Feedwater heating-based deep peak regulation system

Abstract

A feedwater heating-based deep peak regulation system, relating to the technical field of power generation. Steam of a higher pressure level is introduced to replace extraction steam of an existing final-stage high-pressure heater, and a certain feedwater pressure is maintained to enable feedwater at an economizer outlet to be kept at a certain subcooling degree, so that a boiler inlet feedwater temperature of a unit under a deep peak regulation working condition is increased, thereby increasing an economizer inlet water temperature, an economizer outlet water temperature and an economizer outlet flue gas temperature, reducing an enthalpy deficit at the inlet of a water-cooled wall, shortening a hot water section in the water-cooled wall, and keeping the steam at the outlet of the water-cooled wall at a certain superheat degree. Finally, boiler dry-operation of the unit under the deep peak regulation working condition is achieved, the hydrodynamic stability is maintained, and a denitration system is continuously and stably put into operation.

Description

A deep peak-shaving system based on feedwater heating

[0001] This application claims the benefit of Chinese Patent Application No. 2023117673169, filed December 20, 2023. This application incorporates the entirety of the aforementioned Chinese Patent Application. Technical Field

[0002] The present invention relates to the technical field of power generation, and in particular to a deep peak regulation system based on feedwater heating. Background Art

[0003] Currently, ultra-supercritical (USC) units, featuring high performance, large capacity, high efficiency, and low carbon emissions, have become the mainstream choice for new thermal power plant construction. These units primarily feature capacities of 350MW, 660MW, and 1000MW, with a smaller number of 1200MW and 1350MW units also available.

[0004] With the establishment of carbon peak and comprehensive carbon targets (the "30, 60" plan), new energy installed capacity and power generation have reached new highs. Because new energy power generation methods have uncertainty in power generation, traditional thermal power units, especially coal-fired power units, must assume the role of basic power supply and flexible peak-shaving power supply to cooperate with new energy power generation.

[0005] Taking a 1000MW ultra-supercritical unit as an example, the regional grid dispatch load range is 40%-100% THA. The boiler feedwater flow corresponding to this unit's load is higher than the minimum flow required for the boiler to maintain dry operation. Therefore, within the current normal load dispatch range, the boiler always maintains dry operation without any dry-wet state transition. However, with the rapid development of renewable energy, this unit is now required to operate in deep peak-shaving mode, and the load dispatch lower limit must be lowered to 20%. The boiler feedwater flow corresponding to 20% load is already lower than the minimum flow required for the boiler to maintain dry operation, forcing the boiler to switch to wet operation. Therefore, the unit operation faces many problems. For example, under deep peak-shaving conditions, the boiler frequently switches between dry and wet states, making the control of coal, water, and air very difficult, and the risk of boiler shutdown increases sharply. Under deep peak-shaving conditions, the water-wall inlet feedwater deficit increases, the hydrodynamic stability of the boiler water-wall is poor, and the risk of water-wall overheating and tube burst increases sharply. Under deep peak-shaving conditions, the flue gas temperature at the economizer outlet will fall below the lower temperature limit for normal operation of conventional denitrification catalysts (such as 300°C), and the denitrification system will not be able to operate normally. NOx emissions are expected to surge and far exceed the standard requirements (for example, the emission index will surge from 25mg / Nm3 to over 200mg / Nm3, far exceeding the standard value of 50mg / Nm3). Under wet boiler operation conditions, if the water separated from the steam-water separator at the boiler water-wall outlet is directly discharged into the atmospheric expansion tank, a large amount of working fluid and energy will be lost, which will significantly increase the unit's energy consumption and significantly reduce its operating economy. Therefore, how to maintain dry operation of the boiler under deep peak-shaving conditions, and maintain hydrodynamic stability and continuous and stable operation of the denitrification system has become an urgent problem that needs to be solved.

[0006] Therefore, technicians in this field are committed to developing a deep peak-shaving system based on feed water heating to achieve dry operation of the boiler under deep peak-shaving conditions, maintain hydrodynamic stability, and ensure continuous and stable operation of the denitrification system.

