A method for purifying VOCs by a zeolite rotating drum concentration-catalytic oxidation system

Abstract

The present application provides a VOCs purification method of a zeolite rotating drum concentration-catalytic oxidation system, and belongs to the technical field of volatile organic compound waste gas treatment. The method comprises: rotating the zeolite rotating drum, and dividing the rotating drum into an adsorption zone, a desorption zone and a cooling zone; circulating the desorption gas in a closed desorption loop, and the circulating air volume is 8% to 14% of the treatment air volume; controlling the oxygen content in the desorption zone to be maintained at 7% to 10%, and inhibiting the thermal oxidation polymerization coking of high-boiling plasticizer components; arranging a temperature sensor close to the zeolite end face to measure the solid phase temperature at the 20° to 120° arc segment before the adsorption zone outlet, and setting a reference temperature measuring point; calculating the temperature rise value, and determining the temperature rise centroid angle by weighted average; taking the centroid angle as the main controlled variable, and adopting a PI controller to coordinate and adjust the desorption temperature, the rotating drum speed and the cooling zone air supply proportion, so that the adsorption mass transfer front is stabilized at the target position. The present application can prolong the service life of the zeolite and ensure that the outlet is stable and up to standard.

Description

Technical Field

[0001] This invention belongs to the field of volatile organic compound (VOCs) waste gas treatment technology, and specifically relates to a VOCs purification method using a zeolite rotary drum concentration-catalytic oxidation system. Background Technology

[0002] In the production processes of PVC artificial leather, plastic running track materials, packaging printing, and tape coating, the emitted organic waste gas contains not only conventional VOCs such as ethyl acetate, toluene, and methyl ethyl ketone, but also high-boiling-point plasticizer components such as DBP (dibutyl phthalate, boiling point about 340℃) and DOP (dioctyl phthalate, boiling point about 385℃). Although these components account for only about 3% to 5% of the total mass, they have a significant impact on the long-term stable operation of the treatment system.

[0003] The existing zeolite rotary drum + CO catalytic oxidation process for treating this type of waste gas has the following prominent problems: (1) High-boiling-point components are difficult to completely desorb at the conventional desorption temperature of 180~200℃. In the normal oxygen environment (oxygen content of about 21%) of open fresh air desorption, high-boiling-point plasticizers undergo thermal oxidation polymerization reaction at the high desorption temperature, generating macromolecular colloids and coke deposited in the zeolite channels, gradually blocking the micropores, resulting in an irreversible decrease in adsorption capacity, shortening the zeolite life, and frequent exceedance of the outlet concentration, requiring frequent replacement of zeolite or high-temperature regeneration at 300℃ or above.

[0004] (2) The fixed speed operation cannot match the fluctuation of the exhaust gas concentration. At low concentrations, excessive desorption causes energy waste, and at high concentrations, desorption is not timely, resulting in excessive penetration of the adsorption front. Traditional temperature or pressure difference control methods have a lag in response and are difficult to detect changes in adsorption saturation in a timely manner.

[0005] (3) Although the activated carbon filter in the pretreatment section can initially intercept some high-boiling-point components, in the summer when the temperature is high or the inlet concentration increases sharply, the high-boiling-point components adsorbed by the activated carbon will desorb and be released into the rotating drum, forming secondary pollution; and the activated carbon is at risk of spontaneous combustion under the action of high-temperature desorption wind.

[0006] (4) Although the existing closed-loop desorption technology can reduce the oxygen content in the loop, it has problems such as the process heat balance not being closed, difficulty in coordinating the dynamic control of oxygen content with the oxygen demand of catalytic oxidation, and excessively high zeolite temperature after cooling. In particular, unreasonable air volume distribution in the cooling zone, improper fan location leading to lack of power in some branches, and temperature crossover due to mismatched heat exchanger design parameters are engineering defects that affect the long-term stable operation of the system.

[0007] Therefore, there is a need to develop a closed-loop low-oxygen desorption system and control method that can fundamentally inhibit the thermal oxidation and coking of high-boiling-point plasticizers, accurately sense the adsorption state and dynamically adjust the desorption parameters, achieve process thermal balance closure, and have complete safety interlocks. Summary of the Invention

[0008] In view of the above, the main objective of this invention is to propose a VOCs purification method for a zeolite rotary drum concentration-catalytic oxidation system to solve the aforementioned technical problems.

[0009] This invention proposes a method for VOCs purification using a zeolite rotary drum concentration-catalytic oxidation system, the method comprising the following steps: The zeolite drum is rotated, and the zeolite drum is divided into an adsorption zone, a desorption zone and a cooling zone along the rotation direction. The adsorption zone treats large volumes of low-concentration organic waste gas. In a closed desorption loop consisting of a desorption zone, a cooling zone, a desorption fan, a desorption heat exchanger, an electric heater, a desorption cooler, a split mixing section, and a CO catalytic oxidation furnace, the desorbed gas is circulated, with a circulating air volume of 8% to 14% of the processing air volume. The desorbed gas is preheated by the desorption heat exchanger and supplemented by the electric heater before entering the CO catalytic oxidation furnace for catalytic oxidation. The heat released by the reaction is recovered by the desorption heat exchanger. The oxygen content in the desorption zone of the closed desorption circuit is maintained at 7%~10% to suppress the thermal oxidative polymerization and coking of high-boiling-point plasticizer components at the desorption high temperature; Multiple temperature sensors are arranged in the arc segment 20°~120° before the outlet of the adsorption zone to measure the solid phase temperature, and a reference temperature measuring point is set in the arc segment 20°~40° before the adsorption zone. The temperature rise value is calculated based on the reference temperature and the temperature at each measuring point, and the temperature rise centroid angle is determined by the weighted average of the temperature rise. Using the temperature rise centroid angle as the main controlled variable, a PI controller is used to coordinate and adjust the desorption temperature, the drum speed, and the proportion of air supply in the cooling zone, so that the adsorption mass transfer front is stabilized at the target position.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Significant effect of low oxygen inhibition of polymerization: By controlling the oxygen content of the desorption loop in the range of 7% to 10%, the thermal oxidation polymerization rate of high-boiling-point plasticizers such as DBP and DOP at the desorption temperature of 175 to 200℃ is significantly reduced, and the amount of gel coking is significantly reduced; the closed circulation avoids the problem of continuous oxygen introduction and accelerated oxidation in the open system, and the zeolite channels can remain in a loose state for a long time without obvious brown-black coking deposition. The thermal oxidation polymerization of high-boiling-point components is greatly inhibited in the low oxygen environment, and after multiple cycles of gradual desorption, the cumulative effective desorption rate is significantly improved.

