US20130277212A1

US20130277212A1 - Cathode Boss Structure for Aluminum Electrolytic Cell

Info

Publication number: US20130277212A1
Application number: US13/520,932
Authority: US
Inventors: Bin Cao; Tao Yang
Original assignee: China Aluminum International Engr Corp Ltd
Current assignee: CHINA ALUMINUM INTERNATIONAL ENGINEERING Corp Ltd; China Aluminum International Engr Corp Ltd
Priority date: 2010-01-07
Filing date: 2011-01-07
Publication date: 2013-10-24
Also published as: AU2011204685A1; WO2011082659A1; CA2786463A1; MY156281A; CN102121117B; CN102121117A; CA2786463C; AU2011204685B2

Abstract

A cathode boss structure for an aluminum electrolytic cell is disclosed. The cathode boss is arranged on the top surface of the cathode carbon block or on the top of the gap between two cathode carbon blocks. The distance between cathode bosses is 400 mm-900 mm. The length of the throughout elongate cathode boss is 100-250 mm longer than that of cathode carbon block, and two ends thereof are directly embedded into the paste around lateral portion. The length of the embedded and butted cathode boss is in a range of 3000-3200 mm, two ends thereof are fixed by binding carbon blocks respectively, and the binding carbon blocks are embedded into the paste around lateral portion. The cross-section of the cathode boss structure is in the shape of rectangle or isosceles trapezoid. The cathode boss structure is applicable to all types of current electrolytic cells. The strip boss is implanted into the top surface of the cathode of the electrolytic cell conveniently and quickly when the lateral portion of the common electrolytic cell is rammed, thereby forming a “choking effect”, reducing the flow rate of the aluminum liquid layer, decreasing energy dissipation from the aluminum liquid layer, therefore improving the production stability of the electrolytic cell and reducing energy consumption.

Description

FIELD OF THE INVENTION

The present invention relates to a cell lining cathode boss structure applicable for an aluminum electrolytic cell, pertaining to the technical field of aluminum electrolyzing.

