WO2024250052A1

WO2024250052A1 - Electrochemical flow reactor

Info

Publication number: WO2024250052A1
Application number: PCT/AU2023/050499
Authority: WO
Inventors: Bartlomiej Piotr KOLODZIEJCZYK; Bjorn Winther-Jensen
Original assignee: Fortescue Future Industries Pty Ltd
Current assignee: Fortescue Future Industries Pty Ltd
Priority date: 2023-06-07
Filing date: 2023-06-07
Publication date: 2024-12-12
Anticipated expiration: 2025-12-07

Abstract

An electrochemical flow reactor for continuous production of an iron-bearing product from iron ore particles is disclosed. The electrochemical flow reactor includes an electrochemical cell comprising a cathodic compartment and an anodic compartment separated by a separator. The cathodic compartment contains a catholyte comprising a suspension of iron ore particles in a first alkaline solution, and a cathode at least partially immersed in the catholyte to facilitate reduction of the iron ore particles to the iron-bearing product. The cathodic compartment has an inlet for ingress of the catholyte and an outlet for egress of a spent catholyte containing the iron-bearing product, wherein the outlet is in fluid communication with the inlet via a first conduit in an arrangement whereby spent catholyte may be recirculated from the outlet of the cathodic compartment to the inlet thereof. The anodic compartment contains an anolyte comprising a second alkaline solution and an anode at least partially immersed therein. The anodic compartment has an inlet for ingress of the anolyte and an outlet for egress of a spent anolyte, wherein the outlet is in fluid communication with the inlet via a second conduit in an arrangement whereby spent anolyte may be recirculated from the outlet of the anodic compartment to the inlet thereof. The electrochemical flow reactor also includes a separation means associated with the first conduit to separate the iron- bearing product from the spent catholyte. The first and second conduits may be provided with respective means that enable replenishment of the depleted catholyte and spent anolyte prior to recirculation to the cathodic and anodic compartments.

Description

"Electrochemical flow reactor"

Technical Field

[1] The present disclosure relates to an electrochemical flow reactor, in particular an electrochemical flow reactor for continuous production of an iron-bearing product from iron ore particles.

Background

[2] The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.

[3] Metallic iron is conventionally produced via a carbothermal reduction route, i.e. CO2 intensive reduction of iron oxides, in a blast furnace at a temperatures up to of - 2000°C. This process produces a large amount of CO2 emission (i.e. 1 .5 metric tons of CO2 per metric ton of crude Fe produced, (IEA (2022) Achieving Net Zero Heavy Industry Sectors in G7 Members, IEA, Paris)). Gaseous reduction of iron oxide ore with hydrogen and natural gas is an environmental approach to produce metal iron with reduced carbon emission. However, the cost of hydrogen is relatively expensive for iron production.

[4] More recently, the ultra-low CO2 steelmaking (ULCOS) program was undertaken by the European Commission to develop electrochemical techniques to reduce greenhouse gases emissions in iron production. Although electrolytic production of aluminium is well- established, it is challenging to apply analogous process techniques to iron production because iron oxides have high melting temperatures. Molten oxide electrolysis (MOE) is the most studied electrometallurgical technique for the production of liquid iron from iron oxides, according to reaction (1 ).

4Fe³⁺ + 6O²' 4Fe(l) + 3O₂(g) (1 )

[5] Reaction (1 ) requires high temperature (i.e. -1538 °C) to maintain the metallic iron products in liquid phase. Haarberg and co-workers (G.M. Haarberg 2007) reduced iron oxide directly to iron in molten CaCl2-CaF2 at 827-890 °C, while Li and co-workers (Guoming Li 2009) reported direct electrochemical reduction in molten CaCL at 800-900 °C. Additionally, it is difficult to select an inert anode that is effective at high temperature and not subject to oxidation under these reaction conditions. [6] Low temperature processes for the electroreduction of iron oxide to metallic iron has also been reported. Generally, these processes involve electrowinning (i.e. electrodeposition) metallic iron on a stationary, rotating or colloidal cathode from an alkaline or acidic solution. The metallic iron may be recovered by removing the cathode from the electrolytic cell and scraping the metallic iron from the surface of the cathode. Thus, the recovery of the metallic iron requires either disassembly of the electrochemical cell or at least removal of the cathode to recover the iron that is deposited thereon. Such processes can only enable batch mode processing and are not suitable for a continuous production of metallic iron from large volumes of iron ore.

[7] Various embodiments of the electrochemical flow reactor disclosed herein seek to overcome or improve at least some of the above mentioned disadvantages.

Summary

[8] The present disclosure provides an electrochemical flow reactor, in particular an electrochemical flow reactor for continuous production of an iron-bearing product from iron ore particles.

