Low-energy-consumption activated carbon regeneration rotary kiln equipment with waste heat circulation and process thereof

Abstract

The invention discloses low-energy-consumption activated carbon regeneration rotary kiln equipment with waste heat circulation and a process thereof. The equipment comprises a rotary kiln, an airtight feeding mechanism, an exhaust emission groove, a partition combustion chamber, a cooling chamber and a rotary driving mechanism. In order to solve the problems of spontaneous combustion easily caused by local oxygen enrichment of activated carbon and high regeneration energy consumption in the existing direct combustion type regeneration process, the invention provides an integrated scheme of tail gas circulation oxygen control and tail gas waste heat reutilization: high-temperature low-oxygen tail gas intensively collected at the front end of a rotary kiln is sent back to a kiln tail combustion side through a waste gas circulation fan part; on one hand, combustion-supporting air is diluted, the oxygen concentration in a kiln tail combustion area and the kiln is reduced, an adjustable low-oxygen atmosphere is formed, oxidation burning loss of activated carbon in a high-temperature section is inhibited, and the ignition loss rate is reduced; and on the other hand, sensible heat and combustible components are carried as a secondary heat source to participate in heat supply by reflowing to a heat supply end in a high-temperature state, so that the consumption of newly added fuel is reduced, and closed-loop recovery of waste heat is realized.

Description

Technical Field

[0001] This invention belongs to the technical field of equipment for thermal regeneration of waste activated carbon and recycling of solid adsorbents, specifically relating to a low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation and its process. Background Technology

[0002] Activated carbon, due to its high specific surface area and well-developed microporous structure, is widely used in VOCs treatment, industrial exhaust gas purification, water treatment, and solvent recovery, serving as a common terminal adsorption medium. However, with prolonged operation, the pores of activated carbon gradually become clogged by organic pollutants, coke deposits, and inorganic impurities, leading to a decrease in effective pore volume and specific surface area, a significant reduction in adsorption capacity, and the formation of "deactivated" activated carbon. Deactivated activated carbon is generally considered hazardous waste, and traditional incineration or landfill disposal is costly and burdensome. To reduce the purchase of new activated carbon and decrease the amount of hazardous waste disposal, industry is gradually shifting towards the regeneration and recycling of spent activated carbon.

[0003] Currently, the most mature regeneration method used in engineering is thermal regeneration and activation: deactivated activated carbon is heated in stages under a controlled atmosphere, causing the adsorbate to volatilize, decompose, and be discharged; subsequently, an activation medium such as water vapor or carbon dioxide is introduced at high temperature to rebuild the microporous structure and restore adsorption capacity. This process typically includes three stages: drying, pyrolysis, and activation, with processing temperatures reaching up to 800 °C and above. Activated carbon that has undergone thermal regeneration can usually recover its adsorption performance to a high proportion of its original level, thus demonstrating mature industrial feasibility.

[0004] In industrial continuous operation regeneration equipment, rotary kilns have become the mainstream furnace type for the thermal regeneration and activation of waste activated carbon due to their continuous feeding / discharging capabilities, relatively compact design, and low investment threshold. Existing rotary kiln regeneration processes can be broadly classified into two categories: direct heating and indirect heating. Direct heating refers to directly introducing combustion flames or high-temperature flue gas into the kiln, allowing the activated carbon to directly contact the high-temperature flue gas to complete drying, pyrolysis, and activation. This method offers rapid heating, high heat transfer efficiency, and a simple structure, making it suitable for high-throughput processing. However, it also introduces significant risks: because the combustion flue gas itself contains oxygen, and the flame / high-temperature flue gas creates localized high-temperature oxygen-rich zones within the kiln, activated carbon is highly susceptible to localized oxidation or even spontaneous combustion, leading to increased burn-off rate and decreased particle mechanical strength. More seriously, the combined effect of localized high temperature and oxygen enrichment can cause sintering on the activated carbon surface and pore wall collapse, resulting in irreversible damage to the microporous structure, directly affecting the adsorption performance and reusable lifespan after regeneration. In addition, under direct heating mode, the temperature and atmosphere distribution caused by direct flame or high-temperature flue gas is highly uneven, making it difficult to achieve fine zone temperature and oxygen control along the kiln length.

