CN117146253B

CN117146253B - Coal-fired power generating unit and control method thereof

Info

Publication number: CN117146253B
Application number: CN202311118016.8A
Authority: CN
Inventors: 段丽平; 吴昕; 祁文玉; 刘闯; 秦天牧; 刘少杰; 裘闰超; 李殿成; 李文超
Original assignee: Beijing Huairou Laboratory
Current assignee: Beijing Huairou Laboratory
Priority date: 2023-08-31
Filing date: 2023-08-31
Publication date: 2024-08-02
Anticipated expiration: 2043-08-31
Also published as: CN117146253A

Abstract

The invention discloses a coal-fired power generation unit and a control method thereof, wherein the coal-fired power generation unit comprises a boiler, a steam turbine and a water heat storage system, the steam turbine comprises a cylinder group, a condenser, a deaerator, a first water outlet pipeline and a first steam outlet pipeline, the condenser is connected with the deaerator through the first water outlet pipeline, the cylinder group is connected with the deaerator through the first steam outlet pipeline, the water heat storage system comprises a heat accumulator, a second water outlet pipeline, a second steam outlet pipeline and a water supplementing pipeline, the heat accumulator is connected with the condenser through the second water outlet pipeline, the second steam outlet pipeline is also connected with the cylinder group, and steam entering the heat accumulator can be heated through steam of the second steam outlet pipeline, and the heat accumulator is connected with the deaerator through the water supplementing pipeline. The coal-fired power generator unit can rapidly reduce or increase load, so that the generated energy of the coal-fired power generator unit can be flexibly adjusted.

Description

Coal-fired power generating unit and control method thereof

Technical Field

The invention relates to the technical field of coal-fired power generation, in particular to a coal-fired power generation unit and a control method thereof.

Background

With the development of society and the progress of technology, new energy power generation technologies such as wind energy, light energy and the like are continuously popularized, and the new energy power generation technologies become a main supply main body of electric quantity of a power grid gradually. However, the generated energy of new energy power generation is greatly influenced by natural conditions, and the method has the characteristics of randomness, intermittence, uncontrollability and the like, and is not beneficial to the safe and stable operation of a power grid.

Therefore, the flexible collocation of the coal-fired power generation unit for stabilizing the power grid has become a current mainstream technical means. The concrete steps are as follows: when the new energy is sufficient for power generation, the load of the coal-fired power generator set can be properly reduced, so that the consumption of non-renewable resources such as coal and the like and the environmental protection problem caused by the consumption can be reduced; when the new energy is insufficient in power generation, the load of the coal-fired power generator unit can be properly increased so as to supplement the new energy in power generation. This requires a high degree of adjustability for the coal-fired power generation unit.

The coal-fired power generating unit comprises a coal-fired boiler and a turbine unit, the turbine unit can improve the load change rate through blade modification and the like, and the coal-fired boiler is difficult to adapt to the large load change rate due to large thermal inertia, so that the overall adjustability of the coal-fired power generating unit is affected.

Therefore, how to provide a solution to overcome or alleviate the above-mentioned drawbacks is still a technical problem to be solved by those skilled in the art.

Disclosure of Invention

The invention aims to provide a coal-fired power generation unit and a control method thereof, wherein the coal-fired power generation unit can rapidly carry out load reduction or load lifting, so that the generated energy of the coal-fired power generation unit can be flexibly adjusted.

In order to solve the technical problems, the invention provides a coal-fired power generating unit, which comprises a boiler, a steam turbine and a water heat storage system, wherein the steam turbine comprises a cylinder group, a condenser, a deaerator, a first water outlet pipeline and a first steam outlet pipeline, the condenser is connected with the deaerator through the first water outlet pipeline, the cylinder group is connected with the deaerator through the first steam outlet pipeline, the water heat storage system comprises a heat accumulator, a second water outlet pipeline, a second steam outlet pipeline and a water supplementing pipeline, the heat accumulator is connected with the condenser through the second water outlet pipeline, the second steam outlet pipeline is also connected with the cylinder group, and steam entering the heat accumulator can be heated through the water supplementing pipeline and the deaerator through the second steam outlet pipeline.

By adopting the scheme, when the load of the coal-fired power generation unit needs to be reduced, the steam in the cylinder group can be rapidly led out through the second steam outlet pipeline, so that redundant steam generated by the boiler can be timely pumped away from the steam turbine, and the synchronous load reduction of the boiler and the steam turbine is realized; the steam led out by the second steam outlet pipeline can heat the water entering the heat accumulator so as to store heat, and the waste of energy can be reduced. When the load of the coal-fired power generator unit needs to be increased, the water supplementing pipeline can be opened, the heat accumulator can provide hot water for the deaerator, so that the water level, the water temperature and the like in the deaerator can be increased, the steam output of the first steam output pipeline can be reduced, and steam generated by the boiler can be used for acting of the steam turbine more so as to adapt to the load increase of the steam turbine, and the rapid load increase of the coal-fired power generator unit can be realized.

That is, the embodiment of the invention can effectively relieve the problem of large thermal inertia of the boiler by arranging the water heat storage system, and can match the load change rate of the boiler and the steam turbine, so that the whole coal-fired power generator set can rapidly carry out load reduction or load increase, and the generated energy of the coal-fired power generator set can be flexibly adjusted.

Optionally, the second water outlet pipeline is configured with a heat exchange module, the second steam outlet pipeline includes a first heat exchange branch, and the first heat exchange branch is connected with the heat exchange module.

Optionally, the first heat exchange branch includes a main flow path and a steam heating bypass, which are arranged in parallel, the main flow path and the steam heating bypass are all connected with the heat exchange module, and the steam heating bypass can be opened at least when the main flow path is closed.

Optionally, the main flow path is provided with a first heat exchange control valve, the flow area of the main flow path is larger than that of the steam heating bypass, and the steam heating bypass is in a normally open state.

Optionally, the first heat exchange branch is further configured with a desuperheater.

Optionally, the heat exchange module comprises a cooler and a heat exchanger, and the cooler is located upstream of the heat exchanger in the extending direction of the second water outlet pipeline.

Optionally, the second steam outlet pipeline further comprises a second heat exchange branch, the second heat exchange branch is connected with the heat accumulator, and the second heat exchange branch is provided with a second heat exchange control valve.

Optionally, the second water outlet line is further provided with a buffer, which is located upstream of the heat accumulator, and the buffer is arranged in a sealing manner.

Optionally, an air cavity and a liquid cavity are formed in the buffer; the buffer is also provided with an inflation tube which is used for inflating appointed gas into the air cavity; or the air cavity is also communicated with the condenser.

Optionally, the second water outlet pipeline is further connected with a first self-circulation pipeline, the first self-circulation pipeline is connected with the buffer, the second water outlet pipeline is further configured with a booster pump and a water level control valve, the booster pump is located at the downstream of the buffer and located at the upstream of a connection point of the first self-circulation pipeline and the second water outlet pipeline, the water level control valve is located at the upstream of the buffer, and the first self-circulation pipeline is configured with the first self-circulation control valve.

Optionally, the water outlet bypass is further provided with an upstream connecting end and a downstream connecting end of the water outlet bypass are both connected with the second water outlet pipeline, the upstream connecting end is located at the upstream of the water level control valve, the downstream connecting end is located at the downstream of a connecting point of the first self-circulation pipeline and the second water outlet pipeline, a pipe section of the second water outlet pipeline between the upstream connecting end and the downstream connecting end is a main pipe section, and the water outlet bypass can be opened at least when the main pipe section is closed.

Optionally, the flow area of the water outlet bypass is smaller than that of the main pipe section, and the water outlet bypass is in a normally open state.

Optionally, the water supplementing pipeline comprises a first communication pipeline, and the first communication pipeline is provided with a water supplementing pump.

Optionally, the first communication pipeline is further connected with a second self-circulation pipeline, the second self-circulation pipeline is connected with the heat accumulator, and the second self-circulation pipeline is provided with a second self-circulation control valve; the first communication line is further configured with a first communication control valve downstream of a junction point of the second self-circulation line and the first communication line.

Optionally, the water supplementing pipeline further comprises a second communication pipeline, the heat accumulator is connected with the deaerator through the second communication pipeline, and the second communication pipeline is provided with a second communication control valve; and a steam balance pipeline is also connected between the heat accumulator and the deaerator, and is provided with a steam balance control valve.

Optionally, the system further comprises a steam supplementing system, the steam supplementing system comprises a heating module, a water feeding pipeline and a steam supplementing pipeline, the water feeding pipeline and the steam supplementing pipeline are connected with the heating module, the water feeding pipeline is located at the upstream of the heating module, the steam supplementing pipeline is located at the downstream of the heating module, and the steam supplementing pipeline is connected with the cylinder group.

Optionally, the water supply pipeline is connected with the deaerator, and the water supply pipeline is provided with a water supply control valve.

Optionally, the heating module comprises an electrical heating module.

Optionally, the heating module further comprises a molten salt heating module, wherein the molten salt heating module comprises a molten salt boiler, a hot melt salt tank and a cold melt salt tank, and the hot melt salt tank and the cold melt salt tank are connected with the molten salt boiler.

Optionally, the molten salt boiler comprises a molten salt preheater, a molten salt evaporator and a molten salt superheater which are sequentially arranged; the water side outlet of the molten salt preheater is connected with the water side inlet of the molten salt evaporator through a connecting pipeline, the connecting pipeline is further connected with a water drain pipeline, the connecting pipeline is further provided with an evaporator inlet valve, the evaporator inlet valve is positioned at the downstream of the connecting point of the water drain pipeline and the connecting pipeline, and the water drain pipeline is provided with a water drain valve.

Optionally, the heating module further comprises a preheater, wherein the preheater is connected with a backflow preheating steam path, and the backflow preheating steam path is communicated with the steam supplementing pipeline.

Optionally, the preheater is further connected with a standby preheating steam path, and the standby preheating steam path is provided with a standby preheating control valve.

