RU2361968C2 - Method and equipment for anode installation at anode replacement in electrolytic bath - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method and equipment are intended for anode replacement in electrolytic bath where crane with anode grip is exploited for lifting of used anodes and insertion of new anodes. New anode is inserted at height respective to height value calculated on the basis of removed anode height; height values of removed and new anode are measured in relation to overall control level. Laser-based measurement equipment is installed at the crane between the point fixed to height during operation and the point at anode grip that moves with anode; at that specified height values are measured. Measured values are processed by system based on programmable logic controller (PLC), which more accurately determines height of new anode insertion as per defined algorithm.

EFFECT: accurate installation of anode position, high reliability of operation in dusty conditions, on exposure of wear and tear and mechanical stress.

10 cl, 2 dwg, 1 ex

Description

The present invention relates to a method for positioning when replacing anodes in an electrolytic bath and to equipment for performing this method /

Hall-Hero-type electrolytic baths with pre-sintered anodes for aluminum production during operation require regular replacement of used anodes with new ones. Such pre-sintered anodes comprise a pre-sintered or calcined carbon block to which an anode suspension bracket is attached via nipples that are secured to the carbon block. The hanging bracket of the anode and its nipples are made of metal. The combination of the carbon block and the anode suspension bracket is commonly referred to as the anode, and the anode is fixed through the anode suspension bracket on the top of the electrolytic bath structure, more specifically, on the anode beam, which can extend in the longitudinal direction of the electrolytic bath. In the standard design of the electrolytic bath, two anode beams are used, and a certain number of anodes can be located next to each other along each of the beams. Often each anode beam can have 8-10 anodes. The carbon material in the anodes is consumed during the electrolysis process and must be replaced before the metal of the nipples is exposed. This process takes approximately 28 days, and in the electrolysis shop, where several dozen electrolytic baths are located, there may be an acute problem of replacing the used anodes and installing new anodes. When performing this operation, it is important to set the lower side of the new anode as high as possible, which is immersed instead of the used anode. This is necessary because the distance between the poles (the distance between the anode and cathode) is an important parameter in the electrolytic bath.

Currently, this operation is increasingly performed using a traverse crane mounted on rails that run along the rows of electrolytic baths and are usually installed above them. This operation is one of the most time-consuming and frequently performed operations during the operation of electrolytic baths, and various representatives of this industry have developed improvements to simplify and streamline this work, focusing on ensuring the safety and working conditions of operators. A known method for determining the insertion height of a new anode is to place the anode on a table near the remote anode, mark with chalk the general control level on the anode suspension bracket. The measuring stand is used as an auxiliary tool for performing this operation.

US Pat. No. 4,221,641 describes a method and apparatus for replacing electrodes in an electrolytic bath for aluminum production. This method involves transporting the used anode from the electrolytic bath to the first level above the bath, which is recorded so that the electrode length is measured, the new electrode is lowered, and the distance from the second level parallel to the first level is detected to measure the length of the new electrode, the distances between the specified levels, and the new electrode is additionally lowered from the second level by a distance that is equal to the transport path of the used anode minus the distance between the two and levels. To determine the level, there is a lever, which is activated using electrodes and which also has a detector for detecting the movement of the lever. The detector consists of a beam of light and a receiver, and the beam of light is interrupted by a screen mounted on a lever. The detector is an optical-mechanical type detector with moving parts that can easily change its position over time and / or require significant maintenance / inspection efforts to ensure the mobility and proper functioning of the components. This measurement principle is based on the use of an incremental counter in addition to the limit switches when the relative movement of the crane is calculated.

The present invention provides a method and equipment for replacing anodes in an electrolysis plant that provides very accurate positioning of the anodes and is more reliable under dust, wear and mechanical stress than prior art solutions. In addition, this solution requires minor checks and has a good user interface for the operator who controls the crane.

These and other advantages can be achieved using the invention in accordance with paragraphs 1-10 of the claims.

The present invention will be described in more detail below with reference to the drawings and examples, where:

on figa-b shows a block diagram with the main parts of the measuring equipment, with an anode and without an anode;

figure 2 shows a block diagram of the measurement process.

As indicated above, one of the objectives of the present method is to provide more accurate insertion of the anodes by more accurate distance measurement using advanced equipment in which the distance measurement is performed using a laser. This eliminates accidental measurement errors of the anode lift, and is less likely to malfunction due to the selected connection technology. The measurement principles used and the sequence of operations eliminate measurement errors associated with the vertical deflection of the crane bridge and accidental play in a rough construction.

