Combustion air systems and methods adapted for solid waste incineration

Abstract

This invention relates to a combustion air system and method adapted for solid waste incineration, belonging to the field of solid waste treatment technology. The invention includes a primary combustion chamber, a secondary combustion chamber, a flue gas waste heat recovery system, a flue gas purification system, and a combustion air supply system. The combustion air supply system includes a primary heat exchanger, a secondary heat exchanger, a primary air dynamic distribution system, a secondary air and recirculated flue gas coupling system, and a control center. Based on the real-time operating conditions of multiple zones in the primary combustion chamber, this invention dynamically adjusts the primary air volume distributed to each combustion stage, improving the system's ability to adapt to fuel fluctuations. The combustion air undergoes two stages of preheating: purified low-temperature flue gas and pre-purified medium-temperature flue gas, fundamentally avoiding low-temperature corrosion and improving system operational safety and thermal efficiency. The recirculated flue gas is mixed with the secondary air and then sent to the secondary combustion chamber to create an oxygen-deficient atmosphere above the main combustion zone, and, in conjunction with in-furnace non-steam reflux (SNCR), achieves NO removal during combustion. X Source reduction.

Description

Technical Field

[0001] This invention belongs to the field of solid waste disposal technology, and relates to a combustion air system and method adapted for solid waste incineration disposal. Background Technology

[0002] Municipal solid waste and industrial combustible solid waste have complex compositions and fluctuate greatly in calorific value and moisture content, posing challenges to the stable, efficient, and clean operation of their incineration systems. The combustion air system is one of the core subsystems of the incinerator, and its rational air distribution directly affects combustion efficiency, pollutant generation, and equipment safety.

[0003] Currently, the combustion air systems of traditional solid waste incinerators mostly adopt a relatively fixed air distribution pattern, which has the following drawbacks: (1) Rigid air distribution method: The ratio and parameters of primary air and secondary air (such as air temperature and air volume) are usually set according to the design fuel characteristics, which makes it difficult to adapt to the drastic fluctuations in solid waste composition, calorific value and moisture content in real time, resulting in unstable combustion conditions and easy occurrence of local oxygen deficiency (producing CO and unburned carbon) or oxygen excess (increasing exhaust heat loss).

[0004] (2) Insufficient energy utilization: For solid waste with high moisture content, in order to ensure ignition and burnout, a large amount of auxiliary fuel is usually required to preheat the air and fuel, resulting in low overall thermal efficiency of the system.

[0005] (3) Risk of equipment corrosion: Traditional single-stage or disordered multi-stage air preheaters often suffer from severe low-temperature corrosion because the metal wall temperature of the heat exchange surface is lower than the acid dew point of the flue gas, which affects the service life and operational safety of the equipment.

