Method for optimizing thermal desorption process of granular active carbon for waste gas adsorption

Abstract

The invention discloses a method for optimizing a thermal desorption process of granular activated carbon for waste gas adsorption, which comprises the following steps: S1, taking different sources of granular activated carbon for waste gas adsorption as a raw material, and carrying out qualitative analysis on pollutants adsorbed by the granular activated carbon by using solid-phase extraction and gas chromatography-mass spectrometry; s2, grouping the waste granular activated carbon according to components of pollutants adsorbed by the activated carbon by referring to a result obtained by gas chromatography-mass spectrometry; s3, cleaning, sieving and drying the waste granular activated carbon; s4, placing the dried waste granular activated carbon in a nitrogen atmosphere for thermal desorption; and S5, after thermal desorption is finished, keeping the nitrogen atmosphere for cooling. Through precise operation and optimization measures, the desorption efficiency can be improved to 90%-95%, the overall performance is remarkably improved, the energy consumption is reduced, and the equipment stability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste activated carbon treatment, and specifically relates to an optimization method for the thermal desorption process of granular activated carbon used for waste gas adsorption. Background Art

[0002] Due to its high adsorption performance, granular activated carbon is widely used in various waste gas treatment processes to remove volatile organic compounds (VOCs) and other pollutants. After the activated carbon is saturated with adsorption, it needs to be regenerated through a thermal desorption process to restore its adsorption capacity.

[0003] Currently, the optimization of the thermal desorption process mainly relies on empirical temperature control, which has the following problems to a certain extent. For example, traditional thermal desorption processes often use a fixed high temperature for regeneration. Although this method can achieve the desorption of pollutants, it is not the optimal choice for pollutants with different boiling point ranges. Some pollutants can be effectively volatilized at relatively low temperatures, such as around 300°C. High-temperature regeneration not only wastes energy but may also cause premature aging of the activated carbon. Secondly, too high a thermal desorption temperature may cause structural changes in the activated carbon, such as carbonization, which will damage the pore structure of the activated carbon and reduce its adsorption efficiency. In addition, some pollutants may undergo chemical reactions at high temperatures to form new solid substances, which may block the pores of the activated carbon and further affect its regeneration effect and service life. Moreover, the current thermal desorption process lacks accurate characterization of the pollutants adsorbed by the activated carbon and cannot formulate personalized regeneration plans for different pollutants, making the existing thermal desorption strategies not only inefficient but also difficult to achieve the maximum utilization of resources.

[0004] Therefore, there is an urgent need in the art for a method that can classify and optimize the thermal desorption process according to the specific components of the pollutants adsorbed by the activated carbon, so as to achieve efficient energy utilization and long-term maintenance of the adsorption performance of the activated carbon.

[0005] The patent specification with the publication number CN114671433A discloses a method for predicting the carbonization temperature during the thermal regeneration of waste activated carbon based on TG-MS coupling, including a raw material pretreatment module, a TG-MS test module, and a data analysis and processing module. The raw material pretreatment module is used to perform pretreatment such as drying and grinding on the waste activated carbon saturated with adsorption to provide qualified samples for the subsequent TG-MS test module; the TG-MS test module provides an important data set for the subsequent data analysis and processing module; the analysis and processing module will predict the appropriate carbonization temperature during the thermal regeneration of the waste activated carbon through the analysis and processing of the data set, thereby reducing the experimental workload and improving work efficiency.

[0006] Lu Yao et al. ("Experimental Study and Characterization Analysis on Pyrolytic Regeneration of Waste Powdered Activated Carbon", Volume 37, Issue 1, 2018) conducted pyrolytic regeneration experiments on waste powdered activated carbon (WPAC), and used thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), surface area analysis (BET), and X-ray diffraction (XRD) characterization methods to analyze the specific surface area, pore structure of waste powdered activated carbon before and after pyrolytic regeneration, and the preliminary law of organic matter decomposition during the regeneration process. At the same time, the adsorption performance of waste powdered activated carbon before and after regeneration for methylene blue (MB) was compared, and the pyrolytic regeneration effect of WPAC was evaluated. The optimal pyrolytic regeneration conditions obtained from the experiment were using nitrogen as the carrier gas, a pyrolysis temperature of 650 °C, and a pyrolysis time of 2 h. This technology does not distinguish between pollutant types, nor does it give an adaptable regeneration plan according to specific pollutant types. Summary of the Invention

