Environment-friendly regenerated asphalt mixture flue gas treatment method and system

Abstract

The application discloses an environment-friendly regenerated asphalt mixture flue gas treatment method and system, and belongs to the field of asphalt heat regeneration environment-friendly equipment. The method comprises the following steps: cooling the regenerated flue gas to 120 DEG C-160 DEG C, and pre-dusting the primary flue gas; mixing the two flue gases by convection cyclone; performing multi-stage gradient filtration; performing catalytic oxidation treatment after filtration; recovering waste heat, and discharging at high altitude after waste heat recovery is completed. The application provides a technical scheme integrating hierarchical collection, double pretreatment, convection cyclone mixing and sedimentation, multi-stage gradient filtration, catalytic oxidation and waste heat recovery. The application can realize efficient removal of dust, oil fume and VOCs, so that the equipment is not blocked, the process is simplified, energy consumption is reduced, emission is stable and up to standard, and is suitable for flue gas treatment of various asphalt heat regeneration equipment.

Description

Technical Field

[0001] This invention relates to the field of environmental protection equipment for hot asphalt recycling, specifically to an environmentally friendly method and system for treating flue gas from recycled asphalt mixtures. Background Technology

[0002] With the rapid development of highway maintenance in my country, thermal recycling technology for waste asphalt mixtures has been widely applied. During the heating and drying process, recycled materials generate high concentrations of asphalt fumes and volatile organic compounds (VOCs), while virgin materials generate a large amount of mineral dust. Direct emission of both types of fumes will seriously pollute the environment.

[0003] Currently, the industry treats these two types of flue gas separately, often using water / air cooling and activated carbon adsorption or electrostatic adsorption to treat regenerated flue gas, and cyclone dust collectors and bag filters to treat raw flue gas.

[0004] Because regenerated flue gas is highly viscous, separate treatment often results in the regenerated flue gas adhering to and clogging the equipment. At the same time, the regenerated flue gas and the original flue gas are not removed in tandem, resulting in serious energy waste and failing to meet the requirements for energy conservation and consumption reduction. Summary of the Invention

[0005] This invention provides an environmentally friendly method and system for treating flue gas from recycled asphalt mixtures, aiming to solve the technical problems of existing technologies, such as the adhesion and clogging of equipment by recycled flue gas, the inability to simultaneously remove two types of flue gas, and serious energy waste.

[0006] The technical solution provided by this invention is as follows: This invention provides an environmentally friendly method for treating flue gas from recycled asphalt mixtures, comprising the following steps: The regenerated flue gas and the original flue gas are collected separately in a sealed environment. The regenerated flue gas is cooled to 120℃-160℃, and the original flue gas is pre-dust removed to remove dust particles with a diameter ≥50μm. The cooled regenerated flue gas is mixed with the pre-dust-removed original flue gas. After mixing, the mixture is allowed to settle to remove the oil, sludge and dust mixture, resulting in the first mixed flue gas. The first mixed flue gas is subjected to multi-stage gradient filtration, passing sequentially through a coarse filter, an activated carbon adsorption layer, and an oil fume electrostatic adsorber to remove residual dust and liquid oil fumes, thus obtaining the second mixed flue gas. The second mixed flue gas was subjected to catalytic oxidation treatment at 200℃-280℃ to obtain the third mixed flue gas; The third mixed flue gas undergoes waste heat recovery, and after the waste heat recovery is completed, it is discharged at high altitude.

[0007] Optionally, the regenerated flue gas is cooled to 120℃-160℃ by water cooling. The water cooling process is completely sealed and leak-free, and the condensed oil fumes are collected. The method for pre-dust removal of the raw flue gas is cyclone pre-dust removal.

[0008] Optionally, the method for mixing the cooled regenerated flue gas with the pre-dust-removed primary flue gas is as follows: the inlet flow ratio of the cooled regenerated flue gas to the pre-dust-removed primary flue gas is controlled to be 2:(3-5), and the mixture is mixed by strong convective swirling disturbance.

[0009] Optionally, the sedimentation method after mixing is gravity and / or centrifugal sedimentation, and the oil sludge and dust mixture is removed and recycled for later use.

[0010] Optionally, the coarse filter screen is cleaned by compressed air pulse backflushing, with a cleaning pressure of 0.4MPa-0.6MPa.

[0011] Optionally, before catalytic oxidation treatment of the second mixed flue gas, VOCs concentration is detected. If the VOCs concentration exceeds the standard, the second mixed flue gas is controlled to be mixed again, and the flow rate of the second mixed flue gas is 15%-30% of the total inlet flow rate.

[0012] Optionally, when the third mixed flue gas undergoes waste heat recovery, the waste heat recovery temperature is controlled at 80℃-100℃.

[0013] The present invention also provides an environmentally friendly recycled asphalt mixture flue gas treatment system for implementing the above-mentioned environmentally friendly recycled asphalt mixture flue gas treatment method, including a recycled asphalt drying drum, a virgin asphalt drying drum, a flue gas pretreatment unit, a flue gas mixing chamber, a multi-stage filtration unit, a catalytic oxidation unit, a waste heat recovery unit, an online monitoring unit, and a control unit. The recycled asphalt drying drum and the virgin asphalt drying drum are respectively connected to the flue gas mixing chamber via the flue gas pretreatment unit. The flue gas mixing chamber is sequentially connected to the multi-stage filtration unit, the catalytic oxidation unit, and the waste heat recovery unit. The online monitoring unit collects data on flue gas temperature, pressure difference, dust concentration, VOCs concentration, and oxygen content in real time and sends the data to the control unit. The recycled asphalt drying drum, virgin asphalt drying drum, flue gas pretreatment unit, flue gas mixing chamber, multi-stage filtration unit, catalytic oxidation unit, waste heat recovery unit, and online monitoring unit are all electrically connected to the control unit.