Compared with manual measurement, using a measuring stand and a reference level, using the proposed method, replacing the anodes is less time-consuming, since the operator is not required in the workshop to insert the anode and to set the position of the anode height, and the height of the anode insert is set more precisely, which is important for the operation of the electrolytic bath.

As shown in figure 1a, the measuring equipment consists of a laser unit 3 mounted inside a sealed enclosure 4 with a vertical protective tube 5. The laser beam 7 exits through the tube in the direction of the reflective mark 6 mounted on the anode gripper 2. Under these conditions, the laser unit measures the exact distance. The sealed housing, the protective tube and the excess pressure that is supplied to the housing 4 through the air supply pipe 8 prevent fluoride dust and gases from entering the lenses of the unit. This combination ensures accurate measurement without accidental measurement errors. Cables for communication with the PLC (programmable logic controller) exit the housing.

The lifting device, the anode hoist, is mounted on the rotary trolley of the combined crane, which allows you to lift the scorched anode from the electrolytic bath and replace it with a new anode. The anode lift is hydraulically controlled, i.e. the anode and the anode suspension bracket are raised and lowered into the bath by hydraulic force.

The anode lift is equipped with an anode grip. It is a capture device that is mounted on the anode hoist. With its help, the capture of the anode suspension bracket 10 is carried out, which is mounted on the anode 11 (see fig. 1b). Typically, the anode suspension bracket has an opening at the top that can be caught by the capture device. Such gripping devices may include one or more pins that may fit into the hole of the suspension bracket.

PLC (PLC) - programmable logic controller. The PLC can control the output signals (O) using the input signals (I) and a logically constructed program. PLC consists of several microprocessors. The PLC processor is located on the crane, and several decentralized I / O racks are located on the mobile trolleys of the crane and in the operator's cab. Decentralized I / O racks are connected to the PLC processor using high-speed data channels, which have very good noise protection. This eliminates the need for multiple signal cables, which may be subject to noise and error signals.

In this regard, laser measuring equipment allows you to measure the distance between the laser unit and the reflective mark. The accuracy of this combination is approximately 1 mm. The laser unit used in this example has RS-232 for communication with decentralized racks. It is advisable to install the laser unit inside an airtight housing with excess pressure, which is attached to the protective tube with flanges, for example, with a diameter of 50 mm and a length of approximately 2.5 m. The laser beam is installed so that it leaves the housing through the tube downward, in the direction of the reflective mark on the capture of the anode.

Data transfer using RS-232 (ASCII character transfer (ASCII, American Standard Code for Information Interchange) from port to port) is a data transfer method that accurately transfers signals from the laser unit to the PLC.

PanelView (not shown) is an on-screen visualization system that is connected to the PLC using the same data transfer method used for decentralized I / O racks. This visualization system allows you to read all stored values, as described below, which allows the crane operator in the cab to read these values.

The light panel (not shown) consists of a light column with 5 light sources of different colors. This lightbar has 2 functional modes. Mode 1 is used when removing the anode, and it indicates the measurement sequence, step by step. Mode 2 - designation of position setting when inserting the anode. It indicates when the anode is set too high, too low, or in the correct position. His work is based on an algorithm that is programmed in the PLC.

1) PLC lock (PLC lock in PLC program)

The sequence of operations is blocked so that the mechanical free play is always eliminated. This is done by the operator using the control lever to raise the anode in LIFT STAGE 1 mode for at least 2 seconds and simultaneously using the SAVE MEASURED VALUE switch before the anode capture position is stored in the PLC.

When the control lever for the anode elevator is in the LIFT STAGE 1 position, the hydraulic unit provides, using appropriate valves, a lifting force of approximately 60-70% of the weight of the burned anode to the anode elevator.

2) Integrated PLC solution

As a result of the PLC installation, signals are transmitted between the laser unit and the PLC with very good noise protection, while signal transmission is reliable and no random measurement errors occur.

3) Visualization

Simple visualization shows the sequence of operations and allows you to reliably establish the position of the new anode.

In this example, crane control is performed using a PLC with decentralized I / O racks with advanced logic. Laser distance measuring equipment is connected to decentralized I / O racks. The laser unit and one of the decentralized racks must be installed on the anode lift, since the laser unit transmits the measured values to the PLC processor through a decentralized I / O rack with developed logic. When transferring measured values between the laser unit and the PLC, it is important to provide the best possible protection against noise arising from electromagnetic and electrostatic interference, as well as to protect equipment from temperature fluctuations in order to eliminate error signals. This is ensured by the selected PLC design.