[0007] Summary of the Invention

[0008] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to maintain the dry operation of the boiler under deep peak-shaving conditions, and maintain the hydrodynamic stability and continuous and stable operation of the denitrification system.

[0009] To achieve the above-mentioned objectives, the present invention provides a deep peak-shaving system based on feedwater heating, which is characterized in that it includes a deaerator, a pre-pump, a feedwater pump, an existing final-stage high-pressure heater, a boiler, a main steam throttling assembly, a high-pressure cylinder, and a steam extraction isolation valve. The low-pressure condensate at the outlet of the deaerator is pressurized by the pre-pump and the feedwater pump in sequence and then enters the existing final-stage high-pressure heater for heating. The heated feedwater enters the boiler and is heated in sequence by the economizer, water-cooled wall, and superheater heating surface to finally obtain main steam that enters the high-pressure cylinder to perform work.

[0010] The high-pressure cylinder steam inlet valve group is arranged on the high-pressure cylinder steam inlet pipeline;

[0011] The steam inlet source of the existing final stage high pressure heater is the heat recovery extraction steam of the high pressure cylinder. The steam inlet pipe of the existing final stage high pressure heater is provided with an extraction steam isolation valve.

[0012] A cooling module is set in the main steam pipeline from the boiler superheater outlet to the high-pressure cylinder. Cooling water enters the cooling module and mixes with the main steam entering the cooling module. The steam at the outlet of the cooling module is connected to the existing final-stage high-pressure heater steam inlet pipeline through a pipeline. The interface position is located in the downstream pipeline of the extraction isolation valve in the existing final-stage high-pressure heater steam inlet pipeline. By introducing steam with a higher pressure level than the reheat extraction steam of the existing final-stage high-pressure heater into the existing final-stage high-pressure heater, the inlet water temperature of the unit under deep peak-shaving conditions is improved.

[0013] In a preferred embodiment of the present invention, the temperature reduction module includes an isolation valve, a pressure reducing valve and a temperature reducer which are sequentially connected through pipelines.

[0014] In a preferred embodiment of the present invention, the steam with a higher pressure grade than the heat recovery extraction steam of the existing final high-pressure heater is the main steam or superheater steam of the unit or steam from a non-unit.

[0015] In a preferred embodiment of the present invention, a mixer is provided between the outlet of the desuperheater and the steam inlet of the final high-pressure heater, and the steam at the outlet of the desuperheater is mixed with the heat recovery extraction steam of the existing final high-pressure heater or steam with a lower pressure level in the mixer. On the premise that the steam pressure at the outlet of the mixer is higher than the heat recovery extraction steam of the existing final high-pressure heater, the mixed steam enters the existing final high-pressure heater to heat the feed water.

[0016] In a preferred embodiment of the present invention, a heat exchanger is additionally provided, and the heat exchanger is located between the steam extraction isolation valve of the steam extraction pipe at the high-pressure cylinder outlet and the steam inlet of the existing final-stage high-pressure heater, and between the outlet of the desuperheater and the steam inlet of the existing final-stage high-pressure heater.

[0017] In a preferred embodiment of the present invention, a heat exchanger is provided between the mixer outlet and the steam inlet of the existing final high-pressure heater, and a heat exchanger is provided at the steam inlet of the existing final high-pressure heater.

[0018] In a preferred embodiment of the present invention, the mixer is a pressure matcher.

[0019] In a preferred embodiment of the present invention, the main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.

[0020] In a preferred embodiment of the present invention, the main steam throttling assembly is used to throttle the main steam to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of subcooling.

