CN115947553A - Method for preparing alpha high-strength gypsum from natural anhydrite - Google Patents
Method for preparing alpha high-strength gypsum from natural anhydrite Download PDFInfo
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- CN115947553A CN115947553A CN202310117923.4A CN202310117923A CN115947553A CN 115947553 A CN115947553 A CN 115947553A CN 202310117923 A CN202310117923 A CN 202310117923A CN 115947553 A CN115947553 A CN 115947553A
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- 229910052602 gypsum Inorganic materials 0.000 title claims abstract description 133
- 239000010440 gypsum Substances 0.000 title claims abstract description 133
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 title claims abstract description 113
- 238000000034 method Methods 0.000 title claims abstract description 45
- 150000004683 dihydrates Chemical class 0.000 claims abstract description 58
- 239000000843 powder Substances 0.000 claims abstract description 51
- 239000013078 crystal Substances 0.000 claims abstract description 41
- 238000006703 hydration reaction Methods 0.000 claims abstract description 41
- 238000002156 mixing Methods 0.000 claims abstract description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000000227 grinding Methods 0.000 claims abstract description 27
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 18
- 239000003607 modifier Substances 0.000 claims abstract description 18
- 238000000926 separation method Methods 0.000 claims abstract description 18
- 238000001035 drying Methods 0.000 claims abstract description 15
- 239000007788 liquid Substances 0.000 claims abstract description 14
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 9
- 229940037003 alum Drugs 0.000 claims description 18
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 17
- 235000011152 sodium sulphate Nutrition 0.000 claims description 17
- 239000002245 particle Substances 0.000 claims description 12
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 11
- 238000001354 calcination Methods 0.000 claims description 11
- 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
- ZEMWIYASLJTEHQ-UHFFFAOYSA-J aluminum;sodium;disulfate;dodecahydrate Chemical compound 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 description 6
- 238000003756 stirring Methods 0.000 claims description 4
- 230000009466 transformation Effects 0.000 claims description 2
- 230000036571 hydration Effects 0.000 abstract description 28
- 230000000052 comparative effect Effects 0.000 description 15
- 230000006835 compression Effects 0.000 description 14
- 238000007906 compression Methods 0.000 description 14
- 229910052925 anhydrite Inorganic materials 0.000 description 13
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 12
- 230000000694 effects Effects 0.000 description 7
- 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 5
- 239000000654 additive Substances 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000005452 bending Methods 0.000 description 3
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 description 3
- 230000000887 hydrating effect Effects 0.000 description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 239000012266 salt solution Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 239000004566 building material Substances 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention relates to a method for preparing alpha high-strength gypsum from natural anhydrite, which comprises the following steps: (1) Grinding natural anhydrite to obtain natural anhydrite powder; (2) Mixing the natural anhydrite powder obtained in the step (1), an exciting agent, dihydrate gypsum seed crystals and water, and then sequentially carrying out hydration reaction and solid-liquid separation to obtain dihydrate gypsum; (3) And (3) mixing the dihydrate gypsum obtained in the step (2), a crystal modifier and water, then sequentially carrying out pressurized hydrothermal reaction and solid-liquid separation to obtain semi-hydrated gypsum, and sequentially drying and grinding the semi-hydrated gypsum to obtain the alpha high-strength gypsum. The method provided by the invention can greatly improve the hydration rate of the natural anhydrite and obtain a high-quality alpha high-strength gypsum product.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to a method for preparing alpha high-strength gypsum from natural anhydrite.
Background
The natural gypsum mineral resources are rich, the grade is high, the distribution range is wide, and the utilization value is high. Among them, the mineral resources of anhydrite have potential gelling property, but the utilization rate of anhydrite is always low because of some inherent characteristics of anhydrite, such as low hydration activity, poor gelling property, long setting and hardening time and the like. Therefore, in order to make anhydrite industrially applicable like other gypsum products, it is necessary to improve its gelling properties and shorten the setting time as much as possible. Therefore, the research on the activity excitation of the anhydrite is very important to the resource utilization of the anhydrite.
The hydration reaction of the anhydrite is a spontaneous process, the anhydrite is a natural mineral, no waste pollutants are generated in the production and use processes of the anhydrite, and the environmental protection effect is better than that of cement, so how to improve the hydration rate of the anhydrite in a short time has important economic and social benefits no matter from the aspects of resource development, energy conservation and the like, or from the aspect of developing novel building materials, and the economic benefit can be improved to a greater extent by preparing the anhydrite into the high-strength gypsum.
