Master-slave multi-unit cooperative decoupling system

Abstract

A master-slave type multi-unit cooperative decoupling system comprises a master unit thermodynamic system, a slave unit thermodynamic system and a decoupling steam supply main pipe. Each of the driving unit and the subordinate unit is a thermodynamic system composed of a boiler, a high-pressure cylinder, an intermediate-pressure cylinder and a low-pressure cylinder. A hot end outlet of the boiler reheater of the active unit is connected with a decoupling steam supply main pipe, and the decoupling steam supply main pipe is connected with a cold end inlet of the reheater of the slave unit; the driving unit assists the subordinate unit in performing machine-boiler decoupling operation by outputting reheated steam; on the basis, if machine-furnace decoupling transformation is carried out on the active unit, whole-plant decoupling can be achieved; the system is simple in configuration, reliable in switching and good in cost performance; and under the decoupling working condition, the decoupling high bypass is opened, the flow is large, the steam turbine flow is small, and when the steam turbine jumps, the original high bypass flow is small, and the impact degree on the boiler is weakened.

Description

Technical Field

[0001] The present invention belongs to the field of flexible peak regulation of thermal power plants, can meet the large-scale and long-term up and down peak regulation needs of the power grid, and can be unrestricted by heating / non-heating conditions, realize flexible heating, steam supply and energy storage, and belongs to the current new power system, specifically involving a master-slave multi-unit collaborative decoupling system. Background Art

[0003] The flexibility of thermal power is an important part of building a new power system, but thermal power units have two inherent shortcomings: one is the heat-electric coupling phenomenon during cogeneration, and sufficient heat supply must have a corresponding proportion of power generation; the other is that the boiler cannot be started and stopped frequently, and at least 25-30% of the minimum stable combustion load must be maintained when reducing the load. Under the current situation of rapid development of new energy, these two shortcomings lead to a large amount of ineffective power generation (electricity that is not needed by the power grid or electricity below cost price) in thermal power, resulting in its own losses, affecting the consumption of new energy, and generating a large amount of ineffective carbon emissions. It has become a necessary operating mode for thermal power plants to achieve decoupling of the machine and boiler throughout the plant.

[0004] The turbine-boiler decoupling technology has the following advantages.

[0005] 1) Traditional thermal power plants have the rigid constraint of "determining electricity by heat". The thermal system of large thermal power plants is designed according to the best energy efficiency, and heat is usually extracted from the steam turbine side. There is a relatively fixed adaptation relationship between the heat supply and the power generation. Under the heating condition, residential heating or industrial steam supply is a rigid demand, which in turn requires the power plant to operate in a "heat-based electricity" manner. When the heat supply is large or the steam supply parameters are high, the flexibility of the unit will be seriously reduced. However, with the rapid development of the dual-carbon strategy and new energy, the requirements for the flexibility of thermal power are getting higher and higher. During the period of high generation of new energy, thermal power is required to be generated as little as possible or to make up for it; during the period of low generation of new energy, thermal power is required to have peak capacity, which is a great challenge for thermal power plants. Thermal power can only cope with it through thermal power decoupling transformation, and among the many technical routes, machine-boiler decoupling can achieve the greatest degree of decoupling.

[0006] 2) Decoupling of the machine and boiler can completely eliminate the coupling between heat and electricity: During periods of low electricity prices, the large-flow high bypass can be turned on to achieve separate production of heat and electricity, that is, heat and electricity can be freely allocated. Under the premise of ensuring heat supply, the power plant can flexibly generate electricity according to the dispatching instructions of the power grid; adding an external reheater can also achieve shutdown without stopping the boiler.

[0007] 3) Decoupling and superimposed molten salt energy storage: It can solve the flexibility problem of the boiler's stable combustion load conditions: after the decoupling of the turbine and boiler, the main steam of the boiler is directly drawn out through the high bypass, which can achieve long-term and efficient energy storage. In this way, the heat of the boiler's lowest stable combustion load will not enter the steam turbine for power generation but will be stored and used for peak purposes, resulting in the benefit of low storage and high release.

[0008] 4) It has multiple economic and social values: A series of derivative solutions based on boiler-turbine decoupling 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 the losses of coal-fired power are reduced; third, a large amount of space is freed up for the consumption of new energy and green carbon reduction; fourth, efficient molten salt energy storage can be achieved, allowing the units to achieve peak functionality.

