A tetraethylenepentamine based phosphoric acid extraction apparatus and method

Abstract

This invention relates to the field of wet-process phosphoric acid separation and purification technology, specifically disclosing a phosphoric acid extraction apparatus and method based on tetraethylenepentamine. The apparatus includes a reaction tower, a waste liquid diversion system, a TEPA solution diversion system, and a concentration tank. The waste liquid diversion system includes a waste liquid tank for storing phosphoric acid waste liquid to be treated, a heating pipe installed in the tank, a waste liquid pump connected to the waste liquid tank, and a waste liquid main pipe connected to the pump outlet. The TEPA solution diversion system includes a TEPA solution tank for storing tetraethylenepentamine solution, a TEPA solution pump connected to the tank, and a TEPA solution main pipe connected to the pump outlet. The waste liquid main pipe and the TEPA solution main pipe are respectively connected to the reaction tower. The concentration tank is connected to the bottom of the reaction tower through a guide pipe and is used to receive and concentrate the phosphoric acid solution from which metal ions have been removed. This apparatus, through its integrated diversion and reaction structure, achieves efficient complexation removal of metal ions from low-concentration impurity-containing phosphoric acid waste liquid and continuous recovery of phosphoric acid, and has the advantages of compact process, simple operation, and high extraction efficiency.

Description

Technical Field

[0001] This invention relates to the field of wet phosphoric acid separation and purification technology, and in particular to a phosphoric acid extraction apparatus and method based on tetraethylenepentamine. Background Technology

[0002] Phosphoric acid is a basic chemical raw material, mainly used in the production of phosphate fertilizers, acidulants, preservatives, metal surface treatment agents, detergents, and flame retardants. Currently, it is primarily produced using a wet process, where sulfuric acid reacts with phosphate rock to produce phosphoric acid and phosphogypsum. The phosphoric acid and phosphogypsum are then separated by filtration and concentrated to obtain the final product, phosphoric acid. During the filtration, washing, and condensation concentration processes, a large amount of washing and condensate is generated, containing 1%–2% low-concentration phosphoric acid, as well as sulfuric acid and various metal ions such as iron, aluminum, calcium, and magnesium. Direct neutralization not only wastes phosphorus resources but also generates large amounts of difficult-to-treat sludge, severely polluting the environment. Solvent extraction is an effective technical approach for recovering phosphoric acid from such waste liquids.

[0003] Currently, the main reagents used for extracting and purifying phosphoric acid include organophosphates, ketones, alcohols, and composite / novel extractants. However, organophosphates are expensive, have high viscosity leading to difficult phase separation, and are prone to hydrolysis. Ketones require high-concentration phosphoric acid conditions and are ineffective at removing anionic impurities. Alcohols generally have weak extraction capabilities, high solubility in aqueous phases, and significant solvent loss. Composite / novel extractants involve complex formulations and process optimizations, and some novel reagents are costly. Therefore, seeking inexpensive extractants that can effectively and deeply remove metal ions is of great significance for the efficient and economical treatment of phosphoric acid wastewater. Summary of the Invention

[0004] The purpose of this invention is to provide a phosphoric acid extraction apparatus and method based on tetraethylenepentamine, in order to solve the problem that existing low-concentration phosphoric acid extractants are difficult to remove multiple metal ions deeply and effectively and are expensive.

[0005] As a first aspect of the present invention, the present invention provides a phosphoric acid extraction apparatus based on tetraethylenepentamine, comprising: a reaction tower, the reaction tower constituting a site for a complexation reaction between waste liquid and TEPA solution; a waste liquid diversion system, the waste liquid diversion system comprising a waste liquid tank for storing phosphoric acid waste liquid to be treated, a waste liquid tank heating pipe disposed in the waste liquid tank, a waste liquid pump communicating with the waste liquid tank, and a waste liquid main pipe connected to the outlet of the waste liquid pump, the waste liquid main pipe communicating with the reaction tower; a TEPA solution diversion system, the TEPA solution diversion system comprising a TEPA solution tank for storing tetraethylenepentamine solution, a TEPA solution pump communicating with the TEPA solution tank, and a TEPA solution main pipe connected to the outlet of the TEPA solution pump, the TEPA solution main pipe communicating with the reaction tower; and a concentration tank, the concentration tank being connected to the bottom of the reaction tower via a guide pipe for receiving and concentrating the phosphoric acid solution from which metal ions have been removed.