[0011] (2) Accurate and reliable temperature rise centroid tracking: The PT100 probe is close to the zeolite end face by 0~2mm to measure the solid phase temperature, avoiding the dilution interference of the gap air temperature signal by the large volume of exhaust gas, and the signal-to-noise ratio is sufficient; by locating the adsorption mass transfer front by temperature rise weighted centroid, the speed and temperature can be sensed and adjusted within minutes after the concentration shock occurs, and the response speed is much faster than the traditional outlet concentration detection.

[0012] (3) The thermal balance closed-loop engineering is feasible: Through reasonable design of circulating air volume (8%~14% of the processing air volume), heat exchanger heat exchange area, and three-way flow ratio (40%~55% of uncooled bypass flow, 25%~45% of cooling bypass flow, and 12%~20% of cooling zone air supply), the target error between the temperature of the flow mixing section and the desorption temperature is less than 1K, the heat exchanger end difference is reasonable and there is no temperature crossover, the rated power of the electric heater meets the start-up temperature rise requirements, and the CO reaction heat can be used to significantly reduce the supplementary heating power under steady-state conditions.

[0013] (4) Multi-variable coordination strategy to avoid reverse regulation: Temperature priority regulation ensures sufficient thermodynamic driving force for desorption, speed regulation changes the distribution of zeolite residence time, and cooling and heat dissipation assist in controlling the residual temperature of zeolite entering the adsorption zone. The three operating variables are decoupled and coordinated to avoid the positive feedback runaway problem of "increasing the speed shortens the desorption time, resulting in worse regeneration". The secondary interlock prioritizes closing the exhaust gas valve to reduce the load and avoids further increasing the regeneration intensity when the temperature is too high, which in turn aggravates the heat load.

[0014] (5) Complete safety assurance system: the three-level interlock logic direction is correct, the UPS is powered with the same priority, the rupture disc is selected in compliance with regulations, the zirconium oxide fault safety is conservative, the drum is rotated before heating when starting up, the nitrogen inerting is used in emergency shutdown and fresh air is not turned on, and the CO furnace temperature is maintained during normal shutdown to prevent the residue of incomplete oxidation products.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by means of embodiments of the invention. Attached Figure Description

[0016] Figure 1 This is a system architecture diagram of a VOCs purification method using a zeolite rotary drum concentration-catalytic oxidation system according to the present invention; Figure 2 This is a bar chart comparing the core performance indicators of the present invention with those of existing technologies. Figure 3 This is a dynamic concentration curve of NMHC at the outlet during 72 hours of continuous operation, comparing the present invention with existing technologies. Figure 4 This is a comparison chart of the overall performance of the radar between the present invention and existing technologies. Detailed Implementation

[0017] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0018] These and other aspects of the embodiments of the present invention will become clear from the following description and accompanying drawings. In these descriptions and drawings, some specific embodiments of the present invention are specifically disclosed to illustrate some ways of implementing the principles of the embodiments of the present invention; however, it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0019] Please see Figure 1 This embodiment provides a VOCs purification method using a zeolite rotary drum concentration-catalytic oxidation system. The VOCs purification method in this embodiment relies on the zeolite rotary drum concentration-catalytic oxidation system. This system includes a zeolite rotary drum, a closed desorption loop, a CO catalytic oxidation furnace, a low-oxygen maintenance unit, a temperature rise centroid detection unit, and a multi-level safety interlock unit. The method of this invention will be described below in conjunction with the system.

[0020] I. System Composition and Overall Approach The zeolite rotor is a ring-shaped honeycomb zeolite rotor with an outer diameter of 3.8m, an inner diameter of 1.8m, and an axial thickness of 0.4m. The honeycomb zeolite filling volume is approximately 3.5m³, and the total zeolite mass is approximately 1300kg. The zeolite rotor is divided into an adsorption zone, a desorption zone, and a cooling zone along the rotation direction, with angles of 240° for the adsorption zone, 60° for the desorption zone, and 60° for the cooling zone. Each zone is separated by a heat-resistant sealing brush to prevent cross-contamination. The adsorption zone treats large volumes of low-concentration organic waste gas, with a typical treatment volume of 80,000 Nm³ / h and a surface velocity of approximately 3.5~4.0 m / s.

[0021] At the methodological level, the annular honeycomb zeolite drum is continuously rotated, and the zeolite in the adsorption zone adsorbs VOCs in the waste gas; the desorption zone is heated and desorbed by the desorption gas in the closed desorption loop; the cooling zone is purged and cooled by the air supplied from the cooling zone of the closed desorption loop; the concentrated gas after desorption is catalytically oxidized into carbon dioxide and water in a CO catalytic oxidation furnace.

[0022] The closed-loop desorption circuit consists of a desorption zone, a cooling zone, a desorption fan, a desorption heat exchanger, an electric heater, a CO catalytic oxidation furnace, a desorption cooler, a split mixing section, and corresponding regulating valves and pipelines. The circulating air volume is 8% to 14% of the processing air volume, with a typical circulating air volume of approximately 8000 Nm³ / h, corresponding to a concentration ratio of approximately 10 times.

[0023] The desorbed gas circulates in the loop: the desorption fan pressurizes the gas after the mixing section is divided and sends it to the inlet of the desorption zone. The gas flows through the desorption zone, heats the zeolite, and carries the desorbed VOCs. The gas at the outlet of the desorption zone enters the cold side of the desorption heat exchanger and is preheated. Then, it is heated to the catalyst ignition temperature by an electric heater and enters the CO catalytic oxidation furnace. The VOCs are catalytically oxidized and release heat in the CO furnace. The high-temperature purified gas enters the hot side of the desorption heat exchanger and releases heat. The purified gas after the hot side outlet is divided into two paths: one path flows as an uncooled bypass through the bypass regulating valve and directly enters the mixing section; the other path is cooled to 40~60℃ by water cooling in the desorption cooler and then divided into two streams: cooling zone supply air and cooling bypass flow. The cooling zone supply air is sent to the cooling zone through the cooling zone supply valve to purge and cool the zeolite, and the cooling bypass flow is sent directly into the mixing section through the cooling bypass valve. The three gas streams merge in the mixing section and are then sent to the desorption zone by the desorption fan, completing the closed loop.

