Dehydration and impurity removal method for ardealite

Abstract

The invention provides an ardealite dehydration and impurity removal method which comprises the following steps: S1, putting ardealite into a primary crusher, crushing the ardealite into particles with the particle size of less than 3mm, and introducing high-temperature air with the temperature of 100-150 DEG C into the primary crusher at the same time; s2, the ardealite particles are fed into a secondary pulverizer, a plurality of nozzles are arranged on the side wall of the secondary pulverizer in a circumferential array mode, steam with the temperature ranging from 300 DEG C to 500 DEG C is introduced into the nozzles, the injection pressure of the steam ranges from 0.6 Mpa to 1.3 Mpa, and the steam is used for pulverizing the ardealite particles into ardealite powder with the particle size smaller than 20 microns; s3, the ardealite powder is fed into the bottom of an impurity removal reactor, a dispersed powder additive is sprayed into the impurity removal reactor through a spray pipe arranged at the lower end of the side wall of the impurity removal reactor, and the powder additive is calcium carbonate or calcium oxide; and S4, feeding the ardealite powder treated by the impurity removal reactor into a classifier. According to the scheme, water and various impurities in the ardealite can be quickly and effectively removed, the production efficiency is higher, and the energy consumption is lower.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphogypsum preparation, and in particular relates to a method for dehydrating and removing impurities from phosphogypsum. Background Art

[0002] Phosphogypsum is the main by-product of the wet phosphoric acid production process. In addition to the main component CaSO4·2H2O, there are also phosphorus impurities, soluble fluoride impurities, organic impurities, etc. Among them, phosphorus impurities are divided into soluble phosphorus, insoluble phosphorus and eutectic phosphorus. Insoluble phosphorus Ca3(PO4)2 is stable in nature and distributed in large particles of phosphogypsum, which has little effect on the performance of gypsum. Soluble phosphorus and eutectic phosphorus will affect the hydration process of gypsum, resulting in reduced gypsum strength or frosting during later use. Soluble fluoride will reduce the interaction between phosphogypsum molecules. When the soluble fluoride content reaches a certain level, it will reduce the flexural and compressive strength of gypsum. Organic impurities will affect the water demand of gypsum, resulting in loose structure and reduced compressive strength of gypsum.

[0003] There are three methods for removing impurities from phosphogypsum: chemical method, physical method and heat treatment method. Among them, the chemical method is to convert soluble phosphorus and fluorine into inert substances by adding chemical reagents. This method has a long reaction time, low treatment efficiency and may lead to the introduction of new impurities; the physical method mainly includes water washing method and flotation method. The water washing method can effectively remove soluble impurities in phosphogypsum, but it consumes a lot of water resources and produces a large amount of wastewater, which increases the cost of impurity removal. In addition, the water washing has no obvious effect on the removal of eutectic phosphorus. The flotation method does not consume much water resources, but the flotation agent and complex process also lead to high impurity removal costs; the heat treatment method is to decompose the organic impurities in the phosphogypsum at high temperature, volatilize the volatile impurities or react with calcium sulfate to change its state of occurrence in the phosphogypsum to achieve impurity removal, but this method has large equipment investment, high energy consumption and unstable product quality. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a method for dehydrating and removing impurities from phosphogypsum, which can quickly and effectively remove water and various impurities in phosphogypsum, has higher production efficiency, and lower energy consumption.

[0005] In order to achieve the purpose of the present invention, the following scheme is proposed: A method for dehydrating and removing impurities from phosphogypsum comprises the following steps: S1: The phosphogypsum raw material is put into the first-stage pulverizer from the top for the first pulverization, and the phosphogypsum is pulverized into particles with a size of less than 3 mm. At the same time, high-temperature air with a temperature of 100°C to 150°C is introduced into the first-stage pulverizer to remove free water from the phosphogypsum particles; the lower end of the first-stage pulverizer is connected to a first-stage pipeline; S2: The high-temperature air in the primary pulverizer is used to send the phosphogypsum particles into the secondary pulverizer through the primary pipeline. The side wall of the secondary pulverizer is provided with a plurality of nozzles along the circumferential array. The spray trajectories of the nozzles intersect in the middle of the secondary pulverizer and form an airflow convergence point. The primary pipeline throws the phosphogypsum particles to the airflow convergence point. Steam with a temperature of 300°C to 500°C is introduced into the nozzle. The steam spray pressure is 0.6Mpa to 1.3Mpa, which is used to crush the phosphogypsum particles into phosphogypsum powder with a particle size of less than 20μm. S3: using an air pump to deliver the phosphogypsum powder processed by the secondary crusher to the bottom of the impurity removal reactor, spraying a dispersed powder additive into the impurity removal reactor through a nozzle arranged at the lower end of the side wall of the impurity removal reactor, the powder additive being calcium carbonate or calcium oxide, and stirring and mixing the phosphogypsum powder and the powder additive through a dispersing component arranged inside the impurity removal reactor, and the treated phosphogypsum powder is discharged from the upper end of the impurity removal reactor following the airflow; S4: The phosphogypsum powder treated in the impurity removal reactor is sent to a classifier to classify the phosphogypsum powder. The rear end of the classifier is connected with a dust collector and an induced draft fan in sequence. The airflow is discharged through the induced draft fan, and the phosphogypsum powder is collected from the lower end of the dust collector. As a preferred solution, the classifier adopts an impeller for classification.

