Graded desorption regeneration method and system for organic pollutant waste activated carbon

Abstract

The invention discloses a graded desorption regeneration method and system for organic pollutant waste activated carbon, and belongs to the technical field of environmental protection and resource regeneration. The method comprises the following steps: firstly, carrying out pollutant analysis on waste activated carbon, and setting a graded temperature program according to the pollutant analysis; firstly, desorbing water and low-boiling-point VOCs in an inert atmosphere at a low temperature, and condensing and recycling; high-boiling-point SVOCs are desorbed at medium temperature, and desorbed gas is combusted to utilize heat energy of the desorbed gas; and finally, carrying out medium-high temperature activation in a weak oxidizing atmosphere, and removing residues to recover activity. The system comprises a regeneration main furnace, an inert gas supply unit and a graded tail gas treatment system consisting of a first-stage condensation recovery unit, a second-stage combustion utilization unit and a third-stage high-temperature incineration unit. According to the method, efficient, energy-saving, low-carbon-loss, safe and reliable regeneration is realized through graded accurate desorption, the adsorption capacity recovery rate of regenerated carbon is high, resource utilization of pollutants is realized, and many defects in a traditional regeneration technology are overcome.

Description

Technical Field

[0001] This invention belongs to the technical field of environmental protection and resource regeneration, specifically relating to a method and system for the graded desorption and regeneration of waste activated carbon containing organic pollutants. Background Technology

[0002] Activated carbon, due to its large specific surface area and excellent adsorption performance, is widely used in waste gas treatment and wastewater treatment in industries such as chemical, petrochemical, pharmaceutical, and coating. Saturated activated carbon is classified as hazardous waste (HW49), and its treatment and disposal has become an industry challenge. Direct incineration is costly and wasteful of resources; therefore, desorption and regeneration is the best way to achieve recycling, volume reduction, and resource recovery.

[0003] Currently, the most widely used regeneration technology in industry is thermal regeneration, including traditional rotary kilns, fluidized beds, and microwave heating. However, existing technologies generally suffer from the following problems: (1) High energy consumption: Regardless of the type of pollutant adsorbed on the activated carbon, regeneration is carried out at a uniform maximum temperature (usually as high as 800-900℃), resulting in serious energy waste; (2) High activated carbon loss: High temperature will cause the activated carbon skeleton to burn out, and the loss rate of each regeneration is as high as 5%-15%, which shortens the life of activated carbon.

[0004] (3) Safety hazards exist: For waste activated carbon that has adsorbed mixed organic matter with different boiling points and flash points, a one-time heating may lead to local overheating, uncontrolled reaction, or even explosion risk; (4) Secondary pollution exists: At high temperatures, some high molecular weight or chlorine-containing organic compounds may decompose to produce more toxic substances such as dioxins, which greatly increases the burden of exhaust gas treatment. (5) Poor regeneration effect: For complex mixed pollutants, it is difficult to achieve effective desorption of all pollutants at a single temperature, which may lead to incomplete regeneration and low adsorption capacity recovery rate.

[0005] Existing related patent technologies also have obvious limitations: For example, patent CN202210837896.3 uses a counter-current rotary kiln, which has strong universality and high regeneration efficiency, but the temperature curve and residence time control are relatively coarse, making it difficult to achieve the optimal desorption conditions for different adsorbates. This may cause excessive pyrolysis of low-boiling-point substances or insufficient desorption of high-boiling-point substances, and there is still room for improvement in energy utilization. Although patent CN201811222331.4 focuses on the regeneration of hazardous waste activated carbon containing chlorinated hydrocarbons and the resource utilization of waste gas, the main regeneration process is still traditional thermal regeneration, which is not a refined graded desorption design for complex VOCs components (such as mixed hydrocarbons, ketones, esters, etc.).

[0006] Given the shortcomings of the existing technologies, developing a regeneration method that can perform precise and graded desorption based on the characteristics of pollutants is of great practical significance for reducing energy consumption, minimizing carbon loss, ensuring safety, and improving regeneration efficiency, and has become an urgent need for those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a graded desorption and regeneration method and system for waste activated carbon containing organic pollutants. This method performs graded and programmed temperature-increasing desorption based on the boiling point and decomposition temperature characteristics of the pollutants adsorbed on the waste activated carbon, thereby achieving efficient, energy-saving, safe, and low-carbon regeneration. This solves the problems of high energy consumption, large carbon loss, numerous safety hazards, and poor regeneration effect in traditional regeneration technologies.

