A method for microwave pyrolysis of waste tires to regenerate carbon black

Abstract

This invention discloses a method for microwave regenerating activated carbon, the main steps of which include: Step (1): A plurality of waste activated carbon materials are placed into a microwave heating cavity, the microwave heating cavity having at least one air inlet and at least one air outlet, the air outlet being connected to an external air extraction device via a pipe; Step (2): A low-oxygen atmosphere containing inert gas is introduced into the microwave heating cavity through the at least one air inlet, and the plurality of waste activated carbon materials undergo a microwave low-temperature carbonization heat treatment to form a plurality of carbonized activated carbons; Step (3): Under an oxygen-free atmosphere containing inert gas is introduced into the microwave heating cavity through the at least one air inlet, the carbonized activated carbons undergo a microwave activation treatment to form a plurality of regenerated activated carbons; and Step (4): The regenerated activated carbons are removed from the microwave heating cavity into a cooling container.

Description

Technical Field

[0001] This invention relates to a method for regenerating waste activated carbon, and more particularly to a method for regenerating activated carbon using microwave heating treatment of waste activated carbon. Prior Technology

[0002] Activated carbon is a black powdery or granular carbonaceous material. Structurally, activated carbon is a porous carbon due to the irregular arrangement of microcrystalline carbon with fine pores between the cross-links. Upon activation, carbon structure defects are created, resulting in low bulk density and a large specific surface area. It is widely used to remove various pollutants from different media. The porous structure, surface chemistry, and adsorbent type determine the potential of activated carbon as an adsorbent material, leading to its use in numerous industries for various applications, including filtration (e.g., removing color from syrups in the sugar or food processing industry, purifying beverages, treating drinking or industrial water, or treating combustion gases), and it can be used in hundreds of different purification applications. In many cases, when the carbon is used up, it eventually loses its effectiveness and becomes saturated. However, other factors must be considered when using activated carbon, such as the economic feasibility of production and reuse, especially the regeneration capacity of activated carbon after each application.

[0003] Used activated carbon can be recycled through thermal reactivation, a process we call carbon regeneration / reactivation. In the past, high-temperature steam was commonly used for regeneration so that it could be reused. The temperature profile for regeneration is determined based on the specific organic pollutants it contains. After regeneration, the activated carbon restores its original structure and adsorption properties. Therefore, using unique regeneration technologies to reactivate spent activated carbon is an important process in the activated carbon circular economy. In particular, activated carbon materials, mainly those adsorbing acidic, alkaline, organic, and odorous waste gases, can achieve high-speed regeneration using microwave treatment.

[0004] Microwave heating has three key characteristics: Instantaneous heating: high thermal efficiency and short heating time. Selectivity: different materials exhibit significantly different heating characteristics in a microwave field due to their varying dielectric properties. Penetration: electromagnetic waves can penetrate the interior of a medium, thus microwaves possess strong penetrating power. Compared to traditional heating, microwave heating offers shorter heating times and avoids direct contact with the heated material, improving upon the high energy consumption and low efficiency of traditional methods. However, microwave regeneration of activated carbon is currently still in the laboratory-scale stage. While methods for microwave regeneration of activated carbon from waste activated carbon are feasible through various processing techniques, these laboratory-scale methods are often complex and unsuitable for mass production of microwave-regenerated activated carbon on an industrial scale.

[0005] In view of this, it is necessary to propose a rapid and environmentally friendly microwave regeneration method for industrial-scale activated carbon. Summary of the Invention

[0006] To address the aforementioned problems, the main objective of this invention is to provide a microwave-based method for regenerating activated carbon, specifically addressing the shortcomings and deficiencies of existing technologies. This method enables the uniform and efficient recovery of high-value materials from microwave-pyrolyzed waste activated carbon at relatively low temperatures and ambient pressure. The method ensures the integrity of the waste activated carbon by allowing it to undergo low-temperature pyrolysis and surface toxicity removal at appropriate microwave power densities and in a suitable atmosphere. This achieves high-quality regeneration while simultaneously meeting the needs for improved recovery rates, shorter reaction times, simplified reaction processes, energy conservation, and environmental protection.

