CN115057639A - Method for preparing alpha semi-hydrated gypsum from fluorgypsum - Google Patents
Method for preparing alpha semi-hydrated gypsum from fluorgypsum Download PDFInfo
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- CN115057639A CN115057639A CN202210881843.1A CN202210881843A CN115057639A CN 115057639 A CN115057639 A CN 115057639A CN 202210881843 A CN202210881843 A CN 202210881843A CN 115057639 A CN115057639 A CN 115057639A
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- gypsum
- fluorgypsum
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- 229910052602 gypsum Inorganic materials 0.000 title claims abstract description 105
- 239000010440 gypsum Substances 0.000 title claims abstract description 105
- 238000000034 method Methods 0.000 title claims abstract description 48
- 239000013078 crystal Substances 0.000 claims abstract description 63
- 150000004683 dihydrates Chemical class 0.000 claims abstract description 55
- 238000006703 hydration reaction Methods 0.000 claims abstract description 32
- 230000009466 transformation Effects 0.000 claims abstract description 32
- 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 claims abstract description 29
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 17
- 239000002904 solvent Substances 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims abstract description 15
- 230000005284 excitation Effects 0.000 claims abstract description 9
- ZEMWIYASLJTEHQ-UHFFFAOYSA-J aluminum;sodium;disulfate;dodecahydrate Chemical class O.O.O.O.O.O.O.O.O.O.O.O.[Na+].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZEMWIYASLJTEHQ-UHFFFAOYSA-J 0.000 claims abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 29
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 26
- 238000000926 separation method Methods 0.000 claims description 23
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 15
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 15
- 235000011152 sodium sulphate Nutrition 0.000 claims description 15
- 229940037003 alum Drugs 0.000 claims description 14
- KDYFGRWQOYBRFD-UHFFFAOYSA-N succinic acid Chemical compound OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 14
- 230000008569 process Effects 0.000 claims description 13
- 239000011780 sodium chloride Substances 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 11
- 238000001354 calcination Methods 0.000 claims description 10
- 239000007788 liquid Substances 0.000 claims description 10
- 159000000000 sodium salts Chemical class 0.000 claims description 10
- 239000003607 modifier Substances 0.000 claims description 9
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 8
- 239000011268 mixed slurry Substances 0.000 claims description 7
- GNHOJBNSNUXZQA-UHFFFAOYSA-J potassium aluminium sulfate dodecahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.O.O.[Al+3].[K+].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O GNHOJBNSNUXZQA-UHFFFAOYSA-J 0.000 claims description 7
- 239000001384 succinic acid Substances 0.000 claims description 7
- 235000010344 sodium nitrate Nutrition 0.000 claims description 4
- 239000004317 sodium nitrate Substances 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 claims description 2
- 239000002994 raw material Substances 0.000 claims description 2
- 235000002639 sodium chloride Nutrition 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims 1
- 230000036571 hydration Effects 0.000 abstract description 18
- 238000003912 environmental pollution Methods 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 10
- 230000000704 physical effect Effects 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 239000002002 slurry Substances 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000004566 building material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000002910 solid waste Substances 0.000 description 2
- -1 34 parts Chemical class 0.000 description 1
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 229910000323 aluminium silicate Inorganic materials 0.000 description 1
- 229910052925 anhydrite Inorganic materials 0.000 description 1
- 229940095564 anhydrous calcium sulfate Drugs 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 1
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000010436 fluorite Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000000887 hydrating effect Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- 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
- C04B11/028—Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained
- C04B11/032—Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained for the wet process, e.g. dehydrating in solution or under saturated vapour conditions, i.e. to obtain alpha-hemihydrate
-
- 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
- C04B11/005—Preparing or treating the raw materials
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention provides a method for preparing alpha hemihydrate gypsum from fluorgypsum, which comprises the steps of carrying out hydration reaction on fluorgypsum, calcined alum, sodium salt, dihydrate gypsum seed crystal and a first solvent to obtain dihydrate gypsum; mixing dihydrate gypsum, alpha semi-hydrated gypsum seed crystals and a second solvent, and adding a crystal transformation agent to carry out excitation crystal transformation to obtain alpha semi-hydrated gypsum; the method for preparing the alpha semi-hydrated gypsum by using the fluorgypsum relieves the environmental pollution problem of the fluorgypsum, the fluorgypsum is quickly hydrated in 24 hours, the hydration rate reaches more than 85 percent, and the hydration time of the fluorgypsum is greatly shortened; the obtained alpha semi-hydrated gypsum has large granularity and high strength, and meets alpha 40 grade specified by JC/T2038-2010 standard; and the initial setting time and the final setting time are short.
