System and method for directionally converting biomass into synthesis gas by full carbon through cascade energy supply and green hydrogen coupling

Abstract

The invention discloses a cascade energy supply and green hydrogen coupling biomass all-carbon directional conversion synthesis gas system and method, and belongs to the technical field of biomass energy conversion. The system comprises a first-stage gasification furnace, a second-stage gasification furnace, a gas-solid separator, an alkane reforming device, a reverse water-gas shift device and a water electrolysis device. The method comprises the following steps: pyrolyzing a biomass raw material and a catalyst in a primary gasifier (500-700 DEG C) to generate semicoke and tar-containing fuel gas; carrying out catalytic co-gasification on the semicoke and tar-containing fuel gas in a secondary gasifier (800-900 DEG C), and realizing tar cracking and CH4 reforming by using a catalyst to obtain crude synthesis gas; after being subjected to high-temperature dust removal, the crude synthesis gas sequentially passes through a self-heating alkane reforming device (CH4lt; 1%) and a reverse water-gas shift device, and finally synthesis gas with the H2 / CO ratio of 2: 1 is produced, so that the chemical application requirements of methanol, Fischer-Tropsch synthesis and the like are completely met, the high energy consumption bottleneck of a traditional process is broken, and full-life-cycle negative carbon emission is achieved.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy conversion technology, specifically relating to a system and method for the directional conversion of biomass full carbon into syngas through cascade energy supply and green hydrogen coupling. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Biomass gasification technology is a key link in the chemical conversion of renewable energy. Its core objective is to efficiently convert solid biomass resources into syngas (CO / H2 mixture), which can then be used for the synthesis of green liquid fuels such as methanol and jet fuel. However, current mainstream technologies face three common challenges: First, in terms of tar control, traditional single-stage gasifiers (such as fixed-bed or fluidized-bed gasifiers) have limited reaction temperature ranges (typically 800–900℃), making it difficult to effectively crack tar precursors, resulting in tar content in the crude syngas as high as 10–20 g / Nm³. 3 These heavy hydrocarbons are prone to condensation at low temperatures, clogging pipes and equipment, and reducing the proportion of effective gas components, severely restricting the stability of continuous system operation. Secondly, the carbon conversion pathway is inaccurate; the CO2 generation rate during gasification often reaches 20%–30%, while the residual amount of light alkanes such as CH4 exceeds 5%, resulting in a biomass carbon utilization rate of less than 70%, which not only wastes resources but also increases the burden on subsequent carbon capture. Thirdly, the system's energy utilization is unreasonable. In the process of biomass gasification to produce syngas, multiple reaction processes are coupled, making it difficult to rationally match energy levels, and the overall system energy efficiency is generally below 60%.

[0004] To address these challenges, the industry has explored various improvement solutions, but all have limitations. While staged gasification technologies (such as a combination of low-temperature pyrolysis and high-temperature gasification) can partially reduce tar production, they fail to completely eliminate alkane byproducts and have limited effectiveness in in-situ CO2 conversion. CO2 capture technologies (such as amine absorption) consume large amounts of steam, increasing system complexity and operating costs. While external hydrogen-supplying reforming schemes can adjust syngas composition, the hydrogen source largely relies on fossil fuel production, weakening the carbon-neutral advantage of biomass. Therefore, there is an urgent need to develop a system solution that deeply integrates thermodynamic staged gasification, deep tar cracking, in-situ CO2 / alkane conversion, and energy cascade utilization to achieve the directional conversion of all carbon from biomass into high-quality syngas with a specific ratio (e.g., H2 / CO = 2:1), while simultaneously achieving system energy self-sufficiency and efficient carbon utilization. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a system and method for the directional conversion of biomass to syngas through cascaded energy supply and green hydrogen coupling. This invention achieves efficient conversion of all components of biomass into syngas with H2 / CO = 2:1 through the synergistic design of energy cascaded cycling and directional catalytic conversion of biomass, and the system is energy self-sufficient.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: The first aspect of the present invention provides a system for the directional conversion of biomass carbon into syngas through cascaded energy supply and green hydrogen coupling, comprising a primary gasifier, a secondary gasifier, a gas-solid separator, an alkane reforming unit, and a reverse water gas conversion unit connected in sequence. The solid outlet of the gas-solid separator is connected to the primary gasifier, and the gas outlet of the gas-solid separator is connected to the alkane reforming unit.

[0007] In some embodiments of the present invention, a bed material conveying device is provided between the primary gasifier and the secondary gasifier.

[0008] In some embodiments of the present invention, a dust removal device is provided between the gas outlet of the gas-solid separator and the alkane reforming unit.

[0009] In some embodiments of the present invention, the system for cascaded energy supply and green hydrogen coupling of biomass full carbon directional conversion to syngas further includes a water electrolysis device, wherein the hydrogen and heat generated by the water electrolysis device are transported to a reverse water gas conversion device, and the oxygen generated is transported to a primary gasifier and a secondary gasifier.