[0024] In the closed desorption circuit, the oxygen content in the desorption zone is maintained at 7%~10% to inhibit the thermal oxidative polymerization and coking of high-boiling-point plasticizer components such as DBP and DOP at the high desorption temperature. The oxygen content is maintained through a low-oxygen maintenance unit, and the specific control method is described below.

[0025] Multiple PT100 platinum resistance temperature sensors are arranged in an arc segment of 20°~120° (absolute angle approximately 120°~220°) before the outlet of the adsorption zone. The sensor probes are placed 0~2mm close to the zeolite end face (in this embodiment, direct contact with the solid phase surface is used) to measure the solid phase temperature. Simultaneously, two reference temperature measuring points are set in an arc segment of 20°~40° before the adsorption zone. Based on the reference temperature T... o Temperature T at each measuring point in the detection area i Calculate the temperature rise ΔT i =T i T o The temperature rise centroid angle θ is determined by a temperature rise weighted average method. c With the temperature rise center of mass angle θ c As the primary and controlled variables, a PI controller is used to coordinate and adjust the desorption temperature, drum speed, and cooling zone air supply ratio to stabilize the adsorption mass transfer front at the target position. The cooling zone air supply ratio refers to the proportion of cooling zone air supply to the total circulating air volume after the hot side outlet of the desorption heat exchanger.

[0026] The above steps constitute the core process of the VOCs purification method in this embodiment.

[0027] II. Closed-loop desorption circuit for flow splitting and mixing; In a closed desorption loop, the purified gas is split after the hot-side outlet of the desorption heat exchanger in the following manner: Uncooled bypass flow accounts for 40% to 55% of the total circulating air volume. It enters the split mixing section directly through the bypass regulating valve. The gas temperature in this path is relatively high, about 270 to 290°C, and it is used as the main heat source to provide the desorption temperature. The cooling flow entering the desorption cooler accounts for 45% to 60% of the total circulating air volume. After being cooled to 40 to 60°C by the water-cooled desorption cooler, the condensate is discharged through the gas-liquid separator and the U-shaped liquid seal automatic drain valve. After the cooler outlet, it is divided into two streams: cooling zone supply air and cooling bypass flow. The cooling zone supply air accounts for 12% to 20% of the total circulating air volume and is sent into the cooling zone through the cooling zone supply air valve to purge and cool the high-temperature zeolite from the desorption zone. The cooling bypass flow accounts for 25% to 45% of the total circulating air volume, and the temperature is maintained at 40 to 60°C. It directly enters the split mixing section through the cooling bypass valve.

[0028] The three gases are mixed proportionally in the split-mixing section to reach the desorption temperature of 175-200℃, and then fed into the desorption zone inlet by the desorption fan. The total circulating flow rate is measured at the desorption fan inlet (after the split-mixing section), and is maintained constant by frequency conversion regulation of the desorption fan. The three regulating valves are linked to distribute their respective proportions; if pressure fluctuations in any loop cause the total flow rate to deviate from the set value, the fan frequency compensates to ensure stable total circulating flow. The cooling zone outlet air merges into the split-mixing section, is isolated from the adsorption zone by a seal, and does not enter the adsorption zone.

[0029] The desorption fan is located in the full-flow section of the pipeline after the mixing section merges, where the gas is a purified mixture with a temperature of approximately 170~195℃. The desorption fan is a high-temperature centrifugal fan with a temperature resistance of 250℃, a motor power of 30~37kW, and drives 100% circulation flow.

[0030] III. CO Catalytic Oxidation Unit; The CO catalytic oxidation furnace is located downstream of the electric heater and upstream of the hot side of the desorption heat exchanger. The CO furnace uses a precious metal Pt / Pd catalyst with a catalyst loading of approximately 0.7 m³ and a space velocity of 10,000–20,000 h⁻¹. - ¹, Operating temperature 320~400℃. The electric heater is located between the cold side outlet of the desorption heat exchanger and the inlet of the CO furnace, with a rated power of about 300kW, and is used to reheat the preheated gas to the catalyst ignition temperature of 310~330℃.

[0031] The outlet gas temperature of the desorption zone is about 155~180℃. After being preheated on the cold side of the desorption heat exchanger, the temperature rises to 240~270℃. Then, it is further heated by an electric heater to 305~325℃ before entering the CO furnace. The catalytic oxidation of VOCs in the CO furnace releases heat, raising the gas temperature to 350~400℃. After the high-temperature purified gas recovers heat on the hot side of the desorption heat exchanger, the temperature drops to 270~290℃.

[0032] The CO furnace outlet pipe section is equipped with an online CO monitor. When the CO concentration exceeds 100ppm, it automatically increases the opening of the fresh air intake valve by 10%~20% to ensure complete oxidation.

[0033] IV. Hypoxia Maintenance and Control; The low-oxygen maintenance unit includes a fresh air supply valve, a nitrogen supply valve, a zirconia oxygen content analyzer, and a continuous pressure relief device.

[0034] The fresh air intake point is located between the cold-side outlet of the desorption heat exchanger and the inlet of the electric heater. The ambient temperature fresh air is mixed with the preheated circulating air and then uniformly heated by the electric heater, avoiding the direct injection of fresh air into the CO furnace inlet and causing localized cold spots.

[0035] Two zirconia oxygen content analyzers are installed at the CO furnace inlet and the desorption zone outlet, respectively. The CO furnace inlet oxygen content is the primary control variable, and the opening of the fresh air supply valve is controlled in a closed loop to maintain the CO furnace inlet oxygen content at 8%~11%. Since the fresh air supply point is located before the electric heater inlet, the oxygen content in the desorption zone (excluding the fresh air section) is approximately 7%~10%, slightly lower than the CO furnace inlet oxygen content. The catalytic oxidation reaction in the CO furnace consumes approximately 0.3~0.8% of oxygen, resulting in a CO furnace outlet oxygen content of approximately 7.5%~10.5%. After split mixing, the desorption zone inlet oxygen content is approximately 7%~10%, and the loop is closed.

[0036] When the oxygen content at the CO furnace inlet is below 7.0%, the interlock increases the opening of the fresh air supply valve to provide supplementary air; when the oxygen content recovers to 8.0%, the supplementary air is stopped, resulting in a dead zone of approximately 1 percentage point.

