A high efficiency cleaning method of fine mud-adhering granular activated carbon

Abstract

The application discloses a kind of high-efficiency cleaning methods of fine mud-adhered granular activated carbon, and relates to the field of adsorption separation technology.The method comprises the following steps: immersing granular activated carbon in a first aqueous medium, alternately performing pressure swing treatment by reducing pressure and increasing pressure, and discharging the medium containing fine mud that falls off;then, the activated carbon is cleaned by pulse ultrasonic cleaning using a second aqueous medium, at least two different ultrasonic frequencies are used in the cleaning process, and the medium is synchronously circulated, extracted, separated from fine mud and returned;finally, the activated carbon is treated with a final cleaning solution containing tetrasodium glutamate diacetate and sodium gluconate, and then washed with water to obtain cleaned granular activated carbon.By the synergistic effect of pressure disturbance, multi-frequency pulse ultrasonic, circulating mud removal and chelation cleaning, fine mud adhered to the surface and pores of the activated carbon can be efficiently removed, and the adsorption performance can be restored.The process is efficient and has good cleaning effect.

Description

Technical Field

[0001] This invention relates to the field of adsorption and separation technology, specifically to a highly efficient cleaning method for granular activated carbon adhering to fine mud. Background Technology

[0002] Granular activated carbon is characterized by its well-developed pore structure, large specific surface area, strong adsorption capacity, and ease of solid-liquid separation. It is widely used in water treatment, hydrometallurgy, chemical purification, and material decolorization. During use and transportation, granular activated carbon easily comes into contact with slurries containing clay minerals, quartz powder, metal oxides, and other fine solid particles. This causes fine mud to gradually adhere to the surface of the granular activated carbon and enter its fissures and the entrances of larger pores.

[0003] The adhesion of fine clay to the surface of granular activated carbon is not formed by a single action. Some fine clay enters the depressions and fissures on the particle surface through liquid flow, forming mechanical blockages; smaller clay particles may also adhere to the activated carbon surface under the influence of van der Waals forces, electrostatic interactions, and interfacial water films. When the system contains polyvalent metal ions such as calcium, magnesium, iron, or aluminum, these ions may also form bridging structures between the fine clay and the activated carbon surface, making the fine clay layer more compact and stable. Therefore, the adhered fine clay typically includes a loose layer that is easily detached, a blockage layer located in depressions, and a relatively firmly bonded interfacial adhesion layer.

[0004] Fine sludge buildup can clog the external pores of granular activated carbon, increasing the mass transfer resistance of adsorbates into the internal channels and affecting the effective adsorption area. A continuous increase in fine sludge content can also lead to increased pressure drop in the activated carbon bed, uneven fluid distribution, difficulties in solid-liquid separation, and increased subsequent regeneration load. For granular activated carbon that needs to be recycled, failure to remove surface fine sludge in a timely manner will not only reduce its utilization efficiency but also increase the amount of activated carbon replenishment, cleaning water consumption, and wastewater treatment load.

[0005] When using a single water flow for rinsing, the cleaning effect is mainly concentrated on the outer surface of the particles, making it difficult to fully reach cracks, depressions, and pore entrances. Therefore, its ability to remove embedded fine mud and firmly bonded fine mud layers is limited. Increasing the water flow rate, extending the stirring time, or enhancing the air-water scrubbing intensity can increase the amount of fine mud removed, but it will also intensify the collision and friction between the activated carbon particles, causing carbon particle damage, increased carbon powder, and loss of effective carbon. When using ultrasonic treatment alone, the sound field distribution, treatment time, and power control will also affect the cleaning uniformity; insufficient treatment intensity will result in cleaning dead zones, while excessively high treatment intensity or excessively long treatment time may increase particle wear.

[0006] Furthermore, if fine sludge that has loosened or detached from the activated carbon surface is not removed from the cleaning system in a timely manner, it will re-adhere to the surface of the granular activated carbon under the influence of localized high concentrations and multivalent ion bridging, thus limiting the synergistic effect of different cleaning methods. Although the use of strong acids, strong oxidants, or high temperatures can change the state of some pollutants, it may lead to problems such as equipment corrosion, difficulties in treating cleaning wastewater, increased energy consumption, and changes in the surface properties of activated carbon. Therefore, it is not suitable for low-loss cleaning processes aimed solely at removing inorganic fine sludge.

[0007] Therefore, it is necessary to provide a highly efficient cleaning method for granular activated carbon with adhering fine mud. Under relatively mild temperature and chemical conditions, the force is transferred to the cracks and pore entrances on the particle surface to remove fine mud with different adhesion strengths in stages, and to separate the fine mud that has been detached in time. At the same time, the re-adhesion caused by polyvalent ion bridging is reduced, so as to balance the cleaning effect, particle integrity and the subsequent recycling performance of activated carbon. Summary of the Invention

[0008] The purpose of this invention is to provide a highly efficient cleaning method for granular activated carbon adhering to fine mud, so as to solve the technical problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A highly efficient cleaning method for granular activated carbon adhering to fine mud includes the following steps: The granular activated carbon to be cleaned is immersed in a first aqueous medium, and the system containing the granular activated carbon is alternately subjected to a depressurization state and a pressurization state for multiple pressure swing cycles, and at least part of the first aqueous medium containing detached fine mud is discharged. The granular activated carbon after pressure oscillation treatment is subjected to pulsed ultrasonic cleaning using a second aqueous medium. The pulsed ultrasonic cleaning employs at least two different ultrasonic frequencies. During the ultrasonic cleaning process, the second aqueous medium is extracted, fine sludge is separated, and the second aqueous medium after sludge separation is returned for further cleaning. The ultrasonically cleaned granular activated carbon was treated with a final washing solution containing tetrasodium diacetate and sodium gluconate. After the final washing solution was discharged, the granular activated carbon was washed with water to obtain the cleaned granular activated carbon.

