blades that extend outwardly from the impeller body.

[0053] The body of the first impeller may also include passageways for receiving the CO2-containing gas and distributing the gas between the vanes or blades. Each of the passageways may include an inlet to receive at least one gas and an outlet to emit the at least one gas received via the inlet. The outlet of each passageway is spaced apart from the outlets of other passageways. The outlet of each passageway may be positioned in the body between immediately adjacent outer blades. The outer blades may be spaced apart from one another along the external surface of the body of the rotor and the inner blades may be spaced apart from each other and may at least partially define the conduits.

[0054] In one or more embodiments, the rotor housing comprises a plurality of vanes the vanes, each vane comprising a plurality of slots. The slots may in a particular embodiment be located in the upper half of the vanes, in a middle portion of the vanes, and / or in a lower portion of the vanes.

[0055] Each of the slots preferably has a shape that is elongated in a direction along the width of the vane. In a particular embodiment, the slots are rectangular in shape.

[0056] The vanes of the rotor housing may be shaped to complement the shape of the blades of the first impeller.

[0057] In one or more embodiments, the carbonation apparatus is configured to operate at around atmospheric pressure. In one or more embodiments, the carbonation apparatus is configured to operate at temperatures below the boiling point of water (at atmospheric pressure), i.e. at temperature from around 20 - 95 degree C. The temperature is highly dependent of the temperature of the CO2- containing gas. Additionally, the temperature is also dependent on the rate of reaction since the carbonation reaction is an exothermal process.

[0058] To avoid reaching the boiling point of water, and to operate at a desired temperature, the carbonation apparatus may be configured with heating means and / or cooling means. Preferably, the heating means and / or cooling means arelocated externally of the carbonation chamber or integral with the carbonation apparatus.

[0059] According to another aspect, the invention relates to a carbonation system comprising a plurality of carbonation apparatuses according to the first aspect of the invention. The carbonation apparatuses may be fluidly coupled in series such that slurry from a first carbonation apparatus may be provided to a second carbonation apparatus etc. In this way, the first carbonation apparatus would comprise the carbonated material with the lowest degree of carbonation and the last carbonation apparatus would comprise carbonated material with the highest degree of carbonation.

[0060] The carbonation apparatuses may be operated at different temperatures and PH. The carbonation apparatuses may alternatively be operated at similar temperatures.

[0061] In one or more embodiments, the source of CCh-containing gas may be split into individual gas streams, each supplied to a different carbonation apparatus. This embodiment is preferred if the CCh-containing gas is readily available and not a limiting factor for the process, since high concentration of CO2 in all tanks provides the fastest reaction rate.

[0062] Excess gas from each of the carbonation apparatuses may be combined into a single exit gas stream. This configuration would typically provide an exit gas stream with a reduced amount of CO2, but still some CO2.

[0063] If the amount of CCh-containing gas is limited, or the object is to provide a discharge gas with as little CO2 as possible, the excess gas from one carbonation apparatus may be provided to another. In this embodiment the CCh-containing gas with the highest CO2 concentration would preferably be provided to the last carbonation apparatus. Excess gas from the last carbonation apparatus may be provided to the second last carbonation apparatus etc.

[0064] The discharge gas in this configuration may have a lower concentration of CO2, but may require additional carbonation apparatuses or longer residence time.

[0065] The CCE-containing gas may be a flue gas from an industrial process, preferably cement clinker manufacturing process. Alternatively, the CO2- containing gas obtained from a carbon capture process. The CCE-containing gas preferably has a CO2 content of at least 15w / w%, preferably at least 20 w / w%,which is typical from industrial flue gases. Much higher concentrations of CO2 in the CCh-containing gas may be utilized for the process. It may e.g. be possible to provide a CCh-containing gas from a carbon capture process having CO2 content of at least 50 w / w%, preferably at least 60 w / w%.

[0066] In one or more embodiments, the slurry is provided by mixing a raw material with a liquid in a mixing tank. The liquid may be water with or without additives. Additives may as an example be an anti-foam additive. The liquid may also be recycled liquid / water from the carbonation process. The raw material may be a SCM-precursor, i.e. a material which after undergoing carbonation may be used as a component with cementitious properties in a cement or concrete product. The raw material may comprise cured cement and may as an example be concrete. More particularly, it may be recycled concrete fines, i.e. concrete waste grinded to a particle size of less than 2.0 mm, such as less than 1.5 mm, such as less than 1.0 mm. In some embodiments, it may be preferred to grind the raw material to a smaller size such as less than 500 pm, such as less than 250 pm, such as less than 100 pm, such as less than 90 pm.

