Full-working-condition composite dry-wet state conversion system and method for ultra-supercritical boiler

Abstract

The invention provides an ultra-supercritical boiler full-working-condition composite dry-wet state conversion system and method, and belongs to the technical field of coal power unit flexible transformation. The method comprises the steps that in the initial stage of starting of a coal power unit, a coal-fired boiler is in a wet state, and the coal-fired boiler is in a wet state; the wet water separated by the separator is recycled based on a boiler water recycling module and a drainage capacity expansion module; when the operation load of the coal-fired boiler ranges from the first preset load to the second preset load, the water level of a water storage tank of the boiler is controlled based on the boiler water recycling module, and a pipeline of the drainage expansion module is heated through wet water; when the second preset load reaches the third preset load, the boiler water recirculation module is closed, the drain capacity expansion module and the heat exchange deoxidization module are started, and the water level of the water storage tank is finely adjusted; and when the load is larger than the third preset load, the coal-fired boiler is switched into dry-state operation, and the drainage capacity expansion module and the heat exchange deoxidization module are closed. The working medium and heat of circulating water in the coal-fired boiler starting stage and the deep peak load regulation load can be recycled.

Description

Technical Field

[0001] The present application relates to the technical field of flexibility transformation of coal-fired power units, and specifically to a full-operating composite dry-wet state conversion system and method for an ultra-supercritical boiler. Background Art

[0002] Due to the rapid development of new energy, it has become normal for large coal-fired power units to participate in deep peak regulation. During the deep regulation process, as the load decreases, the supercritical unit boiler will experience dry-wet state conversion. At present, there are two main forms and technologies for boiler dry-wet state conversion, namely, supercritical boiler dry-wet state non-disturbance switching system technology coupled with boiler water circulation pump and supercritical boiler dry-wet state switching system technology without boiler water circulation pump.

[0003] In the prior art, it is impossible to recover the working fluid and heat of circulating water during the startup phase of coal-fired boilers and deep peak load regulation. Therefore, how to recover the working fluid and heat of circulating water during the startup phase of coal-fired boilers and deep peak load regulation has become a problem to be solved. Summary of the invention

[0004] The purpose of this application is to provide a system and method for composite dry-wet state conversion of an ultra-supercritical boiler under all operating conditions, which can solve the problem in the prior art that the working fluid and heat of circulating water cannot be recovered during the startup phase of a coal-fired boiler and during deep peak load regulation.

[0005] In a first aspect, an embodiment of the present application provides an ultra-supercritical boiler full-operating condition composite dry-wet state conversion system, comprising: a water storage tank (35), an economizer (32), a water-cooled wall (33), and a separator (34); the system also comprises: a boiler water recirculation module, a drain expansion module, a heat exchange and deoxidation module, a low-temperature heater, and a high-temperature heater; The input end of the water-cooled wall (33) is connected to the output end of the economizer (32), the output end of the water-cooled wall (33) is connected to the input end of the separator (34), and the output end of the separator (34) is connected to the input end of the water storage tank (35); The first output end of the water storage tank (35) is connected to the input end of the boiler water recirculation module, the second output end of the water storage tank (35) is connected to the input end of the drain expansion module, and the output end of the boiler water recirculation module is connected to the input end of the economizer (32); The first output end of the hydrophobic expansion module is connected to the first input end of the heat exchange and deoxygenation module, the second output end of the hydrophobic expansion module is connected to the second input end of the heat exchange and deoxygenation module, the third output end of the hydrophobic expansion module is connected to the input end of the high temperature heater, and the third input end of the heat exchange and deoxygenation module is connected to the output end of the low temperature heater; A boiler water recycling module, used for recycling the wet water separated by the separator (34); The hydrophobic expansion module is used to expand and vaporize the wet water after reducing the temperature and pressure to obtain secondary steam; The heat exchange and deoxygenation module is used to exchange heat between the saturated condensed water remaining after the wet water is expanded and vaporized and the condensed water from the low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module.

[0006] In a possible implementation manner of the first aspect, the system further comprises a high-pressure heater (36), and the boiler water recirculation module comprises: a control unit, a small flow recirculation unit, and a subcooling pipe unit; The first output end of the water storage tank (35) is connected to the input end of the control unit, the second output end of the water storage tank (35) is connected to the input end of the hydrophobic expansion module, and the water storage tank (35) is used to store wet water separated by the separator (34); The input end of the control unit is also connected to the first end of the small flow recirculation unit and the output end of the subcooling pipe unit, the first output end of the control unit is connected to the input end of the economizer (32), and the second output end of the control unit is connected to the second end of the small flow recirculation unit; The control unit is used to control the circulation of wet water in the water storage tank (35), and the small flow recirculation unit is used to recirculate the wet water at a preset flow rate; The input end of the subcooling tube unit is connected to the output end of the high-pressure heater (36), and the output end of the high-pressure heater (36) is also connected to the input end of the economizer (32).

[0007] In a possible implementation manner of the first aspect, the control unit comprises: an electric gate valve (23), a boiler water circulation pump (24), a flow measurement device (25), a check valve (26), an electric regulating valve (27), and a second electric gate valve (28); An electric gate valve (23), a boiler water circulation pump (24), a flow measurement device (25), a check valve (26), an electric regulating valve (27) and a second electric gate valve (28) are connected in series between a first output end of a water storage tank (35) and an input end of an economizer (32); The boiler water circulation pump (24) is used to circulate the wet water in the water storage tank (35).

[0008] In a possible implementation manner of the first aspect, the small flow recirculation unit comprises: an electric gate valve (29) and a flow measurement device (30); The first end of the electric gate valve (29) is connected to the output end of the boiler water circulation pump (24), the second end of the electric gate valve (29) is connected to the first end of the flow measurement device (30), and the second end of the flow measurement device (30) is connected to the first end of the electric gate valve (23).

[0009] In a possible implementation of the first aspect, the supercooling pipe unit comprises: an electric gate valve (31) and a supercooling pipe arranged between a first output end of a water storage tank (35) and an output end of a high-pressure heater (36), wherein the electric gate valve (31) is arranged on the supercooling pipe.

[0010] In a possible implementation of the first aspect, the hydrophobic expansion module comprises: a temperature reduction and pressure reduction unit, an expansion tank (37), a first steam delivery unit, and a second steam delivery unit; The input end of the temperature reduction and pressure reduction unit is connected to the second output end of the boiler water recirculation module, and the output end of the temperature reduction and pressure reduction unit is connected to the input end of the expansion tank (37). The temperature reduction and pressure reduction unit is used to reduce the temperature and pressure of the wet water and then transport it to the expansion tank (37); The first output end of the expansion tank (37) is connected to the first input end of the heat exchange and deoxygenation module, the second output end of the expansion tank (37) is connected to the input end of the first steam delivery unit, and the third output end of the expansion tank (37) is connected to the input end of the second steam delivery unit. The expansion tank (37) is used to expand and vaporize the wet water after the temperature and pressure reduction to obtain secondary steam; The output end of the first steam delivery unit is connected to the second input end of the heat exchange and deoxygenation module, and the output end of the second steam delivery unit is connected to the input end of the high temperature heater.