[0007] The present invention provides an optimization method for the thermal desorption process of granular activated carbon for waste gas adsorption. Based on solid-phase extraction and gas chromatography-mass spectrometry (GC-MS) characterization techniques, it aims to provide a more scientific and efficient solution for the regeneration of activated carbon. Through precise operation and optimization measures, the desorption efficiency can be increased to 90%-95%, significantly improving the overall performance, reducing energy consumption, and enhancing the equipment stability.

[0008] An optimization method for the thermal desorption process of granular activated carbon for waste gas adsorption includes the steps of:

[0009] S1: Using granular activated carbon for waste gas adsorption from different sources as raw materials, and using solid-phase extraction and gas chromatography-mass spectrometry in combination to qualitatively analyze the pollutants adsorbed thereon;

[0010] S2: Referring to the results obtained by gas chromatography-mass spectrometry in combination, grouping the waste granular activated carbon according to the components of the pollutants adsorbed by the activated carbon;

[0011] S3: Cleaning, sieving, and drying the waste granular activated carbon;

[0012] S4: Placing the dried waste granular activated carbon in a nitrogen atmosphere for thermal desorption;

[0013] For waste granular activated carbon mainly adsorbing nitrogen-containing pollutants and / or ketone pollutants, the thermal desorption temperature is 290-310 °C, such as 300 °C, etc., and the thermal desorption time is 0.9-1.1 hours, such as 1 hour, etc.;

[0014] For waste granular activated carbon mainly adsorbing aromatic hydrocarbon pollutants, the thermal desorption temperature is 590-610 °C, such as 600 °C, etc., and the thermal desorption time is 2.9-3.1 hours, such as 3 hours, etc.;

[0015] For the waste granular activated carbon mainly adsorbing halogenated alkane pollutants, the thermal desorption temperature is 490 - 510 °C, such as 500 °C, etc., and the thermal desorption time is 2.9 - 3.1 hours, such as 3 hours, etc.;

[0016] S5: After the thermal desorption ends, keep cooling under a nitrogen atmosphere.

[0017] In some embodiments, in step S1, the granular activated carbon for waste gas adsorption is the columnar granular activated carbon used for waste gas treatment, and its diameter is 4 - 12 mm.

[0018] In step S1, the solid-phase extraction temperature can be 40 - 100 °C.

[0019] In some embodiments, in step S1, the gas chromatograph injection port is 150 - 350 °C, such as 250 °C, etc., the split ratio is 20:1, the carrier gas flow rate is 3 mL / min, the chromatographic column is HP-5MS, the column temperature is 40 °C, it rises to 220 °C at 8 °C / min and holds for 3 min, then rises to 300 °C at 15 °C / min and holds for 3 min.

[0020] In some embodiments, in step S1, the mass spectrometry energy is 70 ev, and the mass range is 35 - 450.

[0021] In step S3, deionized water can be used to wash the ash on the surface of the waste granular activated carbon and remove impurities. After screening by the corresponding size, it is dried by natural ventilation or heating. The temperature range for heating drying can be 60 - 105 °C.

[0022] In step S4, the heating rate can be 5 - 20 °C / min, and the nitrogen atmosphere is maintained throughout. The nitrogen ventilation rate can be 100 - 500 mL / min.

[0023] In some embodiments, in step S4, the nitrogen-containing pollutants include acetaldehyde methyl hydrazone, etc., the ketone pollutants include at least one of 2-pentanone, methyl isobutyl ketone, etc., the aromatic hydrocarbon pollutants include at least one of ethylbenzene, o-xylene, etc., and the halogenated alkane pollutants include 1,3-dichloropropane, etc.