[9] In a first aspect there is provided an electrochemical flow reactor for continuous production of an iron-bearing product from iron ore particles comprising: an electrochemical cell comprising a cathodic compartment and an anodic compartment separated by a separator; the cathodic compartment containing a catholyte comprising a suspension of iron ore particles in a first alkaline solution, and a cathode at least partially in contact with the catholyte and arranged to facilitate reduction of the iron ore particles to the iron-bearing product, the cathodic compartment having an inlet for ingress of the catholyte and an outlet for egress of a spent catholyte containing the iron-bearing product, wherein the outlet is in fluid communication with the inlet via a first conduit in an arrangement whereby spent catholyte may be recirculated from the outlet of the cathodic compartment to the inlet thereof; the anodic compartment containing an anolyte comprising a second alkaline solution and an anode at least partially in contact with the anolyte, the anodic compartment having an inlet for ingress of the anolyte and an outlet for egress of a spent anolyte, wherein the outlet is in fluid communication with the inlet via a second conduit in an arrangement whereby spent anolyte may be recirculated from the outlet of the anodic compartment to the inlet thereof; and, a separation means associated with the first conduit to separate the iron-bearing product from the spent catholyte and produce a depleted catholyte; wherein the first conduit may be provided with an inlet for ingress of iron ore particles and the first alkaline solution that enables replenishment of said depleted catholyte prior to recirculation to the inlet of the cathodic compartment.

[10] In one embodiment, the electrochemical cell comprises an arrangement of alternating cathodic compartments and anodic compartments, wherein adjacent cathodic and anodic compartments are separated by respective separators.

[11] In a second aspect there is provided an electrochemical flow reactor for continuous production of an iron-bearing product from iron ore particles comprising: an electrochemical cell assembly comprising an arrangement of alternating cathodic compartments and anodic compartments, wherein adjacent cathodic and anodic compartments are separated by respective separators; each cathodic compartment containing a catholyte comprising a suspension of iron ore particles in a first alkaline solution, and a cathode at least partially in contact with the catholyte and arranged to facilitate reduction of the iron ore particles to the iron-bearing product, the cathodic compartment having an inlet for ingress of the catholyte and an outlet for egress of a spent catholyte containing the iron-bearing product, wherein the outlet is in fluid communication with the inlet via a first conduit in an arrangement whereby spent catholyte may be recirculated from the outlet of the cathodic compartment to the inlet thereof; each anodic compartment containing an anolyte comprising a second alkaline solution and an anode at least partially in contact with, the anodic compartment having an inlet for ingress of the anolyte and an outlet for egress of a spent anolyte, wherein the outlet is in fluid communication with the inlet via a second conduit in an arrangement whereby spent anolyte may be recirculated from the outlet of the anodic compartment to the inlet thereof; and, a separation means associated with the first conduit to separate the iron-bearing product from the spent catholyte and produce a depleted catholyte; wherein the first conduit may be provided with an inlet for ingress of iron ore particles and the first alkaline solution that enables replenishment of said depleted catholyte prior to recirculation to the inlet of the cathodic compartment.

[12] In one embodiment, the second conduit may be provided with a respective inlet for ingress of the second alkaline solution to replenish the spent anolyte prior to recirculation to the inlet of the anodic compartment.

[13] In one embodiment, the electrochemical flow reactor further comprises a first pump associated with the first conduit to circulate the catholyte through the cathodic compartment, and a second pump associated with the second conduit to circulate the anolyte through the anodic compartment. In one form of the disclosure, the first and second pumps may circulate the catholyte and anolyte in co-current flow with respect to one another. In an alternative form of the disclosure, the first and second pumps may circulate the catholyte and anolyte in counter-current flow with respect to one another.

[14] In one embodiment, the first conduit may be provided with respective inlets for separate ingress of iron ore particles and the first alkaline solution. It will be appreciated that the iron ore particles may be introduced as a slurry through one inlet or if present more than one inlet.

[15] In a further embodiment, the first conduit may be provided with a catholyte chamber configured to receive and mix the iron ore particles and the first alkaline solution.

[16] It is envisaged that the first pump may be operated in a manner to maintain the iron ore particles in suspension in the first alkaline solution. However, in some embodiments the electrochemical flow reactor may further comprise a particle suspending means capable of maintaining the iron ore particles in suspension in the first alkaline solution. For example, said particle suspending means may include, but is not limited to, an agitator or a sonication means. Said particle suspending means may be disposed in, or associated with the catholyte chamber. Alternatively, said particle suspending means may be disposed in-line in the first conduit.

[17] In one embodiment, the separation means may comprise a magnetic separator to separate the iron-bearing product from the spent catholyte. Alternatively, or additionally, the separation means may comprise a filter, centrifugal separator or a cyclonic separator.

[18] In one embodiment, the separation means may be disposed in-line in the first conduit downstream from the outlet of the cathodic compartment. For example, one or more magnets may be arranged in-line in the first conduit in an arrangement whereby the one or more magnets may be removed from the first conduit without disrupting or ceasing operation of the electrochemical flow reactor.

