Patent Publication Number: US-11028494-B2

Title: Device for controlled feeding an electrolytic cell for producing aluminum (variants)

Description:
The invention relates to nonferrous metallurgy, in particular to the electrolytic production of aluminum, namely to the devices for feeding electrolytic cells, and can be used to feed alumina, aluminum fluoride, crushed electrolyte to electrolytic cells for producing aluminum. 
     The prior art discloses a device for feeding electrolytic cells (RU 2226572, 2004, C25 C 3/14, published on 2004 Apr. 10). Said device includes a supply hopper, a metering chamber with a flange resting upon hopper bottom, and a valve stem with an actuator. Upper and lower locking metering valves are rigidly fixed on the valve stem. Moreover, the upper metering valve is located above the metering chamber, wherein the upper metering valve has a shape of a hemisphere with its base down, and the lower metering valve has a shape of a cone with its apex downwards. The diameter of the hemisphere is larger and the diameter of the cone is smaller than the diameter of the metering chamber. A housing is connected to the metering chamber by metal studs, which are distributed uniformly along its circumference. The distance between the housing and the upper metering valve at its lowest position within the metering chamber equals to 2-20 valve stem strokes. The upper metering valve agitates the feed near a loading opening. 
     Disadvantages Of This Device Are As Follows: 
     1. Probability of lumping and bridging of the loose materials above the upper metering valve due to a limited height of the valve impact on feeding materials. 
     2. Dependence of density and flow of the materials on their level in the hopper. 
     These disadvantages impair the continuity of the feed supply and filling of the metering chamber. 
     The closest analog to the device of the present disclosure, in terms of technical essence and technical effect, is a device for feeding an electrolytic cell for producing aluminum (WO2014/011073, C25 C 3/14, published on 2014 Jan. 16). Said device comprises a supply hopper, a metering chamber with a flange resting upon a bottom of the hopper, and a valve stem with an actuator. Upper and lower locking elements are rigidly fixed on the ends of the valve stem in the upper and lower parts of the metering chamber. Loading windows are placed along a perimeter of an upper part of the metering chamber above the hopper bottom. The lower locking element has a tapered metering valve connected to a conical bonnet by a piston; the distance from the base of the tapered metering valve to a lower edge of the metering chamber, when the valve stem is in an upper position, is not less than the distance from the lower surface of the upper locking element to a lower edge of the loading windows. The upper locking element agitates the feed in a limited space near the loading windows. 
     Disadvantages of this solution are as follows: 
     1. Probability of lumping and bridging of the loose materials above the upper metering valve due to a limited height of the valve impact on feeding materials. 
     2. Dependence of density and flow of the materials on the level in the hopper. 
     These disadvantages impair the continuity of the feed supply and filling of the metering chamber. 
     The aim of the present invention is providing a device for controlled feeding an electrolytic cell for producing aluminum, wherein said device, as compared with the prior art, provides an uninterrupted supply to and filling of the metering chamber with loose materials. 
     The technical effect of the present invention is to provide an easy flow of loose materials in the bottom of the hopper near loading windows. 
     According to a first variant of the invention, there is provided a device for feeding an electrolytic cell for producing aluminum comprising a hopper with a feeding material; a metering chamber with loading windows located around a perimeter of an upper part of the metering chamber above a hopper base; a valve stem with an actuator; an upper locking element rigidly fixed to the valve stem at the upper part of the metering chamber, wherein the upper locking element is positioned between upper and lower edges of the loading windows, when the valve stem is in its upper position; and a lower locking element fixed on the end of the valve stem, characterized in that at least one metering shuttle valve is provided in the upper part of the metering chamber above the upper locking element, and the metering shuttle valve is rigidly fixed to the valve stem so that its upper end in an initial position of the valve stem is located below the upper edge of loading windows. 
     Particular embodiments of the device according to the first variant of the present invention have the following features: 
     The metering shuttle valve is configured as a washer, or a hollow truncated cone, or a hollow cylinder, or a sleeve, or a ring. 
     A perimeter of the metering shuttle valve may have at least one row of openings. 
     The metering shuttle valve can be connected to the valve stem by radially extending ribs or pins. 
     These embodiments related to the metering shuttle valve allow for optimizing the device for the agitation efficiency, depending on the properties of the feed material, capacity and design of the hopper. 
