Method for regenerating adsorbent

Abstract

To provide a regeneration method of an adsorbent, by which regeneration efficiency is enhanced and regeneration cost is reduced.SOLUTION: A regeneration method of an adsorbent comprises the step of immersing the adsorbent in washing water containing hydrogen peroxide for 35 to 60 minutes while bubbles are injected. The regeneration method further comprises the step of heating the adsorbent to a temperature in the range of 300°C to 450°C.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for regenerating an adsorbent. [Background technology]

[0002] Porous adsorbents such as activated carbon are used to remove pollutants that pollute the air, such as harmful gases like nitrogen dioxide (NO2), particulate matter like soot, and oils like oil mist, contained in exhaust gases emitted from factories, automobiles, homes, etc. Porous adsorbents remove pollutants from exhaust gases by allowing the pollutants to adhere to their pores. The adsorbent's adsorption capacity decreases as pollutants adhere to the pores, but by removing the adhered pollutants and regenerating the adsorbent, its adsorption capacity can be restored and it can be reused.

[0003] As a method for regenerating conventional adsorbents, a wet regeneration method has been proposed in which the adsorbent is immersed twice in cleaning water containing hydrogen peroxide while aeration is repeated to achieve the desired recovery amount (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-103654 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional method described above, the immersion is repeated twice, which requires the cleaning solution to be replaced and rinsing to be performed after each immersion. This requires a lot of work, which reduces the efficiency of regeneration and increases the cost of regeneration. [Means for solving the problem]

[0006] The present invention has been made in view of the above-mentioned problems, and provides a method for regenerating an adsorbent that adsorbs pollutants, the method comprising: A regeneration method is provided which includes the step of immersing the adsorbent in cleaning water containing hydrogen peroxide for 35 to 60 minutes while injecting air bubbles into the water. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve the regeneration efficiency and reduce the regeneration cost. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an air purification system. [Figure 2] FIG. 1 is a diagram showing an example of the configuration of a denitrification device provided in an air purification system. [Figure 3] FIG. 1 is a diagram showing an example of the configuration of an apparatus for regenerating an adsorbent. [Figure 4] 10 is a flowchart showing an example of an operation for regenerating an adsorbent. [Figure 5] FIG. 10 is a graph showing the relationship between the recovery amount of the pore distribution of the adsorbent and the immersion time. [Figure 6] 10 is a flowchart showing another example of the process of regenerating an adsorbent. [Figure 7] FIG. 10 is a diagram showing test results regarding adsorption performance. [Figure 8] A diagram showing the effect of heating after scrubbing. [Figure 9] FIG. 1 is a diagram showing an example of the configuration of a test device for conducting a test to confirm the adsorption performance of a regenerated adsorbent. [Figure 10] FIG. 10 shows the results of a test to confirm the adsorption performance of the regenerated adsorbent. DETAILED DESCRIPTION OF THE INVENTION

[0009] The adsorbent regeneration method of the present invention is a method for removing adsorbed pollutants from a porous adsorbent that adsorbs and removes air pollutants, and regenerating the adsorbent so that it can be reused. Air pollutants include harmful gases such as nitrogen dioxide (NO2) contained in exhaust gases emitted from factories, automobiles, homes, etc., particulate matter such as soot, and oils such as oil mist. Activated carbon, silica, zeolite, etc. can be used as the porous adsorbent, but other porous materials are also usable.

[0010] Adsorbents that adsorb and remove pollutants that pollute the air can be used in air purification systems installed in ventilation openings of road tunnels, for example. Note that air purification systems are one example of devices and systems in which adsorbents are used, and systems and devices in which adsorbents are used are not limited to air purification systems.