[19] In an alternative embodiment, the separation means may be disposed in fluid communication with the first conduit and externally to a circuit defined by the first conduit extending between the outlet and the inlet of the cathodic compartment. For example, a feed line may be provided from the first conduit at an upstream point of said circuit to direct spent catholyte to the separation means in an arrangement whereby depleted catholyte is subsequently redirected by a return line to the first conduit at a downstream point of said circuit. Generally, the separation means may be disposed upstream of the catholyte chamber so that the iron-bearing product may be separated from the spent catholyte before the depleted catholyte is replenished with iron ore particles and/or the first alkaline solution.

[20] In one embodiment, the electrochemical flow reactor further comprises a means to maintain the catholyte at a predetermined temperature. For example, the first conduit may be arranged to circulate the catholyte and/or replenished catholyte through a heat exchanger.

[21] In one embodiment, the first and second alkaline solutions may be the same or different. The first and second alkaline solution may independently comprise sodium hydroxide, potassium hydroxide, lithium hydroxide, caesium hydroxide, magnesium hydroxide, calcium hydroxide or a mixture of one or more thereof, optionally in combination with a neutral salt of an alkali metal such as lithium chloride. In one embodiment the first and second alkaline solution may comprise 20-80 wt% sodium hydroxide or potassium hydroxide solution, or 30-60 wt% sodium hydroxide or potassium hydroxide solution. In one embodiment, the first alkaline solution may be carbon-free.

[22] In one embodiment, the cathode may comprise a rotating or a non-rotating electrode assembly. The cathode may be formed from a material including, but not limited to, glassy carbon, carbon fibre, graphite, steel, stainless steel or other grades of steel, iron or iron alloys or composite materials.

[23] In one embodiment, the anode may comprise a rotating or a non-rotating electrode assembly. The anode may be formed from any suitable non-sacrificial material including, but not limited to, a plate, mesh, net, foam, fibres, sintered particles or other forms of electrode construction from nickel, nickel-iron alloys or blends, or other metals or conductive materials including composite materials that are suitable for use as oxygen evolution electrodes in alkaline media.

[24] In one embodiment, the cathode and anode are arranged in parallel alignment with one another.

[25] In one embodiment, the separator may comprise any semi-permeable ion conducting membrane suitable for alkaline electrolysis. One suitable example of a semi-permeable ion conducting membrane includes the Zirfon™ (Agfa) separator membrane.

[26] In one embodiment, the iron ore particles may comprise a powder having a P80 less than or equal to 20 pm, a P80 less than or equal to 10 pm, or a P80 less than or equal to 2 pm. Brief Description of Drawings

[27] Preferred embodiments will now be further described and illustrated, by way of example only, with reference to the accompanying drawings in which:

[28] Figure 1 is a schematic representation of one embodiment of an electrochemical flow reactor as described herein comprising a single electrochemical cell arranged for co-current flow of the catholyte and anolyte;

[29] Figure 2 is a schematic representation of the embodiment shown in Figure 1 with cocurrent flow of the catholyte and anolyte in the opposite direction;

[30] Figure 3 is schematic representation of an alternative embodiment of the electrochemical flow reactor comprising a single electrochemical cell arranged for countercurrent flow of the catholyte and anolyte;

[31] Figure 4 is a schematic representation of the embodiment shown in Figure 3 with counter-current flow of the catholyte and anolyte in the opposite direction;

[32] Figure 5 is a schematic representation of another embodiment of the electrochemical flow reactor as described herein comprising a single electrochemical cell arranged for cocurrent flow of the catholyte and anolyte, wherein a separation means for separating the iron- bearing product is depicted outside the electrochemical flow reactor circuit;

[33] Figure 6 is a schematic representation of a further embodiment of the electrochemical flow reactor as described herein comprising a dual electrochemical cell assembly arranged for co-current flow of the catholyte and anolyte;

[34] Figure 7 is a schematic representation of the embodiment shown in Figure 6 but arranged for counter-current-current flow of the catholyte and anolyte;

[35] Figure 8 is a schematic representation of another embodiment of the electrochemical flow reactor as described herein comprising a dual electrochemical cell assembly arranged for co-current flow of the catholyte and anolyte, wherein a separation means for separating the iron-bearing product is depicted outside the electrochemical flow reactor circuit;

[36] Figure 9 is a schematic representation of another embodiment of the electrochemical flow reactor as described herein comprising a triple electrochemical cell assembly arranged for co-current flow of the catholyte and anolyte; [37] Figure 10 is a schematic representation of another embodiment of the electrochemical flow reactor as described herein comprising a triple electrochemical cell assembly arranged for counter-current flow of the catholyte and anolyte; and

[38] Figure 11 is a schematic representation of another embodiment of the electrochemical flow reactor as described herein comprising a triple electrochemical cell assembly arranged for co-current flow of the catholyte and anolyte, wherein a separation means for separating the iron-bearing product is depicted outside the electrochemical flow reactor circuit.

