Hydrogen production system and method by cold plasma micro-bubbles cooperating with biomass supercritical water gasification

Abstract

The application discloses a cold plasma microbubble and biomass supercritical water gasification hydrogen production system and method, and belongs to the field of biomass hydrogen production. The system comprises a raw material processing unit, a cold plasma pre-activation unit, a high-pressure subcritical pretreatment unit, a supercritical gasification reaction unit, a gas-liquid separation unit, a hydrogen gas purification unit, a waste heat recovery unit and a circulating water treatment unit. After being pulped, the raw material is modified by the cold plasma pre-activation unit to improve the activity, and then enters the supercritical reactor with a built-in catalytic bed through the high-pressure subcritical pretreatment unit containing plasma microbubble generated active species to complete the gasification. After the product gas-liquid separation, the hydrogen-containing gas is purified to obtain high-purity hydrogen gas, the liquid phase water is purified and reused, the waste heat is recovered to supply system energy consumption, and the circulating water is treated to discharge crystalline salt to prevent salt analysis. The application realizes the deep cooperation of cold plasma and supercritical water gasification, improves the gasification efficiency and hydrogen production selectivity, reduces the energy consumption, tar and carbon deposition, guarantees the stable operation of the system, reduces the comprehensive cost, and is suitable for the industrialization of biomass hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of biomass hydrogen production technology, specifically relating to a cold plasma microbubble synergistic supercritical water gasification system and method for hydrogen production. Background Technology

[0002] As the global energy structure shifts towards cleaner and lower-carbon energy sources, hydrogen energy, as a zero-carbon emission secondary energy source, has become a key research focus in the energy field due to its efficient production technology. Biomass has significant advantages in terms of its wide availability and carbon neutrality, making it an ideal renewable raw material for hydrogen production. Supercritical water gasification (SCWG) technology is considered one of the core technological pathways for biomass-based hydrogen production because it can directly process biomass raw materials with high water content (such as straw pulp, sludge, kitchen waste, algae, etc.), eliminates the need for expensive drying processes, and offers rapid conversion rates and high product gas cleanliness.

[0003] In recent years, supercritical water gasification technology has been extensively validated in laboratories and pilot-scale tests, but it still faces many bottlenecks in engineering applications: First, the lignin structure in biomass is stable, rich in unbreakable π bonds, and is generally hydrophobic and highly cross-linked. Under conventional supercritical water gasification conditions, its depolymerization and hydration efficiency is extremely low, requiring the reaction to be forcibly advanced by increasing the reaction temperature, pressure, or residence time. This not only leads to a significant increase in system energy consumption but also exacerbates tar formation, carbon deposition, and catalyst deactivation. Second, during supercritical water gasification, heat exchange and temperature control near the critical zone are difficult, and salts are prone to precipitation and deposition. At the same time, equipment corrosion and coking are prominent under high temperature and high pressure conditions, which can easily cause an increase in system pressure drop, requiring frequent shutdowns for cleaning and seriously affecting the stability of continuous operation. Third, the concentration of free radicals (•H, •OH) in the supercritical water system is insufficient, and the interfacial wetting and mass transfer between biomass and supercritical water are limited, further restricting the gasification reaction efficiency and hydrogen production selectivity.

[0004] To address the aforementioned issues, the industry has attempted to introduce cold plasma technology for auxiliary enhancement. Cold plasma, characterized by high electron temperature and low overall gas phase temperature, can rapidly generate active species and charged bodies such as •H, •OH, ozone, and singlet oxygen at room / medium temperatures. This can achieve biomass surface modification, such as introducing oxygen / nitrogen-containing functional groups and lowering apparent activation energy, while also promoting tar cracking and gas reforming, and activating catalysts in situ. However, in existing technologies, the combination of supercritical water gasification and cold plasma is mostly limited to biomass pretreatment or tail gas post-treatment stages; their integrated synergy remains in the exploratory stage. In particular, there are no publicly reported continuous processes and devices that introduce plasma active species in the subcritical preheating zone or high-pressure wet interface and deeply couple them with the catalytic process. This makes it difficult to fully utilize the synergistic effect of plasma-supercritical water-catalyst, and fails to fundamentally solve the engineering bottleneck of supercritical water gasification. Summary of the Invention

[0005] To address these issues, this invention provides a cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system and method, which solves the problems of low supercritical water gasification efficiency due to the difficulty in depolymerizing biomass lignin, high energy consumption requiring high temperature and pressure, excessive tar and carbon deposition, catalyst deactivation, difficulty in heat exchange in the critical region, prominent salt precipitation corrosion, frequent system shutdowns, insufficient free radicals and poor interfacial mass transfer in the supercritical water system, and insufficient synergy between cold plasma and supercritical water gasification.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, comprising a raw material processing unit, a cold plasma pre-activation unit, a high-pressure subcritical pretreatment unit, a supercritical gasification reaction unit, a gas-liquid separation unit, a hydrogen purification unit, a waste heat recovery unit, and a circulating water treatment unit.

[0007] The discharge end of the raw material processing unit is connected to the feed end of the cold plasma pre-activation unit, and the raw material processing unit transports the pulped biomass raw material to the cold plasma pre-activation unit.

[0008] The discharge end of the cold plasma pre-activation unit is connected to the feed end of the high-pressure subcritical pretreatment unit, and the cold plasma pre-activation unit transports the surface-modified raw materials to the high-pressure subcritical pretreatment unit.

[0009] The high-pressure subcritical pretreatment unit has a built-in plasma microbubble / jet component. The discharge end of the high-pressure subcritical pretreatment unit is connected to the feed end of the supercritical gasification reaction unit. The high-pressure subcritical pretreatment unit delivers the pressurized, preheated and active species-enhanced raw materials to the supercritical gasification reaction unit.

[0010] The supercritical gasification reaction unit is equipped with a catalytic bed, and its discharge end is connected to the feed end of the gas-liquid separation unit. The supercritical gasification reaction unit transports the gasification reaction products to the gas-liquid separation unit.

[0011] The gas phase outlet of the gas-liquid separation unit is connected to the feed end of the hydrogen purification unit, and the gas-liquid separation unit delivers hydrogen-containing gas to the hydrogen purification unit.

[0012] The inlet of the waste heat recovery unit is connected to the hydrogen purification unit, and the outlet of the waste heat recovery unit is connected between the raw material processing unit and the cold plasma pre-activation unit.

[0013] The circulating water treatment unit is connected between the gas-liquid separation unit and the raw material processing unit. The circulating water treatment unit reuses the purified and separated water for raw material pulping. The circulating water treatment unit discharges crystalline salts to alleviate salt precipitation and scaling.

[0014] As a preferred embodiment of the cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, the raw material processing unit includes a raw material crusher, a stirring and slurry preparation tank, and an additive addition component.

