A heat transfer medium shunting and bypass mixed temperature supply heat storage steam power generation system for main heat absorbing section and operation method

Abstract

This invention discloses a thermal energy storage steam power generation system and its operation method, which includes a heat transfer medium diversion and bypass mixing supply to the main heat absorption section. The system comprises an external thermal energy storage device, a closed-loop heat transfer medium circuit, and a water / steam power generation circuit. The closed-loop circuit does not have a turbine and indirectly exchanges heat with the water / steam circuit through a heat exchanger. The high-temperature heat transfer medium is divided into a high-temperature steam heat exchanger branch and a high-temperature bypass branch by the diversion device. After pressure regulation, the bypass medium mixes with the heat-released medium from the branch, forming a medium-high temperature stream that enters the main heat absorption heat exchanger. After heat release, the medium is circulated back to the external thermal energy storage device for heat absorption via a circulation drive device. This invention maintains the minimum heat exchange difference at the main heat absorption heat exchanger through high-temperature bypass heating, pressure matching, and T-Q curve pinch control, improving operational stability and achieving stable high-parameter water / steam output. When multiple high-temperature heat exchangers are configured, multiple sets of high-temperature steam can be output simultaneously, adapting to ultra-high pressure to ultra-supercritical multi-pressure stage steam systems.

Description

Technical Field

[0001] This invention belongs to the field of energy storage, thermal storage, and high-parameter water / steam power generation technology, specifically relating to a thermal storage steam power generation system and its operation method that uses a heat transfer medium for diversion and bypass mixing to supply the main heat absorption section. This system and method can transfer heat released from an external thermal energy storage device to the water / steam power generation circuit in stages, and is suitable for applications requiring a stable high-parameter water / steam heat source, such as ultra-high pressure, subcritical, supercritical, and ultra-supercritical water / steam generation. Background Technology

[0002] With the continuous growth of new energy installed capacity, the power system's demand for long-term energy storage, deep peak shaving, and high-parameter dispatchable steam heat sources has significantly increased. Converting off-peak electricity, curtailed wind and solar power, or other dispatchable energy sources into high-temperature heat and storing it in thermal storage media, then releasing heat on demand to produce steam and supply high-parameter heat sources, has become an important technological direction in the field of thermal storage and steam supply. Existing thermal storage and steam supply technologies are diverse and have their own applicable scenarios. However, when facing complex high-parameter operating conditions involving multi-stage steam, evaporative heat absorption, and multi-stage feedwater heating, solutions using a single heat medium and simple series systems cannot simultaneously address heat grade matching, heat exchange terminal differential control, operational safety, and load stability, exhibiting significant technical limitations, mainly in the following aspects:

[0003] First, thermal storage devices have poor adaptability to various operating conditions. Thermal storage equipment is directly connected to high-pressure water / steam circuits and must withstand both high temperature and high pressure, as well as complex phase change or pseudo-phase change conditions. Ultra-high pressure and subcritical systems are prone to problems such as turbulent water-steam flow and deteriorated heat exchange; high-parameter systems require equipment to withstand stronger thermal and mechanical stresses. Conventional thermal storage media are only suitable for thermal storage cycles and cannot match high-pressure phase change conditions, resulting in high design and manufacturing difficulties, high costs, and high operational risks.

[0004] Second, there is an imbalance in heat quality matching and difficulty in controlling the heat exchange difference. A single series heat transfer medium process cannot adapt to the heat absorption requirements of different temperature zones in the water / steam circuit. High-parameter double reheat systems have stringent requirements for high-temperature heat sources. Prioritizing the supply of heat transfer medium to the low-temperature section will lead to insufficient heat exchange and substandard parameters in the high-temperature steam section; prioritizing the supply to the high-temperature section will result in insufficient heating temperature at the downstream end, causing fluctuations in evaporation and steam temperature.

[0005] Third, the ability to simultaneously control multiple high-temperature parameters is insufficient. Ultra-supercritical double reheat systems require independent stabilization of three types of high-temperature steam parameters, but conventional single-branch heat transfer media can only regulate the total heat exchange and cannot independently allocate flow rates and adjust temperatures for each high-temperature section. This makes it difficult to meet the requirements for simultaneous stabilization of multiple parameters and results in poor adaptability to variable load conditions.

[0006] Fourth, the inlet temperature of the main heat exchanger is uncontrollable. The main heat exchanger is the core component with the most stringent heat exchange requirements in the system, and the inlet working fluid temperature directly determines the heat exchange efficiency and terminal temperature difference. Under current operating conditions, its temperature fluctuates with the upstream heat exchange status, which can easily lead to excessive thermal stress, reduced system efficiency, and in severe cases, heat exchange failure and drying out of the evaporation section.

[0007] In summary, stabilizing the heat exchange temperature and terminal temperature difference of the main heat absorption section after the high-grade heat source is consumed is a crucial issue in current thermal storage steam power generation technology. Therefore, there is an urgent need to develop novel thermal storage steam power generation systems based on heat transfer media. These systems would allow the thermal storage devices to operate outside of high-pressure, complex conditions, achieving high-temperature parallel heat exchange, bypass mixing, and main heat absorption terminal temperature difference control through a closed-loop heat transfer media circuit. This would enable a stable output of high-parameter heat sources typical of traditional boilers, suitable for ultra-high pressure, subcritical, supercritical, and ultra-supercritical multi-pressure steam systems. Summary of the Invention

[0008] This invention addresses the issues of heat quality distribution, main heat absorption section end-to-end temperature control, and high-temperature multi-branch mixing stability in water / steam power generation circuits driven by external thermal storage heat sources. It proposes a thermal storage steam power generation system and its operation method that features heat transfer medium diversion and bypass temperature mixing to supply the main heat absorption section.

[0009] This invention addresses at least the following technical problems:

[0010] The compatibility issues of pressure-bearing, phase change, or pseudo-phase change operating conditions when an external thermal energy storage device is directly coupled with a high-pressure water / steam power generation circuit.

[0011] When the main steam superheat, reheat and main heat absorption sections all require heat at the same time, a single series heat transfer process cannot reasonably distribute high-grade heat.

[0012] After the upstream high-temperature heat exchanger consumes high-grade heat, the main heat exchanger inlet heat source temperature is insufficient, the TQ curve pinch point shifts forward, or the minimum heat exchange end difference is insufficient.

[0013] Problems related to pressure matching, fluid backflow, pressure fluctuations, and mixing instability when high-temperature bypass and multiple high-temperature heat exchange branch outlet streams converge.

[0014] To solve the above problems, the present invention adopts the following technical solution:

[0015] A thermal energy storage steam power generation system for diverting and bypassing the heat transfer medium and supplying it to the main heat absorption section includes an external thermal energy storage device, a closed-loop heat transfer medium circuit, and a water / steam power generation circuit. The closed-loop heat transfer medium circuit and the water / steam power generation circuit exchange heat indirectly through a heat exchanger, and the working fluids inside the two circuits do not mix.

[0016] The closed-loop heat transfer working fluid circuit includes a fluid circulation drive device, a high-temperature working fluid diversion device, a heat transfer working fluid side of at least one high-temperature steam heat exchanger, a high-temperature bypass, a heat transfer working fluid mixing device, a heat transfer working fluid side of the main heat absorber heat exchanger, and a return pipeline, and is thermally coupled to an external heat storage device; the heat transfer working fluid outlet of the main heat absorber heat exchanger is connected to the inlet of the external heat storage device via the fluid circulation drive device.

[0017] Furthermore, the outlet of the fluid circulation drive device and the external thermal energy storage device are configured to form an indirect dual heat exchange path; the closed heat transfer working fluid circuit also includes an intermediate heat exchanger disposed between the outlet of the fluid circulation drive device and the high-temperature working fluid diversion device; the system also includes a second heat transfer working fluid circuit containing a second heat transfer working fluid, the second heat transfer working fluid circuit flows through the external thermal energy storage device to obtain heat, and indirectly transfers the heat to the heat transfer working fluid in the closed heat transfer working fluid circuit through the intermediate heat exchanger.