[0005] Indirect heating, through an external combustion chamber, jacketed or sleeve-type heating structure, transfers heat to the material zone of the rotary kiln via conduction or radiation, bringing the material into contact with a process atmosphere that is essentially oxygen-free or strictly oxygen-limited. In this mode, the combustion products are physically isolated from the activated carbon material, significantly inhibiting excessive oxidation of the carbon skeleton, reducing burn-off rate, and preventing sintering and permanent collapse of the pore structure caused by high-temperature oxygen enrichment, thereby improving regeneration yield and product consistency. However, indirect heating has a longer heat transfer path and lower unit heat transfer intensity, typically requiring higher outer wall temperatures, longer material residence times, or larger kiln dimensions to achieve the same level of regeneration, which increases equipment investment and operating energy consumption. Simultaneously, existing indirect heating systems often lack effective heat recovery: the combustible pyrolysis gas released during pyrolysis, and the high-temperature waste heat air discharged from the cooling section, are often not systematically drawn back as a combustion heat source or preheating gas source but are instead dispersed away, resulting in low overall thermal efficiency.

[0006] In summary, while direct-heating rotary kilns offer high heat transfer efficiency and compact structure, they inevitably introduce oxygen into the activation section, creating localized high-temperature points that can lead to over-burning, sintering, and high burn-off rates in activated carbon. This also creates pressure in handling high-temperature, polluting exhaust gases. Indirect-heating rotary kilns, while more easily maintaining a low-oxygen / oxygen-free environment in the regeneration section, significantly reducing burn-off rates and improving product consistency, suffer from insufficient heat transfer efficiency, high equipment scale-up costs, and inadequate utilization of system waste heat. Given this contradiction, there is an urgent need for a complete set of equipment and processes designed for continuous rotary kiln regeneration operations. This system should be able to achieve zoned temperature control along the kiln length, strictly limit oxygen entry into the activation section to prevent activated carbon sintering and over-burning, and integrate the recovery and utilization of pyrolysis gas and cooling waste heat. This would reduce burn-off rates while improving thermal efficiency, increasing regeneration yield, extending the recyclable life of activated carbon, and lowering overall processing costs. Summary of the Invention

[0007] This invention provides a low-energy-consumption rotary kiln equipment and process for regenerating activated carbon with waste heat circulation, in order to optimize the problems of high activated carbon burn-off rate and high combustion energy consumption caused by uncontrolled oxygen content in traditional direct-heating rotary kilns.

[0008] The specific technical solution adopted in this invention is as follows: A low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation includes a rotary kiln, an airtight feeding mechanism, a waste gas discharge trough, an isolated combustion chamber, a cooling chamber, and a rotary drive mechanism for driving the rotary kiln to rotate. The front end of the rotary kiln is rotatably and sealingly connected to the feed chamber, and the rear end is rotatably and sealingly connected to the isolation combustion chamber. Along the material forward direction, the feed chamber, the rotary kiln, and the isolation combustion chamber are all inclined downward at a small angle. The exhaust gas trough is connected to the feed chamber. The airtight feeding mechanism is used to add deactivated activated carbon into the feeding chamber, and the solid discharge port at the bottom of the combustion chamber is connected to the cooling chamber by a pipeline. The partitioned combustion chamber is equipped with an activation steam inlet, a combustion air inlet for introducing combustion air, and a combustion gun for introducing fuel gas. The exhaust outlet of the exhaust gas trough is divided into two paths. One path is sent to the subsequent purification system, and the other path is connected to the combustion air inlet by a pipeline, so that part of the returned exhaust gas is mixed with the combustion air before being sent into the isolation combustion chamber.

[0009] The rotary kiln is installed at a small angle and maintains continuous low-speed rotation. Deactivated activated carbon is fed into the front end of the rotary kiln, where it slowly moves forward due to the kiln's tumbling action and the material's own weight, achieving continuous solid conveying. The interior of the rotary kiln is divided into two functional zones along the material's direction of travel: a drying / preheating zone to remove free water, adsorbed water, and low-boiling-point volatiles from the activated carbon; and a pyrolysis zone where, under high temperature and a restricted oxygen atmosphere, high-boiling-point organic pollutants and coke deposits adsorbed in the activated carbon pores undergo thermal decomposition, volatilization, and desorption, thereby clearing the blocked pore structure. The activated carbon then enters a partitioned combustion chamber for regeneration and activation. Under high-temperature conditions, a certain amount of steam or carbon dioxide is introduced as an activation medium to selectively gasify and activate the carbon skeleton, restoring the microporous structure, specific surface area, and adsorption capacity, thus restoring the deactivated activated carbon's adsorption performance.