[0037] A continuous pressure relief port is located in the bypass pipe section after the hot side outlet of the desorption heat exchanger, continuously releasing approximately 3% to 5% of the circulating gas volume to maintain a slight positive pressure of 50 to 200 Pa in the circuit. The released gas is at a relatively high temperature, and is first cooled to below 120°C through the waste heat recovery section before being led to the main exhaust stack for online FID monitoring to prevent the exhaust stack from overheating.

[0038] When the zirconia oxygen sensor malfunctions, the system automatically switches to safety mode: the fresh air inlet valve maintains approximately 50% of its normal opening, the nitrogen inlet valve is closed, and an alarm is triggered to prompt maintenance personnel to handle the situation promptly, thereby reducing the risk of incomplete CO oxidation due to excessively low oxygen content. One zirconia oxygen sensor is installed at the CO furnace inlet and the desorption zone outlet, providing redundancy; if one fails, the other can still monitor.

[0039] V. Temperature rise centroid detection; Four to six PT100 platinum resistance temperature sensors are arranged in an arc segment of 20° to 120° (absolute angle approximately 120° to 220°) before the adsorption zone outlet to detect the temperature rise distribution of adsorption heat release. Two additional PT100 sensors are set as reference temperature measuring points in an arc segment of 20° to 40° in the front section of the adsorption zone. In this arc segment, the zeolite has been present in the front section of the adsorption zone for 1.7 to 3.3 minutes and has been fully cooled to near the exhaust gas temperature by a large volume of ambient temperature exhaust gas. Adsorption heat release has just begun, and this temperature can be used as the reference temperature T. o Reference temperature T o Take the arithmetic mean (or weighted average) of the measurements from two reference temperature measurement points to eliminate random errors at a single measurement point and improve the reliability of the reference temperature.

[0040] The PT100 probe is positioned 0-2mm close to the zeolite end face via an elastic clamping mechanism to measure the zeolite solid phase temperature, rather than the interstitial air temperature, thus achieving a sufficient signal-to-noise ratio. The probe contact surface is protected by a wear-resistant metal sheet. The elastic clamping mechanism automatically compensates for wear caused by long-term rotational friction. It is recommended to check the probe contact condition and replace worn spring sheets every 6-12 months during maintenance. The sensor signal is connected to the PLC with a sampling period of 0.5-1s, and dynamic compensation is applied to the PT100's first-order inertial hysteresis, resulting in an equivalent response time of approximately 3-5s.

[0041] Temperature rise center of mass angle θ c Calculated using the temperature rise weighted average method: θ c = Σ(ΔT i × θ i ) / ΣΔT i ; Where, ΔT i =T i T o θ represents the temperature rise value at each measuring point in the detection area. i This represents the absolute angular position of each measuring point.

[0042] The location with higher temperature rise corresponds to the adsorption-mass transfer front region (the region where adsorption occurs strongly and heat release is concentrated); a centroid position biased towards the outlet indicates that the adsorption front is advancing too rapidly and regeneration is insufficient, requiring enhanced desorption; a centroid biased towards the inlet indicates sufficient regeneration and low adsorption load, allowing for appropriate speed reduction to save energy. The correspondence between the temperature rise centroid and the adsorption-mass transfer front is confirmed through on-site calibration.

[0043] To address unsteady-state conditions such as concentration shocks and inlet temperature fluctuations, the algorithm incorporates feedforward compensation for inlet exhaust gas concentration and temperature: when the inlet FID or temperature sensor detects a sudden change in exhaust gas parameters, the reference temperature T... oAn adaptive update using a 30-60s sliding window is adopted. Feedforward compensation uses an additive correction term for the inlet concentration change rate and temperature change to eliminate the interference of inlet condition changes on the temperature rise reference under unsteady conditions. At the same time, a first-order filter and dead zone protection are set for the centroid angle signal to avoid signal noise causing misjudgment of control direction.

[0044] VI. Multivariate Coordination Strategies; With the temperature rise center of mass angle θ c As the primary and secondary variables, a PI controller is used to coordinate and adjust the desorption temperature, drum speed, and cooling zone air supply ratio, following a multi-variable coordination strategy of "temperature priority, speed matching, and cooling heat dissipation assistance".

[0045] When the temperature rise centroid angle shifts towards the outlet, prioritize increasing the desorption temperature by 5~15℃ (achieved by increasing the opening of the uncooled bypass valve), and simultaneously increase the drum speed by 10%~20% to increase the air supply ratio of the cooling zone by 5~10 percentage points (achieved by increasing the opening of the cooling zone air supply valve); when the temperature rise centroid angle regresses towards the inlet, adjust in the opposite direction to save energy.

[0046] PI controller parameter range: proportional coefficient Kp = 0.5~2.0, integral time τ i =60~600s, matching the minute-level time constant of the rotary adsorption / desorption process to prevent integral saturation and oscillation. In this embodiment, Kp=1.0~1.5, τ i =120~300s, sampling period 0.5s, centroid target position approximately 180° (60° before exit).

[0047] When the three operating quantities are adjusted in a coordinated manner, a time-sharing control strategy based on the priority of the operating quantities is adopted for decoupling: the temperature regulation loop (bypass regulating valve) acts first, and after the action is completed, the speed regulation is executed after an interval of 10~30s. Finally, the air supply ratio of the cooling zone is adjusted. The time-sharing action of each loop avoids the interactive oscillation caused by simultaneous adjustment, and ensures that the regulation effects do not cancel each other out.

[0048] VII. Multi-level safety interlocks; The multi-level safety interlocking unit provides three levels of protection based on the temperature rise level and the angle of the temperature rise center of mass.

[0049] Level 1 warning: When the temperature rise ΔT at any measuring point exceeds 6~8℃, the current desorption temperature setting will be maintained automatically, the drum speed will be increased by about 10%, the air supply ratio in the cooling zone will be increased by about 5~10 percentage points, and the oxygen content will be maintained at the current closed-loop setting without actively increasing oxygen.

[0050] Second-level interlock: When the absolute temperature at any measuring point exceeds 75-85℃ or the temperature rise centroid distance from the outlet is less than 20°, the system automatically closes the exhaust gas inlet valve to reduce the load by 30%-50%, increases the rotational speed to 110%-120% of the current value, increases cooling heat dissipation, maintains the desorption temperature at the upper limit set value, and triggers an audible and visual alarm. The second-level interlock prioritizes closing the exhaust gas valve to reduce the load, preventing further increases in regeneration intensity when the temperature exceeds the limit, which could exacerbate the heat load.

