Calcination of materials

Abstract

Disclosed herein is an indirectly heated reactor comprising: a reactor tube that in use is configured to be vertically oriented; an outer shell surrounding the reactor tube, the outer shell comprising heating elements that are configured to heat an interior of the outer shell; one or more gas input ports located towards an in-use upper end of the outer shell; a powder input located adjacent to an in-use top end of the reactor tube and configured to feed a powder such that the powder falls downwards in the reactor tube in use; and a reacted powder output positioned at an in-use base of the reactor tube. The outer shell is fluidly connected to the reactor tube by one or more gas feed ports that are arranged towards an in-use lower region of the reactor tube such that, in-use of the reactor, the gas injected in the outer shell is able to be heated by the heating elements to cause the gas to flow from the outer shell and into the reactor tube. Also disclosed herein are other embodiments of indirectly heated reactors and uses of the indirectly heated reactors.

Description

[0001] CALCINATION OF MATERIALS

[0002] PRIORITY

[0003] This application claims priority from Australian Provisional Application Nos. 2024901210 and 2024901390, the entire contents of the specifications of which are incorporated herein by way of cross-reference.

[0004] TECHNICAL FIELD

[0005] This disclosure relates to the scale-up of processes and systems for calcination of materials using indirect heating.

[0006] BACKGROUND ART

[0007] Calcination is a pyro-process that is used to transform solids into valued-added solid and / or gas products by heating the input solids, and injected gases if appropriate. Calcination is an ancient art. The production of lime from limestone was likely to be the first industrial practice, followed by heating iron ore and coal to manufacture iron, in kilns.

[0008] The variety of kiln designs now includes shaft furnaces, rotary kilns, and fluidised beds, all of which have been directly heated by combustion of a fuel. Another approach, called herein, indirect heating, uses an external source of energy to heat a material at a distance by radiation. One such example of indirect heating is the use of microwave heating. Another indirect heating approach is to use thermal radiation from a heated surface. The primary difference with indirect heating is that any combustion materials, as gases or solids, are not mixed, either as reactants, impurities or diluents in the calcination processes within the reactor. The prior art for indirectly heated reactors considers the transfer of heat primarily from radiation emanating from the walls of a heated tube. The prior art of indirect heating describes scale-up through a plurality of such reactor tubes. However, the scale-up of such reactors is limited by the rate at which and depth to which radiative energy emanating from the walls of the heated tube can penetrate into the reactor body. There is a need for alternative approaches to scale-up.

[0009] It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.

[0010] I SUMMARY

[0011] Heated vertical reactor

[0012] Disclosed herein in a first aspect is an indirectly heated reactor. Typically, the reactor is used in a vertical orientation. The indirectly heated reactor may be advantageously suitable for use in a number of applications. For example, the reactor may be suitable for use in processing a-spodumene to P spodumene, aluminium hydroxide to alumina, cement meal to calcined cement meal, for pyrolysis of biomass, for hydrogen reduction of iron ore, and processing of magnesite to magnesia for bioactivity and for magnesium metal. For example, the reactor may be suitable for use in the reduction processes described in the applicant’s Australian Provisional Patent Application No. 2024901210, the entire contents of the specification of which is incorporated herein by way of crossreference. The vertical reactor may be suitable for use in small-scale processes, as well as larger scale (e.g. industrial) processes.

[0013] The reactor of the first aspect can comprise a reactor tube that in use is configured to be vertically oriented. The desired reaction can take place within the reactor tube (e.g., in a falling powder, dilute flow regime). The reactor can also comprise an outer shell surrounding the reactor tube. The outer shell can comprise heating elements that are configured to heat an interior of the outer shell. The outer shell can be used for heating, control and feeding of reactor gases. For example, the outer shell can be used for preheating of reactor gases, such that the gases entering the reactor tube are already at an elevated temperature. In this way, the reactor can efficiently use the thermal energy produced by the heating elements, both for heating the reactor tube and for the preheating of reactor gases.

[0014] The reactor can further comprise one or more gas input ports located towards an in-use upper end of the outer shell. These can allow for the inflow of reactor feed gases, when required.

[0015] The reactor can still further comprise a powder input located adjacent to an in-use top end of the reactor tube. The powder input can be configured to feed a powder such that the powder falls downwards in the reactor tube in-use.

[0016] The reactor can also comprise a reacted powder output positioned at an in-use base of the reactor tube. This can allow for reactor product removal.

[0017] The outer shell of the reactor can be fluidly connected to the reactor tube by one or more gas feed ports that are arranged towards an in-use lower region of the reactor tube such that, in-use of the reactor, gas in the outer shell is able to be heated by the heating elements to cause the gas to flow from the outer shell and into the reactor tube. Thus, heating and / or pressure differentials can be used to control the temperature and flow of reactor gases into the reactor.

[0018] In some embodiments of the first aspect, the heating elements may comprise external heating elements. The external heating elements may be configured to indirectly heat the interior of the outer shell and the gas.

[0019] In some embodiments of the first aspect, the heating elements may comprise resistive heating elements. The resistive heating elements may be powered by, for example, electricity. Alternatively, in other embodiments, the heating elements may comprise inductive heating elements.

[0020] In some embodiments of the first aspect, the reactor may be configured to be operated such that, in-use, a pressure in the reactor tube is less than a pressure within the outer shell. As a result of this pressure differential, the gas may be caused to flow from the outer shell and into the reactor tube.

[0021] In some embodiments of the first aspect, an inner wall of the outer shell may be insulated. This may enhance the thermal efficiency of the reactor, e.g., by reducing heat losses to a surrounding environment. In some of these embodiments, the heating elements may be arranged at the insulated inner wall of the outer shell. For example, they may be embedded in the insulated inner wall.

[0022] In some embodiments of the first aspect, the reactor may further comprise a gas exhaust located towards an in-use upper end of the reactor tube. Exhaust gas from the reactor may exit the reactor tube through the gas exhaust. The gas exhaust may comprise a gas separator which separates the gas from any entrained solids. The entrained solids may be returned to the reactor tube.

[0023] Large-scale externally heated vertical reactor

[0024] Disclosed herein in a second aspect is a reactor that is configured to be vertically oriented in use. The indirectly heated reactor may be advantageously suitable for use in the same applications described above. The reactor of the second aspect may take the form of a reactor bank rather than having the form of a tubular reactor of the first aspect. The reactor of the second aspect may be advantageously employed in industrial-scale processes. For example, the reactor of the second aspect may be used in larger scale industrial settings for the production of iron and steel. The reactor of the second aspect may also be suitable for use as a pyrolyser (e.g., for converting biomass to bio-char and for production of materials for slagging of iron and steel). The reactor of the second aspect can comprise an elongate reactor body comprising one or more material feed inlets located toward an in-use upper end of the reactor body. The reactor may comprise multiple material feed inlets (e.g., spaced out across its length). The material feed inlets can be configured to feed a powder to be reacted such that said powder falls downwards in the reactor body.

[0025] The reactor of the second aspect can also comprise gas input ports arranged toward an in- use lower end of the reactor body for feeding a gas into the reactor body. Again, the reactor may comprise multiple gas input ports that may be spaced out across its length (e.g., spaced so as to generally correspond to the spacing of the material feed inlets).

[0026] The reactor of the second aspect can further comprise a powder outlet positioned toward the lower end of the reactor body. The reactor may comprise multiple powder outlets (e g., spaced so as to generally correspond to the spacing of the material feed inlets).

[0027] The reactor of the second aspect can still further comprise heating elements positioned in an interior space of the reactor body and configured to transfer heat into the interior space of the reactor body, so as to heat the gas and the falling powder and cause the powder to react.

[0028] The configuring of the reactor with heating elements that are positioned in the interior space of the reactor body can readily allow for scale up. In this regard, the heating elements may be spaced out across a length of the reactor so that, when it is desired to increase reactor scale, the reactor can be lengthened, widened and / or height increased to thereby correspondingly allow for an increase in number, density, size, area, etc. of the heating elements. Such scaling is different from scaling a plurality of externally heated reactors tubular reactors.

[0029] In some embodiments of the second aspect, the heating elements can be configured to transfer radiative heat into the interior space of the reactor body. In this regard, because the radiative heat is transferred immediately and directly into the interior space of the reactor body, there is no requirement to resort to combusting a fuel within the reactor (or to combusting a carbon source within the reactor in the context of iron and steelmaking and biomass pyrolysis), and / or to externally heat the reactor. This is in contradistinction to many reactors of the prior art in which heat is either provided: via the combustion of a fuel (e.g., coke) within the reactor body itself; or indirectly by heating the walls of the reactor. There are applications in which combustion processes may occur within a heating element to provide the heat, and applications where both electric and combustion processes may be used together to optimise a specific application.

[0030] Each of the prior art heating methods has disadvantages. Combustion of, e.g., coke produces carbon dioxide. Indirect heating, e.g., by heating the reactor walls, can limit the size of the reactor. This is because radiative heat from the reactor walls can only penetrate to a certain distance within the interior space of the reactor body. Advantageously, by heating the interior of the reactor body using heating elements that are located therewithin, these issues can be avoided. Further, energy for the heating elements can be produced using ‘green’ (e.g., renewable) electricity; and heating elements can be spaced throughout the interior so as to provide adequate and even heating throughout the whole interior of the reactor body.

[0031] In some embodiments of the second aspect, the heating elements may comprise one or more metallic alloy sheets. The one or more metallic alloy sheets may each be configured to be electrified so as to heat up and transfer heat into the interior space of the reactor body. The one or more metallic alloy sheets may be arranged in different ways within the reactor body. In one embodiment, the one or more metallic alloy sheets may be arranged to extend downwards in use from an upper end of the reactor body. The material feed inlets may then be arranged to feed the powder such that the powder falls downwards in the reactor body between adjacent spaced sheets of the or more metallic alloy sheets.

[0032] In some embodiments of the second aspect, the reactor may comprise multiple banks of metallic alloy sheets. Each bank may comprise two or more sheets. Each material feed inlet may be arranged to feed the powder such that the powder falls downwards in the reactor body between adjacent spaced banks of metallic alloy sheets. The height of sheets within each bank may also vary. For example, the sheets that are closer to a material feed inlet may have a small height (e.g., so as to be less likely coated by the powder), and the sheets moving away from the material feed inlet may gradually increase in height to a maximum height sheet.

[0033] In some embodiments of the second aspect, the reactor may further comprise one or more high temperature radiative tubes configured to radiate energy into the interior space of the reactor body. The radiative tubes may provide additional energy to the interior space of the reactor body. For example, when the one or more metallic alloy sheets are arranged to extend downwards in use from an upper end of the reactor body, the one or more high temperature radiative tubes may be arranged to extend within the interior space of the reactor body at a position below the sheets and toward the lower end of the reactor body. In this regard, the one or more metallic alloy sheets may radiate energy into an upper region of the interior space of the reactor body, whilst the radiative tubes may radiate energy into a lower region of the interior space of the reactor body. The radiative tubes may be of a high temperature, resistive material, such as silicon carbide instead of steel.

[0034] In some embodiments of the second aspect, the reactor may further comprise a gas exhaust positioned adj acent to the upper end of the reactor body. Gas to be exhausted may exit the reactor tube through the gas exhaust. The gas exhaust may comprise a gas separator which separates the gas from any entrained solids. The entrained solids may be returned to the reactor.

[0035] In some embodiments of the second aspect, the gas input ports may be arranged to feed the gas into the reactor body such that the rate of the powder falling downwards in the reactor body is able to be controlled. For example, the rate of the powder falling downwards may be controlled so as to provide a desired flow regime and / or residence time of the powder in the interior space.

[0036] In some embodiments of the second aspect, for example when the reactor is vertically oriented, the reactor body may have an elongate configuration both vertically and horizontally. The reactor body may also have a narrower width dimension than its length and height. For example, the reactor may take the form of a long bank. Parallel banks of elongate reactors may be employed in an industrial context, and may also be jointly fed and extracted.

[0037] In some embodiments of the second aspect, the reactor may further comprise one or more external indirect heating elements. The external indirect heating elements may be configured to indirectly heat the interior space of the reactor body. The external indirect heating elements may be in the form of, for example, heating elements connected to the walls of the reactor body. Alternatively, the walls of the reactor body may themselves comprise the external heating elements. The external indirect heating elements may be configured to transfer heat in the form of radiative heat into the reactor body.

[0038] Other embodiments of large-scale vertical reactors

[0039] Disclosed herein in a third aspect is a reactor that in use is configured to be vertically oriented. The reactor may be used in a number of general pyro-processing applications such as: the production, at scale, of lime and cement as a calcination process of limestone and cement raw meal; for the calcination of magnesite to magnesia for many applications such as water treatment, bioactive materials for agriculture, antifouling paints, for disease control in livestock and humans, and magnesium meal; for calcination of aluminium hydroxide to make alumina for aluminium production and for insulator applications, and for bauxite activation; and generally for making nano-active materials for batteries including processing spodumene to enable extraction of lithium. As a further example, the reactor may be used as the first reactor and / or the second reactor in the processes and systems for the reduction of iron ore, or as a pyrolyser for the production of CaO and MgO (e.g., for use in ironmaking / steelmaking), as disclosed in Australian Provisional Patent Application No. 2024901210.

[0040] The reactor can comprise an elongate reactor body. The elongate reactor body can comprise one or more material feed inlets located toward an in-use upper end of the reactor body. The material feed inlets can be configured to feed a powder to be reacted such that said powder falls downwards in the reactor body. The desired reaction can take place within the reactor body (e.g., in a falling powder, dilute flow regime).

[0041] The reactor can also comprise gas input ports arranged toward an in-use lower end of the reactor body for feeding a gas into the reactor body. In this regard, in-use, the gas fed into the reactor body is caused to flow upwardly through the elongate reactor body.

[0042] The reactor can further comprise one or more powder outlets positioned toward the lower end of the reactor body. The one or more powder outlets may be configured such that, in- use, reacted powder can exit the reactor body via the one or more powder outlets.

[0043] The reactor can still further comprise one or more external heating elements arranged around an outside of the reactor body and configured to heat an interior of the reactor body. In this regard, in-use, the reactor body can be indirectly heated by the one or more external heating elements.

[0044] In some embodiments of the third aspect, the reactor may further comprise an outer shell. The outer shell may surround the reactor body. The outer shell may comprise the one or more external heating elements that are configured to heat the interior of the reactor body. The outer shell may be used for heating, control and feeding of reactor gases.

[0045] In some of these embodiments, the outer shell may be fluidly connected to the reactor body by the gas input ports such that, in-use of the reactor, gas in the outer shell is able to be heated by the one or more external heating elements to cause the gas to flow from the outer shell and into the reactor body. Advantageously, this may enable the gas to be pre-heated prior to entering the reactor body.

[0046] In some embodiments of the third aspect, the one or more external heating elements may be configured to transfer radiative heat into the interior of the reactor body. For example, the one or more external heating elements may be configured to be electrified so as to transfer heat into the reactor body. Alternatively, the one or more external heating elements may be configured to transfer heat produced by a combustion reaction into the reactor body.

[0047] In some embodiments of the third aspect, the reactor may further comprise internal heating elements positioned in the interior of the reactor body. Advantageously, and as explained above, heating elements that are positioned in the interior space of the reactor body can readily allow for scale up. In this regard, the heating elements may be spaced out across a length of the reactor so that, when it is desired to increase reactor scale, the reactor can be lengthened, widened and / or height increased to thereby correspondingly allow for an increase in number, density, size, area, etc. of the heating elements. Such scaling can be more problematic for externally heated reactors (e g., tubular reactors).

[0048] The internal heating elements may be configured to transfer heat directly into the interior of the reactor body. For example, the internal heating elements may comprise tubes which are arranged to extend within the interior of the reactor body and extend toward the lower end of the reactor body. In such embodiments, the internal heating elements may be circular. Alternatively, the internal heating elements may comprise other geometries, such as triangular, square, etc.

