CN114644324A - High-strength phosphogypsum powder and production method thereof - Google Patents
High-strength phosphogypsum powder and production method thereof Download PDFInfo
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/18—Phosphoric acid
- C01B25/22—Preparation by reacting phosphate-containing material with an acid, e.g. wet process
- C01B25/222—Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen
- C01B25/228—Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen one form of calcium sulfate being formed and then converted to another form
- C01B25/231—Dihydrate-hemihydrate process
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- 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
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- 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
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Abstract
The invention belongs to the technical field of gypsum powder production, and particularly relates to high-strength phosphogypsum powder and a production method thereof. Adding phosphorite pulp and/or powdered rock phosphate into a reaction tank, then adding sulfuric acid for reaction, and controlling conditions to obtain mixed slurry A; (2) transferring part of the mixed slurry A obtained in the step (1) to a conversion tank; (3) adding sulfuric acid into the conversion tank, respectively adding surfactant crystal transfer agent, organic acid crystal transfer agent and inorganic salt crystal transfer agent, and controlling liquid-solid ratio and H in the mixed slurry3PO4And H2SO4Adopting gradient crystal transformation control conditions to obtain mixed acid slurry D; (4) and (4) carrying out solid-liquid separation, washing and drying on the mixed acid slurry D obtained in the step (3) to obtain high-strength phosphogypsum powder. The invention optimizes the phosphogypsum production process and the crystallizing agent and adoptsThe crystal is transferred in a gradient way, and the strength and the conversion rate of the product are improved.
Description
Technical Field
The invention belongs to the technical field of gypsum powder production, and particularly relates to high-strength phosphogypsum powder and a production method thereof.
Background
At present, most of phosphogypsum is directly piled in the open air without being treated, not only a large amount of land resources are occupied, but also the phosphogypsum contains soluble phosphorus, fluorine, organic matters and a small amount of harmful heavy metal chemical substances such as fortune, arsenic, Lai and the like, and has great harm to the environment.
At present, the comprehensive utilization of the phosphogypsum mainly has two ways: firstly, the cement retarder is used; secondly, producing gypsum building material products. At present, gypsum powder produced by taking phosphogypsum as a raw material mainly comprises building gypsum and high-strength gypsum. High strength gypsum generally refers to a-hemihydrate gypsum having a compressive strength of up to 25MPa to 50 MPa. Although the cost of the pretreatment process and the production process of the phosphogypsum is high, the technical added value of the product is high, and the market application prospect is good.
When the high-strength gypsum powder is prepared by taking the phosphogypsum as a raw material, the production process directly influences the performance and the process cost of the high-strength gypsum powder, and the existing phosphogypsum process has the problems of low strength and low conversion rate.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides high-strength phosphogypsum powder and a production method thereof. The invention optimizes the gypsum production process and the crystallizing agent, and improves the product strength and the conversion rate by adopting gradient crystal transformation.
On one hand, the invention provides a production method of high-strength phosphogypsum powder, which comprises the following steps:
(1) adding phosphorite pulp and/or phosphorite powder into a reaction tank, then adding sulfuric acid to react, wherein the temperature of the reaction tank is 85-95 ℃, and reacting for 2-6 hours under the condition to obtain mixed slurry A;
(2) separating 30-60% of the separated volume of the mixed slurry A obtained in the step (1) to perform solid-liquid separation to obtain clear liquid B and solid C, sending the clear liquid B serving as finished phosphoric acid into an acid base, transferring the solid C into a reaction tank, and transferring the residual mixed slurry A into a conversion tank;
(3) adding sulfuric acid into the conversion tank, adding surfactant type crystal transformation agent, and controlling liquid-solid ratio and H in the mixed slurry3PO4And H2SO4Keeping the temperature of the conversion tank at 50-60 ℃ for reaction for 1-3 hours; adding an organic acid crystal transfer agent, and reacting for 1-3 hours at the temperature of 60-80 ℃ in a conversion tank; adding an inorganic salt crystal transfer agent, and reacting for 1-3 hours at the temperature of the conversion tank between 80 ℃ and 95 ℃ to obtain mixed acid slurry D;
(4) carrying out solid-liquid separation on the mixed acid slurry D obtained in the step (3) to obtain a solid E and a filtrate F, washing the solid E with hot water, and drying the solid E to obtain high-strength phosphogypsum powder; the solid E can be directly processed into a gypsum product;
(5) and (3) introducing the filtrate F obtained in the step (4) into the reaction tank obtained in the step (1) to continuously react with the phosphorus ore pulp and/or the phosphorus ore powder.
