Activated carbon production waste phosphoric acid regeneration device and regeneration process thereof

Abstract

The invention relates to an activated carbon production waste phosphoric acid regeneration device and a regeneration process thereof. The regeneration device comprises a dilution sedimentation tank used for receiving and diluting waste phosphoric acid; the transfer tank is communicated with the supernatant overflow port of the dilution sedimentation tank; the automatic fine filter is communicated with the transfer tank; the first storage tank is communicated with a filtrate outlet of the automatic fine filter; the resin tank is communicated with the first storage tank, and cation exchange resin is filled in the resin tank; the impurity-removed storage tank is communicated with the water outlet of the resin tank; the two-section type evaporation and concentration unit is communicated with the impurity-removed storage tank and is used for concentrating phosphoric acid step by step; and the condensate water storage tank is communicated with the condensate water outlet of the two-section evaporation and concentration unit and is connected back to the dilution and sedimentation tank through a pipeline.

Description

Technical Field

[0001] This invention belongs to the field of industrial waste acid regeneration technology, and specifically relates to a waste phosphoric acid regeneration device and its regeneration process for waste phosphoric acid generated during the production of activated carbon using the phosphoric acid process, and a waste phosphoric acid regeneration system for activated carbon production based on chemical precipitation and multi-effect evaporation. Background Technology

[0002] The production of activated carbon using the phosphoric acid process generates a large amount of complex and highly viscous waste phosphoric acid. Phosphoric acid is used extensively as an activating agent and is subsequently discharged as waste phosphoric acid. This waste phosphoric acid is complex in composition, highly viscous, and contains a large amount of unreacted phosphoric acid, carbon particles, and metallic cation impurities such as potassium (K), calcium (Ca), sodium (Na), and magnesium (Mg) dissolved from the raw materials. Direct discharge of this waste phosphoric acid would cause serious water and soil pollution.

[0003] Currently, the conventional method for treating waste phosphoric acid in the industry is neutralization, which involves adding calcium hydroxide or sodium hydroxide to the waste acid to adjust its pH to neutral or weakly alkaline, resulting in the formation of precipitates such as calcium phosphate or sodium phosphate. While this method is simple to operate, it has significant drawbacks: (1) Waste of resources: Valuable phosphoric acid resources are not recycled and are converted into low-value solid waste.

[0004] (2) Secondary pollution: It generates a large amount of phosphorus-containing sludge, which requires additional disposal sites and costs, and is likely to cause environmental risks.

[0005] (3) Incomplete treatment: Only the acidity problem was solved, but the dissolved salt impurities were not removed.

[0006] Therefore, developing a regeneration process and equipment that can efficiently recover phosphoric acid, realize the resource utilization of waste acid, and be environmentally friendly has become a technical problem that urgently needs to be solved in this field.

[0007] CN202311832364.1 discloses a method for recovering phosphorus-containing waste liquid. In the existing methods for treating phosphorus-containing waste liquid, the removal of impurities in the phosphorus-containing waste liquid cannot be achieved well, and the aluminum ion concentration is still unsatisfactory, which affects the quality of the subsequent preparation of battery-grade iron phosphate products from phosphorus-containing solutions, and affects the economic value and comprehensive utilization value of phosphorus-containing waste liquid. Therefore, the present invention provides a method for recovering phosphorus-containing waste liquid to solve the above problems. The technical solution is a method for recovering phosphorus-containing wastewater, comprising the following steps: S1, adding the phosphorus-containing wastewater to a filter for solid-liquid separation to remove insoluble and suspended solids, and diluting the resulting filtrate with water; S2, adding an alkaline adjuster to the filtrate to adjust the pH of the system to 5.0–8.5, stirring to generate aluminum hydroxide and a small amount of aluminum phosphate precipitate, and filtering to obtain a first-step impurity-removed filtrate; S3, adding an acidic adjuster to the first-step impurity-removed filtrate to adjust the pH of the system to 1.5–4.5, stirring to generate aluminum phosphate precipitate, and filtering to obtain a second-step impurity-removed filtrate; S4, adding a decolorizing agent to the second-step impurity-removed filtrate to adsorb and remove organic matter and metal ions, obtaining a phosphorus-containing solution with organic matter removed; S5, passing the phosphorus-containing solution obtained in S4 through a chelating resin or cation exchange resin to adsorb and remove residual metal impurities, wherein the adsorption stage is 1–4, to obtain a purified phosphorus-containing solution, which is then used to prepare iron phosphate raw material. Its shortcomings are: (1) Functional limitations: It is essentially a "purification" process, not a "regeneration" process. It does not produce high-concentration phosphoric acid that can be directly reused in the original production process, and cannot achieve closed-loop utilization of resources.

[0008] (2) Narrow application scope: Its core impurity removal technology (pH-adjusted precipitation) is optimized for aluminum ions, and its ability to remove major impurities such as K, Ca, Na, and Mg in activated carbon waste acid is limited, making it unsuitable for this scenario.

[0009] (3) Lack of system energy efficiency design: The recycling of energy and resources during the treatment process (such as condensate reuse) is not considered.

[0010] (4) Potential operating cost issues: For some waste liquids with high impurity content, relying on resin for deep purification may lead to frequent resin regeneration and increased operating costs. Summary of the Invention

[0011] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide an efficient activated carbon production waste phosphoric acid regeneration process and equipment that removes impurities, recovers high-quality phosphoric acid, and achieves zero wastewater discharge. It employs a combined process of 'resin adsorption + two-stage low-temperature evaporation' to achieve efficient purification and resource recovery of waste phosphoric acid in an activated carbon production waste phosphoric acid regeneration device and its regeneration process. Another technical problem this invention aims to solve is to overcome the defects of existing resin adsorption methods for regenerating waste phosphoric acid and provide an activated carbon production waste phosphoric acid regeneration system and method based on chemical precipitation and multi-effect evaporation. This solution aims to replace resin adsorption with chemical precipitation and single-stage evaporation with multi-effect evaporation, thereby achieving stable system operation, reduced energy consumption, and reduced regeneration costs.

