Multi-grade waste heat cascade recovery mobile heat storage power generation system and operation method

Abstract

The application discloses a multi-grade waste heat stepwise recovery mobile heat storage power generation system and an operation method, relates to the technical field of energy storage, and comprises a high-temperature flue gas heat storage module, a low-temperature steam turbine exhaust steam temperature-raising heat storage module, a mobile heat storage module and a heat engine power generation module. Three independent heat storage temperature zones are arranged in the multi-phase change material mobile heat storage tank, three sets of heat exchange coils are matched, and the heat storage tank can be disassembled and transported. The low-temperature steam turbine exhaust steam adopts a composite upgrading process of pre-compression, lithium bromide waste heat one-stage temperature-raising and high-temperature flue gas waste heat temperature-raising, and the heat source is stored in the corresponding heat storage temperature zone according to the grade. In the energy release stage, the high and low melting point phase change media in the tank cooperate to inhibit the temperature jump of the working medium. The operation process comprises three steps of heat charging, tank transportation and energy release and power generation. The modules are independently closed and circulate, operation is not coupled and interfered, the energy consumption for upgrading low-grade waste heat is reduced, the waste heat can be allocated across regions, the output fluctuation of new energy can be stabilized, and multi-grade industrial waste heat can be efficiently recovered.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to a multi-grade waste heat cascade recovery mobile thermal power generation system and its operation method. Background Technology

[0002] Industrial park self-owned power plants are the core units of regional energy supply. During operation, these units continuously generate two types of waste heat resources with significantly different grades: high-temperature flue gas waste heat from the boiler tail (500–600℃) and low-grade exhaust steam waste heat from the turbine (30–45℃). Due to limitations in existing waste heat recovery technologies, it is difficult to achieve full-dimensional capture and cascaded utilization of these two types of waste heat. A large amount of heat energy is directly emitted without upgrading or heat storage treatment, resulting in significant irreversible heat transfer losses and reducing the overall energy utilization efficiency of the power plant. This has become a key bottleneck restricting the improvement of energy efficiency in industrial energy systems.

[0003] As industrial parks increasingly demand greater flexibility, continuity, and efficiency in energy supply, traditional stationary, single-module waste heat storage technologies are struggling to meet the dynamic allocation needs of distributed energy networks. Existing thermal storage devices either only accommodate waste heat storage in a single temperature zone, resulting in severe temperature zone mismatch and hindering precise matching and efficient storage of waste heat of different grades; or they utilize a single thermal performance medium, making it difficult to meet the needs of wide-temperature-range thermal storage. Furthermore, the coupling process between the system and the power plant's main thermal system is prone to disturbances, affecting the stable operation of the main unit. Moreover, there is a lack of mobile thermal storage carriers to enable flexible allocation of waste heat across space and time periods. Simultaneously, the technology for upgrading low-grade waste steam heat remains constrained by high energy consumption and low conversion efficiency, making it difficult to achieve an efficient leap from low-grade waste heat to high-grade usable thermal energy. This prevents this massive amount of waste heat from being integrated into a high-grade energy supply system.

[0004] In summary, existing thermal energy storage technologies suffer from several limitations, including low efficiency in recovering multi-grade waste heat, high energy consumption in upgrading low-grade waste heat, fixed storage carriers, mutual interference between subsystems, large fluctuations in heat release temperature, and poor adaptability to renewable energy output. Therefore, there is an urgent need to design an integrated thermal energy storage and power generation system and its operating method that can achieve multi-grade waste heat cascade recovery, efficient upgrading of low-grade waste heat, precise thermal energy storage over a wide temperature range, and flexible mobility, in order to meet the comprehensive needs of full industrial waste heat recovery, flexible energy allocation, and stable power generation. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a multi-grade waste heat cascade recovery mobile thermal storage power generation system and its operation method.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a multi-grade waste heat cascade recovery mobile thermal storage power generation system, including a high-temperature flue gas thermal storage module, a low-temperature steam turbine exhaust steam temperature lifting thermal storage module, a mobile thermal storage module and a thermal power generation module; The mobile thermal storage module includes a multiphase change material mobile thermal storage tank, which is internally divided into a primary thermal storage temperature zone, a secondary thermal storage temperature zone, and a tertiary thermal storage temperature zone. The primary thermal storage temperature zone, the secondary thermal storage temperature zone, and the tertiary thermal storage temperature zone are filled with corresponding exclusive phase change thermal storage media. The interior of the multiphase change material mobile heat storage tank is equipped with high-temperature flue gas heat exchange coils, exhaust steam temperature-raising and heat storage coils, and heat engine power generation heat exchange coils arranged in an alternating manner. The high-temperature flue gas heat storage module, the low-temperature steam turbine exhaust steam temperature-raising and heat storage module, and the heat engine power generation module are respectively connected to the corresponding high-temperature flue gas heat exchange coils, exhaust steam temperature-raising and heat storage coils, and heat engine power generation heat exchange coils, forming a closed loop that does not interfere with each other. The heat engine power generation module and the multiphase change material mobile thermal storage tank form a closed-loop thermal energy-electric energy conversion system, which is used to release thermal energy after the multiphase change material mobile thermal storage tank is transferred to drive power generation.

[0007] Furthermore, the multiphase change material mobile thermal storage tank includes a horizontal cylindrical tank body covered with an insulation layer; the primary thermal storage temperature zone, the secondary thermal storage temperature zone, and the tertiary thermal storage temperature zone are arranged vertically from top to bottom inside the tank body, and each is equipped with an independent safety valve and inspection port; The primary heat storage temperature zone is located in the upper layer of the tank body, accounting for 25% of the total heat storage volume, with a temperature range of 300-400℃, and is filled with a ternary molten salt medium of NaNO3-KNO3-Na2SO4. The secondary thermal storage temperature zone is located in the middle layer of the multiphase change material mobile thermal storage tank, accounting for 50% of the total thermal storage volume. The temperature zone ranges from 400 to 600°C and is filled with Al-12Si eutectic alloy-expanded graphite composite phase change thermal storage medium. The three-stage thermal storage temperature zone is located in the lower layer of the multiphase change material mobile thermal storage tank, accounting for 25% of the total thermal storage volume. The temperature zone ranges from 600 to 700°C and is filled with NaCl-KCl-MgCl2 high-temperature chloride molten salt medium. During the heating process, the high-temperature flue gas is first introduced into the third-level heat storage zone and then flows into the second-level heat storage zone. The upgraded exhaust steam is first introduced into the second-level heat storage zone and then flows into the first-level heat storage zone to complete the cascade heat exchange.

[0008] Furthermore, the high-temperature flue gas heat storage module includes a high-temperature flue gas heat source, pump I, a high-temperature resistant flue gas filter, a heat exchanger I, a flue gas purification device, a compressor I, a throttling device I, and a control valve I; The flue gas outlet of the high-temperature flue gas heat source is connected to the inlet of pump I. The outlet of pump I is connected to the inlet of the high-temperature resistant flue gas filter. The outlet of the high-temperature resistant flue gas filter is connected to the flue gas inlet on the high-temperature side of heat exchanger I. The flue gas outlet of the high-temperature resistant flue gas filter leads out a branch line. Control valve I is installed on this branch line. The flue gas outlet on the high-temperature side of heat exchanger I is connected to the inlet of the flue gas purification device. The outlet pipe of the flue gas purification device is connected back to the high-temperature flue gas heat source, forming a flue gas circulation loop. The working fluid outlet on the low-temperature side of heat exchanger I is connected to the working fluid inlet of compressor I. The working fluid outlet of compressor I is connected to the working fluid inlet of the high-temperature flue gas heat exchange coil inside the multiphase change material mobile heat storage tank. The working fluid outlet of the high-temperature flue gas heat exchange coil is connected to the working fluid inlet of throttling device I. The working fluid outlet of throttling device I flows back to the working fluid inlet on the low-temperature side of heat exchanger I. The above components are connected in series to form an independent closed-loop heat storage cycle.

[0009] Furthermore, the low-temperature turbine exhaust steam temperature lifting and heat storage module includes a low-temperature heat extraction and temperature lifting unit, a primary lithium bromide temperature lifting unit, and a secondary flue gas waste heat temperature lifting and heat storage unit. The low-temperature heat extraction and temperature raising unit includes a low-temperature steam turbine exhaust heat source, compressor II, and evaporator; The outlet of the exhaust steam heat source of the low-temperature steam turbine is connected to the inlet of compressor II, the outlet of compressor II is connected to the high-temperature side inlet of the evaporator, and the high-temperature side outlet of the evaporator flows back to the exhaust steam heat source inlet of the low-temperature steam turbine, forming a closed loop of exhaust steam heat extraction. The primary lithium bromide temperature-raising unit includes an absorber, pump II, a generator, a low-pressure steam extraction source for the power plant, and a power plant condensate drainage system. The gaseous outlet on the low-temperature side of the evaporator is connected to the gaseous inlet of the absorber; the dilute lithium bromide solution outlet of the absorber is connected to the inlet of pump II, and the outlet pipeline of pump II is connected to the dilute lithium bromide solution inlet of the generator; the concentrated lithium bromide solution outlet of the generator is refluxed into the concentrated lithium bromide solution inlet of the absorber; the extraction steam outlet of the low-pressure extraction steam source of the power plant is connected to the shell-side medium inlet of the generator, and the condensate outlet of the shell-side of the generator is connected to the condensate system inlet of the power plant. The secondary flue gas waste heat lifting and storage unit includes pump III, heat exchanger II, pump IV, throttling device II, and control valve II. The medium inlet of pump III is connected to the gaseous working fluid outlet of the generator, and the medium outlet of pump III is connected to the low-temperature side medium inlet of heat exchanger II. The low-temperature side working fluid outlet pipeline of heat exchanger II is connected to the inlet of the waste steam lifting and storage heat exchange coil inside the multiphase change material mobile heat storage tank. The working fluid outlet of the waste steam lifting and storage heat exchange coil inside the multiphase change material mobile heat storage tank is connected to the medium inlet of throttling device II, and the medium outlet of throttling device II flows back to the low-temperature side medium inlet of the evaporator, forming a closed-loop circulation of waste steam working fluid. The branch line from the high-temperature resistant flue gas filter is connected to the flue gas inlet of pump IV after passing through control valve I. The flue gas outlet of pump IV is connected to the flue gas inlet on the high-temperature side of heat exchanger II. The flue gas branch line discharged from heat exchanger I and the flue gas branch line discharged from heat exchanger II merge and are connected to the flue gas purification device. Control valve II is installed at the merging node of the two flue gas branches.

