Activated carbon as well as preparation method and application thereof

Abstract

The invention discloses activated carbon as well as a preparation method and application thereof, and the preparation method of the activated carbon comprises the following steps: carrying out oxidation pretreatment on enriched carbon to obtain the enriched carbon subjected to oxidation pretreatment; the enriched carbon is an organic carbon residue enriched product obtained by carrying out a separation technology on coal gasification slag; mixing the enriched carbon subjected to oxidation pretreatment, potassium hydroxide, high-temperature coal tar and water, and uniformly kneading to obtain coal paste; molding and aging the coal paste to obtain a carbonized precursor; carbonizing the carbonized precursor, and activating the carbonized precursor in activated gas to obtain activated carbon; the activation gas comprises air and water vapor. According to the method, on the basis of unique physical characteristics and chemical structural characteristics of the enriched carbon, a process technology for preparing the activated carbon by combining air pre-oxidation treatment, physical forming, carbonization and micro-oxidation with water vapor activation coupling is formed, the activated carbon product has good mesoporous distribution characteristics, the iodine value is qualified, methylene blue is qualified, and the activated carbon product has a good application prospect. The method is suitable for deep purification of biochemical wastewater.

Description

Technical Field

[0001] The present invention relates to the field of activated carbon, and in particular to activated carbon and a preparation method and application thereof. Background Art

[0002] Coal is the main primary energy source, accounting for about 58% of the total energy consumption in recent years. It is also an important pillar of the country's economic development. It mainly includes combustion power generation and clean conversion. my country's coal chemical industry is developing rapidly, with nearly 100 million tons of coal used for conversion each year. Among them, coal gasification is the leading technology of the modern coal chemical industry and the basis for the development of process industries such as coal-based chemicals, coal-based liquid fuels, IGCC power generation, polygeneration systems, hydrogen production and fuel cells.

[0003] The coal gasification process produces a large amount of solid waste - gasification slag. my country's annual emission of gasification slag exceeds 33 million tons, and the cumulative stockpile is hundreds of millions of tons. Gasification ash slag is divided into two categories: coarse slag and fine slag. Coarse slag is a low-melting point eutectic in coal ash that forms a broken glass body after quenching with water. It is discharged from the ash lock bucket at the bottom of the gasifier, accounting for 60-80% of the total amount of gasification slag. Its composition is similar to boiler ash slag. It can be used as a mixed raw material for building materials, roads and bridges together with boiler ash slag. However, the loss of combustion of gasification coarse slag produced by some furnace types or gasification processes is relatively high, which is greatly limited by application; fine slag is discharged with flue gas in the form of fly ash. The flue gas is washed, purified and precipitated, accounting for 20-40% of the total amount of gasification slag, and the loss of combustion is as high as 20-30%. It cannot be directly used as building and road materials. At present, it can only be landfilled or piled up, resulting in a waste of resources. The leakage of heavy metals will also cause soil and water pollution.

[0004] Coal gasification slag is mainly composed of a large amount of amorphous matter, a small amount of crystalline minerals and organic residual carbon. It has a certain surface area and pore structure. It is a cheap and easily available special carbon source for preparing activated carbon and other adsorbent materials. Making full use of the structural characteristics of gasification slag for the preparation of activated carbon is conducive to exploring a new way for the high-value conversion and utilization of solid waste gasification slag. Summary of the invention

[0005] The present invention is based on the inventor's discovery and understanding of the following facts and problems: currently gasification slag can only be landfilled or piled up, resulting in waste of resources, and the leakage of heavy metals can also cause soil and water pollution. It is necessary to explore the high-value conversion and utilization of solid waste gasification slag.

[0006] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the embodiments of the present invention provide an activated carbon and a preparation method and application thereof, based on the unique physical properties and chemical structure characteristics of enriched carbon, a process technology for preparing activated carbon by air pre-oxidation treatment-physical forming-carbonization-micro-oxidation combined with water vapor activation coupling is formed, and the activated carbon product has good mesopore distribution characteristics, qualified iodine value, qualified methylene blue, and is suitable for use in the fields of deep purification of biochemical wastewater.

[0007] The present invention provides a method for preparing activated carbon, comprising the following steps:

[0008] (1) subjecting the enriched carbon to oxidation pretreatment to obtain an oxidatively pretreated enriched carbon; the enriched carbon is an organic residual carbon enrichment obtained by separation technology of coal gasification slag;

[0009] (2) mixing the oxidatively pretreated enriched carbon, potassium hydroxide, high-temperature coal tar and water, and kneading them uniformly to obtain coal paste;

[0010] (3) forming and aging the coal paste to obtain a carbonized precursor;

[0011] (4) The carbonization precursor is carbonized and then activated in an activation gas to obtain activated carbon; the activation gas includes air and water vapor.

[0012] The advantages and technical effects brought by the preparation method of activated carbon of the embodiment of the present invention are as follows: the organic residual carbon enrichment - enriched carbon obtained by sorting technology of typical solid waste gasification slag of coal chemical industry is used as raw material, and based on the unique physical properties and chemical structure characteristics of enriched carbon, a process technology for preparing activated carbon by air pre-oxidation treatment - physical molding - carbonization - micro-oxidation combined with water vapor activation coupling is formed. The activated carbon product has good mesopore distribution characteristics (for example, mesopore ratio), qualified iodine value, qualified methylene blue, and is suitable for use in fields such as deep purification of biochemical wastewater.