[0012] The first technical solution of the present invention is the activated carbon production waste phosphoric acid regeneration device, which is characterized by comprising a dilution sedimentation tank connected in sequence by pipelines for receiving and diluting waste phosphoric acid; a transfer tank connected to the supernatant overflow outlet of the dilution sedimentation tank; an automatic fine filter connected to the transfer tank; a first storage tank connected to the filtrate outlet of the automatic fine filter; a resin tank connected to the first storage tank and filled with cation exchange resin; a post-purification storage tank connected to the outlet of the resin tank; a two-stage evaporation and concentration unit connected to the post-purification storage tank for stepwise concentration of phosphoric acid; and a condensate storage tank connected to the condensate outlet of the two-stage evaporation and concentration unit and returned to the dilution sedimentation tank via pipelines.

[0013] Preferably, the two-stage evaporation and concentration unit includes a low-temperature evaporator and a high-temperature evaporator connected in series. The outlet of the low-temperature evaporator is connected to the inlet of the high-temperature evaporator through a low-temperature acid storage tank. The operating temperature range of the low-temperature evaporator is 30–40°C, and the operating temperature range of the high-temperature evaporator is 60–70°C. Both the low-temperature evaporator and the high-temperature evaporator adopt a combined cooling and heating system. The condensate outlets of both the low-temperature evaporator and the high-temperature evaporator are connected to the condensate storage tank.

[0014] Preferably: the dilution sedimentation tank is equipped with a stirrer and a level gauge, and its bottom slag discharge port is connected to a plate and frame filter press; the filtrate outlet of the plate and frame filter press is connected to the transfer tank; a water pump is provided between the transfer tank and the automatic fine filter; a metering pump is provided between the storage tank and the resin tank; corrosion-resistant pumps are provided at the discharge ports of both the low-temperature evaporator and the high-temperature evaporator; a corrosion-resistant pump is provided between the condensate storage tank and the dilution sedimentation tank; a feed valve is provided between the impurity-removed storage tank and the low-temperature machine; a feed valve is provided between the low-temperature acid storage tank and the high-temperature machine; the resin tank is a full-bed type with a diameter-to-height ratio of 1:1 to 1:3, and is equipped with a pure water tank, an acid washing tank, and an alkali washing tank; the cation exchange resin is a styrene-based cation exchange resin modified with functional groups; the cations in the waste phosphoric acid include K, Ca, Na, and Mg, with a removal rate of not less than 90%; the functional groups are selected from at least one of sulfonic acid groups, carboxylic acid groups, or phosphate groups.

[0015] The second technical solution of the present invention is a process for producing waste phosphoric acid using activated carbon from the aforementioned apparatus, characterized by the following steps: (1) Dilution, precipitation and filtration: Use condensate from the condensate storage tank to dilute the waste phosphoric acid to a specific gravity of 1.15 to 1.25. After settling, take the supernatant for precision filtration. (2) Resin adsorption for impurity removal: The filtered liquid obtained in step (1) is pumped into a resin tank to remove the metal cations and obtain the impurity-removed liquid. (3) Two-stage evaporation and concentration: The purified liquid obtained in step (2) is subjected to low-temperature evaporation and high-temperature evaporation in sequence to concentrate it into regenerated phosphoric acid, and the condensate generated by evaporation is recovered to the condensate storage tank and reused in step (1).

[0016] Preferably, in step (1), the specific preparation steps of dilution precipitation and filtration further include: (1.1) Measure the specific gravity of waste phosphoric acid, calculate the amount of water to be added based on the specific gravity, and use a pump to transport the condensate and waste phosphoric acid generated by low-temperature evaporation to the dilution sedimentation tank and mix them evenly. (1.2) Let the well-mixed waste phosphoric acid stand for 4–8 h; (1.3) The supernatant after settling is overflowed into the transfer tank and then pumped into an automatic fine filter for precision filtration to obtain diluted waste phosphoric acid; (1.4) The concentrated liquid produced by precision filtration is discharged into the dilution sedimentation tank. When the sedimentation layer in the dilution sedimentation tank reaches a certain height, it is discharged and filtered by plate and frame filter press. The filtrate enters the transfer tank and the filter residue is returned to the process to recover carbon. The precision filtration has a filtration accuracy of 500nm to 1000nm; the settling time is 4 to 8 hours; the concentrated liquid after filtration is returned to the dilution settling tank, the sediment is filtered by plate and frame filter press, the filtrate enters the transfer tank, and the filter residue is recycled carbon.

[0017] Preferably, in step (2), the specific preparation steps for resin adsorption and impurity removal further include: (2.1) Resin filling: The resin tank is made into a full-bed form with a diameter-to-height ratio of 1:1 to 1:3. The resin tank is filled with resin according to the resin expansion coefficient. (2.2) Pickling and regeneration: Acid is introduced at a flow rate of 2-3 BV / h, with an acid volume of 2-3 BV. The acid used can be sulfuric acid or hydrochloric acid, wherein the concentration of sulfuric acid is 8-10% or 15-20%, and the concentration of hydrochloric acid is 7-10%. (2.3) Water washing: Pure water is introduced at a flow rate of 3-5 BV / h, and the amount of pure water introduced is 3-5 BV, so that the concentration of sulfate or chloride ions in the effluent is <100 mg / L; (2.4) Sample injection: Inject the sample at a flow rate of 2-3 BV / h. Measure the total cation concentration before the sample enters the resin. Take a portion of the effluent after the sample enters the resin and measure the total cation concentration. When the total cation concentration of the effluent is close to that of the raw water, stop the injection of raw water and obtain the purified solution. Calculate the cation exchange capacity of the cation resin. (2.5) Cleaning the resin: Introduce pure water at a flow rate of 3-5 BV / h, with a pure water volume of 1-2 BV; (2.6) Repeat steps (2.2) and (2.3) in sequence; (2.7) When the resin adsorption capacity decreases, regenerate it with 1-5% sodium hydroxide solution; The resin is a functionally modified styrene-based cation exchange resin, including sulfonic acid groups, carboxylic acid groups, and phosphate groups.

