CaO / Ca(OH)2 thermo-chemical heat storage and power generation system and method based on steam extraction driving

Abstract

The application belongs to the technical field of thermochemical energy storage and thermal power generation, and discloses a CaO / Ca(OH)2 thermochemical heat storage and power generation system and a power generation method based on steam extraction driving, which comprises the following steps: when heat storage is performed, preheated Ca(OH)2 is decomposed under the heating action of a high-temperature heat source to obtain hot CaO and water vapor; after gas-solid separation, the hot CaO and the water vapor are used for preheating Ca(OH)2 respectively, and the cooled CaO and the cooled water vapor are stored after being condensed into water; when heat release is performed, the preheated CaO is hydrated with the extraction steam of the steam turbine to generate Ca(OH)2 and release heat to obtain hot steam; the Ca(OH)2 is used for preheating CaO and step-by-step heating of the circulating condensate water of the steam turbine, so that the condensate water obtains reheat steam; and the hot steam obtained by hydration is used for power generation of the high-pressure cylinder of the steam turbine after heating of the reheat steam. The steam extraction of the steam turbine releases high-temperature heat energy through hydration reaction and heats the feed water, and compared with the traditional heat recovery mode, the temperature cross phenomenon is effectively avoided, and the feed water temperature is improved.

Description

Technical Field

[0001] This invention belongs to the field of thermochemical energy storage and thermal power generation technology, specifically relating to a CaO / Ca(OH)2 thermochemical thermal power generation system and power generation method based on steam extraction drive, which is applicable to thermal power generation coupling scenarios of concentrated solar energy, coal / biomass fuel, industrial high-temperature waste heat, nuclear energy and other high-temperature heat sources. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Thermal energy storage technology plays a crucial supporting role in improving the flexibility of energy systems and balancing intermittent and fluctuating power supply and demand. Among them, the CaO / Ca(OH)2 reversible reaction system is widely regarded as an important technical path for medium- and high-temperature thermochemical energy storage due to its advantages such as high volumetric energy storage density, low heat loss during long-term storage at room temperature, and low material cost.

[0004] In traditional CaO / Ca(OH)2 thermal storage systems, the typical operating process includes two stages: thermal storage and thermal release. During the heat storage stage (dehydration reaction), medium- and high-temperature heat sources (such as concentrated solar heat flow of ≥550 ℃, industrial furnace flue gas or fuel combustion heat) heat Ca(OH)2 to cause a dehydration decomposition reaction. The generated CaO is separated from gas and solid and its sensible heat is recovered before being cooled to room temperature for storage. The generated low-pressure saturated steam is further condensed into liquid water for storage after the sensible heat is recovered to meet the requirements of long-term storage and material balance.

[0005] During the exothermic phase (hydration reaction), the stored CaO undergoes a hydration reaction with steam formed by the evaporation / superheating of liquid water, and the released medium- and high-temperature heat energy is used to drive power systems such as steam Rankine cycles to generate electricity.

[0006] The large amount of low-pressure steam generated during the dehydration reaction results in significant energy loss as latent heat during condensation, leading to overall system inefficiency. Furthermore, during turbine power generation, the steam at each stage generates a large amount of low-temperature steam after performing work; this low-temperature steam also suffers from substantial latent heat loss during utilization.

[0007] If the organic Rankine cycle (ORC) is used to recover condensation heat, a secondary working fluid and compression equipment are required, making the system complex and difficult to obtain high-parameter steam. If low-pressure steam is used to drive a small steam turbine, there are risks of low output power and dust erosion of the blades. If steam compression is used for storage, it depends on large pressure vessels and high-strength insulation measures, and intermittent operation can easily accelerate equipment aging. Therefore, there is an urgent need to propose a system that can efficiently recover low-temperature latent heat, can be deeply coupled with existing large-scale steam power cycles, and has a simple structure and strong engineering adaptability. Summary of the Invention

[0008] To address the problems of high low-temperature steam condensation loss, low heat recovery efficiency, and difficulty in engineering implementation in traditional CaO / Ca(OH)2 thermochemical thermal energy storage systems, this invention proposes a CaO / Ca(OH)2 thermochemical thermal energy storage power generation system and method based on extraction-driven steam. The system directly drives the CaO hydration reaction by extracting steam from a steam turbine, utilizing the chemical heat pump effect to release the latent heat of low-temperature steam condensation at the high-temperature end. This replaces conventional regenerative heaters, overcomes the feedwater temperature limitations of the Rankine cycle, and achieves enhanced latent heat utilization, improved cycle efficiency, and simplified system structure. Furthermore, it exhibits broad adaptability to various high-temperature heat sources.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a CaO / Ca(OH)2 thermochemical thermal power generation system based on steam extraction drive, comprising a thermal storage unit and a heat release unit, wherein, In the heat storage unit, the dehydration reactor is connected to both a Ca(OH)2 source and a high-temperature heat source for heating and dehydrating Ca(OH)2. The material outlet of the dehydration reactor is connected to a cyclone separator, and the solid outlet of the cyclone separator is connected to a second solid-solid heat exchanger for heat exchange between Ca(OH)2 and hot CaO. The Ca(OH)2 outlet of the second solid-solid heat exchanger is connected to the inlet of the dehydration reactor. The steam outlet of the second solid-solid heat exchanger is connected to a first solid-liquid heat exchanger for heat exchange between steam and Ca(OH)2. The Ca(OH)2 outlet of the first solid-liquid heat exchanger is connected to the inlet of the dehydration reactor. In the heat release unit, the hydration reactor is connected to the CaO source and the steam outlets of each stage of the turbine to realize the hydration heat release of CaO; the steam outlet of the hydration reactor is connected to the evaporator / superheater, or the evaporator / superheater is set inside the hydration reactor to heat the working fluid of the Rankine cycle of the turbine. The heated main steam enters the high-pressure cylinder of the turbine to generate electricity. The solid phase outlet of the hydration reactor is connected to each heat exchanger to preheat CaO and heat the turbine circulating condensate in stages.

