Anti-freezing and energy-saving control method and equipment for indirect air cooling system of thermal power plant

Abstract

The invention provides an anti-freezing and energy-saving control method and device for an indirect air cooling system of a thermal power plant. The method comprises the steps that meteorological information and unit working conditions of the environment where the thermal power plant is located are obtained; the meteorological information comprises environment temperature and environment wind speed, and the unit working conditions comprise load and back pressure; determining a heat transfer relationship of the circulating water system by utilizing a pre-constructed heat exchange balance equation; based on the meteorological information, the unit working condition and the heat transfer relation, the temperature deviation between the actual temperature of the circulating return water and the preset freezing damage point temperature is obtained; based on the temperature deviation, the circulating water flow and the cooling air flow are adjusted, so that the actual temperature of the circulating water is larger than or equal to the preset freezing damage point temperature; the preset freezing damage point temperature represents the lowest allowable value of the return water temperature of the circulating water, and the preset freezing damage point temperature is an arbitrary value between 14 DEG C and 18 DEG C. Under the condition that the energy consumption is reduced to the maximum extent, the actual temperature of the circulating water is accurately controlled, and freezing damage of the circulating water system is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of antifreeze of thermal power plants, and in particular to an antifreeze and energy-saving control method and equipment for an indirect air cooling system of a thermal power plant. Background Art

[0002] In the operation of thermal power plants, antifreeze measures for circulating water systems are essential to ensure the safety and stability of equipment. Especially in winter, antifreeze of circulating water systems becomes a top priority to avoid equipment damage and operation interruption caused by low temperatures.

[0003] Existing antifreeze technologies mainly rely on maintaining the circulating water return temperature within a safe range. The usual practice is to raise the circulating water return temperature to above 20°C to ensure the antifreeze safety of the system. However, although this practice improves safety, it also increases energy consumption and affects the economic operation of the power plant. Alternatively, in order to prevent freezing, all shutters are usually closed, a measure that may lead to unnecessary energy waste. Summary of the invention

[0004] The present invention provides an antifreeze and energy-saving control method and equipment for an indirect air cooling system of a thermal power plant, which is used to solve the problem that the circulating water system cannot be antifreeze under the condition of reasonably controlling energy consumption in the prior art.

[0005] In one aspect, the present invention provides an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant, comprising: Acquire meteorological information and unit operating conditions of the environment in which the thermal power plant is located; wherein the meteorological information includes ambient temperature and ambient wind speed, and the unit operating conditions include load and back pressure; Determine the heat transfer relationship of the circulating water system using the pre-built heat exchange balance equation; Based on the meteorological information, the unit operating conditions and the heat transfer relationship, a temperature deviation between an actual temperature of circulating water return water and a preset freezing damage point temperature is obtained; Based on the temperature deviation, the circulating water flow rate and the cooling air flow rate are adjusted so that the actual temperature of the circulating water is greater than or equal to the preset freezing point temperature; wherein the preset freezing point temperature represents the minimum allowable value of the circulating water return temperature, and the preset freezing point temperature is any value between 14-18°C.

[0006] According to an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant provided by the present invention, the heat exchange balance equation includes: D C (h C -h N ′ )=D W (t R-t L )C W =D F (T OUT -T IN )C F ;in, D C is the exhaust flow rate of steam turbine; h C is the exhaust enthalpy of the steam turbine; h N is the condensation enthalpy; D W is the circulating water flow rate; t R is the inlet water temperature of the intercooler; t L is the outlet water temperature of the intercooler; C W is the specific volume of circulating water; D F is the cooling air flow rate; T OUT is the outlet air temperature of the cooling triangle; T IN is the cooling triangle inlet air temperature; C F is the specific volume of cooling air.

[0007] According to the present invention, an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant further comprises: Optimize the operating parameters of the circulating water system, including at least one of the following: Set the inlet water temperature of the intercooler to ≥ the inlet water temperature of the circulating water under rated load; Set the unit back pressure to rated back pressure or minimum back pressure; Keep the condenser end difference constant; Under the condition that the ambient wind speed at a preset height of the thermal power plant is less than the preset wind speed, the circulating water flow rate or the opening degree of the shutters is adjusted.

[0008] According to the present invention, an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant further comprises: Determine the first critical temperature and the second critical temperature as two ambient temperature critical points; wherein, The first critical temperature is the limit ambient temperature value at which the inlet water temperature of the intercooler can be maintained at 39°C. When the ambient temperature is greater than the first critical temperature, the cooling system operates at full output; The second critical temperature is the extreme ambient temperature value at which the outlet water temperature of the intercooler is maintained at 18°C. When the ambient temperature is lower than the second critical temperature, the circulating water flow rate at this moment is kept unchanged, and the shutter opening is reduced to maintain the outlet water temperature of the intercooler ≥18°C.