[0018] In the indirect dual heat exchange path, when the external thermal energy storage device uses a graphite-containing carbon-based thermal storage medium with a maximum operating temperature of not less than 1000℃, the second heat transfer medium in the second heat transfer medium loop is pure nitrogen or argon; the heat transfer medium in the closed heat transfer medium loop is pure carbon dioxide or a mixed medium with carbon dioxide as the main heat transfer component.

[0019] Furthermore, the closed-loop heat transfer medium circuit is equipped with an online moisture monitoring and active explosion-proof isolation system; the system includes a high-frequency trace moisture detector installed on the inlet pipe of the external thermal energy storage device, and quick-cut-off isolation valves installed on the inlet and outlet main pipes of the external thermal energy storage device. When the moisture detector detects that the water vapor concentration in the heat transfer medium exceeds a set threshold, the control unit triggers the quick-cut-off isolation valve to close, cutting off the fluid connection between the external thermal energy storage device and the heat exchange area.

[0020] Furthermore, the closed-loop heat transfer medium circuit and the water / steam power generation circuit directly exchange heat in the heat exchanger without any other intermediate transition fluid circuits; high-pressure water or supercritical water / steam flows inside the heat exchanger tubes, while the outside of the tubes is scourd by the high-temperature heat transfer medium. Relying on the heat transfer coefficient of the water-side convective surface inside the tubes, the maximum temperature of the metal tube wall of the heat exchanger is controlled within a preset safe range lower than the temperature of the heat transfer medium outside the tubes.

[0021] The high-temperature heat transfer medium diversion device divides the high-temperature heat transfer medium at the outlet of the external thermal energy storage device into at least a high-temperature heat exchange branch and a high-temperature bypass independent of the high-temperature heat exchange branch; the high-temperature steam heat exchanger branch enters the high-temperature steam heat exchanger, and the high-temperature bypass bypasses the high-temperature steam heat exchanger. In the secondary reheat implementation, when adapted to a supercritical and / or ultra-supercritical water / steam power generation circuit, the heat transfer medium is distributed in parallel to at least one high-temperature steam heat exchanger, which includes a high-temperature steam superheater, a first-stage reheater, a second-stage reheater, and optional multi-stage reheaters; when adapted to an ultra-high pressure and / or subcritical water / steam power generation circuit, the heat transfer medium is distributed in parallel to at least one high-temperature steam heat exchanger, which includes a main steam superheater and optional reheaters; and the high-temperature bypass is retained as a heat source compensation branch at the inlet of the main heat absorption heat exchanger.

[0022] The heat transfer medium stream after releasing heat from the high-temperature steam heat exchanger is mixed with the heat transfer medium with a higher enthalpy value in the regulated high-temperature bypass stream in the heat transfer medium mixing device to form a medium-high temperature heat transfer medium stream that enters the main heat absorber heat exchanger.

[0023] By adjusting the flow rate, pressure, and outlet temperature of the heat transfer medium mixing device in the high-temperature bypass, the heat source curve entering the main heat exchanger can be reconstructed, and the minimum heat exchange end difference of the main heat exchanger can be maintained.

[0024] A high-temperature bypass regulating valve is installed on the high-temperature bypass to match the pressure before the high-temperature bypass enters the heat transfer working fluid mixing device with the outlet back pressure of the superheated branch of the high-temperature steam heat exchanger after the flow resistance pressure drop generated by its corresponding heat exchanger, thereby reducing the risk of backflow, pressure fluctuation or mixing instability.

[0025] In one embodiment, a pressure matching valve station is provided on the high-temperature bypass. The high-temperature bypass regulating valve is further configured to dynamically adjust the throttling degree of the high-temperature bypass based on the real-time flow resistance pressure drop of the high-temperature steam heat exchanger branch, so that the outlet pressure of the high-temperature bypass matches the back pressure at the outlet of each heat exchange branch. The pressure matching valve station is located between the high-temperature heat transfer medium splitting device and the heat transfer medium mixing device, and includes a high-temperature bypass regulating valve, and may include one or more of the following: differential pressure measuring point, temperature measuring point, pressure balancing header, and bypass low-flow pressure equalization path. The differential pressure measuring point is used to detect the pressure difference between the regulated high-temperature bypass stream and the heat transfer medium stream at the outlet of the high-temperature steam heat exchanger; when the pressure difference exceeds a preset range, the controller adjusts the opening of the high-temperature bypass regulating valve or activates the bypass low-flow pressure equalization path.

[0026] The main heat exchanger can correspond to an ultra-high pressure evaporation section, a subcritical evaporation section, a supercritical pseudo-evaporation section, a supercritical strong heat absorption section, or an ultra-supercritical main heat absorption section; the outlet target temperature of the heat transfer working fluid mixing device can be set according to the water / steam side heat absorption curve, the pinch point position of the TQ curve, or the minimum heat exchange end difference.

[0027] The system may further include a mixing-temperature decoupling controller and a main heat exchanger TQ curve and pinch point control module. The mixing-temperature decoupling controller uses the main steam outlet temperature, reheat steam outlet temperature, and the minimum heat transfer end difference of the main heat exchanger as control targets to adjust the heat transfer fluid flow rates of the high-temperature steam heat exchanger branch and the high-temperature bypass stream, respectively. The main heat exchanger TQ curve and pinch point control module estimates the minimum temperature difference between the hot-side heat release curve and the cold-side heat absorption curve based on the temperature, pressure, flow rate, or enthalpy state of the heat transfer fluid side and the water / steam side of the main heat exchanger, and adjusts the flow rate of the high-temperature bypass and / or corrects the outlet target temperature of the heat transfer fluid mixing device accordingly.

[0028] Furthermore, the water / steam power generation circuit is equipped with an industrial extraction steam branch, which is equipped with flow and pressure detection devices. The control unit dynamically adjusts the opening of the high-temperature bypass regulating valve and the high-temperature working fluid diversion ratio based on the real-time collected flow and pressure data. In addition, the heat transfer medium that has released heat in the main heat absorber can further indirectly heat other heat exchangers in the water / steam power generation circuit whose water / steam temperature is lower than that of the main heat absorber, thereby partially or completely replacing the heat recovery from the extraction steam in the water / steam power generation circuit.

[0029] The present invention also provides an operating method, comprising: absorbing heat from an external thermal energy storage device to form a high-temperature heat transfer medium main stream; dividing the high-temperature heat transfer medium main stream into at least one high-temperature steam heat exchanger branch and a high-temperature bypass via a high-temperature working medium diversion device; releasing high-grade heat from at least one high-temperature steam heat exchanger branch to a water / steam power generation circuit; adjusting the pressure of the high-temperature bypass via a high-temperature bypass regulating valve to form a high-temperature bypass stream after pressure matching adjustment; and allowing the heat transfer medium at the outlet of at least one high-temperature steam heat exchanger to flow... The high-temperature bypass stream, after pressure matching and adjustment, is mixed in a heat transfer medium mixing device to form a medium-high temperature heat transfer medium stream. The mixed medium-high temperature heat transfer medium stream before entering the main heat exchanger enters the main heat exchanger, and the high-temperature bypass stream is adjusted according to the pinch point or minimum heat transfer end difference of the main heat exchanger's TQ curve. The heat transfer medium stream at the outlet of the main heat exchanger is processed by a fluid circulation drive device to form a return heat transfer medium stream, which absorbs heat again from the external thermal energy storage device through the direct or indirect thermal coupling path.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects: it isolates the heat storage side from the high-pressure water / steam side by using an external heat storage device and a closed heat transfer medium loop; it meets the heat demand of the high-temperature steam heat exchanger by parallel distribution of the high-temperature heat transfer medium; it actively adjusts the inlet heat source state of the main heat absorber by mixing the high-temperature bypass stream with the outlet stream of the high-temperature heat exchange branch; and it improves the system's operational stability by controlling the TQ curve pinch point and the minimum heat exchange end difference. Attached Figure Description

[0031] Figure 1 This is a flowchart of a heat transfer working fluid diversion and bypass mixing supply to the main heat absorption section provided in Embodiment 1 of the present invention.

