Gas purification module and method of purifying gases during electrolysis of aluminium

Abstract

A gas purification module for collecting and purifying the gases formed in a reduction cell during the electrolysis of aluminium comprises at least two reactor-adsorbers (1) connected by a transfer pipe (3) to a bag filter (2) consisting of a dirty gas chamber (4), a clean gas chamber (5), filter bags (6) and a fluorinated alumina hopper (7). The module comprises two adsorbent feed lines. The first of these is configured to permit a feed of pure alumina to the reactor-adsorber (1) and to airlifts (9) for spraying the pure alumina into the filter bags (6). The second line is configured to feed fluorinated alumina into the reactor-adsorbers and into a reduction cell via an airlift (11). The result is an increase in the efficiency in the purification of fluorinated gases from a single reduction cell incorporating a variety of different electrolysis technologies.

Description

[0001] GAS CLEANING MODULE AND METHOD FOR PURIFYING GASES IN ALUMINUM ELECTROLYSIS

[0002] Field of technology

[0003] The invention relates to the production of aluminum by the method of electrolysis of molten salts with the purification of exhaust gases during the electrolysis of aluminum, namely, to gas cleaning equipment that can be used for dry adsorption purification of exhaust electrolysis gases from aluminum production from electrolyzers.

[0004] State of the art

[0005] For the production of aluminum, methods and devices for dry gas cleaning have been developed and are widely used, including cyclones, dust collectors, ash collectors and electrostatic filters of various types, which use gravitational, centrifugal and electrostatic forces to clean gases from dust and other substances, followed by their discharge.

[0006] The main disadvantages of known methods and devices for gas purification are: the impossibility of purifying gas from hydrogen fluoride compounds, as well as purifying gases in a centralized gas purification unit (GPU) with the connection of several electrolyzers, averaging the characteristics of the returned adsorbent, and high CAPEX (Capital Expenditure - English, capital expenditure of the company).

[0007] A combined dust collector (RU 2288782, 10.12.2006) is known, comprising a horizontal electrostatic precipitator followed by a vertical tubular electrostatic precipitator, with a vertical to horizontal electrostatic precipitator active volume ratio of 0.1-0.9. The horizontal plate electrostatic precipitator and vertical tubular electrostatic precipitator are housed in a single housing. Electrodes in the vertical tubular electrostatic precipitator are cleaned mechanically with the gas supply disconnected from the section. Sections of the tubular electrostatic precipitator are cleaned by periodic flushing with liquid with the gas supply disconnected from the section.

[0008] The disadvantage of the well-known analogue is the increased size of the structure and the inability to connect the filter to a single electrolyzer for more optimal cleaning settings.

[0009] A gas cleaning unit for cleaning electrolysis gases is known (RU 2668926, 04.10.2018), comprising a bag filter and a reactor, in which gas cleaning is carried out by dry adsorption with the return of the adsorption material back into production by means of at least one gas cleaning device, comprising at least one reactor made in the form of a Venturi tube with a design that ensures the alignment of the gas flow according to speed modes, and at least one bag filter made in the form of a self-supporting structure, wherein the inlet pipe of the reactor is located opposite the outlet pipe of the corresponding filter.

[0010] A two-stage gas cleaning device for purifying electrolysis gases is also known (RU 2749421, June 9, 2021), comprising at least one reactor, designed as a Venturi tube and providing gas flow equalization according to velocity regimes, connected via a transition pipe to at least one bag filter, a chute for feeding an adsorbent into the reactor, dirty and clean gas chambers, filter bags, and a hopper. The device is characterized in that the dirty and clean gas chambers of the bag filter are divided into at least two sections by a partition with the ability to shut off at least one of the sections. Moreover, the gas cleaning device further comprises a system for spraying the filter bags with an adsorbent, with a pipe for supplying clean air and configured to supply said adsorbent through an additional chute.In this case, the connection point of the spraying system to the bag filter is located between the reactor and the filter, and the bin is divided into at least two sections and equipped with pipes for unloading the adsorbent.

[0011] The aforementioned chute is used to convey material over short distances. It is an open or closed trough, usually circular or rectangular in cross-section, installed at an angle to allow gravity flow of the material. The angle can be significantly reduced by oscillating the chute with a vibrator.

[0012] A common drawback of known analogs is that several electrolyzers are connected to the dry gas cleaning unit (DGU) block, and control of the technological process of gas purification is ensured, ensuring the required amount of adsorbent in the production of aluminum, taking into account the volumes of gases removed from the electrolyzers with averaging indicators and characteristics of the adsorbent returned from the electrolyzers connected to it, without ensuring individual preparation of raw materials.

[0013] Each electrolytic cell in the electrolysis building has its own individual production parameters. These parameters depend on the volume of gas removal from the cell, the volume of pure / recycled alumina fed directly to the cell, the voltage drop across the anode device, and the heat losses from the cell.

[0014] When using shared gas cleaning systems, it is necessary to maintain the temperature of both pure and fluorinated alumina as high as possible. Fluorinated alumina, after exiting the gas cleaning system, is sent to the electrolytic cell via the centralized alumina distribution system and, as a rule, enters the molten bath after a few hours already cooled. This process causes heat losses and a current drop for each cell. Dependencies on the cryolite ratio arise in the electrolytic cell bath, so it is necessary to accurately balance the fluorine content. Time intervals in the shared gas cleaning system (for the electrolysis body) provide a generalized fluorine indicator. Since fluorinated alumina from the bag filter enters the electrolytic cell at frequent intervals, the required fluorine concentration at the time the adsorbent is added to the bath cannot coincide with the actual one.The problem arises in reducing the transportation of fluorinated alumina from the filter to the electrolyzer.