[0010] Secondly, the present invention provides a power generation method based on steam extraction-driven CaO / Ca(OH)2 thermochemical thermal storage, which generates electricity using the steam extraction-driven CaO / Ca(OH)2 thermochemical thermal storage power generation system, and includes the following steps: During heat storage, preheated Ca(OH)2 decomposes under the heating action of a high-temperature heat source to obtain hot CaO and water vapor. After gas-solid separation, the hot CaO and water vapor are used to preheat Ca(OH)2 separately. The cooled CaO is stored, and the cooled water vapor is condensed into water for storage. During heat release, CaO is preheated and then hydrated with steam extracted from each stage of the steam turbine to generate Ca(OH)2, which releases heat and produces hot steam. Ca(OH)2 is used to preheat CaO and to heat the circulating condensate of the steam turbine in stages, so that the condensate can be reheated into steam. The hot steam obtained by hydration is then used to generate electricity by heating the reheated steam in the high-pressure cylinder of the steam turbine.

[0011] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: In this invention, the interstage extraction steam from the turbine directly participates in the hydration reaction, which can effectively reduce system condensation losses. The turbine extraction steam releases high-temperature heat energy through the hydration reaction and heats the feedwater. Compared with traditional regenerative methods, this effectively avoids temperature cross-contamination and increases the feedwater temperature.

[0012] This invention eliminates the need for additional latent heat recovery devices, thereby reducing investment and operational complexity.

[0013] Power response is achieved by adjusting the steam extraction rate, supporting grid peak shaving and standby operation. Attached Figure Description

[0014] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0015] Figure 1 This is a schematic diagram of the process flow of the extraction-driven CaO / Ca(OH)2 thermochemical thermal storage system according to an embodiment of the present invention during the thermal storage process; Figure 2 This is a schematic diagram of the process flow of the CaO / Ca(OH)2 thermochemical thermal storage system based on steam extraction drive during the heat release process, according to an embodiment of the present invention.

[0016] Among them, 1-CaO storage tank, 2-Ca(OH)2 storage tank, 3-second solid-solid heat exchanger, 4-first solid-liquid heat exchanger, 5-cyclone separator, 6-dehydration reactor, 7-hydration reactor, 8-first solid-solid heat exchanger, 9-gas-solid heat exchanger, 10-third solid-liquid heat exchanger, 11-evaporator / superheater, 12-high-pressure cylinder of steam turbine, 13-intermediate-pressure cylinder of steam turbine, 14-low-pressure cylinder of steam turbine, 15-condenser of Rankine cycle system, 16-condensate pump, 17-fourth solid-liquid heat exchanger, 18-deaerator, 19-feed water pump, 20-first high-pressure heater, 21-second high-pressure heater, 22-third high-pressure heater. Detailed Implementation

[0017] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] To address the technical problems mentioned in the background section, this invention provides a CaO / Ca(OH)2 thermochemical thermal power generation system based on steam extraction drive, comprising a thermal storage unit and a heat release unit, wherein... In the heat storage unit, the dehydration reactor is connected to both a Ca(OH)2 source and a high-temperature heat source for heating and dehydrating Ca(OH)2. The material outlet of the dehydration reactor is connected to a cyclone separator, and the solid outlet of the cyclone separator is connected to a second solid-solid heat exchanger for heat exchange between Ca(OH)2 and hot CaO. The Ca(OH)2 outlet of the second solid-solid heat exchanger is connected to the inlet of the dehydration reactor. The steam outlet of the cyclone separator is connected to a first solid-liquid heat exchanger for heat exchange between steam and Ca(OH)2. The Ca(OH)2 outlet of the first solid-liquid heat exchanger is connected to the inlet of the dehydration reactor. In the heat release unit, the hydration reactor is connected to the CaO source and the steam outlets of each stage of the turbine to realize the hydration heat release of CaO; the steam outlet of the hydration reactor is connected to the evaporator / superheater, or the evaporator / superheater is set inside the hydration reactor to heat the working fluid of the Rankine cycle of the turbine. The heated main steam enters the high-pressure cylinder of the turbine to generate electricity. The solid phase outlet of the hydration reactor is connected to each heat exchanger to preheat CaO and heat the turbine circulating condensate in stages.

