RU2606365C1 - Method for forming self-calcinating anode of aluminium electrolyser with upper current lead - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to electrolytic production of aluminium, specifically to a method for forming self-calcinating anode of aluminium electrolyser with upper current lead. Method involves loading anode mass in anode casing, installation into liquid phase of anode along longitudinal axis of anode of electrolyzer partially buried, equal-height metal cooling elements, lifting anode casing, rearrangement of steel anode pins on a higher level of anode with extraction of steel rods from body of carbon anode, loading a dosed amount of pin mass and installation of pins in hole of anode, wherein loaded anode mass is based on oil coke with content of coal-tar pitch of 27÷29 %, installing horizontally oriented metal cooling elements in one line between central rows of anode pins at equal depth of immersion into liquid phase of anode, and lifting of anode casing is carried out with raising of metal cooling elements in a single step by not more than 3.0 cm.

EFFECT: reduced consumption of anode mass, reduced output of coal froth, reduced electric power consumption and emissions of pollutants due to higher quality of anode.

4 cl, 1 dwg, 2 tbl

Description

The invention relates to the electrolytic production of aluminum, and in particular to a technology for the formation of a self-burning anode of an aluminum electrolyzer with a top current lead.

One of the tasks associated with the formation of a high-quality self-baking anode is to equalize the thermal load between the colder peripheral and hot central parts of the anode. One of the solutions to this problem is to install partially buried, metal cooling elements in the liquid phase of the anode of the electrolyzer.

A device is known for removing heat from a self-burning anode of an aluminum electrolyzer containing heat-removing elements immersed in the liquid anode mass and made in the form of metal plates with holes for the flow of the anode mass, as well as a node for suspending the element to the anode casing, characterized in that in order to improve conditions the formation of a sintering cone by means of differentiated heat removal, the heat-removing elements in their lower part are made thickened, with the ratios of the sections of the lower part to the upper as (1,2 ÷ 2): 1, Rich lower ends of the heat-removing elements are provided with projections facing the cone sintered anode (AS USSR №908962, S25S 12/03, publ. 02.28.1982 g).

A device is known for removing heat from a self-burning anode of an aluminum electrolysis cell using heat-removing elements immersed at the lower end in a liquid anode mass, characterized in that, for the purpose of differentiated heat removal without using manual labor to adjust the device, it is made of a set of heat-conducting plates of various lengths holes located in their center, and bearing rods passing through the holes of the plates. The lower ends of the heat-conducting plates in the central part of the anode are immersed in the liquid anode mass to the maximum depth with a gradual decrease in the depth of immersion to the periphery and ends of the anode, and the upper ends of the plates are located above the level of the liquid anode mass in the form of protrusions of the maximum height in the central part of the anode with a gradual decrease in their height to the periphery and ends of the anode (AS USSR No. 268663, C22d 3/02, 3/12, publ. 01.01.1970).

A known method of heat dissipation from a self-burning anode of an aluminum electrolyzer using heat dissipating elements, one ends immersed in the liquid anode mass, and the other protruding above the surface of the anode, characterized in that in order to differentially remove heat from the anode, the heat dissipating elements in the central part of the anode are immersed with lower ends into the liquid anode mass to the maximum depth with a gradual decrease in the depth of their immersion to the periphery and ends of the anode, and their upper ends rise at the level of the liquid nodnoy mass in the central part of the maximum height, with a gradual decrease in its periphery and the ends of the anode (AS USSR №268664, C22d 3/02, 3/12, publ. 01.01.1970 city).

