Antifreeze device and method for intercooling system of indirect air-cooling unit

Abstract

The present invention relates to an antifreeze device and method for an intercooling system of an indirect air-cooling unit, comprising an antifreeze device, the antifreeze device comprising an air supply pipe, an injection assembly, a first heat exchanger, and a second circulation loop connected between the first heat exchanger and the first circulation loop. The air supply pipe exchanges heat with the second circulation loop through the first heat exchanger; the injection assembly is arranged at the terminal end of the air supply pipe, and the injection direction of the injection assembly is toward the low-temperature zone of the cooling triangle radiator. The present invention utilizes the second circulation loop to draw out part of the high-temperature circulating medium, and utilizes the first heat exchanger to transfer heat to the gas in the air supply pipe, thereby obtaining gas with a temperature higher than the ambient temperature, and then injects the gas into the low-temperature zone to increase the temperature of the low-temperature zone and prevent the cooling triangle radiator from freezing. This utilizes heat that would otherwise be wasted, improves energy utilization, effectively reduces the back pressure of the steam turbine during winter operation, and improves the economic efficiency, safety, and stability of the unit during winter operation.

Description

Technical Field

[0001] The present invention relates to the technical field of indirect air cooling, and in particular to an antifreeze device and method for an intercooling system of an indirect air cooling unit. Background Art

[0002] In recent years, with the rapid development of my country's electric power industry, large-capacity, high-parameter thermal power generating units have been built all over the country. For the vast areas of northwest my country, due to the serious shortage of water resources and the country's environmental protection requirements for newly built units, air-cooled units have become a relatively common way to cool the exhaust steam of steam turbine units. Air cooling methods include direct air cooling and indirect air cooling. For indirect air-cooled units, according to different cooling principles, the indirect cooling system can be divided into Harmon's indirect air cooling system and Heller's indirect air cooling system. The cooling cycle process of the two indirect air cooling systems is a closed cycle, so the water consumption required for unit cooling is almost zero, which minimizes the consumption of water resources by thermal power generating units. The indirect cooling system in the prior art is such as Figure 1 shown.

[0003] However, the environment in which indirect air-cooling units are located is generally colder in winter. At the same time, the cooling characteristics of the air-cooling system of the indirect air-cooling unit determine that the operation of the air-cooling unit is greatly affected by the ambient temperature factors. Especially in winter, due to the influence of extremely low ambient temperature, the heat exchange tube bundle of the indirect cooling tower of the air-cooling unit is prone to freezing and cracking, which seriously affects the safety and stability of the unit operation. There are generally two existing solutions. One is to increase the operating back pressure of the indirect air-cooling unit during winter operation. In some areas of Xinjiang, the operating back pressure of the indirect air-cooling unit in winter can even reach 20kPa, which is much higher than the design back pressure (generally 12-14kPa), seriously affecting the economic efficiency of the unit operation. The other is to install shielding devices such as shutters, but the anti-freeze effect is not ideal. In addition, when the various connecting flanges and sealing rings in the indirect air-cooling tower are installed, they may leak due to wear and mechanical damage, causing a large amount of circulating cooling water to flow out of the shutters. The shutters on the outer periphery of the indirect air-cooling unit will quickly freeze together with the radiator due to this internal leakage, resulting in the problem of ice melting after freezing. Otherwise, the indirect air-cooling tower cannot start working. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects in the prior art, thereby providing an antifreeze device and method for an intercooling system of an indirect air-cooling unit.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] An antifreeze system for an indirect air-cooling unit intercooling system, comprising an exhaust pipe and an indirect air-cooling unit, wherein the indirect air-cooling unit comprises a condenser and an intercooling tower, wherein the exhaust pipe connects the exhaust port of the steam turbine and the condenser, and a first circulation loop is provided between the condenser and the intercooling tower;

[0007] It also includes an antifreeze device, which includes an air supply pipe, several jet assemblies, a first heat exchanger and a second circulation loop connected between the first heat exchanger and the first circulation loop, the second circulation loop is used to draw out part of the high-temperature circulating medium from the first circulation loop, the air supply pipe exchanges heat with the second circulation loop through the first heat exchanger to increase the gas temperature in the air supply pipe; the jet assembly is arranged at the terminal of the air supply pipe, and several of the jet assemblies correspond to several cooling triangle radiators of the intercooler, and the jet direction of the jet assembly is toward the low-temperature area of ​​the cooling triangle radiator.

[0008] Preferably, the first circulation loop includes a low-temperature pipe that guides the low-temperature circulating medium of the intercooler to the condenser, and a high-temperature pipe and a circulation pump that guides the high-temperature circulating medium of the condenser to the intercooler; the inlet of the second circulation loop is connected to the high-temperature pipe, and the outlet of the second circulation loop is connected to the low-temperature pipe;

[0009] The condenser is a hybrid condenser, the circulating pump is provided on the high-temperature pipeline, and the inlet of the second circulating pipeline is located between the circulating pump and the cooling triangle radiator; or,

[0010] The condenser is a surface condenser, the circulation pump is arranged on the low-temperature pipeline, and the outlet of the second circulation loop is located between the circulation pump and the cooling triangle radiator.

[0011] Preferably, the cooling triangle radiator has a connected water inlet pipe and a return pipe inside, and the antifreeze system further includes a control module and a plurality of return water temperature detection modules, wherein the return water temperature detection modules are located in the low temperature zone at the lower end of the return water pipe, and the return water temperature detection modules are communicatively connected to the control module, and the control module is communicatively connected to the gas supply pipe, and is used to adjust the gas temperature in the gas supply pipe based on the return water temperature;

[0012] The second circulation loop is provided with a first regulating valve; the control module is communicatively connected to the first regulating valve and is used to regulate the flow of the high-temperature circulating medium in the second circulation loop based on the return water temperature.

