Master-slave multi-unit cooperative decoupling system

Abstract

A master-slave type multi-unit cooperative decoupling system, comprising a master unit thermal system, a slave unit thermal system and a decoupling steam delivery main pipe; the master unit and the slave unit each comprise a boiler, a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder to form a thermal system; the master unit boiler reheater hot end outlet is connected to the decoupling steam delivery main pipe, and the decoupling steam delivery main pipe is connected to the slave unit reheater cold end inlet; the master unit uses output reheated steam to assist the slave unit to perform unit-boiler decoupling operation; on this basis, if the master unit is reformed to perform unit-boiler decoupling, the whole plant decoupling can be realized; the system has simple configuration, reliable switching, good performance-price ratio, high steam and heat supply guarantee rate and strong anti-accident capability; under the decoupling working condition, the decoupling high bypass is opened and has large flow, the steam turbine flow is small, and when the steam turbine is tripped, the original high bypass flow is small, the impact on the boiler is weakened.

Description

Technical Field

[0001] This invention belongs to the field of flexible peak shaving in thermal power plants. It can meet the large-scale and long-term peak shaving needs of the power grid, and can realize flexible heating, steam supply and energy storage without being restricted by heating / non-heating conditions. It belongs to the current new power system, specifically involving a master-slave multi-unit collaborative decoupling system. Background Technology

[0002] Flexibility in thermal power is a crucial aspect of building a new power system. However, thermal power units have two inherent shortcomings: first, in combined heat and power (CHP) systems, thermoelectric coupling occurs, requiring a corresponding proportion of power generation for sufficient heat supply; second, boilers cannot be frequently started and stopped, and at least 25-30% of the minimum stable combustion load must be maintained during load reduction. Under the current trend of rapid development of new energy sources, these two shortcomings lead to a large amount of ineffective power generation from thermal power plants (electricity not needed by the grid or electricity below cost price), resulting in losses for the plants themselves, hindering the absorption of new energy sources, and generating significant amounts of ineffective carbon emissions. Therefore, decoupling of the boiler and turbine throughout the entire thermal power plant becomes a necessary operating mode.

[0003] The decoupling technology of furnace and turbine has the following advantages.

[0004] 1) Traditional thermal power plants are subject to the rigid constraint of "heat-driven power generation." The thermal systems of large thermal power plants are designed for optimal energy efficiency, with heat typically extracted from the turbine side. There is a relatively fixed matching relationship between heat supply and power generation. Under heating conditions, residential heating or industrial steam supply is a rigid demand, conversely requiring power plants to operate in a "heat-driven power generation" manner. When the heat supply is high or the steam parameters are high, the flexibility of the units will be severely reduced. However, with the rapid development of new energy sources, the requirements for the flexibility of thermal power are becoming increasingly stringent. During periods of high new energy generation, thermal power generation should be minimized or supplemented; during periods of low new energy generation, thermal power should have peak capacity, posing a significant challenge to thermal power plants. Thermal power must undergo decoupling retrofitting to cope with this, and among the many technical routes, boiler-turbine decoupling can achieve the greatest degree of decoupling.

[0005] 2) Decoupling of the boiler and turbine can completely eliminate the thermoelectric coupling: During periods of low electricity price, the high flow rate bypass can achieve separate production of heat and electricity, that is, heat and electricity can be freely allocated. The power plant can generate electricity flexibly according to the grid dispatch instructions while ensuring heat supply; the addition of an external reheater can also achieve boiler operation without shutting down the boiler.

[0006] 3) Decoupled superimposed molten salt energy storage: can solve the flexibility problem of boiler stable combustion load operation: after decoupling the boiler and turbine, the main steam of the boiler is directly drawn out through the high-pressure bypass, which can achieve long-term and efficient energy storage. In this way, the heat of the boiler at the minimum stable combustion load is not sent to the turbine for power generation but is stored and used for peak load, resulting in the benefits of low storage and high release.

[0007] 4) Possesses multiple economic and social values: A series of derivative solutions based on decoupling of boiler and turbine can greatly enhance the flexibility of thermal power plants: First, the heating capacity and heating guarantee rate are improved; second, the ineffective power generation and losses from coal-fired power plant inversion are reduced; third, a large amount of space is freed up for the consumption of new energy sources, and green carbon reduction is achieved; fourth, efficient molten salt energy storage can be achieved, allowing the unit to obtain peak performance.