[0014] Optionally, the flue gas pretreatment unit includes a regenerated flue gas indirect cooler and a primary flue gas cyclone pre-dust collector; the flue gas mixing chamber is equipped with a counter-current swirl guide device and a frequency conversion regulating damper, and the bottom of the flue gas mixing chamber is equipped with a sludge scraping mechanism and an oil sludge collection hopper.

[0015] Optionally, the multi-stage filtration unit includes a coarse filter, an activated carbon adsorption layer, and an electrostatic oil fume adsorber connected in sequence, and the coarse filter is equipped with a compressed air pulse backflushing cleaning system; The catalytic oxidation unit includes a catalytic reactor, which incorporates a noble metal honeycomb catalyst. The waste heat recovery unit includes a gas-to-gas plate / tube heat exchanger, the output end of which is connected to the preheating port of the recycled asphalt drying drum. The online monitoring unit includes a temperature sensor, a pressure sensor, a differential pressure sensor, an online dust concentration monitor, a VOCs concentration monitor, and an oxygen content analyzer; The control unit includes a PLC controller, a touch screen, a frequency converter drive module, an alarm module, a data storage module, and a remote monitoring module.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The environmentally friendly method for treating flue gas from recycled asphalt mixtures provided in this application significantly reduces the viscosity of asphalt fumes by cooling the recycled flue gas to 120℃-160℃. This reduces the adhesion of fumes to pipelines, filter units, and catalytic equipment, thereby reducing the risk of clogging at the source and solving the problems of easy scaling, clogging, and short lifespan of equipment in existing technologies. Addressing the issue of the inability to remove the two types of flue gas simultaneously, this method pre-treats the recycled and virgin flue gas separately, then mixes them. The fumes in the recycled flue gas coat the dust in the virgin flue gas, achieving synergistic settling and significantly improving purification efficiency. This avoids the drawbacks of separate treatment of the two types of flue gas, high purification load, and poor effect in existing technologies, achieving simultaneous removal of dust and fumes. Addressing the serious problem of energy waste, this method recovers waste heat, using the waste heat from the catalytically treated flue gas for preheating the recycled asphalt drying drum, reducing burner energy consumption and solving the problems of direct emission of waste heat and low energy utilization in existing technologies, thus meeting low-carbon and energy-saving requirements. Attached Figure Description

[0017] Figure 1 This is a flowchart of the environmentally friendly recycled asphalt mixture flue gas treatment method in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the environmentally friendly recycled asphalt mixture flue gas treatment system in an embodiment of the present invention.

[0018] The attached figures are labeled as follows: 1-Recycled asphalt drying drum; 2-Virgin asphalt drying drum; 3-Flue gas pretreatment unit; 301-Water-cooled cooler; 302-Condensed oil collection port; 303-Sealed oil tank; 304-Cyclone pre-dust collector; 305-Centrifugal separator blades; 306-Airlock ash discharge valve; 4-Flue gas mixing chamber; 401-Opposing air inlet; 402-Swirl guide device; 403-Variable frequency regulating damper; 404-Ash hopper; 405-Sludge scraping mechanism; 406-Oil sludge dust recovery port; 5-Multi-stage filtration unit; 501-Coarse filter screen; 502-Activated carbon adsorption layer; 503-Oil fume electrostatic adsorber; 505-Compressed air pulse backflushing cleaning system; 6-Catalytic oxidation unit; 601-Catalytic reactor; 602-Precious metal honeycomb catalyst. 603-Electric auxiliary heating device, 7-Waste heat recovery unit, 701-Heat exchanger, 702-Heat exchange surface, 703-Hot air output pipe, 704-Temperature control valve, 705-Heat exchanger inlet, 706-Clean flue gas outlet, 707-Hot air outlet, 8-Online monitoring unit, 801-Temperature sensor, 802-Pressure sensor, 803-Differential pressure sensor, 804-Dust concentration monitor, 805-VOCs concentration monitor, 806-Oxygen content analyzer, 807-Data acquisition module, 9-Control unit, 901-PLC controller, 902-Touch screen, 903-Variable frequency drive module, 904-Alarm module, 905-Data storage module, 906-Remote monitoring module, 10-Exhaust fan, 11-Chimney. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in conjunction with the accompanying drawings is intended merely to illustrate selected embodiments of the invention and is not intended to limit the scope of protection claimed by the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0020] It should be understood that in the description of embodiments of the present invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of the stated features.

[0021] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for mutual communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0022] See Figure 1 This invention provides an environmentally friendly method for treating flue gas from recycled asphalt mixtures, comprising the following steps: S1. Collect regenerated flue gas and original flue gas separately in a sealed environment. Cool the regenerated flue gas to 120℃-160℃ and pre-remove dust from the original flue gas to remove dust particles with a diameter ≥50μm.

[0023] S2. The cooled regenerated flue gas is mixed with the pre-dust-removed original flue gas. After mixing, the mixture is allowed to settle to remove the oil, sludge and dust mixture, resulting in the first mixed flue gas.

[0024] S3. The first mixed flue gas is subjected to multi-stage gradient filtration, passing through a coarse filter, an activated carbon adsorption layer, and an oil fume electrostatic adsorber in sequence to remove residual dust and liquid oil fumes, thus obtaining the second mixed flue gas.

[0025] S4. The second mixed flue gas is subjected to catalytic oxidation treatment at 200℃-280℃ to obtain the third mixed flue gas.

[0026] S5. The third mixed flue gas is subjected to waste heat recovery, and after the waste heat recovery is completed, it is discharged at high altitude.

[0027] Specifically, step S1 is the core pretreatment step in the entire flue gas treatment process. Using a closed collection system can prevent the leakage and diffusion of asphalt fumes, dust, and VOCs from the source, eliminating odors and safety hazards in the plant area and meeting the requirements for environmentally friendly closed collection. Cooling the regenerated flue gas to 120℃-160℃ can significantly reduce the viscosity and volatility of asphalt fumes, preventing adhesion and blockage in pipes, fans, and other equipment. Pre-dust removal of the raw flue gas and removal of large particles ≥50μm can eliminate the scouring and wear of hard particles on subsequent equipment in advance, preventing filter clogging and catalytic reactor bed blockage caused by large dust particles, and significantly extending the service life of core purification components.