[0019] The dehydration reactor, as the core equipment of the heat storage unit, is connected to the Ca(OH)2 source and the high-temperature heat source. Its main function is to use the high-temperature heat source to heat Ca(OH)2, so as to promote the dehydration and decomposition reaction of Ca(OH)2 to generate CaO and water vapor, thereby realizing the conversion and storage of thermal energy into chemical energy.

[0020] The cyclone separator is connected to the material outlet of the dewatering reactor to separate the mixture (CaO and water vapor) discharged from the dewatering reactor, separating the solid CaO and water vapor for subsequent processing and storage.

[0021] The second solid-solid heat exchanger is connected to the solid outlet of the cyclone separator to achieve heat exchange between Ca(OH)2 and hot CaO. On the one hand, the heat from the hot CaO is used to preheat Ca(OH)2, increasing the temperature of Ca(OH)2 entering the dehydration reactor and reducing the heat consumption of the high-temperature heat source; on the other hand, the temperature of the hot CaO is lowered, facilitating the storage and subsequent transportation of CaO.

[0022] The first solid-liquid heat exchanger is connected to the steam outlet of the cyclone separator to achieve heat exchange between water vapor and Ca(OH)2. The heat from the water vapor is used to preheat the Ca(OH)2, increasing its temperature before it enters the dehydration reactor and improving energy efficiency.

[0023] The hydration reactor is the core equipment of the heat release unit, connected to the CaO source and the steam outlets of each stage of the steam turbine. Its main function is to receive CaO and steam extracted from the turbine, causing the CaO and water vapor to undergo a hydration reaction, releasing heat and realizing the conversion of chemical energy into thermal energy.

[0024] The evaporator / superheater is connected between the steam outlet of the hydration reactor and the high-pressure cylinder of the turbine. It utilizes the heat released from the hydration reaction to heat or superheat the main steam of the Rankine cycle, increasing its temperature and pressure to provide high-quality steam for the turbine and thus improving power generation efficiency. If the evaporator / superheater is located inside the hydration reactor, it can be installed in the form of heat exchange tubes. The gas and solid phases inside the hydration reactor can then reheat the main steam flowing within the heat exchange tubes to meet the steam temperature requirements of the turbine's high-pressure cylinder.

[0025] Multi-stage heat exchanger assembly: Connected in series to the reheat steam and feedwater circuits, it is used for cascade heating of feedwater and reheat steam. Through multi-stage heat exchange, the final feedwater temperature reaches above 290℃, improving the efficiency of the Rankine cycle while reducing heat emissions from the condenser.

[0026] During the heat storage stage, a high-temperature heat source provides heat to the dehydration reactor, causing the Ca(OH)₂ to undergo a dehydration reaction. The mixture discharged from the dehydration reactor is separated by a cyclone separator; the hot CaO enters the second solid-solid heat exchanger to exchange heat with Ca(OH)₂, preheating the Ca(OH)₂ while simultaneously cooling the hot CaO. The water vapor discharged from the second solid-solid heat exchanger enters the first solid-liquid heat exchanger to exchange heat with Ca(OH)₂, preheating it. The preheated Ca(OH)₂ then enters the dehydration reactor, reducing the heat demand from the high-temperature heat source and improving energy utilization efficiency. The entire process achieves the dehydration and decomposition of Ca(OH)₂ and the storage of heat. Simultaneously, through the cascade heat exchange of the heat exchangers, the heat generated during the reaction is fully utilized, reducing energy loss.

[0027] During the heat release stage, CaO enters the hydration reactor and undergoes a hydration reaction with the extracted steam from the turbine, releasing heat. The evaporator / superheater utilizes this heat to heat the main steam, improving its quality and providing better conditions for the turbine to perform its work. The multi-stage heat exchanger assembly utilizes the heat from the hydration reaction to heat the feedwater and reheat steam in stages, increasing the feedwater temperature, reducing heat emissions from the condenser, and thus improving the efficiency of the Rankine cycle. By directly driving the CaO hydration reaction with extracted steam from the turbine, the latent heat of condensation of the extracted steam is released at the high-temperature end using the chemical heat pump effect, replacing the conventional regenerative heater. This breaks through the feedwater temperature limitation of the Rankine cycle, achieving upgraded utilization of latent heat, improved cycle efficiency, and simplified system structure. It solves the problems of large low-temperature steam condensation losses, low heat recovery efficiency, and difficult engineering implementation in traditional CaO / Ca(OH)2 thermochemical thermal storage systems.

[0028] In some embodiments, the heat exchanger includes a first solid-solid heat exchanger, a gas-solid heat exchanger and a third solid-liquid heat exchanger, wherein the first solid-solid heat exchanger is disposed between the CaO storage tank and the hydration reactor. The gas-solid heat exchanger is located between the exhaust gas outlet of the high-pressure cylinder of the steam turbine and the inlet of the intermediate-pressure cylinder of the steam turbine. The third solid-liquid heat exchanger is located between the coolant outlet of the low-pressure cylinder of the steam turbine and the evaporator / superheater.

[0029] After Ca(OH)₂ is generated in the hydration reaction, it reaches a high temperature and retains a significant amount of sensible heat when stored in the Ca(OH)₂ tank. By placing the first solid-solid heat exchanger between the CaO tank and the hydration reactor, the sensible heat of Ca(OH)₂ can be used to preheat the CaO entering the hydration reactor, increasing the temperature of the CaO upon entry and reducing the need for external heat during the hydration reaction, thereby improving energy efficiency.