[0015] In this regard, to ensure that each electrolyzer achieves maximum productivity, there is a need to connect an individual gas cleaning unit (or its individual parts) with its own gas removal units, gas purification, alumina storage and feeding it to the electrolyzer.

[0016] The closest prior art to the proposed invention (prototype) is a method for collecting and pre-treating process gases generated in an electrolysis cell (AU2020242088A1, 10 / 28 / 2021), which includes a pre-treatment unit.

[0017] The prototype and the proposed invention share a number of features. The prototype includes a device for collecting gases directly exiting the electrolytic cell and a pre-treatment unit for process gases. One embodiment utilizes a fluidized-bed alumina reactor and a filter unit connected to the pre-treatment unit for reintroducing fluorinated alumina into the adsorption process. The prototype incorporates a pneumatic system for transporting alumina to the gas processing units. The prototype device can be connected to at least one electrolytic cell. An exhaust system (fan or exhaust fan) is used. The prototype is equipped with a device for returning and injecting a portion of the fluorinated alumina back into the electrolytic cell. The objective of the prototype is to reduce the cost of the electrolysis process by installing separate treatment units for each electrolytic cell. However, there is no centralized distribution of alumina from the silo.The proposed concept and operating process clearly indicate the use of two reactors, followed by a filtering device for gas purification. The prototype clarifies the ability to regulate the alumina feed (quantity) of both pure alumina (PA) to the reactors and fluorinated alumina (FA) to the electrolyzer.

[0018] To increase the efficiency of hydrogen fluoride (HF) removal, the prototype proposes using a second reactor. Or, as the prototype describes it, a fluidized bed scrubber. The entire process results in thorough mixing of the gas with fluorinated alumina.

[0019] The prototype's operation describes the possibility of installing individual components in close proximity to the electrolyzer. The actual arrangement of the components and assemblies is proposed to be at a certain distance from each other. Therefore, a unified gas purification system is not present and is not proposed in the prototype.

[0020] A drawback of the prototype is its use of a single, non-variable method for purifying electrolysis gases, without the ability to change the purification scenarios for electrolyzers using electrolysis technology, such as a baked anode. This means there is no flexibility in increasing the efficiency of fluorinated gas purification with possible changes in the electrolyzer operating parameters, which differentiates the proposed invention from the prototype in its objective and the achieved result.

[0021] The prototype has a pre-cleaning unit for electrolysis gases, connected to a single filter that serves as the main gas purification system. The prototype also proposes a pre-cleaning unit for gases from the electrolyzer, which uses a reactor or similar fluidized bed adsorption unit. However, the dust-gas mixture is then transported to the second purification stage—to a filter that separates the gas stream from dust and returns a portion of the fluorinated alumina to the first purification stage for recirculation. This means that this installation is not positioned correctly across the industrial site.

[0022] Disclosure of the essence of the invention

[0023] The technical objective and result of the proposed invention is to increase the efficiency of fluorine-containing gas purification from a single electrolyzer with various electrolysis technologies used in aluminum electrolysis production, i.e., versatility. This is achieved without the need for additional process equipment for dust and gas mixture purification, thereby reducing CAPEX compared to known analogues.

[0024] The dimensions of a gas cleaning module typically do not exceed the dimensions of a 20-foot container. The term "module" encompasses the entire gas cleaning system for a single electrolysis cell, allowing for localized movement within the production site. The module incorporates key equipment, including a bag filter, adsorber reactors, alumina transport, and a fan. This allows for minimal capital expenditures when upgrading aluminum smelter cells.

[0025] The stated problem is solved, and the technical result is achieved through design features and selection of the most appropriate operating mode of the GPU for a specific electrolysis technology, taking into account the requirements and operating modes of each individual electrolyzer. This excludes the implementation of a centralized GPU, which averages the parameters and characteristics of the adsorbent returned from the connected electrolyzers. Brief description of the drawings.

[0026] The essence of the invention is explained by drawings.

[0027] Fig. 1 shows a basic diagram of the gas flow cleaning; Fig. 2 shows the external appearance of the gas cleaning module; Fig. 3 shows a diagram of the gas flow through the gas cleaning module; Figs. 4-8 show diagrams of gas cleaning in five technological modes, where:

[0028] 1 - reactor-adsorber;

[0029] 2 - sleeve filter;

[0030] 3 - transition pipe;

[0031] 4 - dirty gas chamber;

[0032] 5 - clean gas chamber;

[0033] 6 - filter sleeves;

[0034] 7 - fluorinated alumina filter bin;

[0035] 8 - transverse partition;

[0036] 9 - aerolift CHG (pure alumina);

[0037] 10 - FG (fluorinated alumina) bunker;

[0038] 11 - FG (fluorinated alumina) airlift;

[0039] 12 - bunker CHG (pure alumina);

[0040] 13.1, 13.2 - cleaning unit;

[0041] 14.1, 14.2, 14.3 - feeding device;

[0042] 15.1, 15.2, 15.3 - distribution box;

[0043] 16 - estrus of ChG (pure alumina);

[0044] 17 - FG air chute for recirculation;

[0045] 18 - aero ring;

[0046] 19 - distributor;

[0047] 20 - heating element;

[0048] 21 - fan;

[0049] 22 - Electrolyzer. The arrows in the drawings indicate the direction of gas supply to the inlet bell, the direction of adsorbent (pure and fluorinated alumina) supply, the direction of dust-gas mixture movement, the direction of pure gas movement, and the direction of return of the alumina used for purification.

