WO2023233190A1

WO2023233190A1 - A magnetic shielding assembly for balancing magnetic field in an electrolytic cell assembly

Info

Publication number: WO2023233190A1
Application number: PCT/IB2022/056579
Authority: WO
Inventors: Bibhudatta MOHANTY; Nitin Tiwari; Shubham Kurvey
Original assignee: Vedanta Limited (Aluminium & Power)
Priority date: 2022-06-03
Filing date: 2022-07-18
Publication date: 2023-12-07

Abstract

Examples of an electrolytic cell assembly including a cost-effective, efficient, and user-friendly magnetic shielding assembly are described. The approaches of the present subject matter balances the magnetic field responsible for MHD instability and noise in the electrolytic cell assembly of an aluminum smelting apparatus. In one example, the electrolytic cell assembly includes a housing which may house a plurality of components of the electrolytic cell assembly. The cell assembly may further include a plurality of magnetic sensors to monitor a magnetic field at a plurality of locations in and around the electrolytic cell assembly. Based on the monitored magnetic field, at least one of a plurality of regions of high magnetic field in the electrolytic cell assembly may be determined, and a magnetic shielding assembly including a plurality of shielding plates may then be installed on at least one of the plurality of determined regions.

Description

A MAGNETIC SHIELDING ASSEMBLY FOR BALANCING MAGNETIC FIELD IN AN ELECTROLYTIC CELL ASSEMBLY

TECHNICAL FIELD

[0001] The present disclosure relates to the field of aluminum smelters. More particularly the present disclosure relates to a cost-effective, efficient, and user-friendly solution for balancing the magnetic field responsible for Magnetohydrodynamics (MHD) instability and noise in pots of an aluminum smelter, which can be easily modified and implemented in any pot according to the pot’s design.

BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Aluminum smelting is the process of extracting aluminum from its oxide, alumina, generally by the Hall-Heroult process, which is an electrolysis process. An aluminum smelter consists of a large number of electrolytic cells (pots) in which the electrolysis takes place, each of which is capable of producing aluminum. Conventional electrolytic cells (pots) are made of a steel shell with a series of insulating linings of refractory materials. The cell consists of a brick-lined outer steel shell as a container and support. Inside the shell, cathode blocks are cemented together by ramming paste. The top lining of the cathode block remains in contact with the molten metal and acts as the cathode. The molten electrolyte is maintained at a high temperature inside the cell. Further, prebaked anode made of carbon in the form of large sintered blocks is suspended in the electrolyte. The electrolyte is generally a molten bath of cryolite (Na^AlF,-,) and dissolved alumina. Upon energization of the cathode and anode by supplying electrical current therethrough, the electrolysis reduction takes place, wherein aluminum is produced by the electrolytic reduction of aluminum oxide dissolved in the molten cryolite.

[0004] An aluminum smelter typically comprises several hundred electrolytic cells aligned transversely in parallel rows and connected in series. An electrolysis current of the order of several hundred thousand amperes passes through these electrolytic cells, which creates a large magnetic field. The vertical component of this magnetic field, which is mainly produced by the linking conductors delivering current from one electrolytic cell to the next, is known to cause instabilities known as magnetohydrodynamic (MHD) instabilities. MHD plays an important role in the performance of electrolysis cells. These MHD instabilities are known to reduce the performance of the process. The vertical component of this magnetic field leads to pot noise and pot instability, therefore, there is a need to reduce the effect of the vertical component of the magnetic field (Bz) on the cell.

[0005] The existing technologies for reducing this magnetic field in aluminum smelters involve a magnetic compensation loop. These existing technologies include an electrical compensating circuit extending under or around the aluminum smelter and which can be traversed by a compensating current in the opposite direction to that of the electrolysis current in order to compensate the vertical component of the generated magnetic field. However, the magnetic compensation loop is highly expensive and requires expert guidance for installation. Besides, the compensation loop cannot be installed in a single pot separately as it requires a lot of design modifications in the present design.

[0006] There is, therefore, a need to overcome the above drawback, limitations, and shortcomings associated with the existing aluminum smelters and magnetic field compensation techniques, and provide a cost-effective, efficient, and user-friendly solution for balancing the magnetic field responsible for Magnetohydrodynamics (MHD) instability and noise in pots of an aluminum smelter using shielding plates, which can be easily modified and implemented in any pot according to the pot’s design.

BRIEF DESCRIPTION OF DRAWINGS

[0007] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.

[0008] In the figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. [0009] FIG. 1 illustrates an exemplary view depicting higher magnetic field regions of an electrolytic cell, where the shielding plates of the proposed magnetic shielding assembly are to be configured, in accordance with an embodiment of the present disclosure;

[0010] FIG. 2A illustrates an exemplary plot depicting voltage comparison before and after placement of the shielding plate in the cell, in accordance with an embodiment of the present disclosure;

[0011] FIG. 2B illustrates an exemplary plot depicting voltage comparison after the removal of the shielding plate in the cell, in accordance with an embodiment of the present disclosure;

[0012] FIG. 2C illustrates an exemplary plot depicting noise and Xs AIF3 comparison before and after placement of the shielding plate in the cell, in accordance with an embodiment of the present disclosure; and

[0013] FIG. 3 illustrates an exemplary modeling validation of magnetic field reduction using the proposed assembly, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0014] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0015] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some

[0016] Embodiments of the present disclosure relate to a cost-effective, efficient, and user-friendly solution for balancing the magnetic field responsible for Magnetohydrodynamics (MHD) instability and noise in pots of an aluminum smelter, which can be easily modified and implemented in any pot according to the pot’s design.

