Power plant high-salt wastewater co-drying system for direct air-cooling unit and energy-saving operation method

Abstract

The application discloses a power plant high-salt wastewater collaborative drying system and an energy-saving operation method for a direct air cooling unit. The system comprises an air cooling tower, an air cooling fan, a finned tube heat exchanger, a wastewater atomization device, a dust collector and a matched control system. The energy-saving operation method comprises the following steps: step one, data acquisition and initialization; step two, safety mode judgment; step three, collaborative optimization solution; and step four, closed loop verification and dynamic adjustment. Compared with the traditional technology, the application fully utilizes the low-grade heat carried by the huge air inlet of the air cooling tower, realizes zero discharge of high-salt wastewater drying at low operation cost, and significantly strengthens the air cooling heat exchange through air inlet humidification, so that the fan air volume and power consumption can be reduced under the premise of ensuring the cooling effect, and the operation economy and system operation safety of the unit are improved.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation and environmental protection technology for thermal power plants, and specifically relates to a co-drying system for high-salt wastewater in power plants and an energy-saving operation method for direct air-cooled units. Background Technology

[0002] Direct air cooling technology is a widely used cooling process in large thermal power plants. Its working principle involves forcibly introducing ambient cold air into the air-cooled island using a high-power fan. The cold air flows over the finned tube bundle surface of the air-cooled condenser, indirectly exchanging heat with the high-temperature exhaust steam discharged from the turbine inside the tubes. The exhaust steam is condensed into condensate, while the air is heated and discharged into the atmosphere from the top of the tower. During this process, maintaining the high vacuum of the condenser requires an extremely large ventilation volume, resulting in persistently high power consumption for the supporting fans, which has become a key factor affecting the economic efficiency of direct air-cooled units.

[0003] On the other hand, thermal power plants generate various types of high-salinity wastewater during production, with desulfurization wastewater being a typical example. This wastewater is characterized by its complex composition, high corrosiveness, and difficulty in treatment. To achieve the environmental requirement of "zero emissions," current mainstream technologies such as multi-effect evaporation, mechanical steam recompression, and bypass flue evaporation generally suffer from high initial investment, huge operating energy consumption, complex systems, or susceptibility to scaling and clogging, placing a heavy operational burden and maintenance challenges on power plants.

[0004] In order to explore low-cost solutions, attempts have been made to combine direct air cooling systems with wastewater treatment in existing technologies. However, most of these solutions adopt the idea of ​​"cooling first and then utilizing", that is, first use air to cool the exhaust steam, and then collect or utilize the waste heat of the exhaust after heat exchange to evaporate the wastewater. Such strategies have the following inherent defects: (1) easy to scale and blockage: using the waste heat of the exhaust that has been reduced in grade, the driving force for wastewater evaporation is weak, it is difficult to completely evaporate the wastewater, and scale is easily formed on the surface of the equipment, affecting stable operation. (2) large fluctuation in treatment capacity: its treatment effect depends on the exhaust parameters, and the treatment capacity decreases synchronously when the unit is under low load, which cannot meet the continuous treatment needs. (3) increased system energy consumption: adding equipment on the exhaust path will increase the system resistance, causing the fan to consume more electrical energy to overcome the resistance, resulting in a decrease in overall energy efficiency.

[0005] Therefore, there is an urgent need in this field for an innovative technology that can synergistically solve the problems of high cost of high-salt wastewater treatment and high power consumption of air-cooled systems, while avoiding the aforementioned defects. Summary of the Invention

[0006] To address the problems existing in the background art, the present invention provides a power plant high-salt wastewater co-drying system and energy-saving operation method for direct air-cooled units, which synergistically solves the technical problems of high-salt wastewater treatment cost and high power consumption of air-cooling system.

[0007] The technical solution adopted in this invention is:

[0008] I. A co-drying system for high-salinity wastewater from power plants used in direct air-cooled units:

[0009] The air-cooled tower has an air inlet at the bottom to draw in ambient air and an exhaust outlet at the top to discharge the hot and humid air that has exchanged heat with the exhaust steam from the turbine.

[0010] Air-cooled fans are located at the bottom or side of the air-cooled tower to supply air into the tower.

[0011] Finned tube heat exchangers are arranged inside air-cooled towers. The inside of the finned tubes is used to introduce exhaust steam from the steam turbine after it has done its work, while the outside of the finned tubes is used to introduce air through the air-cooled fan.

[0012] The wastewater atomization device is installed after the air-cooled fan and connected to the internal air duct of the air-cooled tower. It is used to atomize the high-salt wastewater from the power plant into droplets and spray them into the air duct of the air-cooled tower.

[0013] The dust collector is installed in the air duct downstream of the wastewater atomization device and upstream of the finned tube heat exchanger. It is used to capture solid salt particles formed after the liquid droplets evaporate, output clean air free of salt particles and with increased relative humidity, and discharge the removed solid salt in a concentrated manner.

