Method and system for hydrogen production from two-stage biomass alkaline thermal treatment

Abstract

This invention discloses a two-stage method and system for hydrogen production from biomass through alkaline thermal treatment. The method includes: a first-stage reaction in which a mixture of biomass and alkali is reacted in an inert gas atmosphere at a temperature of 180–235°C; followed by a second reaction in an inert gas atmosphere containing water vapor at a temperature of 500–600°C. Compared to traditional one-stage alkaline thermal treatment for hydrogen production with gradually increasing temperatures, this invention significantly improves the total hydrogen yield, biomass utilization rate, and hydrogen purity by promoting the thermochemical conversion of byproducts such as coke and tar. This is beneficial for the application of real biomass in alkaline thermal treatment for hydrogen production, and the process is simple and has wide applicability of raw materials.

Description

Technical Field

[0001] This invention relates to the field of biomass energy technology, and more specifically, to a method and system for hydrogen production from biomass through a two-stage alkaline thermal treatment process. Background Technology

[0002] Hydrogen energy, with its high gravimetric energy density (120-142 MJ / kg), wide range of conversion and reuse technologies, and zero carbon emissions during use, aligns closely with societal development trends and is hailed as the "ultimate energy source" of the 21st century. The International Energy Agency predicts that global hydrogen demand will reach 115 million tons by 2030 to achieve net-zero carbon emissions by 2050. However, currently, over 98% of global hydrogen energy comes from the reforming of fossil resources with high carbon emissions (~9 kg CO2 / kg H2), such as methane reforming and coal gasification, which severely compromises the environmental cleanliness of hydrogen. Hydrogen produced from biomass is considered carbon-neutral because plants consume the CO2 released as fuel through photosynthesis, and produce almost no other harmful gases (e.g., NO). x and SO x (etc.). Therefore, hydrogen production from biomass, which has a wide range of sources and abundant reserves, can significantly reduce carbon emissions from fossil fuel-based hydrogen production and alleviate the increasingly serious energy and environmental problems.

[0003] Currently, biomass hydrogen production methods mainly include thermochemical and biological methods. The former, due to its greater scalability, has been widely studied and primarily includes pyrolysis-reforming hydrogen production, steam gasification hydrogen production, and supercritical water gasification hydrogen production. However, it suffers from lower hydrogen production efficiency, higher tar and CO content. x The development and application of the aforementioned methods are limited by byproducts, high energy consumption, and high costs. Biomass alkaline thermal treatment for hydrogen production is a novel pyrolysis-based process developed in recent years, typically conducted at atmospheric pressure and relatively low temperatures (≤600℃). Compared to traditional biomass hydrogen production technologies, alkaline thermal treatment offers advantages such as mild reaction conditions, simple process, excellent in-situ carbon fixation, and high hydrogen yield, leading to its widespread research. Due to the "zero carbon emission" characteristic of biomass, alkaline thermal treatment for hydrogen production is a "negative carbon emission" technology with enormous application potential in the hydrogen production field.

[0004] Zhao Ming et al., in their patent (CN108130346A), described a method and system for producing hydrogen through the direct thermochemical conversion of sodium hydroxide and sludge. The method and system are simple to operate and the reaction conditions are easy to control, enabling the harmless treatment of sludge. However, the byproducts such as tar and coke produced significantly reduce the grade of the hydrogen produced, resulting in low overall utilization of the reactants. Furthermore, the complex solid-phase products pose challenges to the recovery and reuse of the carbonate products. Hu Mian et al., in their patent (CN113372934A), described a method for in-situ decarbonization and hydrogen production from biomass using potassium-calcium co-catalysis. This method has the advantages of a simple reactor and high decarbonization efficiency. However, it suffers from high energy consumption during the preparation process, the need for further improvement in hydrogen yield and purity (~70%), and low system utilization. Similarly, the scheme developed by Xiong Yuanquan et al. in patent (CN115650161A) for the co-production of hydrogen and porous carbon by biomass alkaline thermal treatment further improves the overall utilization rate of the system. However, the structure of porous carbon is affected by many factors (e.g., process conditions, raw material composition and structure), and the process stability still needs to be improved, which impairs the hydrogen production effect.

