A method for producing hydrogen using iron-rich coal gangue as raw material

Abstract

This invention proposes a method for hydrogen production using iron-rich coal gangue as raw material, relating to the field of hydrogen energy technology, and includes the following steps: Step 1, pretreatment of iron-rich coal gangue and preparation of iron-rich concentrate: The iron-rich coal gangue contains ≥10% total iron (TFe) and ≥10% ferrous iron (Fe²⁺). + The proportion of the first step is ≥70%; Step 2, high-temperature and high-pressure hydrothermal hydrogen production reaction: The iron-rich concentrate prepared in Step 1, together with water or steam and Cr / Ni / Mo composite catalyst, is placed in a high-temperature and high-pressure hydrothermal reactor to carry out a hydrothermal reaction to generate a mixed gas containing hydrogen; Step 3, hydrogen purification: The mixed gas containing hydrogen generated in Step 2 is first purified using pressure swing adsorption, with activated carbon and 13X molecular sieve as the adsorbent, through a four-tower circulation process; then a second purification is carried out using palladium-silver alloy membrane separation, with an operating temperature of 350~400℃; This invention helps to solve the high carbon emission problem caused by traditional fossil energy hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy technology, specifically relating to a method for producing hydrogen using coal gangue as raw material. Background Technology

[0002] Hydrogen energy, as a clean energy source with zero carbon emissions, is an important pathway to achieving the "dual carbon" goal (carbon reduction, carbon emission reduction, and carbon sequestration). Current mainstream hydrogen production methods include fossil fuel reforming (grey hydrogen), water electrolysis (green hydrogen), and industrial by-product hydrogen, but these generally suffer from high carbon emissions, high energy consumption, or high costs. my country's coal mining process generates over 800 million tons of coal gangue annually, with a cumulative stockpile exceeding 7 billion tons, some of which has a high iron content. Iron-rich coal gangue refers to coal gangue with a total iron (TFe) content ≥10%, commonly found in marine-continental transitional sedimentary mining areas. Iron-rich coal gangue is rich in divalent iron (Fe²⁺). + ), which has potential reducing activity.

[0003] In recent years, the natural hydrogen generation mechanism based on serpentinization has attracted widespread attention. Studies have shown that minerals rich in ferrous iron can generate hydrogen through Fe²⁺ under hydrothermal conditions. + Oxidized to Fe³ + Releasing hydrogen through a mild reaction requiring no external energy supply is a promising low-carbon hydrogen production route. However, existing technologies are mostly focused on basic to ultrabasic rocks or metallurgical slag, and a large-scale hydrogen production process using iron-rich coal gangue as raw material has not yet been systematically developed. Furthermore, iron in coal gangue is mainly present in the form of siderite (FeCO3) and pyrite (FeS2), with fine particle size and many impurities, resulting in low direct reaction efficiency. How to efficiently extract iron-rich minerals and construct a controllable hydrothermal reaction system has become a technical challenge in this field. Currently, there is no mature process for using iron-rich coal gangue as a hydrogen production feedstock. Coal gangue has a complex composition and low iron content; without efficient sorting and catalytic enhancement, stable hydrogen production is difficult to achieve. Summary of the Invention

[0004] In view of the shortcomings in this field, the first objective of this invention is to propose a method for producing hydrogen using iron-rich coal gangue as raw material, thereby achieving a deep integration of solid waste resource utilization and clean energy production.

[0005] The second objective of this invention is to provide a hydrogen production system using iron-rich coal gangue.

[0006] The technical solution for achieving the above-mentioned objective of this invention is as follows:

[0007] A method for producing hydrogen using iron-rich coal gangue as raw material includes the following steps:

[0008] Step 1, Pretreatment of rich iron coal gangue and preparation of rich iron concentrate: Select coal with a total iron (TFe) content ≥10% and a ferrous iron (Fe²⁺) content ≥10%. +Using iron-rich coal gangue with an iron content of ≥70% (ΣFe) as raw material, the iron-rich coal gangue is crushed and enriched; the iron-rich coal gangue is then processed into iron-rich concentrate with an iron content of ≥60% and an iron recovery rate of ≥75% through multi-stage magnetic separation.

