A method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum

Abstract

The present invention provides a method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum. The method includes: mixing an alkali, a first surfactant, and water to obtain a first dispersant; mixing phosphogypsum and water and stirring to obtain a phosphogypsum slurry; mixing the first dispersant and the phosphogypsum slurry and stirring to obtain an initial slurry; aging the initial slurry and then stirring it, and feeding it into a first chute for gravity separation to obtain a first impurity-removed product and a first slag slurry; mixing an acid, a second surfactant, and water to obtain a second dispersant; mixing the first impurity-removed product and water and stirring to obtain a first impurity-removed product slurry; mixing the second dispersant and the first impurity-removed product slurry and stirring to obtain a second-stage slurry; aging the second-stage slurry and then stirring it, and feeding it into a second chute for gravity separation to obtain calcium sulfate and a second slag slurry. The method has simple process, low cost, and high impurity separation efficiency, and can achieve comprehensive and in-depth impurity removal from phosphogypsum.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical material preparation, and particularly relates to a method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum. Background Art

[0002] Phosphogypsum can be used to prepare calcium sulfate and as a raw material for building gypsum and building gypsum products. If phosphogypsum is comprehensively and deeply purified to prepare high-purity / high-whiteness calcium sulfate, it is expected to replace natural gypsum as a raw material for industrial building materials. The related industries have a market space of hundreds of billions of yuan, with great growth potential. However, it has very high requirements for the whiteness and purity of phosphogypsum. Due to the presence of carbon-based impurities and non-ferrous metal compounds, phosphogypsum is grayish-white or grayish-black, which greatly limits its industrial application. The composition of phosphogypsum is complex, with many coexisting impurities. The impurity removal technology is extensive, and the product profit is not enough to offset the transportation cost. This is an important reason for the difficult resource utilization, low added value, and large accumulation of phosphogypsum. It is urgent to develop low-cost and high-efficiency impurity removal technologies to promote the large-scale clean and high-value utilization of phosphogypsum. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems in the related technologies to some extent. To this end, an object of the present invention is to propose a method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum. This method has a simple process, low cost, and high impurity separation efficiency, and can achieve comprehensive and deep impurity removal of phosphogypsum. Specifically, the purity of the calcium sulfate prepared by this method is not less than 99%, and the whiteness is not less than 90%.

[0004] In one aspect of the present invention, the present invention proposes a method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum. According to an embodiment of the present invention, the method includes:

[0005] (1) Mix an alkali, a first surfactant, and water to obtain a first dispersant;

[0006] (2) Mix phosphogypsum and water and stir to obtain a phosphogypsum slurry;

[0007] (3) Mix the first dispersant and the phosphogypsum slurry and stir to obtain an initial slurry;

[0008] (4) After aging the initial slurry and stirring, send it to a primary chute for gravity separation to obtain a primary impurity removal product and a primary slurry;

[0009] (5) Mix an acid, a second surfactant, and water to obtain a second dispersant;

[0010] (6) Mix the primary impurity removal product and water and stir to obtain a primary impurity removal product slurry;

[0011] (7) Mix and stir the second dispersant and the primary impurity-removed product slurry to obtain a secondary slurry;

[0012] (8) Age and stir the secondary slurry, and then feed it into a secondary chute for gravity separation to obtain calcium sulfate and a secondary slag slurry.

[0013] According to a method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum according to the above embodiments of the present invention, an alkali, a first surfactant, and water are mixed to obtain a first dispersant. Phosphogypsum and water are mixed and stirred to obtain a phosphogypsum slurry. The first dispersant and the phosphogypsum slurry are mixed and stirred to obtain an initial slurry. After the initial slurry is aged and stirred, a primary impurity-removed product and a primary slag slurry are obtained. Under the action of the above first dispersant, the phosphogypsum particles are in a state of mutual dissociation in terms of spatial distribution, and then fed into a primary chute for gravity separation to remove impurities with a large specific gravity on the inner side of the chute and impurities with a small specific gravity on the outer side of the chute. The impurities with a large specific gravity and the impurities with a small specific gravity are combined into a primary slag slurry, and the middle part of the chute is the primary impurity-removed product. Most of the impurities in the phosphogypsum are acidic. That is, through the above-mentioned way of separating the head and the tail, most of the impurities in the phosphogypsum can be removed; an acid, a second surfactant, and water are mixed to obtain a second dispersant. The primary impurity-removed product and water are mixed and stirred to obtain a primary impurity-removed product slurry. The second dispersant and the primary impurity-removed product slurry are mixed and stirred to obtain a secondary slurry. The above secondary slurry is aged and stirred. Under the action of the second dispersant, controllable crystal form transformation and recrystallization of calcium sulfate can be realized, and then fed into a secondary chute for gravity separation. After separation, the middle part of the chute is calcium sulfate (secondary impurity-removed slurry), and the impurities with a large specific gravity on the inner side of the chute and the impurities with a small specific gravity on the outer side of the chute are combined into a secondary slag slurry. Through further impurity removal, deep impurity removal of phosphogypsum can be realized, that is, deep impurity removal is carried out on the basis of the precipitation and recrystallization of calcium sulfate. The impurity removal process is divided into two-stage impurity removal with alkali first and then acid, so that organic and inorganic impurities in phosphogypsum can be comprehensively and deeply removed from coarse to fine and from the surface to the inside. Thus, this method has a simple process, low cost, and high impurity separation efficiency, and can realize comprehensive and deep impurity removal of phosphogypsum. Specifically, the purity of the calcium sulfate prepared by this method is not less than 99%, and the whiteness is not less than 90%.

