Biomass gasification furnace with water-cooled fire grate and biomass gasification method

Abstract

The invention belongs to the field of new energy, and particularly relates to a water-cooled grate biomass gasifier and a biomass gasification method. The water-cooled grate biomass gasification furnace comprises a gasification furnace body of a downdraft structure, the gasification furnace body is internally provided with a feeding system, the feeding system comprises a feeding chute, a feeding sealing door and a feeding sealing door, the feeding chute is provided with an anaerobic system pipeline, and a feeding grate is located below the feeding sealing door; the water-cooling fire grate assembly is composed of multi-stage welding type water-cooling fire grate segments, and a cooling water cavity is formed in the water-cooling fire grate assembly. The hearth is divided into a drying layer, a pyrolysis layer, a reduction layer and an oxidation layer in the material moving direction. The gasifying agent supply system comprises a primary air duct, a secondary air duct, a steam injection pipeline I and a water vapor injection pipeline II, wherein pure oxygen is introduced into the primary air duct; the cooling circulation system comprises a circulation pipeline, a circulation water pump and a radiator, wherein the circulation water pump and the radiator are installed on the circulation pipeline. The circulation pipeline is communicated with the water-cooling fire grate assembly to form a closed circulation loop. The device is high in reliability, long in service life, low in emission, easy to control and good in gasification effect.

Description

Technical Field

[0001] The present invention belongs to the field of new energy, and particularly relates to the technology of producing methanol synthesis gas from straw biomass, in particular to a water-cooled grate biomass gasifier and a biomass gasification method. Background Art

[0002] The technology of producing methanol from biomass is generally divided into two parts. The first part is the thermochemical gasification of biomass to produce raw gas and synthesis gas; the second part is the catalytic synthesis of crude methanol from synthesis gas under certain pressure and temperature conditions, and the crude methanol is obtained as a methanol product after rectification.

[0003] At present, the furnace types of domestic biomass gasifiers mainly include fixed-bed gasifiers, fluidized-bed gasifiers and rotating-bed gasifiers. Among them, (1) The fixed-bed gasifier converts solid raw materials into combustible gas through stratified reaction, which is suitable for medium and small-scale production; however, the gasification efficiency is relatively low, and the requirements for the particle size and humidity of the raw materials are relatively high. Improper treatment of tar and ash may cause pollution. (2) Solid fuels (such as coal, biomass) and inert bed materials (such as sand) are placed at the bottom of the reactor, and a gasifying agent (air, oxygen or steam) is introduced. When the gas flow rate reaches a certain value, the bed material particles are suspended to form a fluidized bed; the manufacturing and maintenance costs of fluidized-bed gasifiers are high, the operating energy consumption is large, and the operating parameters need to be precisely controlled. (3) The rotating-bed gasifier is a device for placing solid fuel into a rotatable bed layer, and the fuel is evenly distributed here to be converted into combustible gas; the manufacturing and maintenance costs of rotating-bed gasifiers are high, the operating energy consumption is large, and the operating parameters also need to be precisely controlled. No matter which type of gasifier is used, biomass raw gas can be produced, but the quality of the produced raw gas varies greatly.

[0004] Moreover, the gasification efficiency of many biomass gasifiers on the market is currently <70%, and the low calorific value of the gas is <4.6 MJ / Nm3, which is lower than the NY / T443-2016 standard, resulting in both energy waste and a threat to the life safety of users. Therefore, how to reasonably design a gasifier to have high gasification efficiency, good gas quality, gas indexes meeting national standards, and being compatible with the methanol synthesis gas production process technology is a technical problem to be solved urgently at present. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: In order to solve the problems of low gasification efficiency, poor gas quality and incompatibility with the methanol synthesis gas production process technology of the existing biomass gasifier in the above background art, a water-cooled grate biomass gasifier is provided, which has high gasification efficiency, good gas quality, is durable and operates stably, has good material adaptability, and is compatible with the methanol synthesis gas production process technology.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a water-cooled grate biomass gasifier, including a gasifier main body with a downward suction structure, and the following are provided in the gasifier main body: A feeding system, including a feeding chute, a feeding seal door and a feeding seal door respectively located at the upper end and the lower end of the feeding chute. An anaerobic system pipeline is provided on the feeding chute, and the feeding chute maintains a state of being filled with materials during operation. The feeding seal door and the feeding seal door are hydraulically driven and alternately opened and closed to achieve continuous feeding; A feeding grate, located below the feeding seal door, A water-cooled grate assembly, composed of multiple levels of welded water-cooled grate plates, with a cooling water cavity inside; A furnace chamber, which is divided into a drying layer, a pyrolysis layer, a reduction layer and an oxidation layer along the direction of material movement; A gasifying agent supply system, including a primary air duct for introducing pure oxygen, a secondary air duct, a steam injection pipeline I and a water vapor injection pipeline II; A cooling circulation system, including a circulation pipeline, a circulation water pump and a radiator installed on the circulation pipeline. The circulation pipeline is connected to the water-cooled grate assembly to form a closed circulation loop.