[0017] The approaches of the present subject matter reduces the effect of the vertical component of magnetic field (Bz) on the electrolysis cell, referred to as electrolytic cell assembly (or reduction cell or pot), using a novel magnetic shielding assembly. The magnetic shielding assembly, as per the approaches of the presnt subject matte includes shielding plates.

[0018] In one example, the electrolytic cell assemblymay include a housing, which may house a plurality of components of the electrolytic cell assembly, such as a pot cavity, a cathode assembly, an anode assembly, an anode clamp, a power source, etc. The electrolytic cell assembly may further include a plurality of magnetic sensors to monitor a magnetic field at a plurality of locations in and around the electrolytic assembly. Based on the monitored magnetic field, at least one of a plurality of regions of high magnetic field in the electrolytic cell assembly may be determined. In one example, a computing device may determine the regions of high magnetic field using a finite element modelling technique. However, other techniques may also be used without deviating from the scope of the present subject matter.

[0019] Returning to the present subject matter, a magnetic shielding assembly may then be installed on at least one of the plurality of determined regions of high magnetic field. The magnetic shielding assembly, as described previously, may include a plurality of shielding plates. In one example, the shielding plates may be made of a material comprising anumetal and nickel-iron alloy.

[0020] Thus, the approaches of the present subject matter may reduce the effect of the vertical component of magnetic field (Bz) on the electrolysis cell by installing the magnetic shielding assembly on the regions of high magnetic field.

[0021] In one example, the magnetic fields at a plurality of regions of various electrolytic cell assemblies were analyzed using finite element modeling, with and without the shielding plates being installed at the regions of high magnetic field and in different orientations in the cell. The results showed that the use of shielding plates at some important regions in the electrolytic cell assembly played a significant role in balancing the vertical components of the magnetic field. Further, such shielding plates were also capable of reducing the noise in the cells by 5-10 mV, thereby improving the MHD stability of the cell. Furthermore, the use of simple magnetic shielding plates, instead of using the existing magnetic compensation loop, makes the proposed shielding assembly cost-effective as well as user-friendly.

[0022] Referring to FIG. 1, the existing electrolytic cell includes a housing defining the shape of the electrolytic cell. The housing may include a bottom lining, and side linings extending from the sides of the bottom lining in an upward direction such that a pot shell or pot cavity may be created within the housing. The electrolytic cell is adapted to receive, in the pot shell, a mixture of aluminum ore dissolved in an electrolytic bath. The size or dimension of the electrolytic cell may be based on the amount of alumina ore to be smelted or the amount of aluminum to be produced. In an exemplary embodiment, the aluminum ore may be alumina, but not limited to the like, and the electrolytic bath can be a molten bath of cryolite (NasAlFe), but not limited to the like.

[0023] The electrolytic cell further includes a cathode assembly comprising a graphitized cathode having a collector bar disposed of therewithin. The collector bar can be in form of a longitudinal hollow member having an opening window and a chamber therewithin. Further, the electrolytic cell includes an anode assembly including a graphitized anode rod, wherein the pot shell is adapted to receive the anode therewithin through an opening provided over the pot shell, such that a gap is present between the anode and the cathode assembly. The anode is configured in the cell using anode clamps. The volume created by the gap between the cathode and the anode assembly can receive the mixture of the aluminum ore and electrolytic bath such that the cathode remains in contact with the mixture.

[0024] Further, the cathode and anode assemblies are connected to a power source, which can energize the cathode and anode by supplying electrical current to initiate an electrolytic reaction in the mixture present in the pot shell, which can facilitate aluminum smelting, leading to the conversion of the mixture of aluminum ore into aluminum. However, the electrical current through the cell also generates a magnetic field, which leads to MHD instability and noise in the corresponding cell.

[0025] To this end, cost-effective, efficient, and user-friendly approaches for balancing the magnetic field in an electrolytic cel assembly of an aluminium smelting apparatus are described. In one example, as per the approaches of the present subject matter, the electrolytic cell assembly may include a housing which may house a plurality of components such as a pot cavity, a cathode assembly, an anode assembly, an anode clamp, a power source, etc. The electrolytic cell assembly may further include a pluraliy of magnetic sensors. The magnetic sensors may monitor a magnetic field at a plurality of locations in and around the electrolytic cell assembly.