[0009] According to the present invention, an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant further comprises: When the second critical temperature is ≤ the ambient temperature ≤ the first critical temperature, the shutters are controlled to be fully opened to maintain the maximum cooling air flow; When 0°C ≤ ambient temperature ≤ the second critical temperature, the circulating water flow rate is maintained unchanged, and the shutters are controlled to be fully opened to maintain the outlet water temperature of the intercooler tower equal to 18°C; When the ambient temperature is ≤0℃, while controlling the shutters to close, the circulating water flow rate needs to be increased as the ambient temperature drops.

[0010] According to the antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant provided by the present invention, the preset freezing damage point temperature is 14°C.

[0011] According to the antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant provided by the present invention, the preset height is 9-11m, and the preset wind speed is 4-5m / s.

[0012] According to the present invention, an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant further comprises: Determine the original exhaust steam flow rate before the circulating water temperature changes and the new exhaust steam flow rate after the circulating water temperature changes; By comparing the new exhaust steam flow rate with the original exhaust steam flow rate, the actual exhaust steam pressure after the circulating water temperature changes is determined; Based on the actual exhaust pressure, the vacuum degree of the condenser is obtained; Based on the vacuum degree, adjust the circulating water flow and cooling air flow.

[0013] According to the present invention, an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant further comprises: Calculate the exhaust pressure change rate at different circulating water inlet temperatures; Determine the coal consumption change rate of the unit corresponding to the exhaust pressure change rate; Based on the coal consumption change rate, the circulating water flow rate and the cooling air flow rate are controlled.

[0014] On the other hand, the present invention also provides an antifreeze and energy-saving control device for an indirect air cooling system of a thermal power plant, comprising: An information acquisition module is used to acquire meteorological information and unit operating conditions of the environment in which the thermal power plant is located; wherein the meteorological information includes ambient temperature and ambient wind speed, and the unit operating conditions include load and back pressure; Heat exchange module, used to determine the heat transfer relationship of the circulating water system using pre-built heat exchange balance equations; A temperature determination module, based on the meteorological information, the unit operating conditions and the heat transfer relationship, obtains a temperature deviation between an actual temperature of circulating water return water and a preset freezing damage point temperature; A control module is used to adjust the circulating water flow rate and the cooling air flow rate based on the temperature deviation so that the actual temperature of the circulating water is greater than or equal to the preset freezing point temperature; wherein the preset freezing point temperature represents the minimum allowable value of the circulating water return temperature, and the preset freezing point temperature is any value between 14-18°C.

[0015] On the other hand, the present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant as described in any one of the above-mentioned methods is implemented.

[0016] The antifreeze and energy-saving control method and equipment for the indirect air cooling system of a thermal power plant provided by the present invention obtain meteorological information and unit operating conditions of the environment in which the thermal power plant is located; wherein the meteorological information includes ambient temperature and ambient wind speed, and the unit operating conditions include load and back pressure; a heat transfer relationship of a circulating water system is determined by using a pre-constructed heat exchange balance equation; based on the meteorological information, the unit operating conditions and the heat transfer relationship, a temperature deviation between the actual temperature of circulating water return water and a preset freezing damage point temperature is obtained; based on the temperature deviation, the circulating water flow rate and the cooling air flow rate are adjusted so that the temperature of the circulating water is greater than or equal to the preset freezing damage point temperature, thereby achieving accurate control of the actual temperature of the circulating water while maximizing energy consumption reduction, thereby avoiding freezing damage to the circulating water system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the 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 creative work.

[0018] Figure 1 It is a flow chart of an antifreeze and energy-saving control method for an indirect air cooling system of a thermal power plant provided by an embodiment of the present invention; Figure 2 It is a structural schematic diagram of an antifreeze and energy-saving control device for an indirect air cooling system of a thermal power plant provided by an embodiment of the present invention; Figure 3 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Figure 1 Schematic diagram of the flow chart of the antifreeze and energy-saving control method of the indirect air cooling system of a thermal power plant provided by the embodiment of the present invention. Figure 1 The antifreeze and energy-saving control method of the indirect air cooling system of a thermal power plant may include the following steps.

[0021] Step 101: Obtain meteorological information and unit operating conditions of the environment in which the thermal power plant is located; wherein the meteorological information may include ambient temperature and ambient wind speed, and the unit operating conditions may include load and back pressure.

