A method for dehydrating and removing impurities from phosphogypsum

Abstract

This application provides a method for dehydrating and removing impurities from phosphogypsum, comprising the following steps: S1: pulverizing phosphogypsum into particles less than 3 mm in size in a primary pulverizer while simultaneously introducing high-temperature air at 100°C to 150°C into the primary pulverizer; S2: feeding the phosphogypsum particles into a secondary pulverizer. A plurality of nozzles are arranged along the circumference of the secondary pulverizer's sidewalls, and steam at a temperature of 300°C to 500°C is introduced into the nozzles at a pressure of 0.6 MPa to 1.3 MPa to pulverize the phosphogypsum particles into phosphogypsum powder with a particle size less than 20 μm; S3: feeding the phosphogypsum powder into the bottom of an impurity removal reactor, and spraying a dispersed powder additive such as calcium carbonate or calcium oxide into the reactor through a nozzle disposed at the lower end of the reactor's sidewall; S4: feeding the phosphogypsum powder treated in the impurity removal reactor into a classifier. This solution can quickly and effectively remove water and various impurities from phosphogypsum, achieving higher production efficiency and lower energy consumption.

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 a major byproduct of the wet-process phosphoric acid production process. Besides its primary component, CaSO₄·2H₂O, it also contains phosphorus impurities, soluble fluoride impurities, and organic impurities. Phosphorus impurities are classified as soluble, sparingly soluble, and eutectic. Sparingly soluble phosphorus, Ca₃(PO₄)₂, is stable and distributed within the large particles of phosphogypsum, having little impact on its performance. Soluble and eutectic phosphorus, however, can affect the hydration process, leading to reduced strength and frosting during later use. Soluble fluoride reduces the intermolecular interactions of phosphogypsum. When the soluble fluoride content reaches a certain level, it reduces the flexural and compressive strength of the gypsum. Organic impurities reduce the gypsum's water requirement, resulting in a loose structure and reduced compressive strength.

[0003] Phosphogypsum impurity removal methods include chemical, physical, and thermal treatment. The chemical method involves adding chemical reagents to convert soluble phosphorus and fluorine into inert substances. This method has a long reaction time, low treatment efficiency, and may introduce new impurities. Physical methods primarily include water washing and flotation. Water washing can effectively remove soluble impurities from phosphogypsum, but it consumes significant amounts of water resources and produces a large amount of wastewater, increasing removal costs. Furthermore, water washing is not effective for removing eutectic phosphorus. Flotation, while not consuming much water resources, also requires flotation agents and complex processes, resulting in high impurity removal costs. Thermal treatment removes impurities by decomposing organic impurities in phosphogypsum at high temperatures, volatilizing volatile impurities, or reacting with calcium sulfate to change their state of existence in the phosphogypsum. However, this method requires large equipment investment, high energy consumption, and unstable product quality. Summary of the Invention

[0004] To address the deficiencies in 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 from 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:

[0006] A method for dehydrating and removing impurities from phosphogypsum comprises the following steps:

[0007] S1: Phosphogypsum raw materials are fed into a primary pulverizer from the top for the first pulverization, pulverizing the phosphogypsum into particles less than 3 mm in size. At the same time, high-temperature air with a temperature of 100°C to 150°C is introduced into the primary pulverizer to remove free water from the phosphogypsum particles. A primary pipeline is provided at the lower end of the primary pulverizer.

[0008] S2: Using the high-temperature air in the primary pulverizer, the phosphogypsum particles are sent to the secondary pulverizer through the primary pipe. The side wall of the secondary pulverizer is provided with a plurality of nozzles in a circular array. The spray trajectories of the nozzles intersect in the middle of the secondary pulverizer and form an airflow convergence point. The primary pipe delivers 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 injection 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.

[0009] S3: Using an air pump, the phosphogypsum powder processed by the secondary crusher is delivered to the bottom of the impurity removal reactor. A dispersed powder additive, which is calcium carbonate or calcium oxide, is sprayed into the impurity removal reactor through a nozzle provided at the lower end of the side wall of the impurity removal reactor. The phosphogypsum powder and the powder additive are stirred and mixed by a dispersing component provided inside the impurity removal reactor. The treated phosphogypsum powder is discharged from the upper end of the impurity removal reactor along with the air flow.

[0010] S4: The phosphogypsum powder treated in the impurity removal reactor is sent to a classifier for classification. The rear end of the classifier is connected to a dust collector and an induced draft fan in sequence. The air flow 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.

