System for efficiently preparing green methanol by coupling biomass gasification gas and green hydrogen

Abstract

The application discloses a system for efficiently preparing green methanol by coupling biomass gasification and green hydrogen, wherein the system is sequentially connected by pipelines with a biomass pretreatment unit, a low-tar hydrogen-rich gasification unit, a multi-stage gradient purification unit, a green hydrogen blending unit, a methanol synthesis unit and a methanol rectification unit. The biomass pretreatment unit completes the homogenization modification and drying of raw materials; the low-tar hydrogen-rich gasification unit outputs low-impurity crude synthesis gas; the multi-stage gradient purification unit removes impurities and controls components of the crude synthesis gas step by step to obtain high-quality synthesis gas; the green hydrogen blending unit accurately adjusts the hydrogen-carbon ratio to prepare raw gas suitable for catalytic reaction; the methanol synthesis unit outputs crude methanol, and the methanol rectification unit refines to obtain high-purity methanol products. The system is provided with a waste heat reuse loop and a purge gas circulation pipeline, low-temperature waste heat of rectification is transported to the pretreatment unit, and synthesis process purge gas is returned to the gasification unit for reuse. The application can stably output green methanol at low cost, for a long period and on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of biomass clean energy conversion technology, specifically to a system for the efficient production of green methanol from biomass gasification gas coupled with green hydrogen. Background Technology

[0002] With the advancement of green transformation in the chemical industry, low-emission, low-carbon, and renewable fuel and chemical raw material substitution technologies have become key research and development directions. Methanol, as a basic chemical raw material and liquid energy storage medium, is widely used in many industrial scenarios such as fine chemical preparation, new energy storage, and marine fuel substitution. Currently, conventional methanol products are mostly produced from fossil fuels such as coal and natural gas, resulting in high carbon emission intensity and large energy consumption in the production process. This high-carbon production model is no longer suitable for current green production and low-carbon access requirements. Compared with traditional fossil-based methanol, green methanol produced using renewable raw materials has the advantages of carbon cycle neutrality, low pollutant emissions, and large-scale production, making it a core carrier for achieving deep decarbonization in the industrial sector. Agricultural and forestry biomass includes waste such as straw, sawdust, rice husks, and forestry residues. With abundant and recyclable resources, using biomass gasification to produce syngas, and then catalytically synthesizing green methanol, is currently the mainstream process route for high-value resource utilization of agricultural and forestry waste, possessing good industrial adaptability and application prospects.

[0003] Currently, the biomass-to-methanol processes used in industrial applications employ biomass feedstocks rich in alkali metals such as potassium and sodium. During the high-temperature gasification reaction, these feedstocks are prone to slagging and corrosion within the furnace, significantly shortening the continuous operation cycle of the gasification equipment and leading to frequent start-ups and shutdowns, making it difficult to meet the requirements of long-term continuous industrial production. Furthermore, the crude syngas obtained from biomass gasification has a complex composition, containing impurities such as tar, dust, and trace amounts of sulfides. Conventional purification processes are insufficient in achieving the required purification precision, and residual impurities can easily poison the methanol synthesis catalyst and cause activity degradation, significantly increasing equipment maintenance and catalyst replacement costs. In addition, the fixed hydrogen-to-carbon monoxide ratio in the biomass-produced syngas cannot be adapted to the optimal reaction ratio for methanol synthesis, resulting in low feedstock conversion efficiency, poor methanol output per unit of biomass feedstock, and overall unsatisfactory production economics.

[0004] To address the aforementioned technical challenges, two mainstream production processes have gradually emerged in the industry: the traditional biomass gasification to methanol process and the biomass gasification coupled with green hydrogen to methanol process. The traditional process involves biomass gasification via a fluidized bed or fixed bed to obtain crude syngas. The hydrogen-to-carbon ratio is then adjusted using a water-gas shift reaction (WGS), followed by impurity removal, decarbonization, and distillation to produce finished methanol. This process is mature, has strong equipment adaptability, and can achieve basic mass production. To overcome the high energy consumption and high carbon emissions of the traditional process, existing improved technologies eliminate the energy-intensive WGS step and introduce a green hydrogen coupling control scheme. This utilizes photovoltaic and wind power to drive proton exchange membrane electrolysis to produce hydrogen (PEM). External green hydrogen is then added to adjust the syngas composition, effectively reducing production steam consumption and carbon emissions, and optimizing the process's environmental friendliness and energy consumption to a certain extent.