[0010] Furthermore, in the low-temperature turbine exhaust steam temperature-raising and heat storage module, the low-pressure exhaust steam output from the low-temperature turbine exhaust steam heat source at 30-45°C is first fed into compressor II to complete pre-compression and temperature rise, resulting in medium-temperature high-pressure exhaust steam at 110-135°C, which is then sent to the high-temperature side of the evaporator to release heat. After the heat exchange medium on the low-temperature side of the evaporator absorbs the heat of the exhaust steam, it forms a gaseous medium that enters the first-stage lithium bromide temperature-raising unit to complete heat and mass exchange. After being upgraded by lithium bromide absorption cycle, it obtains a medium-temperature gaseous heat-carrying medium at 170-190°C. The medium-temperature gaseous heat-carrying medium is transported to the low-temperature side of heat exchanger II via pump III. At the same time, the high-temperature flue gas, filtered by the high-temperature resistant flue gas filter, is sent to the high-temperature side of heat exchanger II via pump IV. The two exchange heat inside heat exchanger II, completing a secondary high-temperature flue gas temperature rise, forming a high-grade heat-carrying medium of 410-425℃. The high-grade heat-carrying medium of 410-425℃ is transported to the waste steam temperature rise and heat exchange coil of the multiphase change material mobile heat storage tank to complete the staged heat storage. After releasing heat and cooling down, the working fluid is depressurized and stabilized by the throttling device II and then flows back to the low-temperature side of the evaporator, continuously circulating to achieve the quality improvement and storage of waste steam heat.

[0011] Furthermore, the heat engine power generation module includes a turbine, heat exchanger III, pump V, and a cold source; The working fluid outlet of the heat exchange coil for power generation inside the multiphase change material mobile thermal storage tank is connected to the working fluid inlet of the turbine. The low-temperature working fluid outlet after the turbine has done work is connected to the high-temperature working fluid inlet of heat exchanger III. The high-temperature working fluid outlet of heat exchanger III is connected to the inlet of pump V. The working fluid outlet after pump V pressurizes is connected back to the working fluid inlet of the heat exchange coil for power generation inside the multiphase change material mobile thermal storage tank, forming a heat energy conversion working fluid cycle. The outlet of the low-temperature medium on the heat exchanger III is connected to the inlet of the cold source medium, and the outlet of the cold source medium is reconnected to the inlet of the low-temperature medium on the heat exchanger III, forming a cooling medium circulation loop.

[0012] Furthermore, the mobile thermal storage module also includes a tractor truck, a loading trailer, a steel frame structure, a multi-functional operation control box, and detachable fixing components. The multiphase change material mobile thermal storage tank is assembled onto the steel frame structure via the detachable fixing components, enabling the tank to be separated and transported. The steel frame structure is fixedly mounted on the loading trailer's bearing plane, and the multi-functional operation control box is located at the rear of the loading trailer. The multi-functional operation control box is used to manage the entire process of the thermal storage tank's charging, transport, and energy release. The front end of the loading trailer is mechanically connected to the tractor end of the tractor truck, which provides the driving power to transport the loading trailer equipped with the multiphase change material mobile thermal storage tank as a whole.

[0013] This invention also provides an operation method for a multi-grade waste heat cascade recovery mobile thermal storage power generation system, which includes the following steps: The charging process involves simultaneously starting the high-temperature flue gas heat storage module and the low-temperature turbine exhaust steam temperature-raising heat storage module at the power plant end, or starting them separately to carry out independent charging operations. The high-temperature flue gas waste heat carried by the high-temperature flue gas heat source and the low-pressure turbine exhaust steam waste heat after being upgraded by the low-temperature turbine exhaust steam temperature-raising heat storage module are stored in the primary, secondary, and tertiary heat storage zones of the multiphase change material mobile heat storage tank according to the heat source grade. Tank transfer steps: After the multiphase change material mobile thermal storage tank completes thermal storage and charging, disconnect the multiphase change material mobile thermal storage tank from the high-temperature flue gas thermal storage module and the low-temperature steam turbine exhaust steam temperature-raising thermal storage module; fix the multiphase change material mobile thermal storage tank onto the steel frame structure of the mobile thermal storage module using detachable fixing components, and have a tractor truck pull the loading trailer to transfer the multiphase change material mobile thermal storage tank to the industrial park end; Energy release and power generation steps: After being transferred, the multiphase change material mobile thermal storage tank is connected to the thermal power generation module. The thermal power generation module is started, and the thermal energy stored inside the multiphase change material mobile thermal storage tank is converted into electrical energy output through the turbine, completing the closed-loop conversion of thermal energy into electrical energy.

[0014] Furthermore, in the heat charging step, the operation of the high-temperature flue gas heat storage module is as follows: the high-temperature flue gas output from the high-temperature flue gas heat source is pumped to the high-temperature resistant flue gas filter by pump I to complete the impurity filtration. The filtered high-temperature flue gas is then introduced into the high-temperature side of heat exchanger I to complete heat exchange. The flue gas after heat exchange is then processed by the flue gas purification device and returned. The surplus power of the power grid is used to drive compressor I to compress and heat the circulating working fluid flowing out from the low-temperature side of heat exchanger I. The heated high-temperature and high-pressure circulating working fluid is then introduced into the high-temperature flue gas heat exchange coil inside the multiphase change material mobile heat storage tank to exchange heat with the tertiary heat storage temperature zone and release heat. The remaining heat carried by the circulating working fluid after heat exchange and cooling continues to exchange heat with the secondary heat storage temperature zone for storage. After heat release, the circulating working fluid is returned to the low-temperature side of heat exchanger I through throttling device I to form a closed loop. The operation process of the low-temperature turbine exhaust steam temperature lifting and heat storage module is as follows: the low-pressure turbine exhaust steam at 30-45℃ is output from the low-temperature turbine exhaust steam heat source, pre-compressed by compressor II and heated to 110-135℃ and sent to the high-temperature side of the evaporator for heat release; the gaseous medium generated on the low-temperature side of the evaporator enters the first-stage lithium bromide temperature lifting unit to complete heat and mass exchange: the gaseous medium on the low-temperature side of the evaporator is passed into the absorber and fully exchanged heat with the concentrated lithium bromide solution to generate a dilute lithium bromide solution, which is then transported to the generator by pump II; the low-pressure extraction steam source of the power plant is introduced into the shell side of the generator to provide a driving heat source, the dilute lithium bromide solution in the generator is heated and concentrated, and the precipitated concentrated lithium bromide solution flows back to the absorber to form a closed-loop lithium bromide cycle, while the generator evaporates a medium-temperature gaseous heat-carrying medium at 170-190℃. A medium-temperature gaseous heat-carrying medium at 170–190℃ is pumped to the low-temperature side of heat exchanger II via pump III. A high-temperature flue gas is separated from the high-temperature flue gas filter and sent to the high-temperature side of heat exchanger II via pump IV. The flue gas and the medium-temperature gaseous heat-carrying medium exchange heat inside heat exchanger II, achieving secondary high-temperature flue gas temperature rise and generating a high-grade heat-carrying medium at 410–425℃. This high-grade heat-carrying medium is introduced into the exhaust steam temperature rise and heat storage coil inside the multiphase change material mobile heat storage tank. It first exchanges heat with the secondary heat storage temperature zone and then flows into the primary heat storage temperature zone for heat exchange and storage. After the staged heat storage is completed, the low-temperature working fluid is depressurized and stabilized by the throttling device II and then flows back to the low-temperature side of the evaporator, continuously circulating in a closed loop to complete the staged heat storage operation of the exhaust steam of the low-pressure steam turbine.

[0015] Furthermore, in the energy release and power generation step: Pump V outputs a low-temperature circulating working fluid and delivers it to the working fluid inlet of the heat exchange coil for power generation inside the multiphase change material mobile thermal storage tank. The low-temperature circulating working fluid flows upward from the bottom of the tank inside the heat exchange coil for power generation, sequentially absorbing the heat energy stored in the thermal storage medium in the third-level thermal storage zone, the second-level thermal storage zone, and the first-level thermal storage zone. After sufficient heat absorption, a high-temperature heat-carrying circulating working fluid is formed, which is delivered to the turbine from the heat exchange outlet for power generation, driving the turbine to rotate and perform work, and linking with the matching power generation unit to output electrical energy. After the turbine finishes its work, the low-temperature circulating working fluid is discharged and introduced into the high-temperature side of heat exchanger III. A cold source supplies a cooling medium, and the low-temperature circulating working fluid condenses and liquefies inside heat exchanger III through heat exchange with the cooling medium. The liquefied circulating working fluid flows into pump V for pressurization, and the pressurized low-temperature circulating working fluid flows back to the heat exchange coil of the multiphase change material mobile heat storage tank to continuously absorb the heat energy stored in the heat storage medium. The low-melting-point phase change heat storage medium arranged at the rear end of the working fluid flow path of the heat exchange coil inside the multiphase change material mobile heat storage tank undergoes solidification phase change in the later stage of energy release and power generation operation and continuously releases the latent heat of phase change, stabilizing the output temperature of the circulating working fluid at the outlet of the heat exchange coil of the heat release tank, thereby weakening the temperature jump phenomenon that occurs during the heat release stage.