[0011] FIG. 1 shows an example of the configuration of an air purification system installed at a ventilation opening of a road tunnel. In a road tunnel 10, vehicles 11 travel on a road constructed inside the tunnel, and exhaust gases from the vehicles 11 are emitted and accumulate after burning fuels such as gasoline or diesel. The road tunnel 10 is provided with a ventilation opening that connects the inside of the tunnel to the outside and exhausts the exhaust gases accumulated inside the tunnel to the outside and takes in fresh air from the outside. The ventilation opening includes a ventilation passage 12 and a ventilation tower 13 connected to the ventilation passage 12, and an air purification system is installed in the ventilation passage 12. Therefore, the exhaust gases inside the tunnel have pollutants removed by the air purification system before being released to the outside from the ventilation tower 13.

[0012] The air purification system includes a ventilation fan 14, a dust collector 15, a denitration device 16, a silencer 17, and auxiliary equipment 18. The ventilation fan 14 draws in exhaust gas from inside the road tunnel 10. The dust collector 15 charges particulate matter in the exhaust gas drawn in by the ventilation fan 14, attracts the charged particulate matter to a dust collecting electrode, and causes it to adhere to the collecting electrode, thereby removing the particulate matter from the air.

[0013] The denitration device 16 removes nitric oxide (NO) and NO2 from the exhaust gas using an adsorbent. The denitration device 16 may be a device that primarily removes NO2, or a device that removes both NO and NO2. A device that removes both NO and NO2 includes an oxidation device that oxidizes NO to generate NO2, a humidification device that improves the adsorption performance of NO2, and an adsorption device that uses an adsorbent to adsorb and remove NO2. A device that primarily removes NO2 does not include an oxidation device and is composed of a humidification device and an adsorption device.

[0014] The silencer 17 reduces the noise of exhaust gases being emitted to the outside. The auxiliary equipment 18 includes a power supply, a control panel, etc., and is used to drive and control the ventilation fan 14, the dust collector 15, and the denitration device 16.

[0015] An apparatus that primarily removes NO2 will be described with reference to Fig. 2. The denitration apparatus 16 includes a humidification apparatus 20 and an adsorption apparatus 21.

[0016] The humidifier 20 humidifies the exhaust gas flowing through the ventilation passage 12. Humidifying the exhaust gas enables water to undergo capillary condensation in the pores of the adsorbent provided in the adsorption device 21. The water that has undergone capillary condensation in the pores absorbs NO2 in the exhaust gas, which causes liquid-phase adsorption and improves adsorption performance.

[0017] The humidifier 20 includes a spray nozzle, a water tank, and a water supply pump. The water tank contains water, and the water supply pump supplies the water contained in the water tank to the spray nozzle. The spray nozzle sprays water into the exhaust gas in the form of a mist.

[0018] The adsorption device 21 includes one or more adsorption layers 22 filled with adsorbents. The exhaust gas humidified by the humidifier 20 is sent to the adsorption device 21, and as it passes through the adsorption layer 22, NO2 in the exhaust gas is adsorbed by the adsorbents and removed from the exhaust gas.

[0019] The adsorbent may be a porous material such as activated carbon formed into pellets, although the shape of the adsorbent is not limited to pellets.

[0020] The adsorption bed 22 is disposed within an adsorption vessel 23, which has a supply port 24 for receiving exhaust gas on one side and an exhaust port 25 for discharging exhaust gas on the other side. The supply port 24 is connected to the bottom of the adsorption bed 22, and the exhaust port 25 is connected to the top of the adsorption bed 22. Thus, exhaust gas is supplied to the bottom of the adsorption bed 22 through a passage 26 that connects from the supply port 24 to the bottom of the adsorption bed 22. The adsorption bed 22 is constructed by packing an adsorbent onto a perforated plate or mesh having numerous holes through which the adsorbent cannot pass. The exhaust gas supplied to the bottom of the adsorption bed 22 passes through the numerous holes in the perforated plate or mesh, passes to the top of the adsorption bed 22 while coming into contact with the adsorbent, and is then discharged from the exhaust port 25 through a passage 27 that connects to the exhaust port 25.

[0021] The adsorption device 21 is provided with a damper at the supply port 24 of the adsorption vessel 23 for opening and closing the supply port 24. When the adsorption device 21 has multiple adsorption beds 22, it has multiple adsorption vessels 23 and therefore multiple supply ports 24, and each supply port 24 is provided with a damper.