[0013] Preferably, the jet assembly includes a first nozzle and a second nozzle, the first nozzle and the second nozzle are both directed toward the return pipe on the same side, the jet range of the second nozzle is larger than that of the first nozzle, and the first nozzle is located within the jet range of the second nozzle;

[0014] The control module is connected to the jet assembly and is used to select to open the first nozzle or the second nozzle or both the first nozzle and the second nozzle based on the return water temperature;

[0015] The plurality of jet assemblies are vertically arranged at positions corresponding to the low-temperature area of ​​the cooling triangle radiator and the lower end of the return water pipe, and are controlled by the control module to be opened in sequence from bottom to top based on the return water temperature; the opening priority of all the first nozzles and the second nozzles of the jet assemblies at the same height is higher than the opening priority of all the first nozzles and the second nozzles of the jet assemblies at a higher height;

[0016] The spraying ranges of two upper and lower adjacent second nozzles partially overlap, and the spraying range of the second nozzle touches or partially overlaps with the edge of the spraying range of the first nozzle in another nozzle assembly;

[0017] The air supply pipeline includes an air compressor, the gas in the air supply pipeline is compressed air, the air compressor is an adjustable pressure air compressor, and the control module is communicatively connected to the air compressor for adjusting the pressure of the air compressor based on the circulating water temperature.

[0018] Preferably, the antifreeze system further comprises a back pressure detection module for detecting the back pressure of the steam turbine, the back pressure detection module being communicatively connected to the control module; the antifreeze device further comprises a secondary heating pipeline connected to a heat source and a second heat exchanger, the secondary heating pipeline being provided with an on-off unit, the on-off unit being communicatively connected to the control module and being configured to open the secondary heating pipeline when the back pressure of the steam turbine is higher than a set back pressure and the opening of the first regulating valve is at its maximum;

[0019] The temperature of the high-temperature steam in the secondary heating pipeline is higher than the temperature of the high-temperature circulating medium in the second circulation loop. The second heat exchanger is arranged between the first heat exchanger and the jet assembly. The air supply pipeline exchanges heat with the secondary heating pipeline through the second heat exchanger.

[0020] The secondary heating pipeline is provided with a condensate recovery tank and a multi-stage water seal, and the terminal end of the secondary heating pipeline is communicated with the condenser.

[0021] Preferably, the antifreeze device also includes a first temperature detector and a second temperature detector, the first temperature detector is located between the first heat exchanger and the second heat exchanger, the second temperature detector is located between the second heat exchanger and the injection assembly, and a second regulating valve is provided on the secondary heating pipeline. The first temperature detector and the second temperature detector are respectively connected to the control module, and are used to adjust the flow rate of the high-temperature circulating medium in the second circulation loop and the steam flow rate in the secondary heating pipeline based on the detected temperature.

[0022] Preferably, a first isolation valve is provided on the second circulation loop, and the first isolation valve is located between the inlet of the second circulation loop and the first heat exchanger;

[0023] A second isolation valve is provided on the second circulation loop, and the second isolation valve is located between the first heat exchanger and the outlet of the second circulation loop;

[0024] A third isolation valve is provided on the air supply pipeline, and the third isolation valve is located between the air compressor and the first heat exchanger;

[0025] A fourth isolation valve is provided on the gas supply pipeline, and the fourth isolation valve is located between the first heat exchanger and the second heat exchanger;

[0026] A fifth isolation valve is provided on the secondary heating pipeline, and the fifth isolation valve is located upstream of the second heat exchanger;

[0027] A sixth isolation valve is provided on the secondary heating pipeline, and the sixth isolation valve is located between the second heat exchanger and the condensate recovery tank;

[0028] A seventh isolation valve is provided on the secondary heating pipeline, and the seventh isolation valve is located between the condensate recovery tank and the multi-stage water seal;

[0029] An eighth isolation valve is provided on the secondary heating pipeline, and the eighth isolation valve is located between the multi-stage water seal and the condenser.

[0030] To achieve the above object, the present invention adopts the following technical solutions:

[0031] A method for antifreezing an intercooling system of an indirect air-cooling unit, using the antifreezing system of the intercooling system of the indirect air-cooling unit, comprises the following steps:

[0032] opening the second circulation loop and drawing out a portion of the high-temperature circulating medium from the first circulation loop;

[0033] Open the gas supply pipeline, allowing the internal gas to flow through the first heat exchanger, exchanging heat with part of the high-temperature circulating medium to increase the gas temperature, and the circulating medium cooled in the second circulation loop flows back to the first circulation loop;

[0034] The jet assembly is started, and the gas with the increased temperature is sprayed into the low-temperature area of ​​the cooling triangle radiator of the intercooling tower.

[0035] Preferably, the method further comprises: detecting the return water temperature at the lower end of the return water pipe inside the cooling triangle radiator, and controlling the start-up number of the jet assembly and the gas temperature and jet range of the jet assembly after start-up according to the return water temperature.

[0036] Preferably, the control logic of the jetting component is as follows:

[0037] If the return water temperature is lower than the first set value, the first regulating valve on the second circulation loop is opened, the air compressor on the air supply pipe is turned on, and the first nozzle in the jet assembly at the lower end of the return water pipe is turned on to heat the low temperature area at the lower end of the return water pipe;

[0038] If the return water temperature is lower than the second set value, the opening of the first regulating valve on the second circulation loop is increased to increase the flow rate of the high-temperature circulating medium in the second circulation loop, and the pressure of the air compressor on the air supply pipe is increased. The first nozzle in the jet assembly at the lowest end of the return pipe is closed, and the second nozzle is opened to heat the low-temperature area at the lowest end of the return pipe;

[0039] If the return water temperature is lower than the third set value, the opening of the first regulating valve on the second circulation loop is further increased to further increase the flow rate of the high-temperature circulating medium in the second circulation loop, and the pressure of the air compressor on the air supply pipe is increased. The first nozzle in the jet assembly at the lowest end of the return pipe is turned on, and the second nozzle is turned on to heat the low-temperature area at the lowest end of the return pipe;

[0040] If the return water temperature is lower than the fourth set value, the opening of the first regulating valve on the second circulation loop is adjusted to the maximum, further increasing the flow rate of the high-temperature circulating medium in the second circulation loop, increasing the pressure of the air compressor on the air supply pipe, and at the same time opening the first nozzle and the second nozzle of the higher-elevation jet assembly to heat the low-temperature area at the lower end of the return water pipe;

