Phosphogypsum leachate purification device

Abstract

The utility model provides a kind of phosphogypsum percolate purification device, pre-treatment tank is connected with the feed inlet of reaction kettle by pipeline;Reaction kettle is also connected with dosing tank, dosing tank is communicated with reaction kettle by second pump body;The supernatant outlet of reaction kettle is connected with buffer tank by fourth pump body, buffer tank is connected with the liquid inlet of first adsorption column by fifth pump body;The liquid outlet of first adsorption column is connected with the liquid inlet of second adsorption column, the liquid outlet of second adsorption column is connected with reverse osmosis membrane treatment pool by sixth pump body;The blow-off port of the bottom of reaction kettle is connected to plate-and-frame filter by pipeline, and the solid outlet of plate-and-frame filter is communicated with screw conveyor below.The device can remove various pollutants in percolate in depth;Especially by seventh pump body, the concentrated solution of reverse osmosis membrane treatment pool, the blow-off liquid of adsorption column and the filtrate of plate-and-frame filter are returned to front end pre-treatment tank, realize the closed loop circulation and liquid low emission of whole system.

Description

Technical Field

[0001] This utility model relates to the field of phosphogypsum leachate purification, and in particular to a phosphogypsum leachate purification device. Background Technology

[0002] Phosphogypsum is a solid waste generated during the production of phosphoric acid. The leachate from its stockpile has a complex composition, containing high concentrations of pollutants such as phosphorus, fluorine, organic matter, and heavy metals, and is highly acidic.

[0003] Currently, most existing phosphogypsum leachate treatment technologies employ traditional chemical precipitation methods. While these methods can remove some pollutants, they often suffer from insufficient treatment depth and difficulty in meeting stringent emission standards. In particular, poor pretreatment before reverse osmosis membrane treatment leads to easy membrane clogging.

[0004] In addition, existing devices have low solid-liquid separation efficiency during the reaction and precipitation process, and fine particles are often carried into the supernatant and enter subsequent processes, affecting the life of the equipment. At the same time, if the concentrate produced by subsequent deep treatment and the filtrate produced by pressure filtration are directly discharged, it will cause serious secondary pollution and waste of water resources. There is a lack of a complete integrated device that can achieve efficient solid-liquid separation and closed-loop recycling of the concentrate. Utility Model Content

[0005] The main purpose of this utility model is to provide a phosphogypsum leachate purification device, which solves the problems of incomplete removal of pollutants, poor solid-liquid separation effect in the reaction process leading to easy clogging of subsequent equipment, and direct discharge of concentrated liquid generated from deep treatment causing secondary pollution and waste of resources in existing phosphogypsum leachate treatment devices.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a phosphogypsum leachate purification device, wherein the pretreatment tank is connected to the feed inlet of the reaction vessel through a pipeline; A dosing tank is also connected to the reactor, and the dosing tank is connected to the reactor through a second pump body; The supernatant outlet of the reactor is connected to the buffer tank via the fourth pump body, and the buffer tank is connected to the inlet of the first adsorption column via the fifth pump body; the outlet of the first adsorption column is connected to the inlet of the second adsorption column, and the outlet of the second adsorption column is connected to the reverse osmosis membrane treatment tank via the sixth pump body. The bottom drain of the reactor is connected to a plate and frame filter via a pipeline, and the solid outlet of the plate and frame filter is connected to a screw conveyor below.

[0007] In the preferred embodiment, the pretreatment tank is connected to the reactor via a first pump body, and a filter screen is installed inside the pretreatment tank, with the pipes inside the filter screen connected to the first pump body.

[0008] In the preferred embodiment, a vertically installed liquid extraction pipe is provided inside the reactor. The top end of the liquid extraction pipe extends to the outside of the reactor and is connected to the liquid inlet of the fourth pump body. The lower end of the liquid extraction pipe extends along the inner wall of the reactor to the bottom drain port. A filter cover is provided on the liquid extraction pipe.

[0009] In the preferred embodiment, a third pump body is provided on the connecting pipeline between the bottom drain port of the reactor and the plate and frame filter.

[0010] In the preferred embodiment, a concentrate return pipeline is connected to the reverse osmosis membrane treatment tank, and the reverse osmosis membrane treatment tank is connected to the inlet end of the pretreatment tank through the seventh pump body, which is used to return the concentrate to the front end for circulation treatment.