[0007] The downward suction gasifier main body can improve the gasification efficiency, ensure that the materials pass through the drying, pyrolysis, reduction and oxidation layers from top to bottom in sequence, and achieve staged reactions; the double-seal door design of the feeding system prevents air leakage while ensuring continuous feeding and maintains an anaerobic environment in the furnace; the multiple levels of welded grate plates reduce the damage of high temperature to the grate through the cooling water cavity and extend the service life; the closed-circuit circulation cooling system realizes efficient heat management; the supply of pure oxygen as the gasifying agent increases the reaction temperature, promotes tar cracking and improves the gas quality; the layered furnace chamber design clearly divides the drying, pyrolysis, reduction and oxidation layers, optimizes the reaction conditions and improves the gasification efficiency.

[0008] As an embodiment of the present invention, it further includes a slag treatment system. The slag treatment system includes an ash hopper and a water-sealed slag collector. The ash hopper is arranged below the water-cooled grate assembly, and the water-sealed slag collector is located at the lower part of the end of the reaction zone; the primary air duct is arranged below the ash hopper, and the pure oxygen injection direction of the primary air duct is opposite to the material movement direction.

[0009] The water-sealed slag collector prevents gas leakage and realizes wet slag discharge; the countercurrent injection of pure oxygen enhances the combustion intensity of the oxidation layer and improves the burnout rate of the slag.

[0010] As an embodiment of the present invention, the ash hopper is inclined, and the inclined plane angle is 45-60°; a screw slag discharger is arranged inside the water-sealed slag collector.

[0011] The hopper is inclined to optimize the gravity self-flow of ash and slag, facilitating ash and slag collection and reducing the risk of blockage. The screw slag discharger automatically discharges slag, reducing the need for manual intervention.

[0012] As an embodiment of the present invention, both the secondary air duct and the steam injection pipe Ⅰ are arranged at a position slightly above the throat of the furnace. The secondary air duct is provided with downwardly inclined secondary air nozzles, and the secondary air duct forms a swirling flow field above the throat of the furnace through the secondary air nozzles; a primary steam generator is connected to the steam injection pipe Ⅰ, and the primary steam generator generates low-pressure steam by absorbing the radiant heat in the furnace, and its steam outlet is directly connected to the reduction layer of the furnace.

[0013] Secondary air swirling flow field: above the throat + inclined nozzles, enhancing gas mixing and promoting secondary combustion of tar. Primary steam generator: recovering radiant heat, using the waste heat in the furnace to generate low-pressure steam, injecting it into the reduction layer to participate in the water gas reaction (CO + H2O → CO2 + H2), and increasing the hydrogen production.

[0014] As an embodiment of the present invention, it further includes a gas collection system, which has a gas outlet channel and a burner. The gas outlet channel is in an inverted L shape and is connected above the throat of the furnace, and the burner is arranged at the end of the gas outlet channel.

[0015] Inverted L-shaped gas outlet, preventing ash and slag from entering the pipeline, and at the same time extending the residence time in the high-temperature area (≥2 seconds) to promote tar cracking. The burner is used for emergency treatment of low calorific value gas or auxiliary combustion during the start-up stage.

