A wood-plastic floor pelletizing exhaust gas comprehensive treatment device and a treatment method thereof

Abstract

This invention relates to the field of waste gas treatment technology, specifically to a comprehensive waste gas treatment device and method for wood-plastic flooring granulation, comprising a condenser, an waste gas inlet pipe on one side of the condenser, and an air distribution valve assembly on the waste gas inlet pipe, through which waste gas enters the condenser for condensation and cooling; the outlet of the condenser is connected to an electrostatic precipitator, and the outlet of the electrostatic precipitator is connected to a spray scrubbing tower; multiple spray layers are arranged along the height direction inside the spray scrubbing tower, each spray layer including a sprayer and a coarse filter plate. Compared with the prior art, this application, by setting up a front-end combination of a condenser, an electrostatic precipitator, and a multi-stage spray / coarse filter plate, achieves graded removal of condensable wax and submicron oil mist, significantly reducing the mist load entering the wet scrubbing and adsorption sections, and inhibiting nozzle scaling, tower entrainment, and waxing on the activated carbon surface.

Description

Technical Field

[0001] This invention relates to the field of wood-plastic composite flooring granulation technology, and in particular to a comprehensive treatment device and method for waste gas from wood-plastic composite flooring granulation. Background Technology

[0002] Wood-plastic composite (WPC) flooring is a composite material made by mixing wood fibers or wood powder into plastic. Its production process typically includes melt extrusion and granulation. During the granulation process, waste gas containing oil fumes and volatile organic compounds (VOCs) is generated. This waste gas not only contains oil mist and waxy fumes released from heating the plastic and wood components, but may also carry fine wood powder particles and VOCs. If directly emitted without effective treatment, it will cause air pollution and deterioration of the workshop environment.

[0003] In existing technologies, waste gas from wood granulation generally contains condensable wax, oil mist, and various forms of VOCs. However, conventional series systems using "spraying + activated carbon" are prone to insufficient mist interception at the front end, scaling of nozzles and packings, and entrainment of VOCs under high-temperature, waxy conditions. Once in the adsorption section, the carbon layer surface becomes waxy and rapidly degrades, leading to frequent replacements and sudden increases in pressure drop. Furthermore, for regeneration after adsorption saturation, most solutions employ external heating for purging or send the desorbed gas to a catalytic combustion / regenerative oxidation unit for treatment. This results in high regeneration energy consumption, the need for secondary treatment of the exhaust gas, and the failure to recover heat. For example, the activated carbon adsorption and regeneration device for waste gas treatment in Chinese patent literature (CN205700032U) focuses on using steam or... The system regenerates activated carbon with hot gas and treats steam via a heat exchanger, but still requires an external heat source and does not recover the exothermic reaction from catalytic oxidation to the preheated desorbed gas in a closed loop, resulting in insufficient energy utilization. Other solutions, such as the VOCs adsorption-concentration-catalytic combustion treatment process in Chinese patent document CN117160187A, adopt a regeneration path of "adsorption-concentration-catalytic combustion," with the desorbed gas or activated carbon being sent to the catalytic combustion unit. However, the desorbed gas has weak heat coupling with the main process, and there is insufficient consideration for the stability of the front-end load containing wax and oil mist and energy recovery. This makes it difficult to adapt to the wax mist characteristics and energy efficiency requirements of wood-plastic flooring granulation. Therefore, this application discloses a comprehensive treatment device and method for waste gas from wood-plastic flooring granulation. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose a comprehensive treatment device and method for exhaust gas from wood-plastic composite flooring granulation, in order to solve the problems in the existing wood-plastic composite exhaust gas treatment, such as insufficient front-end mist interception and load stability of the "spray + activated carbon" series scheme, which leads to scaling and waxing of spray / adsorption, sudden increase in pressure drop; regeneration relies on external heating and exhaust gas requires secondary treatment, heat release is difficult to recover, overall energy efficiency is low and it is not suitable for waxy and oily mist conditions.

[0005] Based on the above objectives, the present invention provides a comprehensive treatment device for waste gas from wood-plastic flooring granulation, comprising: a condenser, wherein a waste gas inlet pipe is provided on one side of the condenser, and an air distribution valve group is provided on the waste gas inlet pipe, wherein the waste gas enters the condenser through the waste gas inlet pipe for condensation and cooling;

[0006] The outlet of the condenser is connected to an electrostatic precipitator, and the outlet of the electrostatic precipitator is connected to a spray scrubbing tower. The spray scrubbing tower has multiple spray layers arranged along the height direction inside. Each spray layer includes a sprayer and a coarse filter plate. A circulation pump is connected to one side of the spray scrubbing tower. All the sprayers are connected to the circulation pump to supply circulating scrubbing liquid.

[0007] The spray scrubbing tower outlet is equipped with a variable frequency centrifugal fan, which is connected to an activated carbon adsorption box. The activated carbon adsorption box has a baffle at the air inlet and filter cotton plates on both sides. The outlet of the activated carbon adsorption box is connected to an exhaust pipe for discharging purified gas.

[0008] One side of the activated carbon adsorption box is equipped with a regeneration desorption gas circuit, which is connected in sequence to a heat exchanger and a low-temperature catalytic oxidation device.

[0009] Preferably, the desorbed gas is drawn from the bottom of the activated carbon adsorption box and first enters the cold side channel of the heat exchanger, where it is preheated by countercurrent heat exchange with the high-temperature purified gas from the low-temperature catalytic oxidation device. The preheated desorbed gas then enters the low-temperature catalytic oxidation device for oxidative decomposition. The high-temperature gas generated by the oxidative decomposition returns to the hot side channel of the heat exchanger to release heat, which is used to preheat the cold desorbed gas of the next cycle. The cooled regenerated gas returns to the activated carbon adsorption box to regenerate the next carbon layer.

[0010] Preferably, the low-temperature catalytic oxidation device is equipped with a porous ceramic catalyst carrier, which can complete the oxidation and decomposition reaction of VOCs at a temperature not exceeding 260°C. The heat exchanger is a shell-and-tube or plate structure, installed on one side of the activated carbon adsorption box, and forms a closed-loop path for the desorption gas between it and the low-temperature catalytic oxidation device.