[0010] Preferably, the water electrolysis device is powered by renewable energy.

[0011] In some embodiments of the present invention, the system for biomass full carbon directional conversion of syngas through cascaded energy supply and green hydrogen coupling further includes a waste heat recovery device, which recovers the heat energy of the syngas generated by the reverse water gas conversion device and produces steam.

[0012] A second aspect of the present invention provides a method for the directional conversion of biomass to syngas via cascaded energy supply and green hydrogen coupling, employing the system described in the first aspect, and comprising the following steps: Biomass feedstock and catalyst are sent to a primary gasifier for pyrolysis, producing semi-coke and tar-containing fuel gas. Semi-coke and tar-containing gas are fed to a secondary gasifier for gasification to obtain gasification products. The gasification products are separated by a gas-solid separator. The solids are returned to the primary gasifier for energy supply, while the crude syngas enters the low-quality alkane reforming unit to obtain syngas. The syngas then enters the reverse water gas conversion unit to obtain pure syngas with an H2 / CO molar ratio of 2:1.

[0013] In some embodiments of the present invention, the catalyst includes any one or more of limestone and dolomite.

[0014] In some embodiments of the present invention, the amount of catalyst used is 5% to 15% of the mass of the biomass feedstock.

[0015] In some embodiments of the present invention, the pyrolysis temperature of the primary gasifier is 500-700°C.

[0016] In some embodiments of the present invention, the furnace temperature of the primary gasifier is dynamically adjusted by the pure oxygen feed rate.

[0017] In some embodiments of the present invention, the furnace temperature of the secondary gasifier is 800-900°C.

[0018] In some embodiments of the present invention, semi-coke and tar-containing gas are fed to a secondary gasifier and co-gasified under pure oxygen and steam conditions to obtain gasification products. The gasification products include crude syngas and solid bed material. The gasification products are separated by a gas-solid separator, and the gas enters the alkane reforming unit after dust removal. The solid bed material is returned to the primary gasifier for energy supply.

[0019] In some embodiments of the present invention, the crude synthesis gas comprises carbon monoxide, hydrogen, carbon dioxide, and alkanes, with an alkane content of <5%.

[0020] In some embodiments of the present invention, hydrogen and pure oxygen are provided by a water electrolysis device.

[0021] In some embodiments of the present invention, in an alkane reforming unit, crude syngas uses its own sensible heat to drive the alkane reforming reaction, and after the reaction, the alkane content in the resulting syngas drops to below 1%.

[0022] In some embodiments of the present invention, hydrogen is supplied to the reverse water gas conversion device using an electrolysis water device, and the hydrogen flow rate is controlled according to the H2 / CO molar ratio in the product being 2:1. The sensible heat of the syngas or the waste heat of the electrolysis water device drives the hydrogen to react with carbon dioxide to obtain pure syngas with an H2 / CO ratio of 2:1.

[0023] The beneficial effects of this invention are as follows: The system and method for the directional conversion of biomass to syngas through cascaded energy supply and green hydrogen coupling provided by this invention achieves significant improvements in efficiency, quality, and energy utilization of syngas through the construction of a refined structure that integrates staged gasification, material recycling, cascaded energy supply, and green hydrogen coupling.

[0024] The system employs a primary gasifier for low-to-medium temperature pyrolysis, initially decomposing biomass and inhibiting tar formation, followed by high-temperature gasification in a secondary gasifier. This cascade design precisely matches the reaction temperature range with the material conversion stage, effectively promoting deep tar cracking. A gas-solid separator returns the high-temperature bed material to the primary gasifier for recycling, significantly improving carbon conversion efficiency. In the alkane reforming unit, water vapor reacts with light alkanes such as methane and a small amount of residual tar in the gasification products, generating CO and H2, eliminating alkane components from the syngas. In the reverse water-gas shift unit, green hydrogen reacts with CO2 generated during gasification, producing CO and water, directly reducing the CO2 content in the syngas, achieving directional conversion and efficient utilization of all carbon. This coupling mechanism enables full carbon conversion and utilization, significantly reducing tar, CH4, and CO2 content, increasing the proportion of effective components (CO+H2) in the syngas to a higher level, and stabilizing the H2 / CO ratio in the syngas at approximately 2:1, meeting the stringent requirements of downstream chemical synthesis.

[0025] The energy flow between the various stages of the system is effectively integrated. First, the sensible heat of the high-temperature bed material (800–900℃) generated by the secondary gasifier directly drives the low-temperature pyrolysis reaction (500–700℃) in the primary gasifier, reducing the need for external heating. Second, the purified high-temperature crude syngas (>800℃), after exiting the secondary gasifier, uses its own high-quality sensible heat to drive strongly endothermic processes such as alkane reforming and reverse water-gas shift reaction, completely eliminating the need for supplementary combustion energy consumption and avoiding the waste of high-temperature heat in traditional technologies. The waste heat from the water electrolysis unit drives the reverse water-gas shift reaction, and the sensible heat of the syngas is used to raise the temperature of the SOEC inlet material to 700℃ through three-stage preheating, significantly improving electrolysis efficiency. The waste heat recovery unit recovers the waste heat of the syngas below 300℃, producing 0.5 MPa saturated steam for the system's own use, achieving 100% steam self-sufficiency. This energy cascade utilization mode forms internal heat coupling within the system, reducing dependence on external supplementary energy and significantly improving the overall energy efficiency of the system. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0027] Figure 1 This is a schematic diagram of the system for the directional conversion of biomass to syngas through cascaded energy supply and green hydrogen coupling in Embodiment 1 of the present invention.