Description
Technical Field
The invention belongs to the technical field of building materials, and particularly relates to a method for preparing alpha hemihydrate gypsum from fluorgypsum.
Background
The fluorgypsum is a byproduct in the process of producing hydrofluoric acid, contains residual fluorite and sulfuric acid when just taken out of a kiln, has high content of fluorine and sulfuric acid in the leaching solution, and belongs to harmful solid waste with strong corrosivity. Enterprises generally pile the waste after slight neutralization treatment as general solid waste, and direct pile not only occupies land, but also pollutes soil and underground water environment, so the enterprises have to use a large amount of land and maintain the surrounding environment, the fluorgypsum is not fully utilized, and the pollution to the surrounding environment is caused while the production burden of the enterprises is brought by the large amount of piled fluorgypsum.
The fluorgypsum belongs to one of the anhydrite, is difficult to dissolve in water, has extremely poor hydration activity and long setting and hardening time, does not generate setting and hardening even for a long time, and does not have early strength, but has potential gelling property, and can be used as an industrial production civil building material like other gypsum products after being modified. The fluorgypsum is mainly anhydrous calcium sulfate, and has low activity and is difficult to hydrate without treatment; the modification research is carried out on the fluorgypsum, and the fluorgypsum is converted into the gypsum building material for comprehensive utilization, so that the environment can be protected, the waste can be changed into the valuable, and the resources can be saved.
CN102173620A discloses a method for producing building gypsum powder by wet fluorgypsum modification, which comprises the following steps: and (2) naturally air-drying or drying the wet fluorgypsum to remove part of free water, primarily crushing the wet fluorgypsum to be less than 2mm, adding a part of modifier formed by mixing aluminosilicate, sulfate and calcium-containing compound into the wet fluorgypsum, roasting the mixture for 1 to 3 hours at the low temperature of 80 to 180 ℃, then fully mixing the mixture with the rest of modifier, and finely grinding the mixture to obtain the modified building gypsum powder material meeting the requirement of building gypsum GB/T9776-2008, wherein the particle size of the finely ground powder is not more than 0.147 mm. Wherein, the wet fluorgypsum accounts for 92-98 percent by mass and the total amount of the modifier accounts for 2-8 percent by mass; the dosage of the modifier added in the two times is 65-85% and 15-35% of the total dosage of the modifier in sequence. The method has the technical characteristics of short process flow, low roasting temperature, low cost and stable product quality, and the modifier is added in two steps. However, the method has high requirements on the particle size of the finely ground powder, and the obtained building gypsum powder has poor mechanical properties.
Therefore, it is needed to provide a green and environment-friendly method for treating fluorgypsum as a resource, which solves the problem of fluorgypsum accumulation and waste, can obtain gypsum with large granularity and high strength, improves the industrial application value of fluorgypsum, and reduces pollution.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for preparing alpha hemihydrate gypsum from fluorgypsum, wherein the fluorgypsum, calcined alum, sodium salt, dihydrate gypsum seed crystal and a first solvent are subjected to hydration reaction to obtain dihydrate gypsum; mixing dihydrate gypsum, alpha semi-hydrated gypsum seed crystals and a second solvent, and adding a crystal transformation agent to carry out excitation crystal transformation to obtain alpha semi-hydrated gypsum; the method for preparing the alpha semi-hydrated gypsum from the fluorgypsum relieves the environmental pollution problem of the fluorgypsum, the fluorgypsum is quickly hydrated in 24 hours, the hydration rate reaches more than 85 percent, and the hydration time of the fluorgypsum is greatly shortened; the obtained alpha semi-hydrated gypsum has large granularity and high strength, and meets alpha 40 grade specified by JC/T2038-2010 standard; and the initial setting time and the final setting time are short.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention aims to provide a method for preparing alpha hemihydrate gypsum from fluorgypsum, which comprises the following steps:
(1) mixing fluorgypsum, calcined alum, sodium salt and dihydrate gypsum seed crystals with a first solvent, then carrying out hydration reaction, and carrying out first solid-liquid separation to obtain dihydrate gypsum;
(2) and (2) mixing alpha semi-hydrated gypsum seed crystals, a second solvent and the dihydrate gypsum in the step (1) to obtain mixed slurry, adding a crystal transformation agent to perform excitation crystal transformation at the temperature of 121-128 ℃, and performing second solid-liquid separation to obtain the alpha semi-hydrated gypsum.
