Device and method for producing hydrogen by using multi-stage coupled chemical looping

Abstract

Provided in the present invention is a device for producing hydrogen by using multi-stage coupled chemical looping, the device comprising a first-stage reducer, a water vapor oxidation hydrogen generator, a second-stage reducer, a methane converter and an air oxidizer, wherein identical first oxygen carriers are provided in the first-stage reducer and the water vapor oxidation hydrogen generator, and identical second oxygen carriers are provided in the second-stage reducer, the methane converter and the air oxidizer; the methane converter is connected to the first-stage reducer and is configured to convey to the first-stage reducer a synthesis gas obtained after methane conversion; the second-stage reducer is connected to the methane converter and is configured to make carbon dioxide or water vapor or both flow back to the methane converter; and the first-stage reducer is connected to the second-stage reducer and is configured to convey to the second-stage reducer a reduced tail gas containing carbon monoxide or hydrogen or both. Thus, provided in the present invention are a device and method for producing hydrogen by using multi-stage coupled chemical looping, which device and method can achieve self-sustaining energy without the need for the input of external energy.

Description

A multi-stage coupled chemical chain hydrogen production device and method Technical Field

[0001] The present invention relates to a novel hydrogen production device and method, and in particular to a device and method for producing hydrogen by water splitting using multi-stage coupled chemical chain conversion. Background Art

[0002] As a clean energy, hydrogen does not produce pollutants such as CO2 when used, so it is considered to be one of the important energy sources for achieving the global "carbon neutrality" goal in the future. However, hydrogen is usually found in nature as H2O or C n H m It exists in the form of compounds such as hydrogen, so additional energy is required to extract it from the compounds and prepare it into hydrogen.

[0003] One of the primary applications of hydrogen is in hydrogen fuel cells, which require very high purity, typically above 99.9%. Therefore, the efficient and safe production of high-purity hydrogen is a key issue in achieving large-scale hydrogen energy applications and a key area of ​​research and development for all parties involved in this field.

[0004] The chemical chain hydrogen production process is a new hydrogen production technology. Tsinghua University has been committed to research in this field for many years, and in 2021 applied for an invention patent entitled "A process and application of preparing high-purity hydrogen by coupling chemical chain with methane-containing combustible gas reforming" with application number 202110963317.5 (now transferred to the applicant of this patent). The patent (patent document 1) discloses a device for preparing high-purity hydrogen, including a reforming reactor, a hydrogen production reactor and a controller, the hydrogen production reactor containing an oxygen carrier, the reforming reactor containing a reforming catalyst, the controller controlling the gas entering the hydrogen production reactor, the controller being used to switch the gas entering the hydrogen production reactor so that the three chemical reactions of oxygen carrier reduction reaction, water vapor hydrogen production reaction and oxygen carrier oxidation reaction are completed in the hydrogen production reactor, and the controller controls the three reaction cycles, thereby obtaining high-purity hydrogen while reducing the oxygen-carrying volume carbon, and completely capturing carbon dioxide to prevent greenhouse gas emissions.

[0005] However, Patent Document 1 does not provide an in-depth discussion of the heat balance problem of the entire system.

[0006] Specifically, in the three-reaction stage of chemical chain hydrogen production, the oxygen carrier reduction reaction is an endothermic reaction or a thermal equilibrium process, and the oxygen carrier water vapor oxidation hydrogen production reaction and the oxygen carrier air deep oxidation reaction are exothermic processes. The total heat release of the latter two is greater than the total heat absorption of the methane reforming conversion reaction. From the perspective of total heat balance, heat matching can be carried out throughout the process to achieve energy self-sustaining. However, in reality, the following problems exist.

[0007] (1) The heat generated by the two exothermic reaction processes of chemical chain hydrogen production will accumulate in the oxygen carrier bed in large quantities. It is necessary to remove the heat accumulated in the bed through a heat carrier medium, and then transfer the heat in the heat carrier medium to the reforming reactor through a heat exchange system. This requires a relatively complex heat exchange system to achieve.

[0008] (2) In order to achieve a higher methane conversion rate, the methane reforming process needs to be carried out at a reaction temperature of >800°C, and the process is a strongly endothermic reaction. In order to form a sufficient heat transfer temperature difference between the inside and outside of the reactor, a higher temperature (>1100°C) heat supply source is required (usually burner flame thermal radiation heating); and to avoid sintering of the oxygen carrier, it is necessary to control the oxygen carrier bed temperature to <950°C at the end of the two exothermic reverse processes of chemical chain hydrogen production. When the heat accumulated in the reaction is removed by the heat carrier, the final temperature of the heat carrier when it flows out of the reactor is usually <920°C, which is a large difference from the required heat source temperature of 1100°C. As a result, the temperature difference between the heat carrier temperature and the methane reforming reaction temperature is small (ΔT = 920-800 = 120°C), and the heat released by the chemical chain hydrogen production reaction process cannot be fully transferred to the methane reforming conversion process, which in some cases affects the overall efficiency.

[0009] More specifically, as shown in FIG1 , the original “chemical chaining hydrogen production using methane-containing fuel gas as raw material” process disclosed in Patent Document 1 has four reaction stages, namely, ① methane reforming, ② oxygen carrier reduction, ③ oxygen carrier water vapor oxidation to produce hydrogen, and ④ oxygen carrier air oxidation, wherein the three reaction processes of ② oxygen carrier reduction, ③ oxygen carrier water vapor oxidation to produce hydrogen, and ④ oxygen carrier air oxidation are carried out in a cycle.

[0010] The aforementioned methane reforming (1) is a highly endothermic process requiring a large amount of high-grade heat, while the oxygen-carrier air oxidation (4) is a highly exothermic process capable of releasing a large amount of heat. However, since the heat released by the oxygen-carrier air oxidation process is largely absorbed by the oxygen-carrier material in the reactor (the oxygen-carrier itself is a metal oxide with a large heat capacity), the majority of the heat released in this process (70-90%) is stored in the oxygen-carrier bed after the reaction, and cannot directly contribute heat to the highly endothermic methane reforming conversion at the front end. Removing heat from the oxygen-carrier bed via a gaseous heat-conducting medium would require the addition of a complex heat exchange system, and the temperature of the heat-conducting gas used to remove the bed heat would not meet the heating requirements of the methane reforming conversion.

[0011] Patent Document 1: Publication No. CN113753857A (Patent Application No. CN202110963317.5) Summary of the Invention

[0012] In view of this, the main purpose of the present invention is to provide a multi-stage coupled chemical chain hydrogen production device and method that can achieve energy self-sustaining and does not require external energy input.

[0013] In order to more clearly illustrate the present invention, the following first describes how the research and development team of this patent decoupled and improved the structure of the above-mentioned patent document 1 to obtain the structure of the present invention in order to achieve the above-mentioned purpose.

[0014] (1) Decoupling of three-process chemical cycles

[0015] First of all, the research and development team of this patent hopes to invent a method to effectively couple the oxygen carrier air oxidation process with the methane reforming conversion process, without using a gas heat transfer medium or other heat exchange methods, and directly use the heat released by the oxygen carrier air oxidation process to provide heat to the methane reforming conversion process.