In a further improvement of the scheme, the mass ratio of the liquid to the solid in the reaction tank in the step (1) is (1.5-4): 1.
the scheme is further improved, the fineness of the phosphorus mineral powder in the step (1) is 80-100 meshes, and the mass fractions of the components are as follows: containing phosphorus as P20525 to 33 percent of calcium oxide, 35 to 45 percent of calcium oxide, less than or equal to 3 percent of magnesium oxide, 0.5 to 4 percent of total iron oxide and aluminum oxide, 2 to 3.5 percent of fluorine, and less than or equal to 20 percent of acid insoluble substance in terms of silicon dioxide;
the mass fraction of sulfate ions in the liquid component in the mixed slurry A is 1-4%;
phosphoric acid in liquid component of mixed slurry A as P2O5The mass fraction is 18-25%.
In a further improvement of the scheme, in the step (3), the organic acid type crystal-transforming agent is sodium citrate; the surfactant type crystal transformation agent is cetyl trimethyl ammonium bromide; the inorganic salt crystal transformation agent in the step (3) is trivalent aluminum salt.
Preferably, the mass ratio of the surfactant type crystal modifier to the organic acid type crystal modifier to the trivalent aluminum salt is 1:2: 1.
in the step (3), the liquid-solid mass ratio of the mixed slurry is (1.5-4): 1, phosphoric acid in liquid thereof is represented by P2O5Accounting for 18 to 25 percent of the mass fraction of the mixed acid, and the sulfuric acid is H2SO4Accounting for 6 to 15 percent of the mixed acid by mass.
In a further improvement of the present embodiment, in the step (3), the mass fraction of alumina in the liquid phase is higher than 0.4% calculated by alumina.
In the further improvement of the scheme, the temperature of the hot water in the step (4) is 60-90 ℃; the temperature of the dried material is 80-110 ℃.
On the other hand, the invention provides the high-strength phosphogypsum powder prepared by the production method, and the high-strength phosphogypsum powder comprises the following components in parts by weight: 15-25% of anhydrous II type gypsum (CaSO4), 50-90% of semi-hydrated gypsum, 0-7% of dihydrate gypsum and 0-20% of silicon dioxide.
The invention has the beneficial effects that:
(1) the invention provides a production process of high-strength phosphogypsum powder, which optimizes parameters of each link, selects proper key crystal transformation indexes such as concentration of sulfuric acid, phosphoric acid and aluminum ions, reaction temperature and the like, comprehensively utilizes intermediate products and realizes maximum utilization of raw materials.
(2) The invention provides a gradient crystal transformation method, which adopts a mode of carrying out crystal transformation by three temperature gradients and combines the growth attributes of each link of different stages of semi-hydrated gypsum to ensure the crystal transformation rate of the semi-hydrated gypsum to the maximum.
(3) The invention preferably selects the crystal transformation agent, respectively adopts the surfactant crystal transformation agent, the organic acid crystal transformation agent and the inorganic salt crystal transformation agent, combines the crystal transformation and growth characteristics of the semi-hydrated gypsum, and is respectively used in different stages, thereby improving the conversion rate and the strength of the semi-hydrated gypsum.
Drawings
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a process flow diagram of the present invention.