[0051] Level 3 Emergency Shutdown: When the temperature exceeds 90-100℃ or the temperature rise rate exceeds 5℃ / min, immediately close the exhaust gas inlet valve and the fresh air supply valve, open the nitrogen supply valve to a nitrogen flow rate of approximately 250-400 Nm³ / h (corresponding to approximately 40%-60% opening) for inerting protection, de-energize the electric heater, and maintain operation of the desorption fan and cooler. The continuous pressure relief port remains open during emergency shutdown to release potential overpressure, and nitrogen is continuously injected to create a positive pressure inerting environment. Steam fire suppression is only used as an extreme fallback measure when nitrogen inerting fails and the temperature continues to rise above 120℃.

[0052] 8. Power-on and normal shutdown; The boot sequence is as follows: (1) Before starting the machine, start the drum to rotate at the lowest speed (about 1 r / h); (2) Start the desorption fan and cooler to establish a closed air circulation; (3) The oxygen content in the loop is initially reduced to below about 15% by nitrogen pre-purification; (4) Start the electric heater to raise the temperature to above 280°C; (5) A small amount of waste gas is introduced for ignition by starting the bypass valve. The amount introduced is controlled to be less than 25% of the lower explosive limit (LEL), and the amount of waste gas introduced at this stage is controlled to be within 5% to 10% of the normal waste gas volume, and the duration does not exceed 10 to 15 minutes. Since the oxygen content in the circuit has been initially reduced to about 15% (about two-thirds of that in the normal oxygen environment), the thermal oxidation polymerization rate is significantly reduced compared to the 21% normal oxygen environment. The amount of coking of high boiling point components at this stage can be ignored. (6) After the catalytic reaction stabilizes and releases heat, oxygen is further reduced by replacing nitrogen through the nitrogen injection valve. The nitrogen flow rate is about 200~350 Nm³ / h, controlled by the closed loop of the oxygen analyzer. The oxygen content in the loop is reduced to the target range of 8%~11% within about 15~20 minutes. (7) After the temperature stabilizes, gradually open the exhaust gas inlet valve to normal operating conditions.

[0053] The normal shutdown sequence is as follows: First, close the exhaust gas inlet valve, and maintain the electric heater at a certain power to keep the CO furnace temperature no lower than 300℃ for scavenging. After the temperature of the desorption zone drops below 120℃ and the VOCs concentration of the desorbed gas is less than 20% of the concentration of the inlet exhaust gas under normal operating conditions, gradually reduce the electric heating power and finally stop the operation of all equipment.

[0054] IX. Temperature Nodes and Pretreatment; In the closed desorption loop of this embodiment, the main temperature nodes are: the inlet temperature of the carrier gas in the desorption zone is 175~200℃, and the outlet temperature of the desorption zone is about 155~180℃; after preheating by the desorption heat exchanger, the temperature rises to 240~270℃, and then is further heated to 305~325℃ by the electric heater before entering the CO furnace; the catalytic oxidation in the CO furnace releases heat, raising the temperature to 350~400℃; the hot side outlet temperature of the desorption heat exchanger is about 270~290℃, with a terminal difference of about 25~50K between it and the cold side outlet, and there is no temperature crossover.

[0055] The pretreatment section adopts a four-stage dry filtration system consisting of a G4 primary filter, an F7 medium-efficiency filter, a dry demister, and an F9 sub-high-efficiency filter. No activated carbon filter layer is installed to avoid the risk of spontaneous combustion of activated carbon and to prevent the desorption of VOCs adsorbed by activated carbon from interfering with the operation of the zeolite drum under high temperature conditions.

[0056] 10. Example 1: Low load condition (inlet NMHC approximately 200 mg / m³). Steady-state operating parameters of the system: inlet concentration approximately 200 mg / m³, drum rotation speed approximately 1.2~1.5 r / h, residence time in the adsorption zone approximately 27~33 min, and residence time in the desorption zone and cooling zone approximately 6.7~8.3 min each; the inlet temperature of the desorption zone is controlled at approximately 175℃. The oxygen content at the CO furnace inlet is controlled at approximately 9%~10%, and the fresh air replenishment rate is approximately 4%~5%. The proportion of uncooled bypass flow is approximately 50%, the proportion of cooled bypass flow is approximately 35%, and the proportion of supply air in the cooling zone is approximately 15%.

[0057] The cold-side inlet of the heat exchanger is approximately 153-158°C, preheated to approximately 245-255°C, and electrically heated to 300-310°C before entering the CO furnace. The exothermic catalytic reaction in the CO furnace raises the gas temperature to approximately 340-360°C, resulting in a hot-side outlet temperature of approximately 270-280°C for the desorption heat exchanger. Air supply to the cooling zone cools the zeolite from approximately 160-170°C to approximately 95-110°C, with the cooling zone outlet air reaching approximately 110-130°C. The three-way mixing temperature is approximately 173-177°C, coinciding with the desorption temperature target.

[0058] The temperature rise centroid angle remained stable near the target position under PI control. Under three concentration shocks (reaching 2, 2.5, and 3 times the inlet concentration, respectively), the control system dynamically adjusted the desorption temperature, drum speed, and cooling zone air supply ratio, ensuring that the outlet NMHC peak value remained within the range of 17-22 mg / m³, with no sustained exceedances. After 72 hours of operation, the cumulative effective desorption rate of high-boiling-point components was approximately 63%, the average outlet concentration was approximately 15 mg / m³, the exceedance time was approximately 0.4%, there were zero alarms, and the zeolite lifespan is expected to be approximately 155 months.

[0059] XI. Example 2: Medium load condition (inlet NMHC approximately 300 mg / m³); Steady-state operating parameters of the system: inlet concentration approximately 300 mg / m³, drum rotation speed approximately 1.8~2.2 r / h, residence time in the adsorption zone approximately 18~22 min, and residence time in the desorption zone and cooling zone approximately 4.5~5.6 min each; the inlet temperature of the desorption zone is controlled at approximately 185℃. The oxygen content at the CO furnace inlet is controlled at approximately 8.5%~9.5%, and the fresh air replenishment rate is approximately 4%~5%. The proportion of uncooled bypass flow is approximately 48%~52%, the proportion of cooled bypass flow is approximately 33%~37%, and the proportion of supply air in the cooling zone is approximately 13%~17%.

