Electrolysis apparatus for the production of iron with an improved gas permeable anode plate

Abstract

An apparatus for the production of iron through reduction of iron ore by an electrolysis reaction, the electrolysis reaction emitting a gas, the apparatus including a casing including a gas-permeable anode plate being made of a cellular material, a cathode plate, both facing each other and being separated by an electrolyte chamber, the gas-permeable anode plate being made of a cellular material including a plurality of cells, each cell being delimited by a circumferential wall and being open on the two opposite sides of the gas-permeable anode plate, the circumferential wall being made from a plurality of metallic sheets which are interlocked together with interlocking means.

Description

[0001] The present invention is related to an apparatus to produce iron by an electrolysis process.BACKGROUND

[0002] Steel can be currently produced at an industrial scale through two main manufacturing routes. Nowadays, the most commonly used production route consists of producing pig iron in a blast furnace, by use of a reducing agent, mainly coke, to reduce iron oxides. In this method, approx. 450 to 600 kg of coke, is consumed per metric ton of pig iron. this method, both in the production of coke from coal in a coking plant and in the production of the pig iron, releases significant quantities of CO2.SUMMARY OF THE INVENTION

[0003] The second main route involves so-called “direct reduction methods”. Among them are methods according to the brands MIDREX, FINMET, ENERGIRON / HYL, COREX, FINEX etc., in which sponge iron is produced in the form of HDRI (Hot Direct Reduced Iron), CDRI (cold direct reduced iron), or HBI (hot briquetted iron) from the direct reduction of iron oxide carriers. Sponge iron in the form of HDRI, CDRI, and HBI usually undergo further processing in electric arc furnaces. Even if this second route emits less CO2 than the previous one, it still releases some and rely moreover on carbon fossil fuels.

[0004] Current developments thus focus on methods allowing to produce iron which release less or even no CO2 and which is carbon-neutral.

[0005] A known alternative method to produce steel from iron ores is based on electrochemical techniques. In such techniques, iron is produced from iron oxide using an electrolyser unit comprising two electrodes—an anode and a cathode—connected to a source of electric current, an electrolyte circuit and an iron oxide entry into the electrolyser unit. The anode and cathode are constantly immersed in the circulating electrolyte in order to ensure good electrical conduction between said electrodes. The electrolytic reaction produces pure iron plates at the cathode and gaseous oxygen at the anode. Iron plates thus obtained may be then melted with other elements such as carbon-bearing materials and / or scrap in electrical or smelting furnaces to produce either steel or pig iron.

[0006] One of the problems of existing electrolysis cells is the gas accumulation. Indeed, gases formed by the electrolysis reactions tend to remain trapped between the anode and the cathode where they accumulate. Gaseous oxygen being an electrical insulator, it has a detrimental effect on the electrical conduction between the electrodes and thus on the productivity of the cell. One solution would be to have a continuous extraction of the electrolyte containing said gases, but this would mean a constant supply of fresh electrolyte which would also be detrimental to the productivity and to the environmental footprint of the process.

[0007] Another solution is to have a permeable anode allowing the electrolyte to pass through, thus drawing the gases out of the space between the anode and the cathode. However, the permeability has to be controlled in order to be able to evacuate continuously the gases without disturbing the electrolysis reaction. An aim of the present invention is therefore to remedy the drawbacks of the prior art by providing a gas permeable anode ensuring an improved extraction of the gases formed by the electrolysis reactions. The aim of the invention is also to provide an anode which is easy to manufacture and cost effective.

[0008] The present invention provides an apparatus for the production of iron through reduction of iron ore by an electrolysis reaction, said electrolysis reaction emitting a gas, the apparatus comprising a casing including a gas-permeable anode plate, a cathode plate, both facing each other and being separated by an electrolyte chamber said casing being provided with means for circulating an electrolyte within the electrolyte chamber and with means to supply iron ore to said electrolyte chamber, the casing further including a degassing unit comprising a gas recovery part extending along the opposite side of the gas-permeable anode plate to the chamber and being able to recover gas from the electrolysis reaction escaping through the gas-permeable anode plate, said gas-permeable anode plate being made of a cellular material comprising a plurality of cells extending from the electrolyte chamber to the gas recovery part, each cell being delimited by a circumferential wall and being open on the two opposite sides of the gas-permeable anode plate, said circumferential wall of each cell being made from a plurality of metallic sheets which are interlocked together with interlocking means.

