Phosphogypsum harmless treatment device, treatment process and application thereof

Abstract

The present application relates to the technical field of phosphogypsum building new material production, in particular to a phosphogypsum harmless treatment device, a treatment process and application thereof, the device comprising an aggregate bin, a powder bin, a powder mixer, a conveyor, a mixing blender, a discharge bin and a reservoir, and a phosphogypsum solidified body bin, a phosphogypsum solidification and air drying all-in-one machine, and a phosphogypsum raw material crusher, the device with the above structure is needed to realize the harmless treatment of phosphogypsum, the crushing and harmless treatment processes of phosphogypsum are added to the existing mixing station, the phosphogypsum raw material crusher and the phosphogypsum solidification and air drying all-in-one machine are arranged in the treatment device to crush and harmlessly treat the phosphogypsum, so that the phosphogypsum can be uniformly mixed with other building materials to improve the product quality, and the phosphogypsum harmless treatment process is designed, the material formed by the process forms a complete new technology which can be popularized from manufacturing to application, and achieves the application performance of industrialization and scaling.

Description

Technical Field

[0001] This invention relates to the field of phosphogypsum building material production technology, specifically to a phosphogypsum harmless treatment device, treatment process and its application. Background Technology

[0002] Phosphogypsum is a byproduct of the wet process for producing phosphoric acid from phosphate rock. Approximately 5 tons of phosphogypsum are generated for every ton of phosphoric acid produced. Currently, my country has over 700 million tons of phosphogypsum stockpiled, with an annual increase of about 80 million tons. However, the comprehensive utilization rate is less than 40%. Unutilized phosphogypsum is mainly disposed of through stockpiling, occupying large amounts of land. Residual acids, phosphorus, fluorine, and organic matter can also cause serious pollution to the land and groundwater with rainwater runoff. 54% of the phosphogypsum stockpile poses ecological and environmental problems. Therefore, how to safely dispose of and comprehensively utilize phosphogypsum to achieve economies of scale is an urgent problem to be solved.

[0003] The main comprehensive utilization of phosphogypsum is in the manufacture of building materials, including cement retarders, gypsum board, gypsum blocks, and gypsum mortar, but the comprehensive utilization rate is low. In contrast, highway construction is characterized by a stable scale, numerous construction sites, long routes, and wide coverage. According to incomplete statistics, my country's highway construction and maintenance require over a billion tons of sand, gravel, and binders annually. However, the increasing scarcity of traditional raw materials has led to increasingly expensive and difficult-to-obtain natural aggregates. Using phosphogypsum as a road material can not only rapidly and massively utilize phosphogypsum but also promote the green and sustainable development of road infrastructure construction, which has significant practical implications.

[0004] The invention application filed on September 28, 2023 (application number: 202311277836.1) relates to a phosphogypsum curing agent, a phosphogypsum cured body, and their applications. It mentions a phosphogypsum cured body in which the mass ratio of phosphogypsum to phosphogypsum curing agent is 100:25-40. The phosphogypsum cured body is used in road base courses, riverbank slopes, pool bottoms, or roller-compacted earth-rock dam foundations. Current mixing plants only include aggregate silos, powder tanks, mixing silos, unloading silos, agitators, and admixture equipment silos. Due to the special characteristics of this phosphogypsum cured body, it requires sequential mixing of phosphogypsum and phosphogypsum curing agent. Therefore, current mixing plants cannot produce new materials using phosphogypsum; adaptations are needed based on the physicochemical properties of the phosphogypsum raw materials and the production mix ratio of the phosphogypsum-based new materials.

[0005] The invention filed on February 7, 2025 (publication number CN 119858239 A) discloses a phosphogypsum mixing plant. The mixing plant includes a powder batching machine, an aggregate batching machine, a curing agent metering device, a conveying device, a mixing host, and a finished product silo. The powder batching machine, aggregate batching machine, and curing agent metering device feed materials into the first conveying device according to the mixing ratio, enabling accurate metering and stable conveying of each material. Subsequently, each material enters the mixing host for continuous vibration mixing. The finished product is then transferred to the finished product silo via a second conveying device. During this process, the anti-segregation mechanism can greatly reduce the segregation of the finished product. In this invention, each batching unit can be stacked according to the actual site conditions, and the continuous mixing of the mixing host greatly improves production efficiency.

[0006] Although this mixing plant is designed for phosphogypsum, it is unsuitable for the production of the new phosphogypsum material described in "A phosphogypsum curing agent, a phosphogypsum cured body and its application," for two reasons:

[0007] First, phosphogypsum contains a great many impurities. The main components of phosphogypsum are SO3 and CaO, with a dry basis mass fraction of 86.86% to 93.95%. It also contains varying amounts of impurities such as P2O5, Fe2O3, and F. In addition, phosphogypsum also contains some organic carbon, unreacted apatite, heavy metals, and radioactive nuclides. There are three types of impurities that have a significant impact on the quality of phosphogypsum products: P2O5, soluble fluorides, and organic impurities. Impurities that have a significant impact on the environment include heavy metals, radioactive nuclides, and soluble phosphorus and fluorides. Although the content of impurities in phosphogypsum is low, they can have a significant impact on the quality of phosphogypsum products and even directly determine whether phosphogypsum can be processed into a certain type of product. This patent (publication number CN 119858239 A) does not involve pretreatment equipment for phosphogypsum in the mixing plant. If phosphogypsum is directly used to make building materials for mixing, due to the poor water stability and easy expansion of phosphogypsum, the building materials will continuously emit harmful substances. Long-term exposure to phosphogypsum may lead to illness or death in humans. Therefore, strictly speaking, it does not meet environmental protection standards.

[0008] Secondly, the composition of phosphogypsum fluctuates greatly. Different manufacturers use different phosphate rock and have different production process controls, resulting in differences in the moisture content, particle size, particle morphology, and impurity content of the final phosphogypsum. This causes phosphogypsum to often clump together, and the clumps are very tight, making it impossible to mix directly with aggregates, powders, and other roadbed materials. It needs to be treated in advance.