[0014] In addition, a method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum according to the above embodiments of the present invention may further have the following technical features:

[0015] In some embodiments of the present invention, in step (1), the mass ratio of the alkali, the first surfactant, and the water is (0.8 - 1.5):(0.5 - 1.2):(0.8 - 2.0). Thus, most of the acidic impurities in the phosphogypsum can be deeply removed.

[0016] In some embodiments of the present invention, in step (1), the alkali includes at least one of calcium oxide, sodium oxide, and potassium oxide.

[0017] In some embodiments of the present invention, in step (1), the first surfactant includes at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, stearic acid, oleic acid, cetyltrimethylammonium bromide, and octadecylamine.

[0018] In some embodiments of the present invention, in step (2), the solid content of the phosphogypsum slurry is 4 wt% - 20 wt%. Thereby, most of the acidic impurities in the phosphogypsum can be deeply removed.

[0019] In some embodiments of the present invention, in step (3), the mass ratio of the first dispersant in the initial slurry is 0.01% - 1%. Thereby, most of the acidic impurities in the phosphogypsum can be deeply removed.

[0020] In some embodiments of the present invention, in step (3), the stirring includes shear stirring, the rotation speed of the shear stirring is 4000 r / min - 12000 r / min, and the time is 40 min - 100 min. Thereby, most of the acidic impurities in the phosphogypsum can be deeply removed.

[0021] In some embodiments of the present invention, in step (4), the aging time is 2 h - 24 h. Thereby, most of the acidic impurities in the phosphogypsum can be deeply removed.

[0022] In some embodiments of the present invention, in step (4), the stirring time is 30 min - 60 min, and the rotation speed is 80 r / min - 160 r / min.

[0023] In some embodiments of the present invention, in step (5), the mass ratio of the acid, the second surfactant, and the water is (0.8 - 1.5):(0.5 - 1.2):(0.8 - 2.0). Thereby, comprehensive and deep impurity removal of phosphogypsum can be achieved.

[0024] In some embodiments of the present invention, in step (5), the acid includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, and citric acid.

[0025] In some embodiments of the present invention, in step (5), the second surfactant includes at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, stearic acid, oleic acid, cetyltrimethylammonium bromide, and octadecylamine.

[0026] In some embodiments of the present invention, in step (6), the solid content of the primary impurity removal product slurry is 4 wt% - 20 wt%. Thereby, comprehensive and deep impurity removal of phosphogypsum can be achieved.

[0027] In some embodiments of the present invention, in step (7), the mass proportion of the second dispersant in the secondary slurry is 0.01%-1%. Thus, comprehensive and in-depth impurity removal of phosphogypsum can be achieved.

[0028] In some embodiments of the present invention, in step (7), the stirring includes shear stirring, the rotation speed of the shear stirring is 4000 r / min - 12000 r / min, and the time is 40 min - 100 min. Thus, comprehensive and in-depth impurity removal of phosphogypsum can be achieved.

[0029] In some embodiments of the present invention, in step (8), the aging time is 2 h - 24 h. Thus, comprehensive and in-depth impurity removal of phosphogypsum can be achieved.

[0030] In some embodiments of the present invention, in step (8), the stirring time is 30 min - 60 min, and the rotation speed is 80 r / min - 160 r / min.

[0031] In some embodiments of the present invention, the primary slag slurry, the secondary slag slurry and water are mixed and stirred, then alkali is added to adjust the pH to 6.5 - 7.5, and then filtered and dried to obtain the raw material for preparing compound fertilizer. Thus, the deep utilization function of the primary slag slurry and the secondary slag slurry can be developed.

[0032] The additional aspects and advantages of the present invention will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present invention. Detailed Description of the Invention

[0033] The embodiments of the present invention will be described in detail below, which are intended to explain the present invention and should not be construed as a limitation to the present invention.

[0034] In one aspect of the present invention, the present invention provides a method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum. According to the embodiments of the present invention, the method includes:

[0035] S100: Mix alkali, a first surfactant and water

[0036] In this step, alkali, a first surfactant and water are mixed uniformly to form a first dispersant. It should be noted that alkali and the first surfactant are conventional materials in the art, and those skilled in the art can select according to the actual situation. For example, the alkali includes at least one of calcium oxide, sodium oxide and potassium oxide; the first surfactant includes at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, stearic acid, oleic acid, cetyltrimethylammonium bromide and octadecylamine. Further, the mass ratio of alkali, the first surfactant to water is (0.8 - 1.5):(0.5 - 1.2):(0.8 - 2.0), so as to ensure the maximization of the benefits and functions of the first surfactant.