[0006] (4) Pollutant control relies on end-of-pipe treatment: to control NO X Emissions typically rely on separate end-of-pipe flue gas purification devices (such as SCR or SNCR), which are not only costly to invest in and operate, but also fail to effectively suppress emissions from the combustion process. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a combustion air system and method adapted to solid waste incineration, so as to achieve adaptive air distribution and improve the system's ability to adapt to fuel fluctuations.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A combustion air system adapted for solid waste incineration includes a primary combustion chamber, a secondary combustion chamber, a flue gas waste heat recovery system, a flue gas purification system, a flue gas recirculation system, and a combustion air supply system arranged sequentially along the flue gas flow direction. The combustion air supply system includes a primary heat exchanger, a secondary heat exchanger, a primary air dynamic distribution system, a secondary air and recirculated flue gas coupling system, and a control center. The primary heat exchanger uses purified low-temperature flue gas to preheat the combustion air entering the system. The flue gas inlet of the primary heat exchanger is connected to the outlet of the flue gas purification system, the flue gas outlet of the primary heat exchanger is connected to the flue gas inlet of the flue gas recirculation system, and the air outlet of the primary heat exchanger is connected to the air inlet of the secondary heat exchanger. The secondary heat exchanger uses the pre-purified medium-temperature flue gas to heat the preheated combustion air. The flue gas inlet of the secondary heat exchanger is connected to the flue gas outlet of the flue gas waste heat recovery system. The flue gas outlet of the secondary heat exchanger is connected to the flue gas inlet of the flue gas purification system. The air outlet of the secondary heat exchanger is connected to the primary air dynamic distribution system and the secondary air and recirculated flue gas coupling system. The primary air dynamic distribution system includes a graded air distribution device, which includes a primary air header connected to the air outlet of the secondary heat exchanger. The primary air header is divided into multiple independent chambers by multiple baffles located inside it. Each chamber is connected to the drying zone, combustion zone and burnout zone of the primary combustion chamber, and each chamber inlet is equipped with a regulating damper. The secondary air and recirculated flue gas coupling system includes a secondary air header connected to the air outlet of the secondary heat exchanger, a recirculated flue gas duct connected to the outlet of the flue gas recirculation system, and a mixing duct for mixing the two gases. The secondary air header and the recirculated flue gas duct are equipped with regulating valves to control the mixing amount. The mixing duct leads to a low-oxygen mixed gas nozzle located at the throat of the secondary combustion chamber to form an oxygen-deficient atmosphere above the main combustion zone. The control center is connected to infrared temperature monitors located above each combustion zone in the combustion chamber, an online gas analyzer located on the side wall of the furnace, and a feeding system. The control center generates control commands based on the received real-time data, drives the operation of each regulating damper in the primary air dynamic distribution system, and controls the operation of the regulating valves in the secondary air and recirculated flue gas coupling system.

[0009] This invention enables adaptive air distribution, improves the system's ability to adapt to fuel fluctuations, enhances the overall thermal efficiency of the system, eliminates the risk of low-temperature corrosion of heat exchangers, significantly improves the safety, reliability and lifespan of the equipment, and reduces maintenance costs.

[0010] Optionally, the upper part of the secondary combustion chamber is provided with a normal oxygen secondary air nozzle for injecting normal oxygen secondary air.

[0011] Optionally, the secondary combustion chamber is equipped with an SNCR in the temperature range of 850~1050℃.

[0012] Optionally, the flue gas purification system includes an acid removal device and a dust removal device.

[0013] Optionally, the deacidification device is a dry deacidification device or a semi-dry deacidification device, and the dust removal device is a bag filter.

[0014] Optionally, the combustion chamber can be a grate, a fluidized bed, or a rotary kiln.

[0015] Optionally, the flue gas waste heat recovery system is a waste heat boiler.

[0016] Optionally, the regulating dampers at the entrance of each chamber are combined regulating dampers.

[0017] A combustion air method adapted for solid waste incineration, based on the aforementioned combustion air system adapted for solid waste incineration, includes the following steps: S1. Heat energy cascade recovery and air preheating: Combustion air enters the first-stage heat exchanger and exchanges heat with the purified low-temperature flue gas from the flue gas purification system outlet to achieve preliminary preheating of the combustion air and avoid low-temperature corrosion of the equipment; the preheated combustion air enters the second-stage heat exchanger and exchanges heat with the pre-purified medium-temperature flue gas from the flue gas waste heat recovery system outlet to be heated to the required temperature. S2. Dynamic primary air supply: Part of the combustion air, which has been preheated in step S1, is distributed through the primary air dynamic distribution system; by monitoring the operating conditions of each combustion zone in the primary combustion chamber in real time, the primary air volume delivered to the drying zone, combustion zone and burnout zone of the primary combustion chamber is dynamically calculated and independently adjusted. S3. Low-NOx combustion coupled with secondary air and recirculated flue gas: Part of the combustion air, which has been preheated in step S1, is mixed with recirculated flue gas from the flue gas purification system in proportion to form a low-oxygen mixture, which is injected into the throat of the secondary combustion chamber to form an oxygen-deficient combustion zone; at the same time, normal-oxygen secondary air is injected into the upper part of the secondary combustion chamber to enhance combustion; and a reducing agent is injected into the secondary combustion chamber at a suitable temperature window for in-furnace SNCR denitrification.