[0009] The decoupling of the turbine and boiler completely breaks the coupling constraints of heat and electricity: thermal power plants do not need to be forced to maintain high-load operation due to steam / heat supply needs, support a higher proportion of new energy consumption, reduce the total amount of social coal burning, and effectively promote the carbon peak and carbon neutrality strategies. The decoupling of the turbine and boiler and its derivative solutions can well 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 cause. The current patents related to the decoupling of the turbine and boiler include an energy storage system based on the decoupling of the turbine and boiler, publication number: CN219159037U; a thermal power system that uses external reheating to achieve turbine and boiler decoupling and low-exergy energy storage, publication number: CN218820288U. Although the decoupling of the turbine and boiler and energy storage can be achieved, there are still some shortcomings.

[0010] The decoupling of the machine and boiler involves the modification of four major pipelines, the addition of high-pressure ejectors, external reheaters, high-pressure valves, etc., and the project cost is very high. In addition, the thermal power units are currently operated and dispatched according to the unit system. To achieve the decoupling of the whole plant, they must be configured one by one, resulting in the investment amount doubling according to the number of units, but the benefits are difficult to double. If the traditional one-machine-one-boiler decoupling transformation is carried out, each unit needs to be transformed, which is a heavy investment burden. If the ejectors in the machine-boiler decoupling system are set as a public system, the main steam of multiple units needs to be interconnected, the hot section is interconnected, and the cold section is interconnected. The piping system is complex and the investment is not low. According to the actual problems of the current power industry, it is necessary to provide an innovative multi-machine machine and boiler decoupling system. Summary of the invention

[0011] The purpose and task of the present invention is to realize the decoupling of the machine and boiler of each unit in the whole plant with the lowest transformation investment. After the transformation, both upper and lower peak regulation can be achieved, and the flexibility of adjustment (synchronous or individual) of different units can be achieved without affecting the external steam / heat supply, so as to provide the most powerful guarantee measure for the consumption of new energy in the power grid system.

[0012] To achieve the above object, the present invention adopts the following technical solution: A master-slave multi-unit cooperative decoupling system, comprising a master unit thermal system, a slave unit thermal system, and a decoupled steam supply main pipe; characterized in that: The active unit and the subordinate unit are composed of boiler, high-pressure cylinder, medium-pressure cylinder and low-pressure cylinder to form a thermal system; The hot end outlet of the boiler reheater of the active unit is connected to the decoupled steam supply mother pipe, and the decoupled steam supply mother pipe is connected to the cold end inlet of the reheater of the slave unit; The active unit uses the output reheated steam to assist the slave units in performing boiler-turbine decoupling operation.

[0013] Furthermore, it includes one or more slave units, wherein the decoupled steam supply pipeline is the entire steam pipe or is composed of multi-stage steam pipes, and the multi-stage steam pipes are respectively connected to the cold end inlets of the reheaters of multiple slave units; a mother pipe pressure isolation valve is arranged between the multi-stage steam pipes.

[0014] Furthermore, a heat recirculation module constructed by a steam ejector is connected between the cold end inlet and the hot end outlet of the boiler reheater of the active unit; One of the first-stage steam 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 pipe connects the hot-end outlet of the first-stage slave unit's reheater to the cold-end inlet of the second-stage slave unit's reheater. The connections are made in sequence, and the method of the temporary hot section reentering the cold section is repeated between multiple slave units to achieve multi-unit cascade decoupling in the entire plant. The main pipe pressure isolation valve is in the off state to ensure isolation between each stage of the steam pipes.

[0015] Furthermore, the first decoupled high-pressure bypass of the active unit is connected to the motive steam inlet of the steam ejector. As motive steam, the hot end outlet of the main unit is connected to the injection 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 boiler reheater of the main unit.

[0016] Furthermore, one of the first-stage steam pipes connects the hot-end outlet of the active unit reheater to the cold-end inlet of the first-stage slave unit reheater, and similarly, the second-stage steam pipe also connects the hot-end outlet of the active unit reheater to the cold-end inlet of the second-stage slave unit reheater; multiple slave units are connected in parallel to realize synchronous decoupling of multiple units in the whole plant; the main pipe pressure isolation valve is in the open state to ensure the connectivity between the steam pipes of each stage.

