Process and system for separating and purifying hydrogen in sulfur-iodine circulating hydrogen production
By combining multi-stage heat recovery and pressurized cryogenics, the problem of low efficiency in hydrogen separation and purification in sulfur-iodine cycle hydrogen production was solved, achieving efficient hydrogen separation and purification and reducing energy consumption and operating costs.
Patent Information
- Application Number
- CN202511071545.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-01
- Publication Date
- 2025-12-23
AI Technical Summary
In the sulfur-iodine cycle hydrogen production process, the low efficiency of hydrogen separation and purification leads to insufficient decomposition rate of hydrogen iodide, affecting system balance and energy efficiency. Furthermore, existing technologies are unable to effectively recover undecomposed hydrogen iodide, which may result in excessive system energy consumption and material loss.
By employing a combination of multi-stage heat recovery and pressurized cryogenics, hydrogen iodide gas is catalytically decomposed, and multi-stage separation is achieved using multi-stage heat exchangers and gas-liquid separators, combined with water spray absorption, thus realizing the efficient separation and purification of hydrogen iodide and hydrogen.
It greatly reduces the total energy consumption of the system, achieves complete material recovery, prevents material loss, improves hydrogen purity and system energy efficiency, and reduces operating costs.
Smart Images
Figure CN121180947A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of sulfur-iodine cycle hydrogen production technology, specifically to a process and system for hydrogen separation and purification in sulfur-iodine cycle hydrogen production. Background Technology
[0002] Hydrogen, as an important clean energy source and chemical feedstock, has always attracted much attention regarding its production methods. Depending on its source, hydrogen can be categorized into gray hydrogen, blue hydrogen, and green hydrogen, corresponding to fossil fuels, industrial byproducts, and water, respectively. Utilizing renewable energy, specifically water, as a feedstock is currently the most promising hydrogen production method. Methods using water as a feedstock for hydrogen production can be further divided into water electrolysis, photocatalytic water splitting, pyrolysis, and thermochemical cycle water splitting. Thermochemical sulfur-iodine cycle hydrogen production is currently the most ideal and mature method among thermochemical hydrogen production methods and has garnered widespread attention. Its main reactions are as follows:
[0003]
[0004] The three steps are the Bunsen reaction, sulfuric acid decomposition, and hydrogen iodide decomposition. Through material recycling, the three reactions can be combined, and the overall reaction is the decomposition of water into hydrogen and oxygen. Compared with other hydrogen production methods, thermochemical sulfur-iodine cycle hydrogen production has the following advantages: 1. The reaction conditions are milder than those for water pyrolysis; 2. It can be coupled with solar energy, nuclear energy, etc.; 3. It has scalability and can produce hydrogen on a large scale; 4. It has high overall energy efficiency.
[0005] In the sulfur-iodine cycle hydrogen production process, many challenges remain to be solved to achieve industrial-scale operation standards, one of which is the separation and purification of hydrogen. In the cycle, hydrogen is produced by the decomposition of hydrogen iodide. Because the decomposition efficiency of hydrogen iodide is affected by reaction equilibrium and reaction rate, its decomposition rate is very low even at high temperatures. Without a catalyst, the decomposition rate is generally no more than 1%, and even with a catalyst, it is less than 30%. This low decomposition rate results in a large amount of hydrogen iodide in the product, causing many problems for the decomposition of hydrogen iodide and hydrogen. Due to the characteristics of the sulfur-iodine cycle, theoretically, all materials except water do not need to be replenished. Therefore, undecomposed hydrogen iodide should be completely recovered and reintroduced into the system. Since the entire cycle only consumes water, the system needs continuous water replenishment. The molar amount of water consumed should equal the molar amount of hydrogen produced. Too much or too little water replenishment will disrupt the system equilibrium, making the cycle unsustainable. Therefore, the main challenges in separating hydrogen iodide and hydrogen are: 1. minimizing material loss during the separation process; 2. avoiding the addition of substances other than water during the separation process, with the maximum amount of water added matching the amount of hydrogen produced; 3. ensuring the purity of the separated hydrogen meets the requirements for downstream use; and 4. minimizing energy consumption during the separation process, otherwise reducing the overall energy efficiency of the system. Summary of the Invention
[0006] To address the problems mentioned in the background art, this application proposes a process and system for hydrogen separation and purification in sulfur-iodine cycle hydrogen production.