FIG. 2 shows the crystal form of hemihydrate gypsum obtained in inventive example 9.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
First, control of gradient crystal transformation
Example 1:
a production method of high-strength phosphogypsum powder comprises the following steps:
(1) adding phosphorite pulp and/or powdered rock phosphate into a reaction tank, then adding sulfuric acid to react, wherein the temperature of the reaction tank is 90 ℃, and reacting for 4 hours under the condition to obtain mixed slurry A;
(2) carrying out solid-liquid separation on 40% of the separated volume of the mixed slurry A obtained in the step (1) to obtain clear liquid B and solid C, sending the clear liquid B serving as finished phosphoric acid into an acid base, transferring the solid C into a reaction tank, and transferring the residual mixed slurry A into a conversion tank;
(3) adding sulfuric acid into the conversion tank, adding surfactant type crystal transformation agent, and controlling liquid-solid ratio and H in the mixed slurry3PO4And H2SO4Maintaining the temperature of the conversion tank at 60 ℃ for reaction for 2 hours; adding an organic acid crystal-transforming agent, and maintaining the temperature of the transforming tank at 80 ℃ for reacting for 2 hours; adding an inorganic salt crystal transfer agent, and reacting for 2 hours at the temperature of 95 ℃ in the conversion tank to obtain mixed acid slurry D;
(4) carrying out solid-liquid separation on the mixed acid slurry D obtained in the step (3) to obtain a solid E and a filtrate F, washing the solid E with hot water, and drying the solid E to obtain high-strength phosphogypsum powder; the solid E can be directly processed into a gypsum product; wherein the gypsum product is preferably gypsum board, gypsum block, gypsum lath.
(5) And (3) introducing the filtrate F obtained in the step (4) into the reaction tank obtained in the step (1) to continuously react with the phosphorus ore pulp and/or the phosphorus ore powder.
The mass ratio of liquid to solid in the reaction tank in the step (1) is 3: 1.
in the step (1), the fineness of the phosphate ore powder is 80-100 meshes, and the components are as follows in mass fraction: containing phosphorus as P20525 to 33 percent of calcium oxide, 35 to 45 percent of calcium oxide, less than or equal to 3 percent of magnesium oxide, 0.5 to 4 percent of total iron oxide and aluminum oxide, 2 to 3.5 percent of fluorine, and less than or equal to 20 percent of acid insoluble substance in terms of silicon dioxide;
the mass fraction of sulfate ions in the liquid component in the mixed slurry A is 1-4%;
phosphoric acid in liquid component of mixed slurry A as P2O5The mass fraction is 18-25%.
Phosphate rock (Ca5F (P04)3) reacts with sulfuric acid to form calcium sulfate dihydrate and phosphoric acid.
The organic acid type crystal transformation agent in the step (3) is sodium citrate; the surfactant type crystal transformation agent is cetyl trimethyl ammonium bromide; the inorganic salt crystal transformation agent in the step (3) is trivalent aluminum salt gibbsite.
The mass ratio of the surfactant type crystal modifier to the organic acid type crystal modifier to the trivalent aluminum salt is 1:1: 1.
in the step (3), the liquid-solid mass ratio of the mixed slurry is 3: 1, phosphoric acid in the liquid is P2O5Accounting for 18 to 25 percent of the mass fraction of the mixed acid, and the sulfuric acid is H2SO4Accounting for 6 to 15 percent of the mixed acid by mass.
In the step (3), the mass fraction content of the alumina in the liquid phase is higher than 0.4% calculated by the alumina.
The temperature of the hot water in the step (4) is 80 ℃; the temperature of the dried material was 110 ℃.
Example 2:
the difference from the example 1 is that the step (3) is to add sulfuric acid into the conversion tank, add surfactant type crystal transformation agent cetyl trimethyl ammonium bromide, and control the liquid-solid ratio and H in the mixed slurry3PO4And H2SO4And (3) obtaining mixed slurry, and reacting for 6 hours under the condition of maintaining the temperature of the conversion tank at 60 ℃ to obtain mixed acid slurry D.
Example 3:
the difference from the embodiment 1 is that the step (3) is to add sulfuric acid into the conversion tank, add organic acid type crystal transformation agent sodium citrate, and control the liquid-solid ratio and H in the mixed slurry3PO4And H2SO4And (3) obtaining mixed slurry, and reacting for 6 hours under the condition of maintaining the temperature of the conversion tank at 80 ℃ to obtain mixed acid slurry D.
Example 4:
the difference from the embodiment 1 is that the step (3) is to add sulfuric acid into the conversion tank, add inorganic salt type crystal conversion agent, and control the liquid-solid ratio and H in the mixed slurry3PO4And H2SO4Obtaining mixed slurry, and controlling liquid-solid ratio and H in the mixed slurry3PO4And H2SO4And (3) obtaining mixed slurry, and reacting for 6 hours at the temperature of the conversion tank under the condition of 95 ℃ to obtain mixed acid slurry D.
