Method and device for hydrogen production by thermochemical decomposition of water using manganese oxides and carbonates

Abstract

This invention provides a thermochemical cycle method for hydrogen production by water splitting of manganese oxides and carbonates, comprising: heating high-valence manganese oxides to a first temperature to undergo a thermal deoxygenation reaction, generating low-valence manganese oxides and oxygen; reacting the low-valence manganese oxides generated from the thermal deoxygenation reaction with carbonates at a second temperature to generate manganite, carbon dioxide, and carbon monoxide; reacting the generated manganite with carbon dioxide at a third temperature to generate high-valence manganese oxides and carbonates; separating the carbon monoxide and carbon dioxide generated from the reaction of low-valence manganese oxides and carbonates; and reacting the carbon monoxide with water vapor in a water-vapor shift reaction to generate carbon dioxide and hydrogen. This method consumes H₂O. 2 O and thermal energy enable the phased generation of hydrogen and oxygen products. Other substances in the system are recycled through different reaction configurations, effectively overcoming the problems of high temperature, low oxygen partial pressure, and poor stability in traditional thermochemical two-step cyclic reactions.

Description

A thermochemical cycle method and apparatus for hydrogen production by decomposing water from manganese oxides and carbonates. Technical Field

[0001] This invention relates to the field of thermochemical hydrogen production technology, and in particular to a thermochemical cycle water decomposition method and apparatus for producing hydrogen from manganese oxides and carbonates. Background Technology

[0002] Accelerating the development of green and low-carbon energy is of great significance for building a clean, low-carbon, safe, and efficient modern energy system. Hydrogen energy, with its advantages of high calorific value, clean operation, and zero carbon emissions, is an ideal alternative to fossil fuels. Utilizing thermochemical water splitting to produce hydrogen, and then releasing the chemical energy of hydrogen through combustion, can achieve the recycling of hydrogen elements and is considered an important technological approach for sustainable energy utilization. However, directly pyrolyzing H2O into H2 and O2 requires extremely high reaction temperatures (>3000℃), and the mixture of H2 and O2 produces unsafe and difficult-to-separate compounds. These drawbacks mean that thermochemical direct water splitting technology does not yet have a promising prospect for large-scale application.

[0003] Thermochemical cycles, through the appropriate configuration of two or more steps, achieve indirect water splitting for hydrogen production. This effectively lowers the temperature of direct water pyrolysis and releases hydrogen and oxygen products at different reaction stages, effectively overcoming the shortcomings of direct water splitting for hydrogen production. While the two-step thermochemical cycle lowers the temperature of direct water pyrolysis to some extent, its reduction reaction temperature remains high (above 2000℃ at atmospheric pressure). This high reaction temperature makes it difficult to find a suitable heat source. To lower the temperature, methods such as vacuum pumping or purging the reaction chamber with inert gas to dilute the oxygen product concentration are generally used to allow the reduction reaction to occur under low oxygen partial pressure conditions (10). -2 ~10 -7 Koepf et al. used a combination of vacuum pump and inert gas purging to reduce the oxygen partial pressure to approximately 10. -6The ZnO reduction and oxygen release reaction was carried out at approximately 1600℃ (Koepf et al. Applied Energy, 2016, 165: 1004-1023). However, the low pump efficiency due to the low oxygen partial pressure of the vacuum pump and the large amount of inert purge gas introduced to dilute the oxygen product concentration, which was heated along with the reactant (ZnO), resulted in high reaction energy consumption, making the solar-to-chemical energy conversion efficiency only about 3%. Furthermore, the reaction temperature of 1600℃ is still relatively high, making it difficult to guarantee the recyclability of the metal oxides and the long-term durability and stability of the reactor materials. Compared to the thermochemical two-step cycle decomposition of H2O to H2, the thermochemical multi-step cycle has a lower reaction temperature. In the sulfur-iodine three-step cycle, the atmospheric pressure reaction temperature of the sulfuric acid decomposition reaction is generally 850–1000℃, a temperature requirement that is relatively easy to meet. It can also be well-matched with some new energy technologies, such as nuclear reactors, tower or dish concentrator solar collectors, etc. However, the thermochemical multi-step cycle, represented by the sulfur-iodine cycle, still has many problems. First, strong acids are involved in each step of the reaction in the recycling system. At higher reaction temperatures, sulfuric acid and hydroiodic acid are even more corrosive, thus imposing stringent requirements on the corrosion resistance of the reactor and catalyst materials, as well as the safety of system operation. On the other hand, compared to the simple gas-solid separation reaction system of a two-step thermochemical cycle, the multi-step thermochemical cycle leads to the generation of homogeneous products due to the increased amount of recycled substances. For example, in the Bunsen reaction, hydroiodic acid and sulfuric acid are both in the liquid phase, making separation difficult and hindering material recycling.

