Anti-freezing system and method for air-cooling unit based on boiler flue gas waste heat

Abstract

The present application relates to a kind of air cooling unit anti-freezing system and method based on boiler flue gas waste heat, and anti-freezing device includes first heat exchanger, gas supply pipeline and nozzle, first heat exchanger is set between the gas outlet of desulfurization tower and the gas inlet of chimney, gas supply pipeline exchanges heat with the exhaust of desulfurization tower by first heat exchanger, and the terminal of gas supply pipeline is equipped with several nozzles, the nozzle is respectively corresponding the low temperature area of the air cooling unit, and the low temperature area is sprayed with heated gas.It is characterized in that, the waste heat of originally wasted low-temperature flue gas is utilized in the present application, the utilization rate of boiler flue gas waste heat is improved, and the normal exhaust volume of entering steam turbine in air cooling unit is not affected, the anti-freezing effect of air cooling unit is better by heating the low temperature area of air cooling unit in external, and implementation is relatively simple, energy utilization is improved, steam turbine winter operation back pressure can be effectively reduced, and the economy, safety and stability of unit in winter operation are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of direct air cooling technology, in particular to an air cooling unit anti-freezing system and method based on boiler flue gas waste heat. BACKGROUND

[0002] In recent years, with the rapid development of China's power industry, large-capacity and high-parameter thermal power generating units are being built all over the country. Air cooling units generally include two types. One is the structure of a direct air cooling unit as shown in the accompanying drawings. The exhaust steam of the steam turbine directly enters the cooling system of the air cooling island of the unit, and the air is driven by the air cooling fan to cool the unit exhaust steam by convection heat exchange. The other is an indirect air cooling unit, which cools by heat exchange between the circulating medium and the exhaust steam of the steam turbine unit. Figure 1

[0003] However, the cooling characteristics of the air cooling unit determine that the operation of the air cooling unit is greatly affected by the environmental temperature. In extremely low environmental temperature, the pipe bundle in the low temperature area of the air cooling unit may freeze and crack, thereby seriously affecting the safety and stability of the unit operation. The existing anti-freezing system generally adds a shutter or other shielding device, but the anti-freezing effect is not ideal. At the same time, in thermal power generating units, the tail flue gas at the outlet of the boiler needs to meet the emission standard, which generally needs to be treated by a coal economizer-air preheater-desulfurization tower and other equipment. The flue gas temperature at the outlet of the desulfurization tower is about 50℃. The temperature of the flue gas is low, and the heat grade is low, which is difficult to be recycled and utilized, and is generally directly discharged, causing waste. Therefore, a new type of air cooling unit anti-freezing system and method based on boiler flue gas waste heat needs to be designed. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the defects in the prior art, thereby providing an air cooling unit anti-freezing system and method based on boiler flue gas waste heat.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0006] An air cooling unit anti-freezing system based on boiler flue gas waste heat, comprising an exhaust pipe, an air cooling unit, a boiler flue gas waste heat utilization system and an anti-freezing device, the boiler flue gas waste heat utilization system comprising a flue gas pipe, a coal economizer, an air preheater, a dust remover, a blower, a desulfurization tower and a chimney connected in sequence;

[0007] The anti-freezing device comprises a first heat exchanger, a gas supply pipe and a nozzle. The first heat exchanger is arranged between the gas outlet of the desulfurization tower and the gas inlet of the chimney. The gas supply pipe exchanges heat with the exhaust gas of the desulfurization tower through the first heat exchanger to increase the temperature of the gas in the gas supply pipe.

[0008] ​The terminal of the air supply pipeline is provided with a plurality of nozzles, which correspond to the low-temperature areas of the air-cooled unit respectively and spray the heated gas to the low-temperature areas.

[0009] Preferably, the anti-freezing device further comprises a second heat exchanger arranged between the air preheater and the dust collector, the air supply pipeline comprises an air compressor, a first main pipe, a first branch pipe, a second branch pipe and a second main pipe, the gas in the air supply pipeline is compressed air, the main pipe is connected with the first heat exchanger and the air compressor, the first branch pipe and the second branch pipe are connected with the main pipe and the second main pipe respectively, and the middle part of the second branch pipe is connected with the second heat exchanger, so that the compressed air in the second branch pipe is heated again by the second heat exchanger; the nozzles are arranged at the terminal of the second main pipe.

[0010] Preferably, a first regulating valve for regulating the total air volume is arranged on the first main pipe, a second regulating valve for regulating the air volume in the first branch pipe is arranged on the first branch pipe, and a first temperature measuring point for detecting the temperature of the gas in the first branch pipe is further arranged.

[0011] A third regulating valve for regulating the air volume in the second branch pipe is arranged on the second branch pipe, and a second temperature measuring point for detecting the temperature of the gas in the second branch pipe is further arranged.

[0012] Preferably, when the air-cooled unit is a direct air-cooled unit, the direct air-cooled unit comprises an air cooling island and a condensate tank, the air cooling island is connected with the condensate tank, the exhaust steam pipeline is connected with the exhaust port of the steam turbine and the air cooling island, the air cooling island comprises a plurality of triangular cooling units, the triangular cooling units comprise a forward flow pipe bundle and a reverse flow pipe bundle; a plurality of the nozzles are divided into a plurality of groups, the number of groups corresponds to the number of the triangular cooling units, each group of the nozzles is located in a low-temperature area of the air-cooled unit, and the nozzles in each group correspond to the lower end of the forward flow pipe bundle and the upper end of the reverse flow pipe bundle respectively and spray toward the lower end of the forward flow pipe bundle and the upper end of the reverse flow pipe bundle.

[0013] When the air-cooled unit is an indirect air-cooled unit, the indirect air-cooled unit comprises a condenser and an indirect cooling tower, the exhaust steam pipeline is connected with the exhaust port of the steam turbine and the condenser, the indirect cooling tower comprises a plurality of cooling triangular radiators, the cooling triangular radiators have a water inlet pipe and a water return pipe which are communicated, the lower end of the water return pipe is a low-temperature area, and a plurality of the nozzles correspond to a plurality of the cooling triangular radiators of the indirect cooling tower respectively, and the direction of the jet of the nozzles is toward the lower end of the water return pipe.

[0014] Preferably, the anti-freezing system further comprises a control module.

[0015] When the air-cooled unit is a direct air-cooled unit, the anti-freezing system further comprises a plurality of condensate water temperature detection modules, which are respectively located in the condensate water header at the lower end of the parallel flow tube bundle and in the vacuum extraction header at the upper end of the counter flow tube bundle, the condensate water temperature detection modules are in communication connection with the control module, the control module is in communication connection with the air supply pipeline, the opening degrees of the first regulating valve, the second regulating valve and the third regulating valve are adjusted based on the condensate water temperature, and the opening degrees of the first regulating valve, the second regulating valve and the third regulating valve are all 0-100;

[0016] When the air-cooled unit is an indirect air-cooled unit, the anti-freezing system further comprises a return water temperature detection module, which is located in the low-temperature area at the lower end of the return water pipe, the return water temperature detection module is in communication connection with the control module, the control module is in communication connection with the air supply pipeline, the opening degrees of the first regulating valve, the second regulating valve and the third regulating valve are adjusted based on the return water temperature, and the opening degrees of the first regulating valve, the second regulating valve and the third regulating valve are all 0-100;

[0017] The anti-freezing system further comprises a back pressure detection module for detecting the back pressure of the steam turbine, and the back pressure detection module is in communication connection with the control module;

[0018] The first regulating valve, the second regulating valve and the third regulating valve are all connected with the control module, and when the back pressure detection module detects that the back pressure is not lower than the set back pressure, the first regulating valve is opened to the maximum, the second regulating valve is closed, and the third regulating valve is opened.

[0019] Preferably, the nozzle comprises a first nozzle and a second nozzle, the spraying range of the second nozzle is greater than that of the first nozzle, and at least one of the first nozzle and the nozzle is opened when the anti-freezing device works.

