Modular feed kit assembly for electrolytic cell

Abstract

It is disclosed a modular feed kit assembly and methods for delivering alumina powder to an electrolytic bath of an electrolytic cell. The feed kit assembly comprises a cleaning module vertically positioned over and aligned with a point of entry of the cell, and having a moving cleaning element configured to controllably move and extend downwardly trough and beyond the point of entry into the electrolytic bath; and a delivery module, for delivering alumina to the electrolytic bath through the point of entry by gravity, inclined with respect to the vertical cleaning module. The cleaning element allows cleaning the point of entry for feeding the bath with alumina from the delivery module, while clearing deposits of solid material on molten electrolyte surface of the bath, also known as bridging, that could prevent alumina powder from entering the electrolytic bath, and reducing corrosive gas entering the delivery module.

Description

 Cross-Reference to Related Applications

[0001] The present patent application claims the benefits of priority of U.S. Provisional Patent Application No. 63 / 564,112 entitled “MODULAR FEED KIT ASSEMBLY FOR ELECTROLYTIC CELL”and filed at the United States Patent and Trademark Office on March 12, 2024, the content of which is incorporated herein by reference.Field of the invention

[0002] The present invention generally relates to an apparatus and method for feeding an electrolytic cell with an electrolyte, such as alumina, for instance for the production of a metal, such as aluminum. In particular, it is disclosed a modular feed kit assembly for inert anode type electrolytic cells.Background

[0003] In conventional Hall-Heroult technology for aluminum production, alumina is fed in large batches or slugs. There is no need for small and regularly batches.

[0004] There are numerous patent publications describing alumina feeding systems for supplying fresh alumina to an operating electrolytic cell. In particular, it has been developed devices which can both reliably break through the crust on top of the electrolyte as the bath level rises and falls during the reaction and supply an appropriate dose of alumina into that hole. Other patent publications describe devices for reliably and accurately directing the flow of alumina into the hole using various types of valves, pistons, and nozzles. Recent developed techniques address ways to automate the feeding process, for example, by using measured cell parameters like cell voltage to control the feed rate of alumina.

[0005] US 4,439,964 (Aluminium Pechiney), describes a detachable assembly for spot feeding alumina to a tank for the production of aluminum. A fixed hopper is made integral with horizontal metal girders which form at least part of its side walls. The hopper is provided with a bottom aperture for discharge of alumina therethrough. An impervious metal case is positioned vertically in said hopper with the upper part of the case open and substantially at the level of the upper part of the hopper. The case has two substantially parallel vertical branches, the first branch opening, at its lower portion, outside the hopper, and the second branch opening, at its lower portion, inside the hopper, in the immediate vicinity and on the axis of the aperture for the discharge of alumina. The second branch of outside the hopper supports a vertical crust beaker having an extension of jack that moves central rod downward and moves seal into a lowered sealing position on an upper bearing surface. At the same time, seal moves downward from its bearing surface, thus allowing a dose of alumina to flow out through a tube and a dispensing spout adjacent the crust breaker, the alumina flowing directly into the aperture made in a crust of electrolyte by the crust breaker.

[0006] In US 4,439,964 cited above, both the alumina feeder and the crust breaker are a parallel and vertical position directly above the electrolyte bath, the devices being puts it in a location where the temperature is high and the atmosphere is overly corrosive, leading to a rapid deterioration of the devices. Also, the alumina flowing down from the feeder can accumulate while exiting the feeding tube on the dispensing spout, forming a crust and blocking the alumina’s dispense.

[0007] US 10,633,752 B2 (ELYSIS LIMITED PARTNERSHIP) teaches a feed system for distributing fluidized feed material having a distribution unit configured to fluidize feed material; and a control unit fluidly coupled to the distribution unit. The control unit comprises a chamber configured to hold the feed material provided from the distribution unit and a feeder unit fluidly coupled to the chamber, a second gas inlet configured to provide gas to the chamber, and a material discharge pipe fluidly coupled to the chamber and the second gas inlet. In this patent, the amount of fluidized feed material provided to the electrolytic cell is controllable for each of the plurality of control units by varying the period of time during which gas is provided to the chamber. The use of a gas impulse to fluidize the alumina leads to a highly complex equipment. The distribution unit of the feed system is also located above the bath and is therefore subject to high heat and gas corrosion. US 10,633,752 B2 also teaches the use of a crust breaker for breaking the crust formed at the bath’s surface, and which is not adapted for continuously cleaning the point of entry of the cell to allow distribution of alumina.