[0032] Figure 2 This is a system flow diagram of an embodiment of the present invention adapted to ultra-high pressure and subcritical water / steam circuits;

[0033] Figure 3 TQ curves for inlet temperature regulation of the ultra-supercritical main heat exchanger;

[0034] Figure 4 TQ curves for regulating the inlet temperature of ultra-high pressure and subcritical main heat exchangers.

[0035] Explanation of reference numerals in the attached figures:

[0036] TES is an external thermal energy storage device; CC is a fluid circulation drive device; DIV1 is a high-temperature working fluid diversion device; DIV2 is a first-stage turbine outlet diversion device; DIV3 is a second-stage turbine outlet diversion device; DIV4 is a subsequent turbine stage outlet diversion device; MIX1 is a heat transfer working fluid mixing device; MIX2 is an open feedwater regenerative mixer; MIX3 is a low-pressure exhaust / regenerative return mixer; HX-SH is the main steam superheater; HX-RH1 is the first-stage reheater; HX-RH2 is the second-stage reheater; HX-EV is the main heat absorption heat exchanger; HX-EC is the high-pressure... Regenerative heater; HX-DO is a low-pressure regenerative heater; WP1 is a low-pressure feedwater pump; WP2 is a high-pressure feedwater pump; AC is a condenser; T1 is the first-stage steam turbine; T2 is the second-stage steam turbine; T3A is the subsequent steam turbine stage A; T3B is the subsequent steam turbine stage B; SP is a steam-water separator; C1B-V is a high-temperature bypass regulating valve; V1 is a high-pressure regenerative heater outlet throttle valve; V2 is a low-pressure regenerative heater outlet throttle valve; V-Q1 is an inlet quick-cut-off isolation valve for the external thermal energy storage device; V-Q2 is an outlet quick-cut-off isolation valve for the external thermal energy storage device; MT is a high-frequency trace moisture detector.

[0037] C1 is the main high-temperature carbon dioxide stream from the external thermal energy storage unit (TES outlet to DIV1 inlet); C1A is the main steam superheater branch stream (DIV1 outlet to HX-SH inlet); C1C is the first-stage reheat branch stream (DIV1 outlet to HX-RH1 inlet); C1D is the second-stage reheat branch stream (DIV1 outlet to HX-RH2 inlet); C1B is the high-temperature bypass stream (DIV1 outlet to C1B-V inlet); C1B-2 is the regulated high-temperature bypass stream (C1B-V outlet to MIX1 inlet); C2A is the main steam superheater outlet carbon dioxide stream (HX-SH outlet to MIX1 inlet); C2C is the first-stage reheater outlet carbon dioxide stream (HX-RH1 outlet to MIX1 inlet); C2D is the second-stage reheater outlet carbon dioxide stream (HX-RH2 outlet to MIX1). C1 is the mixed high-temperature carbon dioxide stream before entering the main heat exchanger (MIX1 outlet to HX-EV inlet); C2 is the carbon dioxide stream at the outlet of the main heat exchanger (HX-EV outlet to CC inlet); C4 is the return carbon dioxide stream at the outlet of the fluid circulation drive device and entering the external thermal energy storage device (CC outlet to TES inlet).

[0038] W1 is the condensate stream from the condenser outlet (AC outlet to WP1 inlet); W2 is the low-pressure feedwater pump outlet stream (WP1 outlet to HX-DO inlet); W3 is the low-pressure regenerative heater outlet stream (HX-DO outlet to MIX2 inlet); W4 is the open feedwater regenerative mixer outlet stream (MIX2 outlet to WP2 inlet); W5 is the high-pressure feedwater pump outlet stream (WP2 outlet to HX-EC inlet); W6 is the high-pressure regenerative heater outlet stream (HX-EC outlet to HX-EV inlet); W7 is the main heat exchanger outlet stream (HX-EV outlet to HX-SH inlet, in ultra-high pressure and subcritical embodiments, HX-EV outlet to SP inlet); W7-1 is the steam stream from the steam-water separator outlet (SP outlet to HX-SH inlet); W7-2 is the liquid water return stream from the steam-water separator outlet (SP...). W8 is the main steam stream from the main steam superheater outlet (HX-SH outlet to T1 inlet); W9 is the first-stage turbine outlet stream (T1 outlet to DIV2 inlet); W9A is the primary cold reheat steam stream entering the first-stage reheater (DIV2 outlet to HX-RH1 inlet); W9B is the extraction steam stream entering the high-pressure regenerative heater (DIV2 outlet to HX-EC heating side inlet); W10 is the primary hot reheat steam stream from the first-stage reheater outlet (HX-RH1 outlet to T2 inlet); W11 is the second-stage turbine outlet stream (T2 outlet to DIV3 inlet); W11A is the secondary cold reheat steam stream entering the second-stage reheater (DIV3 outlet to HX-RH2 inlet); W11B is the extraction steam stream entering the open feedwater regenerative mixer (DIV3 outlet to MIX2). W12 is the secondary reheat steam stream from the outlet of the second-stage reheater (from HX-RH2 outlet to T3A inlet); W13 is the intermediate exhaust or extraction steam stream from the subsequent turbine stage (from T3A outlet to DIV4 inlet); W13A is the final stage power branch stream entering the subsequent turbine stage B (from DIV4 outlet to T3B inlet); W13B is the extraction steam stream entering the low-pressure regenerative heater (from DIV4 outlet to HX-DO heating side inlet); W14 is the exhaust steam stream from the final stage turbine (from T3B outlet to MIX3 inlet); W15 is the heating side outlet stream of the high-pressure regenerative heater (from HX-EC outlet to V1 inlet); W16 is the high-pressure regenerative return stream (from V1 outlet to MIX2 inlet); W17 is the heating side outlet stream of the low-pressure regenerative heater (from HX-DO outlet to V2 inlet); W18 It is a low-pressure regenerative return stream (V2 outlet to MIX3 inlet);W19 is a low-pressure exhaust / regenerative mixed stream (MIX3 outlet to AC inlet). Detailed Implementation

[0039] The present invention will now be described in conjunction with the accompanying drawings and specific embodiments. These embodiments are used to explain the technical solutions of the present invention and do not limit the scope of protection of the present invention.

[0040] This invention proposes a thermal storage steam power generation system that uses a heat transfer medium for diversion and bypass mixing to supply the main heat absorption section. For external heat storage media with different operating temperature ranges and chemical properties, the closed-loop heat transfer medium circuit can flexibly select pure carbon dioxide, pure nitrogen, argon, air, or mixtures thereof as the heat transfer medium, and accordingly match a suitable fluid circulation drive device.

[0041] To further illustrate the system configuration and operating mechanism of the present invention, the following will describe in detail the technical solution of the present invention using carbon dioxide (Example 1) and direct-drive pure nitrogen (Example 2) as typical application scenarios for heat transfer working fluids. It should be understood that although specific working fluids and parameters are listed in the examples, this is only used to explain the flow field topology and mixing temperature control logic of the present invention, and does not constitute a limitation on the scope of protection of the present invention.

[0042] Example 1: Thermal power generation system based on carbon dioxide or mixed working fluid

[0043] I. Definition of Terms

[0044] External thermal energy storage (TES) refers to a thermal energy storage device or group of thermal energy storage devices that is set up independently relative to the water / steam power generation circuit, used to store heat and release heat to the closed carbon dioxide heat transfer circuit during the heat release phase.