[0018] Optionally, the inlet flue gas temperature of the first-stage heat exchanger is 150~200℃, the outlet flue gas temperature of the first-stage heat exchanger is >110℃ (flue gas acid dew point), the inlet flue gas temperature of the second-stage heat exchanger is 235~280℃, the temperature of the combustion air after the first-stage preheating is >110℃ (flue gas acid dew point), and the temperature of the combustion air after the two-stage preheating is 150~220℃.

[0019] Optionally, the ratio of primary wind to secondary wind is 6:4 to 8:2.

[0020] Optionally, the distribution ratio of each zone in the primary air is 20-30% for the dry zone, 50-65% for the combustion zone, and 10-20% for the burnout zone.

[0021] Optionally, the suitable temperature for SNCR denitrification is 850~1050℃.

[0022] Optionally, in step S3, the oxygen concentration in the low-oxygen mixed gas is 15%~18%, and the temperature of the low-oxygen mixed gas is 130~210℃.

[0023] Optionally, in step S2, the real-time monitored operating conditions include the infrared temperature of each combustion zone, the concentration of CO and O2 in the furnace, and the signals of the feeding system, so as to realize dynamic perception of the combustion state and calculate the optimal air volume command through the built-in algorithm model.

[0024] The beneficial effects of this invention are as follows: 1. Strong self-adaptability, stable and efficient combustion: A primary air dynamic distribution system based on real-time operating condition perception (temperature, atmosphere, feed) of multiple areas in a combustion chamber has been established. This system enables independent, closed-loop, and precise control of air volume in each combustion stage, allowing the air supply to adapt to changes in fuel characteristics and combustion state in real time. This effectively overcomes the impact of large fluctuations in solid waste, significantly improves combustion stability and burnout rate, and reduces CO generation and smoke loss.

[0025] 2. High energy utilization and high system efficiency: The innovative two-stage preheating design enables deep recovery of waste heat from flue gas, increases the temperature of combustion air, which is particularly beneficial for the combustion of high-moisture solid waste and improves the overall thermal efficiency of the system.

[0026] 3. High equipment reliability and low maintenance cost: By preheating with purified low-temperature flue gas and then heating with pre-purified medium-temperature flue gas, the low-temperature heat exchange link that is prone to acid dew point corrosion is completely placed on the clean flue gas side. This eliminates the risk of low-temperature corrosion of the heat exchanger from the design source, significantly improving the safety, reliability and lifespan of the equipment and reducing maintenance costs.

[0027] 4. Synergistic control of pollutants to reduce end-point load: By coupling recirculated flue gas with the secondary air system, oxygen-deficient combustion conditions are created in the secondary combustion chamber, suppressing NO at the source. X It generates and combines with the in-furnace SNCR arranged in the optimal reaction temperature window to form a synergistic control mechanism of "inhibition during combustion + reduction in the furnace", which greatly reduces the load and operating cost of the terminal flue gas denitrification system.

[0028] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Fig. 1 This is a schematic diagram of the combustion air system adapted for solid waste incineration treatment according to the present invention; Fig. 2 This is a schematic diagram of a primary air distribution system.

