Hydrogen production process by municipal solid waste temporary oxygen activation and staged gasification

Abstract

The application provides a hydrogen production process of municipal solid waste temporary oxygen activation-grading gasification, which integrates the steps of temporary oxygen activation, screening of municipal solid waste into coarse particles and fine particles with different particle sizes, gas-solid decoupling grading gasification, simultaneous removal of pollutants and hydrogen refining, and the like, so that high-purity hydrogen with high yield and high output is integrally prepared. The prepared hydrogen has a purity of 99.97%, low tar content and low pollutant emission, and meets the national emission standard, which provides an innovative technical solution for preparation of vehicle hydrogen fuel from municipal solid waste resources.

Description

Technical Field

[0001] This invention belongs to the technical field of solid waste resource utilization and vehicle clean energy preparation, specifically involving a hydrogen production process of urban domestic waste through oxygen activation-stage gasification. Background Technology

[0002] Urban solid waste disposal has become a widespread environmental problem. Achieving efficient resource utilization of urban solid waste is key to solving the problem of ineffective waste conversion and utilization, which leads to resource waste and environmental burden. Hydrogen is considered a clean energy source for the 21st century, characterized by high energy density and zero carbon emissions during its utilization. It is an important carrier for achieving sustainable development and a crucial pathway to meet the growing demand for vehicle fuel.

[0003] Gasification technology can convert organic components in municipal solid waste into syngas for hydrogen production, providing an important pathway for the resource utilization and low-carbon treatment of organic solid waste. However, this technology still faces significant challenges, including uneven raw material distribution, low hydrogen yield, and difficulty in controlling pollutants. Particularly in the area of ​​vehicle fuel, existing technologies struggle to efficiently convert the complex composition of municipal solid waste into high-purity hydrogen fuel that meets vehicle standards, thus limiting the application of waste-to-hydrogen production in relevant scenarios.

[0004] Against this backdrop, relevant research has gradually commenced. Patent application CN116554931A discloses a process for producing hydrogen through carbonization and gasification of municipal solid waste. This process involves treating municipal solid waste through curing, dehydration, drying, anaerobic pyrolysis, and thermal sorting. This transforms the waste into homogeneous carbon powder gasification feedstock with low moisture content, high energy density, and high calorific value before gasification. This process eliminates the need for external fossil fuels such as natural gas, resulting in a low-carbon emission hydrogen production process that does not require complex and costly pretreatment. The entire process yields 0.4 Nm³ of hydrogen from 1 kg of municipal solid waste. 3 The process also involves treating the slag water discharged from the gasifier as ash water, followed by a salt purification system, to achieve the recovery and resource utilization of salt in municipal solid waste.

[0005] However, such processes have not yet overcome the technical challenge of efficiently converting municipal solid waste into high-purity hydrogen fuel that meets vehicle standards. At the same time, the following problems exist: (1) Oxygen-free pyrolysis has high requirements for the reactor, and there is still a risk of uneven gasification feed and unstable reaction; (2) The biomass or waste-derived fuel bio-carbon powder cannot be fully converted, making it difficult to improve hydrogen conversion efficiency and output; (3) The tar and various pollutants such as sulfur, chlorine and nitrogen are not removed in a synergistic and deep manner, and the hydrogen purity does not meet vehicle standards.

[0006] Therefore, developing an integrated technology and system that can efficiently convert municipal solid waste into high-purity hydrogen fuel that meets vehicle standards and achieve ultra-low emissions of pollutants is of urgent industrial demand and significant environmental value. Summary of the Invention