[0016] As an embodiment of the present invention, the water vapor injection pipe II is arranged at the rear side of the furnace, and the nozzle of the water vapor injection pipe II is located at the junction of the reduction layer and the oxidation layer; a secondary steam generator is connected to the water vapor injection pipe II, and the secondary steam generator is arranged on the flue gas path of the gas outlet channel, generating medium-pressure steam by recovering the waste heat of the flue gas, and its steam outlet is directly connected to the pyrolysis layer of the furnace.

[0017] Secondary steam generator: recovering waste heat of flue gas, generating medium-pressure steam, injecting it into the pyrolysis layer to accelerate biomass decomposition, and realizing cascaded utilization of energy.

[0018] As an embodiment of the present invention, the water-cooled grate assembly includes: 8 levels of welded grate bars arranged horizontally. Each level of grate bar is formed with a cooling water cavity by welding an upper surface steel plate and a lower surface steel plate, and each level of grate bar is provided with a water pressure sensor and a temperature sensor; a serpentine flow channel is arranged in the cooling water cavity; Side wall grate bars, which are formed with a cavity by welding an inner surface steel plate and an outer surface steel plate.

[0019] 8-stage serpentine grate fins provide uniform cooling and prevent local overheating. Water pressure and temperature sensors monitor real-time operation to ensure safe operation. The side wall grate fins are hollow to protect the furnace structure and reduce heat loss.

[0020] As an embodiment of the present invention, the temperature of the drying layer is 100-200°C; the temperature of the pyrolysis layer is 200-500°C; the temperature of the oxidation layer is 700-1200°C; and the temperature of the reduction layer is 600-900°C.

[0021] This setting optimizes the reaction conditions, the high-temperature oxidation layer ensures tar cracking, and the low-temperature drying layer avoids energy waste.

[0022] A biomass gasification method for the water-cooled grate biomass gasifier described in the above scheme is also provided, comprising the following steps: pushing the biomass material into the furnace through a hydraulically driven feeding grate, controlling the molar ratio of oxygen to water vapor to be 1:0.3-0.5, maintaining the excess air coefficient in the oxidation layer to be 0.2-0.3, and ensuring that the fuel gas stays in the high temperature zone for ≥2 seconds to achieve tar cracking.

[0023] Set the oxygen / steam molar ratio to 1:0.3-0.5 to balance oxidation and reduction reactions and improve syngas quality. Set the excess air coefficient to 0.2-0.3, limiting the amount of oxygen to minimize nitrogen dilution and increase the calorific value of the gas. Stay in the high-temperature zone for ≥2 seconds to ensure sufficient tar cracking.

[0024] As an embodiment of the present invention, it also includes: The cooling water flow is adjusted by the circulating water pump (5) to control the surface temperature of the grate to be ≤100°C; The working pressure of the first-stage steam generator (16) is 0.3-0.5 MPa, and the working pressure of the second-stage steam generator (17) is 1.0-1.5 MPa, thereby realizing cascade utilization of steam; The tar content in the synthesis gas is ≤50mg / Nm³.

[0025] The grate surface temperature is ≤100℃ to prevent slagging and deformation; two-stage steam pressure division of labor, low-pressure steam is used for the reduction layer, and medium-pressure steam is used for the pyrolysis layer to maximize energy utilization.

[0026] Beneficial effects of the present invention: Compared with other gasifiers, it has the following advantages: (1) High reliability Grate structure: The mechanical structure is relatively simple, the design of the grate furnace is mature, the failure rate is low, maintenance is convenient, the operation is stable, it is suitable for long-term continuous work, and it is suitable for industrial applications.

[0027] (2) Long service life The water-cooled grate bars are adopted, and the grate bars are always in a low-temperature state during operation, overcoming the disadvantages of easy deformation and easy burning of the grate bars of other gasifiers.

[0028] (3) Low emissions Less pollutants are generated during the gasification process. Through a reasonable tail gas treatment system, emissions can be further reduced.

[0029] (4) Easy to control Flexible operation: Operating parameters (such as temperature, gasifying agent flow rate, etc.) are easy to adjust and can be optimized according to different fuels and gasification requirements; Real-time monitoring of parameters such as the pressure and temperature of the cooling water can infer the combustion situation and conduct control; High degree of automation: Equipped with an automated control system, it can achieve precise control and monitoring; The gasifier operates stably and can operate continuously for more than 24 hours. The gasifier has a high degree of automation, reducing the pressure on operating personnel.

