Hot flue gas backflow method for increasing temperature of waste gas at inlet of incinerator

Abstract

The invention relates to the technical field of waste gas treatment, discloses a hot flue gas backflow method for increasing the temperature of waste gas at an inlet of an incinerator, and is applied to a heat accumulating type incinerator. According to the method, part of purified flue gas is led back to a waste gas inlet pipeline through a branch pipeline connected between a purified flue gas outlet and a waste gas inlet of the heat accumulating type incinerator; mixing the returned purified flue gas with the original waste gas; monitoring the temperature of the mixed waste gas in real time; and the backflow amount of the purified flue gas in the branch pipeline is dynamically adjusted according to the temperature. According to the method, the initial temperature of the waste gas entering the incinerator is increased, the risk that substances prone to crystallization are separated out due to low-temperature waste gas is effectively relieved, and heat accumulator smoothness and system operation stability are maintained. And by adjusting the temperature, the stability of the combustion working condition is ensured while excessive consumption of auxiliary fuel is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of waste gas treatment, and in particular to a hot flue gas reflow method for increasing the temperature of waste gas at an incinerator inlet. Background Art

[0002] In the field of industrial waste gas treatment, the regenerative thermal incinerator (RTO) is a widely used device for the efficient treatment of pollutants such as volatile organic compounds (VOCs). Its core principle is to use the regenerative body to recover the heat of the high-temperature flue gas after combustion and preheat the low-temperature waste gas entering the incinerator to achieve energy saving. However, in actual operation, the inlet waste gas temperature is often too low, especially when treating waste gas containing easily crystallized components (such as naphthalene). The low temperature can easily lead to the precipitation of crystals, resulting in blockage of the regenerative body and uneven airflow distribution, which seriously affects the stability of the system operation and the treatment efficiency. Traditional methods mainly try to increase the inlet temperature by optimizing the structure of the regenerative body or extending the preheating time, but the effect is limited and may increase energy consumption or system complexity. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a hot flue gas reflow method for increasing the temperature of the exhaust gas at the incinerator inlet.

[0004] The present invention provides a hot flue gas recirculation method for increasing the temperature of exhaust gas at an incinerator inlet, which is applied to a regenerative thermal incinerator. The method comprises: S1, through a branch pipe connected between the purified flue gas outlet and the exhaust gas inlet of the regenerative thermal incinerator, leading part of the purified flue gas back to the exhaust gas inlet of the regenerative thermal incinerator; S2, mixing the returned part of the purified flue gas with the original waste gas; S3, real-time monitoring of the temperature of the mixed exhaust gas; S4. Adjusting the amount of purified flue gas reflux through the branch pipe according to the temperature of the mixed exhaust gas.

[0005] Optionally, Said S3 also includes real-time monitoring of the temperature of the combustion regenerator of said regenerative incinerator; The S4 further includes adjusting the reflux rate of the purified flue gas according to the difference between the monitored temperature of the mixed exhaust gas and the temperature of the combustion regenerator.

[0006] Optionally, after S4, the step further includes: S5. Monitoring the oxygen content of the mixed exhaust gas at the exhaust gas inlet pipe; S6. When it is monitored that the oxygen content of the mixed exhaust gas is lower than the set content threshold, the reflux amount of the purified flue gas in S1 is reduced.

[0007] Optionally, after S4, the step further includes: S7, monitoring the pressure difference of the branch pipeline; S8. When it is monitored that the pressure difference of the branch pipeline exceeds a set pressure difference threshold, a dust cleaning operation for the branch pipeline is triggered.

[0008] Optionally, the mixing step in S2 is achieved by a static mixer. Optionally, after S4, the step further includes: S9. Introducing compressed air into the static mixer for purging through a compressed air purging interface provided on the static mixer.

[0009] Optionally, the step S1 further includes maintaining the pressure in the branch pipe within a target pressure range by means of a bursting disc disposed in the branch pipe.