[0018] Preferably, in step (3), the low-temperature evaporation includes both low-temperature evaporation and high-temperature evaporation, wherein the low-temperature evaporation temperature is 30–40°C, and the high-temperature evaporation temperature is 60–70°C; the specific steps of the low-temperature evaporation include: (3.1) The impurity-removed liquid is transported to the cryogenic machine through the feed valve and evaporated and concentrated at a temperature of 30-40℃. After being concentrated to a specific gravity of 1.4-1.45, the concentrated liquid is discharged through the discharge valve and pump and enters the cryogenic acid collection tank to obtain cryogenic acid. The condensate is discharged through the top and enters the condensate collection tank. (3.2) The low-temperature acid is transported to the high-temperature machine through the feed valve and evaporated and concentrated at a temperature of 60-70℃. After being concentrated to a specific gravity of 1.75, the concentrated liquid is discharged through the discharge valve and pump and enters the regenerated acid collection tank to obtain regenerated acid. The condensate is discharged through the top and enters the condensate collection tank. (3.3) The condensate generated by the low-temperature machine and the high-temperature machine is collected in a condensate collection tank and used to dilute the waste phosphoric acid instead of pure water.

[0019] The third technical solution of the present invention is the activated carbon production waste phosphoric acid regeneration system based on chemical precipitation and multi-effect evaporation, which is characterized by including the following components connected in sequence via pipes and pumps / valve: The dilution and precipitation unit is used to receive and dilute waste phosphoric acid and perform preliminary solid-liquid separation. A chemical impurity removal unit, connected to the liquid outlet of the dilution and precipitation unit, is used to add a composite precipitant to the preliminarily purified waste phosphoric acid to remove cationic impurities. A solid-liquid separation unit is connected to the outlet of the chemical purification unit and is used to separate the precipitate produced by the chemical purification unit to obtain purified acid; A multi-effect evaporation and concentration unit is connected to the liquid outlet of the solid-liquid separation unit and is used to perform multi-stage evaporation and concentration of the purified acid to obtain high-concentration regenerated phosphoric acid. The condensate recycling unit is connected to the steam condensation port of the multi-effect evaporation and concentration unit, and is used to collect condensate and reuse it in the dilution and precipitation unit.

[0020] Preferably, the chemical impurity removal unit includes at least one reaction vessel with stirring and online pH monitoring functions, and a metering and dosing device for adding the composite precipitant; The composite precipitant is a compound solution of soluble fluoride and soluble sulfate, wherein the fluoride is selected from at least one of sodium fluoride and ammonium fluoride, and the sulfate is selected from at least one of sodium sulfate and ammonium sulfate. The solid-liquid separation unit is a plate and frame filter press, a chamber filter press, or a centrifuge; The multi-effect evaporation and concentration unit is a two-effect or three-effect evaporator, wherein the evaporation temperature of the first effect is controlled at 70-85℃, the evaporation temperature of the second effect is controlled at 50-65℃, and the evaporation temperature of the third effect is controlled at 35-50℃. The effects of the multi-effect evaporation and concentration unit are coupled to the material pipelines through steam pipelines. The secondary steam generated by the previous effect serves as the heating source for the next effect, and the secondary steam generated by the last effect enters the condenser. The dilution and sedimentation unit includes a dilution and sedimentation tank with a sludge discharge outlet at the bottom. The sludge discharge outlet is connected to the solid-liquid separation unit to treat the settled sludge and the precipitate generated by chemical purification together.

[0021] The fourth technical solution of the present invention is a method for producing waste phosphoric acid regeneration using activated carbon from the aforementioned system, characterized by the following steps: (1) Dilution and preliminary precipitation steps: Mix waste phosphoric acid with the system's own condensate to dilute it, let it stand to precipitate, and then separate the supernatant. (2) Chemical precipitation impurity removal step: A composite precipitant is added to the supernatant. After the reaction, insoluble fluoride and sulfate precipitates are generated to remove potassium, calcium, sodium, and magnesium cations. The pH of the reaction system is controlled at 2.0–4.0, and the reaction time is 30–90 minutes. The amount of the composite precipitant added, calculated as fluoride ions, is 1.0–1.5 times the molar amount of total cations in the waste phosphoric acid; calculated as sulfate ions, it is 1.0–1.2 times the molar amount of calcium ions. (3) Deep solid-liquid separation step: The slurry after reaction is subjected to solid-liquid separation to obtain a purified dilute phosphoric acid solution; (4) Multi-effect evaporation and concentration step: The purified dilute phosphoric acid solution is sent to a multi-effect evaporation device for concentration to obtain regenerated phosphoric acid with a specific gravity that meets the requirements for reuse; (5) Condensate reuse step: Collect the condensate generated during the evaporation process and return it to the dilution and preliminary sedimentation step as dilution water.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) High phosphoric acid recovery rate and good quality: Through the core process of "resin adsorption + two-stage evaporation", the phosphoric acid in waste phosphoric acid is efficiently recovered (the recovery rate can reach more than 95%), and the regenerated acid has high purity and extremely low metal impurity content, which can be directly reused in activated carbon production.

[0023] (2) Low energy consumption and economical operating costs: The use of low-temperature evaporation technology (maximum temperature of only 70°C) and the use of condensate circulation significantly reduces steam energy consumption and fresh water consumption.

[0024] (3) Environmentally friendly with near-zero emissions: The entire process achieves a closed-loop cycle of phosphoric acid, water and carbon residue, with no wastewater discharge. The small amount of filter residue (mainly carbon) produced can be returned to the production system, solving the problem of large amounts of sludge generated by the traditional neutralization method.

[0025] (4) High degree of automation: The equipment has a high degree of integration, and key steps can be automatically controlled, such as automatic fine filtration and metering pumping, which reduces the intensity of manual operation.

[0026] (5) Deep impurity removal: Targeted removal of metal cations such as potassium, calcium, sodium, and magnesium using specific resins, which is difficult to achieve with traditional methods.