At present, the preparation method of the high-strength gypsum mainly comprises the following steps: pressurized hydrothermal method, steam pressure method, normal pressure salt solution method and the like. Wherein, the steam pressing method is to add dihydrate gypsum into a closed reaction kettle, and introduce saturated water vapor, so that the dihydrate gypsum reacts under the condition of pressurized steam to prepare alpha hemihydrate gypsum wet material, and the alpha hemihydrate gypsum powder is obtained after drying and grinding. However, the utilization rate of the additive in the steam-pressing method is low, the blocky dihydrate gypsum is difficult to combine with the additive, and the effective volume of the autoclave is not well utilized. The normal pressure salt solution method is to add raw material gypsum powder and additive into salt solution under the condition of not pressurizing the reaction, react for a period of time at a certain temperature to convert dihydrate gypsum into hemihydrate gypsum, and then obtain alpha hemihydrate gypsum powder by filtering, washing and drying. Therefore, the pressurized hydrothermal method is the main method for preparing the alpha high-strength gypsum at present.
CN114538811A discloses a method for preparing high-strength gypsum from phosphogypsum, which comprises drying phosphogypsum once and then dividing the phosphogypsum into two parts, and calcining the first part to obtain anhydrous gypsum; adding a regulator and a crystal medium into the second part, placing the second part in a crystal transfer box, reacting for 6-10h at the reaction temperature of 110-140 ℃, dehydrating after the reaction is finished, and drying for the second time at 60-100 ℃ until the water content is 5% -7% to prepare the alpha-beta composite semi-hydrated gypsum; and respectively grinding the obtained anhydrous gypsum and the alpha-beta composite semi-hydrated gypsum and mixing to obtain the high-strength gypsum. However, the preparation method is not suitable for anhydrite, and the prepared high-strength gypsum has poor performance.
CN108423701A discloses a method for preparing alpha high-strength gypsum by using waste gypsum molds, which comprises the steps of crushing and grinding waste ceramic gypsum molds, adding a certain amount of water to prepare slurry, and converting dihydrate gypsum into the alpha high-strength gypsum by an autoclave process under the action of a crystal modifier. However, the method has low utilization rate of the additive and is not suitable for the treatment of the natural anhydrite.
Therefore, the method for preparing the alpha high-strength gypsum by using the natural anhydrite has important significance.
Disclosure of Invention
In view of the above problems, the present invention aims to provide a method for preparing alpha high-strength gypsum from natural anhydrite, which can greatly increase the hydration rate of natural anhydrite and obtain high-quality alpha high-strength gypsum products, compared with the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for preparing alpha high-strength gypsum from natural anhydrite, which comprises the following steps:
(1) Grinding natural anhydrite to obtain natural anhydrite powder;
(2) Mixing the natural anhydrite powder obtained in the step (1), an exciting agent, dihydrate gypsum seed crystals and water, and then sequentially carrying out hydration reaction and solid-liquid separation to obtain dihydrate gypsum;
(3) And (3) mixing the dihydrate gypsum obtained in the step (2), a crystal modifier and water, then sequentially carrying out pressurized hydrothermal reaction and solid-liquid separation to obtain semi-hydrated gypsum, and sequentially drying and grinding the semi-hydrated gypsum to obtain the alpha high-strength gypsum.
The natural anhydrite adopted in the invention has potential gel property, slow dissolution, low hydration activity and long setting and hardening time, so the utilization rate in the existing research is lower, and the invention adopts a method of grinding and adding an exciting agent and a method of carrying out hydration reaction and controlling the condition of the hydration reaction to accelerate the hydration rate of the anhydrite according to the principle of dissolution-crystallization-regrowth, thereby greatly improving the hydration rate of the natural anhydrite; then, carrying out pressurized hydrothermal reaction on dihydrate gypsum prepared by hydrating natural anhydrite and controlling the conditions of the pressurized hydrothermal reaction to finally prepare the high-strength gypsum with excellent performance.
In the present invention, the dihydrate gypsum seed crystal includes, but is not limited to, desulfurized gypsum, salt gypsum or dihydrate gypsum obtained by hydrating natural anhydrite in the present invention.
The type of the crystal modifier is not particularly limited in the invention, and the crystal modifier can be any crystal modifier commonly used in the field for preparing alpha high-strength gypsum, such as citric acid.
