Method for regenerating spent activated carbon

Abstract

The present application relates to the technical field of activated carbon regeneration, and particularly relates to a waste activated carbon regeneration method, comprising the following steps: (a) pretreatment and impurity removal to obtain pretreated activated carbon; (b) impregnation of a repair liquid to obtain a cake; and (c) controllable heat activation to obtain regenerated activated carbon. The present application realizes the improvement of product stability, the reduction of dust loss in a high-temperature activation furnace and the guarantee of the adsorption performance of the activated carbon after activation treatment by pretreating the waste activated carbon and optimizing the process under the condition of existing production basic equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of activated carbon regeneration, and particularly relates to a waste activated carbon regeneration method. BACKGROUND

[0002] At present, as the mainstream technology for disposing waste activated carbon, the thermal regeneration method still has room for improvement in actual industrial application. For example, the problem of dust loss caused by the impact of high-temperature gas flow and the turning of the kiln body on the powdered activated carbon in the rotary kiln is particularly prominent. This not only directly reduces the carbon yield, but also puts a great pressure on the equipment operating environment and the tail gas purification system. At the same time, the irreversible damage to the pore structure during the regeneration process, and the metal impurities adsorbed in the carbon body becoming catalytic oxidation centers at high temperatures, aggravate the ablation of the carbon skeleton, leading to the melting and collapse of the micropore wall and the merging of the mesopore, resulting in a significant decrease in the specific surface area of the regenerated carbon and the deterioration of the adsorption performance. In addition, due to the diverse sources of waste activated carbon and the large fluctuation of the adsorbent composition, combined with the extensive control of the traditional process on the pretreatment of the feed and the activation parameters, and the lack of unified regulation of the material properties, the performance of the regenerated carbon products finally has significant batch-to-batch differences, and the stability is difficult to guarantee, which seriously restricts its recycling in high-value fields. These interrelated pain points need an innovative regeneration process that can balance efficiency, low consumption and stability to be systematically solved.

[0003] CN 109351354 A provides a waste powder activated carbon regeneration process, comprising the following steps: (1) the waste powder activated carbon is first dried by a drying device, and the water content is controlled to be 15-25%; (2) the dried waste powder activated carbon is mixed with a binder, stirred and kneaded, and then formed into a cylindrical activated carbon with a size of 4-6 mm by a granulator; (3) the formed cylindrical activated carbon is dried and solidified, the drying temperature is adjusted, and the drying time is controlled to be 1-2 h; (4) the solidified activated carbon column enters a specific vertical multi-tube multi-stage activation furnace for regeneration treatment; the invention provides continuous heat supply to the regeneration tube by a combustion machine, and the activated carbon in the regeneration tube respectively undergoes low-temperature, medium-temperature and high-temperature processes, the low-temperature process releases the moisture and volatile components of the activated carbon, the medium-temperature process further releases or burns the difficult-to-desorb substances in the activated carbon, and the high-temperature process completely burns the substances in the pores of the activated carbon to realize regeneration. CN 119349577 A discloses a powdered waste activated carbon regeneration production process, comprising the following steps: S1, the powdered waste activated carbon is sent into a crushing and drying furnace for crushing and drying; S2, the powdered waste activated carbon is sent into a cyclone separator and a bag separator for solid-gas separation, and then sent into an activation furnace for activation through a feeder; S3, the activation furnace is preheated before starting feeding, and then high-pressure steam generated by a boiler is sent into the activation furnace; S4, the powdered waste activated carbon is activated after being sent into the activation furnace, and then cooled and separated to obtain finished product activated carbon; S5, the finished product activated carbon is sent to a mixing bin for discharging and bagging. Compared with the traditional regeneration of powdered waste activated carbon by soil kiln technology, the process can restore the powdered waste activated carbon to the same quality as the original activated carbon by using high-temperature activation physical action, and has stable technology, high finished product yield, good finished product quality and high yield. The above schemes cannot solve the problem of dust raising in the high-temperature activation furnace, and the key equipment needs to be improved, which is not easy to match with the existing production. SUMMARY