BACKGROUND OF THE INVENTION

In recent ten years, aluminum electrolyzing technologies focused on aluminum electrolytic cell have been fully developed, and seriation of capacity of the electrolytic cell (grades 200 KA, 300 KA, 400 KA, etc.) and large-scale of electrolytic serial (from 100000 tons to 250000 tons) are essentially realized. However, aluminum electrolyzing is a typical high energy-loaded industry, with the integrated power consumption per ton aluminum generally being more than 14000 kwh/t-Al. Given 15 million tons of primary aluminum production in 2008 in China, the annual total energy consumption of aluminum electrolyzing industry should be more than 210 billion kWh. The energy utilization efficiency of aluminum electrolyzing production is 45% to 48%, thereby existing much space for energy-saving.
At present, both domestic and international large pre-baked anode electrolytic cell linings utilize the longitudinal arrangement configuration of cathodes of the same specifications, all of top surfaces of the cathodes being at the same horizontal plane. During the normal production, due to the action of electromagnetic force, the layer of liquid aluminum in the electrolytic cell is always at a flowing state, the flow field thereof as shown in FIG. 5. The flowing of the electrolyte liquid, especially the irregular flowing, is one of the main unstable factors of the electrolytic cell, for the following reasons: (1) the electrolyte system is unstable, thereby reducing the efficiency of the electrochemical reaction; (2) the noise of electrolytic cell increases, so that the control system will increase the cell voltage to reduce noise. The above two points both cause the power consumption per ton aluminum to increase. With the development of large scale of the capacity, the furnace and current of the electrolytic cell is larger and larger, resulting in more serious flow field problems as follows: the probability of uneven distribution of electrolytic liquid temperature and various materials in the cell increases; the flow rate of the electrolytic liquid increases; the production of aluminum in the cell increases; the possibility that turbulence of molten fluid occurs in some locations of the cell increases.
The aluminum liquid in the cell is a heat dissipation medium of the electrolytic cell, so increasing or reducing the amount of aluminum production is one of the main means for adjusting the thermal balance of the aluminum electrolytic cell.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a cathode boss structure for an aluminum electrolytic cell, so that cathode boss can be implanted into the top surface of the cathode of the electrolytic cell conveniently and quickly when the lateral portion of the common electrolytic cell is rammed, without revising the present cathode and lining. Implanting the cathode boss can efficiently form a “choking effect”, reducing the flow rate of the aluminum liquid layer, decreasing energy dissipation from the aluminum liquid layer, therefore improving the production stability of electrolytic cell and reducing energy consumption, so as to overcome the defects present in the prior art.
The technical solution of the present invention is as follows: the cathode boss is arranged on the top surface of the cathode carbon block or on the top of the gap between two cathode carbon blocks.
The distance between cathode boss is 400 mm-900 mm. For different cell types, it may use sparse configuration or dense configuration.
The cathode boss may utilize a throughout elongate structure, i,e, the throughout elongate cathode boss, the length thereof is 100-250 mm longer than that of cathode carbon block, and two ends thereof are directly embedded into the paste around the lateral portion.
The cathode boss may also utilize an embedded and butted structure, i,e, the embedded and butted cathode boss, the length thereof is in a range of 3000-3200 mm, two ends thereof are fixed by binding carbon blocks respectively, and the binding carbon blocks are embedded into the paste around the lateral portion.
The cross-section of the cathode boss is in the shape of rectangle or isosceles trapezoid, has a height (a) of 80-200 mm and a width (b) of 100-400 mm.
The material of the cathode boss is graphitic carbon block or full graphitized carbon block.
According to the principle of the invention, the distribution of the energy consumption of the aluminum electrolytic cell is as follows:
Total energy consumption=decomposition consumption of electrochemical reaction+power consumption of rectifier unit+through-flow loss of bus bar, anode and cathode+through-flow loss of electrolyte+system heat dissipation of electrolytic cell.
The consumption reduction of the invention starts from the through-flow loss of electrolyte and the system heat dissipation of electrolytic cell. According to “jetty” principle, providing a dam at the bottom of the fluid will increase the flow resistance, and may efficiently reduce the flow rate. The cross configuration of various cathodes at the bottom of the cell may reduce the flow of aluminum liquid and electrolyte, reduce disturbance of the electrolyte resistance induced by the flow of aluminum liquid, and reduce the distance of the anode bottom from the surface of the aluminum liquid (electrode spacing), thereby reducing through-flow loss of the current in the electrolyte. In addition, according to heat transfer theory, the less the volume and area of the heat transfer medium, the lower the heat transfer efficiency. Given the same aluminum level, because the high cathode occupies a part of aluminum liquid space, the volume of the aluminum liquid and the heat dissipation area of the lateral portion are reduced, so as to achieve the object to reduce the heat dissipation from the lateral portion.
As compared with the prior arts cathode structure and configuration ways with the longitudinal arrangement configuration of cathodes of the same specifications and all of top surfaces of the cathodes being at the same horizontal plane, the invention achieves the following advantages: (1) slowing the flow rate of the aluminum liquid, reducing the probability of localized turbulence, and enhancing the production stability of the electrolytic cell; (2) reducing the production of aluminum in the cell, reducing the volume and area for heat dissipation of the aluminum liquid, and reducing capital backlog; (3) enhancing the system stability of the electrolyte, and may reducing energy consumption following the reduction in heat dissipation.
As compared with the prior arts of boss forming ways by directly cutting on the whole cathode, forming boss by embedding, forming boss by ramming into the paste, the invention can implanting strip boss into the top surface of the cathode of the electrolytic cell conveniently and quickly when the lateral portion of the common aluminum electrolytic cell is rammed, without revising the present cathode and lining. Implanting the cathode boss can also form a “choking effect”, achieving effects of energy saving. In addition, as compared with various boss forming ways described above, there is no direct connection between the boss and the cathode of the invention, thereby reducing through-flow amount, reducing electrochemical corrosion of the boss, and may enhance the service life of the boss.
The invention is applicable to all types of current electrolytic cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of the present invention;

FIG. 2 is a schematic cross-sectional view of the present invention;

FIG. 3 is a schematic longitudinal-sectional view of the present invention;

FIG. 4 is a schematic view of the cathode boss with a trapezoid cross-section of the present invention;

FIG. 5 is a schematic view of the cathode boss with a rectangular cross-section of the present invention; and