[0009] If the phosphogypsum is pre-treated before being mixed into the mixing plant, new problems will arise, such as increased costs and the difficulty of transporting the raw materials to the mixing plant. Designing an integrated, multi-functional, and large-scale phosphogypsum harmless treatment device and process is an urgent technical problem to be solved. Summary of the Invention

[0010] To address the aforementioned technical problems, the present invention aims to provide a harmless treatment device, treatment process, and its application for phosphogypsum. This technology focuses on the resource utilization of bulk industrial solid waste. Based on research into high-quality water-stabilized phosphogypsum and long-term solidification technology for harmful impurities, it develops a new equipment system for the resource utilization of phosphogypsum from raw materials to finished products. It clarifies the technical process for the entire harmless treatment of phosphogypsum building materials, from mixing plant to road construction, ensuring the performance of the developed phosphogypsum-based new materials in industrial-scale applications such as roads, backfilling, and underground filling. This efficient and harmless treatment technology for phosphogypsum, as a component in solving the problem of large-scale application of phosphogypsum, has important theoretical foundations and applied research significance.

[0011] To achieve the above objectives, the technical solution of the present invention is as follows:

[0012] A harmless treatment device for phosphogypsum includes an aggregate silo, a powder silo, a powder mixer, a conveyor, a mixing mixer, a discharge silo, and a water storage tank. The conveyor connects the discharge end of the aggregate silo to the feed end of the mixing mixer. The powder silo is connected to the powder mixer, which is connected to the feed end of the mixing mixer. The discharge silo is connected to the discharge end of the mixing mixer. The water storage tank is connected to the mixing mixer.

[0013] The invention is characterized by further comprising a phosphogypsum solidified body silo located upstream of the aggregate silo, a phosphogypsum solidification and drying integrated machine connected to and located upstream of the phosphogypsum solidified body silo, and a phosphogypsum raw material crusher located upstream of the phosphogypsum solidification and drying integrated machine. The phosphogypsum solidified body is a harmless phosphogypsum formed by the thorough mixing and reaction of phosphogypsum and a curing agent.

[0014] The phosphogypsum curing and drying integrated machine mainly consists of a diluent, an atomizer, a mixing and dispersing tank, and a dryer. It is used for the harmless treatment of phosphogypsum. The dryer is fitted around the mixing and dispersing tank. The diluent is installed on a frame outside the mixing and dispersing tank. The atomizer is connected between the diluent and the mixing and dispersing tank. The mixing and dispersing tank is provided with a raw material inlet and a solidified body outlet. The phosphogypsum raw material crusher is connected to the raw material inlet. The solidified body outlet is located at the feed end of the phosphogypsum solidified body silo.

[0015] The phosphogypsum curing and drying integrated machine is also connected to an admixture dosing machine, which is used to fill the phosphogypsum curing agent and supply it to the diluent.

[0016] Furthermore, the phosphogypsum raw material crusher is a hammer crusher used for crushing sticky and wet materials.

[0017] Furthermore, a propulsion stirring blade and a blade drive are installed inside the diluter. The blade drive is installed on the top of the diluter, and the shaft end of the propulsion stirring blade is connected to the blade drive, with the stirring end extending into the interior of the diluter.

[0018] Furthermore, the atomizer includes an ultrasonic atomizing body, an atomizing tube, and an atomizing nozzle. The fluid inlet of the ultrasonic atomizing body is connected to the diluent, and the fluid channel of the ultrasonic atomizing body is connected to the atomizing tube. Two or more sets of atomizing tubes are arranged evenly along the length of the mixing and dispersing tank. The atomizing nozzle is fixed at the front end of the atomizing tube and placed inside the mixing and dispersing tank.

[0019] Furthermore, a ribbon-type stirring blade is installed on the stirring shaft inside the stirring and dispersing tank.

[0020] Furthermore, the phosphogypsum solidified material silo includes a funnel-shaped silo body and a rotary vibration arch-breaking component. The funnel-shaped silo body is divided into an outer shell layer and an inner shell layer. The cross-section of the inner shell layer is inverted trapezoidal. The rotary vibration arch-breaking component is installed at the discharge port of the inner shell layer to control the vibration arch-breaking discharge of the phosphogypsum solidified material.

[0021] Furthermore, at least one set of aggregate bins is provided, arranged side by side in the funnel-shaped bin body. The starting end of the conveyor is located below the discharge port of the funnel-shaped bin body and extends along the direction of the aggregate bins, all the way to the feed end of the mixing mixer.

[0022] Furthermore, the mixing machine consists of two sets of mixing cylinders stacked one on top of the other. The admixture dosage machine and the water storage tank are connected to the upper mixing cylinder, the end of the conveyor is connected to the upper mixing cylinder, and the outlet of the lower mixing cylinder is connected to the unloading hopper.

[0023] A process for the harmless treatment of phosphogypsum includes the following steps.

[0024] S1. Test the moisture content of the phosphogypsum raw material. When the moisture content is less than 15%, select a hammer crusher with a discharge particle size of 0.1~2mm. When the moisture content of the phosphogypsum raw material is greater than 15%, use a hammer crusher for crushing sticky and wet materials with a discharge particle size of 0.1-5mm.

[0025] S2. Use a crusher to crush the phosphogypsum raw material and transport it to the phosphogypsum curing and drying integrated machine for harmless treatment.

[0026] S3. Add 5-10 parts of water to each part of the curing agent liquid in the admixture dosing machine for dilution. After dilution, supply the diluent and turn on the propeller-type stirring blade for stirring during dilution. Then turn on the atomizer to spray the curing agent into the stirring and dispersing tank. The atomized particle size is less than 10 micrometers and the atomization speed is 40 ml / min. The atomization spraying and stirring and dispersing are carried out simultaneously. After the phosphogypsum is uniformly cured and rendered harmless, turn on the dryer to dry it. The drying temperature range is 50℃~300℃. After drying, a phosphogypsum solidified body with a moisture content of less than 15% is formed.