[0011] The beneficial effects of the present invention are:

[0012] 1. The traditional process for preparing phosphogypsum involves first removing impurities, then calcining, dehydrating, and finally pulverizing. This process takes a long time. This process simultaneously performs pulverization and dehydration, with dehydration continuing during the impurity removal process. The pulverized material has a large specific surface area, allowing for full contact with high-temperature air, steam, and additives, resulting in a more rapid reaction. This shortens processing time, improves production efficiency, and reduces energy consumption.

[0013] 2. The first-stage crusher, the second-stage crusher and the impurity removal reactor all have dispersion and drying functions, forming a multi-stage series connection with each other. Therefore, the phosphogypsum is in a well-dispersed state throughout the entire process, which can effectively avoid pipeline wall clogging. The accumulation and adhesion of phosphogypsum in the crushing chamber will seriously affect the crushing energy efficiency. This solution effectively avoids the problem of phosphogypsum wall clogging by continuously dehydrating and drying during the crushing process, thereby improving production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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.

[0015] Figure 1 A schematic flow chart of the method of the present application is shown.

[0016] Figure 2The figure shows a schematic diagram of the equipment structure used in the method of the present application.

[0017] Figure 3 A cross-sectional view of a primary pulverizer used in step S1 is shown.

[0018] Figure 4 A schematic diagram of a preferred structure of the dispersed components used in step S3 is shown.

[0019] Markings in the figure: first-stage crusher-1, first-stage pipeline-11, shell-12, annular chamber-121, high-temperature air inlet pipe-122, rotating drum-13, cylindrical roller-14, wear-resistant plate-15, annular groove-151, through-hole-152, second-stage 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

[0020] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments 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.

[0021] like Figure 1 、 Figure 2 As shown, a method for dehydrating and removing impurities from phosphogypsum comprises the following steps:

[0022] S1: Phosphogypsum raw materials are fed from the top into a primary crusher 1 for the first crushing, and the phosphogypsum is crushed into particles with a size of less than 3 mm. The primary crusher 1 is a stirred mill or a ball mill. At the same time, high-temperature air (100°C~150°C) is introduced into the primary crusher 1 to remove free water and part of the crystalline water in the phosphogypsum particles. A primary pipe 11 is provided at the lower end of the primary crusher 1. The water in the phosphogypsum includes free water and crystalline water. The free water is rapidly evaporated at about 100°C. As the temperature rises from 120°C to 150°C, the crystalline water gradually separates from the phosphogypsum, and dihydrate gypsum (CaSO4·2H2O) gradually transforms into hemihydrate gypsum (CaSO4·0.5H2O). The primary crushing can preheat and disperse the phosphogypsum while removing the free water and part of the crystalline water in the phosphogypsum, so that the phosphogypsum particles can be fully dispersed in the subsequent crushing process, thereby improving the crushing efficiency and effect, and preventing the phosphogypsum particles from aggregating and adhering to the equipment or the inner wall of the pipeline.

[0023] S2: After the first stage of pulverization, the phosphogypsum enters the secondary pulverizer 2 through the first-stage pipe 11 at the lower end of the first-stage pulverizer 1. A number of nozzles 21 are arranged in a circular array on the side wall of the secondary pulverizer 2. The spray trajectories of the nozzles 21 intersect in the middle of the secondary pulverizer 2 and form an airflow convergence point. The end of the first-stage pipe 11 passes through the side wall of the secondary pulverizer 2 and is located above the airflow convergence point, throwing the phosphogypsum particles to the airflow convergence point. Steam with a temperature of 300℃~500℃ is introduced into the nozzle 21, and the steam injection pressure is 0.6Mpa~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 collide violently under the drive of the high-speed steam airflow, and the phosphogypsum particles are further crushed, which increases the specific surface area of the phosphogypsum material and converts internal water into surface water. During the full contact with superheated steam, part of the crystalline water remaining in the primary crushing is converted into gaseous state within 3s to 10s and is quickly carried away by the high-speed airflow, thereby realizing the transformation from hemihydrated phosphogypsum to anhydrous phosphogypsum. In addition, under the synergistic effect of violent collision, high temperature and high-speed airflow, organic impurities, fluorine impurities and phosphorus impurities in the phosphogypsum are separated from the material and discharged with the high-speed airflow.

[0024] 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 air flow. 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 provision of a dispersion component can make the powder additive more evenly mixed with the air flow and the phosphogypsum powder, promote the reaction effect and speed, and thus further improve the impurity removal effect.