[0030] Figure reference numerals: 1. Primary combustion chamber; 1.1. Feed inlet; 1.2. Start-up burner; 1.3. Staged air distribution device; 2. Secondary combustion chamber; 2. Auxiliary burner; 2.1. SNCR; 2.2. Flue gas waste heat recovery system; 3. Secondary heat exchanger; 4. Flue gas purification system; 5. Primary heat exchanger; 6. Flue gas recirculation system; 7. Chimney; 8. Primary air main pipe; 11. Combined regulating damper; 12. Primary air branch pipe of drying section; 13. Primary air branch pipe of combustion section; 14. Primary air branch pipe of burnout section; 15. Primary air regulating damper of drying section; 16. Primary air regulating damper of combustion section; 17. Primary air regulating damper of burnout section; 18. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0033] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0034] Please see Figs. 1-2A combustion air system adapted for solid waste incineration is shown in the figure, comprising: a primary combustion chamber 1, a feed inlet 1.1, a start-up burner 1.2, a staged air distribution device 1.3, a secondary combustion chamber 2, an auxiliary burner 2.1, an SNCR 2.2, a flue gas waste heat recovery system 3, a secondary heat exchanger 4, a flue gas purification system 5, a primary heat exchanger 6, a flue gas recirculation system 7, a chimney 8, a primary air main duct 11, a combined regulating damper 12, a primary air branch duct for the drying section 13, a primary air branch duct for the combustion section 14, a primary air branch duct for the burnout section 15, a primary air regulating damper for the drying section 16, a primary air regulating damper for the combustion section 17, and a primary air regulating damper for the burnout section 18. The system mainly includes a primary combustion chamber 1 (e.g., grate, fluidized bed, rotary kiln, etc.), a secondary combustion chamber 2, a flue gas waste heat recovery system 3 (e.g., waste heat boiler, etc.), a flue gas purification system 5 (e.g., bag filter, dry / semi-dry deacidification, etc.), a two-stage series flue gas-air heat exchanger, and a flue gas recirculation system 7.

[0035] 1. Heat Recovery and Air Preheating Process: The heating path of the combustion air is optimized to balance energy recovery efficiency and equipment operation safety. The combustion air first enters the primary heat exchanger, where it exchanges heat with the purified low-temperature flue gas (approximately 150~200℃) from the flue gas purification system outlet. The key to this step is utilizing the purified flue gas, from which acidic gases and dust have been removed, to recover low-grade waste heat. This ensures that the stage with the lowest metal wall temperature in the entire heat exchange process completely avoids a corrosive environment, fundamentally eliminating the risk of low-temperature acid dew point corrosion. Subsequently, the preheated combustion air enters the secondary heat exchanger, where it is heated to the required process temperature by the pre-purification medium-temperature flue gas (approximately 235~280℃) from the flue gas waste heat recovery system outlet, with the primary air at approximately 150~220℃. Because the air inlet temperature entering the secondary heat exchanger is already increased, the heat exchanger wall temperature is always higher than the acid dew point of the original flue gas, thus achieving efficient and safe primary heating. This invention, through its innovative process of "preheating with purified low-temperature flue gas first, and then heating with pre-purified medium-temperature flue gas," places the easily corroded low-temperature heat exchange section on the clean flue gas side, solving the low-temperature corrosion problem of air heat exchangers from the design source and significantly improving system reliability.

[0036] 2. Primary Air Dynamic Graded Supply Process: After preheating, the primary air enters an integrated graded air distribution device 1.3. This device consists of multiple independent chambers (corresponding to the grate drying zone, combustion zone, and burnout zone) separated by the same main pipe and internal partitions. Each chamber inlet is equipped with a high-precision regulating damper. The combustion state is dynamically sensed by real-time analysis of signals from infrared temperature monitors installed above each area of ​​the grate, online CO / O2 analyzers on the furnace sidewalls, and the feeding system. Based on this real-time data, the algorithm model built into the control center calculates and outputs the optimal airflow command for each zone, driving the corresponding regulating damper to achieve targeted closed-loop airflow management for different combustion stages of the grate, thereby accurately adapting to fluctuations in the characteristics of the fuel entering the furnace. This invention establishes a primary air dynamic distribution system based on real-time operating condition sensing of multiple zones within a combustion chamber, realizing independent closed-loop control of airflow at each combustion stage, enabling the air supply to adapt to changes in fuel characteristics and combustion state.