[0014] The control system is connected to the air-cooled fan and the wastewater atomization device, respectively, and is used to collect the load L, condenser back pressure P0, and ambient temperature T of the direct air-cooled unit. e Ambient relative humidity (RH) e The parameters for the available supply of high-salt wastewater are also considered. Based on the preset allowable range of condenser back pressure P0 and environmental conditions, the injection rate of high-salt wastewater and the airflow of the air-cooled fan are adjusted in combination to maintain the condenser back pressure P0 within the allowable range, ensuring that the injected high-salt wastewater is completely evaporated before reaching the dust collector. The condenser back pressure P0 refers to the back pressure of the finned tube heat exchanger.

[0015] The high-salt wastewater is desulfurization wastewater generated by wet desulfurization process, or high-salt wastewater containing calcium sulfate and chloride salts.

[0016] The wastewater atomization device includes at least one of a high-pressure atomizing nozzle, a dual-fluid atomizing nozzle, and a rotary atomizer. The wastewater atomization device atomizes high-salt wastewater to form droplets with an average Sottle diameter of less than 100 μm. The dust collector is a metal sintered plate dust collector or a wet electrostatic precipitator.

[0017] The control system includes a core controller and a data acquisition unit and an execution unit electrically connected to the core controller; the data acquisition unit includes a function for measuring ambient temperature T. e and ambient relative humidity (RH) eThe system includes an environmental parameter sensor, a pressure sensor for measuring the condenser back pressure P0, and an operating condition signal interface for acquiring the real-time load L and high-salt wastewater supply of the direct air-cooled unit; the execution unit includes a fan frequency conversion speed control device for adjusting the air volume of the air-cooled fan and an atomized liquid supply adjustment device for adjusting the injection volume of high-salt wastewater.

[0018] The core controller has a built-in ambient temperature safety threshold T. s Humidity operating threshold RH low and humidity shutdown threshold RH high , of which RH low <RH high .

[0019] When the ambient temperature T is detected e <T s At this time, the core controller sets the high-salt wastewater injection volume to 0 and maintains the condenser back pressure P0 within the allowable range only by adjusting the air volume of the air-cooled fan.

[0020] When the ambient temperature T is detected e ≥T s And the relative humidity (RH) of the environment e ≤RH low At that time, the wastewater atomization device is activated, and the maximum instantaneous injection rate W of high-salinity wastewater is calculated according to the evaporation capacity constraint model. e,max High-salt wastewater was sprayed in.

[0021] Specifically, the maximum instantaneous injection volume of high-salinity wastewater W e,max =k×V c ×ρ a ×(x s -x a ) was calculated.

[0022] When the ambient temperature T is detected e ≥T s And the relative humidity (RH) of the environment e ≥RH high At this time, the power plant's high-salt wastewater co-drying system must not be started or the wastewater atomization device must be stopped immediately.

[0023] When the ambient temperature T is detected e ≥T s And RH low <RH e <RH high At that time, the core controller optimized the high-salinity wastewater injection rate W under the constraints of evaporation capacity, cooling demand, and resource supply. s And according to the high-salt wastewater injection volume W s Limits are set to control the actual injection volume.

[0024] The core controller incorporates an evaporation capacity constraint model, a cooling demand constraint model, and a resource supply constraint model to limit the feasible range of high-salt wastewater injection volume and air-cooled fan volume.

[0025] The evaporation capacity constraint model calculates the maximum allowable instantaneous injection volume of high-salt wastewater under a given evaporation safety factor k, based on the current airflow of the air-cooled fan, air density, ambient air humidity, and saturated humidity at the finned tube wall temperature.

[0026] The cooling demand constraint model is based on the real-time load L and ambient temperature T of the direct air-cooled unit. e Calculate the total heat exchange required by the condenser to ensure that the condenser back pressure P0 does not exceed the preset upper limit P under a given combination of high-salt wastewater injection rate and air-cooled fan flow rate. max .

[0027] The resource supply constraint model is used to limit the amount of high-salinity wastewater injected to no more than the current available supply of high-salinity wastewater.

[0028] The evaporation capacity constraint model, cooling demand constraint model, and resource supply constraint model are set according to the following formulas:

[0029] W e ≤k×V c ×ρ a ×(x s -x a )

[0030] Q r =f(L)+K1×(T e -T ref )

[0031] W s ≤Q a

[0032] Among them, W e V is the allowable instantaneous injection rate of high-salinity wastewater under evaporation capacity constraints, k is the evaporation safety factor, and V is the allowable instantaneous injection rate of high-salinity wastewater. c ρ is the air volume of the air-cooled fan. a x is the air density. s x represents the saturated moisture content of air at the finned tube wall temperature. a Q represents the humidity content of ambient air. r Let f(L) be the total heat exchange required by the condenser, f(L) be the basic heat dissipation function corresponding to the real-time load L of the direct air-cooled unit, and K1 be the coefficient of performance relative to the ambient temperature T. e The relevant correction factor, T ref Design ambient temperature for air-cooled systems, W s Q represents the injection rate of high-salinity wastewater. aThis represents the current available supply of high-salinity wastewater.

[0033] The core controller, based on the evaporation capacity constraint model, cooling demand constraint model, and resource supply constraint model, uses the minimization of the total power of the air-cooled fan as the optimization objective function to solve for the high-salt wastewater injection rate and the air-cooled fan airflow, and outputs the corresponding control commands to the execution unit.