[0009] Step 2, High-temperature and high-pressure hydrothermal hydrogen production reaction: The iron-rich concentrate prepared in Step 1, together with water or steam and a Cr / Ni / Mo composite catalyst, are placed in a high-temperature and high-pressure hydrothermal reactor. The reaction temperature is controlled at 600~750℃ and the reaction pressure at 10–20MPa to carry out a hydrothermal reaction to generate a mixed gas containing hydrogen. The mass ratio of Cr, Ni, and Mo in the composite catalyst is 1~2:2~4:1.

[0010] Step 3, hydrogen purification: The hydrogen-containing mixed gas generated in Step 2 is first passed through a gas-liquid separator, and then subjected to primary purification. The primary purification adopts the pressure swing adsorption (PSA) method, with activated carbon and 13X molecular sieve as adsorbents, and is purified by a four-tower circulation process; then secondary purification is carried out, using palladium-silver alloy membrane separation, with an operating temperature of 350–400℃.

[0011] In step one, the multi-stage magnetic separation includes the following operations: crushing the iron-rich coal gangue to a particle size ≤ 5mm, then using a high-gradient permanent magnet drum separator to initially enrich the iron-rich coal gangue, with a magnetic field strength of 0.8~1.5T; and then using jigging or spiral chute to assist in gravity separation of the resulting weakly magnetic minerals.

[0012] After crushing, the iron-rich coal gangue should be dried to prevent particle agglomeration due to moisture content, which would affect the reaction rate. The initially enriched weakly magnetic minerals, such as siderite FeCO3 and pyrite FeS2, are the main hydrogen source for subsequent hydrothermal reactions.

[0013] In step two, the Cr / Ni / Mo composite catalyst is prepared by a co-precipitation-impregnation method, wherein the mass ratio of Cr, Ni, and Mo can be 2:3:1. This ratio of catalyst can effectively increase the reaction rate of iron-rich concentrate with water or steam, thereby increasing the hydrogen yield.

[0014] In step two, the heating rate of the hydrothermal reaction is controlled at 5-8°C / min. During the heating process, an inert gas is introduced into the reactor to remove air, and the flow rate of the inert gas is 150-200 mL / min. The introduction of an inert gas (such as argon) is to prevent the oxidation of ferrous iron in the iron-rich concentrate.

[0015] A preferred embodiment of the present invention is as follows: In step two, the rich iron concentrate is mixed with water or steam at a water-to-solid ratio of 5 to 10:1, and 0.5 to 2 wt% of Cr / Ni / Mo composite catalyst is added, and the mixture is placed together in a high-temperature and high-pressure hydrothermal reactor.

[0016] The proportion of composite catalyst added = catalyst mass / iron-rich concentrate mass × 100%

[0017] By conducting reactions under different conditions and optimizing process parameters, the present invention is more preferably carried out in step two by adding 1.5-2 wt% of Cr / Ni / Mo composite catalyst to water or steam at a water-to-solid ratio of 9-10:1 and placing them together in a high-temperature and high-pressure hydrothermal reactor.

[0018] Furthermore, in step three, the pressure swing adsorption (PSA) process for primary purification has an adsorption time of 5-8 min, a desorption time of 3-5 min, an adsorption stage pressure of 2.0-2.5 MPa, a desorption stage pressure of 0.8-1.0 MPa, and an operating pressure between 0.8 and 2.5 MPa.

[0019] The high pressure of 2.0–2.5 MPa during the adsorption stage is conducive to impurity adsorption. The low pressure of 0.8–1.0 MPa during the desorption stage is conducive to impurity desorption. The pressure in each column fluctuates periodically over time.

