Waste pyrolysis gas combustion device and combustion method

Abstract

This invention provides a waste pyrolysis gas combustion device and its combustion method, belonging to the field of waste treatment technology. The invention includes: a shell, foam ceramic balls, a central tube, a preheater, a mixing tube, a co-firing air sleeve, and a flow-dispersing component. This invention uses foam ceramic balls as a heat storage carrier in conjunction with a preheater to achieve stable ignition of pyrolysis gas with low calorific value fluctuations, effectively adapting to the combustion requirements of waste pyrolysis gas with low calorific value and parameter fluctuations, and improving combustion stability. The flow-dispersing component in the mixing tube enhances gas-gas mixing, improving combustion efficiency and pollutant control, increasing combustion completeness, reducing pollutant generation, and optimizing combustion efficiency. The compact structure of the nested central tube and mixing tube with annular slot air intake achieves efficient space utilization and integrated application, realizing precise gas distribution and efficient mixing within a limited space. The overall layout of the device is compact and easy to integrate.

Description

Technical Field

[0001] This invention relates to the field of waste treatment technology, and in particular to a waste pyrolysis gas combustion device and its combustion method. Background Technology

[0002] For household waste, medical waste, floating debris, and industrial organic waste such as wind turbine blades and waste asphalt residue, the first step is to pyrolyze them to generate pyrolysis gas with a certain calorific value and containing combustible components. The purified pyrolysis gas is then used as fuel or directly burned to recover heat. This "two-stage" treatment method is an effective way to achieve the "reduction, resource utilization, and harmlessness" of organic solid waste, and it is also an important technological development direction for achieving ultra-low pollutant emissions from waste treatment.

[0003] However, for small and medium-sized fixed-bed pyrolysis reactors with low heat capacity, the reaction process is easily disturbed by factors such as batch feeding through the furnace door, airflow through the chimney, and the operation of control valves in the gas flow pipeline. This leads to fluctuations in flow field parameters such as pressure and velocity within the gas flow pipeline, resulting in significant fluctuations in key state parameters of the pyrolysis gas, including its calorific value, flow rate, temperature, and composition. This poses a significant challenge to the efficient and stable combustion of the pyrolysis gas. For example, opening the furnace door allows air to rush into the furnace, interrupting the pyrolysis reaction and causing the calorific value of the pyrolysis gas to drop sharply or even to zero. When a new batch of waste is fed, the endothermic processes such as preheating cause the temperature inside the reactor to drop rapidly, severely affecting the pyrolysis reaction. The moisture content of the pyrolysis gas from some types of waste, such as municipal solid waste and floating debris, can even surge to over 74%, resulting in extremely low calorific value. This situation leads to highly unstable combustion of the pyrolysis gas, low overall combustion efficiency, and increased difficulty in controlling pollutant emissions.

[0004] To address this issue, engineers have conducted extensive research. For example, patent CN 202210176886.X proposed a two-stage counter-swirling partially premixed combustion technology. Practice has shown that this technology has high combustion efficiency for pyrolysis gases with a calorific value above 4.2 MJ / Nm³ and relatively small parameter fluctuations. However, it is less adaptable to pyrolysis gases with low calorific values ​​and large parameter fluctuations. The ignition system needs frequent restarts, and re-ignition after flameout is difficult and time-consuming, resulting in low overall combustion efficiency. Patent CN202410907168.4 proposed a single-stage swirling burner with a flame stabilizer and a heat storage body downstream of the combustion chamber. This significantly improves the flame's lateral propagation capability, flame stability, and the ability to promote pyrolysis gas combustion and maintain flue gas temperature stability after flameout. Overall combustion efficiency and flame stability are also improved. However, the heat storage body cannot ignite the upstream burner, requiring repeated restarts of the ignition system. Therefore, for waste pyrolysis gas with large fluctuations in parameters such as calorific value and flow rate, developing a combustion method and equipment with high combustion efficiency, good stability, and no need for frequent re-ignition is of great significance for promoting the development of organic combustible waste pyrolysis treatment technology and achieving ultra-low pollutant emissions in the waste treatment process. Summary of the Invention

[0005] In view of this, to address the technical problems of unstable combustion of pyrolysis gas and low overall combustion efficiency in existing pyrolysis reactors, this invention provides a waste pyrolysis gas combustion device and its combustion method. It utilizes foamed ceramic balls as a heat storage carrier in conjunction with a preheater to achieve stable ignition of pyrolysis gas with low calorific value fluctuations, effectively adapting to the combustion requirements of waste pyrolysis gas with low calorific value and parameter fluctuations, thus improving combustion stability. By relying on a mixing tube turbulence component to enhance gas-gas mixing, combustion efficiency and pollutant control levels are improved, combustion completeness is enhanced, pollutant generation is reduced, and combustion efficiency is optimized. The compact structure of nested central and mixing tubes and annular slot air inlet achieves efficient space utilization and integrated application, realizing precise gas distribution and efficient mixing within a limited space. The overall layout of the device is compact and easy to integrate.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a waste pyrolysis gas combustion apparatus, comprising: The casing has a smoke exhaust port and contains foam ceramic balls. These foam ceramic balls, acting as a porous medium, are arranged between the upper and lower parts of the casing to form a stable combustion bed. The blockage status is determined by monitoring the static pressure difference (P1, P2) before and after the porous medium, and this serves as one of the shutdown trigger conditions. The foam ceramic balls, consisting of an upper and lower sphere, are arranged around the central tube. A limiting rod is circumferentially positioned at the junction of the upper and lower spheres. Its function is to constrain the alignment of the upper and lower spheres, preventing pressure fluctuations from causing relative positional shifts, ensuring the structural stability of the foam ceramic balls, and avoiding positional shifts that could affect the combustion flow field and combustion efficiency.