     The distance from the lower edge of the loading window to the bottom end of the upper locking element can be 0.3-1 D MC , the distance from the upper end of the upper locking element to the lower end of the metering shuttle valve can be 0.5-3 D MC , and the distance from the upper end of the metering shuttle valve to the upper end of the loading windows can be 0.2-3 D MC , a metering shuttle valve diameter is 0.4-1.0 D MC , where D MC  is a metering chamber diameter. 
     The invention is characterized in that the metering shuttle valve is movable in the upper part of the metering chamber. In contrast to the prior art solutions, the movements of the valve stem make the metering shuttle valve, placed under a layer of alumina, agitate alumina occurring above the locking element and force its supply to the loading windows. As a result, the valve crushes lumps and bridges of the loose materials above the upper locking element and facilitates material flow, and thus ensures the continuity of its supply to and filling of the metering chamber. Such technical solution is particularly useful for improving industrial feeders as a low-cost and easy-to-implement technical solution in a production environment without shutting down the electrolytic cell; for example, by replacing the valve stem and providing it with the metering shuttle valve. 
     According to a second variant of the invention, there is provided a device for feeding an electrolytic cell for producing aluminum comprising a hopper with a feeding material; a metering chamber with loading windows located around a perimeter of an upper part of the metering chamber above a hopper base; a valve stem with a pneumatic actuator; an upper locking element rigidly fixed to the valve stem at the upper part of the metering chamber, wherein the upper locking element is positioned between upper and lower edges of the loading windows, when the valve stem is in its upper position; and a lower locking element fixed on an end of the valve stem, characterized in that, inside the hopper above the upper locking element, the device comprises at least one circular rib fixed into the upper part of the metering chamber, at least one rib and at least one baffle plate fixed to hopper walls so that the material can pass through gaps between plate ends and the walls of the hopper and the metering chamber. 
     Particular embodiments of the device according to the second variant of the present invention have the following features: 
     The ribs fixed to the walls of the hopper and the metering chamber can be perforated, and the baffle plate can be made of a perforated steel sheet, which reduces the overall metal consumption. 
     The baffle plate can be fixed to the hopper walls by means of ribs and/or pins, which facilitate rigging up and ensure predetermined orientation of the plate and the structure rigidity. 
     The baffle plate can be configured as a washer, or truncated cone, or truncated pyramid, or plate, or set of plates positioned coaxially to the metering chamber. 
     These embodiments related to a baffle plate configuration provide a possibility of optimizing the metal consumption and rigidity of the device depending on the specific configuration of the hopper. 
     The outside upper part of the metering chamber can be provided with at least two radially directed vertical ribs to strengthen the structure at the loading windows. 
     For better adaptation to the hopper design, the metering chamber can be made of a pipe having a circular, or square, or rectangular, or hexagonal, or triangular cross-section. 
     The ribs on the walls of the hopper and metering chamber can be secured at an angle, and the angle between the ribs and the metering chamber axis can be between 40-90°. Furthermore, the baffle plate can be mounted on the wall at an angle, and the angle between the baffle and the metering chamber axis may vary from −45° to 90° and from 90° to +45°. 
     A distance from the upper end of the upper locking element to the above circular rib and the upper edge of the loading windows can be 0.3-3 D MC , the distance between the circular ribs can be 1-6 D MC , the distance from the upper end of the upper locking element to the lower end of the above baffle plate can be 1-12 D MC , the gap between the baffle plate ends and the walls of the hopper and the metering chamber can be 0.5-6 D MC , the vertical distance between the plates can be 2-12 D MC , the distance between the plate and the rib fixed on the hopper wall and between the ribs can be 1-6 D MC  and 2-12 D MC , respectively, and the width of the ribs fixed to the walls of the metering chamber and the hopper can be 0.3-3 D MC . 
     The invention is characterized in that, inside the hopper above the upper locking element, the device comprises at least one circular rib fixed into the upper part of the metering chamber, at least one rib and at least one baffle plate fixed to hopper walls so that a material can pass through gaps between plate ends and the walls of the hopper and the metering chamber. 
     This technical solution limits the gravitational pressure from upper layers to the materials below the baffle plate on bottom of the hopper, and thereby ensures their easy flowing, eliminates compaction, lumping, formation of bridges and immobilized zones, changes in a flow ability when the hopper level of fill fluctuates. The result is not only the continuity, but also the sustainable repeatability of the metering chamber feed. The use of ribs and plates increases the useful hopper volume, eliminates caking by excluding immobilized zones in the hopper bottom part, increases the structure rigidity and decreases metal consumption by reducing the thickness of hopper walls. 
    