[0020] Preferably, when the air-cooled unit is a direct air-cooled unit, one parallel flow tube bundle corresponds to at least two nozzles, and one counter flow tube bundle corresponds to at least two nozzles;

[0021] In two adjacent nozzles, the spraying ranges of two second nozzles partially overlap, and the spraying range of the second nozzle is in contact with or partially overlaps with the edge of the spraying range of the first nozzle of another nozzle;

[0022] The spraying range of the second nozzle of the nozzle close to the edge of the parallel flow tube bundle exceeds the edge of the parallel flow tube bundle;

[0023] When the air cooling unit is an indirect air cooling unit, a plurality of the nozzles are vertically arranged at positions corresponding to low-temperature regions of the cooling delta radiators and lower ends of the return water pipes, and are controlled by the control module to be sequentially opened from bottom to top based on return water temperature; the opening priority of all the first nozzles and the second nozzles of the nozzles at the same height is higher than the opening priority of all the first nozzles and the second nozzles of the nozzles at higher heights.

[0024] The spray ranges of two adjacent second nozzles partially overlap, and the spray range of the second nozzle is in contact with or partially overlaps with the edge of the spray range of the first nozzle in another nozzle.

[0025] Preferably, the first main pipe is provided with a first isolation valve; the first isolation valve is located between the first heat exchanger and the air compressor,

[0026] The first main pipe is further provided with a second isolation valve on a section connected with an outlet end of the first heat exchanger;

[0027] The first branch pipe is provided with a third isolation valve;

[0028] The second branch pipe is provided with a fourth isolation valve and a fifth isolation valve; the fourth isolation valve and the fifth isolation valve are respectively located on sections of the second branch pipe connected with an inlet end of the second heat exchanger and an outlet end of the second heat exchanger.

[0029] To achieve the above object, the present application also adopts the following technical solutions:

[0030] A boiler flue gas waste heat based air cooling unit anti-freezing method, which adopts the above-mentioned boiler flue gas waste heat based air cooling unit anti-freezing system, and comprises the following steps:

[0031] The boiler flue gas waste heat utilization system is in normal operation, and the waste heat flue gas flowing out of the gas outlet of the desulfurization tower flows into the first heat exchanger,

[0032] The gas supply pipeline is started, and the gas in the pipeline exchanges heat with the first heat exchanger to increase the temperature;

[0033] The cooled flue gas flows into the gas inlet of the chimney;

[0034] The nozzles are started, and the gas with increased temperature is sprayed in the low-temperature region of the air cooling unit.

[0035] Preferably, when the air cooling unit is a direct air cooling unit, the anti-freezing device adopts the following control logic:

[0036] detecting the condensate temperature in the condensate header at the lower end of the parallel flow tube bundle, controlling the gas temperature and the spraying range of the nozzles corresponding to the lower end of the parallel flow tube bundle according to the condensate temperature in the condensate header;

[0037] detecting the condensate temperature in the vacuumizing header at the upper end of the counter flow tube bundle, controlling the gas temperature and the spraying range of the nozzles corresponding to the upper end of the counter flow tube bundle according to the condensate temperature in the vacuumizing header;

[0038] detecting the back pressure of the steam turbine, and determining whether it is not lower than the set back pressure, and then controlling the gas flow and the gas temperature in the gas supply pipeline;

[0039] The specific control logic of the anti-freezing device is as follows:

[0040] If the condensate temperature is lower than the first set value, the first regulating valve on the first main pipe is opened, the air compressor on the gas supply pipeline is opened, the second regulating valve on the first branch pipe is opened, the third regulating valve on the second branch pipe is kept closed, the first nozzle is opened, the lower end of the parallel flow tube bundle and the upper end of the counter flow tube bundle are heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0041] If the condensate temperature is lower than the second set value, the opening degree of the first regulating valve on the first main pipe is increased, the opening degree of the second regulating valve on the first branch pipe is increased, the pressure of the air compressor on the gas supply pipeline is increased, the first nozzle is closed, the second nozzle is opened, the lower end of the parallel flow tube bundle and the upper end of the counter flow tube bundle are heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0042] If the condensate temperature is lower than the third set value, the opening degree of the first regulating valve on the first main pipe is adjusted to the maximum, the pressure of the air compressor on the gas supply pipeline is increased, the opening degree of the third regulating valve on the second branch pipe is opened, part of the gas flowing out of the first heat exchanger flows into the second branch pipe to be heated again by the second heat exchanger, part of the gas continues to pass through the first branch pipe, the gas in the second branch pipe and the first branch pipe is combined in the second main pipe; the first nozzle is opened, the second nozzle is opened, the lower end of the parallel flow tube bundle and the upper end of the counter flow tube bundle are heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0043] If the condensate temperature is lower than the fourth set value, and the back pressure of the steam turbine is detected to be not lower than the set back pressure, the opening degree of the first regulating valve on the first main pipe is adjusted to the maximum, the pressure of the air compressor on the gas supply pipeline is increased, the second regulating valve on the first branch pipe is closed, the third regulating valve on the second branch pipe is opened to the maximum, the pressure of the air compressor on the gas supply pipeline is increased, all the gas flowing out of the first heat exchanger flows into the second branch pipe to be heated again by the second heat exchanger; the first nozzle is kept opened, the second nozzle is kept opened, the lower end of the parallel flow tube bundle and the upper end of the counter flow tube bundle are heated;

[0044] After the continuous setting time, if the back pressure of the steam turbine is detected to be lower than the set back pressure and the condensate temperature is still lower than the fourth set value, the state is kept until the condensate temperature is higher than the fourth set value;

[0045] When the air-cooled unit is an indirect air-cooled unit, the specific control logic of the anti-freezing device is as follows:

[0046] If the return water temperature is lower than the first set value, the first regulating valve on the first main pipe is opened, the air compressor on the air supply pipe is opened, the second regulating valve on the first branch pipe is opened, the third regulating valve on the second branch pipe is kept closed, the first nozzle in the nozzle at the lowermost end of the return water pipe is opened, the low-temperature area at the lowermost end of the return water pipe is heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0047] If the return water temperature is lower than the second set value, the opening degree of the first regulating valve on the first main pipe is adjusted to be larger, the opening degree of the second regulating valve on the first branch pipe is adjusted to be larger, the pressure of the air compressor on the air supply pipe is increased, the first nozzle in the nozzle at the lowermost end of the return water pipe is closed, the second nozzle is opened, the low-temperature area at the lowermost end of the return water pipe is heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0048] If the return water temperature is lower than the third set value, the opening degree of the first regulating valve on the first main pipe is adjusted to be maximum, the pressure of the air compressor on the air supply pipe is increased, the opening degree of the third regulating valve on the second branch pipe is opened, part of the gas flowing out of the first heat exchanger flows into the second branch pipe and is heated by the second heat exchanger, and part of the gas continues to pass through the first branch pipe, the gas in the second branch pipe and the first branch pipe is combined in the second main pipe; meanwhile, the first nozzle and the second nozzle in the nozzle at the lowermost end of the return water pipe are opened, the low-temperature area at the lowermost end of the return water pipe is heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0049] If the return water temperature is lower than the fourth set value and the back pressure of the steam turbine is detected to be not lower than the set back pressure, the opening degree of the first regulating valve on the first main pipe is adjusted to be maximum, the pressure of the air compressor on the air supply pipe is increased, the second regulating valve on the first branch pipe is closed, the third regulating valve on the second branch pipe is opened to be maximum, the pressure of the air compressor on the air supply pipe is increased, all the gas flowing out of the first heat exchanger flows into the second branch pipe and is heated by the second heat exchanger; meanwhile, the first nozzle and the second nozzle of at least two groups of nozzles in the height direction of the lower end of the return water pipe are opened, and the low-temperature area at the middle and lower end of the return water pipe is heated.

[0050] After the continuous setting time, if the back pressure of the steam turbine is detected to be lower than the set back pressure and the return water temperature is still lower than the fourth set value, the state is kept until the return water temperature is higher than the fourth set value.

[0051] Compared with the prior art, the present application has the following beneficial effects:

[0052] The boiler flue gas waste heat based air cooling unit anti-freezing system and method provided by the technical scheme has the heat of flue gas of about 50 DEG C discharged from the desulfurization tower used to heat the gas in the gas supply pipeline, and then the heated gas is sprayed to the low temperature area of the air cooling unit to improve the temperature of the low temperature area from the outside, prevent the condensate or return water in the low temperature area from freezing in the tube bundle, and even freeze the tube bundle. Compared with the existing air cooling unit anti-freezing method, the application utilizes the waste heat of low temperature flue gas, improves the utilization rate of boiler flue gas waste heat, and does not affect the normal exhaust volume of the turbine in the air cooling unit, that is, ensures the exhaust flow and temperature in the air cooling unit, at the same time, the air cooling unit is heated in the low temperature area, the anti-freezing effect of the air cooling unit is better, and the implementation is relatively simple, the energy utilization rate is improved, the turbine operation back pressure can be effectively reduced, and the economy, safety and stability of the unit operation are improved. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0054] Figure 1 It is a structural schematic diagram of the existing direct air cooling unit.

