A countercurrent two-stage inner and outer air distribution self-heating biomass fixed bed gasifier

Abstract

The present application relates to the technical fields of biomass boiler and new gasification furnace, and discloses a countercurrent two-stage internal and external gas distribution self-heating type biomass fixed bed gasification furnace, which comprises a furnace body, and a drying zone, a pyrolysis zone, an upper combustion zone, a gasification zone and a lower combustion zone are sequentially arranged in the furnace body from top to bottom. The present application realizes the graded countercurrent reaction of biomass raw materials through the drying zone, the pyrolysis zone, the upper combustion zone, the gasification zone and the lower combustion zone in the furnace body from top to bottom, the upper and lower two-stage gas distribution structure is adopted for the air inlet system, the upper air inlet mechanism utilizes the internal and external staggered arrangement of the annular pipe first air inlet and the air outlet pipe second air inlet to uniformly distribute the air in the upper combustion zone, so that the local oxygen deficiency, overheating and coking are avoided, the initial cracking of tar, the oxidation and heat release of semi-coke form a self-heating heat source, external heating is not needed, the overall structure improves the gasification efficiency and heat utilization rate, reduces the energy consumption and operation cost, the reaction is stable, and the present application has good practicability and economy.

Description

Technical Field

[0001] This invention relates to the field of biomass boilers and novel gasifiers, and particularly to a counter-current, two-stage, internal and external gas distribution self-heating biomass fixed-bed gasifier. Background Technology

[0002] Biomass, as an important renewable energy source, plays a crucial role in the transformation of the energy structure through its efficient and clean utilization. Biomass gasification technology is a key pathway to convert biomass feedstock into syngas through thermochemical conversion. Its principle involves heating and decomposing the biomass feedstock under conditions of limited oxygen or a combination of several gasifying agents (such as air, oxygen-enriched air, and water vapor) to convert it into syngas containing combustible components such as carbon monoxide, hydrogen, and methane. The gasification medium typically enters the furnace reaction zone through the inlet to react with the biomass feedstock. Among these technologies, fixed-bed gasifiers are particularly advantageous due to their simple structure, reliable operation, and low cost. Widely used in small and medium-sized distributed energy systems, the furnace body is conventionally divided into reaction zones such as drying, pyrolysis, oxidation, and gasification from top to bottom. Biomass raw materials are fed from the top of the furnace and move down layer by layer by gravity. The gasifying agent is mostly introduced from the bottom of the furnace or a single point on one side. The airflow flows in the opposite or the same direction as the raw materials. The drying, pyrolysis, oxidation, and gasification reactions are completed by relying on the natural stratification of the material layer inside the furnace. The produced syngas is exported from the top or bottom of the furnace body. The whole system relies on the heat generated by the reaction inside the furnace to maintain basic operation. It is a commonly used equipment for biomass resource utilization at present and is suitable for gasification and conversion of various agricultural and forestry wastes.

[0003] However, traditional biomass fixed-bed gasifiers generally adopt a single-stage gas inlet method, with the gasifying agent mostly introduced from a single point or side outside the furnace body. This easily leads to uneven gas distribution inside the furnace, resulting in incomplete combustion and coking / caking in some areas, which in turn leads to low gasification efficiency and thus cannot meet the demand for efficient biomass gasification utilization. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a counter-current, two-stage, internal and external gas distribution self-heating biomass fixed-bed gasifier, which solves the technical problems of uneven gasification agent distribution, incomplete local combustion, and coking and agglomeration in the prior art.