[0017] Further, it includes decoupling the steam return main pipe; The hot end outlet of the boiler reheater of the slave unit is connected to the decoupling steam return mother pipe, and the decoupling steam return mother pipe is connected to the air inlet pipe of the intermediate pressure cylinder of the active unit; the decoupling steam return mother pipe is reasonably set with gas consumption points for driving small steam turbines, external heat supply or steam supply.

[0018] Furthermore, a pressure holding valve is provided on the steam inlet pipe of the intermediate pressure cylinder of the active unit, and is located between the hot end outlet of the reheater of the active unit and the confluence point of the decoupling return steam mother pipe.

[0019] Furthermore, a pressure relief bypass is provided between the medium-pressure cylinder steam inlet pipeline and the low-pressure cylinder steam inlet pipeline of the slave unit, and a pressure relief valve is installed on the pressure relief bypass.

[0020] Furthermore, the active unit outputs reheated steam in a one-way steam delivery mode; In the one-way steam supply mode, the heat recirculation module is put into operation, the pressure-holding valve is fully opened, and part of the steam at the hot end outlet of the reheater of the subordinate unit is used for small turbine steam and / or external heat supply.

[0021] Furthermore, the active unit outputs reheated steam in a circulating steam delivery mode; In the circulating steam supply mode, the hot recirculation module is cut off, and part of the steam at the hot end outlet of the reheater of the slave unit enters the intermediate pressure cylinder air inlet pipe of the active unit through the decoupling return steam mother pipe, and the pressure holding valve works in the pressure isolation state.

[0022] The beneficial effects of the present invention are: 1) Low cost: It is not necessary to transform all units according to the boiler-turbine decoupling module, but only according to the basic decoupling module. And as long as there is one decoupling unit in operation, the decoupling of multiple units can be guaranteed; 2) The system configuration mode switching is simple and reliable; 3) High steam and heat supply guarantee rate (strong anti-accident capability): If any steam turbine trips or multiple units trip at the same time, the steam supply can be guaranteed to be unaffected. Even in the decoupled condition, the impact on the boiler and auxiliary equipment is relatively weak (compared with the pressure holding condition) because the proportion of high bypass flow to boiler flow is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 , is a schematic diagram of system connection.

[0024] Figure 2 , which is a schematic diagram of the one-way steam supply mode.

[0025] Figure 3-5 , an example of matching algorithm for units in one-way steam delivery mode; Figure 6 , an example of matching algorithm for multi-machine cascade decoupling units; Figure 7 , schematic diagram of circulating steam supply mode; Figure 8 , an example of matching algorithm for units in circulating steam delivery mode; Fig. 9 , schematic diagram of the pressure drop process. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The technical solution of the present invention is not limited by the capacity of the power plant units.

[0028] The technical solution of the present invention is not limited to whether the power plant units are newly built or already in operation.

[0029] The technical solution of the present invention is not limited by the number of power plant units involved in deep thermal-electric decoupling and heating.

[0030] The technical solution of the present invention is not limited by the steam parameters of the power plant units.

[0031] The technical solution of the present invention is not limited by the cogeneration or pure condensing conditions of the power plant units.

[0032] The technical solution of the present invention is not limited by the thermal system of the power plant.

[0033] 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, and the location.

[0034] The technical solution of the present invention is not limited by whether the active unit and the slave unit have undergone boiler-machine decoupling transformation, and whether an external boiler reheater is configured.

[0035] like Figure 1 , 2 As shown in , 7, the system includes an active unit, a slave unit, a decoupled steam supply mother pipe, a decoupled steam return mother pipe, and an external steam supply mother pipe.

[0036] The active unit and the slave unit are composed of a thermal system consisting of a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. In the thermal system of the active unit, the active unit is composed of a thermal system consisting of a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. The superheater in the boiler generates main steam and is connected to the high-pressure cylinder of the steam turbine through the main steam pipeline. The high-temperature and high-pressure main steam from the main steam pipeline enters the high-pressure cylinder of the steam turbine. The exhaust steam of the high-pressure cylinder enters the cold end inlet of the boiler reheater; the outlet of the hot section of the boiler reheater is connected to the steam inlet pipe of the intermediate-pressure cylinder. Part of the reheated steam at the outlet of the hot section enters the intermediate-pressure cylinder of the steam turbine to perform work.

[0037] A steam ejector assembly is connected between the cold end inlet and the hot section outlet of the boiler reheater to form a heat recirculation module.