[0009] The apparatus of the invention may also include the following optional characteristics considered individually or according to all possible combination of techniques:

[0010] The interlocking mean comprises transverse notches extending at least from a longitudinal edge of the considered metallic sheet,

[0011] each cell is made from three straight metallic sheets coming respectively from a first, a second and a third set of metallic sheets, thus having a triangular cross section,

[0012] two adjacent cells share a common cell straight wall,

[0013] the space between two adjacent interlocking mean is the same for each sheet, of each set of sheets, the circumferential wall of each cell thus having an equilateral triangular cross section,

[0014] the equilateral triangle of the cross section of each circumferential wall is defined according to the formula eS / h<0.1, eS being the thickness of the triangular circumferential wall and h being the height of the triangle,

[0015] all sheets have the same thickness eS,

[0016] the thickness eA of the anode is constant,

[0017] all sheets have the same width W and wherein the cumulated length of one transverse notch of the sheets of the first and second sets of sheets, and of one transverse notch of the sheets of the third set of sheets equals the width W of said sheets, and wherein the length of one notch of the sheets of the third set of sheets is smaller than half the width of any sheet,

[0018] the gas-permeable anode plate is made of nickel alloy,

[0019] the metallic sheets have a surface coating,

[0020] said surface coating is an anti-corrosion coating, and

[0021] the apparatus is electrically supplied by renewable energy.

[0022] The present invention also provides a method for the assembling of a gas-permeable anode plate for an apparatus according to the invention the method comprising:

[0023] Providing a first set of n metallic straight sheets and a second set of n metallic straight sheets, n being an integer greater than two,

[0024] Interlocking one sheet of the second set of sheets with all the sheets of the first set of sheets via transverse notches extending at least from a longitudinal edge of the considered sheet, wherein each interlocking edge is formed by interlocking at least one notch of one sheet of one set of sheets with one notch of one sheet of another set of sheets, and

[0025] Repeating the preceding step until all sheets of the first and second sets of sheets are interlocked with each other forming (n-1)2 cells of the cellular material of the gas-permeable anode plate.

[0026] The method may also include the following optional characteristics considered individually or according to all possible combination of techniques:

[0027] Providing a third set of 2n-3 straight sheets, the sheets of the first set of sheets being regularly spaced and the sheets of the second set of sheets being regularly spaced,

[0028] Interlocking one sheet of the third set of sheets with interlocking edges via transverse notches extending at least from a longitudinal edge of the considered sheet, each interlocking edge being the intersecting edge between two sheets of the first and second sets of sheets, and

[0029] Repeating the preceding steps until all sheets of the third set of sheets are interlocked with the n2 interlocking edges forming 2(n-1)2 cells of the cellular material of the cellular anode plate, the cells having a triangular cross section and the sheets of the third set of sheets being regularly spaced.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other characteristics and advantages of the present invention will be apparent in the below descriptions, by way of indication and in no way limiting, and referring to the annexed figures among which:

[0031] FIG. 1, which represents a longitudinal section view of an apparatus according to the invention,

[0032] FIG. 2, which represents three plane metallic sheets interlocking to each other,

[0033] FIG. 3, which represents a perspective view of the cellular material constituting the anode plate, and

[0034] FIG. 4, which represents a top view of the cellular material of FIG. 3.DETAILED DESCRIPTION

[0035] First, it is noted that on the figures, the same references designate the same elements regardless of the figure on which they feature and regardless of the form of these elements.

[0036] It is also noted that the figures represent mainly one embodiment of the invention but other embodiments which correspond to the definition of the invention may exist.

[0037] Elements in the figures are illustration and may not have been drawn to scale.

[0038] The invention refers to an apparatus 1 provided for the production of iron metal (Fe) through the reduction of iron ore, containing notably hematite (Fe2O3) and other iron oxides or hydroxides, by an electrolysis reaction. Said chemical reaction is well known and may be described by the following equation (1):  (1) Fe2O3↔2Fe+3 / 2I2

[0039] It thus appears that the electrolysis reaction emits gases—mainly oxygen—that must be extracted from the apparatus 1.

