WO2019098888A1

WO2019098888A1 - Device for collecting and removing gases in an aluminum electrolysis cell

Info

Publication number: WO2019098888A1
Application number: PCT/RU2018/050084
Authority: WO
Inventors: Валерий Георгиевич Шадрин; Ярослав Александрович Третьяков; Алексей Сергеевич ЖЕРДЕВ
Original assignee: Общество С Ограниченной Ответственностью "Объединенная Компания Русал Инженерно -Технологический Центр"
Priority date: 2017-11-20
Filing date: 2018-07-26
Publication date: 2019-05-23
Also published as: NO20200539A1; CA3082087C; RU2668617C1; CA3082087A1; CN111356788A; CN111356788B

Abstract

The invention relates to the production of aluminum in electrolysis cells with baked anodes. A device comprises a system of gas ducts and gas-collecting caps. Each of the caps is connected by a first channel to a horizontal gas duct so as to form a main gas removal circuit, and is connected by a second channel to an additional gas duct so as to form an additional gas removal circuit. The height of each subsequent channel of the main loop is increased by 16-24% of the height of the preceding channel, and the height of each subsequent channel of the additional loop is increased by 24-26% of the height of the preceding channel. Separator plates are mounted inside the caps. The length of each subsequent plate is reduced with respect to the preceding by 25-35%. The technical effect is to reduce the volumes of gases removed from the electrolysis cell, and to maintain gas removal efficiency.

Description

DEVICE FOR COLLECTION AND REMOVAL OF GASES IN ALUMINUM

ELECTRIC

The technical field to which the invention relates.

The invention relates to non-ferrous metallurgy, in particular to the production of aluminum in electrolyzers with prebaked anodes, and can be used to reduce the volume of exhaust gases from the electrolyzer while maintaining high removal efficiency during the interoperational period and when performing technological operations on the electrolyzer associated with depressurization of shelters.

The level of technology

A device is known in which the gas collection cap is in contact with the crust at the opening of the crust. The purpose of this invention is the collection of waste gases from the electrolyzer for the purification of fluorine components of alumina. (US Patent 4,770,752 (1988)).

The disadvantages of the known device are that this invention has limitations in terms of maintaining the alumina feed system located inside the hood and possible damage during replacement of the anodes, since the hood is close to the anodes and to the crust.

A device is known in which in the interoperative period a standardized amount of process gases and an increased amount of process gases are removed when the covers of the anode case are opened, by turning on an additional exhaust fan. Inside the shelter, a separating wall is installed to direct the flow upwards into the gas channels to reduce emissions into the hull (patent RU 2251593 C2, MIK S25SZ / 20, published on November 15, 2000). The disadvantage of the analog device is that during the depressurization of the electrolyzer, the air flow tightened under the cover moves the electrolysis gases along the electrolyzer and creates stagnant areas with a high concentration of electrolysis gases under the lower flange of the beam. In these areas, gases are discharged into the working area of the cell body through the gaps between the anode rods and the flange, as well as through the gaps between the shields of the shelter.

A device for collecting and removing gases from an aluminum electrolyzer according to patent RU 2553137, С25С 3/22 publ. 06/10/2015, containing a beam-collector, having upper and lower stiffness belts and double vertical walls, between which in the upper part of the collector beam along the vertical walls are formed the main flue channels of variable cross-section with confuser located along the longitudinal axis of the beam-collector above the anodes, one end fixed at the entrance to the fairing, and the other with holes in the lower zone of rigidity, the height of the main duct increases to the end of the beam-collector connected to the gas cleaning system. Between the upper and lower stiffness belts, symmetrically to the longitudinal axis of the collector beam, there are two additional gas passage channels of variable section connected to the lower stiffness belt by confusors equipped with flaps and located along the longitudinal axis above the anodes between the confusors of the main fluff channel, with each face The main gas conduit has a confuser installed in the metal intake zone.