[0011] In the preferred embodiment, the drain ports of the first and second adsorption columns are connected to the inlet of the pretreatment tank via a seventh pump body.

[0012] In the preferred embodiment, the plate and frame filter is equipped with a filtrate return pipe, one end of which is connected to the liquid outlet of the plate and frame filter, and the other end is connected to the liquid inlet pipe of the pretreatment tank.

[0013] In the preferred embodiment, a stirring motor is provided at the top of the reactor, and a stirring shaft and stirring blades connected to the stirring motor are provided inside the reactor for stirring and mixing the materials inside the reactor.

[0014] In the preferred embodiment, control valves are provided on the inlet and outlet pipelines of the first pump body, the second pump body, the third pump body, the fourth pump body, the fifth pump body, the sixth pump body, and the seventh pump body.

[0015] This invention provides a phosphogypsum leachate purification device with multi-stage deep purification and low discharge: The device adopts a tiered purification process of "pretreatment + reaction precipitation + secondary adsorption + reverse osmosis membrane treatment", which can deeply remove various pollutants in the leachate; In particular, by using the seventh pump, the concentrate from the reverse osmosis membrane treatment tank, the sludge from the adsorption column, and the filtrate from the plate and frame filter are returned to the front-end pretreatment tank, realizing a closed-loop circulation of the entire system and low liquid discharge, which greatly improves the utilization rate of water resources and eliminates the risk of secondary pollution.

[0016] Optimized reaction and separation structure: The uniquely designed suction pipe with a filter cover inside the reactor can directly extract the supernatant after preliminary filtration from inside the reactor, effectively preventing large particles of sediment from entering the subsequent buffer and adsorption units, protecting the pump body and reducing the load on subsequent processing; together with the top stirring device, it ensures that the reagents and leachate react fully, improving processing efficiency.

[0017] The highly efficient solid waste treatment system connects directly to a plate and frame filter and a screw conveyor through the bottom drain of the reactor, enabling automatic extraction, dewatering, and solid conveying of precipitated sludge. This significantly reduces the intensity of manual cleaning and achieves the initial separation and collection of pollutants for resource utilization.

[0018] The system boasts high operational stability: the pretreatment tank is equipped with a filter screen, the reaction vessel with a filter cover, and the series connection of each stage of pumps and adsorption columns ensures layer-by-layer control, effectively preventing clogging of pipelines and precision membrane modules. Combined with the control valves on each pipeline, this facilitates automated control and maintenance of the system. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a diagram of the phosphogypsum leachate purification system of this utility model; Figure 2 This is a structural diagram of the reaction vessel of this utility model.

[0020] In the diagram: Pretreatment tank 1; Filter screen 101; First pump body 2; Dosing tank 3; Second pump body 4; Reactor 5; Liquid extraction pipe 501; Filter cover 502; Third pump body 503; Fourth pump body 6; Buffer tank 7; Fifth pump body 8; First adsorption column 9; Second adsorption column 10; Sixth pump body 11; Reverse osmosis membrane treatment tank 12; Seventh pump body 13; Screw conveyor 14; Plate and frame filter 15. Detailed Implementation

[0021] like Figure 1-2 As shown, a phosphogypsum leachate purification device includes a pretreatment tank 1 connected to the inlet of a reactor 5 via a pipeline; a dosing tank 3 is also connected to the reactor 5, and the dosing tank 3 is connected to the reactor 5 via a second pump body 4; the supernatant outlet of the reactor 5 is connected to a buffer tank 7 via a fourth pump body 6, and the buffer tank 7 is connected to the inlet of a first adsorption column 9 via a fifth pump body 8; the outlet of the first adsorption column 9 is connected to the inlet of a second adsorption column 10, and the outlet of the second adsorption column 10 is connected to a reverse osmosis membrane treatment tank 12 via a sixth pump body 11; the bottom drain of the reactor 5 is connected to a plate and frame filter 15 via a pipeline, and the solid outlet of the plate and frame filter 15 is connected to a screw conveyor 14 below.

[0022] The raw phosphogypsum leachate first enters the pretreatment tank 1, where it undergoes preliminary water homogenization or removal of large particulate impurities, and is then transported to subsequent processes via pipelines.

[0023] The pretreated liquid enters reactor 5. At this time, the reagents in dosing tank 3 are precisely pumped into reactor 5 via the second pump 4. Inside the reactor, the reagents react chemically with the leachate, converting dissolved pollutants into insoluble precipitates.

