Electrolyzer for iron production using improved iron oxide feeder

Abstract

The present invention relates to an apparatus (1) for producing iron through the reduction of iron ore by electrolytic reaction, in which the means for feeding iron ore comprises a twin screw feeder (32) arranged to discharge iron ore powder (46) into an electrolyte feed pipe (31) upstream of 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 most commonly used production route today is the production of pig iron in a blast furnace by using a reducing agent, primarily coke, to reduce iron oxide. This process consumes approximately 450 to 600 kg of coke per metric ton of pig iron. This process releases significant amounts of CO2, both in the production of coke from coal in the coking plant and in the production of pig iron.

[0003] The second main route involves the so-called "direct reduction process." Among them are processes under the brands MIDREX, FINMET, ENERGIRON / HYL, COREX, FINEX, etc., in which sponge iron is produced by direct reduction of an iron oxide support in the form of HDRI (high-temperature direct reduced iron), CDRI (low-temperature direct reduced iron), or HBI (high-temperature briquetted iron). Sponge iron in the form of HDRI, CDRI, and HBI is usually further processed in an electric arc furnace. Even though this second route emits less CO2 than the previous one, it still emits some and relies on carbon-rich fossil fuels.

[0004] Current developments are therefore focused on methods that make it possible to produce iron that emits less or no CO2 and is carbon neutral.

[0005] A known alternative method for producing steel from iron ore is based on electrochemical technology. In this technology, iron is produced from iron oxide using an electrolysis unit comprising two electrodes (anode and cathode) connected to a current source, an electrolyte circuit, and iron oxide entering the electrolysis unit. The anode and cathode are constantly immersed in a circulating electrolyte to ensure good electrical conduction between the electrodes. The electrolysis reaction produces a pure iron plate and gaseous oxygen on the cathode. The iron plate thus obtained can then be melted in an electric furnace with other elements, such as carbon-containing materials and scrap, to produce steel.

[0006] A continuous and automated supply of iron oxide to the electrolyte is a critical component. The supply system must supply the iron oxide solid particles at the rate of their consumption by the electrolyte. Loss of control of the iron oxide content in the electrolyte reduces the faradaic yield and therefore adversely affects cell productivity. One such control problem results from the propension of iron oxide, which becomes pasty and sticky when wet, especially when placed on a metal surface.

[0007] One solution is to stir the iron oxide with the liquid before dissolving it in the electrolyte, but this introduces air into the liquid, which should be avoided because of neutralization of the alkalinity due to carbonation from atmospheric carbon dioxide. Furthermore, if such stirring is done manually, this action is dangerous due to the proximity to the alkaline electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0008] It is therefore an object of the present invention to ameliorate the shortcomings of the prior art by providing an improved oxide delivery apparatus that can automatically discharge iron oxide powder in an electrolyte in a precisely controlled manner while preventing any air contact with the powder. It is also an object of the present invention to provide such an apparatus that is easy to manufacture and cost-effective. [Means for solving the problem]

[0009] For this purpose, the device of the invention comprises a casing containing a gas-permeable anode plate and a cathode plate, both of which face each other and are separated by an electrolytic solution (electrolyte) chamber. The casing further includes a degassing unit having a gas recovery section extending along the side of the gas-permeable anode plate opposite the chamber, and the casing is provided with means for circulating an electrolyte in an electrolyte chamber having an electrolyte inlet and an electrolyte outlet, and means for supplying iron ore to the electrolyte chamber, the means for supplying iron ore to the electrolyte chamber comprising a twin-screw supply section configured to discharge iron ore powder into an electrolyte supply pipe fluidly connected to the electrolyte inlet, the twin-screw supply section having two parallel screws disposed inside a barrel, maintaining a shaft distance A therebetween, the two screws rotating in opposite directions while engaged with each other, the barrel extending from the screw rotation drive means to a discharge opening immersed in the electrolyte flowing through the electrolyte supply pipe, and the barrel comprising an iron ore powder supply opening connected to the iron ore powder supply means.

