Device for improving the performance of an aluminium reduction cell in a smelting process

Abstract

This invention relates to an apparatus for improving the performance of an aluminum reduction cell in a smelting process. It includes a current collector rod and a metal insert placed inside the current collector rod. The insert is constructed of a different material than the current collector rod. Furthermore, heat-insulating strips placed along the bottom of the electrolytic cell prevent heat from escaping from each end of the cathode.

Description

Technical Field

[0001] The present invention relates to a device for improving the performance of an aluminum reduction cell in a smelting process. More specifically, the present invention relates to a device having a current collector bar with a metal insert and an electrolytic cell refractory lining to improve the performance of an aluminum reduction cell. Background Art

[0002] Aluminum is conventionally produced by the Hall-Héroult process by electrolyzing alumina dissolved in a cryolite-based molten electrolyte. Specifically, an electric current enters an electrolytic cell (cell) through an anode, then passes through a molten cryolite bath (electrolytic bath), molten aluminum, into a carbon cathode, and is then collected by a current collector bar.

[0003] The electric current flows out of the electrolytic cell through the current collector bar. The flow of the electric current through the carbon cathode and the current collector bar follows the path of least resistance. The resistance of the current path between the current collector bar and the nearest external busbar is low, so the electric current flowing through the molten aluminum, the cathode, and the current collector bar is concentrated and flows towards the outlet of the current collector bar, thereby generating a horizontal current component as shown in Figure 1 (resistance: R1 < R2). Such a horizontal current component interacts with the vertical component of the magnetic field, resulting in magnetohydrodynamic (MHD) instability and having an adverse effect on the effective operation of the electrolytic cell, thereby limiting the reduction of the distance between electrodes.

[0004] Generally, in the industry, steel current collector bars extending from an external busbar through each side of the electrolytic cell into the carbon cathode blocks are used. To increase the electric current flowing through these current collector bars, inserts formed of a secondary material having a higher electrical conductivity than the main material of the current collector bar are also used. The use of the current collector bar and the metal insert reduces the energy consumption by reducing the inter-electrode gap and the voltage drop in the cathode and current collector bar assembly. In addition, it has also been noted that the generation of horizontal current is reduced in this design. However, there is a need for a novel design of a current collector bar with a metal insert that further reduces the energy consumption and voltage drop and reduces the generation of horizontal current components, thereby providing a uniform current distribution in the electrolytic cell. Figure 1 A cross-sectional view of a conventional aluminum smelting furnace is shown, showing the resistance paths (R2 and R1) from the anode (1) to the outlet of the current collector bar (6), which simultaneously pass through the electrolytic bath (2), molten metal (3), and cathode (4), which together with the refractory lining (5) are housed inside a steel shell enclosure (7). The electric current generally flows out from both sides of the electrolytic cell and is transported to the next electrolytic cell using an external aluminum busbar. This results in voltage drop and energy consumption.

[0005] Furthermore, the current in the electrolytic cell contributes to electrolysis and generates the heat required to operate the cell at high temperatures. In the event of a power outage / disruption, the electrolytic cell begins to freeze, and the high thermal conductivity of all types of current collector rods increases heat loss. This leads to the electrolytic cell shutting down more quickly. Replacing a frozen electrolytic cell with a new one requires significant investment. This also applies to existing current collector rod designs with metal inserts. In existing designs, metal inserts are not effective at reducing heat loss. Therefore, a new design is needed for the current collector rods and the refractory lining of the electrolytic cell to slow down the cooling rate of the cell during power outages.

[0006] Therefore, a new design for an aluminum reduction tank is needed to address some of the problems with existing technologies. Summary of the Invention

[0007] According to an embodiment of the present invention, an apparatus for improving the performance of an aluminum reduction pool in a smelting process is provided, the apparatus comprising: a current collector rod (6) and at least one insert (8) therein, the insert (8) tapering towards one end of the current collector rod (6) in a continuous or stepped manner, such that current is collected at the tapered end, provided that the construction material of the insert (8) is different from the construction material of the current collector rod (6).