[0034] The core controller also includes safety override control logic and efficiency optimization control logic.

[0035] When the condenser back pressure P0 is detected to be higher than the preset upper limit P max When the time is right, the safety override control is triggered, which prioritizes reducing the injection volume of high-salt wastewater and increasing the air volume of the air-cooled fan until the condenser back pressure P0 drops back to the allowable range.

[0036] When the condenser back pressure P0 is detected to be lower than the preset lower limit P min At that time, efficiency optimization control is triggered, prioritizing increasing the injection volume of high-salt wastewater and reducing the air volume of the air-cooled fan until the condenser back pressure P0 rises back to the allowable range.

[0037] II. An energy-saving operation method for a synergistic drying system:

[0038] Step 1, Data Acquisition and Initialization: The control system acquires the real-time load L, condenser back pressure P0, and ambient temperature T of the direct air-cooled unit. e Ambient relative humidity (RH) e The system also reads the current available supply of high-salinity wastewater and the preset allowable range of condenser back pressure P0 and ambient temperature safety threshold T. s Humidity operating threshold RH low and humidity shutdown threshold RH high .

[0039] Step 2, Safety Mode Determination: When the ambient temperature T e <T s At that time, the high-salt wastewater injection rate was set to 0, and the condenser back pressure P0 was maintained within the allowable range only by adjusting the airflow of the air-cooled fan; when the ambient temperature T e ≥T s At that time, according to the ambient relative humidity (RH) e With humidity operating threshold RH low Humidity shutdown threshold RH high The relationship between the device and its operating intensity determines whether the wastewater atomization device is allowed to be put into operation.

[0040] Step 3, Collaborative Optimization Solution: Under the condition that the wastewater atomization device is allowed to be put into operation, based on the constraints of evaporation capacity, cooling demand, and resource supply, an optimization algorithm with the objective of minimizing the total power of the air-cooled fan is used to solve for the high-salt wastewater injection rate and the air volume of the air-cooled fan.

[0041] Step 4, Closed-loop verification and dynamic adjustment: Apply the high-salt wastewater injection rate and air-cooled fan volume obtained in Step 3 to the wastewater atomization device and the air-cooled fan, and detect the condenser back pressure P0 at this operating point. When the condenser back pressure P0 is within the allowable range, maintain this operating point; when the condenser back pressure P0 exceeds the allowable range, prioritize adjusting the high-salt wastewater injection rate and air-cooled fan volume through safety override control or efficiency optimization control, and perform the verification cyclically until the condenser back pressure P0 returns to the allowable range.

[0042] The beneficial effects of this invention are:

[0043] (1) Achieving zero emissions at low cost: By directly utilizing the low-grade energy contained in the inherent huge air volume of the air-cooling system, the drying treatment of high-salt wastewater from the power plant was achieved at extremely low operating costs, meeting the strict zero-emission requirements.

[0044] (2) Significant energy-saving benefits: By humidifying the intake air, the specific heat capacity of the air is significantly increased. Furthermore, when the humidified air flows through finned tubes with a temperature lower than its dew point, water vapor condenses, releasing a large amount of latent heat, thereby greatly improving the heat exchange efficiency of the air-cooled condenser. Under typical operating conditions, the fan air volume can be reduced by about 5% to 15% while ensuring the same cooling effect, thus reducing the fan's operating power consumption accordingly.

[0045] (3) The main equipment is safe and reliable: By setting the wastewater treatment process before the core heat exchanger and equipping it with a high-efficiency dust collector, the corrosive salts are completely isolated from the core main equipment such as the finned tube heat exchanger. At the same time, multiple safety barriers are built through safety mode and safety override control to ensure the long-term safe operation of the main unit.

[0046] (4) High system integration and intelligent controllability: The wastewater treatment system is deeply integrated into the existing air-cooled island structure. Its core lies in the intelligent control logic, which can automatically optimize according to the unit's operating conditions and environmental conditions, respond quickly, adjust precisely, and realize the automatic coordination of "treatment" and "energy saving".

[0047] (5) Strong applicability and versatility: The method of the present invention is not only applicable to newly built direct air-cooled units, but also convenient for upgrading existing old units. It has a wide range of applications and broad market prospects. Attached Figure Description

[0048] Figure 1 This is a system module diagram of the present invention.

[0049] Figure 2 This is a flowchart of the method of the present invention. Detailed Implementation

[0050] The present invention will now be described in more detail with reference to the accompanying drawings and embodiments. However, the present invention is not limited thereto. For those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

[0051] like Figure 1 As shown in this embodiment, the power plant high-salinity wastewater co-drying system for direct air-cooled units includes:

[0052] The air-cooled tower has an air inlet at the bottom to draw in ambient air and an exhaust outlet at the top to discharge the hot and humid air that has exchanged heat with the exhaust steam from the turbine, thus forming a ventilation channel from bottom to top.

[0053] Air-cooled fans are located at the bottom or side of the air-cooled tower to supply a large flow of air into the tower.

[0054] Finned tube heat exchangers are arranged inside air-cooled towers. The finned tubes are used to introduce exhaust steam from the turbine after it has done its work, while the outside of the finned tubes is used to introduce air through the air-cooled fan, so as to achieve indirect heat exchange between the exhaust steam and the air.

