[001] The invention is related to an apparatus to produce iron by an electrolysis process.

[002] Steel can be currently produced at an industrial scale through two main manufacturing routes. Nowadays, most commonly used production route consists in 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.

[003] 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.

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

[005] 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 furnaces to produce steel.

[006] 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.

[007] An aim of the present invention is therefore to remedy the drawbacks of the prior art by providing a system for electrochemical iron production with an improved productivity. The apparatus according to the invention allows notably to provide an enhanced gas discharge while reducing electrolyte losses.

[008] For this purpose, the invention is related to 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 cell cover plate, 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 chamber, the casing further comprising a degassing unit which comprises a gas recovery part extending along the opposite side of the anode plate to the electrolyte chamber, said gas recovery part comprising a plurality of channels extending longitudinally along the anode plate and in fluidic connection with a gas outlet.

[009] The apparatus according to the invention may also include the following optional characteristics considered individually or according to all possible combination of techniques: • each channel is delimited by two lateral walls whose free edges are in contact with the anode plate,

• the channels are arranged in the thickness of the cell cover plate;

• the casing extends along a longitudinal axis and the channels extend longitudinally over the entire length of the anode plate;

• the channels extend over the entire width of the anode plate;

• the ratio between the maximum height H of each channel and the width W between the free edges of the lateral walls of each channel is from 0,5 to 5;

• two adjacent channels are separated by a rib having a thickness from 0,1 to 10mm;

• each channel has a rectangular cross section;

• each channel has a width from 4 to 20 mm and a height from 4 to 20mm;

• each channel has an ellipsoidal cross section;

• each channel has a width equal to the minor axis of the ellipse, said minor axis being from 4 to 20mm, and a height equal to half of the major axis of the ellipse, said major axis being from 4 to 20mm;

• the channels and the anode plate are in electrical contact and are made of the same electrical conductor material;

• the channels and the anode plate are made of nickel coated steel.,

• the apparatus is supplied by renewable energy.

[0010] Other characteristics and advantages of the 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:

- Figure 1 , which represents a cross-sectional view of an apparatus according to the invention;

- Figure 2, which represents a detailed cross-sectional view of the casing of figure 1 ; - Figure 3, which represents a schematic view of a cell cover plate of the casing of figure 1 ;

- Figures 4 to 6, representing different embodiments of the cell cover plate of figure 3.

[0011] 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. Similarly, should elements not be specifically referenced on one of the figures, their references may be easily found by referring oneself to another figure.

[0012] It is also noted that the figures represent mainly one embodiment of the object of the invention but other embodiments which correspond to the definition of the invention may exist. Elements in the figures are illustration and may not have been drawn to scale.

[0013] The figures primarily represent three embodiments of the subject matter of the invention, but other embodiments may be encompassed by the invention as defined.

[0014] 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 described by the following equation (1 ):

(1 ) Fe ₂ O ₃ 2Fe + -O ₂

[0015] It thus appears that the electrolysis reaction emits gases - mainly oxygen - that must be extracted from the apparatus 1 .

[0016] With reference to figure 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 16, a cover plate 28 and two lateral plates 24. The cover plate 28 comprises a cell cover plate 12 and a top cover plate 17 solidarized to said cell cover plate 12. In addition, the casing includes a gas permeable anode plate 2 facing the cell cover plate 12 and intended to be totally immersed in an electrolyte 5 and a cathode plate 3, both plates 2, 3 facing each other and being kept at the required distance with fastening means (not depicted). The casing 4 also includes an electrolyte chamber s extending longitudinally between the anode plate 2 and the cathode plate 3 up to an electrolyte evacuation chamber 27. The apparatus 1 finally comprises an electrical power source (not depicted) connected to the anode plate 2 and the cathode plate 3.

[0017] In a preferred embodiment the electrical power source 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.

[0018] 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 comprises for example an electrolyte circuit (not depicted) connected to an inlet 21 and an outlet 22 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 21 .

[0019] 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.

[0020] For this purpose, the casing 4 includes a degassing unit 7 comprising a gas recovery part 8 extending longitudinally along the side 23 of the anode plate 2 opposite 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 cell cover plate 12. Said gas recovery part 8 is thus provided to recover gases escaping through the anode plate 2. [0021] As depicted in figure 1 , the degassing unit 7 also comprises an electrolyte recirculation part 9 extending in continuity with the gas recovery part 8 up to a gas outlet 10 arranged in the casing 4. The electrolyte recirculation part 9 is provided to be at least partly filled with the electrolyte 5. In addition, said recirculation part 9 is in fluidic connection with the electrolyte chamber s. When the apparatus 1 is operating, the recirculation part 9 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 25 which is adjacent to the anode plate 2 and fluidically connected to the electrolyte chamber 6.

