AU1150583A - Conversion of fluoroanhydrite to plaster - Google Patents
Conversion of fluoroanhydrite to plasterInfo
- Publication number
- AU1150583A AU1150583A AU11505/83A AU1150583A AU1150583A AU 1150583 A AU1150583 A AU 1150583A AU 11505/83 A AU11505/83 A AU 11505/83A AU 1150583 A AU1150583 A AU 1150583A AU 1150583 A AU1150583 A AU 1150583A
- Authority
- AU
- Australia
- Prior art keywords
- fluoroanhydrite
- calcium sulfate
- siliceous material
- water
- fluorogypsum
- 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.)
- Abandoned
Links
- 238000006243 chemical reaction Methods 0.000 title claims description 9
- 239000011505 plaster Substances 0.000 title description 7
- 239000000463 material Substances 0.000 claims description 43
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims description 30
- 239000010440 gypsum Substances 0.000 claims description 30
- 229910052602 gypsum Inorganic materials 0.000 claims description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 19
- 230000008569 process Effects 0.000 claims description 19
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 16
- 238000004519 manufacturing process Methods 0.000 claims description 12
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 7
- 239000005909 Kieselgur Substances 0.000 claims description 6
- 239000011398 Portland cement Substances 0.000 claims description 6
- 229910000040 hydrogen fluoride Inorganic materials 0.000 claims description 6
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 5
- 239000010451 perlite Substances 0.000 claims description 4
- 235000019362 perlite Nutrition 0.000 claims description 4
- 239000004115 Sodium Silicate Substances 0.000 claims description 3
- 239000004111 Potassium silicate Substances 0.000 claims description 2
- 239000000378 calcium silicate Substances 0.000 claims description 2
- 229910052918 calcium silicate Inorganic materials 0.000 claims description 2
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 claims description 2
- 229910052913 potassium silicate Inorganic materials 0.000 claims description 2
- 235000019353 potassium silicate Nutrition 0.000 claims description 2
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims 1
- 239000011575 calcium Substances 0.000 claims 1
- 229910052791 calcium Inorganic materials 0.000 claims 1
- NNHHDJVEYQHLHG-UHFFFAOYSA-N potassium silicate Chemical compound [K+].[K+].[O-][Si]([O-])=O NNHHDJVEYQHLHG-UHFFFAOYSA-N 0.000 claims 1
- 238000001354 calcination Methods 0.000 description 21
- 239000012535 impurity Substances 0.000 description 15
- 239000000654 additive Substances 0.000 description 14
- 239000000047 product Substances 0.000 description 10
- 238000007792 addition Methods 0.000 description 9
- 230000036571 hydration Effects 0.000 description 9
- 238000006703 hydration reaction Methods 0.000 description 9
- 239000013078 crystal Substances 0.000 description 7
- 239000006185 dispersion Substances 0.000 description 7
- 238000005406 washing Methods 0.000 description 7
- 230000000996 additive effect Effects 0.000 description 6
- 239000000356 contaminant Substances 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 238000011282 treatment Methods 0.000 description 5
- 150000004683 dihydrates Chemical group 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- -1 [AlF-H2O-2] Chemical class 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 229910052731 fluorine Inorganic materials 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 239000004571 lime Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 230000004044 response Effects 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- 235000011941 Tilia x europaea Nutrition 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052925 anhydrite Inorganic materials 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 229910001634 calcium fluoride Inorganic materials 0.000 description 2
- ZOMBKNNSYQHRCA-UHFFFAOYSA-J calcium sulfate hemihydrate Chemical compound O.[Ca+2].[Ca+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZOMBKNNSYQHRCA-UHFFFAOYSA-J 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 230000002301 combined effect Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910002012 Aerosil® Inorganic materials 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910052910 alkali metal silicate Inorganic materials 0.000 description 1
- 229910052915 alkaline earth metal silicate Inorganic materials 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000008119 colloidal silica Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000010436 fluorite Substances 0.000 description 1
- 125000001153 fluoro group Chemical group F* 0.000 description 1
- APURLPHDHPNUFL-UHFFFAOYSA-M fluoroaluminum Chemical compound [Al]F APURLPHDHPNUFL-UHFFFAOYSA-M 0.000 description 1
- 229910021485 fumed silica Inorganic materials 0.000 description 1
- 239000011507 gypsum plaster Substances 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 235000012204 lemonade/lime carbonate Nutrition 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 238000005453 pelletization Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 230000007096 poisonous effect Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
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
- C01F11/466—Conversion of one form of calcium sulfate to another
-
- 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
- C04B11/00—Calcium sulfate cements
- C04B11/02—Methods and apparatus for dehydrating gypsum
- C04B11/024—Ingredients added before, or during, the calcining process, e.g. calcination modifiers
-
- 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
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/02—Granular materials, e.g. microballoons
- C04B14/04—Silica-rich materials; Silicates
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Civil Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Glass Compositions (AREA)
Description
Conversion of Fluoroanhydrite to Plaster
Background of the Invention Field of the Invention
This invention relates to a process for transforming fluoroanhydrite into gypsum plaster and gypsum wallboard products.