[0004] The aforementioned problems severely limit the development of thermochemical cycle decomposition of H2O to H2 technology, necessitating the exploration of new thermochemical cycle methods to overcome and solve these issues. Currently, the academic community generally believes that developing a two-step thermochemical cycle or a multi-step thermochemical cycle system with simple product separation processes and atmospheric pressure and lower temperature reduction is the direction to accelerate the large-scale application of this technology (Xu et al. Chemistry of Materials, 2013, 25: 1564-1571; Jiao et al. Science Bulletin, 2022, 67: 2142-2157). Summary of the Invention

[0005] In view of the above problems, this invention provides a thermochemical cyclic water splitting method and apparatus for hydrogen production from manganese oxides and carbonates, to solve the problems of high temperature, low energy efficiency, poor stability, severe acid corrosion, and difficulty in separating homogeneous products in existing thermochemical two-step cyclic reactions. Based on the academic suggestion of constructing an acid-neutral thermochemical multi-step cycle with simple product separation, this method and apparatus provides a thermochemical cyclic decomposition method for H2O to H2 production from neutral manganese oxides and weakly basic carbonates. This method can achieve thermochemical water splitting to hydrogen production at temperatures below 1000℃, avoiding acid corrosion while enabling simple product separation.

[0006] This invention provides a thermochemical cycle method for producing hydrogen by decomposing water using manganese oxides and carbonates, comprising: heating high-valence manganese oxides to a first temperature to undergo a thermal deoxygenation reaction, generating low-valence manganese oxides and oxygen; reacting the low-valence manganese oxides generated by the thermal deoxygenation reaction with carbonates at a second temperature to generate manganite, carbon dioxide, and carbon monoxide; obtaining the manganite as a solid-phase reactant, and reacting it with carbon dioxide at a third temperature to generate the high-valence manganese oxides and carbonates; separating the carbon monoxide and carbon dioxide generated by the reaction of the low-valence manganese oxides and carbonates, and reacting the carbon monoxide with water vapor in a water-vapor shift reaction to generate carbon dioxide and hydrogen.

[0007] Optionally, the first temperature is 850–1000°C, the second temperature is 600–800°C, the third temperature is 350–550°C, and the pressure condition for each step is atmospheric pressure.

[0008] Optionally, the high-valence manganese oxide is manganese trioxide, and the low-valence manganese oxide is manganese tetroxide.

[0009] Optionally, the overall reaction equation of the method is that one part water (H2O) decomposes into one part hydrogen and 0.5 parts oxygen.

[0010] Optionally, the method for separating the high-valent manganese oxide and carbonate mixture produced by the reaction of the manganese oxide and carbon dioxide is as follows: taking advantage of the characteristic that the high-valent manganese oxide is sparingly soluble in water and the carbonate is soluble in water, the high-valent manganese oxide and carbonate mixture produced by the reaction of the manganese oxide and carbon dioxide is dissolved in water, and after precipitation, evaporation, crystallization and drying, pure high-valent manganese oxide and carbonate are obtained respectively.

[0011] Optionally, separating the carbon monoxide and carbon dioxide produced by the reaction of the low-valent manganese oxide and the carbonate includes: cooling the carbon dioxide and carbon monoxide produced at a second temperature, and then separating the carbon monoxide by pressure swing adsorption.

