Process for preparing activated carbon by oxidation-reduction method, activated carbon material prepared by process and application of activated carbon material

Abstract

The invention discloses a process for preparing activated carbon by an oxidation-reduction method, an activated carbon material prepared by the process and application of the activated carbon material. The process comprises an activation step of activating raw materials, the activation step is carried out in an activation channel of a multi-tube activation furnace, and a heating area, a centralized activation area, a supplementary activation area and a buffer balance area which are sequentially arranged in the material advancing direction are formed in the activation channel; the activation step comprises the following steps: heating the raw materials to 700-750 DEG C in a heating area; activating the raw materials for 3-5 hours at the temperature of 750-850 DEG C in the centralized activation area; activating the raw materials for 2-3 hours at the temperature of 700-750 DEG C in the supplementary activation area; and the temperature of the activated material is reduced to the temperature suitable for discharging in the buffer balance area. The whole activation process is compact, the activation is sufficient, and the yield is high; the specific surface area of the prepared activated carbon material is greater than 2000m < 2 > / g, the micropore diameter is less than 2nm, the strength is greater than 97%, and the tap density is greater than 350g / L.

Description

Technical Field

[0001] The invention belongs to the technical field of activated carbon, and specifically relates to a process for preparing activated carbon by an oxidation-reduction method, and an activated carbon material prepared by the process and application thereof. Background Art

[0002] Transforming and upgrading biomass materials or low-grade coal to obtain high-value-added activated carbon is one of the current means of recycling biomass materials and low-grade coal. According to the nature of the reaction, the conversion methods include physical activation and redox activation.

[0003] Among them, the redox method is that in the absence of oxygen, carbon (i.e. from biomass materials or low-grade coal) first reacts with water vapor at high temperature to generate carbon dioxide and hydrogen; then carbon dioxide reacts with carbon again to generate carbon monoxide; the generated reaction gas containing carbon monoxide and hydrogen is introduced into the combustion chamber filled with oxygen by negative pressure, and the reaction gas burns violently in the combustion chamber, and the high temperature generated promotes the reaction between carbon and water vapor. In this way, carbon is continuously captured, forming countless tiny holes in the biomass material, and obtaining activated carbon in a porous state.

[0004] A Chinese utility model patent with publication number CN217535482U discloses a multi-tubular activated carbon processing equipment, which includes an activation furnace, which includes a furnace body, a central combustion chamber and a plurality of activation channels circumferentially distributed around the central combustion chamber, the central combustion chamber and the activation channels both extend axially along the furnace body, and each activation channel is connected to the central combustion chamber at its discharge end; a negative pressure suction device connected to the central combustion chamber and a self-loading device connected to the activation channel are provided at the feed end of the furnace body, an air inlet connected to the central combustion chamber is provided on the furnace body, and the negative pressure suction device is used to suck air and activated tail gas generated in each activation channel into the central combustion chamber for combustion and heat release to supply heat to each activation channel.

[0005] This technology discloses a device that can prepare activated carbon by redox method, but does not disclose its specific activation process and the performance parameters of the prepared activated carbon. Summary of the invention

[0006] The purpose of the present invention is to provide a process for preparing activated carbon by a redox method and the activated carbon material and application obtained by the process. The process is fully activated and has a high yield. The activated carbon material prepared has a large specific surface area, a concentrated micropore size distribution, good strength and high energy density.

[0007] To achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0008] A process for preparing activated carbon by redox method, comprising an activation step of activating raw materials, the activation step being carried out in an activation channel of a multi-tube activation furnace, wherein the activation channel is provided with a temperature rising zone, a concentrated activation zone, a supplementary activation zone and a buffer balance zone arranged in sequence along the forward direction of the material;

[0009] The activation step comprises:

[0010] The step of heating the raw material to 700-750° C. in the temperature rising zone;

[0011] The step of activating the raw material at 750-850° C. for 3-5 hours in the centralized activation zone;

[0012] The step of activating the raw material at 700-750° C. for 2-3 hours in the supplementary activation zone;

[0013] The step of reducing the temperature of the activated material to a temperature suitable for discharging in the buffer equilibrium zone.