The method for preparing the alpha semi-hydrated gypsum from the fluorgypsum relieves the environmental pollution problem of the fluorgypsum, the fluorgypsum is quickly hydrated in 24 hours, the hydration rate reaches more than 85 percent, and the hydration time of the fluorgypsum is greatly shortened; the obtained alpha semi-hydrated gypsum has large granularity and high strength, and meets alpha 40 grade specified by JC/T2038-2010 standard; and the initial setting time and the final setting time are short.
It is to be noted that the temperature for inducing the crystal transformation is 121-128 ℃, and may be, for example, 121 ℃, 121.5 ℃, 122 ℃, 122.5 ℃, 123 ℃, 123.5 ℃, 124 ℃, 124.5 ℃, 125 ℃, 125.5 ℃, 126.5 ℃, 127 ℃, 127.5 ℃, 128 ℃, etc., but it is not limited to the recited values, and other values not recited in the above-mentioned range of values are also applicable.
As a preferred embodiment of the present invention, in the step (A), (B) and (C)1) Before the mixing, the fluorgypsum is ground until the specific surface area is more than or equal to 500m 2 Kg, e.g. 500m 2 ·kg，550m 2 ·kg，600m 2 ·kg，630m 2 ·kg，670m 2 ·kg，700m 2 ·kg，740m 2 ·kg，780m 2 ·kg，800m 2 ·kg，850m 2 ·kg，900m 2 Kg, etc., but are not limited to the recited values, and other values not recited in the above numerical ranges are also applicable.
Preferably, the preparation process of the calcined alum in the step (1) comprises the following steps: calcining the potassium aluminum sulfate dodecahydrate at the temperature of 600-670 ℃ for 1-2h, wherein the calcining temperature is 600-670 ℃, and can be 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃, 650 ℃, 660 ℃, 670 ℃ and the like; the calcination time is 1 to 2 hours, and for example, 1 hour, 1.1 hour, 1.2 hour, 1.3 hour, 1.4 hour, 1.5 hour, 1.6 hour, 1.7 hour, 1.8 hour, 1.9 hour, 2 hour and the like are possible, but the calcination time is not limited to the enumerated values, and other values not enumerated within the above numerical range are also applicable.
However, the numerical values are not limited to the specific ones, and other numerical values not specified in the above numerical ranges are also applicable.
As a preferred embodiment of the present invention, the sodium salt in step (1) includes any one or a combination of at least two of sodium sulfate, sodium chloride or sodium nitrate, and typical but non-limiting examples of the combination include a combination of sodium sulfate and sodium chloride, a combination of sodium sulfate and sodium nitrate, and a combination of sodium chloride and sodium nitrate; further preferred are sodium sulfate and sodium chloride.
Preferably, the first solvent of step (1) comprises water.
As a preferable technical scheme of the invention, in the step (1), the raw material components comprise the following components in parts by weight: 98-103 parts of fluorgypsum, such as 98 parts, 99 parts, 100 parts, 101 parts, 102 parts, 103 parts and the like; calcined alum 4-6 parts, such as 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, etc.; 34-38 parts of sodium salt, such as 34 parts, 34.5 parts, 35 parts, 35.5 parts, 36 parts, 36.5 parts, 37 parts, 37.5 parts, 38 parts and the like; the dihydrate gypsum seed crystal 19 to 21 parts may be, for example, 19 parts, 19.5 parts, 20 parts, 20.5 parts, 21 parts, etc., but is not limited to the enumerated values, and other values not enumerated within the above numerical range are also applicable.
