A method for preparing activated carbon from tar residue and sludge

Abstract

The present application belongs to the technical field of activated carbon preparation, and particularly relates to a method for preparing activated carbon from tar residue and sludge, which takes the tar residue generated at the bottom of a tar-ammonia separation facility in a raw gas purification process as a main material, and takes sludge in a coking wastewater treatment process as an auxiliary material, and prepares activated carbon through steps of drying, grinding, molding, carbonization and water vapor activation, etc. The content of the tar residue in the mixed powder is 90wt%-95wt%, and the content of the sludge is 5wt%-10wt%. The present application has the advantages that: the present application uses metallurgical solid waste tar residue as a raw material to prepare activated carbon material, and the prepared activated carbon has a good adsorption effect on organic matters in wastewater and waste gas. The present application treats waste with waste, and has a simple process, low cost, and is suitable for solid waste resource utilization in steel coking enterprises.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon preparation technology, and particularly relates to a method for preparing activated carbon using coal tar residue from the coal gas purification process as the main raw material and sludge as a supplement. Background Technology

[0002] Coking tar residue is a highly viscous and easily agglomerated waste residue produced during the coking process. It mainly consists of coke powder, coal dust, coal tar, and pitch, and is a typical carbon-rich polymer containing aromatic hydrocarbons. Its chemical composition shows a fixed carbon content of approximately 60%, volatile matter of approximately 33%, ash content of only about 4%, and sulfur content of approximately 1.6%. It also possesses a porosity of approximately 63% and a density of 1.27–1.30 t / m³. 3 The true density of tar residue exhibits excellent porous structure characteristics. Currently, the treatment methods for tar residue mainly fall into two categories: one is as fuel for brick burning, but due to incomplete combustion, it easily releases large amounts of highly carcinogenic polycyclic aromatic hydrocarbons, posing significant environmental risks; the other is to reduce the volume through technologies such as centrifugal extraction and dry distillation to recover tar and coal powder, but these methods generally suffer from low separation efficiency, difficulty in effectively disposing of heavy components, difficulty in recovering extractants, and high costs, resulting in a comprehensive utilization rate of less than 30% for tar residue. Furthermore, tar residue has been classified as hazardous waste and is prohibited from being transported off-site for disposal. However, enterprises lack economical and efficient environmentally friendly treatment methods, often resulting in long-term stockpiling within the plant area, causing groundwater and air pollution, and becoming a significant bottleneck restricting the capacity expansion of coal chemical enterprises. Therefore, developing a comprehensive technology for the resource-based and harmless treatment of tar residue has become a key issue that the industry urgently needs to address. It is noteworthy that tar residue is rich in unburned carbon components and naturally possesses a porous structure, providing a good foundation for the preparation of adsorbent carbon materials, indicating a feasible direction for its high-value utilization.

[0003] In the prior art, patent publication number CN102674344A discloses a method for producing activated carbon from coal tar. The method involves soaking coal tar residue in phosphoric acid at room temperature, then performing one-step carbon activation by heating it to different constant temperatures in a high-temperature furnace, then cooling it to room temperature and washing it with hot water at 60-70°C until the filtrate is neutral, and finally drying it to obtain activated carbon from coal tar residue. Patent publication number CN117658131A discloses a method for preparing shaped activated carbon using coal tar residue as a binder and carbon-containing powder. The method involves mixing carbon-containing powder, tar residue, and a small amount of water as raw materials, uniformly mixing them, extruding them into shaped materials, and then carbonizing and activating them to obtain shaped activated carbon. The carbon-containing powder includes straw, wood, fruit shells, coal powder, semi-coke powder, and sugarcane bagasse, etc. Patent publication number CN118954504A discloses a sludge-based activated carbon based on tar residue binder and its preparation method. The method involves mixing coal, tar residue, sludge, and binder components in a specific ratio, and then molding them to obtain an activated carbon precursor. The activated carbon precursor is then carbonized to obtain a carbonized product. Finally, the carbonized product is activated to obtain sludge-based activated carbon. Patent publication number CN119706835A discloses a method for preparing porous carbon sheet materials based on coal tar residue and its application. Using an organic reagent as the extractant, microwave-assisted extraction is employed to separate the oily components from the coal tar residue. The extracted coal tar residue is then ball-milled and mixed with K3C6H5O7, gently activated under an inert atmosphere, and subsequently washed, dried, and ground to obtain the porous carbon sheet material. Patent publication number CN121247791A discloses a method for preparing macroporous carbon based on coal tar residue nano-sponge and its application. Under an inert gas atmosphere, coal tar residue is carbonized to obtain a coal tar residue carbonized material. The carbonized material is dissolved in an organic solvent to prepare an impregnation solution. Using a nano-sponge as the matrix, the nano-sponge is immersed in the impregnation solution until the nano-sponge is saturated with the solution. After removing the organic solvent, a nano-sponge containing coal tar residue is obtained.

