Sulfur-iodine circulating photo-thermal-thermal chemical hydrogen production method and system

Abstract

The invention relates to a sulfur-iodine cycle photo-thermal-thermal chemical hydrogen production method and system, and the method comprises the following steps: mixing purified water, SO2 gas and an I2 solution, carrying out a Bensen reaction, and carrying out liquid-liquid separation on the Bensen reaction product to obtain an H2SO4 phase solution and an HIx phase solution; carrying out concentration treatment on the H2SO4 phase solution to obtain concentrated sulfuric acid; concentrated sulfuric acid is fed into a sulfuric acid decomposition reactor for a sulfuric acid decomposition reaction, obtained SO2 gas is circularly used for the raw reaction, the sulfuric acid decomposition reaction is carried out under the catalytic action of a V2O5 / diatomite catalyst, and the V2O5 / diatomite catalyst takes diatomite as a carrier and V2O5 as an active component; the HIX phase solution is concentrated, an HI concentrated solution is obtained, the HI concentrated solution is fed into an HI decomposition reactor to be subjected to an HI decomposition reaction, H2 gas and an I2 solution are obtained, the H2 gas is collected after being purified, and the I2 solution is circularly used for the raw reaction. The V2O5 / diatomite catalyst is porous in surface, has good high temperature resistance and thermal shock resistance, can continuously run in a high-temperature environment for a long time, can resist sulfuric acid steam corrosion, does not separate out impurities to influence the product purity and process stability, and reduces the loss of the catalyst; a unique anchoring site and a dispersion environment are provided for the V2O5 active component by a naturally formed and interconnected micro-nano hierarchical pore structure of diatomite, the catalytic effect and efficiency can be further improved, meanwhile, rapid diffusion and escape of macromolecular products SO2 gas and O2 are facilitated, and the problems that active sites are blocked and the like are prevented.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy production technology, specifically relating to a sulfur-iodine cycle photothermal-thermochemical hydrogen production method and a sulfur-iodine cycle photothermal-thermochemical hydrogen production system. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy carrier, has become one of the core directions of energy transformation. Currently, the mainstream hydrogen production technologies mainly fall into three categories: fossil fuel hydrogen production, water electrolysis hydrogen production, and thermochemical hydrogen production. Among them, fossil fuel hydrogen production has high carbon emissions and cannot meet the needs of low-carbon development. Water electrolysis hydrogen production requires the conversion of electrical energy into chemical energy, and the electrical energy mostly comes from renewable energy sources such as photovoltaic and wind power or traditional thermal power. This not only involves multiple conversion losses in the "electricity-thermal-chemical energy" process, resulting in low energy utilization efficiency (only 20-35%), but is also affected by electricity price fluctuations, leading to high manufacturing costs. Furthermore, it relies on grid infrastructure, making it difficult to apply on a large scale in remote areas with abundant solar energy.

[0003] Photothermal-thermochemical hydrogen production technology, as a novel green hydrogen production route, has the core advantage of directly converting solar energy into high-temperature thermal energy through concentrated solar power, skipping the intermediate stage of electrical energy conversion, and directly driving the hydrogen production chemical reaction, which greatly reduces energy conversion loss. The theoretical energy utilization efficiency can reach 40-55%, far exceeding the traditional water electrolysis hydrogen production route. Besides its core advantage of skipping electricity conversion and achieving higher efficiency, solar thermal-thermochemical hydrogen production also boasts several other significant advantages: First, the entire process is zero-carbon, consuming only water and solar energy, with no greenhouse gas or pollutant emissions, perfectly aligning with the needs of low-carbon and environmentally friendly development. Second, it can store thermal energy through heat storage media such as molten salt, effectively solving the problems of intermittent and fluctuating solar energy, achieving 24-hour continuous and stable hydrogen production, and improving the system's annual utilization rate. Third, the products hydrogen and oxygen naturally separate at different reaction stages, eliminating the need for expensive gas separation equipment, resulting in low purification costs and product purity exceeding 99.99%. Fourth, it does not rely on grid electricity, avoiding the cost risks caused by electricity price fluctuations, making it particularly suitable for regions with abundant solar energy but weak grid infrastructure, such as the Northwest desert and the Qinghai-Tibet Plateau, enabling large-scale, distributed hydrogen production. Fifth, it offers significant advantages in energy cascade utilization; the high-temperature and medium-temperature thermal energy provided by the solar thermal system can be matched to the temperature requirements of different hydrogen production reactions, maximizing solar energy utilization. Sixth, it can be efficiently coupled with existing concentrated solar power (CSP) power plant infrastructure to achieve combined electricity and hydrogen production, further enhancing the system's economy and flexibility.

