AU652881B2 - Process for the disposal of residual materials which contain fluorine- and cyanide-containing compounds - Google Patents
Process for the disposal of residual materials which contain fluorine- and cyanide-containing compounds Download PDFInfo
- Publication number
- AU652881B2 AU652881B2 AU31941/93A AU3194193A AU652881B2 AU 652881 B2 AU652881 B2 AU 652881B2 AU 31941/93 A AU31941/93 A AU 31941/93A AU 3194193 A AU3194193 A AU 3194193A AU 652881 B2 AU652881 B2 AU 652881B2
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- Australia
- Prior art keywords
- fluidized bed
- stage
- bed system
- process according
- residual materials
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Classifications
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
- A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
- A62D3/33—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by chemical fixing the harmful substance, e.g. by chelation or complexation
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/40—Inorganic substances
- A62D2101/45—Inorganic substances containing nitrogen or phosphorus
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/40—Inorganic substances
- A62D2101/49—Inorganic substances containing halogen
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2203/00—Aspects of processes for making harmful chemical substances harmless, or less harmful, by effecting chemical change in the substances
- A62D2203/02—Combined processes involving two or more distinct steps covered by groups A62D3/10 - A62D3/40
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2203/00—Aspects of processes for making harmful chemical substances harmless, or less harmful, by effecting chemical change in the substances
- A62D2203/10—Apparatus specially adapted for treating harmful chemical agents; Details thereof
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- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Processing Of Solid Wastes (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
- Treating Waste Gases (AREA)
Description
l1(IU1 11 2&5d91 Regulation 3.2(2)
AUSTRALIA
Petents Act 1990 2e8 I
ORIGINAL
COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: as. I as a.
Invention Title: PROCESS FOR THE DISPOSAL OF RESIDUAL MATERIALS WHICH CONTAIN FLUORINE- AND CYANIDE-CONTAINING COMPOUNDS The following statement Is a full description of this Invention, Including the best method of performing It known to S
U
PROCESS FOR THE DISPOSAL OF RESIDUAL MATERIALS WHICH CONTAIN FLUORINE- AND CYANIDE-CONTAINING COMPOUNDS Some residual materials contain water-soluble fluorides and cyanides as well as nitrogen compounds and for this reason cannot readily be dumped.
Such a hazardous residual material is particularly constituted by the material broken out from furnaces used for the electrolytic production of aluminum, which material consists of the refractory lining and of carbonaceous cathode material, or may be constituted by the dust which is formed in the electrolytic production of aluminum. For a safe dumping, the water-soluble compounds must be converted to water-insoluble compounds.
From JP-A-50 75 564 it is known to mix waste materials which contain water-soluble fluorine compounds, such as linings of electrolytic cells for the production of aluminum, with calcium salts, mainly calcium chloride and calcium sulfate, and to burn the resulting mixtures in an oxidizing atmosphere at 600 to o•i 15 9000C. Electric retort furnaces and rotary kilns are mentioned as burning units.
In that process the water-soluble fluorides are converted to water-insoluble calciumetd within a treating time of 30 to 60 minutes, and the nitrogen compounds contained in the waste materials are converted to NOx, which is emitted with the exhaust gas. HCI gas will also be formed if calcium chloride is 20 used.
.l.l.i From CEP, March 1986, pages 34 to 38, and from "Application of the transportable circulating bed combustor for the treatment of hazardous waste", .Presentation at the 79th Annual Meeting of the Air Pollution Control Association, Minneapolis, Minnesota, June 22-27, 1986, it is known that after an addition of limestone to the material broken out from furnaces used for the electrolytic production of aluminum said material can be burnt in a circulating fluidized bed under oxidizing conditions at temperatures from 790 to 8700C. The use of limestone will result in the formation of a molten phase, in an agglomeration and formation of crusts.
It is an object of the invention to convert the water-soluble fluorides in the residual materials as completely as possible to water-insoluble compounds, to decompose the cyanides as completely as possible, and also substantially to avoid a formation of NOx derived from the nitrogen compounds.
That object is accomplished in accordance with the invention by a process which serves for the disposal of residual materials which contain fluorine- and cyanide-containing compounds and which is characterized in that a) the residual materials are thermally treated after an addition of calcium and/or magnesium w.\zQ.
b) the thermal treatment is effected in a two-stage fluidized bed system, c) a temperature from 650 to 900 0 C is maintained in the two-stage fluidized bed system, d) the first stage of the fluidized bed system is operated under slightly reducing conditions with an air ratio <1, e) the second stage of the fluidized bed system is operated under oxidizing conditions with an oxygen content by volume, and f) the treated material is withdrawn from the second stage.