[0010] Preferably, the minimum particle size of the granular activated carbon is not less than 0.50 mm, and the D90 of the fine mud is not greater than 75 μm; during the washing process, a limiting screen with a pore size of 0.15 to 0.25 mm is used to retain the granular activated carbon.

[0011] Preferably, before performing the pressure swing treatment, 4-6 L of the first aqueous medium is added per kilogram of dry granular activated carbon, and the mixture is soaked at 20-35°C for 5-20 minutes, and the free fine mud separated during the soaking process is discharged.

[0012] Preferably, each pressure oscillation cycle includes: Reduce the absolute pressure of the system to 45–60 kPa and maintain it for 20–40 s; After restoring the system to atmospheric pressure, increase the pressure to 0.08–0.15 MPa gauge pressure and maintain it for 20–40 seconds; and Release the system to normal pressure; The pressure transition time between adjacent pressure states is 8 seconds, and the pressure oscillation cycle is performed 8 times.

[0013] Preferably, after every two pressure swing cycles, 10% to 20% of the total amount of the first aqueous medium is discharged, and an equal volume of cleaning water is added; during the pressure swing process, the carbon bed expansion rate of the granular activated carbon is controlled within 5%.

[0014] Preferably, the pulsed ultrasonic cleaning uses two ultrasonic frequencies, 28±1kHz and 40±1kHz, to alternate. Each ultrasonic treatment cycle consists of 10s of running at 28±1kHz, 20s of running at 40±1kHz, and a 10s stop. This process is repeated for 15 ultrasonic treatment cycles.

[0015] Preferably, the effective acoustic power density of the pulsed ultrasonic cleaning is 10-20 W / L, and the temperature of the second aqueous medium is 20-35°C; during the ultrasonic cleaning process, mechanical stirring components such as impellers, grinding media, or direct impact on granular activated carbon are not used.

[0016] Preferably, during the ultrasonic cleaning process, the second aqueous medium is extracted at a flow rate of 0.3 to 0.6 times the total volume of the second aqueous medium per minute, and the extracted second aqueous medium is passed through a solid-liquid separation unit with a filtration accuracy of 5 to 20 μm. The second aqueous medium after separation of fine mud is then returned along the tangential direction of the cleaning container.

[0017] Preferably, the final washing solution uses softened water with a hardness not exceeding 1.0 mmol / L as the solvent, wherein: The concentration of tetrasodium glutamate diacetate, based on the active ingredient, is 0.25–0.50 g / L; The concentration of sodium gluconate is 0.40–0.80 g / L; The pH of the final washing solution is 8.0–10.5.

[0018] Preferably, when preparing the final washing solution, sodium gluconate is first dissolved in softened water, and then tetrasodium diacetate aqueous solution is added; the granular activated carbon is then circulated and treated with the final washing solution at 20-35°C for 8-12 minutes.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. Pressure-driven penetrating stripping primarily treats loose fine mud on the surface of granular activated carbon, as well as fine mud embedded in cracks, depressions, and pore entrances. During alternating periods of depressurization and pressurization, the washing water repeatedly enters and exits these areas, generating localized scouring and interfacial shearing, gradually disrupting the adhesion between the fine mud layer and the activated carbon surface. Compared to high-speed water flushing or intense mechanical agitation, this treatment method can deliver the cleaning action to locations difficult for conventional water flow to reach, while reducing violent collisions between activated carbon particles, creating conditions for subsequent removal of firmly bonded residual fine mud.

[0020] 2. Dual-frequency pulsed ultrasonic bypass desliming is used to further remove fine particles remaining after pressure oscillation. The lower frequency generates relatively strong cavitation, loosening residual fine mud on uneven surfaces and at fissure entrances; the higher frequency provides a more uniform sound field distribution, which is beneficial for treating fine particles dispersed on the activated carbon surface. Alternating between the two frequencies reduces cleaning dead zones caused by fixed sound field nodes, while pulsed operation helps control liquid temperature rise and activated carbon wear. The bypass filtration system simultaneously removes the detached fine mud, preventing its continuous accumulation in the cleaning solution, ensuring the ultrasonic action remains focused on the remaining fine mud layer.

[0021] 3. A key issue to address when using two physical cleaning methods in combination is the persistent adhesion and re-aggregation of fine sludge caused by polyvalent ion bridging. Both fine sludge and granular activated carbon surfaces possess negatively charged oxygen-containing sites. Polyvalent ions in the water, such as calcium, magnesium, iron, and aluminum, can simultaneously bind to both surfaces, forming a bridging structure that makes it difficult for the fine sludge to detach completely. While pressure oscillation and pulsed ultrasound can temporarily loosen or peel off the fine sludge, they cannot eliminate the residual bridging sites. After the physical action weakens, the detached fine sludge may re-adhere to the activated carbon surface or aggregate, becoming trapped again in the interparticle gaps and pore inlets. Therefore, simply increasing the intensity of physical cleaning is unlikely to further improve the cleaning effect and may even increase activated carbon wear. Polyvalent ion bridging thus becomes a key factor limiting the synergistic effect of the two physical cleaning methods. Therefore, this solution introduces tetrasodium glutamate diacetate (TGA) and sodium gluconate: TGA focuses on weakening the bridging effect of polyvalent ions such as calcium, magnesium, iron, and aluminum on the surface of fine mud and activated carbon, allowing the loosened fine mud after pressure oscillation and ultrasonic treatment to truly detach; sodium gluconate focuses on maintaining the dispersion and migration state of the detached fine mud in the final washing solution, reducing the re-aggregation of fine mud and its return to the activated carbon surface. When using TGA alone, although it can weaken ion bridging, it cannot fully guarantee that the detached fine mud remains stably dispersed before drainage; when using sodium gluconate alone, although it can improve the dispersion state of fine mud, it is insufficient in breaking down the tightly bound polyvalent ion bridging structures. When both are used together, the former is responsible for reducing the basis for continued adhesion of fine mud, and the latter is responsible for maintaining the migratory state of the detached fine mud, thus forming a continuous action path of breaking bridging—stabilizing dispersion—draining with the liquid. The absence of any component will interrupt this path, making it difficult to achieve the synergistic cleaning effect expected by this solution. Attached Figure Description