[0004] The sulfur-iodine cycle (SI cycle), as one of the most industrially promising multi-step thermochemical hydrogen production routes in the field of solar thermal-thermochemical hydrogen production, breaks down water decomposition into three mild reactions—Bunsen reaction, sulfuric acid decomposition, and HI decomposition—through the cyclical exchange of sulfur and iodine. It does not require extreme high temperatures above 2500℃ and is perfectly suited to the 400-850℃ thermal energy provided by solar thermal systems, achieving efficient conversion of solar energy into hydrogen energy. However, existing sulfur-iodine cycle solar thermal hydrogen production processes have many technical drawbacks, such as high energy consumption and low conversion efficiency due to unreasonable process parameters, severe equipment corrosion and short service life under high-concentration acid and high-temperature environments, and high replenishment costs due to large losses of the circulating media (SO2, I2). Summary of the Invention

[0005] This invention relates to a sulfur-iodine cycle photothermal-thermochemical hydrogen production method and a sulfur-iodine cycle photothermal-thermochemical hydrogen production system, which can at least solve some of the defects of the prior art.

[0006] This invention relates to a sulfur-iodine cycle photothermal-thermochemical hydrogen production method, the method comprising:

[0007] Purified water, SO2 gas, and I2 solution were mixed and subjected to the Bunsen reaction. The Bunsen reaction products were then separated into H2SO4 phase solution and HI. x Phase solution;

[0008] The H2SO4 phase solution is concentrated to obtain concentrated sulfuric acid. The concentrated sulfuric acid is then fed into a sulfuric acid decomposition reactor to undergo a sulfuric acid decomposition reaction, yielding SO2 gas, H2O, and O2. The sulfuric acid decomposition reaction is carried out under the catalysis of a V2O5 / diatomaceous earth catalyst. This V2O5 / diatomaceous earth catalyst uses diatomaceous earth as a support and V2O5 as the active component. The total mass of the catalyst contains 6.5–8.5 wt% V2O5 and 68.5–82.0 wt% diatomaceous earth. The SO2 gas is recycled for the Bunsen reaction.

[0009] For the HI X The phase solution is concentrated to obtain HI concentrate, which is then fed into an HI decomposition reactor to carry out HI decomposition reaction, yielding H2 gas and I2 solution. The H2 gas is purified and collected, and the I2 solution is recycled for the Bunsen reaction.

[0010] As one embodiment, in the V2O5 / diatomite catalyst, 8.0~20.0 wt% of macroporous silica is added to the diatomite support. The average pore size of the macroporous silica is 100~500 nm, and the weight ratio of the macroporous silica to the diatomite is (6-20):(40-55).

[0011] As one implementation method, the HIX Concentration of the phase solution includes:

[0012] For the HI X The phase solution was purified to obtain HI. X Purification solution;

[0013] The HI X The purified solution was purified by electrodialysis to obtain the HI concentrate.

[0014] As one implementation method, during electrodialysis purification, the ratio of anion and cation membranes is (1.5~2):1.

[0015] As one embodiment, the HI decomposition reaction is carried out under the catalysis of a Pt / CeO2 bicomponent catalyst. In the Pt / CeO2 bicomponent catalyst, CeO2 is used as the support and Pt is the active component. The loading of Pt is 0.5~1.0 wt%, and the specific surface area of ​​the CeO2 support is ≥150 m². 2 / g.

[0016] As one embodiment, the Bunsen reaction is carried out in a Bunsen reaction tower, wherein the purified water, the SO2 gas and the I2 solution are mixed in a static mixer outside the tower before the mixture is fed into the Bunsen reaction tower for reaction.

[0017] This invention also relates to a sulfur-iodine cycle photothermal-thermochemical hydrogen production system, the system comprising:

[0018] The Bunsen reaction apparatus is used to mix purified water, SO2 gas and I2 solution and carry out the Bunsen reaction.

[0019] A liquid-liquid separation device, connected to the product discharge channel of the Bunsen reaction apparatus, is used to separate the Bunsen reaction products into an H2SO4 phase solution and HI. x Phase solution;

[0020] A sulfuric acid concentration device is connected to the H2SO4 phase solution discharge channel of the liquid-liquid separation device, and is used to concentrate the H2SO4 phase solution to obtain concentrated sulfuric acid;

[0021] A sulfuric acid decomposition reactor is connected to the concentrated sulfuric acid discharge channel of the sulfuric acid concentration device, and is used to decompose the concentrated sulfuric acid to obtain SO2 gas, H2O and O2. The SO2 gas outlet of the sulfuric acid decomposition reactor is connected to the SO2 gas inlet of the Bunsen reactor. The sulfuric acid decomposition reactor is equipped with a V2O5 / diatomite catalyst addition channel.

[0022] HI concentration device, which is related to the HI of the liquid-liquid separation device xPhase solution discharge channel connection, used for the HI X The phase solution was concentrated to obtain a concentrated HI solution.

[0023] The HI decomposition device is connected to the HI concentrate discharge channel of the HI concentration device, and is used to decompose the HI concentrate to obtain H2 gas and I2 solution. The I2 solution outlet of the HI decomposition device is connected to the I2 solution inlet of the Bunsen reaction device.

[0024] As one embodiment, the HI concentration apparatus includes:

[0025] HI purification device, which is related to the HI of the liquid-liquid separation device. x Phase solution discharge channel connection, used for the HI X The phase solution was purified to obtain HI. X Purification solution;

[0026] The electrodialysis purification apparatus, which is connected to the HI purification apparatus of the aforementioned HI purification apparatus. X The purification solution discharge channel is connected to connect the HI solution. X The purified solution was purified by electrodialysis to obtain the HI concentrate.