[0008] Boiler-turbine decoupling completely breaks the constraints of thermoelectric coupling: thermal power plants are no longer forced to maintain high-load operation due to steam / heat supply demands, supporting a higher proportion of renewable energy consumption and reducing the total amount of coal consumed in society. Boiler-turbine decoupling and its derivative solutions can effectively realize the transformation of thermal power, improve the healthy development level of the thermal power industry, and promote the development of China's dual-carbon strategy. Currently, patents related to boiler-turbine decoupling include: an energy storage system based on boiler-turbine decoupling (publication number: CN219159037U); and a thermal power system using external reheat to achieve boiler-turbine decoupling and low-temperature energy storage (publication number: CN218820288U). Although these technologies can achieve boiler-turbine decoupling and energy storage, they still have shortcomings.

[0009] Boiler-turbine decoupling involves modifications to four major pipeline systems, the addition of high-pressure injectors, external reheaters, and high-pressure valves, resulting in high engineering costs. Furthermore, current thermal power units operate and are scheduled using a unit-based system; to achieve decoupling across the entire plant, each unit must be configured individually, causing the investment to double with the number of units, while the returns are unlikely to double. Traditional one-unit-one-boiler decoupling retrofits require modifications to each unit, resulting in a significant investment burden. If the injectors in the decoupling system are configured as a shared system, multiple units need interconnected main steam lines, hot sections, and cold sections, leading to complex piping systems and substantial investments. Based on the current realities of the power industry, an innovative multi-unit boiler-turbine decoupling system is needed. Summary of the Invention

[0010] The purpose and task of this invention is to achieve decoupling of the boiler and turbine for each unit in the plant, with the lowest possible investment in the retrofit, and to enable both peak shaving and off-peak shaving after the retrofit. This allows for flexible adjustment of different units (synchronously or individually) without affecting external steam / heat supply, thus providing the strongest guarantee for the consumption of new energy in the power grid system.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A master-slave multi-unit collaborative decoupling system includes a master unit thermal system, a slave unit thermal system, and a decoupled steam header; characterized in that:

[0013] Both the active and subordinate units consist of a thermal system composed of a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder.

[0014] The hot end outlet of the boiler reheater of the active unit is connected to the decoupled steam supply header, and the decoupled steam supply header is connected to the cold end inlet of the reheater of the slave unit.

[0015] The active unit uses its output reheat steam to assist the slave unit in decoupled operation of the boiler and turbine.

[0016] Furthermore, it includes one or more subordinate units, wherein the decoupled steam supply pipeline is a whole steam pipeline or is composed of multi-stage steam pipelines, and the multi-stage steam pipelines are respectively connected to the cold end inlets of the reheaters of multiple subordinate units; a main pipe pressure isolation valve is installed between the multi-stage steam pipelines.

[0017] Furthermore, a heat recirculation module constructed by steam ejectors is connected between the cold end inlet and the hot end outlet of the reheater of the active unit boiler.

[0018] One of the first-stage steam transmission pipes connects the hot end outlet of the reheater of the active unit to the cold end inlet of the reheater of the first-stage slave unit. Similarly, the second-stage steam transmission pipe connects the hot end outlet of the reheater of the first-stage slave unit to the cold end inlet of the reheater of the second-stage slave unit. The connection is made sequentially, and the process of re-entering the cold section from the hot section is repeated among multiple slave units to achieve multi-unit decoupling throughout the plant. The main pipe pressure relief valve is in the closed state to ensure isolation between the steam transmission pipes of each stage.

[0019] Furthermore, the first decoupled high-pressure bypass of the active unit is connected to the power steam inlet of the steam ejector. As power steam, the hot end outlet of the main unit is connected to the ejector inlet of the steam ejector through the reheat cycle bypass, and the exhaust outlet of the steam ejector is connected to the cold end inlet of the reheater of the main unit boiler.

[0020] Furthermore, one of the first-stage steam transmission pipes connects the hot end outlet of the active unit's reheater to the cold end inlet of the first-stage slave unit's reheater. Similarly, the second-stage steam transmission pipe also connects the hot end outlet of the active unit's reheater to the cold end inlet of the second-stage slave unit's reheater. Multiple slave units are connected in parallel to achieve synchronous decoupling of multiple units throughout the plant. The main pipe pressure relief valve is in the open state to ensure the connection between the steam transmission pipes of each stage.

