AU2017287821A1

AU2017287821A1 - Device for determining current distribution across the anodes of an aluminum electrolyser

Info

Publication number: AU2017287821A1
Application number: AU2017287821A
Authority: AU
Inventors: Aleksej Gennad'evich BURTSEV; Aleksandr Olegovich GUSEV
Original assignee: Rusal Engineering and Technological Center LLC
Current assignee: Rusal Engineering and Technological Center LLC
Priority date: 2016-06-28
Filing date: 2017-05-18
Publication date: 2018-04-05
Also published as: CA2997990A1; CN108138342A; BR112018006565A2; RU2634817C1; WO2018004382A1

Abstract

The invention relates to the field of non-ferrous metallurgy, particularly to the production of aluminium by the electrolysis method, and can be used during the automated control of aluminum production processes and in the diagnostics of problems on anodes. A device for determining the current distribution across the anodes of an aluminum electrolyser, which are mounted on anode rods secured to an anode bus, contains one or more magnetic field measurement sensors connected to a computer unit. In order to enhance the measurement precision of current distribution across the anodes of an aluminum electrolyser, magnetic field measurement sensors are disposed within the body of an anode rod electrically connected to the anode, or are rigidly secured directly to the surface thereof. The sensors are connected to one another by wires, and are connected by means of a cable and/or by wireless communication to a computer unit located at a safe distance from the effect of high temperatures. The use of the device makes it possible to increase the measurement precision of current distribution across the anodes of an aluminum electrolyser.

Description

DEVICE FOR DETERMINING CURRENT DISTRIBUTION ACROSS THE ANODES OF AN ALUMINUM REDUCTION CELL

Field of the invention

This invention relates to nonferrous metallurgy, in particular to the electrolytic production of aluminum, and can be used during the automated monitoring of aluminum production processes and in the diagnostics of anode problems.

Prior art

There is known a method for automatic monitoring of process status of an aluminum reduction cell having backed anodes secured to an anode bus (RU Patent 2307881,1PC C25C 3/20, published on 10.10.2007), which comprises measuring the voltage on structural components of the reduction cell by means of voltage sensors connected to a computer unit and determining currents across anodes.

This method for automatic monitoring has a drawback which is in that the voltage on the reduction cell is measured at several points along the length of the anode bus, but calculations do not include electrical contact connection between the anode bus and the anode rod, besides, the correction of temperature dependence of electrical conductivity is neither included. All factors mentioned above can negatively impact the measurement precision of current distribution across anodes of the reduction cell.

Also, it is known a method for automatic process status monitoring of an aluminum reduction cell having backed anodes secured to an anode bus, which includes measuring voltage on structural components of the reduction cell by means of voltage sensors connected to a computer unit, and determining current distribution across anodes (US Patent 4786379, IPC C25C 3/20, 1988). Electrical currents in a separate anode are determined based on voltage values measured on a vertical section of a fixed length of an anode rod. The temperature dependence of electrical conductivity is corrected based on measurement results obtained from temperature sensors mounted on anode rods.

The main drawback of the method according to US 4786379 is in that the voltage is measured directly on anode rods. When applying the said method for continuous monitoring of current distribution across all anodes of a reduction cell, the system must be reconfigured periodically, in particular, a measuring unit on the anode rod must be dismantled, completely or partially, each time when the anode is to be replaced.

The closest to the claimed invention is a method for determining current distribution across anodes, which includes providing one or more sensors adapted to measure the magnetic field in the vicinity of each anode rod (US Patent 6136177, C25C3/20, C25C1/00, published on 24.10.2000). In this method, it is suggested to employ current sensors adapted to measure the magnetic field (Hall effect). This method includes determining current distribution across anodes in one or more alumina reduction cells by: i) providing one or more sensors adapted to measure the magnetic field in the vicinity of each of one or more conductors carrying electrical power to or from the cell and to generate one or more signals proportional to said magnetic fields; (ii) communicating said signals to a remote control device; iii) compensating said signals for ambient magnetic effects and temperature either before or after said communication step; and iv) generating control signals to said reduction cell based on said signals.

The main drawback of this prototype method is in that the measuring unit on the anode rod must be dismantled, completely or partially, each time when the anode is to be replaced. Accordingly, it inevitably involves frame shifts and rotations with respect to the previous mounting place, thus, leading to a further measuring error. Moreover, in some cases, sensors can be subjected to high temperatures (an open flap, adjacent anode replacement, processing treatment, etc.), resulting in sensor breakdown.

Disclosure of the invention

The object of the present invention is to improve the measuring precision of current distribution across anodes of an aluminum reduction cell. The technical effect provided by the present invention allows to stabilize process parameters and a reduction cell operation mode, thus, improving technical and economical characteristics of an aluminum reduction cell.

The process monitoring of aluminum reduction cells is based on the continuous sensing of potline current and reduction cell voltage, and calculation of instantaneous reduction cell resistance. In order to continuously monitor all processes within a reduction cell, it is not enough to know a voltage value measured on the reduction cell. To make diagnostics of active processes more precise and timely respond to these processes additional signals from the reduction cell are required. Current load values of each anode obtained by measuring the current passing through the anode rod mechanically or electrically connected to the anode can be used as additional signals. Under such measurements, due to the series connection of the anode and the anode rod, the current passing through the anode rod is equal to the anode current. The information about current distribution, known in the aluminum industry as "current distribution", in a reduction cell across parallel anodes allows to promptly make decisions about leveling the current across anodes to obtain the maximum performance at a predetermined current of the reduction cell.