[0011] In a possible implementation manner of the first aspect, the temperature reduction and pressure reduction unit comprises: an electric gate valve (1), a shutoff valve (2), a flow measurement device (3), a small flow 361 valve (4) and a multi-stage flow limiting device (5); the electric gate valve (1), the shutoff valve (2), the flow measurement device (3), the small flow 361 valve (4) and the multi-stage flow limiting device (5) are connected in series between the second output end of the boiler water recirculation module and the input end of the expansion tank (37).

[0012] In a possible implementation of the first aspect, the first steam delivery unit comprises: a shutoff valve (6), an electric regulating valve (7), an electric gate valve (8) and a check valve (9); the shutoff valve (6), the electric regulating valve (7), the electric gate valve (8) and the check valve (9) are connected in series between the second output end of the hydrophobic expansion module and the input end of the high-temperature heater.

[0013] In a possible implementation of the first aspect, the second steam delivery unit comprises: a block valve (10), an electric regulating valve (11), an electric gate valve (12) and a check valve (13); the block valve (10), the electric regulating valve (11), the electric gate valve (12) and the check valve (13) are connected in series between a second output end of the hydrophobic expansion module and a second input end of the heat exchange deoxygenation module, and a first end of the block valve (10) is connected to a first end of the block valve (6).

[0014] In a possible implementation of the first aspect, the system further includes a wastewater discharge module, an atmospheric expansion tank (39), and a condenser (40); The input end of the wastewater discharge module is connected to the first output end of the expansion tank (37), and the output end of the wastewater discharge module is connected to the first end of the atmospheric expansion tank (39). The wastewater discharge module is used to discharge unqualified water obtained when flushing the expansion tank (37) to the atmospheric expansion tank (39); the second end of the atmospheric expansion tank (39) is connected to the first output end of the boiler water recirculation module and the input end of the condenser (40).

[0015] In a possible implementation of the first aspect, the wastewater discharge module comprises: an isolation valve (21), an electric gate valve (22), and a drain pipe arranged between a first output end of the drain expansion module and an output end of the heat exchange deoxygenation module; the isolation valve (21) and the electric gate valve (22) are connected in series to the drain pipe.

[0016] In a possible implementation manner of the first aspect, the heat exchange and deoxygenation module includes: a heat exchange unit and a deoxygenation unit; The first input end of the heat exchange unit is connected to the first output end of the hydrophobic expansion module, the second input end of the heat exchange unit is connected to the output end of the low-temperature heater, the first output end of the heat exchange unit is connected to the output end of the deoxygenation unit, and the second output end of the heat exchange unit is connected to the first input end of the deoxygenation unit; The second input end of the deaerator unit is connected to the second output end of the drain expansion module, and the output end of the deaerator unit is also connected to the first output end of the boiler water recirculation module; The heat exchange unit is used to exchange heat between the saturated condensed water remaining after the wet water is expanded and vaporized and the condensed water from the low-temperature heater to obtain supercooled water, so that the supercooled water enters the deoxygenation unit; the deoxygenation unit is used to recover the supercooled water.

[0017] In a possible implementation manner of the first aspect, the heat exchange unit comprises: an electric gate valve (14), an electric regulating valve (15), a water-to-water heat exchanger (16), an electric gate valve (18), an electric gate valve (19), and an electric regulating valve (20); The electric gate valve (14), the electric regulating valve (15) and the water-to-water heat exchanger (16) are connected in series between the first output end of the hydrophobic expansion module and the output end of the deoxygenation unit, the first input end of the water-to-water heat exchanger (16) is connected to the first end of the electric gate valve (18), and the first output end of the water-to-water heat exchanger (16) is connected to the first end of the electric gate valve (19); The second end of the electric gate valve (18) is connected to the first end of the electric regulating valve (20) and the input end of the low-temperature heater, and the second end of the electric gate valve (19) is connected to the second end of the electric regulating valve (20) and the first input end of the deoxygenation unit.

[0018] In a possible implementation manner of the first aspect, the deaerator unit comprises: a deaerator (38), an energy dissipation device (17), and a water discharge pipe arranged between an output end of the deaerator (38) and a first output end of the boiler water recirculation module; The energy dissipation device (17) is arranged at the output end of the deaerator (38) and inside the deaerator (38). The output end of the deaerator (38) is connected to the first output end of the heat exchange unit and the first output end of the boiler water recirculation module.

[0019] In a second aspect, an embodiment of the present application provides a method for converting a supercritical boiler into a composite dry-wet state under full working conditions, which is implemented based on the supercritical boiler composite dry-wet state conversion system under full working conditions of any one of the first aspects, and the method includes: At the initial start-up of the coal-fired power unit, the coal-fired boiler is in wet operation. The wet water separated by the separator (34) is recycled based on the boiler water recycling module. The wet water is reduced in temperature and pressure based on the hydrophobic expansion module, and then expanded and vaporized to obtain secondary steam, which enters the heat exchange and deoxidation module. Based on the heat exchange and deoxidation module, the saturated condensate remaining after the wet water is expanded and vaporized is exchanged with the condensate from the low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxidation module. When the operating load of the coal-fired boiler is between a first preset load and a second preset load, the water level of the water storage tank (35) is controlled based on the boiler water recirculation module, and the pipes of the drainage expansion module are heated using wet water; When the operating load of the coal-fired boiler is between the second preset load and the third preset load, the boiler water recirculation module is closed, the drainage expansion module and the heat exchange and deoxygenation module are opened, and the water level is adjusted; When the operating load of the coal-fired boiler is greater than the third preset load, the coal-fired boiler switches to dry operation, and the drain expansion module and the heat exchange deoxidation module are closed.

[0020] In a possible implementation of the second aspect, the system includes a water storage tank (35), an economizer (32), a boiler water recirculation module includes a control unit, and the control unit includes a boiler water circulation pump (24); recirculating saturated water in the boiler based on the boiler water recirculation module includes: The wet water in the water storage tank (35) is circulated and input into the economizer (32) based on the boiler water circulation pump (24).

[0021] In a possible implementation of the second aspect, the hydrophobic expansion module comprises: a temperature reduction and pressure reduction unit and an expansion container (37); based on the hydrophobic expansion module, the wet water is reduced in temperature and pressure, and then expanded and vaporized to obtain secondary steam, which enters the heat exchange and deoxygenation module, comprising: Based on the temperature reduction and pressure reduction unit, the wet water is reduced in temperature and pressure and then transported to the expansion tank (37); The expansion vessel (37) is used to expand and vaporize the wet water after the temperature and pressure reduction to obtain secondary steam, which enters the heat exchange and deoxygenation module.

