Method and system for chemical looping hydrogen production and CO2 separation through oxygen carrier cascade conversion

Abstract

The invention provides a method and a system for chemical looping hydrogen production and CO2 separation through oxygen carrier cascade conversion. The method comprises the following steps: completely oxidizing a reduction state oxygen carrier into an oxidation state oxygen carrier carrying heat; carrying out countercurrent contact reaction on the oxidation-state oxygen carrier carrying heat and the carbon-rich mixed gas to obtain H2O, CO2 and a first reduction-state oxygen carrier carrying heat; a first reduction state oxygen carrier carrying heat reacts with hydrocarbon fuel and water vapor in a downstream or countercurrent mode at the temperature of 500-700 DEG C, the hydrocarbon fuel is partially oxidized by the first reduction state oxygen carrier to generate hydrogen-rich mixed gas and a second reduction state oxygen carrier, the water vapor and H2 in the hydrogen-rich mixed gas are sequentially separated, and the remaining carbon-rich mixed gas is output. According to the method, oxygen carriers with different oxidation degrees are adopted to react with the gas containing the carbon component in different process stages, chemical looping hydrogen production and CO2 source separation are achieved, the temperature needed by the reaction can be reduced, the technological process can be simplified, and the hydrogen production amount can be increased.

Description

Technical Field

[0001] The present invention belongs to the field of hydrogen production, and relates to a thermochemical decarbonization hydrogen production technology, and specifically relates to a chemical chain hydrogen production and CO separation method by step-by-step conversion of oxygen carriers. 2 methods and systems. Background Art

[0002] Hydrogen is an ideal energy carrier with high energy density and only produces water during combustion. It is widely used in hydrogen fuel cells, hydrogen-powered vehicles, hydrogen-fired power generation, metal smelting, high-efficiency fuels, synthetic ammonia, petrochemicals and other fields. Currently, methane wet reforming and chemical chain hydrogen production are among the most widely used technologies.

[0003] Methane wet reforming hydrogen production involves multiple processes such as methane and water reforming reaction, medium-temperature water-gas shift and multi-stage pressure swing adsorption. The main reaction temperature of the whole reaction process is high, the energy consumption of hydrogen production is high, and CO 2 High emissions and CO 2 Capture will incur a large energy cost.

[0004] Chemical chaining hydrogen production is a new technology that uses the reduction and oxidation process of oxygen carriers to achieve hydrogen production, which usually includes two processes: reduction reaction and oxidation reaction. The process route of chemical chaining hydrogen production from hydrocarbon fuels has an important influence on the hydrogen production performance. In the existing chemical chaining hydrogen production technology, hydrocarbon fuels are completely oxidized to CO 2 and H 2 O, and at the same time the oxygen carrier is reduced, the reduced oxygen carrier is partially oxidized by water vapor and produces hydrogen, and the partially oxidized oxygen carrier is further oxidized by air to achieve regeneration. 2 The separation of the source of CO and the pursuit of complete conversion of hydrocarbon fuels during the reduction reaction result in high process temperature and high oxygen carrier circulation excess coefficient. 2 Decarbonization at the source leads to a decrease in hydrogen production performance per unit principle, resulting in higher energy consumption for hydrogen production. In addition, carbon deposits are often generated during the reduction reaction. For example, Chinese patent CN2022180617 discloses a method for hydrogen production from methane chemical chain in conjunction with carbon dioxide capture. In order to increase the conversion rate of methane, the reduction reaction temperature is controlled at above 850°C. The temperature of the reaction process is relatively high. At the same time, in order to eliminate carbon deposits during the reduction process, carbon deposit elimination and secondary reduction processes are also set up, which complicates the reaction path. Summary of the invention

[0005] In order to solve the technical problems of high reaction temperature in the existing chemical chain hydrogen production process, the pursuit of complete conversion of hydrocarbon fuels in the reduction reaction, and the resulting complex process and low hydrogen production efficiency, the embodiment of the present invention discloses a chemical chain hydrogen production and separation of CO by step-by-step conversion of oxygen carriers.2 The method uses oxygen carriers with different oxidizing properties to react with gas raw materials in different process stages to produce hydrogen through chemical chain and separate CO from the source. 2 Specifically, the method comprises the following steps:

[0006] Step 1: completely oxidizing the reduced oxygen carrier into an oxidized oxygen carrier that carries heat through air;

[0007] Step 2: The oxidized oxygen carrier carrying heat is countercurrently contacted with the carbon-rich mixed gas to react, and the carbon-rich mixed gas is completely oxidized to H 2 O and CO 2 CO generation 2 The oxidized oxygen carrier releases oxygen to generate a first reduced oxygen carrier that carries heat, and the carbon-rich mixed gas includes unreacted hydrocarbon fuel, a small amount of CO, CO 2 and residual H 2 ;