[0067] A smaller grain size requires more energy during grinding but allows for easier carbonation.

[0068] The carbonation apparatus may comprise one or more sensors configured to measure the operational conditions of the carbonation apparatus. The one or more sensors may be configured to measure one or more of the below parameters:

[0069] -Temperature of gas and / or slurry

[0070] -gas composition of inlet and outlet gas

[0071] -inlet and outlet gas flow in mass and / or volume

[0072] -gas pressures

[0073] -rotational speeds of the rotor arrangement

[0074] -pH of the slurry.

[0075] Gas analyzing means may be connected to the gas outlet such that the concentration of CO2 may be provided during operation. The gas analyzing means may be connected to a control device, which may regulate the amount of CO2- containing gas provided to the slurry. Any of the sensors may be coupled to a control device. Based on information from the sensors, the control device may beconfigured to control the inlet of slurry, inlet of CCh-containing gas, rotational speed of the rotor arrangement, the heating means, and / or cooling means.

[0076] In another aspect, the invention relates to the use of a carbonation apparatus according to the first aspect for carbonating a raw material. In another aspect, the invention relates to a method for carbonating a raw material with the carbonation apparatus. The carbonation apparatus may be operated as a batch process or as a continuous process. It may also be operated as a so-called semi -continuous process where a number of carbonation apparatuses are run in batch with a time-offset such that the carbonation apparatuses are filled and emptied in turn to provide a substantially continuous input and output. During operation a slurry comprising a raw material is provided to the carbonation apparatus. The slurry is agitated in the carbonation apparatus by rotating the rotor arrangement. A CCh-containing gas is provided to the central opening in the rotor housing. By means of the rotor arrangement and the rotor housing, the gas is broken into smaller bubbles and distributed in the slurry. The CCh-containing gas dissolves in the water and forms carbonic acid. Upon contact between the carbonic acid and the raw material, a carbonatable side group or molecule may be carbonated and binds the CO2.

[0077] By the term slurry is meant a semi-liquid mixture, i.e., a liquid in which particles are suspended. Preferably, the liquid is water.

[0078] In one or more embodiments, the bubble size of the CCh-containing gas is decreased to below a diameter of around 5 mm, such as below around 3 mm. Preferably, the bubble size of the CCh-containing gas is decreased to a diameter of between 0.1 mm to 3 mm, preferably between 0.2 mm to 1.0 mm. The small bubble size in combination with agitation of the slurry provides for a better gas hold up. The gas hold up may be measured as volume gas pr volume of fluid. Preferably, the gas hold up may be larger than 40%, such as above 50% such as above 60 %, such as above 70%, such as above or around 80%.

[0079] Suitable conditions for efficient bubble size reduction are achieved by rotating the first impeller with a tip speed of at least between 5 m / s to 8 m / s tip speed, such as 6 m / s or 7 m / s. The tip speed may be larger or smaller than 5 m / s.

[0080] In one or more embodiments, the temperature of the slurry is kept at temperatures around 50°C to 95°C. The carbonation reaction is exothermic and thus heat is created during the carbonation. Depending on the starting temperature of theCCh-containing gas and the slurry, it may be necessary to heat and / or cool the slurry during agitation to maintain a temperature below the boiling point of water and to ensure a temperature which is above 50°C.

[0081] In one or more embodiments the carbonation vessel is operated such that a change in pH of the slurry from alkaline to acidic is used as an indicator for substantially complete carbonation, and / or wherein an increase in CO2 concentration of the outlet gas is used as an indicator for substantially complete carbonation.

[0082] In the carbonation process, carbonatable material may be carbonated until either the pH change from alkaline to acidic or until the concentration of CO2 in the outlet gas increase.

[0083] In one or more embodiments, the solids to liquid ratio in the slurry is around 10 to 50 w / w%, preferably 20-30 w / w%.

[0084] Further presently preferred embodiments and further advantages will be apparent from the following detailed description and the appended dependent claims.