[0027] S4. The solidified phosphogypsum is discharged from the mixing and dispersing tank and transferred to the phosphogypsum solidified material silo.

[0028] S5. Simultaneously open the phosphogypsum solidified body silo and the aggregate silo. The aggregate silo is loaded with building aggregates. Discharge the solidified phosphogypsum solidified body and building aggregates onto the conveyor according to the metering. The conveyor transports the mixed materials to the mixing mixer.

[0029] S6. The powder silo and powder mixer operate simultaneously. Cement and other powders are mixed according to the metering and then fed into the mixing mixer.

[0030] S7. All materials, additives, and water are mixed in the upper and lower mixing tanks to obtain a new phosphogypsum-based material, which is then discharged into the unloading hopper.

[0031] On the other hand, the application of harmless phosphogypsum-based new materials obtained through harmless treatment processes in roadbed construction includes the following steps.

[0032] S1. A short-bed transport vehicle is used, which loads the phosphogypsum-based new material from the unloading bin.

[0033] S2. During transportation, tarpaulins should be used for covering. When the ambient temperature is above 30℃, the time from mixing to transportation to on-site paving should not exceed 2 hours. If it exceeds 3 hours, the material should be disposed of as waste. When the ambient temperature is between 15℃ and 30℃, the time from mixing to transportation to on-site paving should not exceed 3 hours. When the ambient temperature is below 15℃, the time from mixing to transportation to on-site paving should preferably exceed 4 hours.

[0034] S3. During unloading, the transport vehicle raises the unloading angle and is equipped with a vibrator to assist in unloading.

[0035] S4. During paving, a two-layer continuous paving construction method is adopted. Each layer is equipped with independent paving and compaction equipment. Sufficient thickness is ensured during paving. After compaction, the thickness of each layer should not be less than 160mm. During the paving process, the speed of the paver should be controlled between 1.0 and 3.0m / min.

[0036] Maintain transverse joints during paving. During construction, the distance between pavers should not exceed 10 meters, and adjacent construction sections should have a longitudinal overlap of 30cm to 40cm.

[0037] When the width of a single operation in the stabilization layer is 11-12m, the length of each operation section should be 300m; when the width of a single operation in the stabilization layer is greater than 12m, the length of the operation section should be shortened accordingly.

[0038] S5. During compaction, follow the sequence of steady compaction – strong vibration – weak vibration – steady compaction, and compact the outer side first, then the inner side. In hot weather, if the subgrade material becomes loose or shifts during compaction, spray water mist to moisten it, mix it thoroughly, adjust it to the factory moisture content, and then compact it.

[0039] S6. During the curing process, after the phosphogypsum stabilized layer has been rolled and passed the compaction test, it should be covered for curing within 2 hours. The curing time is 7 to 14 days.

[0040] The beneficial effects of this invention compared with the prior art are: 1. It improves the phosphogypsum machine road base material equipment by combining the existing road base water-stabilized material mixing plant equipment and designing it in conjunction with the existing equipment to reduce equipment costs.

[0041] 2. To address the process requirements of curing phosphogypsum, improving its water stability, and reducing pollutant leaching, an integrated curing-dehydration machine was added after grinding. Basic components such as propeller-driven agitation and dilution, ultrasonic atomization, ribbon stirring, and heat-conducting pipe dehydration were selected to form an integrated device. Key technologies for each step were clearly defined, achieving efficient processing of phosphogypsum from raw material to solidified form. After curing, harmful components of the phosphogypsum are decomposed, yielding a new phosphogypsum-based material.

[0042] 3. In response to the existing problems of material arching and blockage in phosphogypsum silos, this equipment features a new gypsum solidification silo at the discharge port. Utilizing the characteristic that the axis of a Reuleaux triangle rotates in a circular motion, the mixing shaft is installed at the center of the Reuleaux triangle, causing it to rotate continuously around the center point while rotating, thus generating a vibration effect. This achieves simultaneous mixing and vibration, improving the silo structure and increasing the discharge efficiency at the discharge port compared to the original equipment, resulting in smoother material flow.

[0043] 4. Taking into full account the characteristics of phosphogypsum, such as high impurity content, large fluctuations in composition, and easy agglomeration, the production unit is equipped with equipment such as a phosphogypsum raw material crusher and a phosphogypsum curing and drying integrated machine to carry out harmless pretreatment of phosphogypsum, ensuring that it can be evenly mixed with other roadbed materials and improving product quality.

[0044] 5. Some existing mixing plants do not treat impurities in phosphogypsum during processing. Direct mixing can cause the roadbed materials to release harmful substances, which does not meet environmental standards. This invention reduces the generation of harmful substances by pre-treating phosphogypsum, making the produced phosphogypsum-based new materials more environmentally friendly and reducing harm to the environment and human health.

[0045] 6. Based on the physical and chemical properties of phosphogypsum and its harmless treatment, and combined with existing road paving application processes, this paper proposes the application technology of phosphogypsum-based new materials in roadbed construction. It is compatible with existing engineering technologies, can reduce the consumption of natural aggregates and road construction costs, promote the high-value utilization of phosphogypsum, and provide theoretical and practical basis for phosphogypsum road paving. Attached Figure Description

[0046] Figure 1 A top view of the layout 1 of the phosphogypsum harmless treatment device;

[0047] Figure 2 A three-dimensional structural schematic diagram of layout 1 for the harmless treatment device of phosphogypsum;

[0048] Figure 3 A schematic diagram of the main structure of layout 2 for the harmless treatment device of phosphogypsum;

[0049] Figure 4 A schematic diagram of the planar structure for pouring phosphogypsum raw materials into the phosphogypsum raw material crusher;

[0050] Figure 5 A top view schematic diagram of the integrated phosphogypsum curing and drying machine;

[0051] Figure 6 A cross-sectional view of the integrated phosphogypsum curing and drying machine;

[0052] Figure 7 A simplified side view of the atomizer mounted on the stirring and dispersing tank;

[0053] Figure 8 This is a schematic diagram of the main structure of an admixture dosing machine;