[0008] According to another embodiment of the invention, an apparatus for improving the performance of an aluminum reduction cell in a smelting process is provided, the apparatus comprising: at least one current collector rod (6) and at least one insert (8) therein, the insert (8) being placed within the current collector rod (6) such that the end of each insert (8) having the largest cross-section is positioned in the middle of the aluminum reduction cell, and the tapering end of each insert (8) is adjacent to a corresponding end of the current collector rod (6), similar ends of each insert (8) being equidistant from corresponding lateral ends of the current collector rod (6), the ends of each insert (8) in the middle of the aluminum reduction cell facing each other to define a gap between the inserts (8), provided that the construction material of the insert (8) is different from the construction material of the current collector rod (6), and current is collected from both sides of the electrolytic cell. Attached Figure Description

[0009] Figure 1 A cross-sectional view of a conventional aluminum smelting furnace according to an embodiment of the present invention is depicted;

[0010] Figure 2(a) , 2(b) Figures 2(c) illustrate isometric views of various designs of a metal insert (8) inside a current collector rod (6) according to an embodiment of the present invention, having a large cross-sectional area on one side of the current collector rod;

[0011] Figure 3A cross-sectional view of an aluminum smelting furnace according to an embodiment of the present invention is depicted, the aluminum smelting furnace having an asymmetric heat insulation strip (9) with a thickness 1.2 to 5 times greater along the current outlet side than the opposite side;

[0012] Figure 4(a) and 4(b) The figure shows an isometric view of two current collector rods (6) having at least one insert (8) according to an embodiment of the present invention, wherein the insert (8) has a large cross-sectional area in the middle of the current collector rods (6);

[0013] Figure 5 A cross-sectional view of the aluminum smelting furnace of the present invention, which has symmetrical heat insulation strips (9) on the two current outlet sides of the electrolytic cell according to an embodiment of the present invention, is shown.

[0014] Figure 6 A cross-sectional view showing the positions of the current collector rod (6) and the metal insert (8) within the current collector rod (6) according to an embodiment of the present invention is shown;

[0015] Figure 7(a) and 7(b) A comparison of electrolyzer stability between a prior art apparatus and the apparatus of the present invention, according to embodiments of the present invention, is shown; and

[0016] Figure 7(c) shows a graph comparing the operating current during a power outage and the electrolyte temperature of the prior art device and the device of the present invention, according to an embodiment of the present invention. Detailed Implementation

[0017] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to embodiments, which will be described using specific language. However, it should be understood that this is not intended to limit the scope of the invention, and such changes and further modifications to the disclosed processes and systems, as well as further applications of the principles of the invention therein, are contemplated as would normally occur to those skilled in the art to which this invention pertains.

[0018] Those skilled in the art will understand that the foregoing general description and the following detailed description are exemplary and illustrative of the invention, and are not intended to limit it.

[0019] Throughout this specification, references to "an embodiment," "embodiment," or similar language mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the use of phrases such as "in one embodiment," "in an embodiment," and similar language throughout this specification may refer to the same embodiment, but not necessarily the same embodiment.

[0020] As stated in the claims, the present invention eliminates or reduces the aforementioned problems of the prior art by providing a novel design for an apparatus for an aluminum reduction cell, the apparatus comprising a current collector rod (6) having at least one insert (8) therein with a tapering design. Furthermore, the apparatus provides a heat-insulating strip (9) positioned along the bottom of the electrolytic cell and extending from the bottom of the electrolytic cell along the underside of the cell to the top of the cathode (4), thereby reducing heat loss from the cathode (4) from the side where the current is collected. Finally, the present invention demonstrates the ability to collect current from one side of the apparatus to save energy in the external aluminum bus network without adversely affecting the MHD stability of the electrolytic cell.

[0021] According to one embodiment of the present invention, an apparatus for improving the performance of an aluminum reduction cell in a smelting process is provided, the apparatus comprising a current collector rod (6) and at least one insert (8) therein. Placing the metal insert (8) within the current collector rod results in a reduction of the horizontal current in the metal region, thereby reducing the MHD instability for energy reduction without increasing heat loss in the current collector rod region. Therefore, the lifespan of the electrolytic cell is maintained during power outages. Furthermore, the current is collected at a gradually tapering end. The cross-sectional area of ​​the insert (8) gradually tapers towards one end of the current collector rod (6), such as... Figure 2(a) , 2(b) As shown in 2(c), in cases where current is required to be collected only at one end, the taper can be either continuous or stepped, as indicated. The taper helps ensure similar resistance paths throughout the cathode (4) and current collector rod (6) assembly, providing greater MHD stability.