[0021] In a preferred embodiment of the present invention, a throttling component is provided in the feed water or steam piping system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

[0022] Technical Effects

[0023] The deep peak-shaving system based on feed water heating targets the existing last-stage high-pressure heater and its extraction steam of the unit. It replaces the extraction steam of the existing last-stage high-pressure heater by introducing steam of higher pressure grade, while maintaining a certain feed water pressure so that the feed water at the economizer outlet maintains a certain degree of subcooling, so as to increase the unit's inlet feed water temperature under deep peak-shaving conditions, thereby increasing the economizer inlet water temperature, economizer outlet water temperature, economizer outlet flue gas temperature, reducing the water-wall inlet enthalpy deficiency, shortening the hot water section in the water-wall and maintaining a certain degree of superheat of the water-wall outlet steam, ultimately achieving the unit's boiler dry operation under deep peak-shaving conditions, maintaining hydrodynamic stability, and continuous and stable operation of the denitrification system.

[0024] The higher pressure steam used to replace the existing final stage high-pressure steam extraction steam can come from: the main steam of this unit or other units, the steam in the superheater system, or a mixture of the above steam and other relatively low pressure steam (such as unit heat recovery extraction steam, reheat steam, etc.).

[0025] At the same time, maintain a certain feed water pressure and keep the economizer outlet feed water at a certain subcooling degree.

[0026] Furthermore, as the economizer outlet water temperature increases, the water wall inlet water temperature also increases, thereby reducing the water wall inlet enthalpy deficit and enhancing the hydrodynamic stability.

[0027] Furthermore, as the water temperature at the water wall inlet increases, the steam at the water wall outlet can maintain a certain degree of superheat, that is, the boiler can be operated in a dry state.

[0028] The present invention introduces steam of higher pressure grade to replace the extraction steam of the existing last-stage high-pressure heater, so as to increase the feed water temperature of the unit under deep peak-shaving conditions, thereby realizing the dry operation of the boiler under deep peak-shaving conditions (such as 20% THA or even lower), maintaining the hydrodynamic stability, and continuously and stably putting the denitrification system into operation, while avoiding large-scale transformation of the boiler and turbine thermal systems, better adapting to the wide load range operation of the unit in response to deep peak-shaving of the power grid, and improving the economy and flexibility of the unit operation.

[0029] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic diagram of a conventional boiler feed water heating system.

[0031] FIG2 is a schematic diagram of heating feed water into a boiler according to the present invention.

[0032] FIG3 is a schematic diagram of a heating steam system according to a preferred embodiment.

[0033] FIG4 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0034] FIG5 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0035] FIG6 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0036] FIG7 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0037] FIG8 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0038] FIG9 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0039] FIG10 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0040] FIG11 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0041] FIG12 is a schematic diagram of a heating steam system according to another preferred embodiment.

[0042] FIG13 is a schematic diagram of a heating steam system according to another preferred embodiment. DETAILED DESCRIPTION

[0043] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0044] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0045] As shown in Figure 1, in the existing boiler feed water heating system, the low-pressure condensate at the deaerator outlet is pressurized by the pre-pump and feed water pump in sequence and then enters the high-pressure heater for heating. The heated feed water enters the boiler and is heated by the economizer, water-cooled wall, superheater and other heating surfaces in sequence, and finally the main steam is obtained and enters the high-pressure cylinder to perform work.

[0046] in:

[0047] A high-pressure cylinder steam inlet valve group is arranged on the high-pressure cylinder steam inlet pipeline, which can adjust the pressure and flow of the main steam.

[0048] The steam inlet source of the existing last-stage high-pressure heater is the heat recovery extraction steam of the high-pressure cylinder. An extraction steam isolation valve is arranged on the steam inlet pipeline of the last-stage high-pressure heater.

[0049] Implementation Method 1

[0050] The schematic diagram of the feed water heating for the boiler of this application is shown in FIG2 . The low-pressure condensate at the outlet of the deaerator is pressurized by the pre-pump and the feed water pump in sequence and then enters the high-pressure heater for heating. The heated feed water enters the boiler and is heated by the economizer, water-cooled wall, superheater and other heating surfaces in sequence, and finally the main steam is obtained and enters the high-pressure cylinder to perform work.