[0015] The raw material crusher crushes the biomass raw material to a particle size of 0.1-5mm, the stirring speed of the stirring and slurrying tank is ≥300rpm, and <0.1wt% of dispersant is added to the stirring and slurrying tank;

[0016] The additive component contains 0.2-3 wt% K2CO3 or KOH additives and 0.05-2 wt% metal precursors.

[0017] As a preferred embodiment of the cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, the biomass raw material is selected from at least one of straw, forest residue, algae, sludge, and kitchen waste, the metal precursor is at least one of Ni, Ru, and Ni-Ce-Zr, the solid content of the raw material in the stirred slurry tank is controlled at 1-20 wt%, and the pH of the system is adjusted to 7-12.

[0018] As a preferred embodiment of the cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, the cold plasma pre-activation unit includes a plasma generator and a temperature control system.

[0019] The plasma generator discharges in any one of dielectric barrier discharge, sliding arc, or plasma jet. The power of the plasma generator is 10-300W, the frequency is 1-50kHz, the processing time is 10-300s, and the working gas is N2, CO2, air, water vapor, or a mixture thereof.

[0020] The temperature control system keeps the unit outlet temperature below 80°C.

[0021] As a preferred embodiment of the cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, the high-pressure subcritical pretreatment unit includes a high-pressure pump, a subcritical preheater, and a plasma microbubble / jet assembly.

[0022] The high-pressure pump is a multi-stage plunger pump or a high-pressure screw pump, which pressurizes the raw material to 20-25 MPa; the subcritical preheater preheats the raw material to the subcritical zone of 340°C, and the residence time of the raw material in the preheater is 2-30 seconds.

[0023] The power supply of the plasma microbubble / jet assembly is a 5-30kHz, 10-200W nanosecond pulse power supply, microsecond pulse power supply or RF power supply. The plasma microbubble / jet assembly generates microbubbles with an average Sauter diameter of 50-300μm, and the gas volume fraction corresponding to the microbubbles is controlled to be 0.5-10%.

[0024] As a preferred embodiment of the cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, the supercritical gasification reaction unit includes a supercritical reactor and a catalytic bed.

[0025] The supercritical reactor is designed with two sections: an inlet empty bed section and a catalytic bed section. The reactor is lined with high-Ni alloy or Hastelloy alloy. The supercritical reactor is treated with corrosion-resistant welding or coating. The temperature inside the supercritical reactor is controlled at 420-650°C, the pressure is controlled at 24-30MPa, and the residence time of the raw material in the reactor is 10-120s.

[0026] The catalyst bed is filled with Ni-Ce x Zr1₋ x At least one catalyst selected from O2 / Al2O3, Ni-Mg-Al oxide, and Ru / C, with a catalyst space velocity of 0.5-5 h⁻¹.

[0027] As a preferred embodiment of the cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, the gas-liquid separation unit includes a first-stage cyclone-gravity separator and a second-stage high-pressure gas-liquid separator connected in sequence.

[0028] The feed end of the first-stage cyclone-gravity separator is connected to the discharge end of the supercritical gasification reaction unit, and is used to remove condensate and fine solid particles from the gasification reaction products.

[0029] The feed end of the secondary high-pressure vapor-liquid separator is connected to the discharge end of the primary cyclone-gravity separator. The operating pressure of the secondary high-pressure vapor-liquid separator is controlled at 20-28 MPa. The secondary high-pressure vapor-liquid separator is used to separate the gas phase component and the liquid phase component in the product. The gas phase component is sent to the hydrogen purification unit, and the liquid phase component is sent to the circulating water treatment unit.

[0030] As a preferred embodiment of the cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, the hydrogen purification unit includes a purification device and a residual gas treatment component; the purification device adopts any one of a PSA pressure swing adsorption device, a membrane separation device, or a temperature swing adsorption device, the feed end of the purification device is connected to the gas phase discharge end of the gas-liquid separation unit, and the purification device purifies the hydrogen-containing gas to a purity ≥99.9%;

[0031] The feed end of the waste gas treatment component is connected to the tail gas outlet of the purification device, and the waste gas treatment component transports the waste gas containing CO, CO2, and CH4 to the waste heat recovery unit as fuel.

[0032] As a preferred embodiment of the cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, the waste heat recovery unit includes heat exchanger HE-1, heat exchanger HE-2, waste heat distribution components and insulation layer;

[0033] The hot-side feed end of the heat exchanger HE-1 is connected to the discharge end of the supercritical gasification reaction unit, and the cold-side feed end of the heat exchanger HE-1 is connected to the feed end of the high-pressure subcritical pretreatment unit.

[0034] The hot side feed end of the heat exchanger HE-2 is connected to the hot side discharge end of the heat exchanger HE-1, and the cold side feed end of the heat exchanger HE-2 is connected to the discharge end of the raw material processing unit so as to use the waste heat discharged from the heat exchanger HE-1 to preheat the raw material after pulping.

[0035] The waste heat distribution component delivers unused waste heat to the power generation device or plasma power source.

[0036] The insulation layer is wrapped around the outside of the heat exchanger. The insulation material is aluminum silicate cotton or rock wool, and the thickness is controlled to be 50-150mm.

[0037] The circulating water treatment unit includes a filter assembly, a desalination device, a water quality monitoring assembly, and a bypass desalination structure connected in sequence; the feed end of the filter assembly is connected to the liquid phase discharge end of the gas-liquid separation unit; the desalination device uses an ion exchange resin device or an electrodialysis device to reduce the salt content of the circulating water.

[0038] The water quality monitoring component monitors the pH value and conductivity of the circulating water in real time; the bypass salt discharge structure is connected to the concentrated water outlet of the desalination device for discharging crystalline salt.

[0039] The filter assembly adopts a multi-media filter, and the filter media includes quartz sand and anthracite. The filtration speed is controlled at 5-10m / h.

[0040] If the desalination device is an ion exchange resin device, the cation exchange resin of the desalination device shall be a strong acid type styrene-based cation exchange resin, and the anion exchange resin shall be a strong base type styrene-based anion exchange resin, and the resin filling height shall be controlled at 1-2m.

[0041] This invention also provides a method for hydrogen production via cold plasma microbubble synergistic supercritical water gasification of biomass, employing the aforementioned cold plasma microbubble synergistic supercritical water gasification system of biomass, comprising the following steps:

[0042] The biomass raw materials are pre-treated by pulping in the raw material processing unit to obtain a raw material slurry that meets the reaction requirements;

[0043] The raw material slurry is transported to the cold plasma pre-activation unit, where the surface of the raw material slurry is modified and activated by the action of cold plasma to enhance the reactivity of the raw material.

[0044] The activated raw material slurry is sent to the high-pressure subcritical pretreatment unit, where it is pressurized and preheated under high pressure. The plasma microbubble / jet component built into the high-pressure subcritical pretreatment unit is used to generate active species and enhance the reaction conditions.