[0030] The coolant discharged from the low-pressure cylinder of the steam turbine is at a relatively low temperature. By placing the third solid-liquid heat exchanger between the coolant outlet of the low-pressure cylinder and the evaporator / superheater, the heat released by the hydration reaction can be used to preheat the coolant, increasing its temperature before it enters the evaporator / superheater. This reduces the evaporator / superheater's need for external heat, thereby improving energy efficiency. Based on fundamental thermodynamic principles, the theoretical upper limit of the Rankine cycle's efficiency is determined by its average heat absorption temperature and average heat release temperature. In this invention, the low-temperature coolant is preheated in the third solid-liquid heat exchanger using the heat of hydration reaction before entering the evaporator / superheater, effectively increasing the average heat absorption temperature of the working fluid in the boiler (evaporator / superheater). According to Carnot's theorem, under the condition of constant heat release temperature, increasing the average heat absorption temperature directly improves the cycle's theoretical thermal efficiency.

[0031] Preferably, a fourth solid-liquid heat exchanger, a deaerator, a feedwater pump, a first high-pressure heater, a second high-pressure heater, and a third high-pressure heater are sequentially arranged between the third solid-liquid heat exchanger and the coolant outlet of the low-pressure cylinder of the steam turbine along the fluid flow direction.

[0032] The deaerator removes oxygen from the coolant to prevent corrosion of the equipment. Deoxygenation before the coolant enters the high-pressure heater ensures safe operation. The first, second, and third high-pressure heaters utilize steam extracted from the turbine to heat the coolant, raising its temperature to meet the boiler's feedwater requirements, thereby improving boiler efficiency and power generation efficiency.

[0033] The water pump can increase the pressure of the coolant to meet the working pressure requirements of the high-pressure heater.

[0034] In a further preferred embodiment, a Rankine cycle condenser and a condensate pump are sequentially installed between the coolant outlet of the low-pressure cylinder of the steam turbine and the fourth solid-liquid heat exchanger.

[0035] The function of the condenser in a Rankine cycle system is to condense the steam discharged from the low-pressure cylinder of the steam turbine into liquid water and collect the condensate to form coolant. Coolant is the working fluid in the Rankine cycle; it can only be recycled by condensing steam into liquid water.

[0036] In a further preferred embodiment, the extraction steam outlet of the intermediate pressure cylinder of the steam turbine is connected to the first high-pressure heater, the extraction steam outlet of the high-pressure cylinder of the steam turbine is connected to the second high-pressure heater, and the power steam of the high-pressure cylinder of the steam turbine is connected to the third high-pressure heater.

[0037] The extraction steam pressure and temperature of the intermediate-pressure cylinder of the steam turbine are relatively low, while the first high-pressure heater is typically a low-pressure heater in the feedwater regeneration system. Connecting the extraction steam from the intermediate-pressure cylinder to the first high-pressure heater allows for the preheating of the lower-temperature feedwater using the extracted steam, achieving rational utilization of low-grade heat. The extraction steam pressure and temperature of the high-pressure cylinder of the steam turbine are higher. Connecting it to the second high-pressure heater allows for further heating of the feedwater using the high-temperature and high-pressure characteristics of the extracted steam, increasing the feedwater temperature. Connecting the power steam from the high-pressure cylinder to the third high-pressure heater, where the power steam still possesses high energy, provides sufficient heat to further increase the feedwater temperature. This achieves cascaded utilization of heat, reduces energy loss, and improves the overall energy efficiency of the system.

[0038] More preferably, the steam outlet of the third high-pressure heater is connected to the steam inlet of the second high-pressure heater, the steam outlet of the second high-pressure heater is connected to the steam inlet of the first high-pressure heater, and the steam outlet of the first high-pressure heater is connected to the deaerator.

[0039] The steam in the third high-pressure heater typically comes from the extraction steam from the high-pressure cylinder of the turbine, and has a relatively high pressure and temperature. The steam in the second high-pressure heater comes from the extraction steam from the intermediate-pressure cylinder, and has a relatively lower pressure and temperature. The steam in the first high-pressure heater comes from the extraction steam from the low-pressure cylinder, and has an even lower pressure and temperature. Connecting the steam outlet of the third high-pressure heater to the steam inlet of the second high-pressure heater, and connecting the steam outlet of the second high-pressure heater to the steam inlet of the first high-pressure heater, allows the steam to flow through each heater sequentially in descending order of pressure and temperature, achieving cascaded utilization of heat. This fully utilizes the heat of steam at different pressures and temperatures, improving energy efficiency and reducing energy loss.

[0040] In a further preferred embodiment, the flow path of Ca(OH)2 obtained by CaO hydration is sequentially a gas-solid heat exchanger, a third solid-liquid heat exchanger, a fourth solid-liquid heat exchanger, and a Ca(OH)2 storage tank.