[0040] With reference to FIG. 1, the apparatus 1 comprises a casing 4 extending along a longitudinal axis X in which the electrolysis reaction occurs. Said casing 4 is delimited by a base plate 20, a cover plate 13 and two lateral plates 21. In addition, the casing 4 includes a gas permeable anode plate 2 intended to be totally immersed in an electrolyte 5 and a cathode plate 3, both plates facing each other and being kept at required distance with fastening means. The casing 4 also includes an electrolyte chamber 6 extending longitudinally between the anode plate 2 and the cathode plate 3 up to an evacuation chamber 22. The apparatus 1 finally comprises an electrical power source connected to the anode plate 2 and the cathode plate 3.

[0041] In order to produce iron through the electrolysis reaction, the electrolyte 5—preferably a water-based solution like a sodium hydroxide aqueous solution—flows through the casing 4 inside the electrolyte chamber 6 while the apparatus 1 is operating. The apparatus 1 thus comprises means for circulating the electrolyte which may comprise an electrolyte circuit connected to an inlet 24 and an outlet 25 managed in the casing 4 and both fluidically connected to the electrolyte chamber 6. Iron ore is preferentially introduced into the apparatus 1 as a powder suspension within the electrolyte 5 through the inlet 24.

[0042] During the electrolysis reaction, oxidised iron is reduced to iron according to reaction (1) and reduced iron is deposited on the cathode plate 3 while gaseous oxygen is emitted inside the casing 4. Since these gases are electrical insulator, they prevent the good working of the electrolysis reaction and must be continuously evacuated outside of the casing 4.

[0043] For this purpose, the casing 4 includes a degassing unit 7 comprising a gas recovery part 8 extending longitudinally along the opposite side 27 of the anode plate 2 to the electrolyte chamber 6. This gas recovery part 8 is a compartment provided to be filled with the electrolyte 5 and disposed between the anode plate 2 and the cover plate 13. Said gas recovery part 8 is thus provided to recover gases escaping through the anode plate 2.

[0044] As depicted in FIG. 1, the degassing unit 7 also comprises an electrolyte recirculation part 28 extending in continuity with the gas recovery part 8 up to a gas outlet 29 managed in the casing 4. The electrolyte recirculation part 28 is provided to be at least partly filled with the electrolyte 5. In addition, said recirculation part 28 is in fluidic connection with the electrolyte chamber 6. When the apparatus 1 is operating, the recirculation part 28 allows the electrolyte 5 flowing from the gas recovery part 8 to be redirected towards the electrolyte chamber 6 via for example an elbow duct 30 of the electrolyte recirculation part 28 which is adjacent to the anode plate 2 and fluidically connected to the electrolyte chamber 6.

[0045] With reference to FIGS. 2 to 4 and according to the invention, the gas permeable anode plate 2 is made of a cellular material comprising a plurality of cells 9. Each cell 9 is delimited by a circumferential wall 10 and opened on both opposite sides of the anode plate 2, thus extending from the electrolyte chamber 6 to the gas recovery part 8 (see FIG. 1). Such configuration allows the gas bubbles to flow together with the electrolytes 5 through the anode plate 2 for the gas evacuation.

[0046] In addition to its role for the evacuation of gas bubbles, the gas permeable anode plate 2 must contribute to a homogeneous electrolysis reaction to generate a uniform growth of the iron deposit. Moreover, the gas permeable anode plate 2 must be sufficiently robust to withstand environmental conditions, particularly to withstand continuous immersion into the electrolyte 5 and continuous submission to an anodic current. Especially, the electrolyte may comprise caustic soda at a concentration of 50% and thin iron oxide particles (10-40 μm diameter). The temperature inside the casing 4 may be from 100 to 130° C. The power supplied to the electrodes may be of 5 VDC for a current intensity of about 1000 A / m2 .