[0007] The central tube, connected at one end to the foam ceramic spheres and at the other end to allow heat dissipation gas to enter the circulation, comprises a vertical pipe, a tray, and a co-firing air sleeve. The vertical pipe, the main vertical pipe of the central tube, connects at one end to the foam ceramic spheres, providing support and flow space for the mixing pipe and foam ceramic spheres, allowing premixed gas flow and guiding high-temperature flue gas, integrating multi-path gas flow, and optimizing the combustion system layout. The tray is located inside the vertical pipe near the foam ceramic spheres, providing stable support and preventing combustion carrier displacement that could disrupt combustion conditions. The co-firing air sleeve connects to the annular seam between the central tube and the mixing pipe, guiding the co-firing air flow to the mixing area, optimizing the co-firing air flow path, and ensuring effective gas mixing.

[0008] The preheater, connected to the foam ceramic spheres near the central pipe, is used to supply fuel gas and preheated air, and to ignite the fuel gas and preheated air. The preheater includes a fuel pipe, a conductive wire, an outer horizontal pipe, a reducing elbow, a flame arrestor, a vertical outer pipe, and an ignition nozzle. The fuel pipe serves as a transport channel for auxiliary fuel gas during preheating, providing a fuel input path for the preheating stage. The conductive wire serves as the power supply line for the ignition nozzle, transmitting electrical energy to support the ignition nozzle in generating an electric spark, ensuring the normal triggering of the preheating ignition function. The outer horizontal pipe acts as a lateral guide structure for preheating high-temperature flue gas, directionally transporting the preheated flue gas to the foam ceramic sphere area, achieving rapid heating of the combustion carrier. The reducing elbow is a transition component for pipes of different diameters, adapting to the pipe diameter parameters of different passages. It reduces the flow velocity of the gas mixed with preheated air, which is conducive to forming a short and stout flame. This prevents the preheated flame from being too thin and elongated, thus avoiding contact with the unheated foam ceramic balls and quenching, or causing uneven heating and cracking of the foam ceramic balls. This improves combustion efficiency during preheating, reduces pollutant emissions, and extends the life of the foam ceramic balls. The flame arrestor is a porous medium structure set on the gas outlet side, physically blocking the backfire path of the preheated flame and preventing backfire from entering the upstream gas path and causing safety hazards. The vertical outer pipe is the vertical main load-bearing structure of the preheater, integrating and installing internal components such as the gas pipe and ignition nozzle. It also serves as the external enclosure structure for the mixing and flow of preheated air and gas, reducing heat loss during the preheating stage. The ignition nozzle is the ignition execution component during the preheating start-up stage. After being energized, it generates an electric spark to ignite the mixture of gas and preheated air, triggering the preheating combustion process and providing an initial heat source for the foam ceramic balls to heat up.

[0009] A mixing tube is disposed inside the central tube, near the other end of the central tube, and has an annular seam between it and the central tube.

[0010] A combustion air sleeve, connected to the annular seam, is used to transport combustion air; The mixing pipe is a straight pipe with a flow-dispersing component, which is used to make the co-fired air and the pyrolysis gas mixed evenly in the annular gap, thereby improving the premixing degree and thus improving the uniformity of fuel and air entering the foam ceramic ball, avoiding local air-fuel ratio unevenness that affects combustion efficiency.

[0011] Secondly, the present invention provides a combustion method for the above-mentioned waste pyrolysis gas combustion device, comprising the following steps: Step (1) Preheating condition The combustion of fuel gas and preheated air at a theoretical equivalence ratio produces high-temperature flue gas, which heats the porous media combustion carrier until it is capable of ignition. This preheating operation focuses on shortening the preheating time and saving the fuel gas required for preheating. It uses a theoretical equivalence ratio and applies a small flow rate of high-temperature flue gas through the foam ceramic balls to rapidly raise their temperature.

[0012] Step (2), Initial Operating Conditions Pyrolysis gas and co-fired air are mixed at a near-theoretical equivalence ratio and then fed into the combustion system. The flow rate is gradually increased to achieve smooth ignition of the pyrolysis gas. The initial operating condition focuses on stabilizing the temperature of the foam ceramic balls. Therefore, the pyrolysis gas and co-fired air are fed into the reactor at a theoretical equivalence ratio with gradually increasing flow rates, while the preheater remains operational.