[0010] The heating method of this invention involves coordinated control of combustion heating in a partitioned combustion chamber at the rear end of the rotary kiln and waste gas recirculation. Fuel gas (e.g., natural gas) and combustion air are burned in the partitioned combustion chamber to generate high-temperature flue gas. This high-temperature flue gas flows along the interior of the rotary kiln, providing heat to the drying / preheating section and pyrolysis section inside the kiln. The heat is transferred to the regenerating activated carbon through convective and radiative heat transfer. Unlike traditional direct high-oxygen combustion heating, this invention does not only use fresh combustion air at the heating end, but also mixes a portion of the high-temperature exhaust gas discharged from the waste gas discharge trough with the combustion air in a specific ratio before sending it into the kiln tail combustion zone. Through this "exhaust gas recirculation" step, on the one hand, the oxygen content of the mixed atmosphere entering the isolation combustion chamber can be diluted, as well as the oxygen content of the high-temperature flue gas flowing along the inside of the rotary kiln, so that the inside of the rotary kiln is in a low-oxygen, controllable oxygen regeneration atmosphere, which inhibits the excessive oxidation and burn-off of activated carbon in the high-temperature zone; on the other hand, the recirculated exhaust gas itself carries a considerable amount of sensible heat and a certain amount of combustible pyrolysis gas components, which are returned to the isolation combustion chamber to participate in heat release and heating again, which is equivalent to recovering and reusing the heat that should have been discharged, thereby significantly reducing the system's demand for new fuel gas and external heat sources.

[0011] The aforementioned waste gas recirculation loop is as follows: a closed-loop exhaust gas collection structure is installed at the front end of the rotary kiln to centrally extract the high-temperature exhaust gas continuously released from the drying / preheating and pyrolysis sections within the kiln. This high-temperature exhaust gas is then piped into the recirculation branch, where, with the cooperation of a recirculation fan and regulating valve, it is mixed with combustion air in a set ratio before entering the isolated combustion chamber. The remaining exhaust gas that does not participate in the recirculation is introduced into the exhaust gas treatment unit for subsequent purification (such as combustion oxidation, desulfurization, and denitrification) and ultimately meets emission standards. The system can be equipped with an online oxygen monitoring device to detect the oxygen content at the exhaust gas collection point in real time and use this as feedback to adjust the ratio of recirculated exhaust gas to fresh combustion air, thereby controlling the oxygen partial pressure inside the entire rotary kiln within the target range and achieving a stable low-oxygen regeneration environment.

[0012] By using this "oxygen regulation with waste gas" method, the present invention does not rely on additional inert gas purging, nor does it require a large amount of excess air for temperature control. Instead, it uses the high-temperature exhaust gas generated by its own operating conditions to dilute and replace the combustion air, thereby reducing and maintaining a uniform oxygen concentration in the kiln atmosphere. This avoids the problems of rapid oxidation, sintering, or even spontaneous combustion of activated carbon caused by local high oxygen and high temperature points in traditional processes, reduces the burn-off rate during regeneration, and improves the mechanical strength and pore structure integrity of the regenerated activated carbon.

[0013] Meanwhile, the waste gas recirculation loop also serves as a waste heat recovery system. The returned waste gas is not cooled to a low emission level before being discharged; instead, it is directly incorporated into the isolation combustion chamber at a high temperature. This effectively "transfers" the heat released from the front end of the rotary kiln back to the isolation combustion chamber at the kiln tail, allowing for its reuse. This closed-loop recovery path significantly reduces the system's overall heat rate: external fuel consumption decreases, and the overall thermal efficiency of the kiln improves, thus achieving low-energy operation.