[0028] Step S2 is the key innovative step in this invention for achieving the synergistic removal of dust and oil fumes. Mixing the cooled regenerated flue gas with the pre-dust-removed primary flue gas fully utilizes the wetting, coating, and agglomeration effects of the asphalt fumes in the regenerated flue gas. This causes the fine dust particles in the primary flue gas to be encapsulated by oil fume droplets, forming a denser, coarser oil sludge-dust mixture. Under gravity and / or centrifugal force, this mixture rapidly settles and separates, achieving efficient pre-treatment purification without consumables. Through the mixing and settling in step S2, the concentration of dust and oil fumes in the first mixed flue gas can be significantly reduced, significantly lessening the processing load on subsequent multi-stage filtration and catalytic oxidation, while simultaneously preventing oil sludge and dust from entering the downstream stages and causing blockage.

[0029] Step S3 is the deep pretreatment stage, which plays a crucial role in "fine dust removal, oil mist removal, and catalytic protection." It employs a three-stage gradient combination of a coarse filter, an activated carbon adsorption layer, and an electrostatic precipitator for oil fumes, achieving progressive load reduction and precise purification: the coarse filter intercepts incompletely settled oil sludge clumps and large particulate impurities, protecting the downstream adsorption materials; the activated carbon adsorption layer captures small and medium-sized oil fumes and some VOCs, reducing odor and organic load; the electrostatic precipitator utilizes a high-voltage electric field to efficiently capture submicron-sized oil mist droplets, achieving clear, dry, and oil-free flue gas. After three stages of filtration, the second mixed flue gas is essentially free of liquid oil and visible dust, preventing oil mist from entering the catalytic oxidation unit and causing catalyst poisoning, deactivation, and blockage, thus ensuring a stable and efficient catalytic reaction.

[0030] Step S4 is crucial for the complete degradation of toxic and harmful substances such as VOCs and asphalt fumes. Catalytic oxidation, performed at a low temperature range of 200℃-280℃, efficiently decomposes residual organic pollutants in the second mixed flue gas under mild conditions, ultimately producing harmless CO2 and H2O without generating secondary pollutants. Compared to high-temperature incineration, catalytic oxidation consumes less energy, is safer, produces no NOx byproducts, and is more suitable for asphalt fume conditions. After this step, the third mixed flue gas is non-toxic, odorless, VOC-free, and meets emission standards, satisfying the most stringent environmental emission requirements.

[0031] In step S5, the third mixed flue gas still carries a large amount of usable waste heat, and direct emission would result in significant energy waste. Waste heat recovery allows the heat to be recycled for preheating the recycled asphalt drying drum, reducing burner fuel consumption, improving overall system energy efficiency, and complying with low-carbon energy conservation and "dual-carbon" policy requirements. The temperature of the flue gas after waste heat recovery is further reduced, which is more conducive to stable operation of the induced draft fan and high-altitude diffusion and dilution. Finally, high-altitude emission avoids the accumulation of pollutants on the ground, reducing the impact on the plant area and surrounding environment. Therefore, step S5 not only completes the emission closed loop but also achieves waste heat resource utilization, system energy conservation, and emission safety, improving the overall economic and environmental benefits of this invention.

[0032] In other embodiments, the regenerated flue gas is cooled to 120°C-160°C by water cooling. The water cooling process is completely sealed and leak-free, and the condensed oil fumes are collected. The original flue gas is pre-dust removed by cyclone pre-dust removal.

[0033] Specifically, this embodiment further defines the implementation method of the flue gas pretreatment step in step S1. Water cooling can stably reduce the temperature of the regenerated flue gas to 120℃-160℃ in a short time, with high cooling efficiency and small temperature fluctuations, effectively reducing the viscosity of asphalt fumes and minimizing the risk of clogging. The fully enclosed, leak-free structure fundamentally prevents flue gas leakage and odor diffusion, meeting environmental protection requirements for closed collection and safe production. Collecting condensed fumes allows for the early recovery of high-boiling-point liquid asphalt fumes, achieving pollutant reduction and lowering the downstream purification load. The primary flue gas is pre-treated with a cyclone dust collector, which efficiently removes ≥50μm large-particle mineral dust without consumables and under low resistance conditions, preventing dust from scouring and clogging pipelines, fans, and filters, protecting subsequent core equipment. This design is also simple in structure, stable in operation, and has low maintenance costs.

[0034] In other embodiments, the method for mixing the cooled regenerated flue gas with the pre-dust-removed original flue gas is as follows: the inlet flow ratio of the cooled regenerated flue gas to the pre-dust-removed original flue gas is controlled to be 2:(3-5), and the mixture is mixed by strong convective swirling disturbance.

[0035] Specifically, this embodiment defines key parameters and structures for the mixing method in step S2, which are the core conditions for achieving efficient mixing and coating. Setting the airflow ratio to 2:(3-5) is the optimal ratio verified through extensive testing. This ensures sufficient asphalt fumes in the recycled flue gas, adequately wetting and coating the fine dust in the virgin flue gas, resulting in optimal mixing and settling. Too low a flow rate leads to insufficient coating, while too high a flow rate easily causes excessive fumes and equipment blockage. Employing convective swirling strong disturbance mixing allows the two flue gas streams to form intense turbulence in the mixing chamber, extending the contact time, improving the collision and agglomeration efficiency of fumes and dust, and enhancing the coating effect.

[0036] In other embodiments, the sedimentation process after mixing is performed by gravity and / or centrifugal sedimentation, and the oil sludge and dust mixture is removed and recycled for later use.