[0004] In order to make up for the above shortcomings, the present application provides a waste activated carbon regeneration method, which pre-treats the waste activated carbon and optimizes the process, so as to improve the product stability, reduce the dust loss in the high-temperature activation furnace, and ensure the adsorption performance of the activated carbon after activation treatment under the condition of existing production basic equipment.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0006] A waste activated carbon regeneration method, comprising the following steps:

[0007] (a) pre-treatment and impurity removal: the waste activated carbon is sequentially subjected to acid treatment, alkali treatment and cleaning treatment to obtain pre-treated activated carbon;

[0008] (b) Repair liquid impregnation: the pretreated activated carbon is mixed with the repair liquid at a mass ratio of 1:1-2 and added into a ball mill, ground to 80-120 mesh, then the solid phase is separated, and the material moisture content is controlled at 13-18%, to obtain a material cake;

[0009] The repair liquid comprises the following components by mass percentage: viscous carbon source 3-8%, small molecule carbon source 1-5%, pore forming agent 0.5-3%, and the balance is water;

[0010] (c) Controllable thermal activation: the material cake is fed into a high-temperature activation furnace through an auger, the oxygen volume fraction at the kiln tail is controlled to be less than 1%, the temperature is raised to 850-950℃, and the temperature is maintained for 0.5-2h, and the reactivated activated carbon is obtained after cooling.

[0011] The present application first controls the properties of the raw material. The present application removes metal impurities loaded in the pores of the waste activated carbon through pretreatment, which will become catalytic oxidation centers at high temperatures, severely accelerating the ablation of the carbon skeleton, resulting in irreversible collapse and excessive loss of the pore structure; therefore, it is necessary to eliminate this negative catalytic factor by sufficient acid treatment and alkali treatment cleaning to obtain a pure pretreated activated carbon substrate. Subsequently, the present application introduces a synergistic process of repair liquid impregnation and ball milling, which realizes the reconstruction of the material level: the viscous carbon source acts as a binder to enable the subsequent material cake to roll into spherical particles with certain strength in the high-temperature activation furnace, and to form a stable carbon skeleton network during pyrolysis in the early stage, effectively enhancing the strength of the spherical particles and preventing dust loss when they are turned over in the activation furnace; the small molecule carbon source can be deposited in the defect sites of the activated carbon after pyrolysis, playing a role in repairing the carbon matrix; and the pore forming agent is completely decomposed and gasified at high temperature, and the space left in situ becomes a new pore, thereby optimizing and widening the pore size distribution. The ball milling not only ensures the uniform dispersion of each component at the microscale, but more importantly controls the material to a particle size range of 80-120 mesh, which enables the material to achieve the purpose of "rolling into spherical particles with certain strength", improving the efficiency of heat and mass transfer. The final controllable thermal activation is the decisive link in the whole process, which strictly controls the oxygen volume fraction at the kiln tail to be below 1%, ensuring that the system is in a mild and controllable gasification reaction dominated by steam activation, rather than a violent combustion reaction; this reducing atmosphere selectively etches carbon atoms at a high temperature of 850-950℃, orderly cleaning and expanding the existing pores, while avoiding the collapse of the pores and the deterioration of the performance caused by local overheating or uncontrolled oxidation. Any ratio of components beyond the specified range or process parameters out of control will destroy this delicate coordination, such as too much viscous carbon source causing caking and blocking the pores, and too little resulting in insufficient forming strength; excessive pore forming agent may damage the mechanical strength, and insufficient pore forming agent may not achieve good pore forming effect, such as an increase in oxygen concentration will trigger combustion, and a too fast heating rate will result in uneven pyrolysis of the repair liquid components, ultimately failing to achieve the three goals of low ignition loss, high adsorption, and structural stability.

[0012] As preferred, the acid treatment is: soaking in 0.5-5 mol / L inorganic acid solution at 20-60℃ with solid-liquid ratio of 1:3-1:10 for 1-4 hours, and then centrifugal separation to obtain acid-treated solid phase with water content of 18-25%; the alkali treatment is: passing ammonia gas into the acid-treated solid phase until pH is 8.5-10 to obtain alkali-treated material; the washing treatment is: washing the alkali-treated material with 3-5 times of water, and then centrifugal separation to obtain pretreated activated carbon with water content of 12-18%.

