AU2004200431B8 - Protecting an inert anode from thermal shock - Google Patents
Protecting an inert anode from thermal shock Download PDFInfo
- Publication number
- AU2004200431B8 AU2004200431B8 AU2004200431A AU2004200431A AU2004200431B8 AU 2004200431 B8 AU2004200431 B8 AU 2004200431B8 AU 2004200431 A AU2004200431 A AU 2004200431A AU 2004200431 A AU2004200431 A AU 2004200431A AU 2004200431 B8 AU2004200431 B8 AU 2004200431B8
- Authority
- AU
- Australia
- Prior art keywords
- insulating layer
- anode
- thermal
- ceramic
- plate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000035939 shock Effects 0.000 title claims description 22
- 239000000463 material Substances 0.000 claims description 34
- 238000000034 method Methods 0.000 claims description 32
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 23
- 239000000919 ceramic Substances 0.000 claims description 18
- 239000000377 silicon dioxide Substances 0.000 claims description 11
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 10
- 239000011195 cermet Substances 0.000 claims description 10
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 9
- 239000003792 electrolyte Substances 0.000 claims description 8
- 238000012546 transfer Methods 0.000 claims description 7
- 229910010293 ceramic material Inorganic materials 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 9
- 239000002184 metal Substances 0.000 description 9
- 150000003839 salts Chemical class 0.000 description 9
- 238000005336 cracking Methods 0.000 description 8
- 238000001816 cooling Methods 0.000 description 5
- 239000004744 fabric Substances 0.000 description 5
- 238000009413 insulation Methods 0.000 description 5
- 230000000712 assembly Effects 0.000 description 4
- 238000000429 assembly Methods 0.000 description 4
- 229910001610 cryolite Inorganic materials 0.000 description 4
- 239000000835 fiber Substances 0.000 description 4
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 238000005868 electrolysis reaction Methods 0.000 description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 229910000323 aluminium silicate Inorganic materials 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 239000011819 refractory material Substances 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 238000009626 Hall-Héroult process Methods 0.000 description 1
- 229910052778 Plutonium Inorganic materials 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- YKTSYUJCYHOUJP-UHFFFAOYSA-N [O--].[Al+3].[Al+3].[O-][Si]([O-])([O-])[O-] Chemical compound [O--].[Al+3].[Al+3].[O-][Si]([O-])([O-])[O-] YKTSYUJCYHOUJP-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 239000002657 fibrous material Substances 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 238000004901 spalling Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 231100000167 toxic agent Toxicity 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Description
FIELD OF THE INVENTION [0001] The present invention relates to methods for protecting electrodes from thermal shock. More specifically, the present invention relates to protection of inert anodes and their support structure from thermal shock during electrolytic cell start-up operations.
BACKGROUND INFORMATION [0002] Aluminum is produced conventionally by the electrolysis of alumina dissolved in cryolite-based molten electrolytes at temperatures between about 900 and 1000 0 C; the process is known as the Hall-Heroult process. A Hall-Heroult reduction cell typically comprises a steel shell having an insulating lining of refractory material, which in turn has a lining of carbon that contacts the molten constituents. Conductor bars connected to the negative pole of a direct current source are embedded in the carbon cathode substrate that forms the cell bottom floor. The carbon lining and cathode substrate have a useful life of three to eight years, or even less under adverse conditions. The deterioration of the cathode bottom is due to erosion and penetration of electrolyte and liquid aluminum as well as intercalation of sodium, which causes swelling and deformation of the cathode carbon blocks and ramming mix. In addition, the penetration of sodium species and other ingredients of cryolite or air leads to the formation of toxic compounds including cyanides. Anodes are at least partially submerged in the bath.
[0003] In operation, the conventional cell contains an electrolytic, molten cryolite-based bath in which alumina is dissolved. A molten aluminum pool acts as the cathode. A crust of frozen electrolyte and alumina forms on top of the bath and around the anode blocks. As electric current passes through the bath between the anode and cathode surfaces, alumina is reduced to aluminum, which is deposited in the pad of molten metal.