[0055] The wastewater atomization device is installed after the air-cooled fan and connected to the internal air duct of the air-cooled tower. It is used to atomize the high-salt wastewater from the power plant into droplets and spray them into the air duct of the air-cooled tower. The droplets are evaporated and dried by utilizing the sensible heat of the air and the latent heat of condensation as they rise with the airflow.

[0056] High-salinity wastewater refers to desulfurization wastewater generated by wet desulfurization processes, or high-salinity wastewater containing calcium sulfate and chloride salts.

[0057] The wastewater atomization device includes at least one of a high-pressure atomizing nozzle, a dual-fluid atomizing nozzle, and a rotary atomizer. The wastewater atomization device atomizes high-salt wastewater to form droplets with a Sottle average diameter of less than 100 μm. The Sottle average diameter of less than 100 μm is to ensure that the droplets can be basically completely evaporated within the air residence time corresponding to the design ventilation volume of the air-cooled tower.

[0058] The dust collector is located in the duct downstream of the wastewater atomization device and upstream of the finned tube heat exchanger. It is used to capture solid salt particles formed after the liquid droplets evaporate, and output clean air that is basically free of salt particles and has increased relative humidity, and discharge the removed solid salt in a concentrated manner.

[0059] The dust collector is either a sintered metal plate dust collector or a wet electrostatic precipitator to prevent salt particles from entering the finned tube heat exchanger and downstream equipment. The type of dust collector is chosen to efficiently capture salt particles (efficiency > 99.5%), preventing them from entering the finned tube heat exchanger and causing blockage or corrosion.

[0060] The control system is connected to the air-cooled fan and the wastewater atomization device, respectively, and is used to collect data on the load L, condenser back pressure P0, and ambient temperature T of the direct air-cooled unit. e Ambient relative humidity (RH) e The system also includes parameters for the available supply of high-salt wastewater. Based on the preset allowable range of condenser back pressure P0 and environmental conditions, and on the premise that the injected high-salt wastewater is completely evaporated before reaching the dust collector, the system jointly adjusts the injection volume of high-salt wastewater and the air volume of the air-cooled fan to keep the condenser back pressure P0 within the allowable range, thereby achieving synergy between high-salt wastewater drying treatment and reduced energy consumption of air-cooled fan operation.

[0061] Specifically, finned tube heat exchangers are a type of condenser, and collecting the condenser back pressure P0 is the same as collecting the exhaust steam back pressure of the finned tube heat exchanger.

[0062] The power plant high-salt wastewater co-drying system in this embodiment mainly consists of an air-cooled tower, an air-cooled fan, a finned tube heat exchanger, a wastewater atomizing device, a dust collector, and a supporting control system. The air-cooled tower, air-cooled fan, and finned tube heat exchanger are also inherent core components of direct air-cooled units. The air-cooled tower is used to construct the ventilation channel, drawing in dry, cold ambient air at its bottom and discharging humid, hot air after heat exchange at its top. The air-cooled fan provides power for the airflow. The finned tube heat exchanger is arranged inside the air-cooled tower and is responsible for surface heat exchange between the exhaust steam and the air. Exhaust steam from the turbine flows inside the tubes, while a large flow of air driven by the air-cooled fan flows outside.

[0063] The control system includes a core controller and data acquisition and execution units electrically connected to the core controller.

[0064] The data acquisition unit includes a device for measuring ambient temperature T. e and ambient relative humidity (RH) e The system includes environmental parameter sensors, pressure sensors for measuring condenser back pressure P0, and operating condition signal interfaces for acquiring real-time load L and high-salt wastewater supply of the direct air-cooled unit.

[0065] The execution unit includes a fan frequency converter for adjusting the air volume of the air-cooled fan and an atomizing liquid supply regulator for adjusting the injection volume of high-salt wastewater.

[0066] The core controller has a built-in ambient temperature safety threshold T. s Humidity operating threshold RH low and humidity shutdown threshold RH high, of which RH low <RH high When the ambient temperature T is detected e <T s At this time, the core controller sets the high-salt wastewater injection volume to 0 and only adjusts the air volume of the air-cooled fan to maintain the condenser back pressure P0 within the allowable range, so as to avoid the wastewater droplets freezing and causing blockage of the air duct or dust collector.

[0067] When the ambient temperature T is detected e ≥T s And the relative humidity (RH) of the environment e ≤RH low At that time, the power plant's high-salinity wastewater co-drying system enters the high-efficiency drying mode, the wastewater atomization device is activated, and the maximum instantaneous injection rate W of high-salinity wastewater calculated according to the evaporation capacity constraint model is activated. e,max High-salinity wastewater is sprayed in, with a maximum instantaneous spray volume W. e,max =k×V c ×ρ a ×(x s -x a ).

[0068] When the ambient temperature T is detected e ≥T s And the relative humidity (RH) of the environment e ≥RH high At this time, the co-drying system for high-salt wastewater in power plants must not be started or the wastewater atomization device must be stopped immediately to avoid incomplete evaporation of wastewater causing scaling. When the ambient temperature T is detected... e ≥T s And RH low <RH e <RH high At that time, the core controller optimized the high-salinity wastewater injection rate W under the constraints of evaporation capacity, cooling demand, and resource supply. s And according to the high-salt wastewater injection volume W s The actual injection volume is controlled by a limit to achieve a cautious commissioning that balances drying effect and operational safety.

