EP1028916A1 - Method for making calcium carbonate - Google Patents

Method for making calcium carbonate

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Publication number
EP1028916A1
EP1028916A1 EP98952452A EP98952452A EP1028916A1 EP 1028916 A1 EP1028916 A1 EP 1028916A1 EP 98952452 A EP98952452 A EP 98952452A EP 98952452 A EP98952452 A EP 98952452A EP 1028916 A1 EP1028916 A1 EP 1028916A1
Authority
EP
European Patent Office
Prior art keywords
aqueous medium
ppm
treatment
additive
less
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Withdrawn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
EP98952452A
Other languages
German (de)
French (fr)
Inventor
Henri René LANGELIN
Alain Laudet
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.)
Lhoist Recherche et Developpement SA
Original Assignee
Lhoist Recherche et Developpement 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.)
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Publication date
Application filed by Lhoist Recherche et Developpement SA filed Critical Lhoist Recherche et Developpement SA
Publication of EP1028916A1 publication Critical patent/EP1028916A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/182—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/24—Magnesium carbonates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity

Definitions

  • the subject of the present invention is a process for the manufacture of calcium carbonate and / or calcium and magnesium carbonate particles, in which an aqueous medium of basic pH and containing Ca (OH) 2 and / or Ca is treated. (OH) 2 -Mg (OH) 2 by injecting CO 2 gas therein to form calcium carbonate and / or calcium and magnesium carbonate, and in which the carbonate particles formed are recovered.
  • Document FR 2405903 also discloses a process in which the calcium is dissolved in an aqueous medium using ethanolammonium nitrate to transform the calcium into soluble calcium nitrate, and the calcium-rich filtrate is recovered by carbonation by means of CO 2 .
  • the particles thus obtained are of high purity and have a whiteness index of approximately 99.5 and a zero yellow index.
  • the process according to this document requires two stages of filtration which makes it expensive.
  • CN 85103821 describes a process for carbonating lime milk by adding sodium hydrogen carbonate, in the presence of ethanolamine and hydrazine or Na dithionite. This process has the drawback of using a carbonation mode which involves the production of NaOH which is then removed by washing. The degree of whiteness to be obtained by this process is moreover insufficient for many applications.
  • the present invention relates to a simple process which makes it possible, by the use of particular additive (s), to reduce the harmful influence of the impurities on the whiteness of the carbonate particles, while avoiding excessively excessive whiteness.
  • the aqueous medium is treated in the presence of at least one additive chosen from the group consisting of hydrazine, hydroxylamine, soluble salts of hydroxylamine, and their mixtures.
  • This group has the advantage of introducing into the reaction medium a powerful reducing agent which will reduce in basic medium, inter alia Mn 4+ to Mn 2+ and Fe 3+ to Fe 2+ , without requiring any other additive .
  • said aqueous medium contains an amount of said additive corresponding to 0.035 to 5% by weight of Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 .
  • the Mn content of the Ca (OH) 2 and / or of the Ca (OH) 2 -Mg (OH) 2 is determined and the aqueous medium is treated in the presence of an aforementioned additive so that said aqueous medium contains from 1 to 8 moles, preferably from 2 to 6 moles, of additives per mole of Mn.
  • said treatment is carried out at atmospheric pressure, advantageously under a pressure higher than atmospheric pressure, preferably under an actual pressure between 1, 2.10 5 Pa and 10J0 5 Pa, this treatment being carried out at a temperature between 10 and 100 ° C, advantageously between 20 and 95 ° C, preferably between 30 and 60 ⁇ C, for example around 40 ° C.
  • the carbonate particles formed or a suspension containing these particles are subjected to a treatment to decompose the additive.
  • a suspension of carbonate particles formed is recovered and then subjected to a treatment to decompose the additive still present in the particles.
  • Such treatments are, for example, a treatment with hypochlorite (for example sodium) and / or with water having a temperature above 20 ° C., for example a temperature between 20 and 100 ° C., in particular a temperature of 70 ° C or more and / or with steam.
  • the carbonate particles formed are separated from the medium, and the medium is at least partially reused to form an aqueous medium containing Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 and at least one of said additives.
  • the aqueous medium containing Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 is formed by quenching CaO and / or CaO-MgO by aqueous medium, the additive being added to said aqueous medium before, during and / or after extinction.
  • the subject of the invention is also particles of calcium carbonate having an Mn content expressed in MnO of between 80 ppm and 500 ppm, in particular between 90 and 250 ppm, and more precisely between 100 and 200 ppm, a content as Fe expressed as Fe 2 0 3 between 500 and 2000 ppm, in particular less than 1000 ppm, an average diameter by weight less than 5 ⁇ m, a whiteness index measured at 457 nm greater than or equal to 95, but less than 99 , and a yellow index less than or equal to 1.5, but greater than 0.5.
  • Such particles have sufficient whiteness, but not excessive whiteness.
  • a subject of the invention is also particles of calcium and magnesium carbonate having an Mn content expressed in MnO of between 50 ppm and 500 ppm, in particular between 90 and 250 ppm, and more precisely between 100 and 200 ppm, a Fe content expressed as Fe 2 O 3 less than 2000 ppm, in particular less than 1000 ppm, an average diameter by weight less than 5 ⁇ m, a whiteness index measured at 457 nm greater than or equal to 95, but less than 99, and .a yellow index less than or equal to 1.5, but greater than 0.5.