[0012] Another aspect of the present invention provides a thermochemical cycle water splitting device for producing hydrogen from manganese oxide and carbonate, comprising: a first reactor for heating high-valence manganese oxide to a first temperature to undergo a thermal decomposition oxygen reaction, generating low-valence manganese oxide and oxygen; a second reactor for reacting the low-valence manganese oxide generated by the thermal decomposition oxygen reaction with carbonate at a second temperature, generating manganite, carbon dioxide and carbon monoxide; a third reactor for obtaining the manganite as a solid-phase reactant, and reacting it with carbon dioxide at a third temperature to generate high-valence manganese oxide and carbonate; a first gas separation unit for obtaining the carbon monoxide and carbon dioxide generated by the reaction of the low-valence manganese oxide and carbonate; and a water-vapor shift reactor for reacting the carbon monoxide with water vapor to generate carbon dioxide and hydrogen.

[0013] Optionally, the apparatus further includes: a first cooler for cooling the oxygen produced by the first reactor; a second cooler for cooling the carbon dioxide and carbon monoxide produced by the second reactor and outputting them to the first gas separation unit; a third cooler for cooling the carbon dioxide and hydrogen produced by the steam generator; a second gas separation unit for separating the carbon dioxide and hydrogen cooled by the third cooler; and a mixer for mixing the carbon dioxide separated from the first gas separation unit and the second gas separation unit and inputting the carbon dioxide to the third reactor.

[0014] Optionally, the apparatus further includes: a solid-phase material separation unit, which utilizes the property that high-valent manganese oxides are sparingly soluble in water while carbonates are soluble in water, to dissolve the mixture of high-valent manganese oxides and carbonates obtained from the reaction of the permanganate with carbon dioxide in water, and after precipitation, evaporation, crystallization and drying, to obtain pure high-valent manganese oxides and carbonates respectively; and a fourth cooler, used to cool the high-valent manganese oxides and carbonates produced by the third reactor before inputting them into the solid-phase material separation unit.

[0015] Optionally, the apparatus further includes a steam generator for generating steam to be output to the steam-water shift reactor.

[0016] The above-described technical solutions employed in the embodiments of the present invention can achieve the following beneficial effects:

[0017] (1) By using the reaction of reducing high-valence manganese oxide (Mn2O3) to low-valence manganese oxide (Mn3O4) to construct a thermochemical cycle, H2 can be produced by thermochemical decomposition of H2O at atmospheric pressure and below 1000℃, which effectively overcomes the problems of high temperature, low oxygen partial pressure and poor stability of traditional thermochemical two-step cycle reaction.

[0018] (2) By using neutral manganese oxide and weakly alkaline carbonate to construct a thermochemical decomposition H2O to produce H2 cycle, the problems of severe acid corrosion and difficulty in separating homogeneous products in existing thermochemical multi-step cycles represented by sulfur-iodine cycle are solved. Attached Figure Description

[0019] To more fully understand the invention and its advantages, a description will be given with reference to the accompanying drawings, in which:

[0020] Figure 1 is a process flow diagram of the thermochemical cyclic decomposition of manganese oxide and sodium carbonate to produce H2O according to the first embodiment of the present invention.

[0021] Figure 2 is a process flow diagram of the thermochemical cyclic decomposition of manganese oxide and potassium carbonate to produce H2O according to the second embodiment of the present invention. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0024] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0025] This invention provides a method for producing H2 from H2 through thermochemical cyclic decomposition of manganese oxides and carbonates. This method achieves thermochemical decomposition of H2 at atmospheric pressure and below 1000℃ by consuming H2O and heat energy. The generated H2 and O2 are produced at different reaction stages, overcoming the defects of poor safety and difficulty in separation caused by the mixing of products from direct pyrolysis of water. It effectively solves the problems of high reaction temperature, low energy efficiency, and poor operational stability in traditional thermochemical two-step cyclic decomposition of water to produce hydrogen, as well as the severe acid corrosion and difficulty in separating homogeneous products in existing sulfur-iodine cycles.

[0026] Specifically, the present invention provides a thermochemical cycle water splitting method for producing hydrogen from manganese oxides and carbonates, comprising S1 to S4.

[0027] S1, high-valence manganese oxide is heated to the first temperature, and a thermal decomposition oxygen reaction occurs, producing low-valence manganese oxide and oxygen.