[0006] The beneficial effects of the present invention are: 1. The traditional process for preparing phosphogypsum is to remove impurities first, then calcine, dehydrate and then crush. The impurity removal and calcination time is long. This process method is to crush and dehydrate simultaneously, and continue to dehydrate during the impurity removal process. The crushed material has a large specific surface area and is fully exposed to high-temperature air, steam and additives, so the reaction is faster, the processing time is shorter, the production efficiency is higher, and the energy consumption is lower.

[0007] 2. The first-stage crusher, the second-stage crusher and the impurity removal reactor all have the function of dispersion and drying, and they are connected in series in multiple stages. Therefore, the phosphogypsum is in a well-dispersed state throughout the entire process, which can effectively avoid the blockage of pipeline walls. The accumulation and adhesion of phosphogypsum in the crushing chamber will seriously affect the crushing energy efficiency. This solution effectively avoids the blockage of phosphogypsum walls by continuously dehydrating and drying during the crushing process, thereby improving production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present invention.

[0009] Figure 1 A schematic diagram of the method flow of the present application is shown.

[0010] Figure 2 A schematic diagram of the equipment structure used in the method of the present application is shown.

[0011] Figure 3 A cross-sectional view of a primary pulverizer used in step S1 is shown.

[0012] Figure 4 A schematic diagram of a preferred structure of the dispersed components used in step S3 is shown.

[0013] Markings in the figure: primary crusher -1, primary pipeline -11, shell -12, annular chamber -121, high-temperature air inlet pipe -122, drum -13, cylindrical roller -14, wear-resistant plate -15, annular groove -151, through hole -152, secondary crusher -2, nozzle -21, air pump -22, impurity removal reactor -3, nozzle -31, rotating shaft -32, outer tooth tube -321, mesh plate -33, mesh -331, inner gear ring -332, idler wheel -34, classifier -4, dust collector -5, induced draft fan -6. DETAILED DESCRIPTION

[0014] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the implementation modes of the present invention are described in detail below with reference to the accompanying drawings. However, the embodiments described in the present invention are only part of the embodiments of the present invention, rather than all the embodiments.

[0015] like Figure 1 , Figure 2 As shown, a method for dehydrating and removing impurities from phosphogypsum comprises the following steps: S1: The phosphogypsum raw material is put into the first-level pulverizer 1 from the top for the first pulverization, and the phosphogypsum is pulverized into particles with a particle size of less than 3 mm. The first-level pulverizer 1 is a stirred mill or a ball mill. At the same time, high-temperature air (100℃~150℃) is introduced into the first-level pulverizer 1 to remove free water and part of the crystal water of the phosphogypsum particles; the lower end of the first-level pulverizer 1 is connected with a first-level pipeline 11. The water in the phosphogypsum includes free water and crystal water. The free water is rapidly evaporated at about 100℃. As the temperature rises from 120℃~150℃, the crystal water gradually separates from the phosphogypsum, and the dihydrate gypsum (CaSO4·2H2O) gradually turns into hemihydrate gypsum (CaSO4·0.5H2O). The first-level pulverization can preheat and disperse the phosphogypsum while removing the free water and part of the crystal water in the phosphogypsum, so that the phosphogypsum particles can be fully dispersed in the subsequent pulverization process, so as to improve the pulverization efficiency and effect, and prevent the phosphogypsum particles from aggregating and adhering to the equipment or the inner wall of the pipeline.