[0069] In practice, the environmental temperature safety threshold T s The temperature is typically set to 5°C to prevent freezing in winter; the humidity threshold for operation is RH. low Set to 40%~65%, humidity shutdown threshold RH high Set it to 75%~85%.

[0070] The core controller incorporates an evaporation capacity constraint model, a cooling demand constraint model, and a resource supply constraint model to limit the feasible range of high-salt wastewater injection volume and air-cooled fan volume.

[0071] The evaporation capacity constraint model calculates the maximum allowable instantaneous injection rate of high-salinity wastewater under a given evaporation safety factor k, based on the current airflow of the air-cooled fan, air density, ambient air humidity, and saturated humidity at the finned tube wall temperature. The cooling demand constraint model is based on the real-time load L of the direct air-cooled unit and the ambient temperature T. e Calculate the total heat exchange required by the condenser to ensure that the condenser back pressure P0 does not exceed the preset upper limit P under a given combination of high-salt wastewater injection rate and air-cooled fan flow rate. max The resource supply constraint model is used to limit the amount of high-salinity wastewater injected to no more than the current available supply.

[0072] The evaporation capacity constraint model, cooling demand constraint model, and resource supply constraint model are set according to the following formulas:

[0073] Evaporation capacity constraint model: W e ≤k×V c ×ρ a ×(x s -x a )

[0074] Cooling demand constraint model: Q r =f(L)+K1×(T e -T ref )

[0075] Resource supply constraint model: W s ≤Q a

[0076] Among them, W e V represents the allowable instantaneous injection rate of high-salinity wastewater under evaporation capacity constraints, k is the evaporation safety factor (0 < k < 1), and V c Air volume of air-cooled fan (m³) 3 / s), ρ a air density (kg / m³) 3 ), x s x represents the saturated moisture content (kg / kg) of air at the finned tube wall temperature. a Moisture content of ambient air (kg / kg), determined by ambient temperature T. e and ambient relative humidity (RH) e Calculations show that Q r Let f(L) be the total heat exchange required by the condenser, f(L) be the basic heat dissipation function corresponding to the real-time load L of the direct air-cooled unit, and K1 be the coefficient of performance relative to the ambient temperature T. e The relevant correction factor, T ref Design ambient temperature for air-cooled systems, W s The injection volume of high-salinity wastewater must meet W. s ≤W e Qa The current available supply of high-salinity wastewater is given by the maximum supply of high-salinity wastewater, Q. max And the level of the buffer tank, etc., are determined.

[0077] In practice, the evaporation capacity constraint model ensures that the droplets have sufficient thermodynamic driving force to complete the phase change, avoiding the dust collector from being clogged, scaled, or blocked by wet droplets; the cooling demand constraint model ensures that the cooling capacity matches the heat load; and the resource supply constraint model ensures that the wastewater treatment capacity is limited by on-site supply.

[0078] In practice, f(L) is the basic heat dissipation function corresponding to the real-time load L of the direct air-cooled unit.

[0079] The basic heat release function f(L) characterizes the basic heat that the turbine exhaust steam needs to release to the environment under different unit loads L. This function can be obtained by fitting the turbine's design heat balance diagram or actual operating data, and its typical form is as follows:

[0080] f(L) = a0 + a1 × L + a2 × L²

[0081] Among them, a0, a1 and a2 are fitting coefficients, which can be obtained by regression analysis of the heat dissipation data of the turbine design operating point (such as 100%THA, 75%THA, 50%THA, 30%THA, etc.) using the least squares method.

[0082] The core controller is based on the evaporation capacity constraint model, cooling demand constraint model and resource supply constraint model. It takes the minimization of the total power of the air-cooled fan as the optimization objective function, solves the high-salt wastewater injection rate and air-cooled fan air volume, and outputs the corresponding control commands to the execution unit.

[0083] In practice, the objective function is set according to the following formula:

[0084] MinΣ(a×(V s ) 3 +b)

[0085] Where a and b are coefficients related to the characteristics of the wind turbine, V s This refers to the airflow of the air-cooled fan.

[0086] The optimization algorithm can be linear programming, quadratic programming, or intelligent algorithms (such as particle swarm optimization). In this embodiment, quadratic programming is specifically used.

[0087] The core controller also includes safety override control logic and efficiency optimization control logic. When the condenser back pressure P0 is detected to be higher than the preset upper limit P... maxWhen this occurs, safety override control is triggered, prioritizing a rapid reduction in the injection rate of high-salt wastewater and an increase in the airflow of the air-cooled fan until the condenser back pressure P0 drops back to the allowable range. min ,P max [Within. When the condenser back pressure P0 is detected to be lower than the preset lower limit P] min At that time, efficiency optimization control is triggered, prioritizing increasing the injection rate of high-salt wastewater and reducing the airflow of the air-cooled fan until the condenser back pressure P0 rises back to the allowable range. min ,P max Within [the specified range], to ensure that the condenser back pressure P0 does not exceed the preset upper limit P. max Further reduce wind turbine power consumption under the premise of [the goal of] ...