Laser measuring equipment with a laser unit, as described above, is located inside the dustproof housing 4 (electrical designation IP 56) on the rotary trolley of the anode lift. The housing has a pipe 5 with a flange with a diameter of 50 mm and a length of approximately 2.5 m, which is mounted on the housing and extends downward towards the reflective mark 6. The reflective mark 6 is mounted on the anode gripper 2. Laser measuring equipment measures the distance between a fixed point in this sealed enclosure (installation location) on the anode hoist through the pipe, down towards the reflective mark on the anode grip. The pressurized housing is under overpressure and contains a long tube, such as described above, as a result of which powerful ascending air currents (hot air with a significant amount of gas containing fluorine and dust, when replacing the anode) do not fall on the lenses of the laser unit. This important detail prevents measurement errors. The described laser measurement principle is a central part of the present invention because it is not subject to mechanical wear and does not require maintenance.

The PanelView 550 visualization panel is installed inside the crane trolley, which allows you to sequentially read all measurement results and steps. Management of its work is carried out using PLC.

A functional light panel is installed in front of the operator and contains 5 indicator lights. Such a functional display has 2 operating modes. This allows the operator to track the functions associated with the insertion of anodes, in particular the height of the new anode (for more information, see the description of functions).

The operator controls using the control lever mounted on the left side, which allows you to perform 3 stages of upward movement of the capture of the anode.

LIFTING STAGE 1: a lifting force is applied to the anode grip, comprising approximately 60-70% of the weight of the burned anode; relatively low lift speed. This force is used when it is necessary to measure the grip height of the anode using laser equipment.

LIFTING STAGE 2: a lifting force is applied to the anode grip, approximately 300% of the weight of the burned anode (separation force when the anode is removed); same speed as LIFT STAGE 1.

LIFTING STAGE 3: a lifting force is applied to the anode grip, approximately 200% of the weight of the burned anode; high speed for fast anode processing.

On the same control lever indicated above, on its front side, a push button switch is installed. It is used to enable the SAVE ANODE POSITION POSITION mode.

Description of functions, see figure 2

All the described functions are performed by the operator located in the crane cabin. The operator first sets the offset values on the PanelView, that is, how much higher it is necessary to insert a new anode in relation to the burned anode (the usual setting value is 20 mm). The operator controls the crane in such a way that it grabs the anode suspension bracket (anode) by the grip of the anode. Then he lifts the scorched anode, controlling the anode hoist in the LIFT STAGE 1 position using the control lever (see Fig. 2a). When this is carried out by lifting the anode with a given force, which is approximately 60-70% of the weight of the anode (constant force). This leads to the elimination of backlash. When the lift is completed, the operator presses the SAVE POSITION switch on the control lever. The position of the anode capture is stored in the PLC if the LIFT STAGE 1 mode has been activated continuously for 2 seconds. If the operator uses LIFT STAGE 2, the anode pickup position will not be stored in the PLC. In doing so, the important locking function in the PLC is fulfilled, which eliminates the free play and ensures the deflection of the crane to approximately the same extent for all measurements. The PLC confirms this operation in accordance with this method of turning on the yellow light of the indicator on the light panel. This means that measurement A has been performed. Anode trapping is released, and the scorched anode is removed from the electrolytic bath.

The scorched anode is placed down to the reference level (test plate), see FIG. 2b. The anode is lifted using the anode elevator mode. LIFT STAGE 1, that is, a lifting force is again applied to the anode elevator, which is approximately 60-70% of the weight of the anode. In this case, the scorched anode will not rise from the reference level, but the crane design will be located in the same way as when lifting the anode from the electrolytic bath. As a result, the free movement of the crane is eliminated. During lifting, the operator presses the SAVE POSITION switch on the control lever. This position is stored in the PLC if the LIFT STAGE 1 mode is active for 2 seconds. The PLC confirms the correct execution of the procedure by the green light indicator on the light panel. This means that measurement B has been performed.

The old anode is then placed in a waste container. A new anode is attached to the anode grip. Then it is installed at the same reference level as the scorched anode, see Fig. 2c. The anode is lifted using the LIFT STAGE 1 mode, that is, the anode lifter again provides a lifting force of approximately 60-70% of the weight of the anode. During lifting, the operator presses the SAVE POSITION switch on the control lever. This position is stored in the PLC if the LIFT STAGE 1 mode is active for 2 seconds. The PLC confirms the correct operation by the red indicator light on the light panel. This means that measurement C has been performed. All measurements on this end.