[0051] At the same time, part of the main steam is extracted from the main steam pipeline between the boiler superheater outlet and the high-pressure cylinder, and enters the desuperheater through the isolation valve and the pressure reducing valve in sequence to be mixed with the desuperheating water. The steam at the desuperheater outlet is connected to the existing last-stage high-pressure heater steam inlet pipeline through a pipeline. The interface position is located at a suitable position in the downstream pipeline of the extraction isolation valve in the existing last-stage high-pressure heater steam inlet pipeline, so that the steam at the desuperheater outlet replaces the existing last-stage high-pressure heater heat recovery extraction steam, so as to improve the unit's inlet water temperature under deep peak regulation conditions.

[0052] Among them, when the unit is running, the pressure of the steam at the desuperheater outlet will be relatively higher than the heat recovery extraction steam of the existing last-stage high-pressure heater, and when the steam at the desuperheater outlet heats the feed water in the existing last-stage high-pressure heater, the extraction isolation valve on the existing last-stage high-pressure heater extraction steam pipeline is in a closed state.

[0053] At the same time, the high-pressure cylinder steam inlet valve group is used to throttle the main steam to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling. It should be emphasized here that when introducing steam with a higher pressure grade than the existing final-stage high-pressure heater reheat extraction steam to increase the unit's boiler feedwater temperature under deep peak-shaving conditions, the high-pressure cylinder steam inlet valve group is operated to throttle the main steam using the original high-pressure cylinder steam inlet valve group to maintain a certain feedwater pressure so that the economizer outlet feedwater maintains a certain degree of subcooling. This is used to increase the unit's boiler feedwater temperature under deep peak-shaving conditions, thereby increasing the economizer inlet and outlet water temperatures, increasing the economizer outlet flue gas temperature, reducing the water wall inlet enthalpy deficit, shortening the hot water section in the water wall, and maintaining a certain degree of superheat at the water wall outlet steam. While increasing the boiler feedwater temperature, vaporization of the feedwater between the economizer outlet and the water wall inlet is prevented. Ultimately, dry boiler operation of the unit under deep peak-shaving conditions is achieved, maintaining hydrodynamic stability, and continuously and stably operating the denitrification system. It should be noted that a throttling component (such as a regulating valve, etc.) can also be installed in the water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain water feed pressure (the throttling component installed in the water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet is not shown in Figures 1 to 13).

[0054] So, under deep peak load regulation conditions, taking 20% ​​THA conditions as an example:

[0055] The feed water temperature of the unit can be increased to 75% THA or even 100% THA;

[0056] Furthermore, as the feed water temperature of the unit increases, the economizer inlet water temperature is increased, and then the economizer outlet water temperature is increased, and the economizer outlet flue gas temperature is increased and meets the denitrification inlet flue gas temperature requirement;

[0057] Furthermore, while the outlet water temperature of the economizer is increased, a certain feed water pressure is maintained, so that the outlet feed water of the economizer maintains a certain degree of subcooling;

[0058] Furthermore, as the economizer outlet water temperature increases, the water wall inlet water temperature also increases, thereby reducing the water wall inlet enthalpy deficit and enhancing the hydrodynamic stability.

[0059] Furthermore, as the water temperature at the water wall inlet increases, the steam at the water wall outlet can maintain a certain degree of superheat, that is, the boiler can be operated in a dry state.

[0060] Implementation Method 2

[0061] As shown in Figure 3, part of the extracted main steam is optimized to be used as steam in the superheater system, such as the steam in the superheater intermediate header. Since the temperature of the steam in the superheater intermediate header will be lower than the main steam temperature, the use of related high-temperature grade pipelines can be reduced.

[0062] Implementation 3

[0063] As shown in Figure 4, based on the above scheme, part of the extracted main steam is optimized to be converted into superheated steam or heat recovery extraction steam for other units. Under the premise that the steam pressure at the desuperheater outlet is higher than the existing last-stage high-pressure heat recovery extraction steam, the operating flexibility of this unit is improved.