Description of Embodiments

[39] The present disclosure relates to an electrochemical flow reactor, in particular an electrochemical flow reactor for continuous production of an iron-bearing product from iron ore particles.

GENERAL TERMS

[40] Throughout this specification, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e. one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms "a", "an" and "the" include plural aspects unless the context clearly dictates otherwise. For example, reference to "a" includes a single as well as two or more; reference to "an" includes a single as well as two or more; reference to "the" includes a single as well as two or more and so forth.

[41] Each example of the present disclosure described herein is to be applied mutatis mutandis to each and every other example unless specifically stated otherwise. The present disclosure is not to be limited in scope by the specific examples described herein, which are intended for the purpose of exemplification only. Functionally-equivalent products, compositions and methods are clearly within the scope of the disclosure as described herein.

[42] The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[43] When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.).

[44] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

[45] Reference to positional descriptions, such as lower and upper, are to be taken in context of the embodiments depicted in the figures, and are not to be taken as limiting the invention to the literal interpretation of the term but rather as would be understood by the skilled addressee.

[46] Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[47] The term "and/or", e.g., "X and/or Y" shall be understood to mean either "X and Y" or "X or Y" and shall be taken to provide explicit support for both meanings or for either meaning.

[48] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[49] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

[50] The term “about” as used herein means within 5%, and more preferably within 1%, of a given value or range. For example, “about 3.7%” means from 3.5 to 3.9%, preferably from 3.66 to 3.74%. When the term “about” is associated with a range of values, e.g., “about X% to Y%”, the term “about” is intended to modify both the lower (X) and upper (Y) values of the recited range. For example, “about 20% to 40%” is equivalent to “about 20% to about 40%”.

SPECIFIC TERMS

[51] The term ‘iron ore’ as used herein refers to iron-bearing minerals including, but not limited to haematite, goethite, magnetite, limonite, taconite, iron aluminosilicate minerals or any other ore types that contain iron oxide.

[52] The term ‘iron-bearing product’ as used herein refers to metallic iron particles or metallic iron particles containing one or more phases of iron oxide including but not limited to haematite (FesOg), goethite (FeO(OH)), limonite, taconite and magnetite (FegO^. The iron- bearing product may be produced by reducing the iron ore particles in the electrochemical flow reactor via one or more electrochemical reduction steps.

[53] The term ‘anolyte’ as used herein refers to an aqueous salt solution capable of allowing electrons to flow from a positively-charged anode.

[54] As used herein, the term “catholyte” refers to an aqueous salt solution capable of allowing electrons to flow to a negatively-charged cathode.

[55] In the embodiments described herein, the catholyte comprises a suspension of iron ore particles in a first alkaline solution, whereby the first alkaline solution allows the electrons to flow to the negatively-charged cathode and the iron ore particles undergo reduction to the iron-bearing product via one or more electrochemical reduction steps in the cathodic compartment. Accordingly, a reference to the term ‘spent catholyte’, as used herein, refers to said suspension of iron ore particles, wherein the iron ore particles have at least partially undergone one or more reduction reactions. In other words, the spent catholyte may refer to a suspension of iron-bearing product in the first alkaline solution and/or the first alkaline solution at least partially depleted in iron ore particles. It will be appreciated by those skilled in the art that the spent catholyte may contain iron-bearing product and unreduced iron ore particles suspended in the first alkaline solution. The term ‘depleted catholyte’, as used herein, refers to the spent catholyte from which the iron bearing product has been at least partially separated therefrom.

[56] The term ‘spent anolyte’, as used herein, refers to the second alkaline solution that has undergone one or more oxidation reactions in the anodic compartment of the electrochemical cell.

[57] The term “Px” is defined in the art as a size distribution for which x% of the particles are smaller than the specified value. Accordingly, a P80 of 2 pm means size distribution for which 80% of the particles are smaller than 2 pm.

[58] The term ‘at least partially in contact with’, as used herein refers to a portion of an electrochemical surface area of the cathode or the anode being available for liquid-solid interface interactions respectively between the catholyte and cathode electrode or the anolyte and the anode electrode. The portion of the electrochemical surface area of the cathode or the anode being available for said interactions may be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%,

41 %, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%,

57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%,

73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%,

89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%.

ELECTROCHEMICAL FLOW REACTOR

[59] Referring to the figures, where like numerals refer to like parts throughout, Figures 1 - 11 show various embodiments of an electrochemical flow reactor 10 arranged for continuous production of an iron-bearing product from iron ore particles.

[60] The electrochemical flow reactor 10 includes an electrochemical cell 12 including a cathodic compartment 14 and an anodic compartment 16 separated by a separator 18. [61] The cathodic compartment 14 contains a catholyte 20 comprising a suspension of iron ore particles in a first alkaline solution, and a cathode 22 at least partially in contact with the catholyte 20 and arranged to facilitate reduction of the iron ore particles to the iron-bearing product via one or more reduction reactions.