[0016] The beneficial effects of this invention are: 1. This invention establishes three independent primary, secondary, and tertiary heat storage zones within a multiphase change material mobile heat storage tank, matching the corresponding heat storage zones according to the thermodynamic grade of the heat source. High-temperature flue gas preferentially exchanges heat with the heat storage medium within the tertiary heat storage zone via a high-temperature flue gas heat exchange coil. The low-pressure turbine exhaust steam, after being upgraded by a low-temperature turbine exhaust steam temperature-raising heat storage module, carries the heat-carrying medium and sequentially enters the secondary and primary heat storage zones through the exhaust steam temperature-raising heat storage heat exchange coil to complete heat storage. This fundamentally avoids significant energy loss caused by direct heat exchange between the high-grade heat source and the low-temperature heat storage medium. The entire system can simultaneously recover two industrial waste heats with vastly different grades: high-temperature flue gas from power plants and 30-45°C low-pressure turbine exhaust steam. It is also compatible with low-temperature waste heat sources from photovoltaic and wind power plants, broadening the coverage of industrial waste heat recovery and significantly improving the overall waste heat utilization efficiency of the plant area.

[0017] 2. For low-pressure turbine exhaust steam with a temperature of 30-45℃, this invention abandons the high-energy-consuming multi-stage mechanical compression scheme and adopts a three-stage composite heating process: pre-compression and heating by compressor II, waste heat upgrading by a first-stage lithium bromide heating unit, and secondary heating by high-temperature flue gas waste heat. Among them, the first-stage lithium bromide heating unit relies on the low-pressure steam extraction source of the power plant as the driving heat source, and does not consume additional electricity throughout the process. It uses the high-temperature flue gas produced by the system to complete the secondary upgrading, completely avoiding the energy loss of high-power mechanical compression. It can stably upgrade the low-grade exhaust steam to high-grade heat energy of 410-425℃, which can be used for turbine power generation, and truly realize the low-energy consumption and high-value resource utilization of low-grade industrial waste heat.

[0018] 3. High and low melting point dedicated phase change thermal storage media are arranged in a gradient along the working fluid flow path inside the heat exchange coil of the heat engine power generation mobile thermal storage tank to construct an integrated sensible heat-latent heat composite thermal storage system. In the later stage of energy release power generation operation, the low melting point phase change thermal storage media corresponding to the primary thermal storage temperature zone undergoes solidification phase change and continuously releases the latent heat of phase change, stabilizing the output working fluid temperature at the heat exchange outlet of the heat engine power generation, effectively weakening the temperature jump phenomenon during the heat release process, preventing drastic fluctuations in the input working fluid temperature of the turbine equipment, extending the effective stable power generation time of the turbine unit, and improving the stability and overall conversion efficiency of thermal energy to electrical energy conversion.

[0019] 4. After the multiphase change material mobile thermal storage tank completes all the charging and energy storage operations at the power plant, it is locked and fixed to the steel frame structure by detachable fixing components. Then, it is transported as a whole to the concentrated power load area of ​​the industrial park by a towing truck and loading trailer. This breaks the site constraints of traditional fixed thermal storage equipment that is fixed and cannot be moved, and realizes the flexible allocation of industrial waste heat resources across regions. It is suitable for various application scenarios such as peak and valley regulation of the power grid, emergency power supply in the plant area, and continuous power supply in remote areas.

[0020] 5. The high-temperature flue gas thermal storage module, the low-temperature steam turbine exhaust steam temperature-raising thermal storage module, and the thermal power generation module are respectively connected to the high-temperature flue gas heat exchange coil, the exhaust steam temperature-raising thermal storage heat exchange coil, and the thermal power generation heat exchange coil. The three sets of heat exchange pipelines are independent of each other and form closed-loop circulation loops that do not interfere with each other. The two sets of heat charging units of the high-temperature flue gas thermal storage module and the low-temperature steam turbine exhaust steam temperature-raising thermal storage module can be started simultaneously to carry out joint heat charging, or either set of heat charging units can be started and stopped independently to complete the storage of waste heat of the corresponding grade. Adjustment of the operating conditions of any subsystem will not disturb the other modules. The entire process of commissioning, adjustment, and shutdown of the thermal storage system will not interfere with the stable operation of the original boiler and steam turbine thermal main unit of the power plant, ensuring the long-term safe and continuous operation of the core thermal equipment of the power plant.

[0021] 6. This invention can store industrial waste heat in a multiphase change material mobile thermal storage tank during periods of surplus renewable energy output. During periods of insufficient renewable energy output and peak electricity load, the heat energy is transferred and released to drive turbines for stable power generation. This can effectively mitigate the inherent intermittency and volatility of photovoltaic and wind power generation, reduce the impact of renewable energy output fluctuations on the power grid, and enable the system to continuously and stably output electricity on demand. This reduces the peak-valley load difference of the power grid, increases the proportion of low-carbon electricity supply in the power grid, and enhances the peak-shaving regulation capability and overall power supply stability of the power system. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0023] Figure 2 This is a schematic diagram of the transport state of the multiphase change material mobile thermal storage tank in this invention.

[0024] Figure 3 This is a schematic diagram illustrating the fixed structure in this invention.

[0025] Figure 4 This is a schematic diagram illustrating the internal structure of the mobile thermal storage tank for multiphase change materials in this invention.

[0026] In the diagram: 1. High-temperature flue gas heat source; 2. Pump I; 3. High-temperature resistant flue gas filter; 4. Heat exchanger I; 5. Flue gas purification device; 6. Compressor I; 7. Multiphase change material mobile heat storage tank; 701. Tertiary heat storage zone; 702. Secondary heat storage zone; 703. Primary heat storage zone; 704. High-temperature flue gas heat exchange inlet; 705. High-temperature flue gas heat exchange coil; 706. High-temperature flue gas heat exchange outlet; 70 7. Exhaust steam overheating and heat storage heat exchange inlet; 708. Exhaust steam overheating and heat storage heat exchange coil; 709. Exhaust steam overheating and heat storage heat exchange outlet; 710. Heat exchange inlet for thermal power generation; 711. Heat exchange coil for thermal power generation; 712. Heat exchange outlet for thermal power generation; 713. Tank body; 714. Insulation layer; 715. Primary temperature zone safety valve; 716. Secondary temperature zone safety valve; 717. Tertiary temperature zone safety valve; 718. Primary Temperature zone inspection port; 719, Primary temperature zone protective cover; 720, Secondary temperature zone inspection port; 721, Secondary temperature zone protective cover; 722, Tertiary temperature zone inspection port; 723, Tertiary temperature zone protective cover; 8, Throttling device I; 9, Low-temperature steam turbine exhaust heat source; 10, Compressor II; 11, Evaporator; 12, Absorber; 13, Pump II; 14, Generator; 15, Pump III; 16, Heat exchanger II; 17. Throttling device II; 18. Pump IV; 19. Control valve I; 20. Low-pressure steam extraction source for power plant; 21. Power plant condensate system; 22. Turbine; 23. Heat exchanger III; 24. Pump V; 25. Cold source; 26. Control valve II; 501. Tractor truck; 502. Loading trailer; 503. Steel frame structure; 504. Multi-functional operation control box; 505. Bottom fixing structure; 506. Side fixing structure. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings.

[0028] This invention discloses a multi-grade waste heat cascade recovery mobile thermal energy storage and power generation system.

[0029] Reference Figures 1 to 4This multi-grade waste heat cascade recovery mobile thermal energy storage and power generation system mainly consists of four independent functional modules: a high-temperature flue gas thermal energy storage module, a low-temperature steam turbine exhaust steam temperature lifting and thermal energy storage module, a mobile thermal energy storage module, and a thermal power generation module. Each functional module is equipped with independent heat exchange pipelines and control valves. During operation, the pipelines do not interfere with each other and form their own dedicated closed-loop circulation. The thermal power generation module can cooperate with the multiphase change material mobile thermal energy storage tank 7 inside the mobile thermal energy storage module to form a complete closed-loop cycle of heat energy to electricity conversion. After the multiphase change material mobile thermal energy storage tank 7 is transferred to the power load area, it can release all the waste heat energy stored inside the tank 713 to drive the power generation unit to stably produce electricity. The modular and independent layout can avoid the problem of mutual coupling and disturbance of the operating conditions of each subsystem and will not have a negative impact on the operation of the original thermal power host of the power plant.

[0030] Reference Figure 4 The mobile thermal energy storage module includes a multiphase change material (MPC) mobile thermal energy storage tank 7, which serves as the core energy storage carrier of the entire system. The MPC mobile thermal energy storage tank 7 comprises a tank body 713, which adopts a horizontal cylindrical structure. The outer wall of the tank body 713 is completely covered with an insulation layer 714. The insulation layer 714 is a fully enclosed structure that can block heat conduction and radiation between the tank body 713 and the external environment, reducing heat loss during the thermal energy storage process and improving overall thermal energy storage efficiency. The interior of the tank body 713 is vertically divided into three independent thermal energy storage zones from top to bottom: a primary thermal energy storage zone 703, a secondary thermal energy storage zone 702, and a tertiary thermal energy storage zone 701, each filled with its corresponding dedicated phase change thermal energy storage medium.

