A regeneration method for VOCs adsorbing activated carbon

Abstract

The present invention discloses a method for regenerating activated carbon that adsorbs VOCs. The method employs an externally heated regeneration converter. Several material pipes are disposed within the furnace body. The activated carbon to be treated moves in the material pipes from a high position at the feed end to a low position at the discharge end, rotating with the furnace body. The activated carbon is gradually heated from room temperature to 300-500°C, causing the VOCs adsorbed on the activated carbon to boil, vaporize, and desorb. The regenerated activated carbon is then discharged from the discharge end of the regeneration converter. The desorbed VOC gas moves in the same direction as the material. At the discharge end, it is pumped through a pipeline into an incinerator for complete incineration, then enters a waste heat boiler and, after treatment in an exhaust gas treatment device, is discharged by an induced draft fan. Heated heat source gas is fed through a central pipe at the discharge end into the shell of the externally heated regeneration converter, heating the material pipes. The low-temperature gas, after heat exchange with the material pipes, passes through the central pipe at the feed end and is drawn by the induced draft fan of the regeneration furnace and discharged into a chimney. The present invention is suitable for industrial batch regeneration, with multiple cycles, low process temperatures, high processing capacity, stable operation, and a long equipment life.

Description

Technical Field

[0001] The invention relates to a regeneration method for VOCs-adsorbing activated carbon, belonging to the technical field of activated carbon regeneration. Background Art

[0002] During industrial production, a large amount of waste gas is easily generated. The main technology for industrial VOCs treatment is adsorption through activated carbon. There are many methods for regenerating activated carbon, such as: heating regeneration method, biological regeneration method, wet oxidation method, solvent regeneration method, electrochemical regeneration method, catalytic wet oxidation method, etc.

[0003] For example, a VOCs activated carbon adsorption regeneration treatment device disclosed in patent application number 202021046932.7 includes a filter adsorption box, the top of which is connected to an air inlet pipe and an air outlet pipe, a support plate fixedly installed in the filter adsorption box, an adsorption box placed on top of the support plate, and a movably connected adsorption box to the filter adsorption box. The adsorption box is provided with a plurality of activated carbon adsorption particles, and a plurality of filter holes are provided on both sides and the bottom of the adsorption box. A drying structure is provided on one side of the filter adsorption box, and a flow guide box is connected to the drying structure. Obviously, this structure and method can only be used in small batches or in the experimental stage, and cannot be used for industrial production.

[0004] Another example is a VOCs activated carbon desorption and regeneration device disclosed in application number 202120546830.X, which includes an induced draft fan, an electric heater and a first heat exchanger. The tail end of the induced draft fan is fixedly connected to one side of the fresh air filter through a connecting pipe, and the other side of the fresh air filter is fixedly connected to the air inlet at the front end of the first heat exchanger tube through a connecting pipe. The air outlet at the rear end of the first heat exchanger is fixedly connected to one end of the electric heater through a connecting pipe, and the other end of the electric heater is fixedly connected to the front end of the VOCs activated carbon desorption mechanism through a connecting pipe. The VOCs activated carbon desorption mechanism includes a casing, and the connecting pipe at the other end of the electric heater is fixedly connected to the front end of the casing. It can adsorb and purify VOCs, or regenerate the enterprise's waste activated carbon on site, and catalytically oxidize the high-concentration VOCs generated during the desorption and regeneration process until they meet the emission standards. The VOCs activated carbon desorption mechanism 4 disclosed therein includes a casing 41, a connecting pipe 11 at the other end of the electric heater 3 is fixedly connected to the front end of the casing 41, and several groups of activated carbon adsorption blocks 42 are fixedly installed on the inner wall of the casing 4. The inner wall of the casing 41 is fixedly connected to the periphery of the mesh plate 43 near the tail end, the rear side of the mesh plate 43 is fixedly connected to the front end of the bell mouth 44, the tail end of the bell mouth 44 is fixedly connected to one end of the tail pipe 45, and the periphery of the tail pipe 45 is sealed and connected through the inner side of the rear end wall of the casing 41. The tail end of the tail pipe 45 is fixedly connected to the air inlet of the desorption fan 5, and the air outlet of the desorption fan 5 is fixedly connected to one side of the exhaust gas filter 6. The other side of the exhaust gas filter 6 is fixedly connected to the front air inlet of the second heat exchanger 7. The rear air outlet of the second heat exchanger 7 is fixedly connected to the air inlet end of the electric heating chamber 8 and the catalytic oxidation chamber 9 through the connecting pipe 11, and the air outlet end of the electric heating chamber 8 and the catalytic oxidation chamber 9 is fixedly connected to the connecting pipe 11 at the front end of the second heat exchanger 7 through the connecting pipe 11. Obviously, the VOCs activated carbon desorption mechanism in this patent is also difficult to achieve large-scale industrial application.