[0008] Step 3: At 500-700° C., the first reduced oxygen carrier carrying heat is contacted with hydrocarbon fuel and water vapor in a co-current or counter-current manner to react, the first reduced oxygen carrier partially oxidizes the hydrocarbon fuel to generate a hydrogen-rich mixed gas and the second reduced oxygen carrier, and the water vapor in the hydrogen-rich mixed gas is first separated, and then separated and purified to obtain H 2 and the carbon-rich mixed gas, the second reduced oxygen carrier comprising the reduced oxygen carrier;

[0009] The oxidizing properties of the oxidized oxygen carrier, the first reduced oxygen carrier and the second reduced oxygen carrier gradually decrease.

[0010] In an improved example, in the above step 1, when the reduced oxygen carrier is completely oxidized into an oxidized oxygen carrier that carries heat by oxygen in the air, the output oxygen-depleted air is used to preheat the hydrocarbon fuel and water vapor.

[0011] In an improved example, the method further comprises:

[0012] Step 4: Use the second reduced-state oxygen carrier that carries heat to contact with water vapor in co-current or counter-current flow, and the reduced-state oxygen carrier in the second reduced-state oxygen carrier reacts with the water vapor to generate hydrogen and a third reduced-state oxygen carrier, wherein the oxidizing property of the third reduced-state oxygen carrier is greater than that of the second reduced-state oxygen carrier.

[0013] In an improved example, the oxidized oxygen carrier, the reduced oxygen carrier, the first reduced oxygen carrier and the third reduced oxygen carrier are any one or more of iron-based metal oxides, nickel-based metal oxides, Mn-based metal oxides and perovskite oxygen carriers.

[0014] The embodiment of the present invention also provides a chemical chain hydrogen production and CO separation by oxygen carrier cascade conversion. 2 The system is used to realize the chemical chain hydrogen production and CO separation by the above-mentioned oxygen carrier cascade conversion 2 The method comprises: an air oxidation reactor, a primary reduction reactor and a secondary reduction reactor connected in series in sequence, and the air oxidation reactor is provided with an air inlet, an oxygen-depleted air outlet, a solid inlet and a solid outlet.

[0015] The first oxygen carrier inlet and CO 2 A gas outlet, the lower end of which is provided with a carbon-rich mixed gas inlet and a first oxygen carrier outlet, wherein the first oxygen carrier inlet is connected to the solid outlet;

[0016] The secondary reduction reactor is provided with a second oxygen carrier inlet and a hydrocarbon fuel inlet at the upper end, and a hydrogen-rich mixed gas outlet and a second oxygen carrier outlet at the lower end, wherein the second oxygen carrier inlet is connected to the first oxygen carrier outlet;

[0017] The outlet of the hydrogen-rich mixed gas is connected to a pressure swing adsorption separation device via a gas-liquid separator, and the pressure swing adsorption separation device is connected to the inlet of the carbon-rich mixed gas. The pressure swing adsorption separation device is used to separate and purify the hydrogen in the hydrogen-rich mixed gas output from the secondary reduction reactor to obtain purified H 2 and a carbon-rich mixed gas, and inputting the carbon-rich mixed gas into the primary reduction reactor.

[0018] In an improved example, the system further comprises a steam oxidation hydrogen production reactor, which is connected to the second oxygen carrier outlet; the steam oxidation hydrogen production reactor is provided with a water vapor inlet and a third oxygen carrier outlet at the lower end and a hydrogen outlet at the upper end.

[0019] In an improved example, the third oxygen carrier outlet or the second oxygen carrier outlet is connected to the solid inlet via a riser.

[0020] In an improved example, a lifting gas is introduced into one end of the lifting pipe close to the third oxygen carrier outlet or the second oxygen carrier outlet, and the lifting gas is nitrogen or air.

[0021] In an improved example, both the primary reduction reactor and the secondary reduction reactor are provided with a heat preservation structure.

[0022] In an improved example, the reaction in the air oxidation reactor generates the oxidized oxygen carrier carrying heat, and the heat carried by the oxidized oxygen carrier provides heat for the reaction in the primary reduction reactor to generate the first reduced oxygen carrier carrying heat, and the heat carried by the first reduced oxygen carrier provides heat for the reaction in the secondary reduction reactor.