[0014] Regarding the cooling of the regenerated activated carbon, this invention employs a two-stage cooling process: the regenerated high-temperature activated carbon is first cooled by heat exchange with cooling water, rapidly decreasing from the regeneration activation temperature to a medium temperature range where it is less prone to spontaneous combustion; subsequently, air blowing is used to further reduce the discharge temperature. The recirculated gas heated during the secondary cooling process is not directly discharged but is instead returned to the isolated combustion chamber as combustion / preheating gas, thereby recovering waste heat and reducing system energy consumption.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Waste gas recirculation for oxygen control, creating an adjustable low-oxygen regeneration atmosphere. The system proportionally recirculates the high-temperature exhaust gas generated at the front end of the rotary kiln, mixes it with combustion air, and then sends it into the partitioned combustion chamber. Through this internal exhaust gas recirculation, rather than introducing additional inert gas or a large amount of dilution air, the system actively reduces and stabilizes the oxygen concentration in the partitioned combustion chamber and the rotary kiln, ensuring that the partitioned combustion chamber is always in an adjustable low-oxygen atmosphere. This significantly inhibits the oxidation and burn-off of activated carbon in the high-temperature zone, reducing the burn-off rate. This "oxygen-regulating with its own exhaust gas" method differs from traditional regeneration processes that rely on unidirectional emissions and controlled intake air.

[0016] 2) Effluent sensible heat recovery participates in heating, significantly reducing energy consumption. The exhaust gas extracted at the front end is not cooled before being discharged, but is kept at a high temperature and directly incorporated into the isolated combustion chamber, allowing the sensible heat and combustible components such as pyrolysis gas to be reused. This is equivalent to returning the heat released at the front end to the kiln tail for reuse, forming an internal heat closed loop. This approach uses exhaust gas as a "second heat source" for the regeneration process, significantly reducing the need for external fuel gas and fresh high-temperature flue gas, thereby achieving overall low-energy operation, rather than relying solely on traditional heat exchange-type waste heat recovery.

[0017] This invention achieves low-oxygen controllable regeneration, low burn-off rate, and low-energy consumption operation under continuous working conditions without the need for external inert protective gas, thereby improving the recyclable lifespan of waste activated carbon and reducing overall treatment costs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a low-energy-consumption rotary kiln equipment and process for regenerating activated carbon with waste heat circulation according to the present invention. In the diagram: 1. Exhaust gas discharge trough; 2. Feed hopper; 3. Supporting roller; 4. Rotary motor; 5. Kiln body roller; 6. Rotary kiln body; 7. Kiln body gear; 8. Activating steam inlet; 9. Combustion air inlet; 10. Isolation combustion chamber; 11. Combustion gun; 12. Cooling air inlet trough; 13. Cooling chamber; 14. Cooling water inlet trough; 15. Exhaust gas oxygen content detector; 16. Exhaust gas circulation fan. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0020] Example: Control Figure 1 A low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation includes a rotary kiln 6, an airtight feeding mechanism, a waste gas discharge trough 1, an isolated combustion chamber 10, a cooling chamber 13, and a rotary drive mechanism for driving the rotary kiln 6 to rotate.

[0021] The rotary kiln 6 is a hollow cylindrical structure. The front end of the rotary kiln 6 is rotatably and sealingly connected to the feed chamber, and the rear end is rotatably and sealingly connected to the isolation combustion chamber 10. Along the material forward direction, the feed chamber, the rotary kiln 6 and the isolation combustion chamber 10 are inclined downward at a small angle of 3°.

[0022] The solid discharge port at the bottom of the isolated combustion chamber 10 is connected to the cooling chamber 13 by a pipeline. The isolated combustion chamber 10 is equipped with an activation steam inlet 8, a combustion air inlet 9 for introducing combustion air, and a combustion gun 11 for introducing fuel gas. The exhaust gas outlet of the exhaust gas discharge tank 1 is divided into two paths. One path is sent to the subsequent purification system, and the other path is connected to the combustion air inlet 9 by a pipeline, so that part of the returned exhaust gas is mixed with the combustion air before being sent into the isolated combustion chamber 10.

[0023] The rotary drive mechanism includes a supporting roller 3, a kiln body gear 7, kiln body rollers 5, a rotary motor 4, a motor gear, and a support device. The kiln body gear 7 is located on the outer side of the middle section of the rotary kiln 6, and the kiln body rollers 5 are located on the outer sides of both ends. The kiln body gear 7 is meshed with the motor gear, which is rotatably mounted on the support device and connected to the output shaft of the rotary motor 4. Under the action of the rotary motor 4, the motor gear drives the kiln body gear 7 to rotate. The supporting roller 3 is mounted on the support device and supports the kiln body rollers 5 on the side of the rotary kiln 6. The supporting roller 3 and the kiln body rollers 5 are in a rolling connection.