[0024] In step S5, normal-temperature nitrogen can be introduced during cooling until the temperature is below 200 °C.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] Through precise operation and optimization measures, the desorption efficiency of the present invention can be increased to 90%-95%, significantly improving the overall performance, reducing energy consumption and enhancing equipment stability. By finely controlling each link (qualitative analysis of pollutants, grouped treatment, temperature-controlled atmosphere control, cleaning and drying, nitrogen protection, etc.), the desorption efficiency is significantly improved and can reach 90%-95%. Energy waste and time loss are greatly reduced, and at the same time, the service life of the activated carbon is extended. Detailed implementation manners

[0027] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The operation methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0028] An optimization method for the thermal desorption process of granular activated carbon for waste gas adsorption includes the following steps:

[0029] S1: Using granular activated carbon for waste gas adsorption from different sources as raw materials, and using solid-phase extraction and gas chromatography-mass spectrometry to qualitatively analyze the pollutants adsorbed thereon;

[0030] The granular activated carbon for waste gas adsorption is the columnar granular activated carbon used for waste gas treatment, with a diameter of 4-12 mm. The design of the columnar granular activated carbon usually provides a large specific surface area. Due to its internal pore structure and surface chemical properties, it can effectively adsorb pollutants in waste gas. This range of particle diameters enables the carbon particles to maintain a high adsorption capacity while avoiding an overly dense pore structure, maintaining a good balance between the adsorption rate and capacity, thereby improving the effect of waste gas adsorption, that is, improving the quality of waste gas adsorption.

[0031] Compared with smaller particles, the columnar granular activated carbon with a diameter of 4-12 mm has better air permeability during the adsorption process. The gaps between the particles are larger, and the gas flow is not easily blocked. Therefore, waste gas treatment can be carried out at a higher flow rate, improving the treatment efficiency of the system. This is particularly important for the treatment of high-flow waste gas, which can ensure that there is not too much resistance to the air flow, reduce energy loss, and facilitate solid-phase extraction and gas chromatography-mass spectrometry for qualitative analysis of pollutants.

[0032] Finally, the columnar granular activated carbon is usually more durable than granular carbon. Its shape helps to reduce the fragmentation and pulverization of particles during the regeneration process, enabling this granular carbon to maintain a long service life during multiple adsorption and regeneration processes. Compared with small granular activated carbon, the columnar granular activated carbon has a lower loss rate during the regeneration process, reducing the operating cost.

[0033] In step S1, the solid-phase extraction temperature is 40 - 100 °C. During the extraction process, the desorption step in solid-phase extraction can often be accelerated under the influence of temperature. At higher temperatures, the volatility of the solvent increases, and the target substance is more likely to desorb from the adsorption material. Heating helps to shorten the desorption time and improve the efficiency of the entire extraction process. A higher temperature can increase the interaction rate between the sample and the adsorbent, thereby shortening the extraction time. Controlling the temperature within the range of 40 - 100 °C can effectively reduce the sample processing time and improve the experimental efficiency.

[0034] In step S1, the gas chromatography injection port is at 150 - 350 °C, the split ratio is 20:1, the carrier gas flow rate is 3 mL / min, the chromatographic column is HP-5MS, the column temperature is 40 °C, rising to 220 °C at 8 °C / min and holding for 3 min, then rising to 300 °C at 15 °C / min and holding for 3 min. This gas chromatography condition (injection port 150 - 350 °C, split ratio 20:1, carrier gas flow rate 3 mL / min, HP-5MS chromatographic column, column temperature program) provides good separation, sensitivity, and analysis time control. The precise control of the temperature program ensures the separation of volatile substances and high-boiling substances. At the same time, the reasonable design of the flow rate and split ratio protects the chromatographic column and detector, ensuring the accuracy, efficiency, and sensitivity of the analysis.

[0035] In step S1, the gas chromatography - mass spectrometry energy is 70 eV, and the mass range is 35 - 450. The setting of 70 eV electron impact energy and 35 - 450 amu mass range in gas chromatography - mass spectrometry analysis provides various benefits, including optimizing the fragmentation process, improving the accuracy of compound identification, ensuring comprehensive coverage of the target substance, increasing sensitivity and signal-to-noise ratio, and enhancing the reliability of quantitative analysis.

