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WO2011141630A1 - Process for the preparation of gypsym - Google Patents

Process for the preparation of gypsym Download PDF

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Publication number
WO2011141630A1
WO2011141630A1 PCT/FI2011/050424 FI2011050424W WO2011141630A1 WO 2011141630 A1 WO2011141630 A1 WO 2011141630A1 FI 2011050424 W FI2011050424 W FI 2011050424W WO 2011141630 A1 WO2011141630 A1 WO 2011141630A1
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WO
WIPO (PCT)
Prior art keywords
calcium
sulphate
process according
hydrate
gypsum
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.)
Ceased
Application number
PCT/FI2011/050424
Other languages
French (fr)
Inventor
Tarja Turkki
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.)
Kemira Oyj
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Kemira Oyj
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Filing date
Publication date
Application filed by Kemira Oyj filed Critical Kemira Oyj
Publication of WO2011141630A1 publication Critical patent/WO2011141630A1/en
Anticipated expiration legal-status Critical
Ceased 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
    • C01F11/46—Sulfates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
    • 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
    • C01F11/20—Halides
    • C01F11/24—Chlorides
    • 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
    • C01F11/36—Nitrates
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/02—Compounds of alkaline earth metals or magnesium
    • C09C1/025—Calcium sulfates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
    • C01P2004/12—Particle morphology extending in one dimension, e.g. needle-like with a cylindrical shape
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/39—Particle morphology extending in three dimensions parallelepiped-like
    • 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
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 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