[0037] 3. Low-NOx Combustion Process Coupled with Secondary Air and Recirculated Flue Gas: Preheated secondary air is statically mixed with recirculated flue gas from the flue gas purification system in a preset ratio in the delivery pipeline. The mixing amount is precisely controlled by a regulating valve to form a mixed gas with a temperature controlled at 130~210℃ and an oxygen concentration reduced to 15%~18%. This low-oxygen mixed gas is injected through a nozzle located at the throat of the secondary combustion chamber, creating an oxygen-deficient atmosphere above the main combustion zone, effectively suppressing thermal NOx. X The generation of NO. Simultaneously, an additional layer of normal oxygen secondary air nozzles is installed in the upper part of the secondary combustion chamber to create strong turbulence and ensure complete combustion of combustible components. Furthermore, an in-furnace SNCR is installed in the temperature window layer of 850~1050℃, and its injection rate is controlled by the control center according to the combustion load and NO. X Real-time concentration is controlled by a feedforward-feedback composite method to further reduce NO. X This invention creates oxygen-deficient conditions by coupling recirculated flue gas with secondary air, and combines this with in-furnace non-steam combustion (SNCR), thereby achieving NO reduction during combustion. X The integrated control of "inhibition + reduction" reduces the burden on end-of-pipe treatment.

[0038] Example 1 Please see Figs. 1-2 This is a combustion air system adapted for solid waste incineration. The system mainly includes a primary combustion chamber 1 (mechanical grate), a secondary combustion chamber 2 (vertical), a flue gas waste heat recovery system 3 (waste heat boiler), a flue gas purification system 5 (dry deacidification reaction tower + bag filter), a two-stage flue gas-air heat exchanger connected in series, and a flue gas recirculation system 7 (flue gas recirculation fan and pipeline).

[0039] Target of treatment: Mixed municipal solid waste with a calorific value ranging from 7000 to 11000 kJ / kg and a moisture content ranging from 30% to 50%.

[0040] Key design parameters: (1) Primary heat exchanger (corrosion resistant grade): Inlet flue gas: Low-temperature flue gas that has been purified after being taken from the bag filter, with a temperature of about 155℃.

[0041] Exit air: Ambient air (20°C) is heated to approximately 118°C after heat exchange.

[0042] Exit flue gas: The temperature drops to about 110.5°C, after which part of it enters the flue gas recirculation system and the rest is discharged into the chimney.

[0043] (2) Secondary heat exchanger (main heating stage): Inlet flue gas: Taken from the economizer of the waste heat boiler, the unpurified medium-temperature raw flue gas has a temperature of about 250℃.

[0044] Exit air: The air that has been preheated in the first stage (118°C) is heated to about 180°C here.

[0045] Exit flue gas: The temperature drops to approximately 222°C, and then it enters the flue gas purification system.

[0046] (3) Combustion air distribution: In the total combustion air, the volume ratio of primary air to secondary air is approximately 7:3 (which can be slightly adjusted according to the characteristics of the waste entering the furnace).

[0047] The primary air at a temperature of 180℃ is distributed through a zoned air distribution box in a ratio of approximately 25% : 60% : 15% for the drying zone : combustion zone : burnout zone (which can be finely adjusted based on infrared temperature feedback from the upper part of the grate).

[0048] (4) Ratio of recirculated flue gas to secondary air: The recirculated flue gas is taken from the outlet of the primary heat exchanger, with a temperature of approximately 110.5℃ and an oxygen content of approximately 5%~6% (taken from the monitoring value at the outlet of the secondary combustion chamber).

[0049] The recirculated flue gas accounts for 18% to 30% of the total volume of the mixed secondary air. It is adjusted in real time according to the oxygen concentration monitoring value at the top of the secondary combustion chamber (the target is set at 5% to 6%) so that the oxygen concentration after mixing is controlled within the target range of 15% to 18%.

