Biomass gasification system based on double furnace linkage and intermediate product internal digestion

Abstract

The application discloses a biomass gasification system based on double-furnace linkage and intermediate product internal digestion, which comprises a downdraft gasifier, a water gas gasifier and an adiabatic combustor. The downdraft gasifier can direct the gasification of biomass, generate combustible gas and charcoal, and avoid the loss of carbon source due to early oxidation. The charcoal enters the water gas gasifier, the combustible gas containing tar enters the adiabatic combustor, mixes with oxygen-rich air and burns to generate high-temperature flue gas and water vapor. The high-temperature flue gas and water vapor enter the water gas gasifier, the high-temperature flue gas can provide heat energy for the water gas reaction in the water gas gasifier, and the water vapor can also react with the charcoal from the downdraft gasifier as a gasification agent. Finally, the water gas gasifier generates clean synthesis gas which does not contain tar and is rich in H2 and CO. The whole system does not need additional tar treatment, improves the gasification efficiency and the proportion of target gas, breaks through the limitation of traditional furnace type, and can meet the demand of high-value-added chemical synthesis for high-quality raw material gas.

Description

Technical Field

[0001] This application relates to the field of biomass feedstock gasification technology, and in particular to a biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products. Background Technology

[0002] Biomass gasification is an important biomass energy utilization technology. It refers to the process in which biomass reacts with a certain amount of gasifying agent (such as air, oxygen or water vapor) at a relatively high reaction temperature to be converted into combustible gases rich in CO, H2, CH4 and other gases.

[0003] Currently, the most widely used and mature type of gasifier is the upward suction gasifier. This type of gasifier has the advantages of low residual carbon in ash and slag, high gasification efficiency, and stable and reliable operation. However, the gas it produces has problems such as low calorific value and low percentage content of target gases (hydrogen and carbon monoxide), making it difficult to obtain hydrogen with industrial separation value. More importantly, the gas produced has a high tar content, which brings great difficulty and cost to subsequent purification and tar utilization.

[0004] Although downdraft gasifiers can reduce the tar content in fuel gas to some extent, their gasification efficiency is generally low, and the percentage content of hydrogen and carbon monoxide in the obtained target gas is still not ideal, which limits their application in the field of high value-added chemical synthesis.

[0005] In summary, all types of biomass gasifiers—updraft, downdraft, and fluidized bed—share a common technical bottleneck: during gasification, a portion of the already limited (approximately 16%) fixed carbon in the biomass feedstock must be consumed, with the heat generated through an exothermic oxidation reaction to provide the necessary heat for the entire gasification process. This directly leads to the loss of carbon source and inevitably produces a large amount of inert carbon dioxide gas with negative value. Simultaneously, the complex composition of the dry distillation gas is directly mixed into the main combustion gas, resulting in a complex final gaseous product composition that is difficult to separate. This typically limits its use as a low-grade crude fuel in applications with less stringent combustion requirements, severely restricting the efficient and high-value utilization and promotion of biomass energy.

[0006] With industrial upgrading, the utilization of biomass energy is exploring development towards the production of high-value-added chemicals such as hydrogen, methanol, methane, and acetic acid. All of this relies on the efficient acquisition of basic feedstock gases—hydrogen and carbon monoxide. Therefore, developing a novel biomass gasification reactor capable of producing tar-free biomass with high percentages of hydrogen and carbon monoxide is crucial for achieving the clean and efficient utilization of biomass energy on a large scale. Summary of the Invention

[0007] The purpose of this application is to overcome the shortcomings of the existing technology and provide a biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products.

[0008] This application provides a biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products, comprising: a downdraft gasifier for gasifying biomass fuel to produce combustible gas and charcoal; a water gas gasifier for receiving charcoal from the downdraft gasifier; and an adiabatic burner for receiving combustible gas from the downdraft gasifier. By mixing the combustible gas with oxygen-enriched air, combustion produces high-temperature flue gas and water vapor. During operation, the high-temperature flue gas and water vapor generated by the adiabatic burner are transported to the water gas gasifier. The high-temperature flue gas provides reaction heat energy so that the water vapor reacts with the charcoal to produce clean syngas that is free of tar and rich in hydrogen and carbon monoxide.

[0009] Furthermore, the downdraft gasifier is connected to the silo via a feed pipe. Valves 1 and 2 are spaced apart on the feed pipe, with an intermediate buffer section between them. During feeding, valves 1 and 2 open and close at different times to transport the biomass fuel in the atmospheric pressure silo to the pressurized downdraft gasifier. And / or, the downdraft gasifier is connected to the water gasifier via a charcoal conveying pipe. Gate valves 1 and 2 are spaced apart on the charcoal conveying pipe. During operation, gate valves 1 and 2 open and close at different times to allow charcoal to intermittently enter the water gasifier. And / or, the bottom of the downdraft gasifier is equipped with a rotatable upper grate, and there is a gap between the outer edge of the upper grate and the inner wall of the downdraft gasifier. During operation, the upper grate rotates so that charcoal can be transported downstream through the gap; and / or, the gas outlet of the downdraft gasifier is connected to an external vent through a pipe. During the start-up stage, the gas composition generated by the downdraft gasifier is unstable and is discharged through the vent. After the downdraft gasifier stabilizes, the valve connected to the vent is closed and the valve connected to the insulated burner is opened so that combustible gas can enter the insulated burner.

[0010] Furthermore, the downdraft gasifier is equipped with a central air inlet pipe, which runs through the material pile and horizontally through the downdraft gasifier. The central air inlet pipe is connected to an external gas supply pipe. The central air inlet pipe has a downward-facing, trumpet-shaped diffuser in the middle of its section within the downdraft gasifier. Due to the umbrella effect, an olive-shaped cavity can be formed below the diffuser to improve the uniformity of air distribution. And / or, a triangular guide cone is provided above the central air inlet pipe to guide the biomass fuel to disperse and fall in all directions, thereby preventing the biomass fuel from forming a pile-up and bridging on the central air inlet pipe. And / or, cooling water channels are provided inside the central air inlet pipe and / or the guide cone to protect the metal components and ensure their long-term structural safety through the circulation of cooling water.

[0011] Furthermore, the downdraft gasifier is equipped with a central air inlet pipe and an outlet jacket on its side, located below the central air inlet pipe, with the inlet of the outlet jacket facing the bottom of the downdraft gasifier. The outlet of the downdraft gasifier is located on its side and connected to the outlet jacket, with the outlet position higher than the inlet of the outlet jacket. During operation, oxygen-enriched air flows into the downdraft gasifier through the central air inlet pipe, penetrates and acts on the material pile, and after completing the reaction with the material pile, the generated combustible gas diffuses to the edge, enters the outlet jacket, and is finally discharged from the higher outlet.

[0012] Furthermore, a water jacket is installed outside the section of the carbon conveying pipe near the water gasifier. The inlet end of the water jacket is connected to an external soft water supply device. During operation, the soft water flowing through the water jacket can cool the carbon conveying pipe. And / or, the biomass gasification system also includes a steam-water separator. A water jacket is installed outside the section of the carbon conveying pipe near the water gasifier. The outlet end of the water jacket is connected to the steam-water separator. The softened water after heat exchange can replenish the steam-water separator. The steam-water separator can supply steam to the water gasifier. And / or, the biomass gasification system also includes a steam-water separator. An auxiliary steam inlet is installed on the section of the carbon conveying pipe near the water gasifier. The auxiliary steam inlet is connected to the steam outlet of the steam-water separator. Part of the steam output from the steam-water separator enters the auxiliary steam inlet. The temperature of the steam is lower than that of the high-temperature flue gas, which can block the high-temperature radiation and upward flow of hot air inside the water gasifier.

[0013] Furthermore, the adiabatic burner is equipped with an ignition device. During the start-up phase, the ignition device is connected to liquefied petroleum gas as fuel. After the biomass gas is ignited and the flame detection signal is received by the control system, the ignition device is shut off, and the combustible gas produced by the downdraft gasifier becomes the main flare fuel of the adiabatic burner. And / or, the adiabatic burner is equipped with an online oxygen analyzer. The online oxygen analyzer monitors the oxygen concentration in the adiabatic burner in real time and adjusts the amount of oxygen-enriched air entering the adiabatic burner according to the heat energy demand of the water gas reaction in the water gas gasifier, so that the heat generation in the adiabatic burner matches the heat consumption of the water gas gasifier.

[0014] Furthermore, the top of the water gas gasifier is equipped with a charcoal inlet, which is connected to the downdraft gasifier via a charcoal conveying pipe; and / or, a water seal is provided on one side of the water gas gasifier, which serves as a safety explosion relief vent. When the pressure inside the water gas gasifier exceeds a preset value, the water seal automatically opens to release pressure, ensuring the safe operation of the water gas gasifier; and / or, a level gauge is provided on one side of the water gas gasifier, which is used to detect the material level inside the water gas gasifier; and / or, the bottom of the water gas gasifier is equipped with a rotatable lower grate, with a gap between the outer edge of the lower grate and the inner wall of the water gas gasifier. During operation, the lower grate rotates to allow ash and slag to be discharged through the gap; and / or, the bottom of the water gas gasifier is equipped with an ash discharge pipe, on which ash lock one and ash lock two are spaced apart. During ash discharge, ash lock one and ash lock two open and close at different times to transport the ash and slag inside the pressurized water gas gasifier to the outside of the furnace at atmospheric pressure.

[0015] Furthermore, the downdraft gasifier is equipped with three layers of temperature measuring points: the upper layer corresponds to the preheating and dry distillation zone, the middle layer corresponds to the carbonization reaction zone, and the lower layer corresponds to the oxygen-deficient cooling zone of the carbon layer. When the upper layer temperature measuring point detects that the temperature of the preheating and dry distillation zone is close to or exceeds the temperature of the carbonization reaction zone, the upper grate is accelerated to increase the carbon output. When the lower layer temperature measuring point detects that the temperature of the oxygen-deficient cooling zone of the carbon layer is close to or exceeds the temperature of the carbonization reaction zone, the upper grate is decelerated to reduce the carbon output.

[0016] Furthermore, the water gas gasifier is equipped with a level gauge and a lower grate, and the level gauge and the lower grate are linked for control. When the level gauge detects that the material level in the water gas gasifier is higher than the preset value, the lower grate is accelerated to rotate. When the level gauge detects that the material level in the water gas gasifier is lower than the preset value, the lower grate is decelerated to rotate.

[0017] Furthermore, the water gasifier is equipped with a central gas outlet pipe, which runs through the material pile and horizontally through the water gasifier. The central gas outlet pipe has a downward-facing, funnel-shaped syngas inlet in the middle of its section within the gasifier. A horizontal cavity is formed below the syngas inlet to counteract gas flow deviation caused by unevenness in the conical material layer, thereby improving the uniformity of gas collection. And / or, a triangular guide cone is provided above the central gas outlet pipe to guide the charcoal to disperse and fall in all directions, thus preventing charcoal from forming bridging on the central gas outlet pipe. And / or, cooling water channels are provided inside the central gas outlet pipe and / or the guide cone to protect metal components and ensure their long-term structural safety through the flow of cooling water.

[0018] Furthermore, the biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products also includes: a cyclone dust collector connected to the exhaust port of the water gasification furnace, used to separate solid particles in the syngas; a heat exchanger connected to the exhaust port of the cyclone dust collector, used to recover the heat energy carried by the syngas; and a steam-water separator connected to the heat exchanger. The heat exchanger and the steam-water separator form a circulation loop. The heat exchanger recovers the heat energy in the syngas and transfers it to the soft water. The heated soft water enters the steam-water separator, and the separated water vapor can be returned to the water gasification furnace and participate in the water gas reaction.