The disadvantage of the proposed device is that the device provides for a local increase in vacuum in the area of replacement of the anodes, without equalizing the vacuum under the entire cover. To do this, include additional gas ducts connected to the confuser, which are equipped with automatic valves. Through openings where the shutters are removed for replacement the anode, under the shelter is drawn in a large volume of air with the formation of vortex flows distributed under the entire shelter. As a result, in other shelter zones confuser can not cope with the removal of gases, and the gas through the leaks of shelter will break out into the case. The proposed device does not provide effective removal of gases during the operation of replacing the anodes.

Closest to the claimed invention to the technical essence is a device for collecting hot gas, waste in the process of electrolysis, proposed in patent WO 2010/033037 A1., IPC S25SZ / 22, publ. 03/25/2010, taken as a prototype. In the device, the cap for gas removal is located directly above the hole in the crust and provides a smaller total volume of gas withdrawn from the electrolyzer with a higher concentration of C0 ₂ and elevated temperature, which allows reducing the number of gas cleaning plants and increasing the heat exchange potential. In addition, the gas collection cap has at least two entrances, i.e. its walls are made double. The suction speed between the double walls considerably exceeds the speed in the center of the cap, which creates additional thrust, which creates an artificial “air wall”, providing more efficient collection of exhaust gases and reduces interference from transverse flows.

The disadvantages of the device prototype:

In the design of the prototype cap, effective removal of electrolysis gases is provided by double walls, which create an artificial “air wall” and reduce interference from the side of transverse flows. In this case, the displacement of caps away from the piercers will make the removal of gases not effective, and placing the cap directly above the hole in the crust will result in damage to the mechanisms controlling the flow of the reflector and the feeder of the electrolyzer as a result of working in an aggressive environment. The desired range of placement of the cap over the crust is from 10 to 1000 mm, determined by the rate of alumina ablation and the possibility of performing the anode replacement operation. To fulfill this condition, it is necessary to change the installation height of the cap during various operations, which violates the tightness of the gas removal device.

For effective removal of gas from the electrolyzer, it is necessary to ensure equal volumes of gas removal from all caps placed under the shelter of the electrolyzer. For this amount of vacuum at the entrance to each cap should be the same, but in the device of the prototype system, regulating the uniform gas intake under the shelter of the electrolyzer, is absent.

In the device according to WO 2010/033037, a cap for collecting process gases can be installed next to the feeder, and not represent a single whole with it. In this case, most of the gas will be dragged to the periphery of the cap, but for this it is necessary to ensure a uniform intake of gases along the length of the base of the cap.

During the operation of replacing the anodes, the covers of the shelter open and the air drawn in through the formed opening forms vortex flows that displace gas into one of the ends of the electrolyzer, caps in this zone will not cope with the removal of the increased volume of gas. In addition, the "air wall" prevents the transverse flow of gas emitted through the large faults of the electrolyte crust to be in place at the place of the anodes to be removed.

Thus, the device of the prototype does not allow for the efficient removal of electrolysis gases, both in the inter-operation mode of the electrolyzer and in the performance of technological operations. In addition, the equipment placed under the shelter, is experiencing heavy loads from the aggressive environment. Disclosure of the invention

The basis of the invention is the reduction of heat loss from the exhaust gases from the electrolyzer and reducing the load on the gas treatment plant while maintaining the efficiency of removal of gases.

The load on the gas treatment facilities is determined by the volume of exhaust gases from the electrolyzers. The total volume of exhaust gases from the electrolyzer with burnt anodes is 3000 tons - 20,000 Nm ³ / hour, of which only 1% 2% are electrolysis gases, and the rest is air. The efficiency of the removal of gases from the electrolyzer is determined by the efficiency factor. systems for removal of gases from the electrolyzer, usually this value is 98%.

The technical result of the claimed invention is to reduce the total volume of gases removed from the electrolyzer several times due to a decrease in the volume of air, when the following conditions are met:

1. The value of efficiency gas removal systems remain at a level of at least 98%, both in the inter-operation mode of the electrolyzer, and when performing technological operations.