[0045] The raw materials, after high-pressure subcritical pretreatment, are transported to the supercritical gasification reaction unit. Under the action of the catalytic bed in the supercritical gasification reaction unit, the supercritical water gasification and reforming reaction of biomass is completed, generating hydrogen-containing gasification reaction products.

[0046] The gasification reaction products are transported to a gas-liquid separation unit, where hydrogen-containing gas and liquid water are separated to obtain hydrogen-containing gas and liquid water.

[0047] The hydrogen-containing gas separated by the gas-liquid separation unit is transported to the hydrogen purification unit, where it is purified to obtain high-purity hydrogen. At the same time, the residual gas generated during the purification process is collected.

[0048] The waste heat generated by the hydrogen purification unit is recovered through the waste heat recovery unit. The recovered waste heat is used for preheating raw materials in the raw material processing unit, generating electricity for the system, or powering the plasma equipment in the cold plasma preactivation unit.

[0049] The liquid water separated by the gas-liquid separation unit is transported to the circulating water treatment unit for purification. The purified water is then recycled back to the pulping stage of the raw material processing unit. At the same time, the circulating water treatment unit discharges crystalline salts to alleviate system salt precipitation and scaling.

[0050] The present invention has the following advantages:

[0051] First, by pre-activating and modifying lignin with cold plasma, and combining it with the in-situ generation of active species such as ·OH and ·H by plasma microbubbles in the subcritical section, efficient depolymerization of lignin can be achieved under relatively mild operating conditions, and the efficiency of supercritical water gasification is improved. At the same time, the water-gas reaction is enhanced, the hydrogen production selectivity is improved, the hydrogen purity is stable at over 99.9%, and the tar generation is reduced by 40%-60%, effectively alleviating catalyst carbon deposition and deactivation.

[0052] Secondly, the plasma microbubbles in the high-pressure subcritical pretreatment unit also have a shearing effect, which can slow down the adhesion and deposition of salts; the bypass salt discharge structure and multi-media filtration and desalination design of the circulating water treatment unit can reduce the system salt precipitation and scaling rate by more than 50%; and can avoid the problem of pressure drop caused by coking and corrosion.

[0053] Third, the waste heat recovery unit offsets 30%-40% of the system's energy consumption; the plasma power supply and raw material preheating can directly utilize recovered waste heat; the circulating water treatment has a high water reuse rate, reducing the consumption of fresh water; the waste gas containing CO, CO2, and CH4 produced by hydrogen purification is used as fuel for waste heat recovery, further reducing energy waste. Overall, it combines environmental protection and economic efficiency.

[0054] Fourth, this invention achieves deep synergy between cold plasma and supercritical water gasification, solving the technical defects of their integrated coupling. It can meet the needs of scenarios such as distributed hydrogen production, industrial waste heat coupling, and organic solid waste resource utilization, providing a feasible technical path for the industrialization of biomass hydrogen production. Attached Figure Description

[0055] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0056] Figure 1 This is a schematic diagram of a cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system provided in an embodiment of the present invention;

[0057] Figure 2 This is a schematic diagram of the process for hydrogen production by cold plasma microbubbles in conjunction with supercritical biomass water gasification, provided in an embodiment of the present invention. Detailed Implementation

[0058] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] See Figure 1This invention provides a cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system, including a raw material processing unit, a cold plasma pre-activation unit, a high-pressure subcritical pretreatment unit, a supercritical gasification reaction unit, a gas-liquid separation unit, a hydrogen purification unit, a waste heat recovery unit, and a circulating water treatment unit.

[0060] The discharge end of the raw material processing unit is connected to the feed end of the cold plasma pre-activation unit, and the raw material processing unit transports the pulped biomass raw material to the cold plasma pre-activation unit; the discharge end of the cold plasma pre-activation unit is connected to the feed end of the high-pressure subcritical pretreatment unit, and the cold plasma pre-activation unit transports the surface-modified raw material to the high-pressure subcritical pretreatment unit; the high-pressure subcritical pretreatment unit has a built-in plasma microbubble / jet assembly, and the discharge end of the high-pressure subcritical pretreatment unit is connected to the feed end of the supercritical gasification reaction unit, and the high-pressure subcritical pretreatment unit transports the pressurized, preheated, and active species-enhanced raw material to the supercritical gasification reaction unit; the supercritical gasification reaction unit... The system includes a catalytic bed, the discharge end of which is connected to the feed end of a gas-liquid separation unit. The supercritical gasification reaction unit transports the gasification reaction products to the gas-liquid separation unit. The gas phase discharge end of the gas-liquid separation unit is connected to the feed end of a hydrogen purification unit, which then transports hydrogen-containing gas to the hydrogen purification unit. The inlet end of a waste heat recovery unit is connected to the hydrogen purification unit, and the outlet end of the waste heat recovery unit is connected between the raw material processing unit and the cold plasma pre-activation unit. A circulating water treatment unit is connected between the gas-liquid separation unit and the raw material processing unit. The circulating water treatment unit reuses the purified and separated water for raw material pulping and discharges crystalline salts to alleviate salt precipitation and scaling.

[0061] In this embodiment, the raw material processing unit includes a raw material crusher, a stirring and pulping tank, and an additive addition component; the raw material crusher crushes the biomass raw material to a particle size of 0.1-5mm, the stirring speed of the stirring and pulping tank is ≥300rpm, and <0.1wt% of dispersant is added to the stirring and pulping tank; the additive addition component adds 0.2-3wt% of K2CO3 or KOH additive and 0.05-2wt% of metal precursor.

[0062] Specifically, the raw material crusher pulverizes biomass to 0.1-5mm, which increases the specific surface area of ​​the raw material, shortens the molecular diffusion path in subsequent reactions, and improves the contact efficiency with supercritical water and active species; a stirring speed of ≥300rpm can prevent the raw material particles from settling, ensure the homogenization of the slurry, and reduce tar carbon buildup caused by uneven local reactions; <0.1wt% dispersant can further enhance particle dispersibility and prevent agglomeration; K2CO3 or KOH additives can adjust the alkalinity of the system, on the one hand promoting the breaking of lignin ether bonds, on the other hand inhibiting carbon buildup at acidic sites of the catalyst, while accelerating the water-gas reaction; metal precursors can be converted into active catalytic components in subsequent high-temperature reactions, and their early addition facilitates their uniform distribution in the raw material, laying the foundation for catalytic reforming in the supercritical gasification stage.

[0063] In this embodiment, the biomass raw material is selected from at least one of straw, forest residue, algae, sludge, and kitchen waste, the metal precursor is at least one of Ni, Ru, and Ni-Ce-Zr, the solid content of the raw material in the stirred pulping tank is controlled at 1-20 wt%, and the pH of the system is adjusted to 7-12.