[0037] Specifically, this embodiment optimizes and limits the sedimentation method and solid waste treatment method in step S2, achieving both purification effect and resource utilization value. Gravity and / or centrifugal sedimentation can significantly improve the separation efficiency of the oil sludge-dust mixture by utilizing gravity sedimentation and / or cyclone centrifugation, resulting in more thorough and faster sedimentation. The separated oil sludge-dust mixture can be recycled and reused directly as a component of recycled asphalt mixture, achieving solid waste resource utilization and zero emissions. This avoids secondary pollution, reduces raw material waste, and improves economic efficiency. This embodiment improves the implementation path of the mixing and sedimentation process, solving the problems of difficult sediment treatment, easy clogging, and easy solid waste generation in traditional processes, making the system more environmentally friendly and economical.

[0038] In other embodiments, the coarse filter screen is cleaned by compressed air pulse backflushing at a pressure of 0.4 MPa to 0.6 MPa.

[0039] Specifically, this embodiment limits the cleaning method and operating parameters of the multi-stage gradient filtration in step S3 to ensure the long-term stability of the filtration system. After intercepting sludge and dust, the coarse filter screen is prone to adhesion and blockage. Using compressed air pulse backflushing for cleaning can quickly and efficiently remove the deposits without shutting down the system, maintaining filter screen permeability and system resistance stability. The cleaning pressure is set to 0.4MPa-0.6MPa, which is the optimal pressure range. Too low a pressure will result in incomplete cleaning, while too high a pressure can damage the filter screen and increase energy consumption.

[0040] In other embodiments, before the second mixed flue gas is subjected to catalytic oxidation treatment, the VOCs concentration is detected. If the VOCs concentration exceeds the standard, the second mixed flue gas is controlled to be mixed again. The flow rate of the second mixed flue gas is 15%-30% of the total inlet flow rate.

[0041] Specifically, this embodiment defines the monitoring and reflux strategy before catalytic oxidation in step S4, forming a safe closed-loop control to ensure absolute compliance with emission standards. Detecting VOC concentration before catalytic oxidation allows for early identification of concentration anomalies caused by raw material fluctuations and changes in operating conditions, preventing direct emission of excessive flue gas. If the concentration exceeds the standard, the gas is refluxed to the mixing chamber for reprocessing. Secondary mixing, settling, and filtration further reduce the pollutant load, ensuring that the concentration of the flue gas undergoing catalytic oxidation remains within a reasonable range. The reflux flow rate is controlled at 15%–30% of the total intake air, ensuring effective reflux treatment without causing a surge in system load or airflow imbalance due to excessive reflux.

[0042] In other embodiments, when the third mixed flue gas undergoes waste heat recovery, the waste heat recovery temperature is controlled at 80°C-100°C.

[0043] Specifically, this embodiment limits the key parameters of the waste heat recovery process in step S5 to achieve dual protection of energy saving and safety. Maintaining the waste heat recovery temperature at 80℃-100℃ provides a mild and stable preheating heat source for preheating the inner wall of the recycled asphalt drying drum and insulating the feed inlet, effectively reducing the burner load and achieving energy savings of over 10%. Simultaneously, this temperature range prevents overheating from causing localized high temperatures in the recycled asphalt drying drum, insulation layer failure, or flue gas condensation, thus balancing preheating effectiveness and equipment safety.

[0044] like Figure 2 As shown, this invention provides an environmentally friendly recycled asphalt mixture flue gas treatment system for implementing the aforementioned environmentally friendly recycled asphalt mixture flue gas treatment method. The system includes a recycled asphalt drying drum 1, a virgin asphalt drying drum 2, a flue gas pretreatment unit 3, a flue gas mixing chamber 4, a multi-stage filtration unit 5, a catalytic oxidation unit 6, a waste heat recovery unit 7, an online monitoring unit 8, and a control unit 9. Each functional unit is connected in series according to the flue gas treatment process flow, forming a complete treatment path of data collection – pretreatment – ​​mixing and settling – multi-stage filtration – deep catalysis – waste heat recovery – compliant emission. The online monitoring unit 8 collects key parameters throughout the process, and the control unit 9 uniformly schedules and executes the process, achieving fully automated, intelligent, and stable operation.

[0045] The recycled asphalt drying drum 1 and the virgin asphalt drying drum 2 are connected to the flue gas mixing chamber 4 via the flue gas pretreatment unit 3. The flue gas mixing chamber 4 is connected in sequence to the multi-stage filtration unit 5, the catalytic oxidation unit 6, and the waste heat recovery unit 7. The online monitoring unit 8 collects data on flue gas temperature, pressure difference, dust concentration, VOCs concentration, and oxygen content in real time and sends the data to the control unit 9.

[0046] Specifically, the recycled asphalt drying drum 1 is the core equipment for heating and drying waste asphalt mixtures. The drum body adopts a heat-insulating structure, and the inner wall is lined with high-temperature and wear-resistant plates. A sealed gas collection hood is installed at the flue gas outlet to ensure leak-free flue gas collection. The flue gas outlet of the recycled asphalt drying drum 1 is directly connected to the recycled flue gas treatment unit in the flue gas pretreatment unit 3 through a sealed flue, realizing the directional transportation of recycled flue gas. The recycled asphalt drying drum 1 is used to heat waste asphalt mixtures and is the source of recycled flue gas; the generated flue gas contains asphalt fumes, VOCs, and a small amount of dust, which is one of the main targets of treatment in this system.

[0047] The virgin asphalt drying drum 2 is used for heating and drying new aggregates. The flue gas outlet of the virgin asphalt drying drum 2 is equipped with a gas collection box and a guide flue. The inner wall of the guide flue is treated with wear-resistant and corrosion-resistant materials to prevent damage from dust erosion. The flue gas outlet of the virgin asphalt drying drum 2 is connected to the virgin flue gas cyclone pre-dust collector 304 in the flue gas pretreatment unit 3 via the gas collection box and guide flue, achieving closed-loop conveying of the virgin flue gas. The virgin asphalt drying drum 2 is used to heat virgin aggregates and is the source of virgin flue gas; the generated flue gas mainly consists of high-concentration mineral dust, which is another major target of treatment in this system.