[0021] Furthermore, this includes decoupling the return steam header;

[0022] The decoupled return steam header is connected to the hot end outlet of the boiler reheater of the auxiliary unit, and the decoupled return steam header is connected to the air intake pipe of the intermediate pressure cylinder of the active unit. Gas consumption points are reasonably set on the decoupled return steam header for small steam turbine drive, external heating or steam supply.

[0023] Furthermore, a pressure relief valve is installed on the steam inlet pipe of the intermediate pressure cylinder of the active unit, located between the hot end outlet of the reheater of the active unit and the junction point of the decoupled return steam header.

[0024] Furthermore, a pressure relief bypass is provided between the steam inlet pipe of the intermediate pressure cylinder and the steam inlet pipe of the low pressure cylinder of the subordinate unit, and a pressure relief valve is installed on the pressure relief bypass.

[0025] Furthermore, the active unit adopts a unidirectional steam delivery mode to output reheat steam;

[0026] In unidirectional steam supply mode, the heat recirculation module is put into operation, the pressure relief valve is fully opened and connected, and part of the steam from the hot end outlet of the reheater of the subordinate unit is used for steam for the small turbine and / or for external heating.

[0027] Furthermore, the active unit adopts a recycle steam supply mode to output reheat steam;

[0028] In the recirculating steam supply mode, the hot recirculation module is disconnected, and part of the steam from the hot end outlet of the reheater of the subordinate unit enters the intake pipe of the intermediate pressure cylinder of the active unit through the decoupled return steam header, and the pressure relief valve operates in the pressure isolation state.

[0029] The beneficial effects of this invention are:

[0030] 1) Low cost: It is not necessary to modify all units according to the boiler-turbine decoupling module; only the basic decoupling module needs to be modified. Furthermore, as long as one decoupled unit is in operation, multi-unit decoupling can be guaranteed.

[0031] 2) The system configuration mode switching is simple and reliable;

[0032] 3) High steam and heat supply guarantee rate (strong accident resistance): Steam supply can be guaranteed to remain unaffected even if any turbine trips or multiple units trip simultaneously. Even in decoupled operation, the impact on the boiler and auxiliary equipment is weaker because the high proportion of bypass flow to boiler flow is relatively high (compared to pressure buildup operation). Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the system connection.

[0034] Figure 2 This is a schematic diagram of a one-way steam delivery mode.

[0035] Figure 3-5 Example of matching algorithm for units in unidirectional steam delivery mode;

[0036] Figure 6 Example of a matching algorithm for multi-unit cascade decoupling units;

[0037] Figure 7 A schematic diagram of the circulating steam delivery mode;

[0038] Figure 8 Example of matching algorithm for units in cyclic steam supply mode;

[0039] Figure 9. Schematic diagram of the pressure drop process. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The technical solution of the present invention is not limited by the capacity of power plant units.

[0042] The technical solution of the present invention is not limited to whether the power plant unit is newly built or already in operation.

[0043] The technical solution of the present invention is not limited by the number of power plant units involved in deep thermoelectric decoupling and the number of heating units.

[0044] The technical solution of the present invention is not limited by the steam parameters of power plant units.

[0045] The technical solution of the present invention is not limited by the combined heat and power or pure condensing operation of power plant units.

[0046] The technical solution of the present invention is not limited by the heating system of a power plant.

[0047] The technical solution of the present invention is not limited by the energy storage medium (molten salt, heat transfer oil, solid heat storage, phase change heat storage, etc.), the type of energy storage reheater, or its location.

[0048] The technical solution of the present invention is not limited by whether the active unit and the slave unit have undergone decoupling modification of the boiler and furnace, or whether an external reheater is configured.

[0049] like Figure 1 , 2 As shown in Figure 7, the system includes a main unit, a slave unit, a decoupled steam supply busbar, a decoupled return steam busbar, and an external steam supply busbar.

[0050] Both the active and subordinate units consist of a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder forming a thermal system. In the active unit's thermal system, the boiler's superheater generates main steam, which is connected to the turbine's high-pressure cylinder via a main steam pipeline. The high-temperature, high-pressure main steam from the main steam pipeline enters the turbine's high-pressure cylinder. The high-pressure cylinder exhaust steam enters the cold-end inlet of the boiler reheater; the hot-section outlet of the boiler reheater connects to the intermediate-pressure cylinder's steam inlet pipeline. A portion of the reheated steam from the hot-section outlet enters the turbine's intermediate-pressure cylinder to perform work.