[0007] This application discloses a process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production, including:
[0008] S1: Preheat the purified aqueous hydrogen iodide gas to bring it close to its decomposition temperature;
[0009] S2: Catalytic decomposition of hydrogen iodide gas at temperatures of 400–600℃ and pressures of 1–10 atm. The decomposition results in iodine, hydrogen iodide, water, and hydrogen.
[0010] S3: The gas heat is recovered to step S1, and the gas is cooled. It continues to be cooled to 20-80°C by heat exchange between the hydrogen iodide liquid and the cooling medium in steps S4 and S5. Gas-liquid separation occurs, and the liquid obtained is hydrogen iodide, iodine and water, while the gas is hydrogen iodide and hydrogen. The liquid is sent back to the Bunsen tower, and the gas enters the next unit.
[0011] S4: Pressurize the gas to 20-50 atm, then cool it to 30-60°C, and separate the gas and liquid. The liquid obtained is hydrogen iodide, and the gas is hydrogen iodide and hydrogen. The hydrogen iodide liquid is first depressurized to atmospheric pressure, and then the cold energy is recovered to step S3. At the same time, the hydrogen iodide liquid is vaporized and sent back to step S1. The gas enters the next unit.
[0012] S5: Cool the gas to -30 to -50°C, separate the gas and liquid, and obtain the liquid as hydrogen iodide, the gas as hydrogen and hydrogen iodide. The hydrogen iodide liquid is first reduced to atmospheric pressure, and then the cold energy is recovered to step S3. At the same time, the hydrogen iodide liquid is vaporized and sent back to step S1, and the gas enters the next unit.
[0013] S6: Water sprays the gas, with the water coming from makeup water, resulting in an aqueous solution of hydrogen and hydrogen iodide. The aqueous solution of hydrogen iodide is then sent back to the Bunsen tower.
[0014] Furthermore, the purified aqueous hydrogen iodide gas has an iodine content of 0–10 wt.%, a water content of 0–40 wt.%, a temperature of 100–150 °C, and a pressure of 1–10 atm.
[0015] Furthermore, the catalytic decomposition of hydrogen iodide gas is carried out in a decomposition tower, which is equipped with a catalyst bed. The catalyst is one or more of Al2O3, zeolite, and activated carbon, and is loaded with one or more of Pt, Pd, and Ru.
[0016] Furthermore, the decomposition tower is made of metal or ceramic.
[0017] Furthermore, the decomposition tower is equipped with a heating device to maintain the catalyst bed temperature.
[0018] Furthermore, the decomposition rate of hydrogen iodide gas in step S2 is 5-30%.
[0019] Furthermore, the pressurization in step S4 is carried out by a compressor, specifically a diaphragm compressor, and the compressed gas is kept at a temperature above 100°C at the compressor outlet.
[0020] Furthermore, circulating cooling water is used as the cooling medium in steps S3 and S4.
[0021] Furthermore, the gas obtained from gas-liquid separation in step S4 contains 30-70% by volume hydrogen iodide.
[0022] This application also discloses a system for hydrogen separation and purification in a sulfur-iodine cycle hydrogen production process. The system includes a first buffer tank, a first heat exchanger, a decomposition tower, a second heat exchanger, a third heat exchanger, a first gas-liquid separator, a compressor, a fourth heat exchanger, a second gas-liquid separator, a cryogenic heat exchanger, a third gas-liquid separator, a spray tower, a hydrogen storage tank, and a second buffer tank. The first buffer tank, the first heat exchanger, and the decomposition tower are connected in sequence. The outlet of the decomposition tower is connected to the first heat exchanger. The first heat exchanger, the second heat exchanger, the third heat exchanger, and the first gas-liquid separator are connected in sequence. The first outlet of the first gas-liquid separator is connected to the second buffer tank. The second outlet of the first gas-liquid separator, the compressor, the fourth heat exchanger, and the second gas-liquid separator are connected in sequence. The first outlet of the second gas-liquid separator is connected to the second heat exchanger. The second outlet of the second gas-liquid separator, the cryogenic heat exchanger, and the third gas-liquid separator are connected in sequence. The first outlet of the third gas-liquid separator is connected to the second heat exchanger. The second outlet of the third gas-liquid separator is connected to the spray tower. The first outlet of the spray tower is connected to the hydrogen storage tank. The second outlet of the spray tower is connected to the second buffer tank.
