A full solid waste phosphogypsum-based aggregate, a preparation method and application thereof

Abstract

The application discloses a kind of full solid waste phosphogypsum-based aggregate and its preparation method and application, belong to building material artificial aggregate technical field.The method includes the following steps: pre-stirring is obtained to granulation material with water, then pre-mixture is granulated, and water droplet state green ball is obtained;Granulation material or reconfiguration material is continuously added to water droplet state green ball, and water droplet state green ball is reconfigured, then granulation is continuously carried out, and capillary state green ball is obtained;Capillary state green ball is cured, and full solid waste phosphogypsum-based aggregate is obtained.The application can realize the quantitative control of water consumption of granulation by mixing granulation material and water first, thereby significantly improving the quality and efficiency of granulation;In addition, by adding granulation material or reconfiguration material, water droplet state green ball is reconfigured, not only simplifies the process, but also can significantly improve the adaptability of aggregate and portland cement.

Description

Technical Field

[0001] This invention belongs to the field of artificial aggregate technology in building materials, specifically relating to a solid waste phosphogypsum-based aggregate, its preparation method, and its application. Background Technology

[0002] The wet process for producing phosphoric acid involves using concentrated sulfuric acid to decompose phosphate rock (fluorapatite) at 75-80℃ to extract phosphoric acid. This process generates an industrial byproduct, phosphogypsum. The main component of phosphogypsum is CaSO4·2H2O, but unlike natural gypsum, it contains numerous impurities, including phosphorus and fluorine compounds, residual organic mineral flotation agents and acids, and heavy metals. These impurities significantly affect the properties of phosphogypsum, making it difficult to recycle in large quantities. Currently, the overall effective utilization rate of phosphogypsum is less than 40%, and since its production is 4-5 times that of phosphoric acid, effectively disposing of phosphogypsum has become a major challenge restricting the healthy development of the phosphorus chemical industry.

[0003] Some practices have proven that using phosphogypsum to prepare phosphogypsum-based cold-bonded aggregates (hereinafter referred to as phosphogypsum-based aggregates) based on "hypersulfurized phosphogypsum slag cement" is an effective way to dispose of phosphogypsum on a large scale. For example, Chinese patent document CN113354376A discloses a phosphogypsum-based aggregate for road engineering and its preparation method. This aggregate is made by mixing 50-80% phosphogypsum, 15-45% waste residue powder and 3-6% alkaline activator into powder, and then spraying a solution of sodium hexametaphosphate, cellulose ether and water using a pelletizing machine to obtain raw aggregate. The raw pellets are soaked in water for curing and then coated with organosilicon to obtain the desired aggregate. Chinese patent document CN110451864A discloses a phosphogypsum non-fired ceramsite lightweight aggregate and its preparation method. The aggregate is made by mixing 80-90% phosphogypsum, 3.3-10% mineral powder, 6.5-10% cement and a small amount of water, and then using a granulation equipment to granulate while adding water at a rate of 1.25-1.5L / min to obtain raw pellets. After initial and final setting, the pellets are soaked or sprinkled with water for curing for 14-28 days, and then dried, crushed and screened to obtain the desired aggregate.

[0004] The existing manufacturing process for phosphogypsum-based aggregates has problems such as uneven control of water used in granulation, which leads to the easy adhesion of green pellets. As a result, the prepared phosphogypsum-based aggregates have problems such as uneven particle size, low strength, and excessive sulfate content, which leads to incompatibility with silicate cement. Summary of the Invention

[0005] The purpose of this invention is to provide a solid waste phosphogypsum-based aggregate, its preparation method, and its application, in order to solve the problems in the existing phosphogypsum-based aggregate manufacturing process, such as uneven control of granulation water, which leads to the easy adhesion of green pellets, resulting in uneven particle size, low strength, and incompatibility with silicate cement due to excessive sulfate content.

[0006] In a first aspect, the present invention provides a method for preparing all-solid waste phosphogypsum-based aggregate, comprising the following steps: adding water to granulated material and pre-stirring to obtain a premix; then granulating the premix to obtain water-droplet-shaped green pellets; continuing to add granulated material or reconstructed material to the water-droplet-shaped green pellets to reconstruct them; then continuing to granulate to obtain capillary-shaped green pellets; and curing the capillary-shaped green pellets to obtain all-solid waste phosphogypsum-based aggregate; wherein, by mass percentage, the granulated material comprises 70-85% phosphogypsum, 10-25% solid waste silica-alumina material, and 1-20% solid waste alkali activator; the reconstructed material comprises 0-20% phosphogypsum, 60-90% solid waste silica-alumina material, and 1-20% solid waste alkali activator.