[0027] As one implementation method, in the electrodialysis purification device, the ratio of anion and cation membranes is 2:1.

[0028] As one embodiment, the Bunsen reaction apparatus includes a Bunsen reaction tower and a static mixer located outside the tower. The static mixer has a purified water inlet, an SO2 gas inlet, an I2 solution inlet, and a mixture outlet connected to the Bunsen reaction tower.

[0029] The present invention has at least the following beneficial effects:

[0030] In this invention, the sulfuric acid decomposition reaction employs a V2O5 / diatomaceous earth catalyst. This catalyst has a porous surface, exhibiting excellent high-temperature resistance and thermal shock resistance, allowing for long-term continuous operation in high-temperature environments. It is also resistant to sulfuric acid vapor corrosion, does not chemically react with concentrated sulfuric acid, and produces no impurities that affect product purity and process stability. Therefore, it is well-suited to the gas flow distribution requirements of segmented catalyst beds, and is easy to load and replace, reducing catalyst loss. Based on the use of the aforementioned V2O5 / diatomaceous earth catalyst, while utilizing its high-efficiency catalytic decomposition of sulfuric acid, the invention creatively utilizes the naturally formed, interconnected micro-nano hierarchical pore structure of diatomaceous earth. This special structure provides unique anchoring points and dispersion environments for the V2O5 active components, further improving catalytic effect and efficiency. Simultaneously, this pore structure is more conducive to the rapid diffusion and escape of large molecular products SO2 gas and O2, preventing problems such as blockage of active sites. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic diagram of the composition of the sulfur-iodine cycle photothermal-thermochemical hydrogen production system provided in an embodiment of the present invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] like Figure 1 This invention provides a sulfur-iodine cycle photothermal-thermochemical hydrogen production method, the method comprising:

[0036] Purified water, SO2 gas, and I2 solution were mixed and subjected to the Bunsen reaction. The Bunsen reaction products were then separated into H2SO4 phase solution and HI. x Phase solution;

[0037] The H2SO4 phase solution is concentrated to obtain concentrated sulfuric acid; the concentrated sulfuric acid is fed into sulfuric acid decomposition reactor 42 for sulfuric acid decomposition reaction to obtain SO2 gas, H2O and O2, wherein the sulfuric acid decomposition reaction is carried out under the catalysis of V2O5 / diatomite catalyst, and the SO2 gas is recycled for Bunsen reaction;

[0038] For the HI X The phase solution is concentrated to obtain HI concentrate, which is then fed into an HI decomposition reactor to carry out HI decomposition reaction, yielding H2 gas and I2 solution. The H2 gas is purified and collected, and the I2 solution is recycled for the Bunsen reaction.

[0039] Optionally, the purified water is ultrapure water with a resistivity ≥18 MΩ·cm, specifically obtained after pretreatment of the water source, including but not limited to multi-stage purification through quartz sand filtration, activated carbon adsorption, reverse osmosis (RO), and EDI. Furthermore, preferably, the purified water can be preheated to 80~120℃ using the exothermic waste heat from the Bunsen reaction, which can increase the rate of subsequent Bunsen reactions and achieve energy recovery and utilization.

[0040] Preferably, the heat required for the aforementioned sulfuric acid decomposition reaction and HI decomposition reaction comes from solar energy. Specifically, dispersed solar energy can be focused onto a central cavity receiver 12 using a heliostat 11 (e.g., a dual-axis tracking heliostat 11), converting solar energy into high-temperature heat energy to heat the molten salt medium and store it in a molten salt high-temperature tank 13. The molten salt heat energy is then transported to a heat exchange network via a molten salt circulation pump to provide the required heat energy for the sulfuric acid decomposition reaction and HI decomposition reaction. Excess heat energy is stored in the molten salt high-temperature tank 13, enabling 24-hour continuous hydrogen production and solving the problem of intermittent solar energy. Preferably, the heliostat 11 has a concentration ratio of 2000±200 times, a reflectivity ≥95%, and a tracking accuracy of ±0.1°. Preferably, the molten salt medium is a mixture of sodium nitrate and potassium nitrate (including but not limited to controlling the mass ratio of the two to be 60:40). Preferably, the operating temperature of the molten salt high-temperature tank 13 is controlled at 565°C, and the operating temperature of the molten salt low-temperature tank is controlled at 300±5°C.

[0041] More preferably, a heat recovery network is formed using multi-stage shell-and-tube / plate heat exchangers to recover the high-temperature waste heat from sulfuric acid decomposition products, HI decomposition products, and the exothermic reaction of Bunsen. This recovered heat energy can be used to preheat purified water, concentrated sulfuric acid, and HI concentrate, maximizing energy utilization efficiency and reducing system energy consumption. Optionally, the heat-absorbing surface of the heat exchanger is made of silicon carbide ceramic material, and the outer shell is wrapped with an alumina fiber insulation layer, achieving a heat absorption efficiency of ≥90% and a heat loss of <10%.

