Process for recovering extractant from oily wastewater of potassium dihydrogen phosphate plant and device thereof

Abstract

The present application relates to potassium dihydrogen phosphate preparation technical field, specifically to a kind of phosphorus dihydrogen potassium device oily wastewater recovery extractant process and its device, including cyclone pretreatment equipment, pressurized dissolved air flotation equipment and extractant regeneration equipment;Cyclone pretreatment equipment is equipped with feed inlet, light phase outlet and heavy phase outlet, the heavy phase outlet is connected to sedimentation tank;Pressurized dissolved air flotation equipment includes box, box is equipped with air float contact zone, air float separation zone and clean water tank in sequence;Cyclone pretreatment equipment's light phase outlet and the extractant collection tank are all connected extractant recovery tank, extractant recovery tank is connected the extractant regeneration equipment;Through cyclone pretreatment+micro-nano partial reflux pressurized dissolved air flotation+extractant regeneration synergistic technical scheme, accurately solved the emulsion of alcohol, amine extractant in wastewater during the preparation of refined phosphoric acid / phosphorus dihydrogen potassium by extraction method is difficult to break, recovery rate is low, wastewater cannot be reused, the core technical problem of high energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of potassium dihydrogen phosphate preparation, in particular to a process for recovering an extractant from oily wastewater of a potassium dihydrogen phosphate device and a device thereof. BACKGROUND

[0002] Currently, 100-1000 mg / L of extractants are often mixed in the wastewater produced by a device for preparing refined phosphoric acid or potassium dihydrogen phosphate by extraction. The extractants are mainly a mixture of alcohols and amines. The amines and alcohol substances in the wastewater are affected by other solvents and pump movement external forces, and part of them form a cosolvent emulsion with water. In the existing various oil-water separation technologies, the commonly used method is air flotation technology, which uses air blowing and aeration method to mix oil-water mixed liquid, forms rapid floating of oil, and then takes out the oil by overflow method. The general problems of this method include: (1) it is difficult to truly realize oil-water separation in the production process, which leads to that the wastewater cannot be directly utilized or the material quality of subsequent sections and each link is affected during utilization due to the introduction of the extractant; (2) the oil-water separation is not complete, and only large-volume oil droplets can be separated, and small-molecule oil droplets cannot be separated; (3) the recovery rate of the extractant is low, which can only reach 30-40%, and if the recovery rate of the extractant in the wastewater is increased, other reagents (such as demulsifiers, flocculants PAC or PAM, etc.) must be added, and the recovery rate can be increased to about 90%, but the introduction of other substances leads to that the extractant cannot be recycled in production; (4) the important problem in treatment is the emulsification of small-molecule oil droplets, so the oil-water separation equipment must end the water quality purification operation while separating the oil droplets, and the conventional air flotation method cannot complete this operation.

[0003] The full-flow micro-nano pressurized dissolved air flotation method increases the emulsification degree of the oily wastewater because all the wastewater passes through a pressure pump, so the process is complex, the energy consumption is large, the investment and operation power consumption are high, and the recovered extractant waste liquid cannot be regenerated and reused, but can only be sold as low-value waste oil. SUMMARY

[0004] The present application aims to provide a process for recovering an extractant from oily wastewater of a potassium dihydrogen phosphate device and a device thereof, which adopts a synergistic technical scheme of cyclone pretreatment + micro-nano partial reflux pressurized dissolved air flotation + extractant regeneration, and can efficiently realize the core function of recovering the extractant from the wastewater, so as to solve the defects in the background technology.