[0055] Figure 2 It is a structural schematic diagram of the boiler flue gas waste heat based air cooling unit anti-freezing system of the embodiment one of the present application.

[0056] Figure 3 It is a structural schematic diagram of the triangular cooling unit of the embodiment one of the present application, which shows the position of the nozzle in the parallel flow tube bundle.

[0057] Figure 4 It is a structural schematic diagram of the triangular cooling unit of the embodiment one of the present application, which shows the position of the nozzle in the counter flow tube bundle.

[0058] Figure 5 It is a structural schematic diagram of the nozzle of the embodiment of the present application.

[0059] Figure 6 It is a distribution schematic diagram of the nozzle of the embodiment one of the present application on the single side condensing unit.

[0060] Figure 7 It is a structural schematic diagram of the boiler flue gas waste heat based air cooling unit anti-freezing system of the embodiment two of the present application.

[0061] Figure 8Fig. 2 is a structural schematic diagram of the cooling triangle radiator of the second embodiment of the present application, showing the position of the nozzle in the return water pipe.

[0062] Figure 9 Fig. 3 is a distribution schematic diagram of the nozzle in the return water pipe of the second embodiment of the present application.

[0063] Legend of reference signs:

[0064] 10, exhaust pipe;

[0065] 20, air cooling unit; 21, triangle cooling unit; 211, parallel flow pipe bundle; 212, counter flow pipe bundle; 22, condensate collecting pipe; 23, vacuum extraction system; 231, vacuum extraction collecting pipe; 24, temperature sensor; 25, condensate tank; 26, axial flow cooling fan; 27, inter-cooling tower; 28, cooling triangle radiator; 281, water inlet pipe; 282, return water pipe;

[0066] 30, boiler flue gas waste heat utilization system; 31, flue gas pipe; 32, economizer; 33, air preheater; 34, dust remover; 35, air blower; 36, desulfurization tower; 37, chimney; 38, first heat exchanger; 39, second heat exchanger;

[0067] 40, air supply pipe; 41, first main pipe; 411, first regulating valve; 412, first isolation valve; 413, second isolation valve; 42, first branch pipe; 421, second regulating valve; 422, first temperature measuring point; 423, third isolation valve; 43, second branch pipe; 431, third regulating valve; 432, second temperature measuring point; 433, fourth isolation valve; 434, fifth isolation valve; 44, second main pipe; 45, air compressor;

[0068] 50, nozzle; 51, first nozzle; 52, second nozzle; 53, first regulating valve; 54, second regulating valve. DETAILED DESCRIPTION

[0069] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0070] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the 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.

[0071] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0072] The antifreeze system and method of this invention vary depending on the air-cooled unit, specifically in the nozzle placement and the temperature detected by the control module. The following is a brief explanation of the integration of the antifreeze system with different air-cooled units to illustrate the working principle of the antifreeze system and method of this invention.

[0073] Example 1

[0074] The air-cooled unit in this embodiment is a direct air-cooled unit, and the existing direct air-cooled unit 20 is shown in the attached figure. Figure 1 As shown, the exhaust steam from the steam turbine of the thermal power generating unit is discharged to an outdoor air-cooled island through the exhaust pipe 10. The air-cooled island includes several triangular cooling units 21, each triangularly shaped like an inverted "V". Each triangular cooling unit 21 includes a co-current tube bundle 211 and a counter-current tube bundle 212. An axial flow cooling fan 26 is installed below the triangular cooling units 21, allowing air to flow over the outer surfaces of the co-current and counter-current tube bundles 211 and 212, cooling the turbine exhaust steam within the tube bundles into water. The condensate flows into a condensate tank 25 and is then returned to the turbine's cooling system. The exhaust pipe 10 is located above the co-current tube bundle 211, and the condensate manifold 22 is located below the co-current tube bundle 211. The upper end of the co-current tube bundle 211 is connected to the exhaust pipe 10, and the lower end is connected to the condensate manifold 22. The flow direction within the bundle is as follows: Figure 1 As indicated by the arrow above, the flow is from top to bottom. Therefore, in cold weather, the lower end of the flow tube bundle 211 is prone to freezing and cracking.

[0075] As attached Figure 1As shown, the direct air cooling system further comprises a vacuum extraction system 23, which functions to establish and maintain a low back pressure (exhaust pressure) of the turbine unit and a tube bundle vacuum of the triangular cooling unit 21, to ensure that the turbine exhaust steam smoothly enters the air cooling island during the start-up and operation of the thermal power generating unit, to timely extract air and other non-condensable gases in the direct air cooling system during normal operation of the unit, to maintain the air cooling condenser vacuum, to reduce internal corrosion of the pipeline and the air cooling condenser, to reduce the volume of non-condensable gases in the air cooling condenser, to reduce the back pressure of the unit, and the lower the back pressure of the unit, the higher the economy. The counter-flow tube bundle 212 is used to connect the parallel-flow tube bundle 211 and the vacuum extraction system 23, and is located in the middle of the parallel-flow tube bundle. The lower end of the counter-flow tube bundle 212 is in communication with the parallel-flow tube bundle 211, and the upper end thereof is in communication with the vacuum extraction system 23. The temperature of the air flow in the counter-flow tube bundle 212 decreases, and a small amount of water vapor contained therein will form condensate water at the upper end of the counter-flow tube bundle, which will be frozen, resulting in freezing and cracking. Therefore, the low-temperature region of the direct air cooling unit is the lower end of the parallel-flow tube bundle 211 and the upper end of the counter-flow tube bundle 212.

[0076] Based on this, the embodiment includes a boiler flue gas waste heat utilization system and an anti-freezing device, the anti-freezing device is connected with the boiler flue gas waste heat utilization system, the waste heat of the boiler is transferred to the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212 through the anti-freezing device, and the low temperature area of the air cooling island is prevented from freezing. Specifically, the boiler flue gas waste heat utilization system 30 includes a flue gas pipeline 31, an economizer 32, an air preheater 33, a dust remover 34, a blower 35, a desulfurization tower 36 and a chimney 37 connected in sequence, the high temperature flue gas discharged by the boiler enters the economizer 32 from the flue gas passage, then enters the air preheater 33 (air preheater) from the economizer 32, at this time, the temperature of the flue gas is about 120℃, then the flue gas enters the dust remover 34 to remove dust, the clean flue gas is pressurized by the blower 35 and then enters the desulfurization tower 36 to remove sulfur, the temperature of the flue gas out of the desulfurization tower 36 is about 50℃, and finally the flue gas enters the chimney 37 to further cool and discharge. In the prior art, the utilization rate of the flue gas out of the desulfurization tower 36 is low due to the low temperature of the flue gas, and the anti-freezing device of the embodiment includes a first heat exchanger 38, a gas supply pipeline 40 and a nozzle 50, the first heat exchanger 38 is arranged between the gas outlet of the desulfurization tower 36 and the gas inlet of the chimney 37, the flue gas flows through the first heat exchanger 38 and exchanges heat with the first heat exchanger 38, and the gas supply pipeline 40 also communicates with the first heat exchanger 38, the gas in the gas supply pipeline 40 also flows through the first heat exchanger 38 and exchanges heat with the first heat exchanger 38 to increase the temperature, at this time, the temperature of the gas after being raised is generally close to 30℃, and the temperature of the gas to be started is generally lower than zero, so the temperature of the gas is at least 30℃ higher than the ambient temperature, which can heat the low temperature area of the triangular cooling unit 21. At the same time, the terminal end of the gas supply pipeline 40 is provided with a plurality of nozzles 50, the plurality of nozzles 50 are divided into a plurality of groups, the number of groups corresponds to the number of triangular cooling units 21, and each group of nozzles 50 is located in a triangular cooling unit 21, wherein the nozzles 50 correspond to the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212 respectively, the heated gas is sprayed to the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212, and local heating is realized.

