HIx phase purification process and system for hydrogen production through thermochemical sulfur-iodine circulation

Abstract

The invention relates to the field of hydrogen production by water decomposition through thermochemical sulfur-iodine circulation, in particular to an HIx phase purification process and system for hydrogen production through thermochemical sulfur-iodine circulation, the process comprises a Bunsen reaction, a sulfuric acid decomposition reaction and an HI decomposition reaction, and an HIx phase obtained through the Bunsen reaction flows into an HIx phase purification tower; sulfuric acid impurities in the HIx phase are subjected to temperature reduction, pressure reduction and temperature rise in the tower to be converted into hydrogen sulfide; hydrogen sulfide gas is separated out from the solution and then enters a hydrogen sulfide combustion tower, the hydrogen sulfide gas and oxygen generated by decomposition of sulfuric acid are combusted into sulfur dioxide under the oxygen-enriched condition, and sulfur is returned to Bunsen for reaction in the form of sulfur dioxide. According to the method, a side reaction path regulation strategy is adopted, sulfuric acid impurities in the HIx phase are completely converted into sulfur dioxide, harm of sulfur dioxide to a hydroiodic acid decomposition catalyst is avoided, extra impurities are not introduced in the whole purification process, extra energy consumption input is not needed, system heat management is optimized, and the heat efficiency and the energy utilization rate of the whole system are improved.

Description

Technical Field

[0001] The present disclosure relates to the field of hydrogen production by decomposing water through a thermochemical sulfur-iodine cycle, and in particular to a HIx phase purification process and system for hydrogen production through a thermochemical sulfur-iodine cycle. Background Art

[0002] Thermochemical sulfur-iodine cycle system generally includes three subsystems: Bunsen reaction subsystem, H2SO4 decomposition subsystem, HI decomposition subsystem. Among them, sulfur dioxide and iodine react with excess water to form a mixed solution of sulfuric acid and hydroiodic acid. Under the condition of excess iodine, the solution can spontaneously undergo liquid-liquid stratification, and the upper light phase solution is sulfuric acid phase, mainly sulfuric acid solution. Due to the limitations of liquid-liquid stratification, HI and iodine impurities will inevitably be included. The lower heavy phase is HIx phase, mainly HI-I2-H2O ternary mixed solution, and also contains a small amount of sulfuric acid impurities. The decomposition reaction of HI is the most critical step in the entire hydrogen production cycle due to its low reaction rate, low thermodynamic equilibrium conversion rate and high energy consumption. Both simulation and experimental research results show that the homogeneous decomposition rate of HI is extremely low, and the decomposition rate is less than 2% at a temperature of 773K, so it is necessary to develop efficient catalysts to increase the HI decomposition reaction rate, thereby reducing energy consumption and improving the efficiency of the entire sulfur-iodine cycle hydrogen production.

[0003] In the HIx phase solution, the impure sulfuric acid will reduce the selectivity and conversion rate of the catalyst, causing sulfur poisoning of the HI decomposition catalyst, resulting in a faster catalyst deactivation rate, thereby reducing the H2 yield and affecting the entire thermochemical sulfur-iodine cycle hydrogen production process system. The effects of sulfuric acid impurities in the HIx phase on the catalyst are mainly reflected in the following aspects: (1) Compared with HI, gaseous sulfides are more strongly adsorbed on the catalyst surface, reducing the HI conversion rate; (2) For the poisoned catalyst, the ability of the carrier to interact with the active metal is weakened, and the degree of dispersion is reduced. The specific surface area of ​​the poisoned catalyst is lower than that of the fresh catalyst, and a part of the metal particles loaded on the surface undergo significant agglomeration, the particle size becomes larger, and the micropores are blocked; (3) The competitive adsorption of the adsorbed S substance on the catalyst surface will lead to the destruction of the active site function, and after the poisoning process, the catalyst will be irreversibly deactivated.

[0004] The current disclosed technology and literature have studied the HIx phase purification process of the sulfur-iodine cycle hydrogen production system. Among them, patent CN114195094B discloses a full-process method and device for thermochemical sulfur-iodine cycle hydrogen production. The invention uses a mixed gas of SO2, O2 and H2O at high temperature to remove the impurity H2SO4 in the HIx phase. The side reaction of generating H2S mainly occurs in the tower, and the generated S and H2S react with oxygen in an oxygen-rich high-temperature environment to generate SO2. The mixed gas of SO2, H2O, O2 and I2 in the HIx purification and concentration tower leaves the top of the tower and returns to the Bunsen reaction separation tower. However, in the invention patent, the gas from the H2SO4 decomposition section is passed into the HIx phase purification section. The conversion rate of the above reaction is low, and the time required for the by-product to be completely converted into SO2 is long, which seriously limits the efficiency of the whole process. At present, the material flow rate of the H2SO4 section can only be reduced to extend the reaction time, so as to react the S element and H2S to generate SO2 as much as possible. Patent CN116143079B discloses a method and device for purifying the HIx phase of thermochemical sulfur-iodine cycle hydrogen production. Excessive barium compounds are sent to the HIx phase purification tower 6 to react with impurity sulfuric acid to generate BaSO4 precipitation, thereby achieving the purpose of purifying the HIx solution; the generated BaSO4 is decomposed in a high temperature environment to generate BaO, O2 and SO2, thereby realizing the recycling of barium. At the same time, the generated high-temperature O2 and SO2 gases enter the sulfuric acid decomposition tower 4 to recover energy. However, the patent introduces other substances into the system. In order to enable sulfate to fully form a precipitate, excessive barium ions need to be added, resulting in excessive consumption of hydroiodic acid, and the formed barium iodide is difficult to handle. Patent CN101830443B discloses a process for purifying the sulfuric acid phase and the hydroiodic acid phase in the iodine-sulfur cycle. The invention provides a two-phase purification process using a mixture of oxygen and inert gas as an active purge gas. For HIx phase purification, the active purge gas can inhibit the generation of S and H2S, thereby increasing the selectivity of H2SO4 to SO2. However, this method cannot ensure that all H2SO4 is converted into SO2. Some H2SO4 will still be reduced to S and H2S. The S element will be deposited on the surface of the pipeline or reactor and form sulfide iodide, which will block the pipeline. The sulfur content in the Bunsen reaction gradually decreases, and the device cannot operate continuously. H2S enters the hydroiodic acid decomposition unit, which seriously reduces the service life of the catalyst. The results of the literature Simulation study about the effect of pressure on purification of H2SO4 and HIx phases in theiodine–sulfur hydrogen production cycle (DOI: 10.1016 / j.ijhydene.2012.05.070) show that reducing the system pressure can improve the conversion rate of sulfuric acid and adjust the selectivity of the reaction.Below 0.7 atm, the main reaction is the generation of H2S. This may be because the solubility of H2S is lower than that of SO2, making it easier for H2S to transfer from the liquid phase to the gas phase, thus promoting the generation of H2S.

