Process for regenerating waste coconut shell activated carbon using green high temperature plasma method

Abstract

The present application relates to the field of environmental protection technology, especially to the field of IPC B01J20, further to a process for regenerating waste coconut shell activated carbon using green high-temperature plasma method, comprising the following steps: S1, introducing waste coconut shell activated carbon into a vertical fluidized bed and introducing gas for heating, so that the waste coconut shell activated carbon reaches a fluidized state; S2, carrying out plasma heating treatment on the waste coconut shell activated carbon in the fluidized state; S3, discharging the gas generated by heating into a combustion chamber for combustion; S4, passing the waste coconut shell activated carbon treated by plasma heating into water for reactivation, cooling and drying to obtain regenerated coconut shell activated carbon. The present application can clean the polymers attached to the surface and cavities of the waste coconut shell activated carbon, and can also avoid the destruction of the structure.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, particularly to the field of IPC B01J20, and further to a process for regenerating waste coconut shell activated carbon using a green high-temperature plasma method. Background Technology

[0002] Chlorothalonil is a broad-spectrum, highly effective, low-toxicity, and low-residue fungicide for agricultural and forestry use. Activated carbon is used as a catalyst in its production process to improve reaction efficiency. However, because chlorothalonil requires excessive chlorine gas in its production process, it is easy to produce polymer byproducts. These polymers will adhere to the pores of the activated carbon, thereby causing the activated carbon to deactivate. Its service life is usually only about one month, or even shorter.

[0003] To enable activated carbon to be recycled, physical, chemical, and physicochemical methods are used to remove adsorbates from spent activated carbon without damaging its original structure, thereby restoring its adsorption performance. Current technologies mostly use aerobic combustion to regenerate activated carbon, but this method not only produces dioxins, causing environmental pollution, but also leads to a large loss rate and reduced strength of the regenerated activated carbon.

[0004] In addition, some novel regeneration methods have received widespread attention. For example, Chinese patent CN201410708893 discloses a pulsed discharge plasma regeneration method and apparatus for activated carbon, which uses pulsed discharge technology to degrade organic pollutants adsorbed on activated carbon, thus achieving activated carbon regeneration. However, this technical solution cannot be industrialized on a large scale, and the nylon mesh reactor used has an excessively low temperature, which cannot quickly decompose difficult-to-decompose organic matter. Chinese patent CN111790361A discloses a low-temperature plasma regeneration system and method for deactivated activated carbon. This technical solution requires low energy consumption for regeneration and does not produce pollutants, making it more energy-efficient and environmentally friendly. It also has a stronger oxidation effect, higher regeneration efficiency, and better results. However, this technical solution can cause activated carbon to collapse, resulting in a significant decrease in strength and activity. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a process for regenerating waste coconut shell activated carbon using a green high-temperature plasma method, comprising at least the following steps:

[0006] S1. The waste coconut shell activated carbon is introduced into a vertical fluidized bed and heated with nitrogen to make the waste coconut shell activated carbon reach a fluidized state.

[0007] S2. The fluidized waste coconut shell activated carbon is subjected to plasma heating treatment.

[0008] S3. The gas generated by heating is discharged into the combustion chamber for combustion;

[0009] S4. Pass the waste coconut shell activated carbon after plasma heating treatment into water for reactivation, cooling, and drying to obtain regenerated coconut shell activated carbon.

[0010] In some preferred embodiments, the process for regenerating waste coconut shell activated carbon using the green high-temperature plasma method further includes:

[0011] S5. The exhaust gas generated in the combustion chamber is discharged into the atmosphere through a chimney after being treated by adsorption.

[0012] S6. Waste heat recovery: Waste heat generated throughout the entire process is collected using a waste heat recovery device.

[0013] In some preferred embodiments, the heating method in S1 is direct heating or indirect heating; the direct heating is that the vertical fluidized bed contains oxygen, with an oxygen content of less than one part per thousand; the indirect heating is that the three-dimensional fluidized bed does not contain oxygen.

[0014] Preferably, the heating method in S1 is direct heating.

[0015] Preferably, the process of introducing nitrogen in S1 also includes air, so that the vertical fluidized bed contains oxygen, with an oxygen content of less than one part per thousand.

[0016] Preferably, the heating temperature in S1 is 800-1500℃.

[0017] Preferably, the heating temperature in S1 is 1200°C.

[0018] In some preferred embodiments, the plasma heating temperature in S2 is 1500-2000°C.

[0019] In some preferred embodiments, the plasma heating time in S2 is 5-20 min.

