US4138246A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for lowering the concentration of sodium in aluminum melts
Assignee: Rio Tinto Switzerland AG
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Filing: 1977-03-22
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Granted: 1979-02-06
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Expires: 1997-03-22
Abstract
Abstract The sodium content of aluminum melt is reduced efficiently to within acceptable limits by filtering the primary metal from the electrolytic cell through a loosely packed filter bed of granular material which in part comprises carbon. The treatment is carried out before alloy additions are made, and the temperature of the melt before entering the filter is higher than 780° C.
Inventors
- 👤 Kurt Buxmann
- 👤 Jean-Daniel Bornand
- 👤 Alfred Steinegger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 17:58
CPC Classifications
C; C22; C22B; C22B21/00; C22B21/06; C22B21/066
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
109 words
In a process for lowering the sodium concentration in an aluminum melt from at least 15 ppm to at most 1 ppm thereby representing a sodium reduction of at least 93%, the improvement which comprises passing said melt through a filter bed of granular material, said granular material being comprised at least in part of carbon, the temperature of said aluminum melt on entry to said filter bed being about 785° C. to 885° C. and the temperature of said aluminum melt at exit from said filter bed being about 770° C. to 870° C. wherein said sodium concentration is reduced to a level of at most 1 ppm.
Claim 2
Dependent Claim
109 words
In a process for lowering the sodium concentration in an aluminum melt from at least 15 ppm to at most 1 ppm thereby representing a sodium reduction of at least 93%, the improvement which comprises passing said melt through a filter bed of granular material, said granular material being comprised at least in part of carbon, the temperature of said aluminum melt on entry to said filter bed being about 785° C. to 885° C. and the temperature of said aluminum melt at exit from said filter bed being about 770° C. to 870° C. wherein said sodium concentration is reduced to a level of at most 1 ppm.
Claim 3
Dependent Claim
27 words
A process according to claim 1 in which an inert gas is passed through the aluminum melt in a direction counter to the flow of the melt.
Claim 4
Dependent Claim
47 words
A process according to claim 1, in which said granular material contains a chemically active component which comprises at least in part, at least one carbon containing substance selected from the group consisting of petroleum carbon, ethylene coke, acetylene coke, graphite, bituminous coal or coal tar pitch.
Claim 5
Dependent Claim
13 words
A process according to claim 2 in which the inert gas is nitrogen.
Claim 6
Dependent Claim
17 words
A process according to claim 2 in which the inert gas comprises at least one noble gas.
Claim 7
Dependent Claim
21 words
A process according to claim 2 in which the inert gas contains 1 - 5% volume of an aliphatic halogenated hydrocarbon.
Claim 8
Dependent Claim
33 words
A process according to claim 1 in which the throughput rate of the filter bed is between 7 and 20 metric tons of molten aluminum per hour per cubic meter of filter bed.
Claim 9
Dependent Claim
20 words
A process according to claim 1 in which the particle diameter of said granular material is 1 - 20 cm.
Claim 10
Dependent Claim
44 words
A process according to claim 1 in which said granular material which comprises a carrier material, the density of which is greater than that of the molten aluminum, and the surface of which is provided at least in part with a layer of carbon.
Claim 11
Dependent Claim
24 words
A process according to claim 9 in which the carrier material comprises at least in part corundum, magnesite, zirconium oxide, zirconium silicate or basalt.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-02-05 | 1982-08-07 | 1983-02-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-02-05 | 1986-08-07 | 1987-02-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-02-05 | 1990-08-07 | 1991-02-06 | $7700.00 | Window Closed / Lapsed |