[0036] S2: Refer to the results obtained by gas chromatography - mass spectrometry, and group the waste granular activated carbon according to the components of pollutants adsorbed by the activated carbon;

[0037] Through the above method, more precise recycling can be achieved: Different pollutants will be adsorbed onto the activated carbon in different ways and to different degrees. By analyzing the component information of the adsorbed pollutants through GC-MS, it is possible to accurately understand which types of pollutants are adsorbed by each group of waste granular activated carbon. Based on this information, different treatment methods can be targeted selected during subsequent treatment or recycling, optimizing the regeneration process of the activated carbon and enhancing the reuse value of the activated carbon; targeted regeneration and treatment. According to the types of adsorbed pollutants, the waste granular activated carbon can be grouped and then subjected to targeted regeneration treatment. For example, some activated carbon may adsorb common organic solvents. For such pollutants, different regeneration methods (such as thermal regeneration, steam regeneration, etc.) can be used to distinguish and treat them from other waste activated carbon adsorbed with different pollutants, thereby improving the regeneration effect and reducing resource waste.

[0038] In step S2, according to the results obtained by gas chromatography-mass spectrometry, classifying granular activated carbons from different sources according to the components of adsorbed pollutants can reduce environmental pollution. The types and contents of pollutants adsorbed in waste activated carbon may have different degrees of impact on the environment. By grouping according to the components of pollutants, these waste activated carbons can be disposed of in a targeted manner. For example, waste activated carbon adsorbed with highly toxic harmful substances (such as heavy metals or organic pollutants) requires more stringent disposal measures, while waste activated carbon adsorbed with less toxic or recyclable substances can adopt simpler treatment methods; ensuring safe disposal: Different pollutants have different disposal requirements. The GC-MS analysis results help identify the specific types of pollutants, which can avoid environmental safety problems caused by improper treatment and ensure that the treatment of waste activated carbon complies with environmental protection regulations and safety standards.

[0039] Solid-phase extraction-gas chromatography-mass spectrometry was used for qualitative analysis of the pollutants adsorbed by activated carbon. The sample was incubated at 100 °C for 30 minutes; the inlet temperature was set at 250 °C, and split injection was used with a split ratio of 20:1. The flow rate of the carrier gas (usually helium) was controlled at 3 mL / min. Chromatographic separation was carried out using an HP-5MS chromatographic column (30 m × 250 μm × 0.25 μm), with an initial column temperature of 40 °C and held for 5 minutes. Subsequently, the temperature was raised to 220 °C at a rate of 8 °C / min and held for 3 minutes; then the temperature was raised to 300 °C at a rate of 15 °C / min and held for 3 minutes. During the mass spectrometry detection, an electron impact energy of 70 eV was used, and the mass scan range was set from 35 to 450 amu to achieve qualitative analysis of the target compounds.

[0040] It was found through solid-phase extraction-GC-MS characterization that the components of pollutants adsorbed by granular activated carbons for waste gas adsorption from different sources vary greatly, as shown in Table 1.

[0041] The main components of pollutants in waste granular activated carbon with label SA are nitrogen-containing pollutants (acetaldehyde methylhydrazone) and ketone pollutants (2-pentanone and methyl isobutyl ketone);

[0042] The main components of pollutants in waste granular activated carbon with label KS are aromatic hydrocarbons (ethylbenzene and o-xylene);

[0043] The main component of pollutants in waste granular activated carbon with label HB is halogenated alkanes (1,3-dichloropropane).

[0044] Table 1

[0045]

[0046] Optimization of the thermal desorption process of granular activated carbon for waste gas adsorption:

[0047] Weigh a certain mass of waste activated carbon, place it in a corundum boat and transfer it to a tube furnace. Under a nitrogen atmosphere, heat it at a heating rate of 10 °C / min to 300 °C, 400 °C, 500 °C and 600 °C, and hold for 1 h, 2 h and 3 h. Turn off the heating, maintain the nitrogen atmosphere, and after cooling to room temperature, take out the solid to obtain desorbed granular activated carbon.