[0008] This invention provides a method for the graded desorption and regeneration of spent activated carbon containing organic pollutants, comprising the following steps: S1. Pretreatment and analysis stage: Sampling and analysis of waste activated carbon to determine the types, boiling point distribution and decomposition temperature range of the main organic pollutants adsorbed on it. S2, First-stage low-temperature desorption stage: Under the protection of an inert atmosphere, waste activated carbon is loaded into the regeneration main furnace, heated to the first temperature T1 and kept at that temperature for desorption of moisture and low-boiling-point volatile organic compounds. S3, Secondary Medium-Temperature Desorption Stage: After completing the primary desorption, the activated carbon is heated to the second temperature T2 and kept at that temperature for the desorption of medium- and high-boiling-point semi-volatile organic compounds. S4, Third-level high-temperature purification stage: After the second-level desorption is completed, a weak oxidizing medium is introduced to heat the activated carbon to the third temperature T3 and keep it at that temperature for a short time to decompose the residual recalcitrant substances and purify the microporous structure of the activated carbon. S5. Cooling stage: Under the protection of an inert atmosphere, the regenerated activated carbon is cooled to a safe temperature and then removed from the furnace.

[0009] Preferably, the analytical method in step S1 is thermogravimetric analysis or gas chromatography-mass spectrometry; the specific set values ​​of T1, T2, and T3 are determined based on the analytical results of step S1.

[0010] Preferably, the first temperature T1 is 80-150℃, the second temperature T2 is 250-400℃, and the third temperature T3 is 450-550℃.

[0011] Preferably, the heating rates in steps S2, S3, and S4 are all controlled at 3-100℃ / min. A lower and milder heating rate can be used in the laboratory pilot stage. In the industrial-scale production stage, a higher heating rate can be adapted based on the heat exchange efficiency of the main regeneration furnace, the loading of waste activated carbon in the kilogram range or more, and the actual characteristics of the pollutants. The holding time in each stage is determined according to the loading of waste activated carbon and the load of pollutants.

[0012] Preferably, steps S2 and S3 are carried out under an absolutely inert atmosphere, the medium of which is nitrogen; the weak oxidizing medium in step S4 is water vapor or carbon dioxide.

[0013] Preferably, the gas generated by desorption in step S2 is condensed and recovered to recover the low-boiling-point solvent; the gas generated by desorption in step S3 is introduced into a combustion device for combustion, and the heat energy generated by combustion is used to supplement the heat source of the system; the gas generated in step S4 is treated by high-temperature incineration and then discharged in compliance with standards.

[0014] This invention also provides a staged desorption and regeneration system for spent activated carbon containing organic pollutants, comprising: The main regeneration furnace is equipped with a programmed temperature control function and is used to carry waste activated carbon and complete the staged desorption and regeneration process. An inert gas supply unit, which is connected to the main regeneration furnace, is used to provide an inert protective atmosphere; A staged exhaust gas treatment system is connected to the exhaust port of the regeneration main furnace and is used to treat the exhaust gas generated in each desorption stage separately. The staged exhaust gas treatment system includes: a primary condensation and recovery unit for treating the gas generated in the primary low-temperature desorption stage; a secondary combustion and utilization unit for treating the gas generated in the secondary medium-temperature desorption stage and recovering its heat energy; and a tertiary high-temperature incineration unit for treating the waste gas generated in the tertiary high-temperature purification stage. The program control system is electrically connected to the main regeneration furnace, the inert gas supply unit, and the staged tail gas treatment system. It is used to receive pollutant component analysis data and automatically control the temperature program, holding time, and atmosphere switching of the main regeneration furnace according to a preset algorithm. It can also precisely adapt and adjust the heating rate of each desorption stage according to different application scenarios such as laboratory pilot-scale testing and industrial-scale production, taking into account both the controllability of laboratory research and development and the efficiency of industrial production.

[0015] Preferably, the regeneration main furnace is a rotary kiln, a rake furnace, or a fluidized bed furnace.

[0016] Preferably, the primary condensation and recovery unit includes a condenser and a condensate collection tank for condensing and recovering low-boiling-point solvents.

[0017] Preferably, the secondary combustion utilization unit includes a burner and a waste heat recovery device, which is connected to the heating system of the main regeneration furnace and is used to recover the heat energy generated by combustion to the main regeneration furnace as a supplementary heat source.