The sulfates are used at a hyperstoichiometric rate as regards the formation of CaF 2 or MgF 2 from the water-soluble fluorides. Inexpensive waste V gypsum can desirably be used as calcium sulfate and will thus be disposed of at S the same time. The two-stage fluidized bed system may consist of a circulating fluidized bed system, in which the first fluidized bed is formed in the lower part of the fluidized bed reactor by means of the fluidizing air flowing through the bottom and the second fluidized bed is formed in an upper part of the fluidized S bed reactor by means of secondary air and optionally tertiary air. Alternatively, .i the two-stage fluidized bed system may comprise two separate orthodox fluidized bed units and in that case the solids and the gas are withdrawn from the first fluidized bed unit and supplied to the second fluidized bed unit. The temperature in the first fluidized bed will always lie in the lower part of the temperature range stated because endothermic reactions are performed in the first fluidized bed owing to the deficiency of oxygen, As the residual material is charged into a circulating fluidized bed system it has a particle size below 2 mm, preferably below 1 mm, and as the material is charged into an orthodox fluidized Sbed system it has a particle size below 3 mm, preferably below 2 mm. The material is always charged into the first stage. The residual material may be supplied in a solid state or as a slurry. In case of a processing of material broken out from furnaces for the electrolytic production of aluminum the feed material will contain in most cases carbon in such an amount that its combustion will generate the reaction heat which is required. If the residual material does not contain enough carbon, the additional amount required will be supplied as solid, liquid or gaseous fuel. An optimum temperature for the reaction is suitably adjusted by a suitable cooling of the solids and where two orthodox fluidized bed units are employed that cooling will be effected between said units whereas in case of a circulating fluidized bed system the solids separated from the discharged suspension will be cooled before they are recycled to the fluidized bed reactor.
:i The advantages afforded by the invention reside in that the water-soluble tot.
fluorine compounds are substantially converted to water-insoluble compounds, S 15 the cyanides are substantially decomposed and the resulting exhaust gas has a low content of NOx and this is accomplished without an occurrence of agglomeration and a formation of crusts.
According to a preferred feature a temperature of 750 to 8500C is S: maintained in the two-stage fluidized bed system. An effective conversation to 20 water-insoluble fluorides and an effective decomposition of the cyanides in iolol conjunction with a formation of NOx at a low rate are achieved at temperatures in that range and HF will be emitted at a low rate even in the presence of water.
According to a preferred feature the first stage of the fluidized bed system is operated with an air ratio of 0.7 to 0.9. This will result in an emission of NOx at a very low rate.
According to a preferred feature the second stage of the fluidized bed system is operated with an oxygen content of 6 to 10% by volume. This will result in a very effective decomposition of the cyanides and in an effective conversion to water-insoluble fluorides and in an emission of NOx at a very low rate.
According to a preferred feature, sulfates of calcium and/or of magnesium are added at a rate which is 1.2 to 1.5 times the rate which is stoichiometrically required for the conversation of the water-soluble fluorides contained in the residual material to CaF 2 or MgF 2 In that case the addition of the sulfates at a relatively low rate will result in an effective conversion to water-insoluble fluorides.
According to a preferred feature, in case of the processing of residual materials having a high SiO 2 content an A1 2 0 3 content of at least 15% by weight is adjusted in the mixture by an addition of substances which contain A1 2 0 3 That addition will be required if the Si0 2 content is about 30% or more. The material which contains Ai 2 0 3 may consist of A1 2 0 3 bauxite, clay, flue dust, sodium silicate or the like. This will avoid the formation of a molten phase in the presence of a high Si0 2 content.
According to a preferred feature, the two-stage treatment is effected in a circulating fluidized bed system and is accompanied by a supply of secondary air and optionally tertiary air to the upper part of the fluidized bed reactor. The 15 fluidized bed system consists of a fluidized bed reactor, a recycle cyclone and a recycle line. Whereas in an "orthodox" fluidized bed system a dense phase is separated by a distinct density step from theA tig gas space, a circulating fluidized bed system involves states of distribution having no defined boundary layer. There is no dersity step between a dense phase and an overlying dust 20 space but in the fluidized bed reactor the solids concentration decreases gradually from bottom to top. A gas-solids suspension is discharged from the upper part of the reactor. The following ranges will be obtained if the operating conditions are defined by the Froude and Archimedes numbers: 0.1<3/4x Fr 2 X "8 510 3k -g and 0.01 Ar< 100 wherein Ar= dk 3 xg(8 g) 6 xv 2
U
2 Fr 2 gx d and u the relative gas velocity in m/sec, Ar the Archimedes number Fr the Froude number 8 the density of the gas in kg/m 2 k the density of the solid particle in kg/m2 dk the diameter of the solid spherical particle in m D the kinematic viscosity in m2/sec.
