A direct air-cooling unit air-cooling island antifreeze system and method

Abstract

The present invention relates to an antifreeze system and method for an air-cooling island of a direct air-cooling unit, wherein the antifreeze device includes an air supply pipe, a nozzle, a first heat exchanger, and a first branch pipe connected to the exhaust pipe; the first branch pipe is used to draw out part of the turbine exhaust steam from the exhaust pipe, the air supply pipe exchanges heat with the first branch pipe through the first heat exchanger, the nozzle is arranged at the terminal end of the air supply pipe, and a plurality of nozzles are arranged between two inclined condensing units, and are respectively located at the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle. The present invention directly utilizes the turbine exhaust steam of part of the exhaust pipe to heat the gas in the air supply pipe, and then sprays the gas to a position with a lower temperature in the air-cooling island, thereby raising the temperature of the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle, preventing the condensed water therein from freezing in the tube bundle, or even freezing and cracking the tube bundle, which can effectively reduce the back pressure of the turbine during winter operation and improve the economy, safety and stability of the unit during winter operation.

Description

Technical Field

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

[0002] In recent years, with the rapid development of my country's 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 severe shortage of water resources and the country's environmental protection requirements for new units, direct air cooling has become a relatively common method for cooling the exhaust steam of steam turbine units. The structure of the direct air cooling unit is shown in the attached figure. Figure 1 As shown, the exhaust steam of the steam turbine directly enters the cooling system of the unit's air-cooling island, and the air is driven by the air-cooling fan to cool the exhaust steam of the unit by convection heat exchange.

[0003] However, the cooling characteristics of direct air-cooled units' air-cooling systems mean that their operation is significantly affected by ambient temperature. This is particularly true in winter, when extremely low ambient temperatures can easily cause freezing and cracking of the heat exchange tubes in the cooling island of the unit, seriously impacting the unit's operational safety and stability. Existing antifreeze systems typically incorporate shielding devices such as blinds, but these are not ideal. Therefore, a novel antifreeze system and method for the cooling island of direct air-cooled units is needed. 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 air-cooling island antifreeze system and method for a direct air-cooling unit.

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

[0006] An air-cooling island antifreeze system for a direct air-cooling unit comprises an exhaust pipe, a direct air-cooling unit, and an antifreeze device. The direct air-cooling unit comprises an air-cooling island and a condensate tank. The air-cooling island is connected to the condensate tank. The exhaust pipe connects the exhaust port of the steam turbine and the air-cooling island. The air-cooling island as a whole comprises a plurality of triangular cooling units. The triangular cooling units are in an inverted "V" shape and include two inclined condensing units. The condensing units include a downstream tube bundle and a countercurrent tube bundle.

[0007] The antifreeze device includes an air supply pipe, a nozzle, a first heat exchanger and a first branch pipe connected to the exhaust pipe; the first branch pipe is used to draw out part of the turbine exhaust steam from the exhaust pipe, and the air supply pipe exchanges heat with the first branch pipe through the first heat exchanger to increase the gas temperature in the air supply pipe. The nozzle is arranged at the terminal end of the air supply pipe, and several of the nozzles are arranged between the two inclined condensing units and are respectively located at the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle. The nozzle head of the nozzle is facing the downstream tube bundle and the countercurrent tube bundle, and the first branch pipe is connected to the condensate tank.

[0008] Preferably, the antifreeze system also includes a control module and several condensate temperature detection modules, the condensate temperature detection modules are respectively located in the condensate collection pipe at the lower end of the downstream tube bundle and in the vacuum collection pipe at the upper end of the countercurrent tube bundle, the condensate temperature detection module is communicatively connected to the control module, and the control module is communicatively connected to the air supply pipe, and is used to adjust the gas temperature in the air supply pipe based on the condensate temperature.

[0009] Preferably, a first regulating valve is provided on the first branch pipe; the control module is in communication with the first regulating valve and is configured to regulate the exhaust flow of the steam turbine in the first branch pipe based on the ambient temperature;

[0010] The nozzle includes a first nozzle and a second nozzle, the spray range of the second nozzle is larger than the spray range of the first nozzle, and the control module is connected to the nozzle and is used to select to open the first nozzle or the second nozzle or open the first nozzle and the second nozzle at the same time based on the condensate temperature;

[0011] 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 condensate temperature.

[0012] Preferably, at least two nozzles are correspondingly provided for one downstream tube bundle, and at least two nozzles are correspondingly provided for one upstream tube bundle;

[0013] In two adjacent nozzles, the spraying ranges of the two 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 of the other nozzle;

[0014] The spraying range of the second nozzle of the nozzle close to the edge of the downstream tube bundle exceeds the edge of the downstream tube bundle.