[0042] The Bunsen reaction described above takes place in Bunsen reaction tower 3, including but not limited to the use of a bubble-type Bunsen reaction tower 3. Optionally, the main body of the Bunsen reaction tower 3 is made of Hastelloy C276 and lined with polytetrafluoroethylene, which can effectively improve the equipment's resistance to high-concentration acid corrosion and extend the equipment's service life.

[0043] More preferably, the purified water, SO2 gas and I2 solution are mixed in a static mixer outside the tower before being fed into the Bunsen reactor 3 for reaction. This external static mixer method can effectively enhance the gas-liquid mass transfer efficiency and avoid problems such as gas short circuit, uneven local mixing and easy failure of the stirring shaft in a strong corrosive environment that are easily caused by the built-in agitator in the Bunsen reactor 3.

[0044] The Bunsen reaction products automatically separate into a light phase and a heavy phase. These two phases can be separated by a liquid-liquid separator 31, with the light phase separating from the upper part and the heavy phase from the lower part. No additional energy consumption is required, ensuring efficient separation. The light phase is the H₂SO₄ phase mentioned above, and the heavy phase is the HI phase mentioned above. x Mutually.

[0045] In one embodiment, the concentration of the H2SO4 phase solution can be carried out in a vacuum sulfuric acid concentration tower to concentrate it to 98±0.5% concentrated sulfuric acid.

[0046] In one embodiment, the sulfuric acid decomposition reactor 42 is equipped with a segmented catalyst bed. By optimizing the airflow distribution through the segmented catalyst bed, the sulfuric acid decomposition efficiency can be significantly improved.

[0047] The aforementioned V₂O₅ / diatomaceous earth catalyst specifically uses diatomaceous earth as a carrier and vanadium pentoxide (V₂O₅) as the active component. Further, the catalyst uses potassium sulfate (K₂SO₄) and sodium sulfate (Na₂SO₄) as co-catalysts, and phosphorus-containing or cesium-containing compounds as auxiliary agents. Specifically, the total mass of the catalyst comprises: 6.5–8.5 wt% of the active component V₂O₅; 4.0–6.0 wt% of the potassium sulfate co-catalyst; 3.0–6.0 wt% of the sodium sulfate co-catalyst; 0.5–2.0 wt% of the auxiliary agent; and 68.5–82.0 wt% of the diatomaceous earth.

[0048] The V2O5 / diatomite catalyst has a porous surface, which provides excellent high temperature resistance and thermal shock resistance. It can operate continuously for a long time in high temperature environments (850±20℃ in this embodiment), and it can withstand sulfuric acid vapor corrosion. It does not react chemically with concentrated sulfuric acid and there is no impurity precipitation that affects product purity and process stability. Therefore, it is suitable for the airflow distribution requirements of segmented catalyst beds, and it is also easy to fill and replace, reducing catalyst loss.

[0049] Based on the use of the above-mentioned V2O5 / diatomite catalyst, while utilizing its high efficiency in catalyzing the decomposition of sulfuric acid, the interconnected micro-nano hierarchical pore structure naturally formed in diatomite is creatively utilized. This special structure provides unique anchoring sites and dispersion environment for the active components of V2O5, which can further improve the catalytic effect and efficiency. At the same time, this pore structure is more conducive to the rapid diffusion and escape of macromolecular products SO2 gas and O2, preventing problems such as the blockage of active sites.

[0050] More preferably, in order to improve the high temperature resistance of the catalyst, 8.0~20.0wt% of macroporous silica (average pore size 100~500nm) can be added to the diatomaceous earth support. The weight ratio of macroporous silica to diatomaceous earth is (6-20):(40-55). This can enhance the dispersibility of the active components and avoid catalyst deactivation at high temperatures.

[0051] Furthermore, the specifications of the above-mentioned V2O5 / diatomite catalyst particles are as follows: diameter 11~13mm (outer diameter), inner diameter 3.0~4.5mm, length 12-17mm; approximate bulk density 420~500kg / m³, specific surface area ≥120m² / g, pore size distribution concentrated in 10~100nm, pore volume ≥0.3cm³ / g. This ensures sufficient contact between concentrated sulfuric acid vapor and active components, improves decomposition efficiency, reduces airflow resistance, avoids catalyst bed blockage affecting continuous reaction, and reduces catalyst loss.

[0052] Furthermore, the aforementioned V2O5 / diatomite catalyst is layered and packed into the segmented catalyst bed of the sulfuric acid decomposition reactor 42. From the feed end to the discharge end, the catalyst particle size gradually decreases (2~3mm at the feed end, 1~2mm in the middle section, and 0.5~1mm at the discharge end). The catalyst packing height of each section is 1 / 3 of the total height of the reactor bed. During packing, the catalyst is spread evenly to avoid gaps and uneven accumulation, ensuring that concentrated sulfuric acid vapor passes through the catalyst bed evenly and improving the decomposition efficiency. The packing density is controlled at 380~500kg / m³ (adjusted according to the bed segmentation).

[0053] Preferably, SO2 gas in the decomposition products of sulfuric acid is recovered through an SO2 absorption tower with an absorption efficiency of ≥99.5%, reducing the volatilization and loss of the circulating medium and lowering the cost of replenishing the medium.

