EP1671682A1 - Procede pour la decomposition de l' amiante avec des hydroxydes des metaux alcalins - Google Patents

Procede pour la decomposition de l' amiante avec des hydroxydes des metaux alcalins Download PDF

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Publication number
EP1671682A1
EP1671682A1 EP04293047A EP04293047A EP1671682A1 EP 1671682 A1 EP1671682 A1 EP 1671682A1 EP 04293047 A EP04293047 A EP 04293047A EP 04293047 A EP04293047 A EP 04293047A EP 1671682 A1 EP1671682 A1 EP 1671682A1
Authority
EP
European Patent Office
Prior art keywords
asbestos
alkali metal
process according
naoh
hydroxide
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Withdrawn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
EP04293047A
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German (de)
English (en)
Inventor
Tomasz Hubert Cioska
Artur Dorywala
Thorsten Gerdes
Ralph Borchert
Andreas Rosin
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.)
InVerTec
INERTEC
Plazmatronika SA
Original Assignee
InVerTec
INERTEC
Plazmatronika 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 InVerTec, INERTEC, Plazmatronika SA filed Critical InVerTec
Priority to EP04293047A priority Critical patent/EP1671682A1/fr
Publication of EP1671682A1 publication Critical patent/EP1671682A1/fr
Withdrawn legal-status Critical Current

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    • 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
    • A62D3/32—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by treatment in molten chemical reagent, e.g. salts or metals
    • 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
    • A62D3/36—Detoxification by using acid or alkaline reagents
    • 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
    • A62D2101/41—Inorganic fibres, e.g. asbestos