[0020] Preferably, the plasma heating temperature in S2 is 1700-1900℃, and the heating time is 5-15 min.

[0021] Preferably, the plasma heating temperature in S2 is 1800℃, and the heating time is 5-15 min.

[0022] Preferably, the plasma heating temperature in S2 is 1800℃ and the heating time is 10min.

[0023] During the experiment, the applicant discovered that by using indirect heating, where the gas in S1 includes not only nitrogen but also a certain amount of air, the vertical fluidized bed contains oxygen with an oxygen content of less than one part per thousand, achieving a fluidized state for the waste coconut shell activated carbon. The heating temperature is controlled at 800-1500℃, especially when the temperature is controlled at 1200℃, followed by plasma heating. This effectively decomposes the polymers adhering to the surface and pores of the waste coconut shell activated carbon while protecting and improving the structure of the regenerated activated carbon. The applicant hypothesizes that the reason for this is that the waste coconut shell activated carbon is first heated in a vertical fluidized bed with a certain oxygen content. Compared with indirect heating, direct heating, in addition to nitrogen, also contains a certain amount of oxygen. On the one hand, the waste coconut shell activated carbon can undergo an exothermic reaction with oxygen, thus enabling it to reach a fluidized state more quickly. On the other hand, by limiting the oxygen content, the decomposition of the waste coconut shell activated carbon itself can be reduced and the contact area can be increased, thereby improving its regeneration efficiency and activity. This ensures that the regeneration efficiency of the activated carbon reaches more than 80%. When it is then subjected to plasma heating, the decomposition of polymers on the active surface and in the pores of the waste coconut shell can be further enhanced. More importantly, it can also prevent the rapid heating from causing damage to the activated carbon structure.

[0024] During the experiment, the applicant further discovered that when the plasma heating temperature in S2 is 1500-2000℃ and the heating time is 5-20 minutes, followed by reactivation in water, the molecular bonds of the polymers attached to the surface and pores of the activated carbon can be broken, allowing most of the organic matter in the waste coconut shell activated carbon to be desorbed and cracked. At the same time, the organic residue in the waste coconut shell activated carbon can also be removed. Furthermore, when the plasma-treated waste coconut shell activated carbon is passed through water, the water molecules instantly vaporize due to the high temperature of the waste coconut shell activated carbon. The instantaneous vaporization of water molecules can further increase the specific surface area of ​​the activated carbon, thus regenerating the waste coconut shell activated carbon. It can also further protect the rigid structure of the regenerated waste coconut shell activated carbon. In particular, the effect is best when the plasma heating temperature in S2 is 1800℃ and the heating time is 10 minutes.

[0025] Preferably, the plasma is generated by a plasma generator; the plasma arc is a non-transfer arc; and the working gas is nitrogen.

[0026] In some preferred embodiments, the S3 combustion chamber includes two ignition devices, the burner is equipped with a permanent flame and has a built-in flame detection device, and if the flame goes out midway, it will automatically interlock and alarm.

[0027] Preferably, the combustion temperature of the S3 combustion chamber is >1100℃ and the flue gas residence time is ≥2s.

[0028] More preferably, the fuel in the S3 combustion chamber is natural gas.

[0029] Beneficial effects:

[0030] 1. This application adopts a direct heating method. Even if the vertical fluidized bed contains oxygen, the oxygen content is less than one-thousandth. Compared with indirect heating, since direct heating has a certain oxygen content in addition to nitrogen, on the one hand, the waste coconut shell activated carbon can undergo an exothermic reaction with oxygen, thereby making the waste coconut shell activated carbon reach the fluidization state more quickly; on the other hand, by limiting the oxygen content, the decomposition of the waste coconut shell activated carbon itself can be reduced and the contact area can be increased, thereby improving its regeneration efficiency and activity.

[0031] 2. This application controls the heating temperature of S1 to 800-1500℃. In particular, when the controlled temperature is 1200℃, plasma heating is then performed. This can effectively decompose the polymers attached to the surface and pores of waste coconut shell activated carbon while protecting the structure of the regenerated activated carbon and improving its structure.

