A peak shaving system using steam extraction to heat a mixture of air and pulverized coal

Abstract

The application discloses a peak regulation system for heating air-powder mixture by steam extraction, which comprises a pulverizing system, a powder feeding pipeline, a primary air heater, a coal powder distributor and a low-pressure cylinder of a steam turbine; the outlet end of the pulverizing system is provided with the powder feeding pipeline, the powder feeding pipeline is communicated with the coal powder distributor through the primary air heater; the steam inlet end of the low-pressure cylinder of the steam turbine receives high-temperature steam discharged from the intermediate-pressure cylinder of the steam turbine, the steam inlet end of the low-pressure cylinder of the steam turbine is provided with a steam extraction pipeline, the steam extraction pipeline is connected with the primary air heater, the high-temperature steam discharged from the intermediate-pressure cylinder of the steam turbine is introduced into the primary air heater, the air-powder mixture in the powder feeding pipeline is heated, the steam extraction amount in the steam extraction pipeline is adjusted to change the steam inlet amount of the low-pressure cylinder of the steam turbine, and the rapid change of the corresponding unit load is realized. The unit load change rate is improved by the structural arrangement of the system.

Description

Technical Field

[0001] This invention belongs to the field of power plant boiler technology, and particularly relates to a peak-shaving system that utilizes extracted steam to heat a mixture of air and pulverized coal. Background Technology

[0002] In recent years, with the vigorous development of renewable energy sources such as wind power and solar energy, the total power generation of renewable energy has continued to climb. Due to the temporal and spatial differences between wind and solar resources and residential electricity consumption, the rapid development of wind and solar power has also led to increasingly prominent issues of wind and solar curtailment in areas rich in these resources. As the main force for peak shaving in the power system, improving the peak shaving capacity of coal-fired power units is one of the most direct and effective means to solve the problem of wind and solar curtailment.

[0003] The peak-shaving capacity of coal-fired power units includes both low-load operation capability and rapid load change capability. Currently, most coal-fired power units have a load change rate of 1% to 2% per minute. Improving this rate is limited by various factors, such as the pulverizing system response rate, combustion delay, and heat transfer delay. To improve the load change rate of coal-fired power units, the industry has developed regulation methods such as hot water thermal storage, molten salt thermal storage, feedwater throttling, and condensate throttling. However, thermal storage methods are costly, and feedwater regulation methods are limited by the limited range of steam drum water level adjustment. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of the prior art by disclosing a peak-shaving system that uses extracted steam to heat a mixture of air and pulverized coal, thereby improving the unit's load change rate through the structural design of the system.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A peak-shaving system that utilizes extracted steam to heat a mixture of air and pulverized coal, the peak-shaving system comprising: a pulverizing system, a pulverized coal delivery pipeline, a primary air heater, a pulverized coal distributor, and a low-pressure cylinder of a steam turbine;

[0007] The pulverizing system is equipped with a pulverizing pipe at its outlet, and the pulverizing pipe is connected to the pulverized coal distributor via a primary air heater.

[0008] The steam turbine's low-pressure cylinder inlet receives high-temperature steam discharged from the turbine's intermediate-pressure cylinder. The steam turbine's low-pressure cylinder inlet is equipped with an extraction steam pipeline connected to the primary air heater. High-temperature steam discharged from the turbine's intermediate-pressure cylinder is introduced into the primary air heater to heat the air-coal mixture in the pulverized coal conveying pipeline. By adjusting the extraction steam rate in the extraction pipeline, the steam intake rate of the turbine's low-pressure cylinder can be changed, thereby enabling rapid changes in the unit's load.

[0009] According to a preferred embodiment, the extraction steam pipeline is provided with an extraction steam regulating valve for controlling the amount of steam extracted from the inlet end of the low-pressure cylinder of the steam turbine.

[0010] According to a preferred embodiment, the peak-shaving system further includes: a first low-pressure heater and a second low-pressure heater;

[0011] The exhaust end of the primary air heater is connected to the first low-pressure heater and the second low-pressure heater via the first low-pressure heater extraction pipe and the second low-pressure heater extraction pipe, respectively.

[0012] According to a preferred embodiment, a first low-pressure heater extraction regulating valve is provided on the first low-pressure heater extraction steam pipeline.

[0013] According to a preferred embodiment, a second low-pressure heater extraction regulating valve is provided on the second low-pressure heater extraction pipeline.