[0010] Optionally, the inner wall of the branch pipe is coated with a PTFE coating. Optionally, the process of adjusting the reflux flow rate is performed by controlling the opening of a pneumatic regulating valve.

[0011] The present invention has the following technical effects: The present invention introduces part of the purified flue gas into the exhaust gas inlet pipe of the heat storage incinerator and fully mixes it with the original exhaust gas, which directly increases the initial temperature of the exhaust gas entering the incinerator, effectively alleviates the risk of precipitation of easily crystallized substances caused by low-temperature exhaust gas, and maintains the patency of the heat storage body and the stability of system operation.

[0012] By real-time monitoring of the mixed exhaust gas temperature and dynamically adjusting the reflux flow rate, the inlet temperature is maintained in an appropriate range, which not only avoids excessive consumption of auxiliary fuel but also prevents combustion chamber temperature fluctuations.

[0013] After monitoring the temperature of the combustion regenerator and performing linkage adjustment based on the mixed temperature difference, the balance of the temperature field distribution is further optimized and local high or low temperature areas are reduced.

[0014] Monitoring the oxygen content at the mixing position and timely reducing the reflux flow under low oxygen conditions ensures the adequacy of the subsequent combustion reaction.

[0015] Real-time monitoring of branch pipeline pressure differences and dust cleaning operations significantly reduce the risk of pipeline blockage.

[0016] Using a static mixer for gas mixing improves the uniformity of heat exchange, and combined with compressed air purging, it effectively suppresses dust accumulation inside the mixer.

[0017] Bursting discs are installed in the branch pipes to maintain a safe pressure range, and the PTFE coating on the inner wall enhances corrosion resistance.

[0018] The pneumatic regulating valve is used to control the opening for flow regulation, achieving accurate and rapid control of the return flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic flow chart of a hot flue gas recirculation method for increasing the exhaust gas temperature at an incinerator inlet provided by an embodiment of the present invention; Figure 2 A schematic structural diagram of a regenerative incinerator provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0022] Figure 1 A schematic flow chart of a hot flue gas recirculation method for increasing the exhaust gas temperature at the inlet of an incinerator provided in an embodiment of the present invention, which is applied to a regenerative thermal incinerator, includes: S1, through the branch pipe connected between the purified flue gas outlet and the waste gas inlet of the regenerative incinerator, a part of the purified flue gas is led back to the waste gas inlet of the regenerative incinerator; S2, mixing the returned part of the purified flue gas with the original waste gas; S3, real-time monitoring of the temperature of the mixed exhaust gas; S4. According to the temperature of the mixed exhaust gas, the amount of purified flue gas reflux through the branch pipe is adjusted.

[0023] Figure 2 A schematic diagram of the structure of a regenerative incinerator provided in an embodiment of the present invention. Although the embodiment of the present invention involves certain structures, it actually focuses more on the improvement of the method. Therefore, the specific structure of the regenerative incinerator will not be described in detail. Only a simple diagram of the regenerative incinerator with a branch pipe is provided. Figure 2 Schematically shows a regenerative incinerator 100 , a purified flue gas outlet 101 , a waste gas inlet 102 and a branch pipe 103 .

[0024] During operation, a specially designed branch pipe connects the purified flue gas outlet and the exhaust gas inlet. This branch pipe directs a portion of the purified flue gas produced by high-temperature oxidation in the combustion chamber to the exhaust gas inlet. Inside the exhaust gas inlet, the returned purified flue gas meets the low-temperature raw exhaust gas from the production process. The two streams are thoroughly mixed within the pipe, forming a mixed exhaust gas with a relatively elevated temperature.

[0025] The mixing process ensures that airflows of different temperatures are evenly mixed. The temperature status of the mixed exhaust gas can be monitored in real time by a temperature monitoring device installed on the pipeline. This monitoring signal is continuously fed back to the control system.