[62] The anodic compartment 16 contains an anolyte 24 comprising a second alkaline solution, and an anode 26 at least partially in contact with the anolyte 24.

[63] The iron ore particles may comprise a powder having a P80 less than or equal to 20 pm, a P80 less than or equal to 10 pm, or a P80 less than or equal to 2 pm. The solids density of the catholyte may be 1 -25 wt%.

[64] The first and second alkaline solutions may independently comprise sodium hydroxide, potassium hydroxide, lithium hydroxide, caesium hydroxide, magnesium hydroxide, calcium hydroxide or a mixture of one or more thereof, optionally in combination with a neutral salt of an alkali metal such as lithium chloride. In particular, the first and second alkaline solutions may comprise 20-80 wt% sodium hydroxide or potassium hydroxide solution, or 30-60 wt% sodium hydroxide or potassium hydroxide solution. In one embodiment, the catholyte may be carbon free.

[65] In contrast to prior art electrochemical reduction processes for iron ore, the electrochemical flow reactor 10 as will be described below is configured and operated to deter deposition and/or adhesion of the iron-bearing product on the cathode 22 so that it may be readily separated from the catholyte 20. In this way, the electrochemical flow reactor 1 may be operated continuously without the need to cease production and disassemble the electrochemical cell 1 to recover electrodeposited iron-bearing product from the cathode 22.

[66] The cathodic and anodic compartments 14, 16 may be fabricated from any suitable solid material that is chemically inert under the operating conditions of the electrochemical cell 12. Suitable solid materials include, but are not limited to, glass, metals, alloys or solid plastic materials.

[67] The separator 18 separates the cathodic and anodic compartments 14, 16 to prevent physical contact between the cathode 22 and the anode 26 while allowing transport of ionic charge carriers between the cathodic and anodic compartments 14, 16. The separator 18 may be any semi-permeable membrane suitable for alkaline electrolysis that allows water, cations and/or anions to pass therethrough. One suitable example of a semi-permeable ion conducting membrane includes the Zirfon™ (Agfa) separator membrane. In use, hydrogen gas may be produced in the cathodic compartment 14 at the cathode 22 as a product of a competing side reaction (i.e. water electrolysis), and oxygen gas may be generated in the anodic compartment 16 due to oxidation of water at the anode 26. The separator 18 also deters passage of these gases into the other compartments 14, 16. Gases generated in the electrochemical flow reactor 10 may be either vented or captured via bleed lines (not shown).

[68] The cathode 22 and the anode 26 may be fabricated from respective electrically conductive materials that are inert or insoluble under the alkaline electrolysis conditions maintained in the electrochemical cell 12. In particular, the cathode 22 may be fabricated from an electrically conductive material having poor catalytic properties for the hydrogen evolution reaction, leading to high overvoltage for hydrogen evolution and surface properties that deter deposition and/or adhesion of the iron-bearing product thereon. Suitable examples of electrically conductive materials from which the cathode 22 may be fabricated include, but are not limited to, glassy carbon, carbon fibre, graphite, steel, stainless steel or other grades of steel, iron, iron alloys or composite materials. The anode 26 may be fabricated from an electrically conductive material having acceptable catalytic properties towards the oxygen evolution reaction leading to acceptable overvoltage for oxygen evolution and minimum side reactions. Suitable examples of electrically conductive materials from which the anode 26 may be fabricated include, but are not limited to, a plate, mesh, net, foam, fibers, sintered particles or other forms of electrode construction fabricated from nickel, iron, steel, stainless steel, nickel-iron alloys, composites or blends, or other metals or conductive materials including composite materials that is suitable for use as oxygen evolution electrodes in alkaline media..

[69] The cathode 22 and the anode 26 may be a rotating electrode assembly. Alternatively, the cathode 22 and the anode 26 may be a non-rotating electrode assembly. In particular, the cathode 22 and the anode 26 may comprise respective stationary plates in parallel alignment with one another, as shown in the Figures.

[70] Generally, the anode 26 may have a larger electrochemically active surface area than the cathode 22.

[71] A suitable power supply (not shown) may be configured in electrical communication with the cathode 22 and the anode 26 to supply a cell potential of greater than 1 .4 V to the electrochemical cell 12 to maintain a current density of at least greater than or equal to 0.05 A/cm2. In particular, the power supply may supply a cell potential of about 1 .5 V to 2.5 V, more particularly about 1 .5 V to 1.9 V. It will be appreciated that the cathode 22 and the anode 26 will be provided with a respective current collector configured to electrically connect the cathode 22 and the anode 26 to the power supply. [72] The cathodic compartment 14 is provided with an inlet 28 for ingress of the catholyte and an outlet 30 for egress of a spent catholyte containing the iron-bearing product. The outlet 30 is in fluid communication with the inlet 28 via a first conduit 32 in an arrangement whereby spent catholyte may be recirculated from the outlet 30 of the cathodic compartment to the inlet 28 thereof. A first pump 34 may be associated with the first conduit 32 to facilitate flow of catholyte, spent catholyte and/or depleted catholyte through the cathodic compartment 14. In this way, non-reduced iron ore particles may be passed through the cathodic compartment 14 for more than one reduction cycle, thereby increasing the yield of iron-bearing product. The first pump 34 may be any suitable pump including, but not limited to, a peristaltic pump, diaphragm pump, rotary vane pump, centrifugal pump, gear pump, progressive cavity pump or scroll pump.