[0005] This invention provides a counter-current, two-stage, internally and externally distributed, self-heating biomass fixed-bed gasifier, characterized in that it comprises: The furnace body has, from top to bottom, a drying zone, a pyrolysis zone, an upper combustion zone, a gasification zone, and a lower combustion zone, and the top of the furnace body is provided with a chimney opening; The air intake system includes an upper air intake mechanism and a lower air intake mechanism. The upper air intake mechanism includes an annular pipe disposed on the outer wall of the upper combustion zone and an air outlet pipe disposed in the central region inside the furnace body. The annular pipe has a gasifying agent inlet. Multiple first air inlets are axially arranged on the outer wall of the upper combustion zone, which is in contact with the annular pipe. These first air inlets communicate with the gasifying agent inlets, and the gasifying agent inlets are connected to the interior of the upper combustion zone through the multiple first air inlets. One end of the air outlet pipe penetrates the furnace body and extends to its outer side. The end extends to the lower combustion zone. The exhaust pipe includes an inner pipe and an outer pipe nested together. A gasifying agent channel is formed between the inner pipe and the outer pipe. Multiple second air inlets are opened on the pipe wall of the outer pipe. Multiple first air inlets and multiple second air inlets are staggered inward and outward along the circumference of the furnace body. The lower air intake mechanism includes multiple bottom air intake pipes fixedly installed at the bottom of the lower combustion zone. The multiple bottom air intake pipes are distributed in a circumferential array in the lower combustion zone. Gasifying agent is introduced into the bottom air intake pipes, the annular pipe and the gasifying agent channel.

[0006] Preferably, a central air inlet pipe is connected to the gasifying agent inlet, and a check valve and a rotor flow meter are installed on the central air inlet pipe. The central air inlet pipe is connected to the gasifying agent supply source.

[0007] Preferably, a check valve and a rotor flow meter are sequentially installed at the ends of the plurality of bottom air inlets away from the bottom of the furnace body, and then connected to the gasifying agent supply source.

[0008] Preferably, a gas intake pipe is provided at one end of the gas outlet pipe extending out of the furnace body. The gas intake pipe is connected to the inner pipe of the gas outlet pipe and is used to extract the synthesis gas generated in the furnace reaction and increase the contact time between the external cold air and the synthesis gas, so as to achieve the cooling treatment of the synthesis gas by natural condensation.

[0009] Preferably, a plurality of temperature sensors are evenly distributed along the axial direction on the side wall of the furnace body. The plurality of temperature sensors correspond to the drying zone, pyrolysis zone, upper combustion zone, gasification zone and lower combustion zone respectively. A temperature sensor is also provided at one end of the gas outlet pipe extending out of the furnace body.

[0010] Preferred options also include: The control system is electrically connected to multiple temperature sensors to monitor the temperature of each area inside the furnace and the outlet of the gas pipe in real time, and to regulate the gasification process based on the monitoring data.

[0011] Preferably, the furnace body is provided with a plurality of ignition ports, including a bottom ignition port at the bottom of the furnace body and a middle ignition port at the middle of the furnace body. The bottom ignition port corresponds to the lower combustion zone, and the middle ignition port corresponds to the upper combustion zone.

[0012] Compared with the prior art, the technical solution provided by the embodiments of the present invention has the following advantages: The present invention realizes the graded countercurrent reaction of biomass raw materials through a drying zone, pyrolysis zone, upper combustion zone, gasification zone and lower combustion zone arranged from top to bottom inside the furnace body. The air intake system adopts a two-stage air distribution with an upper air intake mechanism and a lower air intake mechanism. The upper air intake mechanism achieves uniform air distribution throughout the upper combustion zone by staggering the first air inlet of the annular pipe and the second air inlet of the outlet pipe, avoiding local oxygen deficiency, overheating and coking, so that the tar is initially cracked and the semi-coke is partially oxidized and releases heat to form a self-heating heat source without the need for external heating. The lower air intake mechanism provides sufficient air to the lower combustion zone through multiple bottom air intake pipes distributed in a circumferential array. Sufficient and uniform gasifying agent enhances combustion to generate enough heat for the gasification reaction. Semi-coke reacts efficiently in the gasification zone to generate combustible syngas. The lower combustion zone further completes oxidation and releases heat to maintain the reaction temperature. When the combustible gas is discharged through the inner pipe of the outlet pipe, it undergoes high-temperature treatment in the lower combustion zone to achieve deep tar cracking and gas purification, significantly improving the quality of syngas. The overall structure not only improves the gasification reaction rate and efficiency, but also realizes heat recovery and utilization, reducing energy consumption. This can effectively improve the biomass gasification efficiency and gas quality, reduce energy waste, enhance the stability of the reaction inside the furnace, and reduce operating costs, thus adapting to the needs of biomass gasification of different scales and possessing good practicality and economy. Attached Figure Description