[0026] The control system compares and analyzes the received actual mixed exhaust gas temperature data with the preset temperature target range. Based on this analysis, the control system generates an adjustment command. This command acts on the flow control mechanism on the branch pipe, changing the opening and closing state of the mechanism to control the return flow of the purified flue gas. When the monitored temperature is below the target range, the return flow is increased to introduce more heat; when the temperature approaches or exceeds the upper limit of the target range, the return flow is reduced accordingly.

[0027] The above method forms a closed-loop control loop. By continuously monitoring the mixing effect and adjusting the hot flue gas input ratio, the exhaust gas entering the incinerator can be actively maintained in a suitable temperature range. This directly increases the initial temperature level of the exhaust gas before entering the incinerator regenerator, which helps to reduce the possibility of easily condensed components in the exhaust gas precipitating in the low temperature section and adhering to the surface of the regenerator, thereby supporting the regenerator to maintain good ventilation performance. The thermal state of the entire incinerator system is therefore stabilized, reducing the operational instability caused by excessively low or drastic fluctuations in the inlet temperature. This process reduces the demand for auxiliary fuel consumption while providing a guarantee for the continuous, efficient and reliable operation of the regenerative incinerator.

[0028] In some embodiments, S3 also includes real-time monitoring of the temperature of the combustion regenerator of the regenerative incinerator; S4 also includes adjusting the amount of purified flue gas reflux according to the difference between the monitored temperature of the mixed exhaust gas and the temperature of the combustion regenerator.

[0029] During operation, the regenerative incinerator monitors the temperature of the mixed exhaust gas at the inlet pipe. Temperature sensors are also installed at key locations within the combustion regenerator. These sensors continuously collect temperature data from different areas within the regenerator. After system processing, they generate representative combustion regenerator temperature parameters. These temperature parameters, along with the mixed exhaust gas temperature signal from the inlet pipe, are synchronously transmitted to the control system.

[0030] The control system compares these two temperature parameters in real time, calculating the instantaneous temperature difference between them. This temperature difference serves as a key process control variable in reflux regulation decisions. If the temperature difference exceeds a predefined acceptable fluctuation range, it indicates a deviation from the system's thermal equilibrium. The control system generates targeted regulation instructions based on the specific direction and magnitude of the temperature difference.

[0031] This control command drives the flow control mechanism on the branch pipe to perform a compensatory action. For example, if the combustion regenerator temperature is significantly higher than the mixed exhaust gas temperature, it may indicate insufficient inlet heat input, and the system will instruct an appropriate increase in the purified flue gas return flow. Conversely, if the combustion regenerator temperature is relatively low, the return flow may be reduced to avoid overcooling the combustion zone. The entire control process continuously adjusts according to the trend of the temperature difference.

[0032] This approach enhances temperature field control capabilities. By capturing the temperature correlation between the incinerator's core reaction zone and the inlet preheating zone, it enables a more precise balance between heat input and heat consumption. This helps reduce axial and radial temperature gradients within the regenerator, enabling the high-temperature oxidation reaction to proceed in a more balanced and stable thermal environment, thereby improving the overall efficiency of thermal energy utilization and mitigating localized thermal stresses.

[0033] In some embodiments, S4 further includes: S5. Monitoring the oxygen content of the mixed exhaust gas at the exhaust gas inlet pipe; S6. When it is monitored that the oxygen content of the mixed exhaust gas is lower than the set content threshold, the reflux amount of the purified flue gas in S1 is reduced.

[0034] An oxygen concentration monitoring device is installed downstream of the mixing area in the exhaust gas inlet duct. This device continuously measures the oxygen content in the mixed exhaust gas and transmits real-time oxygen concentration data to the control system. The control system is internally programmed with a minimum oxygen concentration safety threshold required to maintain normal combustion.

[0035] When the monitored real-time oxygen concentration falls below this safety threshold, the control system immediately determines that the current mixed gas lacks combustion-supporting oxygen. The system then automatically generates an adjustment command, which takes precedence over other temperature control signals. This command drives the flow control mechanism on the branch pipe to reduce the flow, directly reducing the amount of purified flue gas reflux.