[0047] To this end, the cellular material constituting the gas permeable anode plate 2 comprises a plurality of cells 9 extending from the electrolyte chamber 6 to the gas recovery part 8. The cells 9 are periodically repeated on the anode plate 2 for both gas evacuation and uniformity of electrical conduction purpose. Moreover, the circumferential wall 10 delimiting each cell 9 is made from a plurality of metallic sheets 12a, 12b, 12c which are interlocked together via interlocking mean. This interlocking mean preferentially comprising notches 17a, 17b1, 17b2, 17c. Such configuration makes it possible to avoid welding spots in the manufacture of the anode plate 2, thus facilitating the flow of gases through the cells 9 since gas bubbles tends to adhere to welding spots.

[0048] Moreover, as there is no need to weld the metallic sheets together it is possible to apply a coating and thus to offer more possibilities in terms of surface treatment of the anode. This was not possible with anodes according to prior art as the welding and the mechanical constraints applied to form the anode would have deteriorated the coating. This coating may be for example an anti-corrosion coating allowing to increase lifetime of the anode.

[0049] More precisely, the anode plate 2 is made of three sets of spaced metallic sheets 19a, 19b, 19c, typically a first set 19a, a second set 19c and a third set of regularly spaced metallic sheets 19b which are interlocked together, preferably via transverse notches 17a, 17b1, 17b2, 17c, so that each cell 9 is made from three metallic sheets 12a-12c thus having a triangular cross-section. In other words, the three sets 19a-19c of interlocked metallic sheets 12a-12c define a plurality of triangular cross-section cells 9 for each of which the circumferential wall 10 is made from one metallic sheet 12a of the first set of sheets 19a, one metallic sheet 12c of the second set of sheets 19c and one metallic sheet 12b of the third set of sheets 19b.

[0050] The sheets 12a-12c of all sets of sheets 19a-19c preferably have the same general shape and the same dimensions: each sheet 12a-12c has a rectangular shape with two longitudinal opposite edges 20a, 20b1, 20b2, 20c and two transverse opposite edges. The sheets 12a-12c have a thicknesses which corresponds to the thickness of their longitudinal edges. Each sheet 12a, 12c of the first and second sets of sheets 19a, 19c preferably comprises n regularly spaced transverse notches 17a, 17c extending from one longitudinal edge 20a, 20c, while each sheet 12b of the third set of sheets 19b comprises n first regularly spaced transverse notches 17b1 extending from one longitudinal edge 20b1 and n second regularly spaced transverse notches 17b2 extending from the opposite longitudinal edge 20b2 of said sheet 12b and facing the first transverse notches 17b1, n being an integer greeter than 1. The notches 17a, 17b1, 17b2, 17c thus define a plurality of cell straight walls 11 respectively part of the first 19a, second 19c and third set of sheets 19b.

[0051] More preferably, the space between two adjacent notches 17a-17c is the same for each sheet 12a-12c of the first 19a, second 19c and third set of sheets 19b, so that the circumferential wall 10 of each cell 9 has an equilateral triangular cross-section.

[0052] Preferably, all sheets 12a, 12b, 12c of the first, second and third set of sheets 19a, 19b, 19c have the same width W, and the cumulated length of:

[0053] one transverse notch 17a, 17c of the sheets 12a, 12c of the first and second sets of sheets 19a, 19c, and

[0054] one transverse notch 17b1, 17b2 of the sheets 12b of the third set of sheets 19b is equal to the width W of said sheets 12a, 12b, 12c so that the thickness es of the anode is constant all along the anode plate 2 and is equal to the width W of each sheet 12a-12c, making the manufacture of the apparatus 1 for producing iron easier, cheaper and quicker. In addition, the length of one notch 17b1, 17b2 of the sheets 12b of the third set of sheets 19b is smaller than half the width W of any sheet 12a-12c in order to keep enough structural resistance to the sheets 12b of the third set of sheets 19b.

[0055] The width W is defined as the distance between the two respective longitudinal edges 20a, 20b1, 20b2, 20c of a sheet 12a-12c.

[0056] The thickness eA of the anode is defined as the distance between the top and the bottom of the anode, the bottom side being the one facing the electrolyte chamber 6 while the top is the opposite side facing the gas recovery part 8.