[0013] Figure 1 A schematic diagram of the overall structure of the counter-current two-stage internal and external gas distribution self-heating biomass fixed bed gasifier provided by the present invention. Figure 2 This is a half-sectional schematic diagram of the overall structure of the present invention; Figure 3 A schematic diagram of the built-in air outlet pipe structure provided by the present invention; Figure 4 This is a schematic diagram of the upper air intake mechanism provided by the present invention; Figure 5 This is a schematic diagram of the lower air intake mechanism provided by the present invention.

[0014] Explanation of reference numerals in the attached figures: 1. Furnace body; 2. Upper air inlet mechanism; 3. Lower air inlet mechanism; 4. Material cylinder; 5. Screw feeder; 6. Gasifying agent air inlet; 7. Exhaust fan; 8. Rotary grate; 9. Ignition port; 10. Gas outlet pipe; 11. Temperature sensor; 12. Gas intake pipe; 13. Ash hopper; 14. Chimney opening; 15. Drying zone; 16. Pyrolysis zone; 17. Upper combustion zone; 18. Gasification zone; 19. Lower combustion zone; 20. Second air inlet; 21. First air inlet. Detailed Implementation

[0015] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0016] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the technical solution of this 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, they should not be construed as limitations on this invention.

[0017] The present invention will be described below through several specific embodiments. To keep the following description of the embodiments clear and concise, detailed descriptions of known functions and components may be omitted. When any component of an embodiment of the present invention appears in more than one drawing, the component may be represented by the same reference numerals in each drawing.