[0077] In the cold season, the embodiment utilizes the heat of the low-temperature flue gas discharged from the desulfurization tower 36, which is originally wasted, to heat the gas in the gas supply pipeline 40, and then inject the gas into the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212, which are the positions with lower temperature in the air cooling island, so as to increase the temperature of the low-temperature area of the triangular cooling unit 21 and prevent the condensate water in it from freezing in the tube bundle. Compared with the existing anti-freezing methods of the direct air cooling unit 20, such as the anti-freezing method based on the temperature and humidity of the vacuum pipeline, the anti-freezing method of setting a roller shutter or a louver, the anti-freezing method of setting an electric heating pipe, etc., the application utilizes the waste heat of the low-temperature flue gas, improves the utilization rate of the boiler flue gas waste heat, and does not affect the normal exhaust volume of the steam turbine entering the air cooling unit 20, that is, ensures the exhaust flow and temperature inside the air cooling unit 20. At the same time, by heating the local low temperature outside, the anti-freezing effect of the triangular cooling unit 21 is better, and the implementation is relatively simple, which improves the energy utilization rate, can effectively reduce the operating back pressure of the steam turbine, and improves the economy, safety and stability of the unit operation.

[0078] At the same time, the embodiment sets the nozzle 50 inside the triangular cooling unit 21, and uses the parallel flow tube bundle 211 and the counter flow tube bundle 212 to shield the environmental wind in the horizontal direction, so that the hot gas sprayed by the nozzle 50 covers more on the parallel flow tube bundle 211 and the counter flow tube bundle 212, improves the temperature of the specific area, and improves the heat utilization rate.

[0079] In some more severe and cold areas, the heat transferred by the first heat exchanger 38 is not enough to prevent the tube bundle at the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212 from freezing, therefore, preferably, the anti-freezing device further comprises a second heat exchanger 39, which is arranged between the air preheater 33 and the dust remover 34. As known from the above, the flue gas temperature out of the air preheater 33 is 120℃, which can further improve the temperature of the gas in the gas supply pipeline 40 and improve the anti-freezing effect. As shown in the attached Figure 2 The gas in the gas supply pipeline 40 is compressed air, the main pipe is connected with the first heat exchanger 38 and the air compressor 45, the first branch pipe 42 and the second branch pipe 43 are respectively connected with the main pipe and the second main pipe 44, and the middle part of the second branch pipe 43 is connected with the second heat exchanger 39, so that the compressed air in it is heated twice by the second heat exchanger 39; the nozzle 50 is arranged at the terminal end of the second main pipe 44.

[0080] Specifically, the first total pipe 41 is provided with a first regulating valve 411 for regulating the total gas amount, the first branch pipe 42 is provided with a second regulating valve 421 for regulating the gas amount in the first branch pipe 42, and a first temperature measuring point 422 is further provided for detecting the gas temperature in the first branch pipe 42; the second branch pipe 43 is provided with a third regulating valve 431 for regulating the gas amount in the second branch pipe 43, and a second temperature measuring point 432 is further provided for detecting the gas temperature in the second branch pipe 43.

[0081] When only the first regulating valve 411 and the second regulating valve 421 are opened, the path of the gas is: from being raised in pressure and flow rate by the air compressor 45, into the first total pipe 41, through the first heat exchanger 38 to be raised in temperature for the first time, into the first branch pipe 42, to the second total pipe 44, and finally sprayed to the corresponding position by the nozzle 50; when the first regulating valve 411, the second regulating valve 421 and the third regulating valve 431 are all opened, the path of the gas is: from being raised in pressure and flow rate by the air compressor 45, into the first total pipe 41, through the first heat exchanger 38 to be raised in temperature for the first time, part of which enters the first branch pipe 42, and part of which enters the second branch pipe 43 and is heated for the second time by the second heat exchanger 39, and then the gas all enters the second total pipe 44 and is collected, and finally sprayed to the corresponding position by the nozzle 50; when only the first regulating valve 411 and the third regulating valve 431 are opened, the path of the gas is: from being raised in pressure and flow rate by the air compressor 45, into the first total pipe 41, through the first heat exchanger 38 to be raised in temperature for the first time, all of which enters the second branch pipe 43, and is heated for the second time by the second heat exchanger 39, and then the gas enters the second total pipe 44, and finally sprayed to the corresponding position by the nozzle 50.

[0082] The first temperature measuring point 422 and the second temperature measuring point 432 can be provided with temperature sensors 24 for detecting the gas temperature in the first branch pipe 42 and the gas temperature in the second branch pipe 43, respectively, to ensure that the first heat exchanger 38 and the second heat exchanger 39 are in normal working condition, and to facilitate adjustment of the opening degree of the second regulating valve 421 and the third regulating valve 431.

[0083] The anti-freezing device of the embodiment can be artificially controlled, including artificially starting, artificially adjusting the gas flow in the gas supply pipeline 40, artificially adjusting the pressure of the first regulating valve 411, the second regulating valve 421, the third regulating valve 431 and the air compressor 45 to adjust the gas temperature and the gas flow rate in the gas supply pipeline 40, and artificially replacing the nozzle 50 as needed to adjust the spraying range of the nozzle 50.

[0084] Of course, as a preferred embodiment, the present embodiment can also be in an automatic control mode. Specifically, the anti-freezing system of the present embodiment further comprises a control module and a plurality of low-temperature area 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. The anti-freezing device is controlled based on the temperature of the low-temperature area, the ambient temperature, and the unit back pressure.

[0085] Specifically, the low-temperature area temperature detection module in the direct air-cooled unit comprises a temperature sensor located in the condensate collecting pipe at the lower end of the parallel flow tube bundle and a temperature sensor located in the vacuum collecting pipe at the upper end of the counter flow tube bundle. The condensate temperature detection module is located at the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212, respectively, to detect the condensate temperature at the easy freezing position, which is referred to as the condensate temperature detection module. The temperature sensor 24 is located in the condensate collecting pipe 22 at the lower end of each column of parallel flow tube bundle 211 and in the vacuum collecting pipe 231 at the upper end of the counter flow tube bundle 212, respectively, to avoid the nozzle 50 and avoid the interference of the detection result by the hot gas sprayed by the nozzle 50, thereby improving the accuracy of the detection. The temperature sensor 24 transmits the detected temperature data back to the control module. The control module is in communication connection with the gas supply pipeline 40, adjusts the gas temperature in the gas supply pipeline 40 based on the condensate temperature, and is in communication connection with the first regulating valve 411, the second regulating valve 421, the third regulating valve 431, and the air compressor 45, respectively, to adjust the opening degree of the first regulating valve 411, the second regulating valve 421, and the third regulating valve 431 based on the condensate temperature. The opening degree of the first regulating valve 411, the second regulating valve 421, and the third regulating valve 431 is 0-100. At the same time, the air compressor 45 is an adjustable pressure air compressor 45. The control module is in communication connection with the air compressor 45, and is used to adjust the pressure of the air compressor 45 based on the condensate temperature. When only the first nozzle 51 is opened, the pressure of the air compressor 45 can be the first pressure. When only the second nozzle 52 is opened, the pressure of the air compressor 45 needs to be increased to the second pressure because the spraying range is larger and the gas flow is larger. When the first nozzle 51 and the second nozzle 52 are opened at the same time, the pressure of the air compressor 45 needs to be further increased to the third pressure. The specific data of the first pressure, the second pressure, and the third pressure are set according to the pipe diameter of the gas supply pipeline 40 and the size of the nozzle 50.

[0086] Each column of the parallel flow tube bundle 211 or the counter flow tube bundle 212 can correspond to one or more temperature sensors 24. If multiple temperature sensors 24 are provided, the average of the detected temperatures of the multiple temperature sensors 24 can be taken to improve the detection accuracy. The corresponding nozzles 50 of each column of the parallel flow tube bundle 211 or the counter flow tube bundle 212 can be independently controlled according to the temperature detected by the corresponding temperature sensor 24. In addition, temperature sensors 24 can be additionally provided inside or near the nozzles 50 to detect the temperature of the hot gas sprayed by the nozzles 50 in real time, and the temperature sensors 24 at the first temperature measuring point 422 and the second temperature measuring point 432 can be combined to determine whether the anti-freezing device is normal and the fault position.