[0031] The tertiary thermal storage zone 701, located in the lower layer of tank 713, occupies 25% of the total thermal storage volume of tank 713. Its operating temperature range is 600–700℃. It is filled with NaCl-KCl-MgCl2 high-temperature chloride molten salt, with NaCl, KCl, and MgCl2 mass fractions of 35%, 25%, and 40%, respectively. This chloride salt system is characterized by high temperature resistance, large specific heat capacity, high thermal stability, and high thermal storage density, allowing it to operate under high-temperature conditions of 600–700℃ for extended periods. The tertiary thermal storage zone 701 is primarily designed to accommodate high-grade heat energy carried by high-temperature flue gas, achieving full storage of high-temperature waste heat. It forms a tiered thermal storage system with the secondary thermal storage zone 702, improving the overall utilization efficiency of industrial waste heat of different grades within the entire mobile thermal storage power generation system.

[0032] The secondary thermal storage zone 702, located in the middle layer of tank 713, occupies 50% of the total thermal storage volume of tank 713. Its working temperature range covers 400-600℃. It is filled with an Al-12Si eutectic alloy-expanded graphite composite phase change thermal storage medium. The mass fractions of Al-12Si eutectic alloy and expanded graphite are 85% and 15%, respectively. Expanded graphite builds a continuous high thermal conductivity network inside the composite medium, improving the overall heat exchange capacity of the medium. Al-12Si eutectic alloy provides high phase change thermal storage density. The two work together to achieve both rapid heat exchange and large-capacity thermal storage. As the core buffer thermal storage unit of the system, it can not only receive the medium-temperature waste heat after the high-temperature flue gas is cooled down, but also store the waste heat of the exhaust steam after the secondary flue gas is heated up. At the same time, it undertakes the functions of heat buffering and cascade transfer between the primary and tertiary thermal storage zones, ensuring the continuous and stable temperature field during the synchronous charging process of multiple heat sources.

[0033] The primary heat storage zone 703, located on the upper layer of tank 713, occupies 25% of the total heat storage volume of tank 713. Its operating temperature range is 300-400℃. It is filled with a ternary molten salt medium of NaNO3-KNO3-Na2SO4, with mass fractions of NaNO3, KNO3, and Na2SO4 of 45%, 45%, and 10%, respectively. This ternary molten salt has high latent heat of phase change, excellent thermal cycle stability, and good thermal conductivity. It is suitable for the waste heat of medium-high temperature exhaust steam at 410-425℃ after secondary flue gas temperature enhancement and quality improvement. It can complete the efficient phase change storage of medium-temperature waste heat in the range of 300-400℃. During the energy release stage, the low-melting-point molten salt in this zone can continuously release the latent heat of phase change in the later stage, stabilize the outlet temperature of the power generation working fluid, weaken the temperature jump phenomenon in the heat release process, and ensure the stable power generation of the turbine unit.

[0034] The tank 713 is equipped with three sets of heat exchange coils arranged in an alternating pattern. Each set of heat exchange coils is matched with a separate circulation loop and a corresponding heat exchange inlet and outlet structure. The three sets of heat exchange coils are respectively high-temperature flue gas heat exchange coil 705, exhaust steam temperature rise and heat storage heat exchange coil 708, and heat engine power generation heat exchange coil 711. The high-temperature flue gas heat exchange coil 705 has a fluid inlet at high-temperature flue gas heat exchange inlet 704 and a fluid outlet at high-temperature flue gas heat exchange outlet 706. High-temperature flue gas heat exchange inlet 704 is located in the tertiary heat storage zone 701, and high-temperature flue gas heat exchange outlet 706 is located in the secondary heat storage zone 702. The exhaust steam temperature-raising heat storage coil 708 has a fluid inlet at exhaust steam temperature-raising heat storage inlet 707 and a fluid outlet at exhaust steam temperature-raising heat storage outlet 709. The heat exchange inlet 707 for the thermal storage is located in the secondary thermal storage zone 702, and the heat exchange outlet 709 for the thermal storage is located in the primary thermal storage zone 703. The fluid inlet of the heat exchange coil 711 for the thermal power generation is the heat exchange inlet 710 for the thermal power generation, and the fluid outlet is the heat exchange outlet 712 for the thermal power generation. The heat exchange inlet 710 for the thermal power generation is located in the tertiary thermal storage zone 701, and the heat exchange outlet 712 for the thermal power generation is located in the primary thermal storage zone 703. The high-temperature flue gas heat exchange coil 705, the exhaust steam temperature-raising and heat storage coil 708, and the heat engine power generation heat exchange coil 711 are arranged in an alternating pattern. During the charging stage, a uniformly diffused alternating heat flow field can be formed, avoiding local overheating of the tank 713 and forming a stable temperature field with a gradient decreasing from top to bottom inside the tank. At the same time, along the working fluid flow path inside the heat engine power generation heat exchange coil 711, the front end of the heat engine power generation heat exchange coil 711 is arranged with a high-melting-point phase change heat storage medium, namely NaCl-KCl-MgCl2 high-temperature chloride molten salt, corresponding to the third-level heat storage temperature zone 701; the rear end of the coil is arranged with a low-melting-point phase change heat storage medium, namely NaNO3-KNO3-Na2SO4 ternary molten salt, corresponding to the first-level heat storage temperature zone 703. Relying on the layered arrangement of high and low melting point dedicated phase change media to construct a continuous latent heat-sensible heat composite heat storage system, the low-melting-point ternary molten salt solidifies and releases heat to stabilize the working fluid outlet temperature in the later stage of energy release, which can effectively suppress the temperature jump phenomenon that occurs during the energy release and power generation stage.

[0035] The temperature jump phenomenon that this solution aims to suppress refers to the abrupt and rapid drop in the outlet working fluid temperature of the heat exchange coil 711 during the later stages of continuous energy release and power generation using a multiphase change material (MPM) mobile thermal storage tank 7. This occurs when the latent heat of phase change in the MPM medium is completely released, leaving only the sensible heat of the medium to release heat, leading to a sudden temperature change. This abrupt temperature change directly causes significant fluctuations in the turbine 22 intake temperature, resulting in drastic fluctuations in the generator output power and reducing power generation stability and thermoelectric conversion efficiency. In the later stages of energy release, this system relies on the solidification phase change of the low-melting-point ternary molten salt within the primary thermal storage zone 703 to continuously release the latent heat of phase change, thus stabilizing the outlet working fluid temperature of the heat exchange coil 711 and effectively mitigating or eliminating the temperature jump phenomenon that occurs during the energy release and power generation phase.

[0036] To ensure the safe operation of tank 713, each of the three thermal storage zones is equipped with an independent pressure protection component: the first-level temperature zone safety valve 715 corresponds to the upper first-level thermal storage zone 703, the second-level temperature zone safety valve 716 corresponds to the middle second-level thermal storage zone 702, and the third-level temperature zone safety valve 717 corresponds to the lower third-level thermal storage zone 701. Each safety valve can independently complete the overpressure relief and pressure stabilization of the corresponding temperature zone, eliminating safety hazards caused by abnormal pressure inside the tank.

[0037] To facilitate equipment maintenance and monitoring of the thermal storage medium's condition, each of the three temperature zones is equipped with an independent inspection port and a sealed protective structure: the primary thermal storage zone 703 is equipped with a primary temperature zone inspection port 718, and the outside of the primary temperature zone inspection port 718 is fitted with a primary temperature zone protective cover 719; the secondary thermal storage zone 702 is equipped with a secondary temperature zone inspection port 720, and the outside of the secondary temperature zone inspection port 720 is fitted with a secondary temperature zone protective cover 721; the tertiary thermal storage zone 701 is equipped with a tertiary temperature zone inspection port 722, and the outside of the tertiary temperature zone inspection port 722 is fitted with a tertiary temperature zone protective cover 723. Each protective cover completely seals the corresponding inspection port when not under maintenance, preventing the thermal medium inside the tank from leaking out and external dust and impurities from entering the tank body 713, thus ensuring the sealing performance of the tank body 713 and the long-term cyclic use performance of the thermal storage medium.

[0038] The system's heat exchange operation follows a tiered heat exchange matching logic: the high-temperature flue gas heat-carrying medium enters the high-temperature flue gas heat exchange coil 705 through the high-temperature flue gas heat exchange inlet 704, preferentially exchanging heat with the heat storage medium in the lower three-stage heat storage zone 701 to release high-grade heat. After the working medium's temperature decreases, the remaining heat it carries continues to exchange heat with the medium in the middle two-stage heat storage zone 702 for storage, and finally flows out from the high-temperature flue gas heat exchange outlet 706. The turbine exhaust steam heat-carrying medium, after two stages of temperature and quality improvement, is sent from the exhaust steam temperature improvement and heat storage heat exchange inlet 707 to the exhaust steam temperature improvement and heat storage heat exchange coil 708, first exchanging heat with the heat storage medium in the middle two-stage heat storage zone 702, and then flowing upward to fully exchange heat with the medium in the upper first-stage heat storage zone 703, and finally flowing out from the exhaust steam temperature improvement and heat storage heat exchange outlet 709. The heat source grade and the heat storage temperature are precisely matched, reducing irreversible heat transfer losses during the heat exchange process and improving the overall heat storage efficiency.

[0039] The high-temperature flue gas heat storage module is used to recover waste heat from high-temperature flue gas in power plants. It includes a high-temperature flue gas heat source 1, pump I 2, high-temperature resistant flue gas filter 3, heat exchanger I 4, flue gas purification device 5, compressor I 6, and throttling device I 8. The entire module is divided into two independent pipelines: a flue gas circulation loop and a closed-loop heat storage circulation loop for the working fluid.