Example 5:
the difference from the example 1 is that the step (3) adds the sulfuric acid into the conversion tank, does not add the crystal conversion agent, and controls the liquid-solid ratio and the H in the mixed slurry3PO4And H2SO4The mixed slurry is obtained, and the temperature of the conversion tank is maintained to react for 2 hours at 60 ℃; then the temperature of the conversion tank is maintained at 800 ℃ for reaction for 2 hours, and then the temperature of the conversion tank is maintained at 95 ℃ for reaction for 2 hours, so that mixed acid slurry D is obtained.
The content of the hemihydrate gypsum in the product is measured by referring to the standard building gypsum phase composition analysis method (GB/T36141-2018), and the concrete content is shown in Table 1.
TABLE 1 hemihydrate Gypsum content (%) and compressive Strength under different gradient conditions
It can be seen that the amount of the hemihydrate gypsum is significantly increased by adding the crystal transformation agent, and the amount and strength of the hemihydrate gypsum are significantly increased by using the gradient crystal transformation, as can be seen from comparing example 1 with examples 2 to 4.
The surfactant type crystal modifier mainly plays a role in reducing surface tension and promoting the generation of subsequent hemihydrate gypsum.
The crystal adjusting effect of the organic acid crystal modifier on the semi-hydrated gypsum crystal is realized through the adsorption effect, and the organic acid crystal modifier is mixed with Ca in the water solution2+The complex reaction is generated, the generated complex is selectively adsorbed on the crystal face of the (002) crystal face of the a-hemihydrate gypsum to inhibit the growth of the crystal face, and finally, the crystal face is subjected to the reactionThe crystals of a-hemihydrate gypsum obtained are short cylinders and the water consumption for standard consistency is reduced accordingly. Carboxyl and Ca ionized by organic acid crystal modifier2+And a small amount of insoluble matters are formed through interaction, so that the dissolving of the phosphogypsum in the solution is promoted, the content of the product a-hemihydrate gypsum is increased, and the strength is obviously improved.
The positive valence metal ions in the inorganic salt crystal modifier are mainly adsorbed on the (110) crystal face, and the specific surface energy of the crystal face is changed, so that S0 is hindered4 2-The crystal faces are continuously superposed to inhibit radial growth of the crystals, and the shape of the generated a-hemihydrate gypsum is still needle-shaped or rod-shaped, so that the inorganic salt cannot play a role in crystal adjustment. However, the addition of gibbsite to the set of inorganic salt crystallizers will result in A13+The non-uniionic increases ion solubility in the solution, thereby promoting dissolution of dihydrate gypsum and increasing Ca content in the solution2+And S042-The concentration of (c). Increase Ca2+The concentration has a stabilizing effect on the calcium sulfate hemihydrate, so that the generation of the a-hemihydrate gypsum is facilitated. Therefore, the addition of the gibbsite increases the content of the product a-hemihydrate gypsum, so that the strength is remarkably improved.
The contrast adopts gradient crystal transformation, the effect is obviously improved, and the analysis is as follows:
in the first crystal transformation process, crystals generated by the primary crystallization are in a small regular cube shape, and the generation of the seed crystals needs to be promoted at a gentle temperature. During the recrystallization, the generated crystal is repaired, and then the temperature is slowly increased.
The second crystallization, which is primarily a crystal growth process, increases the temperature to promote rapid formation of hemihydrate.
Example 6:
the difference from the example 1 is that in the step (3), sulfuric acid is added into the conversion tank, a surfactant type crystal transformation agent is added, and the liquid-solid ratio and the H in the mixed slurry are controlled3PO4And H2SO4The mixed slurry is obtained, and the temperature of the conversion tank is maintained at 60 ℃ for reaction for 2 hours; adding organic acid crystal-transformation agent, controlling liquid-solid ratio and H in mixed slurry3PO4And H2SO4To obtain mixed slurry; and (3) maintaining the temperature of the conversion tank at 80 ℃ for reaction for 2 hours, then adding an inorganic salt crystal transformation agent, and maintaining the temperature of the conversion tank at 95 ℃ for reaction for 2 hours to obtain mixed acid slurry D. Wherein the mass ratio of the surfactant type crystal modifier to the organic acid type crystal modifier to the inorganic salt type crystal modifier is 1:1: 1.