[0005] To achieve the above object, the present application provides the following technical scheme:

[0006] The application discloses a device for recovering and extracting oil-containing wastewater of potassium dihydrogen phosphate, which comprises a cyclone pretreatment device, a pressurized dissolved air flotation device and an extractant regenerating device; the cyclone pretreatment device is provided with a feed inlet, a light phase outlet and a heavy phase outlet, and the heavy phase outlet is connected with a sedimentation tank; the pressurized dissolved air flotation device comprises a box, and the box is provided with a flotation contact zone, a flotation separation zone and a clean water tank which are sequentially connected; the flotation contact zone is provided with a water inlet, and the water inlet is connected with the sedimentation tank; the flotation contact zone is also connected with a dissolved air releasing system; the flotation separation zone is provided with an extractant collecting tank which is used for collecting extractant oil floating on the liquid surface; the flotation separation zone is also provided with a slag scraper which is used for scraping the extractant oil into the extractant collecting tank; the clean water tank is provided with a water outlet and a backflow port, and the backflow port is connected with the dissolved air releasing system; the light phase outlet of the cyclone pretreatment device and the extractant collecting tank are both connected with an extractant recovery tank, and the extractant recovery tank is connected with the extractant regenerating device.

[0007] As a further improvement, the bottom of the flotation separation zone is provided with a water collecting pipe, and the water outlet of the water collecting pipe is connected with the clean water tank.

[0008] As a further improvement, the dissolved air releasing system comprises a dissolved air tank and a dissolved air releaser, the dissolved air releaser is installed in the flotation contact zone, the dissolved air tank is provided with an air inlet, a liquid inlet and a liquid outlet, the air inlet is connected with an air compressor, the liquid inlet is connected with the backflow port, and the liquid outlet is connected with the dissolved air releaser.

[0009] As a further improvement, the cyclone pretreatment device is a cyclone.

[0010] As a further improvement, the extractant regenerating device is a phase separation tower.

[0011] As a further improvement, the slag scraper comprises a chain which is driven by a driving part to rotate in a vertical plane, and flexible scrapers are fixedly installed on the chain; when the chain rotates, the scrapers at the bottom of the chain horizontally move and scrape the extractant oil into the extractant collecting tank; a supporting arm is movably installed above the extractant collecting tank, one end of the supporting arm is hinged to one side wall of the extractant collecting tank, the rotating plane of the supporting arm is parallel to the plane of the chain, and the other end of the supporting arm is fixedly installed with a cleaning plate; when the scrapers move above the extractant collecting tank, the cleaning plate contacts one side of the scrapers and scrapes off the extractant oil adhered to the scrapers.

[0012] As a further improvement, a spring rod for pushing the support arm to rotate downward is further hinged between the support arm and the sidewall of the extractant collecting tank, when the scraper moves to the turning point of the chain through the bottom of the chain and rotates upward, the scraper contacts the cleaning plate and drives the support arm to rotate upward, compressing the spring rod.

[0013] A process for recovering extractant from oily wastewater of a potassium dihydrogen phosphate device, the process comprising the following steps:

[0014] S1, cyclone pretreatment link,

[0015] The production wastewater containing alcohol and amine extractant first enters the cyclone pretreatment equipment, the free extractant droplets with lighter density overflow from the light phase outlet, and the solid impurities and water phase with larger density are discharged from the heavy phase outlet into the sedimentation tank, and a micro air flotation agent is added to the sedimentation tank for pretreatment;

[0016] S2, air flotation deep separation link,

[0017] The water phase pretreated in the sedimentation tank enters the air flotation contact zone and is fully contacted and mixed with the dissolved air water released by the dissolved air release system, the dissolved air water releases a large number of micro-nano bubbles, which are adsorbed and combined with the emulsified extractant droplets in the wastewater to form extractant oil slick and float upward, and then enter the air flotation separation zone, the extractant oil slick is scraped by the slag scraper to the extractant collecting tank for collection; the clear water in the lower layer of the air flotation separation zone flows to the clear water tank, part of which flows to the dissolved air release system for recycling, and the other part is directly discharged;

[0018] S3, extractant regeneration and reuse link,

[0019] The crude extractant collected by the light phase outlet and the extractant collecting tank enters the extractant recovery tank, and after adding a regenerating agent into the extractant recovery tank, it is punched into a phase separation tower to remove trace impurities in the separated extractant, realizing the recovery of the extractant.

[0020] As a further improvement, the micro air flotation agent in S1 is composed of polyether type organic amine salt, quaternary amine salt cationic decoloring flocculant and cationic polyacrylamide, and the mass ratio is 20%-30%, 30%-50% and 20%-30% respectively; the mass ratio of the micro air flotation agent to the treated wastewater is 0.03%-0.3%.