[0006] Optionally, the reaction tower is provided with an upper waste liquid tray, an upper grid, a lower waste liquid tray, and a lower grid in sequence from top to bottom; the waste liquid main pipe splits into an upper waste liquid pipe and a lower waste liquid pipe near the reaction tower, which are respectively connected to the upper waste liquid tray and the lower waste liquid tray; the TEPA solution main pipe splits into an upper TEPA liquid pipe and a lower TEPA liquid pipe near the reaction tower, and the ends of the pipes are respectively provided with an upper TEPA nozzle and a lower TEPA nozzle. The upper TEPA nozzle is located above the upper waste liquid tray, and the lower TEPA nozzle is located between the upper waste liquid tray and the lower waste liquid tray.

[0007] Optionally, both the upper waste liquid tray and the lower waste liquid tray are conical structures with a larger upper section and a smaller lower section, and their shrinkage ratio is 15:1 to 16:1.

[0008] Optionally, the top opening diameter of the lower waste liquid tray is 5-8 mm larger than the maximum diameter of the upper waste liquid tray.

[0009] Optionally, the upper and lower grilles are multi-layer filter structures, with the meshes of adjacent filter layers staggered and the mesh diameter being 0.5~0.8mm.

[0010] Optionally, sodium carbonate is pre-added to the TEPA solution tank, and the amount of sodium carbonate added is 1.1 to 1.2 times the molar amount of fluorosilicic acid in the waste liquid to be treated.

[0011] Optionally, a heating pipe is installed inside the concentration tank, and an exhaust valve is provided at the top of the concentration tank.

[0012] Optionally, the wall material of the heating pipe in the waste liquid tank and the heating pipe in the concentration tank is stainless steel resistant to phosphoric acid corrosion.

[0013] As a second aspect of the present invention, the present invention provides a phosphoric acid extraction method based on tetraethylenepentamine, using the phosphoric acid extraction apparatus based on tetraethylenepentamine described in the first aspect above, the method comprising the following steps: S1. Pretreatment: Prepare a TEPA solution containing sodium carbonate in a TEPA solution tank, store waste liquid containing phosphoric acid and metal ion impurities in a waste liquid tank, and preheat the waste liquid using a heating pipe in the waste liquid tank. S2. Feeding and Reaction: Start the waste liquid pump and TEPA solution pump to make the waste liquid flow into the upper waste liquid pan and lower waste liquid pan in the reaction tower respectively, while the TEPA solution is atomized into droplets and sprayed out through the upper TEPA nozzle and lower TEPA nozzle respectively. S3. Countercurrent mixing and complexation: TEPA droplets and waste liquid undergo countercurrent mixing in the reaction tower. TEPA and metal ions in the waste liquid undergo complexation reaction and agglomerate into flocs under weak alkaline environment and precipitation induction. S4. Filtration and separation: The mixture containing complex flocs and precipitates flows through the grid in the reaction tower, where the flocs and precipitates are retained, resulting in a purified phosphoric acid solution. S5. Concentration and purification: The purified phosphoric acid solution is introduced into a concentration tank, and the solution is heated and evaporated using the heating tubes of the concentration tank to obtain a pure phosphoric acid product.

