A thermo-chemical combined cycle fuel production method and system

Abstract

The present application belongs to the technical field of thermochemical cycle fuel production, and particularly relates to a thermochemical combined cycle fuel production method and system, aiming at solving the problem of low thermal efficiency of thermochemical cycle fuel production. The thermochemical combined cycle fuel production method provided by the present application comprises the following steps: heating an oxygen carrier material to a first temperature interval to make the oxygen carrier material pyrolytic oxygen; cooling the reduced oxygen carrier to a second temperature interval and contacting with water vapor or carbon dioxide to perform an oxidation reaction; capturing heat energy released by the oxidation reaction; and driving a multi-step thermochemical reaction of a circulating medium comprising sulfur, iodine and water by using the captured heat energy, wherein the multi-step thermochemical reaction at least comprises a Benson reaction, a sulfuric acid decomposition reaction and a hydrogen iodide acid decomposition reaction. The present application improves the energy utilization rate of the system and further improves the thermal efficiency of the thermochemical cycle fuel production by coupling and step utilization of high-temperature thermochemical cycle and medium-low temperature thermochemical cycle.

Description

Technical Field

[0001] This invention belongs to the field of thermochemical cycle fuel production technology, specifically relating to a thermochemical combined cycle fuel production method and system. Background Technology

[0002] Thermochemical cycles for producing clean fuels utilize redox reactions on solid oxygen carriers to drive water splitting or carbon dioxide conversion to produce hydrogen or carbon monoxide. This is a crucial technological route for clean fuel production using renewable energy sources such as solar energy. Existing thermochemical cycle systems are broadly categorized into high-temperature thermochemical cycles and medium- and low-temperature thermochemical cycles based on reaction temperature. Common high-temperature thermochemical cycles typically require reduction reactions at temperatures of 1500°C and above. While they can absorb high-grade heat energy, downstream processes do not fully utilize this heat energy, and the use of inert gas purging results in significant partial pressure losses, leading to problems such as high reaction energy consumption and low efficiency. On the other hand, common medium- and low-temperature thermochemical cycles, such as the sulfur-iodine cycle, have critical reaction temperatures ranging from 120°C to 900°C, requiring lower heat energy grades, but their overall thermal efficiency is limited by the supply of high-temperature heat sources.

[0003] In existing technologies, thermochemical cycles operate as independent systems, failing to achieve tiered utilization of thermal energy of different grades. Furthermore, due to significant irreversible losses such as partial pressure loss, the overall system energy utilization rate is low and the cost is high. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, namely the low thermal efficiency of thermochemical cycle fuel production, this invention provides a thermochemical combined cycle fuel production method and system.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A thermochemical combined cycle method for producing fuel includes the following steps: Top cycle reduction: The oxygen carrier material is heated to the first temperature range, causing the oxygen carrier material to thermally decompose oxygen, generating reduced oxygen carrier and oxygen. Top cycle oxidation: The reduced oxygen carrier is cooled to the second temperature range and contacted with water vapor or carbon dioxide to carry out an oxidation reaction, regenerating the oxygen carrier material and correspondingly generating hydrogen or carbon monoxide. Thermal energy capture: Capturing the thermal energy released by the top cycle; Bottom cycle reaction: using captured thermal energy to drive a multi-step thermochemical reaction in a circulating medium including sulfur, iodine, and water, wherein the multi-step thermochemical reaction includes at least the Benson reaction, sulfuric acid decomposition reaction, and hydroiodic acid decomposition reaction to generate hydrogen and oxygen. The values ​​in the first temperature range are higher than those in the second temperature range.

[0007] Furthermore, in the bottom cycle reaction step, the bottom cycle includes: Benson reaction steps: Water, sulfur dioxide and iodine are reacted at a temperature of 293K to 393K to produce a first liquid phase containing sulfuric acid and a second liquid phase containing hydroiodic acid; Sulfuric acid decomposition step: The first liquid phase is decomposed stepwise at a temperature of 923K to 1273K to produce oxygen; Hydroiodic acid decomposition step: The second liquid phase is decomposed at a temperature of 553K to 773K to produce hydrogen gas.

[0008] Furthermore, the top cycle is heated by concentrated solar power or a nuclear reactor, and the top cycle reduction step also includes a step of cooling the products discharged from the top cycle to achieve gas-solid separation or gas-liquid separation.

[0009] Furthermore, prior to the sulfuric acid decomposition step and the hydroiodic acid decomposition step, a step of purifying the first liquid phase and the second liquid phase by the reverse reaction of the Benson reaction is also included. Prior to the hydroiodic acid decomposition step, a step is also included to increase the concentration of hydroiodic acid in the second liquid phase by electrodialysis.

[0010] Furthermore, the oxygen carrier material is a metal oxide capable of thermochemical cycling.

[0011] Furthermore, the metal oxide is ZnO, Fe2O3, CeO2, spinel, or perovskite.

[0012] Furthermore, the first temperature range is 1200K-2300K; the second temperature range is 650K-1150K.