[0018] like Figures 1-5 As shown, this embodiment provides a counter-current, two-stage, internally and externally distributed, self-heating biomass fixed-bed gasifier, comprising: The furnace body 1 has a drying zone 15, a pyrolysis zone 16, an upper combustion zone 17, a gasification zone 18 and a lower combustion zone 19 arranged from top to bottom inside the furnace body 1, and a chimney opening 14 is provided at the top of the furnace body 1. The air intake system includes an upper air intake mechanism 2 and a lower air intake mechanism 3. The upper air intake mechanism 2 includes an annular pipe on the outer wall of the upper combustion zone 17 and an exhaust pipe 10 in the central region inside the furnace body 1. The annular pipe is provided with a gasifying agent inlet 6. The outer wall of the upper combustion zone 17, which is in contact with the annular pipe, is axially provided with multiple first air inlets 21. The first air inlets 21 are connected to the gasifying agent inlets 6. The gasifying agent inlets 6 are connected to the interior of the upper combustion zone 17 through the multiple first air inlets 21. One end of the exhaust pipe 10 penetrates the furnace body 1 and extends to... On its outer side, the other end extends to the lower combustion zone 19. The exhaust pipe 10 includes an inner pipe and an outer pipe nested together. A gasifying agent channel is formed between the inner pipe and the outer pipe. Multiple second air inlets 20 are opened on the pipe wall of the outer pipe. Multiple first air inlets 21 and multiple second air inlets 20 are staggered inward and outward along the circumference of the furnace body 1. The lower air intake mechanism 3 includes multiple bottom air intake pipes fixedly installed at the bottom of the lower combustion zone 19. The multiple bottom air intake pipes are distributed in a circumferential array in the lower combustion zone 19. Gasifying agent is introduced into the bottom air intake pipes, the annular pipe and the gasifying agent channel. With the furnace body 1 as the core reaction carrier, the interior is divided into a drying zone 15, a pyrolysis zone 16, an upper combustion zone 17, a gasification zone 18, and a lower combustion zone 19 from top to bottom to achieve staged reactions. Biomass enters from the top and passes through each reaction zone sequentially, ultimately generating syngas. The top chimney 14 is used to discharge the exhaust gas generated during gasification, ensuring stable gas pressure inside the furnace. The air intake system supplies gasifying agents to each reaction zone through the upper air intake mechanism 2 and the lower air intake mechanism 3. During operation, the biomass feedstock enters from the top of the furnace body 1. The feed is fed into the inlet and, under the influence of gravity, passes through each reaction zone sequentially from top to bottom. First, it is preheated and dried by high-temperature flue gas in the drying zone 15 to remove internal moisture. The dried feed then enters the pyrolysis zone 16, where it is decomposed at high temperature, releasing volatiles, tar, and generating semi-coke. The generated tar and semi-coke then enter the upper combustion zone 17, where they come into contact with the gasifying agent introduced through the upper air intake mechanism 2. The gasifying agent enters the annular pipe through the gasifying agent inlet 6 and then flows into the upper combustion zone through multiple first air inlets 21. Inside the upper combustion zone 17, the gasifying agent channel formed by the inner and outer pipes along the gas outlet pipe 10 is staggered with the gasifying agent delivered from the center of the furnace through multiple second air inlets 20. This achieves uniform gas distribution throughout the upper combustion zone 17, avoiding local oxygen deficiency or overheating. This allows for the initial cracking of tar and partial oxidation of semi-coke, releasing a large amount of heat and providing a self-heating heat source for the overall reaction inside the furnace, eliminating the need for continuous external heating. The remaining semi-coke falls into the gasification zone 18 by gravity, where it gasifies with the carbon dioxide and water vapor generated in the upper combustion zone 17. The reaction produces combustible syngas such as carbon monoxide and hydrogen. The unreacted semi-coke continues to fall into the lower combustion zone 19, where it mixes thoroughly with the gasifying agent supplied by multiple bottom air inlets arranged in a circular array at the bottom of the furnace body 1, undergoing a complete oxidation reaction and further releasing heat. This heat, combined with the thermal radiation from the upper combustion zone 17, maintains the reaction temperature in the gasification zone 18. After the reaction is complete, the semi-coke is converted into ash and discharged. The combustible gas generated inside the furnace is discharged through the inner pipe of the exhaust pipe 10, flowing through the lower combustion zone 19 before being discharged. The gas undergoes another high-temperature treatment to achieve deep tar cracking and gas purification, improve the quality of syngas, and reduce impurities and tar content. The exhaust gas is discharged in time through the chimney outlet 14 at the top of the furnace body 1, stabilizing the pressure inside the furnace and ensuring the safe, continuous, and stable operation of the entire gasification process. The entire process achieves uniform distribution of the gasifying agent through two-stage internal and external gas distribution, and utilizes the heat generated by combustion to achieve self-heating gasification. It can achieve efficient and stable gasification of biomass without external heating, thereby improving the utilization rate of biomass and gasification efficiency, and ensuring the continuous and stable self-heating countercurrent gasification operation of the gasifier.

[0019] Furthermore, such as Figures 1-5As shown, a central air inlet pipe is connected to the gasifying agent inlet 6. A check valve and a rotor flow meter are installed on the central air inlet pipe. The central air inlet pipe is connected to the gasifying agent supply source. The gasifying agent supply source sends the gasifying agent into the annular pipe through the central air inlet pipe, and then into the upper combustion zone 17 through multiple first air inlets 21, which can form a circulating gas distribution effect. The check valve effectively prevents the backflow of gasifying agent and high-temperature gas in the furnace, ensuring gas supply safety and equipment stability. The rotor flow meter is used to monitor and accurately control the gasifying agent flow in real time, ensuring stable reaction conditions in the furnace, thereby improving gasification efficiency and operational reliability.