[0014] According to a preferred embodiment, the first low-pressure heater is also connected to the low-pressure cylinder of the steam turbine, and a first regulating valve is provided on the corresponding connecting pipeline.

[0015] According to a preferred embodiment, the second low-pressure heater is also connected to the low-pressure cylinder of the steam turbine, and a second regulating valve is provided on the corresponding connecting pipeline.

[0016] According to a preferred embodiment, when the system is in steady-state operation, the steam extraction rate is adjusted using an extraction steam regulating valve, the flow distribution is adjusted through the extraction steam pipelines of the first and second low-pressure heaters, and the steam entering the first and second low-pressure heaters is controlled by adjusting the first and second regulating valves, so that the condensate temperature at the outlet of the first and second low-pressure heaters is consistent with that of the standard condition unit.

[0017] According to a preferred embodiment, when a rapid increase in load is required, the first regulating valve and the second regulating valve are fully closed, and the extraction steam regulating valve is quickly closed to directly increase the steam intake of the turbine low-pressure cylinder, thereby increasing the output of the turbine low-pressure cylinder and achieving a rapid increase in load. At the same time, the first low-pressure heater extraction steam regulating valve and the second low-pressure heater extraction steam regulating valve are opened to keep the outlet water temperature of the first low-pressure heater constant.

[0018] When it is necessary to increase the load rate, while closing the extraction steam regulating valve, the extraction steam regulating valves of the first low-pressure heater and the second low-pressure heater are closed. At this time, the condensate water temperature entering the first low-pressure heater and the second low-pressure heater continues to decrease, and when it decreases to the preset value, the extraction steam regulating valves of the first low-pressure heater and the second low-pressure heater are reopened.

[0019] According to a preferred embodiment, when it is necessary to rapidly reduce the load, the first regulating valve and the second regulating valve are fully opened, the extraction steam regulating valve is rapidly opened, the steam intake of the intermediate pressure cylinder of the steam turbine is directly reduced, the output of the intermediate pressure cylinder of the steam turbine is reduced, and the load is rapidly reduced. Then the first regulating valve and the second regulating valve are closed to ensure that the outlet water temperature of the first low-pressure heater remains unchanged.

[0020] When it is necessary to increase the load reduction rate, while opening the extraction steam regulating valve, the first regulating valve and the second regulating valve are not closed. At this time, the condensate water temperature of the first low-pressure heater and the second low-pressure heater continues to rise. When it rises to the threshold, the extraction steam regulating valve of the first low-pressure heater and the extraction steam regulating valve of the second low-pressure heater are closed to reduce the condensate water temperature.

[0021] The aforementioned main solution of the present invention and its various further alternative solutions can be freely combined to form multiple solutions, all of which are solutions that can be adopted and are claimed by the present invention. Those skilled in the art, after understanding the solution of the present invention, will realize that there are many combinations based on existing technology and common knowledge, all of which are technical solutions to be protected by the present invention, and will not be exhaustively listed here.

[0022] The beneficial effects of this invention are:

[0023] This invention's peak-shaving system adds a primary air heater, extracting a portion of steam from the turbine's intermediate-pressure cylinder exhaust to heat the air-coal mixture. During load changes, adjusting the extraction steam volume rapidly alters the steam intake to the turbine's low-pressure cylinder, thus achieving rapid load changes. Compared to conventional regenerative systems, this invention uses intermediate-pressure cylinder exhaust to heat the air-coal mixture, replacing the extraction steam from the first and second low-pressure heaters with the heated exhaust steam. While the low-pressure cylinder extraction volume remains the same, the extraction point is advanced, increasing the degree of regeneration, improving thermal system efficiency, increasing the total enthalpy of the extracted steam, and increasing the heat storage capacity of the regenerative system. Furthermore, using the air-coal mixture as an additional heat storage medium ensures that the temperature of the air-coal mixture changes first during rapid load changes, rather than the condensate temperature, resulting in more stable thermal system operation. Additionally, heating the air-coal mixture at low loads improves the stable combustion performance of pulverized coal. Compared to heat storage systems equipped with additional heat storage media, this system does not require additional heat storage devices or media, making it simpler and less expensive than traditional heat storage devices. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the system structure of the peak-shaving system of the present invention;

[0025] Among them, 1-Pulverizing system, 2-Pulverized coal conveying pipeline, 3-Primary air heater, 4-Pulverized coal distributor, 5-Steam turbine low-pressure cylinder, 6-First low-pressure heater, 7-Second low-pressure heater, 8-First regulating valve, 9-First low-pressure heater extraction steam regulating valve, 10-Second regulating valve, 11-Second low-pressure heater extraction steam regulating valve, 12-Extraction steam regulating valve. Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0030] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] Furthermore, it should be noted that, unless otherwise specified, the structures, connections, positions, power sources, etc. involved in this invention are all things that a person skilled in the art can know without creative effort based on the prior art.