[0021] As a further improvement, the regenerating agent in S3 is secondary steam condensed water of ammonium chloride, and the temperature of the regenerating agent is 85-95 degrees.

[0022] Compared with the prior art, the application has the beneficial effects that:

[0023] The application solves the core technical problems of emulsion difficulty in breaking, low recovery rate, waste water cannot be reused, and high energy consumption of alcohol and amine extractant in the process of preparing refined phosphoric acid / potassium dihydrogen phosphate by extraction method through the synergistic technical scheme of cyclone pretreatment + micro-nano partial reflux pressurized dissolved air flotation + extractant regeneration.

[0024] The recovery efficiency and quality of the extractant meet the recycling requirements, for waste water containing alcohol and amine extractant, after the treatment of the device, the recovery rate of the extractant reaches 92%-95%, which is much higher than that of the traditional normal pressure flotation process (65%-75%) and the chemical demulsification process (70%-80%), and when the extractant is recycled in the extraction process, the extraction efficiency is basically the same as that of fresh extractant, and there is no performance degradation (the extraction efficiency of the extractant recovered by the traditional chemical demulsification is reduced to below 85% after 3 cycles).

[0025] The micro-floatation reagent is developed for waste water containing amine and alcohol mixture or amine and alcohol derivatives, the demulsification rate reaches more than 90%, and no new substances are introduced, so that the main components of the extractant remain unchanged.

[0026] The regenerated activator is the by-product condensate water of the device, which has low energy consumption, and the obtained water is clear and can meet the reuse requirements, which has significant environmental, social and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] Figure 1 is a structural schematic diagram of the embodiment of the application;

[0029] Figure 2 is a structural schematic diagram of the slag scraper of the embodiment of the application;

[0030] Figure 3 is a structural schematic diagram of the spring rod of the embodiment of the application;

[0031] Figure 4 is a flow chart of the process of the device for recovering extractant from oil-containing waste water of the potassium dihydrogen phosphate device of the embodiment of the application.

[0032] In the diagram: 1-Swirl pretreatment equipment; 2-Pressurized dissolved air flotation equipment; 3-Extractant regeneration equipment; 301-Phase separation tower; 4-Swirl converter; 5-Inlet; 6-Light phase outlet; 7-Heavy phase outlet; 8-Sedimentation tank; 9-Box body; 10-First baffle; 11-Second baffle; 12-Flotation contact zone; 13-Flotation separation zone; 14-Clear water tank; 15-Inlet; 16-Dissolved gas release system; 17-Extractant collection tank; 18-Slag scraper; 19-Chain; 20-Support shaft; 21-Sprocket; 22-Scraper; 23-Slag guide plate; 24-Support arm; 25-Cleaning plate; 26-Spring rod; 27-Sleeve; 28-Moving column; 29-Baffle; 30-Spring; 31-Outlet; 32-Return port; 33-Dissolved gas tank; 34-Dissolved gas release device; 35-Air compressor; 36-Water collection pipe; 37-Extractant recovery tank; 38-L-shaped plate. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] like Figures 1 to 3 As shown, a device for recovering extractant from oily wastewater from a potassium dihydrogen phosphate plant includes a cyclone pretreatment device 1, a pressurized dissolved air flotation device 2, and an extractant regeneration device 3.

[0035] The hydrocyclone pretreatment device 1 is a hydrocyclone 4, which is φ300mm and has a cone angle of 8°-12°. The hydrocyclone 4 has a feed inlet 5 on its side, a light phase outlet 6 at its top, and a heavy phase outlet 7 at its bottom. The heavy phase outlet 7 is connected to the sedimentation tank 8 through a pipeline.