[0040] Flue gas circulation loop: The flue gas outlet of high-temperature flue gas heat source 1 is connected to the inlet of pump I2, and the outlet of pump I2 is connected to high-temperature resistant flue gas filter 3. After filtering dust and impurities, the flue gas is passed into the high-temperature side of heat exchanger I4 to complete the heat release. After heat exchange, the flue gas is sent to flue gas purification device 5 to treat pollutants. The purified flue gas is returned to high-temperature flue gas heat source 1 to achieve circulation. Closed-loop heat storage cycle of working fluid: The outlet of the working fluid on the low-temperature side of heat exchanger I4 is connected to compressor I6. Compressor I6 compresses the working fluid by relying on surplus off-peak electricity from the power grid. The outlet of compressor I6 is connected to the high-temperature flue gas heat exchange inlet 704 of tank 713. The high-temperature and high-pressure working fluid flows through the high-temperature flue gas heat exchange coil 705 and releases heat step by step to the third-stage heat storage temperature zone 701 and the second-stage heat storage temperature zone 702. After releasing heat and cooling down, the working fluid flows out from the high-temperature flue gas heat exchange outlet 706 and is connected to the throttling device I8 to complete the pressure reduction and flow stabilization. The outlet of the throttling device I8 flows back to the low-temperature side of heat exchanger I4, forming a continuous cycle to recover the waste heat of high-temperature flue gas.

[0041] The low-temperature turbine exhaust steam temperature lifting and heat storage module is designed for low-grade turbine exhaust steam at 30-45℃ and incorporates a pre-compression and two-stage gradient temperature lifting composite process. The low-temperature turbine exhaust steam temperature lifting and heat storage module includes a low-temperature heat extraction and temperature lifting unit, a first-stage lithium bromide temperature lifting unit, and a second-stage flue gas waste heat temperature lifting and heat storage unit.

[0042] The low-temperature heat extraction and temperature-raising unit includes a low-temperature turbine exhaust steam heat source 9, compressor II 10, and evaporator 11. The outlet of the low-temperature turbine exhaust steam heat source 9 is connected to the inlet of compressor II 10, and the outlet of compressor II 10 is connected to the high-temperature side inlet of evaporator 11. The high-temperature side outlet of evaporator 11 flows back to the inlet of the low-temperature turbine exhaust steam heat source 9, forming a closed loop for exhaust steam heat extraction. The low-pressure exhaust steam at 30-45℃ is pre-compressed and heated to 110-135℃ by compressor II 10 before being sent to evaporator 11 to release heat, thus pre-raising the basic temperature of the exhaust steam. This reduces the heat exchange temperature difference required for subsequent primary lithium bromide temperature raising and secondary flue gas waste heat temperature raising stages, reduces the heat exchanger configuration area, and lowers the equipment investment and irreversible heat exchange losses of the entire exhaust steam upgrading system.

[0043] The primary lithium bromide temperature-raising unit includes an absorber 12, a pump II 13, a generator 14, a low-pressure steam extraction source 20 from the power plant, and a power plant condensate drainage system 21. The low-temperature gaseous outlet of the evaporator 11 is connected to the gaseous inlet of the absorber 12. The dilute lithium bromide solution outlet of the absorber 12 is connected to the inlet of the pump II 13, and the outlet pipeline of the pump II is connected to the dilute lithium bromide solution inlet of the generator 14. The concentrated lithium bromide solution outlet of the generator 14 is returned to the concentrated lithium bromide solution inlet of the absorber 12. The steam extraction outlet of the low-pressure steam extraction source 20 from the power plant is connected to the shell-side medium inlet of the generator 14, and the shell-side condensate drainage outlet of the generator 14 is connected to the inlet of the power plant condensate drainage system 21, forming a closed-loop temperature-raising cycle for the lithium bromide medium. This unit relies on the power plant's self-produced low-pressure extracted steam as the driving heat source, requiring no additional power consumption throughout the process. It can upgrade the gaseous heat exchange medium from the evaporator to 170-190°C, complete the first-level grade improvement of the low-pressure exhaust steam waste heat, reduce the heat exchange temperature difference required by the subsequent secondary flue gas waste heat temperature raising unit, reduce the heat exchange load of high-temperature flue gas, and reduce the overall heat loss of the system.

[0044] The secondary flue gas waste heat lifting and storage unit includes pump III 15, heat exchanger II 16, pump IV 18, and throttling device II 17. The medium inlet of pump III 15 is connected to the gaseous working fluid outlet of generator 14, and the medium outlet of pump III 15 is connected to the low-temperature side medium inlet of heat exchanger II 16. The low-temperature side working fluid outlet of heat exchanger II 16 is connected to the inlet of the waste steam lifting and storage heat exchange coil 708 of multiphase change material mobile heat storage tank 7. The working fluid outlet of waste steam lifting and storage heat exchange coil 708 is returned to the low-temperature side medium inlet of evaporator 11 through throttling device II 17, forming a closed loop of waste steam working fluid. A high-temperature flue gas is separated from the high-temperature flue gas filter 3 and sent to the high-temperature side of heat exchanger II 16 by pump IV 18 to exchange heat with the medium-temperature gaseous working fluid on the low-temperature side. The flue gas after heat exchange and cooling is sent to the flue gas purification device 5 for purification treatment.

[0045] The 170-190℃ medium-temperature gaseous heat-carrying medium output from the low-temperature side of heat exchanger II16 is transported to the low-temperature side channel of heat exchanger II16 via pump III15. It uses the waste heat of high-temperature flue gas to complete the secondary flue gas temperature rise, raising the temperature to 410-425℃ for high-grade heat-carrying medium. The high-temperature heat-carrying medium is sent from the waste steam temperature rise and heat storage heat exchange inlet 707 into the waste steam temperature rise and heat storage heat exchange coil 708, and sequentially stores heat in the secondary heat storage temperature zone 702 and the primary heat storage temperature zone 703. After completing the heat release and cooling, the low-temperature working fluid flows out from the waste steam temperature rise and heat storage heat exchange outlet 709, and after being depressurized and stabilized by the throttling device II17, it flows back to the low-temperature side of evaporator 11, continuously completing the closed-loop quality improvement and heat storage. This unit utilizes the waste heat from the high-temperature flue gas produced by the power plant to replace mechanical compression for secondary upgrading, eliminating the need for additional compression power consumption and reducing the overall power consumption of the low-grade exhaust steam waste heat upgrading process. At the same time, the higher working fluid output temperature can fully match the temperature range of the high-temperature heat storage zone in the heat storage tank, reducing heat exchange losses.

[0046] Low-pressure exhaust steam is preheated to 110–135°C by compressor II10 and then sent to evaporator 11 to release heat. The heat exchange medium undergoes a lithium bromide cycle to complete the first-stage temperature rise to 170–190°C. The heated medium is then sent to the second-stage flue gas waste heat lifting and storage unit, where it undergoes a second-stage heat exchange and quality improvement to 410–425°C using the high-temperature flue gas waste heat. The resulting high-grade, high-temperature medium is then sent to exhaust steam lifting and storage heat exchange coil 708 to complete staged heat storage. This three-stage waste heat quality improvement process consumes only a small amount of electricity in the pre-compression stage. The first-stage temperature rise relies on the power plant's low-pressure extraction steam, and the second-stage temperature rise utilizes the power plant's high-temperature flue gas waste heat to achieve the temperature rise. There is no need to add high-power compression equipment, reducing the overall power consumption of waste heat quality improvement and efficiently achieving high-value storage of low-grade waste heat at 30–45°C across temperature zones.

[0047] Control valve I19 is installed on the flue gas pipeline at the outlet of the high-temperature flue gas filter 3. Control valve I19 is an electric regulating valve, which is arranged at the high-temperature flue gas diversion point. By adjusting the opening of control valve I19, the flow rate of high-temperature flue gas diverted into the secondary flue gas waste heat lifting and storage unit can be controlled, so as to achieve precise control of flue gas flow direction and flue gas supply. This matches the different heat charging load conditions of the heat storage tank and ensures the stable operation of the heat exchange process in each heat storage temperature zone of the multiphase change material mobile heat storage tank.

[0048] After heat exchange by the high-temperature flue gas heat storage module and the secondary flue gas waste heat lifting and heat storage unit, the flue gas branches are finally merged and connected to the flue gas purification device 5. A control valve II26 is installed at the merging node of the flue gas merging pipeline. The control valve II26 is also an electric regulating valve. The control valve II26 can balance the flue gas flow of the two flue gas branches in real time, stabilize the flue gas pressure inside the merging pipeline, adapt to the flue gas volume fluctuation caused by the variable operating conditions of each heat exchange module, effectively avoid the problem of uneven airflow distribution at the inlet of the flue gas purifier caused by the imbalance of branch flow, and ensure the continuous, stable and efficient operation of purification processes such as flue gas dust removal, desulfurization and denitrification.

[0049] The heat engine power generation module includes a turbine 22, a heat exchanger III 23, a pump V 24, and a cold source 25, forming two independent loops: a heat energy conversion working fluid loop and a cooling medium loop. Specifically, the working fluid outlet of the heat engine power generation heat exchange coil 711 inside the multiphase change material mobile heat storage tank 7 is connected to the working fluid inlet of the turbine 22. The low-temperature working fluid outlet after the turbine 22 performs work is connected to the high-temperature working fluid inlet of the heat exchanger III 23. The high-temperature working fluid outlet of the heat exchanger III 23 is connected to the inlet of the pump V 24. The pressurized working fluid outlet of the pump V 24 is reconnected to the working fluid inlet of the heat engine power generation heat exchange coil 711 in the multiphase change material mobile heat storage tank 7, forming a heat energy conversion working fluid loop. The low-temperature medium outlet of the heat exchanger III 23 is connected to the medium inlet of the cold source 25, and the medium outlet of the cold source 25 is reconnected to the low-temperature medium inlet of the heat exchanger III 23, forming a cooling medium loop.