[0030] (5) Good gasification effect It can make the fuel evenly distributed on the grate, be evenly heated, and have a high pyrolysis efficiency; By controlling the supply of the gasifying agent, efficient gasification reactions can be achieved to generate high-quality syngas; Optimize the energy efficiency of the gasification process to achieve a gasification efficiency of ≥70% in the gasification process, a residual ash content of ≤15%, adjust the process parameters of the gasification process to achieve a hydrogen content of ≥25% in the gasified gas, and after treatment, the tar content in the gasified gas is ≤50mg / Nm³. Description of the drawings

[0031] The present invention will be further described below in conjunction with the drawings and embodiments.

[0032] Figure 1 It is a schematic structural diagram of the water-cooled grate biomass gasifier of the present invention.

[0033] Figure 2 It is a schematic structural diagram of the grate bars in the water-cooled grate biomass gasifier of the present invention.

[0034] Figure 3 It is a schematic structural diagram of the side wall grate bars in the water-cooled grate biomass gasifier of the present invention.

[0035] Figure 4 It is a flowchart of the biomass gasification method using the water-cooled grate biomass gasifier of the present invention.

[0036] In the figure: 1. Feed sealing door; 2. Feeding chute; 3. Feeding sealing door; 4. Feeding grate; 5. Circulating water pump; 6. Radiator; 7. Water-cooled grate assembly; 8. Furnace; 9. Ash hopper; 10. Primary air duct; 11. Secondary air duct; 12. Slag collecting hopper; 13. Ignition burner; 14. Gas outlet channel; 15. Burner; 16. Primary steam generator; 17. Secondary steam generator; 18. Secondary air nozzle; 19. Anaerobic system pipeline. Detailed implementation mode

[0037] Now, the present invention will be further described in detail with reference to the accompanying drawings. These drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic way, so they only show the components related to the present invention.

[0038] Now, the professional terms and nouns used in this embodiment will be explained: Biomass gasifier: It refers to a device that uses organic biomass as fuel and adopts flameless gasification technology to quickly convert it into high-energy fuel gas (mainly methane). Water-cooled grate plate: A component unit used to form the grate, which is in direct contact with the burning fuel and has a water channel inside to cool the grate plate, which can greatly increase the service life of the grate plate. Feeding grate: A grate used to push biomass fuel into the furnace for combustion. Gasifying agent: The general term for gas media such as air, oxygen, enriched air, water vapor, etc. input when biomass raw materials are gasified in a gasifier. Gasification efficiency: The ratio of the heat released when a unit mass of biomass raw material is converted into a gas fuel and completely burned to the heat of the unit mass of biomass raw material.

[0039] The water-cooled grate biomass gasifier of this embodiment comprehensively considers various indicators such as biomass combustion amount, impurity content (especially tar), simple furnace body structure, good stability, continuous feeding, etc. After long-term experimental research and comparative analysis, a downdraft gasifier structure is selected. The working principle of the downdraft gasifier: Biomass raw materials are put into the furnace body from the feeding port at the top of the furnace, and air as the gasifying agent also enters the furnace through the air inlet. The materials in the furnace are divided into a drying layer, a pyrolysis layer, a reduction layer, and an oxidation layer from top to bottom. The downdraft gasifier has a relatively simple structure, good working stability, and can add materials by opening the cover at any time. When the tar in the gas passes through the lower high-temperature area, a part of it is decomposed into small molecule permanent gases (which do not condense into liquids when cooled), so the tar content in the combustible gas leaving the furnace is less.

[0040] Embodiment 1 As Figure 1As shown in the figure, the water-cooled grate biomass gasifier includes a gasifier body with a downward suction structure. Inside the gasifier body, there are a feeding system, a feeding grate, a water-cooled grate assembly 7, a furnace chamber 8, a gasifying agent supply system, a cooling circulation system, a slag handling system, and a gas collection system. Among them, the feeding system includes a feeding chute 2, a feeding sealing door 1 and a feeding sealing door 3 located at the upper and lower ends of the feeding chute 2 respectively. An anaerobic system pipeline 19 is provided on the feeding chute 2, and the feeding chute 2 is kept in a state of being filled with materials during operation. The feeding sealing door 1 and the feeding sealing door 3 are hydraulically driven and alternately opened and closed to achieve continuous feeding. Biomass materials enter the feeding chute 2 from the feeding sealing door 1. The feeding chute 2 is in a filled state and is almost isolated from the outside world.