[0010] The device of the present invention may also include the following optional features, taken into account by the techniques individually or in all possible combinations: - the screw is aligned parallel to the gravitational force; - the electrolyte supply pipe is arranged perpendicular to the screw; -The surfaces of the two screws are smooth. -The two screws are twin concave coarse screws, The ratio of the screw diameter (D) to the screw pitch (B) of each screw is in the range of 0.8 to 1.2; the barrel has a roughened inner surface and is placed in mechanical contact with the screw; -The barrel is under nitrogen atmosphere, the iron ore powder supply means comprises a pinch valve; -The equipment is powered by renewable energy.

[0011] Other features 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 explanation of the drawings]

[0012] [Figure 1] 1 is a longitudinal section of an apparatus according to the invention including a twin screw feed section shown diagrammatically; [Figure 2] FIG. 1 is a front view of a twin screw feeder positioned to discharge iron ore powder into an electrolyte feed pipe. [Figure 3] FIG. 1 is a perspective view of the ends of two screws of a twin screw feed section. [Figure 4] FIG. 1 is a front view of two interlocking screws of a twin screw feed section. DETAILED DESCRIPTION OF THE INVENTION

[0013] First, it should be noted that in the figures, the same reference numerals refer to the same elements regardless of the figure they feature in and regardless of the form of those elements. Similarly, if elements are not specifically referenced in one of the figures, their reference can be easily found by referencing them in another figure.

[0014] It should also be noted that the figures primarily represent one embodiment of the subject matter of the invention, but that other embodiments may exist that correspond to the definition of the invention.

[0015] The present invention refers to an apparatus 1 provided for the production of iron metal (Fe) through the reduction of iron ore, in particular containing hematite (FeO) and other iron oxides or hydroxides, by electrolytic reaction. The said chemical reaction is well known and is described in particular in the case of hematite by the following equation (1):

number

[0016] It is therefore believed that the electrolysis reaction releases gases - primarily oxygen - which must be extracted from the device 1 .

[0017] Referring to FIG. 1, the device 1 comprises a casing 4 extending along a longitudinal axis X along which the electrolysis reaction takes place. The casing 4 is defined by a base plate 20, a cover plate 13, and two side plates 21. In addition, the casing comprises a gas-permeable anode plate 2 intended to be completely immersed in an electrolytic solution (electrolyte) 5, and a cathode plate 3, both plates facing each other and held at the required distance by fastening 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] In a preferred embodiment, the power source uses renewable energy, which is 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 some embodiments, the use of nuclear-derived electricity can be utilized because it does not emit CO2 produced. This further limits the CO2 footprint of the iron production process.

[0019] To produce iron by electrolysis, an electrolyte 5, preferably an aqueous solution such as, for example, aqueous sodium hydroxide, flows through the casing 4 in the electrolyte chamber 6 during operation of the apparatus 1. Accordingly, the apparatus 1 includes means for circulating the electrolyte, such as an electrolyte circuit managed by the casing 4 and connected to an inlet 24 and an outlet 25, both of which are fluidly connected to the electrolyte chamber 6. Iron ore is introduced into the apparatus 1 through the inlet 24 as a powder suspension in the electrolyte 5, as will be further described.

[0020] During the electrolysis reaction, the oxidized iron is reduced to iron by reaction (1), and the reduced iron is deposited on the cathode plate 3, while gaseous oxygen is released inside the casing 4. This gas is an electrical insulator, so it interferes with the good operation of the electrolysis reaction and must be continuously vented outside the casing 4.

[0021] For this purpose, the casing 4 contains a degassing unit 7 with a gas recovery section 8 extending longitudinally along the side 27 of the anode plate 2 opposite to the electrolyte chamber 6. This gas recovery section 8 is a compartment arranged to be filled with the electrolyte 5 and located between the anode plate 2 and the cover plate 13. The gas recovery section 8 is therefore arranged to recover gases leaking through the anode plate 2.