[0015] Preferably, the antifreeze system further comprises a back pressure detection module for detecting the back pressure of the steam turbine, and the back pressure detection module is communicatively connected to the control module;

[0016] The antifreeze device further includes a second branch pipe connected to the heat source and a second heat exchanger, the second branch pipe being provided with an on-off unit, the on-off unit being communicatively connected to the control module and configured to open the second branch pipe 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;

[0017] The temperature of the steam in the second branch pipe is higher than the temperature of the turbine exhaust steam in the first branch pipe. The second heat exchanger is arranged between the first heat exchanger and the nozzle. The air supply pipe exchanges heat with the second branch pipe through the second heat exchanger.

[0018] 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 nozzle, and a second regulating valve is provided on the second branch pipe. The first temperature detector and the second temperature detector are respectively connected to the control module, and are used to adjust the turbine exhaust flow in the first branch pipe and the steam flow in the second branch pipe based on the detected temperature.

[0019] Preferably, the second branch pipe is connected to the condensate tank;

[0020] A first isolation valve is provided on the first branch pipe, and the first isolation valve is located between the first regulating valve and the first heat exchanger;

[0021] A second isolation valve is provided on the first branch pipe, and the second isolation valve is located between the first heat exchanger and the condensate tank;

[0022] 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;

[0023] 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;

[0024] A fifth isolation valve is provided on the second branch pipe, and the fifth isolation valve is located upstream of the second heat exchanger;

[0025] The second branch pipe is provided with a sixth isolation valve, and the sixth isolation valve is located between the second heat exchanger and the condensate tank.

[0026] To achieve the above purpose, the present invention also adopts the following technical solutions:

[0027] A method for antifreezing an air-cooling island of a direct air-cooling unit adopts the above-mentioned antifreezing system for the air-cooling island of a direct air-cooling unit, comprising the following steps:

[0028] opening the first branch pipe to lead out part of the steam turbine exhaust steam from the exhaust pipe;

[0029] The gas supply pipe is opened, and the internal gas flows through the first heat exchanger, exchanges heat with part of the turbine exhaust steam, thereby increasing the gas temperature, and the cooled and condensed water in the first branch pipe flows into the condensate tank;

[0030] The nozzle is started to spray the gas with a raised temperature onto the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle, thereby heating the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle from the outside.

[0031] Preferably, the condensate temperature in the condensate header at the lower end of the downstream tube bundle is detected, and the gas temperature and injection range of the nozzle corresponding to the lower end of the downstream tube bundle are controlled according to the condensate temperature in the condensate header;

[0032] The condensate temperature of the vacuum header at the upper end of the countercurrent tube bundle is detected, and the gas temperature and injection range of the nozzle corresponding to the upper end of the countercurrent tube bundle are controlled according to the condensate temperature of the vacuum header.

[0033] Preferably, the control logic of the gas temperature sprayed by the nozzle and the spray range is as follows:

[0034] If the condensate temperature is lower than the first set value, the first regulating valve on the first branch pipe is opened, the air compressor on the air supply pipe is turned on, and the first nozzle is turned on to heat the lower end of the downstream tube bundle and the upper end of the upstream tube bundle;

[0035] If the condensate temperature is lower than a second set value, the opening of the first regulating valve on the first branch pipe is increased to increase the exhaust flow of the steam turbine in the first branch pipe and the pressure of the air compressor on the air supply pipe. The first nozzle is closed and the second nozzle is opened to heat the lower end of the downstream tube bundle and the upper end of the upstream tube bundle.

[0036] If the condensate temperature is lower than a third set value, the first regulating valve on the first branch pipe is adjusted to a maximum opening, the turbine exhaust flow in the first branch pipe is increased, the pressure of the air compressor on the air supply pipe is increased, the first nozzle is opened, and the second nozzle is opened to heat the lower end of the downstream tube bundle and the upper end of the upstream tube bundle;

[0037] If the condensate temperature is lower than the fourth set value and it is detected that the back pressure of the steam turbine is higher than the set back pressure, the second branch pipe is opened to increase the pressure of the air compressor on the air supply pipe. The gas in the air supply pipe passes through the first heat exchanger and the second heat exchanger in sequence for secondary heating. The first nozzle is opened and the second nozzle is opened to heat the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The antifreeze system and method for the air-cooling island of a direct air-cooled unit provided in the above technical solution directly utilizes part of the turbine exhaust steam in the exhaust pipe to heat the gas in the gas supply pipe, and then sprays the gas to a position with a lower temperature in the air-cooling island, thereby raising the temperature of the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle, thereby preventing the condensed water therein from freezing in the tube bundle, and even freezing and cracking the tube bundle. The above technical solution sets the nozzle inside the air-cooling island, between two inclined condensing units, and uses the condensing units to block the ambient wind in the horizontal direction, so that the hot air ejected from the nozzle covers more of the condensing units, thereby increasing the temperature of the specific area and improving the heat utilization rate. Compared with the existing antifreeze methods of direct air-cooling units, such as the antifreeze method based on the temperature and humidity of the vacuum pipe, the antifreeze method of setting roller curtains or blinds, and the antifreeze method of setting electric heating pipes, the above technical solution directly extracts part of the turbine exhaust steam from the exhaust pipe, and by readjusting 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, improves energy utilization, and is relatively simple to implement, with good antifreeze effect, and does not affect the back pressure of the turbine. The operation of the direct air-cooling unit is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] 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.