[0018] The beneficial effects of this invention are: This invention achieves efficient, energy-saving, safe, and low-carbon regeneration by using a staged, programmed temperature-controlled desorption process based on the boiling point and decomposition temperature characteristics of pollutants adsorbed on waste activated carbon. It offers the following advantages: (1) Significant energy saving and consumption reduction: Through the staged heating design, different desorption temperatures are set according to the characteristics of pollutants, avoiding the need to heat all materials to high temperatures at the same time, and the energy utilization rate is increased by more than 30%; at the same time, the heat value of the secondary desorption gas itself is used to supplement the system heat source, further reducing external energy consumption and greatly improving the economic efficiency of the process.

[0019] (2) Greatly reduce carbon loss: The maximum regeneration temperature is reduced from the traditional 800℃ or above to below 550℃, which significantly reduces the burn-off rate and volatilization loss of activated carbon. The loss per regeneration can be controlled within 3%, which effectively extends the service life of activated carbon and reduces the user's operating costs.

[0020] (3) Safe and reliable: The staged heating desorption avoids the risk of deflagration that may be caused by the simultaneous and violent precipitation of pollutants with different boiling points at high temperatures. Moreover, the key desorption stages are carried out under the protection of an inert atmosphere throughout the process. The process is mild and controllable, which solves the safety hazards of traditional regeneration technology.

[0021] (4) High regeneration efficiency: The targeted temperature setting ensures the complete desorption of pollutants with different characteristics. Combined with the activation treatment of the three-stage high-temperature purification stage, the pores are effectively unblocked and the pore volume is restored. The regenerated carbon adsorption capacity recovery rate can reach more than 95%, and the adsorption performance is excellent.

[0022] (5) Balancing resource recovery and waste reduction: The first-stage condensation and recovery unit realizes the recovery and reuse of low-boiling-point solvents, the second-stage combustion and utilization unit realizes the energy utilization of medium and high-boiling-point organic matter, and the third-stage high-temperature incineration unit ensures that the exhaust gas meets the emission standards. This not only realizes the resource recycling of waste, but also reduces the amount of exhaust gas from the final incineration treatment and reduces the risk of secondary pollution. Attached Figure Description

[0023] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0024] Figure 1 This is a schematic diagram of the process flow of the graded desorption and regeneration system of the present invention; Figure 2 This is a schematic diagram of the temperature-time program curve for the staged desorption and regeneration method of the present invention; Figure 3 This is an enlarged schematic diagram of the primary desorption gas treatment section in Embodiment 3 of the present invention (treatment of chlorine-containing waste); Figure 4 This is an enlarged schematic diagram of the secondary desorption gas treatment section in Embodiment 3 of the present invention (treatment of chlorine-containing waste).

[0025] In the picture: 1-Regeneration main furnace; 2-Inert gas supply unit; 3-First-stage condensation and recovery unit; 301-Condenser; 302-Condensate collection and tank; 4-Second-stage combustion and utilization unit; 401-Burner; 402-Waste heat recovery device; 5-Third-stage high-temperature incineration unit; 6-Programmable control system; 7-Alkali spray absorption tower; 8-High-temperature incinerator. Detailed Implementation

[0026] The following are specific embodiments of the present invention described in conjunction with the accompanying drawings, further illustrating the technical solutions of the present invention. However, the present invention is not limited to these embodiments. Specific details, such as particular configurations and components, are provided in the following description merely to aid in a comprehensive understanding of the embodiments of the present invention. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Furthermore, for clarity and brevity, descriptions of known functions and structures have been omitted.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0028] like Figures 1-4 As shown, this invention provides a method and system for the graded desorption and regeneration of spent activated carbon containing organic pollutants. The graded desorption and regeneration method includes the following steps: Pretreatment and analysis stage: Waste activated carbon is sampled and analyzed. Thermogravimetric analysis (TGA) or gas chromatography-mass spectrometry (GC-MS) is used to determine the types, boiling point distribution and decomposition temperature range of the main organic pollutants adsorbed on it, so as to provide a basis for setting the temperature parameters for subsequent staged desorption. Primary low-temperature desorption stage: Under an inert atmosphere (nitrogen as the medium), the waste activated carbon is loaded into the regeneration furnace and heated to the first temperature T1 (80-150℃) at a heating rate of 3-100℃ / min, and then held at that temperature. Laboratory tests use a low heating rate of 3-8℃ / min, while industrial-scale production can use a suitable heating rate of 8-10℃ / min. The holding time is determined based on the amount of waste activated carbon loaded and the amount of pollutants. This stage is mainly used for desorbing moisture and low-boiling-point volatile organic compounds (such as acetone, ethanol, benzene compounds, etc.). The gas generated during desorption is condensed and recovered to remove the low-boiling-point solvent, thus achieving resource recovery. Secondary medium-temperature desorption stage: After primary desorption, the activated carbon is heated to the second temperature T2 (250-400℃) at a heating rate of 3-100℃ / min and held at that temperature. In laboratory tests, a heating rate of 5-10℃ / min is used. For industrial-scale production, a high heating rate of 10-50℃ / min can be used depending on the material heat exchange efficiency. The holding time is determined according to the loading of waste activated carbon and the amount of pollutants. This stage is used to desorb medium- and high-boiling-point semi-volatile organic compounds (such as xylene, phenols, and some pesticide intermediates). The gas produced by desorption is introduced into a combustion device for combustion, and the heat energy generated by combustion is used to supplement the system's heat source, realizing the cascade utilization of energy. The third-stage high-temperature purification phase: After the second-stage desorption, a weak oxidizing medium (water vapor or carbon dioxide) is introduced, and the activated carbon is heated to the third temperature T3 (450-550℃) at a heating rate of 3-100℃ / min and held at that temperature for a short time. Laboratory tests use a heating rate of 5-10℃ / min, while industrial-scale production can use a heating rate of 10-50℃ / min. The holding time is determined based on the amount of waste activated carbon and the amount of pollutants. This stage is used to decompose residual recalcitrant substances (such as tar-like substances, polymers, or carbon residue) and purify the microporous structure of the activated carbon, restoring its adsorption activity. The generated gas is then treated by high-temperature incineration before being discharged in compliance with standards. Cooling stage: Under the protection of an inert atmosphere (nitrogen gas), the regenerated activated carbon is cooled to a safe temperature (e.g., <40℃) and then removed from the furnace to complete the regeneration process.

