Activated carbon electrothermal regeneration waste gas circulation in-situ activation method and device

Abstract

The invention discloses an activated carbon electric heating regeneration waste gas circulation in-situ activation method and device, waste gas is extracted at a corresponding position of a 400-500 DEG C temperature interval in an activated carbon electric heating regeneration process, high-concentration CO2 is recycled, CO2 and water vapor are supplemented for the waste gas, and then the waste gas is conveyed to an activated carbon position with the temperature reaching 800-900 DEG C to serve as an activation medium to be recycled. The activated carbon with the temperature of 800-900 DEG C is more fully activated and then output, the activated carbon with the temperature of 800-900 DEG C enables CO and VOCs organic gas in conveyed waste gas to be fully combusted, and meanwhile maximum utilization of waste gas resources is achieved. The production efficiency of saturated activated carbon regeneration and the activity degree of activated carbon after regeneration are improved, CO and VOCs organic gas are combusted more sufficiently in the whole regeneration and activation process, waste gas emission is remarkably reduced, the treatment cost is reduced, and meanwhile environmental pollution is reduced.

Description

Technical Field

[0001] This invention relates to the field of saturated activated carbon regeneration technology, specifically to a method and apparatus for in-situ activation of activated carbon electrothermal regeneration waste gas circulation. Background Technology

[0002] Electrothermal regeneration technology for activated carbon utilizes the Joule heating effect (resistive heating) generated when an electric current passes through an activated carbon bed as a heat source. Under an inert or low-oxygen atmosphere, saturated activated carbon is heated to a certain temperature, causing the adsorbed organic matter to volatilize, decompose, carbonize, and ultimately desorb, while simultaneously restoring the pore structure and adsorption performance of the activated carbon. Low-pressure arc regeneration technology, building upon electrothermal regeneration, leverages the electrical conductivity of activated carbon. A low voltage or low current is input across the regeneration device, causing the activated carbon to generate Joule heating. When the activated carbon is in a flowing state, the collision and separation between the activated carbon particles generate a low-pressure electric arc effect. The regeneration of saturated activated carbon is achieved through the combined effects of Joule heating and arc heating. As the regeneration temperature increases, the generated arc becomes more pronounced, resulting in better heat generation and enabling rapid temperature rise to reach the regeneration temperature in a shorter time.

[0003] When the thermal regeneration temperature of activated carbon reaches 800-900℃, it generally needs to be carried out under vacuum or inert gas protection to prevent the regenerated activated carbon from being oxidized by contact with air. However, in order to optimize the regeneration effect, an appropriate amount of activating gas is often introduced into the system. Activating gases that can be introduced during the activation stage include CO2, O2, and water vapor, among which the concentration of O2 must not exceed the threshold. When activated carbon is activated by using an activating gas, the activating gas reacts with disordered carbon atoms and heteroatoms to activate them, opening up the pores blocked by disordered carbon atoms and heteroatoms formed during carbonization. This exposes the basic microcrystalline surface, which reacts with the activating gas and is burned off, causing the opened pores to continuously expand, connect, and develop vertically. As the activation reaction continues, new active sites are exposed on the microcrystalline surface and react with the activating gas, leading to the formation of new pores.

[0004] The low-pressure arc-ignition regeneration technology generates a mixed waste gas containing CO, CO2, H2, O2, H2O, and organic gases during the regeneration process. CO2, O2, and water vapor themselves can act as activating gases in the regeneration reaction. Furthermore, the emission of VOCs (volatile organic compounds) from this mixed waste gas not only harms the environment but also wastes and depletes resources. Therefore, how to recover and effectively utilize this waste gas has become a crucial issue that urgently needs to be addressed. Summary of the Invention

[0005] This invention addresses the shortcomings of existing saturated activated carbon regeneration technologies by proposing a method and apparatus for in-situ activation of activated carbon through waste gas circulation during electrothermal regeneration.