[0020] Furthermore, such as Figures 1-5 As shown, the gasifying agent channel between the bottom of the outer pipe and the inner pipe of the gas outlet pipe 10 is sealed, and the top of the gas outlet pipe 10 is connected to the gasifying agent supply source after a check valve and a rotor flow meter are installed in sequence through the pipe. The sealing of the bottom of the outer pipe of the gas outlet pipe 10 can ensure that the gasifying agent is evenly fed into the furnace only from the second air inlet 20, forming an alternating arrangement with the gasifying agent introduced through the first air inlet 21, realizing uniform gas distribution throughout the upper combustion zone 17, ensuring that the biomass raw materials are fully combusted. At the same time, the top of the gas outlet pipe is equipped with a check valve and a rotor flow meter in sequence through the pipe, which can prevent the backflow of gasifying agent and high-temperature gas in the furnace, accurately measure and stably control the gasifying agent supply, thereby improving the stability and safety of the gasification reaction.

[0021] Furthermore, such as Figures 1-5 As shown, multiple bottom air inlet pipes are connected to the gasifying agent supply source after a check valve and a rotor flow meter are installed sequentially at the ends away from the bottom of the furnace body 1. The check valve can prevent the backflow of gasifying agent and high-temperature gas in the furnace, ensuring the safety of gas supply. The rotor flow meter can accurately monitor and stably control the flow rate of gasifying agent entering the lower combustion zone 19, ensuring complete combustion in the lower part and providing sufficient heat for the stable gasification reaction, thereby improving the reliability of equipment operation.

[0022] Furthermore, such as Figures 1-5 As shown, a gas intake pipe 12 is provided at one end of the gas outlet pipe 10 extending out of the furnace body 1. The gas intake pipe 12 is connected to the inner pipe of the gas outlet pipe 10 and is used to extract the syngas generated in the furnace reaction and increase the contact time between the external cold air and the syngas. The syngas is cooled by natural condensation. Relying on the gas pressure generated by the gasification reaction in the furnace and the external induced draft / extraction power, the high-temperature syngas generated in the furnace reaction is extracted from the inner pipe of the gas outlet pipe 10. At the same time, the contact time between the external cold air and the syngas is extended during the extraction process. The syngas is cooled by natural condensation, which reduces the gas temperature, improves the gas discharge state, and reduces the impact of high-temperature gas on subsequent pipelines and equipment, thereby improving the safety and stability of gas transportation and use.

[0023] Furthermore, such as Figures 1-5As shown, multiple temperature sensors 11 are evenly distributed along the axial direction on the side wall of the furnace body 1. The multiple temperature sensors 11 correspond to the drying zone 15, the pyrolysis zone 16, the upper combustion zone 17, the gasification zone 18 and the lower combustion zone 19, respectively. A temperature sensor 11 is also provided at one end of the gas outlet pipe 10 extending out of the furnace body 1. The multiple temperature sensors 11 are electrically connected to the control system. The control system is used to monitor the temperature of each area in the furnace and the outlet of the gas outlet pipe 10 in real time, and to regulate the gasification process according to the monitoring data. The distribution of the multiple temperature sensors 11 is as follows: T1: Located inside the inner tube of the gas outlet pipe 10, it measures the temperature of the produced combustible gas; T2: Located on the side wall of furnace body 1 corresponding to drying zone 15; T3: Located on the side wall of furnace body 1 corresponding to pyrolysis zone 16; T4: Located on the side wall of furnace body 1, corresponding to the upper combustion zone 17; T5: Located on the side wall of furnace body 1 corresponding to gasification zone 18; T6: Located in the lower combustion zone 19, corresponding to the side wall of furnace body 1; Temperature sensor 11 is a K-type thermocouple temperature sensor, which is directly embedded in the reserved opening on the side wall of furnace body 1. The probe of temperature sensor 11 extends into the reaction zone inside the furnace, and the outer side is sealed with the insulation layer of furnace body 1. All output terminals of temperature sensor 11 are connected to the control system through the line. It can not only collect accurate temperature data of each area in real time, but also transmit the data to the control system synchronously, realize the real-time monitoring and recording of the temperature of the entire furnace, and can also adjust the gas inlet parameters according to the temperature feedback to maintain the stability of the temperature field inside the furnace, ensure the efficient and orderly gasification reaction, and monitor the syngas temperature to control the quality of the produced gas.