[0050] Implementation of the invention

[0051] Below, with links to drawings, is an example of the design of the installation to help a specialist understand the possibility of implementing the invention.

[0052] The installation includes at least two identical reactor-adsorbers (1), rigidly connected to a sleeve filter (2) through a transition pipe (3), which is a conical transition from the round cross-section of the reactor-adsorber (1) to the rectangular cross-section of the sleeve filter (2).

[0053] The bag filter (2) includes a dirty gas chamber (4), a clean gas chamber (5), filter bags (6), and a fluorinated alumina filter bin (7). The dirty gas chamber of the gas cleaning module is divided into at least two sections by a transverse partition (8).

[0054] At least one pure alumina (PAL) airlift (9) is installed in the under-arm space.

[0055] The FG (fluorinated alumina) bin (10) is used for storing spent adsorbent (fluorinated alumina). It is rigidly connected to the bag filter (2) via an air chute. The FG (10) bin has a discharge pipe that is connected to the FG (fluorinated alumina) airlift (11).

[0056] The Pure Alumina (CA) hopper (12) is integrated into the bag filter (2) design. This unit (12) has at least one discharge pipe and is connected through it to the cleaning units (13.1, 13.2). Further along the line, the cleaning units (13.1, 13.2) are connected to the feeding devices (14.1, 14.2, 14.3) and distribution boxes (15.1, 15.2, 15.3) by means of air chutes. One distribution box (15.1) is connected to the Pure Alumina (CA) air lifts (9) by means of Pure Alumina (CA) chutes (16). The second distribution box (15.2) is connected by means of at least one Pure Alumina (FA) air chute for recirculation (17) to the air ring (18), which is located on the reactor-adsorber (1) and is connected by chutes.

[0057] An air duct is installed at the bottom of the sleeve filter (2), which is rigidly connected to the third distribution box (15.3) via a distributor (19).

[0058] The gas cleaning module operates as follows.

[0059] The gas cleaning module for an electrolyzer using electrolysis technology (e.g., prebaked anode) has two stages of gas flow purification: adsorber reactors (1) and a sectional bag filter (2). The first stage adsorbs fluoride compounds by mixing the gas-adsorbent mixture, while the second stage provides additional purification and separation of the purified gas from dust.

[0060] The gas flow from the electrolyzer enters the feedstock fluorination unit through at least two identical adsorber reactors (1), which divide the feed gas flow equally. The adsorber reactors are constructed as Venturi tubes, mixing the "dirty" gas with the adsorbent (alumina) through turbulence in the ascending gas flow and equalizing the velocity of the incoming gas-dust mixture. The reactor body is a conical tube with at least two chutes for feeding fresh and / or fluorinated alumina, located equidistantly around the circumference and elevated at some distance from the smaller-diameter flange.

[0061] The dust-gas mixture is then directed through transition pipes (3), which reduce the dust-gas flow velocity and evenly distribute the volume of alumina particles and gas exiting the reactor. This mixture enters the dirty gas chamber (4) and passes through filter bags. A rectangular transition pipe (3) is inserted into the dirty gas chamber. The purified gas is collected in the clean gas chamber (5) and directed into the flue gas stack.

[0062] The dirty gas chamber (4) is typically parallelepiped-shaped and occupies most of the volume of the bag filter (2). Two rectangular flanges are located at the bottom of the chamber for connecting the adsorber reactors via a transition pipe.

[0063] The clean gas chamber (5) collects all incoming gas from the two sections and discharges it through a common flue through its own fan (21), which is mounted directly on the gas cleaning module, into the aeration lantern of the electrolysis building. The chamber is equipped with a pulsed hose purge system, consisting of supply pipes with connections to each hose.

[0064] The transition pipe (3), the dirty gas chamber (4) and the clean gas chamber (5) are the structural elements of the bag filter (2).

[0065] The bag filter (2) includes a pure alumina bin (12). It has a wall adjacent to the filter and is a vertical rectangular box of the same height and width as the filter. To prevent caking and transfer alumina to subsequent lines, an aerodrome with at least one outlet pipe (chute) is installed at the bottom of the silo. The chute distributes the adsorbent across two air chutes. The first is the main line and supplies alumina to the adsorber reactors (1). The second is for feeding two pure alumina airlifts (9), which spray alumina onto the filter bags.

[0066] The aeroslide (17) is an alumina transport unit that can be positioned at an angle (0-3°) relative to the horizontal. It consists of a profile pipe with an aerodome installed at the bottom. The aerodome and working sections of the aeroslide (17) are connected by a flange joint. An aerofabric is installed between these components, allowing air to pass through but retaining the adsorbent on the surface. Air is blown into the bottom of the aerodome, thereby ensuring unimpeded transport of alumina through the aerofabric.

[0067] The gas cleaning module uses two alumina supply lines: the first line supplies pure alumina, the second line supplies fluorinated alumina.