[0048] The quality changes of granular activated carbon for waste gas adsorption under different process parameters are shown in Table 2. After thermal desorption treatment, the quality of activated carbon decreases with the increase of time and temperature. The main reasons are the thermal desorption and pyrolysis of pollutants, and the volatilization of some disordered carbon atoms. The sample numbering rule in Table 2 is waste granular activated carbon label - thermal desorption temperature (unit: °C) - thermal desorption time (unit: hour), the same below. For example, the sample number SA-300-1 represents the case of waste granular activated carbon SA thermally desorbed at 300 °C for 1 hour.

[0049] Table 2

[0050]

[0051] Analysis of the pore structure of thermally desorbed granular activated carbon:

[0052] The specific surface area, micropore surface area, total pore volume, micropore volume, average pore diameter and most probable pore diameter of each sample are shown in Table 3.

[0053] Table 3

[0054]

[0055] Based on the above results, it can be known that:

[0056] For waste granular activated carbon mainly adsorbing nitrogen-containing pollutants and ketone pollutants, such as waste granular activated carbon SA, the optimal thermal desorption temperature is 300 °C and the optimal thermal desorption time is 1 hour;

[0057] For waste granular activated carbon mainly adsorbing aromatic hydrocarbon pollutants, such as waste granular activated carbon KS, the optimal thermal desorption temperature is 600 °C and the optimal thermal desorption time is 3 hours;

[0058] For waste granular activated carbon mainly adsorbing halogenated alkane pollutants, such as waste granular activated carbon HB, the optimal thermal desorption temperature is 500 °C and the optimal thermal desorption time is 3 hours.

[0059] After the SA sample is thermally desorbed at 600 °C for 3 h, the specific surface area decreases from 505 m 2 / g to 469 m 2 / g, and the total pore volume decreases from 0.25 cm 3 / g to 0.24 cm 3 / g. Excessive thermal desorption treatment, although removing pollutants, also volatilizes disordered carbon atoms, collapses the original pores of the activated carbon, and reduces its specific surface area.

[0060] After the KS sample was treated by thermal desorption at 300 °C for 1 h, the specific surface area only increased from 358 m 2 / g to 451 m 2 / g, and the total pore volume only increased from 0.19 cm 3 / g to 0.25 cm 3 / g, indicating that after heat treatment with these process parameters, only a part of the original specific surface area and pore volume of the activated carbon were restored, and the best effect was not achieved.

[0061] After the HB sample was treated by thermal desorption at 300 °C for 1 h, the specific surface area only increased from 294 m 2 / g to 923 m 2 / g, and the total pore volume only increased from 0.25 m 3 / g to 0.75 m 3 / g, indicating that after heat treatment with these process parameters, only a part of the original specific surface area and pore volume of the activated carbon were restored, and the best effect was not achieved.

[0062] S3: Wash, screen, and dry the waste granular activated carbon for later use;

[0063] In the above, by washing the activated carbon, its adsorption capacity can be restored: by removing the adsorbed impurities, the pore structure of the activated carbon is restored, making it have stronger adsorption capacity; extending the service life: after removing pollutants, the activated carbon can be reused, reducing the replacement cost and extending its service life; reducing environmental pollution: avoiding the waste activated carbon from entering the environment and reducing pollutant emissions.

[0064] Sieving it can make the particle size uniform: through sieving, it is ensured that the particle size of the used activated carbon is uniform, which helps to improve the adsorption efficiency; removing fine impurities: fine impurities and debris can be removed during the sieving process to ensure that the activated carbon will not affect the equipment or adsorption effect during subsequent use; improving the use effect: uniform particles can provide a larger surface area, making it show higher efficiency during the adsorption process.