[0041] The Ca(OH)₂ produced by the hydration reaction of CaO is at a high temperature and carries a large amount of waste heat. The gas-solid heat exchanger, the third solid-liquid heat exchanger, and the fourth solid-liquid heat exchanger are designed for different heat exchange objects and temperature requirements. The gas-solid heat exchanger is typically used to preheat media with relatively high temperature requirements, such as reheat steam from a steam turbine; the third solid-liquid heat exchanger is used to preheat feedwater; and the fourth solid-liquid heat exchanger is used to preheat condensate with lower temperature requirements. By allowing Ca(OH)₂ to flow sequentially through these heat exchangers, the heat can be utilized in a tiered manner according to the temperature requirements of the media, avoiding energy waste caused by direct heat exchange between high-temperature Ca(OH)₂ and low-temperature media, maximizing the recovery of waste heat, and improving the overall energy efficiency of the system.

[0042] In some embodiments, the hydration reactor is connected to the extraction outlet of the high-pressure cylinder, intermediate-pressure cylinder and / or low-pressure cylinder of the steam turbine, and valves and pumps are provided on the connecting pipeline.

[0043] Secondly, the present invention provides a power generation method based on steam extraction-driven CaO / Ca(OH)2 thermochemical thermal storage, which generates electricity using the steam extraction-driven CaO / Ca(OH)2 thermochemical thermal storage power generation system, and includes the following steps: During heat storage, preheated Ca(OH)2 decomposes under the heating action of a high-temperature heat source to obtain hot CaO and water vapor. After gas-solid separation, the hot CaO and water vapor are used to preheat Ca(OH)2 separately. The cooled CaO is stored, and the cooled water vapor is condensed into water for storage. During heat release, CaO is preheated and then hydrated with steam extracted from each stage of the steam turbine to generate Ca(OH)2, which releases heat and produces hot steam. Ca(OH)2 is used to preheat CaO and to heat the circulating condensate of the steam turbine in stages, so that the condensate can be reheated into steam. The hot steam obtained by hydration is then used to generate electricity by heating the reheated steam in the high-pressure cylinder of the steam turbine.

[0044] In some embodiments, the process requirements for the hydration reaction are: pressure of 0.1~2.0 MPa and exothermic temperature of 400~600 ℃.

[0045] Increasing pressure can shift the equilibrium towards a direction with fewer gas molecules, thereby promoting the forward hydration reaction and increasing the conversion rate of reactants and the yield of products. Increased pressure also increases the concentration of reactant molecules, leading to a higher frequency of intermolecular collisions and a greater probability of effective collisions, thus accelerating the reaction rate. Furthermore, increased pressure facilitates achieving higher reaction temperatures in engineering applications; in thermodynamic systems, higher exothermic temperatures contribute to improved system efficiency.

[0046] Hydration reactions require a certain temperature to activate reactant molecules, providing them with sufficient energy to overcome the activation energy and allow the reaction to occur. A temperature range of 400–600°C provides enough heat to keep the reactant molecules in an active state, ensuring the reaction's activity and rate. Within this temperature range, catalysts can also exert a good catalytic effect, further improving reaction efficiency (similar to the above, 400–600°C is actually pressure-dependent; 600°C can only be carried out under high pressure).

[0047] Preferably, the extraction steam pressure introduced during the hydration process is not less than 1.1 to 1.3 times the equilibrium steam partial pressure of the hydration reaction at the corresponding hydration temperature.

[0048] More preferably, the extracted steam is taken from the interstage extraction steam of the high-pressure cylinder, intermediate-pressure cylinder or low-pressure cylinder of the steam turbine, and the extraction steam dryness is ≥0.95.

[0049] A steam dryness fraction ≥0.95 indicates a low moisture content in the steam. Moisture in wet steam does not participate in work; instead, it absorbs heat from the steam, resulting in energy loss. A higher dryness fraction reduces this energy loss, allowing the steam to release more energy during work processes and improving energy efficiency.

[0050] Preferably, the CaO conversion rate during the hydration reaction is 75%~85%.

[0051] In some embodiments, the high-temperature heat source is selected from at least one of molten metal, heat transfer oil, high-temperature flue gas, or high-pressure steam.

[0052] Preferably, the temperature of the high-temperature heat source is ≥550 ℃.

[0053] In some embodiments, the steam after work is done in the high-pressure cylinder of the turbine is used to generate electricity by doing work in the intermediate-pressure cylinder of the turbine, and the steam after work is done in the intermediate-pressure cylinder of the turbine is used to generate electricity by doing work in the low-pressure cylinder of the turbine.

[0054] The high-pressure, intermediate-pressure, and low-pressure cylinders of a steam turbine have different design parameters, each adapted to steam at different pressures and temperatures. The steam at the high-pressure cylinder inlet has the highest pressure and temperature. After performing work in the high-pressure cylinder, the steam's pressure and temperature decrease, but it still retains a high level of energy. The steam after its work in the high-pressure cylinder is then introduced into the intermediate-pressure cylinder to continue performing work. At this point, the steam's parameters match the design parameters of the intermediate-pressure cylinder, fully utilizing the steam's remaining energy. The steam after its work in the intermediate-pressure cylinder further decreases in pressure and temperature, but it can still continue to expand and perform work in the low-pressure cylinder until it approaches the condenser pressure. This sequential work-per-stage method allows for effective utilization of steam under different parameters, achieving cascaded energy utilization and improving the overall thermal efficiency of the unit.