[0041] The feeding grate 4 is located below the feeding sealing door 3. Biomass materials enter the furnace chamber 8 under the push of the oil cylinder of the feeding grate 4. The water-cooled grate assembly 7 is composed of multiple stages of welded water-cooled grate plates and has a cooling water cavity inside. Biomass materials will be spread flat on the water-cooled grate assembly 7 and move from top to bottom along the grate. As Figure 2 shown, the water-cooled grate assembly 7 includes 8 stages of horizontally arranged welded grate plates and side wall grate plates. Each stage of grate plate is formed by welding an upper surface steel plate and a lower surface steel plate to form a cooling water cavity. A serpentine flow channel is provided in the cooling water cavity, and each stage of grate plate is provided with a water pressure sensor and a temperature sensor, which can judge the combustion conditions in areas such as the combustion section and the burnout section according to the water temperature, and adjust the pushing speed and frequency of the oil cylinder according to the temperature difference between the inlet and outlet of the cooling water. Cooling water enters the cooling water cavity from the inlet flange to cool the grate plates and reduce the surface temperature. As Figure 3 shown, the side wall grate plate is formed by welding an inner surface steel plate and an outer surface steel plate to form a cavity. Cooling water enters the inner cavity from the inlet flange to cool the side wall grate plate and reduce the surface temperature.

[0042] The furnace chamber 8 is divided into a drying layer, a pyrolysis layer, a reduction layer, and an oxidation layer along the direction of material movement. The temperature of the drying layer is 100 - 200 °C, the temperature of the pyrolysis layer is 200 - 500 °C, the temperature of the oxidation layer is 700 - 1200 °C, and the temperature of the reduction layer is 600 - 900 °C.

[0043] The principle of the biomass gasifier is to convert solid biomass into combustible gas through thermochemical reactions. Its core processes include drying, pyrolysis, oxidation, and reduction. The following are the specific steps: a. Drying: After the biomass enters the gasifier, the moisture is first removed at a temperature of 100 - 200 °C.

[0044] b. Pyrolysis: The dried biomass undergoes pyrolysis at 200 - 500 °C, decomposing into volatile gases, tar, and solid carbon.

[0045] c. Oxidation: The pyrolysis products react with a gasifying agent (such as air, oxygen, or steam) at a high temperature of 700 - 1200 °C to undergo an oxidation reaction, releasing a large amount of heat to maintain the gasification process.

[0046] d. Reduction: The carbon dioxide and steam generated by oxidation react with solid carbon at a high temperature to undergo a reduction reaction, generating combustible gases such as carbon monoxide, hydrogen, and methane.

[0047] Main reactions: Oxidation reaction: C + O2 → CO2 + heat, Reduction reaction: C + CO2 → 2CO, Water gas reaction: C + H2O → CO + H2, The finally produced combustible gas (syngas) mainly contains carbon monoxide, hydrogen, methane, and a small amount of carbon dioxide and nitrogen. Under suitable operating conditions, the gasification gas composition can reach the level shown in the following table.

[0048] Gas composition H2 CO <![CDATA[CO2]]> <![CDATA[CH4]]> Proportion / % 30 40 25 5 The gasifying agents of the gasifier can be classified into the following categories: Air gasification: Using air as the gasifying agent, air contains approximately 79% nitrogen and 21% oxygen. This gasification method is simple and economical, but the gas calorific value is relatively low, mainly used for industrial raw materials or chemical raw materials.

[0049] Oxygen gasification: Using pure oxygen as the gasifying agent, without the dilution of nitrogen, the thermal efficiency is relatively high, and the gas calorific value is medium, suitable for the raw materials of fuel gas and chemical synthesis gas.

[0050] Steam gasification: Using steam as the gasifying agent, the generated gas contains a relatively high amount of hydrogen and alkanes, and the gas calorific value is medium, suitable for the raw materials of fuel gas and chemical synthesis gas.