[0023] Beneficial effects:
[0024] This application employs multi-stage heat recovery, which greatly reduces the total energy consumption of the system and improves the overall energy efficiency of the sulfur-iodine cycle system.
[0025] This application achieves complete material recovery, prevents material loss during hydrogen purification, and reduces system operating costs.
[0026] This application employs a combination of pressurization and cryogenic treatment to assist in the liquefaction of hydrogen iodide. Compared with the direct cryogenic method, this significantly reduces energy consumption. Furthermore, since hydrogen generally requires pressurization for downstream applications, this method pre-pressurizes the hydrogen during separation and purification, reducing the energy consumption required for subsequent pressurization.
[0027] This application does not add any materials other than water during the hydrogen separation and purification process, thus preventing impurities from entering the system. Furthermore, the water added is the supplementary water that the system originally needed to add, and the amount of water required to absorb hydrogen iodide does not exceed the amount of supplementary water used, thus preventing subsequent water removal processes from being disrupted due to the addition of excessive water.
[0028] This application restricts the circulation of undecomposed hydrogen iodide to the hydrogen separation process, thereby reducing the circulation energy consumption of other units in the system. Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Some specific embodiments of this application will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings indicate the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale.
[0030] Figure 1 This is a schematic diagram of the process principle for hydrogen separation and purification in a sulfur-iodine cycle hydrogen production process according to this application.
[0031] Figure 2 This is a schematic diagram of the process system connection for hydrogen separation and purification in a sulfur-iodine cycle hydrogen production process according to this application.
[0032] 1-Feed containing aqueous hydrogen iodide gas; 2-Hydrogen iodide gas mixed with circulating hydrogen iodide; 3-Preheated hydrogen iodide gas; 4-Mixed gas after decomposition; 5-Mixed gas after primary heat recovery; 6-Mixed gas after secondary heat recovery; 7-Mixed gas after water cooling; 8-Iodine-containing hydroiodic acid solution; 9-Hydrogen iodide-hydrogen gas mixture; 10-Compressed hydrogen iodide-hydrogen gas mixture; 11-Water-cooled hydrogen iodide-hydrogen gas mixture; 12-Compressed liquefied hydrogen iodide liquid; 13-Hydrogen iodide-hydrogen gas mixture after compression and separation; 14-Cryogenically cooled hydrogen iodide-hydrogen gas mixture; 15-Cryogenically cooled hydrogen iodide liquid; 16-Mixed hydrogen iodide liquid; 17-Cryogenically cooled hydrogen iodide-hydrogen gas mixture; 18-Make-up water ; 19-Liquid after spray absorption; 20-High-purity hydrogen; 21-Liquid in the recovery tower; 22-Hydrogen iodide after heating and vaporization; 23-Cooling water inlet for the third heat exchanger; 24-Cooling water outlet for the third heat exchanger; 25-Cooling water inlet for the fourth heat exchanger; 26-Cooling water outlet for the fourth heat exchanger; 27-Cryogenic refrigerant inlet; 28-Cryogenic refrigerant outlet; 31-First buffer tank; 32-First heat exchanger; 33-Hydrogen iodide decomposition tower; 34-Second heat exchanger; 35-Third heat exchanger; 36-First gas-liquid separator; 37-Compressor; 38-Fourth heat exchanger; 39-Second gas-liquid separator; 40-Cryogenic heat exchanger; 41-Third gas-liquid separator; 42-Spray tower; 43-Hydrogen storage tank; 44-Second buffer tank; 45-Pressure reducing valve. Detailed Implementation
[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0034] This application proposes a process and system for the separation and purification of hydrogen in a thermochemical sulfur-iodine cycle hydrogen production process, wherein the hydrogen is generated by the decomposition of hydrogen iodide. The initial material of this application is purified aqueous hydrogen iodide gas; the purification process of the hydrogen iodide phase in the sulfur-iodine cycle is not within the scope of this application.
[0035] like Figure 1 The diagram shows a schematic of the process principle for hydrogen separation and purification in a sulfur-iodine cycle hydrogen production process, including the following steps:
[0036] S1: Preheat the purified aqueous hydrogen iodide gas to bring it close to its decomposition temperature.
[0037] Hydrogen iodide gas may contain varying amounts of iodine and water impurities depending on the purification process. Generally, the iodine content is 0–10 wt.%, and the water content is 0–40 wt.%. Its temperature is typically 100–150℃, and its pressure is 1–10 atm. Preheating aims to reduce the heat load on the decomposition tower and prevent uneven heating of the gas.