[0032] refer to Figure 1 As shown, the present invention discloses a peak-shaving system for heating a coal-air mixture using extraction steam, comprising: a pulverizing system 1, a coal feeding pipeline 2, a primary air heater 3, a coal powder distributor 4, a low-pressure cylinder of a steam turbine 5, a first low-pressure heater 6, a second low-pressure heater 7, a first regulating valve 8, a first low-pressure heater extraction steam regulating valve 9, a second regulating valve 10, a second low-pressure heater extraction steam regulating valve 11, and an extraction steam regulating valve 12.

[0033] The arrangement sequence of the pulverizing system 1, pulverized coal feeding pipeline 2, pulverized coal distributor 4, turbine low-pressure cylinder 5, first low-pressure heater 6, and second low-pressure heater 7 is the same as that of conventional units. On the basis of conventional coal-fired units, a primary air heater 3, a first regulating valve 8, a first low-pressure heater extraction steam regulating valve 9, a second regulating valve 10, a second low-pressure heater extraction steam regulating valve 11, and an extraction steam regulating valve 12 are added.

[0034] The pulverizing system 1, the pulverizing pipeline 2, the primary air heater 3, and the pulverized coal distributor 4 are connected in sequence. The pulverized coal generated by the pulverizing system is carried into the pulverizing pipeline 2 by the primary air. The air-pulverized coal mixture is heated by the primary air heater 3 and then enters the pulverized coal distributor 4. The steam inlet of the low-pressure cylinder 5 of the steam turbine is the exhaust steam from the intermediate-pressure cylinder of the steam turbine. A portion of the intermediate-pressure cylinder exhaust steam is extracted and enters the primary air heater 3. The intermediate-pressure cylinder exhaust steam heats the air-pulverized coal mixture in the primary air heater 3. The amount of intermediate-pressure cylinder exhaust steam extracted is adjusted by the extraction steam regulating valve 12.

[0035] After heat exchange, the exhaust steam is divided into two streams and enters the first low-pressure heater extraction pipeline of the first low-pressure heater 6 and the second low-pressure heater extraction pipeline of the second low-pressure heater 7 respectively. The distribution of the steam flow of the two streams is controlled by the first low-pressure heater extraction regulating valve 9 and the second low-pressure heater extraction regulating valve 11.

[0036] The first low-pressure heater 6 is also connected to the low-pressure cylinder 5 of the steam turbine, and a first regulating valve 8 is provided on the corresponding connecting pipeline; the second low-pressure heater 7 is also connected to the low-pressure cylinder 5 of the steam turbine, and a second regulating valve 10 is provided on the corresponding connecting pipeline. The first regulating valve 8 and the second regulating valve 10 are closed when the steam extraction rate of the primary air heater reaches its maximum, and can be selectively opened when the steam extraction rate decreases, in order to regulate the condensate temperature at the outlet of the first low-pressure heater 6 and the second low-pressure heater 7.

[0037] In practical operation, the thermal system of a subcritical coal-fired power unit typically consists of three high-pressure heaters, one deaerator, and three low-pressure heaters. The working fluid temperature, from highest to lowest, is sequentially assigned to high-pressure heaters No. 1, 2, and 3, the deaerator, and low-pressure heaters No. 5, 6, and 7. Condensate from the condenser, after being pressurized by the condensate pump, sequentially enters low-pressure heaters No. 7, 6, and 5, and then the deaerator. The working fluid at the deaerator outlet is called boiler feedwater, which, after being heated by the feedwater pump, sequentially enters high-pressure heaters No. 3, 2, and 1, and finally the boiler economizer. For working fluid temperature matching, this invention focuses on low-pressure heaters No. 6 and 7.

[0038] Low-pressure heaters: The function of low-pressure heaters is to heat the condensate from the condenser. Steam drum boilers typically have three stages of low-pressure heaters connected in series. The working fluid entering the low-pressure heaters is condensate that has been pressurized by the condensate pump and superheated steam extracted from the intermediate or low-pressure cylinder of the turbine. The two working fluids do not mix directly. After heat exchange, the condensate enters the next stage of low-pressure heater and finally enters the deaerator. The extracted superheated steam cools down and condenses, becoming condensate that ultimately enters the condenser.