Optionally, the steam supplementing pipeline is provided with a steam supplementing control valve.

The invention also provides a control method of the coal-fired power generation unit, which is suitable for the coal-fired power generation unit, and comprises a load reduction control step and a load lifting control step; the load reduction control step comprises the following steps: controlling the second steam outlet pipeline to heat water entering the heat accumulator; the load-up control step comprises a first sub-step comprising: and controlling the water supplementing pipeline to be opened so as to introduce the hot water in the heat accumulator into the deaerator, controlling the first steam outlet pipeline to reduce the flow, and controlling the second steam outlet pipeline to reduce the flow.

Optionally, the second water outlet pipeline is configured with a heat exchange module, the second steam outlet pipeline comprises a first heat exchange branch and a second heat exchange branch, the first heat exchange branch comprises a main flow path and a steam heating bypass which are arranged in parallel, the main flow path and the steam heating bypass are both connected with the heat exchange module, and the second heat exchange branch is connected with the heat accumulator; the second water outlet pipeline is further provided with a buffer, the buffer is positioned at the upstream of the heat accumulator, the coal-fired power generator unit further comprises a water outlet bypass, an upstream connecting end and a downstream connecting end of the water outlet bypass are both connected with the second water outlet pipeline, and a pipe section of the second water outlet pipeline positioned between the upstream connecting end and the downstream connecting end is a main pipe section; the water supplementing pipeline comprises a first communication pipeline, the first communication pipeline is connected with the heat accumulator and the deaerator, the first communication pipeline is also connected with a second self-circulation pipeline, the second self-circulation pipeline is connected with the heat accumulator, the first communication pipeline is provided with a first communication control valve, and the first communication control valve is positioned at the downstream of the connection point of the second self-circulation pipeline and the first communication pipeline; the control method further comprises a first heating pipe control step, wherein the first heating pipe control step comprises the following steps: controlling the second steam outlet pipeline to operate in a low-flow steam outlet mode, controlling the main flow path to be closed, and controlling the second heat exchange branch to be opened; and controlling the second water outlet pipeline to run in a low-flow water outlet mode, controlling the main through pipe section to be closed, controlling the first communication control valve to be closed, and controlling the second self-circulation pipeline to be opened.

Optionally, the coal-fired power generation unit further comprises a steam supplementing system, the steam supplementing system comprises a heating module, a water feeding pipeline and a steam supplementing pipeline, the water feeding pipeline and the steam supplementing pipeline are connected with the heating module, the water feeding pipeline is positioned at the upstream of the heating module, the steam supplementing pipeline is positioned at the downstream of the heating module, and the steam supplementing pipeline is connected with the cylinder group; the load-up control step further comprises a second sub-step comprising: and controlling the opening of the steam supplementing pipeline to supplement steam into the cylinder group.

Optionally, the heating module further comprises a preheater, wherein the preheater is connected with a backflow preheating steam path, and the backflow preheating steam path is communicated with the steam supplementing pipeline; the control method further comprises a second heating pipe control step, wherein the second heating pipe control step comprises the following steps: the water supply pipeline is controlled to run in a low-flow water supply mode, the heating module is controlled to run in a low-power mode, the communication between the steam supplementing pipeline and the cylinder group is controlled to be cut off, and the reflux preheating steam path is controlled to be opened.

Optionally, the heating module further comprises a molten salt heating module, wherein the molten salt heating module comprises a molten salt boiler, a hot melt salt tank and a cold melt salt tank, and the hot melt salt tank and the cold melt salt tank are both connected with the molten salt boiler; the molten salt boiler comprises a molten salt preheater, a molten salt evaporator and a molten salt superheater which are sequentially arranged, wherein a water side outlet of the molten salt preheater is connected with a water side inlet of the molten salt evaporator through a connecting pipeline, the connecting pipeline is further connected with a water drain pipeline, and the connecting pipeline is further provided with an evaporator inlet valve; the preheater is also connected with a standby preheating steam path, and the standby preheating steam path is provided with a standby preheating control valve; the steam supplementing pipeline is provided with a steam supplementing control valve;

the control method further comprises a steam supplementing system throwing step, and the steam supplementing system throwing step comprises the following steps:

Controlling the steam supplementing control valve to be closed;

Controlling the water supply pipeline to operate in a low-flow water supply mode, and controlling the water discharge pipeline to be opened;

the standby preheating steam path is controlled to be opened, and the standby preheating steam path is controlled to be communicated with the reflux preheating steam path;

Controlling to open the evaporator inlet valve and controlling the molten salt evaporator to be introduced with water of a set water level;

judging whether the temperatures of the molten salt superheater and the molten salt evaporator reach a set temperature, if so, executing the following steps;

controlling the hot melt salt tank to introduce hot molten salt into the molten salt boiler;

continuously feeding water to the molten salt evaporator according to the water level of the molten salt evaporator, gradually closing down the water discharge pipeline, and adjusting the water feeding amount of the water feeding pipeline until the water discharge pipeline is completely closed;

And controlling to gradually turn off the standby preheating steam path.

Optionally, the step of controlling the load up and the step of controlling the load down each include: determining N load change intervals according to the difference value between the target load and the current load; controlling the steam turbine to carry out load adjustment in each load change interval according to a first set load change rate, controlling the boiler to carry out load adjustment in each load change interval according to a second set load change rate, wherein the first set load change rate is larger than the second set load change rate, and controlling the steam turbine to suspend load change after load change is completed in the ith load change interval until the boiler also completes load change in the ith load change interval; wherein, i and N are positive integers, N is more than or equal to 2, i is more than or equal to 1 and is less than or equal to N.

Drawings

FIG. 1 is a schematic diagram of one implementation of a coal-fired power unit according to the present invention;

FIG. 2 is a connection block diagram of the boiler, steam turbine and thermal storage system of FIG. 1;

FIG. 3 is a connection block diagram of the thermal storage system and deaerator of FIG. 2;

FIG. 4 is a connection block diagram of the steam turbine and the steam compensating system of FIG. 1;

FIG. 5 is a connection structure diagram of the molten salt boiler, the hot melt salt tank and the cold melt salt tank of FIG. 4;

FIG. 6 is a schematic flow chart of the putting step of the steam supplementing system;

FIG. 7 is a schematic diagram of the load change of the boiler and turbine during the load up and down of the unit.

The reference numerals are explained as follows:

A 100 boiler;

200 steam turbines, 210 cylinder groups, 211 high-pressure cylinders, 212 medium-pressure cylinders, 213 low-pressure cylinders, 220 condensers, 230 deaerators, 231 pre-pumps, 232 water supply pumps, 240 first water outlet pipelines, 241 water outlet control valves, 242 first low-pressure heaters, 243 second low-pressure heaters, 244 third low-pressure heaters, 244 fourth low-pressure heaters, 250 first steam outlet pipelines, 251 first steam outlet control valves, 260 condenser pumps, 270 fine treatment devices and 280 shaft seal heaters;

The heat storage system comprises a water heat storage system, a 310 heat accumulator, a 320 second water outlet pipeline, a 320a main through pipe section, a 321 heat exchange module, a 321a cooling device, a 321b heat exchanger, a 322 buffer, a 322a gas charging pipe, a 323 first self-circulation pipeline, a 323a first self-circulation control valve, a 324 booster pump, a 325 water level control valve, a 326 water outlet bypass, a 326a upstream connecting end, a 326b downstream connecting end, a 330 second steam outlet pipeline, a 331 first heat exchange branch, a 331a main flow path, a 331a-1 desuperheater, a 331a-2 first heat exchange control valve, a 331b steam heating bypass, a 332 second heat exchange branch, a 332a second heat exchange control valve, a 340 water supplementing pipeline, a 341b second self-circulation pipeline, a 341b-1 second self-circulation control valve, a 341c first communication control valve, a 342 second communication pipeline, a 342a second communication control valve, a 350 steam balancing pipeline and a 351 steam balancing control valve;

400 steam supplementing system, 410 heating module, 411 electric heating module, 412 fused salt boiler, 412a fused salt preheater, 412b fused salt evaporator, 412c fused salt superheater, 412d connecting pipeline, 412d-1 evaporator inlet valve, 412e water draining pipeline, 412e-1 water drain valve, 413 hot melt salt tank, 414 cold melt salt tank, 415 steam preheater, 415a back flow preheating steam path, 415b standby preheating steam path, 415b-1 standby preheating control valve, 416 standby steam source, 417 fused salt pump, 420 water feeding pipeline, 421 water feeding control valve, 430 steam supplementing pipeline, 431 steam supplementing control valve.

Detailed Description

In order to make the technical solution of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

In embodiments of the present invention, the terms "first," "second," "third," "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", "a third" and a fourth "may explicitly or implicitly include one or more such feature.

In describing embodiments of the present invention, it should be noted that, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "connected" should be construed broadly, and for example, "connected" may be either detachably connected or non-detachably connected; may be directly connected or indirectly connected through an intermediate medium.

In the description of embodiments of the present invention, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

In the embodiment of the present invention, "and/or" is merely an association relationship describing an association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

Example 1

Referring to fig. 1 to 4, fig. 1 is a schematic structural diagram of an implementation manner of a coal-fired power generating unit provided by the present invention, fig. 2 is a connection structure diagram of a boiler, a steam turbine and a heat storage system in fig. 1, fig. 3 is a connection structure diagram of a heat storage system and a deaerator in fig. 2, fig. 4 is a connection structure diagram of a steam turbine and a steam supplementing system in fig. 1, and fig. 5 is a connection structure diagram of a molten salt boiler, a hot-melt salt tank and a cold-melt salt tank in fig. 4.

As shown in fig. 1 and 2, the present invention provides a coal-fired power generation unit including a boiler 100, a steam turbine 200, and a water heat storage system 300.

The steam turbine 200 includes a cylinder bank 210, a condenser 220, and a deaerator 230.