[0022] In this step, you can obtain weather information by subscribing to weather services to obtain real-time updated weather forecasts; or, deploy a weather sensor network in the environment where the thermal power plant is located to monitor weather information in real time. These sensors may include temperature sensors, wind speed sensors, humidity sensors, etc. Install sensors at key locations of the unit to monitor parameters such as load, back pressure, and flow; or, integrate the unit's operating data into the distributed control system (DCS) or monitoring control system of the thermal power plant to monitor operating parameters such as load and back pressure in real time.

[0023] Step 102: Determine the heat transfer relationship of the circulating water system using the pre-constructed heat exchange balance equation.

[0024] In this step, the heat exchange balance equation may include the following formula (1): D C (h C -h N ′ )=D W (t R -t L )C W =D F (T OUT -T IN )C F (1); among which, D C is the exhaust flow rate of steam turbine; h C is the exhaust enthalpy of the steam turbine; h N is the condensation enthalpy; D W is the circulating water flow rate; t Ris the inlet water temperature of the intercooler (also called the inlet water temperature of the intercooler); t L is the outlet water temperature of the intercooler (also called the outlet water temperature of the intercooler); C W is the specific volume of circulating water; D F is the cooling air flow rate; T OUT is the outlet air temperature of the cooling triangle; T IN is the cooling triangle inlet air temperature; C F is the specific volume of cooling air.

[0025] This step can obtain the heat information of the turbine exhaust, the heat change of the circulating water, the heat exchange of the cooling air and other information.

[0026] Step 103: Based on meteorological information, unit operating conditions and heat transfer relationship, obtain the temperature deviation between the actual temperature of circulating water return water and the preset freezing damage point temperature.

[0027] In this step, by calculating and predicting the actual temperature of the circulating water return water instead of relying solely on sensor measurements, potential freezing damage risks can be identified in advance and system parameters can be adjusted proactively. Comprehensive consideration of meteorological conditions and unit operating conditions can be used to provide a comprehensive system analysis to ensure the safe and efficient operation of the circulating water system. The heat exchange balance equation can be used for precise calculations to reduce dependence on a single sensor and improve system reliability and accuracy.

[0028] Step 104: Based on the temperature deviation, adjust the circulating water flow rate and the cooling air flow rate so that the actual temperature of the circulating water is greater than or equal to the preset freezing point temperature; wherein the preset freezing point temperature represents the minimum allowable value of the circulating water return temperature, and the preset freezing point temperature is any value between 14-18°C.

[0029] In this step, if the temperature deviation indicates that the actual temperature of the circulating water return water is lower than the preset freezing point temperature, the circulating water flow rate can be increased to increase the circulating water temperature. If it is higher than the preset freezing point temperature, the circulating water flow rate can be reduced to reduce energy consumption. If increasing the circulating water flow rate still cannot make the temperature reach the preset freezing point, the cooling air flow rate can be increased to improve the cooling efficiency. If the temperature is too high, the cooling air flow rate can be reduced to reduce the cooling effect.

[0030] In this embodiment, meteorological information and unit operating conditions of the environment in which the thermal power plant is located are obtained; wherein the meteorological information includes ambient temperature and ambient wind speed, and the unit operating conditions include load and back pressure; the heat transfer relationship of the circulating water system is determined by using a pre-constructed heat exchange balance equation; based on the meteorological information, the unit operating conditions and the heat transfer relationship, the temperature deviation between the actual temperature of the circulating water return water and the preset freezing damage point temperature is obtained; based on the temperature deviation, the circulating water flow rate and the cooling air flow rate are adjusted so that the temperature of the circulating water is greater than or equal to the preset freezing damage point temperature, thereby achieving precise control of the actual temperature of the circulating water while minimizing energy consumption to avoid freezing damage to the circulating water system.

[0031] In one embodiment of the present specification, the antifreeze control method may further include: Optimizing the operating parameters of the circulating water system may include at least one of the following: Set the inlet water temperature of the intercooler R ≥ Rated load circulating water inlet temperature; Set the unit back pressure to rated back pressure or minimum back pressure; Keep the condenser end difference constant; Under the condition that the ambient wind speed at a preset height of the thermal power plant is less than the preset wind speed, the circulating water flow rate or the opening degree of the shutters is adjusted.

