CN115745443B - Method for preparing alpha-hemihydrate gypsum from undisturbed phosphogypsum with low reaction medium dosage - Google Patents
Method for preparing alpha-hemihydrate gypsum from undisturbed phosphogypsum with low reaction medium dosage Download PDFInfo
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- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 title claims abstract description 82
- 239000012429 reaction media Substances 0.000 title claims abstract description 25
- 238000000034 method Methods 0.000 title claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 44
- 239000010440 gypsum Substances 0.000 claims abstract description 32
- 229910052602 gypsum Inorganic materials 0.000 claims abstract description 32
- 239000002002 slurry Substances 0.000 claims abstract description 25
- 238000006243 chemical reaction Methods 0.000 claims abstract description 15
- 239000013078 crystal Substances 0.000 claims abstract description 14
- 239000004014 plasticizer Substances 0.000 claims abstract description 14
- 230000009466 transformation Effects 0.000 claims abstract description 10
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 8
- 150000003839 salts Chemical class 0.000 claims abstract description 8
- 238000003756 stirring Methods 0.000 claims abstract description 8
- 239000007787 solid Substances 0.000 claims abstract description 7
- 230000032683 aging Effects 0.000 claims abstract description 6
- 238000002156 mixing Methods 0.000 claims abstract description 5
- 238000010438 heat treatment Methods 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims abstract description 4
- 238000001694 spray drying Methods 0.000 claims abstract description 4
- 239000003638 chemical reducing agent Substances 0.000 claims description 21
- 229920005646 polycarboxylate Polymers 0.000 claims description 17
- 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 description 13
- 239000002245 particle Substances 0.000 claims description 12
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 9
- 125000002467 phosphate group Chemical group [H]OP(=O)(O[H])O[*] 0.000 claims description 9
- 235000002639 sodium chloride Nutrition 0.000 claims description 9
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 7
- 229910000077 silane Inorganic materials 0.000 claims description 7
- 239000000292 calcium oxide Substances 0.000 claims description 5
- 235000012255 calcium oxide Nutrition 0.000 claims description 5
- 230000008878 coupling Effects 0.000 claims description 5
- 238000010168 coupling process Methods 0.000 claims description 5
- 238000005859 coupling reaction Methods 0.000 claims description 5
- 239000002893 slag Substances 0.000 claims description 5
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 4
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 claims description 4
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 4
- 239000001110 calcium chloride Substances 0.000 claims description 4
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 4
- 235000011148 calcium chloride Nutrition 0.000 claims description 4
- DGVVJWXRCWCCOD-UHFFFAOYSA-N naphthalene;hydrate Chemical compound O.C1=CC=CC2=CC=CC=C21 DGVVJWXRCWCCOD-UHFFFAOYSA-N 0.000 claims description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 3
- 238000005243 fluidization Methods 0.000 claims description 3
- 239000010959 steel Substances 0.000 claims description 3
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052943 magnesium sulfate Inorganic materials 0.000 claims description 2
- 235000019341 magnesium sulphate Nutrition 0.000 claims description 2
- 239000001103 potassium chloride Substances 0.000 claims description 2
- 235000011164 potassium chloride Nutrition 0.000 claims description 2
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 claims description 2
- 229910052939 potassium sulfate Inorganic materials 0.000 claims description 2
- 235000011151 potassium sulphates Nutrition 0.000 claims description 2
- 239000011780 sodium chloride Substances 0.000 claims description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 2
- 235000011152 sodium sulphate Nutrition 0.000 claims description 2
- 238000005265 energy consumption Methods 0.000 abstract description 3
- 238000001027 hydrothermal synthesis Methods 0.000 abstract description 3
- 238000001035 drying Methods 0.000 abstract description 2
- 239000011148 porous material Substances 0.000 abstract description 2
- 238000000879 optical micrograph Methods 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 239000012266 salt solution Substances 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 239000004566 building material Substances 0.000 description 3