[0041] If the return water temperature is lower than the fifth set value and the back pressure of the steam turbine is detected to be higher than the set back pressure, the secondary heating pipeline is opened to increase the pressure of the air compressor on the air supply pipeline. The gas in the air supply pipeline passes through the first heat exchanger and the second heat exchanger in turn for secondary heating. The first nozzles and the second nozzles of several vertically arranged jet assemblies are opened to heat the low-temperature area at the lower end of the return water pipe.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The antifreeze system and method provided in the above technical solution include an antifreeze device comprising an air supply pipe, a plurality of jet components, a first heat exchanger, and a second circulation loop connected between the first heat exchanger and the first circulation loop. When the circulating medium in the first circulation loop flows out of the condenser, the temperature is relatively high, and it is a high-temperature circulating medium. In the prior art, the temperature of these high-temperature circulating media is wasted. However, the present invention utilizes the second circulation loop to draw out part of the high-temperature circulating medium, and utilizes the first heat exchanger to transfer heat to the gas in the air supply pipe, thereby obtaining gas with a temperature higher than the ambient temperature, and injects it into the low-temperature zone to raise the temperature of the low-temperature zone, thereby preventing the circulating medium from freezing in the cooling triangle radiator, and even freezing and cracking the tube bundle. The embodiment of the present invention readjusts the heat distribution, transfers part of the heat to areas prone to freezing and cracking, utilizes the heat that would have been wasted, and improves energy utilization. The implementation method is relatively simple, the antifreeze effect is good, and it can effectively reduce the back pressure of the turbine operation, thereby improving the economy, safety and stability of the unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 It is a structural diagram of the intercooling system of the existing indirect air-cooling unit.

[0046] Figure 2 This is a structural schematic diagram of an antifreeze system of an indirect air-cooling unit intercooling system according to a first embodiment of the present invention, wherein the indirect air-cooling unit intercooling system is a Heller type.

[0047] Figure 3 This is a structural diagram of an antifreeze system of an indirect air-cooling unit intercooling system according to a second embodiment of the present invention, wherein the indirect air-cooling unit intercooling system is a Harmon type.

[0048] Figure 4 This is a schematic diagram of the positions of the cooling triangle radiator and the jet assembly according to an embodiment of the present invention.

[0049] Figure 5 Schematic diagram of the structure of the jet assembly according to an embodiment of the present invention.

[0050] Figure 6Schematic diagram of the distribution of the jet assembly at the middle and lower ends of the return pipe according to an embodiment of the present invention.

[0051] Description of reference numerals:

[0052] 10. Exhaust pipe; 20. Indirect air-cooling unit; 21. Indirect cooling tower; 211. Cooling triangle radiator; 212. Water inlet pipe; 213. Water return pipe; 214. Temperature sensor; 22. Condenser; 221. Hybrid condenser; 222. Surface condenser; 23. First circulation loop; 231. High-temperature pipe; 232. Low-temperature pipe; 233. Circulating pump; 30. Air supply pipe; 31. Air compressor; 32. First temperature detector; 33. Second temperature detector; 34. Third isolation valve; 35. Fourth isolation valve; 36. Ninth isolation valve Isolation valve; 40. Injection assembly; 41. First nozzle; 42. Second nozzle; 43. First regulating valve; 44. Second regulating valve; 50. First heat exchanger; 60. Second circulation loop; 61. First isolating valve; 62. Second isolating valve; 63. First regulating valve; 70. Secondary heating pipeline; 71. Condensate recovery tank; 711. Drain pipe; 712. Drain pipe isolation valve; 72. Multi-stage water seal; 73. Second regulating valve; 74. Fifth isolating valve; 75. Sixth isolating valve; 76. Seventh isolating valve; 77. Eighth isolating valve; 80. Second heat exchanger. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0054] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0055] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0056] The existing indirect air cooling unit intercooling system is as follows Figure 1 As shown, the exhaust steam of the steam turbine of the thermal power generator set is discharged to the indirect air-cooling unit 20 arranged outdoors through the exhaust pipe 10. The indirect air-cooling unit 20 includes a condenser 22 and an intercooling tower 21. The exhaust pipe 10 connects the exhaust port of the steam turbine and the condenser 22. A first circulation loop 23 is provided between the condenser 22 and the intercooling tower 21. The circulating medium can be water. The heat of the high-temperature circulating medium is transferred to the low-temperature circulating medium. The low-temperature circulating medium becomes a high-temperature circulating medium, and then flows back to the intercooling tower 21 through the first circulation loop 23. It is cooled to a low-temperature circulating medium in the intercooling tower 21 and then flows to the condenser 22 through the first circulation loop 23. Based on the different types of condensers 22, the intercooling system of the indirect air-cooling unit is divided into a Harmon intercooling system and a Heller intercooling system. Specifically, when the condenser 22 is a mixed condenser 221, the intercooling system of the indirect air-cooling unit is a Heller intercooling system. When the condenser 22 is a surface condenser 222, the intercooling system of the indirect air-cooling unit is a Harmon intercooling system. The cooling process of the high-temperature circulating medium in the intercooling tower 21 mainly depends on the cooling triangle radiator 211. The cooling triangle radiator 211 is generally around the outer periphery of the tower body of the intercooling tower 21. The first circulation loop 23 is connected to the cooling triangle radiator 211. When the cold air passes through the cooling triangle radiator 211, heat exchange occurs. The formed hot air is discharged upward from the center of the intercooling tower 21. The high-temperature circulating medium is cooled in the cooling triangle radiator 211 to become a low-temperature circulating medium. Therefore, there is a low-temperature zone in the cooling triangle radiator 211, and the low-temperature zone is easily frozen when the ambient temperature is below 0°C, causing the radiator to malfunction. Appendix Figure 4 It is one of the radiators that make up the cooling triangle radiator.

[0057] Based on this, an embodiment of the present invention provides an antifreeze system for an intercooling system of an indirect air-cooling unit, wherein the antifreeze device includes an air supply pipe 30, a plurality of jet components 40, a first heat exchanger 50, and a second circulation loop 60 connected between the first heat exchanger 50 and the first circulation loop 23, the second circulation loop 60 is used to draw out part of the high-temperature circulating medium from the first circulation loop 23, the air supply pipe 30 exchanges heat with the second circulation loop 60 through the first heat exchanger 50 to increase the gas temperature in the air supply pipe 30; the jet component 40 is arranged at the terminal of the air supply pipe 30, and the plurality of jet components 40 respectively correspond to the plurality of cooling triangle radiators 211 of the intercooling tower 21, and the jet direction of the jet component 40 is toward the low-temperature zone of the cooling triangle radiator 211, centralized heating, and providing the temperature of the low-temperature zone, as shown in the attached figure. Figure 2 and attached Figure 3 shown.

