Process and system for cyclically producing hydrogen by using thermochemical iodine-sulfur-barium

Abstract

The invention relates to the technical field of sulfur-iodine circulating hydrogen production, in particular to a thermochemical iodine-sulfur-barium circulating hydrogen production process and a thermochemical iodine-sulfur-barium circulating hydrogen production system, which comprises the following steps: reacting excessive Ba < 2 + > with sulfuric acid in a Bunsen reaction product to obtain barium sulfate so as to obtain a first reaction mixed solution containing HI, BaSO4, H2O, BaI2 and a small amount of unreacted I2; sequentially carrying out cyclone separation, liquid removal and filter pressing to obtain a barium sulfate filter cake and a second mixed solution containing HI, H2O and BaI2; the method comprises the following steps: crushing a barium sulfate filter cake, performing high-temperature decomposition, returning gas generated by decomposition to participate in Bunsen reaction, and dissolving BaO generated by decomposition into Ba < 2 + >; and reboiling the second mixed solution to obtain hydrogen iodide steam, cooling a product obtained by decomposing the hydrogen iodide steam, carrying out gas-liquid separation to obtain hydrogen, and returning liquid obtained by gas-liquid separation to participate in the Bunsen reaction of the next cycle. Barium circulation is introduced, the process is simplified, the dosage of elemental iodine is reduced, and the cost is low.

Description

Technical Field

[0001] The present application relates to the technical field of sulfur-iodine cycle hydrogen production, and specifically to a process and system for thermochemical iodine-sulfur-barium cycle hydrogen production. Background Art

[0002] Thermochemical sulfur-iodine cycle hydrogen production is considered to be one of the most likely process technologies in the world to achieve commercial large-scale production of green hydrogen. After decades of research, sulfur-iodine cycle hydrogen production technology still has many technical difficulties, such as the mixed acid separation and side reaction problems of the Bunsen reaction products. The Bunsen reaction is an exothermic reaction. When the temperature rises, the solubility of SO2 decreases and the solubility of iodine in hydroiodic acid increases, and vice versa. When the Bunsen reaction temperature is high, Bunsen side reactions are also prone to occur, such as the reaction of hydrogen iodide with sulfuric acid to produce sulfur, hydrogen sulfide and sulfur dioxide, resulting in a large loss of hydrogen iodide. When the Bunsen reaction temperature is low, sulfuric acid and hydroiodic acid are difficult to separate, the stratification time is long, and the stratified products have many impurities.

[0003] The traditional sulfur-iodine cycle hydrogen production process must put excess iodine into the Bunsen tower. The density difference between sulfuric acid and hydroiodic acid is small. In order to achieve rapid stratification of sulfuric acid and hydroiodic acid, excess iodine must be added to the mixed acid to form a HIx complex, increase the density difference between hydroiodic acid and sulfuric acid, and accelerate the stratification of hydroiodic acid and sulfuric acid. However, the price of iodine is expensive, reaching 300,000 yuan per ton. In order to accelerate the stratification of the mixed acid, for every 1 mol of iodine consumed in the Bunsen reaction, an additional 1-10 mol of iodine must be added to complex hydroiodic acid to accelerate stratification, which makes the mass of excess iodine large, resulting in the cost of iodine input in the system even exceeding the total investment cost of the entire sulfur-iodine cycle hydrogen production system.

[0004] Adding excessive iodine can accelerate the separation of sulfuric acid and hydroiodic acid, but it is impossible to completely separate sulfuric acid and hydroiodic acid. Therefore, the two phases after separation need to be further purified and concentrated. The related process consumes a lot of energy and has a complicated process. In the concentrated acid treatment process, equipment leakage, corrosion and other failure problems are prone to occur, which increases the operation and maintenance costs and operation risks.

[0005] In order to reduce the energy consumption of hydroiodic acid phase purification and reduce the loss of hydrogen iodide during the purification process, for example, the Chinese patent publication number: CN116143079B, title: A method and device for thermochemical sulfur-iodine cycle hydrogen production HIx phase purification, the application sends excess barium compounds into the HIx phase purification tower to react with impurity sulfuric acid to generate BaSO4 precipitation, so as to achieve the purpose of purifying the HIx solution; the generated BaSO4 decomposes in a high temperature environment to generate BaO, O2 and SO2, realizing the recycling of barium. Although the application solves the problem of removing sulfuric acid impurities in the HIx phase and avoids the risk of subsequent sulfur poisoning of the HI decomposition catalyst, the complex sulfur-iodine cycle hydrogen production process needs to be simplified, and the problem of excessive iodine input in the mixed acid stratification process generated by the Bunsen reaction is difficult to solve.