[0007] In the preparation method of the solid waste phosphogypsum-based aggregate provided by this invention, the inventors discovered that traditional water spraying granulation refers to wetting the particles by spraying water mist during the granulation process, forming a water film on the surface. Due to the surface tension of water (0.072 N / m at 25°C), liquid bridges are formed between the particles, promoting particle agglomeration and growth. However, uneven water spraying leads to a decrease in the performance of the prepared aggregate. Specifically, insufficient water spraying results in low pelleting efficiency, low green pellet strength, numerous aggregate defects, and poor performance; excessive water spraying easily leads to the formation of "mud balls," deformation, poor particle size uniformity, mutual adhesion, and difficulties in storage and transportation. Currently, a process of alternating water spraying and material addition is commonly used to prepare aggregates, but this requires high granulation skills from workers, has strict labor requirements, and also suffers from long granulation times and low production efficiency.

[0008] Based on this, the inventors further discovered that mixing the granulation material with water before granulation and using mechanical stirring significantly improves the uniformity of water dispersion, thus avoiding problems such as uneven hydration and dust pollution during the granulation process to some extent. The wetted material collides and rubs under the mechanical rotation, and the gaps between the material particles are compacted and filled with water, shortening the distance between particles and increasing the liquid phase saturation. According to particle strength theory, the bonding force between particles is mainly composed of the capillary negative pressure and the tensile force generated by the surface tension of the liquid bridge. Compaction and increased liquid phase saturation both increase the volume of the liquid bridge between particles, thereby fully wetting the particles and reducing the contact angle, increasing the effective area of ​​the capillary negative pressure and the effective area of ​​the surface tension, and thus improving the bonding force between particles and the adhesion strength of the green pellets. Furthermore, the reduction in pore size leads to tight aggregation of particles, gradually squeezing water out of the surface of the green pellets. Depending on the degree to which the pores between particles are filled with water, the pellets undergo four states: "pendulum state," "ribbon state," "capillary state," and "droplet state." The green pellets exhibit the highest bonding strength when they reach the capillary state. The droplet state, due to the presence of a surface water film, promotes efficient agglomeration and growth between materials. It is difficult for materials with low moisture content to directly enter the capillary state. Traditional processes increase the water spraying volume, granulation time, and mechanical action, but this can easily cause the material to bypass the capillary state and directly enter the droplet state, forming "mud balls." In this invention, the granulation water is appropriately abundant, allowing the material to first enter the droplet state and grow under mechanical action. Then, granulation materials or reconstructed materials are added through "moisture neutralization" to "reconstruct the capillary state." The prepared capillary green pellets are surface-dry, exhibiting high bonding strength, which is beneficial for stabilizing particle morphology and preventing the green pellets from adhering or deforming again during storage and transportation.

[0009] Furthermore, based on the principle of adhesion and agglomeration, when the material properties (such as moisture content and fineness) and granulation mechanical parameters (such as diameter, inclination angle, and rotation speed) are determined, the time point at which the material enters the water droplet state is also determined. That is, the granulation process of this invention constitutes a cycle, thereby achieving automated control of the granulation process. The total time for one cycle depends on the material properties and target performance, generally ranging from 5 to 15 minutes. The preparation process of this invention can significantly improve granulation efficiency, optimize the moisture uniformity, liquid phase saturation, and pore structure of green pellets, thereby improving the early bonding strength of the green pellets.

[0010] In some embodiments, during the preparation of the water-droplet biospheres, the water-to-granulation material ratio is (0.17-0.21):1, for example, 0.17:1, 0.18:1, 0.19:1, 0.20:1, 0.21:1 or other values ​​within this range; pre-mixing is carried out in a mixer, and granulation includes: placing a premix containing 60-80 parts (for example, 60, 65, 70, 75, 80 parts or other values ​​within this range) of granulation material into a centrifugal granulator and granulating for 3-10 minutes, for example, 3 minutes, 5 minutes, 7 minutes, 10 minutes or other values ​​within this range; the rotation speed of the centrifugal granulator is 20-45 r / min, for example, 20 r / min, 25 r / min, 30 r / min, 35 r / min, 40 r / min, 45 r / min or other values ​​within this range.