[0022] In a possible implementation of the second aspect, the hydrophobic expansion module includes an expansion tank (37), the heat exchange and deoxygenation module includes: a heat exchange unit and a deoxygenation unit, the heat exchange unit includes a water-to-water heat exchanger (16); based on the heat exchange and deoxygenation module, saturated condensed water remaining after the wet water is expanded and vaporized is heat exchanged with condensed water from a low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module, including: Based on the water-to-water heat exchanger (16), the remaining saturated condensed water after the expansion tank (37) is expanded and vaporized is heat exchanged with the condensed water from the low-temperature heater to obtain supercooled water, and the supercooled water enters the deoxygenation unit.

[0023] The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system of the present application comprises a boiler water recirculation module for recirculating the wet water separated by the separator (34), a hydrophobic expansion module for reducing the temperature and pressure of the wet water and then expanding and vaporizing the wet water to obtain secondary steam, and a heat exchange and deoxygenation module for exchanging heat between the saturated condensate remaining after the wet water is expanded and vaporized and the condensate from the low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module.

[0024] The ultra-supercritical boiler full-operating condition composite dry-wet state conversion method of the present application performs dry-wet state conversion on the operating state of the coal-fired boiler according to the operating load of the coal-fired boiler, and opens or closes the boiler water recirculation module, the drain expansion module, and the heat exchange and deoxygenation module.

[0025] The application scheme can recover the working fluid and heat of circulating water during the startup phase of a coal-fired boiler and during deep peak load regulation, and has strong ease of use and practicality.

[0026] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 It is a schematic block diagram of a full-operating composite dry-wet state conversion system for an ultra-supercritical boiler provided in an embodiment of the present application; Figure 2 It is a schematic block diagram of a full-operating composite dry-wet state conversion system for an ultra-supercritical boiler provided in an embodiment of the present application; Figure 3 It is a schematic diagram of the steps of a method for composite dry-wet state conversion of an ultra-supercritical boiler under full operating conditions provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0030] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0031] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0032] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0033] As used in this specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0034] In addition, in the description of the present application, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0035] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0036] In the present application specification, unless otherwise specified, directional words such as "up, down, left, right" generally refer to the orientation or position relationship shown in the accompanying drawings, or the orientation or position relationship in which the invented product is usually placed when in use.

[0037] In the present application specification, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In recent years, with the large-scale development of new energy such as wind power and photovoltaics, the installed capacity and power generation of new energy have accounted for an increasingly high proportion, and China's energy consumption structure and production structure have shown a trend of shifting towards clean energy. Due to the characteristics of new energy such as randomness, intermittency and instability, the rapid development of new energy has made the challenges of new energy consumption and grid peak regulation increasingly greater. Coal-fired power units are facing the need to transform from electric power sources to regulating power sources, but the existing coal-fired units are not flexible enough, and the peak regulation capacity is limited, so the production capacity of wind power and photovoltaic power cannot be effectively released.

[0039] Due to the rapid development of new energy, it has become normal for large thermal power units to participate in deep peak regulation. During the deep regulation process, as the load decreases (30% BMCR (Boiler Maximum Continuous Rating)), the supercritical unit boiler will experience a dry-wet state conversion. Since the supercritical unit is designed, the dry-wet state switching only involves the unit startup and shutdown process, and the unit does not consider continuous operation in the wet state during normal operation. Therefore, there is a huge waste of working fluid and heat during the state transition process. The dry-wet state conversion has become a bottleneck restricting the supercritical unit from participating in deep peak regulation.

[0040] Now we need to implement the flexibility transformation of coal-fired power units, further improve the flexibility and regulation capabilities of coal-fired power units, and promote the transformation of coal-fired power to a power source that is both basic and system-regulated. Whether from a policy perspective or from the perspective of improving the online competitiveness and profitability of power plants, it is an inevitable trend for coal-fired units to carry out technical research on dry-wet switching systems.

[0041] There are two conventional dry-wet state conversion modes for boilers. The first mode of operation is the start-up mode without a boiler water circulation pump: the saturated water produced by the steam-water separator enters the water storage tank, and the water with qualified water quality is introduced into the main body hydrophobic expansion tank or directly discharged into the condenser. If the water quality is unqualified, it is directly discharged. This operation mode causes a great waste of working fluid and heat.

[0042] The second operation mode is the start-up mode with a boiler water circulation pump: in this mode, a boiler water circulation pump is set under the water storage tank. If the water quality is qualified during the startup process, the circulation pump is started, so that the saturated water in the water storage tank is input to the economizer inlet through the circulation pump to achieve the recovery of working fluid and heat. However, since the circulation pump delivers saturated water, frequent start-stop and long-cycle operation are likely to cause cavitation of the circulation pump, affecting the reliability of the unit operation.

[0043] In response to the above problems, there are currently two main forms and technologies for boiler dry-wet state conversion, namely, supercritical boiler dry-wet state disturbance-free switching system technology coupled with boiler water circulating pump and supercritical boiler dry-wet state switching system technology without boiler water circulating pump.

[0044] Among them, the supercritical boiler dry-wet state disturbance-free switching system technology coupled with the boiler water circulation pump is the boiler water pump circulation system + water storage tank fine-tuning system. When the unit frequently performs deep peak regulation in the 25% to 35% load segment, the fine-tuning system is started to adjust the water level, and the high-temperature saturated water from the water storage tank is led to the deaerator through a pipeline. When the unit's deep peak regulation reaches 20%, the boiler water circulation pump is started to lead the high-temperature saturated water from the water storage tank to the economizer inlet.

[0045] Supercritical boiler dry-wet state switching system technology without boiler water circulation pump: high-temperature saturated water from the water storage tank enters the expansion tank after multi-stage flow limiting and pressure reduction, flash steam enters the No. 2 high-pressure heater, and drain enters the deaerator, thereby realizing full recovery of working fluid and heat after wet state operation and continuous operation after deep peak regulation.

[0046] In the prior art, the feed water temperature is low during the boiler startup phase, the steam production in the furnace is low, and the flow of superheated and reheated steam in the furnace is small. When the unit quickly switches to high-load operation, the furnace heat load will increase sharply, and the wall temperature of the intermediate, high and high reheating furnaces will rise sharply or even overheat.

[0047] In addition, the existing technology cannot recover the working fluid and heat of the circulating water during the startup phase of the coal-fired boiler and the deep peak load regulation. Therefore, how to recover the working fluid and heat of the circulating water during the startup phase of the coal-fired boiler and the deep peak load regulation has become a problem to be solved.

[0048] In view of the above-mentioned defects, an embodiment of the present application provides an ultra-supercritical boiler full-operating condition composite dry-wet state conversion system and method, in which a boiler water recycling module recirculates the wet water separated by the separator (34), a hydrophobic expansion module reduces the temperature and pressure of the wet water and then expands and vaporizes it to obtain secondary steam, and a heat exchange and deoxygenation module exchanges heat with condensate from a low-temperature heater to obtain supercooled water from the saturated condensate remaining after the wet water is expanded and vaporized, and the supercooled water enters the heat exchange and deoxygenation module.

[0049] The method converts the operating state of the coal-fired boiler into a dry state and a wet state according to the operating load of the coal-fired boiler, and opens or closes a boiler water recirculation module, a drain expansion module, and a heat exchange and deoxygenation module.