[0028] S2, at the second temperature, reacts the low-valent manganese oxide generated by the thermal decomposition oxygen reaction with carbonate to produce manganite, carbon dioxide and carbon monoxide.

[0029] S3, obtaining manganite as a solid reactant, reacts with carbon dioxide at a third temperature to produce high-valence manganese oxides and carbonates.

[0030] S4 separates the carbon monoxide and carbon dioxide produced by the reaction of low-valent manganese oxides with carbonates, and then reacts the carbon monoxide with water vapor to produce carbon dioxide and hydrogen.

[0031] In this embodiment, the first temperature is 850–1000°C, the second temperature is 600–800°C, the third temperature is 350–550°C, and the pressure condition for each step is atmospheric pressure.

[0032] In this embodiment, the high-valence manganese oxide is manganese trioxide (Mn2O3), and the low-valence manganese oxide is manganese tetroxide (Mn3O4).

[0033] In reactor S1, Mn₂O₃ is heated to 850–1000°C in reactor O1, undergoing a thermal deoxygenation reaction to produce the solid-phase product Mn₃O₄ and the gas-phase product O₂. The two are then separated into solid and gas phases; the O₂ is cooled in the first cooler O₂ to obtain pure O₂. The equation for the thermal deoxygenation reaction of high-valence manganese oxides is:

[0034] 3Mn₂O₃→2Mn₃O₄+0.5O₂

[0035] In S2, the equation for the reaction between low-valent manganese oxides and carbonates is:

[0036] 2Mn3O4+3A2CO3→6AMnO2+2CO2+CO

[0037] A2CO3 is a carbonate, and A represents metallic elements such as potassium, sodium, and lithium.

[0038] In S3, the equation for the reaction between permanganate and carbon dioxide is:

[0039] 6AMnO2 + 3CO2 → 3Mn2O3 + 3Na2CO3

[0040] In S4, the equation for the water-vapor shift reaction between carbon monoxide and water vapor is as follows:

[0041] CO + H₂O → CO₂ + H₂

[0042] Based on the above equation, the overall reaction equation of this method is the pyrolysis of water to produce hydrogen, that is, one part water (H2O) decomposes into one part hydrogen and 0.5 parts oxygen: H2O → H2 + 0.5O2.

[0043] Another aspect of this disclosure provides a thermochemical cycle water splitting device for producing hydrogen from manganese oxides and carbonates, comprising: a first reactor 01, a first cooler 02, a solid matter separation unit 03, a second reactor 04, a second cooler 05, a first gas separation unit 06, a water-gas shift reactor 07, a fourth cooler 08, a third reactor 09, a mixer 10, a third cooler 11, a second gas separation unit 12, and a steam generator 13.

[0044] The first reactor 01 is used to heat the high-valence manganese oxide to a first temperature, where a thermal decomposition oxygen reaction occurs, producing low-valence manganese oxide and oxygen.

[0045] The first cooler 02 is used to cool the oxygen produced by the first reactor 01.

[0046] Solid matter separator 03 is used to utilize the property that high-valence manganese oxides are poorly soluble in water while carbonates are soluble in water. It dissolves the mixture of high-valence manganese oxides and carbonates obtained in the third reactor 09 in water. After precipitation, evaporation, crystallization and drying, pure high-valence manganese oxides and carbonates are obtained respectively.

[0047] The second reactor 04 is used to react the low-valent manganese oxide generated by the thermal decomposition oxygen reaction with carbonate at a second temperature to produce manganite, carbon dioxide and carbon monoxide.

[0048] The second cooler 05 is used to cool the carbon dioxide and carbon monoxide produced by the second reactor 04 and output them to the first gas separation unit 06.

[0049] The first gas separation unit 06 is used to cool the carbon monoxide and carbon dioxide produced by the reaction of low-valence manganese oxides and carbonates, and the carbon monoxide is separated by pressure swing adsorption.

[0050] The water-steam shift reactor 07 reacts carbon monoxide with water vapor to produce carbon dioxide and hydrogen.

[0051] The fourth cooler 08 is used to cool the high-valence manganese oxides and carbonates produced by the third reactor 09 before feeding them into the solid matter separation unit 03.