[0050] Secondary air at 180°C is mixed with recirculated flue gas at 110.5°C. The resulting secondary air temperature is approximately 159°C to 168°C (depending on the real-time recirculation rate), and then introduced through the nozzle at the throat of the secondary combustion chamber.

[0051] Workflow: (1) Air preheating process: Ambient air (20°C) first enters the primary heat exchanger, where it exchanges heat with the purified low-temperature flue gas (approximately 155°C) and is heated to approximately 118°C. This design ensures that the corrosive low-temperature section is entirely on the clean flue gas side. Subsequently, the air enters the secondary heat exchanger, where it exchanges heat with the unpurified medium-temperature raw flue gas (approximately 250°C) and is finally heated to 180°C.

[0052] (2) Primary air supply process: Primary air at 180°C enters the graded air distribution device 1.3, is separated and distributed to the drying zone, combustion zone and burnout zone air chambers at the bottom of the grate. Based on the feedback from the temperature measuring points above each section, the regulating dampers of each branch are automatically adjusted to distribute the air volume in a ratio of 25%:60%:15% to meet the combustion needs of the waste at different stages on the grate.

[0053] (3) Secondary air and low-NOx combustion process: Secondary air at 180°C is mixed with recirculated flue gas at approximately 110.5°C in the pipeline. By adjusting the recirculation rate (18%~30%), the temperature of the mixed secondary air is controlled at 159~168°C, while its oxygen concentration is reduced to 15%~18%. This low-oxygen secondary air is introduced through the nozzle at the throat of the secondary combustion chamber, forming an oxygen-deficient zone in the middle of the furnace to suppress NO. X Generation. An SNCR ammonia injection device is installed in the upper part of the secondary combustion chamber (approximately 900~1000℃ region) to further remove NO. X .

[0054] (4) Flue gas flow: The high-temperature flue gas generated in the primary combustion chamber enters the secondary combustion chamber for complete combustion. Then it flows sequentially through the waste heat boiler to recover heat, the dry deacidification reaction tower for deacidification, and the bag filter for dust removal. After dust removal, the flue gas recovers waste heat through the primary heat exchanger. A portion (about 110.5°C) is drawn back as recirculated flue gas, and the remainder is discharged into the chimney.

[0055] Implementation Results: Using the system and method of this embodiment, the furnace combustion conditions are stable, and the slag loss on ignition can be stably controlled below 3%; the heat exchanger has operated continuously for over 8000 hours without corrosion failure; NO X The initial emissions can be stably controlled below 150 mg / m³; the air is preheated to 180℃ in two stages, which effectively improves the system's thermal efficiency.

[0056] Example 2 The system composition and workflow of this embodiment are the same as those of Embodiment 1, except that the following parameter settings are used: Key design parameters: (1) Primary heat exchanger (corrosion resistant grade): Inlet flue gas temperature: 165℃ (taken from after the bag filter) Outlet air temperature: 130℃ (ambient air 20℃ after heat exchange) Exit flue gas temperature: 115℃ (partially used as recirculated flue gas) (2) Secondary heat exchanger (main heating stage): Inlet flue gas temperature: 260℃ (taken after economizer) Outlet air temperature: 200℃ (first stage air is heated to 130℃) Exit flue gas temperature: 228℃ (entering the deacidification reaction tower) (3) Combustion air distribution: Primary air temperature: 200℃, Secondary air temperature (before mixing): 200℃ Primary air zone distribution ratio: Dry zone 25%, Combustion zone 60%, Combustion burnout zone 15%. (4) Ratio of recirculated flue gas to secondary air: Recirculated flue gas temperature: 115℃ (primary outlet), oxygen content 5%~6% Recirculation rate: 18%~30% (adjusted according to the oxygen concentration in the secondary combustion chamber of 5%~6%) Secondary air oxygen concentration after mixing: 15%~18% Secondary air temperature after mixing: 175℃ ~ 185℃ Implementation Results: Using the parameters of this embodiment, furnace combustion is stable, slag loss on ignition is <3%, heat exchangers show no corrosion after more than 8000 hours of continuous operation, and NO0.05 X The initial emissions were <150 mg / m³. Compared to Example 1, the higher preheating temperature (200°C) further enhanced the drying effect on high-moisture solid waste, and the system thermal efficiency was slightly improved.