[0008] There is thus a need for a new feeding system for an electrolytic cell that will be capable of supplying alumina by gravity to the electrolytic cell, while being positioned to be protected from heat and corrosion, and modular to facilitate maintenance and replacement while continuing aluminum production. Summary

[0009] The shortcomings of the prior art are generally mitigated by a new assembly and method for feeding an electrolytic cell with alumina powder typically used for the electrolytic production of aluminum.

[0010] According to a first aspect, the invention is directed to a modular feed kit assembly for delivering alumina powder to an electrolytic bath contained by vertical sidewalls of an electrolytic cell, the electrolytic cell comprising at least one point of entry located above the electrolytic bath adjacent the vertical sidewalls, the feed kit assembly comprising for each of said at least one point of entry:a cleaning module vertically positioned over and aligned with the point of entry, the cleaning module comprising a moving cleaning element configured to controllably move and extend downwardly trough and beyond the point of entry into the electrolytic cell; anda delivery module for delivering alumina powder to the electrolytic bath through the point of entry by gravity, the delivery module being inclined with respect to the vertical cleaning module in order to outwardly extend from the cleaning module, the delivery module extending above and optionally beyond the sidewalls of the electrolytic cell; whereby, in use, the moving cleaning element of the cleaning module allows cleaning the point of entry for regularly feeding the electrolytic bath with alumina powder from the delivery module, while clearing deposits of solid material on molten electrolyte surface of the bath, also known as bridging, that could prevent alumina powder from entering the electrolytic bath, and reducing an amount of corrosive gas entering the delivery module.

[0011] According to a preferred embodiment, the modular feed kit assembly further comprises a modular frame for supporting the cleaning and delivery modules over the point of entry and sidewalls of the cell.

[0012] According to a preferred embodiment, the vertical cleaning module is configured to be removably attached to a sidewall insulation lining block inwardly extending form the sidewalls, the point of entry extending through the sidewall insulation lining block, the moving cleaning element being configured to extend beyond the sidewall insulation lining block into the bath. Preferably, the modular feed kit assembly further comprises a modular frame for supporting the cleaning and delivery modules over the point of entry and sidewalls of the cell, the modular frame being detachably fixed to the sidewall insulation lining block.

[0013] According to a preferred embodiment, the point of entry forms an inlet comprising a tubular element going through a top portion of the sidewall insulation lining block of the electrolytic cell andconfigured in size to let the moving cleaning element moving therethrough.

[0014] According to a preferred embodiment, the tubular element is made of copper, SiC, nickel, alumina or alloys thereof, more preferably the tubular element is made of copper.

[0015] According to a preferred embodiment, the cleaning element comprises a moving piston extending from a vertical cylinder.

[0016] According to a preferred embodiment, the cleaning module and the delivery module are removable to facilitate regular maintenance of the modular feed kit assembly.

[0017] According to a preferred embodiment, the cleaning module, the delivery module and the frame are removable to facilitate regular maintenance of the modular feed kit assembly.

[0018] According to a preferred embodiment, the modular feed kit assembly is for use for delivering up to about 6 g / s of alumina powder to the bath per modular feed kit, more preferably between about 1.5 and about 4 g / s of alumina powder to the bath per modular feed kit.

[0019] According to a second aspect, the invention is directed to an electrolytic cell for the production of aluminum by reaction of alumina, wherein the cell comprises a cell reservoir having a bottom wall and vertical sidewalls extending therefrom and configured for retaining an electrolytic bath containing molten alumina, at least one anode and one cathode configured to be immersed into the electrolytic bath, the electrolytic cell further comprising one or more modular feed kit assembly as defined herein.