[0005] Currently, the reported biomass alkali thermal treatment hydrogen production processes mainly employ a one-stage reaction, where the feedstock reacts to the final temperature at a constant heating rate, exhibiting good hydrogen production and in-situ carbon fixation effects. Some studies have improved hydrogen production efficiency by changing the amount of alkali and optimizing process parameters (such as temperature and heating rate). However, the still relatively low hydrogen yield and purity, along with the inherent mass and heat transfer problems in the solid-solid reaction system leading to low overall system utilization, severely hinder the development of alkali thermal treatment hydrogen production technology. Furthermore, the unavoidable coke in the solid-phase products damages the quality of the product alkalis (alkali metal hydroxides and carbonates), increasing the difficulty and cost of separation and recovery, while also limiting the improvement of hydrogen production efficiency.

[0006] Therefore, developing technologies that facilitate efficient coke conversion in biomass alkali thermal treatment systems can simultaneously improve hydrogen production efficiency, reactant utilization, and the quality of the alkali product, thereby further reducing costs.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a method and system for hydrogen production through two-stage biomass alkali thermal treatment, thereby improving the efficiency of hydrogen production through biomass alkali thermal treatment, the utilization rate of reactants, and the quality of the product alkali.

[0009] This invention is implemented as follows:

[0010] In a first aspect, the present invention provides a two-stage biomass alkaline thermal treatment method for hydrogen production, comprising:

[0011] A single-stage reaction involves placing a mixture of biomass and alkali in an inert gas atmosphere and reacting at a temperature of 180–235°C to produce hydrogen and obtain a single-stage reaction solid residue.

[0012] The second-stage reaction involves placing the solid residue from the first-stage reaction in an inert gas atmosphere containing water vapor and reacting it at a temperature of 500–600°C to produce hydrogen and obtain the solid residue from the second-stage reaction.

[0013] In an optional implementation, the biomass includes real biomass and model biomass separated from real biomass;

[0014] Preferably, the real biomass includes at least one of bamboo residue, wood residue, and straw;

[0015] Preferably, the model biomass includes at least one of glucose, cellulose, hemicellulose, xylose, and lignin.

[0016] In an optional embodiment, the alkali is an alkali metal hydroxide; preferably, the alkali is at least one of sodium hydroxide and potassium hydroxide.

[0017] In an optional embodiment, the mass ratio of biomass to alkali in the mixture is 1:1 to 1:4.

[0018] In an optional embodiment, the duration of the first-stage reaction and / or the second-stage reaction is 20-60 minutes.

[0019] In an optional embodiment, the mixture is dried before the first stage of reaction;

[0020] Preferably, the drying temperature is 105-115℃ and the drying time is 20-40 min;

[0021] Preferably, an inert gas is introduced during the first stage of the reaction, and the flow rate of the inert gas is 20-80 mL / min.

[0022] In an optional embodiment, before the first stage of reaction, the mixture is heated to 180-235°C at a rate of 2-10°C / min.

[0023] In an optional embodiment, in the two-stage reaction step, an inert gas is introduced, and the flow rate of the inert gas is 20-80 mL / min.

[0024] Preferably, water is introduced into the second stage reaction, and the water flow rate is 0.007 to 0.04 mL / min.

[0025] Secondly, the present invention provides a two-stage biomass alkaline thermal treatment hydrogen production system applicable to any of the methods described in the foregoing embodiments, comprising a first-stage reactor for performing a first-stage reaction and a second-stage reactor for performing a second-stage reaction, wherein the first-stage reactor is connected to an inert gas source and the second-stage reactor is connected to an inert gas source and a steam generator.