[0058] When the circulating medium in the first circulation loop 23 flows out of the condenser 22, the temperature is relatively high, and it is a high-temperature circulating medium. In the prior art, the temperature of these high-temperature circulating media will be wasted. However, the present invention utilizes the second circulation loop 60 to lead out part of the high-temperature circulating medium, and utilizes the first heat exchanger 50 to transfer the heat to the gas in the gas supply pipe 30, thereby obtaining gas with a temperature higher than the ambient temperature, and injecting it into the low-temperature zone to increase the temperature of the low-temperature zone, thereby preventing the circulating medium from freezing in the cooling triangle radiator 211, and even freezing and cracking the tube bundle. The embodiment of the present invention readjusts the heat distribution, transfers part of the heat to the parts that are prone to freezing and cracking, utilizes the heat that was originally wasted, and improves energy utilization. The implementation method is relatively simple, the anti-freezing effect is good, and it can effectively reduce the back pressure of the turbine operation, thereby improving the economy, safety and stability of the unit operation.

[0059] Specifically, the first circulation loop 23 includes a low-temperature pipe 232 that guides the low-temperature circulating medium of the intercooler 21 to the condenser 22, and a high-temperature pipe 231 and a circulation pump 233 that guide the high-temperature circulating medium of the condenser 22 to the intercooler 21; the inlet of the second circulation loop 60 is connected to the high-temperature pipe 231, and the outlet of the second circulation loop 60 is connected to the low-temperature pipe 232, thereby obtaining a high-temperature circulating medium.

[0060] As attached Figure 2 In the illustrated embodiment 1, the intercooling system of the indirect air-cooling unit is a Heller-type intercooling system, the condenser 22 is a hybrid condenser 221, the circulating pump 233 is arranged on the high-temperature pipe 231, and the inlet of the second circulation pipeline is located between the circulating pump 233 and the cooling triangle radiator 211, which is conducive to sending the higher temperature part of the high-temperature circulating medium just out of the condenser 22 into the second circulation pipeline as soon as possible, thereby ensuring the temperature of the high-temperature circulating medium in the second circulation pipeline.

[0061] The antifreeze device of this embodiment can be manually controlled, including manual start-up, manual adjustment of the gas flow in the gas supply pipe 30, and manual adjustment of the flow of the high-temperature circulating medium in the second circulation loop 60 to adjust the gas temperature in the gas supply pipe 30. The jet assembly 40 can be manually replaced as needed to adjust the injection range of the jet assembly 40.

[0062] Of course, as a preferred implementation method, this embodiment can also adopt an automatic control method. Specifically, the antifreeze system of this embodiment also includes a control module (not shown) and several return water temperature detection modules. The control module can be integrated into the DCS system of the thermal power generator set, and has a built-in control program to control the antifreeze device based on the return water temperature, ambient temperature and unit back pressure.

[0063] The cooling triangle radiator 211 has a connected water inlet pipe 212 and a return pipe 213 inside. The water inlet pipe 212 is connected to the high-temperature pipe 231, and the return pipe 213 is connected to the low-temperature pipe 232. The cooled low-temperature circulating medium flows in the return pipe 213. The closer to the lower end of the return pipe 213, the lower the temperature of the circulating medium, and the easier it is to freeze. The position of the jet assembly 40 in this embodiment corresponds to the lower end of the return pipe 213. In some cases, the return pipe 213 is located on the windward side of the cooling triangle radiator 211, and the jet assembly 40 is set between the cooling triangle radiator 211 and the louver, and sprays air toward the cooling triangle radiator 211; in other cases, the return pipe 213 is located on the leeward side of the cooling triangle radiator 211, and the jet assembly 40 is set on the inner side of the cooling triangle radiator 211.

[0064] Meanwhile, a return water temperature detection module, located in the low-temperature zone at the lower end of the return pipe 213, monitors the return water temperature at locations prone to freezing. The module includes several temperature sensors 214, located at the lower end of the return pipe 213. These sensors accurately detect the return water temperature, avoiding the jet assembly 40 and preventing the detection results from being affected by the hot gas ejected by the jet assembly 40. The temperature sensors 214 transmit the detected temperature data to the control module, which communicates with the gas supply pipe 30 and adjusts the gas temperature within the gas supply pipe 30 based on the return water temperature. Each return pipe 213 can be equipped with one or more temperature sensors 214. If multiple temperature sensors 214 are installed in a return pipe 213, the temperatures detected by these multiple temperature sensors 214 can be averaged to improve detection accuracy. The jet assembly 40 corresponding to each return pipe 213 can be independently controlled. Specifically, the jet range of each jet assembly 40 is controlled based on the temperature detected by the corresponding temperature sensor 214 at the lower end of each row of return pipes 213. In addition, a temperature sensor 214 may be provided inside or near the jet assembly 40 to detect the temperature of the hot air jetted from the jet assembly 40 in real time and determine whether the antifreeze device is functioning normally.

[0065] As attached Figure 2 As shown, a first regulating valve 63 is provided on the second circulation loop 60; the control module is in communication with the first regulating valve 63 and is configured to regulate the flow of the high-temperature circulating medium in the second circulation loop 60 based on the return water temperature. When the return water temperature decreases, the opening of the first regulating valve 63 increases, allowing more high-temperature circulating medium to flow into the second circulation loop 60 and increasing the temperature of the gas ejected by the jet assembly 40. When the return water temperature increases, the opening of the first regulating valve 63 decreases, reducing the flow of the high-temperature circulating medium into the second circulation loop 60 and decreasing the temperature of the gas ejected by the jet assembly 40. When the return water temperature exceeds a first set value, it is determined that the cooling triangle radiator 211 is not likely to freeze, and the first regulating valve 63 can be closed. The specific value of the first set value is set according to the actual operating conditions of the intercooling system of the indirect air-cooled unit.

