Electrolytic apparatus for producing iron having improved gas-permeable anode plates

Abstract

The invention relates to an apparatus (1) for producing iron by reducing iron ore by means of an electrolytic reaction which releases gas, the apparatus comprising a casing (4) containing gas-permeable anode plates (2) and cathode plates (3) facing each other and separated by an electrolyte chamber (6).

Description

[Technical field]

[0001] The present invention relates to an apparatus for producing iron by an electrolytic process. [Background technology]

[0002] Currently, steel can be produced on an industrial scale through two main production routes. The production route most commonly used today is the production of pig iron in a blast furnace using a reducing agent, primarily coke, to reduce the iron oxide. This process consumes approximately 450-600 kg of coke per metric tonne of pig iron, and this process emits large amounts of CO2, both during the production of coke from coal in the coke plant, and during the production of pig iron.

[0003] The second main route involves the so-called "direct reduction" process, which includes processes under brands such as MIDREX, FINMET, ENERGIRON / HYL, COREX, and FINEX, in which sponge iron is produced in the form of HDRI (hot direct reduced iron), CDRI (cold direct reduced iron) and HBI (hot briquetted iron) from the direct reduction of an iron oxide carrier. Sponge iron in the form of HDRI, CDRI, and HBI is usually further processed in an electric arc furnace. Even if this second route has lower CO2 emissions than the previous one, it still has some emissions and relies on carbon fossil fuels.

[0004] Current developments are therefore focused on methods that would make it possible to produce carbon-neutral iron with low or no CO2 emissions.

[0005] A known alternative method for producing steel from iron ore is based on electrochemical technology. In such technology, iron is produced from iron oxide using an electrolytic cell unit with two electrodes - an anode and a cathode - connected to a current source, an electrolyte circuit, and an iron oxide feed into the electrolytic cell unit. The anode and cathode are constantly immersed in a circulating electrolyte to ensure good electrical conduction between the electrodes. The electrolytic reaction produces a pure iron sheet at the cathode and gaseous oxygen at the anode. The iron sheet thus obtained can then be melted with other elements, such as carbon-containing materials and / or scrap in an electric furnace, to produce steel. Summary of the Invention [Problem to be solved by the invention]

[0006] One of the problems of existing electrolysis cells is the accumulation of gas. Indeed, the gas formed by the electrolysis reaction tends to accumulate, remaining trapped between the anode and the cathode. Gaseous oxygen is an electrical insulator, which has a detrimental effect on the electrical conduction between the electrodes and therefore on the productivity of the cell. One solution is to continuously extract the electrolyte containing said gas, but this means constantly supplying fresh electrolyte, which also has a negative impact on the productivity and the environmental footprint of the process.

[0007] Another solution is to provide a permeable anode through which the electrolyte can pass and the gas can be extracted from the space between the anode and the cathode. However, the permeability must be controlled to allow the gas to be continuously extracted without interfering with the electrolytic reaction. It is therefore an object of the present invention to remedy the shortcomings of the prior art by providing a gas-permeable anode that improves the extraction of the gas formed by the electrolytic reaction. It is also an object of the present invention to provide an anode that is easy to manufacture and cost-effective. [Means for solving the problem]

[0008] To this end, the device of the invention comprises a casing containing an anode plate and a cathode plate facing each other and separated by an electrolyte chamber, said casing being provided with means for circulating an electrolyte in the electrolyte chamber and means for feeding iron ore to said electrolyte chamber, said casing further comprising a degassing unit including a gas recovery section extending along the side of the gas-permeable anode plate opposite the chamber and capable of recovering gas from the electrolysis reaction escaping through the gas-permeable anode plate. According to the invention, said gas-permeable anode plate is made of a cellular material comprising a plurality of cells extending from the electrolyte flow chamber to the gas recovery section, each cell being separated by a peripheral wall and open on two opposite sides of the gas-permeable anode plate.

[0009] The device of the invention may also include any of the following characteristics, taken individually or according to any possible technical combination: -The cells are regularly and periodically repeated on the gas-permeable anode plate. The peripheral wall of each cell has a hexagonal cross section. -Two adjacent cells share one straight wall of each of the cells' hexagonal perimeters. - The hexagon formed by the hexagonal peripheral walls of each cell is a regular hexagon. -A regular hexagon is defined according to the equation e / h<0.1, where e is the thickness of the hexagon's wall and h is the distance between two opposing parallel straight walls of the hexagon. The cellular material forming the gas-permeable anode plate has a honeycomb structure. The cellular material of the gas permeable anode plate is manufactured by welding together several corrugated sheets. the casing comprises a cover plate facing the gas-permeable anode plate, the gas-permeable anode plate extending laterally along a side of the gas-permeable anode plate opposite the chamber and comprising at least one T-shaped groove for receiving a corresponding T-shaped rod, the fixing means traversing the cover plate to the T-shaped rod so that the gas-permeable anode plate is maintained at the required distance from the cathode plate; The gas-permeable anode plate is made from a nickel alloy.