[0027] (6) Energy-saving and efficient: The system uses its own condensate for dilution and concentrates it through low-temperature (30-70℃) evaporation, which significantly reduces energy consumption and avoids the decomposition of phosphoric acid and equipment corrosion at high temperatures; all condensate is reused, achieving zero wastewater discharge.

[0028] (7) Closed-loop recycling: The entire process realizes the recycling of water, acid and carbon residue, with almost no secondary pollution, making it a truly green recycling process.

[0029] (8) The resin tank is used to remove cations by using sulfonic acid-modified styrene resin and a flow rate of 2-3 BV / h; the evaporator is used to concentrate phosphoric acid by using low-temperature evaporation at 30-40℃ and high-temperature evaporation at 60-70℃; zero discharge is achieved by recycling all condensate into the dilution process.

[0030] (9) Stable operation and low cost: The chemical precipitation method completely eliminates ion exchange resin, avoiding the problems of frequent regeneration and replacement caused by resin pollution and poisoning. The system is more stable, simple to maintain, and the long-term operating cost is significantly lower than that of the resin adsorption method.

[0031] (10) Significantly reduced energy consumption: By adopting multi-effect evaporation technology, the latent heat of steam is fully utilized, which reduces the amount of live steam consumed per unit of evaporation by about 50% (two-effect) or 67% (three-effect) compared to single-stage evaporation. The energy-saving effect is extremely significant and is in line with the national policy guidance of green manufacturing.

[0032] ⑪ High impurity removal efficiency and good quality regenerated acid: The composite precipitant can specifically form insoluble precipitates with the target cations, resulting in thorough impurity removal. By controlling the reaction conditions, the phosphoric acid loss rate is low (<2%), and the resulting regenerated acid has high purity with impurity content meeting the requirements for reuse.

[0033] 12. Environmentally friendly: The manufacturing method of the activated carbon production waste phosphoric acid regeneration system based on chemical precipitation and multi-effect evaporation does not produce waste acid or waste alkali from resin regeneration. The entire system forms an internal cycle of "condensate reuse - waste acid regeneration", realizing closed-loop treatment of waste phosphoric acid and maximizing resource utilization.

[0034] 13. Comparison Table of Technical Issues, Technical Characteristics, and Beneficial Effects of Waste Phosphoric Acid Regeneration Device and Regeneration Process in Activated Carbon Production

[0035] 14. Comparison Table of Technical Issues, Technical Characteristics, and Beneficial Effects of Activated Carbon Production Waste Phosphoric Acid Regeneration System Based on Chemical Precipitation and Multi-Effect Evaporation Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the activated carbon production waste phosphoric acid regeneration device according to the first embodiment of the present invention; Figure 2 This is a flow chart of the activated carbon production waste phosphoric acid regeneration process according to the first embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of the waste phosphoric acid regeneration system according to the second embodiment of the present invention; In the diagram, 1 is a dilution sedimentation tank; 2 is a chemical purification reaction vessel; 3 is a plate and frame filter press; 4 is a purified acid storage tank; 5 is a double-effect evaporator (of which: the first-effect evaporator is 5a and the second-effect evaporator is 5b); 6 is a regenerated acid storage tank; 7 is a condensate storage tank; P1, P2, and P3 are transfer pumps; and V1 and V2 are feed valves. Figure 4 This is a process flow diagram of the waste phosphoric acid regeneration system according to the second embodiment of the present invention. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: Figure 1 , Figure 2 The first embodiment of the present invention is shown.

[0039] Please see Figure 1 As shown, the activated carbon production waste phosphoric acid regeneration device includes the following components connected in sequence via pipelines: A dilution sedimentation tank is used to receive and dilute waste phosphoric acid. The tank is equipped with a stirrer and a level gauge (not shown in the figure). Its bottom discharge port is connected to a plate and frame filter press, and the filtrate outlet of the filter press is connected to the transfer tank. A water pump is installed between the transfer tank and the automatic fine filter. A metering pump is installed between the storage tank and the resin tank. Corrosion-resistant pumps are installed at the discharge ports of both the low-temperature evaporator and the high-temperature evaporator. A corrosion-resistant pump is installed between the condensate storage tank and the dilution sedimentation tank. A feed valve is installed between the impurity-removed storage tank and the low-temperature machine. A feed valve is installed between the low-temperature acid storage tank and the high-temperature machine. The transfer tank is connected to the supernatant overflow outlet of the dilution sedimentation tank; An automatic fine filter is connected to the transfer tank; The first storage tank is connected to the filtrate outlet of the automatic fine filter; A resin tank, connected to the first storage tank, is filled with cation exchange resin. The resin tank is a full-bed type with a diameter-to-height ratio of 1:1 to 1:3, and is equipped with a pure water tank, an acid washing tank, and an alkaline washing tank. The cation exchange resin is a styrene-based cation exchange resin modified with functional groups. The cations in the waste phosphoric acid include K, Ca, Na, and Mg, with a removal rate of not less than 90%. The functional groups are selected from at least one of sulfonic acid groups, carboxylic acid groups, or phosphate groups. The storage tank after impurity removal is connected to the outlet of the resin tank; A two-stage evaporation and concentration unit, connected to the impurity-removed storage tank, is used for stepwise concentration of phosphoric acid. The two-stage evaporation and concentration unit includes a low-temperature evaporator and a high-temperature evaporator connected in series. The outlet of the low-temperature evaporator is connected to the inlet of the high-temperature evaporator through a low-temperature acid storage tank. The operating temperature range of the low-temperature evaporator is 30–40°C, and the operating temperature range of the high-temperature evaporator is 60–70°C. Both the low-temperature evaporator and the high-temperature evaporator adopt a combined cooling and heating system. The condensate outlets of both the low-temperature evaporator and the high-temperature evaporator are connected to a condensate storage tank.

[0040] The condensate storage tank is connected to the condensate outlet of the two-stage evaporation and concentration unit, and is connected back to the dilution and sedimentation tank through a pipeline.