[0019] This application provides a biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products, including a downdraft gasifier, a water gasifier, and an adiabatic burner. The downdraft gasifier can directionally gasify biomass to generate combustible gas and charcoal, avoiding premature oxidation and loss of carbon sources. The charcoal enters the water gasifier, while the tar-containing combustible gas enters the adiabatic burner and mixes with oxygen-enriched air for combustion. This effectively cracks the tar, solving the problem of difficult tar treatment, and generates high-temperature flue gas and water vapor. The high-temperature flue gas and water vapor enter the water gasifier. The high-temperature flue gas provides heat energy for the water gas reaction in the water gasifier, while the water vapor acts as a gasifying agent to react with the charcoal from the downdraft gasifier. Finally, the water gasifier generates clean syngas that is free of tar and rich in H2 and CO. The entire system eliminates the need for additional tar treatment, improves gasification efficiency and the proportion of target gases, breaks through the limitations of traditional furnace types, and can meet the demand for high-quality feedstock gas in high-value-added chemical synthesis. Attached Figure Description

[0020] Figure 1 A schematic diagram of a biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products provided in this application;

[0021] Figure 2 for Figure 1 The diagram shows the structure of the downdraft gasifier in a biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products.

[0022] Figure 3 A schematic diagram of the gas inlet and outlet of a downdraft gasifier provided in this application;

[0023] Figure 4 for Figure 1 The diagram shows the structure of the water gasification furnace in a biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products. Detailed Implementation

[0024] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0025] This application provides a biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products, comprising: a downdraft gasifier 1 for gasifying biomass fuel to produce combustible gas and charcoal; a water gas gasifier 2 for receiving charcoal from the downdraft gasifier 1; and an adiabatic burner 3 for receiving combustible gas from the downdraft gasifier 1. By mixing the combustible gas with oxygen-enriched air, high-temperature flue gas and water vapor are generated after combustion. During operation, the high-temperature flue gas and water vapor generated by the adiabatic burner 3 are transported to the water gas gasifier 2. The high-temperature flue gas is used to provide reaction heat energy so that the water vapor reacts with the charcoal to produce clean syngas that is free of tar and rich in hydrogen and carbon monoxide.

[0026] The downdraft gasifier 1, the water gasifier 2, and the adiabatic burner 3 are the core linkage units of the gasification system. The three form a closed loop of "material-energy-reaction" through dedicated pipelines and valve groups.

[0027] For details, please refer to Figure 1 In the illustrated embodiment, the downdraft gasifier 1 is equipped with an air inlet (central air inlet pipe 11). A blower delivers oxygen-enriched air into the furnace to react with biomass fuel, producing charcoal and combustible gas. The downdraft gasifier 1 and the water gasifier 2 are connected by a charcoal conveying pipe 34 to transport solid materials (charcoal). The downdraft gasifier 1 and the adiabatic burner 3 are connected by a gas delivery pipe to transport gaseous materials (combustible gas containing tar). The adiabatic burner 3 and the water gasifier 2 are connected by a high-temperature flue gas pipe to transport the energy-carrying gasifying agent (high-temperature flue gas and steam), providing heat and gasifying agent for the water gas reaction.

[0028] It should be explained that the downdraft gasifier 1 is used for the directional carbonization of biomass fuel to generate intermediate products required for subsequent processes, rather than directly producing clean gas.

[0029] Specifically, biomass fuel (such as sawdust, straw briquettes, etc.) undergoes preheating and dry distillation (corresponding to the upper temperature measurement point area), carbonization reaction (corresponding to the middle temperature measurement point area, temperature ≤700℃), and charcoal layer cooling (corresponding to the lower temperature measurement point area) in the downdraft gasifier 1. After these processes, moisture and volatiles are removed, forming a solid material (charcoal) mainly composed of fixed carbon. This provides a high-purity carbon source for the water gas reaction in the water gasifier 2. At the same time, the volatiles released during the carbonization process (including H2, CO, CH4, heavy tar, etc.) form crude combustion gas. This gas carries tar and chemical energy and can be used as fuel for the adiabatic burner 3. Under high temperature conditions, the tar is completely decomposed, providing thermal energy for subsequent water gas production.

[0030] The adiabatic burner 3 is used to process the tar-containing combustible gas produced by the downdraft gasifier 1, and at the same time convert its chemical energy into the heat energy and gasifying agent required by the water gasifier 2, so as to realize the resource utilization of pollutants (tar).

[0031] Specifically, tar-containing crude combustion gas is mixed and burned with oxygen-enriched air in the adiabatic burner 3. The tar (complex hydrocarbons) is completely decomposed and participates in combustion, ultimately being converted into CO2 and H2O (water vapor). Through the adiabatic burner 3, tar pollution is completely eliminated, while the hydrogen in the tar is converted into the gasifying agent (water vapor) required for subsequent reactions. At the same time, the heat energy released by combustion can raise the product temperature to 900-1200℃, forming high-temperature flue gas containing N2 (from oxygen-enriched air), CO2 (combustion products), and a large amount of water vapor (generated by the combustion of H2 and hydrocarbons). This flue gas is the heat energy carrier for the water gas reaction in the water gas gasifier 2, ensuring the continuous endothermic reaction.

[0032] Due to the influence of high-temperature flue gas, the temperature inside the water gas gasifier 2 can reach 700-900℃. Under this environment, the water gas gasifier 2 can utilize the charcoal produced by the downdraft gasifier 1 and the energy-carrying gasifying agent produced by the adiabatic burner 3 to carry out a highly efficient water gas reaction (C+H2O→CO+H2), converting the fixed carbon prepared by the downdraft gasifier 1 into a high-value-added target gas. Since the tar has been treated in the adiabatic burner 3, clean syngas with no tar and high H2 and CO content is finally generated.

[0033] In summary, the downdraft gasifier 1, the water-gas gasifier 2, and the adiabatic burner 3 achieve a continuous process of "carbonization → digestion → conversion" through a closed-loop linkage of "material flow - energy flow - signal flow". Specifically, the coordinated material flow (charcoal link transmission and tar-containing crude gas link transmission) ensures the directional transfer of intermediate products with no waste and no external discharge; the coordinated energy flow (the chemical energy of biomass fuel is converted into the raw materials and heat required for the water-gas reaction through gasification and combustion) enables the cascade utilization of chemical energy without additional energy consumption.

[0034] By linking the downdraft gasifier 1, the water gas gasifier 2, and the adiabatic burner 3, the problem of tar requiring additional treatment in traditional gasifiers is avoided. The tar is converted into a gasifying agent through combustion, realizing the resource utilization of pollutants. The energy utilization rate of the system is also improved, so that the combustible gas containing tar is no longer discharged into the air, but is used as fuel. The heat energy of combustion can also be used as the heat energy required for the water gas reaction, realizing zero energy waste. Finally, the water gas gasifier 2 directly produces clean syngas with no tar and high H2 and CO content, which can be directly used in methanol synthesis, high-end power generation and other scenarios, avoiding the limitation of traditional crude gas being used only for low-grade combustion.

[0035] The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products provided in this application uses a downdraft gasifier 1 to directionally gasify biomass, generating combustible gas and charcoal, thus avoiding premature oxidation and loss of carbon sources. Adiabatic burner 3 receives tar-containing combustible gas and mixes it with oxygen-enriched air for combustion, effectively cracking tar and solving the problem of difficult tar treatment, while also generating high-temperature flue gas and water vapor. The high-temperature flue gas provides heat energy for the water gas reaction in the water gas gasifier 2, and the water vapor acts as a gasifying agent to react with the charcoal from the downdraft gasifier 1. Finally, the water gas gasifier 2 generates clean syngas that is free of tar and rich in H2 and CO. The entire system eliminates the need for additional tar treatment, improves gasification efficiency and the proportion of target gases, breaks through the limitations of traditional furnace types, and can meet the demand for high-quality feedstock gas in high-value-added chemical synthesis.

[0036] Optionally, the downdraft gasifier 1 is connected to the silo via a feed pipe 31. Valves 32 and 33 are spaced apart on the feed pipe 31. There is an intermediate buffer section between valves 32 and 33. When feeding, valves 32 and 33 open and close at different times so as to transport the biomass fuel in the atmospheric pressure silo to the pressurized downdraft gasifier 1.

[0037] For details, please refer to Figure 1 and Figure 2 In the illustrated embodiment, the top of the downdraft gasifier 1 is equipped with a feed pipe 31, which extends vertically and connects to the normal pressure silo. Valves 32 and 33 are vertically spaced, with valve 32 located near the silo and valve 33 located near the downdraft gasifier 1. The pipe section between them serves as an intermediate buffer section. During feeding, valve 32 is opened first, and valve 33 is closed, allowing the biomass fuel in the normal pressure silo to fall into the intermediate buffer section under gravity. Once the fuel in the buffer section reaches a certain amount, or the silo outputs a preset amount of fuel, valve 32 is closed and valve 33 is opened, allowing the fuel in the buffer section to enter the downdraft gasifier 1.

[0038] This design effectively isolates the pressure connection between the atmospheric pressure silo and the pressurized gasifier, preventing pressure changes in the downdraft gasifier 1 from affecting the gasification reaction. At the same time, it ensures that biomass fuel can be stably and on demand transported from the atmospheric pressure environment to the pressurized furnace, meeting the fuel supply requirements of the gasification operation. Furthermore, it eliminates the need for additional complex pressurization and feeding equipment, simplifying the feeding structure and reducing equipment costs and operating energy consumption.

[0039] Optionally, the downdraft gasifier 1 is connected to the water gasifier 2 via a charcoal conveying pipe 34. A first gate valve 35 and a second gate valve 36 are spaced apart on the charcoal conveying pipe 34. During operation, the first gate valve 35 and the second gate valve 36 open and close at different times so that charcoal enters the water gasifier 2 intermittently.

[0040] For details, please refer to Figure 1 and Figure 2 In the illustrated embodiment, the bottom of the downdraft gasifier 1 is equipped with a charcoal conveying pipe 34, which extends vertically and connects to the water gasifier 2. A first gate valve 35 and a second gate valve 36 are vertically spaced, with the first gate valve 35 located closer to the downdraft gasifier 1 and the second gate valve 36 located closer to the water gasifier 2, forming a charcoal buffer section for temporary storage of charcoal. During operation, the first gate valve 35 is opened and the second gate valve 36 is closed, allowing the charcoal generated in the downdraft gasifier 1 to fall into the charcoal buffer section under gravity. After a certain amount of charcoal has been temporarily stored, or after a preset storage time, or after the system sends a downstream feeding signal, the first gate valve 35 is closed and the second gate valve 36 is opened, allowing the temporarily stored charcoal to enter the water gasifier 2.

[0041] This design effectively isolates the pressure connection between the downdraft gasifier 1 and the water gasifier 2, preventing interference between the different pressure environments in the two furnaces, which could lead to gas mixing or pressure leakage. At the same time, by intermittently feeding charcoal, the height of the charcoal bed in the water gasifier 2 is kept stable, providing a stable and uniform carbon source for the water gas reaction and ensuring efficient reaction. Furthermore, it eliminates the need for additional complex pressure balancing or intermittent feeding equipment, simplifying the charcoal conveying structure and reducing the operating and maintenance costs of the equipment.

[0042] Optionally, the bottom of the downdraft gasifier 1 is provided with a rotatable upper grate 37. There is a gap between the outer edge of the upper grate 37 and the inner wall of the downdraft gasifier 1. During operation, the upper grate 37 rotates so that charcoal can be conveyed downstream through the gap.