[0007] To achieve the objectives of this invention, this invention provides a method for microwave regeneration of activated carbon, the main steps of which include: Step (1): Place a plurality of waste activated carbon materials into a microwave heating cavity, the microwave heating cavity having at least one air inlet and at least one air outlet, the air outlet being connected to an external air extraction device via a pipe; Step (2): A low-oxygen atmosphere of compressed air is introduced into the microwave heating cavity through the at least one air inlet, and the plurality of waste activated carbon materials undergo a microwave low-temperature carbonization heat treatment to form a plurality of carbonized activated carbons. The temperature of the microwave low-temperature carbonization heat treatment is between 300 and 450°C, and the time is between 0.1 and 0.3 hours. Step (3): In the microwave heating cavity, an oxygen-free atmosphere containing inert gas is introduced through at least one air inlet, and the carbonized activated carbon undergoes a microwave activation treatment to form a plurality of regenerated activated carbons. The temperature of the microwave activation treatment is between 450 and 650°C, and the time is between 0.1 and 0.2 hours. Step (4): The regenerated activated carbon enters a cooling container from the microwave heating cavity and is cooled to below 200°C before being taken out by a conveyor belt.

[0008] According to one feature of the present invention, the waste activated carbon material is mainly derived from activated carbon materials that adsorb acidic waste gas, alkaline waste gas, organic waste gas and odor.

[0009] According to one feature of the present invention, the at least one air inlet of the microwave heating cavity is located in the lower half of the ceramic container, and the at least one air outlet of the microwave heating cavity is located in the upper half of the ceramic container.

[0010] According to one feature of the present invention, the microwave power density of the microwave low-temperature carbonization heat treatment is between 0.1 kW / kg and 2 kW / kg, wherein kg is the unit weight of the waste activated carbon sheets.

[0011] According to one feature of the present invention, the compressed air introduced into the microwave low-temperature carbonization heat treatment is nitrogen, and its flow rate is between 1 LPM / kg and 5 LPM / kg, where LPM is liters per minute [L / min] and kg is the unit weight of the waste activated carbon sheets.

[0012] According to one feature of the present invention, during the microwave low-temperature carbonization heat treatment, the external air extraction device extracts the compressed air introduced into the microwave heating cavity at a speed equal to that of the compressed air introduced during the microwave low-temperature carbonization heat treatment, so as to keep the microwave heating cavity in the low-oxygen atmosphere.

[0013] According to one feature of the present invention, the microwave power density of the microwave activation treatment is between 0.4 kW / kg and 0.6 kW / kg, where kg is the unit weight of the waste activated carbon sheets.

[0014] According to one feature of the invention, the inert gas system introduced into the microwave activation treatment contains at least one nitrogen gas with a flow rate between 1 LPM / kg and 10 LPM / kg, where LPM is liters per minute [L / min] and kg is the unit weight of the waste activated carbon sheets.

[0015] According to one feature of the present invention, during the microwave activation process, the external evacuation device extracts the introduced inert gas from the microwave heating cavity at a gas velocity greater than that of the introduced inert gas, so as to keep the microwave heating cavity in the oxygen-free atmosphere.

[0016] According to one feature of the present invention, during the microwave activation process, the external evacuation device extracts the inert gas introduced into the microwave heating cavity at a gas velocity equal to that of the introduced inert gas, so as to keep the microwave heating cavity in the oxygen-free atmosphere.

[0017] The microwave regeneration method of the present invention is mainly used for the regeneration of waste activated carbon materials that adsorb acidic waste gas, alkaline waste gas, organic waste gas and odor.

[0018] The advantages of this invention's microwave regeneration method for activated carbon: (1) Waste activated carbon is heated rapidly by microwaves using the selective heating characteristics of the materials in the waste activated carbon composition, which shortens the overall processing time and improves the recovery efficiency and effect of activated carbon. (2) Compressed air or oxygen-containing inert gas is introduced at different times under normal pressure and a certain temperature is controlled so that the organic pollutants in the waste activated carbon are degraded and then combined with oxidation reaction. The activated carbon does not react, thereby removing the organic pollutants in the waste activated carbon and obtaining activated carbon with improved performance. (3) The heat released by the oxidation reaction is used for heat preservation, which reduces the energy consumption of microwave power and saves energy significantly. (4) The regenerated activated carbon obtained by microwave treatment has excellent performance and can adsorb polluting gases again. It can be applied to different fields and is a green and environmentally friendly recycling method. Simple Explanation of the Diagram