[0041] Figure 1 This is a structural diagram of an existing direct air cooling unit.

[0042] Figure 2 This is a structural schematic diagram of an air-cooling island antifreeze system for a direct air-cooling unit according to an embodiment of the present invention.

[0043] Figure 3 Schematic diagram of the structure of a triangular cooling unit according to an embodiment of the present invention, showing the position of the nozzle in the downstream tube bundle.

[0044] Figure 4 Schematic diagram of the structure of a triangular cooling unit according to an embodiment of the present invention, showing the position of the nozzle in the countercurrent tube bundle.

[0045] Figure 5 Schematic diagram of the structure of the nozzle according to an embodiment of the present invention.

[0046] Figure 6 Schematic diagram of the distribution of nozzles on a single-side condensing unit according to an embodiment of the present invention.

[0047] Description of reference numerals:

[0048] 10. Air-cooling island; 11. Condensing unit; 111. Downstream tube bundle; 112. Countercurrent tube bundle; 12. Condensate manifold; 13. Vacuuming system; 131. Vacuuming manifold; 14. Temperature sensor; 20. Exhaust pipe; 30. Condensate tank; 40. Air supply pipe; 41. Air compressor; 42. Third isolating valve; 43. Fourth isolating valve; 44. First temperature detector; 45. Second temperature detector; 50. Nozzle; 51. First nozzle; 52. Second nozzle; 53. First regulating valve; 54. Second regulating valve; 60. First heat exchanger; 70. First branch pipe; 71. First isolating valve; 72. Second isolating valve; 73. First regulating valve; 80. Second branch pipe; 81. On-off unit; 82. Fifth isolating valve; 83. Sixth isolating valve; 84. Second regulating valve; 90. Second heat exchanger. DETAILED DESCRIPTION

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Existing direct air cooling units are as follows Figure 1 As shown, the exhaust steam of the steam turbine of the thermal power generator set is discharged to the air-cooling island 10 arranged outdoors through the exhaust pipe. The air-cooling island includes a number of triangular cooling units. The triangular cooling units are in an inverted "V" shape and include two inclined condensing units 11. The triangular cooling units are cooling triangle radiators. An axial cooling fan is set below the air-cooling island 10 to make air flow through the outer surface of the condensing unit 11, cooling the turbine exhaust steam in the condensing unit 11 into water. The condensed water flows into the condensate tank and is then sent back to the cooling system of the steam turbine. Each condensing unit 11 includes a downstream tube bundle 111 and a countercurrent tube bundle 112. The exhaust pipe 20 is located at the top and the condensate header 12 is located at the bottom. The upper end of the downstream tube bundle 111 is connected to the exhaust pipe, and the lower end is connected to the condensate header 12. The flow direction therein is as shown in FIG. Figure 1 As shown by the arrow on the top, it is from top to bottom. Therefore, in cold weather, the lower end of the downstream tube bundle 111 is prone to freezing and cracking. The direct air cooling system also includes a vacuum system 13, which is used to establish and maintain the low back pressure (exhaust pressure) of the steam turbine unit and the vacuum of the condensing unit 11, to ensure that the exhaust steam of the steam turbine smoothly enters the air-cooling island 10 when the thermal power generator unit is started and operated, and to timely remove the air and other non-condensable gases in the direct air cooling system when the unit is operating normally, to maintain the vacuum of the air-cooled condenser, and to reduce the corrosion of the pipeline and the air-cooled condenser. Corrosion, reducing the volume of non-condensable gas in the air-cooled condenser, and reducing the operating back pressure of the unit. The lower the operating back pressure of the unit, the higher the economic efficiency. The function of the countercurrent tube bundle 112 is to connect the downstream tube bundle 111 and the vacuum system 13. The countercurrent tube bundle 112 is located in the middle of the condensing unit 11. The lower end of the countercurrent tube bundle 112 is connected to the downstream tube bundle 111, and the upper end is connected to the vacuum system 13. The temperature of the air flow inside the countercurrent tube bundle 112 is reduced, and a small amount of water vapor contained in it will form condensed water at the upper end of the countercurrent light beam, which will then freeze, causing freeze blockage and freeze cracking.