[73] The anodic compartment 16 is provided with an inlet 36 for ingress of the anolyte and an outlet 38 for egress of spent anolyte. The outlet 38 is in fluid communication with the inlet 36 via a second conduit 40 in an arrangement whereby spent anolyte may be recirculated from the outlet 38 of the anodic compartment to the inlet 36 thereof. A second pump 42 may be associated with the second conduit 40 to facilitate flow of anolyte and/or spent anolyte through the anodic compartment 16. The second pump 42 may be any suitable pump including, but not limited to, a peristaltic pump, diaphragm pump, rotary vane pump, centrifugal pump, gear pump, progressive cavity pump or scroll pump.

[74] The first and second pumps 34, 42 may circulate the catholyte and anolyte in cocurrent flow with respect to one another, as shown in Figures 1 , 2, 5, 6, 8, 9 and 11. Alternatively, the first and second pumps 34, 42 may circulate the catholyte and anolyte in counter-current flow with respect to one another, as shown in Figures 3, 4, 7 and 10.

[75] Referring to the Figures, the first conduit 32 is provided with a catholyte chamber 44 having an inlet 46 for ingress of iron ore particles and an inlet 48 for ingress of the first alkaline solution to replenish said depleted catholyte prior to recirculation to the inlet 28 of the cathodic compartment 14. In this particular embodiment, the catholyte chamber 44 may be configured to receive and mix the iron ore particles and the first alkaline solution. It will be appreciated, however, that in alternative arrangements, the catholyte chamber 44 may be provided with a single inlet to receive a ready-mixed catholyte of iron ore particles suspended in the first alkaline solution.

[76] It is envisaged that the first pump 34 may be operated in a manner to maintain the iron ore particles in suspension in the first alkaline solution. However, in some embodiments the electrochemical flow reactor 10 may include a particle suspending means capable of maintaining the iron ore particles in suspension in the first alkaline solution (not shown). For example, said particle suspending means may include, but is not limited to, an agitator or a sonication means or a combination of means such as an agitator and a sonicator. Said particle suspending means may be disposed in, or associated with the catholyte chamber 44. Alternatively, said particle suspending means may be disposed inline in the first conduit 32.

[77] Referring to the Figures, the second conduit 40 is provided with an anolyte chamber 50 having an inlet 52 for ingress of the second alkaline solution to add anolyte to the anolyte chamber 50 or replenish the spent anolyte prior to recirculation to the inlet 36 of the anodic compartment 16.

[78] In alternative embodiments, the respective inlets 46, 48, 52 may be integral with the first and second conduits 32, 40.

[79] A separation means 54 may be associated with the first conduit 32 to separate the iron-bearing product from the spent catholyte. The resulting depleted catholyte may then be recirculated to the inlet 28 of the cathodic compartment 14. The separation means 54 may include a magnetic separator to separate the iron-bearing product from the spent catholyte. Alternatively, or additionally, the separation means 54 may comprise a filter, centrifugal separator or a cyclonic separator, or a combination of separation means. The separation means may separate the iron-bearing product from the spent catholyte in a batch or continuous (in-line) mode.

[80] As shown in Figures 1 -4, 6, 7, 9 and 10, the separation means 54 may be disposed in-line in the first conduit 32 downstream from the outlet 30 of the cathodic compartment 14. For example, the separation means may be one or more magnets that may be arranged inline in the first conduit 32 in an arrangement whereby the one or more magnets may be removed from the first conduit 32 without disrupting or ceasing operation of the electrochemical flow reactor 10. The separated iron-bearing product may then be collected from the one or more magnets by well-known conventional techniques.

[81] Alternatively, as shown in Figures 5, 8 and 11 , the separation means 54 may be disposed in fluid communication with the first conduit 32 and externally to a circuit defined by the first conduit 32 extending between the outlet 30 and the inlet 28 of the cathodic compartment 14. For example, a feed line 56 may be provided from the first conduit 32 at an upstream point of said circuit to direct spent catholyte to the separation means 54 in an arrangement whereby depleted catholyte is subsequently redirected by a return line 58 to the first conduit at a downstream point of said circuit. [82] Generally, the separation means 54 may be disposed upstream of the catholyte chamber 44 so that the iron-bearing product may be separated from the spent catholyte before the resulting depleted catholyte is replenished with iron ore particles and/or the first alkaline solution.