[0028] The components include: 1. Primary gasifier; 2. Secondary gasifier; 3. Bed material conveying device; 4. Gas-solid separator; 5. Dust removal device; 6. Alkane reforming device; 7. Water electrolysis device; and 8. Reverse water gas conversion device. Detailed Implementation

[0029] The core of this invention is to provide a system and method for the directional conversion of biomass into syngas through cascaded energy supply and green hydrogen coupling, aiming to solve the technical bottlenecks of high tar content, low carbon utilization and high external energy consumption in traditional gasification processes.

[0030] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This invention provides a system for the directional conversion of biomass to syngas through cascaded energy supply and green hydrogen coupling. Please refer to [link / reference]. Figure 1 The system includes a primary gasifier 1, a secondary gasifier 2, a gas-solid separator 4, an alkane reforming unit 6, and a reverse water gas conversion unit 8 connected in sequence. The solid outlet of the gas-solid separator 4 is connected to the primary gasifier 1, and the gas outlet of the gas-solid separator 4 is connected to the alkane reforming unit 6.

[0031] The core of the system consists of a primary gasifier 1, a secondary gasifier 2, a gas-solid separator 4, an alkane reforming unit 6, and a reverse water gas conversion unit 8. Through the synergistic design of energy cascade circulation and full carbon directional catalytic conversion, the system achieves efficient conversion of all components of biomass into syngas with an H2 / CO ratio of 2:1, and the system is energy self-sufficient.

[0032] The primary gasifier 1 is used for pyrolysis of biomass feedstock, producing semi-coke and tar-containing fuel gas. The secondary gasifier 2 is used for high-temperature catalytic gasification, where the semi-coke and tar-containing fuel gas from the primary gasifier 1 undergo a triple transformation: semi-coke is gasified to generate syngas; tar is cracked into smaller molecules under the action of semi-coke and a Ca-based catalyst; and alkanes such as CH4 (i.e., smaller molecules) are catalytically reformed into syngas. The crude syngas obtained in the secondary gasifier 2 contains CO, H2, CO2, and CH4, with a CH4 content of <5%. A gas-solid separator 4 separates the products from the secondary gasifier 2. The high-temperature bed material from the secondary gasifier 2 is returned to the primary gasifier 1 for energy supply, achieving material recycling. The crude syngas enters the alkane reforming unit 6. This completes the first stage of energy utilization: the high-temperature bed material from the secondary gasifier 2 directly drives the pyrolysis reaction in the primary gasifier 1, eliminating the need for external heating for the primary gasifier 1.

[0033] Alkane reforming unit 6 is used to reduce the methane content in crude syngas. When crude syngas enters reforming unit 6, the sensible heat of the crude syngas drives the reforming reaction of alkanes such as methane / ethane with water vapor at the catalytic interface, reducing the alkane content in the crude syngas to below 1% and simultaneously increasing the hydrogen concentration.

[0034] The reverse-flow gas conversion unit 8 is used to directionally convert carbon dioxide in crude syngas into carbon monoxide, achieving near-zero CO2 emissions, and fine-tuning the syngas to obtain pure syngas with H2 / CO = 2:1, which can be directly used for methanol synthesis or Fischer-Tropsch synthesis.

[0035] In some specific embodiments, the primary gasifier 1 is preferably a fluidized bed gasifier. To enhance gas-solid contact and achieve high-temperature catalytic gasification, the secondary gasifier 2 is preferably a circulating fluidized bed reactor.

[0036] In some specific embodiments, a bed material conveying device 3 is provided between the primary gasifier 1 and the secondary gasifier 2. The bed material conveying device is used to convey the semi-coke produced by the primary gasifier 1 to the secondary gasifier 2.

[0037] In some specific embodiments, a dust removal device 5 is provided between the gas outlet of the gas-solid separator 4 and the alkane reforming unit 6.

[0038] Understandably, dust removal device 5 is used to remove dust from the crude syngas. Because the temperature of the crude syngas is as high as 800-900℃, dust removal device 5 is a high-temperature dust removal device.

[0039] In some specific embodiments, the system for cascaded energy supply and green hydrogen coupling of biomass full carbon directional conversion to syngas also includes a water electrolysis device 7. The hydrogen and heat generated by the water electrolysis device 7 are transported to the reverse water gas conversion device 8, and the generated oxygen is transported to the primary gasifier 1 and the secondary gasifier 2.