[0054] Figure 9 This is a schematic diagram of the main structure of a mixing mixer;

[0055] Figure 10 Vector and streamline diagrams of the phosphogypsum curing and drying integrated machine were analyzed using ANSYS software. Among them, a is the longitudinal section velocity cloud diagram, b is the longitudinal section velocity streamline diagram, c is the longitudinal section two-phase cloud diagram, and d is the cross-sectional cloud diagram vector diagram. Detailed Implementation

[0056] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0057] like Figure 1 — Figure 10 As shown, a harmless treatment device for phosphogypsum includes an aggregate silo 1, a powder silo 2, a powder mixer 3, a conveyor 4, a mixing mixer 5, a discharge silo 6, and a water storage tank 7. The conveyor 4 connects the discharge end of the aggregate silo 1 to the feed end of the mixing mixer 5. The powder silo 2 is connected to the powder mixer 3, and the powder mixer 3 is connected to the feed end of the mixing mixer 5. The discharge silo 6 is connected to the discharge end of the mixing mixer 5, and the water storage tank 7 is connected to the mixing mixer 5.

[0058] Based on the existing mixing plant, it also includes a phosphogypsum solidified body silo 8 located upstream of the aggregate silo 1, a phosphogypsum solidified air-drying integrated machine 9 connected to and located upstream of the phosphogypsum solidified body silo, and a phosphogypsum raw material crusher 10 located upstream of the phosphogypsum solidified air-drying integrated machine. An admixture dosing machine 11 is also connected to the phosphogypsum solidified air-drying integrated machine for filling phosphogypsum solidifying agent and supplying it to the diluent.

[0059] The admixture dosing machine 11 includes a curing agent mixing tank 11-1, a curing agent mother liquor tank 11-2 and a temporary storage tank 11-3, as well as a reduction weighing scale 11-4. After the phosphogypsum curing agent and water are mixed in proportion, it is supplied to the phosphogypsum raw material for curing and stirring.

[0060] The admixture dosing machine 11 is divided into two groups. The first group is located next to the phosphogypsum curing and drying integrated machine 9, where a professional curing agent for phosphogypsum curing and drying is filled, diluted, and stored. This curing agent is the product described in application publication number CN 117303846 A. The second group of admixtures consists of commonly used admixtures in existing mud mixing plants. This admixture dosing machine is designed next to the mixing mixer 5 to provide the mixing mixer with commonly used mud admixtures, including lubricants, water loss reducers, flocculants, thickeners, water-reducing agents, weighting agents, retarders, and defoamers.

[0061] The structural layout diagram of the entire mixing plant is as follows: Figures 1-3 As shown, the entire mixing plant can be as follows: Figure 1 , Figure 2 The layout shown is more space-saving and occupies less area. It can also be done as follows: Figure 3 The layout shown is linear, which facilitates equipment installation.

[0062] The phosphogypsum raw material crusher 10 adopts a hammer crusher. A hammer crusher is a machine that uses high-speed rotating hammers to impact materials, causing them to break along weak parts such as natural fissures, bedding planes, and cleavage planes. The hammers are freely suspended on a turntable and driven to rotate, while the material is crushed by the rapidly rotating hammers. The hammer crusher structure adopts a screenless grate design, and the output particle size can be changed by adjusting the grate gap. The grateless design avoids the problem of wet material clogging the discharge port. The hammer crusher is suitable for a wide range of materials. When processing wet materials, the rotor is equipped with a scraper system to scrape off the wet material adhering to the chamber wall, preventing blockage. Based on the characteristics of phosphogypsum in a certain region, when the moisture content of the phosphogypsum raw material is less than 15%, this type of hammer crusher is most suitable for crushing phosphogypsum raw materials. It meets the requirements of ≥80% for 0.6mm sieve openings and ≥90% for 2.36mm sieve openings.

[0063] The phosphogypsum raw material crusher 10 can also be a hammer crusher for crushing sticky and wet materials. Fresh phosphogypsum has a moisture content >25%, which is a sticky and wet material and is prone to clogging. In order to improve the adaptability of the hammer crusher to sticky and wet materials, a hammer crusher for crushing sticky and wet materials is adopted. The crusher shell contains a rotor, and a tracked rotary impact plate is installed in front of the rotor as a crushing plate. This impact plate can prevent material from accumulating at the inlet of the crushing chamber. The material adhering to the impact plate is swept away by the hammer. The impact plate is driven by a separate motor through a rotating shaft. There is a pad at the bottom of the impact plate to withstand the impact force of the hammer. When the material is fed onto the rotary impact plate, it is forced into the range of action of the rotor. In order to avoid clogging, a grate screen is generally not installed under the rotor. A cleaning device is installed behind the rotor. It is a vertical closed chain belt with transverse scrapers installed on it. The chain belt is driven by a separate motor. It can loosen the material accumulated behind the rotor after crushing for discharge, and at the same time scrape off the material adhering to the outer shell wall. Hammer crushers for crushing sticky and wet materials must meet the requirements of ≥80% for 0.6mm sieve openings and ≥90% for 2.36mm sieve openings.

[0064] The phosphogypsum curing and drying integrated machine 9 mainly consists of a diluent 90, an atomizer 91, a mixing and dispersing tank 92, and a dryer 93. The dryer 93 is fitted around the outer periphery of the mixing and dispersing tank 92. The diluent 90 is installed on a frame outside the mixing and dispersing tank 92. The atomizer 91 connects the diluent 90 and the mixing and dispersing tank. The mixing and dispersing tank 92 has a raw material inlet and a solidified body outlet. The phosphogypsum raw material crusher 10 is connected to the raw material inlet, and the solidified body outlet is located at the feed end of the phosphogypsum solidified body silo 8. After the raw phosphogypsum is crushed to reach the target particle size, it enters the mixing and dispersing tank 92. A curing agent of 0.3% to 1% is needed to stabilize harmful substances in the phosphogypsum and improve its water stability. Therefore, the curing agent is sprayed into the mixing and dispersing tank by the atomizer 91. Because the curing agent content is low, it is difficult to mix evenly. The curing agent needs to be diluted first. The diluted curing agent is added to the mixing and dispersing tank in the form of spray. After mixing evenly, the moisture content of phosphogypsum is controlled to below 15%. The moisture content is then controlled by a dryer before it can be used as the raw material for the next step of road base material.

