FR2654020A1 - Process for the treatment of fly ashes in order to remove the calcium sulphite therefrom - Google Patents
Process for the treatment of fly ashes in order to remove the calcium sulphite therefrom Download PDFInfo
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- FR2654020A1 FR2654020A1 FR8914465A FR8914465A FR2654020A1 FR 2654020 A1 FR2654020 A1 FR 2654020A1 FR 8914465 A FR8914465 A FR 8914465A FR 8914465 A FR8914465 A FR 8914465A FR 2654020 A1 FR2654020 A1 FR 2654020A1
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- ash
- hydrogen peroxide
- treatment
- reaction
- remove
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Classifications
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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
- A62D3/38—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by oxidation; by combustion
-
- 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
- C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
- C04B20/02—Treatment
-
- 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
- A62D2101/08—Toxic combustion residues, e.g. toxic substances contained in fly ash from waste incineration
-
- 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
- A62D2101/47—Inorganic substances containing oxygen, sulfur, selenium or tellurium, i.e. chalcogen
-
- 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
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- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Engineering & Computer Science (AREA)
- Toxicology (AREA)
- General Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Health & Medical Sciences (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Treating Waste Gases (AREA)
Abstract
Description
La présente invention a pour objet un procédé de traitement des cendres volantes pour en éliminer le sulfite de calcium. The present invention relates to a process for treating fly ash to remove calcium sulphite.
Les cendres volantes sont, de façon connue, obtenues dans les centrales thermiques utilisant différents combustibles tels que lignites calcaires, charbons bitumeux, houilles et/ou coke. Fly ash is, in known manner, obtained in thermal power plants using different fuels such as calcareous lignites, bituminous coals, coal and / or coke.
Cependant, dans de nombreux cas, en particulier, lorsque les cendres sont mélangées aux résidus de traitement des fumées, la teneur en sulfite de calcium des cendres volantes dépasse la limite tolérable pour leur utilisation comme additifs dans les ciments. However, in many cases, in particular, when the ashes are mixed with the flue gas treatment residues, the calcium sulphite content of the fly ash exceeds the tolerable limit for their use as additives in the cements.
En effet, la présence dans les cendres de sulfite de calcium anhydre ou hydraté en quantité supérieure à environ 1 à 2 % provoque la formation d'espèces gonflantes telles que l'étringite, ces espèces gonflantes provoquant l'effritement du ciment après environ un à deux ans. Dans ces conditions, les cendres volantes ayant une teneur en sulfite trop élevée, doivent donc entre rejetées, ce qui pose des problèmes écologiques. In fact, the presence in the ash of anhydrous or hydrated calcium sulphite in an amount greater than about 1 to 2% causes the formation of swelling species such as étanging, these swelling species causing the disintegration of the cement after about one to two years. two years. Under these conditions, fly ash with a sulphite content too high, must therefore between rejected, which poses ecological problems.
On a déjà proposé dans la demande de brevet français 89-01684 déposée le 8 février 1989, un procédé de traitement hydrothermal à chaud (120 à 1500C) et sous faible pression (2,5 à 5 bars) pour éliminer des cendres, les agents gonflants et transformer l'oxyde de calcium (cas) en chaux éteinte Ca(OH)2. Ce procédé permet une élimination d'une fraction très importante des agents gonflants. Mais ce procédé, d'une part, demande une grande dépense d'énergie et, d'autre part, ne permet pas une élimination tout-à-fait complète des agents gonflants. It has already been proposed in French patent application 89-01684 filed February 8, 1989, a hot hydrothermal treatment process (120 to 1500C) and low pressure (2.5 to 5 bar) to remove ash, the agents swelling and transforming calcium oxide (case) into lime Ca (OH) 2. This process makes it possible to eliminate a very large fraction of blowing agents. But this process, on the one hand, requires a large expenditure of energy and, on the other hand, does not allow an entirely complete elimination of blowing agents.