[0013] In another aspect, the present invention provides a thermochemical combined cycle fuel production system, comprising: The top circulation reduction reaction zone is used to contain and heat the oxygen carrier material, so that the oxygen carrier material thermally decomposes oxygen in the first temperature range to generate reduced oxygen carrier and oxygen. The top circulating oxidation reaction zone is used to receive the reduced oxygen carrier and make it contact water vapor or carbon dioxide in the second temperature range to undergo an oxidation reaction, regenerating the oxygen carrier material and correspondingly generating hydrogen or carbon monoxide. A heat transfer device is used to capture the heat energy released by the top circulation oxidation reaction zone and transfer the heat energy to the bottom circulation reaction zone; The bottom circulation reaction zone is used to receive the heat energy provided by the heat transfer device to drive the circulation medium, including sulfur, iodine and water, to undergo a multi-step thermochemical reaction to generate hydrogen and oxygen; wherein the multi-step thermochemical reaction includes at least the Benson reaction, sulfuric acid decomposition reaction and hydroiodic acid decomposition reaction.

[0014] Furthermore, the bottom cycle reaction zone includes: The Benson reactor is used to react water, sulfur dioxide and iodine to produce a first liquid phase including sulfuric acid and a second liquid phase including hydroiodic acid. A sulfuric acid decomposition unit, connected to the Benson reactor, is used to receive the first liquid phase and decompose sulfuric acid in stages at a temperature of 923K to 1273K to produce oxygen. A hydroiodic acid decomposition unit, connected to the Benson reactor, is used to receive the second liquid phase and decompose hydroiodic acid at 553K to 773K to produce hydrogen.

[0015] Furthermore, the top-cycle reduction reaction zone is heated by concentrated solar energy or a nuclear reactor, and the top-cycle reduction reaction zone is connected to a cooler, which is used to cool the products discharged from the top-cycle reduction reaction zone, while realizing gas-solid separation or gas-liquid separation. The bottom circulation reaction zone also includes: The purification unit is used to reduce the concentration of impurities in the respective solutions by means of the reverse reaction of the Benson reaction before the decomposition of sulfuric acid and hydroiodic acid. An electrodialysis device is used to increase the concentration of hydroiodic acid before it decomposes.

[0016] In summary, the technical effects achieved by this invention are as follows: 1. It achieves the tiered utilization of thermal energy of different grades. The thermochemical cycle with a higher reaction temperature (1200-2300K) is used as the top cycle, and the medium-to-high temperature thermal energy released in its oxidation step (650-1150K) is used to drive the bottom cycle with a lower reaction temperature (Benson reaction 293-393K, sulfuric acid decomposition 923-1273K, hydroiodic acid decomposition 553-773K). This avoids the waste caused by the direct dissipation of high-grade thermal energy or the temperature mismatch in the recovery process during the independent operation of the high-temperature thermochemical cycle.

[0017] 2. Reduced demand for external high-grade heat sources in the bottom cycle. By utilizing the heat released during the operation of the high-temperature thermochemical cycle to provide the energy required for the decomposition of sulfuric acid and hydroiodic acid in the sulfur-iodine cycle, the bottom cycle's demand for independent external high-grade heat sources is reduced.

[0018] 3. Improved overall energy utilization efficiency. Through the coordinated operation of high-temperature thermochemical cycle and medium-low temperature thermochemical cycle, efficient recovery and reuse of thermal energy within the system are achieved, increasing the effective utilization ratio of thermal energy for fuel gas production, and improving the fuel production efficiency of combined cycle at the system level. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 The fuel production steps for the top cycle are based on the zinc-based ZnO / Zn cycle; Figure 2 The top cycle uses cerium-based CeO2 / CeO 2-δ The fuel production process in a cycle; Figure 3 This is a schematic diagram of a heat transfer device; Figure 4 This is another schematic diagram of a heat transfer device.

[0021] Icons: 01. Concentrated solar reactor; 02. Cooler; 03. Oxidation reactor; 04. Benson reactor; 05. First purification reactor; 06. First distillation column; 07. Sulfuric acid decomposition reactor; 08. Sulfur trioxide decomposer; 09. Absorber; 10. Second purification reactor; 11. Electrolytic dialysis unit; 12. Second distillation column; 13. Hydroiodic acid separation unit; 14. Separator; 100. Circulation pump; 200. First switching valve; 300. Second switching valve; 400. Check valve. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0025] The thermochemical combined cycle fuel production method provided in this embodiment includes the following steps: (1) Top cycle reduction step: The metal oxygen support (MeO) is heated to the first temperature range. Under high temperature conditions, the oxygen support undergoes pyrolysis to generate reduced oxygen support (MeO). 1-δ The reaction involves the reaction of oxygen (O2) with oxygen, absorbing a large amount of heat. The reaction equation is as follows: MeO→MeO 1-δ + O2.

[0026] Specifically, the first temperature range is 1200-2300K. At this temperature, the metal oxide support (MeO) decomposes and releases oxygen. The reduced metal oxide support can exist in solid or gaseous phases. Pure oxygen can be obtained through gas-solid separation or gas-liquid separation. Typically, the metal oxide support needs to be heated to 1500℃ or higher.

[0027] (2) Top-cycle oxidation step: The high-temperature reduced oxygen carrier from step (1) is cooled and reacted with water vapor or carbon dioxide to generate an oxidized metal oxygen carrier and the corresponding hydrogen or carbon monoxide. During the cooling process, the reverse reaction of step (1) may occur. The reaction equations involved in this step are as follows: MeO 1-δ +H2O→MeO+H2; MeO 1-δ +CO2→MeO+CO.