[0043] The grate refers to the rotatable load-bearing component installed at the bottom of the furnace. Its shape is adapted to the bottom structure of the downdraft gasifier 1. It is used to carry the biomass fuel and the charcoal produced after carbonization in the furnace, and at the same time, it realizes the transportation of charcoal through its own rotation.

[0044] In use, the upper grate 37 rotates continuously or intermittently under the action of the drive device (such as a motor). Since there is a gap between the outer edge of the upper grate 37 and the inner wall of the downward suction gasifier 1, the charcoal carried on the grate will move towards the edge of the grate under the action of centrifugal force and gravity during the rotation process, and finally fall into the charcoal conveying pipe 34 through the gap, thus completing the pre-transfer of charcoal from the downward suction gasifier 1 to the water gasifier 2.

[0045] The rotatable upper grate 37 enables orderly and stable charcoal conveying, which not only prevents charcoal from accumulating and clogging at the bottom of the furnace, but also allows for indirect adjustment of the charcoal output rate by utilizing the controllability of the grate's rotation to meet the charcoal demand of the subsequent water-gas reaction. This ensures the smooth material conveying of the entire system and eliminates the need for additional complex active charcoal feeding mechanisms, simplifying the material conveying structure inside the furnace and reducing the risk of equipment failure and maintenance costs.

[0046] Optionally, the gas outlet of the downdraft gasifier 1 is connected to the external vent 4 through a pipeline. During the start-up stage, the gas composition generated by the downdraft gasifier 1 is unstable and is discharged through the vent 4. After the downdraft gasifier 1 is working stably, the valve connected to the vent 4 is closed and the valve connected to the insulated burner 3 is opened so that the combustible gas can enter the insulated burner 3.

[0047] For details, please refer to Figure 1 In the illustrated embodiment, the gas outlet of the downdraft gasifier 1 is connected to two pipelines: one connecting to the insulated burner 3 and the other connecting to the vent 4. Both pipelines are equipped with valves to control the gas flow. The vent 4 is an exhaust port. During the system start-up phase, because the biomass fuel in the downdraft gasifier 1 has just begun gasification and the reaction is not yet stable, the resulting combustible gas composition is complex and unstable. The valve connecting to the vent 4 is opened (the valve connecting to the insulated burner 3 is closed), allowing these unstable gases to be directly discharged through the vent 4. Once the gasification reaction in the downdraft gasifier 1 has stabilized and the composition of the produced combustible gas meets the requirements of subsequent processes, the valve connecting to the vent 4 is closed, and the valve connecting to the insulated burner 3 is opened simultaneously, allowing the stable combustible gas to flow to the insulated burner 3 and participate in the subsequent combustion reaction.

[0048] By timely venting the unstable gases during the start-up stage through the vent 4, it is possible to prevent these substandard gases from entering the insulated burner 3 and affecting the combustion effect. This helps ensure that the insulated burner 3 can work normally when receiving stable combustible gases in the future. It also provides a guarantee for the reasonable transportation and utilization of combustible gases after the downdraft gasifier 1 is running stably, ensuring the stability and safety of the subsequent process links of the entire system.

[0049] Optionally, the downdraft gasifier 1 is provided with a central air inlet pipe 11, which passes through the material pile and runs horizontally through the downdraft gasifier 1. The central air inlet pipe 11 is connected to an external gas supply pipe.

[0050] For details, please refer to Figure 1 and Figure 2 In the illustrated embodiment, the central air inlet pipe 11 is a tubular structure that extends horizontally in the left-right direction and penetrates the furnace body of the downdraft gasifier 1. The entire pipe is installed in the biomass fuel pile inside the furnace, and the two ends that are installed outside are connected to the blower and the oxygen supply equipment, respectively, forming two air inlets. It can simultaneously receive oxygen-enriched air delivered from the blower and the oxygen supply equipment. At the same time, the part of the pipe body that is in the material pile inside the furnace is provided with an air outlet (i.e., the diffuser in the following text).

[0051] With the help of two air inlets on the pipe body, oxygen-enriched air can be stably input into the central air inlet pipe 11 from two positions, and then the oxygen-enriched air is evenly blown in through the air outlet in the material pile in the furnace, providing sufficient and evenly distributed oxygen-enriched air for the gasification reaction of biomass fuel in the downdraft gasifier 1, thereby ensuring that the gasification reaction is efficient and stable, and thus ensuring the continuous generation of combustible gas and charcoal.

[0052] Optionally, the central air inlet pipe 11 is provided with a downward-facing, funnel-shaped diffuser in the middle of the pipe section inside the downward-suction gasifier 1. Due to the umbrella effect, an olive-shaped cavity can be formed below the diffuser to improve the uniformity of air distribution.

[0053] For details, please refer to Figure 2 In the illustrated embodiment, the diffuser is located in the middle of the central air inlet pipe 11 within the downward-suction gasifier 1, and has a downward-flaring opening structure with the flared opening facing the bottom of the furnace. The opening becomes larger as it goes downward, so as to provide a channel for the output and diffusion of oxygen-enriched air.

[0054] It needs to be explained that the umbrella effect refers to the phenomenon that when the air output by the blower is mixed with oxygen to form oxygen-rich air, it is delivered to the diffuser through the central air intake pipe 11. The airflow is guided by the umbrella-shaped structure of the flared mouth and diffuses evenly in all directions from the central axis position, similar to the dispersion effect of an umbrella on liquids or gases when it is unfolded.

[0055] It also needs to be explained that the reason why olive-shaped cavities can be formed is that as the material moves downward in the bed, it is compressed and closes into the space below the flared opening. At the same time, the radially diffused oxygen-rich air will have a uniform impact and airflow support on the material pile below, so that the material pile below the diffuser is pushed away evenly by the airflow. Meanwhile, the pressure field formed by the airflow during the diffusion process is balanced with the weight and permeability of the material pile itself, and finally an olive-shaped cavity with a thicker middle and slightly thinner top and bottom ends is formed below the diffuser.

[0056] The formation of an olive-shaped cavity serves two purposes. First, from a hydrodynamic perspective, it ensures that the distance between the diffuser and any point at the lower dry distillation gas outlet is relatively consistent, avoiding the "flow deviation" or "fire layer tilting" problems that easily occur with traditional sidewall air distribution or simple downdraft pipes, thus significantly improving the uniformity of air distribution. Second, uniform air distribution maximizes the contact area between oxygen and biomass charcoal, forming a figure-eight-shaped high-temperature carbonization reaction zone around the cavity and extending to the gas outlet. This stable high-temperature zone is an important prerequisite for the efficient gasification and pyrolysis of tar in the downdraft gasifier 1, and provides a guarantee for the subsequent generation of stable combustible gases and charcoal.

[0057] Optionally, a triangular guide cone is provided above the central air intake pipe 11. The guide cone is used to guide the biomass fuel to disperse and fall in all directions, thereby avoiding the formation of a bridging of biomass fuel on the central air intake pipe 11.

[0058] The guide cone is a triangular structural component (which can be a triangular pyramid, a square pyramid, or other pointed cone-shaped component, or it can be formed by two metal plates with their tops touching) located above the central air inlet pipe 11. Its overall shape is adapted to the feeding path inside the downdraft gasifier 1. The guide cone is located directly below the feed inlet (feed pipe 31) and can contact the biomass fuel transported from the feed pipe 31 before the central air inlet pipe 11.

[0059] The feed cone has two main functions. First, it can effectively disperse the falling biomass fuel and guide it to spread outwards, preventing the fuel from accumulating directly on the central air inlet pipe 11 and causing bridging, thus ensuring smooth fuel delivery. Second, by guiding the fuel to be evenly distributed around the furnace, it can prevent local voids caused by feeding only in the central area, thereby ensuring a consistent feed layer density across the entire cross-section of the furnace and laying the foundation for the uniform effect of subsequent oxygen-enriched air.

[0060] Optionally, the central air inlet pipe 11 and / or the guide cone are provided with cooling water channels to protect the metal components and ensure their long-term structural safety by circulating cooling water.

[0061] For example, the central air inlet pipe 11 is in the form of a jacket, with the jacket serving as a cooling water channel; similarly, the guide cone can also be set in the form of a jacket, with the jacket serving as a cooling water channel.

[0062] For example, the interior of the central air intake pipe 11 and / or the interior of the cone of the guide cone are machined along the structural contour of the component to allow cooling water to flow.

[0063] This application does not limit the specific configuration of the cooling water passage.

[0064] When the guide cone is in direct contact with the central air inlet pipe 11 or is close to it, a cooling water channel can be provided on only one of them.

[0065] The cooling water channel has an inlet and an outlet at each end. The inlet is connected to a cooling water supply device, and the outlet is connected to a cooling water recovery or recycling system to form a complete cooling water flow loop. In use, the cooling water output from the cooling water supply device enters the cooling water channel through the inlet and flows continuously within the channel. During this process, it continuously absorbs the heat accumulated in the central air inlet pipe 11 and the guide cone due to their high-temperature reaction environment in the downdraft gasifier 1. After absorbing the heat, the cooling water flows out from the outlet and enters the recovery or recycling system. After cooling down, it can be reused.

[0066] Setting up a cooling water channel can effectively remove the heat absorbed by the two metal components, the central air inlet pipe 11 and the feed cone, which are located in the high-temperature zone. This prevents them from overheating, deforming, or burning due to prolonged exposure to high temperatures, ensuring the long-term structural safety of the metal components and thus ensuring the long-term continuous and stable operation of the entire biomass gasification device.

[0067] Optionally, the downdraft gasifier 1 is provided with a central air inlet pipe 11 and an outlet jacket 12 is provided on the side of the downdraft gasifier 1. The outlet jacket 12 is located below the central air inlet pipe 11, and the air inlet of the outlet jacket 12 faces the bottom of the downdraft gasifier 1. The outlet of the downdraft gasifier 1 is located on its side and connected to the outlet jacket 12. The outlet of the downdraft gasifier 1 is higher than the air inlet of the outlet jacket 12. During operation, oxygen-enriched air flows into the downdraft gasifier 1 through the central air inlet pipe, penetrates and acts on the material pile. After completing the reaction with the material pile, the generated combustible gas diffuses to the edge, enters the outlet jacket 12, and is finally discharged from the higher outlet.

[0068] For details, please refer to Figure 3 In the illustrated embodiment, a central air inlet pipe 11 passes through the downdraft gasifier 1 and is connected to a blower and oxygen supply equipment via a gas supply pipe. An outlet is located in the middle of the section of the central air inlet pipe 11 within the downdraft gasifier 1. A gas outlet jacket 12 is provided on the furnace wall below the central air inlet pipe 11. The bottom of the gas outlet jacket 12 is open and serves as an air inlet, allowing the combustible gas generated during gasification to flow into the gas outlet jacket 12 from all directions, thus preventing localized gas accumulation during single-point extraction and ensuring uniform oxygen-enriched air distribution. A final gas outlet is located on the side wall of the downdraft gasifier 1, which is connected to a vent 4 and an adiabatic burner 3 via a pipe. The final gas outlet is positioned higher than the air inlet of the gas outlet jacket 12.

[0069] In one specific embodiment, during operation, oxygen-enriched air flows in through the central air inlet pipe 11, then flows downwards through the diffuser under the umbrella effect, uniformly penetrating and acting on the material pile below the central air inlet pipe 11, reacting with the material pile. The combustible gas generated by the reaction flows downwards and towards the edge area of ​​the furnace body under the pressure difference and the suction of the induced draft fan, enters the exhaust jacket 12 through the air inlet, then turns upwards and converges towards the final exhaust port, finally being discharged from the higher final exhaust port.