[0024] The supernatant after the reaction is pumped to the buffer tank 7 via the fourth pump body 6. The function of the buffer tank is to stabilize the water pressure and flow rate, providing stable inlet conditions for subsequent precision treatment.

[0025] The liquid in buffer tank 7 is pressurized by the fifth pump body 8 and sent into the first adsorption column 9, and then connected in series into the second adsorption column 10. The interior of the two-stage adsorption column is filled with specific adsorption material for deep adsorption of residual trace pollutants, ensuring further purification of the water.

[0026] The liquid, after adsorption treatment, is finally sent to the reverse osmosis membrane treatment tank 12 through the sixth pump body 11. Utilizing the retention effect of the reverse osmosis membrane, dissolved salts and trace amounts of pollutants in the water are removed, achieving compliant discharge or reuse.

[0027] The high-concentration sludge / crystal slurry accumulated at the bottom of reactor 5 is directly transported to plate and frame filter 15 through the bottom drain pipe. The plate and frame filter dewaters the sludge by pressure filtration, achieving solid-liquid separation.

[0028] The dehydrated sludge cake falls from the solid outlet of the plate and frame filter 15 and directly enters the screw conveyor 14 below. The screw conveyor automatically transports the solid waste to the designated collection point, completing the solid waste cleaning.

[0029] In the preferred embodiment, the pretreatment tank 1 is connected to the reaction vessel 5 via the first pump body 2. The pretreatment tank 1 is equipped with a filter screen 101, and the internal pipes of the filter screen 101 are connected to the first pump body 2. The instruction manual should detail the installation location and pore size range of the filter screen 101, which is 20-50 mesh. Its function is to physically intercept large particles of gypsum residue or suspended impurities carried in the phosphogypsum leachate, preventing blockage of the first pump body 2 or impeller wear, and protecting downstream equipment.

[0030] In the preferred embodiment, a vertically arranged liquid extraction pipe 501 is provided inside the reactor 5. The top end of the liquid extraction pipe 501 extends to the outside of the reactor 5 and is connected to the liquid inlet of the fourth pump body 6. The lower end of the liquid extraction pipe 501 extends along the inner wall of the reactor 5 to the bottom drain port. A filter cover 502 is provided on the liquid extraction pipe 501.

[0031] Traditional supernatant overflow may carry flocs, while this solution achieves "in-situ filtration within the vessel" by using a suction pipe inserted into the vessel and a filter cover at the end. The function of the filter cover 502 is to prevent the precipitates generated by the reaction from entering the suction pipe, ensuring that the turbidity of the liquid entering the buffer tank 7 is low, and reducing the load on the subsequent adsorption column. The filter cover 502 is made of stainless steel sintered mesh or acid-resistant filter cloth.

[0032] In the preferred embodiment, a third pump body 503 is installed on the connecting pipeline between the bottom drain port of the reactor 5 and the plate and frame filter 15. Its function is to forcibly extract the high-concentration sludge from the bottom of the reactor and transport it to the plate and frame filter 15 at a higher position, thus solving the problem of incomplete gravity sludge discharge.

[0033] In the preferred embodiment, the reverse osmosis membrane treatment tank 12 is connected to a concentrate return pipeline, and the reverse osmosis membrane treatment tank 12 is connected to the inlet end of the pretreatment tank 1 through the seventh pump body 13, which is used to return the concentrate to the front end for circulation treatment.

[0034] The reverse osmosis process produces a concentrated solution with high salt content, which would cause secondary pollution if directly discharged. This solution is returned to the pretreatment tank 1 via the seventh pump 13, allowing it to participate in the reaction and adsorption processes again, thus achieving a closed-loop circulation within the system and minimizing liquid discharge.

[0035] In the preferred embodiment, the drain ports of the first adsorption column 9 and the second adsorption column 10 are connected to the inlet of the pretreatment tank 1 via the seventh pump body 13.

[0036] When the first adsorption column 9 and the second adsorption column 10 are backwashed or regenerated, the high-concentration desorption liquid or backwash water generated is not discharged externally, but flows into the return pipeline and is sent back to the front end for reprocessing through the seventh pump body 13, which further enhances the environmental protection closed-loop characteristics of the system.

[0037] In the preferred embodiment, the plate and frame filter 15 is equipped with a filtrate return pipe. One end of the filtrate return pipe is connected to the liquid outlet of the plate and frame filter 15, and the other end is connected to the liquid inlet pipe of the pretreatment tank 1. Returning the filtrate to the pretreatment tank 1 not only recovers water resources but also prevents on-site pollution caused by leakage of filtrate.