[0040] In some specific embodiments, the water electrolysis device 7 is powered by renewable energy. Powered by renewable energy sources such as photovoltaic / wind power, the water electrolysis device 7 provides pure oxygen (for primary and secondary gasification) and hydrogen (for the CO2 conversion reaction), eliminating dependence on fossil fuels.

[0041] In some specific embodiments, the system for biomass full carbon directional conversion of syngas through cascaded energy supply and green hydrogen coupling also includes a waste heat recovery device, which recovers the heat energy of the syngas generated by the reverse water gas conversion device 8 and produces steam.

[0042] Understandably, waste heat recovery devices can function as waste heat boilers, recovering heat from the cooling process of the synthesizer and producing steam for the system's own use, further reducing energy consumption.

[0043] In some specific embodiments, the raw materials are added to the primary gasifier 1, where they are gasified / pyrolyzed to produce semi-coke and tar-containing fuel gas. The tar-containing fuel gas exits from the top of the primary gasifier 1 and enters the secondary gasifier 2. The semi-coke enters the secondary gasifier 2 via the bed conveyor 3. O2 and steam are introduced into the secondary gasifier 2 to co-gasify with the semi-coke and tar-containing fuel gas to prepare crude syngas. The gasification products from the secondary gasifier 2 enter the gas-solid separator 4 for gas-solid separation. The bed material enters the primary gasifier 1, and the crude syngas enters the dust removal device 5. After purification by the dust removal device 5, the crude syngas enters the alkane reforming unit 6, where the light alkanes in the crude syngas are reformed with steam to produce CO and H2. The crude syngas leaving the alkane reforming unit 6 is mixed with H2 from the water electrolysis unit 7 and then enters the reverse water gas conversion unit 8, where CO2 and H2 in the crude syngas undergo a reverse water gas reaction to produce CO and H2. The syngas leaving the reverse water gas conversion unit 8 mainly consists of CO and H2. The water electrolysis unit 7 provides O2 to the primary gasifier 1 and the secondary gasifier 2, and H2 to the reverse water gas conversion unit 8.

[0044] This invention also provides a method for the directional conversion of biomass to syngas using a cascaded energy supply and green hydrogen coupling system, comprising the following steps: Biomass feedstock and catalyst are fed to primary gasifier 1 for pyrolysis, producing semi-coke and tar-containing fuel gas; Semi-coke and tar-containing gas are fed to secondary gasifier 2 for gasification to obtain gasification products; The gasification products are separated by the gas-solid separator 4. The solids are returned to the primary gasifier 1 for energy supply. The crude syngas enters the alkane reforming unit 6 and the countercurrent gas conversion unit 8 in sequence to obtain pure syngas with an H2 / CO ratio of 2:1.

[0045] In some specific embodiments, the biomass material can be a common renewable biomass raw material, specifically including one or more of corn stalks, sorghum stalks, and poplar wood. In some embodiments of the present invention, the biomass material is a dried biomass material.

[0046] In some specific embodiments, the catalyst includes, but is not limited to, any one or more of limestone and dolomite. The catalyst initially catalyzes the cracking of tar in the primary gasifier 1, laying the foundation for secondary gasification.

[0047] In the two-stage gasification process of primary gasifier 1 and secondary gasifier 2, limestone / dolomite (CaO / CaCO3) catalytically cracks the tar stepwise, greatly improving the tar conversion rate.

[0048] In some specific embodiments, the amount of catalyst used is 5% to 15% of the biomass feedstock mass.

[0049] In some specific embodiments, the pyrolysis temperature of the primary gasifier is 500-700℃, specifically 500℃, 550℃, 600℃, 650℃, 700℃, or any range of two values.

[0050] In some specific embodiments, the furnace temperature of the primary gasifier is dynamically adjusted by the pure oxygen flow rate to ensure pyrolysis stability.

[0051] In some specific embodiments, the furnace temperature of the secondary gasifier is 800-900℃, specifically 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, etc., or any range of two values.

[0052] In some specific embodiments, semi-coke and tar-containing fuel gas are fed to a secondary gasifier 2, where they are co-gasified under pure oxygen and steam conditions to obtain gasification products. The steam in the secondary gasifier 2 plays a dual role: firstly, it enhances the semi-coke gasification by intensifying the reaction C + 2H₂O → CO₂ + 2H₂, compensating for the limitations of the Boudouard reaction (C + CO₂ → 2CO) at 800-900℃; secondly, it drives the reforming reaction of alkanes such as CH₄ (CH₄ + H₂O → CO + 3H₂). The CaO / CaCO₃ catalyst generated from the decomposition of limestone or dolomite circulates between the two gasifiers, promoting deep catalytic cracking of tar and efficient catalytic reforming of alkanes, producing crude syngas.