[0022] Figure 1 This is a SEM image of the dry-based adherent fine mud particle activated carbon in Example 1 of the present invention before cleaning.

[0023] Figure 2 This is a SEM image of the dry-based adherent fine mud particle activated carbon in Example 1 of the present invention after cleaning. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0025] Example 1 A highly efficient cleaning method for granular activated carbon adhering to fine mud includes the following steps: (1) Raw material preparation and impregnation: Take 10.0 kg of granular activated carbon with adhering fine mud on a dry basis. The particle size of the granular activated carbon was measured to be 0.80 mm by sieving, and the D90 of the adhering fine mud was measured to be 60 μm by laser particle size analysis. The granular activated carbon was placed into a limiting sieve basket with a pore size of 0.2 mm, and then the limiting sieve basket was placed into a sealed cleaning container with an effective volume of 100 L that could withstand vacuum and positive pressure. 55 L of cleaning water with a temperature of 30 °C and a suspended solids content of no more than 10 mg / L was added to the container to completely submerge the granular activated carbon, and it was allowed to stand for 15 min to impregnate. After impregnation, the initial washing liquid containing free fine mud was slowly discharged from the bottom of the container, and an equal volume of cleaning water was added to restore the total liquid volume in the container to 55 L.

[0026] (2) Pressure Swing Permeation Stripping: A gas phase space of approximately 15% of the effective volume of the cleaning container is maintained at the top. The inlet and outlet valves are closed, and the absolute pressure of the container is reduced to 50 kPa within 8 seconds and maintained for 35 seconds. Then, the pressure is restored to atmospheric pressure within 8 seconds, and the container pressure is increased to 0.13 MPa gauge pressure using a liquid pressurization system and maintained for 35 seconds. Finally, the pressure is released to atmospheric pressure within 8 seconds, thus constituting one pressure swing cycle. Eight pressure swing cycles are performed continuously in the above manner. After every two cycles, 7.5 L of washing liquid is discharged from the bottom of the container, and 7.5 L of cleaning water at 28°C is added. During the treatment, a limiting screen basket is used to restrict the overall movement of the granular activated carbon, controlling the carbon bed expansion rate to within 5%. After completing eight cycles, the container pressure is released, and all the first aqueous medium is discharged.

[0027] (3) Dual-frequency pulsed ultrasound and bypass desludge removal: Add 50L of cleaning water at 28℃ back into the cleaning container as the second aqueous medium, start the dual-frequency ultrasonic system, and set the effective sound power density to 18W / L. An ultrasonic treatment cycle is formed by running at 28kHz for 10s, running at 40kHz for 20s, and stopping for 10s. Perform 15 cycles continuously, for a total treatment time of 10 minutes. During ultrasonic treatment, do not use impellers or other mechanical stirring devices that directly contact the granular activated carbon. Simultaneously, extract the second aqueous medium at a flow rate of 0.5 times the total volume of the second aqueous medium per minute, allowing it to pass through a bypass filter unit with a filtration accuracy of 18μm. After removing the fine sludge, return tangentially along the container sidewall. Use cooling water to control the temperature of the second aqueous medium at 32℃. After ultrasonic treatment, stop the circulation and discharge all the second aqueous medium.

[0028] (4) Composite final wash and water wash: Take another 40L of softened water with a hardness not exceeding 1.0mmol / L and a temperature of 30℃. First, add sodium gluconate and stir until completely dissolved. Then, add a 47% (w / w) tetrasodium glutamate diacetate aqueous solution to make the concentration of sodium gluconate in the final wash solution 0.7g / L and the effective component concentration of tetrasodium glutamate diacetate 0.45g / L. After measuring and confirming that the pH of the final wash solution is 9, add the final wash solution to the cleaning container and gently circulate it at 32℃ with a flow rate of 12L / min for 11min. During the circulation, turn off the ultrasonic system. After the treatment is completed, drain the final wash solution within 2min and then replace the granular activated carbon with softened water for water washing. When the carbon bed volume is 20L, the total amount of softened water used is 80L. Continuously monitor the effluent at the end. Stop the water washing when the turbidity is not higher than 5NTU and the increase in conductivity relative to the influent is not more than 10%. Drain the free water to obtain the cleaned wet granular activated carbon.