[0055] The control unit monitors the reactor temperature, extraction steam pressure and material flow rate in real time, adjusts the opening of the extraction steam valve according to load demand, and coordinates the switching between energy storage and energy release conditions. The source of the extracted steam is selected according to the hydration heat release temperature requirement, and can be taken from the exhaust steam of the high-pressure cylinder of the steam turbine, the interstage extraction steam of the intermediate-pressure cylinder, or the front stage extraction steam of the low-pressure cylinder, with a steam dryness fraction ≥0.95. The minimum heat transfer end difference of the multi-stage heat exchanger group is 10~15 ℃, and the heat exchange tube is made of high temperature resistant stainless steel or nickel-based alloy with a temperature resistance of ≥650 ℃. The hydration reaction rate is controlled by adjusting the opening degree of the extraction steam valve to match the external load demand. The control unit dynamically selects the extraction steam source and opening degree according to the grid demand: higher pressure extraction steam is selected when a higher hydration temperature is required; extraction steam can be cut off when the load is low.

[0056] The present invention will be further described below with reference to the embodiments.

[0057] This embodiment uses the integration of a subcritical Rankine cycle unit with a CaO / Ca(OH)2 thermochemical thermal storage system as an example. The system includes an energy storage stage and an energy release stage, and operates in deep coupling with the Rankine cycle system.

[0058] like Figure 1 and Figure 2 As shown, a CaO / Ca(OH)2 thermochemical thermal power generation system based on steam extraction drive includes a thermal storage unit and a heat release unit, wherein, In the heat storage unit, the dehydration reactor 6 is connected to the Ca(OH)2 storage tank 2 and the high-temperature heat source respectively, and is used to heat and dehydrate Ca(OH)2; the material outlet of the dehydration reactor 6 is connected to the cyclone separator 5, the solid outlet of the cyclone separator 5 is connected to the second solid-solid heat exchanger 3, and the heat exchange between Ca(OH)2 and hot CaO is carried out using the second solid-solid heat exchanger 3; the Ca(OH)2 outlet of the second solid-solid heat exchanger 3 is connected to the inlet of the dehydration reactor 6; the steam outlet of the cyclone separator 5 is connected to the first solid-liquid heat exchanger 4, and the heat exchange between steam and Ca(OH)2 is carried out using the first solid-liquid heat exchanger 4; the Ca(OH)2 outlet of the first solid-liquid heat exchanger 4 is connected to the inlet of the dehydration reactor 6. In the heat release unit, the hydration reactor 7 is connected to the CaO storage tank 1 and the steam outlets of each stage of the steam turbine to realize the hydration heat release of CaO; the steam outlet of the hydration reactor 7 is connected to the evaporator / superheater 11, or the evaporator / superheater is set inside the hydration reactor to heat the working fluid of the Rankine cycle of the steam turbine. The heated main steam enters the high-pressure cylinder 12 of the steam turbine to do power generation. The solid phase outlet of the hydration reactor 7 is connected to each heat exchanger to preheat CaO and heat the circulating condensate of the steam turbine in stages.

[0059] The heat exchanger includes a first solid-solid heat exchanger 8, a gas-solid heat exchanger 9 and a third solid-liquid heat exchanger 10, with the first solid-solid heat exchanger 8 disposed between the CaO storage tank 1 and the hydration reactor 7. The gas-solid heat exchanger 9 is located between the exhaust gas outlet of the high-pressure cylinder 12 of the steam turbine and the inlet of the intermediate-pressure cylinder 13 of the steam turbine. The third solid-liquid heat exchanger 10 is located between the coolant outlet of the low-pressure cylinder 14 of the steam turbine and the evaporator / superheater 11.

[0060] A fourth solid-liquid heat exchanger 17, a deaerator 18, a feedwater pump 19, a first high-pressure heater 20, a second high-pressure heater 21, and a third high-pressure heater 22 are sequentially arranged between the third solid-liquid heat exchanger 10 and the coolant outlet of the low-pressure cylinder 14 of the steam turbine along the direction of fluid flow.

[0061] A Rankine cycle condenser 15 and a condensate pump 16 are sequentially installed between the coolant outlet of the low-pressure cylinder 14 of the steam turbine and the fourth solid-liquid heat exchanger 17. The extraction steam outlet of the intermediate pressure cylinder 13 of the steam turbine is connected to the first high-pressure heater 20, the extraction steam outlet of the high-pressure cylinder 12 of the steam turbine is connected to the second high-pressure heater 21, and the power steam of the high-pressure cylinder 12 of the steam turbine is connected to the third high-pressure heater 22. The steam outlet of the third high-pressure heater 22 is connected to the steam inlet of the second high-pressure heater 21, the steam outlet of the second high-pressure heater 21 is connected to the steam inlet of the first high-pressure heater 20, and the steam outlet of the first high-pressure heater 20 is connected to the deaerator 18. The flow path of Ca(OH)2 obtained by CaO hydration is sequentially through gas-solid heat exchanger 9, third solid-liquid heat exchanger 10, fourth solid-liquid heat exchanger 17 and Ca(OH)2 storage tank 2.