[0013] Step (3) Stable operating conditions The air-fuel mixture flow rate is adjusted to control the oxygen concentration in the flue gas within a preset range, while maintaining the flue gas temperature within the range that meets environmental protection requirements. Emphasis is placed on a smooth transition to stable operating conditions and successful ignition of the pyrolysis gas. Therefore, the air-fuel ratio is gradually increased from 1 (theoretical equivalence ratio), i.e., the proportion of air-fuel mixture is increased, until the [O2] in the flue gas is 11±2% and the temperature is ≥850℃ (beneficial for dioxin elimination), and the preheater is shut off only after stabilization. Stable operating conditions prioritize combustion efficiency to improve environmental friendliness and operational safety. Therefore, the [O2] in the flue gas is controlled to around 11% to promote complete combustion; when the flue gas temperature is too high, more air is introduced to lower the temperature; when the flue gas temperature is too low, the air input is reduced to prevent flameout and improve combustion stability. Overall, this control method has higher comprehensive combustion efficiency and combustion stability. Under stable operating conditions, if the static pressure difference before and after the foam ceramic balls, i.e., the difference between static pressure gauge P1 and static pressure gauge P2, exceeds the set value (usually 85 Pa), it means that there is a large amount of inorganic matter deposited inside the foam ceramic balls, which reduces the porosity and increases airflow resistance, requiring shutdown for maintenance. Under stable operating conditions, if the temperature and [O2] conditions cannot be met, it indicates that the calorific value of the pyrolysis gas is insufficient and exceeds the operating range of this device, requiring shutdown.

[0014] Step (4) Adaptive Adjustment of Operating Conditions The amount of co-firing air is adjusted in conjunction with the parameters of high-temperature flue gas temperature and oxygen concentration to ensure the lower limit of flue gas temperature to reduce pollutants, while controlling the upper limit of temperature to protect the equipment.

[0015] Step (5), Safe shutdown condition When the porous ceramic balls become clogged or the pyrolysis gas parameters exceed the system's adaptability range, the input of pyrolysis gas and co-firing air is sequentially cut off to terminate the combustion process.

[0016] Compared with the prior art, the present invention has the following beneficial effects: High adaptability and stable combustion guarantee: Foam ceramic balls are used as porous media combustion carriers and arranged between the upper and lower shells to form a stable combustion bed. Its core function is efficient ignition under high temperature, thereby improving combustion stability. It also utilizes the large specific surface area of ​​foam ceramics to improve combustion efficiency. Combined with the preheater for rapid heating and temperature rise, it can continuously maintain a high temperature ignition environment, effectively adapting to waste pyrolysis gas with low calorific value and parameter fluctuations. It solves the problems of frequent ignition and poor stability of traditional combustion technology, and achieves smooth ignition and continuous stable combustion of pyrolysis gas.

[0017] Synergistic effect of high-efficiency combustion and low emissions: The built-in turbulence component in the mixing tube enhances the uniform mixing of co-fired air and pyrolysis gas, improving combustion completeness; combined with the high-temperature regenerative combustion characteristics of foam ceramic balls, the overall combustion efficiency can be increased to over 99.5%, while suppressing dioxins and NOx. x To achieve ultra-low emissions, pollutants are generated.

[0018] Compact integrated design: It adopts a nested layout of central tube and mixing tube, and is equipped with an annular slit air intake structure of co-firing air tube sleeve. It integrates gas distribution, mixing and combustion functions in a limited space. The device has a compact structure and is easy to deploy and apply flexibly in small and medium-sized waste treatment scenarios. Attached Figure Description

[0019] Figure 1 This is a flowchart of the process of the present invention; Figure 2 This is the front view of the present invention; Figure 3 for Figure 1 Enlarged view of point I; Figure 4 for Figure 1 Enlarged view of section II; Figure 5 for Figure 4 Enlarged view of section III; Figure 6 Exploded view of the assembly of the central tube, asbestos pad, upper sphere, and lower sphere; Figure 6 This is an isometric view of the central tube; Figure 7This is an isometric view of the mixing tube; Figure 8 This is a schematic diagram of the structure of the turbulence component; In the diagram, 1. High-temperature flue gas; 2. Exhaust port; 3. Upper shell; 4. Lower shell; 5. Foam ceramic ball; 6. Limiting rod; 7. Central tube; 8. Preheater; 9. Gas valve; 10. Gas; 11. Preheating air valve; 12. Preheating air; 13. Mixed air; 14. Mixed air valve; 15. Mixed air pipe; 16. Pyrolysis gas; 17. Pyrolysis gas valve; 18. Pyrolysis gas pipe; 19. First static pressure gauge; 20. Temperature sensor; 21. Second static pressure gauge. 22. Oxygen sensor; 23. Asbestos pad; 24. Flame arrestor grid; 25. Mixing pipe; 251. Straight pipe; 252. Inner baffle; 253. Outer baffle; 501. Upper sphere; 502. Lower sphere; 701. Vertical pipe; 702. Tray; 703. Air mixing sleeve; 801. Gas pipe; 802. Conductive wire; 803. Outer horizontal pipe; 804. Reducing elbow; 805. Flame arrestor medium; 806. Vertical outer pipe; 807. Ignition nozzle. Detailed Implementation

[0020] 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 described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] like Figure 2 , 4 As shown, the present invention provides a waste pyrolysis gas combustion device, including a shell, foam ceramic balls 5, a central tube 7, a preheater 8, and a mixing tube 25, etc.

[0022] The casing has a flue gas outlet 2, and foam ceramic balls 5 are arranged inside. The combustion reaction produces high-temperature flue gas 1, which is eventually discharged from the flue gas outlet 2. During the preheating stage, the high-temperature flue gas 1 heats the foam ceramic balls 5, rapidly increasing the temperature of the foam ceramic balls 5 and shortening the preheating time. Under stable operating conditions, it carries the heat of combustion, reflects the combustion state, and achieves precise control through parameter monitoring, ensuring combustion efficiency and environmental protection.