[0007] In view of the aforementioned problems in the existing technology, the primary objective of this invention is to provide a hydrogen production process for municipal solid waste through oxygen activation and staged gasification.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention claims protection for a hydrogen production process based on oxygen activation and staged gasification of municipal solid waste, comprising the following steps: (1) Preparation of bio-carbon powder by oxygen activation: Bio-carbon powder is prepared by pyrolysis of municipal solid waste in an inert atmosphere containing oxygen; the volume fraction of oxygen in the inert atmosphere is 2%-6%; (2) Crush and sieve the biochar powder in step (1) to obtain coarse particles with a particle size of 1~2 mm and fine particles with a particle size of 0.1~1 mm; (3) Gas-solid decoupling staged gasification: The fine particles in step (2) are deeply reformed in a suspended bed at a temperature of 850~900℃; the coarse particles are initially gasified in a fluidized bed at a temperature of 750-800℃, and then enter the suspended bed for deep reforming; during the gasification process, a calcium-based adsorbent is introduced into the suspended bed to adsorb carbon dioxide in situ to obtain crude syngas; (4) Catalytic reforming and tar removal: The crude syngas in step (3) is subjected to catalytic reforming to obtain reformed gas; (5) Synergistic deep removal of pollutants: The gas after reforming in step (4) is desulfurized, dechlorinated and denitrified, and then hydrogen is obtained by pressure swing adsorption.

[0009] This invention provides a hydrogen production process for municipal solid waste through oxygen-activated and staged gasification. The process involves oxygen activation, screening into coarse and fine particles of different sizes, gas-solid decoupling and staged gasification, synergistic removal of pollutants, and hydrogen refining, all integrated to produce high-yield, high-purity hydrogen (purity ≥99.97%). The inventors discovered that when preparing biochar from municipal solid waste, introducing a certain volume of oxygen into an inert gas atmosphere can transform the complex and varied raw waste into homogeneous and highly reactive biochar. While excessively high oxygen concentrations can help form some pores, they exacerbate the loss of organic matter in the pretreated waste, reducing solid yield and subsequent effective carbon source supply. Conversely, excessively low oxygen concentrations result in lower fixed carbon reactivity, leading to significantly lower effective carbon source conversion efficiency compared to biochar prepared through oxygen activation, thus reducing the activity of the biochar and the subsequent hydrogen production effect.

[0010] Furthermore, during the gasification process, coarse and fine particles of different sizes are obtained by crushing the bio-carbon powder. These coarse and fine particles are then subjected to staged gasification. Simultaneously, a calcium-based adsorbent is introduced to adsorb CO2 in situ, promoting the water-gas shift reaction and increasing hydrogen yield. The inventors discovered that traditional single gasifiers suffer from an inherent spatial-temporal mismatch in gas-solid reaction when processing bio-carbon powder with a wide particle size distribution: large carbon particles require a longer reaction time for complete gasification, but tend to settle and be discharged from the fluidized bed; small particles have high reactivity with volatiles, but their residence time in the bed is too short, causing them to escape with the gas flow before proper reorganization, resulting in significant chemical energy loss. To address this issue, this invention innovatively proposes a dual-bed coupled staged gasification strategy: coarse particles first collide with sufficient bed material at a relatively low temperature, extending the effective reaction time of the coarse particles and gradually breaking them down into smaller particles and volatiles, thus completing the initial gasification. Fine particles undergo deep reforming and gasification directly at relatively high temperatures. The higher temperatures and intense turbulent fields ensure that the fine particles and volatiles escaping to this point are rapidly and completely converted into small-molecule gases (CO, H2), greatly suppressing tar formation and achieving deep release of chemical energy. By coupling and functionally dividing the bio-carbon powder of different sizes with the temperature gradients of fluidized beds and suspended beds, this invention constructs a cascade reaction system from "slow-release gasification" to "instantaneous decomposition and scale-up," ensuring that the bio-carbon powder can achieve near-complete conversion in the most suitable reaction zone, thereby significantly improving carbon conversion rate, gasification efficiency, and final hydrogen yield.

[0011] Furthermore, the gasified crude syngas undergoes catalytic reforming to achieve efficient removal of tar and deep conversion of low-reactive volatiles, thereby further improving resource utilization and conversion efficiency. The reformed gas is then subjected to multi-stage purification units to remove pollutants such as H2S, HCl, and NH3, and finally purified by the PSA (Pressure Swing Adsorption) stage to obtain high-purity hydrogen.

[0012] The hydrogen production process provided by this invention has undemanding requirements for the reactor and employs gas-solid decoupled staged gasification and in-situ CO2 adsorption enhancement technology to strengthen the matching of gas-solid reactions, achieve full conversion of biochar powder or volatiles, promote hydrogen generation, achieve a gasification efficiency of ≥81.5%, produce hydrogen with a purity of ≥99.97%, low tar content, and ultra-low pollutant emissions, meeting the GB / T 37244-2018 standard. This provides an innovative technical solution for the resource-based production of hydrogen fuel for vehicles from municipal solid waste.