Definitions

  • the present invention relates to a process for degrading asbestos-containing materials (ACMs) by mixing them with one or more alkali metal hydroxides and heating the mixture to a temperature at which it is molten in order that the alkali metal hydroxide(s) may chemically degrade the asbestos in the ACMs.
  • ACMs asbestos-containing materials
  • the process for degrading asbestos-containing materials according to the present invention comprises the following steps:
  • mixture is understood as meaning that the ACMs and solid alkali metal hydroxide(s) are in intimate contact, without necessarily being actually mixed.
  • ACMs and solid alkali metal hydroxides be (intimately) mixed in order to ensure maximum homogeneity. Indeed, in the context of asbestos decontamination, it may well be preferable to avoid physically mixing the two materials in order to reduce the dust hazard associated with a homogenisation procedure. However, the (intimate) mixing of ACMs and solid alkali metal hydroxides naturally improves contact between the reacting materials and therefore reduces the process time, and such homogenisation may be of particular utility when carrying out ACM degradation on an industrial (tonne) scale.
  • any solid alkali metal hydroxide including lithium hydroxide (LiOH), sodium hydroxide (NaOH) and potassium hydroxide (KOH) may be used, since all of these are capable of giving rise to the desired asbestos-degrading effect at appropriate temperatures.
  • LiOH lithium hydroxide
  • NaOH sodium hydroxide
  • KOH potassium hydroxide
  • NaOH sodium hydroxide
  • KOH potassium hydroxide
  • CaOH sodium hydroxide
  • caustic soda sodium hydroxide
  • an NaOH/KOH mixture also constitutes a preferred embodiment of the present invention, since the melting of the hydroxide is necessary in order for the asbestos degradation reaction to be efficient.
  • a weight ratio of NaOH to KOH of about 60:40 to about 40:60 will generally be used, a weight ratio of about 50:50 being preferred, since this ratio of NaOH to KOH provides the lowest melting points (a eutectic mixture with a melting point of 170°C is obtained for 51.5% NaOH and 48.5 % KOH).
  • the preferred reaction temperature for the process of the present invention with caustic soda will lie between about 320°C and about 550°C, preferably between about 400°C and about 500°C.
  • Concerning the duration of the ACM-degradation reaction this duration will preferably lie between about 10 minutes and about 1 day, even more preferably between about 20 minutes and about 5 hours, and most preferably between about 30 minutes and about 60 minutes.
  • the ratio of the weight of alkali metal hydroxide to the weight of asbestos-containing materials will preferably lie between about 3:1 and about 10:1, most preferably between about 3:1 and about 5:1.
  • reactor made of a material resistant to such caustic conditions.
  • preferred reactor materials include carbon and alloyed steels, standard steel, nickel alloys, graphite and silver.
  • a preferred material for the reactor in the context of the present invention is standard steel, in the form of barrels. These have been observed by the inventors to show abrasion rates of approximately 0.5 ⁇ m per hour with caustic soda melt at 450°C. With a process time of less than 5 h and a wall thickness tolerance of 0.2 mm, the steel barrels may thus be used at least 75 times as reactor vessel for ACM dissolution in a caustic soda melt. Furthermore, at the end of their economic life-time, the used barrels can be recycled as scrap metal and replaced by new barrels. Because of the low unit costs of standard steel barrels and the low installation costs for the melt reactor, the use of standard steel barrels provides a cost effective process route for the decomposition of ACMs with caustic soda melts.
  • microwave heating is used for at least part of the overall heat energy introduced into the reactive mixture.
  • Microwave heating provides the advantage of heating the reaction mixture in its heart, whereas many traditional heating processes necessarily heat the reaction mixture from the outside.
  • the use of microwave heating also enables the problematic large-scale production of exhaust gases to be avoided, which is a disadvantage associated with gas burners, as are widely used to produce high temperatures in glass melting furnaces.
  • Microwave sources for heating the reaction mixture in the present invention include a magnetron or klystron, and irradiation of the reaction mixture is carried out via a microwave heating hood.
  • a mixture of microwave and non-microwave heating methods are used to achieve and maintain a suitable reaction temperature. Any relative percentages of heat energy contributed by the microwave- with respect to the non-microwave heating source can be envisaged. However, when used in combination with steel reactor vessels, it is preferred that the relative amount of microwave energy does not exceed 50% of the total heating energy.
  • microwave energy exceed 50% of the total heating energy are possible, up to and including 100%, i.e. microwaves are used as the sole source of heat energy.
  • the major part of the ACM components in building materials is formed by lime (CaCO 3 ) and gypsum (CaSO 4 ).
  • Sources of lime and gypsum-containing ACMs in buildings include asbestos cement pipes, panels and shingles, asbestos concrete parts, insulating cardboards and fibre reinforced plaster.
  • the decomposition of these materials in alkali hydroxide melts is believed to be performed in the context of the process of the present invention by a substitution reaction of the metal ions according to the following equations (1) and (2): 2 NaOH + CaCO 3 ⁇ Na 2 CO 3 + Ca(OH) 2 (1) 2 NaOH + CaSO 4 ⁇ Na 2 SO 4 + Ca(OH) 2 (2)
  • the sodium hydroxide is thus transformed into carbonate or sulfate whilst the lime and gypsum are transformed into calcium hydroxide.
  • silica from silicates, alumina and iron oxide are thought to be dissolved by caustic soda melts according to the following equations (6) to (9): SiO 2 + 2 NaOH ⁇ Na 2 SiO 3 + H 2 O (6) Al 2 O 3 + 2 NaOH ⁇ 2 NaAlO 2 + H 2 O (7) Fe 2 O 3 + 2 NaOH ⁇ 2 NaFeO 2 + H 2 O (8) Fe 2 O 3 + 4 NaOH ⁇ Na 2 FeO 2 + Na 2 FeO 3 + 2 H 2 O (9)
  • gases that may be released during the asbestos degradation process notably CO 2 and SO 2
  • CO 2 and SO 2 gases that may be released during the asbestos degradation process
  • a part of these gases may arise from organic substances in the ACM.
  • the used alkali metal hydroxide is recycled. This can be done by e.g. dissolution of the reaction mixture in water, separation of liquid/solid phases and recrystallisation of solid alkali metal hydroxide from aqueous solution.
  • the percentage of alkali metal hydroxide recovered in the context of step (c) in the present invention, varies from about 60% to about 99%, most commonly between about 60% to about 90%. The exact percentage is dependent on the ratio of alkali metal hydroxide to ACM. When a high ratio of alkali metal hydroxide to ACM is used, a higher recovery rate of alkali metal hydroxide is naturally observed, because an increasing part of the alkali metal hydroxide is in chemical excess and is not consumed during the ACM degradation process.
  • a steel barrel (1) is filled with ACM (2). This can be done at the ACM removal site or at the ACM treatment plant. If the barrel is filled at the ACM removal site the steel barrel can be sealed to ensure safe transport.
  • solid alkali hydroxide (4) is added to the barrel containing ACM. Then, the filled barrel is moved to the heating station (5) where it is heated to form a melt (6).
  • the alkali hydroxide When the alkali hydroxide is molten it infiltrates and decomposes the asbestos containing material and the asbestos fibres are destroyed. The resulting molten solution is then dissolved in water in a dissolution reactor (9).
  • the product of the dissolution reactor is conducted into a solid/liquid separator (10), e.g. a filter or a centrifuge.
  • the solid product of the separation process (11) consists mainly of lime, gypsum and silica and can be recycled e.g. in the cement industry.
  • the liquid product of the separation process is transferred into an evaporator (12), where it is concentrated. Then, the alkali hydroxide is recovered in a cristallizer (13).
  • the recycled alkali hydroxide (4) can be reused in the filling station (3).
  • FIG. 2 Another embodiment of the process according to the invention is provided in Figure 2.
  • the process illustrated in Figure 2 is identical to the one illustrated in Figure 1, except that in addition to conventional heating of the barrel surface, microwave heating is used to accelerate and homogenize the heating process.
  • the microwave radiation is produced in a microwave source (7), e.g. a magnetron or klystron, and irradiated into the steel barrel by a microwave heating hood (8).
  • This example demonstrates the dissolution of different building materials (lime bricks, clinker, gypsum, clay, mortar, marble, cement, concrete, glass, quartz) in a caustic soda melt.
  • Examples 2-5 demonstrate the ability of alkali hydroxide melts to dissolve asbestos in ACMs.
  • Table 1 demonstrates the ACMs used, the amounts of ACM and alkali metal hydroxide, the temperature and reaction time, as well as the results observed for a number of representative examples of the dissolution of asbestos in melts according to the present invention. In each of the reactions illustrated in Examples 2-5, only microwave heating was used.
  • XRD X-ray diffraction
  • SEM scanning electron microscopy
  • EDX energy dispersive X-ray analysis
  • X-ray diffraction allows a quantitative determination of crystalline phases like asbestos minerals to less than one weight percent.
  • SEM Manual scanning electron microscopy methods
  • This example demonstrates the decontamination of ACM with combined microwave and infra-red heating in a steel drum. 6 kg of sprayed asbestos coating are mixed with 25 kg of caustic soda and treated at 400 °C for 90 minutes.
  • Figures 3 and 4 show a comparison between sprayed asbestos coating before and after treatment by NaOH melt. In the SEM pictures, the destruction of the asbestos fibres is evident.
  • This example relates to the determination of degradation rates for steel and lime in a caustic soda melt.
  • a piece of marble (a massive form of lime) and two steel plates were combined with a large excess of NaOH (sufficient to encase all parts if molten).
  • the mixture was heated to 450°C for 15 hours in a steel vessel as the reactor.
  • lime was dissolved in caustic soda melt and then re-precipitation was carried out in aqueous solution.
  • 10 g of CaCO 3 and 40 g of NaOH were mixed and heated to 400°C for 15 hours in a steel vessel. Then, the cold melt was dissolved in water. Subsequently, after sedimentation of the re-precipitated lime and decantation of the clear solution, the product was dried at 300°C