[0010] Other characteristics and advantages of the present invention will become apparent in the following description, given by way of indication and in no way limiting, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0011] [Figure 1] 1 shows a longitudinal section of a device according to the invention; [Diagram 2] FIG. 2 depicts a perspective view of the cellular material that makes up the anode plate. [Diagram 3] FIG. 3 illustrates a top view of the cellular material of FIG. 2. [Figure 4] FIG. 2 represents one block made of cellular material, and the positive plate is made of a plurality of such blocks. [Diagram 5] 2 represents a longitudinal section through a portion of a casing of the invention, showing the fixing means of the anode plate within the casing; [Figure 6] Representing the main manufacturing steps for one block of cell material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] First, it should be noted that in the figures, like reference numbers refer to like elements regardless of the figure in which they are depicted and regardless of the form of those elements. Similarly, if elements are not specifically referred to in one figure, their reference numbers can easily be found by reference to another figure.

[0013] It should be noted that the figure represents primarily one embodiment of the subject matter of the invention, but other embodiments may exist that correspond to the definition of the invention.

[0014] Elements in the figures are illustrative and may not be drawn to scale.

[0015] The present invention relates to an apparatus 1 provided for the production of iron metal (Fe) by electrolytic reaction, in particular by reduction of iron ores containing hematite (Fe2O3) and other iron oxides or hydroxides. Said chemical reaction is well known and can be described by the following equation (1):

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[0016] It is therefore envisaged that the electrolytic reaction will release gases - mainly oxygen - which will need to be extracted from the device 1 .

[0017] With reference to Fig. 1, the device 1 comprises a casing 4 extending along a longitudinal axis X, in which the electrolytic reaction takes place. Said casing 4 is delimited by a base plate 20, a cover plate 13 and two side plates 21. The casing 4 further comprises a gas-permeable anode plate 2 and a cathode plate 3 intended to be completely immersed in an electrolyte 5, facing each other and kept at the required distance by fixing means (not shown in this figure). The casing 4 also comprises an electrolyte chamber 6 extending longitudinally between the anode plate 2 and the cathode plate 3 to an exhaust chamber 22. The device 1 finally comprises a power supply (not shown) connected to the anode plate 2 and the cathode plate 3.

[0018] To produce iron by electrolytic reaction, an electrolyte 5 - preferably an aqueous solution such as aqueous sodium hydroxide - flows through the casing 4 in an electrolyte chamber 6 while the device 1 is in operation. The device 1 therefore comprises means for circulating the electrolyte, which may comprise an electrolyte circuit (not shown) connected to an inlet 24 and an outlet 25 managed within the casing 4 and fluidly connected to the electrolyte chamber 6. Iron ore is preferentially introduced into the device 1 as a powder suspension in the electrolyte 5 via the inlet 24.

[0019] During the electrolysis reaction, iron oxide is reduced to iron by reaction (1), which is deposited on the cathode plate 3 and releases gaseous oxygen inside the casing 4. These gases, being electrical insulators, interfere with the good operation of the electrolysis reaction and must therefore be constantly vented outside the casing 4.

[0020] For this purpose, the casing 4 contains a degassing unit 7, which is provided with a gas collection section 8 extending longitudinally along the face 27 of the electrolyte chamber 6 facing away from the anode plate 2. This gas collection section 8 is a compartment intended to be filled with the electrolyte 5 and is arranged between the anode plate 2 and the cover plate 13. Said gas collection section 8 is thus provided for collecting the gas escaping through the anode plate 2.

[0021] As shown in Fig. 1, the degassing unit 7 also comprises an electrolyte recirculation section 28 extending in series with the gas recovery section 8 up to a gas outlet 29 managed within the casing 4. The electrolyte recirculation section 28 is arranged to be at least partially filled with electrolyte 5. Furthermore, said recirculation section 28 is fluidly connected to the electrolyte chamber 6. When the device 1 is in operation, the recirculation section 28 can redirect the electrolyte 5 flowing from the gas recovery section 8 towards the electrolyte chamber 6, for example via an elbow duct 30 of the electrolyte recirculation section 28 adjacent to the anode plate 2 and fluidly connected to the electrolyte chamber 6.