  • an aqueous medium is prepared in 1 containing, for example, from 0.05 to 2.5% of additive.
  • CaO particles are added to the aqueous medium so as to form a suspension or milk of Ca (OH) 2 .
  • C0 2 is injected into the suspension, for example at a flow rate of 10 to 200 g of COj / hour / liter.
  • the temperature of the suspension is adjusted in 3, for example between 20 and 60 ⁇ C, preferably around 40 ⁇ C.
  • the injection of CO 2 is advantageously carried out in a tank maintained at an actual pressure of 1.2.10 5 to 10. 10 5 Pa, preferably 1.5 to 3.10 S Pa.
  • calcium carbonate particles are recovered by filtration. The filtrate or liquid phase is then reused for the preparation in 1 of the aqueous medium intended for the extinction of CaO.
  • FIG. 2 The process represented in FIG. 2 is similar to that represented in FIG. 1, except that hydrazine is used as an additive and that a suspension of particles of calcium carbonate to treatment with an aqueous solution containing sodium hypochlorite, so as to remove all traces of hydrazine. By drying in 6, dry particles are then obtained.
  • the process according to FIG. 3 is similar to that of FIG.
  • a soluble salt of hydroxylamine for example a salt of strong acid
  • this additive being added in 2 during, but preferably after the quicklime has died out, and in 5 the suspension of carbonate particles recovered in 4 is subjected to a treatment with heated water, for example by means of steam ( more than 120 ° C), this treatment being able to decompose all traces of hydroxylamine.
  • EXAMPLE 1 A milk of lime was prepared by reaction of quicklime and water.
  • the lime used contained 510 ppm of Fe expressed in the form of Fe 2 0 3 and 125 ppm of Mn expressed in the form of MnO.
  • the solid content of the milk was 10% by weight for example. Other contents of calcium hydroxide are possible.
  • the pH of the lime milk thus formed was approximately 12.
  • additives according to the invention were added in an amount corresponding to 0.2% of the weight of quicklime used.
  • the whiteness index measured at 457 nm (R 457) and the yellowness index (I.J.) were measured on an Elrepho 2000 device from DATACOLOR.
  • Example 1 was repeated, except that quicklime with different Fe and Mn contents (expressed as Fe 2 0 3 and MnO) was used, and hydrazine was used as an additive in an amount of 0.2% by weight of quicklime.
  • the following table gives the whiteness index of the calcium carbonate particles prepared without hydrazine (R457 reference) and with hydrazine (R457 hydrazine).
  • Example 2 was repeated except that 0.1% hydrazine was used.
  • the particles can be subjected to treatment with an aqueous solution containing sodium hypochlorite.
  • Example 2 was repeated, except that a quicklime containing 910 ppm of Fe expressed in the form of Fe 2 O 3 and 175 ppm of Mn expressed in the form of MnO was used.
  • the additives used were hydrazine (HZ) at 0.1 and 0.2% by weight of quicklime, hydroxylamine hydrochloride (CHA) at 0.1 and 0.2% by weight of lime quicklime, hydroxylamine sulfate (SHA) at 0.2% by weight of quicklime, and mixtures of these additives.
  • HZ hydrazine
  • CHA hydroxylamine hydrochloride
  • SHA hydroxylamine sulfate
  • the following table gives the whiteness index and the yellowness index of calcium carbonate particles with an average diameter of between 2 and 2.5 ⁇ m.
  • the particles of calcium carbonate produced by the process according to the invention in particular the particles having:
  • MnO an Mn content expressed as MnO of between 80 ppm and 500 ppm, preferably of between 90 and 250 ppm, more precisely between 100 and 200 ppm,
  • MnO an Mn content expressed as MnO of between 50 ppm and 500 ppm, preferably of between 90 and 250 ppm, more precisely between 100 and 200 ppm,

Abstract

The invention concerns a method for making calcium carbonate and/or calcium and magnesium carbonate particles, which consists in treating a basic pH aqueous medium containing Ca(OH)2 and/or Ca(OH)2-Mg(OH)2 by injecting therein gaseous CO2 to form calcium carbonate and/or calcium and magnesium carbonate, and recuperating the formed carbonate particles. The invention is characterised in that the treatment of the aqueous medium is carried out in the presence of at least an additive selected among the group consisting of hydrazine, hydroxylamine, hydroxylamine soluble salts, and their mixtures.

Description

"Procédé de fabrication de carbonate de calcium" "Process for the production of calcium carbonate"
La présente invention a pour objet un procédé de fabrication de particules de carbonate de calcium et/ou de carbonate de calcium et de magnésium, dans lequel on traite un milieu aqueux de pH basique et contenant du Ca(OH)2 et/ou du Ca(OH)2-Mg(OH)2 en y injectant du CO2 gazeux pour former du carbonate de calcium et/ou du carbonate de calcium et de magnésium, et dans lequel on récupère les particules de carbonate formées.The subject of the present invention is a process for the manufacture of calcium carbonate and / or calcium and magnesium carbonate particles, in which an aqueous medium of basic pH and containing Ca (OH) 2 and / or Ca is treated. (OH) 2 -Mg (OH) 2 by injecting CO 2 gas therein to form calcium carbonate and / or calcium and magnesium carbonate, and in which the carbonate particles formed are recovered.