[0038] S2: Catalytic decomposition of hydrogen iodide gas at temperatures of 400–600℃ and pressures of 1–10 atm. The decomposition produces iodine, hydrogen iodide, water, and hydrogen.
[0039] Preheated hydrogen iodide gas enters the decomposition tower for decomposition. The tower contains a catalyst bed, and the catalyst can typically be Al₂O₃, zeolite, activated carbon, or corresponding supported Pt, Pd, and Ru catalysts. The decomposition tower can be made of metal or ceramic, and materials such as stainless steel, titanium, Hastelloy, and silicon carbide can be used. A heating device is required to maintain the bed temperature. Due to the influence of reaction equilibrium, the decomposition rate is generally only 5–30%.
[0040] S3: The gas heat is recovered to step S1, and the gas is cooled. It continues to be cooled to 20-80°C through heat exchange between the hydrogen iodide liquid and the cooling medium in steps S4 and S5. The gas and liquid are separated, and the liquid is hydrogen iodide, iodine and water, and the gas is hydrogen iodide and hydrogen. The liquid is sent back to the Bunsen tower, and the gas enters the next unit.
[0041] The decomposed gas still has a high temperature, and its heat is used to preheat the inlet material through heat exchange. Since the average specific heat capacity of the inlet and outlet materials of the decomposition tower is not significantly different, the heat can be almost completely recovered. Even after heat recovery, the gas temperature is still above 100°C, so further cooling is required to separate the water, iodine, and some hydrogen iodide within the gas through liquefaction. Circulating cooling water is typically used as the cooling medium. The liquid is returned to the Bunsen tower, while the gas enters the next unit for further separation.
[0042] S4: Pressurize the gas to 20-50 atm, then cool it to 30-60°C and perform gas-liquid separation. The resulting liquid is hydrogen iodide, and the gases are hydrogen iodide and hydrogen. The hydrogen iodide liquid is first depressurized to atmospheric pressure, and then the cold energy is recovered to step S3. At the same time, the hydrogen iodide liquid is vaporized and sent back to step S1, and the gas enters the next unit.
[0043] The gas is pressurized to 20–50 atm using a compressor, typically a diaphragm compressor, which offers good sealing and prevents the introduction of impurities. The pressurized gas is maintained at a temperature above 100°C at the compressor outlet to prevent the hydrogen iodide in the gas from liquefying, which would otherwise corrode the compressor and damage the diaphragm. Subsequently, the gas is cooled to liquefy, reducing the temperature to 30–60°C. Circulating cooling water is typically used as the cooling medium. After gas-liquid separation, the liquid phase consists of liquefied hydrogen iodide, and the gas phase consists of hydrogen iodide and hydrogen gas. According to Raoult's law, due to the boiling point of hydrogen gas, even though the temperature is below the boiling point of hydrogen iodide at the corresponding pressure, the hydrogen iodide cannot be completely liquefied; at this point, the gas phase still contains 30–70% hydrogen iodide by volume. The separated liquid hydrogen iodide is first depressurized to atmospheric pressure, then the cooling capacity is recovered in step S3 for gas cooling. Simultaneously, the liquid hydrogen iodide vaporizes and mixes with the initial hydrogen iodide material to participate in the cycle, and the gas enters the next unit.
[0044] S5: Cool the gas to -30 to -50°C, separate the gas and liquid, and obtain the liquid as hydrogen iodide, and the gas as hydrogen and hydrogen iodide. The hydrogen iodide liquid is first depressurized to atmospheric pressure, and then the cold energy is recovered to step S3. At the same time, the hydrogen iodide liquid is vaporized and sent back to step S1, and the gas enters the next unit.
[0045] The gas is further cooled, with the temperature controlled between -30 and -50°C. Excessive cooling should be avoided, as the boiling and melting points of hydrogen iodide are very close; low temperatures can cause the hydrogen iodide to solidify and clog the pipes. The cryogenically cooled material becomes a gas-liquid mixture again, which is then separated. The liquid phase component after separation is still hydrogen iodide. This liquid is first depressurized to atmospheric pressure, and then the cooling capacity is recovered in step S3 for gas cooling. Simultaneously, the liquid hydrogen iodide vaporizes and mixes with the initial hydrogen iodide material to participate in the cycle. The gas then enters the next unit. The separated gas phase component is mainly hydrogen, but still contains a small amount of hydrogen iodide.