[0005] While the two mainstream processes mentioned above can achieve basic green methanol production, they still have significant technological shortcomings that are difficult to overcome, making them unsuitable for the demands of efficient, low-carbon, and low-cost large-scale industrial production. Traditional processes rely on WGS reactions, resulting in high steam consumption, abundant carbon dioxide byproducts, low effective component ratio in syngas, poor feedstock utilization, and short catalyst lifespan. Existing green hydrogen coupling processes lack precise component control and a uniform gas mixing structure, leading to large fluctuations in the hydrogen-to-carbon ratio, an inability to stably maintain optimal synthesis conditions, limited improvement in feedstock conversion rates, and the absence of a refined deep purification system, resulting in continuous catalyst depletion due to trace impurities. Furthermore, existing processes lack a comprehensive energy cascade recovery and byproduct closed-loop utilization system, resulting in significant waste of system waste heat, low resource utilization rates of byproducts such as gasification ash and syngas purge gas, and overall low energy efficiency and high production costs, severely limiting the large-scale implementation and iterative upgrading of the green methanol industry. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a system for the efficient production of green methanol from biomass gasification gas coupled with green hydrogen. The system optimizes the original quality of the syngas through a low-tar, hydrogen-rich gasification process, and completes high-precision impurity removal and quality improvement of the syngas using a gradient-type deep purification process. It combines online precise proportioning of green hydrogen with uniform gas mixing technology to match the optimal reaction atmosphere for methanol synthesis. Furthermore, it incorporates a dynamic operating condition adjustment mechanism that links the entire process, and is supplemented by a closed-loop technology for the resource utilization of by-products. This constructs an integrated, adaptive, low-consumption, and low-carbon green methanol production technology system, achieving efficient, low-carbon, low-cost, and large-scale stable production of green methanol.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a system for the efficient preparation of green methanol from biomass gasification gas coupled with green hydrogen, comprising a biomass pretreatment unit, a low-tar hydrogen-rich gasification unit, a multi-stage gradient purification unit, a green hydrogen blending unit, a methanol synthesis unit, and a methanol distillation unit connected in sequence by pipelines, wherein: the biomass pretreatment unit is used to homogenize, modify, and dry the raw biomass feedstock; the low-tar hydrogen-rich gasification unit is used to convert the modified biomass feedstock into crude syngas with low impurities and high effective components; the multi-stage gradient purification unit is used to process the crude syngas... The process involves stepwise impurity removal, cooling, and component regulation to remove impurities and enrich effective reaction components, outputting high-quality syngas. The green hydrogen blending unit dynamically matches the blending amounts of high-quality syngas and green hydrogen, outputting feedstock gas suitable for methanol synthesis. The methanol synthesis unit utilizes the feedstock gas to produce crude methanol. The methanol distillation unit refines and purifies the crude methanol to obtain high-purity methanol. The heat source input of the biomass pretreatment unit is connected to the waste heat output of the methanol distillation unit via a pipeline. The purge gas output of the methanol synthesis unit is connected to the feedstock of the low-tar hydrogen-rich gasification unit.

[0008] Furthermore, the biomass pretreatment unit is equipped with raw material crushing equipment, waste heat drying equipment, and material blending equipment. The raw material crushing equipment is used to crush the biomass raw materials to a particle size ≤20mm to ensure uniform feed particles. The waste heat drying equipment is used to receive the low-temperature waste heat from the methanol distillation unit to dry and dehumidify the crushed biomass raw materials, adjusting the raw material moisture content to 12%~18%. The material blending equipment is used to mix silicon-aluminum based mineral additives with the biomass raw materials. The amount of silicon-aluminum based mineral additives added is 2%~5% of the total mass of the biomass raw materials. The silicon-aluminum based mineral additives include, by mass percentage: 45% silicon dioxide, 35% aluminum oxide, 10% calcium oxide, and 5% iron oxide.

[0009] Furthermore, the multi-stage gradient purification unit is sequentially equipped with a waste heat recovery device, a cyclone dust collector, a tar catalytic cracking reactor, a dry desulfurization device, and a temperature-switched adsorption decarbonization device along the crude syngas flow direction. This allows for the sequential completion of heat recovery from the crude syngas, solid particle removal, complete tar cracking, trace sulfide removal, and redundant carbon dioxide regulation. The waste heat recovery device recovers the waste heat from the high-temperature syngas produced by the low-tar hydrogen-rich gasification unit, preparing process steam to supply heat to the low-tar hydrogen-rich gasification unit and the methanol distillation unit. The cyclone dust collector has a dust recovery rate ≥95%, the tar conversion rate of the tar catalytic cracking reactor is ≥99%, the dry desulfurization device controls the sulfide content of the syngas to ≤0.05ppm, and the temperature-switched adsorption decarbonization device regulates the carbon dioxide volume content of the syngas to 3%~5%.

[0010] Furthermore, the low-tar hydrogen-rich gasification unit employs a circulating fluidized bed gasification device. The operating parameters of the device include: gasification temperature 850℃~900℃, oxygen equivalence ratio 0.25~0.3, water-to-gas ratio 0.1~0.15, and crude syngas tar content ≤20mg / Nm³. 3 .

[0011] Furthermore, the green hydrogen blending unit is equipped with a green hydrogen preparation component, a gas detection component, a flow regulation component, and a homogenizing gas mixing component. The gas detection component is used to monitor the high-quality syngas component parameters output by the multi-stage gradient purification unit in real time. The flow regulation component is used to dynamically adjust the green hydrogen blending ratio according to the high-quality syngas component parameters. The homogenizing gas mixing component is used to complete the uniform mixing of high-quality syngas and green hydrogen and output the feed gas suitable for methanol synthesis reaction.