[0053] The gasification products include crude syngas and solid bed material. The gasification products are separated by gas-solid separator 4. After dust removal, the crude syngas enters alkane reforming unit 6 to provide raw materials and energy for downstream alkane reforming and CO2 reverse water-gas conversion reaction. The solid bed material is returned to primary gasifier 1 for energy supply.

[0054] In some specific embodiments, the crude syngas comprises carbon monoxide, hydrogen, carbon dioxide, and alkanes, with an alkane content of <5%.

[0055] In some specific embodiments, the pure oxygen supplied to the secondary gasifier 2 is provided by the water electrolysis device 7, and the water vapor supplied to the secondary gasifier 2 is provided by the waste heat recovery device.

[0056] In some specific embodiments, in the alkane reforming unit 6, the crude syngas uses its own sensible heat to drive the alkane reforming reaction. After the reaction, the alkane content in the resulting syngas drops to below 1%, and the H2 concentration increases simultaneously.

[0057] Specifically, the purified crude syngas is driven by its own sensible heat (780-820℃) in the alkane reforming unit 6: alkanes such as CH4 and C2H6 undergo catalytic reforming with water vapor to be converted into CO and H2; the CH4 concentration at the outlet of the alkane reforming unit 6 can be monitored in real time, and the amount of water vapor added to the secondary gasifier 2 can be dynamically adjusted according to the concentration to ensure that the CH4 residue is reduced to below 0.5%.

[0058] In some specific embodiments, hydrogen is supplied to the reverse water-gas conversion device 8 using the water electrolysis device 7. The amount of hydrogen introduced is controlled according to the H2 / CO molar ratio in the product being 2:1. The sensible heat of the dealkane synthesis gas or the residual heat of the water electrolysis device 7 drives the hydrogen to react with carbon dioxide (CO2+H2→CO+H2O) to obtain pure synthesis gas with an H2 / CO ratio of 2:1.

[0059] In some specific embodiments, the pyrolysis reaction in the primary gasifier 1, the gasification reaction in the secondary gasifier 2, the reforming reaction in the alkane reforming unit 6, and the conversion reaction in the reverse water gas conversion unit 8 all need to be carried out at high temperatures. This is because, firstly, the thermodynamic equilibrium is more likely to shift towards the desired direction at high temperatures, and secondly, the kinetics of the reaction are more intense at high temperatures. This invention completely breaks through the high energy consumption bottleneck of traditional processes by constructing a four-level energy transfer closed loop: First, the sensible heat of the high-temperature bed material (800-900℃) generated by the secondary gasifier 2 directly drives the low-temperature pyrolysis reaction (500-700℃) in the primary gasifier 1, reducing the external heating demand; Second, the purified crude syngas (800-900℃) supplies the alkane reforming reaction with its own sensible heat, completely eliminating the need for supplementary combustion energy consumption; Third, the waste heat (750-800℃) of the integrated water electrolysis device 7 drives the reverse water-gas conversion reaction, and the sensible heat of the syngas is used to raise the temperature of the inlet material of the water electrolysis device 7 to 700℃ through three-stage preheating, significantly improving the electrolysis efficiency; Finally, the waste heat of the syngas below 300℃ is recovered through the waste heat boiler to produce 0.5 MPa saturated steam for the system's own use, achieving 100% steam self-sufficiency. This energy cascade architecture enables the system's overall energy efficiency to exceed 80%, which is more than 20% higher than that of traditional gasification processes (≤60%), and reduces the carbon emission intensity per unit energy consumption to -50 kg CO2 / GJ.

[0060] This invention achieves precise component control through a synergistic mechanism of Ca-based catalysis, steam efficiency enhancement, and electrolysis hydrogen supply: In the two-stage gasification process, limestone / dolomite (CaO / CaCO3) catalytically cracks tar stepwise, achieving a tar conversion rate exceeding 98% (outlet tar content ≤0.15g / Nm³). 3 Compared to traditional processes (>10g / Nm), 3This process improves efficiency by two orders of magnitude; it enhances semi-coke gasification efficiency and strengthens CH4 catalytic reforming (conversion rate >90%) through steam regulation, and reduces CH4 residual pressure to below 0.5% (compared to 5-8% in traditional processes) by combining a self-heating alkane reforming unit; based on this, the water electrolysis unit 7 provides high-purity hydrogen for precise injection into the reverse water-gas conversion unit 8, driving efficient CO2 conversion, ultimately producing syngas with an H2 / CO ratio of 2.00 ± 0.05. This regulation pathway results in an effective component (CO+H2) content of over 98% in the syngas and a green carbon conversion rate of over 96%, an improvement of over 30% compared to the ≤70% of traditional processes, fully meeting the requirements of chemical applications such as methanol and Fischer-Tropsch synthesis.

[0061] This invention integrates a dual carbon reduction pathway: renewable energy supply and in-situ carbon conversion. The water electrolysis unit 7 is directly driven by photovoltaic / wind power, achieving zero carbon emissions in the hydrogen production process. Biomass carbon undergoes a four-stage directional conversion process: pyrolysis → gasification → reforming → shift conversion, achieving a green carbon utilization rate exceeding 95%. CO2 in the crude syngas is converted into effective syngas components through a reverse water-gas shift reaction. Simultaneously, the gasification ash is processed into potassium phosphate fertilizer (resource utilization rate >90%), ultimately achieving a negative carbon intensity throughout the entire life cycle.