[0054] Optionally, the outer shell of the sulfuric acid decomposition reactor 42 is made of 310S stainless steel, and the inner lining is integrally cast with silicon carbide, which has the advantages of high temperature corrosion resistance and thermal shock resistance.

[0055] In one embodiment, the HI X Concentration of the phase solution includes:

[0056] For the HI X The phase solution was purified to obtain HI. X Purification solution; wherein, purification treatment can remove HI X Sulfuric acid impurities entrained in the phase solution, including but not limited to HI X The purification process is carried out in purification tower 21, ensuring a sulfuric acid impurity removal rate ≥99.8% and a HI loss rate <0.5%. Optionally, HI... XThe main body of purification tower 21 is made of Hastelloy C276 and lined with polytetrafluoroethylene, which can effectively improve the equipment's resistance to high-concentration acid corrosion and extend the equipment's service life.

[0057] The HI X The purified solution is purified by electrodialysis to obtain the HI concentrate; preferably, the HI concentration is concentrated from 10~20% to an azeotropic concentration (preferably not less than 57%), and the concentration energy consumption is controlled to be ≤800kWh / t-HI.

[0058] In one embodiment, during electrodialysis purification, the ratio of anion and cation exchange membranes is (1.5~2):1. This ratio represents the quantity ratio of the anion and cation exchange membranes, and is essentially the effective area ratio of the anion and cation exchange membranes. More preferably, the ratio of anion and cation exchange membranes is controlled at 2:1. This specific ratio of anion and cation exchange membranes can better match HI, I2, and H+. + I - The difference in migration rate of complex ions during the concentration process effectively suppresses concentration polarization and maintains high current efficiency at / near azeotropic concentrations. This avoids the problems of severe concentration polarization, low current efficiency, and sharp drop in efficiency when approaching azeotropic concentrations in traditional electrodialysis purification, significantly improving the efficiency and reliability of HI concentration production. It can eliminate the distillation step, achieving high-efficiency production while reducing production costs.

[0059] In one embodiment, the HI decomposition reaction is carried out under the catalysis of a Pt / CeO2 bicomponent catalyst, wherein CeO2 is used as the support and Pt is the active component, the Pt loading is 0.5~1.0 wt%, and the specific surface area of ​​the CeO2 support is ≥150 m². 2 / g, utilizing the oxygen vacancies in CeO2 to enhance the HI decomposition reaction can improve the catalytic activity and stability of the catalyst. In this embodiment, the single-pass conversion rate of the HI decomposition reaction can be controlled to ≥28%.

[0060] Preferably, I2 in the HI decomposition products is recovered by an I2 condenser crystallizer to obtain an I2 solution, which can then be reused in the Bunsen reaction, with a recovery efficiency of ≥99.8%.

[0061] Example 2

[0062] like Figure 1 This invention provides a sulfur-iodine cycle photothermal-thermochemical hydrogen production system, the system comprising:

[0063] The Bunsen reaction apparatus is used to mix purified water, SO2 gas and I2 solution and carry out the Bunsen reaction.

[0064] Liquid-liquid separation device 31, which is connected to the product discharge channel of the Bunsen reaction apparatus, is used to separate the Bunsen reaction products into H2SO4 phase solution and HI. x Phase solution;

[0065] Sulfuric acid concentration device 41 is connected to the H2SO4 phase solution discharge channel of the liquid-liquid separation device 31, and is used to concentrate the H2SO4 phase solution to obtain concentrated sulfuric acid;

[0066] The sulfuric acid decomposition reactor 42 is connected to the concentrated sulfuric acid discharge channel of the sulfuric acid concentration device 41, and is used to decompose the concentrated sulfuric acid to obtain SO2 gas, H2O and O2. The SO2 gas outlet of the sulfuric acid decomposition reactor 42 is connected to the SO2 gas inlet of the Bunsen reactor. The sulfuric acid decomposition reactor 42 is equipped with a V2O5 / diatomite catalyst addition channel.

[0067] The HI concentration device, which is connected to the HI of the liquid-liquid separation device 31 x Phase solution discharge channel connection, used for the HI X The phase solution was concentrated to obtain a concentrated HI solution.

[0068] The HI decomposition device 23 is connected to the HI concentrate discharge channel of the HI concentration device and is used to decompose the HI concentrate to obtain H2 gas and I2 solution. The I2 solution outlet of the HI decomposition device 23 is connected to the I2 solution inlet of the Bunsen reaction device.

[0069] The components of this system have been described in the above embodiment 1. For example, the HI concentration device includes an HI purification device 21 and an electrodialysis purification device 22; the Bunsen reaction device includes a Bunsen reaction tower 3 and a static mixer placed outside the tower; etc., which will not be described in detail here.