[0014] Furthermore, in step S5, the heating tube of the concentration tank utilizes the waste heat from the high-temperature exhaust gas or flue gas emitted from the factory for heating, and its outer wall temperature is maintained at 110℃~120℃. Compared with the prior art, the present invention discloses at least the following beneficial effects: This invention provides an integrated, continuously operating phosphoric acid extraction device. Through the systematic coordination of its various functional units, it can efficiently recover pure phosphoric acid from low-concentration wastewater containing impurities. The device integrates key processes such as wastewater preheating, TEPA complexation reaction, floc separation, and phosphoric acid concentration. The pretreated wastewater and the TEPA solution containing sodium carbonate are precisely delivered to the reaction tower via a wastewater diversion system and a TEPA solution diversion system, respectively. Multi-stage countercurrent mixing and complexation reactions are completed within the tower. After the reaction, the floc-containing mixture undergoes preliminary solid-liquid separation within the tower. The purified phosphoric acid solution then enters a concentration tank for waste heat concentration, ultimately obtaining a high-purity phosphoric acid product. The entire device has a compact structure and continuous process, significantly improving the removal efficiency of metal ions and the recovery rate of phosphoric acid. It also achieves energy recovery through waste heat utilization, reducing operating energy consumption. Furthermore, by using readily available and inexpensive TEPA as the main extractant, combined with sodium carbonate conditioning, it effectively controls reagent costs while ensuring deep impurity removal, demonstrating good economic benefits and environmental friendliness. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A front view of the phosphoric acid extraction apparatus based on tetraethylenepentamine provided by the present invention; Figure 2 Axiometric view of the phosphoric acid extraction apparatus based on tetraethylenepentamine provided by the present invention Figure 1 ; Figure 3 Axiometric view of the phosphoric acid extraction apparatus based on tetraethylenepentamine provided by the present invention Figure 2 .

[0017] In the diagram: 1. TEPA solution tank; 12. TEPA solution pump; 13. TEPA solution main pipe; 14. TEPA upper liquid pipe; 141. TEPA upper liquid valve; 142. TEPA upper nozzle; 15. TEPA lower liquid pipe; 151. TEPA lower liquid valve; 152. TEPA lower nozzle; 2. Waste liquid tank; 21. Waste liquid tank heating pipe; 22. Waste liquid pump; 23. Waste liquid main pipe; 24. Waste liquid lower pipe; 241. Lower waste liquid valve; 242. Lower waste liquid tray; 25. Upper waste liquid pipe; 251. Upper waste liquid valve; 252. Upper waste liquid tray; 26. Liquid inlet; 3. Reaction tower; 31. Upper grid; 32. Lower grid; 4. Concentrator; 41. Drain pipe; 42. Concentrator heating pipe; 43. Exhaust valve. Detailed Implementation

[0018] 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Reference Figures 1 to 3 As shown in the figure, this embodiment of the invention provides a phosphoric acid extraction device based on tetraethylenepentamine. The device mainly includes a waste liquid diversion system, a TEPA solution diversion system, a reaction tower 3 and a concentration tank 4. Through the coordinated cooperation of each component, phosphoric acid can be efficiently and deeply recovered from low-concentration phosphoric acid waste liquid containing metal ions.

[0021] In one specific embodiment, the waste liquid diversion system includes a waste liquid tank 2 for storing phosphoric acid waste liquid to be treated, and a liquid inlet 26 is provided on the waste liquid tank 2. A waste liquid tank heating pipe 21 is installed inside the waste liquid tank 2 to preheat the waste liquid in the tank. The waste liquid tank 2 is connected to a waste liquid pump 22 through a pipe, and the outlet of the waste liquid pump 22 is connected to a waste liquid main pipe 23. The waste liquid main pipe 23 splits into two branches near the reaction tower 3: one is an upper waste liquid pipe 25, which extends into the reaction tower 3 and is equipped with an upper waste liquid tray 252 at its end; the other is a lower waste liquid pipe 24, which also extends into the reaction tower 3 and is equipped with a lower waste liquid tray 242 at its end. An upper waste liquid valve 251 and a lower waste liquid valve 241 are respectively provided on the upper waste liquid pipe 25 and the lower waste liquid pipe 24 to regulate the flow rate of waste liquid entering the two waste liquid trays.