The cylinder block 210 is a core component of the steam turbine 200 for isolating steam from the atmosphere, forming an enclosed space where the steam performs energy conversion. The cylinder bank 210 includes a plurality of cylinders. In the implementation of fig. 1, cylinder group 210 may include a high pressure cylinder 211, a medium pressure cylinder 212, and two low pressure cylinders 213. In other implementations, the cylinder bank 210 may take other configurations as well; for example, the cylinder group 210 may include a high pressure cylinder 211, a medium pressure cylinder 212, and one low pressure cylinder 213, or the cylinder group 210 may include a high and medium pressure cylinder, one low pressure cylinder, and the like.

The condenser 220 may be located at the lower side of the low pressure cylinder 213, and the two may be commonly provided with a housing to enhance the integration level of the apparatus. The steam may be discharged into the condenser 220 after completion of working in the low pressure cylinder 213, and may be condensed in the condenser 220 to form condensed water.

In connection with fig. 2, downstream of the condenser 220 there is arranged in sequence a condenser pump 260, a finishing device 270 and a shaft seal heater 280. The condensate pump 260 is used to power the discharge of condensate within the condenser 220. The finishing device 270 is used for finishing the condensed water to remove metal corrosion products, trace dissolved salts, leaked suspended matters and the like in the condensed water, so that the quality of the condensed water can be improved and ensured. The shaft seal heater 280 can recover the shaft seal leakage steam and heat the condensed water by utilizing the heat of the shaft seal leakage steam, thereby reducing energy loss and being beneficial to improving the thermal efficiency of the unit.

The shaft seal heater 280 may be provided at its outlet with a first water outlet line 240, the first water outlet line 240 being adapted to direct condensate into the deaerator 230 for thermal deaeration. The first water outlet line 240 may be provided with an outlet control valve 241 for on-off adjustment and flow adjustment of the first water outlet line 240.

The first low pressure heater 242, the second low pressure heater 243, the third low pressure heater 244 and the fourth low pressure heater 245 are sequentially provided on the first water outlet pipe 240 to gradually raise the temperature of the condensed water, so that the temperature rise pressure of the deaerator 230 can be reduced. The heat sources of the first low pressure heater 242, the second low pressure heater 243, the third low pressure heater 244, and the fourth low pressure heater 245 may all be from the cylinder bank 210. Specifically, the steam turbine 200 may further include a first steam outlet pipe 250, where the first steam outlet pipe 250 may be connected to any one of the cylinders in the cylinder group 210, for example, may be connected to the middle pressure cylinder 212, so as to draw steam in the cylinder group 210 and guide the steam to the first low pressure heater 242, the second low pressure heater 243, the third low pressure heater 244, and the fourth low pressure heater 245 for heating the condensed water; the first steam outlet pipe 250 is provided with a first steam outlet control valve 251 for on-off adjustment and flow adjustment of the first steam outlet pipe 250. In addition, the first steam outlet pipe 250 may be connected to the deaerator 230 to directly guide steam into the deaerator 230, thereby heating up and deaerating the condensed water.

The water outlet of the deaerator 230 is sequentially provided with a pre-pump 231 and a water feed pump 232 for delivering the condensed water to the boiler 100 for recycling. The pre-pump 231 is located at the upstream of the water feeding pump 232 and is used for lifting the pressure at the inlet of the water feeding pump 232, so that cavitation of the water feeding pump 232 can be avoided to a large extent, and safe and stable operation of the water feeding pump 232 is guaranteed.

With continued reference to fig. 2, the water thermal storage system 300 includes a thermal storage 310, a second water outlet line 320, a second steam outlet line 330, and a water replenishment line 340.

The heat accumulator 310 is connected to the condenser 220 through a second water outlet pipeline 320, specifically, may be connected to an outlet of the shaft seal heater 280, so as to form a parallel pipeline with the first water outlet pipeline 240. Thus, the condensed water discharged from the condenser 220 may be divided into two paths, one path being supplied to the deaerator 230 and the other path being introduced into the heat accumulator 310.

A second outlet line 330 is also connected to the cylinder block 210, for example, may be connected to the intermediate pressure cylinder 212 for directing steam from the cylinder block 210. The second steam outlet pipeline 330 and the first steam outlet pipeline 250 may be arranged in parallel, so that the steam led out by the cylinder group 210 may be divided into two paths, one path is used for heating the water entering the deaerator 230, and the other path is used for heating the water entering the heat accumulator 310 so as to raise the temperature of the condensed water in the heat accumulator 310. The heat accumulator 310 is connected to the deaerator 230 through a water supplementing line 340, and can supply hot water to the deaerator 230.

In practical application, when the load of the coal-fired power generation unit is to be reduced, the steam in the cylinder group 210 can be rapidly led out through the second steam outlet pipeline 330, so that the redundant steam generated by the boiler 100 can be timely pumped away from the steam turbine 200, and the synchronous load reduction of the boiler 100 and the steam turbine 200 is realized; the steam led out by the second steam outlet pipeline 330 can heat the water entering the heat accumulator 310 to store heat, so that the energy waste can be reduced. When the load of the coal-fired power generation unit is to be increased, the water supplementing pipeline 340 can be opened, the heat accumulator 310 can provide hot water for the deaerator 230, so that the water level, the water temperature and the like in the deaerator 230 can be increased, the steam output of the first steam output pipeline 250 can be reduced, and steam generated by the boiler 100 can be used for acting of the steam turbine 200 more so as to adapt to the load increase of the steam turbine 200, and the rapid load increase of the coal-fired power generation unit can be realized.

That is, the embodiment of the invention can effectively alleviate the problem of large thermal inertia of the boiler 100 by arranging the water heat storage system 300, and can match the load change rates of the boiler 100 and the steam turbine 200, so that the whole coal-fired power generator set can rapidly carry out load reduction or load increase, and the generated energy of the coal-fired power generator set can be flexibly adjusted.

In addition, in the embodiment of the present invention, the water in the heat accumulator 310 is the circulating condensation water from the condenser 220, so that no external water source is required to be introduced, the structural form of the water heat accumulation system 300 can be relatively simple, the initial investment of equipment can be relatively small, and meanwhile, the water quality and the water vapor balance of the unit can be ensured.

The heat accumulator 310 may be a general water storage tank, and in this case, the heat accumulator 310 only has functions of water storage and heat storage. Alternatively, the heat accumulator 310 may have a similar structure to the deaerator 230, so that the heat accumulator 310 may have a deaeration function. The specific structure of the deaerator 230 may be referred to in the art, and is not limited herein.

With continued reference to fig. 2, the second water outlet pipeline 320 may be configured with a heat exchange module 321, the second steam outlet pipeline 330 may include a first heat exchange branch 331, and the first heat exchange branch 331 may be connected to the heat exchange module 321, so as to indirectly heat water in the second water outlet pipeline 320 through the heat exchange module 321. The steam passing through the heat exchange module 321 may be discharged into the condenser 220 of the steam turbine 200 to be circulated.

The heat exchange module 321 may include a cooler 321a and a heat exchanger 321b, and the cooler 321a may be located upstream of the heat exchanger 321b in the extending direction of the second water outlet line 320. The cryocooler 321a is capable of cooling and reheating the condensed water, and is mainly used for reducing heat loss caused by low-pressure steam extraction by drainage and displacement. The heat exchanger 321b may be a plate heat exchanger, a tube heat exchanger, or the like, and is not limited herein. It should be appreciated that in some implementations, the chiller 321a and the heat exchanger 321b may also be integrally provided.

The cooling device 321a and the heat exchanger 321b are respectively arranged, so that the gradual increase of the temperature of the condensed water can be realized, and the temperature rise pressure of the heat exchanger 321b can be reduced.

The second steam outlet pipeline 330 may further include a second heat exchange branch 332, where the second heat exchange branch 332 is configured with a second heat exchange control valve 332a, and the second heat exchange control valve 332a is used to control on-off of the second heat exchange branch 332.

A second heat exchange branch 332 may be connected to the heat accumulator 310 for directly introducing steam into the heat accumulator 310 to directly heat the water in the heat accumulator 310. In this way, the heat accumulator 310 may actually be equivalent to a heat exchange component, and in cooperation with the foregoing cooling device 321a and heat exchanger 321b, the embodiment of the present invention is equivalent to adopting a multi-stage heat exchange mode, so as to gradually raise the temperature of the condensate water, and further reduce the temperature rise pressure caused by the overhigh single temperature rise on the corresponding heat exchange component.

It should be understood that, in practical applications, the first heat exchange branch 331 and the second heat exchange branch 332 may be alternatively arranged.

In some implementations, as shown in fig. 2 and 3, the first heat exchange branch 331 may include a main flow path 331a and a steam heating bypass 331b disposed in parallel, and both the main flow path 331a and the steam heating bypass 331b may be connected to the heat exchange module 321.

When the load of the coal-fired power generation unit needs to be reduced, at least the main flow path 331a of the main flow path 331a and the steam heating bypass 331b can be opened so as to introduce the steam of the first heat exchange branch 331 into the heat exchange module 321. When the load of the coal-fired power generation unit does not need to be reduced, the main flow path 331a can be closed, the steam heating bypass 331b can be opened, the second steam outlet pipeline 330 can operate in a low-flow steam outlet mode and can flow into the heat exchange module 321 through the heating pipe bypass 331b so as to perform heating pipe operation on the heat exchange module 321 and the heat accumulator 310, and therefore, the heat exchange module 321 and the heat accumulator 310 can be in a standby state, and the water heat storage system 300 in the embodiment of the invention can be started quickly when the load of the unit needs to be reduced, so that the load reducing speed of the unit is improved.