[0046] S6: Water sprays the gas, with the water coming from makeup water, resulting in an aqueous solution of hydrogen and hydrogen iodide. The aqueous solution of hydrogen iodide is then sent back to the Bunsen tower.
[0047] To obtain high-purity hydrogen, the remaining hydrogen iodide in the gas needs to be absorbed. Considering that water has a good absorption effect on hydrogen iodide, a spray-feed method is used to absorb the remaining hydrogen iodide. Calculations show that the amount of water needed for supplementary water is sufficient to completely absorb the hydrogen iodide. After spray absorption, the gas phase contains only hydrogen, and the liquid phase is an aqueous solution of hydrogen iodide, which can be returned to the Bunsen tower for recycling.
[0048] like Figure 2The diagram shows a schematic of a hydrogen separation and purification system in a sulfur-iodine cycle hydrogen production process. It includes a first buffer tank 31, a first heat exchanger 32, a decomposition tower 33, a second heat exchanger 34, a third heat exchanger 35, a first gas-liquid separator 36, a compressor 37, a fourth heat exchanger 38, a second gas-liquid separator 39, a cryogenic heat exchanger 40, a third gas-liquid separator 41, a spray tower 42, a hydrogen storage tank 43, and a second buffer tank 44. The first buffer tank 31, the first heat exchanger 32, and the decomposition tower 33 are connected in sequence. The outlet of the decomposition tower 33 is connected to the first heat exchanger 32. The first heat exchanger 32, the second heat exchanger 34, the third heat exchanger 35, and the first gas-liquid separator 36 are connected in sequence. Then, the first outlet of the first gas-liquid separator 36 is connected to the second buffer tank 44. The second outlet of the first gas-liquid separator 36, the compressor 37, the fourth heat exchanger 38, and the second gas-liquid separator 39 are connected in sequence. The first outlet of the second gas-liquid separator 39 is connected to the second heat exchanger 34. The second outlet of the second gas-liquid separator 39, the cryogenic heat exchanger 40, and the third gas-liquid separator 41 are connected in sequence. The first outlet of the third gas-liquid separator 41 is connected to the second heat exchanger 34. The second outlet of the third gas-liquid separator 41 is connected to the spray tower 42. The first outlet of the spray tower 42 is connected to the hydrogen storage tank 43. The second outlet of the spray tower 42 is connected to the second buffer tank 44.
[0049] The system workflow is as follows: Purified aqueous hydrogen iodide gas 1 first enters the first buffer tank 31. Then, hydrogen iodide gas 2 is preheated by the first heat exchanger 32 before entering the decomposition tower 33 for decomposition. The decomposed gas 4 then enters the first heat exchanger 32 to exchange heat with the hydrogen iodide gas 2 for heat recovery. The gas 5 after heat exchange still has a high temperature, so it is cooled by passing it through the second heat exchanger 34 and the third heat exchanger 35. The second heat exchanger 34 uses subsequently generated liquid hydrogen iodide for cooling, while the third heat exchanger 35 uses circulating cooling water, which enters from 23 and exits from 24. The cooled mixed gas 7 enters the first gas-liquid separator 36 for gas-liquid phase separation. The liquid phase 8 mainly contains hydrogen iodide, iodine, and water, and after separation, it enters the second buffer tank 44. Gas phase 9 is mainly a mixture of hydrogen iodide and hydrogen. Gas phase 9 is then compressed by compressor 37. The mixed gas 10 exits compressor 37 and enters the fourth heat exchanger 38 for heat exchange and cooling, with cooling water entering from 25 and exiting from 26. The cooled material 11 then enters the second gas-liquid separator 39 for two-phase separation. Gas phase component 13 enters the cryogenic heat exchanger 40 for cooling, with refrigerant entering from 27 and exiting from 28. The cryogenic heat exchanger 40 cools material 13 to -30 to -50°C. The cryogenically cooled material 14 becomes a gas-liquid mixture and enters the third gas-liquid separator 41 for gas and liquid phase separation. Liquid material 15 mixes with the liquid phase 12 separated in the second gas-liquid separator 39, and the pressure is restored to atmospheric pressure through pressure reducing valve 45. The mixture 16 then returns to the second heat exchanger 34 as a cooling medium for heat exchange with the aforementioned material 5. After heat exchange, the vaporized hydrogen iodide 22 returns to the first buffer tank 31, mixes with the feed, and is then prepared to enter the decomposition tower 33 again. The gas phase 17 separated in the third gas-liquid separator 41 is mainly hydrogen, but still contains a small amount of hydrogen iodide gas. Material 17 then enters the spray tower 42 for hydrogen iodide absorption. The spray tower 42 uses the makeup water 18 required by the sulfur-iodine circulation system as the spray medium. After water absorption, the gas phase component 20 contains only hydrogen and is transported to the hydrogen storage tank 43 for temporary storage. The liquid phase component 19 enters the second buffer tank 44 and mixes with material 8. The mixed material 21 is then recycled back to the Bunsen tower.