In step (1), the sodium salt is sodium sulfate and sodium chloride, and the sodium sulfate is 5 to 7 parts by weight, for example, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, etc., and the sodium chloride is 29 to 31 parts by weight, for example, 29 parts, 29.5 parts, 30 parts, 30.5 parts, 31 parts, etc., but the sodium salt is not limited to the recited values, and other values not recited in the above-mentioned range of values are also applicable.
Preferably, the mass ratio of the first solvent to the fluorogypsum in step (1) is (5-7):1, and may be, for example, 5:1, 5.2:1, 5.5:1, 5.7:1, 6:1, 6.3:1, 6.5:1, 6.8:1, 7:1, etc., but is not limited to the enumerated values, and other unrecited values within the above-mentioned range of values are also applicable.
As a preferred embodiment of the present invention, the temperature of the hydration reaction in step (1) is 20 to 35 ℃ and may be, for example, 20 ℃, 22 ℃, 24 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 34 ℃, 35 ℃ or the like, but is not limited to the values listed above, and other values not listed above within the above range of values are also applicable.
Preferably, the hydration time in step (1) is 20-24h, such as 20h, 20.5h, 21h, 21.5h, 22h, 22.5h, 23h, 23.5h, 24h, etc., but not limited to the recited values, and other values not recited in the above range are also applicable.
Preferably, the stirring speed of the hydration reaction in step (1) is 100-250r/min, such as 100r/min, 120r/min, 140r/min, 160r/min, 180r/min, 200r/min, 210r/min, 230r/min, 250r/min, etc., but not limited to the enumerated values, and other unrecited values within the above-mentioned range of values are also applicable.
Preferably, the first solid-liquid separation in step (1) is centrifugal separation.
In a preferred embodiment of the present invention, the mass ratio of the alpha hemihydrate gypsum seed crystals to the dihydrate gypsum in the step (2) is (0.2-0.4):1, and examples thereof include 0.2:1, 0.22:1, 0.25:1, 0.27:1, 0.3:1, 0.33:1, 0.35:1, 0.38:1, and 0.4:1, but the present invention is not limited to the above-mentioned values, and other values not shown in the above-mentioned value range are also applicable.
Preferably, the second solvent of step (2) comprises water.
Preferably, the mass ratio of the second solvent to the dihydrate gypsum in step (2) is (2-3):1, and may be, for example, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, etc., but not limited to the enumerated values, and other unrecited values within the above-mentioned range of values are also applicable.
As a preferable technical scheme of the invention, the crystal modifier in the step (2) comprises succinic acid.
Preferably, the amount of the crystal modifier added in step (2) is 0.2-0.4 wt% of the dihydrate gypsum, and may be, for example, 0.2 wt%, 0.22 wt%, 0.25 wt%, 0.27 wt%, 0.3 wt%, 0.33 wt%, 0.35 wt%, 0.38 wt%, 0.4 wt%, and the like, but is not limited to the recited values, and other values not recited in the above-mentioned range of values are also applicable.
In a preferred embodiment of the present invention, the time for the crystal transformation in step (2) is 2 to 3 hours, and may be, for example, 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, 3 hours, etc., but is not limited to the values listed above, and other values not listed above in the above range of values are also applicable.
In a preferred embodiment of the present invention, the second solid-liquid separation in step (2) is centrifugal separation.
Preferably, after the second solid-liquid separation in the step (2), drying is carried out to obtain the alpha hemihydrate gypsum.