[0012] Furthermore, the green hydrogen preparation component is a proton exchange membrane electrolysis device, which produces green hydrogen with a purity of ≥99.9%; the green hydrogen mixing unit is used to control the H2 / CO ratio of the mixed gas at 2.0~2.2, with a ratio fluctuation of ≤±0.05 and a gas mixing uniformity of ≥99%.

[0013] Furthermore, the methanol synthesis unit incorporates a modified copper-based catalyst with a Cu-Zn-Al substrate and zirconium oxide doping as an auxiliary agent. Operating parameters include: reaction pressure 5.5 MPa~6.5 MPa, reaction temperature 220℃~260℃, and gas space velocity 8000 h⁻¹. -1 ~10000h -1 The catalytic conversion efficiency of the feed gas is ≥92%.

[0014] Furthermore, the methanol distillation unit adopts a three-tower differential pressure distillation device, which can produce green methanol product with a purity of ≥99.9%; the low-temperature waste heat generated by the methanol distillation unit has a temperature range of 120℃~150℃, and its low-temperature waste heat is transported to the biomass pretreatment unit.

[0015] Furthermore, it also includes a global dynamic control unit, which is electrically connected to the biomass pretreatment unit, the low-tar hydrogen-rich gasification unit, the multi-stage gradient purification unit, the green hydrogen blending unit, the methanol synthesis unit, and the methanol distillation unit, respectively. It is used to collect raw material parameters, gasification parameters, syngas components, hydrogen blending parameters, and distillation operating parameters in real time, and adaptively adjust the operating conditions of each unit according to the collected parameters. The global dynamic control unit adapts to changes in operating conditions such as biomass raw material moisture content of 10%~30% and raw material calorific value fluctuation of ±15%.

[0016] Furthermore, it also includes an energy by-product utilization unit, which is connected to the methanol distillation unit, the low-tar hydrogen-rich gasification unit and the methanol synthesis unit respectively. It is used to recover the low-temperature waste heat generated by the methanol distillation unit and transport it to the biomass pretreatment unit to realize waste heat reuse; it is also used to collect the gasification ash residue produced by the low-tar hydrogen-rich gasification unit and the synthesis off-gas produced by the methanol synthesis unit for resource utilization.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides a system for the efficient production of green methanol from biomass gasification coupled with green hydrogen. It integrates various functional units—biomass pretreatment, low-tar hydrogen-rich gasification, multi-stage gradient purification, green hydrogen blending, methanol synthesis, and methanol distillation—through orderly pipeline connections according to the production process flow, constructing a continuous and integrated production system. Simultaneously, it includes a waste heat recovery loop and a purge gas circulation loop, forming a dual closed-loop operation structure for materials and energy. This invention abandons the traditional fragmented equipment layout model, streamlining the material and energy transfer paths and simplifying supporting facilities through overall process integration and structural optimization. It achieves coordinated operation across the entire process from biomass raw material processing, gasification and upgrading, precise gas blending to synthesis and distillation, enabling the low-carbon, efficient, and low-cost large-scale continuous production of green methanol. This system overcomes the technical bottlenecks of traditional large-scale industrial-scale biomass-to-methanol production, aligning with the industrial development direction of high-value resource utilization of agricultural and forestry solid waste, and providing a feasible and replicable industrial technology solution for the industrialization and large-scale promotion of low-carbon green methanol.

[0018] Furthermore, the system of this invention is equipped with dedicated crushing, waste heat drying, and material blending equipment. By standardizing the particle size of raw materials and utilizing the waste heat from distillation to control humidity and stabilize the feed, the gasification feed conditions are effectively stabilized, reducing external energy consumption. By adding silicon-aluminum based mineral additives, alkali metal components in biomass are complexed, suppressing slagging and equipment corrosion in the gasifier from the source, significantly extending the continuous operation cycle of the gasification unit, stabilizing the quality of crude syngas, and reducing the load on downstream purification processes. This invention employs a multi-stage gradient purification process, sequentially treating the crude syngas with dust removal, tar cracking, fine desulfurization, and precise decarbonization, removing harmful impurities and optimizing the syngas composition step by step; simultaneously, the waste heat from the high-temperature syngas is recovered for steam supply in the process section, improving the overall energy efficiency of the system, effectively avoiding the risk of catalyst poisoning and failure, and ensuring long-term stable operation of the unit. By optimizing core parameters such as gasification temperature, oxygen equivalence ratio, and water-to-gas ratio, tar formation is significantly suppressed, the proportion of effective reactive components is increased, further improving the stability of gasification conditions and reducing equipment start-up and shutdown losses and maintenance costs.