[0026] In an optional embodiment, a tee is connected to the gas outlet of the first-stage reactor, one outlet of which is sequentially connected to a drying device, a detection device, and a gas collection device, and the other outlet of which is connected to the gas inlet of the second-stage reactor; and / or, the gas outlet of the second-stage reactor is sequentially connected to a condensing device, a liquid phase collection device, a drying device, a detection device, and a gas collection device.

[0027] In an optional embodiment, a flow meter and a water storage tank are also provided between the steam generator and the second-stage reactor.

[0028] The present invention has the following beneficial effects:

[0029] A two-stage alkaline thermal treatment reaction method and system were developed to achieve the preparation and collection of high-purity hydrogen in the low-temperature stage and high-yield hydrogen in the medium-temperature stage. This significantly promotes hydrogen production from coke conversion. The solid-phase products mainly consist of metal carbonates and a small amount of alkali, with trace / micro-scale coke products. Therefore, the system has a high overall utilization rate.

[0030] Lignin, one of the three major components of lignocellulosic biomass, is mainly converted into coke during alkaline thermal treatment of biomass due to its rigid structure and high carbon content, resulting in a low hydrogen conversion rate. This hinders the large-scale application of alkaline thermal treatment technology in real biomass. This application can significantly promote the conversion of lignin into hydrogen, which is beneficial for the application of real biomass in alkaline thermal hydrogen production. It maintains the advantages of low energy consumption and easy scalability of the original alkaline thermal treatment process and has high hydrogen production stability, providing a new approach and technology for solving the problem of difficult-to-treat agricultural, forestry, and domestic waste.

[0031] Compared with the commonly used alkaline heat treatment process, this method is simple to operate, has high hydrogen production efficiency, high hydrogen purity, and is applicable to real biomass. The hydrogen purity obtained can reach 90 vol.%, which improves its usability. The separation, recovery and purification of solid products are easy, and the whole method has environmental, economic and social benefits. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A schematic diagram of a two-stage biomass alkaline thermal treatment system for hydrogen production;

[0034] Figure 2 The formation rates of hydrogen and methane in the one-stage (a) and two-stage (b) glucose alkali heat treatments;

[0035] Figure 3 The hydrogen production yields of the one-stage and two-stage biomass alkaline thermal treatment in Examples 1-6;

[0036] Figure 4 The content of (a) sodium carbonate and (b) coke in the solid residue of the one-stage and two-stage biomass alkaline thermal treatment in Examples 1-6.

[0037] Diagram: 1-High-purity argon / nitrogen storage tank; 2-Pressure reducing valve; 3-Flow meter; 4-First stage reactor; 5-Second stage reactor; 6-T-way valve; 7-Drying device; 8-Detection device; 9-Gas collection device; 10-Condensation device; 11-Liquid phase collection device; 12-Steam generator; 13-Water storage tank. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] This invention provides a two-stage biomass alkaline thermal treatment method for hydrogen production, comprising:

[0040] A single-stage reaction involves placing a mixture of biomass and alkali in an inert gas atmosphere and reacting at a temperature of 180–235°C to produce hydrogen and obtain a single-stage reaction solid residue.

[0041] The second-stage reaction involves placing the solid residue from the first-stage reaction in an inert gas atmosphere containing water vapor and reacting it at a temperature of 500–600°C to produce hydrogen and obtain the solid residue from the second-stage reaction.

[0042] This application employs a two-stage alkaline thermal treatment for hydrogen production. In the first stage, the hydrogen production rate reaches a small peak, generating hydrogen with relatively high purity. Immediately after the first stage, the process is rapidly transferred to a second stage at 500–600°C. The solid residue from the first stage is rapidly heated from 180–235°C to 500–600°C without a prolonged heating process. During the second stage, the biomass conversion rate rapidly increases to its peak. Compared to traditional one-stage alkaline thermal treatment for hydrogen production with gradual temperature increases, this method significantly improves total hydrogen yield, biomass utilization rate, and hydrogen purity. The solid residue mainly consists of carbonates, coke, and unreacted alkali, with a reduced coke content, which facilitates the recovery and utilization of the solid residue.