Preferably, the natural anhydrite powder has an average particle size of 18 μm or less, and may be, for example, 18 μm, 16 μm, 12 μm, 14 μm, 10 μm, 8 μm, 6 μm or 4 μm, but is not limited to the recited values, and other values not recited within the range of values are also applicable.
In the present invention, the average particle size of the natural anhydrite powder is preferably controlled to be within a specific range, so that the hydration of the natural anhydrite can be further promoted, and the hydration rate of the natural anhydrite can be increased.
Preferably, the exciting agent in the step (2) comprises calcined alum and sodium sulfate.
Preferably, the calcined alum is calcined from potassium aluminum sulfate dodecahydrate, followed by grinding.
Preferably, the calcination temperature is 650-700 ℃, for example 650 ℃, 660 ℃, 670 ℃, 680 ℃, 690 ℃ or 700 ℃, but is not limited to the recited values, and other values not recited in the numerical ranges are equally applicable.
Preferably, the calcination is carried out for a period of time of 1 to 1.5h, for example 1h, 1.1h, 1.2h, 1.3h, 1.4h or 1.5h, but not limited to the recited values, and other values not recited in the numerical ranges are equally applicable.
Preferably, the mixing in the step (2) comprises the following components in parts by weight: 95 to 105 parts of natural anhydrite powder, such as 95, 96, 97, 98, 99 or 105 parts, 2.5 to 5 parts of calcined alum, such as 2.5, 3, 3.5, 4, 4.5 or 5 parts, 4 to 7 parts of sodium sulfate, such as 4, 5, 6 or 7 parts, 25 to 35 parts of dihydrate gypsum seed crystal, such as 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35 parts, but not limited to the recited values, and other values not recited in the range of values are also applicable.
In the present invention, the hydration rate of natural anhydrite can be further improved by preferably controlling the weight parts of the natural anhydrite powder, the calcined alum, the sodium sulfate and the dihydrate gypsum seed crystal within a specific range.
Preferably, the mass ratio of water to natural anhydrite powder in the mixing in step (2) is (5-7): 1, which may be, for example, 5.
Preferably, the temperature of the hydration reaction in step (2) is 20-35 ℃, for example, 20 ℃, 22 ℃, 24 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 34 ℃ or 35 ℃, but not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the hydration reaction is carried out at a stirring speed of 100 to 250r/min, which may be, for example, 100r/min, 120r/min, 140r/min, 160r/min, 180r/min, 200r/min, 220r/min or 250r/min, but is not limited to the values listed, and other values not listed within the range of values are equally applicable.
Preferably, the hydration time is 20-24h, for example 20h, 21h, 22h, 23h or 24h, but not limited to the recited values, and other values not recited in the range of values are equally applicable.
Preferably, the solid-liquid separation mode in the step (2) is spin-drying centrifugal separation.
Preferably, the mixing in the step (3) comprises the following components in parts by weight: 95 to 105 parts of dihydrate gypsum, for example 95 parts, 96 parts, 97 parts, 98 parts, 99 parts, 100 parts, 102 parts or 105 parts, and 0.6 to 1 part of crystal modifier, for example 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts or 1 part, but not limited to the values listed, and other values not listed in the numerical range are also applicable.
Preferably, the mass ratio of water to dihydrate gypsum in the mixture in step (3) is (2.5-4): 1, which can be, for example, 2.5.
Preferably, the temperature of the pressurized hydrothermal reaction in step (3) is 120 to 140 ℃, for example, 120 ℃, 125 ℃, 130 ℃, 135 ℃ or 140 ℃, but not limited to the recited values, and other values not recited in the numerical ranges are also applicable.
The invention preferably controls the temperature of the pressurized hydrothermal reaction within a specific range, and can further improve the performance of the prepared alpha high-strength gypsum.
Preferably, the time of the pressurized hydrothermal reaction is 2 to 3 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the pressure of the pressurized hydrothermal reaction is 0.2 to 0.3MPa, and may be, for example, 0.2MPa, 0.22MPa, 0.24MPa, 0.26MPa, 0.28MPa or 0.3MPa, but is not limited to the values listed, and other values not listed in the numerical range are also applicable.
The invention preferably controls the pressure of the pressurized hydrothermal reaction within a specific range, and can further improve the performance of the prepared alpha high-strength gypsum.