[0064] Specifically, a variety of biomass raw materials, such as straw and forest residue, are selected to adapt to renewable resources from different sources, meeting the requirements for carbon-neutral hydrogen production. The metal and alloy catalysts corresponding to Ni, Ru, and Ni-Ce-Zr precursors have excellent C / C bond breaking and water-gas reaction catalytic activity. Among them, Ce and Zr elements can enhance the catalyst's resistance to carbon deposition and thermal stability. The raw material solid content of 1-20wt% balances reaction efficiency and transportation safety. Too low a solid content will increase the energy consumption of subsequent pressurization and equipment volume, while too high a content will easily lead to high slurry viscosity and transportation blockage. The alkaline environment of pH 7-12 can inhibit the corrosion of equipment by acidic components in biomass and promote the dissociation of OH⁻ in supercritical water, increase the concentration of ・OH free radicals in the system, and accelerate lignin depolymerization and organic gasification.

[0065] In this embodiment, the cold plasma pre-activation unit includes a plasma generator and a temperature control system; the discharge mode of the plasma generator is any one of dielectric barrier discharge, sliding arc, and plasma jet; the power of the plasma generator is 10-300W, the frequency is 1-50kHz, the processing time is 10-300s, and the working gas is N2, CO2, air, water vapor, or a mixture thereof; the temperature control system controls the unit outlet temperature to <80°C.

[0066] Specifically, discharge methods such as dielectric barrier discharge can generate non-equilibrium cold plasma at room temperature and pressure. After gaining high energy, electrons collide with working gas molecules to generate active species such as •H, •OH, and O2⁻. The combination of 10-300W power and 1-50kHz frequency ensures that the yield of active species meets the modification requirements while avoiding excessive power that could lead to local overheating of the raw materials. The 10-300s processing time allows for precise control of the degree of modification; too short a time results in insufficient introduction of functional groups on the lignin surface, while too long a time can easily cause excessive oxidation of the raw materials. Working gases such as N2 / CO2 can specifically generate specific active species, such as N2-derived NO. x The introduction of auxiliary functional groups and CO2 promote carbon chain breakage; an outlet temperature of <80°C can prevent the loss of volatile components in the raw materials, while avoiding premature hydrolysis reactions, ensuring that pre-activation only acts on the surface structure modification of the raw materials without changing their main components.

[0067] In this embodiment, the high-pressure subcritical pretreatment unit includes a high-pressure pump, a subcritical preheater, and a plasma microbubble / jet assembly. The high-pressure pump is a multi-stage plunger pump or a high-pressure screw pump, which pressurizes the raw material to 20-25 MPa. The subcritical preheater preheats the raw material to the subcritical region of 280-340°C, and the residence time of the raw material in the preheater is 2-30 s. The power supply for the plasma microbubble / jet assembly is a 5-30 kHz, 10-200 W nanosecond pulse power supply, microsecond pulse power supply, or RF power supply. The plasma microbubble / jet assembly generates microbubbles with an average Sauter diameter of 50-300 μm, and the gas volume fraction corresponding to the microbubbles is controlled to be 0.5-10%.

[0068] Specifically, the multi-stage plunger / screw pump can stably output 20-25MPa high pressure, laying the pressure foundation for entering the supercritical region and avoiding instability of the supercritical state caused by pressure fluctuations; the 280-340°C subcritical region is the transition stage of water properties, at which time the dielectric constant of water decreases, the solubility increases, and the raw material is initially softened, preparing for supercritical gasification; the 2-30s residence time can ensure uniform preheating of the raw material; the nanosecond / microsecond pulse power supply of the plasma microbubble / jet component can generate high-frequency pulse discharge, generating 50-300μm microbubbles in a high-pressure humid environment. The microbubbles have a large specific surface area, which can significantly improve the contact efficiency between active species and raw materials. At the same time, the bursting of microbubbles generates local high pressure and turbulence, which enhances mass transfer; 0.5-10% gas volume fraction can balance the yield of active species and the fluidity of the slurry, preventing excessive microbubbles from causing "gas blockage" in the slurry.

[0069] In this embodiment, the supercritical gasification reaction unit includes a supercritical reactor and a catalytic bed. The supercritical reactor is designed with two sections: an inlet empty bed section and a catalytic bed section. The reactor is lined with a high-Ni alloy or Hastelloy alloy. The supercritical reactor is treated with corrosion-resistant welding or coating. The temperature inside the supercritical reactor is controlled at 420-650°C, the pressure is controlled at 24-30 MPa, and the residence time of the raw material in the reactor is 10-120 s. The catalytic bed is filled with Ni-Ce. x Zr1₋ x At least one catalyst selected from O2 / Al2O3, Ni-Mg-Al oxide, and Ru / C, with a catalyst space velocity of 0.5-5 h⁻¹.

[0070] Specifically, the empty bed section at the inlet allows the feedstock to undergo preliminary gasification before entering the supercritical zone, preventing insufficiently dispersed feedstock from directly contacting the catalyst and causing localized carbon buildup; the catalyst in the catalytic bed section is the core of the reaction, Ni-Ce x Zr1₋ x Catalysts such as O2 / Al2O3 can adsorb raw material molecules and activate C-C and CH bonds, accelerating their breakage to generate small molecule gases. Simultaneously, they catalyze the water-gas reaction (CO + H2O → CO2 + H2) to enhance hydrogen production. 420-650°C and 24-30 MPa are the efficient range for supercritical water gasification; too low a temperature results in a slow reaction rate, while too high a temperature exacerbates equipment corrosion and energy consumption. A pressure higher than the critical pressure of 22.1 MPa ensures the water remains in a supercritical state. A residence time of 10-120 s and a space velocity of 0.5-5 h⁻¹ ensure sufficient gasification of the raw materials and prevent excessive residence leading to carbon buildup. High-Ni alloys / Hastelloy alloys and corrosion-resistant weld overlays can withstand the highly corrosive environment under the high temperature and pressure of supercritical water, extending equipment lifespan.

[0071] In this embodiment, the gas-liquid separation unit includes a primary cyclone-gravity separator and a secondary high-pressure gas-liquid separator connected in sequence. The feed end of the primary cyclone-gravity separator is connected to the discharge end of the supercritical gasification reaction unit, and is used to remove condensate and fine solid particles from the gasification reaction products. The feed end of the secondary high-pressure gas-liquid separator is connected to the discharge end of the primary cyclone-gravity separator. The operating pressure of the secondary high-pressure gas-liquid separator is controlled at 20-28 MPa. The secondary high-pressure gas-liquid separator is used to separate the gas phase component and the liquid phase component in the product. The gas phase component is transported to the hydrogen purification unit, and the liquid phase component is transported to the circulating water treatment unit.