The amount of hemihydrate gypsum in the product was also determined to show a content of 44.79% and a strength of 47.35MPa, and it can be seen that there are different suitable temperatures for the different crystal transformation stages and the crystal transformation agent.
The organic acid crystal-transforming agent and the surfactant crystal-transforming agent are used for regulating and controlling the growth rate of each crystal face of the semi-hydrated gypsum crystal so as to change the crystal appearance, and the complex doping effect of the crystal-transforming agent is stronger than that of a single crystal-transforming agent under the condition of conventional heating. The organic acid crystal transformation agent has an adsorption effect with all crystal faces, and mainly inhibits the growth of (002) crystal faces of the semi-hydrated gypsum along the c-axis direction, so that the growth rate of the a-semi-hydrated gypsum crystal along each direction is close to balance, the average diameter is increased, the length is reduced, the length-diameter ratio is reduced, and the crystal is in a six-edge short column shape.
The interaction energy of the potassium sulfate on the surface of the alpha-hemihydrate gypsum crystal (110) is the largest, so the potassium sulfate is preferentially and selectively adsorbed to the side surface of the crystal to inhibit the radial growth of the crystal, the crystal is still needle-shaped, and the potassium sulfate has no obvious effect on changing the appearance of the hemihydrate gypsum crystal. The inorganic salt crystal transformation agent has the functions of increasing the solubility of the dihydrate gypsum and coarsening a-gypsum crystals.
Therefore, the surface tension is reduced by using a surfactant type crystal converter in the early stage to promote the generation of fine crystals, and then the organic acid type crystal converter is used, so that the organic acid is adsorbed, reacted or enters the a-hemihydrate gypsum crystals, the growth rate on the crystal plane of the C axis of the hemihydrate gypsum crystals is slowed down, and the crystal appearance of the alpha-hemihydrate gypsum is changed. Finally, the inorganic salt crystal transformation agent promotes the generation of the semi-hydrated gypsum.
Secondly, regulating and controlling the time of the crystal transformation agent of each link
Example 7
Different from the embodiment 6, in the step (3), sulfuric acid is added into the conversion tank,adding surfactant crystal-transformation agent, controlling liquid-solid ratio and H in mixed slurry3PO4And H2SO4The mixed slurry is obtained, and the temperature of the conversion tank is maintained at 60 ℃ for reaction for 3 hours; adding organic acid crystal-transformation agent, controlling liquid-solid ratio and H in mixed slurry3PO4And H2SO4To obtain mixed slurry; maintaining the temperature of the conversion tank at 80 ℃ for reaction for 1.5 hours, then adding an inorganic salt crystal transformation agent, and maintaining the temperature of the conversion tank at 95 ℃ for reaction for 1.5 hours to obtain mixed acid slurry D. Wherein the mass ratio of the surfactant type crystal modifier to the organic acid type crystal modifier to the inorganic salt type crystal modifier is 1:1: 1.
Example 8
The difference from the example 6 is that in the step (3), sulfuric acid is added into the conversion tank, a surfactant type crystal transformation agent is added, and the liquid-solid ratio and the H in the mixed slurry are controlled3PO4And H2SO4The mixed slurry is obtained, and the temperature of the conversion tank is maintained at 50 ℃ for reaction for 1.5 hours; adding organic acid crystal-transformation agent, controlling liquid-solid ratio and H in mixed slurry3PO4And H2SO4To obtain mixed slurry; maintaining the temperature of the conversion tank at 60 ℃ for reaction for 3 hours, then adding an inorganic salt crystal-transforming agent, and maintaining the temperature of the conversion tank at 80 ℃ for reaction for 1.5 hours to obtain mixed acid slurry D. Wherein the mass ratio of the surfactant type crystal modifier to the organic acid type crystal modifier to the inorganic salt type crystal modifier is 1:1: 1.