[0011] In some embodiments, during the preparation of capillary green pellets, 20-40 parts (e.g., 20, 25, 30, 35, 40 parts or other values ​​within this range) of granulating material or reconstituted material are added to the droplet green pellets. Granulation includes granulation for 4-10 minutes, e.g., 4 minutes, 5 minutes, 7 minutes, 10 minutes or other values ​​within this range.

[0012] In some implementations, when 20-40 parts of granulating material are added to the water-drop-shaped green pellets, capillary homogeneous green pellets are obtained; the capillary homogeneous green pellets are sealed and preserved for 1-3 days, for example, 1 day, 2 days, 3 days or other values ​​within this range; then they are immersed in water for further curing for 13-27 days, for example, 13 days, 15 days, 17 days, 20 days, 25 days, 27 days or other values ​​within this range; homogeneous solid waste phosphogypsum-based aggregate is obtained.

[0013] In some implementations, when 20-40 parts of reconstituted material are added to the water-drop-shaped green pellets, capillary core-shell green pellets are obtained; the capillary core-shell green pellets are sealed and preserved for 1-3 days, and then immersed in water for 13-27 days or immersed in sodium silicate curing solution with a mass concentration of 3-15% (e.g., 3%, 6%, 9%, 12%, 15% or other values ​​within this range) for 6-27 days, e.g., 6 days, 8 days, 10 days, 13 days, 16 days, 19 days, 22 days, 25 days or other values ​​within this range); core-shell solid waste phosphogypsum-based aggregate is obtained.

[0014] In this invention, due to the high content of active materials in the reconstituted material, the hydration degree is higher and the structure is more compact after hydration hardening. This allows the material to chemically combine with internal sulfates through the formation of ettringite, or to inhibit sulfate dissolution through physical sealing, thereby achieving compatibility with silicate cement systems. Furthermore, the use of sodium silicate curing solution can significantly improve the early strength and carbonation resistance of aggregates, as well as enhance their bonding with the matrix cement.

[0015] In some embodiments, phosphogypsum is in the form of raw powder or wet lumps with a moisture content of 0-15%, a solid content of not less than 85%, and a content of soluble P and F impurities ≤3%.

[0016] In some implementation schemes, the solid waste silica-alumina material includes at least one of S95 grade or higher granulated blast furnace slag, and Grade II or higher high-calcium fly ash or L95 granulated yellow phosphorus slag, wherein the CaO content in the high-calcium fly ash is greater than 10%, and the S95 grade or higher granulated blast furnace slag, Grade II or higher high-calcium fly ash, and L95 granulated yellow phosphorus slag are all treated with a screen of 200 mesh or higher.

[0017] In this invention, the solid waste silicon-aluminum material includes at least one of S95 grade or higher granulated blast furnace slag, and Grade II or higher high-calcium fly ash or L95 granulated yellow phosphorus slag. For example, the solid waste silicon-aluminum material may only include S95 grade or higher granulated blast furnace slag and Grade II or higher high-calcium fly ash; or it may only include S95 grade or higher granulated blast furnace slag and L95 granulated yellow phosphorus slag; or it may simultaneously include S95 grade or higher granulated blast furnace slag, Grade II or higher high-calcium fly ash, and L95 granulated yellow phosphorus slag.

[0018] It should also be noted that the proportions of each component in solid waste silicon-aluminum materials can be adjusted according to actual usage.

[0019] In some implementation schemes, the solid waste alkali activator includes at least one of grade II or higher steel slag powder, carbide slag, and red mud, wherein the CaO content in the carbide slag is ≥65%, the pH value of the red mud is greater than 10, the Na2O content is greater than 5%, and the grade II or higher steel slag powder, carbide slag, and red mud are all treated with a sieve of 100 mesh or higher.

[0020] In this invention, the solid waste alkali activator includes at least one of grade II or higher steel slag powder, carbide slag, and red mud. For example, the solid waste alkali activator may include only grade II or higher steel slag powder; or only carbide slag; or only red mud; or only grade II or higher steel slag powder and carbide slag; or only grade II or higher steel slag powder and red mud; or only carbide slag and red mud; or simultaneously include grade II or higher steel slag powder, carbide slag, and red mud.