[0019] Furthermore, this invention establishes a closed-loop green hydrogen gas mixing system with real-time monitoring, adaptive parameter adjustment, and homogeneous mixing. This changes the traditional extensive production mode with fixed ratios, allowing for dynamic adjustment of the green hydrogen blending amount based on the real-time composition of the syngas, completely solving the technical pain point of hydrogen-carbon ratio imbalance and ensuring that the methanol synthesis reaction is under optimal conditions. High-purity green hydrogen is prepared using proton exchange membrane electrolysis, achieving zero-carbon feed from the raw material end and significantly reducing carbon emissions throughout the product's life cycle. Precise control of the hydrogen-carbon ratio and gas mixing uniformity significantly improves the catalytic conversion rate of the raw material gas and the methanol yield, reducing raw material consumption per unit product. This invention uses a zirconium-modified copper-based catalyst matched with optimal synthesis conditions, effectively improving catalytic activity and stability, reducing the circulating load of unreacted gas, slowing down the catalyst decay rate, and saving consumables and downtime maintenance costs. Combined with a three-tower differential pressure distillation process, it stably produces high-purity, superior-grade methanol, while recovering low-temperature waste heat for raw material drying, achieving cascade utilization of waste heat. With the integration of dynamic control and energy by-product utilization units, the system can adapt to wide fluctuations in raw material conditions, meet the needs of large-scale industrial continuous production, realize the full resource utilization of waste heat, solid waste and exhaust gas, and achieve no pollutant discharge, highlighting its environmental advantages and engineering scalability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a system for the efficient preparation of green methanol by coupling biomass gasification gas with green hydrogen according to the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] This invention provides a system for the efficient production of green methanol from biomass gasification gas coupled with green hydrogen, comprising a biomass pretreatment unit, a low-tar hydrogen-rich gasification unit, a multi-stage deep purification unit, a green hydrogen preparation and coupling ratio adjustment unit, a methanol synthesis unit, a methanol distillation unit, an energy recovery and by-product utilization unit, and a full-process dynamic control unit. The biomass pretreatment unit is the upstream starting unit of the system, where solid biomass feedstock is modified, homogenized, and dried, and then transported to the downstream low-tar hydrogen-rich gasification unit as qualified solid material. The low-tar hydrogen-rich gasification unit receives the upstream solid material... Modified biomass feedstock undergoes a controlled gasification reaction to generate crude syngas, which is then transported in gaseous form to a multi-stage deep purification unit. This unit receives the upstream gaseous crude syngas and sequentially completes waste heat recovery, dust removal, tar cracking, fine desulfurization, and selective decarbonization. The resulting high-purity gaseous syngas, after impurity removal, is stably transported to the green hydrogen preparation and coupling ratio unit. This unit produces its own high-purity green hydrogen, which is then precisely proportioned and homogenized online with the upstream high-purity gaseous syngas to generate a gaseous feedstock gas that meets the optimal hydrogen-to-carbon ratio for methanol synthesis, and is then transported to the methanol synthesis unit. The methanol synthesis unit receives a properly proportioned gaseous feed gas, which undergoes a catalytic reaction to produce liquid crude methanol. This liquid crude methanol is then transported to the methanol distillation unit for refining and purification. The methanol distillation unit further refines the upstream liquid crude methanol in stages, producing high-purity liquid finished methanol. The energy recovery and by-product utilization unit is connected in parallel to all process units, responsible for the graded recovery of waste heat at different levels and its distribution to various heat-using equipment as needed. Simultaneously, it coordinates the full resource utilization of gasification ash and synthesis off-gas. A dynamic control unit throughout the entire process is electrically connected to all functional units, collecting real-time operating parameters such as temperature, pressure, material composition, and equipment load. Through closed-loop control logic, it adaptively adjusts the process conditions of each unit, ensuring long-term continuous, stable, efficient, and low-carbon operation of the entire system.

[0023] The specific settings for each unit are as follows: 1) The biomass pretreatment unit is used to complete the standardized pretreatment of biomass feedstock, eliminating the impact of feedstock operating condition fluctuations on subsequent processes, and simultaneously suppressing gasification slag corrosion problems at the source. Specific processes are as follows: First, the biomass raw materials such as straw, sawdust, rice husks, and forestry residues are cleaned manually and mechanically to remove ineffective impurities such as stones, metals, and weeds. Subsequently, the raw materials are uniformly crushed to a particle size of ≤20mm using crushing equipment to ensure uniform feed particles and avoid uneven local reactions during subsequent gasification.

[0024] Secondly, the low-temperature waste heat generated in the distillation process is used to dry and adjust the moisture content of the crushed biomass raw materials, so as to precisely control the moisture content of the raw materials to 12%-18%. This avoids the decrease in gasification efficiency and fluctuation in syngas composition caused by excessive moisture content, and also prevents high-temperature slagging in the furnace caused by excessively low moisture content.

[0025] Finally, a silicon-aluminum based mineral additive is uniformly mixed at a ratio of 2%-5% of the biomass raw material mass. The additive consists of 45% silicon dioxide, 35% aluminum oxide, 10% calcium oxide, and 5% iron oxide by mass. This additive can effectively complex the alkali metal components in the biomass, thereby inhibiting slagging and equipment corrosion problems during the gasification process from the source.

[0026] 2) The low-tar hydrogen-rich gasification unit uses a circulating fluidized bed gasifier as the main equipment. The gasifier is equipped with a high-temperature resistant and corrosion-resistant lining structure and a special return material device to enhance the material circulation reaction effect in the furnace and improve the uniformity of the gasification reaction.

