Patent Application
20250027221
The invention is related to an apparatus to produce iron by an electrolysis process.
Steel can be currently produced at an industrial scale through two main manufacturing routes. Nowadays, the 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 pig iron, releases significant quantities of CO2.
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 relies moreover on carbon fossil fuels.
Current developments thus focus on methods allowing to produce iron which release less or even no CO2 and which is carbon-neutral.
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 on the cathode and gaseous oxygen. Iron plates thus obtained may be then melted with other elements such as carbon-bearing materials and scrap in electrical furnaces to produce steel.
The continuous and automated supply of iron oxide into the electrolyte is a key component. The supply system must provide iron oxide solid particles at the rate of their consumption by the electrolyte. A loss of control of iron oxide content in the electrolyte would lead a reduction the faradaic yield and thus to a detrimental effect on the productivity of the cell. One of the problems of such control is due to the propension of iron oxide to turn pasty and sticky when wetted, especially when put on metal surfaces.
One solution would be to stir iron oxide with a liquid before supplying the suspension in the electrolyte, but this would lead to the incorporation of air into the liquid, which is to be avoided due to alkaline neutralization by carbonation from carbon dioxide in the atmosphere. Furthermore, when such stirring is manually operated, this operation is dangerous due to the proximity to the alkaline electrolyte.
An object of the present invention is to remedy the drawbacks of the prior art by providing an improved oxide supply device able to automatically discharge iron oxide powder in the electrolyte in a precisely controlled way while preventing any air contact with the powder. The aim of the invention is also to provide such device which is easy to manufacture and cost effective.
The apparatus of the invention comprises a casing including a gas-permeable anode plate, a cathode plate, both facing each other and being separated by an electrolyte chamber. The casing further includes a degassing unit comprising a gas recovery part extending along the opposite side of the gas-permeable anode plate to the chamber, said casing being provided with means for circulating an electrolyte within the electrolyte chamber which comprises and electrolyte inlet and an electrolyte outlet, and with means to supply iron ore to said electrolyte chamber, said means to supply iron ore to said electrolyte chamber comprising a twin-screw supplier provided to discharge iron ore powder into an electrolyte feed pipe in fluidic connection with the electrolyte inlet, said twin-screw supplier comprising two screws parallel to each other inside a barrel, maintaining a shaft distance A between them and rotating in opposite directions while said two screws engage with each other, said barrel extending from screw rotating drive means to a discharge opening immersed in the electrolyte flowing through the electrolyte feed pipe, and comprising an iron ore powder feed opening, said iron ore powder feed opening being connected to iron ore powder feed means.
The apparatus of the invention may also include the following optional characteristics considered individually or according to all possible combination of techniques:
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:
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.
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.
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 is notably described in the case of hematite by the following equation (1):
The electrolysis reaction thus emits gases—mainly oxygen—that must be extracted from the apparatus 1.
With reference to
In a preferred embodiment this 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.
In order to produce iron through the electrolysis reaction, the electrolyte 5—preferably a water-based solution like, for example 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 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 introduced into the apparatus 1 as a powder suspension within the electrolyte 5 through the inlet 24 as it will further described.
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 this gas is an electrical insulator, it prevents the good working of the electrolysis reaction and must be continuously evacuated outside of the casing 4.
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.
As depicted in
As illustrated in
Referring to
The basal portions of the two screws 38,39 are connected to the output shaft 35,36 while their opposite free portions 42,43 are immersed in the electrolyte 5 flowing through the electrolyte feed pipe 31.
The two screws 38,39 are provided parallel in a barrel 40, maintaining the shaft distance between them. The two screws 38,39 thus rotate in the opposite direction inside of the barrel 40 while they are engaged with each other.
The barrel 40 extends from the gear box 34 to a discharge opening 41 immersed in the electrolyte 5. The 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 the dimensions of the two screws 38,39 with a small mechanical clearance between the screws 38,39 and the barrel 40 for a low free surface of the electrolyte 5. The electrolyte 5 is therefore able to rise in the barrel 40 at least up to the level of the wall 33 of the electrolyte feed pipe 31 thereby defining a dry conveyed area and a wet conveyed area allowing to discharge the iron oxide powder into the electrolyte 5 in a non-agglomerated state.
The internal surface of the barrel 40 is advantageously rough and rifted with counter rotating spirals to provide a high friction with the two screws 38,39 in opposite rotation. This allows to prevent bridges and cavities to be formed.
The barrel 40 comprises an iron feed opening 44 through which the iron oxide powder 46 is discharged inside of the barrel 40 on the surface of the two screws 38,39 which rotate in the opposite direction, thus conveying the iron oxide powder 46 up to the discharge opening 41.
The iron feed opening 44 is connected to a valve 45, for example a pinch valve, through which the iron oxide powder 46 is supplied up to the iron feed opening 44.
The iron feed opening 44 is located above the maximum level of electrolyte inside the barrel 40 when operating. Such location allows to disperse the iron oxide powder in the electrolyte after its conveyance by the two screws 38,39 in mild mixing conditions thus avoiding any powder aggregation. These conditions achieve wetting of powder by ensuring maximum exposure to the electrolyte.
The amount of iron oxide powder 46 discharged into the electrolyte 5 is controlled by command means (not depicted) depending on the rate of consumption of the iron oxide by electrolysis.
The barrel 40 is airtight and maintained under nitrogen atmosphere, so that the dry iron oxide powder conveyed by the two screws is airless, thus avoiding any air contact with the electrolyte.
The twin-screw supplier 32 is advantageously arranged parallel to the force of gravitational attraction (vertically) to benefit from gravity assistance for conveying the iron oxide powder into the electrolyte.
Advantageously, the electrolyte feed pipe 31 is perpendicular to the twin-screw supplier 32 and is then horizontally arranged.
Referring to the
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/061745 | 12/15/2021 | WO |