[0051] A steam ejector assembly is connected between the cold end inlet and the hot end outlet of the boiler reheater to form a reheating and recirculation module.

[0052] A first decoupled high-pressure bypass is constructed from the main steam pipeline. The high-temperature, high-pressure main steam in this bypass, after being desuperheated and depressurized, is connected to the power steam inlet of the steam ejector as power steam. The hot section outlet is connected to the ejector inlet of the steam ejector via a reheat cycle bypass, which also includes a desuperheater and pressure reducer. The exhaust outlet of the steam ejector is connected to the cold end inlet of the reheater. The high-temperature, high-pressure main steam in the first decoupled high-pressure bypass, after being desuperheated and depressurized, enters the steam ejector as power steam, used to draw in the reheat cycle steam introduced through the ejector inlet. The power steam and reheat cycle steam mix and re-enter the cold end inlet of the reheater, thus forming a hot reheat recycle.

[0053] A second high-pressure bypass is also connected between the main steam pipeline and the cold end inlet of the boiler reheater, through which part of the main steam is directly connected to the reheater without passing through the high-pressure cylinder.

[0054] It also includes the thermal systems of several subordinate units.

[0055] In the auxiliary unit's thermal system, the auxiliary unit consists of a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. Within the auxiliary unit's thermal system, the superheater in the boiler generates main steam, which is connected to the turbine's high-pressure cylinder via the main steam pipeline. The high-temperature, high-pressure main steam from the main steam pipeline enters the turbine's high-pressure cylinder. The exhaust steam from the high-pressure cylinder enters the cold-end inlet of the boiler's reheater.

[0056] The hot section outlet of the boiler reheater is connected to the intermediate-pressure cylinder inlet steam pipeline. A portion of the reheat steam from the hot section outlet enters the intermediate-pressure cylinder of the turbine to perform work. The intermediate-pressure cylinder exhaust pipeline is connected to the low-pressure cylinder inlet steam pipeline. The exhaust steam from the intermediate-pressure cylinder enters the low-pressure cylinder of the turbine to perform work. A first decoupled high-pressure bypass is newly constructed from the main steam pipeline. The high-temperature, high-pressure main steam in the first decoupled high-pressure bypass is desuperheated and depressurized before being supplied as external steam. A second high-pressure bypass is also connected between the main steam pipeline and the cold-end inlet of the boiler reheater, through which a portion of the main steam is directly connected to the reheater without passing through the high-pressure cylinder.

[0057] Both the active and slave units are connected to the decoupled steam supply header, the decoupled return steam header, and the external steam supply header.

[0058] The hot section outlet of the active unit's reheater is connected to the decoupled steam supply pipeline and then to the decoupled steam supply header. The cold end inlet of the slave unit's reheater is connected to the decoupled makeup steam pipeline and then to the decoupled steam supply header. The hot section outlet of the slave unit's reheater is connected to the decoupled return steam pipeline and then to the decoupled return steam header.

[0059] The decoupled return steam header is further connected to the return steam pipeline of the intermediate pressure cylinder of the active unit, and then to the inlet steam pipeline of the intermediate pressure cylinder of the active unit. The decoupled return steam header also connects to the small turbines of the active unit and / or the small turbines of the subordinate units, and can also provide external steam supply. Steam from the hot section of the reheater of the active unit can be input into the decoupled steam header and then into the cold end of the reheater of the subordinate unit. Steam from the hot section of the reheater of the subordinate unit can be input into the decoupled return steam pipeline and returned to the intermediate pressure cylinder of the active unit. Appropriate steam consumption points are set on the decoupled return steam header for small turbine drive, external heating, or steam supply.

[0060] The first decoupled high-pressure bypass of the active and slave units can provide external steam output, supplying steam and heat, and can be connected to the molten salt energy storage system. The first decoupled high-pressure bypass of the active and slave units can be connected to different steam outputs, or connected to the external steam supply header, and then uniformly connected to the steam output through the external steam supply header.

[0061] In the active unit, a pressure relief valve is installed on the intermediate-pressure cylinder inlet steam pipeline, located between the reheater hot section outlet of the intermediate-pressure cylinder inlet steam pipeline and the junction point of the intermediate-pressure cylinder return steam pipeline. In the slave unit, a pressure relief bypass is installed between the intermediate-pressure cylinder inlet steam pipeline and the low-pressure cylinder inlet steam pipeline, and a pressure relief valve is installed on the pressure relief bypass.

