CN117940611A - Cathode device for aluminum electrolysis cell - Google Patents
Cathode device for aluminum electrolysis cell Download PDFInfo
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- CN117940611A CN117940611A CN202280062243.0A CN202280062243A CN117940611A CN 117940611 A CN117940611 A CN 117940611A CN 202280062243 A CN202280062243 A CN 202280062243A CN 117940611 A CN117940611 A CN 117940611A
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- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 42
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 238000005868 electrolysis reaction Methods 0.000 title description 21
- 229910052751 metal Inorganic materials 0.000 claims abstract description 53
- 239000002184 metal Substances 0.000 claims abstract description 53
- 239000002131 composite material Substances 0.000 claims abstract description 36
- 238000001816 cooling Methods 0.000 claims abstract description 25
- 239000004411 aluminium Substances 0.000 claims description 23
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 239000000463 material Substances 0.000 claims description 11
- 238000003466 welding Methods 0.000 claims description 11
- 239000010949 copper Substances 0.000 claims description 10
- 229910052802 copper Inorganic materials 0.000 claims description 10
- 239000010936 titanium Substances 0.000 claims description 10
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 8
- 229910052719 titanium Inorganic materials 0.000 claims description 8
- 229910000838 Al alloy Inorganic materials 0.000 claims description 6
- 229910000881 Cu alloy Inorganic materials 0.000 claims description 6
- 230000000087 stabilizing effect Effects 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 5
- 230000017525 heat dissipation Effects 0.000 abstract description 5
- 238000010438 heat treatment Methods 0.000 abstract description 5
- 239000000155 melt Substances 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 39
- 229910000831 Steel Inorganic materials 0.000 description 30
- 239000010959 steel Substances 0.000 description 30
- 238000012546 transfer Methods 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 9
- 230000001965 increasing effect Effects 0.000 description 8
- 239000003351 stiffener Substances 0.000 description 8
- 238000013461 design Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 229910000906 Bronze Inorganic materials 0.000 description 4
- 239000010974 bronze Substances 0.000 description 4
- 230000015271 coagulation Effects 0.000 description 4
- 238000005345 coagulation Methods 0.000 description 4
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical compound [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 description 4
- 238000004880 explosion Methods 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 230000002411 adverse Effects 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 230000003014 reinforcing effect Effects 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 230000001932 seasonal effect Effects 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- 229910001369 Brass Inorganic materials 0.000 description 1
- 229910001136 Kr alloy Inorganic materials 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- JECXXFXYJAQVAH-UHFFFAOYSA-N amg-3 Chemical compound C=1C(O)=C2C3CC(C)=CCC3C(C)(C)OC2=CC=1C1(CCCCCC)SCCS1 JECXXFXYJAQVAH-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 238000005219 brazing Methods 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000021715 photosynthesis, light harvesting Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
- C25C3/10—External supporting frames or structures
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
A cathode assembly for an electrolytic cell for producing aluminum includes a metal bath having a bottom, longitudinal walls and end walls covering the bath, and a support member for the bottom, a liner enclosed therein, a cathode rod, and a cathode block, thereby forming a cathode of the electrolytic cell. On the longitudinal walls and end walls of the metal bath, in the gaps between the support members, plate-shaped or finger-shaped heat sinks with improved structure are provided, and strips made of composite material for uniform heat dissipation are mounted on the upper portions of the longitudinal walls and end walls of the metal bath. The cooling effect is achieved by a convective air flow caused by the lift force created by the heating of air in the space between the ribs at the melt level and the resulting temperature difference along the height of the walls of the cathode casing.
Description
Technical Field
The present invention relates to aluminium production by molten salt electrolysis, in particular to the cathode assembly of an electrolysis cell, and the assembly of the upper strip of the longitudinal and end walls of the cathode casing was studied.
Background
The cathode assembly is typically an assembly comprising a cathode casing and an inner liner that enables electrolysis to take place within a cryolite-alumina melt (also known as a bath).