[0006] The present invention provides a method for in-situ activation of activated carbon electrothermal regeneration waste gas through circulation, as detailed below:

[0007] Saturated activated carbon enters each stage of the regeneration chamber. Once the chamber is full, the two graphite conductive plates in each chamber are energized. Temperature sensors in each chamber detect the activated carbon temperature. As the activated carbon flows through the chambers, a low-voltage arc is generated by the corresponding two graphite conductive plates. The first three chambers dry and preheat the activated carbon, while the remaining chambers regenerate it. When the temperature sensors in the third and fourth chambers detect the activated carbon in the 400-500℃ range, and the temperature sensor above the outlet connected to the last chamber detects it in the 800-900℃ range, the controller activates a fan to draw exhaust gas from the lower part of the third chamber and the upper part of the fourth chamber into the exhaust gas treatment box. An air pump draws a mixture of CO2 and water vapor from the gas box and directs it into the exhaust gas treatment box through nozzles. A mixture of CO2 and water vapor is injected and mixed with the waste gas to obtain a waste gas mixture with increased CO2 and water vapor content. A gas flow meter detects the volumetric flow rate of the waste gas mixture. A flow control valve at the middle constriction of the outlet controls the ratio of the mass flow rate of activated carbon at the outlet to the volumetric flow rate of the waste gas mixture. The waste gas mixture output by the fan is sprayed onto the activated carbon at the outlet. The CO2 and water vapor in the waste gas mixture activate the activated carbon at the outlet, improving the recovery rate of iodine adsorption value after regeneration. The activated carbon at the outlet also promotes the combustion of CO and VOCs in the waste gas mixture. After regeneration and activation, the activated carbon flows into the silo.

[0008] Preferably, after cooling the activated carbon in the carbon silo, multiple samples are taken to conduct iodine adsorption value experiments. The average of the calculated iodine adsorption values ​​of the multiple activated carbon samples is taken as the final iodine adsorption value of the activated carbon sample. The final iodine adsorption value of the activated carbon sample is compared with the iodine adsorption value of unused activated carbon to obtain the iodine adsorption value recovery rate of the activated carbon sample.

[0009] This invention relates to an in-situ activation device for activated carbon electrothermal regeneration waste gas circulation, comprising an inlet, a regeneration chamber, an outlet, a waste gas recovery pipe, a waste gas treatment box, an air inlet pipe, and a blower. Each stage of the regeneration chamber is equipped with a temperature sensor and two opposing graphite conductive plates. The inlet is connected to the top of the first-stage regeneration chamber, and the outlet is connected to the bottom of the last-stage regeneration chamber. A temperature sensor is located above the outlet, and a flow control valve is located at the middle constriction of the outlet. The lower side wall of the third-stage regeneration chamber has pores. The waste gas recovery pipe connects the pores to the air inlet of the waste gas treatment box. The air inlet of the blower is connected to the air outlet of the waste gas treatment box, and the air outlet of the blower is connected to the opening of the outlet. A nozzle is located at the opening of the outlet. A gas flow meter is installed on the blower. A second nozzle is located at the air replenishment port of the waste gas treatment box. The second nozzle is connected to a gas box containing a mixture of CO2 and water vapor through an air inlet pipe and an air pump.

[0010] Preferably, the final stage regeneration chamber and discharge port are both fixed on the support frame.

[0011] Preferably, a hopper is located directly below the discharge port.

[0012] More preferably, the discharge port is an hourglass shape with openings at both ends, the upper opening connecting to the last stage regeneration chamber, and the lower opening located directly above the hopper.

[0013] More preferably, the air outlet of the blower is connected to the opening at the middle constriction of the discharge port and the opening on the bottom side wall through a two-part pipe.

[0014] Preferably, the two electrode plates facing each other on each stage of the regeneration chamber are connected to the power supply via wiring terminals.