[0005] Since the separated HIx solution contains H2SO4 impurities, and the impurities contained in it will have a great impact on the subsequent processes, it is urgent to develop a new method for purifying the HIx solution. Summary of the invention

[0006] The purpose of the present disclosure is to provide a HIx phase purification process and system for thermochemical sulfur-iodine cycle hydrogen production, so as to avoid the generation of S by HIx phase purification and blockage of pipelines, solve the problem that H2SO4 present in the HI feed flow may cause poisoning of HI decomposition catalyst, and ensure long-term continuous operation of the system.

[0007] The technical solution of the present disclosure is as follows: On the one hand, the present disclosure provides a HIx phase purification process for thermochemical sulfur-iodine cycle hydrogen production, wherein the thermochemical sulfur-iodine cycle hydrogen production includes a Bunsen reaction, a sulfuric acid decomposition reaction and a HI decomposition reaction. After the Bunsen reaction, the reaction liquid is separated into two phases to obtain a lower HIx phase, and the HIx phase is introduced into a HIx phase purification tower 6. The HIx phase reduces the temperature from 110-150° C. to 20-40° C. within 5-20 minutes, and the pressure inside the tower is reduced to 0.1-0.4 atm. Subsequently, the temperature inside the tower is increased from 20-40° C. to 110-150° C. again within 5-10 minutes, and the pressure is maintained at 0.1-0.4 atm. The generated hydrogen sulfide is precipitated from the HIx phase, and the precipitated hydrogen sulfide gas is introduced into a hydrogen sulfide combustion tower 2. The hydrogen sulfide gas is burned with oxygen generated by the decomposition of sulfuric acid to generate sulfur dioxide, and the sulfur dioxide is used as a raw material for the Bunsen reaction. The purified HIx phase is subjected to a HI decomposition reaction to obtain hydrogen.

[0008] Preferably, the HIx phase liquid produced by the Bunsen reaction is passed through the HIx buffer tank 5 into the HIx phase purification tower 6, first cooled by the cooling circulating water in the jacket, and the pressure inside the tower is reduced by a vacuum pump, and then heated by the water vapor generated by the sulfuric acid multiple-effect evaporator.

[0009] Preferably, the hydrogen sulfide gas generated in the HIx phase purification tower 6 is introduced into the hydrogen sulfide combustion tower 2, while the temperature in the HIx phase purification tower 6 is maintained at 110-150° C. and the pressure is increased to normal pressure.

[0010] Preferably, the hydrogen sulfide gas precipitated in the HIx phase purification tower 6 and the sulfur dioxide and oxygen separated by the gas-liquid separator 3 are burned in the hydrogen sulfide combustion tower 2 through nozzle high-speed jets.

[0011] On the other hand, the present disclosure provides a HIx phase purification system for thermochemical sulfur-iodine cycle hydrogen production, the system implementing the above-mentioned purification process, including a Bunsen reaction tower 1 connected to a HIx buffer tank 5 and a sulfuric acid multiple-effect evaporator 8 respectively, the HIx buffer tank 5 is connected to a HIx phase purification tower 6, the sulfuric acid multiple-effect evaporator 8 is connected to a sulfuric acid decomposition tower 4 and a gas-liquid separator 3 in sequence, and the gas-liquid separator 3 and the HIx phase purification tower 6 are respectively connected to a hydrogen sulfide combustion tower 2.

[0012] Preferably, the HIx phase purification tower 6 is a sandwich tank, and the shell of the HIx phase purification tower 6 has at least one liquid phase inlet, one gas phase inlet, one liquid phase outlet, and one gas phase outlet; one liquid phase inlet inside the shell is used to receive the HIx phase liquid obtained by the Bunsen reaction upstream of the thermochemical sulfur-iodine cycle, and one gas phase inlet is used to receive the water vapor generated by the sulfuric acid multiple-effect evaporator 8; one liquid phase outlet is used to discharge the purified HIx phase solution to the buffer tank before the HI distillation tower 9, and one gas phase outlet is used to discharge the hydrogen sulfide gas generated by the side reaction; the jacket of the HIx phase purification tower 6 has at least one liquid phase inlet, one gas phase inlet, and two liquid phase outlets; one liquid phase inlet in the jacket is used to receive cooling water for adjusting the HIx phase temperature inside the shell, one gas phase inlet is used to receive the water vapor generated by the sulfuric acid multiple-effect evaporator 8 to adjust the internal pressure of the shell, one liquid phase outlet is used to reflux the solution generated after heat exchange with water vapor to the HIx phase storage tank, and one liquid phase outlet is used to discharge the cooling water.