[0087] The existing air-cooled unit 20 generally has a method of increasing the back pressure of the unit to prevent freezing. In some cases, the ambient temperature drops suddenly, and the anti-freezing system cannot start or starts slowly, resulting in the back pressure of the unit exceeding the set back pressure, which causes a loss of economic efficiency of the unit. In this case, to quickly increase the temperature of the low-temperature area of the air-cooled island, the first regulating valve 411 and the third regulating valve 431 can be directly opened and adjusted to the maximum, so that the gas is quickly heated once and twice and sprayed to the corresponding position. The anti-freezing system of the present embodiment includes a back pressure detection module for detecting the back pressure of the steam turbine, which is in communication connection with the control module. The first regulating valve 411, the second regulating valve 421, and the third regulating valve 431 are all connected with the control module, and are used to open the first regulating valve 411 to the maximum, close the second regulating valve 421, and open the third regulating valve 431 when the back pressure detection module detects that the back pressure is not lower than the set back pressure. The back pressure detection module is a conventional detection unit in the DCS system of the thermal power generator unit, which is prior art and will not be described here. The back pressure detection module is in communication connection with the control module, and can transmit the back pressure data of the steam turbine to the control module, thereby controlling the anti-freezing device.

[0088] As shown in FIG. 6, the anti-freezing device of the present embodiment includes a first temperature measuring point 422 and a second temperature measuring point 432. The first temperature measuring point 422 is arranged at the inlet of the first regulating valve 411, and the second temperature measuring point 432 is arranged at the outlet of the third regulating valve 431. The first temperature measuring point 422 and the second temperature measuring point 432 are in communication connection with the control module, and can transmit the temperature data of the first temperature measuring point 422 and the second temperature measuring point 432 to the control module, thereby controlling the anti-freezing device. Figure 5As shown, the nozzle 50 of the embodiment includes a first nozzle head 51 and a second nozzle head 52, the spraying range of the second nozzle head 52 is larger than that of the first nozzle head 51, and a control module is connected with the nozzle 50, for selecting to open the first nozzle head 51 or the second nozzle head 52 or both the first nozzle head 51 and the second nozzle head 52 based on the condensate water temperature, that is, when the condensate water temperature is lower, the first nozzle head 51 is opened, the first nozzle head 51 is relatively closer to the tube bundle, the spraying range is smaller, but more accurate, and the gas temperature loss is less; when the condensate water temperature is lower, the first nozzle head 51 is closed and the second nozzle head 52 is opened, although the second nozzle head 52 is relatively far away from the tube bundle, the spraying range of the second nozzle head 52 is larger, and the gas temperature in the gas supply pipeline 40 is higher at this time, therefore, the gas temperature sprayed by the second nozzle head 52 is higher, and a warmer environment can be formed to improve the temperature of a specific part; when the condensate water temperature is further reduced, the ambient temperature is lower, and there may also be a strong wind, the first nozzle head 51 and the second nozzle head 52 are opened at the same time, the gas sprayed by the second nozzle head 52 is arranged outside the periphery of the gas sprayed by the first nozzle head 51, forming a gas shield, which is beneficial to retaining heat and less gas temperature loss, and the local temperature raising effect on the triangular cooling unit 21 is better.

[0089] As shown in the accompanying drawings Figure 6 As shown, one co-current tube bundle 211 corresponds to at least two nozzles 50, and one counter-current tube bundle 212 corresponds to at least two nozzles 50; the condensate water temperature and the ambient temperature when the first nozzle head 51 and the second nozzle head 52 need to be opened at the same time are very low, and the sprayed gas is easily cooled quickly in such a cold environment, therefore, in two adjacent nozzles 50, the spraying ranges of the two second nozzle heads 52 partially overlap, and the spraying range of the second nozzle head 52 contacts or partially overlaps with the edge of the spraying range of the first nozzle head 51 of the other nozzle 50, thereby forming multiple layers of gas barriers, so that the gas temperature in the total spraying range of the nozzle 50 is relatively average, and heat loss is less likely to occur, and the triangular cooling unit 21 has a good heating effect.

[0090] For the co-current tube bundle 211 located at the edge, the spraying range of the second nozzle head 52 provided in the embodiment exceeds the edge of the co-current tube bundle 211, thereby, even if the hot gas sprayed by the second nozzle head 52 is affected by the environmental wind and moves towards the inside of the triangular cooling unit 21, it can be ensured that the edge of the co-current tube bundle 211 is within the spraying range of the second nozzle head 52, so as to avoid the occurrence of local freezing of the co-current tube bundle 211.

[0091] The nozzles 50 corresponding to each row of co-current tube bundles 211 or counter-current tube bundles 212 can be independently adjusted. Based on the temperature detected by the temperature sensor 24 corresponding to each row of co-current tube bundles 211 or counter-current tube bundles 212, the spray range of each nozzle 50 can be controlled. This means that each nozzle 50 can be individually controlled to open the first nozzle 51 or the second nozzle 52, or both the first nozzle 51 and the second nozzle 52 can be opened simultaneously, so that more hot air is sprayed to the colder part, achieving precise heating and improving heat utilization.

[0092] Specifically, a first regulating valve 53 is provided on the connection section between the first nozzle 51 and the second main pipe 44, and a second regulating valve 54 is provided on the connection section between the second nozzle 52 and the second main pipe 44. Both the first regulating valve 53 and the second regulating valve 54 are electrically controlled valves and are connected to the control module for communication, enabling remote selection and control of the nozzle 50.

[0093] As attached Figure 2 As shown, a first isolation valve 412 is provided on the first main pipe 41; the first isolation valve 412 is located between the first heat exchanger 38 and the air compressor 45. A second isolation valve 413 is also provided on the section connecting the first main pipe 41 to the outlet end of the first heat exchanger 38; a third isolation valve 423 is provided on the first branch pipe 42; a fourth isolation valve 433 and a fifth isolation valve 434 are provided on the second branch pipe 43, located on the section connecting the second branch pipe 43 to the inlet end of the second heat exchanger 39 and the section connecting the second branch pipe 43 to the outlet end of the second heat exchanger 39, respectively. The function of each of the above isolation valves is to separate the antifreeze system from the boiler flue gas waste heat utilization system during maintenance, and to separate the internal components of the antifreeze system, facilitating overall or partial maintenance.

[0094] Based on the anti-freezing system for air-cooled units based on boiler flue gas waste heat in this embodiment, this embodiment also provides an anti-freezing method for air-cooled units based on boiler flue gas waste heat, including the following steps:

[0095] The boiler flue gas waste heat recovery system is operating normally. The waste heat flue gas flowing out of the outlet of the desulfurization tower 36 flows into the first heat exchanger 38.

[0096] Start the gas supply pipeline 40, and the gas inside it exchanges heat with the first heat exchanger 38 to increase the temperature;

[0097] The cooled flue gas flows into the air inlet of chimney 37;

[0098] The nozzle 50 is activated, and the heated gas is injected onto the lower end of the co-current tube bundle 211 and the upper end of the counter-current tube bundle 212, thereby heating the low-temperature regions of the co-current tube bundle 211 and the counter-current tube bundle 212 from the outside.

[0099] Preferably, in the anti-freezing method of the present embodiment, the anti-freezing device adopts the following control logic:

[0100] detecting the condensate temperature in the condensate header 22 at the lower end of the parallel flow tube bundle 211, and controlling the gas temperature and the spraying range of the nozzles 50 corresponding to the lower end of the parallel flow tube bundle 211 according to the condensate temperature in the condensate header 22;

[0101] detecting the condensate temperature of the vacuumizing header 231 at the upper end of the counter flow tube bundle 212, and controlling the gas temperature and the spraying range of the nozzles 50 corresponding to the upper end of the counter flow tube bundle 212 according to the condensate temperature of the vacuumizing header 231;

[0102] detecting the back pressure of the steam turbine, and judging whether it is not lower than the set back pressure, and further controlling the gas flow and the gas temperature in the gas supply pipeline 40.