[0036] The pressurized dissolved air flotation (DAF) device 2 includes a housing 9. A first partition 10 and a second partition 11 located to the right of the first partition 10 are welded inside the housing 9. The housing 9 to the left of the first partition 10 contains the flotation contact zone 12. The housing 9 between the first partition 10 and the second partition 11 contains the flotation separation zone 13. The housing 9 to the right of the second partition 11 contains a clear water tank 14. The upper end of the first partition 10 is lower than the upper end of the second partition 11. The top of the flotation contact zone 12 is connected to the top of the flotation separation zone 13. The water phase in the flotation contact zone 12 can enter the flotation separation zone 13 through the upper end of the first partition 10. A water collection pipe 36 is provided at the bottom of the flotation separation zone 13. The water collection pipe 36 is fixedly installed to the left of the second partition 11, and its outlet end is connected to the clear water tank 14. The clear water in the lower layer of the flotation separation zone 13 can enter the clear water tank 14 through the water collection pipe 36 for collection.

[0037] The left end of the tank 9 is provided with an inlet 15 that connects to the air flotation contact area 12. The inlet end of the inlet 15 is connected to the sedimentation tank 8 through a pipeline. The air flotation contact area 12 is also connected to the dissolved air release system 16.

[0038] The air flotation separation zone 13 is equipped with an extractant collection tank 17 for collecting extractant oil floating on the liquid surface. An L-shaped plate 38 is welded inside the box 9 on the left side of the second partition 11. The front and rear ends of the L-shaped plate 38 are in contact with the front and rear side walls of the box 9, respectively. The horizontal part of the L-shaped plate 38 is in contact with the left side of the second partition 11 to the right. The extractant collection tank 17 is located inside the box 9 between the L-shaped plate 38 and the second partition 11. A discharge port communicating with the extractant collection tank 17 is provided on one side wall of the box 9.

[0039] The flotation separation zone 13 is also equipped with a scraper 18 for scraping the extractant oil onto the extractant collection tank 17, such as... Figure 2 As shown, the scraper 18 includes a chain 19 driven by a drive unit to operate in a vertical plane. Two support shafts 20, arranged opposite each other, are rotatably mounted on the side wall of the housing 9 above the flotation separation zone 13 via bearing seats. The support shafts 20 extend forward and backward, and sprockets 21 are fixedly mounted on each of the two support shafts 20. The chain 19 is connected to the two sprockets 21, and one of the support shafts 20 is connected to a drive motor. The right end of the chain 19 extends above the extractant collection tank 17. A flexible scraper 22 is fixedly mounted on the outer side of the chain 19 by bolts. The scraper 22 has one or more... The upper end of the vertical part of the L-shaped plate 38 is provided with an inclined slag guide plate 23. One end of the slag guide plate 23 is welded to the upper end of the vertical part of the L-shaped plate 38, and the other end of the slag guide plate 23 is inclined to the right and upward towards the extractant collection tank 17. The lower end of the slag guide plate 23 is below the liquid surface of the air flotation separation zone 13, and the upper end is above the liquid surface. When the drive motor drives the chain 19 to rotate counterclockwise, the chain 19 drives the scraper 22 at its bottom to move horizontally to the right. The scraper 22 can scrape the extractant floating oil on the liquid surface of the air flotation separation zone 13 along the slag guide plate 23 into the extractant collection tank 17.

[0040] like Figure 3 As shown, a support arm 24 is movably installed above the extractant collection tank 17. The right end of the support arm 24 is hinged to the left side of the second partition 11. The plane in which the support arm 24 rotates is parallel to the plane in which the chain 19 is located. The left end of the support arm 24 extends toward the chain 19 and is fixedly installed with a cleaning plate 25 by bolts. When the scraper 22 moves above the extractant collection tank 17 after passing the slag guide plate 23, the cleaning plate 25 contacts the working side of the scraper 22 and scrapes off the extractant floating oil adhering to the scraper 22, thereby preventing the extractant floating oil from adhering to the cleaning plate 25 and being carried back into the air flotation separation zone 13.