[0013] The acid treatment step uses the synergistic effect of specific temperature, concentration, solid-liquid ratio and time, aiming to efficiently dissolve and remove the metal ion impurities loaded in the pores of the waste activated carbon; if these metal impurities are not completely removed, they will become strong catalytic oxidation centers in the subsequent high-temperature stage, sharply accelerating the gasification reaction of the carbon skeleton, leading to the failure of selective pore etching and causing large-area collapse and excessive loss of pore structure. Controlling the water content to 18-25% after centrifugal separation provides a suitable liquid phase environment for the subsequent alkali treatment reaction, while avoiding excessive water dilution of the reaction concentration or insufficient mass transfer. The alkali treatment by passing ammonia gas is a key design. Compared with liquid alkali reagents, gaseous ammonia can more gently and uniformly penetrate into the micropores of the filter cake for reaction, effectively avoiding the corrosive damage to the carbon matrix caused by local pH peak, and accurately controlling the end point pH to 8.5-10 can ensure that part of the residual metal impurities are precipitated in the form of complexes, while minimizing the damage to the acidic functional groups on the surface of the activated carbon, maintaining the chemical stability of the carbon skeleton. The subsequent washing step removes the soluble salts and residual ammonium produced by the alkali treatment through quantitative water washing and secondary centrifugation, and neutralizes the pH; if these residues are not removed, they will melt and sinter in the high-temperature furnace, block the pores or produce corrosive gases; finally, the water content of the pretreated activated carbon is precisely controlled to 12-18%, which matches the ideal humidity level of the subsequent repair liquid impregnation step; this water content neither needs to spend a lot of cost to remove water, nor excessively dilutes the effective concentration of each functional component in the repair liquid, thereby ensuring the effective infiltration and adhesion of the repair liquid to the pores of the activated carbon, and providing a material precursor with complete structure and uniform composition for the final realization of high-performance regeneration.

[0014] In this scheme, ammonia gas is used for alkali treatment, so a higher water content needs to be retained in the solid phase after acid treatment, and the ammonia gas treatment saves water consumption in the alkali treatment process.

[0015] As preferred, the inorganic acid is preferably hydrochloric acid or nitric acid.

[0016] As preferred, in step (b), the viscous carbon source is preferably polyvinyl alcohol; and the small molecule carbon source is preferably one or more of glucose, sucrose and fructose.

[0017] As preferred, in step (b), the pore-forming agent is polyethylene glycol, and the average molecular weight is 400-600 g / mol.

[0018] The primary function of the viscous carbon source is to act as a builder of macrostructure. Their long molecular chains form a high-viscosity gel network in water, just like cement firmly binds the dispersed waste activated carbon particles together, which is the key to rolling into a ball with a certain strength and ultimately overcoming the loss of dust in the rotary kiln. Small molecule carbon sources play the role of micro-defect repairers. With small molecular weight and excellent fluidity, they can fully penetrate into the deep pores and even defect cracks of activated carbon with the water phase. In the early stage of pyrolysis, they will quickly melt and caramelize, and their products can selectively deposit on the micro-cracks and weak points of the activated carbon matrix. PEG with an average molecular weight of 400-600 g / mol is liquid and water-soluble, and can be uniformly dispersed throughout the system. Its core role is to act as a "sacrificial template" during heat treatment. In the range of 300-400℃, PEG will completely decompose and gasify, leaving a space in situ, thereby forming new mesopores with relatively uniform pore size distribution. The choice of molecular weight is crucial: if the molecular weight is too low (such as PEG-200), the decomposition is too early and the remaining pores are too small, and the effect is not obvious; if the molecular weight is too high (such as PEG-4000), its viscosity is large, and the decomposition temperature is higher, which may not be synchronized with the gasification process of activated carbon, or even incomplete decomposition and carbon deposition, which may block the pores.

[0019] As preferred, the rotation speed of the high-temperature activation furnace is 1.5-3 revolutions per minute, or the inner wall linear velocity of the high-temperature activation furnace is 5-10 m / min.

[0020] The control of the rotation speed of the high-temperature activation furnace / the inner wall linear velocity of the high-temperature activation furnace is to prevent the movement of the high-temperature activation furnace body from being too fast to cause the ball particles to break, and the movement from being too slow to cause the balling to be unsuccessful.