[0029] Example 2 A highly efficient cleaning method for granular activated carbon adhering to fine mud includes the following steps: (1) Raw material preparation and impregnation: Take 10.0 kg of granular activated carbon with adhering fine mud on a dry basis. The particle size of the granular activated carbon was measured to be 0.80 mm by sieving, and the D90 of the adhering fine mud was measured to be 60 μm by laser particle size analysis. The granular activated carbon was placed into a limiting sieve basket with a pore size of 0.2 mm, and then the limiting sieve basket was placed into a sealed cleaning container with an effective volume of 100 L that could withstand vacuum and positive pressure. 45 L of cleaning water at a temperature of 25 °C and a suspended solids content of no more than 10 mg / L was added to the container to completely submerge the granular activated carbon, and it was allowed to stand for 10 min to impregnate. After impregnation, the initial washing liquid containing free fine mud was slowly drained from the bottom of the container, and an equal volume of cleaning water was added to restore the total liquid volume in the container to 45 L.

[0030] (2) Pressure Swing Permeation Stripping: A gas phase space of approximately 15% of the effective volume of the cleaning container is maintained at the top. The inlet and outlet valves are closed, and the absolute pressure of the container is reduced to 50 kPa within 8 seconds and maintained for 25 seconds. Then, the pressure is restored to atmospheric pressure within 8 seconds, and the container pressure is increased to 0.09 MPa gauge pressure using a liquid pressurization system and maintained for 25 seconds. Finally, the pressure is released to atmospheric pressure within 8 seconds, thus constituting one pressure swing cycle. Eight pressure swing cycles are performed continuously in the above manner. After every two cycles, 7.5 L of washing liquid is discharged from the bottom of the container, and 7.5 L of cleaning water at 28°C is added. During the treatment, a limiting screen basket is used to restrict the overall movement of the granular activated carbon, controlling the carbon bed expansion rate to within 5%. After completing eight cycles, the container pressure is released, and all the first aqueous medium is discharged.

[0031] (3) Dual-frequency pulsed ultrasound and bypass desludge removal: Add 50L of cleaning water at 28℃ back into the cleaning container as the second aqueous medium, start the dual-frequency ultrasonic system, and set the effective sound power density to 12W / L. An ultrasonic treatment cycle is formed by running at 28kHz for 10s, running at 40kHz for 20s, and stopping for 10s. Perform 15 cycles continuously, for a total treatment time of 10min. During ultrasonic treatment, do not use impellers or other mechanical stirring devices that directly contact the granular activated carbon. Simultaneously, extract the second aqueous medium at a flow rate of 0.4 times the total volume of the second aqueous medium per minute, allowing it to pass through a bypass filter unit with a filtration accuracy of 8μm. After removing the fine sludge, return tangentially along the container sidewall. Use cooling water to control the temperature of the second aqueous medium at 25℃. After ultrasonic treatment, stop the circulation and discharge all the second aqueous medium.

[0032] (4) Composite final wash and water wash: Take another 40L of softened water with a hardness not exceeding 1.0mmol / L and a temperature of 30℃. First, add sodium gluconate and stir until completely dissolved. Then, add a 47% (w / w) tetrasodium glutamate diacetate aqueous solution to make the concentration of sodium gluconate in the final wash solution 0.5g / L and the effective component concentration of tetrasodium glutamate diacetate 0.3g / L. After measuring and confirming that the pH of the final wash solution is 9, add the final wash solution to the cleaning container and gently circulate it at 25℃ with a flow rate of 12L / min for 9min. During the circulation, turn off the ultrasonic system. After the treatment is completed, drain the final wash solution within 2min and then replace the granular activated carbon with softened water for water washing. When the carbon bed volume is 20L, the total amount of softened water used is 80L. Continuously monitor the effluent at the end. Stop the water washing when the turbidity is not higher than 5NTU and the increase in conductivity relative to the influent is not more than 10%. Drain the free water to obtain the cleaned wet granular activated carbon.

[0033] Example 3 A highly efficient cleaning method for granular activated carbon adhering to fine mud includes the following steps: (1) Raw material preparation and impregnation: Take 10.0 kg of granular activated carbon with adhering fine mud on a dry basis. The particle size of the granular activated carbon was measured to be 0.80 mm by sieving, and the D90 of the adhering fine mud was measured to be 60 μm by laser particle size analysis. The granular activated carbon was placed into a limiting sieve basket with a pore size of 0.2 mm, and then the limiting sieve basket was placed into a sealed cleaning container with an effective volume of 100 L that could withstand vacuum and positive pressure. 50 L of cleaning water with a temperature of 28 °C and a suspended solids content of no more than 10 mg / L was added to the container to completely submerge the granular activated carbon, and it was allowed to stand for 10 min to impregnate. After impregnation, the initial washing liquid containing free fine mud was slowly discharged from the bottom of the container, and an equal volume of cleaning water was added to restore the total liquid volume in the container to 50 L.

[0034] (2) Pressure Swing Permeation Stripping: A gas phase space of approximately 15% of the effective volume of the cleaning container is maintained at the top. The inlet and outlet valves are closed, and the absolute pressure of the container is reduced to 50 kPa within 8 seconds and maintained for 30 seconds. Then, the pressure is restored to atmospheric pressure within 8 seconds, and the container pressure is increased to 0.1 MPa gauge pressure using a liquid pressurization system and maintained for 30 seconds. Finally, the pressure is released to atmospheric pressure within 8 seconds, thus constituting one pressure swing cycle. Eight pressure swing cycles are performed continuously in the above manner. After every two cycles, 7.5 L of washing liquid is discharged from the bottom of the container, and 7.5 L of cleaning water at 28°C is added. During the treatment, a limiting screen basket is used to restrict the overall movement of the granular activated carbon, controlling the carbon bed expansion rate to within 5%. After completing eight cycles, the container pressure is released, and all the first aqueous medium is discharged.