[0041] In addition, a spring rod 26 for pushing the support arm 24 to rotate downward is hingedly connected between the top of the support arm 24 and the left side of the second partition plate 11, the spring rod 26 comprises a sleeve 27, one end of the sleeve 27 is hingedly connected to the second partition plate 11, the other end of the sleeve 27 is provided with a through hole arranged along the axial direction of the sleeve 27, a movable column 28 is movably installed in the through hole, one end of the movable column 28 located in the sleeve 27 is fixedly installed with a baffle 29 for preventing the movable column 28 from completely separating from the sleeve 27, a spring 30 is connected between the side of the baffle 29 away from the movable column 28 and the inner wall of the sleeve 27, the other end of the movable column 28 away from the baffle 29 extends out of the sleeve 27 and is hingedly connected to the top of the support arm 24, when the spring 30 pushes the baffle 29 to abut against the inner wall of the end of the sleeve 27 provided with the through hole and makes the movable column 28 extend out of the sleeve 27 by the maximum distance, the cleaning plate 25 is located in the path of movement of the scraper 22. After the scraper 22 passes through the guide slag plate 23 through the bottom of the chain 19, the scraper 22 continues to move rightward along with the chain 19 to the right side sprocket 21, the chain 19 is upwardly turned through the bottom of the right side sprocket 21, at the same time, the chain 19 drives the scraper 22 to rotate upward around the center of the right side sprocket 21, the scraper 22 contacts the cleaning plate 25 first drives the cleaning plate 25 and the support arm 24 to rotate upward by a certain angle, and then makes the movable column 28 retract into the sleeve 27 by a certain size and compresses the spring 30; subsequently, the flexible scraper 22 is bent and deformed to pass through the cleaning plate 25, at the same time, the cleaning plate 25 scrapes off the extractant floating oil attached to the working side of the scraper 22; when the scraper 22 separates from the cleaning plate 25, the spring 30 extends and pushes the movable column 28 to extend out of the sleeve 27 again, and then the spring rod 26 extends as a whole and drives the cleaning plate 25 and the support arm 24 to rotate downward, the cleaning plate 25 throws the scraped extractant floating oil downward into the extractant collecting tank 17.

[0042] The right end of the box body 9 is provided with a clean water tank 14 provided with a water outlet 31 and a backflow port 32, the backflow port 32 is located above the water outlet 31, and the backflow port 32 is connected to the dissolved air releasing system 16.

[0043] The dissolved air releasing system comprises a dissolved air tank 33 and a dissolved air releaser 34, the dissolved air releaser 34 is installed in the air flotation contact zone 12, the dissolved air tank 33 is provided with an air inlet, a liquid inlet and a liquid outlet, the air inlet is connected to an air compressor 35, the liquid inlet is connected to the backflow port 32, and the liquid outlet is connected to the dissolved air releaser 34.

[0044] The light phase outlet 6 of the cyclone pretreatment device and the discharge port of the extractant collecting tank 17 are both connected to an extractant recovery tank 37 through pipelines, the extractant recovery tank 37 is connected to an extractant regeneration device through a pipeline, and the extractant regeneration device 3 is a phase separation tower 301.

[0045] As Figure 4As shown, a potassium dihydrogen phosphate device oily wastewater recovery extraction agent device process, application potassium dihydrogen phosphate device oily wastewater recovery extraction agent device, the process comprises the following steps:

[0046] S1, cyclone pretreatment link,

[0047] The production wastewater containing alcohol and amine extractant first enters the cyclone 4 through the feed inlet 5, and under the action of pressure, it rotates at high speed along the cavity wall of the cyclone 4 to form a centrifugal field. The free extractant droplets with lighter density overflow from the light phase outlet 6 at the top of the cyclone 4 to form a crude extractant, and the solid impurities and water phase with larger density are discharged from the heavy phase outlet 7 at the lower end of the cyclone 4 into the sedimentation tank 8. After adding a micro air flotation agent for pretreatment, it enters the next link.

[0048] The wastewater containing amine and alcohol mixture or amine and alcohol derivatives mainly has a flow rate of 10 m 3 / h, a pH value of 9-11, and a content of 100-1000 mg / L.

[0049] The pressure of the feed inlet 5 of the cyclone 4 is 0.15-0.30 MPa, and the split ratio (overflow flow rate of light phase outlet 6 / total water flow rate of feed inlet 5) is 5%-15%.

[0050] The micro air flotation agent is composed of polyether type organic amine salt, quaternary amine salt cationic decolorizing flocculant and cationic polyacrylamide (molecular weight: 6-8 million), and the mass ratio is 20%-30%, 30%-50% and 20%-30% respectively. The composite type oily wastewater micro air flotation agent is prepared by compounding. The mass ratio of micro air flotation agent addition amount to treated wastewater is 0.03%-0.3%.