Specifically, the main flow path 331a may be configured with the first heat exchange control valve 331a-2, the flow area of the main flow path 331a may be larger than that of the warming bypass 331b, and the warming bypass 331b may be in a normally open state, i.e., the warming bypass 331b may not be provided with a control valve, so that the structural form of the warming bypass 331b may be relatively simple, and control may also be relatively simple. When load reduction is required, the first heat exchange control valve 331a-2 may be opened, and steam may flow into the heat exchange module 321 through the main flow path 331a and the warming bypass 331 b. During the heating operation, the first heat exchange control valve 331a-2 may be closed, and steam may flow into the heat exchange module 321 only through the steam heating bypass 331 b; the flow area of the steam heating bypass 331b is smaller than that of the main flow path 331a, so that the steam heating bypass 331b can be better suitable for the passage of small-flow steam, the cost can be reduced, and the installation occupied space can be reduced.

In particular practice, a control valve may also be provided for the warm-air bypass 331b to control the on or off of the warm-air bypass 331 b. Thus, when the load is reduced, the control valve of the steam heating bypass 331b can be selectively opened or closed according to the requirement; the control valve of the warming bypass 331b may be opened at the time of the heating pipe operation.

It should be understood that, in some other implementations of the embodiment of the present invention, the first heat exchange branch 331 may also include only the main flow path 331a, where the flow rate of steam may be controlled by adjusting the opening of the first heat exchange control valve 331a-2, and/or adjusting the operation mode of the second steam outlet pipe 330, so as to perform a small flow heating operation on the heat exchange unit 321 and the heat accumulator 310.

In addition, for the implementation including the second heat exchanging branch 332, the second heat exchanging control valve 332a may still be opened to directly introduce steam into the heat accumulator 310 during the heating operation, so that it is advantageous to maintain the water temperature and the internal state of the heat accumulator 310.

The first heat exchange branch 331 may further be configured with a desuperheater 331a-1, where the desuperheater 331a-1 is used for cooling steam to reduce an operation temperature difference of the heat exchange module 321, so as to improve an operation condition of the heat exchange module 321, and be beneficial to ensuring a service life of the heat exchange module 321. Referring to fig. 3, for an implementation including a main flow path 331a and a heater bypass 331b, the desuperheater 331a-1 may be specifically disposed in the main flow path 331a.

In some implementations, the second water outlet line 320 may also be configured with a buffer 322, and the buffer 322 may be located upstream of the regenerator 310. The condensed water from the condenser 220 can first enter the buffer 322 to be buffered, and then enter the heat accumulator 310, so that the control of relevant parameters such as the liquid level height and the water temperature in the heat accumulator 310 is more facilitated, and the stability of the water heat storage system 300 can be improved.

When the load is increased, the hot water in the heat accumulator 310 is introduced into the deaerator 230, so that the water level in the deaerator 230 is increased, and thus, the flow rate of the first water outlet line 240 needs to be reduced. Under such a working condition, the flow rate of the second water outlet pipeline 320 can be appropriately increased, and the increased water amount of the second water outlet pipeline 320 is stored through the buffer 322, so that the water level in the condenser 220 can be prevented from being too high.

In addition, the water temperature in the buffer 322 is relatively low compared to the heat accumulator 310, and thus the heat accumulator 310 corresponds to a hot water tank and the buffer 322 corresponds to a cold water tank. The buffer 322 and the heat accumulator 310 are respectively arranged, so that cold water and hot water can be stored respectively, and the mixing of water with different temperatures can be avoided.

The buffer 310 may be hermetically provided to reduce the possibility of contact between the water entering the inside thereof and the outside, thereby ensuring water quality.

Specifically, an air cavity and a liquid cavity may be formed in the buffer 322, and the buffer 322 may be further configured with an air tube 322a, where the air tube 322a is used to inflate a specified gas into the air cavity, so as to seal the buffer 322 in an air manner, and ensure the pressure inside the buffer 322, so that the buffer 322 may operate under a set pressure (e.g., micro positive pressure). The type of the specified gas is not limited herein, and in specific practice, a person skilled in the art may select the specified gas according to actual needs, so long as the specified gas can meet the requirements of use; for example, the specified gas may be an inert gas such as nitrogen or helium.

In addition, a scheme of communicating the air cavity with the condenser 220 may be adopted, and it should be appreciated that the condenser 220 is in a state of being close to vacuum, and communicating the air cavity with the condenser 220 may enable the air cavity to be close to vacuum, which may also achieve sealing.

The second water outlet pipe 320 may be further connected with a first self-circulation pipe 323, and the first self-circulation pipe 323 may be connected with the buffer 322. The second water outlet line 320 may also be configured with a booster pump 324 and a water level control valve 325. The booster pump 324 may be located upstream of the junction of the first self-circulation line 323 and the second water outlet line 320 and downstream of the buffer 322. The water level control valve 325 may be located upstream of the buffer 322. The first self-circulation line 323 may be configured with a first self-circulation control valve 323a.

The water level control valve 325 may be associated with the water level within the buffer 322, and when the water level within the buffer 322 is low, the opening of the water level control valve 325 may be adjusted higher to deliver more water into the buffer 322. The booster pump 324 can cooperate with the first self-circulation pipeline 323, so as to realize self-circulation of water in the buffer 322, and the operation mode can be specifically started when no load reduction is needed, and the first self-circulation pipeline 323 can avoid frequent opening and closing of the booster pump 324, so that the working stability of the booster pump 324 can be ensured. Meanwhile, the booster pump 324 can also boost the pressure of the water flowing to the heat exchange module 321.

In some implementations, the water thermal storage system 300 may further include a water outlet bypass 326, and the water outlet bypass 326 may include an upstream connection end 326a and a downstream connection end 326b, and both the upstream connection end 326a and the downstream connection end 326b may be connected to the second water outlet line 320. Specifically, the upstream connection end 326a may be located upstream of the water level control valve 325, and the downstream connection end 326b may be located downstream of the connection point of the first self-circulation line 323 and the second water outlet line 320. For ease of description, the section of the second water outlet line 320 between the upstream and downstream connection ends 326a, 326b may be referred to as the main pipe section 320a, and the water outlet bypass 326 may be opened at least when the main pipe section 320a is closed.

When the load of the coal-fired power generation unit needs to be reduced, condensed water in the second water outlet pipeline 320 can flow to the heat exchange module 321 and the heat accumulator 310 through the main through pipe section 320 a; of course, it is also possible to flow to the regenerator 310 via the outlet bypass 326 at the same time, and this is particularly relevant to the communication state of the outlet bypass 326. When the load of the coal-fired power generation unit does not need to be reduced, the main through pipe section 320a can be self-circulated through the first self-circulation pipeline 323, water is not supplied to the heat exchange module 321 and the heat accumulator 310 any more, the second water outlet pipeline 320 can be operated in a low-flow water outlet mode and can flow to the heat exchange module 321 and the heat accumulator 310 through the water outlet bypass 326 so as to perform heating pipe operation on the heat exchange module 321 and the heat accumulator 310, and therefore, the heat exchange module 321 and the heat accumulator 310 can be in a standby state, and the water heat accumulation system 300 in the embodiment of the invention can be started quickly when the load of the unit needs to be reduced, so that the load reducing speed of the unit is improved.

The water outlet bypass 326 has a smaller flow area than the second water outlet line 320, thus being better adapted to the passage of small water flows, reducing costs and installation space.

In particular practice, a control valve may also be provided for the outlet bypass 326 to control the connection or disconnection of the outlet bypass 326. Thus, during load reduction, the control valve of the water outlet bypass 326 can be selectively opened or closed as required; during a heating operation, the control valve of the outlet bypass 326 may be opened.

In some implementations, the water make-up line 340 may include a first communication line 341, the first communication line 341 may be configured with a water make-up pump 341a, and the water make-up pump 341a may power the first communication line 341 to pump hot water in the thermal storage 310 into the deaerator 230. In this implementation, the installation heights of the heat accumulator 310 and the deaerator 230 may not be limited, and the installation of the heat accumulator 310 and the deaerator 230 may have greater flexibility.

The first communication pipeline 341 may be provided with a first communication control valve 341c, and the first communication control valve 341c is used for controlling the connection or disconnection of the first communication pipeline 341 so as to adjust the connection state of the first communication pipeline 341 according to the unit operation requirement.

Referring to fig. 3, a second self-circulation line 341b may be further connected to the first communication line 341, the second self-circulation line 341b may be connected to the regenerator 310, the second self-circulation line 341b may be provided with a second self-circulation control valve 341b-1, and a connection point of the second self-circulation line 341b and the first communication line 341 may be located upstream of the first communication control valve 341 c.

In this way, when the first communication control valve 341c is closed and the second self-circulation line 341b is opened, the water in the heat accumulator 310 can flow again into the heat accumulator 310 after passing through the water replenishment pump 341a and the second self-circulation line 341 b. This mode of operation may be specifically initiated during a heating operation to facilitate ensuring uniform distribution of the water temperature within the regenerator 310. And, can also make moisturizing pump 341a be in the open-state all the time, can avoid moisturizing pump 341 a's frequent start and stop, be favorable to guaranteeing moisturizing pump 341 a's job stabilization nature.

In other implementations, the water supplementing pipeline 340 may further include a second communication pipeline 342, the installation height of the heat accumulator 310 may be higher than or equal to that of the deaerator 230, the heat accumulator 310 may be connected to the deaerator 230 through the second communication pipeline 342, and the second communication pipeline 342 may be configured with a second communication control valve 342a; in this implementation manner, the water supplementing pump 341a is not needed, and when the second communication control valve 342a is opened, the hot water in the heat accumulator 310 can automatically flow into the deaerator 230 under the action of gravity, so that the system energy consumption of the water heat accumulation system 300 can be effectively reduced. In addition, a vapor balance pipeline 350 can be connected between the heat accumulator 310 and the deaerator 230, and the vapor balance pipeline 350 can be provided with a vapor balance control valve 351; after the vapor balance control valve 351 is opened, the vapor balance line 350 may be opened, enabling pressure balancing of the regenerator 310 and the deaerator 230.

