A method and apparatus for preparing activated carbon

Abstract

This invention belongs to the field of activated carbon technology, specifically relating to a method and apparatus for preparing activated carbon. The method for preparing activated carbon provided in this embodiment includes the following steps: (1) mechanically activating coal powder and iron ore powder; (2) carbonizing the treated material to obtain carbonized material; (3) activating the carbonized material obtained in step (2) to obtain activated carbon; wherein the activation treatment is performed by indirect heating, with microwave assistance. Mechanical activation after mixing with iron ore powder can improve the reactivity of coal powder particles, forming an intercalation of coal powder particles and iron ore particles. Microwave assistance heating can balance the temperature in the furnace area, allowing the defects formed by mechanical activation of coal powder particles to further develop, thereby improving the quality of activated coke and reducing the tar content in the pyrolysis gas.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon technology, specifically relating to a method and apparatus for preparing activated carbon. Background Technology

[0002] The one-step coking oven is divided into a carbonization section and an activation section, in which the raw materials are carbonized and activated sequentially. Carbonization is carried out under air-isolated conditions, and the volatile components in the raw materials are released by heating and transformed into carbonized material. In the activation furnace, steam is introduced as an activation medium to react with the carbonized material and generate activated carbon or activated coke.

[0003] The coking ovens widely used in current processes are externally heated, resulting in high surface temperatures and low internal temperatures for the materials inside the oven, leading to uneven temperature distribution and variations in the quality of the produced activated carbon.

[0004] Therefore, how to achieve uniform temperature distribution within the coking oven and produce activated carbon of consistent quality is an urgent problem to be solved. Summary of the Invention

[0005] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0006] CN105645407A discloses an industrial method and system for producing activated carbon from hemp stalks using an externally heated carbonization method. This method utilizes the exhaust gas from a carbonization furnace during the pretreatment and drying process of the hemp stalks to remove moisture and some volatile matter from the raw materials. This improves the adsorption performance and yield of the activated carbon product and enables large-scale industrial production of activated carbon from hemp stalks. However, this method uses external heating for carbonization, resulting in a slow heating rate and uneven temperature distribution within the material layer. This leads to inconsistent activation reaction rates and unstable activated carbon quality.

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for preparing activated carbon. By mechanically activating the activated carbon after mixing it with iron ore powder, the reactivity of the coal powder particles can be improved, forming an intercalation of coal powder and iron ore particles. Microwave-assisted heating can balance the temperature within the furnace, allowing the defects formed by the mechanical activation of the coal powder particles to further develop, thereby improving the quality of the activated coke and reducing the tar content in the pyrolysis gas.

[0008] The method for preparing activated carbon according to embodiments of the present invention includes the following steps:

[0009] (1) Mechanical activation treatment of coal powder and iron ore powder;

[0010] (2) The material processed in step (1) is carbonized to obtain carbonized material;

[0011] (3) The carbonized material obtained in step (2) is activated to obtain activated carbon; wherein the activation process is carried out by indirect heating and microwave-assisted heating.

[0012] The advantages and technical effects of the activated carbon preparation method of this invention are as follows: 1. The method of this invention mechanically activates coal powder and iron ore powder, which increases the specific surface area, surface free energy, and internal energy of the materials, and puts the materials in an excited state, thereby reducing the activation energy of the reaction and increasing the reaction rate. Furthermore, the cracks and defects caused by mechanical activation also improve the adsorption capacity and reactivity of the obtained activated carbon. 2. In the method of this invention, the highly reactive materials, when mixed with coal powder and iron ore powder and mechanically activated, promote the oxidation reaction of iron oxides on carbon during the activation process. In addition, the intense impact and compression during mechanical activation cause harder iron ore particles to embed into the coal powder particles, forming a chimeric structure. 3. In this invention, the coal powder mixed with iron ore powder and mechanically activated is catalyzed by the iron ore powder during both the carbonization and activation stages. In the carbonization stage, the iron ore… The presence of powder allows for a more thorough analysis of volatile components in the material, which is beneficial for pore formation. In the activation stage, ferrooxides with a chimeric structure can effectively promote deeper pore formation of carbon particles under gasification reaction, further developing the pore structure. 4. The method of this embodiment uses both indirect heating and microwave-assisted heating simultaneously. Microwave heating is an internal heating method with high heating rate and rapid temperature rise. When microwaves heat the material layer, the temperature field distribution is high internally and low externally. Indirect heating of the material layer results in a temperature field distribution of high externally and low internally. The combined external and microwave heating ensures a uniform temperature field in the material layer, guaranteeing a constant rate of activation reaction and improving the quality of activated carbon. 5. In the method of this embodiment, both coal powder and iron ore powder are microwave absorbing media. Microwave catalysis can further develop defects and cracks generated by mechanical activation, improving the adsorption capacity of activated carbon.