[0015] Preferably, both the regeneration chamber and the hopper are wrapped with thermal insulation material.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. This invention extracts waste gas containing CO2, O2, and water vapor from the 400-500℃ temperature range during the electrothermal regeneration of activated carbon, achieving the recovery of high-concentration CO2. The waste gas is then replenished with CO2 and water vapor (indirectly reducing oxygen content, ensuring the O2 concentration does not exceed the threshold, and enhancing the activation effect of the regenerated activated carbon) before being transported to activated carbon at 800-900℃ for recycling as an activation medium. This ensures more complete activation of the activated carbon at 800-900℃ before output. The 800-900℃ activated carbon also ensures complete combustion of CO and VOCs in the transported waste gas, maximizing the utilization of waste gas resources. Therefore, this invention not only improves the production efficiency of saturated activated carbon regeneration and the activity level of the regenerated activated carbon, but also ensures more complete combustion of CO and VOCs throughout the regeneration and activation process, significantly reducing waste gas emissions, lowering treatment costs, and minimizing environmental pollution.

[0018] 2. This invention features innovative and optimized design of the discharge port structure, employing a unique hourglass shape to create a leak-proof structure that effectively prevents the escape of the waste gas mixture after it is delivered to the discharge port. Furthermore, the discharge port has openings at the central constriction and the bottom sidewall, allowing the waste gas mixture to fully contact the activated carbon at the discharge port, enabling multi-stage and multi-location reactions. This ensures that the activated carbon at the discharge port is more fully activated and that the CO and VOCs in the waste gas introduced into the discharge port are more completely combusted.

[0019] 3. The activated carbon regenerated and activated under various mass flow conditions of the present invention shows a stable improvement in the recovery rate of iodine adsorption value, which can be up to 10% higher than that of conventional regeneration processes, proving that the present invention has good process adaptability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the activated carbon electrothermal regeneration waste gas circulation in-situ activation device of the present invention;

[0021] Figure 2 This is a graph showing the proportions of CO, CO2, O2, and H2O in the waste gas generated at different temperatures during activated carbon regeneration.

[0022] Figure 3 This is a graph showing the proportions of CO2 and H2O in the exhaust gas extracted from the exhaust gas recovery pipe before and after passing through the exhaust gas treatment box.

[0023] Figure 4 This is a comparison chart showing the recovery rate of iodine adsorption values ​​obtained after regenerating and activating saturated activated carbon using the method of this invention and conventional regeneration methods at different mass flow rates. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments.

[0025] This invention, through experimental research, discovered that during the electrothermal regeneration of activated carbon, a significant CO2 release peak occurs in the temperature range of 400-500℃. Figure 2 In-depth analysis revealed that this was due to the significant increase in the carbon skeleton oxidation rate in the 400-500℃ temperature range, leading to a sharp increase in CO2 production and the complete combustion of organic matter in this temperature range, generating additional CO2. Furthermore, the local hot spots near the graphite conductive plate accelerated the reaction under electrothermal conditions, resulting in a higher CO2 concentration compared to other areas. Consequently, the total amount of CO2 and water vapor produced in the 400-500℃ temperature range was the highest.

[0026] Therefore, this invention proposes an in-situ activation method and apparatus for activated carbon electrothermal regeneration waste gas circulation. During the activated carbon electrothermal regeneration process, waste gas containing CO2, O2, and water vapor is extracted from a corresponding position in the temperature range of 400-500℃. The waste gas is then replenished with CO2 and water vapor (indirectly reducing the oxygen content) and transported to activated carbon at 800-900℃, so that the activated carbon is more fully activated and the CO and VOCs organic gases in the waste gas transported to the activated carbon at 800-900℃ are fully combusted.