[0028] Specifically, the reduced oxygen support needs to be cooled to the second temperature range, which is the temperature required for this reaction step. The second temperature range is 650-1150K, and the reduced metal oxygen support (MeO) generated in step (1) 1-δ It can be in a partially reduced or completely reduced state. It reacts with water vapor (H2O) or carbon dioxide (CO2) to generate a metal oxygen support (MeO) and release hydrogen (H2) or carbon monoxide (CO). Pure hydrogen or carbon monoxide products can be obtained by gas-solid or gas-liquid separation. (3) Heat capture: capturing the heat released by the top cycle, including the heat released by the cooling process and oxidation reaction in the top cycle oxidation step.

[0029] (4) Bottom cycle reactions, including Benson reaction, sulfuric acid decomposition, and hydroiodic acid decomposition.

[0030] The Benson reaction is the connecting link in the sulfur-iodine cycle. The reaction temperature is 293-393 K. It combines water with the circulating medium, and the reaction products can be separated into two phases: a heavy liquid and a light liquid, i.e., a first liquid phase and a second liquid phase. The first liquid phase is the light liquid, mainly composed of sulfuric acid; the second liquid phase is the heavy liquid, mainly composed of hydroiodic acid. The reaction equation is as follows: SO2 + I2 + 2H2O → H2SO4 + 2HI.

[0031] Sulfuric acid decomposition: The sulfuric acid separated from the Benson reaction is purified and then fed into a distillation column. The residue after distillation is returned to the Benson reaction step as a recycling medium. Hydroiodic acid impurities are removed by the reverse reaction of the Benson reaction before the sulfuric acid decomposition reaction.

[0032] Sulfuric acid is decomposed stepwise at temperatures of 923-1273 K. The generated sulfur dioxide is absorbed, and the oxygen produced in the reaction product is naturally separated. The remaining products are returned to the distillation column for further distillation with the purified sulfuric acid. The heat energy required for the stepwise decomposition of sulfuric acid is not provided by an external independent heat source, but rather by the sensible heat released from the top cycle captured in step (3). This step has the highest required temperature and the largest heat absorption in the bottom cycle. Its stepwise reaction equation is as follows: H2SO4→SO3+H2O; SO3→SO2+0.5O2; Hydroiodic acid decomposition: Before the decomposition reaction, sulfuric acid impurities are removed by the reverse reaction of the Benson reaction, and the concentration of hydroiodic acid is increased by electrolytic dialysis and distillation. The reaction temperature required for the hydroiodic acid decomposition reaction is 553-773K.

[0033] Specifically, the purified hydroiodic acid separated from the Benson reaction is subjected to electrolytic dialysis to increase its concentration. The remaining liquid is then returned to the Benson reaction step for further reaction. The main stream enters the distillation column for distillation and then enters the decomposer for decomposition. The generated hydrogen gas can be naturally separated, and the remaining liquid is returned to the distillation column. The heat energy required for this decomposition step comes from the sensible heat released by the top cycle captured in step (3). The reaction equation is as follows: 2HI→H2+I2.

[0034] Among them, the mainstream stock index is the stream of material that is taken out as the main target product in a certain production node (such as distillation in a distillation column); the residual liquid refers to the stream of material that is not taken out as the target product after separation and other operations, but is sent back to the system for circulation.

[0035] In this embodiment, the top cycle and bottom cycle are coupled through the heat required for the reaction, achieving energy cascade utilization. The overall reaction in the bottom cycle is water decomposition: H₂O → H₂ + 0.5O₂. The overall reaction in the top cycle can be either water decomposition or carbon dioxide decomposition: CO₂ → CO + 0.5O₂.

[0036] Based on the thermochemical combined cycle fuel production method provided in this embodiment, a thermochemical combined cycle fuel production system is proposed, including a top cycle reduction reaction zone, a top cycle oxidation reaction zone, a heat transfer device, and a material circulation pipeline. The top cycle reduction reaction zone is used to contain and heat the oxygen carrier material, causing the oxygen carrier material to thermally decompose oxygen within a first temperature range, generating reduced oxygen carrier and oxygen. The top cycle oxidation reaction zone is used to receive the reduced oxygen carrier and cause it to undergo an oxidation reaction with water vapor or carbon dioxide within a second temperature range, regenerating the oxygen carrier material and correspondingly generating hydrogen or carbon monoxide. The heat transfer device is used to capture the heat energy released from the top cycle oxidation reaction zone and transfer this heat energy to the bottom cycle reaction zone. The bottom cycle reaction zone is used to receive the heat energy provided by the heat transfer device to drive a multi-step thermochemical reaction of the circulating medium, including sulfur, iodine, and water, to generate hydrogen and oxygen; wherein the multi-step thermochemical reaction includes at least the Benson reaction, sulfuric acid decomposition reaction, and hydroiodic acid decomposition reaction. The material circulation pipeline is used to return the unreacted circulating medium in the bottom circulation reaction zone to the reaction zone, and to return the oxygen carrier material regenerated in the top circulation oxidation reaction zone to the top circulation reduction reaction zone. The material circulation pipeline is a common structure and will not be described in detail here.