[0062] like Figure 2 As shown, the system configuration in this application is a one-way steam delivery mode.

[0063] Unit #1, acting as the active unit, is equipped with a heat recirculation module. Unit #1 is first decoupled, and then the surplus hot-section steam is sent to the downstream units. During the decoupling of the boiler and turbine in Unit #1, the addition of power steam and desuperheating water significantly increases the steam surplus within the system, which can then be used for decoupling downstream units.

[0064] The first decoupled high-pressure bypass (decoupling bypass) of Unit #1 is divided into two paths. One path, after desuperheating and depressurization, supplies steam / heat / molten salt for energy storage. The other path, via an ejector, serves as the motive steam for heat recirculation (steam heated by the boiler reheater after high-pressure exhaust). After being pressurized by the ejector, it re-enters the boiler reheater to compensate for the insufficient reheat steam. Because the initial flow rate of superheated steam is large, a portion is desuperheated and depressurized for external use, while the original high-pressure exhaust steam entering the reheater is insufficient. Heat recirculation balances the superheater and reheater, thereby achieving decoupling of Unit #1 from the boiler.

[0065] To achieve boiler-turbine decoupling of Unit #2 (a first-order slave unit), the first decoupling high-pressure bypass (decoupling bypass) of Unit #2 is also depressurized and de-temperatured before supplying steam / heat / molten salt energy storage. The reheater of Unit #2 will also experience flow shortages. At this time, the hot reheat steam from Unit #1, through the decoupling steam supply pipeline, sequentially through the decoupling steam supply header and the decoupling make-up steam pipeline, merges with the original high-pressure exhaust steam from Unit #2 before entering the reheater of Boiler #2. This ensures safe operation of the reheater flow. After being heated by the reheater and becoming reheat steam, a portion enters the intermediate-pressure cylinder for power generation according to the steam volume required by the corresponding load heat balance diagram. The other portion is supplied to the small turbines and / or externally via the decoupling return steam pipeline.

[0066] Because the system is equipped with a desuperheating device, the reheated steam will generate an incremental portion after desuperheating. A pressure relief bypass can be installed between the intermediate-pressure cylinder inlet pipe and the low-pressure cylinder inlet pipe of Unit #2. A pressure relief valve is installed on the pressure relief bypass, which diverts part of the steam, allowing the incremental portion of the reheated steam to bypass to the low-pressure cylinder. When the active unit uses a steam ejector for decoupling, the delivered steam is surplus reheated steam and does not need to be returned to the active unit. In this case, the return steam header can be closed, the pressure relief valve can be fully opened, and the system operates in a unidirectional steam delivery mode. Further simplification of the system can be achieved by eliminating the return steam header and the pressure relief valve.

[0067] Example of a one-way steam delivery configuration mode.

[0068] Figure 3 As shown, in the example of the matching algorithm for a 600MW hot section re-entering a 1000MW cold section, when Unit #1 has a load factor of >= 43%, Unit #2 can be decoupled when its load factor is <= 34%.

[0069] Figure 4 As shown, an example of the matching algorithm for 1000MW and 600MW units is provided. When Unit #1 has a load factor of >= 27%, Unit #2 can be decoupled at a load factor of 38%.

[0070] Figure 5 As shown, an example of a matching algorithm for 600MW units is provided. When Unit #1 has a load factor of >= 43%, Unit #2 can be decoupled at a load factor of 38%.

[0071] In the unidirectional steam supply decoupling mode, taking the row indicated by the arrow as an example: the main steam inlet flow rate of the 600MW unit is 750t, and the hot section pressure PM = 1.62MPa. The pressure drop of the connecting pipe between the two units ▲P = 0.05MPa; therefore, the cold section pressure of the 1000MW unit can be obtained as: PM - ▲P = 1.57MPa; at this time, the main steam inlet flow rate of the 1000MW unit is 934t, and the load factor is 34%.

[0072] When the hot section pressure Ph of the 600MW unit exceeds the cold section pressure PL of the 1000MW unit, it can assist in decoupling the 1000MW unit, allowing for flexible operating condition combinations. Decoupling is possible as long as the operating point of the active unit is higher than that of the slave unit. The load factor of the two units has a high degree of freedom.