[0051] Hydrogen gasification: Using hydrogen as the gasifying agent, the generated gas has a high calorific value, but the reaction conditions are harsh and it is not often used.

[0052] Composite gas gasification: Using two or more gasifying agents simultaneously or alternately, such as the combined use of oxygen and steam, can improve the gasification efficiency and gas quality, suitable for the raw materials of fuel gas and chemical synthesis gas.

[0053] Other gasifying agents: Also include oxygen-enriched air, carbon dioxide, methane, etc., and select a suitable gasifying agent according to specific requirements.

[0054] The present invention adopts a composite gas gasifying agent, using the combined use of oxygen and steam, and can flexibly adjust the gas composition and calorific value according to requirements.

[0055] The gasifying agent supply system includes a primary air duct 10 for introducing pure oxygen, a secondary air duct 11, a steam injection pipeline I, and a water vapor injection pipeline II. The secondary air duct 11 and the steam injection pipeline I are both arranged at a position slightly above the throat of the furnace chamber 8. The secondary air duct 11 is provided with a secondary air nozzle 18 arranged obliquely downward. The secondary air duct 11 forms a swirling flow field above the throat of the furnace chamber 8 through the secondary air nozzle 18. A primary steam generator 16 is connected to the steam injection pipeline I. The primary steam generator 16 generates low-pressure steam by absorbing the radiant heat in the furnace chamber 8, and its steam outlet is directly connected to the reduction layer of the furnace chamber 8. The water vapor injection pipeline II is arranged at the rear side of the furnace chamber 8, and the nozzle of the water vapor injection pipeline II is located at the junction of the reduction layer and the oxidation layer. A secondary steam generator 17 is connected to the water vapor injection pipeline II. The secondary steam generator 17 is arranged on the flue gas path of the gas outlet passage 14 and generates medium-pressure steam by recovering the waste heat of the flue gas. Its steam outlet is directly connected to the pyrolysis layer of the furnace chamber 8. The steam of the secondary steam generator 17 enters from the rear of the furnace chamber 8. The primary air in the primary air duct 10 mainly undergoes a combustion reaction with the carbon layer in the oxidation zone. The secondary air in the secondary air duct 11 and the steam from the primary steam generator 16 are supplemented at a position slightly above the throat of the furnace chamber 8. The secondary air is obliquely sprayed into the furnace chamber 8 through the secondary air nozzle 18, undergoes a secondary gasification reaction, simultaneously increases the temperature above, promotes the cracking of tar, and reduces the tar content in the gas.

[0056] An ignition burner 13 is arranged on the furnace chamber wall below the secondary steam generator 17. When the gasifier is initially operating, the temperature of the furnace chamber 8 has not reached the self-ignition condition of the biomass. The ignition burner 13 quickly raises the temperature of the furnace chamber 8 to the threshold required for stable gasification by burning auxiliary fuel. When processing high-moisture or low-calorific-value biomass (such as straw, sludge), the temperature of the oxidation layer may be insufficient, and the ignition burner 13 can supplement heat to prevent the interruption of the gasification reaction. During the startup stage, when the waste heat of the flue gas is insufficient, the ignition burner 13 can provide an initial heat source for the steam generator to accelerate the generation of medium-pressure steam and ensure the rapid operation of the steam cascade utilization system. When the ignition burner 13 is operating, it can cooperate with the pure oxygen injection of the primary air duct 10 to improve the combustion efficiency.

[0057] The ash and slag treatment system includes an ash hopper 9 and a water-sealed slag hopper 12. The ash hopper 9 is arranged below the water-cooled grate assembly 7, and the water-sealed slag hopper 12 is located at the lower part of the end of the reaction zone of the furnace chamber 8. The primary air duct 10 is arranged below the ash hopper 9, and the pure oxygen injection direction of the primary air duct 10 is opposite to the material movement direction. The ash hopper 9 is inclined, and its inclined surface angle is 45 - 60°. A screw slag extractor is arranged inside the water-sealed slag hopper 12. The ash and slag finally fall into the slag hopper 12 under the movement of the grate. The slag hopper 12 adopts a water-sealed design, which can not only isolate oxygen but also cool the ash and slag.