[0064] Implementation 4

[0065] As shown in Figure 5, on the basis of the above scheme, the steam at the outlet of the desuperheater is mixed with the heat recovery extraction steam of the existing last-stage high-pressure heater (the extraction isolation valve on the existing last-stage high-pressure heater extraction pipe is in an open state) or steam with a lower pressure level in a mixer (such as a pressure matcher, etc.). Under the premise that the steam pressure at the outlet of the mixer is higher than the heat recovery extraction steam of the existing last-stage high-pressure heater, the mixed steam enters the existing last-stage high-pressure heater to heat the feed water.

[0066] Implementation 5

[0067] As shown in Figure 6, based on the above scheme, the extracted part of the main steam is optimized to steam in the superheater system, such as steam in the superheater intermediate header; at the same time, the steam at the outlet of the desuperheater is mixed with the heat recovery extraction steam of the existing last-stage high-pressure heater (the extraction isolation valve on the existing last-stage high-pressure heater extraction pipeline is in the open state) or steam with a lower pressure level in a mixer (such as a pressure matcher, etc.). Under the premise that the steam pressure at the outlet of the mixer is higher than the heat recovery extraction steam of the existing last-stage high-pressure heater, the mixed steam enters the existing last-stage high-pressure heater to heat the feed water.

[0068] Implementation Method 6

[0069] As shown in Figure 7, based on the above scheme, part of the extracted main steam is optimized to be superheated steam or heat recovery extraction steam of other units. On the premise that the steam pressure at the outlet of the desuperheater is higher than the heat recovery extraction steam of the existing last-stage high-pressure heater, the steam at the outlet of the desuperheater is mixed with the heat recovery extraction steam of the existing last-stage high-pressure heater (the extraction isolation valve on the existing last-stage high-pressure heater extraction pipe is in an open state) or steam with a lower pressure level in a mixer (such as a pressure matcher, etc.). On the premise that the steam pressure at the outlet of the mixer is higher than the heat recovery extraction steam of the existing last-stage high-pressure heater, the mixed steam enters the existing last-stage high-pressure heater to heat the feed water.

[0070] Implementation 7

[0071] As shown in Figure 8, on the basis of the above scheme, a heat exchanger is added to the existing last-stage high-pressure heater steam inlet pipe. The steam can heat other working media (such as air, water, coal, etc.) in the heat exchanger, and then enter the existing last-stage high-pressure heater to heat the feed water. In this way, the steam inlet flow rate of the existing last-stage high-pressure heater can be relatively increased.

[0072] Implementation 8

[0073] As shown in Figure 9, based on the above scheme, part of the extracted main steam is optimized to steam in the superheater system, such as the steam in the superheater intermediate header. Since the temperature of the steam in the superheater intermediate header will be lower than the main steam temperature, the use of related high-temperature grade pipelines can be reduced; at the same time, a heat exchanger is added to the existing last-stage high-pressure heater inlet steam pipeline. The steam can heat other working media (such as air, water, coal, etc.) in the heat exchanger, and then enter the existing last-stage high-pressure heater to heat the feed water. In this way, the inlet steam flow rate of the existing last-stage high-pressure heater can be relatively increased.

[0074] Implementation Method 9

[0075] As shown in Figure 10, based on the above scheme, part of the extracted main steam is optimized to be superheated steam or heat recovery extraction steam of other units. Under the premise that the steam pressure at the outlet of the desuperheater is higher than the heat recovery extraction steam of the existing last-stage high-pressure heater, the operating flexibility of this unit is improved; at the same time, a heat exchanger is added to the steam inlet pipeline of the existing last-stage high-pressure heater. The steam can heat other working media (such as air, water, coal, etc.) in the heat exchanger, and then enter the existing last-stage high-pressure heater to heat the feed water. In this way, the steam inlet flow rate of the existing last-stage high-pressure heater can be relatively increased.