[0021] As preferred, in step (b), the method for separating the solid phase is centrifugation or pressure filtration.

[0022] As preferred, in step (c), the method for controlling the oxygen volume fraction in the kiln tail to be less than 1% is: adding nitrogen to the gas obtained after flue gas purification until the oxygen volume fraction is less than 1%, and then introducing it into the kiln body after compression; the process of flue gas purification is: the tail gas is led out from the kiln head, and then subjected to deacidification, dust removal, and moisture removal.

[0023] As preferred, the deacidifying agent for deacidification is slaked lime; the process of moisture removal is condensation dehumidification.

[0024] Generally, the tail gas is discharged into the atmosphere after purification, and the present scheme re-introduces part of the purified tail gas into the high-temperature activation furnace, which is beneficial to better control the atmosphere in the furnace, and at the same time, the part of the heat energy is recycled, which greatly reduces the consumption cost of fresh nitrogen gas, and realizes the high unification of environmental benefits and economic benefits.

[0025] Compared with the prior art, the advantages of the present scheme are:

[0026] From the component point of view, the present application realizes the synergistic effect of macroscopic adhesion enhancement and microscopic defect repair in the pyrolysis process by using a complex system of preferred viscous carbon sources such as polyvinyl alcohol and small molecule carbon sources such as glucose, effectively overcoming the mechanical strength degradation and dust problem of regenerated particles; at the same time, polyethylene glycol with a specific molecular weight is used as a pore former, and its controlled thermal decomposition behavior precisely introduces through mesopores, optimizing the pore size distribution and mass transfer efficiency of activated carbon. From the process point of view, the closed system of recycling and coupling nitrogen gas after purification is innovatively used, which realizes the accurate and stable control of the oxygen concentration in the activation furnace, thereby preventing the collapse of the pore structure caused by excessive oxidation; and the high-precision pretreatment process based on ammonia gas neutralization and centrifugal dewatering ensures the high uniformity of the material properties, providing a solid foundation for the stable operation of the subsequent process and the consistency of the performance of the regenerated carbon product; at the same time, it can adapt to the existing production line without introducing high-end equipment. SPECIFIC EMBODIMENT

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0028] Embodiment 1

[0029] A method for regenerating waste activated carbon, comprising the following steps:

[0030] (a) Pretreatment of impurity removal: the waste activated carbon is sequentially subjected to acid treatment, alkali treatment and washing treatment to obtain pretreated activated carbon;

[0031] The acid treatment is: soaking in a 3 mol / L hydrochloric acid solution at 40℃ for 2 hours at a solid-liquid ratio of 1:6, and then centrifugally separating to obtain an acid-treated solid phase with a water content of 22%;

[0032] The alkali treatment is: introducing ammonia gas into the acid-treated solid phase until the pH is 9.0, and obtaining an alkali-treated material;

[0033] The washing treatment is: rinsing the alkali-treated material with 4 times the mass of water, and obtaining pretreated activated carbon with a water content of 15% after centrifugal separation;

[0034] (b) Repair liquid impregnation: the pretreated activated carbon and the repair liquid were mixed in a mass ratio of 1:1.5 and added to a ball mill, ground to 100 mesh, and then the solid phase was separated by pressure filtration, and the water content of the material was controlled to be 15%, to obtain a cake;

[0035] The repair liquid comprises the following components in mass percentage: polyvinyl alcohol 5%, glucose 3%, polyethylene glycol 500 g / mol 1.5%, and the balance is water;

[0036] (c) Controllable thermal activation: the cake was put into a high-temperature activation furnace through a screw, the oxygen volume fraction at the kiln tail was controlled to be 0.8%, the rotation speed of the high-temperature activation furnace was 2 revolutions per minute, the temperature was raised to 900℃, and the temperature was maintained for 1.0h, and then the regenerated activated carbon was obtained after cooling;

[0037] The method for controlling the oxygen volume fraction at the kiln tail is as follows: the tail gas is led out from the kiln head, and after deacidification by slaked lime, dust removal, and condensation and dehumidification, nitrogen is added to the obtained gas to make the oxygen volume fraction be 0.8%, and then the gas is compressed and introduced into the kiln tail of the high-temperature activation furnace.