[0014] The present invention organically divides the activation channel into four functional areas according to the reaction process, and designs the temperature in each functional area and the residence time of the raw material. As the activation furnace rotates, the raw material passes through different functional areas in turn, and is oxidized and reduced to activated material. The entire reaction process is compact, the activation is sufficient, and the yield is high.

[0015] Preferably, in the above process, the activation channel has a length of 10-15 m and a diameter of 15-30 cm; more preferably, the length is 12-13 m, and more preferably, the diameter is 20 cm. The process of the present invention is carried out in an activation channel with a relatively small diameter and a relatively short length, and sufficient activation can be achieved even when the activation furnace is small in size.

[0016] Preferably, in the above process, the raw materials are preheated to 100-200° C. in the self-loading device of the multi-tube activation furnace, and then enter the temperature rising zone of the activation channel;

[0017] The residence time of the raw materials in the temperature rising zone is 3-4h.

[0018] The self-feeding device is located on the flow path of the activated exhaust gas and water vapor, so the activated exhaust gas and water vapor (especially the activated exhaust gas) can preheat the raw materials in the self-feeding device; on the one hand, the preheating process can make full use of the temperature of the activated exhaust gas and water vapor, and on the other hand, it helps to shorten the length of the heating zone.

[0019] Preferably, in the above process, the concentrated activation zone includes an oxidation reaction zone and a reduction reaction zone arranged in sequence along the material forward direction, the oxidation reaction zone is used to activate the raw material at 750-850°C for 1-3h, and the reduction reaction zone is used to activate the raw material at 800-850°C for 2-4h.

[0020] In the oxidation reaction zone, carbon first reacts with water vapor at 750-850°C to generate carbon dioxide and hydrogen; while in the reduction reaction zone, the carbon dioxide from the oxidation reaction zone reacts again with carbon to generate carbon monoxide.

[0021] Preferably, in the above process, a steam pipe is provided in the activation channel, and the gas outlet of the steam pipe is located between the temperature rising zone and the concentrated activation zone;

[0022] Alternatively, the steam pipe has several gas outlets, and all the gas outlets are distributed in the redox zone.

[0023] The steam outlet of the steam pipe is directly arranged between the temperature rising zone and the concentrated activation zone or in the oxidation-reduction zone, so as to provide sufficient water vapor for the oxidation reaction zone and promote the oxidation reaction to occur rapidly;

[0024] Preferably, in the above process, the amount of steam in each activation channel is 0.013-0.017 ton / h.

[0025] Preferably, in the above process, the steam pipe is also fixedly connected or integrally formed with a stirring shaft extending to the discharge end of the activation channel, and a turning plate is fixedly provided on the outer periphery of the stirring shaft.

[0026] Preferably, in the above process, at the discharge end of the buffer equilibrium zone, the temperature of the activated material drops to below 500°C.

[0027] The present invention also provides an activated carbon material, which is prepared by the above process;

[0028] The specific surface area of ​​the activated carbon is greater than 2000m 2 / g, the average pore size of the micropores is less than 2nm, the strength is greater than 97%, and the tap density is greater than 350g / L.

[0029] The present invention also provides the use of the above-mentioned activated carbon material in preparing a supercapacitor or a silicon-carbon battery negative electrode.