[0050] The application scheme can recover the working fluid and heat of circulating water during the startup phase of a coal-fired boiler and during deep peak load regulation, and has strong ease of use and practicality.

[0051] The overall structure of the ultra-supercritical boiler full-operating condition composite dry-wet state conversion system provided in the embodiments of the present application is introduced below through specific embodiments.

[0052] See also Figure 1 , Figure 1 1 is a schematic block diagram of a full-operation composite dry-wet state conversion system 100 for an ultra-supercritical boiler provided in an embodiment of the present application. Figure 1 As shown, the system 100 includes: a water storage tank (35), an economizer (32), a water-cooled wall (33), a separator (34), a boiler water recirculation module 110, a drain expansion module 12, a heat exchange and deoxidation module 130, a No. 5 low-temperature (low-pressure) heater, and a No. 2 high-temperature (high-pressure) heater.

[0053] In some embodiments, the input end of the water-cooled wall (33) is connected to the output end of the economizer (32), the output end of the water-cooled wall (33) is connected to the input end of the separator (34), and the output end of the separator (34) is connected to the input end of the water storage tank (35).

[0054] In some embodiments, the first output end of the water storage tank (35) is connected to the input end of the boiler water recirculation module, the second output end of the water storage tank (35) is connected to the input end of the drain expansion module, and the output end of the boiler water recirculation module is connected to the input end of the economizer (32).

[0055] In some embodiments, the first output end of the hydrophobic expansion module is connected to the first input end of the heat exchange and deoxygenation module, the second output end of the hydrophobic expansion module is connected to the second input end of the heat exchange and deoxygenation module, the third output end of the hydrophobic expansion module is connected to the input end of high-temperature heater No. 5, and the third input end of the heat exchange and deoxygenation module is connected to the output end of low-temperature heater No. 2.

[0056] In some embodiments, the boiler water recycling module 110 is used to recirculate the wet water separated by the boiler separator (34). The water-draining expansion module 120 is used to expand and vaporize the wet water after reducing the temperature and pressure to obtain secondary steam.

[0057] In some embodiments, the heat exchange and deoxygenation module 130 is used to exchange heat between the saturated condensate remaining after the wet water is expanded and vaporized and the condensate from the No. 5 low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module 130 .

[0058] See also Figure 2 , Figure 2 1 is a schematic block diagram of a full-operation composite dry-wet state conversion system 100 for an ultra-supercritical boiler provided in an embodiment of the present application. Figure 2 As shown, the boiler water recirculation module 110 includes: a control unit 112, a small flow recirculation unit 114 and a subcooling pipe unit 116. The first output end of the water storage tank (35) is connected to the input end of the control unit 112, and the second output end of the water storage tank (35) is connected to the input end of the drain expansion module 120. The water storage tank (35) is used to store the wet water separated by the separator (34).

[0059] In some embodiments, the input end of the control unit 112 is also connected to the first end of the small flow recirculation unit 114 and the output end of the subcooling pipe unit 116, the first output end of the control unit 112 is connected to the input end of the economizer (32), and the second output end of the control unit 112 is connected to the second end of the small flow recirculation unit 114.

[0060] In some embodiments, the control unit 112 is used to control the circulation of wet water in the water storage tank (35). The small flow recirculation unit 114 is used to recirculate wet water of a preset flow rate (small flow rate), thereby improving the regulation characteristics of the boiler water circulation pump (24) and preventing the boiler water circulation pump (24) from overheating.

[0061] In some embodiments, the input end of the subcooling pipe unit 116 is connected to the output end of the high pressure heater (36), and the output end of the high pressure heater (36) is also connected to the input end of the economizer (32). The subcooling pipe unit 116 is used to prevent the flash evaporation of the circulating water at the inlet of the boiler water circulating pump (24) when the load is rapidly reduced and the operation enters the wet state.

[0062] Please continue to see Figure 2 According to one embodiment of the present application, the control unit 112 includes: an electric gate valve (23), a boiler water circulation pump (24), a flow measurement device (25), a check valve (26), an electric regulating valve (27) and a second electric gate valve (28).

[0063] In some embodiments, the electric gate valve (23), the boiler water circulation pump (24), the flow measurement device (25), the check valve (26), the electric regulating valve (27) and the second electric gate valve (28) are connected in series between the first output end of the water storage tank (35) and the input end of the economizer (32). The boiler water circulation pump (24) is used to circulate the wet water in the water storage tank (35).

[0064] Please continue to see Figure 2 According to an embodiment of the present application, the small flow recirculation unit 114 includes: an electric gate valve (29) and a flow measurement device (30). The first end of the electric gate valve (29) is connected to the output end of the boiler water circulation pump (24), the second end of the electric gate valve (29) is connected to the first end of the flow measurement device (30), and the second end of the flow measurement device (30) is connected to the first end of the electric gate valve (23).

[0065] Please continue to see Figure 2 According to one embodiment of the present application, the supercooling pipe unit 116 includes: an electric gate valve (31) and a supercooling pipe arranged between a first output end of a water storage tank (35) and an output end of a high-pressure heater (36), and the electric gate valve (31) is arranged on the supercooling pipe.

[0066] Please continue to see Figure 2 According to an embodiment of the present application, the drain expansion module 120 includes: a temperature reduction and pressure reduction unit 122, an expansion tank 37, a first steam delivery unit 124, and a second steam delivery unit 126. The input end of the temperature reduction and pressure reduction unit 122 is connected to the second output end of the boiler water recirculation module 110, and the output end of the temperature reduction and pressure reduction unit 122 is connected to the input end of the expansion tank 37. The temperature reduction and pressure reduction unit 122 is used to reduce the temperature and pressure of the wet water and then deliver it to the expansion tank 37.

[0067] In some embodiments, the first output end of the expansion tank 37 is connected to the first input end of the heat exchange and deoxygenation module 130, and the second output end of the expansion tank 37 is connected to the input end of the first steam delivery unit 124 and the input end of the second steam delivery unit 126. The expansion tank 37 is used to expand and vaporize the wet water after cooling and pressure reduction to obtain secondary steam.

[0068] Among them, after being depressurized by the expansion tank 37, a part of the secondary steam is flashed and the rest is low-pressure saturated condensate.

[0069] In some embodiments, the output end of the first steam delivery unit 124 is connected to the second input end of the heat exchange deoxygenation module 130 , and the output end of the second steam delivery unit 126 is connected to the input end of the No. 2 high temperature heater.

[0070] In some embodiments, the secondary steam generated by the expansion and vaporization of wet water entering the expansion tank (37) is split into two paths, one of which is led to the No. 2 high-temperature heater to replace part of the second-stage extraction steam to heat the feed water. The pipeline is provided with an isolation valve (6), an electric regulating valve (7), an electric gate valve (8) and a check valve (9); the other path is led to the deaerator (38) to heat the condensate, and the pipeline is provided with an isolation valve (10), an electric regulating valve (11), an electric gate valve (12) and a check valve (13).