[0070] This design forces uniform air distribution, avoiding "flow deviation" and reaction dead zones caused by sidewall air intake, ensuring uniform gasification reaction in the fuel pile. Because the air inlet of the outlet jacket 12 is located low, it forces the gas to penetrate the thickest layer of fuel before flowing out, maximizing gas-solid contact efficiency, improving char conversion rate and fuel quality. It also allows some fly ash and solid particles in the gas to be retained due to gravity settling and inertial separation, achieving preliminary dust removal. Furthermore, because the final outlet is located high, the combustible gas flows "downwards then upwards," forming a U-shaped flow field, equivalent to a dynamic seal, preventing short circuits and ensuring all fuel undergoes a complete reaction path. In addition, the outlet jacket 12 is integrated into the furnace wall, with a compact structure. The downward flow of gas also washes away dust, giving the downdraft gasifier 1 a self-cleaning function.

[0071] Optionally, a water jacket 38 is provided outside the section of the carbon conveying pipe 34 near the water gas gasifier 2. The water inlet of the water jacket 38 is connected to an external soft water supply device. During operation, the soft water flowing through the water jacket 38 can cool the carbon conveying pipe 34.

[0072] For details, please refer to Figure 1 and Figure 4 In the illustrated embodiment, the water jacket 38 is fitted outside the carbon conveying pipe 34 and adjacent to the water-gas gasifier 2. Its specific configuration is a jacketed structure wrapped around the carbon conveying pipe 34, with channels inside the jacket for the flow of soft water. The water jacket 38 has an inlet end and an outlet end. The inlet end connects to an external soft water supply device, and the outlet end connects to a soft water recovery or recycling system. During operation, the soft water supply device delivers room temperature or low temperature soft water into the water jacket 38. The soft water flows continuously within the jacket channels, absorbing heat transferred from the carbon conveying pipe 34 during the flow, thus cooling the carbon conveying pipe 34 before flowing out from the outlet end of the water jacket 38.

[0073] It needs to be explained that soft water refers to water in which soluble metal ions such as calcium and magnesium have been removed or significantly reduced. These ions are the root cause of scale formation (mainly composed of calcium carbonate and magnesium hydroxide) when ordinary hard water is heated. Soft water is chosen because the carbon conveying pipe 34 and its matching slide valve are in extremely high ambient temperatures. If ordinary hard water is used, it will be rapidly heated when flowing in the water jacket 38, causing the calcium and magnesium ions to quickly precipitate and form scale. The scale will block the narrow flow channels in the water jacket 38, resulting in poor water flow and loss of cooling effect. Furthermore, due to its poor thermal conductivity, it will form an "insulation layer" between the metal pipe wall and the cooling water, preventing the carbon conveying pipe 34 and slide valve from being effectively cooled, which may lead to deformation, jamming, or burnout.

[0074] The water jacket 38 is used in conjunction with soft water. On the one hand, the water jacket 38 can effectively reduce the temperature of the carbon conveying pipe 34 near the water gasification furnace 2 by the flow of soft water, so as to avoid damage to the pipe body and the slide valve on it due to high temperature, and ensure the structural safety and normal operation of the equipment. On the other hand, the use of soft water can completely avoid the formation of scale, prevent the flow channel from being blocked and the cooling failure, and ensure the long-term stable operation of the cooling system.

[0075] Optionally, the biomass gasification system also includes a steam-water separator 5. A water jacket 38 is provided outside the section of the carbon conveying pipe 34 near the water gas gasifier 2. The water outlet of the water jacket 38 is connected to the steam-water separator 5. The soft water after heat exchange can replenish the steam-water separator 5, and the steam-water separator 5 can deliver water vapor to the water gas gasifier 2.

[0076] The steam-water separator 5 is a device used to separate water and steam, realize the recycling of water resources and the supply of steam.

[0077] As can be seen from the above, steam can be used as a gasifying agent in the water-gas reaction, while water can be used as cooling water (a water tank can be configured to temporarily store the separated, high-temperature water, and then cool it down before use). The cooling water can be used in the cooling water channels related to the central air inlet pipe 11 and the central air outlet pipe 21, or it can be used in the water jacket 38.

[0078] Specifically, after the soft water completes the cooling task of the carbon conveying pipe 34 in the water jacket 38, it is heated into hot water carrying residual heat. This hot water is transported to the steam-water separator 5 through pipelines to replenish its water source. The steam-water separator 5 can process the incoming hot water and separate it into water and water vapor. The generated water vapor is transported to the water gasification furnace 2 through a dedicated pipeline as a gasifying agent for the water gas reaction, providing the necessary material basis for the reaction. The separated water can be further recycled or participate in the heat exchange process again, realizing the efficient turnover of water resources within the system.

[0079] Optionally, the biomass gasification system also includes a steam-water separator 5. An auxiliary steam inlet is provided on the section of the carbon conveying pipe 34 near the water gas gasifier 2. The auxiliary steam inlet is connected to the steam outlet of the steam-water separator 5. Part of the steam output from the steam-water separator 5 enters the auxiliary steam inlet. The temperature of the steam is lower than that of the high-temperature flue gas, which can block the high-temperature radiation and the upward flow of hot air in the water gas gasifier 2.

[0080] For details, please refer to Figure 2 In the illustrated embodiment, the auxiliary steam inlet is located on the pipe wall of the charcoal conveying pipe 34 near the end of the water gas gasifier 2, and below the gate valve on the charcoal conveying pipe 34, corresponding to the critical barrier position between the high-temperature area of ​​the water gas gasifier 2 and the gate valve. The auxiliary steam inlet is connected to the steam outlet of the steam-water separator 5 through a pipeline, and can receive part of the steam output from the steam-water separator 5.

[0081] The auxiliary steam inlet serves two main purposes. First, it isolates high temperatures and controls the temperature. Since the water-gas gasifier 2 generates intense high-temperature radiation and may backflow high-temperature flue gas, these high temperatures threaten the safety of the upper gate valve. Injecting water vapor at a temperature lower than the high-temperature flue gas into the charcoal conveying pipe 34 via the auxiliary steam inlet creates an "air curtain" or "steam barrier" below the gate valve and inside the charcoal conveying pipe 34. This effectively blocks the high-temperature radiation and upward flow of hot air from the water-gas gasifier 2, while simultaneously diluting and cooling any potential backflow of flue gas, ensuring that the temperature in the area where the gate valve is located remains stable within the safe range that the metal material can withstand, thus protecting this precision device. Second, the water vapor entering through the auxiliary steam inlet flows downwards and can participate in the water-gas reaction, thereby regulating the reaction process. Under specific circumstances, the water vapor can also prevent charcoal from accumulating and bridging (blocking) inside the charcoal conveying pipe 34, further ensuring smooth charcoal transport.

[0082] Optionally, the adiabatic burner 3 is equipped with an ignition device. During the start-up stage, the ignition device is connected to liquefied petroleum gas as fuel. After the biomass gas is ignited and the flame detection signal is received by the control system, the ignition device is shut off, and the combustible gas generated by the downdraft gasifier 1 becomes the main flare fuel for the adiabatic burner 3.

[0083] Specifically, during the system start-up phase, since the downdraft gasifier 1 is not yet working stably and cannot continuously produce qualified combustible gas, the adiabatic burner 3 is connected to liquefied petroleum gas as fuel to meet the needs of the burner starting and generating high-temperature flue gas during start-up. After the downdraft gasifier 1 completes the start-up process, enters a stable working state, and can continuously produce combustible gas, the adiabatic burner 3 switches fuel and no longer relies on external liquefied petroleum gas. Instead, it uses the combustible gas generated by the downdraft gasifier 1 as fuel to continue the combustion reaction and generate high-temperature flue gas and water vapor.

[0084] This design allows for the rapid start-up and heating of the adiabatic burner 3 using liquefied petroleum gas during the start-up phase. This provides an initial guarantee for the subsequent stable operation of the downdraft gasifier 1 and the reaction of the water gasifier 2, preventing the adiabatic burner 3 from failing to start due to the instability of the downdraft gasifier 1. During the stable operation phase, the combustible gas is switched as fuel, eliminating the need for continuous external fuel consumption and reducing the fuel cost of the system. At the same time, the combustible gas produced by the downdraft gasifier 1 is fully utilized to achieve the circulation of materials and energy within the system, which aligns with the design concept of "internal digestion of intermediate products" and ensures the overall economic efficiency and high efficiency of the system.

[0085] Optionally, the adiabatic burner 3 is equipped with an online oxygen analyzer. The online oxygen analyzer monitors the oxygen concentration in the adiabatic burner 3 in real time and adjusts the amount of oxygen-enriched air entering the adiabatic burner 3 according to the heat energy requirements of the water gas reaction in the water gas gasifier 2, so that the heat generation in the adiabatic burner 3 matches the heat consumption of the water gas gasifier 2.

[0086] The online oxygen analyzer is a dedicated detection device installed on the adiabatic burner 3 to monitor the oxygen concentration inside the burner in real time. It can continuously capture the dynamic changes in the oxygen content inside the adiabatic burner 3 and feed back the monitored concentration data to the system control unit (such as the PLC control system) in real time, providing data support for subsequent adjustment operations.

[0087] It should be explained that the water-gas reaction is a strongly endothermic reaction, requiring a continuous and stable supply of heat energy to proceed efficiently. Matching the heat generation within the adiabatic burner 3 with the heat consumption of the water-gas gasifier 2 ensures that the gasifier 2 maintains the optimal reaction temperature range of 700-900℃. This prevents problems such as reaction stagnation and reduced production of target gases (H2, CO) due to insufficient heat, or slagging and equipment damage caused by excessive heat leading to overheating. Simultaneously, precise heat matching prevents the adiabatic burner 3 from over-supplying energy, thus avoiding waste of oxygen-rich air and combustible gases, thereby improving the system's energy utilization efficiency and ensuring the stable and efficient operation of the entire biomass gasification system's process chain from "intermediate product combustion for energy supply" to "final clean syngas generation."

[0088] Specifically, during the operation of the adiabatic burner 3, the online oxygen analyzer is always running, monitoring the oxygen concentration inside the burner in real time. When the heat energy demand of the water gas reaction in the water gasification furnace 2 changes (such as the reaction rate increases, requiring more heat, or the reaction becomes more stable, requiring less heat input), the control unit adjusts the supply of oxygen-enriched air to the adiabatic burner 3 based on the heat energy demand signal of the water gasification furnace 2 and the real-time oxygen concentration data fed back by the online oxygen analyzer. If it is necessary to increase heat generation, the oxygen content of the oxygen-enriched air can be adjusted appropriately according to the oxygen concentration to optimize combustion efficiency; if it is necessary to reduce heat generation, the oxygen content of the oxygen-enriched air is adjusted accordingly to reduce combustion intensity, ultimately achieving the adaptation between the heat generation in the adiabatic burner 3 and the heat consumption of the water gasification furnace 2.

[0089] It should be added that the control unit needs to obtain the heat energy demand signal of the water-gas gasifier 2 by real-time monitoring and analysis of four key parameters. First, it uses thermocouples or infrared temperature measuring devices to collect the temperature of different areas inside the furnace. If the temperature is lower than the set value (optimal range of 700-900℃), it determines that heating is needed; if it is higher, it determines that heating is needed. Second, it monitors the concentration, flow rate, and CO content of H2 and CO in the syngas. If the concentration and flow rate decrease, it determines that heating is needed; if the flow rate increases suddenly or CO2 is excessive, it determines that heating is needed. Third, it receives feedback on the temperature distribution, height, density, and pressure inside the furnace of the feed bed. If the feed bed is uneven or there are cold zones, it determines that supplemental heating is needed; if the pressure rises abnormally, it determines that heating is needed. Fourth, it receives signals from upstream and downstream equipment. If the frequency of carbon replenishment or the amount of steam supply increases, synchronous heating is needed. These parameters can be converted into clear demand signals by the algorithm analysis of the control unit. Combined with oxygen concentration data, the burner energy supply can be adjusted to achieve a balance between heat supply and demand.