[0022] The adsorption device 21 includes a regenerating solution tank 28 and a regenerating solution pump 29. The adsorption device 21 supplies the regenerating solution stored in the regenerating solution tank 28 to the adsorption vessel 23 by the regenerating solution pump 29 every time a predetermined adsorption time has elapsed during which exhaust gas is supplied to the adsorption layer 22 and NO2 in the exhaust gas is adsorbed, or at any time. The regenerating solution is supplied to a height sufficient to immerse the adsorbent. The adsorbent is regenerated by being immersed in the regenerating solution for a certain period of time.

[0023] The regenerating solution can be an aqueous solution of sodium sulfite (Na2SO3), which chemically reacts with NO2, to remove it from the adsorbent by chemically reacting with the NO2 adsorbed on the adsorbent. The concentration of Na2SO3 can be, for example, 1% by mass. Unless otherwise specified, hereinafter, when simply indicated as % it means % by mass. Note that the regenerating solution is not limited to an aqueous solution of Na2SO3, as long as it is a substance that chemically reacts with NO2.

[0024] The adsorption device 21 can switch between adsorption and regeneration by switching the damper between open and closed. Specifically, the adsorption device 21 closes the damper to stop the flow of exhaust gas, and then supplies a regenerating solution to the adsorption vessel 23 to regenerate the adsorbent. After the adsorption device 21 has completed regeneration of the adsorbent, the adsorption device 21 opens the damper, receives exhaust gas, and adsorbs NO2 in the exhaust gas. Since the adsorption device 21 regenerates the adsorbent without stopping the operation of the air purification system, if the adsorption device 21 has multiple stages of adsorption layers 22, the adsorption layer 22 in each stage can be regenerated one by one in sequence.

[0025] By the way, adsorbents can be thought of as being able to be used forever by repeatedly regenerating them. However, exhaust gases contain oil, and as this oil accumulates, it covers the pores and surface of the adsorbent, reducing its performance. This is because the oil does not dissolve in the regeneration solution. For this reason, when the adsorbent no longer achieves the desired adsorption performance after long-term use, it must be disposed of as industrial waste.

[0026] The oil adhering to the adsorbent can be removed by the method (conventional method) described in Patent Document 1. This restores the adsorption performance of the adsorbent, making it possible to reuse it.

[0027] In conventional methods, cleaning water is placed in a first container, and the pH is adjusted to 3-5 with an acidic solution such as hydrochloric acid, after which hydrogen peroxide (H2O2) is added. Used adsorbent is placed in the cleaning water to which H2O2 has been added. In the first container, the adsorbent is immersed for 15-30 minutes while aeration is performed by supplying air bubbles to the cleaning water. During this time, oil floating on the surface of the water is removed, and the adsorbent is recovered from the cleaning water 15-30 minutes after the start of immersion.

[0028] Thereafter, the cleaning water is poured into a second container, the pH is adjusted to 3 to 5, and the adsorbent recovered from the cleaning water in the first container is poured in. In the second container, the adsorbent is immersed for 15 to 30 minutes while aerating the cleaning water by supplying air bubbles to it, and then rinsed.

[0029] It has been found that immersion twice in cleaning water with added H2O2 can achieve approximately twice the cleaning effect compared to immersion once in cleaning water with added H2O2, and two immersions are necessary to restore sufficient adsorption capacity. It has been found that the amount of recovery is greatest when the immersion time for one cycle is 15 to 20 minutes, and that the amount of recovery decreases if the immersion time exceeds 20 minutes. For this reason, when immersing twice, the immersion time should be 15 to 30 minutes for both cycles.

[0030] However, in the conventional method, the immersion is repeated twice, which requires the cleaning solution to be replaced and rinsing to be performed after each immersion. This labor-intensive process reduces the efficiency of regeneration and increases the cost of regeneration.