[0038] A first decoupled high-pressure bypass is newly drawn out from the main steam pipeline. The high-temperature and high-pressure main steam in the first decoupled high-pressure bypass is connected to the motive steam inlet of the steam ejector as motive steam after being cooled and reduced in pressure. The hot section outlet is connected to the injection inlet of the steam ejector through the reheat cycle bypass, and a cooling and pressure reducing device is also provided on the reheat steam bypass. The exhaust steam outlet of the steam ejector is connected to the cold end inlet of the reheater. The high-temperature and high-pressure main steam in the first decoupled high-pressure bypass is cooled and reduced in pressure and enters the steam ejector as motive steam, which is used to extract the reheat cycle steam connected to the injection inlet of the steam ejector. After the motive steam is mixed with the reheat cycle steam, it enters the cold end inlet of the reheater again, thereby forming a heat recirculation.

[0039] 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.

[0040] It also includes several slave unit thermal systems.

[0041] In the slave unit thermal system, the slave unit consists of a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. In the slave unit thermal system, the superheater in the boiler generates main steam and is connected to the high-pressure cylinder of the steam turbine through the main steam pipeline. The high-temperature and high-pressure main steam from the main steam pipeline enters the high-pressure cylinder of the steam turbine. The exhaust steam of the high-pressure cylinder enters the cold end inlet of the boiler reheater; The outlet of the hot section of the boiler reheater is connected to the steam inlet pipe of the medium-pressure cylinder. Part of the reheated steam at the outlet of the hot section enters the medium-pressure cylinder of the steam turbine to perform work. The exhaust pipe of the medium-pressure cylinder is connected to the steam inlet pipe of the low-pressure cylinder. The exhaust steam of the medium-pressure cylinder enters the low-pressure cylinder of the steam turbine to perform work. A first decoupled high-pressure bypass is newly drawn out from the main steam pipeline. The high-temperature and high-pressure main steam in the first decoupled high-pressure bypass is provided for external steam output after being cooled and reduced in pressure. A second high-pressure bypass is also connected between the main steam pipeline and the cold end inlet of the boiler reheater. Through the second high-pressure bypass, part of the main steam is directly connected to the reheater without passing through the high-pressure cylinder.

[0042] The active unit and the slave unit are all connected to the decoupled steam supply mother pipe, the decoupled steam return mother pipe and the external steam supply mother pipe.

[0043] The hot section outlet of the active unit reheater is connected to the decoupled steam supply pipeline and connected to the decoupled steam supply mother pipe. The cold end inlet of the slave unit reheater is connected to the decoupled supplementary steam pipeline and connected to the decoupled steam supply mother pipe. The hot section outlet of the slave unit reheater is connected to the decoupled steam return pipeline and connected to the decoupled steam return mother pipe.

[0044] The decoupling steam return mother pipe is further connected to the steam return pipe of the intermediate pressure cylinder of the active unit, and connected to the steam inlet pipe of the intermediate pressure cylinder of the active unit. The decoupling steam return mother pipe is also connected to the small steam turbine of the active unit and / or the small steam turbine of the slave unit, and can also provide external steam supply. The steam from the hot section of the reheater of the active unit can be input into the decoupling steam supply mother pipe and input into the cold end of the reheater of the slave unit. The steam from the hot section of the reheater of the slave unit can be input into the decoupling steam return pipe and returned to the intermediate pressure cylinder of the active unit. Reasonable gas usage points are set on the decoupling steam return mother pipe for small steam turbine driving, external heat supply or steam supply.

[0045] The first decoupled high-pressure bypass of the active unit and the slave unit can provide external steam output, provide external steam and heat supply, and can be connected to the molten salt energy storage system. The first decoupled high-pressure bypass of the active unit and the slave unit can be connected to different steam supply outputs respectively, or connected to the external steam supply mother pipe, and the steam supply output is uniformly connected through the external steam supply mother pipe.

[0046] A pressure-holding valve is installed on the steam inlet pipe of the intermediate pressure cylinder in the active unit, located between the outlet of the hot section of the reheater of the intermediate pressure cylinder steam inlet pipe and the confluence point of the intermediate pressure cylinder return steam pipe. A pressure relief bypass is installed between the steam inlet pipe of the intermediate pressure cylinder and the steam inlet pipe of the low pressure cylinder in the slave unit, and a pressure relief valve is installed on the pressure relief bypass.