[0029] The specific settings for T1, T2, and T3 are customized based on the analysis results of step S1 to ensure the targeted and effective desorption process.

[0030] This invention involves in-depth research and optimization of the heating rate; the research found that the heating rate has a dual impact on the regeneration effect: (1) In the first-stage low-temperature desorption stage, a relatively slow heating rate should be used for low-boiling-point VOCs. This is because if the temperature rises too quickly in the low-temperature stage, the low-boiling-point solvent adsorbed in the micropores will vaporize violently and instantly, generating huge internal pressure, which can easily cause the activated carbon pore structure to collapse and break due to physical erosion, thereby reducing the strength and adsorption performance of the regenerated carbon; a slower heating rate is conducive to the stable release of gas and protects the carbon skeleton.

[0031] (2) In the secondary medium-temperature desorption and tertiary high-temperature purification stages, a relatively fast heating rate should be adopted for high-boiling-point SVOCs and recalcitrant substances. This is because high-boiling-point organic compounds are prone to deep cracking or polymerization reactions at high temperatures. If the residence time in the intermediate temperature range is too long (i.e., the heating is too slow), tar-like polymers or carbonization and coking are easily formed in the pores of activated carbon, causing pore blockage and leading to regeneration failure. Rapid heating can enable activated carbon to quickly cross the reaction-sensitive zone and rapidly desorb or decompose at the target temperature, significantly reducing coking.

[0032] Furthermore, in large-scale continuous industrial production (such as fluidized bed or high-capacity rotary kilns), the actual heating rate is often rapid due to the high thermal efficiency of the equipment and the continuous movement of materials. The heating rate range set in this invention can meet the needs of precise control in the laboratory and fully cover the conditions of rapid large-scale industrial production, thus possessing strong industrial applicability.

[0033] This invention provides a staged desorption and regeneration system for spent activated carbon containing organic pollutants, comprising a main regeneration furnace 1, an inert gas supply unit 2, a staged tail gas treatment system, and a programmable control system 6. The main regeneration furnace 1 has a programmable temperature control function and is used to hold the spent activated carbon and complete the staged desorption and regeneration process; the main regeneration furnace 1 can be a rotary kiln, a rake furnace, or a fluidized bed furnace. The inert gas supply unit 2 is connected to the main regeneration furnace 1 and provides nitrogen as an inert protective atmosphere to ensure process safety during the primary low-temperature desorption, secondary medium-temperature desorption, and cooling stages. The staged exhaust gas treatment system is connected to the exhaust port of the main regeneration furnace 1 to treat the exhaust gas generated in each desorption stage, ensuring that pollutants are discharged in compliance with standards and that resources are recycled. Specifically, the staged exhaust gas treatment system includes a primary condensation and recovery unit 3, a secondary combustion and utilization unit 4, and a tertiary high-temperature incineration unit 5. The primary condensation and recovery unit 3 includes a condenser 301 and a condensate collection tank 302, which is used to treat the gas generated in the primary low-temperature desorption stage and condense and recover low-boiling-point solvents. The secondary combustion and utilization unit 4 includes a burner 401 and a waste heat recovery device 402. The waste heat recovery device is connected to the heating system of the main regeneration furnace 1 to treat the gas generated in the secondary medium-temperature desorption stage and recover the heat energy generated by combustion to the main regeneration furnace 1 as a supplementary heat source. The tertiary high-temperature incineration unit 5 is used to treat the waste gas generated in the tertiary high-temperature purification stage, and thoroughly decomposes residual pollutants through high-temperature incineration to ensure that the exhaust gas is discharged in compliance with standards. The program control system 6 is electrically connected to the main regeneration furnace 1, the inert gas supply unit 2, and the staged tail gas treatment system, respectively. It is used to receive pollutant component analysis data and automatically control the temperature program, holding time, and atmosphere switching of the main regeneration furnace 1 according to the preset algorithm. At the same time, it can precisely adjust the heating rate of each desorption stage according to different scenarios of laboratory pilot-scale / industrial large-scale production, so as to realize the automation, precision, and scenario-based control of the entire regeneration process, taking into account the controllability of laboratory research and development and the efficiency of industrial production.