[0071] Please continue to see Figure 2 According to an embodiment of the present application, the temperature reduction and pressure reduction unit 122 comprises: an electric gate valve (1), a cut-off valve (2), a flow measurement device (3), a small flow 361 valve (4) and a multi-stage current limiting device (5). The electric gate valve (1), the cut-off valve (2), the flow measurement device (3), the small flow 361 valve (4) and the multi-stage current limiting device (5) are connected in series between the second output end of the boiler water recirculation module 110 and the input end of the expansion tank 37.

[0072] Please continue to see Figure 2 According to an embodiment of the present application, the first steam delivery unit 124 comprises: a cut-off valve (6), an electric regulating valve (7), an electric gate valve (8) and a check valve (9). The cut-off valve (6), the electric regulating valve (7), the electric gate valve (8) and the check valve (9) are connected in series between the first output end of the drain expansion module 120 and the input end of the No. 2 high-temperature heater.

[0073] Please continue to see Figure 2 According to an embodiment of the present application, the second steam delivery unit 126 comprises: a block valve (10), an electric regulating valve (11), an electric gate valve (12) and a check valve (13). The block valve (10), the electric regulating valve (11), the electric gate valve (12) and the check valve (13) are connected in series between the first output end of the hydrophobic expansion module 120 and the second input end of the heat exchange deoxygenation module 130, and the first end of the block valve (10) is connected to the first end of the block valve (6).

[0074] Please continue to see Figure 2 According to one embodiment of the present application, the system 100 further includes a wastewater discharge module 140, an atmospheric expansion tank (39) and a condenser (40).

[0075] In some embodiments, the input end of the wastewater discharge module 140 is connected to the first output end of the expansion tank 37, and the output end of the wastewater discharge module 140 is connected to the first end of the atmospheric expansion tank (39). The wastewater discharge module 140 is used to discharge unqualified water obtained when flushing the expansion tank 37 to the atmospheric expansion tank (39). The second end of the atmospheric expansion tank (39) is connected to the second output end of the boiler water recirculation module 110 and the input end of the condenser (40).

[0076] Please continue to see Figure 2 According to one embodiment of the present application, the wastewater discharge module 140 includes: an isolation valve (21), an electric gate valve (22), and a drain pipe arranged between the first output end of the drain expansion module 120 and the output end of the heat exchange deoxygenation module 130, and the isolation valve (21) and the electric gate valve (22) are connected in series to the drain pipe.

[0077] Please continue to see Figure 2 According to one embodiment of the present application, the heat exchange and deoxygenation module 130 includes: a heat exchange unit 132 and a deoxygenation unit 134. The first input end of the heat exchange unit 132 is connected to the first output end of the hydrophobic expansion module 120, the second input end of the heat exchange unit 132 is connected to the output end of the No. 5 low-temperature heater, the first output end of the heat exchange unit 132 is connected to the output end of the deoxygenation unit 134, and the second output end of the heat exchange unit 132 is connected to the first input end of the deoxygenation unit 134.

[0078] In some embodiments, the second input end of the deoxygenation unit 134 is connected to the second output end of the drain expansion module 120, and the output end of the deoxygenation unit 134 is also connected to the first output end of the boiler water recycling module 110; the heat exchange unit 132 is used to exchange heat between the saturated condensed water remaining after the wet water is expanded and vaporized and the condensed water from the No. 5 low-temperature heater to obtain supercooled water, so that the supercooled water enters the deoxygenation unit 134. The deoxygenation unit 134 is used to recycle the supercooled water.

[0079] Please continue to see Figure 2 According to one embodiment of the present application, the heat exchange unit 132 includes: an electric gate valve (14), an electric regulating valve (15), a water-to-water heat exchanger (16), an electric gate valve (18), an electric gate valve (19) and an electric regulating valve (20).

[0080] In some embodiments, the electric gate valve (14), the electric regulating valve (15) and the water-to-water heat exchanger (16) are connected in series between the first output end of the hydrophobic expansion module 120 and the output end of the deoxygenation unit 134, the first input end of the water-to-water heat exchanger (16) is connected to the first end of the electric gate valve (18), and the first output end of the water-to-water heat exchanger (16) is connected to the first end of the electric gate valve (19).

[0081] In some embodiments, the second end of the electric gate valve (18) is connected to the first end of the electric regulating valve (20) and the input end of the No. 5 low-temperature heater, and the second end of the electric gate valve (19) is connected to the second end of the electric regulating valve (20) and the first input end of the deoxygenation unit 134.

[0082] Please continue to see Figure 2 According to one embodiment of the present application, the deaerator unit 134 includes: a deaerator (38), an energy dissipation device (17), and a water discharge pipe arranged between the output end of the deaerator (38) and the first output end of the boiler water recirculation module 110.

[0083] In some embodiments, the energy dissipation device (17) is disposed at the output end of the deaerator (38) and inside the deaerator (38), and the output end of the deaerator (38) is connected to the first output end of the heat exchange unit 132 and the first output end of the boiler water recirculation module 110.

[0084] In some embodiments, wet water enters the expansion tank (37) and is vaporized, and the saturated water at the bottom enters the water-to-water heat exchanger (16) and is cooled by condensed water from the No. 5 low-temperature heater into slightly subcooled water and enters the deaerator (38). An electric gate valve (14), an electric regulating valve (15), a water-to-water heat exchanger (16) and an energy dissipation device (17) are sequentially arranged on the pipeline.

[0085] In some embodiments, the condensate at the outlet of the No. 5 low-temperature heater is bypassed to pass through the water-to-water heat exchanger (16) for heat exchange before entering the deaerator (38). A first electric gate valve (18) and a second electric gate valve (19) are sequentially arranged on the bypass pipeline.

[0086] In some embodiments, a pipeline is led out from the outlet drain pipeline of the expansion tank (37) to the water discharge pipeline of the deaerator (38). When the coal-fired power unit is started to flush the expansion tank (37), unqualified water is discharged to the atmospheric expansion tank (39) through the pipeline. An isolation valve (21) and an electric gate valve (22) are provided on the pipeline.

[0087] See also Figure 3 , Figure 3 1 is a schematic diagram of the steps of a method for converting a supercritical boiler to a dry-wet state under full working conditions provided by an embodiment of the present application. The method is implemented based on a system 100 for converting a supercritical boiler to a dry-wet state under full working conditions. The method may include the following steps: S301, at the initial start-up of the coal-fired power unit, the coal-fired boiler is in wet operation. Based on the boiler water recycling module 110, the wet water separated by the separator (34) is recycled. Based on the hydrophobic expansion module 120, the boiler saturated water is cooled and depressurized, and then expanded and vaporized to obtain secondary steam, which enters the heat exchange and deoxygenation module 130. Based on the heat exchange and deoxygenation module 130, the saturated condensate remaining after the wet water is expanded and vaporized is heat exchanged with the condensate from the No. 5 low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module 130.

[0088] The remaining water after the expansion and evaporation of the wet water by the hydrophobic expansion module 120 is low-pressure saturated condensate water, and the supercooled water obtained after the heat exchange and deoxygenation module 130 obtains slightly supercooled water.