[0066] As attached Figure 4 and attached Figure 5 As shown, the jet assembly 40 of this embodiment includes a first nozzle 41 and a second nozzle 42. The spray range of the second nozzle 42 is larger than the spray range of the first nozzle 41. The control module is connected to the jet assembly 40 and is used to select to open the first nozzle 41 or the second nozzle 42 or to open the first nozzle 41 and the second nozzle 42 at the same time based on the return water temperature. That is, when the return water temperature is low, the first nozzle 41 is opened. The first nozzle 41 is relatively closer to the return water pipe 213, and the spray range is smaller, but more accurate, and the gas temperature loss is less; when the return water temperature is lower, the first nozzle 41 is closed and the second nozzle 42 is opened. Although the second nozzle 4 2 is relatively far away from the return pipe 213, but the spray range of the second nozzle 42 is larger, and the gas temperature in the gas supply pipe 30 is higher at this time. Therefore, the gas temperature sprayed by the second nozzle 42 is higher, which can create a warmer environment and increase the temperature of the specific part of the return pipe 213; when the return water temperature drops further, indicating that the ambient temperature is even lower and there may be strong winds, the first nozzle 41 and the second nozzle 42 are turned on at the same time. The gas sprayed by the second nozzle 42 is shielded by the gas sprayed by the first nozzle 41 to form a gas shield, which is conducive to retaining heat, reducing gas temperature loss, and having a better temperature-raising effect on the return pipe 213.

[0067] As attached Figure 4As shown, several jet assemblies 40 are arranged vertically at positions corresponding to the low-temperature zone at the lower end of the cooling triangle radiator 211 and the return pipe 213. They are controlled by the control module and are turned on sequentially from bottom to top based on the return water temperature. The activation priority of all first nozzles 41 and second nozzles 42 of the jet assemblies 40 at the same height is higher than the activation priority of all first nozzles 41 and second nozzles 42 of the jet assemblies 40 at a higher height. Specifically, when the return water temperature is low, the first nozzle 41 of the jet assembly 40 corresponding to the lowest end of the return pipe 213 is turned on. When the return water temperature is even lower, the first nozzle 41 corresponding to the lowest end of the return pipe 213 is turned off and the second nozzle 42 is turned on. When the return water temperature drops further, the first nozzle 41 and the second nozzle 42 are turned on simultaneously. When the return water temperature drops further, the first nozzle 41 and / or the second nozzle 42 of the jet assembly 40 at a higher level than the jet assembly 40 corresponding to the lowest end of the return pipe 213 are turned on, thereby turning on each jet assembly 40 sequentially from bottom to top.

[0068] The spray ranges of the two upper and lower adjacent second nozzles 42 partially overlap, and the spray range of the second nozzle 42 contacts or partially overlaps with the edge of the spray range of the first nozzle 41 in another nozzle assembly 40. Figure 6 As shown, at least two jet assemblies 40 are correspondingly provided for a return water pipe 213; when the first nozzle 41 and the second nozzle 42 need to be opened at the same time, the return water temperature and the ambient temperature are very low, and the ejected gas is easy to cool down quickly in such a cold environment. Therefore, in two adjacent jet assemblies 40, the injection ranges of the two second nozzles 42 partially overlap, and the injection range of the second nozzle 42 contacts or partially overlaps with the edge of the injection range of the first nozzle 41 of the other jet assembly 40, thereby forming a multi-layer gas barrier, so that the gas temperature within the total injection range of the jet assembly 40 is relatively uniform, and heat is not easily lost, which has a good heating effect on the return water pipe 213.

[0069] The jet assembly 40 corresponding to each row of return pipes 213 can be independently adjusted. The spray range of each jet assembly 40 is controlled according to the temperature detected by the temperature sensor 214 corresponding to each row of return pipes 213. That is, each jet assembly 40 can be controlled to individually open the first nozzle 41 or the second nozzle 42 or open the first nozzle 41 and the second nozzle 42 at the same time, so as to spray more hot air to colder parts, achieve precise heating, and improve heat utilization.

[0070] Specifically, a first regulating valve 43 is provided on the connecting pipe between the first nozzle 41 and the air supply pipe 30, and a second regulating valve 44 is provided on the connecting pipe between the second nozzle 42 and the air supply pipe 30. The first regulating valve 43 and the second regulating valve 44 are both electrically controlled valves, which are communicatively connected to the control module to realize remote selection and control of the jet assembly 40.

[0071] The air supply pipeline 30 includes an air compressor 31. The gas in the air supply pipeline 30 is compressed air. The air compressor 31 is an adjustable pressure air compressor 31. The control module is in communication with the air compressor 31 and is used to adjust the pressure of the air compressor 31 based on the condensate temperature. When only the first nozzle 41 is turned on, the pressure of the air compressor 31 can be a first pressure. When only the second nozzle 42 is turned on, the pressure of the air compressor 31 needs to be increased to a second pressure due to the larger spray range and higher gas flow rate. When the first nozzle 41 and the second nozzle 42 are turned on simultaneously, the pressure of the air compressor 31 needs to be further increased to a third pressure. The specific data of the first pressure, the second pressure, and the third pressure are set according to the diameter of the air supply pipeline 30 and the size of the injection assembly.

[0072] Preferably, the antifreeze system of this embodiment further includes a backpressure detection module (not shown) for detecting turbine backpressure. This module is a conventional detection unit in the DCS system of a thermal power generator set and is therefore not described in detail here. The backpressure detection module is communicatively connected to the control module, transmitting turbine backpressure data to the control module for controlling the antifreeze device.