[0032] In this embodiment, the preset height can be 9-11m, the preset wind speed can be 4-5m / s, and the optimal values ​​of the preset height and the preset wind speed are as follows: the preset height can be 10m, and the preset wind speed can be 4m / s. Optimizing the operating parameters of the circulating water system can generally be performed after step 104. Of course, the execution time of optimizing the operating parameters of the circulating water system can also be selected according to actual conditions. Set the inlet water temperature of the intercooler t R ≥ Rated load circulating water inlet temperature, ensure that the inlet temperature of the intercooler is not lower than a safety threshold to maintain the thermal efficiency of the system and prevent equipment damage caused by low temperature. Setting the unit back pressure to the rated back pressure or minimum back pressure can optimize the operating efficiency and thermal efficiency of the unit and ensure that the system can operate stably under different load conditions. Keep the condenser end difference constant to ensure the efficient operation of the condenser and avoid the decrease in thermal efficiency due to changes in the end difference. When the ambient wind speed at the preset height of the thermal power plant is less than the preset wind speed, adjust the circulating water flow rate or adjust the opening of the shutters to optimize the cooling effect and prevent freezing damage. The intercooler outlet water temperature t can also be set. L ≥18℃ to prevent the circulating water return temperature from being too low and causing freezing damage.

[0033] Under the condition that the ambient wind speed at the preset height of the thermal power plant is less than the preset wind speed, the circulating water flow rate or the opening of the shutters is adjusted. For example, when the ambient wind speed is less than the preset wind speed, the cooling effect may be insufficient, so it is necessary to increase the circulating water flow rate to improve the cooling efficiency, which can be achieved by adjusting the operating frequency of the circulating water pump or opening more circulating water pumps; if the ambient wind speed is lower than the preset wind speed, but the cooling effect still meets the requirements, the energy consumption can be reduced by reducing the circulating water flow rate, which can be achieved by reducing the operating frequency of the circulating water pump or shutting down some circulating water pumps. When the ambient wind speed is less than the preset wind speed, in order to increase the air flow rate and improve the cooling effect, the opening of the shutters can be increased to allow more air to enter the cooling system, thereby improving the cooling efficiency; if the ambient wind speed is lower than the preset wind speed, but the cooling effect is too strong, resulting in too low a circulating water temperature, the air flow rate can be reduced by reducing the opening of the shutters, thereby reducing the cooling effect.

[0034] In one embodiment of the present specification, the antifreeze control method may further include: The first critical temperature th1 is the limit ambient temperature value at which the inlet water temperature of the intercooler can be maintained at 39°C. When the ambient temperature is greater than the first critical temperature th1, the cooling system operates at full output. The second critical temperature th2 is the limit ambient temperature value for the outlet water temperature of the intercooler to maintain 18°C. When the ambient temperature is lower than the second critical temperature th2, the circulating water flow rate at this moment is kept unchanged, and the shutter opening is adjusted down to maintain the outlet water temperature t L ≥18℃.

[0035] In this embodiment, the cooling system operates at full capacity, which may include full fan section, full shutter, 100% circulating water flow, etc. When the ambient temperature is greater than the first critical temperature th1, the cooling system operates at full capacity to meet the minimum back pressure requirements of the unit at different ambient temperatures. By determining the first critical temperature th1 and the second critical temperature th2, the system can perform precise temperature control according to the change of ambient temperature to ensure that the temperature of the circulating water is always kept within a safe range.

[0036] In different ambient temperature ranges, the system can adopt different operation strategies to optimize system operation. For example, when the ambient temperature is greater than the first critical temperature th1, the inlet water temperature of the intercooler cannot be maintained at 39°C, and the cooling system operates at full output; when the ambient temperature is less than the second critical temperature th2, the outlet water temperature of the intercooler cannot be maintained at 18°C, and the shutter opening is adjusted to maintain the outlet water temperature t L≥18℃. The second critical temperature th2 is set as the extreme ambient temperature value of 18℃ for the outlet water temperature, ensuring that the circulating water temperature is prevented from being too low by adjusting the circulating water flow and the shutter opening under low temperature conditions, thereby providing effective antifreeze protection. The system can dynamically adjust the operating parameters according to the real-time monitored ambient temperature to adapt to different environmental conditions and ensure the stable and efficient operation of the system.

[0037] In one embodiment of the present specification, the antifreeze control method may further include: When the second critical temperature th2≤ambient temperature≤first critical temperature th1, the shutters are controlled to be fully opened to maintain the maximum cooling air flow; When 0℃≤ambient temperature≤second critical temperature th2, maintain the circulating water flow unchanged and control the shutters to be fully open to maintain the outlet water temperature of the intercooler t L =18℃; When the ambient temperature is ≤0℃, while controlling the shutters to close, the circulating water flow rate needs to be increased as the ambient temperature drops.