[0023] The foam ceramic ball 5 stores heat during the preheating stage and acts as a combustion carrier under stable operating conditions, achieving efficient ignition in an incandescent state and maintaining combustion stability. It utilizes a large specific surface area to improve combustion efficiency and stores heat to smooth flue gas temperature fluctuations. This foam ceramic ball 5 combines heat storage and ignition functions, eliminating the need for frequent start-ups and shutdowns of the ignition system; its slow percolation velocity helps smooth fluctuations in the pyrolysis gas parameters; thus, it increases the overall combustion efficiency to over 99.5%, significantly reducing pollutant emissions.

[0024] The shell, consisting of an upper shell 3 and a lower shell 4, helps reduce thermal stress damage caused by uneven temperature fields, thereby improving the lifespan of the device. The upper shell 3 forms the external protection and containment space for the equipment, supporting internal components, protecting internal parts, and maintaining the overall structural stability of the equipment. The lower shell 4 constitutes the bottom structure of the equipment, bearing the internal components, stably supporting the equipment, and sealing the internal space.

[0025] The central tube 7 is connected at one end to the foam ceramic ball 5, and the other end is supplied with heat and gas 16 for circulation.

[0026] The preheater 8 is connected to one end of the central tube 7 that is connected to the foam ceramic ball 5, and is used to supply gas 10 and preheated air 12 and ignite the gas 10 and preheated air 12.

[0027] A mixing tube 25 is disposed inside the central tube 7, near the other end of the central tube 7, and has an annular gap between it and the central tube 7.

[0028] The air mixing sleeve 703 is connected to the annular seam and is used to transport the mixed air 13. The air mixing sleeve 703 guides the mixed air 13 to flow to the mixing area, optimizes the flow path of the mixed air 13, and ensures the mixing effect.

[0029] The mixing tube 25 has a flow-disrupting component for uniformly mixing the combustion air 13 and the pyrolysis gas 16 in the annular gap.

[0030] In this technical solution, the foam ceramic spheres 5 inside the shell serve as the heat storage combustion carrier. Pyrolysis gas 16 is transported through the central pipe 7, and co-firing air 13 enters the central pipe 7 through the co-firing air sleeve 703 and annular seam. The turbulence component inside the mixing pipe 25 ensures that the pyrolysis gas 16 and co-firing air 13 are fully mixed in the annular seam area. The preheater 8 introduces and ignites the fuel gas 10 and preheated air 12, heating the foam ceramic spheres 5 to ignition capability. The uniformly mixed pyrolysis gas 16 and air then burn stably in the area of ​​the foam ceramic spheres 5, and the high-temperature flue gas 1 is discharged through the exhaust port 2. By combining a porous media combustion carrier with a precise gas-to-gas mixing structure, the problem of stable ignition of low-calorific-value, parameter-fluctuating waste pyrolysis gas 16 is solved; the compact nested layout improves space utilization and is suitable for flexible deployment in small and medium-sized waste treatment scenarios.

[0031] In this invention, the foam ceramic spheres 5, consisting of an upper sphere 501 and a lower sphere 502, are arranged around the central tube 7. The modular design facilitates installation, disassembly, and replacement within the housing. This reduces the maintenance difficulty of the combustion carrier, allowing for the inspection or replacement of the foam ceramic spheres 5 without the need for a complete disassembly device, significantly improving equipment operation and maintenance efficiency.

[0032] In this invention, the limiting rod 6 is circumferentially arranged between the upper sphere 501 and the lower sphere 502 of the foam ceramic ball 5, constraining the upper sphere 501 and the lower sphere 502 to align and prevent relative positional displacement caused by air pressure fluctuations. This ensures the structural stability of the foam ceramic ball 5 and avoids affecting the combustion flow field and efficiency due to positional displacement.

[0033] In this invention, a flame arrestor 24 is installed inside the central tube 7 above the mixing tube 25, located on the flow path of the mixed gas. This prevents the flame from burning back to the upstream mixing port, avoiding safety hazards caused by gas pressure differences. This is especially important when there is a large pressure difference between the combustion air 13 and the pyrolysis gas 16, causing the mixed gas to flow towards the lower pressure path, thus creating a safety hazard. This improves the safety of the combustion system and protects upstream components.

[0034] In this technical solution, the flame arrestor 24 can physically block the flame from spreading back to the pyrolysis gas 16 input end, cutting off the backfire propagation path. This enhances the safety protection level of the device and prevents safety accidents such as explosions and combustion caused by backfire on the pyrolysis gas 16 conveying side.

[0035] like Figure 3 , 5 As shown, in this invention, the preheater 8 includes: The outer horizontal pipe 803 serves as the horizontal pipe of the preheater 8, and a gas pipe 801 is installed inside it. The outer horizontal pipe 803 is used to transport preheated air 12 and preheat the gas pipe 801, thereby improving the efficiency and safety of the preheater 8. The gas pipe 801 is used to transport gas 10 to the combustion zone and is preheated by the preheated air 12, thereby improving safety and service life.

[0036] The vertical outer pipe 806, serving as the vertical pipe of the preheater 8, connects at one end to the outer horizontal pipe 803 (which serves as the horizontal pipe of the preheater 8), forming a reducing elbow 804. The diameter of the vertical outer pipe 806 is larger than that of the horizontal outer pipe, causing the airflow to change from horizontal to vertical. Simultaneously, the increased pipe diameter reduces the flow velocity, resulting in a short, stout flame. This prevents the preheating flame from contacting the unheated foam ceramic balls 5, which could lead to quenching and breakage, thus improving preheating efficiency and extending the lifespan of the foam ceramic balls 5. The other end connects to the central pipe 7. The vertical outer pipe 806 guides the high-temperature flue gas 1 into the vertical pipe 701 of the central pipe 7, optimizing the flue gas flow path and ensuring the preheating effect.