[83] It will be appreciated that there may be temperature differentials between incoming first and second alkaline solutions and the respective catholyte, spent catholyte or depleted catholyte and anolyte or spent anolyte circulating through the electrochemical flow reactor 10. To reduce temperature differentials and fluctuations in temperature due to mixing said streams, the electrochemical flow reactor 10 may be configured to recirculate the catholyte, spent catholyte or depleted catholyte through a heat exchanger (not shown). In this way, the catholyte and anolyte may be maintained at a temperature of greater than or equal to 90 °C and preferably up to boiling point of the first and second alkaline solutions.

[84] Furthermore, it will be appreciated that a heating means may be associated with the electrochemical cell 12, 12’, 12” to maintain the anolyte and the catholyte at a desired temperature. Suitable heating means includes, but is not limited to, a heating jacket, heating mantle or heating plate configured in a suitable arrangement to heat the electrochemical cell.

[85] Referring to Figures 6-8 and Figures 9-11 , there is shown an assembly of electrochemical cells 12’, 12” comprising a plurality of cathodic compartments 14 and anodic compartments 16 in alternating parallel alignment with one another. The cathodic compartments 14 and the anodic compartments 16 may be arranged as described above.

[86] In use, iron ore particles and the first alkaline solution may be fed through inlets 46, 48 into the catholyte chamber 44 where they are mixed until the catholyte comprising the suspension of iron ore particles in the first alkaline solution is produced. The catholyte is circulated by first pump 34 through the first conduit 32 to inlet 28 of the cathodic compartment 14 of the electrochemical cell 12. The catholyte may be heated to a temperature greater than or equal to 90 °C before it is circulated to inlet 28 of the cathodic compartment 14. It will be appreciated, however, that in alternative arrangements, the catholyte chamber 44 may be provided with a single inlet to receive a ready-mixed catholyte of iron ore particles suspended in the first alkaline solution. The ready-mixed catholyte may be heated to a temperature greater than or equal to 90 °C.

[87] A cell potential of greater than 1.4 V, in particular a cell potential of about 1.5 V to about 2.5 V per cell is supplied to the electrochemical cell(s) 12 by the power supply (not shown) to maintain a current density of at least greater than or equal to 0.05 A/cm² , whereupon at least some of the iron ore particles in the catholyte undergo one or more reduction reactions to produce an iron-bearing product. The spent catholyte then leaves the cathodic compartment 14 via outlet 30. Iron-bearing product may be separated from the spent catholyte by the separation means 54 disposed inline in first conduit 32, thereby producing a depleted catholyte. Alternatively, the spent catholyte may be directed via feed line 56 to the separation means 54 which separates the iron-bearing product from the spent catholyte, whereupon the resulting depleted catholyte is re-directed to the first conduit 32 via return line 58.

[88] The depleted catholyte may then be recirculated to the catholyte chamber 44 and replenished with incoming iron ore particles and/or the first alkaline solution via inlets 46, 48.

[89] The second alkaline solution may be fed through inlet 52 into the anolyte chamber 50 and then circulated by second pump 42 via second conduit 40 to inlet 36 of the anodic compartment 16. The anolyte may be heated to a temperature greater than or equal to 90 °C before it is circulated to inlet 36. The anolyte undergoes an oxidation reaction at the anode 26 and the spent anolyte exits the anodic compartment 16 via outlet 38. The spent anolyte may be recirculated to the anolyte chamber 50 where it may be replenished with the second alkaline solution.

[90] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. An electrochemical flow reactor for continuous production of an iron-bearing product from iron ore particles comprising: an electrochemical cell comprising a cathodic compartment and an anodic compartment separated by a separator; the cathodic compartment containing a catholyte comprising a suspension of iron ore particles in a first alkaline solution, and a cathode at least partially in contact with the catholyte and arranged to facilitate reduction of the iron ore particles to the iron- bearing product, the cathodic compartment having an inlet for ingress of the catholyte and an outlet for egress of a spent catholyte containing the iron-bearing product, wherein the outlet is in fluid communication with the inlet via a first conduit in an arrangement whereby spent catholyte may be recirculated from the outlet of the cathodic compartment to the inlet thereof; the anodic compartment containing an anolyte comprising a second alkaline solution and an anode at least partially in contact with the anolyte, the anodic compartment having an inlet for ingress of the anolyte and an outlet for egress of a spent anolyte, wherein the outlet is in fluid communication with the inlet via a second conduit in an arrangement whereby spent anolyte may be recirculated from the outlet of the anodic compartment to the inlet thereof; and, a separation means associated with the first conduit to separate the iron-bearing product from the spent catholyte and produce a depleted catholyte; wherein the first conduit is provided with an inlet for ingress of iron ore particles and the first alkaline solution that enables replenishment of said depleted catholyte prior to recirculation to the inlet of the cathodic compartment.

2. The electrochemical flow reactor according to claim 1 , wherein the electrochemical cell comprises an arrangement of alternating cathodic compartments and anodic compartments, wherein adjacent cathodic and anodic compartments are separated by respective separators.