[0037] S200: Mix and stir phosphogypsum and water

[0038] In this step, phosphogypsum and water are mixed and stirred to obtain a phosphogypsum slurry. Further, the solid content of the phosphogypsum slurry is 4wt%-20wt%. Thus, it is beneficial to the subsequent reaction.

[0039] S300: Mix and stir the first dispersant and the phosphogypsum slurry

[0040] In this step, the first dispersant obtained in S100 and the phosphogypsum slurry obtained in S200 are mixed and stirred to obtain an initial slurry. Under the action of the first dispersant, the phosphogypsum particles are in a state of mutual dissociation in terms of spatial distribution, which is beneficial to the separation of impurities. Those skilled in the art can understand that stirring is a conventional operation method in the art. Here, stirring can promote the mixing degree of the first dispersant and the phosphogypsum slurry, and further can affect the particle dispersion degree and aggregation degree. Further, the stirring includes shear stirring, the rotation speed of the shear stirring is 4000r / min - 12000r / min, and the time is 40min - 100min.

[0041] According to the embodiment of the present invention, the mass ratio of the first dispersant in the initial slurry is 0.01% - 1%. The inventor found that if the mass ratio of the first dispersant in the initial slurry is too small, the spatial dissociation between gypsum and impurity particles cannot be fully achieved; if the mass ratio of the first dispersant in the initial slurry is too large, excessive cost consumption will be caused. Thus, the present application adopts an initial slurry with a mass ratio of the first dispersant of 0.01% - 1% to deeply remove most of the acidic impurities in phosphogypsum.

[0042] S400: Age the initial slurry, stir it, and then send it to a primary chute for gravity separation

[0043] In this step, the initial slurry is aged in an aging tank and then stirred in a stirring tank. Through aging, the first dispersant and the phosphogypsum slurry fully react. Through stirring, full mixing and full reaction are promoted, so that different particles are evenly distributed, which is beneficial to subsequent rapid and efficient separation. Then the stirred slurry is sent to a primary chute for gravity separation to remove impurities with a large specific gravity on the inner side of the chute and impurities with a small specific gravity on the outer side of the chute. The impurities with a large specific gravity and the impurities with a small specific gravity are combined into a primary slag slurry, and the middle part of the chute is the primary impurity-removing product. Most of the impurities in phosphogypsum are acidic. That is, through the above-mentioned head-and-tail separation method, most of the impurities in phosphogypsum can be removed. Further, the stirring time is 30 min - 60 min, and the rotation speed is 80 - 160 r / min. It should be noted that the primary impurity-removing product and the primary slag slurry obtained by gravity separation are in a slurry state. The primary impurity-removing product and the primary slag slurry in the form of filter cakes are obtained through filtration. The filtrate after the above filtration can be returned to continue preparing the phosphogypsum slurry, and the amount of the first dispersant added to the initial slurry prepared with the above filtrate is 20% - 50% of the amount of the first dispersant added to the initial slurry not prepared with the above filtrate. On the one hand, the filtrate can be recycled, thus reducing sewage discharge. On the other hand, the amount of the first dispersant added is reduced, saving costs. Further, the aging time is 2 h - 24 h, so that most of the acidic impurities in phosphogypsum can be deeply removed.

[0044] S500: Mix an acid, a second surfactant, and water

[0045] In this step, the acid, the second surfactant, and water are mixed evenly to obtain a second dispersant. It should be noted that the acid and the second surfactant are conventional materials in the art, and those skilled in the art can select according to the actual situation. For example, the acid includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, and citric acid; the second surfactant includes at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, stearic acid, oleic acid, cetylammonium bromide, and octadecylamine. Further, the mass ratio of the acid, the second surfactant, and water is (0.8 - 1.5):(0.5 - 1.2):(0.8 - 2.0), so as to ensure the maximization of the benefits and functions of the second surfactant.

[0046] S600: Mix and stir the primary impurity-removing product and water

[0047] In this step, the primary impurity-removing product and water are mixed and stirred to obtain a primary impurity-removing product slurry. Further, the solid content of the primary impurity-removing product slurry is 4 wt% - 20 wt%, so as to achieve comprehensive and deep impurity removal of phosphogypsum.

[0048] S700: Mix and stir the second dispersant and the primary impurity-removing product slurry

[0049] In this step, the second dispersant obtained in S500 and the primary impurity-removed product slurry obtained in S600 are mixed and stirred to obtain a secondary slurry. Further, the stirring includes shear stirring, the rotation speed of the shear stirring is 4000 r / min - 12000 r / min, and the time is 40 min - 100 min.