Un procédé de ce type est décrit par exemple dans le U-S- A-4900533.A process of this type is described for example in U-S-A-4900533.
On connaît par le document WO 92/01629 un procédé de fabrication de vatérite. Dans ce procédé, on injecte du CO2 de manière contrôlée dans un milieu contenant de l'hydroxyde de calcium et un sel acide d'aminé organique. Le sel d'aminé réagit avec Ca (OH)2 pour donner une aminé qui maintient le milieu à un pH basique et un sel de calcium soluble avec l'acide du sel d'aminé. Le sel ainsi formé est alors carbonate pour donner de la vatérite.Document WO 92/01629 discloses a process for manufacturing vaterite. In this process, CO 2 is injected in a controlled manner into a medium containing calcium hydroxide and an organic amino acid salt. The amine salt reacts with Ca (OH) 2 to give an amine which maintains the medium at a basic pH and a calcium salt soluble with the acid of the amine salt. The salt thus formed is then carbonated to give vaterite.
On connaît également par le document FR 2405903 un procédé dans lequel on solubilise dans un milieu aqueux le calcium grâce à du nitrate d'éthanolammonium pour transformer le calcium en nitrate de calcium soluble, et on récupère le filtrat riche en calcium à une carbonatation au moyen de CO2. Les particules ainsi obtenues sont de grande pureté et présentent un indice de blancheur d'environ 99,5 et un indice de jaune nul. Le procédé selon ce document nécessite deux étapes de filtration ce qui le rend coûteux. Dans le CN 85103821 , on décrit un procédé de carbonatation de lait de chaux par addition de carbonate acide de sodium, en présence d'éthanolamine et d'hydrazine ou de dithionite de Na. Ce procédé présente l'inconvénient de faire appel à un mode de carbonatation qui implique la production de NaOH à éliminer ensuite par lavage. Le degré de blancheur à obtenir par ce procédé est par ailleurs insuffisant pour de nombreuses applications.Document FR 2405903 also discloses a process in which the calcium is dissolved in an aqueous medium using ethanolammonium nitrate to transform the calcium into soluble calcium nitrate, and the calcium-rich filtrate is recovered by carbonation by means of CO 2 . The particles thus obtained are of high purity and have a whiteness index of approximately 99.5 and a zero yellow index. The process according to this document requires two stages of filtration which makes it expensive. CN 85103821 describes a process for carbonating lime milk by adding sodium hydrogen carbonate, in the presence of ethanolamine and hydrazine or Na dithionite. This process has the drawback of using a carbonation mode which involves the production of NaOH which is then removed by washing. The degree of whiteness to be obtained by this process is moreover insufficient for many applications.
La présente invention vise un procédé simple qui permet, par l'utilisation d'additif(s) particulier(s), de réduire l'influence néfaste des impuretés sur la blancheur des particules de carbonate, tout en évitant une blancheur trop excessive.The present invention relates to a simple process which makes it possible, by the use of particular additive (s), to reduce the harmful influence of the impurities on the whiteness of the carbonate particles, while avoiding excessively excessive whiteness.
Dans le procédé selon l'invention, on effectue le traitement du milieu aqueux en présence d'au moins un additif choisi parmi le groupe constitué de l'hydrazine, de l'hydroxylamine, des sels solubles d'hydroxylamine, et de leurs mélanges. Ce groupe présente l'avantage d'introduire dans le milieu réactionnel un agent réducteur puissant qui va réduire en milieu basique, entre autres le Mn4+ en Mn2+ et le Fe3+ en Fe2+, sans nécessiter d'autre additif.In the process according to the invention, the aqueous medium is treated in the presence of at least one additive chosen from the group consisting of hydrazine, hydroxylamine, soluble salts of hydroxylamine, and their mixtures. This group has the advantage of introducing into the reaction medium a powerful reducing agent which will reduce in basic medium, inter alia Mn 4+ to Mn 2+ and Fe 3+ to Fe 2+ , without requiring any other additive .
De façon avantageuse, ledit milieu aqueux contient une quantité dudit additif correspondant à 0,035 à 5% en poids de Ca(OH)2 et/ou du Ca(OH)2-Mg(OH)2.Advantageously, said aqueous medium contains an amount of said additive corresponding to 0.035 to 5% by weight of Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 .
De préférence, on détermine la teneur en Mn du Ca(OH)2 et/ou du Ca(OH)2-Mg(OH)2 et l'on effectue le traitement du milieu aqueux en présence d'un additif susdit de façon que ledit milieu aqueux contienne de 1 à 8 moles, de préférence de 2 à 6 moles, d'additifs par mole de Mn.Preferably, the Mn content of the Ca (OH) 2 and / or of the Ca (OH) 2 -Mg (OH) 2 is determined and the aqueous medium is treated in the presence of an aforementioned additive so that said aqueous medium contains from 1 to 8 moles, preferably from 2 to 6 moles, of additives per mole of Mn.
Selon une particularité, on effectue ledit traitement à pression atmosphérique, avantageusement sous une pression supérieure à la pression atmosphérique, de préférence sous une pression réelle comprise entre 1 ,2.105 Pa et 10J05 Pa, ce traitement étant effectué à une température comprise entre 10 et 100°C, avantageusement entre 20 et 95°C, de préférence entre 30 et 60βC, par exemple d'environ 40°C.According to a particular feature, said treatment is carried out at atmospheric pressure, advantageously under a pressure higher than atmospheric pressure, preferably under an actual pressure between 1, 2.10 5 Pa and 10J0 5 Pa, this treatment being carried out at a temperature between 10 and 100 ° C, advantageously between 20 and 95 ° C, preferably between 30 and 60 β C, for example around 40 ° C.