[0027] Example 1:

[0028] like Figure 1As shown, the activated carbon electrothermal regeneration waste gas circulation in-situ activation device includes an inlet 1, a regeneration chamber 2, an outlet 4, a waste gas recovery pipe 6, a waste gas treatment box 7, an air inlet pipe 8, and a fan 9. Each stage of the regeneration chamber 2 is equipped with a temperature sensor and two graphite conductive plates. The temperature sensor monitors the temperature of the activated carbon inside in real time. The inlet 1 is connected to the top of the first-stage regeneration chamber 2, and the outlet 4 is connected to the bottom of the last-stage regeneration chamber 2. A temperature sensor is installed on the top of the outlet 4 to detect the temperature of the activated carbon at the outlet. A flow control valve is installed at the middle constriction of the outlet 4 to control the mass flow rate of the activated carbon. The last-stage regeneration chamber 2 and the outlet 4 are both fixed on a support frame 3. A hopper 5 is located directly below the outlet 4 to collect the activated carbon after regeneration and activation. The lower side wall of the third-stage regeneration chamber 2 has pores. The waste gas recovery pipe 6 connects the pores and the air inlet of the waste gas treatment box 7. The air inlet of the blower 9 is connected to the air outlet of the waste gas treatment box 7, and the air outlet of the blower 9 is connected to the opening of the discharge port 4. A nozzle is provided at the opening of the discharge port 4. A gas flow meter is provided on the blower 9 to detect the volumetric flow rate of the waste gas mixture flowing through the blower 9. A nozzle is provided at the air replenishment port of the waste gas treatment box 7. The nozzle is connected to a gas box containing a mixture of CO2 and water vapor through the air inlet pipe 8 and the air pump. The mixture of CO2 and water vapor is replenished from the air replenishment port of the waste gas treatment box 7 and mixed with the waste gas extracted from the pores of the third-stage regeneration chamber 2 to obtain a waste gas mixture. The waste gas mixture is transported to the discharge port 4.

[0029] Among them, the fan 9, flow control valve and air pump are all controlled by the controller, and the signal output terminals of the gas flow meter and each temperature sensor are all connected to the controller.

[0030] Example 2:

[0031] Based on Example 1, the discharge port 4 is shaped like an hourglass with openings at both ends. The upper opening connects to the last-stage regeneration chamber 2, and the lower opening is located directly above the hopper 5. The air outlet of the blower 9 is connected to the opening at the middle constriction and the bottom side wall of the discharge port 4 via a two-part pipe. The hourglass shape of the discharge port 4 creates a leak-proof structure at the bottom, effectively preventing the escape of the waste gas mixture after it is delivered to the discharge port 4. The openings at the middle constriction and the bottom side wall of the discharge port 4 allow the waste gas mixture to fully contact the activated carbon at the discharge port 4, enabling multi-stage and multi-location reactions. This ensures that the activated carbon at the discharge port 4 is more fully activated, and that CO and VOCs are more fully combusted during the entire regeneration and activation process.

[0032] Example 3:

[0033] Based on Example 1 or Example 2, this invention proposes an in-situ activation method for activated carbon electrothermal regeneration waste gas circulation, as detailed below:

[0034] Saturated activated carbon enters each stage of the regeneration chamber 2 through the feed inlet 1. Once the regeneration chamber 2 is full (indicated by activated carbon flowing out of the discharge outlet 4), the power supply is activated via the terminals to energize the two graphite conductive plates within each stage of the regeneration chamber 2. Temperature sensors on each stage of the regeneration chamber 2 monitor the temperature of the activated carbon in real time, and a temperature sensor above the discharge outlet 4 monitors the temperature of the activated carbon at the discharge outlet. A flow control valve at the constriction in the middle of the discharge outlet controls the mass flow rate of the activated carbon. In this embodiment, the first three stages of the regeneration chamber 2 are mainly used for drying and preheating the activated carbon, while the latter three stages are mainly used for high-temperature regeneration. The flow of activated carbon within each stage of the regeneration chamber 2 generates a low-voltage arc under the action of the corresponding two graphite conductive plates, thereby achieving drying, preheating, or regeneration. When the temperature sensors in the third and fourth stage regeneration chambers 2 detect that the activated carbon is in the temperature range of 400-500℃, and the temperature sensor above the discharge port detects that the activated carbon has reached the temperature range of 800-900℃, the controller controls the fan 9 to draw the waste gas from the lower end of the third stage and the upper end of the fourth stage regeneration chamber through the waste gas recovery pipe 6 and introduce it into the waste gas treatment box 7. The air pump draws out a mixture of CO2 and water vapor from the gas box and injects the mixture into the waste gas treatment box 7 through nozzle 2. The mixture mixes with the waste gas, resulting in a waste gas mixture with increased CO2 and water vapor content (indirectly reducing oxygen content). The comparison of CO2 and water vapor content before and after the waste gas enters the waste gas treatment box 7 is shown in [reference needed]. Figure 3 A gas flow meter detects the volumetric flow rate of the waste gas mixture. A flow control valve controls the ratio (dimensionless ratio) of the activated carbon mass flow rate at outlet 4 to the volumetric flow rate of the waste gas mixture to be 1:1. The waste gas mixture output by fan 9 is sprayed onto the activated carbon at outlet 4. The CO2 and water vapor in the waste gas mixture activate the activated carbon at outlet 4. The high temperature of the activated carbon at outlet 4 promotes the complete combustion of CO and VOCs in the waste gas mixture. This not only improves the recovery rate of iodine adsorption value after regeneration of the activated carbon at outlet 4, but also indirectly reduces the production and emission of CO and VOCs during the regeneration and activation process, thus reducing the cost of waste gas treatment. The activated carbon after regeneration and activation flows into silo 5. After cooling, the activated carbon in the carbon silo 5 was sampled multiple times for iodine adsorption value experiments. The average of the calculated iodine adsorption values ​​of the multiple activated carbon samples was taken as the final iodine adsorption value of the activated carbon sample. The final iodine adsorption value of the activated carbon sample was compared with the iodine adsorption value of the unused activated carbon to obtain the iodine adsorption value recovery rate of the activated carbon sample (the final iodine adsorption value of the activated carbon sample is denoted as a, the iodine adsorption value of the unused activated carbon is denoted as b, and the iodine adsorption value recovery rate of the activated carbon sample is denoted as c, then c = a / b).

[0035] To verify the effect of this invention on improving the iodine adsorption value recovery rate after activated carbon regeneration, a comparative experiment was conducted on coal-based columnar granular activated carbon that had been operating in a waterworks for nearly 10 years. Conventional regeneration and the method of this invention were performed. A gradient flow rate test method was used, with conventional regeneration and regeneration by this invention performed at activated carbon mass flow rates of 100 kg / h, 200 kg / h, 300 kg / h, and 400 kg / h, respectively. During regeneration by this invention, the recovered waste gas mixture was introduced at volumetric flow rates of 100 L / h, 200 L / h, 300 L / h, and 400 L / h, respectively. The iodine adsorption value recovery rate of activated carbon regenerated by conventional regeneration was compared with that of activated carbon regenerated by this invention. It was found that the activated carbon regenerated by this invention showed an average 10% improvement in iodine adsorption value recovery rate compared to the conventional regeneration process. Figure 4 .