[0013] Preferably, the volume fraction of oxygen in the inert atmosphere is 4.5%-5.5%. Under these preferred conditions, contact between oxygen and biochar powder can remove some volatiles and form biochar powder with well-developed pores and enhanced reactivity.

[0014] Preferably, in step (1), the pyrolysis temperature is 350~450℃.

[0015] Preferably, in step (3), the mass ratio of coarse or fine particles to calcium-based adsorbent is 0.05-0.2:1. More preferably, the mass ratio of coarse or fine particles to calcium-based adsorbent is 0.08-0.15:1.

[0016] Preferably, in step (3), the calcium-based adsorbent is an adsorbent based on calcium oxide. Injecting inexpensive and readily available calcium oxide into the suspended bed during or after gasification can adsorb CO2 in situ, promote the water-gas shift reaction, and thus increase the hydrogen yield.

[0017] Preferably, in step (3), the in-situ adsorption conditions are 750~800℃.

[0018] Preferably, in step (4), the crude syngas undergoes catalytic reforming under a Ni-CaO / Al2O3 catalyst.

[0019] Preferably, in step (4), the Ni-CaO / Al2O3 catalyst has a Ni loading of 5-15 wt% and a CaO loading of 10-30 wt%; more preferably, the Ni loading is 10-15 wt% and the CaO loading is 15-25 wt%. Most preferably, the Ni loading is 10 wt% and the CaO loading is 20 wt%. Under these preferred catalyst conditions, the crude syngas can be catalytically reformed more effectively, achieving efficient removal of tar and deep conversion of low-reactive volatiles.

[0020] Preferably, in step (4), the catalytic reforming conditions are: a packing volume of 0.1~0.5 m³. 3 The reaction temperature is 750~800℃, and the space velocity is 1500~2500 h⁻¹. -1 .

[0021] Preferably, in step (4), the reformed gas is cooled to 150~250℃ for desulfurization, dechlorination and denitrification operations.

[0022] Preferably, in step (4), desulfurization is performed using a ZnO-based adsorbent at an operating temperature of 200-300℃.

[0023] Preferably, in step (4), dechlorination is performed using an alkaline adsorbent at an operating temperature of 150-250℃.

[0024] Preferably, in step (4), denitrification is performed using a process combining molecular sieve adsorption and low-temperature SCR (Selective Catalytic Reduction) catalysis, with an operating temperature of 180-280℃.

[0025] Preferably, in step (5), the pressure swing adsorption operation is as follows: S1. Under a pressure of 1.0-1.5 MPa, the gas flows through a bed containing adsorbent to remove residual moisture and impurities such as CO2, CH4, CO, and N2. S2. Perform pressure equalization and depressurization 2-3 times to bring the pressure down to 0.5-0.6 MPa while recovering hydrogen from the voids inside the tower; S3. Gradually reduce the pressure to normal and then to negative pressure to desorb and release the impurity gases adsorbed by the adsorbent; S4. Perform equalization and pressure increase 2-3 times to raise the pressure to 1.0-1.5MPa, and repeat the above steps S1 to S3.

[0026] Preferably, the moisture content of the municipal solid waste is ≥30 wt%; more preferably, the moisture content of the municipal solid waste is ≥45 wt%; even more preferably, the moisture content of the municipal solid waste is 45~60 wt%. Furthermore, the present invention provides an implementation system based on the above-mentioned hydrogen production process, the implementation system comprising the following devices connected in sequence: an oxygen activation unit, a gas-solid decoupling staged gasification furnace, an in-situ adsorption enhancement unit, a catalytic reforming unit, a pollutant synergistic deep removal unit, and a hydrogen separation and purification unit.