[0006] For example, in the Chinese invention patent publication number: CN107904617B, the name: Method and device for producing hydrogen by electrochemical decomposition of HI in sulfur-iodine cycle hydrogen production, the invention uses a single cell as a reactor, has an anode graphite electrode, a cathode graphite electrode, and a proton exchange membrane as a diaphragm; the anode side is injected with HIx phase solution from the sulfur-iodine cycle hydrogen production system, and the cathode side is injected with deionized water; power is applied to perform the decomposition reaction, and I in the HIx phase solution on the anode side is - Oxidized to I2, the generated H + It reaches the cathode side through the proton exchange membrane and is reduced to hydrogen at the cathode; the HIx phase solution on the anode side is circulated back to the Bunsen reactor as a Bunsen reaction raw material after the electrolysis reaction, and the hydrogen generated at the cathode is sent out. Although the invention does not need to concentrate and distill the hydroiodic acid phase, avoiding the separation problem of hydrogen and hydroiodic acid, electricity is a high-grade energy source, and the economic efficiency of using electricity to decompose hydroiodic acid is relatively poor. The corrosion and penetration of concentrated acid on the diaphragm also reduces its service life and destroys the continuous operation of the system. Summary of the invention

[0007] In order to solve the problems of insufficient separation of mixed acid, complex process of two-phase purification and two-phase concentration in the traditional sulfur-iodine cycle hydrogen production process, avoid the problem of Bunsen side reaction at high temperature, and the problem of increased cost due to excessive iodine addition, the present application proposes a process and system for thermochemical iodine-sulfur barium cycle hydrogen production. By adding excess Ba to the mixed acid solution, 2+ By separating sulfuric acid, the raw material sulfate ion of the side reaction is immediately separated from the solution in solid form.

[0008] On the one hand, the present application proposes a process for producing hydrogen by thermochemical iodine-barium-sulfur cycle, comprising the following steps: S1, reactants H2O, I2 and SO2 undergo a Bunsen reaction to generate H2SO4 and HI, and an excess of Ba 2+The H2SO4 reacts with the BaSO4 to obtain a first reaction mixture containing HI, BaSO4, H2O, BaI2 and I2. The molar ratio of the components of the first reaction mixture is HI: BaSO4: I2: H2O: BaI2 = (5-7.17): (0.46-0.66): (0-0.2): (19.08-26.68): (0.1-0.3); S2, the first reaction mixture of S1 is subjected to solid-liquid separation to obtain a wet solid phase including barium sulfate, HI, H2O, BaI2 and a second mixed solution including HI, H2O, BaI2; S3, after removing part of the liquid from the wet solid phase of S2, filter press to obtain a barium sulfate filter cake, the barium sulfate filter cake is crushed and then decomposed into BaO, SO2 and O2 at high temperature, the gas generated by the high temperature decomposition of barium sulfate is returned to S1 to participate in the next cycle of Bunsen reaction, and the generated BaO is also returned to S1; S4, the second mixed solution of S2 and the liquid removed from the wet solid phase in S3 and the liquid obtained by filter press are mixed, the mixed liquid is reboiled to obtain hydrogen iodide vapor, and the remaining liquid after reboiled is returned to S1 to participate in the next cycle of Bunsen reaction; S5, the hydrogen iodide vapor of S4 is decomposed into iodine and hydrogen, the decomposition reaction product is heat exchanged and cooled, and then separated by gas-liquid to obtain hydrogen, and the liquid obtained by gas-liquid separation is returned to S1 to participate in the next cycle of Bunsen reaction.

[0009] Particularly, the Bunsen reaction temperature in S1 is 20°C-120°C, and the operating pressure is 1-10 atm; the hydrogen iodide vapor in S4 is decomposed under the action of the catalyst at a temperature not lower than 400°C.

[0010] In particular, the barium sulfate filter cake in the S3 is crushed into 6mm-10mm particles and then decomposed at high temperature. The heat source for the high temperature decomposition of barium sulfate is the high temperature helium of 1300℃-1600℃ of the high temperature gas-cooled reactor. The heat of the high temperature helium decomposes BaSO4 into BaO, SO2 and O2, and then the high temperature helium is cooled to 1200℃-1300℃.

[0011] In particular, the heat for decomposing hydrogen iodide in S5 comes from the high-temperature helium at 1200-1300°C after heat exchange with the decomposition of barium sulfate. The heat of the high-temperature helium decomposes hydrogen iodide into iodine and hydrogen, and then the high-temperature helium is cooled to 1000-1100°C.

[0012] Particularly, the hydrogen iodide decomposition reaction product in S5 is returned to S4 for heat exchange to provide heat for reboiling.