The cathode casing is constituted by a metal can comprising longitudinal walls and end walls, having a base and support members (casing reinforcing bars, reaction brackets, beams, etc.) covering the can walls and base, and is generally constituted by steel. The inside of the cathode casing is lined with lining material (refractory insulating bricks, silicon carbide plates, carbon graphite cathode blocks with steel cathode rods, etc.).
The cathode casing is designed to protect the inner lining from any deformation or damage caused by forces generated within the cathode assembly during operation of the cell. It must therefore have the necessary mechanical strength and rigidity to ensure a long service life of the cathode assembly.
Another important function of the cathode casing is to ensure intense heat removal from the electrolytic treatment area and the dissipation of excess heat into the environment. This helps to form a solidified cryolite-alumina melt/scale layer (scale) on the inner liner (side) walls of the cathode assembly, which protects them from aggressive environments and high temperatures (870-970 ℃) thus providing optimal conditions for electrolytic reduction and protects the side walls from aggressive effects of the bath and electrolytic reduction products.
Thus, by creating suitable conditions for intense cooling of the cathode casing, three problems can be solved:
Protecting the side walls from wear and tear and ensuring a long service life of the side walls,
Enhancing the electrolytic aluminium production process by increasing the unit capacity of the electrolytic cell,
-Increasing the efficiency of the cell operation by controlled adjustment of the temperature conditions.
A method of cooling an aluminium electrolysis cell comprising a cathode casing in the form of a steel can comprising a vertical (longitudinal and end) wall with a bottom is known (US 4087345, C25C 3/08, 1978, day 5/2). Vertical stiffeners (T-beams and/or I-beams) are attached to the wall at intervals along the length and width of the shell. The beam is in good thermal contact with the wall of the steel can. The walls of the steel tank are surrounded by horizontal stiffeners (T-beams and/or I-beams) around the entire perimeter forming a single rigid structure. In some modifications, the wall may additionally be covered by a support member (housing stiffener, reaction mount).
Thus, along the perimeter of the cathode casing between the vertical stiffeners, the vertical walls of the can and the horizontal stiffeners, vertical air channels are formed, designed for unobstructed passage of air, to remove and dissipate heat from the structural casing walls and vertical stiffeners.
The walls are cooled by a convective air flow caused by the lift force (archimedes force) created by the heating of the air in the upper part of the vertical air channel (at the melt level) and the temperature difference created along the wall height. This allows for increased heat removal through the vertical side walls of the shell and reduced shell wall temperature, thereby allowing for the formation of a solidified cryolite-alumina melt/scale layer on the inner liner wall of the cathode assembly.
The main disadvantage of the existing methods is that the efficiency of removing and consuming heat from the cathode casing is low due to the limited cooling area and low speed of the convective air flow. Therefore, in this case, it becomes problematic to apply a stable and sufficiently thick scale layer on the inner surface of the sidewall lining. The lack of scale often results in strong wear of the side lining, which adversely affects the service life of the cell.
A cathode assembly of an aluminium electrolysis cell (RU 2230834, C25C 3/08, 6/20 th 2004) is known, equipped with a cathode casing comprising a metal can lined from the inside, having longitudinal and end walls and a bottom, mounted in a rigid frame formed by transverse casing reinforcing bars (support members). The end walls of the cans are reinforced with reinforcing straps formed of vertical and horizontal stiffeners connected to each other by strapping (bending) plates. In this case, the horizontal reinforcement is spaced apart from the vertical end wall in the horizontal plane so that a vertical air passage is formed between them, which has a width of 1/3 to 2/3 of the distance from the tank end wall to the strapping plate, for the flow of air for cooling the shell. In addition, between the vertical stiffening ribs there are 1-4 pieces of vertical steel cooling ribs, the height of which is equal to the height of the side lining, preferably the ribs are dimensioned as follows: the thickness is 6-8mm, the height is 640-650mm, and the width is 120mm.
The known method enables air to flow along the vertical air channels through cooling ribs welded to the walls to remove and dissipate heat from the end walls of the cathode casing by natural convective heat exchange with the environment.