[0013] Preferably, the hydrogen sulfide combustion tower 2 has at least two gas phase inlets and one gas phase outlet, one gas phase inlet is used to receive the hydrogen sulfide gas produced by HIx phase purification, and one gas phase inlet is used to receive the sulfur dioxide and oxygen remaining after the product of the sulfuric acid decomposition tower 4 is cooled, and the gas phase outlet is used to discharge the sulfur dioxide, oxygen and water vapor mixed gas produced by combustion.

[0014] Preferably, the sulfuric acid multiple-effect evaporator 8 has at least one liquid phase inlet, one liquid phase outlet, and one gas phase outlet, wherein the liquid phase inlet is a purified low-concentration sulfuric acid solution, the liquid phase outlet is a high-concentration sulfuric acid solution, and the gas phase outlet at the top is water vapor, which is introduced into the HIx phase purification tower 6 as a heat source for regulating the temperature of the solution in the tower.

[0015] Preferably, the inlet of the sulfuric acid decomposition tower 4 is a high-concentration sulfuric acid solution concentrated by a sulfuric acid multiple-effect evaporator 8, and the outlet is sulfur dioxide, sulfur trioxide, water and oxygen produced after high-temperature decomposition, wherein sulfur trioxide and water can react to generate sulfuric acid, which is then separated by a gas-liquid separator 3, and the separated sulfur dioxide and oxygen are introduced into a hydrogen sulfide burner, and oxygen is used as a combustion aid to burn with hydrogen sulfide to generate sulfur dioxide.

[0016] Preferably, the liquid phase reaction raw material in the Bunsen reaction tower 1 comes from the solution at the bottom outlet of the HI distillation tower 9, and the gas phase reaction raw material comes from the sulfuric acid decomposition tower 4. The Bunsen reaction material is introduced into the reactor through a nozzle high-speed jet to complete the Bunsen reaction. The generated sulfuric acid and hydroiodic acid are allowed to stand for stratification. The separated sulfuric acid phase is introduced into the sulfuric acid phase purification tower, and the HIx phase is introduced into the HIx phase purification tower 6 after passing through the HIx phase buffer tank 5; the temperature of the HIx phase solution is first reduced from 110-150° C. to 20-40° C., and the pressure is reduced to 0.1-0.4 atm. The temperature is adjusted by the flow rate of cooling water in the purification tower jacket, and the pressure is discharged from the tower by a vacuum pump. The pressure is then maintained at 0.1-0.4 atm, and the temperature is raised to 110-150°C by the water vapor generated by the sulfuric acid multiple-effect evaporator 8; the impurity sulfuric acid in the HIx phase undergoes a side reaction under low pressure and high temperature to produce hydrogen sulfide, and the generated hydrogen sulfide gas is sent to the hydrogen sulfide combustion tower 2, and the water vapor generated by the sulfuric acid multiple-effect evaporator 8 is used as a gas source to adjust the pressure of the HIx phase purification tower 6, and the pressure is increased to normal pressure. Subsequently, the liquid in the HIx phase purification tower 6 is transported to the HI distillation tower 9; the purified HIx phase solution, the system's supplementary water, and the HI, I2, and H2O mixed solution remaining after HI decomposition are passed to the HI distillation tower 9 , the upper part of the HI distillation tower 9 is a HI solution without I2, and the lower part of the tower is a HIx phase mixture containing HI, I2, and H2O; the HI solution in the upper part of the tower is passed into the heat exchanger tube for heat exchange, and the gas formed after heating is passed into the HI decomposition tower, and the mixed gas of I2, H2, HI, and H2O in the decomposition tower is then passed to the steam-water separator, and H2 flows out from the top of the steam-water separator, and the remaining HIx phase liquid refluxes from the bottom of the tower; the sulfuric acid phase flows into the sulfuric acid phase purification tower after the two phases are separated, and the HI impurities in the sulfuric acid phase are removed by the reverse reaction of the Bunsen reaction; the purified low-concentration sulfuric acid solution is passed into the sulfuric acid multiple-effect evaporator 8, and a high-concentration sulfuric acid solution is obtained after multiple-effect concentration, and the produced Water vapor is used as a heat source for the HIx phase purification tower 6 to change from low temperature and low pressure to high temperature and low pressure; a high-concentration sulfuric acid solution is used as a raw material for the sulfuric acid decomposition tower 4, and a decomposition reaction is carried out in the sulfuric acid decomposition tower 4 with high-temperature helium as a heat source, and the product is introduced into the gas-liquid separator 3, and the separated sulfur dioxide and oxygen are introduced into the hydrogen sulfide combustion tower 2; oxygen and hydrogen sulfide produced by the HIx phase purification tower 6 generate sulfur dioxide under ignition conditions, and the sulfur dioxide, I2 generated by the sulfuric acid phase purification tower, and the bottom liquid of the HI distillation tower 9 are used as raw materials for the Bunsen reaction, and are introduced into the Bunsen reaction tower 1 for the next cycle reaction, and oxygen is discharged from the top of the Bunsen reactor 1.

[0017] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present disclosure.