[0034] The following are application examples for different processing scenarios: Example 1: Treatment of waste activated carbon containing alcohols and benzene series compounds from chemical enterprises (I) Preprocessing and Analysis The waste activated carbon produced by a chemical enterprise was analyzed by GC-MS and its main pollutants were methanol (boiling point 65℃), toluene (boiling point 111℃) and o-xylene (boiling point 144℃). 100 kg of this waste activated carbon was selected as the treatment target.

[0035] (II) Configuration of the Regeneration System The main regeneration furnace uses a programmable temperature-controlled rotary kiln, and the inert gas supply unit provides high-purity nitrogen. The staged tail gas treatment system includes a condenser, condensate collection tank, burner, waste heat recovery device, and high-temperature incinerator. The programmable control system presets process parameters based on pollutant analysis results.

[0036] (III) Regeneration Process First-stage low-temperature desorption: Nitrogen gas is introduced into the rotary kiln and heated to 100°C at a heating rate of 5°C / min, and held at that temperature for 60 minutes; the desorbed gas is cooled by a condenser and a mixture of methanol and some toluene is recovered. Secondary medium-temperature desorption: Continue heating at a rate of 10℃ / min to 300℃ and hold for 90 minutes; the desorbed toluene and xylene vapors are introduced into the burner for combustion, and the generated high-temperature flue gas provides part of the heat source for the subsequent heating of the rotary kiln through the waste heat recovery device. Three-stage high-temperature purification: A small amount of water vapor is introduced into the kiln, and the temperature is raised to 500℃ at a rate of 10℃ / min. The temperature is maintained for 20 minutes to remove any remaining small amount of large molecular impurities. The generated waste gas is treated in a high-temperature incinerator and then discharged in compliance with emission standards. Cooling stage: Stop heating and cool the activated carbon to below 40°C under nitrogen protection before removing it from the furnace.

[0037] (iv) Regeneration effect Tests showed that the iodine value of the recycled char was restored to 98% of that of the new char, the strength retention rate was over 97%, and the char loss was only 2.5%. All indicators met the requirements for industrial reuse.

[0038] Example 2: Treatment of waste activated carbon containing mixed ester and ketone solvents in automotive painting workshops (I) Preprocessing and Analysis Waste activated carbon generated in an automotive painting workshop was analyzed by TGA-DSC (thermogravimetric-differential scanning calorimetry). The adsorbed pollutants were a complex mixture of solvents, including ethyl acetate (boiling point 77℃), methyl ethyl ketone (boiling point 80℃), and propylene glycol methyl ether acetate (boiling point 146℃). The adsorption capacity was relatively large, so this waste activated carbon was selected for treatment.

[0039] (II) Configuration of the Regeneration System The main regeneration furnace adopts a rake furnace, and the remaining system components are the same as in Example 1. The program control system adjusts the temperature program according to the boiling point characteristics of the mixed solvent.

[0040] (III) Regeneration Process First-stage low-temperature desorption: Under nitrogen protection, the temperature is raised to 85°C at a rate of 6°C / min and held for 120 minutes; deep condensation is performed using -5°C chilled water to recover the mixed solvent, which can be reused in the spraying process after separation. Secondary medium-temperature desorption: The temperature is increased to 280℃ at a rate of 15℃ / min and held for 100 minutes to desorb the remaining propylene glycol methyl ether acetate and other high-boiling-point components; the generated gas is introduced into a thermal oxidizer (TO) for combustion, and the heat generated by combustion is used to preheat the inert gas entering the regeneration furnace, realizing energy cascade utilization. Three-stage high-temperature purification: A small amount of water vapor is introduced, and the temperature is raised to 480°C at a rate of 10°C / min, and held for 15 minutes to remove residual resinous substances; the exhaust gas is then incinerated at high temperature and discharged in compliance with standards. Cooling stage: Cool to below 40°C under nitrogen protection before unloading.