Selon une forme avantageuse d'un procédé suivant l'invention, on soumet les particules de carbonate formées ou une suspension contenant ces particules à un traitement pour décomposer l'additif. Par exemple, on récupère une suspension de particules de carbonate formées et on la soumet ensuite à un traitement pour décomposer l'additif encore présent dans les particules. De tels traitements sont par exemple un traitement avec de l'hypochlorite (par exemple de sodium) et/ou avec de l'eau présentant une température supérieure à 20°C, par exemple une température comprise entre 20 et 100°C, en particulier une température de 70°C ou plus et/ou avec de la vapeur d'eau. Selon une mise en oeuvre du procédé, après le traitement du milieu aqueux par injection de CO2, on sépare les particules de carbonate formées du milieu, et on réutilise au moins partiellement le milieu pour former un milieu aqueux contenant du Ca(OH)2 et/ou du Ca(OH)2-Mg(OH)2 et au moins un desdits additifs. Par exemple, dans le procédé suivant l'invention, le milieu aqueux contenant du Ca(OH)2 et/ou du Ca(OH)2-Mg(OH)2 est formé par extinction de CaO et/ou CaO-MgO par un milieu aqueux, l'additif étant ajouté audit milieu aqueux avant, pendant et/ou après l'extinction.According to an advantageous form of a process according to the invention, the carbonate particles formed or a suspension containing these particles are subjected to a treatment to decompose the additive. For example, a suspension of carbonate particles formed is recovered and then subjected to a treatment to decompose the additive still present in the particles. Such treatments are, for example, a treatment with hypochlorite (for example sodium) and / or with water having a temperature above 20 ° C., for example a temperature between 20 and 100 ° C., in particular a temperature of 70 ° C or more and / or with steam. According to one implementation of the method, after the treatment of the aqueous medium by injection of CO 2 , the carbonate particles formed are separated from the medium, and the medium is at least partially reused to form an aqueous medium containing Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 and at least one of said additives. For example, in the process according to the invention, the aqueous medium containing Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 is formed by quenching CaO and / or CaO-MgO by aqueous medium, the additive being added to said aqueous medium before, during and / or after extinction.
Enfin, l'invention a également pour objet des particules de carbonate de calcium présentant une teneur en Mn exprimée en MnO comprise entre 80 ppm et 500 ppm, en particulier entre 90 et 250 ppm, et plus précisément entre 100 et 200 ppm, une teneur en Fe exprimée en Fe203 comprise entre 500 et 2000 ppm, en particulier inférieure à 1000 ppm, un diamètre moyen en poids inférieur à 5 μm, un indice de blancheur mesuré à 457 nm supérieur ou égal à 95, mais inférieur à 99, et un indice de jaune inférieur ou égal à 1 ,5, mais supérieur à 0,5. De telles particules ont une blancheur suffisante, mais pas excessive.Finally, the subject of the invention is also particles of calcium carbonate having an Mn content expressed in MnO of between 80 ppm and 500 ppm, in particular between 90 and 250 ppm, and more precisely between 100 and 200 ppm, a content as Fe expressed as Fe 2 0 3 between 500 and 2000 ppm, in particular less than 1000 ppm, an average diameter by weight less than 5 μm, a whiteness index measured at 457 nm greater than or equal to 95, but less than 99 , and a yellow index less than or equal to 1.5, but greater than 0.5. Such particles have sufficient whiteness, but not excessive whiteness.
L'invention a aussi pour objet des particules de carbonate de calcium et de magnésium présentant une teneur en Mn exprimée en MnO comprise entre 50 ppm et 500 ppm, en particulier entre 90 et 250 ppm, et plus précisément entre 100 et 200 ppm, une teneur en Fe exprimée en Fe2O3 inférieure à 2000 ppm, en particulier inférieure à 1000 ppm, un diamètre moyen en poids inférieur à 5 μm, un indice de blancheur mesuré à 457 nm supérieur ou égal à 95, mais inférieur à 99, et .un indice de jaune inférieur ou égal à 1 ,5, mais supérieur à 0,5.A subject of the invention is also particles of calcium and magnesium carbonate having an Mn content expressed in MnO of between 50 ppm and 500 ppm, in particular between 90 and 250 ppm, and more precisely between 100 and 200 ppm, a Fe content expressed as Fe 2 O 3 less than 2000 ppm, in particular less than 1000 ppm, an average diameter by weight less than 5 μm, a whiteness index measured at 457 nm greater than or equal to 95, but less than 99, and .a yellow index less than or equal to 1.5, but greater than 0.5.
Des particularités et détails de l'invention ressortiront de la description détaillée suivante dans laquelle il est fait référence aux dessins ci-annexés.Special features and details of the invention will emerge from the following detailed description in which reference is made to the accompanying drawings.
Dans ces dessins, les figures 1 à 3 montrent schématiquement des procédés selon l'invention.In these drawings, Figures 1 to 3 schematically show methods according to the invention.