[0035] (3) Dual-frequency pulsed ultrasound and bypass desludge removal: Add 50L of cleaning water at 28℃ back into the cleaning container as the second aqueous medium, start the dual-frequency ultrasonic system, and set the effective sound power density to 15W / L. An ultrasonic treatment cycle is formed by running at 28kHz for 10s, running at 40kHz for 20s, and stopping for 10s. Perform 15 cycles continuously, for a total treatment time of 10min. During ultrasonic treatment, do not use impellers or other mechanical stirring devices that directly contact the granular activated carbon. Simultaneously, extract the second aqueous medium at a flow rate of 0.45 times the total volume of the second aqueous medium per minute, allowing it to pass through a bypass filter unit with a filtration accuracy of 10μm. After removing the fine sludge, return tangentially along the container sidewall. Use cooling water to control the temperature of the second aqueous medium at 30℃. After ultrasonic treatment, stop the circulation and discharge all the second aqueous medium.

[0036] (4) Composite final wash and water wash: Take another 40L of softened water with a hardness not exceeding 1.0mmol / L and a temperature of 30℃. First, add sodium gluconate and stir until completely dissolved. Then, add a 47% (w / w) tetrasodium glutamate diacetate aqueous solution to make the concentration of sodium gluconate in the final wash solution 0.6g / L and the concentration of the effective component of tetrasodium glutamate diacetate 0.4g / L. After measuring and confirming that the pH of the final wash solution is 9, add the final wash solution to the cleaning container and gently circulate it at 25℃ with a flow rate of 12L / min for 10min. During the circulation, turn off the ultrasonic system. After the treatment is completed, drain the final wash solution within 2min and then replace the granular activated carbon with softened water for water washing. When the carbon bed volume is 20L, the total amount of softened water used is 80L. Continuously monitor the effluent at the end. Stop the water washing when the turbidity is not higher than 5NTU and the increase in conductivity relative to the influent is not more than 10%. Drain the free water to obtain the cleaned wet granular activated carbon.

[0037] Example 4 A highly efficient cleaning method for granular activated carbon adhering to fine mud includes the following steps: (1) Raw material preparation and impregnation: Take 10.0 kg of granular activated carbon with adhering fine mud on a dry basis. The particle size of the granular activated carbon was measured to be 0.80 mm by sieving, and the D90 of the adhering fine mud was measured to be 60 μm by laser particle size analysis. The granular activated carbon was placed into a limiting sieve basket with a pore size of 0.25 mm, and then the limiting sieve basket was placed into a sealed cleaning container with an effective volume of 100 L that could withstand vacuum and positive pressure. 60 L of cleaning water at a temperature of 35 °C with a suspended solids content of no more than 10 mg / L was added to the container to completely submerge the granular activated carbon, and it was allowed to stand for 20 min to impregnate. After impregnation, the initial washing liquid containing free fine mud was slowly discharged from the bottom of the container, and an equal volume of cleaning water was added to restore the total liquid volume in the container to 60 L.

[0038] (2) Pressure Swing Permeation Stripping: A gas phase space of approximately 15% of the effective volume of the cleaning container is maintained at the top. The inlet and outlet valves are closed, and the absolute pressure of the container is reduced to 60 kPa within 8 seconds and maintained for 40 seconds. Then, the pressure is restored to atmospheric pressure within 8 seconds, and the container pressure is increased to 0.15 MPa gauge pressure using a liquid pressurization system and maintained for 40 seconds. Finally, the pressure is released to atmospheric pressure within 8 seconds, thus constituting one pressure swing cycle. Eight pressure swing cycles are performed continuously in the above manner. After every two cycles, 7.5 L of washing liquid is discharged from the bottom of the container, and 7.5 L of cleaning water at 28°C is added. During the treatment, a limiting screen basket is used to restrict the overall movement of the granular activated carbon, controlling the carbon bed expansion rate to within 5%. After completing eight cycles, the container pressure is released, and all the first aqueous medium is discharged.

[0039] (3) Dual-frequency pulsed ultrasound and bypass desludge removal: Add 50L of cleaning water at 28℃ back into the cleaning container as the second aqueous medium, start the dual-frequency ultrasonic system, and set the effective sound power density to 20W / L. An ultrasonic treatment cycle is formed by running at 28kHz for 10s, then at 40kHz for 20s, and stopping for 10s. Perform 15 cycles continuously, for a total treatment time of 10 minutes. During ultrasonic treatment, do not use impellers or other mechanical stirring devices that directly contact the granular activated carbon. Simultaneously, extract the second aqueous medium at a flow rate of 0.6 times the total volume of the second aqueous medium per minute, allowing it to pass through a bypass filter unit with a filtration accuracy of 20μm. After removing the fine sludge, return tangentially along the container sidewall. Use cooling water to control the temperature of the second aqueous medium at 35℃. After ultrasonic treatment, stop the circulation and discharge all the second aqueous medium.

[0040] (4) Composite final wash and water wash: Take another 40L of softened water with a hardness not exceeding 1.0mmol / L and a temperature of 30℃. First, add sodium gluconate and stir until completely dissolved. Then, add a 47% (w / w) tetrasodium glutamate diacetate aqueous solution to make the concentration of sodium gluconate in the final wash solution 0.8g / L and the effective component concentration of tetrasodium glutamate diacetate 0.5g / L. After measuring and confirming that the pH of the final wash solution is 10.5, add the final wash solution to the cleaning container and gently circulate it at 35℃ with a flow rate of 12L / min for 12min. During the circulation, turn off the ultrasonic system. After the treatment is completed, drain the final wash solution within 2min and then replace the granular activated carbon with softened water for water washing. When the carbon bed volume is 20L, the total amount of softened water used is 80L. Continuously monitor the effluent at the end. Stop the water washing when the turbidity is not higher than 5NTU and the increase in conductivity relative to the influent is not more than 10%. Drain the free water to obtain the cleaned wet granular activated carbon.