[0073] When all the jet assemblies 40 corresponding to a return water pipe 213 are opened, and the return water temperature in the return water pipe 213 is still lower than the freezing temperature, the opening of the first regulating valve 63 reaches the maximum. If the antifreeze method of the prior art is adopted, it is generally necessary to increase the back pressure of the steam turbine, which will affect the economic efficiency of the unit operation. However, this embodiment adopts the introduction of other heat sources, such as the introduction of partial low-pressure extraction steam of the unit (such as five-stage extraction steam), and uses this antifreeze device for antifreeze. Compared with the traditional operation mode of increasing the back pressure of the steam turbine unit for antifreeze, it has less impact on the overall economic efficiency of the unit, thereby increasing the jet temperature without increasing the back pressure of the steam turbine. Specifically, the antifreeze device also includes a secondary heating pipeline 70 and a second heat exchanger 80 connected to the heat source. The secondary heating pipeline 70 is provided with an on-off unit (not shown), which is communicated with the control module and is used to conduct the secondary heating pipeline 70 when the back pressure of the turbine is higher than the set back pressure and the opening of the first regulating valve 63 is maximum; the temperature of the high-temperature steam in the secondary heating pipeline 70 is higher than the temperature of the high-temperature circulating medium in the second circulation loop 60. The second heat exchanger 80 is arranged between the first heat exchanger 50 and the injection assembly 40. The air supply pipeline 30 exchanges heat with the secondary heating pipeline 70 through the second heat exchanger 80. The gas in the air supply pipeline 30 is first heated by the first heat exchanger 50 to increase its temperature for the first time, and then exchanges heat with the second heat exchanger 80 to further increase its temperature, thereby increasing the temperature of the gas ejected from the injection assembly 40.

[0074] The secondary heating line 70 is equipped with a condensate recovery tank 71 and a multi-stage water seal 72. The terminal of the secondary heating line is connected to the condenser 22. The medium in the secondary heating line is high-temperature steam. After passing through the second heat exchanger 80, some of the high-temperature steam cools and condenses, forming condensate, which enters the condensate recovery tank 71. The multi-stage water seal 72 ensures the airtightness of the secondary heating line, preventing vacuum leaks. The remaining high-temperature steam in the secondary heating line then enters the condenser 22, where it combines with the turbine exhaust steam to heat the circulating medium, raising the temperature of the high-temperature circulating medium entering the second circulation loop 60. This further increases the heat transferred from the first heat exchanger 50 to the gas in the gas supply line 30, further raising the overall temperature of the gas in the gas supply line 30 and reducing heat loss. A drain pipe 711 is provided on the condensate recovery tank 71 to discharge non-condensable gases from the secondary heating line. A drain pipe isolation valve 712 is installed on the drain pipe 711 of the condensate recovery tank 71 to facilitate system maintenance and isolation.

[0075] The antifreeze device also includes a first temperature detector 32 and a second temperature detector 33. The first temperature detector 32 is located between the first heat exchanger 50 and the second heat exchanger 80, and the second temperature detector 33 is located between the second heat exchanger 80 and the injection assembly 40. A second regulating valve 73 is provided on the secondary heating pipeline 70. The first temperature detector 32 and the second temperature detector 33 are respectively connected to the control module, and are used to adjust the flow rate of the high-temperature circulating medium in the second circulation loop 60 and the steam flow rate in the secondary heating pipeline 70 based on the detected temperature.

[0076] When the on-off unit of the secondary heating pipeline 70 is turned on, at this time, the pressure of the air compressor 31 is greater than or equal to the third pressure, the gas flow rate in the air supply pipeline 30 increases, and the contact time with the first heat exchanger 50 is reduced. At the same time, the remaining high-temperature steam in the secondary heating pipeline 70 is passed into the condenser 22, and the temperature of the high-temperature circulating medium in the second circulation loop 60 is increased. The first temperature detector 32 detects that the temperature may remain unchanged or slightly decrease, and the second regulating valve 73 on the second branch pipe can be controlled to open more, and the second heat exchanger 80 can transfer more heat. As a result, the gas temperature in the air supply pipeline 30 is increased as a whole, and the heating effect on the lower end of the return pipe 213 is better.

[0077] As attached Figure 2As shown, the second circulation loop 60 is provided with a first isolation valve 61, located between the inlet of the second circulation loop 60 and the first heat exchanger 50. The second circulation loop 60 is provided with a second isolation valve 62, located between the outlet of the first heat exchanger 50 and the second circulation loop 60. The first isolation valve 61 and the second isolation valve 62 are used to disconnect the antifreeze device from the first circulation loop 23 during maintenance, facilitating isolation and maintenance. The air supply pipeline 30 is provided with a third isolation valve 34, located between the air compressor 31 and the first heat exchanger 50. The third isolation valve 34 is used to facilitate isolation of the air supply pipeline 30 from the first heat exchanger 50 during maintenance. The gas supply pipeline 30 is equipped with a fourth isolation valve 35, located between the first heat exchanger 50 and the second heat exchanger 80. The fourth isolation valve 35 facilitates the isolation and disconnection of the first heat exchanger 50 and the second heat exchanger 80 during maintenance. The gas supply pipeline 30 is equipped with a ninth isolation valve 36, located between the second heat exchanger and the end of the gas supply pipeline. The ninth isolation valve 36 facilitates the isolation and disconnection of the second heat exchanger from the injection assembly during maintenance. The secondary heating pipeline 70 is equipped with a fifth isolation valve 74, located upstream of the second heat exchanger 80. The fifth isolation valve 74 disconnects the heat source from the secondary heating pipeline 70 during system maintenance. A sixth isolation valve 75 is provided on the secondary heating pipeline 70, and the sixth isolation valve 75 is located between the second heat exchanger 80 and the condensate recovery tank 71; a seventh isolation valve 76 is provided on the secondary heating pipeline 70, and the seventh isolation valve 76 is located between the condensate recovery tank 71 and the multi-stage water seal 72; an eighth isolation valve 77 is provided on the secondary heating pipeline 70, and the eighth isolation valve 77 is located between the multi-stage water seal 72 and the condenser 22. The functions of the sixth isolation valve 75, the seventh isolation valve 76 and the eighth isolation valve 77 are to facilitate system maintenance isolation and prevent vacuum leakage of the condensate recovery tank 71 and the condenser 22 in emergency situations.

[0078] As attached Figure 3 In the second embodiment shown, the intercooling system of the indirect air-cooling unit is a Harmon-type intercooling system, the condenser 22 is a surface condenser 222, the circulating pump 233 is arranged on the low-temperature pipe 232, and the outlet of the second circulation loop 60 is located between the circulating pump 233 and the cooling triangle radiator 211, and the cooled circulating medium is quickly transported back to the low-temperature pipe 232, and then quickly input into the intercooling tower 21; the operating logic of the antifreeze system of this embodiment is the same as that of the first embodiment, and will not be repeated here.