[0013] On the other hand, the present application also proposes a system for thermochemical iodine-barium-sulfur cycle hydrogen production, which operates according to the process of any one of claims 1 to 5. The system includes a Bunsen tower 1, a cyclone separator 2, a pulping tank 3, a filter press 4, a crusher 5, and a barium sulfate decomposition tower 6 connected in sequence. The solution separated by the cyclone separator 2, the pulping tank 3, and the filter press 4 is fed into a hydrogen iodide evaporator 7, and a reboiler 9 is provided outside the lower part of the hydrogen iodide evaporator 7. The hydrogen iodide vapor generated by the hydrogen iodide evaporator 7 is then fed into a hydrogen iodide decomposition tower 8, and the gas produced by the hydrogen iodide decomposition tower 8 is then returned to the reboiler 9 for heat exchange.

[0014] In particular, the Bunsen tower 1 is provided with a pure water inlet 11, an iodine inlet 14, an SO2 inlet 13, a barium oxide inlet 15, and a product outlet 17. A gas distributor 12 is provided at the lower part of the Bunsen tower 1. SO2 enters the Bunsen tower 1 from the SO2 inlet 13 and is evenly distributed through the gas distributor 12. During the rising process of the evenly distributed bubbles, SO2 dissolves in the solution and a Bunsen reaction occurs.

[0015] In particular, the first reaction mixture in the S2 enters the cyclone separator 2 through the separator inlet 21, and the wet solid phase obtained by solid-liquid separation is discharged from the wet solid phase outlet 23 and sent to the beating tank 3; the lower part of the beating tank 3 is a stirring area and the upper part is a filtering area, the stirring area is provided with a stirring device 32, the flow rate of the slurry outlet 33 of the beating tank 3 is controlled to be 30% to 60% of the flow rate of the wet solid phase outlet 23 of the cyclone separator 2 to drive the solution through the filter 31 set in the filtering area, and the separated filtrate is then sent out from the filtrate outlet 34, and the concentrated wet solid phase is then sent to the filter press 4.

[0016] In particular, the second mixed solution obtained by solid-liquid separation in the cyclone separator 2, the filtrate obtained by filtering the filter 31 of the pulping tank 3 and the liquid obtained by the filter press 4 are mixed and sent to the hydrogen iodide evaporator 7. The hydrogen iodide evaporator 7 sends part of the solution to the reboiler 9 through the bottom circulation port 73 to recover the heat of gas production in the hydrogen iodide decomposition tower 8. The hydrogen iodide vapor is sent to the hydrogen iodide decomposition tower 8 from the hydrogen iodide outlet 72 of the hydrogen iodide evaporator 7, and the unevaporated HI, H2O, and BaI2 are discharged from the bottom return tower port 74 of the hydrogen iodide evaporator 7 and returned to the Bunsen tower 1 through the iodine inlet 14.

[0017] In particular, the decomposition gas produced by the hydrogen iodide decomposition tower 8 is sent to the reboiler 9 to provide evaporation heat for the hydrogen iodide evaporator 7, and then sent to the gas-liquid separator 10. The steam of I2, HI, and H2O in the gas-liquid separator 10 is condensed into liquid, discharged from the condensate outlet 102 at the bottom and returned to the Bunsen tower 1 through the iodine inlet 14. After H2 is cooled, it is discharged from the hydrogen outlet 101 in the upper middle part.

[0018] On the basis of conforming to the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present application.

[0019] The above technical solution has the following advantages or beneficial effects: the present application introduces a barium cycle based on the traditional sulfur-iodine cycle hydrogen production, and sulfuric acid and hydroiodic acid can be separated into two phases without adding excess iodine. The subsequent purification process of the traditional sulfur-iodine cycle hydrogen production process is no longer required, which simplifies the traditional sulfur-iodine cycle hydrogen production process system, eliminates the energy consumption of mixed acid stratification, two-phase purification and other processes, solves the problem that the traditional sulfur-iodine cycle hydrogen production must add excess iodine for mixed acid stratification, and reduces the amount of iodine. 2+ After salting, the sulfuric acid produced by the Bunsen reaction is immediately converted into solid barium sulfate particles, eliminating the sulfuric acid as the reactant of the Bunsen side reaction and reverse reaction, thereby solving the problem of the Bunsen side reaction and reverse reaction from the root. The decomposition of barium sulfate instead of sulfuric acid solves the problem of sulfuric acid corrosion to the equipment, and does not require the use of a catalyst, thereby avoiding problems such as catalyst deactivation, reducing equipment manufacturing requirements and production costs, and can use conventional incinerators, multi-stage furnaces, etc. to decompose barium sulfate, improving system stability. Of course, any technical solution of the present application does not necessarily achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art description. Obviously, for those skilled in the art, other drawings can be obtained based on the provided drawings without creative work.

[0021] Figure 1 It is a schematic diagram of the process of thermochemical iodine-barium-sulfur cycle hydrogen production according to one embodiment of the present application.