Selon la présente invention, on a trouvé que l'on obtenait une élimination complète des agents gonflants par oxydation des cendres. En particulier, on a constaté que les sulfites de calcium, plus particulièrement l'hannebachite, sont entièrement transformés en sulfate de calcium selon le schéma réactionnel suivant
Sulfite de calcium + Oxygène ---- > Sulfate de calcium
La réaction d'oxydation étant fortement exothermique, la température du mélange réactionnel s'élève rapidement.In accordance with the present invention, it has been found that complete removal of swelling agents by ash oxidation is achieved. In particular, it has been found that calcium sulphites, more particularly hannebachite, are entirely converted into calcium sulphate according to the following reaction scheme
Calcium sulphite + Oxygen ----> Calcium sulphate
Since the oxidation reaction is highly exothermic, the temperature of the reaction mixture rises rapidly.
La présente invention a donc pour objet un procédé de traitement de cendres volantes contenant des sulfites, caractérisé par le fait que l'on soumet les cendres à une réaction d'oxydation. The present invention therefore relates to a process for treating fly ash containing sulphites, characterized in that the ash is subjected to an oxidation reaction.
Selon un premier mode de réalisation de l'invention, on effectue la réaction en mettant en contact les cendres volantes avec de l'eau oxygénée ayant une concentration de 10 à 298 volumes, c'est-à- dire une concentration en H 202 comprise entre 3 et 70 % en poids. According to a first embodiment of the invention, the reaction is carried out by contacting the fly ash with oxygenated water having a concentration of 10 to 298 volumes, that is to say a concentration of H 202 included between 3 and 70% by weight.
Le rapport massique de l'eau oxygénée aux cendres volantes dépend de la concentration de l'eau oxygénée utilisée. Il est, avantageusement, choisi de manière à Entre voisin du rapport stoechiométrique correspondant à l'oxydation du sulfite en sulfate. The mass ratio of oxygenated water to fly ash depends on the concentration of hydrogen peroxide used. It is advantageously chosen in such a way as to be in the vicinity of the stoichiometric ratio corresponding to the oxidation of sulphite to sulphate.
Selon un second mode de réalisation de l'invention, on effectue la réaction en faisant passer de l'oxygène dans une suspension aqueuse de cendres. According to a second embodiment of the invention, the reaction is carried out by passing oxygen in an aqueous suspension of ash.
Les cendres traitées contiennent le plus souvent 3 à 70 % de sulfite de calcium et 3 à 20 % d'hydroxyde de calcium Ca(OH)2 associés à du sulfate de calcium, du sulfure de magnésium, des aluminosilicates, des sulfates de fer hydratés, de la halite et de la calcite. The treated ash usually contains 3 to 70% calcium sulphite and 3 to 20% calcium hydroxide Ca (OH) 2 combined with calcium sulphate, magnesium sulphide, aluminosilicates, hydrated iron sulphates , halite and calcite.
On a trouvé que l'oxydation selon l'invention permet d'effectuer une transformation complète des sulfites en sulfates sans provoquer la formation de produits d'oxydation gênantes, par exemple à partir des sulfures ou oxydes de métaux polyvalents présents dans les cendres. It has been found that the oxidation according to the invention makes it possible to carry out a complete conversion of sulphites into sulphates without causing the formation of troublesome oxidation products, for example from sulphides or oxides of polyvalent metals present in the ashes.