[0020] According to a third aspect, the invention is directed to a method for delivering alumina powder to the electrolytic bath of the electrolytic cell as defined herein, the electrolytic bath being contained by the vertical sidewalls, the method comprising:delivering alumina powder to the electrolytic bath by gravity, the delivering being made via the inclined delivery module extending from above and beyond the vertical sidewalls to the point of entry located above the bath and adjacent the vertical sidewalls;wherein the delivering of alumina powder is made while cleaning the point of entry via the cleaning module vertically positioned over and aligned with the point of entry.

[0021] According to a fourth aspect, the invention is directed to method for delivering alumina powder to an electrolytic bath of an electrolytic cell, the electrolytic bath being contained by vertical sidewalls, the method comprising:delivering alumina powder to the electrolytic bath by gravity, the delivering being made via an inclined delivery module extending from above and beyond the vertical sidewalls to a point of entry located above the electrolytic bath and adjacent the vertical sidewalls;wherein the delivering of alumina powder is made while cleaning the point of entry via a cleaning module vertically positioned over and aligned with the point of entry.

[0022] The moving cleaning element of the cleaning module allows cleaning the point of entry for feeding of the electrolytic bath with alumina powder from the delivery module, while clearing deposits of solid material on molten electrolyte surface of the bath, also known as bridging, that could prevent alumina powder from entering the electrolytic bath, and reducing an amount of corrosive gas entering the delivery module.

[0023] The invention as disclosed herein is particularly adapted for being used with inert or oxygen evolving anodes that require multiple feed kit assembly located around the cell for regularly feeding the cell with small batches of alumina, while preserving each delivery module from heat and corrosion.

[0024] The feed kit assembly as disclosed herein is also entirely modular for easing maintenance of the electrolytic cell during production of aluminum.

[0025] Other and further aspects and advantages of the present invention will be better understood upon the reading of the illustrative embodiments about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.Brief Description of the Drawings

[0026] The above and other aspects, features and advantages of the invention will become more readily apparent from the following description, reference being made to the accompanying drawings in which:

[0027] Figure 1 is a lateral schematic illustration of a modular feed kit assembly according to a preferred embodiment;

[0028] Figure 2 is an isometric lateral schematic illustration of a modular feed kit assembly according to a preferred embodiment; and

[0029] Figure 3 is a front schematic illustration of a modular feed kit assembly according to a preferred embodiment.Detailed Description of the Preferred Embodiment

[0030] A novel apparatus and method will be described hereinafter. Although the invention is described in terms of specific illustrative embodiments, it is to be understood that the embodiments described herein are by way of example only and that the scope of the invention is not intended to be limited thereby.

[0031] The terminology used herein is in accordance with definitions set out below.

[0032] As used herein % or wt.% means weight % unless otherwise indicated. When used herein % refers to weight % as compared to the total weight percent of the phase or composition that is being discussed.

[0033] By "about", it is meant that the value of data disclosed herein can vary within a certain range depending on the margin of error of the method or device used to evaluate or measure such data. A margin of ± 10% is generally accepted.

[0034] As “electrolytic cell” or “cell” mentioned herein, it is understood a cell comprising at least one cathode or a cathode assembly having at least one cathode, such as, but not limited to vertical cathodes, and configured for receiving or interacting with at least one corresponding anode or an anode assembly having at least one anode, such as, but not limited to vertical anodes. The cell is also configured to receive an electrolytic bath of a molten electrolyte (such as cryolite) for the electrolytic production of metals, such as aluminum.

[0035] The description which follows, and the embodiments described therein are provided by way of illustration of an example of particular embodiments of principles and aspects of the present invention. These examples are provided for the purposes of explanation and not of limitation, of those principles of the invention. In the description that follows, like parts and / or steps are marked throughout the specification and the drawing with the same respective reference numerals.

[0036] As disclosed inUS 10,633,752 B2 (ELYSIS LIMITED PARTNERSHIP) cited above, the content of which is incorporated herein by reference, discontinuous feeding was used with the first generations of electrolytic cells using inert anode. However, bridging was observed under the feed kit and inside the feeding tube causing a blockage and requiring attention and maintenance. Also, with discontinuous feeding, gas can enter the feeding tube during a period when not performing a feeding operation, reducing feed kit life.