[0090] Optionally, the top of the water gas gasifier 2 is provided with a charcoal inlet, which is connected to the downdraft gasifier 1 through a charcoal conveying pipe 34.

[0091] Optionally, the upper side wall of the water gasification furnace 2 is provided with a gas-water inlet, which is connected to the insulated burner 3.

[0092] For details, please refer to Figure 1 and Figure 4 In the illustrated embodiment, the top of the water gas gasifier 2 is provided with a charcoal inlet, which is connected to the downdraft gasifier 1 via a charcoal conveying pipe 34, so that charcoal can move from the downdraft gasifier 1 to the water gas gasifier 2. A gas-water inlet is provided on the upper right side wall of the water gas gasifier 2, which is connected to the outlet of the insulated burner 3 via a high-temperature flue gas pipe, for receiving the high-temperature flue gas and water vapor generated by the insulated burner 3.

[0093] By placing the charcoal inlet at the top of the water gas gasifier 2, the charcoal transported from the downdraft gasifier 1 through the charcoal conveying pipe 34 can fall naturally under gravity and accumulate evenly in the water gas gasifier 2, forming a stable material layer. There is no need to set up an additional forced charcoal feeding mechanism. While simplifying the structure, it ensures that the charcoal material layer is evenly distributed, providing a continuous and uniform carbon source for the subsequent water gas reaction.

[0094] By placing the gas-water inlet on the upper side wall of the water-gas gasifier 2, the high-temperature flue gas and water vapor delivered by the insulated burner 3 can directly enter the middle and upper part of the charcoal material layer inside the furnace. This area is the core area of ​​the water-gas reaction. The high-temperature flue gas can quickly transfer heat to the charcoal material layer, maintaining the optimal reaction temperature of 700-900℃. The water vapor can directly contact the hot charcoal and undergo the water-gas reaction.

[0095] The synergistic effect of the two ensures efficient reaction, while avoiding heat loss or incomplete reaction due to improper inlet location of high-temperature flue gas and water vapor.

[0096] Optionally, a water seal 41 is provided on one side of the water gas gasifier 2. The water seal 41 is used as a safety explosion relief port. When the pressure inside the water gas gasifier 2 exceeds the preset value, the water seal 41 automatically opens to release pressure, so as to ensure the safe operation of the water gas gasifier 2.

[0097] The water seal 41 is a safety device installed on one side of the water gas gasifier 2, designed based on the liquid sealing characteristics and pressure balance principle. Its core structure includes a cavity that can hold sealing water and a channel that connects to the water gas gasifier 2. The sealing and pressure control of the gas inside the furnace are achieved by the liquid column pressure formed by the water in the cavity.

[0098] Water seal 41 serves as a safety vent for the water gas gasifier 2. During normal operation of the water gas gasifier 2, the pressure inside the furnace is stable and lower than the pressure formed by the water column inside water seal 41. At this time, water seal 41 prevents gas leakage from the furnace through the sealing effect of water, maintaining a stable pressure environment inside the furnace. When the pressure inside the furnace exceeds the preset value due to abnormal water gas reaction (such as a sudden increase in reaction rate or blockage of gas discharge channel), the high-pressure gas inside the furnace will overcome the pressure of the water column inside water seal 41, pushing the water to form a liquid level difference, and then discharge from the pressure relief channel of water seal 41, achieving automatic pressure relief. After the pressure inside the furnace drops to a safe range, the water in water seal 41 returns to equilibrium and re-forms a seal, preventing continuous gas leakage inside the furnace.

[0099] Through the automatic response process of "sealing-depressurization-reset" of water seal 41, safety accidents such as furnace deformation, cracking or even explosion caused by overpressure in water gas gasifier 2 can be effectively prevented, providing a safety guarantee for the stable operation of water gas reaction.

[0100] Optionally, a level gauge 42 is provided on one side of the water gasification furnace 2, which is used to detect the material level inside the water gasification furnace 2.

[0101] The level gauge 42 is a special detection device installed on one side of the water gas gasifier 2 for real-time monitoring of the charcoal material layer height inside the furnace. It uses detection components (such as contact or non-contact detection units) adapted to the furnace structure of the water gas gasifier 2 to continuously monitor the material layer height by going deep into the furnace or close to the furnace wall, and feeds back the material level data to the control unit in real time.

[0102] The material level gauge 42 can accurately grasp the real-time height of the charcoal material layer in the furnace, avoiding excessive material feeding leading to an excessively high material layer, affecting the penetration of high-temperature flue gas and water vapor, or insufficient material feeding leading to an excessively low material layer, causing instability in the reaction zone or even heat loss in the furnace.

[0103] Optionally, the bottom of the water gas gasifier 2 is provided with a rotatable lower grate 43. There is a gap between the outer edge of the lower grate 43 and the inner wall of the water gas gasifier 2. During operation, the lower grate 43 rotates so that ash and slag can be discharged through the gap.

[0104] The lower grate 43 is a load-bearing structural component installed at the bottom of the water gas gasifier 2 and capable of rotation (equipped with a motor and other rotating drive components). Its shape is adapted to the bottom space of the water gas gasifier 2. A gap is reserved between the outer edge and the inner wall of the furnace for ash and slag discharge. It is mainly used to support the charcoal material layer in the furnace and the ash and slag produced after the gasification reaction, and achieves orderly discharge of ash and slag through its own rotation.

[0105] The lower grate 43, as a supporting component, can stably support the charcoal layer inside the water-gas gasifier 2, providing a stable reaction space for the water-gas reaction and ensuring that high-temperature flue gas and water vapor can act evenly on the charcoal layer, thus ensuring the full progress of the reaction. At the same time, as a slag discharge component, through its rotational motion, it utilizes the combined effect of centrifugal force and gravity to move the ash and slag produced after the gasification reaction towards the outer edge of the grate, and finally fall into the bottom slag discharge system through the gap between the grate and the inner wall of the furnace, achieving continuous and smooth discharge of ash and slag.

[0106] Optionally, the bottom of the water gasification furnace 2 is provided with an ash discharge pipe 44, and ash lock 1 45 and ash lock 2 46 are provided at intervals on the ash discharge pipe 44. When discharging ash, ash lock 1 45 and ash lock 2 46 are opened and closed at different times so as to transport the ash and slag in the pressurized water gasification furnace 2 to the outside of the furnace at atmospheric pressure.

[0107] For details, please refer to Figure 4In the illustrated embodiment, the ash discharge pipe 44 is a vertically extending tubular structure connecting the bottom ash outlet of the water-gas gasifier 2 with the external ash discharge system, used to transport the ash generated in the furnace reaction. Ash lock one 45 and ash lock two 46 are two transition containers spaced apart on the ash discharge pipe 44. Their structures are adapted to the diameter of the ash discharge pipe 44, and they have internal space for temporary storage of ash. Each is equipped with a valve to control its opening and closing, and there is an ash buffer area between the two ash locks.

[0108] During the ash removal process, the staggered opening and closing of ash lock 1 (45) and ash lock 2 (46) are performed; for example... Figure 4 In the process, ash lock 1 45 is closer to the water gas gasifier 2 than ash lock 2 46. When discharging ash, ash lock 2 46 is closed first and ash lock 1 45 is opened, so that the ash and slag in the pressurized environment inside the water gas gasifier 2 falls into ash lock 1 45 and the ash and slag buffer area between the two ash locks under the action of gravity through the ash discharge pipe 44. After the ash and slag have been temporarily stored to a certain amount or after the preset ash discharge time, ash lock 1 45 is closed and the pressure of ash lock 1 45 and the ash and slag buffer area is released so that the internal gas pressure is close to the normal pressure. Then ash lock 2 46 is opened so that the temporarily stored ash and slag is transported to the outside of the furnace. After the ash and slag are discharged, ash lock 2 46 is closed and ash lock 1 45 and the ash and slag buffer area are pressurized to the same pressure as the water gas gasifier 2, and the next round of ash discharge cycle begins.

[0109] By utilizing the staggered opening and closing and pressure switching of two ash locks, the pressurized environment of the water-gas gasifier 2 can be effectively isolated from the atmospheric pressure environment outside the furnace. This prevents high-pressure gas leakage during ash removal, ensuring stable pressure inside the furnace to maintain normal conditions for the water-gas reaction. It solves the problem of frequent start-stop cycles and pressure fluctuations that occur with traditional single ash locks. Furthermore, no additional complex pressurization or depressurization equipment is required. The periodic operation of the ash locks enables stable ash transport from the pressurized furnace to the atmospheric pressure environment outside, ensuring continuous ash removal without affecting the normal operation of the gasification system. This meets the requirements of pressurized gasification processes for equipment sealing and operational stability.

[0110] Optionally, the downdraft gasifier 1 is equipped with three layers of temperature measuring points: the upper layer corresponds to the preheating dry distillation zone, the middle layer corresponds to the carbonization reaction zone, and the lower layer corresponds to the carbon layer oxygen-deficient cooling zone. When the upper layer temperature measuring point detects that the temperature of the preheating dry distillation zone is close to or exceeds the temperature of the carbonization reaction zone, the upper grate 37 is accelerated to increase the carbon output. When the lower layer temperature measuring point detects that the temperature of the carbon layer oxygen-deficient cooling zone is close to or exceeds the temperature of the carbonization reaction zone, the upper grate 37 is decelerated to reduce the carbon output.

[0111] It should be explained that the preheating dry distillation zone, the carbonization reaction zone, and the carbon bed oxygen-deficient cooling zone are three functional areas distributed from top to bottom along the height of the biomass fuel bed in the downdraft gasifier 1. The three can work together to complete the biomass gasification conversion process.

[0112] Specifically, the preheating and pyrolysis zone is located above the material layer and mainly undertakes the preheating and pyrolysis of biomass fuel. By absorbing the heat transferred from the carbonization reaction zone below, it dries the newly added wet biomass fuel and decomposes it to produce pyrolysis gas (i.e., combustible gas leading to the adiabatic burner 3, containing tar, volatile organic compounds, etc.), preparing for subsequent carbonization.

[0113] The carbonization reaction zone is located in the middle of the feed layer and is the core area of ​​the gasification process. In an oxygen-deficient environment, the biomass after preheating and dry distillation will undergo a high-temperature carbonization reaction here to generate charcoal with a high fixed carbon content. At the same time, it releases heat to provide a heat source for the upper preheating and dry distillation zone. Its stable temperature and position are key to ensuring gasification efficiency and product quality.

[0114] The oxygen-deficient cooling zone of the charcoal layer is located in the lower part of the material layer, below the carbonization reaction zone. Due to the extremely low oxygen content in this area, the charcoal basically does not undergo a combustion reaction. It mainly reduces the temperature of the high-temperature charcoal through indirect heat exchange with the cold air or cooling structure below, preventing the high-temperature charcoal from directly entering the downstream equipment and causing damage. At the same time, it provides stable lower support for the carbonization reaction zone and maintains the stability of the material layer structure.