[0058] The cooling circulation system includes a circulation pipeline, a circulation water pump 5 and a radiator 6 installed on the circulation pipeline. The circulation pipeline is connected to the water-cooled grate assembly 7 to form a closed circulation loop. Cooling water is introduced into the water-cooled grate assembly 7 through the circulation pipeline, and the heat of the water-cooled grate assembly 7 is carried away by the cooling water.

[0059] The gas collection system has a gas outlet channel 14 and a burner 15. The gas outlet channel 14 is in an inverted L shape and is connected above the throat of the furnace chamber 8. The burner 15 is arranged at the end of the gas outlet channel 14, and the combustible gas goes out from the gas outlet channel 14 and is collected at the burner 15 for centralized treatment.

[0060] For the water-cooled grate biomass gasifier of this embodiment, pure oxygen combustion + stratified temperature control results in high calorific value of the syngas; secondary air swirl and high-temperature residence ensure that the tar content ≤ 50 mg / Nm³. Radiant heat and flue gas waste heat are used for steam generation, and the system thermal efficiency is increased by more than 30%. The water-cooled grate assembly 7 and sensors are monitored to avoid high-temperature deformation. Water seal slag collection and oxygen-free feeding ensure no leakage risk.

[0061] Embodiment Two The biomass gasification method of the water-cooled grate biomass gasifier of Embodiment One includes the following steps: The biomass material is pushed into the furnace chamber 8 through the hydraulically driven feeding grate 4, the molar ratio of oxygen to water vapor is controlled to be 1:0.3 - 0.5, the excess air coefficient is maintained at 0.2 - 0.3 in the oxidation layer, and the residence time of the gas in the high-temperature zone is ≥ 2 seconds to achieve tar cracking; The surface temperature of the grate bars is controlled ≤ 100 °C by adjusting the cooling water flow through the circulation water pump 5; the working pressure of the primary steam generator 16 is 0.3 - 0.5 MPa, and the working pressure of the secondary steam generator 17 is 1.0 - 1.5 MPa to achieve cascaded utilization of steam; the tar content in the syngas is ≤ 50 mg / Nm³.

[0062] For the biomass gasification method of this embodiment, the parameters are precisely controlled, and it can adapt to different biomass raw materials, such as: high-moisture straw or high-ash rice. Cascaded utilization of steam reduces the external energy demand, and the tar content meets the standard, which can be directly used in gas turbines or chemical synthesis.

[0063] Embodiment Three: The difference from Embodiment One is: A pretreatment module (such as crushing, drying) is added to adapt to agricultural and forestry waste with a moisture content > 30%. Based on the AI algorithm, the oxygen / steam ratio is dynamically adjusted to optimize the syngas composition, such as: increasing the H2 ratio to 35%, and the operation is fully automated to reduce manual intervention.

[0064] Embodiment Four: The difference from the first embodiment is that an amine absorption tower is connected after the gas outlet channel 14 to separate CO2 with a purity > 90%, achieving negative carbon emissions and a net reduction of 1.5 tons of CO2 per ton of biomass processed.

[0065] Inspired by the above ideal embodiments of the present invention, through the above description, relevant staff can make various changes and modifications completely within the scope not deviating from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A water-cooled grate biomass gasifier, characterized in that, An entrained-flow gasifier body including a downward-draft structure, and the following components are provided inside the entrained-flow gasifier body: A feeding system, including a feed chute (2), a feeding seal door (1) and a feeding seal door (3) respectively located at the upper end and the lower end of the feed chute (2). An anaerobic system pipeline (19) is provided on the feed chute (2), and the feed chute (2) maintains a state of being filled with materials during operation. The feeding seal door (1) and the feeding seal door (3) are hydraulically driven and alternately opened and closed to achieve continuous feeding; A feeding grate (4), located below the feeding seal door (3); A water-cooled grate assembly (7), composed of multiple levels of welded water-cooled grate plates, with a cooling water cavity provided inside; A furnace chamber (8), which is divided into a drying layer, a pyrolysis layer, a reduction layer and an oxidation layer along the material movement direction; An oxidant supply system, including a primary air duct (10) for introducing pure oxygen, a secondary air duct (11), a steam injection pipeline I and a water-vapor injection pipeline II; A cooling circulation system, including a circulation pipeline, a circulation water pump (5) and a radiator (6) installed on the circulation pipeline. The circulation pipeline is connected to the water-cooled grate assembly (7) to form a closed circulation loop; 2. The water-cooled grate biomass gasifier according to claim 1, characterized in that: It further includes a slag treatment system, which includes a slag hopper (9) and a water-sealed slag collecting hopper (12). The slag hopper (9) is arranged below the water-cooled grate assembly (7), and the water-sealed slag collecting hopper (12) is located at the lower part of the end of the reaction zone (8); the primary air duct (10) is arranged below the slag hopper (9), and the pure oxygen injection direction of the primary air duct (10) is opposite to the material movement direction.