Preferably, the solid-liquid separation mode in the step (3) is spin-drying centrifugal separation.
Preferably, the drying temperature in step (3) is 135-160 ℃, for example 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃ or 160 ℃, but not limited to the recited values, and other values not recited in the range of values are equally applicable.
Preferably, the drying time is 2-2.5h, for example 2h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h, but not limited to the recited values, and other values not recited in the range of values are equally applicable.
Preferably, the grinding time in step (3) is equal to or longer than 30min, such as 30min, 35min, 40min, 45min or 50min, but not limited to the recited values, and other unrecited values in the range of values are also applicable.
Preferably, the alpha high strength gypsum has an average particle size of 5 to 15 μm, for example, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm or 15 μm, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) Grinding natural anhydrite to obtain natural anhydrite powder, wherein the average particle size of the natural anhydrite powder is less than or equal to 18 mu m;
(2) Mixing the natural anhydrite powder obtained in the step (1), calcined alum, sodium sulfate, dihydrate gypsum seed crystals and water, wherein the mixing comprises the following components in parts by weight: 95-105 parts of natural anhydrite powder, 2.5-5 parts of calcined alum, 4-7 parts of sodium sulfate and 25-35 parts of dihydrate gypsum seed crystal, wherein the mass ratio of the water to the natural anhydrite powder is (5-7) to 1, then hydration reaction is carried out for 20-24h at the temperature of 20-35 ℃ and the stirring speed of 100-250r/min, and then solid-liquid separation is carried out to obtain dihydrate gypsum;
the calcined alum is prepared by calcining aluminum potassium sulfate dodecahydrate at 650-700 ℃ for 1-1.5h and then grinding;
(3) Mixing the dihydrate gypsum obtained in the step (2), a crystal modifier and water, wherein the mixing comprises the following components in parts by weight: 95-105 parts of dihydrate gypsum and 0.6-1 part of crystal modifier, wherein the mass ratio of water to dihydrate gypsum in the mixing is (2.5-4): 1, then the pressurized hydrothermal reaction is carried out for 2-3h at 120-140 ℃ and 0.2-0.3MPa, then the solid-liquid separation is carried out to obtain semi-hydrated gypsum, the semi-hydrated gypsum is dried for 2-2.5h at 135-160 ℃, and then the semi-hydrated gypsum is ground for more than or equal to 30min to obtain the alpha high-strength gypsum.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the method provided by the invention, the natural anhydrite is quickly hydrated in 24 hours in a simple and economic manner such as grinding, adding of an excitant and the like in the hydration process of the natural anhydrite, the hydration rate can reach more than 83.58 percent, under a better condition, the hydration rate can reach more than 88.12 percent, the hydration time of the natural anhydrite is greatly shortened, and the performance of a hydration product meets the condition for preparing the alpha semi-hydrated gypsum.
(2) According to the method provided by the invention, the dihydrate gypsum is prepared by adopting the natural anhydrite, the pressurized hydrothermal reaction is carried out to prepare the hemihydrate gypsum, and then the alpha high-strength gypsum powder is obtained in one step, so that the utilization rate of the crystal modifier is high, and the performance of the high-strength gypsum is excellent.
(3) The alpha high-strength gypsum prepared by the method provided by the invention has high strength, the 2h bending resistance can reach more than 2.4MPa, the 2h compression resistance can reach more than 12.3MPa, and the dry compression resistance can reach more than 30.5 MPa; under better conditions, the 2h bending resistance can reach more than 6.5MPa, the 2h compression resistance can reach more than 22.9MPa, the dry compression resistance can reach more than 49.1MPa, and the alpha 50 grade specified by JC/T2038-2010 standard is met.
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.
Example 1
This embodiment provides a method for preparing alpha high-strength gypsum from natural anhydrite, which includes the following steps:
(1) Grinding natural anhydrite to obtain natural anhydrite powder, wherein the average grain diameter of the natural anhydrite powder is 17 mu m;
(2) Mixing the natural anhydrite powder obtained in the step (1), calcined alum, sodium sulfate, dihydrate gypsum seed crystals and water, wherein the mixing comprises the following components in parts by weight: 100 parts of natural anhydrite powder, 3 parts of calcined alum, 6 parts of sodium sulfate and 30 parts of dihydrate gypsum seed crystals (desulfurized gypsum), wherein the mass ratio of the water to the natural anhydrite powder is 6;
the calcined alum is prepared by calcining aluminum potassium sulfate dodecahydrate at 670 ℃ for 1.2h and then grinding;
(3) Mixing the dihydrate gypsum obtained in the step (2), a crystal modifier and water, wherein the mixing comprises the following components in parts by weight: 100 parts of dihydrate gypsum and 0.9 part of crystal transformation agent (citric acid), wherein the mass ratio of water to dihydrate gypsum in the mixing is 3.