[0037] The ignition nozzle 807 is used to ignite the mixture of gas 10 and preheated air 12, generating high-temperature flue gas 1 for reliable ignition and ensuring smooth start-up during the preheating stage. It is located near the other end of the vertical outer pipe 806, where it connects to the central pipe 7, and is connected to a conductive wire 802. The conductive wire 802 is preferably located inside the preheater 8 and supplies power to the ignition nozzle 807 to achieve ignition and ensure reliable ignition.

[0038] In this technical solution, the gas pipe 801 inside the outer horizontal pipe 803 delivers gas 10, which mixes with preheated air 12 and then is delivered to the central pipe 7 via the vertical outer pipe 806 (with a reducing elbow structure 804). The ignition nozzle 807 ignites the mixed gas near the foam ceramic ball 5, generating high-temperature flue gas 1 to heat the foam ceramic ball 5 to the ignition temperature. By adopting the reducing elbow 804 and precise ignition layout, efficient mixing and rapid ignition of gas 10 and air are achieved, shortening the system preheating time and improving start-up response efficiency.

[0039] This invention also includes: The flame-retardant medium 805 is installed near the other end of the vertical outer pipe 806 where it connects to the central pipe 7. For example, it is installed inside the reducing elbow 804 to prevent the flame from burning back into the outer horizontal pipe 803 or the gas pipe 801 when the pressure difference between the gas 10 and the preheated air 12 is too large, thus protecting the preheater 8 components and improving system safety.

[0040] This technical solution prevents the flame from backflashing towards preheater 8, forming a double backfire protection barrier. Enhanced safety protection at the connection point between preheater 8 and the combustion core area further reduces the risk of equipment failure caused by backfire.

[0041] like Figure 8 As shown, in this invention, the turbulence-disrupting component includes: An inner turbulence deflector 252 is disposed in the straight pipe 251 of the mixing pipe 25 and is inclined inward to the straight pipe 251 or perpendicular to the axis of the straight pipe 251.

[0042] An external spoiler 253 is disposed on the straight pipe 251 of the mixing pipe 25 and is inclined outward from the straight pipe 251 or perpendicular to the axis of the straight pipe 251.

[0043] In this technical solution, the straight pipe 251, as the main part of the mixing pipe 25, guides the flow of pyrolysis gas 16, optimizes the flow path of pyrolysis gas 16, and ensures the orderly progress of the mixing process. The inner baffle 252 disturbs the flow of pyrolysis gas 16, promotes mixing with the co-combustion air 13, improves premixing uniformity, and lays the foundation for complete combustion. The outer baffle 253 is located outside the mixing pipe 25, between the vertical pipe 701 of the central pipe 7 and the straight pipe 251 of the mixing pipe 25, disturbs the flow of co-combustion air 13, promotes mixing with pyrolysis gas 16, and works in conjunction with the inner baffle 252 to achieve efficient and uniform gas mixing and improve combustion efficiency.

[0044] In this technical solution, the inner baffle 252 and outer baffle 253 on the straight pipe 251 of the mixing tube 25 can disrupt the laminar flow state of the mixed air 13 and the pyrolysis gas 16, causing them to form turbulence in the annular gap region, thus improving the mixing uniformity. This enhances the gas-gas mixing effect, avoids incomplete local combustion, improves the combustion efficiency of the pyrolysis gas 16, and reduces dioxins and NOx emissions. xPollutants such as these are generated.

[0045] like Figure 7 As shown, in this invention, the central tube 7 includes: The vertical pipe 701, as the main vertical pipe of the central pipe 7, is connected at one end to the foam ceramic ball 5. It is used to premix gas flow and guide high-temperature flue gas 1, providing support and flow space for the mixing pipe 25 and the foam ceramic ball 5, integrating multi-path gas flow, and optimizing the layout of the combustion system.

[0046] The tray 702 is disposed inside the vertical tube 701 and is used to support the foam ceramic ball 5.

[0047] In this technical solution, the vertical pipe 701 clearly defines the gas flow path to ensure smooth exhaust of flue gas; the tray 702 provides stable support for the combustion carrier, preventing carrier displacement from causing combustion disorder.

[0048] like Figure 6 As shown, in this invention, an asbestos pad 23 is provided between the tray 702 and the foam ceramic ball 5 to improve the sealing between the tray 702 and the lower ball 502, preventing a small amount of premixed gas from flowing through the gap between the outer vertical pipe 701 and the lower ball 502, and the gap between the lower ball 502 and the tray 702, thus affecting the overall combustion efficiency; improving the uniformity of the flow field when the premixed gas flows through the foam ceramic ball 5, and reducing the thermal stress of the foam ceramic ball 5.

[0049] like Figure 2 As shown, in this invention, the housing is provided with: A static pressure gauge is used to monitor the pressure difference across the foam ceramic ball 5. The static pressure gauge includes: The first static pressure gauge 19 is arranged on the upstream side of the foam ceramic ball 5 to monitor the upstream static pressure of the foam ceramic ball 5. The second static pressure gauge 21 is located downstream of the foam ceramic ball 5 to monitor the static pressure downstream of the foam ceramic ball 5. In conjunction with the first static pressure gauge 19, it can determine the blockage status of the foam ceramic ball 5 through pressure difference, trigger maintenance in time, and ensure combustion efficiency.