[0004] Electrolytic reduction cells must be heated from room temperature to approximately the desired operating temperature before the production of metal can be initiated. Heating should be done gradually and evenly to avoid thermal shock, which can in turn cause breakage or spalling. The heating operation minimizes thermal shock to the lining, the electrodes and the support structure assemblies upon introduction of the electrolyte and molten metal to the cell. Once at operating temperatures carbon anodes wear out and are replaced. Carbon anodes can be placed in to the electrolyte cold and heated by the energy of the cell to operating temperatures, at which time the nominal current of the anode will be attained. Ceramic anodes that have much longer lives are prone to thermal shock and therefore need to be preheated in a furnace outside of the electrolytic cell prior to insertion into the hot electrolyte. During transfer, the cooling or heating of the anodes must also be minimized to avoid thermal shock. The thermal shock/cracking can occur both during movement of the anodes into position and during their placement into the molten salt. Thermal shock relates to the thermal gradient (positive or negative) through the anode that occurs during the movement from the preheat furnace to the cell, and also upon insertion of the anodes into the molten salt. A thermal gradient as low as 50 0 C can cause cracking. An attempt to protect electrodes in an electrolysis cell from thermal shock during start-up, U.S. Patent No. 4,265,717, taught protection of hollow cylindrical TiB 2 cathodes by inserting aluminum alloy plugs into the cathode cavity and further protecting the cathode with a heat dispersing metal jacket having an inside heat insulating layer contacting the TiB 2 made of expanded, fibrous kaolin-china clay (A1 2 0 3 *2SiO 2 *2H 2 which would subsequently dissolve in the molten electrolyte.
[00051 Aluminum electrolysis cells have historically employed carbon anodes on a commercial scale. The energy and cost efficiency of aluminum smelting can be significantly reduced with the use of inert, non-consumable, and dimensionally stable anodes. Use of inert anodes rather than traditional carbon anodes allows a highly productive cell design to be utilized, thereby reducing capital costs. Significant environmental benefits are also realized because inert anodes produce essentially no
CO
2 or CF 4 emissions. Some examples of inert anode compositions are provided in U.S. Patent Nos. 4,374,050; 4,374,761; 4,399,088; 4,455,211; 4,582,585; 4,584,172; 4,620,905; 5,279,715; 5,794,112; 5,865,980; and 6,126,799 assigned to Alcoa Inc.
These patents are incorporated herein by reference. Ceramic anodes, unlike their carbon predecessors, can undergo thermal shock and cracking if heated or cooled too quickly. Methods of protecting inert anodes from thermal shock are therefore desired.
SUMMARY OF THE INVENTION [0006] The present invention is directed to methods for protecting ceramic or cermet inert anodes from thermal shock. The methods generally comprise applying a thermal insulating layer, or "boot" around the inert anode. The insulating layer or boot is applied to the anode before preheating begins, and remains on the anode during positioning of the anode into the cell and submersion of the anode into the molten bath.
Inert anodes, which are often made of a cermet or ceramic material, are prone to thermal shock that can cause cracking of the anode material. Preheating of the anodes to the approximate operating temperature of the Hall cell before placing them into the cell is therefore desired to minimize the thermal shock experienced when the anodes are placed in the molten salt. Because the anodes can be rapidly cooled or heated, heat transfer during movement of the anodes from the preheat furnace to the cell must also be minimized.
[0007] Similarly, the castable box or plate to which the anodes are attached are subject to thermal shock. The plates, typically made of a refractory material such as a silica or alumina ceramic, can also crack as a result of thermal gradients experienced during transfer from the pre-heat furnace to the cell. Accordingly, the present invention is further directed to methods for protecting castable plates from thermal shock by applying a thermal insulating drape, or "sweater" around the plates.