[0004] Currently published patents show that most methods for preparing carbon materials using tar residue as raw material only use it as an auxiliary material or binder, with the amount of tar residue typically less than 40%. In schemes with higher amounts, the pretreatment process is complex, the preparation process has many uncontrollable factors, and material loss is serious. Regarding the co-utilization of tar residue and sludge, existing technologies either require the addition of third components such as pulverized coal or asphalt, or require complex pretreatment processes such as microwave-assisted extraction and aerobic fermentation, resulting in long process flows and high costs. Therefore, it is basically difficult to achieve mass production in factories.

[0005] To address this issue, a method for preparing activated carbon using tar residue as the main raw material and sludge from coking wastewater treatment as an auxiliary material has been developed. This method requires no external activators or organic solvents, has a simple process route, and enables high-volume resource utilization of tar residue. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, the purpose of this invention is to provide a simple and low-cost method for preparing activated carbon from tar residue and sludge. The method uses tar residue from the raw coal gas purification process and sludge from the coking wastewater treatment process as raw materials to prepare activated carbon adsorbent materials with well-developed pores and abundant active sites.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing activated carbon from tar residue and sludge includes the following steps: 1) Dry the tar residue and sludge separately at 105±5℃ until the moisture content is ≤4%, and then break up the tar residue after drying; 2) Add the sludge to the tar residue, mix and grind until the particle size is ≤74μm to obtain a mixed powder; 3) The mixed powder obtained in step 2) is loaded into a mold and shaped under a pressure of 12±0.5kPa for 30~40s to obtain the molded material. The molded material is placed in a moisture-proof space. 4) The molding material is heated from room temperature to 600±5℃ at a heating rate of 10±2℃ / min under an inert atmosphere and held for 1.5~2.5h to obtain carbonized material; 5) Activate immediately after carbonization. The carbonized material is heated from 600±5℃ to 800±5℃ at a heating rate of 10±2℃ / min. Water vapor is introduced at a flow rate of 0.5~0.8ml / min·g. The temperature is maintained and the gas is circulated for 2~3 hours. After cooling, activated carbon is obtained.

[0008] Furthermore, in step 2), the mixed powder contains 90wt%~95wt% tar residue and 5wt%~10wt% sludge.

[0009] Furthermore, the tar residue is the residue generated at the bottom of the tar-ammonia-water separation facility during the raw coal gas purification process.

[0010] Furthermore, the tar-ammonia water separation facility is a mechanized ammonia water clarification tank.

[0011] Furthermore, the sludge mentioned is sludge generated during the coking wastewater treatment process.

[0012] Further, in step 4), the inert atmosphere is a nitrogen or helium atmosphere.

[0013] Furthermore, the activated carbon has an iodine adsorption value of 950–1050 mg / g and a specific surface area of ​​1150–1250 m². 2 / g.

[0014] Furthermore, the activated carbon can be used for the adsorption and treatment of organic matter in wastewater and exhaust gas in steel plants or coking plants, thereby realizing the resource utilization of solid waste.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention utilizes two typical difficult-to-treat solid wastes from coking plants—tar residue and sludge—as raw materials to prepare activated carbon. The tar residue content is ≥90%, achieving a raw material utilization model with tar residue as the main component and sludge as an auxiliary material. The resulting activated carbon material possesses high active sites and high selective adsorption rate for organic matter, achieving performance comparable to ordinary commercial activated carbon at a lower cost. Simultaneously, it solves the solid waste treatment problem, forming a virtuous cycle of "treating waste with waste."

[0016] The introduction of sludge has multiple synergistic effects: the trace elements in the sludge are beneficial to the formation and development of mesopores in activated carbon; the sludge and tar residue have good adhesion and strong formability, achieving good molding results without the need for additional binders; the activated carbon based on the mixture of tar residue and sludge has a well-developed pore structure, a large specific surface area, and abundant surface chemical groups, resulting in rich micropores and mesopores and strong selective adsorption capacity for trace components in the gas and liquid phases. This synergistic utilization model of "treating waste with waste" reduces raw material costs while improving product performance. Attached Figure Description

[0017] Figure 1 This is a picture of the appearance of activated carbon.