[0013] In the embodiment of the present invention, the gasified slag is sorted and ash is removed to obtain enriched carbon. Compared with other raw materials for preparing activated carbon, the enriched carbon has low reaction activity, a developed pore structure and a large specific surface area, and has the potential to prepare activated carbon and other high value-added carbon materials. It is a cheap and readily available special carbon source. After the raw material enriched carbon is subjected to high-temperature refining in a gasifier, the volatile matter is low and the activation reaction performance is poor. Therefore, the use of pre-oxidation treatment and micro-oxidation activation technology can enhance the activation reaction ability of the enriched carbon and improve the surface properties of the activated carbon. The enriched carbon is pre-oxidized to selectively oxidize the fat structure (such as side chains, bridge bonds, etc.) in the enriched carbon to generate more oxygen-containing functional groups, which is beneficial to amplify the active sites of the enriched carbon, improve the reaction activity of the enriched carbon, and enhance the improvement of the surface properties of the enriched carbon by the activator in the activation process. After carbonization treatment, micro-oxidation activation treatment is carried out. In the activation process of the gas-solid multiphase micro-oxidation reaction of the enriched carbon, an appropriate activation method of air combined with water vapor is adopted, and potassium hydroxide is used as an activator. The activated gas (water vapor combined with air) in the system contacts the carbonaceous deposits and coking materials that block the pores on the surface of the enriched carbon to undergo an oxidation reaction to remove the deposits, exposing the internal polar functional groups, achieving deep etching of the enriched carbon and enhancing the pore-forming and pore-expanding effects, and improving the surface properties and pore structure distribution characteristics of the product. The combined means of pre-oxidation treatment and micro-oxidation activation technology improve the reaction activity of the enriched carbon and moderate the activation temperature. Usually, the activation of gasified slag enriched carbon requires a high temperature of 950°C. After pre-oxidation treatment, the reaction activity of the enriched carbon is improved. Therefore, the subsequent activation temperature can be reduced to 850°C, reducing the operating cost.

[0014] In the embodiment of the present invention, the volatile matter of the enriched carbon is low, and the volatiles such as CO, H2, CH4, tar, etc. generated by carbonization are greatly reduced, and the carbonized tail gas is less, which is conducive to reducing the cost of tail gas treatment. The binder used is high-temperature coal tar, which forms a supporting skeleton and is easy to solidify during the carbonization and activation process, which is conducive to improving the strength of the activated carbon product. The activator potassium hydroxide can not only improve the activity of the enriched carbon, but also be conducive to the pore expansion reaction and improve the index of the product. Moreover, the alkali decomposes during the high-temperature activation process and is almost not retained in the product, so the activated carbon product does not need a water washing process, and no wastewater is generated, which improves the environmental protection performance of the whole process. Water and the binder work together to produce interfacial chemical condensation of the enriched carbon into a paste-like material, and the plasticity of extrusion deformation is improved, which is easy to shape and improve the product strength. The preparation of activated carbon using gasification slag sorting enriched carbon as raw material highlights the structural advantages of enriched carbon, solves the problem of gasification slag accumulation and landfill occupying land resources and seriously damaging the ecological environment, and explores a new way with broad market economic prospects for realizing the high-value utilization of coal chemical industry bulk solid waste gasification slag resources.

[0015] In some embodiments, in step (1), the ash content of the enriched carbon is ≤15%;

[0016] And / or, the temperature of the oxidation pretreatment is 280-350°C;

[0017] And / or, the oxidation pretreatment time is 3-7h;

[0018] and / or, the oxidation pretreatment is carried out in air;

[0019] And / or, the particle size of the enriched carbon obtained by oxidation pretreatment is ≤0.075 mm.

[0020] In some embodiments, in step (2), the mass ratio of the oxidatively pretreated enriched carbon, potassium hydroxide, high-temperature coal tar and water is 1: (0.02-0.05): (0.10-0.30): (0.10-0.20).

[0021] In some embodiments, in the step (2), before mixing, the potassium hydroxide is first prepared into a potassium hydroxide aqueous solution with a mass fraction of 15 to 45%;

[0022] and / or, the viscosity of the high temperature coal tar is E80≤5; the relative density of the high temperature coal tar is d4 20 is 1.13 to 1.22; the asphalt mass content of the high temperature coal tar is 60% to 70%; the toluene insoluble matter mass content of the high temperature coal tar is 3.5% to 7.0%; the ash content of the high temperature coal tar is ≤0.13%; the water content of the high temperature coal tar is ≤4%;

[0023] And / or, the uniform kneading temperature is 70-80°C.

[0024] In some embodiments, in step (3), the aging includes natural drying for 2-3 days;

[0025] And / or, the mass content of water in the carbonized precursor is 7-9%.

[0026] In some embodiments, in step (4), the carbonization temperature is 500-600°C;

[0027] And / or, the constant temperature time of the carbonization is 30-60min;

[0028] And / or, the carbonization is performed under an inert atmosphere.

[0029] In some embodiments, in step (4), the activation temperature is 800-900°C;

[0030] And / or, the activation time is 90-120 min;

[0031] and / or, the volume flow ratio of air and water vapor in the activated gas is 10-20:0.5-1;

[0032] And / or, the activation gas also includes an inert gas, and the volume flow ratio of the inert gas, air and water vapor is 100:10-20:0.5-1.

[0033] The present invention provides an activated carbon, which is prepared by the preparation method described in the present invention. In the present invention, the activated carbon product has good mesopore distribution characteristics, qualified iodine value, qualified methylene blue, and is suitable for deep purification of biochemical wastewater and other fields.

