A biomass pyrolysis coupled with direct combustion composite double grate boiler

Abstract

The application discloses a biomass pyrolysis coupling direct combustion composite double-grate boiler, which comprises a pyrolysis cavity, a spiral feeder, a front-arch membrane type water-cooled micro-vibration auxiliary grate, an auxiliary material bin, a solid fuel combustion main grate and a main material bin; the front-arch membrane type water-cooled micro-vibration auxiliary grate is inwardly concave to form the pyrolysis cavity; the bottom of the auxiliary material bin 13 is connected with the spiral feeder 2, and the outlet of the spiral feeder 2 is communicated with the pyrolysis cavity 1; the main material bin is arranged outside a hearth, and the solid fuel combustion main grate is located below the hearth; the pyrolysis cavity and the inwardly concave part of a rear wall water-cooled wall are respectively communicated with a burn-out chamber through a pyrolysis gas front-arch suction nozzle and a pyrolysis gas rear-arch suction nozzle, and the pyrolysis gas rear-arch suction nozzle is communicated with the pyrolysis cavity; the coupling of the two heat utilization modes of single furnace pyrolysis and direct combustion improves the front-arch structure of the traditional layer combustion furnace on the basis of not changing the main fuel layer combustion mode, forms an independent pyrolysis cavity, and the auxiliary fuel is pyrolyzed in the front-arch membrane type water-cooled micro-vibration auxiliary grate in the pyrolysis cavity, the generated pyrolysis gas is sent into the burn-out chamber by the secondary air suction to reduce NO x and reburn.

Description

Technical Field

[0001] This invention belongs to the field of solid fuel, especially biomass, thermal utilization technology, specifically a composite double grate boiler with biomass pyrolysis coupled direct combustion. Background Technology

[0002] Emission reduction during solid fuel utilization has a significant impact on carbon emissions, especially NO. x To address the emission reduction issue, it is urgent to reduce the emission reduction pressure on subsequent denitrification equipment through multi-path efficient denitrification during the combustion process, thereby reducing equipment and operating costs and achieving carbon emission reduction. At the same time, the rational and efficient utilization of low-carbon energy such as biomass is key to reducing carbon emissions. Biomass has huge potential for development as an energy source, with widespread distribution and abundant total amount. High-efficiency thermal utilization equipment suitable for biomass will effectively increase the proportion of renewable low-carbon energy utilization and achieve carbon emission reduction.

[0003] Direct combustion and pyrolysis gasification are conventional methods for utilizing solid fuels. Direct combustion is low-cost and simple to operate, while pyrolysis gasification can achieve further clean and efficient utilization of solid fuels, especially biomass. In recent years, researchers have conducted extensive research on the reuse of biomass gasification pyrolysis gas, achieving many results. However, existing technologies generally separate the gasification pyrolysis furnace from the combustion furnace, resulting in a large and complex system with high requirements for syngas delivery pipelines. Furthermore, the system is prone to tar blockage, making long-term safe and stable operation difficult. Therefore, developing a high-efficiency, low-NOx, and low-carbon boiler that couples pyrolysis and direct combustion can simplify the system, reduce costs, and achieve clean, efficient, and low-carbon utilization of traditional and low-carbon energy sources, which is crucial for low-carbon development and energy conservation and emission reduction. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a composite double-grate boiler with biomass pyrolysis coupled direct combustion, which simplifies the system, reduces costs, and enables the clean, efficient, and low-carbon utilization of traditional and low-carbon energy sources, thus contributing to my country's low-carbon development and energy conservation and emission reduction.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A composite double-grate boiler with biomass pyrolysis coupled direct combustion, comprising a pyrolysis chamber, a screw feeder, a front arched membrane water-cooled micro-vibration auxiliary grate, an auxiliary feed hopper, a solid fuel combustion main grate, and a main feed hopper; the front arched membrane water-cooled micro-vibration auxiliary grate is located below the front water-cooled wall, and the front arched membrane water-cooled micro-vibration auxiliary grate is concave to form the pyrolysis chamber; the bottom of the auxiliary feed hopper is connected to the screw feeder, and the outlet of the screw feeder is connected to the pyrolysis chamber; the main feed hopper is located outside the furnace, and the solid fuel combustion main grate is located below the furnace; the pyrolysis chamber and the concave part of the rear water-cooled wall are respectively connected to the combustion chamber through the front arch ejector nozzle and the rear arch ejector nozzle of the pyrolysis gas, and the rear arch ejector nozzle of the pyrolysis gas is connected to the pyrolysis chamber.