[0115] The relationship between the preheating dry distillation zone, the carbonization reaction zone, and the charcoal layer oxygen-deficient cooling zone is as follows: heat is transferred upward from the middle carbonization reaction zone to provide energy for the upper preheating dry distillation zone; the material passes through the three stages of preheating dry distillation, carbonization, and cooling from top to bottom, forming a synergistic mechanism of "heat supplying upward and material moving downward" to jointly complete the conversion of biomass into charcoal and combustible gas.

[0116] The upper, middle, and lower temperature measuring points are temperature detection components adapted to the three functional areas within the downdraft gasifier 1. Specifically, each temperature measuring point consists of a high-temperature resistant temperature sensor (such as a thermocouple or resistance temperature detector), a signal transmission line, and a data acquisition unit. The sensor probe is directly inserted into the corresponding material layer or close to the furnace wall to monitor the area temperature. The sensor at the upper temperature measuring point is located in the middle of the material layer in the preheating and dry distillation zone, the sensor at the middle temperature measuring point is located in the core reaction area of ​​the carbonization reaction zone, and the sensor at the lower temperature measuring point is located in the upper-middle part of the oxygen-deficient cooling zone of the carbon layer. During temperature measurement, the sensor collects the temperature signal of its area in real time and transmits the data to the control unit (such as a PLC controller) through the signal transmission line. The control unit processes and displays the temperature data in real time, providing a basis for subsequent control operations.

[0117] The actual working mode of the downdraft gasifier 1 is divided into three states. Under normal and stable conditions, the temperature of the middle carbonization reaction zone is the highest, the temperature of the upper preheating and dry distillation zone is lower, and the temperature of the lower carbon layer oxygen-deficient cooling zone is moderate. At this time, the upper grate 37 rotates at the reference speed, and the amount of carbon output is balanced with the amount of feed from the top, maintaining the stability of the reaction zone. When the temperature of the preheating and dry distillation zone detected by the upper temperature measuring point is close to or exceeds the temperature of the middle carbonization reaction zone, it indicates that the core reaction zone has moved upward. The reason is mostly that the carbon output speed is too slow, resulting in an excessively thick carbon layer. The system controls the upper grate 37 to accelerate its rotation to increase the amount of carbon output. By "thinning" the carbon layer, the reaction zone is forced to fall back to the middle layer. When the temperature of the carbon layer oxygen-deficient cooling zone detected by the lower temperature measuring point is close to or exceeds the temperature of the middle carbonization reaction zone, it indicates that the core reaction zone has moved downward. The reason is mostly that the carbon output speed is too fast, resulting in an excessively thin carbon layer. The system controls the upper grate 37 to decelerate its rotation to reduce the amount of carbon output. By "thickening" the carbon layer, the reaction zone is pushed back upward to the middle layer.

[0118] In this way, firstly, it can maintain the carbonization reaction zone within the optimal temperature range, ensuring the efficient conversion of biomass into high-quality charcoal and combustible gas, and avoiding incomplete pyrolysis or premature char discharge caused by reaction zone displacement; secondly, a stable carbonization reaction zone can ensure that the tar-containing pyrolysis gas is cracked in situ within the furnace, which helps solve the tar problem and reduces the subsequent combustion burden; thirdly, it prevents the reaction zone from shifting downwards and causing high-temperature contact with downstream gate valves, water jacket 38, and other equipment, protecting key components from being burned; fourthly, it transforms the traditional manual "fire watching" into fully automatic control, reducing the difficulty of operation and dependence on skilled workers, and achieving long-term stable operation of the system; fifthly, a stable reaction zone keeps the gasification reaction at its optimal operating condition, which helps improve the gasification efficiency and energy conversion efficiency of the entire downdraft gasifier 1.

[0119] Optionally, the water gas gasifier 2 is equipped with a level gauge 42 and a lower grate 43, and the level gauge 42 and the lower grate 43 are linked for control; when the level gauge 42 detects that the material layer height in the water gas gasifier 2 is higher than the preset value, the lower grate 43 is accelerated to rotate; when the level gauge 42 detects that the material layer height in the water gas gasifier 2 is lower than the preset value, the lower grate 43 is decelerated to rotate.

[0120] The linkage control between the level gauge 42 and the lower grate 43 refers to a closed-loop control method in which the level gauge 42 monitors the height of the charcoal material layer in the water-gas gasifier 2 in real time, converts the material layer height data into a control signal, and transmits it to the drive system of the lower grate 43, so that the rotation speed of the lower grate 43 is automatically adjusted according to the change of the material layer height.

[0121] Specifically, when the level gauge 42 detects that the material level in the furnace is higher than the preset value, the control signal triggers the lower grate 43 to accelerate its rotation, thereby speeding up the ash and slag discharge and reducing the material level. When the level gauge 42 detects that the material level in the furnace is lower than the preset value, the control signal triggers the lower grate 43 to decelerate its rotation, thereby slowing down the ash and slag discharge and maintaining or raising the material level, always keeping the material level within the preset range that meets the requirements of the water-gas reaction.

[0122] The purpose of this coordinated control is to ensure a consistently stable charcoal bed thickness within the water-gas gasifier 2, providing a continuous and uniform carbon source for the water-gas reaction. This prevents, on the one hand, the high charcoal bed from hindering the penetration of high-temperature flue gas and steam, increasing gasification resistance, and causing incomplete reactions and reduced production of the target gases (H2, CO). On the other hand, it prevents heat loss from the furnace due to an excessively low charcoal bed, which could prevent the maintenance of the optimal reaction temperature of 700-900℃, or even lead to "blank burning" and affect system operation. Simultaneously, it eliminates the need for frequent manual intervention in the charcoal bed height and grate speed, achieving a dynamic balance between slag discharge and feeding in the water-gas gasifier 2, ensuring the stability and continuity of the water-gas reaction.

[0123] Optionally, the water gas gasifier 2 is provided with a central gas outlet pipe 21, which passes through the material pile and runs horizontally through the water gas gasifier 2.

[0124] For details, please refer to Figure 4 In the illustrated embodiment, the central exhaust pipe 21 is a tubular structure extending horizontally in the left-right direction and penetrating the furnace body of the water-gas gasifier 2. It is entirely embedded within the charcoal pile inside the furnace, and the pipe body is adapted to the dimensions of the furnace space. The central exhaust pipe 21 has vents on its inner wall for collecting syngas. One end of the central exhaust pipe 21 extends to the outside of the furnace body, connecting to downstream equipment (such as the cyclone dust collector 6 described below) for discharging the syngas. The central exhaust pipe 21 is a dedicated channel for transporting syngas from inside the furnace to the outside.

[0125] The central outlet pipe 21 efficiently and uniformly collects the water gas (i.e., syngas) generated within the water gasification furnace 2. Specifically, the water gas reaction takes place in the charcoal pile inside the furnace. The generated water gas permeates and diffuses into the pile under the pressure difference within the furnace. The central outlet pipe 21, penetrating the pile, can directly contact and collect the water gas from different areas of the pile through pores on its pipe wall, preventing localized accumulation of water gas within the furnace or compositional changes due to lower temperatures near the furnace wall. Simultaneously, the horizontally penetrating structural design covers most of the furnace's cross-section, ensuring that the water gas enters the pipe uniformly from all parts of the pile, reducing gas flow resistance and improving collection efficiency. The collected water gas is then transported through the central outlet pipe 21 to subsequent systems outside the furnace, providing a stable gas source for subsequent purification and utilization (such as synthetic fuel production and power generation).

[0126] Optionally, the central gas outlet pipe 21 is provided with a downward-facing, trumpet-shaped synthesis gas inlet in the middle of the pipe section inside the water gas gasifier 2. A horizontal model cavity can be formed below the synthesis gas inlet to improve the uniformity of gas collection.

[0127] For details, please refer to Figure 4 In the illustrated embodiment, the syngas inlet is an opening structure located in the middle of the inner pipe section of the central gas outlet pipe 21 in the water gas gasifier 2. The overall shape is a downward-opening trumpet shape with the opening facing the bottom of the furnace and connected to the horizontal pipe body of the central gas outlet pipe 21.

[0128] Because the central gas outlet pipe 21 horizontally penetrates the water gas gasifier 2, under the action of the grate, the charcoal moves and is compressed, converging from all sides towards the center, gradually forming a cavity that matches the shape of a funnel. In addition, when the induced draft fan is working, it will have a suction effect on the syngas in the furnace. The syngas is drawn out from the material layer and converges towards the funnel-shaped syngas inlet. Under the action of strong suction, the highest point (peak) of the material layer directly below the syngas inlet will be scoured by the airflow, gradually forming a cavity that matches the shape of a funnel. Because the airflow converges from all sides towards the center and flows upward during the suction process, the final cavity shape tends to be a horizontal, flat ellipsoid or model, hence it is called a "horizontal model cavity".

[0129] It needs to be explained that the olive-shaped void is formed by the pressure of oxygen-enriched air "expanding" the material layer through the central air inlet pipe 11 of the downdraft gasifier 1. It has a slightly thicker central section and thinner ends, forming a longitudinal structure that serves for air intake and distribution. The horizontal void, on the other hand, is formed by the suction force of the induced draft fan through the central exhaust pipe 21 of the water-gas gasifier 2, forming a horizontally flat structure that serves for gas exhaust and collection. These two types of voids, one "pushing" and the other "suctioning," one "vertical" and the other "horizontal," respectively meet the air intake and collection requirements of the two gasifiers.

[0130] It needs to be explained that the feed layer in the water-gas gasifier 2 is shaped like a "mountain" due to the top center feed, resulting in varying thicknesses. If only gas outlets are provided on the furnace wall, gas tends to preferentially pass through the thinner, less resistant sections of the furnace wall, potentially leading to poor reaction in the central area. After the horizontal model voids are formed, the flow resistance from any point on the feed layer surface to the syngas inlet is essentially equal to the straight-line distance, effectively creating an equipotential surface for gas flow. This forces the mixture of water vapor and high-temperature flue gas to penetrate the entire feed layer cross-section uniformly before being collected, ensuring a uniform and efficient gasification reaction in the reaction zone. Simultaneously, the funnel-shaped syngas inlet, in conjunction with the horizontal model voids, reduces the airflow velocity. The cross-sectional area of ​​the funnel opening is much larger than that of the horizontal main pipe at the center outlet, causing a sharp decrease in gas velocity as the gas flows through this area. This reduces the ability to carry fly ash, allowing some heavier fly ash to fall back into the feed layer due to gravity, achieving primary dust removal before the outlet. This reduces the workload of the subsequent cyclone dust collector and facilitates subsequent gas treatment processes.

[0131] Optionally, a triangular guide cone is provided above the central vent pipe 21. The guide cone is used to guide the charcoal to fall in all directions, thereby preventing the charcoal from forming a pile-up and bridging on the central vent pipe 21.

[0132] The guide cone on the central air outlet pipe 21 is similar to the guide cone on the central air inlet pipe 11 mentioned above, and will not be described in detail here.

[0133] By setting a guide cone on the central gas outlet pipe 21 and positioning it directly opposite the charcoal inlet, the system can guide the charcoal to fall in a dispersed manner, ensuring that the charcoal falling from the top of the water gas gasifier 2 is smoothly guided to the perimeter of the furnace, preventing the charcoal from directly accumulating on the central gas outlet pipe 21 and ensuring the smooth flow of the charcoal conveying channel and the gas collection channel of the central gas outlet pipe 21. Secondly, it maintains the material layer shape. By guiding the charcoal to evenly cover the material layer in the reaction zone, it helps maintain the ideal "mountain-shaped" material surface in the furnace (after the guide cone guides the charcoal to disperse in all directions, the charcoal naturally accumulates under gravity, and the central area will still be slightly higher than the surrounding area due to the concentrated feed, forming a "mountain" shape that meets the reaction requirements; at the same time, the dispersion effect prevents the material layer around the perimeter from being too thin, ensuring that the overall thickness of the material pile is uniform. This retains the airflow guidance advantage of the "mountain-shaped" material pile while avoiding gas flow deviation caused by the central peak, ultimately ensuring uniform airflow and carbon source distribution in the reaction section). This provides a stable and uniform carbon source distribution for the water gas reaction and ensures uniform airflow distribution in the reaction section.