[0041] (iv) Regeneration effect The adsorption performance of the regenerated carbon is restored to 96% of that of the new carbon, the solvent recovery rate exceeds 85%, and the overall energy consumption is reduced by 40% compared with the traditional single high-temperature regeneration method, achieving the dual goals of resource recovery and energy conservation.

[0042] Example 3: Treatment of waste activated carbon containing chlorinated hydrocarbons and heterocyclic compounds from the pharmaceutical and chemical industries (I) Preprocessing and Analysis GC-MS analysis of spent activated carbon generated during the production of a certain active pharmaceutical ingredient showed that it contained dichloromethane (boiling point 40℃), pyridine (boiling point 115℃), and a small amount of polymeric intermediates (decomposition temperature >300℃). These chlorine- and nitrogen-containing organic compounds are prone to generating dioxins or NO at high temperatures. x The waste activated carbon was selected for treatment.

[0043] (II) Configuration of the Regeneration System The main regeneration furnace is a fluidized bed furnace, and the staged tail gas treatment system is equipped with an alkali spray absorption tower (such as...). Figures 3-4 As shown in the figure, it is used to treat chlorine- and nitrogen-containing waste gas, and the rest of the configuration is the same as in Example 1.

[0044] (III) Regeneration Process First-stage low-temperature desorption: Under nitrogen protection, the temperature is slowly raised to 60°C at a rate of 5°C / min and held for 150 minutes to ensure that dichloromethane is completely and gently desorbed; the desorbed gas is immediately sent to an alkaline spray absorption tower for treatment to prevent equipment corrosion and remove harmful components. Secondary intermediate-temperature desorption: The temperature is increased to 320℃ at a rate of 10℃ / min and held for 90 minutes to desorb organic compounds such as pyridine; during this stage, the gas is introduced into a specially designed thermal oxidizer for high-temperature combustion (>1100℃), and an alkaline absorption tower is used to treat any NO that may be generated. x ; Three-stage high-temperature purification: CO2 is introduced as an activation medium, and the temperature is raised to 520°C at a rate of 8°C / min and held for 10 minutes; CO2 has a milder oxidizing property than water vapor, which can effectively vaporize residues and at the same time greatly inhibit the formation of dioxins; the generated waste gas is treated by high-temperature incineration and alkaline absorption before being discharged in compliance with standards. Cooling stage: Cool to below 40°C under nitrogen protection before unloading.

[0045] (iv) Regeneration effect The regeneration process is safe and controllable, and the exhaust emissions strictly meet the standards, with no dioxins detected. The quality of the regenerated carbon meets pharmaceutical requirements, solving the problem of regenerating waste activated carbon containing special pollutants.

[0046] Example 4: Treatment of waste activated carbon containing light hydrocarbons from the petrochemical industry (I) Preprocessing and Analysis GC-MS analysis of spent activated carbon from a petrochemical plant revealed that its main adsorbed pollutants were light hydrocarbons, such as n-hexane and cyclohexane. These pollutants have low boiling points, are highly volatile, and possess clear explosion limits. Conventional temperature-based desorption poses safety hazards, thus this spent activated carbon was selected as the target for treatment.

[0047] (II) Configuration of the Regeneration System The regeneration main furnace uses a programmable temperature-controlled rotary kiln, with an added vacuum generation unit and pressure control system to ensure a vacuum environment during the first-stage desorption stage; the inert gas supply unit provides high-purity nitrogen; the staged tail gas treatment system includes a high-efficiency condenser, condensate collection and tanking, a flare combustion system, and a high-temperature incinerator; the programmable control system integrates vacuum, temperature, and atmosphere linkage control functions to adjust process parameters in real time.

[0048] (III) Regeneration Process First-stage low-temperature desorption: Close the rotary kiln exhaust port, start the vacuum generating unit, and maintain the vacuum level inside the kiln at -0.095 MPa; under vacuum, heat to 75°C at a heating rate of 8°C / min and hold for 60 minutes. The vacuum environment significantly lowers the boiling point of light hydrocarbons, enabling efficient desorption at a mild temperature and completely avoiding the risk of explosion; the desorbed n-hexane and cyclohexane vapors are rapidly condensed in a condenser to recover high-purity mixed hydrocarbon solvents.