[0052] The third reactor 09 is used to obtain manganite as a solid reactant, which reacts with carbon dioxide at a third temperature to produce high-valence manganese oxides and carbonates.

[0053] The mixer 10 is used to mix the carbon dioxide separated from the first gas separation unit 06 and the second gas separation unit 12, and then feed the carbon dioxide into the third reactor 09.

[0054] The third cooler 11 is used to cool the carbon dioxide and hydrogen produced by the steam generator 13.

[0055] The second gas separation unit 12 is used to separate carbon dioxide and hydrogen after they have been cooled by the third cooler 11.

[0056] Steam generator 13 is used to generate steam for output to water-steam shift reactor 07.

[0057] The following will provide a detailed description of the thermochemical cycle water splitting method and apparatus for hydrogen production from manganese oxides and carbonates provided in this application, with reference to specific embodiments.

[0058] Example 1

[0059] In this embodiment, sodium carbonate (Na₂CO₃) is used, meaning that sodium carbonate and manganese oxide are cyclically decomposed to produce H₂ through thermochemical decomposition of H₂O. The reaction equation for this thermochemical cyclic decomposition of H₂O using sodium carbonate to produce H₂ is as follows:

[0060] Thermal decomposition of high-valence manganese oxides to produce oxygen reaction:

[0061] 3Mn₂O₃→2Mn₃O₄+0.5O₂

[0062] Low-valent manganese oxides react with sodium carbonate:

[0063] 2Mn3O4+3Na2CO3→6NaMnO2+2CO2+CO

[0064] Regeneration reaction of high-valent manganese oxides with sodium carbonate:

[0065] 6NaMnO2 + 3CO2 → 3Mn2O3 + 3Na2CO3

[0066] Water-gas shift reaction: CO + H₂O → CO₂ + H₂

[0067] The system process corresponding to the above-mentioned thermochemical cyclic decomposition of manganese oxide and sodium carbonate to produce H2O is shown in Figure 1.

[0068] Mn2O3 is heated to 850–1000°C in the first reactor 01, undergoing a thermal decomposition reaction to produce the solid-phase product Mn3O4 and the gas-phase product O2. The two are separated into gas and solid phases, and the O2 is cooled in the first cooler 02 to obtain pure O2 product.

[0069] The Mn3O4 obtained in the first reactor 01 is used to preheat the Na2CO3 obtained in the solid material separation unit 03, which carries the sensible heat. The two react in the second reactor 04 at 600-800℃ to produce sodium manganite (NaMnO2), CO2 and CO.

[0070] The gaseous mixture of CO2 and CO obtained from the outlet of the second reactor 04 is cooled by the second cooler 05 and then enters the first gas separation unit 06 (such as pressure swing adsorption) to obtain pure CO2 and CO.

[0071] The CO obtained from the first gas separation unit 06 enters the water-steam shift reactor 07 and undergoes a water-steam shift reaction with the superheated steam H2O(g) generated by the steam generator 13 to produce CO2 and H2.

[0072] After being cooled by the third cooler 11, the CO2 and H2 mixture enters the second gas separation unit 12 to obtain pure H2 and CO2 respectively.

[0073] The solid-phase reaction product NaMnO2 generated in the second reactor 04 preheats the CO2 from the mixer 10 using its sensible heat, and undergoes a regeneration reaction at 350–550°C to generate Mn2O3 and Na2CO3. The incompletely reacted CO2 in the third reactor 09 is mixed with the CO2 separated in separator 12 and separator 06 in the mixer 10, serving as one of the raw materials for the third reactor 09.

[0074] The solid-phase reaction products Mn2O3 and Na2CO3 obtained in the third reactor 09 are cooled by the fourth cooler 08 and then enter the solid matter separation unit 03. Taking advantage of the fact that Na2CO3 is soluble in water and Mn2O3 is insoluble in water, pure Na2CO3 and Mn2O3 are obtained through processes such as dissolution-precipitation-evaporation-crystallization-drying.