Flύororanhydrite is a by-product in the manufacture of hydrogen fluoride from the sulfuric acid treatment of fluorite (calcium fluoride). Historically, the fluoroanhydrite, which is contaminated with sulfuric acid, is neutralized with lime or calcium carbonate additions and allowed to hydrate naturally over a several year period of time while weathering in waste heaps. It had been hoped that upon weathering such materials would then be usable in the industrial manufacture of various products. This has not proven to be the case. Description of the Prior Art
Some early attempts to utilize the naturally weathered materials looked at the relationship of this material to Keenes cement (U.S. 1,304,148) and attempted to convert the
weathering anhydrite material directly to the dihydrate form by the inclusion of various hydration catalysts and accelerators. Such proposed means to convert this waste product into an industrially usable product have focused upon the quick setting or hardening of the anhydrite content into a dihydrate material in the presence of reactive silica compounds coupled with pozzolonic materials and lime. See for example U.S. Patent Nos. 2,060,127; 2,606,128; 2,608,491 and the like. There is little demand for such inorganic binders; the primary commercial usage for calcium sulfate materials being in the formation of gypsum wallboard.
In addition to residual acids, fluoroanhydrite contains other impurities. Fluoroanhydrite or fluorogypsum can contain up to 2-3% fluoride, probably derived from unreacted calcium fluoride, together with smaller quantities of unreacted soluble and insoluble silicofluorides. These fluorine impurity species, probably a fluoroaluminum complex anion such as [AlF-H2O-2], impede the practical commercial conversion of the stockpiled material into calcium sulfate hemihydrate. First, these impurities inhibit the hydration
of the fluoroanhydrite to gypsum. Secondly, they raise the calcining temperature for conversion of the fluorogypsum to stucco. Thirdly, they inhibit the setting of the stucco to a degree unreasonable for present day commercial wallboard formation and result in producing gypsum products of poor quality. Some of the residual fluoride species in the weathering stockpile material form compounds which are water soluble and may be washed away; while other species form water insoluble compounds that tend to co-crystallize with the dihydrate crystals being formed on weathering. These latter impurities, on attempts to convert the fluorogypsum to hemihydrate, cause extreme difficulties in the calcination conversion to hemihydrate and inhibit response of the formed stucco to set control agents. Further the stucco exhibits slow disintegration when mixed with gauging water. These are significant problems because all gypsum board lines employ set control agents as being critical in production rate and cost of production. Finally, stucco from such material exhibits low maximum rate of hydration and slow disintegration upon mixing with gauging water. This is critical in determining the strength of the set product. Natural gypsum, immediately after being calcined, characteristically
disintegrates to a large degree upon dispersion in water. This disintegration may be measured as a large increase in the particle surface area. When fluoroanhydrite is neutralized with lime and hydrated, the resulting fluorogypsum it has been found, after being calcined to a fluorostucco, disintegrates only to a small degree upon dispersion, and the degree of disintegration is further reduced upon exposure to humidity such that an aged fluorostucco approaches the unpredictable, erratic dispersion properties of aged natural stucco unsuitable for building plaster or gypsum wallboard usage. Summary of the Invention
It has now been found that by allowing a controlled gradual weathering of stockpiled waste fluoroanhydrite materials and calcination to calcium sulfate hemihydrate in the presence of a reactive silica, a truly industrially usable stucco is obtained. The impurities in fluorogypsum are present on the surfaces as well as throughout the crystal. Acid or water washing, particularly with grinding in between washings, is effective to remove the surface exposed impurities. Coupling this with calcination and hydration additives to remove co-crystalline impurities gives a combined effect making the material usable. The obtained fluorostucco has satisfactory calcination characteristics, rheological and physical properties customary to plaster made from natural gypsum rock when mixed with water and is suitable for formation into gypsum wallboard.