[0068] First line (supply of pure alumina)

[0069] Pure alumina is fed into the adsorber reactors (1). This line consists of the following units: a cleaning unit (13.2), a feeding device (14.1), a distribution box (15.2), a pure alumina chute (16), a FG recirculation aeration chute (17), and an aeration ring (18). The cleaning unit (13.2) is connected via the lower flange through the chute, which is a vertical conical transition.

[0070] In this design, the purification unit (13.2) is a vertical profile pipe into which pure alumina is fed from a chute at the top. A constant air supply is provided to the aeration fabric at the bottom, creating a bubbling layer. Alumina, along with some foreign inclusions, enters the purification unit and begins to fill the entire space, forming a fluidized bed. All heavy, small inclusions settle to the bottom, thereby purifying the alumina. As the level gradually fills, the now-purified adsorbent enters the feeder (14.1) through a pipe located at the top of the purification unit. A hatch is located on one side of the profile pipe for easy access and maintenance of the internal components.

[0071] The feeding device (14.1) can be, for example, a roller feeder based on an aeroslide with an adjustable variable cross-section. This mechanism has no permanent rotating parts, eliminating jamming and abrasion. The variable cross-section mechanism itself is a strip bent to a specified diameter along its length, halfway around the circumference, covering the entire cross-section of the aeroslide. This unit is mounted on a shaft and can rotate around its axis. The strip has a conical slit through which alumina flows along the aerofabric. A gearbox mounted outside the aeroslide and aligned with the strip shaft regulates the adsorbent feed. For ease of adjustment, a steering wheel is provided; turning it adjusts the opening position of the internal cross-section in degrees.The more the strip tilt angle changes relative to its initial position, the more the strip slot opens and, consequently, the more alumina is supplied.

[0072] After the feeding device, the adsorbent is fed into the distribution box (15.2) using an air chute. The distribution box is a rectangular bin with outlet chutes. An air supply pipe is installed at the bottom, an aspiration pipe and a pure alumina loading chute (16) are installed at the top. A vibration fork sensor is screwed into the upper part of the pure alumina loading chute into the alumina box, which allows determining the level of the adsorbent loading in the distribution box (15.2). Inside, an aeration fabric is stretched across the entire lower section of the distribution box (15.2), which allows for the formation of a fluidized bed with a constant supply of air and alumina. Outlet chutes located on the walls of the distribution box (15.2) allow for an even supply of adsorbent throughout the system by achieving an overflow effect.When the alumina is evenly distributed across the aerodynamic bottom and reaches the level of the chutes, it will be divided with the same volume into two chutes to supply the adsorbent to the adsorber reactors through the aeroslide (17) and aeroring (18) of the first and second sections.

[0073] To ensure uniform mixing and distribution of the adsorbent across the reactor chutes, an aero ring (18) is used. Its cross-section resembles a standard aero chute, shaped like a ring. A longitudinal dividing wall is installed within the inner portion of the aero ring's working section (18). This wall divides the aero ring's working section in half, stopping short of the aero bottom by a distance determined by material parameters such as flowability and density. This distance is selected empirically, based on the conditions for unimpeded material flow from one half of the aero ring's working section to the other. Alumina loading is located at the top of the aero ring on the inner side. Discharge is established through at least two side chutes, both located above the dividing wall.This ensures both uniform distribution of alumina across the aerodynamic ring's aerodynamic bottom, with the simultaneous mixing of pure and fluorinated alumina, and uniform flow into the chutes. The chutes are designed as nozzles arranged circumferentially. Each nozzle enters the reactor at a specific angle.

[0074] Second line

[0075] It supplies fluorinated (recirculation) alumina to the adsorber reactors (1) and consists of the following units: distributor (19), feeder (14), distribution box (15.3), FG (fluorinated alumina) air chute for recirculation (17).

[0076] The distributor (19) combines the discharge from two sections of the bag filter into a single chute and is designed to move alumina from vertical (falling) to horizontal. It consists of two chutes passing into a tee body, which is a vertical pipe with an air bottom. An air supply pipe is installed at the bottom of the air bottom. At some distance above the air bottom, a side discharge into the feeding device (14.3) is installed. The distance from the air bottom to the discharge is determined by the supplied air pressure. To achieve the overflow effect, it is necessary to maintain the height of the bubbling layer of alumina and then set the discharge at this level. A hatch is located on the side wall for servicing the internal unit of the unloader. Alumina, filling the space of the air bottom, forms a bubbling layer and flows with an overflow into the discharge pipe. Then - into the feeding device (14.3).

[0077] The feeder (14.3) and the distribution box (15.3) have a similar design to the feeder and the distribution box of the first line.

[0078] The fluorinated alumina hopper (bottom) (7) of the bag filter (2) has an outlet from each section via chutes through an overflow. As the filter hopper fills with fluorinated alumina poured from the filter bags, the adsorbent is distributed for recirculation into the aero rings (18) and for feeding into a tank called the FG hopper, through at least one chute. The adsorbent is transported via a fluorinated alumina recirculation aeroslide, which is no different in design features from the aeroslides described above. This unit is located under the bag filter and is connected via chutes exiting from the bottom of each section. The chutes are two truncated cones. In the central upper part of the aeroslide, there is an access hatch. This hatch allows for checking the alumina transport through the aero fabric. The adsorbent then flows into the FG hopper (10).