[0065] In this embodiment, the composition of the phosphogypsum curing agent is as described in application publication number CN 117303846 A, namely, the composition of the phosphogypsum curing agent is: 65.02-91.23% phosphogypsum slag cement, 5.47-16.25% admixtures, 0.55-3.84% modifiers, and 2.74-15.6% anti-permeability agents. The admixtures include adsorbents, precipitants, coagulants, and complexing agents; the modifiers include surfactants and hydrophobic modifiers. When using the curing agent, a propeller-type stirring blade and a blade drive are installed in the diluent. The blade drive is installed at the top of the diluent, and the shaft end of the propeller-type stirring blade is connected to the blade drive, with the stirring end extending into the interior of the diluent. The curing agent is diluted with water and then poured into the diluent. Since the curing agent is a low-viscosity fluid with a viscosity of less than 2 Pa·s, it needs to be continuously stirred by the propeller-type stirring blade until it is evenly mixed before being supplied to the atomizer.

[0066] In this embodiment, the atomizer 91 includes an ultrasonic atomizing body 91-1, an atomizing tube 91-2, and an atomizing nozzle 91-3. The fluid inlet of the ultrasonic atomizing body 91-1 is connected to the diluter 90, and the fluid channel of the ultrasonic atomizing body is connected to the atomizing tube 91-2. Two or more sets of atomizing tubes 91-2 are arranged evenly along the length of the stirring and dispersing tank. The number of atomizing tubes is determined by the volume of the stirring and dispersing tank. The atomizing nozzle is fixed at the front end of the atomizing tube and placed inside the stirring and dispersing tank.

[0067] The atomization rate is related to the volume of the mixing and dispersing tank. Based on a mixing efficiency of 1t / h and a curing agent dosage of 0.5%, the curing agent spray flow rate of the integrated phosphogypsum curing and drying machine should be 80ml / min. The spray is diluted with water at a ratio of 1:5. If 10 nozzles are installed, the target flow rate of each nozzle is about 40ml / min.

[0068] Considering the atomization flow rate and particle size requirements of this project, the atomized particle size needs to be below 10μm for industrial production, and an atomization speed of about 40ml / min is required. Therefore, ultrasonic atomization is selected to atomize the curing agent liquid in this project. Ultrasonic waves can effectively process materials with a maximum viscosity of 4000 cps and an upper limit of operating temperature of about 65°C.

[0069] In this embodiment, to render phosphogypsum harmless and stable, the curing agent needs to be diluted and sprayed evenly dispersed in the phosphogypsum powder to maximize contact between the powder and the curing agent, thereby completing the required mixing and reaction process in the shortest possible time. A ribbon-type stirring blade 92-2 is installed on the stirring shaft 92-1 inside the stirring and dispersing tank 92. The ribbon-type stirring blade is bolted to the stirring arm, facilitating replacement and adjustment after wear and tear. When the ribbon-type stirring shaft rotates, its internal shaft rotates axially, driving the stirring blade to rotate and mixing the powder and liquid in the container. As the shaft rotates, the material also rotates around the shaft within the container, forming a vortex. Because the material rotates in the same direction as the shaft, this leads to localized misalignment and reduced friction, resulting in more uniform mixing in certain areas, suitable for the curing and stirring of phosphogypsum.

[0070] The structural design of the mixing and dispersion tank 92, as seen from the vector and streamline diagrams, demonstrates that the materials are thoroughly agitated, moving as the tank rotates. The mixture, after entering through the nozzle, also rotates along with the main flow. The two-phase cloud diagram shows a relatively uniform distribution of the two materials overall, although localized high-concentration areas exist near the blades. In later implementation, sampling within the tank can be used to achieve a mixing uniformity coefficient of variation (CV) ≤ 5%, allowing for parameter adjustments.

[0071] The dryer 93 is fitted around the mixing and dispersing tank 92. The dryer 93 is a conduit-type dehydrator. Because dihydrate phosphogypsum gradually transforms into β-hemihydrate phosphogypsum after reaching 120℃, a dehydrator capable of controlling the dehydration temperature below 120℃ is required. Simultaneously, to save energy and reduce carbon emissions, indirect heating via heat conduction is preferred. The drying process requires little or no gas to remove moisture, significantly reducing heat loss carried away by the airflow and improving heat utilization. Furthermore, to achieve integrated curing and dehydration, the dehydration system needs to be integrated into the curing machine; therefore, a heat-conducting pipe-type dehydration system is selected, with a dehydration temperature range of 50℃ to 300℃.

[0072] Furthermore, the phosphogypsum solidified material silo 8 includes a funnel-shaped silo body and a rotary vibration arch-breaking component. The funnel-shaped silo body is divided into an outer shell layer and an inner shell layer. The cross-section of the inner shell layer is an inverted trapezoidal shape. The rotary vibration arch-breaking component is installed at the discharge port of the inner shell layer to control the vibration arch-breaking discharge of the phosphogypsum solidified material. The specific structure of the phosphogypsum solidified material silo has been patented in advance, specifically referring to a silo rotary vibration arch-breaking device with publication number CN 117228174 A.

[0073] In this embodiment, based on the capacity of the phosphogypsum solidified silo 8 and the phosphogypsum solidification and drying integrated machine 9, the aggregate silo 1 is provided in four sets, which are arranged side by side in the funnel-shaped silo body. The starting end of the conveyor is located below the discharge port of the funnel-shaped silo body and extends along the direction of the aggregate silo arrangement, all the way to the feed end of the mixing mixer.