Preferably, the drying temperature is 100-160 ℃, and may be, for example, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃ and the like, but is not limited to the recited values, and other unrecited values within the above-mentioned range are also applicable.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) the specific surface area is more than or equal to 500m 2 98-103 kg of fluorgypsum, 4-6 parts of calcined alum, 34-38 parts of sodium salt, 19-21 parts of dihydrate gypsum seed crystal and water are mixed, and the mass ratio of the water to the fluorgypsum is controlled to be (5-7) to 1; carrying out hydration reaction at the temperature of 20-35 ℃ and the stirring speed of 100-;
wherein the calcined alum is obtained by calcining aluminum potassium sulfate dodecahydrate at the temperature of 600-670 ℃ for 1-2 h;
(2) mixing alpha semi-hydrated gypsum seed crystals and water with the dihydrate gypsum in the step (1) to obtain mixed slurry, wherein the mass ratio of the alpha semi-hydrated gypsum seed crystals to the dihydrate gypsum is controlled to be (0.2-0.4):1, and the mass ratio of the water to the dihydrate gypsum is controlled to be (2-3): 1; adding a crystal transformation agent succinic acid to perform excitation crystal transformation for 2-3h at the temperature of 121-; after centrifugal separation, alpha hemihydrate gypsum is obtained by drying at 100-160 ℃.
The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the method for preparing the alpha semi-hydrated gypsum from the fluorgypsum, the fluorgypsum is hydrated and crystallized to prepare the alpha semi-hydrated gypsum, so that the problem of environmental pollution of the fluorgypsum is relieved, the fluorgypsum is rapidly hydrated within 24 hours, the hydration rate reaches over 85 percent, and the hydration time of the fluorgypsum is greatly shortened;
(2) according to the method for preparing alpha semi-hydrated gypsum from fluorine gypsum, the obtained alpha semi-hydrated gypsum has large granularity and high strength, and meets the alpha 40 grade specified by JC/T2038-2010 standard; and the initial setting time and the final setting time are short.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
It is worth to say that the inventionThe chemical components of the fluorgypsum used in the specific embodiment of (1) comprise the following components in parts by weight: CaO 40.66%, SO 3 56.57％、SiO 2 0.841％、Al 2 O 3 0.165％、Fe 2 O 3 0.0871％、MgO 0.0448％、K 2 O 0.0377％、P 2 O 5 0.0185％、TiO 2 0.0119%, Cl 0.0108%, SrO 0.01%, MnO 0.0071%, PbO 0.0048%, LOI 1.52%, and crystal water 1.21%.
Example 1
The embodiment provides a method for preparing alpha hemihydrate gypsum from fluorgypsum, which comprises the following steps:
(1) the specific surface area is 550m 2 100 kg of fluorgypsum, 5 parts of calcined alum, 5 parts of sodium sulfate, 29 parts of sodium chloride, 20 parts of dihydrate gypsum seed crystal and water are mixed, and the mass ratio of the water to the fluorgypsum is controlled to be 6: 1; carrying out hydration reaction at the temperature of 25 ℃ and the stirring speed of 200r/min for 24h, and carrying out centrifugal separation to obtain dihydrate gypsum;
wherein the calcined alum is obtained by calcining aluminum potassium sulfate dodecahydrate at 650 ℃ for 1 h;
(2) mixing alpha semi-hydrated gypsum seed crystal, water and the dihydrate gypsum in the step (1) to obtain mixed slurry, wherein the mass ratio of the alpha semi-hydrated gypsum seed crystal to the dihydrate gypsum is controlled to be 0.2:1, and the mass ratio of the water to the dihydrate gypsum is controlled to be 2: 1; adding a crystal transformation agent succinic acid to perform excitation crystal transformation for 3 hours at 125 ℃, and controlling the addition amount of the crystal transformation agent to be 0.3 wt% of the dihydrate gypsum; after centrifugal separation, alpha hemihydrate gypsum is obtained after drying at 160 ℃.
Example 2
The embodiment provides a method for preparing alpha hemihydrate gypsum from fluorgypsum, which comprises the following steps:
(1) the specific surface area is 600m 2 103 kg of fluorgypsum, 4 kg of calcined alum, 6 kg of sodium sulfate, 30 kg of sodium chloride, 19 kg of dihydrate gypsum seed crystal and water are mixed, and the mass ratio of the water to the fluorgypsum is controlled to be 5: 1; carrying out hydration reaction for 22h at the temperature of 20 ℃ and the stirring speed of 250r/min, and carrying out centrifugal separation to obtain dihydrate gypsum;
wherein the calcined alum is obtained by calcining aluminum potassium sulfate dodecahydrate at 600 ℃ for 2 hours;
(2) mixing alpha semi-hydrated gypsum seed crystal, water and the dihydrate gypsum in the step (1) to obtain mixed slurry, wherein the mass ratio of the alpha semi-hydrated gypsum seed crystal to the dihydrate gypsum is controlled to be 0.3:1, and the mass ratio of the water to the dihydrate gypsum is controlled to be 3: 1; adding a crystal transformation agent succinic acid to perform excitation crystal transformation for 2.5h at 121 ℃, and controlling the addition amount of the crystal transformation agent to be 0.4 wt% of the dihydrate gypsum; after centrifugal separation, alpha hemihydrate gypsum is obtained after drying at 140 ℃.