[0041] Please see Figure 2 As shown, the activated carbon production process for waste phosphoric acid regeneration using the above-mentioned apparatus includes the following steps: (1) Dilution, sedimentation and filtration: The waste phosphoric acid is diluted to a specific gravity of 1.15 to 1.25 using condensate from the condensate storage tank. After settling, the supernatant is taken for precision filtration. The precision filtration accuracy is 500 nm to 1000 nm. The settling time is 4 to 8 hours. The concentrated liquid after filtration is returned to the dilution sedimentation tank. After the sediment is filtered by plate and frame filter press, the filtrate enters the transfer tank, and the filter residue is used to recover carbon. In step (1), the specific preparation steps of dilution precipitation and filtration further include: (1.1) Measure the specific gravity of waste phosphoric acid, calculate the amount of water to be added based on the specific gravity, and use a pump to transport the condensate and waste phosphoric acid generated by low-temperature evaporation to the dilution sedimentation tank and mix them evenly. (1.2) Let the well-mixed waste phosphoric acid stand for 4–8 h; (1.3) The supernatant after settling is overflowed into the transfer tank and then pumped into an automatic fine filter for precision filtration to obtain diluted waste phosphoric acid; (1.4) The concentrated liquid produced by precision filtration is discharged into the dilution sedimentation tank. When the sedimentation layer in the dilution sedimentation tank reaches a certain height, it is discharged and filtered by plate and frame filter press. The filtrate enters the transfer tank and the filter residue is returned to the process to recover carbon. The precision filtration has a filtration accuracy of 500nm to 1000nm; the settling time is 4 to 8 hours; the concentrated liquid after filtration is returned to the dilution settling tank, the sediment is filtered by plate and frame filter press, the filtrate enters the transfer tank, and the filter residue is recycled carbon.

[0042] (2) Resin adsorption and impurity removal: The filtered liquid obtained in step (1) is pumped into a resin tank to remove the metal cations therein, resulting in a purified liquid; the resin is a functionally modified styrene-based cation exchange resin; the adsorption process includes acid washing and regeneration, water washing, sample injection, cleaning, and alkali regeneration steps; the flow rate of the liquid through the resin tank is 2-3 BV / h; and when the resin adsorption capacity decreases, a regeneration step is performed, which includes: first, alkali washing and regeneration with a 1-5% sodium hydroxide solution, and then acid washing and regeneration with a 7-20% sulfuric acid or hydrochloric acid solution; In step (2), the specific preparation steps for resin adsorption and impurity removal further include: (2.1) Resin filling: The resin tank is made into a full-bed form with a diameter-to-height ratio of 1:1 to 1:3. The resin tank is filled with resin according to the resin expansion coefficient. (2.2) Acid washing and regeneration: Acid is fed at a flow rate of 2-3 BV / h, with an acid volume of 2-3 BV. The acid used can be sulfuric acid or hydrochloric acid, wherein the concentration of sulfuric acid is 8-10% or 15-20%, and the concentration of hydrochloric acid is 7-10%. (2.3) Water washing: Pure water is introduced at a flow rate of 3-5 BV / h, and the amount of pure water introduced is 3-5 BV, so that the concentration of sulfate or chloride ions in the effluent is <100 mg / L; (2.4) Sample injection: Inject the sample at a flow rate of 2-3 BV / h. Measure the total cation concentration before the sample enters the resin. Take a portion of the effluent after the sample enters the resin and measure the total cation concentration. When the total cation concentration of the effluent is close to that of the raw water, stop the injection of raw water and obtain the purified solution. Calculate the cation exchange capacity of the cation resin. (2.5) Cleaning the resin: Introduce pure water at a flow rate of 3-5 BV / h, with a pure water volume of 1-2 BV; (2.6) Repeat steps (2.2) and (2.3) in sequence; (2.7) When the resin adsorption capacity decreases, it is regenerated with 1-5% sodium hydroxide solution; The resin is a styrene-based cation exchange resin modified with functional groups, including sulfonic acid groups, carboxylic acid groups, and phosphate groups; (3) Two-stage evaporation and concentration: The purified liquid obtained in step (2) is subjected to low-temperature evaporation and high-temperature evaporation in sequence to concentrate the phosphoric acid and recycle the condensate generated by evaporation to the condensate storage tank (12) for reuse in step (1); the low-temperature evaporation concentrates the phosphoric acid to a specific gravity of 1.4 to 1.45, and the high-temperature evaporation finally concentrates the phosphoric acid to a specific gravity of not less than 1.75. In step (3), the low-temperature evaporation includes low-temperature evaporation and high-temperature evaporation, wherein the low-temperature evaporation temperature is 30–40°C; the high-temperature evaporation temperature is 60–70°C; the specific steps of the low-temperature evaporation include: (3.1) The impurity-removed liquid is transported to the cryogenic machine through the feed valve and evaporated and concentrated at a temperature of 30-40℃. After being concentrated to a specific gravity of 1.4-1.45, the concentrated liquid is discharged through the discharge valve and pump and enters the cryogenic acid collection tank to obtain cryogenic acid. The condensate is discharged through the top and enters the condensate collection tank. (3.2) The low-temperature acid is transported to the high-temperature machine through the feed valve and evaporated and concentrated at a temperature of 60-70℃. After being concentrated to a specific gravity of 1.75, the concentrated liquid is discharged through the discharge valve and pump and enters the regenerated acid collection tank to obtain regenerated acid. The condensate is discharged through the top and enters the condensate collection tank. (3.3) The condensate generated by the low-temperature machine and the high-temperature machine is collected in a condensate collection tank and used to dilute the waste phosphoric acid instead of pure water.

[0043] A specific implementation of Example 1: A waste phosphoric acid regeneration project at an activated carbon plant in Fujian Province. The plant generates thousands of tons of waste phosphoric acid per month, the composition of which is as follows:

[0044] The results showed that the cation removal rate exceeded 90% and the phosphoric acid recovery rate reached 96%.

[0045] The process steps performed using the apparatus of this invention are as follows: (1) Dilution and filtration: Dilute the waste phosphoric acid to a specific gravity of 1.20 with condensate, let it stand for 6 hours, and then filter the supernatant through an 800 nm fine filter.