[0018] Figure 2 This is a SEM image of activated carbon. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0020] A method for preparing activated carbon from tar residue and sludge includes the following steps: 1) Dry the tar residue and sludge separately at 105±5℃ until the moisture content is ≤4%, and then break up the tar residue after drying; Tar residue is the residue produced at the bottom of the tar-ammonia-water separation facility during the purification of raw coal gas. Tar residue can also be the residue produced at the bottom of a mechanized ammonia-water clarification tank.

[0021] The sludge is generated during the treatment of coking wastewater. K and Na in the sludge promote pore development, while other elements such as Fe and Zn promote mesopore formation. The sludge moisture content ranges from 2.5% to 17.9%, fluctuating significantly and directly related to the separation process efficiency. Volatile matter content is 25.81% to 33%, ash content is 4% to 15%, and fixed carbon content is 38.51% to 60%.

[0022] 2) Add the sludge to the tar residue, mix and grind until the particle size is ≤74μm to obtain a mixed powder; The mixed powder contains 90wt%~95wt% tar residue and 5wt%~10wt% sludge.

[0023] 3) The mixed powder obtained in step 2) is loaded into a mold and shaped under a pressure of 12±0.5kPa for 30~40s to obtain the molded material. The molded material is placed in a moisture-proof space. 4) The molding material is heated from room temperature to 600±5℃ at a heating rate of 8~12℃ / min under the protection of an inert atmosphere, and held for 2~3 hours to obtain carbonized material; wherein, the inert atmosphere is a nitrogen or helium atmosphere.

[0024] 5) Activate immediately after carbonization. The carbonized material is heated from 600±5℃ to 800±5℃ at a heating rate of 8~12℃ / min. Water vapor is introduced at a flow rate of 0.5~0.8ml / min·g. The material is kept at this temperature and ventilated for 2 hours. After cooling with nitrogen or helium, activated carbon is obtained.

[0025] Tests showed that the iodine adsorption value of activated carbon was 950–1050 mg / g, and the specific surface area was 1150–1250 m². 2 The adsorption rate of carbon tetrachloride is 65%~69%, and the adsorption value of methylene blue is 150~175 mg / g. Activated carbon is used for the adsorption treatment of organic matter in wastewater and exhaust gas in steel plants or coking plants.

[0026] Example 1:

[0027] A method for preparing activated carbon from tar residue and sludge includes the following steps: 1) Spread the tar residue and sludge separately in a container and dry them at 105±5℃ for 120 minutes, so that the moisture content of the tar residue is ≤4% and the moisture content of the sludge is ≤4%. After drying, break up the tar residue and sludge. Take 90g of dried tar residue and 10g of sludge, mix them evenly and grind them until they pass through a 200-mesh sieve.

[0028] 2) Prepare columnar raw material blocks in a circular mold under a pressure of 12 kPa.

[0029] 3) The molding material is placed in a heating furnace and heated from room temperature to 600°C at a heating rate of 10°C / min under the protection of an inert atmosphere of nitrogen or helium, and held at that temperature for 2 hours. Then, the temperature is increased from 600°C to 800°C at a rate of 10°C / min, and water vapor is introduced at a flow rate of 55 ml / min, and the temperature is maintained and the gas is introduced for 2 hours.

[0030] 4) Perform routine performance characterization on activated carbon materials cooled to room temperature by continuously introducing nitrogen or helium gas.

[0031] The following standards were used: GB / T7702.7-2023 Test Methods for Granular Activated Carbon of Coal - Part 7: Determination of Iodine Adsorption Value; GB / T7702.19-2008 Test Methods for Granular Activated Carbon of Coal - Determination of Carbon Tetrachloride Desorption Rate; GB / T7702.15-2008 Test Methods for Granular Activated Carbon of Coal - Determination of Ash Content; GB / T7702.20-2025 Test Methods for Granular Activated Carbon of Coal - Part 20: Determination of Pore Volume and Specific Surface Area; and GB / T7702.6-2008 Test Methods for Granular Activated Carbon of Coal - Determination of Methylene Blue Adsorption Value. The test data showed an iodine adsorption value of 970 mg / g, a carbon tetrachloride adsorption rate of 68.7%, and a specific surface area of ​​1187.6 m². 2 / g, methylene blue adsorption value is 172.3mg / g, ash content is 10.5%.

[0032] Example 2:

[0033] A method for preparing activated carbon from tar residue and sludge includes the following steps: 1) Take 95g of dried tar residue and 5g of sludge, mix them evenly and grind them until they pass through a 200-mesh sieve.