[0045] A closed-loop carbon dioxide heat transfer circuit refers to a closed loop in which carbon dioxide or a mixture of working fluids with carbon dioxide as the main heat transfer component is used as the circulating medium. The circuit circulates and transfers heat between the external thermal energy storage device (TES), the high-temperature carbon dioxide diversion device (DIV1), each water / steam side heat exchanger, the carbon dioxide mixing device (MIX1), the main heat absorption heat exchanger (HX-EV), and the carbon dioxide return compressor (CC).

[0046] In this invention, the closed-loop carbon dioxide heat transfer circuit is used for sensible heat transfer between the external thermal energy storage device (TES) and the water / steam power generation circuit, and does not constitute a Brayton power generation cycle using carbon dioxide as the working fluid. The first-stage steam turbine (T1), the second-stage steam turbine (T2), and the subsequent turbine stages (T3A, T3B) in the system are all water / steam side turbines, not carbon dioxide power turbines. In other words, the closed-loop heat transfer circuit only serves as an intermediate decoupling layer for heat transfer, and the main heat transfer cycle path strictly does not include power turbine equipment intended to output shaft power or electrical power.

[0047] The high-temperature bypass stream (C1B) refers to the branch that branches off from the high-temperature carbon dioxide main stream C1 at the outlet of the external thermal energy storage device (TES), bypasses the main steam superheater (HX-SH) and at least one stage of reheater, and enters the high-temperature bypass regulating valve (C1B-V).

[0048] The main heat exchanger (HX-EV) is a heat exchanger that undertakes the main heat absorption task of high-pressure feedwater, supercritical water or water / steam working fluid in a water / steam power generation circuit.

[0049] The TQ curve is a curve showing the relationship between temperature T and heat transfer Q. For ease of representation, Figure 3 and Figure 4 The graph uses temperature T on the horizontal axis and heat exchange Q on the vertical axis.

[0050] The pinch point refers to the location where the temperature difference between the hot side curve and the cold side curve is the smallest at the corresponding heat exchange location.

[0051] II. Overall System Structure

[0052] like Figure 1 As shown, the system of the present invention includes an external thermal energy storage device (TES), a closed carbon dioxide heat transfer loop, and a water / steam power generation loop. The external thermal energy storage device (TES) supplies heat to the closed carbon dioxide heat transfer loop through a heat release interface; the closed carbon dioxide heat transfer loop distributes this heat to multiple heat absorption devices in the water / steam power generation loop.

[0053] The closed-loop carbon dioxide heat transfer circuit includes a carbon dioxide reflux compressor (CC), an external thermal energy storage device (TES), a high-temperature carbon dioxide diversion device (DIV1), the heat transfer medium side of the main steam superheater (HX-SH), a high-temperature bypass stream C1B, a carbon dioxide mixing device (MIX1), the heat transfer medium side of the main heat exchanger (HX-EV), and a reflux pipeline. The heat transfer medium always flows in a single-phase form in a pressurized gaseous state, near-critical state, dense phase, or supercritical state. The pressure of the heat transfer medium in the closed-loop heat transfer medium circuit is from 0.5 MPa to 40 MPa.

[0054] The carbon dioxide reflux compressor (CC) outlet stream C4 enters the external thermal energy storage device (TES) and absorbs heat to form a high-temperature carbon dioxide main stream C1. The high-temperature carbon dioxide main stream C1 formed by the external thermal energy storage device (TES) after absorbing heat enters the high-temperature carbon dioxide splitter (DIV1) and is divided into a main steam superheated branch stream C1A, at least one reheat branch, and a high-temperature bypass stream C1B.

[0055] In one optional implementation, the main heating system of the closed-loop carbon dioxide heat transfer circuit can be constructed as an indirect dual heat exchange path. In this case, an intermediate heat exchanger is added between the outlet of the carbon dioxide reflux compressor (CC) and the high-temperature carbon dioxide diversion device (DIV1), and a second heat transfer medium circuit is configured. The second heat transfer medium absorbs heat from the external thermal energy storage device (TES) and heats the carbon dioxide or heat transfer medium in the closed loop in the intermediate heat exchanger. The heated heat transfer medium then enters the high-temperature carbon dioxide diversion device (DIV1). This indirect dual heat exchange architecture effectively isolates the heat storage medium from the high-pressure gaseous heat transfer medium, further improving the operational safety and stability of the system's core equipment. For external thermal energy storage devices that use a graphite-containing carbon-based heat storage medium with a maximum operating temperature of not less than 1000℃, the second heat transfer medium circuit is filled with inert gases such as pure nitrogen or argon to block the carbothermic reduction reaction at extremely high temperatures; while the external closed-loop heat transfer medium circuit can still use supercritical carbon dioxide as the heat transfer medium. This architecture decouples the ultra-high temperature heat storage section from the high pressure heat transfer section, balancing the chemical safety of the medium with the high power density of the circuit.

[0056] III. High-temperature diversion and bypass mixing

[0057] The main steam superheater branch stream C1A enters the main steam superheater (HX-SH), and after releasing heat, forms the main steam superheater outlet carbon dioxide stream C2A; the first-stage reheater branch stream C1C enters the first-stage reheater (HX-RH1), and after releasing heat, forms the first-stage reheater outlet carbon dioxide stream C2C; the second-stage reheater branch stream C1D enters the second-stage reheater (HX-RH2), and after releasing heat, forms the second-stage reheater outlet carbon dioxide stream C2D. Through the parallel allocation of these multiple branches, the system can flexibly adapt to water / steam power generation circuits of all levels from ultra-high pressure and subcritical to supercritical and ultra-supercritical, while retaining the high-temperature bypass as a heat source compensation branch at the inlet of the main heat exchanger.

[0058] After being regulated by the high-temperature bypass stream C1B, it forms the regulated high-temperature bypass stream C1B-2. The carbon dioxide streams C2A (outlet of the main steam superheater), C2C (outlet of the first-stage reheater), and C2D (outlet of the second-stage reheater) are mixed with the regulated high-temperature bypass stream C1B-2 in the carbon dioxide mixing unit (MIX1) to form the mixed high-temperature carbon dioxide stream C2 before entering the main heat exchanger (HX-EV).

[0059] In this embodiment, the high-temperature bypass stream C1B is used to supplement carbon dioxide with a higher enthalpy value, so that the inlet heat source temperature of the main heat exchanger (HX-EV) is not completely limited by the outlet temperature of the main steam superheater (HX-SH) and the reheater.

[0060] Furthermore, the closed-loop carbon dioxide heat transfer circuit and the water / steam power generation circuit directly exchange heat in the main steam superheater (HX-SH) and the main heat absorber (HX-EV), without any other intermediate transition fluid circuits. During the heat exchange process, high-pressure water, steam, or supercritical water flows inside the heat exchanger tubes, while the outside of the tubes is scoured by high-temperature carbon dioxide. This system relies on the extremely high convective surface heat transfer coefficient on the water side inside the tubes to control the maximum temperature of the heat exchanger metal tube wall within a preset safe range lower than the temperature of the heat transfer medium outside the tubes. This thermodynamic constraint mechanism at the physical structural level allows the heating surface tubes to be made of conventional heat-resistant steel, eliminating the need for intermediate isolation circuits, reducing the cost of special alloys, and ensuring the structural safety of the heat exchanger body under extreme high-temperature heat sources.

[0061] IV. High-Temperature Bypass Pressure Matching and Terminal Difference Control

[0062] A high-temperature bypass regulating valve (C1B-V) is installed on the high-temperature bypass stream C1B. The high-temperature bypass regulating valve (C1B-V) is used to regulate the pressure of the high-temperature bypass stream C1B before it enters the carbon dioxide mixing unit (MIX1), so that it matches the outlet back pressure of the main steam superheater outlet carbon dioxide stream C2A, the first stage reheater outlet carbon dioxide stream C2C, and the second stage reheater outlet carbon dioxide stream C2D.