[0046] (2) Resin adsorption: The filtered acid solution is passed through a sulfonic acid-modified styrene-based cation exchange resin tank at a flow rate of 2.5 BV / h.

[0047] (3) Evaporation and concentration: After impurity removal, the liquid is first concentrated at 35℃ to a specific gravity of 1.42, and then concentrated at 65℃ to a final specific gravity of 1.75.

[0048] Processing results: The regenerated phosphoric acid composition is as follows: specific gravity 1.75, P 260 g / kg, Cl - 6g / L, SO4² - 2.64g / L, Ca 14 mg / L, Na11mg / L, K6mg / L, Mg1.5mg / L.

[0049] Performance analysis: The phosphoric acid recovery rate reached 97.7%, and the removal rates of key metal cations (Ca, Na, K, Mg) all exceeded 99%. The quality of the regenerated acid fully met the requirements for reuse. The entire system operated stably, realizing the resource utilization and clean production of waste phosphoric acid.

[0050] Example 2: Figure 3 , Figure 4 A second embodiment of the present invention is shown.

[0051] Please see Figure 3 As shown, the activated carbon production waste phosphoric acid regeneration system based on chemical precipitation and multi-effect evaporation includes: (The system is connected in sequence via pipes and pumps / valve). A dilution and sedimentation unit is used to receive and dilute waste phosphoric acid and perform preliminary solid-liquid separation. The dilution and sedimentation unit includes a dilution and sedimentation tank with a sludge discharge outlet at the bottom. The sludge discharge outlet is connected to the solid-liquid separation unit to treat the settled sludge and the precipitate generated by chemical purification together. A chemical impurity removal unit, connected to the liquid outlet of the dilution and precipitation unit, is used to add a composite precipitant to the preliminarily purified waste phosphoric acid to remove cationic impurities. The chemical impurity removal unit includes at least one reaction vessel with stirring and online pH monitoring functions, and a metering and dosing device for adding the composite precipitant. The composite precipitant is a compound solution of soluble fluoride and soluble sulfate, wherein the fluoride can be selected from at least one of sodium fluoride and ammonium fluoride, and the sulfate can be selected from at least one of sodium sulfate and ammonium sulfate. A solid-liquid separation unit is connected to the outlet of the chemical impurity removal unit and is used to separate the precipitate produced by the chemical impurity removal unit to obtain purified acid; the solid-liquid separation unit is a plate and frame filter press, a chamber filter press, or a centrifuge. A multi-effect evaporation and concentration unit, connected to the liquid outlet of the solid-liquid separation unit, is used to perform multi-stage evaporation and concentration of the purified acid to obtain high-concentration regenerated phosphoric acid. The multi-effect evaporation and concentration unit is a two-effect or three-effect evaporator, wherein the evaporation temperature of the first effect is controlled at 70-85℃, the evaporation temperature of the second effect is controlled at 50-65℃, and the evaporation temperature of the third effect is controlled at 35-50℃. The effects of the multi-effect evaporation and concentration unit are coupled to the material pipelines through steam pipelines. The secondary steam generated by the previous effect serves as the heating source for the next effect, and the secondary steam generated by the last effect enters the condenser. The condensate recycling unit is connected to the steam condensation port of the multi-effect evaporation and concentration unit, and is used to collect condensate and reuse it in the dilution and precipitation unit.

[0052] Please see Figure 4 As shown, the method for regenerating waste phosphoric acid using activated carbon in the above system includes the following steps: (1) Dilution and preliminary precipitation steps: Mix waste phosphoric acid with the system's own condensate to dilute it, let it stand to precipitate, and then separate the supernatant. (2) Chemical precipitation impurity removal step: A composite precipitant is added to the supernatant. After the reaction, insoluble fluoride and sulfate precipitates are generated to remove potassium, calcium, sodium, and magnesium cations. The pH of the reaction system is controlled at 2.0–4.0, and the reaction time is 30–90 minutes. The amount of the composite precipitant added, calculated as fluoride ions, is 1.0–1.5 times the molar amount of total cations in the waste phosphoric acid; calculated as sulfate ions, it is 1.0–1.2 times the molar amount of calcium ions. (3) Deep solid-liquid separation step: The slurry after reaction is subjected to solid-liquid separation to obtain a purified dilute phosphoric acid solution; (4) Multi-effect evaporation and concentration step: The purified dilute phosphoric acid solution is sent to a multi-effect evaporation device for concentration to obtain regenerated phosphoric acid with a specific gravity that meets the requirements for reuse; (5) Condensate reuse step: Collect the condensate generated during the evaporation process and return it to the dilution and preliminary sedimentation step as dilution water.

[0053] A specific implementation of Example 2: Waste phosphoric acid regeneration project of an activated carbon plant in Fujian. The system in this embodiment includes a dilution sedimentation tank 1, a chemical purification reaction vessel 2, a plate and frame filter press 3, a purified acid storage tank 4, a double-effect evaporator (including a first-effect evaporator 5a and a second-effect evaporator 5b), a regenerated acid storage tank 6, and a condensate storage tank 7.

[0054] The object of treatment was waste phosphoric acid from an activated carbon plant in Fujian Province, and its composition was the same as that of the first embodiment: specific gravity 1.75, P 266 g / kg, Ca 1.6 g / L, Na 1 g / L, K 5.4 g / L, Mg 0.7 g / L.

[0055] The specific steps for processing using the system and method of this invention are as follows: (1) Removing impurities by chemical precipitation: In a chemical purification reaction vessel, a composite precipitant consisting of sodium fluoride and sodium sulfate is added to the supernatant; the pH is controlled at 3.0, and the reaction is carried out for 60 minutes; (2) Use a composite precipitant and control the acidic environment: fluoride ions and K + Na + Mg 2+ Fluoride precipitate forms, sulfate ions react with Ca 2+ Calcium sulfate precipitate forms; under acidic conditions of pH 3.0, phosphate ions mainly react as H3PO4 or H2PO4. - It exists in a form that does not easily form phosphate precipitates; (3) A two-effect evaporation system is adopted: the first effect is heated by live steam, and the temperature is controlled at 80℃; the secondary steam generated therefrom is used as the heat source for the second effect, and the temperature is controlled at 60℃. (4) Integrated solid-liquid separation: The bottom sludge from the dilution sedimentation tank and the slurry from the chemical impurity removal reactor are fed together into a plate and frame filter press for filtration; (5) Full recycling of condensate: All condensate generated by the double-effect evaporator is collected in a condensate storage tank and used entirely for the dilution of the initial waste phosphoric acid.