[0022] In one specific embodiment, the TEPA solution guiding system includes a TEPA solution tank 1 for storing tetraethylenepentamine (TEPA) solution. The TEPA solution tank 1 is connected to a TEPA solution pump 12 via a pipe, and the outlet of the TEPA solution pump 12 is connected to a TEPA solution manifold 13. The TEPA solution manifold 13 also splits into two branches near the reaction tower 3: one is a TEPA upper pipe 14, which extends into the reaction tower 3 and is equipped with a TEPA upper nozzle 142 at its end; the other is a TEPA lower pipe 15, which extends into the reaction tower 3 and is equipped with a TEPA lower nozzle 152 at its end. A TEPA upper valve 141 and a TEPA lower valve 151 are respectively installed on the TEPA upper pipe 14 and TEPA lower pipe 15 to regulate the flow rate of the TEPA solution ejected from the two nozzles, ensuring that it forms uniformly falling droplets.

[0023] In one specific embodiment, the reaction tower 3 constitutes the core site for the complexation reaction between the waste liquid and the TEPA solution. The interior of the reaction tower 3, from top to bottom, is provided with an upper waste liquid tray 252, an upper grid 31, a lower waste liquid tray 242, and a lower grid 32. The upper TEPA nozzle 142 is located above the upper waste liquid tray 252, and the lower TEPA nozzle 152 is located between the upper waste liquid tray 252 and the lower waste liquid tray 242. Both the upper waste liquid tray 252 and the lower waste liquid tray 242 are designed as a conical structure, wider at the top and narrower at the bottom, with a preferred shrinkage ratio (the ratio of the top diameter to the bottom outlet diameter) of 15:1 to 16:1.

[0024] Based on the above embodiments, the top opening diameter of the lower waste liquid tray 242 is further 5-8 mm larger than the maximum diameter of the upper waste liquid tray 252. This structural design allows the waste liquid to be sprayed at high speed from the constriction opening of the tray, forming a strong countercurrent mixing with the existing liquid and TEPA droplets in the tray; at the same time, the liquid overflowing from the upper waste liquid tray 252 can slide along the inner wall of the lower waste liquid tray 242, forming a strong secondary countercurrent mixing with the high-speed liquid flow surging from the bottom, greatly improving mass transfer and reaction efficiency.

[0025] Building upon the above embodiments, the upper grid 31 and lower grid 32 are further used to trap precipitates and complex flocs generated during the reaction. They are made of corrosion-resistant stainless steel and form a 2- to 3-layer filter structure.

[0026] Furthermore, the meshes of adjacent filter layers are staggered, with mesh diameters between 0.5 and 0.8 mm, to effectively intercept solid particles ranging from micrometers to millimeters in size.

[0027] Furthermore, the upper grille 31 and the lower grille 32 are designed to be detachable, making it easy to remove them periodically for cleaning or replacement, ensuring long-term stable operation of the device.

[0028] In one specific embodiment, the concentration tank 4 is connected to the bottom of the reaction tower 3 via a guide pipe 41, and is used to receive and concentrate the phosphoric acid solution from which metal ions have been removed. A concentration tank heating pipe 42 is installed inside the concentration tank 4, and an exhaust valve 43 is installed at its top. The concentration tank heating pipe 42 is used to introduce high-temperature waste gas or flue gas emitted from the factory, using residual heat to maintain the temperature of the outer wall of the pipe at 110℃~120℃, causing the water in the phosphoric acid solution to evaporate into water vapor and be discharged through the exhaust valve 43, thereby obtaining a concentrated, pure phosphoric acid product.