[0006] The front arched membrane water-cooled micro-vibration auxiliary grate includes, from top to bottom, an auxiliary grate suspension section, an auxiliary grate slow descent section, an auxiliary grate steep descent section, and an auxiliary grate bare tube section. The gaps between the tubes of the auxiliary grate bare tube section serve as channels for introducing high-temperature flue gas and coke falling into the pyrolysis chamber.

[0007] The pyrolysis gas ejector nozzle in the rear arch is connected to the pyrolysis chamber through a U-shaped ejector duct. The U-shaped ejector duct includes a pyrolysis gas inlet pipe, a rear arch ejector secondary air duct, and a rear arch pyrolysis gas main pipe. The pyrolysis gas inlet pipe is equipped with multiple pyrolysis gas inlet holes and is perpendicular to the left and right side walls. The pyrolysis gas inlet pipe is fixed in the pyrolysis chamber. The rear arch ejector secondary air duct is fixed to the outside of the water-cooled wall of the side wall. The rear arch pyrolysis gas main pipe is perpendicular to the left and right side walls and is fixed in the rear arch cavity. The rear arch pyrolysis gas main pipe is connected to multiple pyrolysis gas branch pipes and the pyrolysis gas rear arch ejector nozzle in the rear arch through multiple connecting pipes.

[0008] Fuel levers are arranged inside the pyrolysis chamber. Each fuel lever includes a main lever and a movable auxiliary lever. The fuel lever is connected to a slider, which is set in a slide rail on the front wall of the pyrolysis chamber. The main lever and the movable auxiliary lever are slidably connected. A pull rod is provided on the main lever. The pull rod is a manual lever or an electric lead screw assembly. The driven end of the pull rod is connected to the movable auxiliary lever.

[0009] The front arched membrane water-cooled micro-vibration auxiliary grate is equipped with a micro-vibration mechanism, and the output of the micro-vibration mechanism acts on the front arched membrane water-cooled micro-vibration auxiliary grate.

[0010] The pyrolysis chamber is equipped with a front wall, which is composed of a refractory lining and a detachable steel plate shell. The upper and lower ends of the front arched membrane water-cooled micro-vibration auxiliary grate are respectively equipped with an upper water-cooled wall header and a lower water-cooled wall header. The upper and lower water-cooled wall headers are made of thick-walled tubes and rigidly fixed to limit the vibration range of the water-cooled grate micro-vibration mechanism and improve the high-cycle fatigue life of the front arched membrane water-cooled micro-vibration auxiliary grate. The upper and lower ends of the pyrolysis chamber front wall are respectively connected to the flange structures leading out from the upper and lower water-cooled wall headers of the auxiliary furnace drainage cold wall.

[0011] The arrangement of the screw feeders is as follows: one screw feeder with the same width as the front wall or two coaxial screw feeders with a length of half the width of the front wall are arranged. The feed cylinder is arranged horizontally along the front wall of the boiler, and multiple discharge ports are evenly arranged on the lower side of the feed cylinder. The discharge ports extend to the inside of the pyrolysis chamber and are close to the upper end of the auxiliary grate slow descent section.

[0012] A spiral charcoal extractor is installed in the pyrolysis chamber, which is connected to the main grate for solid fuel combustion. The main grate for solid fuel combustion is configured as a chain grate, reciprocating grate, or vibrating grate according to the characteristics of the main fuel. Superheated steam pipes and flue gas recirculation pipes are arranged on the primary air pipe at the bottom of the main grate for solid fuel combustion.

[0013] The spiral coke extractor includes a feed cylinder with a rotatable coke extraction port baffle on it. A coke extraction port is opened below the baffle. One end of the baffle is hinged to the feed cylinder, and a coke outlet is opened at the bottom of one end of the feed cylinder. When coke needs to be extracted, the baffle is lowered to connect with the steep drop section of the auxiliary grate, and the coke can fall into the feed cylinder and be extracted through the outlet. The coke particles fall into the main grate for solid fuel combustion through the gap between the baffle and the steep drop section of the auxiliary grate. The rotation of the baffle regulates the flow rate of the high-temperature flue gas introduced into the pyrolysis chamber, thereby controlling the temperature in the pyrolysis chamber to achieve low-temperature pyrolysis, medium-temperature pyrolysis, or high-temperature pyrolysis as needed.