[0056] After the above process, the final regenerated acid composition is: specific gravity 1.75, P 261g / kg, Ca 25mg / L, Na 20mg / L, K 15mg / L, Mg 3mg / L; all indicators meet or even exceed the treatment effect of the original resin adsorption method, and fully meet the requirements for reuse in activated carbon production.

[0057] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A device for regenerating waste phosphoric acid from activated carbon production, characterized in that, The system includes a dilution sedimentation tank connected in sequence via pipelines for receiving and diluting waste phosphoric acid; a transfer tank connected to the supernatant overflow outlet of the dilution sedimentation tank; an automatic fine filter connected to the transfer tank; a first storage tank connected to the filtrate outlet of the automatic fine filter; a resin tank connected to the first storage tank and filled with cation exchange resin; a post-purification storage tank connected to the outlet of the resin tank; a two-stage evaporation and concentration unit connected to the post-purification storage tank for stepwise concentration of phosphoric acid; and a condensate storage tank connected to the condensate outlet of the two-stage evaporation and concentration unit and returned to the dilution sedimentation tank via pipelines.

2. The activated carbon production waste phosphoric acid regeneration device according to claim 1, characterized in that, The two-stage evaporation and concentration unit includes a low-temperature evaporator and a high-temperature evaporator connected in series. The outlet of the low-temperature evaporator is connected to the inlet of the high-temperature evaporator through a low-temperature acid storage tank. The operating temperature range of the low-temperature evaporator is 30–40°C, and the operating temperature range of the high-temperature evaporator is 60–70°C. Both the low-temperature evaporator and the high-temperature evaporator adopt a combined cooling and heating system. The condensate outlets of both the low-temperature evaporator and the high-temperature evaporator are connected to the condensate storage tank.

3. The activated carbon production waste phosphoric acid regeneration device according to claim 1, characterized in that, The dilution sedimentation tank is equipped with a stirrer and a level gauge. Its bottom slag discharge port is connected to a plate and frame filter press, and the filtrate outlet of the plate and frame filter press is connected to the transfer tank. A water pump is installed between the transfer tank and the automatic fine filter. A metering pump is installed between the storage tank and the resin tank. Corrosion-resistant pumps are installed at the discharge ports of both the low-temperature evaporator and the high-temperature evaporator. A corrosion-resistant pump is installed between the condensate storage tank and the dilution sedimentation tank. A feed valve is installed between the impurity-removed storage tank and the low-temperature machine. A feed valve is installed between the low-temperature acid storage tank and the high-temperature machine. The resin tank is a full-bed type with a diameter-to-height ratio of 1:1 to 1:3, and is equipped with a pure water tank, an acid washing tank, and an alkali washing tank. The cation exchange resin is a styrene-based cation exchange resin modified with functional groups. The cations in the waste phosphoric acid include K, Ca, Na, and Mg, with a removal rate of not less than 90%. The functional groups are selected from at least one of sulfonic acid groups, carboxylic acid groups, or phosphate groups.

4. A process for producing waste phosphoric acid regeneration using activated carbon employing any one of the apparatuses described in claims 1 to 3, characterized in that, Includes the following steps: (1) Dilution, precipitation and filtration: Use condensate from the condensate storage tank to dilute the waste phosphoric acid to a specific gravity of 1.15 to 1.

25. After settling, take the supernatant for precision filtration. (2) Resin adsorption for impurity removal: The filtered liquid obtained in step (1) is pumped into a resin tank to remove the metal cations and obtain the impurity-removed liquid. (3) Two-stage evaporation and concentration: The purified liquid obtained in step (2) is subjected to low-temperature evaporation and high-temperature evaporation in sequence to concentrate it into regenerated phosphoric acid, and the condensate generated by evaporation is recovered to the condensate storage tank and reused in step (1).

5. The activated carbon production waste phosphoric acid regeneration process of the device according to claim 4, characterized in that, In step (1), the specific preparation steps of dilution precipitation and filtration further include: (1.1) Measure the specific gravity of waste phosphoric acid, calculate the amount of water to be added based on the specific gravity, and use a pump to transport the condensate and waste phosphoric acid generated by low-temperature evaporation to the dilution sedimentation tank and mix them evenly. (1.2) Let the well-mixed waste phosphoric acid stand for 4–8 h; (1.3) The supernatant after settling is overflowed into the transfer tank and then pumped into an automatic fine filter for precision filtration to obtain diluted waste phosphoric acid; (1.4) The concentrated liquid produced by precision filtration is discharged into the dilution sedimentation tank. When the sedimentation layer in the dilution sedimentation tank reaches a certain height, it is discharged and filtered by plate and frame filter press. The filtrate enters the transfer tank and the filter residue is returned to the process to recover carbon. The precision filtration has a filtration accuracy of 500nm to 1000nm; the settling time is 4 to 8 hours; the concentrated liquid after filtration is returned to the dilution settling tank, the sediment is filtered by plate and frame filter press, the filtrate enters the transfer tank, and the filter residue is recycled carbon.