[0016] After intensive research, the R&D team of this patent discovered that in the original chemical chain hydrogen production process, the oxygen carrier reduction stage is a coupled process of several reactions, namely:

[0017] Changes in oxygen carrier state: Process ②Fe2O3→Fe3O4→FeO→Fe;

[0018] However, (process ③ + process ④) actually undergoes the reverse process of process ②: the state of the oxygen carrier changes during the steam oxidation process: process ③ Fe→FeO→Fe3O4; the state of the oxygen carrier changes during the air oxidation process: process ④ Fe3O4→Fe2O3;

[0019] If the original oxygen carrier reduction stage (process ②) is decoupled and split into two steps by thermodynamic control, the decoupling and splitting can be performed as follows, as shown in Figure 2:

[0020] Process ② = Process ⑤ + Process ⑥

[0021] Process ⑤: The oxygen carrier reduces Fe2O3 to Fe3O4 in the first stage

[0022] Process ⑥: The second stage of oxygen carrier reduction Fe3O4→FeO→Fe

[0023] If the initial state of the oxygen carrier in the reactor is Fe2O3, by controlling the CO / CO2 molar ratio and the H2 / H2O molar ratio in the reducing gas, according to the thermodynamic limitations of the reaction, Fe2O3 can be controlled to be reduced only to Fe3O4 (for example, below 800°C, if the CO / CO2 molar ratio in the reducing gas is less than 33 / 67, Fe2O3 can only generate Fe3O4), and after reduction, the oxygen carrier is oxidized by air. Then, process ④ and process ⑤ can independently constitute a redox cycle (i.e., the "second stage chemical chain reaction cycle" referred to in the present invention):

[0024] Oxygen carrier reduction: process ⑤Fe2O3→Fe3O4

[0025] Oxygen carrier oxidation: process ④Fe3O4→Fe2O3

[0026] This redox cycle includes the highly exothermic air oxidation process in the original chemical chain hydrogen production process. At the same time, since the initial state of the oxygen carrier and the highest valence state after air oxidation are both Fe2O3, according to thermodynamic equilibrium, as long as there is unreacted Fe2O3 in the reactor, the gas phase at the outlet of the reduction reactor will be entirely CO2 and H2O. The reduction time can be controlled to prevent the reducing gas from penetrating the reactor. After a simple dehydration of the tail gas, the CO2 can be separated in situ to obtain high-purity CO2.

[0027] If the initial state of the oxygen carrier in the reactor is controlled to be Fe3O4, under certain reducing gas composition conditions, the oxygen carrier can be reduced to FeO (such as 800℃, CO / CO2 molar ratio>33 / 67), or further reduced to Fe (such as 800℃, CO / CO2 molar ratio>65 / 35), and then oxidized with water vapor, then process ③ and process ⑥ can also constitute a redox cycle (called the first chemical chain reaction cycle) independently:

[0028] Oxygen carrier reduction: process ⑥Fe3O4→FeO→Fe

[0029] Oxygen carrier oxidation: Process ③Fe→FeO→Fe3O4

[0030] This redox cycle encompasses the water vapor oxidation process in the original chemical loop hydrogen production process. Furthermore, during this cyclic oxygen carrier reduction process, since the initial state of the oxygen carrier in the reactor and its highest valence state after water vapor oxidation are both Fe₃O₄, according to thermodynamic equilibrium characteristics, as long as there is unreacted Fe₃O₄ in the reactor, the reduced exhaust gas flowing out of the reactor will be at the equilibrium concentration under these conditions (for example, at 800°C, in the presence of Fe₃O₄, the CO / CO₂ equilibrium molar composition is 33 / 67).

[0031] Through the above two independent redox cycles and their respective thermodynamic chemical equilibrium characteristics, the reducing tail gas of the first chemical chain reaction cycle can be used as the reducing feed gas of the second chemical chain reaction cycle.

[0032] (2) Decoupling chemical cycle coupled with methane conversion

[0033] By decoupling the three processes of the original chemical chain hydrogen production, "reduction-water vapor oxidation-air oxidation", the air oxidation process can be separated from the hydrogen production process and constitute a separate chemical cycle (i.e., the "second stage chemical chain reaction cycle" referred to in the present invention), which makes it possible to thermally couple the highly exothermic process of air oxidation with the highly endothermic process of methane conversion.

[0034] The research and development team behind this patent aims to directly utilize the heat released and stored in the oxygen carrier bed during the air oxidation process in the second chemical chain reaction cycle for the highly endothermic methane conversion reaction (i.e., process ①). This requires three conditions: (a) the heat released by the air oxidation process must be greater than the heat absorbed by the methane reforming conversion process; (b) process ① can share a reactor with the chemical loop consisting of processes ⑤ and ④, and the cycle can be switched. (c) The oxygen carrier used in the chemical chain loops of processes ④ and ⑤ can, at some point during the cycle, provide catalytic action for methane conversion.

[0035] To meet conditions (a) + (b), process ① needs to be incorporated into a new chemical chain cycle consisting of "process ④ + process ⑤". To meet condition (c), the oxygen carrier state is generally in the form of elemental metal, so process ① needs to be placed after process ⑤, and process ⑤ must be an exothermic reaction or a thermal equilibrium reaction. Based on the above analysis, the research and development team of this patent proposed the following two-stage chemical chain reaction cycle coupled with methane conversion hydrogen production process, as shown in Figure 3 (new process).

[0036] In order to achieve the ultimate purpose of the present invention, the present invention provides a multi-stage coupled chemical chain hydrogen production device, characterized in that the multi-stage coupled chemical chain hydrogen production device includes a first-stage chemical chain reaction unit and a second-stage chemical chain reaction unit, the first-stage chemical chain reaction unit includes a first-stage reducer and a water vapor oxidation hydrogen producer, and these two parts can be converted into each other and repeated in a cycle as a whole according to the reaction stage; the second-stage chemical chain reaction unit includes a second-stage reducer, a methane converter, and an air oxidizer, and these three parts can be converted into each other and repeated in a cycle as a whole according to the reaction stage; the same first oxygen carrier is provided in the first-stage reducer and the water vapor oxidation hydrogen producer, and the first oxygen carrier changes into a metal element or a metal oxide with different chemical valence in each reaction stage, and the metal has multiple valence; the same second oxygen carrier is arranged in the second-stage reducer, the methane converter and the air oxidizer, and the second oxygen carrier changes into a metal element or a metal oxide with different chemical valences in each reaction stage, and the metal element corresponding to the second oxygen carrier acts as a catalyst in the methane conversion reaction in the methane conversion reactor; the methane converter is connected to the first-stage reducer for conveying the synthesis gas after methane conversion to the first-stage reducer; the second-stage reducer is connected to the methane converter for refluxing carbon dioxide or water vapor or both to the methane converter; the first-stage reducer is connected to the second-stage reducer for conveying a reduced tail gas containing carbon monoxide or hydrogen or both to the second-stage reducer.

[0037] In a preferred embodiment, the first oxygen carrier contains an active ingredient and selectively contains a secondary active ingredient or an inactive ingredient or both, the active ingredient is Fe3O4, the secondary active ingredient is one or more of MoO3, GeO2, WO3, Mn2O3, ZnO, CeO2, and the inactive ingredient can be one or more of Al2O3, MgO, ZrO2, Y2O3, MgO, MgAl2O4, CaAl2O4, TiO2, CaO.

[0038] As an alternative, the first oxygen carrier does not contain an active ingredient, contains a secondary active ingredient, and selectively contains an inactive ingredient, the secondary active ingredient is one or more of MoO3, GeO2, WO3, Mn2O3, ZnO, CeO2, and the inactive ingredient can be one or more of Al2O3, MgO, ZrO2, Y2O3, MgAl2O4, CaAl2O4, TiO2, CaO.

[0039] In a preferred embodiment, the active component content of the first oxygen carrier is 50-95 wt.%, the secondary active component content is 0-5 wt.%, and the inactive component content is 5-50 wt.%.

[0040] In a preferred embodiment, the first oxygen carrier comprises Fe3O4 as an active component and Al2O3 or MgO as an inactive component.

[0041] In a preferred embodiment, the composition of the first stage oxygen carrier is 75 wt.% of Fe3O4 as an active ingredient and 25 wt.% of Al2O3 as an inactive ingredient, or the composition of the first stage oxygen carrier is 80 wt.% of Fe3O4 as an active ingredient and 20 wt.% of MgO+Al2O3 as an inactive ingredient.

[0042] In a preferred embodiment, the second oxygen carrier contains an active ingredient and selectively contains a secondary active ingredient or an inactive ingredient or both, the active ingredient is one or more of NiO, CuO, and ZnO, the secondary active ingredient is one or more of Fe2O3, CeO2, Co3O4, and Mn2O3, and the inactive ingredient can be one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2.