[0030] Compared with the prior art, the technical solution of the present invention is as follows:

[0031] The present invention organically divides the activation channel into four functional areas according to the reaction process, and designs the temperature in each functional area and the residence time of the raw materials. As the activation furnace rotates, the raw materials pass through different functional areas in turn, and are oxidized and reduced to activated carbon materials. The entire reaction process is compact, fully activated, and has a high yield; the specific surface area of ​​the activated carbon material obtained is greater than 2000m 2 / g, the pore size distribution of the micropores is relatively concentrated, the average pore size is less than 2nm, the strength is greater than 97%, and the tap density is greater than 350g / L, which provides a raw material with excellent performance for the preparation of supercapacitors and silicon-carbon battery negative electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The nitrogen adsorption-desorption isotherm of the activated carbon material prepared in Example 1 of the present invention;

[0033] Wherein, Relative pressure (P / Po) represents relative pressure (P / Po), Volume (cc / g) represents adsorption volume (cc / g); the same below;

[0034] Figure 2 Isotherm analysis results of the activated carbon material prepared in Example 1 of the present invention;

[0035] Figure 3 The nitrogen adsorption and desorption BET curve of the activated carbon material prepared in Example 1 of the present invention;

[0036] Figure 4 Langmuir curve of nitrogen adsorption and desorption of the activated carbon material prepared in Example 1 of the present invention;

[0037] Figure 5 BJH (adsorption) pore volume distribution dV / dD analysis of the activated carbon material prepared in Example 1 of the present invention;

[0038] Wherein, Pore Diameter [nm] represents the pore diameter (nm), Volume dV / dD (cc / g / nm) represents the differential volume dV / dD (cc / g / nm); the same below;

[0039] Figure 6 BJH (desorption) pore volume distribution dV / dD analysis of the activated carbon material prepared in Example 1 of the present invention;

[0040] Figure 7 BJH (adsorption) pore volume distribution dV / dlog (D) analysis of the activated carbon material prepared in Example 1 of the present invention;

[0041] Wherein, Volume dV / dlog(cc / g) represents differential volume dV / dlog(cc / g); the same below;

[0042] Figure 8 BJH (desorption) pore volume distribution dV / dlog analysis of the activated carbon material prepared in Example 1 of the present invention;

[0043] Fig. 9 t-Plot (adsorption) curve of the activated carbon material prepared in Example 1 of the present invention;

[0044] Wherein, Thickness[nm] represents thickness (nm), the same below;

[0045] Fig.10 The t-Plot (adsorption) curve analysis results of the activated carbon material prepared in Example 1 of the present invention;

[0046] Fig.11 HK micropore distribution curve of the activated carbon material prepared in Example 1 of the present invention;

[0047] Fig.12 This is the HK micropore distribution curve analysis result of the activated carbon material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0049] Example 1

[0050] The present embodiment provides an activated carbon material, which is prepared by an activation process using a redox method. The activation process using the redox method is carried out in a multi-tube activation furnace (the structure of which is described in the Chinese utility model patent with publication number CN217535482U, which is not described in detail in the present embodiment). The multi-tube activation furnace is provided with 18 activation channels evenly arranged around a central combustion chamber. The diameter of each activation channel is 20 cm and the length is 13 m. A heating zone (4 m), a concentrated activation zone (5 m), a supplementary activation zone (3 m) and a buffer balance zone (1 m) are formed in each activation channel. The activation channels are arranged in sequence along the material forward direction.

[0051] Each activation channel is provided with a shaft, the end of which facing the activation channel feed end is hollow and used to transport water vapor, thus forming a steam pipe; the steam pipe has an outlet located between the temperature rising zone and the concentrated activation zone; the downstream of the outlet, i.e., the end of the shaft facing the activation channel discharge end is solid and forms a stirring shaft, and a plurality of turning plates are provided on the outer periphery of the stirring shaft;

[0052] In this embodiment, the temperature of each functional area of ​​the activation channel is adjusted by introducing different amounts of air into different positions in the central combustion chamber;

[0053] The above-mentioned redox activation process includes an activation step of activating the raw material into activated carbon, and the activation step includes:

[0054] (1) Preheating: The feed end of each activation channel is connected to the self-feeding device, and the self-feeding device is located on the path of the water vapor flowing to the activation channel. Therefore, the water vapor can preheat the raw material in the self-feeding device (the present embodiment uses wood carbonized material, and other biomass carbonized materials such as bamboo can also be used). In this embodiment, the raw material is preheated to 200° C., and the preheating time is 1.5 hours;

[0055] (2) Heating: The preheated material is introduced into the heating zone of the activation channel. In this embodiment, the length of the heating zone is 3 m, the material residence time is 3 h, and the material temperature in the heating zone rises to 750° C.