[0041] Example 5 A highly efficient cleaning method for granular activated carbon adhering to fine mud includes the following steps: (1) Raw material preparation and impregnation: Take 10.0 kg of granular activated carbon with adhering fine mud on a dry basis. The particle size of the granular activated carbon was measured to be 0.80 mm by sieving, and the D90 of the adhering fine mud was measured to be 60 μm by laser particle size analysis. The granular activated carbon was placed into a limiting sieve basket with a pore size of 0.15 mm, and then the limiting sieve basket was placed into a sealed cleaning container with an effective volume of 100 L that could withstand vacuum and positive pressure. 40 L of cleaning water with a temperature of 20 °C and a suspended solids content of no more than 10 mg / L was added to the container to completely submerge the granular activated carbon, and it was allowed to stand for 5 min to impregnate. After impregnation, the initial washing liquid containing free fine mud was slowly discharged from the bottom of the container, and an equal volume of cleaning water was added to restore the total liquid volume in the container to 40 L.

[0042] (2) Pressure Swing Permeation Stripping: A gas phase space of approximately 15% of the effective volume of the cleaning container is maintained at the top. The inlet and outlet valves are closed, and the absolute pressure of the container is reduced to 45 kPa within 8 seconds and maintained for 20 seconds. Then, the pressure is restored to atmospheric pressure within 8 seconds, and the container pressure is increased to 0.08 MPa gauge pressure using a liquid pressurization system and maintained for 20 seconds. Finally, the pressure is released to atmospheric pressure within 8 seconds, thus constituting one pressure swing cycle. Eight pressure swing cycles are performed continuously in the above manner. After every two cycles, 7.5 L of washing liquid is discharged from the bottom of the container, and 7.5 L of cleaning water at 28°C is added. During the treatment, a limiting screen basket is used to restrict the overall movement of the granular activated carbon, controlling the carbon bed expansion rate to within 5%. After completing eight cycles, the container pressure is released, and all the first aqueous medium is discharged.

[0043] (3) Dual-frequency pulsed ultrasound and bypass desludge removal: Add 50L of cleaning water at 28℃ back into the cleaning container as the second aqueous medium, start the dual-frequency ultrasonic system, and set the effective sound power density to 10W / L. An ultrasonic treatment cycle is formed by running at 28kHz for 10s, running at 40kHz for 20s, and stopping for 10s. Perform 15 cycles continuously, for a total treatment time of 10min. During ultrasonic treatment, do not use impellers or other mechanical stirring devices that directly contact the granular activated carbon. Simultaneously, extract the second aqueous medium at a flow rate of 0.3 times the total volume of the second aqueous medium per minute, allowing it to pass through a bypass filter unit with a filtration accuracy of 5μm. After removing the fine sludge, return tangentially along the container sidewall. Use cooling water to control the temperature of the second aqueous medium at 20℃. After ultrasonic treatment, stop the circulation and discharge all the second aqueous medium.

[0044] (4) Composite final wash and water wash: Take another 40L of softened water with a hardness not exceeding 1.0mmol / L and a temperature of 30℃. First, add sodium gluconate and stir until completely dissolved. Then, add a 47% (w / w) tetrasodium glutamate diacetate aqueous solution to make the concentration of sodium gluconate in the final wash solution 0.4g / L and the effective component concentration of tetrasodium glutamate diacetate 0.25g / L. After measuring and confirming that the pH of the final wash solution is 8.0, add the final wash solution to the cleaning container and gently circulate it at 20℃ with a flow rate of 12L / min for 8min. During the circulation, turn off the ultrasonic system. After the treatment is completed, drain the final wash solution within 2min and then replace the granular activated carbon with softened water for water washing. When the carbon bed volume is 20L, the total amount of softened water used is 80L. Continuously monitor the effluent at the end. Stop the water washing when the turbidity is not higher than 5NTU and the increase in conductivity relative to the influent is not more than 10%. Drain the free water to obtain the cleaned wet granular activated carbon.

[0045] Comparative Example 1: Except for the elimination of the pressure swing treatment and the replacement with soaking for the same time under normal pressure, the granular activated carbon used and the remaining operating steps and process parameters were the same as in Example 5.

[0046] Comparative Example 2: Except for canceling the pulsed ultrasonic treatment and continuously circulating the second aqueous medium for the same time as in Example 5, the granular activated carbon used and the remaining operating steps and process parameters were the same as in Example 5.

[0047] Comparative Example 3: Except for simultaneously canceling the pressure swing treatment and pulse ultrasonic treatment, and replacing them with atmospheric pressure immersion and second aqueous medium circulation treatment for the same time, the granular activated carbon used and the remaining operation steps and process parameters are the same as in Example 5.

[0048] Comparative Example 4: Except for changing the alternating 28kHz and 40kHz ultrasound to a single 28kHz ultrasound, and continuously processing for 15 cycles with each cycle consisting of 30s ultrasound run and 10s stop, the granular activated carbon used and the other operating steps and process parameters were the same as in Example 5.