[0038] In this embodiment, when the second critical temperature th2≤ambient temperature≤first critical temperature th1, the shutters are controlled to be fully open to maintain the maximum cooling air flow, ensuring that the system can make full use of environmental conditions for effective cooling within the medium temperature range. When 0℃≤ambient temperature≤second critical temperature th2, the circulating water flow is maintained unchanged and the shutters are controlled to be fully open, which helps to maintain stable operation of the system under low temperature conditions and prevent freezing damage caused by too low water temperature. When the ambient temperature is ≤0℃, while closing the shutters, the circulating water flow needs to be increased as the ambient temperature drops, which helps prevent the circulating water temperature from being too low, thereby providing more effective antifreeze protection. In summary, by adjusting the circulating water flow and shutter opening according to different intervals of ambient temperature, the system can flexibly respond to environmental changes, ensure that it can maintain optimal operation under various temperature conditions, and reduce unnecessary energy consumption.

[0039] In one embodiment of the present specification, the preset freezing point temperature is 14°C.

[0040] In this embodiment, the preset freezing point temperature is set to 14° C., which can minimize energy consumption while preventing freezing. In other words, 14° C. is the most preferred temperature for the preset freezing point temperature.

[0041] In one embodiment of the present specification, the antifreeze control method may further include: Determine the original exhaust steam flow rate before the circulating water temperature changes and the new exhaust steam flow rate after the circulating water temperature changes; By comparing the new exhaust steam flow rate with the original exhaust steam flow rate, the actual exhaust steam pressure after the circulating water temperature changes is determined; Based on the actual exhaust pressure, the vacuum degree of the condenser is obtained; Based on the vacuum degree, adjust the circulating water flow and cooling air flow.

[0042] In this embodiment, the vacuum system of the thermal power plant plays a vital role in the operational safety and economy of the unit. The specific vacuum value not only affects the thermal efficiency of the unit, but is also directly related to the operational stability and life of the equipment. Among the many influencing factors, the influence of the circulating water temperature of the wet cooling unit and the Harmon indirect air cooling unit on the vacuum value is particularly significant. The change of the circulating water temperature and the adjustment of the circulating water volume both directly affect the condensation process of the steam, thereby affecting the change range of the vacuum value.

[0043] By precisely controlling the exhaust flow rate before and after the circulating water temperature changes, the actual exhaust pressure is accurately determined, thereby optimizing the vacuum degree of the condenser, and dynamically adjusting the circulating water flow rate and cooling air flow rate based on this to ensure efficient operation of the system. For example, when the vacuum degree is low (lower than the preset vacuum threshold), by increasing the circulating water flow rate, the cooling effect of the condenser is improved, thereby reducing the exhaust pressure and improving the vacuum degree; increasing the cooling air flow rate can improve the heat exchange efficiency of the finned tubes, help reduce the exhaust temperature, and further improve the vacuum degree. When the vacuum degree is high (higher than the preset vacuum threshold), appropriately reduce the circulating water flow rate to reduce energy consumption; appropriately reduce the cooling air flow rate, which can also reduce energy consumption while ensuring system safety.

[0044] In one embodiment of the present specification, the antifreeze control method may further include: Calculate the exhaust pressure change rate at different circulating water inlet temperatures; Determine the coal consumption change rate of the unit corresponding to the exhaust pressure change rate; Based on the coal consumption change rate, the circulating water flow rate and the cooling air flow rate are controlled.

[0045] In this embodiment, by calculating the exhaust pressure change rate at different circulating water inlet temperatures and determining the corresponding unit coal consumption change rate, the circulating water flow rate and cooling air flow rate control based on energy efficiency optimization are realized to achieve energy saving and improve the system operation efficiency. For example, when the coal consumption change rate is high (higher than the preset change threshold), reducing the circulating water flow rate can reduce the energy consumption of the water pump, thereby reducing coal consumption; reducing the cooling air flow rate can reduce the energy consumption of the fan and further reduce coal consumption. When the coal consumption change rate is low (lower than the preset change threshold), the circulating water flow rate is appropriately adjusted to achieve economic operation while ensuring the vacuum degree; similarly, the cooling air flow rate is appropriately adjusted to achieve economic operation while ensuring the vacuum degree.

[0046] Appropriately adjust the circulating water flow rate, which may include: Increase flow rate: If the circulating water flow rate is low (below the preset water flow threshold), it may limit the heat exchange efficiency and cause the vacuum degree to decrease. In this case, appropriately increasing the circulating water flow rate can improve the heat exchange efficiency, which may further improve the vacuum degree and reduce coal consumption.

[0047] Reduce the flow rate: If the circulating water flow rate is high, it may lead to increased energy consumption of the circulating water pump. Under the premise of ensuring the vacuum degree, appropriately reducing the circulating water flow rate can reduce energy consumption and achieve more economical operation.

[0048] Appropriately adjust the cooling air flow, which may include: Increase the flow rate: If the cooling air flow rate is low (below the preset air flow threshold), it may limit the cooling effect of the finned tubes, resulting in an increase in exhaust pressure. In this case, increasing the cooling air flow rate appropriately can improve the cooling effect, reduce the exhaust pressure, and further improve the vacuum degree.