[0053] Based on this, an embodiment of the present invention provides an antifreeze system for an air-cooled island of a direct air-cooled unit, wherein the antifreeze device includes an air supply pipe 40, a nozzle 50, a first heat exchanger 60, and a first branch pipe 70 connected to the exhaust pipe 20; the first branch pipe 70 is used to draw out part of the turbine exhaust steam from the exhaust pipe 20, and after heat exchange with the first heat exchanger 60, the generated condensate flows into the condensate tank 30, and is then sent back to the cooling system of the turbine. The air supply pipe 40 exchanges heat with the first branch pipe 70 through the first heat exchanger 60 to increase the gas temperature in the air supply pipe 40, and the heated gas is ejected from the nozzle 50. A plurality of nozzles 50 are arranged between two inclined condensing units 11, and are respectively located at the lower end of the downstream tube bundle 111 and the upper end of the countercurrent tube bundle 112. The nozzles of the nozzles 50 are oriented toward the downstream tube bundle 111 and the countercurrent tube bundle 112, as shown in the attached figure. Figure 3 and attached Figure 4 shown.

[0054] In severe cold seasons, this embodiment directly utilizes part of the turbine exhaust steam from the exhaust pipe 20 to heat the gas in the gas supply pipe 40, and then injects the gas to a lower temperature position in the air-cooling island 10, thereby raising the temperature of the lower end of the downstream tube bundle 111 and the upper end of the countercurrent tube bundle 112, thereby preventing the condensed water therein from freezing in the tube bundle, or even freezing and cracking the tube bundle. In this embodiment, the nozzle 50 is arranged inside the air-cooling island 10, between two inclined condensing units 11, and the condensing units 11 are used to block the ambient wind in the horizontal direction, so that the hot air ejected by the nozzle 50 covers more of the condensing units 11, thereby increasing the temperature of the specific area and improving the heat utilization rate. Compared with the existing antifreeze methods of direct air-cooling units, such as the antifreeze method based on the temperature and humidity of the vacuum pipe, the antifreeze method of setting roller curtains or blinds, and the antifreeze method of setting electric heating pipes, this embodiment directly extracts part of the turbine exhaust steam from the exhaust pipe 20, and by readjusting 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, improves the energy utilization rate, and is relatively simple to implement, with good antifreeze effect, and does not affect the back pressure of the turbine. The operation of the direct air-cooling unit is more stable.

[0055] 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 40, and manual adjustment of the turbine exhaust flow in the first branch pipe 70 to adjust the gas temperature in the gas supply pipe 40. The nozzle 50 can be manually replaced as needed to adjust the spray range of the nozzle 50.

[0056] Of course, as a preferred embodiment, this embodiment can also adopt an automatic control method. Specifically, the antifreeze system of this embodiment also includes a control module and several condensate 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 condensate temperature, ambient temperature and unit back pressure.

[0057] Specifically, condensate temperature detection modules are located at the lower end of the downstream tube bundle 111 and the upper end of the countercurrent tube bundle 112, respectively, to detect condensate temperatures at locations prone to freezing. These modules include several temperature sensors 14, located within the condensate manifold at the lower end of each downstream tube bundle 111 and within the vacuum manifold at the upper end of the countercurrent tube bundle 112, respectively. These sensors 14 are positioned away from the nozzles 50 to prevent the detection results from being affected by the hot gas ejected from the nozzles 50. The temperature sensors transmit the detected temperature data to the control module, which is in communication with the gas supply pipeline 40 and adjusts the gas temperature within the pipeline 40 based on the condensate temperature. One or more temperature sensors 14 can be installed for each downstream tube bundle 111 or countercurrent tube bundle 112. If multiple temperature sensors 14 are installed, the temperatures detected by these multiple temperature sensors 14 can be averaged to improve detection accuracy. The nozzles 50 corresponding to each downstream tube bundle 111 or countercurrent tube bundle 112 can be independently controlled. Specifically, the spray range of each nozzle 50 is controlled based on the temperature detected by the temperature sensor 14 corresponding to each downstream tube bundle 111 or countercurrent tube bundle 112. Furthermore, additional temperature sensors can be installed inside or near the nozzles 50 to monitor the temperature of the hot air sprayed from the nozzles 50 in real time and determine whether the antifreeze device is functioning properly.

[0058] As attached Figure 2 As shown, a first regulating valve 73 is provided on the first branch pipe 70; the control module is in communication with the first regulating valve 73 and is configured to regulate the flow rate of turbine exhaust steam in the first branch pipe 70 based on the condensate temperature. When the condensate temperature decreases, the opening of the first regulating valve 73 increases, more turbine exhaust steam flows into the first branch pipe 70, and the temperature of the gas ejected from the nozzle 50 increases. When the condensate temperature increases, the opening of the first regulating valve 73 decreases, less turbine exhaust steam flows into the first branch pipe 70, and the temperature of the gas ejected from the nozzle 50 decreases. When the condensate temperature exceeds a first set value, it is determined that the air-cooling island 10 is not likely to freeze, and the first regulating valve 73 can be closed. The specific value of the first set value is set based on the actual operating conditions of the direct air-cooled steam turbine unit.

