EP0946449A1 - Verfahren zum unloeslichmachen und konsolidieren von verbrauchten auskleidungender elektrolytischen hall- heroult zellen - Google Patents

Verfahren zum unloeslichmachen und konsolidieren von verbrauchten auskleidungender elektrolytischen hall- heroult zellen

Info

Publication number
EP0946449A1
EP0946449A1 EP97947133A EP97947133A EP0946449A1 EP 0946449 A1 EP0946449 A1 EP 0946449A1 EP 97947133 A EP97947133 A EP 97947133A EP 97947133 A EP97947133 A EP 97947133A EP 0946449 A1 EP0946449 A1 EP 0946449A1
Authority
EP
European Patent Office
Prior art keywords
pellets
additive
cooking
mixture
consolidation
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.)
Withdrawn
Application number
EP97947133A
Other languages
English (en)
French (fr)
Inventor
Pierre Personnet
Gilbert Bouzat
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rio Tinto France SAS
Original Assignee
Aluminium Pechiney SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Aluminium Pechiney SA filed Critical Aluminium Pechiney SA
Publication of EP0946449A1 publication Critical patent/EP0946449A1/de
Withdrawn legal-status Critical Current

Links

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
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/02—Agglomerated materials, e.g. artificial aggregates
    • C04B18/023—Fired or melted materials
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