[0079] Based on the antifreeze system of the intercooling system of the indirect air-cooling unit in the above embodiment, the present invention further provides an antifreeze method of the intercooling system of the indirect air-cooling unit, comprising the following steps:

[0080] Open the second circulation loop 60 to draw out part of the high-temperature circulating medium from the first circulation loop 23;

[0081] The gas supply pipe 30 is opened, and the internal gas flows through the first heat exchanger 50 to exchange heat with part of the high-temperature circulating medium, thereby increasing the gas temperature. The circulating medium cooled in the second circulation loop 60 flows back to the first circulation loop 23;

[0082] The jet assembly 40 is started, and the gas with a raised temperature is jetted into the low-temperature area of ​​the cooling triangle radiator 211 of the intercooler 21 .

[0083] Preferably, the method of this embodiment also includes: detecting the return water temperature at the lower end of the return water pipe 213 inside the cooling triangle radiator 211, and controlling the start-up number of the jet assembly 40 and the gas temperature and jet range of the jet assembly 40 after start-up according to the return water temperature.

[0084] Specifically, the control logic of the jet assembly 40 is as follows:

[0085] If the return water temperature is lower than the first set value T1, the first regulating valve on the second circulation loop 60 is opened, the air compressor 31 on the air supply pipe 30 is turned on, and the first nozzle 41 in the jet assembly 40 at the bottom of the return water pipe 213 is turned on to heat the low-temperature area at the bottom of the return water pipe 213;

[0086] If the return water temperature is lower than the second set value T2, the opening of the first regulating valve on the second circulation loop 60 is increased to increase the flow rate of the high-temperature circulating medium in the second circulation loop 60, and the pressure of the air compressor 31 on the air supply pipe 30 is increased. The first nozzle 41 in the jet assembly 40 at the bottom end of the return water pipe 213 is closed, and the second nozzle 42 is opened to heat the low-temperature area at the bottom end of the return water pipe 213;

[0087] If the return water temperature is lower than the third set value T3, the opening of the first regulating valve on the second circulation loop 60 is further increased to further increase the flow rate of the high-temperature circulating medium in the second circulation loop 60, increase the pressure of the air compressor 31 on the air supply pipe 30, and open the first nozzle 41 and the second nozzle 42 of the jet assembly 40 at the lowest end of the return water pipe 213 to heat the low-temperature area at the lowest end of the return water pipe 213;

[0088] If the return water temperature is lower than the fourth set value T4, the first regulating valve on the second circulation loop 60 is opened to the maximum, further increasing the flow rate of the high-temperature circulating medium in the second circulation loop 60, increasing the pressure of the air compressor 31 on the air supply pipe 30, and simultaneously opening the first nozzle 41 and the second nozzle 42 of the higher-level jet assembly 40 to heat the low-temperature area at the middle and lower end of the return water pipe 213;

[0089] If the return water temperature is lower than the fifth set value T5, and the back pressure of the steam turbine is detected to be higher than the set back pressure, the secondary heating pipeline 70 is opened to increase the pressure of the air compressor 31 on the air supply pipe 30. The gas in the air supply pipe 30 passes through the first heat exchanger 50 and the second heat exchanger 80 in sequence for secondary heating. The first nozzles 41 and the second nozzles 42 of the vertically arranged several injection assemblies 40 are all opened to heat the low-temperature area at the middle and lower end of the return water pipe 213.

[0090] T1 to T5 can be set according to the following rules: T1>T2>T3>T4>T5. The specific values ​​are set by the actual environment and operating conditions of the unit.

[0091] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. An antifreeze system for an indirect air-cooled unit intercooling system, comprising an exhaust pipe and an indirect air-cooled unit, wherein the indirect air-cooled unit includes a condenser and an intercooling tower, the exhaust pipe connecting the exhaust port of a steam turbine and the condenser, and a first circulation loop being provided between the condenser and the intercooling tower; It is characterized by: The system further includes an antifreeze device, which includes an air supply pipe, a plurality of jet assemblies, a first heat exchanger, and a second circulation loop connected between the first heat exchanger and the first circulation loop, wherein the second circulation loop is used to draw out part of the high-temperature circulating medium from the first circulation loop, and the air supply pipe exchanges heat with the second circulation loop through the first heat exchanger to increase the gas temperature in the air supply pipe; the jet assembly is arranged at the terminal of the air supply pipe, and the plurality of jet assemblies respectively correspond to the plurality of cooling triangle radiators of the intercooler, and the jet direction of the jet assembly is toward the low-temperature area of ​​the cooling triangle radiator; The cooling triangle radiator has a connected water inlet pipe and a return pipe inside, and the antifreeze system also includes a control module and a plurality of return water temperature detection modules. The return water temperature detection module is located in the low temperature area at the lower end of the return water pipe. The return water temperature detection module is communicatively connected to the control module, and the control module is communicatively connected to the gas supply pipe for adjusting the gas temperature in the gas supply pipe based on the return water temperature; The second circulation loop is provided with a first regulating valve; the control module is in communication with the first regulating valve and is used to regulate the flow of the high-temperature circulating medium in the second circulation loop based on the return water temperature; The spray assembly includes a first nozzle and a second nozzle, the first nozzle and the second nozzle are both directed toward the return pipe on the same side, the spray range of the second nozzle is larger than the spray range of the first nozzle, and the first nozzle is located within the spray range of the second nozzle; The control module is connected to the jet assembly and is used to select to open the first nozzle or the second nozzle or both the first nozzle and the second nozzle based on the return water temperature; The plurality of jet assemblies are vertically arranged at positions corresponding to the low-temperature area of ​​the cooling triangle radiator and the lower end of the return water pipe, and are controlled by the control module to be opened in sequence from bottom to top based on the return water temperature; the opening priority of all the first nozzles and the second nozzles of the jet assemblies at the same height is higher than the opening priority of all the first nozzles and the second nozzles of the jet assemblies at a higher height; The spraying ranges of two upper and lower adjacent second nozzles partially overlap, and the spraying range of the second nozzle touches or partially overlaps with the edge of the spraying range of the first nozzle in another nozzle assembly; The air supply pipeline includes an air compressor, the gas in the air supply pipeline is compressed air, the air compressor is an adjustable pressure air compressor, and the control module is communicatively connected to the air compressor for adjusting the pressure of the air compressor based on the circulating water temperature.