[0050] In the heat energy conversion working fluid cycle, the low-temperature working fluid, pressurized by pump V24, is sent to the heat engine power generation heat exchange coil 711 through the heat engine power generation heat exchange inlet 710 of tank 713. The working fluid flows upward from the lower layer of tank 713, absorbing the heat stored in the heat storage medium inside the third-level heat storage temperature zone 701, the second-level heat storage temperature zone 702, and the first-level heat storage temperature zone 703 in sequence. After fully absorbing heat, it forms a high-temperature heat-carrying working fluid, which flows out from the heat engine power generation heat exchange outlet 712 and is transported to turbine 22, driving turbine 22 to rotate and do work, and linking with the matching power generation unit to output electrical energy. After turbine 22 finishes doing work, it discharges the low-temperature working fluid into the high-temperature side of heat exchanger III23. After being cooled and liquefied by cold source 25, it is pressurized again by pump V24 and flows back to the heat engine power generation heat exchange inlet 710.

[0051] In the cooling medium circulation loop, the low-temperature side of heat exchanger Ⅲ23 is interconnected with the cold source 25, continuously providing cooling for the low-temperature working fluid after work is done, ensuring the condensation and liquefaction effect of the working fluid. In the later stage of energy release operation, the low-melting-point phase change medium corresponding to the primary heat storage temperature zone 703 at the rear end of the heat exchange coil 711 of the heat engine solidifies and continuously releases the latent heat of phase change, stabilizing the working fluid output temperature at the heat exchange outlet 712 of the heat engine, avoiding drastic fluctuations in power generation, and extending the stable power generation time of the unit.

[0052] In addition to the multiphase change material mobile thermal storage tank 7, the mobile thermal storage module is also equipped with a towing truck 501, a loading trailer 502, a steel frame structure 503, a multi-functional operation control box 504, and detachable fixing components. The detachable fixing components include a bottom fixing structure 505 and a side fixing structure 506. The bottom fixing structure 505 abuts against the bottom of the tank body 713, and the side fixing structure 506 abuts against the side wall of the tank body 713. The two sets of structures work together to achieve quick assembly and disassembly of the tank body 713 and the steel frame structure 503. The steel frame structure 503 is fixedly mounted on the bearing plane of the loading trailer 502. The multi-functional operation control box 504 is installed on the rear side of the loading trailer 502. It integrates automatic control functions such as real-time temperature monitoring of the three-stage thermal storage temperature zone 701, pressure data acquisition of each temperature zone in the tank, electric valve regulation, and transfer safety interlock protection to achieve automated management and control. After the tank 713 completes its heat storage, it is locked and fixed to the steel frame structure 503 by a detachable fixing component. The front end of the loading trailer 502 is mechanically connected to the traction end of the tractor truck 501, and the tractor truck 501 pulls the loading trailer 502 to be transported as a whole to the load end of the industrial park. This breaks through the geographical limitations of traditional fixed heat storage equipment and solves the problem of the time and space mismatch between energy supply and demand in the power plant waste heat accumulation area and the power load area.

[0053] The present invention also discloses an operation method for a multi-grade waste heat cascade recovery mobile thermal energy storage power generation system.

[0054] The operation method of the multi-grade waste heat cascade recovery mobile thermal energy storage power generation system is based on the above-mentioned mobile thermal energy storage power generation system. The operation method includes three stages: a heat charging step, a tank 713 transfer step, and an energy release power generation step.

[0055] The charging process involves simultaneously starting the high-temperature flue gas heat storage module and the low-temperature turbine exhaust steam temperature-raising heat storage module at the power plant end, or starting them separately to carry out independent charging operations. The high-temperature flue gas waste heat carried by the high-temperature flue gas heat source 1 and the low-pressure turbine exhaust steam waste heat after being upgraded by the low-temperature turbine exhaust steam temperature-raising heat storage module are stored in the first-level heat storage temperature zone 703, the second-level heat storage temperature zone 702, and the third-level heat storage temperature zone 701 of the multiphase change material mobile heat storage tank 7 according to the heat source grade. Transfer steps for tank 713: After the multiphase change material mobile thermal storage tank 7 has completed thermal storage and charging, disconnect the connection between the multiphase change material mobile thermal storage tank 7 and the high-temperature flue gas thermal storage module and the low-temperature steam turbine exhaust steam temperature-raising thermal storage module; fix the multiphase change material mobile thermal storage tank 7 onto the steel frame structure 503 of the mobile thermal storage module using detachable fixing components, and have the loading trailer 502 towed by the tractor truck 501 to transfer the multiphase change material mobile thermal storage tank 7 to the industrial park end; Energy release and power generation steps: The multiphase change material mobile thermal storage tank 7 after transfer is connected to the thermal power generation module. The thermal power generation module is started, and the thermal energy stored inside the multiphase change material mobile thermal storage tank 7 is converted into electrical energy output through the turbine 22, completing the closed-loop conversion of thermal energy to electrical energy.

[0056] Specifically, when only the high-temperature flue gas thermal storage module is activated for independent charging, all pipeline valves inside the low-temperature turbine exhaust steam thermal storage module are closed, and the entire low-temperature turbine exhaust steam thermal storage module is shut down and isolated. Similarly, when only the low-temperature turbine exhaust steam thermal storage module is activated for independent charging, all pipeline valves inside the high-temperature flue gas thermal storage module are closed, and the entire high-temperature flue gas thermal storage module is shut down and isolated. When both charging modules operate synchronously, the two independent closed-loop systems complete the energy storage operation in parallel without interference. The operation process of the high-temperature flue gas thermal storage module during the charging step is as follows: the high-temperature flue gas output from high-temperature flue gas heat source 1 is transported to the high-temperature resistant flue gas storage module via pump I2. The gas filter 3 filters impurities, and the filtered high-temperature flue gas is introduced into the high-temperature side of heat exchanger I4 to complete heat exchange. The flue gas after heat exchange is then treated by the flue gas purification device 5 and returned. The surplus power of the power grid drives the compressor I6 to compress and heat the circulating working fluid flowing out of the low-temperature side of heat exchanger I4. The heated high-temperature and high-pressure circulating working fluid is introduced into the high-temperature flue gas heat exchange coil 705 inside the multiphase change material mobile heat storage tank 7, where it exchanges heat with the tertiary heat storage temperature zone 701 to release heat. The remaining heat carried by the circulating working fluid after heat exchange and cooling continues to exchange heat with the secondary heat storage temperature zone 702 for storage. After heat release, the circulating working fluid is returned to the low-temperature side of heat exchanger I4 through the throttling device I8 to form a closed loop.

[0057] The operation process of the low-temperature turbine exhaust steam temperature lifting and heat storage module is as follows: the low-pressure turbine exhaust steam at 30-45℃ is output from the low-temperature turbine exhaust steam heat source 9, pre-compressed by compressor II 10 and heated to 110-135℃ and sent to the high-temperature side of evaporator 11 for heat release; the gaseous medium generated on the low-temperature side of evaporator 11 enters the first-stage lithium bromide temperature lifting unit to complete heat and mass exchange: the gaseous medium on the low-temperature side of evaporator 11 is passed into absorber 12 and fully exchanged heat with concentrated lithium bromide solution to generate dilute lithium bromide solution, which is then transported to generator 14 by pump II 13; the power plant low-pressure extraction steam source 20 passes low-pressure extraction steam into the shell side of generator 14 to provide driving heat source, the dilute lithium bromide solution in generator 14 is heated and concentrated, and the precipitated concentrated lithium bromide solution flows back to absorber 12 to form a closed-loop lithium bromide cycle, while generator 14 evaporates a medium-temperature gaseous heat-carrying medium at 170-190℃. A medium-temperature gaseous heat-carrying medium at 170–190°C is transported to the low-temperature side of heat exchanger II16 via pump III15. A high-temperature flue gas is separated from the high-temperature flue gas filter 3 and sent to the high-temperature side of heat exchanger II16 via pump IV18. The flue gas and the medium-temperature gaseous heat-carrying medium exchange heat inside heat exchanger II16, achieving secondary high-temperature flue gas temperature rise and generating a high-grade heat-carrying medium at 410–425°C. This high-grade heat-carrying medium is introduced into the exhaust steam temperature rise and heat storage heat exchange coil 708 inside the multiphase change material mobile heat storage tank 7. It first exchanges heat with the secondary heat storage temperature zone 702 and then flows into the primary heat storage temperature zone 703 for heat exchange and heat storage. After the staged heat storage is completed, the low-temperature working fluid is depressurized and stabilized by the throttling device II17 and then flows back to the low-temperature side of evaporator 11, continuously circulating in a closed loop to complete the staged heat storage operation of the exhaust steam of the low-pressure steam turbine.

[0058] In the energy release and power generation process: Pump V24 outputs a low-temperature circulating working fluid and delivers it to the working fluid inlet of the heat exchange coil 711 inside the multiphase change material mobile thermal storage tank 7. The low-temperature circulating working fluid flows upward from the lower side of the tank 713 inside the heat exchange coil 711, sequentially absorbing the heat energy stored in the thermal storage medium inside the tertiary thermal storage temperature zone 701, the secondary thermal storage temperature zone 702, and the primary thermal storage temperature zone 703. After sufficient heat absorption, a high-temperature heat-carrying circulating working fluid is formed, which is delivered to the turbine 22 through the heat exchange outlet 712, driving the turbine 22 to rotate and perform work, and linking with the matching power generation unit to output electrical energy. After the turbine 22 finishes its work, it discharges the low-temperature circulating working fluid, which is then introduced into the high-temperature side of the heat exchanger III23. The low-temperature side of heat exchanger Ⅲ23 is connected to cold source 25 to supply cooling medium. The low-temperature circulating working fluid exchanges heat with the cooling medium inside heat exchanger Ⅲ23 to achieve condensation and liquefaction. The liquefied circulating working fluid flows into pump ⤔24 to complete the pressurization process. The pressurized low-temperature circulating working fluid flows back to the heat engine power generation heat exchange coil 711 of the multiphase change material mobile heat storage tank 7 to continuously absorb the heat energy stored in the heat storage medium. The low-melting-point phase change heat storage medium arranged inside the multiphase change material mobile heat storage tank 7 along the rear end of the working fluid flow path of the heat engine power generation heat exchange coil 711 undergoes solidification phase change in the later stage of energy release power generation operation and continuously releases the latent heat of phase change, stabilizing the output temperature of the circulating working fluid at the outlet of the heat engine power generation heat exchange coil 711 and weakening the temperature jump phenomenon that occurs during the heat release stage.