[0034] In some embodiments, the specific surface area of ​​the activated carbon is 500-550m 2 ·g -1 ;

[0035] And / or, the iodine value of the activated carbon is 550-620 mg·g -1 ;

[0036] And / or, the methylene blue value of the activated carbon is 90-100 mg·g -1 ;

[0037] And / or, the pore volume of the activated carbon is 0.32-0.36 ml·g -1 ;

[0038] And / or, the mesopore volume of the activated carbon is 0.21-0.23 ml·g -1 .

[0039] The present invention provides an application of activated carbon for wastewater purification. In the present invention, the activated carbon product has good mesopore distribution characteristics, qualified iodine value, qualified methylene blue, and is suitable for wastewater purification, especially deep purification of biochemical wastewater and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the FT-IR spectra of the enriched carbon after oxidation pretreatment in Example 1 and the enriched carbon without oxidation pretreatment in Comparative Example 2.

[0041] Figure 2 It is the SEM analysis of the surface morphology of the enriched carbon raw material.

[0042] Figure 3 This is the SEM analysis of the activated carbon surface morphology of Example 1. DETAILED DESCRIPTION

[0043] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0044] A method for preparing activated carbon according to an embodiment of the present invention comprises the following steps:

[0045] (1) subjecting the enriched carbon to oxidation pretreatment to obtain an oxidatively pretreated enriched carbon; the enriched carbon is an organic residual carbon enrichment obtained by separation technology of coal gasification slag;

[0046] (2) mixing the oxidatively pretreated enriched carbon, potassium hydroxide, high-temperature coal tar and water, and kneading them uniformly to obtain coal paste;

[0047] (3) forming and aging the coal paste to obtain a carbonized precursor;

[0048] (4) The carbonization precursor is carbonized and then activated in an activation gas to obtain activated carbon; the activation gas includes air and water vapor.

[0049] The method for preparing activated carbon of the embodiment of the present invention uses the organic residual carbon enrichment - enriched carbon obtained by sorting technology of typical solid waste gasification slag of coal chemical industry as raw material, and based on the unique physical properties and chemical structure characteristics of enriched carbon, forms a process technology for preparing activated carbon by air pre-oxidation treatment-physical molding-carbonization-micro-oxidation combined with water vapor activation coupling. The activated carbon product has good mesopore distribution characteristics, qualified iodine value, qualified methylene blue, and is suitable for use in fields such as deep purification of biochemical wastewater.

[0050] In the embodiment of the present invention, the gasified slag is sorted and ash is removed to obtain enriched carbon. Compared with other raw materials for preparing activated carbon, the enriched carbon has low reaction activity, a developed pore structure and a large specific surface area, and has the potential to prepare activated carbon and other high value-added carbon materials. It is a cheap and readily available special carbon source. After the raw material enriched carbon is subjected to high-temperature refining in a gasifier, the volatile matter is low and the activation reaction performance is poor. Therefore, the use of pre-oxidation treatment and micro-oxidation activation technology can enhance the activation reaction ability of the enriched carbon and improve the surface properties of the activated carbon. The enriched carbon is pre-oxidized to selectively oxidize the fat structure (such as side chains, bridge bonds, etc.) in the enriched carbon to generate more oxygen-containing functional groups, which is beneficial to amplify the active sites of the enriched carbon, improve the reaction activity of the enriched carbon, and enhance the improvement of the surface properties of the enriched carbon by the activator in the activation process. After carbonization treatment, micro-oxidation activation treatment is carried out. In the activation process of the gas-solid multiphase micro-oxidation reaction of the enriched carbon, an appropriate activation method of air combined with water vapor is adopted, and potassium hydroxide is used as an activator. The activated gas (water vapor combined with air) in the system contacts the carbonaceous deposits and coking materials that block the pores on the surface of the enriched carbon to undergo an oxidation reaction to remove the deposits, exposing the internal polar functional groups, achieving deep etching of the enriched carbon and enhancing the pore-forming and pore-expanding effects, and improving the surface properties and pore structure distribution characteristics of the product. The combined means of pre-oxidation treatment and micro-oxidation activation technology improve the reaction activity of the enriched carbon and moderate the activation temperature. Usually, the activation of gasified slag enriched carbon requires a high temperature of 950°C. After pre-oxidation treatment, the reaction activity of the enriched carbon is improved. Therefore, the subsequent activation temperature can be reduced to 850°C, reducing the operating cost.

[0051] In the embodiment of the present invention, the volatile matter of the enriched carbon is low, and the volatiles such as CO, H2, CH4, tar, etc. generated by carbonization are greatly reduced, and the carbonized tail gas is less, which is conducive to reducing the cost of tail gas treatment. The binder used is high-temperature coal tar, which forms a supporting skeleton and is easy to solidify during the carbonization and activation process, which is conducive to improving the strength of the activated carbon product. The activator potassium hydroxide can not only improve the activity of the enriched carbon, but also be conducive to the pore expansion reaction and improve the index of the product. Moreover, the alkali decomposes during the high-temperature activation process and is almost not retained in the product, so the activated carbon product does not need a water washing process, and no wastewater is generated, which improves the environmental protection performance of the whole process. Water and the binder work together to produce interfacial chemical condensation of the enriched carbon into a paste-like material, and the plasticity of extrusion deformation is improved, which is easy to shape and improve the product strength. The preparation of activated carbon using gasification slag sorting enriched carbon as raw material highlights the structural advantages of enriched carbon, solves the problem of gasification slag accumulation and landfill occupying land resources and seriously damaging the ecological environment, and explores a new way with broad market economic prospects for realizing the high-value utilization of coal chemical industry bulk solid waste gasification slag resources.