[0011] Preferably, the filter cotton plate is provided with a differential pressure detection interface to monitor its blockage status; the baffle divides the air inlet end into a buffer chamber to evenly distribute the air velocity.

[0012] Preferably, the activated carbon adsorption box is provided with several inclined guide flaps on both sides. The guide flaps are closed by default and deflect and open when impacted by airflow. The variable frequency centrifugal fan and the air distribution valve group constitute a coordinated control system to achieve stable negative pressure in the system.

[0013] Preferably, the bottom of the condenser is connected to a condensed oil and wax recovery tank for collecting the condensed oil and wax.

[0014] This invention also discloses a method for treating waste gas from wood-plastic composite flooring granulation, applied to the aforementioned comprehensive waste gas treatment device for wood-plastic composite flooring granulation, comprising the following steps:

[0015] S1. Granulation exhaust gas enters the condenser through the exhaust gas inlet pipe for cooling and oil wax precipitation. The condensate flows into the condensed oil wax recovery tank, and its outlet passes through the electrostatic precipitator and spray scrubbing tower for mist droplet and VOCs pretreatment.

[0016] S2. The gas is drawn to the activated carbon adsorption box for deep purification by a variable frequency centrifugal fan, and then discharged through the exhaust pipe.

[0017] S3. After the activated carbon adsorption is saturated, the desorbed gas is drawn out from the bottom of the activated carbon adsorption box, first enters the heat exchanger to be preheated, and then enters the low temperature catalytic oxidation device for oxidation and decomposition. The high temperature gas after oxidation returns to the heat exchanger to release heat to preheat the cold desorbed gas of the next cycle. The treated regenerated gas flows back to the top of the activated carbon adsorption box to complete the regeneration closed loop.

[0018] S4. By adjusting the speed of the variable frequency centrifugal fan and the opening of the air distribution valve group, the system pressure is kept stable. The pressure difference on both sides of the filter cotton plate is monitored to determine whether the filter cotton plate is blocked, thereby triggering the maintenance operation of replacing the filter cotton plate.

[0019] Preferably, in the regeneration-heat exchange process of step S3, the high-temperature gas at the outlet of the low-temperature catalytic oxidation unit exchanges heat countercurrently with the cold desorption gas entering the heat exchanger, and the heat exchange capacity of a single cycle meets the requirements.

[0020] Q = m·c_p·(T_out) T_in),

[0021] Where Q is the heat of a single cycle, m is the mass flow rate of the desorbed gas, c_p is the specific heat capacity at constant pressure, and T_out and T_in are the temperatures of the outlet gas and the cold desorbed gas entering the heat exchanger of the low-temperature catalytic oxidation device, respectively. After heat exchange in the heat exchanger, the oxidized regenerated gas returns to the upper part of the activated carbon adsorption box or the regeneration inlet to complete the closed loop of the desorbed gas and use the released heat for preheating the next cycle.

[0022] Preferably, in step S2, the filter cotton plate and baffle on the air inlet side of the activated carbon adsorption box perform mist interception, flow stabilization and uniform distribution treatment on the airflow to keep the apparent velocity entering the carbon layer within a set range; when the pressure difference on both sides of the filter cotton plate reaches the threshold, the controller links the variable frequency centrifugal fan and the air distribution valve group to reduce the local wind speed and issue an instruction to replace or advance the filter material, thereby inhibiting fine mist and dust from entering the carbon layer and maintaining the long-term stability of adsorption efficiency and pressure drop.

[0023] Preferably, in step S3, the operating temperature of the low-temperature catalytic oxidation device is maintained within the activity window of the selected low-temperature catalyst, and the catalytic oxidation rate of volatile organic compounds satisfies k=A·e^{-E / (R·T)}, where E is the activation energy, R is the gas constant, and T is the absolute temperature. By selecting the catalyst and managing the bed thermal management, the equivalent E is reduced and T is stabilized, so that the heat released at the outlet of the low-temperature catalytic oxidation device can be recovered in the heat exchanger in a countercurrent manner and used for preheating of the desorption gas, thereby shortening the regeneration cycle, reducing energy consumption, and reducing the thermal shock to the adsorbed phase of the activated carbon adsorption box.

[0024] The beneficial effects of this invention are:

[0025] This comprehensive waste gas treatment device and method for wood-plastic flooring granulation utilizes a front-end combination of a condenser, an electrostatic precipitator, and a multi-stage spray / coarse filter plate to achieve graded removal of condensable wax and submicron oil mist. This significantly reduces the mist load entering the wet washing and adsorption sections, inhibiting nozzle scaling, tower entrainment, and wax formation on the activated carbon surface. Under the same operating conditions, the face velocity entering the adsorption box is more stable, the mist content is lower, the carbon bed pressure drop rises more slowly, the activated carbon replacement cycle is extended, and the overall line maintenance frequency decreases. Simultaneously, the condensate phase is centrally collected in a recovery tank, balancing resource utilization and reducing secondary pollution, achieving synergistic effects of "source load reduction—process steady state—end polishing".

[0026] By setting up a closed regeneration loop of "activated carbon adsorption box - heat exchanger - low temperature catalytic oxidation device - heat exchanger - activated carbon adsorption box", the system achieves on-site harmless treatment and exothermic recovery of the desorbed gas: the exothermic gas from catalytic oxidation is recovered countercurrently by the heat exchanger and used to preheat the desorbed gas in the next cycle, significantly reducing the need for external heating, compressing the regeneration time, and eliminating the need for external discharge of regeneration tail gas, thus avoiding secondary treatment; under the dual closed-loop effect of energy and materials, the regeneration temperature is more uniform, the thermal shock of the carbon layer is smaller, the adsorption performance is more fully restored, and the energy consumption, fluctuations and risks of long-term system operation are reduced simultaneously.