[0059] The entire system can simultaneously recover high- and low-grade industrial waste heat from power plants, is compatible with low-temperature heat sources from wind and solar energy, alleviates the pressure of new energy consumption, and is suitable for diverse application scenarios such as distributed energy peak shaving, industrial waste heat recovery, and emergency power supply.

Claims

1. A multi-grade waste heat cascade recovery mobile thermal storage power generation system, characterized in that: This includes high-temperature flue gas thermal storage modules, low-temperature steam turbine exhaust steam temperature-raising thermal storage modules, mobile thermal storage modules, and thermal power generation modules; The mobile thermal storage module includes a multiphase change material mobile thermal storage tank (7), which is divided into an independent primary thermal storage temperature zone (703), a secondary thermal storage temperature zone (702), and a tertiary thermal storage temperature zone (701). The primary thermal storage temperature zone (703), the secondary thermal storage temperature zone (702), and the tertiary thermal storage temperature zone (701) are filled with corresponding dedicated phase change thermal storage media. The interior of the multiphase change material mobile heat storage tank (7) is provided with high-temperature flue gas heat exchange coils (705), exhaust steam temperature-raising heat storage heat exchange coils (708), and heat engine power generation heat exchange coils (711) arranged in an alternating manner. The high-temperature flue gas heat storage module, the low-temperature steam turbine exhaust steam temperature-raising heat storage module, and the heat engine power generation module are respectively connected to the corresponding high-temperature flue gas heat exchange coils (705), exhaust steam temperature-raising heat storage heat exchange coils (708), and heat engine power generation heat exchange coils (711), forming a closed loop that does not interfere with each other. The heat engine power generation module and the multiphase change material mobile heat storage tank (7) form a closed-loop heat-electric energy conversion system, which is used to release heat energy after the multiphase change material mobile heat storage tank (7) is transferred to drive power generation. The low-temperature steam turbine exhaust steam temperature lifting and storage module includes a low-temperature heat extraction and temperature lifting unit, a primary lithium bromide temperature lifting unit, and a secondary flue gas waste heat temperature lifting and storage unit. The low-temperature heat extraction and temperature raising unit includes a low-temperature steam turbine exhaust heat source (9), compressor II (10), and evaporator (11); The outlet of the low-temperature steam turbine exhaust heat source (9) is connected to the inlet of compressor II (10), the outlet of compressor II (10) is connected to the high-temperature side inlet of evaporator (11), and the high-temperature side outlet of evaporator (11) flows back to the inlet of the low-temperature steam turbine exhaust heat source (9), forming a closed loop of exhaust heat extraction. The primary lithium bromide temperature-raising unit includes an absorber (12), a pump II (13), a generator (14), a low-pressure steam extraction source for the power plant (20), and a power plant condensate drainage system (21). The gaseous outlet of the evaporator (11) on the low temperature side is connected to the gaseous inlet of the absorber (12); the dilute lithium bromide solution outlet of the absorber (12) is connected to the inlet of pump II (13), and the outlet pipeline of pump II is connected to the dilute lithium bromide solution inlet of the generator (14); the concentrated lithium bromide solution outlet of the generator (14) is returned to the concentrated lithium bromide solution inlet of the absorber (12); the extraction steam outlet of the low-pressure extraction steam source (20) of the power plant is connected to the shell-side medium inlet of the generator (14), and the shell-side condensate outlet of the generator (14) is connected to the inlet of the power plant condensate system (21); The secondary flue gas waste heat lifting and storage unit includes pump III (15), heat exchanger II (16), pump IV (18), throttling device II (17), and control valve II (26). The medium inlet of pump III (15) is connected to the gaseous working fluid outlet of generator (14), and the medium outlet of pump III (15) is connected to the low-temperature side medium inlet of heat exchanger II (16). The low-temperature side working fluid outlet pipeline of heat exchanger II (16) is connected to the inlet of the waste steam lifting and storage heat exchange coil (708) inside the multiphase change material mobile heat storage tank (7). The working fluid outlet of the waste steam lifting and storage heat exchange coil (708) inside the multiphase change material mobile heat storage tank (7) is connected to the medium inlet of throttling device II (17), and the medium outlet of throttling device II (17) flows back to the low-temperature side medium inlet of evaporator (11), forming a closed-loop cycle of waste steam working fluid.

2. The multi-grade waste heat cascade recovery mobile thermal storage power generation system according to claim 1, characterized in that: The multiphase change material mobile thermal storage tank (7) includes a horizontal cylindrical tank body (713), the tank body (713) is covered with an insulation layer (714); the primary thermal storage temperature zone (703), the secondary thermal storage temperature zone (702) and the tertiary thermal storage temperature zone (701) are arranged vertically from top to bottom inside the tank body (713), and each is equipped with an independent safety valve and inspection port; The primary heat storage temperature zone (703) is located in the upper layer of the tank body (713), accounting for 25% of the total heat storage volume. The temperature range is 300-400℃, and the interior is filled with NaNO3-KNO3-Na2SO4 ternary molten salt medium. The secondary thermal storage temperature zone (702) is located in the middle layer of the tank body (713) of the multiphase change material mobile thermal storage tank (7), accounting for 50% of the total thermal storage volume. The temperature range is 400 to 600°C, and the interior is filled with Al-12Si eutectic alloy-expanded graphite composite phase change thermal storage medium. The three-level heat storage temperature zone (701) is located in the lower layer of the tank body (713) of the multiphase change material mobile heat storage tank (7), accounting for 25% of the total heat storage volume. The temperature range is 600-700℃, and the interior is filled with NaCl-KCl-MgCl2 high-temperature chloride salt molten salt medium. During the heating process, the high-temperature flue gas first enters the third-level heat storage zone (701) and then flows into the second-level heat storage zone (702). The upgraded exhaust steam first enters the second-level heat storage zone (702) and then flows into the first-level heat storage zone (703) to complete the cascade heat exchange.

3. The multi-grade waste heat cascade recovery mobile thermal storage power generation system according to claim 2, characterized in that: The high-temperature flue gas heat storage module includes a high-temperature flue gas heat source (1), pump I (2), high-temperature resistant flue gas filter (3), heat exchanger I (4), flue gas purification device (5), compressor I (6), throttling device I (8), and control valve I (19); The flue gas outlet of the high-temperature flue gas heat source (1) is connected to the inlet of pump I (2). The outlet of pump I (2) is connected to the inlet of the high-temperature resistant flue gas filter (3). The outlet of the high-temperature resistant flue gas filter (3) is connected to the high-temperature side flue gas inlet of heat exchanger I (4). The flue gas outlet of the high-temperature resistant flue gas filter (3) is led out to a branch. A control valve I (19) is installed on the branch. The high-temperature side flue gas outlet of heat exchanger I (4) is connected to the inlet of the flue gas purification device (5). The outlet pipe of the flue gas purification device (5) is connected back to the high-temperature flue gas heat source (1), forming a flue gas circulation loop. The working fluid outlet on the low-temperature side of heat exchanger I (4) is connected to the working fluid inlet of compressor I (6). The working fluid outlet of compressor I (6) is connected to the working fluid inlet of the high-temperature flue gas heat exchange coil (705) inside the multiphase change material mobile heat storage tank (7). The working fluid outlet of the high-temperature flue gas heat exchange coil (705) is connected to the working fluid inlet of throttling device I (8). The working fluid outlet of throttling device I (8) flows back to the working fluid inlet on the low-temperature side of heat exchanger I (4). The above components are connected in series to form an independent closed-loop heat storage cycle of working fluid.

4. A multi-grade waste heat cascade recovery mobile thermal storage power generation system according to claim 3, characterized in that: The branch line from the high-temperature resistant flue gas filter (3) is connected to the flue gas inlet of pump IV (18) after passing through control valve I (19). The flue gas outlet of pump IV (18) is connected to the high-temperature side flue gas inlet of heat exchanger II (16). The flue gas branch line discharged from heat exchanger I (4) and the flue gas branch line discharged from heat exchanger II (16) merge and are connected to the flue gas purification device (5). Control valve II (26) is installed at the confluence node of the two flue gas branches.

5. A multi-grade waste heat cascade recovery mobile thermal storage power generation system according to claim 4, characterized in that: In the low-temperature turbine exhaust steam temperature-raising and heat storage module, the low-pressure exhaust steam output from the low-temperature turbine exhaust steam heat source (9) at 30-45℃ is first fed into compressor II (10) to complete pre-compression and temperature rise, and then sent to the high-temperature side of the evaporator (11) to release heat. After the heat exchange medium on the low-temperature side of the evaporator (11) absorbs the heat of the exhaust steam, it forms a gaseous medium that enters the first-stage lithium bromide temperature-raising unit to complete heat and mass exchange. After being upgraded by lithium bromide absorption cycle, a medium-temperature gaseous heat-carrying medium at 170-190℃ is obtained. The medium-temperature gaseous heat-carrying medium is transported to the low-temperature side of heat exchanger II (16) by pump III (15). At the same time, the high-temperature flue gas filtered by the high-temperature resistant flue gas filter (3) is sent to the high-temperature side of heat exchanger II (16) by pump IV (18). The two exchange heat inside heat exchanger II (16) to complete the secondary high-temperature flue gas temperature rise and form a high-grade heat-carrying medium of 410-425℃. The high-grade heat-carrying medium of 410-425℃ is transported to the waste steam temperature rise and heat exchange coil (708) of the multiphase change material mobile heat storage tank (7) to complete the staged heat storage. After the heat is released and the working fluid is cooled down, it is depressurized and stabilized by the throttling device II (17) and then flows back to the low-temperature side of evaporator (11) to continuously circulate and realize the quality improvement and storage of waste steam heat.