[0037] It has been discovered that feeding small amounts regularly rather than large amounts discontinuously, improves control over alumina saturation, reducing as such, even eliminating, bridging, preventing pot gas from entering the feed kit, and providing for more control over alumina saturation.

[0038] The feed kit assembly according to the present invention allows delivering a metered quantity of alumina powder into an orifice made in the “bridge” or crust above the electrolyte. The device is intended to be modular to facilitate its regular maintenance. To this end, the device is preferably placed in the cell superstructure recess, above the sidewall insulation lining bricks or blocks, and in a lateral position of the cell (on the side or periphery), for ease of removal and / or replacement. The position of the device also puts it in a location where the temperature is quite low (e.g. about 100 °C), and the atmosphere is not overly corrosive.

[0039] The structure of the feed kit device is preferably modular, can be sat and fixed on the sidewall insulation lining bricks or blocks, and as aforesaid is easily removable for maintenance, and replaceable by a new kit assembly without impacting the general aluminum production and operation of the electrolytic cell.

[0040] The modular feed kit assembly as disclosed herein is the system which deliver alumina to the electrolytic bath. The feed kit has multiple functions:1) regularly delivering alumina to the electrolytic cell;2) cleaning the delivery module of the kit, and3) clearing deposits of solid material on the molten electrolyte surface (bridging) that could prevent alumina feed from entering the electrolytic bath (or electrolyte).

[0041] The feed kit by being on a lateral position of the electrolytic cell or pot, is easier to access than in the center of the pot. The feed kit device is thus “protected” in the superstructure recess, above the sidewall insulation lining bricks or blocks where the temperature is low less than 100°C and there is nearly no vapor / fume from the bath. The material used for the upper part of the feed kit is thus not a specific one for high temperature and HF environment, reducing as such production costs.

[0042] Reference is now made to the drawings to described preferred embodiments of the disclosed technology.

[0043] As illustrated on Figures 1, 2 and 3, a modular feed kit assembly 1 for delivering alumina powder to an electrolytic bath 3 contained by vertical sidewalls 5 of an electrolytic cell 7 (partially illustrated). The electrolytic cell 7 comprising at least one point of entry 9, located above the electrolytic bath 3 adjacent the vertical sidewalls 5. As shown on Figure 1, the bath defines a bath / vapor interface 11. The sidewalls typically comprises sidewall insulation lining bricks or blocks 13 extending from the sidewalls towards the bath 3.

[0044] Typically, a cell 7 comprises multiple point of entries along its periphery. Reference can be made to Figure 1 of US 10,633,752 B2, the content of which is enclosed herewith by reference, depicting a schematic top view of a feed system with multiple points of entry. Accordingly, each of the points of entry is configured to operatively connect with one feed kit assembly according to the present invention.

[0045] A feed kit assembly 1 according to the present invention first comprises a cleaning module 100 vertically positioned over and aligned with the point of entry 9. The cleaning module 100 is therefore parallel to the cell’s vertical sidewalls. The cleaning module comprising a moving cleaning element 110 configured to controllably move and extend downwardly trough and beyond the point of entry 9 into the electrolytic cell. The cleaning element preferably comprises a moving piston 120 extending from a vertical cylinder 130.

[0046] The vertical cleaning module is configured to be removably attached to a sidewall insulation lining block 140 inwardly extending form the sidewall 5, the point of entry 9 extending through the upper insulation lining block. The moving cleaning element 110 being configured to extend beyond the lining block 140 into the bath 3. The moving piston 120 extending from a vertical cylinder 130 forms the cleaning element 110for bridge breaking (at the interface 11) and point of entry / inlet 9 cleaning.

[0047] According to a preferred embodiment, the point of entry 9 may comprise an inlet, such as for instance a tubular element going through the sidewall insulation lining block 140 above the bath 3 of the electrolytic cell, andconfigured in size to let the moving cleaning element 110 moving through it. More preferably, the tubular element is made of SiC, alumina, nickel or copper, or alloys thereof. Copper for instance preferably reacts with oxygen (vs. fluoride) to create a passivation layer without volumetric expansion, maintaining as such the physical integrity of the inlet. Nickel-Copper alloy, such as Monel®, can be used. It is worth mentioning that the presence of copper in particular does not affect the purity of the metal produced with the electrolytic cell.