[0014] The main fuels are raw biomass, biomass pellets and / or coal, and the secondary fuels are dried and crushed raw biomass, biomass pellets and / or dried sludge with a water content of less than 40%.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] This invention couples two heat utilization methods: in-furnace pyrolysis and direct combustion. Without changing the main fuel stoker combustion method, it improves the front arch structure of the traditional stoker combustion furnace to form an independent pyrolysis chamber. The auxiliary fuel is pyrolyzed in the front arch membrane water-cooled micro-vibration auxiliary grate within the pyrolysis chamber, and the generated pyrolysis gas is injected into the combustion chamber by secondary air to reduce NO. x The pyrolysis coke can be freely removed or returned to the main combustion grate for further combustion as needed, solving the problems of large and complex heat utilization systems and tar clogging pipes caused by separating the pyrolysis furnace and combustion furnace. This achieves coupled pyrolysis and direct combustion heat utilization of fuel within a single furnace, greatly simplifying the structure of the integrated fuel heat utilization system, reducing equipment costs and floor space, avoiding potential pipe blockage problems caused by separating the pyrolysis furnace and combustion furnace, and improving the safety and stability of the system operation. Furthermore, this invention effectively reduces NO during the heat utilization of main and auxiliary fuels through a multi-path, high-efficiency, low-NOx combustion technology combining flue gas recirculation, air staging, and fuel staging. x This invention reduces initial emissions and achieves energy conservation and emission reduction. It provides a highly efficient thermal utilization method for solid fuels, especially biomass, which reduces the thermal utilization cost of solid fuels, especially biomass, and can effectively improve biomass utilization rate, improve energy structure, and reduce carbon emissions.

[0017] Furthermore, the micro-vibration mechanism enables micro-vibration of the front arched membrane water-cooled micro-vibration auxiliary grate, loosening the biomass in the pyrolysis chamber, enhancing the direct pyrolysis process of flue gas, and promoting fuel movement.

[0018] Furthermore, the movable and retractable fuel lever can move up and down within a certain range along the inclined section outside the pyrolysis chamber. At the same time, by extending and retracting to change the length of the lever, a relatively enclosed pyrolysis space can be separated to facilitate control of the degree of pyrolysis.

[0019] Furthermore, the upper and lower ends of the detachable steel plate shell of the front wall of the pyrolysis chamber are respectively connected to the flanges leading out from the upper and lower headers. After the steel plate shell is disassembled, all the mechanical components of the pyrolysis chamber are in sight, which facilitates the maintenance of the pyrolysis chamber and allows for the regular cleaning of tar and adhesive ash. Observation holes are arranged on the steel plate shell to monitor the working status of the pyrolysis chamber online. Attached Figure Description

[0020] Figure 1 A schematic diagram of the overall structure of a composite double-grate boiler coupled with biomass pyrolysis and direct combustion;

[0021] Figure 2 Schematic diagram of a U-shaped ejector duct;

[0022] Figure 3 This is a schematic diagram of a screw feeder;

[0023] Figure 4 This is a schematic diagram of the arrangement of a twin-helix feeder;

[0024] Figure 5 Schematic diagram of the fuel lever structure in the pyrolysis chamber: (a) Fuel lever in the pyrolysis chamber in the shortened state; (b) Fuel lever in the pyrolysis chamber in the extended state;

[0025] Figure 6 Here are schematic diagrams of the spiral carbon collector: (a) Front view of the spiral carbon collector; (b) Right view of the spiral carbon collector;

[0026] Figure 7 A schematic diagram showing the connection between the carbon inlet baffle of the screw feeder and the front arched membrane water-cooled micro-vibration auxiliary grate: (a) front view; (b) view from direction B.