[0013] In some embodiments, in step (1), the mass ratio of the coal powder to the iron ore powder is (4-20):1; and / or, the iron ore powder includes at least one of hematite and limonite; the coal powder includes at least one of gas coal, fat coal, prime coking coal, lean coal, anthracite, poor coal, weakly caking coal, non-caking coal, long-flame coal, lignite, and natural coke.

[0014] In some embodiments, in step (1), the mechanical activation treatment is carried out at a stirring speed of 500 to 4500 r / min for 0.5 to 2 h.

[0015] In some embodiments, in step (1), before mechanical activation, coal powder and iron ore powder are mixed at a stirring speed of 5 to 30 r / min.

[0016] In some embodiments, in step (2), the temperature of the carbonization stage is 300–500°C; and / or, the carbonization is carried out under a nitrogen atmosphere.

[0017] In some embodiments, in step (3), the temperature of the activation treatment stage is 700-1000°C; and / or, the activation treatment uses water vapor as an activator.

[0018] In some embodiments, the exhaust gas generated by the carbonization treatment in step (2) and / or the activation treatment in step (3) is reformed and heat exchanged to obtain combustible gas.

[0019] This invention also provides an apparatus for preparing activated carbon, including a coal powder silo, an iron ore powder silo, a feeder, a high-speed ore mill, and a carbon-making furnace;

[0020] The outlets of the pulverized coal silo and the iron ore silo are respectively connected to the inlet of the high-speed ore mill.

[0021] The high-speed ore mill is used to mechanically activate pulverized coal and iron ore powder, and the outlet of the high-speed ore mill is connected to the inlet of the charcoal making furnace.

[0022] The charcoal-making furnace includes a carbonization section and an activation section, wherein the activation section is heated by indirect heating and microwave-assisted heating.

[0023] In some embodiments, the grinding mill includes at least one of a ball mill, a rod mill, a pebble mill, and an autogenous mill.

[0024] In some embodiments, the apparatus further includes a high-temperature reforming device, a high-temperature heat exchanger, and a low-temperature heat exchanger connected in sequence. The gas inlet of the high-temperature reforming device is connected to the gas outlet of the charcoal furnace and is used to reform the tail gas generated in the carbonization section and the activation section. The reformed tail gas is then processed by the high-temperature heat exchanger and the low-temperature heat exchanger to obtain combustible gas. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the apparatus used to prepare activated carbon in Example 1;

[0026] Attached reference numerals: 1-Powdered coal silo, 2-Iron ore powder silo, 3-Low-speed ore mill, 4-High-speed ore mill, 5-Charcoal furnace, 6-High-temperature reforming unit, 7-High-temperature heat exchanger, 8-Low-temperature heat exchanger. Detailed Implementation

[0027] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0028] The method for preparing activated carbon according to embodiments of the present invention includes the following steps:

[0029] (1) Mechanical activation treatment of coal powder and iron ore powder;

[0030] (2) The material processed in step (1) is carbonized to obtain carbonized material;

[0031] (3) The carbonized material obtained in step (2) is activated to obtain activated carbon; wherein the activation process is carried out by indirect heating and microwave-assisted heating.