[0008] The present invention minimizes the thermal gradient to which inert anodes and castable plates are exposed while being transferred from a preheat furnace to an electrolytic cell. A significant advantage of the present invention is that the insulating boots and sweaters do not have to be removed prior to inserting the anodes into the cell. In past systems it was necessary to remove the boots before placing the anodes in the Hall cells; this exposed personnel to high temperatures and potential burns. These previous methods also delay anode transfer, and still result in exposure of the anode to cooling that can cause thermal gradients in excess of 50 0 C. In addition, since the boots remain on the anodes during submersion into the molten bath, they also protect the anodes from a sudden increase in heat from the hot bath that can also cause cracking.
BRIEF DESCRIPTION OF THE FIGURES [009] Figure 1 shows an anode assembly of the present invention in which an insulating layer is applied to the anodes and castable plate such that the layer is in direct contact with the anode; and [00101 Figure 2 shows an anode assembly of the present invention in which the insulating layer is hung from the anode so as to create an air gap between the layer and the anode.
DETAILED DESCRIPTION OF THE INVENTION [0011] The present invention is directed to a method for protecting an inert anode from thermal shock comprising applying a thermal insulating layer to the anode; preheating the anode, preferably in an external furnace; and transferring the heated anode to an electrolytic cell. Preferably, the inert anode is made of a ceramic or cermet material. The present invention is further directed to a method for protecting a castable box or plate from thermal shock comprising applying a thermal insulating layer to the plate prior to pre-heating. The plate is preferably made from a silica or alumina ceramic material.
[0012] "Insulating layer" is used herein to refer collectively to thermal insulation materials including insulating "boots", used for anode protection, and insulating drapes or "sweaters", used for castable plate protection. The anodes and castable plate are sometimes referred to collectively herein as the anode assembly. It will be appreciated that inert anodes and their support structure assemblies typically comprise additional components, such as a lid fastened over the castable box or plate and a support beam that supports the lid. These additional components may also be protected with an insulating layer according to the present invention, although their risk of thermal shock is significantly less.
[0013] The insulating boots of the present invention are made of materials that can be placed into the molten salt, and thus the anodes can go from the preheat furnace to the cell without requiring the additional step of boot removal. The molten salt will penetrate and dissolve the boots, thereby permitting the inert anode to begin carrying current almost immediately upon immersion into the cell. Thus, according to the present invention the cermet inert anodes are protected from the cooling environment of the air during transfer, and are also protected from the potentially higher temperatures of the molten salt. Both positive and negative thermal gradients, which are potential causes of thermal shock and cracking, are therefore minimized, if not eliminated, according to the present methods. Similarly, the insulating drapes used in the present methods can go from the preheat furnace to the cell without being removed from the castable plate. While the castable plate is not itself immersed into the cell, fumes emanating from the molten salt will eventually dissolve the drape or sweater used to protect the plate. As with the anode, the plate is protected from cooling when being transported from the preheat furnace to the cell according to the present methods.
[0014] The thermal insulating layers of the present invention can be made from any material having a thermal conductivity at 900 0 C to 1000 0 C sufficient to prevent the anode assembly from experiencing a thermal gradient of greater than 50 0
C.
Typically, the thermal conductivity between 900 0 C and 1000 0 C will be between about 0.2 and 1 watt/meter 'K (w/m It will be appreciated that the lower the thermal conductivity the better the insulation ability of the material. In addition, the material is preferably in the form of cloth, fiber, felt and the like. Such a material provides ease of handling due to its flexibility, and can be more readily applied to the anode assembly.
Following submersion of the anodes into the molten bath, a boot having a cloth, fiber or felt consistency will absorb the molten bath and dissolve relatively quickly. It is preferred that the insulating boot dissolve in one minute or less following submersion in the bath. Thus, while materials such as wood, dense ceramics, or glass can be used for the insulating layer, they are not preferred.
