An air separation system and method for co-producing hydrogen

Abstract

This invention discloses an air separation system and method for co-producing hydrogen, belonging to the field of air separation and hydrogen production technology. It includes four oxygen-permeable membrane reactors and two condensers. The oxygen-producing outlet of the fourth oxygen-permeable membrane reactor (R4) is connected to the second condenser (C2), which has a condensate drain outlet and an oxygen outlet. The nitrogen-producing inlet of the third oxygen-permeable membrane reactor (R3) is connected to the air-producing outlet of the fourth oxygen-permeable membrane reactor (R4). The fuel-producing inlet of the second oxygen-permeable membrane reactor (R2) is connected to the fuel-producing outlet of the third oxygen-permeable membrane reactor (R3). The fuel-producing inlet of the first oxygen-permeable membrane reactor (R1) is connected to both the fuel-producing outlet and the hydrogen-producing outlet of the second oxygen-permeable membrane reactor (R2), and the hydrogen-producing outlet of the first oxygen-permeable membrane reactor (R1) is connected to the first condenser (C1), which has a condensate drain outlet and a hydrogen outlet. This invention simultaneously produces hydrogen, oxygen, and nitrogen through a reasonable process arrangement. The method is simple, efficient, and highly economical and practical.

Description

Technical Field

[0001] This invention relates to the field of air separation and hydrogen production technology, specifically to an air separation system and method for co-producing hydrogen. Background Technology

[0002] Oxygen and nitrogen are important chemical raw materials with wide applications in chemical, metallurgical, oil refining, medical, and military fields. Air separation technology is a key technology for producing oxygen and nitrogen. Currently, commonly used air separation technologies for producing oxygen and nitrogen include cryogenic distillation, membrane separation, pressure swing adsorption (PSA), and chemical looping air separation. Cryogenic distillation is currently the most mature air separation technology. Its principle is based on the difference in boiling points between nitrogen and oxygen in the air; after liquefying the air, cryogenic distillation is performed to separate nitrogen and oxygen. This technology involves large investment, high cost, high energy consumption, and complex operation. Pressure swing adsorption (PSA) air separation technology suffers from low production capacity and high energy consumption. Membrane separation technology suffers from difficulties in membrane material preparation and high cost. Chemical looping air separation technology suffers from system complexity, high energy consumption, poor economic efficiency, and difficulty in long-term operation.

[0003] Oxygen-permeable membranes are a novel type of oxygen separation membrane. Their principle is based on the oxygen partial pressure difference across the membrane at a certain temperature. Under the separation effect of the membrane, oxygen in a mixed gas diffuses and migrates from the high partial pressure side to the low partial pressure side, thus enriching the oxygen. Compared to conventional oxygen production technologies, it has advantages such as system simplicity, low energy consumption, fast start-up, low cost, and convenient operation. Furthermore, under certain temperature and conditions, oxygen-permeable membranes can also diffuse oxygen from water vapor from the high partial pressure side to the low partial pressure side. While transferring oxygen, a certain amount of hydrogen is generated simultaneously. Using oxygen-permeable membranes to produce oxygen, nitrogen, and hydrogen will significantly improve the economics and system efficiency of oxygen-permeable membrane air separation technology.