[0018] The above technical solution has the following advantages or beneficial effects: The present disclosure innovatively adopts a side reaction path control strategy, and by precisely controlling the reaction conditions, promotes the efficient reaction of sulfuric acid impurities with hydroiodic acid solution to generate hydrogen sulfide and water, ensuring that the main byproduct is hydrogen sulfide (H2S), rather than sulfur (S). Subsequently, the generated hydrogen sulfide and the oxygen released during the decomposition of sulfuric acid are burned in an oxygen-rich environment and converted into sulfur dioxide and water vapor, and the product is refluxed into the Bunsen reaction tower for further circulation. This method not only completely converts sulfuric acid impurities in the HIx phase into sulfur dioxide, effectively avoids potential harm to the hydroiodic acid decomposition catalyst, and avoids the problem of sulfur element deposition in the pipeline system, but also the only raw material introduced into the system during the whole process is water, and no additional impurities need to be introduced into the system, and no additional energy consumption is required, thereby optimizing the system thermal management, significantly reducing the complexity and maintenance cost of the system operation, and is conducive to improving the overall system The convenience of operation and operational stability, significantly improving the thermal efficiency and energy utilization of the overall system. This innovative technology not only optimizes resource utilization efficiency, but also greatly enhances the potential for coupling with advanced energy systems such as high-temperature gas-cooled reactors, opens up new avenues for large-scale production of green hydrogen, and demonstrates broad application prospects and industrial value. Of course, any technical solution disclosed in the present invention does not necessarily achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the drawings required for use in the embodiments or the prior art description are briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on the provided drawings without creative work.

[0020] Figure 1 is a schematic diagram of the system disclosed in the present invention; Figure 2 It is a schematic diagram of the temperature and pressure reduction process of HIx phase purification disclosed in the present invention; Figure 3 It is a schematic diagram of the temperature increase and pressure maintenance process of HIx phase purification disclosed in the present invention; Among them: Bunsen reaction tower 1, hydrogen sulfide combustion tower 2, gas-liquid separator 3, sulfuric acid decomposition tower 4, HIx phase buffer tank 5, HIx phase purification tower 6, H2SO4 storage tank 7, sulfuric acid multi-effect evaporator 8, HI distillation tower 9. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present disclosure are clearly and completely described below in conjunction with the drawings of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure and are intended to be used to explain the inventive concept. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0022] The orientation or position relationship indicated by the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", "center", "longitudinal", "lateral", "length direction", "width direction", "thickness direction", etc. used in the description are based on the orientation or position relationship shown in the drawings and are only for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation.

[0023] The terms "first", "second", etc. used in the description are only used for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features specified as "first" or "second" may explicitly or implicitly include one or more of the features. The term "plurality" means two or more, unless otherwise clearly and specifically specified.

[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 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 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 disclosure. In this specification, the schematic representations of the above terms do 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] The present disclosure proposes a HIx phase purification process and system for thermochemical sulfur-iodine cycle hydrogen production, wherein the thermochemical sulfur-iodine cycle water decomposition hydrogen production has been reported in many literatures, and the technical solution provided by the present disclosure particularly relates to some links in the whole process of thermochemical sulfur-iodine cycle water decomposition hydrogen production, and more precisely, belongs to the HIx phase purification process. The present disclosure does not specifically limit other links in the thermochemical sulfur-iodine cycle water decomposition hydrogen production, such as the Bunsen reaction and two-phase stratification, the purification and concentration process of the sulfuric acid phase, the HI decomposition process, etc.; the technical solution of the present disclosure can be combined with any existing thermochemical sulfur-iodine cycle water decomposition hydrogen production whole process to replace the HIx phase purification process in the existing process.

[0028] like Figure 1 As shown, a system for thermochemical sulfur-iodine cycle hydrogen production HIx phase purification provided by a specific embodiment of the present disclosure mainly includes a Bunsen reaction tower 1, a hydrogen sulfide combustion tower 2, a gas-liquid separator 3, a sulfuric acid decomposition tower 4, a HIx buffer tank 5, a HIx phase purification tower 6, a sulfuric acid storage tank 7, a sulfuric acid multiple-effect evaporator 8, and a HI distillation tower 9.

[0029] The HIx phase purification tower 6 is a sandwich tank, and the shell of the HIx phase purification tower 6 has at least one liquid phase inlet, one gas phase inlet, one liquid phase outlet, and one gas phase outlet; one liquid phase inlet inside the shell is used to receive the HIx phase liquid obtained by the Bunsen reaction upstream of the thermochemical sulfur-iodine cycle, and one gas phase inlet is used to receive the water vapor generated by the sulfuric acid multiple-effect evaporator 8; one liquid phase outlet is used to discharge the purified HIx phase solution to the buffer tank in front of the HI distillation tower 9, and one gas phase outlet is used to discharge the H2S gas generated by the side reaction; the jacket of the HIx phase purification tower 6 has at least one liquid phase inlet, one gas phase inlet, and two liquid phase outlets; one liquid phase inlet in the jacket is used to receive cooling water for adjusting the HIx phase temperature inside the shell, one gas phase inlet is used to receive the water vapor generated by the sulfuric acid multiple-effect evaporator 8 to adjust the internal pressure of the shell, one liquid phase outlet is used to reflux the solution generated after heat exchange with water vapor to the HIx phase storage tank, and one liquid phase outlet is used to discharge the cooling water.

[0030] The hydrogen sulfide combustion tower 2 has at least two gas phase inlets and one gas phase outlet, one gas phase inlet is used to receive the H2S gas produced by HIx phase purification, and the other gas phase inlet is used to receive the SO2 and O2 remaining after the product of the sulfuric acid decomposition tower 4 is cooled, and the gas phase outlet is used to discharge the mixed gas of SO2, O2 and water vapor produced by combustion.