[0022] Among them, 1-Bunsen tower; 11-pure water inlet; 12-gas distributor; 13-SO2 inlet; 14-iodine inlet; 15-barium oxide inlet; 16-oxygen outlet; 17-product outlet; 2-cyclone separator; 21-separator inlet; 22-liquid phase outlet; 23-wet solid phase outlet; 3-beating tank; 31-filter; 32-mixing equipment; 33-slurry outlet; 34-filtrate outlet; 4-filter press; 41-filter cake outlet; 42-filtrate outlet; 5-crushing Crusher; 6-barium sulfate decomposition tower; 61-decomposition gas outlet; 62-barium oxide outlet; 63-hot helium inlet; 64-hot helium outlet; 7-hydrogen iodide evaporator; 71-hydriodic acid inlet; 72-hydrogen iodide outlet; 73-kettle bottom circulation port; 74-kettle bottom return tower port; 8-hydrogen iodide decomposition tower; 81-hydrogen iodide inlet; 82-helium inlet; 83-helium outlet; 84-gas production outlet; 9-reboiler; 10-gas-liquid separator; 101-hydrogen outlet; 102-condensate outlet. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application are clearly and completely described below in conjunction with the drawings of the present application. Obviously, the described embodiments are only part of the embodiments of the present application and are intended to be used to explain the inventive concept. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0024] Unless otherwise clearly specified and limited, the terms "connected", "connected" and the like used in the description should be understood in a broad sense, for example, it can be fixedly connected, detachably connected, or integrated; it can be mechanically connected, electrically connected; it can be directly connected, indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments can be understood according to specific circumstances.

[0025] Unless otherwise clearly specified and limited, when a first feature is “above”, “below” or “above” a second feature, it may be that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is “above”, “above” or “above” a second feature, it may be that the first feature is directly above or obliquely above the second feature, or it may simply mean that the first feature is higher in level than the second feature. When a first feature is “below”, “below” or “below” a second feature, it may be that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is “below”, “below” or “below” a second feature, it may be that the first feature is directly below or obliquely below the second feature, or it may simply mean that the first feature is lower in level than the second feature.

[0026] The term "a specific embodiment" used in the description means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0027] like Figure 1 As shown, one embodiment of the present application proposes a process for producing hydrogen by thermochemical iodine-barium-sulfur cycle, wherein SO2, I2 and H2O introduced into Bunsen tower 1 undergo the following Bunsen reaction to produce sulfuric acid and hydroiodic acid, reaction formula: SO2+I2+2H2O→H2SO4+2HI, Bunsen reaction temperature is 20℃-120℃, and operating pressure is 1-10 atm. Excess Ba is distributed in the reaction solution of Bunsen tower 1 2+ , circulates in the system in the form of BaI2. When the Bunsen reaction produces sulfate, it immediately reacts with Ba 2+ Combined to produce barium sulfate precipitate H2SO4+Ba 2+ →2H + +BaSO4↓, thereby consuming sulfuric acid in real time, and finally obtaining a first reaction mixture containing HI, BaSO4, H2O, BaI2 and a small amount of unreacted I2, the molar ratio of the components of the first reaction mixture is HI:BaSO4:I2:H2O:BaI2 = (5-7.17):(0.46-0.66):(0-0.2):(19.08-26.68):(0.1-0.3). Since sulfuric acid is never present in the Bunsen tower 1 solution, the Bunsen reverse reaction and side reactions are completely avoided. Iodine is insoluble in water, but can react with I - A complex is formed to dissolve the iodine element. When the solution contains BaI2, for example, I2 at the condensate outlet can be dissolved and brought back to the Bunsen tower 1, reducing the risk of iodine element blocking the pipeline.

[0028] The first reaction mixture containing HI, BaSO4, H2O, BaI2 and a small amount of unreacted I2 in the Bunsen tower 1 is sent to the cyclone separator 2. The mixed suspension of barium sulfate particles with high density and part of HI, H2O and BaI2 is discharged from the bottom of the cyclone separator 2, and the second mixed solution without barium sulfate particles is discharged from the top.

[0029] The mixed suspension discharged from the bottom of the cyclone separator 2 is sent to the pulping tank 3, which includes a stirring device 32 and a filter 31. The mixed suspension is kept in a suspended state by continuous stirring of the stirring device 32 to avoid the deposition of barium sulfate particles. By controlling the slurry outlet flow of the pulping tank 3, part of the solution is filtered through the filter 31 and then discharged from the pulping tank 3 from the filtrate outlet 34. The mixed suspension treated by the pulping tank 3 becomes a thicker slurry and is sent to the filter press 4 through the slurry outlet 33. The pulping tank 3 reduces the amount of filtered liquid of the filter press 4, thereby improving the filtration efficiency of the filter press 4. The filter press 4 further separates the wet barium sulfate filter cake from the solution by filtration, and the solution obtained by filtration is mixed with the filtrate of the pulping tank 3 and the second mixed solution discharged from the top of the cyclone separator 2 and sent to the hydrogen iodide evaporator 7. The filter cake of the filter press 4 is broken into small pieces by a crusher 5 and sent to the barium sulfate decomposition tower 6.