[0020] Pressure swing adsorption (PSA) technology ensures effective impurity removal and hydrogen recovery by rationally controlling adsorption and desorption times.

[0021] In step three, the secondary purification employs a palladium-silver alloy membrane separation with a membrane thickness of 15–20 μm and a Pd-Ag alloy containing 23% Ag; the operating temperature is 350–400℃, and the hydrogen permeability is >20 mL / (cm²). min (atm). Through the above-described hydrogen purification process, high-purity hydrogen with a purity ≥99.999% can be obtained. Another preferred embodiment of the present invention further includes a reaction residue treatment step, in which the residue after the hydrothermal reaction in step two is collected, ground, and sieved for use in the preparation of iron oxide red pigment; the sieve aperture size is 0.074~0.15mm. The reaction residue treatment step of the present invention realizes the resource utilization of the residue.

[0022] The present invention further proposes a hydrogen production system for iron-rich coal gangue to implement the hydrogen production method, including a crushing and screening unit, a combined strong magnetic separation and gravity separation device, a high-temperature and high-pressure hydrothermal reactor, a gas-liquid separator, a PSA adsorption tower group, a palladium-silver alloy membrane purification unit and a PLC automatic control system.

[0023] The crushing and screening unit is connected to a combined strong magnetic separation and gravity separation device; the outlet of the combined gravity separation device is connected to the high-temperature and high-pressure hydrothermal reactor, which has a gas phase outlet at the top. The gas phase outlet is sequentially connected to the gas-liquid separator, the PSA adsorption tower group, and the palladium-silver alloy membrane purification unit via pipelines; the PLC automatic control system is electrically connected to the crushing and screening unit, the combined strong magnetic separation and gravity separation device, the high-temperature and high-pressure hydrothermal reactor, the gas-liquid separator, the PSA adsorption tower group, and the palladium-silver alloy membrane purification unit, respectively, and is used to control the operation of the entire hydrogen production process.

[0024] Specifically, the crushing and screening unit is used to crush iron-rich coal gangue to a particle size ≤5mm and screen it to remove impurities; the combined strong magnetic separation and gravity separation device is used to separate and enrich iron-rich minerals in the crushed coal gangue; the high-temperature and high-pressure hydrothermal reactor is used to carry out hydrothermal hydrogen production reaction; the gas-liquid separator is used to separate liquid water from the mixed gas after the reaction; the PSA adsorption tower group is used for primary hydrogen purification; the palladium-silver alloy membrane purification unit is used for secondary hydrogen purification; and the PLC automatic control system is electrically connected to each unit, device, and equipment to control the parameters of the entire hydrogen production process (such as temperature, pressure, flow rate, etc.) to achieve automated operation.

[0025] A drying device is installed between the outlet of the gas-liquid separator and the inlet of the PSA adsorption tower group. The drying device is filled with anhydrous calcium chloride desiccant, and / or

[0026] The reactor is made of Inconel 625 alloy, with a built-in stirring paddle, and is equipped with a safety valve, pressure sensor, temperature probe and online gas chromatograph. The online gas chromatograph is used to monitor the composition of the outlet gas in real time.

[0027] The drying unit is used to further remove moisture from the mixed gas, ensuring that the moisture content of the gas entering the PSA adsorption tower group is ≤0.1%, thereby improving the purification efficiency and service life of the PSA adsorption tower group.

[0028] This hydrogen production method can be applied to coal gangue comprehensive utilization parks, mining area distributed energy stations, or "zero-waste city" construction projects to achieve synergistic coupling of solid waste resource utilization and clean energy production.