[0050] According to an embodiment of the present invention, the mass ratio of the second dispersant in the secondary slurry is 0.01% - 1%. The inventor found that if the mass ratio of the second dispersant in the secondary slurry is too small, the spatial dissociation between gypsum and impurity particles cannot be fully achieved; if the mass ratio of the second dispersant in the secondary slurry is too large, excessive cost consumption will be caused. Therefore, the secondary slurry with a mass ratio of the second dispersant of 0.01% - 1% is adopted in this application, which can achieve comprehensive and in-depth impurity removal of phosphogypsum.

[0051] S800: After aging the secondary slurry, stir it and then send it to a secondary chute for gravity separation.

[0052] In this step, the secondary slurry is aged in an aging tank, stirred in a stirring tank, and then sent to a secondary chute for gravity separation. Under the action of the second dispersant, the controllable crystal form transformation and recrystallization of calcium sulfate can be achieved. After the gravity separation in the secondary chute, the middle part of the chute is calcium sulfate (secondary impurity-removed slurry), and the impurities with a larger specific gravity on the inner side of the chute and the impurities with a smaller specific gravity on the outer side of the chute are combined into a secondary slag slurry. Through further impurity removal, the in-depth impurity removal of phosphogypsum can be realized, that is, in-depth impurity removal on the basis of the precipitation and recrystallization of calcium sulfate. Further, the stirring time is 30 min - 60 min, and the rotation speed is 80 - 160 r / min. It should be noted that after the gravity separation in the secondary chute, the obtained calcium sulfate and secondary slag slurry are also in a slurry state. Filter them to obtain calcium sulfate in a cake state. The filtrate obtained from the above filtration can be returned to prepare the primary impurity-removed product slurry, and the amount of the second dispersant added to the secondary slurry prepared by using the above filtrate is 20% - 50% of the amount of the second dispersant added to the secondary slurry prepared without using the above filtrate. On the one hand, the filtrate can be recycled, thereby reducing sewage discharge. On the other hand, the amount of the second dispersant added is reduced, saving costs. The calcium sulfate cake is dried at 105°C - 135°C for 2 - 6 hours to obtain high-purity / high-whiteness calcium sulfate with a purity of not less than 99% and a whiteness of not less than 90%. The calcium sulfate product prepared in this application fully meets the high-performance index requirements of high-purity / high-whiteness calcium sulfate powder, α-high-strength gypsum powder, mold gypsum, calcium sulfate whiskers and other industrial raw materials in the market, and can also be directly used as gypsum powder for high-grade building materials, with broad market prospects.

[0053] According to an embodiment of the present invention, the primary slurry obtained in S400, the secondary slurry obtained in S800, and water are mixed and stirred to prepare a slurry with a solid content of 10 wt% - 30 wt%. Then, alkali is added to the above slurry to adjust the pH to 6.5 - 7.5, and then it is filtered and dried. The filtrate can replace the water in the next slurry preparation process, and the filter cake is dried at 105 - 130 °C for 2 - 6 hours, so that the component content can be adjusted according to the compound fertilizer standard to obtain a compound fertilizer product. The primary slurry and the secondary slurry are rich in plant nutrient components such as humic acid, phosphorus, and sulfur, and can be used as compound fertilizers after neutralization, reducing the discharge of waste residues and better realizing the resource utilization of solid waste.

[0054] The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0055] Example 1

[0056] (1) Calcium oxide, sodium dodecyl sulfonate, and water are uniformly mixed in a mass ratio of 1:1:1 to prepare a first dispersant.

[0057] (2) Phosphogypsum and water are added to a high-speed shear stirring kettle to prepare a phosphogypsum slurry with a solid content of 4 wt%. Then, 0.01 wt% of the first dispersant (the addition amount of the first dispersant is 0.01 wt% of the total amount of the phosphogypsum slurry and the first dispersant) is added, and it is stirred at a speed of 4000 revolutions per minute for 40 minutes to prepare an initial slurry.

[0058] (3) After the initial slurry is aged in an aging tank for 2 hours, it is put into a stirring kettle, stirred for 30 minutes, and then pumped into a first chute for gravity separation. After separation, the middle part is the first impurity removal product, and the impurities slurry with a larger specific gravity on the inner side and a smaller specific gravity on the outer side is combined into the primary slurry.

[0059] (4) Hydrochloric acid, sodium dodecyl sulfonate, and water are uniformly mixed in a mass ratio of 1:1:1 to prepare a second dispersant.

[0060] (5) Water and the first impurity removal product are put into a high-speed shear stirring kettle to prepare a first impurity removal product slurry with a solid content of 4 wt%. 0.01 wt% of the second dispersant (the addition amount of the first dispersant is 0.01 wt% of the total amount of the first impurity removal product slurry and the second dispersant) is added, and it is stirred at a speed of 4000 revolutions per minute for 40 minutes to prepare a secondary slurry.