[0134] Optionally, the central vent pipe 21 and / or the guide cone are provided with cooling water channels to protect the metal components and ensure their long-term structural safety by circulating cooling water.

[0135] The cooling water passages associated with the central exhaust pipe 21 are similar to those associated with the central intake pipe 11 mentioned above, and will not be described in detail here.

[0136] By setting up cooling water channels to circulate cooling water, the central gas outlet pipe 21 and the guide cone, two metal components located in the high-temperature reaction environment of the water-gas gasifier 2, can be cooled and protected. The water-gas gasifier 2 operates in a high-temperature reaction environment of 700-900℃. The central gas outlet pipe 21 needs to continuously contact the high-temperature water gas, while the guide cone directly receives the falling high-temperature charcoal. Both are exposed to high temperatures for extended periods, making them prone to overheating, deformation, and burnout. As the cooling water flows through the channels, it continuously absorbs and carries away the heat from the metal components, maintaining their temperature within the safe range that the metal materials can withstand. This prevents structural damage caused by high temperatures, thus ensuring the long-term structural safety of the central gas outlet pipe 21 and the guide cone.

[0137] Optionally, the biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products provided in this application further includes: a cyclone dust collector 6, connected to the exhaust port of the water gasification furnace 2, used to separate solid particles in the syngas; a heat exchanger 7, connected to the exhaust port of the cyclone dust collector 6, used to recover the heat energy carried by the syngas; and a steam-water separator 5, connected to the heat exchanger 7. The heat exchanger 7 and the steam-water separator 5 form a circulation loop. The heat exchanger 7 recovers the heat energy in the syngas and transfers it to the soft water. The heated soft water enters the steam-water separator 5, and the separated water vapor can be returned to the water gasification furnace 2 to participate in the water gas reaction.

[0138] The cyclone dust collector 6 is used for gas-solid separation, using centrifugal force to efficiently separate and remove solid particles such as fly ash and unreacted carbon particles carried in the syngas discharged from the water gas gasifier 2. If these particles are not removed first, they will wear down and clog the pipes of the subsequent heat exchanger 7, and may also form scale on the heat exchange surface, ultimately reducing the heat exchange efficiency.

[0139] The function of heat exchanger 7 is heat energy recovery and conversion. Heat exchanger 7 receives high-temperature clean syngas from cyclone dust collector 6 and transfers the high-temperature heat energy (300-450℃) it carries to the low-temperature soft water flowing on the other side. In the process, the temperature of the syngas is reduced and heat energy is recovered, which facilitates subsequent pressurization and transportation by the blower. The soft water is heated to vaporize and form a gas-water mixture.

[0140] The function of the steam-water separator 5 is to separate steam and water and distribute steam. The steam-water separator 5 receives the steam-water mixture from the heat exchanger 7 and separates the "dry" saturated steam from the liquid water. The separated dry steam can be divided into two paths for distribution. The main path mixes with the high-temperature flue gas generated by the adiabatic burner 3 and enters the water gas gasifier 2 as a gasifying agent to participate in the reaction. The auxiliary path sends the steam to the auxiliary steam inlet on the carbon conveying pipe 34 for equipment protection and temperature control. At the same time, hot water from other sources in the system (such as the water jacket 38 and the outlet water of the cooling water channel) can also be gathered here to participate in steam generation and realize thermal energy integration.

[0141] For details, please refer to Figure 1In the illustrated embodiment, the inlet of the cyclone dust collector 6 is connected to the exhaust port of the water gas gasifier 2, and can receive the syngas discharged from the furnace; the exhaust port of the cyclone dust collector 6 is connected to the inlet of the heat exchanger 7, and can transport the high-temperature syngas after dust removal to the heat exchanger 7; the steam-water outlet of the heat exchanger 7 is connected to the inlet of the steam-water separator 5, and can send the steam-water mixture formed after heating into the steam-water separator 5; the steam outlet of the steam-water separator 5 is divided into two paths, one of which returns to the water gas gasifier 2 and participates in the water gas reaction, and the other is connected to the auxiliary steam inlet of the carbon conveying pipe 34.

[0142] To facilitate water flow within the system pipeline, heat exchanger 7 also uses soft water for heat exchange. In this case, the inlet of heat exchanger 7 can be connected to an external soft water supply device, or it can be connected to the outlet of steam-water separator 5 so that the incompletely vaporized soft water can flow back to heat exchanger 7 for further heating, forming a soft water circulation loop.

[0143] The cyclone dust collector 6, heat exchanger 7, and steam-water separator 5 work together to create a continuous process of "gas-solid purification → heat recovery → steam-water separation → steam reuse," forming a closed-loop system. This effectively prevents impurities in the syngas from affecting downstream equipment, while ensuring that the heat energy of the high-temperature syngas is fully extracted rather than wasted, thereby improving resource utilization. Furthermore, the steam-water separator 5's steam distribution not only meets the core requirements of the water-gas reaction but also protects the equipment in the carbon conveying pipe 34. Integrating hot water from multiple sources into steam generation enables centralized utilization of heat energy, further reducing energy dispersion and loss.

[0144] Cyclone dust collector 6 protects heat exchanger 7 from particle abrasion and scaling. Heat exchanger 7 lowers the temperature of syngas to facilitate its subsequent transport. Steam-water separator 5 ensures the quality and precise supply of steam. The three work together to ensure the stable operation of the entire biomass gasification system from syngas treatment to feedstock recycling, which is in line with the design concept of "internal digestion of intermediate products". At the same time, it reduces the system's dependence on external energy and water resources, and improves the overall economy and environmental protection of the system.

[0145] To summarize, the source and flow path of water vapor in the gasification system provided in this application.

[0146] The main source of water vapor is heat exchanger 7. Heat exchanger 7 recovers the waste heat of water gas, and the soft water absorbs heat and vaporizes to produce a large amount of water vapor.

[0147] The auxiliary source of water vapor is the water jacket 38. The low-temperature soft water in the water jacket 38 absorbs heat from the equipment and its temperature rises. The hot water carrying the residual heat is transported to the steam-water separator 5. In the steam-water separator 5, the hot water further absorbs heat and is converted into water vapor, which can indirectly supplement the amount of water vapor in the system.

[0148] The source of water vapor replenishment is the adiabatic burner 3. When the adiabatic burner 3 is working (especially when oxygen-enriched air and combustible gas are used as fuel), the hydrogen element in the fuel reacts with oxygen to generate water. Under high temperature conditions, some of the water will vaporize into water vapor.

[0149] "Intra-product consumption" is the core design concept of the gasification system provided in this application. It means that the intermediate products (such as combustible gas, waste heat, water vapor, water, etc.) generated during the operation of the gasification system are not directly discharged, but are reused inside the system, ultimately realizing the cycle of resources and energy.

[0150] Specifically, the tar-containing combustible gas produced by the downdraft gasifier 1 after it has been operating stably can be directly used as fuel for the insulated burner 3; the high-temperature flue gas (containing heat and some water vapor) produced after combustion is then transported to the water gas gasifier 2 as a heat source and gasifying agent supplement for the water gas reaction, thus realizing an internal cycle of "gas production by downdraft gasifier 1 - gas consumption by burner - heat consumption by water gas gasifier 2".

[0151] Furthermore, the high-temperature syngas (300-450℃) output from the water gasifier 2 has its heat recovered through the heat exchanger 7 to generate steam. The steam is then returned to continue serving the reaction and equipment protection of the water gasifier 2. In addition, the heat dissipation from equipment such as the gate valve and the waste heat from the combustion of the insulated burner 3 are ultimately converted into steam or used to supplement the reaction heat through the steam-water separator 5, realizing an energy closed loop of "waste heat-soft water-steam-reaction".

[0152] Furthermore, the fly ash and unreacted carbon particles in the syngas separated by the cyclone dust collector 6, although not directly participating in the reaction cycle, can be exported as fuel (such as for boiler combustion) to reduce solid waste emissions; the ash and slag discharged from the bottom of the water gas gasifier 2 can also be used as building materials and other resources to reduce external pollution.

[0153] Ultimately, the gasification system produces clean syngas, which is generated through a water gas reaction. The main components are H2 and CO, and it does not contain tar (because the carbonization reaction zone of the downdraft gasifier 1 is stable, tar can be cracked in situ, the oxygen-enriched combustion of the adiabatic burner 3 can consume tar, and the high-temperature reaction of the water gasifier 2 can further ensure that no tar is generated). After being purified by the cyclone dust collector 6 and cooled by the heat exchanger 7, the syngas can be directly used for power generation (such as driving gas turbines), the preparation of synthetic fuels (such as methanol and ethanol), or as industrial fuel gas, making it a high-value-added clean energy carrier.

[0154] In one specific embodiment, refer to Figure 1 The transmission chain of charcoal is as follows:

[0155] Charcoal generated by the downdraft gasifier 1 → rotated and pushed by the upper grate 37 (discharged downward through the gap in the furnace wall) → charcoal conveying pipe 34 → staggered opening and closing of slide gate valve 1 35 and slide gate valve 2 36 (to avoid pressure mixing) → charcoal inlet of water gas gasifier 2 → falls into the material layer of water gas gasifier 2.

[0156] The water jacket 38 on the charcoal conveying pipe 34 works in conjunction with the auxiliary steam inlet (connected to the steam-water separator 5) to cool the pipe and prevent the charcoal from spontaneously combusting, while also using water vapor to block the high-temperature upward movement of the water gas gasifier 2, ensuring that the charcoal enters the reaction zone at a suitable temperature.

[0157] The transmission path of tar-containing fuel gas is as follows:

[0158] The crude gas produced by the downdraft gasifier 1 → gas outlet jacket 12 (collects edge gas to avoid short circuit) → gas transmission pipeline → start-up stage (unstable gas) → venting port 4; stabilization stage → gas inlet of adiabatic burner 3 → mixed with oxygen-enriched air for combustion → generating high-temperature flue gas (containing water vapor) → gas-water inlet of water gas gasifier 2 → enters the charcoal material layer.

[0159] The energy conversion pathway is as follows:

[0160] The chemical energy of biomass fuel → carbonization in downdraft gasifier 1 → conversion into fixed carbon energy of charcoal and chemical energy of crude gas (including tar) → crude gas enters adiabatic burner 3 → combustion is converted into the thermal energy of high-temperature flue gas + the chemical energy of water vapor (gasifying agent potential energy) → high-temperature flue gas enters water gas gasifier 2 → thermal energy is used for water gas reaction (maintaining high temperature), and water vapor participates in the reaction as a gasifying agent → conversion into the chemical energy of clean syngas.

[0161] The entire process requires no external heat input and achieves self-sustaining reaction solely through internal energy transfer.

[0162] The matching control of thermal energy is as follows:

[0163] The adiabatic burner 3 monitors the combustion status in real time through an online oxygen analyzer. If the bed temperature of the water gas gasifier 2 is too low (the water gas reaction rate decreases), the amount of oxygen-enriched air is increased to raise the combustion temperature, allowing the flue gas to carry more heat energy. If the temperature of the water gas gasifier 2 is too high (there is a risk of slagging), the amount of oxygen-enriched air is reduced or the amount of fuel gas is finely adjusted to lower the flue gas temperature, ensuring that the reaction temperature of the water gas gasifier 2 is stable in the optimal range of 700-900℃.