[0031] As a result of extensive research, the inventors of the present invention have found that even if the number of immersions is reduced from two to one, by setting the immersion time to 35 to 60 minutes, regeneration efficiency surpasses that achieved by immersing twice. The present invention was made based on this finding.

[0032] Fig. 3 shows an example of the configuration of an apparatus for regenerating an adsorbent. Unlike apparatuses for carrying out conventional methods, the apparatus shown in Fig. 3 is composed of a single vessel 30 and a blower 31 as air supply means. Wash water is introduced into vessel 30, the pH is appropriately adjusted, and H2O2 is added.

[0033] The cleaning water can be introduced into the container 30 so that the volume ratio of the cleaning water to the used adsorbent 32 to be regenerated is 3:1. This volume ratio is an example, and other volume ratios may be used. In order to efficiently regenerate while minimizing the amount of cleaning water used, the above-mentioned 3:1 volume ratio is desirable.

[0034] The cleaning water may be tap water or groundwater. The temperature of the cleaning water may be room temperature, and there is no need to adjust the temperature.

[0035] The pH of the cleaning water is adjusted to 3 to 5 with an acidic solution such as hydrochloric acid. The acidic solution is not limited to hydrochloric acid, but may be sulfuric acid or nitric acid. H2O2 can be added to a concentration of 1% to 5%, preferably 1% to 2%, and more preferably 1%.

[0036] The adsorbent 32 may be directly introduced into the solution 33 to which H2O2 has been added, or it may be placed in a net 34 and the net 34 introduced together, or it may be placed in a bucket and the bucket introduced together. By introducing the net 34 or the bucket together, all of the introduced adsorbent 32 can be easily removed when removing it. Note that the adsorbent 32 may be placed in a sieve or basket, or placed on a mesh material, and then immersed in the container 30 as is, in addition to the net 34 or bucket.

[0037] After the adsorbent 32 is placed in the solution 33, compressed air is supplied from the blower 31 to aerate the adsorbent 32. The adsorbent 32 is immersed for a predetermined time while aeration is being performed. Note that the compressed air is supplied from the blower 31 as a supply source, but this is not limited thereto and a compressor, a cylinder, or the like may also be used as the supply source. Here, compressed air is supplied to the solution 33 to supply the bubbles 35, but the gas supplied is not limited to compressed air and may be oxygen, ozone, or the like at a predetermined pressure.

[0038] The adsorbent 32 is immersed in the solution 33, whereby oil adhering to the adsorbent 32 is oxidatively decomposed. The oil adhering to the adsorbent 32 is removed by aeration. Aeration supplies oxygen used for the oxidative decomposition of the oil, increasing the oxygen concentration in the solution 33. The size of the bubbles 35 generated in the solution 33 by aeration may be any of millibubbles, microbubbles, and nanobubbles, with smaller diameters being preferable because they make it easier to remove the oil and increase the oxygen concentration in the solution 33.

[0039] For oxidative decomposition by H2O2, it is preferable that the solution 33 is acidic, and the pH is preferably 3 to 5. In this way, by adjusting the solution 33 to the acidic side, it is possible to promote oxidative decomposition by H2O2.

[0040] Unlike conventional methods, the immersion time of the adsorbent 32 in the solution 33 is set to 35 to 60 minutes. Aeration is performed while the adsorbent 32 is immersed in the solution 33. The oil that has been peeled off from the adsorbent 32 floats to the surface of the solution 33, but can be removed appropriately by absorbing it with paper, for example. The method of removing the oil is not limited to using paper, and methods such as scooping the oil or sucking the oil may also be used.

[0041] Immersion of the adsorbent 32 in solution 33 can regenerate the adsorbent 32. However, if H2O2 remains in the regenerated adsorbent 32, NO2 in the exhaust gas is reduced to NO, and the NO is released into the atmosphere without being adsorbed by the adsorbent 32. Therefore, the adsorbent 32 recovered from solution 33 is rinsed to remove any oil or remaining H2O2 that may have reattached to the adsorbent 32. To this end, the container 30 is provided with a valve 36 at its bottom. The valve 36 is opened to remove the solution 33, and the container 30 is lightly cleaned. Then, the valve 36 is closed and rinsing water is added as second rinsing water. The container is then left for 15 to 30 minutes, allowing the rinsing water to stand. In this case, an acidic solution may be used to adjust the pH of the rinsing water to 3 to 5. Conventional rinsing is performed after each immersion.