[0016] S2: After the first-stage crushing, the phosphogypsum enters the secondary crusher 2 through the first-stage pipe 11 at the lower end of the first-stage crusher 1. The side wall of the secondary crusher 2 is provided with a plurality of nozzles 21 along the circumferential array. The spraying trajectories of the nozzles 21 intersect at the middle of the secondary crusher 2 and form an airflow convergence point. The end of the first-stage pipe 11 passes through the side wall of the secondary crusher 2 and is located above the airflow convergence point. The phosphogypsum particles are thrown to the airflow convergence point. Steam with a temperature of 300°C to 500°C is introduced into the nozzle 21. The spraying pressure of the steam is 0.6Mpa to 1.3Mpa, which is used to crush the phosphogypsum particles into phosphogypsum particles with a particle size of less than 20μm. Gypsum powder; during the operation of the secondary crusher 2, the phosphogypsum particles are driven by the high-speed steam airflow to violently collide, and the phosphogypsum particles are further crushed, so that the specific surface area of ​​the phosphogypsum material increases, and the internal water becomes surface water. In the process of full contact with superheated steam, part of the crystal water remaining in the first-level crushing is converted into gaseous state during 3s to 10s, and is quickly taken away by the high-speed airflow, thereby realizing the transformation from semi-hydrated phosphogypsum to anhydrous phosphogypsum. In addition, under the synergistic effect of violent collision, high temperature and high-speed airflow, the organic impurities, fluorine impurities and phosphorus impurities in the phosphogypsum are separated from the material and discharged with the high-speed airflow.

[0017] S3: The phosphogypsum powder processed by the secondary crusher 2 is sent to the bottom of the impurity removal reactor 3 by means of an air pump 22, and a dispersed powder additive is sprayed into the impurity removal reactor 3 through a nozzle 31 arranged at the lower end of the side wall of the impurity removal reactor 3. The powder additive is calcium carbonate or calcium oxide, and the phosphogypsum powder and the powder additive are stirred and mixed by a dispersion component arranged inside the impurity removal reactor 3. The treated phosphogypsum powder is discharged from the upper end of the impurity removal reactor 3 along with the airflow. In this step, calcium carbonate or calcium oxide is mixed with phosphogypsum to adjust the pH of gypsum, and at the same time, soluble fluorine impurities and phosphorus impurities are prevented from adhering to the surface of the phosphogypsum powder to form calcium phosphate or calcium fluoride, thereby avoiding hindering the hydration of the finished phosphogypsum and achieving the purpose of adjusting the pH of the phosphogypsum powder. The dispersion component can make the powder additive, airflow and phosphogypsum powder mixed more evenly, promote the reaction effect and speed, and further improve the impurity removal effect.

[0018] S4: The phosphogypsum powder treated by the impurity removal reactor 3 is sent to the classifier 4, and the phosphogypsum powder is classified to control the particle size of the finished product. The rear end of the classifier 4 is connected with the dust collector 5 and the induced draft fan 6 in sequence. The air flow is discharged through the induced draft fan 6, and the phosphogypsum powder is collected from the lower end of the dust collector 5. As a preferred solution, the classifier 4 adopts impeller classification.

[0019] Preferably, in step S3, while the impurity removal reactor 3 is processing the phosphogypsum powder, steam at a temperature of 200°C to 300°C is injected into the impurity removal reactor 3 to maintain a high temperature state inside the impurity removal reactor 3, so as to achieve the purpose of continuously removing crystallization water and further dehydrating the phosphogypsum powder.

[0020] Preferably, the high-temperature air introduced into the primary pulverizer 1 in step S1, the steam introduced into the secondary pulverizer in step S2, and the steam introduced into the impurity removal reactor 3 in step S3 are all increased by industrial waste heat, which can effectively reduce energy consumption.

[0021] Preferably, in step S1, the processing time of the primary crusher 1 is 5 min to 10 min; in step S2, the processing time of the secondary crusher 2 is 3 s to 10 s; and in step S3, the processing time of the impurity removal reactor 3 is 10 s to 20 s.