[0029] The beneficial effects of this invention are as follows:

[0030] This invention provides a hydrogen production method using iron-rich coal gangue as raw material. It employs an integrated "sorting-reaction-purification" technology, transforming long-accumulated, environmentally polluting coal gangue into high-value hydrogen energy, fundamentally changing its traditional role as an "environmental burden" and endowing it with the new attribute of "urban mining." This process fully utilizes the abundant ferrous iron (Fe²⁺) in coal gangue. +Under high-temperature, high-pressure hydrothermal conditions, the reducing activity releases hydrogen through a controlled chemical reaction. This not only avoids the high carbon emissions associated with traditional fossil fuel-based hydrogen production but also circumvents the reliance on expensive equipment and massive amounts of green electricity required for water electrolysis. The entire process requires no external combustion power, produces no carbon dioxide, and utilizes physical sorting instead of chemical leaching to eliminate acid and alkaline wastewater pollution. This truly achieves green, clean, and sustainable hydrogen production, demonstrating significant ecological benefits and environmental friendliness.

[0031] In terms of economics, this invention exhibits a significant cost advantage. The raw material is derived from large quantities of waste coal gangue from coal mines, resulting in near-zero acquisition costs. Furthermore, the pretreatment utilizes a mature combined high-intensity magnetic separation and gravity separation process, leading to low equipment investment and stable operation. The hydrogen production system can operate efficiently under medium- and high-pressure conditions. Combined with PSA and palladium membrane coupling purification technology, it ultimately yields high-purity hydrogen with a purity exceeding 99.999%, fully meeting the demands of high-end applications such as fuel cell vehicles, fine chemicals, and large-scale energy storage. It is estimated that the unit cost of hydrogen production can be controlled below 20 yuan / kg, providing a foundation for large-scale commercialization. Simultaneously, the residue after the reaction primarily generates stable magnetite (Fe3O4), and analysis shows that Fe²⁺… + With a conversion rate exceeding 89%, the solid product is non-toxic and harmless, and can be further used to prepare iron oxide red pigment or as a high-performance building material additive, achieving closed-loop utilization across the entire chain and significantly improving the overall benefits of the project.

[0032] This invention also possesses excellent engineering adaptability and industrial extension potential, making it particularly suitable for distributed energy construction in coal-rich mining areas. The system can be flexibly integrated into existing coal mines or solid waste treatment parks, operating in conjunction with the mine's power and heating facilities, reducing redundant infrastructure investment and improving energy efficiency. Whether used as an independent hydrogen production station or incorporated into the overall planning of "zero-waste cities" and carbon neutrality demonstration zones, it demonstrates excellent technical compatibility and scenario adaptability. This technology opens up a new path for the high-value utilization of coal-related solid waste, alleviating ecological and environmental pressures while providing a low-cost, localized green hydrogen source for the hydrogen energy industry, possessing social, economic, and energy security value, and has broad prospects for widespread application. Attached Figure Description

[0033] Figure 1 This refers to the PSA adsorption tower assembly of a hydrogen production system using iron-rich coal gangue as raw material. Detailed Implementation

[0034] The following examples are used to illustrate the present invention, but should not be used to limit the scope of the invention.

[0035] In the embodiments, unless otherwise specified, all methods used are conventional techniques in the art; and all raw materials used are commercially available unless otherwise specified.

[0036] The iron-rich coal gangue used in this example is from the Qinshui coalfield in Shanxi Province. Its TFe content is 18.7%, and its Fe²⁺ content is [missing information]. + / ΣFe>80%.

[0037] Example 1

[0038] This embodiment provides a hydrogen production system from iron-rich coal gangue, including a crushing and screening unit, a combined strong magnetic separation and gravity separation device, a high-temperature and high-pressure hydrothermal reactor, a gas-liquid separator, and a PSA adsorption tower assembly (see [link]). Figure 1 ), palladium-silver alloy membrane purification unit and PLC automatic control system;