[0043] As an alternative, the second oxygen carrier does not contain an active ingredient, contains a secondary active ingredient, and selectively contains an inactive ingredient, the secondary active ingredient is one or more of Fe2O3, CeO2, Co3O4, Mn2O3, and the inactive ingredient can be one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, TiO2.

[0044] In a preferred embodiment, the active component content of the second oxygen carrier is 8 wt.% to 40 wt.%, the secondary active component content is 0 to 5 wt.%, and the inactive component content is 60 wt.% to 92 wt.%.

[0045] In a preferred embodiment, the second oxygen carrier comprises NiO as an active component.

[0046] In a preferred embodiment, the composition of the second oxygen carrier is 18 wt.% of NiO as an active component and 82 wt.% of MgAl2O4 as an inactive component, or the composition of the second oxygen carrier is 18 wt.% of NiO as an active component and 82 wt.% of CaAl2O4 as an inactive component.

[0047] The present invention also provides a multi-stage coupled chemical chain hydrogen production method, characterized in that the multi-stage coupled chemical chain hydrogen production device is used and includes the following steps:

[0048] The device is started and oxygen carrier and reactor preparation steps are performed, in which the device is started and the first oxygen carrier is respectively filled into the two reactors corresponding to the first chemical chain reaction unit, and the second oxygen carrier is respectively filled into the three reactors corresponding to the second reaction chain unit;

[0049] A reactor pretreatment step, in which the temperatures of the five reactors are raised and the system is adjusted to be suitable for the following reactions by means of pre-reduction and pre-oxidation, namely: the two reactors corresponding to the first stage chemical chain reaction unit are switched to cyclically repeat the first stage reduction reaction and water vapor oxidation hydrogen production reaction, and the three reactors corresponding to the second stage chemical chain reaction unit are switched to cyclically repeat the second stage reduction reaction, methane conversion reaction and air oxidation reaction;

[0050] In the methane conversion step, methane-containing combustible gas is introduced into the methane converter and first mixed with the reduced tail gas partially recycled from the second-stage reducer. Then, the methane and the mixed gas containing CO2 or H2O, or both, undergo a methane conversion reaction under the catalytic action of the elemental metal, fully utilizing the heat accumulated in the oxygen carrier during the air oxidation step to generate a synthesis gas containing CO, H2, CO2, and H2O. The synthesis gas then enters the first-stage reducer of the first-stage chemical chain reaction unit.

[0051] Air oxidation step: After the methane conversion reaction is completed, the reactor is switched to the air oxidizer state and the air oxidation process is carried out. That is, air or oxygen is introduced into the air oxidizer to oxidize the metal elemental oxygen carrier to a high-valent state and release a large amount of reaction heat. Most of this reaction heat is accumulated in the oxidized oxygen carrier bed, storing the reaction heat required for the subsequent methane conversion process in advance;

[0052] In the second reduction step, after the air oxidation is completed, the reactor is switched to the state of the second reducer and the second reduction process is carried out, that is, the remaining CO and H2 in the first reduction tail gas reduce the second oxygen carrier in the second reducer from a high-valent oxide state to a single substance state, and at the same time, CO and H2 are completely oxidized to CO2 and H2O. The switching time is controlled and adjusted to ensure that the second reduction process does not penetrate, so that the second reduction tail gas is entirely CO2 and H2O, and a portion of the tail gas is refluxed to the methanogen and mixed with the methane-containing fuel gas to carry out a methane conversion reaction. After the remaining portion recovers heat, the H2O therein is condensed to obtain high-purity CO2 and CO2 capture;

[0053] In the first reduction step, a synthesis gas containing CO and H2 produced by the methanogen is introduced into the first reducer, so that the second-highest-valent metal oxide of the first oxygen carrier is reduced to a low-valent metal oxide or a metal element by the CO and H2 in the synthesis gas. The synthesis gas is partially oxidized by the first chemical chaining oxygen carrier to generate a mixed gas containing unreacted residual CO, H2, CO2, and H2O, namely the first-stage reduced tail gas, which is then returned to the second reducer of the second chemical chaining reaction unit;

[0054] In the steam oxidation hydrogen production step, steam is introduced into the steam oxidation hydrogen generator to oxidize the low-valent metal oxide oxygen carrier or metal element produced in the first reduction step to a second-highest-valent oxidation state, and simultaneously produce high-purity hydrogen.

[0055] In a preferred embodiment, 70-93% of the heat generated by the oxidation reaction in the air oxidizer is accumulated in the bed of the second oxygen carrier, and further 55-85% of the heat generated by the oxidation reaction in the air oxidizer is used for the endothermic demand of the methane conversion reaction.

[0056] In a more preferred embodiment, 80-93% of the heat generated by the oxidation reaction in the air oxidizer is accumulated in the bed of the second oxygen carrier, and then 70-85% of the heat generated by the oxidation reaction in the air oxidizer is used for the endothermic demand of the methane conversion reaction.

[0057] In a further preferred embodiment, 85-91% of the heat generated by the oxidation reaction in the air oxidizer is accumulated in the bed of the second oxygen carrier, and then 70-79% of the heat generated by the oxidation reaction in the air oxidizer is used for the endothermic demand of the methane conversion reaction.

[0058] In a preferred embodiment, the initial filled oxidation state of the first oxygen carrier is different from the metal oxidation state during repeated cycles.

[0059] In a preferred embodiment, the metal oxidation state of the first oxygen carrier during repeated cycles is Fe3O4, and the initial filling oxidation state is Fe2O3.

[0060] In a preferred embodiment, the methane-containing combustible gas is natural gas, biogas, coalbed methane or petroleum gas, but is not limited thereto.

[0061] Wherein, when the methane-containing combustible gas is biogas, the typical concentration of methane is 40-60 vol.%, but not limited thereto.

[0062] As described above, the multi-stage coupled chemical looping hydrogen production apparatus and method of the present invention can be used to adjust reaction conditions such as the initial valence state of the oxygen carrier and the composition of the reducing gas inlet gas phase. The two exothermic reaction stages—the oxygen carrier water vapor oxidation hydrogen production reaction and the oxygen carrier air deep oxidation reaction—are separated from the three-reaction-stage cycle, allowing them to form a separate two-reaction-stage "reduction-oxidation" reaction cycle with the corresponding decoupled reduction reaction processes. Essentially, this decoupling of the original three-reaction chemical looping hydrogen production stages alters the heat removal process and heat transfer with the methane reforming conversion process, thereby achieving direct heat transfer and utilization.

[0063] The first "reduction-oxidation" cycle must include two reaction stages: "oxygen carrier reduction-oxygen carrier water vapor oxidation to produce hydrogen". It can produce partially oxidized first-stage tail gas for use in the second-stage reduction after the first-stage reduction, and produce hydrogen in the oxygen carrier water vapor oxidation stage.

[0064] The second "reduction-oxidation" cycle includes two reaction stages: "oxygen carrier reduction-oxygen carrier air deep oxidation reaction." The ultimate goal is to utilize the large amount of heat released in the oxygen carrier air oxidation reaction stage to supply the strong endothermic demand of the methane conversion reaction process. However, as mentioned earlier, if the heat of the oxygen carrier bed is removed from the reactor to supply the methane conversion reactor, a heat carrier medium is required to be used through heat exchange, which will lead to problems such as complex system and mismatch between the heat source temperature and the heat exchange temperature difference. However, if a suitable metal oxygen carrier is selected, the "reduction-oxidation" cycle can be achieved while having methane conversion catalytic properties. In this way, the heat accumulated in the bed after the oxygen carrier air oxidation can be directly used to carry out the strong endothermic reaction of methane conversion. Without the need for a heat carrier medium and a complex heat exchange process, the energy of the two processes can be directly matched and supplied. The present invention perfectly solves this problem through the above technical solution.