[0043] In an optional embodiment, the biomass includes real biomass and model biomass separated from real biomass; the real biomass includes, but is not limited to, at least one of bamboo residue, wood residue, and straw; the model biomass includes, but is not limited to, at least one of glucose, cellulose, hemicellulose, xylose, and lignin.

[0044] The two-stage alkaline heat treatment hydrogen production method described in this application is applicable to biomass that are artificially extracted or synthesized, such as glucose, cellulose, hemicellulose, xylose, and lignin, as well as biomass obtained directly from nature, such as bamboo, wood, straw, and plant roots, stems, and leaves, which contain or can be converted into glucose, cellulose, hemicellulose, xylose, and lignin.

[0045] In some embodiments, in order to facilitate a rapid and complete reaction of the biomass, the biomass is crushed, then mixed with alkali and then thoroughly ground to ensure a more complete mixture.

[0046] In an optional embodiment, the alkali is an alkali metal hydroxide; preferably, the alkali is at least one of sodium hydroxide and potassium hydroxide.

[0047] In an optional embodiment, the mass ratio of biomass to alkali in the mixture is 1:1 to 1:4.

[0048] The reactions of glucose, cellulose, and xylose with sodium hydroxide are shown in equations ①-③ below. In order to ensure that glucose, cellulose, and xylose can react fully, the amount of alkali should not be too large, and it is usually sufficient to add it according to the stoichiometric ratio.

[0049] C6H 12 O6 (s) + 12 NaOH (s) = 6 Na2CO3 (s) + 12 H2 (g) ①

[0050] C6H 10O5 (s) + 12 NaOH (s) + H2O (g) = 6 Na2CO3 (s) + 12 H2 (g) ②

[0051] C5H 10 O5 (s) + 10 NaOH (s) = 5 Na2CO3 (s) + 10 H2 (g) ③

[0052] When the biomass is other than glucose, cellulose and xylose, the amount of alkali added is related to the composition of the biomass and needs to match the carbon content in the biomass. Generally, the mass ratio of biomass to alkali is 1:1 to 1:4.

[0053] In an optional embodiment, the time for the first and / or second stage reaction is 20-60 minutes. The release of hydrogen in the first and second stage reactions is mainly concentrated in the first 20 minutes. In order to make the reactants react as completely and fully as possible, the reaction time can be extended to 30-60 minutes.

[0054] In an optional embodiment, the mixture is dried before the first stage of reaction;

[0055] In an optional embodiment, the drying temperature is 105-115℃ and the drying time is 20-40 minutes. If the raw material has low moisture content and small particle size, the drying time can be appropriately shortened. If the raw material has high moisture content and large particle size, the drying time can be appropriately extended.

[0056] In an optional embodiment, an inert gas is introduced into the reaction section, and the flow rate of the inert gas is 20-80 mL / min. In some embodiments, the inert gas can be argon, nitrogen, etc., to prevent the reactants or hydrogen from being oxidized.

[0057] In an optional embodiment, before the first stage of reaction, the mixture is heated to 180-235°C at a rate of 2-10°C / min.

[0058] In an optional embodiment, an inert gas is introduced into the second-stage reaction, and the flow rate of the inert gas is 20-80 mL / min. In some embodiments, the inert gas can be argon, nitrogen, etc., to prevent the reactants or hydrogen from being oxidized.

[0059] In an optional embodiment, water is introduced into the two-stage reaction at a flow rate of 0.007–0.04 mL / min.

[0060] Secondly, the present invention provides a two-stage biomass alkaline thermal treatment system for hydrogen production applicable to any of the methods described in the foregoing embodiments, such as... Figure 1As shown, it includes a first-stage reactor 4 for a first-stage reaction and a second-stage reactor 5 for a second-stage reaction. The first-stage reactor 4 is connected to an inert gas source, and the second-stage reactor 5 is connected to an inert gas source and a steam generator 12.