Said technical effect consisted in the improvement of measurement accuracy of current distribution across anodes of an aluminum reduction cell is achieved by that a device for determining current distribution across anodes of an aluminum reduction cell secured to an anode bus comprises in a body or on a surface of each anode rod one or more magnetic field measurement sensors, wherein the sensors, if more than one, are interconnected by wires and connected to a computer unit mounted at a safe distance from high temperatures sources by means of a cable and/or via wireless connection.

The present invention is completed with specific features helping to achieve the said technical effect.

Prior to being installed inside the anode rod, the sensors can be enclosed by an isolation material in order to prevent the electrical contact between current measurement sensors and an anode rod. In addition, in order to protect sensors from mechanical damages and reduce temperature impacts, sensor surfaces can be covered with a metal cover secured to the anode rod, and wires connecting the sensors can be laid in ducts inside the anode rod body. The cable connecting the sensors with the computer unit can be placed in a cable duct secured to the anode bus, and the computer unit can be placed on the anode bus.

Specific embodiments of the present invention described above are not intended to be exhaustive. There are different modifications and improvements fall within the scope of the invention defined in the independent claim.

By installing the magnetic field measurement sensors inside the anode rod body and thanks to the unchanged position of the sensor in the case of anode replacement, the error of the current measurement sensor is significantly reduced leading to the correct interpretation of the reduction cell monitoring and diagnostics of the ongoing processes. Since the sensors are installed inside the anode rod body, they are protected from high temperatures impacting with an opened flap, the adjacent anode replacement, processing treatment, etc. In addition, the anode position inside the anode rod body allows to prevent breakages, measurement system failures occurred during anode replacement and transportation, because the sensors are installed in the manufacturing stage and stay fixed with respect to the rod during the anode replacement.

Brief description of the drawings

The essence of the invention will be better understood upon studying following drawings:

Fig. 1 shows an overall view of a device.

Fig. 2 shows an installation diagram of magnetic field measurement sensors on an anode rod.

Fig. 3 shows a scheme of preparing an anode rod for a magnetic field measurement sensor being installed thereon.

Fig. 4 shows a diagram of the installation of magnetic field measurement sensors on an anode rod surface.

Embodiments of the invention A device for determining current distribution across anodes of an aluminum reduction cell comprises an anode 1 connected via an anode rod 2 to an anode bus 3 by means of a clamp 4. The anode rod 2 comprises Hall sensors 5 for magnetic field measurement (hereinafter sensors 5). It can be one or more sensors 5. If the number of sensors is more than one, they are installed in one plane perpendicular to the anode rod axis and are interconnected with electrical wires. The wires connecting the sensors 5 through an electric connector 6 via a cable 7 laid inside a cable duct 8 are connected to a computer unit 9. To prevent electrical contact between current measurement sensors and the anode rod the sensors 5 can be enclosed by an insulation material 10. The wires connecting the sensors 5 are preferably laid in ducts 11 made inside the anode rod section.

The magnetic field produced by the electrical current passing through the anode rod can be measured with the sensors 5. The sensors 5 are integrated with a conductor, i.e., the anode rod 2. Signals from the sensors 5 are transmitted via the cables 7 laid in the cable duct 8 to the computer unit 9, where these signals are collected, processed and then these processed signals (electrical current values across anodes) are transmitted to a control cabinet (not shown).

The sensors 5 are mounted in the following way: In the anode rod 2 a recess 2a is formed (milled-out) for receiving the sensors 5 which, if necessary, are enclosed by the insulation material 10, for instance, a coating from a glass-cloth-base laminate, the sensors 5 are secured inside the recess 2a and interconnected with electrical wires leading to the electrical connector 6 where the cable 7 is connected to. The electrical wires can be laid inside the anode rod body in the cable ducts 11. The recess 2a with the sensor 5 enclosed by the insulation material 10 can be covered with a metal plate 12 secured to the anode rod 2 to protect measuring tools (the sensor 5) from any damages.

During the anode 1 replacement procedure, the cable 7 is plugged out the electrical connector 6. Using a crane, the anode rod 2 with the used anode 1 is gripped, the clamp 4 is unclamped and the anode 1 is removed from the reduction cell. Then, a new anode 1 is secured to the anode rod 2 with the sensors 5 mounted therein and interconnected via electrical wires, the clamp 4 is clamped and the cable 7 from the electrical connector 6 is connected to the cables connecting the sensors 5 together.

The use of the claimed device makes it possible to increase the measurement precision of current distribution across the anodes of an aluminum reduction cell.

The embodiment with sensors 5 mounted on a conductor (an anode rod 2) surface is also possible.

In this case, sensors 5 are mounted in the following way: The anode rod 2 is fitted with sensors 5 which are previously enclosed by the insulation material 10 and are secured with screws screwed into the anode rod 2 body. The sensors 5 are protected against mechanical damages by the metal plate 12 secured to the anode rod 2 on top of the sensor 5.

The device operation having such sensor configuration is identical to the operation of sensors arranged inside the anode rod body.

Claims

1. A device for determining current distribution across anodes of an aluminum reduction cell which are mounted on anode rods secured to an anode bus, comprising one or more magnetic field measurement sensors connected to a computer unit, characterized in that the magnetic field measurement sensor or sensors are placed inside an anode rod body or rigidly fixed directly on a surface thereof, and if the number of sensors is two or more they are interconnected by wires and connected to a computer unit.

2. The device of claim 1, characterized in that the magnetic field measurement sensors are enclosed by an insulation material.

3. The device of claim 1, characterized in that the surface of the magnetic field measurement sensors is covered with a metal cover secured to the anode rod.

4. The device of claim 1, characterized in that the cable connecting the wires from the sensors with the computer unit is laid in a cable duct secured to the anode bus.

5. The device of claim 1, characterized in that the wires interconnecting the sensors are laid in ducts inside the anode rod body.

6. The device of claim 1, characterized in that the computer unit is mounted on the anode bus.