[0063] In one embodiment, a pressure matching valve station (not shown in the figure) is provided on the high-temperature bypass stream C1B. The pressure matching valve station includes a high-temperature bypass regulating valve C1B-V, and may include one or more of the following: a check valve, a differential pressure measuring point, a temperature measuring point, a pressure balancing header, and a bypass low-flow equalization path. The differential pressure measuring point is used to detect the pressure difference between the regulated high-temperature bypass stream C1B-2 and at least one of the following outlet streams: the main steam superheater outlet carbon dioxide stream C2A, the first-stage reheater outlet carbon dioxide stream C2C, and the second-stage reheater outlet carbon dioxide stream C2D. When the pressure difference exceeds a preset range, the opening of the high-temperature bypass regulating valve (C1B-V) is adjusted, or the bypass low-flow equalization path is activated, so that the regulated high-temperature bypass stream C1B-2 and each high-temperature heat exchange branch outlet stream meet the preset mixing pressure difference before entering the carbon dioxide mixing device (MIX1).

[0064] The outlet temperature of the carbon dioxide mixing unit (MIX1) is set based on the pinch point of the TQ curve of the main heat exchanger (HX-EV) or the minimum heat transfer difference. When the minimum heat transfer difference of the main heat exchanger (HX-EV) approaches the lower limit, the heat compensation ratio of the high-temperature bypass stream C1B is increased first, or the heat extraction of the main steam superheated branch stream C1A and the reheat branch is restricted.

[0065] In one control implementation, the system includes a mixing temperature decoupling controller (not shown in the figure). The mixing temperature decoupling controller receives the main steam outlet temperature, the reheat steam outlet temperature, the carbon dioxide mixing unit (MIX1) outlet temperature, the water / steam side inlet status, the outlet status, the heat transfer medium side inlet status, and the outlet status of the main heat exchanger (HX-EV), and outputs flow regulation commands for the main steam superheated branch stream C1A, at least one reheat branch, and the high-temperature bypass stream C1B.

[0066] During the control process, the main steam outlet temperature primarily corresponds to adjusting the flow rate of the main steam superheated branch stream C1A, while the reheat steam outlet temperature primarily corresponds to adjusting the flow rate of the first-stage reheat branch stream C1C, the second-stage reheat branch stream C1D, or other reheat branches. The inlet heat source temperature, TQ curve pinch point position, or minimum heat exchange terminal difference of the main heat exchanger (HX-EV) primarily corresponds to adjusting the opening of the high-temperature bypass stream C1B or the high-temperature bypass regulating valve (C1B-V). The main heat exchanger TQ curve and pinch point control module (not marked in the figure) estimates the minimum temperature difference between the hot-side heat release curve and the cold-side heat absorption curve based on the temperature, pressure, flow rate, or enthalpy state of the heat transfer medium side and the water / steam side of the main heat exchanger (HX-EV), and compares this minimum temperature difference with a set threshold to correct the target outlet temperature of the carbon dioxide mixing unit (MIX1).

[0067] The mixing temperature decoupling controller and the TQ curve and pinch point control module of the main heat exchanger can be functional modules in a distributed control system, programmable logic controller or upper control system, and are not required to be set up as independent physical devices.

[0068] V. Example of a water / steam power generation circuit

[0069] In one embodiment of ultra-supercritical double reheat power generation, the water / steam power generation circuit sequentially includes a condenser (AC), a low-pressure feedwater pump (WP1), a low-pressure regenerative heater (HX-DO), an open feedwater regenerative mixer (MIX2), a high-pressure feedwater pump (WP2), a high-pressure regenerative heater (HX-EC), the water / steam side of the main heat exchanger (HX-EV), the water / steam side of the main steam superheater (HX-SH), the first-stage turbine (T1), the water / steam side of the first-stage reheater (HX-RH1), the second-stage turbine (T2), the water / steam side of the second-stage reheater (HX-RH2), and subsequent turbine stages (T3A) and (T3B).

[0070] In the water / steam power generation circuit, condensate W1 is pressurized by the low-pressure feedwater pump (WP1) to form the low-pressure feedwater pump outlet stream W2. The low-pressure feedwater pump outlet stream W2 is heated by the low-pressure regenerative heater (HX-DO) to form the low-pressure regenerative heater outlet stream W3. The low-pressure regenerative heater outlet stream W3 enters the open feedwater regenerative mixer (MIX2) to form the open feedwater regenerative mixer outlet stream W4. The open feedwater regenerative mixer outlet stream W4 is then fed by the high-pressure feedwater pump... The water pump (WP2) pressurizes the water to form a high-pressure feedwater pump outlet stream W5. The high-pressure feedwater pump outlet stream W5 is heated by the high-pressure regenerative heater (HX-EC) to form a high-pressure regenerative heater outlet stream W6. The high-pressure regenerative heater outlet stream W6 enters the main heat exchanger (HX-EV) to absorb heat and form the main heat exchanger outlet stream W7. The main heat exchanger outlet stream W7 passes through the main steam superheater (HX-SH) to form the main steam outlet stream W8.

[0071] The main steam stream W8 from the outlet of the main steam superheater enters the first-stage steam turbine (T1) and expands to form the first-stage steam turbine outlet stream W9. At least a portion of the first-stage steam turbine outlet stream W9 is heated by the first-stage reheater (HX-RH1) to form the first-stage reheater outlet primary reheat steam stream W10, which then enters the second-stage steam turbine (T2). At least a portion of the second-stage steam turbine outlet stream W11 from the outlet of the second-stage steam turbine (T2) is heated by the second-stage reheater (HX-RH2) to form the second-stage reheat steam stream W12, which then enters the subsequent steam turbine stages (T3A, T3B) to continue expanding and doing work.

[0072] exist Figure 1In the illustrated embodiment, the outlet stream W9 of the first-stage turbine (T1) is divided by the first-stage turbine outlet splitter (DIV2) into a primary cold reheat steam stream W9A entering the first-stage reheater (HX-RH1) and an extraction steam stream W9B entering the heating side of the high-pressure regenerative heater (HX-EC); the outlet stream W11 of the second-stage turbine (T2) is divided by the second-stage turbine outlet splitter (DIV3) into a secondary cold reheat steam stream W11A entering the second-stage reheater (HX-RH2) and an extraction steam stream W11B entering the open feedwater regenerative mixer (MIX2); the outlet stream W13 of the subsequent turbine stage A (T3A) is divided by the subsequent turbine stage outlet splitter (DIV4) into a final-stage power branch stream W13A entering the subsequent turbine stage B (T3B) and an extraction steam stream W13B entering the low-pressure regenerative heater (HX-DO). The exhaust steam stream W14 from the final stage turbine and the low-pressure regenerative return stream W18 can be mixed in the low-pressure exhaust / regenerative return mixer (MIX3) to form W19, which then enters the condenser (AC).

[0073] In the regenerative return branch, the outlet stream W15 of the high-pressure regenerative heater (HX-EC) is converted into a high-pressure regenerative return stream W16 via the high-pressure regenerative heater outlet throttle valve (V1) and returns to the open feedwater regenerative mixer (MIX2); the outlet stream W17 of the low-pressure regenerative heater (HX-DO) is converted into a low-pressure regenerative return stream W18 via the low-pressure regenerative heater (HX-DO) outlet throttle valve (V2) and returns to the low-pressure exhaust / regenerative return mixer (MIX3).

[0074] In addition to the direct return path where the heat transfer fluid stream C3 at the outlet of the main heat exchanger (HX-EV) is directly connected to the inlet of the fluid circulation drive device, this system also provides an alternative implementation scheme for realizing the cascade utilization of waste heat.