[0027] In the attached diagram, 1-pyrolysis chamber, 2-screw feeder, 3-auxiliary grate tube section, 4-auxiliary grate steep descent section, 5-auxiliary grate gentle descent section, 6-pyrolysis chamber front wall, 7-screw charcoal collector, 8-micro-vibration mechanism, 9-fuel lever, 10-pyrolysis gas front arch ejector nozzle, 11-auxiliary grate suspension section, 12-front arch membrane water-cooled micro-vibration auxiliary grate, 13-auxiliary silo, 14-main silo, 15-feed gate, 16-auxiliary furnace drainage cooling wall upper header, 17-solid fuel combustion main grate, 18-pyrolysis gas rear arch ejector nozzle, 19-U-shaped ejector duct, 20-rear wall water-cooled wall, 21-slag condensation pipe. 22-Boiler drum, 23-Front wall water-cooled wall, 24-Primary air duct, 25-Superheated steam duct, 26-Flue gas recirculation duct, 191-Pyrolysis gas inlet, 192-Pyrolysis gas inlet pipe, 193-Rear arch ejector secondary air duct, 194-Rear arch pyrolysis gas main pipe, 195-Connecting pipe, 196-Rear arch pyrolysis gas branch pipe, 197-Side wall water-cooled wall, 201-Motor, 202-Spiral shaft, 203-Spiral blade, 204-Discharge port, 71-Bullet cylinder, 72-Carbon extraction port baffle, 73-Carbon extraction port, 74-Carbon discharge port, 91-Main deflector, 92-Movable auxiliary deflector. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0029] To address the problems of complex equipment, high cost, and poor safety and stability in the efficient thermal utilization of solid fuels, especially biomass, this invention designs a pyrolysis-direct combustion coupled composite double-grate boiler. This boiler achieves the coupling of pyrolysis and direct combustion of solid fuels within the furnace, while simultaneously reducing NOx emissions through multi-path, high-efficiency, low-NOx combustion technology. x Initial discharge; the biomass pyrolysis coupled direct combustion composite double grate boiler includes a pyrolysis chamber 1, a screw feeder 2, a front arched membrane water-cooled micro-vibration auxiliary grate 12, an auxiliary feed hopper 13, a solid fuel combustion main grate 17, and a main feed hopper 14; the front arched membrane water-cooled micro-vibration auxiliary grate 12 is concave to form the pyrolysis chamber 1; the bottom of the auxiliary feed hopper 13 is connected to the screw feeder 2, and the outlet of the screw feeder 2 is connected to the pyrolysis chamber 1; the main feed hopper 14 is located outside the furnace, and solid fuel combustion... The main grate 17 is located below the furnace; the concave parts of the pyrolysis chamber 1 and the rear water-cooled wall 20 are connected to the combustion chamber through the front arch ejector nozzle 10 and the rear arch ejector nozzle 18 of the pyrolysis gas, respectively, and the rear arch ejector nozzle 18 of the pyrolysis gas is connected to the pyrolysis chamber 1; the boiler drum 22 and the slag-collecting pipe 21 are arranged according to the existing boiler structure; the front arch membrane water-cooled micro-vibration auxiliary grate 12 is set below the front water-cooled wall 23, the boiler drum 22 is set at the top of the furnace, and the slag-collecting pipe 21 is set at the flue gas outlet of the furnace.

[0030] A superheated steam pipe 25 and a flue gas recirculation pipe 26 are arranged on the primary air duct 24 at the bottom of the solid fuel combustion main grate 17.

[0031] refer to Figure 1 and Figure 5 , Figure 5 (a) The fuel trolley is shortened in the pyrolysis chamber; (b) The fuel trolley is extended in the pyrolysis chamber. A fuel trolley 9 is arranged in the pyrolysis chamber 1. The fuel trolley 9 includes a main trolley 91 and a movable auxiliary trolley 92. The fuel trolley 9 is connected to a slider, which is set in the slide rail of the front wall 6 of the pyrolysis chamber. The main trolley 91 and the movable auxiliary trolley 92 are slidably connected. A pull rod is set on the main trolley 91. The pull rod is a manual rod or an electric screw assembly. The driven end of the pull rod is connected to the movable auxiliary trolley 92. The trolley area is adjusted by adjusting the overlap of the main and auxiliary trolleys. The entire trolley moves up and down within a set range through the inclined section of the slide rail of the front wall 6 of the pyrolysis chamber, thereby realizing the movement and extension of the fuel trolley.

[0032] refer to Figure 6 and Figure 7 A spiral carbon collector 7 is installed in the pyrolysis chamber 1. The pyrolysis chamber 1 is connected to the main grate 17 for solid fuel combustion. The spiral carbon collector 7 includes a material cylinder 71. A rotatable carbon collection port baffle 72 is arranged on the material cylinder 71. A carbon collection port 73 is opened below the carbon collection port baffle. One end of the carbon collection port baffle 72 is hinged to the material cylinder 71. A carbon outlet port 74 is opened at the bottom of one end of the material cylinder 71.

[0033] The spiral feeder 2 is arranged as follows: one spiral feeder with the same width as the front wall or two coaxial spiral feeders with a length equal to half the width of the front wall are arranged. The feed cylinder is arranged horizontally along the front wall of the boiler, and multiple discharge ports 204 are evenly arranged on the lower side of the feed cylinder. The discharge ports 204 extend to the inside of the pyrolysis chamber 1, close to the upper end of the auxiliary grate slow-descent section 5. (Reference) Figure 4 .