[0023] Compared with the prior art, the beneficial effects achieved by at least one of the above technical solutions adopted in the embodiments of this specification include at least: the chemical chain hydrogen production and separation of CO by the step-by-step conversion of oxygen carriers of the present invention 2 The method rationally utilizes oxygen carriers with different oxidation degrees to react with carbon-containing gases at different process stages to achieve chemical chain hydrogen production and CO 2 The source separation can reduce the temperature required for the reaction, simplify the process, increase the amount of hydrogen produced, etc. The method and system of the present invention have the following advantages:

[0024] 1. The oxygen carrier is used in a two-step cascade reduction form to combine the partial oxidation process and complete oxidation process of hydrocarbon fuels by the oxygen carrier, thus achieving complete conversion of fuel gas and CO 2 The fuel gas first undergoes partial oxidation reaction with the oxygen carrier in the secondary reduction reactor to produce H 2 After cooling and separation, the gas product is further subjected to a complete oxidation reaction with a high-oxidation state oxygen carrier in the primary reduction reactor. The two-step reduction process can achieve complete conversion of fuel gas and CO 2 Efficient capture.

[0025] 2. The present invention combines partial oxidation of hydrocarbon fuels with oxygen carriers to produce hydrogen and water-gas shift to enhance hydrogen production. This is different from the oxidation of reduced oxygen carriers by water vapor to produce hydrogen in traditional steam reactors. The present invention uses partial oxidation of oxygen carriers and fuel gas to produce hydrogen. The oxygen carrier partially oxidizes the fuel gas to produce H 2 and CO, which will be further promoted by water vapor 2 O produces hydrogen through the change of water vapor, thus achieving efficient hydrogen production from fuel gas.

[0026] 3. Make full use of the reaction performance of oxygen carriers at different oxidation degrees, combining hydrogen production and CO separation 2 The positive promotion of the reaction during the process reduces the reaction temperature and realizes efficient energy utilization. This method uses the energy released by the reduced oxygen carrier during the oxidation process to heat the two-stage reduction reactor, thereby improving the overall energy utilization efficiency of the system. In the partial oxidation process of the fuel gas, water vapor is added to promote the reaction to move toward hydrogen production, and H is separated before the fuel gas enters the complete oxidation process. 2 O and H 2This promotes the reaction to move towards complete oxidation. Overall, with the help of multi-stage utilization of oxygen carriers, the temperature of the reduction reaction is reduced by strengthening the reaction.

[0027] 4. High-efficiency medium and low temperature hydrogen production: by efficiently producing hydrogen under medium and low temperature conditions (500-600°C). In the primary reduction reactor, carbon monoxide and unreacted fuel gas are used for pre-reduction, which not only effectively recycles the mixed gas, but also converts the hydrogen element in the fuel into hydrogen as much as possible to improve the fuel conversion rate. In addition, by optimizing the reaction design of the oxygen carrier particles in the secondary reduction reactor, the reaction rate is significantly improved and the required operating temperature is reduced. Compared with the higher reaction temperature (750-900°C) required by the existing one-step reduction process, the process design of the oxygen carrier step-by-step conversion of the present invention avoids the need to burn hydrocarbon raw materials to supplement energy, thereby improving the conversion rate of the fuel gas and the proportion of complete oxidation to achieve CO 2 For the purpose of separation and purification.

[0028] 5. Improve the reduction degree of oxygen carrier: Use carbon monoxide (H 2 and CO) and the residual hydrogen that has not been separated out, so that the reduction performance of the oxygen carrier is good under low temperature conditions, and the reduction rate is much higher than the direct reaction of methane and the oxygen carrier. This design enables the oxygen carrier to be reduced quickly, thereby enhancing the degree of reduction of the oxygen carrier, while improving the reduction performance of the oxygen carrier and eliminating CO, H 2 , CH 4 Impurity gas, realizing the CO 2 Complete capture of.

[0029] 6. Improve the thermal management and energy self-sufficiency of the system: By lowering the reaction temperature, the system significantly reduces heat loss. The heat generated in the air oxidation reactor is transferred to the two reduction reactors in series through the moving oxygen carrier particles to supply heat to these endothermic reactions. The design achieves overall thermal balance without the need for additional external heating, thereby reducing energy consumption and enhancing the energy efficiency and environmental sustainability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 The present invention discloses a first oxygen carrier cascade conversion chemical chain hydrogen production and CO separation 2 Schematic diagram of the method principle;

[0032] Figure 2 The present invention discloses a second oxygen carrier cascade conversion chemical chain hydrogen production and CO separation 2 Schematic diagram of the method principle;

[0033] Figure 3 Chemical chain hydrogen production and CO separation by oxygen carrier cascade conversion disclosed in the embodiment of the present invention 2 An architectural diagram of a system;

[0034] Figure 4 Chemical chain hydrogen production and CO separation by oxygen carrier cascade conversion disclosed in the embodiment of the present invention 2 Another architectural diagram of the system;

[0035] Figure 5 Hydrogen production and source CO by oxygen carrier step conversion disclosed in the embodiment of the present invention 2 Product distribution curve under typical separation conditions;