[0070] Example 3

[0071] This embodiment provides a sulfur-iodine cycle photothermal-thermochemical hydrogen production method (pilot scale, 100 Nm³ / h hydrogen production), the specific steps of which are as follows:

[0072] (1) Raw material pretreatment: Tap water is used as the water source and is successively filtered through quartz sand to remove particulate matter, activated carbon adsorption to remove organic matter, reverse osmosis (RO) device to remove most ions, and EDI device for deep purification to prepare ultrapure water with a resistivity of about 18.5 MΩ·cm; the ultrapure water is passed into the raw material water preheater and preheated to 100°C by utilizing the exothermic waste heat of the Bunsen reaction before entering the subsequent Bunsen reaction stage.

[0073] (2) Concentrating and storing heat: 18 hexagonal biaxial tracking heliostats are used to form a heliostat field 11, with a single mirror area of ​​25m². 2 The reflective layer uses a high-purity silver film + SiO2 protective coating, with a reflectivity of 95.5%, a tracking accuracy of ±0.1°, and a concentration ratio controlled at 2000 times. Solar energy is focused onto a central cavity receiver 12 via a heliostat field 11. The heat-absorbing surface of the central cavity receiver 12 is made of silicon carbide ceramic, and the outer shell is wrapped with an alumina fiber insulation layer, achieving a heat absorption efficiency of 91% and a heat loss of 9%. The receiver converts solar energy into high-temperature heat energy to heat a molten salt medium (sodium nitrate:potassium nitrate = 60:40) in a molten salt high-temperature tank 13 (50m³ / h). 3 The operating temperature is controlled at 565℃. Molten salt cryogenic tank (80m³ / s) 3 The operating temperature is controlled at 300℃; molten salt is circulated via a pump (flow rate 50m³ / h). 3 The pump (with a pump body made of Inconel 625 and an impeller made of SiC) delivers molten salt heat energy to the heat exchange network to provide heat energy for sulfuric acid decomposition and HI decomposition reactions. Excess heat energy is stored in the molten salt high-temperature tank 13 to ensure continuous hydrogen production even when there is no solar energy at night.

[0074] (3) Bunsen reaction and liquid-liquid separation: Preheated ultrapure water to 100℃, recycled SO2 gas, and I2 solution are thoroughly mixed by an external static mixer and then introduced into a bubble-type Bunsen reaction tower 3 (Φ1.2m×6m, main body material Hastelloy C276, PTFE lining); the molar ratio of SO2 to I2 is controlled at 1:1.2, the reaction temperature is 110℃, the reaction pressure is 0.3MPa, and the reaction residence time is 15min; the external static mixer achieves uniform mixing of SO2 and I2 solution, sufficient gas-liquid mass transfer, and SO2 conversion rate reaches 99.3%; the Bunsen reaction products automatically separate into a light phase (H2SO4 phase) and a heavy phase (HI). x The phases are separated by liquid-liquid separator 31. The light phase (containing H2SO4 and a small amount of water) is separated from the upper part, and the heavy phase (containing HI, I2 and excess water) is separated from the lower part, with a separation efficiency of 99.6%.

[0075] (4) Sulfuric acid concentration and decomposition: The separated light phase (H2SO4 phase) is passed into a vacuum sulfuric acid concentration tower (Φ0.8m×8m, made of titanium alloy TA2, packed with SiC Pall rings), and the vacuum degree is controlled at -0.085MPa and the temperature at 180℃ for vacuum distillation concentration to obtain concentrated sulfuric acid with a concentration of 98.2%; the concentrated sulfuric acid is then passed into a horizontal fixed-bed sulfuric acid decomposition reactor 42 (Φ1m×5m, outer shell of 310S stainless steel, inner lining of SiC integral casting). The reactor is equipped with a 3-stage catalyst bed, each stage filled with V2O5 / diatomaceous earth catalyst of different particle sizes (particle size at the feed end 2-3mm, middle section 1-2mm, and discharge end 0.5-1mm), and the reaction temperature is controlled at 850℃, the reaction pressure at 0.3MPa, and the space velocity at 1.2h. -1 The sulfuric acid decomposition efficiency reached 92.5%. The decomposition products were cooled to below 100°C by a cooling separator to separate SO2, H2O and O2. SO2 was recycled to Bunsen reactor 3 for reuse. O2 was cooled, dehydrated, and filtered to remove dust, achieving a purity of 99.6%, and was then stored in a low-pressure oxygen storage tank (0.8MPa).

[0076] (5) HI x Phase processing and HI decomposition: The separated heavy phase (HI) x (phase) enters HI x Purification tower 21 (Φ0.6m×7m, made of Hastelloy C276, with PTFE packing) removes entrained sulfuric acid impurities, achieving a sulfuric acid impurity removal rate of 99.85% and a HI loss rate of 0.4%. The purified HI is then... x Phase (HI concentration 15%) is passed into EED electrodialysis purification unit 22 (processing capacity 5m³). 3 The flow rate is 3 m³ / h, with membrane materials consisting of a perfluorosulfonic acid cation exchange membrane and a perfluoroquaternary ammonium salt anion exchange membrane. The membrane stack ratio of cation to anion exchange membrane is 2:1. The electrode plates are made of titanium coated with ruthenium. The control voltage is 12V, and the flow rate is 3 m³ / h. 3 The concentration of HI is concentrated to 57% at a rate of 780 kWh / t-HI. The concentrated HI is then fed into a vertical HI decomposition reactor (Φ0.8m×6m, Inconel 625 material), which is filled with a Pt / CeO2 bicomponent catalyst (Pt loading 0.8wt%, CeO2 support specific surface area 160 m²). 2 / g), the reaction temperature was controlled at 400℃ and the reaction pressure at 0.3MPa; the single-pass conversion rate of HI reached 28.5%. The decomposition products were cooled to below 120℃ by a cooling separator to separate H2 and I2. I2 was condensed and crystallized and recycled to Bunsen reaction tower 3 for reuse, while H2 entered the subsequent purification stage.