[0079] The FG (fluorinated alumina) bin (10) serves as an intermediate storage tank for a portion of the adsorbent being discharged into the module. It is a horizontally positioned box, the design of which is determined solely by space constraints of adjacent equipment and the daily volume of fluorinated alumina produced. To prevent caking and ensure uniform material flow, the bin is equipped with an air floor. At the end of the air floor is a discharge port for the FG (fluorinated alumina) airlift (11). An aspiration port can be located on one of the bin's walls (10). A service hatch is also located on one of the side walls. This hatch allows for checking the tension of the air fabric and, if necessary, providing access to the airlift's discharge plate.

[0080] The FG (fluorinated alumina) airlift (11) is required for vertical feeding of the spent material into the electrolyzer (22). The FG airlift body (11) is a vertical pipe. An air floor is installed in the lower part of the body. In the upper side part there is a loading branch pipe connected to the FG hopper (10). Unloading is carried out using a vertically installed stainless steel pipe into the upper end of the airlift body (11). In the airlift body, the vertical pipe approaches the lower high-pressure air supply branch pipe and forms a gap, which is necessary for the material to be captured by air into the vertical pipe for unloading. At the end of the high-pressure air supply branch pipe there is a cylindrical bushing on a threaded connection, which is used to regulate the volume of air supplied to the vertical pipe. On the side wall of the air floor there is a second low-pressure air supply branch pipe, which performs the function of mixing alumina.The loaded adsorbent fills the space within the aerofoil and rises to a predetermined level within the airlift body. A lateral air injection into the aerofoil creates a bubbling layer to prevent material caking. Air is then fed through the side inlet into the high-pressure inlet, which picks up the material from the aerofoil and transports it through a vertical stainless steel pipe. This pipe has no connecting bushings or clamps to prevent abrasion of these components by the alumina.

[0081] Following the FG airlift (11), the adsorbent (fluorinated alumina) enters the centralized alumina distribution system (CAD) for loading into the electrolytic cell (22). At this stage, the alumina, passing through the trough system, is heated by a heating element (20), such as a tubular coil, using feed gas pumped by a fan (21) from the chimney. The heating system divides the outgoing clean gas stream into two parts. The first is directed to the CAD system. Heat exchange between the gas and the alumina occurs, after which the exhaust gas returns to the chimney and is released into the atmosphere, while the second is directed to the aeration lantern of the electrolytic cell building and then to the atmosphere.

[0082] To calculate the cross-section of aeroslides, formulas are used based on the volume of alumina delivered through the aeroslide, the amount of air required to transport the alumina, and the physical characteristics of the material being transported. When performing the calculation, it is important to select the minimum possible weight of the aeroslides to reduce metal consumption. When selecting chutes without air injection, the shortest possible chute lengths should be used, and steeper chute angles should be used to ensure minimal abrasive wear (for alumina, no more than 38°).

[0083] The gas cleaning module can operate in five modes to maximize the cleaning performance of exhaust gases from various electrolysis processes. The use of each mode is determined empirically, depending on the identified cell characteristics and the gas volumes supplied. One of the five operating modes is selected for different cell operating parameters, such as: gas removal volume from the cell, cryolite ratio, pure / recirculated alumina feed volume directly into the cell, voltage drop across the anode device, and heat losses from the cell. Based on the specific electrolysis technology, this module allows for the regulation of adsorbent feed to the reactors and the filter inter-bag space. The volume of purified gas supplied through the module can also be adjusted using a fan frequency converter (21). A description of the operating modes and sequence of operations is provided below:

[0084] 1. Classic mode

[0085] This mode is advantageous when working with baked anode technology. It is applicable to the current output parameter (voltage drop).

[0086] Brief description of the operating mode of the SGOU:

[0087] The distribution of gases leaving the electrolyzer is as follows: 50%Q (gas volume) to the 1st reactor; 50%Q (gas volume) to the 2nd reactor.

[0088] Amount of pure alumina (PA) fed: 50% PA per reactor 1; 50% PA per reactor 2.

[0089] Amount of fluorinated alumina (FA) supplied: up to 50% FA for recirculation into the 1st reactor; up to 50% FA for recirculation into the 2nd reactor.

[0090] The unloading of the FG into the electrolyzer is carried out from the 1st and 2nd sections of the bag filter.

[0091] Fig. 4 shows the operation diagram of the classic mode.

[0092] The "dirty" gas from one electrolyzer is fed evenly to both reactor-adsorbers (1). In this scheme, pure alumina is fed from the chute of the CHG hopper (12) to the cleaning unit (13.2) and then into the feeding device (14.1). In this scheme, the feeding device is adjusted by the angle of the inner plate so that the cross-section of the feeding device allows for the distribution of 50% of the pure adsorbent into two aeration rings (18). After the feeding device, the adsorbent is transported through the chute to the distribution box (15.2). By overflow, the adsorbent passes in equal proportions through the FG aeration chutes (17) for recirculation into the aeration rings (18) of the first and second sections.

[0093] At the same time, fluorinated alumina from sections 1 and 2 of the bag filter is fed by the feeding device (14.3) through the fluorinated alumina distribution box (15.3) into the FG air troughs for recirculation (17) and then into the air rings (18) with a proportion of 50% of the adsorbent per air ring. Fluorinated alumina is unloaded from the filter's fluorinated alumina hopper (7) from sections 1 and 2 of the bag filter (2) using chutes via an overflow. The adsorbent then enters the FG hopper (10), the volume for unloading accumulates, and is sent via the FG air lift (11) to the electrolyzer by the centralized alumina distribution system (CADS).