[0038] Example 2

[0039] A method for regenerating waste activated carbon, comprising the following steps:

[0040] (a) Pretreatment and impurity removal: the waste activated carbon was sequentially subjected to acid treatment, alkali treatment, and washing treatment to obtain pretreated activated carbon;

[0041] The acid treatment is as follows: the acid-treated solid phase was obtained by soaking the waste activated carbon in a 0.5 mol / L nitric acid solution at 20℃ for 4 hours at a solid-liquid ratio of 1:3, and then centrifugally separating the solid phase;

[0042] The alkali treatment is as follows: ammonia gas was introduced into the acid-treated solid phase until the pH was 8.5, and the alkali-treated material was obtained;

[0043] The washing treatment is as follows: the alkali-treated material was washed with 3 times the mass of water, and then the pretreated activated carbon with a water content of 12% was obtained by centrifugal separation;

[0044] (b) Repair liquid impregnation: the pretreated activated carbon and the repair liquid were mixed in a mass ratio of 1:1 and added to a ball mill, ground to 80 mesh, and then the solid phase was separated by centrifugal separation, and the water content of the material was controlled to be 13%, to obtain a cake;

[0045] The repair liquid comprises the following components in mass percentage: polyvinyl alcohol 3%, glucose 1%, polyethylene glycol 600 g / mol 0.5%, and the balance is water;

[0046] (c) Controllable thermal activation: the cake is put into a high-temperature activation furnace through an auger, the oxygen volume fraction at the kiln tail is controlled to be 0.8%, the inner wall linear velocity of the high-temperature activation furnace is 5 m / min, the temperature is raised to 850°C, and the cake is activated for 2 h, and then the regenerated activated carbon is obtained after cooling;

[0047] The method for controlling the oxygen volume fraction at the kiln tail to be 0.8% is as follows: the tail gas is led out from the kiln head, and nitrogen is added to the gas obtained after lime deacidification, dust removal and condensation dehumidification until the oxygen volume fraction is 0.8%, and then the gas is compressed and introduced into the kiln tail of the high-temperature activation furnace.

[0048] Example 3

[0049] A method for regenerating waste activated carbon, comprising the following steps:

[0050] (a) Pretreatment and impurity removal: the waste activated carbon is sequentially subjected to acid treatment, alkali treatment and washing treatment to obtain pretreated activated carbon;

[0051] The acid treatment is as follows: the acid treatment is carried out in a hydrochloric acid solution with a concentration of 5 mol / L at 60°C, and the solid-liquid ratio is 1:10, and the soaking time is 1 hour, and then the acid-treated solid phase with a water content of 25% is obtained by centrifugal separation;

[0052] The alkali treatment is as follows: ammonia gas is introduced into the acid-treated solid phase until the pH value is 10, and the alkali-treated material is obtained;

[0053] The washing treatment is as follows: the alkali-treated material is washed with 5 times the mass of water, and the pretreated activated carbon with a water content of 18% is obtained by centrifugal separation;

[0054] (b) Impregnation with repair solution: the pretreated activated carbon is mixed with the repair solution at a mass ratio of 1:2 and added to a ball mill, and ground to 120 mesh, and then the solid phase is separated by pressure filtration, and the water content of the material is controlled to be 18%, and the cake is obtained;

[0055] The repair solution comprises the following components in mass percentage: polyvinyl alcohol 8%, sucrose 5%, polyethylene glycol with a molecular weight of 400 g / mol 3%, and the balance is water;

[0056] (c) Controllable thermal activation: the cake is put into a high-temperature activation furnace through an auger, the oxygen volume fraction at the kiln tail is controlled to be 0.8%, the rotation speed of the high-temperature activation furnace is 3 revolutions per minute, the temperature is raised to 950°C, and the cake is activated for 0.5 h, and then the regenerated activated carbon is obtained after cooling;

[0057] The method for controlling the oxygen volume fraction at the kiln tail to be 0.8% is as follows: the tail gas is led out from the kiln head, and nitrogen is added to the gas obtained after lime deacidification, dust removal and condensation dehumidification until the oxygen volume fraction is 0.8%, and then the gas is compressed and introduced into the kiln tail of the high-temperature activation furnace.