[0059] As attached Figure 5As shown, the nozzle 50 of this embodiment includes a first nozzle 51 and a second nozzle 52. The spray range of the second nozzle 52 is larger than the spray range of the first nozzle 51. The control module is connected to the nozzle 50 and is used to select to open the first nozzle 51 or the second nozzle 52 or to open the first nozzle 51 and the second nozzle 52 at the same time based on the condensate temperature. That is, when the condensate temperature is low, the first nozzle 51 is opened. The first nozzle 51 is relatively closer to the condensing unit 11, and the spray range is smaller, but more accurate, and the gas temperature loss is less. When the condensate temperature is lower, the first nozzle 51 is closed and the second nozzle 52 is opened. Although the second nozzle 52 It is relatively far away from the condensing unit 11, but the spraying range of the second nozzle 52 is larger, and the gas temperature in the air supply pipe 40 is higher at this time. Therefore, the gas temperature sprayed by the second nozzle 52 is higher, which can form a warmer environment and increase the temperature of the specific part of the condensing unit 11; when the condensate temperature drops further, it means that the ambient temperature is lower and may be accompanied by strong winds, then the first nozzle 51 and the second nozzle 52 are turned on at the same time, and the gas hood sprayed by the second nozzle 52 is arranged on the periphery of the gas sprayed by the first nozzle 51 to form a layer of gas shield, which is conducive to retaining heat, less gas temperature loss, and better heating effect on the condensing unit 11.

[0060] As attached Figure 6 As shown, a downstream tube bundle 111 is provided with at least two nozzles 50, and a countercurrent tube bundle 112 is provided with at least two nozzles 50; when the first nozzle 51 and the second nozzle 52 need to be opened at the same time, the condensate 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 nozzles 50, the injection ranges of the two second nozzles 52 partially overlap, and the injection range of the second nozzle 52 contacts or partially overlaps with the edge of the injection range of the first nozzle 51 of the other nozzle 50, thereby forming a multi-layer gas barrier, so that the gas temperature within the total injection range of the nozzle 50 is relatively uniform, and heat is not easily lost, which has a good heating effect on the condensing unit 11.

[0061] For the downstream tube bundle 111 located at the edge of the condensing unit 11, the spraying range of the second nozzle 52 provided in this embodiment exceeds the edge of the downstream tube bundle 111. Therefore, even if the hot air sprayed from the second nozzle 52 is affected by the ambient wind and moves toward the inside of the air-cooling island 10, it can be ensured that the edge of the downstream tube bundle 111 is within the spraying range of the second nozzle 52, so as to avoid the occurrence of local freezing and blockage of the downstream tube bundle 111.

[0062] The nozzles 50 corresponding to each column of downstream tube bundles 111 or countercurrent tube bundles 112 can be independently adjusted. The spray range of each nozzle 50 is controlled according to the temperature detected by the temperature sensor corresponding to each column of downstream tube bundles 111 or countercurrent tube bundles 112. That is, each nozzle 50 can be controlled to open the first nozzle 51 or the second nozzle 52 individually or simultaneously, so as to spray more hot air to colder parts, achieve precise heating, and improve heat utilization.

[0063] Specifically, a first regulating valve 53 is provided on the connecting pipe between the first nozzle 51 and the air supply pipe 40, and a second regulating valve 54 is provided on the connecting pipe between the second nozzle 52 and the air supply pipe 40. The first regulating valve 53 and the second regulating valve 54 are both electrically controlled valves, which are communicatively connected to the control module to realize remote selection and control of the nozzle 50.

[0064] The air supply pipeline 40 includes an air compressor 41. The gas in the air supply pipeline 40 is compressed air. The air compressor 41 is an adjustable pressure air compressor 41. The control module is in communication with the air compressor 41 and is used to adjust the pressure of the air compressor 41 based on the condensate temperature. When only the first nozzle 51 is turned on, the pressure of the air compressor 41 can be a first pressure. When only the second nozzle 52 is turned on, the pressure of the air compressor 41 needs to be increased to a second pressure due to the larger spray range and higher gas flow rate. When the first nozzle 51 and the second nozzle 52 are turned on simultaneously, the pressure of the air compressor 41 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 and the size of the nozzle.

[0065] 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.