[0027] By setting up a rectification-filtration-differential pressure linkage chain, including filter cotton differential pressure monitoring, baffle buffering and uniform distribution, passive airflow guidance with guide flaps, and coordinated control of variable frequency centrifugal fans and adaptive valve groups, the airflow entering the carbon layer achieves "mist interception-flow stabilization-uniform distribution": the apparent surface wind speed is locked within the design window, short-circuit flow and corner cold zones are suppressed, the breakthrough curve is smoother, and the pressure drop curve is healthier; when the differential pressure approaches the threshold, the speed and filter material are adjusted as needed, changing maintenance from experience-based to quantitative triggering, which avoids penetrating the contaminated carbon layer and does not cause excessive airflow restriction and increased energy consumption, ultimately achieving low energy consumption, low wear, and long-term stable emission compliance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2This is a schematic diagram of the planar structure of the activated carbon adsorption box of the present invention;

[0030] Figure 3 This is a schematic diagram of the internal structure of the activated carbon adsorption box of the present invention;

[0031] Figure 4 This is a schematic diagram of the front structure of the activated carbon adsorption box of the present invention;

[0032] Figure 5 This is a top-view cross-sectional structural diagram of the activated carbon adsorption box of the present invention;

[0033] Figure 6 This is a schematic diagram of the system flow of the present invention;

[0034] Figure 7 This is a block diagram of the energy flow in the regeneration-heat exchange process of the present invention;

[0035] Figure 8 This is a block diagram of the intelligent maintenance control system of the present invention;

[0036] Figure 9 This is a block diagram for optimizing the control of catalytic oxidation temperature in this invention.

[0037] The diagram is marked as follows:

[0038] 1. Condenser; 2. Electrostatic precipitator; 3. Condensed oil and wax recovery tank; 4. Exhaust gas inlet pipe; 5. Air distribution valve assembly; 6. Spray scrubbing tower; 7. Circulating pump; 8. Coarse filter plate; 9. Sprayer; 10. Variable frequency centrifugal fan; 11. Activated carbon adsorption box; 12. Baffle; 13. Discharge pipe; 14. Low temperature catalytic oxidation device; 15. Heat exchanger; 16. Filter cotton plate; 17. Guide hinge. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0040] like Figures 1 to 9As shown, the comprehensive waste gas treatment device for wood-plastic flooring granulation includes a condenser 1. A waste gas inlet pipe 4 is installed on one side of the condenser 1, and an air distribution valve group 5 is installed on the waste gas inlet pipe 4. The waste gas enters the condenser 1 through the waste gas inlet pipe 4 for condensation and cooling. The outlet of the condenser 1 is connected to an electrostatic precipitator 2, and the outlet of the electrostatic precipitator 2 is connected to a spray scrubbing tower 6. Multiple spray layers are arranged along the height direction inside the spray scrubbing tower 6. Each spray layer includes a sprayer 9 and a coarse filter plate 8. A circulating pump 7 is connected to one side of the spray scrubbing tower 6, and all sprayers 9 are connected to the circulating pump 7 for power supply. The washing liquid is circulated; a variable frequency centrifugal fan 10 is installed at the outlet of the spray washing tower 6, and the variable frequency centrifugal fan 10 is connected to the activated carbon adsorption box 11. The air inlet of the activated carbon adsorption box 11 is equipped with a baffle 12, and filter cotton plates 16 are installed on both sides of the activated carbon adsorption box 11; the outlet of the activated carbon adsorption box 11 is connected to the discharge pipe 13 for discharging purified gas; a regeneration desorption gas circuit is provided on one side of the activated carbon adsorption box 11, which is connected in sequence to the heat exchanger 15 and the low temperature catalytic oxidation device 14, wherein the bottom of the condenser 1 is equipped with a condensed oil and wax recovery tank 3 for collecting the condensed oil and wax;

[0041] The high-temperature waxy waste gas generated at the granulation station first enters the system through the inlet pipe. Under the linkage of the air distribution valve group 5 and the terminal variable frequency centrifugal fan 10, a stable negative pressure and a suitable instantaneous air volume are formed. It then enters the condenser 1 and is rapidly cooled. The wax oil and condensable substances in the airflow precipitate out and settle into the recovery tank for resource recovery, reducing the oil pollution load of subsequent units from the source. The gas then enters the electrostatic precipitator 2. The submicron oil mist that is still difficult to intercept after condensation is agglomerated and collected under the action of a strong electric field, which significantly reduces the impact of oil mist penetration on the spray tower and activated carbon section, making subsequent units less prone to scaling and clogging. The pretreated gas is introduced into the spray scrubbing tower 6, where it comes into full contact with the circulating liquid in the uniform droplet curtain formed by the layered sprayers 9. The coarse filter plate 8 receives and redistributes the liquid flow below each sprayer 9, while trapping entrained liquid and larger particles, resulting in more thorough gas-liquid contact, lower entrainment, and easier control of the liquid-to-gas ratio. The gas is further cooled within the tower, removing water-soluble / polar contaminants, and exits from the top of the tower with lower dust and mist content and a lower temperature. The variable frequency centrifugal fan 10 automatically adjusts its speed based on the pipeline pressure difference and set airflow, ensuring the apparent wind speed window for subsequent adsorption sections while avoiding excessive suction that would increase energy consumption. The variable frequency centrifugal fan 10 delivers the airflow into the activated carbon adsorption box 11. The gas is first stabilized and then evenly distributed in the buffer zone formed by the inlet baffle 12, and then further removed by the filter cotton plates 16 on both sides before entering the carbon layer for "polishing" and adsorption. The uniform flow of the activated carbon layer results in less short-circuiting and a slower pressure drop, extending the activated carbon replacement cycle. The purified gas is discharged in an organized manner through the discharge pipe 13, meeting emission standards. When the activated carbon reaches the set saturation threshold, the system switches to regeneration mode (online TVOC / hydrocarbon monitoring points are set at the discharge pipe or carbon box outlet; when the outlet concentration reaches the set threshold (e.g., ≤5–10 mg / m³) and gradually increases, it is determined that the activated carbon layer has broken through and is approaching saturation. The system sends a signal and automatically switches to the regeneration loop): the desorbed gas drawn from the bottom of the activated carbon adsorption box 11 first enters the heat exchanger 15 for preheating, and then enters the low-temperature catalytic oxidation device 14 for on-site harmless treatment into regeneration gas containing carbon dioxide and water, while releasing the heat of reaction. The regenerated gas flows back into heat exchanger 15 and exchanges heat countercurrently with the next batch of cold desorption gas, transferring the exothermic gas into the preheating power for the next cycle. The regenerated gas finally flows back to the regeneration inlet or upper part of the activated carbon adsorption box 11 to complete the closed-loop circulation. This avoids the secondary treatment problems caused by the external discharge of regeneration tail gas and significantly reduces the external heating and regeneration time, realizing the energy closed loop of "desorption - catalytic harmlessness - waste heat recovery". In the whole process, the air distribution valve group 5 and the variable frequency centrifugal fan 10 are coordinated and adjusted with pressure difference and air volume as feedback targets, so that each unit of the main channel is always within a suitable air velocity and negative pressure range. With the pressure difference monitoring of the filter cotton plate 16, maintenance and early warning are carried out. The overall effect is high removal rate, low energy consumption, less maintenance and long-term stable compliance.