[0036] 1. Air oxidation reactor; 11. Solid inlet; 12. Solid outlet; 2. Primary reduction reactor; 21. First oxygen carrier inlet; 22. CO 2 Gas outlet; 23, carbon-rich mixed gas inlet; 24, first oxygen carrier outlet; 3, secondary reduction reactor; 31, second oxygen carrier inlet; 32, hydrocarbon fuel inlet; 33, hydrogen-rich mixed gas outlet; 34, second oxygen carrier outlet; 4, pressure swing adsorption separation device; 5, steam oxidation hydrogen production reactor; 51, water vapor inlet; 52, third oxygen carrier outlet; 53, hydrogen outlet; 6, riser; 7, gas condensation device; 8, gas-liquid separator; 9, thermal insulation structure. DETAILED DESCRIPTION

[0037] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0038] The following describes the implementation methods of the present application through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and the features of the embodiments can be combined with each other in the absence of conflict. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0039] The embodiment of the present invention discloses a chemical chain hydrogen production and CO separation method using oxygen carrier cascade conversion 2 The method is described in Figure 1 As shown, the following steps are included:

[0040] Step 1: completely oxidizing the reduced oxygen carrier into an oxidized oxygen carrier that carries heat through air;

[0041] Step 2: The oxidized oxygen carrier carrying heat is countercurrently contacted with the carbon-rich mixed gas to react, and the carbon-rich mixed gas is completely oxidized to H 2 O and CO 2 CO generation 2 The oxidized oxygen carrier initially releases oxygen to generate a first reduced oxygen carrier that carries heat. The carbon-rich mixed gas includes unreacted hydrocarbon fuel, a small amount of CO, CO 2 and residual H 2 ;

[0042] Step 3: At 500-700° C., the first reduced oxygen carrier carrying heat is contacted with hydrocarbon fuel and water vapor in a co-current or counter-current manner to react, the first reduced oxygen carrier partially oxidizes the hydrocarbon fuel to generate a hydrogen-rich mixed gas and the second reduced oxygen carrier, and the water vapor in the hydrogen-rich mixed gas is first separated, and then separated and purified to obtain H 2 and the carbon-rich mixed gas, the second reduced oxygen carrier comprising the reduced oxygen carrier;

[0043] The oxidizing properties of the oxidized oxygen carrier, the first reduced oxygen carrier and the second reduced oxygen carrier gradually decrease.

[0044] In the present invention, step 2 can be used to completely oxidize the highly oxidizing oxygen carrier and the carbon-rich mixed gas output in step 3 to generate CO 2 The stream and the medium oxidizing oxygen carrier are separated from the pure carbon dioxide in this step, avoiding the operation of absorbing carbon dioxide from the carbon-rich mixed gas with a carbon dioxide absorbent and then releasing it in the traditional technology. At the same time, by reducing the oxidizing property of the oxygen carrier, the reaction in the subsequent process step 3 is facilitated. In step 3, the medium oxidizing oxygen carrier output in step 2 is contacted with the hydrocarbon fuel and water vapor in the downstream or parallel flow to carry out partial redox reaction to generate a hydrogen-rich mixed gas and a low oxidizing oxygen carrier, and the H in the hydrogen-rich mixed gas is separated. 2 The above carbon-rich mixed gas is obtained. The hydrogen separated in this step comes from hydrocarbon fuel.

[0045] In the present invention, the oxidized oxygen carrier, the reduced oxygen carrier, the first reduced oxygen carrier and the third reduced oxygen carrier in the above steps 1 to 3 are any one or more of iron-based metal oxides, nickel-based metal oxides, Mn-based metal oxides and perovskite oxygen carriers.

[0046] Among them, the oxidized oxygen carrier can be represented by MeO; the first reduced oxygen carrier can be represented by Me 1-δ O, the second reduced oxygen carrier can be expressed as Me 1-β O. Taking iron-based oxides as an example, the oxidized oxygen carrier MeO is Fe 2 O 3 ; The first reduced oxygen carrier Me 1-δ O has two components, including FeO and Fe 3 O 4 ; Second reduced oxygen carrier Me 1-β O contains two components, including FeO and Fe 3 O 4 .Me 1-δ O and Me 1-β The difference between O and Me is that they have different oxidizing properties. 1-δ O is less oxidizing than Me 1-β Oxidizing property of O. Taking iron-based oxide as an example, the reaction processes of steps 1 to 3 above are respectively:

[0047] Step 1: 4Fe 3 O 4 +O 2 →6Fe 2 O 3 ; 4FeO+O 2 →2Fe 2 O 3 ;

[0048] Step 2: Fe 2 O 3 +CH 4 →2Fe 3 O 4 +CO 2 +2H 2 O;

[0049] Fe 2 O 3 +3CO → 2FeO + 3CO 2 ;

[0050] Fe 2 O 3 +CO→Fe 3 O 4 +CO 2 ;

[0051] Step 3: aFe 2 O 3 +bFe 2 O 3 +CH 4 →cFeO+xCO+yCO 2 +mH 2 +nH 2 O.