Definitions

  • the invention relates to a new process for producing gypsum having a regular, well-defined crystal structure.
  • Gypsum or calcium sulphate dihydrate occurs as a natural mineral or it is formed as a by-product of chemical processes, e.g. as phosphogypsum or flue gas gypsum.
  • it In order to refine the gypsum further by crystallizing the same, it must first be calcined into calcium sulphate hemihydrate (CaSO 4 1 ⁇ 2H 2 O), after which it may be hydrated back by dissolving the hemihydrate in water and precipitating to give pure gypsum.
  • Calcium sulphate may also occur in the form of anhydrite lacking crystal water (CaSO 4 ).
  • WO 01/05706 discloses a method of producing surgical grade calcium sulphate by forming an initial calcium sulphate dihydrate from synthetic constituents, dehydrating the initial calcium sulphate dihydrate to form calcium sulphate anhydrite and subsequently rehydrating the calcium sulphate anhydrite and allowing the calcium sulphate dihydrate to crystallize out.
  • the initial calcium sulphate dihydrate may be formed by mixing an aqueous solution of calcium and sulphate salts such that calcium sulphate dihydrate precipitates out. The dihydrate thus formed may be washed, and subsequently filtered, crushed and/or dried.
  • the initial calcium sulphate dihydrate may be formed by neutralizing lime with sulphuric acid. Summary of the invention
  • calcium sulphate dihydrate can be produced by simply mixing a water soluble calcium compound and a water soluble sulphate compound without the addition of free water. At least one of the compounds is in the form of a hydrate.
  • Fig. 1 shows scanning electron microscope (SEM) micrograph of calcium sulphate dihydrate produced from hydrate forms of sodium sulphate and calcium nitrate according to the present invention
  • Fig. 2 shows scanning electron microscope (SEM) micrograph of calcium sulphate dihydrate produced from hydrate forms of sodium sulphate and calcium chloride according to the present invention
  • SEM scanning electron microscope
  • Fig. 3 shows scanning electron microscope (SEM) micrograph of prior art calcium sulphate dihydrate.
  • a process for the preparation of gypsum comprising mixing a water soluble calcium compound and a water soluble sulphate compound together in the absence or in the essential absence of free water such that gypsum crystals precipitate, wherein at least one of the calcium and sulphate compounds is in the form of a hydrate.
  • the expression "in the absence or in the essential absence of free water” means that the calcium and sulphate compounds are introduced in dry solid form or introduced in a form where the calcium and sulphate compounds are predominantly in undissolved form.
  • the free water content should not exceed 10% by weight of the calcium and sulphate compounds. More preferably the free water content should not exceed 5% by weight of the calcium and sulphate compounds. Most preferably the calcium and sulphate compounds are free of free water.
  • the two starting materials i.e. the calcium compound and the sulphate compound are both provided as solid compounds.
  • the crystal water is released and the compounds are dissolved and react with each other to form a slurry of gypsum and another salt.
  • gypsum is water insoluble the other salt can be removed by washing with water.
  • the amount of crystal water in the calcium and/or sulphate compounds has to be greater than the dihydrate amount in the gypsum.
  • the formed gypsum crystals preferably have a size of at most 5 ⁇ , preferably between 0.1 and 5 ⁇ , more preferably between 0.1 and 4 ⁇ and most preferably between 0.2 and 4 ⁇ .
  • the size of the particles may also be between 0.1 and 2 ⁇ , preferably between 0.2 and 2 ⁇ .
  • the crystals are rod shaped or rhombo- hedral. During storage the crystal size is slightly increased.
  • both the calcium and sulphate compounds are in the form of a hydrate.
  • the water solubility of the calcium and sulphate compounds is at least 100 g/l, preferably at least 200 g/l, determined at a temperature of 25°C.
  • Suitable calcium compounds include organic salts, such as calcium acetate and hydrate forms thereof, and inorganic salts, such as calcium bromide, calcium chloride, calcium chromate, calcium iodide, calcium nitrate and hydrate forms thereof.
  • Especially suitable calcium compounds include (the solubility in water at 25°C is in brackets) calcium acetate dihydrate Ca(CH 3 COO)2'2H 2 O (340 g/l), calcium bro- mide hexahydrate CaBr 2 6H 2 O (1530 g/l), calcium chloride hexahydrate CaCI 2 -6H 2 O (830 g/l), calcium chromate dihydrate CaCrO 4 2H 2 O (170 g/l), calcium iodide Cal 2 (2100 g/l) and calcium nitrate tetrahydrate Ca(NO 3 ) 2 -4H 2 O (1380 g/l).
  • Suitable sulphate compounds include inorganic salts, such as ammonium sulphate, magnesium sulphate, potassium sulphate, sodium sulphate and hydrate forms thereof.
  • Especially suitable sulphate compounds include (the solubility in water at 25°C is in brackets) ammonium sulphate (760 g/l), magnesium sulphate heptahydrate (NH 4 ) 2 SO 4 -7H 2 O (364 g/l), potassium sulphate K 2 SO 4 (120 g/l), sodium sulphate Na 2 SO 4 , sodium sulphate heptahydrate Na 2 SO 4 7H 2 O and sodium sulphate deca- hydrate Na 2 SO 4 OH 2 O (280 g/l).
  • ammonium sulphate 760 g/l
  • magnesium sulphate heptahydrate NH 4 ) 2 SO 4 -7H 2 O (364 g/l)
  • potassium sulphate K 2 SO 4 120 g/l
  • sodium sulphate Na 2 SO 4 sodium sulphate heptahydrate Na 2 SO 4 7H 2 O
  • sodium sulphate deca- hydrate Na 2 SO 4 OH 2 O 280
  • Preferred combinations of calcium and sulphate salts include calcium nitrate or calcium chloride in hydrate form, such as calcium nitrate tetrahydrate or calcium chloride hexahydrate and sodium sulphate or sodium sulphate in hydrate form, such as sodium sulphate heptahydrate or sodium sulphate decahydrate.
  • the molar ratio of calcium to sulphate in the calcium and sulphate compounds is typically from 0.7 to 1 .3:1 , preferably from 0.8 to 1 .2:1 , more preferably from 0.9 to 1 .1 :1 , and most preferably the compounds are introduced in stoichiometric amounts.
  • the formed gypsum crystals may be filtered and/or washed and filtered.
  • the process of the invention is typically carried out at a temperature of about 10-40°C, preferably at ambient temperature.
  • the present invention makes it possible to produce highly pure gypsum which can be used for example as pigments in paints and lacquers etc., in cosmetics, in pharmaceuticals and in food industry.
  • the produced gypsum may also be used as a filler pigment or coating pigment in paper products.
  • Calcium sulphate dihydrate was prepared from fluidized bed calcined ⁇ -calcium sulphate hemihydrate according to the process described in WO 2008/092991 .
  • the crystal structure is shown in Fig. 3.
  • the crystals are flat and show a large variation in size.
  • Example 1 was repeated with the exception that calcium chloride hexahydrate was used in stead of calcium nitrate tetrahydrate.
  • Rod shaped calcium sulphate di- hydrate crystals were formed. The crystal structure is shown in Fig. 2, wherein the rod shaped crystals having a length of about 2 ⁇ are calcium sulphate dihydrate and the big square like crystals are sodium chloride also formed in the reaction.
  • Example 4 The brightness of the gypsum of Example 1 and Reference example 1 were measured.
  • the gypsum of Example 1 gave the ISO brightness of 92% and the gypsum of Reference example 1 gave the ISO brightness of 91 .65%.
  • the application test results show that the gypsum of Example 1 gave a higher brightness than the gypsum of Reference example 1 .