[0052] In some embodiments, in step (1), the gasified slag includes gasified fine slag. In the embodiment of the present invention, the gasified slag escapes in the gasifier in the form of fly ash and is captured outside the furnace, and the enriched carbon is obtained after sorting and removing the ash.

[0053] In some embodiments, in step (1), the ash content of the enriched carbon is ≤15%; the enriched carbon is an organic residual carbon concentrate obtained by sorting the coal gasification slag. The present invention has no special restrictions on the sorting technology, and the ash can be removed by sorting. For example, the sorting technology includes at least one of flotation, gravity separation, electrostatic separation, and combustion, preferably flotation.

[0054] In the embodiment of the present invention, the char in the coal gasification slag produced by coal gasification is sorted, recovered and dried to obtain enriched char. There is no special restriction on the sorting method. The enriched char with an ash content of ≤15% can be obtained by a conventional sorting method in the art. The ash content of the enriched char is ≤15%, which is conducive to improving the liquid phase adsorption performance of the activated carbon product.

[0055] In some embodiments, in step (1), there is no particular limitation on the particle size of the enriched carbon. For example, the particle size of the enriched carbon may be ≤0.075 mm.

[0056] In some embodiments, in step (1), the temperature of the oxidation pretreatment is 280-350°C, specifically, for example, 280°C, 290°C, 300°C, 310°C, 320°C, 340°C, 350°C; the time of the oxidation pretreatment is 3-7h, specifically, for example, 3h, 4h, 5h, 6h, 7h; the oxidation pretreatment is carried out in air.

[0057] In the embodiment of the present invention, the enriched carbon is pre-oxidized. Under suitable oxidation conditions, high temperature air selectively oxidizes the fat structure (such as side chain, bridge bond, etc.) in the enriched carbon to generate more oxygen-containing functional groups, which is beneficial to expand the active sites of the enriched carbon, improve the reaction activity of the enriched carbon, and improve the surface properties of the enriched carbon by the activator in the activation process. In addition, air pre-oxidation also plays a drying role, and the dried enriched carbon is conducive to powder making.

[0058] In some embodiments, in step (1), the enriched carbon after oxidation pretreatment is crushed and screened in sequence to obtain enriched carbon after oxidation pretreatment.

[0059] In some embodiments, in step (1), the particle size of the oxidatively pretreated enriched carbon is ≤0.075 mm; or, the particle size of the oxidatively pretreated enriched carbon powder is ≤0.075 mm. In the embodiment of the present invention, the particle size is ≤0.075 mm, which is conducive to increasing the surface area of ​​the oxidatively pretreated enriched carbon, facilitating molding and improving product strength.

[0060] In some embodiments, in the step (2), the mass ratio of the oxidatively pretreated enriched carbon, potassium hydroxide, high-temperature coal tar and water is 1: (0.02-0.05): (0.10-0.30): (0.10-0.20), specifically, 1: 0.02-0.05 (for example, 0.02, 0.03, 0.04, 0.05): 0.10-0.30 (for example, 0.10, 0.12, 0.15, 0.18, 0.20, 0.30): 0.10-0.20 (for example, 0.10, 0.12, 0.15, 0.18, 0.20).

[0061] In the embodiment of the present invention, on the basis of pre-oxidation treatment and micro-oxidation activation technology, a shallow activation method is proposed to treat the activated enriched carbon in the activation process so that the iodine value of the product is qualified and the methylene blue is qualified, that is, the present invention only needs to add 2-5% KOH to the enriched carbon pre-treated by oxidation, and the conventional chemical activation method usually needs to add up to 200%-300% KOH. When the amount of KOH added exceeds 10%, the activation process causes the pore wall of the enriched carbon to burn out and collapse, the surface area of ​​the enriched carbon is reduced after activation, the macropores are significantly increased, and the surface properties are deteriorated. The shallow activation method of the present invention, the oxidation pretreatment and the micro-oxidation activation work together, which can not only improve the activity of the enriched carbon, but also facilitate the pore expansion reaction and improve the product index, and the alkali is decomposed during the high-temperature activation process and is almost not retained in the product, so the activated carbon product does not need a water washing process, no waste water is generated, and the environmental protection performance of the whole process is improved.

[0062] In the embodiment of the present invention, the binder is high-temperature coal tar with an asphalt content of 60% to 70%, which has good compatibility with the enriched carbon, is easier to form a supporting skeleton and is easy to solidify during the carbonization and activation process, and is beneficial to improving the strength of the activated carbon product; under the joint action of water and the binder, the enriched carbon produces interfacial chemical condensation to form a paste-like material, the plasticity of extrusion deformation is improved, and it is easy to shape and improve the product strength; by regulating the mass ratio of the oxidatively pretreated enriched carbon, potassium hydroxide, high-temperature coal tar and water, it is beneficial to the pore expansion reaction and pore development of the carbon matrix in the enriched carbon, thereby promoting further improvement of the adsorption performance.

[0063] In some embodiments, in step (2), before mixing, the potassium hydroxide is first prepared into a potassium hydroxide aqueous solution with a mass fraction of 15-45%, specifically, for example, 15%, 30%, 45%.