[0048] The flue gas pretreatment unit 3 has a dual-path parallel structure, including a regenerated flue gas treatment unit and a primary flue gas treatment unit. The regenerated flue gas treatment unit includes a water-cooled cooler 301, which can be a shell-and-tube indirect water-cooled cooler with a fully enclosed structure. A condensate collection port 302 and a sealed oil tank 303 are located at the bottom. The primary flue gas treatment unit uses a cyclone pre-dust collector 304, which has centrifugal separation blades 305 inside and an airlock ash discharge valve 306 at the bottom. The inlets of the water-cooled cooler 301 and the cyclone pre-dust collector 304 are connected to the regenerated asphalt drying drum 1 and the primary asphalt drying drum 2, respectively, and their outlets are all connected to the inlet of the flue gas mixing chamber 4. The flue gas pretreatment unit 3 indirectly cools the regenerated flue gas to 120℃-160℃ using water cooling, reducing the viscosity of the oil fume and condensing and recovering some of the liquid asphalt oil fume; it also performs cyclone pre-dust removal on the original flue gas to remove large dust particles with a diameter ≥50μm, reducing wear and blockage of subsequent equipment; it achieves separate pretreatment and unified output of the two flue gas streams, providing stable, safe, and low-load air intake conditions for subsequent mixing and settling.

[0049] The flue gas mixing chamber 4 is a horizontal / vertical sealed cavity with a high-temperature resistant and corrosion-resistant coating on the inner wall. It is equipped with opposing air inlets 401, a swirling flow guide device 402, and a frequency conversion regulating damper 403. The bottom is equipped with a dust collection hopper 404, a sludge scraping mechanism 405, and an oil sludge dust recovery port 406. The inlet of the flue gas mixing chamber 4 is connected to the outlet of the flue gas pretreatment unit 3, and the outlet of the flue gas mixing chamber 4 is directly connected to the inlet of the multi-stage filtration unit 5. The flue gas mixing chamber 4 mixes the pretreated regenerated flue gas and the original flue gas at a flow ratio of 2:(3-5) through convective swirling strong disturbance. Utilizing the wetting and coating effect of asphalt fumes on the dust, the oil sludge dust mixture is separated by gravity and / or centrifugal combined sedimentation, achieving synergistic pre-removal of dust and fumes, significantly reducing the downstream purification load and preventing equipment blockage.

[0050] The multi-stage filtration unit 5 adopts a three-stage gradient structure, with a coarse filter 501, an activated carbon adsorption layer 502, and an electrostatic oil fume adsorber 503 arranged sequentially along the airflow direction. The coarse filter 501 is equipped with a compressed air pulse backflushing cleaning system 505, with the cleaning pressure set at 0.4MPa-0.6MPa. The inlet of the multi-stage filtration unit 5 is connected to the outlet of the flue gas mixing chamber 4, and the outlet is connected to the inlet of the catalytic oxidation unit 6. The coarse filter 501 intercepts residual oil sludge clumps and large particulate impurities, the activated carbon adsorption layer 502 adsorbs small molecule oil fumes, odors, and some VOCs, and the electrostatic oil fume adsorber 503 efficiently captures submicron-sized oil mist droplets, achieving the drying, clarification, and oil-free treatment of the flue gas, protecting the downstream catalyst from poisoning and clogging.

[0051] The catalytic oxidation unit 6 includes a catalytic reactor 601, a precious metal honeycomb catalyst 602, and an electrically auxiliary heating device 603. The catalytic reaction temperature is controlled between 200℃ and 280℃. The inlet of the catalytic reactor 601 is connected to the outlet of the multi-stage filtration unit 5, and the outlet is connected to the inlet of the waste heat recovery unit 7. A VOCs concentration detector 805 and a flue gas recirculation branch are installed at the inlet to recirculate excess flue gas back to the flue gas mixing chamber 4. Under low-temperature and mild conditions, the catalytic oxidation unit 6 can catalytically oxidize and decompose residual VOCs, asphalt fumes, and other organic pollutants in the flue gas into CO2 and H2O, ensuring that emissions are non-toxic, odorless, and meet standards.

[0052] The waste heat recovery unit 7 includes a heat exchanger 701, which can be a plate / tube heat exchanger. The heat exchange surface 702 of the heat exchanger 701 is treated to prevent sticking, clogging, and corrosion. The heat exchanger 701 is equipped with a hot air output pipe 703 and a temperature control valve 704, and the recovery temperature is stabilized at 80℃-100℃. The heat exchanger inlet 705 of the heat exchanger 701 is connected to the outlet of the catalytic oxidation unit 6, the clean flue gas outlet 706 is connected to the induced draft fan 10 and the chimney 11, and the hot air outlet 707 is connected to the preheating air duct of the recycled asphalt drying drum 1 through the hot air output pipe 703. The waste heat recovery unit 7 is used to recover the waste heat in the purified flue gas, heat the fresh air and send it into the recycled asphalt drying drum 1 for drum wall preheating and feed inlet insulation, reducing burner energy consumption by more than 10%, and achieving energy saving, carbon reduction and heat energy recycling.

[0053] The online monitoring unit 8 consists of a temperature sensor 801, a pressure sensor 802, a differential pressure sensor 803, an online dust concentration monitor 804, a VOCs concentration monitor 805, an oxygen content analyzer 806, and a data acquisition module 807. The specific settings are as follows: Temperature sensor 801: It adopts a multi-point setting and is installed at the pipeline after cooling of regenerated flue gas, the pipeline after pre-dust removal of original flue gas, the outlet of flue gas mixing chamber 4, the inlet and outlet of catalytic oxidation unit 6, and the inlet and outlet of waste heat recovery unit 7. It is used to monitor the flue gas temperature at each key node in real time and ensure the stability of cooling, catalytic temperature and waste heat recovery temperature of regenerated flue gas.