[0088] like Figure 2 As shown, this embodiment is implemented according to the following steps:

[0089] Step 1, Data Acquisition and Initialization: The control system acquires the real-time load L, condenser back pressure P0, and ambient temperature T of the direct air-cooled unit. e Ambient relative humidity (RH) e And the current available supply of high-salinity wastewater, and read the preset allowable range of condenser back pressure P0 [P min ,P max ] Safe threshold temperature T s Humidity operating threshold RH low and humidity shutdown threshold RH high .

[0090] Step 2, Safety Mode Determination: When the ambient temperature T e <T s At that time, the high-salt wastewater injection rate was set to 0, and the condenser back pressure P0 was maintained within the allowable range only by adjusting the airflow of the air-cooled fan. min ,P max [Inside; when the ambient temperature T] e ≥T s At that time, according to the ambient relative humidity (RH) e With humidity operating threshold RH low Humidity shutdown threshold RH high The relationship between the device and its operating intensity determines whether the wastewater atomization device is allowed to be put into operation.

[0091] Step 3, Collaborative Optimization Solution: Under the condition that the wastewater atomization device is allowed to be put into operation, based on the constraints of evaporation capacity, cooling demand, and resource supply, an optimization algorithm with the objective of minimizing the total power of the air-cooled fan is used to solve for the high-salt wastewater injection rate and the air volume of the air-cooled fan.

[0092] Step 4, Closed-loop verification and dynamic adjustment: Apply the high-salt wastewater injection rate and air-cooled fan volume obtained in Step 3 to the wastewater atomization device and the air-cooled fan, and detect the condenser back pressure P0 at this operating point. When the condenser back pressure P0 is within the allowable range [P min ,P max Maintain this operating point within the specified range; when the condenser back pressure P0 exceeds the allowable range [P min ,P max When [the situation is as described], the high-salinity wastewater injection rate and air-cooled fan volume are preferentially adjusted through safety override control or efficiency optimization control, and the process is cyclically verified until the condenser back pressure P0 returns to the allowable range. min ,P max ]Inside.

[0093] This embodiment takes a typical 300MW coal-fired power generating unit as an example. Its direct air-cooling system has an extremely large design ventilation volume, reaching approximately 6 million Nm³. 3 The core idea of ​​this invention lies in the ingenious integration and synergy between the drying process of high-salt wastewater and the cooling process of the air-cooling system.

[0094] Specifically, this invention involves injecting a small amount of atomized high-salt wastewater after the air-cooling fan during the operation of the air-cooling system. On one hand, the large airflow and sensible heat of the air within the air-cooling tower rapidly evaporate and dry the atomized droplets, achieving zero-discharge treatment of the wastewater. On the other hand, the evaporation of the wastewater increases the relative humidity and specific heat capacity of the air. When this humidified air flows through the rear-end finned tube heat exchanger, it significantly enhances the heat exchange efficiency with the exhaust steam inside the tubes. This improved heat exchange efficiency creates conditions for reducing the operating airflow of the air-cooling fan while maintaining the same cooling effect, thereby directly saving the fan's operating power consumption.

[0095] Based on the above ideas, this embodiment can simultaneously achieve the synergistic drying of high-salinity wastewater and the reduction of fan operating energy consumption, while ensuring the cooling effect on turbine exhaust steam.

[0096] The improvement of this invention lies in the addition of a wastewater atomization device and a dust collector after the air-cooled fan. The wastewater atomization device atomizes the high-salt wastewater from the power plant into extremely fine droplets. Specifically, it is a high-pressure atomizing nozzle, a two-fluid atomizing nozzle, or a rotary atomizer, ensuring that the generated droplets have a Sottle average diameter of less than 100 micrometers, allowing them to completely evaporate and dry in the airflow within a short residence time. The dust collector collects the solid salt particles formed after evaporation, and can be a high-efficiency dust removal device such as a sintered metal plate dust collector or a wet electrostatic precipitator. The control system monitors the system operating parameters in real time and intelligently adjusts the inflow rate of the high-salt wastewater and the inflow rate of the air-cooled fan accordingly.

[0097] The operation of the system in this embodiment relies on the synergistic control process of the method in this embodiment, which ultimately achieves reliable drying of high-salt wastewater and synergistic reduction of system operating energy consumption.

[0098] To further verify the beneficial effects of this embodiment:

[0099] A 600MW coal-fired unit at an inland power plant uses direct air cooling technology for condensation of its turbine exhaust steam. This air-cooling system employs mechanical ventilation, with a designed total air intake of approximately 12 million Nm³ / h. Simultaneously, the unit utilizes a limestone-gypsum wet desulfurization process, generating approximately 5-6 tons / h of desulfurization wastewater.

[0100] Before the upgrade, the condenser back pressure was maintained entirely by adjusting the speed of the air-cooled fans (i.e., the air intake) when the unit load changed, and the total power consumption of the fan group was about 4200 kW on average. The generated desulfurization wastewater was treated using the "bypass flue gas evaporation" technology, and its treatment cost per ton of water (mainly heat and electricity consumption) was as high as about 100 yuan / ton.