Claims

1. A method for in-situ activation of activated carbon through electrothermal regeneration waste gas circulation, characterized in that: Saturated activated carbon enters each stage of the regeneration chamber. Once the chamber is full, the two graphite conductive plates in each chamber are energized. Temperature sensors in each chamber detect the activated carbon's temperature. As the activated carbon flows through each chamber, a low-voltage arc is generated by the corresponding two graphite conductive plates. The first three chambers dry and preheat the activated carbon, while the remaining chambers regenerate it. When the temperature sensors in the third and fourth chambers detect the activated carbon is in the 400-500℃ range, and the temperature sensor above the outlet connected to the last chamber detects it reaching 800-900℃, the controller activates the fan to extract heat from the lower part of the third chamber and the upper part of the fourth chamber. The exhaust gas from the end is introduced into the exhaust gas treatment box. The air pump extracts a mixture of CO2 and water vapor from the air box and sprays it into the exhaust gas treatment box through nozzle two. The mixture mixes with the exhaust gas to obtain an exhaust gas mixture with increased CO2 and water vapor content. The gas flow meter detects the volumetric flow rate of the exhaust gas mixture. The flow control valve at the middle constriction of the outlet controls the ratio of the mass flow rate of activated carbon at the outlet to the volumetric flow rate of the exhaust gas mixture. The exhaust gas mixture output by the fan is sprayed onto the activated carbon at the outlet. The CO2 and water vapor in the exhaust gas mixture activate the activated carbon at the outlet, improving the recovery rate of iodine adsorption value after regeneration. The activated carbon at the outlet also promotes the combustion of CO and VOCs organic gases in the exhaust gas mixture.

2. The method for in-situ activation of activated carbon electrothermal regeneration waste gas circulation according to claim 1, characterized in that: After cooling the activated carbon in the carbon silo, samples were taken multiple times for iodine adsorption value experiments. The average of the calculated iodine adsorption values ​​of the multiple activated carbon samples was taken as the final iodine adsorption value of the activated carbon sample. The final iodine adsorption value of the activated carbon sample was compared with the iodine adsorption value of unused activated carbon to obtain the iodine adsorption value recovery rate of the activated carbon sample.

3. An in-situ activation device for activated carbon electrothermal regeneration waste gas circulation, comprising a regeneration chamber and a discharge port, characterized in that: It also includes a waste gas recovery pipeline, a waste gas treatment box, an air inlet pipeline, and a fan; each stage of the regeneration chamber is equipped with a temperature sensor and two opposing graphite conductive plates; the first stage of the regeneration chamber is connected to the feed inlet at the top, and the last stage of the regeneration chamber is connected to the discharge outlet at the bottom; the discharge outlet is equipped with a temperature sensor at the top, and a flow control valve is installed at the middle constriction of the discharge outlet; the lower side wall of the third stage of the regeneration chamber has pores, the waste gas recovery pipeline connects the pores to the air inlet of the waste gas treatment box, the air inlet of the fan is connected to the air outlet of the waste gas treatment box, and the air outlet of the fan is connected to the opening of the discharge outlet; a nozzle is installed at the opening of the discharge outlet; a gas flow meter is installed on the fan; a nozzle is installed at the air replenishment port of the waste gas treatment box, and the nozzle is connected to a gas box storing a mixture of CO2 and water vapor through an air inlet pipeline and an air pump.

4. The activated carbon electrothermal regeneration waste gas circulation in-situ activation device according to claim 3, characterized in that: The final stage regeneration chamber and discharge port are both fixed on the support frame.

5. The activated carbon electrothermal regeneration waste gas circulation in-situ activation device according to claim 3, characterized in that: A hopper is located directly below the discharge port.

6. The activated carbon electrothermal regeneration waste gas circulation in-situ activation device according to claim 5, characterized in that: The discharge port is shaped like an hourglass with openings at both ends. The upper opening connects to the last stage of the regeneration chamber, and the lower opening is located directly above the hopper.

7. The activated carbon electrothermal regeneration waste gas circulation in-situ activation device according to claim 6, characterized in that: The air outlet of the blower is connected to the opening at the middle constriction of the discharge port and the opening on the bottom side wall through a two-part pipe.

8. The activated carbon electrothermal regeneration waste gas circulation in-situ activation device according to claim 3, characterized in that: The two electrode plates facing each other on the regeneration chamber of each stage are connected to the power supply through wiring terminals.

9. The activated carbon electrothermal regeneration waste gas circulation in-situ activation device according to claim 3, characterized in that: Both the regeneration chamber and the hopper are wrapped with thermal insulation material.

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