[0066] If the opening of the first regulating valve 73 reaches the maximum, and the ambient temperature or condensate temperature is still decreasing, it is generally necessary to increase the back pressure of the turbine, which will affect the economic efficiency of the unit operation. At this time, other heat sources can be introduced, such as partial low-pressure extraction steam from the unit (such as five-stage extraction steam), and the antifreeze device can be used for antifreeze. Compared with the traditional operation mode of increasing the back pressure of the turbine unit for antifreeze, it has less impact on the overall economic efficiency of the unit. Specifically, the system of this embodiment also includes a second branch pipe 80 and a second heat exchanger 90 connected to other heat sources. The second branch pipe 80 is provided with an on-off unit 81, which is communicated with the control module and is used to conduct the second branch pipe 80 when the back pressure of the turbine is higher than the set back pressure and the opening of the first regulating valve 73 is maximum. The temperature of the steam in the second branch pipe 80 is higher than the temperature of the turbine exhaust steam in the first branch pipe 70. The second heat exchanger 90 is arranged between the first heat exchanger 60 and the nozzle 50. The air supply pipe 40 exchanges heat with the second branch pipe 80 through the second heat exchanger 90. The gas in the air supply pipe 40 is first heated by the first heat exchanger 60 to increase its temperature for the first time, and then exchanges heat with the second heat exchanger 90 to further increase its temperature, thereby increasing the temperature of the gas ejected from the nozzle 50.

[0067] Preferably, the antifreeze device also includes a first temperature detector 44 and a second temperature detector 45. The first temperature detector 44 is located between the first heat exchanger 60 and the second heat exchanger 90, and is used to detect the temperature of the gas heated once by the first heat exchanger 60. The second temperature detector 45 is located between the second heat exchanger 90 and the nozzle 50, and is used to detect the temperature of the gas heated for the second time by the second heat exchanger 90, that is, the temperature of the gas flowing to the nozzle 50; a second regulating valve 84 is provided on the second branch pipe 80, and the first temperature detector 44 and the second temperature detector 45 are respectively connected to the control module, and are used to adjust the turbine exhaust flow in the first branch pipe 70 and the steam flow in the second branch pipe 80 based on the detected temperature, so that the gas temperature in the gas supply pipe 40 reaches the required temperature.

[0068] When the on-off unit 81 of the second branch pipe 80 is turned on, the pressure of the air compressor 41 is greater than or equal to the third pressure, the gas flow rate in the air supply pipe 40 increases, and the contact time with the first heat exchanger 60 is reduced, while the turbine exhaust flow in the first branch pipe 70 cannot be further increased. Therefore, the first temperature detector 44 detects a slight decrease in temperature, and the second regulating valve 84 on the second branch pipe 80 can be controlled to open more. The second heat exchanger 90 can further increase the gas temperature in the air supply pipe 40, thereby improving the heating effect on the condensing unit 11.

[0069] Preferably, the second branch pipe 80 is connected to the condensate tank 30 , so that the condensate in the second branch pipe 80 can be input into the condensate tank 30 for further use.

[0070] As attached Figure 2 As shown, the first branch pipe 70 is equipped with a first isolation valve 71, located between the first regulating valve 73 and the first heat exchanger 60. The function of the first isolation valve 71 is to disconnect the gas flow between the antifreeze device and the first branch pipe 70 during maintenance, facilitating isolation and maintenance. The first branch pipe 70 is equipped with a second isolation valve 72, located between the first heat exchanger 60 and the condensate tank 30. This valve facilitates system isolation during equipment maintenance and prevents vacuum leaks in the condensate tank 30 during emergencies. The air supply pipe 40 is equipped with a third isolation valve 42, located between the air compressor 41 and the first heat exchanger 60. The air supply pipe 40 is equipped with a fourth isolation valve 43, located between the first heat exchanger 60 and the second heat exchanger 90. Both the third isolation valve 42 and the fourth isolation valve 43 facilitate system isolation during maintenance. A fifth isolation valve 82 is provided on the second branch pipe 80, and the fifth isolation valve 82 is located upstream of the second heat exchanger 90; a sixth isolation valve 83 is provided on the second branch pipe 80, and the sixth isolation valve 83 is located between the second heat exchanger 90 and the condensate tank 30. The functions of the fifth isolation valve 82 and the sixth isolation valve 83 are to facilitate system maintenance isolation and prevent vacuum leakage of the condensate tank 30 in an emergency.

[0071] Based on the antifreeze system for the air-cooling island of a direct air-cooling unit in the above embodiment, the present invention further provides an antifreeze method for the air-cooling island of a direct air-cooling unit, comprising the following steps:

[0072] Open the first branch pipe 70 to lead part of the turbine exhaust steam from the exhaust pipe 20;

[0073] Open the gas supply pipe 40, and the internal gas flows through the first heat exchanger 60, exchanges heat with part of the turbine exhaust steam, raising the gas temperature. The cooled and condensed water in the first branch pipe 70 flows into the condensate tank 30;

[0074] The nozzle 50 is started, and the gas with a raised temperature is sprayed onto the lower end of the downstream tube bundle 111 and the upper end of the countercurrent tube bundle 112, thereby heating the lower end of the downstream tube bundle 111 and the upper end of the countercurrent tube bundle 112 from the outside.