[0085] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.BRIEF DESCRIPTION OF DRAWINGS

[0086] A better understanding of embodiments of the present disclosure (including alternatives and / or variations thereof) may be obtained with reference to the detailed description of the embodiments along with the following drawings, in which:

[0087] Fig. 1 shows a schematic cross-sectional view of a carbonation apparatus according to an embodiment of the invention;

[0088] Fig. 2 shows schematic perspective view of a carbonation apparatus according to an embodiment of the invention;

[0089] Fig. 3 shows a schematic perspective view of a rotor housing according to an embodiment of the invention;

[0090] Fig. 4 shows a schematic perspective view of an impeller according to an embodiment of the invention;

[0091] Fig. 5 shows a perspective view of a carbonation apparatus comprising a first impeller and a rotor housing according to an embodiment of the invention;

[0092] Fig. 6 shows a perspective view of a carbonation apparatus comprising a first impeller, a second impeller and a rotor housing according to an embodiment of the invention;

[0093] Fig. 7 shows a schematic illustration of a carbonation apparatus comprising a first impeller, a rotor housing and a second impeller according to another embodiment of the invention;

[0094] Fig. 8 shows a perspective view of a second impeller according to an embodiment of the invention;

[0095] Fig. 9 shows a schematic illustration of a second impeller seen from a top view;

[0096] Fig. 10 shows a schematic illustration of second impeller seen from a side view;

[0097] Fig. 11 shows a carbonation system comprising a plurality of carbonation apparatus’ according to an embodiment of the invention.DETAILED DESCRIPTION

[0098] Fig. 1 shows a carbonation apparatus 1 for carbonating a carbonatable raw material. The carbonation apparatus 1 has a carbonation chamber 3 configured to receive and accommodate a slurry. A slurry inlet 4 is fluidly connected to the carbonation chamber 3. One or more gas inlet(s) 7a, 7b is fluidly connected to the carbonation chamber 3 and configured to provide a CO2-containing gas into the carbonation chamber 3. A gas outlet 5 is fluidly connected to the carbonation chamber 3 and configured to remove excess gas from the carbonation chamber 3. A rotor arrangement 2 is positioned at least partially in the carbonation chamberand being rotatable with respect to the carbonation chamber 3. In the embodiment shown, a portion of the rotor arrangement 2 extends through the top of the carbonation chamber 3 and is connected to a drive 23. The drive may be fixedly connected to the carbonation apparatus 1 and provide rotational motion to the rotor arrangement 2. The carbonation apparatus 1 further comprises a rotor housing 10 comprising a plurality of vanes 8. The vanes 8 are spaced apart from each other and positioned along a periphery of the rotor housing 10 to define a central opening 9 within the rotor housing 10. The central opening being configured for accommodating a lower portion of the rotor arrangement 2.

[0099] In the embodiment shown, the one or more gas inlet(s) 7a, 7b are located in a bottom portion of the rotor arrangement 2, or in a lower portion of the carbonation chamber immediately below the rotor arrangement 2. The gas inlet(s) 7a, 7b are positioned such that at least some of the CCh-containing gas is introduced into the central opening 9 of rotor housing 10.

[0100] It should be understood that even though two different gas inlets 7a, 7b are shown in Fig. 1, only one of them is required.

[0101] The rotor arrangement 2 comprises a first impeller 22 located towards the bottom end of a rotor shaft 21. The rotor shaft 21 is hollow such that a CO2- containing gas may be provided through the center of the rotor shaft 21 and into the central opening 9 through the gas inlet 7a. In an alternative embodiment, one or more gas inlets may be provided in the first impeller 22.

[0102] An optional second impeller 24 is attached to the rotor shaft 21 above the first impeller 22. In the embodiment in Fig. 1, the second impeller 24 is Rushton type impeller having a plurality of blades extending from the shaft 21. The blades may be substantially parallel to a shaft axis or they may be slightly inclined with respect to the shaft axis, to promote desired flow patterns in the carbonation apparatus.

[0103] The carbonation apparatus 3 further comprises a slurry outlet 6. The slurry outlet 6 may be provided in a bottom portion of the carbonation apparatus 3. This position is particularly relevant in a batch type carbonation apparatus, where the batch is removed between each cycle. For continuously operated carbonationapparatuses, the slurry outlet 6 may be located dependent on the flow patent and turbulence in the vessel. As an example, the slurry outlet may be located at a central or upper portion of the carbonation apparatus 3.