[0054] Pressure sensor 802: Installed at the air inlet of flue gas mixing chamber 4, multi-stage filtration unit 5, and catalytic oxidation unit 6, it monitors the air inlet pressure of each unit, helps to determine whether the pipeline is unobstructed, and provides timely warning of potential blockage.

[0055] Differential pressure sensor 803: Installed at the inlet and outlet of coarse filter 501, activated carbon adsorption layer 502, oil fume electrostatic adsorber 503, and waste heat recovery unit 7, it collects the pressure difference between the inlet and outlet of each component, reflects the filtration and heat exchange effect, and provides a basis for dust removal and maintenance.

[0056] Dust Concentration Online Monitoring Instrument 804: Its probes are installed at the outlet of flue gas mixing chamber 4, the outlet of multi-stage filtration unit 5, and the emission port of chimney 11. It focuses on monitoring the dust concentration after settling, after filtration, and in the final emission to ensure that dust emissions meet standards.

[0057] VOCs Concentration Monitor 805: The core is installed at the inlet of the catalytic oxidation unit 6 to monitor the VOCs concentration of the filtered flue gas and trigger the over-limit backflow mechanism; it is also installed at the outlet of the catalytic oxidation unit 6 to verify the deep purification effect.

[0058] Oxygen content analyzer 806: Installed at the inlet of catalytic oxidation unit 6, it monitors the oxygen content in the flue gas to ensure that the catalytic oxidation reaction proceeds fully and avoids incomplete degradation of organic pollutants due to insufficient oxygen content.

[0059] Data acquisition module 807: Integrated and installed next to control unit 8, it is connected to all the above sensors and monitors via cables, collects monitoring data from each component in real time, performs preliminary processing, and transmits the data to control unit 8 to achieve closed-loop monitoring data throughout the entire process.

[0060] The control unit 9 employs a programmable logic PLC controller 901, equipped with a touch screen 902, a frequency converter drive module 903, an alarm module 904, a data storage module 905, and a remote monitoring module 906. The PLC controller 901 is electrically / signally connected to the recycled asphalt drying drum 1, the virgin asphalt drying drum 2, the flue gas pretreatment unit 3, the flue gas mixing chamber 4, the multi-stage filtration unit 5, the catalytic oxidation unit 6, the waste heat recovery unit 7, and the online monitoring unit 8. The control unit 9 receives data from the online monitoring unit 8, performs logical judgments and intelligent calculations, and automatically adjusts the cooling water volume, damper opening, induced draft fan frequency 10, dust removal cycle, catalytic temperature, and hot air temperature. This enables automatic VOCs over-limit recirculation, automatic alarm for abnormalities, fault interlock protection, and fully automatic unattended operation; ensuring the system is always in optimal operating condition and stably meets emission standards. Example 1 This embodiment provides a method for treating flue gas from environmentally friendly recycled asphalt mixtures using the aforementioned environmentally friendly recycled asphalt mixture flue gas treatment system, including: (1) First, the recycled flue gas generated during the operation of the recycled asphalt drying drum and the original flue gas generated during the operation of the virgin asphalt drying drum are collected separately in a sealed manner. The recycled flue gas is passed into a shell-and-tube indirect water-cooled cooler for sealed cooling treatment, so that the flue gas temperature is stably controlled within the range of 120℃-160℃. At the same time, the condensed oil fumes that are released during the cooling process are collected in a completely sealed manner to avoid leakage and secondary pollution. The original flue gas is passed into a cyclone pre-dust collector to remove large mineral dust particles with a particle size of 50μm or greater, reduce the coarse particle content in the flue gas, reduce the load on subsequent processing units, and prevent wear on pipelines and equipment.

[0061] (2) The regenerated flue gas that has been cooled and the original flue gas that has been pre-dust removed are fed into the flue gas mixing chamber in a set ratio. The inlet flow ratio of the two flue gases is controlled to be 1:2 by the frequency conversion damper. Under the action of the convection swirl guide device inside the flue gas mixing chamber, a strong disturbance mixing state is formed, so that the asphalt oil fume component in the regenerated flue gas is fully wetted and coated with the fine dust particles in the original flue gas, forming a mixture of oil sludge and dust with higher density and coarser particle size. Under the combined action of gravity and centrifugation, efficient sedimentation separation is achieved. After sedimentation, the first mixed flue gas with significantly improved cleanliness is obtained.

[0062] (3) The first mixed flue gas is sent into a multi-stage filtration unit under the negative pressure of the system for step-by-step purification. It passes through a coarse filter to intercept incompletely settled oil sludge clumps and large particulate impurities. The activated carbon adsorption layer adsorbs small molecule oil fumes, odor substances and some volatile organic compounds in the flue gas. The oil fume electrostatic adsorber uses a high voltage electric field to efficiently capture submicron-sized liquid oil droplets. The coarse filter is equipped with a pulse backflushing cleaning device that automatically cleans the dust under a pressure of 0.4MPa-0.6MPa. Finally, a dry, oil-free and low-dust second mixed flue gas is obtained.

[0063] (4) The VOCs concentration of the second mixed flue gas is detected in real time by an online monitoring device at the inlet of the catalytic oxidation unit. When the detected concentration is qualified, the flue gas is sent into the catalytic reactor. Under the reaction temperature of 200℃-280℃ and the action of the precious metal honeycomb catalyst, the residual VOCs, asphalt fumes and other organic pollutants in the flue gas undergo catalytic oxidation reaction and are completely decomposed into carbon dioxide and water to obtain the harmless third mixed flue gas. When the VOCs concentration exceeds the standard, the flue gas is controlled to flow back to the flue gas mixing chamber for re-mixing and settling treatment. The flow rate of the returned flue gas is controlled at 15%-30% of the total inlet flow rate to ensure that the flue gas concentration entering the catalytic oxidation unit is within a safe and stable range.