- 239000011575 calcium Substances 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- XDLMVUHYZWKMMD-UHFFFAOYSA-N 3-trimethoxysilylpropyl 2-methylprop-2-enoate Chemical compound CO[Si](OC)(OC)CCCOC(=O)C(C)=C XDLMVUHYZWKMMD-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 239000004035 construction material Substances 0.000 description 2
- 239000008151 electrolyte solution Substances 0.000 description 2
- 238000005189 flocculation Methods 0.000 description 2
- 230000016615 flocculation Effects 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 239000008030 superplasticizer Substances 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 238000000889 atomisation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 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
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011507 gypsum plaster Substances 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- -1 phosphate ester Chemical class 0.000 description 1
- 239000002686 phosphate fertilizer Substances 0.000 description 1
- 239000002367 phosphate rock Substances 0.000 description 1
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 229910021487 silica fume Inorganic materials 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Landscapes
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention relates to a method for preparing alpha-hemihydrate gypsum by using undisturbed phosphogypsum under the condition of low reaction medium dosage, which comprises the following specific steps: 1) Uniformly mixing water and a plasticizer, adding the mixture into undisturbed phosphogypsum, adding a passivating agent, uniformly stirring and aging to obtain high-flow phosphogypsum slurry; 2) Adding a salt medium into the high-flow-state phosphogypsum slurry, uniformly stirring, and heating to perform a crystal transformation reaction to obtain high-solid-content alpha-type high-strength gypsum slurry; 3) And (3) carrying out spray drying on the alpha-type high-strength gypsum slurry with high solid content to obtain the alpha-type semi-hydrated gypsum. According to the invention, the plasticizer is added to release water in phosphogypsum pores, so that the water utilization rate is improved, the alpha-type semi-hydrated gypsum is prepared by carrying out the reaction under the condition of lower water-paste ratio, the water consumption is low, the post-treatment is simple and convenient, the drying is quick, and the problems that a large amount of reaction medium is required to be consumed and the energy consumption required by the post-treatment is high in the conventional normal-pressure hydrothermal method are solved.
Description
Technical Field
The invention belongs to the technical field of building materials using phosphogypsum as a raw material, and particularly relates to a method for preparing alpha-hemihydrate gypsum by using undisturbed phosphogypsum under the condition of low reaction medium consumption.
Background
Phosphogypsum is a solid byproduct generated when sulfuric acid is used for treating phosphorite in the process of producing phosphoric acid by a wet method, and contains soluble phosphorus, eutectic phosphorus, fluorine, organic matters, alkali metal and other impurities according to different production processes. About 4-5 tons of phosphogypsum are discharged per 1 ton of phosphoric acid produced. The phosphogypsum storage amount in China is huge, and along with the increase of the yield of the phosphate fertilizer, the phosphogypsum storage amount is increased day by day, so that serious environmental pollution and ecological hazard problems are caused. The alpha-type high-strength gypsum produced by using phosphogypsum is an important way and research direction for the resource utilization of phosphogypsum, and has wide commercial prospect and social significance.
The existing method for preparing the alpha high-strength gypsum generally adopts a normal-pressure hydrothermal process to carry out a crystal phase transformation reaction, a large amount of electrolyte solution with higher concentration is needed to be added as a reaction medium, 2.4-5.9 tons of reaction medium is needed for each 1 ton of alpha high-strength gypsum produced on average, the reaction medium is not consumed in the reaction process, so that the product alpha high-strength gypsum is obtained after the crystal phase transformation, the reaction medium is filtered, washed and dried, most of the reaction medium faces to the discharge pressure after the reaction is finished, the whole production process has overlarge consumption of the reaction medium and energy, and 2.2-5.3 tons of electrolyte waste liquid is discharged for each 1 ton of high-strength gypsum produced, and the method is high in difficulty in waste liquid treatment due to the fact that the electrolyte solution with high concentration contains complex impurities, increases the production cost and is not green and environment-friendly.