[0050] Temperature sensor 20 is used to monitor the temperature of the high-temperature flue gas 1 discharged from the exhaust port 2. During the preheating stage, it determines whether the foam ceramic balls 5 have reached the preset temperature; during the stabilization stage, it monitors the flue gas temperature as a basis for operating condition adjustment and shutdown. Accurate temperature parameter feedback ensures the accuracy of operating condition transitions and combustion control.

[0051] Oxygen sensor 22 is used to monitor the oxygen concentration in the high-temperature flue gas 1 discharged from the exhaust port 2. Under stable operating conditions, the flow rate of the co-firing air 13 is adjusted to control the oxygen concentration at 11±2%, ensuring combustion efficiency and environmental friendliness. Real-time feedback of combustion status enables closed-loop control to maintain optimal combustion conditions.

[0052] In this technical solution, the static pressure gauge and sensors enable real-time monitoring of multiple parameters in the combustion process, providing data support for adaptive adjustment of operating conditions, ensuring combustion stability and compliance with environmental emission standards; and timely detection of blockage faults in the foam ceramic balls 5, facilitating early maintenance and avoiding equipment downtime.

[0053] like Figure 1 As shown, the present invention provides a combustion method for the above-mentioned waste pyrolysis gas 16-body combustion device, comprising the following steps: Step (1) Preheating condition The combustion gas 10 is mixed with preheated air 12 at a theoretical equivalence ratio to generate high-temperature flue gas 1, which heats the porous media combustion carrier until it has ignition capability. This preheating condition focuses on shortening the preheating time and saving the combustion gas 10 required for preheating. It adopts a theoretical equivalence ratio and uses a small flow rate and high temperature flue gas to pass through the foam ceramic balls 5 to rapidly raise their temperature.

[0054] Step (2), Initial Operating Conditions Pyrolysis gas 16 and co-fired air 13 are mixed at a near-theoretical equivalence ratio and then fed into the combustion system. The flow rate is gradually increased to achieve smooth ignition of the pyrolysis gas 16. This initial operating condition focuses on stabilizing the temperature of the foam ceramic balls 5. Therefore, the pyrolysis gas 16 and co-fired air 13 are fed into the reactor at a theoretical equivalence mixing ratio with gradually increasing flow rates, while the preheater 8 remains operational.

[0055] There is a transition phase between step (2) and step (3) below, such as entering a stable operating condition: The focus is on a smooth entry into a stable operating condition, and the pyrolysis gas 16 is successfully ignited. Therefore, the air-fuel ratio is gradually increased from 1 (theoretical equivalence ratio), that is, the proportion of blended air 13 is increased, until the oxygen concentration in the flue gas is 11±2% and the temperature is ≥850℃ (which is beneficial for the elimination of dioxins), and the preheater 8 is shut off only after the flue gas has stabilized.

[0056] Step (3) Stable operating conditions The flow rate of the co-firing air (13) is adjusted to control the oxygen concentration in the flue gas within a preset range, while maintaining the flue gas temperature within a range that meets environmental protection requirements. This stable operating condition prioritizes combustion efficiency to improve environmental friendliness and operational safety. Therefore, the oxygen concentration in the flue gas is controlled to around 11% to promote complete combustion; when the flue gas temperature is too high, more air is introduced to lower it; when the flue gas temperature is too low, the air input is reduced to prevent flameout and improve combustion stability. Overall, this control method offers higher comprehensive combustion efficiency and combustion stability.

[0057] Step (4) Adaptive Adjustment of Operating Conditions The input of co-firing air 13 is adjusted in conjunction with the temperature and oxygen concentration parameters of the high-temperature flue gas 1 to ensure the lower limit of flue gas temperature to reduce pollutants, while controlling the upper limit of temperature to protect the equipment. In this adaptive adjustment, when the static pressure difference before and after the foam ceramic ball 5, that is, the difference between the first static pressure gauge 19 and the second static pressure gauge 21, is greater than the set value (usually 85 Pa), it means that there is a lot of inorganic matter deposited inside the foam ceramic ball 5, which reduces the porosity and increases the airflow resistance, requiring shutdown for maintenance.

[0058] Step (5), Safe shutdown condition When the porous ceramic balls become clogged or the parameters of pyrolysis gas 16 exceed the system's adaptability range, the input of pyrolysis gas 16 and co-firing air 13 should be cut off in sequence to terminate the combustion process. For example, if the two conditions of temperature and oxygen concentration cannot be met, it indicates that the calorific value of the pyrolysis gas 16 is insufficient and exceeds the operating range of this device, requiring shutdown.

[0059] The workflow and principle of this invention are as follows: When the equipment starts running, the gas valve 9 and the preheating air valve are opened. Natural gas or liquefied petroleum gas (LPG) gas 10 enters the gas pipe 801, and preheating air 12 enters the outer horizontal pipe 803. The two gases, in theoretical equivalent ratio, simultaneously pass through the reducing elbow 804 of the preheater 8, the flame arrestor medium 805, and the vertical outer pipe 806 into the vertical pipe 701. The control system uses the conductive wire 802 to ignite the ignition nozzle 807, which ignites the gas 10, causing combustion and releasing heat to form high-temperature flue gas 1.