[0031] The sulfuric acid multiple-effect evaporator 8 has at least one liquid phase inlet, one liquid phase outlet, and one gas phase outlet. The liquid phase inlet is a purified low-concentration sulfuric acid solution, the liquid phase outlet is a high-concentration sulfuric acid solution, and the gas phase outlet at the top is water vapor, which is introduced into the HIx phase purification tower 6 as a heat source for regulating the temperature of the solution in the tower.

[0032] The sulfuric acid decomposition tower 4 has an inlet of a high-concentration sulfuric acid solution concentrated by a sulfuric acid multiple-effect evaporator 8, and an outlet of SO2, SO3, H2O, and O2 produced after high-temperature decomposition, wherein SO3 and H2O can react to generate H2SO4. After passing through a gas-liquid separator 3, SO2 and O2 are introduced into a hydrogen sulfide burner, and O2, as an oxidant, burns with H2S to generate SO2.

[0033] In the full-process system disclosed in the present invention, the H2S produced by the HIx phase purification tower 6 and the O2 produced by the sulfuric acid decomposition tower 4 are in the hydrogen sulfide combustion tower 2, and the H2S and O2 generate SO2 and H2O under ignition conditions. The SO2, H2O and remaining O2 in the hydrogen sulfide combustion tower 2 are combined and sent to the Bunsen reaction tower 1.

[0034] like Figure 2-Figure 3 As shown, a specific embodiment of the present disclosure provides a HIx phase purification process and system for thermochemical sulfur-iodine cycle hydrogen production, which can be implemented according to the following steps: (1) Figure 2 As shown, the HIx phase liquid produced by the Bunsen reaction is passed through the HIx buffer tank 5 into the HIx phase purification tower 6, and cooling water is passed into the jacket of the HIx phase purification tower 6. The temperature of the liquid in the tower is reduced from 110-150°C to 20-40°C within 5-20 minutes by the cooling circulating water in the jacket. At the same time, the pressure inside the tower is reduced to 0.1-0.4atm using a vacuum pump. This process can suppress the side reaction of generating sulfur or hydrogen sulfide. Subsequently, as Figure 3As shown, the water vapor generated by the sulfuric acid multiple-effect evaporator raises the temperature in the tower from 20-40°C to 110-150°C in 5-10 minutes. At the same time, the pressure is maintained at 0.1-0.4atm, thereby promoting the following side reaction between sulfuric acid and hydroiodic acid: H2SO4 + 8HI = H2S + 4I2 + 4H2O, and inhibiting the following side reaction between sulfuric acid and hydroiodic acid: H2SO4 + 6HI = S + 3I2 +4H2O; (2) the H2S produced in the HIx phase purification tower 6 is passed into the hydrogen sulfide combustion tower 2, the temperature in the HIx phase purification tower 6 is maintained at 110-150°C, and the pressure is increased from 0.1-0.4atm to normal pressure to prevent the negative pressure environment in the tower from causing the solution in the HI distillation tower 9 to reflux; (3) the H2S produced in the HIx phase purification tower 6 and the SO2 and O2 gases in the gas-liquid separator 3 are burned in the hydrogen sulfide combustion tower 2 through a nozzle high-speed jet, and the following reaction occurs: 2H2S + 3O2 = 2SO2 + 2H2O, and the SO2, H2O and the remaining O2 in the hydrogen sulfide combustion tower 2 are returned to the Bunsen reaction tower 1. The present disclosure establishes a cycle of sulfur elements, and the purpose of purifying the HIx phase is achieved without adding other substances through the H2S produced by the side reaction and the O2 produced by the decomposition reaction of sulfuric acid, thereby avoiding the risk of subsequent poisoning of the HI decomposition catalyst S.

[0035] As a typical application case of the present disclosure, the full process of thermochemical sulfur-iodine cycle hydrogen production using the purification process of the present disclosure is as follows: the liquid phase reaction raw material in the Bunsen reaction tower 1 comes from the solution at the bottom outlet of the HI distillation tower 9, and the gas phase reaction raw material comes from the sulfuric acid decomposition tower 4. The Bunsen reaction material is injected into the reactor through a nozzle at a high speed to complete the Bunsen reaction, and the generated sulfuric acid and hydroiodic acid are allowed to stand and stratify. The separated sulfuric acid phase is passed into the sulfuric acid phase purification tower through the side outlet of the tower, and the HIx phase flows from the bottom of the tower through the HIx phase buffer tank 5 into the HIx phase purification tower 6. The operating environment of the Bunsen reaction tower 1 is a temperature of 70°C-150°C and a pressure of 0-5atm, and the reaction is a spontaneous exothermic reaction. The HIx phase solution from the HIx phase buffer tank 5 is treated according to the HIx phase purification method described above in the present disclosure, wherein the HIx phase temperature is first reduced from 110-150°C to 20-40°C, and the pressure is reduced to 0.1-0.4atm, the temperature is adjusted by the flow rate of cooling water in the purification tower jacket, and the pressure is discharged by a vacuum pump to discharge the gas in the tower so that the inside of the tower is a low-pressure environment. Subsequently, the pressure is maintained at 0.1-0.4atm, and the temperature is raised to 110-150°C by the water vapor generated by the sulfuric acid multiple-effect evaporator 8. The impurity H2SO4 in the HIx phase undergoes a side reaction with the product being H2S under low pressure and high temperature. The generated H2S gas is sent to the hydrogen sulfide combustion tower 2, and the water vapor generated by the sulfuric acid multiple-effect evaporator 8 is used as a gas source to adjust the pressure of the HIx phase purification tower 6, and the pressure is raised to normal pressure. Subsequently, the liquid in the HIx phase purification tower 6 is transported to the HI distillation tower 9.