[0051] S2, gas flotation deep separation link,

[0052] The water phase after pretreatment in the sedimentation tank 8 enters the gas flotation contact zone 12 and fully contacts and mixes with the dissolved air water released by the dissolved air releaser 34. The dissolved air water releases a large number of micro-nano bubbles, which adsorb and combine with the emulsified extractant droplets in the wastewater to form extractant oil slick and float up, and then enter the gas flotation separation zone 13. The extractant oil slick is scraped by the slag scraper 18 to the extractant collection tank 17 for collection; the clear water in the lower layer of the gas flotation separation zone 13 is collected by the water collecting pipe 36 to the clear water tank 14, and a part of the water phase in the clear water tank 14 is returned to the dissolved air tank 33 through the backflow port 32 for recycling, and the other part is directly discharged through the water outlet 31 (standard reuse).

[0053] The outlet flow rate of the dissolved air releaser 34 is 0.4-0.5 m / s.

[0054] The dissolved air pressure of the dissolved air releaser 34 is 0.3-0.5 MPa, and the dissolved air water backflow ratio is 25-35%.

[0055] The micro-nano bubble particle size of the dissolved gas release device 34 is 5-20 μm.

[0056] The water flow upflow velocity of the air floatation contact zone 12 is 10-20 mm / s, and the water flow residence time in the air floatation contact zone 12 is ≥60 seconds.

[0057] S3, the extraction agent regeneration and reuse link,

[0058] The crude extraction agent collected by the light phase outlet 6 and the extraction agent collection tank 17 enters the extraction agent recovery tank 37, the reactivation agent is added into the extraction agent recovery tank 37 and combined with the crude extraction agent, the crude extraction agent is then punched into the phase separation tower 301, the trace impurities (such as fine particles, moisture, etc.) remaining in the separated extraction agent are removed, the purity of the extraction agent meets the production and recycling requirements, and the extraction agent is recovered.

[0059] The reactivation agent is the secondary steam condensate water of ammonium chloride, and the temperature of the reactivation agent is controlled at 85-95 degrees.

[0060] Embodiment:

[0061] The extraction agent in the wastewater of 40,000 tons / year extraction method potassium dihydrogen phosphate device is recycled, and the specific steps are as follows:

[0062] 1. First, the wastewater containing 100-1000 mg / L of alcohol and amine extraction agent from the confluence of each process of the 40,000 tons / year extraction method potassium dihydrogen phosphate device is flowed into the adjustment pool through the channel, and the large particle impurities larger than 2-3 mm are filtered through the front grid well of the adjustment pool and then flowed into the adjustment pool, and settled for 8 hours.

[0063] 2. The wastewater is introduced into the cyclone pretreatment equipment 1. Under the action of centrifugal sedimentation, the pressure of the feed inlet 5 of the cyclone 4 is controlled at 0.15-0.30 MPa, and the split ratio (overflow flow rate of the light phase outlet 6 / total water flow rate of the feed inlet 5) is 5%-15%; under the action of centrifugal force, the free extraction agent small droplets with lighter density overflow from the light phase outlet 6 at the top of the cyclone 4 to form a crude extraction agent and flow into the extraction agent recovery tank 37; the solid particle impurities and water phase with larger density move to the cavity wall due to the difference in centrifugal force, and finally are discharged from the heavy phase outlet 7 at the bottom of the cyclone 4 into the settling tank 8, and the micro air floatation reagent is added and stirred to be uniformly mixed, and the preliminary solid-liquid and liquid-liquid separation is completed, so as to reduce the load for subsequent treatment.