[0060] High-temperature flue gas 1 rises in the vertical pipe 701 and enters the cavity formed by the upper sphere 501 and the lower sphere 502 of the foam ceramic ball 5. Then it flows radially and seeps through the foam ceramic ball 5, heating the foam ceramic ball 5 and raising its temperature.

[0061] When the temperature of the foam ceramic ball 5 rises to above 900℃, that is, when the temperature of the high-temperature flue gas 1 measured by the temperature sensor 20 reaches the preset value, such as above 850℃, it indicates that the temperature of the foam ceramic ball 5 has reached the set requirement and has sufficient ignition capability, and the preheating process ends.

[0062] Simultaneously, the co-firing air valve 14 and the pyrolysis gas valve 17 are gradually opened. Co-firing air 13 enters the annular gap between the inner wall of the vertical pipe 701 of the central pipe 7 and the outer wall of the straight pipe 251 of the mixing pipe 25 via the co-firing air valve 14 and the co-firing air pipe 15, and then rises. Pyrolysis gas 16 enters the interior of the straight pipe 251 of the mixing pipe 25 via the pyrolysis gas valve 17 and the pyrolysis gas pipe 18, and then rises. Under the combined action of the inner flow vanes and the outer turbulence vanes 253 of the mixing pipe 25, the co-firing air 13 and the pyrolysis gas 16 are mixed evenly to form a combustible premixed gas. The combustible premixed gas has a near-theoretical mixing ratio, meaning the equivalence ratio of co-firing air 13 to pyrolysis gas 16 is close, and both have just completed their reaction. The combustible premixed gas continues to rise within the vertical pipe 701 of the central pipe 7. After passing through the flame arrestor 24, it comes into contact with the high-temperature flue gas 1 formed by the preheater 8 and is ignited. The high-temperature flue gas 1 then enters the interior of the foam ceramic balls 5 and flows radially through them. During this stage, the pyrolysis gas 16 and the co-firing air 13, as well as the fuel gas 10 and the preheated air 12, all undergo combustion reactions at the theoretical mixing ratio. As the opening of the pyrolysis gas valve 17 increases, the flow rate of the pyrolysis gas 16 reaches the rated processing load of the device described in this invention. The fuel gas valve 9 and the preheated air valve 11 are gradually closed, meaning the preheater 8 stops working. The initial operating condition ends. At this point, due to potential local unevenness in the oxygen-to-fuel ratio, the concentration of pollutants such as CO, HC, and VOCs in the high-temperature flue gas 1 may exceed the standard.

[0063] Further increase the opening of the co-firing air valve 14 to increase the flow rate of co-firing air 13 until the oxygen sensor 22 displays an oxygen concentration in the high-temperature flue gas 1 within the range of 11±2% and the temperature sensor 20 displays a temperature in the high-temperature flue gas 1 above 850℃, thus entering a stable operating condition. In this condition, the flame from the combustion reaction between the pyrolysis gas 16 and the co-firing air 13 gradually moves downstream to the internal pores of the foam ceramic balls 5, where the incandescent porous medium of the foam ceramic balls 5 ignites the reaction. When the oxygen concentration in the high-temperature flue gas 1 exceeds the set upper limit, the flow rate of co-firing air 13 is appropriately reduced; conversely, when the oxygen concentration in the high-temperature flue gas 1 is below the set lower limit, the flow rate of co-firing air 13 is appropriately increased.

[0064] Because the calorific value of the waste pyrolysis gas 16 may be very low in some cases, maintaining the ideal oxygen concentration in the high-temperature flue gas 1 would prevent its temperature from reaching 850°C, which would lead to excessive concentrations of dioxins. Therefore, maintaining the temperature of the high-temperature flue gas 1 is prioritized, and the flow rate of the co-firing air 13 should be appropriately reduced. If the oxygen concentration in the high-temperature flue gas 1 is below 4% and the temperature still cannot exceed 850°C, it indicates that the calorific value of the pyrolysis gas 16 is too low, exceeding the applicable range of the device described in this invention, and the system should be shut down.

[0065] Because the pyrolysis gas 16 contains inorganic materials (inert substances) such as aluminosilicates, after the pyrolysis gas 16 is burned, some inorganic particles will be deposited inside the foam ceramic balls 5, causing its porosity to gradually decrease and its seepage resistance to gradually increase. When the pressure difference across the foam ceramic balls 5, that is, the difference between the readings of the first static pressure gauge 19 and the second static pressure gauge 21, exceeds the set value, the machine will be shut down, and the staff will need to maintain, regenerate, or replace the foam ceramic balls 5.

[0066] After entering the shutdown condition, first close the pyrolysis gas valve 17 and cut off the input of pyrolysis gas 16 until the temperature of high-temperature flue gas 1 is lower than the preset value. Then close the co-firing air valve 14 and cut off the input of co-firing air 13.

[0067] In summary, the waste pyrolysis gas 16 combustion device and its combustion method provided by this invention shorten the preheating time and energy consumption by using the theoretical equivalence ratio of preheated gas 10 to preheated air 12 during the preheating process. During the initial operation, the pyrolysis gas 16 and co-fired air 13 gradually increase in the theoretical equivalence ratio, resulting in smoother ignition of the pyrolysis gas 16 and a more stable reaction process, avoiding pipeline pressure pulsations caused by large airflow rates through porous media. After entering stable operating conditions, priority is given to achieving the lower limit of the combustion temperature, which is more conducive to reducing the total emission of dioxins, a significant pollutant in the flue gas. Furthermore, by increasing the supply of co-fired air 13, the flue gas temperature is controlled below the upper limit, which is more conducive to extending the lifespan of hot-end components and preventing the formation of NOx pollutants. This method has better overall reliability, stability, environmental friendliness, and economy.