3. The water-cooled grate biomass gasifier according to claim 2, characterized in that: The slag hopper (9) is inclined, and its inclined surface angle is 45 - 60°; a screw slag discharger is provided inside the water-sealed slag collecting hopper (12).

4. The water-cooled grate biomass gasifier according to claim 1, wherein: The secondary air duct (11) and the steam injection pipeline I are both arranged at a position slightly above the throat of the furnace chamber (8). An inclined downward secondary air nozzle (18) is provided on the secondary air duct (11), and the secondary air duct (11) forms a swirling flow field above the throat of the furnace chamber (8) through the secondary air nozzle (18); a primary steam generator (16) is connected to the steam injection pipeline I, and the primary steam generator (16) generates low-pressure steam by absorbing the radiant heat in the furnace chamber (8), and its steam outlet is directly connected to the reduction layer of the furnace chamber (8).

5. The water-cooled grate biomass gasifier according to claim 1, characterized in that: It further includes a gas collection system, which has a gas outlet channel (14) and a burner (15). The gas outlet channel (14) is in an inverted L shape, and it is connected above the throat of the furnace chamber (8), and the burner (15) is arranged at the end of the gas outlet channel (14).

6. The water-cooled grate biomass gasifier according to claim 5, wherein: The water-vapor injection pipeline II is arranged at the rear side of the furnace chamber (8), and the nozzle of the water-vapor injection pipeline II is located at the junction of the reduction layer and the oxidation layer; a secondary steam generator (17) is connected to the water-vapor injection pipeline II, and the secondary steam generator (17) is arranged on the flue gas path of the gas outlet channel (14) and generates medium-pressure steam by recovering the waste heat of the flue gas, and its steam outlet is directly connected to the pyrolysis layer of the furnace chamber (8).

7. The water-cooled grate biomass gasifier according to claim 1, wherein: The water-cooled grate assembly (7) includes: The horizontally arranged 8-stage welded grate bars, each stage of grate bars is formed by welding an upper surface steel plate and a lower surface steel plate to form a cooling water cavity, and each stage of grate bars is provided with a water pressure sensor and a temperature sensor; a serpentine flow channel is arranged in the cooling water cavity; The side wall grate bars are formed by welding an inner surface steel plate and an outer surface steel plate to form a cavity.

8. The water-cooled grate biomass gasifier according to claim 1, characterized in that: The temperature of the drying layer is 100-200 °C; the temperature of the pyrolysis layer is 200-500 °C; the temperature of the oxidation layer is 700-1200 °C; the temperature of the reduction layer is 600-900 °C.

9. A biomass gasification method for the water-cooled grate biomass gasifier according to any one of claims 1 to 8, characterized in that, It includes the following steps: pushing biomass materials into the furnace (8) through the hydraulically driven feeding grate (4), controlling the molar ratio of oxygen to steam to be 1:0.3-0.5, maintaining the excess air coefficient at 0.2-0.3 in the oxidation layer, and making the residence time of the gas in the high-temperature zone ≥ 2 seconds to achieve tar cracking.

10. The biomass gasification method of the water-cooled grate biomass gasifier according to claim 9, characterized in that, It also includes: Adjusting the cooling water flow through the circulating water pump (5) to control the surface temperature of the grate bars ≤ 100 °C; The working pressure of the primary steam generator (16) is 0.3-0.5 MPa, and the working pressure of the secondary steam generator (17) is 1.0-1.5 MPa to achieve cascaded utilization of steam; The tar content in the syngas ≤ 50 mg / Nm³.

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