[0042] like Figures 1 to 5As shown, the desorbed gas is drawn from the bottom of the activated carbon adsorption box 11 and first enters the cold side channel of the heat exchanger 15, where it is preheated by countercurrent heat exchange with the high-temperature purified gas from the low-temperature catalytic oxidation device 14. The preheated desorbed gas then enters the low-temperature catalytic oxidation device 14 for oxidation and decomposition. The high-temperature gas generated by oxidation and decomposition returns to the hot side channel of the heat exchanger 15 to release heat, which is used to preheat the cold desorbed gas of the next cycle. The cooled regenerated gas returns to the activated carbon adsorption box 11 to regenerate the next carbon layer. The low-temperature catalytic oxidation device 14 is equipped with a porous ceramic catalyst carrier, which can complete the oxidation and decomposition reaction of VOCs at a temperature not exceeding 260°C. The heat exchanger 15 is a shell-and-tube or plate structure, installed on one side of the activated carbon adsorption box 11, and forms a closed-loop path for the desorbed gas with the low-temperature catalytic oxidation device 14.

[0043] After the activated carbon adsorption box 11 has been running for a period of time, the carbon layer gradually becomes saturated, and the control system switches to regeneration mode. The desorbed gas is first drawn from the bottom of the activated carbon adsorption box 11, carrying a certain amount of desorbed VOCs and some water vapor. The desorbed gas first enters the cold side channel of the heat exchanger 15, and then enters the low-temperature catalytic oxidation device 14. The device is filled with a porous ceramic catalyst support with a high specific surface area. When the gas passes through the catalytic bed, the desorbed organic components are rapidly oxidized into carbon dioxide and water on the catalyst surface, releasing a large amount of heat energy. This reaction only needs to be controlled below 260℃ (preferably 180-240℃) to complete, thus avoiding the problem of high-temperature heating required by traditional catalytic combustion, reducing energy consumption and improving safety. The gas after catalytic oxidation is converted into a high-temperature harmless gas (regenerated gas), which has a stable temperature and clean composition, making it suitable as a heat exchange medium. Subsequently, the regenerated gas flows back to the heat exchanger 15, where it undergoes countercurrent heat exchange with the cold desorption gas entering the next cycle. The regenerated gas transfers its heat energy to the cold desorption gas that is about to enter the low-temperature catalytic oxidation unit 14, achieving self-sufficient preheating. Through this process, the system directly recovers and utilizes the exothermic reaction, realizing "on-site energy circulation," so that the heat source required for regeneration comes from its own reaction, no longer relying on external heating equipment. After heat exchange, the temperature of the regenerated gas gradually decreases to a safe range and flows back to the upper part of the activated carbon adsorption box 11 or the regeneration inlet through an insulated pipe, re-merging with the gas flow field in the carbon layer. This maintains a stable and uniform regeneration temperature and ensures that the gas circulation is closed within the system, eliminating the need for exhaust gas and preventing secondary pollution. The entire cycle is conducted at low temperatures. The heat released from the oxidation reaction is transferred to the cold desorption gas via heat exchanger 15, ensuring energy recovery and preventing localized overheating. During continuous operation, the activated carbon layer, under the action of the regeneration gas, causes the adsorbed VOCs molecules to gradually detach from the activated carbon micropores, forming a high-concentration desorption gas. The activated carbon pores reopen, and its adsorption performance is restored. The system does not require shutdown to replace the carbon material; on-site regeneration can be completed simply by automatically switching to the regeneration loop. The entire process is energy-efficient, has a fast response time, and the regeneration tail gas requires no secondary treatment, achieving the triple goals of desorption gas harmlessness, heat recovery, and carbon layer regeneration.

[0044] It is worth noting that CO2 and H2O do not circulate infinitely in a completely closed, rigid circuit. Instead, they are naturally carried out with the slight "system air leakage" in the adsorption box. In fact, during the operation of the adsorption box, there is a natural small amount of fresh air replacement caused by the variable frequency fan's suction, and an unavoidable trace of gas release from the carbon bed pores. The CO2 / H2O carried in the clean main airflow normally discharged from the exhaust pipe (these come from the original exhaust gas, scrubbing tower, and humid air) will all be naturally discharged from the system along with the main exhaust gas (at extremely low concentrations, compliant and pollution-free). Therefore, there will be no "accumulation and overflow" situation. And with typical wood pellets... Taking VOCs intensity as an example, the amount of desorbed gas is much lower than the main air volume, and the amount of VOCs adsorbed in the carbon layer is limited. In the regeneration circuit, these products only exist as dilution carrier gas and will not have an adverse effect on pressure, oxidation reaction, heat balance, or adsorption and regeneration efficiency. Furthermore, when the desorbed gas switches between regeneration mode and adsorption mode, it will exchange with the main gas flow field. When regeneration ends and the system switches back to adsorption mode, the CO2 and H2O contained in the regeneration circuit will be carried into the main adsorption process by negative pressure suction, or discharged together with the clean exhaust gas after passing through activated carbon, thereby avoiding the secondary treatment problem caused by the external discharge of regeneration tail gas.