The main drawback of the known solution is that it is recommended to install cooling ribs only on the end walls of the cathode casing, as a result of which the heat will be removed only more intensively from the end portions of the cathode casing, while the problem of cooling of the longitudinal walls still remains. Another disadvantage of this solution is the low efficiency of heat removal from the end wall of the cathode casing, since the increase in heat transfer coefficient is not significant (from about 15 to 25W/m2·k). This is explained by the presence of a solid flange plate which prevents free air flow and the relatively low thermal conductivity of the cooling ribs made of St3 steel, which have a thermal conductivity of 50W/m·k at 300 ℃), the heat transfer efficiency of the ribs is low.
A method for cooling an electrolytic cell for aluminium production is known (US 4608134, C25C 3/08, 8/26 of 1986) comprising an outer cathode casing made in the form of a steel can, wherein there is a lining made up of refractory and insulating lining material and carbon-graphite cathode blocks enclosed inside it, and the outer cathode casing is located on the inside of the side walls of the cathode casing side of the lining (carbon-graphite or silicon carbide plate). Along the side of the cathode assembly at the melt level, between the inner surface of the cathode casing and the outer wall of the side portion of the liner, there is an air chamber communicating with an inlet for air ingress and an outlet equipped with an air flow control valve. The cooling is performed as follows: cold air drawn from the environment on the sides of the cell is drawn in through the inlet and directed along the side lining into the air cavity, thereby cooling it, while controlling the flow of hot air through the outlet fitted with a valve. Thus, by adjusting the flow rate of the hot air, the formation of a scale layer on the side of the cathode assembly can be controlled.
The main drawbacks of the known solutions are the need to make significant modifications to the cathode assembly of the electrolyzer to place the cooling tubes (coils), to pump large amounts of coolant (air) through the tubes, and to place additional infrastructure designed to pump coolant (air). All of this requires considerable financial costs.
Furthermore, the problem of protecting the side lining from oxidation by oxygen in the air inhaled from the outside must be solved, or if the inner lining is insulated with an oxidation resistant material (e.g. steel), the problem of protecting the side lining from oxidation by oxygen in the air inhaled from the outside must be solved to ensure good thermal contact between the material and the lining.
Another disadvantage of this solution is that since a large amount of air is sucked in from the environment for cooling and released into the hood, a large amount of heated gas-air mixture (exhaust gas and air) has to be removed from under the cell hood. This results in an increased capacity of the fume extraction and gas treatment apparatus.
Electrolytic cells for aluminium production are known (SU 605865, C25C 3/08, 5 th 1978) comprising a metal cathode casing in the form of a steel can internally lined, the bottom and vertical walls of which are provided with box-shaped sections made in the form of airtight chambers. A heat shield made of separate plates is mounted in the airtight chamber and an air line with an air distribution valve is connected to them, into which air is blown by a fan or compressor.
A drawback of the known solutions is the need to form a complex and cumbersome network of air lines, which considerably clutter the space around the electrolyzer, while the high noise level created by the air blown into the atmosphere of the airtight chamber or housing creates adverse conditions for the operator. Furthermore, due to the low heat capacity of air, a considerable air flow rate is required for effective heat removal, so a compressor station or a powerful fan is required and thus not economically viable.
In terms of technical nature and the results achieved, the closest to the proposed invention is the design of the cathode assembly of an aluminium electrolysis cell according to patent RU 2321682, C25C 3/08, month 4 and 10 of 2008. The assembly includes a metal can having a bottom and a support member covering the wall and bottom of the bath, thereby forming a cathode casing. Inside the cathode casing are an inner liner and a cathode block with cathode rods that form the cell cathode. On the longitudinal walls and end walls of the metal can, in the gaps between the support members, there are provided fixing plate ribs made of a material having high thermal conductivity. The area of one plate rib is 0.03-0.3m2. The plate ribs are fastened to the metal cans by means of aluminum-steel or copper-steel bimetallic joints made by explosion welding. The steel part of the bimetal joint is welded to the wall of the metal can and the plate ribs are welded to the aluminum or copper part, the plate ribs being made of aluminum or an aluminum alloy or a copper alloy, respectively. In the upper part of the support member, an actuator designed as a pivoting flap is provided, which controls the heat removal efficiency from the tank wall. In the gap between the support members means for forced cooling of the plate ribs in the form of fans and blowers are mounted. The apparatus enables the electrolytic aluminum production process in an aluminum electrolysis cell to be enhanced by adjusting the heat removal efficiency to provide conditions for stabilizing the production process and to increase the service life of the cathode assembly of the aluminum electrolysis cell.