[0027] This invention optimizes gasification process parameters, employing a high-temperature, low-oxygen-equivalent-ratio, and micro-steam coupled gasification mode. Specifically, the gasification temperature is controlled at 850-900℃, the oxygen-equivalent-ratio at 0.25-0.3, and the in-furnace water-to-gas ratio maintained at 0.1-0.15. This process parameter system can directionally suppress the formation of tar precursors, significantly reduce the tar content in crude syngas, and simultaneously increase the proportion of effective reactive components such as carbon monoxide and hydrogen.

[0028] After gasification in this unit, the crude syngas produced has a stable composition, with carbon monoxide accounting for 25%-30% by volume, hydrogen accounting for 35%-40% by volume, carbon dioxide accounting for 20%-25% by volume, and tar content ≤20mg / Nm³. 3 Dust content ≤5g / Nm 3 The ash and slag produced by the gasification reaction are collected uniformly for subsequent resource utilization. At the same time, the addition of silicon-aluminum based mineral additives can effectively inhibit alkali metal corrosion and slagging, extending the continuous and stable operation cycle of the gasifier to more than 6 months.

[0029] 3) The multi-stage deep purification unit adopts a multi-process coupled step-by-step deep purification process to thoroughly remove impurities from the crude syngas, producing high-purity, high-quality syngas and fundamentally solving the problem of catalyst poisoning and deactivation, as detailed below: The first step is waste heat recovery. High-temperature crude syngas at 850-900℃ is introduced into a waste heat boiler to recover high-temperature waste heat to produce industrial steam. At the same time, the temperature of the syngas is reduced to 350-400℃, achieving preliminary energy recovery.

[0030] The second step is cyclone dust removal, which removes coarse dust with a particle size of ≥10μm from the syngas using cyclone dust removal equipment. The dust recovery rate is ≥95%, which significantly reduces the dust load of the syngas.

[0031] The third step is high-temperature catalytic tar cracking. The syngas after dust removal is introduced into a tar cracking reactor with a built-in nickel-based catalyst. The reactor temperature is controlled at 400-450℃ to completely crack the residual tar into carbon monoxide and hydrogen. The overall tar conversion rate is ≥99%, which completely eliminates the risk of tar blockage and corrosion.

[0032] The fourth step is dry desulfurization, which uses a zinc oxide-specific desulfurizing agent to precisely remove sulfide impurities from the synthesis gas, controlling the residual sulfide content to ≤0.05ppm.

[0033] The fifth step is temperature-switched adsorption for carbon removal and impurity removal. Through TSA temperature-switched adsorption technology, some carbon dioxide is selectively removed, and the carbon dioxide content in the syngas is stably controlled at 3%-5%. At the same time, trace amounts of organic and inorganic impurities are removed, and finally, high-purity syngas with an effective component of carbon monoxide + hydrogen ratio ≥85% is obtained.

[0034] 4) The green hydrogen production and coupling ratio control unit achieves green hydrogen production and precise and stable control of the hydrogen-to-carbon ratio of syngas through green electricity-to-hydrogen production and intelligent closed-loop control technology, as detailed below: The first step involves using zero-carbon green electricity such as wind power and photovoltaic power to produce green hydrogen through PEM water electrolysis. The produced green hydrogen has a purity of ≥99.9%, and is stored in hydrogen storage tanks with a pressure rating of 2.0-3.0 MPa to achieve stable storage and pressure-stabilized supply of green hydrogen.

[0035] The second step involves continuously introducing the purified high-purity syngas into a dynamic proportioning mixer. The equipment is equipped with an online infrared component analyzer and a PLC intelligent control system, which can monitor the real-time component content of carbon monoxide, hydrogen, and carbon dioxide in the syngas in real time and continuously. Based on the optimal hydrogen-to-carbon ratio parameter for methanol synthesis, the flow rate of green hydrogen is precisely controlled to stably maintain the H2 / CO ratio of the syngas within the range of 2.0-2.2, with a fluctuation range of ≤±0.05.

[0036] This unit adopts a composite mixing structure of Venturi premixing + static mixing enhancement, breaking the traditional simple mixing mode and achieving molecular-level uniform mixing of green hydrogen and syngas. The gas mixing uniformity is ≥99%, which completely solves the problem of local hydrogen-carbon ratio imbalance and provides stable feed gas conditions for subsequent methanol synthesis reaction.

[0037] 5) The methanol synthesis unit uses a fixed-bed isothermal synthesis reactor as the main reaction equipment. The specific steps for synthesizing methanol are as follows: The first step involves introducing the qualified syngas after precise hydrogenation into a fixed-bed isothermal synthesis reactor. Under optimal process conditions and with the action of a highly efficient catalyst, the syngas reacts efficiently to produce crude methanol, with an overall conversion rate of ≥92%.

[0038] The second step involves introducing the reacted mixed gas into a gas-liquid separator to complete the gas-liquid two-phase separation, obtaining crude methanol product with a methanol mass content of 85%-90%. All the separated unreacted purge gas (containing residual carbon monoxide and hydrogen) is recovered and transported to the gasifier as auxiliary fuel for recycling, achieving zero waste of raw material gas.