[0089] According to an embodiment of the present application, a dry-wet state conversion system 100 includes: a water storage tank (35), an economizer (32), a boiler water recycling module 110 includes a control unit 112, and the control unit 112 includes a boiler water circulation pump (24). Recirculating the wet water separated by the separator (34) based on the boiler water recycling module 110 may include the following steps: The wet water in the water storage tank (35) is circulated and input into the economizer (32) based on the boiler water circulation pump (24).

[0090] According to an embodiment of the present application, the hydrophobic expansion module 120 includes: a temperature reduction and pressure reduction unit 122 and an expansion tank 37. Based on the hydrophobic expansion module 120, the wet water is reduced in temperature and pressure, and then expanded and vaporized to obtain secondary steam, which enters the heat exchange and deoxygenation module 130, which may include the following steps: Based on the temperature reduction and pressure reduction unit 122, the wet water is reduced in temperature and pressure and then transported to the expansion tank 37. Based on the expansion tank 37, the reduced in temperature and pressure wet water is expanded and vaporized to obtain secondary steam, which enters the heat exchange and deoxygenation module 130.

[0091] According to an embodiment of the present application, the hydrophobic expansion module 120 includes an expansion tank (37), the heat exchange and deoxygenation module 130 includes a heat exchange unit 132 and a deoxygenation unit 134, and the heat exchange unit 132 includes a water-to-water heat exchanger (16). Based on the heat exchange and deoxygenation module 130, the saturated condensed water remaining after the wet water is expanded and vaporized is heat exchanged with the condensed water from the low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module 130, which may include the following steps: Based on the water-to-water heat exchanger (16), the remaining saturated condensate after expansion and vaporization in the expansion tank (37) is heat-exchanged with the condensate from the No. 5 low-temperature heater to obtain supercooled water, and the supercooled water enters the deoxygenation unit 134.

[0092] S302, when the operating load of the coal-fired boiler is between the first preset load and the second preset load, the water level of the water storage tank (35) is controlled based on the boiler water recirculation module 110, and the pipes of the drain expansion module 120 are heated using wet water.

[0093] In one embodiment, the boiler water recirculation module 110 recirculates the wet water in the water storage tank (35), controls the water level in the water storage tank (35), and performs high water level regulation.

[0094] S303, when the operating load of the coal-fired boiler is between the second preset load and the third preset load, the boiler water recirculation module 110 is turned off, and the drainage expansion module 120 and the heat exchange deoxygenation module 130 are turned on to adjust the water level.

[0095] In one embodiment, the hydrophobic expansion module 120 and the heat exchange and deoxygenation module 130 are turned on to perform low water level regulation.

[0096] S304, when the operating load of the coal-fired boiler is greater than the third preset load, the coal-fired boiler switches to dry operation, and the drainage expansion module 120 and the heat exchange deoxygenation module 130 are turned off.

[0097] In some embodiments, the output end of the water storage tank 35 is respectively connected to the boiler water recycling module 110 and the drain expansion module 120, the output end of the boiler water recycling module 110 is connected to the economizer 32, and the steam generated by the expansion tank 37 is respectively connected to the No. 2 high temperature heater and the deaerator 38. The saturated condensate generated by the expansion tank 37 is cooled by the condensate from the No. 5 low temperature heater through the water-to-water heat exchanger 16 and then enters the deaerator 38.

[0098] In some embodiments, the deep peak load is divided into boiler water circulation regulation and fine-tuning according to different load intervals: the connection part between the output end of the water storage tank 35 and the boiler water recirculation module 110 belongs to the boiler water recirculation regulation system (boiler water pump regulation system), and the connection part between the output end of the water storage tank 35 and the drain expansion module 120 belongs to the water storage tank fine-tuning system (fine-tuning system). The boiler water circulation regulation and fine-tuning are started at the same time during the boiler startup phase, and the boiler water recirculation module 110 and the drain expansion module 120 are in a parallel relationship.

[0099] In some embodiments, at the initial start-up of the coal-fired power unit, the evaporation amount of the dry-wet conversion system 100 is small, and the amount of circulating water entering the water storage tank 35 is relatively large. The boiler water circulation system can be coupled with the water storage tank fine-adjustment system to recover the working medium and heat. A part of the wet water in the water storage tank 35 is input to the inlet of the economizer 32 through the boiler water circulation pump 24, and the other part enters the expansion tank 37 to expand the steam generated by two paths and enters the deaerator 38 and the No. 2 high-temperature heater respectively. The saturated water in the expansion tank 37 enters the water-to-water heat exchanger and is cooled by the condensed water from the No. 5 low-temperature heater into supercooled water and enters the deaerator 38.

[0100] Through the above methods, on the one hand, the recovery of working fluid and heat is achieved, and on the other hand, the low feed water temperature during the boiler startup phase can be used to solve the problem of low steam production in the furnace, small superheating and reheating steam flow in the furnace. When the coal-fired boiler quickly switches to high-load operation, the furnace heat load increases sharply, and the wall temperature of the furnace rises sharply or even overheats.

[0101] In some embodiments, when the coal-fired boiler is deeply peak-regulated to 20%-25% load, the water volume in the water storage tank 35 is relatively large, and the boiler water circulation pump 24 is started to perform high water level regulation. The saturated water in the water storage tank 35 is circulated to the inlet of the economizer 32 through the boiler water circulation pump 24 to achieve working fluid and heat recycling. At this time, the opening of the small flow 361 valve (4) of the micro-regulation system is set to 5%, which plays a role in warming the pipe.

[0102] In some embodiments, when the coal-fired boiler frequently performs deep peak regulation in the 25% to 30% load range and enters wet operation, the water level in the water storage tank 35 is low and the water storage tank fine-adjustment system can be used to adjust the water level without frequently starting the boiler water circulation system. At this time, the electric gate valve (1) can be opened, and the wet water in the water storage tank 35 passes through the isolation valve (2), the flow measurement device (3), the small flow 361 valve (4) and the multi-stage current limiting device (5) in sequence and enters the expansion tank (37).

[0103] Since the wet water is decompressed and vaporized after passing through the small flow valve 361 (4) and the multi-stage flow limiting device 5 to form a two-phase flow, which will cause problems such as pipeline vibration, the multi-stage flow limiting device 5 is installed as close to the inlet of the expansion tank 37 as possible. The saturated steam generated by the wet water expanding through the expansion tank 37 enters the deaerator 38 to increase the deoxygenation effect, or enters the No. 2 high-temperature heater to replace part of the second-stage steam extraction. The saturated water enters the water-to-water heat exchanger 16 and is cooled by condensed water to become supercooled water, which enters the deaerator 38 through the deaerator 38 water discharge pipe.

[0104] In some embodiments, when the load of the coal-fired boiler is higher than 30%, the coal-fired boiler switches to dry operation, there is no water in the water storage tank 35, and the water storage tank fine-tuning system is turned off.

[0105] The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system 100 of the present application, the boiler water recycling module recirculates the wet water separated by the separator (34), the hydrophobic expansion module reduces the temperature and pressure of the wet water and then expands and vaporizes it to obtain secondary steam, the heat exchange and deoxygenation module exchanges heat with the saturated condensate remaining after the wet water is expanded and vaporized with the condensate from the low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module.