[0049] Secondary intermediate-temperature desorption: Remove the vacuum, introduce nitrogen, and continue to heat to 180°C at a rate of 10°C / min (since most of the substances have been desorbed under vacuum, the temperature at this stage can be lower), desorb the remaining components and lead them to the flare system for combustion.

[0050] Three-stage high-temperature purification: Water vapor is introduced as a weak oxidizing medium, and the temperature is raised to 500℃ at a rate of 6℃ / min, held for 20 minutes, and the residual trace amounts of colloidal substances in the micropores of activated carbon are vaporized and decomposed, thus clearing the pore structure. The resulting waste gas is treated in a high-temperature incinerator and then discharged in compliance with emission standards.

[0051] Cooling stage: Stop heating and cool the activated carbon to below 40°C under nitrogen protection before removing it from the furnace.

[0052] (iv) Regeneration effect The regeneration process is safe and controllable with no risk of explosion; the overall energy consumption is significantly reduced compared to traditional regeneration methods, achieving the recovery of high-value solvents.

[0053] Example 5: Treatment of waste activated carbon containing high concentrations of N-methylpyrrolidone from a fine chemical plant (I) Preprocessing and Analysis Waste activated carbon generated during the production process of a fine chemical plant was identified by TGA analysis as having a high concentration of N-methylpyrrolidone (NMP, boiling point 202℃) as its main adsorbate. This waste activated carbon was selected for treatment.

[0054] (II) Configuration of the Regeneration System The main regeneration furnace is a rake furnace; the inert gas supply unit provides nitrogen; the primary condensation and recovery unit uses a high-efficiency condenser to ensure the purity of NMP recovery; the secondary combustion and utilization unit includes a burner and a waste heat recovery heat exchanger, which are linked with the rake furnace heating system; the program control system presets a constant temperature and heat preservation program based on the NMP desorption characteristics.

[0055] (III) Regeneration Process Primary low-temperature desorption: Nitrogen gas is introduced into the rake furnace, and the temperature is increased to 110°C at a rate of 6°C / min, and held for 30 minutes. This stage mainly desorbs free water in the pores of activated carbon. The water vapor generated is condensed by a condenser and treated as industrial wastewater to avoid the water affecting the purity of subsequent NMP recovery.

[0056] Secondary medium-temperature desorption: As the main desorption stage, the temperature continues to rise at a programmed rate of 15℃ / min to 230℃ (above the boiling point of NMP), and is held at this temperature for 180 minutes. The desorbed pure NMP vapor is condensed by a high-efficiency condenser and collected in a dedicated storage tank. The recovered NMP has a purity of 98.7% and can be directly reused in production.

[0057] Three-stage high-temperature purification: Because the pollutant is singular and desorbed completely, a small amount of water vapor is introduced into the furnace, and the temperature is raised to 480°C at a rate of 10°C / min. The temperature is maintained for 5 minutes to quickly remove trace amounts of residual NMP polymer in the micropores.

[0058] Cooling stage: Stop heating and cool the activated carbon to below 40°C under nitrogen protection before removing it from the furnace.

[0059] (iv) Regeneration effect It achieves nearly 100% recovery of the high-value solvent NMP, and the overall operating cost is close to zero due to the recovery and utilization of waste heat in the regeneration process, resulting in significant economic benefits.

[0060] Comparative Example: Treatment of Waste Activated Carbon from Example 2 using Traditional High-Temperature Regeneration Method The same batch of waste activated carbon from Example 2 was treated using a traditional single high-temperature regeneration method: water vapor was directly introduced, the temperature was raised to 850°C and kept at that temperature for 30 minutes.

[0061] Processing results: Extremely high energy consumption, with all materials heated to 850℃; activated carbon burn-off rate as high as 22%; all mixed solvents were burned and could not be recovered, resulting in resource waste; the regenerated carbon adsorption capacity recovery rate was only 88%, and the strength decreased significantly; multiple solvents vaporized instantly, posing significant safety risks.

[0062] As can be seen from the comparison between the above embodiments and comparative examples, the graded desorption and regeneration method and system of the present invention have significant comprehensive advantages in terms of energy saving and consumption reduction, carbon loss reduction, safety and controllability, resource recovery and regeneration effect. It completely solves many drawbacks of traditional regeneration technology and has broad industrial application prospects.