[0056] (3) Centralized activation: After the material passes through the temperature rising zone and before entering the centralized activation zone, it encounters the water vapor flowing out of the steam outlet of the steam pipe; in this embodiment, the steam flow rate required for the entire activation furnace is 0.25 tons / h of water evaporation;

[0057] According to the different nature of the reactions, the centralized activation zone of this embodiment is composed of an oxidation reaction zone and a reduction reaction zone arranged in sequence along the forward direction of the material; wherein the length of the oxidation reaction zone is 2m, and the material residence time is 2h; in the oxidation reaction zone, the exothermic reaction between carbon and water vapor mainly occurs, and carbon dioxide and hydrogen are generated by the reaction. Therefore, under the support of the central combustion chamber heating and the reaction heat release, the material temperature is raised from 750°C to 850°C;

[0058] The length of the reduction reaction zone is 3m, and the material residence time is 3h; in the reduction reaction zone, the main reduction reaction that occurs is the reaction of carbon dioxide with carbon to generate carbon monoxide; the temperature in the reduction reaction zone is maintained between 800-850°C;

[0059] (4) Supplementary activation: The temperature in the supplementary activation zone is about 700-750°C, and the redox reaction continues to occur for supplementary activation;

[0060] (5) Buffer balance: The temperature in the buffer balance zone drops significantly, so that water vapor no longer reacts with carbon; and the cessation of the reaction further promotes the temperature drop. At the discharge end of the activation channel, the temperature of the activated material has dropped to about 500°C.

[0061] The discharging step after the activation step is completed can be referred to the existing technology and will not be described in detail in this embodiment; after discharging, the activated carbon material of this embodiment is obtained.

[0062] Example 2

[0063] This embodiment provides an activated carbon material, and the preparation process of the activated carbon material is basically the same as that of Embodiment 1, except that;

[0064] The raw material used is coconut shell carbonized material, and the length of the activation channel is 10m. The activation steps include:

[0065] (1) Preheating: In this embodiment, the raw material is preheated to 150° C. for 2 h;

[0066] (2) Heating: In this embodiment, the length of the heating zone is 3.5 m, the material residence time is 3.5 h, and the material temperature in the heating zone rises to 750 ° C;

[0067] (3) Centralized activation: In this embodiment, the steam flow rate required for the entire activation furnace is 0.28 tons / h of water evaporation;

[0068] The length of the oxidation reaction zone is 1m, the material residence time is 1h, and the material temperature rises from 750°C to 850°C; the length of the reduction reaction zone is 2m, the material residence time is 2h; the temperature in the reduction reaction zone is maintained between 800-850°C;

[0069] (4) Supplementary activation: In this embodiment, the length of the supplementary activation zone is 2 m, and the material residence time is 2 h. The temperature in the supplementary activation zone is about 700-750° C., and the redox reaction continues to occur for supplementary activation.

[0070] (5) Buffer balance: The length of the buffer balance zone is 1.5 m. At the discharge end of the activation channel, the temperature of the activated material has dropped below 500°C.