[0062] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0063] Example 1 This embodiment provides a system for the directional conversion of biomass to syngas through cascaded energy supply and green hydrogen coupling, such as... Figure 1 As shown, it includes a primary gasifier 1, a secondary gasifier 2, a gas-solid separator 4, a dust removal device 5, an alkane reforming device 6, and a reverse water gas conversion device 8 connected in sequence.

[0064] The solid outlet of the gas-solid separator 4 is connected to the primary gasifier 1, and the gas outlet of the gas-solid separator 4 is connected to the dust removal device 5. A bed material conveying device for conveying semi-coke is provided between the primary gasifier 1 and the secondary gasifier 2.

[0065] It also includes a water electrolysis unit 7, whose hydrogen gas is mixed with the dealkane synthesis gas produced by the alkane reforming unit 6 and then enters the reverse water gas conversion unit 8, and the oxygen produced is supplied to the secondary gasifier 2.

[0066] It also includes a waste heat recovery device to recover the heat from the synthesizer produced by the reverse water gas conversion device 8 and produce steam for the system's own use.

[0067] Example 2 This embodiment provides a method for the directional conversion of biomass into syngas via cascaded energy supply and green hydrogen coupling, using the system of Example 1, processing 100 tons of corn stalks daily. The primary gasifier 1 has a volume of 15m³. 3 The system includes a primary fluidized bed gasifier (temperature control range 500-700℃), a secondary gasifier 2 (2.5m diameter circulating fluidized bed secondary gasifier, operating temperature 800-900℃), and an electrolysis water unit 7 (oxygen production 1300 Nm³). 3 / h and hydrogen production 2600 Nm 3 The PEM electrolyzer (with an 80MW photovoltaic power station) has a capacity of 10000h / h, and the waste heat recovery device is a steam boiler with a waste heat recovery temperature range of 300-600℃.

[0068] The biomass feedstock consists of corn stalks with a dry basis moisture content of ≤15% and a crushed particle size of <5 mm, and a carbon content of 45.2 wt%. Limestone is added as a catalyst at 10% of the biomass mass to the primary gasifier 1.

[0069] The process flow is as follows: After the corn stalk and limestone mixture enters the primary gasifier 1, the sensible heat required for pyrolysis is provided by the 850℃ high-temperature bed material from the gas-solid separator 4, and the furnace temperature is stably maintained at 650±20℃. The pure oxygen feed rate is dynamically adjusted using a PID algorithm (oxygen is reduced by 10% when the temperature is above 670℃ and increased by 15% when the temperature is below 630℃), ensuring a stable and controllable pyrolysis process. This stage produces semi-coke (32% mass yield) and tar-containing fuel gas (initial tar content 8.5 g / Nm³). The semi-coke and tar-containing fuel gas enter the secondary gasifier 2 via the bed material conveyor 3, simultaneously fed with steam (0.3 tons / hour) and pure oxygen prepared by the water electrolysis device 7. Under 800℃ conditions, the CaO / CaCO3 catalyst generated from limestone decomposition achieves deep tar cracking (conversion rate 98.3%, outlet tar content ≤0.15 g / Nm³). 3 The gas is then reformed with CH4 (conversion rate over 80%, with CH4 residue in the crude syngas at 3.8%). The crude syngas produced by the secondary gasification consists of: CO (37.2%), H2 (28.7%), CO2 (22.1%), CH4 (3.8%), and trace impurities.

[0070] The high-temperature bed material is returned to the primary gasifier 1 via gas-solid separator 4; the crude syngas is purified by a ceramic filter high-temperature dust collector 5 (dust removal efficiency 99.9%), maintaining a temperature of 820℃ before entering subsequent units. After purification, the syngas first enters the alkane reforming unit 6, where its own sensible heat drives the reaction of CH4 with water vapor at 780℃, further reducing the CH4 content to below 0.5%. Subsequently, the syngas reacts with hydrogen (flow rate 2600 Nm³) supplied by the water electrolysis unit 7. 3The mixture ( / h) is fed into the reverse water-gas shift unit 8, where CO2 reacts with H2 under the action of a catalyst to generate CO (CO2 conversion rate 83.6%). The final composition of the syngas is adjusted to H2 (66.2%), CO (33.1%), CO2 (0.5%) and other trace components, with the H2 / CO molar ratio remaining stable at 2.00±0.05, meeting the feedstock requirements for methanol synthesis or Fischer-Tropsch synthesis.

[0071] The energy closed loop is achieved through a triple design: the photovoltaic power station provides an average of 6.2 hours of power per day to drive the electrolyzer; the waste heat boiler recovers the heat energy from the syngas cooling process and produces 1.2 tons / hour of 0.5 MPa saturated steam for the system's own use, achieving a steam self-sufficiency rate of 100%.