[0104] Turning to Fig. 2 showing a carbonation apparatus 100 comprising a rotor arrangement 102 in the form of an impeller 122 attached to the bottom end of a rotor shaft 121. The rotor shaft 121 and the impeller 122 is rotated via a drive system (not shown). The impeller 122 may have a plurality of blades 108 and is configured for being rotated within a central opening defined by a rotor housing 110. The rotor housing may be affixed to the floor 130 of the carbonation chamber 103 such that the impeller 122 is rotatable with relative to the rotor housing 110, to agitate slurry retained in the carbonation chamber 103. The blades 108 may comprise slots 111. The slots may be comprised on all of the blades 108 or on some of the blades 108. In the particular embodiment, every second blade 108 comprises slots 111. The provision of the impeller 122 in the central opening 109 of the rotor housing 110 allows gas bubbles to be dissipated when introduced into the carbonation chamber 103. The rotor shaft 121 comprises an inner channel 123 allowing a gas to flow through the rotor shaft 121 and into the carbonation chamber 103 through openings in a lower portion of the shaft 121 or in the impeller 122. Baffle members 106 are attached to an inner surface of the carbonation chamber 103. In the embodiment, only two baffle members 106 are shown, but the carbonation chamber 103 may comprise any number of baffles members 106, such as 2, 4, 5, 6, 7, or 8 baffle members. The baffle members 106 may comprise slots 107, said slots 107 extending through the baffle members. The slots 107 may in particular have a square shape such as a rectangular shape.

[0105] Turning now to Fig. 3 showing a rotor housing 300 comprising base plate 302 having a ring shape. The base plate 302 is configured for being attached to the floor of a carbonation chamber via fasteners such as bolts. A plurality of vanes 301 extend from the bottom plate 302 to a top plate 303. The top plate 303 may have a similar shape as the base plate 302, such as a ring shape. The vanes 301 are arranged in series adjacent a periphery of the rotor housing 300 such that they define a central opening 309 sized to receive an impeller (not shown). The vanes 301 are spaced apart from each other so that there is a gap between adjacent vanes 301 such thatagitated slurry with gas bubbles can exit the rotor housing 300. The vanes 301 comprise rectangular slots 307 to improve the turbulence and mixing of gas and slurry.

[0106] In Fig. 3, the vanes of the rotor housing 300 are substantially rectangular, whereas the vanes 111 in the rotor housing 110 have a round or bowed shape such as an arc shape or segment of a circle.

[0107] Turning now to Fig. 4 showing an embodiment of an impeller 400. The impeller 400 has an impeller body 401 comprising an upper plate 402. The upper plate 402 is configured for attachment to a rotor shaft (not shown). The upper plate comprises an opening forming together with the rotor body 401 a central duct 403 for receiving gas from the rotor shaft. The duct 403 may also be considered a central channel, conduit, or passageway. The gas passes through the duct 403 and out one or more outlets 404 formed in the rotor body 42. Preferably, there is an outlet positioned between immediately adjacent outer blades 408 that extend from the rotor body 401. The outer blades 408 may be formed on the body, adhered to the body, cast with the body, integrally attached to the body 401 or otherwise attached to the body 401 via one or more fastening mechanisms such as welding, rivets, or other fasteners. The outer blades 408 may be members such as walls or profiled fins that agitate the slurry when the rotor 400 is rotated.

[0108] Each of the outer blades 408 has an outer edge 449 extending from the upper plate 402 to a bottom portion of the rotor body. The outer edge 449 has a curved path extending from the upper plate 402 towards the bottom portion in a downwards and inwards direction, providing a substantially bowl shape / half sphere shape of the impeller. In the embodiment shown, the outer edge of the upper portion 450 of the outer blade 408 is substantially flush with the periphery of the upper plate 402. The distance from the center of the impeller to the outer edge 449 is larger towards upper portion 450 of the blades than in a lower portion 451 of the blades. Alternative shapes of the blades 408 may be a generally half-hearted shape, a generally square shape, or a substantially circular shape.

[0109] Turning now to Fig. 5 and Fig. 6 showing a carbonation apparatus 500 and 600 according to different embodiments in greater detail. The carbonationapparatus 500 has a cylindrical upper portion 530 and a frustum conical lower portion 531. The carbonation apparatus 500 comprising a rotor arrangement 502 in the form of an impeller 422 attached to the bottom end of a rotor shaft 521. The rotor shaft 521 and the impeller 522 are rotated via a drive system (not shown). The impeller 522 is configured for being rotated within a central opening (not shown) in a rotor housing 510. The rotor shaft 521 comprises an inner channel allowing a gas to flow through the rotor shaft 521 and into the carbonation chamber 503 through openings in a lower portion of the shaft 521 or in the impeller 522.