In patent RU No. 2315822 an anode device of an aluminum electrolyzer with an upper current supply is declared, including a carbon anode, anode pins consisting of a cylindrical and conical parts, characterized in that anode pins with a larger diameter of the cylindrical part than the diameter of the cylindrical part are installed in the middle part of the carbon anode anode pins in the outer rows and ends of the carbon anode of the plan view. Moreover, in the middle part of the carbon anode installed anode pins with a diameter of a cylindrical part 1.1-1.5 times larger than the diameter of the anode pins installed in the outer rows and ends of the carbon anode of the plan view (Patent RU No. 2315822, C25C 3/12, published on January 27, 2008). Anode pins with an increased diameter of the cylindrical part, along with the function of supplying current to the anode, play the role of heat-removing metal elements. When installing larger diameter anode pins only in the middle part of the carbon anode, the voltage drop in the carbon anode is reduced, the thermal tension of the carbon anode is reduced, the quality of the secondary anode is improved without deterioration of the state of the carbon anode at the periphery and at the ends.

The disadvantages of the known solutions include the difficulty in manufacturing heat-releasing elements of variable cross section with protrusions, the possibility of sticking of the liquid anode mass at the points of expansion of the heat-releasing elements, as well as the risk of baking protrusions of the heat-releasing elements into the anode sintering cone.

A device is known for removing heat from a self-burning anode of an aluminum electrolyzer, consisting of metal heat-removing elements made in the form of solid ribs, mounted in the upper part of the anode casing and partially immersed by the lower ends in the liquid anode mass, in which, in order to regulate heat removal from the anode, the atmosphere of the workshop and the uniform distribution of heat throughout the entire volume of the liquid anode mass, the heat-removing elements are made with cutouts at the ends and with holes located above the center of their weight ty for suspension on the anode (AS USSR No. 278124, C25C 3/02, 3/12, publ. 01.01.1970).

In a known solution, metal heat sink elements are located across the longitudinal axis of the electrolyzer and are designed to redistribute heat between the Central part of the anode and its periphery with the possibility of flow of the liquid anode mass through the windows in the heat sink elements. The disadvantages of the device include the complexity of manufacturing heat-removing elements with windows and cutouts, their large length, which is almost the width of the anode, as well as their applicability only for self-baking anodes with an ordinary anode mass.

The closest in technical essence, the presence of similar features to the claimed solution is "Device for heat removal from the surface of the anode", which is selected as the closest analogue. The claimed device, including a bell gas collector, a casing and current-carrying pins, additionally contains metal ribs having the same height and installed with increasing depth from the center to the periphery of the anode into the coke pitch layer. The ratio of the height of the rib to the height of its part protruding above the surface of the mass is 2 ÷ 6. The device allows due to equalization of temperature across all zones of the surface of the coke-pitch layer to achieve its uniformity in volume and thereby ensure a reduction in the consumption of carbon raw materials (Patent RU No. 1611991, C25C 3/12, publ. 07.12.1990).

The disadvantages of the known device are the need to install a large number of metal ribs over the entire area of the anode and regulate the depth of immersion of the ribs in the coke pitch layer. This circumstance complicates the maintenance of the anode. Also, the device for heat removal was tested on electrolyzers with a current strength of 156 kA operating on an anode mass using low-temperature coal tar pitch as a binder, which limits the scope of the known technical solution.

The task of the invention is to improve the quality of the self-burning anode of an aluminum electrolysis cell, to reduce emissions of harmful substances from the surface of the anode during the stationary period of operation, to reduce the material consumption and labor costs of maintaining the anode.

In this case, the technical result is a decrease in the consumption of the anode mass, a decrease in the yield of electrolyte carbon foam, a reduction in the consumption of electricity and emissions of pollutants by improving the quality of the anode.

The technical result is achieved due to the fact that in the method of forming a self-burning anode of an aluminum electrolyzer with an upper current lead, including loading the anode mass into the anode casing, installing in the liquid phase of the anode along the longitudinal axis of the anode of the electrolyzer partially buried metal cooling elements of equal height, raising the anode casing , rearrangement of steel anode pins to a higher anode horizon with the removal of steel pins from the body of the carbon anode, loading a metered amount of one-pin mass and the installation of the pins in the hole of the anode, according to the claimed invention load the anode mass based on petroleum coke with a coal tar content of 27-29%, install horizontally oriented metal cooling elements in one line between the Central rows of anode pins with the same depth of immersion in the liquid phase of the anode and the lifting of the anode casing is carried out with the lifting of the metal cooling elements in one go not more than 3.0 cm

The method is supplemented by special cases of its implementation.