[0064] 3. The flotation contact zone 12 and the flotation separation zone 13 of the pressurized dissolved air flotation device 2 are filled with clean water, the dissolved air release system 16 is running, the clean water is pressurized into the dissolved air tank 33 by the pressurized pump, the air and water are dissolved and separated in the dissolved air tank 33 and circulated, the water after sufficient dissolution is released into the flotation contact zone 12 by the dissolved air releaser 34, the micro-nano bubble particle size of the dissolved air releaser 34 is 5-20 μm, the outlet flow rate is controlled to be 0.4-0.5 m / s, the dissolved air pressure is 0.5 MPa, the dissolved air water reflux ratio is 30%, and the gas-liquid density ratio is 1:6, at this time a large number of micro-bubbles appear in the flotation contact zone 12, making the color of the clean water become milky white.

[0065] 4. The upper liquid of the waste water containing emulsified extractant in the sedimentation tank 8 is pumped into the flotation contact zone 12 by the sewage pump and fully mixed and contacted with the dissolved air water released by the dissolved air releaser 34, the water flow rising velocity of the flotation contact zone 12 is 15 mm / s, and the water flow residence time in the flotation contact zone 12 is ≥60 seconds; the amine and alcohol oil mixture in the waste water fully absorbs and adheres to the micro-bubbles, and then enters the flotation separation zone 13, the water flow residence time in the flotation separation zone 13 is 15 min, the amine and alcohol mixture floats to the water surface to form an oil layer under the action of the micro-nano bubble buoyancy, the oil is scraped by the slag scraper 18 to the extractant collection tank 17, the clean water in the lower layer of the flotation separation zone 13 is collected by the water collecting pipe 36 to the clean water tank 14, a small part of the clean water continues to return to the dissolved air tank 33 for use as reflux dissolved air water, and most of the clean water is discharged through the water outlet 31 and pumped into the dissolved solution preparation system for use in the production system.

[0066] 5. The crude extractant collected in the extractant collection tank 17 is pumped into the extractant recovery tank 37, the crude extractant is combined with the reactivating agent in the extractant recovery tank 37, the trace impurities (such as fine particles, moisture, etc.) remaining in the separated extractant are removed in the phase separation tower 301, the water phase is further discharged and the influence of the impurities on the performance of the extractant is reduced, the extractant with purity ≥95% and water content ≤3% is obtained, which meets the requirements of recycling and is used in the extraction production process, and the water containing trace impurities is discharged and pumped into the phosphate-potash fertilizer filtration system for use as filter cake washing water.

[0067] Table 1 is the analysis data of the process of recovering the extractant from the oil-containing waste water by the potassium dihydrogen phosphate device and the device for treating the oil-containing waste water.

[0068] Table 1

[0069]

[0070] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A device for recovering extractant from oily wastewater from a potassium dihydrogen phosphate plant, characterized in that: It includes a cyclone pretreatment device (1), a pressurized dissolved air flotation device (2), and an extractant regeneration device (3); The cyclone pretreatment device (1) is provided with a feed inlet (5), a light phase outlet (6) and a heavy phase outlet (7), and the heavy phase outlet (7) is connected to a settling tank (8). The pressurized dissolved air flotation equipment (2) includes a housing (9), which contains a flotation contact area (12), a flotation separation area (13), and a clear water tank (14) connected in sequence. The flotation contact area (12) has an inlet (15), the inlet end of which is connected to the sedimentation tank (8). The flotation contact area (12) is also connected to a dissolved air release system (16). The flotation separation area (13) has an extractant collection tank (17) for collecting extractant oil floating on the liquid surface. The flotation separation area (13) also has a scraper (18) for scraping extractant oil into the extractant collection tank (17). The clear water tank (14) has an outlet (31) and a return outlet (32), which is connected to the dissolved air release system (16). The light phase outlet (6) of the cyclone pretreatment device (1) and the extractant collection tank (17) are both connected to the extractant recovery tank (37), and the extractant recovery tank (37) is connected to the extractant regeneration device (3). The scraper (18) includes a chain (19) driven by a drive component to operate in a vertical plane. A flexible scraper (22) is fixedly installed on the chain (19). When the chain (19) operates, the scraper (22) at its bottom moves horizontally and scrapes the extractant oil into the extractant collection tank (17). A support arm (24) is movably installed above the extractant collection tank (17). One end of the support arm (24) is hinged to a side wall of the extractant collection tank (17). The plane in which the support arm (24) rotates is parallel to the plane in which the chain (19) is located. A cleaning plate (25) is fixedly installed at the other end of the support arm (24). When the scraper (22) moves above the extractant collection tank, the cleaning plate (25) contacts one side of the scraper (22) and scrapes off the extractant oil adhering to the scraper (22). A spring rod (26) for pushing the support arm (24) to rotate downwards is also hinged between the support arm (24) and the side wall of the extractant collection tank (17). When the scraper (22) moves from the bottom of the chain (19) to the turning point of the chain (19) and rotates upwards, the scraper (22) contacts the cleaning plate (25) and drives the support arm (24) to rotate upwards, compressing the spring rod (26).