[0042] 4 is a flowchart showing an example of the operation of regenerating the adsorbent 32. The regeneration operation can be performed when it becomes necessary to regenerate the adsorbent 32. In one example, the regeneration operation can be performed when a predetermined regeneration period has elapsed. When performing the regeneration operation, the used adsorbent 32 is recovered from the adsorption vessel 23 of the adsorption device 21.

[0043] The operation starts at step 100, and in step 101, cleaning water is poured into the container 30. The cleaning water may be tap water, groundwater, or the like, and may be supplied into the container 30 via a hose or the like from a tap, or by pumping up groundwater. The amount of cleaning water may be approximately three times the volume of the adsorbent 32 to be poured into the container 30. For example, if one bucket of adsorbent 32 is poured into the container 30, three buckets' worth of cleaning water may be poured. The cleaning water poured into the container 30 does not need to be temperature-adjusted.

[0044] In step 102, an acidic solution is used to adjust the pH of the cleaning water in container 30. The pH of cleaning water is between 3 and 5. The acidic solution is added to the cleaning water while measuring the pH using a pH meter, and the mixture is stirred to adjust the pH of the cleaning water. H2O2 is then added to the pH-adjusted cleaning water to create a solution 33 with an H2O2 concentration of approximately 1%. If the amount of cleaning water is three buckets' worth, the mass of the three buckets' worth of water is measured, and the mass of H2O2 required to achieve a 1% concentration is calculated from the mass of the water. The calculated mass of H2O2 can then be weighed and added to container 30.

[0045] In step 103, the recovered adsorbent 32 is placed into the prepared solution 33. If three buckets of cleaning water are placed in the container 30, one bucket of adsorbent 32 is placed in. Immersion begins with the addition of the adsorbent 32, and in step 104, compressed air is sent from the blower 31 into the solution 33 in the container 30 to generate air bubbles in the solution 33, thereby aerating the solution. The adsorbent 32 is immersed for 35 to 60 minutes. This immersion causes the oil adhering to the adsorbent 32 to be oxidatively decomposed. The oil floating to the surface of the solution 33 due to the oxidative decomposition of the oil is removed as appropriate.

[0046] After 35 to 60 minutes have passed since the start of immersion of the adsorbent 32 in the solution 33, the process proceeds to step 105, where the valve 36 of the container 30 is opened, the solution 33 inside the container 30 is removed, and the container 30 is lightly washed with water. After that, the valve 36 is closed, and rinsing water is added, and the container is left for about 15 to 30 minutes to rinse the adsorbent 32. The rinsing may be done with water alone, or with an acidic solution adjusted to a pH of 3 to 5.

[0047] In step 106, the adsorbent 32 after rinsing is collected and air-dried, completing the process.

[0048] Here, a test was conducted to regenerate used adsorbent 32 that had actually been used in an air purification system installed in a road tunnel, and the recovery rate of adsorbent 32 was verified from the test results. Activated carbon was used as the main material for adsorbent 32, and room temperature water was used for the cleaning water. The cumulative exposure amount for adsorbent 32 was the cumulative number of moles of NO2 and other substances absorbed by adsorbent 32 per unit mass (1 ton), and a used denitrification material with a cumulative exposure of 2,320 mol / t was used. The adsorbent 32 and cleaning water were mixed in a volume ratio of 1:3, and hydrochloric acid was added to adjust the pH to 3 to 5. H2O2 was also added to the cleaning water, and the H2O2 concentration of solution 33 was adjusted to 1%.