  • the invention relates to a process of insolubilization and consolidation in the form of spent pot lining pellets originating from the dismantling of aluminum production tanks by igneous electrolysis according to the Hall-Héroult technique.
  • These spent pot liners are formed by the carbonaceous cathode blocks, the seals and the side linings based on carbonaceous materials but also by all of the refractory and aluminous or silico-aluminous insulators arranged on the lateral walls and the bottom of the metal box forming the electrolysis tank.
  • these pot liners are heavily impregnated with harmful products, such as soluble sodium or sodo-aluminous fluorides and cyanides, which must be insolubilized or destroyed before landfill or possible reuse.
  • thermal treatment methods generally operating in a fluidized bed and based either on a pyrohydrolysis at more than 1000 ° C. of the spent linings according to US 4065551 Elkem, or US 41 13832 and US 41 16809 Kaiser, or on a simple combustion. in the air or in an oxidizing atmosphere of carbon elements, at a temperature of about 800 ° C, sufficient to decompose cyanides without causing significant release of volatile fluorinated compounds, according to US 4053375 Reynolds or according to the article by LC Blayden and SG Epstein, Journal of Metals, July 1984 page 24.
  • the methods and devices using the thermal route are limited in their possibilities by the nature and the composition of the pot linings to be treated.
  • the pot lining particles due to the fusion of certain eutectic compounds formed during combustion, the pot lining particles have a strong tendency to agglomerate. It becomes impossible to avoid their solidification and consequently to maintain a fluidized bed and a fortiori a dense bed if the combustion is carried out for example in a rotating oven with a long residence time.
  • this process must be completed at the end of the heat treatment carried out at a temperature sufficient to decompose the cyanides, by a final operation of insolubilization of the soluble residual fluorides consisting in spraying milk of lime on the pulverulent mixture leaving the oven. heat treatment.
  • this additional operation carried out in a semi-humid environment complicates and increases the cost of the process, the final product thus obtained is difficult to store or handle in the state given the presence of dust and fine particles.
  • US 52451 15 EP 0465388B
  • US 5365012 EP 0465388B
  • Aluminum Pechiney recommend the introduction of a single additive based on lime and preferably gypsum, mixed with the finely ground pot lining to insolubilize the fluorinated compounds in the state of CaF 2 after a heat treatment carried out at a temperature sufficient to decompose the cyanides but of a very short duration to avoid the bonding phenomena.
  • the pulverulent mixture is injected under gas pressure at the top of a cyclonic reactor to be recovered at its base in the form of inert pulverulent residue.
  • the method according to the invention satisfies this triple condition. It is based on the observation that by adding appropriate additives to the old crushed pot lining, it is possible to effectively insolubilize not only the fluorine of the fluorinated impregnation compounds but also the alkali metals such as sodium, and this while promoting contrary to the usual practices the agglomeration of the constituents of the mixture by suitable shaping before cooking, preferably in the form of pellets whose consolidation continues during cooking then allowing their handling, transport, storage or landfill without formation of dust.
  • the invention relates to a process of insolubilization and consolidation in the form of pellets of old pot lining from electrolysis tanks for the production of aluminum
  • said pot lining consisting of carbon products and impregnated silico-aluminous products of fluorinated alkaline compounds and cyanides as well as their intimate mixture with various refractory pulverulent additives before heat treatment or cooking, characterized in that after introduction: of a first additive intended during cooking to fix the alkali metals, in particular sodium, coming from fluorinated compounds and which is chosen from the group of silicoaluminates, then from a second additive intended during cooking, on the one hand to combine, with or without fusion, with fluorinated impregnating compounds to form new stable and insoluble compounds such as CaF 2 , on the other hand, by its uncombined excess fraction , to ensure before but especially during and after cooking, the consolidation of the mixture, said second additive being chosen from the group of calcium oxides and salts and preferably cements and limestone mortars
  • This consolidation has many advantages by allowing, for example, landfill or storage in a dense and thick bed of the inert final residue without the risk of crushing the pellets which have become sufficiently resistant or even in the case of a new use, the transport and handling without risk of spalling of said pellets with formation of dust and pollution of the atmosphere.
  • cyanides CN ⁇ 1% of the total weight
  • fluorinated compounds mainly in the state of sodium fluoride, which can represent up to 35% or even 40% of the total weight.
  • the old, previously crushed pot lining is crushed to obtain particles of dimension less than 5 mm and preferably less than
  • the first additive intended mainly during cooking to fix the alkali metals and in particular sodium, chosen from the group of silicoaluminates, is a feldspar or a clay such as for example kaolin or bentonite, some typical compositions of which are indicated in Table 1. below.
  • the second additive intended during cooking to combine with or without fusion with the fluorinated impregnation compounds, in particular NaF, AIF 3 and Na 3 AlF ⁇ , while ensuring the consolidation of the agglomerated mixture during its elaboration, can be lime CaO, calcium carbonate CaC0 3 but is preferably chosen from the group of cements and calcareous mortars.
  • the Applicant has advantageously experimented with Portland type quick-setting cements which, while having good performance in insolubilizing fluorine by combination in the form of CaF 2 , ensure excellent consolidation of the agglomerates during baking (see table 2).
  • Another essential characteristic of the process is the shaping by agglomeration of the crushed spent pot lining mixture / additives before cooking.
  • This shaping of the powder mixture by agglomeration can be obtained by any means for shaping known powder materials such as compression or extrusion of the mixture dry or slightly humidified. This gives pellets or granules which can then be enlarged and rounded in the form of pellets by granulation, but even more simply by direct granulation of the pre-humidified mixture at a humidity level preferably set between 15 % and 25% of the weight of the dry mixture, pellets with excellent cohesion are obtained as will be described later in the detailed implementation of the process.
  • Cooking or heat treatment of the pellets must be carried out at a temperature of at least 700 ° C to decompose the cyanides, but without exceeding 950 ° C so as not to risk the onset of dissociation of the already stabilized fluorides.
  • the temperature is preferably set between 800 ° C and 900 ° C (see table 3).
  • the cooking time can vary from 1 hour to 6 hours depending on the nature of the additives and the weight composition of the mixture, but especially depending on the cooking method adopted and the average size of the pellets.
  • the optimal cooking time is no more than 3 hours in a pass-through oven with cradles and 1 to 2 hours in a rotary oven or in a fluidized bed oven, the latter being particularly suitable for the process according to the invention taking into account the excellent cohesion of the dumplings during cooking in spite of the shocks and the effects of attrition between dumplings (see table 2).
  • the carbon content of spent pot lining is very high and makes it possible to reach, after mixing, a carbon content of at least 25% in raw pellets, these can be used as auxiliary fuel in an oven incineration.
  • the inert residue in the form of pellets can either be landfilled, stored or reused in a new application, for example as a fill for backfill.
  • Crush resistance test consisting of dropping a steel ball of 11 grams at a height of 65 cm onto a dumpling; this in order to check the resistance of the pellets during loading and unloading.
  • the result is expressed as a percentage of pellets that have remained intact.
  • FIG. 1 is the schematic representation of the successive stages of the method.
  • One tonne of spent pot lining 1 coming from the dry unmasking of aluminum production electrolysis tanks and constituting a complete mixture of silico-aluminous refractories and carbon blocks with a particle size of 0-700 mm is crushed and then ground A to obtain a powder product 2 with a particle size of 0-2.5 mm, the weight contents of carbon, fluorine, sodium, silicon and cyanide being 38.4%, 9.2%, 14.6%, 1 1, 1% and 0 respectively , 12%.
  • the pulverulent product 2 is mixed B with on the one hand 500 kg of a first pulverulent additive 3 consisting of feldspar FHB200 (sodium feldspar albite type, a typical analysis of which is given in table 1) and on the other hand 500 kg of a second powder additive 4 consisting of Portland cement with rapid setting, for example Lafarge CEM cement 52, 5.
  • a first pulverulent additive 3 consisting of feldspar FHB200 (sodium feldspar albite type, a typical analysis of which is given in table 1)
  • a second powder additive 4 consisting of Portland cement with rapid setting, for example Lafarge CEM cement 52, 5.
  • the resulting powder mixture 5 is moistened by spraying water 6 at a rate of 15% to 25% of the dry mix weight before being C-shaped in the state of pellets in a pelletizer constituted by an inclined circular table and in rotation allowing the formation of small nodules.
  • These nodules grow by coating in contact with the humidified pulverulent mixture 5 which is continuously recycled, to form increasingly large pellets which are removed from the device when they reach the desired size, generally a diameter of between 6 mm and 20 mm and fixed in this case 10 mm.
  • the raw dumplings 7 calibrated with a diameter of 10 mm and whose specific volume before cooking is between 1 and 1, 2 g / cm 3 are then baked for 1 hour at 900 ° CD in a fluidized bed reactor by adjusting appropriately the fluidization air flow.
  • the fluorine content of the gases leaving the reactor at constant flow rate is checked by taking a gas sample every 15 minutes.
  • the cooked pellets 8 representing 1600 kg of residue are then subjected to the various insolubilization control tests (according to standard NF-X31210) and mechanical strength. The following results were obtained:
  • Na leachable% 0.1 7 mechanical strength: a) cohesion test (Turbula): good ( ⁇ 1% of fines) b) resilience test: 100% c) crush resistance test: 84%.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Civil Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • General Health & Medical Sciences (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Processing Of Solid Wastes (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Cookers (AREA)
EP97947133A 1996-11-26 1997-11-25 Verfahren zum unloeslichmachen und konsolidieren von verbrauchten auskleidungender elektrolytischen hall- heroult zellen Withdrawn EP0946449A1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9614723A FR2756198B1 (fr) 1996-11-26 1996-11-26 Procede d'insolubilisation et de consolidation de brasques usees provenant des cuves d'electrolyse hall-heroult
FR9614723 1996-11-26
PCT/FR1997/002123 WO1998023551A1 (fr) 1996-11-26 1997-11-25 Procede d'insolubilisation et de consolidation de brasques usees provenant des cuves d'electrolyse hall-heroult