[0025] S4: The phosphogypsum powder treated in the impurity removal reactor 3 is fed into the classifier 4 for classification to control the particle size of the finished product. The rear end of the classifier 4 is connected in sequence to a dust collector 5 and an induced draft fan 6. 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 uses an impeller for classification.

[0026] Preferably, in step S3, while the impurity removal reactor 3 processes the phosphogypsum powder, steam with 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, thereby achieving the purpose of continuously removing crystallization water and further dehydrating the phosphogypsum powder.

[0027] 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 provided by industrial waste heat, which can effectively reduce energy consumption.

[0028] Preferably, in step S1, the processing time of the primary crusher 1 is 5 minutes to 10 minutes; in step S2, the processing time of the secondary crusher 2 is 3 seconds to 10 seconds; and in step S3, the processing time of the impurity removal reactor 3 is 10 seconds to 20 seconds.

[0029] 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 provided. The rotating drum 13 is arranged to rotate around the axis. Specifically, a motor can be provided on the top of the shell 12 to directly drive the rotating drum 13 to rotate. The outer side of the rotating drum 13 is provided with multiple layers of cylindrical rollers 14 at intervals along the axial direction, and each layer of cylindrical rollers 14 is provided with multiple cylindrical rollers 14 along the circumferential array of the rotating drum 13. The cylindrical rollers 14 are arranged to rotate around the axis, and their axes are parallel to the axis of the rotating drum 13. A wear-resistant plate 15 with a circular tubular structure is coaxially provided on the outer side of the shell 12 corresponding to 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 by 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 the phenomenon of eccentric wear of the cylindrical roller 14; the phosphogypsum that has completed the first crushing will automatically fall between the lower cylindrical roller 14 and the annular groove 151, 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 multiple times, and the multiple crushing process can be used to increase the contact time and probability of the phosphogypsum with high-temperature air, thereby improving the preheating and dehydration effects.

[0030] Further preferably, in order to make the phosphogypsum contact with the high temperature air more fully during the crushing process of step S1, Figure 3As shown, wear-resistant plates 15 are spaced apart within the housing 12, forming an annular chamber 121 between the housing 12 and the wear-resistant plates 15. A through hole 152 is provided on the side wall of the wear-resistant plate 15, and the through hole 152 is spaced apart from the annular groove 151. A high-temperature air inlet pipe 122 is provided on the outer wall of the housing 12 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 inlet pipe 122, and then enters the pulverization area through the through hole 152 provided in the wear-resistant plate 15. Injecting high-temperature air into the primary pulverizer 1 in the above-mentioned manner not only makes the high-temperature air concentration in various parts of the primary pulverizer 1 more balanced, but also increases the probability of contact between the high-temperature air and the phosphogypsum, which helps 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 pulverization 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 holes 152 are opened below the annular groove 151, so that the phosphogypsum can be preheated and the moisture of the phosphogypsum can be removed in real time during the process of falling after pulverization, thereby reducing the moisture content of the phosphogypsum during the next pulverization, thereby preventing the phosphogypsum from adhering to the surface of the pulverized parts; as a preferred solution, the high-temperature air inlet pipe 122 is a branch pipe structure connected to the air inlet main pipe 123, and the air inlet main pipe 123 is connected to the shell 12, and is used to directly inject high-temperature air into the interior of the inner shell 12 to provide a greater airflow pressure.

[0031] Preferably, Figure 2 、 Figure 4 As shown, in order to make the phosphogypsum powder and the powder additive more fully mixed in step S3, a dispersing component is provided, which includes a rotating shaft 32, on which a plurality of mesh plates 33 are spaced apart along the axial direction, and each mesh plate 33 is provided with a mesh 331. The top of the dust removal reactor 3 is provided with a driving motor for driving the rotating shaft 32 to rotate; 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 interior of the impurity removal reactor 3 by the nozzle 31. The positive pressure airflow generated by the air pump 22 and the negative pressure airflow generated by the induced draft fan 6 are combined to form a mixed powder. 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 dispersing component rotates driven by the driving motor, and the multiple mesh plates 33 arranged at intervals on the rotating shaft 32 rotate along with the rotating shaft 32. The phosphogypsum powder and the powder additive rise step by step through the mesh 331 on the mesh plate 33. During the rising process, the stirring of the mesh plate 33 is utilized to make the phosphogypsum powder and the powder additive mix more fully, further improving the reaction speed and efficiency of calcium carbonate or calcium oxide with soluble organic impurities, fluorine impurities and phosphorus impurities.