[0061] (6) After the secondary slurry is aged in an aging tank for 2 hours, it is put into a stirring kettle and stirred for 30 minutes, and then pumped into a second chute for secondary gravity separation. After separation, the middle part is the secondary impurity removal slurry, and the combined part with a larger specific gravity on the inner side and a smaller specific gravity on the outer side is the secondary slurry. The secondary impurity removal slurry is filtered, and the filter cake is the secondary impurity removal product (calcium sulfate).

[0062] (7) The secondary impurity-removed product is dried at 105 °C for 6 hours to obtain high-purity / high-whiteness calcium sulfate with a purity of 99% and a whiteness of 90%.

[0063] Example 2

[0064] (1) Sodium oxide, sodium dodecyl sulfate, and water are uniformly mixed in a mass ratio of 1:1:1 to prepare a first dispersant.

[0065] (2) Phosphogypsum and water are added to a high-speed shear stirring kettle to prepare a phosphogypsum slurry with a solid content of 20 wt%, and then 1 wt% of the first dispersant is added. It is stirred at a speed of 12,000 revolutions per minute for 100 minutes to prepare an initial slurry.

[0066] (3) After the initial slurry is aged in an aging tank for 24 hours, it is put into a stirring kettle, stirred for 60 minutes, and then pumped into a first-stage chute for gravity separation. The middle part after separation is the first-stage impurity-removed product, and the impurities slurry with a larger specific gravity on the inner side and a smaller specific gravity on the outer side is combined into a first-stage slag slurry.

[0067] (4) Sulfuric acid, sodium dodecyl sulfate, and water are uniformly mixed in a mass ratio of 1:1:1 to prepare a second dispersant.

[0068] (5) Water and the first-stage impurity-removed product are put into a high-speed shear stirring kettle to prepare a 20 wt% first-stage impurity-removed product slurry, and 1 wt% of the second dispersant is added. It is stirred at a speed of 12,000 revolutions per minute for 100 minutes to prepare a second-stage slurry.

[0069] (6) After the second-stage slurry is aged in an aging tank for 24 hours, it is put into a stirring kettle and stirred for 60 minutes, and then pumped into a second-stage chute for second-stage gravity separation. The middle part after separation is the secondary impurity-removed slurry, and the combined part with a larger specific gravity on the inner side and a smaller specific gravity on the outer side is the second-stage slag slurry. The secondary impurity-removed slurry is filtered, and the filter cake is the secondary impurity-removed product (calcium sulfate).

[0070] (7) The secondary impurity-removed product is dried at 105 °C for 6 hours to obtain high-purity / high-whiteness calcium sulfate with a purity of 99.9% and a whiteness of 98%.

[0071] Example 3

[0072] (1) Potassium oxide, stearic acid, and water are uniformly mixed in a mass ratio of 1:1:1 to prepare a first dispersant.

[0073] (2) Phosphogypsum and water are added to a high-speed shear stirring kettle to prepare a phosphogypsum slurry with a solid content of 20 wt%, and then 1 wt% of the first dispersant is added. It is stirred at a speed of 8,000 revolutions per minute for 100 minutes to prepare an initial slurry.

[0074] (3) After the initial slurry is aged in the aging tank for 20 hours, it is put into the stirring kettle, stirred for 60 minutes, and then pumped into the first chute for gravity separation. After separation, the middle part is the first impurity removal product, and the impurity slurries with a higher specific gravity on the inner side and a lower specific gravity on the outer side are combined into the first slag slurry;

[0075] (4) Phosphoric acid, stearic acid, and water are uniformly mixed in a mass ratio of 1:1:1 to prepare the second dispersant;

[0076] (5) Water and the first impurity removal product are put into the high-speed shear stirring kettle to prepare a 20wt% first impurity removal product slurry, 1wt% of the second dispersant is added, and it is stirred at a speed of 8000 revolutions per minute for 100 minutes to prepare the second-stage slurry;

[0077] (6) After the second-stage slurry is aged in the aging tank for 20 hours, it is put into the stirring kettle and stirred for 30 minutes, and then pumped into the second chute for secondary gravity separation. After separation, the middle part is the secondary impurity removal slurry, and the combined inner part with a higher specific gravity and the outer part with a lower specific gravity is the second-stage slag slurry. The secondary impurity removal slurry is filtered, and the filter cake is the secondary impurity removal product (calcium sulfate);

[0078] (7) The secondary impurity removal product is dried at 105 °C for 6 hours to obtain high-purity / high-whiteness calcium sulfate with a purity of 99.5% and a whiteness of 90%.