6. The activated carbon production waste phosphoric acid regeneration process of the apparatus according to claim 4, characterized in that, In step (2), the specific preparation steps for resin adsorption and impurity removal further include: (2.1) Resin filling: The resin tank is made into a full-bed form with a diameter-to-height ratio of 1:1 to 1:

3. The resin tank is filled with resin according to the resin expansion coefficient. (2.2) Pickling and regeneration: Acid is fed in at a flow rate of 2-3 BV / h, and the acid volume is 2-3 BV. The acid used can be sulfuric acid or hydrochloric acid, wherein the concentration of sulfuric acid is 8-10% or 15-20%, and the concentration of hydrochloric acid is 7-10%. (2.3) Water washing: Pure water is introduced at a flow rate of 3-5 BV / h, and the amount of pure water introduced is 3-5 BV, so that the concentration of sulfate or chloride ions in the effluent is <100 mg / L. (2.4) Sample injection: Inject the sample at a flow rate of 2-3 BV / h. Measure the total cation concentration before the sample enters the resin. Take a portion of the effluent after the sample enters the resin and measure the total cation concentration. When the total cation concentration of the effluent is close to that of the raw water, stop the injection of raw water and obtain the purified solution. Calculate the cation exchange capacity of the cation resin. (2.5) Cleaning the resin: Introduce pure water at a flow rate of 3-5 BV / h, with a pure water volume of 1-2 BV; (2.6) Repeat steps (2.2) and (2.3) in sequence; (2.7) When the resin adsorption capacity decreases, it is regenerated with 1-5% sodium hydroxide solution; The resin is a functionally modified styrene-based cation exchange resin, including sulfonic acid groups, carboxylic acid groups, and phosphate groups.

7. The activated carbon production waste phosphoric acid regeneration process of the apparatus according to claim 4, characterized in that, In step (3), the low-temperature evaporation includes low-temperature evaporation and high-temperature evaporation, wherein the low-temperature evaporation temperature is 30–40°C; the high-temperature evaporation temperature is 60–70°C; the specific steps of the low-temperature evaporation include: (3.1) The impurity-removed liquid is transported to the cryogenic machine through the feed valve and evaporated and concentrated at a temperature of 30-40℃. After being concentrated to a specific gravity of 1.4-1.45, the concentrated liquid is discharged through the discharge valve and pump and enters the cryogenic acid collection tank to obtain cryogenic acid. The condensate is discharged through the top and enters the condensate collection tank. (3.2) The low-temperature acid is transported to the high-temperature machine through the feed valve and evaporated and concentrated at a temperature of 60-70℃. After being concentrated to a specific gravity of 1.75, the concentrated liquid is discharged through the discharge valve and pump and enters the regenerated acid collection tank to obtain regenerated acid. The condensate is discharged through the top and enters the condensate collection tank. (3.3) The condensate generated by the low-temperature machine and the high-temperature machine is collected in a condensate collection tank and used to dilute the waste phosphoric acid instead of pure water.

8. A system for regenerating waste phosphoric acid from activated carbon based on chemical precipitation and multi-effect evaporation, characterized in that, Including those connected in sequence via pipes and pumps / valve: The dilution and precipitation unit is used to receive and dilute waste phosphoric acid and perform preliminary solid-liquid separation. A chemical impurity removal unit, connected to the liquid outlet of the dilution and precipitation unit, is used to add a composite precipitant to the preliminarily purified waste phosphoric acid to remove cationic impurities. A solid-liquid separation unit is connected to the outlet of the chemical purification unit and is used to separate the precipitate produced by the chemical purification unit to obtain purified acid; A multi-effect evaporation and concentration unit is connected to the liquid outlet of the solid-liquid separation unit and is used to perform multi-stage evaporation and concentration of the purified acid to obtain high-concentration regenerated phosphoric acid. The condensate recycling unit is connected to the steam condensation port of the multi-effect evaporation and concentration unit, and is used to collect condensate and reuse it in the dilution and precipitation unit.

9. The activated carbon production waste phosphoric acid regeneration system based on chemical precipitation and multi-effect evaporation according to claim 8, characterized in that, The chemical impurity removal unit includes at least one reaction vessel with stirring and online pH monitoring functions, and a metering and dosing device for adding the composite precipitant; The composite precipitant is a compound solution of soluble fluoride and soluble sulfate, wherein the fluoride is selected from at least one of sodium fluoride and ammonium fluoride, and the sulfate is selected from at least one of sodium sulfate and ammonium sulfate. The solid-liquid separation unit is a plate and frame filter press, a chamber filter press, or a centrifuge; The multi-effect evaporation and concentration unit is a two-effect or three-effect evaporator, wherein the evaporation temperature of the first effect is controlled at 70-85℃, the evaporation temperature of the second effect is controlled at 50-65℃, and the evaporation temperature of the third effect is controlled at 35-50℃. The effects of the multi-effect evaporation and concentration unit are coupled to the material pipelines through steam pipelines. The secondary steam generated by the previous effect serves as the heating source for the next effect, and the secondary steam generated by the last effect enters the condenser. The dilution and sedimentation unit includes a dilution and sedimentation tank with a sludge discharge outlet at the bottom. The sludge discharge outlet is connected to the solid-liquid separation unit to treat the settled sludge and the precipitate generated by chemical purification together.

10. A method for producing waste phosphoric acid regeneration using activated carbon from the system of claim 8, characterized in that, Includes the following steps: (1) Dilution and preliminary precipitation steps: Mix waste phosphoric acid with the system's own condensate to dilute it, let it stand to precipitate, and then separate the supernatant. (2) Chemical precipitation impurity removal step: A composite precipitant is added to the supernatant. After the reaction, insoluble fluoride and sulfate precipitates are generated to remove potassium, calcium, sodium, and magnesium cations. The pH of the reaction system is controlled at 2.0–4.0, and the reaction time is 30–90 minutes. The amount of the composite precipitant added, calculated as fluoride ions, is 1.0–1.5 times the molar amount of total cations in the waste phosphoric acid; calculated as sulfate ions, it is 1.0–1.2 times the molar amount of calcium ions. (3) Deep solid-liquid separation step: The slurry after reaction is subjected to solid-liquid separation to obtain a purified dilute phosphoric acid solution; (4) Multi-effect evaporation and concentration step: The purified dilute phosphoric acid solution is sent to a multi-effect evaporation device for concentration to obtain regenerated phosphoric acid with a specific gravity that meets the requirements for reuse; (5) Condensate reuse step: Collect the condensate generated during the evaporation process and return it to the dilution and preliminary sedimentation step as dilution water.

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