[0049] Reduce the flow rate: If the cooling air flow rate is high, it may increase the fan energy consumption. Under the premise of ensuring the vacuum degree, appropriately reducing the cooling air flow rate can reduce energy consumption and achieve more economical operation.

[0050] Below, in order to facilitate easier understanding of the present invention, the present invention is introduced in some more detail. The heat exchange mechanism of the surface-type indirect air-cooled radiator is as follows. The heat transfer process of the surface-type indirect air-cooled radiator is as follows: the temperature of the cooling water rises after cooling the exhaust steam of the steam turbine in the surface condenser, and the high-temperature cooling water is pumped into the base tube of the air-cooled radiator by the circulating water pump, and forced convection heat exchange occurs with the inner wall of the base tube. The heat is transferred to the inner wall of the base tube, and then transferred to the outer wall of the base tube and the fins outside the tube by heat conduction. When the air horizontally flushes the outer wall of the fin tube, the heat is transferred to the air by convection heat release, thereby heating the air. The circulating cooling water after heat release is sent back to the condenser by the circulating water pump to continue cooling the exhaust steam of the steam turbine. In the indirect air-cooled radiator, the circulating water flowing in the base tube and the air flowing on the fin side belong to two-process cross-flow.

[0051] Determination of heat transfer coefficient: Through the analysis of the heat transfer process, it can be found that the size of the total heat transfer coefficient of the radiator is affected by the combined influence of the heat transfer coefficient on the cooling water side and the heat transfer coefficient on the air side.

[0052] Determination of the heat transfer coefficient on the cooling water side: The heat transfer between the cooling water and the tube wall in the indirect air-cooled radiator tube belongs to forced convection heat transfer in the tube. Its Nusselt number Nu can be determined by the Deittus-Boillter formula, as shown in the following formula (2): (2); where Re is the Reynolds number; Pr is the Prandtl number; and n is an exponent, which is an empirical constant used to modify the formula to adapt to specific flow conditions. In the Deittus-Boillter formula, n is usually taken as 0.4.

[0053] When the fluid is cooled, n can be equal to 3, then, , , .d i Indicates the internal diameter of the tube, L1 indicates the length of the tube, L1 / d i Represents the ratio of the length of the pipe to its diameter. This ratio needs to be greater than or equal to 60 to ensure the applicability of the Deittus-Boillter formula.

[0054] Surface heat transfer coefficient on the cooling water side It is shown in the following formula (3): (3), where is the thermal conductivity of cooling water, .

[0055] Then, the air side heat transfer coefficient is determined. The indirect air-cooled radiator is a fin-tube heat exchanger. The metal tubes in the air flow direction are arranged in a staggered pattern. Therefore, the air side heat transfer coefficient can be calculated by the heat transfer coefficient of the air flowing horizontally through the horizontal rectangular fin tube bundle outside the staggered circular tube. The formula can be shown as follows (4).

[0056] (4); The d in formula (4) e It can be expressed by formula (5).

[0057] (5).

[0058] Among them, h a is the air side heat transfer coefficient, G max is the minimum cross-sectional air mass velocity, μ is the dynamic viscosity, which indicates the viscous resistance of air, X t is the length of the fin, d 0 is the thickness of the fin, s is the spacing between the fins, is the thermal conductivity of air, is the equivalent diameter of the air sweeping across the fin side, and X1 is the extended length of the fin. is the surface area of ​​the non-finned portion of the light tube per unit length, is the surface area of ​​the fin per unit length. N f It is the cooling air flow from outside the tower into the tower.

[0059] Then, the total heat transfer coefficient is determined: the total heat transfer coefficient of the finned tube can be expressed in two ways: The total heat transfer coefficient based on the finned tube surface area The overall heat transfer coefficient is the benchmark.

[0060] Among them, the surface area of ​​the light tube The overall heat transfer coefficient is based on the formula (6): (6); Fin tube surface area The overall heat transfer coefficient based on the formula (7) is: (7); In the formula is the thermal conductivity of the pipe wall material, ; is the thermal conductivity of the dust, which is taken as 0.4 ; is the dust accumulation thickness assuming uniform dust accumulation on the outer surface of the fin tube base tube and the upper surface of the fin, m; The dust accumulation coefficient introduced to take into account the dust accumulation only on the surface of the fin is taken as 0.4.

[0061] is the outer surface area of ​​the light pipe, ; is the wing ratio, ,in, is the inner surface area of ​​the light pipe, ; is the total fin wall efficiency.