[0049] Comparative Example 5: Except that the extracted second aqueous medium was returned directly to the cleaning tank without passing through a 5μm bag filter during the pulsed ultrasonic cleaning process, the granular activated carbon used and the other operating steps and process parameters were the same as in Example 5.

[0050] Comparative Example 6: Except that sodium gluconate was not added to the final washing solution, which contained only 0.25 g / L tetrasodium diacetate of glutamic acid, and the pH of the final washing solution was adjusted to 8.0, the granular activated carbon used and the other operating steps and process parameters were the same as in Example 5.

[0051] Comparative Example 7: Except that tetrasodium diacetate of glutamic acid was not added to the final washing solution, which contained only 0.40 g / L sodium gluconate, and the pH of the final washing solution was adjusted to 8.0, the granular activated carbon used and the other operating steps and process parameters were the same as in Example 5.

[0052] Comparative Example 8: Except for replacing the final washing solution containing tetrasodium diacetate and sodium gluconate with softened water at pH 8.0, the granular activated carbon used and the remaining operating steps and process parameters were the same as in Example 5.

[0053] Performance testing: 1. Test of residual fine mud content and fine mud removal rate: Weigh 50.00g of granular activated carbon dried to constant weight at 105℃, add 500mL of sodium hexametaphosphate aqueous solution with a concentration of 1.00g / L, and ultrasonically disperse for 20min at 40kHz, effective sound power density of 20W / L, and liquid temperature of 30℃, then shake at 150r / min for 10min to remove residual fine mud from the surface of activated carbon; pass the mixture through a 0.15mm sieve to retain carbon particles, and extract three times consecutively under the same conditions, combine the extracts, and filter using a 0.45μm filter membrane. The solid was dried to constant weight at 05℃; the filtered solid was ignited to constant weight at 650℃. The ash mass fraction of the unadhered fine mud reference activated carbon in the same batch was determined to be 9.46%, and the ash mass fraction of the separated fine mud was determined to be 91.80%. The mass fraction of fine mud in the filtered solid was calculated based on the ash mass fraction. The residual fine mud content was calculated as "residual fine mud mass ÷ 50.00g × 100%". The fine mud removal rate was calculated as "(fine mud content before washing - residual fine mud content after washing) ÷ fine mud content before washing × 100%". The fine mud content of the granular activated carbon before washing was 8.62%.

[0054] 2. Iodine adsorption value test: The determination was carried out in accordance with GB / T 7702.7-2023. Each sample was reduced to quarters using the quartering method and prepared according to the standard requirements. The sample was pretreated with hydrochloric acid, and then a standardized iodine-potassium iodide solution was added for adsorption. After shaking and filtration, the residual iodine in the filtrate was determined by titration with a 0.1000 mol / L sodium thiosulfate standard solution. The iodine adsorption value was calculated based on the sample mass, initial iodine concentration, and adsorption equilibrium concentration. Two parallel determinations were performed for each sample, and the arithmetic mean was taken.

[0055] 3. Strength test: The test shall be conducted in accordance with GB / T 7702.3-2008. Approximately 200 mL of sample shall be placed in a drying oven at 150℃ and dried for 2 hours. After cooling, the original dust shall be removed by sieving. 50 mL of sample shall be measured and weighed. The sample shall be placed in a drum containing 5 steel balls with a diameter of 14.3 mm and the drum shall be run at 50 r / min for 5 minutes. Then the sample shall be transferred to a specified test sieve and vibrated for 5 minutes. The percentage of the mass of the sample retained on the sieve relative to the mass of the sample before treatment shall be taken as the strength of the granular activated carbon.

[0056] 4. New Particle Breakage Rate Test: Referring to the vibrating sieve method of GB / T 7702.2-1997, weigh 100.0g of dry sample, and sieve it for 5min using standard sieves with apertures of 0.50mm and 0.15mm respectively. Collect and weigh the material with a particle size of 0.15~0.50mm. Based on the ash content determination result of this particle size material, deduct the mass of residual fine mud, and subtract the mass fraction of the corresponding carbonaceous particles in the raw material before washing from the mass fraction of carbonaceous broken particles in the treated sample. The difference obtained is taken as the new particle breakage rate.

[0057] 5. Turbidity test of sludge release liquid: Weigh 20.00g of dried sample and place it in a 500mL stoppered conical flask. Add 200mL of softened water with an initial turbidity of 0.20NTU. Shake at 150r / min for 10min at 25℃. After standing for 60s, take the supernatant from 20mm below the liquid surface. Measure the turbidity of the supernatant using a scattering light turbidimeter according to HJ 1075-2019. Subtract the initial turbidity of the softened water. The result is taken as the turbidity of the sludge release liquid.

[0058] Table 1:

[0059] The fine mud removal rate of Example 5 was 88.4%, while that of Comparative Example 1 (without pressure oscillation treatment) was only 66.2%, and that of Comparative Example 2 (without pulsed ultrasound treatment) was only 64.0%. Furthermore, Comparative Example 3 (without both pressure oscillation and pulsed ultrasound treatment) further reduced the rate to 47.6%. Based on Comparative Example 3, adding pulsed ultrasound treatment alone increased the fine mud removal rate by 18.6 percentage points, and adding pressure oscillation treatment alone increased it by 16.4 percentage points. The expected removal rate obtained by simply adding the two effects was 82.6%, while Example 5 achieved 88.4%, which is 5.8 percentage points higher. This indicates that the pre-loosening effect of pressure oscillation on the fine mud in cracks and depressions can improve the efficiency of subsequent ultrasonic stripping.