g the constant of gravitation in m/sec 2 The suspension discharged from the fluidized bed reactor is supplied to the recycle cyclone of the circulating fluidized bed system and solids are substantially removed in that cyclone and are recycled to the fluidized bed reactor of such a rate that the amount of solids within the circulating fluidized bed system per hour is at least four times the weight of the solids contained in the fluidized bed reactor. The solids which have been separated and are to be 15 recycled are recycled to the first stage of the fluidized bed reactor. The first stage extends from the bottom ol the fluidized bed reactor over about 20 to of the total height of the fluidized bed reactor. In the circulating fluidized bed system the required operating parameters can be very exactly maintained so that particularly good results can be produced.
20 According to a preferred feature the solids to be recycled are cooled in a fluidized bed cooler before they are charged into the fluidized bed reactor. The fluidized bed cooler consists of an orthodox fluidized bed unit. The heated fluidizing air leaving the fluidized bed cooler may be supplied to the unit for purifying the exhaust gas that has left the circulating fluidized bed system, or may be supplied as secondary air to the fluidized bed reactor. The cooling in the fluidized bed cooler permits an effective and simple automatic control of the temperature in the circulating fluidized bed system.
According to a preferred feature, the solids which have been withdrawn are after-treated by being slurried. So much water is added that a transportation without a raising of dust and/or a dumping without a raising of dust will be possible. The slurrying will also result in a further decrease of the solid fluorine compounds. If the thermally treated solids are after-treated it will be preferable to add a part of the calcium sulfate or magnesium sulfate during the aftertreatment rather than during the thermal treatment.
The invention will be explained more in detail with reference to a flow scheme and to examples.
Figure 1 is a flow scheme of a plant comprising a circulating fluidized bed system.
The fluidized bed system comprises a fluidized bed reactor 1, a recycle cyclone 2 and a recycle line 3. Material broken out of a furnace and having a suitable particle size is charged through line 4 into a mixer 5, which is supplied with calcium sulfate thrcugh line 6 and with an A1 2 0-containing material through line 7. Through line 8 the mixture is charged into the lower part of the fluidized bed reactor 1. Fluidizing air is supplied to the reactor through its bottom from .i line 9 and in the lower part of the fluidized bed reactor is used to form the first S 15 fluidized bed. Secondary air from line 10 and tertiary air from line 11 are supplied to the upper part of the fluidized bed reactor and in said upper part are used to form the second fluidized bed. The gas-solids suspension is conducted in line 12 from the fluidized bed reactor 1 to the recycle cyclone 2. The collected solids are recycled in the recycle line 3 to the lower part of the fluidized bed 20 reactor. All or part of the separated solids can be supplied through line 13 to the fluidized bed cooler 14, which consists of an orthodox fluidized bed unit and is supplied with fluidizing air through line 15. The cooled solids are recycled in line 16 to the lower part of the fluidized bed reactor 1. From the separating cyclone 2 the gas phase is conducted in line 17 to a second cyclone 18, from which the collected solids are recycled in line 19 to the lower part of the fluidized bed reactor 1. The gas phase from the cyclone 18 is conducted in line 20 to the venturi scrubber 21. Dust-containing fluidized air which has been heated in the fluidized bed cooler 14 is supplied in line 22 also to the venturi scrubber 21, from which the gas is supplied in line 23 to a wet-process deduster 24. The purified gas is discharged through line 25. The sludge formed in the wetprocess deduster is supplied in line 26 to the sedimentation tank 27. The overflow is supplied in line 28 to the venturi scrubber 21 and the underflow is supplied in line 29 to the stirred tank 30, which is supplied with calcium sulfate from line 31. The suspension is supplied in line 32 to the mixer 33, which is supplied in line 34 with separated solids from the fluidized bed cooler. The separated solids are after-treated in the stirred tank 30 and in the mixer 33. The solids are conducted in line 35 to the dump.