[0110] The similar carbonation apparatus 600 additionally comprises a second impeller 624 attached to the rotor shaft 621. The second impeller 624 is positioned at a height T / 3 from the top of the carbonation apparatus. In the embodiment shown, the height T is measured as the height of the cylindrical portion 630 of the carbonation apparatus. The position of the second impeller is merely an example. It may be positioned at any position between T / 5 - T / 2 measured from either the top of the carbonation apparatus 600 or from the bottom of the cylindrical portion 630 of the carbonation apparatus 600. The second impeller 624 is shown as a simple Rushton turbine with a number of rectangular plates 625. The second impeller 624 may be any suitable impeller which can provide turbulence and mix the slurry. As shown in the subsequent drawings, the second impeller 624 may also be a spiral rotor.

[0111] Turning now to Fig. 7 showing a carbonation apparatus 700 comprising a second impeller 800. The second impeller is shown in different views in Fig. 8, Fig. 9 and Fig. 10. In the shown embodiment, the second impeller 800 is located in such a way that mid plane of the second impeller 800 is provided at height of M measured from either bottom or top side of the cylindrical portion of carbonation apparatus 1 8700 and it varies between — T to — T, where T is height of the cylindrical portionof the carbonation apparatus 700. Secondary rotor has a clearance on top and bottom. Clearance at top in Fig. 7 shown as Cl and clearance at bottom shown as C2. Cl and C2 varies depending upon the value of M and ‘h’ is height of the secondary rotor 800, measured from the top of the first vane portion 811 to bottom 2 4 of the second vane portion 812 along shaft axis and it can vary from - T to - T.Height of cylindrical portion of the carbonation apparatus T is equal to Cl + h + C2.

[0112] The second impeller 800 comprises four vane parts 801 equally spaced around the periphery of the rotor shaft 721. Each of the four vane parts 801 having a first end 802 and second end 803. The first end 802 is attached to the rotor shaft 721 at a position above where the second end is attached to the rotor shaft 721. Additionally, the first end 802 and the second end 803 are attached to the rotor shaft 721 at positions having an angularly offset. In the embodiment shown in Fig. 7 - Fig. 10, the angular offset is 90°, but it may vary depending on the number of vane parts 801. Preferably, the angular offset is between 45° and 135°. In the embodiment shown, each of the vane parts 801 are positioned on the rotor shaft 721 with a displacement of 90°. This provides that a first end 802 of one vane part is located directly above a second end 803 of an adjacent vane part 801.

[0113] A first vane portion 811 near the first end 802 of the vane part 801 extends radially from the rotor shaft 721 in a first radial direction. A second vane portion 812 near the second end of the vane part 801 extends in a second radial direction different from the first radial direction. In the embodiment shown, the first radial direction and the second radial direction are perpendicular to each other. Alternatively, they may be arranged with an angle of between 45° and 135°. The first vane portion has a first vane surface which has an inclination 02 with respect to the shaft axis 720. In the embodiment shown, 02 is around 24.5°, but it may range between 10°-60°. The second vane portion has a second vane surface which has an inclination of 01 with respect to the shaft axis 720.

[0114] The first vane portion 811 and the second vane portion 812 are connected by an intermediate vane portion 813. The second vane portion 812 may be inclined with an angle of 01 with respect to the shaft axis 720 which may vary between 0° to 45°. The intermediate vane portion has a vane surface 814 which is parallel to1 1 the shaft axis 720. The Vane surface 814 height ‘f may vary between — h to - h.An upper portion of the intermediate vane portion 813 is connected to the first vane portion 811 and has an inclination of 02. A lower portion of the intermediate vane portion 813 is connected to the second vane portion 812 and has an inclination of 04. The angle 04 is defined as the angle between the shaft axis 720 and the lowerportion of the intermediate vane portion 813. In the embodiment shown, 04 is around 26.6° but may range between 10°-60°. As can be seen from Fig. 11, ‘Di’ is a distance measured between shaft axis (720) and vane surface (814), and R1 is a radius between first vane portion (811) and upper portion of intermediate vane portion (813), and R2 is an end radius of second vane portion (812).