[0029] Building upon the above embodiments, to further optimize the reaction process and treat fluorosilicic acid impurities in the waste liquid, sodium carbonate is pre-added to the TEPA solution in TEPA solution tank 1. The amount of sodium carbonate added is 1.1 to 1.2 times the molar amount of fluorosilicic acid in the waste liquid. Its function is twofold: firstly, it combines with the hexafluorosilicate ions generated from the reaction of TEPA and fluorosilicic acid, transforming them into sodium silicate (Na₂O·nSiO₂) or sodium metasilicate (Na₂SiO₃) precipitates, which are then removed; secondly, by adjusting the amount of sodium carbonate added, the pH value of the system after mixing the TEPA solution and the waste liquid is raised to a weakly alkaline range of 5 to 6. Under this alkaline environment, coupled with the presence of sodium silicate / sodium metasilicate precipitates, the complexes formed by TEPA and metal ions such as iron, aluminum, calcium, and magnesium can be effectively induced to aggregate, generating millimeter-sized flocculent substances, greatly improving the efficiency and convenience of these impurities being removed by subsequent grid filtration.

[0030] In one specific embodiment, the wall material of both the waste liquid tank heating pipe 21 and the concentration tank heating pipe 42 is made of stainless steel resistant to phosphoric acid corrosion. The waste liquid tank heating pipe 21 can also utilize waste heat from the factory exhaust gas to maintain its outer wall temperature at 100℃~110℃, thereby stabilizing the waste liquid temperature in the waste liquid tank 2 at approximately 85℃. This temperature condition significantly promotes the reaction between TEPA and fluorosilicic acid, as well as the complexation reaction with various metal ions, improving overall extraction efficiency and shortening the necessary reaction time.

[0031] This embodiment of the device achieves the goal of efficiently recovering phosphoric acid from complex, low-concentration phosphoric acid waste liquid. The device uses inexpensive tetraethylenepentamine (TEPA) as the core extractant. By precisely adding sodium carbonate to its solution, not only are fluorosilicic acid impurities in the waste liquid effectively removed, converting them into easily filterable silicate precipitates, but more importantly, the pH of the reaction system is adjusted to a weakly alkaline range of 5-6. Under this environment, TEPA forms complexes with various metal ions such as iron, aluminum, calcium, and magnesium, which aggregate under precipitation-induced conditions, generating millimeter-sized flocs, greatly facilitating subsequent solid-liquid separation. The core reaction tower 3 of the device is ingeniously designed. Its conical waste liquid tray (shrinkage ratio 15:1~16:1), wider at the top and narrower at the bottom, combined with the size difference between the upper and lower trays, generates intense countercurrent and secondary mixing when the waste liquid flows in, ensuring full contact with the uniformly sprayed TEPA droplets from top to bottom. This significantly enhances mass transfer and the reaction process, ensuring deep removal of metal ions. The multi-layered, detachable stainless steel grille (0.5~0.8mm mesh) effectively traps flocs and sediments, and is easy to clean and maintain, ensuring long-term stable operation. Furthermore, the device innovatively integrates a waste heat utilization system, introducing high-temperature waste gas from the factory through heating pipes 21 in the waste liquid tank and 42 in the concentration tank. This preheats the waste liquid to 85°C to increase the reaction rate and concentrates and purifies the purified phosphoric acid solution. The entire device thus offers comprehensive benefits, including high extraction efficiency, good separation effect, significant energy saving and consumption reduction, low operating costs, and a compact structure.

[0032] This invention also provides a phosphoric acid extraction method based on tetraethylenepentamine, using a phosphoric acid extraction apparatus based on tetraethylenepentamine as described above. The method includes the following steps: S1. Pretreatment: Prepare a TEPA solution containing sodium carbonate in TEPA solution tank 1, and store waste liquid containing 1%~2% phosphoric acid and metal ion impurities in waste liquid tank 2. Turn on the heating pipe 21 of the waste liquid tank to preheat the waste liquid to about 85°C.

