AU2011204685B2

AU2011204685B2 - Cathode with protrusion structure for aluminum electrolytic cell

Info

Publication number: AU2011204685B2
Application number: AU2011204685A
Authority: AU
Inventors: Bin Cao; Tao Yang
Original assignee: China Aluminum Int Eng Corp Ltd; China Aluminum International Engineering Corp Ltd
Current assignee: China Aluminum International Engineering Corp Ltd
Priority date: 2010-01-07
Filing date: 2011-01-07
Publication date: 2014-09-25
Anticipated expiration: 2031-01-07
Also published as: US20130277212A1; CN102121117A; CN102121117B; MY156281A; CA2786463A1; CA2786463C; WO2011082659A1; AU2011204685A1

Abstract

A cathode with a protrusion structure for an aluminum electrolytic cell is disclosed. The cathode protrusion structure (2) is arranged on the top of the cathode carbon block (1) or across the gap (3) between two cathode carbon blocks (1). The distance between cathode protrusion structures is in a range of 400mm-900 mm. The length of the traversely extended cathode protrusion structure is 100-250 mm longer than that of cathode carbon block. Two ends of protrusion structures are directly embedded into the paste around the sidewall. The length of the embedded and butted cathode protrusion structure is in a range of 3000-3200 mm. Two ends of the embedded and butted cathode protrusion structure are fixed by binding carbon blocks (4) respectively, and the binding carbon blocks are embedded into the paste around the sidewall (5). The cross-section of the cathode protrusion structure is in the shape of rectangle or isosceles trapezoid. The cathode protrusion structure is applicable to all types of aluminum electrolytic cells. The strip cathode protrusion structure can be implanted into the upper surface of the cathode conveniently and quickly when the sidewall of the common aluminum electrolytic cell is rammed, thereby forming a "flow retardation effect", reducing the flow rate of the aluminum liquid layer, decreasing energy dissipation from the aluminum liquid layer, therefore improving the stability of production and reducing energy consumption.

Description

CATHODE WITH PROTRUSION STRUCTURE FOR ALUMINUM ELECTROLYTIC CELL 5 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. 10 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, 400KA, etc.) and large-scale of electrolytic serial (from 100000 tons to 250000 tons) 15 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 14000kwh/t-A. Given 15 million tons of primary aluminum production in 2008 in China, the annual total energy consumption of aluminum electrolyzing industry 20 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 25 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 30 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 -1I.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 5 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 10 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. 15 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 20 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 25 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. 30 The distance between cathode boss is 400mm-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 - 2 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, 5 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 10 isosceles trapezoid, has a height (a) of 80-200mm and a width (b) of 100~400mm. 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 15 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. 20 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 25 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 30 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, - 3 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 5 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 10 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. 15 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 20 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 25 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 30 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 -4invention; 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 5 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 10 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 400mm-900 mm. For different cell types, 15 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 20 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 25 or isosceles trapezoid, as shown in figs. 4 and 5. The cathode boss 2 has a height (a) of 80~200mm and a width (b) (average width for isosceles trapezoid) of 100~400mm, as shown in figs. 4 and 5. The material of the cathode boss 2 is graphitic carbon block or full 30 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 -5each 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 5 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 10 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 15 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 20 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 25 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 figy6. 30

Claims

1. A cathode boss structure for an aluminum electrolytic cell, the cathode boss structure 5 including cathode carbon blocks (1), and a cathode boss (2) 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), wherein: (i) the cathode boss (2) is elongate and having a length 100-250 mm longer than that 10 of the cathode carbon blocks (1), and configured such that, in use, two ends of the cathode boss (2) are embedded into a paste (5) disposed within both lateral portions of an aluminum electrolytic cell; or (ii) where the cathode boss (2) is an embedded and butted cathode boss (2), the 15 cathode boss (2) has a length in the range of 3000-3200 mm, and two ends of the cathode boss (2) are butted by binding carbon blocks (4) which, in use, are embedded into a paste (5) disposed within both lateral portions of an aluminum electrolytic cell.

2. The cathode boss structure of claim 1, comprising two cathode bosses (2) wherein the 20 distance between the two cathode bosses (2) is 400mm-900 mm.

3. The cathode boss structure of claim 1, wherein the cross-section of the cathode boss (2) is in the shape of a rectangle or an isosceles trapezoid. 25

4. The cathode boss structure of any one of claims 1 to 3, wherein the cathode boss (2) has a height (a) of 80-200mm and a width (b) of 100-400mm.

5. The cathode boss structure of any one of claims 1 to 4, wherein the material of the cathode boss (2) is graphitic carbon block or full graphitized carbon 30 block.