[0015] Preferred materials for use in the thermal insulating layers of the present invention are "silica materials", which term refers collectively to materials comprised of silica in any chemical form, alone or in conjunction with other elements; examples include aluminum silicate (A1 2 0 3 *3SiO 2 or 3A1 2 0 3 *2SiO 2 and silica dioxide (SiO 2 [0016] The aluminosilicate material is preferably in the form of a fibrous blanket that is made of fine fibers. The fine fibers usually go into solution easily, and thus the boot is readily dissolved in the molten salt bath. The boot provides a minor source of 1is alumina available for reduction to aluminum during the electrolytic process. The amount of silica introduced to the cell from the boot is a minimal amount, such that no appreciable contamination or adverse effect is caused by its introduction. A preferred aluminosilicate material is commercially available from 3MTM Ceramic Textiles Composites under the tradename Nextel. It is very strong fabric that can be used to support other insulating materials.
[00171 Other preferred materials are comprised of SiO 2 An SiO 2 fiber material approximately half an inch thick is commercially available from Cooperknit, Piscataway, NJ, under the trademark "Cooperknit"' This material has a thermal conductivity at 900 0 C of about 0.338 w/m 0 K, and thus is ideally suited for the present invention. Again, the amount of silica introduced to the electrolytic cell from the boots is insignificant, and will be removed from the bath by the aluminum metal pad and diluted by metal production within a matter of days. A silica needled mat can also be used according to the present invention. One such material is sold under the trademark "PyroSil SNM" and is commercially available from PyroShield Inc., Crown Point, IN in various thicknesses; the product has a thermal conductivity at 1000 0 C of about 0.268 w/m 'K.
[0018] In one embodiment of the present invention the boots and/or drapes are comprised of two or more different materials. The materials used in the multilayer embodiment are as described above. It will be appreciated that some of these materials will have a higher risk than others of being ripped, flaked off, brushed off or otherwise damaged during the handling of the preheat steps. Other materials offer greater durability. A tear in the boots and/or drape can result in localized cooling that could lead to cracking of the anode assembly. Preferably, the outermost portion of the insulating layer is of a more durable material that can withstand the handling to which the anode assembly is subjected during preheat and placement into the cell. A preferred combination is a CooperKnit layer adjacent the anode assembly covered by a Nextel layer. "Insulating layer", as used herein, encompasses such multi-layer embodiments. Also, when using an insulating layer on the anodes and the plate, the layers used for each can be made of different materials.
[0019] The insulating layer should be physically attached to the anode and lid, such as during assembly of the anode assembly. For example, the boot can be slipped over the anode and attached with wire, ceramic string or cloth. When the anode is submerged the attachment means will melt or dissolve in the bath. Again, any contamination resulting from the attachment means is insignificant. Alternatively, the boots/drapes can be adhered to the anode assembly. If an adhering compound is used in the present methods it is preferably a non-organic cement or alumina or silica material, as the introduction of organic adhesives to the system could result in undesirable by-products.
[0020] The insulating boot 8 can be applied so that it is directly attached to the anode 2, as shown in Figure 1, or so that it creates an air gap 14 along with drape 16 around the anode, as shown in Figure 2. With further reference to Figure 1, anode 2 is attached to steel plate 17 by means of pins 10 and supports the castable plate 4 and insulation around the castable plate 4. Drape 16 is attached to plate 4 by means of wire, ceramic string or cloth (not shown). Insulating boot 8 is in direct contact with the majority of the anode 2. In Figure 2, insulating boot 8 is attached to anode 2 near the point 12 at which the anode 2 meets the castable plate 4. Here, drape section 16 hangs down around anode 2, creating air gap 14. The drape 16 in Fig. 1 is a short drape while the drape 16 in Fig. 2 is a long drape.
[0021] The thickness of the boot and drape will vary depending on the insulation qualiies of the particular material used. For example, if the thermal conductivity of the material is high, a thicker boot or drape will be required. The closer the thermal conductivity is to 0.2 w/m 'K the thinner the boot/drape may be while still providing the desired level of insulation. If a multilayer boot/drape is used, the thickness of the outer most layer will typically be less than any other layers. Typically, the thickness of insulating layers of the present invention is about 5 cm. (2 inches) or less. The thermal insulating layer or layers must have a total thickness of at least about 1 mm., preferably at least about 5 mm. A thickness in a range of about 5-50 mm. is preferred.