[0064] In some embodiments, in step (2), the viscosity of the high temperature coal tar is E80≤5; the relative density of the high temperature coal tar is d4 20is 1.13-1.22; the asphalt mass content of the high-temperature coal tar is 60%-70%, specifically, for example, 60%, 62%, 65%, 68%, 70%; the toluene insoluble matter mass content of the high-temperature coal tar is 3.5%-7.0%; the ash content (mass content) of the high-temperature coal tar is ≤0.13%; the water content (mass content) of the high-temperature coal tar is ≤4%.

[0065] In the embodiment of the present invention, the binder used is high-temperature coal tar, which has a higher asphalt content (60-70%) than the conventional high-temperature coal tar asphalt content (55-60%), has good compatibility with enriched carbon, is easier to form a supporting skeleton and is easy to solidify during the carbonization and activation process, which is beneficial to improving the strength of the activated carbon product.

[0066] In some embodiments, in step (2), the mixing includes: first preparing potassium hydroxide into a potassium hydroxide aqueous solution, and then adding potassium hydroxide, high-temperature coal tar and water in sequence into the oxidatively pretreated enriched carbon for mixing.

[0067] In some embodiments, in step (2), the temperature of the high temperature coal tar is 70-80°C, that is, the high temperature coal tar is preheated to 70-80°C, specifically, for example, 70°C, 75°C, 80°C.

[0068] In some embodiments, in step (2), the temperature of the water is 60-80° C., specifically, for example, 60° C., 70° C., 80° C. In the embodiments of the present invention, the temperature of the water is 60-80° C., which is beneficial to maintain the fluidity of the binder during the molding process and improve the wetting effect of the binder and the enriched carbon.

[0069] In some embodiments, in step (2), the temperature for uniform mixing is 70-80°C, specifically, for example, 70°C, 75°C, 80°C; optionally, the uniform mixing is carried out using a high-power mixer, and the mixture is strongly mixed and kneaded in the high-power mixer to form coal paste; optionally, the mixture is heated at 70-80°C.

[0070] In some embodiments, in step (3), there is no particular limitation on the shape of the molding, for example, it can be cylindrical or spherical; optionally, the molding is performed by extrusion molding; the molding is performed by hydraulic press extrusion molding.

[0071] In some embodiments, in step (3), the aging includes natural drying for 2-3 days.

[0072] In some embodiments, in step (3), the mass content of water in the carbonized precursor is 7-9%, specifically, for example, 7%, 8%, 9%.

[0073] In some embodiments, the carbonized precursor may be cut into carbon strips having a length of about 1-1.5 cm.

[0074] In some embodiments, in the step (4), the carbonization temperature is 500-600°C, specifically, for example, 500°C, 520°C, 550°C, 580°C, 600°C; the carbonization heating rate is 5-10°C / min, specifically, for example, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min; the carbonization constant temperature time is 30-60min, specifically, for example, 30min, 40min, 50min, 60min; the carbonization is carried out under an inert atmosphere; optionally, the inert atmosphere includes nitrogen; the nitrogen introduction volume flow rate in the reaction system is 50-250ml / min; optionally, an inert atmosphere is introduced and then the temperature is raised to the carbonization temperature for carbonization.

[0075] In some embodiments, in the step (4), the temperature is raised to the activation temperature after carbonization for activation. Optionally, the heating rate is 2-6°C / min, specifically, for example, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min. In the embodiment of the present invention, the heating rate is 2-6°C / min. A lower heating rate means that the time to heat up to the target temperature is extended, which is conducive to the activator entering the carbon matrix and promoting pore development, and also provides more time for pyrolysis reaction and pyrolysis gas escape, forming more pore channels.

[0076] In some embodiments, in step (4), activation is performed in an activation gas;

[0077] The activation temperature is 800-900°C, specifically, for example, 800°C, 820°C, 850°C, 880°C, 890°C, 895°C, 900°C; the activation time is 90-120min, specifically, for example, 90min, 100min, 110min, 120min;

[0078] The volume flow ratio of air and water vapor in the activated gas is 10-20:0.5-1, specifically, 10-20 (e.g., 10, 12, 14, 16, 18, 20):0.5-1 (e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1);

[0079] Optionally, the volume flow rate of air is 10-40 ml / min, specifically, for example, 10 ml / min, 12 ml / min, 14 ml / min, 16 ml / min, 18 ml / min, 20 ml / min, 30 ml / min, 40 ml / min; the volume flow rate of water vapor is 30-110 ml / h, specifically, for example, 30 ml / h, 35 ml / h, 40 ml / h, 45 ml / h, 50 ml / h, 55 ml / h, 60 ml / h, 70 ml / h, 80 ml / h, 110 ml / h;

[0080] Optionally, when the activation temperature is raised to the activation temperature, activation gas is introduced to start activation;

[0081] Optionally, the activation gas also includes an inert gas, and the volume flow ratio of the inert gas, air and water vapor is 100:10-20:0.5-1, specifically, 100:10-20 (for example, 10, 12, 14, 16, 18, 20):0.5-1 (for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1); the inert gas includes nitrogen; optionally, during the activation process, air and the inert gas (nitrogen) are mixed in a gas mixing tank, and then mixed with water vapor in a heated and insulated gas outlet pipeline and enter the furnace body to start activation. After the activation is completed, the introduction of water vapor and air is stopped, and the inert gas (nitrogen) is continued to be cooled until the temperature is lower than 150°C and the introduction of the inert gas (nitrogen) is stopped.