[0022] Preferably, Figure 3 As shown, in step S1, the primary crusher 1 performs multi-stage crushing on the phosphogypsum raw material. The primary crusher 1 includes a cylindrical shell 12, inside which a rotating drum 13 is coaxially arranged, and the rotating drum 13 is rotatably arranged around an axis. Specifically, a motor may be provided on the top of the shell 12 for directly driving the rotating drum 13 to rotate. A plurality of cylindrical rollers 14 are provided at intervals along the axial direction on the outer side of the rotating drum 13, and a plurality of cylindrical rollers 14 of each layer are provided along the circumferential array of the rotating drum 13. The cylindrical rollers 14 are rotatably arranged around an axis, and the axis thereof is parallel to the axis of the rotating drum 13. A wear-resistant plate 15 of a circular tube structure is coaxially arranged inside the shell 12 corresponding to the outer side of the rotating drum 13. An annular groove 151 is provided on the inner wall of the wear-resistant plate 15 corresponding to each layer of cylindrical rollers 14, and the distance between the annular groove 151 at the upper end and the corresponding cylindrical roller 14 is greater than the distance between the annular groove 151 at the lower end and the corresponding cylindrical roller 14. In step S1, when the primary crusher 1 is used to crush the phosphogypsum raw material, the drum 13 rotates around its own axis, thereby driving the cylindrical roller 14 to rotate along with the drum 13, and the phosphogypsum is squeezed through the uppermost cylindrical roller 14 and the corresponding annular groove 151, so that the phosphogypsum completes the first crushing in the primary crusher 1, and in the process of squeezing the phosphogypsum, the cylindrical roller 14 will simultaneously rotate around its own axis to avoid eccentric wear of the cylindrical roller 14; the phosphogypsum that has completed the first crushing will automatically fall between the cylindrical roller 14 and the annular groove 151 below, and continue to complete the second crushing in the primary crusher 1, and so on, the primary crusher 1 can be used to crush the phosphogypsum raw material for multiple times, and the multiple crushing process can be used to increase the contact time and probability of the phosphogypsum with the high-temperature air, thereby improving the preheating and dehydration effects.

[0023] Further preferably, in order to make the phosphogypsum contact with the high-temperature air more fully during the crushing process in step S1, Figure 3As shown, the wear-resistant plate 15 is arranged inside the housing 12 at intervals, so that an annular chamber 121 is formed between the housing 12 and the wear-resistant plate 15, and a through hole 152 is opened on the side wall of the wear-resistant plate 15, and the through hole 152 is arranged at intervals from the annular groove 151, and the outer wall of the housing 12 is connected with a high-temperature air intake pipe 122 for injecting high-temperature air into the primary pulverizer 1. In step S1, the introduced high-temperature air enters the annular chamber 121 formed between the housing 12 and the wear-resistant plate 15 through the high-temperature air intake pipe 122, and then enters the pulverizing area through the through hole 152 opened on the wear-resistant plate 15. Injecting high-temperature air into the primary pulverizer 1 in the above-mentioned manner can not only make the high-temperature air concentration in various places inside the primary pulverizer 1 more balanced, but also increase the contact probability between the high-temperature air and the phosphogypsum, which is helpful to further improve the preheating and dehydration effect of the phosphogypsum; and the annular chamber 121 is used to form a cylindrical insulation layer outside the crushing area, which can effectively ensure the constant temperature inside the primary pulverizer 1; as a preferred solution, a plurality of through holes 152 are provided along the circumferential array of the wear-resistant plate 15; as a further preferred solution, the through hole 152 is opened below the annular groove 151, so that the phosphogypsum can be preheated and the moisture of the phosphogypsum can be removed immediately during the process of the phosphogypsum falling after crushing, thereby reducing the moisture content of the phosphogypsum during the next crushing, thereby preventing the phosphogypsum from adhering to the surface of the crushed parts; as a preferred solution, the high-temperature air intake pipe 122 is a branch pipe structure connected to the air intake main pipe 123, and the air intake main pipe 123 is connected to the shell 12, which is used to directly inject high-temperature air into the inner shell 12 to provide a greater air flow pressure.