[0024] Furthermore, such as Figures 1-5 As shown, it also includes: The feeding system includes a material cylinder 4 and a screw feeder 5 located on one side of the furnace body 1. The material cylinder 4 is connected to the feed end of the screw feeder 5, and the discharge end of the screw feeder 5 is connected to the feed inlet located at the top of the furnace body 1. The bottom of the material cylinder 4 is connected to the feed end of the screw feeder 5. The screw rod inside the screw feeder 5 is connected to the output shaft of the motor. The screw feeder 5 is equipped with a frequency converter motor, a reducer and a coupling, and is electrically connected to the control system. The control system can adjust the motor speed to change the rotation speed of the screw shaft, and continuously supply biomass raw materials into the furnace through the feed inlet at the top of the furnace body 1 to ensure uniform supply of biomass raw materials. The gas exhaust system includes a syngas outlet pipe for exporting the generated syngas. The gas exhaust system efficiently exports the syngas generated in the furnace through the syngas outlet pipe, ensuring smooth collection of the produced gas. A rotating grate 8 is located at the bottom of the furnace body 1. The rotating grate 8 is driven to rotate by a transmission device, which includes a large-diameter slewing bearing, a large slewing gear ring, a slewing platform, and a slewing geared motor. The motor drives the rotating grate 8 to rotate, thereby achieving mechanical slag removal. The ash discharge device, in conjunction with the rotary grate 8, is used to collect and discharge ash. The rotary grate 8 at the bottom of the furnace body 1 rotates smoothly under the drive of the rotary reduction motor, the large-diameter rotary bearing and the rotary large gear transmission device, so that the ash is pushed in an orderly manner. In conjunction with the ash discharge device, continuous and stable mechanical ash discharge is achieved, avoiding slag formation and material blockage in the furnace that would affect the gasification reaction.

[0025] Furthermore, such as Figures 1-5 As shown, the ash discharge device is a screw conveyor, which is set at the bottom of the furnace body 1. It is used to guide the ash from the bottom of the furnace to the ash hopper 13. The screw conveyor-type ash discharge device set at the bottom of the furnace body 1 can stably and continuously transport the ash falling from the rotating grate 8 to the ash hopper 13 for centralized collection and external discharge, avoiding ash blockage, ash accumulation and air leakage at the bottom of the furnace, thereby ensuring the stability of the pressure field inside the furnace and maintaining the continuous, smooth and safe operation of the gasifier.

[0026] Furthermore, such as Figures 1-5 As shown, the furnace body 1 is provided with multiple ignition ports 9, including bottom ignition ports at the bottom of the furnace body 1 and middle ignition ports in the middle of the furnace body 1. The bottom ignition ports correspond to the lower combustion zone 19, and the middle ignition ports correspond to the upper combustion zone 17. The bottom of the furnace body 1 is provided with four bottom ignition ports, which correspond to the lower combustion zone 19. They are opened when igniting and closed when not in operation. The ignition device is a spray gun, which extends into the furnace from the ignition port 9 to ignite the biomass raw materials. The middle ignition port is an auxiliary ignition structure that can supplement the fire when the combustion in the furnace is incomplete. It is closed after ignition to ensure the airtightness of the furnace body 1.

[0027] Furthermore, such as Figures 1-5 As shown, it also includes an induced draft fan 7, which is located outside the furnace body 1. The induced draft fan 7 works in conjunction with multiple ignition ports 9 to adjust the negative pressure and airflow velocity inside the furnace during ignition and start-up, guide the air to be distributed reasonably, make ignition smoother and combustion more stable, and ensure that the temperature field inside the furnace is established uniformly, thereby ensuring the safe and efficient start-up of the gasifier.