[0004] Existing technologies for hydrogen (or oxygen, or nitrogen) production using oxygen-permeable membranes are mostly complex and cannot simultaneously produce hydrogen, oxygen, and nitrogen. For example, Chinese patent document CN200810034740.1 discloses a high-temperature coke oven gas hydrogen production system and process. This system includes a high-temperature coke oven gas supply system, an oxygen source air supply system, a high-temperature steam supply system, a dry gasification furnace oxygen supply system, a high-temperature desulfurization system, and a coal gas reforming reaction product output system. It can convert as much of the high sensible heat and high chemical energy components of the large amount of high-temperature coke oven gas produced during the coking process as possible into hydrogen. Due to the use of dry gasification, high-temperature desulfurization, and a mixed conductor oxygen-permeable membrane for oxygen supply, the hydrogen production efficiency is higher, and the hydrogen production volume is significantly increased. Chinese patent document CN201410440172.0 provides a device for producing hydrogen by alternating decomposition of water using oxygen-permeable membranes and hydrogen-permeable membranes. The device comprises: a flat box-shaped body internally divided into several spaced-apart oxygen-permeable chambers and hydrogen-permeable chambers; and internal pipes extending into each oxygen-permeable and hydrogen-permeable chamber. The internal pipes of adjacent chambers are connected end-to-end by external pipes, forming a connected serpentine vapor channel. The internal pipes in the oxygen-permeable chambers are made of oxygen-permeable membranes, and the internal pipes in the hydrogen-permeable chambers are made of hydrogen-permeable membranes. A chemical potential difference exists between the inner and outer sides of the hydrogen-permeable membranes in the hydrogen-permeable chambers and between the inner and outer sides of the oxygen-permeable membranes in the oxygen-permeable chambers. Under the influence of this chemical potential difference, oxygen permeates through the oxygen-permeable membrane, and hydrogen permeates through the hydrogen-permeable membrane, entering the area between the inner pipe and the corresponding chamber's inner wall, respectively. While the above research has achieved certain technical results, it still suffers from problems such as a cumbersome and complex system and the inability to simultaneously produce oxygen, nitrogen, and hydrogen, requiring further improvement. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an air separation system and method for co-producing hydrogen, which solves the problems of complex systems, high energy consumption and poor stability of traditional air separation technology. This invention uses the oxygen-permeable membrane to enrich oxygen, and realizes the simultaneous production of high-purity oxygen, nitrogen and hydrogen, which greatly improves the economy and system efficiency of oxygen-permeable membrane air separation technology.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an air separation system for co-producing hydrogen, comprising a fourth oxygen-permeable membrane reactor, a third oxygen-permeable membrane reactor, a second oxygen-permeable membrane reactor, a first oxygen-permeable membrane reactor, a second condenser, and a first condenser; each oxygen-permeable membrane reactor is provided with an oxygen-permeable membrane dividing the reactor into two sides; wherein the fourth oxygen-permeable membrane reactor is divided into an air side and an oxygen-producing side, the air side and the oxygen-producing side are respectively provided with an inlet and an outlet, wherein the outlet of the oxygen-producing side is connected to the second condenser, and the second condenser is provided with a condensate drain outlet and an oxygen outlet; the third oxygen-permeable membrane reactor is divided into a fuel side and a nitrogen-producing side, the fuel side and the nitrogen-producing side are respectively The reactor is equipped with an inlet and an outlet. The nitrogen-generating inlet is connected to the air-side outlet of the fourth oxygen-permeable membrane reactor. The second oxygen-permeable membrane reactor is divided into a fuel side and a hydrogen side, each with its own inlet and outlet. The fuel-side inlet is connected to the fuel-side outlet of the third oxygen-permeable membrane reactor. The first oxygen-permeable membrane reactor is also divided into a fuel side and a hydrogen side, each with its own inlet and outlet. The fuel-side inlet is connected to both the fuel-side outlet and the hydrogen-side outlet of the second oxygen-permeable membrane reactor. The hydrogen-side outlet of the first oxygen-permeable membrane reactor is connected to the first condenser, which has a condensate drain outlet and a hydrogen outlet.

[0008] As a further preferred embodiment of the technical solution of the present invention, the fuel side of the first oxygen-permeable membrane reactor is provided with an outlet that is connected to the fuel side inlet of the third oxygen-permeable membrane reactor.

[0009] Secondly, the present invention provides an air separation method for co-producing hydrogen using the above-described system, comprising the following steps:

[0010] S1. Air enters the air side of the fourth oxygen-permeable membrane reactor, and water vapor enters the oxygen-generating side of the fourth oxygen-permeable membrane reactor. The oxygen on the air side migrates to the oxygen-generating side through the oxygen-permeable membrane, and forms a mixed gas with the water vapor, which enters the second condenser to condense water vapor and obtain high-purity oxygen.

[0011] S2. The remaining oxygen-deficient air on the air side of the fourth oxygen-permeable membrane reactor enters the nitrogen-generating side of the third oxygen-permeable membrane reactor. The oxygen in the oxygen-deficient air migrates through the oxygen-permeable membrane to the fuel side of the third oxygen-permeable membrane reactor and undergoes an incomplete reaction with the fuel to generate high-temperature gas a. The oxygen-deficient air on the nitrogen-generating side transfers oxygen to obtain high-purity nitrogen.

[0012] S3. High-temperature gas a from the fuel side of the third oxygen-permeable membrane reactor enters the fuel side of the second oxygen-permeable membrane reactor, and water vapor enters the hydrogen side of the second oxygen-permeable membrane reactor. The water vapor decomposes on the hydrogen side to produce hydrogen and oxygen. Among them, the oxygen migrates through the oxygen-permeable membrane to the fuel side of the second oxygen-permeable membrane reactor and reacts with high-temperature gas a to generate high-temperature gas b. The remaining hydrogen side contains hydrogen gas containing water vapor.

[0013] S4. The high-temperature gas b from the fuel side of the second oxygen-permeable membrane reactor mixes with the hydrogen-containing gas containing water vapor from the hydrogen side of the second oxygen-permeable membrane reactor to form high-temperature gas c, which enters the fuel side of the first oxygen-permeable membrane reactor. The water vapor enters the hydrogen side of the first oxygen-permeable membrane reactor and decomposes to produce hydrogen and oxygen. The oxygen migrates through the oxygen-permeable membrane to the fuel side of the first oxygen-permeable membrane reactor and reacts with the high-temperature gas c to generate high-temperature gas d. Part of the high-temperature gas d is used as exhaust gas, and the other part is recycled to the fuel side of the third oxygen-permeable membrane reactor. The remaining hydrogen-rich gas containing water vapor from the hydrogen side of the first oxygen-permeable membrane reactor enters the first condenser, where water vapor is condensed to obtain high-purity hydrogen.

[0014] As a further preferred embodiment of the technical solution of the present invention, the oxygen-permeable membrane reactor is one or both of the tube sheet structure and the flat plate structure.