[0019] To make the above and other objects, features and advantages of the present invention more apparent and understandable, several preferred embodiments are described below in detail with reference to the accompanying drawings. Figure 1 shows a flowchart of a microwave regeneration method for activated carbon according to the present invention. Implementation

[0020] While the present invention may be embodied in various forms, those shown in the accompanying drawings and described herein are preferred embodiments of the invention. Those skilled in the art will understand that the apparatus and methods specifically described herein and illustrated in the drawings are intended as examples of the invention, not limiting illustrative embodiments, and the scope of the invention is defined only by the claims. Features illustrated or described in connection with an illustrative embodiment may be combined with features of other embodiments. Such modifications and variations are included within the scope of the invention.

[0021] To achieve the objectives of this invention, a method for microwave regenerating activated carbon is provided. Please refer to Figure 1, which shows a flowchart of a microwave regenerating activated carbon method according to this invention. The main steps of this microwave regenerating activated carbon method include: Step (1): Place a plurality of waste activated carbon materials into a microwave heating cavity, the microwave heating cavity having at least one air inlet and at least one air outlet, the air outlet being connected to an external air extraction device via a pipe; Step (2): A low-oxygen atmosphere of compressed air is introduced into the microwave heating cavity through the at least one air inlet, and the plurality of waste activated carbon materials undergo a microwave low-temperature carbonization heat treatment to form a plurality of carbonized activated carbons. The temperature of the microwave low-temperature carbonization heat treatment is between 300 and 450°C, and the time is between 0.1 and 0.3 hours. Step (3): In the microwave heating cavity, an oxygen-free atmosphere containing inert gas is introduced through at least one air inlet, and the carbonized activated carbon undergoes a microwave activation treatment to form a plurality of regenerated activated carbons. The temperature of the microwave activation treatment is between 450 and 650°C, and the time is between 0.1 and 0.2 hours. Step (4): The regenerated activated carbon enters a cooling container from the microwave heating cavity and is cooled to below 200°C before being taken out by a conveyor belt.

[0022] In this invention, activated carbon is primarily powder or granules, which are highly porous particles or granules or powders made from carbon-rich materials (such as coal, wood, coconut shells, or other carbon sources). They typically undergo an activation process, usually involving high-temperature heat treatment in the presence of steam or carbon dioxide, thereby forming a porous network and increasing the surface area. This unique structure enables them to effectively adsorb and capture various impurities, pollutants, and contaminants in gases or liquids.

[0023] In this invention, the waste activated carbon material primarily utilizes the surface forces of the high-performance activated carbon adsorbent itself to attract and adhere the adsorbate of volatile organic compound (VOC) molecules to the surface of the activated carbon material, thereby achieving the purpose of removing VOC substances. Activated carbon adsorption can ideally remove volatile organic compounds from waste gas under low-concentration VOC conditions, and is a dry waste gas treatment method. In this invention, the activated carbon material can treat various waste gases by selecting different fillers, mainly including three categories: 1. acidic waste gas, 2. alkaline waste gas, and 3. organic waste gas and odorous waste gas, which are then processed into the waste activated carbon material over a period of time.

[0024] In step (1), the microwave heating cavity system is mainly a ceramic container with an outer metal shell. At least one air inlet is located in the lower half of the ceramic container, and at least one air outlet is located in the upper half. The at least one air inlet at the bottom effectively provides airflow to the entire microwave processing. A plurality of microwave power sources are arranged around the metal shell to provide microwave power to the waste activated carbon sheets inside the ceramic container of the microwave heating cavity. The required microwave power is related to the capacity of the heating cavity and the weight of the waste activated carbon material being processed. The power of these microwave power sources is adjustable, providing an appropriate power density based on the weight of the heated waste activated carbon material. Microwaves are electromagnetic waves, using a microwave power at a frequency of 915MHz or 2450MHz. Microwave heating utilizes the principle of radiation, penetrating the surface of the medium to enter the interior of the waste activated carbon sheets. The waste activated carbon sheets convert the absorbed microwave energy into heat to achieve the purpose of heating and decomposition. These waste activated carbon sheets are placed into the microwave heating cavity from above, and these waste activated carbon sheets occupy about one-third to two-thirds of the space of the ceramic container in the microwave heating cavity.