Optimally, the insulating layer has a thickness of about 10-30 mm. The insulating layer has a density of less than lg/cm 3 preferably less than about 0.5 g/cm 3 and more preferably less than about 0.2 g/cm 3 The most suitable insulating materials have a density of about 0.1-0.2 g/cm 3 [0022] Following application of the insulating boot to the anode, and optionally the application of the drapes to the lid, the anode assembly can then be heated in a furnace external to the electrolytic cell. Heating is typically effected at a rate of between about 15'C and 45°C per hour; preferably, the rate is between about 250C and 30'C per hour. Thus, heating of the anode assembly from room temperature to approximately 1000°C can take several days.
[0023] Following the heating step, the anode assembly is transferred to the electrolytic cell. Typically, the external furnace is 22.9 -27.5 meters (25-30 yards) away from the cell. In open air, the temperature of the anode will drop quickly absent the presence of the insulating boot. Thus, the boot maintains the temperature of the anodes and avoids a thermal gradient sufficient to cause cracking. The drape similarly maintains the temperature of the plate. Transport can be effected by any means known in the art, such as by use of a crane.
[0024] It is a significant advantage of the present invention that the insulating layers do not need to be removed from the anode assembly prior to positioning of the anode assembly in the cell and submersion of the anodes into the molten salt bath.
Following submersion of the anodes into the bath, the insulating boots of the present invention will preferably dissolve in approximately a minute or less and the drape at a slower rate. Because the plate need not conduct current like the anodes, the rate at which the drape dissolves is not thought to be important.
[0025] The present invention is also directed to an inert anode covered at least in part with a thermal insulating boot. The boot is as described above. The present invention is further directed to an anode assembly comprising a plurality of inert anodes attached to a castable plate; the inert anodes are covered at least in part with thermal insulating boots as described above and the castable lid is covered at least in part with a thermal insulating drape or sweater.
[0026] Any inert anode can be used in the present invention, for example, those described in U.S. Patent Nos. 4,374,050; 4,374,761; 4,399,088; 4,455,211; 4,582,585; 4,584,172; 4,620,905; 5,279,715; 5,794,112; 5,865,980; and 6,126,799. "Inert anode" as used herein refers to a substantially nonconsumable anode that possesses satisfactory corrosion resistance and stability during the aluminum production process. Preferably, the inert anode is a ceramic inert anode or a cermet inert anode. "Cermet" refers to an inert anode comprising a ceramic phase and a metal phase. For example, the ceramic phase can contain oxides of iron, nickel and/or other metals; the metal phase can contain one or more metals such as Cu, Ag, Pd, Pt, Au, Ph, Pu, Ir or Os. The cermet inert anodes used in the present invention can be made entirely of cermet material, or can comprise an outer coating or layer of cermet material over a central core.
EXAMPLES
100271 The following examples are intended to illustrate the invention, and should not be construed as limiting the invention in any way.
100281 The methods of the present invention were successfully tested using the anode assemblies depicted in Figures 1 and 2. Anodes and lids were covered with a twolayer thermal insulating layer, comprised of Cooperknit
T
M insulation and preheated in a furnace to a temperature of between about 900'C and 1 000C. The anode assemblies were transferred to an electrolytic cell with a crane, positioned into the cell, and submerged in molten cryolite. The temperature gradient experienced by the anode assembly between the furnace and the cell was between 30 0 C and 100°C depending on the insulating layers and time of the transfer. Another insulating layer test used PyroSil covered with CooperknitTM. In all cases the anode was successfully protected.
100291 Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.
Claims (14)
1. A method for protecting from thermal shock, a ceramic inert anode used in electrolytic production of aluminum, comprising: applying to a ceramic inert anode a thermal insulating layer having a thickness of at least about 1 mm; heating said ceramic inert anode at a rate of between about 15' C. and 450 C. per hour; transferring said heatd anode to an electrolytic cell, wherein the insulating ceramic inert layer maintains the temperature of the ceramic inert anode during transfer to avoid a thermal gradient sufficient to crack the ceramic inert anode.