[0022] Preferably, the ratio of the maximum cross-section of the insert (8) to the cross-section of the current collector rod (6) is in the range of 0.1 to 0.6. The ratio of the cross-section of the tapering end of the insert (8) to the cross-section of the current collector rod (6) is in the range of 0.05 to 0.4. The ratio of the length of the insert (8) to the length of the current collector rod (6) is in the range of 0.5 to 0.8.

[0023] In an embodiment, the electrical conductivity of the material used to construct the insert (8) is greater than that of the material used to construct the current collector rod (6). Preferably, the material used to construct the insert (8) is copper, a copper alloy, gold, silver, platinum, or a mixture thereof. The use of all these alternative materials for the construction of the insert (8), etc., is considered to be within the scope of the invention.

[0024] In an embodiment, such as Figure 3As shown, the electrolytic cell for aluminum reduction exhibits improved performance in the smelting process. This electrolytic cell includes insulating strips (9) placed along the bottom of the cell and extending from the bottom along the lower side of the cell to the top of the cathode (4), thereby reducing heat loss from the cathode (4) from the side where current is collected. This heat loss leads to thermal equilibrium during power outages, thus preventing the electrolytic cell from freezing. Preferably, the insulating strip (9) placed on the current outlet side is thicker than the insulating strip (9) placed on the other side. Since the current flows out from one side of the electrolytic cell using a metal current collector rod (6), it acts as a thermal window compared to the opposite non-current outlet end. Therefore, the thicker insulating strip (9) adjacent to the current outlet region helps maintain a balance of heat flux along the two long sides of the electrolytic cell, achieving effective thermal equilibrium and electrolytic cell performance.

[0025] In another embodiment of the invention, an apparatus for improving the performance of an aluminum reduction pool in a smelting process is provided, the apparatus comprising at least one current collector rod (6) and at least one insert (8) therein. The inserts (8) are placed within the current collector rod (6) such that the end of each insert (8) having the largest cross-section is positioned in the middle of the aluminum reduction pool, and the tapering end of each insert is adjacent to a corresponding end of the current collector rod (6), such that similar ends of each insert (8) are equidistant from corresponding lateral ends of the current collector rod (6), and the ends of each insert (8) in the middle of the aluminum reduction pool face each other to define a gap between the inserts (8).

[0026] As shown in Figures 4(a) and 4(b), with at least one insert (8) placed within one or more current collector bars (6), the ends of each insert (8) in the middle of the aluminum reduction cell face each other to define a gap between the inserts (8). The metal insert (8) in the middle of the aluminum reduction cell attracts the least current, so the small gap is not only economically feasible but also helps to allow current to pass through the ends of the insert (8) placed in the middle of the electrolytic cell, thereby reducing the horizontal component of the current. In other words, due to the larger cross-sectional area of ​​the metal insert (8) in the middle of the aluminum reduction cell, the conductivity at the center is increased compared to the conductivity at the sides. This allows more current to pass through the center, thereby reducing the horizontal component of the current in the molten aluminum deposited on the cathode (4). Preferably, the current collector bars (6) can also be single or multiple to compensate for the stress caused by the thermal expansion of the current collector bars (6) at the operating temperature.

[0027] Preferably, the ratio of the maximum cross-section of the insert (8) to the cross-section of the current collector rod (6) is in the range of 0.1 to 0.6. The ratio of the cross-section of the tapering end of the insert (8) to the cross-section of the current collector rod (6) is in the range of 0.05 to 0.4. The ratio of the length of the insert (8) to the length of the current collector rod (6) is in the range of 0.5 to 0.8.

[0028] In an embodiment, the electrical conductivity of the material used to construct the insert (8) is greater than that of the material used to construct the current collector rod (6). Preferably, the material used to construct the insert (8) is copper, a copper alloy, gold, silver, platinum, or a mixture thereof. The use of all these alternative materials for the construction of the insert (8), etc., is considered to be within the scope of the invention.