2. The load from the aggressive environment on the equipment placed under the shelter does not increase.

To fulfill the first condition in the proposed technical solution in the inter-operation mode of operation of the electrolyzer, the gases are taken to be evenly distributed along the length of the cell cover and the length of the base of each gas collection cap.

To fulfill the second condition, the gas-collecting caps are arranged so that the mechanisms for feeding alumina are outside the gas intake zone, and the caps are designed to ensure uniform gas intake along the base of each gas-collecting cap at the specified location - outside the gas intake zone. In one of the embodiments, the solution of the problem is achieved by a device for collecting and disposing of gases in an aluminum electrolysis cell, which contains a flue system containing horizontal main and additional flue ducts made with the possibility of switching on / off the main and additional flue ducts; and gas collecting caps, each of the gas collecting caps connected by the first channel to the horizontal main gas duct, forming the main gas removal circuit, and the second channel to the additional vertical gas duct, forming an additional gas removal circuit. The height of each subsequent first channel of the main circuit increases by gas flow by 16 ^ 24% from the height of the previous first channel, and the height of each subsequent second channel of the additional circuit is increased by gas flow by 24 ^ 26% from the height of the previous second channel. In the lower part, on the inner surface of the longitudinal sides of at least one gas collection cap along the direction of gas movement, separating plates are installed, the length of which is not more than 50% of the height of the gas collection cap, while on each side of the central axis of the gas collection cap symmetrically at least two separation plates and the length of each next in the direction of the central axis of the cap plate decreases with respect to the previous one by 25-35%.

According to one variant of the proposed invention, the caps are made in the form of confusion.

According to one variant of the proposed invention, the main and additional circuit in the upper part of the caps are combined.

According to one variant of the proposed invention, the distance between the separation plates is at least 15% of the length of the base of the gas collection cap. In addition, the proposed system for the collection and removal of gases in an aluminum electrolysis cell, which contains an electrolyzer containing at least anodes and electrolyte peels, an electrolytic shelter, which is made of removable shields, a system of gas ducts, including horizontal main and additional ducts made with the ability to turn on / off the main and additional gas ducts and gas collection caps placed under the shelter of the electrolyzer along its longitudinal axis between the electrolyte core punches, Forming the gas intake zone in the center of the electrolyzer. On the inner side of the removable shelter covers, horizontally with respect to the electrolyte crust, guide elements are installed that are designed to direct gas flows into the gas intake zone, with each of the gas collection caps connected by a first channel to the horizontal main gas duct, forming the main gas removal loop, and the second channel with the additional vertical gas duct, forming an additional contour of removal of gases. The height of each subsequent first channel of the main circuit increases by gas flow by 16 ^ 24% from the height of the previous first channel, and the height of each subsequent second channel of the additional circuit is increased by gas flow by 24 ^ 26% from the height of the previous second channel. At the same time in the lower part on the inner surface of the longitudinal sides of at least one gas collection cap along the direction of movement of the gas, separation plates are installed, the length of which is not more than 50% of the height of the gas collection cap. On each side of the central axis of the gas collecting cap, at least two separator plates are symmetrically installed, and the length of each next plate towards the central axis of the cap plate decreases relative to the previous one by 25-35%. According to one embodiment of the proposed invention, gas collecting caps in the system are placed above the crust of the electrolyte at a distance of 0.5-1.5 of the height of the new anode of the electrolyzer.

According to one of the variants of the proposed invention, the height of the cover in relation to the level of electrolyte is 1.5-5 height of the new anode.

Also proposed is an electrolyzer that contains a device for collecting and removing gases in an aluminum electrolyzer, as described above.

The options for private implementation of the invention are not the only possible. Various modifications and improvements are allowed, without departing from the scope of the invention defined by the independent claims.