[0060] The cold-side inlet of the heat exchanger is approximately 160-170°C, preheated to approximately 250-260°C, and electrically heated to 310-320°C before entering the CO furnace. The exothermic reaction in the CO furnace raises the gas temperature to approximately 360-380°C, resulting in a hot-side outlet temperature of approximately 275-285°C for the desorption heat exchanger. Air supply to the cooling zone cools the zeolite from approximately 170-180°C to approximately 100-115°C, with the cooling zone outlet temperature at approximately 115-130°C. The three-way mixing temperature is approximately 183-187°C. The dynamic response of the temperature rise centroid angle control is excellent; the outlet peak concentration under three concentration shocks is consistently controlled within the range of 13-18 mg / m³, meeting the standard stably. The cumulative effective desorption rate of high-boiling-point components over 72 hours is approximately 68%, with an average outlet concentration of approximately 12 mg / m³, exceeding the standard for approximately 0.1% of the time, zero alarms, and an expected zeolite lifespan of approximately 162 months.

[0061] 12. Example 3: High-load operation (inlet NMHC approximately 400 mg / m³); System steady-state operating parameters: inlet concentration approximately 400 mg / m³, drum speed approximately 2.5~2.8 r / h, residence time in the adsorption zone approximately 14~16 min, and residence time in the desorption zone and cooling zone approximately 3.6~4 min each; inlet temperature of the desorption zone controlled at approximately 195℃. Oxygen content at the CO furnace inlet controlled at approximately 8%~9%, fresh air replenishment rate approximately 4%~5%. Uncooled bypass flow accounts for approximately 50%~55%, cooled bypass flow accounts for approximately 27%~35%, and supply air to the cooling zone accounts for approximately 18%~20%.

[0062] The cold-side inlet of the heat exchanger is approximately 165-175°C, and after preheating, it reaches approximately 255-265°C. Electric heating further heats the gas to 315-325°C before it enters the CO furnace. At high concentrations, the CO furnace reaction releases a large amount of heat, resulting in a temperature rise of approximately 70-80K, raising the gas temperature to approximately 385-400°C. The hot-side outlet of the desorption heat exchanger is approximately 280-295°C. The cooling zone air supply is increased to 18%-20%, cooling the zeolite from approximately 175-185°C to approximately 95-110°C. The three-way mixing temperature is approximately 193-197°C. Although the desorption temperature is higher under high-load conditions, due to the large self-sufficiency of the CO reaction heat, the actual supplementary heating power of electric heating is lower than under low-load conditions, resulting in a slightly lower desorption power consumption index.

[0063] Under three concentration shocks, the peak outlet concentration was consistently controlled within the range of 12-18 mg / m³, meeting the standard stably. The cumulative effective desorption rate of high-boiling-point components over 72 hours was approximately 72%, with an average outlet concentration of approximately 11 mg / m³. The period of exceeding the standard was approximately 0.1%, with zero alarms. The expected zeolite lifespan is approximately 168 months.

[0064] High-boiling-point components (DBP, DOP, etc.) exhibit low physical desorption rates per cycle at desorption temperatures of 175–195°C, initially around 8%–12%, then 3%–5%, and finally 1%–2%, decreasing with decreasing residual concentration within the pores. However, the low-oxygen environment significantly inhibits the thermal oxidative polymerization reaction. Undesorbed high-boiling-point components remain in the zeolite pores as monomers or oligomers, significantly reducing the blockage of pores by brown-black colloidal coking. Through multiple cycles (approximately 80–200 drum cycles within 72 hours), desorption can be gradually achieved, with the cumulative effective desorption rate reaching the aforementioned values. After catalytic oxidation in the CO furnace, the background concentration of VOCs in the carrier gas remains low, not significantly inhibiting desorption mass transfer. For components with extremely high boiling points (approximately 385°C) such as DOP, a high-temperature deep regeneration at 220–230°C is recommended every 500–1000 hours of operation.

[0065] Thirteen, Comparison of Examples and Performance; Comparative Example 1: Open-loop ambient oxygen desorption + fixed rotation speed + activated carbon filtration; An open-loop fresh air desorption system (oxygen content approximately 21%) was used, with a fixed drum speed of 2 rpm and a desorption temperature of 180℃. An activated carbon filter was installed in the pretreatment stage. During 72 hours of operation, high-boiling-point components underwent continuous thermal oxidation, polymerization, and coking under normal oxygen conditions, gradually clogging the pores. The fixed drum speed could not keep up with concentration fluctuations. The activated carbon experienced a brief abnormal temperature rise during the second impact. The outlet concentration fluctuated significantly (approximately 18–40 mg / m³), with peak values ​​of approximately 55, 68, and 78 mg / m³ for the three impacts, and an average outlet concentration of approximately 28 mg / m³. The exceedance rate occurred in approximately 8.5% of the time, triggering three alarms. The cumulative effective desorption rate of high-boiling-point components was only approximately 37%, and the expected zeolite lifespan is approximately 95 months.

[0066] Comparative Example 2: Closed-loop low-oxygen desorption + fixed rotation speed + dry filtration; Closed-loop low-oxygen desorption (oxygen content 8%~10%) is employed, but the drum rotation speed is fixed at 2 rpm without adjustment, and the pretreatment dry filter lacks activated carbon. The closed-loop low-oxygen system significantly reduces coking, but the fixed rotation speed cannot dynamically match load changes. Under low load, over-desorption wastes energy, while under high load impact, desorption is not timely. The outlet concentration is approximately 14~25 mg / m³, with three impact peaks of approximately 36, 30, and 28 mg / m³, and an average outlet concentration of approximately 19 mg / m³. The exceedance time is approximately 2.5%, with two alarms. The cumulative effective desorption rate of high-boiling-point components is approximately 56%, and the expected zeolite lifespan is approximately 135 months.

[0067] Comparative Example 3: Closed-loop low-oxygen system + centroid control + activated carbon filtration; Closed-loop low-oxygen desorption with temperature rise centroid control was implemented, but the activated carbon filter was retained in the pretreatment stage. The initial performance was similar to Example 2, but during the first concentration surge (around 18 hours), the inlet concentration briefly increased to more than 2.5 times the normal level. The activated carbon adsorption capacity approached saturation, causing breakthrough. Some VOCs previously adsorbed in the activated carbon entered the rotary drum with the exhaust gas, resulting in a short-term abnormal increase in the inlet concentration and generating an additional temperature rise signal in the front section of the adsorption zone. The temperature rise centroid algorithm experienced 1-2 directional deviations due to occasional interference, recovering after a brief closed-loop oscillation of 2-3 minutes. The average outlet concentration over 72 hours was approximately 17 mg / m³, with an exceedance time of approximately 1.8%, one alarm, a cumulative effective desorption rate of approximately 60% for high-boiling-point components, and an expected zeolite lifespan of approximately 142 months.