[0005] A search revealed that existing industrial production methods primarily utilize internal heating regeneration furnaces or multi-chamber regeneration furnaces to regenerate VOC-adsorbing activated carbon. However, these furnaces present significant safety risks during low-temperature regeneration. Therefore, the process typically operates within a temperature range of 800–1000°C. At these temperatures, the activated carbon's microstructure continues to crystallize toward an ordered state, resulting in a breakdown of the pore structure and a reduction in the adsorption capacity of the regenerated activated carbon. This reduces the porosity of the activated carbon by regenerating pores. Since pore formation consumes fixed carbon, the more pore formation occurs, the more carbon is consumed, and the greater the strength of the activated carbon is degraded. Therefore, using internal heating to regenerate activated carbon significantly limits the number of regeneration cycles. A low regeneration rate results in a low utilization rate of the activated carbon, significantly increasing its cost. Furthermore, the internal heating regeneration process requires the activated carbon to be heated in an oxygen-containing atmosphere during regeneration, which damages its strength, pore structure, and fixed carbon consumption. The internal heat regeneration process mixes the clean exhaust gas generated by the heating source and the desorbed gas together and enters the exhaust gas treatment device, which greatly reduces the concentration of the desorbed gas and significantly increases the difficulty and cost of gas treatment.

[0006] Externally heated regeneration furnaces are constructed as a single-tube structure or with an internal jacketed tube, where the material is heated within the furnace's rotating shell. The shell serves as both a heat transfer component and a load-bearing component. A shell that is too thick will result in poor thermal conductivity, while a shell that is too thin will not be able to bear the weight. When the processing volume is large, the material piles up higher within the shell. Since activated carbon is a carbon material and a poor conductor of heat, the increased pile thickness significantly increases the time required for heat transfer, severely impacting production. The only solution to this problem is to increase the shell's heating temperature, creating a larger temperature difference between the shell and the material to increase the heat transfer rate. However, increasing the shell's heating temperature significantly reduces the shell's material yield strength, while increasing the shell's thickness to improve its rigidity further reduces its thermal conductivity, creating a contradiction. Therefore, currently, single-tube regeneration converters are primarily small-capacity regeneration equipment, resulting in poor economic benefits and ineffective reductions in regeneration costs.

[0007] In order to meet the huge demand for activated carbon for environmental protection, there is an urgent need for a method that can be regenerated at low temperature, has a large processing capacity, and can operate stably to achieve multiple regeneration of activated carbon that adsorbs VOCs gases, so as to realize the economy of activated carbon in VOCs treatment. Summary of the Invention

[0008] In view of the above problems existing in the prior art, the main purpose of the present invention is to provide a method for regenerating activated carbon that adsorbs VOCs.

[0009] The present invention aims to solve the above-mentioned problems in the prior art and provides a regeneration method for VOCs-adsorbing activated carbon, which adopts an externally heated regeneration converter. Several material pipes are arranged in the furnace body of the externally heated regeneration converter. The activated carbon to be treated is fed into the material pipe and moves from the feed side located at a high position to the discharge side located at a low position. It follows the rotation of the furnace body and is gradually heated from room temperature to 300-500°C in the material pipe, so that the VOCs adsorbed on the activated carbon boil, vaporize and desorb. The regenerated activated carbon is discharged from the discharge end of the regeneration converter; the desorbed VOCs gas moves in the same direction as the material due to the negative pressure in the tube pass and is drawn into the incinerator at the discharge end for incineration. The high-temperature gas generated after complete incineration enters the waste heat boiler, is treated by the exhaust gas treatment device after heat exchange, and is discharged by the induced draft fan; the heat source gas is fed from the central pipe at the discharge end of the externally heated regeneration converter into the furnace cavity to heat the material pipe, and the low-temperature gas formed after heat exchange with the material pipe passes through the central pipe at the feed end and is drawn into the chimney by the induced draft fan of the regeneration furnace for discharge.

[0010] Furthermore, the heat source gas for heating is high-temperature exhaust gas from low-nitrogen combustion of natural gas.

[0011] Furthermore, the activated carbon to be treated is fed into the feed end of the externally heated regenerative converter through a feeding screw, and the material is fed into the material pipe through a lifting plate at the feed end. Through the rotation of the furnace body, the material is heated section by section at different positions of the material pipe.