[0048] A feed kit assembly 1 according to the present invention secondly comprises a delivery module 200 for delivering alumina powder to the electrolytic bath 5 through the point of entry 9 by gravity. As shown on Figures 1 and 2, the delivery module 200 may comprise a cylinder 210 inclined with respect to the vertical cleaning module 100 in order to outwardly extend from the cleaning module. Therefore, the delivery module is configured to extend above and optionally beyond the insulation lining block 13 and the sidewall 5 of the electrolytic cell 7, where the temperature is 100°C or less.

[0049] As shown on Figure 1, the delivery module may further comprise a feeding bin 220 for providing alumina to the delivery module 200 and a flow inversing system 230 allowing removing the delivery module 200 from the feed kit assembly when necessary.

[0050] The moving cleaning element 110 of the cleaning module 100 allows cleaning the point of entry 9 for regularly feeding of the electrolytic bath 3 with alumina powder from the delivery module 200. If the piston 120 is long enough, the cleaning module 100 also allows clearing deposits of solid material on molten electrolyte surface 11 of the bath 3, also known as bridging, that could prevent alumina powder from entering the electrolytic bath, and reducing an amount of corrosive gas entering the feeding or delivery module.

[0051] As shown on Figures 1, 2 and 3, the modular feed kit assembly may further comprise a modular frame 300 for supporting the cleaning and delivery modules 100, 200 over the point of entry 9 and sidewalls 5, 13 of the cell 7. To ease maintenance, the modular frame 300 is also detachably fixed to the sidewall insulation lining block 140.

[0052] The cleaning module 100, the delivery module 200 and the frame 300 are removable to facilitate regular maintenance of the modular feed kit assembly 1.

[0053] Each of the modular feed kit assembly as disclosed here can be installed on the edge of the cell and be further protected by a shield (not illustrated) configured to contain the cleaning module 100, the delivery module 200 and the frame 300. The shield can be also modular, easily detachable from the cell for maintenance.

[0054] Each modular feed kit assembly according to the present invention can be used for delivering up to up to about 6 g / s, preferably between about 1.5 and about 4g / s of alumina powder to the bath.

[0055] According to another aspect, the present invention thus provides a method for delivering alumina powder to an electrolytic bath 3 of an electrolytic cell 7, the electrolytic bath 3 being contained by vertical sidewalls 5. The method comprises at least the step of delivering alumina powder to the electrolytic bath by gravity, the delivering being made via an inclined delivery module 200 extending from above and beyond the sidewalls 5, 13 to a point of entry 9 located above the bath 3 and adjacent the vertical sidewalls 5, 13. The delivering of alumina powder is made while cleaning the point of entry 9 via a cleaning module 100 vertically positioned over and aligned with the point of entry 9.

[0056] The cleaning module as disclosed herein has different functions comprising cleaning the point of entry or inlet 9 to assure regular feeding of the bath, reducing and / or eliminating the bridging or crust formed at the interface bath / vapor 7, and reducing the amount of corrosive gas entering the feed kit. It is to be understood that the cleaning element can be a straight shaft 110 as shown on Figure 1 for instance. The alumina flow can be then controlled by varying the number of feed kit assemblies feeding at a time.

[0057] The modular feed kit assembly and method thereof disclosed herein allows putting a seal-leg on the feeding / delivery tubes, reducing and / or eliminating the bridging and reducing the amount of corrosive gas entering the feed kit.

[0058] While illustrative and presently preferred embodiments of the invention have been described in detail hereinabove, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art. 

