Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1995-07-17
1996-12-10
Bell, Mark L.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
106737, 106688, 106801, 106819, 106692, 501124, 428206, 428688, 428689, 204290R, 204280, 204291, C04B 732, C04B 1404, C04B 1402, C04B 1430
Patent
active
055826954
DESCRIPTION:
BRIEF SUMMARY
This is an application under 35 USC 371 of International Application No. PCT/NO93/00178 filed Nov. 25, 1993.
The present invention relates to structural parts for electrolytic reduction cells for aluminum, which parks are intended to be in contact with the gas atmosphere in the cell during operation of the cells.
TECHNOLOGICAL BACKGROUND
Electrolytic cells or furnaces for production of aluminum according to the Hall-Heroult method, comprise a generally rectangular, low, flat shell with refractory material and carbon blocks in its sides and bottom. The carbon blocks constitute a vessel for the produced aluminum and for the molten electrolyte. The carbon blocks in the bottom of the vessel are equipped with steel bars for electric coupling of the bus bars for the electric current. The bottom carbon blocks thus form the cathode for the electrolytic cell.
The molten electrolyte, which has a lower density than molten aluminium, consists of molten cryolite, certain inorganic salts, such as for example, aluminum fluoride and calcium fluoride, and dissolved aluminum oxide. Aluminum oxide is consumed during the electrolysis and aluminum oxide therefore has to be added to the electrolyte quite frequently. During operation of the electrolytic cells corrosive fluorine- and sulphur-containing gases are produced.
In electrolytic cells for production of aluminum equipped with self-baking anodes or S.o slashed.derberg anodes, each cell usually is equipped with one substantially rectangular anode. The S.o slashed.derberg anode consists of a permanent outer casing made from cast iron or steel, which casing surrounds the self-baking carbon anode. Unbaked carbonaceous electrode paste is charged at the top of the anode and this unbaked electrode paste is baked into a solid carbon anode due to the heat which evolves during the supply of electric operating current to the anode and the heat from the molten bath. A major feature of the S.o slashed.derberg anode is thus that the baked solid anode moves relatively to the permanent anode casing.
In order to collect gases which evolve during the electrolytic reduction process, S.o slashed.derberg anodes are equipped with so-called gas shirts which run from the anode casing and outwardly and downwardly against the electrolyte where a seal is formed against the crust which forms on the top of the molten electrolyte. The gases which evolve are collected under the gas shirts, sucked off and are burned outside the electrolytic cell. The gas shirts are normally made from east iron which is reasonably resistant against the atmosphere and the temperature in the electrolytic cell. Even if cast iron is reasonably resistant against the gases, the gas shirts have to be replaced at intervals. Cast iron has further a low resistance against the molten electrolyte and by contact with molten electrolyte, for example by splashing, the cast iron erodes very quickly.
Recently, for environmental reasons, it has been proposed to replace the gas shirts with cover plates that run from the anode casing and to the sidewall of the furnace. This solution is disclosed in Norwegian patent no. 1628868. The electrolytic cells are thereby completely closed. The cover plates have been made from steel, but it has been found that even though the distance from the molten electrolyte to the cover plates is substantial longer than the distance from the molten electrolyte to the gas shirts, the steel in the cover plates is eroded rapidly and must therefore be replaced with short intervals.
Further the lower ends of the anode casing made from cast iron or steel is also eroded and must be replaced. The erosion of steel and cast iron parts in the electrolytic cells also gives an increase in the iron content in the produced aluminum.
The CO-containing gas which is produced in electrolytic reduction cells for production of aluminum is collected and combusted by air in burners arranged in gas collection pipes in the cells. These burners which are made from east iron have a short life-time due to erosion and must be replaced fre
REFERENCES:
patent: 2511724 (1950-06-01), Lobaugh
patent: 3060043 (1962-10-01), Renkey
patent: 3802894 (1974-04-01), Prost et al.
patent: 4111711 (1978-09-01), Kiehl et al.
patent: 4174972 (1979-11-01), Drouzy et al.
patent: 4239606 (1980-12-01), Dawless et al.
patent: 4246035 (1981-01-01), Maczura et al.
patent: 4619750 (1986-10-01), Bessard
patent: 4680279 (1987-07-01), Kleeh
patent: 4787965 (1988-11-01), Audras et al.
patent: 4943544 (1990-07-01), McGarry et al.
patent: 5135576 (1992-08-01), Johansen et al.
Edwards, Leslie C. et al., "Evaluation of a Bauxite Low Cement Castable in Aluminium Smelting Applications", Light Metals 1992 (no month).
Warrendale, PA: The Minerals, Metals & Materials Society, 1991, pp. 407-412 .
Bell Mark L.
Elkem Aluminium ANS
Marcheschi Michael
LandOfFree
Structural parts for electrolytic reduction cells for aluminum does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Structural parts for electrolytic reduction cells for aluminum, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Structural parts for electrolytic reduction cells for aluminum will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-421491