[0022] 2 and 3, in accordance with the present invention, the gas permeable anode plate 2 is made of a cellular material comprising a plurality of cells 9. Each cell 9 is bounded by a peripheral wall 10 and is open on opposite sides of the anode plate 2, thereby extending from the electrolyte chamber 6 to the gas collection section 8 (see FIG. 1). This configuration allows gas bubbles to flow through the anode plate 2 together with the electrolyte 5 for gas evacuation.

[0023] All cells preferably have the same height so that the anode has a constant thickness e A The thickness of the anode is e Ais defined as the distance between the top and bottom of the anode, the bottom side being the side facing the electrolyte chamber 6 and the top being the opposite side facing the gas collection section 8. The thickness of the anode e A is preferably 5 to 50 mm, more preferably 10 to 20 mm, which makes it possible to improve gas discharge while maintaining a compact design of the device.

[0024] In addition to its role of discharging gas bubbles, the gas-permeable anode plate 2 must contribute to a uniform electrolytic reaction in order to grow the iron deposits uniformly. Furthermore, the gas-permeable anode plate 2 must be sufficiently robust to withstand the environmental conditions, in particular the continuous immersion in the electrolyte and the continuous application of the anode current. In particular, the electrolyte may contain caustic soda at a concentration of 50% and thin iron oxide particles (diameter 10-40 μm). The temperature inside the casing may be 100-130 °C. The power supplied to the electrodes may be 5 VDC for a current strength of about 1000 A / m2.

[0025] For this purpose, the cellular material constituting the gas-permeable anode plate 2 preferably has a honeycomb structure in which the cells 9 are regularly and periodically repeated on the anode plate 2 for the purposes of both gas evacuation and uniform electrical conduction. More precisely, each cell 9 has a hexagonal cross section, preferably each hexagon being a regular hexagon. Such an arrangement provides perfect structural uniformity which enhances the effective robustness of the anode plate and improves electrical performance. Moreover, such an arrangement maximizes the perimeter of each cell 9, allowing for better gas evacuation.

[0026] Furthermore, two adjacent cells 9 of the cellular material are directly adjacent by sharing one common straight wall 11. Thus, each cell 9 is directly surrounded by six identical cells 9, except for the cells 9 located at the periphery of the anode plate 2. Such a configuration allows the number of gas exhaust cells 9 to be maximized, while allowing for a uniform metal thickness for improved electrical conductivity. Such a configuration also aids in the robustness of the anode plate, since the forces that the anode plate may be subjected to are uniformly distributed over its entire surface.

[0027] 4 and 5, the anode plate 2 is made from a number of blocks 32, each of which is a quadrilateral plate made entirely from the cellular material described above. Fixation means are used to form the anode plate 2 and to maintain each block 32 (and the resulting anode plate 2) at the required distance from the cathode plate 3 in the device 1, and are governed by the thickness of the block 32, and may include two T-shaped grooves 14 extending laterally along the face 27 of the block 32 opposite the electrolyte chamber 6.

[0028] As shown in FIG. 5, each T-shaped groove 14 accommodates a T-shaped rod 15, which is inserted into the corresponding T-shaped groove 14 by sliding it from one end 31. Once locked in the T-shaped groove 14, the T-shaped rod 15 cannot be pulled out from the top of the T-shaped groove 14. The fixing means 16 cross the cover plate 13 along the corresponding holes to the T-shaped rod 15. Thus, the block 32 is securely held in the casing 4 at the required distance from the cathode plate 3. This process is repeated for each block 32. The number of blocks 32 is adjusted by a person skilled in the art according to the required dimensions of the anode plate 2.

[0029] The method of manufacturing the block 32 will now be described with reference to figure 6. Firstly, metal sheets are pressed between toothed rollers 33. The resulting corrugated sheets 12 are welded together to form an initial block 34, which is sliced ​​to a thickness corresponding to the desired thickness of the anode plate 2, thus providing a block 32 ready to be assembled to form the anode plate 2 as described above. The T-shaped grooves 14 may finally be machined to obtain the block 32 of figure 4 (not shown in figure 6).

[0030] Such an approach implies robustness of the anode plate while being easy and cost effective to implement.