[0094] 2. Sequential mode

[0095] This mode is advantageous when working with baked anode technology. It can be used to maintain the highest possible alumina temperature.

[0096] Brief description of the sequential operating mode of the SGOU:

[0097] The distribution of gases leaving the electrolyzer is as follows: 50%Q (gas volume) to the 1st reactor; 50%Q (gas volume) to the 2nd reactor.

[0098] Amount of supplied pure alumina (PA): 100% PA per 1 reactor.

[0099] Amount of fluorinated alumina (FA) fed: 100% FA to the 2nd reactor. FA from the 1st section of the bag filter to the 2nd reactor.

[0100] The unloading of the FG into the electrolyzer is carried out from the 2nd section of the bag filter.

[0101] Fig. 5 shows the operation diagram of the sequential mode.

[0102] The "dirty" gas is fed from one electrolyzer evenly to both reactor-adsorbers (1). In this scheme, pure alumina is fed from the silo chute (12) to the cleaning unit (13.2) and then to the feeding device (14.1). Unlike the first operating mode, in this scheme the feeding device is adjusted by the angle of inclination of the inner plate so that the cross-section of the feeding device allows 100% of the adsorbent (pure alumina) to be sent to the aeration ring (18) of the first section of the bag filter. After the feeding device (14.1), the adsorbent (pure alumina) is transported through the chute to the distribution box (15.2) and then to the reactor-adsorber (1) of the first section of the bag filter. In this mode, the knife valve shuts off the feed of pure alumina to the second reactor-adsorber (1).

[0103] At the same time, 100% of fluorinated alumina is fed from the 1st section of the bag filter (2) using the feeding device (14.3) through the fluorinated alumina distribution box (15.3) into the FG air chute for recirculation (17) of the second section of the bag filter and then into the air ring (18) of the 2nd reactor-adsorber (1). Fluorinated alumina is unloaded from the FG hopper of the bag filter (7) from the 2nd section using chutes by means of an overflow. Then, the adsorbent (fluorinated alumina) enters the FG hopper (10), the volume for unloading accumulates and is sent using the FG air lift (11) to the electrolyzer by the CRG system.

[0104] 3. Reverse mode

[0105] Ideal for Soderberg-type electrolysis or self-baking anode technologies. Suitable for current efficiency (voltage drop).

[0106] Brief description of the reversible operating mode of the SGOU:

[0107] The distribution of gases leaving the electrolyzer is as follows: 50%Q (gas volume) to the 1st reactor; 50%Q (gas volume) to the 2nd reactor.

[0108] Amount of pure alumina (PA) supplied: 50% PA to the 1st airlift; 50% PA to the 2nd airlift.

[0109] The amount of fluorinated alumina (FA) fed: 50% of FA is fed from the 1st section of the bag filter to the 1st reactor; 50% of FA is fed from the 2nd section of the bag filter to the 2nd reactor.

[0110] The unloading of the FG into the electrolyzer is carried out from the 1st and 2nd sections of the bag filter.

[0111] Fig. 6 shows the diagram of the reverse mode operation.

[0112] The "dirty" gas from one electrolyzer is fed evenly to both adsorber reactors (1). In this scheme, pure alumina is fed from the silo chute (12) to the cleaning unit (13.1) and then to the feeder (14.2). Pure alumina is transported exclusively by airlifts (9) installed in the bin of the bag filter (7). In this scheme, the feeder (14.2) is adjusted by the angle of the inner plate so that the feeder cross-section allows 50% of the adsorbent (pure alumina) to be delivered to each airlift of the silo (9). In this mode, knife valves shut off the supply of pure alumina to both reactors.

[0113] At the same time, 50% of fluorinated alumina is fed from the 1st and 2nd sections of the bag filter hopper (7) using the feeding device (14.3) through the fluorinated alumina distribution box (15.3) into the FG aeroslide for recirculation (17) and then into the aerorings (18) to two adsorber reactors (1). Unloading of fluorinated alumina from the bag filter hopper (7) and transport of the adsorbent to the electrolyzer is carried out in the same way as in the classical operating mode.

[0114] 4. Efficiency Enhancement Mode

[0115] This mode can be used to maintain maximum fluoride capture (cryolite ratio).

[0116] Brief description of the specified operating mode of the SGOU:

[0117] The distribution of gases leaving the electrolyzer is as follows: 50%Q (gas volume) to reactor 1; 50%Q (gas volume) to reactor 2.

[0118] Amount of pure alumina (PA) fed: 25% PA to the 1st reactor; 25% PA to the 2nd reactor; 25% PA to the 1st airlift; 25% PA to the 2nd airlift.

[0119] The amount of fluorinated alumina (FA) fed: 50% of FA is fed from the 1st section of the bag filter to the 1st reactor; 50% of FA is fed from the 2nd section of the bag filter to the 2nd reactor.

[0120] The FG is unloaded into the electrolyzer from sections 1 and 2 of the bag filter. Fig. 7 shows the operating diagram of the efficiency-enhancing mode.