[0030] The barium sulfate decomposition tower 6 can be selected from incinerators in the form of multi-stage furnaces, fixed beds, fluidized beds, etc., preferably with high-temperature helium of a high-temperature gas-cooled reactor as a heat source, the temperature of the high-temperature helium is 1300-1600° C. The high-temperature helium flowing in from the hot helium inlet 63 is the circulating cooling gas of the high-temperature gas-cooled reactor, and the temperature of the high-temperature helium flowing out from the hot helium outlet 64 is 1200-1300° C. The heat brought by the high-temperature helium decomposes BaSO4 into BaO, SO2 and O2, and the reaction equation is as follows: BaSO4→BaO+SO2↑+1 / 2O2↑. The decomposition temperature of BaSO4 is 1150-1400℃. The heating decomposition of barium sulfate wet filter cake is divided into two stages: when the temperature rises from 20-120℃ to 200-220℃, the water, hydrogen iodide and iodine in the filter cake are evaporated layer by layer from the outside to the inside, and the filter cake is dried and agglomerated; when the temperature continues to rise to 1150-1400℃, barium sulfate begins to decompose layer by layer from the outside to the inside, and cavities are generated when SO2 and O2 escape, forming porous BaO that gradually expands to the center of the filter cake.

[0031] In order to increase the decomposition rate of barium sulfate, the barium sulfate filter cake is made into particles with a particle size of 6-10 mm by a crusher 5 before being sent to the barium sulfate decomposition tower 6, thereby significantly increasing its decomposition rate, and the porous BaO particles produced by the decomposition have a small particle size, which reduces the difficulty of transportation. The porous BaO particles are sent back to the Bunsen tower 1 through the barium oxide outlet 62. The porous BaO with a particle size not higher than 10 mm can be quickly dissolved in the Bunsen tower 1 and circulated for precipitation and separation of sulfate radicals. SO2 and O2 produced by the decomposition of barium sulfate return to the Bunsen tower 1 through the SO2 inlet at the bottom of the Bunsen tower 1. A gas distributor is installed at the bottom of the Bunsen tower 1 to make SO2 float upward in tiny bubbles to improve the SO2 absorption efficiency. O2 is sent out of the system from the oxygen outlet at the top of the Bunsen tower 1. Compared with the sulfuric acid decomposition tower in the prior art, there is no need to add a catalyst in the barium sulfate decomposition tower, so its maintenance frequency is low, the maintenance time is short, the catalyst use cost is saved, and the barium sulfate decomposition tower can operate continuously and stably for a long time. Since barium sulfate does not have strong oxidizing properties, the requirements for equipment materials are significantly reduced. The barium sulfate decomposition tower used in the present application can be manufactured using common engineering materials and only needs to be resistant to high temperatures but not corrosion. The cost and safety risks are significantly lower than those of the sulfuric acid decomposition tower in the prior art.

[0032] The hydroiodic acid solution enters the hydrogen iodide evaporator 7 from the hydroiodic acid inlet 71. A reboiler 9 is provided outside the lower middle part of the hydrogen iodide evaporator 7. After the hydroiodic acid is introduced into the reboiler 9 from the bottom circulation port of the kettle for heating, it is sent back to the hydrogen iodide evaporator 7, so that the hydrogen iodide is continuously evaporated in a gaseous state. The reboiler 9 is a heat exchange device, which heats the hydroiodic acid solution by recovering the decomposition gas heat of the hydrogen iodide decomposition tower 8. The hydroiodic acid solution contains HI, BaI2 and H2O. After absorbing heat, HI and H2O are vaporized and sent to the hydrogen iodide decomposition tower 8 from the hydrogen iodide outlet 72 at the top of the evaporator, while the non-volatile and non-vaporized hydroiodic acid mother liquor of BaI2 is sent back to the Bunsen tower 1 from the bottom return tower port 74.