[0025] In step (2), the microwave power density of the microwave low-temperature carbonization heat treatment is between 0.1 kW / kg and 2 kW / kg, where kg is the unit weight of the waste activated carbon sheets. The compressed air flow rate introduced for the microwave low-temperature carbonization heat treatment is between 1 LPM / kg and 5 LPM / kg, where LPM is liters per minute (L / min) and kg is the unit weight of the waste activated carbon sheets. It should be noted that during the microwave low-temperature carbonization heat treatment, the external air extraction device extracts the compressed air from the microwave heating cavity at a speed equal to the compressed air flow rate, thereby maintaining the microwave heating cavity in a low-oxygen atmosphere. That is, the low-oxygen condition refers to the oxygen content in the heating cavity being less than that in ordinary air during the microwave heat treatment process. Alternatively, the low-oxygen atmosphere can be achieved by continuously introducing compressed air, including at least one type of compressed air system, and by using an external extraction device to extract the introduced inert gas from the microwave heating cavity at a gas velocity greater than or equal to that of the introduced inert gas. The flow rate of the introduced inert gas is proportional to the capacity of the heating cavity.

[0026] In step (2), microwave low-temperature carbonization heat treatment decomposes the waste activated carbon sheets into a low-carbon chain gaseous substance. The gaseous substance is extracted from the microwave heating cavity by the external air extraction device and can be used as an energy fuel.

[0027] In step (3), the microwave power density of the microwave activation treatment is between 0.4 kW / kg and 0.6 kW / kg, where kg is the unit weight of the waste activated carbon sheets. The inert gas system introduced into the microwave activation treatment contains at least nitrogen gas, with a flow rate between 1 LPM / kg and 10 LPM / kg, where LPM is liters per minute (L / min) and kg is the unit weight of the waste activated carbon sheets. It should be noted that during the microwave activation treatment, the external evacuation device extracts the inert gas from the microwave heating cavity at a gas velocity greater than or equal to that of the introduced inert gas, thus maintaining the microwave heating cavity in an oxygen-free atmosphere. This oxygen-free atmosphere can be achieved through a restricted air intake design, meaning that during the reaction process, the heating cavity only evacuates air and does not introduce air. This oxygen-free condition refers to the absence of oxygen during the microwave heat treatment process. By continuously introducing compressed air, such as nitrogen or argon, the oxygen in the microwave heating cavity is consumed, and there is no subsequent oxygen replenishment, thus achieving the restricted air intake design. The flow rate of compressed air is directly proportional to the capacity of the heating chamber.

[0028] In step (4), the regenerated activated carbon is cooled to below 200°C in an oxygen-free atmosphere mixed with air within the microwave heating cavity, and then fed into a conveyor belt for removal. Once cooled to below 200°C, the regenerated activated carbon is fed from below the microwave heating cavity, preventing oxidation and combustion, thus accelerating the cooling to room temperature.

[0029] The material is removed from the microwave heating cavity, washed with clean water to remove impurities, and dried to obtain high-quality product.

[0030] This two-stage microwave heat treatment, which includes control methods for different microwave power densities, different heating temperatures, different heating times, different gas compositions and flow rates, and different extraction conditions, effectively yields high-quality regenerated activated carbon.

[0031] This invention provides a microwave regeneration method for activated carbon, primarily used for regenerating waste activated carbon materials that adsorb acidic waste gases, alkaline waste gases, organic waste gases, and odors. The advantages of this invention are: (1) Waste activated carbon is heated rapidly by microwaves using the selective heating characteristics of the materials in the waste activated carbon composition, which shortens the overall processing time and improves the recovery efficiency and effect of activated carbon. (2) Under normal pressure, oxygen-containing compressed air or inert gas is introduced for different times and a certain temperature is controlled so that the organic pollutants in the waste activated carbon are degraded and then combined with oxidation reaction. The activated carbon does not react, thereby removing the organic pollutants in the waste activated carbon and obtaining activated carbon with improved performance. (3) The heat released by the oxidation reaction is used for heat preservation, which reduces the energy consumption of microwave power and saves energy significantly. (4) The regenerated activated carbon obtained by microwave treatment has excellent performance and can adsorb polluting gases again. It can be applied to different fields and is a green and environmentally friendly recycling method.