[0039] Preferably, the optimal process conditions are a reaction pressure of 5.5-6.5 MPa, a reaction temperature of 220-260℃, and a gas hourly space velocity of 8000-10000 h⁻¹. -1 .

[0040] Preferably, the fixed-bed isothermal synthesis reactor is filled with a modified copper-based catalyst. The modified copper-based catalyst uses a Cu-Zn-Al substrate combined with ZrO2 promoter, which can effectively improve the catalytic activity and stability of methanol synthesis.

[0041] 6) The methanol distillation unit uses a three-tower differential pressure distillation process to deeply purify crude methanol. The crude methanol is sequentially purified by passing it through a pre-distillation tower, a pressurized distillation tower, and an atmospheric distillation tower to remove water, fusel oils, light impurities, and heavy impurities, thus thoroughly purifying the crude methanol system and finally producing a high-purity green methanol product with a purity of ≥99.9%, which fully meets the superior grade methanol standard in GB / T 338.

[0042] The low-temperature waste heat generated during the distillation process at 120-150℃ is recovered through a heat exchange system and used entirely for the raw material drying process in the biomass pretreatment unit, thus realizing the resource utilization of low-temperature waste heat.

[0043] 7) The energy recovery and by-product utilization unit constructs an energy cascade recovery system and a by-product closed-loop utilization system to maximize the system's energy utilization rate and resource recovery rate. Specifically: In terms of energy cascade recovery, different grades of waste heat are recovered in stages: the high-temperature waste heat of 800-900℃ generated in the gasification process is used to prepare high-temperature steam, which provides a heat source for the gasification reaction and methanol distillation process; the low-temperature waste heat of 120-150℃ in the distillation process is used for drying biomass raw materials; and the waste heat of the methanol synthesis reaction is used for preheating of pretreated raw materials. Through multi-dimensional waste heat recovery and utilization, the overall energy efficiency of the system is improved to ≥85%.

[0044] In terms of by-product utilization, two types of by-products have been utilized: the ash slag containing silica and alumina generated by gasification is ground into raw materials for building blocks, thus realizing the utilization of solid waste; the off-gas generated in the synthesis process is all returned to the gasifier for combustion, achieving zero emissions of waste gas and completely solving the problems of waste and pollution from by-products of traditional technologies.

[0045] 8) The full-process dynamic control unit adopts a PLC+DCS linkage intelligent control system to build a full-process data acquisition and dynamic control system. It collects all major operating data in real time, including biomass feedstock moisture content, calorific value, gasifier temperature and pressure, syngas composition, hydrogen-to-carbon ratio, methanol synthesis conditions, and distillation parameters. Based on a built-in optimal operating condition model, the system achieves multi-parameter linkage automatic control. It can adapt to a wide range of operating conditions, including biomass feedstock moisture content of 10%-30% and calorific value fluctuations of ±15%, and automatically adjusts gasification process parameters, green hydrogen feed rate, synthesis reaction temperature and pressure, and distillation operating parameters. It avoids production instability caused by operating condition fluctuations throughout the process, ensuring continuous, stable, and efficient operation of the entire process, and is suitable for industrial production needs of 100,000-500,000 tons / year.

[0046] like Figure 1 As shown, the specific steps of the above-mentioned system for efficiently producing green methanol by coupling biomass gasification gas with green hydrogen are as follows: Step 1: Pretreatment of biomass raw materials.

[0047] Field straw, sawdust, and forestry residues are selected as raw materials. Screening equipment removes stones, debris, and other impurities. Crushing equipment breaks the raw materials to a particle size of 15-20mm to ensure uniform particle size. Low-temperature waste heat from the methanol distillation process (120-150℃) is recovered and dried using a hot air heat exchange system, precisely controlling the moisture content to 15% (optimal range 12%-18%). A silica-alumina based mineral additive (45% silica, 35% alumina, 10% calcium oxide, and 5% iron oxide) is uniformly mixed at a ratio of 3% by weight of the raw materials. This thorough mixing effectively inhibits alkali metal slagging corrosion during subsequent gasification.

[0048] Step 2: Low-tar hydrogen-rich gasification to prepare crude syngas.

[0049] The pretreated biomass feedstock is transported to a circulating fluidized bed gasifier, and the gasification system is started. Strict control of the process parameters within the furnace is maintained: gasification temperature 880℃, oxygen equivalence ratio 0.28, and water-to-gas ratio 0.12, ensuring a stable gasification reaction. After gasification, a stable crude syngas is generated. Testing shows that the crude syngas contains 28% carbon monoxide, 38% hydrogen, 22% carbon dioxide, and 18 mg / Nm³ of tar. 3 Dust content 4.2g / Nm 3 All indicators are superior to traditional gasification processes. The ash and slag produced by gasification are collected and stored uniformly for subsequent grinding to prepare building materials. The gasifier can operate continuously for up to 6.5 months without significant slagging or corrosion.

[0050] Step 3: Multi-stage deep purification of syngas.