[0028] Furthermore, such as Figures 1-5 As shown, the gasifying agent supply source includes an air supply source and a water vapor supply source. The air supply source includes a blower, and the water vapor supply source includes a peristaltic pump. The gasifying agent supply source adopts a dual-source structure with the blower supplying air and the peristaltic pump supplying water vapor. It can accurately proportion and stably deliver the gasifying agent according to the working conditions, meet the requirements of oxidation exothermic reaction and gasification reaction, thereby improving the gas production quality and gasification efficiency, and ensuring that the reaction is stable and controllable.

[0029] like Figures 1-5 As shown, the working principle of the counter-current two-stage internal and external gas distribution self-heating biomass fixed bed gasifier provided in this embodiment is as follows: During operation, the furnace body 1 serves as the core reaction carrier, forming a graded countercurrent reaction structure from top to bottom: a drying zone 15, a pyrolysis zone 16, an upper combustion zone 17, a gasification zone 18, and a lower combustion zone 19. Biomass feedstock is fed into the top of the furnace body 1 via the feed cylinder 4 and screw feeder 5. Under gravity, it descends sequentially, first being preheated and dehydrated by high-temperature flue gas in the drying zone 15, then entering the pyrolysis zone 16 to decompose and release volatiles and tar, generating semi-coke. Subsequently, it enters the upper combustion zone 17, where it comes into full contact with the gasifying agent introduced by the upper air inlet mechanism 2. The gasifying agent enters the annular pipe through the gasifying agent inlet 6 and then passes through multiple first air inlets. 21 is introduced into the upper combustion zone 17, and the gasifying agent channel formed by the inner and outer pipes along the outlet pipe 10 is staggered with the gasifying agent sent from the center of the furnace through multiple second air inlets 20, so as to achieve uniform gas distribution throughout the upper combustion zone 17. This allows for the initial cracking of tar and the partial oxidation of semi-coke to release heat and provide a self-heating heat source for the furnace. The remaining semi-coke falls into the gasification zone 18 by gravity and reacts with the carbon dioxide and water vapor generated in the upper combustion zone 17 to produce combustible syngas such as carbon monoxide and hydrogen. The semi-coke that has not fully reacted continues to fall into the lower combustion zone 19, where it is fully mixed with the gasifying agent sent in by multiple bottom air inlets arranged in a circumferential array at the bottom. The total oxidation process is exothermic, and together with the thermal radiation from the upper combustion zone 17, it maintains a stable high temperature in the gasification zone 18. The ash produced by the reaction is discharged in an orderly manner by the rotating grate 8 at the bottom of the furnace under the drive of the transmission device, and then transported to the ash hopper 13 for centralized external discharge via a screw conveyor-type ash discharge device. The syngas generated in the furnace is discharged upward along the inner pipe of the outlet pipe 10, and achieves deep tar cracking and gas purification when flowing through the lower combustion zone 19. It is then output by the gas intake pipe 12 relying on the gas pressure inside the furnace and the external induced draft / extraction power, and is cooled by natural condensation. Throughout the process, check valves and rotor flow meters are installed in the middle inlet pipe, the top of the outlet pipe 10, and the bottom inlet pipe, respectively. To achieve backflow prevention and precise gas control, multiple K-type thermocouple temperature sensors T1-T6 on the side wall of furnace body 1 and at the outlet of gas pipe 10 monitor the temperature of each area in real time and transmit the data to the control system. Based on the temperature feedback, the speed of screw feeder 5, the amount of gasifying agent supplied, and the negative pressure of induced draft fan 7 are adjusted in linkage. The gasifying agent supply source adopts a blower and a peristaltic pump to supply air and water vapor respectively to be mixed as needed. The bottom ignition port and the middle ignition port on furnace body 1 work together with induced draft fan 7 to complete the ignition start-up. The exhaust gas is discharged from the top chimney 14 to stabilize the pressure inside the furnace, thereby realizing continuous, stable, efficient, and low-consumption self-heating gasification of biomass and producing high-quality clean syngas.