[0031] The cellular material, and thus the resulting anode plate, is preferably made from a nickel alloy, for example, available under the tradename Nickel 200(R) or Nickel 201(R).

[0032] In a preferred embodiment, this source of power supplying the apparatus 1 uses renewable energy, defined as energy collected from renewable sources that are naturally replenished on human timescales, including sources such as sunlight, wind, rain, tides, waves, and geothermal heat. In an embodiment, the use of nuclear-derived electricity can be utilized, as it does not emit the CO2 produced. This further limits the CO2 footprint of the steel manufacturing process.

[0033] Working Example Each block 32 is made of Nickel 200(R) or Nickel 201(R). The cellular material is made in a honeycomb structure as described above. The thickness e of the hexagonal wall 10 of each cell 9 is 0.25 mm, and the distance h between two opposing parallel straight walls 11 of one cell 9 is 3.175 mm. The ratio of thickness e to distance h is therefore 0.079.

[0034] The dimensions of each block 32 are as follows: - Height: 20mm+ / -0.5mm -Width, 250mm+ / -0.5mm - Length: 250mm + / - 0.5mm

[0035] Each block 32 is obtained in the manner described above, as shown in FIG.

[0036] The anode plate 2 is made of 44 blocks and the resulting surface area of ​​the anode plate 2 is 2.75 m 2 It is.

[0037] The anode plate according to the present invention promotes good evacuation of gases outside the electrolyte chamber, thus enabling good manufacturability of the electrolyte cell, whilst being easy and cost-effective to manufacture.

Claims

1. An apparatus (1) for producing iron via the reduction of iron ore by an electrolytic reaction, said electrolytic reaction releasing a gas, the apparatus comprising a casing (4) containing gas-permeable anode plates (2) and cathode plates (3) facing each other and separated by an electrolyte chamber (6), The casing (4) is provided with means (24, 25) for circulating an electrolyte (5) in an electrolyte chamber (6) and with means (24) for supplying iron ore to the electrolyte chamber (6), The casing (4) further includes a degassing unit (7) extending along the side of the gas-permeable anode plate (2) opposite the chamber (6) and including a gas recovery section (8) capable of recovering gas from the electrolysis reaction escaping through the gas-permeable anode plate (2); The gas-permeable anode plate (2) is made of a cellular material with a plurality of cells (9) extending from an electrolyte chamber (6) to a gas collection section (8), each cell (9) being separated by a peripheral wall (10) and open on two opposite sides of the gas-permeable anode plate (2).

2. 2. The device according to claim 1, wherein the cells (9) are regularly and periodically repeated on the gas-permeable anode plate (2).

3. 3. A device according to claim 1 or 2, wherein the peripheral wall (10) of each cell (9) has a hexagonal cross section.

4. 4. The device according to claim 3, wherein two adjacent cells (9) share one straight wall (11) of their respective hexagonal peripheral walls (10).

5. 5. A device according to claim 3 or 4, wherein the hexagon formed by the hexagonal peripheral wall of each cell (9) is a regular hexagon.

6. 6. The device according to claim 5, wherein the regular hexagon is defined according to the equation e / h<0.1, where e is the thickness of the wall (10) of the hexagon and h is the distance between two opposite parallel straight walls (11) of the hexagon.

7. An apparatus according to any one of the preceding claims, wherein the cellular material forming the gas-permeable anode plate (2) has a honeycomb structure.

8. An apparatus according to any one of claims 3 to 7, wherein the cellular material of the gas-permeable anode plate (2) is manufactured by welding together a number of corrugated sheets (12).

9. 9. Apparatus according to any one of claims 1 to 8, wherein the casing (4) comprises a cover plate (13) facing the gas-permeable anode plate (2), the gas-permeable anode plate (2) extending transversely along the side of the gas-permeable anode plate (2) opposite the chamber (6) and comprising at least one T-shaped groove (14) for receiving a corresponding T-shaped rod (15), and wherein fixing means (16) traverse the cover plate (13) to the T-shaped rod (15), thus maintaining the gas-permeable anode plate (2) at the required distance from the cathode plate (3).

10. The device according to any one of the preceding claims, wherein the gas-permeable anode plate (2) is made of a nickel alloy.

11. The device according to any one of claims 1 to 10, wherein the device is electrically powered by renewable energy.

12. The gas-permeable anode plate (2) has a thickness e of 5 to 50 mm. Ａ The device according to any one of claims 1 to 11, comprising:

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