[0022] 1 , the degassing unit 7 also includes an electrolyte recirculation section 28, which extends continuously with the gas recovery section 8 up to a gas outlet 29 managed by the casing 4. The electrolyte recirculation section 28 is arranged to be at least partially filled with the electrolyte 5. In addition, the recirculation section 28 is fluidly connected to the electrolyte chamber 6. When the device 1 is in operation, the recirculation section 28 allows the electrolyte 5 flowing from the gas recovery section 8 to be redirected towards the electrolyte chamber 6, for example, via an elbow duct 30 adjacent to the anode plate 2 and fluidly connected to the electrolyte chamber 6.

[0023] 1, in accordance with the present invention, the means for feeding iron ore to the electrolyte chamber 6 comprises a twin screw feed 32 positioned on an electrolyte feed pipe 31 in fluid connection with the electrolyte inlet 24. The twin screw feed 32 traverses a wall 33 of the electrolyte feed pipe 31 and discharges the iron ore powder into the electrolyte stream 5.

[0024] 2, the twin-screw supply unit 32 includes two output shafts 35, 36 arranged parallel to each other, maintaining a constant shaft distance therebetween, and a gearbox 34 that rotates in opposite directions. The gearbox 34 transmits torque obtained from a drive motor 37 connected to the gearbox 34 through the output shafts 35, 36 to two screws 38, 39.

[0025] The bases of the two screws 38 , 39 are connected to the output shafts 35 , 36 , and the free portions 42 , 43 opposite the bases are immersed in the electrolyte 5 flowing through the electrolyte supply pipe 31 .

[0026] The two screws 38, 39 are arranged parallel to each other in the barrel 40, maintaining a shaft distance therebetween. Thus, the two screws 38, 39 rotate in opposite directions inside the barrel 40 while engaging with each other.

[0027] The barrel 40 extends from the gearbox 34 to a discharge opening 41 immersed in the electrolyte 5. Free portions 42, 43 of the two screws 38, 39 are located at the discharge opening 41. The dimensions of the barrel 40 are adapted to those of the two screws 38, 39, with a small mechanical clearance between the screws 38, 39 and the barrel 40 due to the low free surface of the electrolyte 5. The electrolyte 5 can therefore rise in the barrel 40 at least to the level of the wall 33 of the electrolyte supply pipe 31, thereby defining dry and wet conveying regions and enabling the iron oxide powder to be discharged into the electrolyte 5 in a non-agglomerated state.

[0028] The inner surface of the barrel 40 is advantageously roughened and edged with counter-rotating helices to provide high friction with the two counter-rotating screws 38, 39, thereby preventing bridges and cavities from forming.

[0029] The barrel 40 has an iron feed opening 44 through which iron oxide powder 46 is discharged into the interior of the barrel 40 onto the surfaces of the two counter-rotating screws 38, 39, and thus the iron oxide powder 46 is conveyed to the discharge opening 41.

[0030] The iron supply opening 44 is connected to a valve 45, for example a pinch valve, through which iron oxide powder 46 is supplied to the iron supply opening 44.

[0031] The iron feed opening 44 is positioned above the maximum level of electrolyte in the barrel 40 during operation. Such a position allows for the dispersion of the iron oxide powder in the electrolyte under gentle mixing conditions after being conveyed by the two screws 38, 39, thus avoiding agglomeration of the powder. These conditions achieve wetting of the powder by ensuring maximum exposure to the electrolyte.

[0032] The amount of iron oxide powder 46 discharged into the electrolytic solution 5 is controlled by a command means (not shown) in accordance with the rate at which iron oxide is consumed by electrolysis.

[0033] The barrel 40 is airtight and maintained under a nitrogen atmosphere by means not shown, so that the dry iron oxide powder conveyed by the two screws is air-free, thus avoiding any air contact with the electrolyte.