[0075] In this scheme, the high-pressure regenerative heater (HX-EC) and / or the low-pressure regenerative heater (HX-DO) employ a dual-heating surface or composite tube bundle architecture. The heat transfer fluid stream C3 flowing out of the outlet of the self-absorbing heat exchanger (HX-EV) passes sequentially or in parallel through the shell side or auxiliary tube bundle of the high-pressure regenerative heater (HX-EC) and / or the low-pressure regenerative heater (HX-DO) in the physical pipeline returning to the inlet of the fluid circulation drive device. During this process, the heat transfer fluid stream C3 releases sensible heat as an auxiliary heat source, indirectly heating the feedwater stream at the outlet of the high-pressure feedwater pump or the condensate stream at the outlet of the low-pressure feedwater pump, preheating it before it enters the next stage heat exchange equipment. This reduces or partially replaces the heat recovery from the turbine extraction in the water / steam power generation circuit.

[0076] In the extreme condition of complete heat recovery without extraction steam regeneration, the extraction steam regeneration-related components in the water / steam power generation loop, such as the open feedwater regeneration mixer (MIX2) and the low-pressure exhaust / regeneration return mixer (MIX3), are removed. The turbine is set to a no-extraction steam operation mode, and all the heating load of feedwater and condensate is borne by the sensible heat flow of the heat transfer medium in the closed loop, so as to minimize the turbine's cold source loss and simplify the water-steam loop structure.

[0077] VI. Examples of Different Parameter Levels

[0078] When the water / steam power generation circuit is an ultra-high pressure or subcritical circuit, the main heat exchanger (HX-EV) can be connected to the evaporation section or steam-water separator. For example... Figure 2 As shown, the outlet stream W6 of the high-pressure regenerative heater enters the main heat exchanger (HX-EV) to form the main heat exchanger outlet stream W7. The main heat exchanger outlet stream W7 then enters the steam-liquid separator (SP) for vapor-liquid separation. The steam stream W7-1 from the steam-liquid separator (SP) enters the main steam superheater (HX-SH), and the liquid water return stream W7-2 from the steam-liquid separator (SP) returns to the main heat exchanger (HX-EV) or its inlet side for circulation. The controller can limit the outlet temperature of the carbon dioxide mixing unit (MIX1) or the proportion of the high-temperature bypass stream C1B to reduce the risk of localized overheating or drying out.

[0079] When the water / steam power generation circuit is a supercritical or ultra-supercritical circuit, the main heat exchanger (HX-EV) can be operated as a pseudo-evaporation section, a strong heat absorption section, or a direct-flow main heat absorption section. The controller can increase the proportion of high-temperature bypass stream C1B or increase the target outlet temperature of the carbon dioxide mixing unit (MIX1) to cross the pseudo-critical high specific heat zone and maintain the minimum heat exchange end difference.

[0080] Figure 3 In the diagram, curve W represents the heat absorption curve from the outlet stream W6 of the high-pressure regenerative heater to the outlet stream W7 of the main heat exchanger; curves 1 to 4 represent the sensible heat release curves of the mixed high-temperature carbon dioxide stream C2 before entering the main heat exchanger from the outlet of the carbon dioxide mixing device (MIX1) under different adjusted high-temperature bypass stream C1B-2 temperatures or flow rates, and the carbon dioxide stream C3 at the outlet of the main heat exchanger. By adjusting the temperature, pressure, or flow rate of the adjusted high-temperature bypass stream C1B-2, the inlet temperature of the mixed high-temperature carbon dioxide stream C2 before entering the main heat exchanger and the sensible heat release curve on the carbon dioxide side can be changed, thereby altering the minimum heat exchange terminal difference of the main heat exchanger (HX-EV). Figure 4The matching relationship between the heat absorption curves of the high-pressure regenerating heater outlet stream W6 to the main heat exchanger outlet stream W7 in the ultra-high pressure and subcritical main heat exchanger (HX-EV) and the heat release curves of the mixed high-temperature carbon dioxide stream C2 before entering the main heat exchanger to the main heat exchanger outlet carbon dioxide stream C3 under different mixing temperature conditions is shown.

[0081] In the steam generation modules of the above parameter levels, the steam turbines of the water / steam power generation circuit can all be equipped with industrial extraction steam branches. The industrial extraction steam branch extracts steam from the interstage diversion device (such as the first-stage steam turbine outlet diversion device (DIV2) or the second-stage steam turbine outlet diversion device (DIV3)) corresponding to the pressure level of the steam turbine, and outputs saturated or superheated industrial steam with a pressure level of 0.3MPa~4.0MPa.

[0082] To address the disturbances to the internal heat balance caused by wide fluctuations in industrial extraction steam load, flow and pressure detection devices are installed on the industrial extraction steam branch. Based on the real-time industrial extraction steam flow and pressure data collected by these devices, the control unit dynamically adjusts the opening of the high-temperature bypass regulating valve (C1B-V), thereby changing the flow ratio of the high-temperature bypass stream C1B and the outlet mixing temperature of the heat transfer medium mixing device (MIX1). This regulation logic actively compensates for the inlet heat source state of the main heat exchanger (HX-EV) when the industrial extraction steam volume changes significantly, thus maintaining the minimum heat exchange end difference of the main heat exchanger and ensuring the stability of the outlet parameters of the main steam and corresponding reheat steam.

[0083] VII. System Operation Method

[0084] The operating method of the present invention includes:

[0085] S1 causes the carbon dioxide to flow back to the compressor outlet and into the external thermal energy storage device, where the reflux carbon dioxide stream C4 enters the external thermal energy storage device (TES) to absorb heat, forming the high-temperature carbon dioxide total stream C1 at the outlet of the external thermal energy storage device.

[0086] S2, through the high-temperature carbon dioxide diversion device (DIV1), distributes the high-temperature carbon dioxide total flow C1 from the outlet of the external thermal energy storage device to the main steam superheated branch flow C1A and the high-temperature bypass flow C1B.

[0087] S3-1, which enables at least one high-temperature steam heat exchanger branch to release high-grade heat into the water / steam power generation circuit;

[0088] S3-2, the high temperature bypass stream C1B is pressure matched and regulated by the high temperature bypass regulating valve (C1B-V) to form the regulated high temperature bypass stream C1B-2;

[0089] S4A, the high-temperature heat exchange branch outlet stream, the main steam superheater outlet carbon dioxide stream C2A, the first stage reheater outlet carbon dioxide stream C2C, the second stage reheater outlet carbon dioxide stream C2D, and the high-temperature bypass stream C1B-2 after pressure matching and regulation are mixed in the carbon dioxide mixing device (MIX1) to form the mixed high-temperature carbon dioxide stream C2 before entering the main heat absorber.

[0090] S4B, the heat transfer medium at the outlet of the main heat exchanger is further used to indirectly heat other heat exchangers in the water / steam power generation circuit whose water / steam temperature is lower than that of the main heat exchanger, so as to reduce the heat recovery of steam extraction in the water / steam power generation circuit. Then, after being processed by the fluid circulation drive device, heat is absorbed again from the external thermal energy storage device through the direct or indirect thermal coupling path.

[0091] S5 allows the mixed high-temperature carbon dioxide stream C2 before entering the main heat exchanger to enter the main heat exchanger (HX-EV), and provides heat from the main heat exchange section to the water / steam power generation circuit while maintaining the minimum heat exchange end difference, and adjusts the high-temperature bypass stream (C1B) according to the pinch point of the TQ curve or the minimum heat exchange end difference.

[0092] S6, the carbon dioxide stream C3 at the outlet of the main heat exchanger is pressurized by the carbon dioxide reflux compressor (CC) to form the carbon dioxide reflux compressor outlet and enter the reflux carbon dioxide stream C4 of the external thermal energy storage device, and absorbs heat again from the external thermal energy storage device (TES) through the direct or indirect thermal coupling path.

[0093] The carbon dioxide high-temperature diversion device (DIV1) may include an adjustable diversion valve group, or branch regulating valves may be installed on the main steam superheated branch and the high-temperature bypass to regulate the carbon dioxide flow rate of each branch.