[0039] The crushing and screening unit is connected to a combined magnetic and gravity separation device. The outlet of the combined gravity separation device is connected to the high-temperature and high-pressure hydrothermal reactor. The high-temperature and high-pressure hydrothermal reactor is connected to a steam pipeline and has a gas phase outlet at the top. The gas phase outlet is sequentially connected to a gas-liquid separator, a drying device, a PSA adsorption tower group, and a palladium-silver alloy membrane purification unit via pipelines. The PLC automatic control system is electrically connected to the crushing and screening unit, the combined magnetic and gravity separation device, the high-temperature and high-pressure hydrothermal reactor, the gas-liquid separator, the PSA adsorption tower group, and the palladium-silver alloy membrane purification unit, respectively, and is used to control the operation of the entire hydrogen production process. The four towers of the PSA adsorption tower group are connected in parallel, and the channels are switched by valves. Each of the four towers is equipped with an outlet for discharging regeneration gas (waste gas generated during the desorption process) and is connected to a regeneration gas discharge pipeline. This four-tower system is connected to a buffer tank, which is used to stabilize the gas flow rate and pressure to ensure the smooth operation of the adsorption and desorption processes.

[0040] In this embodiment, the high-temperature, high-pressure hydrothermal reactor is made of Inconel 625 alloy, with a built-in stirrer, and is equipped with a safety valve, pressure sensor, temperature probe, and online gas chromatograph. The online gas chromatograph is used to monitor the composition of the outlet gas in real time. The safety valve, pressure sensor, temperature probe, and online gas chromatograph are all electrically connected to the PLC automatic control system.

[0041] The Cr / Ni / Mo composite catalyst filled in the high-temperature and high-pressure hydrothermal reactor was prepared by co-precipitation-impregnation method, wherein the mass ratio of Cr, Ni and Mo was 2:3:1. This ratio of catalyst can effectively improve the reaction rate of iron-rich concentrate with water or steam and increase the hydrogen yield.

[0042] Example 2

[0043] This embodiment proposes a method for producing hydrogen using iron-rich coal gangue as raw material, employing the system of Example 1, and includes the following steps:

[0044] Step 1: The raw material is rich iron coal gangue. First, the rich iron coal gangue is pretreated and rich iron concentrate is prepared: the rich iron coal gangue is crushed to a particle size ≤5mm, dried, and then a high gradient permanent magnet drum magnetic separator (magnetic field strength 0.8~1.5T) is used to preliminarily enrich the magnetic minerals. Then, the weakly magnetic minerals are separated by hydraulic jigging.

[0045] A rich iron concentrate with an iron grade of 61% and an iron recovery rate of 75% was obtained.

[0046] Step 2: High-temperature and high-pressure hydrothermal hydrogen production reaction: The iron-rich concentrate prepared in Step 1 and steam are added together with 1 wt% Cr / Ni / Mo composite catalyst at a water-to-solid ratio of 5:1. The mixture is placed in a high-temperature and high-pressure hydrothermal reactor. The reaction temperature is controlled at 600~750℃ and the reaction pressure is controlled at 10~20MPa to carry out the hydrothermal reaction and generate a mixed gas containing hydrogen.

[0047] Step 3: Hydrogen Purification: The hydrogen-containing gas mixture generated in Step 2 is first passed through gas-liquid separator 3, followed by primary purification. This primary purification employs Pressure Swing Adsorption (PSA) with activated carbon and 13X molecular sieve as the adsorbents, using a four-tower circulating process. The adsorption time is 5-8 min, the desorption time is 3-5 min, the adsorption pressure is 2.0-2.5 MPa, and the desorption pressure is 0.8-1.0 MPa (operating pressure between 0.8 and 2.5 MPa). This removes impurities such as CO2, CH4, N2, and H2O from the gas mixture, achieving a hydrogen purity of 99.9%. Secondary purification is then performed using a palladium-silver alloy membrane (Pd-Ag, containing 23% Ag) with a membrane thickness of 15-20 μm. The operating temperature is controlled within the range of 350-400℃, and the hydrogen permeability is 20.5 mL / (cm²). min atm).

[0048] In step two, the heating rate of the hydrothermal reaction is controlled at 5℃ / min. During the heating process, argon gas is introduced into the reactor to remove air and prevent the ferrous iron in the iron-rich concentrate from being oxidized. The argon gas flow rate is 150mL / min.