Example 9
The difference from the example 6 is that in the step (3), sulfuric acid is added into the conversion tank, a surfactant type crystal transformation agent is added, and the liquid-solid ratio and the H in the mixed slurry are controlled3PO4And H2SO4The mixed slurry is obtained, and the temperature of the conversion tank is maintained at 50 ℃ for reaction for 1.5 hours; adding organic acid crystal-transformation agent, controlling liquid-solid ratio and H in mixed slurry3PO4And H2SO4To obtain mixed slurry; maintaining the temperature of the conversion tank at 60 ℃ for reaction for 1.5 hours, and adding inorganic substancesAnd (3) reacting the salt crystal transfer agent for 3 hours at the temperature of 80 ℃ in the conversion tank to obtain mixed acid slurry D. Wherein the mass ratio of the surfactant type crystal modifier to the organic acid type crystal modifier to the inorganic salt type crystal modifier is 1:1: 1.
TABLE 2 hemihydrate (%) and compressive strength at different time of the crystal transformation agent in each link
Through experiments, the experiment proves that the example 8 can effectively improve the production of the hemihydrate gypsum by increasing the time of the organic acid type crystal transformation agent. The organic acid crystal transformation agent has obvious influence on changing the growth habit and the crystal appearance of the semi-hydrated gypsum crystal, and improves the generation amount and the strength.
Example 10
The difference from the example 8 is that in the step (3), sulfuric acid is added into the conversion tank, a surfactant type crystal transformation agent is added, and the liquid-solid ratio and the H in the mixed slurry are controlled3PO4And H2SO4The mixed slurry is obtained, and the temperature of the conversion tank is maintained at 50 ℃ for reaction for 1.5 hours; adding organic acid crystal-transformation agent, controlling liquid-solid ratio and H in mixed slurry3PO4And H2SO4To obtain mixed slurry; maintaining the temperature of the conversion tank at 60 ℃ for reaction for 1.5 hours, adding an inorganic salt crystal-transforming agent, and maintaining the temperature of the conversion tank at 80 ℃ for reaction for 3 hours to obtain mixed acid slurry D. Wherein the mass ratio of the surfactant type crystal modifier to the organic acid type crystal modifier to the inorganic salt type crystal modifier is 1:2: 1.
In order to highlight the influence of the organic acid type crystal transformation agent on the change of the growth habit and the crystal morphology of the hemihydrate gypsum crystal and improve the dosage of the organic acid type crystal transformation agent, experiments show that the yield (%) and the strength of the hemihydrate gypsum are respectively as follows: 89.34 percent and 49.12 MPa.
In the crystal transformation process, the flaky dihydrate gypsum crystals are transformed into semi-hydrated gypsum crystals with the length-diameter ratio of a regular hexagonal prism of 1-3, and the obtained semi-hydrated gypsum is shown in figure 2.
Third, suitability test
Example 11
The difference from example 10 is that sodium dodecylbenzenesulfonate is used as a surfactant-type crystal-transforming agent.
Example 12
The difference from the example 10 is that maleic acid is selected as the organic acid type crystal modifier.
Example 13
The difference from the example 10 is that boehmite is selected as the inorganic salt type crystal transformation agent.
Example 14
The difference from example 10 is that aluminum hydroxide is used as the inorganic salt-type crystal modifier.
TABLE 3 hemihydrate Gypsum formation (%) and compressive strength of different Transformers
It can be seen that the gradient crystal transformation method can effectively improve the yield and compressive strength of the hemihydrate gypsum, and meanwhile, the product performances of different crystal transformation agents have a large difference.
Example 14
The test on the phosphorite in different areas shows that:
the phosphorite obtained by floatation of the northern iron ore associated phosphorite has the characteristics of low aluminum and low fluorine, and the mass fraction of sulfuric acid required in the crystal transformation process is low, and about 6 percent of sulfuric acid can obtain the optimal gypsum crystal.
Phosphate ores with relatively high aluminum and fluorine contents, represented by Hubei phosphate ores, require sulfuric acid with a mass fraction of about 12-15% to obtain the best gypsum crystals.