6. A multi-grade waste heat cascade recovery mobile thermal storage power generation system according to claim 5, characterized in that: The heat engine power generation module includes a turbine (22), a heat exchanger III (23), a pump V (24), and a cold source (25); The working fluid outlet of the heat exchange coil (711) inside the multiphase change material mobile heat storage tank (7) is connected to the working fluid inlet of the turbine (22). The low-temperature working fluid outlet after the turbine (22) has done work is connected to the high-temperature working fluid inlet of the heat exchanger III (23). The high-temperature working fluid outlet of the heat exchanger III (23) is connected to the inlet of the pump V (24). The working fluid outlet after the pump V (24) has been pressurized is connected back to the working fluid inlet of the heat exchange coil (711) of the multiphase change material mobile heat storage tank (7), forming a heat energy conversion working fluid cycle. The low-temperature side medium outlet of heat exchanger III (23) is connected to the medium inlet of cold source (25), and the medium outlet of cold source (25) is connected back to the low-temperature side medium inlet of heat exchanger III (23) to form a cooling medium circulation loop.

7. A multi-grade waste heat cascade recovery mobile thermal storage power generation system according to claim 6, characterized in that: The mobile thermal storage module also includes a tractor truck (501), a loading trailer (502), a steel frame structure (503), a multi-functional operation control box (504), and detachable fixing components. The multi-phase change material mobile thermal storage tank (7) is assembled onto the steel frame structure (503) through the detachable fixing components to realize the separation and transfer of the tank body (713). The steel frame structure (503) is fixedly mounted on the bearing plane of the loading trailer (502), and the multi-functional operation control box (504) is arranged at the rear of the loading trailer (502). The multi-functional operation control box (504) is used to manage the operating parameters of the entire process of the thermal storage tank charging, transfer and energy release; the front end of the loading trailer (502) is mechanically connected to the traction end of the tractor truck (501), and the tractor truck (501) provides the driving power to transfer the loading trailer (502) with the assembled multiphase change material mobile thermal storage tank (7) as a whole.

8. An operation method for a multi-grade waste heat cascade recovery mobile thermal energy storage power generation system, characterized in that: The multi-grade waste heat cascade recovery mobile thermal energy storage power generation system as described in claim 7 includes the following steps: The charging steps are as follows: At the power plant end, the high-temperature flue gas heat storage module and the low-temperature steam turbine exhaust steam temperature-raising heat storage module are started simultaneously or the high-temperature flue gas heat storage module and the low-temperature steam turbine exhaust steam temperature-raising heat storage module are started separately to carry out independent charging operations; the high-temperature flue gas waste heat carried by the high-temperature flue gas heat source (1) and the low-pressure steam turbine exhaust steam waste heat after being upgraded by the low-temperature steam turbine exhaust steam temperature-raising heat storage module are stored in the first-level heat storage temperature zone (703), the second-level heat storage temperature zone (702) and the third-level heat storage temperature zone (701) set in the multiphase change material mobile heat storage tank (7) according to the heat source grade. Tank transfer steps: After the multiphase change material mobile thermal storage tank (7) has completed thermal storage and charging, disconnect the connection between the multiphase change material mobile thermal storage tank (7) and the high temperature flue gas thermal storage module and the low temperature steam turbine exhaust steam temperature-raising thermal storage module; fix the multiphase change material mobile thermal storage tank (7) on the steel frame structure (503) of the mobile thermal storage module by means of detachable fixing components, and have the loading trailer (502) pulled by the tractor truck (501) to transfer the multiphase change material mobile thermal storage tank (7) to the industrial park end; Energy release and power generation steps: The multiphase change material mobile thermal storage tank (7) after transfer is connected to the thermal power generation module. The thermal power generation module is started. The thermal energy stored inside the multiphase change material mobile thermal storage tank (7) is converted into electrical energy output through the turbine (22), completing the closed-loop conversion of thermal energy to electrical energy.

9. The operation method of a multi-grade waste heat cascade recovery mobile thermal storage power generation system according to claim 8, characterized in that: In the heat charging step, the operation process of the high-temperature flue gas heat storage module is as follows: the high-temperature flue gas output from the high-temperature flue gas heat source (1) is transported to the high-temperature resistant flue gas filter (3) by pump I (2) to complete the impurity filtration. The filtered high-temperature flue gas is passed into the heat exchanger I (4) to complete the heat exchange on the high-temperature side. The flue gas after heat exchange is passed into the flue gas purification device (5) for treatment and then returned. The surplus power of the power grid is used to drive the compressor I (6) to compress and heat up the circulating working fluid flowing out of the low-temperature side of the heat exchanger I (4). The heated high-temperature and high-pressure circulating working fluid is passed into the high-temperature flue gas heat exchange coil (705) inside the multiphase change material mobile heat storage tank (7) to exchange heat with the third-level heat storage temperature zone (701) to release heat. The remaining heat carried by the circulating working fluid after heat exchange and cooling continues to exchange heat with the second-level heat storage temperature zone (702) for storage. After the heat release is completed, the circulating working fluid is returned to the low-temperature side of the heat exchanger I (4) through the throttling device I (8) to form a closed loop. The operation process of the low-temperature turbine exhaust steam temperature-raising and heat storage module is as follows: the low-pressure turbine exhaust steam at 30-45℃ is output from the low-temperature turbine exhaust steam heat source (9), pre-compressed and heated to 110-135℃ by compressor II (10), and sent to the high-temperature side of evaporator (11) for heat release; the gaseous medium generated on the low-temperature side of evaporator (11) enters the first-stage lithium bromide temperature-raising unit to complete heat and mass exchange; the gaseous medium on the low-temperature side of evaporator (11) is passed into absorber (12) to react with concentrated... The lithium bromide solution is fully absorbed by heat exchange to generate a dilute lithium bromide solution, which is then transported to the generator (14) via pump II (13). The low-pressure extraction steam source (20) of the power plant is introduced into the shell side of the generator (14) to provide a driving heat source. The dilute lithium bromide solution in the generator (14) is heated and concentrated. The precipitated concentrated lithium bromide solution is returned to the absorber (12) to form a closed-loop lithium bromide cycle. At the same time, the generator (14) evaporates a medium-temperature gaseous heat-carrying medium at 170-190°C. A medium-temperature gaseous heat-carrying medium at 170–190°C is transported to the low-temperature side of heat exchanger II (16) via pump III (15); a high-temperature flue gas is separated from the high-temperature flue gas filter (3) and sent to the high-temperature side of heat exchanger II (16) by pump IV (18). The flue gas and the medium-temperature gaseous heat-carrying medium exchange heat inside heat exchanger II (16), achieving a secondary high-temperature flue gas temperature rise and generating a high-grade heat-carrying medium at 410–425°C; this high-grade heat-carrying medium The waste steam heat exchange coil (708) inside the multiphase change material mobile heat storage tank (7) is introduced into the heat exchange coil. It first exchanges heat with the secondary heat storage zone (702) and then flows into the primary heat storage zone (703) for heat exchange and storage. After the graded heat storage is completed, the low-temperature working fluid is depressurized and stabilized by the throttling device II (17) and then flows back to the low-temperature side of the evaporator (11) for continuous closed-loop circulation, thus completing the graded heat storage operation of the waste steam of the low-pressure steam turbine.

10. The operation method of a multi-grade waste heat cascade recovery mobile thermal energy storage power generation system according to claim 9, characterized in that: In the energy release and power generation step: Pump V (24) outputs low-temperature circulating working fluid and delivers it to the working fluid inlet of the heat exchange coil (711) inside the multiphase change material mobile heat storage tank (7). The low-temperature circulating working fluid flows upward from the bottom of the tank (713) inside the heat exchange coil (711), and absorbs the heat energy stored in the heat storage medium inside the third-level heat storage temperature zone (701), the second-level heat storage temperature zone (702), and the first-level heat storage temperature zone (703) in sequence. After fully absorbing heat, it forms a high-temperature heat-carrying circulating working fluid, which is delivered to the turbine (22) from the heat exchange outlet (712) to drive the turbine (22) to rotate and do work, and output electrical energy in conjunction with the matching power generation unit. After the turbine (22) finishes doing work, it discharges the low-temperature circulating working fluid, which is then introduced into the high-temperature side of the heat exchanger III (23). The low-temperature side of heat exchanger Ⅲ (23) is connected to a cold source (25) to supply cooling medium. The low-temperature circulating working medium exchanges heat with the cooling medium inside heat exchanger Ⅲ (23) to achieve condensation and liquefaction. The liquefied circulating working medium flows into pump Ⅴ (24) to complete the pressurization process. The pressurized low-temperature circulating working medium flows back to the heat engine power generation heat exchange coil (711) of the multiphase change material mobile heat storage tank (7) to continuously absorb the heat energy stored in the heat storage medium. The low-melting-point phase change heat storage medium arranged inside the multiphase change material mobile heat storage tank (7) along the working medium flow path of the heat engine power generation heat exchange coil (711) undergoes solidification phase change in the later stage of energy release power generation operation and continuously releases the latent heat of phase change, stabilizing the output temperature of the circulating working medium at the outlet of the heat engine power generation heat exchange coil (711) to weaken the temperature jump phenomenon that occurs during the heat release stage.

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