Brief Description of the Drawings

The invention is illustrated by the following drawings:

figure 1 shows a General view of the electrolyzer, which contains a device for the collection and removal of gases;

figure 2 shows the arrangement of structural elements for the collection and removal of gases inside the cell;

on fig.Z shows the elements of the primary and secondary contours of the removal of gases;

figure 4 shows a variant of the guide element of the device for the collection and removal of gases made in the form of a protrusion (cross section of the electrolyzer);

in fig. 5 shows an embodiment of the guide element of the device for collecting and removing gases in the form of plates (cross section of the electrolyzer);

in fig. 6 shows the arrangement of the separating plates in the gas collection cap (cross section of the cap); in fig. 7 shows the main and additional contours of the removal of gases with gas collection caps in a longitudinal section.

The implementation of the invention

A device for collecting and removing gases is installed in the electrolyzer. An electrolyzer is a device for the production of aluminum by the electrolysis of melts, containing, as a rule, anodes, point feeders with alumina with punchers, a collector beam with gas ducts and gas collection caps, and also shelter. All structural elements of the claimed device are mounted on the beam-collector (1). The shelter of the electrolyzer (2) is made of individual shields, on which the guiding elements 3 are rigidly mounted on the inner side horizontally with respect to the electrolyte melt crust. The guiding elements can be structurally made in the form of plates or protrusions (Fig. 4 and Fig. 5) of the materials used for the manufacture of shelter panels, such as aluminum. The number of guiding elements is determined by the speed of the flow between the guides and must provide air velocity greater than 2 m / s and less than 7 m / s in order to exclude dislodging of gases from the electrolyzer and alumina entrainment from the surface of the crust. The location and length of the guide elements is determined by the configuration of the shelter under the condition of a uniform flow around the anodes.

The gas collecting caps (4) are placed under the shelter of the electrolyzer along its longitudinal axis between the electrolyte peels above the anodes (5), between the punches (6), forming a gas intake zone in the center of the electrolyzer.

Each gas cap (4) is connected by the first channel (8) to the horizontal main gas duct (9), forming the main gas removal circuit, and the second channel (8 ') with the additional vertical gas duct (10), forming an additional gas removal circuit (Fig. 3 ). The height of each subsequent first channel of the main circuit increases with the gas flow by 16 ^ 24% of the height of the previous first channel, and the height of each the subsequent second channel of the additional circuit increases with the gas flow by 24 ^ 26% of the height of the previous second channel. The main (9) and additional (10) horizontal ducts are connected to a body gas removal system (not shown).

In the lower part, on the inner surface of the longitudinal sides of at least one gas collection cap along the direction of gas movement, separation plates are installed, the length of which is not more than 50% of the height of the gas collection cap (Fig. 7). Separating plates are rigidly fixed on each side of the central axis of the gas collecting cap, while the length of each next plate towards the central axis of the cap of the plate decreases relative to the previous one by 25-35%. Plates are arranged symmetrically with respect to the central axis of the cap, which ensures equal conditions for gas intake along the length of the base of the cap. To exclude stagnant zones in the cap, the number of plates must be at least two on each side of the central axis. The separator plates installed in this way break up the volume of the cap into sectors (channels) with equal speeds at the base of the cap, without the formation of stagnant zones through which gas will not be removed, ensuring the same efficiency of gas intake in the center of the cap and at its periphery. The width of each parallel channel, preferably, may be at least 15% of the length of the base of the cap. The achieved effect allows you to place the caps between the punches, when the mechanisms for feeding alumina are outside the zone of intake of gases and the load on them from the aggressive environment is minimal.

With an excellent arrangement and dimensions of the plates, the effect of uniform gas intake at the base of the cap, as unexpectedly revealed by the developers, is not achieved.

For example, an increase in the length of the plates or their direction toward the center of the cap led to a collision of flows of individual channels between themselves and respectively to the formation of zones with positive pressure. The gas in this case was knocked back under cover. The location of the plates in the top of the cap led to an increase in speed at the exit of the cap. As a result, the gas-dynamic resistance of the cap increased, i.e. the load on gas cleaning resistances also increased. The irregularity of gas intake at the base of the cap also increased, since in this case, at the entrance to the cap, zones with different vacuum values are formed. In addition, the formation of "air walls" similar to the "air walls" in the prototype, which prevent the collection of gases on the periphery of the cap.