[0052] It should be noted that the carbon dioxide contained in the carbon-rich mixed gas in step 2 does not participate in the reaction.

[0053] In an improved example, the carbon-rich mixed gas obtained after separating hydrogen from the hydrogen-rich mixed gas in step 3 may still contain a small amount of hydrogen. In this case, in addition to the hydrocarbon raw materials and carbon monoxide participating in the reaction in step 2, hydrogen also participates in the reaction. Specifically, the hydrogen undergoes a complete redox reaction with the oxidized oxygen carrier to generate a completely reduced oxygen carrier and H 2 O, the reaction formula is: Fe 2 O 3 +3H 2 →2FeO+3H 2 O;3Fe 2 O 3 +H 2 →2Fe 3 O 4 +H 2 O.

[0054] In an improved example, in order to obtain pure dry carbon dioxide, the method further comprises: 2 The stream is condensed to remove water to obtain pure CO 2 At the same time, the present invention can also condense and remove water from the hydrogen-rich mixed gas to obtain H 2 Flowing stocks.

[0055] In an improved example, in the above step 1, when the oxygen carrier is completely oxidized into an oxidized oxygen carrier that carries heat by oxygen in the air, the reaction temperature can reach 800°C or above. Heat will be released during the reaction, and the output oxygen-depleted air has a certain temperature that can be used to preheat the hydrocarbon fuel and water vapor input to step 3. At the same time, the oxidized oxygen carrier output from the reactor also has a certain temperature. When its output undergoes a subsequent endothermic reaction process, the heat supplement of the system can be reduced. Self-heating operation can be achieved in the entire process without the need for external combustion heat supply.

[0056] In an improved example, after the hydrogen-rich mixture is separated by the heat carrier in the above step 3, the remaining carbon-rich mixture may still contain a small amount of hydrogen, which will react with the oxygen carrier to consume the hydrogen. This process can store the small amount of hydrogen in the form of a reduced oxygen carrier on the one hand, and on the other hand, it can improve the purity of the carbon dioxide.

[0057] At the same time, in order to increase the hydrogen production of the entire process and improve the utilization rate of hydrocarbon fuels, see Figure 2 As shown, the method further includes: step 4, making the second reduced oxygen carrier contact with water vapor in a co-current or counter-current manner, and generating hydrogen and a third reduced oxygen carrier by reacting the reduced oxygen carrier in the second reduced oxygen carrier with the water vapor, wherein the oxidizing property of the third reduced oxygen carrier is greater than the oxidizing property of the second reduced oxygen carrier, and the third reduced oxygen carrier can be expressed as Me 1-γ O, the reaction process of this step is: 3FeO+H 2 O=Fe 3 O 4 +H 2 .

[0058] The embodiment of the present invention also provides a chemical chain hydrogen production and CO separation by oxygen carrier cascade conversion. 2 The system is used to realize the chemical chain hydrogen production and CO separation by the above-mentioned oxygen carrier cascade conversion 2 See the method Figure 3 and Figure 4 As shown, the system comprises: an air oxidation reactor 1, a primary reduction reactor 2 and a secondary reduction reactor 3 which are connected in series in sequence.

[0059] The air oxidation reactor 1 is provided with an air inlet, an oxygen-depleted air outlet, a solid inlet 11 and a solid outlet 12, and the reaction process of step 1 in the above method is carried out in the air oxidation reactor 1. After the air input from the air inlet into the air oxidation reactor 1 reacts with the reduced oxygen carrier, the oxygen-depleted air remaining after the oxygen is consumed is output through the oxygen-depleted air outlet, and the reduced oxygen carrier is input from the solid inlet 11, and is completely oxidized into an oxidized oxygen carrier in the air oxidation reactor 1 and then output from the solid outlet 12. Since the air oxidation reactor 1 is an exothermic reaction and releases a large amount of heat, the output oxygen-depleted air can be used to preheat the gas in the process, and the oxidized oxygen carrier also carries a certain amount of heat energy, which can provide the heat energy required for the reaction after being output to the first-level reduction reactor 2 of the next level, thereby reducing or avoiding the demand for exogenous heat in the system.

[0060] See also Figure 3 and Figure 4 As shown, the first reduction reactor 2 is provided with a first oxygen carrier inlet 21 and a CO2 The gas outlet 22 has a carbon-rich mixed gas inlet 23 and a first oxygen carrier outlet 24 at the lower end. The first oxygen carrier inlet 21 is connected to the solid outlet 12. The reaction process of step 2 in the above method is carried out in the primary reduction reactor 2. The primary reduction reactor 2 inputs the hydrogen-rich mixed gas generated in the rear-end secondary reduction reactor 3, and the carbon-rich mixed gas is obtained after dehydrogenation.