[0073] To ensure the dual units maintain operational independence, the operating point of the active unit should be at least 1-2 levels higher than that of the slave unit during actual operation. This allows for sufficient capacity for the active unit's AGC to reduce load or the slave unit's AGC to increase load. During unidirectional steam transmission, some of the decoupled steam can be used for external heating, steam supply from the small turbine, or it can enter the low-pressure cylinder of Unit #2 through the pressure relief valve.

[0074] Furthermore, in the unidirectional steam delivery decoupling mode, multi-machine cascade decoupling can also be formed throughout the plant: such as Figure 2 , Figure 6 As shown, the method of re-entering the cold section from the hot section can be repeated between multiple slave units. That is, the hot re-steam from Unit #1 is decoupled to Unit #2, and then the hot re-steam from Unit #2 is decoupled to Unit #3, thus realizing multi-unit cascade decoupling throughout the plant.

[0075] The decoupled steam supply pipeline consists of multi-stage steam pipes. The first-stage steam pipe connects the hot-end outlet of the reheater of the active unit to the cold-end inlet of the reheater of the first-stage slave unit. Similarly, the second-stage steam pipe connects the hot-end outlet of the reheater of the first-stage slave unit to the cold-end inlet of the reheater of the second-stage slave unit. These sequential connections, using a hot-section re-entry-cold-section method, can be repeated between multiple slave units, achieving multi-stage decoupling across the entire plant.

[0076] A main pipe pressure isolation valve is installed between the multi-stage steam transmission pipes. When each stage of subordinate unit is connected in sequence, the main pipe pressure isolation valve is in the closed state to ensure isolation between the steam transmission pipes of each stage.

[0077] In the above process: the hot section outlet of the reheater of the first-stage unit is connected to the second-stage decoupling steam pipe, and the second-stage decoupling steam pipe is connected to the cold section inlet of the reheater of the second-stage slave unit, thus achieving decoupling of the second-stage slave unit. This process can be repeated as long as the hot section pressure of the upstream unit is higher than the cold section pressure of the downstream unit, achieving subsequent decoupling. The active unit can construct a heat recirculation module using a steam ejector or turbocompressor to achieve its own decoupling.

[0078] During multi-unit cascade decoupling, the reheat hot section Ph pressure continuously decreases, requiring a decrease in load rate between units. When the system operates in unidirectional steam supply decoupling mode: 1) Only unidirectional steam supply is needed; surplus steam from the active unit does not need to return to the active unit. 2) The load rate combination between units is very flexible: as long as the upstream load rate is greater than the downstream load rate, it is acceptable. This is beneficial for AGC (Automatic Generation Control) commissioning. 3) All units can be decoupled in a cascade manner.

[0079] like Figure 7As shown, the system in this application is configured in a cyclic steam supply mode.

[0080] Unit #1, acting as the active unit, does not operate the thermal recirculation module and sends hot-section steam to Unit #2 (the subordinate unit). After decoupling the boiler and turbine of Unit #2, the steam is returned to Unit #1. When Unit #1, as the active unit, disconnects and puts the thermal recirculation module into operation, its first decoupled high-pressure bypass (decoupling bypass) is de-temperatured and depressurized before supplying steam / heat / molten salt energy storage to the outside.

[0081] To achieve boiler-machine decoupling of Unit #2, the first decoupling high-pressure bypass (decoupling bypass) of Unit #2 is also de-cooled and depressurized before supplying steam / heat / molten salt energy storage. The reheater of Unit #2 will also experience a flow shortage. At this time, the hot reheat steam from Unit #1 passes through the decoupling steam supply pipeline, then through the decoupling steam supply header and the decoupling steam replenishment pipeline, and merges with the original high-pressure exhaust steam from Unit #2 before entering the reheater of Boiler #2. This ensures the safe operation of the reheater flow. After being heated by the reheater and becoming reheated steam, a portion of it enters the intermediate-pressure cylinder for power generation according to the steam volume required by the corresponding load heat balance diagram. Because there is an upper limit to the proportion of intermediate-pressure steam extracted from Unit #1, some of the steam returned from Unit #2 must be re-entered into the intermediate-pressure cylinder of Unit #1. A portion of the reheat steam is connected to the return steam pipeline of the intermediate-pressure cylinder of Unit #1 via the decoupled return steam pipeline to ensure the safe steam intake of the intermediate-pressure cylinder of the active unit. The steam is then connected to the intermediate-pressure cylinder inlet pipeline of Unit #1 to generate electricity. The decoupled return steam header can also simultaneously provide steam for the small turbine and / or external steam supply.