Gas collection caps (4) are placed above the electrolyte crust, for example, at a distance of 0.5, 5 N, 5 the height of the new anode, and the height of the cover is 1.5 K2.0 from the height of the new anode. Increasing the height of the shelter will increase the volume of air in the composition of the gases to be removed; in order to remove gases, it will be necessary to increase the discharge to the values realized in the existing designs of electrolyzers, the load on the gas cleaning facilities will increase, as well as the amount of heat loss. In the case of a decrease in volume, it will be impossible to perform the operation of replacing anodes.

In one of the variants, the gas collection cap, designed during the development of the invention, was made in the form of a confuser, a device in which the channel smoothly lends out, which increases the velocity of the removed gases and reduces the energy losses spent on the removal of gas. The height of the cap was 800 mm, and the base length 1800 mm, with a base width of 170 mm. Separating plates were fixed at a height of 30 mm from the base of the cap and directed along the side walls, forming parallel channels for the movement of gases. The length of the first plate was 400 mm, which is 50% of the height of the cap. The lengths of the second and third plates are 260 mm and 170 mm, respectively. The shape of the base of the caps was determined the condition for the replacement of anodes and the location of the power supply mechanisms for alumina under cover, while the caps cover the entire space in the center of the cell between the anodes, except for the space for the work of the punches and feeders. The width of each of the parallel channels was 180 mm. Caps were installed at a height of 50 mm above the anodes.

The device works as follows. During the inter-operation period of the cell operation, the gas entering the cell shelter (2) through the holes in the crust destruction places by the punchers (6) is mixed with air, which does not get through the density of the shelter and is drawn into caps (4) of the main horizontal gas duct (9). and then sent to the corpus removal system gases (not shown). The separation plates (7) in the caps (4) evenly distribute the gas flow along the base of the caps. The uniform distribution of gas flows between the caps (4) is ensured by the distribution of resistance along the length of the main horizontal gas duct (9) by changing the height of the channels (8) and (8 ’) in the main gas duct. The arrangement of caps (4) above the crust is preferably at a height of 0.5 t – 1.5 from the height of the anode (5), between the punchers (6), which provides a vacuum value sufficient for complete removal of gases.

When performing operations on the electrolyzer associated with partial depressurization of the electrolyzer, under the shelter (2), air is drawn in, which mixes with the anode gases, forming vertical and horizontal vortex flows. Guide elements (3), attached to the shields of the shelter on the inside, break the vortex flows and direct them to the caps (4). During operations (for example, when replacing anodes), gas is removed simultaneously through the main (9) and additional (10) gas ducts. Thus, the amount of rarefaction under the shelter can be increased 3 ^ 4 times, which is enough to remove gases during partial depressurization shelters. Turning on and off the main and additional ducts is performed by known mechanisms, such as a gate.

When implementing the inventive device, the volume of exhaust gases from one electrolyzer decrease by 2 + 4 times due to the cumulative effect of reducing the volume of exhaust gases, the redistribution of gas flows into the gas intake zone and the location of caps near the exit of electrolysis gases under the shelter. When this is achieved, the efficiency of gas removal efficiency = 98% t- 99%, depending on the operations performed on the electrolyzer.

Installing caps under the cover, near the exit of electrolysis gases allows to increase the efficiency of removal of gases with a smaller volume of gases to be removed, and the specified height of installation of caps over the electrolyte crust makes it possible to replace the anodes without damaging the caps. Plates inside the caps provide a uniform intake of gases along the length of the base caps.

Caps are simultaneously included in the main and additional gas removal systems, which ensures efficient gas removal both during the inter-operation period of work and during operations.

The specified range of variation in the height of the connecting channels with caps ensures efficient operation of all caps, i.e. effective removal of gases along the length of the electrolyzer.