[0045] like Figures 1 to 5 As shown, the filter cotton plate 16 is equipped with a differential pressure detection interface to monitor its blockage status; the baffle 12 divides the air inlet into a buffer chamber to evenly distribute the air velocity; both sides of the activated carbon adsorption box 11 are provided with several inclined guide flaps 17, which are closed by default and deflect and open when impacted by airflow; the variable frequency centrifugal fan 10 and the air distribution valve group 5 constitute a coordinated control system to achieve stable negative pressure in the system;

[0046] After pretreatment, the airflow containing mist and powder enters the inlet of the activated carbon adsorption box 11 under controlled negative pressure under the coordinated control of the variable frequency centrifugal fan 10 and the air distribution valve group 5. First, it completes momentum diffusion and flow field shaping through the buffer chamber formed by the baffle 12. After the inlet jet is "pulse-free" and "peak-free", the cross-sectional air velocity becomes more uniform. Then, the airflow crosses the filter cotton plates 16 arranged on both sides. The residual fine mist and fine powder are effectively intercepted and form real-time "blockage fingerprints" at the upstream and downstream pressure difference sensor ports. When the pressure difference approaches the threshold, the control system issues a maintenance warning on the one hand, and adjusts the speed of the variable frequency centrifugal fan 10 and slightly reduces the opening of the air distribution valve group 5 on the other hand. This avoids local penetration of the carbon bed and prevents the system from fluctuating due to excessive air restriction. The airflow continues to move forward into the windward side of the carbon layer. At this time, if the flow rate in some corners or near the wall is still low, the inclined guide hinges 17 are passively opened on the high-velocity side to guide part of the airflow. By shifting to the low-speed zone to fill the "cold zone," the surface velocity and residence time of the carbon layer become more consistent across the cross-section, ultimately achieving "polished" adsorption of trace VOCs and completing purification output with lower entrainment and a slower pressure drop growth rate. In this continuous process, the baffle 12 significantly reduces inlet momentum scouring, reducing dust re-entrainment and carbon particle erosion caused by local high shear. The filter cotton plate 16 stably intercepts unavoidable fine mist and powder and drives "on-demand maintenance" with pressure difference as a signal. The guide hinge 17 continuously corrects the uneven cross-sectional flow through passive adaptive means. The variable frequency centrifugal fan 10 and the air distribution valve group 5 maintain the negative pressure of the main pipeline and the synchronous convergence of the distribution air volume target. The whole set of actions ensures that the air velocity entering the carbon bed is within the design window, resulting in more complete adsorption, more controllable penetration, and more on-demand energy consumption. This leads to an extended activated carbon service life, a smoother pressure drop steady state, smaller fluctuations in purification efficiency, and long-term compliance.

[0047] like Figures 1 to 9 As shown, a method for treating waste gas from wood-plastic composite flooring granulation, applied to the aforementioned comprehensive waste gas treatment device for wood-plastic composite flooring granulation, includes the following steps:

[0048] S1. Granulation exhaust gas enters condenser 1 through exhaust gas inlet pipe 4 for cooling and oil wax precipitation. The condensate flows into condensed oil wax recovery tank 3, and its outlet passes through electrostatic precipitator 2 and spray scrubbing tower 6 for mist droplet and VOCs pretreatment.

[0049] S2. The gas is drawn to the activated carbon adsorption box 11 for deep purification by the variable frequency centrifugal fan 10, and then discharged through the discharge pipe 13.

[0050] S3. After the activated carbon adsorption is saturated, the desorbed gas is drawn out from the bottom of the activated carbon adsorption box 11, first enters the heat exchanger 15 to be preheated, and then enters the low temperature catalytic oxidation device 14 for oxidation and decomposition. The high temperature gas after oxidation returns to the heat exchanger 15 to release heat to preheat the cold desorbed gas of the next cycle. The treated regenerated gas flows back to the top of the activated carbon adsorption box 11 to complete the regeneration closed loop.

[0051] S4. By adjusting the speed of the variable frequency centrifugal fan 10 and the opening of the air distribution valve group 5, the pressure in the system is kept stable. The pressure difference on both sides of the filter cotton plate 16 is monitored to determine whether the filter cotton plate 16 is blocked, thereby triggering the maintenance operation of replacing the filter cotton plate 16.

[0052] Compared to existing technologies, by installing a condenser 1 and an electrostatic precipitator 2 at the front end, condensable wax and fine oil mist are effectively removed before entering the spray tower, avoiding clogging and scaling problems caused by high-temperature waxy waste gas directly entering the wet scrubbing or adsorption section, and significantly extending the service life of downstream equipment. The combination structure of the multi-stage spraying and coarse filter plate 8 in the spray scrubbing tower improves the gas-liquid contact efficiency, achieving full absorption of acidic and polar pollutants. Compared with traditional activated carbon adsorption, this method adds a filter cotton plate 16 and a flow stabilizing baffle 12 to the adsorption section, making the airflow into the carbon layer more uniform and preventing short circuits. The design of the regeneration stage is particularly innovative, with the desorbed gas first entering the heat exchanger 15 for preheating, and then entering the low-temperature catalytic oxidation device 14 to achieve on-site harmless treatment of VOCs. The heat released by oxidation is used in the heat exchanger 15 to preheat the desorbed gas for the next cycle, forming an energy closed loop and reducing external heating energy consumption and secondary pollution. The variable frequency centrifugal fan 10 and the air distribution valve group 5 work together to regulate the system pressure and flow, so that the whole process operates in the negative pressure and optimal wind speed zone, thereby achieving low energy consumption, high removal rate, and long-term stable operation. The overall treatment efficiency and reliability are better than those of traditional series systems.

[0053] like Figure 1 , Figures 6 to 9 As shown, in the regeneration-heat exchange process of step S3, the high-temperature gas at the outlet of the low-temperature catalytic oxidation unit 14 and the cold desorption gas entering the heat exchanger 15 undergo countercurrent heat exchange, and the single-cycle heat exchange satisfies:

[0054] Q = m·c_p·(T_out) T_in);

[0055] Where Q is the heat of a single cycle, m is the mass flow rate of the desorbed gas, c_p is the specific heat capacity at constant pressure, and T_out and T_in are the temperatures of the outlet gas of the low-temperature catalytic oxidation device 14 and the cold desorbed gas entering the heat exchanger 15, respectively. After heat exchange in the heat exchanger 15, the oxidized regenerated gas returns to the upper part of the activated carbon adsorption box 11 or the regeneration inlet to complete the closed loop of the desorbed gas and use the released heat for preheating the next cycle.