[0039] Control methods:

[0040] When the system is running in normal steady state, the extraction steam regulating valve 12 is used to regulate the extraction steam volume of the primary air heater 3, the extraction steam regulating valve 9 of the first low-pressure heater and the extraction steam regulating valve 11 of the second low-pressure heater are used to regulate the flow distribution, and the first regulating valve 8 and the second regulating valve 10 are used in conjunction with the extraction steam regulating valve 12 to regulate the amount of steam entering the first low-pressure heater 6 and the second low-pressure heater, so that the condensate temperature at the outlet of the first low-pressure heater 6 and the second low-pressure heater is consistent with that of conventional units.

[0041] When the unit is at a low load and a rapid load increase is anticipated, the first regulating valve 8 and the second regulating valve 10 can be fully closed in advance, with steam extracted only from the intermediate-pressure cylinder. When the power grid issues a load increase command, the extraction regulating valve 12 is quickly closed to directly increase the steam intake of the low-pressure cylinder, thereby increasing the output of the low-pressure cylinder and achieving a rapid load increase. At the same time, the first low-pressure heater extraction regulating valve 9 and the second low-pressure heater extraction regulating valve 11 are opened to keep the outlet water temperature of the low-pressure heater constant.

[0042] If it is necessary to further increase the load increase rate, the first low-pressure heater extraction steam regulating valve 9 and the second low-pressure heater extraction steam regulating valve 11 can be closed when the extraction steam regulating valve 12 is closed. At this time, the condensate temperature entering the low-pressure heater will drop rapidly. After reaching the low limit, the first low-pressure heater extraction steam regulating valve 9 and the second low-pressure heater extraction steam regulating valve 11 need to be opened in time to increase the condensate temperature.

[0043] When the unit is under high load, a rapid load reduction is expected, so the first regulating valve 8 and the second regulating valve 10 can be fully opened in advance. When the power grid issues a load reduction command, the extraction steam regulating valve 12 is quickly opened to directly reduce the steam intake of the turbine's low-pressure cylinder 5, thereby reducing the output of the turbine's low-pressure cylinder 5 and achieving a rapid load reduction. At the same time, the first regulating valve 8 and the second regulating valve 10 are closed to ensure that the outlet water temperature of the first low-pressure heater remains unchanged.

[0044] If it is necessary to further increase the load reduction rate, the first regulating valve 8 and the second regulating valve 10 can be opened while the extraction steam regulating valve 12 is not closed. At this time, the condensate temperature entering the low-pressure heater will rise rapidly. After reaching the high limit, the first low-pressure heater extraction steam regulating valve 9 and the second low-pressure heater extraction steam regulating valve 11 need to be closed in time to reduce the condensate temperature.

[0045] It should be noted that the improvement of the variable load rate of coal-fired units by the present invention is limited by the condensate temperature, and the amount of steam extracted that the first low-pressure heater and the second low-pressure heater can absorb cannot be increased indefinitely.

[0046] This invention's peak-shaving system adds a primary air heater, extracting a portion of steam from the turbine's intermediate-pressure cylinder exhaust to heat the air-coal mixture. During load changes, adjusting the extraction steam volume rapidly alters the steam intake to the turbine's low-pressure cylinder, thus achieving rapid load changes. Compared to conventional regenerative systems, this invention uses intermediate-pressure cylinder exhaust to heat the air-coal mixture, replacing the extraction steam from the first and second low-pressure heaters with the heated exhaust steam. While the low-pressure cylinder extraction volume remains the same, the extraction point is advanced, increasing the degree of regeneration, improving thermal system efficiency, increasing the total enthalpy of the extracted steam, and increasing the heat storage capacity of the regenerative system. Furthermore, using the air-coal mixture as an additional heat storage medium ensures that the temperature of the air-coal mixture changes first during rapid load changes, rather than the condensate temperature, resulting in more stable thermal system operation. Additionally, heating the air-coal mixture at low loads improves the stable combustion performance of pulverized coal. Compared to heat storage systems equipped with additional heat storage media, this system does not require additional heat storage devices or media, making it simpler and less expensive than traditional heat storage devices.