Example 2
This embodiment provides a method for preparing alpha high-strength gypsum from natural anhydrite, which includes the following steps:
(1) Grinding natural anhydrite to obtain natural anhydrite powder, wherein the average particle size of the natural anhydrite powder is 6.5 mu m;
(2) Mixing the natural anhydrite powder obtained in the step (1), calcined alum, sodium sulfate, dihydrate gypsum seed crystals and water, wherein the mixing comprises the following components in parts by weight: 105 parts of natural anhydrite powder, 5 parts of calcined alum, 4 parts of sodium sulfate and 35 parts of dihydrate gypsum seed crystal (salt gypsum), wherein the mass ratio of the water to the natural anhydrite powder is 5;
the calcined alum is prepared by calcining aluminum potassium sulfate dodecahydrate at 650 ℃ for 1h and then grinding;
(3) Mixing the dihydrate gypsum obtained in the step (2), a crystal modifier and water, wherein the mixing comprises the following components in parts by weight: 100 parts of dihydrate gypsum and 0.8 part of a crystal modifier (citric acid), wherein the mass ratio of water to the dihydrate gypsum in the mixing is 4.
Example 3
This embodiment provides a method for preparing alpha high-strength gypsum from natural anhydrite, which includes the following steps:
(1) Grinding natural anhydrite to obtain natural anhydrite powder, wherein the average particle size of the natural anhydrite powder is 18 mu m;
(2) Mixing the natural anhydrite powder obtained in the step (1), calcined alum, sodium sulfate, dihydrate gypsum seed crystals and water, wherein the mixing comprises the following components in parts by weight: 95 parts of natural anhydrite powder, 4 parts of calcined alum, 5 parts of sodium sulfate and 25 parts of dihydrate gypsum seed crystals (dihydrate gypsum obtained in the step (2) in the example 1), wherein the mass ratio of the water to the natural anhydrite powder is 7;
the calcined alum is obtained by calcining aluminum potassium sulfate dodecahydrate at 700 ℃ for 1.5h and then grinding;
(3) Mixing the dihydrate gypsum obtained in the step (2), a crystal modifier and water, wherein the mixing comprises the following components in parts by weight: 100 parts of dihydrate gypsum and 1 part of a crystal modifier (citric acid), wherein the mass ratio of the mixed reclaimed water to the dihydrate gypsum is 3.5.
Example 4
This example provides a method for preparing alpha high strength gypsum from natural anhydrite, which is different from example 1 only in that the natural anhydrite powder of step (1) has an average particle size of 20 μm.
Example 5
This example provides a method for preparing alpha high strength gypsum from natural anhydrite, which is different from example 1 only in that the natural anhydrite powder is mixed in the step (2) in 80 parts.
Example 6
This example provides a method for preparing alpha high strength gypsum from natural anhydrite, which is different from example 1 only in that the natural anhydrite powder is mixed in the step (2) in 120 parts.
Comparative example 1
This comparative example provides a method for preparing alpha high strength gypsum from natural anhydrite, which is different from that of example 1 only in that sodium sulfate and calcined alum are not added to the mixing in the step (2).
Comparative example 2
The present comparative example provides a method for preparing alpha high strength gypsum from natural anhydrite, which is different from example 1 only in that step (1) is not performed, i.e., natural gypsum is not ground, and step (2) is performed by directly mixing with calcined alum, sodium sulfate, dihydrate gypsum seed crystals, and water.
The hydration rate of the natural anhydrite of examples 1 to 6 and comparative examples 1 to 2 was measured by: the hydration of natural anhydrite hydrated to a prescribed age was terminated with absolute ethanol, dried at 50 ℃, accurately weighed to a constant weight, hydrated samples of natural anhydrite were calcined at 450 ℃ for 30min, and the mass fraction of crystal water was measured, from which the mass fraction of dihydrate gypsum and the hydration rate of natural anhydrite were calculated, with the results shown in table 1.