[0115] In the embodiment shown in Fig. 7- Fig. 11, the second impeller comprises four vanes parts 801, but in alternative embodiments the second impeller 800 may comprise a plurality of vane parts 801, in particular 2, 3, 4, 5, 6, 7, or 8 vane parts 801.

[0116] The vane surface 814 may be located substantially centrally in the carbonation apparatus 600 as shown in Fig. 7. Alternatively, it may be positioned1 3 at a distance ranging from - h to - h, where h is height of the secondary rotor 800.2The first vane portion 11 and second vane portion 812 extend -r from the shaft axis 720, where r is the inner radius of the carbonation apparatus 600. In alternative embodiments, the first vane portion 811 and second vane portion 812 may extend different lengths from the shaft axis 720. Preferably, the first vane portion 811 and 1 4 second vane portion 812 extend from -r to -r from the shaft axis 720.

[0117] Turning now to Fig. 12 showing a carbonation system 900 comprising a mixing tank 901 which is fluidly coupled to a plurality of carbonation apparatuses 902a-902d. The carbonation apparatuses are fluidly coupled in series such that slurry from the first carbonation apparatus 902a is provided to the second carbonation apparatus 902b etc. The slurry from the last carbonation apparatus 902d is provided to a dewatering process such as a filtration device 903. The filter cake from the filtration device 903 may be provided to a dryer 904.

[0118] Water and an SCM-precursor are provided to the mixing tank 901 for preparing a slurry. The slurry is then provided to the series of carbonation apparatus’ 902a-902d where a CO2-comprising gas is provided in the form of a flue gas from an industrial process, preferably from a cement clinker manufacturing process.

[0119] The CO2-comprising gas is split into separate streams provided to each of the carbonation apparatuses 902a-902d. The CCh-comprising gas may additionally be utilized in the dryer 904 for further drying the filter cake under CO2 rich conditions. The outlet gas from each of the carbonation apparatus’ 902a-902d and the dryer 904 are combined and returned to the stack. The filter water from the filtration device 903 is returned and reused in the mixing tank 901 for providing new slurry to the process.

[0120] In the carbonation system shown, the pH of the slurry decreases through the carbonation apparatus’ 902a-902d. As the SCM-precursor gets carbonated and the excess carbon acid is present in the slurry, the pH decreases. Typically, the first carbonation apparatus 902a may have a pH of around 12, whereas the pH in the fourth carbonation apparatus 902d may have a pH of around 7.

[0121] If no heating or cooling are provided to the carbonation apparatuses, the temperature through the carbonation process will increase due to heat development during carbonation. The temperature development depends on ambient temperature and the temperature of the CCh-comprising gas.

[0122] Turning now to Fig. 13 showing a carbonation system 1300 comprising a mixing tank 1301 which is fluidly coupled to a plurality of carbonation apparatuses 1302a-1302c. The carbonation system 1300 is configured as a semi-continuous system such that slurry in turn is provided to the carbonation apparatuses. As the carbonation of slurry is completed in an individual the carbonation apparatus’ it is emptied, and slurry is provided to a dewatering process such as a filtration device1303. The filter cake from the filtration device 1303 may be provided to a dryer1304. Water from the dewatering process may be recirculated to the mixing tank 1301.

Claims

CLAIMS1. A carbonation apparatus (1) for carbonating a carbonatable raw material comprising: a carbonation chamber (3) configured to receiving and accommodating a slurry; a slurry inlet (4) fluidly connected to the carbonation chamber (3); a gas inlet (7) configured to provide a CO2-containing gas into the carbonation chamber (3); a rotor arrangement (2) positioned at least partially in the carbonation chamber (3) and being rotatable with respect to the carbonation chamber (3); a rotor housing (10) comprising a plurality of vanes (8) being spaced apart from each other and positioned along a periphery of the rotor housing (10) to define a central opening (9) within the rotor housing (10) for accommodating a portion of the rotor arrangement (2); wherein the gas inlet (7) is positioned such that at least some of the CO2-containing gas is introduced into the central opening (9) of rotor housing (10) wherein during intended use of the carbonation apparatus (1) and rotation of the rotor arrangement (2), slurry and provided CO2-containing gas are agitated from the central opening (9) towards the rotor housing vanes (8) whereby the gas bubbles upon impact with the vanes are broken into smaller bubbles, thereby facilitating dissolution of gas into the aqueous phase of the slurry.