[0065] Therefore, the present invention can provide a multi-stage coupled chemical chain hydrogen production device and method that achieves energy self-sustaining and does not require external energy input. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] FIG1 is a schematic structural diagram showing the chemical looping hydrogen production process of Reference 1.

[0067] FIG2 is a schematic diagram showing the decoupling process of the chemical looping hydrogen production process of the present invention.

[0068] FIG3 is a schematic diagram showing the decoupling process and the new process of the chemical looping hydrogen production process of the present invention.

[0069] FIG4 is a schematic structural diagram of a multi-stage coupled chemical loop hydrogen production device according to an embodiment of the present invention.

[0070] FIG5 is a flow chart showing a multi-stage coupled chemical looping method for producing hydrogen according to an embodiment of the present invention.

[0071] FIG6 is a schematic diagram showing the timing of reactions at various stages of the first chemical chain reaction cycle of the present invention.

[0072] FIG7 is a schematic diagram showing the timing of the reactions at each stage of the second chemical chain reaction cycle of the present invention. DETAILED DESCRIPTION

[0073] Below, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that those skilled in the art should understand that the present invention is not limited to these specific embodiments, and that various equivalent variations, modifications, or substitutions may be made to the present invention without departing from the basic concept and purpose of the present invention. Therefore, the scope of protection of the present invention should include such equivalent variations, modifications, or substitutions and should be determined according to the scope defined by the appended claims, rather than relying solely on the specific embodiments described herein.

[0074] Figure 4 is a schematic diagram of the structure of a multi-stage coupled chemical chain hydrogen production device according to an embodiment of the present invention. Figure 5 is a flow chart of a multi-stage coupled chemical chain hydrogen production method according to an embodiment of the present invention. Figure 6 is a schematic diagram of the timing of the reactions at each stage of the first chemical chain reaction cycle of the present invention. Figure 7 is a schematic diagram of the timing of the reactions at each stage of the second chemical chain reaction cycle of the present invention. Below, first, based on Figure 4, the structure of the multi-stage coupled chemical chain hydrogen production device according to an embodiment of the invention and the related reactions are described. Secondly, based on Figures 5, 6, and 7, the multi-stage coupled chemical chain hydrogen production method according to an embodiment of the present invention is described.

[0075] (Overall structure of a multi-stage coupled chemical chain hydrogen production device)

[0076] As shown in FIG4 , the multi-stage coupled chemical chain hydrogen production device of the present invention includes a first-stage chemical chain reaction unit represented by the upper frame in the figure and a second-stage chemical chain reaction unit represented by the lower frame.

[0077] The first-stage chemical chain reaction unit includes a first-stage reducer and a water vapor oxidation hydrogen generator, and these two parts can be converted into each other according to the reaction stage.

[0078] A metal oxide (represented by metal N) is placed in both the first-stage reducer and the steam oxidation hydrogen generator as an oxygen carrier in the reduction-oxidation reaction (hereinafter referred to as the "first oxygen carrier"). The metal N must be selected from a metal with multiple valence states, and the initial state of the first oxygen carrier can be an oxide of the metal N, for example, a metal oxide with a second highest valence. Furthermore, if N is Fe, it can be Fe3O4. However, its initial state can be a metal oxide state of other valences. For example, if N is Fe, the initial state of the first oxygen carrier can be Fe2O3.

[0079] The first oxygen carrier contains an active component and may optionally contain a secondary active component or an inactive component, or both. The active component may be, but is not limited to, Fe3O4; the secondary active component may be one or more of MoO3, GeO2, WO3, Mn2O3, ZnO, and CeO2; and the inactive component may be one or more of Al2O3, ZrO2, Y2O3, MgO, MgAl2O4, CaAl2O4, TiO2, and CaO. The primary function of the active component is to carry out redox cycles and produce pure hydrogen through steam oxidation; the primary function of the secondary active component is to enhance and stabilize the activity of the active component; and the primary function of the inactive component is to stabilize the properties of the oxygen carrier, prevent sintering, and construct a stable pore structure.

[0080] As an alternative, the first oxygen carrier may contain no active ingredient, only a secondary active ingredient, and optionally an inactive ingredient, wherein the secondary active ingredient is one or more of MoO3, GeO2, WO3, Mn2O3, ZnO, and CeO2, and the inactive ingredient may be one or more of Al2O3, MgO, ZrO2, Y2O3, MgAl2O4, CaAl2O4, TiO2, and CaO. The reason why the secondary active ingredient is not used as the active ingredient in the present invention is due to various factors such as cost. If factors such as cost are not considered, or under special conditions, those skilled in the art may completely not use the active ingredient and only use the secondary active ingredient.

[0081] The first oxygen carrier can be prepared by calcining the active component, the secondary active component, or the inactive component in a high-temperature solid state reaction, wherein the active component content is 50-95 wt.%, the secondary active component content is 0-5 wt.%, and the inactive component content is 5-50 wt.%. The high-temperature calcination temperature is 750°C to 1150°C. After forming, the average particle size of the oxygen carrier is 1 mm to 10 mm.

[0082] The first-stage reducer and the steam oxidation hydrogen producer can achieve mutual switching of the functions of the two reaction units by using multiple pipelines and valves provided on the pipelines in a manner similar to that described in Patent Document 1. For example, when the two reactors corresponding to the first-stage reducer and the steam oxidation hydrogen producer are defined as reactor D and reactor E ( FIG. 6 ), initially reactor D performs the function of the first-stage reducer and reactor E performs the function of the steam oxidation hydrogen producer. However, after the pipelines are switched by the valves, reactor D performs the function of the steam oxidation hydrogen producer and reactor E performs the function of the first-stage reducer.

[0083] The multi-stage coupled chemical chain hydrogen production device of the present invention may also include a controller, which controls or monitors each pipeline, valve, temperature, pressure, etc. within the device and makes control adjustments at any time. For example, it can switch the input and output of gases, switch the reaction of each reactor according to the reaction stage, transfer or recover heat or energy, capture carbon dioxide, cool water vapor, etc.

[0084] Next, the reactions occurring in the first-stage reducer and the steam oxidation hydrogen generator are described.

[0085] After the system is preheated and the cycle begins, syngas containing CO and H₂, generated by the methanogen (described below), is introduced into the first-stage reducer. The CO and H₂ in the syngas reduce the lower-valent metal oxides (e.g., Fe₃O₄) to lower-valent metal oxides or elemental metals (e.g., FeO and Fe in the iron-based oxygen carrier). Due to the thermodynamic constraints of the chemical chain reaction, the syngas is partially oxidized by the first-stage oxygen carrier, generating a mixture containing unreacted CO and H₂, as well as CO₂ and H₂O (first-stage reduction tail gas). This mixture then returns to the second-stage chemical chain reaction unit to reduce the second-stage oxygen carrier. The reduction reaction temperature in the first-stage reducer is 400-915°C.

[0086] The reaction in the first stage reducer is (first stage reduction) the following process ⑥:

[0087] N represents a metal element, and a, b, and i represent numbers (0<i<b) a O b +iCO / H2→N a O b-i +iCO2 / H2O N a O b +bCO / H2→aN+bCO2 / H2O N a O b-i +(bi)CO / H2→aN+(bi)CO2 / H2O

[0088] When the first oxygen carrier is Fe, the reduction process of the oxygen carrier in process ⑥ is Fe3O4→FeO→Fe.

[0089] In addition, water vapor is introduced into the steam oxidation hydrogen generator (actually the reactor after the reduction reaction in the first stage reducer has completed), oxidizing the low-valent metal oxide oxygen carrier or metal element oxygen carrier produced in the first stage of reduction to a second-highest valent oxidation state, while simultaneously generating hydrogen. For example, when the metal N corresponding to the first oxygen carrier is Fe, the Fe element (or Fe / FeO) in the oxygen carrier is oxidized to Fe3O4. The reduction reaction temperature in the steam oxidation hydrogen generator is 450-900°C.