On a vérifié que, lorsqu'on oxyde des cendres l'aide d'eau oxygénée dans un réacteur ouvert, on obtient la réaction suivante 2(CaS03, 1/2 H2O) + 4H202 > 2(CaSO4, 2H?O) + H2O + 0
Cette réaction s'accompagne d'une élévation de température, qui est d'autant plus grande que la concentration de l'eau oxygénée est plus élevée. Par exemple avec de l'eau oxygénée à 30 volumes (9 % en poids), la température s'élève jusqu'à 650C environ et avec de l'eau oxygénée à 130 volumes (35 % en poids), la température s'élève jusqu'à 1000C environ.It has been verified that, when the ash is oxidized using oxygenated water in an open reactor, the following reaction is obtained 2 (CaSO 3, 1/2H 2 O) + 4H 2 O 2> 2 (CaSO 4, 2H 2 O) + H 2 O + 0
This reaction is accompanied by a rise in temperature, which is even greater than the concentration of oxygenated water is higher. For example with hydrogen peroxide at 30 volumes (9% by weight), the temperature rises to about 650C and with hydrogen peroxide at 130 volumes (35% by weight), the temperature rises up to about 1000C.
Si on opère dans un réacteur fermé, il y a une augmentation de la pression due au dégagement gazeux et à l'élévation de la température et la réaction d'oxydation de l'hannebachite donne lieu à la formation d'un mélange d'anhydrite et d'hémihydrate de formule CaS04 , E H20, formule dans laquelle est compris entre 0,15 et 0,67 , probablement par déshydratation de la phase transitoire CaSO , 2H O
2 (gypse).If operating in a closed reactor, there is an increase in pressure due to gas evolution and temperature rise and the oxidation reaction of hannebachite gives rise to the formation of a mixture of anhydrite and of hemihydrate of formula CaSO 4, E H 2 O, in which is between 0.15 and 0.67, probably by dehydration of the transient phase CaSO, 2H O
2 (gypsum).
Par ailleurs, on a noté que la présence d'une phase aqueuse permet la solubilisation de sels minéraux, en particulier des chlorures qui peuvent éventuellement entre éliminés par lessivage. Furthermore, it has been noted that the presence of an aqueous phase allows the solubilization of inorganic salts, in particular chlorides which may optionally be eliminated by leaching.
Les exemples donnés ci-dessous, à titre purement illustratif et non limitatif, permettront de mieux comprendre l'invention. The examples given below, for purely illustrative and non-limiting purposes, will better understand the invention.
EXEMPLE 1
On traite des cendres, provenant d'une centrale thermique scandinave, ayant la composition suivante en % en poids - sulfite de calcium semi-hydraté (hannebachite) .................... 60 * - hydroxyde de calcium Ca(OH)2
(portlandite) ..................... 15 % - halite NaCl ...................... 15 % - calcite CaCO .................... 5 %
3 - gypse ............................. 5 %
On mélange dans un réacteur ouvert un premier échantillon de ces cendres avec de l'eau oxygénée à 30 volumes (10 % en poids d'H2O2) dans un rapport massique eau oxygénée/cendres égal à 5. On observe que la température s'est élevée à 650C en 15 minutes. Cet échantillon a été filtré puis séché.EXAMPLE 1
Ash, from a Scandinavian thermal power station, having the following composition in% by weight - semi-hydrated calcium sulphite (hannebachite) is treated ................... 60 * - Calcium hydroxide Ca (OH) 2
(portlandite) ..................... 15% - halite NaCl ..................... 15% - calcite CaCO .................... 5%
3 - gypsum ............................. 5%
A first sample of these ashes is mixed in an open reactor with 30 volumes of hydrogen peroxide (10% by weight of H 2 O 2) in an oxygen peroxide / ash mass ratio of 5. It is observed that the temperature raised to 650C in 15 minutes. This sample was filtered and dried.
Un second échantillon de cendres a été conservé comme témoin. A second sample of ash was kept as a control.
On a soumis les deux échantillons à une analyse thermique différentielle. Les courbes obtenues sont représentées sur la figure 1, la courbe (1) correspondant à l'échantillon témoin et la courbe (2) à l'échantillon traité. Both samples were subjected to differential thermal analysis. The curves obtained are shown in FIG. 1, the curve (1) corresponding to the control sample and the curve (2) to the treated sample.