[0049] The tubular internal heating elements may comprise a hollow internal chamber. In some variations of these embodiments, the hollow internal chamber of the internal heating elements may be fluidly connected to the gas input ports at a lower end thereof. In-use, gas injected into the hollow internal chamber may be able to be heated by the heating elements, with a resultant preheated gas fed into the reactor body. In other variations of these embodiments, the hollow internal chamber of the heating elements may be fluidly connected to the reactor body at a lower end thereof and to an exhaust of the reactor body at an upper end thereof, such that, when the reactor is operated in a co-flow regime, exhaust gas from the reactor body is able to pass upwardly through the hollow internal chambers to the exhaust.

[0050] In some embodiments of the third aspect, the internal heating elements may be configured to transfer radiative heat directly into the interior of the reactor body. In this regard, because the radiative heat is transferred immediately and directly into the interior space of the reactor body, there is no requirement to resort to combusting a fuel within the reactor (or to combusting a carbon source within the reactor in certain contexts). This is in contradistinction to many reactors of the prior art in which heat is provided via the combustion of a fuel (e.g., coke) within the reactor body itself. For example, the internal heating elements may be configured to be electrified so as to transfer heat directly into the interior of the reactor body. Alternatively, the internal heating elements may be configured to transfer heat produced by a combustion reaction directly into the interior of reactor body. As yet another alternative, a subset of the internal heating elements may be configured to be electrified, whilst another subset of the internal heating elements may be configured to transfer heat produced by a combustion reaction. As yet a further alternative, the heating elements can comprise annular heating elements that can be resistively or inductively heated, as well as heated via a combustion reaction that takes place in a chamber / annulus of the element. The latter two embodiments represent ‘hybrid’ processes in which a combination of electrical and combustion heating is employed. In this regard, there are applications in which combustion processes may occur within a heating element to provide the heat, and applications where both electric and combustion processes may be used together to optimise a specific application. In some embodiments of the third aspect, the reactor may further comprise a gas exhaust positioned adjacent to the upper end of the reactor body. For example, in some embodiments, the gas input ports may be arranged to feed the gas into the reactor body such that the rate of the powder falling downwards in the reactor body is able to be controlled.

[0051] In some embodiments of the third aspect, such as when the reactor is vertically oriented, the reactor body may be elongate both vertically and horizontally. The reactor body may also have a narrower width dimension than its length and height. For example, the reactor may take the form of a long bank. Parallel banks of reactors may be employed in an industrial context and may be jointly fed and extracted.

[0052] Reactor Ancillaries

[0053] Also disclosed herein are various systems which comprise the reactors of the preceding aspects. For example, disclosed herein in a fourth aspect is a system for reacting a powder. The system can comprise the reactor of any one of the first to third aspects. The system can also comprise a fusion grinder configured to agglomerate a powder to be fed into the reactor. For example, the fusion grinder may be configured to agglomerate the powder such that the powder has a mean particle size of about 250 pm. The powder, having a mean particle size of about 250 pm, can then be fed into the reactor.

[0054] In some embodiments of the fourth aspect, the system may further comprise a hot briquetting plant to which reacted powder from the reactor is passed and in which the reacted powder is hot briquetted. For example, the hot briquetting plant may be configured to produce briquettes with a mean particle size of about 1,000 pm to about 3,000 pm.

[0055] Disclosed herein in a fifth aspect is a process for inducing a phase change in a powder. The process can comprise feeding the powder to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor of any one of the first, second or third aspects. The process can also comprise heating the interior of the reactor body so as to cause the phase change. The powder fed to the reactor may comprise any powder which can undergo a phase change when heated. For example, the powder may comprise a- spodumene, and the phase change may comprise a phase change from a-spodumene to 0- spodumene.

[0056] Disclosed herein in a sixth aspect is a process for calcining aluminium hydroxide. The process can comprise feeding a powder comprising aluminium hydroxide to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor of any one of the first, second or third aspects. The process can also comprise heating the interior of the reactor body so as to cause the aluminium hydroxide to be calcined, thereby producing alumina and steam. The alumina may be advantageously used as or as part of a feed to a process for producing aluminium metal. At the same time, the steam, typically comprising a low-grade steam, may be used to produce high-grade steam.

[0057] Disclosed herein in a seventh aspect is a process for producing metal oxide from metal carbonate. The process can comprise feeding a powder comprising the metal carbonate to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor of any one of the first, second or third aspects. The process can further comprise heating the interior of the reactor body so as to cause the metal carbonate to be decomposed, thereby producing the metal oxide and carbon dioxide.

[0058] In some embodiments of the seventh aspect, the metal carbonate may comprise limestone, dolomite, magnesite and / or cement raw meal.

[0059] In some embodiments of the seventh aspect, the carbon dioxide may be captured. Advantageously, the carbon dioxide may comprise a pure CO2 stream. In this regard, in some embodiments, the captured carbon dioxide may be reacted with hydrogen under conditions by which methanol and / or synthetic aviation fuel are produced.

[0060] In some embodiments of the seventh aspect, the metal carbonate powder may comprise magnesium, and the gas fed into the reactor body may comprise hydrogen.

[0061] In some embodiments of the seventh aspect, the metal carbonate powder may comprise magnesium and, prior to being fed into the reactor, the metal carbonate powder may be mixed with a copper salt and / or an iron salt, with the resultant mixture comprising the metal carbonate powder, copper salt and / or iron salt fed into the reactor. In some of these embodiments, a gas comprising hydrogen may be fed (e.g., injected) into the reactor. This may enhance the bioactivity of the resultant reacted powder.

[0062] Disclosed herein in an eighth aspect is a process for gasification of carbon-based powders. The process can comprise feeding the carbon-based powder to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor of any one of the first, second or third aspects. The process can also comprise heating the interior of the reactor body so as to cause gasification of the carbon-based powder.

[0063] In some embodiments of the eighth aspect, the carbon-based powder may comprise biomass, organic waste, and / or recycled char.

[0064] In some embodiments of the eighth aspect, the gas fed into the reactor body may comprise oxygen. In such embodiments, the gas exhaust from the reactor may comprise syngas, and the reacted powder may comprise a mixture of powdered char and ash. In some embodiments of the eighth aspect, the process may further comprise feeding a powder comprising calcium oxide to the reactor such that the gasification of the carbonbased powder causes hydrogen and calcium carbonate to be produced. In such embodiments, the calcium oxide may act to sorb the CO / CO2 produced during gasification, such that the resulting gas comprises hydrogen.

[0065] In some embodiments of the eighth aspect, the powder comprising calcium oxide may be produced by the process of the seventh aspect.

[0066] In some embodiments of the eighth aspect, the calcium carbonate may be collected and calcined by the process of the seventh aspect, thereby reproducing calcium oxide.

[0067] Disclosed herein in a ninth aspect is a process for producing calcined cement meal. The process can comprise feeding a powder comprising cement raw meal to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor of any one of the first, second or third aspects. The process can also comprise operating the reactor so as to cause the cement raw meal to be reacted to form calcined cement meal.

[0068] In some embodiments of the ninth aspect, the process may further comprise fusing the calcined cement meal powder to form a fused powder with a mean particle size of about 250 pm.

[0069] In some embodiments of the ninth aspect, the process may further comprise subjecting the fused powder to a pyro-process configured to operate at a temperature of about 1450 °C so as to produce cement clinker.

[0070] Disclosed herein in a tenth aspect is a process for producing magnesium metal. The process can comprise producing a powder comprising magnesium oxide from a powder comprising dolomite and magnesite using the process as defined in the seventh aspect. The process can also comprise briquetting the powder comprising magnesium oxide and aluminium, thereby producing briquettes comprising magnesium oxide, calcium oxide, and aluminium. The process can further comprise heating the briquettes to a temperature at which the magnesium oxide is converted to magnesium metal.

[0071] In some embodiments of the tenth aspect, the process may further comprise cooling and grinding the resultant mixture comprising magnesium metal.

[0072] In some embodiments of the tenth aspect, the process may further comprise heating the ground mixture so as to cause the magnesium metal to be vaporised.

[0073] In some embodiments of the tenth aspect, the process may further comprise condensing the magnesium metal vapour. In some embodiments of the tenth aspect, a resultant solid comprising calcium and aluminium is collected, and the aluminium is recovered therefrom.

[0074] Broad reactor embodiments

[0075] Disclosed herein in an eleventh aspect is a reactor. The reactor is indirectly heated. Typically, the reactor is used in a vertical orientation. The indirectly heated reactor may be advantageously suitable for use in a number of applications. In particular, the vertical reactor may be suitable for use in small-scale processes, as well as larger scale (e.g. industrial) processes.

[0076] The reactor of the eleventh aspect can comprise an elongate reactor body comprising one or more material feed inlets located toward an in-use upper end of the reactor body. The reactor may comprise multiple material feed inlets (e.g., spaced out across its length). The material feed inlets can be configured to feed a powder to be reacted such that said powder falls downwards in the reactor body.

[0077] The reactor of the eleventh aspect can further comprise a powder outlet positioned toward the lower end of the reactor body. The reactor may comprise multiple powder outlets (e.g., spaced so as to generally correspond to the spacing of the material feed inlets).

[0078] The reactor of the eleventh aspect can still further comprise heating elements positioned in an interior space of the reactor body and configured to transfer heat into the interior space of the reactor body, so as to heat the gas and the falling powder and cause the powder to react. The configuring of the reactor with heating elements that are positioned in the interior space of the reactor body can readily allow for scale up. In this regard, the heating elements may be spaced out across a length of the reactor so that, when it is desired to increase reactor scale, the reactor can be lengthened, widened and / or height increased to thereby correspondingly allow for an increase in number, density, size, area, etc. of the heating elements. Such scaling can be more problematic for externally heated reactors (e.g., tubular reactors).

[0079] In some embodiments of the eleventh aspect, the reactor may further comprise gas input ports arranged toward an in-use lower end of the reactor body for feeding a gas into the reactor body. Again, the reactor may comprise multiple gas input ports that may be spaced out across its length (e.g., spaced so as to generally correspond to the spacing of the material feed inlets). In these embodiments, the heating elements may be configured to transfer heat into the interior space of the reactor body, so as to heat the gas and the falling powder and cause the gas and the powder to react therewith.

[0080] In some embodiments of the eleventh aspect, the reactor may comprise the reactor as defined in the second aspect. Disclosed herein in a twelfth aspect is a reactor that in use is configured to be vertically oriented. The reactor can comprise an elongate reactor body. The elongate reactor body can comprise one or more material feed inlets located toward an in-use upper end of the reactor body. The material feed inlets can be configured to feed a powder to be reacted such that said powder falls downwards in the reactor body. The desired reaction can take place within the reactor body (e.g., in a falling powder, dilute flow regime).

[0081] The reactor can further comprise one or more powder outlets positioned toward the lower end of the reactor body. The one or more powder outlets may be configured such that, in- use, reacted powder can exit the reactor body via the one or more powder outlets.

[0082] The reactor can still further comprise one or more external heating elements arranged around an outside of the reactor body and configured to heat an interior of the reactor body. In this regard, in-use, the reactor body can be indirectly heated by the one or more external heating elements.

[0083] In some embodiments of the twelfth aspect, the reactor may comprise gas input ports arranged toward an in-use lower end of the reactor body for feeding a gas into the reactor body. In this regard, in-use, the gas fed into the reactor body is caused to flow upwardly through the elongate reactor body.

[0084] In some embodiments of the twelfth aspect, the reactor may comprise the reactor of the third aspect.

[0085] BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

[0087] Fig. 1 is a schematic of a cross-section of an embodiment of an indirectly heated reactor.

[0088] Fig. 2 is a schematic of a cross-section of another embodiment of an indirectly heated reactor.

[0089] Fig. 3 is a schematic of a top view of a cross-section of an embodiment of an indirectly heated reactor with external electric heating.

[0090] Fig. 4 is a schematic of a top view of a cross-section of an embodiment of an indirectly heated reactor with external combustion heating.

[0091] Fig. 5 is a schematic of a top view of a cross-section of an embodiment of an indirectly heated reactor with external electric heating and internal electric heating elements. Fig- 6 is a schematic of a top view of a cross-section of an embodiment of an indirectly heated reactor with external combustion heating and internal combustion heating elements.

[0092] Fig- 7 is a schematic of a top view of a cross-section of an embodiment of an indirectly heated reactor with external electric heating and internal combustion heating elements.

[0093] Fig. 8 is a schematic of a top view of a cross-section of an embodiment of an indirectly heated reactor with external electric heating and internal electric heating elements which are further configured to provide preheating of a gas.

[0094] The same reference numerals are used to denote the same features in each diagram.

[0095] DETAILED DESCRIPTION

[0096] In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised, and other changes may be made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure.

[0097] Disclosed herein are a number of heated vertical reactors which can be used in a variety of applications, such as in calcination processes. In general, each of these variations contemplates the use of indirect heating within the reactor. A benefit of indirect heating is that any combustion materials, as gases or solids, are not mixed in the calcination processes within the reactor. Furthermore, in some variations, by using a combination of internal and external heating, scale-up of the reactors disclosed herein can be more easily achieved, compared to the scale-up of tubular reactors of the prior art.

[0098] Classes of Calcination Reactions

[0099] For convenience, indirect heating applications are herein categorised by the roles of gas and particle flows during calcination. For example, indirect heating applications and, in particular, indirect heating calcinations, are herein classified as follows:

[0100] Class A: in which indirect heating causes a phase change in the powder;

[0101] Class B: in which indirect heating causes a chemical change of the powder with the release of one or more gaseous products; or Class C: in which an injected gas reacts with the powder, or the calcined powder, or the gas released from a calcination process, to form either new powder or gas products or both.

[0102] The processes A to B to C imply an increase of the complexity of indirect heating processes. While example embodiments of classes A-C will be described in this disclosure, which may be known in the art, the focus of the disclosure is the design of indirectly heated reactors, with some specific applications. It will be appreciated that the indirectly heated reactors disclosed herein can have a wide variety of other applications, aside from those specifically described, and all of which are contemplated within the disclosure.

[0103] Notwithstanding the categorisation of calcination process considered above, the substantial difference with direct heating (i.e., within the reactor) by hot combustion, is that there are no combustion powders or gases that are mixed with the process gases from calcination processes A-C. Simply, the only gases in the reactor are process gases. This feature of indirectly heated reactors is retained in this disclosure. There may be no process gases in class A embodiments, often one process gas as a product in class B embodiments, or two or more process gases in class C embodiments.

[0104] Without being bound by theory, it is thought that gas input ports may be included in practice for reactors employed for all embodiments A-C. For example, gas input ports may be included even when process gases are not introduced. In such examples, the gas input ports may be used to introduce inert (i.e., non-reactive) gases. Such inert gases may be introduced for a variety of reasons. For example, inert gases may be used as a carrier gas within the reactor to establish a desired flow regime therein. As another example, inert gases may be used to dilute the process gases. This can lower the gas partial pressure of other (i.e., the non-inert) gases in the reactor which can, in turn, lower the temperature required for calcination. Alternatively, the introduction of an inert gas may be used to: remove build-up of other gases within the reactor; enabling or cause a change of direction of flow of a process gas (for example, between counter-flow and co-flow with falling powder). As another example, if the input gas is not used in any particular process, an inert gas may be used for cleaning the walls of the reactor during maintenance. Alternatively or additionally, gases can be introduced into the reactor to react with undesirable impurities in the powders or gases. Such gases are typically inert with respect to the feed material itself. As another example, gases can be input to control a reaction, either alone or, for example, by a mix of the resultant gas flows within the reactor (i.e., when other gases are present).