[0032] 3. In this application, when the plasma heating temperature in S2 is 1500-2000℃ and the heating time is 5-20min, the activated carbon is reactivated by passing it through water. This not only breaks the molecular bonds of the polymers attached to the surface and pores of the activated carbon, allowing most of the organic matter in the waste coconut shell activated carbon to be desorbed and cracked, but also removes the organic residue in the waste coconut shell activated carbon. At the same time, when the plasma-treated waste coconut shell activated carbon is passed through water, the water molecules instantly vaporize due to the high temperature of the waste coconut shell activated carbon. The instantaneous vaporization of the water molecules can further increase the specific surface area of ​​the activated carbon, thus regenerating the waste coconut shell activated carbon. It can also further protect the rigid structure of the regenerated waste coconut shell activated carbon and improve the activity of the regenerated activated carbon.

[0033] 4. This application uses plasma heating treatment with a heating temperature of 1800℃ and a heating time of 10min, and discharges the gas generated by heating into the combustion chamber for combustion; it can be used to treat complex and highly hazardous wastes mixed in with materials that require high-temperature pyrolysis, such as polychlorinated biphenyls and heterocyclic aromatic hydrocarbons (PCBs, PCDDS); at the same time, it has high environmental protection standards, uses gas combustion, completely oxidizes organic gases, has no odor, and does not produce highly toxic substances such as dioxins.

[0034] 5. This application uses a waste heat recovery device to collect the waste heat generated in the entire process flow without using any fossil fuels, thus saving costs. If waste heat recovery is used for power generation, it basically does not consume grid electricity and can output commercial or heating low-pressure steam with low operating costs. Detailed Implementation

[0035] Example 1

[0036] Example 1 provides a process for regenerating waste coconut shell activated carbon using a green high-temperature plasma method, comprising the following steps:

[0037] S1. The waste coconut shell activated carbon is introduced into a vertical fluidized bed and heated with nitrogen to make the waste coconut shell activated carbon reach a fluidized state.

[0038] S2. The fluidized waste coconut shell activated carbon is subjected to plasma heating treatment.

[0039] S3. The generated gas is discharged into the combustion chamber for combustion;

[0040] S4. Pass the waste coconut shell activated carbon after plasma heating treatment into water for reactivation, cooling, and drying to obtain regenerated coconut shell activated carbon.

[0041] S5. The exhaust gas generated in the combustion chamber is discharged into the atmosphere through a chimney after being treated by adsorption.

[0042] S6. Waste heat recovery: Waste heat generated throughout the entire process is collected using a waste heat recovery device.

[0043] The heating method in S1 is direct heating.

[0044] The process of introducing nitrogen in S1 also includes air, so that the vertical fluidized bed contains oxygen, with an oxygen content of less than one part per thousand.

[0045] The heating temperature in S1 is 1200℃.

[0046] The plasma heating temperature in S2 is 1800℃, and the heating time is 10 minutes.

[0047] The plasma is generated by a plasma generator; the plasma arc is a non-transfer arc; and the working gas is nitrogen.

[0048] The combustion chamber in S3 includes two ignition devices. The burner is equipped with a permanent flame and has its own flame detection device. If the flame goes out midway, it will automatically interlock and alarm.

[0049] The combustion temperature in the combustion chamber of S3 is 1200℃, and the flue gas residence time is 3s.

[0050] The fuel in the combustion chamber of S3 is natural gas.

[0051] Example 2

[0052] Example 2 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon. The only difference from Example 1 is that the plasma heating temperature is 500°C and the heating time is 10 minutes.

[0053] Example 3

[0054] Example 3 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon. The only difference from Example 1 is that the plasma heating temperature is 1000℃ and the heating time is 10min.

[0055] Example 4

[0056] Example 4 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon. The only difference from Example 1 is that the plasma heating temperature is 1500℃ and the heating time is 10min.

[0057] Example 5

[0058] Example 5 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon. The only difference from Example 1 is that the plasma heating temperature is 2000℃ and the heating time is 10min.

[0059] Example 6

[0060] Example 6 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon. The only difference from Example 1 is that the plasma heating temperature is 2500℃ and the heating time is 10min.

[0061] Example 7

[0062] Example 7 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon. The only difference from Example 1 is that the plasma heating temperature is 1800℃ and the heating time is 5min.

[0063] Example 8

[0064] Example 8 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon, which differs from Example 1 only in that the plasma heating temperature is 1800℃ and the heating time is 15min.

[0065] Example 9

[0066] Example 9 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon, which differs from Example 1 only in that the plasma heating temperature is 1800℃ and the heating time is 20min.

[0067] Example 10

[0068] Example 10 provides a green high-temperature plasma method for regenerating waste coconut shell activated carbon. The only difference from Example 1 is that the plasma heating temperature is 1800℃ and the heating time is 25min.