The main and additional flue pipes are connected to the caps in the upper part of the caps (at the top of the confuser). The flow rates at the outlet of confuser are already aligned, and the connection of an additional circuit will not lead to a change in the nature of the flow of gases inside the confuser, i.e. will not affect the uniformity of gas intake at the base of the caps. Gas is redistributed along the contours in proportion to the vacuum in the contours and the cross-sectional area of the gas ducts. The arrangement of caps between the punches at a height equal to from 0.5 to 1.5 of the anode height allows the operation of replacing the anode without damaging the structural elements of the device for removing gases and reduces the effect of temperatures and abrasive particles on the performance of the punches and feeders of the electrolyzer.

Claims

CLAIM

1. A device for the collection and removal of gases in an aluminum electrolysis cell, containing

a duct system containing a horizontal main and additional ducts made with the possibility of switching on / off the main and supplemental ducts; and

gas collection caps;

each of the gas collecting caps is connected to the first channel with the horizontal main gas duct, forming the main gas removal loop, and the second channel with an additional vertical gas duct, forming an additional gas removal loop; the height of each subsequent first channel of the main circuit increases along the gas flow by 16 ^ 24% from the height of the previous first channel, and the height of each subsequent second channel of the additional circuit increases by gas flow by 24 ^ 26% of the height of the previous second channel;

at the same time in the lower part on the inner surface of the longitudinal sides of at least one gas collection cap along the direction of movement of the gas, separation plates are installed, the length of which is not more than 50% of the height of the gas collection cap;

On each side of the central axis of the gas collection cap, at least two separator plates are installed symmetrically, and the length of each next one in the direction towards the central axis of the cap of the plate decreases relative to the previous one by 25-35%.

2. The device according to claim 1, characterized in that the main and additional circuit in the upper part of the caps are combined.

3. The device according to claim 1, characterized in that the caps are made in the form of confuser.

15

SUBSTITUTE SHEETS (RULE 26)

4. The device according to claim 1, characterized in that the distance between the separation plates is not less than 15% of the length of the base of the gas collection cap.

5. The system of collection and removal of gases in an aluminum electrolysis cell, containing

a cell containing at least anodes and electrolyte peels,

the shelter of the electrolyzer, while the shelter is made of removable shields; gas duct system, including horizontal main and additional ducts, made with the ability to enable / disable the main and additional ducts;

gas collecting caps placed under the shelter of the electrolyzer along its longitudinal axis between the punches electrolyte peel, forming a zone of gas intake in the center of the electrolyzer;

while on the inside of the removable shields shelter horizontally with respect to the electrolyte peel installed guide elements made with the ability to direct the flow of gases in the area of the intake of gases; each of the gas collecting caps is connected to the first channel with the horizontal main gas duct, forming the main gas removal loop, and the second channel with an additional vertical gas duct, forming an additional gas removal loop; the height of each subsequent first channel of the main circuit increases with the gas flow by 16 ^ 24% from the height of the previous first channel, and the height of each subsequent second channel of the additional circuit increases with the gas flow by 24 ^ 26% from the height of the previous second channel;

while in the lower part on the inner surface of the longitudinal sides of at least one gas collection cap along the direction of movement

sixteen

SUBSTITUTE SHEETS (RULE 26) gas separation plates are installed, the length of which is not more than 50% of the height of the gas collection cap;

6. The system according to claim 5, characterized in that the caps are made in the form of confuser.

7. The system according to claim 5, characterized in that the gas collection caps are placed above the crust of the electrolyte at a distance of 0.5%, 5 the height of the new anode.

8. The system according to claim 5, characterized in that the height of the shelter in relation to the level of electrolyte is 1.5-2 heights of the new anode.

9. The system according to claim 5, characterized in that the main and additional circuit in the upper part of the caps are combined.

10. The system according to claim 5, characterized in that the distance between the separation plates is not less than 15% of the length of the base of the gas collection cap.

11. An electrolyzer containing a device for the collection and removal of gases according to claim 1.

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SUBSTITUTE SHEETS (RULE 26)