[0065] After drying, the adsorption performance is restored: excessive moisture will occupy the pores of the activated carbon and affect its adsorption performance. Drying can remove the moisture and restore the adsorption capacity of the activated carbon; avoiding mildew: moisture will cause mold growth or corrosion on the surface of the activated carbon, and drying can prevent this problem and maintain the quality of the activated carbon; facilitating subsequent treatment and use: after removing the moisture, the quality of the activated carbon is more stable, not prone to agglomeration, and convenient for storage and transportation.

[0066] In step S3, deionized water is used to wash the surface ash and remove impurities. After screening by corresponding sizes, it is dried by natural ventilation or heating. The optimal temperature range for heating drying is 60-105°C. Deionized water can effectively remove the ash and inorganic impurities attached to the surface. Since deionized water does not contain minerals and ions, it can avoid unnecessary ion contamination on the surface of activated carbon, ensure the integrity of its pore structure, and restore its adsorption capacity. By screening, fragments or particles with unqualified particle sizes can be removed, so as to ensure that the remaining particles are uniform in size, which helps to improve the subsequent adsorption effect. Within the temperature range of 60-105°C, the pore structure of activated carbon will not be damaged by excessive temperature. This temperature range can effectively remove moisture and avoid the charring of carbon materials or the decline of the adsorption performance of activated carbon caused by too high temperature. All in all, using deionized water for washing, sieving, and heating drying these treatment steps can effectively restore the adsorption performance of waste granular activated carbon, extend its service life, and gentle heating drying (60-105°C) can not only ensure the removal of moisture but also not damage the structure of activated carbon. Through these treatments, not only can the reuse rate of activated carbon be improved, but also energy and costs can be saved, meeting the environmental protection requirements and having significant economic and environmental benefits.

[0067] S4: Place the dried waste granular activated carbon in a tube furnace, heat it to a certain temperature at a preset heating rate, and maintain it for a certain time, keeping a nitrogen atmosphere throughout the process;

[0068] By heating in a tube furnace, some of the attached organic substances, dirt, and adsorbed substances on the surface of the waste granular activated carbon can be removed through thermal activation, restoring its internal pore structure. During the heating process, the specific surface area and pore volume of the activated carbon can be enhanced, thereby restoring or improving its adsorption performance. When heating in air, high temperature will cause oxidation on the surface of the activated carbon, generating carbon dioxide or other harmful gases and damaging its pore structure. In a nitrogen atmosphere, due to the inertness of nitrogen, it will not chemically react with the activated carbon, avoiding the occurrence of oxidation. This can ensure that the internal pores of the activated carbon are not damaged and the adsorption performance is protected.

[0069] In step S4, at a heating rate of 5-20°C / min, keeping a nitrogen atmosphere throughout the process, and the nitrogen rate is 100-500 mL / min. By placing the dried waste granular activated carbon in a tube furnace and heating it to a certain temperature at a preset heating rate and maintaining it for a certain time in a nitrogen atmosphere, its adsorption performance can be effectively restored, avoiding oxidation from damaging the pore structure of the activated carbon, optimizing the regeneration effect of the activated carbon, extending its service life, and at the same time ensuring that the regeneration process is environmentally friendly, energy-saving, and controllable.

[0070] S5: After the thermal desorption is completed, keep the nitrogen atmosphere, cool it to below 200°C, take out the obtained solid product, and sieve it for standby;

[0071] During the cooling period in Step S5, a nitrogen atmosphere is maintained, and normal-temperature nitrogen is introduced to lower the temperature inside the tube furnace and the sample temperature. After it cools down below 200°C, the solid is taken out. By continuously maintaining a nitrogen atmosphere during the cooling period and introducing normal-temperature nitrogen to lower the temperature until it cools down below 200°C, oxidation reactions can be effectively avoided, thermal stress can be reduced, the sample structure can be protected, the regeneration effect can be improved, and the safety, controllability, and environmental friendliness of the entire process can be optimized. This method not only helps to maintain the performance and quality of the sample, but also improves work efficiency, extends the service life of the equipment, and meets the requirements of high efficiency, energy conservation, and environmental protection in industrial production.

[0072] Compared with the prior art, using the method in the present invention for the adsorption of activated carbon has the following advantages, as shown in Table 4.