Dans le procédé selon la figure 1 , on prépare en 1 un milieu aqueux contenant par exemple de 0,05 à 2,5% d'additif. En 2, on ajoute au milieu aqueux des particules de CaO de manière à former une suspension ou lait de Ca(OH)2. En 3, on injecte dans la suspension du C02 par exemple à un débit de 10 à 200g de COj/heure/litre. Avantageusement on règle la température de la suspension en 3 par exemple entre 20 et 60βC, de préférence à environ 40βC. L'injection de CO2 se fait avantageusement dans une cuve maintenue à une pression réelle de 1.2.105 à 10. 105 Pa, de préférence de 1,5 à 3.10S Pa. En 4 on récupère par exemple par filtration des particules de carbonate de calcium. Le filtrat ou phase liquide est alors réutilisé pour la préparation en 1 du milieu aqueux destiné à l'extinction de CaO.In the process according to FIG. 1, an aqueous medium is prepared in 1 containing, for example, from 0.05 to 2.5% of additive. In 2, CaO particles are added to the aqueous medium so as to form a suspension or milk of Ca (OH) 2 . In 3, C0 2 is injected into the suspension, for example at a flow rate of 10 to 200 g of COj / hour / liter. Advantageously, the temperature of the suspension is adjusted in 3, for example between 20 and 60 β C, preferably around 40 β C. The injection of CO 2 is advantageously carried out in a tank maintained at an actual pressure of 1.2.10 5 to 10. 10 5 Pa, preferably 1.5 to 3.10 S Pa. In 4, for example, calcium carbonate particles are recovered by filtration. The filtrate or liquid phase is then reused for the preparation in 1 of the aqueous medium intended for the extinction of CaO.
Le procédé représenté à la figure 2 est similaire à celui représenté à la figure 1, si ce n'est qu'on utilise comme additif de l'hydrazine et qu'on soumet en 5 une suspension de particules de carbonate de calcium à un traitement au moyen d'une solution aqueuse contenant de l'hypochlorite de sodium, de manière à éliminer toutes traces d'hydrazine. Par séchage en 6 on obtient alors des particules sèches. Le procédé suivant la figure 3 est similaire à celui de la figure 2, si ce n'est qu'on utilise un sel soluble d'hydroxylamine (par exemple un sel d'acide fort) en tant qu'additif, cet additif étant ajouté en 2 pendant, mais de préférence après l'extinction de la chaux vive, et qu'en 5 on soumet la suspension de particules de carbonate récupérée en 4 à un traitement à l'eau chauffée par exemple au moyen de vapeur d'eau (plus de 120°C), ce traitement étant apte pour décomposer toutes traces d'hydroxylamine.The process represented in FIG. 2 is similar to that represented in FIG. 1, except that hydrazine is used as an additive and that a suspension of particles of calcium carbonate to treatment with an aqueous solution containing sodium hypochlorite, so as to remove all traces of hydrazine. By drying in 6, dry particles are then obtained. The process according to FIG. 3 is similar to that of FIG. 2, except that a soluble salt of hydroxylamine (for example a salt of strong acid) is used as an additive, this additive being added in 2 during, but preferably after the quicklime has died out, and in 5 the suspension of carbonate particles recovered in 4 is subjected to a treatment with heated water, for example by means of steam ( more than 120 ° C), this treatment being able to decompose all traces of hydroxylamine.
Des exemples de réalisation seront décrits ci-après : EXEMPLE 1 On a préparé un lait de chaux par réaction de chaux vive et d'eau. La chaux utilisée contenait 510 ppm de Fe exprimé sous forme de Fe203 et 125 ppm de Mn exprimé sous forme de MnO. La teneur en solide du lait était de 10% en poids par exemple. D'autres teneurs en hydroxyde de calcium sont possibles. Le pH du lait de chaux ainsi formé était d'environ 12. Après avoir ramené la température à 40°C on a ajouté des additifs suivant l'invention en une quantité correspondant à 0,2% du poids de chaux vive utilisée. On a ensuite fait barboter du CO2 dans le lait à raison de 20g COj heure/litre. Lors de ce barbotage de CO2, le pH a diminué pour atteindre une valeur d'environ 8-8,5 en fin d'opération de barbotage.Examples of embodiments will be described below: EXAMPLE 1 A milk of lime was prepared by reaction of quicklime and water. The lime used contained 510 ppm of Fe expressed in the form of Fe 2 0 3 and 125 ppm of Mn expressed in the form of MnO. The solid content of the milk was 10% by weight for example. Other contents of calcium hydroxide are possible. The pH of the lime milk thus formed was approximately 12. After having brought the temperature to 40 ° C., additives according to the invention were added in an amount corresponding to 0.2% of the weight of quicklime used. Was then bubbled CO 2 in the milk in an amount of 20g CO j hour / liter. During this CO 2 bubbling, the pH decreased to reach a value of approximately 8-8.5 at the end of the bubbling operation.
Le tableau suivant donne les caractéristiques des carbonates ainsi obtenus. The following table gives the characteristics of the carbonates thus obtained.