[0032] Although the present invention has been disclosed with reference to the foregoing preferred embodiments, it is not intended to limit the invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention. As explained above, various modifications and variations can be made without destroying the spirit of the invention. Therefore, the scope of protection of this invention shall be determined by the claims outlined in the appended patent claims.

Claims

1. A method for microwave regenerating activated carbon, comprising the following main steps: Step (1): placing a plurality of waste activated carbon materials into a microwave heating cavity, the microwave heating cavity having at least one air inlet and at least one air outlet, the air outlet being connected to an external air extraction device via a pipe; Step (2): introducing an inert gas low-oxygen atmosphere into the microwave heating cavity through the at least one air inlet, the plurality of waste activated carbon materials undergoing a microwave low-temperature carbonization heat treatment to form a plurality of carbonized activated carbons, the temperature of the microwave low-temperature carbonization heat treatment being between 300 and 450°C, the time being 0.1 to 0.3 hours, and the microwave power density of the microwave low-temperature carbonization heat treatment being between 0.4 kW / kg and 1 kW / kg. The waste activated carbon material is in the range of kg, where kg is the unit weight of the waste activated carbon material; Step (3): In the microwave heating cavity, under an oxygen-free atmosphere containing inert gas, the carbonized activated carbon is subjected to a microwave activation treatment to form a plurality of regenerated activated carbons. The temperature of the microwave activation treatment is between 450 and 650°C, the time is 0.1 to 0.2 hours, and the microwave power density of the microwave activation treatment is between 0.4 kW / kg and 0.6 kW / kg, where kg is the unit weight of the waste activated carbon material; and Step (4): The regenerated activated carbon enters a cooling container from the microwave heating cavity, is cooled to below 200°C, and then enters a conveyor belt for removal; wherein, In step (2), during the microwave low-temperature carbonization treatment, the external exhaust device extracts the inert gas from the microwave heating cavity at a speed equal to that of the inert gas being introduced, so that the microwave heating cavity is kept in the low-oxygen atmosphere; and in step (3), during the microwave activation treatment, the external exhaust device extracts the inert gas from the microwave heating cavity at a speed greater than that of the inert gas being introduced, so that the microwave heating cavity is kept in the oxygen-free atmosphere.

2. The microwave regeneration method for activated carbon as described in claim 1, wherein the waste activated carbon material is mainly derived from activated carbon material that adsorbs acidic waste gas, alkaline waste gas, organic waste gas, and odor.

3. The microwave regeneration method for activated carbon as described in claim 1, wherein the microwave heating cavity is primarily a ceramic container with an outer metal shell, the at least one air inlet is located in the lower half of the ceramic container, and the at least one air outlet is located in the upper half of the ceramic container.

4. The microwave regeneration method for activated carbon as described in claim 1, wherein in step (1), the waste activated carbon material occupies approximately one-third to two-thirds of the space of the ceramic container of the microwave heating cavity.

5. The microwave regeneration method for activated carbon as described in claim 1, wherein in step (2), the flow rate of the inert gas introduced into the microwave low-temperature carbonization heat treatment is between 1 LPM / kg and 5 LPM / kg, where LPM is liters per minute [L / min] and kg is the unit weight of the waste activated carbon material.

6. The microwave regeneration method for activated carbon as described in claim 1, wherein in step (2), the microwave used in the microwave low-temperature carbonization heat treatment is a microwave power with a frequency of 915 MHz.

7. The microwave regeneration method for activated carbon as described in claim 1, wherein in step (2), the microwave used in the microwave low-temperature carbonization heat treatment is a microwave power with a frequency of 2450 MHz.

8. The microwave regeneration method for activated carbon as described in claim 1, wherein in step (3), the flow rate of the inert gas introduced into the microwave activation treatment is between 1 LPM / kg and 10 LPM / kg, where LPM is liters per minute [L / min] and kg is the unit weight of the waste activated carbon material.

9. The method for microwave regeneration of activated carbon as claimed in claim 1, wherein in step (3), the microwave used in the microwave activation treatment is a microwave power with a frequency of 915 MHz.

10. The method for microwave regeneration of activated carbon as claimed in claim 1, wherein in step (3), the microwave used in the microwave activation treatment is a microwave power with a frequency of 2450 MHz.