[0057] Moreover, two adjacent cells 9 of the cellular material are directly contiguous by sharing one common straight wall 11. Each cell 9 therefore shares its straight walls 11 with three other surrounding cells 9. Such configuration allows to maximize the number of gas evacuation cells 9 while having a uniform thickness eS of metal for enhancing the electrical conduction. Such configuration also plays a role in the robustness of the anode plate 2 since the constraints which may be applied to the anode plate 2 are uniformly distributed over its entire surface.

[0058] A manufacturing method of the anode plate 2 is now described regarding FIGS. 2 and 3.

[0059] In a first step, a first set 19a of n metallic straight sheets 12a and a second set 19b of n metallic straight sheets 12b are provided, n being an integer greater than 2. The sheets 12a of the first set 19a each have n notches 17a extending from one longitudinal edge 20a, while the sheets 12b of the second set 19b each have n first notches 17b1 extending from one longitudinal edge 20b1 of the sheet 12b and n second notches 17b2 extending from the opposite longitudinal edge 20b2 of said sheet 12b and facing the first notches 17b1. In other words, each sheet 12b of the third set of sheets 19b comprises n couple of opposite and aligned notches 17b1, 17b2.

[0060] In a second step, one sheet 12b of the second set of sheets 19b is interlocked with all the sheets 12a of the first set of sheets 19a via the considered transverse notches 17a, 17b1, defining interlocking edges 18. At this step, each interlocking edge 18 is thus formed by interlocking at least one notch 17a of one sheet 12a of the first set of sheets 19a with one notch 17b1 of one sheet 12b of the second set of sheets 19b.

[0061] The second step is repeated until all sheets 12a, 12b of the first and second sets of sheets 19a, 19b are interlocked with each other, forming (n-1)2 quadrilateral cavities, since the sheets 12a of the first set of sheets 19a and the sheets 12b of the second set of sheets 19b are regularly spaced.

[0062] In a third step, a third set of 2n-3 sheets 19c is provided, each sheet 12c comprising n notches 17c extending from one longitudinal edge 20c.

[0063] In a fourth step, one sheet 12c of the third set of sheets 19c is interlocked via its transverse notches 17c with the transverse notches 17a of sheets 12a of the first set 19a and with the second notches 17b2 of sheets 12b of the second set 19b. At this step, each interlocking edge 18 is thus formed by interlocking at least one notch 17a of one sheet 12a of the first set of sheets 19a with one notch 17b1 of one sheet 12b of the second set of sheets 19b and by interlocking the opposite notch 17b2 of said sheet 12b of the second set of sheets 19b with one notch 17c of one sheet 12c of the third set of sheets 19c.

[0064] The fourth step is repeated until all sheets 12c of the third set of sheets 19c are interlocked with the n 2 interlocking edges 18 forming 2(n-1)2 cells 9 of the cellular material of the cellular anode plate 2, the cells 9 having a triangular cross section and the sheets 12c of the third set of sheets 19c being regularly spaced.

[0065] Such method implies robustness of the resulting anode plate 2 while being easy to implement and cost effective.

[0066] The cellular material and therefore the resulting anode plate 2 are advantageously made of nickel alloy, for example commercialised under the tradename Nickel® 200 or Nickel® 201.

[0067] In a preferred embodiment this electrical power source supplying the apparatus 1 uses renewable energy which is defined as energy that is collected from renewable resources, which are naturally replenished on a human timescale, including sources like sunlight, wind, rain, tides, waves, and geothermal heat. In some embodiments, the use of electricity coming from nuclear sources can be used as it is not emitting CO2 to be produced. This further limit the CO2 footprint of the iron production process.Example

[0068] The anode plate 2 which is obtained with the previously described method is made of Nickel® 200 or Nickel® 201. The cellular material is made of metallic sheet which are interlocked together without welding as previously described. The thickness es of the circumferential wall 10 of each cell 9 is of 0,25 mm and the height h of the triangle of each cell 9 is of 3,175 mm. The ratio between the thickness e and the distance h is therefore of 0,079. In a general manner, e / h<0.1. The surface of the anode plate 2 is about 2,75 m2.

[0069] The anode plate 2 according to the invention promotes good evacuation of the gases outside of the electrolyte chamber 6 and therefore allows a good productivity of the electrolyte cell while being easily manufactured and cost effective.