[0032] The activated carbon preparation method of this invention involves mechanically activating coal powder and iron ore powder. This increases the specific surface area, surface free energy, and internal energy of the materials, and puts them in an excited state, reducing the activation energy for the reaction and thus increasing the reaction rate. Furthermore, the cracks and defects caused by mechanical activation also enhance the adsorption capacity and reactivity of the resulting activated carbon. The mechanical activation of the coal powder and iron ore powder, combined with the highly reactive materials during the activation process, promotes the oxidation of carbon by iron oxides. Additionally, the intense impact and compression during mechanical activation cause harder iron ore particles to embed into the coal powder particles, forming a chimeric structure. The coal powder, after being mixed with iron ore powder and mechanically activated, is catalyzed by the iron ore powder during both the carbonization and activation stages. In the carbonization stage, the presence of iron ore powder increases the adsorption capacity and reactivity of the material. The volatile matter analysis is more thorough, which is conducive to pore formation. In the activation section, the iron oxides existing in the chimeric structure can effectively promote deeper pore formation of carbon particles under gasification reaction, and further develop the pore structure. Indirect heating and microwave-assisted heating are used simultaneously. Microwave heating is an internal heating method with the characteristics of high heating rate and fast temperature rise. When microwaves heat the material layer, the temperature field distribution is that the internal temperature is high and the external temperature is low. When indirect heating heats the material layer, the temperature field distribution is that the external temperature is high and the internal temperature is low. The external and microwave synergistic heating makes the temperature field of the material layer uniform, ensuring the constant rate of the activation reaction and improving the quality of activated carbon. The coal powder and iron ore powder used are both microwave absorbing media. Microwave catalysis can further develop the defects and cracks generated by mechanical activation, and improve the adsorption capacity of activated carbon.

[0033] In some embodiments, preferably, in step (1), the mass ratio of pulverized coal to iron ore powder is (4-20):1; and / or, the iron ore powder includes at least one of hematite and limonite; the pulverized coal includes at least one of gas coal, coking coal, prime coking coal, lean coal, anthracite, poor coal, weakly caking coal, non-caking coal, long-flame coal, lignite, and natural coke. More preferably, the hematite includes at least one of raw ore, concentrate, and slag; the limonite includes at least one of raw ore, concentrate, and slag.

[0034] In this embodiment of the invention, the preferred ratio of coal powder to iron ore powder ensures the formation of a uniform intercalation structure, which is beneficial to improving the pore-forming effect of carbon particles. If the amount of coal powder is too large, the pore-forming effect of iron ore powder on carbon particles will be weakened, which is not conducive to the formation of a well-developed pore structure. If the amount of coal powder is too small, the pore-forming effect of iron ore powder will be strong, resulting in a decrease in activated carbon yield and a decrease in activated carbon strength.

[0035] In some embodiments, preferably, in step (1), the mechanical activation treatment is carried out at a stirring speed of 500–4500 r / min for 0.5–2 h. More preferably, in step (1), before the mechanical activation, the coal powder and iron ore powder are mixed at a stirring speed of 15–30 r / min. Even more preferably, the mixing treatment is carried out for 15–30 min.

[0036] In this embodiment of the invention, the mechanical activation conditions are further optimized to ensure that the material is fully mechanically activated in the shortest possible time, thus guaranteeing the effectiveness of the mechanical activation process and reducing production time costs. Furthermore, the mixing process is carried out under low-speed conditions before mechanical activation, which ensures that the coal powder and iron ore powder are mixed evenly, further improving the uniformity of the quality of the obtained activated carbon.

[0037] In some embodiments, preferably, in step (2), the temperature of the carbonization stage is 300–500°C; and / or, the carbonization is carried out under a nitrogen atmosphere.

[0038] In some embodiments, preferably, in step (3), the temperature of the activation treatment stage is 700-1000°C; and / or, the activation treatment uses water vapor as an activator.