[0103] Specifically, based on the condensate temperature, the back pressure detection module, the first regulating valve 411, the second regulating valve 421, the third regulating valve 431 and the air compressor 45, the specific control logic of the anti-freezing device is as follows:

[0104] If the condensate temperature is lower than the first set value T1, the first regulating valve 411 on the first main pipe 41 is opened, the air compressor 45 on the gas supply pipeline 40 is opened, the second regulating valve 421 on the first branch pipe 42 is opened, the third regulating valve 431 on the second branch pipe 43 is kept closed, the first nozzle 51 is opened, the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212 are heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0105] If the condensate temperature is lower than the second set value T2, the opening degree of the first regulating valve 411 on the first main pipe 41 is increased, the opening degree of the second regulating valve 421 on the first branch pipe 42 is increased, the pressure of the air compressor 45 on the gas supply pipeline 40 is increased, the first nozzle 51 is closed, the second nozzle 52 is opened, the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212 are heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0106] If the condensate temperature is lower than the third set value T3, the opening degree of the first regulating valve 411 on the first main pipe 41 is adjusted to the maximum, the pressure of the air compressor 45 on the gas supply pipeline 40 is increased, the opening degree of the third regulating valve 431 on the second branch pipe 43 is opened, part of the gas flowing out of the first heat exchanger 38 flows into the second branch pipe 43 for secondary heating by the second heat exchanger 39, part of the gas continues to pass through the first branch pipe 42, the gas in the second branch pipe 43 and the first branch pipe 42 converges in the second main pipe 44; the first nozzle 51 is opened, the second nozzle 52 is opened, the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212 are heated, and the back pressure of the steam turbine is lower than the set back pressure;

[0107] If the condensate temperature is lower than the fourth set value T4 and the back pressure of the steam turbine is detected to be not lower than the set back pressure, the first regulating valve 411 on the first branch pipe 41 is opened to the maximum, the pressure of the air compressor 45 on the air supply pipe 40 is increased, the second regulating valve 421 on the second branch pipe 42 is closed, the third regulating valve 431 on the second branch pipe 43 is opened to the maximum, the pressure of the air compressor 45 on the air supply pipe 40 is increased, and all the gas flowing out of the first heat exchanger 38 flows into the second branch pipe 43 and is heated by the second heat exchanger 39; the first nozzle 51 is kept open, the second nozzle 52 is kept open, and the lower end of the parallel flow tube bundle 211 and the upper end of the counter flow tube bundle 212 are heated.

[0108] After the set time, if the back pressure of the steam turbine is detected to be lower than the set back pressure and the condensate temperature is still lower than the fourth set value, the above operation is continuously kept until the condensate temperature is higher than the fourth set value.

[0109] In the above control logic, the set temperature and the pressure values of the first regulating valve 411, the second regulating valve 421, the third regulating valve 431 and the air compressor 45 can be associated in the design stage, so that in actual use, if the ambient temperature suddenly drops, resulting in a sudden drop of the condensate temperature, for example, the condensate temperature directly drops to be lower than the fourth set value, the corresponding opening degrees of the first regulating valve 411 and the third regulating valve 431 and the corresponding pressure value of the air compressor 45 can be directly adjusted according to the situation that the condensate temperature is lower than the fourth set value and the back pressure of the steam turbine is detected to be not lower than the set back pressure, instead of being adjusted step by step.

[0110] T1 to T4 can be set according to the following rules: T1>T2>T3>T4, and the specific values are set according to the actual environment of the unit and the working condition of the unit.

[0111] Embodiment Two

[0112] As shown in FIG. 2, the air supply pipe 40 is connected to the air compressor 45, and the air compressor 45 is connected to the first branch pipe 41, the second branch pipe 42 and the third branch pipe 43 through the first regulating valve 411, the second regulating valve 421 and the third regulating valve 431 respectively. Figure 7As shown, the air cooling unit in the embodiment is an indirect air cooling unit, and the exhaust steam of the steam turbine of the thermal power generating unit is discharged to the outdoor arranged indirect air cooling unit through the exhaust steam pipeline, the indirect air cooling unit comprises a condenser and an indirect air cooling tower 27, the exhaust steam pipeline is connected with the exhaust port of the steam turbine and the condenser, and the first circulating loop is arranged between the condenser and the indirect air cooling tower 27, 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 the high-temperature circulating medium, and then flows back to the indirect air cooling tower 27, is cooled to the low-temperature circulating medium in the indirect air cooling tower 27, and then flows to the condenser. The cooling process of the high-temperature circulating medium in the indirect air cooling tower 27 mainly relies on the cooling triangular heat sink 28, the cooling triangular heat sink 28 is generally arranged around the outer periphery of the tower body of the indirect air cooling tower 27, the circulating loop is connected to the cooling triangular heat sink 28, and heat exchange is generated when the cold air passes through the cooling triangular heat sink 28, the hot air formed is discharged upward from the center of the indirect air cooling tower 27, and the high-temperature circulating medium is cooled to the low-temperature circulating medium in the cooling triangular heat sink 28. Therefore, the low-temperature region of the air cooling unit of the embodiment exists in the cooling triangular heat sink 28, and specifically, the cooling triangular heat sink 28 has the water inlet pipe 281 and the water return pipe 282 connected therein, and the lower end of the water return pipe 282 is the low-temperature region.

[0113] Based on this, the embodiment differs from the first embodiment in that, as shown in Figure 8 As shown, the cooling triangular heat sink 28 has the water inlet pipe 281 and the water return pipe 282 connected therein, the lower end of the water return pipe 282 is the low-temperature region, the plurality of nozzles 50 correspond to the plurality of cooling triangular heat sinks 28 of the indirect air cooling tower 27 respectively, and the air injection direction of the nozzles 50 is towards the lower end of the water return pipe 282.

[0114] As shown in Figure 8 As shown, the cooling triangular heat sink 28 has the water inlet pipe 281 and the water return pipe 282 connected therein, the lower end of the water return pipe 282 is the low-temperature region, the plurality of nozzles 50 correspond to the plurality of cooling triangular heat sinks 28 of the indirect air cooling tower 27 respectively, and the air injection direction of the nozzles 50 is towards the lower end of the water return pipe 282.

[0115] Specifically, when the air cooling unit is an indirect air cooling unit, the anti-freezing system further comprises a control module and a return water temperature detection module. The return water temperature detection module is located in the low-temperature area at the lower end of the return water pipe 282, and detects the return water temperature at the easy-freezing position through a temperature sensor. The return water temperature detection module is in communication connection with the control module. The control module is in communication connection with the air supply pipeline 40. The opening degrees of the first regulating valve 411, the second regulating valve 421 and the third regulating valve 431 are adjusted based on the return water temperature. The opening degrees of the first regulating valve 411, the second regulating valve 421 and the third regulating valve 431 are all 0-100. Similarly, the anti-freezing system of the embodiment also comprises a back pressure detection module for detecting the back pressure of the steam turbine. The back pressure detection module is in communication connection with the control module. The first regulating valve 411, the second regulating valve 421 and the third regulating valve 431 are all connected with the control module, so as to open the first regulating valve 411 to the maximum, close the second regulating valve 421 and open the third regulating valve 431 when the back pressure detection module detects that the back pressure is not lower than the set back pressure.

[0116] Preferably, as shown in Figs. 6 and 7, when the air cooling unit is an indirect air cooling unit, the plurality of nozzles 50 are vertically arranged at positions corresponding to the low-temperature area at the lower end of the return water pipe 282 of the cooling triangular radiator 28, and are controlled by the control module to be opened from bottom to top based on the return water temperature. Figure 8 and Figs. 8 and 9 show that when the air cooling unit is an indirect air cooling unit, the plurality of nozzles 50 are vertically arranged at positions corresponding to the low-temperature area at the lower end of the return water pipe 282 of the cooling triangular radiator 28, and are controlled by the control module to be opened from bottom to top based on the return water temperature. Figure 9 The opening priority of all the first spray heads 51 and the second spray heads 52 of the nozzles 50 at the same height is higher than that of all the first spray heads 51 and the second spray heads 52 of the nozzles 50 at higher heights. The spray ranges of the two second spray heads 52 adjacent to each other partially overlap, and the spray range of the second spray head 52 is in contact with or partially overlaps with the edge of the spray range of the first spray head 51 in another nozzle 50.

[0117] The spray ranges of the two second spray heads 52 adjacent to each other partially overlap, and the spray range of the second spray head 52 is in contact with or partially overlaps with the edge of the spray range of the first spray head 51 in another nozzle 50.