[0015] As a further preferred embodiment of the technical solution of the present invention, the tube diameter of the tube-type oxygen permeable membrane is 1-20 mm, the membrane thickness is 0.1-5 mm, and the tube spacing is 0.5-5 times the tube diameter; the membrane thickness of the plate-type oxygen permeable membrane is 0.1-5 mm, and the membrane spacing is 0.5-25 mm.

[0016] As a further preferred embodiment of the technical solution of the present invention, the oxygen-permeable membrane is one or more of the following: tubular membrane, sheet membrane, and hollow fiber membrane.

[0017] As a further preferred embodiment of the technical solution of the present invention, the oxygen-permeable membrane is one or more of the following structures: perovskite, fluorite-perovskite, fluorite-metal, and perovskite-metal.

[0018] As a further preferred embodiment of the technical solution of the present invention, the oxygen-permeable membrane is one or more of a single-layer membrane, a double-layer membrane, and a mixed conductor oxygen-permeable membrane.

[0019] As a further preferred embodiment of the technical solution of the present invention, the first oxygen-permeable membrane reactor (R1) and the second oxygen-permeable membrane reactor (R2) are selected from double-layer oxygen-permeable membranes with fluorite-metal and / or perovskite-metal structures.

[0020] As a further preferred embodiment of the technical solution of the present invention, the working temperature of the oxygen permeable membrane reactor is 400-1000℃, the pressure difference across the oxygen permeable membrane is 0-9MPa, and the pressure inside the membrane cavity is not lower than the pressure outside the membrane cavity.

[0021] As a further preferred embodiment of the technical solution of the present invention, the volume concentration of oxygen in the mixture of water vapor and oxygen on the oxygen-generating side in step S1 is 0-95%.

[0022] As a further preferred embodiment of the technical solution of the present invention, the volume concentration of oxygen in the mixture of water vapor and oxygen on the oxygen-generating side in step S1 is 50% to 80%.

[0023] As a further preferred embodiment of the technical solution of the present invention, the volume concentration of hydrogen in the hydrogen-containing gas containing water vapor in step S3 is 0-40%.

[0024] As a further preferred embodiment of the technical solution of the present invention, the volume concentration of hydrogen in the hydrogen-containing gas containing water vapor in step S3 is 5% to 20%.

[0025] As a further preferred embodiment of the technical solution of the present invention, the volume concentration of hydrogen in the hydrogen-rich gas containing water vapor in step S4 is 0-95%.

[0026] As a further preferred embodiment of the technical solution of the present invention, the volume concentration of hydrogen in the hydrogen-rich gas containing water vapor in step S4 is 50% to 80%.

[0027] As a further preferred embodiment of the technical solution of the present invention, in step S4, the circulating gas accounts for 10% to 90% of the volume of the high-temperature gas d.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The oxygen-permeable membrane air separation method of this invention features low energy consumption, low operating costs, and convenient operation. Compared with conventional oxygen generation technologies, the oxygen-permeable membrane air separation method has advantages such as system simplicity, low energy consumption, fast start-up, low cost, and convenient operation. Operating costs are reduced by approximately one-third compared to conventional air separation technologies, and the system is simple and easy to operate.

[0030] 2. The oxygen-permeable membrane air separation system of this invention can simultaneously produce nitrogen, oxygen, and hydrogen with a purity of 99%, exhibiting high system efficiency and economic performance. This invention utilizes the oxygen enrichment characteristics of the oxygen-permeable membrane, while simultaneously leveraging the reducing properties of fuel and hydrogen-containing gases, to separate oxygen and nitrogen from the air, as well as hydrogen and oxygen from water vapor, simultaneously producing oxygen, nitrogen, and hydrogen with a purity of over 99%, significantly improving the economic efficiency and system efficiency of the oxygen-permeable membrane air separation technology.

[0031] 3. The hydrogen production section of this invention uses two oxygen-permeable membrane reactors. The hydrogen produced by water vapor decomposition on the hydrogen side of R2 is not used as a final product (entering the hydrogen side of R1 or Cl), but is used as fuel gas to enter the fuel side of R1 and react with the oxygen migrated from the water vapor decomposition of R1. This can greatly accelerate the rate of hydrogen production by water vapor decomposition in R1 and produce more hydrogen. Compared with single-stage oxygen-permeable membrane hydrogen production technology, the hydrogen production efficiency of this invention can be improved by more than 20%.

[0032] 4. In this invention, the fuel enters the oxygen-permeable membrane reactor and undergoes an incomplete combustion reaction with oxygen to generate a high-temperature gas containing CO. This process consumes oxygen and releases heat, providing heat for the migration of oxygen within the reactor. Generally, the reaction rate between fuel and oxygen is: hydrogen > CO > hydrocarbon fuel. The presence of CO and hydrogen in the mixed gas can accelerate the reaction rate with oxygen. Therefore, the high-temperature gas containing CO entering R2 and the high-temperature gas containing hydrogen entering R1 can quickly react with the oxygen migrating from the decomposition of water vapor, accelerating the rate of hydrogen production from water vapor decomposition. Simultaneously, the heat released by the reaction is used to maintain the reaction temperature for hydrogen separation, ensuring the hydrogen production rate.