[0105] An example embodiment of Class A calcination is the transformation of a-spodumene to P-spodumene. This is a phase change which increases the powder porosity, thereby enabling lithium extraction in a later stage. It can be classified as a Class A reaction because, by employing an indirectly heated reactor, there are no substantial gases in the reactor to be heated. Some non-process gases may be used to flush gases, such as moisture and CO2 from carbonate mineral impurities from the reactor. The reactor can be heated by renewable sources, thereby reducing the carbon footprint of the calcination reaction.

[0106] Example embodiments of Class B indirect heating processes include:

[0107] (i) the extraction of water, as steam. For example by: removing moisture from a powder (i.e., drying a powder); dehydrating mineral hydroxides such as bauxite to activate the powder for digestion in the production of aluminium metal; or the production of alumina from aluminium hydroxide for electrolysis in the production of aluminium metal; or the production of a-alumina for many uses including semiconductor insulators; or the dehydration of clays to manufacture Portland Cement substitutes; or

[0108] (ii) the extraction of CO2 from carbonate materials such as magnesite, dolomite and limestone minerals, or synthetic equivalents, to make oxides or the extraction of CO2 from limestone in raw cement meal. The CO2 extracted may be used for Carbon Capture Storage and Use (CCSU). For example, calcination-carbonation cycles such as Direct Air Capture (DAC) in which lime is used to capture CO2 in the atmosphere. The captured CO2 may be released (e.g., by employing the calciner described herein), for example, for use elsewhere (e.g., to make steel); and

[0109] (iii) the production of magnesium metal from dolomite and magnesite calcination, where the magnesium oxide from such indirectly heated calcination of dolomite and / or limestone, at the same time, produces pure CO2 for CCSU. The low emission magnesia powder can then be reduced to magnesium metal (e g., by carbothermic, silicothermic or aluminothermic reduction processes). The magnesium metal can be used in the production of low weight, high strength alloys for efficient lightweight electric vehicles and other products. Magnesium metal made in this way can have low Scope 3 CO2 emissions.

[0110] Example embodiments of Class C indirect heating processes include:

[0111] (i) the reaction of oxides (e.g., an oxide formed in class B calcination processes) such as lime. Specifically, lime can be reacted with steam injected into the reactor to form an hydroxide powder within the reactor; or

[0112] (ii) the activation of an oxide (e.g., an oxide formed in class B calcination processes) such as MgO formed during calcination of magnesite powders, and optionally mixed with other powders such as CuO from CuCCh. The oxide can be calcined in the presence of injected hydrogen gas. The reaction between the oxide and hydrogen gas can be controlled such that a powder product with additional chemical defects is formed. The additional chemical defects can advantageously enhance an innate bioactivity of the powder product; or

[0113] (iii) reduction of iron ore powders (e.g., to iron) by injecting hydrogen or carbon monoxide gases into the reactor; or

[0114] (v) any other gas reduction processes with powders; or

[0115] (vi) the gasification of powdered carbon materials with injected air or oxygen to produce carbon and an ash, or ash and a syngas fuel. Optionally, CaO may also be injected to remove CO2 and CO from the syngas in the reactor to make hydrogen for use in reduction process or generation of low emissions power by combustion with air or oxygen, where the carbon materials include biomass or waste; or

[0116] (vii) other oxidation processes typically using oxygen or air.

[0117] Thus, there are many calcination processes that can benefit from indirect heating compared to direct heating process in which the presence of flue gases is undesirable from a CO2 emissions perspective and from a process perspective (as combustion flue gases generally contain excess oxygen). Such benefits apply to the indirectly heated reactors disclosed herein. It will also be appreciated that the above is not an exhaustive list and that the application of the indirectly heated reactors disclosed herein is not limited to the applications expressly listed above.

[0118] In the disclosure, the process for calcination for Case B (ii) with respect to the calcination of limestone CaCCh to produce lime CaO and CO2 gas is used as a reference case. This process is directly relevant to the production of zero emissions lime and cement using either electric or combustion heating elements. As stated above, reactor designs disclosed herein may apply to other indirect heating processes mentioned above, using such a reactor, by integrating with known arts.

[0119] Indirectly heated reactors were initially described by Sceats et. al. in PCT / AU2007 / 000424, the entire disclosure of which is incorporated herein by way of cross-reference. Named later as direct separation reactors, such reactors were described in WO2015 / 077818, the entire disclosure of which is incorporated herein by way of crossreference. In particular, WO2015 / 077818 describes single tube reactors where the input powder materials are typically injected into the reactor in the order of 8-10 tonnes per hour; generally, for a range of materials, the use of indirect heating of materials for commercial applications in which the characteristics of the powder flow regime of the reactor operate in a dilute powder flow, i.e. a low particle volume fraction of about 10'4, in which particles of diameter less than about 250 pm fall downwards under gravity in an externally heated metal tube. The typical tube diameter is limited to about 2 metres so that the penetration of thermal radiation through the particle flow ensures that the particles are sufficiently uniformly calcined within a reactor length of about 10-30 m. That is, the powder flow regime is far from laminar flow and the heating is primarily from adsorption of radiation at a distance. A typical mass flow rate is the order of about 5-10 tonnes per hour in such a tube reactor, with a wall temperature distribution controlled to optimise the heat flow for the calcination process to limit the reactor height. If metal walls are used, the maximum temperature is about 1050 °C, limited by the creep of special steels such as 253MA. Ceramic walls may be used for higher temperature operation. The residence time of the particles in such an indirectly heated reactor is about 120 seconds or lower for reactors of about 15-30 m high, depending on whether the gases, if any, produced from calcination reactions or injected into the reactor are in co-flow or counter-flow with the falling particles. The energy efficiency of the reactor is very high because refractories are used to surround the external heating elements which limit radiation loss, typically less than 15% in most applications. The energy efficiency of the reaction process is primarily determined by the recuperation of energy from hot solids and hot gases powder to input powders and gasses. The energy efficiency of electrical heating is influenced by transformer losses, while the energy efficiency of indirect combustion heaters depends on factors such as the mode of combustion, such as flame or flameless, and energy recuperation from the hot combustion exhaust to the combustion inputs, and also with the input solids and gases. A higher degree of calcination of a powder may be obtained using a polishing stage such as a heated bed at the base of the reactor. The pressure of the gas is controlled at positive gauge to ensure that the tube does not implode by buckling. The powder may be preheated before injection into the reactor to a temperature where onset of significant calcination of the particles begins to take place. The powder may be hot briquetted or hot pelletised at the base of the reactor for some applications. Other powder materials may be added prior to such mixing and briquetting, depending on the application in which the briquettes / pellets are employed. Persons skilled in the art would recognise that the characteristics of the flows described above will vary depending on the details of the materials and the calcination process steps.

[0120] The scale-up of such indirectly heated tubular reactors was described by Sceats et. al. in PCT / AU / 2021 / 051183 in terms of a plurality of vertical reactor tubes. In the present disclosure an alternative to scale up of indirectly heated reactors is considered. In tubular reactors of the prior art, such as of the type described in PCT / AU / 2021 / 051183, heat transfer to the interior of the reactor tube is primarily through radiative heat transfer from the reactor walls. The size of such a reactor is limited because there is a limit as to how far into the interior space the energy radiated from the reactor walls can penetrate. The reactors disclosed herein contemplate a number of heating mechanisms, at least some of which can allow for easier scale-up. As above, the reactors disclosed herein can be advantageously employed in many different applications. Heated Reactor - Fig, 1

[0121] Disclosed in Figure l is a vertical reactor. The vertical reactor may be suitable for use as a calciner, for example, for converting limestone and / or dolomite into calcium oxide and / or magnesium oxide. It is thought that the vertical reactor as disclosed herein may be suitable for use in small-scale processes, as well as larger scale (e.g. industrial) processes.

[0122] A schematic of a cross-section of an embodiment of such a vertical reactor 100 is shown in Fig. 1. The reactor 100 comprises a vertically oriented reactor tube 102. In this embodiment, the reactor tube 102 is in the form of a central metallic vessel. Surrounding the reactor tube 102 is an outer shell 104. The outer shell 104 surrounds the reactor tube 102 such that a void 106 is created between an outer face 108 of the reactor tube 102 and an inner face 110 of the outer shell 104.

[0123] The outer shell 104 comprises heating elements, in this embodiment in the form of resistive heating elements 112 which are mounted to the inner face 110 of the outer shell 104. It will be appreciated that the resistive heating elements can take other forms, such as rods which are mounted within or otherwise extend into the interior of the void 106. The resistive heating elements 112 are typically powered by electricity. In particular, the resistive heating elements 112 can be powered by green electricity, so as to minimise the carbon footprint of the reactor 100. Alternatively, the heating elements can be heated through induction.

[0124] The outer shell 104 can further comprise internal insulation, e.g., located between the inner face 110 of the outer shell 104 and the heating elements 112. In this regard, the heating elements 112 can be secured at (e.g., attached to) the internal insulation. The insulation can minimise the extent to which heat generated by the heating elements 112 is transferred from the elements to an external environment (i.e., as heat losses). The insulation can also help to reduce a surface temperature of an outer face 114 of the reactor 100 which can, e g., increase the safety of the reactor 100.

[0125] Located toward an upper end 120 of the outer shell 104 are one or more gas input ports 116 (two such ports 116 are shown in Fig. 1). The outer shell 104 is fluidly connected to the reactor tube 102 by one or more input ports 118 located toward a lower end 118 of the outer shell 304 and reactor tube 102 (two such ports 118 are shown in Fig. 1). As a result, in-use, gas fed into the outer shell 104 (when present) via the gas input port(s) 116 is caused to flow through the void 106 before entering the reactor tube 102 toward a lower end thereof. The reactor tube 102 further comprises a material feed 124 located adjacent to a top end 120 of the reactor tube 102 and a reacted powder output 126 positioned at a base 128 of the reactor tube 102. The material feed 124 is configured to allow a material in the form of a powder to be fed into the reactor tube 102 such that said powder falls down the reactor tube 102 and exits the reactor tube 102 via the reacted powder output 126. The material feed 124 can take the form of a suitable hopper, feed auger, etc.

[0126] The reactor tube 102 typically also comprises a gas exhaust 130 positioned adjacent the top end 120 of the reactor tube 102 and configured to remove exhaust gases from the reactor tube 102. The reactor 100 can further comprise a gas separator positioned adjacent to the gas exhaust 130 and configured to separate gas in the exhaust from any entrained powder. The entrained powder typically comprises ultra-fine particles which become entrained with the gas inside the reactor and, as a consequence, are elutriated from the reactor tube 102 along with the exhaust gas. The entrained powder is typically reinjected and / or re-fed back into the reactor tube 102 (e.g., via the material feed 124 or separately). For example, in some embodiments, the entrained powder is reinjected into the reactor tube 102 along with the gas, such that the entrained powder is reinjected into the reactor tube 102 via the one or more input ports 118. It is thought that reinjecting the ultra-fine powder into the lower end of the reactor tube can minimise further elutriation of these ultra-fines, because, in-use, downwardly falling powder can act to suppress further elutriation of the ultra-fines. The reaction extent of the ultra-fines can also be increased.

[0127] In-use, a powder to be reacted 134 is fed into the reactor tube 102 via the material feed 124. The powder 134 is fed such that the powder falls downwardly through the reactor tube 102. At the same time, a suitable gas 132 (e.g., if required for the application) is fed into the outer shell void 106 via the gas input port(s) 116. The suitable gas 132 is typically at an ambient temperature. Alternatively, the suitable gas 132 may be preheated. For example, when the reactor 100 is part of a wider process, the suitable gas 132 can be preheated so as to reuse process heat from elsewhere in the process. However, the temperature of the suitable gas 132 is still typically below a required operating temperature of the reactor tube 102. It is noted that, when a gas is not required, the outer shell may be omitted from the reactor 100. Alternatively, the outer shell may be present, but not in-use.

[0128] The suitable gas (when used) fed through the gas port(s) 116 flows into the void 106. It will be appreciated that the composition of the gas 122 will depend on the application in which the reactor 100 is employed. For example, when the reactor 100 is used to reduce iron ore, the gas 122 can comprise any suitable reducing gas. In the void 106, the heating elements 112 provide thermal energy in the form of radiative heat to the suitable gas as it passes into and flows through the void 106. As the gas flows through the void 106, the suitable gas is thereby heated (i.e., due to heat radiating from the heating elements 112). In the void 106, the suitable gas 122 is typically heated to a maximum temperature at which the reactor tube 102 operates.

[0129] By maintaining a constant flowrate of the suitable gas 132 through the gas input port(s) 116, gas within the void 106 is pushed downwards. At the same time, because the gas within the void 106 is heated, it expands. The result is that a gas pressure within the void 106 is increased, compared to the pressure in the reactor tube 102. This creates a pressure differential between the void 106 and reactor tube 102, causing the heated gas to flow downwards 127, and then into the reactor tube 102 via the one or more ports 118. The gas entering the reactor tube 102 is therefore heated gas 136. In this regard, during operation of the reactor 100, the pressures within the void 106 and the reactor tube 102 are monitored and controlled so as to maintain said pressure differential. By maintaining a pressure in the reactor tube 102 that is lower than a pressure within the void 106, heated gas 136 is caused to flow into the reactor tube 102.

[0130] In the reactor tube 102, the now-heated gas 136 flows upwards. In this regard, the heated gas 136 and the falling powder 134 flow in a counter-flow arrangement. However, in other embodiments, the heated gas 136 and the powder 134 may flow in a co-flow arrangement. For example, by arranging the gas input port(s) 116 toward an upper end of the reactor tube 102.

[0131] As the upwardly flowing heated gas 136 contacts the downwardly falling powder 134, energy is transferred from the gas 136 to the powder 134. At the same time, radiative heat emanated from the heating elements 112 heats up the walls 138 of the reactor tube 102. In turn, the heated walls 138 radiate energy both into the reactor tube 102 and back into the void 106. The heat radiated into the void 106 acts to further heat the gases therein. Meanwhile, the heat radiated into the reactor tube 102 acts to heat the downwardly falling powder 134, as well as to further heat the gas 136. The energy transfer (i.e., due to radiative heat from the reactor walls 138 and heat transfer between the heated gas 136 and the powder 134 causes the powder 134 to be heated to a temperature at which it reacts.

[0132] Consequently, exiting the reactor tube 102 at a lower end thereof 122 is the reacted powder 126. The vertical nature of the reactor tube 102, together with the use of powders in a dilute flow regime, result in short residences times of between about 10 to 50 s. The flowrates are such that the reactor 100 is typically between 15-30 m high, i.e., to provide the required residence time.

[0133] It is thought that the reactor 100 may provide a suitable alternative to the indirectly heated vertical reactor previous described. In this regard, the reactor 100 may be employed in the same applications as the indirectly heated vertical reactors previously described, as well as in other applications.

[0134] It is noted that the particles are significantly smaller than pellets used for shaft kilns or rotary kilns and may be smaller than those used in fluidised bends. The powder and the gas can be fed into the reactor tube 102 so as to assume a dilute flow regime. In this regard, the powder can be fed into the reactor tube 102 at a flux in the range of 0.5-1 kg m'2s'1and with an average downward velocity of between about 0.2 to 3.0 m / s. The reactor tube 102 is sized so as to provide a residence time of the fine powder within the reactor tube 102 of between about 10 to 120 s, such as between about 40 to 120 s. Of course, it will be appreciated that these conditions can be varied (e.g., depending on the application) so as to optimise the reaction of the powder. Due to the low particle to gas ratios, mass flows are such that the kinetics of the reduction reaction are fast, and fluidised bed reactors are not required. Advantageously, this enables continuous operation of the reactors as herein disclosed. On the other hand, fluidised beds are generally not operated in a continuous mode because they have processes for loading and unloading powders or are prone to slugging instabilities that impact of quality. The reactors disclosed herein are described as vertical reactors as there is no need for purposeful horizontal displacement of particles in the reactors. It is noted that, in the reactor 100, some of the thermal energy to heat the powder in the reactor tube 102 is provided by the preheated powder. However, it is thought that the bulk of the energy requirements within the reactor tube 102 is still provided by indirect radiative heat transfer from the heated walls 138 of the reactor tube 102, which has a penetration depth in the downwardly falling powder of less than about several metres. Thus, the solids volume fraction is limited by the penetration of heat from the heated reactor walls 138 to the reactor tube. In this regard, the powder should be injected as particles with a volumetric-solids-fraction for a radiation penetration depth of about Im, of about 10'4to achieve uniform reaction across the reactor. The issue of heat transfer from the heated reactor walls can also limit the diameter of such a reactor (i.e., because the thermal energy radiated from the heated walls must be able to penetrate to the centre of the reactor tube to ensure an even heat distribution and to heat powder / gas at the centre of the reactor tube).