[0069] Example 11

[0070] Example 11 provides a process for regenerating waste coconut shell activated carbon using a green high-temperature plasma method. The only difference from Example 1 is that the plasma heating time is 0 min.

[0071] Referring to GB / T12496, the regenerated waste coconut shell activated carbon obtained in Examples 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 was subjected to iodine adsorption and strength tests; the specific surface area was tested according to GB / T 7702.20-2008; the regeneration yield was calculated according to the formula: mass of regenerated waste coconut shell activated carbon / (total mass of initial waste coconut shell activated carbon - mass of adsorbed impurities in initial waste coconut shell activated carbon).

[0072] The performance test results are shown in the table below.

[0073] Table 1: Iodine adsorption value test of recycled waste coconut shell activated carbon:

[0074]

[0075] Results Analysis: Iodine adsorption value is used to characterize the degree of development of micropores in activated carbon, indicating the adsorption capacity of activated carbon for small molecules. As can be seen from Table 1, the iodine adsorption values ​​of the regenerated waste coconut shell activated carbon prepared in Examples 1 to 10 of this invention are all higher than 800 mg / g; among them, the iodine adsorption value of the regenerated waste coconut shell activated carbon prepared in Example 1 is as high as 1398 mg / g; and the regeneration yield can be guaranteed to be 72%.

[0076] Table 2: Specific surface area test of recycled waste coconut shells:

[0077]

[0078]

[0079] Results Analysis: The specific surface area of ​​activated carbon is directly proportional to its adsorption capacity; the larger the specific surface area, the stronger the adsorption capacity. As shown in Table 2, the specific surface area of ​​the regenerated waste coconut shell activated carbon prepared in Examples 1 and 4-10 of this invention is significantly increased compared to the initial waste coconut shell activated carbon. The specific surface area of ​​the regenerated waste coconut shell activated carbon prepared in Example 1 reaches as high as 1689 m². 2 / g significantly improved the activity of recycled waste coconut shell activated carbon.

[0080] Table 3: Strength test of recycled waste coconut shell activated carbon:

[0081]

[0082]

[0083] Results Analysis: The strength of activated carbon determines its service life. As can be seen from Table 3, the strength of the recycled waste coconut shell activated carbon prepared in Examples 1 to 10 of the present invention is as high as 97% or more, of which the strength of the recycled waste coconut shell activated carbon prepared in Example 1 is as high as 98.5%. This shows that the technical solution of the present invention can improve the activity of the recycled waste coconut shell activated carbon while ensuring its service life.

Claims

1. A process for regeneration of spent coconut shell activated carbon using green high temperature plasma method, characterized by, At least comprising the following steps: S1, introducing waste coconut shell activated carbon into a vertical fluidized bed, and introducing nitrogen for heating, so that the waste coconut shell activated carbon reaches a fluidized state; S2, plasma heating treatment is carried out on the waste coconut shell activated carbon in the fluidized state; S3, the gas generated by heating is discharged into a combustion chamber for combustion; S4, the waste coconut shell activated carbon after plasma heating treatment is activated again, cooled in water, dried, and then the regenerated coconut shell activated carbon is obtained; The heating mode in S1 is direct heating; the direct heating contains oxygen in the vertical fluidized bed, and the oxygen content is below one thousandth; the heating temperature in S1 is 800-1500℃; the plasma heating temperature in S2 is 1500-2000℃; the plasma heating time in S2 is 5-20min.

2. The process for regeneration of spent coconut shell activated carbon using green high temperature plasma method as claimed in claim 1 wherein, Further comprising: S5, the waste flue gas generated by the combustion chamber is treated by adsorption and then discharged into the atmosphere through a chimney; S6, waste heat recovery: a waste heat recovery device is used to collect the waste heat generated in the whole process.

3. The process for regeneration of spent coconut shell activated carbon using green high temperature plasma method as claimed in claim 1 wherein, The heating temperature in S1 is 1200℃.

4. The process for regeneration of spent coconut shell activated carbon using green high temperature plasma method as claimed in claim 1 wherein, The plasma heating temperature in S2 is 1700-1900℃, and the heating time is 5-15min.

5. The process for regeneration of spent coconut shell activated carbon using green high temperature plasma method as claimed in claim 4, wherein, The plasma heating temperature in S2 is 1800℃, and the heating time is 10min.

6. The process for regeneration of spent coconut shell activated carbon using green high temperature plasma method as claimed in claim 1 wherein, The combustion temperature of the combustion chamber in S3 is >1100℃, and the flue gas residence time is ≥2s.

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