[0057] This invention achieves stable and efficient combustion of complex and variable solid waste fuels, improving the burnout rate; it also achieves source reduction of pollutants, effectively reducing NO. X The original emission concentration was reduced; the overall thermal efficiency of the system was improved, and the dependence on auxiliary fuel was reduced through energy cascade utilization, especially for high moisture solid waste.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A combustion air system adapted for solid waste incineration, characterized in that: It includes a primary combustion chamber (1), a secondary combustion chamber (2), a flue gas waste heat recovery system (3) arranged sequentially along the flue gas flow direction, as well as a flue gas purification system (5), a flue gas recirculation system (7), and a combustion air supply system; The combustion air supply system includes a primary heat exchanger (6), a secondary heat exchanger (4), a primary air dynamic distribution system, a secondary air and recirculated flue gas coupling system, and a control center; The first-stage heat exchanger (6) uses the purified low-temperature flue gas to preheat the combustion air entering the system. The flue gas inlet of the first-stage heat exchanger (6) is connected to the outlet of the flue gas purification system (5). The flue gas outlet of the first-stage heat exchanger (6) is connected to the flue gas inlet of the flue gas recirculation system (7). The air outlet of the first-stage heat exchanger (6) is connected to the air inlet of the second-stage heat exchanger (4). The secondary heat exchanger (4) uses the pre-purified medium-temperature flue gas to heat the preheated combustion air. The flue gas inlet of the secondary heat exchanger (4) is connected to the flue gas outlet of the flue gas waste heat recovery system (3). The flue gas outlet of the secondary heat exchanger (4) is connected to the flue gas inlet of the flue gas purification system (5). The air outlet of the secondary heat exchanger (4) is connected to the primary air dynamic distribution system and the secondary air and recirculated flue gas coupling system. The primary air dynamic distribution system includes a graded air distribution device (1.3). The graded air distribution device (1.3) includes a primary air header (11) connected to the air outlet of the secondary heat exchanger. The primary air header (11) is divided into multiple independent chambers by multiple partitions located inside it. Each chamber is connected to the drying zone, combustion zone and burnout zone of the combustion chamber. Each chamber inlet is equipped with a regulating damper. The secondary air and recirculated flue gas coupling system includes a secondary air header connected to the air outlet of the secondary heat exchanger (4), a recirculated flue gas duct connected to the outlet of the flue gas recirculation system (7), and a mixing duct for mixing the two gases. The secondary air header and the recirculated flue gas duct are equipped with regulating valves to control the mixing amount. The mixing duct leads to a low-oxygen mixed gas nozzle located at the throat of the secondary combustion chamber to form an oxygen-deficient atmosphere above the main combustion zone. The control center is connected to infrared temperature monitors located above each combustion zone in the combustion chamber, an online gas analyzer located on the side wall of the furnace, and a feeding system. The control center generates control commands based on the received real-time data, drives the operation of each regulating damper in the primary air dynamic distribution system, and controls the operation of the regulating valves in the secondary air and recirculated flue gas coupling system.

2. The combustion air system adapted for solid waste incineration as described in claim 1, characterized in that: The upper part of the secondary combustion chamber is equipped with a normal oxygen secondary air nozzle for injecting normal oxygen secondary air.