[0135] It is thought that the reactor 100 may be employed in larger-scale processes by making use of modules of reactors 100 in series. The number of reactors 100 can be selected so as to provide the required throughput.

[0136] Reactor for Scale-up - Fig, 2

[0137] Disclosed herein is a reactor that is configured to be vertically oriented in use. The vertical reactor may be suitable for use in the calcination of powders, for example, for production of magnesia, lime, dolime, calcined cement meal, the production of alumina or activated bauxite, or gasification of carbon fuels to make syngas and char for various applications. Alternatively or additionally, the vertical reactor may be suitable for other uses, such as the conversion of hematite and / or goethite to magnetite. The vertical reactor may also be suitable for use in the reduction of magnetite to iron. As a further examples, the vertical reactor may be suitable for use as a pyrolyser (i.e., for converting biomass to bio-char). It is thought that the vertical reactor as disclosed herein may be suitable for use in large scale (e.g. industrial) processes. The vertically oriented reactor comprises an elongate reactor body comprising one or more material feed inlets located toward an in-use upper end of the reactor body, the material feed inlets configured to feed a powder to be reacted such that said powder falls downwards in the reactor body; gas input ports arranged toward an in-use lower end of the reactor body for feeding a gas into the reactor body; a powder outlet positioned toward the lower end of the reactor body; and heating elements positioned in an interior space of the reactor body and configured to transfer heat into the interior space of the reactor body, so as to heat the gas and the falling powder and cause the powder to react.

[0138] A schematic of a cross-section of an embodiment of such a reactor 200 is shown in Fig. 2. The vertical reactor 200 comprises a vertically elongate reactor body 202. Arranged toward an in-use upper end 206 of the reactor body 202 are multiple, spaced material feed inlets 204a, 204b,... 204n. The multiple material feed inlets 204a, 204b,... 204n effectively define corresponding sections 208a, 208b,... 208n of the reactor body 202. Each of the sections 208a, 208b, . .. 208n of the reactor body comprises a corresponding one of the material feed inlets 204a, 204b, . .. 204n. In this regard, the reactor body 202 is also horizontally elongate. That is, the reactor body 202 is elongate both vertically and horizontally. In this regard, the reactor 200 can have the form of a long bank.

[0139] Each of the material feed inlets 204a, 204b,... 204n is configured to feed a powder to be reacted into the reactor body 202 such that the powder falls downwardly through the reactor body 202. In particular, each of the material feed inlets 204a, 204b,... 204n are configured to feed the powder into, to be reacted in, a respective one of the sections 208a, 208b, ... 208n such that the powder falls downwardly through its respective section 208a, 208b,... 208n. In this regard, each of the sections 208a, 208b, 208n further comprises a respective powder outlet 218a, 218b,... 218n, located at a lower end of the respective section from which the reacted powder can be collected.

[0140] The sections 208a, 208b, 208n can be configured along the reactor body 202 such that, in-use, powder falling through one section of the reactor body via the associated material inlet does not interact (to any significant extent) with powder falling through an adjacent section of the reactor body via an adjacent material inlet. In this regard, each of the one or more sections 208a, 208b,... 208n can be configured to operate essentially independently of each other section. Alternatively, if it is desirable to promote such interaction (e.g., for certain materials to be reacted) the spacing between the one or more material feed inlets 204a, 204b,. . . 204n can be such as to allow for or to even promote such interactions (e g., mixing) between the falling powder of adjacent sections 208a, 208b,... 208n.

[0141] It will be appreciated that the number of material feed inlets 204a, 204b,. . . 204n can be adjusted (e.g., based on the throughput required). It will further be appreciated that the length of the reactor body 202 can be adjusted based on the number of material feed inlets 204a, 204b, ... 204n selected and a required spacing between each of the inlets.

[0142] The reactor 200 further comprises gas input ports 210, if and as required for specific calcination processes, that are typically arranged to feed gas into the reactor at a conical region 21 la, 211b,.. . 21 In located toward an in-use lower end 212 of the reactor body 202. In particular, the gas input ports 210 are located and arranged such that each of the one or more sections 208a, 208b,. .. 08n has at least one gas input port 210 associated therewith. Typically, each of section 208a, 208b, 208n comprises the same number of gas input ports. The gas input ports 210 are each configured to feed a gas into the reactor body 202 in-use such that the gas is directed upwardly through the reactor body 202. In this regard, in-use, the gas and the powder are configured in a counter-flow arrangement. However, it is noted that, alternatively, the gas input ports 210 may be configured to feed a gas into the reactor body in-use such that the gas and the powder follow a co-flow arrangement, i.e., both the gas and the powder flow downwardly through the reactor. Also arranged at the upper end of the reactor body 202 to correspond with each of the sections 208a, 208b,... 208n are exhaust outlets 213, through which the reactor gas, after having travelled up through a respective one of the sections 208a, 208b, ... 208n, exits the reactor body 202.

[0143] The reactor 200 can further comprise one or more gas separators positioned adjacent to the exhaust outlets 213 and configured to separate gas in the exhaust from any entrained powder. The entrained powder typically comprises ultra-fine particles which become entrained with the gas inside the reactor and, as a consequence, are elutriated from the reactor body 202 along with the exhaust gas. The entrained powder is typically reinjected and / or re-fed back into the reactor body 202 (e.g., via the material feed inlets 204a, 204b,... 204n or separately). For example, in some embodiments, the entrained powder is reinjected into the reactor body 202 along with the gas, such that the entrained powder is reinjected into the reactor body 202 via the gas input ports 210. As described above, it is thought that reinjecting the ultra-fine powder into the lower end of the reactor body can minimise further elutriation of these ultra-fines, because, in-use, downwardly falling powder can act to suppress further elutriation of the ultra-fines. The reaction extent of the ultra-fines can also be increased.

[0144] The reactor body 202 is defined by an interior space 220 in which the powder to be reacted flows downwards and the reactor gas flows upwards, in-use.

[0145] In this regard, heating elements 214, 216 are positioned in the interior space 220 of the reactor body 202. The heating elements 214 comprise a series of suspended, spaced sheet elements (e.g., plates of metallic alloy) of varying height. The sheet elements can be directly electrified to transfer energy via thermal transfer to the process stream (powder down-flow, gas up-flow). The heating elements 216 may comprise a number of discretely spaced, directly electrified high temperature silicon carbide radiative elements (e.g., rods) that are positioned towards the final stages of the process stream. The heating elements 216 transfer additional energy to this region of each section 208a, 208b, . .. 208n.

[0146] The heating elements 214, 216 together transfer heat into the interior space 220 of the reactor body 202, so as to heat the rising gas and the falling powder, thereby providing the energy required to cause the powder to react. Typically, the heating elements 214, 216 are heated either resistively or inductively and are configured to directly radiate heat into the interior space 220 of the reactor body 202. The energy for the heating elements 214, 216 may be provided by any known means, e.g., electricity. To reduce the carbon footprint of the reactor 200, the electrical (or thermal) energy for the heating elements 214, 216 can be sourced from, e.g., solar, wind, geothermal sources, etc.

[0147] Advantageously, by employing heating elements 214, 216 located in the interior space 220, the interior space 220 of the reactor body 202 is directly heated. This can increase the efficiency of the heating compared to extemal / indirect heating sources. For instance, in some indirectly heated reactors of the prior art, heat is provided to the reactor body via the reactor walls. In the prior art reactors, the reactor walls are heated, for example, by heat from the combustion of a fuel source. The heated walls then radiate energy into the interior of the reactor, causing the reactants therein to be heated. However, the size of such a reactor is limited because there is a limit as to how far into the interior space the energy radiated from the reactor walls can penetrate. Also, for industrial scale processing, a series of such reactors, for instance in the form of an enclosed bank of reactors in which the powder flows down within each reactor tubular element, can be required, and such adjacent reactors may thermally interfere with each other. For instance, while the external heat for such reactors is centred around the reactor elements, the temperature in the space between the heating elements will be heated towards the heater temperature surrounding each reactor, so that the temperature profile in such a scaled-up reactor will constitute symmetric reactor elements and an asymmetric heating system at a higher temperature. Further, it is undesirable to operate such reactors at reactor wall temperatures that are too high, as this can result in a large temperature gradient within the interior space. Moreover, heat loss inevitably occurs as the heated reactor walls also radiate heat outwardly into a surrounding environment.

[0148] By arranging the heating elements 214, 216 within the interior space 220, such that the interior space 220 of the reactor body is directly heated, it is noted that reactor size and interference issues may be overcome. This is because, in contrast to the prior art, the reactor disclosed herein is based on an enclosed bank of symmetric heating elements, where powder, in dilute flow conditions, flows down under gravity, promoted or retarded by the gas flow, in the asymmetric spaces between the bank of symmetric heating elements. The configuring of the reactor with heating elements 214, 216 that are positioned within the interior space 220 of the reactor body 202 can better allow for scale up. In this regard, the heating elements may be spaced out, at desired / required spacings, across a length of the reactor so that, when it is desired to increase reactor scale, the reactor can be lengthened, widened and / or height increased with a corresponding increase in number, density, size, area, etc. of the heating elements. Such scaling is generally more problematic for externally heated (e g., tubular reactors). In particular, it is noted that heating of the powder and gas within the reactor is dominantly radiative heating (i.e., due to thermal energy radiated from the heating elements 214, 216). The penetration depth of this radiation in the downwardly falling powder is typically less than about several metres. Therefore, it can be desirable to provide a separation between heating elements 214, 216 of about 1-2 m2to achieve sufficiently uniform heating (and thus pyro-processing) of the powders in the reactor.

[0149] The configuration of the reactor 200 may allow for reactors with a larger volume and a higher throughput to be employed, whilst still maintaining good thermal efficiency. This is because the heating elements 214, 216 can be distributed within the interior space 220 so as to ensure an even distribution of radiative heat within the reactor, eliminating the need for externally heated tubes, etc. Typically, the spacing between the heating elements 214, 216 is selected such that the radiation can penetrate the gas / powder in the space between adjacent heating elements 214, 216. In addition, because the heating elements 214, 216 are spaced away from the reactor walls, there is no heat transfer directly from the heating elements 214, 216 to the surrounding environment.

[0150] Of further advantage is that the heating elements 214, 216 provide for the interior space 220 of larger reactors to be efficiently achieved without having to resort to undesirable processes such as direct combustion within the interior space 220, as in prior art reactors. As above, the energy for the heating elements 214, 216 can be provided by zero-emissions sources. This can reduce the CO2 emissions of the reactor 200 (e.g., compared to the reactors of the prior art which typically rely on combustion within the reactor to provide the energy for the reactions).

[0151] As set forth above, the heating elements take the form of a number of spaced metallic alloy sheets 214 and a number of spaced radiative tubes 216. Each of the sections 208a, 208b,... 208n comprises multiple metallic alloy sheets 214, as well as multiple radiative tubes 216. In the illustrated embodiment of Fig. 2, there are multiple banks 222a, 222b,. . . 222n of metallic alloy sheets. Each bank 222a, 222b, . . . 222n comprises up to nine sheets Each of the metallic alloy sheets 214 within a bank are configured to be electrified (or otherwise heated or powered) so as to transfer heat directly into the interior space 220 of the reactor body 202. Each metallic alloy sheet 214 is suspended from an upper reactor wall 223 to extend downwards in use from the upper end 206 of the reactor body 202. The metallic alloy sheets 214 can comprise different lengths of sheet (e g., shortest length sheets are located adjacent to each material feed inlet 204, with the sheets gradually increasing in length moving away from the material feed inlet 204, as shown in Fig. 2 and as further explained below). In this way, radiative energy can be provided along a downwards length of the interior space 202. Also, falling powder is less likely to coat the adjacent short sheets. It will also be appreciated that the number and configuration of the metallic alloy sheets 214 can be selected so as to achieve a desired temperature profile within the interior space 220.

[0152] Typically, the material feed inlets 204a, 204b,... 204n are arranged in relation to their respective sections 208a, 208b, . .. 208n so as to feed the powder such that the powder falls downwards in the reactor body 202 between adjacent spaced metallic alloy sheets 214. In the illustrated embodiment of Fig. 2, the material feed inlets 204a, 204b,... 204n are arranged to feed the powder such that the powder falls downwards in the reactor body 202 between two adjacent spaced sheets, with these two adjacent spaced sheets being the shortest sheet in the respective bank 222a, 222b,. .. 222n of metallic alloy sheets. The length of the metallic alloy sheets in the respective bank 222a, 222b,. .. 222n gradually increases as a horizontal distance between the material feed inlet 204a, 204b, 4204n and the metallic alloy sheet increases, the sheet reaching a maximum length at an intermediate location between adjacent material feed inlets. As above, by having metallic alloy sheets of different lengths, radiative energy can be provided along a downwards length of the interior space 202. As above, by having the shortest sheets located closest to the material feed inlet, the risk of the sheets becoming coated by the powder can be reduced. However, it will be appreciated that other configurations of material feed inlet and metallic alloy sheets are possible. For example, the reactor body 202 can comprise more material feed inlets, with each material feed inlet being located between a two adjacent metallic alloy sheets.

[0153] As above, the reactor 200 also comprises one or more high temperature radiative tubes 216. The radiative tubes 216 are configured to radiate energy into the interior space 220. The radiative tubes 216 are generally arranged to extend horizontally (i.e., from reactor front to reactor back) within the interior space 220 of the reactor body 202 at a position toward the lower end of the reactor body 202. As shown in Fig. 2, three such radiative tubes 216 are arranged in a ‘ shallow triangular’ configuration in each of the sections 208a, 208b, ... 208n. In this way, the radiative tubes 216 can transfer additional thermal energy along and into the final stages of the reaction pathway. This can help to increase and ensure the overall reaction of the downwardly falling powder. As above, the radiative tubes 216 may comprise silicon carbide or steel.

[0154] In-use, a powder to be reacted is fed into the reactor body 202 via each of the material feed inlets 204a, 204b,... 204n. The powder is fed by the material feed inlets 204a, 204b, ... 204n such that it falls downwardly through the reactor body 202. It will be appreciated that the composition of the powder will depend on the process in which the reactor 200 is being employed.

[0155] At the same time, a gas may be fed into the reactor body 202 via the gas input ports 210 arranged at each of the conical regions 21 la, 21 lb,.. . 21 In at the lower end of the reactor body 202. The gas is fed by the gas input ports 210 such that it flows upwardly through the reactor body 202. The gas may be at or near an ambient temperature. Alternatively, the gas may be a preheated gas. It will be appreciated that the composition of the gas will depend on the process in which the reactor 200 is being employed.