[0077] (6) Heat recovery: A heat recovery network is formed by five shell-and-tube heat exchangers. The first heat exchanger 52 recovers the waste heat of sulfuric acid decomposition products (850°C) and is used to preheat concentrated sulfuric acid to 400°C. The second heat exchanger 51 recovers the waste heat of HI decomposition products (400°C) and is used to preheat HI solution to 180°C. The third heat exchanger recovers the exothermic reaction of Bunsen and is used to preheat raw water. The fourth and fifth heat exchangers recover the waste heat of molten salt and are used to supplement the system heat. The heat recovery efficiency of the entire heat recovery network reaches 86%, which greatly reduces the energy consumption of the system for solar and thermal supplementation.

[0078] (7) Product purification and storage: H2 is purified by membrane separation + PSA pressure swing adsorption (palladium-based alloy membrane, PSA adsorption tower material 304 stainless steel) to a purity of 99.999% and a dew point of -62℃. It is then compressed to 350 bar by a three-stage diaphragm compressor and stored in a high-pressure hydrogen storage tank. O2 is purified by cooling dehydration + PSA pressure swing adsorption to a purity of 99.6% and a water content of <8ppm. It is then stored in a low-pressure oxygen storage tank. I2 in the HI decomposition products is recovered by an I2 condenser crystallizer with a recovery efficiency of 99.9%. SO2 in the sulfuric acid decomposition products is recovered by an SO2 absorption tower with an absorption efficiency of 99.6%, reducing the loss of circulating media.

[0079] (8) Auxiliary control: The DCS distributed control system (Siemens S7-400 core module) is adopted to monitor the temperature, pressure, flow rate, medium concentration and other parameters of each link in real time, with a control accuracy of ±1%; safety interlocks such as over-temperature (e.g., the temperature of sulfuric acid decomposition reactor 42 exceeds 890℃), over-pressure (e.g., the pressure of Bunsen reaction tower 3 exceeds 0.4MPa), and leakage are set. After the interlock is triggered, the equipment will automatically shut down within 5 seconds to ensure the safe and stable operation of the system; the heliostat tracking angle and molten salt flow rate are automatically adjusted to adapt to the fluctuation of solar irradiance.

[0080] Example 4

[0081] This invention provides a sulfur-iodine cycle photothermal-thermochemical hydrogen production method (scale-up to 1000 Nm³ / h hydrogen production). This embodiment is basically the same as the method in Embodiment 3 above, with the only difference being:

[0082] (1) Raw material pretreatment: The resistivity of the ultrapure water prepared by the EDI device is about 18.8 MΩ·cm, and it is preheated to 110℃;

[0083] (2) Concentrating solar energy and heat storage: A heliostat field 11 is composed of 180 hexagonal biaxial tracking heliostats, with a concentration ratio controlled at 2100 times and a reflectivity of 96%; a molten salt high-temperature tank 13 has a volume of 500m³. 3 Molten salt cryogenic tank with a volume of 800m³ 3 Molten salt circulation pump flow rate 500m³ 3 / h, head 50m;

[0084] (3) Bunsen reaction and liquid-liquid separation: The specifications of Bunsen reaction tower 3 are Φ3m×10m, the molar ratio of SO2 to I2 is 1:1.22, the reaction residence time is 16min, and the SO2 conversion rate reaches 99.4%;

[0085] (4) Sulfuric acid concentration and decomposition: The sulfuric acid concentration tower has a specification of Φ2m×12m and a concentrated sulfuric acid concentration of 98.3%; the sulfuric acid decomposition reactor 42 has a specification of Φ2.5m×8m, a reaction temperature of 860℃, and a sulfuric acid decomposition efficiency of 93%;

[0086] (5) HI x Phase treatment and HI decomposition: HI x Purification tower 21 has a specification of Φ1.5m×9m, and EED electrodialysis purification unit 22 has a processing capacity of 50m³. 3 The energy consumption for HI concentration is 770 kWh / t-HI; the HI decomposition reactor has a specification of Φ2m×8m, and the HI single-pass conversion rate reaches 29%.