[0050] Example 1
[0051] like Figure 2As shown, hydrogen iodide gas at 130℃, after purification, enters the hydrogen separation and purification unit. Its flow composition is 133 mol / h hydrogen iodide and 150 mol / h water, with a total mass flow rate of 19.7 kg / h and a pressure of 1 atm. Passing through the first gas buffer tank 31, it mixes with the heat-exchanged and vaporized hydrogen iodide gas at a flow rate of 367 mol / h, a temperature of 130℃, and a pressure of 1 atm. The mixed gas is preheated by the first heat exchanger 32, raising its temperature to 400℃. Subsequently, the gas enters the hydrogen iodide decomposition tower 33 for decomposition. The decomposition tower 33 is electrically heated, maintaining the temperature at 450℃ and the pressure at 1 atm. The catalyst used is an Al₂O₃-supported Pt catalyst with a mass hourly space velocity (MSV) of 1000 h⁻¹. -1 The decomposition rate of the hydrogen iodide mixture is 20%, resulting in a gaseous composition of 400 mol / h hydrogen iodide, 150 mol / h water, 50 mol / h iodine, and 50 mol / h hydrogen. The decomposed gas then enters the first heat exchanger 32 to preheat the inlet gas of the decomposition tower 33, recovering heat. The temperature of the mixed gas after heat exchange is approximately 180°C. It then enters the second heat exchanger 34 for further heat recovery, vaporizing the hydrogen iodide liquid generated in subsequent units. The cooled hydrogen iodide decomposed gas enters the third heat exchanger 35 for further cooling, reducing the temperature to 40°C. The cooled hydrogen iodide decomposed gas becomes a gas-liquid mixture. The condensed liquid contains 150 mol / h water, 50 mol / h iodine, and 28 mol / h hydrogen iodide, while the gaseous composition is 372 mol / h hydrogen iodide and 50 mol / h hydrogen. The gas-liquid mixture enters the first gas-liquid separator 36 for separation. The liquid is sent to the second buffer tank 44, while the gas enters the compressor 37 for pressurization. After compression, the gas pressure increases to 30 atm, and the temperature becomes 180°C. The compressed gas then enters the fourth heat exchanger 38 for cooling to 40°C and liquefying the hydrogen iodide. The cooled gas-liquid mixture enters the second gas-liquid separator 39 for further separation. The liquid is depressurized to 1 atm through the pressure reducing valve 45 and then sent to the aforementioned second heat exchanger 34 to exchange heat with the 180°C decomposed hydrogen iodide gas. The gas component contains approximately 60 mol / h of hydrogen iodide and 50 mol / h of hydrogen gas, and is then cryogenically cooled to -50°C. The cooled gas-liquid mixture is then separated in the third gas-liquid separator 41, where the liquid component mixes with the hydrogen iodide liquid produced in the previous unit. The gas component enters the spray tower 42 for absorption. At this point, the gas component contains approximately 5 mol / h of hydrogen iodide, and the water added to the spray tower is 50 mol / h. The liquid after spraying is an aqueous solution of hydrogen iodide, which is transported to the second buffer tank 44 and mixed with the previously generated mixed solution of iodine, hydrogen iodide, and water before being fed into the Bunsen tower. The gaseous component after spraying is high-purity hydrogen, which is stored in the hydrogen storage tank 43.
[0052] The above description is only a partial embodiment of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the protection scope of this application.