The known cathode assembly makes it possible to provide effective heat removal from the electrolyzer to the tank side walls and further to the plate ribs which are cooled during the air flow by convective heat exchange caused by the air heating in the spaces between the ribs and the temperature difference along the height of the tank walls. This makes it possible to ensure the formation of a stable coagulation bath (scale layer) layer on the inner surface of the side lining of the cathode assembly under dense operating conditions of the aluminium electrolysis cell, thereby increasing the service life of the cathode assembly of the aluminium electrolysis cell.
A disadvantage of the cathode assembly in the prototype is that under conditions of the intensive reduction process, a necessary condition to increase the production efficiency is the ability to ensure operation of the electrolyzer at high temperatures of bath superheat (difference between operating temperature and liquidus temperature) to avoid dross deposition and formation of crust on the bottom, which reduces the process efficiency and leads to the associated drawbacks. The main task is therefore to produce a protective scale layer at an superheat above 25 ℃ (preferably about 40 ℃), whereas the known solutions only guarantee scale layer formation at an superheat of about 20 ℃. This is because this design provides for efficient heat transfer from the electrolyzer to the tank side walls, while heat dissipation from the outer surface of the housing and thus the plate ribs are not sufficiently efficient for the production process.
Typically, the ribs are made of aluminum or aluminum alloy, copper or copper alloy, or special steel, i.e., a material having high thermal conductivity. The plate ribs are attached at their ends to the longitudinal wall and end wall of the metal can by means of a bimetallic joint made by explosion welding or by bolting and/or riveting.
If a bimetallic joint is used, there are too many layers with low thermal conductivity: the walls of the metal cans are 12-30mm steel and the steel portion plus the bimetallic joint is 24-35mm, which is a total of about 36-65mm steel having a thermal conductivity of about 50W/m·k (W/m·k=w/m·c) at 300 ℃. Furthermore, the plate ribs are fixed by means of welded joints, i.e. the heat is transferred only through the fillets and not the entire cross section of the bimetallic joint. This ensures a minimum temperature difference of about 30-50 c.
In the case of a bolted or riveted connection, the thermal resistance between the rib and the metal can wall is too high; if the splice joint is not permanently tightened, it will loosen due to temperature fluctuations.
Disclosure of Invention
The task of the present invention is to develop a design for a cathode assembly for an aluminium electrolysis cell with increased heat dissipation from the upper part of the side of the metal can, capable of operating at an overheat above 25 ℃.
The technical effect is to solve the problem that aluminum is produced more in the aluminum electrolysis cell by reduction (increase of unit current) since the design of the cathode assembly is able to remove and dissipate the thermal energy released in the cell.
This problem is solved and a technical effect is achieved in a cathode assembly for an electrolytic cell for aluminium production comprising a metal can (1) having a bottom (3), a support member (5) covering the can wall (2) and the bottom, a liner (6) enclosed within the metal can, a cathode block (7) and a cathode rod (8) forming the cathode of the electrolytic cell, according to the invention on the longitudinal walls and end walls (2) of the metal can (1) in the gap between the support members (5) a fixing plate rib (15) and/or a finger rib (16) with an improved structure for heat removal made of a material with a high thermal conductivity, a strip (9) made of a composite material being mounted on the upper part of the longitudinal walls and end walls (2) of the metal can.
The invention is supplemented by specific embodiments thereof which contribute to achieving technical effects.
The tape composite may comprise at least two metal layers, wherein the total height of the tape is 0.2-0.5m. If the height is less than 0.2m, the heat removed and dissipated from the belt is insufficient and the solution will be ineffective. If the height is greater than 0.5m, the heat removal becomes excessive, with the result that cooling will affect the metal area (liquid aluminium), which will adversely affect the reduction process.