Example 3
The embodiment provides a method for preparing alpha hemihydrate gypsum from fluorgypsum, which comprises the following steps:
(1) the specific surface area is 500m 2 98 parts of kg fluorgypsum, 6 parts of calcined alum, 7 parts of sodium sulfate, 31 parts of sodium chloride, 21 parts of dihydrate gypsum seed crystal and water are mixed, and the mass ratio of the water to the fluorgypsum is controlled to be 7: 1; carrying out hydration reaction for 20h at the temperature of 35 ℃ and the stirring speed of 100r/min, and carrying out centrifugal separation to obtain dihydrate gypsum;
wherein the calcined alum is obtained by calcining aluminum potassium sulfate dodecahydrate at 670 ℃ for 0.5 h;
(2) mixing alpha semi-hydrated gypsum seed crystal, water and the dihydrate gypsum in the step (1) to obtain mixed slurry, wherein the mass ratio of the alpha semi-hydrated gypsum seed crystal to the dihydrate gypsum is controlled to be 0.4:1, and the mass ratio of the water to the dihydrate gypsum is controlled to be 2.5: 1; adding a crystal transformation agent succinic acid to perform excitation crystal transformation for 2 hours at 128 ℃, and controlling the addition amount of the crystal transformation agent to be 0.2 wt% of the dihydrate gypsum; after centrifugal separation, alpha hemihydrate gypsum is obtained after drying at 100 ℃.
Example 4
This example provides a process for making alpha hemihydrate gypsum from fluorogypsum, the process being as described with reference to example 1, except that: and (2) replacing 5 parts of sodium sulfate and 29 parts of sodium chloride in the step (1) by 34 parts of sodium sulfate.
Example 5
This example provides a process for making alpha hemihydrate gypsum from fluorogypsum, the process being as described with reference to example 1, except that: the addition amount of the crystal transformation agent in the step (2) accounts for 0.1 wt% of the dihydrate gypsum.
Example 6
This example provides a process for making alpha hemihydrate gypsum from fluorogypsum, the process being as described with reference to example 1, except that: the addition amount of the crystal transformation agent in the step (2) accounts for 0.5 wt% of the dihydrate gypsum.
Comparative example 1
This comparative example provides a process for making alpha hemihydrate gypsum from fluorogypsum, the process being as described with reference to example 1, except that: the temperature of the crystal transformation in the step (2) is 112 ℃.
Comparative example 2
This comparative example provides a process for making alpha hemihydrate gypsum from fluorogypsum, the process being as described with reference to example 1, except that: the temperature of the crystal transformation in the step (2) is 135 ℃.