[0021] It should also be noted that the proportions of each component in the solid waste alkali activator can be adjusted according to the actual usage.

[0022] In this invention, phosphogypsum, solid waste silica-alumina material, and solid waste alkaline activator work synergistically, wherein the solid waste alkaline activator provides OH... - It also breaks the chemical bonds of solid waste silica-alumina materials, promoting their dissolution and hydration to form hydrated calcium silicate gel, while phosphogypsum provides a large amount of SO4. 2- It also promotes the conversion of some hydration products into ettringite; the needle-like ettringite and amorphous CSH gel interweave, encapsulating and solidifying excess unreacted phosphogypsum, thus giving the cemented system strength. Furthermore, the preparation process of this invention ensures uniform dispersion of moisture among the materials, creating conditions for full hydration of the material components. At the same time, this process optimizes the internal micro and mesoscopic pore structure of the aggregate, thereby resulting in excellent performance.

[0023] In a second aspect, the present invention provides a solid waste phosphogypsum-based aggregate prepared using any of the above-described preparation methods.

[0024] In a third aspect, the present invention provides the application of the above-mentioned all-solid waste phosphogypsum-based aggregate in the preparation of concrete products.

[0025] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention, by first mixing the granulating material with water, can quantitatively control the amount of water used in granulation, precisely control the granulation time, and achieve parameterized, automated, and clean production of the granulation process, significantly improving granulation efficiency. Simultaneously, the use of stirring and dispersion significantly improves the uniformity of water dispersion, resulting in a more uniform green pellet size distribution, optimizing the liquid phase saturation, particle packing, and pore structure of the green pellets, and enhancing their early bonding strength. Furthermore, by adding granulating materials or reconstructing materials, the droplet-like green pellets are reconstructed, simplifying the process and significantly improving the compatibility of aggregates with silicate cement. In addition, it improves the recycling rate of solid waste, enabling the value-added application of low-quality solid waste, and eliminates the need for artificially high-enthalpy materials such as cement and lime, reducing material costs, saving energy, and protecting the environment, thus possessing extremely high environmental value and economic benefits. Attached Figure Description

[0026] Figure 1 This is a process flow diagram for preparing the all-solid waste phosphogypsum-based aggregate in this invention;

[0027] Figure 2 The images show the morphology of the solid waste phosphogypsum-based aggregate prepared in Example 1 of this invention, where (A) is a capillary spheroid morphology image and (B) is a CT image of the aggregate. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Experimental methods not specified in the examples are generally performed under conventional conditions and as described in the manual, or as recommended by the manufacturer. Unless otherwise specified, the general equipment, materials, reagents, etc. used are commercially available.

[0030] In this invention, phosphogypsum is in its original form as fine sand or wet lumps with a moisture content of 6.42%. Its main component is CaSO4·2H2O, with a solid content of 85% and a soluble P (calculated as P2O5) and F impurity content of 3%. S95 grade granulated blast furnace slag is processed through a 600-mesh sieve, Grade II high-calcium fly ash (CaO content of 12.1%) is processed through a 400-mesh sieve, L95 grade granulated yellow phosphorus slag is processed through a 600-mesh sieve, Grade II steel slag powder is processed through a 400-mesh sieve, calcium carbide slag (CaO content of 65.2%) is processed through a 100-mesh sieve, and red mud (pH value greater than 10, Na2O content of 5.6%) is processed through a 100-mesh sieve.

[0031] Please see Figure 1 This is a flow chart of the preparation process of the all-solid waste phosphogypsum-based aggregate in this invention. The preparation of the all-solid waste phosphogypsum-based aggregate includes the following steps: adding water to the granulating material and pre-stirring to obtain a premix; then granulating the premix to obtain water-droplet green balls; continuing to add granulating material or reconstructing material to the water-droplet green balls to reconstruct them; then continuing to granulate to obtain capillary green balls; curing the capillary green balls to obtain the all-solid waste phosphogypsum-based aggregate; wherein, by mass percentage, the granulating material includes 70-85% phosphogypsum, 10-25% solid waste silicon-aluminum material and 1-20% solid waste alkali activator; the reconstructing material includes 0-20% phosphogypsum, 60-90% solid waste silicon-aluminum material and 1-20% solid waste alkali activator.