[0030] The above inventions are merely a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A counter-current, two-stage, internally and externally distributed, self-heating biomass fixed-bed gasifier, characterized in that, include: The furnace body has, from top to bottom, a drying zone, a pyrolysis zone, an upper combustion zone, a gasification zone, and a lower combustion zone, and the top of the furnace body is provided with a chimney opening; The air intake system includes an upper air intake mechanism and a lower air intake mechanism. The upper air intake mechanism includes an annular pipe disposed on the outer wall of the upper combustion zone and an air outlet pipe disposed in the central region inside the furnace body. The annular pipe has a gasifying agent inlet. Multiple first air inlets are axially arranged on the outer wall of the upper combustion zone, which is in contact with the annular pipe. These first air inlets communicate with the gasifying agent inlets, and the gasifying agent inlets are connected to the interior of the upper combustion zone through the multiple first air inlets. One end of the air outlet pipe penetrates the furnace body and extends to its outer side. The end extends to the lower combustion zone. The exhaust pipe includes an inner pipe and an outer pipe nested together. A gasifying agent channel is formed between the inner pipe and the outer pipe. Multiple second air inlets are opened on the pipe wall of the outer pipe. Multiple first air inlets and multiple second air inlets are staggered inward and outward along the circumference of the furnace body. The lower air intake mechanism includes multiple bottom air intake pipes fixedly installed at the bottom of the lower combustion zone. The multiple bottom air intake pipes are distributed in a circumferential array in the lower combustion zone. Gasifying agent is introduced into the bottom air intake pipes, the annular pipe and the gasifying agent channel.

2. The counter-current, two-stage, internally and externally distributed, self-heating biomass fixed-bed gasifier as described in claim 1, characterized in that, The gasifying agent inlet is connected to a central inlet pipe, which is equipped with a check valve and a rotor flow meter. The central inlet pipe is connected to the gasifying agent supply source.

3. The counter-current, two-stage, internal and external gas distribution self-heating biomass fixed-bed gasifier as described in claim 1, characterized in that, A check valve and a rotor flow meter are sequentially installed at the end of the multiple bottom air inlet pipes that is away from the bottom of the furnace body, and then connected to the gasifying agent supply source.

4. The counter-current, two-stage, internal and external gas distribution self-heating biomass fixed-bed gasifier as described in claim 1, characterized in that, A gas intake pipe is provided at one end of the gas outlet pipe extending out of the furnace body. The gas intake pipe is connected to the inner pipe of the gas outlet pipe and is used to extract the synthesis gas generated in the furnace reaction and increase the contact time between the external cold air and the synthesis gas, so as to achieve the cooling treatment of the synthesis gas by natural condensation.

5. The counter-current, two-stage, internal and external gas distribution self-heating biomass fixed-bed gasifier as described in claim 1, characterized in that, Multiple temperature sensors are evenly distributed along the axial direction on the side wall of the furnace body. The multiple temperature sensors correspond to the drying zone, pyrolysis zone, upper combustion zone, gasification zone and lower combustion zone, respectively. A temperature sensor is also provided at one end of the gas outlet pipe that extends out of the furnace body.

6. The counter-current two-stage internal and external gas distribution self-heating biomass fixed bed gasifier as described in claim 5, characterized in that, Also includes: The control system is electrically connected to multiple temperature sensors to monitor the temperature of each area inside the furnace and the outlet of the gas pipe in real time, and to regulate the gasification process based on the monitoring data.

7. The counter-current, two-stage, internal and external gas distribution self-heating biomass fixed-bed gasifier as described in claim 1, characterized in that, The furnace body is provided with multiple ignition ports, including a bottom ignition port at the bottom of the furnace body and a middle ignition port in the middle of the furnace body. The bottom ignition port corresponds to the lower combustion zone, and the middle ignition port corresponds to the upper combustion zone.

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