[0037] In this embodiment, the top-cycle reduction reaction zone includes a concentrating solar reactor 01, heated by concentrated solar energy; alternatively, a nuclear reactor or other high-temperature heat sources can be used. Vacuuming and purging with inert gas can be employed to promote the forward reaction.

[0038] In this embodiment, the top circulation reduction reaction zone also includes a rapid cooler 02. The high-temperature products discharged from the concentrating solar reactor 01 enter the rapid cooler 02 for rapid cooling, thereby achieving gas-solid separation or gas-liquid separation, which improves the selectivity of subsequent reactions and the material recovery rate.

[0039] In this embodiment, the top-circulation oxidation reaction zone includes an oxidation reactor 03. Cooled reduced oxygen carrier is transported to the oxidation reactor 03 and undergoes an oxidation reaction with the oxygen-containing fluid within a second temperature range. The heat energy released during the oxidation reaction is recovered via a heat transfer device and preferentially supplied to the bottom-circulation reaction zone to drive the sulfur-iodine cycle for subsequent reactions. Specifically, the oxygen-containing fluid can be water vapor or carbon dioxide; when the oxygen-containing fluid is water vapor, hydrogen is generated as fuel gas; when the oxygen-containing fluid is carbon dioxide, carbon monoxide is generated as fuel gas.

[0040] In this embodiment, the bottom circulation reaction zone includes a Benson reactor, a sulfuric acid decomposition unit, a hydroiodic acid decomposition unit, a purification unit, and an electrodialysis device. The Benson reactor 04 reacts water, sulfur dioxide, and iodine to generate a first liquid phase containing sulfuric acid and a second liquid phase containing hydroiodic acid. The sulfuric acid decomposition unit, connected to the Benson reactor, receives the first liquid phase and decomposes the sulfuric acid in stages at a temperature of 923K to 1273K to produce oxygen. The sulfuric acid decomposition unit includes a sulfuric acid decomposition reactor 07 and a sulfur trioxide decomposer 08. The hydroiodic acid decomposition unit, also connected to the Benson reactor, receives the second liquid phase and decomposes the hydroiodic acid at a temperature of 553K to 773K to produce hydrogen. The hydroiodic acid decomposition unit includes a hydroiodic acid separation device 13. The electrodialysis device 11 increases the concentration of hydroiodic acid before its decomposition.

[0041] In this embodiment, the purification unit is used to reduce the concentration of impurities in the respective solutions by means of the reverse reaction of the Benson reaction before the decomposition of sulfuric acid and hydroiodic acid. Specifically, the purification unit includes a first purification reactor 05 and a second purification reactor 10, such as... Figure 1 , Figure 2 As shown, the first purification reactor 05 is connected between the Benson reactor 04 and the sulfuric acid decomposition reactor 07 to reduce the concentration of impurities in the first liquid phase; the second purification reactor 10 is connected between the Benson reactor 04 and the electrodialysis device 11 to reduce the concentration of impurities in the second liquid phase.

[0042] In this embodiment, the bottom circulation reaction zone further includes a first distillation column 06, an absorber 09, and a second distillation column 12. The first distillation column 06 is connected between the first purification reactor 05 and the sulfuric acid decomposition reactor 07; the absorber 09 is connected to the sulfur trioxide decomposer 08 and is used to absorb sulfur dioxide and undecomposed sulfur trioxide. The second distillation column 12 is connected between the electrolytic dialysis unit 11 and the hydroiodic acid separation unit 13.

[0043] In this embodiment, the top circulation oxidation reaction zone also includes a separator 14, which is used to separate argon (Ar) and oxygen (O2).

[0044] In this embodiment, the heat transfer device is used to achieve efficient thermal coupling and energy cascade utilization between the top and bottom circulation cycles, including a heat capture component and a heat transfer medium circulation loop. Specifically, the heat capture component is configured as a high-temperature heat exchange structure closely attached to or surrounding the outer wall of the oxidation reactor 03, and can be a plate heat exchanger, a spiral tube heat exchanger, or a radiant heat exchange component. The heat capture component is connected to a closed heat transfer medium circulation loop through a pipeline. This loop is filled with a heat transfer medium, preferably high-temperature molten salt or high-pressure supersaturated steam, and is equipped with a circulation pump 100 to drive the heat transfer medium to circulate between the heat capture component and the heat-using equipment in the bottom circulation. The outlet of the heat transfer medium circulation loop is connected to various heat-using devices in the bottom circulation reaction zone via pipelines. Several on / off valves and flow controllers are installed on the pipelines. The opening and closing of the on / off valves controls whether the heat transfer medium enters the corresponding heat-using device. The flow controllers regulate the flow rate of the heat transfer medium entering each unit, thereby achieving precise distribution and control of the heat supply to each heat-using device. At the same time, the insulation layer and temperature sensor are installed to ensure the stability and controllability of heat during the transmission process.