[0049] Secondary purification uses a palladium-silver alloy membrane (Pd-Ag, containing 23% Ag) for separation, and the separated hydrogen enters the hydrogen collection device 6. In this embodiment, high-purity hydrogen with a purity ≥99.999% is finally obtained, with a hydrogen yield of approximately 50 L / kg of rich iron concentrate.

[0050] Example 3

[0051] This embodiment proposes a method for producing hydrogen using iron-rich coal gangue as raw material, employing the system of Example 1, and includes the following steps:

[0052] Step 1: The raw material is iron-rich coal gangue, with a total iron (TFe) content ≥10% and a ferrous iron (Fe²⁺) content ≥10%. + The proportion of iron-rich coal gangue is ≥70%; pretreatment of iron-rich coal gangue and preparation of iron-rich concentrate: first, the iron-rich coal gangue is crushed to a particle size ≤5mm, dried, and then a high-gradient permanent magnet drum magnetic separator (magnetic field strength 0.8–1.5T) is used to preliminarily enrich the magnetic minerals, and then the weakly magnetic minerals obtained from the preliminary enrichment are assisted by hydraulic jigging.

[0053] A rich iron concentrate with an iron grade of 61.3% and an iron recovery rate of 75% was obtained.

[0054] Step 2: High-temperature and high-pressure hydrothermal hydrogen production reaction: The iron-rich concentrate prepared in Step 1 is mixed with water or steam at a water-to-solid ratio of 8:1, and 1 wt% of Cr / Ni / Mo composite catalyst is added. The mixture is placed in a high-temperature and high-pressure hydrothermal reactor. The reaction temperature is controlled at 600–750℃ and the reaction pressure is controlled at 10–20 MPa to carry out the hydrothermal reaction and generate a mixed gas containing hydrogen.

[0055] Step 3: Hydrogen Purification: After passing the hydrogen-containing gas mixture generated in Step 2 through a gas-liquid separator, it undergoes primary purification using Pressure Swing Adsorption (PSA) with a combination of activated carbon and 13X molecular sieve as the adsorbent. A four-tower circulation process (operating pressure 0.8–2.5 MPa, process parameters same as in Example 2) removes impurities such as CO2, CH4, N2, and H2O from the gas mixture, achieving a hydrogen purity of 99.9%. Secondary purification is then performed using a palladium-silver alloy membrane (Pd-Ag, containing 23% Ag) with a membrane thickness of 15–20 μm, an operating temperature of 350–400 °C, and a hydrogen permeability of 22 mL / (cm²). min atm).

[0056] In step two, the heating rate of the hydrothermal reaction is controlled at 5~8℃ / min. During the heating process, argon gas is introduced into the reactor to remove air and prevent the ferrous iron in the iron-rich concentrate from being oxidized. The argon gas flow rate is 180mL / min.

[0057] A palladium-silver alloy membrane (Pd-Ag, containing 23% Ag) was used for separation, and the separated hydrogen gas entered the hydrogen collection device 6. This embodiment ultimately yielded high-purity hydrogen gas with a purity ≥99.999%. The hydrogen yield in this embodiment was increased to approximately 55 L / kg of rich iron concentrate.

[0058] Example 4

[0059] This embodiment proposes a method for producing hydrogen using iron-rich coal gangue as raw material, employing the system of Example 1, and includes the following steps:

[0060] Step 1: The raw material is iron-rich coal gangue, with a total iron (TFe) content ≥10% and a ferrous iron (Fe²⁺) content ≥10%. + The proportion of iron-rich coal gangue is ≥70%; pretreatment of iron-rich coal gangue and preparation of iron-rich concentrate: first, the iron-rich coal gangue is crushed to a particle size ≤5mm, and after drying, a high-gradient permanent magnet drum magnetic separator (magnetic field strength 0.8–1.5T) is used to initially enrich the magnetic minerals, and then the weakly magnetic minerals are separated by gravity using jigging or spiral chute.