[0079] Example 4

[0080] (1) Potassium oxide, oleic acid, and water are uniformly mixed in a mass ratio of 1:1:1 to prepare the first dispersant;

[0081] (2) Phosphogypsum and water are added to the high-speed shear stirring kettle to prepare a phosphogypsum slurry with a solid content of 15wt%, and then 0.8wt% of the first dispersant is added, and it is stirred at a speed of 10000 revolutions per minute for 100 minutes to prepare the initial slurry;

[0082] (3) After the initial slurry is aged in the aging tank for 23 hours, it is put into the stirring kettle, stirred for 39 minutes, and then pumped into the first chute for gravity separation. After separation, the middle part is the first impurity removal product, and the impurity slurries with a higher specific gravity on the inner side and a lower specific gravity on the outer side are combined into the first slag slurry;

[0083] (4) Acetic acid, oleic acid, and water are uniformly mixed in a mass ratio of 1:1:1 to prepare the second dispersant;

[0084] (5) Water and the first impurity removal product are put into the high-speed shear stirring kettle to prepare a 19wt% first impurity removal product slurry, 0.85wt% of the second dispersant is added, and it is stirred at a speed of 9000 revolutions per minute for 100 minutes to prepare the second-stage slurry;

[0085] (6) After the secondary slurry is aged in the aging tank for 22 hours, it is put into the stirring kettle and stirred for 49 minutes, then pumped into the secondary chute for secondary gravity separation. After separation, the middle part is the secondary impurity-removing slurry, and the heavier inner part and the lighter outer part are combined into the secondary slag slurry. The secondary impurity-removing slurry is filtered, and the filter cake is the secondary impurity-removing product (calcium sulfate);

[0086] (7) The secondary impurity-removing product is dried at 105 °C for 2 hours to obtain a high-purity / high-whiteness calcium sulfate product with a purity of 99.2% and a whiteness of 91%.

[0087] Example 5

[0088] (1) Potassium oxide, cetyltrimethylammonium bromide and water are uniformly mixed in a mass ratio of 1:1:1 to prepare the first dispersant;

[0089] (2) Phosphogypsum and water are added to a high-speed shear stirring kettle to prepare a phosphogypsum slurry with a solid content of 20 wt%. 1 wt% of the first dispersant is added, and it is stirred at a speed of 5000 revolutions per minute for 90 minutes to prepare the initial slurry;

[0090] (3) After the initial slurry is aged in the aging tank for 15 hours, it is put into the stirring kettle, stirred for 35 minutes, and then pumped into the primary chute for gravity separation. After separation, the middle part is the primary impurity-removing product, and the heavier inner part and the lighter outer part of the impurity slurry are combined into the primary slag slurry;

[0091] (4) Citric acid, cetyltrimethylammonium bromide and water are uniformly mixed in a mass ratio of 1:1:1 to prepare the second dispersant;

[0092] (5) Water and the primary impurity-removing product are put into a high-speed shear stirring kettle to prepare a 16 wt% primary impurity-removing product slurry. 0.5 wt% of the second dispersant is added, and it is stirred at a speed of 6500 revolutions per minute for 49 minutes to prepare the secondary slurry;

[0093] (6) After the secondary slurry is aged in the aging tank for 23 hours, it is put into the stirring kettle and stirred for 55 minutes, then pumped into the secondary chute for secondary gravity separation. After separation, the middle part is the secondary impurity-removing slurry, and the heavier inner part and the lighter outer part are combined into the secondary slag slurry. The secondary impurity-removing slurry is filtered, and the filter cake is the secondary impurity-removing product (calcium sulfate);

[0094] (7) The secondary impurity-removing product is dried at 105 °C for 2 hours to obtain a high-purity / high-whiteness calcium sulfate with a purity of 99.4% and a whiteness of 93%.

[0095] Example 6

[0096] (1) Potassium oxide, octadecylamine and water are uniformly mixed in a mass ratio of 1:1:1 to prepare the first dispersant;

[0097] (2) Add phosphogypsum and water to a high-speed shearing and stirring kettle to prepare a phosphogypsum slurry with a solid content of 4 wt%, add 0.95 wt% of the first dispersant, and stir at a speed of 8000 revolutions per minute for 80 minutes to prepare an initial slurry;

[0098] (3) After the initial slurry is aged in an aging tank for 24 hours, put it into a stirring kettle, stir for 60 minutes, and pump it into a primary chute for gravity separation. After separation, the middle part is the primary impurity removal product, and the impurity slurries with a higher specific gravity on the inner side and a lower specific gravity on the outer side are combined into a primary slag slurry;

[0099] (4) Uniformly mix sulfuric acid, octadecylamine and water in a mass ratio of 1:1:1 to prepare a second dispersant;

[0100] (5) Put water and the primary impurity removal product into a high-speed shearing and stirring kettle to prepare a 20 wt% primary impurity removal product slurry, add 1 wt% of the second dispersant, and stir at a speed of 12000 revolutions per minute for 100 minutes to prepare a secondary slurry;

[0101] (6) After the secondary slurry is aged in an aging tank for 24 hours, put it into a stirring kettle and stir for 30 minutes, then pump it into a secondary chute for secondary gravity separation. After separation, the middle part is the secondary impurity removal slurry, and the combined part with a higher specific gravity on the inner side and a lower specific gravity on the outer side is the secondary slag slurry. The secondary impurity removal slurry is filtered, and the filter cake is the secondary impurity removal product (calcium sulfate);

[0102] (7) Dry the secondary impurity removal product at 105 °C for 2 hours to obtain high-purity / high-whiteness calcium sulfate with a purity of 99.6% and a whiteness of 92%.