[0027] Specifically, the oxygen-activated unit is a rotary kiln pyrolysis furnace equipped with a controllable low-concentration oxygen supply system; the gas-solid decoupling staged gasification furnace includes a pressurized bubbling fluidized bed and a high aspect ratio contrast spray suspension bed connected in series, and is equipped with a zoned feeding system and a staged air distribution system; the hydrogen separation and purification unit is a membrane separation-pressure swing adsorption integrated system.

[0028] Preferably, in the above-described implementation system, a dehydration and drying pretreatment unit is connected after the oxygen activation unit.

[0029] The present invention provides a hydrogen production process for the oxygen-activated and staged gasification of municipal solid waste, which produces high-purity hydrogen that meets automotive standards. This process can be widely used in the production of automotive hydrogen fuel, industrial high-purity hydrogen, fuel cells, and other fields.

[0030] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a hydrogen production process for municipal solid waste through oxygen-activated, staged gasification. The process involves several steps, including oxygen activation, screening into coarse and fine particles of different sizes, gas-solid decoupling staged gasification, synergistic pollutant removal, and hydrogen refining. This integrated approach yields high-purity hydrogen with high yield and high output. The produced hydrogen has a purity ≥99.97%, low tar content, and ultra-low pollutant emissions, meeting the GB / T 37244-2018 standard. This provides an innovative technical solution for the resource-based production of hydrogen fuel for vehicles from municipal solid waste. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the hydrogen production process of municipal solid waste oxygen activation-stage gasification in Example 5. Detailed Implementation

[0032] The present invention will be further described below with reference to the specification and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0033] In this invention, the preparation method of the Ni(10 wt%)-CaO(20 wt%) / Al2O3 bifunctional catalyst is as follows: Ni (10 wt%) and CaO (20 wt%) are weighed and dissolved in 300 mL of deionized water, stirred until completely dissolved, to obtain a mixed metal salt solution. Separately, measured amounts of NaOH and Na2CO3 are dissolved in 200 mL of deionized water to obtain a precipitant solution. The mixed metal salt solution is heated to 70°C under stirring, and the precipitant solution is rapidly added, controlling the pH value between 10 and 11, and the reaction is stirred for 60 min. After the reaction is complete, the temperature is raised to 96°C for aging and crystallization for 10 h. The precipitate is collected by centrifugation, repeatedly washed with deionized water until the filtrate is neutral, and dried at 120°C for 12 h to obtain the catalyst precursor. The precursor is placed in a muffle furnace and calcined at 800°C at a rate of 5°C / min under air atmosphere for 2 h to obtain the NiO / CaO-Al2O3 composite oxide. Before use, the catalyst was reduced at 700℃ for 1 h under H2 atmosphere to obtain an activated Ni / CaO-Al2O3 bifunctional catalyst.

[0034] Example 1 This invention provides a hydrogen production process for municipal solid waste through oxygen activation and staged gasification, comprising the following steps: (1) Preparation of bio-carbon powder by oxygen activation: 1 ton of sorted, crushed and dried municipal solid waste was fed into a rotary kiln oxygen activation furnace. O2 with a volume fraction (concentration) of 5% was introduced under N2 carrier gas conditions, the furnace temperature was controlled at 400℃, the residence time was 40 minutes, and some volatile matter was removed to obtain about 0.3 tons of bio-carbon powder.

[0035] (2) Bio-carbon powder pretreatment: The bio-carbon powder is sent into the pretreatment system and is coarsely crushed by a hammer crusher (outlet particle size ≤ 8 mm) and finely ground by an ultra-micro grinding mill. Then it enters a multi-layer vibrating screen for grading and screening. By adjusting the screen, coarse particles with a particle size of 1~2 mm and fine particles with a particle size of 0.1~1 mm are obtained.

[0036] (3) Gas-solid decoupling staged gasification: The pretreated biochar powder is fed into a dual-bed coupled gasifier and gas-solid decoupling staged gasification is carried out in an oxygen-water vapor atmosphere; fine particles (0.5~1mm) and volatiles are deeply reformed in a suspended bed (850℃); coarse particles (1~2mm) are initially gasified in a fluidized bed (800℃) and then enter the suspended bed for deep reforming.