[0032] Example 1

[0033] The solid waste phosphogypsum-based aggregate includes granulated materials, which include solid waste silicon-aluminum material composed of 80% phosphogypsum, 10% blast furnace slag and 5% yellow phosphorus slag, and solid waste alkali activator composed of 2% steel slag powder, 2% carbide slag and 1% red mud. The above raw materials are put into a mixer and mixed evenly to obtain granulated materials.

[0034] The preparation method of this solid waste phosphogypsum-based aggregate includes the following steps:

[0035] 1) Add the granulated material into the mixer, add water to control the water-to-material ratio at 0.19:1, and pre-mix to obtain a premix. Then, take the premix containing 70 parts of granulated material and put it into a disc granulator rotating at a uniform speed of 25 r / min for 4 min. The disc has an inclination angle of 42°, a diameter of 2 m, and a depth of 0.2 m to obtain water droplet-shaped granules.

[0036] 2) Add 30 parts of granulation material to the disc granulator containing water droplet-shaped green pellets, and continue granulation for 7 minutes to obtain capillary green pellets;

[0037] 3) After sealing and preserving the capillary green pellets for 3 days, they were then immersed in water for another 25 days to obtain homogeneous solid waste phosphogypsum-based aggregate.

[0038] The performance of the capillary green pellets and the all-solid waste phosphogypsum-based aggregates prepared in this embodiment was tested, and the results are as follows: Figure 2 As shown.

[0039] Example 2

[0040] The solid waste phosphogypsum-based aggregate includes granulated materials, which include solid waste silica-alumina material composed of 80% phosphogypsum, 4% blast furnace slag, 10% yellow phosphorus slag, and 1% high-calcium fly ash, and solid waste alkali activator composed of 2% steel slag powder, 2% carbide slag, and 1% red mud. The above raw materials are put into a mixer and mixed evenly to obtain granulated materials.

[0041] The preparation method of this solid waste phosphogypsum-based aggregate includes the following steps:

[0042] 1) Add the granulated material into the mixer, add water to control the water-to-material ratio at 0.19:1, and pre-mix to obtain a premix. Then, take the premix containing 70 parts of granulated material and put it into a disc granulator rotating at a uniform speed of 25 r / min for 4 min. The disc has an inclination angle of 42°, a diameter of 2 m, and a depth of 0.2 m to obtain water droplet-shaped granules.

[0043] 2) Add 30 parts of granulation material to the disc granulator containing water droplet-shaped green pellets, and continue granulation for 7 minutes to obtain capillary green pellets;

[0044] 3) After sealing and preserving the capillary green pellets for 3 days, they were then immersed in water for another 25 days to obtain homogeneous solid waste phosphogypsum-based aggregate.

[0045] Example 3

[0046] The solid waste phosphogypsum-based aggregate includes granulated materials, which include solid waste silicon-aluminum material composed of 80% phosphogypsum, 10% blast furnace slag and 5% yellow phosphorus slag, and solid waste alkali activator composed of 1% steel slag powder and 4% carbide slag. The above raw materials are put into a mixer and mixed evenly to obtain granulated materials.

[0047] The preparation method of this solid waste phosphogypsum-based aggregate includes the following steps:

[0048] 1) Add the granulated material into the mixer, add water to control the water-to-material ratio at 0.19:1, and pre-mix to obtain a premix. Then, take the premix containing 70 parts of granulated material and put it into a disc granulator rotating at a uniform speed of 25 r / min for 4 min. The disc has an inclination angle of 42°, a diameter of 2 m, and a depth of 0.2 m to obtain water droplet-shaped granules.

[0049] 2) Add 30 parts of granulation material to the disc granulator containing water droplet-shaped green pellets, and continue granulation for 7 minutes to obtain capillary green pellets;

[0050] 3) After sealing and preserving the capillary green pellets for 3 days, they were then immersed in water for another 25 days to obtain homogeneous solid waste phosphogypsum-based aggregate.

[0051] Example 4

[0052] The solid waste phosphogypsum-based aggregate comprises granulated material and reconstituted material. The granulated material includes a solid waste aluminosilicate material composed of 80% phosphogypsum, 10% blast furnace slag, and 5% yellow phosphorus slag, and a solid waste alkaline activator composed of 2% steel slag powder, 2% carbide slag, and 1% red mud. The reconstituted material includes a solid waste aluminosilicate material composed of 10% phosphogypsum, 15% blast furnace slag, 45% yellow phosphorus slag, and 10% high-calcium fly ash, and a solid waste alkaline activator composed of 12% steel slag powder, 2% carbide slag, and 6% red mud. The above raw materials are fed into a mixer and mixed evenly to obtain the granulated material and the reconstituted material respectively.