A part of the findings of the present invention is that while some of the fluorine and aluminum species contamination in by-product fluoroanhydrite can bo removed by careful washing during the various conversion stages, complex species are
trapped in the growing calcium sulfate crystal. By including reactive silicates during various stages of the processing, the crystallized species can either be inhibited in their growth and/or removed from the calcium sulfate crystals. Employing about 1-10% by weight of an active siliceous material in some manner frees the calcium sulfate from the poisonous fluoro and aluminum complex impurities that inhibit hydration of the fluoroanhydrite to gypsum, that inhibit subsequent calcination of the fluorogypsum to fluorostucco, that inhibit the setting action and strength development of the fluorostucco product. Description of the Preferred Embodiments
The starting material is a residue from the process of manufacturing hydrofluoric acid from fluorospar. Fluoroanhydrite fresh from the reactor may be treated by the process of this invention and then stored for gradual conversion. Alternatively, or in addition, weathered stockpile material containing fluorogypsum as well as fluoroanhydrite may be treated. Alternatively, or in addition, treatment may be carried out during calcination of the fluorogypsum to fluorostucco. Thus, in one preferred embodiment, hot fluoroanhydrite directly from the reactor may be blended with the reactive siliceous material and passed to briquetting or pelletizing apparatus for mixing with a suitable binder while being formed into briquettes or pellets. The briquettes may then be warehoused or stockpiled while the conversion to fluorogypsum occurs. Thereafter, the fluorogypsum is calcined to fluorostucco for use as plaster products or subsequent rehydration in gypsum board manufacture.
Suitable active siliceous materials preferably include Portland cement, finely ground expanded perlite, diatomaceous
earth, reactive colloidal silica such as Cab-O-Sil® silica or Aerosil® fumed pyrogenic silica and alkaline earth metal silicates such as sodium, potassium and calcium silicate. These are all siliceous products having high surface areas (greater than about 10,000 square centimeters per gram) and having chemically reactive sites due to surface deformaties, such as chemically incomplete silicon dioxide surfaces, missing oxygen atoms in the alkali metal silicates and Portland cement, or stressed crystal configurations in expanded perlite sintered or fumed silicas and diatomaceous earth. Other reactive siliceous products suitable for use in this invention will be evident from this description. Generally inclusion of about 1-10% by weight of the active siliceous material based on the weight of calcium sulfate present in the fluoroanhydrite will produce satisfactory results. Preferred amounts of siliceous material are dependent upon the time at which the material is added in the process and the particular siliceous material.
Extensive studies on a partially hydrated fluoroanhydrite-fluorogypsum stockpile material showed the material to be northomogeneous, and calcination to stucco resulted in very slow setting even when accelerators were used. The slow setting properties were caused by poor disintegration of the stucco upon dispersion in water, and by a chemical interference to the growth of calcium sulfate crystals in the gypsum phase. In comparison to natural gypsum, calcination of the stockpile materials exhibited higher drag and dump temperatures. The resultant fluorostucco upon mixing with water had a smaller particle size initially, but a larger particle size upon dispersion. While having a surface area initially comparable to natural gypsum, the fluorostucco
exhibited a lower surface area upon dispersion with water in a board machine mixer.
It is now believed that while some of the contaminant species are water and/or acid soluble and may be washed off the surfaces of the fluoroanhydrite or fluorogypsum, the difficult contaminant species are co-crystalline or occluded, i.e., as the fluoroanhydrite is undergoing the transformation to fluorogypsum, contaminant ions in the surrounding solution crystallize on the growing gypsum phase and are occluded or co-crystallized in the gypsum matrix. It has now been found that these contaminating ions can be rendered inactive in the solution phase, and then the gypsum which re-crystallizes is relatively free of impurities and has properties similar to those of natural gypsum.
The preferred first step for fresh or weathered fluoroanhydrite material is a water or dilute acid wash. For example, it has been found that washing the weathered material twice with water, with a light grinding in between washings, drammatically increased the surface area from about 6,000 cm2/g to 15,900 cm2/g; and reduces the set time with a standard amount of accelerator from approximately 12 minutes without washing to 6.3 minutes after the double washing. Apparently, the light grinding and second wash released some of the impurities. The same treatment steps using 32% sulfuric acid instead of water gave an even better accelerated set time response of 4 minutes. However, neither of these treatments provided sufficient strength or the dispersion disintegration characteristics of natural gypsum. Further, during calcination these materials were difficult to stir, had a high drag temperature and the calcination temperature was difficult to maintain and not uniform throughout the kettle.
Coupling this step with active siliceous material addition to inhibit co*-crystalline impurities gives a combined effect making the fluoroanhydrite material usable for building plaster and gypsum wallboard production.