[0049] The test was conducted for immersion times of 10, 15, 20, 30, and 40 minutes. Because contaminants clog the pores, the recovery amount was calculated as the difference between the pore distribution before immersion and the pore distribution after immersion for each immersion time. The pore distribution is the value measured for the pore volume distribution of pores with a size of less than 2 nm (pore volume value).

[0050] FIG. 5 is a diagram showing the relationship between the recovery amount of the pore distribution of the adsorbent 32 and the immersion time. For comparison, FIG. 5 also shows the pore volume value of a new adsorbent 32. Note that the pore volume value of the new adsorbent 32 is below the upper recovery amount limit (approximately 0.032 cm). 3 / g).

[0051] Referring to Figure 5, the amount of recovery increased as the immersion time increased to 10, 15, and 20 minutes, and then decreased at 30 minutes. This shows that the recovery reaches a maximum value at 20 minutes of immersion. In the conventional method, it is assumed that the recovery reaches a maximum value at 20 minutes of immersion and then decreases, and the immersion time is set to 15 to 30 minutes.

[0052] However, when the immersion time was extended to 40 minutes, the recovery rate, which had decreased once, increased again, and it was found that the recovery rate was significantly higher than that after immersion for 20 minutes. The test results showed that the pore size distribution after immersion for 20 minutes was approximately 0.008 cm 3 / g, the recovery amount is about 25%, and at 40 minutes, it is about 0.016 cm 3 / g, the recovery amount was about 50%, and the result of 40 minutes of immersion was about twice the result of 20 minutes of immersion.

[0053] In the conventional method, a single immersion in solution 33 for 15 to 20 minutes followed by rinsing only achieved a recovery of about 20%. Therefore, a second immersion in solution 33 for 20 minutes followed by rinsing achieved a recovery of about 40%. In contrast, in the present method, a single immersion in solution 33 for 40 minutes followed by rinsing achieved a recovery of about 50%. Therefore, to achieve the desired recovery (e.g., 30% or more), the amount of H2O2 used can be halved, and two immersions are not required, eliminating the need to replace solution 33. This improves regeneration efficiency and reduces regeneration costs.

[0054] 5 shows only the results for an immersion time of 40 minutes, but the recovery amount is 30% or more for an immersion time of 35 to 60 minutes. Therefore, in this method, the immersion time is set to 35 to 60 minutes, and efficient regeneration of the adsorbent 32 can be achieved with just one immersion.

[0055] FIG. 6 is a flowchart showing another example of the process for regenerating the adsorbent 32. Steps 200 to 205 are the same as steps 100 to 105, and therefore a description of these steps will be omitted. In step 206, the rinsed adsorbent 32 is placed in a dryer and heated to 300°C to 450°C. Heating the adsorbent 32 volatilizes and removes excess moisture and remaining oil contained in the adsorbent 32. The process then ends in step 207.

[0056] Figure 7 shows the test results for adsorption performance. The test involved immersing the adsorbent in the solution 33 once and rinsing it, followed by heating the adsorbent 32 at a temperature of 450°C inside a dryer to regenerate the adsorbent 32. A used denitration material with a cumulative exposure of 2320 mol / t was used as the adsorbent 32. The pH and H2O2 concentration of the solution 33 were set to 3 to 5, and the H2O2 concentration was 1%. The amount of washing water was three times the volume of the adsorbent 32.

[0057] Figure 7(a) is a graph comparing the benzene adsorption amount of the adsorbent 32 before regeneration (untreated) and after regeneration. The adsorption amount is the mass of benzene adsorbed by the adsorbent 32 per unit mass, expressed as a percentage (%), and the benzene adsorption amount of the new adsorbent 32 is 23.2%. The results shown in Figure 7(a) are the average of three benzene adsorption tests performed on the untreated adsorbent 32 and the regenerated adsorbent 32.

[0058] The untreated adsorbent 32 had an average adsorption capacity of 21.6%, whereas the regenerated adsorbent 32 had an average adsorption capacity of 25.0%. The regenerated adsorbent 32 showed an improvement equal to or greater than that of the new adsorbent 32.