[0082] In the embodiment of the present invention, micro-oxidation activation treatment is performed after carbonization treatment. In the activation process of the gas-solid multiphase micro-oxidation reaction of the enriched carbon, a suitable activation method of air combined with water vapor is adopted, and an appropriate amount of activator potassium hydroxide is used. Through the regulation of different activation process parameters and the "appropriate" oxygen content in the activated gas ((air flow rate*oxygen content in air) / (air flow rate+inert gas flow rate)), a suitable activation effect is achieved. The activated gas (water vapor combined with air) in the system contacts the carbonaceous sediments and coking materials that block the pores on the surface of the enriched carbon to undergo an oxidation reaction to remove the sediments, expose the internal polar functional groups, achieve deep etching of the enriched carbon, and enhance the pore formation and expansion effects, thereby improving the surface properties and pore structure distribution characteristics of the product. Excessive "oxygen content" will cause the pore wall to collapse, reduce the distribution and development of pores in the surface, and lead to a decrease in the adsorption performance of the activated carbon. Further increase in oxygen content will aggravate the oxidation and ablation of the activated carbon into ash. When only water vapor is used without air or only air is used without water vapor, the synergistic effect of the two active gases is missing, which is not conducive to the pore-forming and pore-expanding reaction of carbon in low-activity enriched carbon. The volume flow ratio of air and water vapor is 10-20:0.5-1. The two different oxidants, air and water vapor, are alternately mixed with enriched carbon to synergize. The appropriate oxygen content in the activated gas is conducive to the carbon-consuming etching and pore-expanding reaction of low-activity enriched carbon, and promotes the pore development of activated carbon; when the air content is too high, the carbon in the activated carbon is oxidized into ash at high temperature.

[0083] In the embodiment of the present invention, the pre-oxidation treatment and micro-oxidation activation technology are combined to improve the reactivity of the enriched carbon and moderate the activation temperature. After the pre-oxidation treatment, the reactivity of the enriched carbon is improved, and the subsequent activation temperature can be reduced to below 900°C, thereby reducing the operating cost. Usually, the activation of the gasified slag enriched carbon without pre-oxidation treatment requires a high temperature of 950°C to achieve similar surface properties and pore structures.

[0084] An activated carbon according to an embodiment of the present invention is prepared by the preparation method according to an embodiment of the present invention. In the embodiment of the present invention, the activated carbon product has good mesopore distribution characteristics, qualified iodine value, qualified methylene blue, and is suitable for deep purification of biochemical wastewater and other fields.

[0085] In some embodiments, the specific surface area of ​​the activated carbon is 500-550m 2 ·g -1 ; The iodine value of the activated carbon is 550-620 mg g -1 ; The methylene blue of the activated carbon is 90-100 mg g -1 The pore volume of the activated carbon is 0.32-0.36 ml·g -1 The mesopore volume of the activated carbon is 0.21-0.23 ml·g -1 ; The average pore size of the activated carbon is 3.2-3.5nm.

[0086] In some embodiments, the activated carbon has good mesopore distribution characteristics, for example, the mesopore ratio, etc. Mesopores are also called mesopores, which are pores with a pore size range of 2-50nm. They are channels connecting micropores (<2nm) and macropores (>50nm). The mesopore ratio is mesopore volume / total pore volume. The mesopore ratio of the activated carbon is greater than 50%, optionally, greater than 55%, greater than 60%.

[0087] An application of activated carbon in an embodiment of the present invention is used for wastewater purification. In the embodiment of the present invention, the activated carbon product has good mesopore distribution characteristics, qualified iodine value, qualified methylene blue, and is suitable for wastewater purification, especially deep purification of biochemical wastewater and other fields.

[0088] In some embodiments, it is used for purification of biochemical wastewater; optionally, it is used for deep purification of biochemical wastewater; the biochemical wastewater contains organic matter.

[0089] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0090] Example 1

[0091] A method for preparing activated carbon comprises the following steps:

[0092] (1) Enriched carbon with an ash content of 15% is pre-oxidized at 320°C for 5 hours, and then crushed, ground, and sieved to obtain an oxidized pre-treated enriched carbon powder with a particle size of ≤0.075 mm;

[0093] (2) High temperature coal tar: viscosity (E80): 2.7, relative density (d4 20 ): 1.19, asphalt content 65%, toluene insoluble matter: 4.2%, ash: 0.1%, moisture: 2%.

[0094] According to the mass ratio of oxidatively pretreated enriched carbon powder: 20% potassium hydroxide solution: high-temperature coal tar: water of 1:0.20:0.30:0.15, 20% potassium hydroxide solution, high-temperature coal tar and water are added to the oxidatively pretreated enriched carbon powder in sequence, wherein the high-temperature coal tar is preheated to 80°C and the water temperature is 60°C, and then vigorously kneaded in a kneader (heated to 80°C) to form a coal paste.

[0095] (3) The coal paste is extruded into a smooth cylindrical shape in a hydraulic press and naturally dried for 2 days with a water content of 8% to form a carbonized precursor.

[0096] (4) Nitrogen was introduced into the system at 200 ml / min, and the temperature was raised to 550°C at a rate of 7°C / min, and the temperature was kept constant for 30 min. The temperature was then raised to 850°C at a rate of 3°C / min. When the temperature reached 850°C, air was introduced at 20 ml / min. At the same time, water vapor was introduced at 60 ml / h to start activation. The activation time was 120 min. After the activation was completed, the injection of air and water vapor was stopped, and the nitrogen was continued to cool down until the temperature was below 150°C. The nitrogen was stopped and the temperature was naturally cooled to obtain activated carbon.