As one alternative, active siliceous materials may be added to the mixing (gauging) water of fluorostucco. For example, the following were evaluated as slurry additives to fluorostucco obtained by calcining different weathered fluorogypsum samples without any adjustments. The samples were from different locations in the fluorogypsum pile and analysis indicated widely varying degrees of hydration and chemicals content:
Slurry Addition Alone
Untreated Slurry Vicat 1 Temperature
Fluorostucco Additive Amount Set Time Rise Set Time
Control — — 10.5 minutes 17.0
Na2SiO3 1 gram 8.8 14.0
Elapsed time from mixing 50 g. plaster with gauging water to when a 300 g. Vicat needle will not penetrate more than half way (20 + 2mm) into the setting slurry.
From the results it is clear this addition rendered the co-crystalline impurity, non-interfering in the through solution setting of stucco recrystallizing as dihydrate.
As another alternative, active siliceous materials may be added to the fluorogypsum at the stage of calcination to fluorostucco. The additives were mixed with weathered fluorogypsum and then kettle calcined under standard conditions. Since kettle calcination itself is a topatactic dehydration, the additives at this point should have a surface effect rather than a crystallographic effect.
Calcination Addition
Additive Amt. Amt. Drag Dump Hydration Analysis
Added Cal. TempºF TempºF Hem. Dihyd.Anh. other
Untreated - 4 kg 268 293 B3.6 3.7 2.8 9.9 Control
Na2 40g 4.04kg 273 302 86 2.1 1.7 10.2 siO3
Diatomaceous earth 80g 4.08kg 262 293 79 3.2 2.8 15
Portland cement 80g 4.08kg 266 293 81.5 2.8 2.9 12.8
From the table it may be seen that the additives did not significantly affect the calcination properties. Diatomaceous earth reduced the drag temperature by a slight amount, but still significantly above that of natural gypsum. Following calcination, the materials were evaluated for setting and disintegration properties of the fluorogypsum calcined with the additives: Setting & Disintegration Properties of Calcination Addition
Additive Accelerator Vicat Temp/Rise Set
Control
Untreated 10 lb/ton 17.0 min 23.5 (w/o accel.) 11.5 18.5 (w/acceler.)
Na2SiO3 10 lb/ton 13.8 18.5 10.8 15.0
Diatomaceous 10 lb/ton 19.0 25.0 earth 12.0 19.0
Portland 10 lb/ton 16.2 23.0 cement 10.3 18.0
The subsequent rehydration of stucco when mixed with gauging water is a through solution process thus the additives having only a surface effect during calcination when cairied through the rehydration also have a crystal lographic effect. From the table it may be seen that sodium silicate and Portland cement shortened the with accelerator sotting timcs and were thus found to increase accelerator response of the calcined
fluorogypsum. Thus, it seems that the silicate active ion appears to have a beneficial effect. The diatomaceous earth increased the disintegration of the treated stucco to a level equal to that of natural land plaster; however, the set time was not affected.
Thus, while some of the contaminant species are water and/or acid soluble and may be washed off the surfaces of the fluoroanhydrite or fluorogypsum, the difficult-to-remove contaminant species are co-crystalline. As the fluoroanhydrite is undergoing the transformation to fluorogypsum, contaminant ions in the surrounding solution crystallize on the growing gypsum phase and are occluded in the gypsum matrix. The high drag temperature of the fluorogypsum demonstrates the adverse effect of even low concentrations of the impurities in the gypsum lattice. The impurity species, probably a fluoroaluminum ion complex such as [A1F5(H2O)]-2, desensitizes the calcined fluorostucco to the presence of accelerators in the mixing water.
Fluoroanhydrate Hydration Additive The additives listed below were mixed with fluoroanhydrite and neutralized gypsum pond water and allowed to weather hydrate over time. When the samples had hydrated to an appreciable extent above 70% gypsum they were kettle calcined without further additive addition to fluorostucco and the Vicat and temperature rise set times of the materials with and without 10 pounds per ton setting accelerator and gauging water without further additive addition were determined:
The above shows Portland cement and perlite additions at this one processing step lowered calcination temperature of the treated materials. The long unaccelerated set times of treated fluorostucco with some of the materials is not a significant problem because virtually all commercial gypsum, board lines employ set control agents.
It has now been found that these contaminating ions can be rendered inactive in the solution phase, and then the gypsum which crystallizes out would be relatively free of impurities and have properties similar to natural gypsum. With sufficient treatment, the occlusion of these fluorine and aluminum ion species as the fluoroanhydrite is undergoing transformation to fluorogypsum can bo prevented completely, and treatment in the calcination and/or gauging water hydration stages may not be necessary.