[0061] See also Figure 3 and Figure 4 As shown, the secondary reduction reactor 3 is provided with a second oxygen carrier inlet 31 and a hydrocarbon fuel inlet 32 ​​at the upper end, and a hydrogen-rich mixed gas outlet 33 and a second oxygen carrier outlet 34 at the lower end. The second oxygen carrier inlet 31 is connected to the first oxygen carrier outlet 24.

[0062] See also Figure 3 and Figure 4 As shown, the hydrogen-rich mixed gas outlet 33 is connected to the pressure swing adsorption separation device 4 through the gas-liquid separator 8, and the pressure swing adsorption separation device 4 is connected to the carbon-rich mixed gas inlet 23. The pressure swing adsorption separation device 4 is used to separate and purify the hydrogen-rich mixed gas output from the secondary reduction reactor 3 to obtain purified H 2 and carbon-rich mixed gas, and the carbon-rich mixed gas is input into the primary reduction reactor 2. In specific implementation, the gas-liquid separator 8 is used to separate the hydrogen from the hydrogen-rich mixed gas, and the hydrogen-rich mixed gas is condensed by the gas condensation device 7 to convert the gaseous water in the synthesizer into liquid water and then take it out. This avoids the water in the hydrogen-rich mixed gas input from the bottom of the primary reduction reactor 2 to react with the completely reduced oxygen carrier to generate hydrogen, which affects the purity of carbon dioxide.

[0063] In an improved embodiment, see Figure 4 As shown, the system also includes a steam oxidation hydrogen production reactor 5, which is connected to the second oxygen carrier outlet 34; the steam oxidation hydrogen production reactor 5 is provided with a water vapor inlet 51 and a third oxygen carrier outlet 52 at the lower end, and a hydrogen outlet 53 at the upper end.

[0064] In an improved embodiment, see Figure 3 and Figure 4 As shown, the third oxygen carrier outlet 52 or the second oxygen carrier outlet 34 is connected to the solid inlet 11 via a lift pipe 6. Preferably, a lift gas is introduced into the lift pipe 6 at one end close to the third oxygen carrier outlet 52 or the second oxygen carrier outlet 34, and the lift gas is nitrogen or air.

[0065] In an improved embodiment, see Figure 3 and Figure 4As shown, both the primary reduction reactor 2 and the secondary reduction reactor 3 are provided with a thermal insulation structure 9, which can ensure that the heat in the reactor will not be dissipated so that the oxygen carrier output from the reactor can carry the heat to the next-stage reactor to provide thermal energy for the reaction in the next-stage reactor.

[0066] Specifically, the reaction in the air oxidation reactor 1 generates the oxidized oxygen carrier carrying heat, and the heat carried by the oxidized oxygen carrier provides heat for the reaction in the primary reduction reactor 2 to generate the first reduced oxygen carrier carrying heat, and the heat carried by the first reduced oxygen carrier provides heat for the reaction in the secondary reduction reactor 3.

[0067] The present invention discloses experimental data of the composition distribution of gas phase products of the first-stage reduction reaction and the second-stage reduction reaction under typical working conditions of hydrogen production and source CO2 separation by oxygen carrier step conversion, see Figure 5 The oxygen carrier used reacts with the methane and water vapor mixture at 650°C and releases oxygen in a stepwise manner. In the initial stage, i.e., the second stage of the reduction reaction, the oxidized oxygen carrier completely oxidizes the carbon-rich mixture into CO 2 , achieving complete conversion of fuel gas and CO 2 With the release of oxygen from the oxygen carrier, the first reduction reaction process begins. After the initial release of oxygen, the oxygen carrier undergoes partial oxidation with methane and water vapor to produce high-concentration hydrogen. The hydrogen production per unit of methane can reach 2.9 molH 2 / mol CH 4 The experimental results show that the hydrocarbon fuel (CH 4 ) Efficient hydrogen production and decarbonization at the source.

[0068] Chemical chain hydrogen production and CO separation by oxygen carrier cascade conversion of the present invention 2 The method rationally utilizes oxygen carriers with different oxidation degrees to react with carbon-containing gases at different process stages to achieve chemical chain hydrogen production and CO 2 The source separation can reduce the temperature required for the reaction, simplify the process, increase the amount of hydrogen produced, etc. The method and system of the present invention have the following advantages:

[0069] 1. The oxygen carrier is used in a two-step cascade reduction form to combine the partial oxidation process and complete oxidation process of hydrocarbon fuels by the oxygen carrier, thus achieving complete conversion of fuel gas and CO 2 The fuel gas first undergoes partial oxidation reaction with the oxygen carrier in the secondary reduction reactor to produce H 2After cooling and separation, the gas product is further subjected to a complete oxidation reaction with a high-oxidation state oxygen carrier in the primary reduction reactor. The two-step reduction process can achieve complete conversion of fuel gas and CO 2 Efficient capture.