[0061] To obtain a rich iron concentrate with an iron grade of 62% and an iron recovery rate of 75%;

[0062] Step 2: High-temperature and high-pressure hydrothermal hydrogen production reaction: The iron-rich concentrate prepared in Step 1 is mixed with water or steam at a water-to-solid ratio of 10:1, and 2wt% of Cr / Ni / Mo composite catalyst is added. The mixture is placed in a high-temperature and high-pressure hydrothermal reactor. The reaction temperature is controlled at 600–750℃ and the reaction pressure is controlled at 10–20MPa to carry out the hydrothermal reaction and generate a mixed gas containing hydrogen.

[0063] Step 3: Hydrogen Purification: After passing the hydrogen-containing gas mixture generated in Step 2 through a gas-liquid separator, it undergoes primary purification using Pressure Swing Adsorption (PSA). The adsorbent is a combination of activated carbon and 13X molecular sieve. A four-tower circulation process (operating pressure 0.8~2.5MPa, specific process parameters are the same as in Example 2) removes impurities such as CO2, CH4, N2, and H2O from the gas mixture, achieving a hydrogen purity of 99.9%. Secondary purification is then performed using a palladium-silver alloy membrane (Pd-Ag, containing 23% Ag) with a membrane thickness of 15~20μm, an operating temperature of 350–400℃, and a hydrogen permeability of 21mL / (cm²). min atm).

[0064] In step two, the heating rate of the hydrothermal reaction is controlled at 8℃ / min. During the heating process, argon gas is introduced into the reactor to remove air and prevent the ferrous iron in the rich iron concentrate from being oxidized. The argon gas flow rate is 200mL / min.

[0065] Secondary purification employs a palladium-silver alloy membrane (Pd-Ag, containing 23% Ag) for separation, and the separated hydrogen enters the hydrogen collection device 6. This embodiment ultimately yields high-purity hydrogen with a purity ≥99.999%. The hydrogen yield in this embodiment is increased to approximately 60 L / kg of rich iron concentrate.

[0066] Although the present invention has been described in detail above, 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 are within the scope of protection claimed by the present invention.

Claims

1. A method for producing hydrogen using iron-rich coal gangue as raw material, characterized in that, Includes the following steps: Step 1, Pretreatment of rich iron coal gangue and preparation of rich iron concentrate: Select rich iron coal gangue with a total iron content ≥10% and a divalent iron content ≥70% as raw material, and prepare the rich iron coal gangue into rich iron concentrate with an iron grade ≥60% and an iron recovery rate ≥75% through multi-stage magnetic separation. Step 2, High-Temperature and High-Pressure Hydrothermal Hydrogen Production Reaction: The iron-rich concentrate prepared in Step 1, along with water or steam and a Cr / Ni / Mo composite catalyst, are placed together in a high-temperature and high-pressure hydrothermal reactor. The reaction temperature is controlled at 600~750℃ and the reaction pressure at 10~20MPa to carry out a hydrothermal reaction to generate a mixed gas containing hydrogen. The mass ratio of Cr, Ni, and Mo in the composite catalyst is 1~2:2~4:

1. Step 3, hydrogen purification: The hydrogen-containing mixed gas generated in Step 2 is passed through a gas-liquid separator and then undergoes primary purification. The primary purification adopts the pressure swing adsorption method, with activated carbon and 13X molecular sieve as the adsorbents, and is purified through a four-tower circulation process. Then, secondary purification is carried out, using palladium-silver alloy membrane separation, with an operating temperature of 350~400℃.

2. The method for producing hydrogen using iron-rich coal gangue as raw material according to claim 1, characterized in that, In step one, the multi-stage magnetic separation includes the following operations: crushing the iron-rich coal gangue to a particle size ≤ 5mm, then using a high-gradient permanent magnet drum separator to initially enrich the iron-rich coal gangue, with a magnetic field strength of 0.8~1.5T; and then using jigging or spiral chute to assist in gravity separation of the weakly magnetic minerals obtained from the initial enrichment.