[0062] The hydration reactor 7 is connected to the extraction outlet of the high-pressure cylinder 12, the intermediate-pressure cylinder 13 and / or the low-pressure cylinder 14 of the steam turbine, and valves and pumps are installed on the connecting pipeline.

[0063] During the energy storage phase, under a steam atmosphere of approximately 0.1 MPa and a temperature of 600 °C, the dehydration reactor 6 is driven by an external heat source to decompose Ca(OH)₂, generating a mixture of CaO and water vapor. This mixture flows through a cyclone separator 5 for gas-solid separation, and the resulting CaO enters the second solid-liquid separation stage. Solid heat exchanger 3 exchanges sensible heat with Ca(OH)2 from Ca(OH)2 storage tank 2, ultimately cooling to approximately 80 °C and storing in CaO storage tank 1. Simultaneously, the separated water vapor enters the first solid heat exchanger. Liquid heat exchanger 4 performs preliminary heat recovery from Ca(OH)2 in Ca(OH)2 storage tank 2, and then condenses it into liquid water at approximately 40 °C before storage. Liquid heat exchanger 4 and the second solid The Ca(OH)2, after being preheated in two stages by the solid heat exchanger 3, then enters the dehydration reactor 6, completing the closed-loop material circulation.

[0064] like Figure 2 As shown, during the energy release stage, the CaO stored in CaO storage tank 1 is first preheated by the first solid-solid heat exchanger 8 and then enters the hydration reactor 7. Steam extracted from the 8th stage of the intermediate pressure cylinder 13 of the steam turbine (pressure 1.12 MPa, temperature 353.4 ℃) is introduced as reaction steam to maintain the system pressure and drive the strong exothermic hydration reaction, so that the reactor temperature is stabilized above 600 ℃.

[0065] The heat released by the reaction is then efficiently utilized through two paths: the main steam loop and the heat exchange chain loop. In the main steam loop, part of the heat is used in the evaporator / superheater 11 to heat the feedwater to generate superheated main steam (pressure 16.723 MPa, temperature 536.2 ℃), which is then sent to the high-pressure cylinder 12 of the steam turbine to do work.

[0066] In the heat exchange chain loop, the generated high-temperature Ca(OH)2 flows out of the hydration reactor 7 and is split. One stream returns to the first solid-solid heat exchanger 8 to preheat the feed CaO, while the other stream flows sequentially through the gas-solid heat exchanger 9, the third solid-liquid heat exchanger 10, and the fourth solid-liquid heat exchanger 17. The gas-solid heat exchanger 9 is used to reheat the exhaust steam from the high-pressure cylinder 12 of the steam turbine to about 535.6 ℃ (pressure 3.98 MPa, temperature 535.6 ℃) and then send it back to the intermediate-pressure cylinder 13 of the steam turbine. The third solid-liquid heat exchanger 10 and the fourth solid-liquid heat exchanger 17 perform cascade heating of the main feedwater.

[0067] Based on this, the key operating process on the Rankine cycle side is as follows: The main condensate (pressure 1.12 MPa, temperature 39.3℃) is first heated to 147.2℃ by the fourth solid-liquid heat exchanger 17, and then enters the deaerator 18. Under the action of the first high-pressure heater 20, the second high-pressure heater 21 and the third high-pressure heater 22 driven by the extraction steam at each stage (the corresponding extraction steam parameters are: first high-pressure heater 20: 6.59 MPa, 395.8℃; second high-pressure heater 21: 3.98 MPa, 329.4℃; third high-pressure heater 22: 2.21 MPa, 450.9℃), the feedwater temperature is successively increased to 207.4℃, 241.6℃ and 270.2℃. Then it is further heated to 297.8℃ by the third solid-liquid heat exchanger 10, and finally superheated main steam is generated in the evaporator / superheater 11 and enters the turbine to do work.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A CaO / Ca(OH)2 thermochemical thermal power generation system based on steam extraction drive, characterized in that: It includes a heat storage unit and a heat release unit, wherein, In the heat storage unit, the dehydration reactor is connected to both a Ca(OH)2 source and a high-temperature heat source for heating and dehydrating Ca(OH)2. The material outlet of the dehydration reactor is connected to a cyclone separator, and the solid outlet of the cyclone separator is connected to a second solid-solid heat exchanger for heat exchange between Ca(OH)2 and hot CaO. The Ca(OH)2 outlet of the second solid-solid heat exchanger is connected to the inlet of the dehydration reactor. The steam outlet of the cyclone separator is connected to a first solid-liquid heat exchanger for heat exchange between steam and Ca(OH)2. The Ca(OH)2 outlet of the first solid-liquid heat exchanger is connected to the inlet of the dehydration reactor. In the heat release unit, the hydration reactor is connected to the CaO source and the steam outlets of each stage of the turbine to realize the hydration heat release of CaO; the steam outlet of the hydration reactor is connected to the evaporator / superheater, or the evaporator / superheater is set inside the hydration reactor to heat the working fluid of the Rankine cycle of the turbine. The heated main steam enters the high-pressure cylinder of the turbine to generate electricity. The solid phase outlet of the hydration reactor is connected to each heat exchanger to preheat CaO and heat the turbine circulating condensate in stages.