[0059] 7(b) is a diagram comparing the specific surface area of the untreated adsorbent 32 with the specific surface area of the regenerated adsorbent 32. The specific surface area is the surface area per unit mass or the surface area per unit volume, and can be measured by a permeation method, a gas adsorption method, or the like. The permeation method and the gas adsorption method are well known, and will not be described in detail here.

[0060] The specific surface area of new adsorbent 32 is 753 m 2 / g. The results shown in Fig. 7(b) are the average of three measurements of the specific surface area of the untreated adsorbent 32 and the regenerated adsorbent 32.

[0061] Untreated adsorbent 32 has an average specific surface area of 679 m 2 / g, whereas the average specific surface area of the regenerated adsorbent 32 was 772 m 2 The regenerated adsorbent 32 showed an improvement equal to or greater than that of the new adsorbent 32.

[0062] Figure 7(c) is a graph comparing the iodine adsorption amount of the untreated adsorbent 32 with the iodine adsorption amount of the regenerated adsorbent 32. The adsorption amount represents the mass of iodine adsorbed by the adsorbent 32 per unit mass. The results shown in Figure 7(c) are the average of three benzene adsorption tests performed on the untreated adsorbent 32 and the regenerated adsorbent 32.

[0063] The untreated adsorbent 32 had an average iodine adsorption capacity of 460 mg / g, whereas the regenerated adsorbent 32 had an average iodine adsorption capacity of 760 mg / g. The regenerated adsorbent 32 had a significantly increased adsorption capacity compared to the untreated adsorbent 32, and a significant improvement was observed.

[0064] Figure 8 shows the effect of heating after rinsing. Figure 8(a) shows the amount of benzene adsorption (%) and specific surface area (m) when the temperature inside the dryer was changed to 250°C, 300°C, 350°C, 400°C, and 450°C. 2 / g) and the amount of volatile matter (oil) adsorbed (%). Figure 8(b) shows the amount of benzene adsorbed (%) and the specific surface area (m 2 / g), the amount of volatile matter (oil) attached (%), and hardness (%).

[0065] The amount of volatile matter adsorbed (%) is the mass of volatile matter adsorbed to the adsorbent 32 per unit mass, expressed as a percentage. The hardness (%) is the hardness of the adsorbent 32 after heating to each temperature, expressed as a percentage, based on the hardness of a new adsorbent 32 at room temperature. The hardness can be measured using a hardness tester or the like.

[0066] The results shown in Figure 8 show that the amount of benzene adsorption and the specific surface area increased as the heating temperature increased. In particular, the specific surface area increased significantly and was significantly improved when the temperature rose from 250°C to 300°C. Furthermore, the amount of benzene adsorption also increased and was improved as the temperature rose.

[0067] It was found that the volatile content decreased and improved as the temperature increased. In particular, it was found that the volatile content decreased significantly and improved significantly when the temperature increased from 400°C to 450°C. However, it was found that the hardness decreased and tended to become more brittle as the temperature increased. When the heating temperature reached 500°C or higher, the adsorbent 32 became brittle and the pores collapsed.

[0068] From the above, it was found that the heating temperature should be 300°C or higher, which significantly improves the specific surface area, and 450°C or lower, which does not cause the pores to collapse. Therefore, it was found that the heating temperature in the dryer after rinsing should be 300°C to 450°C.

[0069] 9 shows an example of the configuration of a testing device for conducting a test to confirm the adsorption performance of the regenerated adsorbent. The testing device is an apparatus for conducting a test to confirm the NO2 removal performance of the adsorbent 32 regenerated by this method.

[0070] The test device 40 includes a fan 41, a column 42, and a chamber 43. The fan 41 draws in indoor air and supplies it to the column 42. NO is supplied to the column 42 from an NO cylinder together with the air, and the NO is oxidized into ozone, and NO is released. x The gas was converted to (NO+NO2) gas and supplied as a low-concentration NO2 test gas. Also, NO2 was supplied from an NO2 cylinder to the low-concentration NO2 test gas, and this was supplied as a high-concentration NO2 test gas to the column 42. The concentration was adjusted using a mass flow meter, and the inlet NO2 x A total of 44 were confirmed.