[0047] like Figure 2 As shown, the system in this application is configured as a one-way steam delivery mode.

[0048] As the active unit, the #1 unit is equipped with a heat recirculation module. The #1 unit is first decoupled, and then the surplus hot section steam is sent to the downstream unit. When the #1 unit is decoupled from the boiler, the steam in the system will be greatly abundant due to the addition of power steam and desuperheating water. It can be used as decoupling steam for the downstream unit.

[0049] Among them, the first decoupled high-pressure bypass (decoupled bypass) of the #1 unit is divided into two paths. One path is for external steam supply / heating / molten salt energy storage after temperature reduction and pressure reduction, and the other path is through the ejector, as the power steam to eject the heat-recirculated steam (the steam after the high-discharge steam is heated by the boiler reheater), and then enters the boiler reheater again after the ejector pressure is increased to make up for the shortage of reheated steam. Because the initial flow of superheated steam is large, a part of it is supplied to the outside after temperature reduction and pressure reduction, while the original high-discharge steam entering the reheater lacks flow. Through heat recirculation, the superheater and reheater are balanced, thereby realizing the decoupling of the #1 unit and boiler.

[0050] In order to achieve the decoupling of the #2 unit (first-order subordinate unit) and the boiler, the first decoupled high-pressure bypass (decoupled bypass) of the #2 unit also reduces the temperature and pressure to the outside and then supplies steam / heat / molten salt energy storage to the outside. The reheater of the #2 unit will also lack flow. At this time, the hot resteam from the #1 unit passes through the decoupled steam delivery pipeline, the decoupled steam delivery mother pipe, the decoupled steam supplement pipeline in turn, and merges with the original #2 high-pressure exhaust steam before entering the #2 boiler reheater, so that the reheater flow can operate safely. After being heated by the reheater and converted into reheated steam, a part of it enters the medium-pressure cylinder to generate electricity according to the steam volume required by the corresponding load heat balance diagram. The other part is provided with steam for small units and / or external steam supply through the decoupled steam return pipeline.

[0051] Since a cooling device is provided in the system, an incremental portion of hot resteam will be generated after cooling. A pressure relief bypass can be provided between the medium-pressure cylinder steam inlet pipe and the low-pressure cylinder steam inlet pipe of the #2 unit. A pressure relief valve is installed on the pressure relief bypass. The pressure relief valve diverts part of the steam, and the incremental portion of the hot resteam can be bypassed to the low-pressure cylinder. When the active unit is decoupled by a steam ejector, the steam delivered is abundant hot resteam and does not need to be returned to the active unit. At this time, the return steam mother pipe can be closed, the pressure holding valve is fully opened, and the system operates in a one-way steam transmission mode. Further, if the system needs to be simplified, the return steam mother pipe and the pressure holding valve can be cancelled.

[0052] Example of one-way steam delivery configuration mode.

[0053] Figure 3 As shown in the figure, the matching algorithm example of the 600MW hot section reentering the 1000MW cold section, when the #1 unit is >= 43% load factor, the #2 unit <= 34% load factor can be decoupled; Figure 4 As shown in the figure, an example of the matching algorithm for 1000MW and 600MW units is shown. When the load rate of #1 unit is greater than or equal to 27%, the load rate of #2 unit at 38% can be decoupled. Figure 5 As shown in the figure, an example of the matching algorithm between 600MW and 600MW units is shown. When the load factor of #1 unit is >= 43%, the load factor of #2 unit can be decoupled at 38%. In the one-way steam decoupling mode, take the arrow line as an example: the main steam inlet 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; then the cold section value of the 1000MW unit can be obtained as: PM-▲P=1.57MPa; at this time, the main steam inlet of the 1000MW unit is 934t, and the load rate is 34%.

[0054] When the 600MW unit hot section pressure Ph>1000MW unit cold section pressure PL, it can assist the 1000MW unit to decouple, and the operating conditions are flexible. As long as the operating point of the active unit is higher than that of the slave unit, it can be decoupled. The load rate of the dual units has a large degree of freedom.

[0055] In order to facilitate the two units to maintain independent operation, the operating point of the active unit should be at least 1~2 levels higher than the operating point of the slave unit during actual operation, leaving a certain space for the AGC load reduction of the active unit or the AGC load increase of the slave unit. When steam is transmitted in one direction, part of the steam can be used for external heat supply after decoupling, small unit steam supply, or enter the low-pressure cylinder of the #2 unit through the "pressure relief valve".