[0156] In a variation of the reactor 200, the reactor 200 further comprises tubes that extend from the upper end 206 of the reactor chamber (208a, 208b... 208n) to near the lower end 212 of the reactor chamber or, alternatively, to near the lower end of the metallic alloy sheets (222a, 222b,... 222n). The tubes are constructed of a thermally conductive material, so as to allow heat transfer between gas flowing through the tubes in-use and the interior of the reactor. In-use, the gas to be preheated is injected into the tubes and flows through the tubes. The gas can be input so as to flow either upwardly or downwardly through the tubes. As the gas flows within the tubes, heat from the reactor chamber (208a, 208b. .. 208n) is transferred to the gas, causing the gas to be preheated. In some variations, the tubes are located near the metallic alloy sheets (222a, 222b,.. . 222n) such that radiative heat from the metallic alloy sheets (222a, 222b,... 222n) is also transferred to the gas. The (preheated) gas exiting the tubes can then be input into the reactor (i.e., as preheated gas) via the gas input ports 210. It will be appreciated that further heating of the gas can be performed, if required, prior to inputting the gas into the reactor.

[0157] As the powder falls down the reactor body 202, the powder is heated by radiative heat from the heating elements 214, 216. At the same time, the upwardly flowing gas is likewise heated (i.e., again, by the radiative heat from the heating elements 214, 4216). The powder and the gas are heated so as to cause the powder to react. Again, it will be appreciated that the target temperature of the powder and the gas within the reactor body 202, and therefore the amount of heating provided by the heating elements 214, 216, is dependent on the application.

[0158] The gas input ports 210 are typically arranged to feed the gas upwards into the reactor body 202 such that the rate of the powder falling downwards in the reactor body is able to be controlled. In particular, the flowrate of the gas and the powder typically assumes a dilute flow regime in which the powder and gas flow in a counter-flow arrangement. However, it is thought that a co-flow arrangement may alternatively be employed. It is thought that, due to the vertical nature of the reactor and by employing a dilute flow regime, sufficient calcination of the powder may be achieved with residence times as low as about 10 to 120 s, such as about 40 to 120 s. At typical flowrates, this corresponds to a reactor height of between about 15-30 m. It will be appreciated by a person skilled in the art that the propensity for deformation of materials increases with temperature, and asymmetries between materials in terms of junctions, defined by the local curvature, become the points from which stresses may grow, so that deformations may occur to lower the local surface tension by sintering. Some deformation may be negligible, while others may lead to buckling and collapse of the reactor elements and, ultimately, the reactor itself. These potential impacts may be minimised by, for example, minimising the curvatures of all the heating elements. Importantly, all the space in the interior of the reactor, other than the heating elements, is then available for reaction. A fundamental difference between this design and those of the prior art is that prior art designs typically provide symmetry for the reacting materials inside each tube, whereas, in the present design, heating elements and the unfilled spaces between the tubes are inherently asymmetric.

[0159] The flow uniformity in this asymmetric configuration may be assisted by surrounding the reactor in the module by an externally heated radiative element in contact with the surrounding refractory, called herein the external reactor heating elements. In this regard, in some embodiments, the reactor body 202 of the reactor 200 is surrounded by an external heating element (not shown). In these embodiments, the heat transfer into the reactor body 202 occurs from a combination of this external heating source and from the heating elements 214, 216 embedded inside the reactor body 202. External reactor heating elements are typically designed to enable a flow of heat to be optimised at various depths within the reactor. The external reactor heating elements may be designed to deliver power around the surface to minimise radiative shadowing from heating elements 214, 216 within the reactor body 202 (i.e., to ensure uniform heating within the reactor body 202). It is noted that it can be optimal to provide a uniform radiation density within the reactor body 202 both with and without powder loading. The input and output gas flow for each effective section 208a, 208b, .. 208n may be controlled so as to maintain these desirable conditions. For example, the input and output gas flow can be controlled to create swirls of gas and powder within each reactor section 208a, 208b,.. . 208n. In such a system, a high degree of conversion may be obtained using not only the controls of external heating, but also the flows of gas and powder in the reactor. In these embodiments, the external heating reactor design for scale-up is therefore a module which comprises a number of reactor sections 208a, 208b,... 208n, each comprising internal heating elements 214, 216, which are all surrounded by a refractory structure that defines the reactor body 202. The organisation of reactor sections and reactor section volumes may be selected so as to achieve uniform reactions and high throughputs. Further Embodiments of Reactors for Scale-up - Figs. 3 to 8

[0160] Disclosed herein are further embodiments and variations of a reactor that is configured to be vertically oriented in-use. The vertical reactor may be suitable for use in calcination of powders.

[0161] It is thought that the vertical reactor as disclosed herein may be suitable for use in small- scale processes, as well as larger scale (e.g. industrial) processes. For instance, other specific examples include the production materials for special steels for alloys from iron ores sufficiently rich with these elements in an oxidised state, where a process may include first and second indirectly heated reduction reactors using hydrogen as the reductant to reduce the iron in the ores prior to reduction in a third reactor. The configuration of the reactors may allow for reactors with a larger volume and a higher throughput to be employed, whilst still maintaining good thermal efficiency. Different variations of the reactor will now be described with reference to Figs. 3 to 8.

[0162] The vertical reactor comprises an elongate reactor body. The elongate reactor body comprises one or more material feed inlets located toward an in-use upper end of the reactor body, the material feed inlets configured to feed a powder to be reacted such that said powder falls downwards in the reactor body; gas input ports arranged toward an in- use lower end of the reactor body for feeding a gas into the reactor body; one or more powder outlets positioned toward the lower end of the reactor body; one or more external heating elements arranged around an outside of the reactor body and configured to heat an interior of the reactor body.

[0163] A schematic top-view of a cross-section of various embodiments of reactors 300a to 300f are respectively shown in Figs. 3 to 8. The vertical reactors 300 each comprise a vertically elongate reactor body 302. Arranged toward an in-use upper end of the reactor body 302 are multiple, spaced material feed inlets 304. The multiple material feed inlets 304 effectively define sections of the reactor body 302. Each of the sections of the reactor body comprises a corresponding one of the material feed inlets 304. In this regard, the reactor body 302 is also horizontally elongate. That is, the reactor body 302 is elongate both vertically and horizontally. In this regard, the reactor 300 can have the form of a long bank.

[0164] Each of the material feed inlets 304 is configured to feed a powder to be reacted into the reactor body 302 such that the powder falls downwardly through the reactor body 302. In particular, each of the material feed inlets 304 is configured to feed the powder into, to be reacted in, a respective one of the sections such that the powder falls downwardly through its respective section. In this regard, each of the sections further comprises a respective powder outlet located at a lower end of the respective section from which the reacted powder can be collected. Typically, the respective powder outlet is vertically opposite the respective one of the material feed inlets.

[0165] The sections can be configured along the reactor body 302 such that, in-use, powder falling through one section of the reactor body via the associated material inlet does not interact (to any significant extent) with powder falling through an adjacent section of the reactor body via an adjacent material inlet. Alternatively, if it is desirable to promote such interaction (e.g., for certain materials to be reacted) the spacing between the one or more material feed inlets 304 can be such as to allow for or to even promote such interactions (e.g., mixing) between the falling powder of adjacent sections.

[0166] It will be appreciated that the number of material feed inlets 304 can be adjusted (e.g., based on the throughput required). It will further be appreciated that the length of the reactor body 302 can be adjusted based on the number of material feed inlets 304 selected and a required spacing between each of the inlets.

[0167] The reactor 300 further comprises gas input ports (not visible from the top-view shown) that are typically arranged to feed gas into the reactor at a lower end of the reactor body 302. The reactor body can comprise a conical region located toward an in-use lower end and at which the gas input ports (if required) are located and arranged (e.g., such as the conical regions of Fig. 2). However, the reactor can comprise other geometries. For example, the reactor body can be elongate (e.g., such as the reactor body of Fig. 2).

[0168] As required, the gas input ports are located and arranged such that each of the one or more sections has at least one gas input port associated therewith. Typically, each section comprises the same number of gas input ports. The gas input ports are each configured to feed a gas into the reactor body 302 in-use such that the gas is directed upwardly through the reactor body 302. In this regard, in-use, the gas and the powder are configured in a counter-flow arrangement. However, it is noted that, alternatively, the gas input ports may be configured to feed a gas into the reactor body in-use such that the gas and the powder follow a co-flow arrangement, i.e., both the gas and the powder flow downwardly through the reactor. The gas input ports are further arranged to feed the gas into the reactor body such that the rate of the powder falling downwards in the reactor body is able to be controlled. For example, to allow the flow regime within the reactor body 302 to assume a dilute gas flow.

[0169] Also arranged at the upper end of the reactor body 302 to correspond with each of the sections are exhaust outlets 313, through which the reactor gas, after having travelled up through a respective one of the sections (i.e., in the case of a counter-flow arrangement), exits the reactor body 302. The reactor 300 can further comprise one or more gas separators positioned adjacent to the exhaust outlets 313 and configured to separate gas in the exhaust from any entrained powder. The entrained powder typically comprises ultra-fine particles which become entrained with the gas inside the reactor and, as a consequence, are elutriated from the reactor body 302 along with the exhaust gas. The entrained powder is typically reinjected and / or re-fed back into the reactor body 302 (e.g., via the material feed inlets 304 or separately). For example, and as will be described in more detail below, in some embodiments, the entrained powder is reinjected into the reactor body 302 along with the gas, such that the entrained powder is reinjected into the reactor 302 via the one or more gas input ports. It is thought that this can be particulary advantageous when the reactor is operated in a counter-flow regime such that the gas (and ultra-fine powder) is reinjected into a lower end of the reactor body 302 because reinjection of the ultra-fine powder into the lower end of the reactor body can minimise further elutriation of these ultra-fines, because, in-use, downwardly falling powder can act to suppress further elutriation of the ultra-fines. The reaction extent of the ultra-fines can also be increased.

[0170] The reactor body 302 is defined by an interior space 320 in which the powder to be reacted flows downwards and the reactor gas flows upwards, in-use. The interior space 320 is defined by an interior reactor wall 324. Surrounding the interior reactor wall 324 is a steel casing 326. The steel casing 326 is typically lined with refractory material 328 on an inner wall thereof. The steel casing 326 may be lined such that the refractory material 328 occupies the entire distance between the steel casing 326 and the interior reactor wall 324. Alternatively, the steel casing 326 may be lined with the refractory material 328 such that there is a gap 330 between the refractory material 328 and the interior reactor wall 324. Such a gap 330 may be used to preheat the gas, as will be explained in further detail below.

[0171] Those skilled will also understand that most calcination processes (e.g., calcination of limestone) are endothermic, requiring energy to proceed. In this regard, each of the reactors 300 are provided with various forms of heating, which will be described in further detail below. The forms of heating can comprise either electric heating, combustive heating or a combination of both. It is noted that the type of heating employed in the reactor 300 can be selected based on the nature and location of the process in which the reactor 300 is employed. For example, where renewable energy can be easily located, the reactors can comprise electric heating. Alternatively or additionally, the reactors can comprise combustion heating. In some embodiments, a hybrid of electric heating and combustion heating is used. For example, as a process is being transitioned to renewable energy sources. In addition, the heating can be provided externally via the reactor walls, by internal heating elements, or by a combination of both. The type of heating elements can be selected based on the scale of the reactor 300. For example, for larger scale reactors, the addition of internal heating elements 300 can be advantageous, as described above in detail with reference to Fig. 2.

[0172] In-use, a powder to be reacted is fed into the reactor body 302 via each of the material feed inlets 304. The powder is fed by the material feed inlets 304 such that it falls downwardly through the reactor body 302. It will be appreciated that the composition of the powder will depend on the process in which the reactor 300 is being employed. For example, when the reactor 300 is being used to calcine limestone, the powder will comprise the limestone to be calcined. The powder comprises particles in which the majority of particles in the powder have diameters of less than about 250 pm.

[0173] At the same time, a gas is fed into the reactor body 302 via the gas input ports arranged at the lower end of the reactor body 302. Typically, the gas is fed by the gas input ports such that it flows upwardly through the reactor body 302. The gas may be at or near an ambient temperature. Alternatively, the gas may be a preheated gas. It will be appreciated that the composition of the gas will depend on the process in which the reactor 300 is being employed. For example, when the reactor 300 is being used to reduce iron ore, the gas will comprise a reducing gas, such as hydrogen. In other application, such as when the reactor is being used to calcine limestone, no additional gas may be required. In these applications, the gas input ports may be eliminated from the reactor body altogether. Alternatively, the gas input ports may be present, but not used for feeding a gas into the reactor body during typical reactor use. It is noted that such gas input ports may be included to enable flushing and / or cleaning of the reactor, e.g., with an inert gas.

[0174] As the powder falls down the reactor body 302, the powder is heated by the external and / or internal indirect heating elements. At the same time, the upwardly flowing gas is likewise heated (i.e., again, by the radiative heat from the heating elements). The powder and the gas are heated so as to cause the powder to react. Again, it will be appreciated that the target temperature of the powder and the gas within the reactor body 302, and therefore the amount of heating provided by the heating elements is dependent on the application. For example, when the reactor 300 is being used to calcine limestone, typical operating temperatures within the reactor body 302 are within the range of about 900 to 980 °C.

[0175] The gas input ports are typically arranged to feed the gas upwards into the reactor body such that the rate of the powder falling downwards in the reactor body is able to be controlled. In particular, the flowrate of the gas and the powder typically assumes a dilute flow regime in which the powder and gas flow in a counter-flow arrangement. However, it is thought that a co-flow arrangement may alternatively be employed. It is thought that, due to the vertical nature of the reactor and by employing a dilute flow regime, sufficient reduction of the powder may be achieved with residence times as low as about 10 to 120 s, such as about 40 to 120 s. At typical flowrates, this corresponds to a reactor height of between about 15-30 m.

[0176] As alluded to above, different arrangements of external and internal heating elements may be employed in the reactor 300. Several variations are provided by way of reactors 300a to 300f of Figs. 3 to 8 respectively. The reactors 300a to 300f use a combination of external heating elements and internal heating elements, as well as a combination of electrical heating and combustive heating. It will be appreciated that variations other than those illustrated are possible. Each of the illustrated variations will now be described.

[0177] Turning first to the reactor 300a of Fig. 3, heating is provided in the form of electric heating. In this regard, the interior reactor wall 324 comprises or is comprised of an electric heating element. Alternatively, the interior reactor wall 324 may comprise or be comprised of multiple electric heating elements. That is, the interior reactor wall 324 may be constructed from the heating element(s). Alternatively, the heating element(s) may be attached to the interior reactor wall 324. The electric heating element(s) are configured to provide energy, in the form of radiative heat, to the interior space 320 of the reactor body 302. Typically, the electric heating element(s) comprise either resistive or inductive heating elements, which are powered by electricity. The electricity can be provided by renewable energy to reduce the carbon footprint of the reactor 300a.

[0178] At the same time, radiative heat from the heating element(s) of the interior reactor wall 324 will radiate outwardly, i.e., in a direction away from the interior space 320 and into the gap 330. This energy may be used to preheat the gas before it is introduced into the interior space 320. For example, as explained above with reference to Fig. 2, the gas may be introduced into the gap 330 at an upper end of the reactor body 302. As the gas flows in the gap 330, the gas is preheated, due to the radiative heat emitted from the heating element(s) into the gap 330. The preheated gas is caused to flow downwardly, where it can enter the interior space 320 at a lower end of the reactor body 302. In this regard, the gas can be preheated in the gap 330 when a counter-flow gas-powder regime is employed within the reactor body 302.

[0179] Turning now to the reactor 300b of Fig. 4, the configuration and operation of the reactor 300b is similar to the reactor 300a, so will not be described again in detail. The primary difference between the reactor 300b and the reactor 300a is that the reactor 300b is heated by external combustion, rather than by external electric heating elements. In this regard, surrounding the interior reactor wall 324 of the reactor 300b is an external combustion chamber 332. In-use, a suitable fuel (e.g., natural gas) is combusted within the external combustion chamber 332, thereby producing heat. The heat from the combustion is transferred to the interior space 320 via conductive and radiative heat transfer through the interior reactor wall 324. It will be appreciated that, in this variation, the interior reactor wall 324 is comprised of a material with low resistance to heat transfer. For example, the interior reactor wall 324 may be comprised of steel. To reduce the carbon footprint of the reactor 300b, any carbon dioxide generated in the external combustion chamber 332 (e.g., when a hydrocarbon-based fuel is used) can be scrubbed from the exhaust gas.