[0061] The first-stage reactor 4 and the second-stage reactor 5 can be two separate reactors or two reaction zones within the same reactor, as long as the individual temperature control of the two stages is possible. In some embodiments, the mixture of biomass and alkali can be placed in a quartz boat and then transferred to heating zone I of the tubular furnace. After the first stage reaction is completed, it can be quickly transferred to heating zone II. In other embodiments, a conveying mechanism or conveying channel for transferring materials can be provided between the two reactors.

[0062] In an optional embodiment, a tee 6 is connected to the gas outlet of the first-stage reactor 4. One outlet of the tee 6 is sequentially connected to a drying device 7, a detection device 8, and a gas collection device 9. The other outlet of the tee 6 is connected to the air inlet of the second-stage reactor 5. The air outlet of the second-stage reactor 5 is sequentially connected to a condensing device 10, a liquid phase collection device 11, a drying device 7, a detection device 8, and a gas collection device 9. A flow meter 3 and a water storage tank 13 are also provided between the steam generator 12 and the second-stage reactor 5.

[0063] Using this system to produce hydrogen facilitates the sampling of gases generated in the first and second stages of the reaction. In some embodiments, the detection device 8 can be a gas chromatograph.

[0064] Specifically, the system includes an inert gas source, reaction section a, and reaction section b. The inert gas source includes a high-purity argon / nitrogen storage tank 1 and a pressure reducing valve 2 and a flow meter 3 connected to it in sequence. Reaction section a consists of heating zone I and a three-way valve 6, a drying device 7, a gas chromatograph, and an aluminum foil gas collection bag connected to it, which meets the needs of the first stage reaction. Reaction section b consists of a water storage tank 13, a flow meter 3, a steam generator 12, heating zone II, a condenser 10, a liquid phase collector, a drying device 7, a gas chromatograph, and an aluminum foil gas collection bag, which meets the needs of the second stage reaction.

[0065] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0066] Example 1---Comparative Study of Hydrogen Production by One-Stage and Two-Stage Glucose Alkaloid Thermal Treatment.

[0067] One-stage alkaline heat treatment reaction: The amount of glucose and NaOH added is 185.3 mg and 485.4 mg respectively. After being mixed evenly and ground thoroughly, the mixture is placed in a quartz boat and sent to heating zone II. The reaction device is then connected in sequence. Only reaction section b is used. The argon gas purging system is purged at 40 mL / min for 20 min. The heating program is set.

[0068] Maintaining a constant purge gas rate, heat to 110℃ at a rate of 10℃ / min and hold for 30 min to complete drying and dehydration. Begin the alkaline heat treatment reaction, increasing the temperature to the final temperature of 600℃ at 5℃ / min and holding for 30 min to ensure complete reaction. During the reaction, chromatographic sampling is performed every 5 min, collecting the total gas. The hydrogen production after the one-stage alkaline heat treatment is 28.33 mmol / g glucose. The formation rates of hydrogen and methane are as follows: Figure 2 As shown in (a).

[0069] Two-stage alkaline heat treatment reaction: The amount of glucose and NaOH added is 184.7 mg and 486.1 mg respectively. After being mixed evenly and ground thoroughly, the mixture is placed in a quartz boat and sent to heating zone I. Then, it is connected to the total reaction device in sequence. Argon gas at 40 mL / min is introduced to purge the entire system for 20 min. The heating program is set.

[0070] Close the gas collecting valve of reaction section b, keep the purge gas speed constant, and the drying and dehydration process of the reactants is the same as the one-stage alkaline heat treatment process. After drying is completed, start the reaction according to the heating program.

[0071] Keep the gas collecting valve of reaction section b closed, raise the temperature to the endpoint of 210℃ at 5℃ / min and maintain it at a constant temperature for 40min. During the reaction, the chromatographic sampling time is 5min / time. Collect the total gas and analyze and quantify the hydrogen production of alkaline heat treatment in section a, which is 12.06mmol / g glucose with a purity >97vol.%.