Although the present invention has been described in detail in connection with the preferred embodiments with reference to the accompanying drawings, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A production method of high-strength phosphogypsum powder is characterized by comprising the following steps:
(1) adding phosphorite pulp and/or phosphorite powder into a reaction tank, then adding sulfuric acid to react, wherein the temperature of the reaction tank is 85-95 ℃, and reacting for 2-6 hours under the condition to obtain mixed slurry A;
(2) separating 30-60% of the separated volume of the mixed slurry A obtained in the step (1) to perform solid-liquid separation to obtain clear liquid B and solid C, sending the clear liquid B serving as finished phosphoric acid into an acid base, transferring the solid C into a reaction tank, and transferring the residual mixed slurry A into a conversion tank;
(3) adding sulfuric acid into the conversion tank, adding surfactant type crystal-converting agent, controlling liquid-solid ratio and H in the mixed slurry3PO4And H2SO4Keeping the temperature of the conversion tank at 50-60 ℃ for reaction for 1-3 hours; adding an organic acid crystal transfer agent, and reacting for 1-3 hours at the temperature of 60-80 ℃ in a conversion tank; adding an inorganic salt crystal transfer agent, and reacting for 1-3 hours at the temperature of the conversion tank between 80 ℃ and 95 ℃ to obtain mixed acid slurry D;
(4) carrying out solid-liquid separation on the mixed acid slurry D obtained in the step (3) to obtain a solid E and a filtrate F, washing the solid E with hot water, and drying the solid E to obtain high-strength phosphogypsum powder; the solid E can be directly processed into a gypsum product;
(5) and (3) introducing the filtrate F obtained in the step (4) into the reaction tank obtained in the step (1) to continuously react with the phosphorus ore pulp and/or the phosphorus ore powder.
2. The method of producing high-strength phosphogypsum powder according to claim 1, characterized in that: the mass ratio of liquid to solid in the reaction tank in the step (1) is (1.5-4): 1.
3. the method of producing high-strength phosphogypsum powder according to claim 1, characterized in that: in the step (1), the fineness of the phosphate ore powder is 80-100 meshes, and the components are as follows in mass fraction: containing phosphorus as P20525 to 33 percent of calcium oxide, 35 to 45 percent of calcium oxide, less than or equal to 3 percent of magnesium oxide, 0.5 to 4 percent of total iron oxide and aluminum oxide, 2 to 3.5 percent of fluorine, and less than or equal to 20 percent of acid insoluble substance in terms of silicon dioxide.
4. The method of producing high-strength phosphogypsum powder according to claim 1, characterized in that: the mass fraction of sulfate ions in the liquid component in the mixed slurry A is 1-4%;
phosphoric acid in liquid component of mixed slurry A as P2O5The mass fraction is 18-25%.
5. The method of producing high-strength phosphogypsum powder according to claim 1, characterized in that: the organic acid type crystal transformation agent in the step (3) is sodium citrate; the surfactant type crystal transformation agent is cetyl trimethyl ammonium bromide; the inorganic salt crystal transformation agent in the step (3) is trivalent aluminum salt.
6. The method of producing high-strength phosphogypsum powder according to claim 5, characterized in that: the mass ratio of the surfactant type crystal modifier to the organic acid type crystal modifier to the trivalent aluminum salt is 1:2: 1.
7. the method of producing high-strength phosphogypsum powder according to claim 1, characterized in that: in the step (3), the liquid-solid mass ratio of the mixed slurry is (1.5-4): 1, phosphoric acid in liquid thereof is represented by P2O5Accounting for 18 to 25 percent of the mixed acid by mass percent, and the sulfuric acid is H2SO4Accounting for 6 to 15 percent of the mixed acid by mass.
8. The method of producing high-strength phosphogypsum powder according to claim 6, characterized in that: in the step (3), the mass fraction content of the alumina in the liquid phase is higher than 0.4% calculated by the alumina.
9. The method of producing high-strength phosphogypsum powder according to claim 1, characterized in that: the temperature of the hot water in the step (4) is 60-90 ℃; the temperature of the dried material is 80-110 ℃.
10. A high strength phosphogypsum powder prepared by the production method according to any one of claims 1-9, characterized in that: the high-strength phosphogypsum powder comprises the following components in parts by weight: 15-25% of anhydrous II type gypsum, 50-90% of semi-hydrated gypsum, 0-7% of dihydrate gypsum and 0-20% of silicon dioxide.
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