[0033] Hydrogen iodide vapor is fed into the hydrogen iodide inlet 81 of the hydrogen iodide decomposition tower 8, and under the action of a catalyst, the temperature is not less than 400°C, and it is decomposed into iodine and hydrogen. The hydrogen iodide decomposition tower 8 uses the hot helium from the barium sulfate decomposition tower as a heat source, and its temperature is 1200-1300°C. After the hydrogen iodide decomposition tower 8 is heated, it is discharged from the helium outlet, and its temperature is 1000-1100°C. The helium discharged from the helium outlet is used for steam power generation. The gas produced by the hydrogen iodide decomposition tower 8 is a mixed gas of hydrogen, iodine vapor, hydrogen iodide and water vapor. The temperature when it flows out from the gas production outlet is 400-600°C, and it enters the kettle bottom reboiler 9 of the hydrogen iodide evaporator 7. After heat exchange, the temperature drops to 140°C-200°C, and it is sent to the gas-liquid separator 10 for further cooling, and the iodine vapor, hydrogen iodide gas and water vapor are condensed, and hydrogen is discharged from the hydrogen outlet, and the condensate is sent back to the Bunsen tower 1 from the condensate outlet.

[0034] like Figure 1 As shown, one embodiment of the present application proposes a system for thermochemical iodine-barium-sulfur cycle hydrogen production, the system comprising a Bunsen tower 1, a cyclone separator 2, a pulping tank 3, a filter press 4, a crusher 5, a barium sulfate decomposition tower 6, a hydrogen iodide evaporator 7, a hydrogen iodide decomposition tower 8, and a gas-liquid separator 10.

[0035] The reactants H2O, I2 and SO2 of the Bunsen reaction enter the Bunsen tower 1 from the pure water inlet 11, the iodine inlet 14 and the SO2 inlet 13 respectively; the circulating BaI2 and iodine return together from the iodine inlet 14, and the BaO particles produced by the decomposition of barium sulfate are sent to the Bunsen tower 1 from the barium oxide inlet 15. After the mixed gas of SO2 and O2 produced by the decomposition of barium sulfate is sent to the Bunsen tower 1 from the SO2 inlet 13, the bubbles are evenly distributed through the gas distributor 12. During the rising process of the bubbles, SO2 dissolves in the solution, and O2 floats to the surface and is discharged from the Bunsen tower 1 from the oxygen outlet 16. The reaction product in the Bunsen tower 1 is sent out from the product outlet 17, and then enters the cyclone separator 2 from the separator inlet 21. The cyclone separator 2 separates the Bunsen reaction product into a solution without barium sulfate particles and discharges it from the liquid phase outlet 22, and the separated wet solid phase containing barium sulfate particles is sent to the pulping tank 3 from the wet solid phase outlet 23.

[0036] The lower part of the beating tank 3 is a stirring area, and the upper part is a filtering area. The stirring area is provided with a stirring device 32 to mix the wet and solid phases evenly to prevent precipitation. The flow rate of the slurry outlet 33 of the beating tank 3 is controlled to be 30%-60% of the flow rate of the wet and solid phase outlet 23 of the cyclone separator 2, and the excess solution is driven to pass through the filter 31 and then sent out from the filtrate outlet 34. The filter 31 can pass the solution and block the particulate matter.

[0037] The concentrated wet solid phase is sent to the filter press 4 to further separate the barium sulfate and the solution. The filter press 4 squeezes the slurry and squeezes out the solution to form a wet filter cake containing barium sulfate. The solution is sent out from the filtrate outlet 042, and the filter cake is sent out from the filter cake outlet 041 and sent to the crusher 5 through the conveyor belt. The crusher 5 crushes the large filter cake into irregularly shaped small particles with a particle size of 6-10 mm, which are then sent to the barium sulfate decomposition tower 6.

[0038] The barium sulfate particles absorb heat in the barium sulfate decomposition tower 6 and decompose into BaO, SO2 and O2. BaO is discharged from the barium oxide outlet 62, and SO2 and O2 are discharged from the decomposition gas outlet 61. The porous small particles of BaO are sent back to the Bunsen tower 1 from the barium oxide inlet 15, and the mixed gas of SO2 and O2 is sent back to the Bunsen tower 1 from the SO2 inlet 13. The high temperature gas-cooled reactor provides a high temperature environment and heat for the decomposition of barium sulfate. High temperature helium enters the barium sulfate decomposition tower 6 from the hot helium inlet 63 with a temperature of 1300-1600°C. After heat exchange, it is discharged from the barium sulfate decomposition tower 6 from the hot helium outlet 64 with a temperature of 1200-1300°C. Heat is transferred to the barium sulfate particles in the barium sulfate decomposition tower 6 by interlayer heat exchange.

[0039] The hydroiodic acid solution separated by the cyclone separator 2, the pulping tank 3 and the filter press 4 is sent to the hydrogen iodide evaporator 7. The hydrogen iodide evaporator 7 sends part of the solution to the reboiler 9 through the bottom circulation port 73 to recover the heat of gas production in the hydrogen iodide decomposition tower 8, evaporates part of the hydrogen iodide and water in the hydroiodic acid solution, and sends them to the hydrogen iodide decomposition tower 8 from the hydrogen iodide outlet 72, and the unevaporated HI, H2O, BaI2, etc. are sent back to the Bunsen tower 1 from the bottom return tower port 74.