[0071] Example 3

[0072] This embodiment provides an activated carbon material, and the preparation process of the activated carbon material is basically the same as that of Embodiment 1, except that;

[0073] The raw material used is coal-based (less than 180 million years old) carbonized material, and the length of the activation channel is 14m. The activation steps include:

[0074] (1) Preheating: In this embodiment, the raw material is preheated to 100° C. for 2 h;

[0075] (2) Heating: In this embodiment, the length of the heating zone is 4 m, the material residence time is 4 h, and the material temperature in the heating zone rises to 700 ° C;

[0076] (3) Centralized activation: In this embodiment, the steam flow rate required for the entire activation furnace is 0.3 tons / h of water evaporation;

[0077] The length of the oxidation reaction zone is 2m, the material residence time is 2h, and the material temperature rises from 750°C to 850°C; the length of the reduction reaction zone is 3m, the material residence time is 3h; the temperature in the reduction reaction zone is maintained between 800-850°C;

[0078] (4) Supplementary activation: In this embodiment, the length of the supplementary activation zone is 3 m, the material residence time is 3 h, and the temperature in the supplementary activation zone is about 700-750° C.;

[0079] (5) Buffer balance: The length of the buffer balance zone is 2m. At the discharge end of the activation channel, the temperature of the activated material has dropped below 500°C.

[0080] The physical properties of the activated carbon materials obtained in Examples 1-3 were analyzed. Figures 1 to 12 ,right Figures 1 to 12 The analysis results are summarized in Table 1.

[0081] Table 1

[0082]

[0083] As can be seen from Table 1, the specific surface area of ​​the activated carbon materials prepared by the present invention is greater than 2136.7944 m 2 / g, and the pore size distribution of micropores is concentrated, with an average pore size of less than 2nm.

[0084] Table 2

[0085]

[0086] As can be seen from Table 2, the strength of the activated carbon materials prepared in the present invention all reached more than 97%, and all had a relatively high tap density, indicating a high energy density.

Claims

1. A process for preparing activated carbon by redox method, comprising an activation step of activating raw materials, characterized in that: The activation step is carried out in the activation channel of the multi-tube activation furnace, wherein the activation channel is provided with a temperature rising zone, a concentrated activation zone, a supplementary activation zone and a buffer balance zone arranged in sequence along the forward direction of the material; The activation step comprises: The step of heating the raw material to 700-750° C. in the temperature rising zone; The step of activating the raw material at 750-850° C. for 3-5 hours in the centralized activation zone; The step of activating the raw material at 700-750° C. for 2-3 hours in the supplementary activation zone; The step of reducing the temperature of the activated material to a temperature suitable for discharging in the buffer equilibrium zone.

2. The process according to claim 1, characterized in that The activation channel has a length of 10-15 m and a diameter of 15-30 cm.

3. The process according to claim 1, characterized in that The raw materials are preheated to 100-200°C in the self-loading device of the multi-tube activation furnace, and then enter the temperature rising zone of the activation channel; The residence time of the raw materials in the temperature rising zone is 3-4h.

4. The process according to claim 1, characterized in that The centralized activation zone includes an oxidation reaction zone and a reduction reaction zone arranged in sequence along the material forward direction. The oxidation reaction zone is used to activate the raw material at 750-850°C for 1-3h, and the reduction reaction zone is used to activate the raw material at 800-850°C for 2-4h.

5. The process according to claim 4, characterized in that A steam pipe is provided in the activation channel, and the gas outlet of the steam pipe is located between the temperature rising zone and the concentrated activation zone; Alternatively, the steam pipe has several gas outlets, and all the gas outlets are distributed in the redox zone.

6. The process according to claim 5, characterized in that The amount of steam in each activation channel is 0.013-0.017 tons / h.

7. The process according to claim 5, characterized in that The steam pipe is also fixedly connected or integrally formed with a stirring shaft extending to the discharge end of the activation channel, and a turning plate is fixedly arranged on the outer periphery of the stirring shaft.

8. The process according to claim 1, characterized in that At the discharge end of the buffer equilibrium zone, the temperature of the activated material drops below 500°C.

9. An activated carbon material, characterized in that Prepared by the process as described in any one of claims 1 to 8; The specific surface area of ​​the activated carbon is greater than 2000m 2 / g, the average pore size of the micropores is less than 2nm, the strength is greater than 97%, and the tap density is greater than 350g / L.

10. Use of the activated carbon material according to claim 9 in preparing a negative electrode of a supercapacitor or a silicon-carbon battery.

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