[0094] In the later stages of heat storage and release or under load changes, when the outlet temperature of the external thermal energy storage device (TES) drops, the outlet temperature of the carbon dioxide mixing device (MIX1) is insufficient, or the minimum heat exchange terminal difference of the main heat absorption heat exchanger (HX-EV) approaches the lower limit, the controller prioritizes increasing the flow rate ratio of the high-temperature bypass stream C1B, or restricts further heat extraction from the main steam superheating branch and reheating branch, in order to maintain stable operation of the main heat absorption section.

[0095] Example 2: Ultra-high temperature and supercritical steam supply system based on pure nitrogen direct drive

[0096] This embodiment presents an optimized solution adapted to ultra-high temperature all-carbon-based thermal storage media. The system flow field topology, high-temperature bypass setup, and anti-pinch temperature control logic are consistent with Embodiment 1. The system flow and topology are reused and referenced in Figure 1. The main differences lie in the selection of the heat transfer medium, the form of the fluid drive equipment, and the active explosion-proof isolation system that is forcibly activated due to changes in physical properties.

[0097] 1. Replacement of working fluid and drive equipment

[0098] In this embodiment, the external thermal energy storage device uses pure graphite or other carbon-based thermal storage media, with a maximum operating temperature of 1500℃. To prevent the strong carbothermic reduction reaction between conventional working fluids and carbon-based materials at extremely high temperatures, this embodiment uses pure nitrogen, which is chemically inert to carbon-based materials, as the heat transfer medium in the closed loop. The operating pressure range of pure nitrogen in the loop is 2.0~2.5 MPa, and it remains in an ideal gaseous state throughout the entire closed loop.

[0099] Accordingly, since this embodiment does not require gas compression phase change, the fluid circulation drive device in Embodiment 1 is replaced by a high-temperature resistant circulating fan instead of a compressor. The fan only needs to provide low-pressure head circulation power to overcome the friction resistance along the pipeline, and no high-power compressor is configured in the circuit, thus reducing the additional power consumption of auxiliary equipment.

[0100] 2. Direct-drive heat exchange and temperature control adaptation under nitrogen conditions

[0101] The exothermic curve of pure nitrogen gas in the main endothermic heat exchanger has a constant slope, but when matched with an ultra-supercritical water / steam loop, the water side still exhibits a significant nonlinear endothermic curve in the quasi-critical high specific heat region. This embodiment reuses the "bypass diversion and mixing" control logic described in Embodiment 1 to avoid heat transfer pinch points.

[0102] High-temperature nitrogen, driven by a high-temperature circulating fan, exits from the external thermal energy storage device at a temperature of 700°C. After being diverted, the high-temperature heat exchange branch sequentially releases high-grade heat to the main steam superheater and each stage of reheater. After heat release and cooling, the temperature drops to approximately 520°C before entering the mixing device. The high-temperature bypass retains and transports the unheated 700°C nitrogen. By dynamically adjusting the opening of the bypass valve through the control unit, the 700°C bypass nitrogen is uniformly mixed with the approximately 520°C branch nitrogen in the mixing device. This adjusts the nitrogen temperature before entering the main heat exchanger to the target value (e.g., around 650°C), corrects the inclination angle of the heat release curve, and reduces the risk of heat transfer deterioration in the quasi-critical zone.

[0103] Furthermore, the closed-loop pure nitrogen circuit directly exchanges heat with the supercritical water / steam circuit, eliminating the need for an intermediate isolation circuit. Utilizing the extremely high convective surface heat transfer coefficient of the supercritical water side inside the tubes, the metal tube walls of the heat exchanger can be controlled within a safe temperature range, and conventional ultra-supercritical heat-resistant steel can be used for the heated surface tubes, reducing the cost of special alloys.

[0104] 3. Online security protection and isolation logic for carbon-based materials

[0105] Because high-temperature carbon-based thermal storage medium (graphite) will produce a violent water-gas reaction upon contact with water, posing a risk of combustion and explosion. Therefore, in this embodiment, the online moisture monitoring and active explosion-proof isolation system shown in Figure 1 is forcibly activated and operates in conjunction with it.

[0106] The protection system includes a high-frequency trace moisture detector (MT) and quick-shutdown isolation valves (V-Q1, V-Q2) installed on the inlet and outlet main pipes of the external thermal energy storage device. When the detector detects that the water vapor concentration in the closed loop exceeds a preset threshold, the control unit triggers the quick-shutdown isolation valves to close urgently, physically cutting off and blocking the fluid connection between the external thermal energy storage device and the high-end heat exchange area, ensuring the safe operation of the ultra-high temperature unit under extreme conditions.

Claims

1. A thermal energy storage steam power generation system for diverting and bypassing the heat transfer working fluid and supplying it to the main heat absorption section, comprising an external thermal energy storage device, a closed-loop heat transfer working fluid circuit, and a water / steam power generation circuit, wherein the closed-loop heat transfer working fluid circuit serves as an intermediate heat transfer circuit and indirectly exchanges heat with the water / steam power generation circuit through a heat exchanger, and the working fluids inside the two circuits do not mix, characterized in that: The heat transfer medium in the closed heat transfer medium loop is selected from pure nitrogen, argon, air, carbon dioxide or a mixture thereof. The closed heat transfer working fluid loop includes a fluid circulation drive device, a high-temperature working fluid diversion device, a heat transfer working fluid side of at least one high-temperature steam heat exchanger, a high-temperature bypass, a heat transfer working fluid mixing device, a heat transfer working fluid side of the main heat absorption heat exchanger, and a return pipeline, and is thermally coupled to an external thermal energy storage device. The outlet of the fluid circulation drive device is configured with a direct or indirect thermal coupling path to the external thermal energy storage device, so that the heat transfer medium in the closed heat transfer medium loop can obtain heat from the external thermal energy storage device and form a high-temperature heat transfer medium. The output end of the high-temperature heat transfer medium is fluidly connected to the high-temperature medium diversion device. The high-temperature medium diversion device divides the high-temperature heat transfer medium from the external thermal energy storage device into at least a high-temperature heat exchange branch and a high-temperature bypass independent of the high-temperature heat exchange branch. The high-temperature heat exchange branch is in fluid communication with the heat transfer working fluid inlet of the at least one high-temperature steam heat exchanger. The high-temperature bypass bypasses the high-temperature steam heat exchanger, and a high-temperature bypass regulating valve is provided on the high-temperature bypass to form a regulated high-temperature bypass stream after regulation. The heat transfer medium at the outlet of at least one high-temperature steam heat exchanger and the regulated high-temperature bypass stream are both combined in the heat transfer medium mixing device. The outlet of the heat transfer medium mixing device is connected to the heat transfer medium inlet of the main heat absorber, so that the heat transfer medium after the heat is released by the high temperature steam heat exchanger is mixed with the heat transfer medium from the regulated high temperature bypass stream to form a medium-high temperature heat transfer medium stream supplied to the main heat absorber. The heat transfer medium outlet of the main heat exchanger is connected to the inlet of the fluid circulation drive device. After being processed by the fluid circulation drive device, a reflux heat transfer medium stream is formed, which absorbs heat again from the external thermal energy storage device through the direct or indirect thermal coupling path.

2. The system according to claim 1, characterized in that, The heat transfer medium flows in a single-phase form in the closed heat transfer medium loop as a gas, near-critical, dense, or supercritical state; the pressure of the heat transfer medium in the closed heat transfer medium loop is from 0.5 MPa to 40 MPa; the closed heat transfer medium loop is only used for heat transfer and does not include a power turbine used to expand the heat transfer medium and output shaft work or electrical work.