[0103] Example 7

[0104] (1) Uniformly mix sodium oxide, octadecylamine and water in a mass ratio of 1:1:1 to prepare a first dispersant;

[0105] (2) Add phosphogypsum and water to a high-speed shearing and stirring kettle to prepare a phosphogypsum slurry with a solid content of 20 wt%, add 1 wt% of the first dispersant, and stir at a speed of 12000 revolutions per minute for 100 minutes to prepare an initial slurry;

[0106] (3) After the initial slurry is aged in an aging tank for 24 hours, put it into a stirring kettle, stir for 60 minutes, and pump it into a primary chute for gravity separation. After separation, the middle part is the primary impurity removal product, and the impurity slurries with a higher specific gravity on the inner side and a lower specific gravity on the outer side are combined into a primary slag slurry;

[0107] (4) Uniformly mix sulfuric acid, sodium dodecylsulfonate and water in a mass ratio of 1:1:1 to prepare a second dispersant;

[0108] (5) Put the water and the primary impurity-removed product into a high-speed shear stirring kettle to prepare a 20 wt% primary impurity-removed product slurry, add 1 wt% of the second dispersant, and stir at a speed of 12,000 revolutions per minute for 100 minutes to prepare a secondary slurry;

[0109] (6) After the secondary slurry is aged in an aging tank for 24 hours, put it into a stirring kettle and stir for 60 minutes, then pump it into a secondary chute for secondary gravity separation. After separation, the middle part is the secondary impurity-removed slurry, and the heavier inner part and the lighter outer part are combined into a secondary slag slurry. The secondary impurity-removed slurry is filtered, and the filter cake is the secondary impurity-removed product (calcium sulfate);

[0110] (7) The secondary impurity-removed product is dried at 105 °C for 6 hours to obtain high-purity / high-whiteness calcium sulfate with a purity of 99.7% and a whiteness of 97%.

[0111] Example 8

[0112] (1) Uniformly mix sodium oxide, sodium dodecyl sulfonate and water in a mass ratio of 1:1:1 to prepare a first dispersant;

[0113] (2) Put phosphogypsum and water into a high-speed shear stirring kettle to prepare a phosphogypsum slurry with a solid content of 4 wt%, add 0.01 wt% of the first dispersant, and stir at a speed of 4,000 revolutions per minute for 40 minutes to prepare an initial slurry;

[0114] (3) After the initial slurry is aged in an aging tank for 2 hours, put it into a stirring kettle, stir for 30 minutes, then pump it into a primary chute for gravity separation. After separation, the middle part is the primary impurity-removed product, and the heavier inner part and the lighter outer part of the impurity slurry are combined into a primary slag slurry;

[0115] (4) Uniformly mix citric acid, sodium dodecyl sulfonate and water in a mass ratio of 1:1:1 to prepare a second dispersant;

[0116] (5) Put the water and the primary impurity-removed product into a high-speed shear stirring kettle to prepare a 4 wt% primary impurity-removed product slurry, add 0.01 wt% of the second dispersant, and stir at a speed of 4,000 revolutions per minute for 40 minutes to prepare a secondary slurry;

[0117] (6) After the secondary slurry is aged in an aging tank for 2 hours, put it into a stirring kettle and stir for 30 minutes, then pump it into a secondary chute for secondary gravity separation. After separation, the middle part is the secondary impurity-removed slurry, and the heavier inner part and the lighter outer part are combined into a secondary slag slurry. The secondary impurity-removed slurry is filtered, and the filter cake is the secondary impurity-removed product (calcium sulfate);

[0118] (7) The secondary impurity-removed product is dried at 105 °C for 2 hours to obtain a high-purity / high-whiteness calcium sulfate product with a purity of 99% and a whiteness of 90%.

[0119] Example 9

[0120] (1) Mix sodium oxide, stearic acid, and water in a mass ratio of 1:1:1 to make the first dispersant;

[0121] (2) Add phosphogypsum and water to a high-speed shear stirring kettle to prepare a phosphogypsum slurry with a solid content of 5 wt%, add 1 wt% of the first dispersant, and stir at a speed of 12,000 revolutions per minute for 40 minutes to make the initial slurry;

[0122] (3) After the initial slurry is aged in an aging tank for 20 hours, put it into a stirring kettle, stir for 30 minutes, and pump it into a first-stage chute for gravity separation. The middle part after separation is the first-stage impurity-removing product, and the impurity slurries with a higher specific gravity on the inner side and a lower specific gravity on the outer side are combined into the first-stage slag slurry;

[0123] (4) Mix hydrochloric acid, stearic acid, and water in a mass ratio of 1:1:1 to make the second dispersant;