[0033] In summary, this invention, through a reasonable process arrangement, simultaneously produces hydrogen, oxygen, and nitrogen in high purity and high yield; furthermore, the system and method provided by this invention are simple, efficient, and easy to implement for industrial application. Attached Figure Description

[0034] Figure 1 A process flow diagram of the air separation method for co-producing hydrogen provided by the present invention;

[0035] Among them, R1 is the first oxygen-permeable membrane reactor; R2 is the second oxygen-permeable membrane reactor; R3 is the third oxygen-permeable membrane reactor; R4 is the fourth oxygen-permeable membrane reactor; C1 is the first condenser; and C2 is the second condenser. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention in light of the specific circumstances.

[0039] Please see Figure 1 This invention provides an air separation system for co-producing hydrogen, comprising a fourth oxygen-permeable membrane reactor R4, a third oxygen-permeable membrane reactor R3, a second oxygen-permeable membrane reactor R2, a first oxygen-permeable membrane reactor R1, a second condenser C2, and a first condenser C1; each oxygen-permeable membrane reactor is provided with an oxygen-permeable membrane dividing the reactor into two sides; wherein, the fourth oxygen-permeable membrane reactor R4 is divided into an air side and an oxygen-producing side, the air side and the oxygen-producing side are respectively provided with an inlet and an outlet, wherein the outlet of the oxygen-producing side is connected to the second condenser C2, the second condenser C2 is provided with a condensate drain outlet and an oxygen outlet; the third oxygen-permeable membrane reactor R3 is divided into a fuel side and a nitrogen-producing side, the fuel side and the nitrogen-producing side are respectively The reactor is equipped with an inlet and an outlet. The nitrogen-generating inlet is connected to the air-side outlet of the fourth oxygen-permeable membrane reactor R4. The second oxygen-permeable membrane reactor R2 is divided into a fuel side and a hydrogen side, each with its own inlet and outlet. The fuel-side inlet is connected to the fuel-side outlet of the third oxygen-permeable membrane reactor R3. The first oxygen-permeable membrane reactor R1 is also divided into a fuel side and a hydrogen side, each with its own inlet and outlet. The fuel-side inlet is connected to both the fuel-side outlet and the hydrogen-side outlet of the second oxygen-permeable membrane reactor R2. The hydrogen-side outlet of the first oxygen-permeable membrane reactor R1 is connected to the first condenser C1, which has a condensate drain outlet and a hydrogen outlet.

[0040] Furthermore, the first oxygen-permeable membrane reactor R1 has an outlet on the fuel side that is connected to the inlet on the fuel side of the third oxygen-permeable membrane reactor R3.

[0041] In the above technical solution, high-temperature steam is introduced into the oxygen-generating side of the fourth oxygen-permeable membrane reactor. This steam can be used to balance the pressure difference across the high-temperature oxygen-permeable membrane during oxygen generation, maintain the operating temperature, and prevent damage to the membrane. Simultaneously, it can reduce the thickness of the oxygen-permeable membrane and improve oxygen generation efficiency. The heat source required for the steam can be supplied by an independent heating unit or coupled with other systems, utilizing the waste heat from the high-temperature exhaust gas of other systems through a heat exchanger.

[0042] The present invention also provides an air separation method for co-producing hydrogen using the above system, comprising the following steps:

[0043] S1. Air enters the air side of the fourth oxygen-permeable membrane reactor R4, and water vapor enters the oxygen-generating side of the fourth oxygen-permeable membrane reactor R4. The oxygen on the air side migrates to the oxygen-generating side through the oxygen-permeable membrane, and forms a mixed gas with the water vapor, which enters the second condenser C2 to condense water vapor and obtain high-purity oxygen.

[0044] S2. The remaining oxygen-deficient air on the air side of the fourth oxygen-permeable membrane reactor R4 enters the nitrogen-generating side of the third oxygen-permeable membrane reactor R3. The oxygen in the oxygen-deficient air migrates through the oxygen-permeable membrane to the fuel side of the third oxygen-permeable membrane reactor R3 and undergoes an incomplete reaction with the fuel to generate high-temperature gas a. After the oxygen-deficient air on the nitrogen-generating side transfers oxygen, high-purity nitrogen is obtained.

[0045] S3. High-temperature gas a from the fuel side of the third oxygen permeable membrane reactor R3 enters the fuel side of the second oxygen permeable membrane reactor R2. Water vapor enters the hydrogen side of the second oxygen permeable membrane reactor R2. Water vapor decomposes on the hydrogen side to produce hydrogen and oxygen. Among them, oxygen migrates through the oxygen permeable membrane to the fuel side of the second oxygen permeable membrane reactor R2 and reacts with high-temperature gas a to produce high-temperature gas b. The remaining hydrogen side contains hydrogen gas containing water vapor.