[0090] The steam oxidation reaction in the steam oxidation hydrogen generator is as follows③:

[0091] When N represents a metal element and a, b, and i represent numbers (0<i<b) aN+bH2O→N a O b +bH2 N a O b-i +iH2O→N a O b+iH2 aN+(bi)H2O→N a O b-i +(bi)H2

[0092] When the first oxygen carrier is Fe oxide, the oxidation process of the oxygen carrier in process ③ is Fe→FeO→Fe3O4

[0093] The following describes the various reactors in the second stage chemical chain reaction unit. As shown in FIG4 , the second stage chemical chain reaction unit includes a second stage reducer, a methanogen, and an air oxidizer, which can be interchanged according to the reaction stage.

[0094] The second-stage reducer, methanogen, and air oxidizer all use a metal oxide (represented by metal M) as an oxygen carrier in the reduction-oxidation reaction (hereinafter referred to as the "second oxygen carrier"). The metal M must be a metal that can catalyze the methane conversion reaction and can also store sufficient heat through the redox reaction.

[0095] The second oxygen carrier contains an active ingredient and may selectively contain a secondary active ingredient or an inactive ingredient, or contain both a secondary active ingredient and an inactive ingredient.

[0096] The active component can be one or more of NiO, CuO, and ZnO, preferably consisting solely of NiO, but not limited thereto; the secondary active component can be one or more of Fe2O3, CeO2, Co3O4, and Mn2O3; and the inactive component can be one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2. The primary function of the active component is to carry out redox cycles, release and store heat during air oxidation, and catalyze the methane conversion reaction after reduction; the primary function of the secondary active component is to enhance and stabilize the active component, while the primary function of the inactive component is to stabilize the reaction of the second oxygen carrier, prevent sintering, achieve a reasonable pore structure, and achieve a better heat storage structure.

[0097] As an alternative, the second oxygen carrier does not contain an active ingredient, contains a secondary active ingredient, and optionally contains an inactive ingredient, the secondary active ingredient is one or more of Fe2O3, CeO2, Co3O4, and Mn2O3, and the inactive ingredient can be one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2. The reason why the above-mentioned secondary active ingredients are not used as active ingredients in the present invention is to take into account many factors such as cost. If factors such as cost are not considered, or under special conditions, those skilled in the art can completely use only the secondary active ingredients without using active ingredients.

[0098] The second oxygen carrier can be prepared by calcining the active ingredient, the secondary active ingredient, or the inactive ingredient in a high-temperature solid state reaction, wherein the total content of the active ingredient is 8 wt.% to 40 wt.%, the total content of the secondary active ingredient is 0 to 5 wt.%, and the total content of the inactive ingredient is 60 wt.% to 92 wt.%, the high-temperature calcination temperature is 550°C to 1250°C, and the average particle size of the oxygen carrier after forming is 1 mm to 8 mm.

[0099] The second section reducer, methanogen and air oxidizer can be realized by switching the functions of the three reaction units using multiple pipelines and valves arranged on the pipelines in a manner similar to that described in Patent Document 1. For example, when the three reactors corresponding to the second section reducer, methanogen and air oxidizer are defined as reactor B, reactor A and reactor C (see Figure 7), after the system is preheated and enters the circulation system, at the beginning, reactor A realizes the function of methanogen, reactor B realizes the function of the second section reducer and reactor C realizes the function of air oxidizer, but after switching the pipeline by the valve, reactor A realizes the function of air oxidizer, reactor B realizes the function of methanogen and reactor C realizes the function of the second section reducer, and then, after switching the pipeline by the valve, reactor A realizes the function of the second section reducer, reactor B realizes the function of air oxidizer and reactor C realizes the function of methanogen, and so on.

[0100] Next, the reactions occurring in the second-stage reducer, methanogen, and air oxidizer will be described.

[0101] After the system is preheated and circulation begins, methane-containing combustible gas is introduced into the methanogen. This gas is first mixed with a portion of the recycled second-stage reduction tail gas, and the mixed gas undergoes a methane conversion reaction. During the methane conversion reaction, the second-stage oxygen carrier in the reactor has been pre-reduced to a metallic state, and heat has been accumulated in the oxygen carrier bed. The methane entering the system and any CO2, H2O, or a mixture of CO2 and H2O undergo a methane conversion reaction under the catalytic action of the metallic element (process ①). This reaction utilizes the accumulated heat of the oxygen carrier to generate a synthesis gas (referred to as "syngas") containing CO, H2, CO2, and H2O, which enters the first-stage reducer of the first-stage chemical chain reaction unit. The reaction temperature in the methane generator ranges from 500°C to 1050°C.

[0102] The methane conversion reaction that may occur in the methanogen is as follows:

[0103]

[0104]

[0105] When the first oxygen carrier is Ni oxide, the oxygen carrier remains unchanged as elemental Ni in process ①.

[0106] After the methane conversion reaction is completed, the temperature of the oxygen carrier and the bed drops to 400-700°C. At this time, the reactor is switched to the air oxidizer state through the controller and the air oxidation process (process ④) is carried out. That is, air or oxygen is introduced into the air oxidizer, and the oxygen oxidizes the metal elemental oxygen carrier to a high valence state and releases a large amount of heat. Most of the reaction heat is accumulated in the oxidized oxygen carrier bed, and heat is stored in advance for the reaction heat required for the subsequent methane conversion process. Among them, the reaction temperature of the air oxidation process of the first chemical chain reaction unit is 400-950°C.

[0107] The reaction in the air oxidizer is the following process ④: xM+1 / 2yO2→M x O y

[0108] When the first oxygen carrier is Ni oxide, the change of the oxygen carrier in process ④ is Ni→NiO.

[0109] After the air oxidation is complete, the reactor is switched to the second-stage reducer state via a controller and the second stage reduction process (process ⑤) is carried out. The remaining CO and H2 in the first-stage reduction tail gas reduce the second oxygen carrier in the second stage chemical chain from a high-valent oxide state to a single-element state. The heat released by the reaction is accumulated in the oxygen carrier bed. This heat, combined with the oxygen-carrying volume heat stored in the previous stage of the air oxidation process, provides the heat required for the next stage of the methane conversion process. At the same time, CO and H2 are completely oxidized to CO2 and H2O. The switching time is adjusted by the controller to ensure that the second stage reduction process does not penetrate (i.e., no CO and H2 flow out). The second-stage reduction tail gas is entirely CO2 and H2O. Depending on specific needs, a portion of the tail gas (CO2, H2O) can be refluxed to the methane conversion stage of the second stage chemical chain to mix with the methane-containing fuel gas and then enter the methane conversion reactor. The remaining portion is used to recover heat and condense the H2O to obtain high-purity CO2, which can be used for CO2 capture. The reaction temperature of the oxygen carrier reduction process in the second chemical chain reaction unit is 450-1000°C.

[0110] (Description of the multi-stage coupled chemical chain hydrogen production method)

[0111] Next, a multi-stage coupled chemical looping hydrogen production method using the multi-stage coupled chemical looping hydrogen production device of the present invention is described.

[0112] As shown in FIG5 , when the multi-stage coupled chemical chain hydrogen production device of the present invention is used to produce hydrogen, the device must first be started and the oxygen carrier and reactor preparations must be carried out. Specifically, in the five reactors (A / B / C / D / E) in the multi-stage coupled chemical chain hydrogen production device, the two reactors D and E corresponding to the first chemical chain reaction unit are respectively filled with the above-mentioned first oxygen carrier, and the reactors A / B / C corresponding to the second reaction chain unit are filled with the second oxygen carrier. The initial filling oxidation state of the oxygen carrier can use the metal oxide in the oxidation state during the actual cycle, or can use metal oxides in other oxidation states. For example, although the form of the first oxygen carrier in the two reactors D and E corresponding to the first chemical chain reaction unit after the cycle starts is Fe3O4, the initial filling oxide can be Fe2O3.

[0113] Next, all five reactors (A / B / C / D / E) were heated to the designated temperatures.