[0056] Based on the premise of single-cycle equilibrium with energy conservation: the amount of desorbed gas remains basically stable within this cycle, the pressure drop does not cause a significant enthalpy change, c_p is approximately constant within the operating temperature range, and no phase change occurs or is negligible within heat exchanger 15. Accordingly, Q = m·c_p·(T_out) can be used. T_in represents the heat gained by the heated side (cold desorption gas) after passing through heat exchanger 15. The interpolation condition of this formula is steady state, constant pressure, single channel (or single) heat exchange, and the inlet / outlet temperature of the desorption gas side is used as a parameter. In the same cycle, the high-temperature oxidizing gas from the low-temperature catalytic oxidation unit 14 will lose an equal amount of heat (ignoring heat dissipation and shell-side loss). Therefore, paired temperature measurement points can be set in the control: T_hot,in (outlet of low-temperature catalytic oxidation unit 14), T_hot,out (after heat exchanger 15 back to activated carbon adsorption box 11), T_cold,in (activated carbon adsorption box 11 → before heat exchanger 15), T_cold,out (heat exchanger 15 → before low-temperature catalytic oxidation unit 14). Combined with mass flow rate m and c_p, Q is estimated online and compared with the target regeneration heat required Q_set. The working temperature of the catalytic bed and the effective heat exchange capacity of heat exchanger 15 are dynamically adjusted (e.g., by switching heat exchange channels or adjusting relevant valves) so that the actual heat exchange Q approaches the set regeneration requirement Q_set.

[0057] In application, the calculation of Q can be used directly as a criterion for "whether the preheating requirement of the heat exchanger is met", or it can be used to derive the effectiveness of heat exchanger 15 for comparative evaluation. The heat capacity C is defined as C = m·c_p. If the heat exchanger gas is taken as the C_min side, then the theoretical limit is Q_max = C_min·(T_hot,in) T_cold,in); with ε=Q / Q_max representing effectiveness, the closer ε is to one, the more fully the driving force (temperature difference) of countercurrent heat exchange is utilized. Under the same boundary conditions, the countercurrent type has a higher ε than the cocurrent type and can obtain a smaller "close temperature difference" (the temperature difference between T_hot,out and T_cold,in). This is particularly critical in low-temperature regeneration scenarios: the desorbed gas can reach the set regeneration target temperature T_target without additional heating, thereby maximizing the recovery of the heat released by the low-temperature catalytic oxidation device 14 to the next cycle. If the online measured ε or T_cold,out is lower than the target, the bed temperature of the low-temperature catalytic oxidation device 14 can be temporarily increased or the residence time can be slightly increased. If ε is sufficient but T_hot,out is still too high, it indicates that there is usable residual heat. The system can further reduce the setting of the low-temperature catalytic oxidation device 14 or introduce the residual heat into other low-level heat-using branches.

[0058] When comparing with baseline schemes, a common approach is "external heating of desorbed gas → exhaust gas discharge or alternative treatment." In contrast, this approach directly transfers the heat released from the on-site oxidation of the low-temperature catalytic oxidation unit 14 to the cold desorbed gas via heat exchanger 15, which is equivalent to "internalizing" the external heating load. This ensures that Q mainly comes from the system itself, thus coupling the heat source of the regeneration process and pollutant removal into the same closed loop and avoiding the secondary treatment burden of exhaust gas discharge. From an energy consumption perspective, if the external heat required per unit of desorbed gas under the same operating conditions is denoted as q_ext,base, this scheme aims to reduce q_ext to q_ext. The relative index q_ext,base can be used to quantify energy savings in engineering assessments.

[0059] In terms of process outcome, the high-temperature oxidizing gas releases heat through heat exchanger 15 and its temperature drops to T_hot,out, with the returned regeneration reflux already in a temperature range of "safety without thermal shock". The cold desorption gas absorbs heat through heat exchanger 15 and rises to T_cold,out≈T_target. When it enters the low-temperature catalytic oxidation device 14, it has sufficient desorption driving force without overheating, thus ensuring that the desorption rate and catalytic oxidation rate match in the next small cycle. The heat balance reaches a quasi-steady state in the average sense of multiple cycles. The final state is: the outlet of the low-temperature catalytic oxidation device 14 and the temperature patterns on both sides of the heat exchanger 15 maintain a positive temperature difference distribution in the counterflow along the length direction. The carbon layer in the activated carbon adsorption box 11 undergoes uniform and mild thermal regeneration. The desorbed substances are oxidized into CO2 and H2O in the low-temperature catalytic oxidation device 14. The gas circulates in a closed loop inside the system with no external discharge, minimal external heating, and low-temperature operation. The system maintains the target state of "energy closed loop - pollution closed loop - pressure stability" for a long time.

[0060] In step S2, the filter cotton plate 16 and baffle 12 on the air inlet side of the activated carbon adsorption box 11 perform mist interception, flow stabilization and uniform distribution treatment on the airflow to keep the apparent velocity entering the carbon layer within the set range. When the pressure difference between the two sides of the filter cotton plate 16 reaches the threshold, the controller links the variable frequency centrifugal fan 10 and the air distribution valve group 5 to reduce the local wind speed and issue a command to replace or advance the filter material, thereby inhibiting fine mist and dust from entering the carbon layer and maintaining the long-term stability of adsorption efficiency and pressure drop.