As shown in fig. 1 and 4, the coal-fired power generation unit provided by the invention may further include a steam supplementing system 400, and the steam supplementing system 400 may include a heating module 410, a water supply pipeline 420 and a steam supplementing pipeline 430. The water supply pipe 420 and the steam supplementing pipe 430 may be connected to the heating module 410, the water supply pipe 420 may be located upstream of the heating module 410, and the steam supplementing pipe 430 may be located downstream of the heating module 410. The vapor supply line 430 may be coupled to the cylinder bank 210, and may specifically be coupled to the intermediate pressure cylinder 212 for supplying vapor to the cylinder bank 210.

With this scheme, when the load of the coal-fired power generation unit needs to be increased, the heating module 410 can heat the water provided by the water supply pipeline 420 to form steam, and the steam can be introduced into the cylinder group 210 through the steam supplementing pipeline 430, so that the steam required by the cylinder group 210 can be directly supplemented, and the load increase of the unit can be rapidly realized.

The water supply pipeline 420 may be specifically connected to the deaerator 230 to directly use the water discharged from the deaerator 230 to generate steam, so that no external water source is required to be introduced, the structural form of the steam supplementing system 400 may be relatively simple, the initial investment of equipment may be relatively small, and meanwhile, the water quality and the water vapor balance of the unit are also guaranteed. Specifically, as shown in fig. 4, the water supply pipeline 420 may be connected to the outlet of the pre-pump 231, so that the water supply of the water supply pipeline 420 is the medium-pressure water from the deaerator 230, and an independent molten salt water supply pump is not required, which can simplify the unit structure and is beneficial to reducing the unit cost.

The water supply line 420 may be further provided with a water supply control valve 421 for on-off adjustment, flow adjustment, etc. of the water supply line 420.

Here, the embodiment of the present invention is not limited to the specific structural form of the heating module 410, and in practical application, a person skilled in the art may select according to actual needs, so long as the requirement of use can be met.

In some implementations, the heating module 410 may include a molten salt heating module that may include a molten salt boiler 412, a hot molten salt tank 413, and a cold molten salt tank 414, each of the hot molten salt tank 413 and the cold molten salt tank 414 may be connected to the molten salt boiler 412.

The molten salt may be ternary molten salt (mixed nitrate composed of 53% potassium nitrate, 40% sodium nitrite and 7% sodium nitrate), the temperature of the hot molten salt in the hot molten salt tank 413 may be 400 ℃, and the temperature of the cold molten salt in the cold molten salt tank 414 may be 200 ℃. A molten salt pump 417 may be disposed between the hot molten salt tank 413 and the molten salt boiler 412, and the molten salt pump 417 may pump the hot molten salt in the hot molten salt tank 413 into the molten salt boiler 412 to heat water entering the molten salt boiler 412 through the water supply pipeline 420, thereby generating steam, and molten salt flowing out of the molten salt boiler 412 may flow into the cold molten salt tank 414. The parameters of the generated steam may be set according to the requirements of the cylinder group 210, for example, 380 ℃/2.5MPa, etc.

In connection with fig. 5, the molten salt boiler 412 may include a molten salt preheater 412a, a molten salt evaporator 412b, and a molten salt superheater 412c, arranged in sequence. Wherein the water side outlet of the molten salt preheater 412a and the water side inlet of the molten salt evaporator 412b may be connected by a connection pipe 412d, the connection pipe 412d being provided with an evaporator inlet valve 412d-1, and the connection pipe 412d being further connected with a drain pipe 412e, the drain pipe 412e being for draining water in the connection pipe 412d for operation and debugging of the molten salt boiler 412. The water drain pipeline 412d may be specifically connected to the deaerator 230, so as to guide the discharged water into the deaerator 230, thereby avoiding waste of water resources and being beneficial to ensuring water balance inside the unit. The drain line 412e may be configured with a drain valve 412e-1 for controlling on-off and flow regulation of the drain line 412 e.

Further, the heating module 410 may further include a steam preheater 415, the steam preheater 415 may be connected with a backflow preheating steam path 415a, and the backflow preheating steam path 415a may be connected with a steam supplementing pipeline 430, so as to lead out a part of steam in the steam supplementing pipeline 430 to the steam preheater 415, so as to preheat the water in the water feeding pipeline 420, so that the water entering the molten salt boiler 412 may have a set temperature, and adverse situations such as condensation of molten salt caused by too low water temperature can be avoided to a greater extent.

The embodiment of the present invention is not limited to the specific value of the set temperature, and in practical application, a person skilled in the art may determine the set temperature according to the relevant parameters such as the property of the molten salt, so long as the set temperature can meet the use requirement. For example, for the ternary molten salt described above, which is liquid at 160-420 ℃, the set temperature may be greater than or equal to 160 ℃.

It should be understood that, the above-mentioned backflow preheating steam path 415a can stably supply gas to preheat the steam preheater 415 only when the steam supplementing system 400 is stably operated, and the steam supplementing system 400 cannot stably produce steam under the working conditions of equipment debugging and initial operation, which cannot stably preheat the steam preheater 415 in practice.

In this regard, in an embodiment of the present invention, a backup pre-heat steam circuit 415b may also be connected to the steam pre-heater 415. The backup preheating steam path 415b may be connected with a backup steam source 416, and the backup steam source 416 may be a dedicated steam source or may also be cold-section steam of the coal-fired power generation unit. The backup pre-heat steam path 415b may be configured with a backup pre-heat control valve 415b-1 for on-off and flow regulation of the backup pre-heat steam path 415b.

In the debugging stage of the steam supplementing system 400, the water supply can be preheated by the standby preheating steam path 415b, and after the steam supplementing system 400 can produce steam, the preheating control valve 415b-1 can be gradually reduced until the steam supplementing system 400 can stably run.

The steam compensating pipeline 430 may be configured with a steam compensating control valve 431 for on-off adjustment, opening adjustment, related parameter adjustment, etc. of the steam compensating pipeline 430.

In some implementations, the heating module 410 may also include an electrical heating module 411 to produce steam by way of electrical heating.

The electric heating module 411 and the aforementioned molten salt heating module may be independent of each other, and in specific practice, one skilled in the art may select one of the electric heating module 411 and the molten salt heating module to use as needed. Or the electric heating module 411 and the molten salt heating module may be used simultaneously, in this implementation manner, referring to fig. 1 and fig. 4, the water fed into the water feeding pipeline 420 may first pass through the molten salt heating module and then pass through the electric heating module 411, and the electric heating module 411 may be used for supplementing the molten salt heating module, so as to ensure that the steam flowing into the cylinder group 210 from the steam supplementing pipeline 430 may have sufficient temperature and pressure.

Example two

Referring to fig. 6 and 7, fig. 6 is a schematic flow chart of a feeding step of the steam compensating system, and fig. 7 is a schematic load change diagram of the boiler and the steam turbine in the load raising and lowering processes of the unit.

The invention also provides a control method of the coal-fired power generation unit, which is applicable to the coal-fired power generation unit related to each implementation mode of the first embodiment. The control method comprises a step of load rising control and a step of load falling control.

The step of load reduction control comprises the following steps: the second outlet line 330 is controlled to heat the water entering the regenerator 310. In this way, the redundant steam generated by the boiler 100 can be timely extracted from the steam turbine 200, so that the synchronous load reduction of the boiler 100 and the steam turbine 200 is realized, and the rapid load reduction of the coal-fired power generation unit is realized. Meanwhile, the steam led out by the second steam outlet pipeline 330 can heat the water entering the heat accumulator 310 to store heat, so that the energy waste can be reduced.

Specifically: after the water heat storage system 300 receives the load reducing instruction, the booster pump 324 can be controlled to boost according to a certain speed, and the flow of the second water outlet pipeline 320 can be increased so as to increase the water side flow of the heat exchange module 321, and meanwhile, the opening of the first self-circulation control valve 323a is gradually reduced until the first self-circulation pipeline 323 is completely closed; as the water side flow rate of the heat exchange module 321 increases, the steam side is subjected to cold condensation, the pressure is reduced, the flow rate of the second steam outlet pipeline 330 can be increased, so that the steam extraction amount is increased, and the unit can rapidly reduce the load; the desuperheater 331a-1 tracks the steam temperature after the desuperheater 331a-1, adjusts the superheat to 30 ℃ or other set point; the hot water at the outlet of the heat exchange module 321 flows into the heat accumulator 310 to store and accumulate heat, at this time, the first communication control valve 341c is in a closed state, the second self-circulation control valve 341b-1 is in an open state, and the water supplementing pump 341a is operated in a recirculation state; the second heat exchange control valve 332a is in an open state, and the steam of the second heat exchange branch 332 can directly enter the heat accumulator 310 for mixed heating.

During the unit load shedding process, the water heat storage system 300 adjusts the difference of the load change rate between the boiler 100 and the turbine 200, and in some implementations, the turbine 200 may shed load at a rate of 6% pe/min, while the boiler 100 may shed load only at a rate of 4% pe/min, so the water heat storage system 300 is subject to an adjustment of 2% pe/min. When the load is reduced, the water side flow of the heat exchange module 321 is increased, the booster pump 324 can adopt Proportional, integral and differential (pro-port INTEGRAL DERIVATIVE, PID) control and feedforward control, the controlled object is the water side flow of the heat exchange module 321, the water side flow set value is obtained by converting the extraction flow of the second steam outlet pipeline 330, the extraction flow is converted by a load reducing instruction, the feedforward signal is formed by the load reducing instruction, meanwhile, the second self-circulation control valve 341b-1 is gradually closed at a certain speed, and the water side flow is timely adjusted through adjustment of the booster pump 324, so that the extraction flow is synchronously adjusted, and the load reducing speed is ensured. The controlled object of the desuperheater 331a-1 is the superheat degree of the steam at the inlet of the heat exchange module 321, cascade PID and feedforward control are adopted, the superheat degree set value of the main flow path 331a is 30 ℃ (the control can be carried out according to specific conditions), the feedforward signal is composed of the steam extraction flow and the differential signal of the steam extraction temperature, the steam temperature fluctuation of the heat exchange module 321 is reduced through the adjustment of the desuperheater 331a-1, and the influence of the temperature fluctuation on the safety of equipment is avoided. The controlled object of the drain valve of the heat exchange module 321 is the water level of the heat exchange module 321, PID control is adopted, and meanwhile, the logic of the high-water-level override drain valve of the heat exchange module 321 is set, so that the safety of the equipment body is ensured. The accumulator 310 may also be configured with an overflow valve (not labeled in the figure), the controlled object of the overflow valve is the water level of the accumulator 310, and PID control is adopted, and meanwhile, the logic of the overflow valve is set to be high in the water level of the accumulator 310 and is overridden.