[0060] In Comparative Example 4, after changing the alternating dual-frequency ultrasound to a single 28kHz ultrasound, the fine sludge removal rate decreased from 88.4% in Example 5 to 83.9%, and the turbidity of the sludge release liquid increased from 8.5 NTU to 13.6 NTU, indicating that alternating operation of 28kHz and 40kHz is beneficial to reducing the cleaning dead zones caused by the fixed sound field. In Comparative Example 5, after removing the bypass filter, the fine sludge removal rate decreased to 80.2%, the residual fine sludge content increased to 1.71%, and the turbidity of the sludge release liquid increased to 18.4 NTU, indicating that timely separation of the detached fine sludge can reduce the re-adhesion of fine sludge during the circulating cleaning process.

[0061] Comparative Example 8, without the addition of tetrasodium glutamate diacetate and sodium gluconate, achieved a fine sludge removal rate of 73.3%; Comparative Example 6, with only tetrasodium glutamate diacetate, achieved a fine sludge removal rate of 78.9%; Comparative Example 7, with only sodium gluconate, achieved a fine sludge removal rate of 76.5%; and Example 5, with the simultaneous addition of both tetrasodium glutamate diacetate and sodium gluconate, achieved a fine sludge removal rate of 88.4%. Based on Comparative Example 8, tetrasodium glutamate diacetate alone increased the fine sludge removal rate by 5.6 percentage points, and sodium gluconate alone increased it by 3.2 percentage points. The expected removal rate obtained by simply adding the two effects was 82.1%, which was 6.3 percentage points higher than that of Example 5. Furthermore, the expected residual fine sludge content calculated based on the individual effects of the two substances was 1.55%, while the residual fine sludge content in Example 5 was 1.00%, indicating that the combined use of the two substances produced a significant synergistic cleaning effect.

[0062] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the essence and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A highly efficient cleaning method for granular activated carbon adhering to fine mud, characterized in that, Includes the following steps: The granular activated carbon to be cleaned is immersed in a first aqueous medium, and the system containing the granular activated carbon is alternately subjected to a depressurization state and a pressurization state for multiple pressure swing cycles, and at least part of the first aqueous medium containing detached fine mud is discharged. The granular activated carbon after pressure oscillation treatment is subjected to pulsed ultrasonic cleaning using a second aqueous medium. The pulsed ultrasonic cleaning uses at least two different ultrasonic frequencies. During the ultrasonic cleaning process, the second aqueous medium is extracted, the fine mud is separated, and the second aqueous medium after the fine mud is separated is returned to continue cleaning. The granular activated carbon after ultrasonic cleaning is treated with a final washing solution containing tetrasodium diacetate and sodium gluconate. After the final washing solution is discharged, it is washed with water to obtain the cleaned granular activated carbon. Each pressure oscillation cycle includes: reducing the absolute pressure of the system to 45–60 kPa and holding it for 20–40 s; restoring the system to atmospheric pressure and then increasing the pressure to 0.08–0.15 MPa gauge pressure and holding it for 20–40 s; and releasing the system to atmospheric pressure; wherein the pressure transition time between adjacent pressure states is 8 s, and the pressure oscillation cycle is performed 8 times; during the pressure oscillation, the carbon bed expansion rate of the granular activated carbon is controlled within 5%; The pulsed ultrasonic cleaning uses two ultrasonic frequencies, 28±1kHz and 40±1kHz, to alternate. Each ultrasonic treatment cycle consists of 10 seconds of operation at 28±1kHz, 20 seconds of operation at 40±1kHz, and a 10-second pause. This cycle is repeated for 15 consecutive times. The effective acoustic power density of the pulsed ultrasonic cleaning is 10–20 W / L, and the temperature of the second aqueous medium is 20–35℃. No impellers, grinding media, or mechanical agitators that directly impact the granular activated carbon are used during the ultrasonic cleaning process. During the ultrasonic cleaning process, the second aqueous medium is extracted at a flow rate of 0.3 to 0.6 times the total volume of the second aqueous medium per minute. The extracted second aqueous medium is then passed through a solid-liquid separation unit with a filtration accuracy of 5 to 20 μm, and the second aqueous medium after separating the fine mud is returned along the tangential direction of the cleaning container. The final washing solution uses softened water with a hardness not exceeding 1.0 mmol / L as the solvent, wherein: based on the effective ingredients, the concentration of tetrasodium glutamate diacetate is 0.25–0.50 g / L; the concentration of sodium gluconate is 0.40–0.80 g / L; and the pH of the final washing solution is 8.0–10.

5.

2. The efficient cleaning method for granular activated carbon adhering to fine mud according to claim 1, characterized in that, The minimum particle size of the granular activated carbon is not less than 0.50 mm, and the D90 of the fine mud is not greater than 75 μm; during the washing process, a limiting screen with a pore size of 0.15 to 0.25 mm is used to retain the granular activated carbon.

3. The efficient cleaning method for granular activated carbon adhering to fine mud according to claim 1, characterized in that, Before performing the pressure swing treatment, add 4-6 L of the first aqueous medium per kilogram of dry granular activated carbon, soak at 20-35°C for 5-20 minutes, and drain the free fine mud separated during the soaking process.

4. The efficient cleaning method for granular activated carbon adhering to fine mud according to claim 1, characterized in that, When preparing the final washing solution, first dissolve sodium gluconate in softened water, then add tetrasodium diacetate diglutamate aqueous solution; use the final washing solution to circulate and treat granular activated carbon at 20-35℃ for 8-12 minutes.

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