[0024] Preferably, Figure 2 , Figure 4 As shown, in order to make the phosphogypsum powder and the powder additive mixed more fully in step S3, a dispersing component is provided, which includes a rotating shaft 32, on which a plurality of mesh plates 33 are arranged at intervals along the axial direction, and meshes 331 are opened on the mesh plates 33, and a driving motor for driving the rotating shaft 32 to rotate is provided on the top of the dust removal reactor 3; in step S3, the phosphogypsum powder processed by the secondary crusher 2 is sent to the bottom of the impurity removal reactor 3 by the air pump 22, and the dispersed powder additive is sprayed into the impurity removal reactor 3 by the nozzle 31, and the positive pressure airflow generated by the air pump 22 and the negative pressure airflow generated by the induced draft fan 6 are combined. Under the same action, the phosphogypsum powder and the powder additive move toward the top of the impurity removal reactor 3 at the same time. During the upward movement of the phosphogypsum powder and the powder additive, the rotating shaft 32 of the dispersion component rotates driven by the driving motor, and a plurality of mesh plates 33 arranged at intervals on the rotating shaft 32 rotate with the rotating shaft 32. The phosphogypsum powder and the powder additive rise step by step through the meshes 331 on the mesh plates 33. During the rising process, the stirring of the mesh plates 33 is utilized to make the phosphogypsum powder and the powder additive mix more fully, thereby further improving the reaction speed and efficiency of calcium carbonate or calcium oxide with soluble organic impurities, fluorine impurities and phosphorus impurities.

[0025] Further preferably, in order to further improve the reaction effect of the powder additive with various impurities, such as Figure 4 As shown, there are two adjacent mesh plates 33 on the rotating shaft 32, one of which is fixedly connected to the rotating shaft 32, and the other mesh plate 33 is coaxially sleeved on the rotating shaft 32. The so-called fixed connection here means that the fixedly connected mesh plate 33 rotates together with the rotating shaft 32, which can be specifically achieved by screw locking or welding. The mesh plate 33 sleeved on the rotating shaft 32 can rotate relative to the rotating shaft 32, wherein an inner gear ring 332 is coaxially provided at the bottom of the mesh plate 33 sleeved on the rotating shaft 32, and an outer gear ring 321 corresponding to the inner gear ring 332 is coaxially fixed on the rotating shaft 32. The inner gear ring 332 and the outer gear ring 321 are meshed with an idler wheel 34 together. A bracket is provided on the inner wall of the impurity removal reactor 3, and the bracket is located below the mesh plate 33 provided with the inner gear ring 332. The lower end of the idler wheel 34 is rotatably provided on the bracket. Through the above structural design, when the rotating shaft 32 rotates, the mesh plate 33 fixed on the rotating shaft 32 will rotate synchronously with the rotating shaft 32 in the same direction, and the mesh plate 33 sleeved on the rotating shaft 32 will rotate in the opposite direction of the rotating shaft 32, thereby effectively improving the stirring effect of the airflow and the phosphogypsum powder and powder additives driven by the airflow, and further improving the reaction speed and efficiency of calcium carbonate or calcium oxide with soluble organic impurities, fluorine impurities and phosphorus impurities.

[0026] The above description is only a preferred embodiment of the present invention, and is not intended to be the only one or to limit the present invention. Those skilled in the art should understand that various changes or equivalent substitutions made to the present invention without departing from the scope of the present invention are within the scope of protection of the present invention.

Claims

1. A method for dehydrating and removing impurities from phosphogypsum, characterized in that: The following steps are involved: S1: Phosphogypsum raw materials are fed into a primary pulverizer (1) from the top for pulverization, the phosphogypsum is pulverized into particles with a particle size of less than 3 mm, and high-temperature air is introduced into the primary pulverizer (1) at a temperature of 100° C. to 150° C. to remove free water from the phosphogypsum particles; the lower end of the primary pulverizer (1) is connected to a primary pipeline (11); S2: using the high-temperature air in the primary pulverizer (1) to send the phosphogypsum particles into the secondary pulverizer (2) through the primary pipe (11); a plurality of nozzles (21) are arranged in a circular array along the side wall of the secondary pulverizer (2); the spray trajectories of the nozzles (21) intersect at the middle of the secondary pulverizer (2) to form an airflow convergence point; the primary pipe (11) delivers the phosphogypsum particles to the airflow convergence point; steam at a temperature of 300° C. to 500° C. is introduced into the nozzle (21); the steam spray pressure is 0.6 Mpa to 1.3 Mpa, and is used to pulverize the phosphogypsum particles into phosphogypsum powder with a particle size of less than 20 μm; S3: using an air pump (22) to deliver the phosphogypsum powder processed by the secondary crusher (2) to the bottom of the impurity removal reactor (3), spraying a dispersed powder additive into the impurity removal reactor (3) through a nozzle (31) arranged at the lower end of the side wall of the impurity removal reactor (3), wherein the powder additive is calcium carbonate or calcium oxide, and stirring and mixing the phosphogypsum powder and the powder additive through a dispersion component arranged inside the impurity removal reactor (3), and the treated phosphogypsum powder is discharged from the upper end of the impurity removal reactor (3) along with the air flow; S4: The phosphogypsum powder treated in the impurity removal reactor (3) is sent to a classifier (4) to classify the phosphogypsum powder. The rear end of the classifier (4) is connected in sequence to a dust collector (5) and an induced draft fan (6). The airflow is discharged through the induced draft fan (6), and the phosphogypsum powder is collected from the lower end of the dust collector (5).