[0024] The rotary kiln 6 is supported by the supporting rollers 3 and the kiln body rollers 5. The rotating motor 4 drives the rotary kiln 6 to rotate continuously at a low speed of 1 rpm via the kiln body gear 7. This arrangement allows the material to be continuously tumbled and evenly heated inside the rotary kiln 6, while being slowly propelled towards the kiln tail under gravity, achieving continuous conveying. Under typical operating conditions, the total residence time of a single batch of deactivated activated carbon in the rotary kiln 6 can be controlled within 60 minutes, thus completing the drying / preheating and pyrolysis stages sequentially.

[0025] The airtight feeding mechanism includes a feed hopper 2. The bottom outlet of the feed hopper 2 is connected to a discharge pipe via a star-shaped discharge device. The discharge pipe is sealed and extends into the feed chamber. The feed hopper 2 adopts an airtight or near-airtight feeding structure to reduce the direct entry of outside air into the rotary kiln 6 from the feed inlet, thus preventing the formation of a high-oxygen point at the kiln head of the rotary kiln 6. The material is gradually pushed towards the kiln tail as the rotary kiln 6 tilts and rotates.

[0026] Along the material feeding direction, the rotary kiln 6 sequentially forms two functional zones: a drying / preheating zone and a pyrolysis zone. The drying / preheating zone is located at the end of the rotary kiln 6 closest to the feed hopper 2. This zone primarily removes free water, adsorbed water, and low-boiling-point volatiles from the surface and pores of the activated carbon particles, with an average operating temperature of approximately 200 °C. By completing dehydration and removal of low-boiling-point components at a lower temperature, the instantaneous large-scale volatilization of these light substances in the subsequent high-temperature zone is avoided, thus preventing safety hazards caused by heat fluctuations and localized unstable heat release. The pyrolysis zone is located at the end of the rotary kiln 6 closest to the partitioned combustion chamber 10. This zone operates under essentially low-oxygen conditions, with an average operating temperature of approximately 400 °C. In this zone, high-boiling-point organic pollutants and colloidal / coke deposits adhering to the pores of the deactivated activated carbon gradually undergo thermal decomposition and volatilize, opening up blocked pores and restoring flow, thus initially unblocking the pore structure. To prevent significant oxidation loss of the activated carbon during this stage, the pyrolysis zone maintains a low-oxygen atmosphere, with the oxygen content controlled to no more than 1% by volume. The isolation combustion chamber 10 houses the regeneration and activation zone, the highest temperature section, typically operating at 800–1200 °C. An activation medium (e.g., steam or carbon dioxide) is introduced through the activation steam inlet 8. Within this zone, the activation medium undergoes a selective gasification reaction with the carbon skeleton at high temperatures, opening micropores previously blocked by coke, restoring the microporous structure, specific surface area, and adsorption capacity, thus enabling the activated carbon to regain its adsorption and recycling capabilities. The activation zone also maintains a low-oxygen environment with an oxygen content of 5–8% to prevent significant direct combustion of the carbon skeleton and structural ablation under high-temperature conditions.

[0027] This embodiment employs direct combustion heating at the kiln tail. A partitioned combustion chamber 10 is located at the tail end of the rotary kiln 6, with the combustion lance 11 extending directly into it. Fuel gas (such as natural gas) is injected into the combustion lance 11, and combustion air is introduced through the combustion air inlet 9. The fuel gas and combustion lance 11 directly combust within the partitioned combustion chamber 10, generating a high-temperature flame and high-temperature flue gas. The high-temperature flame extends from the kiln tail into the interior of the kiln body 6, while the high-temperature flue gas flows axially along the kiln body 6 towards the kiln head, sequentially providing heat to the pyrolysis zone and the drying / preheating zone. It also heats the regenerating activated carbon through convective and radiative heat transfer. The temperature of the high-temperature flue gas after combustion can be controlled within the range of approximately 800–1200 °C to ensure sufficient regeneration activation temperature in the activation zone, while simultaneously providing the necessary heat to the upstream sections.