Claims

1. A modular feed kit assembly for delivering alumina powder to an electrolytic bath contained by vertical sidewalls of an electrolytic cell, the electrolytic cell comprising at least one point of entry located above the electrolytic bath adjacent the vertical sidewalls, the feed kit assembly comprising for each of said at least one point of entry:a cleaning module vertically positioned over and aligned with the point of entry, the cleaning module comprising a moving cleaning element configured to controllably move and extend downwardly trough and beyond the point of entry into the electrolytic cell; anda delivery module for delivering alumina powder to the electrolytic bath through the point of entry by gravity, the delivery module being inclined with respect to the vertical cleaning module in order to outwardly extend from the cleaning module, the delivery module extending above and optionally beyond the sidewalls of the electrolytic cell; whereby, in use, the moving cleaning element of the cleaning module allows cleaning the point of entry for regularly feeding the electrolytic bath with alumina powder from the delivery module, while clearing deposits of solid material on molten electrolyte surface of the bath, also known as bridging, that could prevent alumina powder from entering the electrolytic bath, and reducing an amount of corrosive gas entering the delivery module.

2. The modular feed kit assembly according to claim 1, further comprising a modular frame for supporting the cleaning and delivery modules over the point of entry and sidewalls of the cell.

3. The modular feed kit assembly according to claim 1, wherein the vertical cleaning module is configured to be removably attached to a sidewall insulation lining block inwardly extending form the sidewalls, the point of entry extending through the sidewall insulation lining block, the moving cleaning element being configured to extend beyond the sidewall insulation lining block into the bath.

4. The modular feed kit assembly according to claim 3, further comprising a modular frame for supporting the cleaning and delivery modules over the point of entry and sidewalls of the cell, the modular frame being detachably fixed to the sidewall insulation lining block.

5. The modular feed kit assembly according to claim 3 or 4, wherein the point of entry forms an inlet comprising a tubular element going through a top portion of the sidewall insulation lining block of the electrolytic cell andconfigured in size to let the moving cleaning element moving therethrough.

6. The modular feed kit assembly according to claim 5, wherein the tubular element is made of copper, SiC, nickel, alumina or alloys thereof.

7. The modular feed kit assembly according to claim 6, wherein the tubular element is made of copper.

8. The modular feed kit assembly according to any one of claims 1 to 7, wherein the cleaning element comprises a moving piston extending from a vertical cylinder.

9. The modular feed kit assembly according to any one of claims 1 to 8, wherein the cleaning module and the delivery module are removable to facilitate regular maintenance of the modular feed kit assembly.

10. The modular feed kit assembly according to claim 2 or 4, wherein the cleaning module, the delivery module and the frame are removable to facilitate regular maintenance of the modular feed kit assembly.

11. The modular feed kit assembly according to any one of claims 1 to 10, for use for delivering up to about 6 g / s of alumina powder to the bath per modular feed kit.

12. The modular feed kit assembly according to any one of claims 1 to 11, for use for delivering up to between about 1.5 and about 4 / s of alumina powder to the bath per modular feed kit.

13. An electrolytic cell for the production of aluminum by reaction of alumina, wherein the cell comprises a cell reservoir having a bottom wall and vertical sidewalls extending therefrom and configured for retaining an electrolytic bath containing molten alumina, at least one anode and one cathode configured to be immersed into the electrolytic bath, the electrolytic cell further comprising one or more modular feed kit assembly as claimed in any one of claims 1 to 12.

14. A method for delivering alumina powder to the electrolytic bath of the electrolytic cell as claimed in claim 13, the electrolytic bath being contained by the vertical sidewalls, the method comprising:delivering alumina powder to the electrolytic bath by gravity, the delivering being made via the inclined delivery module extending from above and beyond the vertical sidewalls to the point of entry located above the electrolytic bath and adjacent the vertical sidewalls;wherein the delivering of alumina powder is made while cleaning the point of entry via the cleaning module vertically positioned over and aligned with the point of entry.

15. A method for delivering alumina powder to an electrolytic bath of an electrolytic cell, the electrolytic bath being contained by vertical sidewalls, the method comprising:delivering alumina powder to the electrolytic bath by gravity, the delivering being made via an inclined delivery module extending from above and beyond the vertical sidewalls to a point of entry located above the electrolytic bath and adjacent the vertical sidewalls;wherein the delivering of alumina powder is made while cleaning the point of entry via a cleaning module vertically positioned over and aligned with the point of entry.

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