[0037] (4) Enhanced in-situ carbon dioxide adsorption: After 1 hour of gasification reaction, CaO powder is injected from the middle of the suspension bed. The mass ratio of CaO to carbonaceous powder (i.e., the coarse or fine particles from step (3)) is 0.10:1. The adsorption temperature is 750℃, and the adsorption reaction time is controlled to be 15-20 minutes. The CO2 concentration in the outlet gas of the suspension bed is monitored by an online gas analyzer. When the outlet CO2 concentration fluctuates less than ±1% within 5 minutes (i.e., continuously stable), it indicates that the CaO adsorption capacity has been basically saturated, and crude syngas is finally obtained after in-situ adsorption of carbon dioxide.

[0038] (5) Catalytic reforming and tar removal: The crude syngas enters the reforming reactor, and the Ni (10 wt%)-CaO (20 wt%) / Al2O3 bifunctional catalyst is packed in a volume of 0.1 m³. 3 The reaction temperature was 780℃ and the space velocity was 2000 h⁻¹. -1 The reformed gas is obtained to achieve tar cracking, light hydrocarbon reforming and partial CO2 capture coupled enhancement.

[0039] (6) Synergistic deep removal of pollutants: After the reformed gas is cooled to 200℃, it is sequentially passed through a ZnO desulfurization bed, a Na2CO3 / activated carbon dechlorination bed, and a molecular sieve + low-temperature SCR denitrification bed to ensure that the H2S content in the purified syngas is ≤45 mg / m³. 3 NH3 content ≤10 mg / m 3 HCl content ≤60 mg / m 3 .

[0040] (7) Hydrogen separation and purification: The purified hydrogen-rich synthesis gas (approximately 75% H2, 1.2 MPa, 40℃) from step (6) enters a four-tower pressure swing adsorption (PSA) system. Hydrogen is separated from impurity gases through periodic pressure changes to obtain high-purity hydrogen (purity ≥ 99.97%). The specific operation is as follows: 1) The purified hydrogen-rich synthesis gas enters the adsorption tower from the bottom and flows through the layered adsorbent bed (contains activated alumina, 5A molecular sieve, and activated carbon) from bottom to top under a pressure of 1.2 MPa. Activated alumina is mainly used to remove residual moisture, while activated carbon and 5A molecular sieve selectively adsorb impurity gases such as CO2, CH4, CO, and N2. H2, due to its extremely weak adsorption capacity, passes directly through the bed and is output from the top of the tower as product gas for collection.

[0041] 2) When the impurity adsorption front in the adsorption tower approaches the outlet, stop the gas intake. Connect the tower to the upper part of the adsorption tower that has completed regeneration and has a lower pressure, and perform pressure equalization and depressurization 2-3 times to recover hydrogen in the voids in the tower, while reducing the tower pressure to about 0.5-0.6 MPa.

[0042] 3) The pressure inside the tower is further reduced to atmospheric pressure, causing some of the adsorbed impurity gases to desorb and be discharged. Subsequently, a vacuum pump is used to evacuate the pressure inside the tower to -0.07 to -0.08 MPa, causing the impurities adsorbed on the adsorbent to be completely desorbed and restoring the adsorption capacity of the adsorbent. The desorbed gas is then recycled into the tail gas system.

[0043] 4) Using the gas discharged from other adsorption towers during the depressurization stage, perform 2-3 pressure equalization and boosting cycles on this tower to raise the tower pressure to approximately 1.0-1.1 MPa. Finally, use product hydrogen to pressurize the tower to the adsorption pressure (1.2 MPa) to prepare for the next round of adsorption. High-purity hydrogen is then obtained.

[0044] Example 2 Compared with Example 1, the only difference is that in step (1), the volume fraction of O2 in the oxygen activation stage is adjusted to 3%, and the remaining steps and process conditions are the same as in Example 1.

[0045] Example 3 Compared with Example 1, the only difference is that in step (3), the fluidized bed temperature is adjusted to 780°C, while the suspended bed temperature remains at 850°C. The remaining steps and process conditions are the same as in Example 1.

[0046] Example 4 Compared with Example 1, the only difference is that in step (3), the fluidized bed temperature is maintained at 800°C and the suspended bed temperature is adjusted to 900°C. The remaining steps and process conditions are the same as in Example 1.