[0124] (5) Put water and the first-stage impurity-removing product into a high-speed shear stirring kettle to prepare a 4 wt% first-stage impurity-removing product slurry, add 1 wt% of the second dispersant, and stir at a speed of 12,000 revolutions per minute for 100 minutes to make the second-stage slurry;

[0125] (6) After the second-stage slurry is aged in an aging tank for 2 hours, put it into a stirring kettle and stir for 60 minutes, then pump it into a second-stage chute for second-stage gravity separation. The middle part after separation is the second-stage impurity-removing slurry, and the combined inner part with a higher specific gravity and the outer part with a lower specific gravity is the second-stage slag slurry. Filter the second-stage impurity-removing slurry, and the filter cake is the second-stage impurity-removing product (calcium sulfate);

[0126] (7) Dry the second-stage impurity-removing product at 105 °C for 5 hours to obtain high-purity / high-whiteness calcium sulfate with a purity of 99.2% and a whiteness of 93%.

[0127] Example 10

[0128] (1) Mix sodium oxide, oleic acid, and water in a mass ratio of 1:1:1 to make the first dispersant;

[0129] (2) Add phosphogypsum and water to a high-speed shear stirring kettle to prepare a phosphogypsum slurry with a solid content of 10 wt%, add 1 wt% of the first dispersant, and stir at a speed of 7,000 revolutions per minute for 70 minutes to make the initial slurry;

[0130] (3) After the initial slurry is aged in an aging tank for 14 hours, put it into a stirring kettle, stir for 40 minutes, and pump it into a first-stage chute for gravity separation. The middle part after separation is the first-stage impurity-removing product, and the impurity slurries with a higher specific gravity on the inner side and a lower specific gravity on the outer side are combined into the first-stage slag slurry;

[0131] (4) Mix phosphoric acid, oleic acid, and water in a mass ratio of 1:1:1 to make the second dispersant;

[0132] (5) The water and the primary impurity-removed product are put into a high-speed shearing and stirring kettle to form a 10 wt% slurry of the primary impurity-removed product, 0.8 wt% of a second dispersant is added, and the mixture is stirred at a speed of 6000 revolutions per minute for 70 minutes to form a secondary slurry;

[0133] (6) After the secondary slurry is aged in an aging tank for 14 hours, it is put into a stirring kettle and stirred for 52 minutes, and then pumped into a secondary chute for secondary gravity separation. The middle part after separation is the secondary impurity-removed slurry, and the heavier part on the inner side and the lighter part on the outer side are combined into a secondary slag slurry. The secondary impurity-removed slurry is filtered, and the filter cake is the secondary impurity-removed product (calcium sulfate);

[0134] (7) The secondary impurity-removed product is dried at 105 °C for 2 hours to obtain high-purity / high-whiteness calcium sulfate with a purity of 99.4% and a whiteness of 94%.

[0135] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0136] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing high-purity and high-whiteness calcium sulfate from phosphogypsum, characterized in that, Including: (1) Mix an alkali, a first surfactant and water to obtain a first dispersant; (2) Mix phosphogypsum and water and stir to obtain a phosphogypsum slurry; (3) Mix and stir the first dispersant and the phosphogypsum slurry to obtain an initial slurry; (4) Age the initial slurry and then stir it, and send it to a first chute for gravity separation to obtain a first impurity-removed product and a first slag slurry; (5) Mix an acid, a second surfactant and water to obtain a second dispersant; (6) Mix and stir the first impurity-removed product and water to obtain a first impurity-removed product slurry; (7) Mix and stir the second dispersant and the first impurity-removed product slurry to obtain a second-stage slurry; (8) Age the second-stage slurry and then stir it, and send it to a second chute for gravity separation to obtain calcium sulfate and a second slag slurry; In step (1), the mass ratio of the alkali, the first surfactant to the water is (0.8 - 1.5):(0.5 - 1.2):(0.8 - 2.0); the alkali includes at least one of calcium oxide, sodium oxide and potassium oxide; the first surfactant includes at least one of sodium dodecylsulfonate, sodium dodecyl sulfate, stearic acid, oleic acid, cetylammonium bromide and octadecylamine; In step (5), the mass ratio of the acid, the second surfactant to the water is (0.8 - 1.5):(0.5 - 1.2):(0.8 - 2.0); the acid includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid and citric acid; the second surfactant includes at least one of sodium dodecylsulfonate, sodium dodecyl sulfate, stearic acid, oleic acid, cetylammonium bromide and octadecylamine.

2. The method according to claim 1, wherein In step (2), the solid content of the phosphogypsum slurry is 4wt% - 20wt%.

3. The method according to claim 1, wherein [[ID= ​ 4. The method according to claim 1, wherein ​ ​ 5. The method according to claim 1, characterized in that ​ 6. The method according to claim 1, characterized in that, ​ ​ 7. The method according to claim 1, wherein ​ ​ 8. The method according to claim 1, characterized in that, ​