[0076] Implementation 10

[0077] As shown in Figure 11, on the basis of the above scheme, the steam at the outlet of the desuperheater is mixed with the heat recovery extraction steam of the existing last-stage high-pressure heater (the extraction isolation valve on the existing last-stage high-pressure heater extraction pipe is in an open state) or steam with a lower pressure level in a mixer (such as a pressure matcher, etc.). Under the premise that the steam pressure at the outlet of the mixer is higher than the heat recovery extraction steam of the existing last-stage high-pressure heater, the mixed steam enters the existing last-stage high-pressure heater to heat the feed water; at the same time, a heat exchanger is added to the existing last-stage high-pressure heater steam inlet pipe. The steam can heat other working media (such as air, water, coal, etc.) in the heat exchanger, and then enter the existing last-stage high-pressure heater to heat the feed water. In this way, the steam inlet flow rate of the existing last-stage high-pressure heater can be relatively increased.

[0078] Implementation 11

[0079] As shown in Figure 12, based on the above scheme, part of the extracted main steam is optimized to steam in the superheater system, such as steam in the superheater intermediate header; at the same time, the steam at the outlet of the desuperheater is mixed with the heat recovery extraction steam of the existing last-stage HP heater (the extraction isolation valve on the existing last-stage HP heater extraction pipe is in the open state) or steam with a lower pressure level in a mixer (such as a pressure matcher, etc.). Under the premise that the steam pressure at the outlet of the mixer is higher than the heat recovery extraction steam of the existing last-stage HP heater, the mixed steam enters the existing last-stage HP heater to heat the feed water; in addition, a heat exchanger is added to the existing last-stage HP heater inlet steam pipe. The steam can heat other working media (such as air, water, coal, etc.) in the heat exchanger before entering the existing last-stage HP heater to heat the feed water. In this way, the inlet steam flow rate of the existing last-stage HP heater can be relatively increased.

[0080] Implementation 12

[0081] As shown in Figure 13, based on the above scheme, part of the extracted main steam is optimized to be superheated steam or heat recovery extraction steam of other units. On the premise that the steam pressure at the desuperheater outlet is higher than the heat recovery extraction steam of the existing last-stage HP heater, the steam at the desuperheater outlet is mixed with the heat recovery extraction steam of the existing last-stage HP heater (the extraction isolation valve on the existing last-stage HP heater extraction steam pipeline is in an open state) or steam with a lower pressure level in a mixer (such as a pressure matcher, etc.). On the premise that the steam pressure at the mixer outlet is higher than the heat recovery extraction steam of the existing last-stage HP heater, the mixed steam enters the existing last-stage HP heater to heat the feed water. At the same time, a heat exchanger is added to the existing last-stage HP heater inlet steam pipeline. The steam can heat other working media (such as air, water, coal, etc.) in the heat exchanger before entering the existing last-stage HP heater to heat the feed water. In this way, the steam inlet flow rate of the existing last-stage HP heater can be relatively increased.

[0082] Implementation 13

[0083] Taking the data of 20% THA operating conditions of a 1000MW unit as an example, the main generator load is 200MW, the existing last-stage high-pressure steam inlet parameters are 1.75MPa, 436℃ and the outlet feed water parameters are 6MPa, 192℃, the economizer outlet water temperature is 240℃ (subcooling 36℃, under-enthalpy 176kJ / kg), the economizer outlet flue gas temperature is 245℃, the water-cooled wall outlet is wet saturated steam, the unit is in wet operation state, and the denitrification system cannot be put into use.

[0084] By using the above system: the main generator load is 200MW, the existing last-stage high-pressure heater inlet steam parameters are 6.8MPa, 500℃ and the outlet feed water parameters are 12MPa, 280℃, the economizer outlet water temperature is 304℃ (subcooling 10℃, under-enthalpy 64kJ / kg), the economizer outlet flue gas temperature is 310℃, the water wall outlet superheat is 10℃, the unit is in dry operation state, the under-enthalpy of the water at the water wall inlet is relatively reduced by 112kJ / kg, the water wall outlet steam temperature deviation is controlled, the hydrodynamic stability is enhanced, and the denitrification system is stably and continuously put into use.