[0180] The inventors note that the reactor 300b may be converted to the reactor 300a by removing the external combustion chamber 332 and installing electric heating elements (e.g., to the internal reactor wall 324 or altogether replacing the internal reactor wall 324 with the electric heating elements). In this regard, the reactor 300b may be initially employed when access to renewable forms of electricity is limited. As above, carbon capture measures can be employed to reduce the carbon footprint of the reactor 300b. As access to renewable forms of electricity become more readily available, the reactor 300b can be converted to the reactor 300a (i.e., by replacing the external combustion chamber 332 with electric heating elements). By converting the reactor 300b to the reactor 300a when renewable forms of electricity are available, the carbon footprint of the reactor may be further reduced.

[0181] As discussed above, scaling up of externally heated reactors, such as reactors 300a and 300b, can be problematic. This is because heating of the powder and gas within the reactor is dominantly radiative heating (i.e., due to thermal energy radiated from the internal reactor wall 324, with the thermal energy provided either electrically or through combustive heating). The penetration depth of this radiation in the downwardly falling powder is typically less than about several metres. As a consequence, as externally heated reactors are scaled-up, thermal energy from the reactor walls may be unable to penetrate throughout the interior space 320 of the reactor. Further, it is undesirable to operate such reactors at reactor wall temperatures that are too high, as this can result in a large temperature gradient within the interior space. Therefore, it can be desirable to provide internal heating elements within the interior space 320 of the reactor. It is thought that a spacing of about 1-2 m between the internal heating elements can achieve sufficiently uniform heating (and thus pyro-processing) of the powders in the reactor. As described above, the addition of interior heating elements results in asymmetry within the interior space, the provision of external heating elements in combination with internal heating elements assists in ensuring thermal uniformity within the interior space.

[0182] In this regard, Figs. 5 to 8 illustrate variations of externally heated reactors 300c to 300f respectively which further comprise one or more internal heating elements 334. That is the reactors 300c to 300f comprise both an external heat source and internal heating elements. The internal heating elements 334 are positioned in the interior space 320 of the reactor body 302. The heating elements 332 typically comprise a series of discretely spaced, suspended rods. The rods extend downwardly through the interior space 320 so as to provide heat energy along a height of the interior space 320. As will be described below, the heating elements 334 are heated either resistively or inductively. The heating elements 332 are configured to directly radiate heat into the interior space 320 of the reactor body 302. The energy for the heating elements 334 may be provided by, e.g., electricity or through direct combustion within the heating elements 334.

[0183] As explained above with reference to Fig. 4, employing heating elements 334 located in the interior space 320 of the reactor body 302 so as to directly heat the interior space 320 has several advantages. For instance, this can increase the efficiency of the heating compared to only using external / indirect heating sources. As above, the size of reactors in which only external / indirect heating mechanisms are employed are limited by the penetration of the radiative heat into the interior space of the reactor. By arranging the heating elements 334 within the interior space 320, such that interior space 320 of the reactor body is directly heated, it is noted that reactor size issues may be overcome. In this regard, the heating elements 334 may be spaced out, at desired / required spacings, across a length of the reactor so that, when it is desired to increase reactor scale, the reactor can be lengthened, widened and / or height increased with a corresponding increase in number, density, size, area, etc. of the internal heating elements.

[0184] It will be appreciated that the size, location and density of the internal heating elements 334 can be selected based on the heating requirements of the reactor 300. For example, in the illustrated embodiments of Figs. 5 to 8, the heating elements 334 are arranged such that each of the material inlets 304 is surrounded by four internal heating elements 334. In particular, the internal heating elements 334 are symmetrically arranged around each of the material inlets 304 and form two rows 336, 338 of internal heating elements 334. The first row 336 is located on one side of the material feed inlets 304 and the second row 338 is located on an opposite side of the material feed inlets 304. However, it will be appreciated that other configurations and arrangements are possible. For example, one or more internal heating elements may be placed between the material feed inlets.

[0185] Each of the reactors 300c to 300f illustrated in Figs. 5 to 8 respectively differ only in the heat source used to heat the reactor via the external heating elements and the internal heating elements. For example, in Fig. 5, indirect heat is provided to the reactor 300c by electric heating elements. As discussed in detail with reference to Fig. 3, the interior reactor wall 324 comprises or is comprised of one or more heating elements arranged and configured to radiate heat into the interior space 302 of the reactor body. In addition, the reactor 300c comprises internal heating elements 334 which are configured to be heated either resistively or inductively by electricity and to radiate heat into the interior space 302. As another example, in Fig. 6, indirect heat is provided to the reactor 300d via the external combustion chamber 332. However, the internal heating elements 334 are each likewise in the form of combustion chambers in which a suitable gas (e g., natural gas, syngas or hydrogen) is combusted. Heat from the combustion reaction heats the walls 340 of the internal heating elements 334. The heated walls 340 are then caused to radiate heat into the interior space 302.

[0186] In this regard, it will be appreciated that each of the reactors 300c and 300d employ the same form of heating for both the external heating and the internal heating of the respective reactor. Reactor 300c, which relies on electricity, can be advantageously employed where there is a nearby source of renewable electricity. On the other hand, reactor 300d, which relies on combustion, can be employed where there may not be a reliable source of renewable electricity nearby. To reduce the footprint of the reactor 300d, carbon dioxide emitted from the combustion exhaust gases may be captured. Alternatively, it is thought that hydrogen may be employed as the fuel for combustion, the only product of the combustion of hydrogen being water, when cooled.

[0187] In some embodiments in which the internal heating elements comprise or consist of electrical heating elements, some or all of the internal heating elements are designed as hollow or tubular structures. For example, a further variation of the reactor 300f is shown in Fig. 8 in which all of the internal heating elements are designed as tubular structures. The reactor 300f is similar to the reactor 300c described above with reference to Fig. 5. However, in the reactor 300f, the internal heating elements 334 are in the form of annular heating elements comprising a wall 340 surrounding a hollow central chamber 341. The walls 340 of the annular heating elements are configured to be electrically heated (e.g., inductively or resistively). Heat from the wall 340 is radiated both outwardly into the interior space 320 of the reactor body and inwardly into the hollow central chamber 341 of the annular heating elements 334. The thermal energy radiated into the hollow central chamber 341 can be advantageously used to preheat a gas, e.g., a gas that is to be inputted into the reactor 300f. To preheat the gas, the gas is passed through the hollow central chamber 341. As the gas passes through the hollow central chamber 341, the gas is preheated, i.e., because heat from the walls 340 of the annular heating elements is radiated into the hollow central chamber 341. The preheated gas is then passed into the reactor body. The preheated gas can be further heated, e.g., if the temperature of the preheated gas is less than a required temperature.

[0188] Conversely, it is thought that the internal heating elements 334 can instead be configured to promote heat transfer from a hot product gas to the interior space 320 of the reactor body, when the powder and gas flow in a co-flow arrangement within the reactor body. In such embodiments, the heating elements again comprise annular heating elements 334 with a wall 340 and a hollow central chamber 341. As above, the walls 340 can be further configured to be electrically heated. As the powder and the hot product gas (which both flow downwardly through the reactor body) reach a bottom of the reactor body, the hot product gas is directed upwardly through the hollow central chamber 341 of the annular heating elements 334. As the hot product gas rises through the hollow central chamber 341, heat is transferred from the hot product gas via the walls 340 to the interior space 320 of the reactor body. If additional heating is required, some or all of the internal heating elements 334 can additionally or alternatively be electrically heated. For example, the hot product gas can be directed to flow through a subset of the internal heating elements, whilst the remaining internal heating elements provide electrical heating.

[0189] Another advantage of designing the heating elements as hollow or tubular structures, as in the reactor 300f of Fig. 8, is that this geometry can allow for the injection of gas, powder, or both through the hollow central chamber 341. Accordingly, the reactor 300f can enable pre-heating of gases, prior to their entry into the interior space 320 of the reactor body. Furthermore, powders, such as entrained material recovered from the gaspowder separator and / or ultra-fines with a particle size distribution prone to elutriation, may also be injected through the hollow central chamber 341. This approach can facilitate the processing of ultra-fine, elutriation-prone particles within a co-flow arrangement, with or without accompanying gas injection. The injected materials are then combined with bulk powders in the lower section of the interior space 320, maximising product yield and reducing losses due to entrainment.

[0190] The inventors note that, in some processes in which the reactor 300 is employed, there may initially not be a reliable source of renewable electricity nearby. As a result, the reactor 300d (which relies on combustive heating) may be employed. However, it may be that as infrastructure and technology progress, eventually a reliable source of renewable electricity becomes available. Advantageously, the reactor 300d (which relies on combustive heating) can be converted to the reactor 300c (which relies on electricity). For example, by replacing the external combustion chamber 332 with electric heating elements (e.g., to the internal reactor wall 324 or altogether replacing the internal reactor wall 324 with the electric heating elements), and by replacing each of the combustive internal heating elements with electrical internal heating elements. It is noted that replacement of these parts can either be performed at once or in stages. For example, Fig. 7 shows a hybrid reactor 300e in which the external combustion chamber 332 has been replaced with an internal reactor wall 324 comprising, or which is comprised of electric heating elements, but in which the internal heating elements 334 are still in the form of combustion chambers. In this way, the hybrid reactor 300e relies on both electrical heating (for the external heating) and combustive heating (for the internal heating elements). It is noted that, as an alternative, the (combustive) internal heating elements may instead first be replaced with electrical heating elements, such that the reactor is externally heated by combustion and internally heated by electricity. Of course, it will also be appreciated that hybrid reactors, such as reactor 300e, may be employed in the first instance. For example, when it is desirable to use a combination of both combustion and electricity as an energy source for the reactor 300e. In yet a further embodiment, the reactor can be configured with internal heating elements which can be both electrically heated and heated via combustion. In such embodiments, the internal heating elements can comprise annular heating elements. The internal heating elements are configured to be electrically heated (e.g., resistively or inductively). The internal heating elements are further configured to be in the form of combustion chambers or to comprise an annulus in which a suitable gas (e.g., natural gas, syngas or hydrogen) is combusted. Heat from the combustion reaction heats (or further heats) the walls of the internal heating elements.

[0191] In still a further embodiment, the reactor can comprise hollow tubular elements in addition to the internal heating elements. That is, in such embodiments, the hollow tubular elements may not themselves be specifically configured to provide thermal energy to the reactor body. The hollow tubular elements are configured to allow powders, such as entrained material recovered from the gas-powder separator and / or ultra-fines with a particle size distribution prone to elutriation, to be injected therethrough. As the powder passes through the hollow tubular elements, heat from the reactor body is passed to the powder, causing the powder to be heated and further reaction of the powder to occur. In this regard, the powder can be injected into the hollow tubular elements along with a gas, such as a reducing gas, when it is desirable to do so. Again, this approach can facilitate the processing of ultra-fine, elutriation-prone particles within a co-flow arrangement, with or without accompanying gas injection. The injected materials are then combined with bulk powders in the lower section of the interior space, maximising product yield and reducing losses due to entrainment.

[0192] Examples of Applications

[0193] The applications of the indirectly heated reactors shown in Figures 1-8 for calcination processes are very broad, and have been categorised above, as belonging to classes A, B, C depending on the process flows required within the reactor, as well as the pre-and postprocessing of the powders required to facilitate the applications where necessary. Some specific, but non-limiting embodiments have been introduced and are now described.

[0194] Class A Calcination - Heating-Induced Phase Chage

[0195] As above, the class A calcinations involve a physical phase change, with no gaseous product. Typically, no gas is required during the calcination. It is noted that, for class A applications, gas input ports can be eliminated from the reactor altogether. Alternatively, the gas input ports can still be included, but not used during typical operation. The gas input ports can be used for, e g., flushing and / or cleaning the reactor with an inert gas.

[0196] An example of this class of calcination reactions is the transformation of a-spodumene to P-spodumene for lithium extraction. Advantageously, by using renewable power to heat the reactor, there are no substantial CO2 emissions arising from the calcination process. Of further advantage is that, by employing indirectly heated reactors of the type described above with reference to Figs. 1 to 7, the process may be more easily scaled up for industrial application.

[0197] In a spodumene calcination process, in which the reactors of Figs. 1 to 8 are employed, the a-spodumene is ground to form a powder in which the average particle size is less than about 250 pm. The powder is then injected into the reactors described above with reference to Figs. 1 to 8. Typically, the powder is injected toward an upper end of the in- use reactor. The reactor is heated to about 900°C, so as to cause the phase change from the refractory a-spodumene to the porous and highly reactive P-spodumene, from which the lithium may be subsequently extracted. In this application, at least in some embodiments, there is no need for gas injection (i.e., because no gas is required to facilitate, promote, achieve, etc. the calcination reaction), and the hot product (in the form of a powder comprising the calcined spodumene) is exhausted from base of the reactor. However, in other embodiments, gases can be introduced into the reactor to moderate the atmosphere, e.g., to be oxidising, inert or reducing, so as to promote or limit certain side reactions. Such gases do not participate in the main calcination reaction but act to promote or limit the certain side reactions. For example, the atmosphere can be moderated so as to limit side reactions such as clinkering reactions (i.e., the formation and melting of eutectics that form between the impurities / gangue). For instance, when calcining a- spodumene, it can be advantageous to maintain a reducing atmosphere within the reactor so as to suppress clinkering reactions. This can also allow the reactor to be operated at higher temperatures, whilst reducing and / or eliminating unwanted sticking / melting / glassing, i.e., that can occur as a result of clinkering reactions.

[0198] As another example, when a-alumina is being calcined, it can be advantageous to introduce a gas comprising or consisting of super-heated steam into the reactor to promote a-alumina formation and sintering. In some embodiments, it can be desirable to introduce a small amount of hydrogen and oxygen into the reactor atmosphere. This can promote higher localised temperatures through direct combustion heating, without comprising the purity / composition of the exhaust gases at the outlet of the process.

[0199] As yet a further example, during the processing of kaolin clays to meta-koalin as a Portland cement substitute, a reducing gas can be introduced into the reactor. The reducing gas can prevent undesirable colour changes in high iron bearing clays. The reducing gas acts to supress oxidation of the iron to hematite, thereby preventing the formation of undesirable red / pink cement products.

[0200] Typically, there will be some impurities present in the powder that is to be calcined. These impurities may result in the liberation of moisture, CO2, SOx and the like during calcination. These gases are exhausted at the top of the reactor (i.e., via the gas exhaust). The heat in the hot product powder may be recovered by conventional means and used to preheat the feed powder.

[0201] Class B Calcination - Powder Production by Chemical Change from Heating a Precursor Process in an Indirectly Heated Reactor

[0202] As above, the class B calcinations involve a chemical change of the powder, with the release of one or more gaseous products. Aside from the several applications which are explicitly disclosed, the skilled person would understand that there are numerous examples of class B calcinations which can each employ a reactor of the type described above with reference to Figs. 1 to 8. As above, by employing a reactor of the type described above with reference to Figures 1 to 8, each of these processes can be more efficiently performed on an industrial scale.

[0203] One example of a class B calcination (in which any of the reactors described above with reference to Figs. 1 to 8 may be employed) is the dehydration of a metal oxide. For example, the heating of aluminium hydroxide to remove water as steam. One use for aluminium hydroxide thereby produced is for the production of aluminium metal, e.g., from particles of aluminium hydroxide produced by dissolution of bauxite in NaOH. Said particles can themselves be processed at a temperature of about 600°C in a reactor (e.g., calciner) described above with reference to Figs. 1 to 8 to produce porous amorphous alumina. The calciner may employ electric heating using renewable power to reduce the Scope 3 CO2 emissions intensity.