[0058] Example 4

[0059] A waste activated carbon regeneration method, comprising the following steps:

[0060] (a) Pretreatment and impurity removal: the waste activated carbon is sequentially subjected to acid treatment, alkali treatment and cleaning treatment to obtain pretreated activated carbon;

[0061] The acid treatment is: soaking in a 1 mol / L nitric acid solution at 30℃ for 3 hours at a solid-liquid ratio of 1:4, and then centrifugally separating to obtain an acid-treated solid phase with a water content of 20%;

[0062] The alkali treatment is: introducing ammonia gas into the acid-treated solid phase until the pH is 9.5 to obtain an alkali-treated material;

[0063] The cleaning treatment is: washing the alkali-treated material with 4 times the mass of water, and then centrifugally separating to obtain pretreated activated carbon with a water content of 14%;

[0064] (b) Impregnation with repair solution: mixing the pretreated activated carbon with the repair solution at a mass ratio of 1:1.2 and adding them into a ball mill for grinding to 90 mesh, and then pressure-filtering to separate the solid phase, controlling the water content of the material to be 14% to obtain a material cake;

[0065] The repair solution comprises the following components in mass percentage: 3% of polyvinyl alcohol, 2% of fructose, 1% of polyethylene glycol with a molecular weight of 400 g / mol, and the balance being water;

[0066] (c) Controllable thermal activation: introducing the material cake into a high-temperature activation furnace through a screw conveyor, controlling the oxygen volume fraction at the kiln tail to be 0.8%, the inner wall linear velocity of the high-temperature activation furnace to be 7 m / min, and the temperature to be raised to 880℃, and then maintaining the activation for 1.5 hours, and then cooling to obtain regenerated activated carbon;

[0067] The method for controlling the oxygen volume fraction at the kiln tail to be 0.8% is: adding nitrogen gas to the gas obtained by deacidifying, dedusting and dehumidifying the tail gas from the kiln head until the oxygen volume fraction is 0.8%, and then compressing and introducing the gas into the kiln tail of the high-temperature activation furnace.

[0068] Example 5

[0069] A waste activated carbon regeneration method, comprising the following steps:

[0070] (a) Pretreatment and impurity removal: the waste activated carbon is sequentially subjected to acid treatment, alkali treatment and cleaning treatment to obtain pretreated activated carbon;

[0071] The acid treatment is: soaking in a 4 mol / L hydrochloric acid solution at 50℃ for 1.5 hours at a solid-liquid ratio of 1:8, and then centrifugally separating to obtain an acid-treated solid phase with a water content of 24%;

[0072] The alkali treatment is: introducing ammonia gas into the acid-treated solid phase until the pH is 9.8 to obtain an alkali-treated material;

[0073] The washing treatment is: the alkali-treated material is washed with 5 times the mass of water, and the pretreated activated carbon with a water content of 17% is obtained after centrifugal separation;

[0074] (b) Repair liquid impregnation: the pretreated activated carbon is mixed with the repair liquid at a mass ratio of 1:1.8 and added to a ball mill, ground to 110 mesh, and then the solid phase is centrifugally separated, and the material cake with a water content of 17% is obtained;

[0075] The repair liquid contains the following components by mass percentage: polyvinyl alcohol 5%, glucose 4%, polyethylene glycol 500 g / mol 2.5%, and the balance is water;

[0076] (c) Controllable thermal activation: the material cake is fed into a high-temperature activation furnace through a screw conveyor, the oxygen volume fraction at the kiln tail is controlled to be 0.8%, the inner wall linear velocity of the high-temperature activation furnace is 9 m / min, the temperature is raised to 930°C, and the activated carbon is obtained after 0.8h of heat preservation and activation and cooling;

[0077] The method for controlling the oxygen volume fraction at the kiln tail to be 0.8% is: the tail gas is led out from the kiln head, and nitrogen is added to the gas obtained after lime acid removal, dust removal, and condensation and dehumidification to make the oxygen volume fraction 0.8%, and then compressed and introduced into the kiln tail of the high-temperature activation furnace.

[0078] Comparative Example 1

[0079] The difference from Example 1 is only that the repair liquid is not impregnated.

[0080] Comparative Example 2

[0081] The difference from Example 1 is only that the repair liquid impregnation is only mechanical stirring and mixing, and the 80-120 mesh slurry is not prepared.