FIG. 6 is a schematic view of the heat dissipation of the aluminum liquid of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment of the present invention as shown in FIGS. 1, 2 and 3 mainly comprises cathode carbon blocks 1, cathode bosses 2, and binding carbon blocks 4, wherein the cathode bosses 2 are placed on the top surface of the cathode carbon blocks 1 or across cathode gaps 3. The distance between cathode boss is 400 mm-900 mm. For different cell types, it may use sparse configuration or dense configuration.
There are two implanting ways for the cathode bosses 2: (1) a throughout elongate cathode boss, the length thereof is 100-250 mm longer than that of cathode carbon block, and two ends thereof are directly embedded into the paste 5 around the lateral portion; and (2) an embedded and butted cathode boss, the length thereof is in a range of 3000-3200 mm, two ends thereof are fixed by binding carbon blocks 4 respectively, and the binding carbon blocks are embedded into the paste 5 around the lateral portion.
The cross-section of the cathode boss 2 is in the shape of rectangle or isosceles trapezoid, as shown in FIGS. 4 and 5.
The cathode boss 2 has a height (a) of 80-200 mm and a width (b) (average width for isosceles trapezoid) of 100-400 mm, as shown in FIGS. 4 and 5.
The material of the cathode boss 2 is graphitic carbon block or full graphitized carbon block.
The cathode boss of the invention may be implanted one by one via electrode change operation of the electrolytic cell. Implanting steps of each cathode boss are as follows:
Step 1:
After lateral portion block laying and cathode gap ramming are finished for major repair cell, the cathode bosses and carbon blocks are placed on the top surface of the cathode according to predetermined configuration solution (intensity).
Step 2:
The paste around the cell lining is rammed according to the prior method, wherein the paste may maintain the original design height, or increases 2-10 cm.
Step 3:
The electrolytic cell utilizing the cathode boss of the invention may be carried out baking startup according to aluminum liquid baking, etc.
According to “jetty” principle, providing a dam at the bottom of the fluid will increase the flow resistance, and may efficiently reduce the flow rate. The cross configuration of various cathodes at the bottom of the cell may reduce the flow of aluminum liquid and electrolyte, reduce disturbance of the electrolyte resistance induced by the flow of aluminum liquid, and reduce the distance of the anode bottom from the surface of the aluminum liquid (electrode spacing), thereby reducing through-flow loss of the current in the electrolyte.
According to heat transfer theory, the less the volume and area of the heat transfer medium, the lower the heat transfer efficiency. Given the same aluminum level, because the high cathode occupies a part of aluminum liquid space, the volume of the aluminum liquid and the heat dissipation area of the lateral portion are reduced, so as to achieve the object to reduce the heat dissipation from the lateral portion, as illustrated in FIG. 6.

Claims

1. A cathode boss structure for an aluminum electrolytic cell which includes cathode carbon blocks (1), characterized in that, a cathode boss (2) is arranged on the top surface of the cathode carbon blocks (1) or on the top of the gap (3) between two cathode carbon blocks (1).

2. The cathode boss structure for an aluminum electrolytic cell of claim 1, characterized in that, the distance between cathode bosses (2) is 400-900 mm.

3. The cathode boss structure for an aluminum electrolytic cell of claim 1, characterized in that, the cathode boss may utilize a throughout elongate structure, i,e, the throughout elongate cathode boss (2), the length thereof is 100-250 mm longer than that of cathode carbon block (1), and two ends thereof are directly embedded into the paste (5) around lateral portion.

4. The cathode boss structure for an aluminum electrolytic cell of claim 1, characterized in that, the cathode boss may also utilize an embedded and butted structure, i,e, the embedded and butted cathode boss (2), the length thereof is in a range of 3000-3200 mm, two ends thereof are fixed by binding carbon blocks (4) respectively, and the binding carbon blocks (4) are embedded into the paste (5) around lateral portion.

5. The cathode boss structure for an aluminum electrolytic cell of claim 1, characterized in that, the cross-section of the cathode boss (2) is in the shape of rectangle or isosceles trapezoid.

6. The cathode boss structure for an aluminum electrolytic cell of claim 1, characterized in that, the cathode boss (2) has a height (a) of 80-200 mm and a width (b) of 100-400 mm.

7. The cathode boss structure for an aluminum electrolytic cell of claim 1, characterized in that, the material of the cathode boss (2) is graphitic carbon block or full graphitized carbon block.