[0121] The "dirty" gas is fed from one electrolyzer evenly to both adsorber reactors (1). In this scheme, pure alumina is fed to the aero rings (18) and the CHG airlifts (9). Pure alumina is fed from two chutes of the CHG silo (12), then distributed among the cleaning units (13.1, 13.2) and enters the feeding devices (14.1, 14.2). Two pure alumina feed lines are described below. In this scheme, both feeding devices (14.1, 14.2) are adjusted by the inclination angle of the inner plate so that the cross-section of the feeding device allows 25% of the adsorbent to be sent to each CHG airlift (9) and each aero ring (18). After the feeding devices (14.1, 14.2) the adsorbent is transported through the chutes through the distribution boxes (15.1, 15.2) and then from the first line into the adsorber reactors (1) through the aero rings (18), from the second line into the inter-sleeve space of the filter (2) through the CHG airlifts (9).

[0122] At the same time, 50% of fluorinated alumina is fed from the 1st and 2nd sections of the bag filter hopper (7) using the feeding device (14.3) through the fluorinated alumina distribution box (15.3) into the FG aeroslides for recirculation (17) and then into the aerorings (18) to two adsorber reactors (1). Unloading of fluorinated alumina from the bag filter hopper (7) and transport of the adsorbent is carried out in the same way as in the classical operating mode.

[0123] 5. Mode with sequential unloading of adsorbent (fluorinated alumina)

[0124] This mode is advantageous when working with baked anode technologies. It can be used to maintain maximum fluorine capture (cryolite ratio).

[0125] Brief description of the operating mode of the SGOU:

[0126] The distribution of gases leaving the electrolyzer is as follows: 50%Q (gas volume) to reactor 1; 50%Q (gas volume) to reactor 2.

[0127] Amount of supplied pure alumina (PA): 50% PA per 1 reactor; 50% PA per 1 airlift.

[0128] Amount of fluorinated alumina (FA) fed: 100% FA is fed from section 1 of the bag filter to the 2nd reactor.

[0129] The unloading of the FG into the electrolyzer is carried out from the 2nd section of the bag filter.

[0130] Fig. 8 shows the operation diagram of the mode with sequential unloading of the adsorbent.

[0131] The "dirty" gas is fed from one electrolyzer evenly to both reactor-adsorbers (1). In this scheme, pure alumina is fed to one aeration ring (18) of the first section and one airlift CHG (9) of the first section. Pure alumina is fed from two chutes of the CHG silo (12) and then distributed among the cleaning units (13.1, 13.2) and gets into the feeding devices (14.1, 14.2). Two lines for feeding pure alumina are described below. In this scheme, both feeding devices (14.1, 14.2) are adjusted by the angle of inclination of the inner plate so that the cross-section of the feeding device allows sending 50% of the adsorbent to the airlift CHG (9) of the first section and 50% of the adsorbent to the aeration ring (18) of the first section. After the feeding devices (14.1, 14.2) the adsorbent is transported through the chutes to the distribution boxes (15.1, 15.2) and then enters from the first line into the reactor-adsorber (1) of the first section through the aeration ring (18), from the second line into the inter-bag space of the bag filter (2) through the air lift CHG (9) of the first section of the bag filter. In this mode, the knife valve shuts off the supply of pure alumina to the reactor-adsorber (1) of the second section of the bag filter.

[0132] At the same time, 100% of the fluorinated alumina is fed from the 1st section of the bag filter (2) using the feeding device (14.3) through the fluorinated alumina distribution box (15.3) into the FG aeroslide chute for recirculation (17) of the second section and then into the aeroring (18) of the adsorber-reactor (1) of the second section. Unloading of the fluorinated alumina from the bag filter hopper (7) and transport of the adsorbent is carried out in the same way as in the sequential operating mode.

[0133] The fluorination plant for aluminum production raw materials has a number of similarities with the prototype:

[0134] Mixing of gas with adsorbent by means of turbulent flows.

[0135] The presence of an adsorber reactor for adsorbing fluorine.

[0136] The installation includes a filter unit in the form of a sleeve filter.

[0137] The differences between the design of the installation and the adopted prototype include the following:

[0138] The unit is not connected to a centralized dry gas cleaning system (DGS), which allows for autonomous operation. This configuration allows for the gas cleaning module to be relocated for connection to different electrolyzers without the expense of extensive ductwork, thus providing versatility. This advantage is achieved by constructing the module as a monolithic unit. It can be moved using construction equipment.

[0139] The unit is not a pre-treatment unit, but rather operates independently without the aid of third-party post-treatment units, as the pre-treatment in the analogous unit is performed for the operation of a centralized gas purification system (the gas purification system cannot be excluded from the adsorption process). Therefore, the proposed gas purification module is individually configured for gas adsorption for each electrolyzer. This advantage is achieved by adjusting the adsorbent feed to the adsorber reactors (1) and the filter inter-bag space (2) using feeders (14.1) and knife valves.

[0140] The geometric shapes of the various plant components are specified in the description and shown in the drawings as examples and are not limited to the design examples. Raw materials for the electrolyzer are prepared individually (without averaging), improving the overall technical and economic performance of the electrolyzer series. Maximum efficiency can be extracted from the electrolyzer bath. This advantage is achieved by feeding fluorinated alumina back into the electrolyzer via air chutes in real time (without time delays).

[0141] The system has only one smoke exhauster (fan) for the entire gas cleaning cycle, unlike the prototype, which has one smoke exhauster installed in the pre-cleaning unit and a second in the common centralized gas cleaning system. This allows for individual engine speed adjustment, ensuring high-quality tuning of the gas extraction system from the electrolyzer.