2. The device for recovering extractant from oily wastewater from a potassium dihydrogen phosphate plant as described in claim 1, characterized in that: The bottom of the air flotation separation zone (13) is provided with a water collection pipe (36), and the water outlet end of the water collection pipe (36) is connected to the clear water tank (14).

3. The device for recovering extractant from oily wastewater from a potassium dihydrogen phosphate plant as described in claim 1, characterized in that: The dissolved gas release system (16) includes a dissolved gas tank (33) and a dissolved gas release device (34). The dissolved gas release device (34) is installed in the air flotation contact area (12). The dissolved gas tank (33) is provided with an air inlet, a liquid inlet and a liquid outlet. The air inlet is connected to an air compressor (35), the liquid inlet is connected to the reflux port (32), and the liquid outlet is connected to the dissolved gas release device (34).

4. The extractant recovery device for oily wastewater from a potassium dihydrogen phosphate plant as described in claim 1, characterized in that: The cyclone pretreatment device (1) is a cyclone separator (4).

5. The device for recovering extractant from oily wastewater from a potassium dihydrogen phosphate plant as described in claim 1, characterized in that: The extractant regeneration equipment (3) is a phase separation tower (301).

6. A process for recovering extractant from oily wastewater from a potassium dihydrogen phosphate plant, using the extractant recovery device for oily wastewater from a potassium dihydrogen phosphate plant as described in any one of claims 1-5, characterized in that, The process includes the following steps: S1, cyclone pretreatment stage The production wastewater containing alcohol and amine extractants first enters the cyclone pretreatment equipment (1). The lighter free extractant droplets overflow from the light phase outlet (6), while the denser solid impurities and water phase are discharged from the heavy phase outlet (7) and enter the settling tank (8). Micro-flotation agent is added to the settling tank (8) for pretreatment. S2, Deep air flotation separation stage The pretreated water phase in the settling tank (8) enters the air flotation contact zone (12) and is fully mixed with the dissolved air water released by the dissolved air release system (16). The dissolved air water releases a large number of micro-nano bubbles, which adsorb and combine with the emulsified extractant droplets in the wastewater to form extractant oil and float to the surface. Then it enters the air flotation separation zone (13). The extractant oil is scraped by the scraper (18) to the extractant collection tank (17) for collection. The clear water in the lower layer of the air flotation separation zone (13) flows to the clear water tank (14), part of which flows to the dissolved air release system (16) for recycling, and the other part is directly discharged. S3, Extractant Regeneration and Reuse Stage The crude extractant collected by the light phase outlet (6) and the extractant collection tank (17) enters the extractant recovery tank (37). After adding a regeneration activator to the extractant recovery tank (37), it is pumped into the phase separation tower (301) to remove the trace impurities remaining in the separated extractant and realize the recovery of the extractant.

7. The process for recovering the extractant from oily wastewater from a potassium dihydrogen phosphate plant as described in claim 6, characterized in that: The micro-flotation agent described in S1 is composed of polyether-type organic amine salt, quaternary ammonium salt cationic decolorizing flocculant, and cationic polyacrylamide, with a mass ratio of 20%-30%, 30%-50%, and 20%-30%, respectively; the mass ratio of the micro-flotation agent added to the treated wastewater is 0.03%-0.3%.

8. The process for recovering the extractant from oily wastewater from a potassium dihydrogen phosphate plant as described in claim 6, characterized in that: The regeneration activator mentioned in S3 is ammonium chloride secondary steam condensate, and the temperature of the regeneration activator is 85-95 degrees Celsius.

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