[0068] The performance comparison data of each embodiment and the comparative example are shown in the table below:

[0069] Note: The cumulative effective desorption rate of high-boiling-point components is the cumulative effective desorption rate within a 72-hour operating cycle, which is the proportion of high-boiling-point components that are ultimately oxidized and decomposed by the CO furnace to the high-boiling-point components entering the system; the power consumption index is a relative value, with the steady-state power consumption of Comparative Example 1 as the benchmark of 100, and the lower the value, the more energy-efficient; the expected lifespan is the expected value extrapolated based on the 72-hour coking rate and the trend of adsorption capacity decay.

[0070] As shown in the table above, compared to open-circuit normal oxygen, closed-circuit low-oxygen can increase the cumulative effective desorption rate of high-boiling-point components from 37% to 56% and reduce the exceedance time from 8.5% to 2.5%, proving that the low-oxygen environment has a significant effect on inhibiting coking. Compared to fixed speed, temperature rise centroid control can further increase the cumulative effective desorption rate from 56% to 63%~68% and reduce the exceedance time from 2.5% to 0.1%~0.4%, proving the control effect of dynamic matching load. Removing activated carbon pretreatment can avoid occasional interference of activated carbon penetration desorption on the control signal, and the exceedance time is reduced from 1.8% to 0.1%. The synergistic effect of closed-circuit low-oxygen, temperature rise centroid control, and no activated carbon pretreatment results in significantly better outlet stability, cumulative effective desorption rate of high-boiling-point components, and equipment life than any single measure, demonstrating a significant synergistic effect.

[0071] Figure 2 The steady-state performance of each scheme was further quantitatively compared from six core dimensions. The results showed that Example 3 achieved the best values ​​in six indicators: apparent desorption rate at high boiling point (72%), average NMHC concentration at outlet (11 mg / m³), desorption power consumption index (70), percentage of time exceeding the standard (0.1%), number of safety alarms (0 times), and expected zeolite lifespan (168 months). Compared with Comparative Example 1, Example 3 improved the desorption rate by 35 percentage points, reduced energy consumption by 33%, extended lifespan by 77%, and achieved zero safety alarms and near-zero exceedances, fully verifying the synergistic effect of the "closed-loop low-oxygen + centroid control + dry filtration" combined technology, which is completely consistent with the analysis conclusions in the table above.

[0072] To further verify the dynamic reliability of the above conclusions under actual operating condition fluctuations, a 72-hour continuous operation test was conducted. During this period, 2 times, 2.5 times, and 3 times the inlet concentration shocks were applied at the 12th, 36th, and 60th hours, respectively. The results are as follows: Figure 2 As shown. By Figure 3 It can be seen that Comparative Example 1 showed peak outlet concentrations of 55, 68, and 78 mg / m³ under three impacts, exceeding the 40 mg / m³ emission limit multiple times. While Comparative Example 2 showed some improvement, it still posed a risk of exceeding the limit in the first two impacts. In contrast, Examples 1-3 consistently maintained outlet concentrations below the limit throughout the entire testing period, with peak concentrations controlled within the 12-22 mg / m³ range even under a 3x impact, demonstrating superior impact resistance. It is noteworthy that Comparative Example 3's curve exhibited brief oscillations and spikes during the impact phase, confirming the closed-loop recovery process of the aforementioned temperature rise centroid algorithm after interference. The Examples 1 and 3, through optimized control strategies, completely eliminated this phenomenon, which corroborates the data on "percentage of time exceeding the limit" in the table.

[0073] Based on the above dynamic process verification and steady-state index quantification results, a six-dimensional performance radar chart is plotted as follows: Figure 4As shown in the figure, this graph uses desorption energy consumption, outlet stability, high-boiling-point desorption rate, equipment lifespan, operational safety, and shock resistance as evaluation dimensions to intuitively reflect the comprehensive technical level of each scheme. It can be seen that the radar chart of Comparative Example 1 has a very small surface area, indicating a significant weakness; Comparative Examples 2 and 3 show improvement but are still unbalanced. The radar charts of Examples 1-3 are all close to a perfect outer circle, with Example 3 showing the most complete and regular shape, indicating that it has no weaknesses in any dimension and its overall performance is significantly superior to existing technologies. This further confirms the outstanding progress and practical value of the technical solution proposed in this invention in solving the problem of high-boiling-point VOCs purification, and also provides overall evidence for the superiority of the aforementioned individual indicators.

[0074] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for purifying VOCs using a zeolite rotary drum concentration-catalytic oxidation system, characterized in that, The method includes the following steps: The zeolite drum is rotated, and the zeolite drum is divided into an adsorption zone, a desorption zone and a cooling zone along the rotation direction. The adsorption zone treats large volumes of low-concentration organic waste gas. In a closed desorption loop consisting of a desorption zone, a cooling zone, a desorption fan, a desorption heat exchanger, an electric heater, a desorption cooler, a split mixing section, and a CO catalytic oxidation furnace, the desorbed gas is circulated, with a circulating air volume of 8% to 14% of the processing air volume. The desorbed gas is preheated by the desorption heat exchanger and supplemented by the electric heater before entering the CO catalytic oxidation furnace for catalytic oxidation. The heat released by the reaction is recovered by the desorption heat exchanger. The oxygen content in the desorption zone of the closed desorption circuit is maintained at 7%~10% to suppress the thermal oxidative polymerization and coking of high-boiling-point plasticizer components at the desorption high temperature; Multiple temperature sensors are arranged in the arc segment 20°~120° before the outlet of the adsorption zone to measure the solid phase temperature, and a reference temperature measuring point is set in the arc segment 20°~40° before the adsorption zone. The temperature rise value is calculated based on the reference temperature and the temperature at each measuring point, and the temperature rise centroid angle is determined by the weighted average of the temperature rise. Using the temperature rise centroid angle as the main controlled variable, a PI controller is used to coordinate and adjust the desorption temperature, the drum speed, and the proportion of air supply in the cooling zone, so that the adsorption mass transfer front is stabilized at the target position.