[0036] Oxygen concentration monitoring is linked to reflux regulation. Reducing the amount of reflux reduces the proportion of high-temperature, low-oxygen flue gas entering the system, allowing more fresh air to enter the system along with the original exhaust gas, gradually restoring the oxygen concentration in the mixed exhaust gas. The control system continuously tracks oxygen concentration changes until it rises above a safe threshold, at which point the flow restriction is lifted and normal temperature regulation is resumed.

[0037] This oxygen content guarantee mechanism ensures combustion stability. By promptly intervening in potential oxygen deficiency conditions, it prevents incomplete combustion caused by insufficient oxygen. This helps maintain flame stability and reaction efficiency, avoids the risk of unburned material deposits in the thermal storage body or piping, and reduces the formation of incomplete combustion products such as carbon monoxide, ensuring that exhaust gas meets environmental requirements.

[0038] In some embodiments, S4 further includes: S7, monitoring the pressure difference of the branch pipeline; S8. When the pressure difference of the branch pipeline is monitored to exceed the set pressure difference threshold, a dust cleaning operation for the branch pipeline is triggered.

[0039] A pressure differential detection device is installed in a specific section of the branch pipeline. This device continuously measures pressure changes at both ends of the pipeline. This data is transmitted in real time to the control system, which has a set pressure differential safety threshold that indicates pipeline patency. When continuous monitoring data indicates that the pressure differential exceeds this threshold, the control system automatically determines that there is an abnormal increase in flow resistance within the pipeline.

[0040] Once the determination is made, the system immediately triggers the pre-set duct cleaning procedure. This command activates the cleaning device actuator mounted on the outside of the duct. This actuator, according to the pre-set procedure, initiates a physical cleaning process, such as compressed air pulses or mechanical scraping, to remove particulate matter accumulated on the duct walls. The cleaning process continues until the differential pressure value falls below the safety threshold.

[0041] After cleaning is complete, the system automatically resumes normal monitoring and continues to track pressure differential trends. If the pressure differential rises abnormally again, the system will trigger cleaning again at a set interval. This solution ensures that the pipe flow cross-section remains relatively stable, preventing flow attenuation or blockage caused by continued ash accumulation.

[0042] This proactive maintenance mechanism, based on pressure differential feedback, significantly improves system operation sustainability. By promptly eliminating internal duct obstructions, it ensures unobstructed flue gas return paths. This maintains the designed transport capacity of the return system while minimizing system pressure fluctuations caused by localized blockages, ensuring the stability of the incinerator's overall airflow distribution.

[0043] In some embodiments, the mixing step in S2 is achieved by a static mixer. A static mixer is installed in the mixing area of the exhaust gas inlet duct. This device consists of multiple sets of fixed-angle guide vanes, arranged in a regular pattern along the duct's axis. When the returned purified flue gas and the original exhaust gas simultaneously enter the duct and flow through this area, the guide vanes create a composite flow pattern. The airflow is alternately divided and redirected, forming rotating and counter-swirl flows.

[0044] The mixing process creates a uniform temperature distribution across the pipe cross section, eliminating localized high or low temperature air masses. After the mixed airflow continuously passes through the entire blade structure of the static mixer, it reaches a fully balanced state of heat exchange.

[0045] As a passive mixing device, a static mixer requires no external power source. Its structural design ensures that heat and mass transfer is achieved within a limited pipe length. The entire mixing process relies solely on the kinetic energy of the fluid, without incurring additional energy consumption.

[0046] In some embodiments, S4 further includes: S9. Compressed air is introduced into the static mixer through a compressed air purge interface provided on the static mixer for purge.

[0047] The present invention also features a compressed air purge port located at a specific location on the static mixer's outer shell. This port is connected via a pipeline to the factory's compressed air supply system. The purge operation can be initiated automatically at a preset time interval or manually by an operator. When the purge sequence is activated, the compressed air control valve opens, and high-pressure air is injected into the static mixer's internal cavity through the port.