[0072] Overall performance indicators: The syngas yield of this system is 2.42 Nm³. 3 / kg straw, compared to traditional processing (1.45 Nm 3 The carbon conversion rate increased by 60% (per kg); the carbon conversion rate reached 96.3%, significantly higher than the industry average of 68%. The unit syngas cost decreased to US$0.115 / Nm³. 3 (Traditional process costs $0.17 / Nm) 3 When high-quality syngas with an H2 / CO ratio of 2:1 is used directly in Fischer-Tropsch synthesis, its economic value is 40% higher than that of ordinary syngas, and the investment payback period can be shortened to 5.3 years under large-scale operation.

[0073] This embodiment confirms that the technical solution of the present invention achieves three major breakthroughs in a hundred-ton-level industrial system: energy self-sufficiency, carbon-directed conversion (96.3% carbon conversion rate + precise H2 / CO control), and economic feasibility (cost reduction of 35%), providing a replicable technical paradigm for the large-scale application of biomass energy.

[0074] Example 3 This embodiment provides a method for the directional conversion of biomass into syngas via cascaded energy supply and green hydrogen coupling, using the system of Example 1, processing 100 tons of corn stalks daily. The primary gasifier 1 has a volume of 15 m³. 3 The primary fluidized bed gasifier (temperature control range 500-700℃), the secondary gasifier 2 is a circulating fluidized bed secondary gasifier with a diameter of 2.5 m (operating temperature 800-900℃), the water electrolysis device 7 is a solid oxide electrolyzer system (SOEC, designed electrolysis temperature 800℃, with a 70 MW photovoltaic power station as the main driving energy), and the waste heat recovery device is a steam boiler with a waste heat recovery temperature range of 300-600℃.

[0075] The biomass feedstock consists of corn stalks with a dry basis moisture content of ≤15% and a crushed particle size of <5 mm, containing 45.2 wt% carbon. Limestone is added as a catalyst at 6% of the biomass mass to the primary gasifier 1. The SOEC system provides pure oxygen (for the secondary gasifier 2) and hydrogen (for the reverse water gas conversion unit 8), and integrates an innovative heat recovery module to achieve energy cascade optimization.

[0076] The process flow is as follows: A mixture of corn stalks and limestone enters the primary gasifier 1, where a low-temperature pyrolysis reaction occurs within a temperature range of 650±20℃. Energy is directly supplied by the sensible heat from the high-temperature bed material (870℃) in the gas-solid separator 4, ensuring efficient heat transfer. Pyrolysis stability is maintained by dynamically adjusting the pure oxygen flow rate (based on a PID algorithm responding to temperature fluctuations), producing semi-coke (32% mass yield) and tar-containing fuel gas (initial tar content 8.5 g / Nm³). 3 The semi-coke, along with the tar-containing gas, enters the secondary gasifier 2 simultaneously via the bed material conveying device 2. At 900℃, pure oxygen and steam (0.3 tons / hour) prepared by the SOEC system are introduced to achieve semi-coke gasification and tar catalytic cracking: the CaO / CaCO3 catalyst generated from limestone decomposition promotes a tar conversion rate exceeding 95% and a CH4 reforming rate exceeding 80%, producing crude syngas (composition: CO 36.2%, H2 28.7%, CO2 22.1%, CH4 4.8%). The high-temperature bed material is returned to the primary gasifier 1 via the gas-solid separator 4 for energy recycling, while the crude syngas is purified by the high-temperature dust removal device 5 (dust removal efficiency 99.9%, temperature 870℃) before entering the downstream unit.

[0077] After purification, the syngas first enters the low-quality alkane reforming unit 6, where its own sensible heat (870℃) drives the reaction of CH4 with water vapor, reducing its content to below 0.5%. Subsequently, the syngas enters the reverse water gas shift reactor 8. The core innovation at this stage lies in the optimization of the heat supply method: the solid oxide electrolyzer (SOEC) generates high-temperature waste heat (approximately 750-800℃) during operation, which is directly transferred to the reverse water gas shift reactor via an integrated heat exchanger to supply the energy required for the reverse water gas shift reaction, ensuring the supply of CO2 and hydrogen (flow rate 2600 Nm³) from the SOEC. 3 The reaction is highly efficient (CO2 conversion rate 83.6%), and finally produces pure syngas with H2 / CO = 2.00 ± 0.05 (composition: H2 66.2%, CO 33.1%, CO2 0.5%).