Based on this, it is necessary to study a method for preparing alpha hemihydrate gypsum using a low amount of reaction medium.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for preparing alpha-type hemihydrate gypsum by using undisturbed phosphogypsum with low reaction medium consumption, which adopts extremely low reaction medium consumption, has simple and convenient post-treatment and low energy consumption, and the prepared alpha-type hemihydrate gypsum has high purity, excellent performance and high added value.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the method for preparing alpha-hemihydrate gypsum by using the undisturbed phosphogypsum under the condition of low reaction medium dosage comprises the following specific steps:
1) Uniformly mixing water and a plasticizer, adding the mixture into undisturbed phosphogypsum, adding a passivating agent, uniformly stirring and aging to obtain high-flow phosphogypsum slurry;
2) Adding a salt medium into the high-flow-state phosphogypsum slurry obtained in the step 1), uniformly stirring, and heating to perform a crystal transformation reaction to obtain high-solid-content alpha-type high-strength gypsum slurry;
3) And (3) carrying out spray drying on the high-solid-content alpha-type high-strength gypsum slurry obtained in the step (2) to obtain alpha-type semi-hydrated gypsum.
According to the scheme, the water content of the undisturbed phosphogypsum in the step 1) is 10-40 wt%, wherein the calcium sulfate dihydrate accounts for more than 95% of the solid content of the phosphogypsum.
According to the scheme, the plasticizer in the step 1) is a polycarboxylate water reducer containing phosphate groups, and one or more of silane coupling modified polycarboxylate water reducers (such as gamma-methacryloxypropyl trimethoxy silane modified polycarboxylate water reducer) and naphthalene water reducers are used in an amount of 0.1-1% of the mass of the original phosphogypsum. The plasticizer can be adsorbed on the surface of the gypsum particles when being acted on the gypsum, so that the surface of the gypsum particles is negatively charged to form electrostatic repulsion, the mutual dispersion of the gypsum particles is promoted to destroy a flocculation structure, and the wrapped water molecules are released to participate in flowing. The effect of the polycarboxylate water reducer containing phosphate groups and the silane coupling modified polycarboxylate water reducer is better than that of naphthalene water reducer.
According to the scheme, the passivating agent in the step 1) is one or more of quicklime, carbide slag and steel slag. The passivating agent is used for adjusting the pH value and stabilizing impurities in phosphogypsum. The steel slag is alkaline, wherein the content of calcium oxide is 40-60 wt%.
According to the scheme, the mass ratio of the water, the plasticizer, the passivating agent and the undisturbed phosphogypsum in the step 1) is 20-50: 0.3 to 1:1 to 5:100.
according to the scheme, the ageing time of the step 1) is 1-8 h.
According to the scheme, the fluidity of the high-fluidity phosphogypsum slurry in the step 1) is 150-250 mm, and the pH value is 5-7.
According to the scheme, the salt medium in the step 2) is one or more of calcium chloride, sodium chloride, potassium chloride, magnesium sulfate, potassium sulfate and sodium sulfate, and the mass ratio of the salt medium to the water in the step 1) is 1:3 to 5. The salt medium can increase the solubility of calcium sulfate dihydrate in phosphogypsum.
According to the scheme, the crystallization reaction conditions in the step 2) are as follows: reacting for 30-240 min at 95-100 ℃.
The invention also comprises the alpha-hemihydrate gypsum prepared by the method, the purity of the alpha-hemihydrate gypsum is more than 95 weight percent, and the average grain diameter of the alpha-hemihydrate gypsum is 2-50 mu m.