[0033] S2. Feeding and Reaction: Start the waste liquid pump 22 and the TEPA solution pump 12. The waste liquid is distributed through the waste liquid main pipe 23 and flows into the upper waste liquid tray 252 and lower waste liquid tray 242 in the reaction tower 3 through the upper waste liquid pipe 25 and the lower waste liquid pipe, respectively. At the same time, the TEPA solution is distributed through the TEPA solution main pipe 13 and atomized into droplets through the upper TEPA liquid pipe 14 and the lower TEPA liquid pipe 15, respectively, and sprayed out as droplets by the upper TEPA nozzle 142 and the lower TEPA nozzle 152.

[0034] S3. Countercurrent Mixing and Complexation: TEPA droplets fall evenly into the upper and lower waste liquid trays 242, where they undergo strong countercurrent mixing with the high-speed flowing waste liquid. TEPA rapidly undergoes complexation reactions with metal ions such as iron, aluminum, calcium, and magnesium in the waste liquid. The resulting complexes agglomerate into millimeter-sized flocs under the induction of a weakly alkaline environment (pH 5~6) and sodium silicate precipitation.

[0035] S4. Filtration and Separation: Waste liquid containing complex flocs and precipitates overflows from the waste liquid pan and flows downwards, passing sequentially through the upper screen 31 and the lower screen 32. The flocs and precipitates are effectively retained by the screens, while the purified phosphoric acid solution, after the removal of metal ions, passes through the screens.

[0036] S5. Concentration and Purification: The purified phosphoric acid solution flows into the concentration tank 4 through the inlet pipe 41. The heating pipe 42 of the concentration tank is turned on to heat the solution using residual heat, causing the water to evaporate. The water vapor is discharged through the exhaust valve 43, and finally a concentrated pure phosphoric acid solution is obtained in the concentration tank 4.

[0037] This embodiment of the extraction method achieves the dual benefits of resource recovery and environmental protection by optimizing and integrating process steps and reaction conditions. The method first pre-treats the raw materials by adding sodium carbonate to the TEPA solution in stoichiometric proportions, and preheating the waste liquid containing impurities to approximately 85°C in waste liquid tank 2 using waste heat, laying the foundation for efficient reaction. In the core extraction stage, the TEPA droplets are controlled to form multi-stage countercurrent contact with the high-speed turbulent waste liquid in a conical disk. While enhancing mixing, TEPA rapidly undergoes a complexation reaction with metal ions. The weakly alkaline environment (pH 5-6) maintained by sodium carbonate and the generated silicate precipitate together induce the complex to agglomerate into easily separable millimeter-sized flocs. Subsequently, the reaction liquid flows through a multi-layered staggered grid, where the flocs and precipitates are efficiently retained, resulting in a clear phosphoric acid solution free of metal ions. Finally, the method again utilizes industrial waste heat to perform low-temperature evaporation and concentration of the purified liquid in concentration tank 4, obtaining a reusable pure phosphoric acid product. The entire process flows smoothly and the conditions are mild and controllable. It not only removes a variety of impurities and achieves efficient recovery of phosphorus resources, but also makes full use of waste heat throughout the process and avoids the generation of complex sludge. It demonstrates the significant benefits of high efficiency, high product purity, low energy consumption and environmental friendliness.

[0038] In one specific embodiment, to further verify the actual effect of the device and method of this embodiment, the following experimental study was conducted, and the following experimental data were obtained: The complexation and removal rate of typical metal ions by TEPA was investigated under the conditions of an initial phosphoric acid concentration of 1.5%, a temperature of 85℃, and a pH of 5.5. Experimental results showed that TEPA effectively removed iron ions (Fe... 3+ The removal rate of aluminum ions (Al) can reach over 99.2%, and the removal rate of aluminum ions (Al) is also high. 3+ The removal rate of calcium ions (Ca) was 98.5%. 2+ ) and magnesium ions (Mg 2+ The removal rates of TEPA and phosphate were 97.8% and 96.3%, respectively. This confirms that TEPA, as a multidentate ligand, can efficiently and deeply complex and remove various metal impurities from phosphoric acid waste liquid.