[0034] The twin screw feeder 32 is advantageously positioned parallel (perpendicular) to the gravitational pull, thereby providing gravity assistance for conveying the iron oxide powder into the electrolyte.

[0035] Advantageously, the electrolyte supply pipe 31 is arranged vertically to the twin screw supply 32 and then horizontally.

[0036] Referring to Figures 3 and 4, the two screws 38, 39 are identical for optimized bonding. The two screws 38, 39 engage with each other and are maintained parallel to each other at a shaft distance A that is smaller than the diameter D of each screw 38, 39. The surfaces of the two screws 38, 39 are smooth, preferably prepared by electropolishing. By rotating the two screws 38, 39 in opposite directions, the two screws 38, 39 are self-cleaning while finely discharging the iron oxide powder into the electrolyte. Therefore, the screw surfaces remain smooth while avoiding any powder agglomeration. The two screws 38, 39 co-rotate to operate with a small pumping effect, thus limiting air vortices. Preferably, the two screws 38, 39 are twin concave coarse screws, with deep roots 47. Advantageously, the ratio of screw diameter (D) to screw pitch (B) of each screw (38, 39) is between 0.8 and 1.2. Below this range there is a risk of compacting the powder, but above this range there is no sufficient pressure for the forward movement of the powder.

Claims

1. An apparatus (1) for producing iron through the reduction of iron ore by an electrolytic reaction, the electrolytic reaction releasing gas, the apparatus comprising a casing (4), the casing (4) comprising a gas-permeable anode plate (2) and a cathode plate (3), both of which are opposite each other and separated by an electrolyte chamber (6); The casing (4) further includes a degassing unit (7) having a gas collection section (8) extending along the side of the gas-permeable anode plate (2) opposite to the chamber (6); The casing (4) is provided with means for circulating an electrolyte (5) in an electrolyte chamber (6) having an electrolyte inlet (24) and an electrolyte outlet (25), and means for supplying iron ore to the electrolyte chamber (6); the means for feeding iron ore to the electrolyte chamber (6) comprises a twin screw feeder (32) arranged to discharge iron ore powder (46) into an electrolyte feed pipe (31) in fluid communication with an electrolyte inlet (24); The twin screw feeder (32) has two parallel screws (38, 39) disposed inside a barrel (40), maintaining a shaft distance (A) therebetween, and rotating in opposite directions while the two screws (38, 39) are engaged with each other; The barrel (40) extends from the screw rotation drive means (34, 37) to a discharge opening (41) immersed in the electrolyte (5) flowing through the electrolyte supply pipe (31), and the barrel is provided with an iron ore powder supply opening (44), which is connected to an iron ore powder supply means (45). Device.

2. 2. The device according to claim 1, wherein the screws (38, 39) are arranged parallel to the gravitational attraction force.

3. 3. The device according to claim 2, wherein the electrolyte supply pipe (31) is arranged perpendicular to the screws (38, 39).

4. The device according to any one of claims 1 to 3, wherein the surfaces of the two screws (38, 39) are smooth.

5. The device according to any one of claims 1 to 4, wherein the two screws (38, 39) are coarse twin concave screws.

6. 6. The device according to any one of claims 1 to 5, wherein the ratio of the screw diameter (D) to the screw pitch (B) of each screw (38, 39) is in the range of 0.8 to 1.

2.

7. The device according to any one of claims 1 to 6, wherein the inner surface of the barrel (40) is roughened and is placed in mechanical contact with the screws (38, 39).

8. The apparatus according to any one of claims 1 to 6, wherein the barrel (40) is under a nitrogen atmosphere.

9. Apparatus according to any one of the preceding claims, wherein the iron ore powder supply means comprises a pinch valve (45).

10. An apparatus described in any one of claims 1 to 9, wherein power is supplied by renewable energy.

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