On electrolyzers with three-contour anode casings, four cooling metal elements are installed in the liquid phase of the anode; on electrolyzers with four-contour anode casings, three metal cooling elements are installed.

The thickness of the cooling metal elements is maintained within 35-45 mm.

The ratio between the immersed in the liquid phase of the anode and the non-immersed part of the cooling metal elements is maintained equal to 55-65%: 35-45%, while the immersion depth of the cooling elements is maintained within 275-325 mm.

The technical nature of the proposed technical solution is as follows. The inventive method of forming a self-baking anode extends to the technology of forming the anode using a "dry" anode mass with a binder content of coal tar pitch reduced to 27–29%. At a binder concentration in the anode mass of less than 27%, a loose anode is formed with a weak bond between coke particles. The binder content in the anode mass of over 29% contributes to the separation of the liquid phase of the anode in height and segregation of filler particles (coke) in the lower layers of the liquid anode mass.

The use of a “dry” anode mass made it possible to reduce the number of cooling metal elements in the anode and install them in one row along the longitudinal axis of the cell between the central rows of anode pins under the anode maintenance path.

The limitation of the lifting height of the anode casing, and with it the metal cooling elements in one go not more than 3.0 cm, is due to the following: when lifting the cooling elements, a void is formed under them, which is gradually filled with liquid anode mass. The liquid phase of the anode is characterized by a heterogeneity in height, which is expressed in an increased concentration of coke in the lower layers of the liquid anode mass and an increased content of pitch in the upper layers. In order to prevent leakage of anode mass enriched with pitch under the cooling element, the height of the single rise of the cooling elements is limited to not more than 3.0 cm. Otherwise, a porous, loose secondary anode will form under the cooling elements, which will lead to the formation of longitudinal anode recesses, increase the output of electrolyte carbon foam.

In this case, four cooling elements are installed in the anode with a three-contour casing, and three cooling elements are installed with a four-contour casing. Reducing the number of cooling elements, immersing them in the liquid phase of the anode to the same depth reduces the cost of their manufacture and facilitates the maintenance of self-baking anode.

The claimed ratio between the immersed and the non-immersed part of the cooling metal elements, equal to 55-65%: 35-45%, with the immersion depth of the elements 275-325 mm, provides the maximum allowable deepening of the elements in the central part of the self-firing anode and the maximum possible removal of cooling elements above the surface anode, which, with a thickness of cooling elements of 35-45 mm, can effectively remove heat from the central, most overheated part of the anode. The consequence of this is an increase in the level of the liquid phase of the anode by an average of 5-7 cm, a decrease in the temperature of the surface of the anode by 11-17 ° C. With an increase in the level of the liquid phase of the anode and a decrease in its temperature, the stratification of the filler (coke) and the binder (pitch) decreases, the sintering cone of the anode is formed more slowly, which makes it possible to obtain an anode of higher quality, with high strength and low destructibility.

The figure shows a diagram of the installation of metal cooling elements in a self-firing anode, where:

1 - Anode casing

2 - Anode mass

3 - Buttresses

4 - Anode current-carrying pins

5 - Metal cooling elements

Comparison of the proposed solution with the closest analogue shows the following. The proposed solution and the closest analogue are characterized by similar features:

- to improve the quality of the self-baking anode, metal cooling elements are installed in the liquid phase of the anode;

- use metal cooling elements of the same height;

- metal cooling elements are installed along the longitudinal axis of the anode of the electrolyzer;

- metal cooling elements are buried in the liquid phase of the anode to a certain depth.