The upper layer (13) of the belt composite is made of a metal having a high thermal conductivity. The upper layer (13) of the belt composite may be made of aluminum or an aluminum alloy. The upper layer (13) of the belt composite may be made of copper or copper alloy.
The tape composite is made by joining metal layers by pulse welding. The belt composite may include an intermediate layer (14) made of titanium.
In the case of the present application, the application uses a strip made of several layers of metal that differ in chemical composition and are separated by distinct boundaries.
Above the support member a heat removal regulator (17) constructed as a pivoting flap (18) can be mounted.
In this case, a self-regulating system is provided. Heat removal is regulated by increasing and decreasing the scale layer thickness. However, in case an undesired deviation in the operation of the device is observed, a forced cooling element (device) may be provided. A forced cooling device, such as a fan, may be provided in the gap between the support members (5).
The described design of the cathode assembly makes it possible to ensure effective heat removal from the electrolyzer to the tank side walls and to effectively dissipate the thermal energy by convective heat exchange during the air flow, caused by the air heating in the spaces between the ribs and the temperature difference along the height of the tank walls. This makes it possible to ensure the formation of a stable coagulation bath (scale layer) layer on the inner surface of the side lining of the cathode assembly at overheating above 25 ℃ under dense operating conditions of the aluminium electrolysis cell and to ensure a stable and robust operation of the aluminium electrolysis cell.
It is known that operation of the device at up to 25 ℃ is ensured by simple means and above 25 ℃ is extremely difficult since the protective scale layer is detached from the side lining and the wall begins to deteriorate rapidly (oxidize).
The technical expert also knows that high thermal conductivity (for metals) starts from > = 60W/m·k.
The invention is complemented by special cases for the upcoming problem.
The cathode assembly is supplemented by the fact that the composite material is made by pulse welding, the compounds obtained are steel/aluminium, steel/copper, and in the case of titanium (Ti) interlayers, they are steel/titanium/aluminium, steel/titanium/copper. The titanium layer in the composite wall is necessary to operate the side wall at temperatures above 300 ℃ to avoid the formation of intermetallic compounds at the boundary of the two metals joined by pulsing and degradation of the compounds.
To increase the efficiency of the cathode assembly, the outer layer of the composite material is made of a metal having a high thermal conductivity, such as aluminum, copper, bronze or special steel. For example, aluminum grades 0-a 85 (λ=210-230W/m·k, W/m·k=w/m·c) or aluminum alloys (AD 0, AD1, AD31, AD33, AD35, D1, D16, AK7, AK9, AK12, AMz, AMTs, AMg3, AMg4, AMg5, AMg6, B63, B93, B94, B95) having a thermal conductivity of about λ=110-230W/m·k; copper λ=360-390W/m·k or copper alloys (bronze, brass, etc.), having a thermal conductivity of about 70 to 380W/m·k; special steels (55, 60, 65, 70, 20G, 30G, 40G, etc.) have a thermal conductivity of about 50-80W/mK.
In order to more effectively radiate heat from the surface of the upper belt made of a composite material, a plate rib made of a material having high thermal conductivity (aluminum, copper, bronze or special steel) is fixed to the upper belt in an amount of 3 to 10 pieces, and the area of the plate rib is 0.03 to 0.6m 2.
The cathode assembly is supplemented in that, to further increase efficiency, the ribs may be replaced by fingers (which may be in the form of rods, sticks, "sticks" or the like) having a more developed surface for heat dissipation.
The cathode assembly is supplemented by the fact that in the upper part of the support member, a regulator of the heat removal efficiency from the metal tank wall designed as a pivoting flap is mounted, which makes it possible to regulate the scale thickness or to regulate its shape according to seasonal variations in the ambient temperature.
The cathode assembly is supplemented by forced cooling means in the form of fans and blowers located in the gap between the support members.
Drawings
Figure 1 shows a cathode assembly for an aluminium electrolysis cell as proposed.
Fig. 2 shows a cathode assembly having an upper portion of a metal can wall of composite material manufactured by a process such as pulse welding. Fig. 2 also shows a cathode assembly with an upper part of the metal can wall of composite material, the outer layer of which is made of metal with high thermal conductivity.