3. An electrochemical flow reactor for continuous production of an iron-bearing product from iron ore particles comprising: an electrochemical cell assembly comprising an arrangement of alternating cathodic compartments and anodic compartments, wherein adjacent cathodic and anodic compartments are separated by respective separators; each cathodic compartment containing a catholyte comprising a suspension of iron ore particles in a first alkaline solution, and a cathode at least partially in contact with the catholyte and arranged to facilitate reduction of the iron ore particles to the iron- bearing product, the cathodic compartment having an inlet for ingress of the catholyte and an outlet for egress of a spent catholyte containing the iron-bearing product, wherein the outlet is in fluid communication with the inlet via a first conduit in an arrangement whereby spent catholyte may be recirculated from the outlet of the cathodic compartment to the inlet thereof; each anodic compartment containing an anolyte comprising a second alkaline solution and an anode at least partially immersed therein, the anodic compartment having an inlet for ingress of the anolyte and an outlet for egress of a spent anolyte, wherein the outlet is in fluid communication with the inlet via a second conduit in an arrangement whereby spent anolyte may be recirculated from the outlet of the anodic compartment to the inlet thereof; and, a separation means associated with the first conduit to separate the iron-bearing product from the spent catholyte and produce a depleted catholyte; wherein the first conduit is provided with an inlet for ingress of iron ore particles and the first alkaline solution that enables replenishment of said depleted catholyte prior to recirculation to the inlet of the cathodic compartment.

4. The electrochemical flow reactor according to any one of claims 1 to 3, wherein the second conduit is provided with a respective inlet for ingress of the second alkaline solution to replenish the spent anolyte prior to recirculation to the inlet of the anodic compartment.

5. The electrochemical flow reactor according to any one of claims 1 to 4, further comprising a first pump associated with the first conduit to circulate the catholyte through the cathodic compartment, and a second pump associated with the second conduit to circulate the anolyte through the anodic compartment.

6. The electrochemical flow reactor according to claim 5, wherein the first and second pumps circulate the catholyte and anolyte in co-current flow with respect to one another.

7. The electrochemical flow reactor according to claim 5, wherein the first and second pumps circulate the catholyte and anolyte in counter-current flow with respect to one another.

8. The electrochemical flow reactor according to any one of the preceding claims wherein the first conduit is provided with respective inlets for separate ingress of iron ore particles and the first alkaline solution.

9. The electrochemical flow reactor according to any one of the preceding claims, wherein the first conduit is provided with a catholyte chamber configured to receive and mix the iron ore particles and the first alkaline solution.

10. The electrochemical flow reactor according to any one of the preceding claims, wherein the electrochemical flow reactor further comprise a particle suspending means capable of maintaining the iron ore particles in suspension in the first alkaline solution.

11. The electrochemical flow reactor according to claim 10, wherein said particle suspending means comprises an agitator or a sonication means.

12. The electrochemical flow reactor according to claim 10 or claim 11 , when dependent on claim 9, wherein said particle suspending means is disposed in, or associated with the catholyte chamber.

13. The electrochemical flow reactor according to claim 10 or claim 11 , wherein said particle suspending means may be disposed inline in the first conduit.

14. The electrochemical flow reactor according to any one of the preceding claims, wherein the separation means comprises a magnetic separator to separate the iron- bearing product from the spent catholyte and/or a filter, centrifugal separator or a cyclonic separator.

15. The electrochemical flow reactor according to any one of the preceding claims, wherein the separation means is disposed in-line in the first conduit downstream from the outlet of the cathodic compartment.

16. The electrochemical flow reactor according to any one of claims 1 to 14, wherein the separation means is disposed in fluid communication with the first conduit and externally to a circuit defined by the first conduit extending between the outlet and the inlet of the cathodic compartment.

17. The electrochemical flow reactor according to claim 16, wherein a feed line is provided from the first conduit at an upstream point of said circuit to direct spent catholyte to the separation means in an arrangement whereby depleted catholyte is subsequently redirected by a return line to the first conduit at a downstream point of said circuit.

18. The electrochemical flow reactor according to any one of claims 9 to 17, wherein the separation means is disposed upstream of the catholyte chamber so that the iron- bearing product may be separated from the spent catholyte before the depleted catholyte is replenished with iron ore particles and/or the first alkaline solution.

19. The electrochemical flow reactor according to any one of the preceding claims wherein the cathode and the anode independently comprise a rotating electrode assembly.

20. The electrochemical flow reactor according to any one of claims 1 to 18 wherein the cathode and the anode independently comprise a non-rotating electrode assembly.

21 . The electrochemical flow reactor according to any one of the preceding claims wherein the cathode is formed from a material comprising glassy carbon, carbon fibre, graphite, steel, stainless steel or other grades of steel, iron and other iron alloys or composite materials.

22. The electrochemical flow reactor according to any one of the preceding claims wherein the separator comprises an ion conducting membrane suitable for alkaline electrolysis.