[0075] Preferably, the method of this embodiment further includes:

[0076] Detecting the condensate temperature in the condensate header 12 at the lower end of the downstream tube bundle 111, and controlling the gas temperature and injection range of the nozzle 50 corresponding to the lower end of the downstream tube bundle 111 according to the condensate temperature in the condensate header;

[0077] The condensate temperature of the vacuum header 131 at the upper end of the counter-flow tube bundle 112 is detected, and the gas temperature and injection range of the nozzle 50 corresponding to the upper end of the counter-flow tube bundle 112 are controlled according to the condensate temperature of the vacuum header 131.

[0078] Specifically, the control logic of the gas temperature and injection range injected by the nozzle 50 is as follows:

[0079] If the condensate temperature is lower than the first set value T1, the first regulating valve 73 on the first branch pipe 70 opens, the air compressor 41 on the air supply pipe 40 opens, and the first nozzle 51 opens to heat the lower end of the downstream tube bundle 111 and the upper end of the upstream tube bundle 112;

[0080] If the condensate temperature is lower than the second set value T2, the opening of the first regulating valve 73 on the first branch pipe 70 is increased, thereby increasing the turbine exhaust flow rate in the first branch pipe 70 and the pressure of the air compressor 41 on the air supply pipe 40. The first nozzle 51 is closed and the second nozzle 52 is opened to heat the lower end of the downstream tube bundle 111 and the upper end of the upstream tube bundle 112.

[0081] If the condensate temperature is lower than the third set value T3, the first regulating valve 73 on the first branch pipe 70 is opened to the maximum, increasing the turbine exhaust flow in the first branch pipe 70 and the pressure of the air compressor 41 on the air supply pipe 40. The first nozzle 51 and the second nozzle 52 are opened to heat the lower end of the downstream tube bundle 111 and the upper end of the upstream tube bundle 112.

[0082] If the condensate temperature is lower than the fourth set value T4 and the back pressure of the steam turbine is detected to be higher than the set back pressure, the second branch pipe 80 is opened to increase the pressure of the air compressor 41 on the air supply pipe 40. The gas in the air supply pipe 40 passes through the first heat exchanger 60 and the second heat exchanger 90 in sequence for secondary heating. The first nozzle 51 is opened and the second nozzle 52 is opened to heat the lower end of the downstream tube bundle 111 and the upper end of the countercurrent tube bundle 112.

[0083] T1 to T4 can be set according to the following rules: T1>T2>T3>T4. The specific values are set by the actual environment and operating conditions of the unit.

[0084] 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. A direct air-cooling unit air-cooling island antifreeze system, characterized in that: It includes an exhaust pipe, a direct air-cooling unit and an antifreeze device. The direct air-cooling unit includes an air-cooling island and a condensate tank. The air-cooling island is connected to the condensate tank. The exhaust pipe connects the exhaust port of the steam turbine and the air-cooling island. The air-cooling island includes a plurality of triangular cooling units. The triangular cooling units are in an inverted "V" shape and include two inclined condensing units. The condensing units include a downstream tube bundle and a countercurrent tube bundle. The antifreeze device includes an air supply pipe, a nozzle, a first heat exchanger and a first branch pipe connected to the exhaust pipe; the first branch pipe is used to draw out part of the turbine exhaust steam from the exhaust pipe, and the air supply pipe exchanges heat with the first branch pipe through the first heat exchanger to increase the gas temperature in the air supply pipe. The nozzle is arranged at the terminal end of the air supply pipe, and several of the nozzles are arranged between the two inclined condensing units and are respectively located at the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle. The nozzle head of the nozzle is facing the downstream tube bundle and the countercurrent tube bundle, and the first branch pipe is connected to the condensate tank.

2. The air-cooling island antifreeze system of a direct air-cooling unit according to claim 1, characterized in that: It also includes a control module and several condensate temperature detection modules, which are respectively located in the condensate collection pipe at the lower end of the downstream tube bundle and the vacuum collection pipe at the upper end of the countercurrent tube bundle. The condensate temperature detection module is communicatively connected to the control module, and the control module is communicatively connected to the air supply pipeline, and is used to adjust the gas temperature in the air supply pipeline based on the condensate temperature.

3. The antifreeze system for the air-cooling island of a direct air-cooling unit according to claim 2, characterized in that: The first branch pipe is provided with a first regulating valve; the control module is in communication with the first regulating valve and is configured to regulate the exhaust flow of the steam turbine in the first branch pipe based on the condensate temperature; The nozzle includes a first nozzle and a second nozzle, the spray range of the second nozzle is larger than the spray range of the first nozzle, and the control module is connected to the nozzle and is used to select to open the first nozzle or the second nozzle or open the first nozzle and the second nozzle at the same time based on the condensate temperature; 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 condensate temperature.