[0087] (6) The heat recovery efficiency reaches 87%, and the total energy consumption of the system is reduced by 14% compared with the existing technology.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sulfur-iodine cycle photothermal-thermochemical hydrogen production method, characterized in that, The method includes: Purified water, SO2 gas, and I2 solution were mixed and subjected to the Bunsen reaction. The Bunsen reaction products were then separated into H2SO4 phase solution and HI. x Phase solution; The H2SO4 phase solution is concentrated to obtain concentrated sulfuric acid. The concentrated sulfuric acid is then fed into a sulfuric acid decomposition reactor to undergo a sulfuric acid decomposition reaction, yielding SO2 gas, H2O, and O2. The sulfuric acid decomposition reaction is carried out under the catalysis of a V2O5 / diatomaceous earth catalyst. This V2O5 / diatomaceous earth catalyst uses diatomaceous earth as a support and V2O5 as the active component. The total mass of the catalyst contains 6.5–8.5 wt% V2O5 and 68.5–82.0 wt% diatomaceous earth. The SO2 gas is recycled for the Bunsen reaction. For the HI X The phase solution is concentrated to obtain HI concentrate, which is then fed into an HI decomposition reactor to carry out HI decomposition reaction, yielding H2 gas and I2 solution. The H2 gas is purified and collected, and the I2 solution is recycled for the Bunsen reaction.

2. The sulfur-iodine cycle photothermal-thermochemical hydrogen production method as described in claim 1, characterized in that: In the V2O5 / diatomite catalyst, 8.0~20.0 wt% of macroporous silica is added to the diatomite support. The average pore size of the macroporous silica is 100~500 nm, and the weight ratio of the macroporous silica to the diatomite is (6-20):(40-55).

3. The sulfur-iodine cycle photothermal-thermochemical hydrogen production method as described in claim 1, characterized in that, For the HI X Concentration of the phase solution includes: For the HI X The phase solution was purified to obtain HI. X Purification solution; The HI X The purified solution was purified by electrodialysis to obtain the HI concentrate.

4. The sulfur-iodine cycle photothermal-thermochemical hydrogen production method as described in claim 3, characterized in that: During electrodialysis purification, the ratio of anion and cation membranes is 2:

1.

5. The sulfur-iodine cycle photothermal-thermochemical hydrogen production method as described in claim 1, characterized in that: The HI decomposition reaction is carried out under the catalysis of a Pt / CeO2 bicomponent catalyst, in which CeO2 is used as the support and Pt is the active component, with the Pt loading being 0.5~1.0 wt%, and the specific surface area of ​​the CeO2 support being ≥150 m². 2 / g.

6. The sulfur-iodine cycle photothermal-thermochemical hydrogen production method as described in claim 1, characterized in that: The Bunsen reaction is carried out in a Bunsen reaction tower, wherein the purified water, the SO2 gas and the I2 solution are mixed in a static mixer outside the tower before the mixture is fed into the Bunsen reaction tower for reaction.

7. A sulfur-iodine cycle photothermal-thermochemical hydrogen production system, characterized in that, The system includes: The Bunsen reaction apparatus is used to mix purified water, SO2 gas and I2 solution and carry out the Bunsen reaction. A liquid-liquid separation device, connected to the product discharge channel of the Bunsen reaction apparatus, is used to separate the Bunsen reaction products into an H2SO4 phase solution and HI. x Phase solution; A sulfuric acid concentration device is connected to the H2SO4 phase solution discharge channel of the liquid-liquid separation device, and is used to concentrate the H2SO4 phase solution to obtain concentrated sulfuric acid; A sulfuric acid decomposition reactor is connected to the concentrated sulfuric acid discharge channel of the sulfuric acid concentration device, and is used to decompose the concentrated sulfuric acid to obtain SO2 gas, H2O and O2. The SO2 gas outlet of the sulfuric acid decomposition reactor is connected to the SO2 gas inlet of the Bunsen reactor. The sulfuric acid decomposition reactor is equipped with a V2O5 / diatomite catalyst addition channel. HI concentration device, which is related to the HI of the liquid-liquid separation device x Phase solution discharge channel connection, used for the HI X The phase solution was concentrated to obtain a concentrated HI solution. The HI decomposition device is connected to the HI concentrate discharge channel of the HI concentration device, and is used to decompose the HI concentrate to obtain H2 gas and I2 solution. The I2 solution outlet of the HI decomposition device is connected to the I2 solution inlet of the Bunsen reaction device.

8. The sulfur-iodine cycle photothermal-thermochemical hydrogen production system as described in claim 7, characterized in that, The HI concentration device includes: HI purification device, which is related to the HI of the liquid-liquid separation device. x Phase solution discharge channel connection, used for the HI X The phase solution was purified to obtain HI. X Purification solution; The electrodialysis purification apparatus, which is connected to the HI purification apparatus of the aforementioned HI purification apparatus. X The purification solution discharge channel is connected to connect the HI solution. X The purified solution was purified by electrodialysis to obtain the HI concentrate.

9. The sulfur-iodine cycle photothermal-thermochemical hydrogen production system as described in claim 8, characterized in that, In the electrodialysis purification device, the ratio of anion and cation membranes is (1.5~2):

1.

10. The sulfur-iodine cycle photothermal-thermochemical hydrogen production system as described in claim 7, characterized in that, The Bunsen reaction apparatus includes a Bunsen reaction tower and a static mixer located outside the tower. The static mixer has a purified water inlet, an SO2 gas inlet, an I2 solution inlet, and a mixture outlet connected to the Bunsen reaction tower.

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