    
     
       The nature of the invention, however, will best be understood when described in connection with the accompanying drawings, in which. 
         FIGS. 1 and 2  are section views illustrating the devices for feeding an electrolytic cell for producing aluminum according to first and second variants of the present invention respectively; 
         FIGS. 3-7  are section views illustrating embodiments of the metering shuttle valve; 
         FIGS. 8-10  are section views illustrating embodiments of the baffle plate. 
     
    
    
     The feeding device comprises hopper  1 , pneumatic cylinder  2 , and metering chamber  3 . A lower part  4  of metering chamber  3  is located under loading windows  5  under an outlet in the bottom of hopper  1 . An upper part of metering chamber  3  as well as loading windows  5  are located in the lower part of hopper  1 . Inside the metering chamber is located a valve stem  6  actuated by a pneumatic cylinder  2 . To a lower end of valve stem  6  is attached a lower locking element  7 ; in an upper part of metering chamber, an upper locking element  8  and a metering shuttle valve  9  located below the element are rigidly fixed to the valve stem  6 . Metering chamber  3  has a flange  10  that is fixed under loading windows  5  and rests upon a bottom of the hopper  1 . 
     According to the second variant of the invention, unlike the first one, inside hopper  1  above the upper locking element  8  is a circular rib  11  fixed to the outer side of the upper part of metering chamber  3 , and a baffle plate  12 , wherein a material can pass through gaps between ends of the baffle plate  12  and the walls of hopper  1  and metering chamber  3 . Baffle plate  12  is fixed to the wall of hopper  1  by means of vertical ribs  13 . However, instead of ribs  13  pins may be used. Above the baffle plate  12  ribs  14  are fixed to the walls of hopper  1 . To ensure rigidity, the loading windows  5  of metering chamber  3  have vertical ribs  15  connected to support flange  10 . 
       FIGS. 3-7  are section views illustrating metering shuttle valve  8  respectively shaped as a washer  18  with openings  19  along its perimeter, as a hollow truncated cone  20 , as a sleeve  21 , as a hollow cylinder  22  mounted on the valve stem  6  by means of vertical ribs  23  and hub  24 , and as a ring  25  connected by pins  26  to hub  24 . 
       FIGS. 8-10  are section views illustrating a baffle plate shaped respectively as a washer  27 , as a truncated cone  28 , and as a truncated pyramid  29  coaxial to the metering chamber.  FIG. 2  is a section view illustrating a flat-shaped baffle plate  12 . 
     The devices for feeding electrolytic cells function as follows: 
     The feeding materials continuously fill the space in the zone of loading window  5  in metering chamber  3 . In an initial position, valve stem  6  is in its upper position, upper locking element  8  is located between the upper and lower edges of the loading windows  5 , and the outlet in the bottom of metering chamber  4  is closed by locking element  7 . The material in the bottom of hopper  1  fills the lower part of metering chamber  4  through loading windows  5 . To unload metering chamber  4  a control signal goes to pneumatic cylinder  2  that moves downward valve stem  6  with upper and lower locking elements  8  and  7  and metering shuttle valve  9 . At this, the passage under loading windows  5  in lower part  4  of metering chamber  3  is blocked by locking element  7  and the loose materials go through the outlet in the bottom of metering chamber  4 , and then through a chute into a well in the alumina-electrolyte crust. After emptying metering chamber  4 , valve stem  6  makes a backstroke and returns to its initial position. At that, lower locking element  7  blocks the outlet of the metering chamber, upper locking element  8  fully opens a passageway for the material under locking element  8  through loading windows  5  in metering chamber  4 . 
     In the device according to the first variant of the present invention (see  FIG. 1 ), valve stem  6  makes a reciprocal motion from one extreme position to another, and the materials above the upper locking element  8  are impacted by metering shuttle valve  9 , which crushes lumps and bridges, and forces the materials to loading windows  5 . This ensures an uninterrupted supply of the materials to the loading windows and filling metering chamber  4 , and facilitates stabilization of the electrolytic cell feeding. 
     In the device according to the second variant of the present invention (see  FIG. 2 ), circular ribs  11 , baffle plate  12 , and ribs  14  prevent the gravitational pressure from the upper layers onto the materials under plate  12 , thereby excluding compaction and changes in flowing ability in the entire volume of the lower part of hopper  1 , regardless the fluctuations of the fill level in hopper  1 , thereby providing a continuous and repetitive filling of metering chamber  4  and a stable feeding of an electrolytic cell. The materials discharged from the lower part of hopper  1  are replenished with the materials from above baffle plate  12 , the new materials enter through the gaps between plate  12  and the walls of the hopper  1  and metering chamber  3 . 
     The device according to the present invention provides for the better stability of feeding and may improve processing performance of an electrolytic cell. The efficiency of the technical solutions is confirmed by testing prototypes of the device on operating electrolytic cells.