[0028] Unlike traditional direct-combustion rotary kilns, this embodiment does not simply supply fresh combustion air directly for combustion. Instead, it incorporates a waste gas recirculation loop to regulate the combustion atmosphere and thermal efficiency by recovering and recycling the exhaust gas from the kiln head of the rotary kiln 6. Specifically, the high-temperature exhaust gas (containing pyrolysis gases, volatile organic compounds, and high-temperature, low-oxygen flue gas) released during operation in the drying / preheating zone, pyrolysis zone, and activation zone is collected in the gas collection area at the kiln head of the rotary kiln 6 and introduced into the waste gas discharge trough 1. The waste gas discharge trough 1 serves as both the interface for exhaust gas collection and discharge and the intake point for recirculated air. An exhaust gas oxygen content detector 15 is installed in the waste gas discharge trough 1 or its connected location to monitor the oxygen content of the exhaust gas in real time. Driven by the waste gas recirculation fan 16, a portion of the exhaust gas is not directly discharged but is returned to the isolation combustion chamber 10 while maintaining a relatively high temperature. This mixture is then mixed with the combustion air supplied by the combustion air inlet 9 before entering the isolation combustion chamber 10 together and participating in the combustion process in the area where the combustion gun 11 is located.

[0029] The exhaust gas recirculation loop serves two key functions. First, the recirculated exhaust gas is a high-temperature, low-oxygen gas. When mixed with the combustion air, it significantly dilutes the oxygen concentration of the combustion air, resulting in a significantly lower actual oxygen content entering the isolated combustion chamber 10 compared to conventional direct combustion conditions. Thus, even if the burner 11 burns directly at the kiln tail and the flame extends into the rotary kiln body 6, the overall atmosphere inside the kiln remains a low-oxygen or controlled-oxygen regeneration atmosphere.

[0030] In other words, this invention prevents the oxidation and burning of charcoal by controlling the oxygen partial pressure, rather than relying on physical isolation of the flame. The activated carbon maintains its structural integrity in the high-temperature zone, avoiding the problems common in traditional direct-fired rotary kilns, such as localized oxygen-rich high-temperature erosion of the charcoal layer, leading to rapid burn-off, sintering, or even spontaneous combustion. Secondly, the circulating exhaust gas maintains a high temperature and contains some unburned combustible pyrolysis gas components. When returned to the isolated combustion chamber 10, it effectively provides a preheated atmosphere with effective calorific value for the combustion air, enabling the isolated combustion chamber 10 of the rotary kiln to maintain the required high-temperature heating state with a relatively low additional fuel consumption. The signal from the exhaust gas oxygen content detector 15 can be used to adjust the return flow rate of the exhaust gas circulating fan 16 and the fresh air intake rate of the combustion air inlet 9, thereby achieving closed-loop stable control of the oxygen content within the kiln.

[0031] After activation, the high-temperature regenerated activated carbon is fed into the cooling section through the partitioned combustion chamber 10. The cooling section adopts an independent cooling chamber 13 structure, with a two-stage cooling system. The first-stage cooling system is located near the feed end of the cooling chamber 13 and includes a cooling water jacket 14 located on the outer side of the cooling chamber 13. Cooling is achieved by circulating cooling water into the cooling water jacket. The second-stage cooling system is located near the discharge end of the cooling chamber 13 and includes several air inlet chambers 12 located at the bottom of the cooling chamber 13 and several air outlet chambers located at the top of the cooling chamber 13. Cold air is circulated into each air inlet chamber at the bottom of the cooling chamber 13 by an air fan, and the air outlet of each air outlet chamber at the top of the cooling chamber 13 is connected to an air intake pipe, which is then connected to the combustion air inlet 9.

[0032] The first cooling zone of cooling chamber 13 utilizes circulating cooling water or a water jacket for heat exchange to rapidly reduce the regenerated activated carbon from the activation zone temperature (e.g., approximately 700–850 °C) to a medium temperature range, thereby suppressing the material's subsequent tendency to spontaneously combust. The second cooling zone of cooling chamber 13 continues to cool the medium-temperature carbon under forced draft conditions, ultimately reducing the regenerated activated carbon to a safe discharge temperature not exceeding approximately 120 °C. The regenerated activated carbon, after undergoing this two-stage cooling process, is discharged in a stable, low-temperature state and can be directly sent to subsequent temporary storage, screening, or refilling stages, achieving continuous industrial operation.