[0034] The front arched membrane water-cooled micro-vibration auxiliary grate 12 is equipped with a micro-vibration mechanism 8. The micro-vibration mechanism 8 includes a tie rod, an eccentric block vibrator, and a spring plate. The tie rod connects the eccentric block vibrator and the spring plate. The amplitude and frequency of the eccentric block vibrator are adjustable. The spring plate is installed on the front arched membrane water-cooled micro-vibration auxiliary grate 12. The tie rod connects the eccentric block vibrator and the spring plate fixed on the front arched membrane water-cooled micro-vibration auxiliary grate 12 to achieve micro-vibration of the front arched membrane water-cooled micro-vibration auxiliary grate 12.

[0035] Screw feeder reference Figure 3 The output end of the motor 201 is connected to the screw shaft 202. The screw shaft 202 is provided with screw blades 203 along the axial direction on the outside. The screw feeder 2 realizes the conveying of materials from the auxiliary material bin 13 to the pyrolysis chamber 1.

[0036] As an optional embodiment, the micro-vibration mechanism 8 may also employ a commercially available vibrator, the output component of which is in contact with the front arched diaphragm water-cooled micro-vibration auxiliary grate 12.

[0037] Example:

[0038] The biomass pyrolysis coupled direct combustion composite double grate boiler is suitable for the thermal utilization of solid fuels. The main fuels are raw biomass, biomass pellets, coal and other solid fuels, while the auxiliary fuels are dried and crushed raw biomass, biomass pellets, dried sludge with a water content of less than 40% and other high volatile fuels.

[0039] During boiler operation, the main fuel enters the solid fuel combustion grate 17 from the main feed bin 14 for combustion. The combustion process generates sufficient heat, and some of the high-temperature flue gas carries heat through the auxiliary grate tube section 3 at the bottom of the front arch membrane water-cooled micro-vibration auxiliary grate 12 and is introduced into the pyrolysis chamber 1. The amount of high-temperature flue gas entering the pyrolysis chamber 1 can be adjusted by rotating the rotatable carbon-taking port baffle 72 on the spiral carbon taker 7, thereby regulating the temperature in the pyrolysis chamber to achieve low-temperature, medium-temperature, or high-temperature pyrolysis of the auxiliary fuel in the pyrolysis chamber according to actual needs. At the same time, the rear arch is arranged forward and downward to enhance the heat transfer between the main combustion flue gas and the front arch water-cooled wall, supplementing the heat for pyrolysis in the pyrolysis chamber.

[0040] The auxiliary fuel enters the pyrolysis chamber 1 via the screw feeder 2 and is evenly spread laterally on the front arched membrane water-cooled micro-vibration auxiliary grate 12. Under the action of the high-temperature flue gas introduced into the pyrolysis chamber 1, it undergoes pyrolysis. During the feeding process, as the micro-vibration mechanism 8 operates, the auxiliary fuel moves slowly and regularly downward along the auxiliary grate descending section 5 of the front arched membrane water-cooled micro-vibration auxiliary grate 12. The moving speed can be adjusted by changing the amplitude and frequency of the micro-vibration mechanism. At the same time, the fuel paddles 9 arranged in the pyrolysis chamber 1 can operate when necessary to assist fuel movement, prevent fuel accumulation, and also separate a relatively enclosed pyrolysis space to control the degree of pyrolysis. The pyrolyzed coke continues to fall naturally along the auxiliary grate steep descending section 4 of the front arched membrane water-cooled micro-vibration auxiliary grate 12. It can fall directly into the solid fuel combustion main grate 17 for combustion through the gap of the bottom auxiliary grate light tube section 3, or it can be removed by the screw char remover 7. When char is needed, the rotatable char extraction port baffle arranged on the spiral char extractor is connected to the steep drop section 4 of the auxiliary grate of the front arched membrane water-cooled micro-vibration auxiliary grate 12, so that some of the pyrolyzed coke enters the charging cylinder through the char extraction port baffle and is then taken out through the char outlet. Fine coke particles fall directly through the gap between the char extraction port baffle and the steep drop section 4 of the auxiliary grate to the main grate 17 for solid fuel combustion.