Claims

1. -15. (canceled)16. An apparatus for production of iron through reduction of iron ore by an electrolysis reaction, the electrolysis reaction emitting a gas, the apparatus comprising:a casing including a gas-permeable anode plate, a cathode plate, both facing each other and being separated by an electrolyte chamber, the gas-permeable anode plate having a side facing the cathode plate,the casing being provided with a circulator for circulating an electrolyte within the electrolyte chamber and with a supply to supply iron ore to the electrolyte chamber,the casing further including a degassing unit including a gas recovery part extending along an opposite side of the gas-permeable anode plate to the chamber and being able to recover gas from the electrolysis reaction escaping through the gas-permeable anode plate, the gas-permeable anode plate being made of a cellular material including a plurality of cells extending from the electrolyte chamber to the gas recovery part, each cell being delimited by a circumferential wall and being open on the side and the opposite side of the gas-permeable anode plate, the circumferential wall of each cell being made from a plurality of metallic sheets interlocked together via an interlock.

17. The apparatus as recited in claim 16 wherein the interlock includes transverse notches extending at least from a longitudinal edge of a respective sheet of the plurality of metallic sheets.

18. The apparatus as recited in claim 16 wherein each cell is defined by three straight metallic sheets of the plurality of metallic sheets coming respectively from a first, a second and a third set of the metallic sheets, each cell having a triangular cross section.

19. The apparatus as recited in claim 18 wherein two adjacent cells of the cells share a common cell straight wall.

20. The apparatus as recited in claim 18 wherein a space between two adjacent interlock locations is the same for each sheet of each set of sheets, the circumferential wall of each cell thus having an equilateral triangular cross section.

21. The apparatus as recited in claim 20 wherein the equilateral triangle of the cross section of each circumferential wall is defined according to the formula eS / h<0.1, eS being a thickness of the triangular circumferential wall and h being a height of the triangle.

22. The apparatus as recited in claim 16 wherein all sheets of the plurality of metallic sheets have a same thickness.

23. The apparatus as recited in claim 16 wherein a thickness of the anode is constant.

24. The apparatus as recited in claim 17 wherein all sheets of the plurality of metallic sheets have a same width and wherein a cumulated length of one transverse notch of the sheets of the first and second sets of sheets, and of one transverse notch of the sheets of the third set of sheets equals the width of the sheets, and wherein a length of one notch of the sheets of the third set of sheets is smaller than half the width of any sheet of the plurality of metallic sheets.

25. The apparatus as recited in claim 16 wherein the gas-permeable anode plate is made of nickel alloy.

26. The apparatus as recited in claim 16 wherein the metallic sheets have a surface coating.

27. The apparatus as recited in claim 26 wherein the surface coating is an anti-corrosion coating.

28. The apparatus as recited in claim 16 wherein the apparatus is electrically supplied by renewable energy.

29. A method for assembling the apparatus as recited in claim 16, the method comprising:providing a first set of n metallic straight sheets and a second set of n metallic straight sheets, n being an integer greater than two,interlocking one sheet of the second set of sheets with all the sheets of the first set of sheets via transverse notches extending at least from a longitudinal edge of the considered sheet, wherein each interlocking edge is formed by interlocking at least one notch of one sheet of one set of sheets with one notch of one sheet of another set of sheets,repeating the preceding step until all sheets of the first and second sets of sheets are interlocked with each other forming (n-1)2 cells of the cellular material of the gas-permeable anode plate.

30. The method as recited in claim 29 further comprising:providing a third set of 2n-3 straight sheets, the sheets of the first set of sheets being regularly spaced and the sheets of the second set of sheets being regularly spaced,interlocking one sheet of the third set of sheets with interlocking edges via transverse notches extending at least from a longitudinal edge of the considered sheet, each interlocking edge being the intersecting edge between two sheets of the first and second sets of sheets, andrepeating the preceding step until all sheets of the third set of sheets are interlocked with the n2 interlocking edges forming 2(n-1)2 cells of the cellular material of the cellular anode plate, the cells having a triangular cross section and the sheets of the third set of sheets being regularly spaced.

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