[0039] The effect of adjusting the amount of sodium carbonate added on the aggregation behavior of TEPA-metal complexes was observed by controlling the pH of the reaction system. When the pH was maintained in a weakly alkaline range of 5.0–6.0, the generated complexes could effectively aggregate under the induction of sodium silicate precipitation to form dense flocs with an average size of 1.2–2.5 mm, which were easily trapped by the grid. When the pH was below 4.5, the aggregation phenomenon was not obvious, and the particle size formed was less than 0.1 mm, which easily penetrated the grid, resulting in a decrease in separation efficiency. When the pH was above 6.5, although aggregation was complete, it may cause partial neutralization loss of phosphate. Therefore, accurately controlling the pH at 5–6 is one of the key conditions for achieving efficient solid-liquid separation in this method.

[0040] During industrial-scale trial operation, the waste heat from the factory's flue gas at approximately 150°C was used to heat the waste liquid pool and concentration tank. Actual measurement data shows that compared to traditional electric or steam heating methods, this waste heat utilization system can reduce the overall energy consumption of the plant by approximately 65% ​​to 70%. In the concentration process alone, utilizing the waste heat from the exhaust gas at 110 to 120°C for evaporation, recovering 1 ton of pure phosphoric acid (calculated as P2O5) can save approximately 0.15 tons of standard coal, demonstrating significant energy-saving and emission-reduction benefits.

[0041] It should be understood that the apparatus and method of the present invention are not only applicable to the recovery of phosphoric acid from low-concentration wastewater containing impurities generated during the wet-process phosphoric acid production process, but also, based on the core principle of TEPA efficient complexation and induced aggregation separation, have the potential to be extended to a wider range of acidic wastewater containing metal ions. For example, acidic wastewater generated in industries such as metallurgy, electroplating, mining acid leaching, and metal surface treatment often contains various concentrations of heavy metal ions such as iron, copper, zinc, nickel, and chromium. These wastewaters also share characteristics such as high acidity, a wide variety of metal ions, difficulty in direct treatment, and high resource recovery value.

[0042] By adaptively adjusting the concentration of TEPA solution, the dosage of sodium carbonate (or other alkaline pH adjuster), and operating parameters such as reaction temperature and flow rate, this device can effectively complex and remove target metal ions from the aforementioned wastewater. It also utilizes the same induced agglomeration-grid filtration mechanism to achieve efficient separation of metal precipitates from the purified water. The separated metal complex flocs are enriched with valuable metal components, facilitating further recycling. Simultaneously, the acidity of the purified effluent is reduced, improving water quality. Therefore, this invention provides a modular, efficient, and economical general-purpose technology platform for the treatment and resource recovery of acidic metal-containing wastewater, possessing broad market application prospects and environmental value.

[0043] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0044] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A phosphoric acid extraction apparatus based on tetraethylenepentamine, characterized in that, include: Reaction tower (3); Waste liquid diversion system, the waste liquid diversion system includes a waste liquid tank (2) for storing phosphoric acid waste liquid to be treated, a waste liquid tank heating pipe (21) installed in the waste liquid tank (2), a waste liquid pump (22) connected to the waste liquid tank (2), and a waste liquid main pipe (23) connected to the outlet of the waste liquid pump (22), the waste liquid main pipe (23) being connected to the reaction tower (3); The TEPA solution diversion system includes a TEPA solution tank (1) for storing tetraethylenepentamine solution, a TEPA solution pump (12) connected to the TEPA solution tank (1), and a TEPA solution manifold (13) connected to the outlet of the TEPA solution pump (12), which is connected to the reaction tower (3). The concentration tank (4) is connected to the bottom of the reaction tower (3) through a drain pipe (41) and is used to receive and concentrate the phosphoric acid solution that has been demetallized.