[0047] Example 5 like Figure 1As shown, for municipal solid waste with a high proportion of kitchen waste and high moisture content (≥45%), mechanical dehydration and hot air drying pretreatment are first carried out. Specifically, the raw waste is crushed and then dehydrated by screw press, reducing the moisture content from 48 wt% to about 30 wt%; then it is dried under hot air at 120℃ for 2.5 h, so that the equivalent dry basis moisture content is less than 10 wt%.

[0048] Comparative Example 1 Compared with Example 1, the only difference is that in step (1), O2 is not introduced during the oxygen activation stage, and only pure N2 is used as the carrier gas. The other steps and process conditions are the same as in Example 1.

[0049] Comparative Example 2 Compared with Example 1, the only difference is that in step (1), the volume fraction of O2 in the oxygen activation stage is adjusted to 8%, and the remaining steps and process conditions are the same as in Example 1.

[0050] Comparative Example 3 Compared with Example 1, the only difference is that in step (3), the temperature of the fluidized bed and the suspension bed of the dual-bed gasification is set to 800°C, and the other steps and process conditions are the same as in Example 1.

[0051] Comparative Example 4 Compared with Example 1, the only difference is that in step (3), the temperature of the fluidized bed and the suspension bed of the dual-bed gasification is set to 850°C, and the other steps and process conditions are the same as in Example 1.

[0052] Test Example 1 The mass and specific surface area of ​​the bio-carbon powder prepared by oxygen activation in the hydrogen production processes of Examples 1-5 and Comparative Examples 1-4 were measured. The mass was obtained by weighing; the specific surface area was determined by N2 adsorption-BET method. Before the test, the samples were degassed under vacuum at 200℃ for 4 h.

[0053] The hydrogen produced in Examples 1-5 and Comparative Examples 1-4 was tested, including the following tests: The purity of hydrogen was tested by using a gas chromatograph (TCD) to detect the composition of the produced gas, which was expressed as the hydrogen gas integral. The purity of the product gas after PSA purification was calculated as the volume fraction of H2 in the purified gas. The hydrogen production test involved recording the total gas production per unit time under stable operating conditions, and calculating the hydrogen volume yield per unit mass of waste based on the H2 volume fraction measured by gas chromatography, converting it to Nm³ under standard conditions. 3 / ton of garbage; The calculation method and formula for gasification efficiency are as follows: η g =( V gas ×LHV gas ) / ( m feed × LHV feed )×100%; of which V gas The volume of dry gas obtained per unit mass of raw material (Nm³) 3 ), LHV gas The lower heating value of dry gas, m feed For the quality of raw materials, LHV feed It is the lower heating value of the raw material.

[0054] The removal of pollutants from the hydrogen produced by the hydrogen production processes in Examples 1 and 5 was tested, including the detection of CO / H2S / NH3 / HCl / tar. Specifically, a gas bag was used to sample the purified syngas at the outlet. CO was detected by gas chromatography, H2S, NH3 and HCl were determined by ion chromatography or spectrophotometry after absorption with an absorption liquid, and tar was determined by solvent absorption-weighing method.

[0055] The test results are shown in Table 1.

[0056] Table 1

[0057] Note: " / " indicates that it has not been tested.

[0058] As shown in Table 1, the yield of high-purity hydrogen obtained in Example 1 (based on raw waste) was 685 Nm³. 3 / ton of waste, gasification efficiency 86.5%, pollutant emission test results show that the purified syngas contains: H2S 38 mg / m³ 3 NH37 mg / m 3 HCl 52 mg / m 3 Tar 82 mg / Nm 3 It conforms to the GB / T 37244-2018 standard. It can be seen that, under the synergistic conditions of oxygen activation and segmented gasification, the hydrogen production process of this invention can balance precursor activity, gasification efficiency, and hydrogen yield, producing hydrogen with high purity (≥99.97%).