In the following table the results are stated which have been produced by a treatment of material which has been broken out from a furnace used in the electrolytic productior' of aluminum. in experiments 7 and 8 the material broken out from the furnace and having the stated composition was used as feed material without an additive. In experiments 1 to 6 an identical material broken out from the furnace was mixed with AI 2 0 3 In experiments 9 to 12 a different material broken out from a furnace and having the stated composition was used without an addition of A1 2 0-containing substances. In all cases, calcium sulfate or calcium carbonate was added in a molar ratio of Ca:F of 0.6. The data for 15 experiments 1 to 3 and 8 reflect the results of control experiments in which calcium sulfate was not added. The data for experiments 5 and 6 reflect the results produced when calcium carbonate rather than calcium sulfate was added. The data for experiments 7 and 8 reflect the results produced when the material broken out from the furnace had a very high Si02 content. In the column "Solubility" the solubility is stated which was obtained by a leaching according to
DEV-S
4 In experiment 12, 5% CaSO 4 were added du'ring the thermal treatment and 2.7% CaSO 4 were added during the after-treatment.
Wa. 0**
S.
S..
S 5* S S *S S S *eS We S
S
*5 *SS S 555 Exper. Chemical analysis of the material broken out from a No. furnace Operating parameters Exhaust gas analysis A1 2 0 3 SiO 2 M2Q MI% Na Soluble Cyanides Nitrates fluorine
+NH
4 Temp. Air ratio Additives SO 2 HON HF NOx CN ON decomposition Remark F solubility
F
MW~
cC Prim. Sec. Kind BIY2 yppm vl2prn ypp yppm 40.8 40.8 40.8 40.8 40.8 40.8 13.8 13.8 36.8 36.8 36.8 36.8 20.6 20.6 20.6 20.6 20.6 20.6 47.6 47.6 2.6 2.6 2.6 2.6 8.6 8.6 8.6 8.6 8.6 8.6 7.4 7.4 16.6 16.6 16.6 16.6 0.16 0.16 0.16 0.16 0.16 0.16 0.11 0.11 0.06 0.06 0.06 0.06 750 1.2 750 0.9 650 0.9 750 0.9 750 0.9 650 0.9 750 0.9 650 0.9 800 0.9 900 0.9 800 0.5 800 0.9 1.2 1.2 1.2 1.2 CaSO 4 5.1 1.2 CaCO 3 3.8 1.2 CaCO 3 3.8 1.2 CaSO 4 4.7 1.2 1.2 CaSO 4 7.7 1.2 CaSO 4 7.7 1.2 CaSO 4 7.7 1.2 CaSO 4 5.07 <10 <10 <10 40 35 780 30 20 <1 10 1 11 12 10 <1 10 980 99.2 60 99.0 50 76.8 50 99.4 80 99.8 220 99.9 40 98.2 70 99.8 1880 1760 1720 18 agglomeration agglomeration agglomeration agglomeration 12 <1 18 <1 128 10 12 <1 8
Claims (9)
1. A process which serves for the disposal of residual materials which contain fluorine- and cyanide-containing compounds, characterized in that a) the residual materials are thermally treated after an addition of calcium sulfate and/or magnesium sulfate, b) the thermal treatment is effected in a two-stage fluidized bed system, c) a temperature from 650 to 900°C is maintained in the two-stage fluidized bed system, d) the first stage of the fluidized bed system is operated under slightly reducing conditions with an air ratio as hereinbefore defined <1, e) the second stage of the fluidized bed system is operated under oxidizing conditions with a gas having an oxygen content by volume, and f) the treated material is withdrawn from the second stage. S
2. A process according to claim 1, characterized in that a temperature from 750 to 8500°C is maintained in the two-stage fluidized bed system.
3. A process according to claim 1 or 2, characterized in that the first stage of the fluidized bed system is operated with an air ratio as hereinbefore defined from 0.7 to 0.9.
4. A process according to claims 1 to 3, characterized in that the second stage of the fluidized bed system is operated with an oxygen content from 6 to by volume.
A process according to claims 1 to 4, characterized in that sulfates of calcium and/or of magnesium arc added at a rate which is 1.2 to 1.5 times the rate which is stoichiometrically required for the conversion of the water-soluble fluorides contained in the residual material to CaF 2 or MgF 2
6. A process according to claims 1 to 5, characterized in that in case of the XRA processing of residual materials having a high Si0 2 content an A1 2 0 3 content of at least 15% by weight is adjusted in the mixture by an addition of substances which contain A1 2 0 3
7. A process according to claims 1 to 5, characterized in that the two-stage treatment is effected in a circulating fluidized bed system and is accompanied by a supply of secondary air and optionally tertiary air to the upper part of the fluidized bed reactor.
8. '4 process according to claim 7, characterized in that the solids to be recycled are cooled in a fluidized bed cooler before they are charged into the fluidizer bed reactor.