Fig. 3 shows a cathode assembly with an upper part of a metal can wall of composite material, the outer surface of which has a flared surface due to the installation of the plate ribs.
Fig. 4 shows a cathode assembly with an upper portion of a metal can wall of composite material, the outer surface of which has a flared surface due to the installation of the finger ribs.
Fig. 5 shows a cathode assembly with an upper part of a metal can wall of composite material with a regulator designed as a pivoting flap mounted in the upper part of the support member, which regulator controls the efficiency of heat removal from the metal can wall.
Fig. 6 shows a cathode assembly with an upper part of a metal can wall of composite material with forced cooling means in the gap between the support members.
Detailed Description
The cathode assembly of an aluminium electrolysis cell comprises a metal can 1 having longitudinal and end walls 2, a bottom 3 and flange plates 4; a support member 5 covering the tank wall and the bottom; a liner 6 enclosed in the tank 1, a cathode block 7 with a cathode rod 8, the cathode rod 8 forming the cathode of the cell; the upper belt 9 is made of a composite material.
The air flow 10 passing through the holes 11 defined by the support member 5, the longitudinal walls and the end walls 2 passes (cools) the upper belt 9 made of composite material. The flow 10 is generated by a lift force (archimedes force) due to heating in the space defined by the support member 5 and an air flow due to a temperature difference in the height direction of the wall of the tank 2.
As in the prototype, the metal can 1 with longitudinal and end walls 2, bottom 3 and flange plate 4 also participates in the heat exchange with the support member 5 comprising the cathode assembly.
The composite material is produced by pulse welding, i.e. by pressure welding, in which the workpieces are welded when they collide with each other due to an explosion of a thermal charge.
The movable work piece (a metal of a physical nature different from the base, generally softer and less strong) as the upper layer 13 is welded to the base 12 (a fixed steel work piece). In order to maintain the thermal and mechanical properties of the upper strip 9 of composite material under high temperature operating conditions, an intermediate (barrier) layer 14 of Ti (titanium) 0.5-1.5mm thick is placed at the interface (flat or dovetailed) to prevent the formation of brittle intermetallic compounds. Thus, effective heat removal is performed from the upper belt 9 of composite material having the upper layer 13.
When the upper layer 13 of the belt 9 is made of a metal having high thermal conductivity, aluminum, copper, bronze or special steel may be used as such metal.
To increase efficiency, the surface of the upper layer 13 may be formed by mounting plate ribs 15 made of metal having a high thermal conductivity, which are fixed by welding, brazing or other mechanical means (bolting and/or riveting), and by making the flat surface 13 by milling or mounting spacers in advance, for example made of fusible heat conducting material, graphite or silver based heat conducting paste, aluminum foil, refractory cement, etc., which will flatten the uneven surface of the wall.
Since the surface 13 is spread more by installing the finger rib 16 made of metal having high thermal conductivity, the heat removal surface can be increased by 20 to 30% and heat energy dissipation is ensured, so that the efficiency can be further improved.
In order to regulate the heat removal of the upper part of the wall of the composite material tank (belt) 9, a heat removal regulator 17 designed as a pivot flap 18 can be installed in the hole 11 above the support member 5 to vary the opening area in the hole 11. This allows the scale thickness to be adjusted in response to seasonal ambient temperature changes and changes in cell current.
In order to increase the intensity of the heat removal from the cathode assembly and in particular by reducing the surface temperature of the upper band 9 of the metal can 1, forced cooling means 19 may be installed in the gap between the support members 5. The device is, for example, a centrifugal fan having a capacity of 1000-2000m 3/h. Thus, the heat dissipation can be further increased by 30-50%.
Examples of the invention
The installation and removal of the cathode assembly of the aluminium electrolysis cell is performed as follows.
When manufacturing the cathode assembly of the proposed design, wherein heat is strongly removed from the can and dissipated through the upper strip 9 of composite material, this ensures the formation of a stable coagulation bath (scale layer) layer on the inner surface of the side lining of the cathode assembly at an overheat above 25 ℃ and thus a stable and stable operation of the aluminium electrolysis cell.