[0062] Fin wall total efficiency It can be expressed as formula (8): (8); In the formula is the fin efficiency, which is taken as 0.9328. p A is the surface area of ​​the non-finned portion of the light tube per unit length, f is the surface area of ​​the fin portion per unit length.

[0063] Furthermore, the determination of the average heat transfer temperature difference: the flow of cooling water in the indirect air-cooled radiator tube and the air on the fin side belongs to two-process cross flow, and its average heat transfer temperature difference Formula (9): (9); in, is the conversion factor of the two processes; It is the logarithmic mean temperature difference of the cooling water and air in countercurrent arrangement.

[0064] The calculation formula is formula (10): (10); in, , is the cooling water inlet and outlet temperature; , are the inlet and outlet temperatures of the air.

[0065] Conversion factor between the two processes , which is related to the dimensionless parameters P and R, and is obtained by consulting the literature.

[0066] Among them, the calculation formulas of dimensionless parameters P and R are formulas (11) and (12); (11) (12) In the formula is the temperature difference between the cooling water inlet and outlet; is the temperature difference between air inlet and outlet.

[0067] The calculation formula is ; The calculation formula is .

[0068] Furthermore, the heat transfer calculation and heat balance equation: The heat transfer of cooling water to the outside air through the radiator has two calculation methods according to the total heat transfer coefficient, as shown in formula (13) and formula (14).

[0069] (13); (14); In the formula The surface area of ​​the light tube The overall heat transfer coefficient is the benchmark; The surface area of ​​the finned tube The overall heat transfer coefficient is the benchmark.

[0070] The heat release of cooling water in the radiator tube is given by formula (15); (15) In the formula is the mass flow rate of cooling water, kg / s; is the specific heat capacity of cooling water, ; T w1 is the air temperature in the intercooler; T w2 is the air temperature outside the intercooler.

[0071] The uneven flow distribution caused by the layout of the cooling water pipes in the air-cooling tower is ignored in the calculation, as shown in formula (16): (16).

[0072] in, is the cooling water flow entering the cooling tower, ; is the cooling triangle number; is the cooling water density, .

[0073] The amount of heat absorbed by the air outside the radiator after passing through the fins horizontally is shown in formula (17).

[0074] (17); In the formula, is the mass flow rate of air, kg / s; is the specific heat capacity of air, .

[0075] The uneven distribution of axial air velocity in the cooling tower is ignored in the calculation, as shown in formula (18).

[0076] (18); In the formula, is the air density, ; is the air inlet velocity, . L3 is the width of the heat exchange screen.

[0077] According to the first law of thermodynamics, the heat balance equation of the radiator system is .

[0078] Based on the same general inventive concept, the present invention also protects an antifreeze and energy-saving control device for an indirect air cooling system of a thermal power plant, such as Figure 2 As shown, Figure 21 is a schematic diagram of the structure of the antifreeze and energy-saving control device for the indirect air cooling system of a thermal power plant provided by an embodiment of the present invention. The antifreeze and energy-saving control device for the indirect air cooling system of a thermal power plant provided by the present invention is described below. The antifreeze and energy-saving control device for the indirect air cooling system of a thermal power plant described below and the antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant described above can be referred to each other. The antifreeze and energy-saving control device for the indirect air cooling system of a thermal power plant may include an information acquisition module 201, a heat exchange module 202, a temperature determination module 203 and a control module 204.

[0079] The information acquisition module 201 is used to acquire the meteorological information and unit operating conditions of the environment in which the thermal power plant is located; wherein the meteorological information includes the ambient temperature and the ambient wind speed, and the unit operating conditions include the load and the back pressure; The heat exchange module 202 is used to determine the heat transfer relationship of the circulating water system using a pre-built heat exchange balance equation; The temperature determination module 203 obtains the temperature deviation between the actual temperature of the circulating water return water and the preset freezing damage point temperature based on the meteorological information, the unit operating condition and the heat transfer relationship; The control module 204 is used to adjust the circulating water flow and the cooling air flow based on the temperature deviation so that the actual temperature of the circulating water is greater than or equal to the preset freezing point temperature; wherein the preset freezing point temperature represents the minimum allowable value of the circulating water return temperature, and the preset freezing point temperature is any value between 14-18°C.

[0080] Figure 3 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention.

[0081] like Figure 3 As shown, the electronic device may include: a processor 310, a communication interface 320, a memory 330 and a communication bus 340, wherein the processor 310, the communication interface 320 and the memory 330 communicate with each other through the communication bus 340. The processor 310 may call the logic instructions in the memory 330 to execute the antifreeze and energy-saving control method of the indirect air cooling system of the thermal power plant.