[0204] It is noted that the steam released (typically at about 1 bar) from the initial calcination of aluminium hydroxide can contain impurities. The steam may be recovered and used to boil water to high pressure steam that is used in the bauxite digestion process, such that the aluminium has a sufficiently low energy intensity for industrial use. Energy can also be recovered from the hot alumina process to make steam or for preheating the aluminium hydroxide. In addition, at a higher calcination temperature of about 1300°C, alumina is transformed to dense a-alumina which can be used as an insulator in semiconductor chips and for gemstones.

[0205] As another example of a dehydration reaction, the reactors of Figs. 1 to 8 can be employed in a process in which kaolinite clay is dehydrated to manufacture meta-kaolin for manufacture of Portland Cement.

[0206] A second example of a class B calcination is the heating of carbonate powders, generally minerals, to remove CO2 to make oxides. The carbonate powders can comprise, for example, limestone, dolomite, magnesium carbonate, or any other suitable carbonate powder. As another example, the carbonate powder can comprise cement raw meal. Such processes can employ the reactors of Figs. 1 to 8. Advantageously, by employing the reactors of Figs. 1 to 8 and, more specifically, by employing indirect heating, a pure (or nearly pure) process CO2 stream is produced during calcination. This is because, unlike direct heating methods, the CO2 stream is not mixed with combustion products. This CO2 stream can be used to directly make liquid or high-pressure CO2 for CCSU applications at minimal cost compared to, e.g., conventional end-of-pipe CO2 capture processes from combustion flue gas.

[0207] It is noted that the products of calcination (e g., lime, dolime and magnesia) and calcined cement meal are used in many industrial processes, but that the generation of process CO2 is yet to be avoided. Advantageously, however, by generating a pure CO2 stream, the CO2 can be captured and used. For instance, more recently, Direct Air Capture is being developed using calcium oxide (CaO) as a CO2 sorbent, with the CaCCh produced due the sorbing of CO2 by CaO to be reprocessed in a loop, i.e., to re-make CaO. The CO2 thereby produced can be used for CCSU applications. Employing the reactor(s) described above with reference to Figs. 1 to 8 in these processes can enable the scale up of said processes to meet the demand for these products. As an example of how the CO2 can be advantageously used, it is noted that the high grade CO2 produced from the one or more of the processes described in the application can be used to make low emission methanol for shipping and synthetic aviation fuel.

[0208] In the case of shipping, the lime made from the process described above may be used to capture CO2 released from combustion of low emissions methanol and diesel fuels using the known art of CO2 capture using lime, and especially hydrated lime where the energy of hydration and carbonation may be used to provide motive power to a ship. In this regard, the lime may be used in a cyclic process of on-board capture of CO2 from combustion of low emissions methanol using low emissions lime, also made using this process, to capture the CO2, using the energy released to generate motive power for the ship and recycling the calcium carbonate on-shore to produce methanol and lime.

[0209] For the application for the manufacture of cement referred to above, the calcined cement meal outputted from the reactor may be briquetted and heated to about I450°C in a moving bed process using low to zero emission combustion processes of electrical heating to heat the hot briquettes to the clinkering temperature.

[0210] A specific application of calcination of carbonates is related to the production of nanoactive bioactives. This is directed towards improvement of nano-active bioactive salts of MgO and Cu(I) compounds, such a cuprous oxide (CU2O). The prior art of both MgO and Cu(I) salts is their proven bioactivity, particularly in marine anti -fouling paints. Cu(I) is very effective in this role because Cu(I) is chemically bioactive, but its relatively high solubility in water is such that its over-use is detrimental to the marine environment. MgO produced by the flash calcination process described above (e.g., by employing a reactor as described in any one of Figs. 1 to 8 in a process by which magnesite is converted to magnesium oxide) is a nano-active bioactive material with low solubility in water. The bioactivity of MgO is attributed to generation of Reactive Oxygen Species (ROS) from defects in the MgO formed during calcination of magnesite. The reactor processes described in this disclosure may be used to produce this material for industrial purposes. That is, the reactors described may be used to calcine the magnesite so as to produce MgO. The fusion and agglomeration processes disclosed herein in further detail below enable the production of compound salts of the type (MgO)x(Cu(I) salt)i-xwhere the Cu(I) salt may be C O, i.e., by fusing and agglomerating the MgO produced by calcination with Cu(I) salts. It has been found that the bioactivity of this material can be controlled by the processes described above by controlling the percentage of Cu(I) in the salts, as well as by the binding of the salts with MgO during a co-calcination process in which double salts are produced, i.e., where there is a chemical binding between the constituents. Such a binding produces new materials and, for example, a compound material which has a lower solubility of Cu(I) and a higher solubility of MgO. This improves the bio-active efficiency and minimises Cu(I) release to the marine environment. Other compound salts (such as those of Fe(II)) may also be nano-active bioactive materials produced using the disclosures herein. In such embodiments, the Cu(I) salt (or other salt) may be mixed with the magnesite prior to calcination to form a combined powder. The combined powder is then fed into the reactor and the reactor is operated so as to cause the mixed salt to form. Alternatively, as above, the Cu(I) salt (or other salt) may be mixed with the MgO following calcination and before a fusion / agglomeration stage.

[0211] Another specific application of calcination of carbonates is related to the production of low emissions magnesium metal. The electrolytic process of making Mg metal from MgCh electrolysis is expensive. An alternative is to make MgO from magnesite or dolomite by calcination. Processes which employ direct heating powders of pellets or heating in a combustion reactor result in very high emissions intensity. The MgO is then reduced with carbon, silicon or aluminium (any CaO is not reduced and may be slagged).

[0212] The predominant use of Mg metal is the manufacture of high strength, lightweight, non- corrosive magnesium-aluminium oxide alloys, preferably with the Mg content being above 90% so that the weight reduction is considerable. Such alloys are used in aerospace applications and may be used in electric vehicles. However, the emissions intensity of the alloy is so large that the Scope 2 emissions savings from lowering the weight is not sufficient to overcome the Scope 3 emissions over the lifetime of a vehicle.

[0213] There is a need to reduce the Scope 3 emissions of Mg metal production. The carbothermic reduction of MgO to Mg metal is not used because the back reaction of Mg with CO and CO2 is very fast. As a result, Mg metal is predominantly made using silico- thermal reduction of dolime MgO. CaO with ferrosilicon where the slag is an iron calcium silicate that may be used in cement. The process has very high emissions intensity from combustion, from the production of ferrosilicon, and from the process emissions in the manufacture of dolime from dolomite. As an alternative, by employing the reactors of the present disclosure, the emissions intensity of Mg metal production can be significantly reduced. In particular, use of the reactors of the present disclosure can result in a lower (or, potentially, zero) emissions route to making magnesium metal. By instead employing the indirectly heated reactors disclosed herein, any CO2 produced during calcination of carbonates (to produce MgO) can be easily collected.

[0214] Another reduction process involves the aluminothermic reduction of a mixture of magnesite and dolomite using scrap aluminium. The reactors disclosed herein may be employed in a lower (or, potentially, zero) emissions route to making aluminium (i.e., through the dehydration of aluminium hydroxide to alumina, which can then be processed to aluminium). Alternatively, the aluminium can be otherwise produced. The aluminium can be combined with a mixture of MgO and MgO.CaO (dolime), which is produced using the low- (or zero-) emissions calcination process using the reactors described in this disclosure. For example, by calcining magnesite and / or dolomite. An optional hot briquetting process can be used to mix the MgO, MgO.CaO and Al powders for fast Mg metal production, thereby providing a means for making low- (or zero-) emissions Mg metal. Furthermore, the slag from the aluminium reduction process is an aluminium oxide-calcium oxide material from which the aluminium may be recycled to make aluminium oxide. The net process is the zero (or near zero) emissions reduction of magnesium by aluminium.

[0215] Class C Calcination - Chemical Changes in a Powder from a reaction of Injected Gases with Precursor Powders in an Indirectly Heated Reactor

[0216] As above, in class C calcinations, an injected gas reacts with the powder, or the calcined powder, or the gas released from a calcination process to form either new powder or gas products or both. Aside from the several applications which are explicitly disclosed, the skilled person would understand that there are numerous examples of class C calcinations which can each employ a reactor of the type described above with reference to Figs. 1 to 8. As above, by employing a reactor of the type described above with reference to Figures 1 to 8, each of these processes can be more efficiently performed on an industrial scale. It is noted that many class C calcinations are related to the calcination processes induced by calcination where a gas is introduced to participate in the processes.

[0217] One example of a class C calcination is the reaction of an oxide (such as an oxide produced by a class B calcination in which a carbonate is converted to an oxide, thereby producing CO2) with water. In such an application, water (typically in the form of steam) is injected into the reactor. The reactor conditions are controlled such that the hot oxide reacts with steam to form a hydrated material. It is recognised that this steam reaction is exothermic and reverses if the reactor temperature is too high, so that the temperature profile of the reactor is controlled and set to deliver the desired powder product at a desirable low temperature. Where reactions are exothermic, as is the case for CaO hydration, heat must be removed from the process to enable the temperature to be maintained at the target process temperature. In the case of the vertical reactor concept shown in Figure 1, the external annulus of the reactor 127 is exploited to pre-heat water / low T steam for the hydration reaction thereby removing heat from the hydration reaction taking place in the central reactor tube 102 enabling control of the temperature of the exothermic hydration stage and prevent overheating.

[0218] In one application of the process, where Ca(OH)2 is produced, the material is sufficiently porous and can be used for DAC. In a DAC cyclic process, the input material may be a mixture of CaCCh, as well as any remaining Ca(OH)2. The reactor is operated so as to regenerate CaO. The water (i.e., as steam) is exhausted from the reactor along with CO2. The water may be recovered during compression of the CO2 for CCUS. The water can be reintroduced in the lime hydration step considered above to create a DAC cycle.

[0219] In one application, it is envisaged that a two-stage process may be employed for the production of Ca(OH)2, Mg(0H)2, or mixtures thereof, which comprises a first calcination stage and a second hydration stage. In the first stage, a calcination process is employed in which calcium carbonate and / or magnesium carbonate and / or dolomite are calcined, thereby producing calcium oxide, magnesium oxide or a mixture. The released CO2 can be captured for storage. In the second (hydration) stage, the resultant calcium oxide, magnesium oxide or mixture thereof is hydrated. It is noted that the hydration stage is exothermic. As a result, heat removal (i.e., rather than the provision of heat) is required. In such applications, it is thought that the external annulus of the reactor (or the internal tubular elements which, in other applications are used to provide heating) can instead be employed to provide cooling to the second reactor stage. For example, water and / or low temperature steam may be pumped, or otherwise caused to flow, through the external annulus and / or tubular elements such that heat energy is transferred to the water and / or low temperature steam, thereby providing the requisite cooling within the reactor body and preheating the water and / or low temperature steam. The preheated water and / or low temperature steam is then injected into the reactor (i.e., to provide the water required for the hydration reaction). In this way, the temperature of the exothermic hydration stage can be controlled and overheating of the reactor prevented.

[0220] Another example of a class C calcination is the activation of the nano-active bioactive powers, such as those described above, but in which hydrogen is injected into the reactor. This can further induce defect formation of ROS as described above, whilst also reducing copper salts from Cu(II) to Cu(I) and iron salts from Fe(III) to Fe(II), if such cations are present. In this way, bioactive materials can be made from magnesite using calcination and hydrogen reduction and activation. A further example of a class C reaction is the reduction production of syngas, with the option of making carbon char from gasification of a carbon material, such as biomass or waste, using an indirectly heated reactor as described herein. A gas comprising oxygen, such as air, is injected into the reactor at a controlled rate so as to make the desired products above (i.e., syngas, char). The process may further include the use of zero (or low) emissions lime, as described above, as a sorbent for CO2 or CO, using the process of sorbent enhanced gasification which produces CaCOs. At the same time, a gas primarily comprising hydrogen may be produced. The resultant CaCOs may be reprocessed to recover the lime and to make CO2 for CCUS, again as described above. Ash may be recovered and used for cement production. The hydrogen or syngas may be used in the iron ore reduction described below or used for combustion heaters as described herein.

[0221] Yet a further example of a class C reaction is the reduction of iron ores for iron and steel production using hydrogen or other reducing gas such as methane / natural gas, CO, syngas, methanol or ammonia injection into an indirectly heated reactor. One application is the partial reduction of low-grade iron ore powder by a hydrogen-steam mix to make magnetite. The magnetite may be beneficiated by removal of gangue using magnetic separation. A resultant higher-grade magnetite can be subjected to a further reduction process in which the magnetite is reduced to iron using hydrogen as a reducing gas. Briquetting can then be employed to make sponge iron for shipping, or injection into a furnace to make steel, with other additives added as required, including zero emissions carbon (as described above) for carbon steel, or zero emissions lime for slagging (as described above). It is noted that no hydrogen is used for heating the reactors.

[0222] A further example of a Class C reaction is the oxidation of magnetite which can be used to convert magnetite either partially or fully to hematite for subsequent processing. An example is the oxidation of magnetite (FciCf) in an atmosphere comprising air or oxygencontaining gases, which facilitate the partial or complete conversion of magnetite to hematite (Fe2O3) as a preparatory step for reduction in iron and steel production. Magnetite particles are typically dense and exhibit low reactivity towards hydrogen and other reductants due to limited surface area and diffusion pathways. Oxidising magnetite to hematite induces a volumetric expansion and microstructural cracking, which increases porosity and exposes additional reactive surfaces. This structural transformation significantly enhances the material’s reducibility in the subsequent reduction stage. The reduction of manganese ores provides another example of a class C reaction.

[0223] Yet a further example of a Class C reaction is the calcination of black mass, a waste product from battery recycling. This process is typically carried out under inert or reducing atmospheres to achieve one or more of the following objectives: (i) thermal decomposition, pyrolysis, or gasification of organic components (e g. binders and electrolyte solvents) to aid in the separation of critical minerals such as Li, Co, Ni, Mn, Fe, V, P, Cr, Nb, Ti as well as graphite, for recovery via downstream hydrometallurgical processes; (ii) volatilisation and safe capture of fluorine species released from PVDF binders and electrolytes; and (iii) control of the oxidation state of metallic components (typically Ni, Co, Mn, Fe, V, P, Cr, Nb Ti and their mixtures) by injecting reducing or inert gases, thereby facilitating separation through subsequent hydro- and pyro- metallurgical processing routes.

[0224] Typical Auxiliary Equipment

[0225] It will be appreciated that, in many of the processes contemplated herein, the reactors described in Figs. 1 to 8 form part of a larger system. The system typically comprises additional equipment, such as auxiliary equipment, which are used for pre- and postprocessing of the powders and / or reacted powders. By way of example only, two such pieces of auxiliary equipment typically comprise particle fusion and granulation (as a preprocessing stage) and hot briquetting (as a post-processing stage). These are briefly described below. Other pieces of auxiliary equipment will be known to those skilled in the relevant art.

[0226] Particle Fusion and Granulation of the Powder Feed Pre-Calcination

[0227] It is noted that in any gas-particle reactor, such as those contemplated herein, a long tail of small ultra-fines may occur from grinding processes, which may be elutriated from the reactor with an exhaust gas. The entrained particles can require separation from the gas, resulting in the need for a required gas-particle separation stage. To compensate, a specific grinding process, such as a cylindrical grinder, which is a known art, can be used to fuse the tail of small ultra-fine particles by grinding pressure prior to injection of the powder to be reacted into the reactor. This can increase the mean particle size which, in turn, can decrease the extent to which particles are elutriated from the reactor with the exhaust gas. Any elutriated particles can be captured, e.g., in cyclone separators, and be reinjected into the reactor. The minimising of elutriation of particles can reduce the complexity of the process (e.g., by reducing the load on the gas-particle separation stage) and enhance energy efficiency.