[0056] Furthermore, in the one-way steam delivery decoupling mode, multi-machine cascade decoupling can be formed in the whole plant: Figure 2 , Figure 6 As shown, the method of re-entering the cold section of the temporary unit by the hot section can be repeated among multiple subordinate units, that is, after the hot re-steam of the #1 unit is decoupled to the #2 unit, it leaves the #2 unit and enters the #3 unit for decoupling, thus realizing the cascade decoupling of multiple units in the whole plant; The decoupled steam delivery pipeline is composed of multiple steam pipes, in which the first-stage steam pipe connects the hot end outlet of the active unit reheater to the cold end inlet of the first-stage slave unit reheater. Similarly, the second-stage steam pipe connects the hot end outlet of the first-stage slave unit reheater to the cold end inlet of the second-stage slave unit reheater. The connection is sequentially carried out in sequence, and the method of using the temporary hot section to re-enter the cold section can be repeated between multiple slave units to achieve multi-unit cascade decoupling in the whole plant; A main pipe pressure isolation valve is installed between the multi-stage steam pipes. When the subordinate units of each stage are connected in sequence, the main pipe pressure isolation valve is in the closed state to ensure isolation between the steam pipes of each stage.

[0057] 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 of the reheater inlet of the second-stage slave unit, so as to realize the decoupling of the second-stage slave unit. As long as the hot section pressure of the previous stage unit is higher than the cold section pressure of the next stage, the process can be repeated to realize subsequent decoupling. The active unit can build a heat recirculation module with steam ejectors or turbo compressors to realize self-decoupling.

[0058] During the multi-unit cascade decoupling process, the Ph pressure of the reheating hot section continues to decrease, and the load rate between units must decrease. When the system works in the one-way steam delivery decoupling mode: 1) Only one-way steam delivery is required, and the surplus steam delivered by 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 load rate of the previous stage is greater than that of the next stage unit. It is conducive to the commissioning of AGC. 3) All units can be decoupled in cascade.

[0059] like Figure 7 As shown, the system in the present application is configured in a circulating steam delivery mode.

[0060] As the active unit, the #1 unit does not operate the heat recirculation module and sends the hot section steam to the #2 unit (slave unit); after the #2 unit boiler is decoupled, the steam is returned to the #1 unit. As the active unit, the #1 unit removes the heat recirculation module and the first decoupled high-pressure bypass (decoupled bypass) of the #1 unit reduces temperature and pressure before supplying steam / heat / molten salt energy storage.

[0061] In order to achieve the decoupling of the turbine and boiler of #2 unit, the first decoupled high-pressure bypass (decoupling bypass) of #2 unit also reduces the temperature and pressure to the outside and then supplies steam / heat / molten salt energy storage to the outside. The reheater of #2 unit will also lack flow. At this time, the hot resteam from #1 unit passes through the decoupling steam supply pipeline, and successively passes through the decoupling steam supply mother pipe and the decoupling steam supplementary pipeline, and then merges with the original #2 high-pressure exhaust steam and enters the #2 boiler reheater, so that the reheater flow can operate safely. After being heated by the reheater and converted into reheated steam, a part of it enters the medium-pressure cylinder to generate electricity according to the steam volume required by the corresponding load heat balance diagram. Since the intermediate pressure steam extraction ratio of the #1 unit has an upper limit, part of the return steam from the #2 unit must re-enter the intermediate pressure cylinder of the #1 unit. A part of the reheated steam is connected to the intermediate pressure cylinder return steam pipe of the #1 unit via the decoupled return steam pipe to ensure the safe steam intake of the intermediate pressure cylinder of the active unit. The steam is connected to the intermediate pressure cylinder steam intake pipe of the #1 unit to enter the intermediate pressure cylinder for power generation. The decoupled return steam mother pipe can also provide steam for small units and / or supply steam to the outside at the same time.