2. The VOCs purification method of a zeolite rotary drum concentration-catalytic oxidation system according to claim 1, characterized in that, In the closed desorption loop, the purified gas after the hot side outlet of the desorption heat exchanger is divided into two paths: one path, as an uncooled bypass flow, directly enters the split mixing section through the bypass regulating valve; the other path, after being cooled to 40~60℃ by water cooling in the desorption cooler, is further divided into two streams: cooling zone supply air and cooling bypass flow. The cooling zone supply air is sent to the cooling zone through the cooling zone supply air valve to purge and cool the zeolite, and the cooling zone outlet air enters the split mixing section. The cooling bypass flow directly enters the split mixing section. The three streams of gas—the uncooled bypass flow, the cooling bypass flow, and the cooling zone outlet air—converge in the split mixing section and are then sent to the desorption zone by the desorption fan.

3. The VOCs purification method of a zeolite rotary drum concentration-catalytic oxidation system according to claim 2, characterized in that, Controlling the oxygen content in the desorption zone of the closed desorption loop includes: introducing fresh air between the cold-side outlet of the heat exchanger and the inlet of the electric heater; detecting the oxygen content at the CO furnace inlet and the desorption zone outlet using a zirconia oxygen content analyzer, and using the CO furnace inlet oxygen content as the main control variable to control the opening of the fresh air supply valve in a closed loop, so that the CO furnace inlet oxygen content is controlled at 8%~11% and the desorption zone oxygen content is maintained at 7%~10%; and continuously releasing 3%~5% of the circulating gas volume after the hot-side outlet of the desorption heat exchanger to maintain a slight positive pressure of 50~200Pa in the loop.

4. The VOCs purification method of a zeolite rotary drum concentration-catalytic oxidation system according to claim 3, characterized in that, The temperature sensor is a PT100 platinum resistance thermometer, with 4 to 6 measuring points arranged along an arc of 120° to 220° absolute angle, covering a range of 20° to 120° in front of the adsorption zone outlet; the sensor probe is brought close to the zeolite end face by 0 to 2 mm under the action of the elastic clamping mechanism, the sampling period is 0.5 to 1 s, and the signal is subjected to first-order dynamic compensation.

5. The VOCs purification method of a zeolite rotary drum concentration-catalytic oxidation system according to claim 4, characterized in that, The PI controller is adjusted according to a multi-variable coordination strategy that prioritizes temperature, coordinates with rotational speed, and assists with cooling and heat dissipation: when the temperature rise centroid angle shifts towards the outlet, the desorption temperature is increased by 5~15℃, in conjunction with increasing the drum rotational speed by 10%~20% and increasing the proportion of cooling zone air supply by 5~10 percentage points; when the temperature rise centroid angle regresses towards the inlet, the adjustment is performed in the opposite direction; the PI controller parameter range is: proportional coefficient Kp = 0.5~2.0, integral time τ i =60~600s.

6. The VOCs purification method of a zeolite rotary drum concentration-catalytic oxidation system according to claim 5, characterized in that, The multivariate coordination strategy adopts priority time-sharing control of the operation: the temperature regulation loop acts first, and after the action is completed, the speed regulation is executed after an interval of 10~30s, and finally the air supply ratio of the cooling zone is adjusted.

7. The VOCs purification method of a zeolite rotary drum concentration-catalytic oxidation system according to claim 6, characterized in that, It also includes three levels of safety interlocks: Level 1 warning: When the temperature rise at any measuring point exceeds 6~8℃, the current desorption temperature setting will be automatically maintained, the drum speed will be increased by 10%, the air supply ratio of the cooling zone will be increased by 5~10 percentage points, and the oxygen content will be maintained at the current closed-loop setting without actively increasing oxygen. Second-level interlock: When the absolute temperature of any measuring point exceeds 75~85℃ or the temperature rise centroid distance from the outlet is less than 20°, the exhaust gas inlet valve is closed to 30%~50%, the speed is increased to 110%~120% of the current value, the cooling heat dissipation is increased, the upper limit of the desorption temperature is maintained, and the audible and visual alarm is triggered. Level 3 Emergency Shutdown: When the temperature exceeds 90~100℃ or the temperature rise rate exceeds 5℃ / min, immediately close the exhaust gas inlet valve and the fresh air supply valve, open the nitrogen supply valve to a nitrogen flow rate of 250~400Nm³ / h for inerting protection, disconnect the electric heater, and keep the desorption fan and cooler running.

8. The VOCs purification method of a zeolite rotary drum concentration-catalytic oxidation system according to claim 7, characterized in that, The startup sequence is as follows: Before starting the machine, first start the zeolite drum at the lowest speed, then start the desorption fan and cooler to establish a closed loop; use nitrogen pre-purification to initially reduce the oxygen content in the loop to below 15%, then start the electric heater to raise the temperature to above 280°C; introduce a small amount of exhaust gas through the bypass valve to ignite it, and control the amount of exhaust gas introduced to below 25% of the lower explosive limit; continue to purge and reduce oxygen through the nitrogen injection valve, reducing the oxygen content in the loop to the target range of 8% to 11% within 15 to 20 minutes; after the temperature stabilizes, gradually open the exhaust gas inlet valve to normal operating conditions.

9. A method for VOCs purification in a zeolite rotary drum concentration-catalytic oxidation system according to claim 8, characterized in that, During normal shutdown: First, close the exhaust gas inlet valve. The electric heater maintains a certain power to keep the CO furnace temperature no lower than 300℃ for scavenging. After the desorption zone temperature drops below 120℃ and the VOCs concentration in the desorbed gas is less than 20% of the concentration of the inlet exhaust gas under normal operating conditions, gradually reduce the electric heating power.

10. A method for purifying VOCs in a zeolite rotary drum concentration-catalytic oxidation system according to claim 9, characterized in that, In the method described, the inlet temperature of the carrier gas in the desorption zone is controlled at 175~200℃, and the outlet gas temperature in the desorption zone is 155~180℃. After preheating by the heat exchanger, the temperature rises to 240~270℃, and then is further heated to 305~325℃ by the electric heater before entering the CO furnace. The temperature inside the CO furnace rises to 350~400℃, and the hot side outlet temperature of the desorption heat exchanger is 270~290℃. Furthermore, the exhaust gas undergoes a four-stage dry filtration pretreatment process, consisting of a G4 primary filter, an F7 medium-efficiency filter, a dry demisting filter, and an F9 sub-high-efficiency filter, without the installation of an activated carbon filter layer.

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