[0082] Comparative Example 3

[0083] The difference from Example 1 is only that the pore former in the repair liquid is polyethylene glycol 800.

[0084] Comparative Example 4

[0085] The difference from Example 1 is only that in the alkali treatment, 1 mol / L ammonia solution is used for soaking treatment.

[0086] Comparative Example 5

[0087] The difference from Example 1 is only that in the alkali treatment, 1 mol / L sodium hydroxide solution is used for soaking treatment.

[0088] Comparative Example 6

[0089] The difference from Example 1 is only that in the repair liquid, the mass fraction of polyvinyl alcohol is 10%.

[0090] Comparative Example 7

[0091] The difference from Example 1 is that the mass fraction of polyvinyl alcohol in the repair solution is 2%.

[0092] Comparative Example 8

[0093] The difference from Example 1 is that the rotation speed of the high-temperature activation furnace is 3.5 revolutions per minute.

[0094] Comparative Example 9

[0095] The difference from Example 1 is that the rotation speed of the high-temperature activation furnace is 1 revolution per minute.

[0096] Comparative Example 10

[0097] The difference from Example 1 is that the oxygen volume fraction at the kiln tail is controlled at 1.2%.

[0098] Comparative Example 11

[0099] The regenerated activated carbon was prepared by a conventional method: the waste activated carbon was directly put into a high-temperature activation furnace, heated to 900℃, and kept for 1.0h to obtain.

[0100] Detection method:

[0101] 1. According to GB / T 7702.1-7702.15, the moisture content, ash content, iodine adsorption value, and carbon tetrachloride adsorption value of 5 points were detected, and the average value and standard deviation were calculated.

[0102] 2. Calculate the carbon yield: the percentage of the mass of the regenerated activated carbon obtained after regeneration to the mass of the original waste activated carbon (dry basis);

[0103] Carbon yield (%) = m 再生活性炭干重 / m 原始废活性炭干重 × 100%.

[0104] 3. According to the national standard GB / T 19587-2004 "Determination of Specific Surface Area of Solid Substances by Gas Adsorption BET Method".

[0105] The detection results are shown in Table 1.

[0106] Table 1 Detection results of examples and comparative examples

[0107] The performance advantages of the embodiments are derived from the synergistic regulation of pretreatment, repair liquid impregnation, and controllable thermal activation: acid treatment combined with ammonia gas alkaline treatment can gently and completely remove metal impurities in the pores of waste activated carbon, avoiding high-temperature metal catalytic oxidation centers that damage the carbon skeleton, while controlling the moisture content of the pretreated activated carbon to adapt to subsequent repair liquid infiltration; polyvinyl alcohol in the repair liquid acts as a viscous carbon source, and is ball milled to a particle size of 80-120 mesh to control the strength of the ball particles in the activation furnace, effectively inhibiting dust loss, small molecule carbon sources can repair carbon matrix defects, and 400-600 g / mol polyethylene glycol can decompose and form pores at high temperatures to optimize the pore size distribution; in the controllable thermal activation, the oxygen concentration in the kiln tail is less than 1%, and the appropriate furnace speed or linear speed is matched, which not only realizes the selective cleaning and expansion of the pores, but also avoids excessive oxidation leading to carbon loss and pore collapse, and as the activation temperature increases and the concentration of functional components in the repair liquid increases reasonably, the pore structure optimization effect is more significant, and the adsorption performance and carbon yield are further improved.