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Abstract

The invention relates to a process for the preparation of gypsum comprising mixing a water soluble calcium compound and a water soluble sulphate compound together in the absence or in the essential absence of free water such that gypsum crystals precipitate, wherein at least one of the calcium and sulphate compounds is in the form of a hydrate.

Description

PROCESS FOR THE PREPARATION OF GYPSUM
Technical field
The invention relates to a new process for producing gypsum having a regular, well-defined crystal structure.
Background of the invention
Gypsum or calcium sulphate dihydrate (CaSO4-2H2O) occurs as a natural mineral or it is formed as a by-product of chemical processes, e.g. as phosphogypsum or flue gas gypsum. In order to refine the gypsum further by crystallizing the same, it must first be calcined into calcium sulphate hemihydrate (CaSO4 ½H2O), after which it may be hydrated back by dissolving the hemihydrate in water and precipitating to give pure gypsum. Calcium sulphate may also occur in the form of anhydrite lacking crystal water (CaSO4). WO 01/05706 discloses a method of producing surgical grade calcium sulphate by forming an initial calcium sulphate dihydrate from synthetic constituents, dehydrating the initial calcium sulphate dihydrate to form calcium sulphate anhydrite and subsequently rehydrating the calcium sulphate anhydrite and allowing the calcium sulphate dihydrate to crystallize out. The initial calcium sulphate dihydrate may be formed by mixing an aqueous solution of calcium and sulphate salts such that calcium sulphate dihydrate precipitates out. The dihydrate thus formed may be washed, and subsequently filtered, crushed and/or dried. Alternatively the initial calcium sulphate dihydrate may be formed by neutralizing lime with sulphuric acid. Summary of the invention
According to the present invention it was surprisingly found that calcium sulphate dihydrate can be produced by simply mixing a water soluble calcium compound and a water soluble sulphate compound without the addition of free water. At least one of the compounds is in the form of a hydrate. Brief description of the drawings
Fig. 1 shows scanning electron microscope (SEM) micrograph of calcium sulphate dihydrate produced from hydrate forms of sodium sulphate and calcium nitrate according to the present invention, Fig. 2 shows scanning electron microscope (SEM) micrograph of calcium sulphate dihydrate produced from hydrate forms of sodium sulphate and calcium chloride according to the present invention, and
Fig. 3 shows scanning electron microscope (SEM) micrograph of prior art calcium sulphate dihydrate.
Detailed description of the invention
According to the present invention there is provided a process for the preparation of gypsum comprising mixing a water soluble calcium compound and a water soluble sulphate compound together in the absence or in the essential absence of free water such that gypsum crystals precipitate, wherein at least one of the calcium and sulphate compounds is in the form of a hydrate.
The expression "in the absence or in the essential absence of free water" means that the calcium and sulphate compounds are introduced in dry solid form or introduced in a form where the calcium and sulphate compounds are predominantly in undissolved form. Preferably the free water content should not exceed 10% by weight of the calcium and sulphate compounds. More preferably the free water content should not exceed 5% by weight of the calcium and sulphate compounds. Most preferably the calcium and sulphate compounds are free of free water.
The two starting materials, i.e. the calcium compound and the sulphate compound are both provided as solid compounds. As the reaction starts and proceeds the crystal water is released and the compounds are dissolved and react with each other to form a slurry of gypsum and another salt. As gypsum is water insoluble the other salt can be removed by washing with water. The amount of crystal water in the calcium and/or sulphate compounds has to be greater than the dihydrate amount in the gypsum.
Due to the absence of free water the size of the formed gypsum crystals is kept small. The formed gypsum crystals preferably have a size of at most 5 μιτι, preferably between 0.1 and 5 μιτι, more preferably between 0.1 and 4 μιτι and most preferably between 0.2 and 4 μιτι. The size of the particles may also be between 0.1 and 2 μιτι, preferably between 0.2 and 2 μιτι. The crystals are rod shaped or rhombo- hedral. During storage the crystal size is slightly increased.
In one embodiment of the invention, both the calcium and sulphate compounds are in the form of a hydrate.
Preferably the water solubility of the calcium and sulphate compounds is at least 100 g/l, preferably at least 200 g/l, determined at a temperature of 25°C. Suitable calcium compounds include organic salts, such as calcium acetate and hydrate forms thereof, and inorganic salts, such as calcium bromide, calcium chloride, calcium chromate, calcium iodide, calcium nitrate and hydrate forms thereof.