Publications (1)

Publication Number Publication Date
EP0946449A1 true EP0946449A1 (de) 1999-10-06

Family

ID=9498214

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97947133A Withdrawn EP0946449A1 (de) 1996-11-26 1997-11-25 Verfahren zum unloeslichmachen und konsolidieren von verbrauchten auskleidungender elektrolytischen hall- heroult zellen

Country Status (7)

Country Link
US (1) US5947888A (de)
EP (1) EP0946449A1 (de)
AU (1) AU726174B2 (de)
CA (1) CA2273004C (de)
FR (1) FR2756198B1 (de)
NO (1) NO325224B1 (de)
WO (1) WO1998023551A1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GR1006144B (el) * 2006-02-14 2008-11-07 Isocon Α.Ε. Νεου τυπου πλαστικοποιητης κονιαματων αργιλικης βασης.
US8196533B2 (en) 2008-10-27 2012-06-12 Kentucky-Tennessee Clay Co. Methods for operating a fluidized-bed reactor

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4113832A (en) * 1977-11-28 1978-09-12 Kaiser Aluminum & Chemical Corporation Process for the utilization of waste materials from electrolytic aluminum reduction systems
US4763585A (en) * 1987-09-08 1988-08-16 Ogden Environmental Services Method for the combustion of spent potlinings from the manufacture of aluminum
WO1989012498A1 (en) * 1988-06-24 1989-12-28 Rolite, Inc. Incineration residue treatment process and apparatus
US5037286A (en) * 1988-06-24 1991-08-06 Rolite, Inc. Incineration residue treatment apparatus
US5365012A (en) * 1990-07-04 1994-11-15 Aluminium Pechiney Process for the heat treatment of spent pot linings derived from Hall-Heroult electrolytic cells
FR2664297B1 (fr) * 1990-07-04 1992-09-11 Pechiney Aluminium Procede de traitement par choc thermique de brasquages uses provenant de cuves d'electrolyse hall-heroult.
FR2669350B1 (fr) * 1990-11-16 1993-01-15 Pechiney Aluminium Procede de traitement par voie humide de brasquages uses provenant de cuves d'electrolyse hall-heroult.
WO1992020469A1 (en) * 1991-05-16 1992-11-26 Qubator Pty Limited Process for converting spent pot liner
US5164174A (en) * 1991-10-11 1992-11-17 Reynolds Metals Company Detoxification of aluminum spent potliner by thermal treatment, lime slurry quench and post-kiln treatment
JP3175981B2 (ja) * 1992-10-28 2001-06-11 株式会社東芝 トリミング回路
US5772937A (en) * 1996-10-15 1998-06-30 Fuller Company Method to produce aggregate products

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9823551A1 *

Also Published As

Publication number Publication date
FR2756198A1 (fr) 1998-05-29
CA2273004C (fr) 2007-05-15
CA2273004A1 (fr) 1998-06-04
NO325224B1 (no) 2008-03-03
FR2756198B1 (fr) 1998-12-18
NO992511D0 (no) 1999-05-25
AU5229298A (en) 1998-06-22
NO992511L (no) 1999-07-26
AU726174B2 (en) 2000-11-02
WO1998023551A1 (fr) 1998-06-04
US5947888A (en) 1999-09-07

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