[0039] In some embodiments, preferably, in step (3), the indirect heating method includes at least one of electric heating and combustible gas heating.

[0040] like Figure 1 As shown, this embodiment of the invention also provides an activated carbon preparation apparatus, including a coal powder silo 1, an iron ore powder silo 2, a high-speed ore mill 4, and a charcoal making furnace 5;

[0041] The outlet of the pulverized coal bin 1 and the outlet of the iron ore bin 2 are respectively connected to the inlet of the high-speed ore mill 4.

[0042] The high-speed ore mill 4 is used to mechanically activate pulverized coal and iron ore powder, and the outlet of the high-speed ore mill 4 is connected to the inlet of the charcoal furnace 5.

[0043] The charcoal furnace 5 includes a carbonization section and an activation section, wherein the activation section is heated by indirect heating and microwave-assisted heating.

[0044] In some embodiments, preferably, the grinding mill includes at least one of ball mill, rod mill, pebble mill, and autogenous mill.

[0045] In some embodiments, preferably, the device further includes a high-temperature reforming device 6, a high-temperature heat exchanger 7, and a low-temperature heat exchanger 8 connected in sequence. The gas inlet of the high-temperature reforming device 6 is connected to the gas outlet of the charcoal furnace 5, and is used to reform the tail gas generated in the carbonization section and the activation section. The reformed tail gas is then processed by the high-temperature heat exchanger 7 and the low-temperature heat exchanger 8 in sequence to obtain combustible gas.

[0046] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0047] Example 1

[0048] This embodiment adopts Figure 1 The aforementioned apparatus is used to prepare activated carbon.

[0049] (1) Store limonite and lignite in iron ore powder bin 2 and coal powder bin 1 respectively. The feed rate is precisely controlled by the feeder. The material is transported to the low-speed mill 3 at a mass ratio of lignite to limonite of 10:1.

[0050] (2) The mixture is first crushed and mixed in a low-speed mill 3 at 20 r / min for 30 min, and then mechanically activated in a high-speed mill 4 at 1000 r / min for 1 h.

[0051] (3) The mechanically activated material is fed into the charcoal furnace 5 for carbonization and activation. In the carbonization section, N2 is used as the reaction atmosphere, the reaction temperature is controlled at 400℃, and the reaction time is 1h. In the activation section, high-temperature steam is used as the reaction atmosphere, and electric heating and microwave-assisted co-heating are used to control the reaction temperature at 900℃ and the activation time is 30min.

[0052] (4) The iron-containing activated carbon is produced after the temperature is reduced by cooling water. The cooling water is heated into low-temperature steam. The reducing flue gas containing CO and other substances from the outlet of the charcoal furnace 5 is partially burned as fuel and discharged with the flue gas. The other part is reformed at high temperature by the high-temperature reforming device 6 to reduce the tar content and increase the content of H2 and other substances. Then, it passes through the high-temperature heat exchanger 7 and the low-temperature heat exchanger 8 in sequence to reduce the temperature and is produced as a gaseous product. The steam from the cooling section is further heated by the high-temperature heat exchanger 7 to obtain high-temperature steam. The high-temperature steam enters the activation section to participate in the activation reaction.

[0053] Example 2

[0054] (1) Hematite and coking coal are stored in iron ore powder bin 2 and coal powder bin 1 respectively. The feeding amount is precisely controlled by the feeder, and the material is transported to the low-speed mill 3 according to the mass ratio of coking coal to hematite of 20:1.

[0055] (2) The mixture is first crushed and mixed in a low-speed mill 3 at 20 r / min for 20 min, and then mechanically activated in a high-speed mill 4 at 2000 r / min for 1 h.

[0056] (3) The mechanically activated material is fed into the charcoal furnace 5 for carbonization and activation. In the carbonization section, N2 is used as the reaction atmosphere, the reaction temperature is controlled at 500℃, and the reaction time is 1h. In the activation section, high-temperature steam is used as the reaction atmosphere, combustible gas heating and microwave-assisted co-heating are used, the reaction temperature is controlled at 800℃, and the activation time is 30min.