[0228] Alternatively or additionally, for example when the feed powder comprises very small particles, the powder can be fused or granulated prior to the reactor. In particular, the powder can be fused to produce a powder in which the mean particle size is about 250 pm or less.

[0229] It is noted that when a process gas is not required and when no gas is generated by the calcination (e.g., in the case of class A calcinations), elutriation may not pose a significant issue. Hot Particle Briquetting of the Powder Product Post Calcination

[0230] Many of the calcination process for which indirect heating can be applied result in hot powder products that can be compacted for subsequent processes. For example, hot iron from calcination reduction of iron ore by indirect heating may be hot briquetted, cooled and exposed to air. The briquetting process compresses the iron to such an extent that the run-away oxidation and heating of the iron by oxidation in air is suppressed. Another example is the compression of porous lime by hot briquetting which also supresses the reaction with moisture or CO2 in air to enable the lime it to be used as a reactant when required, e.g. by shattering or grinding. Iron and lime are examples of sticky materials that are difficult to transport and store, and briquetting machines are capable of producing large briquettes of about 10 cm size, to granules of mm size. As another example, calcined cement meal may be hot briquetted and heated, e.g., in a moving bed within which a combustion gas is combusted, to quickly form clinker (calcium disilicate and trisilicate) because the compression accelerates the formation of alite and belite from silica and lime particles. Other porous calcined materials formed by indirect heating which are not sufficiently sticky to form stable briquettes / granules may be compressed with the aid of additives, such as potassium carbonate, that flow under pressure to help bind the particles to give a desired strength for the compressed material.

[0231] Variations and modifications may be made to the parts previously described without departing from the spirit or ambit of the disclosure. For example, although each of the illustrated embodiments of the reactors described above include one or more gas input ports, it is noted that the gas input ports can be eliminated in applications where injection of a gas is not required. As another example, exhaust gas may not always be generated during a reaction.

[0232] In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the process, system and reactor as disclosed herein.

Claims

CLAIMS1. An indirectly heated reactor comprising: a reactor tube that in use is configured to be vertically oriented; an outer shell surrounding the reactor tube, the outer shell comprising heating elements that are configured to heat an interior of the outer shell; one or more gas input ports located towards an in-use upper end of the outer shell; a powder input located adjacent to an in-use top end of the reactor tube and configured to feed a powder such that the powder falls downwards in the reactor tube in use; and a reacted powder output positioned at an in-use base of the reactor tube; wherein the outer shell is fluidly connected to the reactor tube by one or more gas feed ports that are arranged towards an in-use lower region of the reactor tube such that, in-use of the reactor, the gas injected in the outer shell is able to be heated by the heating elements to cause the gas to flow from the outer shell and into the reactor tube.

2. A reactor as claimed in claim 1, wherein the heating elements comprise external heating elements that are configured to indirectly heat the interior of the outer shell and the gas.

3. A reactor as claimed in claim 1 or 2, wherein the external indirect heating elements comprise resistive heating elements.

4. A reactor as claimed in claim 3, wherein the resistive heating elements are powered by electricity.

5. A reactor as claimed in any one of claims 1 to 4, wherein the reactor is configured to be operated such that, in-use, a pressure in the reactor tube is less than a pressure within the outer shell which causes the gas to flow from the outer shell and into the reactor tube.

6. A reactor as claimed in any one of claims 1 to 5, wherein an inner wall of the outer shell is insulated.

7. A reactor as claimed in claim 6, wherein the heating elements are arranged at the insulated inner wall of the outer shell.

8. A reactor as claimed in any one of claims 1 to 7, wherein the reactor further comprises a gas exhaust located towards an in-use upper end of the reactor tube.

9. Use of an externally heated reactor as claimed in any one of claims 1 to 8.

10. A reactor that in use is configured to be vertically oriented, the reactor comprising: an elongate reactor body comprising one or more material feed inlets located toward an in-use upper end of the reactor body, the material feed inlets configured to feed a powder to be reacted such that said powder falls downwards in the reactor body; gas input ports arranged toward an in-use lower end of the reactor body for feeding a gas into the reactor body; a powder outlet positioned toward the lower end of the reactor body; and heating elements positioned in an interior space of the reactor body and configured to transfer heat into the interior space of the reactor body, so as to heat the gas and the falling powder and cause the powder to react.

11. A reactor as claimed in claim 10, wherein the heating elements are configured to transfer radiative heat into the interior space of the reactor body.

12. A reactor as claimed in claim 10 or 11, wherein the heating elements comprise one or more metallic alloy sheets which are configured to be electrified so as to transfer heat into the interior space of the reactor body.

13. A reactor as claimed in claim 12, wherein the one or more metallic alloy sheets are arranged to extend downwards in use from an upper end of the reactor body.

14. A reactor as claimed in claim 12 or 13, wherein the material feed inlets are arranged to feed the powder such that the powder falls downwards in the reactor body between adjacent spaced sheets of the or more metallic alloy sheets.

15. A reactor as claimed in claim 14, the reactor comprising multiple banks of metallic alloy sheets, each bank comprising two or more sheets, and wherein each material feed inlet is arranged to feed the powder such that the powder falls downwards in the reactor body between adjacent spaced banks of metallic alloy sheets.

16. A reactor as claimed in any one of claims 10 to 15, the reactor further comprising one or more high temperature radiative tubes configured to radiate energy into the interior space of the reactor body.

17. A reactor as claimed in claim 16 wherein the one or more high temperature radiative tubes are arranged to extend within the interior space of the reactor body at a position toward the lower end of the reactor body.

18. A reactor as claimed in any one of claims 10 to 17, further comprising a gas exhaust positioned adjacent to the upper end of the reactor body.

19. A reactor as claimed in any one of claims 10 to 18, wherein the gas input ports are arranged to feed the gas into the reactor body such that the rate of the powder falling downwards in the reactor body is able to be controlled.

20. A reactor as claimed in any one of claims 10 to 19, wherein, when vertically oriented, the reactor body is elongate both vertically and horizontally.

21. A reactor as claimed in any one of claims 10 to 20, the reactor further comprising one or more external indirect heating elements that are configured to indirectly heat the interior space of the reactor body.

22. A reactor that in use is configured to be vertically oriented, the reactor comprising: an elongate reactor body comprising one or more material feed inlets located toward an in-use upper end of the reactor body, the material feed inlets configured to feed a powder to be reacted such that said powder falls downwards in the reactor body; gas input ports arranged toward an in-use lower end of the reactor body for feeding a gas into the reactor body; one or more powder outlets positioned toward the lower end of the reactor body; one or more external heating elements arranged around an outside of the reactor body and configured to heat an interior of the reactor body.

23. A reactor as claimed in claim 22, further comprising an outer shell surrounding the reactor body, the outer shell comprising the one or more external heating elements that are configured to heat the interior of the reactor body.

24. A reactor as claimed in claim 23, wherein the outer shell is fluidly connected to the reactor body by the gas input ports such that, in-use of the reactor, gas in the outer shell is able to be heated by the one or more external heating elements to cause the gas to flow from the outer shell and into the reactor body.

25. A reactor as claimed in any one of claims 22 to 24, wherein the one or more external heating elements are configured to transfer radiative heat into the interior of the reactor body.

26. A reactor as claimed in claim 25, wherein the one or more external heating elements are configured to be electrified so as to transfer heat into the reactor body.

27. A reactor as claimed in claim 25, wherein the one or more external heating elements are configured to transfer heat produced by a combustion reaction into the reactor body.

28. A reactor as claimed in any one of claims 22 to 27, further comprising internal heating elements positioned in the interior of the reactor body and configured to transfer heat directly into the interior of the reactor body.

29. A reactor as claimed in claim 28, wherein the internal heating elements comprise tubes which are arranged to extend within the interior of the reactor body and extend toward the lower end of the reactor body.

30. A reactor as claimed in claim 28 or 29, wherein the internal heating elements are configured to transfer radiative heat directly into the interior of the reactor body.

31. A reactor as claimed in claim 30, wherein the internal heating elements are configured to be electrified so as to transfer heat directly into the interior of the reactor body.

32. A reactor as claimed in claim 30, wherein the internal heating elements are configured to transfer heat produced by a combustion reaction directly into the interior of reactor body.

33. A reactor as claimed in claim 32, wherein the tubular internal heating elements comprise a hollow internal chamber and are fluidly connected to the gas input ports at a lower end thereof such that, in-use, gas injected into the hollow internal chamber is able to be heated by the heating elements, with a resultant preheated gas fed into the reactor body.

34. A reactor as claimed in any one of claims 22 to 33, further comprising a gas exhaust positioned adjacent to the upper end of the reactor body.

35. A reactor as claimed in claim 34 when dependent on claim 29, wherein the tubular internal heating elements comprise a hollow internal chamber and are fluidly connected to the reactor body at a lower end thereof and to the gas exhaust at an upper end thereof, wherein, when the reactor is operated in a co-flow regime, exhaust gas from the reactor body is able to pass upwardly through the hollow internal chambers to the gas exhaust.

36. A reactor as claimed in any one of claims 22 to 35, wherein, when vertically oriented, the reactor body is elongate both vertically and horizontally.

37. A reactor as claimed in any one of claims 22 to 35, wherein the gas input ports are arranged to feed the gas into the reactor body such that the rate of the powder falling downwards in the reactor body is able to be controlled.

38. A system for reacting a powder, the system comprising: a reactor as claimed in any one of claims 1 to 37; and a fusion grinder configured to agglomerate a powder to be fed into the reactor.

39. A system as claimed in claim 38, wherein the fusion grinder is configured to agglomerate the powder such that the powder has a mean particle size of about 250 pm.

40. A system as claimed in claim 38 or 39, further comprising a hot briquetting plant to which reacted powder from the reactor is passed and in which the reacted powder is hot briquetted.

41. A system as claimed in claim 40, wherein the hot briquetting plant is configured to produce briquettes with a mean particle size of about 1,000 pm to about 3,000 pm.

42. A process for inducing a phase change in a powder, the process comprising: feeding the powder to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor as claimed in any one of claims 1 to 37; and heating the interior of the reactor body so as to cause the phase change.

43. A process as claimed in claim 42, wherein the powder fed to the reactor comprises a-spodumene and the phase change caused is from a-spodumene to P-spodumene.

44. A process for calcining aluminium hydroxide, the process comprising: feeding a powder comprising aluminium hydroxide to a vertically heated reactor, wherein the heated reactor comprises the reactor as claimed in any one of claims 1 to 37; and heating the interior of the reactor body so as to cause the aluminium hydroxide to be calcined, thereby producing alumina and steam.

45. A process as claimed in claim 44, wherein the produced alumina comprises a feed to a process for producing aluminium metal.

46. A process as claimed in claim 44 or 45, wherein the steam comprises a low-grade steam and is used to produce high-grade steam.

47. A process for producing metal oxide from metal carbonate, the process comprising: feeding a powder comprising the metal carbonate to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor as claimed in any one of claims 1 to 37; and heating the interior of the reactor body so as to cause the metal carbonate to be decomposed, thereby producing the metal oxide and carbon dioxide.

48. A process as claimed in claim 47, wherein the metal carbonate comprises limestone, dolomite, magnesite and / or cement raw meal.

49. A process as claimed in claim 47or 48, wherein the carbon dioxide is captured.

50. A process as claimed in claim 49, wherein the captured carbon dioxide is reacted with hydrogen under conditions by which methanol and synthetic aviation fuel are produced.

51. A process as claimed in any one of clams 48 to 50, wherein the metal carbonate powder comprises magnesium, and wherein gas fed into the reactor body comprises hydrogen.

52. A process as claimed in any one of clams 48 to 50, wherein the metal carbonate powder comprises magnesium and, prior to being fed into the reactor, the metal carbonate powder is mixed with a copper salt and / or an iron salt, with the resultant mixture comprising the metal carbonate powder, copper salt and / or iron salt being fed into the reactor.

53. A process for gasification of carbon-based powders, the process comprising: feeding the carbon-based powder to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor as claimed in any one of claims 1 to 37; and heating the interior of the reactor body so as to cause gasification of the carbonbased powder.

54. A process as claimed in claim 53, wherein the carbon-based powder comprises biomass, organic waste, and / or recycled char.

55. A process as claimed in claim 53 or 54, wherein gas is fed into the reactor body and comprises oxygen.

56. A process as claimed in any one of claim 55, wherein a gas exhaust from the reactor comprises syngas and the reacted powder comprises a mixture of powdered char and ash.

57. A process as claimed in claim 56, the process further comprising feeding a powder comprising calcium oxide to the reactor such that the gasification of the carbon-based powder causes hydrogen and calcium carbonate to be produced.

58. A process as claimed in claim 56, wherein the powder comprising calcium oxide is produced by the process as claimed in claim 48.

59. A process as claimed in claim 56 or 57, wherein the calcium carbonate is collected and calcined by the process as claimed in claim 48, thereby reproducing calcium oxide.

60. A process for producing calcined cement meal, the process comprising: feeding a powder comprising cement raw meal to a vertically heated reactor, wherein the vertically heated reactor comprises the reactor as claimed in any one of claims 1 to 37; and operating the reactor so as to cause the cement raw meal to be reacted to form calcined cement meal.

61. The process of claim 60, the process further comprising fusing the calcined cement meal powder to form a fused powder with a mean particle size of about 250 pm.

62. The process of claim 61, the process further comprising subjecting the fused powder to a pyro-process configured to operate at a temperature of about 1450 °C so as to produce cement clinker.

63. A process for producing magnesium metal, the process comprising: producing a powder comprising magnesium oxide from a powder comprising dolomite and magnesite using the process as defined in any one of claim 47 to 50; briquetting the powder comprising magnesium oxide along with aluminium, thereby producing briquettes comprising magnesium oxide, calcium oxide, and aluminium; heating the briquettes to a temperature at which the magnesium oxide is converted to magnesium metal.

64. A process as claimed in claim 63, the process further comprising cooling and grinding the resultant mixture comprising magnesium metal.

65. A process as claimed in claim 64, the process further comprising heating the ground mixture so as to cause the magnesium metal to be vaporised.

66. A process as claimed in claim 65, the process further comprising condensing the magnesium metal vapour.

67. A process as claimed in claim 65 or 66, wherein a resultant solid comprising calcium and aluminium is collected, and the aluminium is recovered therefrom.

68. A reactor that in use is configured to be vertically oriented, the reactor comprising: an elongate reactor body comprising one or more material feed inlets located toward an in-use upper end of the reactor body, the material feed inlets configured to feed a powder to be reacted such that said powder falls downwards in the reactor body; a powder outlet positioned toward the lower end of the reactor body; and heating elements positioned in an interior space of the reactor body and configured to transfer heat into the interior space of the reactor body, so as to heat the falling powder and cause the powder to react.

69. A reactor as claimed in claim 68, further comprising one or more gas input ports arranged toward an in-use lower end of the reactor body for feeding a gas into the reactor body.

70. A reactor as claimed in claim 69, wherein the heating elements are configured to transfer heat into the interior space of the reactor body, so as to heat the gas and the falling powder and cause the gas and the powder to react therewith.

71. A reactor as claimed in any one of claims 68 to 70, the reactor being otherwise as defined in any one of claims 11 to 21.

72. A reactor that in use is configured to be vertically oriented, the reactor comprising: an elongate reactor body comprising one or more material feed inlets located toward an in-use upper end of the reactor body, the material feed inlets configured to feed a powder to be reacted such that said powder falls downwards in the reactor body; one or more powder outlets positioned toward the lower end of the reactor body; one or more external heating elements arranged around an outside of the reactor body and configured to heat an interior of the reactor body.

73. A reactor as claimed in claim 72, further comprising one or more gas input ports arranged toward an in-use lower end of the reactor body for feeding a gas into the reactor body.

74. A reactor as claimed in claim 72 or 73, the reactor being otherwise as defined in any one of claims 22 to 37.

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