[0045] During operation, when the top circulation reaches the oxidation step, the reduced oxygen carrier undergoes an exothermic oxidation reaction with water vapor or carbon dioxide in oxidation reactor 03, regenerating into an oxidized metal oxygen carrier and releasing a large amount of heat energy. At this time, the heat transfer medium in the heat capture assembly flows through the heat exchange jacket or coil of the oxidation reactor, rapidly absorbing this heat energy through heat exchange or thermal radiation, and the temperature of the heat transfer medium rises to the temperature range required for the bottom circulation heat application. Subsequently, the high-temperature heat transfer medium leaves the oxidation reactor and enters the various heat-using equipment in the bottom circulation reaction zone.

[0046] To fully utilize the temperature gradient, this embodiment employs a heat distribution path that is primarily series-connected and secondarily parallel-connected. Specifically, the high-temperature heat transfer medium is first introduced into the sulfur trioxide decomposer 08, which has the highest heat absorption capacity. Here, the high-temperature heat transfer medium releases some heat to drive the efficient decomposition of sulfur trioxide into sulfur dioxide and oxygen. After passing through the sulfur trioxide decomposer 08, it is introduced into the sulfuric acid decomposition reactor 07, where the remaining high-temperature heat energy drives the decomposition of sulfuric acid into sulfur trioxide and water. Subsequently, the heat transfer medium continues to flow downstream and enters the hydroiodic acid separation device 13, providing the necessary heat energy for the medium-temperature hydroiodic acid decomposition reaction, promoting the decomposition of hydroiodic acid into hydrogen and iodine. After heat exchange in the hydroiodic acid separation device 13, the temperature of the heat transfer medium continues to decrease and it is introduced into the Benson reactor 04, providing heat for the low-temperature Benson reaction. Through the above-mentioned series-connected, tiered supply method, the wide-temperature range heat energy released by the top cycle can achieve a step-by-step, efficient matching in the bottom cycle: high temperature for sulfur trioxide decomposition, medium-high temperature for sulfuric acid decomposition, medium temperature for hydroiodic acid decomposition, and low temperature for the Benson reaction. Figure 3 As shown.

[0047] To achieve efficient heat exchange between the heat transfer medium and the reactants in the bottom circulation system, and to avoid cross-contamination caused by direct contact, each heat-using device is equipped with a corresponding heat exchanger. Specifically, the sulfuric acid decomposition reactor 07 and the sulfur trioxide decomposer 08 are configured with heat exchanger jackets or internal coil structures. The heat transfer medium flows through the jacket or coil, transferring heat to the reactants participating in the chemical reaction through indirect heat exchange. For the hydroiodic acid separation device 13, it is externally connected to an independent reboiler. This reboiler, as an independent shell-and-tube heat exchanger, receives the medium-temperature heat transfer medium from the heat transfer medium circulation loop and transfers heat to the hydroiodic acid solution to maintain a decomposition temperature of 553K to 773K. The Benson reactor 04 is equipped with a heating jacket or internal heating coil. The heat transfer medium flows through the jacket or coil, providing heat to the Benson reaction through indirect heat exchange. In addition, in the entire closed loop of the heat transfer device, there are switch valves at the entry and exit points of the heat transfer medium for each heat-using equipment, and each heat exchanger body and its connecting pipes are covered with an insulation layer.

[0048] To further enhance the system's adaptability to load fluctuations, several parallel bypass channels are also provided in the heat transfer medium circulation loop, each independently connected to a corresponding heat-using device. Specifically, each heat-using device's inlet branch pipe is equipped with a three-way valve. One outlet of the three-way valve is connected to the heat exchanger inlet of the current heat-using device in the series main pipeline, while the other outlet is directly connected to the heat exchanger inlet of the next-level heat-using device via a bypass pipeline. By adjusting the opening and closing of each on / off valve and using the flow controller, the heat transfer medium can be selectively introduced directly into any heat-using device through the bypass, thereby achieving independent adjustment of the heat supply to that heat-using device without changing the overall flow distribution of the series main loop. When a heat-using device requires additional heat due to changes in operating conditions, opening the corresponding bypass valve allows the introduction of a higher-temperature heat transfer medium that has not undergone heat exchange with the upstream heat-using device, rapidly raising the temperature of that device to its optimal response window. Conversely, when a heat-using device's temperature is too high, closing or partially closing the valve on the main pipeline while simultaneously opening the valve on the parallel return branch allows some of the high-temperature heat transfer medium to be directly returned to the inlet of the circulating drive pump. This mixed medium is then redistributed, preventing the heat-using device from overheating. Temperature sensors and flow meters are installed on each bypass channel and return branch to monitor and feed back temperature and flow signals to the control system in real time. The control system automatically adjusts the flow rate of each branch based on the deviation between the preset and actual temperature values, forming a closed-loop temperature control. To ensure normal flow of the heat transfer medium, a check valve 400 can be installed in the pipeline to restrict the flow direction.

[0049] Specifically, the heat transfer medium circulation loop includes the main heating line, heating branch lines, connecting branch lines, and return pipeline, such as... Figure 3As shown. The main heating line connects the heat exchangers of oxidation reactor 03, sulfur trioxide decomposer 08, sulfuric acid decomposition reactor 07, hydroiodic acid separation device 13, and Benson reactor 04 in series. A first switching valve 200 is connected in series between adjacent devices. The first switching valve 200 can be used with a flow meter to control the flow rate. The heating branch is connected in parallel with the main heating line and is equipped with a check valve 400 and a switching valve. Both ends of the heating branch are connected to the heat exchanger of oxidation reactor 03 and the return pipeline, respectively. One end of the return pipeline is connected to the heating branch, and the other end is connected to the heat exchanger of oxidation reactor 03. A circulating pump is connected in series on the return pipeline. A connecting branch is used to connect the inlet of the heat-using equipment to the heating branch and is connected in series with a second switching valve 300.