[0070] 2. The present invention combines partial oxidation of hydrocarbon fuels with oxygen carriers to produce hydrogen and water-gas shift to enhance hydrogen production. This is different from the oxidation of reduced oxygen carriers by water vapor to produce hydrogen in traditional steam reactors. The present invention uses partial oxidation of oxygen carriers and fuel gas to produce hydrogen. The oxygen carrier partially oxidizes the fuel gas to produce H 2 and CO, which will be further promoted by water vapor 2 O produces hydrogen through the change of water vapor, thus achieving efficient hydrogen production from fuel gas.

[0071] 3. Make full use of the reaction performance of oxygen carriers at different oxidation degrees, combining hydrogen production and CO separation 2 The positive promotion of the reaction during the process reduces the reaction temperature and realizes efficient energy utilization. This method uses the energy released by the reduced oxygen carrier during the oxidation process to heat the two-stage reduction reactor, thereby improving the overall energy utilization efficiency of the system. In the partial oxidation process of the fuel gas, water vapor is added to promote the reaction to move toward hydrogen production, and H is separated before the fuel gas enters the complete oxidation process. 2 O and H 2 This promotes the reaction to move towards complete oxidation. Overall, with the help of multi-stage utilization of oxygen carriers, the temperature of the reduction reaction is reduced by strengthening the reaction.

[0072] 4. High-efficiency medium and low temperature hydrogen production: by efficiently producing hydrogen under medium and low temperature conditions (500-600°C). In the primary reduction reactor, carbon monoxide and unreacted fuel gas are used for pre-reduction, which not only effectively recycles the mixed gas, but also converts the hydrogen element in the fuel into hydrogen as much as possible to improve the fuel conversion rate. In addition, by optimizing the reaction design of the oxygen carrier particles in the secondary reduction reactor, the reaction rate is significantly improved and the required operating temperature is reduced. Compared with the higher reaction temperature (750-900°C) required by the existing one-step reduction process, the process design of the oxygen carrier step-by-step conversion of the present invention avoids the need to burn hydrocarbon raw materials to supplement energy, thereby improving the conversion rate of the fuel gas and the proportion of complete oxidation to achieve CO 2 For the purpose of separation and purification.

[0073] 5. Improve the reduction degree of oxygen carrier: Use carbon monoxide (H 2and CO) and the residual hydrogen that has not been separated out, so that the reduction performance of the oxygen carrier is good under low temperature conditions, and the reduction rate is much higher than the direct reaction of methane and the oxygen carrier. This design enables the oxygen carrier to be reduced quickly, thereby enhancing the degree of reduction of the oxygen carrier, while improving the reduction performance of the oxygen carrier and eliminating CO, H 2 , CH 4 Impurity gas, realizing the CO 2 Complete capture of.

[0074] 6. Improve the thermal management and energy self-sufficiency of the system: By lowering the reaction temperature, the system significantly reduces heat loss. The heat generated in the air oxidation reactor is transferred to the two reduction reactors in series through the moving oxygen carrier particles to supply heat to these endothermic reactions. The design achieves overall thermal balance without the need for additional external heating, thereby reducing energy consumption and enhancing the energy efficiency and environmental sustainability of the system.

[0075] Obviously, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing hydrogen and separating CO2 by chemical chaining with stepwise conversion of oxygen carriers, characterized in that: The method comprises: The reduced oxygen carrier is completely oxidized into an oxidized oxygen carrier that carries heat by air; The oxidized oxygen carrier carrying heat is countercurrently contacted with the carbon-rich mixed gas to react, and the carbon-rich mixed gas is completely oxidized into H2O and CO2 to generate a CO2 stream, and the oxidized oxygen carrier releases oxygen to generate a first reduced oxygen carrier carrying heat, and the carbon-rich mixed gas includes unreacted hydrocarbon fuel, a small amount of CO, CO2 and residual H2; Under the condition of 500-700°C, the first reduced oxygen carrier carrying heat contacts with hydrocarbon fuel and water vapor in co-current or counter-current flow to react, the first reduced oxygen carrier partially oxidizes the hydrocarbon fuel to generate a hydrogen-rich mixed gas, the first reduced oxygen carrier releases oxygen to generate the second reduced oxygen carrier, the water vapor in the hydrogen-rich mixed gas is first separated, and then separated and purified to obtain H2 and the carbon-rich mixed gas, the second reduced oxygen carrier includes the reduced oxygen carrier; The oxidizing properties of the oxidized oxygen carrier, the first reduced oxygen carrier and the second reduced oxygen carrier gradually decrease.