2. The method of claim 1, wherein said inert anode is a cermet inert anode.
3. The method of claim 1, wherein said thermal insulating layer comprises a silica material disposed around the ceramic inert anode.
4. The method of claim 1 wherein said thermal insulating layer is comprised of more than one material, with an outermost portion of said layer comprising a material more durable than any other material. The method of claim 1, wherein said heating step is effected at a rate of between about 200 C. and 300 C. per hour, up to a temperature of between about 9000 C. and 10000 C.
6. The method of claim I, wherein after step the anode and insulating layer are inserted into an electrolyte after which the insulating layer is dissolved, and where the temperature gradient between steps and is between 300 C. and 1000 C.
7. The method of claim 1, further comprising protecting a castable plate to which the anode is attached by applying a thermal insulating layer to said plate, wherein the thermal insulating layer attached to the plate is the same or different than the thermal insulating layer aft ached to the anode.
8. The method of claim 7, wherein said thermal insulating layer applied to said plate comprises a silica material.
9. The method of claim 7, wherein said thermal insulating layer applied to said plate is comprised of more than one material, with an outermost portion of said layer comprising a material more durable than any other material. The method of claim 7, wherein said castable plate is comprised of a silica ceramic material, an alumina ceramic material or mixtures thereof.
11. The method of claim 1, wherein said insulating layer has a thickness of at least about 5 mm.
12. The method of claim 1, wherein said insulating layer has a thickness of about 5-50 mm.
13. The method of claim 1, wherein said insulating layer has a thickness of about 10-30 mm.
14. The method of claim 1, wherein said insulating layer has a density of less than about 1.0 g/cm 3 The method of claim 1, wherein said insulating layer has a density of less than about 0.5 g/cm 3
16. The method of claim 15, wherein said insulating layer has a thickness of about 10-30 mm.
17. The method of claim 1, wherein said insulating layer has a density of about 0.1-0.2 g/cm 3 12A
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/374,002 | 2003-02-25 | ||
US10/374,002 US7118666B2 (en) | 2001-08-27 | 2003-02-25 | Protecting an inert anode from thermal shock |
Publications (3)
Publication Number | Publication Date |
---|---|
AU2004200431A1 AU2004200431A1 (en) | 2004-09-09 |
AU2004200431B2 AU2004200431B2 (en) | 2008-11-13 |
AU2004200431B8 true AU2004200431B8 (en) | 2009-03-12 |
Family
ID=32907719
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
AU2004200431A Expired AU2004200431B8 (en) | 2003-02-25 | 2004-02-06 | Protecting an inert anode from thermal shock |
Country Status (2)
Country | Link |
---|---|
AU (1) | AU2004200431B8 (en) |
CA (2) | CA2753404C (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN106929879A (en) * | 2017-02-19 | 2017-07-07 | 周俊和 | The method that prebaked anode aluminium electroloysis steel pawl aluminum guide leads power-off |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3238052A (en) * | 1961-03-14 | 1966-03-01 | Crosfield Joseph & Sons | Method of making calcium silicate materials |
US3852107A (en) * | 1971-11-26 | 1974-12-03 | Foseco Int | Protection of graphite electrodes |
US3960678A (en) * | 1973-05-25 | 1976-06-01 | Swiss Aluminium Ltd. | Electrolysis of a molten charge using incomsumable electrodes |
US4612105A (en) * | 1984-05-29 | 1986-09-16 | Aluminium Pechiney | Carbonaceous anode with partially constricted round bars intended for cells for the production of aluminium by electrolysis |
WO1998053120A1 (en) * | 1997-05-23 | 1998-11-26 | Moltech Invent S.A. | Aluminium production cell and cathode |