[0029] In an embodiment, such as Figure 5 As shown, the electrolytic cell for aluminum reduction exhibits improved performance in the smelting process. This electrolytic cell includes heat-insulating strips (9) placed along the bottom of the cell and extending from the bottom along the lower side of the cell to the top of the cathode (4), thereby reducing heat loss from the cathode (4) from both sides of the electrolytic cell where current is collected. This reduced heat loss leads to thermal equilibrium during power outages, thus preventing the electrolytic cell from freezing. Preferably, the heat-insulating strips (9) placed on both sides have the same thickness when current is collected from both sides, because the current collector rod (6) with inserts (8) acts as a thermal window during power outages.

[0030] During a power outage, the electrolytic cell begins to freeze due to lack of heat, thereby lowering the electrolyte temperature and increasing the freezing of the electrolyte at the sidewalls. Because the frozen electrolyte has a lower thermal conductivity compared to the current collector rod, most of the heat flux is transferred to the current collector rod region. The cross-section of the insert (8) decreases as it advances toward the end of the current collector rod (6), which helps to reduce the thermal conductivity at the end, thereby reducing heat loss. The insulating strip (9) in the refractory lining of the electrolytic cell increases the thermal resistance around the current collector rod (6), thereby again reducing heat loss. Preferably, the insulating strip can extend from the corner of the refractory lining of the electrolytic cell to 1 / 3 of the cathode length and twice the cathode width. The height of the insulating strip (9) can start from the bottom and extend to the top of the cathode. The thickness of the insulating strip (9) can vary from one-twentieth to one-third of the gap between the side of the cathode block and the inner wall of the steel shell (7).

[0031] In an embodiment, such as Figure 6As shown, the insert (8) is positioned closer to the top of the current collector rod (6) within the current collector rod (6), such that the cross-sectional area of ​​the current collector rod (6) above the insert (8) is smaller than the cross-sectional area of ​​the current collector rod (6) below the insert (8). Positioning the insert (8) at the upper part of the current collector rod (6) cross-section, as shown, causes heat generation to move upwards, thereby helping to maintain a higher cathode temperature under normal operating conditions. A higher cathode temperature is beneficial for energy-saving processes. In embodiments, there are various ways to place the metal insert (8) inside the current collector rod (6). The insert (8) can be circular, square, rectangular, trapezoidal, parallelogram, U-shaped, V-shaped, or a combination thereof.

[0032] Figures 7(a) and 7(b) illustrate how the reduced horizontal current leads to improved stability of the electrolyzer. As can be seen from the graphs, when performing tank stability tests in an aluminum reduction cell using prior art equipment, the anode-to-cathode distance can be reduced before reaching MHD instability at 4.13 volts, while the device of the present invention can reduce the anode-to-cathode distance before reaching MHD instability at 3.93 volts. This demonstrates that the present invention significantly reduces MHD instability. Figure 7(c) shows an example of a power outage where the current is zero for over 4 hours, resulting in a significant reduction in the average ampere. A significant drop in electrolyte temperature can be observed in the prior art equipment, while the electrolyte temperature in the device of the present invention remains unaffected. This unaffected electrolyte temperature indicates a very slow freezing rate of the electrolyzer.

[0033] Experimental data:

[0034] The advantages and benefits of the embodiments of the present invention will become more apparent to those skilled in the art from the experimental details described below.

[0035] Example 1

[0036] Different ratios of the cross-sectional area of ​​the insert (8) to the current collector rod (6) were analyzed, and it was found that a ratio close to 0.2 provided the best results in reducing CVD (cathode voltage drop) and horizontal current. The amount of material used for the insert (8) also provided good techno-economic feasibility. Ratios higher than the optimal value would significantly increase the amount of material, but would not provide much saving in terms of CVD or horizontal current. Conversely, lower ratios did not provide any power savings.

[0037] Table 1

[0038]

[0039]

[0040] Note that future cost reductions in materials may lead to a shift in the techno-economic optimal point towards higher ratios.

[0041] Example 2:

[0042] Different length ratios of the insert (8) to the current collector rod (6) were also analyzed, and the optimal ratio was found to be approximately 0.75, which provides a desirable reduction in CVD and horizontal current. A length ratio higher than the optimal ratio slightly increases CVD savings, but it also increases the outlet temperature of the current collector rod (6), which is detrimental during power outages. Lower ratios do not provide good power savings. Furthermore, the placement of the insert (8) must ensure that it does not extend too far beyond the cathode (4), as this would lead to an increase in the outlet temperature of the current collector rod (6). From the analysis, the optimal extension beyond the cathode (4) was found to be approximately 150 mm.