[0048] Compressed air forms a high-speed turbulent flow within the static mixer, sweeping across the guide vanes at high speed. This high-speed flow generates shear forces that remove loose sediment adhering to the vane surfaces and corners. The airflow also creates a vortex entrainment effect, pushing suspended particles downstream in the pipeline.

[0049] The purge process does not alter the static mixer's original functionality. During operation, exhaust gases continue to flow through the static mixer normally, with compressed air and exhaust gases briefly coexisting within the mixer but not participating in the mixing reaction. After the purge is complete, the valve closes and the system resumes normal operation. Any loose materials removed flow with the main airflow into the high-temperature zone of the incinerator for decomposition.

[0050] This solution helps maintain the cleanliness of the guide vane surface and ensures the long-term stability of the airflow segmentation and recombination efficiency.

[0051] In some embodiments, S1 further includes maintaining the pressure in the branch pipeline within a target pressure range by using a bursting disc disposed in the branch pipeline.

[0052] A bursting disc assembly is installed in the middle section of the branch pipe. This assembly can consist of a metal pressure-bearing diaphragm and a flange seal. The bursting disc serves as a safety boundary for pipeline pressure control, maintaining a seal during normal system operation.

[0053] When the gas pressure in the pipeline continues to rise due to abnormal operating conditions and reaches a critical threshold, the pressure-bearing surface of the metal diaphragm undergoes plastic deformation. When the deformation exceeds the material's yield point, the diaphragm instantly breaks at a pre-determined weak point. This fracture creates a directional pressure relief channel, through which the high-pressure gas in the pipeline is rapidly discharged.

[0054] During the pressure relief process, the bursting disc irreversibly changes its structural state, creating a permanent pressure relief vent. This action quickly reduces the internal pressure of the pipeline to a safe level, preventing further pressure buildup that could cause mechanical damage to the pipe or connected components. If the bursting disc fails, the system triggers an alarm signal, prompting maintenance intervention.

[0055] This effectively mitigates the risk of pipeline rupture caused by unexpected events such as gas expansion, flow blockage, or combustion flashback. The controllable pressure release process avoids secondary impacts on surrounding equipment, ensuring the integrity of equipment and personal safety in the operating area.

[0056] In some embodiments, the inner wall of the branch conduit is coated with a PTFE coating. After the branch pipeline is welded together but before system installation, the interior surface of the pipe section undergoes a special coating pretreatment. This includes sandblasting the metal substrate to remove rust and achieve the specified cleanliness and roughness requirements. Subsequently, specialized spray equipment is used to completely coat the interior of the pipe with a polytetrafluoroethylene (PTFE) suspension. The coating is applied evenly in multiple passes, each of which cures at a specific temperature to form a dense film.

[0057] The resulting continuous coating covers the internal metal-to-metal contact surfaces of the pipe. This coating is highly chemically inert to acidic components, organic solvents, or water vapor that may be present in the gas mixture. The coating's microscopically smooth surface exhibits extremely low surface adhesion upon contact with the gas stream.

[0058] After the pipeline is put into operation, the purified flue gas flowing through it continuously contacts the coating's protective interface. The tiny ash particles or condensate droplets carried by the flue gas have a weak interaction with the coating surface. Fluctuations in airflow velocity or external vibrations can easily cause deposits to peel off.

[0059] The PTFE coating material itself does not participate in the chemical reactions between flue gas components and does not soften or deform under the continuous passage of high-temperature gases. The coating's elasticity adapts to the slight deformations caused by temperature cycling, preventing cracking or delamination. Its chemical inertness prevents electrochemical corrosion between the metal and complex flue gases, blocking the formation of corrosion products.

[0060] In some embodiments, the process of adjusting the reflux amount is performed by controlling the opening of a pneumatic regulating valve.