[0078] To maximize energy efficiency, this embodiment enhances the SOEC inlet feedstock preheating mechanism, employing a three-stage sequential heat recovery design: First, the waste heat of the final product syngas (whose temperature drops below 300°C after leaving the reverse-flow gas shift reactor) preheats the SOEC inlet water feedstock (initial temperature 25°C) through a waste heat boiler recovery system, producing 0.5 MPa saturated steam (150°C); second, the sensible heat of the syngas (780-820°C) before the reverse-flow gas shift reactor further preheats the SOEC inlet water feedstock (through a series heat exchanger), raising the 150°C saturated steam to 400°C; finally, a portion of the high-temperature crude syngas (900°C, approximately 10% of the total) is diverted from the secondary gasifier 2 to finally preheat the SOEC inlet steam to 700°C (meeting the SOEC operating temperature requirements), after which the diverted syngas is recycled back to the bottom of the secondary gasifier 2. This preheating sequence significantly improves the SOEC electrochemical efficiency, reduces external energy demand, and maintains system thermal balance.

[0079] The energy closed loop is achieved through photovoltaic-driven SOEC (providing an average of 6.2 hours of power per day), self-production of waste heat steam (1.2 tons / hour of 0.5 MPa saturated steam from the waste heat boiler for the gasification system), and cascade heat recycling. The system's syngas yield is increased to 2.3 Nm³. 3 / kg straw (55% improvement over traditional processes), carbon conversion rate up to 97%, and unit syngas cost reduced to $0.10 / Nm³ 3 (A 40% reduction). Precise control of the H2 / CO ratio supports high-end chemical applications, shortening the investment payback period to 5 years.

[0080] This embodiment demonstrates that by integrating a solid oxide electrolyzer and optimizing the heat recovery path, the system achieves further breakthroughs in energy self-sufficiency, directional carbon conversion, and economic efficiency, providing an efficient and low-carbon solution for the large-scale application of biomass energy.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for the directional conversion of biomass to syngas through cascaded energy supply and green hydrogen coupling, characterized in that, It includes a primary gasifier, a secondary gasifier, a gas-solid separator, an alkane reforming unit, and a reverse water gas conversion unit connected in sequence; The solid outlet of the gas-solid separator is connected to the primary gasifier, and the gas outlet of the gas-solid separator is connected to the alkane reforming unit.

2. The system as described in claim 1, characterized in that, A bed material conveying device is provided between the primary gasifier and the secondary gasifier; Preferably, a dust removal device is provided between the gas outlet of the gas-solid separator and the alkane reforming unit.

3. The system as described in claim 1, characterized in that, It also includes a water electrolysis device, wherein the hydrogen and heat generated by the water electrolysis device are transported to the reverse water gas conversion device, and the oxygen generated is transported to the primary gasifier and the secondary gasifier; Preferably, the water electrolysis device is powered by renewable energy.

4. The system as described in claim 1, characterized in that, It also includes a waste heat recovery device, which recovers the heat energy of the syngas generated by the reverse water gas conversion device and produces steam.

5. A method for the directional conversion of biomass to syngas through cascaded energy supply and green hydrogen coupling, characterized in that, The system according to any one of claims 1-4 includes the following steps: Biomass feedstock and catalyst are sent to a primary gasifier for pyrolysis, producing semi-coke and tar-containing fuel gas. Semi-coke and tar-containing gas are fed to a secondary gasifier for gasification to obtain gasification products. The gasification products are separated by a gas-solid separator. The solids are returned to the primary gasifier for energy supply, while the crude syngas enters the alkane reforming unit and the reverse water gas conversion unit in sequence to obtain pure syngas with an H2 / CO molar ratio of 2:

1.

6. The method as described in claim 5, characterized in that, The catalyst includes any one or more of limestone and dolomite; Preferably, the amount of catalyst used is 5% to 15% of the mass of the biomass feedstock; Preferably, the pyrolysis temperature of the primary gasifier is 500-700℃; Preferably, the furnace temperature of the primary gasifier is dynamically adjusted by the pure oxygen feed rate.

7. The method as described in claim 5, characterized in that, The furnace temperature of the secondary gasifier is 800-900℃.

8. The method as described in claim 5, characterized in that, Semi-coke and tar-containing fuel gas are fed to a secondary gasifier and co-gasified under pure oxygen and steam conditions to obtain gasification products; The gasification products include crude syngas and solid bed material. The gasification products are separated by a gas-solid separator. After dust removal, the crude syngas enters the alkane reforming unit, and the solid bed material is returned to the primary gasifier for energy supply. Preferably, the crude syngas comprises carbon monoxide, hydrogen, carbon dioxide, and alkanes, with an alkane content of <5%. Preferably, hydrogen and pure oxygen are provided by a water electrolysis device.

9. The method as described in claim 8, characterized in that, In an alkane reforming unit, crude syngas uses its own sensible heat to drive the alkane reforming reaction. After the reaction, the alkane content in the resulting syngas drops to below 1%.

10. The method as described in claim 5, characterized in that, Hydrogen is supplied to the reverse water gas conversion unit using an electrolysis water device. The amount of hydrogen introduced is controlled according to the H2 / CO molar ratio in the product being 2:

1. The sensible heat of the syngas or the waste heat of the electrolysis water device drives the reaction of hydrogen and carbon dioxide to obtain pure syngas with an H2 / CO ratio of 2:1.

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