[0074] Furthermore, the mixing mixer 5 consists of two sets of mixing cylinders stacked vertically. The second-layer admixture dosage machine 11 and the water storage tank 7 are connected to the upper mixing cylinder. The end of the conveyor 4 is connected to the upper mixing cylinder 5-1, and the outlet of the lower mixing cylinder 5-2 is connected to the unloading hopper. Through two mixing processes, the phosphogypsum solidified body is fully mixed with building aggregates, cement, etc. Since water needs to be added during mixing, the phosphogypsum is prone to adhering to the mixing chamber wall, resulting in uneven mixing. The mixing shaft can be modified to make it movable, and the forward and reverse movement of the mixing shaft can be achieved by controlling the unidirectional motor through a speed change mechanism, so as to achieve stable control and output of mechanical movement. The distance between the mixing blades and the mixing chamber wall can be flexibly adjusted to adapt to different material particle size requirements and mixing needs. Example 2

[0075] Based on the above-mentioned phosphogypsum harmless treatment device, a phosphogypsum harmless treatment process is generated, which includes the following steps:

[0076] S1. Phosphogypsum should be thoroughly dried and crushed before construction. The moisture content of phosphogypsum should be controlled to be ≥15%, preferably ≥12%, and the particle size should be ≥5mm, preferably ≥3mm. The moisture content of phosphogypsum should be tested before mixing. The mixing ratio should be adjusted according to the test results. When the moisture content of the phosphogypsum raw material is less than 15%, a hammer crusher should be used, with a discharge particle size of 0.1~2mm. When the moisture content of the phosphogypsum raw material is greater than 15%, a hammer crusher for crushing sticky and wet materials should be used, with a discharge particle size of 0.1-5mm.

[0077] S2. Use a crusher to crush the phosphogypsum raw material and convey it into the phosphogypsum curing and drying integrated machine;

[0078] S3. Add 5-10 parts of water to each part of curing agent liquid in the admixture dosing machine for dilution. After dilution, supply it to the diluter. During dilution, turn on the propeller-type stirring blade for stirring. Then turn on the atomizer to spray the curing agent into the stirring and dispersing tank. The atomized particle size is less than 10 micrometers and the atomization speed is 40 ml / min. The atomization spraying and stirring and dispersing are carried out simultaneously. After the phosphogypsum is uniformly cured, turn on the dryer to dry it. The drying temperature range is 50℃~300℃. After drying, a phosphogypsum solid body with a moisture content of less than 15% is formed.

[0079] S4. The top cover of the mixing and dispersing tank can be opened. After mixing for a certain period of time, the cover can be opened to take samples from various locations. Once the requirements are met, the mixing and dispersing tank will discharge the phosphogypsum solidified body and input it into the phosphogypsum solidified body silo.

[0080] S5. Simultaneously open the phosphogypsum solidified material silo and the aggregate silo. The aggregate silo is loaded with building aggregate. Discharge the phosphogypsum solidified material and building aggregate onto the conveyor according to the metering. The conveyor transports the mixed material to the mixing mixer.

[0081] S6. The powder silos and powder mixers operate simultaneously. Cement and other powders are mixed according to the metering and then fed into the mixing mixer. The phosphogypsum and cement silos should be kept sealed and equipped with mechanical and vibratory arch-breaking devices to prevent arching. They should also be equipped with metering devices with an accuracy of ±0.5%.

[0082] S7. All materials, additives, and water are mixed in the upper and lower mixing tanks to obtain a new phosphogypsum-based material, which is then discharged into the unloading hopper.

[0083] It should be noted that during mixing, when the ambient temperature is above 30℃, the mixing equipment temperature should not exceed 70℃. When the ambient temperature is below 15℃, the mixing equipment temperature should not be lower than 10℃. Temperature adjustment measures should be taken if the temperature is too high or too low. Example 3

[0084] The application of phosphogypsum-based new materials obtained through a harmless treatment process in roadbed construction includes the following steps.

[0085] S1. Use short-bed transport vehicles. The transport vehicles load the harmless phosphogypsum-based new materials from the unloading bin. During the loading process, the segregation of the mixture should be reduced by adjusting the position of the truck bed.

[0086] S2. During transportation, tarpaulins should be used for covering to reduce moisture evaporation and leakage of mixing materials. When the ambient temperature is above 30℃, the time from mixing to transportation to on-site paving should not exceed 2 hours. If it exceeds 3 hours, it should be disposed of as waste. When the ambient temperature is below 30℃ but above 15℃, the time from mixing to transportation to on-site paving should not exceed 3 hours. If it exceeds 4 hours, it should be disposed of as waste. When the ambient temperature is below 15℃, the time from mixing to transportation to on-site paving should preferably exceed 4 hours. If it exceeds 5 hours, it should be disposed of as waste.

[0087] S3. When unloading, the phosphogypsum mixture has a high moisture content and is easy to stick to the side wall of the transport vehicle, making it difficult to unload to the paver or subbase. It is advisable to use transport vehicles with short beds and increase the unloading angle as much as possible. If possible, a vibrator can be installed on the transport vehicle to assist unloading.

[0088] S4. During paving, a two-layer continuous paving construction method shall be adopted. Each layer shall be equipped with independent paving and compaction equipment. It is not allowed to use one set of equipment to carry out construction back and forth between the upper and lower structural layers. The paving shall ensure sufficient thickness (for example, the maximum paving thickness of supersulfur phosphogypsum stabilized artificial aggregate mixture should not exceed 200 mm). After compaction, the paving thickness of each layer shall not be less than 160 mm. During the paving process, the speed of the paver shall be controlled at 1.0 to 3.0 m / min.

[0089] When paving the mixture, it should be done continuously. If the interruption time is longer than 2 hours, transverse joints should be set. Longitudinal joints should be avoided during paving. When paving in two sections, the longitudinal joints should be compacted. If there are longitudinal joints, they should be joined perpendicularly. Diagonal joints are strictly prohibited. When using multiple pavers, the models and wear levels of the pavers should be the same. During construction, the distance between the front and rear pavers should not be less than 10m, and the longitudinal overlap of adjacent construction sections should be 30cm-40cm.