[0012] Furthermore, the external heat regeneration converter includes a cylinder, a rolling mechanism supporting the cylinder, and a transmission mechanism connected to the rolling mechanism. A feed end center pipe is provided at the feed end of the cylinder, and a discharge end center pipe is provided at the discharge end. The feed end center pipe and the discharge end center pipe are both fixed to the two ends of the cylinder by tube plate welding, forming the inlet and outlet of the heat source gas of the regeneration furnace. The material pipe is a high-temperature resistant metal pipe, and several material pipes are evenly distributed in the cylinder.

[0013] Furthermore, the material pipe is supported by a pipe support frame welded in the cylinder, and the support meets the free expansion amount of the pipe diameter of the material pipe after being heated.

[0014] Furthermore, an expansion joint is provided in the material pipe, which is used to eliminate the different expansion amounts in the pipe length caused by the temperature difference between the material pipe and the shell, ensuring that the VOCs gas generated during the regeneration process is not short-circuited into the shell due to the negative pressure of the shell.

[0015] Preferably, the expansion joint is arranged near the feed end, which is the lowest temperature point of the regeneration furnace, and the expansion joint has higher reliability in use.

[0016] The beneficial effects of the present invention compared to the prior art are:

[0017] 1. Provide a method for industrial batch regeneration, which can achieve multiple regeneration of activated carbon, with low process temperature, large processing capacity and stable operation;

[0018] 2. The external heating regeneration converter has a reasonable structural design. Regeneration is carried out in the material pipe, which can expand freely to prevent bursting and ensure the service life of the equipment.

[0019] 3. The desorbed VOCs gas is completely treated and its residual heat is utilized to ensure environmentally friendly emissions. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0021] Example 1

[0022] A method for regenerating activated carbon for adsorbing VOCs adopts an externally heated regeneration converter. A plurality of material pipes are arranged in the furnace body of the externally heated regeneration converter. The activated carbon to be treated is fed into the material pipes and moves from a high-positioned feed side to a low-positioned discharge side. The activated carbon follows the rotation of the furnace body and is gradually heated from room temperature to 300-500°C in the material pipes, causing the VOCs adsorbed on the activated carbon to boil, vaporize and desorb. The regenerated activated carbon is discharged from the discharge end of the regeneration converter.

[0023] The heat source gas is sent into the furnace cavity from the central tube at the discharge end of the externally heated regenerative converter to heat the material pipe. The low-temperature gas formed after heat exchange with the material pipe passes through the central tube at the feed end and is drawn into the chimney by the regeneration furnace induced draft fan for discharge.

[0024] During the regeneration process of activated carbon that adsorbs VOCs, the thermal desorption temperature of VOCs varies depending on the boiling points of the adsorbed VOCs. Most VOCs are small molecules with low boiling points, so their thermal desorption temperatures are generally low. At a temperature of 400-500°C, activated carbon that adsorbs VOCs can basically be thermally desorbed to achieve regeneration of the activated carbon.

[0025] The desorbed VOCs gas moves in the same direction as the material through the negative pressure in the pipe process, and is drawn into the incinerator for incineration at the discharge end. The high-temperature gas generated after complete incineration enters the waste heat boiler, and after heat exchange, it is treated by the exhaust gas treatment device and discharged by the induced draft fan.

[0026] This embodiment utilizes an externally heated regenerative converter, and a plurality of material pipes are arranged in the converter. The activated carbon to be processed is fed into the material pipes, and the material pipes are directly discharged after heat exchange with heat source gas in the shell. The desorbed VOCs gas is completely incinerated, and the heat is utilized by the waste heat boiler and then processed by the tail gas treatment device for environmentally friendly discharge.

[0027] This embodiment provides a method for industrial batch regeneration, which can achieve multiple regenerations of activated carbon, has low process temperature, large processing capacity, and stable operation; the desorbed VOCs gas is completely treated, and the residual heat is utilized to ensure environmentally friendly emissions.

[0028] Example 2

[0029] Preferably, the heat source gas for heating is high-temperature exhaust gas from low-nitrogen combustion of natural gas.

[0030] As a specific structural design, the activated carbon to be treated is fed into the feed end of the externally heated regenerative converter through a feeding screw. The material is fed into the material pipe through a lifting plate at the feed end. Through the rotation of the furnace body, it is heated section by section at different positions of the material pipe.

[0031] As a specific structural design, the externally heated regenerative converter includes a cylinder, a rolling mechanism supporting the cylinder, and a transmission mechanism connected to the rolling mechanism. A feed end center pipe is provided at the feed end of the cylinder, and a discharge end center pipe is provided at the discharge end. Both the feed end center pipe and the discharge end center pipe are fixed to both ends of the cylinder by tube plate welding, forming the inlet and outlet of the heat source gas of the regeneration furnace. The material pipe is made of high-temperature resistant metal material, and several material pipes are evenly distributed in the cylinder.