[0061] A pneumatic control valve is installed in the branch pipeline as a flow control element. This pneumatic control valve is rigidly connected to the pipeline system via a flange. The valve body of the pneumatic control valve features an axially movable valve core. The movement of the valve core changes the flow area, thereby controlling the flow of purified flue gas through the pipeline. The valve actuator is equipped with a compressed air drive system, with the air source being the stable gas supply network within the plant.

[0062] Pneumatic control valves receive electrical signals from the control system. These signals are converted by an electrical converter into a standard air pressure signal, with the pressure proportional to the desired opening. The varying air pressure signal acts on the actuator's diaphragm cavity, driving the push rod to produce axial displacement. This displacement is transmitted to the valve core via a linkage mechanism, accurately positioning it within the valve seat.

[0063] The valve spool's movement exhibits controllable response characteristics. A position feedback device is built into the actuator, detecting the actual spool displacement in real time and providing feedback to the control system. The system continuously compares the feedback displacement with the target displacement, eliminating positioning deviations by fine-tuning the air pressure signal.

[0064] This device achieves linear control of valve opening and flow rate. The unique profile design of the valve core ensures that the rate of flow change and valve stem displacement maintain a stable proportional relationship at any opening. This makes return flow regulation predictable and repeatable. The actuator's output thrust overcomes the unbalanced force of the fluid on the valve core, maintaining a stable opening despite airflow disturbances.

[0065] The compressed air power system provides continuous and stable driving force. Fluctuations in the air source pressure are eliminated by a pressure stabilizer, ensuring constant actuator output torque. This maintains valve positioning accuracy during long-term operation, preventing flow drift caused by actuation force degradation. This drive method adapts to vibration and temperature fluctuations in industrial environments, enabling the system to achieve precise flow control during continuous operation.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet, characterized in that: Applied to a regenerative thermal incinerator, the method comprises: S1, through a branch pipe connected between the purified flue gas outlet and the exhaust gas inlet of the regenerative thermal incinerator, leading part of the purified flue gas back to the exhaust gas inlet of the regenerative thermal incinerator; S2, mixing the returned part of the purified flue gas with the original waste gas; S3, real-time monitoring of the temperature of the mixed exhaust gas; S4. Adjusting the amount of purified flue gas reflux through the branch pipe according to the temperature of the mixed exhaust gas.

2. A hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet according to claim 1, characterized in that: Said S3 also includes real-time monitoring of the temperature of the combustion regenerator of said regenerative incinerator; The S4 further includes adjusting the reflux rate of the purified flue gas according to the difference between the monitored temperature of the mixed exhaust gas and the temperature of the combustion regenerator.

3. The hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet according to claim 1, characterized in that: The S4 also includes: S5. Monitoring the oxygen content of the mixed exhaust gas at the exhaust gas inlet pipe; S6. When it is monitored that the oxygen content of the mixed exhaust gas is lower than the set content threshold, the reflux amount of the purified flue gas in S1 is reduced.

4. The hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet according to claim 1, characterized in that: The S4 also includes: S7, monitoring the pressure difference of the branch pipeline; S8. When it is monitored that the pressure difference of the branch pipeline exceeds a set pressure difference threshold, a dust cleaning operation for the branch pipeline is triggered.

5. The hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet according to claim 1, characterized in that: The mixing step in S2 is achieved by a static mixer.

6. A hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet according to claim 5, characterized in that: After S4, the method further includes: S9, introducing compressed air into the static mixer through a compressed air purge interface provided on the static mixer for purge.

7. The hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet according to claim 1, characterized in that: The step S1 further includes maintaining the pressure in the branch pipe within a target pressure range by using a bursting disc disposed in the branch pipe.

8. The hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet according to claim 1, characterized in that: The inner wall of the branch pipe is coated with a PTFE coating.

9. The hot flue gas recirculation method for increasing the exhaust gas temperature at the incinerator inlet according to claim 1, characterized in that: The process of adjusting the reflux flow is performed by controlling the opening of the pneumatic control valve.

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