[0072] Specifically, the first-stage cyclone-gravity separator utilizes the combined effect of centrifugal force and gravity. The centrifugal force generated by the cyclone throws denser condensate and fine solid particles (such as unreacted small particles and salt crystals) toward the separator wall, where they are then separated by gravity settling. This process can initially purify the products and prevent blockages in subsequent equipment. The second-stage high-pressure vapor-liquid separator operates at 20-28 MPa, where the partial pressure of water vapor in the gas phase is high. By cooling (using subsequent waste heat recovery), the water vapor is condensed, achieving complete separation of the gas phase (H2, CO, CO2, etc.) from the liquid phase (water, dissolved salts). High-pressure separation avoids the rapid expansion of the gas phase volume caused by sudden pressure drops, reducing the equipment load of the subsequent hydrogen purification unit. At the same time, the liquid phase is transported to the circulating water treatment unit under high pressure, reducing transportation energy consumption.

[0073] In this embodiment, the hydrogen purification unit includes a purification device and a waste gas treatment component. The purification device employs any one of a PSA pressure swing adsorption device, a membrane separation device, or a temperature swing adsorption device. The feed end of the purification device is connected to the gas phase discharge end of the gas-liquid separation unit. The purification device purifies the hydrogen-containing gas to a purity ≥ 99.9%. The feed end of the waste gas treatment component is connected to the tail gas outlet of the purification device. The waste gas treatment component transports the waste gas containing CO, CO2, and CH4 to the waste heat recovery unit as fuel.

[0074] Specifically, devices such as PSA (Pressure Swing Adsorption) utilize the selective adsorption differences of adsorbents for different gas components to adsorb impurities such as CO and CO2 under high pressure and desorb and regenerate under low pressure, which can efficiently obtain hydrogen with a purity of ≥99.9% to meet the hydrogen demand of industry or fuel cells; membrane separation achieves purification through the preferential permeability of polymer membranes to H2, which is flexible in operation and has a small footprint; temperature swing adsorption is suitable for scenarios with high impurity content, and the adsorption capacity is adjusted by temperature changes; the waste gas containing CO, CO2, and CH4 has a calorific value and can be transported to the waste heat recovery unit as fuel, where its chemical energy can be recovered and converted into heat energy for system preheating, realizing energy cascade utilization and reducing external energy consumption.

[0075] In this embodiment, the waste heat recovery unit includes heat exchanger HE-1, heat exchanger HE-2, waste heat distribution assembly, and insulation layer; the hot-side feed end of heat exchanger HE-1 is connected to the discharge end of the supercritical gasification reaction unit, and the cold-side feed end of heat exchanger HE-1 is connected to the feed end of the high-pressure subcritical pretreatment unit; the hot-side feed end of heat exchanger HE-2 is connected to the hot-side discharge end of heat exchanger HE-1, and the cold-side feed end of heat exchanger HE-2 is connected to the discharge end of the raw material processing unit to utilize the waste heat discharged from heat exchanger HE-1 to preheat the raw material after pulping; the waste heat distribution assembly transports the unutilized waste heat to the power generation device or plasma power source; the insulation layer is wrapped around the outside of the heat exchangers, and the insulation material is aluminum silicate cotton or rock wool, with a thickness controlled to be 50-150mm.

[0076] Specifically, heat exchanger HE-1 utilizes the waste heat from supercritical reaction products (high temperature and high pressure) to preheat the raw materials in the high-pressure subcritical pretreatment unit. Heat exchanger HE-2 then utilizes the medium-temperature waste heat discharged from heat exchanger HE-1 to preheat the slurry in the raw material processing unit, forming a stepped heat exchange of high-temperature waste heat - high-demand preheating (subcritical) and medium-temperature waste heat - low-demand preheating (slurry preparation), maximizing waste heat utilization. The waste heat distribution component uses the remaining waste heat for power generation or to power the plasma power source, realizing a closed-loop energy system and reducing dependence on the external power grid. The aluminum silicate cotton / rock wool insulation layer (50-150mm thickness) can effectively reduce heat loss from the heat exchanger. If the thickness is too thin, the insulation effect will be poor, and if it is too thick, it will increase the equipment volume and cost. This thickness range can balance insulation efficiency and economy.

[0077] In this embodiment, the circulating water treatment unit includes a filtration assembly, a desalination device, a water quality monitoring assembly, and a bypass salt discharge structure connected in sequence. The feed end of the filtration assembly is connected to the liquid phase discharge end of the gas-liquid separation unit. The desalination device uses an ion exchange resin device or an electrodialysis device to reduce the salt content of the circulating water. The water quality monitoring assembly monitors the pH value and conductivity of the circulating water in real time. The bypass salt discharge structure is connected to the concentrated water outlet of the desalination device for discharging crystalline salt. The filtration assembly uses a multi-media filter, with filter media including quartz sand and anthracite, and the filtration speed is controlled at 5-10 m / h. If the desalination device is an ion exchange resin device, the cation exchange resin uses a strong acid type styrene-based cation exchange resin, and the anion exchange resin uses a strong base type styrene-based anion exchange resin, with the resin filling height controlled at 1-2 m.

[0078] Specifically, the multi-media filter uses quartz sand (coarse filtration) and anthracite (fine filtration) to remove suspended impurities from the liquid phase layer by layer. A filtration speed of 5-10 m / h ensures filtration efficiency while preventing impurities from penetrating due to excessive flow rate. In the ion exchange resin unit, strong acid cation exchange resin adsorbs metal ions such as Na⁺ and K⁺, while strong base anion exchange resin adsorbs anions such as Cl⁻ and SO₄²⁻. A resin packing height of 1-2 m ensures sufficient ion exchange and facilitates regeneration. Electrodialysis uses an electric field to direct ion migration for desalination. The water quality monitoring component monitors pH and conductivity in real time to ensure that the circulating water quality meets the pulping requirements and prevents salt accumulation that could lead to equipment scaling and affect raw material dispersion. The bypass salt discharge structure removes concentrated water and crystalline salt generated by salt, fundamentally solving the system's salt precipitation problem, preventing blockage and corrosion caused by salt circulation accumulation, and ensuring continuous system operation.

[0079] See Figure 2 This invention also provides a method for hydrogen production via cold plasma microbubble synergistic supercritical water gasification of biomass, employing the aforementioned cold plasma microbubble synergistic supercritical water gasification system of biomass, and comprising the following steps:

[0080] S1. The biomass raw materials are pre-treated by pulping through the raw material processing unit to obtain a raw material slurry that meets the reaction requirements;

[0081] Specifically, biomass raw materials (such as straw and sludge) are initially in a solid or high-viscosity state. Directly introducing them into subsequent reaction units can easily lead to uneven mixing and hindered mass transfer. Pulping pretreatment reduces the particle size of the raw materials by crushing, increases the specific surface area, and shortens the molecular diffusion path. Stirring homogenizes the slurry to avoid localized concentration differences in the reaction. Adding additives adjusts the pH of the system to promote lignin depolymerization. Introducing metal precursors prepares for subsequent catalysis. The final product is a raw material slurry with solid content, pH, and dispersibility that meet the requirements. This provides a homogenized reaction matrix for subsequent cold plasma activation and supercritical gasification, avoiding problems such as low reaction efficiency and excessive by-products caused by uneven raw material states.