[0046] S4. The high-temperature gas b from the fuel side of the second oxygen-permeable membrane reactor R2 mixes with the hydrogen-containing gas containing water vapor from the hydrogen side of the second oxygen-permeable membrane reactor R2 to form high-temperature gas c, which enters the fuel side of the first oxygen-permeable membrane reactor R1. The water vapor enters the hydrogen side of the first oxygen-permeable membrane reactor R1 and decomposes to produce hydrogen and oxygen. The oxygen migrates through the oxygen-permeable membrane to the fuel side of the first oxygen-permeable membrane reactor R1 and reacts with the high-temperature gas c to generate high-temperature gas d. Part of the high-temperature gas d is used as exhaust gas, and the other part is recycled to the fuel side of the third oxygen-permeable membrane reactor R3. The remaining hydrogen-rich gas containing water vapor from the hydrogen side of the first oxygen-permeable membrane reactor R1 enters the first condenser C1, where water vapor is condensed to obtain high-purity hydrogen.

[0047] In the above technical solution, the design of the oxygen-permeable membrane reactor can be carried out with reference to the existing technology, which is an existing mature process mastered by those skilled in the art. This invention does not provide a detailed description or specific limitations of the device.

[0048] As a preferred technical solution of the present invention, in this specific embodiment, the oxygen-permeable membrane reactor is one or both of the tube sheet structure and the flat plate structure.

[0049] Furthermore, the diameter of the tubes in the tube-plate structure oxygen-permeable membrane is 1–20 mm, and in specific implementation, it can be any specific value within the range of 1–20 mm, such as 1 mm, 5 mm, 10 mm, 15 mm, or 20 mm; the membrane thickness is 0.1–5 mm, and in specific implementation, it can be any specific value within the range of 0.1–5 mm, such as 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm; the tube spacing is 0.5–5 times the tube diameter, and in specific implementation, it can be any specific value within the range of 0.5–5, such as a tube spacing of 0.5 times the tube diameter, 1 time the tube diameter, 2 times the tube diameter, 3 times the tube diameter, 4 times the tube diameter, or 5 times the tube diameter.

[0050] Furthermore, the thickness of the flat-plate oxygen-permeable membrane is 0.1–5 mm, and in specific implementation, it can be any specific value within the range of 0.1–5 mm, such as 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm; the membrane spacing is 0.5–25 mm, and in specific implementation, it can be any specific value within the range of 0.5–25 mm, such as 0.5 mm, 1 mm, 5 mm, 10 mm, 15 mm, 20 mm, or 25 mm.

[0051] In this specific embodiment, the oxygen-permeable membrane is one or more of the following: tubular membrane, sheet membrane, and hollow fiber membrane.

[0052] In this specific embodiment, the oxygen-permeable membrane is one or more of the following structures: perovskite, fluorite-perovskite, fluorite-metal, and perovskite-metal.

[0053] In this specific embodiment, the oxygen-permeable membrane is one or more of a single-layer membrane, a double-layer membrane, and a hybrid conductor oxygen-permeable membrane.

[0054] In a further preferred embodiment, the first oxygen-permeable membrane reactor R1 and the second oxygen-permeable membrane reactor R2 are selected from double-layer oxygen-permeable membranes with fluorite-metal and / or perovskite-metal structures.

[0055] Preferably, the operating temperature of the oxygen-permeable membrane reactor is 400–1000℃, and in specific implementation, it can be any specific value within the range of 400–1000℃, such as 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, or 1000℃; the pressure difference across the oxygen-permeable membrane is 0–9MPa, and in specific implementation, it can be any specific value within the range of 0–9MPa, such as 0MPa, 1MPa, 3MPa, 6MPa, or 9MPa; the pressure inside the membrane cavity is not lower than the pressure outside the membrane cavity.

[0056] In the above technical solution, the fuel enters the third oxygen-permeable membrane reactor R3 and undergoes an incomplete combustion reaction with the oxygen transferred from the oxygen-deficient air to generate a mixed gas containing CO. While consuming oxygen, it releases heat to provide heat for the migration of oxygen in the third oxygen-permeable membrane reactor R3.

[0057] The CO-containing mixed gas produced by the incomplete reaction of fuel enters the second oxygen-permeable membrane reactor R2, where it reacts with oxygen that migrates from water vapor through the oxygen-permeable membrane. This reaction consumes oxygen and releases heat, providing heat for oxygen migration and hydrogen separation in the water vapor of the second oxygen-permeable membrane reactor R2.

[0058] It is understood that the fuel described in the above technical solution is a hydrocarbon fuel, which is a compound containing carbon and hydrogen, and can be alkanes, alkenes, alcohols, etc. The present invention does not provide detailed descriptions or limitations on its specific composition and source.

[0059] Preferably, in step S1, the volume concentration of oxygen in the mixture of water vapor and oxygen on the oxygen-generating side is 0-95%, and can be any specific value within the range of 0-95%, such as 10%, 30%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%; preferably 50%-80%.

[0060] In the above technical solution, the volume concentration of oxygen in the mixed gas is mainly adjusted by controlling the temperature, pressure, flow rate of the air entering the oxygen-permeable membrane reactor and the flow rate of water vapor.

[0061] Preferably, the volume concentration of hydrogen in the hydrogen-containing gas containing water vapor in step S3 is 0-40%, which can be any specific value within the range of 0-40%, such as 5%, 10%, 15%, 20%, 30%, or 40%; preferably 5%-20%.