[0022] According to the invention and as depicted in figures 2 to 6, the gas extraction is greatly improved by the presence of a plurality of channels 11a, 11 b, 11 c in the gas recovery part 8 of the degassing unit 7. Advantageously, the channels 11 a, 11 b, 11 c are arranged in the thickness of the cell cover plate 12 and thus have the shape of grooves arranged in said cell cover plate 12. In addition, the cell cover plate 12 extends along the longitudinal axis X of the casing 4, and each channel 11 a, 11 b and 11 c extend longitudinally over the entire length of the anode plate 2, and are in fluidic connection to the gas outlet 10, increasing the gas collection efficiency on the anode plate 2 region.

[0023] Each channel 11 a - 11c can be delimited by at least two lateral walls 14, 15 which have free edges 18 in contact with the gas permeable anode plate 2. Depending on their shape, the channels 11 a - 11 c can optionally be completed by a top wall 26 running sensibly parallel to the anode plate 2. Thanks to the fact that the edges 18 of the lateral walls 14, 15 are in contact with the gas permeable anode plate 2, the channels 11 a, 11 b, 11 c can collect the gas bubbles formed during the electrolysis and floating upwards through the gas permeable anode plate 2. After being collected, the gas bubbles are efficiently guided by the channels 11 a, 11 b, 11 c towards the degassing unit 7 and the gas outlet 10, resulting in an improved gas extraction.

[0024] In addition, the contact between the channels 11 a, 11 b, 11 c and the anode plate 2 provides electrical contact between them. The electrical contact helps in achieving a constant electric potential across the gas permeable anode plate 2, increasing also the electrolysis reaction yield. For an even better electrical contact, the channels 11 a, 11 b, 11 c and the anode plate 2 can be made of the same electrically conductive material.

[0025] Advantageously the channels 11 a, 11 b, 11 c allow an efficient gas extraction keeping a good electrical conductivity between the anode plate 2 and the cathode plate 3. As a consequence, the efficiency of the electrolytic process is not reduced by the accumulation of gas at the electrodes.

[0026] According to an embodiment of the invention, the channels 11 a, 11 b and 11 c cover the entire width of the anode plate 2, increasing the region on which the gas bubbles are collected. As a result, the gas evacuation is more efficient and the efficiency of the electrolysis reaction is also increased.

[0027] According to an embodiment of the invention, the ratio R between the maximum height H of each channel 11 a, 11 b, 11 c and the width W between the free edges 18 of the lateral walls 14, 15 of each channel is from 0,5 to 5. This range of ratios guarantees an optimal gas extraction via the channels in contact with the permeable anode plate 2.

[0028] The lateral walls 14, 15 of adjacent channels 11a - 11 c define a rib separating the two adjacent channels. The rib separating two adjacent channels has a thickness from 0,1 to 1mm. The thinnest the rib is, the better the gas collection through the channels is.

[0029] Figures 4 to 6 show the cross section of the cell cover plate 12 corresponding to different embodiments of the invention in which the channels 11 a - 11 c have different shapes.

[0030] Figure 4 shows a cell cover plate 12 with channels 11 a having an elliptical shape with a ratio R between the maximum channel height H and the channel width Wfrom 0,5 to 2.

[0031] In other words, each channel 11 a has a width equal to the minor axis of the ellipse, said minor axis being from 4 to 20mm, and a height equal to half of the major axis of the ellipse, said major axis being from 4 to 20mm. [0032] Figure 5 shows a cell cover plate 12 with channels 11 b having an elliptical shape with a ratio R between the maximum channel height H and the channel width W from 1 to 5.

[0033] Figure 6 shows a cell cover plate 12 with channels 11 c having a rectangular shape with a ratio R between the maximum channel height H and the channel width Wfrom 0,5 to 5. This specific shape has the advantage of having a highest passage section and the best efficiency in terms of gas evacuation.

[0034] Table 1 shows relevant parameters of the apparatus according to the invention comprising the channel shapes of figures 4 to 6. The values are obtained from numerical simulations of the apparatus according to the invention. Global £ is the mean bubble void fraction in the entire cell and top £ the mean bubble void fraction in the top part of cell above the anode plate 2. V bubbles Top is the velocities of the bubbles in the top part of the cell and V Electrolyte Top is the velocity of the electrolyte in the top part of the cell.

Table 1

[0035] The profile of figure 6, corresponding to rectangular channels, provides concomitantly a low gas fraction in the cell as indicated by Global £ and a high electrolyte velocity at the top of the cell.

[0036] In a general way, the apparatus 1 according to the invention provides an increased electrolysis iron production yield without increasing the amount of electrolyte to be circulated in the electrolysis cell. Moreover, the efficient gas extraction keeps a reliable electrical contact between anode 2 and cathode 3 throughout the electrolysis reaction, providing an increased efficiency and reducing the power consumption.