The proposed solution differs from the closest analogue in the following features:

- for the formation of the anode using a "dry" anode mass based on petroleum coke with a content of coal tar pitch 27 ÷ 29%;

- metal cooling elements are installed only along the longitudinal axis of the cell between the Central rows of anode pins;

- four cooling metal elements are installed on electrolyzers with three-counter anode casings, three metal cooling elements are installed on electrolyzers with four-counter anode casings only between buttresses;

- the immersion depth of all metal cooling elements in the liquid phase of the anode is maintained the same;

- preferably, the ratio between the immersed in the liquid phase of the anode and the non-immersed part of the metal cooling elements is maintained equal to 55-65%: 35-45%, while the immersion depth of the cooling elements is maintained within 275-325 mm;

- the thickness of the metal cooling elements is maintained within 35-45 mm;

- the anode casing together with the metal cooling elements in one go is lifted by no more than 3.0 cm.

The proposed technical solution is characterized by features that are similar to those of the closest analogue, and distinctive features, which allows us to conclude that it meets the patentability condition of "novelty."

A comparative analysis of the proposed technical solution with known solutions in this technical field, carried out according to the search results in the patent and scientific and technical literature, showed that at the time of filing the application for the invention, no technical solutions were found that are characterized by a combination of known and unknown features similar to the proposed solution, which indicates the conformity of the proposed technical solution to the condition of patentability of the invention "inventive step".

Compliance with the patentability condition “industrial applicability” is proved by experimental data obtained during industrial tests.

Example 1. Industrial testing of the technology for the formation of a self-burning anode of an aluminum electrolyzer with an upper current supply using metal cooling elements was carried out on two teams of S-8BM electrolyzers (22 electrolysers in a team) of one aluminum electrolysis case. The electrolyzers are equipped with three- and four-contact anode housings, on which four and three cooling metal elements are installed. Each cooling element had two small holes for hanging with a wire or hooks under the anode service ladders.

Both teams for the formation of the anode used a “dry” anode mass made on the basis of petroleum coke with a binder (coal pitch) content of 28 ± 1.0%. The current strength of the series was 174 kA.

The first team of electrolyzers (witnesses) used aluminum plates with dimensions of 1,500 mm × 350 mm × 30 mm installed in one line along the longitudinal axis of the cell between the central rows of anode pins as metal cooling elements. The immersion depth of all cooling elements in the liquid phase of the anode was 200 ± 20 mm.

The second team of electrolyzers (experimental) used aluminum plates with dimensions of 1500 mm × 500 mm × 40 mm, mounted in one line along the longitudinal axis of the cell between the central rows of anode pins. The immersion depth of all cooling elements in the liquid phase of the anode was 300 ± 25 mm.

The tests were carried out for a long time, covering the warm and cold periods of the year. During this time, all routine technological operations for servicing the anodes (loading the anode mass, rearranging the anode pins, hauling the anode frame, lifting the anode casing, calibrating and discarding the anode pins, replacing sections of the gas bell) were carried out identically in the experimental electrolyzers and witnesses. The lifting of the anode casing with metal cooling elements on all electrolyzers was carried out at least once a day. The target height of the casing with the cooling elements was 1.65-1.70 cm / day.

During tests on experimental electrolyzers and witnesses, control measurements of the following technological parameters were carried out: the height of the anode column and the anode sintering cone, the void in the anode, the level and temperature of the liquid phase of the anode, the voltage drop in the anode, and the consumption of the anode mass. Also recorded the average specific removal of electrolyte coal foam. The temperature of the liquid phase of the anode was measured in the center of the anode at a depth of ~ 50 mm. The averaged test results of the technology for the formation of self-baking anodes using metal cooling elements are presented in table 1.

From the test results shown in table 1, it can be seen that in the experimental electrolyzers, in comparison with the witnesses, an increase in the level of the liquid phase of the anode by an average of 5-7 cm, a decrease in the surface temperature of the liquid phase of the anode by 11-17 ° C was recorded. The consequence of this is an improvement in the quality of the self-burning anode, which is confirmed by a decrease in the voltage drop in the anode from (0.584-0.590) V to (0.574-0.579) V, a decrease in the specific consumption of the anode mass from 0.513 kg / t Al to 0.510 kg / t Al, and reducing the removal of electrolyte coal foam from (33.4-35.3) kg / t Al to (18.6-21.4) kg / t Al. Also, as a result of lowering the surface temperature of the liquid phase of the anode, emissions of pollutants in the summer period of operation of electrolyzers decreased from 0.00015 to 0.00012 mg / cm ³ .