[0043] Table 2

[0044]

[0045] Example 3:

[0046] Table 3 shows the cathode voltage drop and steel shell temperature of the prior art device and the device of the present invention according to embodiments of the present invention.

[0047] Table 3

[0048]

[0049] For descriptive purposes, the foregoing description of specific embodiments of the invention has been presented. These descriptions are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obvious modifications and variations can be made in light of the foregoing teachings.

Claims

1. An apparatus for improving the performance of an aluminum reduction bath in a smelting process, the apparatus comprising: A current collector rod (6) and at least one insert (8) therein, The insert (8) tapers gradually towards one end of the current collector rod (6), and this taper is either continuous or stepped, so that the current is collected at the tapered end. The premise is that the material of the insert (8) is different from the material of the current collector rod (6). The insert (8) is positioned within the current collector rod (6) closer to the top of the current collector rod (6) such that the cross-sectional area of ​​the current collector rod (6) above the insert (8) is smaller than the cross-sectional area of ​​the current collector rod (6) below the insert (8). The ratio of the maximum cross-section of the insert (8) to the cross-section of the current collector rod (6) is in the range of 0.1 to 0.

6. The ratio of the cross-section of the tapering end of the insert (8) to the cross-section of the current collector rod (6) is in the range of 0.05 to 0.4, and The ratio of the length of the insert (8) to the length of the current collector rod (6) is in the range of 0.5 to 0.

8. The electrical conductivity of the structural material of the insert (8) is greater than that of the structural material of the current collector rod (6).

2. The device according to claim 1, wherein the construction material of the insert (8) is copper, copper alloy, gold, silver, platinum or a mixture thereof.

3. An electrolytic cell for aluminum reduction, the electrolytic cell exhibiting improved electrolytic cell performance in smelting processes, the electrolytic cell comprising: Anode (1); Cathode (4); Electroplating solution (2); A heat insulation strip (9) is placed along the bottom of the electrolytic cell and extends from the bottom of the electrolytic cell along the lower side of the electrolytic cell to the top of the cathode (4), thereby reducing heat loss from the cathode (4) from the side where the current is collected; and The apparatus according to claim 1, The heat insulation strip (9) placed on the current outlet side is thicker than the heat insulation strip (9) placed on the other side.

4. An apparatus for improving the performance of an aluminum reduction bath in a smelting process, the apparatus comprising: At least one current collector rod (6) and at least one insert (8) therein, The inserts (8) are placed inside the current collector rod (6) such that the end of each insert (8) with the largest cross-section is placed in the middle of the aluminum reduction tank, and the tapering end of each insert (8) is adjacent to the corresponding end of the current collector rod (6). The similar ends of each insert (8) are equidistant from the corresponding lateral ends of the current collector rod (6), and The ends of each insert (8) face each other in the middle of the aluminum reduction pool to define a gap between the inserts (8). The premise is that the material of the insert (8) is different from the material of the current collector rod (6), and the current is collected from both sides of the pool. The ratio of the maximum cross-section of the insert (8) to the cross-section of the current collector rod (6) is in the range of 0.1 to 0.

6. The ratio of the cross-section of the tapering end of the insert (8) to the cross-section of the current collector rod (6) is in the range of 0.05 to 0.4, and The ratio of the length of the insert (8) to the length of the current collector rod (6) is in the range of 0.5 to 0.

8. The insert (8) is positioned within the current collector rod (6) closer to the top of the current collector rod (6) such that the cross-sectional area of ​​the current collector rod (6) above the insert (8) is smaller than the cross-sectional area of ​​the current collector rod (6) below the insert (8). The electrical conductivity of the structural material of the insert (8) is greater than that of the structural material of the current collector rod (6).

5. The device according to claim 4, wherein the construction material of the insert (8) is copper, copper alloy, gold, silver, platinum or a mixture thereof.

6. An electrolytic cell for aluminum reduction, the electrolytic cell exhibiting improved electrolytic cell performance in smelting processes, the electrolytic cell comprising: Anode (1); Cathode (4); Electroplating solution (2); A heat insulation strip (9) is placed along the bottom of the electrolytic cell and extends from the bottom of the electrolytic cell along the lower side of the electrolytic cell to the top of the cathode (4), thereby reducing the heat loss from the cathode (4). and The apparatus according to claim 4.

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