The invention takes the original phosphogypsum as the raw material, realizes the high solid content in situ crystal transformation of phosphogypsum through plasticizing modification, because the plasticizer contains the functional group with strong adsorptivity, the carried functional group can be complexed with calcium ions in the phosphogypsum to be effectively adsorbed on the surface of the gypsum particles, so that the surface of the gypsum particles has negative charges to form electrostatic repulsive interaction, promote mutual dispersion among the gypsum particles, destroy flocculation structure, release water molecules coated in the phosphogypsum to participate in flowing, thus improving the fluidity of the phosphogypsum under the condition of a small amount of reaction medium (salt solution), being convenient for fully mixing calcium sulfate dihydrate in the phosphogypsum with the salt solution, providing a good liquid phase environment for the crystal transformation of calcium sulfate dihydrate in the phosphogypsum, and when the salt solution meets certain thermodynamic conditions, the solubility of the calcium sulfate dihydrate is higher than alpha-type hemihydrate gypsum, and the calcium sulfate dihydrate is gradually dissolved in the salt solution to release Ca 2+ With SO 4 2+ After reaching the dissolution equilibrium of calcium sulfate dihydrate, these Ca' s 2+ With SO 4 2+ Supersaturation of alpha-hemihydrate gypsum, which combines with 0.5 times of water molecules to produce alpha-hemihydrate gypsum with lower solubility, and precipitation of alpha-hemihydrate gypsum reduces Ca 2+ With SO 4 2+ The concentration of the calcium sulfate dihydrate is promoted to be continuously dissolved, and finally, the complete conversion from the calcium sulfate dihydrate to the alpha-type semi-hydrated gypsum can be realized, so that the alpha-type semi-hydrated gypsum with convenient post-treatment and excellent performance is prepared, and a new way is provided for the high-strength alpha-semi-hydrated gypsum prepared by phosphogypsum with high efficiency and low cost.
The invention has the beneficial effects that: 1. the invention provides a method for preparing alpha-type semi-hydrated gypsum by using undisturbed phosphogypsum under the condition of low reaction medium dosage, which releases water in phosphogypsum pores by adding a plasticizer, improves the utilization rate of water and realizes the preparation of alpha-type semi-hydrated gypsum by carrying out reaction under the condition of lower water-paste ratio, and the method has the advantages of less water consumption, simple and convenient post-treatment and quick drying, and solves the problems that a large amount of reaction medium is required to be consumed and the energy consumption is high in the post-treatment of the existing normal-pressure hydrothermal method. 2. The alpha-type semi-hydrated gypsum provided by the invention has high purity, excellent performance in the aspects of strength, hardness, biocompatibility and the like, and high economic added value.
Drawings
FIG. 1 is a photograph showing the process of preparing alpha-hemihydrate gypsum from raw phosphogypsum in example 1 of the present invention;
FIG. 2 is an optical micrograph of alpha hemihydrate gypsum prepared in example 1;
FIG. 3 is an optical micrograph of alpha hemihydrate gypsum prepared in example 2;
FIG. 4 is an optical micrograph of alpha hemihydrate gypsum prepared in example 3;
FIG. 5 is an optical micrograph of alpha hemihydrate gypsum prepared in comparative example 1;
FIG. 6 is a graph comparing the 3d compressive strength of the alpha hemihydrate gypsum prepared in examples 1-3 and comparative example 1.
Detailed Description
The present invention will be described in further detail below with reference to the accompanying drawings, so that those skilled in the art can better understand the technical scheme of the present invention.
The preparation method of the polycarboxylate water reducer containing phosphate groups used in the embodiment of the invention is as follows: huang, etl. Dispersing silica fume in cementitious materials by silane copolymerizedpolycarboxylate Superplasticizer: on the role of dispersion effectiveness as a function of silane concentration [ J ]. Construction and Building Materials,326 (2022) 126832.
The silane coupling modified polycarboxylate water reducer used in the embodiment of the invention is gamma-methacryloxypropyl trimethoxy silane modified polycarboxylate water reducer, and the preparation method is as follows: h.qi, etl.polycarboxylate superplasticizer modified by phosphate ester in side chain and its basicproperties in gypsum plaster [ J ]. Construction and Building Materials,271 (2021) 121566.