[0041] The front-arch membrane water-cooled micro-vibration auxiliary grate 12 includes, from top to bottom, an auxiliary grate suspension section 11, an auxiliary grate slow-descent section 5, an auxiliary grate steep-descent section 4, and an auxiliary grate bare tube section 3. The gaps between the tubes of the auxiliary grate bare tube section 3 serve as channels for introducing high-temperature flue gas and coke falling into the pyrolysis chamber. Most of the pyrolysis gas generated in the pyrolysis chamber 1 is directly injected into the combustion chamber through the pyrolysis gas front arch injection nozzle 10 arranged on the auxiliary grate suspension section 11 via secondary air injection. The remaining pyrolysis gas is injected into the rear arch via the U-shaped injection duct 19 connecting the front and rear arches via the rear arch injection secondary air. (Reference) Figure 2 The U-shaped ejector duct 19 is divided into a front arch section, a middle section, and a rear arch section. The front arch section is a pyrolysis gas inlet duct 192 with multiple pyrolysis gas inlet holes 191, which is fixed perpendicularly to the left and right side walls inside the front arch pyrolysis chamber. The middle section is fixed to the outside of the water-cooled wall 197 on the left or right side wall, and a rear arch ejector secondary air duct 193 is arranged on it. Under the ejection action of the secondary air, the pyrolysis gas enters the rear arch pyrolysis gas main duct 194, which is fixed perpendicularly to the water-cooled wall of the side wall and in the rear arch cavity, and is sent to the rear arch pyrolysis gas branch ducts 196 through multiple connecting pipes 195, and finally enters the combustion chamber through the pyrolysis gas rear arch ejector nozzle 18. The pyrolysis gas includes the high-temperature flue gas introduced into the pyrolysis chamber and the strong reducing gas components produced by pyrolysis. The slightly downwardly inclined front and rear arch ejector nozzles enhance the mixing of the reducing pyrolysis gas with the main flue gas from the main fuel combustion, and enhance the pyrolysis gas's effect on the NO already present in the flue gas. x The reducing effect.

[0042] To ensure the safe and stable operation of the front-arched membrane water-cooled micro-vibration auxiliary grate 12 and the boiler, the upper auxiliary furnace drainage cold wall header 16 and the lower water-cooled wall header of the front-arched membrane water-cooled micro-vibration auxiliary grate are both made of thick-walled tubes and rigidly fixed to limit the vibration range of the water-cooled grate micro-vibration mechanism, while improving the high-cycle fatigue life of the front-arched membrane water-cooled micro-vibration auxiliary grate 12. The wall thickness of the thick-walled tubes is 15-25mm. The front wall 6 of the pyrolysis chamber is composed of a refractory material lining and a detachable steel plate shell. The upper and lower ends of the steel plate shell are flanged to the flanges leading out from the upper auxiliary furnace drainage cold wall header 16 and the lower water-cooled wall header, respectively. After the steel plate shell is disassembled, all the components of the pyrolysis chamber are exposed, which facilitates the maintenance of the pyrolysis chamber and allows for the periodic cleaning of tar and adhering ash. Observation holes are arranged on the steel plate shell to monitor the working status of the pyrolysis chamber online. The main grate 17 for solid fuel combustion can be configured as a chain grate, reciprocating grate, or vibrating grate according to the characteristics of the main fuel.

[0043] The pyrolysis-direct-fired coupled composite dual-grate boiler described in this invention employs multi-path denitrification technology to reduce the initial NO content in the boiler. x Emission concentration. The high-temperature flue gas introduced into the pyrolysis chamber is a low-oxygen reducing atmosphere, which increases the conversion ratio of fuel nitrogen to N2 during pyrolysis and reduces NO emissions during subsequent utilization of the pyrolysis gas. xThe pyrolysis gas is generated by secondary air injection through the front and rear arch water-cooled walls into the combustion chamber for combustion. The gas combustion surfaces are all water-cooled, effectively reducing the combustion temperature and further reducing NO. x The generation of NO; ​​for the combustion process on the main grate of solid fuel combustion, increasing the water vapor content in the primary air through the water vapor nozzles in the primary air duct 24 and the superheated steam duct helps to increase CO and H2 production through water-gas reaction, strengthens the reducing atmosphere during the combustion of main and auxiliary fuel coke on the main grate of solid fuel combustion, and reduces NO. x The process involves generating and circulating a portion of the low-temperature flue gas through a flue gas recirculation duct. This recirculation utilizes the low temperature and low oxygen characteristics of the flue gas to reduce the local temperature within the furnace and create a localized reducing atmosphere, thereby reducing NOx emissions. Simultaneously, after passing through the furnace arch throat, the combustion flue gas reaches the combustible combustion space above the throat, where NOx emissions are further reduced. x Under the reducing action of pyrolysis gas, it can be further reduced to N2. The downwardly arranged front and rear arched ejector nozzles enhance the mixing of the reducing pyrolysis gas with the main fuel combustion flue gas, thereby increasing the effect of pyrolysis gas on the NO already present in the flue gas. x The reduction effect. By combining the above multi-path denitrification technologies, the initial NO2 emissions of the pyrolysis-direct-fired coupled composite double-grate boiler described in this invention can be effectively reduced. x Reduce emission concentrations and achieve clean utilization of solid fuel energy.