[0062] In the above technical solution, the volume concentration of hydrogen in the hydrogen-containing gas is mainly adjusted by controlling the temperature, pressure, and flow rate of water vapor entering the oxygen-permeable membrane reactor, as well as the flow rates of fuel and air.

[0063] Preferably, the volume concentration of hydrogen in the hydrogen-rich gas containing water vapor in step S4 is 0-95%, and can be any specific value within the range of 0-95%, such as 10%, 30%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%; preferably 50%-80%.

[0064] In the above technical solution, the volume concentration of hydrogen in the hydrogen-containing gas is mainly adjusted by controlling the temperature, pressure, and flow rate of water vapor entering the oxygen-permeable membrane reactor, as well as the flow rates of fuel and air.

[0065] In the above technical solution, part of the reaction gas (high-temperature gas d) generated by the first oxygen-permeable membrane reactor R1 enters the third oxygen-permeable membrane reactor R3 as circulating gas, and the other part is discharged as exhaust gas. The circulating gas entering the third oxygen-permeable membrane reactor R3 accounts for 10% to 90% of the amount of reaction gas extracted, and can be any specific value within the range of 10% to 90%, such as 10%, 30%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and 90%.

[0066] It is understood that in the above technical solutions, condensate can be reused to generate water vapor. The heat required to generate water vapor can be obtained by optimizing the processes of oxygen-containing gas condensation, hydrogen-rich gas condensation, air heating, and high-temperature nitrogen cooling. The above heat exchange processes can be arbitrarily combined and optimized according to the temperature gradient, and are not limited to the listed heat exchange methods.

[0067] The present invention will be further explained below with reference to specific embodiments; it should be noted that, unless otherwise specified in the embodiments, the conditions shall be in accordance with conventional conditions or conditions recommended by the manufacturer; and unless the manufacturer of the reagents or instruments used is specified, they are all conventional products that can be purchased commercially.

[0068] Example 1

[0069] An air separation system for co-producing hydrogen includes a fourth oxygen-permeable membrane reactor R4, a third oxygen-permeable membrane reactor R3, a second oxygen-permeable membrane reactor R2, a first oxygen-permeable membrane reactor R1, a second condenser C2, and a first condenser C1. Each oxygen-permeable membrane reactor has an oxygen-permeable membrane dividing the reactor into two sides. The fourth oxygen-permeable membrane reactor R4 is divided into an air side and an oxygen-producing side, each with an inlet and an outlet. The outlet of the oxygen-producing side is connected to the second condenser C2, which has a condensate drain outlet and an oxygen outlet. The third oxygen-permeable membrane reactor R3 is divided into a fuel side and a nitrogen-producing side, each with an inlet and an outlet. The inlet of the nitrogen-producing side is connected to the fourth oxygen-permeable membrane reactor R4. Reactor R4 has an air-side outlet connected to it; the second oxygen-permeable membrane reactor R2 is divided into a fuel side and a hydrogen side, with inlets and outlets on the fuel side and hydrogen side respectively. The fuel-side inlet is connected to the fuel-side outlet of the third oxygen-permeable membrane reactor R3; the first oxygen-permeable membrane reactor R1 is divided into a fuel side and a hydrogen side, with inlets and outlets on the fuel side and hydrogen side respectively. The fuel-side inlet is connected to the fuel-side outlet and hydrogen-side outlet of the second oxygen-permeable membrane reactor R2, and the hydrogen-side outlet of the first oxygen-permeable membrane reactor R1 is connected to the first condenser C1. The first condenser C1 has a condensate drain outlet and a hydrogen outlet; the fuel-side outlet of the first oxygen-permeable membrane reactor R1 is connected to the fuel-side inlet of the third oxygen-permeable membrane reactor R3.

[0070] Example 2

[0071] In this specific embodiment, an air separation method for co-producing hydrogen using the system described in Example 1 is provided, comprising the following steps:

[0072] S1. 20℃ air enters the air side of the fourth oxygen-permeable membrane reactor R4, and 850℃ water vapor enters the oxygen-generating side of the fourth oxygen-permeable membrane reactor R4. The oxygen on the air side migrates to the oxygen-generating side through the oxygen-permeable membrane and forms an 800℃ oxygen-containing gas with a volume fraction of 60% with the water vapor. The oxygen-containing gas enters the second condenser C2, where water vapor is condensed to obtain oxygen with a purity of over 99%.

[0073] S2. The remaining 800°C oxygen-deficient air from the air side of the fourth oxygen-permeable membrane reactor R4 enters the nitrogen-producing side of the third oxygen-permeable membrane reactor R3. The oxygen in the oxygen-deficient air migrates through the oxygen-permeable membrane to the fuel side of the third oxygen-permeable membrane reactor R3 and undergoes an incomplete reaction with the fuel to generate a 900°C high-temperature gas a. After the oxygen is transferred from the oxygen-deficient air on the nitrogen-producing side, it becomes nitrogen gas with a purity of over 99% at 900°C. It is then cooled down to below 50°C by heat exchange and collected.