[0053] The preparation method of this solid waste phosphogypsum-based aggregate includes the following steps:

[0054] 1) Add the granulated material into the mixer, add water to control the water-to-material ratio at 0.19:1, and pre-mix to obtain a premix. Then, take the premix containing 70 parts of granulated material and put it into a disc granulator rotating at a uniform speed of 25 r / min for 4 min. The disc has an inclination angle of 42°, a diameter of 2 m, and a depth of 0.2 m to obtain water droplet-shaped granules.

[0055] 2) Add 30 parts of reconstituted material to the disc granulator containing water droplet-shaped green pellets, and continue granulation for 7 minutes to obtain capillary-shaped green pellets;

[0056] 3) After sealing and preserving the capillary green pellets for 3 days, they were then immersed in a 13% sodium silicate curing solution (modulus 1.2) for 25 days to obtain core-shell solid waste phosphogypsum-based aggregate.

[0057] Example 5

[0058] The solid waste phosphogypsum-based aggregate comprises granulated material and reconstituted material. The granulated material includes a solid waste aluminosilicate material composed of 80% phosphogypsum, 10% blast furnace slag, and 5% yellow phosphorus slag, and a solid waste alkaline activator composed of 2% steel slag powder, 2% calcium carbide slag, and 1% red mud. The reconstituted material includes a solid waste aluminosilicate material composed of 15% blast furnace slag, 55% yellow phosphorus slag, and 10% high-calcium fly ash, and a solid waste alkaline activator composed of 12% steel slag powder, 2% calcium carbide slag, and 6% red mud. The above raw materials are fed into a mixer and mixed evenly to obtain the granulated material and the reconstituted material respectively.

[0059] The preparation method of this solid waste phosphogypsum-based aggregate includes the following steps:

[0060] 1) Add the granulated material into the mixer, add water to control the water-to-material ratio at 0.19:1, and pre-mix to obtain a premix. Then, take the premix containing 70 parts of granulated material and put it into a disc granulator rotating at a uniform speed of 25 r / min for 4 min. The disc has an inclination angle of 42°, a diameter of 2 m, and a depth of 0.2 m to obtain water droplet-shaped granules.

[0061] 2) Add 30 parts of reconstituted material to the disc granulator containing water droplet-shaped green pellets, and continue granulation for 7 minutes to obtain capillary-shaped green pellets;

[0062] 3) The capillary green pellets were sealed and preserved for 3 days, and then immersed in water for 25 days to obtain core-shell solid waste phosphogypsum-based aggregate.

[0063] Comparative Example 1

[0064] The preparation method of the solid waste phosphogypsum-based aggregate is basically the same as that in Example 1, except that in step 1), the water-to-material ratio is 0.16:1.

[0065] Comparative Example 2

[0066] The preparation method of the solid waste phosphogypsum-based aggregate is basically the same as that in Example 1, except that in step 1), the rotation speed of the disc granulator is 15 r / min.

[0067] Comparative Example 3

[0068] The preparation method of the solid waste phosphogypsum-based aggregate is basically the same as that in Example 1, except that in step 1), the aggregate is granulated in a disc granulator for 2 minutes.

[0069] Comparative Example 4

[0070] The preparation method of the solid waste phosphogypsum-based aggregate is basically the same as that in Example 1, except that in step 2), granulation is continued for 3 minutes.

[0071] Performance testing

[0072] The performance of the all-solid waste phosphogypsum-based aggregates prepared in Examples 1-9 and the comparative example were tested, and the results are shown in Table 1 below:

[0073] Table 1. Performance test results of phosphogypsum-based aggregates from all solid waste.

[0074]

[0075]

[0076] As can be seen from the data in Table 1, the solid waste phosphogypsum-based aggregates prepared in Examples 1-5 have better performance. Furthermore, the reconstituted materials with higher levels of active ingredients used in Examples 4 and 5 have a higher degree of hydration and a denser structure after hydration and hardening. They can chemically combine with the internal sulfates in the form of the product ettringite, or inhibit the dissolution of sulfates in the form of physical solidification, resulting in extremely low S concentration in the leachate. In addition, the use of sodium silicate curing solution can significantly improve the early strength and carbonization resistance of the aggregates.