Sur la courbe (1), le pic endothermique marqué S y A correspond à la réaction de transforma- tion de l'hannebachite en anhydrite qui a lieu à une température d'environ 3600C. In curve (1), the labeled endothermic peak S y A corresponds to the reaction of transformation of hannebachite to anhydrite which takes place at a temperature of about 3600C.
Sur la courbe (2), on peut constater qu'il n'y a plus de pic correspondant à la transformation d'hannebachite en anhydrite ; le pic endothermique marqué G > G' correspond à la transformation du sulfate de calcium déhydraté (gypse) en hémihydrate (CaSO4 , # H2O; 0,15 # # # Q,67) à une température d'environ 1400C, et le pic marqué G' rA correspond à la transformation de l'hémihydrate en anhydrite à une température d'environ 1900C. On curve (2), we can see that there is no more peak corresponding to the transformation of hannebachite into anhydrite; the endothermic peak labeled G> G 'corresponds to the conversion of dehydrated calcium sulfate (gypsum) to hemihydrate (CaSO4, # H2O; 0.15 # # # Q, 67) at a temperature of about 1400C, and the marked peak G 'rA corresponds to the conversion of hemihydrate to anhydrite at a temperature of about 1900C.
On a également soumis ces deux échantillons à une analyse par diffraction des rayons X. La figure 2A représente le diagramme de diffraction de l'échantillon témoin et la figure 2B, le diagramme de diffraction de l'échantillon traité. These two samples were also subjected to X-ray diffraction analysis. FIG. 2A shows the diffraction pattern of the control sample and FIG. 2B shows the diffraction pattern of the treated sample.
Sur ces figures, les pics marqués
1 correspondent à l'hannebachite (CaSO3, 0,5 H20);
2 " au gypse (CaSO4, 2H20) ;
3 e. à la calcite (CaCO3) ;
4 N à l'halite (NaCl) ; 5 N à la portlandite (Ca(OH)2) 2
On voit qu'après traitement, l'hannebachite et l'halite ont complètement disparu, ainsi que la portlandite. La première s'est oxydée en gypse, alors que les deux autres phases ont été solubilisées et éliminées lors du traitement.In these figures, the marked peaks
1 corresponds to hannebachite (CaSO3, 0.5 H2O);
2 "to gypsum (CaSO4, 2H2O);
3 e. with calcite (CaCO3);
4 N with halite (NaCl); 5 N at portlandite (Ca (OH) 2) 2
It can be seen that after treatment, hannebachite and halite have completely disappeared, as well as portlandite. The first was oxidized to gypsum, while the other two phases were solubilized and eliminated during treatment.
EXEMPLE 2
On utilise les memes cendres que dans l'exemple 1.EXAMPLE 2
The same ash is used as in Example 1.
Le mode opératoire est le meme que dans l'exemple 1 sauf que l'on utilise de l'eau oxygénée à 130 volumes (35 % en poids d'H202) et que l'on utilise successivement deux rapports massiques eau oxygénée/cendres égaux respectivement à 1 et à 5, c'est-à-dire des rapports massiques inférieur et supérieur au rapport massique stoechiométrique. The procedure is the same as in Example 1 except that 130 vol. Oxygenated water (35% by weight of H 2 O 2) is used and two hydrogen peroxide / ash equal ratios are successively used. respectively at 1 and 5, that is to say, lower and higher mass ratios to the stoichiometric mass ratio.
Dans les deux cas, la température s'est élevée jusqu'à 1000C en moins d'une minute. In both cases, the temperature rose to 1000C in less than a minute.
Ces deux échantillons, ainsi qu'un échantillon témoin de cendres, ont été analysés par diffraction des rayons X (figure 3). Sur cette figure 3 la courbe (1) correspond à un rapport massique eau oxygénée/cendres de 1 et la courbe (2) à un rapport massique eau oxygénée/cendres de 5. La courbe (3) correspond à l'échantillon témoin. These two samples, together with a control sample of ash, were analyzed by X-ray diffraction (Figure 3). In this FIG. 3, the curve (1) corresponds to a hydrogen peroxide / ash mass ratio of 1 and the curve (2) to a hydrogen peroxide / ash mass ratio of 5. Curve (3) corresponds to the control sample.