[0074] S3. The 900°C high-temperature gas a from the fuel side of the third oxygen-permeable membrane reactor R3 enters the fuel side of the second oxygen-permeable membrane reactor R2. The 850°C water vapor enters the hydrogen side of the second oxygen-permeable membrane reactor R2. The water vapor decomposes on the hydrogen side to produce hydrogen and oxygen. The oxygen migrates through the oxygen-permeable membrane to the fuel side of the second oxygen-permeable membrane reactor R2 and reacts with the 900°C high-temperature gas a to produce the 900°C high-temperature gas b. The remaining hydrogen side contains 900°C hydrogen-containing gas with water vapor (hydrogen accounts for 15%).

[0075] S4. The 900°C high-temperature gas b from the fuel side of the second oxygen-permeable membrane reactor R2 mixes with the 900°C hydrogen-containing gas containing water vapor from the hydrogen side of the second oxygen-permeable membrane reactor R2 to form 900°C high-temperature gas c, which enters the fuel side of the first oxygen-permeable membrane reactor R1. The 900°C water vapor enters the hydrogen side of the first oxygen-permeable membrane reactor R1, where it decomposes to produce hydrogen and oxygen. The oxygen migrates through the oxygen-permeable membrane to the fuel side of the first oxygen-permeable membrane reactor R1 and reacts with the 900°C high-temperature gas c to generate 900°C high-temperature gas d. 20% of the 900°C high-temperature gas d is used as an exhaust gas and is removed from the system, while 80% is recycled to the fuel side of the third oxygen-permeable membrane reactor R3. The remaining 900°C hydrogen-rich gas (80% hydrogen) containing water vapor from the hydrogen side of the first oxygen-permeable membrane reactor R1 enters the first condenser C1, where water vapor is condensed to obtain hydrogen with a purity of over 99%.

[0076] In this embodiment, the oxygen-permeable membranes of the first oxygen-permeable membrane reactor R1 and the second oxygen-permeable membrane reactor R2 are perovskite-metallic double-layer oxygen-permeable membranes with a tube-plate structure. The membrane tube diameter is 10 mm, the membrane thickness is 2 mm, and the pressure difference across the oxygen-permeable membrane tube is 3 MPa. The oxygen-permeable membranes of the third oxygen-permeable membrane reactor R3 and the fourth oxygen-permeable membrane reactor R4 are perovskite-based mixed conductor oxygen-permeable membranes, which are stacked in a flat plate structure. The flat plate oxygen-permeable membrane thickness is 1 mm, the membrane spacing is 1.5 mm, and the pressure difference across the oxygen-permeable membrane is 2.5 MPa.

[0077] In this embodiment, the condensate can be reused to generate water vapor. The heat required to generate water vapor can be obtained by optimizing the processes of oxygen-containing gas condensation, hydrogen-rich gas condensation, air heating, and high-temperature nitrogen cooling.

[0078] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An air separation method for co-producing hydrogen, characterized in that, Includes the following steps: S1. Air enters the air side of the fourth oxygen-permeable membrane reactor (R4), and water vapor enters the oxygen-generating side of the fourth oxygen-permeable membrane reactor (R4). The oxygen on the air side migrates to the oxygen-generating side through the oxygen-permeable membrane and forms a mixed gas with the water vapor, which enters the second condenser (C2) to condense water vapor and obtain high-purity oxygen. S2. The remaining oxygen-deficient air on the air side of the fourth oxygen-permeable membrane reactor (R4) enters the nitrogen-generating side of the third oxygen-permeable membrane reactor (R3). The oxygen in the oxygen-deficient air migrates through the oxygen-permeable membrane to the fuel side of the third oxygen-permeable membrane reactor (R3) and undergoes an incomplete reaction with the fuel to generate high-temperature gas a. The oxygen-deficient air on the nitrogen-generating side transfers oxygen to obtain high-purity nitrogen. S3. High-temperature gas a from the fuel side of the third oxygen-permeable membrane reactor (R3) enters the fuel side of the second oxygen-permeable membrane reactor (R2). Water vapor enters the hydrogen side of the second oxygen-permeable membrane reactor (R2). The water vapor decomposes on the hydrogen side to produce hydrogen and oxygen. Among them, the oxygen migrates through the oxygen-permeable membrane to the fuel side of the second oxygen-permeable membrane reactor (R2) and reacts with high-temperature gas a to produce high-temperature gas b. The remaining hydrogen side contains hydrogen-containing gas with water vapor. S4. The high-temperature gas b from the fuel side of the second oxygen-permeable membrane reactor (R2) mixes with the hydrogen-containing gas containing water vapor from the hydrogen side of the second oxygen-permeable membrane reactor (R2) to form high-temperature gas c, which enters the fuel side of the first oxygen-permeable membrane reactor (R1). The water vapor enters the hydrogen side of the first oxygen-permeable membrane reactor (R1), where it decomposes to produce hydrogen and oxygen. The oxygen migrates through the oxygen-permeable membrane to the fuel side of the first oxygen-permeable membrane reactor (R1) and reacts with the high-temperature gas c to generate high-temperature gas d. Part of the high-temperature gas d is used as exhaust gas, and the other part is recycled to the fuel side of the third oxygen-permeable membrane reactor (R3). The remaining hydrogen-rich gas containing water vapor from the hydrogen side of the first oxygen-permeable membrane reactor (R1) enters the first condenser (C1) to condense water vapor and obtain high-purity hydrogen. In step S4, the circulating gas accounts for 10% to 90% of the volume of the high-temperature gas d; The system includes a fourth oxygen-permeable membrane reactor (R4), a third oxygen-permeable membrane reactor (R3), a second oxygen-permeable membrane reactor (R2), a first oxygen-permeable membrane reactor (R1), a second condenser (C2), and a first condenser (C1). Each oxygen-permeable membrane reactor is divided into two sides by an oxygen-permeable membrane. The fourth oxygen-permeable membrane reactor (R4) is divided into an air side and an oxygen-generating side, each with an inlet and an outlet. The outlet of the oxygen-generating side is connected to the second condenser (C2), which has a condensate drain and an oxygen outlet. The third oxygen-permeable membrane reactor (R3) is divided into a fuel side and a nitrogen-generating side, each with an inlet and an outlet. The nitrogen-generating inlet is connected to the air-side outlet of the fourth oxygen-permeable membrane reactor (R4); the second oxygen-permeable membrane reactor (R2) is divided into a fuel side and a hydrogen side, with inlets and outlets on the fuel side and hydrogen side respectively. The fuel-side inlet is connected to the fuel-side outlet of the third oxygen-permeable membrane reactor (R3); the first oxygen-permeable membrane reactor (R1) is divided into a fuel side and a hydrogen side, with inlets and outlets on the fuel side and hydrogen side respectively. The fuel-side inlet is connected to the fuel-side outlet and hydrogen-side outlet of the second oxygen-permeable membrane reactor (R2), and the hydrogen-side outlet of the first oxygen-permeable membrane reactor (R1) is connected to the first condenser (C1). The first condenser (C1) has a condensate drain outlet and a hydrogen outlet. The first oxygen-permeable membrane reactor (R1) has an outlet on the fuel side that is connected to the inlet on the fuel side of the third oxygen-permeable membrane reactor (R3).