[0038] In the preferred embodiment, a stirring motor is installed at the top of the reactor 5, and a stirring shaft and stirring blades connected to the stirring motor are installed inside the reactor 5 for stirring and mixing the materials inside the reactor. This allows the reagents added from the dosing tank 3 to mix instantly with the leachate, providing the kinetic conditions for crystallization nuclei to form, preventing precipitates from settling to the bottom prematurely before the reaction is complete, and improving reaction efficiency.

[0039] In the preferred embodiment, control valves are installed on the inlet and outlet pipelines of the first pump body 2, the second pump body 4, the third pump body 503, the fourth pump body 6, the fifth pump body 8, the sixth pump body 11, and the seventh pump body 13. The function of the valves is to regulate the flow rate and to cut off and isolate the equipment during maintenance.

[0040] Example 2 Further explanation in conjunction with Example 1, such as Figure 1-2As shown, when the system is started, the raw leachate from the phosphogypsum stockpile enters the pretreatment tank 1. After passing through the filter screen 101 to intercept large particulate impurities, it is pumped into the reactor 5 by the first pump body 2. At the same time, the second pump body 4 is turned on to inject the prepared composite precipitant from the dosing tank 3 into the reactor.

[0041] The stirring motor at the top of the reactor is started, and the stirring blades rotate to fully mix the reagents and wastewater, initiating a precipitation reaction. The precipitate generated by the reaction settles to the bottom of the reactor under gravity. The supernatant after the reaction is filtered twice by the filter cover 502 and then enters the buffer tank 7 through the suction pipe 501 under the action of the fourth pump body 6.

[0042] The effluent from buffer tank 7 is pressurized by the fifth pump 8 and sequentially passes through the first adsorption column 9 and the second adsorption column 10 connected in series to deeply adsorb and remove residual fluoride ions and trace heavy metals. The adsorbed effluent is then sent by the sixth pump 11 to the reverse osmosis membrane treatment tank 12 for desalination treatment. The produced freshwater meets the standards for discharge or reuse.

[0043] Solid waste and reflux treatment: The third pump body 503 is turned on to pump the sludge from the bottom of the reactor to the plate and frame filter 15 for pressure filtration and dewatering. The dewatered dry sludge cake falls into the screw conveyor 14 and is output and collected, which can be used as building material raw material or further purified; the filtrate from the pressure filtration is returned to the pretreatment tank 1 through the filtrate reflux pipe.

[0044] The concentrate produced by the reverse osmosis membrane treatment tank 12 and the wastewater produced by the backwashing of the adsorption column are collected and then pumped back to the pretreatment tank 1 by the seventh pump body 13. After being mixed with the raw water, they re-enter the system for circulation treatment.

[0045] Example 3 Further explanation is provided in conjunction with Examples 1-2, such as Figure 1-2 As shown, The leachate from the phosphogypsum stockpile of a certain phosphate chemical enterprise was selected. The raw water quality indicators are as follows: pH value 2.5, total phosphorus (TP) 2500 mg / L, fluoride (F-) 1800 mg / L, and suspended solids (SS) 400 mg / L.

[0046] Operating steps and parameters: Pretreatment: The leachate is passed through a 40-mesh stainless steel filter screen 101 installed in the pretreatment tank 1 to remove large gypsum particles.

[0047] Primary reaction precipitation: Prepare a 10% lime milk Ca(OH)2 solution and a 0.1% polyacrylamide (PAM) solution in dosing tank 3.

[0048] Lime slurry is added to reactor 5 via the second pump 4 to adjust the pH value in the reactor to 9.5-10.5. The stirring speed is controlled at 60 r / min and the reaction time is 30 minutes to generate calcium phosphate and calcium fluoride precipitates.

[0049] Then a small amount of PAM solution was added to aid coagulation, and the mixture was allowed to settle for 15 minutes.

[0050] Adsorption depth treatment: The supernatant is filtered through a 200-mesh stainless steel sintered mesh or acid-resistant filter cloth filter cover 502 at the end of the extraction pipe 501 and then extracted.

[0051] The first adsorption column 9 and the second adsorption column 10 are filled with modified activated alumina or hydroxyapatite adsorbents. The flow rate through the columns is controlled at 5 BV / h (bed volume / hour), and the fluoride concentration is further reduced to below 10 mg / L by utilizing the specific adsorption capacity of the adsorbent for low concentrations of fluoride ions.