The load-raising control step comprises a first substep, which comprises: the water supplementing pipeline 340 is controlled to be opened so as to introduce the hot water in the heat accumulator 310 into the deaerator 230, the first steam outlet pipeline 250 is controlled to reduce the flow rate, and the second steam outlet pipeline 330 is controlled to reduce the flow rate. Like this, the water level and the temperature etc. in deaerator 230 all can rise, can reduce the play vapour volume of first play vapour pipeline 250 for the produced steam of boiler 100 can be used for the acting of steam turbine 200 more, in order to adapt to the load promotion of steam turbine 200, thereby can realize coal fired generating set's quick load that rises.

The heat release operation mode of the water heat storage system 300 can combine the load lifting and frequency modulation working conditions of the unit, and by providing the condensed water for the deaerator 230, the condensed water flow of the first water outlet pipeline 240 can be rapidly reduced, and the steam entering each low-pressure heater and the deaerator 230 can be displaced, so that more steam can be left in the cylinder group 210 to do work, thereby realizing the load lifting and frequency modulation response of the unit. Specifically, after the water heat storage system 300 receives the load lifting instruction, the first communication control valve 341c may be opened, and the second self-circulation control valve 341b-1 may be gradually closed, the water supplementing pump 341a may supply water to the deaerator 230, the flow rate from the water supplementing pump 341a to the deaerator 230 may be increased according to the instruction, and the water level of the deaerator 230 may be increased; the opening of the water outlet valve of the condenser 220 is reduced, the flow of the condensing pump 260 is gradually reduced, and the synchronous frequency-reducing operation is performed, so that the steam extraction amount of each low-temperature heater is synchronously reduced due to the reduction of the flow of the condensed water, and the load of a unit is increased; when the flow rate of the coagulation pump 260 is reduced to a set flow rate (for example, 220 t/h), the water level control valve 325 of the buffer 322 can be quickly opened to a set opening (for example, 30%), and at this time, the coagulation pump 260 can maintain the low flow rate of the water side of each low-temperature heater on one side and can supplement water for the buffer 322 on the other side.

When the unit increases load, the flow of the outlet of the heat accumulator 310 is increased, the flow from each low-temperature heater to the deaerator 230 is reduced, the water supplementing pump 341a can adopt PID and feedforward control, the controlled object is the outlet flow of the heat accumulator 310, the flow set value is obtained by converting the load increasing instruction, the feedforward signal is formed by the load increasing instruction, meanwhile, the second self-circulation control valve 341b-1 is closed at a certain speed, and the water supplementing flow is timely adjusted by synchronous adjustment of the water supplementing pump 341a and the second self-circulation control valve 341 b-1. The water level of the deaerator 230 is controlled by a water-feeding gate of the deaerator 230, three-impulse control of the water level is adopted, the main control is the water level of the deaerator 230, the auxiliary control is the water-feeding flow, and the feedforward signal is the difference between the water-feeding flow of the boiler 100 and the water-feeding flow of the heat accumulator 310. The frequency converter of the coagulation pump 260 controls the pressure of the deaerator 230, PID control is adopted, meanwhile, in order to avoid the recirculation valve of the coagulation pump 260 to be opened, the water level control valve 325 of the buffer 322 participates in the outlet flow regulation of the coagulation pump 260, and the water level control valve 325 is set to be the difference between the recirculation flow of the coagulation pump 260 and the water flow on the deaerator 230, and a certain margin is reserved. When the buffer 322 level is above the alarm value, the water level control valve 325 is overridden closed.

In some implementations, the control method may further include a first heating control step, where the first heating control step mainly performs heating control on the water heat storage system 300 to cope with the intermittent, rapid, peak, and other characteristics of the water heat storage system 300.

The first heating pipe control step may include: the second steam outlet pipeline 330 is controlled to operate in a low-flow steam outlet mode, the main flow path 331a is closed, and the second heat exchange branch 332 is opened; the second water outlet line 320 is controlled to operate in the low flow water outlet mode, the water level control valve 325 is closed, the water replenishing line 340 is closed, and the second self-circulation line 341b is opened. Therefore, the water heat storage system 300 can be always in a standby state, and can respond to the load reducing instruction of the unit more quickly so as to meet the requirement of quick load reduction of the unit.

For the coal-fired power generation unit including the steam supplementing system 400, the load-up control step may further include a second substep, where the second substep specifically includes: the steam supplementing pipeline 430 is controlled to be opened to supplement steam into the cylinder group 210, so that additional steam is directly provided for the cylinder group 210 to meet the requirement of quick load lifting of the unit.

The water supply of the steam supplementing system 400 is taken from the outlet of the pre-pump 231, and the water quantity is controlled by adopting a water supply control valve 421. After the water is heated by the steam preheater 415, the temperature can rise to 160 ℃ or higher, and the water becomes the water for the molten salt boiler 412. After entering the molten salt boiler 412, the feed water flows through the molten salt preheater 412a, the molten salt evaporator 412b and the molten salt superheater 412c in sequence, and absorbs heat to become steam. Simultaneously, hot molten salt is pumped out of the hot molten salt tank 413 through the molten salt pump 417, sequentially enters the molten salt superheater 412c, the molten salt evaporator 412b and the molten salt preheater 412a, releases heat to the steam-water system, and flows into the cold molten salt tank 414. After the steam exits the molten salt boiler 412, the steam can be heated by the electric heating module 411 to ensure the degree of superheat of the steam, and the electric heating module 411 can be omitted when the degree of superheat of the steam is enough. After exiting the electric heating module 411 (or the molten salt boiler 412), the steam can be divided into two paths, one path directly enters the cylinder group 210 to do work, for example, the steam can enter the medium-pressure cylinder 212 to do work, the other path can enter the steam preheater 415 through the backflow preheating steam path 415a to heat water, and the cooled (wet) steam can be discharged into the deaerator 230, so that waste of water resources is avoided, and meanwhile, the water vapor balance of the unit is guaranteed. Steam preheater 415 is also designed with a backup preheat steam path 415b for use in commissioning of steam make-up system 400.

The steam make-up system 400 may increase the load rate of the unit. Specifically, after the unit receives the load raising instruction, the load raising instruction may be synchronized to the steam turbine 200, the boiler 100, and the steam supplementing system 400; the steam supplementing system 400 can gradually increase the water supply of the water supply pipeline 420 according to the instruction, and the molten salt pump 417 can synchronously improve the flow rate of the hot molten salt; after the upper water absorbs heat to reach a safe water temperature through the steam preheater 415, the upper water can enter the molten salt boiler 412 to further absorb the heat of the high-temperature molten salt so as to generate high-grade steam; the steam then enters the cylinder bank 210 to perform work and power generation, thereby increasing the load on the bank.

When the unit is in load lifting, the steam supplementing control valve 431 adopts a PID controller, the regulating quantity is the steam supplementing pressure, and the set value of the steam supplementing pressure is 1.5 times (can be other times) of the steam pressure of the steam converging point of the cylinder group 210, so that the steam provided by the steam supplementing system 400 can be smoothly converged into the cylinder group 210; the water supply control valve 421 can adopt a PID controller, the adjustment amount is a molten salt water supply flow, the set value is a molten salt water supply flow instruction converted from a molten salt load instruction, wherein the molten salt load instruction is converted from a load lifting instruction, when the molten salt load instruction is lifted, the water supply flow is increased, the opening of the water supply control valve 421 is increased, and the steam flow provided by the steam supplementing system 400 can meet the power adjustment requirement of the unit; the reflux preheating steam path 415a is provided with a preheating regulating valve (not labeled in the figure), the preheating regulating valve adopts PID and feedforward control, the regulating quantity is the water supply temperature at the outlet of the steam preheater 415, the set value is 165 ℃, the feedforward signal is the water supply flow, when the water supply flow is increased, the opening degree of the preheating regulating valve is synchronously increased, and the water supply temperature at the outlet of the steam preheater 415 is ensured to be always kept above 160 ℃; the molten salt pump 417 adopts PID and feedforward control, the regulating variable is steam temperature, the set value is the steam temperature of the steam converging point, the feedforward signal is the water supply flow, when the water supply flow is increased, the output of the molten salt pump 417 is synchronously increased, the hot molten salt flow is increased, and the steam temperature is ensured to be consistent with the steam converging point temperature.

During specific throwing, the steam supplementing system 400 can adopt a step-by-step water feeding step, so that the steam supplementing system 400 can be stably put into operation. Specifically, the control method provided by the present invention may further include a step of putting in a steam supplementing system, as shown in fig. 6, where the step of putting in a steam supplementing system may include steps S110 to S180 described below.

In step S110, the control valve 431 is closed to disconnect the connection between the system 400 and the cylinder bank 210. At the same time, all vapor side hydrophobic doors of the vapor make-up system 400 may be opened to drain condensate generated when the device is started.

In step S120, the water supply line 420 is controlled to operate in the low flow water supply mode, and the water discharge line 412e is controlled to be opened, so that the water supply of the water supply line 420 can flow only to the molten salt preheater 412a, but not to the molten salt evaporator 412b.