2. The CaO / Ca(OH)2 thermochemical thermal power generation system based on steam extraction drive according to claim 1, characterized in that: The heat exchanger includes a first solid-solid heat exchanger, a gas-solid heat exchanger and a third solid-liquid heat exchanger, with the first solid-solid heat exchanger disposed between the CaO storage tank and the hydration reactor. The gas-solid heat exchanger is located between the exhaust gas outlet of the high-pressure cylinder of the steam turbine and the inlet of the intermediate-pressure cylinder of the steam turbine. The third solid-liquid heat exchanger is located between the coolant outlet of the low-pressure cylinder of the steam turbine and the evaporator / superheater.

3. The CaO / Ca(OH)2 thermochemical thermal power generation system based on steam extraction drive according to claim 2, characterized in that: A fourth solid-liquid heat exchanger, a deaerator, a feedwater pump, a first high-pressure heater, a second high-pressure heater, and a third high-pressure heater are sequentially arranged between the third solid-liquid heat exchanger and the coolant outlet of the low-pressure cylinder of the steam turbine along the direction of fluid flow.

4. The CaO / Ca(OH)2 thermochemical thermal power generation system based on steam extraction drive according to claim 3, characterized in that: A Rankine cycle condenser and a condensate pump are sequentially installed between the coolant outlet of the low-pressure cylinder of the steam turbine and the fourth solid-liquid heat exchanger. Alternatively, the extraction steam outlet of the intermediate pressure cylinder of the steam turbine is connected to the first high-pressure heater, the extraction steam outlet of the high-pressure cylinder of the steam turbine is connected to the second high-pressure heater, and the power steam of the high-pressure cylinder of the steam turbine is connected to the third high-pressure heater. Alternatively, the steam outlet of the third high-pressure heater is connected to the steam inlet of the second high-pressure heater, the steam outlet of the second high-pressure heater is connected to the steam inlet of the first high-pressure heater, and the steam outlet of the first high-pressure heater is connected to the deaerator. Alternatively, the flow path of Ca(OH)2 obtained by CaO hydration is sequentially gas-solid heat exchanger, third solid-liquid heat exchanger, fourth solid-liquid heat exchanger and Ca(OH)2 storage tank.

5. The CaO / Ca(OH)2 thermochemical thermal power generation system based on steam extraction drive according to claim 1, characterized in that: The hydration reactor is connected to the extraction outlet of the high-pressure cylinder, intermediate-pressure cylinder and / or low-pressure cylinder of the steam turbine, and valves and pumps are installed on the connecting pipeline.

6. A power generation method based on steam extraction-driven CaO / Ca(OH)2 thermochemical thermal storage, characterized in that: The method of generating electricity using the CaO / Ca(OH)2 thermochemical thermal energy storage power generation system based on steam extraction drive as described in any one of claims 1-5 includes the following steps: During heat storage, preheated Ca(OH)2 decomposes under the heating action of a high-temperature heat source to obtain hot CaO and water vapor. After gas-solid separation, the hot CaO and water vapor are used to preheat Ca(OH)2 separately. The cooled CaO is stored, and the cooled water vapor is condensed into water for storage. During heat release, CaO is preheated and then hydrated with steam extracted from each stage of the steam turbine to generate Ca(OH)2, which releases heat and produces hot steam. Ca(OH)2 is used to preheat CaO and to heat the circulating condensate of the steam turbine in stages, so that the condensate can be reheated into steam. The hot steam obtained by hydration is then used to generate electricity by heating the reheated steam in the high-pressure cylinder of the steam turbine.

7. The power generation method based on steam extraction-driven CaO / Ca(OH)2 thermochemical thermal storage according to claim 6, characterized in that: The process requirements for the hydration reaction are: pressure of 0.1~2.0 MPa and exothermic temperature of 400~600 ℃.

8. The power generation method based on extraction-driven CaO / Ca(OH)2 thermochemical thermal storage according to claim 6, characterized in that: The steam pressure introduced during the hydration process shall not be less than 1.1 to 1.3 times the equilibrium steam partial pressure of the hydration reaction at the corresponding hydration temperature; Preferably, the extracted steam is taken from the interstage extraction of the high-pressure cylinder, intermediate-pressure cylinder, or low-pressure cylinder of the steam turbine, and the extraction steam dryness is ≥0.

95.

9. The power generation method based on extraction-driven CaO / Ca(OH)2 thermochemical thermal storage according to claim 6, characterized in that: The high-temperature heat source is selected from at least one of the following: molten metal, heat transfer oil, high-temperature flue gas, or high-pressure steam.

10. The power generation method based on steam extraction-driven CaO / Ca(OH)2 thermochemical thermal storage according to claim 9, characterized in that: The temperature of the high-temperature heat source is ≥550 ℃; Alternatively, the steam after it has done work in the high-pressure cylinder of the steam turbine can be used to do work in the intermediate-pressure cylinder of the steam turbine to generate electricity, and the steam after it has done work in the intermediate-pressure cylinder of the steam turbine can be used to do work in the low-pressure cylinder of the steam turbine to generate electricity.

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