[0072] Close reaction section a, open the gas collecting valve of reaction section b, and introduce water at a rate of 0.02 mL / min. At the same time, send the solid residue of reaction section a into heating zone II at a temperature of 550℃. After reacting at a constant temperature for 30 min, raise the temperature to the final temperature of 600℃ at a rate of 5℃ / min and maintain the temperature for 30 min to end the reaction.

[0073] The total gas from reaction section b was collected, and quantitative analysis revealed that the hydrogen production from the alkaline thermal treatment in section b was 34.44 mmol / g glucose. The total hydrogen production from both stages was calculated to be 46.50 mmol / g glucose, representing a 64.14% increase in total hydrogen production. The formation rates of hydrogen and methane were as follows: Figure 2 As shown in (b).

[0074] Example 2---Comparative Study of Hydrogen Production by One-Stage and Two-Stage Alkali Thermal Treatment of Cellulose.

[0075] One-stage alkaline heat treatment reaction: The amount of cellulose and NaOH added is 163.5 mg and 485.4 mg respectively. After being mixed evenly and ground thoroughly, the mixture is placed in a quartz boat and sent to heating zone II. The reaction device is then connected in sequence. Only reaction section b is used. Argon gas is purged at 40 mL / min for 20 min. The heating program is set.

[0076] The subsequent one-stage alkali heat treatment reaction heating procedure was the same as in Example 1, except that water vapor was continuously introduced at a rate of 0.007 mL / min throughout the entire alkali heat treatment reaction until the reaction was completed. The total gas was collected, and the hydrogen production after the one-stage alkali heat treatment was 38.5 mmol / g cellulose.

[0077] Two-stage alkaline heat treatment reaction: cellulose and NaOH were added at amounts of 166.4 mg and 486.1 mg respectively. After being uniformly mixed and thoroughly ground, the mixture was placed in a quartz boat and sent to heating zone I. The boat was then connected to the main reaction device. An argon purging system of 40 mL / min was introduced for 20 min, and the heating program was set.

[0078] The subsequent two-stage alkali-thermal treatment process was the same as in Example 1, except for the temperature program. The temperature program was as follows: the temperature of reaction zone I was 180°C, the temperature of reaction zone II was set at 500°C and held for 30 min, then increased at a rate of 5°C / min to the final temperature of 600°C and held for 30 min. The total gas was collected, and quantitative analysis showed that the hydrogen production of the alkali-thermal treatment in stage a was 13.56 mmol / g cellulose, with a purity >98 vol.%; the hydrogen production of the alkali-thermal treatment in stage b was 41.16 mmol / g cellulose; the total hydrogen production of the two stages was calculated to be 54.72 mmol / g cellulose, representing an increase in total hydrogen production of 42.13%.

[0079] Example 3---Comparative Study on Hydrogen Production from One-Stage and Two-Stage Alkali Thermal Treatment of Hemicellulose (Xylose)

[0080] One-stage alkaline heat treatment reaction: Xylose and NaOH were added at amounts of 155.0 mg and 404.7 mg respectively. After being mixed evenly and ground thoroughly, the mixture was placed in a quartz boat and sent to heating zone II. The reaction apparatus was then connected in sequence. Only reaction section b was used. Argon gas was purged at a rate of 40 mL / min for 20 min. The heating program was set.

[0081] The subsequent one-stage alkali heat treatment reaction heating procedure and process were the same as in Example 1. The total gas was collected, and the hydrogen production after the one-stage alkali heat treatment was 26.80 mmol / g xylose.

[0082] Two-stage alkaline heat treatment reaction: Xylose and NaOH were added at amounts of 154.8 mg and 407.8 mg respectively. After being uniformly mixed and thoroughly ground, the mixture was placed in a quartz boat and sent to heating zone I. The boat was then connected to the main reaction device. An argon purging system of 40 mL / min was introduced for 20 min, and the heating program was set.

[0083] The subsequent two-stage alkali-thermal treatment reaction heating procedure and process were the same as in Example 1. The total gas was collected, and the hydrogen production of the alkali-thermal treatment in stage a was 6.4 mmol / g xylose with a purity >95 vol.%; the hydrogen production of the alkali-thermal treatment in stage b was 38.74 mmol / g xylan; the total hydrogen production of the two-stage reaction was calculated to be 45.14 mmol / g xylose, which increased the hydrogen production by 68.46%.