2. The antifreeze system according to claim 1, characterized in that The first circulation loop includes a low-temperature pipe that guides the low-temperature circulating medium of the intercooler to the condenser, and a high-temperature pipe and a circulation pump that guides the high-temperature circulating medium of the condenser to the intercooler; the inlet of the second circulation loop is connected to the high-temperature pipe, and the outlet of the second circulation loop is connected to the low-temperature pipe; The condenser is a hybrid condenser, the circulating pump is provided on the high-temperature pipeline, and the inlet of the second circulation loop is located between the circulating pump and the cooling triangle radiator; or, The condenser is a surface condenser, the circulation pump is arranged on the low-temperature pipeline, and the outlet of the second circulation loop is located between the circulation pump and the cooling triangle radiator.

3. The antifreeze system according to claim 1, characterized in that The antifreeze device further includes a back pressure detection module for detecting the back pressure of the steam turbine, the back pressure detection module being communicatively connected to the control module; the antifreeze device further includes a secondary heating pipeline and a second heat exchanger connected to a heat source, the secondary heating pipeline being provided with an on-off unit, the on-off unit being communicatively connected to the control module and being configured to open the secondary heating pipeline when the back pressure of the steam turbine is higher than a set back pressure and the opening of the first regulating valve is at its maximum; The temperature of the high-temperature steam in the secondary heating pipeline is higher than the temperature of the high-temperature circulating medium in the second circulation loop. The second heat exchanger is arranged between the first heat exchanger and the jet assembly. The air supply pipeline exchanges heat with the secondary heating pipeline through the second heat exchanger. The secondary heating pipeline is provided with a condensate recovery tank and a multi-stage water seal, and the terminal end of the secondary heating pipeline is communicated with the condenser.

4. The antifreeze system according to claim 3, characterized in that The antifreeze device also includes a first temperature detector and a second temperature detector, the first temperature detector is located between the first heat exchanger and the second heat exchanger, and the second temperature detector is located between the second heat exchanger and the injection assembly. A second regulating valve is provided on the secondary heating pipeline, and the first temperature detector and the second temperature detector are respectively connected to the control module, and are used to adjust the flow rate of the high-temperature circulating medium in the second circulation loop and the steam flow rate in the secondary heating pipeline based on the detected temperature.

5. The antifreeze system according to claim 3, characterized in that: The second circulation loop is provided with a first isolation valve, and the first isolation valve is located between the inlet of the second circulation loop and the first heat exchanger; A second isolation valve is provided on the second circulation loop, and the second isolation valve is located between the first heat exchanger and the outlet of the second circulation loop; A third isolation valve is provided on the air supply pipeline, and the third isolation valve is located between the air compressor and the first heat exchanger; A fourth isolation valve is provided on the gas supply pipeline, and the fourth isolation valve is located between the first heat exchanger and the second heat exchanger; A fifth isolation valve is provided on the secondary heating pipeline, and the fifth isolation valve is located upstream of the second heat exchanger; A sixth isolation valve is provided on the secondary heating pipeline, and the sixth isolation valve is located between the second heat exchanger and the condensate recovery tank; A seventh isolation valve is provided on the secondary heating pipeline, and the seventh isolation valve is located between the condensate recovery tank and the multi-stage water seal; An eighth isolation valve is provided on the secondary heating pipeline, and the eighth isolation valve is located between the multi-stage water seal and the condenser.

6. A method for antifreezing the intercooling system of an indirect air-cooling unit, characterized in that: An antifreeze system using the intercooling system of the indirect air-cooling unit according to any one of claims 1 to 5 comprises the following steps: opening the second circulation loop and drawing out a portion of the high-temperature circulating medium from the first circulation loop; Open the gas supply pipeline, allowing the internal gas to flow through the first heat exchanger, exchanging heat with part of the high-temperature circulating medium to increase the gas temperature, and the circulating medium cooled in the second circulation loop flows back to the first circulation loop; The jet assembly is started, and the gas with the increased temperature is sprayed into the low-temperature area of ​​the cooling triangle radiator of the intercooling tower.

7. The antifreeze method according to claim 6, characterized in that: The return water temperature at the lower end of the return water pipe inside the cooling triangle radiator is detected, and the start-up number of the jet assembly and the gas temperature and jet range of the jet assembly after startup are controlled according to the return water temperature.

8. The antifreeze method according to claim 7, characterized in that: The control logic of the jet assembly is as follows: If the return water temperature is lower than the first set value, the first regulating valve on the second circulation loop is opened, the air compressor on the air supply pipe is turned on, and the first nozzle in the jet assembly at the lower end of the return water pipe is turned on to heat the low temperature area at the lower end of the return water pipe; If the return water temperature is lower than the second set value, the opening of the first regulating valve on the second circulation loop is increased to increase the flow of the high-temperature circulating medium in the second circulation loop, and the pressure of the air compressor on the air supply pipe is increased. The first nozzle in the jet assembly at the lowest end of the return pipe is closed and the second nozzle is opened to heat the low-temperature area at the lowest end of the return pipe; If the return water temperature is lower than the third set value, the opening of the first regulating valve on the second circulation loop is further increased to further increase the flow of the high-temperature circulating medium in the second circulation loop, increase the pressure of the air compressor on the air supply pipe, open the first nozzle in the jet assembly at the lowest end of the return pipe, and open the second nozzle to heat the low-temperature area at the lowest end of the return pipe; If the return water temperature is lower than the fourth set value, the opening of the first regulating valve on the second circulation loop is adjusted to the maximum, further increasing the flow rate of the high-temperature circulating medium in the second circulation loop, increasing the pressure of the air compressor on the air supply pipe, and at the same time opening the first nozzle and the second nozzle of the higher-elevation jet assembly to heat the low-temperature area at the lower end of the return water pipe; If the return water temperature is lower than the fifth set value and the back pressure of the steam turbine is detected to be higher than the set back pressure, the secondary heating pipeline is opened to increase the pressure of the air compressor on the air supply pipeline. The gas in the air supply pipeline passes through the first heat exchanger and the second heat exchanger in turn for secondary heating. The first nozzles and the second nozzles of several vertically arranged jet assemblies are opened to heat the low-temperature area at the lower end of the return water pipe.

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