[0142] Taking into account the description and examples, the scope of legal protection is claimed for a gas cleaning module for collecting and cleaning gases generated in an electrolyzer during the production of aluminum, comprising: at least two adsorber reactors (1) connected by means of transition pipes (3) with a bag filter (2) including a dirty gas chamber (4) divided by a partition (8) into two sections, a clean gas chamber (5), filter sleeves (6) and a fluorinated alumina bin (7), wherein the gas cleaning module contains two adsorbent supply lines, one of which is intended for supplying pure alumina, the second for supplying fluorinated alumina, on the first line there is a pure alumina bin (12) with an aerodrome and at least two chutes made for the possibility of supplying pure alumina to the adsorber reactors (1) and to airlifts (9) for spraying pure alumina onto the filter sleeves (6), and the second adsorbent supply line contains a fluorinated alumina bin (7),located in the lower part of the sleeve filter (2), connected to the fluorinated alumina storage bin (7), designed with the possibility of feeding fluorinated alumina into the electrolyzer via an airlift (11) and into the adsorber reactors (1).,

[0143] In this case, the first and second adsorbent supply lines are equipped with supply devices (14.1, 14.2, 14.3) and distribution boxes (15.1, 15.2, 15.3).

[0144] It is advisable that the module be designed with the possibility of being placed in close proximity to the electrolyzer and be connected to the electrolyzer by a channel for feeding fluorinated alumina into the electrolyzer as a raw material.

[0145] Preferably, the module comprises a fan (21) located on the gas outlet line to the atmosphere.

[0146] Also within the scope of legal protection is a method for collecting and purifying gases generated in an electrolytic cell during the production of aluminum using the proposed gas cleaning module, which includes: (a) feeding dirty gas from one electrolytic cell in equal volumes to two adsorber reactors; (b) feeding clean alumina from a clean alumina bin to filter bags and / or to adsorber reactors; (c) simultaneously feeding fluorinated alumina by means of a feeding device and a distribution box into an air chute(s) for recirculation and to the adsorber reactor(s); wherein the fluorinated alumina is unloaded from the bag filter bin from the first and / or second section by means of an overflow, after which the adsorbent is accumulated in the fluorinated alumina bin and subsequently fed to the electrolytic cell.

[0147] In one embodiment, the amount of pure alumina fed to the filter bags and / or adsorber reactors ranges from 25% to 100%, depending on the process conditions. The amount of fluorinated alumina recycled to the adsorber reactors can range from 50% to 100%, depending on the process conditions. Preferably, the fluorinated alumina is preheated before being fed to the electrolytic cell.

Claims

CLAUSES OF THE INVENTION 1. A gas cleaning module for collecting and cleaning gases generated in an electrolyzer during the production of aluminum, comprising at least two adsorber reactors (1) connected by means of transition pipes (3) to a bag filter (2) including a dirty gas chamber (4) divided by a partition (8) into two sections, a clean gas chamber (5), filter bags (6) and a fluorinated alumina hopper (7), wherein the gas cleaning module comprises two adsorbent supply lines, one of which is intended for supplying pure alumina, the second for supplying fluorinated alumina, on the first line there is a pure alumina hopper (12) with an aerodrome and at least two chutes made for the possibility of supplying pure alumina to the adsorber reactors (1) and to airlifts (9) for spraying pure alumina onto the filter bags (6), and the second adsorbent supply line contains a fluorinated alumina hopper (7) located in the lower part of the bag filter (2),connected to a fluorinated alumina storage bin (7), designed with the possibility of feeding fluorinated alumina into the electrolyzer via an airlift (11) and into the adsorber reactors (1)., 2. A gas cleaning module according to item 1, characterized in that the first and second adsorbent supply lines are equipped with supply devices (14.1, 14.2, 14.3) and distribution boxes (15.1, 15.2, 15.3).

3. A gas cleaning module according to paragraph 1, characterized in that it is designed with the possibility of being placed in close proximity to the electrolyzer and is connected to the electrolyzer by a channel for feeding fluorinated alumina into the electrolyzer as raw material.

4. A gas cleaning module according to paragraph 1, characterized in that it contains a fan (21) located on the gas outlet line into the atmosphere.

5. A method for collecting and purifying gases generated in an electrolytic cell during the production of aluminum using a gas cleaning module according to any one of paragraphs. 1-4, comprising: (a) feeding dirty gas from one electrolytic cell in equal volume to two adsorber reactors; (b) feeding clean alumina from a clean alumina bin to filter bags and / or to adsorber reactors; (c) simultaneously feeding fluorinated alumina by means of a feeding device and a distribution box into an air chute(s) for recirculation and to the adsorber reactor(s); wherein the fluorinated alumina is unloaded from the bag filter bin from the first and / or second section by means of an overflow, after which the adsorbent is accumulated in the fluorinated alumina bin and subsequently fed to the electrolytic cell.

6. The method according to paragraph 5, characterized in that the amount of pure alumina supplied to the filter bags and / or to the adsorber reactors is from 25% to 100%, depending on the mode specified by the technology.

7. The method according to paragraph 5, characterized in that the amount of fluorinated alumina supplied for recirculation into the adsorber reactors is from 50% to 100%, depending on the mode specified by the technology.

8. The method according to paragraph 5, characterized in that before feeding the fluorinated alumina into the electrolyzer, it is subjected to preliminary heating.

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