3. The system according to claim 1, characterized in that: The outlet of the fluid circulation drive device and the external thermal energy storage device form an indirect dual heat exchange path; the closed heat transfer working fluid circuit also includes an intermediate heat exchanger disposed between the outlet of the fluid circulation drive device and the high-temperature working fluid diversion device; the system also includes a second heat transfer working fluid circuit containing a second heat transfer working fluid, the second heat transfer working fluid circuit flows through the external thermal energy storage device to obtain heat, and indirectly transfers the heat to the heat transfer working fluid in the closed heat transfer working fluid circuit through the intermediate heat exchanger; the second heat transfer working fluid in the second heat transfer working fluid circuit is pure nitrogen or argon, and the external thermal energy storage device uses a graphite-containing carbon-based thermal storage medium with a maximum operating temperature of not less than 1000℃.

4. The system according to claim 1, characterized in that, The heat transfer medium, after releasing heat in the main heat exchanger, further indirectly heats other heat exchangers in the water / steam power generation circuit whose water / steam temperature is lower than that of the main heat exchanger, thereby reducing the amount of heat recovered from steam extraction in the water / steam power generation circuit.

5. The system according to claim 1, characterized in that, The closed-loop heat transfer medium circuit and the water / steam power generation circuit exchange heat directly in the heat exchanger without any other intermediate transition fluid circuits. High-pressure water, supercritical water, steam, or a mixture of steam and water circulate inside the heat exchanger tubes, while the outside of the tubes is scourd by a high-temperature heat transfer medium. Relying on the heat transfer coefficient of the water-side convective surface inside the tubes, the maximum temperature of the metal tube wall of the heat exchanger is controlled within a preset safe range lower than the temperature of the heat transfer medium outside the tubes.

6. The system according to claim 1, characterized in that, The closed heat transfer working fluid loop is equipped with an online moisture monitoring and active explosion-proof isolation system; the system includes a high-frequency trace moisture detector installed on the inlet pipeline of the external thermal energy storage device, and a quick-cut-off isolation valve installed on the inlet and outlet main pipelines of the external thermal energy storage device.

7. The system according to claim 1, characterized in that, The water / steam power generation circuit includes a steam turbine and is equipped with an industrial extraction steam branch. The industrial extraction steam branch is led out from the interstage splitting device of the steam turbine and can output saturated or superheated industrial steam with a pressure level of 0.3MPa to 4.0MPa. Based on the real-time acquisition of flow and pressure data of industrial extraction steam by the detection device, the opening degree of the high-temperature bypass regulating valve and the high-temperature working fluid splitting ratio are dynamically adjusted.

8. The system according to claim 1, characterized in that, The high-temperature bypass regulating valve is configured to regulate the pressure of the high-temperature bypass before it enters the heat transfer working fluid mixing device, so that it matches the outlet back pressure of the high-temperature steam heat exchanger after the superheated branch generates a flow resistance pressure drop through its corresponding heat exchanger.

9. The system according to claim 1, characterized in that, The high-temperature bypass is configured as an independent temperature regulation branch, used to introduce the high-temperature heat transfer medium that has not passed through the high-temperature steam heat exchanger into the heat transfer medium mixing device, so as to regulate the temperature of the heat transfer medium before the inlet of the main heat absorber and maintain it at a temperature not less than the preset minimum heat exchange end difference.

10. The system according to any one of claims 1 to 9, characterized in that, The high-temperature bypass regulating valve is further configured to dynamically adjust the throttling degree of the high-temperature bypass according to the real-time flow resistance pressure drop of the high-temperature steam heat exchanger branch, so that the outlet pressure of the high-temperature bypass matches the back pressure of the outlet of each heat exchange branch.

11. The system according to any one of claims 1 to 9, characterized in that, A pressure matching valve station is provided on the high-temperature bypass. The pressure matching valve station includes the high-temperature bypass regulating valve and includes at least one of the following: differential pressure measuring point, temperature measuring point, pressure balancing manifold, or bypass small flow pressure equalization path.

12. The system according to any one of claims 1 to 9, characterized in that, The system also includes a mixing and decoupling controller, which is configured to: adjust the flow rate of the heat transfer medium in the high-temperature steam heat exchanger branch according to the outlet temperature of the high-temperature steam heat exchanger; and acquire the internal pinch point position data of the main heat absorber, and adjust the flow rate of the heat transfer medium in the high-temperature bypass according to the outlet temperature of the heat transfer medium mixing device, the inlet heat source temperature of the main heat absorber, or the minimum heat exchange end difference.

13. The system according to claim 12, characterized in that, The system also includes a main heat exchanger TQ curve and pinch point control module. The main heat exchanger TQ curve and pinch point control module is configured to estimate the TQ curve, pinch point position or minimum heat exchange end difference online based on the state of the heat transfer medium side and water / steam side of the main heat exchanger, and adjust the flow rate of the high temperature bypass and the outlet target temperature of the heat transfer medium mixing device accordingly.

14. The system according to any one of claims 1 to 9, characterized in that, The main heat exchanger corresponds to an ultra-high pressure evaporator, a subcritical evaporator, a subcritical evaporation section, a supercritical pseudo-evaporation section, a supercritical strong heat absorption section, or an ultra-supercritical main heat absorption section; the outlet target temperature of the heat transfer working fluid mixing device is set according to the heat absorption curve of the corresponding water / steam power generation circuit.

15. A method for operating a thermal storage steam power generation system, characterized in that, Using the system of claim 1, the operating method includes the following steps: The heat transfer medium absorbs heat from the external heat storage device to form a high-temperature heat transfer medium flow stream. The main stream of high-temperature heat transfer medium is divided into at least one high-temperature steam heat exchanger branch and a high-temperature bypass through a high-temperature working medium diversion device. At least one branch of a high-temperature steam heat exchanger releases high-grade heat into the water / steam power generation circuit; The high-temperature bypass is pressure matched and regulated by the high-temperature bypass regulating valve to form a high-temperature bypass stream after pressure matching and regulation. At least one high-temperature steam heat exchanger outlet heat transfer medium stream is mixed with a high-temperature bypass stream that has been regulated and pressure matched in a heat transfer medium mixing device to form a medium-high temperature heat transfer medium stream. The medium- and high-temperature heat transfer fluid stream is introduced into the main heat exchanger, and heat from the main heat absorption section is provided to the water / steam power generation circuit while maintaining the minimum heat exchange end difference. The heat transfer fluid stream at the outlet of the main heat exchanger is processed by a fluid circulation drive device to form a reflux heat transfer fluid stream, which then absorbs heat again from the external thermal energy storage device through the direct or indirect thermal coupling path; or, the heat transfer fluid stream at the outlet of the main heat exchanger flows sequentially through at least one downstream regenerative device in the water / steam power generation circuit, the downstream regenerative device including a high-pressure regenerative heater and / or a low-pressure regenerative heater to heat the condensate, partially or completely replacing the steam extracted from the turbine, and then processed by a fluid circulation drive device to form a reflux heat transfer fluid stream, which then absorbs heat again from the external thermal energy storage device through the direct or indirect thermal coupling path.

16. The method according to claim 15, characterized in that, In the multi-branch dynamic regulation, the outlet parameters of the high-temperature steam heat exchanger are used as the control target for the high-temperature steam parameters to regulate the flow of the high-temperature steam entering the high-temperature steam heat exchanger; at the same time, the inlet heat source temperature or the minimum heat exchange end difference of the main heat absorber is used as an independent controlled parameter to prioritize the regulation of the heat transfer fluid flow rate of the high-temperature bypass.

17. The method according to claim 15, characterized in that, When adapted to supercritical and / or ultra-supercritical water / steam power generation circuits, the heat transfer medium is distributed in parallel to at least one high-temperature steam heat exchanger, which includes a high-temperature steam superheater, a first-stage reheater, a second-stage reheater, and an optional multi-stage reheater; when adapted to ultra-high pressure and / or subcritical water / steam power generation circuits, the heat transfer medium is distributed in parallel to at least one high-temperature steam heat exchanger, which includes a main steam superheater and an optional reheater; and the high-temperature bypass is retained as a heat source compensation branch at the inlet of the main heat-absorbing heat exchanger.

Images