[0040] After the mixed steam of hydrogen iodide and water enters the hydrogen iodide decomposition tower 8, it is decomposed into iodine and hydrogen under the action of the catalyst. The decomposed I2, H2 and the mixed gas of HI and H2O are discharged from the gas outlet 84. The decomposition temperature of the hydrogen iodide decomposition tower 8 is 400-600°C. The hot helium discharged from the hot helium outlet 64 of the barium sulfate decomposition tower 6 enters the hydrogen iodide decomposition tower 8 from the helium inlet 82 at a temperature of 1200-1300°C, and is discharged from the hydrogen iodide decomposition tower 806 from the helium outlet 83 at a temperature of 1000-1100°C. Helium increases the appropriate temperature environment for the hydrogen iodide decomposition reaction, and the mixed steam of hydrogen iodide and water is heated to 400-600°C by interlayer heat transfer. The decomposed gas is sent to the reboiler 9 to provide evaporation heat for the hydrogen iodide evaporator 7, and then sent to the gas-liquid separator 10. In the gas-liquid separator 10 , the vapors of I2, HI, and H2O are condensed into liquid and sent to the Bunsen tower 1 from the bottom condensate outlet 102 . H2 remains as gas after cooling and is discharged from the hydrogen outlet 101 . Example 1

[0041] First, add 360.3g of water to the Bunsen tower, and then continue to add SO2:I2:H2O:BaO=1:1:2:1.2 at a molar ratio of 12.5L / min until the system runs stably. When running stably, add water to the Bunsen tower at a flow rate of 20mL / min, stop other external feeds, the average mass of barium sulfate fed to the barium sulfate decomposition tower is 130g / min, the average mass of barium oxide after regeneration is 86g / min, the total flow of barium sulfate decomposition gas at the bottom of the Bunsen tower is 18.8L / min, the oxygen flow at the top of the tower is 6.3L / min, and the hydrogen output of the gas-liquid separator 10 is 12.6L / min.

[0042] Although the embodiments of the present application have been shown and described above, it is to be understood that the above embodiments are exemplary and cannot be construed as limiting the present application. Without departing from the spirit and scope of the present application, the present application may also have various changes and improvements, which all fall within the scope of the present application to be protected.

Claims

1. A process for producing hydrogen by thermochemical iodine-barium-sulfur cycle, comprising S1, reactants H2O, I2 and SO2 undergoing Bunsen reaction to produce H2SO4 and HI, characterized in that: The excess Ba in S1 2+ Reacting with H2SO4 therein to generate BaSO4, thereby obtaining a first reaction mixture containing HI, BaSO4, H2O, BaI2 and I2, wherein the molar ratio of the components of the first reaction mixture is HI:BaSO4: I2: H2O: BaI2 = (5-7.17): (0.46-0.66): (0-0.2): (19.08-26.68): (0.1-0.3); S2, the first reaction mixture of S1 is subjected to solid-liquid separation to obtain a wet solid phase including barium sulfate, HI, H2O, and BaI2 and a second mixed solution including HI, H2O, and BaI2; After removing part of the liquid from the wet solid phase of S3 and S2, a barium sulfate filter cake is obtained by filter pressing. The barium sulfate filter cake is crushed and decomposed into BaO, SO2 and O2 at high temperature. The gas produced by the high temperature decomposition of barium sulfate is returned to S1 to participate in the Bunsen reaction of the next cycle, and the produced BaO is also returned to S1; S4, the second mixed solution of S2 and the liquid removed from the wet solid phase in S3 and the liquid obtained by filter pressing are mixed, the mixed liquid is reboiled to obtain hydrogen iodide vapor, and the remaining liquid after reboiled is returned to S1 to participate in the next cycle of Bunsen reaction; The hydrogen iodide vapor in S5 and S4 is decomposed into iodine and hydrogen. The decomposition reaction product is cooled by heat exchange and then separated into gas and liquid to obtain hydrogen. The liquid obtained by gas-liquid separation is returned to S1 to participate in the next cycle of Bunsen reaction.

2. The process for producing hydrogen by thermochemical iodine-barium-sulfur cycle according to claim 1, characterized in that: The Bunsen reaction temperature in S1 is 20°C-120°C and the operating pressure is 1-10 atm; the hydrogen iodide vapor in S4 is decomposed under the action of a catalyst at a temperature not lower than 400°C.