[0063] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0064] In the description of this application, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

Claims

1. A method for the staged desorption and regeneration of spent activated carbon containing organic pollutants, characterized in that, Includes the following steps: S1. Pretreatment and analysis stage: Sampling and analysis of waste activated carbon to determine the types, boiling point distribution and decomposition temperature range of the main organic pollutants adsorbed on it. S2, First-stage low-temperature desorption stage: Under the protection of an inert atmosphere, waste activated carbon is loaded into the regeneration main furnace, heated to the first temperature T1 and kept at that temperature for desorption of moisture and low-boiling-point volatile organic compounds. S3, Secondary Medium-Temperature Desorption Stage: After completing the primary desorption, the activated carbon is heated to the second temperature T2 and kept at that temperature for the desorption of medium- and high-boiling-point semi-volatile organic compounds. S4, Third-level high-temperature purification stage: After the second-level desorption is completed, a weak oxidizing medium is introduced to heat the activated carbon to the third temperature T3 and keep it at that temperature for a short time to decompose the residual recalcitrant substances and purify the microporous structure of the activated carbon. S5. Cooling stage: Under the protection of an inert atmosphere, the regenerated activated carbon is cooled to a safe temperature and then removed from the furnace.

2. The method for staged desorption and regeneration of spent activated carbon containing organic pollutants according to claim 1, characterized in that, The analytical method in step S1 is thermogravimetric analysis or gas chromatography-mass spectrometry; the specific set values ​​of T1, T2, and T3 are determined based on the analytical results of step S1.

3. The method for staged desorption and regeneration of spent activated carbon containing organic pollutants according to claim 1, characterized in that, The first temperature T1 is 80-150℃, the second temperature T2 is 250-400℃, and the third temperature T3 is 450-550℃.

4. The method for staged desorption and regeneration of spent activated carbon containing organic pollutants according to claim 1, characterized in that, The heating rate in steps S2, S3, and S4 is controlled at 3-100℃ / min, and the holding time is determined based on the loading amount of waste activated carbon and the pollutant load.

5. The method for staged desorption and regeneration of spent activated carbon containing organic pollutants according to claim 1, characterized in that, Steps S2 and S3 are carried out under an absolutely inert atmosphere, the medium of which is nitrogen; the weak oxidizing medium in step S4 is water vapor or carbon dioxide.

6. The method for staged desorption and regeneration of spent activated carbon containing organic pollutants according to claim 1, characterized in that, The gas generated by desorption in step S2 is condensed and recovered to recover the low-boiling-point solvent; the gas generated by desorption in step S3 is introduced into a combustion device for combustion, and the heat energy generated by combustion is used to supplement the heat source of the system; the gas generated in step S4 is treated by high-temperature incineration and then discharged in compliance with emission standards.

7. A staged desorption and regeneration system for spent activated carbon containing organic pollutants, characterized in that, include: The main regeneration furnace (1) has a programmable temperature control function and is used to carry waste activated carbon and complete the graded desorption and regeneration process. An inert gas supply unit (2) is connected to the main regeneration furnace (1) and is used to provide an inert protective atmosphere; A staged tail gas treatment system is connected to the exhaust port of the regeneration main furnace (1) and is used to treat the tail gas generated in each desorption stage. The staged tail gas treatment system includes: a primary condensation and recovery unit (3) for treating the gas generated in the primary low-temperature desorption stage; a secondary combustion and utilization unit (4) for treating the gas generated in the secondary medium-temperature desorption stage and recovering its heat energy; and a tertiary high-temperature incineration unit (5) for treating the waste gas generated in the tertiary high-temperature purification stage. The program control system (6) is electrically connected to the regeneration main furnace (1), the inert gas supply unit (2) and the staged tail gas treatment system, respectively. It is used to receive pollutant component analysis data and automatically control the temperature program, heat preservation time and atmosphere switching of the regeneration main furnace (1) according to the preset algorithm.

8. The staged desorption and regeneration system for spent activated carbon containing organic pollutants according to claim 7, characterized in that, The main regeneration furnace (1) is a rotary kiln, a rake furnace, or a fluidized bed furnace.

9. A staged desorption and regeneration system for spent activated carbon containing organic pollutants according to claim 7, characterized in that, The primary condensation and recovery unit (3) includes a condenser (301) and a condensate collection tank (302) for condensing and recovering low-boiling-point solvents.

10. A staged desorption and regeneration system for spent activated carbon containing organic pollutants according to claim 7, characterized in that, The secondary combustion utilization unit (4) includes a burner (401) and a waste heat recovery device (402). The waste heat recovery device is connected to the heating system of the main regeneration furnace (1) and is used to recover the heat energy generated by combustion to the main regeneration furnace (1) as a supplementary heat source.

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