[0036] The purified HIx phase solution, the system's make-up water, and the remaining HI, I2, H2O mixed solution after HI decomposition flow into the HI distillation tower 9. The upper part of the HI distillation tower 9 is a HI solution without I2, and the lower part of the tower is a HIx phase mixture containing HI, I2, and H2O. The HI solution in the upper part of the tower flows into the heat exchanger tube for heat exchange, and the gas formed after heating is passed into the HI decomposition tower. The I2, H2, HI, H2O mixed gas flows into the steam-water separator, and H2 flows out from the top of the steam-water separator. The remaining HIx phase liquid refluxes from the bottom of the tower and circulates in the decomposition unit.

[0037] After the two phases are separated, the sulfuric acid phase flows to the sulfuric acid phase purification tower. When the temperature of the sulfuric acid phase purification tower is 110-150°C and the pressure is normal pressure, the HI impurities in the sulfuric acid phase are removed by the reverse reaction of the Bunsen reaction 2HI + H2SO4 = SO2 + I2 + 2H2O. The purified low-concentration sulfuric acid solution is passed into the sulfuric acid multiple-effect evaporator 8, and a high-concentration sulfuric acid solution is obtained after multiple-effect concentration. The generated water vapor is used as a heat source for the HIx phase purification tower 6 to change from low temperature and low pressure to high temperature and low pressure, thereby improving the thermal efficiency of the entire system. The high-concentration sulfuric acid solution is used as the raw material of the sulfuric acid decomposition tower 4, and the high-temperature helium is used as the heat source. The decomposition reaction is carried out in the sulfuric acid decomposition tower 4, and the products SO2, SO3, O2, and H2O flow into the gas-liquid separator 3. At the same time, SO3 +H2O = H2SO4 inside the gas-liquid separator 3 generates sulfuric acid solution, and the solution flows into the sulfuric acid storage tank 7 from the bottom of the reactor, and the SO2 and O2 at the top of the reactor flow into the hydrogen sulfide combustion tower 2. O2 and H2S produced by the HIx phase purification tower 6 generate SO2, SO2, and O2 under ignition conditions, and the reaction formula is 2H2S +3O2 = 2SO2 + 2H2O. It and the SO2, I2 generated by the sulfuric acid phase purification tower, and the bottom liquid of the HI distillation tower 9 are used as raw materials for the Bunsen reaction and are introduced into the Bunsen reaction tower 1 for the next cycle reaction. O2 is discharged from the top of the Bunsen reactor 1. Example 1

[0038] The initial temperature in Bunsen reaction tower 1 is 120℃, 5atm, and the materials in the tower are 3.7mol SO2, 34.7mol I2, 10mol HI, and 53.3mol water. After the reaction, the SO2 conversion rate reaches 100%. The two phases are allowed to stand for 30 minutes and separated into sulfuric acid phase and HIx phase.

[0039] The sulfuric acid phase is sent to the sulfuric acid phase purification tower, and its composition is H2SO4 45.6 mol / kg, HI 8.0 mol / kg, I2 3mol / kg, H2O 40.0mol / kg. After the sulfuric acid phase is purified by Bunsen reverse reaction, the concentration of dilute sulfuric acid is 52.2 mol / kg, and the mass fraction is 46.7%. It is then passed to the sulfuric acid multi-effect evaporator 8 for concentration, and the concentration of concentrated sulfuric acid is 81.6 mol / kg, and the mass fraction is 96%. The concentrated sulfuric acid is passed into the sulfuric acid decomposition tower 4, and a decomposition reaction occurs under the action of a catalyst at 800°C, H2SO4 = SO3 +H2O, 2SO3 = 2SO2 + O2, and the decomposition rate is more than 95%. The decomposition produces a mixed gas of SO2, H2O and O2 as well as some undecomposed SO3, which leaves the sulfuric acid decomposition tower 4 and passes to the gas-liquid separator 3. SO3 and H2O react in the gas-liquid separator 3 to generate H2SO4, SO3+ H2O = H2SO4. The H2SO4 solution at the bottom of the reactor flows back to the sulfuric acid storage tank 7. SO2 and O2 at the top of the gas-liquid separator 3 flow to the hydrogen sulfide combustion tower 2, and the combustion reaction 2H2S + 3O2 = 2SO2 + 2H2O. The SO2 generated by the reaction flows back to the Bunsen reaction tower 1 to participate in the next cycle.