2. A method for dehydrating and removing impurities from phosphogypsum according to claim 1, characterized in that: Step S3, while the impurity removal reactor (3) is processing the phosphogypsum powder, steam at a temperature of 200° C. to 300° C. is injected into the impurity removal reactor (3).

3. A method for dehydrating and removing impurities from phosphogypsum according to claim 2, characterized in that: The high-temperature air introduced into the primary pulverizer (1) in step S1, the steam introduced into the secondary pulverizer in step S2, and the steam introduced into the impurity removal reactor (3) in step S3 are all increased by industrial waste heat.

4. The method for dehydrating and removing impurities from phosphogypsum according to claim 1, characterized in that: In step S1, the processing time of the primary pulverizer (1) is 5 minutes to 10 minutes; in step S2, the processing time of the secondary pulverizer (2) is 3 seconds to 10 seconds; in step S3, the processing time of the impurity removal reactor (3) is 10 seconds to 20 seconds.

5. The method for dehydrating and removing impurities from phosphogypsum according to claim 1, characterized in that: In step S1, the primary pulverizer (1) performs multi-stage pulverization on the phosphogypsum raw material. The primary pulverizer (1) comprises a cylindrical shell (12), a rotating drum (13) is coaxially arranged inside the rotating drum (13), the rotating drum (13) is arranged to rotate around an axis, and multiple layers of cylindrical rollers (14) are arranged at intervals along the axis direction on the outer side of the rotating drum (13), and each layer of cylindrical rollers (14) is arranged along the circumference of the rotating drum (13). The cylindrical rollers (14) are arranged to rotate around the axis, and the axis is parallel to the axis of the rotating drum (13). A wear-resistant plate (15) with a circular tube structure is coaxially arranged inside the shell (12) corresponding to the outer side of the rotating drum (13), and an annular groove (151) is opened on the inner wall of the wear-resistant plate (15) corresponding to each layer of cylindrical rollers (14), and the distance between the annular groove (151) at the upper end and the corresponding cylindrical roller (14) is greater than the distance between the annular groove (151) at the lower end and the corresponding cylindrical roller (14).

6. A method for dehydrating and removing impurities from phosphogypsum according to claim 5, characterized in that: In step S1, the high-temperature air is introduced into the annular chamber (121) formed between the housing (12) and the wear-resistant plate (15) through the high-temperature air inlet pipe (122), and then enters the crushing area through the through hole (152) provided on the wear-resistant plate (15).

7. The method for dehydrating and removing impurities from phosphogypsum according to claim 1, characterized in that: In step S3, the phosphogypsum powder and the powder additive are simultaneously moved upwardly toward the top of the impurity removal reactor (3). During the upward movement of the phosphogypsum powder and the powder additive, the rotating shaft (32) of the dispersion component is driven by the driving motor to rotate, and a plurality of mesh plates (33) arranged at intervals on the rotating shaft (32) rotate along with the rotating shaft (32), and the phosphogypsum powder and the powder additive are gradually raised through the meshes (331) on the mesh plates (33).

8. The method for dehydrating and removing impurities from phosphogypsum according to claim 7, characterized in that: In order to further improve the reaction effect between the powder additive and various impurities, two adjacent mesh plates (33) on the rotating shaft (32) are provided, one of which is fixedly connected to the rotating shaft (32), and the other mesh plate (33) is coaxially sleeved on the rotating shaft (32), wherein an inner gear ring (332) is coaxially provided at the bottom of the mesh plate (33) sleeved on the rotating shaft (32), an outer gear ring (321) is coaxially fixedly provided on the rotating shaft (32), and the inner gear ring (332) and the outer gear ring (321) are meshed with an idler wheel (34) together, and a bracket is provided on the inner wall of the impurity removal reactor (3), the bracket is located below the mesh plate (33) provided with the inner gear ring (332), and the lower end of the idler wheel (34) is rotatably provided on the bracket.

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