Ce tableau montre qu'en utilisant les additifs selon l'invention (HZ hydrazine hydrate N2H4.H2O, CHA chlorhydrate d'hydroxylamine NH2OH.HCI, SHA sulfate d'hydroxylamine (NH2OH)2.H2SO4), il a été possible par rapport aux particules de référence (sans additif) d'accroître la blancheur des particules d'environ 2 points, tout en réduisant l'indice de jaune de celles-ci d'au moins un point. En utilisant d'autres additifs tels que le tétrahydroborure de sodium (THB), il n'a pas été possible d'obtenir un tel accroissement de blancheur, combiné avec un tel abaissement de jaune.This table shows that by using the additives according to the invention (HZ hydrazine hydrate N 2 H 4 .H 2 O, CHA hydroxylamine hydrochloride NH 2 OH.HCI, SHA hydroxylamine sulfate (NH 2 OH) 2 .H 2 SO 4 ), it was possible compared to the reference particles (without additive) to increase the whiteness of the particles by approximately 2 points, while reducing the yellow index of these by at least one point . By using other additives such as sodium tetrahydroboride (THB), it was not possible to obtain such an increase in whiteness, combined with such a reduction in yellowness.
L'indice de blancheur mesuré à 457 nm (R 457) et l'indice de jaune (I.J.) ont été mesurés sur un appareil Elrepho 2000 de DATACOLOR.The whiteness index measured at 457 nm (R 457) and the yellowness index (I.J.) were measured on an Elrepho 2000 device from DATACOLOR.
Le diamètre moyen en poids (d50) est exprimé en μm. EXEMPLE 2The mean diameter by weight (d 50 ) is expressed in μm. EXAMPLE 2
On a répété l'exemple 1, si ce n'est qu'on a utilisé des chaux vives présentant des teneurs en Fe et en Mn (exprimées en Fe203 et MnO) différentes, et qu'on a utilisé l'hydrazine comme additif à raison de 0,2% en poids de chaux vive. Le tableau suivant donne l'indice de blancheur des particules de carbonate de calcium préparées sans hydrazine (R457 référence) et avec hydrazine (R457 hydrazine). Example 1 was repeated, except that quicklime with different Fe and Mn contents (expressed as Fe 2 0 3 and MnO) was used, and hydrazine was used as an additive in an amount of 0.2% by weight of quicklime. The following table gives the whiteness index of the calcium carbonate particles prepared without hydrazine (R457 reference) and with hydrazine (R457 hydrazine).
EXEMPLE 3EXAMPLE 3
On a répété l'exemple 2, si ce n'est qu'on a utilisé 0,1% d'hydrazine.Example 2 was repeated except that 0.1% hydrazine was used.
Le tableau suivant donne l'indice de blancheur des particules de carbonate de calcium préparées sans additif (R457 référence) et avec hydrazine (R457 HZ).The following table gives the whiteness index of the particles of calcium carbonate prepared without additive (R457 reference) and with hydrazine (R457 HZ).
Pour éliminer toute trace d'hydrazine dans les particules de carbonate, on peut soumettre les particules à un traitement au moyen d'une solution aqueuse contenant de l'hypochlorite de sodium.To remove all traces of hydrazine in the carbonate particles, the particles can be subjected to treatment with an aqueous solution containing sodium hypochlorite.
EXEMPLE 4EXAMPLE 4
On a répété l'exemple 2, si ce n'est qu'on a utilisé une chaux vive contenant 910 ppm de Fe exprimé sous forme de Fe2O3 et 175 ppm de Mn exprimé sous forme de MnO. Les additifs utilisés étaient l'hydrazine (HZ) à raison de 0,1 et 0,2% du poids de chaux vive, le chlorhydrate d'hydroxylamine (CHA) à raison de 0,1 et 0,2% du poids de chaux vive, le sulfate d'hydroxylamine (SHA) à raison de 0,2% du poids de chaux vive, et des mélanges de ces additifs. Le tableau suivant donne l'indice de blancheur et l'indice de jaune des particules de carbonate de calcium de diamètre moyen compris entre 2 et 2,5 μm.Example 2 was repeated, except that a quicklime containing 910 ppm of Fe expressed in the form of Fe 2 O 3 and 175 ppm of Mn expressed in the form of MnO was used. The additives used were hydrazine (HZ) at 0.1 and 0.2% by weight of quicklime, hydroxylamine hydrochloride (CHA) at 0.1 and 0.2% by weight of lime quicklime, hydroxylamine sulfate (SHA) at 0.2% by weight of quicklime, and mixtures of these additives. The following table gives the whiteness index and the yellowness index of calcium carbonate particles with an average diameter of between 2 and 2.5 μm.
On a également effectué des essais en utilisant comme matière de départ de la dolomite cuite (CaO-MgO) au lieu de CaO. On a observé de manière similaire une blancheur plus importante des particules de carbonate et une atténuation de l'aspect jaune.Trials have also been performed using cooked dolomite (CaO-MgO) as the starting material instead of CaO. A similar whiteness of the carbonate particles and a reduction in the yellow appearance were similarly observed.