[0090] When the width of a single operation of the stabilized layer is 11-12m, the length of each continuous operation section should be 300m; when the width of a single operation of the stabilized layer is greater than 12m, the length of the operation section should be shortened accordingly. The following factors should be considered comprehensively to reasonably determine the length of the daily construction operation section: 8) A dedicated person should be assigned behind the paver to eliminate aggregate segregation and phosphogypsum agglomeration, promptly remove segregated or agglomerated areas, and fill them with a good mixture.

[0091] The following factors should be comprehensively considered to reasonably determine the length of the daily construction operation section. A dedicated person should be stationed behind the paver to eliminate aggregate segregation and phosphogypsum clumping, promptly remove segregated or clumped areas, and fill them with a good mixture.

[0092] S5. During compaction, compaction should be carried out in the following order: steady compaction - strong vibration - weak vibration - steady compaction. Compaction should be carried out in the order of first the outer side and then the inner side. A dedicated person should be assigned to direct the operation to prevent missed compaction and wheel tracks. If soft and elastic phenomena occur, the mixture in that part should be removed in time and replaced with roadbed material with a moisture content that meets the design requirements for compaction.

[0093] If the roadbed material becomes loose or shifts during compaction in hot weather, it should be moistened with water mist and mixed evenly to adjust to the factory moisture content before compaction.

[0094] When compacting, side molds should be set up and fixed. Within 30cm of facilities such as manholes and curbs, and on both sides of the roadbed near the molds, small road rollers and plate compactors should be used for initial compaction, followed by compaction with double steel drum rollers and rubber-tired rollers.

[0095] S6. During curing, after the phosphogypsum stabilized layer is rolled and passes the compaction test, it should be covered for curing within 2 hours. The curing time is 7 days. In low-temperature weather such as when the average daily temperature is below 10℃ or during the rainy season, the curing time should be extended to 14 days. The total curing period should be extended to 2 days before the start of the upper layer curing. Except for water trucks and small commuter vehicles, vehicles are strictly prohibited from passing during this period, and tracked engineering vehicles are strictly prohibited from directly compacting it. Ensure that the stabilized material layer is kept warm and moist. In hot and dry weather, cooling measures should be taken. If necessary, the film can be temporarily lifted and covered, and water should be sprinkled on the geotextile to cool it down. During the construction period in winter, necessary insulation measures should be taken.

[0096] Additional notes regarding paving equipment in step S4: 1) A tracked, fully automatic hydraulic paver should be used, equipped with an automatic leveling system and measures to prevent material segregation. 2) A reverse blade should be installed in the middle of the auger spreader to reduce longitudinal segregation. A rubber front baffle should be installed on the auger spreader to reduce vertical segregation. 3) When paving supersulfur phosphogypsum stabilized artificial aggregate mixtures, a rubber baffle should be installed in front of the paver scraper (including widened side plates), and the bottom of the rubber baffle should be no more than 10mm above the top surface of the underlying layer. 4) During paving, the paver must operate its vibrator and tamping hammer. The vibrator frequency must not be lower than 30Hz, and the tamping hammer impact frequency must not be lower than 20Hz with a stroke of no less than 6mm.

[0097] In step S6, curing can be achieved by covering with a thin film, using impermeable geotextile, wet sand, asphalt emulsion, or watering with a water truck. The requirements for watering curing are: the number of times to water each day should be determined according to the climate, and attention should be paid to keeping the surface of the stabilizing material moist at all times.

[0098] Film covering curing: Before covering with film, observe the moisture level of the base layer stabilized by sulfur phosphogypsum cementitious material. Keep the base layer moist and avoid frequent alternation between dry and wet conditions. Curing should continue for 1 to 2 days before the construction of the upper structural layer before removing the film.

[0099] Geotextile curing: It is advisable to use permeable geotextile to cover the entire cross-section of the stabilizing material layer. After laying the geotextile, attention should be paid to watering. The number of times to water each day should be determined according to the weather, and care should be taken to prevent damage to the geotextile.

[0100] The above provides a detailed description of the harmless treatment device, treatment process, and application of phosphogypsum provided by the present invention. The specific embodiments are described only to help understand the method and core ideas of the present invention. It should be noted that the present invention is not only applicable to road materials, but also to underground filling, mine backfilling, site leveling, and many other fields. For those skilled in the art, various improvements and modifications can be made to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A harmless treatment device for phosphogypsum, comprising an aggregate silo, a powder silo, a powder mixer, a conveyor, a mixing mixer, a discharge silo, and a water storage tank, wherein the conveyor is connected to the discharge end of the aggregate silo and the feed end of the mixing mixer, the powder silo is connected to the powder mixer, the powder mixer is connected to the feed end of the mixing mixer, the discharge silo is connected to the discharge end of the mixing mixer, and the water storage tank is connected to the mixing mixer. Its features are, It also includes a phosphogypsum solidified body silo located upstream of the aggregate silo, a phosphogypsum solidification and drying integrated machine connected to and located upstream of the phosphogypsum solidified body silo, and a phosphogypsum raw material crusher located upstream of the phosphogypsum solidification and drying integrated machine. The phosphogypsum solidified body is a harmless phosphogypsum formed by the thorough mixing and reaction of phosphogypsum and a curing agent. The phosphogypsum curing and drying integrated machine mainly consists of a diluent, an atomizer, a mixing and dispersing tank, and a dryer. It is used for the harmless treatment of phosphogypsum. The dryer is fitted around the mixing and dispersing tank, and the diluent is mounted on a frame outside the tank. The atomizer connects the diluent and the mixing and dispersing tank. The mixing and dispersing tank has a raw material inlet and a solidified body outlet. The phosphogypsum raw material crusher is connected to the raw material inlet, and the solidified body outlet is located at the feed end of the phosphogypsum solidified body silo. The phosphogypsum curing and drying integrated machine is also connected to an admixture dosing machine, which is used to fill the phosphogypsum curing agent and supply it to the diluent.

2. The device for harmless treatment of phosphogypsum according to claim 1, characterized in that: The phosphogypsum raw material crusher is a hammer crusher used for crushing sticky and wet materials.