[0033] In summary, in this embodiment, the deactivated activated carbon undergoes drying / preheating dehydration, thermal desorption and pore unblocking, and high-temperature activation to restore the microporous structure along the axial direction within the rotary kiln 6. The pores are reopened, and the specific surface area and adsorption capacity are restored. The isolated combustion chamber 10 provides heat to the rotary kiln via direct combustion. The flame directly enters the kiln tail of the rotary kiln 6 as a heat source and heats the entire kiln process axially. However, the high-temperature, low-oxygen exhaust gas returned by the waste gas circulation fan 16 is fully mixed with the air introduced by the combustion air inlet 9, thus lowering the overall oxygen content within the kiln and maintaining it within a safe range. This inhibits the oxidation and burning of the activated carbon skeleton in the high-temperature section, significantly reducing the burn-off rate. The circulating exhaust gas not only reduces the oxygen content and forms a controlled low-oxygen regeneration atmosphere but also returns to the combustion zone at high temperature to participate in heating, forming an internal heat loop. This reduces external additional fuel consumption and achieves low-energy operation. After two-stage cooling in cooling chamber 13, the final produced regenerated activated carbon is cooled to a safe temperature and discharged, and can be directly put into subsequent stages such as storage, screening or repackaging, ensuring the continuous feasibility of the equipment and process of this invention on an industrial scale.

[0034] A process for a low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation includes the following steps: S1: The airtight feeding mechanism adds deactivated activated carbon into the kiln head of the rotary kiln 6. The material is gradually pushed to the kiln tail direction as the rotary kiln 6 tilts and rotates, and finally discharged in the partitioned combustion chamber 10 and enters the cooling chamber 13. Along the material feeding direction, the interior of the rotary kiln 6 consists of two functional areas: a drying / preheating zone and a pyrolysis zone, while the partitioned combustion chamber 10 is the functional area of ​​the activation zone. S2: Natural gas, combustion air and activation gas are introduced into the partitioned combustion chamber 10 to burn and generate high-temperature flue gas. The high-temperature flue gas flows from the partitioned combustion chamber 10 into the rotary kiln 6, providing heat to the pyrolysis zone and the drying / preheating zone in sequence. The heat is transferred to the regenerating activated carbon through convective heat transfer and radiative heat transfer. S3: High-temperature exhaust gas is centrally discharged from the exhaust gas discharge trough 1 at the front end of the rotary kiln 6. Part of the high-temperature exhaust gas is recirculated, mixed with combustion air in a certain proportion, and then sent into the partitioned combustion chamber 10. The oxygen content of the combustion atmosphere in the partitioned combustion chamber 10 is controlled at 5-8%, and the oxygen content of the exhaust gas centrally discharged from the exhaust gas discharge trough 1 is controlled below 1%.

[0035] According to the process of this invention, the oxygen content of the combustion atmosphere in the isolated combustion chamber 10 is controlled at 5-8%, and the oxygen content of the exhaust gas discharged from the waste gas discharge tank 1 is controlled at less than 1%, which can control the mass loss of activated carbon in the high-temperature regeneration process to less than 10%, while the mass loss of activated carbon in the high-temperature regeneration process under conventional air oxygen concentration is usually more than 25%.

[0036] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation, characterized in that, It includes a rotary kiln (6), an airtight feeding mechanism, a waste gas discharge trough (1), an isolated combustion chamber (10), a cooling chamber (13), and a rotary drive mechanism for rotating the rotary kiln (6); The front end of the rotary kiln (6) is rotatably and sealingly connected to the feed chamber, and the rear end is rotatably and sealingly connected to the isolation combustion chamber (10). Along the material forward direction, the feed chamber, the rotary kiln (6) and the isolation combustion chamber (10) are inclined downward at a small angle as a whole; the exhaust gas discharge trough (1) is connected to the feed chamber. The airtight feeding mechanism is used to add deactivated activated carbon into the feeding chamber, and the solid discharge port at the bottom of the combustion chamber (10) is connected to the cooling chamber (13) by a pipeline; The partitioned combustion chamber (10) is provided with an activation steam inlet (8), a combustion air inlet (9) for introducing combustion air, and a combustion gun (11) for introducing fuel gas. The exhaust outlet of the exhaust gas discharge tank (1) is divided into two paths. One path is sent to the subsequent purification system, and the other path is connected to the combustion air inlet (9) by a pipeline, so that part of the returned exhaust gas is mixed with the combustion air and then sent into the partitioned combustion chamber (10).

2. The low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation as described in claim 1, characterized in that, The airtight feeding mechanism includes a feeding funnel (2), and the bottom outlet of the feeding funnel (2) is connected to the discharge pipe through a star-shaped discharge device. The discharge pipe is sealed and inserted into the feeding chamber.