[0040] The HIx phase is sent to the HIx phase purification tower 6, which has a composition of H2SO4 0.24 mol / kg, HI 16.0 mol / kg, I2 26.3 mol / kg, and H2O 6.4 mol / kg. The temperature in the tank is reduced from 120°C, 5 atm to 30°C, 0.2 atm by adjusting the flow rate of cooling water in the jacket of the HIx phase purification tower 6. The temperature reduction and pressure reduction process can prevent sulfuric acid and hydroiodic acid from having a side reaction of generating S elemental substance, H2SO4 + 6HI = S + 3I2 + 4H2O. Subsequently, the water vapor flow rate at the top of the sulfuric acid multi-effect evaporator 8 is adjusted to increase the temperature in the HIx phase purification tower 6 from 30°C to 130°C, and the pressure is maintained at 0.2 atm. This process causes sulfuric acid and hydroiodic acid to react to generate H2S, H2SO4 + 8HI = H2S + 4I2 + 4H2O. The H2S at the top of the HIx phase purification tower 6 is passed to the hydrogen sulfide combustion tower 2 for combustion to generate SO2, 2H2S + 3O2 = 2SO2 + 2H2O. The HIx phase solution purified in the HIx phase purification tower 6 is decomposed with the system supplementary water and the HI separated by the steam-water separator to form a mixed solution of HI, I2, and H2O. The HI distillation tower 9 separates the HI solution. The bottom of the tower is a hydroiodic acid solution containing I2, and the top of the tower is a 120°C HI solution. The HI solution at the top of the tower flows into the heat exchanger tube for heat exchange. The temperature of the heated HI gas is 280°C, and then it is passed into the HI decomposition tower. The temperature in the HI decomposition tower is 500°C, 2HI = H2 + I2, and the HI conversion rate is 20%. The mixed gas of HI, I2, H2 and H2O flows into the steam-water separator to reduce the temperature to 60°C, H2 flows out from the top of the steam-water separator, and the remaining HIx phase liquid refluxes from the bottom of the tower to the buffer tank after the HIx phase purification tower 6, and circulates internally in the HI decomposition unit.

[0041] Although the embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and cannot be understood as limiting the present disclosure. Without departing from the spirit and scope of the present disclosure, the present disclosure may also have various changes and improvements, which all fall within the scope of the present disclosure claimed for protection.

Claims

1. A HIx phase purification process for thermochemical sulfur-iodine cycle hydrogen production, wherein the thermochemical sulfur-iodine cycle hydrogen production includes a Bunsen reaction, a sulfuric acid decomposition reaction, and a HI decomposition reaction, characterized in that: After the Bunsen reaction, the reaction liquid is separated into two phases to obtain a lower HIx phase, and the HIx phase is introduced into a HIx phase purification tower (6). The temperature of the HIx phase is reduced from 110-150° C. to 20-40° C. within 5-20 minutes, and the pressure inside the tower is reduced to 0.1-0.4 atm. Subsequently, the temperature inside the tower is increased from 20-40° C. to 110-150° C. within 5-10 minutes, and the pressure is maintained at 0.1-0.4 atm. The generated hydrogen sulfide is precipitated from the HIx phase, and the precipitated hydrogen sulfide gas is introduced into a hydrogen sulfide combustion tower (2). The hydrogen sulfide gas is decomposed with sulfuric acid to generate oxygen to generate sulfur dioxide, and the sulfur dioxide is used as a raw material for the Bunsen reaction. The purified HIx phase is subjected to a HI decomposition reaction to obtain hydrogen.

2. The HIx phase purification process for thermochemical sulfur-iodine cycle hydrogen production according to claim 1, characterized in that: The HIx phase liquid produced by the Bunsen reaction is passed through the HIx buffer tank (5) into the HIx phase purification tower (6), where it is first cooled by the cooling circulating water in the jacket, and the pressure inside the tower is reduced by a vacuum pump, and then heated by the water vapor produced by the sulfuric acid multi-effect evaporator.

3. The HIx phase purification process for thermochemical sulfur-iodine cycle hydrogen production according to claim 1, characterized in that: The hydrogen sulfide gas generated in the HIx phase purification tower (6) is introduced into the hydrogen sulfide combustion tower (2), while the temperature in the HIx phase purification tower (6) is maintained at 110-150° C. and the pressure is increased to normal pressure.

4. The HIx phase purification process for thermochemical sulfur-iodine cycle hydrogen production according to claim 1, characterized in that: The hydrogen sulfide gas precipitated in the HIx phase purification tower (6) and the sulfur dioxide and oxygen separated by the gas-liquid separator (3) are burned in the hydrogen sulfide combustion tower (2) through a nozzle high-speed jet.

5. A HIx phase purification system for thermochemical sulfur-iodine cycle hydrogen production, the purification system implementing the purification process according to any one of claims 1 to 4, comprising a Bunsen reaction tower (1) connected to a HIx buffer tank (5) and a sulfuric acid multiple-effect evaporator (8), respectively, the HIx buffer tank (5) connected to a HIx phase purification tower (6), the sulfuric acid multiple-effect evaporator (8) connected in sequence to a sulfuric acid decomposition tower (4) and a gas-liquid separator (3), characterized in that: The gas-liquid separator (3) and the HIx phase purification tower (6) are respectively connected to the hydrogen sulfide combustion tower (2).

6. The HIx phase purification system for thermochemical sulfur-iodine cycle hydrogen production according to claim 5, characterized in that: The HIx phase purification tower (6) is a sandwich tank, and the shell of the HIx phase purification tower (6) has at least one liquid phase inlet, one gas phase inlet, one liquid phase outlet, and one gas phase outlet; the liquid phase inlet inside the shell is used to receive the HIx phase liquid obtained by the Bunsen reaction upstream of the thermochemical sulfur-iodine cycle, and the gas phase inlet is used to receive the water vapor generated by the sulfuric acid multi-effect evaporator (8); the liquid phase outlet is used to discharge the purified HIx phase solution to the buffer tank before the HI distillation tower (9), and the gas phase outlet is used to discharge the hydrogen sulfide gas generated by the side reaction; The jacket of the HIx phase purification tower (6) has at least one liquid phase inlet, one gas phase inlet, and two liquid phase outlets; A liquid phase inlet in the jacket is used to receive cooling water for adjusting the temperature of the HIx phase inside the shell, a gas phase inlet is used to receive water vapor generated by the sulfuric acid multi-effect evaporator (8) to adjust the internal pressure of the shell, a liquid phase outlet is used to return the solution generated after the water vapor heat exchange to the HIx phase storage tank, and a liquid phase outlet is used to discharge the cooling water.