[0082] S2. The raw material slurry is transported to the cold plasma pre-activation unit, where the surface of the raw material slurry is modified and activated by the action of cold plasma to enhance the reactivity of the raw material.

[0083] Specifically, lignin in biomass has a stable structure and is difficult to depolymerize during conventional supercritical water gasification. Cold plasma generates high-energy electrons at room temperature / intermediate temperature, which collide with working gases (such as N2, CO2) to generate •OH, •H, and NO. xThe plasma contains active species that can penetrate the feed slurry interface, introducing oxygen-containing functional groups such as –OH and –COOH onto the lignin surface. This disrupts the hydrophobic structure, enhances wettability with supercritical water, and breaks some inert chemical bonds, lowering the apparent activation energy. Furthermore, the perturbation effect of the plasma reduces feed particle agglomeration, further optimizing the mass transfer environment. This enhances the feed reactivity from both molecular structure and interfacial characteristics, laying the foundation for subsequent low-energy, high-efficiency gasification.

[0084] S3. The activated raw material slurry is sent to the high-pressure subcritical pretreatment unit. The high-pressure subcritical pretreatment unit is pressurized and preheated under high pressure. The plasma microbubble / jet component built into the high-pressure subcritical pretreatment unit is used to generate active species and enhance the reaction conditions.

[0085] Specifically, supercritical water vaporization requires high temperature and high pressure. Directly entering the supercritical state is energy-intensive and prone to causing equipment shock. High-pressure pressurization lays the pressure foundation for subsequent entry into the supercritical region, avoiding system instability caused by sudden pressure rise; subcritical preheating (280-340℃) puts the water in a property transition stage, where the raw materials are initially softened, preparing for deep vaporization in the supercritical state. At the same time, the 50-300μm microbubbles generated by the plasma microbubble / jet component have a large specific surface area and high activity. They can continuously release active species such as •OH and •O2⁻ in a high-pressure humid environment, triggering the chain-opening reaction of raw material molecules in advance (lightening intermediates). The shearing effect of microbubbles can also slow down the adhesion of salts to the equipment wall, achieving multiple effects of pressurization preheating, activity enhancement, and initial scale control, reducing the harshness of the operating conditions in the main reaction zone.

[0086] S4. The raw materials that have undergone high-pressure subcritical pretreatment are transported to the supercritical gasification reaction unit. Under the action of the catalytic bed in the supercritical gasification reaction unit, the supercritical water gasification and reforming reaction of biomass is completed to generate hydrogen-containing gasification reaction products.

[0087] Specifically, supercritical water (420-650℃, 24-30MPa) possesses near-gaseous diffusivity and a low dielectric constant, allowing it to rapidly penetrate the feedstock and dissolve small-molecule intermediates, providing an excellent medium for the gasification reaction. The feedstock first passes through the empty bed section at the reactor inlet, where the strong dissolving effect of supercritical water facilitates initial bond breaking, preventing undispersed feedstock from directly contacting the catalyst and causing carbon buildup, before entering the catalytic bed, such as Ni-Ce. x Zr1₋ x(O2 / Al2O3). The catalyst accelerates the generation of intermediate gases such as CO and CH4 by adsorbing raw material molecules and activating C / C / CH bonds. Simultaneously, it catalyzes the water-gas reaction (CO + H2O ⇌ CO2 + H2), a crucial process for increasing hydrogen production. This reaction converts CO to H2 and inhibits catalyst poisoning caused by CO accumulation. The two-stage design, working synergistically with the catalyst, enables a continuous reaction of bond breaking, gasification, and reforming, efficiently generating gasification products primarily composed of H2 while reducing byproducts such as tar and carbon deposits.

[0088] S5. The gasification reaction products are transported to the gas-liquid separation unit, where hydrogen-containing gas and liquid water are separated.

[0089] Specifically, the supercritical gasification products are a gas-liquid mixture (containing gases such as H2, CO, and CO2, as well as unreacted liquid water, dissolved salts, and trace solid particles). If these directly enter the purification unit, it will lead to clogging and reduced efficiency of the purification equipment. The first-stage cyclone-gravity separation utilizes the combined action of centrifugal force and gravity to remove condensate and solid particles, preventing wear and clogging of subsequent equipment. The second-stage high-pressure gas-liquid separation (20-28 MPa) separates the gas and liquid phases under pressure. The high-pressure environment reduces the water vapor content in the gas phase (reducing the dehydration load of subsequent purification units), while maintaining high pressure in the liquid phase facilitates its transport to the circulating water treatment unit, reducing repressurization energy consumption. Through this two-stage separation, efficient gas-liquid purification and separation are achieved, providing qualified raw materials for subsequent hydrogen purification and water recycling.

[0090] S6. The hydrogen-containing gas separated by the gas-liquid separation unit is transported to the hydrogen purification unit, and high-purity hydrogen is obtained through the hydrogen purification unit. At the same time, the residual gas generated in the purification process is collected.

[0091] Specifically, the hydrogen-containing gas after gas-liquid separation still contains impurities such as CO, CO2, and CH4, which cannot meet the hydrogen requirements of industries (such as fuel cells and chemical synthesis). Pressure swing adsorption (PSA) utilizes the selectivity of adsorbents for different gases. Under high pressure, the adsorbent preferentially adsorbs polar impurities such as CO and CO2, while H2, due to its small molecular size and weak polarity, penetrates the adsorption bed to obtain high-purity hydrogen with a purity ≥99.9%. Under low pressure, the adsorbent is desorbed and regenerated, enabling recycling. The collected residual gas, containing CO, CO2, and CH4, has calorific value and can be used as fuel for subsequent waste heat recovery units, avoiding energy waste and environmental problems caused by direct emissions of exhaust gas, and achieving efficient resource utilization through the purification of main products and the recovery of by-products.

[0092] S7. The waste heat generated by the hydrogen purification unit is recovered through the waste heat recovery unit, and the recovered waste heat is used for raw material preheating in the raw material processing unit, system power generation, or to power the plasma equipment in the cold plasma preactivation unit.