[0082] In addition, the logic instructions in the above-mentioned memory 330 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0083] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the antifreeze and energy-saving control methods for the indirect air cooling system of a thermal power plant provided by the above-mentioned methods.

[0084] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant provided by the above-mentioned methods.

[0085] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0086] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the antifreeze and energy saving of an indirect air cooling system of a thermal power plant, characterized in that: include: Acquire meteorological information and unit operating conditions of the environment in which the thermal power plant is located; wherein the meteorological information includes ambient temperature and ambient wind speed, and the unit operating conditions include load and back pressure; Determine the heat transfer relationship of the circulating water system using the pre-built heat exchange balance equation; Based on the meteorological information, the unit operating conditions and the heat transfer relationship, a temperature deviation between an actual temperature of circulating water return water and a preset freezing damage point temperature is obtained; Based on the temperature deviation, the circulating water flow rate and the cooling air flow rate are adjusted so that the actual temperature of the circulating water is greater than or equal to the preset freezing point temperature; wherein the preset freezing point temperature represents the minimum allowable value of the circulating water return temperature, and the preset freezing point temperature is any value between 14-18°C.

2. The antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant according to claim 1, characterized in that: The heat exchange balance equation includes: D C (h C -h N ′ ) = D W (t R -t L )C W = D F (T OUT -T IN )C F ; wherein, D C is the exhaust flow rate of steam turbine; h C is the exhaust enthalpy of the steam turbine; h N is the condensation enthalpy; D W is the circulating water flow rate; t R is the inlet water temperature of the intercooler; t L is the outlet water temperature of the intercooler; C W is the specific volume of circulating water; D F is the cooling air flow rate; T OUT is the cooling triangle outlet air temperature; T IN is the cooling triangle inlet air temperature; C F is the specific volume of cooling air.

3. The antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant according to claim 1, characterized in that: Also includes: Optimize the operating parameters of the circulating water system, including at least one of the following: Set the inlet water temperature of the intercooler to ≥ the inlet water temperature of the circulating water under rated load; Set the unit back pressure to rated back pressure or minimum back pressure; Keep the condenser end difference constant; Under the condition that the ambient wind speed at a preset height of the thermal power plant is less than the preset wind speed, the circulating water flow rate or the opening degree of the shutters is adjusted.

4. The antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant according to claim 1, characterized in that: Also includes: Determine the first critical temperature and the second critical temperature as two ambient temperature critical points; wherein, The first critical temperature is the limit ambient temperature value at which the inlet water temperature of the intercooler can be maintained at 39°C. When the ambient temperature is greater than the first critical temperature, the cooling system operates at full output; The second critical temperature is the extreme ambient temperature value at which the outlet water temperature of the intercooler is maintained at 18°C. When the ambient temperature is lower than the second critical temperature, the circulating water flow rate at this moment is kept unchanged, and the shutter opening is reduced to maintain the outlet water temperature of the intercooler ≥18°C.

5. The antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant according to claim 4, characterized in that: Also includes: When the second critical temperature is ≤ the ambient temperature ≤ the first critical temperature, the shutters are controlled to be fully opened to maintain the maximum cooling air flow; When 0°C ≤ ambient temperature ≤ the second critical temperature, the circulating water flow rate is maintained unchanged, and the shutters are controlled to be fully opened to keep the outlet water temperature of the intercooler equal to 18°C; When the ambient temperature is ≤0℃, while controlling the shutters to close, the circulating water flow rate needs to be increased as the ambient temperature drops.

6. The antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant according to claim 1, characterized in that: The preset freezing point temperature is 14°C.

7. The antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant according to claim 3, characterized in that: The preset height is 9-11 m, and the preset wind speed is 4-5 m / s.

8. The antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant according to claim 1, characterized in that: Also includes: Determine the original exhaust steam flow rate before the circulating water temperature changes and the new exhaust steam flow rate after the circulating water temperature changes; By comparing the new exhaust steam flow rate with the original exhaust steam flow rate, the actual exhaust steam pressure after the circulating water temperature changes is determined; Based on the actual exhaust pressure, the vacuum degree of the condenser is obtained; Based on the vacuum degree, adjust the circulating water flow and cooling air flow.

9. The antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant according to claim 8, characterized in that: Also includes: Calculate the exhaust steam pressure change rate at different circulating water inlet temperatures; Determine the coal consumption change rate of the unit corresponding to the exhaust pressure change rate; Based on the coal consumption change rate, the circulating water flow rate and the cooling air flow rate are controlled.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the antifreeze and energy-saving control method for the indirect air cooling system of a thermal power plant as described in any one of claims 1 to 9 is implemented.

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