[0114] After the three reactors (A / B / C) in the second chemical loop unit undergo oxygen carrier pre-reduction preparation, H2 is introduced into the three reactors (A / B / C) to initiate oxygen carrier pre-reduction. Once all reactors have completed pre-reduction, air is introduced into one reactor, A, to perform air oxidation and heat storage. Once reactor A has completed air oxidation and heat storage, it switches to H2 reduction and continues to accumulate heat. Simultaneously, the other reactor, B, undergoes air oxidation.

[0115] After completing hydrogen reduction and heat storage, reactor A begins to introduce combustible gas containing CH4 to carry out methane conversion and produce synthesis gas containing CO and H2; at the same time, reactor B switches to oxygen carrier reduction, and the reducing gas comes from the reduction tail gas of the first chemical chain unit (containing penetrated CO and H2); at the same time, reactor C performs air oxidation.

[0116] Reactor A, which has completed methane conversion, switches to an air oxidation process to perform air oxidation and generate and store heat; reactor B switches to methane conversion; and reactor C switches to an oxygen carrier reduction process.

[0117] After completing air oxidation, reactor A switches to the oxygen carrier reduction process; after completing methane conversion, reactor B switches to the air oxidation process; reactor C switches to the methane conversion process at this time.

[0118] The subsequent process of the second chemical loop unit is cyclically switched in three reactors (A / B / C).

[0119] On the other hand, the synthesis gas enters the reactor D of the two reactors (D / E) of the first chemical chain unit to reduce the first oxygen carrier set therein, and the reduced tail gas (containing penetrated CO and H2) returns to enter the reactor in the reduction state of the second chemical chain unit (the second stage reducer) to reduce the second oxygen carrier therein.

[0120] Reactor D, which has completed the reduction of the first oxygen carrier, switches to the steam oxidation hydrogen production process and completes the steam oxidation hydrogen production reaction. Simultaneously, reactor E is fed with synthesis gas to carry out the first oxygen carrier reduction reaction. Next, reactor D, which has completed the oxygen carrier steam oxidation hydrogen production, switches to the oxygen carrier reduction process. Reactor E, which has completed the reduction process, switches to the steam oxidation hydrogen production process, and the above cycle is repeated.

[0121] FIG6 is a schematic diagram illustrating the timing of the various stages of the first chemical chain reaction cycle of the present invention. As shown in FIG6 , reactors D and E are heated together during the startup preparation phase, then enter a standby state (waiting for the second chemical chain unit to complete preheating and pre-reduction). Thereafter, during the first cycle (cycle 1-1), only reactor D is reduced. After reduction is complete, reactor D switches to steam oxidation, while reactor E is reduced. Thereafter, reactors D and E alternate between steam oxidation and the first reduction reaction, repeating the cycle.

[0122] Figure 7 is a schematic diagram illustrating the timing of the reactions in each stage of the second chemical chain reaction cycle of the present invention. As shown in Figure 7 , reactors A, B, and C are heated together during the startup preparation phase, then undergo pre-reduction. Next, reactor A undergoes oxidation. Next, reactor A undergoes reduction while reactor B undergoes oxidation. Starting from the first cycle (cycle 2-1), reactors A, B, and C are switched and repeated to perform the three reactions of methane conversion, reduction, and oxidation.

[0123] According to the device and method of the present invention, 70-93%, preferably 80-93%, and more preferably 85-91% of the heat generated by the oxidation reaction in the air oxidizer is accumulated in the bed of the second oxygen carrier. Furthermore, 55-85%, preferably 70-85%, and more preferably 70-79% of the heat generated by the oxidation reaction in the air oxidizer is ultimately used for the endothermic needs of the methane conversion reaction. Thus, the present invention can achieve an energy-self-sustaining multi-stage coupled chemical chain hydrogen production device and method that does not require external energy input.

[0124] (Example 1)

[0125] Next, Example 1 of the present invention is described. This example uses the multi-stage coupled chemical chain hydrogen production device of the present invention and the multi-stage coupled chemical chain hydrogen production method of the present invention to produce high-purity hydrogen. The specific parameters are as follows:

[0126] First stage chemical chain reactor: 2 reactors, each reactor is loaded with 120kg of first stage oxygen carrier

[0127] The first stage oxygen carrier composition: active ingredient 55wt.%: Fe2O3; inactive ingredient 45wt.%: ZrO2

[0128] The second stage chemical chain reactor: 3 reactors, each reactor is loaded with 200kg of the second stage oxygen carrier,

[0129] The second stage oxygen carrier composition: active ingredient 18wt.%: NiO, oxygen carrier inactive ingredient 82wt.%: CaAl2O4

[0130] Methane-containing fuel gas raw material: biogas (60 vol.% CH4, 40 vol.% CO2), flow rate 34 Nm 3 / h

[0131] Methane conversion (process ①): bed temperature 550-950°C, generated syngas composition (molar ratio): CO / CO2 / H2 / H2O / CH4=47 / 4 / 44.5 / 4.2 / 0.3, syngas outlet temperature 250°C, syngas flow rate 88Nm 3 / h

[0132] First stage reduction (process ⑥): bed temperature 700-850°C, first stage reduction tail gas composition (molar ratio): CO / CO2 / H2 / H2O=17 / 34 / 16 / 33, tail gas temperature 230°C

[0133] Second stage reduction (process ⑤): bed temperature 850-950°C, second stage reduction tail gas composition (molar ratio): CO2 / H2O=51 / 49, tail gas temperature 180°C

[0134] The first stage of oxidation (process ③): bed temperature 600-850℃, steam oxidation outlet gas phase composition (molar ratio): H2 / H2O=46 / 54, crude hydrogen temperature 175℃, heat recovery and cooling, product hydrogen composition: H2 / H2O=99.99 / 0.01, product hydrogen flow rate: 58Nm 3 / h

[0135] Second stage oxidation (process ④): bed temperature 550~900℃, oxidation tail gas outlet composition: N2, tail gas temperature 160℃

[0136] The methane conversion reaction in process ① absorbs heat: 187~225MJ / h; the second stage air oxidation reaction in process ④ releases heat: 380~405MJ / h, of which 80~90% of the heat is accumulated in the oxygen carrier bed of the second stage chemical chain reactor, and 55~70% of the heat can be used for the endothermic demand of the methane conversion reaction in process ①.

[0137] (Example 2)

[0138] Next, Example 2 of the present invention is described. This example uses the multi-stage coupled chemical chain hydrogen production device of the present invention and the multi-stage coupled chemical chain hydrogen production method of the present invention to produce high-purity hydrogen. The specific parameters are as follows:

[0139] First stage chemical chain reactor: 2 reactors, each reactor is loaded with 210kg of first stage oxygen carrier

[0140] The first stage oxygen carrier composition: active ingredient 80wt.%: Fe2O3; inactive ingredient 20%: MgAl2O4+ZrO2

[0141] The second stage chemical chain reactor: 3 reactors, each reactor is loaded with 600kg of the second stage oxygen carrier,

[0142] The second stage oxygen carrier composition: active ingredient 12wt.%: NiO, oxygen carrier inactive ingredient 88wt.%: MgAl2O4

[0143] Methane-containing fuel gas raw material: biogas (55vol.% CH4, 45vol.% CO2), flow rate 108Nm 3 / h

[0144] Methane conversion (process ①): bed temperature 550-950°C, generated syngas composition (molar ratio): CO / CO2 / H2 / H2O / CH4=45 / 4.5 / 46 / 4 / 0.5, syngas outlet temperature 240°C, syngas flow rate 280Nm 3 / h

[0145] First stage reduction (process ⑥): bed temperature 700-850°C, first stage reduction tail gas composition (molar ratio): CO / CO2 / H2 / H2O=16.5 / 33.5 / 15 / 35, tail gas temperature 220°C

[0146] Second stage reduction (process ⑤): bed temperature 850-950°C, second stage reduction tail gas composition (molar ratio): CO2 / H2O=50 / 50, tail gas temperature 170°C

[0147] The first stage of oxidation (process ③): bed temperature 600-850℃, steam oxidation outlet gas phase composition (molar ratio): H2 / H2O=48 / 52, crude hydrogen temperature 170℃, heat recovery and cooling, product hydrogen composition: H2 / H2O=99.992 / 0.008, product hydrogen flow rate: 148.5Nm 3 / h

[0148] Second stage oxidation (process ④): bed temperature 550-900 degrees Celsius, oxidation tail gas outlet composition (molar ratio): N2, tail gas temperature 165°C

[0149] The methane conversion reaction in process ① absorbs heat: 544.5~655MJ / h; the second stage air oxidation reaction in process ④ releases heat: 738~795MJ / h, of which 86~93% of the heat is accumulated in the oxygen carrier bed of the second stage chemical chain reactor, and 73~85% of the heat can be used for the endothermic demand of the methane conversion reaction in process ①.