[0118] In the anti-freezing method of the embodiment, the specific control logic of the anti-freezing device is as follows:

[0119] If the return water temperature is lower than the first set value T1, the first regulating valve 411 on the first main pipe 41 is opened, the air compressor 45 on the air supply pipeline 40 is opened, the second regulating valve 421 on the first branch pipe 42 is opened, the third regulating valve 431 on the second branch pipe 43 is kept closed, the first spray head 51 in the nozzle 50 at the lowermost end of the return water pipe 282 is opened, the low-temperature area at the lowermost end of the return water pipe 282 is heated, and the back pressure of the steam turbine is lower than the set back pressure.

[0120] If the return water temperature is lower than the second set value T2, the opening of the first regulating valve 411 on the first main pipe 41 is increased, the opening of the second regulating valve 421 on the first branch pipe 42 is increased, the pressure of the air compressor 45 on the air supply pipeline 40 is increased, the first nozzle 51 in the nozzle 50 at the lowermost end of the return water pipe 282 is closed, the second nozzle 52 is opened, the low-temperature area at the lowermost end of the return water pipe 282 is heated, and the back pressure of the steam turbine is lower than the set back pressure.

[0121] If the return water temperature is lower than the third set value T3, the opening of the first regulating valve 411 on the first main pipe 41 is adjusted to the maximum, the pressure of the air compressor 45 on the air supply pipeline 40 is increased, the opening of the third regulating valve 431 on the second branch pipe 43 is opened, part of the gas flowing out of the first heat exchanger 38 flows into the second branch pipe 43 and is heated again by the second heat exchanger 39, and part of the gas continues to pass through the first branch pipe 42; the first nozzle 51 and the second nozzle 52 in the nozzle 50 at the lowermost end of the return water pipe 282 are opened, the low-temperature area at the lowermost end of the return water pipe 282 is heated, and the back pressure of the steam turbine is lower than the set back pressure.

[0122] If the return water temperature is lower than the fourth set value T4 and it is detected that the back pressure of the steam turbine is not lower than the set back pressure, the opening of the first regulating valve 411 on the first main pipe 41 is adjusted to the maximum, the pressure of the air compressor 45 on the air supply pipeline 40 is increased, the second regulating valve 421 on the first branch pipe 42 is closed, the third regulating valve 431 on the second branch pipe 43 is opened to the maximum, the pressure of the air compressor 45 on the air supply pipeline 40 is increased, and all the gas flowing out of the first heat exchanger 38 flows into the second branch pipe 43 and is heated again by the second heat exchanger 39; the first nozzle 51 and the second nozzle 52 of at least two groups of nozzles 50 in the height direction of the lower end of the return water pipe 282 are opened, and the low-temperature area at the middle and lower end of the return water pipe 282 is heated.

[0123] After the set time, if it is detected that the back pressure of the steam turbine is lower than the set back pressure and the return water temperature is still lower than the fourth set value, the state is maintained until the return water temperature is higher than the fourth set value.

[0124] T1, T2, T3 and T4 in the embodiment can be the same as those in the first embodiment, or can be reset according to the actual temperature of the indirect air-cooled unit in the embodiment, as long as the following conditions are met: T1>T2>T3>T4, and the specific values are set according to the actual environment and working condition of the unit.

[0125] The above-mentioned embodiments are only preferred embodiments of the present application, and cannot be used to limit the protection scope of the present application. Any non-essential changes and replacements made by those skilled in the art on the basis of the present application shall fall within the protection scope of the present application.

Claims

1. A freeze protection system for air-cooled units based on boiler flue gas waste heat, characterized in that, It includes exhaust pipes, air-cooled units, boiler flue gas waste heat utilization system and anti-freezing device. The boiler flue gas waste heat utilization system includes flue gas pipes, economizer, air preheater, dust collector, blower, desulfurization tower and chimney connected in sequence. The antifreeze device includes a first heat exchanger, a gas supply pipe, and a nozzle. The first heat exchanger is disposed between the gas outlet of the desulfurization tower and the gas inlet of the chimney. The gas supply pipe exchanges heat with the exhaust gas of the desulfurization tower through the first heat exchanger to increase the gas temperature in the gas supply pipe. The gas supply pipeline is equipped with several nozzles at its end. Each nozzle corresponds to a low-temperature zone of the air-cooled unit and sprays heated gas into the low-temperature zone. When the air-cooled unit is a direct air-cooled unit, the direct air-cooled unit includes an air-cooled island and a condensate tank. The air-cooled island is connected to the condensate tank. The exhaust pipe is connected to the exhaust port of the steam turbine and the air-cooled island. The air-cooled island includes several triangular cooling units, each triangular cooling unit comprising a co-current tube bundle and a counter-current tube bundle. Several nozzles are divided into several groups, the number of groups corresponding to the number of triangular cooling units. Each group of nozzles is located in the low-temperature region of the air-cooled unit, and the nozzles respectively correspond to the lower end of the co-current tube bundle and the upper end of the counter-current tube bundle, spraying towards the lower end of the co-current tube bundle and the upper end of the counter-current tube bundle.

2. The anti-freezing system for air-cooled units based on boiler flue gas waste heat as described in claim 1, characterized in that, The antifreeze device further includes a second heat exchanger, which is disposed between the air preheater and the dust collector. The air supply pipeline includes an air compressor, a first main pipe, a first branch pipe, a second branch pipe, and a second main pipe. The gas in the air supply pipeline is compressed air. The main pipe connects the first heat exchanger and the air compressor. The first branch pipe and the second branch pipe are respectively connected to the main pipe and the second main pipe. The middle part of the second branch pipe is connected to the second heat exchanger, so that the compressed air in it is reheated by the second heat exchanger. The nozzle is disposed at the end of the second main pipe.

3. The anti-freezing system for air-cooled units based on boiler flue gas waste heat as described in claim 2, characterized in that, The first main pipe is provided with a first regulating valve for adjusting the total gas volume, the first branch pipe is provided with a second regulating valve for adjusting the gas volume in the first branch pipe, and a first temperature measuring point for detecting the gas temperature in the first branch pipe is also provided. The second branch pipe is equipped with a third regulating valve for adjusting the gas volume in the second branch pipe, and a second temperature measuring point for detecting the gas temperature in the second branch pipe.

4. The anti-freezing system for air-cooled units based on boiler flue gas waste heat as described in claim 3, characterized in that, The air-cooled unit is either an indirect air-cooled unit or a direct air-cooled unit. When the air-cooled unit is an indirect air-cooled unit, the indirect air-cooled unit includes a condenser and an indirect cooling tower. The exhaust pipe connects the exhaust port of the steam turbine and the condenser. The indirect cooling tower includes several cooling triangular radiators. The cooling triangular radiators have a connected inlet water pipe and a return water pipe inside. The lower end of the return water pipe is a low-temperature region. Several nozzles correspond to several cooling triangular radiators of the indirect cooling tower, and the jet direction of the nozzles is towards the lower end of the return water pipe.

5. The anti-freezing system for air-cooled units based on boiler flue gas waste heat as described in claim 4, characterized in that, It also includes a control module; When the air-cooled unit is a direct air-cooled unit, the antifreeze system also includes several condensate temperature detection modules. The condensate temperature detection modules are located in the condensate manifold at the lower end of the co-current tube bundle and in the vacuum manifold at the upper end of the counter-current tube bundle, respectively. The condensate temperature detection modules are communicatively connected to the control module, and the control module is communicatively connected to the gas supply pipeline. The opening degree of the first regulating valve, the second regulating valve, and the third regulating valve is adjusted based on the condensate temperature. The opening degree of the first regulating valve, the second regulating valve, and the third regulating valve is 0-100. When the air-cooled unit is an indirect air-cooled unit, the antifreeze system also includes a return water temperature detection module. The return water temperature detection module is located in the low-temperature zone at the lower end of the return water pipe. The return water temperature detection module is communicatively connected to the control module. The control module is communicatively connected to the air supply pipeline. Based on the return water temperature, the opening degree of the first regulating valve, the second regulating valve, and the third regulating valve is adjusted. The opening degree of the first regulating valve, the second regulating valve, and the third regulating valve is all 0-100. The antifreeze system 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 first regulating valve, the second regulating valve, and the third regulating valve are all connected to the control module and are used to open the first regulating valve to the maximum, close the second regulating valve, and open the third regulating valve when the back pressure detection module detects that the back pressure is not lower than the set back pressure.