[0108] Comparing each comparative example, the reason for its poor performance compared to the embodiments is due to defects in a single process link: Comparative Example 1 does not use repair liquid, lacks a viscous carbon source, and the material cake cannot form a ball, dust loss is intensified, and there is no repair and pore forming effect, and the carbon skeleton defects and pore blockage are not solved; Comparative Example 2 only mechanically mixes the repair liquid without ball milling, the material particle size is uneven, the components are not evenly dispersed, the repair liquid cannot fully infiltrate the pores, and the activation process is locally unbalanced; Comparative Example 3 uses polyethylene glycol with a molecular weight of 800, which does not synchronize with the gasification of activated carbon, and is easy to leave residual carbon to block the pores, weakening the pore forming effect; Comparative Example 4 uses ammonia water soaking instead of ammonia gas alkaline treatment, and the liquid alkali causes local pH to be too high, damaging the carbon skeleton and increasing the ash content due to residual ammonium salt; Comparative Example 5 uses a strong liquid alkali of sodium hydroxide, which has a more severe corrosion effect, causing more severe damage to the carbon skeleton and more serious impurity residue; Comparative Example 6 has a polyvinyl alcohol content that is too high, causing material clumping and blocking the pores, and Comparative Example 7 has a polyvinyl alcohol content that is too low, failing to provide sufficient adhesion to support ball formation, both of which result in increased dust and decreased adsorption performance; Comparative Example 8 has a furnace speed that is too fast, causing ball particles to collide and break, and Comparative Example 9 has a speed that is too slow, making the material cake unable to fully form a ball and causing uneven activation, both of which intensify dust and carbon skeleton damage; Comparative Example 10 has an oxygen concentration in the kiln tail of 1.2%, and the enhanced oxidizing atmosphere causes excessive oxidation, resulting in increased carbon loss and collapsed pore structure; Comparative Example 11 uses a conventional activation method without pretreatment and repair, and the problems of metal impurity catalytic oxidation, dust loss, and pore blockage are not solved, and the performance is the worst among all groups.

[0109] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for regenerating spent activated carbon, characterized by, The method comprises the following steps: (a) pretreatment of removing impurities: the spent activated carbon is sequentially subjected to acid treatment, alkali treatment and cleaning treatment to obtain pretreated activated carbon; The alkali treatment is: passing ammonia gas into the acid-treated solid phase until the pH is 8.5-10 to obtain alkali-treated material; (b) impregnation with repair solution: the pretreated activated carbon is mixed with the repair solution at a mass ratio of 1:1-2, added into a ball mill and ground to 80-120 mesh, and then the solid phase is separated, the water content of the material is controlled to be 13-18%, and a material cake is obtained; The repair solution comprises the following components in mass percentage: 3-8% of viscous carbon source, 1-5% of small-molecule carbon source, 0.5-3% of pore-forming agent, and the balance being water; The pore-forming agent is polyethylene glycol, and the average molecular weight is 400-600 g / mol; (c) controllable heat activation: the material cake is fed into a high-temperature activation furnace through a screw conveyor, the oxygen volume fraction at the kiln tail is controlled to be lower than 1%, the temperature is raised to 850-950 ℃, and the material is activated for 0.5-2 h, and then the regenerated activated carbon is obtained after cooling; The rotation speed of the high-temperature activation furnace is 1.5-3 revolutions per minute, or the inner wall linear velocity of the high-temperature activation furnace is 5-10 m / min.

2. The spent activated carbon regeneration method according to claim 1, characterized by, The acid treatment is: soaking in a 0.5-5 mol / L inorganic acid solution at 20-60 ℃ at a solid-liquid ratio of 1:3-1:10 for 1-4 hours, and then centrifuging to obtain an acid-treated solid phase with a water content of 18-25%; the cleaning treatment is: washing the alkali-treated material with 3-5 times the mass of water, and then centrifuging to obtain pretreated activated carbon with a water content of 12-18%.

3. The spent activated carbon regeneration method according to claim 2, characterized by, The inorganic acid is hydrochloric acid or nitric acid.

4. The spent activated carbon regeneration method according to Claim 1, characterized by In step (b), the viscous carbon source is polyvinyl alcohol; and the small-molecule carbon source is one or more of glucose, sucrose and fructose.

5. The spent activated carbon regeneration method according to Claim 1, characterized by In step (b), the method for separating the solid phase is centrifugation or pressure filtration.

6. The spent activated carbon regeneration method according to Claim 1, characterized by In step (c), the method for controlling the oxygen volume fraction at the kiln tail to be lower than 1% is: adding nitrogen gas to the gas obtained after flue gas purification until the oxygen volume fraction is lower than 1%, and then introducing the compressed gas into the kiln body; the process of flue gas purification is: leading the tail gas out of the kiln head, and then removing acid, dust and moisture.

7. The spent activated carbon regeneration method according to Claim 6, characterized by, The deacidifying agent for deacidification is slaked lime; and the process of moisture removal is condensation dehumidification.

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