[0097] Example 2

[0098] The preparation method is the same as that of Example 1, except that in step (2), the mass ratio of the oxidatively pretreated enriched carbon powder: 20% potassium hydroxide solution: high-temperature coal tar: water is 1:0.10:0.20:0.20.

[0099] Example 3

[0100] The preparation method is the same as that of Example 1, except that in step (4), the activation temperature is 800°C.

[0101] Comparative Example 1

[0102] The preparation method is the same as that of Example 1, except that in step (4), no air is introduced during the activation process.

[0103] Comparative Example 2

[0104] The preparation method is the same as that in Example 1, except that in step (1), the enriched carbon is not pre-oxidized, that is, the enriched carbon with an ash content of 15% is crushed, ground, and sieved in sequence to obtain enriched carbon powder with a particle size of <0.075 mm; in step (2), the enriched carbon powder is used to replace the enriched carbon powder pre-treated by oxidation.

[0105] Comparative Example 3

[0106] The preparation method is the same as that of Example 1, except that in the step (1), the enriched carbon is not pre-oxidized, that is, the enriched carbon with an ash content of 15% is crushed, ground, and sieved in sequence to obtain enriched carbon powder with a particle size of <0.075 mm; in the step (2), the enriched carbon powder is used to replace the enriched carbon powder pre-treated by oxidation; and in the step (4), no air is introduced during the activation process.

[0107] Comparative Example 4

[0108] The preparation method is the same as that of Example 1, except that in step (2), the mass ratio of the oxidatively pretreated enriched carbon powder: 40% potassium hydroxide solution: high-temperature coal tar: water is 1:0.30:0.30:0.15.

[0109] Comparative Example 5

[0110] The preparation method is the same as that of Example 1, except that the air flow rate is 200 ml / min.

[0111] Biochemical wastewater purification test: The initial COD content of biochemical wastewater is 312 mg·L -1 The amount of activated carbon in biochemical wastewater is 0.4 g·L -1 .

[0112] Table 1 Surface property parameters of enriched carbon

[0113]

[0114] Table 2 Activated carbon

[0115]

[0116]

[0117] The surface morphology of the enriched carbon is as follows Figure 2 As shown, the appearance of enriched carbon is a kind of black, odorless, non-adhesive sand-like particles. The surface is composed of a large number of irregular porous matrix and a small number of spherical particles. The substances of various morphologies are mixed, attached and wrapped with each other. There are a certain number of porous matrix in the microscopic morphology of enriched carbon, which preliminarily reflects that it has a certain pore structure, and then forms a certain specific surface area.

[0118] From the surface property parameters of the enriched carbon in Table 1, it can be seen that the enriched carbon has a certain specific surface area and pore structure, and has a certain macromolecular liquid adsorption performance. The iodine value of the enriched carbon is 310 mg·g -1 , methylene blue adsorption value 38mg·g -1 , all failed to meet the technical indicators of activated carbon for industrial water treatment.

[0119] From Table 2, we can see the following points:

[0120] (1) The surface morphology of the activated carbon prepared by air pre-oxidation treatment-physical forming-carbonization-micro-oxidation combined with steam activation coupling method in Example 1 is as follows Figure 3 As shown in the figure, the product surface is angular, forming a large number of pores of different sizes. The flaky carbonaceous components become sparse, the surface pores are obvious and penetrate into the interior, evolving into a rich pore structure, which improves the specific surface area, iodine value, methylene blue, pore volume and micropore volume of the activated carbon. The proportion of mesopores is greater than 60%, which is conducive to the improvement of liquid adsorption performance. The COD content is 312 mg·L -1 The COD value of biochemical wastewater was reduced by more than 85%.

[0121] (2) The enriched carbon was pre-oxidized in air for a period of time, and the surface oxygen-containing functional groups changed. The FTIR of the enriched carbon without oxidation pretreatment in Comparative Example 2 and the enriched carbon after oxidation pretreatment in Example 1 was as follows: Figure 1 shown.

[0122] Figure 1 It shows that the peak shapes of the characteristic peaks of the enriched carbon without oxidation pretreatment and after oxidation pretreatment are similar, but there are certain differences in intensity, indicating that the composition has not changed significantly after pre-oxidation treatment. Under suitable oxidation conditions, high-temperature air selectively oxidizes the fat structure (such as side chains, bridge bonds, etc.) in the enriched carbon to generate more oxygen-containing functional groups, which is beneficial to improve the active sites of the enriched carbon and has a positive effect on improving the surface properties of the activated carbon. As can be seen from Table 2, compared with the activated carbon without oxidation pretreatment in Comparative Example 2, the activated carbon with oxidation pretreatment in Example 1 has a higher specific surface area, iodine value, methylene blue value, etc., and has a higher COD removal efficiency in biochemical wastewater.

[0123] (3) It can be seen from Example 1 and Comparative Examples 1 and 3 that both water vapor and air activation are beneficial to the improvement of the surface properties of activated carbon prepared from enriched carbon. The two gases are used in the enriched carbon activation reaction process, which belongs to a multiphase reaction of a gas-solid phase system. The whole process includes the external diffusion and internal diffusion of the activated gas on the surface of the enriched carbon, the redox reaction between the activated gas and the surface of the enriched carbon to generate intermediate products, the decomposition of the intermediate products into reaction products, the desorption of the reaction products, and the external diffusion. Under high-temperature activation conditions, the activated gas contacts the carbon in the enriched carbon and activates to generate CO, CO2, H2 and other hydrocarbon gases. The activated gas achieves the effect of pore formation by ablation with carbon in the carbonization furnace. For enriched carbon, a substance with very low activity, air pre-oxidation increases the surface active sites of the enriched carbon, reduces the activation temperature of the water vapor and air combined activation of the enriched carbon, and increases the specific surface area of ​​the product at a lower temperature, and the surface properties and pore structure are significantly improved.