[0059] As shown in Examples 1, 2, Comparative Example 1, and 2, changing the O2 volume fraction during the oxygen-activated stage of the process significantly affects hydrogen production. This may be because oxygen activation improves the pore structure and reactivity of the biochar powder, thereby affecting the deep conversion in subsequent gasification and reforming processes. Specifically, when no O2 is introduced, the specific surface area of ​​the biochar powder in Comparative Example 1 is 255 m². 2 / g, compared to Example 1 (520 m) 2 / g) decreased by 265 m 2 / g; hydrogen production is 585 Nm 3 / ton of waste, a reduction of 100 Nm compared to Example 1. 3 / ton of waste; tar content is 156 mg / Nm³ 3 Compared to Example 1 (42 mg / Nm 3 ) increased by 114 mg / Nm 3 When the O2 volume fraction increased from 0% to 3%, the pore structure and reactivity of the resulting carbonaceous powder were improved, and the high-purity hydrogen yield obtained from subsequent gasification in Example 2 was 623 mg / Nm³. 3 Simultaneously, gasification efficiency (81.5%) and tar content (108 mg / Nm³) improved. 3 () also decreased significantly.

[0060] When the volume fraction of O2 introduced was too high (8%), the specific surface area of ​​the bio-carbon powder in Comparative Example 2 was 390 m². 2 / g, still significantly less than in Example 1, with a hydrogen yield of 603 Nm. 3 / ton of waste, a reduction of 82 Nm compared to Example 1. 3 / ton of waste. It is evident that both excessively high and low oxygen concentrations lead to a decrease in the specific surface area of ​​the bio-carbon powder. While excessively high oxygen concentrations help form some pores, they exacerbate the loss of organic matter in the pretreated waste, reducing solids yield and subsequent effective carbon source supply. Conversely, excessively low oxygen concentrations result in lower fixed carbon reactivity, leading to significantly lower effective carbon source conversion efficiency compared to bio-carbon powder prepared through oxygen-activated processes, thus reducing the activity of the bio-carbon powder and subsequent hydrogen production. Therefore, it is necessary to control the oxygen concentration within a suitable range to obtain a larger specific surface area of ​​the bio-carbon powder, appropriate reactivity, and ultimately, a higher hydrogen yield. Therefore, 5% O2 was ultimately selected as a crucial process parameter for the oxygen-activated stage.

[0061] Comparing Examples 1, 3, and 4, it was found that changing the fluidized bed temperature significantly affected hydrogen production. This is likely because the fluidized bed temperature influences the gasification of coarse carbon particles and the degree of volatile matter reforming, thereby affecting hydrogen yield, gasification efficiency, and tar content. Specifically, when the fluidized bed temperature in Example 3 was lower (780°C), the hydrogen production and gasification efficiency were slightly lower than in Example 1, while the tar content was slightly higher. This indicates that a lower temperature leads to a reduced initial gasification degree of coarse carbon particles, thus affecting the overall carbon conversion rate. When the fluidized bed temperature in Comparative Example 4 was higher (850°C), the hydrogen production and gasification efficiency decreased, while the tar content increased significantly, reaching 112 m³. 2 / g, it can be seen that when the fluidized bed and the suspended bed are at the same temperature and both are at a relatively high temperature, the residence and reaction conditions of carbon particles in the fluidized bed are no longer optimal, making it difficult to simultaneously achieve coarse carbon gasification and deep reforming of volatile matter, resulting in a significant decrease in the overall effect.

[0062] Comparing Examples 1, 4, and 3, it was found that changing the temperature of the fluidized bed significantly affected hydrogen production. This is likely because the fluidized bed temperature influences volatile matter reforming and tar cracking, thus affecting the overall effect, including hydrogen production. Specifically, in Comparative Example 3, when the fluidized bed temperature was low, hydrogen production and gasification efficiency decreased. This indicates that when both stages were at the same low temperature, the deep reforming of volatiles in the fluidized bed was insufficient, resulting in poor tar cracking and a significantly worse overall effect. In Example 4, when the fluidized bed temperature was increased to 900°C, hydrogen production and gasification efficiency decreased slightly. This shows that excessively high temperatures increase the system's heat load, weakening the synergistic matching between in-situ adsorption enhancement and staged gasification, leading to a decrease in the overall effect. Therefore, controlling the temperature of the fluidized bed and fluidized bed staged gasification within an appropriate range can better balance the initial gasification of coarse carbon particles with the deep reforming of fine particles and volatiles, thereby achieving higher hydrogen yield, better gasification efficiency, and lower tar content. Ultimately, a staged gasification method with fluidized bed at 800℃ and suspended bed at 850℃ was selected as the key process parameters for the gas-solid decoupling and staged gasification phase.