[0075] The Na₂CO₃ obtained through the solid matter separation unit 03 enters the second reactor 04 and reacts again with low-valence manganese oxides. The resulting Mn₂O₃ then enters the first reactor 01 for a thermal decomposition oxygen reaction. This continuous cycle of manganese oxides and sodium carbonate regeneration is achieved.

[0076] As can be seen from the above process, the system achieves the phased production of hydrogen and oxygen products by consuming H2O and heat energy, while other substances in the system are recycled and regenerated through different reaction configurations.

[0077] Example 2

[0078] In this embodiment, potassium carbonate (K₂CO₃) is used as the carbonate, meaning that potassium carbonate and manganese oxide are cyclically decomposed into H₂O via thermochemical processes to produce H₂. The reaction equation for this thermochemical cyclic decomposition of H₂O using potassium carbonate to produce H₂ is as follows:

[0079] Thermal decomposition of high-valence manganese oxides to produce oxygen reaction:

[0080] 3Mn₂O₃→2Mn₃O₄+0.5O₂

[0081] Low-valent manganese oxides react with potassium carbonate:

[0082] 2Mn3O4+3K2CO3→6KMnO2+2CO2+CO

[0083] Regeneration reaction of high-valence manganese oxides with potassium carbonate:

[0084] 6KMnO2 + 3CO2 → 3Mn2O3 + 3K2CO3

[0085] Water-gas shift reaction: CO + H₂O → CO₂ + H₂

[0086] The system process for producing H2 by thermochemically decomposing H2O from manganese oxide and potassium carbonate is similar to that using sodium carbonate in a cycle, as shown in Figure 2.

[0087] Mn2O3 is heated to 850–1000°C in the first reactor 01, undergoing a thermal decomposition reaction to produce the solid-phase product Mn3O4 and the gas-phase product O2. The two are separated into gas and solid phases, and the O2 is cooled in the first cooler 02 to obtain pure O2 product.

[0088] The Mn3O4 obtained in the first reactor 01 uses its sensible heat to preheat the K2CO3 obtained in the solid matter separator 03. Both are then heated to 600–800°C in the second reactor 04, where they react to produce potassium manganite (KMnO2), CO2, and CO.

[0089] The gaseous mixture of CO2 and CO obtained from the outlet of the second reactor 04 is cooled by the second cooler 05 and then enters the first gas separation unit 06 (such as pressure swing adsorption) to obtain pure CO2 and CO.

[0090] The CO obtained from the first gas separation unit 06 enters the water-steam shift reactor 07 and undergoes a water-steam shift reaction with the superheated steam H2O(g) generated by the steam generator 13 to produce CO2 and H2.

[0091] After being cooled by the third cooler 11, the CO2 and H2 mixture enters the second gas separation unit 12 to obtain pure H2 and CO2 respectively.

[0092] The solid-phase reaction product KMnO2 generated in the second reactor 04 preheats the CO2 from the mixer 10 using its sensible heat, and undergoes a regeneration reaction at 350–550°C to generate Mn2O3 and K2CO3. The incompletely reacted CO2 in the third reactor 09 is mixed with the CO2 separated in separator 12 and separator 06 in the mixer 10, serving as one of the raw materials for the third reactor 09.

[0093] The solid-phase reaction products Mn2O3 and K2CO3 obtained in the third reactor 09 are cooled by the fourth cooler 08 and then enter the solid matter separation unit 03. Taking advantage of the fact that K2CO3 is soluble in water and Mn2O3 is insoluble in water, pure K2CO3 and Mn2O3 are obtained through processes such as dissolution-precipitation-evaporation-crystallization-drying.

[0094] The K₂CO₃ obtained through the solid matter separation unit 03 enters the second reactor 04 for another reaction, and the resulting Mn₂O₃ re-enters the first reactor 01 for a heat-induced oxygen decomposition reaction. This continuous cycle of manganese oxide and potassium carbonate regeneration is achieved.

[0095] The above system process achieves the phased production of hydrogen and oxygen products by consuming H2O and heat energy, while other substances in the system are recycled and regenerated through different reaction configurations.

[0096] Those skilled in the art will understand that the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0097] Although the invention has been shown and described with reference to specific exemplary embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. Therefore, the scope of the invention should not be limited to the above embodiments, but should be determined not only by the appended claims but also by their equivalents.