2. The carbonation apparatus (1) according to claim 1, wherein the carbonation chamber (3) is substantially gas tight.

3. The carbonation apparatus (1) according to any previous claim wherein the rotor arrangement (2) comprising a first impeller (22) located towards one end of a rotor shaft (21).

4. The carbonation apparatus (1) according to any previous claim, wherein the rotor shaft (21) is hollow and configured for having a CO2-containing gas flowing therethrough, the rotor arrangement (2) comprising at least one opening such thatCO2-containing gas may flow out of the rotor arrangement, said opening located such that CO2-containing gas is provided through the rotor shaft to the central opening (9).

5. The carbonation apparatus (1) according to claim 3 or 4, wherein the rotor arrangement (2) comprises a second impeller (24) attached to the rotor shaft and located above the first impeller (22).

6. The carbonation apparatus (1) according to any previous claim having an intended liquid level, and a length T defined from the bottom of the shaft to the intended liquid level and where the second impeller is located at between 0.2T to 0.8T, preferably 0.3T to 0.7T, more preferably 0.4T to 0.6T, such as around 0.5T.

7. The carbonation apparatus (600) according to any previous claim, wherein the second impeller (800) comprising a vane part (801) having a first end (802) and second end (803), the first end (802) and second end (803) being attached to the rotor shaft (721) at different heights and with an angular offset.

8. The carbonation apparatus (600) according to claim 7 wherein the vane part (801) having a first vane portion (811) extending radially from the rotor shaft (721) in a first radial direction and having a first vane surface being inclined with respect to the shaft axis (720), and a second vane portion (812) extending in a second radial direction different from the first radial direction, the second vane portion (812) having a second vane surface being inclined with respect to the shaft axis (720), the first vane portion and second vane portion being connected by an intermediate vane portion (813).

9. The carbonation apparatus (600) according to claim 8, wherein at least a portion of the intermediate vane portion (813) has a vane surface parallel to the shaft axis (720).

10. The carbonation apparatus (1) according to claims 5 to 9, wherein the second impeller (24) comprises a plurality of vane parts (25), in particular 2, 3, 4, 5, 6, 7, or 8 vane parts (25).

11. The carbonation apparatus (1) according to any previous claim, wherein the carbonation vessel is configured to operate at around or above atmospheric pressure and / or below the boiling point of water.

12. The carbonation apparatus (1) according to any previous claim, wherein the vanes (8) of the rotor housing (10) comprising a plurality of slots.

13. The carbonation apparatus (1) according to any previous claim, wherein the impeller comprising a rotor body (401) having a plurality of outer blades (408) that extend outwardly from the body (401) and an opening 403 for receiving a gas from the rotor shaft (721).

14. The carbonation apparatus (1) according to any previous claim, wherein the impeller comprising a rotor body (401) having and upper plate (402) configured for attachment with the rotor shaft (721), the upper plate (402) comprising an opening forming together with the rotor body (401) a central duct for receiving gas from the rotor shaft (721), a plurality of outer blades (408) that extend outwardly from the body (401) and optionally one or more outlet positioned between immediately adjacent outer blades (408) that extend from the rotor body (401).

15. The carbonation apparatus (1) according to any previous claim further comprising heating and / or cooling means.

16. A carbonation system (900) comprising a plurality of carbonation vessels (902) according to any previous claim, in particularly the carbonation vessels being fluidly coupled in series.

17. The carbonation system (900) according to claim 16, wherein the system being coupled to a source of CO2-containing gas through a gas supply conduit, optionally a flue gas stream, the gas supply conduit being split into a plurality of individual gas supply conduits each coupled to one of the plurality of carbonation vessels (902).

18. Use of the carbonation apparatus (1) according to claim 1 to claim 15 or a carbonation system (900) according to claim 16 to claim 17 for carbonating a carbonatable raw material, such as concrete fines.

19. Method of operating a carbonation apparatus according to claims 1 to 15 or a carbonation system (900) according to claim 16 or claim 17 wherein a change in pH of the slurry from alkaline to acidic is used as an indicator for substantially complete carbonation, and / or wherein an increase in CO2 concentration of the outlet gas is used as an indicator for substantially complete carbonation.

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