3. The combustion air system adapted for solid waste incineration as described in claim 1, characterized in that: SNCR is installed in the temperature range of 850~1050℃ in the secondary combustion chamber.

4. The combustion air system adapted for solid waste incineration as described in claim 1, characterized in that: The flue gas purification system (5) includes an acid removal device and a dust removal device.

5. The combustion air system adapted for solid waste incineration as described in claim 4, characterized in that: The deacidification device is a dry deacidification device or a semi-dry deacidification device, and the dust removal device is a bag filter.

6. The combustion air system adapted for solid waste incineration as described in claim 1, characterized in that: The combustion chamber (1) is a grate, fluidized bed or rotary kiln; the flue gas waste heat recovery system (3) is a waste heat boiler; the regulating dampers at the inlet of each chamber are combined regulating dampers.

7. A combustion air method adapted for solid waste incineration, based on the combustion air system adapted for solid waste incineration as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Heat energy cascade recovery and air preheating: Combustion air enters the first-stage heat exchanger (6) and exchanges heat with the purified low-temperature flue gas from the outlet of the flue gas purification system (5) to achieve preliminary preheating of combustion air and avoid low-temperature corrosion of equipment; the preheated combustion air enters the second-stage heat exchanger (4) and exchanges heat with the pre-purified medium-temperature flue gas from the outlet of the flue gas waste heat recovery system (3) to be heated to the required temperature; S2. Dynamic primary air supply: Part of the combustion air, which has been preheated in step S1, is distributed through the primary air dynamic distribution system; by monitoring the operating conditions of each combustion zone in the primary combustion chamber in real time, the primary air volume delivered to the drying zone, combustion zone and burnout zone of the primary combustion chamber is dynamically calculated and independently adjusted. S3. Low-NOx combustion coupled with secondary air and recirculated flue gas: Part of the combustion air, which has been preheated in step S1, is mixed with recirculated flue gas from the flue gas purification system in proportion to form a low-oxygen mixture, which is injected into the throat of the secondary combustion chamber to form an oxygen-deficient combustion zone; at the same time, normal-oxygen secondary air is injected into the upper part of the secondary combustion chamber to enhance combustion; and a reducing agent is injected into the secondary combustion chamber at a suitable temperature window for in-furnace SNCR denitrification.

8. The combustion air treatment method adapted for solid waste incineration disposal according to claim 7, characterized in that: The inlet flue gas temperature of the first-stage heat exchanger is 150~200℃, and the outlet flue gas temperature of the first-stage heat exchanger is >110℃ (flue gas acid dew point). The inlet flue gas temperature of the second-stage heat exchanger is 235~280℃. The temperature of the combustion air after the first-stage preheating is >110℃ (flue gas acid dew point), and the temperature of the combustion air after the two-stage preheating is 150~220℃.

9. The combustion air treatment method adapted for solid waste incineration disposal according to claim 7, characterized in that: The ratio of primary wind to secondary wind is 6:4 to 8:

2.

10. The combustion air treatment method adapted for solid waste incineration disposal according to claim 7, characterized in that: The distribution ratio of each zone in the primary wind is as follows: dry zone 20-30%, combustion zone 50-65%, and burnout zone 10-20%.

11. The combustion air treatment method adapted for solid waste incineration disposal according to claim 7, characterized in that: The suitable temperature for SNCR denitrification is 850~1050℃.

12. The combustion air treatment method adapted for solid waste incineration disposal according to claim 7, characterized in that: In step S3, the oxygen concentration in the low-oxygen mixed gas is 15%~18%, and the temperature of the low-oxygen mixed gas is 130~210℃.

13. The combustion air treatment method adapted for solid waste incineration disposal according to claim 7, characterized in that: In step S2, the real-time monitoring of operating conditions includes infrared temperature of each combustion zone, CO and O2 concentrations in the furnace, and signals from the feeding system, in order to dynamically perceive the combustion status and calculate the optimal air volume command through the built-in algorithm model.

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