[0050] During heating, the heat transfer medium flows sequentially along the main heating path through the sulfur trioxide decomposer 08, the sulfuric acid decomposition reactor 07, the hydroiodic acid separator 13, and the Benson reactor 04, and returns to the oxidation reactor 03 via the return pipeline. When the temperature of one of the heat-using devices is too high, a portion of the heat transfer medium can be diverted through a connecting branch or heating branch to lower the temperature. Taking the high temperature of the sulfuric acid decomposition reactor 07 as an example, the flow rate of the heat transfer medium entering the sulfuric acid decomposition reactor 07 can be reduced by controlling the first switch valve 200 at its inlet and the flow controller. At the same time, the second switch valve 300 of the corresponding connecting branch can be opened to divert a portion of the heat transfer medium that should have entered the sulfuric acid decomposition reactor 07 into the heating branch. The heat transfer medium entering the heating branch can directly enter the return pipeline or enter the hydroiodic acid separator 13 through the next connecting branch to avoid insufficient heating of the hydroiodic acid separator 13. When the temperature of the sulfuric acid decomposition reactor 07 is insufficient, the heat transfer medium can be introduced from the heating branch through a connecting branch to increase the flow rate into the sulfuric acid decomposition reactor 07. The heat transfer medium circulation loop provided in this embodiment controls the switching valve and flow meter to reasonably distribute the flow, so that each heat-using device can obtain matching heat supply.

[0051] In an optional embodiment, multiple heating branches can be set up and associated connecting branches can be set up to achieve more flexible flow control, such as... Figure 4 As shown.

[0052] In this embodiment, the thermochemical combined cycle fuel production system uses the medium-temperature heat released from the oxidation reaction to drive the sulfur-iodine cycle, and primarily uses the high-grade heat source for the reduction reaction in the top cycle. This achieves graded matching of heat energy of different grades, avoiding the waste caused by the direct dissipation of high-grade heat energy or temperature mismatch in the recovery process during the independent operation of the high-temperature thermochemical cycle, thus improving the fuel production efficiency of the combined cycle. Furthermore, it achieves the stepwise production of high-purity oxygen and fuel gas, saving energy consumption required for gas separation and purification to a certain extent.

[0053] When a ZnO / Zn cycle is used as the top cycle, powered by a tower-type concentrated solar power system, the reduction reaction temperature is 2300K. At this temperature, the reduction step proceeds spontaneously without the need for vacuuming or inert gas purging to promote the forward reduction reaction. The reaction equation is as follows: Reduction step: ZnO → Zn + 0.5O2; Oxidation step: Zn + H₂O → ZnO + H₂.

[0054] The bottom cycle is a sulfur-iodine cycle, with the Benson reaction temperature at 353 K, sulfuric acid decomposition temperature at 973 K, sulfur trioxide decomposition temperature at 1100 K, sulfur trioxide absorption temperature at 473 K, and hydroiodic acid decomposition temperature at 723 K. For example... Figure 1 The diagram shown is a detailed flowchart. Solid lines represent material flow, and dashed lines represent energy flow. The specific process is as follows: (1) Zinc oxide (ZnO) is introduced into the concentrated solar reactor 01 and a reduction reaction occurs at 2300K, producing oxygen (O2) and zinc vapor (Zn).

[0055] (2) The gas flow generated in process (1) is cooled to 1150K by the rapid cooler O2. The zinc vapor (Zn) is cooled into liquid state, and the reverse reaction of process (1) may occur, and oxygen (O2) is naturally separated.

[0056] (3) The zinc (Zn) generated in process (2) and the external water (H2O) enter the oxidation reactor 03 together. The reaction temperature is set to 1150K. The reaction generates zinc oxide (ZnO) and hydrogen (H2). The zinc oxide enters the concentrated solar reactor 01 to continue to circulate, and the hydrogen can be separated naturally.

[0057] (4) External water enters Benson reactor 04 and reacts, combines with the circulating medium, and enters the circulation. The heat required to heat the circulating medium is provided by the top circulation.

[0058] (5) The sulfuric acid (H2SO4) separated from process (4) passes through the first purification reactor 05 and undergoes the reverse reaction of the Benson reaction in the first purification reactor 05 to reduce the concentration of hydroiodic acid (HI). After the concentration of hydroiodic acid is reduced, it enters the first distillation column 06. The residue after distillation is returned to process (4) as a recycling medium to carry out a recycling reaction in the Benson reactor 04.

[0059] (6) The main stream flowing out of the first distillation column 06 in process (5) enters the sulfuric acid decomposition reactor 07 to decompose the sulfuric acid. The heat required comes from the top circulation, and the products are sulfur trioxide (SO3) and water (H2O).