[0052] Membrane treatment and reflux: The adsorbed water enters the reverse osmosis membrane treatment tank (12) at an operating pressure of 1.5 MPa.

[0053] The water production rate is controlled at 70%, and the 30% concentrate (rich in salt) produced is returned to the front end through the seventh pump body 13.

[0054] Results: After treatment by the above device, the final effluent (freshwater) water quality indicators are: pH value 7.2, total phosphorus (TP) <0.5 mg / L, fluoride (F-) <1.0 mg / L, and suspended solids (SS) not detected.

[0055] The sludge cake filtered by the plate and frame filter 15 has a moisture content reduced to below 60% and is smoothly discharged via the screw conveyor 14. The main components of the sludge cake are calcium phosphate and calcium fluoride, which can be recycled as cement additives, realizing the resource utilization of pollutants. The entire process has no waste liquid discharge, achieving low-emission operation of the system.

[0056] The above embodiments are merely preferred technical solutions of this utility model and should not be considered as limitations on this utility model. The protection scope of this utility model should be the technical solution described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the protection scope of this utility model.

Claims

1. A purification device for phosphogypsum leachate, characterized in that: The pretreatment tank (1) is connected to the feed inlet of the reactor (5) via a pipeline; A dosing tank (3) is also connected to the reactor (5), and the dosing tank (3) is connected to the reactor (5) through a second pump body (4); The supernatant outlet of the reactor (5) is connected to the buffer tank (7) via the fourth pump body (6), and the buffer tank (7) is connected to the inlet of the first adsorption column (9) via the fifth pump body (8); the outlet of the first adsorption column (9) is connected to the inlet of the second adsorption column (10), and the outlet of the second adsorption column (10) is connected to the reverse osmosis membrane treatment tank (12) via the sixth pump body (11). The reverse osmosis membrane treatment tank (12) is connected to a concentrate return pipeline. The reverse osmosis membrane treatment tank (12) is connected to the inlet end of the pretreatment tank (1) through the seventh pump body (13) to return the concentrate to the front end for circulation treatment. The bottom drain of the reactor (5) is connected to the plate and frame filter (15) through a pipeline, and the solid outlet of the plate and frame filter (15) is connected to the screw conveyor (14) below.

2. The phosphogypsum leachate purification device according to claim 1, characterized in that: The pretreatment tank (1) is connected to the reactor (5) through the first pump body (2). The pretreatment tank (1) is equipped with a filter screen (101), and the pipe inside the filter screen (101) is connected to the first pump body (2).

3. The phosphogypsum leachate purification device according to claim 1, characterized in that: The reactor (5) is vertically equipped with a liquid extraction pipe (501). The top end of the liquid extraction pipe (501) extends to the outside of the reactor (5) and is connected to the liquid inlet of the fourth pump body (6). The lower end of the liquid extraction pipe (501) extends along the inner wall of the reactor (5) to the bottom drain port. A filter cover (502) is provided on the liquid extraction pipe (501).

4. The phosphogypsum leachate purification device according to claim 3, characterized in that: A third pump body (503) is provided on the connecting pipeline between the bottom drain port of the reactor (5) and the plate and frame filter (15).

5. The phosphogypsum leachate purification device according to claim 1, characterized in that: The drain ports of the first adsorption column (9) and the second adsorption column (10) are connected to the inlet of the pretreatment tank (1) through the seventh pump body (13).

6. The phosphogypsum leachate purification device according to claim 1, characterized in that: The plate and frame filter (15) is equipped with a filtrate return pipe. One end of the filtrate return pipe is connected to the liquid outlet of the plate and frame filter (15), and the other end is connected to the liquid inlet pipe of the pretreatment tank (1).

7. The phosphogypsum leachate purification device according to claim 1, characterized in that: The top of the reactor (5) is equipped with a stirring motor, and the reactor (5) is equipped with a stirring shaft and stirring blades connected to the stirring motor for stirring and mixing the materials inside the reactor.

8. The phosphogypsum leachate purification device according to claim 1, characterized in that: Control valves are provided on the inlet and outlet pipelines of the first pump body (2), the second pump body (4), the third pump body (503), the fourth pump body (6), the fifth pump body (8), the sixth pump body (11), and the seventh pump body (13).

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