[0044] This invention can simultaneously achieve initial low nitrogen emissions through multi-path denitrification, which is beneficial to improving biomass utilization and achieving energy conservation and emission reduction.

[0045] This invention solves the problems of large size and complexity, and tar blockage in pipelines caused by the separation of pyrolysis furnace and combustion furnace in heat utilization systems. It realizes coupled pyrolysis and direct combustion heat utilization of fuel in a single furnace, greatly simplifying the structure of the integrated fuel heat utilization system, reducing equipment costs and floor space, avoiding pipeline blockage problems that may occur when the pyrolysis furnace and combustion furnace are separated, and improving the safety and stability of system operation. Furthermore, this invention effectively reduces NO during the heat utilization of primary and secondary fuels through multi-path high-efficiency low-NOx combustion technology combining flue gas recirculation, air staging, and fuel staging. x This invention reduces initial emissions and achieves energy conservation and emission reduction. It provides a highly efficient thermal utilization method for solid fuels, especially biomass, which reduces the thermal utilization cost of solid fuels, especially biomass, and can effectively improve the utilization rate of biomass in my country, improve the energy structure, and reduce carbon emissions.

Claims

1. A biomass pyrolysis coupled direct combustion combined double grate boiler, characterized in that, The pyrolysis cavity (1), the screw feeder (2), the front arch membrane type water-cooled micro-vibration auxiliary furnace (12), the auxiliary bunker (13), the solid fuel combustion main furnace (17) and the main bunker (14) are included; the front arch membrane type water-cooled micro-vibration auxiliary furnace (12) is arranged below the front wall water-cooled wall (23), the front arch membrane type water-cooled micro-vibration auxiliary furnace (12) is inwardly concave and constitutes the pyrolysis cavity (1), the bottom of the auxiliary bunker (13) is connected with the screw feeder (2), and the outlet of the screw feeder (2) is communicated with the pyrolysis cavity (1); the main bunker (14) is arranged outside the hearth, and the solid fuel combustion main furnace (17) is located below the hearth; the pyrolysis cavity (1) and the inwardly concave part of the rear wall water-cooled wall (20) are respectively communicated with the burn-out chamber through the pyrolysis gas front arch injection nozzle (10) and the pyrolysis gas rear arch injection nozzle (18), and the pyrolysis gas rear arch injection nozzle (18) is communicated with the pyrolysis cavity (1); the front arch membrane type water-cooled micro-vibration auxiliary furnace (12) includes the auxiliary furnace suspension section (11), the auxiliary furnace slow descent section (5), the auxiliary furnace steep descent section (4) and the auxiliary furnace light pipe section (3) which are sequentially connected from top to bottom, and the pipe gap of the auxiliary furnace light pipe section (3) is used as a channel for introducing high-temperature flue gas and falling coke into the pyrolysis cavity.

2. The combined dual furnace once-through boiler for biomass pyrolysis coupled direct combustion according to claim 1, characterized in that, The pyrolysis gas rear arch injection nozzle (18) is communicated with the pyrolysis cavity (1) through the U-shaped injection air pipe (19), the U-shaped injection air pipe (19) includes the pyrolysis gas inlet pipe (192), the rear arch injection secondary air pipe (193) and the rear arch pyrolysis gas main pipe (194), the pyrolysis gas inlet pipe (192) is arranged with a plurality of pyrolysis gas inlet holes (191), the pyrolysis gas inlet pipe (192) is perpendicular to the left and right side walls, and the pyrolysis gas inlet pipe (192) is fixed in the pyrolysis cavity (1); the rear arch injection secondary air pipe (193) is fixed outside the side wall water-cooled wall (197), the rear arch pyrolysis gas main pipe (194) is perpendicular to the left and right side walls, the rear arch pyrolysis gas main pipe (194) is fixed in the rear arch cavity, and the rear arch pyrolysis gas main pipe (194) is sequentially connected with a plurality of pyrolysis gas branch pipes (196) and the pyrolysis gas rear arch injection nozzle (18) through a plurality of connecting pipes (195).