[0032] Further preferably, in order to further improve the reaction effect of the powder additive with various impurities, 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 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 the bottom of the mesh plate 33 sleeved on the rotating shaft 32 is coaxially provided with an inner ring gear 332, and the rotating shaft 32 is coaxially fixed with an outer ring gear 321 corresponding to the inner ring gear 332. The inner ring gear 332 and the outer ring gear 321 are jointly engaged with an idler gear 34. 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 ring gear 332. The lower end of the idler gear 34 is rotatably provided on the bracket. Through the above-mentioned 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, while the mesh plate 33 sleeved on the rotating shaft 32 will rotate in the opposite direction of the rotating shaft 32. In this way, the stirring effect on the airflow and the phosphogypsum powder and powder additives driven by the airflow can be effectively improved, and the reaction speed and efficiency of calcium carbonate or calcium oxide with soluble organic impurities, fluorine impurities and phosphorus impurities can be further improved.

[0033] 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. It should be understood by those skilled in the art that various changes or equivalent replacements 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 first-stage pulverizer (1) from the top for pulverization. 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 (1) to remove free water from the phosphogypsum particles. The lower end of the first-stage pulverizer (1) is connected to a first-stage pipe (11). S2: using the high-temperature air in the primary pulverizer (1) to send the phosphogypsum particles through the primary pipe (11) to the secondary pulverizer (2), a plurality of nozzles (21) are provided along the circumference of the side wall of the secondary pulverizer (2), the spraying trajectories of the nozzles (21) intersect at the middle of the secondary pulverizer (2) and form an airflow convergence point, the primary pipe (11) throws the phosphogypsum particles to the airflow convergence point, and steam with a temperature of 300°C to 500°C is introduced into the nozzle (21), and the steam injection pressure is 0.6Mpa to 1.3Mpa, so as to crush the phosphogypsum particles into phosphogypsum powder with a particle size of less than 20μm; 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) provided 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 provided 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: sending the phosphogypsum powder treated by the impurity removal reactor (3) into the classifier (4) to classify the phosphogypsum powder. The rear end of the classifier (4) is connected to a dust collector (5) and an 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); 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), a rotating drum (13) is coaxially provided inside the shell, 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 their axes are parallel to the axis of the rotating drum (13). A wear-resistant plate (15) with a circular tube structure is coaxially provided on the outer side of the shell (12) corresponding to the rotating drum (13). 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).

2. The method for dehydrating and removing impurities from phosphogypsum according to claim 1, wherein: In step S3, steam with a temperature of 200° C. to 300° C. is injected into the impurity removal reactor (3) while the impurity removal reactor (3) processes the phosphogypsum powder.

3. The method for dehydrating and removing impurities from phosphogypsum according to claim 2, wherein: 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 provided by industrial waste heat.

4. The method for dehydrating and removing impurities from phosphogypsum according to claim 1, wherein: In step S1, the processing time of the primary crusher (1) is 5 minutes to 10 minutes; in step S2, the processing time of the secondary crusher (2) is 3 seconds to 10 seconds; and 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, wherein: 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) opened on the wear-resistant plate (15).

6. The method for dehydrating and removing impurities from phosphogypsum according to claim 1, wherein: In step S3, the phosphogypsum powder and the powder additive simultaneously move upwards 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 rotates under the drive of the driving motor, and a plurality of mesh plates (33) arranged at intervals on the rotating shaft (32) rotate along with the rotating shaft (32). The phosphogypsum powder and the powder additive gradually rise through the meshes (331) on the mesh plates (33).

7. The method for dehydrating and removing impurities from phosphogypsum according to claim 6, wherein: In order to further improve the reaction effect between the powder additive and various impurities, two adjacent screen plates (33) on the rotating shaft (32) are provided, wherein one screen plate (33) is fixedly connected to the rotating shaft (32), and the other screen plate (33) is coaxially sleeved on the rotating shaft (32), wherein an inner gear ring (332) is coaxially provided at the bottom of the screen plate (33) sleeved on the rotating shaft (32), and an outer gear ring (321) is coaxially fixed 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. A bracket is provided on the inner wall of the impurity removal reactor (3), and the bracket is located below the screen plate (33) provided with the inner gear ring (332). The lower end of the idler wheel (34) is rotatably provided on the bracket.

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