4. The air cooling island antifreeze system of a direct air cooling unit according to claim 3, characterized in that: At least two nozzles are provided corresponding to one downstream tube bundle, and at least two nozzles are provided corresponding to one upstream tube bundle; In two adjacent nozzles, the spraying ranges of the two 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 of the other nozzle; The spraying range of the second nozzle of the nozzle close to the edge of the downstream tube bundle exceeds the edge of the downstream tube bundle.

5. The antifreeze system for the air-cooling island of a direct air-cooling unit according to claim 3, characterized in that: It also includes a back pressure detection module for detecting the back pressure of the steam turbine, and the back pressure detection module is communicatively connected to the control module; The antifreeze device further includes a second branch pipe connected to the heat source and a second heat exchanger, the second branch pipe being provided with an on-off unit, the on-off unit being communicatively connected to the control module and configured to open the second branch pipe 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 steam in the second branch pipe is higher than the temperature of the turbine exhaust steam in the first branch pipe. The second heat exchanger is arranged between the first heat exchanger and the nozzle. The air supply pipe exchanges heat with the second branch pipe through the second heat exchanger.

6. The antifreeze system for the air-cooling island of a direct air-cooling unit according to claim 5, 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, the second temperature detector is located between the second heat exchanger and the nozzle, and a second regulating valve is provided on the second branch pipe. The first temperature detector and the second temperature detector are respectively connected to the control module, and are used to adjust the turbine exhaust flow in the first branch pipe and the steam flow in the second branch pipe based on the detected temperature.

7. The air-cooling island antifreeze system of a direct air-cooling unit according to claim 5, characterized in that: The second branch pipe is connected to the condensate tank; A first isolation valve is provided on the first branch pipe, and the first isolation valve is located between the first regulating valve and the first heat exchanger; A second isolation valve is provided on the first branch pipe, and the second isolation valve is located between the first heat exchanger and the condensate tank; 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 second branch pipe, and the fifth isolation valve is located upstream of the second heat exchanger; The second branch pipe is provided with a sixth isolation valve, and the sixth isolation valve is located between the second heat exchanger and the condensate tank.

8. A method for antifreezing of the air cooling island of a direct air cooling unit, characterized in that: The air-cooling island antifreeze system of a direct air-cooling unit according to any one of claims 1 to 7 comprises the following steps: opening the first branch pipe to lead out part of the steam turbine exhaust steam from the exhaust pipe; The gas supply pipe is opened, and the internal gas flows through the first heat exchanger, exchanges heat with part of the turbine exhaust steam, thereby increasing the gas temperature, and the cooled and condensed water in the first branch pipe flows into the condensate tank; The nozzle is started to spray the gas with a raised temperature onto the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle, thereby heating the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle from the outside.

9. The antifreeze method for the air-cooling island of a direct air-cooling unit according to claim 8, characterized in that: detecting the condensate temperature in the condensate header at the lower end of the downstream tube bundle, and controlling the gas temperature and injection range of the nozzle corresponding to the lower end of the downstream tube bundle according to the condensate temperature in the condensate header; The condensate temperature of the vacuum header at the upper end of the countercurrent tube bundle is detected, and the gas temperature and injection range of the nozzle corresponding to the upper end of the countercurrent tube bundle are controlled according to the condensate temperature of the vacuum header.

10. The antifreeze method for the air-cooling island of a direct air-cooling unit according to claim 9, characterized in that: The control logic of the gas temperature and the injection range of the nozzle is as follows: If the condensate temperature is lower than the first set value, the first regulating valve on the first branch pipe is opened, the air compressor on the air supply pipe is turned on, and the first nozzle is turned on to heat the lower end of the downstream tube bundle and the upper end of the upstream tube bundle; If the condensate temperature is lower than the second set value, the opening of the first regulating valve on the first branch pipe is increased to increase the exhaust flow of the steam turbine in the first branch pipe and the pressure of the air compressor on the air supply pipe. The first nozzle is closed and the second nozzle is opened to heat the lower end of the downstream tube bundle and the upper end of the upstream tube bundle. If the condensate temperature is lower than the third set value, the first regulating valve on the first branch pipe is opened to the maximum, the exhaust flow of the steam turbine in the first branch pipe is increased, the pressure of the air compressor on the air supply pipe is increased, the first nozzle is opened, and the second nozzle is opened to heat the lower end of the downstream tube bundle and the upper end of the upstream tube bundle; If the condensate temperature is lower than the fourth set value and the back pressure of the steam turbine is detected to be higher than the set back pressure, the second branch pipe is opened to increase the pressure of the air compressor on the air supply pipe. The gas in the air supply pipe passes through the first heat exchanger and the second heat exchanger in sequence for secondary heating. The first nozzle is opened and the second nozzle is opened to heat the lower end of the downstream tube bundle and the upper end of the countercurrent tube bundle.

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