[0047] Example 1:

[0048] Taking a 330MW subcritical unit as an example, before the steam (pressure 0.52MPa, temperature 285℃, flow rate 767661kg / h) from the intermediate pressure cylinder of the steam turbine enters the low pressure cylinder 5 of the steam turbine, a steam extraction channel is set up to extract part of the steam (flow rate 75000kg / h) and enter the primary air heater 3. In the primary air heater 3, the steam heats the air-coal mixture from 65℃ to 100℃.

[0049] After heat exchange, the exhaust steam (temperature 183℃) is divided into two streams and enters the first low-pressure heater extraction pipeline of the first low-pressure heater 6 (flow rate 24500kg / h) and the second low-pressure heater extraction pipeline of the second low-pressure heater 7 (flow rate 50500kg / h).

[0050] A first regulating valve 8 is installed in the extraction steam pipeline, and a second regulating valve 10 is installed in the extraction steam pipeline of the second low-pressure heater. Both regulating valves 8 and 10 are closed when the extraction steam flow of the primary air heater 3 is at its maximum. When the extraction steam flow of the primary air heater 3 decreases, the first regulating valve 8 and 10 can be selectively opened to regulate the condensate temperature at the outlet of the first low-pressure heater. When it is necessary to shut down the system, the first low-pressure heater extraction steam regulating valve 9, the second low-pressure heater extraction steam regulating valve 11, and the extraction steam regulating valve 12 are closed, and the first regulating valve 8 and 10 are opened.

[0051] Control methods:

[0052] When the system is operating in normal steady state, the extraction steam flow rate of the primary air heater is adjusted using extraction steam regulating valve 12, and the flow distribution is adjusted using extraction steam regulating valve 9 of the first low-pressure heater and extraction steam regulating valve 11 of the second low-pressure heater. The steam flow rate entering the first low-pressure heater 6 and the second low-pressure heater is adjusted using the first regulating valve 8 and the second regulating valve 10 in conjunction with extraction steam regulating valve 12, so that the condensate temperature at the outlet of the first low-pressure heater 6 and the second low-pressure heater 7 is consistent with that of conventional units. Taking a 330MW subcritical unit as an example, the condensate temperature at the outlet of the first low-pressure heater is 114℃, and the condensate temperature at the outlet of the No. 5 low-pressure heater is 96℃. At this time, the primary air temperature carrying pulverized coal can be increased from 65℃ to a maximum of 100℃, and the maximum extraction steam flow rate of the primary air heater is 75t / h, which accounts for approximately 9.8% of the total exhaust flow rate of the intermediate-pressure cylinder.

[0053] When the unit is under low load and a rapid load increase is anticipated, the first regulating valve 8 and the second regulating valve 10 can be fully closed in advance, with steam extracted only from the intermediate-pressure cylinder. When the power grid issues a load increase command, the extraction regulating valve 12 is quickly closed to directly increase the steam intake of the low-pressure cylinder, thereby increasing its output and achieving a rapid load increase. Correspondingly, the temperature of the air-coal mixture decreases from 100℃ to a minimum of 65℃, and the outlet water temperature of the first low-pressure heater 6 decreases to a minimum of 56℃. At this point, the condensate temperature entering the low-pressure heater drops rapidly. If it is necessary to maintain the low-pressure heater temperature, the outlet water temperature of the first low-pressure heater can be kept constant at 114℃ by opening the first low-pressure heater extraction regulating valve 9 and the second low-pressure heater extraction regulating valve 11.