[0062] Due to the temperature reduction device in the system, the hot re-steam will produce an incremental part after temperature reduction. A pressure relief bypass can be set between the medium pressure cylinder steam inlet pipeline and the low pressure cylinder steam inlet pipeline of the #2 unit. A pressure relief valve is installed on the pressure relief bypass. Through the pressure relief valve, part of the steam is diverted, and the incremental part of the hot re-steam can be bypassed to the low pressure cylinder. The use of the pressure relief valve can also make the steam pressure at the decoupling return steam mother pipe appropriate. The pressure relief valve allows the excess decoupling steam to have an outlet and maintain the pressure gradient of the system.

[0063] When the system is in operation, it is necessary to consider the pressure drop factor. For example, the hot resteam after the decoupling of the #1 unit needs to maintain high pressure. A pressure-holding valve is set on the steam inlet pipe of the #1 unit's intermediate pressure cylinder. The pressure-holding valve works in a pressure-isolating state to keep the front-end pressure at high pressure and the rear-end pressure at low pressure. When the system is in the one-way steam delivery decoupling mode, there is no need to activate the pressure-holding valve, and the pressure-holding valve is fully open.

[0064] like Fig. 9 As shown, in order to make the system run normally, the pressure drop factor needs to be optimized simultaneously (by optimizing the pipeline, etc.). The pressure at each position of the system pipeline is P1 (#1 unit reheat outlet A→B→C), P2 (decoupled steam supply main pipe→D→E→F), P3 (#2 unit reheater→G→H), P4 (decoupled steam return main pipe), P5 (I→J→K→#1 unit intermediate pressure cylinder), among which P1>P2>P3>P4>P5.

[0065] When the system works in the decoupling mode of circulating steam delivery: Bidirectional steam delivery: Steam returns to the original active unit system. For decoupling of circulating steam delivery, a "pressure holding valve" must be installed on the hot section pipeline to generate a sufficient pressure difference before and after the valve, and the steam sent out (front end of the pressure holding valve) can be returned to the back end of the pressure holding valve through the decoupling application. The pressure difference between the upstream and downstream of the pressure holding valve allows the steam to overcome the resistance and complete the round trip process.

[0066] like Figure 8 As shown, the matching algorithm example of the circulating steam delivery mode unit: after the pressure is held at the working point where the arrow is located: the pressure before the valve is Ph=3.01MPa, the pipeline flow resistance is 0.05, and it drops to 2.96 at the cold section of the million-MW unit, and drops to 2.72MPa at the hot section of the reheater. The return pipeline resistance is 0.05, and there is still a pressure of 2.67MPa at the position after the 600MW valve, which is 0.16MPa higher than the 2.51 after the pressure holding valve. The steam can return smoothly and complete the closed-loop cycle. If the load rate of the 600,000-MW unit is 68%, it can only be paired with the 60% load rate of the million-MW unit; if the load of the 600,000-MW unit is increased to 43%, the million-MW unit can only be matched at 40%.

[0067] Usually due to cooling water spray and other reasons, the return steam volume will become larger, and a part of it must be properly digested so that the steam intake of the 600,000-ton medium-pressure cylinder does not increase too much, otherwise the pressure value behind the pressure-holding valve will rise accordingly, hindering the steam reflux.

[0068] When decoupling the circulating steam, the two units must be in the same working condition to decouple. The load rate of the two units rises and falls synchronously, and the deep adjustment is synchronous, which conforms to the dispatching habits of the power grid. Usually, when entering the medium and high load area, the boiler decoupling is not required. After exiting the decoupling mode, the units can operate freely.

[0069] Furthermore, the circulating steam decoupling mode can also form a synchronous decoupling of multiple machines in the whole plant: Figure 7 As shown, the decoupled steam supply pipeline is composed of multiple-stage steam pipes, wherein the first-stage steam pipe connects the hot-end outlet of the active unit reheater to the cold-end inlet of the first-stage slave unit reheater. Similarly, the second-stage steam pipe also connects the hot-end outlet of the active unit reheater to the cold-end inlet of the second-stage slave unit reheater. A mother pipe pressure-isolating valve is provided between the multiple-stage steam pipes. When the slave units of each stage are connected in parallel, the mother pipe pressure-isolating valve is in the open state to ensure the connection between the steam pipes of each stage. A part of the reheated steam of the second-stage slave unit is also connected to the decoupling steam return pipeline. After connecting multiple slave units in the whole plant in parallel, synchronous decoupling of multiple units in the whole plant can also be achieved; Finally, it should be noted that the above description is only an explanation of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail, those skilled in the art can still modify the technical solutions described above or replace some of the technical features with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in 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 decoupled steam supply main pipe; characterized in that: The active unit and the subordinate unit are composed of boiler, high-pressure cylinder, medium-pressure cylinder and low-pressure cylinder to form a thermal system; The hot end outlet of the boiler reheater of the active unit is connected to the decoupled steam supply mother pipe, and the decoupled steam supply mother pipe is connected to the cold end inlet of the reheater of the slave unit; The active unit uses the output reheated steam to assist the slave units in performing boiler-turbine decoupling operation.