[0057] (4) The iron-containing activated carbon is produced after the temperature is reduced by cooling water. The cooling water is heated into low-temperature steam. The reducing flue gas containing CO and other substances from the outlet of the charcoal furnace 5 is partially burned as fuel and discharged with the flue gas. The other part is reformed at high temperature by the high-temperature reforming device 6 to reduce the tar content and increase the content of H2 and other substances. Then, it passes through the high-temperature heat exchanger 7 and the low-temperature heat exchanger 8 in sequence to reduce the temperature and is produced as a gaseous product. The steam from the cooling section is further heated by the high-temperature heat exchanger 7 to obtain high-temperature steam. The high-temperature steam enters the activation section to participate in the activation reaction.

[0058] Comparative Example 1

[0059] (1) Hematite and coking coal are stored in iron ore powder bin 2 and coal powder bin 1 respectively. The feeding amount is precisely controlled by the feeder, and the material is transported to the grinding mill at a mass ratio of coking coal:hematite of 10:1.

[0060] (2) The mixture is first mixed in a low-speed mill 3 at 20 r / min for 30 min, and then mechanically activated in a high-speed mill 4 at 1000 r / min for 1 h.

[0061] (3) The mechanically activated material is fed into the charcoal furnace 5 for carbonization and activation. In the carbonization section, N2 is used as the reaction atmosphere, the reaction temperature is controlled at 400℃, and the reaction time is 1h. In the activation section, high-temperature steam is used as the reaction atmosphere, electric heating is used, the reaction temperature is controlled at 900℃, and the activation time is 30min.

[0062] (4) The iron-containing activated carbon is produced after the temperature is reduced by cooling water. The cooling water is heated into low-temperature steam. The reducing flue gas containing CO and other substances from the outlet of the charcoal furnace 5 is partially burned as fuel and discharged with the flue gas. The other part is reformed at high temperature by the high-temperature reforming device 6 to reduce the tar content and increase the content of H2 and other substances. Then, it passes through the high-temperature heat exchanger 7 and the low-temperature heat exchanger 8 in sequence to reduce the temperature and is produced as a gaseous product. The steam from the cooling section is further heated by the high-temperature heat exchanger 7 to obtain high-temperature steam. The high-temperature steam enters the activation section to participate in the activation reaction.

[0063] Comparative Example 2

[0064] (1) Hematite and coking coal are stored in iron ore powder bin 2 and coal powder bin 1 respectively. The feeding amount is precisely controlled by the feeder, and the material is transported to the low-speed mill 3 according to the mass ratio of coking coal to hematite of 10:1.

[0065] (2) The mixture is mixed in a low-speed mill 3 at 20 r / min for 30 min, and then fed into a charcoal furnace 5 for carbonization and activation. In the carbonization section, N2 is used as the reaction atmosphere, the reaction temperature is controlled at 400℃, and the reaction time is 1 h. In the activation section, high-temperature steam is used as the reaction atmosphere, and electric heating and microwave-assisted co-heating are used to control the reaction temperature at 900℃ and the activation time is 30 min.

[0066] (3) The iron-containing activated carbon is produced after the temperature is reduced by cooling water. The cooling water is heated into low-temperature steam. The reducing flue gas containing CO and other substances from the outlet of the charcoal furnace 5 is partially burned as fuel and discharged with the flue gas. The other part is reformed at high temperature by the high-temperature reforming device 6 to reduce the tar content and increase the H2 content. Then, it passes through the high-temperature heat exchanger 7 and the low-temperature heat exchanger 8 in sequence to reduce the temperature and is produced as a gaseous product. The steam from the cooling section is further heated by the high-temperature heat exchanger 7 to obtain high-temperature steam. The high-temperature steam enters the activation section to participate in the activation reaction.