[0124] (4) In view of the chemical characteristics of high inertness of enriched carbon, the raw material air oxidation pretreatment, water vapor and air micro-oxidation combined with chemical activation technology are used to treat the activated enriched carbon, and the pore structure of activated carbon is directional controlled. The pore structure of activated carbon is expanded, so that the specific surface area of ​​the product reaches the level of ordinary activated carbon, the iodine value of the activated carbon product is qualified, and the methylene blue is qualified. The activated carbon prepared by the present invention can reduce the COD of biochemical wastewater to 50mg·L -1 The following meets the Class B water quality requirements of the Comprehensive Emission Standard for Water Pollutants (DB11 / 307-2013).

[0125] In Comparative Example 5, when the air flow rate is increased to 200 ml / min, the oxygen content (air flow rate*oxygen content in air) / (air flow rate+inert gas flow rate) is about 10%, and the organic carbon in the enriched carbon is oxidized into ash under the action of high temperature.

[0126] (5) Based on the pre-oxidation treatment and micro-oxidation activation technology, it is proposed to use a shallow activation method to treat the activated enriched carbon in the activation process so that the iodine value of the product is qualified and the methylene blue is qualified. That is, the present invention only needs to add 2-5% KOH to the enriched carbon pre-treated by oxidation. When the amount of KOH added in Comparative Example 4 exceeds 10%, the activation process causes the pore wall of the enriched carbon to burn out and collapse, the surface area of ​​the enriched carbon is reduced after activation, the macropores are significantly increased, and the surface properties are deteriorated. The shallow activation method of the present invention, the oxidation pretreatment and the micro-oxidation activation work together to improve the activity of the enriched carbon, facilitate the pore expansion reaction, and improve the product indicators.

[0127] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0128] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for preparing activated carbon, characterized in that: The following steps are involved: (1) subjecting the enriched carbon to oxidation pretreatment to obtain an oxidatively pretreated enriched carbon; the enriched carbon is an organic residual carbon enrichment obtained by separation technology of coal gasification slag; (2) mixing the oxidatively pretreated enriched carbon, potassium hydroxide, high-temperature coal tar and water, and kneading them uniformly to obtain coal paste; (3) forming and aging the coal paste to obtain a carbonized precursor; (4) The carbonization precursor is carbonized and then activated in an activation gas to obtain activated carbon; the activation gas includes air and water vapor.

2. The method for preparing activated carbon according to claim 1, characterized in that: In the step (1), the ash content of the enriched carbon is ≤15%; And / or, the temperature of the oxidation pretreatment is 280-350°C; And / or, the oxidation pretreatment time is 3-7h; and / or, the oxidation pretreatment is carried out in air; And / or, the particle size of the enriched carbon obtained by oxidation pretreatment is ≤0.075 mm.

3. The method for preparing activated carbon according to claim 1, characterized in that: In the step (2), the mass ratio of the oxidatively pretreated enriched carbon, potassium hydroxide, high-temperature coal tar and water is 1: (0.02-0.05): (0.10-0.30): (0.10-0.20).

4. The method for preparing activated carbon according to claim 1, characterized in that: In the step (2), before mixing, the potassium hydroxide is first prepared into a potassium hydroxide aqueous solution with a mass fraction of 15 to 45%; and / or, the viscosity of the high temperature coal tar is E80≤5; the relative density of the high temperature coal tar is d4 20 is 1.13 to 1.22; the asphalt mass content of the high temperature coal tar is 60% to 70%; the toluene insoluble matter mass content of the high temperature coal tar is 3.5% to 7.0%; the ash content of the high temperature coal tar is ≤0.13%; the water content of the high temperature coal tar is ≤4%; And / or, the uniform kneading temperature is 70-80°C.

5. The method for preparing activated carbon according to claim 1, characterized in that: In the step (3), the aging includes natural drying for 2-3 days; And / or, the mass content of water in the carbonized precursor is 7-9%.

6. The method for preparing activated carbon according to claim 1, characterized in that: In the step (4), the carbonization temperature is 500-600°C; And / or, the constant temperature time of the carbonization is 30-60min; And / or, the carbonization is performed under an inert atmosphere.

7. The method for preparing activated carbon according to claim 1, characterized in that: In the step (4), the activation temperature is 800-900°C; And / or, the activation time is 90-120 min; and / or, the volume flow ratio of air and water vapor in the activated gas is 10-20:0.5-1; And / or, the activation gas also includes an inert gas, and the volume flow ratio of the inert gas, air and water vapor is 100:10-20:0.5-1.

8. An activated carbon, characterized in that It is prepared by the preparation method described in any one of claims 1 to 7.

9. The activated carbon according to claim 8, characterized in that The specific surface area of ​​the activated carbon is 500-550m 2 ·g -1 ; And / or, the iodine value of the activated carbon is 550-620 mg·g -1 ; And / or, the methylene blue value of the activated carbon is 90-100 mg·g -1 ; And / or, the pore volume of the activated carbon is 0.32-0.36 ml·g -1 ; And / or, the mesopore volume of the activated carbon is 0.21-0.23 ml·g -1 .

10. Use of the activated carbon according to claim 8 or 9, characterized in that: Used for wastewater purification.

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