[0085] Therefore, the deep peak-shaving system based on feed water heating, for the existing last-stage high-pressure heater and its extraction steam of the unit, introduces steam of higher pressure grade to replace the extraction steam of the existing last-stage high-pressure heater, and at the same time maintains a certain feed water pressure so that the feed water at the economizer outlet maintains a certain degree of subcooling, so as to increase the unit's inlet feed water temperature under deep peak-shaving conditions, thereby increasing the economizer inlet water temperature, economizer outlet water temperature, economizer outlet flue gas temperature, reducing the water-cooled wall inlet enthalpy, shortening the hot water section in the water-cooled wall and maintaining a certain degree of superheat of the water-cooled wall outlet steam, and finally realizing the dry operation of the boiler under deep peak-shaving conditions of the unit, maintaining hydrodynamic stability, and continuously and stably putting the denitrification system into operation.

[0086] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A deep peak load regulation system based on feedwater heating, characterized in that: It includes a deaerator, a pre-pump, a feed water pump, an existing final-stage high-pressure heater, a boiler, a main steam throttling assembly, a high-pressure cylinder, and a steam extraction isolation valve. The low-pressure condensate at the outlet of the deaerator is pressurized by the pre-pump and the feed water pump in turn and then enters the existing final-stage high-pressure heater for heating. The heated feed water enters the boiler and is heated by the economizer, the water-cooled wall, and the superheater heating surface in turn, and finally the main steam is obtained and enters the high-pressure cylinder to perform work; wherein: A high-pressure cylinder steam inlet valve group is arranged on the high-pressure cylinder steam inlet pipeline; The steam inlet source of the existing final stage high pressure heater is the heat recovery extraction steam of the high pressure cylinder, and an extraction steam isolation valve is arranged on the steam inlet pipeline of the existing final stage high pressure heater; A cooling module is arranged in the main steam pipeline from the boiler superheater outlet to the high-pressure cylinder. Cooling water enters the cooling module and is mixed with the main steam entering the cooling module. The steam at the outlet of the cooling module is connected to the existing final-stage high-pressure heater steam inlet pipeline through a pipeline. The interface is located at the downstream pipeline of the extraction isolation valve in the existing final-stage high-pressure heater steam inlet pipeline. By introducing steam with a higher pressure level than the existing final-stage high-pressure heater reheat extraction steam into the existing final-stage high-pressure heater, the unit's boiler feed water temperature under deep peak regulation conditions is increased; The deep peak regulation system is configured as follows: utilizing the main steam throttling component to throttle the main steam to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling; or utilizing the throttling component provided in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

2. The system according to claim 1, characterized in that The temperature reduction module comprises an isolation valve, a pressure reducing valve and a temperature reducer which are sequentially connected through pipelines.

3. The system according to claim 1, characterized in that The steam with a higher pressure grade than the existing final-stage high-pressure heater heat recovery extraction steam is the main steam or superheater steam of the unit or steam from a non-unit.

4. The system according to claim 2, characterized in that A mixer is arranged between the outlet of the desuperheater and the steam inlet of the final-stage high-pressure heater, and the steam at the outlet of the desuperheater is mixed with the heat recovery extraction steam of the existing final-stage high-pressure heater or steam with a lower pressure level in the mixer. On the premise that the steam pressure at the outlet of the mixer is higher than the heat recovery extraction steam of the existing final-stage high-pressure heater, the mixed steam enters the existing final-stage high-pressure heater to heat the feed water.

5. The system according to claim 2, characterized in that A heat exchanger is added, and the heat exchanger is located between the steam extraction isolation valve of the steam extraction pipeline at the high-pressure cylinder outlet and the steam inlet of the existing final-stage high-pressure heater, and between the outlet of the desuperheater and the steam inlet of the existing final-stage high-pressure heater.

6. The system according to claim 4, characterized in that A heat exchanger is provided between the mixer outlet and the steam inlet of the existing final high-pressure heater, and a heat exchanger is provided at the steam inlet of the existing final high-pressure heater.

7. The system according to claim 4, characterized in that The mixer is a pressure matcher.

8. The system of claim 1, wherein: The main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.

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