3. The method for producing hydrogen using iron-rich coal gangue as raw material according to claim 1, characterized in that, In step two, the heating rate of the hydrothermal reaction is controlled at 5~8℃ / min. During the heating process, an inert gas is introduced into the reactor to remove air, and the flow rate of the inert gas is 150~200mL / min.

4. The method for producing hydrogen using iron-rich coal gangue as raw material according to claim 1, characterized in that, In step two, the iron-rich concentrate is mixed with water or steam at a water-to-solid ratio of 5 to 10:1, and 0.5 to 2 wt% of Cr / Ni / Mo composite catalyst is added. The mixture is then placed together in a high-temperature and high-pressure hydrothermal reactor.

5. The method for producing hydrogen using iron-rich coal gangue as raw material according to claim 4, characterized in that, In step two, the iron-rich concentrate is mixed with water or steam at a water-to-solid ratio of 9-10:1, and 1.5-2 wt% of Cr / Ni / Mo composite catalyst is added. The mixture is then placed in a high-temperature, high-pressure hydrothermal reactor.

6. The method for producing hydrogen using iron-rich coal gangue as raw material according to claim 1, characterized in that, In step three, the pressure swing adsorption process for primary purification has an adsorption time of 5-8 min, a desorption time of 3-5 min, an adsorption stage pressure of 2.0-2.5 MPa, a desorption stage pressure of 0.8-1.0 MPa, and an operating pressure between 0.8 and 2.5 MPa.

7. The method for producing hydrogen using iron-rich coal gangue as raw material according to any one of claims 1 to 6, characterized in that, In step three, the secondary purification uses a palladium-silver alloy membrane separation with a membrane thickness of 15-20 μm and the Pd-Ag alloy containing 23% Ag; the operating temperature is 350-400℃, and the hydrogen permeability is >20 mL / (cm²). min atm).

8. The method for producing hydrogen using iron-rich coal gangue as raw material according to any one of claims 1 to 6, characterized in that, It also includes a reaction residue treatment step, in which the residue after the hydrothermal reaction in step two is collected, ground, and sieved for use in the preparation of iron oxide red pigment; the sieve aperture size is 0.074~0.15mm.

9. A hydrogen production system using iron-rich coal gangue for implementing the hydrogen production method according to any one of claims 1 to 8, characterized in that, It includes a crushing and screening unit, a combined strong magnetic separation and gravity separation device, a high temperature and high pressure hydrothermal reactor, a gas-liquid separator, a PSA adsorption tower group, a palladium-silver alloy membrane purification unit, and a PLC automatic control system. The crushing and screening unit is connected to a combined strong magnetic separation and gravity separation device; the outlet of the combined gravity separation device is connected to the high-temperature and high-pressure hydrothermal reactor, which has a gas phase outlet at the top. The gas phase outlet is sequentially connected to the gas-liquid separator, the PSA adsorption tower group, and the palladium-silver alloy membrane purification unit via pipelines; the PLC automatic control system is electrically connected to the crushing and screening unit, the combined strong magnetic separation and gravity separation device, the high-temperature and high-pressure hydrothermal reactor, the gas-liquid separator, the PSA adsorption tower group, and the palladium-silver alloy membrane purification unit, respectively, and is used to control the operation of the entire hydrogen production process.

10. The iron-rich coal gangue hydrogen production system according to claim 9, characterized in that, A drying device is installed between the outlet of the gas-liquid separator and the inlet of the PSA adsorption tower assembly, and the drying device is filled with anhydrous calcium chloride desiccant; and / or The reactor is made of Inconel 625 alloy, with a built-in stirring paddle, and is equipped with a safety valve, pressure sensor, temperature probe and online gas chromatograph. The online gas chromatograph is used to monitor the composition of the outlet gas in real time.

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