The bottom 3, flange plates 4 and longitudinal and end walls 2 of the metal can 1 are made of 12-20mm thick steel sheet with sufficient ductility and mass. Inside the metal can 1, a lining 6 made of a refractory and heat-insulating material, and a cathode block 7 with a cathode rod 8 mounted therein are placed.
The support members 5 covering the walls and bottom of the tank 1 are made in the form of shell stiffeners (T-beams or I-beams) or hinged reaction brackets (structures with box cross-sections or two welded together I-beams). In the upper part of the longitudinal walls and end walls, a strip 9 made of a composite material consisting of 2 or more layers of different metals is installed, with a height of 0.2-0.5m. The lower part of the strip is welded to the wall 2, the upper part of the strip is welded to the flange plate 4, and the surface of the upper layer 13 is welded to or rests in the support member 5, ensuring free contact.
The strips 9 are individually made of composite material. Pulse welding is a mechanical type of pressure welding in which a joint is formed by collisions caused by explosion of the parts to be welded. The composite strip material generally comprises a steel substrate 12, an upper layer 13 of high thermal conductivity material and an intermediate layer 14 of titanium. The intermediate layer 14 needs to be installed when the belt is operated in the apparatus at a temperature above 300 ℃.
Maximum efficiency is achieved when the upper layer 13 of the strip 9 of composite material has an expanded surface, by inserting plate ribs 15 and/or finger ribs 16 made of a highly heat conductive material such as special steel, aluminum or an aluminum alloy, copper or a copper alloy. The plate ribs 15 are formed in a rectangular or trapezoidal shape having a height of 300-600mm, a width of 100-500mm and a thickness of 6-10mm. The number of ribs is selected based on the desired heat transfer coefficient. For example, 7 ribs were installed from 6mm thick St3 steel, the distance between the ribs being 50mm, the area being 0.3m 2, the heat transfer coefficient αn=75W/m 2 ·k being generated in the free convection mode. For comparison, the maximum possible heat transfer coefficient without plate ribs is an=30w/m 2 ·k. 7 ribs made of aluminum grade A5 were installed, having a thickness of 10mm, an area of 0.3m 2, and a distance between fins of 50mm, resulting in a heat transfer coefficient of approximately αn=150W/m 2 ·k.
These heat transfer coefficient values were obtained on a hot bench simulating the metal tank wall of the cell cathode assembly in experimental studies of different variations of the plate ribs.
The replacement of the plate ribs 15 with finger ribs 16 increases the heat transfer surface by 20-30% and makes it possible to increase the heat transfer coefficient by 15-20%.
If such heat does not need to be dissipated, the heat removal coefficient may be reduced by closing the pivoting shutter 18 of the heat removal regulator 17.
When it is desired to increase the heat emitted from the cathode assembly, forced cooling means 19 in the form of fans and blowers, as well as other suitable cooling means, may be used.
The proposed cathode assembly thus provides a stable coagulation bath (scale layer) layer on the inner surface of the side lining of the cathode assembly at an overheat above 25 ℃ and ensures a stable and documented operation of the aluminium electrolysis cell. For example, the test samples were run in summer (worst condition) at 40 ℃ superheat, and there was minimal protective scale layer on the wall.
Claims (10)
1. Cathode assembly for an electrolytic cell for aluminium production, comprising a metal can (1) having a bottom (3), support members (5) covering the longitudinal walls and end walls (2) of the can and the bottom, a liner (6) enclosed within the can, a cathode block (7) and a cathode rod (8) forming the cathode of the cell, characterized in that on the longitudinal walls and end walls (2) of the metal can (1) in the gap between the support members (5) there is a fixing plate rib (15) and/or finger rib (16) with an improved structure for heat removal, a strip (9) made of composite material for stabilizing heat removal is mounted on top of the longitudinal walls and end walls (2) of the metal can.
2. Cathode assembly according to claim 1, characterized in that the composite material of the strip consists of at least two metal layers, wherein the height of the strip is preferably 0.2-0.5m.