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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)
EP04293047A 2004-12-20 2004-12-20 Procede pour la decomposition de l' amiante avec des hydroxydes des metaux alcalins Withdrawn EP1671682A1 (fr)

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EP04293047A EP1671682A1 (fr) 2004-12-20 2004-12-20 Procede pour la decomposition de l' amiante avec des hydroxydes des metaux alcalins

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EP04293047A EP1671682A1 (fr) 2004-12-20 2004-12-20 Procede pour la decomposition de l' amiante avec des hydroxydes des metaux alcalins

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014054621A (ja) * 2012-08-16 2014-03-27 Kitasato Institute アスベストの無害化処理方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994008661A1 (fr) * 1992-10-08 1994-04-28 Cross-Link Technology Produit et procede de traitement de l'asbeste
DE4416851A1 (de) * 1994-05-13 1995-11-16 Claudia Zuber Verfahren und Einrichtungen zur Beseitigung und/oder Vernichtung von Asbest und/oder mit Asbest kontaminierten bzw. asbesthaltigen Materialien
US5562585A (en) * 1992-03-23 1996-10-08 Karl-Heinrich Lemmerbrock Process for disposal of asbestos or substances containing it
WO1997000099A1 (fr) * 1995-06-16 1997-01-03 Debailleul Gerard Procede et installation de traitement de dechets contenant de l'amiante

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5562585A (en) * 1992-03-23 1996-10-08 Karl-Heinrich Lemmerbrock Process for disposal of asbestos or substances containing it
WO1994008661A1 (fr) * 1992-10-08 1994-04-28 Cross-Link Technology Produit et procede de traitement de l'asbeste
DE4416851A1 (de) * 1994-05-13 1995-11-16 Claudia Zuber Verfahren und Einrichtungen zur Beseitigung und/oder Vernichtung von Asbest und/oder mit Asbest kontaminierten bzw. asbesthaltigen Materialien
WO1997000099A1 (fr) * 1995-06-16 1997-01-03 Debailleul Gerard Procede et installation de traitement de dechets contenant de l'amiante

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014054621A (ja) * 2012-08-16 2014-03-27 Kitasato Institute アスベストの無害化処理方法

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