2. According to claim 1, the master-slave multi-unit cooperative decoupling system is characterized in that: It includes one or more slave units, wherein the decoupled steam supply pipeline is the entire steam pipe or is composed of multi-stage steam pipes, and the multi-stage steam pipes are respectively connected to the cold end inlets of the reheaters of multiple slave units; a mother pipe pressure isolation valve is arranged between the multi-stage steam pipes.

3. The master-slave multi-unit cooperative decoupling system according to claim 2 is characterized in that: A heat recirculation module constructed by a steam ejector is connected between the cold end inlet and the hot end outlet of the boiler reheater of the active unit; One of the first-stage steam 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 pipe connects the hot-end outlet of the first-stage slave unit's reheater to the cold-end inlet of the second-stage slave unit's reheater. The connections are made in sequence, and the method of the temporary hot section reentering the cold section is repeated between multiple slave units to achieve multi-unit cascade decoupling in the entire plant. The main pipe pressure isolation valve is in the off state to ensure isolation between each stage of the steam pipes.

4. The master-slave multi-unit cooperative decoupling system according to claim 3 is characterized in that: The first decoupled high-pressure bypass of the active unit is connected to the motive steam inlet of the steam ejector. As motive steam, the hot end outlet of the main unit is connected to the injection inlet of the steam ejector through a reheat cycle bypass, and the exhaust steam outlet of the steam ejector is connected to the cold end inlet of the main unit boiler reheater.

5. The master-slave multi-unit cooperative decoupling system according to claim 2 is characterized in that: The first-stage steam pipe connects the hot-end outlet of the active unit reheater to the cold-end inlet of the first-stage slave unit reheater. Similarly, the second-stage steam pipe also connects the hot-end outlet of the active unit reheater to the cold-end inlet of the second-stage slave unit reheater. Multiple slave units are connected in parallel to realize synchronous decoupling of multiple units in the whole plant. The main pipe pressure isolation valve is in the open state to ensure the connectivity between the steam pipes of each stage.

6. The master-slave multi-unit cooperative decoupling system according to claim 1 or 3, characterized in that: Including decoupling the steam return main pipe; The hot end outlet of the boiler reheater of the slave unit is connected to the decoupling steam return mother pipe, and the decoupling steam return mother pipe is connected to the air inlet pipe of the intermediate pressure cylinder of the active unit; the decoupling steam return mother pipe is reasonably set with gas consumption points for driving small steam turbines, external heat supply or steam supply.

7. The master-slave multi-unit cooperative decoupling system according to claim 6, characterized in that: A pressure-holding valve is provided on the steam inlet pipe of the intermediate pressure cylinder of the active unit, which is located between the hot end outlet of the reheater of the active unit and the confluence point of the decoupling return steam mother pipe.

8. The master-slave multi-unit cooperative decoupling system according to claim 1, characterized in that: A pressure relief bypass is arranged between the medium-pressure cylinder steam inlet pipeline and the low-pressure cylinder steam inlet pipeline of the slave unit, and a pressure relief valve is installed on the pressure relief bypass.

9. The master-slave multi-unit cooperative decoupling system according to claim 7, characterized in that: The active unit outputs reheated steam in a one-way steam delivery mode; In the one-way steam supply mode, the heat recirculation module is put into operation, the pressure-holding valve is fully opened, and part of the steam at the hot end outlet of the reheater of the subordinate unit is used for small turbine steam and / or external heat supply.

10. The master-slave multi-unit cooperative decoupling system according to claim 8, characterized in that: The active unit outputs reheated steam in a circulating steam delivery mode; In the circulating steam supply mode, the hot recirculation module is cut off, and part of the steam at the hot end outlet of the reheater of the slave unit enters the intermediate pressure cylinder air inlet pipe of the active unit through the decoupling return steam mother pipe, and the pressure holding valve works in the pressure isolation state.

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