3. Cathode assembly according to claim 2, characterized in that the top layer (13) of the belt composite is made of a metal with high thermal conductivity, preferably higher than 60W/m-K.
4. A cathode assembly according to claim 2 or 3, characterized in that the top layer (13) of the belt composite is made of aluminium or an aluminium alloy.
5. A cathode assembly according to claim 2 or 3, characterized in that the top layer (13) of the belt composite is made of copper or a copper alloy.
6. The cathode assembly according to any one of claims 2 to 5, wherein the ribbon composite is made by pulse welding the metal layers.
7. The cathode assembly according to claim 2, wherein the belt composite comprises an intermediate layer (14) made of titanium.
8. Cathode assembly according to claim 1, characterized in that a heat removal regulator (17), preferably designed as a pivot flap (18), is mounted above the support member (5).
9. Cathode assembly according to claim 1, characterized in that forced cooling means, in particular a fan, are placed in the gap between the support members (5).
10. Cathode assembly according to claim 1, characterized in that the plate fins (15) and/or finger fins (16) are made of a material having a thermal conductivity higher than 60W/m-K.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| RU2021127241 | 2021-09-16 | ||
| RU2021127241A RU2770602C1 (en) | 2021-09-16 | 2021-09-16 | Cathode device of aluminum electrolyzer |
| PCT/RU2022/050227 WO2023043334A1 (en) | 2021-09-16 | 2022-07-21 | Cathode device for an aluminium electrolysis cell |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN117940611A true CN117940611A (en) | 2024-04-26 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202280062243.0A Pending CN117940611A (en) | 2021-09-16 | 2022-07-21 | Cathode device for aluminum electrolysis cell |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP4403673A1 (en) |
| CN (1) | CN117940611A (en) |
| CA (1) | CA3231974A1 (en) |
| RU (1) | RU2770602C1 (en) |
| WO (1) | WO2023043334A1 (en) |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU605865A1 (en) | 1976-05-10 | 1978-05-05 | Северо-Западное Отделение Всесоюзного Научно-Исследовательского И Проектноконструкторского Института "Внипиэнергопром" | Aluminium electrolyzer |
| US4087345A (en) | 1977-07-19 | 1978-05-02 | Ardal Og Sunndal Verk A.S. | Potshell for electrolytic aluminum reduction cell |
| US4608134A (en) | 1985-04-22 | 1986-08-26 | Aluminum Company Of America | Hall cell with inert liner |
| FR2842215B1 (en) * | 2002-07-09 | 2004-08-13 | Pechiney Aluminium | METHOD AND SYSTEM FOR COOLING AN ELECTROLYSIS TANK FOR THE PRODUCTION OF ALUMINUM |
| RU2230834C1 (en) | 2002-11-10 | 2004-06-20 | Архипов Геннадий Викторович | Cathode casing of aluminum cell |
| KR100515412B1 (en) * | 2003-01-22 | 2005-09-14 | 도요탄소 가부시키가이샤 | Electrolytic apparatus for molten salt |
| BRPI0516399A (en) * | 2004-10-21 | 2008-09-02 | Bhp Billiton Innovation Pty | electrolytically cell and process for metal production |
| RU2321682C2 (en) * | 2006-05-23 | 2008-04-10 | Общество с ограниченной ответственностью "Русская инжиниринговая компания" | Cathode device of aluminum cell |
-
2021
- 2021-09-16 RU RU2021127241A patent/RU2770602C1/en active
-
2022
- 2022-07-21 CA CA3231974A patent/CA3231974A1/en active Pending
- 2022-07-21 WO PCT/RU2022/050227 patent/WO2023043334A1/en active Application Filing
- 2022-07-21 CN CN202280062243.0A patent/CN117940611A/en active Pending
- 2022-07-21 EP EP22870397.1A patent/EP4403673A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| RU2770602C1 (en) | 2022-04-18 |
| WO2023043334A1 (en) | 2023-03-23 |
| EP4403673A1 (en) | 2024-07-24 |
| CA3231974A1 (en) | 2023-03-23 |
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