[0067] The iron-containing activated carbons prepared in Examples 1-2 and Comparative Examples 1-2 were used for fixed-bed H2S removal and catalytic oxidation. Their desulfurization performance was tested by a sulfur analyzer, and the results are shown in Table 1.

[0068] Table 1

[0069] <![CDATA[H2S adsorption capacity (mmol / g)]]> Example 1 6.3 Example 2 5.3 Comparative Example 1 4.8 Comparative Example 2 4.2

[0070] As can be seen from the data in Table 1, the activated carbon prepared in Examples 1 and 2 has very good adsorption performance for H2S. In Comparative Example 1, only indirect heating was used during the activation stage, resulting in uneven temperature distribution of the material layer and inconsistent quality of the activated carbon, which significantly reduced the adsorption capacity for H2S. Comparative Example 2 did not undergo mechanical activation treatment, resulting in low reactivity during the carbonization and activation stages, and the activated carbon did not generate sufficient cracks and pore structures, resulting in a relatively low adsorption capacity for H2S that could not meet the application requirements.

[0071] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0072] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preparing activated carbon, characterized in that, Includes the following steps: (1) Mechanically activate the coal powder and iron ore powder; the iron ore powder includes at least one of hematite and limonite, and the mass ratio of the coal powder to the iron ore powder is (4~20):1; the mechanical activation treatment is carried out using a high-speed ore mill; (2) The material processed in step (1) is carbonized to obtain carbonized material; (3) The carbonized material obtained in step (2) is activated to obtain activated carbon; wherein the activation treatment is carried out by indirect heating and microwave-assisted heating is used; the temperature of the activation treatment stage is 700~1000℃, and water vapor is used as the activating agent.

2. The method for preparing activated carbon according to claim 1, characterized in that, In step (1), the pulverized coal includes at least one of gas coal, fat coal, prime coking coal, lean coal, anthracite, poor coal, weakly caking coal, non-caking coal, long-flame coal, and lignite.

3. The method for preparing activated carbon according to claim 1 or 2, characterized in that, In step (1), the mechanical activation treatment is carried out at a stirring speed of 500~4500r / min for 0.5~2h.

4. The method for preparing activated carbon according to claim 3, characterized in that, In step (1), before mechanical activation, coal powder and iron ore powder are mixed at a stirring speed of 15~30r / min.

5. The method for preparing activated carbon according to claim 1, characterized in that, In step (2), the temperature of the carbonization process is 300~500℃; and / or, the carbonization process is carried out in a nitrogen atmosphere.

6. The method for preparing activated carbon according to claim 1, characterized in that, The exhaust gas generated by the carbonization treatment in step (2) and / or the activation treatment in step (3) is reformed and heat exchanged to obtain combustible gas.

7. The method for preparing activated carbon according to any one of claims 1 to 6, characterized in that, The preparation method uses a preparation apparatus including a coal powder silo, an iron ore powder silo, a high-speed ore mill, and a charcoal making furnace. The outlets of the pulverized coal silo and the iron ore silo are respectively connected to the inlet of the high-speed ore mill. The high-speed ore mill is used to mechanically activate pulverized coal and iron ore powder, and the outlet of the high-speed ore mill is connected to the inlet of the charcoal making furnace. The charcoal-making furnace includes a carbonization section and an activation section, wherein the activation section is heated by indirect heating and microwave-assisted heating.

8. The method for preparing activated carbon according to claim 7, characterized in that, The high-speed grinding mill includes at least one of ball mills, rod mills, pebble mills, and autogenous mills.

9. The method for preparing activated carbon according to claim 7, characterized in that, The device also includes a high-temperature reforming device, a high-temperature heat exchanger, and a low-temperature heat exchanger connected in sequence. The gas inlet of the high-temperature reforming device is connected to the gas outlet of the charcoal furnace and is used to reform the tail gas generated in the carbonization section and the activation section. The tail gas after reforming is processed by the high-temperature heat exchanger and the low-temperature heat exchanger in sequence to obtain combustible gas.

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