[0150] (Example 3)

[0151] Next, Example 3 of the present invention is described. This example uses the multi-stage coupled chemical chain hydrogen production device of the present invention and the multi-stage coupled chemical chain hydrogen production method of the present invention to produce high-purity hydrogen. The specific parameters are as follows:

[0152] First stage chemical chain reactor: 2 reactors, each reactor is loaded with 50kg of first stage oxygen carrier

[0153] The first stage oxygen carrier composition: active ingredient 80wt.%: Fe3O4; inactive ingredient 20%: Al2O3

[0154] The second stage chemical chain reactor: 3 reactors, each reactor is loaded with 160kg of the second stage oxygen carrier,

[0155] The second stage oxygen carrier composition: active ingredient 16wt.%: NiO, oxygen carrier inactive ingredient 84wt.%: CaAl2O4

[0156] Methane-containing fuel gas raw material: natural gas, flow rate 15Nm 3 / h

[0157] Methane conversion (process ①): bed temperature 550-950°C, generated syngas composition (molar ratio): CO / CO2 / H2 / H2O / CH4=46.2 / 4 / 45.5 / 4.1 / 0.2, syngas outlet temperature 260°C, syngas flow rate 62Nm 3 / h

[0158] First stage reduction (process ⑥): bed temperature 700-850°C, first stage reduction tail gas composition (molar ratio): CO / CO2 / H2 / H2O=17 / 32 / 18 / 323, tail gas temperature 221°C

[0159] Second stage reduction (process ⑤): bed temperature 850-950°C, second stage reduction tail gas composition (molar ratio): CO2 / H2O=49 / 51, tail gas temperature 172°C

[0160] The first stage of oxidation (process ③): bed temperature 600-850°C, steam oxidation outlet gas phase composition (molar ratio): H2 / H2O=45.2 / 54.8, crude hydrogen temperature 182°C, heat recovery and cooling, product hydrogen composition: H2 / H2O=99.99 / 0.01, product hydrogen flow rate: 36.8Nm 3 / h

[0161] Second stage oxidation (process ④): bed temperature 550-900 degrees Celsius, oxidation tail gas outlet composition (molar ratio): N2, tail gas temperature 135°C

[0162] The methane conversion reaction in process ① absorbs heat: 137~165MJ / h; the second stage air oxidation reaction in process ④ releases heat: 270~291MJ / h, of which 85~91% of the heat is accumulated in the oxygen carrier bed of the second stage chemical chain reactor, and 70~79% of the heat can be used for the endothermic demand of the methane conversion reaction in process ①.

[0163] (Heat conversion results)

[0164] According to the results of Examples 1, 2, and 3 above, the relationship between the heat released by the second-stage air oxidation reaction, the percentage of the heat released accumulated in the oxygen carrier bed of the second-stage chemical looping reactor, and the percentage ultimately used for the heat absorption required by the methane-to-methane conversion reaction is as follows.

[0165] According to the device and method of the present invention, 70-93%, preferably 80-93%, and more preferably 85-91% of the heat generated by the oxidation reaction in the air oxidizer is accumulated in the bed of the second oxygen carrier, and finally, 55-85%, preferably 70-85%, and more preferably 70-79% of the heat generated by the oxidation reaction in the air oxidizer is used for the endothermic demand of the methane conversion reaction.

[0166] In summary, the process of the present invention adopts a novel structure, which can efficiently couple the highly exothermic air oxidation process in the chemical chain cycle process with the methane catalytic conversion process, and store most of the heat released after air oxidation in the reactor bed. The oxygen carrier is then reduced to a metal element state through a slightly exothermic oxygen carrier reduction process, and continues to store heat in the reactor. It is then switched to the methane conversion process. The oxygen carrier that has been reduced to a metal element has the catalytic ability to convert methane. At the same time, the heat accumulated in the first two processes can directly supply the heat required for the highly endothermic reaction of methane conversion.

[0167] By decoupling the single, three-reaction, cyclic chemical chain hydrogen production process from existing technologies, splitting it into two distinct chemical chain reaction processes and coupling them with the methane conversion process, the heat generated by air oxidation in one chemical chain is directly fed into the methane conversion process. This allows for self-heating methane conversion of the methane-containing fuel gas to produce synthesis gas in the absence of oxygen, and then oxidation of the oxygen-carrier water vapor to produce hydrogen. This entire process eliminates the need for external heating, heat transfer media, or complex heat exchange systems, achieving self-sustaining heat within the system.

[0168] (Glossary of this patent standard)

[0169] Multi-stage coupled chemical loop hydrogen production device

[0170] The first chemical chain reaction unit

[0171] The second chemical chain reaction unit

[0172] The first stage reducer, steam oxidation hydrogen generator

[0173] Second stage reducer, methane converter, air oxidizer

[0174] First oxygen carrier, second oxygen carrier

[0175] Combustible gas containing methane, synthesis gas, reduction tail gas,

[0176] Active ingredients, sub-active ingredients, inactive ingredients

[0177] The first stage reduction reaction, water vapor oxidation hydrogen production reaction

[0178] Second stage reduction reaction, methane conversion reaction, air oxidation reaction

[0179] Switch and repeat (reaction)

[0180] The first reduction step, the steam oxidation hydrogen production step,

[0181] Second stage reduction step, methane conversion step, air oxidation step

[0182] The first chemical chain reaction cycle and the second chemical chain reaction cycle.

Claims

1. A multistage coupled chemical looping hydrogen production device, characterized in that the multistage coupled chemical looping hydrogen production device includes a first-stage chemical looping reaction unit and a second-stage chemical looping reaction unit, the first-stage chemical looping reaction unit includes a first-stage reducer and a steam oxidation hydrogen producer, and these two parts can be converted into each other according to the reaction stage and the whole cycle repeats; the second-stage chemical looping reaction unit includes a second-stage reducer, a methane converter, and an air oxidizer, and these three parts can be converted into each other according to the reaction stage and the whole cycle repeats; the same first oxygen carrier is provided in the first-stage reducer and the steam oxidation hydrogen producer, and the first oxygen carrier changes into a metal single substance or metal oxides with different chemical valences at each reaction stage, and the metal has multiple chemical valences; the same second oxygen carrier is provided in the second-stage reducer, the methane converter, and the air oxidizer, and the second oxygen carrier changes into a metal single substance or metal oxides with different chemical valences at each reaction stage, and the metal single substance corresponding to the second oxygen carrier plays a catalytic role in the methane conversion reaction in the methane conversion reactor; the methane converter is connected to the first-stage reducer for delivering the syngas after methane conversion to the first-stage reducer; the second-stage reducer is connected to the methane converter for refluxing carbon dioxide or steam or both to the methane converter; the first-stage reducer is connected to the second-stage reducer for delivering the reduction tail gas containing carbon monoxide or hydrogen or both to the second-stage reducer.

2. The multistage coupled chemical looping hydrogen production device according to claim 1, characterized in that the first oxygen carrier contains an active ingredient, and optionally contains a sub-active ingredient or an inactive ingredient or both, the active ingredient is Fe3O4, the sub-active ingredient is one or more of MoO3, GeO2, WO3, Mn2O3, ZnO, CeO2, the inactive ingredient can be one or more of Al2O3, MgO, ZrO2, Y2O3, MgAl2O4, CaAl2O4, TiO2, CaO.