2. The air separation method for co-producing hydrogen according to claim 1, characterized in that, The oxygen-permeable membrane reactor can be one or both of the following structures: tube sheet type and flat plate type.

3. The air separation method for co-producing hydrogen according to claim 2, characterized in that, The tube-plate structure oxygen-permeable membrane has a tube diameter of 1–20 mm, a membrane thickness of 0.1–5 mm, and a tube spacing of 0.5–5 times the tube diameter; the flat plate structure oxygen-permeable membrane has a membrane thickness of 0.1–5 mm and a membrane spacing of 0.5–25 mm.

4. The air separation method for co-producing hydrogen according to claim 1, characterized in that, Oxygen-permeable membranes are one or more of the following: tubular membranes, sheet membranes, and hollow fiber membranes.

5. The air separation method for co-producing hydrogen according to claim 1, characterized in that, The oxygen-permeable membrane is one or more of the following structures: perovskite, fluorite-perovskite, fluorite-metal, and perovskite-metal.

6. The air separation method for co-producing hydrogen according to claim 1, characterized in that, The oxygen-permeable membrane is one or more of the following: single-layer membrane, double-layer membrane, and mixed conductor oxygen-permeable membrane.

7. The air separation method for co-producing hydrogen according to claim 1, characterized in that, The first oxygen-permeable membrane reactor (R1) and the second oxygen-permeable membrane reactor (R2) are equipped with a double-layer oxygen-permeable membrane with a fluorite-metal structure and / or a perovskite-metal structure.

8. The air separation method for co-producing hydrogen according to claim 1, characterized in that, The working temperature of the oxygen-permeable membrane reactor is 400-1000℃, the pressure difference across the oxygen-permeable membrane is 0-9MPa, and the pressure inside the membrane cavity is not lower than the pressure outside the membrane cavity.

9. The air separation method for co-producing hydrogen according to claim 1, characterized in that, In step S1, the volume concentration of oxygen in the mixture of water vapor and oxygen on the oxygen-generating side is 0-95%.

10. The air separation method for co-producing hydrogen according to claim 1, characterized in that, In step S1, the volume concentration of oxygen in the mixture of water vapor and oxygen on the oxygen-generating side is 50% to 80%.

11. The air separation method for co-producing hydrogen according to claim 1, characterized in that, In step S3, the volume concentration of hydrogen in the hydrogen-containing gas containing water vapor is 0-40%.

12. The air separation method for co-producing hydrogen according to claim 1, characterized in that, In step S3, the volume concentration of hydrogen in the hydrogen-containing gas containing water vapor is 5% to 20%.

13. The air separation method for co-producing hydrogen according to claim 1, characterized in that, In step S4, the volume concentration of hydrogen in the hydrogen-rich gas containing water vapor is 0-95%.

14. The air separation method for co-producing hydrogen according to claim 1, characterized in that, In step S4, the volume concentration of hydrogen in the hydrogen-rich gas containing water vapor is 50% to 80%.

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