In step S130, control opens the backup preheat steam path 415b and controls the backup preheat steam path 415b to communicate with the return preheat steam path 415 a. Thus, the steam provided by the backup preheating steam path 415b may be divided into two paths, one path is used for preheating the water supply at the steam preheater 415 and preheating the molten salt preheater 412a by using the water supply, and the other path may flow along the backflow preheating steam path 415a to the molten salt superheater 412c and the molten salt evaporator 412b in a reverse direction so as to reversely preheat the molten salt superheater 412c and the molten salt evaporator 412b by the steam.

In step S140, the evaporator inlet valve 412d-1 is controlled to be opened to introduce the water amount of the set water level into the molten salt evaporator 412b to start the water supply heating of the molten salt evaporator 412 b. The set water level may be set according to actual needs, and is not limited herein.

In step S150, it is determined whether or not the temperatures of the molten salt superheater 412c and the molten salt evaporator 412b reach a set temperature, for example, 180 ℃.

In step S160, the hot molten salt tank 413 is controlled to supply hot molten salt to the molten salt boiler 412 to conduct a passage between the hot molten salt tank 413, the molten salt boiler 412, and the cold molten salt tank 414.

In step S170, water is continuously supplied to the molten salt evaporator 412b according to the water level of the molten salt evaporator 412b, the water drain pipe 412e is gradually closed, and the water supply amount of the water supply pipe 420 is adjusted until the water drain pipe 412e is completely closed.

When the water drain pipeline 412e is completely closed, the molten salt boiler 412 can already meet the requirement of normal steam production, at this time, step S180 may be executed to control to gradually shut down the standby pre-heating steam path 415b, and when the standby pre-heating steam path 415b is completely closed, the steam supplementing system 400 is successfully put in.

The control method of the vapor filling system 400 when receiving the load raising command can be referred to as the second substep. When the unit does not need to be subjected to load-lifting, the steam-supplementing system 400 can also operate according to a second heating pipe control step described below, so as to maintain the steam-supplementing system 400 in a standby state, so that a load-lifting instruction of the unit can be responded relatively quickly. Specifically, the second heating pipe control step may include: the water supply pipeline 420 is controlled to operate in a low-flow water supply mode, the heating module 410 is controlled to operate in a low-power mode, the communication between the steam supplementing pipeline 430 and the cylinder group 210 is controlled to be cut off, and the reflux preheating steam pipeline 415a is controlled to be opened, so that steam generated by the steam supplementing system 400 can be used for heating water at the steam preheater 415 to form self-circulation operation of the steam supplementing system 400.

In addition, the following steps may be adopted in the specific implementation of the load-up control step and the load-down control step: step S120, determining N load change intervals according to the difference value between the target load and the current load; step S220, controlling the steam turbine 200 to perform load adjustment in each load change section according to a first set load change rate, controlling the boiler 100 to perform load adjustment in each load change section according to a second set load change rate, wherein the first set load change rate is larger than the second set load change rate, and controlling the steam turbine 200 to suspend load change after the steam turbine 200 completes load change in the ith load change section until the boiler 100 also completes load change in the ith load change section; wherein, i and N are positive integers, N is more than or equal to 2, i is more than or equal to 1 and is less than or equal to N.

Because the rate of change of the load of the turbine 200 is relatively large, the load of the turbine 200 may be changed more rapidly in response to the load change command. By adopting the scheme, the embodiment of the invention determines a plurality of load change intervals according to the difference between the target load and the current load, and the load change quantity of each load change interval is relatively smaller, so that when the load change is executed in each load change interval, the energy to be compensated for due to the inconsistent load change rates of the steam turbine 200 and the boiler 100 is relatively less, and the stable operation of the unit is more facilitated.

Specifically, as shown in fig. 7, at the time of load reduction, assuming that the turbine 200 is reduced at a load change rate of 6% pe/min and the boiler 100 is only reduced at a load change rate of 4% pe/min, more heat generated by the boiler 100 during the load reduction can be absorbed and stored by the water heat storage system 300, assuming that the current load is 100% tha and the target load is 50% tha, two load change sections of 100% tha to 75% tha and 75% tha to 50% tha can be set accordingly, so that the load peak differences of the turbine 200 and the boiler 100 in the respective load change sections are relatively small, which is more advantageous for the unit to smoothly reduce the load; similarly, at the time of load increase, assuming that the turbine 200 can be increased at a load change rate of 6% pe/min, and the boiler 100 can be increased only at a load change rate of 3% pe/min, the additional energy required for the turbine 200 during the load increase can be provided by the water heat storage system 300 and the steam supplementing system 400, assuming that the current load is 50% tha and the target load is 100% tha, two load change sections, 50% tha to 75% tha and 75% tha to 100% tha, respectively, can be set, so that the load peak differences between the turbine 200 and the boiler 100 in each load change section are relatively small, which is more advantageous for the unit to smoothly increase the load.

In addition, it is also possible to directly control the steam turbine 200 to change the load between the current load and the target load according to the first set load change rate, and control the boiler 100 to change the load between the current load and the target load according to the second set load change rate, i.e., without dividing the N load change sections; alternatively, a scheme of late start of the steam turbine 200 may be adopted to compensate for the difference of the load change rates of the steam turbine 200 and the boiler 100.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims

1. Coal-fired generating set, its characterized in that includes boiler (100), steam turbine (200) and water heat accumulation system (300), steam turbine (200) include cylinder group (210), condenser (220), deaerator (230), first outlet pipe way (240) and first outlet pipe way (250), condenser (220) are through first outlet pipe way (240) with deaerator (230) link to each other, cylinder group (210) are through first outlet pipe way (250) with deaerator (230) link to each other, water heat accumulation system (300) include heat accumulator (310), second outlet pipe way (320), second outlet pipe way (330) and moisturizing pipeline (340), heat accumulator (310) are through second outlet pipe way (320) with condenser (220) link to each other, second outlet pipe way (330) also with cylinder group (210) link to each other, the steam of second outlet pipe way (330) can be to getting into heat accumulator (310) water heater (310) are through moisturizing pipeline (340) link to each other with deaerator (230).

2. The coal-fired power generation unit according to claim 1, wherein the second water outlet pipeline (320) is provided with a heat exchange module (321), the second steam outlet pipeline (330) comprises a first heat exchange branch (331), and the first heat exchange branch (331) is connected with the heat exchange module (321).

3. The coal-fired power generation unit according to claim 2, wherein the first heat exchange branch (331) comprises a main flow path (331 a) and a steam heating bypass (331 b) which are arranged in parallel, the main flow path (331 a) and the steam heating bypass (331 b) are connected with the heat exchange module (321), and the steam heating bypass (331 b) can be opened at least when the main flow path (331 a) is closed.

4. A coal-fired power unit as claimed in claim 3, wherein the main flow path (331 a) is provided with a first heat exchange control valve (331 a-2), the flow area of the main flow path (331 a) is larger than that of the steam heating bypass (331 b), and the steam heating bypass (331 b) is in a normally open state.

5. The coal-fired power generation unit according to claim 2, characterized in that the first heat exchange branch (331) is further provided with a desuperheater (331 a-1).

6. The coal-fired power generation unit according to claim 2, wherein the heat exchange module (321) comprises a cooling device (321 a) and a heat exchanger (321 b), the cooling device (321 a) being located upstream of the heat exchanger (321 b) in the extension direction of the second water outlet line (320).

7. The coal-fired power generation unit according to claim 1, wherein the second steam outlet pipeline (330) further comprises a second heat exchange branch (332), the second heat exchange branch (332) is connected with the heat accumulator (310), and the second heat exchange branch (332) is provided with a second heat exchange control valve (332 a).

8. The coal-fired power unit according to claim 1, wherein the second water outlet line (320) is further provided with a buffer (322), the buffer (322) being located upstream of the heat accumulator (310), the buffer (322) being arranged in a sealing manner.

9. The coal-fired power unit as claimed in claim 8, wherein the buffer (322) has an air cavity and a liquid cavity formed therein;

the buffer (322) is further provided with an inflation tube (322 a), and the inflation tube (322 a) is used for inflating specified gas into the air cavity; or the air cavity is also communicated with the condenser (220).

10. The coal-fired power generation unit according to claim 8, wherein the second water outlet pipeline (320) is further connected with a first self-circulation pipeline (323), the first self-circulation pipeline (323) is connected with the buffer (322), the second water outlet pipeline (320) is further provided with a booster pump (324) and a water level control valve (325), the booster pump (324) is located downstream of the buffer (322) and upstream of a connection point of the first self-circulation pipeline (323) and the second water outlet pipeline (320), the water level control valve (325) is located upstream of the buffer (322), and the first self-circulation pipeline (323) is provided with a first self-circulation control valve (323 a).

11. The coal-fired power unit according to claim 10, further comprising a water outlet bypass (326), wherein an upstream connection end (326 a) and a downstream connection end (326 b) of the water outlet bypass (326) are both connected to the second water outlet pipe (320), wherein the upstream connection end (326 a) is located upstream of the water level control valve (325), wherein the downstream connection end (326 b) is located downstream of a connection point of the first self-circulation pipe (323) and the second water outlet pipe (320), wherein a pipe section of the second water outlet pipe (320) between the upstream connection end (326 a) and the downstream connection end (326 b) is a main through pipe section (320 a), and wherein the water outlet bypass (326) is openable at least when the main through pipe section (320 a) is closed.

12. The coal-fired power unit as recited in claim 11, wherein the water outlet bypass (326) has a smaller flow area than the main duct section (320 a), the water outlet bypass (326) being normally open.

13. The coal-fired power unit according to claim 1, wherein the water replenishment pipeline (340) comprises a first communication pipeline (341), the first communication pipeline (341) being configured with a water replenishment pump (341 a).