The PLC calculates the insertion height of the new anode using the following formula — see FIG. 2d:

D = A-B + C-X

D represents the desired position of the new anode.

A represents the position of the scorched anode in the electrolytic bath.

B represents the position of the scorched anode at a reference level.

C represents the position of the new anode at the same reference level.

X represents the additional height of the new anode in the bath relative to the scorched anode.

The new anode is inserted into the bath at the anode position = D (+/- tolerance, usually +/- 3 mm - tolerance can be adjusted using the operator panel).

The display panel then switches to Mode 2 for indication. The operator installs the anode in the bathtub in accordance with the indicator light in Mode 2, that is, if the yellow indicators (1 or 2 yellow indicators) light up, this means that the anode is set too high, and if the red indicators (1 or 2 red lights up) indicator lights), this means that the anode is set too low. The anode has the correct installation position in height if the green indicator light comes on, that is, the position of the anode is set with a tolerance of D +/- 3 mm. When the anode is installed in the bathtub and the green indicator light comes on, the anode is fixed using the anode clamp. The sequence of operations on this ends, and the equipment can be used to replace the anode in another bath.

An additional installation height of the new anode is necessary to prevent deformation of the anode. Extra height means that the anode will not take “full power” and can be gradually heated before full current is applied through it.

Claims (10)

1. The method of installing the anode when replacing the anodes in the Hall-Hero electrolytic cell with calcined anodes to produce aluminum, including the use of a crane with a grip for lifting spent anodes and installing new anodes, the grip acting on the anode suspension bracket at a given, fixed point, and a new anode set to a height corresponding to a height calculated based on the height of the spent anode, while the height of the spent anode and the height of the new anode are measured with respect to the overall reference level, different the fact that between the point on the crane, which is stationary in height during operations, and the fixed point on the grip of the anode moving together with the anode, measuring equipment is installed that has a laser, by means of which heights are measured, the measured values are processed using a programmable system logical controller (PLC) and determine the installation height of the new anode. 2. The method according to claim 1, characterized in that the installation height of the new anode is determined in accordance with the algorithm defined by the following formula:
D = A-B + CX,
where D is the required position of the new anode:
A - the position of the spent anode in the bath;
B is the position of the spent anode at the general control level;
C is the position of the new anode at the general control level;
X is the additional height for installing a new anode in relation to the spent anode. 3. The method according to claim 1, characterized in that before measuring the indicated height, the free movement of the anode and associated mechanical structures of the crane is eliminated by applying a first lifting force to the anode that is less than the weight of the spent anode. 4. Equipment for installing the anode when replacing the anodes in the Hall-Hero electrolytic cell with calcined anodes for producing aluminum, comprising a crane with an anode grip for lifting spent anodes and installing new anodes, the grip acting on the anode suspension bracket at a given fixed point, using the capture, the new anode is installed at a height corresponding to the height calculated taking into account the height of the spent anode, and the height of the spent anode and the height of the new anode are measured relative to the total control about the level, characterized in that between the point on the crane, which is stationary in height during operations, and the point on the anode grip moving together with the anode, measuring equipment is installed that has a laser, by means of which heights are measured and data signals are transmitted to the programmable logic controller (PLC) for processing the measured, stored values and determining the installation height of the new anode. 5. The equipment according to claim 4, characterized in that the measuring equipment having a laser comprises a laser unit configured to simultaneously emit a laser beam and detect a reflected laser beam, the laser unit being mounted on a crane in a location that is stationary in height and reflective a device for reflecting the laser beam is mounted on the capture of the anode. 6. The equipment according to claim 5, characterized in that the laser unit is installed in a dustproof sealed enclosure with a downwardly facing hole to which a tube is attached through which the laser beam passes. 7. The equipment according to claim 6, characterized in that it is configured to supply compressed air to the laser unit body to establish excess air pressure and to prevent dust from entering the body through the pipe. 8. The equipment according to claim 7, characterized in that the programmable logic controller (PLC) is installed with the ability to save the transmitted measured values and process them after blocking to eliminate the free movement of the capture of the anode. 9. The equipment of claim 8, characterized in that the blocking comprises applying a lifting force of 60-70% of the weight of the spent anode to the anode grip, and this force must be applied for at least 2 seconds before measurement result can be saved. 10. Equipment according to any one of paragraphs.8 and 9, characterized in that the display, light signal or similar device visualizes the completion of the sequence of operations and locks with the ability to save the measured values.

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