Claims
1. A process for hydrogen separation and purification in a sulfur-iodine cycle hydrogen production process, characterized in that, include: S1: Preheat the purified aqueous hydrogen iodide gas to bring it close to its decomposition temperature; S2: Catalytic decomposition of hydrogen iodide gas at temperatures of 400–600℃ and pressures of 1–10 atm. The decomposition results in iodine, hydrogen iodide, water, and hydrogen. S3: The gas heat is recovered to step S1, and the gas is cooled. It continues to be cooled to 20-80°C by heat exchange between the hydrogen iodide liquid and the cooling medium in steps S4 and S5. Gas-liquid separation occurs, and the liquid obtained is hydrogen iodide, iodine and water, while the gas is hydrogen iodide and hydrogen. The liquid is sent back to the Bunsen tower, and the gas enters the next unit. S4: Pressurize the gas to 20-50 atm, then cool it to 30-60°C, and separate the gas and liquid. The liquid obtained is hydrogen iodide, and the gas is hydrogen iodide and hydrogen. The hydrogen iodide liquid is first depressurized to atmospheric pressure, and then the cold energy is recovered to step S3. At the same time, the hydrogen iodide liquid is vaporized and sent back to step S1. The gas enters the next unit. S5: Cool the gas to -30 to -50°C, separate the gas and liquid, and obtain the liquid as hydrogen iodide, the gas as hydrogen and hydrogen iodide. The hydrogen iodide liquid is first reduced to atmospheric pressure, and then the cold energy is recovered to step S3. At the same time, the hydrogen iodide liquid is vaporized and sent back to step S1, and the gas enters the next unit. S6: Water sprays the gas, with the water coming from makeup water, resulting in an aqueous solution of hydrogen and hydrogen iodide. The aqueous solution of hydrogen iodide is then sent back to the Bunsen tower.
2. The process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production as described in claim 1, characterized in that, The purified aqueous hydrogen iodide gas has an iodine content of 0–10 wt.%, a water content of 0–40 wt.%, a temperature of 100–150 °C, and a pressure of 1–10 atm.
3. The process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production as described in claim 1, characterized in that, The catalytic decomposition of hydrogen iodide gas is carried out in a decomposition tower, which is equipped with a catalyst bed. The catalyst is one or more of Al2O3, zeolite, and activated carbon, and is supported with one or more of Pt, Pd, and Ru.
4. The process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production as described in claim 3, characterized in that, The decomposition tower is made of metal or ceramic.
5. The process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production as described in claim 3, characterized in that, The decomposition tower is equipped with a heating device to maintain the temperature of the catalyst bed.
6. The process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production as described in claim 1, characterized in that, The decomposition rate of hydrogen iodide gas in step S2 is 5-30%.
7. The process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production as described in claim 1, characterized in that, The pressurization in step S4 is carried out by a compressor. A diaphragm compressor is selected, and the compressed gas is kept at a temperature above 100°C at the compressor outlet.
8. The process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production as described in claim 1, characterized in that, The cooling medium used in steps S3 and S4 is circulating cooling water.
9. The process for hydrogen separation and purification in sulfur-iodine cycle hydrogen production as described in claim 1, characterized in that, The gas obtained from gas-liquid separation in step S4 contains 30-70% hydrogen iodide by volume.
10. A system for hydrogen separation and purification in a sulfur-iodine cycle hydrogen production process, characterized in that, Implementing the process according to any one of claims 1-9, the system comprises a first buffer tank, a first heat exchanger, a decomposition tower, a second heat exchanger, a third heat exchanger, a first gas-liquid separator, a compressor, a fourth heat exchanger, a second gas-liquid separator, a cryogenic heat exchanger, a third gas-liquid separator, a spray tower, a hydrogen storage tank, and a second buffer tank. The first buffer tank, the first heat exchanger, and the decomposition tower are connected in sequence. The outlet of the decomposition tower is connected to the first heat exchanger. The first heat exchanger, the second heat exchanger, the third heat exchanger, and the first gas-liquid separator are connected in sequence. The first outlet of the separator is connected to the second buffer tank. The second outlet of the first gas-liquid separator, the compressor, the fourth heat exchanger, and the second gas-liquid separator are connected in sequence. The first outlet of the second gas-liquid separator is connected to the second heat exchanger. The second outlet of the second gas-liquid separator, the cryogenic heat exchanger, and the third gas-liquid separator are connected in sequence. The first outlet of the third gas-liquid separator is connected to the second heat exchanger. The second outlet of the third gas-liquid separator is connected to the spray tower. The first outlet of the spray tower is connected to the hydrogen storage tank. The second outlet of the spray tower is connected to the second buffer tank.