[0051] The high-temperature crude syngas is first introduced into a waste heat boiler to recover 880℃ high-temperature waste heat to prepare saturated steam for use in the gasification and distillation processes, and the syngas is cooled to 380℃. Then it enters a cyclone dust collector to remove large particles of dust, with a dust recovery rate of 96%. The dust-removed syngas is sent to a tar cracking reactor, where the reaction temperature is controlled at 420℃. The tar is completely cracked using a nickel-based catalyst, with a tar conversion rate of 99.2%. The cracked syngas undergoes fine desulfurization treatment through a zinc oxide desulfurization bed, reducing the residual sulfide content to 0.04ppm. Finally, some carbon dioxide is removed through a TSA temperature-switching adsorption device, adjusting the carbon dioxide content of the syngas to 4%, ultimately yielding high-purity syngas with an effective component (carbon monoxide + hydrogen) of 86.5%, free of impurities, fully meeting the feed requirements for methanol synthesis.

[0052] Step 4: Green hydrogen preparation and precise coupling and adjustment.

[0053] The plant utilizes photovoltaic and wind power to drive a PEM (Polymer Electrolysis) water electrolysis system to produce high-purity green hydrogen (99.92%), which is stored in a 2.5MPa hydrogen storage tank for stable and continuous gas supply. The purified syngas is continuously fed into a dynamic proportioning mixer. An online infrared analyzer collects syngas composition data every second in real time and transmits it to a PLC control system. Based on the real-time composition data, the system precisely adjusts the green hydrogen inlet flow rate, stabilizing the H2 / CO ratio of the syngas within the range of 2.1, with fluctuations ≤ ±0.03. Through a Venturi premixing + static mixing enhancement structure, complete and uniform mixing of green hydrogen and syngas is achieved, with a mixing uniformity of 99.3% and no local component imbalance issues.

[0054] Step 5: Methanol synthesis reaction.

[0055] The homogenized and qualified syngas was introduced into a fixed-bed isothermal synthesis reactor, which was filled with a Cu-Zn-Al+ZrO2 modified copper-based catalyst. The reaction pressure was controlled at 6.0 MPa, the reaction temperature at 240℃, and the gas space velocity at 9000 h⁻¹. -1 The mixture undergoes a catalytic synthesis reaction of methanol. After the reaction, the mixed gas is introduced into a gas-liquid separator to separate crude methanol product, which has a methanol content of 88% and a synthesis reaction conversion rate of 93.5%. All the separated unreacted purge gas is sent to a gasifier for recycling as auxiliary fuel.

[0056] Step 6: Methanol distillation purification.

[0057] Crude methanol is introduced into a three-tower differential pressure distillation system, where it sequentially passes through a pre-distillation tower to remove light impurities, a pressurized distillation tower to concentrate methanol, and an atmospheric distillation tower to remove heavy impurities and moisture, ultimately yielding a high-purity, green methanol product with a purity of 99.93%, meeting the GB / T 338 superior grade standard. All the 135℃ low-temperature waste heat generated during the distillation process is recovered and used in the biomass feedstock drying process.

[0058] Step 7: Closed-loop utilization and dynamic regulation of energy and by-products.

[0059] The entire process utilizes a graded waste heat recovery system. High-temperature steam is supplied to the gasification and distillation processes, while low-temperature waste heat is used to dry raw materials and preheat feed. The system's overall energy efficiency is 86.2%. Gasification ash is ground and then used to prepare concrete block raw materials, achieving solid waste resource utilization. Throughout the production process, a DCS+PLC system collects, analyzes, and controls parameters of each process in real time, adapting to changes in raw material moisture content (10%-30%) and calorific value fluctuations (±15%). The production line operates continuously and stably throughout the year, producing 102,000 tons of high-grade green methanol annually, with a unit biomass methanol yield of 0.53 t / t, a production cost of 3150 yuan / ton, and a life-cycle carbon footprint of 26.8 gCO2e / MJ.

Claims

1. A system for the efficient production of green methanol from biomass gasification gas coupled with green hydrogen, characterized in that, The system comprises, via sequentially connected pipelines, a biomass pretreatment unit, a low-tar hydrogen-rich gasification unit, a multi-stage gradient purification unit, a green hydrogen blending unit, a methanol synthesis unit, and a methanol distillation unit. Specifically: the biomass pretreatment unit homogenizes, modifies, and dries the raw biomass feedstock; the low-tar hydrogen-rich gasification unit converts the modified biomass feedstock into crude syngas with low impurities and high effective components; the multi-stage gradient purification unit progressively removes impurities, cools, and regulates the composition of the crude syngas, removing impurities and enriching effective reactive components to output high-quality syngas; the green hydrogen blending unit dynamically matches the blending ratio of high-quality syngas and green hydrogen to output feedstock gas suitable for methanol synthesis; the methanol synthesis unit utilizes the feedstock gas to produce crude methanol; and the methanol distillation unit refines and purifies the crude methanol to obtain high-purity methanol. The heat source input of the biomass pretreatment unit is connected via pipeline to the waste heat output of the methanol distillation unit; and the purge gas output of the methanol synthesis unit is connected to the feedstock of the low-tar hydrogen-rich gasification unit.

2. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 1, characterized in that, The biomass pretreatment unit is equipped with raw material crushing equipment, waste heat drying equipment, and material blending equipment. The raw material crushing equipment is used to crush biomass raw materials to a particle size ≤20mm to ensure uniform feed particles. The waste heat drying equipment is used to receive low-temperature waste heat from the methanol distillation unit to dry and dehumidify the crushed biomass raw materials, adjusting the raw material moisture content to 12%~18%. The material blending equipment is used to mix silicon-aluminum based mineral additives with biomass raw materials. The amount of silicon-aluminum based mineral additives added is 2%~5% of the total mass of biomass raw materials. The silicon-aluminum based mineral additives include, by mass percentage: 45% silicon dioxide, 35% aluminum oxide, 10% calcium oxide, and 5% iron oxide.

3. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 1, characterized in that, The multi-stage gradient purification unit is sequentially equipped with a waste heat recovery device, a cyclone dust collector, a tar catalytic cracking reactor, a dry desulfurization device, and a temperature-switched adsorption decarbonization device along the crude syngas flow direction. This allows for the sequential recovery of heat from the crude syngas, removal of solid particles, complete tar cracking, removal of trace sulfides, and regulation of redundant carbon dioxide. The waste heat recovery device recovers the waste heat from the high-temperature syngas produced by the low-tar hydrogen-rich gasification unit, and prepares process steam to supply heat to the low-tar hydrogen-rich gasification unit and the methanol distillation unit. The cyclone dust collector has a dust recovery rate ≥95%, the tar conversion rate of the tar catalytic cracking reactor is ≥99%, the dry desulfurization device controls the sulfide content of the syngas to ≤0.05ppm, and the temperature-switched adsorption decarbonization device regulates the carbon dioxide volume content of the syngas to 3%~5%.

4. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 1, characterized in that, The low-tar hydrogen-rich gasification unit employs a circulating fluidized bed gasification system. The operating parameters include: gasification temperature 850℃~900℃, oxygen equivalence ratio 0.25~0.3, water-to-gas ratio 0.1~0.15, and crude syngas tar content ≤20mg / Nm³. 3 .

5. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 1, characterized in that, The green hydrogen blending unit is equipped with a green hydrogen preparation component, a gas detection component, a flow regulation component, and a homogenizing gas mixing component. The gas detection component is used to monitor the high-quality syngas component parameters output by the multi-stage gradient purification unit in real time. The flow regulation component is used to dynamically adjust the green hydrogen blending ratio according to the high-quality syngas component parameters. The homogenizing gas mixing component is used to complete the uniform mixing of high-quality syngas and green hydrogen and output the feed gas suitable for methanol synthesis reaction.

6. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 5, characterized in that, The green hydrogen preparation component is a proton exchange membrane electrolysis device, which produces green hydrogen with a purity of ≥99.9%; the green hydrogen mixing unit is used to control the H2 / CO ratio of the mixed gas at 2.0~2.2, with a ratio fluctuation of ≤±0.05 and a gas mixing uniformity of ≥99%.

7. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 1, characterized in that, The methanol synthesis unit incorporates a modified copper-based catalyst with a Cu-Zn-Al substrate and zirconium oxide doping as an auxiliary agent. Operating parameters include: reaction pressure 5.5 MPa~6.5 MPa, reaction temperature 220℃~260℃, and gas space velocity 8000 h⁻¹. -1 ~10000h -1 The catalytic conversion efficiency of the feed gas is ≥92%.

8. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 1, characterized in that, The methanol distillation unit uses a three-tower differential pressure distillation device, which can produce green methanol product with a purity of ≥99.9%; the low-temperature waste heat generated by the methanol distillation unit has a temperature range of 120℃~150℃, and its low-temperature waste heat is transported to the biomass pretreatment unit.

9. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 1, characterized in that, It also includes a global dynamic control unit, which is electrically connected to the biomass pretreatment unit, the low-tar hydrogen-rich gasification unit, the multi-stage gradient purification unit, the green hydrogen blending unit, the methanol synthesis unit, and the methanol distillation unit, respectively. It is used to collect raw material parameters, gasification parameters, syngas components, hydrogen blending parameters, and distillation operating parameters in real time, and adaptively adjust the operating conditions of each unit according to the collected parameters. The global dynamic control unit is adaptive to changes in operating conditions such as biomass raw material moisture content of 10%~30% and raw material calorific value fluctuation of ±15%.

10. The system for efficient production of green methanol from biomass gasification gas coupled with green hydrogen according to claim 1, characterized in that, It also includes an energy by-product utilization unit, which is connected to the methanol distillation unit, the low-tar hydrogen-rich gasification unit and the methanol synthesis unit respectively. It is used to recover the low-temperature waste heat generated by the methanol distillation unit and transport it to the biomass pretreatment unit to realize waste heat reuse; and to collect the gasification ash residue produced by the low-tar hydrogen-rich gasification unit and the synthesis off-gas produced by the methanol synthesis unit for resource utilization.

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