The above examples and comparative examples were tested, and the test contents and methods were as follows:
hydration rate of fluorgypsum: stopping hydrating the fluorgypsum hydrated to the specified age by using absolute ethyl alcohol, drying at 50 ℃, accurately weighing a fluorgypsum hydrated sample dried to the constant weight, calcining at 450 ℃ for 30min, and measuring the mass fraction of the crystal water, thereby calculating the mass fraction of the dihydrate gypsum and the hydration rate of the fluorgypsum;
the median particle diameter of dihydrate gypsum and alpha hemihydrate gypsum: testing by using a laser particle size distribution instrument;
③ standard consistency of alpha hemihydrate gypsum: the determination is carried out according to the methods in GB/T17669.3-1999 determination of mechanical properties of building gypsum and GB/T17669.4-1999 determination of physical properties of clean slurry of building gypsum;
initial setting time and final setting time of alpha hemihydrate gypsum: the determination is carried out according to the methods in GB/T17669.3-1999 determination of mechanical properties of building gypsum and GB/T17669.4-1999 determination of physical properties of clean slurry of building gypsum;
the 2h flexural strength of the alpha semi-hydrated gypsum: the determination is carried out according to the methods in GB/T17669.3-1999 determination of mechanical properties of building gypsum and GB/T17669.4-1999 determination of physical properties of clean slurry of building gypsum;
sixthly, the 2h compressive strength of the alpha hemihydrate gypsum: the determination is carried out according to the methods in GB/T17669.3-1999 determination of mechanical properties of building gypsum and GB/T17669.4-1999 determination of physical properties of clean slurry of building gypsum;
and the dry compression strength of the alpha semi-hydrated gypsum: the determination is carried out according to the methods in GB/T17669.3-1999 determination of mechanical properties of the building gypsum and GB/T17669.4-1999 determination of physical properties of the clean slurry of the building gypsum;
the test results of (i) - (iv) are shown in table 1, and the test results of (iv) - (v) are shown in table 2.
TABLE 1
TABLE 2
| Item | 2h flexural strength/MPa | 2h compressive strength/MPa | Dry compressive strength/MPa |
| Example 1 | 5.4 | 26.7 | 42.6 |
| Example 2 | 5.1 | 25.3 | 40.5 |
| Example 3 | 5.2 | 24.1 | 41.2 |
| Example 4 | 5.0 | 23.6 | 40.8 |
| Example 5 | 4.6 | 20.8 | 38.4 |
| Example 6 | 4.9 | 23.4 | 40.1 |
| Comparative example 1 | 4.7 | 24.3 | 40.0 |
| Comparative example 2 | 4.9 | 24.8 | 39.1 |
From tables 1 and 2, the following points can be derived:
(1) from the examples 1 to 3, it can be seen that in the method for preparing alpha hemihydrate gypsum from fluorgypsum, the hydration rate of fluorgypsum reaches more than 85%, the obtained alpha hemihydrate gypsum has large granularity and high strength, and the alpha hemihydrate gypsum meets the alpha 40 grade specified by JC/T2038-2010 standard; the initial setting time and the final setting time are short;
(2) comparing example 1 with example 4, it can be seen that the sodium salts in example 1 are sodium sulfate and sodium chloride, and compared to example 1, the sodium salt in example 4 is only sodium sulfate, resulting in a decrease in the hydration rate of the fluorogypsum, an increase in the final set time, a decrease in the 2h flexural strength, the 2h compressive strength and the dry compressive strength;
(2) comparing example 1 with examples 5 and 6, it can be seen that, since the addition amount of the crystal transformation agent in example 5 is 0.1 wt% of the dihydrate gypsum and is lower than the preferable 0.2-0.4 wt% of the dihydrate gypsum, the hydration rate of the fluorgypsum is reduced, the initial setting time is increased, and the 2h flexural strength, 2h compressive strength and dry compressive strength are reduced; since the addition amount of the crystal transformation agent in example 6 is 0.5 wt% of the dihydrate gypsum and exceeds the preferable 0.2-0.4 wt% of the dihydrate gypsum, the hydration rate of the fluorgypsum is reduced, the final setting time is increased, and the 2h flexural strength, the 2h compressive strength and the dry compressive strength are reduced;
(3) comparing example 1 with comparative examples 1 and 2, it can be seen that the temperature for crystal transformation activation of comparative example 1 is 112 ℃ which is lower than the temperature of 121-128 ℃ preferred in the invention, so that the hydration rate of the fluorgypsum is reduced, the initial setting time and the final setting time are increased, and the 2h flexural strength, the 2h compressive strength and the dry compressive strength are reduced; since the temperature of the induced crystallization of comparative example 2 is 135 ℃ which exceeds the temperature of 121-128 ℃ preferred in the present invention, the hydration rate of the fluorogypsum is reduced, the initial setting time and the final setting time are increased, and the 2h flexural strength, the 2h compressive strength and the dry compressive strength are reduced.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The method for preparing alpha hemihydrate gypsum from fluorgypsum is characterized by comprising the following steps:
(1) mixing fluorgypsum, calcined alum, sodium salt and dihydrate gypsum seed crystals with a first solvent, then carrying out hydration reaction, and carrying out first solid-liquid separation to obtain dihydrate gypsum;
(2) and (2) mixing alpha semi-hydrated gypsum seed crystals, a second solvent and the dihydrate gypsum in the step (1) to obtain mixed slurry, adding a crystal transformation agent to perform excitation crystal transformation at the temperature of 121-128 ℃, and performing second solid-liquid separation to obtain the alpha semi-hydrated gypsum.