[0063] Therefore, in summary, when the oxygen content in the oxygen-activated preparation of bio-carbon powder in step (1) of Example 1 is 5%, the yield of the prepared bio-carbon powder is relatively high, and the pore structure and reactivity are sufficient, which is conducive to the deep conversion in the subsequent gasification and reforming process. In a comprehensive comparison of Examples 1, 3, 4 and Comparative Examples 3, 4, it can be seen that the 800 / 850℃ segmented temperature combination in Example 1 is more balanced in terms of hydrogen production, gasification efficiency and tar control, and the final hydrogen production and gasification efficiency are higher, while the tar content is relatively lower.

[0064] The foregoing examples are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A hydrogen production process for municipal solid waste through oxygen activation and staged gasification, characterized in that, Includes the following steps: (1) Preparation of bio-carbon powder by oxygen activation: Bio-carbon powder is prepared by pyrolysis of municipal solid waste in an inert atmosphere containing oxygen; the volume fraction of oxygen in the inert atmosphere is 2%-6%; (2) Crush and sieve the biochar powder in step (1) to obtain coarse particles with a particle size of 1~2 mm and fine particles with a particle size of 0.1~1 mm; (3) Gas-solid decoupling staged gasification: The fine particles in step (2) are deeply reformed in a suspended bed at a temperature of 850~900℃; the coarse particles are initially gasified in a fluidized bed at a temperature of 750-800℃, and then enter the suspended bed for deep reforming; during the gasification process, a calcium-based adsorbent is introduced into the suspended bed to adsorb carbon dioxide in situ to obtain crude syngas; (4) Catalytic reforming and tar removal: The crude syngas in step (3) is subjected to catalytic reforming to obtain reformed gas; (5) Synergistic deep removal of pollutants: The gas after reforming in step (4) is desulfurized, dechlorinated and denitrified, and then hydrogen is obtained by pressure swing adsorption.

2. The hydrogen production process according to claim 1, characterized in that, In an inert atmosphere, the volume fraction of oxygen is 4.5%-5.5%.

3. The hydrogen production process according to claim 1, characterized in that, In step (1), the pyrolysis temperature is 350~450℃.

4. The hydrogen production process according to claim 1, characterized in that, In step (3), the mass ratio of coarse or fine particles to calcium-based adsorbent is 0.05-0.2:

1.

5. The hydrogen production process according to claim 1 or 4, characterized in that, In step (3), the conditions for in-situ adsorption are 750~800℃.

6. The hydrogen production process according to claim 1, characterized in that, In step (4), the crude syngas undergoes catalytic reforming under a Ni-CaO / Al2O3 catalyst.

7. The hydrogen production process according to claim 1 or 6, characterized in that, In step (4), the conditions for catalytic reforming are: a packing volume of 0.1~0.5 m³. 3 The reaction temperature is 750~800℃, and the space velocity is 1500~2500 h⁻¹. -1 .

8. The hydrogen production process according to claim 1, characterized in that, In step (4), the reformed gas is cooled to 150~250℃ for desulfurization, dechlorination and denitrification operations.

9. The hydrogen production process according to claim 1, characterized in that, In step (5), the pressure swing adsorption operation is as follows: S1. Under a pressure of 1.0-1.5 MPa, the gas flows through a bed containing adsorbent to remove residual moisture and impurities such as CO2, CH4, CO, and N2. S2. Perform pressure equalization and depressurization 2-3 times to bring the pressure down to 0.5-0.6 MPa while recovering hydrogen from the voids inside the tower; S3. Gradually reduce the pressure to normal and then to negative pressure to desorb and release the impurity gases adsorbed by the adsorbent; S4. Perform equalization and pressure increase 2-3 times to raise the pressure to 1.0-1.5MPa, and repeat the above steps S1 to S3.

10. The hydrogen production process according to claim 1, characterized in that, The moisture content of the municipal solid waste is ≥30wt%.

Images