Claims (14)
1. A process for the conversion of fluoroanhydrite to a hydrated calcium sulfate product which comprises mixing a form of calcium sulfate from hydrogen fluoride manufacture with water and about 1-10 weight % of active siliceous material and recrystallizing a hydrated calcium sulfate.
2. The process of Claim 1 in which the hydrogen fluoride manufacture calcium sulfate is fluoroanhydrite, and it is recystallized to fluorogypsum.
3. The process of Claim 1 in which the hydrogen fluoride manufacture calcium sulfate is fluorogypsum, and it is recrystallized to fluorostτιcco .
4. The process of Claim 1 in which the hydrogen fluoride manufacture calcium sulfate is fluorostucco, and it is mixed with gauging water to recrystallize a gypsum product.
5. The process of Claim 1 in which said siliceous material is Portland cement.
6. The process of Claim 1 in which said siliceous material is calcium silicate.
7. The process of Claim 1 in which said siliceous material is potassium silicate.
8. The process of Claim 1 in which said siliceous material is sodium silicate.
9. The process of Claim 1 in which said siliceous material is perlite.
10. The process of Claim 1 in which said siliceous material is pyrogenic colloidal silica.
11. The process of Claim 1 in which said siliceous material is diatomaceous earth.
12. The process of Claim 1 in which the hydrogen fluoride manufacture calcium sulfate is washed before being mixed with water and siliceous material.
13. The process of Claim 12 in which the calcium sulfate is washed with water.
14. The process of Claim 12 in which the calcium, sulfate is washed with sulfuric acid.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US33257981A | 1981-12-21 | 1981-12-21 | |
PCT/US1982/001776 WO1983002266A1 (en) | 1981-12-21 | 1982-12-21 | Conversion of fluoroanhydrite to plaster |
US332,579 | 1989-03-31 |
Publications (1)
Publication Number | Publication Date |
---|---|
AU1150583A true AU1150583A (en) | 1983-07-15 |
Family
ID=23298864
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
AU11505/83A Abandoned AU1150583A (en) | 1981-12-21 | 1982-12-21 | Conversion of fluoroanhydrite to plaster |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0096075A4 (en) |
AU (1) | AU1150583A (en) |
WO (1) | WO1983002266A1 (en) |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA590594A (en) * | 1960-01-12 | Calligaris Giuseppe | Process for de-acidifying anhydrous gypsum produced from fluorspar | |
US1756637A (en) * | 1927-04-09 | 1930-04-29 | Rumford Chemical Works | Method of preparing by-product calcium sulphate for plaster |
US1969449A (en) * | 1931-10-17 | 1934-08-07 | Rumford Chemical Works | Process of producing by-product calcium sulphate |
US2606127A (en) * | 1949-03-25 | 1952-08-05 | Weber Herman | Light-weight building materials and their manufacture from synthetic anhydrous calcium sulfate |
US3042537A (en) * | 1961-06-23 | 1962-07-03 | W J Newell | Gypsum plaster |
GB983204A (en) * | 1962-05-26 | 1965-02-10 | Bayer Ag | A process for the neutralisation of calcium sulphate containing hydrofluoric acid and sulphuric acid |
AT273042B (en) * | 1967-04-07 | 1969-07-25 | Chemie Linz Ag | Process for removing fluorine and phosphate from phosphoric acid precipitation gypsum |
GB1248037A (en) * | 1968-01-13 | 1971-09-29 | Fisons Ltd | Calcium sulphate |
US3847634A (en) * | 1973-03-12 | 1974-11-12 | R Vickery | Synthetic lightweight building material |
AT346223B (en) * | 1974-12-11 | 1978-10-25 | Chemie Linz Ag | METHOD FOR OBTAINING LOW-FLUORINE PLASTER AS WASTE PRODUCT FROM THE WET PHOSPHORIC ACID METHOD |
AT345251B (en) * | 1976-05-31 | 1978-09-11 | Chemie Linz Ag | METHOD FOR MANUFACTURING LOW FLUORINE CALCIUM SULFATE |
JPS5941938B2 (en) * | 1976-12-02 | 1984-10-11 | 日産化学工業株式会社 | Method for improving flow value of gypsum slurry |
-
1982
- 1982-12-21 WO PCT/US1982/001776 patent/WO1983002266A1/en not_active Application Discontinuation
- 1982-12-21 EP EP19830900397 patent/EP0096075A4/en not_active Withdrawn
- 1982-12-21 AU AU11505/83A patent/AU1150583A/en not_active Abandoned
Also Published As
Publication number | Publication date |
---|---|
WO1983002266A1 (en) | 1983-07-07 |
EP0096075A4 (en) | 1984-06-13 |
EP0096075A1 (en) | 1983-12-21 |
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