[0084] Example 4---Comparative Study of One-Stage and Two-Stage Lignin (Dealkalization) Glucose Alkali Thermal Treatment for Hydrogen Production

[0085] One-stage alkaline heat treatment reaction: Bamboo residue and NaOH were added at amounts of 156.7 mg and 459.7 mg respectively. After being mixed evenly and ground thoroughly, the mixture was placed in a quartz boat and sent to heating zone II. The reaction apparatus was then connected in sequence. Only reaction section b was used. Argon gas was purged at a rate of 40 mL / min for 20 min. The heating program was set.

[0086] The subsequent one-stage alkali heat treatment reaction heating procedure and process were the same as in Example 1. The total gas was collected, and the hydrogen production after the one-stage alkali heat treatment was 16.83 mmol / g lignin (alkali removal).

[0087] Two-stage alkaline heat treatment reaction: The bamboo residue and NaOH were added at amounts of 156.1 mg and 457.8 mg respectively. After being mixed evenly and ground thoroughly, the mixture was placed in a quartz boat and sent to heating zone I. The boat was then connected to the main reaction device. An argon purging system of 40 mL / min was introduced for 20 min, and the heating program was set.

[0088] The subsequent two-stage alkali-thermal treatment process was the same as in Example 1, except that the temperature program was adjusted. The temperature program was as follows: the temperature of reaction zone I was 235°C, and the temperature of reaction zone II was set at 600°C. After reaching the final temperature, the temperature was maintained for 40 minutes. The total gas was collected, and quantitative analysis revealed that the hydrogen production of the alkali-thermal treatment in stage a was 2.93 mmol / g lignin (dealkali-treated), with a purity >96 vol.%; the hydrogen production of the alkali-thermal treatment in stage b was 22.72 mmol / g lignin (dealkali-treated); the total hydrogen production of the two stages was calculated to be 25.65 mmol / g lignin (dealkali-treated), representing a 52.46% increase in hydrogen production.

[0089] Example 5---Comparative Study of One-Stage and Two-Stage Poplar Slag Alkali Thermal Treatment for Hydrogen Production

[0090] One-stage alkaline heat treatment reaction: Poplar wood residue and NaOH were added at amounts of 155.4 mg and 457.7 mg respectively. After being mixed evenly and ground thoroughly, the mixture was placed in a quartz boat and sent to heating zone II. The reaction apparatus was then connected in sequence. Only reaction section b was used. Argon gas was purged at a rate of 40 mL / min for 20 min. The heating program was set.

[0091] The subsequent one-stage alkali heat treatment reaction heating procedure and process were the same as in Example 1. The total gas was collected, and the hydrogen production after the one-stage alkali heat treatment was 29.62 mmol / g poplar wood residue.

[0092] Two-stage alkaline heat treatment reaction: Poplar wood residue and NaOH were added at amounts of 157.6 mg and 457.6 mg respectively. After being mixed evenly and ground thoroughly, the mixture was placed in a quartz boat and sent to heating zone I. The boat was then connected to the main reaction device. An argon gas purging system of 40 mL / min was introduced for 20 min, and the heating program was set.

[0093] The subsequent two-stage alkali heat treatment reaction heating procedure and process were the same as in Example 1. The total gas was collected, and the hydrogen production of the first-stage alkali heat treatment was analyzed and quantitatively determined to be 12.2 mmol / g poplar wood residue with a purity >97 vol.%; the hydrogen production of the second-stage alkali heat treatment was 25.04 mmol / g poplar wood residue; the total hydrogen production of the two-stage reaction was calculated to be 37.24 mmol / g poplar wood residue, which increased the hydrogen production by 25.75%.