7. The HIx phase purification system for thermochemical sulfur-iodine cycle hydrogen production according to claim 5, characterized in that: The hydrogen sulfide combustion tower (2) has at least two gas phase inlets and one gas phase outlet, one gas phase inlet is used to receive the hydrogen sulfide gas generated by HIx phase purification, one gas phase inlet is used to receive the sulfur dioxide and oxygen remaining after the product of the sulfuric acid decomposition tower (4) is cooled, and the gas phase outlet is used to discharge the sulfur dioxide, oxygen and water vapor mixed gas generated by the combustion.

8. The HIx phase purification system for thermochemical sulfur-iodine cycle hydrogen production according to claim 5, characterized in that: The sulfuric acid multiple-effect evaporator (8) has at least one liquid phase inlet, one liquid phase outlet, and one gas phase outlet. The liquid phase inlet is a purified low-concentration sulfuric acid solution, the liquid phase outlet is a high-concentration sulfuric acid solution, and the gas phase outlet at the top is water vapor, which is introduced into the HIx phase purification tower (6) as a heat source for regulating the temperature of the solution in the tower.

9. The HIx phase purification system for thermochemical sulfur-iodine cycle hydrogen production according to claim 5, characterized in that: The inlet of the sulfuric acid decomposition tower (4) is a high-concentration sulfuric acid solution concentrated by the sulfuric acid multiple-effect evaporator (8), and the outlet is sulfur dioxide, sulfur trioxide, water and oxygen generated after high-temperature decomposition, wherein sulfur trioxide and water react to generate sulfuric acid, which is then separated by the gas-liquid separator (3). The separated sulfur dioxide and oxygen are introduced into the hydrogen sulfide burner, and the oxygen is used as a combustion aid to burn with hydrogen sulfide to generate sulfur dioxide.

10. The HIx phase purification system for thermochemical sulfur-iodine cycle hydrogen production according to claim 5, characterized in that: The liquid phase reaction raw material in the Bunsen reaction tower (1) comes from the solution at the bottom outlet of the HI distillation tower (9), and the gas phase reaction raw material comes from the sulfuric acid decomposition tower (4). The Bunsen reaction material is introduced into the reactor through a nozzle high-speed jet flow to complete the Bunsen reaction. The generated sulfuric acid and hydroiodic acid are allowed to stand for stratification. The separated sulfuric acid phase is introduced into the sulfuric acid phase purification tower. The HIx phase is introduced into the HIx phase purification tower (6) after passing through the HIx phase buffer tank (5). The temperature of the HIx phase solution is first reduced from 110-150° C. to 20-40° C., and the pressure is reduced to 0.1-0.4 atm. The temperature is adjusted by the flow rate of cooling water in the purification tower jacket, and the pressure is adjusted by exhausting the gas in the tower by a vacuum pump. The pressure is maintained at 0.1-0.4 atm, and the temperature is raised to 110-150° C. by water vapor generated by the sulfuric acid multiple-effect evaporator (8); the impurity sulfuric acid in the HIx phase undergoes a side reaction under low pressure and high temperature to produce hydrogen sulfide, and the generated hydrogen sulfide gas is sent to the hydrogen sulfide combustion tower (2); the water vapor generated by the sulfuric acid multiple-effect evaporator (8) is used as a gas source for adjusting the pressure of the HIx phase purification tower (6), and the pressure is raised to normal pressure. Subsequently, the liquid in the HIx phase purification tower (6) is transported to the HI distillation tower (9); the purified HIx phase solution, the system's supplementary water, and the HI, I2, and H2O mixed solution remaining after the HI decomposition are introduced into the HI distillation tower (9). The upper part of the HI distillation tower (9) contains HI solution without I2, and the lower part of the tower contains HIx phase mixture containing HI, I2, and H2O; the HI solution in the upper part of the tower is passed into the heat exchanger tube for heat exchange, and the gas formed after heating is passed into the HI decomposition tower, and the mixed gas of I2, H2, HI, and H2O in the decomposition tower is then passed into the steam-water separator, and H2 flows out from the top of the steam-water separator, and the remaining HIx phase liquid refluxes from the bottom of the tower; the sulfuric acid phase flows into the sulfuric acid phase purification tower after the two phases are separated, and the HI impurities in the sulfuric acid phase are removed by the reverse reaction of the Bunsen reaction; the purified low-concentration sulfuric acid solution is passed into the sulfuric acid multi-effect evaporator (8), and a high-concentration sulfuric acid solution is obtained after multi-effect concentration, and the generated water vapor is used as HIx The phase purification tower (6) changes from a low temperature and low pressure to a high temperature and low pressure heat source; a high concentration sulfuric acid solution is used as a raw material of the sulfuric acid decomposition tower (4), and a decomposition reaction is carried out in the sulfuric acid decomposition tower (4) with high temperature helium as a heat source, and the product is introduced into a gas-liquid separator (3), and the separated sulfur dioxide and oxygen are introduced into a hydrogen sulfide combustion tower (2); oxygen and hydrogen sulfide generated by the HIx phase purification tower (6) generate sulfur dioxide under ignition conditions, and the sulfur dioxide, I2 generated by the sulfuric acid phase purification tower, and the bottom liquid of the HI distillation tower (9) are used as raw materials for the Bunsen reaction and introduced into the Bunsen reaction tower (1) for the next cycle reaction, and oxygen is discharged from the top of the Bunsen reactor (1).

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