2. The method of claim 1, wherein the fluorgypsum is ground to a specific surface area of 500m or more before the mixing in step (1) 2 ·kg；
Preferably, the preparation process of the calcined alum in the step (1) comprises the following steps: the potassium aluminum sulfate dodecahydrate is calcined at the temperature of 600-670 ℃ for 1-2 h.
3. The method according to claim 1 or 2, wherein the sodium salt of step (1) comprises any one or a combination of at least two of sodium sulfate, sodium chloride or sodium nitrate, further preferably sodium sulfate and sodium chloride;
preferably, the first solvent of step (1) comprises water.
4. The method according to any one of claims 1 to 3, wherein in the step (1), each raw material component comprises the following components in parts by weight: 98-103 parts of fluorgypsum, 4-6 parts of calcined alum, 34-38 parts of sodium salt and 19-21 parts of dihydrate gypsum seed crystal;
preferably, the mass ratio of the first solvent to the fluorgypsum in the step (1) is (5-7): 1.
5. The method according to any one of claims 1 to 4, wherein the temperature of the hydration reaction of step (1) is 20 to 35 ℃;
preferably, the hydration reaction time of the step (1) is 20-24 h;
preferably, the stirring speed of the hydration reaction in the step (1) is 100-;
preferably, the first solid-liquid separation mode in the step (1) is centrifugal separation.
6. The process of any of claims 1-5, wherein the mass ratio of the alpha hemihydrate gypsum seeds to the dihydrate gypsum of step (2) is (0.2-0.4): 1;
preferably, the second solvent of step (2) comprises water;
preferably, the mass ratio of the second solvent to the dihydrate gypsum in the step (2) is (2-3): 1.
7. The method according to any one of claims 1 to 6, wherein the crystal modifier of step (2) comprises succinic acid;
preferably, the addition amount of the crystal transformation agent in the step (2) accounts for 0.2 to 0.4 weight percent of the dihydrate gypsum.
8. The method according to any one of claims 1 to 7, wherein the time for the crystal transformation of step (2) is 2 to 3 hours.
9. The method according to any one of claims 1 to 8, wherein the second solid-liquid separation in step (2) is centrifugal separation;
preferably, after the second solid-liquid separation in the step (2), drying is carried out to obtain alpha hemihydrate gypsum;
preferably, the temperature of the drying is 100-160 ℃.
10. A method according to any of claims 1-9, characterized in that the method comprises the steps of:
(1) the specific surface area is more than or equal to 500m 2 98-103 kg of fluorgypsum, 4-6 parts of calcined alum, 34-38 parts of sodium salt, 19-21 parts of dihydrate gypsum seed crystal and water are mixed, and the mass ratio of the water to the fluorgypsum is controlled to be (5-7) to 1; stirring at 20-35 deg.C and stirring speed of 100Carrying out hydration reaction at-250 r/min for 20-24h, and carrying out centrifugal separation to obtain dihydrate gypsum;
wherein the calcined alum is obtained by calcining aluminum potassium sulfate dodecahydrate at the temperature of 600-670 ℃ for 1-2 h;
(2) mixing alpha semi-hydrated gypsum seed crystals and water with the dihydrate gypsum in the step (1) to obtain mixed slurry, wherein the mass ratio of the alpha semi-hydrated gypsum seed crystals to the dihydrate gypsum is controlled to be (0.2-0.4):1, and the mass ratio of the water to the dihydrate gypsum is controlled to be (2-3): 1; adding a crystal transformation agent succinic acid to perform excitation crystal transformation for 2-3h at the temperature of 121-; after centrifugal separation, alpha hemihydrate gypsum is obtained by drying at 100-160 ℃.
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