Example 1
A method for preparing alpha-hemihydrate gypsum by using undisturbed phosphogypsum under low reaction medium dosage comprises the following specific steps:
1) Uniformly mixing water and a polycarboxylate water reducer containing phosphate groups, adding the mixture into original phosphogypsum (the water content is 37%, and calcium sulfate dihydrate accounts for 95.18% by weight of solid content), and adding quicklime, wherein the mass of the polycarboxylate water reducer containing phosphate groups is 0.8% of that of the original phosphogypsum, the mass of the quicklime is 2% of that of the original phosphogypsum, and the mass ratio of the water to the original phosphogypsum is 1:5, uniformly stirring and aging for 5 hours to obtain high-fluidization phosphogypsum slurry with the fluidity of 180mm and the pH value of 6.7;
2) Adding calcium chloride into the high-fluidization phosphogypsum slurry obtained in the step 1), wherein the mass ratio of the calcium chloride to the water in the step 1) is 1:4, uniformly stirring, heating to 95 ℃ to perform crystal transformation reaction for 3 hours, and obtaining alpha-type semi-hydrated gypsum slurry with high solid content after the reaction for 3 hours;
3) And (3) performing pressure spray drying on the high-solid-content phosphorus-based high-strength gypsum slurry obtained in the step (2) through an atomization spray gun to obtain alpha-hemihydrate gypsum with the average particle size of 19.8 mu m and the purity of 97 wt%.
Fig. 1 is a photograph showing the reaction process of preparing alpha-hemihydrate gypsum from raw phosphogypsum in this example, wherein a is a photograph of raw phosphogypsum, b is a photograph of high-flow phosphogypsum slurry, c is an optical micrograph of phosphogypsum in the high-flow phosphogypsum slurry, and d is an optical micrograph of alpha-hemihydrate gypsum slurry. Comparison shows that the polycarboxylic acid water reducer containing the phosphoric acid group is adopted in the embodiment, only a small amount of water is needed to be added, so that the liquid high-flow-state phosphogypsum slurry can be obtained, and comparison between c and d shows that after the crystal transformation reaction, the parallelogram-plate-shaped calcium sulfate dihydrate in the gypsum slurry is completely converted into the needle-shaped alpha-type semi-hydrated gypsum.
Fig. 2 is an optical micrograph of the alpha-hemihydrate gypsum prepared in this example, and it can be seen that the obtained product has a uniform particle size, is a needle-like crystal, and is alpha-hemihydrate gypsum.
Example 2
This embodiment differs from embodiment 1 in that: the polycarboxylate water reducer containing the phosphate group in the step 1) is replaced by a silane coupling modified polycarboxylate water reducer with equal mass. The remaining steps were the same as in example 1.
The optical micrograph of the alpha-hemihydrate gypsum prepared in the embodiment is shown in fig. 3, and it can be seen that the obtained product has uniform particle size, is a needle-shaped crystal, and is the alpha-hemihydrate gypsum.
Example 3
This embodiment differs from embodiment 1 in that: the polycarboxylate water reducer containing phosphate groups in the step 1) is changed into naphthalene water reducer with equal mass, and the mass ratio of water to raw phosphogypsum is 1:4. the remaining steps were the same as in example 1.
The optical micrograph of the alpha-hemihydrate gypsum prepared in the embodiment is shown in fig. 4, and it can be seen that the obtained product has uniform particle size, is a needle-shaped crystal, and is the alpha-hemihydrate gypsum.
Comparative example 1
The difference between this comparative example and example 1 is that: the polycarboxylate water reducer without phosphate groups is added in the step 1), and the mass ratio of water to the undisturbed phosphogypsum is 1:1. the remaining steps were the same as in example 1.
The optical micrograph of the alpha-hemihydrate gypsum prepared in the comparative example is shown in fig. 5, and it can be seen that the obtained product has uniform particle size, is a needle-shaped crystal, and is the alpha-hemihydrate gypsum.
The high-flow phosphogypsum slurry obtained in step 1) of the above examples 1 to 3 and comparative example 1 was subjected to fluidity test, and the test results are shown in Table 1.
TABLE 1
Compared with the prior art, the invention adopts the plasticizer to modify the undisturbed phosphogypsum, and can effectively reduce the water consumption in the system so as to basically maintain the fluidity of the prepared phosphogypsum slurry.