Especially suitable calcium compounds include (the solubility in water at 25°C is in brackets) calcium acetate dihydrate Ca(CH3COO)2'2H2O (340 g/l), calcium bro- mide hexahydrate CaBr2 6H2O (1530 g/l), calcium chloride hexahydrate CaCI2-6H2O (830 g/l), calcium chromate dihydrate CaCrO4 2H2O (170 g/l), calcium iodide Cal2 (2100 g/l) and calcium nitrate tetrahydrate Ca(NO3)2-4H2O (1380 g/l).
Suitable sulphate compounds include inorganic salts, such as ammonium sulphate, magnesium sulphate, potassium sulphate, sodium sulphate and hydrate forms thereof.
Especially suitable sulphate compounds include (the solubility in water at 25°C is in brackets) ammonium sulphate (760 g/l), magnesium sulphate heptahydrate (NH4)2SO4-7H2O (364 g/l), potassium sulphate K2SO4 (120 g/l), sodium sulphate Na2SO4, sodium sulphate heptahydrate Na2SO4 7H2O and sodium sulphate deca- hydrate Na2SO4 OH2O (280 g/l). The solubility of sodium sulphate and sodium sulphate heptahydrate are probably the same as of the sodium sulphate decahy- drate.
Preferred combinations of calcium and sulphate salts include calcium nitrate or calcium chloride in hydrate form, such as calcium nitrate tetrahydrate or calcium chloride hexahydrate and sodium sulphate or sodium sulphate in hydrate form, such as sodium sulphate heptahydrate or sodium sulphate decahydrate. The molar ratio of calcium to sulphate in the calcium and sulphate compounds is typically from 0.7 to 1 .3:1 , preferably from 0.8 to 1 .2:1 , more preferably from 0.9 to 1 .1 :1 , and most preferably the compounds are introduced in stoichiometric amounts. The formed gypsum crystals may be filtered and/or washed and filtered.
The process of the invention is typically carried out at a temperature of about 10-40°C, preferably at ambient temperature.
The present invention makes it possible to produce highly pure gypsum which can be used for example as pigments in paints and lacquers etc., in cosmetics, in pharmaceuticals and in food industry. The produced gypsum may also be used as a filler pigment or coating pigment in paper products.
EXAMPLES
In the following the invention will be illustrated in more detail by means of exam- pies. The purpose of the examples is not to restrict the scope of the claims. In this specification the percentages refer to % by weight unless otherwise specified. The samples were imaged using SEM microscope FEI XL 30 FEG.
Reference example 1
Calcium sulphate dihydrate was prepared from fluidized bed calcined β-calcium sulphate hemihydrate according to the process described in WO 2008/092991 . The crystal structure is shown in Fig. 3. The crystals are flat and show a large variation in size.
Example 1
1 .38 mols of sodium sulphate decahydrate (444 g) and calcium nitrate tetrahydrate (326 g) were measured and placed in the mixing bowl of Hobart N50CE mixer. No water was added. Mixing was started and when the reaction started water was freed from crystals and white calcium sulphate dihydrate was formed. Mixing was stopped when soft white paste was formed. Solids content of the paste was about 61 % and the calcium sulphate dihydrate content was 30.8%. The crystal structure is shown in Fig. 1 , wherein the rhombohedral crystals having a length of about 1 μιτι are calcium sulphate dihydrate. Example 2
Example 1 was repeated with the exception that calcium chloride hexahydrate was used in stead of calcium nitrate tetrahydrate. Rod shaped calcium sulphate di- hydrate crystals were formed. The crystal structure is shown in Fig. 2, wherein the rod shaped crystals having a length of about 2 μιτι are calcium sulphate dihydrate and the big square like crystals are sodium chloride also formed in the reaction.
Example 3
Application tests were carried out by using the gypsum of Example 1 and Refer- ence example 1 as filler. Hand sheets were made using Rapid-Kothen laboratory sheet former, eucalyptus kraft pulp (SR about 30), Fennopol 3400R (cationic poly- acrylamide) as retention aid and the tested fillers. Target basis weight was 60 g/m2 and filler level was 25%. The tensile strength was measured using L&W tensile tester and ISO standard 1924-3. The gypsum filler of Example 1 gave the tensile strength index of 25.8 kNm/kg and the gypsum filler of Reference example 1 gave the tensile strength index of 23.9 kNm/kg. Thus, the application test results show that the filler of Example 1 gave a higher tensile strength than the filler of Reference example 1 .
Example 4 The brightness of the gypsum of Example 1 and Reference example 1 were measured. The gypsum of Example 1 gave the ISO brightness of 92% and the gypsum of Reference example 1 gave the ISO brightness of 91 .65%. Thus, the application test results show that the gypsum of Example 1 gave a higher brightness than the gypsum of Reference example 1 .