[0101] To reduce operating costs and wastewater volume, the air-cooling system of this unit underwent a synergistic modification according to this invention. A desulfurization wastewater atomization system and a metal sintered plate dust collector were added to the duct between the air-cooled fan outlet and the finned tube heat exchanger, along with a corresponding intelligent control system. The desulfurization wastewater is broken into extremely fine droplets with an average Sottle diameter of less than 50 micrometers by a high-pressure atomizing nozzle and sprayed into the air-cooling tower. These droplets rapidly and completely evaporate and dry in the massive 12 million Nm³ / h of dry, cold inlet air, forming solid salt particles. Subsequently, the salt-containing airflow enters the metal sintered plate dust collector, where over 99.5% of the salt particles are efficiently captured, resulting in a stream of clean and significantly humidified air. This humidified air, flowing through the finned tube heat exchanger, significantly enhances the heat exchange efficiency with the exhaust steam inside the tubes due to its increased specific heat capacity and potential condensation effect. This allows the system to maintain the condenser back pressure within a safe range while reducing the total fan airflow, thus achieving energy savings.

[0102] After the system in this embodiment was put into operation, it operated continuously and stably for more than a year, with excellent response from the intelligent control logic. The total power consumption of the fan group decreased from an average of 4200 kW before the modification to approximately 3800 kW, a reduction of about 9.5%, resulting in annual electricity savings of over 3 million kWh, demonstrating significant economic benefits. The system achieves full and continuous treatment of desulfurization wastewater, with an average treatment capacity of 5.5 t / h, completely replacing the original high-cost bypass flue gas evaporation process. Calculations show that the unit treatment cost of desulfurization wastewater has decreased from 100 yuan / ton to less than 10 yuan / ton (mainly due to pump power consumption). After deducting equipment operation and maintenance and depreciation costs, the annual savings in wastewater treatment costs are nearly 1 million yuan.

[0103] This embodiment fully demonstrates that the proposed co-drying system and energy-saving operation method for high-salt wastewater in power plants for direct air-cooled units is technically feasible and operates stably and reliably. It successfully achieves the synergistic goals of "energy saving and consumption reduction" and "zero wastewater discharge and cost reduction," and has broad prospects for promotion and application in direct air-cooled coal-fired power plants.

[0104] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A co-drying system for high-salinity wastewater from power plants used in direct air-cooled units, characterized in that, include: The air-cooled tower has an air inlet at the bottom to draw in ambient air and an exhaust outlet at the top to discharge the hot and humid air that has exchanged heat with the exhaust steam from the steam turbine. Air-cooled fans are located at the bottom or side of the air-cooled tower to supply air into the tower. Finned tube heat exchangers are arranged inside air-cooled towers. The inside of the finned tubes is used to introduce exhaust steam from the steam turbine after it has done its work, while the outside of the finned tubes is used to introduce air through the air-cooled fan. The wastewater atomization device is installed after the air-cooled fan and connected to the internal air duct of the air-cooled tower. It is used to atomize the high-salt wastewater from the power plant into droplets and spray them into the air duct of the air-cooled tower. The dust collector is located in the duct downstream of the wastewater atomization device and upstream of the finned tube heat exchanger. It is used to capture solid salt particles formed after the liquid droplets evaporate, and output clean air that is free of salt particles and has increased relative humidity, and discharge the removed solid salt in a concentrated manner. The control system is connected to the air-cooled fan and the wastewater atomization device, respectively, and is used to collect the load L, condenser back pressure P0, and ambient temperature T of the direct air-cooled unit. e Ambient relative humidity (RH) e The parameters for the available supply of high-salt wastewater are also included. Based on the preset allowable range of condenser back pressure P0 and environmental conditions, the injection volume of high-salt wastewater and the air volume of the air-cooled fan are adjusted in combination to keep the condenser back pressure P0 within the allowable range, provided that the injected high-salt wastewater is completely evaporated before reaching the dust collector.

2. The power plant high-salinity wastewater co-drying system for direct air-cooled units according to claim 1, characterized in that: The high-salt wastewater is desulfurization wastewater generated by wet desulfurization process, or high-salt wastewater containing calcium sulfate and chloride salts.

3. The power plant high-salinity wastewater co-drying system for direct air-cooled units according to claim 1, characterized in that: The wastewater atomization device includes at least one of a high-pressure atomizing nozzle, a dual-fluid atomizing nozzle, and a rotary atomizer. The wastewater atomization device atomizes high-salt wastewater to form droplets with an average Sottle diameter of less than 100 μm. The dust collector is a metal sintered plate dust collector or a wet electrostatic precipitator.

4. The power plant high-salinity wastewater co-drying system for direct air-cooled units according to claim 1, characterized in that: The control system includes a core controller and a data acquisition unit and an execution unit electrically connected to the core controller; the data acquisition unit includes a function for measuring ambient temperature T. e and ambient relative humidity (RH) e The system includes an environmental parameter sensor, a pressure sensor for measuring the condenser back pressure P0, and an operating condition signal interface for acquiring the real-time load L and high-salt wastewater supply of the direct air-cooled unit; the execution unit includes a fan frequency conversion speed control device for adjusting the air volume of the air-cooled fan and an atomized liquid supply adjustment device for adjusting the injection volume of high-salt wastewater.