Fig. 6 is a graph comparing the 3d compressive strengths of the alpha hemihydrate gypsum prepared in examples 1-3 and comparative example 1, and it can be seen that the 3d compressive strengths of several alpha hemihydrate gypsum are substantially similar, illustrating that the mechanical properties of the prepared samples remain equivalent while the amount of water can be greatly reduced by using the plasticizer, in comparison, the 3d compressive strength of the alpha hemihydrate gypsum prepared in example 1 is highest.
Claims (7)
1. A method for preparing alpha-hemihydrate gypsum by using undisturbed phosphogypsum under low reaction medium dosage is characterized by comprising the following specific steps:
1) Uniformly mixing water and a plasticizer, adding the mixture into original phosphogypsum, and then adding a passivating agent, wherein the mass ratio of the water, the plasticizer and the passivating agent to the original phosphogypsum is 20-50: 0.3-1: 1-5: 100, uniformly stirring and aging to obtain high-fluidization phosphogypsum slurry, wherein the aging time is 1-8 h, and the plasticizer is one or more of a polycarboxylate water reducer containing phosphate groups, a silane coupling modified polycarboxylate water reducer and a naphthalene water reducer;
2) Adding a salt medium into the high-flow-state phosphogypsum slurry obtained in the step 1), uniformly stirring, heating to perform a crystal transformation reaction, wherein the crystal transformation reaction conditions are as follows: reacting for 30-240 min at 95-100 ℃ to obtain high-solid-content alpha-type high-strength gypsum slurry;
3) And (3) carrying out spray drying on the high-solid-content alpha-type high-strength gypsum slurry obtained in the step (2) to obtain alpha-type semi-hydrated gypsum.
2. The method for preparing alpha-hemihydrate gypsum by using the undisturbed phosphogypsum in low reaction medium consumption according to claim 1, wherein the water content of the undisturbed phosphogypsum in step 1) is 10-40 wt%, and calcium sulfate dihydrate accounts for more than 95% of the phosphogypsum solid content.
3. The method for preparing alpha-hemihydrate gypsum by using undisturbed phosphogypsum in low reaction medium dosage as claimed in claim 1, wherein the plasticizer dosage in step 1) is 0.1-1% of the undisturbed phosphogypsum by mass.
4. The method for preparing alpha hemihydrate gypsum with low reaction medium dosage of the raw phosphogypsum according to claim 1, wherein the passivating agent in the step 1) is one or more of quicklime, carbide slag and steel slag.
5. The method for preparing alpha-hemihydrate gypsum from raw phosphogypsum in low reaction medium consumption according to claim 1, wherein the fluidity of the high-fluidity phosphogypsum slurry in step 1) is 150-250 mm, and the pH value is 5-7.
6. The method for preparing alpha-hemihydrate gypsum by using low reaction medium dosage of the raw phosphogypsum according to claim 1, wherein the salt medium in the step 2) is one or more of calcium chloride, sodium chloride, potassium chloride, magnesium sulfate, potassium sulfate and sodium sulfate, and the mass ratio of the salt medium to the water in the step 1) is 1: 3-5.
7. The alpha-hemihydrate gypsum prepared by the method according to any one of claims 1 to 6, which has a purity of 95wt% or more and an average particle size of 2 to 50 μm.
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| CN103288410A (en) * | 2013-05-17 | 2013-09-11 | 武汉理工大学 | Alpha high-strength gypsum based self-leveling material prepared by adopting phosphogypsum and production process thereof |
| CN104671682A (en) * | 2015-02-02 | 2015-06-03 | 武汉理工大学 | Method for preparing hemihydrate gypsum gel material and gypsum products on line by using phosphogypsum at hot stage |
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| CN103288410A (en) * | 2013-05-17 | 2013-09-11 | 武汉理工大学 | Alpha high-strength gypsum based self-leveling material prepared by adopting phosphogypsum and production process thereof |
| CN104671682A (en) * | 2015-02-02 | 2015-06-03 | 武汉理工大学 | Method for preparing hemihydrate gypsum gel material and gypsum products on line by using phosphogypsum at hot stage |
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