[0077] In Comparative Example 1, less water was added; in Comparative Example 2, the granulation speed was lower; and in Comparative Examples 3 and 4, the granulation time was shorter. The results showed that because the water-to-material ratio and granulation parameters were not within the optimal range of this invention, the fresh drop strength was significantly reduced, the granulation (ball formation) efficiency was significantly reduced, and the performance of the prepared all-solid waste phosphogypsum-based aggregate was poor. The above results indicate that by controlling the water-to-material ratio within a specific range, and further controlling the granulation speed and granulation time within a specific range, this invention can prepare all-solid waste phosphogypsum-based aggregate with better performance. At the same time, the granulation process can precisely control the granulation time, realize parameterization, automation, and clean production of the granulation process, and significantly improve the granulation efficiency.

[0078] Application testing

[0079] The raw materials used in the application test are as follows:

[0080] Ordinary cement is silicate cement (P·O 42.5), with a specific surface area of ​​300 m². 2 / kg;

[0081] Sulfurized cement is a type of slag cement made from slag and sulfurized gypsum. Its specific composition (by mass) is as follows: 45% phosphogypsum, 50% slag, and 5% silicate cement.

[0082] The fine aggregate is natural river sand, which is medium sand in Zone 2 with a fineness modulus of 2.8;

[0083] The coarse aggregate is the 4.75-19mm continuously graded all-solid waste phosphogypsum-based aggregate prepared according to this invention;

[0084] The water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate of 15%.

[0085] The all-solid waste phosphogypsum-based aggregates prepared in Examples 1, 2, and 4 were used to prepare concrete. This concrete comprised: 550 parts ordinary cement or supersulfurized cement, 880 parts fine aggregate, 770 parts coarse aggregate, 180 parts water, and 3 parts water-reducing agent. The specific groupings are as follows:

[0086] Application Test Example 1: The coarse aggregate used was the all-solid waste phosphogypsum-based aggregate from Example 1, and the cement used was ordinary cement, with the rest remaining unchanged;

[0087] Application Test Example 2: The coarse aggregate used was the all-solid waste phosphogypsum-based aggregate from Example 2, and the cement used was ordinary cement, with the rest remaining unchanged;

[0088] Application Test Example 3: The coarse aggregate used was the all-solid waste phosphogypsum-based aggregate from Example 4, and the cement used was ordinary cement, with the rest remaining unchanged;

[0089] Application Test Example 4: The coarse aggregate used was the all-solid waste phosphogypsum-based aggregate from Example 1, and the cement used was supersulfurized cement; all other aspects remained unchanged.

[0090] Application Test Example 5: The coarse aggregate used was the all-solid waste phosphogypsum-based aggregate from Example 2, and the cement used was supersulfurized cement, with the rest remaining unchanged;

[0091] Application Test Example 6: The coarse aggregate used was the all-solid waste phosphogypsum-based aggregate from Example 4, and the cement used was supersulfurized cement, with the rest remaining unchanged;

[0092] The specific concrete preparation steps in the above application test examples are as follows:

[0093] Weigh the raw materials according to the formula ratio, add the water-reducing agent to the water and stir evenly; pour the weighed fine aggregate and coarse aggregate into the concrete mixer and stir for 1-3 minutes to mix evenly; then pour the cement into the concrete mixer and stir for 1-3 minutes to ensure that all components are evenly mixed with the fine and coarse aggregates; pour the water mixed with the water-reducing agent into the concrete mixer, stir for 1-2 minutes, and then discharge the material. After molding and standard curing for 7, 28, 90, and 180 days, the all-solid waste phosphogypsum-based aggregate concrete is obtained. The compressive strength is measured at 7, 28, 90, and 180 days, and the test results are shown in Table 2.

[0094] Table 2. Test results of mechanical properties of all-solid-waste phosphogypsum-based aggregate concrete

[0095]

[0096] As shown in Table 2, ordinary cement was used in application tests 1-3, and the aggregates in application tests 1 and 2 were homogeneous aggregates, while the aggregates in application test 3 were core-shell aggregates. The results indicate that the compressive strength of the concrete prepared using core-shell aggregates in application test 3 was significantly higher than that of the concrete in application tests 1 and 2. This suggests that the homogeneous aggregates used in application tests 1 and 2 are not well compatible with silicate cement, resulting in concrete with low strength. Using reconstituted materials can achieve compatibility with the silicate cement system. Furthermore, curing with sodium silicate curing solution can significantly improve the early strength and carbonation resistance of the aggregates, as well as enhance their bonding with the matrix cement, thus significantly increasing the compressive strength of the concrete in application test 3.