3. The combined dual furnace once-through boiler for biomass pyrolysis coupled direct combustion according to claim 1, characterized in that, The front arch membrane type water-cooled micro-vibration auxiliary furnace (12) is arranged with the micro-vibration mechanism (8), and the output part of the micro-vibration mechanism (8) acts on the front arch membrane type water-cooled micro-vibration auxiliary furnace (12).

4. The combined dual furnace once-through boiler for biomass pyrolysis coupled direct combustion according to claim 1, characterized in that, The pyrolysis cavity (1) is provided with the pyrolysis cavity front wall (6), the pyrolysis cavity front wall (6) is composed of a refractory lining and a detachable steel plate shell; the upper and lower ends of the front arch membrane type water-cooled micro-vibration auxiliary furnace (12) are respectively provided with the auxiliary furnace water-cooled wall upper header (16) and the lower water-cooled wall header, the auxiliary furnace water-cooled wall upper header (16) and the lower water-cooled wall header are made of thick-walled pipes and are rigidly fixed to limit the vibration range of the water-cooled furnace micro-vibration mechanism and improve the high-cycle fatigue life of the front arch membrane type water-cooled micro-vibration auxiliary furnace (12); the upper and lower ends of the pyrolysis cavity front wall (6) are respectively connected with the flange structures led out by the auxiliary furnace water-cooled wall upper header (16) and the lower water-cooled wall header.

5. The combined dual furnace once-through boiler for biomass pyrolysis coupled direct combustion according to claim 4, characterized in that, Fuel pushing piece (9) is arranged in pyrolysis cavity (1), fuel pushing piece (9) includes main pushing piece (91) and movable auxiliary pushing piece (92), fuel pushing piece (9) is connected with sliding block, sliding block is arranged in slide rail of front wall (6) of pyrolysis cavity, main pushing piece (91) and movable auxiliary pushing piece (92) are slidingly connected, pulling rod is arranged on main pushing piece (91), the pulling rod adopts manual lever or electric screw rod assembly, driven end of pulling rod is connected with movable auxiliary pushing piece (92).

6. The combined dual furnace once-through boiler for biomass pyrolysis coupled direct combustion according to claim 1, characterized in that, Spiral feeder (2) is arranged as follows: one spiral feeder with the same width as the front wall or two coaxial spiral feeders with the length of half the width of the front wall are arranged, the barrel is arranged horizontally along the front wall of the boiler, a plurality of discharge ports (204) are uniformly arranged on the lower side of the barrel, and the discharge ports (204) extend into the pyrolysis cavity (1) and reach a position close to the upper end of the auxiliary grate gentle descending section (5).

7. The combined dual furnace once-through boiler for biomass pyrolysis coupled direct combustion according to claim 1, characterized in that, Pyrolysis cavity (1) is provided with spiral carbon extractor (7), pyrolysis cavity (1) is communicated with solid fuel combustion main grate (17), and solid fuel combustion main grate (17) is arranged as chain grate, reciprocating grate and vibrating grate according to the characteristics of main fuel; the bottom of solid fuel combustion main grate (17) is provided with superheated steam pipeline (25) and flue gas recirculation pipeline (26) on primary air pipeline (24).

8. The combined dual furnace once-through boiler for biomass pyrolysis coupled direct combustion according to claim 7, characterized in that, Spiral carbon extractor (7) includes barrel (71), rotatable carbon extraction port baffle (72) is arranged on barrel (71), carbon extraction port (73) is arranged below carbon extraction port baffle, one end of carbon extraction port baffle (72) is hinged to barrel (71), and carbon outlet (74) is arranged at the bottom of one end of barrel (71); when carbon is needed, carbon extraction port baffle (72) is lowered to be connected with auxiliary grate steep descending section (4), coke can fall into barrel (71) and be taken out through carbon outlet (74), coke particles fall into solid fuel combustion main grate (17) through the gap between carbon extraction port baffle (72) and auxiliary grate steep descending section (4); rotation of carbon extraction port baffle (72) adjusts the flow of high-temperature flue gas introduced into the pyrolysis cavity, thereby adjusting the temperature in the pyrolysis cavity, so as to realize low-temperature pyrolysis, medium-temperature pyrolysis or high-temperature pyrolysis in the pyrolysis cavity as needed.

9. The combined dual furnace once-through boiler for biomass pyrolysis coupled direct combustion according to claim 1, characterized in that, Main fuel is original ecological biomass, biomass briquettes and / or coal, and auxiliary fuel is original ecological biomass, biomass briquettes and / or dry sludge with water content less than 40% after drying and crushing.

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