Example 2. To assess the influence of the lift height of the metal cooling elements at one time on the quality of the forming anode, an additional experiment was conducted on three groups of electrolyzers (three electrolysers in each) with 1500 mm × 500 mm × 40 mm aluminum plates installed in the anode.

On three electrolyzers of the first group, the lift height of the metal cooling elements at one time was ~ 1.7 cm. On three electrolyzers of the second group, ~ 3.0 cm. On three electrolyzers of the third group, ~ 4.5 cm. The average burning speed of the anodes was 1.65 -1.70 cm / day. Three months after the start of the experiment, they began collecting technological data on the consumption of the anode mass and the removal of electrolyte coal foam. Throughout the experiment on the electrolyzers of the three groups, all other routine technological operations (except lifting the anode casing and metal cooling elements) for the maintenance of the anodes were carried out identically.

The averaged test results of the technology for the formation of self-baking anodes at different lifting heights of metal cooling elements in one go are presented in Table 2.

The data obtained confirm the fact that the quality of the anode under the metal cooling elements deteriorates when they rise at one time to a height of more than 3.0 cm as a result of flowing under the cooling elements the anode mass enriched with pitch and the formation of a porous, loose, secondary anode. This is indicated by the fact of an increase in the consumption of the anode mass and the removal of electrolyte carbon foam.

Comparison of the effectiveness of the proposed solution with the closest analogue showed the following:

The solution for the closest analogue was developed for anodes with a common anode mass on a low-temperature binder (pitch), the content of which in the mass is 30-32%. In accordance with the decision on the closest analogue, metal cooling elements are installed in the central and peripheral zones of the anode with a variable depth in the liquid phase of the anode. The depth is from 50% to ~ 83%. Moreover, in the central zone of the anode, the deepening of the cooling elements is minimal, and in the peripheral zone it is maximum. The presence of a large number of cooling elements in the anode complicates its maintenance, increases operating costs, including for the manufacture of cooling elements. In an example implementation of the solution for the closest analogue, cooling elements 25 mm thick are used.

The proposed solution extends to the formation of anodes with a “dry” anode mass with a binder content of 27-29%. In accordance with the proposed solution, metal cooling elements are installed only in the central zone of the anode with a constant depth. Moreover, the ratio between the immersed in the liquid phase of the anode and the non-immersed part of the cooling metal elements is maintained equal to 55-65%: 35-45%, and the immersion depth of the cooling elements is maintained within 275-325 mm. The thickness of the cooling elements is 35-45 mm, which provides intensive heat dissipation from the central zone of the anode most loaded in the heat plan.

Claims (4)

1. A method of forming a self-baking anode of an aluminum electrolyzer with an upper current supply, including loading the anode mass into the anode casing, installing partially buried, equal in height metal cooling elements along the longitudinal axis of the anode of the electrolyzer, lifting the anode casing, moving the steel anode pins to more a high horizon of the anode with the removal of steel pins from the body of the said anode, loading a metered amount of pin mass and installing the pins in the hole of the anode, characterized in that they load anode mass based on petroleum coke with a coal tar content of 27 ÷ 29%, install horizontally oriented metal cooling elements in one line between the central rows of anode pins with the same immersion depth in the anode liquid phase, and lift the anode casing with lift metal cooling elements in one go not more than 3.0 cm. 2. The method according to p. 1, characterized in that four electrolytic cooling elements are installed in the liquid phase of the anode on electrolyzers with three-counter anode casings, and three metal cooling elements on electrolyzers with four-counter anode casings. 3. The method according to p. 1, characterized in that the thickness of the metal cooling elements is maintained within 35-45 mm 4. The method according to p. 1, characterized in that the ratio between the immersed in the liquid phase of the anode and the non-immersed part of the metal cooling elements is maintained equal to 55-65%: 35-45%, while the immersion depth of the cooling elements is maintained within 275-325 mm

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