14. The coal-fired power generation unit according to claim 13, wherein the first communication pipeline (341) is further connected with a second self-circulation pipeline (341 b), the second self-circulation pipeline (341 b) is connected with the heat accumulator (310), and the second self-circulation pipeline (341 b) is provided with a second self-circulation control valve (341 b-1);

The first communication line (341) is further provided with a first communication control valve (341 c), and the first communication control valve (341 c) is located downstream of a connection point of the second self-circulation line (341 b) and the first communication line (341).

15. The coal-fired power generation unit according to claim 1, wherein the water replenishment pipeline (340) further comprises a second communication pipeline (342), the heat accumulator (310) is connected to the deaerator (230) through the second communication pipeline (342), and the second communication pipeline (342) is provided with a second communication control valve (342 a);

A steam balance pipeline (350) is further connected between the heat accumulator (310) and the deaerator (230), and the steam balance pipeline (350) is provided with a steam balance control valve (351).

16. The coal-fired power unit according to any of claims 1-15, further comprising a steam-make-up system (400), the steam-make-up system (400) comprising a heating module (410), a water supply line (420) and a steam-make-up line (430), the water supply line (420) and the steam-make-up line (430) being connected to the heating module (410), the water supply line (420) being located upstream of the heating module (410), the steam-make-up line (430) being located downstream of the heating module (410), the steam-make-up line (430) being connected to the cylinder block (210).

17. The coal-fired power unit as claimed in claim 16, wherein the water supply line (420) is connected to the deaerator (230), and the water supply line (420) is provided with a water supply control valve (421).

18. The coal-fired power unit as claimed in claim 16, wherein the heating module (410) comprises an electrical heating module (411).

19. The coal-fired power generation unit according to claim 17 or 18, wherein the heating module (410) further comprises a molten salt heating module, the molten salt heating module comprises a molten salt boiler (412), a hot molten salt tank (413) and a cold molten salt tank (414), and the hot molten salt tank (413) and the cold molten salt tank (414) are connected with the molten salt boiler (412).

20. The coal-fired power generation unit according to claim 19, wherein the molten salt boiler (412) comprises a molten salt preheater (412 a), a molten salt evaporator (412 b) and a molten salt superheater (412 c) arranged in that order;

The water side outlet of the molten salt preheater (412 a) is connected with the water side inlet of the molten salt evaporator (412 b) through a connecting pipeline (412 d), the connecting pipeline (412 d) is further connected with a water drain pipeline (412 e), the connecting pipeline (412 d) is further provided with an evaporator inlet valve (412 d-1), the evaporator inlet valve (412 d-1) is positioned at the downstream of the connecting point of the water drain pipeline (412 e) and the connecting pipeline (412 d), and the water drain pipeline (412 e) is provided with a water drain valve (412 e-1).

21. The coal-fired power generation unit according to claim 19, wherein the heating module (410) further comprises a steam preheater (415), the steam preheater (415) is connected with a reflux preheating steam path (415 a), and the reflux preheating steam path (415 a) is communicated with the steam supplementing pipeline (430).

22. The coal-fired power unit as recited in claim 21, wherein the steam preheater (415) is further connected with a backup preheating steam path (415 b), the backup preheating steam path (415 b) being configured with a backup preheating control valve (415 b-1).

23. The coal-fired power generation unit according to claim 16, wherein the steam supplementing pipeline (430) is provided with a steam supplementing control valve (431).

24. A control method of a coal-fired power generation unit, characterized in that it is applied to the coal-fired power generation unit according to any one of claims 1 to 23, and the control method includes a load-down control step and a load-up control step;

the load reduction control step comprises the following steps: controlling the second steam outlet pipeline (330) to heat the water entering the heat accumulator (310);

the load-up control step comprises a first sub-step comprising: and controlling the water supplementing pipeline (340) to be opened so as to introduce the hot water in the heat accumulator (310) into the deaerator (230), controlling the first steam outlet pipeline (250) to reduce the flow, and controlling the second steam outlet pipeline (330) to reduce the flow.

25. The control method of a coal-fired power generation unit according to claim 24, wherein the second water outlet pipeline (320) is provided with a heat exchange module (321), the second steam outlet pipeline (330) comprises a first heat exchange branch (331) and a second heat exchange branch (332), the first heat exchange branch (331) comprises a main flow path (331 a) and a steam heating bypass (331 b) which are arranged in parallel, the main flow path (331 a) and the steam heating bypass (331 b) are both connected with the heat exchange module (321), and the second heat exchange branch (332) is connected with the heat accumulator (310); the second water outlet pipeline (320) is further provided with a buffer (322), the buffer (322) is located at the upstream of the heat accumulator (310), the coal-fired power generation unit further comprises a water outlet bypass (326), an upstream connecting end (326 a) and a downstream connecting end (326 b) of the water outlet bypass (326) are both connected with the second water outlet pipeline (320), and a pipe section of the second water outlet pipeline (320) located between the upstream connecting end (326 a) and the downstream connecting end (326 b) is a main pipe section (320 a); the water supplementing pipeline (340) comprises a first communication pipeline (341), the first communication pipeline (341) is connected with the heat accumulator (310) and the deaerator (230), the first communication pipeline (341) is further connected with a second self-circulation pipeline (341 b), the second self-circulation pipeline (341 b) is connected with the heat accumulator (310), the first communication pipeline (341) is provided with a first communication control valve (341 c), and the first communication control valve (341 c) is positioned at the downstream of a connecting point of the second self-circulation pipeline (341 b) and the first communication pipeline (341);

The control method further comprises a first heating pipe control step, wherein the first heating pipe control step comprises the following steps: controlling the second steam outlet pipeline (330) to operate in a low-flow steam outlet mode, controlling the main flow path (331 a) to be closed, and controlling the second heat exchange branch (332) to be opened; and controlling the second water outlet pipeline (320) to operate in a low-flow water outlet mode, controlling the main through pipe section (320 a) to be closed, controlling the first communication control valve (341 c) to be closed, and controlling the second self-circulation pipeline (341 b) to be opened.

26. The method of claim 24, wherein the coal-fired power generation unit further comprises a steam supplementing system (400), the steam supplementing system (400) comprises a heating module (410), a water feeding pipeline (420) and a steam supplementing pipeline (430), the water feeding pipeline (420) and the steam supplementing pipeline (430) are connected with the heating module (410), the water feeding pipeline (420) is located at the upstream of the heating module (410), the steam supplementing pipeline (430) is located at the downstream of the heating module (410), and the steam supplementing pipeline (430) is connected with the cylinder group (210);

the load-up control step further comprises a second sub-step comprising: and controlling the steam supplementing pipeline (430) to supplement steam into the cylinder group (210).

27. The method of claim 26, wherein the heating module (410) further comprises a steam preheater (415), the steam preheater (415) is connected to a reflux preheating steam path (415 a), and the reflux preheating steam path (415 a) is communicated with the steam supplementing pipeline (430);

The control method further comprises a second heating pipe control step, wherein the second heating pipe control step comprises the following steps: the water supply pipeline (420) is controlled to operate in a low-flow water supply mode, the heating module (410) is controlled to operate in a low-power mode, the communication between the steam supplementing pipeline (430) and the cylinder group (210) is controlled to be cut off, and the backflow preheating steam pipeline (415 a) is controlled to be opened.

28. The control method of a coal-fired power generation unit according to claim 27, wherein the heating module (410) further comprises a molten salt heating module, the molten salt heating module comprises a molten salt boiler (412), a hot molten salt tank (413) and a cold molten salt tank (414), and the hot molten salt tank (413) and the cold molten salt tank (414) are connected with the molten salt boiler (412); the molten salt boiler (412) comprises a molten salt preheater (412 a), a molten salt evaporator (412 b) and a molten salt superheater (412 c) which are sequentially arranged, wherein a water side outlet of the molten salt preheater (412 a) is connected with a water side inlet of the molten salt evaporator (412 b) through a connecting pipeline (412 d), the connecting pipeline (412 d) is further connected with a water drain pipeline (412 e), and the connecting pipeline (412 d) is further provided with an evaporator inlet valve (412 d-1); the steam preheater (415) is also connected with a standby preheating steam path (415 b), and the standby preheating steam path (415 b) is provided with a standby preheating control valve (415 b-1); the steam supplementing pipeline (430) is provided with a steam supplementing control valve (431);

controlling the steam supplementing control valve (431) to be closed;

controlling the water supply pipeline (420) to operate in a low-flow water supply mode, and controlling the water discharge pipeline (412 e) to be opened;

Controlling to open the standby preheating steam path (415 b) and controlling the standby preheating steam path (415 b) to be communicated with the reflux preheating steam path (415 a);

controlling to open the evaporator inlet valve (412 d-1) and controlling the amount of water that is fed to the molten salt evaporator (412 b) at a set water level;

judging whether the temperatures of the molten salt superheater (412 c) and the molten salt evaporator (412 b) reach a set temperature, and if so, executing the following steps;

controlling the hot melt salt tank (413) to feed hot molten salt into the molten salt boiler (412);

Continuously feeding water to the molten salt evaporator (412 b) according to the water level of the molten salt evaporator (412 b), gradually closing the water discharge pipeline (412 e), and adjusting the water feeding amount of the water feeding pipeline (420) until the water discharge pipeline (412 e) is completely closed;

control progressively turns off the backup pre-heat steam circuit (415 b).

29. The control method of a coal-fired power unit according to any one of claims 24 to 28, wherein the step of controlling the load up and the step of controlling the load down each include:

determining N load change intervals according to the difference value between the target load and the current load;

Controlling the steam turbine (200) to perform load adjustment in each load change interval according to a first set load change rate, and controlling the boiler (100) to perform load adjustment in each load change interval according to a second set load change rate, wherein the first set load change rate is larger than the second set load change rate, and controlling the steam turbine (200) to suspend load change after load change is completed in an ith load change interval until the boiler (100) also completes load change in the ith load change interval;

Wherein, i and N are positive integers, N is more than or equal to 2, i is more than or equal to 1 and is less than or equal to N.