[0093] Specifically, supercritical gasification and hydrogen purification processes generate a large amount of waste heat, and direct discharge would lead to increased system energy consumption. The waste heat recovery unit achieves cascade utilization through two-stage heat exchangers, HE-1 and HE-2: HE-1 uses high-temperature waste heat to preheat the raw materials of the high-pressure subcritical pretreatment unit, reducing the heating energy consumption of that unit; HE-2 uses medium-temperature waste heat to preheat the slurry of the raw material processing unit, reducing the energy consumption required for post-slurry heating. Unutilized waste heat is transported to the power generation unit through the waste heat distribution component to generate electricity for the system's own use or plasma equipment, which can offset 30%-40% of the system's external energy consumption, achieving energy closed-loop and significantly reducing the overall cost of hydrogen production.

[0094] S8. The liquid water separated by the gas-liquid separation unit is transported to the circulating water treatment unit. The circulating water treatment unit purifies the liquid water and recycles it for the pulping process of the raw material processing unit. At the same time, the circulating water treatment unit discharges crystallized salt to alleviate the salt precipitation and scaling of the system.

[0095] Specifically, the liquid water after gas-liquid separation contains dissolved salts and suspended impurities. Direct reuse in pulping can lead to salt accumulation, causing equipment salting and scaling. The circulating water treatment unit removes suspended impurities through multi-media filtration, and reduces the salt content of the water through ion exchange or electrodialysis. Water quality monitoring ensures that pH and purity meet pulping requirements, allowing the purified water to be recycled back to the pulping process, reducing fresh water consumption. A bypass salt discharge structure externally removes concentrated water and crystalline salt generated during the salting process, preventing salt accumulation in the system from the source, alleviating equipment corrosion and scaling problems, reducing the frequency of downtime for cleaning, and ensuring continuous and stable system operation.

[0096] To demonstrate the technical effectiveness of the present invention, the following experimental design was conducted:

[0097] Experimental materials: corn stalks (particle size 0.5-1mm after crushing, solid content 8wt%), with 0.8wt% K2CO3 additive and 0.5wt% Ni-Ce-Zr metal precursor added, and pH=9.5 after pulping.

[0098] Comparison group settings:

[0099] Control group: Traditional supercritical water vaporization system (without cold plasma preactivation and microbubble components);

[0100] Experimental group: The system of this invention (including cold plasma pre-activation + subcritical plasma microbubble assembly).

[0101] The core operating parameters are unified as follows: supercritical reactor temperature 500℃, pressure 26MPa, catalyst Ni-Ce0.5Zr0.5O2 / Al2O3 (space velocity 2h⁻¹), and feed residence time 30s. See Table 1 for comparison results.

[0102] Table 1 Performance Comparison of the Invention and Traditional Methods

[0103]

[0104] As shown in Table 1, the gasification efficiency and hydrogen production selectivity of the experimental group were significantly improved. This was due to the introduction of oxygen-containing functional groups (–OH / –COOH) by cold plasma pre-activation, which reduced the apparent activation energy of lignin and accelerated the depolymerization of ·OH free radicals generated by microbubbles in the subcritical section. The hydrogen purity was increased to 99.93%, thanks to the microbubble-enhanced water-gas reaction (CO+H2O⇌CO2+H2), which reduced CO impurity residue. The tar production and catalyst carbonization rate were significantly reduced because the plasma active species pre-lightened the intermediates, inhibiting the formation of heavy tar. At the same time, the microbubble shearing effect reduced carbon adhesion on the catalyst surface and extended the catalyst life. The continuous operation time was extended to 130 hours, and the salt precipitation and scaling rate was reduced by 70.8% because the plasma microbubble shearing slowed down salt deposition and the circulating water treatment unit achieved efficient desalination. The unit hydrogen production energy consumption was reduced by 43%, due to the waste heat cascade recovery and the synergistic cost reduction of plasma-supercritical water, fully demonstrating the engineering application value of this invention.

[0105] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A cold plasma microbubble synergistic supercritical water gasification hydrogen production system for biomass, characterized in that, It includes a raw material processing unit, a cold plasma pre-activation unit, a high-pressure subcritical pretreatment unit, a supercritical gasification reaction unit, a gas-liquid separation unit, a hydrogen purification unit, a waste heat recovery unit, and a circulating water treatment unit. The discharge end of the raw material processing unit is connected to the feed end of the cold plasma pre-activation unit, and the raw material processing unit transports the pulped biomass raw material to the cold plasma pre-activation unit. The discharge end of the cold plasma pre-activation unit is connected to the feed end of the high-pressure subcritical pretreatment unit, and the cold plasma pre-activation unit transports the surface-modified raw materials to the high-pressure subcritical pretreatment unit. The high-pressure subcritical pretreatment unit has a built-in plasma microbubble / jet component. The discharge end of the high-pressure subcritical pretreatment unit is connected to the feed end of the supercritical gasification reaction unit. The high-pressure subcritical pretreatment unit delivers the pressurized, preheated and active species-enhanced raw materials to the supercritical gasification reaction unit. The supercritical gasification reaction unit is equipped with a catalytic bed, and its discharge end is connected to the feed end of the gas-liquid separation unit. The supercritical gasification reaction unit transports the gasification reaction products to the gas-liquid separation unit. The gas phase outlet of the gas-liquid separation unit is connected to the feed end of the hydrogen purification unit, and the gas-liquid separation unit delivers hydrogen-containing gas to the hydrogen purification unit. The inlet of the waste heat recovery unit is connected to the hydrogen purification unit, and the outlet of the waste heat recovery unit is connected between the raw material processing unit and the cold plasma pre-activation unit. The circulating water treatment unit is connected between the gas-liquid separation unit and the raw material processing unit. The circulating water treatment unit reuses the purified and separated water for raw material pulping. The circulating water treatment unit discharges crystalline salts to alleviate salt precipitation and scaling.

2. The cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system according to claim 1, characterized in that, The raw material processing unit includes a raw material crusher, a mixing and pulping tank, and an additive assembly. The raw material crusher crushes the biomass raw material to a particle size of 0.1-5mm, the stirring speed of the stirring and slurrying tank is ≥300rpm, and <0.1wt% of dispersant is added to the stirring and slurrying tank; The additive component contains 0.2-3 wt% K2CO3 or KOH additives and 0.05-2 wt% metal precursors.

3. The cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system according to claim 2, characterized in that, The biomass raw material is selected from at least one of straw, forest residue, algae, sludge, and kitchen waste. The metal precursor is at least one of Ni, Ru, and Ni-Ce-Zr. The solid content of the raw material in the stirred pulping tank is controlled at 1-20 wt%, and the pH of the system is adjusted to 7-12.

4. The cold plasma microbubble synergistic supercritical water gasification hydrogen production system according to claim 1, characterized in that, The cold plasma pre-activation unit includes a plasma generator and a temperature control system; The plasma generator discharges in any one of dielectric barrier discharge, sliding arc, or plasma jet. The power of the plasma generator is 10-300W, the frequency is 1-50kHz, the processing time is 10-300s, and the working gas is N2, CO2, air, water vapor, or a mixture thereof. The temperature control system keeps the unit outlet temperature below 80°C.