[0061] The baffle 12 at the inlet first diffuses the high-speed incoming flow into a low-turbulence buffer flow field, smoothing the momentum peak and reducing the cross-sectional velocity variance, so that when the droplets and fine powder pass through the filter cotton plate 16, they are stably intercepted and do not undergo early secondary entrainment. The system arranges pressure difference ports upstream and downstream of the filter cotton plate 16, using the pressure difference as a joint proxy of the degree of blockage and the apparent surface wind speed. Under normal pressure, low Mach, and approximately constant density conditions, the pressure difference increases monotonically with the increase of dust load and surface wind speed. The controller compares the pressure difference with the set threshold in real time and combines their rise rate to prioritize maintaining the apparent wind speed entering the carbon layer within the design window: when the pressure difference approaches the threshold, the speed of the variable frequency centrifugal fan 10 is first reduced and the flow is slightly reduced. The air distribution valve group opens to 5 degrees to reduce local wind speed and alleviate filter bed load; if the pressure difference continues to rise or there are signs of penetration, an instruction to advance or replace the filter material is issued, so that the equivalent resistance steps back to the healthy zone and restores uniform flow. This changes the judgment of "whether to maintain" from experience to quantitative triggering. The result of the whole link is that the airflow entering the carbon layer is more uniform, the mist and powder content is lower, the apparent wind speed and residence time are matched, the mass transfer zone of the adsorption front remains stable, the carbon bed pressure drop increases more slowly, the breakthrough curve is smoother, the activated carbon replacement cycle is extended, and the total energy consumption of the system does not increase excessively due to on-demand speed adjustment and on-demand distribution. Long-term operation is maintained in a state of low fluctuation, low wear and stable compliance.

[0062] In step S3, the operating temperature of the low-temperature catalytic oxidation device 14 is maintained within the activity window of the selected low-temperature catalyst. The catalytic oxidation rate of volatile organic compounds satisfies k=A·e^{-E / (R·T)}, where E is the activation energy, R is the gas constant, and T is the absolute temperature. By selecting the catalyst and managing the bed thermally, the equivalent E is reduced and T is stabilized, so that the heat released from the outlet of the low-temperature catalytic oxidation device 14 can be recovered in the heat exchanger 15 in a countercurrent manner and used for preheating of the desorption gas, thereby shortening the regeneration cycle, reducing energy consumption, and reducing the thermal shock to the adsorbed phase of the activated carbon adsorption box 11.

[0063] Within the catalytic bed, the main controlling reaction belongs to the surface reaction control region or the weak diffusion coupling region. The axial temperature gradient of the bed can be approximated as a controllable, gradual change after reasonable heat preservation and heat exchange coupling. The reactants do not trigger strong exothermic instability at the operating concentration. Therefore, the exponential sensitivity of the rate constant with temperature can be characterized by k=A·e^{-E / (R·T)}. The conditions for inserting the formula are: (i) the target VOCs are within the operating temperature range of the selected catalyst, and their catalytic oxidation rate is mainly controlled by the surface reaction process. Thus, the Arrhenius form (k=A·e^{-E / (R·T)}) can be used to describe the sensitivity of the rate constant to temperature; (ii) T falls within the "active window" and does not trigger catalyst sintering or poisoning; (iii) A and Within this window, E can be considered relatively constant or calibrated by gradual changes with operating conditions. In practice, absolute mechanistic precision is not pursued, but it serves as a "sensitivity amplifier" for process control: when T is maintained in the upper half of the window, the temperature sensitivity of e^{-E / (R·T)} means that even small fluctuations in T can lead to considerable changes in k, thereby quickly clearing residual VOCs from the desorbed gas and reducing the outlet concentration. Combined with bed thermal management (thermal conductive substrate, segmented electric heating / thermal conductive plates, insulation shell) to reduce T fluctuations, k can be stably maintained at a high level without overheating. The comparison can focus on two core indicators: energy consumption and regeneration time. In traditional external heating regeneration or high-temperature catalytic combustion schemes, to achieve the same outlet concentration, it is necessary to... Significantly higher temperature (T) or longer residence time lead to higher energy consumption per unit of desorption and higher material thermal shock. This solution, within the low-temperature activity window, achieves a double reduction in energy consumption and time by "selecting a model to reduce the equivalent energy (E) and stabilizing the temperature (k)." Using the external heat supply (q_ext) per unit of desorption gas volume and the regeneration cycle (τ_reg) as baselines, the control strategy aims to reduce q_ext and τ_reg, with the trend of total hydrocarbons / TVOC at the catalyst outlet serving as a compliance constraint. Simultaneously, the pass rate of the inlet / outlet temperature of heat exchanger 15 and the desorption gas reaching the preheating target temperature is set as an evaluation of the energy closed loop, ensuring that the heat released by the low-temperature catalytic oxidation unit 14 can be stably recovered by heat exchanger 15 under countercurrent conditions. The state can be described as follows: the catalytic bed forms a stable temperature plateau within the active window, and small fluctuations in temperature (T) are quickly suppressed by thermal management; temperature (k) is maintained at a high level sufficient to cover the current desorption load, and the outlet concentration drops to and remains below the set threshold after a brief transition; the heat released by the low-temperature catalytic oxidation unit 14 is recovered in countercurrent flow through the heat exchanger 15, so that the temperature of the desorption gas entering the low-temperature catalytic oxidation unit 14 has reached the preheating target before the next small cycle. The system presents a quasi-steady-state heat and material closed loop in multiple regeneration-heat exchange small cycles. The activated carbon adsorption box 11 completes regeneration under mild heating conditions, and the adsorbed phase has no obvious thermal shock or pressure drop abrupt change. The entire unit maintains long-term compliant operation with lower energy consumption, shorter regeneration time, and smaller fluctuation amplitude.