The median diameter of dihydrate gypsum obtained by hydrating natural anhydrite in examples 1 to 6 and comparative examples 1 to 2 was measured, and the results are shown in Table 1.
The properties of the alpha high strength gypsum prepared in examples 1 to 6 and comparative examples 1 to 2, such as bulk density, whiteness, standard consistency, initial setting time, final setting time, 2h flexural strength, 2h compressive strength, and dry compressive strength, were measured, and the results are shown in Table 2.
TABLE 1
| Hydration rate/% of natural anhydrite | Median diameter/mum of dihydrate gypsum | |
| Example 1 | 90.57 | 42.06 |
| Example 2 | 91.89 | 48.85 |
| Example 3 | 88.12 | 39.48 |
| Example 4 | 85.28 | 29.23 |
| Example 5 | 91.34 | 41.08 |
| Example 6 | 83.58 | 35.29 |
| Comparative example 1 | 35.18 | 18.49 |
| Comparative example 2 | 55.63 | 23.39 |
TABLE 2
From tables 1 and 2, the following points can be seen:
(1) In examples 1-6, the hydration rate of natural anhydrite can reach more than 83.58%, under better conditions can reach more than 88.12%, the median diameter of dihydrate gypsum can reach more than 29.23 μm, and under better conditions can reach more than 39.48%; the 2h fracture resistance of the alpha high-strength gypsum obtained in the embodiments 1 to 6 can reach more than 2.4MPa, the 2h compression resistance can reach more than 12.3MPa, and the dry compression resistance can reach more than 30.5 MPa; under better conditions, the 2h bending resistance can reach more than 6.5MPa, the 2h compression resistance can reach more than 22.9MPa, and the dry compression resistance can reach more than 49.1 MPa.
(2) Comparing the data of example 1 and example 4 together, it can be seen that the average particle size of the natural anhydrite powder in example 1 is 17 μm, and compared with 20 μm in example 4, the hydration rate in example 1 is significantly better than that in example 4, and furthermore, the 2h compression resistance, 2h fracture resistance and dry compression resistance of the alpha high-strength gypsum in example 1 are significantly better than those in example 4, so that the invention preferably controls the average particle size of the natural anhydrite powder within a specific range, and can further improve the hydration effect of the natural anhydrite and the performance of the alpha high-strength gypsum.
(3) By comprehensively comparing the data of the example 1 and the examples 5 to 6, it can be seen that the hydration rate of the natural anhydrite powder in the example 1 is obviously better than that of the examples 5 to 6, and the 2h compression resistance, the 2h fracture resistance and the dry compression resistance of the alpha high-strength gypsum prepared in the example 1 are obviously better than that of the examples 5 to 6, compared with the 80 parts and the 120 parts of the natural anhydrite powder in the examples 5 to 6, respectively, so that the invention preferably controls the parts of the natural anhydrite powder in a specific range, can further improve the hydration effect of the natural anhydrite, and improve the performance of the alpha high-strength gypsum.
(4) It can be seen by combining the data of comparative example 1 and comparative examples 1-2 that the comparative example 1 is different from the example 1 only in that no exciting agent is added, the comparative example 2 is different from the example 1 only in that no grinding is performed, the hydration rate of the natural anhydrite in the example 1 is obviously superior to that of the comparative examples 1-2, and the 2h compression resistance, 2h fracture resistance and dry compression resistance of the alpha high-strength gypsum prepared in the example 1 are obviously superior to those of the comparative examples 1-2, so that the invention can improve the hydration effect of the natural anhydrite by adding the exciting agent and grinding, and further improve the performance of the alpha high-strength gypsum.
In conclusion, the method for preparing the alpha high-strength gypsum from the natural anhydrite can greatly improve the hydration rate of the natural anhydrite and obtain the high-quality alpha high-strength gypsum product.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. A method for preparing alpha high-strength gypsum from natural anhydrite is characterized by comprising the following steps:
(1) Grinding natural anhydrite to obtain natural anhydrite powder;
(2) Mixing the natural anhydrite powder obtained in the step (1), an exciting agent, dihydrate gypsum seed crystals and water, and then sequentially carrying out hydration reaction and solid-liquid separation to obtain dihydrate gypsum;
(3) And (3) mixing the dihydrate gypsum obtained in the step (2), a crystal transformation agent and water, then sequentially carrying out pressurized hydrothermal reaction and solid-liquid separation to obtain semi-hydrated gypsum, and sequentially drying and grinding the semi-hydrated gypsum to obtain the alpha high-strength gypsum.