[0082] Because the system is equipped with a desuperheating device, an incremental portion of the reheated steam will be generated after desuperheating. A pressure relief bypass can be installed between the inlet pipes of the intermediate-pressure cylinder and the low-pressure cylinder of Unit #2. A pressure relief valve is installed on the pressure relief bypass. By diverting part of the steam through the pressure relief valve, the incremental portion of the reheated steam can be bypassed to the low-pressure cylinder. The pressure relief valve also ensures that the steam pressure at the decoupling return steam header is appropriate. The pressure relief valve provides an outlet for excess decoupling steam and maintains the system's pressure gradient.

[0083] During system operation, pressure drop factors need to be considered. For example, the reheat steam after decoupling from Unit #1 needs to be kept at high pressure. A pressure-retaining valve is installed on the steam inlet pipeline of the intermediate pressure cylinder of Unit #1. The pressure-retaining valve operates in a pressure isolation state, keeping the pressure at the front end high and the pressure at the rear end low. However, when the system is in unidirectional steam supply decoupling mode, the pressure-retaining valve does not need to be activated and is fully open and conductive.

[0084] like Figure 9As shown, to ensure normal system operation, pressure drop factors need to be optimized simultaneously (this can be achieved through pipeline optimization, etc.). The pressures at various locations in the system pipeline are P1 (outlet A→B→C of #1 reheater), P2 (decoupled steam supply header → D→E→F), P3 (reheater of #2 → G→H), P4 (decoupled return steam header), and P5 (I→J→K→intermediate pressure cylinder of #1), where P1>P2>P3>P4>P5.

[0085] When the system operates in the recirculating steam decoupling mode: bidirectional steam transmission: steam returns to the original active unit system. Recirculating steam decoupling requires a "pressure-retaining valve" to be installed on the hot section pipeline, creating a sufficient pressure difference across the valve. The steam delivered (from the front end of the pressure-retaining valve) can return to the rear end of the pressure-retaining valve after decoupling. The pressure difference created across the pressure-retaining valve allows the steam to overcome resistance and complete the round-trip process.

[0086] like Figure 8 As shown, here's an example of the matching algorithm for units in a circulating steam supply mode: After pressure buildup at the operating point indicated by the arrow: the pressure before the valve Ph = 3.01 MPa, the pipeline flow resistance is 0.05, it drops to 2.96 MPa in the cold section of the 1MW unit, and to 2.72 MPa in the hot section of the reheater. The return pipeline resistance is 0.05, and there is still a pressure of 2.67 MPa after the valve at the 600MW unit, which is 0.16 MPa higher than the 2.51 MPa after the pressure buildup valve. Steam can return smoothly, completing the closed-loop cycle. If the 600MW unit has a load rate of 68%, it can only be paired with the 1MW unit at a load rate of 60%; if the 600MW unit increases its load to 43%, the 1MW unit can only be paired with it at 40%.

[0087] Due to factors such as desuperheating and water spraying, the amount of return steam will usually increase. Some of it must be properly absorbed to prevent the steam intake of the intermediate pressure cylinder of the 600,000 kW unit from increasing too much. Otherwise, the pressure value after the pressure relief valve will rise accordingly, hindering the steam return flow.

[0088] When decoupling in a recirculating steam supply system, both units must be operating under the same conditions to achieve decoupling. The load rates of both units rise and fall synchronously, with synchronized deep adjustments, conforming to the grid's dispatching practices. Typically, in medium-to-high load zones, decoupling of the boiler and turbine is not required. After exiting decoupling mode, the units can operate independently.

[0089] Furthermore, in the recirculating steam decoupling mode, multi-machine synchronous decoupling throughout the plant can also be achieved: such as Figure 7As shown, the decoupled steam supply pipeline consists of multi-stage steam pipes. The first-stage steam pipe connects the hot-end outlet of the active unit's reheater to the cold-end inlet of the first-stage slave unit's reheater. Similarly, the second-stage steam pipe connects the hot-end outlet of the active unit's reheater to the cold-end inlet of the second-stage slave unit's reheater. A main pipe pressure relief valve is installed between the multi-stage steam pipes. When the slave units are connected in parallel, the main pipe pressure relief valve is open to ensure connectivity between the steam pipes. A portion of the reheat steam from the second-stage slave unit is also connected to the decoupled return steam pipeline. By connecting all the slave units in parallel throughout the plant, synchronous decoupling of all units can be achieved.