[0054] When the unit is under high load and a rapid load reduction is anticipated, the first regulating valve 8 and the second regulating valve 10 can be fully opened in advance. Upon receiving a load reduction command from the power grid, the extraction steam regulating valve 12 is quickly opened, while the first regulating valve 8 and the second regulating valve 10 are closed, directly reducing the steam intake of the low-pressure cylinder and lowering its output, thus achieving a rapid load reduction. Correspondingly, the temperature of the air-coal mixture rises from 65℃ to a maximum of 100℃, while the outlet water temperature of the first low-pressure heater remains constant at 114℃.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A peak-shaving system that utilizes extracted steam to heat a mixture of air and pulverized coal, characterized in that, The peak-shaving system includes: a pulverizing system (1), a pulverizing pipeline (2), a primary air heater (3), a pulverized coal distributor (4), and a low-pressure cylinder of a steam turbine (5); The pulverizing system (1) is provided with a pulverizing pipe (2) at the outlet end, and the pulverizing pipe (2) is connected to the pulverized coal distributor (4) via a primary air heater (3); The steam inlet of the low-pressure cylinder (5) of the steam turbine receives high-temperature steam discharged from the intermediate-pressure cylinder of the steam turbine, and the steam inlet of the low-pressure cylinder (5) of the steam turbine is provided with a steam extraction pipeline. The steam extraction pipeline is connected to the primary air heater (3) and introduces high-temperature steam discharged from the intermediate-pressure cylinder of the steam turbine into the primary air heater (3) to heat the air-coal mixture in the coal feeding pipeline (2). By adjusting the steam extraction rate in the steam extraction pipeline, the steam inlet of the low-pressure cylinder (5) of the steam turbine is changed, so as to achieve rapid change of the load of the corresponding unit. The peak-shaving system also includes: a first low-pressure heater (6) and a second low-pressure heater (7); The exhaust end of the primary air heater (3) is connected to the first low-pressure heater (6) and the second low-pressure heater (7) via the first low-pressure heater extraction pipe and the second low-pressure heater extraction pipe, respectively. The first low-pressure heater (6) is also connected to the low-pressure cylinder (5) of the steam turbine, and a first regulating valve (8) is provided on the corresponding connecting pipeline. The second low-pressure heater (7) is also connected to the low-pressure cylinder (5) of the steam turbine, and a second regulating valve (10) is provided on the corresponding connecting pipeline.

2. The peak-shaving system as described in claim 1, characterized in that, The extraction pipeline is equipped with an extraction regulating valve (12) to control the amount of steam extracted from the steam inlet of the low-pressure cylinder (5) of the steam turbine.

3. The peak-shaving system as described in claim 1, characterized in that, The first low-pressure heater extraction steam regulating valve (9) is provided on the first low-pressure heater extraction steam pipeline.

4. The peak-shaving system as described in claim 1, characterized in that, The second low-pressure heater extraction steam regulating valve (11) is provided on the second low-pressure heater extraction steam pipeline.

5. The peak-shaving system as described in claim 1, characterized in that, When the system is in steady state, the steam extraction amount is adjusted by the extraction steam regulating valve (12), the flow distribution is adjusted by the extraction steam pipeline of the first low-pressure heater and the extraction steam pipeline of the second low-pressure heater, and the steam entering the first low-pressure heater (6) and the second low-pressure heater (7) is controlled by the first regulating valve (8) and the second regulating valve (10), so that the condensate temperature at the outlet of the first low-pressure heater (6) and the second low-pressure heater (7) is consistent with that of the conventional unit.

6. The peak-shaving system as described in claim 1, characterized in that, When a rapid increase in load is required, the first regulating valve (8) and the second regulating valve (10) are fully closed, and the extraction steam regulating valve (12) is quickly closed to directly increase the steam intake of the turbine low-pressure cylinder (5), thereby increasing the output of the turbine low-pressure cylinder (5) and achieving a rapid increase in load. At the same time, the first low-pressure heater extraction steam regulating valve (9) and the second low-pressure heater extraction steam regulating valve (11) are opened to keep the outlet water temperature of the first low-pressure heater (6) constant. When it is necessary to increase the load rate, while closing the extraction steam regulating valve (12), the extraction steam regulating valve (9) of the first low-pressure heater and the extraction steam regulating valve (11) of the second low-pressure heater are closed. At this time, the condensate water temperature entering the first low-pressure heater (6) and the second low-pressure heater (7) continues to decrease, and when it decreases to the preset value, the extraction steam regulating valve (9) of the first low-pressure heater and the extraction steam regulating valve (11) of the second low-pressure heater are reopened.

7. The peak-shaving system as described in claim 1, characterized in that, When it is necessary to quickly reduce the load, the first regulating valve (8) and the second regulating valve (10) are fully opened, and the extraction steam regulating valve (12) is quickly opened to directly reduce the steam intake of the turbine low-pressure cylinder (5), reduce the output of the turbine low-pressure cylinder (5), and achieve a rapid reduction in load. Then the first regulating valve (8) and the second regulating valve (10) are closed to ensure that the outlet water temperature of the first low-pressure heater (6) remains unchanged. When it is necessary to increase the load reduction rate, while opening the extraction steam regulating valve (12), the first regulating valve (8) and the second regulating valve (10) are not closed. At this time, the condensate water temperature of the first low-pressure heater (6) and the second low-pressure heater (7) continues to rise. When it rises to the threshold, the extraction steam regulating valve (9) of the first low-pressure heater and the extraction steam regulating valve (11) of the second low-pressure heater are closed to reduce the condensate water temperature.

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