[0060] (7) The product of process (6) enters the sulfur trioxide decomposer 08, and the reaction produces sulfur dioxide and oxygen. The undecomposed sulfur trioxide is absorbed in the absorber 09 and the reaction product oxygen can be separated naturally. The remaining products are returned to the first distillation column 06 to be distilled with the purified sulfuric acid. The required heat comes from the top circulation.

[0061] (8) The hydroiodic acid (HI) separated from process (4) passes through the second purification reactor 10, where the reverse Benson reaction is carried out to reduce the concentration of sulfuric acid (H2SO4), and then enters the electrolytic dialysis unit 11 to further increase the concentration of hydroiodic acid (HI). The anolyte is returned to process (4).

[0062] (9) The liquid at the cathode outlet of the electrolytic dialysis device 11 in process (8) enters the second distillation column 12 for distillation, and then enters the hydroiodic acid separation device 13 for decomposition reaction. The energy required for decomposition comes from the top circulation. Hydrogen can be separated naturally, and the remaining liquid enters the electrolytic dialysis device 11 in process (8).

[0063] At this point, the material circulation pipeline is used to return the unreacted circulating medium from Benson reactor 04 and subsequent processes back to Benson reactor 04, while simultaneously returning the regenerated zinc oxide from oxidation reactor 03 to the high-temperature top circulation reaction zone, thus forming a closed loop.

[0064] When using cerium-based CeO2 / CeO 2-δ When the cycle is used as the top cycle, it is powered by a tower-type concentrated solar power system. The reduction reaction temperature is 1500K. At this temperature, an inert gas Ar is used to purge the oxygen partial pressure in the reduction step to promote the forward reduction reaction. The reaction equation is as follows: Reduction step: CeO2 → CeO 2-δ + O2; Oxidation step: CeO 2-δ +CO2→CeO2+CO.

[0065] Similarly, the bottom cycle is the sulfur-iodine cycle, with the Benson reaction temperature at 353 K, the sulfuric acid decomposition temperature at 973 K, the sulfur trioxide decomposition temperature at 1100 K, the sulfur trioxide absorption temperature at 473 K, and the hydroiodic acid decomposition temperature at 723 K. For example... Figure 2 The diagram shown is a detailed flowchart. Solid lines represent material flow, and dashed lines represent energy flow. The specific process is as follows: (1) Cerium oxide (CeO2) is introduced into the concentrating solar reactor 01, and a reduction reaction occurs at 1500K, producing oxygen (O2) and reduced oxygen carrier (CeO2). 2-δ ).

[0066] (2) The material generated in process (1) passes through the rapid cooler O2, and the reduced oxygen carrier (CeO) 2-δ When cooled to 1073K, the reverse reaction of process (1) may occur, and the gas and the solid reduced oxygen carrier are naturally separated. The gas enters the separator 14, and argon (Ar) and oxygen (O2) are separated through the separator 14.

[0067] (3) The reduced oxygen carrier (CeO) generated in process (2) 2-δ The cerium oxide (CeO2) and carbon dioxide (CO2) are introduced into the oxidation reactor 03 together. The reaction temperature is set to 1150K. The reaction produces cerium oxide (CeO2) and carbon monoxide (CO). The cerium oxide (CeO2) enters the concentrating solar reactor 01 to continue the cycle, while the carbon monoxide can be separated naturally.

[0068] (4) External water enters Benson reactor 04 and reacts, combines with the circulating medium, and enters the circulation. The heat required to heat the circulating medium is provided by the top circulation.

[0069] (5) The sulfuric acid (H2SO4) separated from process (4) passes through the first purification reactor 05 and undergoes the reverse reaction of the Benson reaction in the first purification reactor 05 to reduce the concentration of hydroiodic acid (HI). After the concentration of hydroiodic acid (HI) is reduced, it enters the first distillation column 06. The residual liquid after distillation is returned to process (4) as a circulating medium to carry out the circulating reaction in the Benson reactor 04.

[0070] (6) The main stream flowing out of the first distillation column 06 in process (5) enters the sulfuric acid decomposition reactor 07 to decompose the sulfuric acid. The heat required comes from the top circulation, and the products are sulfur trioxide (SO3) and water (H2O).

[0071] (7) The product of process (6) enters the sulfur trioxide decomposer 08, and the reaction produces sulfur dioxide and oxygen. The undecomposed sulfur trioxide is absorbed in the absorber 09 and the reaction product oxygen can be separated naturally. The remaining products are returned to the first distillation column 06 to be distilled with the purified sulfuric acid. The required heat comes from the top circulation.

[0072] (8) The hydroiodic acid (HI) separated from process (4) passes through the second purification reactor 10. The reverse reaction of the Benson reaction is carried out in the second purification reactor 10 to reduce the concentration of sulfuric acid (H2SO4). After the concentration of sulfuric acid (H2SO4) is reduced, it enters the electrolytic dialysis device 11 to further increase the concentration of hydroiodic acid (HI). The anode outlet liquid is returned to process (4).

[0073] (9) The liquid at the cathode outlet of the electrolytic dialysis device 11 in process (8) enters the second distillation column 12 for distillation, and then enters the hydroiodic acid separation device 13 to undergo decomposition reaction. The energy required for decomposition comes from the top circulation. Hydrogen can be separated naturally, and the remaining liquid enters the electrolytic dialysis device 11 in process (8).