[0164] The signal linkage between the downdraft gasifier 1 and the water gasifier 2 is as follows:

[0165] Temperature is detected by the three temperature measuring points of the downdraft gasifier 1 → PLC system → Adjust the rotation speed of the upper grate 37 (to control the amount of char produced) → Material level gauge 42 of the water gas gasifier 2 detects the material layer height → PLC system → Adjust the rotation speed of the lower grate 43 (to control the amount of ash discharged) to ensure that the char production rate of the downdraft gasifier 1 matches the material consumption rate of the water gas gasifier 2, and to avoid the material layer of the water gas gasifier 2 being too high or too low.

[0166] The signal linkage between the downdraft gasifier 1 and the adiabatic burner 3 is as follows:

[0167] The pressure sensor in the outlet jacket 12 of the downdraft gasifier 1 detects the crude gas pressure and then the PLC system adjusts the switching between the vent valve 4 and the burner gas inlet valve (opening the vent when the pressure is unstable during the start-up stage, and closing the vent and opening the burner valve after stabilization); at the same time, the oxygen online analyzer signal of the burner is transmitted to the PLC system to adjust the oxygen-enriched air supply to ensure that the combustion efficiency matches the crude gas supply of the downdraft gasifier 1.

[0168] In summary, the system maximizes the utilization of biomass energy and resources through the design of "internal circulation of water vapor" and "internal consumption of products," ultimately outputting high-purity clean syngas and recyclable ash residue, taking into account thermal efficiency, economy, and environmental protection.

[0169] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products, characterized in that, include: Downdraft gasifier (1) is used to gasify biomass fuel to produce combustible gas and charcoal; Water gas gasifier (2) for receiving charcoal from the downdraft gasifier (1); The insulated burner (3) is used to receive combustible gas from the downdraft gasifier (1), and can generate high-temperature flue gas and water vapor after combustion by mixing combustible gas with oxygen-enriched air. During operation, the high-temperature flue gas and water vapor generated by the adiabatic burner (3) are transported to the water gas gasification furnace (2). The high-temperature flue gas is used to provide reaction heat energy so that the water vapor reacts with the charcoal to produce water gas, and finally generates clean synthesis gas that is free of tar and rich in hydrogen and carbon monoxide. The downdraft gasifier (1) is provided with a central air inlet pipe (11), which is installed inside the material pile and runs horizontally through the downdraft gasifier (1). The central air inlet pipe (11) is connected to an external gas supply pipe. The central air inlet pipe (11) is located in the middle of the pipe section inside the downward suction gasifier (1) and has a downward funnel-shaped diffuser. Due to the umbrella effect, an olive-shaped cavity with a thicker middle and slightly thinner upper and lower ends can be formed below the diffuser to improve the uniformity of air distribution. A triangular guide cone is provided above the central air intake pipe (11). The guide cone is used to guide the biomass fuel to disperse and fall in all directions, thereby avoiding the formation of a bridging of biomass fuel on the central air intake pipe (11). The downdraft gasifier (1) has a ring of gas outlet jacket 12 on the furnace wall below the central gas inlet pipe (11), and the gas inlet of the gas outlet jacket (12) faces the bottom of the downdraft gasifier (1). The gas outlet of the downdraft gasifier (1) is located on its side and connected to the gas outlet jacket (12), and the position of the gas outlet of the downdraft gasifier (1) is higher than the gas inlet of the gas outlet jacket (12). During operation, oxygen-enriched air flows into the downdraft gasifier (1) through the central air inlet pipe (11), penetrates and acts on the material pile, and after completing the reaction with the material pile, the generated combustible gas diffuses to the edge, enters the gas outlet jacket (12), and is finally discharged from the higher gas outlet. The water gas gasifier (2) is provided with a central gas outlet pipe (21), which is installed inside the material pile and runs horizontally through the water gas gasifier (2).

2. The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products according to claim 1, characterized in that, The downdraft gasifier (1) is connected to the silo via a feed pipe (31). A valve (32) and a valve (33) are spaced apart on the feed pipe (31). There is an intermediate buffer section between the valve (32) and the valve (33). When feeding, the valve (32) and the valve (33) open and close at different times so as to transport the biomass fuel in the atmospheric pressure silo to the pressurized downdraft gasifier (1). And / or, the downdraft gasifier (1) is connected to the water gasifier (2) through a charcoal conveying pipe (34). A first gate valve (35) and a second gate valve (36) are provided at intervals on the charcoal conveying pipe (34). During operation, the first gate valve (35) and the second gate valve (36) open and close at different times so that charcoal enters the water gasifier (2) intermittently. And / or, the bottom of the downdraft gasifier (1) is provided with a rotatable upper grate (37), and there is a gap between the outer edge of the upper grate (37) and the inner wall of the downdraft gasifier (1). During operation, the upper grate (37) rotates so that charcoal can be transported downstream through the gap. And / or, the gas outlet of the downdraft gasifier (1) is connected to the vent (4) through a pipe. During the start-up stage, the gas composition generated by the downdraft gasifier (1) is unstable and is discharged through the vent (4). After the downdraft gasifier (1) is working stably, the valve connected to the vent (4) is closed and the valve connected to the insulated burner (3) is opened so that the combustible gas can enter the insulated burner (3).

3. The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products according to claim 1, characterized in that, The central air inlet pipe (11) and / or the guide cone are provided with cooling water channels to protect the metal parts and ensure their long-term structural safety by circulating cooling water.

4. The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products according to claim 1, characterized in that, A water jacket (38) is provided outside the section of the carbon conveying pipe (34) near the water gas gasifier (2). The water inlet of the water jacket (38) is connected to an external soft water supply device. When working, the soft water flowing through the water jacket (38) can cool the carbon conveying pipe (34). And / or, the biomass gasification system further includes a steam-water separator (5), and a water jacket (38) is provided outside the section of the carbon conveying pipe (34) near the water gasification furnace (2). The water outlet of the water jacket (38) is connected to the steam-water separator (5). The soft water after heat exchange can replenish the steam-water separator (5), and the steam-water separator (5) can deliver water vapor to the water gasification furnace (2). And / or, the biomass gasification system also includes a steam-water separator (5), and an auxiliary steam inlet is provided on the section of the carbon conveying pipe (34) near the water gas gasifier (2). The auxiliary steam inlet is connected to the steam outlet of the steam-water separator (5). Part of the steam output from the steam-water separator (5) enters the auxiliary steam inlet. The temperature of the steam is lower than that of the high-temperature flue gas, which can block the high-temperature radiation and hot air flow in the water gas gasifier (2).

5. The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products according to claim 1, characterized in that, The insulated burner (3) is equipped with an ignition device. During the start-up stage, the ignition device is connected to liquefied petroleum gas as fuel. After the biomass gas is ignited and the fire detection signal is received by the control system, the ignition device is shut off, and the combustible gas generated by the downdraft gasifier (1) is used as the main flare fuel of the insulated burner (3). And / or, the adiabatic burner (3) is equipped with an online oxygen analyzer, which monitors the oxygen concentration in the adiabatic burner (3) in real time and adjusts the amount of oxygen-enriched air entering the adiabatic burner (3) according to the heat energy demand of the water gas reaction in the water gas gasifier (2), so that the heat generation in the adiabatic burner (3) matches the heat consumption of the water gas gasifier (2).

6. The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products according to claim 1, characterized in that, The top of the water gas gasifier (2) is provided with a charcoal inlet, which is connected to the down-draft gasifier (1) through a charcoal conveying pipe (34). And / or, a water seal (41) is provided on one side of the water gas gasifier (2). The water seal (41) is used as a safety explosion relief port. When the pressure inside the water gas gasifier (2) exceeds the preset value, the water seal (41) automatically opens to release pressure, so as to ensure the safe operation of the water gas gasifier (2). And / or, a level gauge (42) is provided on one side of the water gasification furnace (2), the level gauge (42) being used to detect the material level inside the water gasification furnace (2); And / or, the bottom of the water gas gasifier (2) is provided with a rotatable lower grate (43), and there is a gap between the outer edge of the lower grate (43) and the inner wall of the water gas gasifier (2). During operation, the lower grate (43) rotates so that ash and slag can be discharged through the gap. And / or, the bottom of the water gas gasifier (2) is provided with an ash discharge pipe (44), and ash lock one (45) and ash lock two (46) are provided at intervals on the ash discharge pipe (44). When discharging ash, ash lock one (45) and ash lock two (46) are opened and closed at different times so as to transport the pressurized ash and slag in the water gas gasifier (2) to the outside of the furnace at atmospheric pressure.

7. The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products according to claim 1, characterized in that, The down-draft gasifier (1) is equipped with three layers of temperature measuring points: upper, middle and lower. The upper temperature measuring point corresponds to the preheating dry distillation zone, the middle temperature measuring point corresponds to the carbonization reaction zone, and the lower temperature measuring point corresponds to the carbon layer oxygen-deficient cooling zone. When the upper temperature measuring point detects that the temperature of the preheating dry distillation zone is close to or exceeds the temperature of the carbonization reaction zone, the upper grate (37) is accelerated to increase the amount of carbon produced. When the temperature of the oxygen-deficient cooling zone of the carbon layer is close to or exceeds the temperature of the carbonization reaction zone, the upper grate (37) is decelerated and rotated to reduce the amount of carbon produced. And / or, The water gas gasifier (2) is equipped with a level gauge (42) and a lower grate (43), and the level gauge (42) and the lower grate (43) are linked for control. When the level gauge (42) detects that the material layer height in the water gas gasifier (2) is higher than the preset value, the lower grate (43) is accelerated to rotate. When the level gauge (42) detects that the material layer height in the water gas gasifier (2) is lower than the preset value, the lower grate (43) is decelerated and rotated.

8. The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products according to claim 1, characterized in that, The central gas outlet pipe (21) is located in the middle of the pipe section inside the water gas gasifier (2) and has a downward-facing trumpet-shaped syngas inlet. When the induced draft fan is working, it will draw the syngas in the furnace. A horizontal model cavity can be formed below the syngas inlet. The shape of the cavity tends to be a horizontal, flat ellipsoid or model, which can counteract the gas flow deviation caused by the unevenness of the conical material layer, thereby improving the uniformity of gas collection. And / or, a triangular guide cone is provided above the central vent pipe (21), the guide cone is used to guide the charcoal to fall in all directions, thereby avoiding the charcoal from forming a pile-up bridge on the central vent pipe (21); And / or, the central air outlet pipe (21) and / or the guide cone are provided with cooling water channels to protect the metal parts by circulating cooling water and ensure their long-term structural safety.

9. The biomass gasification system based on dual-furnace linkage and internal digestion of intermediate products according to any one of claims 1-8, characterized in that, Also includes: Cyclone dust collector (6), connected to the exhaust port of the water gas gasifier (2), is used to separate solid particles in the syngas; The heat exchanger (7) is connected to the exhaust port of the cyclone dust collector (6) and is used to recover the heat energy carried by the synthesis gas. The steam-water separator (5) is connected to the heat exchanger (7). The heat exchanger (7) and the steam-water separator (5) form a circulation loop. The heat exchanger (7) recovers the heat energy in the syngas and transfers it to the soft water. The heated soft water enters the steam-water separator (5). The separated water vapor can flow back to the water gas gasifier (2) and participate in the water gas reaction.

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