Les particules de carbonate de calcium produites par le procédé suivant l'invention, en particulier les particules présentant :The particles of calcium carbonate produced by the process according to the invention, in particular the particles having:
* une teneur en Mn exprimée en MnO comprise entre 80 ppm et 500 ppm, de préférence comprise entre 90 et 250 ppm, plus précisément entre 100 et 200 ppm,an Mn content expressed as MnO of between 80 ppm and 500 ppm, preferably of between 90 and 250 ppm, more precisely between 100 and 200 ppm,
* une teneur en Fe exprimée en Fe2O3 comprise entre 500 ppm et 2000 ppm, de préférence inférieure à 1000 ppm,* an Fe content expressed as Fe 2 O 3 of between 500 ppm and 2000 ppm, preferably less than 1000 ppm,
* un diamètre moyen en poids inférieur à 5 μm, de préférence inférieure à 3 μm,* a mean diameter by weight of less than 5 μm, preferably less than 3 μm,
* un indice de blancheur mesuré à 457 nm supérieur ou égal à 95, mais inférieur à 99, et* a whiteness index measured at 457 nm greater than or equal to 95, but less than 99, and
* un indice de jaune inférieur ou égal à 1 ,5, mais supérieur à 0,5 trouvent de nombreuses applications en tant qu'additifs pour peintures, plastiques, caoutchoucs, colle, papiers, etc. II en est de même pour les particules de carbonate de calcium et de magnésium produites par le procédé suivant l'invention, en particulier celles présentant : * a yellowness index less than or equal to 1.5, but greater than 0.5 finds many applications as additives for paints, plastics, rubbers, glue, papers, etc. It is the same for the particles of calcium and magnesium carbonate produced by the process according to the invention, in particular those having:
* une teneur en Mn exprimée en MnO comprise entre 50 ppm et 500 ppm, de préférence comprise entre 90 et 250 ppm, plus précisément entre 100 et 200 ppm,an Mn content expressed as MnO of between 50 ppm and 500 ppm, preferably of between 90 and 250 ppm, more precisely between 100 and 200 ppm,
* une teneur en Fe exprimée en Fe2O3 inférieure à 2000 ppm, de préférence inférieure à 1000 ppm,* a Fe content expressed as Fe 2 O 3 of less than 2000 ppm, preferably less than 1000 ppm,
* et des valeurs de diamètre moyen en poids, d'indice de blancheur et d'indice de jaune, telles qu'indiquées ci-dessus pour les particules de carbonate de calcium suivant l'invention. * and values of average diameter by weight, whiteness index and yellow index, as indicated above for the calcium carbonate particles according to the invention.

Claims

REVENDICATIONS
1. Procédé de fabrication de particules de carbonate de calcium et/ou de carbonate de calcium et de magnésium, dans lequel on traite un milieu aqueux de pH basique et contenant du Ca(OH)2 et/ou du Ca(OH)2-Mg(OH)2 en y injectant du C02 gazeux pour former du carbonate de calcium et/ou du carbonate de calcium et de magnésium, et dans lequel on récupère les particules de carbonate formées, caractérisé en ce qu'on effectue le traitement du milieu aqueux en présence d'au moins un additif choisi parmi le groupe constitué de l'hydrazine, de l'hydroxylamine, des sels solubles d'hydroxylamine, et de leurs mélanges.1. Method for manufacturing particles of calcium carbonate and / or calcium carbonate and magnesium, in which an aqueous medium of basic pH and containing Ca (OH) 2 and / or Ca (OH) 2 is treated - Mg (OH) 2 by injecting C0 2 gas therein to form calcium carbonate and / or calcium and magnesium carbonate, and in which the carbonate particles formed are recovered, characterized in that the treatment of the aqueous medium in the presence of at least one additive chosen from the group consisting of hydrazine, hydroxylamine, soluble salts of hydroxylamine, and their mixtures.
2. Procédé suivant la revendication 1 , caractérisé en ce que ledit milieu aqueux contient une quantité dudit additif correspondant à 0,035 à 5% en poids de Ca(OH)2 et/ou de Ca(OH)2-Mg(OH)2. 2. Method according to claim 1, characterized in that said aqueous medium contains an amount of said additive corresponding to 0.035 to 5% by weight of Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 .
3. Procédé suivant la revendication 1 ou 2, caractérisé en ce qu'on détermine la teneur en Mn du Ca(OH)2 et ou du Ca(OH)2- Mg(OH)2 et en ce qu'on effectue le traitement du milieu aqueux en présence d'au moins un additif susdit de façon que ledit milieu aqueux contienne de 1 à 8 moles, de préférence de 2 à 6 moles, dudit au moins un additif par mole de Mn.3. Method according to claim 1 or 2, characterized in that one determines the Mn content of Ca (OH) 2 and or of Ca (OH) 2 - Mg (OH) 2 and in that the treatment is carried out aqueous medium in the presence of at least one aforementioned additive so that said aqueous medium contains from 1 to 8 moles, preferably from 2 to 6 moles, of said at least one additive per mole of Mn.
4. Procédé suivant l'une des revendication 1 à 3, caractérisé en ce qu'on effectue ledit traitement sous une pression supérieure à la pression atmosphérique, de préférence sous une pression comprise entre 1.2.105 Pa et 10.105 Pa. 4. Method according to one of claims 1 to 3, characterized in that said treatment is carried out under a pressure greater than atmospheric pressure, preferably under a pressure between 1.2.10 5 Pa and 10.10 5 Pa.
5. Procédé suivant la revendication 4, caractérisé en ce qu'on effectue le traitement à une température comprise entre 10 et 100°C.5. Method according to claim 4, characterized in that the treatment is carried out at a temperature between 10 and 100 ° C.
6. Procédé suivant l'une quelconque des revendications précédentes, caractérisé en ce qu'on soumet les particules de carbonate formées à un traitement pour décomposer ledit au moins un additif. 6. Method according to any one of the preceding claims, characterized in that the carbonate particles formed are subjected to a treatment to decompose said at least one additive.