[0064] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A wood-plastic floor granulation waste gas comprehensive treatment device, characterized in that, include: A condenser (1) is provided with an exhaust gas inlet pipe (4) on one side. An air distribution valve group (5) is provided on the exhaust gas inlet pipe (4). Exhaust gas enters the condenser (1) through the exhaust gas inlet pipe (4) for condensation and cooling. The outlet of the condenser (1) is connected to the electrostatic precipitator (2), and the outlet of the electrostatic precipitator (2) is connected to the spray scrubbing tower (6). The spray scrubbing tower (6) has multiple spray layers arranged along the height direction inside. Each spray layer includes a sprayer (9) and a coarse filter plate (8) installed on the layer. A circulating pump (7) is connected to one side of the spray scrubbing tower (6). All the sprayers (9) are connected to the circulating pump (7) to supply circulating scrubbing liquid. The outlet of the spray scrubbing tower (6) is equipped with a variable frequency centrifugal fan (10), which is connected to the activated carbon adsorption box (11). The air inlet of the activated carbon adsorption box (11) is equipped with a baffle (12), and filter cotton plates (16) are provided on both sides of the activated carbon adsorption box (11). The outlet of the activated carbon adsorption box (11) is connected to the discharge pipe (13) for discharging purified gas. The activated carbon adsorption box (11) is provided with a regeneration desorption gas circuit on one side, which is connected in sequence to the heat exchanger (15) and the low-temperature catalytic oxidation device (14). The desorbed gas is drawn from the bottom of the activated carbon adsorption box (11) and first enters the cold side channel of the heat exchanger (15), where it is preheated by countercurrent heat exchange with the high-temperature purified gas from the low-temperature catalytic oxidation device (14). The preheated desorbed gas then enters the low-temperature catalytic oxidation device (14) for oxidation and decomposition. The high-temperature gas generated by oxidation and decomposition returns to the hot side channel of the heat exchanger (15) to release heat, which is used to preheat the cold desorbed gas of the next cycle. The cooled regenerated gas returns to the activated carbon adsorption box (11) to regenerate the next carbon layer. The filter cotton plate (16) is equipped with a differential pressure detection interface to monitor its blockage status; the baffle (12) divides the air inlet into a buffer chamber to evenly distribute the air velocity; the activated carbon adsorption box (11) is provided with several inclined guide flaps (17) on both sides. The guide flaps (17) are closed in the default state and deflect and open when impacted by airflow; the variable frequency centrifugal fan (10) and the air distribution valve group (5) constitute a coordinated control system to achieve stable negative pressure in the system; the bottom of the condenser (1) is provided with a condensed oil and wax recovery tank (3) for collecting the condensed oil and wax.

2. The comprehensive treatment device for waste gas from wood-plastic flooring granulation according to claim 1, characterized in that, The low-temperature catalytic oxidation device (14) is equipped with a porous ceramic catalyst carrier, which can complete the oxidation and decomposition reaction of VOCs at a temperature not exceeding 260°C. The heat exchanger (15) is a shell-and-tube or plate structure, installed on one side of the activated carbon adsorption box (11), and forms a closed-loop path for the desorption gas between it and the low-temperature catalytic oxidation device (14).

3. A method for treating waste gas from wood-plastic composite flooring granulation, applied to the comprehensive waste gas treatment device for wood-plastic composite flooring granulation as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Granulation waste gas enters the condenser (1) through the waste gas inlet pipe (4) for cooling and oil wax precipitation. The condensate flows into the condensed oil wax recovery tank (3), and its outlet passes through the electrostatic precipitator (2) and the spray scrubbing tower (6) in sequence for mist droplet and VOCs pretreatment. S2, the gas is drawn to the activated carbon adsorption box (11) by the variable frequency centrifugal fan (10) for deep purification, and the gas is discharged through the discharge pipe (13); S3. After the activated carbon adsorption is saturated, the desorbed gas is drawn out from the bottom of the activated carbon adsorption box (11), first enters the heat exchanger (15) to be preheated, and then enters the low temperature catalytic oxidation device (14) for oxidation and decomposition. The high temperature gas after oxidation returns to the heat exchanger (15) to release heat to preheat the cold desorbed gas of the next cycle. The regenerated gas after treatment flows back to the top of the activated carbon adsorption box (11) to complete the regeneration closed loop. S4. By adjusting the speed of the variable frequency centrifugal fan (10) and the opening of the air distribution valve group (5), the pressure in the system is kept stable. The pressure difference on both sides of the filter cotton plate (16) is monitored to determine whether the filter cotton plate (16) is blocked, thereby triggering the maintenance operation of replacing the filter cotton plate (16).

4. The method for treating waste gas from wood-plastic flooring granulation according to claim 3, characterized in that, In the regeneration-heat exchange process of step S3, the high-temperature gas at the outlet of the low-temperature catalytic oxidation device (14) and the cold desorption gas entering the heat exchanger (15) undergo countercurrent heat exchange, and the single-cycle heat exchange meets the following requirements: Q=m·c_p·(T_out T_in); Where Q is the heat of a single cycle, m is the mass flow rate of the desorbed gas, c_p is the specific heat capacity at constant pressure, and T_out and T_in are the temperatures of the outlet gas of the low-temperature catalytic oxidation device (14) and the cold desorbed gas entering the heat exchanger (15), respectively. After heat exchange in the heat exchanger (15), the oxidized regenerated gas returns to the upper part of the activated carbon adsorption box (11) or the regeneration inlet to complete the closed loop of the desorbed gas and use the heat released for preheating of the next cycle.

5. The method for treating waste gas from wood-plastic composite flooring granulation according to claim 3, characterized in that, In step S2, the filter cotton plate (16) and baffle (12) on the air inlet side of the activated carbon adsorption box (11) perform mist interception, flow stabilization and uniform distribution treatment on the airflow, so that the apparent velocity entering the carbon layer is maintained within the set range. When the pressure difference on both sides of the filter cotton plate (16) reaches the threshold, the controller links the variable frequency centrifugal fan (10) and the air distribution valve group (5) to reduce the local wind speed and issue an instruction to replace or advance the filter material, thereby suppressing fine mist and dust from entering the carbon layer and maintaining the long-term stability of adsorption efficiency and pressure drop.

6. The method for treating waste gas from wood-plastic flooring granulation according to claim 3, characterized in that, In step S3, the operating temperature of the low-temperature catalytic oxidation device (14) is maintained within the activity window of the selected low-temperature catalyst, and the catalytic oxidation rate of volatile organic compounds satisfies k=A·e^{-E / (R·T)}, where E is the activation energy, R is the gas constant, and T is the absolute temperature. By selecting the catalyst and managing the bed thermally, the equivalent E is reduced and T is stabilized, so that the heat released from the outlet of the low-temperature catalytic oxidation device (14) can be recovered in the heat exchanger (15) in a countercurrent manner and used for preheating of the desorption gas, thereby shortening the regeneration cycle, reducing energy consumption, and reducing the thermal shock to the adsorption phase of the activated carbon adsorption box (11).

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