3. The low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation as described in claim 1, characterized in that, An online oxygen content detector (15) is installed on the exhaust gas discharge tank (1) to monitor the oxygen content of the exhaust gas in real time; one of the outlets of the exhaust gas discharge tank (1) is connected to the combustion air inlet (9) by a pipeline through an exhaust gas circulation fan (16), and the combustion air inlet (9) is also connected to an air fan through an air intake pipe. The online oxygen content detector (15) is signal-interlocked with the exhaust gas recirculation fan (16) and the air fan to detect the oxygen content at the exhaust gas collection point in real time, and uses this as a feedback signal to adjust the ratio of recirculated exhaust gas to fresh combustion air. When the oxygen content in the exhaust gas is higher than the set value, the recirculated exhaust gas return flow rate is increased and the fresh combustion air flow rate is decreased, thereby increasing the ratio of recirculated exhaust gas to fresh combustion air. Conversely, the ratio of recirculated exhaust gas to fresh combustion air is decreased.

4. The low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation as described in claim 1, characterized in that, The rotary drive mechanism includes a supporting roller (3), a kiln gear (7), a kiln roller (5), a rotating motor (4), a motor gear, and a support device. A kiln gear (7) is provided on the outer side of the middle part of the rotary kiln (6), and kiln rollers (5) are provided on the outer side of both ends. The kiln gear (7) is meshed with the motor gear. The motor gear is rotatably mounted on the support device, and the motor gear is connected to the output shaft of the rotating motor (4). Under the action of the rotating motor (4), the motor gear drives the kiln gear (7) to rotate. The supporting roller (3) is installed on the support device. The supporting roller (3) supports the kiln body roller (5) on the side of the rotary kiln (6). The supporting roller (3) and the kiln body roller (5) are connected by rolling.

5. The low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation as described in claim 1, characterized in that, The tilt angle of the rotary kiln (6) is 2-10°.

6. The low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation as described in claim 1, characterized in that, The cooling chamber (13) is provided with a two-stage cooling system. The first-stage cooling system is located near the feed end of the cooling chamber (13) and includes a cooling water jacket (14) located on the outer side of the cooling chamber (13). Cooling is achieved by introducing cooling water into the cooling water jacket. The second-stage cooling system is located near the discharge end of the cooling chamber (13) and includes several air inlet chambers (12) located at the bottom of the cooling chamber (13) and several air outlet chambers located at the top of the cooling chamber (13). Cold air is introduced into each air inlet chamber at the bottom of the cooling chamber (13) by an air fan. The air outlet of each air outlet chamber at the top of the cooling chamber (13) is connected to an air intake pipe, which is then connected to the combustion air inlet (9).

7. The process of a low-energy-consumption rotary kiln equipment for regenerating activated carbon with waste heat circulation as described in claim 1, characterized in that, Includes the following steps: S1: The airtight feeding mechanism adds deactivated activated carbon into the kiln head of the rotary kiln (6). The material is gradually pushed to the kiln tail direction as the rotary kiln (6) tilts and rotates, and finally discharged in the partitioned combustion chamber (10) and enters the cooling chamber (13). Along the material feeding direction, the rotary kiln (6) has two functional areas in sequence: a drying / preheating zone and a pyrolysis zone. The partitioned combustion chamber (10) is the functional area of ​​the activation zone. S2: Natural gas, combustion air and activation gas are introduced into the partitioned combustion chamber (10) to burn and generate high-temperature flue gas. The high-temperature flue gas flows from the partitioned combustion chamber (10) into the rotary kiln (6) to provide heat to the pyrolysis zone and the drying / preheating zone in sequence. The heat is transferred to the regenerating activated carbon through convective heat transfer and radiative heat transfer. S3: The high-temperature exhaust gas is discharged from the exhaust gas discharge trough (1) at the front end of the rotary kiln (6), and part of the high-temperature exhaust gas is returned and mixed with the combustion air in proportion before being sent into the partitioned combustion chamber (10).

8. The method as described in claim 7, characterized in that, The oxygen content of the combustion atmosphere in the partitioned combustion chamber (10) is controlled at 5-8%, and the oxygen content of the exhaust gas discharged from the waste gas discharge trough (1) is controlled at less than 1%.

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