Claims

Claims
1 . A process for the preparation of gypsum comprising mixing a water soluble calcium compound and a water soluble sulphate compound together in the absence or in the essential absence of free water such that gypsum crystals precipi- tate, wherein at least one of the calcium and sulphate compounds is in the form of a hydrate.
2. The process according to claim 1 , wherein the formed gypsum crystals have a size of at most 5 μιτι, preferably between 0.1 and 5 μιτι, more preferably between 0.1 and 4 μιτι, and most preferably between 0.2 and 4 μιτι.
3. The process according to claim 1 or 2, wherein both the calcium and sulphate compounds are in the form of a hydrate.
4. The process according to any of claims 1 to 3, wherein the water solubility of the calcium and sulphate compounds is at least 100 g/l.
5. The process according to any of claims 1 to 4, wherein the calcium com- pound comprises an organic salt, such as calcium acetate or a hydrate form thereof, or an inorganic salt, such as calcium bromide, calcium chloride, calcium chromate, calcium iodide, calcium nitrate or a hydrate form thereof.
6. The process according claim 5, wherein the calcium compound comprises calcium acetate dihydrate, calcium bromide hexahydrate, calcium chloride hexa- hydrate, calcium chromate dihydrate, calcium iodide or calcium nitrate tetrahydrate.
7. The process according to any of claims 1 to 6, wherein the sulphate compound comprises an inorganic salt, such as ammonium sulphate, magnesium sulphate, potassium sulphate, sodium sulphate or a hydrate form thereof.
8. The process according to claim 7, wherein the sulphate compound comprises ammonium sulphate, magnesium sulphate heptahydrate, potassium sulphate, sodium sulphate, sodium sulphate heptahydrate or sodium sulphate decahydrate.
9. The process according to any of claims 1 to 8, wherein the calcium compound is calcium nitrate or calcium chloride in hydrate form, such as calcium ni- trate tetrahydrate or calcium chloride hexahydrate, and the sulphate compound is sodium sulphate or sodium sulphate in hydrate form, such as sodium sulphate heptahydrate or decahydrate.
10. The process according to any of claims 1 to 9, wherein the formed gypsum crystals are filtered and/or washed and filtered.
PCT/FI2011/050424 2010-05-10 2011-05-09 Process for the preparation of gypsym Ceased WO2011141630A1 (en)

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FI20105500A FI20105500A7 (en) 2010-05-10 2010-05-10 Process for the preparation of gypsym
FI20105500 2010-05-10

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE562385C (en) * 1930-07-12 1932-10-25 Peter Spence & Sons Ltd Process for the production of anhydrous, finely divided calcium sulfate
WO2001005706A1 (en) 1999-07-16 2001-01-25 Biocomposites Limited Method of producing surgical grade calcium sulphate
US6517790B1 (en) * 2002-03-18 2003-02-11 Alcoa Inc. Converting fluorgyp to calcium sulfate
WO2008092991A2 (en) 2007-02-02 2008-08-07 Kemira Oyj A process for producing gypsum

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE562385C (en) * 1930-07-12 1932-10-25 Peter Spence & Sons Ltd Process for the production of anhydrous, finely divided calcium sulfate
WO2001005706A1 (en) 1999-07-16 2001-01-25 Biocomposites Limited Method of producing surgical grade calcium sulphate
US6517790B1 (en) * 2002-03-18 2003-02-11 Alcoa Inc. Converting fluorgyp to calcium sulfate
WO2008092991A2 (en) 2007-02-02 2008-08-07 Kemira Oyj A process for producing gypsum

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FI20105500A7 (en) 2011-11-11
FI20105500A0 (en) 2010-05-10

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