3. The multistage coupled chemical looping hydrogen production device according to claim 2, characterized in that the first oxygen carrier does not contain an active ingredient, contains a sub-active ingredient, and optionally contains an inactive ingredient, the sub-active ingredient is one or more of MoO3, GeO2, WO3, Mn2O3, ZnO, CeO2, the inactive ingredient can be one or more of Al2O3, MgO, ZrO2, Y2O3, MgAl2O4, CaAl2O4, TiO2, CaO.

4. The multistage coupled chemical looping hydrogen production device according to claim 2, characterized in that in the first oxygen carrier, the content of the active ingredient is 50-95 wt.%, the content of the sub-active ingredient is 0-5 wt.%, and the content of the inactive ingredient is 5-50 wt.%.

5. The multistage coupled chemical looping hydrogen production device according to claim 2, characterized in that The first oxygen carrier contains Fe3O4 as the active component and Al2O3 or MgO as the inactive component.

6. The multi-stage coupled chemical-looping hydrogen production device according to claim 5, wherein the composition of the first-stage oxygen carrier is 75 wt.% of Fe3O4 as the active component and 25 wt.% of Al2O3 as the inactive component, or the composition of the first-stage oxygen carrier is 80 wt.% of Fe3O4 as the active component and 20 wt.% of MgO + Al2O3 as the inactive component.

7. The multi-stage coupled chemical-looping hydrogen production device according to claim 1, wherein the second oxygen carrier contains an active component, and optionally contains a sub-active component or an inactive component or both, the active component is one or more of NiO, CuO, ZnO, the sub-active component is one or more of Fe2O3, CeO2, Co3O4, Mn2O3, the inactive component can be one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, TiO2.

8. The multi-stage coupled chemical-looping hydrogen production device according to claim 1, wherein the second oxygen carrier does not contain an active component, contains a sub-active component, and optionally contains an inactive component, the sub-active component is one or more of Fe2O3, CeO2, Co3O4, Mn2O3, the inactive component is one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, TiO2.

9. The multi-stage coupled chemical-looping hydrogen production device according to claim 7, wherein in the second oxygen carrier, the content of the active component is 8 wt.% to 40 wt.%, the content of the sub-active component is 0 to 5 wt.%; the content of the inactive component is 60 wt.% to 92 wt.%.

10. The multi-stage coupled chemical-looping hydrogen production device according to claim 7, wherein the second oxygen carrier contains NiO as the active component.

11. The multi-stage coupled chemical-looping hydrogen production device according to claim 7, wherein the composition of the second oxygen carrier is 18 wt.% of NiO as the active component and 82 wt.% of MgAl2O4 as the inactive component, or the composition of the second oxygen carrier is 18 wt.% of NiO as the active component and 82 wt.% of CaAl2O4 as the inactive component.

12. A multi-stage coupled chemical-looping hydrogen production method, wherein the multi-stage coupled chemical-looping hydrogen production device described in any one of claims 1 to 11 is used, and the method includes the following steps: Device startup and oxygen carrier and reactor preparation step, in this step, start the device, and fill the above-mentioned first oxygen carrier into the two reactors corresponding to the first-stage chemical-looping reaction unit respectively, and fill the second oxygen carrier into the three reactors corresponding to the second reaction chain unit respectively; Reactor pre-treatment step, in which each of the above-mentioned five reactors is heated separately, and the system as a whole is adjusted to be suitable for the following reactions by means of a combination of pre-reduction and pre-oxidation, namely: the two reactors corresponding to the first-stage chemical looping reaction unit are switched between each other and the first-stage reduction reaction and steam oxidation hydrogen production reaction are repeated cyclically, and the three reactors corresponding to the second-stage chemical looping reaction unit are switched between each other and the methane reforming reaction, air oxidation reaction and second-stage reduction reaction are repeated cyclically; Methane reforming step, introducing methane-containing combustible gas into the methane reformer, which first mixes with the reduction tail gas partially recycled from the second-stage reducer, and then methane reacts with a mixed gas containing CO2 or H2O or both under the catalysis of elemental metal to carry out the methane reforming reaction, and fully utilizes the heat already stored in the oxygen carrier during the air oxidation step to generate syngas containing CO, H2, CO2, and H2O components, which enters the first-stage reducer of the first-stage chemical looping reaction unit; Air oxidation step, after the methane reforming reaction is completed, the reactor is switched to the state of the air oxidizer and the air oxidation process is carried out, that is, air or oxygen is introduced into the air oxidizer to oxidize the elemental metal state oxygen carrier to the high-valence state, and a large amount of reaction heat is released at the same time. Most of this reaction heat is stored in the bed layer of the oxidized oxygen carrier in advance for the reaction heat required for the subsequent methane reforming process; Second-stage reduction step, after the air oxidation is completed, the reactor is switched to the state of the second-stage reducer and the second-stage reduction process is carried out, that is, the remaining CO and H2 in the first-stage reduction tail gas reduce the second oxygen carrier in the second-stage reducer from the high-valence oxide state to the elemental state, and at the same time CO and H2 are completely oxidized to CO2 and H2O, and by controlling and adjusting the switching time to ensure that the second-stage reduction process does not penetrate, so that all the second-stage reduction tail gas is CO2 and H2O, and a part of the tail gas is refluxed to the methane reformer and mixed with the methane-containing fuel gas to carry out the methane reforming reaction, and the remaining part is heat recovered and then H2O is condensed to obtain high-purity CO2 and CO2 capture is carried out; First-stage reduction step, introducing the syngas containing CO and H2 generated by the methane reformer into the first-stage reducer, reducing the sub-high-valence metal oxide state of the first oxygen carrier to the low-valence metal oxide or elemental metal by CO and H2 in the syngas, and the syngas is partially oxidized by the first-stage chemical looping oxygen carrier to generate a mixed gas containing unreacted remaining CO, H2, and CO2, H2O, that is, the reduction tail gas, which is then returned to the second-stage reducer of the second-stage chemical looping reaction unit; Steam oxidation hydrogen production step, introducing steam into the steam oxidation hydrogen producer to oxidize the low-valence metal oxide oxygen carrier or elemental metal generated in the first-stage reduction step to the sub-high-valence oxidation state, and at the same time generating high-purity hydrogen.

13. The multi-stage coupled chemical looping hydrogen production method according to claim 12, wherein, 70% to 93% of the heat generated by the oxidation reaction in the air oxidizer is accumulated in the bed of the second oxygen carrier, and then 55% to 85% of the heat generated by the oxidation reaction in the air oxidizer is used for the endothermic requirement of the methane reforming reaction.

14. The multi-stage coupled chemical looping hydrogen production method according to claim 12, wherein 80% to 93% of the heat generated by the oxidation reaction in the air oxidizer is accumulated in the bed of the second oxygen carrier, and then 70% to 85% of the heat generated by the oxidation reaction in the air oxidizer is used for the endothermic requirement of the methane reforming reaction.

15. The multi-stage coupled chemical looping hydrogen production method according to claim 12, wherein 85% to 91% of the heat generated by the oxidation reaction in the air oxidizer is accumulated in the bed of the second oxygen carrier, and then 70% to 79% of the heat generated by the oxidation reaction in the air oxidizer is used for the endothermic requirement of the methane reforming reaction.

16. The multi-stage coupled chemical looping hydrogen production method according to claim 12, wherein The initial filling oxidation state of the first oxygen carrier is different from the metal oxidation state during the repeated cycle process.

17. The multi-stage coupled chemical looping hydrogen production method according to claim 16, wherein The metal oxidation state of the first oxygen carrier during the repeated cycle process is Fe3O4, and the initial filling oxidation state is Fe2O3.

18. The multi-stage coupled chemical looping hydrogen production method according to claim 12, wherein The methane-containing combustible gas is natural gas, biogas, coalbed methane or petroleum gas.

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