6. The anti-freezing system for air-cooled units based on boiler flue gas waste heat as described in claim 5, characterized in that, The nozzle includes a first nozzle and a second nozzle, the spray range of the second nozzle being greater than that of the first nozzle, and at least one of the first nozzle and the second nozzle being activated when the antifreeze device is working.

7. The anti-freezing system for air-cooled units based on boiler flue gas waste heat as described in claim 6, characterized in that, When the air-cooled unit is a direct air-cooled unit, at least two nozzles are provided for each of the co-current tube bundles, and at least two nozzles are provided for each of the counter-current tube bundles. In two adjacent nozzles, the spray ranges of the two second nozzles partially overlap, and the spray range of the second nozzle contacts or partially overlaps with the edge of the spray range of the first nozzle of the other nozzle. The spray range of the second nozzle near the edge of the co-current tube bundle extends beyond the edge of the co-current tube bundle; When the air-cooled unit is an indirect air-cooled unit, a number of nozzles are vertically arranged at the position corresponding to the low-temperature area at the lower end of the cooling triangular radiator and the return water pipe, and are controlled by the control module to be turned on sequentially from bottom to top based on the return water temperature; the opening priority of all the first nozzles and second nozzles of the nozzles at the same height is higher than the opening priority of all the first nozzles and second nozzles of the nozzles at higher heights. The spray ranges of two adjacent second nozzles partially overlap, and the spray range of the second nozzle contacts or partially overlaps with the edge of the spray range of the first nozzle in the other nozzle.

8. The anti-freezing system for air-cooled units based on boiler flue gas waste heat as described in claim 2, characterized in that, A first isolation valve is provided on the first main pipe; the first isolation valve is located between the first heat exchanger and the air compressor. A second isolation valve is also provided on the section connecting the first main pipe to the outlet end of the first heat exchanger; A third isolation valve is installed on the first branch pipe; The second branch pipe is equipped with a fourth isolation valve and a fifth isolation valve, which are located on the section of the second branch pipe that connects to the inlet end of the second heat exchanger and the section that connects to the outlet end of the second heat exchanger, respectively.

9. A method for preventing freezing of air-cooled units based on waste heat from boiler flue gas, characterized in that, The anti-freezing system for air-cooled units based on boiler flue gas waste heat as described in any one of claims 1 to 8 includes the following steps: The boiler flue gas waste heat recovery system is operating normally. The waste heat flue gas flowing out of the desulfurization tower flows into the first heat exchanger. Start the gas supply pipeline, and the gas inside exchanges heat with the first heat exchanger to increase the temperature; The cooled flue gas flows into the chimney's air inlet; The nozzles are activated, and the heated gas is injected into the low-temperature region of the air-cooled unit.

10. The method for preventing freezing of air-cooled units based on boiler flue gas waste heat as described in claim 9, characterized in that, When the air-cooled unit is a direct air-cooled unit, the anti-freeze device adopts the following control logic: The temperature of the condensate in the condensate manifold at the lower end of the co-current tube bundle is detected, and the temperature and range of the gas sprayed by the nozzle corresponding to the lower end of the co-current tube bundle are controlled according to the temperature of the condensate in the condensate manifold. The condensate temperature of the vacuum manifold at the upper end of the countercurrent tube bundle is detected, and the gas temperature and spray range of the nozzle corresponding to the upper end of the countercurrent tube bundle are controlled according to the condensate temperature of the vacuum manifold. The back pressure of the steam turbine is detected and it is determined whether it is not lower than the set back pressure, thereby controlling the gas flow rate and gas temperature in the gas supply pipeline; The specific control logic of the antifreeze device is as follows: If the condensate temperature is lower than the first set value, the first regulating valve on the first main pipe will open, the air compressor on the gas supply pipe will start, the second regulating valve on the first branch pipe will open, the third regulating valve on the second branch pipe will remain closed, the first nozzle will open, and the lower end of the co-current tube bundle and the upper end of the counter-current tube bundle will be heated, and the back pressure of the steam turbine will be lower than the set back pressure. If the condensate temperature is lower than the second set value, the opening of the first regulating valve on the first main pipe is increased, the opening of the second regulating valve on the first branch pipe is increased, the pressure of the air compressor on the air supply pipeline is increased, the first nozzle is closed, the second nozzle is opened, the lower end of the co-current tube bundle and the upper end of the counter-current tube bundle are heated, and the back pressure of the steam turbine is lower than the set back pressure. If the condensate temperature is lower than the third set value, the opening of the first regulating valve on the first main pipe is adjusted to the maximum, increasing the pressure of the air compressor on the gas supply pipeline. The opening of the third regulating valve on the second branch pipe is opened, and part of the gas flowing out from the first heat exchanger flows into the second branch pipe and is heated again by the second heat exchanger. Part of the gas continues to pass through the first branch pipe, and the gas from the second branch pipe and the first branch pipe merge in the second main pipe. The first nozzle opens, and the second nozzle opens to heat the lower end of the co-current tube bundle and the upper end of the counter-current tube bundle. The back pressure of the steam turbine is lower than the set back pressure. If the condensate temperature is lower than the fourth set value, and the back pressure of the turbine is detected to be not lower than the set back pressure, then the opening of the first regulating valve on the first main pipe is adjusted to the maximum to increase the pressure of the air compressor on the gas supply pipeline. The second regulating valve on the first branch pipe is closed, and the third regulating valve on the second branch pipe is opened to the maximum to increase the pressure of the air compressor on the gas supply pipeline. All the gas flowing out of the first heat exchanger flows into the second branch pipe and is heated again by the second heat exchanger. The first nozzle is kept open, and the second nozzle is kept open to heat the lower end of the co-current tube bundle and the upper end of the counter-current tube bundle. If, after a set time, the back pressure of the steam turbine is detected to be lower than the set back pressure and the condensate temperature is still lower than the fourth set value, the setting will continue until the condensate temperature is higher than the fourth set value. When the air-cooled unit is an indirect air-cooled unit, the specific control logic of the anti-freeze device is as follows: If the return water temperature is lower than the first set value, the first regulating valve on the first main pipe will open, the air compressor on the air supply pipe will start, the second regulating valve on the first branch pipe will open, the third regulating valve on the second branch pipe will remain closed, the first nozzle in the nozzle at the bottom of the return water pipe will open, and the low temperature zone at the bottom of the return water pipe will be heated, and the back pressure of the steam turbine will be lower than the set back pressure. If the return water temperature is lower than the second set value, the opening of the first regulating valve on the first main pipe is increased, the opening of the second regulating valve on the first branch pipe is increased, the pressure of the air compressor on the air supply pipe is increased, the first nozzle in the nozzle at the bottom of the return water pipe is closed, the second nozzle is opened, the low temperature zone at the bottom of the return water pipe is heated, and the back pressure of the steam turbine is lower than the set back pressure. If the return water temperature is lower than the third set value, the opening of the first regulating valve on the first main pipe is adjusted to the maximum to increase the pressure of the air compressor on the gas supply pipe. The opening of the third regulating valve on the second branch pipe is opened, and part of the gas flowing out from the first heat exchanger flows into the second branch pipe and is heated again by the second heat exchanger. Part of the gas continues to pass through the first branch pipe, and the gas from the second branch pipe and the first branch pipe merge in the second main pipe. At the same time, the first nozzle and the second nozzle in the nozzle located at the bottom of the return water pipe are opened to heat the low temperature zone at the bottom of the return water pipe, and the back pressure of the steam turbine is lower than the set back pressure. If the return water temperature is lower than the fourth set value, and the back pressure of the steam turbine is detected to be not lower than the set back pressure, then the opening of the first regulating valve on the first main pipe is adjusted to the maximum to increase the pressure of the air compressor on the air supply pipeline, the second regulating valve on the first branch pipe is closed, and the third regulating valve on the second branch pipe is opened to the maximum to increase the pressure of the air compressor on the air supply pipeline. All the gas flowing out from the first heat exchanger flows into the second branch pipe and is heated again by the second heat exchanger. At the same time, the first nozzle and the second nozzle of at least two sets of nozzles located in the height direction of the lower end of the return water pipe are opened to heat the low temperature zone in the lower part of the return water pipe. If, after a set time, the back pressure of the turbine is detected to be lower than the set back pressure and the return water temperature is still lower than the fourth set value, the condition will continue to be maintained until the return water temperature is higher than the fourth set value.

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