La notation des pics est la meme que dans l'exemple 1. De plus, les pics marqués 6 correspondent à l'hémihydrate (CaSO4 , H O ; 0,15 4 # # 0,67). 2
On constate que sur la courbe (2) (rapport massique eau oxygénée/cendres inférieur au rapport stoechiométrique), on observe la subsistance d'hannebachite mais également l'apparition d'hémihydrate à côté du gypse. Sur la courbe (I) (rapport massique eau oxygénée/cendres supérieur au rapport stoechiométrique), toute l'hannebachite a disparu au profit du gypse. The notation of the peaks is the same as in Example 1. In addition, the peaks marked 6 correspond to the hemihydrate (CaSO4, HO, 0.15 4 # # 0.67). 2
It can be seen that on the curve (2) (oxygen / ash mass ratio below the stoichiometric ratio), we observe the existence of hannebachite but also the appearance of hemihydrate next to the gypsum. On the curve (I) (oxygen / ash mass ratio greater than the stoichiometric ratio), all the hannebachite disappeared in favor of the gypsum.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8914465A FR2654020B3 (en) | 1989-11-03 | 1989-11-03 | PROCESS FOR TREATING FLY ASH TO ELIMINATE CALCIUM SULFITE. |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8914465A FR2654020B3 (en) | 1989-11-03 | 1989-11-03 | PROCESS FOR TREATING FLY ASH TO ELIMINATE CALCIUM SULFITE. |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| FR2654020A1 true FR2654020A1 (en) | 1991-05-10 |
| FR2654020B3 FR2654020B3 (en) | 1992-03-06 |
Family
ID=9387079
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| FR8914465A Expired - Fee Related FR2654020B3 (en) | 1989-11-03 | 1989-11-03 | PROCESS FOR TREATING FLY ASH TO ELIMINATE CALCIUM SULFITE. |
Country Status (1)
| Country | Link |
|---|---|
| FR (1) | FR2654020B3 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1993025329A1 (en) * | 1992-06-09 | 1993-12-23 | Matrix Technology Pty. Ltd. | Treatment of waste materials for disposal |
| FR2757272A1 (en) * | 1996-12-13 | 1998-06-19 | Comex Technologies | Evaluating nature and quantity of mineral particles such as asbestos in fluid |
| EP1085104A1 (en) * | 1999-09-16 | 2001-03-21 | Von Roll Umwelttechnik AG | Method of working-up incineration residues into a disposable material using an oxidizing wash treatment |
-
1989
- 1989-11-03 FR FR8914465A patent/FR2654020B3/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1993025329A1 (en) * | 1992-06-09 | 1993-12-23 | Matrix Technology Pty. Ltd. | Treatment of waste materials for disposal |
| AU660822B2 (en) * | 1992-06-09 | 1995-07-06 | Matrix Technology Pty Ltd | Treatment of waste materials for disposal |
| US5568895A (en) * | 1992-06-09 | 1996-10-29 | Matrix Technology Pty. Ltd. | Treatment of waste materials for disposal |
| FR2757272A1 (en) * | 1996-12-13 | 1998-06-19 | Comex Technologies | Evaluating nature and quantity of mineral particles such as asbestos in fluid |
| EP1085104A1 (en) * | 1999-09-16 | 2001-03-21 | Von Roll Umwelttechnik AG | Method of working-up incineration residues into a disposable material using an oxidizing wash treatment |
| CH693612A5 (en) * | 1999-09-16 | 2003-11-14 | Von Roll Umwelttechnik Ag | Method About Check of residues from waste incineration in deponierbares material. |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2654020B3 (en) | 1992-03-06 |
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