[0106] The method converts the operating state of the coal-fired boiler into a dry state and a wet state according to the operating load of the coal-fired boiler, and opens or closes a boiler water recirculation module, a drain expansion module, and a heat exchange and deoxygenation module.

[0107] The application scheme can recover the working fluid and heat of circulating water during the startup phase of a coal-fired boiler and during deep peak load regulation, and has strong ease of use and practicality.

[0108] In this application, the boiler water recirculation and water tank fine-tuning systems are mutually backup and can be adjusted at the same time, reducing the capacity of the boiler water circulation pump. At the same time, due to the existence of the fine-tuning system, the problem of frequent start and stop of the pump group at 25% load up and down is avoided. By adding a dry-wet switching system, the system heat is recovered, and at the same time, it can make up for the problem of low feed water temperature caused by insufficient pressure of the heat recovery system under low load conditions of the unit.

[0109] In addition, the problem of low feed water temperature, low steam production in the furnace, small superheated and reheated steam flow in the furnace during the boiler startup phase, a sharp increase in furnace heat load when the unit quickly switches to high-load operation, and a sharp rise in wall temperature or even overheating in the furnace during the intermediate, high and high reheating phases is solved.

[0110] In addition, the saturated water from the water storage tank is consumed by the No. 2 high-pressure heater and the deaerator, realizing the "double recovery" of boiler water heat and working fluid based on energy cascade utilization. The saturated water in the expansion tank 37 is cooled into supercooled water by condensed water in the water-to-water heat exchanger before being input into the deaerator, avoiding or reducing the flash evaporation of saturated water entering the water space of the deaerator due to the sudden drop in pressure, causing the vibration of the deaerator.

[0111] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0112] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0113] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A full-operation composite dry-wet state conversion system for an ultra-supercritical boiler, comprising: A water storage tank (35), an economizer (32), a water-cooled wall (33), and a separator (34), wherein the system further comprises: a boiler water recirculation module, a drain expansion module, a heat exchange and deoxidation module, a low-temperature heater, and a high-temperature heater; The input end of the water-cooled wall (33) is connected to the output end of the economizer (32), the output end of the water-cooled wall (33) is connected to the input end of the separator (34), and the output end of the separator (34) is connected to the input end of the water storage tank (35); The first output end of the water storage tank (35) is connected to the input end of the boiler water recirculation module, the second output end of the water storage tank (35) is connected to the input end of the drain expansion module, and the output end of the boiler water recirculation module is connected to the input end of the economizer (32); The first output end of the hydrophobic expansion module is connected to the first input end of the heat exchange and deoxygenation module, the second output end of the hydrophobic expansion module is connected to the second input end of the heat exchange and deoxygenation module, the third output end of the hydrophobic expansion module is connected to the input end of the high temperature heater, and the third input end of the heat exchange and deoxygenation module is connected to the output end of the low temperature heater; The boiler water recycling module is used to recirculate the wet water separated by the separator (34); The hydrophobic expansion module is used to expand and vaporize the wet water after reducing the temperature and pressure to obtain secondary steam; The heat exchange and deoxygenation module is used to exchange heat between the saturated condensed water remaining after the wet water is expanded and vaporized and the condensed water from the low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module.

2. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 1 is characterized in that: The system further comprises a high-pressure heater (36), and the boiler water recirculation module comprises: a control unit, a small flow recirculation unit and a subcooling pipe unit; A first output end of the water storage tank (35) is connected to an input end of the control unit, and a second output end of the water storage tank (35) is connected to an input end of the hydrophobic expansion module. The water storage tank (35) is used to store wet water separated by the separator (34); The input end of the control unit is also connected to the first end of the small flow recirculation unit and the output end of the subcooling pipe unit, the first output end of the control unit is connected to the input end of the economizer (32), and the second output end of the control unit is connected to the second end of the small flow recirculation unit; The control unit is used to control the circulation of the wet water in the water storage tank (35), and the small flow recirculation unit is used to recirculate the wet water at a preset flow rate; The input end of the subcooling tube unit is connected to the output end of the high-pressure heater (36), and the output end of the high-pressure heater (36) is also connected to the input end of the economizer (32).

3. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 2 is characterized in that: The control unit comprises: an electric gate valve (23), a boiler water circulation pump (24), a flow measurement device (25), a check valve (26), an electric regulating valve (27), and a second electric gate valve (28); An electric gate valve (23), a boiler water circulation pump (24), a flow measurement device (25), a check valve (26), an electric regulating valve (27) and a second electric gate valve (28) are connected in series between a first output end of a water storage tank (35) and an input end of an economizer (32); The boiler water circulation pump (24) is used to circulate the wet water in the water storage tank (35).

4. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 3 is characterized in that: The small flow recirculation unit comprises: an electric gate valve (29) and a flow measurement device (30); The first end of the electric gate valve (29) is connected to the output end of the boiler water circulation pump (24), the second end of the electric gate valve (29) is connected to the first end of the flow measurement device (30), and the second end of the flow measurement device (30) is connected to the first end of the electric gate valve (23).

5. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 2 is characterized in that: The supercooling pipe unit comprises: an electric gate valve (31) and a supercooling pipe arranged between a first output end of a water storage tank (35) and an output end of a high-pressure heater (36), wherein the electric gate valve (31) is arranged on the supercooling pipe.

6. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 1 is characterized in that: The drain expansion module comprises: a temperature reduction and pressure reduction unit, an expansion tank (37), a first steam delivery unit and a second steam delivery unit; The input end of the temperature reduction and pressure reduction unit is connected to the second output end of the boiler water recirculation module, and the output end of the temperature reduction and pressure reduction unit is connected to the input end of the expansion tank (37). The temperature reduction and pressure reduction unit is used to reduce the temperature and pressure of wet water and then transport it to the expansion tank (37); The first output end of the expansion tank (37) is connected to the first input end of the heat exchange and deoxygenation module, the second output end of the expansion tank (37) is connected to the input end of the first steam delivery unit, and the third output end of the expansion tank (37) is connected to the input end of the second steam delivery unit. The expansion tank (37) is used to expand and vaporize the wet water after the temperature and pressure reduction to obtain secondary steam; The output end of the first steam delivery unit is connected to the second input end of the heat exchange and deoxygenation module, and the output end of the second steam delivery unit is connected to the input end of the high temperature heater.

7. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 6 is characterized in that: The temperature and pressure reduction unit comprises: an electric gate valve (1), a cut-off valve (2), a flow measurement device (3), a small flow 361 valve (4) and a multi-stage flow limiting device (5); The electric gate valve (1), the isolation valve (2), the flow measurement device (3), the small flow 361 valve (4) and the multi-stage flow limiting device (5) are connected in series between the second output end of the boiler water recirculation module and the input end of the expansion tank (37).

8. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 6 is characterized in that: The first steam delivery unit comprises: a block valve (6), an electric regulating valve (7), an electric gate valve (8) and a check valve (9); The isolation valve (6), the electric regulating valve (7), the electric gate valve (8) and the check valve (9) are connected in series between the second output end of the hydrophobic expansion module and the input end of the high-temperature heater.

9. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 8 is characterized in that: The second steam delivery unit comprises: a block valve (10), an electric regulating valve (11), an electric gate valve (12) and a check valve (13); The isolation valve (10), the electric regulating valve (11), the electric gate valve (12) and the check valve (13) are connected in series between the second output end of the hydrophobic expansion module and the second input end of the heat exchange deoxygenation module, and the first end of the isolation valve (10) is connected to the first end of the isolation valve (6).

10. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 6, characterized in that: The system further comprises a wastewater discharge module, an atmospheric expansion tank (39) and a condenser (40); The input end of the wastewater discharge module is connected to the first output end of the expansion vessel (37), and the output end of the wastewater discharge module is connected to the first end of the atmospheric expansion vessel (39). The wastewater discharge module is used to discharge unqualified water obtained when flushing the expansion vessel (37) to the atmospheric expansion vessel (39); The second end of the atmospheric expansion tank (39) is connected to the first output end of the boiler water recirculation module and the input end of the condenser (40).

11. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 10, characterized in that: The wastewater discharge module comprises: an isolation valve (21), an electric gate valve (22), and a drain pipe arranged between a first output end of the drain expansion module and an output end of the heat exchange deoxygenation module; the isolation valve (21) and the electric gate valve (22) are connected in series to the drain pipe.

12. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 1 is characterized in that: The heat exchange and deoxygenation module comprises: a heat exchange unit and a deoxygenation unit; The first input end of the heat exchange unit is connected to the first output end of the hydrophobic expansion module, the second input end of the heat exchange unit is connected to the output end of the low-temperature heater, the first output end of the heat exchange unit is connected to the output end of the deoxygenation unit, and the second output end of the heat exchange unit is connected to the first input end of the deoxygenation unit; The second input end of the deaerator unit is connected to the second output end of the drain expansion module, and the output end of the deaerator unit is also connected to the first output end of the boiler water recycling module; The heat exchange unit is used to exchange heat between the saturated condensed water remaining after the wet water is expanded and vaporized and the condensed water from the low-temperature heater to obtain supercooled water, so that the supercooled water enters the deoxygenation unit; the deoxygenation unit is used to recover the supercooled water.

13. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 12, characterized in that: The heat exchange unit comprises: an electric gate valve (14), an electric regulating valve (15), a water-to-water heat exchanger (16), an electric gate valve (18), an electric gate valve (19), and an electric regulating valve (20); An electric gate valve (14), an electric regulating valve (15) and a water-to-water heat exchanger (16) are connected in series between a first output end of the hydrophobic expansion module and an output end of the deoxygenation unit, a first input end of the water-to-water heat exchanger (16) is connected to a first end of the electric gate valve (18), and a first output end of the water-to-water heat exchanger (16) is connected to a first end of the electric gate valve (19); The second end of the electric gate valve (18) is connected to the first end of the electric regulating valve (20) and the input end of the low-temperature heater, and the second end of the electric gate valve (19) is connected to the second end of the electric regulating valve (20) and the first input end of the deoxygenation unit.

14. The ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to claim 12, characterized in that: The deaerator unit comprises: a deaerator (38), an energy dissipation device (17), and a water discharge pipe arranged between an output end of the deaerator (38) and a first output end of the boiler water recirculation module; The energy dissipation device (17) is arranged at the output end of the deaerator (38) and inside the deaerator (38), and the output end of the deaerator (38) is connected to the first output end of the heat exchange unit and the first output end of the boiler water recirculation module.

15. A method for converting ultra-supercritical boilers into dry and wet states under full working conditions, characterized in that: The method is implemented based on the ultra-supercritical boiler full-operating condition composite dry-wet state conversion system according to any one of claims 1 to 14, and comprises: At the initial start-up of the coal-fired power unit, the coal-fired boiler is in wet operation. The wet water separated by the separator (34) is recycled based on the boiler water recycling module. The wet water is reduced in temperature and pressure based on the hydrophobic expansion module, and then expanded and vaporized to obtain secondary steam, which enters the heat exchange and deoxidation module. The saturated condensed water remaining after the wet water is expanded and vaporized is exchanged with the condensed water from the low-temperature heater based on the heat exchange and deoxidation module to obtain supercooled water, which enters the heat exchange and deoxidation module. When the operating load of the coal-fired boiler is between a first preset load and a second preset load, the water level of the water storage tank (35) is controlled based on the boiler water recirculation module, and the pipes of the drainage expansion module are heated using wet water; When the operating load of the coal-fired boiler is between the second preset load and the third preset load, the boiler water recirculation module is closed, the drainage expansion module and the heat exchange and deoxygenation module are opened, and the water level is adjusted; When the operating load of the coal-fired boiler is greater than the third preset load, the coal-fired boiler switches to dry operation, and the drainage expansion module and the heat exchange and deoxygenation module are turned off.

16. The method for full-operation-condition composite dry-wet state conversion of an ultra-supercritical boiler according to claim 15, characterized in that: The system comprises a water storage tank (35) and an economizer (32); the boiler water recycling module comprises a control unit, and the control unit comprises a boiler water circulation pump (24); and the wet water separated by the separator (34) is recycled based on the boiler water recycling module, comprising: Based on the boiler water circulation pump (24), the wet water in the water storage tank (35) is circulated and input into the economizer (32).

17. The method for full-operation-condition composite dry-wet state conversion of an ultra-supercritical boiler according to claim 15 or 16, characterized in that: The hydrophobic expansion module comprises: a temperature reduction and pressure reduction unit and an expansion container (37); based on the hydrophobic expansion module, the wet water is reduced in temperature and pressure, and then expanded and vaporized to obtain secondary steam, which enters the heat exchange and deoxygenation module, comprising: Based on the temperature reduction and pressure reduction unit, the wet water is reduced in temperature and pressure and then transported to the expansion tank (37); The expansion container (37) expands and vaporizes the wet water after the temperature and pressure reduction to obtain secondary steam, which enters the heat exchange and deoxygenation module.

18. The method for full-operation-condition composite dry-wet state conversion of an ultra-supercritical boiler according to claim 15, characterized in that: The hydrophobic expansion module comprises an expansion tank (37), and the heat exchange and deoxygenation module comprises: a heat exchange unit and a deoxygenation unit, wherein the heat exchange unit comprises a water-to-water heat exchanger (16); based on the heat exchange and deoxygenation module, saturated condensed water remaining after the wet water is expanded and vaporized is heat-exchanged with condensed water from a low-temperature heater to obtain supercooled water, and the supercooled water enters the heat exchange and deoxygenation module, comprising: Based on the water-to-water heat exchanger (16), the remaining saturated condensed water after expansion and vaporization in the expansion tank (37) is heat-exchanged with the condensed water from the low-temperature heater to obtain supercooled water, and the supercooled water enters the deoxygenation unit.

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