[0073] Table 4

[0074]

[0075] As can be seen from Table 4 above, by finely controlling each link (qualitative analysis of pollutants, grouped treatment, temperature-controlled atmosphere control, cleaning and drying, nitrogen protection, etc.), the desorption efficiency is significantly improved, reaching 90%-95%. Energy waste and time loss are greatly reduced, and at the same time, the service life of the activated carbon is also extended, with an overall better effect.

[0076] Among them, the specific experimental data can be seen in Table 5.

[0077] Table 5

[0078]

[0079] As can be seen from the above data table 5, the desorption efficiency of the prior art is generally between 70%-75%, and there are problems such as energy waste, equipment loss, and inefficient pollutant analysis. Through precise operation and optimization measures, the desorption efficiency of the method of the present invention can be increased to 90%-95%, significantly improving the overall performance, reducing energy consumption, and improving equipment stability.

[0080] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption, characterized in that: Includes steps: S1: Using granular activated carbon for waste gas adsorption from different sources as raw materials, solid phase extraction and gas chromatography-mass spectrometry were used to conduct qualitative analysis of the adsorbed pollutants; S2: referring to the results obtained by gas chromatography-mass spectrometry, the waste granular activated carbon is grouped according to the pollutant components adsorbed by the activated carbon; S3: washing, sieving and drying the waste granular activated carbon; S4: placing the dried spent granular activated carbon in a nitrogen atmosphere for thermal desorption; For spent granular activated carbon that mainly adsorbs nitrogen-containing pollutants and / or ketone pollutants, the thermal desorption temperature is 290-310°C and the thermal desorption time is 0.9-1.1 hours; For the spent granular activated carbon that mainly adsorbs aromatic hydrocarbon pollutants, the thermal desorption temperature is 590-610°C and the thermal desorption time is 2.9-3.1 hours; For the spent granular activated carbon that mainly adsorbs halogenated alkane pollutants, the thermal desorption temperature is 490-510°C and the thermal desorption time is 2.9-3.1 hours; S5: After the thermal desorption is completed, the nitrogen atmosphere is maintained for cooling.

2. The method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption according to claim 1, characterized in that: In step S1, the granular activated carbon for exhaust gas adsorption is a columnar granular activated carbon used for exhaust gas treatment, and its diameter is 4-12 mm.

3. The method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption according to claim 1, characterized in that: In step S1, the solid phase extraction temperature is 40-100°C.

4. The method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption according to claim 1, characterized in that: In step S1, the gas chromatography injection port is 150-350°C, the split ratio is 20:1, the carrier gas flow rate is 3 mL / min, the chromatographic column is HP-5MS, the column temperature is 40°C, increased to 220°C at 8°C / min, maintained for 3 min, increased to 300°C at 15°C / min, and maintained for 3 min.

5. The method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption according to claim 1, characterized in that: In step S1, the mass spectrum energy is 70ev and the mass range is 35-450.

6. The method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption according to claim 1, characterized in that: In step S3, deionized water is used to clean the surface ash and impurities of the waste granular activated carbon, and after screening by corresponding size, the waste granular activated carbon is dried by natural ventilation or heating, and the temperature range of heating drying is 60-105°C.

7. The method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption according to claim 1, characterized in that: In step S4, the temperature is increased at a rate of 5-20°C / min, a nitrogen atmosphere is maintained throughout the process, and the nitrogen ventilation rate is 100-500 mL / min.

8. The method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption according to claim 1, characterized in that: In step S4, the nitrogen-containing pollutants include acetaldehyde methylhydrazone, the ketone pollutants include at least one of 2-pentanone and methyl isobutyl ketone, the aromatic hydrocarbon pollutants include at least one of ethylbenzene and o-xylene, and the halogenated alkane pollutants include 1,3-dichloropropane.

9. The method for optimizing the thermal desorption process of granular activated carbon for waste gas adsorption according to claim 1, characterized in that: In step S5, nitrogen gas at room temperature is introduced during cooling to reduce the temperature to below 200°C.

Images