[0090] Finally, it should be noted that the above description is merely an explanation of the present invention and is not intended to limit the invention. Although the present invention has been described in detail, those skilled in the art can still modify the technical solutions described above or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A master-slave multi-unit cooperative decoupling system, comprising a master unit thermal system, a slave unit thermal system, and a decoupling steam delivery main pipe; characterized in that: the master unit and the slave unit each comprise a boiler, a high-pressure cylinder, a medium-pressure cylinder, and a low-pressure cylinder to form a thermal system; the master unit boiler reheater hot end outlet is connected to the decoupling steam delivery main pipe, and the decoupling steam delivery main pipe is connected to the slave unit reheater cold end inlet; the master unit uses output reheated steam to assist the slave unit to operate in a unit-boiler decoupling mode; one or more slave units are included, wherein the decoupling steam delivery pipe is the entire steam delivery pipe or is composed of multiple-stage steam delivery pipes, each of which is connected to the cold end inlet of the reheater of a slave unit; a main pipe pressure isolation valve is arranged between the multiple-stage steam delivery pipes; a steam ejector is arranged between the cold end inlet and the hot end outlet of the master unit boiler reheater to form a thermal re-reheat cycle module; one of the multiple-stage steam delivery pipes connects the hot end outlet of the master unit reheater to the cold end inlet of a first-stage slave unit reheater, and similarly, a second-stage steam delivery pipe connects the hot end outlet of the first-stage slave unit reheater to the cold end inlet of a second-stage slave unit reheater; the connection is sequentially repeated in the multiple slave units in the manner of reheating the hot section and re-entering the cold section, thereby achieving multi-unit cascade decoupling of the entire plant; the main pipe pressure isolation valve is in a closed state to ensure isolation between the multiple-stage steam delivery pipes; a first decoupling high-pressure bypass of the master unit is connected to the power steam inlet of the steam ejector as the power steam, the hot end outlet of the master unit is connected to the injection inlet of the steam ejector through a reheating cycle bypass, and the exhaust outlet of the steam ejector is connected to the cold end inlet of the master unit boiler reheater. 2.The master-slave multi-unit cooperative decoupling system according to claim 1, characterized in that: the multiple slave units are connected in parallel to achieve multi-unit synchronous decoupling of the entire plant; the main pipe pressure isolation valve is in an open state to ensure communication between the multiple-stage steam delivery pipes. a decoupling return steam main pipe is included; 3. The master-slave multi-unit cooperative decoupling system according to claim 1, characterized in that, the hot end outlet of the slave unit boiler reheater is connected to the decoupling return steam main pipe, and the decoupling return steam main pipe is connected to the master unit medium-pressure cylinder inlet pipe; a reasonable number of steam points are arranged on the decoupling return steam main pipe for driving a small steam turbine, external heating, or steam supply. a pressure holding valve is arranged on the master unit medium-pressure cylinder inlet pipe between the hot end outlet of the master unit reheater and the decoupling return steam main pipe merging point.

4. The master-slave multi-unit cooperative decoupling system according to claim 3, characterized in that, a pressure relief bypass is arranged between the slave unit medium-pressure cylinder inlet pipe and the low-pressure cylinder inlet pipe, and a pressure relief valve is installed on the pressure relief bypass.

5. The master-slave multi-unit cooperative decoupling system according to claim 1, wherein, the master unit uses a one-way steam delivery mode to output reheated steam; 6. The master-slave multi-unit cooperative decoupling system according to claim 4, wherein, in the one-way steam delivery mode, the thermal re-reheat cycle module is put into operation, the pressure holding valve is fully opened, and part of the steam at the hot end outlet of the slave unit reheater is used for small steam turbine steam and / or external heating. the master unit uses a circulating steam delivery mode to output reheated steam; 7. The master-slave multi-unit cooperative decoupling system according to claim 5, wherein, in the circulating steam delivery mode, the thermal re-reheat cycle module is cut off, part of the steam at the hot end outlet of the slave unit reheater enters the master unit medium-pressure cylinder inlet pipe through the decoupling return steam main pipe, and the pressure holding valve operates in a pressure isolation state. ​

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