2. The method for producing hydrogen and separating CO2 by chemical chaining through stepwise conversion of oxygen carriers according to claim 1, characterized in that: When the reduced oxygen carrier is completely oxidized into an oxidized oxygen carrier carrying heat by oxygen in the air, the hydrocarbon fuel and water vapor are preheated by the output oxygen-depleted air.

3. The method for producing hydrogen and separating CO2 by chemical chaining through stepwise conversion of oxygen carriers according to claim 1, characterized in that: The method further comprises: The second reduced-state oxygen carrier carrying heat is brought into contact with water vapor in co-current or counter-current flow, and the reduced-state oxygen carrier in the second reduced-state oxygen carrier reacts with the water vapor to generate hydrogen and a third reduced-state oxygen carrier, wherein the oxidizing property of the third reduced-state oxygen carrier is greater than that of the second reduced-state oxygen carrier.

4. The method for producing hydrogen and separating CO2 by chemical chaining through stepwise conversion of oxygen carriers according to any one of claims 1 to 3, characterized in that: The oxidized oxygen carrier, the reduced oxygen carrier, the first reduced oxygen carrier and the third reduced oxygen carrier are any one or more of iron-based metal oxides, nickel-based metal oxides, Mn-based metal oxides and perovskite oxygen carriers.

5. A system for chemical chain hydrogen production and CO2 separation by stepwise conversion of oxygen carriers, characterized in that: The system is used to implement the method for chemical chain hydrogen production and CO2 separation by cascade conversion of oxygen carriers as described in any one of claims 1 to 4, the system comprises an air oxidation reactor (1), a primary reduction reactor (2) and a secondary reduction reactor (3) connected in series in sequence, and the air oxidation reactor (1) is provided with an air inlet, an oxygen-depleted air outlet, a solid inlet (11) and a solid outlet (12); The primary reduction reactor (2) is provided with a first oxygen carrier inlet (21) and a CO2 outlet (22) at the upper end, and a carbon-rich mixed gas inlet (23) and a first oxygen carrier outlet (24) at the lower end, wherein the first oxygen carrier inlet (21) is connected to the solid outlet (12); The secondary reduction reactor (3) is provided with a second oxygen carrier inlet (31) and a hydrocarbon fuel inlet (32) at the upper end, and a hydrogen-rich mixed gas outlet (33) and a second oxygen carrier outlet (34) at the lower end, wherein the second oxygen carrier inlet (31) is connected to the first oxygen carrier outlet (24); The hydrogen-rich mixed gas outlet (33) is connected to a pressure swing adsorption separation device (4) via a gas-liquid separator, and the pressure swing adsorption separation device (4) is connected to the carbon-rich mixed gas inlet (23). The pressure swing adsorption separation device (4) is used to separate and purify the hydrogen in the hydrogen-rich mixed gas output from the secondary reduction reactor (3) to obtain purified H2 and carbon-rich mixed gas, and the carbon-rich mixed gas is input into the primary reduction reactor (2).

6. The system for producing hydrogen and separating CO2 by chemical chaining through stepwise conversion of oxygen carriers according to claim 5, characterized in that: The system further comprises a steam oxidation hydrogen production reactor (5), wherein the steam oxidation hydrogen production reactor (5) is connected to the second oxygen carrier outlet (34); The steam oxidation hydrogen production reactor (5) is provided with a water vapor inlet (51) and a third oxygen carrier outlet (52) at the lower end, and a hydrogen outlet (53) at the upper end.

7. The system for producing hydrogen and separating CO2 by chemical chaining through stepwise conversion of oxygen carriers according to claim 6, characterized in that: The third oxygen carrier outlet (52) or the second oxygen carrier outlet (34) is connected to the solid inlet (11) via a riser (6).

8. The system for producing hydrogen and separating CO2 by chemical chaining through stepwise conversion of oxygen carriers according to claim 7, characterized in that: A lifting gas is introduced into one end of the lifting pipe (6) close to the third oxygen carrier outlet (52) or the second oxygen carrier outlet (34), and the lifting gas is nitrogen or air.

9. The system for producing hydrogen and separating CO2 by chemical chaining through stepwise conversion of oxygen carriers according to claim 5, characterized in that: The primary reduction reactor (2) and the secondary reduction reactor (3) are both provided with a heat preservation structure (9).

10. The system for producing hydrogen and separating CO2 by chemical chaining through stepwise conversion of oxygen carriers according to claim 5, characterized in that: The air oxidation reactor (1) reacts to generate the oxidized oxygen carrier carrying heat, and the heat carried by the oxidized oxygen carrier provides heat for the reaction in the primary reduction reactor (2) to generate the first reduced oxygen carrier carrying heat, and the heat carried by the first reduced oxygen carrier provides heat for the reaction in the secondary reduction reactor (3).

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