3. The process for producing hydrogen by thermochemical iodine-barium-sulfur cycle according to claim 1, characterized in that: The barium sulfate filter cake in the S3 is crushed into 6mm-10mm particles and then decomposed at high temperature. The heat source for the high temperature decomposition of barium sulfate is the high temperature helium of 1300℃-1600℃ of the high temperature gas-cooled reactor. The heat of the high temperature helium decomposes BaSO4 into BaO, SO2 and O2, and then the high temperature helium is cooled to 1200℃-1300℃.

4. A process for producing hydrogen by thermochemical iodine-barium-sulfur cycle according to claim 3, characterized in that: The heat for decomposing hydrogen iodide in S5 comes from the high-temperature helium at 1200-1300°C after heat exchange with the decomposition of barium sulfate. The heat of the high-temperature helium decomposes hydrogen iodide into iodine and hydrogen, and then the high-temperature helium is cooled to 1000-1100°C.

5. A process for producing hydrogen by thermochemical iodine-barium-sulfur cycle according to claim 4, characterized in that: The hydrogen iodide decomposition reaction product in S5 is returned to S4 for heat exchange to provide heat for reboiling.

6. A system for producing hydrogen by thermochemical iodine-barium-sulfur cycle, the system being operated according to the process of any one of claims 1 to 5, characterized in that: The system comprises a Bunsen tower (1), a cyclone separator (2), a pulping tank (3), a filter press (4), a crusher (5), and a barium sulfate decomposition tower (6) which are connected in sequence. The solution separated by the cyclone separator (2), the pulping tank (3), and the filter press (4) is sent to a hydrogen iodide evaporator (7). A reboiler (9) is provided outside the middle and lower part of the hydrogen iodide evaporator (7). The hydrogen iodide vapor generated by the hydrogen iodide evaporator (7) is then sent to a hydrogen iodide decomposition tower (8). The gas produced by the hydrogen iodide decomposition tower (8) is then returned to the reboiler (9) for heat exchange.

7. A thermochemical iodine-barium-sulfur cycle hydrogen production system according to claim 6, characterized in that: The Bunsen tower (1) is provided with a pure water inlet (11), an iodine inlet (14), an SO2 inlet (13), a barium oxide inlet (15), and a product outlet (17). A gas distributor (12) is provided at the middle and lower part of the Bunsen tower (1). SO2 enters the Bunsen tower (1) from the SO2 inlet (13) and is evenly distributed through the gas distributor (12). During the rising process of the evenly distributed bubbles, SO2 dissolves in the solution and a Bunsen reaction occurs.

8. A thermochemical iodine-barium-sulfur cycle hydrogen production system according to claim 6, characterized in that: The first reaction mixture in S2 enters the cyclone separator (2) through the separator inlet (21), and the wet solid phase obtained by solid-liquid separation is discharged from the wet solid phase outlet (23) and sent to the beating tank (3); the lower part of the beating tank (3) is a stirring area and the upper part is a filtering area, and the stirring area is provided with a stirring device (32). The flow rate of the slurry outlet (33) of the beating tank (3) is controlled to be 30% to 60% of the flow rate of the wet solid phase outlet (23) of the cyclone separator (2) to drive the solution to pass through the filter (31) provided in the filtering area, and the separated filtrate is then sent out from the filtrate outlet (34), and the concentrated wet solid phase is then sent to the filter press (4).

9. A thermochemical iodine-barium-sulfur cycle hydrogen production system according to claim 8, characterized in that: The second mixed solution obtained by solid-liquid separation in the cyclone separator (2), the filtrate obtained by filtering the filter (31) of the pulping tank (3), and the liquid obtained by the filter press (4) are mixed and sent to the hydrogen iodide evaporator (7). The hydrogen iodide evaporator (7) sends part of the solution to the reboiler (9) through the bottom circulation port (73) to recover the heat of gas production in the hydrogen iodide decomposition tower (8). The hydrogen iodide vapor is sent to the hydrogen iodide decomposition tower (8) from the hydrogen iodide outlet (72) of the hydrogen iodide evaporator (7), and the unevaporated HI, H2O, and BaI2 are discharged from the bottom return port (74) of the hydrogen iodide evaporator (7) and returned to the Bunsen tower (1) through the iodine inlet (14).

10. A thermochemical iodine-barium-sulfur cycle hydrogen production system according to claim 6, characterized in that: The decomposition gas produced by the hydrogen iodide decomposition tower (8) is sent to the reboiler (9) to provide evaporation heat for the hydrogen iodide evaporator (7), and then sent to the gas-liquid separator (10). The vapors of I2, HI and H2O in the gas-liquid separator (10) are condensed into liquid, discharged from the condensate outlet (102) at the bottom and returned to the Bunsen tower (1) through the iodine inlet (14). After H2 is cooled, it is discharged from the hydrogen outlet (101) at the upper middle part.

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