[0032] Preferably, the material pipe is supported and fixed by a pipe support frame welded to the barrel, ensuring that the material pipe can expand freely within the pipe support. This structure mainly addresses radial expansion. Since regeneration occurs within the material pipe, the free expansion of the material pipe prevents pipe rupture and ensures the service life of the equipment.

[0033] As a preference, although the material pipe can expand freely, an expansion joint still needs to be set in the material pipe. The expansion joint mainly solves the expansion amount in the length direction of the pipe, and is used to eliminate the different expansion amounts caused by the temperature difference between the material pipe and the shell, and ensure that the VOCs gas generated during the regeneration process is not short-circuited into the shell due to the negative pressure of the shell.

[0034] The above structure is the key to achieving large-scale and multiple uses.

[0035] Preferably, the expansion joint is arranged near the feed end, which is the lowest temperature point of the regeneration furnace, and the expansion joint has higher reliability in use.

[0036] This embodiment is an embodiment of a preferred design, with a regeneration time of 20 to 40 minutes and a regeneration processing capacity of 3.75 t / h (compared to the current maximum processing capacity of the internal heat regeneration furnace of 1.25 t / h, the processing capacity is increased by 2 times). After each treatment, the adsorption index recovers to 97 to 100%, and the intensity remains basically unchanged. After 10 treatments, the adsorption index recovers to 90 to 95% of the initial adsorption value, and the intensity is more than 95% of the initial value.

[0037] The above embodiments are merely explanations and illustrations of the technical solution of the present invention and are not intended to limit the scope of protection of the technical solution of the present invention. All simple variations based on this solution fall within the scope of protection of the present invention.

Claims

1. A method for regenerating VOCs-adsorbing activated carbon, characterized by: An externally heated regenerative converter is used. Several material pipes are provided in the furnace body of the externally heated regenerative converter. The activated carbon to be treated is fed into the material pipes and moves from the high-positioned feed side to the low-positioned discharge side. It rotates along with the furnace body and is gradually heated from room temperature to 300-500°C in the material pipes, causing the VOCs adsorbed on the activated carbon to boil, vaporize and desorb. The regenerated activated carbon is then discharged from the discharge end of the regenerative converter. The desorbed VOCs gas moves in the same direction as the material due to the negative pressure in the tube pass and is drawn into the incinerator at the discharge end for incineration. The high-temperature gas generated after complete incineration enters the waste heat boiler, is treated in the tail gas treatment device after heat exchange, and is discharged by the induced draft fan. The heat source gas is sent into the furnace cavity from the central tube at the discharge end of the externally heated regenerative converter to heat the material pipe. The low-temperature gas formed after heat exchange with the material pipe passes through the central tube at the feed end and is drawn into the chimney by the regeneration furnace induced draft fan for discharge.

2. The regeneration method for VOCs-adsorbing activated carbon according to claim 1, characterized in that: The heat source gas is the high-temperature waste gas from the low-nitrogen combustion of natural gas.

3. The regeneration method for VOCs-adsorbing activated carbon according to claim 1, characterized in that: The activated carbon to be treated is fed into the feed end of the externally heated regenerative converter through a feeding screw. The material is fed into the material pipe through a lifting plate at the feed end and is heated section by section at different positions of the material pipe through the rotation of the furnace body.

4. The regeneration method for VOCs-adsorbing activated carbon according to claim 1, characterized in that: The external heat regeneration converter includes a cylinder, a rolling mechanism supporting the cylinder, and a transmission mechanism for driving the cylinder to rotate. A feed end center pipe is provided at the feed end of the cylinder, and a discharge end center pipe is provided at the discharge end. The feed end center pipe and the discharge end center pipe are both fixed to the two ends of the cylinder by tube plate welding, forming the inlet and outlet of the heat source gas of the regeneration furnace. The material pipe is a high-temperature resistant metal pipe, and several material pipes are evenly distributed in the cylinder.

5. The regeneration method for VOCs-adsorbing activated carbon according to claim 4, characterized in that: The material pipe is supported by a pipe support frame welded in the cylinder, and the support can meet the free expansion of the pipe diameter after the material pipe is heated.

6. The regeneration method for VOCs-adsorbing activated carbon according to claim 4, characterized in that: An expansion joint is provided in the material pipe, which is used to eliminate the different expansion amounts on the pipe length caused by the temperature difference between the material pipe and the shell, and ensure that the VOCs gas generated during the regeneration process is not short-circuited into the shell due to the negative pressure of the shell.

7. The regeneration method for VOCs-adsorbing activated carbon according to claim 6, characterized in that: The expansion joint is arranged near the feed end.