3. The device for harmless treatment of phosphogypsum according to claim 1, characterized in that: The diluter is equipped with a propeller-type stirring blade and a blade drive. The blade drive is installed on the top of the diluter, and the shaft end of the propeller-type stirring blade is connected to the blade drive, with the stirring end extending into the interior of the diluter.

4. The device for harmless treatment of phosphogypsum according to claim 3, characterized in that: The atomizer includes an ultrasonic atomizing body, an atomizing tube, and an atomizing nozzle. The fluid inlet of the ultrasonic atomizing body is connected to the diluter, and the fluid channel of the ultrasonic atomizing body is connected to the atomizing tube. Two or more sets of atomizing tubes are arranged evenly along the length of the mixing and dispersing tank. The atomizing nozzle is fixed at the front end of the atomizing tube and placed inside the mixing and dispersing tank.

5. The device for harmless treatment of phosphogypsum according to claim 4, characterized in that: The mixing and dispersing tank is equipped with a ribbon-type mixing blade on the mixing shaft.

6. The device for harmless treatment of phosphogypsum according to claim 1, characterized in that: The phosphogypsum solidified material silo includes a funnel-shaped silo body and a rotary vibration arch-breaking component. The funnel-shaped silo body is divided into an outer shell layer and an inner shell layer. The cross-section of the inner shell layer is inverted trapezoidal. The rotary vibration arch-breaking component is installed at the discharge port of the inner shell layer to control the vibration arch-breaking discharge of the phosphogypsum solidified material.

7. The device for harmless treatment of phosphogypsum according to claim 6, characterized in that: At least one set of aggregate bins is provided and arranged side by side in the funnel-shaped bin body. The starting end of the conveyor is located below the discharge port of the funnel-shaped bin body and extends along the direction of the aggregate bins until it reaches the feed end of the mixer.

8. The device for harmless treatment of phosphogypsum according to claim 7, characterized in that: The mixing machine consists of two sets of mixing cylinders stacked on top of each other. The admixture dosage machine and the water storage tank are connected to the upper mixing cylinder. The end of the conveyor is connected to the upper mixing cylinder, and the outlet of the lower mixing cylinder is connected to the unloading hopper.

9. A process for the harmless treatment of phosphogypsum, using the phosphogypsum harmless treatment device as described in any one of claims 1-8, characterized in that: Includes the following steps, S1. Test the moisture content of the phosphogypsum raw material. When the moisture content is less than 15%, select a hammer crusher with a discharge particle size of 0.1~2mm. When the moisture content of the phosphogypsum raw material is greater than 15%, use a hammer crusher for crushing sticky and wet materials with a discharge particle size of 0.1-5mm. S2. Use a crusher to crush the phosphogypsum raw material and transport it to the phosphogypsum curing and drying integrated machine for harmless treatment. S3. Add 5-10 parts of water to each part of the curing agent liquid in the admixture dosing machine for dilution. After dilution, supply the diluent. During dilution, turn on the propeller-type stirring blade for stirring. Then turn on the atomizer to spray the curing agent into the stirring and dispersing tank. The atomized particle size is less than 10 micrometers and the atomization speed is 40 ml / min. The atomization spraying and stirring and dispersing are carried out simultaneously. After the phosphogypsum is rendered harmless, turn on the dryer to dry it. The drying temperature range is 50℃~300℃. After drying, a phosphogypsum solid body with a moisture content of less than 15% is formed. S4. The phosphogypsum solidified material is discharged from the mixing and dispersing tank and fed into the phosphogypsum solidified material silo. S5. Simultaneously open the phosphogypsum solidified material silo and the aggregate silo. The aggregate silo is loaded with construction aggregate. The phosphogypsum solidified material and construction aggregate are metered and placed onto the conveyor. The conveyor transports the mixed materials to the mixing mixer. S6. The powder silo and powder mixer operate simultaneously. Cement and other powders are mixed according to the metering and then fed into the mixing mixer. S7. All materials, additives, and water are mixed in the upper and lower mixing tanks to obtain a new phosphogypsum-based material, which is then discharged into the unloading hopper.

10. The application of the phosphogypsum-based new material obtained by the harmless treatment process described in claim 9 in roadbed construction, wherein the application steps include: S1. A short-bed transport vehicle is used. The transport vehicle loads the harmless phosphogypsum-based new material from the unloading bin. S2. During transportation, tarpaulins should be used for covering. When the ambient temperature is above 30℃, the time from mixing to transportation to on-site paving should not exceed 2 hours. If it exceeds 3 hours, the material should be disposed of as waste. When the ambient temperature is between 15℃ and 30℃, the time from mixing to transportation to on-site paving should not exceed 3 hours. When the ambient temperature is below 15℃, the time from mixing to transportation to on-site paving should preferably exceed 4 hours. S3. During unloading, the transport vehicle raises the unloading angle and is equipped with a vibrator to assist in unloading. S4. During paving, a two-layer continuous paving construction method is adopted. Each layer is equipped with independent paving and compaction equipment. Sufficient thickness is ensured during paving. After compaction, the thickness of each layer should not be less than 160mm. During the paving process, the speed of the paver should be controlled between 1.0 and 3.0m / min. Maintain transverse joints during paving. During construction, the distance between pavers should not exceed 10 meters, and adjacent construction sections should have a longitudinal overlap of 30cm to 40cm. When the width of a single operation in the stabilization layer is 11-12m, the length of each operation section should be 300m; when the width of a single operation in the stabilization layer is greater than 12m, the length of the operation section should be shortened accordingly. S5. During compaction, follow the sequence of steady compaction – strong vibration – weak vibration – steady compaction, and compact the outer side first, then the inner side. In hot weather, if the subgrade material becomes loose or shifts during compaction, spray water mist to moisten it, mix it thoroughly, adjust it to the factory moisture content, and then compact it. S6. During the curing process, after the phosphogypsum stabilized layer has been rolled and passed the compaction test, it should be covered for curing within 2 hours. The curing time is 7 to 14 days.

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