2. The method according to claim 1, wherein the natural anhydrite powder of step (1) has an average particle size of 18 μm or less.
3. The method of claim 1 or 2, wherein the booster of step (2) comprises calcined alum and sodium sulfate;
preferably, the calcined alum is obtained by calcining aluminum potassium sulfate dodecahydrate and then grinding;
preferably, the temperature of the calcination is 650-700 ℃;
preferably, the calcination time is 1-1.5h;
preferably, the mixing in the step (2) comprises the following components in parts by weight: 95-105 parts of natural anhydrite powder, 2.5-5 parts of calcined alum, 4-7 parts of sodium sulfate and 25-35 parts of dihydrate gypsum seed crystal;
preferably, the mass ratio of the water to the natural anhydrite powder in the mixing in the step (2) is (5-7): 1.
4. The method according to any one of claims 1 to 3, wherein the temperature of the hydration reaction of step (2) is 20 to 35 ℃;
preferably, the stirring speed of the hydration reaction is 100-250r/min;
preferably, the time of the hydration reaction is 20-24h.
5. The method as claimed in any one of claims 1 to 4, wherein the solid-liquid separation in step (2) is spin-drying centrifugal separation.
6. The method according to any one of claims 1 to 5, wherein the mixing in step (3) comprises, in parts by weight: 95-105 parts of dihydrate gypsum and 0.6-1 part of crystal modifier;
preferably, the mass ratio of the water to the dihydrate gypsum in the mixing in the step (3) is (2.5-4): 1.
7. The process according to any one of claims 1 to 6, wherein the temperature of the pressurized hydrothermal reaction of step (3) is 120 to 140 ℃;
preferably, the time of the pressurized hydrothermal reaction is 2-3h;
preferably, the pressure of the pressurized hydrothermal reaction is 0.2-0.3MPa;
preferably, the solid-liquid separation mode in the step (3) is spin-drying centrifugal separation.
8. The method according to any one of claims 1 to 7, wherein the temperature of the drying in step (3) is 135 to 160 ℃;
preferably, the drying time is 2-2.5h.
9. The method according to any one of claims 1 to 8, wherein the grinding time in the step (3) is more than or equal to 30min;
preferably, the alpha high strength gypsum has an average particle size of 5-15 μm.
10. Method according to any of claims 1-9, characterized in that the method comprises the steps of:
(1) Grinding natural anhydrite to obtain natural anhydrite powder, wherein the average particle size of the natural anhydrite powder is less than or equal to 18 mu m;
(2) Mixing the natural anhydrite powder obtained in the step (1), calcined alum, sodium sulfate, dihydrate gypsum seed crystals and water, wherein the mixing comprises the following components in parts by weight: 95-105 parts of natural anhydrite powder, 2.5-5 parts of calcined alum, 4-7 parts of sodium sulfate and 25-35 parts of dihydrate gypsum seed crystal, wherein the mass ratio of the water to the natural anhydrite powder is (5-7) to 1, then hydration reaction is carried out for 20-24h at the temperature of 20-35 ℃ and at the stirring speed of 100-250r/min, and then solid-liquid separation is carried out to obtain dihydrate gypsum;
the calcined alum is prepared by calcining aluminum potassium sulfate dodecahydrate at 650-700 ℃ for 1-1.5h and then grinding;
(3) Mixing the dihydrate gypsum obtained in the step (2), a crystal modifier and water, wherein the mixing comprises the following components in parts by weight: 95-105 parts of dihydrate gypsum and 0.6-1 part of crystal modifier, wherein the mass ratio of water to dihydrate gypsum in the mixing is (2.5-4): 1, then the pressurized hydrothermal reaction is carried out for 2-3h at 120-140 ℃ and 0.2-0.3MPa, then the solid-liquid separation is carried out to obtain semi-hydrated gypsum, the semi-hydrated gypsum is dried for 2-2.5h at 135-160 ℃, and then the semi-hydrated gypsum is ground for more than or equal to 30min to obtain the alpha high-strength gypsum.
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| CN110818304A (en) * | 2019-12-19 | 2020-02-21 | 江苏一夫科技股份有限公司 | Method for preparing α hemihydrate gypsum |
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