2. The pentaethylenehexamine-based phosphoric acid extraction device of claim 1, wherein, The reaction tower (3) is provided with an upper waste liquid tray (252), an upper grid (31), a lower waste liquid tray (242) and a lower grid (32) from top to bottom. The waste liquid main pipe (23) is divided into an upper waste liquid pipe (25) and a lower waste liquid pipe near the reaction tower (3), which are connected to the upper waste liquid tray (252) and the lower waste liquid tray (242) respectively. The TEPA solution main pipe (13) is divided into a TEPA upper liquid pipe (14) and a TEPA lower liquid pipe (15) near the reaction tower (3), and the ends of the pipes are respectively provided with a TEPA upper nozzle (142) and a TEPA lower nozzle (152). The TEPA upper nozzle (142) is located above the upper waste liquid tray (252), and the TEPA lower nozzle (152) is located between the upper waste liquid tray (252) and the lower waste liquid tray (242).

3. The pentaethylenehexamine-based phosphoric acid extraction device of claim 2, wherein, Both the upper waste liquid tray (252) and the lower waste liquid tray (242) are conical structures with a larger upper section and a smaller lower section, and their shrinkage ratio is 15:1 to 16:

1.

4. The pentaethylenehexamine-based phosphoric acid extraction device of claim 3, wherein, The top opening diameter of the lower waste liquid tray (242) is 5-8 mm larger than the maximum diameter of the upper waste liquid tray (252).

5. The pentaethylenehexamine-based phosphoric acid extraction device of claim 2, wherein, The upper grille (31) and the lower grille (32) are multi-layer filter structures, with the meshes of adjacent filter layers staggered and the mesh diameter being 0.5~0.8mm.

6. The pentaethylenehexamine-based phosphorus-based solvent extraction apparatus of claim 1, wherein, Sodium carbonate is pre-added to the TEPA solution tank (1), and the amount of sodium carbonate added is 1.1 to 1.2 times the number of moles of fluorosilicic acid in the waste liquid to be treated.

7. The tetraethylenepentamine-based phosphorus acid extraction apparatus of claim 1, wherein, The thickening tank (4) is equipped with a thickening tank heating pipe (42) and an exhaust valve (43) is installed on its top.

8. The pentaethylenehexamine-based phosphoric acid extraction device of claim 7, wherein, The wall material of the heating pipe (21) in the waste liquid tank and the heating pipe (42) in the concentration tank is stainless steel resistant to phosphoric acid corrosion.

9. A method of phosphoric acid extraction based on tetraethylenepentamine, characterized in that the device for phosphoric acid extraction based on tetraethylenepentamine according to any one of claims 1 to 8 is used. Includes the following steps: S1. Pretreatment: Prepare a TEPA solution containing sodium carbonate in a TEPA solution tank (1), store waste liquid containing phosphoric acid and metal ion impurities in a waste liquid tank (2), and preheat the waste liquid using a waste liquid tank heating pipe (21). S2, Feeding and Reaction: Start the waste liquid pump (22) and TEPA solution pump (12) to make the waste liquid flow into the upper waste liquid pan (252) and lower waste liquid pan (242) in the reaction tower (3) respectively, and at the same time make the TEPA solution atomized into droplets and sprayed out through the upper TEPA nozzle (142) and lower TEPA nozzle (152) respectively; S3, Countercurrent Mixing and Complexation: TEPA droplets and waste liquid undergo countercurrent mixing in the reaction tower (3). TEPA and metal ions in the waste liquid undergo complexation reaction and agglomerate into flocs under weak alkaline environment and precipitation induction. S4. Filtration and separation: The mixture containing complex flocs and precipitates flows through the grid in the reaction tower (3), where the flocs and precipitates are retained, and a purified phosphoric acid solution is obtained. S5. Concentration and purification: The purified phosphoric acid solution is introduced into the concentration tank (4), and the concentration tank heating tube (42) is used for heating, evaporation and concentration to obtain pure phosphoric acid product.

10. The pentaethylenehexamine-based phosphoric acid extraction process of claim 9, wherein, In step S5, the heating tube (42) of the concentration tank is heated by the waste heat of the high-temperature exhaust gas or flue gas emitted by the factory, and its outer wall temperature is maintained at 110℃~120℃.

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