7. Procédé suivant la revendication 6, caractérisé en ce qu'on récupère les particules de carbonate formées et en ce qu'on les soumet à un traitement pour décomposer ledit au moins un additif encore présent dans les particules. 7. Method according to claim 6, characterized in that the carbonate particles formed are recovered and in that they are subjected to a treatment to decompose said at least one additive still present in the particles.
8. Procédé suivant la revendication 6 ou 7, caractérisé en ce qu'on soumet les particules de carbonate formées ou récupérées, de préférence sous forme de suspension, à un traitement avec de l'hypochlorite et/ou avec de l'eau présentant une température supérieure à 70°C. 8. Method according to claim 6 or 7, characterized in that the carbonate particles formed or recovered, preferably in the form of a suspension, are subjected to a treatment with hypochlorite and / or with water having a temperature above 70 ° C.
9. Procédé suivant l'une quelconque des revendications précédentes, caractérisé en ce qu'après le traitement du milieu aqueux par injection de CO2, on sépare les particules de carbonate formées du milieu, et on réutilise au moins partiellement le milieu pour former un milieu aqueux contenant du Ca(OH)2 et/ou du Ca(OH)2-Mg(OH)2 et au moins un desdits additifs.9. Method according to any one of the preceding claims, characterized in that after the treatment of the aqueous medium by injection of CO 2 , the carbonate particles formed are separated from the medium, and the medium is at least partially reused to form a aqueous medium containing Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 and at least one of said additives.
10. Procédé suivant l'une des revendications précédentes, caractérisé en ce que le milieu aqueux contenant du Ca(OH)2 et/ou du Ca(OH)2-Mg(OH)2 est formé par extinction de CaO et/ou CaO-MgO par un milieu aqueux, l'additif étant ajouté audit milieu aqueux avant, pendant et/ou après l'extinction.10. Method according to one of the preceding claims, characterized in that the aqueous medium containing Ca (OH) 2 and / or Ca (OH) 2 -Mg (OH) 2 is formed by quenching CaO and / or CaO -MgO by an aqueous medium, the additive being added to said aqueous medium before, during and / or after extinction.
11. Particules de carbonate de calcium présentant une teneur en Mn exprimée en MnO comprise entre 80 ppm et 500 ppm, une teneur en Fe exprimée en Fe203 comprise entre 500 ppm et 2000 ppm, un diamètre moyen en poids inférieur à 5 μm, un indice de blancheur mesuré à 457 nm supérieur ou égal à 95, mais inférieur à 99, et un indice de jaune inférieur ou égal à 1,5, mais supérieur à 0,5.11. Calcium carbonate particles having an Mn content expressed in MnO of between 80 ppm and 500 ppm, an Fe content expressed in Fe 2 0 3 of between 500 ppm and 2000 ppm, an average diameter by weight of less than 5 μm , a whiteness index measured at 457 nm greater than or equal to 95, but less than 99, and a yellow index less than or equal to 1.5, but greater than 0.5.
12. Particules de carbonate de calcium et de magnésium présentant une teneur en Mn exprimée en MnO comprise entre 50 ppm et 500 ppm, une teneur en Fe exprimée en Fe203 inférieure à 2000 ppm, un diamètre moyen en poids inférieur à 5 μm, un indice de blancheur mesuré à 457 nm supérieur ou égal à 95, mais inférieur à 99, et un indice de jaune inférieur ou égal à 1,5, mais supérieur à 0,5. 12. Particles of calcium and magnesium carbonate having an Mn content expressed in MnO of between 50 ppm and 500 ppm, an Fe content expressed in Fe 2 0 3 of less than 2000 ppm, an average diameter by weight of less than 5 μm , a whiteness index measured at 457 nm greater than or equal to 95, but less than 99, and a yellow index less than or equal to 1.5, but greater than 0.5.
EP98952452A 1997-11-06 1998-11-06 Method for making calcium carbonate Withdrawn EP1028916A1 (en)

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BE9700894A BE1011538A4 (en) 1997-11-06 1997-11-06 METHOD FOR MANUFACTURING Calcium Carbonate.
BE9700894 1997-11-06
PCT/BE1998/000171 WO1999024361A1 (en) 1997-11-06 1998-11-06 Method for making calcium carbonate

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US4900533A (en) * 1981-02-24 1990-02-13 English Clays Lovering Pochin & Company Alkaline earth metal carbonates
DE3510695A1 (en) * 1985-03-23 1986-09-25 Hoechst Ag, 6230 Frankfurt METHOD FOR PRODUCING FINE-PARTICLE CALCIUM CARBONATE OF HIGH PURITY AND HIGH WHITE GRADE
CN85103821A (en) * 1985-05-13 1986-11-12 陈学廉 Increase the method for whiteness of low density calcium carbonate
EP0257458A3 (en) * 1986-08-22 1989-03-29 Akira Matsuzaki Scrubbing agent and process for producing the same
RO105941B1 (en) * 1990-04-20 1993-01-30 Centrul Chim Timisoara Preparation process of a calcium carbonate assortment of high purity and fine granulation
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JP3223589B2 (en) * 1992-07-20 2001-10-29 王子製紙株式会社 Method for producing light calcium carbonate

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