WO1999036591A1 (en) * | 1998-01-20 | 1999-07-22 | Moltech Invent S.A. | Surface coated non-carbon metal-based anodes for aluminium production cells |
US6447667B1 (en) * | 2001-01-18 | 2002-09-10 | Alcoa Inc. | Thermal shock protection for electrolysis cells |
US6558526B2 (en) * | 2000-02-24 | 2003-05-06 | Alcoa Inc. | Method of converting Hall-Heroult cells to inert anode cells for aluminum production |
-
2004
- 2004-02-06 AU AU2004200431A patent/AU2004200431B8/en not_active Expired
- 2004-02-25 CA CA2753404A patent/CA2753404C/en not_active Expired - Lifetime
- 2004-02-25 CA CA2458692A patent/CA2458692C/en not_active Expired - Lifetime
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3238052A (en) * | 1961-03-14 | 1966-03-01 | Crosfield Joseph & Sons | Method of making calcium silicate materials |
US3852107A (en) * | 1971-11-26 | 1974-12-03 | Foseco Int | Protection of graphite electrodes |
US3960678A (en) * | 1973-05-25 | 1976-06-01 | Swiss Aluminium Ltd. | Electrolysis of a molten charge using incomsumable electrodes |
US4612105A (en) * | 1984-05-29 | 1986-09-16 | Aluminium Pechiney | Carbonaceous anode with partially constricted round bars intended for cells for the production of aluminium by electrolysis |
WO1998053120A1 (en) * | 1997-05-23 | 1998-11-26 | Moltech Invent S.A. | Aluminium production cell and cathode |
WO1999036591A1 (en) * | 1998-01-20 | 1999-07-22 | Moltech Invent S.A. | Surface coated non-carbon metal-based anodes for aluminium production cells |
US6558526B2 (en) * | 2000-02-24 | 2003-05-06 | Alcoa Inc. | Method of converting Hall-Heroult cells to inert anode cells for aluminum production |
US6447667B1 (en) * | 2001-01-18 | 2002-09-10 | Alcoa Inc. | Thermal shock protection for electrolysis cells |
Also Published As
Publication number | Publication date |
---|---|
CA2753404C (en) | 2013-07-09 |
AU2004200431A1 (en) | 2004-09-09 |
CA2458692A1 (en) | 2004-08-25 |
CA2753404A1 (en) | 2004-08-25 |
AU2004200431B2 (en) | 2008-11-13 |
CA2458692C (en) | 2011-12-13 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US5527442A (en) | Refractory protective coated electroylytic cell components | |
US20080067060A1 (en) | Cermet inert anode assembly heat radiation shield | |
EP2140044B1 (en) | Aluminium electrowinning cell with metal-based cathodes | |
CA2506219C (en) | Inert anode assembly | |
US7118666B2 (en) | Protecting an inert anode from thermal shock | |
US6338785B1 (en) | Start-up of aluminum electrowinning cells | |
AU2004200431B2 (en) | Protecting an inert anode from thermal shock | |
US20030038039A1 (en) | Cermet inert anode assembly thermal insulating layer | |
EP1112393B1 (en) | Bipolar cell for the production of aluminium with carbon cathodes | |
EP1366214B1 (en) | Aluminium-wettable porous ceramic material | |
CN100515546C (en) | Inert anode assembly | |
EP0953070B1 (en) | The start-up of aluminium electrowinning cells | |
EP0843745A1 (en) | Maintaining protective surfaces on carbon cathodes in aluminium electrowinning cells | |
US6607656B2 (en) | Use of recuperative heating for start-up of electrolytic cells with inert anodes | |
US20040089539A1 (en) | Start-up of aluminium electrowinning cells | |
BRPI0316672B1 (en) | APPARATUS OF ELECTROLYSIS | |
NZ529852A (en) | Aluminium electrowinning cells having a drained cathode bottom and an aluminium collection reservoir |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
FGA | Letters patent sealed or granted (standard patent) | ||
TH | Corrigenda |
Free format text: IN VOL 22, NO 45, PAGE(S) 5335 UNDER THE HEADING APPLICATIONS ACCEPTED: UNDER INID (54) CORRECT THE TITLE TO PROTECTING AN INERT ANODE FROM THERMAL SHOCK |
|
PC | Assignment registered |
Owner name: ALCOA USA CORP. Free format text: FORMER OWNER(S): ALCOA INC. |
|
MK14 | Patent ceased section 143(a) (annual fees not paid) or expired |