[0026] In one example, as shown in FIG. 1, the plurality of magnetic sensors may monitor the magnetic field at an anode rod, an anode clamp, a collector bar, a cathode, etc. of the electrolytic cell assembly. It may be noted that the aforementioned examples are only exemplary, and any other region of high magnetic field in and around the electrolytic cell assembly may be monitored by the plurality of the magnetic sensors without deviating from the scope of the present subject matter. [0027] Continuin further with the present example, based on the monitored magnetic field, at least one of a plurality of regions of high magfnetic field in the electrolytic cell assembly may then be determined. In one example, the determination may be made by a computing device using a finite element modelling technique. However, it may be noted that the same is only exemplary, and any other technique may also be used to determine the regions of high magnetic field without deviating from the scope of the present subject matter. [0028] Continuing with the present example, the electrolytic cell assembly further includes a magnetic shielding assembly which may include a plurality of shielding plates. The magnetic shielding assembly may then be installed on at least one of the plurality of determined regions of high magnetic field. In one example, the shielding plates may be made of a high permeability material comprising anumetal and nicke-iron alloy. However, it may be noted that the aforementioned examples are only exemplary. Even further, the shielding plates may be made of any predefined size and dimension based on the design and requirement of the electrolytic cell assemblies.

[0029] In another example, accordingly, magnetic fields of various electrolytic cell assemblies were analyzed by the plurality of magnetic sensors and the computing device using the finite element modeling, with and without the shielding plates being installed at various corresponding regions and in a different orientation in the cell. The corresponding results are shown in FIGs. 2 A to 3. showed that the use of shielding plates at some important regions of high magnetic field in the electrolytic cell assembly as shown in FIG. 1 played a significant role in balancing the vertical components of the magnetic field. Further, installation of such magnetic shielding assembly was also capable of reducing the noise in the cells by 5-10 mV.

[0030] As would be appreciated, the approaches of the present subject matter are capable of improving the MHD stability of the cell. Further, the use of simple magnetic shielding plates, instead of using the existing magnetic compensation loop, makes the proposed shielding assembly cost-effective as well as user-friendly. Furthermore, the shielding plates may be be fabricated in different shapes and sizes according to cell design and requirements, which allows the proposed shielding assembly to be implemented in any type of cell.

[0031] In an implementation, in the trial phase, after placing the shielding plate in the cell, most of the critical pot parameters such as noise, average voltage, bath temperature, Xs AIF3, and the metal level was tracked daily. After 4-5 days of shielding plate placement in the pot, a significant reduction in noise (5-10 mV) of the pot was observed. Further, to validate whether the noise reduction effect is due to the plate or regular cell room activities, the shielding assembly was removed from the cell for 1 week. It was observed that after the removal of the shielding assembly, the noise of the cell increased drastically and the cell became unstable, thereby proving that the noise reduction in the pot was due to the placement of the shielding plate. Furthermore, to verify if the shielding plate is having any negative effect on the other cell parameters, all the cell parameters were tracked daily during the trial phase as shown. It was found that the shielding plate doesn’t have any negative impact on the other cell parameters. In fact, most of the cell parameters such as bath temperature, and cell voltage were improved during the trial phase.

[0032] Thus, the present invention overcomes the above drawback, limitations, and shortcomings associated with the existing aluminum smelters and magnetic field compensation techniques, and provide a cost-effective, efficient, and user-friendly solution for balancing magnetic field responsible for Magnetohydrodynamics (MHD) instability and noise in pots of an aluminum smelter using shielding plates, which can be easily modified and implemented in any pot according to the pot’s design.

[0033] Moreover, in interpreting the specification, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

[0034] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

Claims

We Claim:

1. An electrolytic cell assembly comprising: a housing, wherein the housing is to house a plurality of components of the electrolytic cell assembly; a plurality of magnetic sensors to monitor a magnetic field at a plurality of locations in and around the electrolytic cell assembly; and a magnetic shielding assembly comprising a plurality of shielding plates to be installed on at least one of the plurality of locations in and around the electrolytic cell assembly, wherein the location of installation of the magnetic shielding assembly is a region of high magnetic field.

2. The electrolytic cell assembly as claimed in claim 1, wherein the plurality of components of the electrolytic cell assembly in the housing comprises one of a pot cavity, a cathode assembly, an anode assembly, an anode clamp, and a power source.

3. The electrolytic cell assembly as claimed in claim 1, wherein the plurality of magnetic sensors is to monitor the magnetic field at an anode rod, an anode clamp, a collector bar, a cathode, or a combination thereof, of the electrolytic cell assembly.

4. The electrolytic cell assembly as claimed in claim 1, further comprising a computing device, wherein the computing device, based on the monitored magnetic field, is to determine at least one of a plurality of regions of high magnetic field from amongst the plurality of locations in and around the electrolytic cell assembly.

5. The electrolytic cell assembly as claimed in claim 4, wherein the computing device, based on the monitored magnetic field, is to determine at least one of the plurality of regions of high magnetic field from amongst the plurality of locations in and around the electrolytic cell assembly using a finite element modelling technique.

6. The electrolytic cell assembly as claimed in claim 1, wherein the plurality of shielding plates of the magnetic shielding assembly is made of a high permeability material comprising anumetal and nickel-iron alloy.

7. The electrolytic cell assembly as claimed in claim 1, wherein the electrolytic cell assembly is a part of an aluminum smelting apparatus.