[0064] (5) The third mixed flue gas after low-temperature catalytic oxidation treatment is passed into an air-to-air plate / tube heat exchanger for heat recovery. The waste heat recovery temperature is stably controlled at 80℃-100℃. The recovered heat is transported to the recycled asphalt drying drum through a hot air pipeline for preheating the inner wall of the recycled asphalt drying drum and heat preservation of the feed inlet, so as to realize energy recycling. The temperature of the clean flue gas after waste heat recovery is further reduced to meet the emission requirements. Under the action of the induced draft fan, it is safely discharged at high altitude through the chimney, thus completing the entire flue gas treatment process.

[0065] Compare with Example 1 Compared with Example 1, this comparative example only treats regenerated flue gas, and the system and operating conditions are exactly the same as in Example 1; The only difference is that the entire process involves only regenerated flue gas, with no original flue gas involved.

[0066] Compare with Example 2 Compared with Example 1, this comparative example only treats raw flue gas, and the system and operating conditions are exactly the same as in Example 1; The only difference is that the entire process involves only raw flue gas, with no regenerated flue gas involved.

[0067] Compare with Example 3 Compared with Example 1, the system and operating conditions of this comparative example are exactly the same as those of Example 1; The only difference is that in (2), the ratio of the intake volume of regenerated flue gas to that of original flue gas is controlled to be 1:1; the other steps are the same.

[0068] Compare with Example 4 Compared with Example 1, the system and operating conditions of this comparative example are exactly the same as those of Example 1; The only difference is that in (2), the ratio of the intake volume of regenerated flue gas to that of original flue gas is controlled to be 1:3; the other steps are the same.

[0069] Compare with Example 5 Compared with Example 1, the system and operating conditions of this comparative example are exactly the same as those of Example 1; The only difference is that: (4) does not have online detection of VOCs concentration, and the second mixed flue gas directly enters the catalytic reactor without reflux reprocessing; the other steps are the same.

[0070] Compare with Example 6 Compared with Example 1, the system and operating conditions of this comparative example are exactly the same as those of Example 1; The only difference is that the third mixed flue gas after catalysis in (4) is directly emitted without waste heat recovery; the other steps are the same.

[0071] Compare with Example 7 Compared with Example 1, the system and operating conditions of this comparative example are exactly the same as those of Example 1; The only difference is that in (3), only a regular filter screen is used for filtration, and the activated carbon adsorption layer and the oil fume electrostatic adsorber are removed; the rest of the steps are the same.

[0072] Compare with Example 8 Compared with Example 1, the system and operating conditions of this comparative example are exactly the same as those of Example 1; The only difference is that: (1) water cooling and cyclone dust removal are cancelled, and the two types of flue gas directly enter the flue gas mixing chamber; the rest of the steps are the same.

[0073] Results analysis: The above-mentioned embodiments and control examples were analyzed based on dust emission concentration (mg / m³), oil fume emission concentration (mg / m³), VOCs emission concentration (mg / m³), system operating resistance (Pa), equipment clogging failure rate (%), average energy consumption reduction rate (%), and continuous stable operation time (h). The results are shown in Table 1. Dust emission concentration (mg / m³): An online dust monitoring instrument was used, with the probe installed at the chimney outlet. Real-time monitoring was conducted in accordance with GB / T16157-1996 "Methods for Determination of Particulate Matter and Sampling of Gaseous Pollutants in Exhaust Gas from Stationary Sources", and data was recorded synchronously.

[0074] Oil fume emission concentration (mg / m³): The oil fume online monitoring instrument was used, and the sampling points were set at the outlet of the multi-stage filtration unit and the chimney outlet. The test was carried out in accordance with GB 18483-2008 "Emission Standard of Oil Fume from Catering Industry" and the average value was taken.

[0075] VOCs emission concentration (mg / m³): VOCs online monitoring instrument was installed at the inlet and outlet of the catalytic oxidation unit and detected according to HJ759-2015 "Determination of Volatile Organic Compounds in Exhaust Gas from Stationary Sources - Solid Phase Adsorption-Thermal Desorption / Gas Chromatography-Mass Spectrometry".

[0076] System operating resistance (Pa): Differential pressure sensors are installed at the inlet and outlet of each unit to collect the pressure difference between the inlet and outlet in real time, which is the system operating resistance. The data are continuously recorded and the average value is taken.

[0077] Equipment clogging failure rate (%): The number of times and duration of equipment shutdown due to clogging during the statistical test period are calculated as "clogging shutdown duration ÷ total running time × 100%".

[0078] Average energy consumption reduction rate (%): The energy consumption of the system with and without waste heat recovery (or complete process and control example) is measured separately and calculated as "(conventional energy consumption - energy consumption of this system) ÷ conventional energy consumption × 100%".

[0079] Continuous stable operation time (h): Record the continuous operation time from system startup to the first failure (blockage, exceeding the standard, etc.) shutdown. If there is no failure, record according to the test set cycle.

[0080] Table 1

[0081] As shown in Table 1, the indicators in Example 1 are optimal, with dust, oil fume, and VOC emission concentrations of 8 mg / m³, 7 mg / m³, and 16 mg / m³, respectively. The system resistance is 680 Pa, the clogging failure rate is 0.8%, energy consumption is reduced by 12.3%, and continuous operation is ≥720 h, achieving synergistic purification and stable energy saving.

[0082] Comparative Examples 1 and 2 only treated one type of flue gas. Due to the lack of synergistic effect of oil fume coating and dust, the purification effect was significantly reduced, and VOCs or dust emissions exceeded the standard. In Comparative Examples 3 and 4, the flow ratio of the two flue gases deviated from the optimal range of 2:(3-5) in this invention, resulting in insufficient coating or excessive dust, and poor purification and operational stability.