Claims

1. A thermochemical cycle method for producing hydrogen by decomposing water using manganese oxides and carbonates, characterized in that, include: When high-valence manganese oxide is heated to a first temperature, a thermal deoxygenation reaction occurs, producing low-valence manganese oxide and oxygen. At a second temperature, the low-valent manganese oxide generated by the thermal decomposition oxygen reaction is reacted with carbonate to produce manganite, carbon dioxide, and carbon monoxide. The manganite is then reacted with carbon dioxide at a third temperature to produce the high-valent manganese oxide and carbonate. Taking advantage of the fact that the high-valent manganese oxide is sparingly soluble in water while the carbonate is soluble, the mixture of the high-valent manganese oxide and carbonate generated by the reaction of the manganite and carbon dioxide is placed in water. After precipitation, evaporation, crystallization, and drying, pure high-valent manganese oxide and pure carbonate are obtained respectively. Carbon monoxide and carbon dioxide generated by the reaction of the low-valent manganese oxide and carbonate are separated. The carbon monoxide is then reacted with water vapor in a water-vapor shift reaction to produce carbon dioxide and hydrogen. The first temperature is 850~1000℃, the second temperature is 600~800℃, and the third temperature is 350~550℃. The pressure conditions for each step are atmospheric pressure. The high-valent manganese oxide is manganese trioxide, and the low-valent manganese oxide is manganese tetroxide.

2. The method according to claim 1, characterized in that, The overall reaction equation for the method is that one part water (H2O) decomposes into one part hydrogen and 0.5 parts oxygen.

3. The method according to claim 1, characterized in that, The separation of carbon monoxide and carbon dioxide produced by the reaction of the low-valent manganese oxide and the carbonate includes: cooling the carbon dioxide and carbon monoxide produced at a second temperature, and then separating the carbon monoxide by pressure swing adsorption.

4. A thermochemical cycle water splitting apparatus for producing hydrogen from manganese oxides and carbonates, applied to the method described in any one of claims 1 to 3, characterized in that, include: The first reactor (01) is used to heat the high-valence manganese oxide to a first temperature to undergo a thermal decomposition oxygen reaction, generating low-valence manganese oxide and oxygen. The second reactor (04) is used to react the low-valent manganese oxide generated by the thermal decomposition oxygen reaction with carbonate at a second temperature to generate manganite, carbon dioxide and carbon monoxide; the third reactor (09) is used to react the manganite with carbon dioxide at a third temperature to regenerate high-valent manganese oxide and carbonate; the solid phase separation unit (03) is used to separate the high-valent manganese oxide and carbonate mixture regenerated in the third reactor (09); taking advantage of the fact that the high-valent manganese oxide is sparingly soluble in water and the carbonate is soluble in water, the high-valent manganese oxide and carbonate generated in the third reactor are dissolved in water, and after precipitation, evaporation, crystallization and drying, the high-valent manganese oxide and the carbonate are obtained; the fourth cooler (08) is used to cool the high-valent manganese oxide and carbonate generated in the third reactor (09) and then input them into the solid phase separation unit (03); the first gas separation unit (06) is used to obtain the carbon monoxide and carbon dioxide generated by the reaction of the low-valent manganese oxide and the carbonate; the water vapor shift reactor (07) reacts the carbon monoxide with water vapor to generate carbon dioxide and hydrogen.

5. The apparatus according to claim 4, characterized in that, The device further includes: a first cooler (02) for cooling the oxygen produced by the first reactor (01); a second cooler (05) for cooling the carbon dioxide and carbon monoxide produced by the second reactor (04) and outputting them to the first gas separation unit (06); a third cooler (11) for cooling the carbon dioxide and hydrogen produced by the water-gas shift reactor (07); a second gas separation unit (12) for separating the carbon dioxide and hydrogen cooled by the third cooler (11); and a mixer (10) for mixing the carbon dioxide separated from the first gas separation unit (06) and the second gas separation unit (12) and inputting the carbon dioxide to the third reactor (09).

6. The apparatus according to claim 4, characterized in that, The device further includes a steam generator (13) for generating steam to be output to the water-steam shift reactor (07).

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