[0097] In application tests 4-6, supersulfurized cement was used. The aggregates in application tests 4 and 5 were homogeneous aggregates, while the aggregate in application test 6 was a core-shell aggregate. The results showed that the concrete prepared in application tests 4 and 5 had higher strength than the concrete prepared in application tests 1 and 2. This indicates that both the core-shell and homogeneous aggregates in this invention are compatible with supersulfurized cement, resulting in high-strength concrete. Furthermore, since supersulfurized cement was used, the strength of the prepared concrete primarily depends on the strength of the aggregates. Therefore, the strength of the concrete in application test 6 was slightly lower than that of the concrete in application test 3, but higher than that of the concrete in application tests 4 and 5.

[0098] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0099] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a solid waste phosphogypsum-based aggregate, characterized in that, Includes the following steps: The granulation material is pre-stirred with water to obtain a premix, and then the premix is ​​granulated to obtain water droplet-shaped spheres; Reconstruction material is added to the water droplet-shaped green spheres to reconstruct them, and then granulation is continued to obtain capillary green spheres. The capillary green pellets are cured to obtain the all-solid waste phosphogypsum-based aggregate; The granulation material, by mass percentage, comprises 70-85% phosphogypsum, 10-25% solid waste silicon-aluminum material, and 1-20% solid waste alkaline activator; the reconstituted material comprises 0-20% phosphogypsum, 60-90% solid waste silicon-aluminum material, and 1-20% solid waste alkaline activator. In the preparation process of the water droplet-shaped spheres, the water-to-granulation material ratio is (0.17-0.21):

1. The pre-mixing is carried out in a mixer. Granulation includes: putting a premix containing 60-80 parts of granulation material into a centrifugal granulator and granulating for 3-10 minutes. The rotation speed of the centrifugal granulator is 20-45 r / min. During the preparation of the capillary biospheres, 20-40 parts of reconstructed material are added to the droplet biospheres, and granulation is performed for 4-10 minutes.

2. The method for preparing all-solid waste phosphogypsum-based aggregate according to claim 1, characterized in that, When 20-40 parts of reconstructed material are added to the water-drop-shaped green pellets, capillary core-shell green pellets are obtained. The capillary core-shell green pellets are sealed and preserved for 1-3 days, and then immersed in water for 13-27 days or immersed in sodium silicate curing solution with a mass concentration of 3-15% for 6-27 days to obtain core-shell solid waste phosphogypsum-based aggregate.

3. The method for preparing all-solid waste phosphogypsum-based aggregate according to any one of claims 1-2, characterized in that, The phosphogypsum is in its original form as powder or wet lumps, with a moisture content of 0-15%, a solid content of not less than 85%, and a content of soluble P and F impurities ≤3%.

4. The method for preparing all-solid waste phosphogypsum-based aggregate according to any one of claims 1-2, characterized in that, The solid waste silicon-aluminum material includes at least one of S95 grade or higher granulated blast furnace slag, and Grade II or higher high-calcium fly ash or L95 granulated yellow phosphorus slag. The high-calcium fly ash contains more than 10% CaO, and the S95 grade or higher granulated blast furnace slag, the Grade II or higher high-calcium fly ash, and the L95 granulated yellow phosphorus slag are all treated with a sieve of 200 mesh or higher.

5. The method for preparing all-solid waste phosphogypsum-based aggregate according to any one of claims 1-2, characterized in that, The solid waste alkaline activator includes at least one of grade II or higher steel slag powder, carbide slag, and red mud, wherein the carbide slag has a CaO content ≥65%, the red mud has a pH value greater than 10 and a Na2O content greater than 5%, and the grade II or higher steel slag powder, carbide slag, and red mud are all treated with a sieve of 100 mesh or higher.

6. A solid waste phosphogypsum-based aggregate prepared by any one of claims 1-5.

7. The application of the all-solid waste phosphogypsum-based aggregate as described in claim 6 in the preparation of concrete products.

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