[0074] In the optional scheme of this embodiment, the metal oxide can also be Fe2O3, spinel, perovskite, etc., and when Fe2O3 is used, the Fe2O3 / FeO cycle is used as the top cycle.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A thermochemical combined cycle method for fuel production, characterized in that, The steps include the following: Top cycle reduction: The oxygen carrier material is heated to the first temperature range, causing the oxygen carrier material to thermally decompose oxygen, generating reduced oxygen carrier and oxygen. Top cycle oxidation: The reduced oxygen carrier is cooled to the second temperature range and contacted with water vapor or carbon dioxide to carry out an oxidation reaction, regenerating the oxygen carrier material and correspondingly generating hydrogen or carbon monoxide. Thermal energy capture: Capturing the thermal energy released by the top cycle; Bottom cycle reaction: using captured thermal energy to drive a multi-step thermochemical reaction in a circulating medium including sulfur, iodine, and water, wherein the multi-step thermochemical reaction includes at least the Benson reaction, sulfuric acid decomposition reaction, and hydroiodic acid decomposition reaction to generate hydrogen and oxygen. The values ​​in the first temperature range are higher than those in the second temperature range.

2. The thermochemical combined cycle fuel production method according to claim 1, characterized in that, In the bottom cycle reaction step, the bottom cycle includes: Benson reaction steps: Water, sulfur dioxide and iodine are reacted at a temperature of 293K to 393K to produce a first liquid phase containing sulfuric acid and a second liquid phase containing hydroiodic acid; Sulfuric acid decomposition step: The first liquid phase is decomposed stepwise at a temperature of 923K to 1273K to produce oxygen; Hydroiodic acid decomposition step: The second liquid phase is decomposed at a temperature of 553K to 773K to produce hydrogen gas.

3. The thermochemical combined cycle fuel production method according to claim 2, characterized in that, The top cycle is heated by concentrated solar power or a nuclear reactor, and the top cycle reduction step also includes a step of cooling the products discharged from the top cycle to achieve gas-solid separation or gas-liquid separation.

4. The thermochemical combined cycle fuel production method according to claim 3, characterized in that, Before the sulfuric acid decomposition step and the hydroiodic acid decomposition step, there is also a step of purifying the first liquid phase and the second liquid phase by the reverse reaction of the Benson reaction; Prior to the hydroiodic acid decomposition step, a step is also included to increase the concentration of hydroiodic acid in the second liquid phase by electrodialysis.

5. The thermochemical combined cycle fuel production method according to claim 4, characterized in that, The oxygen carrier material is a metal oxide capable of thermochemical cycling.

6. The thermochemical combined cycle fuel production method according to claim 5, characterized in that, The metal oxide is ZnO, Fe2O3, CeO2, spinel, or perovskite.

7. The thermochemical combined cycle fuel production method according to claim 1, characterized in that, The first temperature range is 1200K-2300K; the second temperature range is 650K-1150K.

8. A thermochemical combined cycle fuel production system, characterized in that, include: The top circulation reduction reaction zone is used to contain and heat the oxygen carrier material, so that the oxygen carrier material thermally decomposes oxygen in the first temperature range to generate reduced oxygen carrier and oxygen. The top circulating oxidation reaction zone is used to receive the reduced oxygen carrier and make it contact water vapor or carbon dioxide in the second temperature range to undergo an oxidation reaction, regenerating the oxygen carrier material and correspondingly generating hydrogen or carbon monoxide. A heat transfer device is used to capture the heat energy released by the top circulation oxidation reaction zone and transfer the heat energy to the bottom circulation reaction zone; The bottom circulation reaction zone is used to receive the heat energy provided by the heat transfer device to drive the circulation medium, including sulfur, iodine and water, to undergo a multi-step thermochemical reaction to generate hydrogen and oxygen; wherein the multi-step thermochemical reaction includes at least the Benson reaction, sulfuric acid decomposition reaction and hydroiodic acid decomposition reaction.

9. The thermochemical combined cycle fuel production system according to claim 8, characterized in that, The bottom circulation reaction zone includes: The Benson reactor is used to react water, sulfur dioxide and iodine to produce a first liquid phase including sulfuric acid and a second liquid phase including hydroiodic acid. A sulfuric acid decomposition unit, connected to the Benson reactor, is used to receive the first liquid phase and decompose sulfuric acid in stages at a temperature of 923K to 1273K to produce oxygen. A hydroiodic acid decomposition unit, connected to the Benson reactor, is used to receive the second liquid phase and decompose hydroiodic acid at 553K to 773K to produce hydrogen.

10. The thermochemical combined cycle fuel production system according to claim 9, characterized in that, The top-cycle reduction reaction zone is heated by concentrated solar power or a nuclear reactor, and the top-cycle reduction reaction zone is connected to a cooler, which is used to cool the products discharged from the top-cycle reduction reaction zone and at the same time realize gas-solid separation or gas-liquid separation. The bottom circulation reaction zone also includes: The purification unit is used to reduce the concentration of impurities in the respective solutions by means of the reverse reaction of the Benson reaction before the decomposition of sulfuric acid and hydroiodic acid. An electrodialysis device is used to increase the concentration of hydroiodic acid before it decomposes.

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