[0071] The test conditions were a space velocity (SV), which is the amount of gas passing through the test device 40 per hour, of 12,000, and the linear velocity was measured with an anemometer 45 provided on the outlet side of the column 42 to adjust the SV. The column 42 was packed with the regenerated adsorbent 32, and straightening plates 46, 47 were installed on the upstream and downstream sides of the column 42. The NO in the gas passing through the column 42 was measured. x The concentration was measured by the outlet NO. x The temperature and humidity of the air in the test gas were measured by a thermo-hygrometer 49.

[0072] Figure 10 shows the test results confirming the adsorption performance of the regenerated adsorbent. The test results, which show the NO2 removal rate, were obtained by repeating the test three times. The NO2 concentration at the inlet of column 42 in the first test was 0.440 ppm, in the second test it was 0.433 ppm, and in the third test it was 0.417 ppm. In each test, the NO2 concentration at the outlet of column 42 was 0 ppm, and the NO2 removal rate was 100%.

[0073] From this, it was confirmed that the adsorbent 32 after regeneration by this method was restored to an adsorption capacity equivalent to that of a new adsorbent 32.

[0074] Therefore, according to the present invention, by extending the immersion time to 35 to 60 minutes, it is possible to achieve a recovery amount of the adsorbent 32 with only one immersion that exceeds the recovery amount obtained with the conventional method in which the immersion is performed twice with an immersion time of 15 to 30 minutes, thereby improving the regeneration efficiency and reducing the regeneration costs by reducing the number of immersions.

[0075] In addition, by heating the adsorbent 32 to 300°C to 450°C, excess solution 33 can be removed while also removing oil that was not removed by immersion, resulting in the recovery of NO2 removal performance comparable to that of a new adsorbent 32.

[0076] The adsorbent regeneration method of the present invention has been described in detail above with reference to the embodiments shown in the drawings. However, the present invention is not limited to the above-described embodiments, and can be modified within the scope of what a person skilled in the art can conceive, such as other embodiments, additions, modifications, deletions, etc., and any embodiment is within the scope of the present invention as long as it achieves the functions and effects of the present invention. [Explanation of symbols]

[0077] 10...Road tunnel 11...Vehicle 12...Ventilation passage 13...Ventilation tower 14...Ventilation fan 15...Dust collector 16...Denitration equipment 17...Silencer 18...Auxiliary equipment 20…humidifier 21...Adsorption device 22...Adsorption layer 23...Adsorption container 24...Supply port 25…Discharge port 26, 27...Aisles 28…Regeneration solution tank 29...Regenerated solution pump 30…Container 31...Blower 32...Adsorbent 33...solution 34...Net 35...bubbles 36...Valve 40...Test equipment 41...Fan 42...Column 43...Chamber 44...Entrance No. x total 45...Anemometer 46, 47…straightening plate 48…Exit NO. x total 49…Thermo-hygrometer

Claims

1. 1. A method for regenerating an adsorbent material that adsorbs contaminants, comprising: The regeneration method includes the step of immersing the adsorbent in cleaning water containing hydrogen peroxide for 35 to 60 minutes while injecting air bubbles into the water.

2. 2. The regeneration method according to claim 1, further comprising the step of heating the adsorbent to 300°C to 450°C after immersion in the cleaning water.

3. 3. The regeneration method according to claim 1, further comprising, before the heating step, a step of immersing the adsorbent after immersion in the cleaning water in second cleaning water for 15 to 30 minutes.

4. The regeneration method according to claim 3, wherein the second wash water is adjusted to a pH of 3 to 5 using an acidic solution.

5. 3. The regeneration method according to claim 1, wherein the concentration of the hydrogen peroxide in the cleaning water is 1% by mass to 5% by mass.

6. 3. The regeneration method according to claim 1, wherein the pH of the wash water is adjusted to 3 to 5 using an acidic solution.

Images