9. A process according to claims 1 to 8, characterized in that the solids which have been withdrawn are after-treated by being slurried. SDATED THIS 11TH DAY OF DECEMBER, 1992 METALLGESELLSCHAFT AKTIENGESELLSCHAFT THE ATRIUM 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA SKP:JC DOC 27: AU000352.WPC To convert water-soluble fluorine compounds to water-insoluble compounds, to decompose the cyanides and to ensure that NO x will be emitted only at a low rate, sulfates of calcium or of magnesium are added to the residual materials and the latter are then treated at temperatures from 650 to 9000°C in a two-stage fluidized bed system. The first stage is operated under slightly reducing conditions and the second stage under oxidizing conditions. Figure 1
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19924201831 DE4201831A1 (en) | 1992-01-24 | 1992-01-24 | METHOD FOR THE DISPOSAL OF RESIDUES CONTAINING FLUORINE AND CYANIDE CONTAINERS |
| DE4201831 | 1992-01-24 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| AU3194193A AU3194193A (en) | 1993-07-29 |
| AU652881B2 true AU652881B2 (en) | 1994-09-08 |
Family
ID=6450128
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU31941/93A Ceased AU652881B2 (en) | 1992-01-24 | 1993-01-22 | Process for the disposal of residual materials which contain fluorine- and cyanide-containing compounds |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0553511A1 (en) |
| AU (1) | AU652881B2 (en) |
| CA (1) | CA2084710A1 (en) |
| DE (1) | DE4201831A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5558690A (en) * | 1994-12-23 | 1996-09-24 | Vortec Corporation | Manufacture of ceramic tiles from spent aluminum potlining |
| US5660125A (en) * | 1995-05-05 | 1997-08-26 | Combustion Engineering, Inc. | Circulating fluid bed steam generator NOx control |
| DE19723194C2 (en) * | 1996-09-18 | 2000-05-18 | Kerr Mcgee Pigments Gmbh & Co | Process for the processing of nitrogenous organic waste |
| US6371970B1 (en) | 1999-07-30 | 2002-04-16 | Incept Llc | Vascular filter having articulation region and methods of use in the ascending aorta |
| US6540768B1 (en) | 2000-02-09 | 2003-04-01 | Cordis Corporation | Vascular filter system |
| WO2007024218A1 (en) * | 2005-08-23 | 2007-03-01 | Studsvik, Inc. | Mineralization of alkali metals, sulfur and halogens |
| CN103239828B (en) * | 2013-05-31 | 2015-06-10 | 吴正建 | Harmless production process of program-control and manual-control electrolytic aluminum overhaul residues |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2198722A (en) * | 1986-12-22 | 1988-06-22 | Comalco Alu | Recovery of aluminium and fluoride values |
| AU2817292A (en) * | 1991-11-07 | 1993-05-13 | Elkem Technology A/S | Method for the treatment of potlining residue from primary aluminium smelters |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4355017A (en) * | 1981-05-14 | 1982-10-19 | Martin Marietta Corporation | Aluminum electrolytic cell cathode waste recovery |
| DE3426913A1 (en) * | 1984-07-20 | 1986-01-30 | Adsorptionstech Lab | METHOD FOR THE REMOVAL OF NITROGEN OXIDES AND FOR THE COMMON REMOVAL OF NITROGEN OXIDS AND SULFUR OXIDS FROM GASES |
| CA1294111C (en) * | 1986-08-08 | 1992-01-14 | Douglas J. Hallett | Process for the destruction of organic waste material |
| DE3640318A1 (en) * | 1986-11-26 | 1988-06-09 | Boehringer Mannheim Gmbh | METHOD AND TEST CARRIER FOR DETERMINING AN ANALYT |
-
1992
- 1992-01-24 DE DE19924201831 patent/DE4201831A1/en not_active Withdrawn
- 1992-12-03 EP EP92203736A patent/EP0553511A1/en not_active Withdrawn
- 1992-12-07 CA CA002084710A patent/CA2084710A1/en not_active Abandoned
-
1993
- 1993-01-22 AU AU31941/93A patent/AU652881B2/en not_active Ceased
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2198722A (en) * | 1986-12-22 | 1988-06-22 | Comalco Alu | Recovery of aluminium and fluoride values |
| AU2817292A (en) * | 1991-11-07 | 1993-05-13 | Elkem Technology A/S | Method for the treatment of potlining residue from primary aluminium smelters |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2084710A1 (en) | 1993-07-25 |
| DE4201831A1 (en) | 1993-07-29 |
| AU3194193A (en) | 1993-07-29 |
| EP0553511A1 (en) | 1993-08-04 |
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