[0034] 2) Prepare columnar raw material blocks in a circular mold under a pressure of 12 kPa.

[0035] 3) The molding material is placed in a heating furnace and heated from room temperature to 600°C at a rate of 10°C / min under the protection of an inert atmosphere such as nitrogen / helium, and held at that temperature for 2 hours. Then, the temperature is increased from 600°C to 800°C at a rate of 10°C / min, and water vapor is introduced at a flow rate of 60 ml / min, and the temperature is maintained and the gas is introduced for 2 hours.

[0036] 4) Perform routine performance characterization on activated carbon materials cooled to room temperature by continuously introducing nitrogen or helium gas.

[0037] Test data showed that the iodine adsorption value was 1030 mg / g, the carbon tetrachloride adsorption rate was 65.5%, and the specific surface area was 1246.9 m². 2 / g, methylene blue adsorption value is 155.6mg / g, ash content is 9.1%.

[0038] Example 3:

[0039] A method for preparing activated carbon from tar residue and sludge includes the following steps: 1) Take 92.5g of dried tar residue and 7.5g of sludge, mix them evenly and grind them until they pass through a 200-mesh sieve.

[0040] 2) Prepare columnar raw material blocks in a mold under a pressure of 12 kPa.

[0041] 3) The molding material is placed in a heating furnace and heated from room temperature to 600°C at a rate of 10°C / min under the protection of an inert atmosphere such as nitrogen / helium, and held at that temperature for 2 hours. Then, the temperature is increased from 600°C to 800°C at a rate of 10°C / min, and water vapor is introduced at a flow rate of 65 ml / min, and the temperature is maintained and the gas is introduced for 2 hours.

[0042] 4) The activated carbon material, cooled to room temperature after continuous purging with nitrogen or helium, underwent routine performance characterization. Test data showed an iodine adsorption value of 998 mg / g, a carbon tetrachloride adsorption rate of 66.9%, and a specific surface area of ​​1212.5 m². 2 / g, methylene blue adsorption value is 162.3mg / g, ash content is 9.7%.

[0043] The activated carbon material prepared in this invention can be used for the adsorption of organic matter in wastewater and exhaust gas in steel and coking plants.

Claims

1. A method for preparing activated carbon from tar residue and sludge, characterized in that, Includes the following steps: 1) Dry the tar residue and sludge separately at 105±5℃ until the moisture content is ≤4%, and then break up the tar residue after drying; 2) Add the sludge to the tar residue, mix and grind until the particle size is ≤74μm to obtain a mixed powder; 3) The mixed powder obtained in step 2) is loaded into the mold and shaped under a pressure of 12±0.5kPa for 30~40s to obtain the molding material. The molding material is placed in a moisture-proof space. 4) The molding material is heated from room temperature to 600±5℃ at a heating rate of 10±2℃ / min under an inert atmosphere and held for 1.5~2.5h to obtain carbonized material; 5) Activate immediately after carbonization. The carbonized material is heated from 600±5℃ to 800±5℃ at a heating rate of 10±2℃ / min. Water vapor is introduced at a flow rate of 0.5~0.8ml / min·g. The temperature is maintained and the gas is circulated for 2~3 hours. After cooling, activated carbon is obtained.

2. The method for preparing activated carbon from tar residue and sludge according to claim 1, characterized in that, In step 2), the mixed powder contains 90wt%~95wt% tar residue and 5wt%~10wt% sludge.

3. The method for preparing activated carbon from tar residue and sludge according to claim 1, characterized in that, The tar residue mentioned above is the residue generated at the bottom of the tar-ammonia-water separation facility during the purification of raw coal gas.

4. The method for preparing activated carbon from tar residue and sludge according to claim 3, characterized in that, The aforementioned tar-ammonia water separation facility is a mechanized ammonia water clarification tank.

5. The method for preparing activated carbon from tar residue and sludge according to claim 1, characterized in that, The sludge mentioned is the sludge generated during the treatment of coking wastewater.

6. The method for preparing activated carbon from tar residue and sludge according to claim 1, characterized in that, In step 4), the inert atmosphere is a nitrogen or helium atmosphere.

7. The method for preparing activated carbon from tar residue and sludge according to claim 1, characterized in that, The activated carbon has an iodine adsorption value of 950–1050 mg / g and a specific surface area of ​​1150–1250 m². 2 / g.

8. The method for preparing activated carbon from tar residue and sludge according to claim 1, characterized in that, The activated carbon can be used for the adsorption and treatment of organic matter in wastewater and waste gas in steel plants or coking plants, thereby realizing the resource utilization of solid waste.

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