5. The cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system according to claim 1, characterized in that, The high-pressure subcritical pretreatment unit includes a high-pressure pump, a subcritical preheater, and a plasma microbubble / jet assembly. The high-pressure pump is a multi-stage plunger pump or a high-pressure screw pump, which pressurizes the raw material to 20-25 MPa; the subcritical preheater preheats the raw material to the subcritical zone of 340°C, and the residence time of the raw material in the preheater is 2-30 seconds. The power supply of the plasma microbubble / jet assembly is a 5-30kHz, 10-200W nanosecond pulse power supply, microsecond pulse power supply or RF power supply. The plasma microbubble / jet assembly generates microbubbles with an average Sauter diameter of 50-300μm, and the gas volume fraction corresponding to the microbubbles is controlled to be 0.5-10%.

6. The cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system according to claim 1, characterized in that, The supercritical gasification reaction unit includes a supercritical reactor and a catalytic bed; The supercritical reactor is designed with two sections: an inlet empty bed section and a catalytic bed section. The reactor is lined with high-Ni alloy or Hastelloy alloy. The supercritical reactor is treated with corrosion-resistant welding or coating. The temperature inside the supercritical reactor is controlled at 420-650°C, the pressure is controlled at 24-30MPa, and the residence time of the raw material in the reactor is 10-120s. The catalyst bed is filled with Ni-Ce x Zr1₋ x At least one catalyst selected from O2 / Al2O3, Ni-Mg-Al oxide, and Ru / C, with a catalyst space velocity of 0.5-5 h⁻¹.

7. The cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system according to claim 1, characterized in that, The gas-liquid separation unit includes a first-stage cyclone-gravity separator and a second-stage high-pressure gas-liquid separator connected in sequence. The feed end of the first-stage cyclone-gravity separator is connected to the discharge end of the supercritical gasification reaction unit, and is used to remove condensate and fine solid particles from the gasification reaction products. The feed end of the secondary high-pressure vapor-liquid separator is connected to the discharge end of the primary cyclone-gravity separator. The operating pressure of the secondary high-pressure vapor-liquid separator is controlled at 20-28 MPa. The secondary high-pressure vapor-liquid separator is used to separate the gas phase component and the liquid phase component in the product. The gas phase component is sent to the hydrogen purification unit, and the liquid phase component is sent to the circulating water treatment unit.

8. The cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system according to claim 7, characterized in that, The hydrogen purification unit includes a purification device and a residual gas treatment component; the purification device adopts any one of a PSA pressure swing adsorption device, a membrane separation device, or a temperature swing adsorption device, the feed end of the purification device is connected to the gas phase discharge end of the gas-liquid separation unit, and the purification device purifies the hydrogen-containing gas to a purity ≥99.9%; The feed end of the waste gas treatment component is connected to the tail gas outlet of the purification device, and the waste gas treatment component transports the waste gas containing CO, CO2, and CH4 to the waste heat recovery unit as fuel.

9. The cold plasma microbubble synergistic biomass supercritical water gasification hydrogen production system according to claim 7, characterized in that, The waste heat recovery unit includes heat exchanger HE-1, heat exchanger HE-2, waste heat distribution assembly and insulation layer; The hot-side feed end of the heat exchanger HE-1 is connected to the discharge end of the supercritical gasification reaction unit, and the cold-side feed end of the heat exchanger HE-1 is connected to the feed end of the high-pressure subcritical pretreatment unit. The hot side feed end of the heat exchanger HE-2 is connected to the hot side discharge end of the heat exchanger HE-1, and the cold side feed end of the heat exchanger HE-2 is connected to the discharge end of the raw material processing unit so as to use the waste heat discharged from the heat exchanger HE-1 to preheat the raw material after pulping. The waste heat distribution component delivers unused waste heat to the power generation device or plasma power source. The insulation layer is wrapped around the outside of the heat exchanger. The insulation material is aluminum silicate cotton or rock wool, and the thickness is controlled to be 50-150mm. The circulating water treatment unit includes a filter assembly, a desalination device, a water quality monitoring assembly, and a bypass desalination structure connected in sequence; the feed end of the filter assembly is connected to the liquid phase discharge end of the gas-liquid separation unit; the desalination device uses an ion exchange resin device or an electrodialysis device to reduce the salt content of the circulating water. The water quality monitoring component monitors the pH value and conductivity of the circulating water in real time; the bypass salt discharge structure is connected to the concentrated water outlet of the desalination device for discharging crystalline salt. The filter assembly adopts a multi-media filter, and the filter media includes quartz sand and anthracite. The filtration speed is controlled at 5-10m / h. If the desalination device is an ion exchange resin device, the cation exchange resin of the desalination device shall be a strong acid type styrene-based cation exchange resin, and the anion exchange resin shall be a strong base type styrene-based anion exchange resin, and the resin filling height shall be controlled at 1-2m.

10. A method for hydrogen production by cold plasma microbubble synergistic supercritical water gasification of biomass, employing the cold plasma microbubble synergistic supercritical water gasification hydrogen production system according to any one of claims 1-9, characterized in that, Includes the following steps: The biomass raw materials are pre-treated by pulping in the raw material processing unit to obtain a raw material slurry that meets the reaction requirements; The raw material slurry is transported to the cold plasma pre-activation unit, where the surface of the raw material slurry is modified and activated by the action of cold plasma to enhance the reactivity of the raw material. The activated raw material slurry is sent to the high-pressure subcritical pretreatment unit, where it is pressurized and preheated under high pressure. The plasma microbubble / jet component built into the high-pressure subcritical pretreatment unit is used to generate active species and enhance the reaction conditions. The raw materials, after high-pressure subcritical pretreatment, are transported to the supercritical gasification reaction unit. Under the action of the catalytic bed in the supercritical gasification reaction unit, the supercritical water gasification and reforming reaction of biomass is completed, generating hydrogen-containing gasification reaction products. The gasification reaction products are transported to a gas-liquid separation unit, where hydrogen-containing gas and liquid water are separated to obtain hydrogen-containing gas and liquid water. The hydrogen-containing gas separated by the gas-liquid separation unit is transported to the hydrogen purification unit, where it is purified to obtain high-purity hydrogen. At the same time, the residual gas generated during the purification process is collected. The waste heat generated by the hydrogen purification unit is recovered through the waste heat recovery unit. The recovered waste heat is used for preheating raw materials in the raw material processing unit, generating electricity for the system, or powering the plasma equipment in the cold plasma preactivation unit. The liquid water separated by the gas-liquid separation unit is transported to the circulating water treatment unit for purification. The purified water is then recycled back to the pulping stage of the raw material processing unit. At the same time, the circulating water treatment unit discharges crystalline salts to alleviate system salt precipitation and scaling.

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