[0083] Comparative Example 5, lacking VOCs detection and reflux, saw VOCs emissions rise to 41 mg / m³, easily exceeding VOCs standards. Comparative Example 6, lacking a waste heat recovery step, achieved zero energy savings, failing to meet low-carbon requirements. Comparative Example 7, using only ordinary filter screens, experienced system operating resistance of 1350 Pa and a clogging failure rate of 16.8%. Comparative Example 8, without pretreatment of either type of flue gas, achieved a clogging failure rate of 22.4% and a continuous stable operating time of only 96 hours, highlighting the necessity of pretreatment and three-stage filtration.

[0084] The above description is merely the preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for treating flue gas from environmentally friendly recycled asphalt mixtures, characterized in that, Includes the following steps: The regenerated flue gas and the original flue gas are collected separately in a sealed environment. The regenerated flue gas is cooled to 120℃-160℃, and the original flue gas is pre-dust removed to remove dust particles with a diameter ≥50μm. The cooled regenerated flue gas is mixed with the pre-dust-removed original flue gas. After mixing, the mixture is allowed to settle to remove the oil, sludge and dust mixture, resulting in the first mixed flue gas. The first mixed flue gas is subjected to multi-stage gradient filtration, passing sequentially through a coarse filter, an activated carbon adsorption layer, and an oil fume electrostatic adsorber to remove residual dust and liquid oil fumes, thus obtaining the second mixed flue gas. The second mixed flue gas was subjected to catalytic oxidation treatment at 200℃-280℃ to obtain the third mixed flue gas; The third mixed flue gas undergoes waste heat recovery, and after the waste heat recovery is completed, it is discharged at high altitude.

2. The method for treating flue gas from environmentally friendly recycled asphalt mixtures according to claim 1, characterized in that, The regenerated flue gas is cooled to 120℃-160℃ by water cooling. The water cooling process is completely sealed and leak-free, and the condensed oil fumes are collected. The method for pre-dust removal of the raw flue gas is cyclone pre-dust removal.

3. The method for treating flue gas from environmentally friendly recycled asphalt mixtures according to claim 1, characterized in that, The method for mixing the cooled regenerated flue gas with the pre-dust-removed original flue gas is as follows: the inlet flow ratio of the cooled regenerated flue gas to the pre-dust-removed original flue gas is controlled at 2:(3-5), and the mixture is mixed by strong convective swirling disturbance.

4. The method for treating flue gas from environmentally friendly recycled asphalt mixtures according to claim 1, characterized in that, After mixing, the sedimentation process is carried out by gravity and / or centrifugal sedimentation, and the oil sludge and dust mixture is removed and recycled for later use.

5. The method for treating flue gas from environmentally friendly recycled asphalt mixtures according to claim 1, characterized in that, The coarse filter screen is cleaned by compressed air pulse backflushing, with a cleaning pressure of 0.4MPa-0.6MPa.

6. The method for treating flue gas from environmentally friendly recycled asphalt mixtures according to claim 1, characterized in that, Before catalytic oxidation treatment of the second mixed flue gas, VOCs concentration is detected. If the VOCs concentration exceeds the standard, the second mixed flue gas is controlled to be mixed again. The flow rate of the second mixed flue gas is 15%-30% of the total inlet flow rate.

7. The method for treating flue gas from environmentally friendly recycled asphalt mixtures according to claim 1, characterized in that, When the third mixed flue gas undergoes waste heat recovery, the waste heat recovery temperature is controlled between 80℃ and 100℃.

8. An environmentally friendly recycled asphalt mixture flue gas treatment system, used to implement the environmentally friendly recycled asphalt mixture flue gas treatment method as described in any one of claims 1-7, characterized in that: It includes a recycled asphalt drying drum, a virgin asphalt drying drum, a flue gas pretreatment unit, a flue gas mixing chamber, a multi-stage filtration unit, a catalytic oxidation unit, a waste heat recovery unit, an online monitoring unit, and a control unit; The recycled asphalt drying drum and the virgin asphalt drying drum are respectively connected to the flue gas mixing chamber via the flue gas pretreatment unit. The flue gas mixing chamber is sequentially connected to the multi-stage filtration unit, the catalytic oxidation unit, and the waste heat recovery unit. The online monitoring unit collects data on flue gas temperature, pressure difference, dust concentration, VOCs concentration, and oxygen content in real time and sends the data to the control unit. The recycled asphalt drying drum, virgin asphalt drying drum, flue gas pretreatment unit, flue gas mixing chamber, multi-stage filtration unit, catalytic oxidation unit, waste heat recovery unit, and online monitoring unit are all electrically connected to the control unit.

9. The environmentally friendly recycled asphalt mixture flue gas treatment system according to claim 8, characterized in that, The flue gas pretreatment unit includes a regenerated flue gas indirect cooler and a primary flue gas cyclone pre-dust collector; the flue gas mixing chamber is equipped with a counter-current swirl guide device and a frequency conversion regulating damper, and the bottom of the flue gas mixing chamber is equipped with a sludge scraping mechanism and an oil sludge collection hopper.

10. The environmentally friendly recycled asphalt mixture flue gas treatment system according to claim 8, characterized in that, The multi-stage filtration unit includes a coarse filter, an activated carbon adsorption layer, and an electrostatic oil fume adsorber connected in sequence. The coarse filter is equipped with a compressed air pulse backflushing cleaning system. The catalytic oxidation unit includes a catalytic reactor, which incorporates a noble metal honeycomb catalyst. The waste heat recovery unit includes a gas-to-gas plate / tube heat exchanger, the output end of which is connected to the preheating port of the recycled asphalt drying drum. The online monitoring unit includes a temperature sensor, a pressure sensor, a differential pressure sensor, an online dust concentration monitor, a VOCs concentration monitor, and an oxygen content analyzer; The control unit includes a PLC controller, a touch screen, a frequency converter drive module, an alarm module, a data storage module, and a remote monitoring module.

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