[0068] When gas burns inside a porous medium, it exhibits the following distinct characteristics: First, the temperature of the porous medium is the same as the flame temperature, maintaining a consistently incandescent state. This allows the porous medium to simultaneously perform heat storage and ignition functions, eliminating the need for frequent start-stop cycles of the ignition system once the fuel is ignited. Second, the gas flow rate within the porous medium is very slow. Even if the pyrolysis gas fluctuates due to variations in calorific value, temperature, and flow rate, the heat storage and release within the porous medium can effectively mitigate these fluctuations over a considerable period. This maintains good combustion stability and high combustion efficiency, preventing excessive load impact on downstream flue gas purification systems caused by fluctuations in pollutant concentrations in the flue gas.

[0069] Furthermore, using porous media as a carrier for gaseous fuel combustion involves a high heat load, and even slight unevenness in the temperature field distribution can lead to the fragmentation of the porous media. In the structure described in this invention, the porous media foam ceramic spheres 5 are divided into upper and lower parts and then joined together, which helps to reduce thermal stress damage caused by uneven temperature field, thereby improving the lifespan of the carrier.

[0070] The above description is merely a preferred embodiment of the present invention. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A waste pyrolysis gas combustion device, characterized in that, include: The casing has a smoke vent and is filled with foam ceramic balls. The central tube has one end connected to the foam ceramic ball, and the other end is heated and degassed to enter the circulation. The preheater, connected to the foam ceramic ball near the central tube, is used to supply gas and preheated air and ignite the gas and preheated air; A mixing tube is disposed inside the central tube, near the other end of the central tube, and has an annular seam between it and the central tube; A combustion air sleeve, connected to the annular seam, is used to transport combustion air; The mixing tube has a flow-disrupting component for uniformly mixing the combustion air and the pyrolysis gas in the annular gap.

2. The waste pyrolysis gas combustion device according to claim 1, characterized in that, The foam ceramic ball is formed by an upper sphere and a lower sphere.

3. The waste pyrolysis gas combustion device according to claim 1, characterized in that, A fire-resistant grid is installed inside the central tube above the mixing tube.

4. The waste pyrolysis gas combustion device according to claim 1, characterized in that, The preheater includes: An outer horizontal pipe, inside which a gas pipe is installed; The vertical outer pipe has one end connected to the outer horizontal pipe to form a reducing elbow, and the other end connected to the central pipe; The ignition nozzle is located near the other end of the vertical outer tube where it connects to the central tube, and is connected to a conductive wire.

5. The waste pyrolysis gas combustion device according to claim 4, characterized in that, Also includes: The fire-retardant medium is installed near the other end of the vertical outer pipe where it connects with the central pipe.

6. The waste pyrolysis gas combustion device according to claim 1, characterized in that, The turbulence-disrupting component includes: An internal turbulence vane is disposed in the straight section of the mixing tube and is inclined inward or perpendicular to the axis of the straight tube; An external spoiler is disposed on the straight section of the mixing tube and is inclined outward from the straight section or perpendicular to the axis of the straight section.

7. The waste pyrolysis gas combustion device according to claim 1, characterized in that, The central tube includes: A vertical pipe, one end of which is connected to the foam ceramic ball, is used for premixed gas flow and to guide high-temperature flue gas. A tray, located inside the vertical tube, is used to support the foam ceramic balls.

8. The waste pyrolysis gas combustion device according to claim 7, characterized in that, An asbestos pad is provided between the tray and the foam ceramic ball.

9. The waste pyrolysis gas combustion device according to any one of claims 1-8, characterized in that, The housing is provided with: A hydrostatic gauge is used to monitor the pressure difference across the foam ceramic balls. A temperature sensor is used to monitor the temperature of the high-temperature flue gas discharged from the exhaust port; An oxygen sensor is used to monitor the oxygen concentration in the high-temperature flue gas discharged from the exhaust port.

10. The combustion method of the waste pyrolysis gas combustion device according to any one of claims 1-9, characterized in that, Includes the following steps: Step (1) Preheating condition The combustion of fuel gas and preheated air in a theoretical equivalence ratio produces high-temperature flue gas, which heats the porous media combustion carrier to the point that it has ignition capability. Step (2), Initial Operating Conditions Pyrolysis gas is mixed with co-fired air at a near-theoretical equivalence ratio and then fed into the combustion system. The flow rate is gradually increased to achieve smooth ignition of the pyrolysis gas. Step (3) Stable operating conditions Adjust the air flow rate for co-firing to control the oxygen concentration in the flue gas within a preset range, while maintaining the flue gas temperature within a range that meets environmental protection requirements. Step (4) Adaptive Adjustment of Operating Conditions The amount of co-firing air is adjusted in conjunction with the parameters of high-temperature flue gas temperature and oxygen concentration to ensure the lower limit of flue gas temperature to reduce pollutants, while controlling the upper limit of temperature to protect the equipment. Step (5), Safe shutdown condition When the porous ceramic balls become clogged or the pyrolysis gas parameters exceed the system's adaptability range, the input of pyrolysis gas and co-firing air is sequentially cut off to terminate the combustion process.

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