[0094] Example 6---Comparative Study of One-Stage and Two-Stage Bamboo Slag Alkali Thermal Treatment for Hydrogen Production

[0095] One-stage alkaline heat treatment reaction: Bamboo residue and NaOH were added at amounts of 157.9 mg and 459.2 mg respectively. After being mixed evenly and ground thoroughly, the mixture was placed in a quartz boat and sent to heating zone II. The reaction apparatus was then connected in sequence. Only reaction section b was used. Argon gas was purged at a rate of 40 mL / min for 20 min. The heating program was set.

[0096] The subsequent one-stage alkali heat treatment reaction heating procedure and process were the same as in Example 1. The total gas was collected, and the hydrogen production after the one-stage alkali heat treatment was 33.49 mmol / g bamboo residue.

[0097] Two-stage alkaline heat treatment reaction: bamboo residue and NaOH were added at amounts of 156.2 mg and 455.9 mg respectively. After being mixed evenly and ground thoroughly, the mixture was placed in a quartz boat and sent to heating zone I. The boat was then connected to the main reaction device. An argon purging system of 40 mL / min was introduced for 20 min, and the heating program was set.

[0098] The subsequent two-stage alkali heat treatment reaction heating procedure and process were the same as in Example 1. The total gas was collected, and the hydrogen production of the first-stage alkali heat treatment was analyzed and quantitatively determined to be 6.87 mmol / g bamboo residue with a purity >98 vol.%; the hydrogen production of the second-stage alkali heat treatment was 47.51 mmol / g bamboo residue; the total hydrogen production of the two-stage reaction was calculated to be 54.38 mmol / g bamboo residue, representing an increase in hydrogen production of 62.39%.

[0099] The hydrogen production yield and solid residue composition of the one-stage and two-stage biomass alkaline thermal treatment in each embodiment are as follows: Figure 3 and Figure 4 As shown, compared with the one-stage biomass alkali thermal treatment for hydrogen production, the two-stage biomass alkali thermal treatment for hydrogen production significantly increases the hydrogen yield, and the total hydrogen purity can be maintained at 83% to 90% (methane content of about 8% to 15%). The purity of hydrogen produced in the low-temperature stage can reach more than 95%. At the same time, the sodium carbonate yield is significantly improved, and the residual coke content is significantly reduced.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing hydrogen by two-stage biomass alkali thermal treatment, characterized by, include: A single-stage reaction involves placing a mixture of biomass and alkali in an inert gas atmosphere and reacting at a temperature of 180–235 °C to produce hydrogen and obtain a single-stage reaction solid residue. The second-stage reaction involves placing the solid residue from the first-stage reaction in an inert gas atmosphere containing water vapor and reacting it at a temperature of 500-600 °C to produce hydrogen and obtain the solid residue from the second-stage reaction. The time for the first and second stage reactions is 20-60 minutes.

2. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, The biomass includes real biomass and model biomass separated from real biomass.

3. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 2, characterized in that, The real biomass includes at least one of bamboo residue, wood residue, and straw.

4. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 2, characterized in that, The model biomass includes at least one of glucose, cellulose, hemicellulose, xylose, and lignin.

5. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, The alkali is an alkali metal hydroxide.

6. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, The alkali is at least one of sodium hydroxide and potassium hydroxide.

7. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, The mass ratio of biomass to alkali in the mixture is 1:1 to 1:

4.

8. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, The mixture is dried before the first stage of the reaction.

9. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 8, characterized in that, The drying temperature is 105-115℃, and the drying time is 20-40 minutes.

10. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, An inert gas is introduced during the first stage of the reaction, and the flow rate of the inert gas is 20~80 mL / min.

11. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, Before the first stage of reaction, the mixture is heated to 180-235 °C at a rate of 2-10 °C / min.

12. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, In the two-stage reaction step, an inert gas is introduced at a flow rate of 20-80 mL / min.

13. The method for hydrogen production from biomass through two-stage alkaline thermal treatment according to claim 1, characterized in that, Water is introduced into the two-stage reaction at a flow rate of 0.007~0.04 mL / min.

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