5. The power plant high-salinity wastewater co-drying system for direct air-cooled units according to claim 4, characterized in that: The core controller has a built-in ambient temperature safety threshold T. s Humidity operating threshold RH low and humidity shutdown threshold RH high , of which RH low <RH high ; When the ambient temperature T is detected e <T s At that time, the core controller sets the high-salt wastewater injection volume to 0 and maintains the condenser back pressure P0 within the allowable range only by adjusting the air volume of the air-cooled fan. When the ambient temperature T is detected e ≥T s And the relative humidity (RH) of the environment e ≤RH low At that time, the wastewater atomization device is activated, and the maximum instantaneous injection rate W of high-salinity wastewater is calculated according to the evaporation capacity constraint model. e,max Spray in high-salt wastewater; When the ambient temperature T is detected e ≥T s And the relative humidity (RH) of the environment e ≥RH high At that time, the power plant's high-salt wastewater co-drying system must not be started or the wastewater atomization device must be stopped immediately; When the ambient temperature T is detected e ≥T s And RH low <RH e <RH high At that time, the core controller optimized the high-salinity wastewater injection rate W under the constraints of evaporation capacity, cooling demand, and resource supply. s And according to the high-salt wastewater injection volume W s Limits are set to control the actual injection volume.

6. The power plant high-salinity wastewater co-drying system for direct air-cooled units according to claim 5, characterized in that: The core controller incorporates an evaporation capacity constraint model, a cooling demand constraint model, and a resource supply constraint model to limit the feasible range of high-salt wastewater injection volume and air-cooled fan volume. The evaporation capacity constraint model calculates the maximum allowable instantaneous injection volume of high-salt wastewater under a given evaporation safety factor k, based on the current air volume of the air-cooled fan, air density, ambient air humidity, and saturated humidity at the finned tube wall temperature. The cooling demand constraint model is based on the real-time load L and ambient temperature T of the direct air-cooled unit. e Calculate the total heat exchange required by the condenser to ensure that the condenser back pressure P0 does not exceed the preset upper limit P under a given combination of high-salt wastewater injection rate and air-cooled fan flow rate. max ; The resource supply constraint model is used to limit the amount of high-salinity wastewater injected to no more than the current available supply of high-salinity wastewater.

7. The power plant high-salinity wastewater co-drying system for direct air-cooled units according to claim 6, characterized in that: The evaporation capacity constraint model, cooling demand constraint model, and resource supply constraint model are set according to the following formulas: W e ≤k×V c ×ρ a ×(x s -x a ) Q r =f(L)+K1×(T e -T ref ) IN s ≤Q a Among them, W e V is the allowable instantaneous injection rate of high-salinity wastewater under evaporation capacity constraints, k is the evaporation safety factor, and V is the allowable instantaneous injection rate of high-salinity wastewater. c ρ is the air volume of the air-cooled fan. a x is the air density. s x represents the saturated moisture content of air at the finned tube wall temperature. a Q represents the humidity content of ambient air. r Let f(L) be the total heat exchange required by the condenser, f(L) be the basic heat dissipation function corresponding to the real-time load L of the direct air-cooled unit, and K1 be the coefficient of performance relative to the ambient temperature T. e The relevant correction factor, T ref Design ambient temperature for air-cooled systems, W s Q represents the injection rate of high-salinity wastewater. a This represents the current available supply of high-salinity wastewater.

8. The power plant high-salinity wastewater co-drying system for direct air-cooled units according to claim 5, characterized in that: The core controller, based on the evaporation capacity constraint model, cooling demand constraint model, and resource supply constraint model, uses the minimization of the total power of the air-cooled fan as the optimization objective function to solve for the high-salt wastewater injection rate and the air-cooled fan airflow, and outputs the corresponding control commands to the execution unit.

9. The power plant high-salinity wastewater co-drying system for direct air-cooled units according to any one of claims 4 to 8, characterized in that: The core controller also includes safety override control logic and efficiency optimization control logic; When the condenser back pressure P0 is detected to be higher than the preset upper limit P max When the time is right, the safety override control is triggered, which prioritizes reducing the injection volume of high-salt wastewater and increasing the air volume of the air-cooled fan until the condenser back pressure P0 drops back to the allowable range. When the condenser back pressure P0 is detected to be lower than the preset lower limit P min At that time, efficiency optimization control is triggered, prioritizing increasing the injection volume of high-salt wastewater and reducing the air volume of the air-cooled fan until the condenser back pressure P0 rises back to the allowable range.

10. An energy-saving operation method using the synergistic drying system as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Step 1, Data Acquisition and Initialization: The control system acquires the real-time load L, condenser back pressure P0, and ambient temperature T of the direct air-cooled unit. e Ambient relative humidity (RH) e The system also reads the current available supply of high-salinity wastewater and the preset allowable range of condenser back pressure P0 and ambient temperature safety threshold T. s Humidity operating threshold RH low and humidity shutdown threshold RH high ; Step 2, Safety Mode Determination: When the ambient temperature T e <T s At that time, the high-salt wastewater injection rate was set to 0, and the condenser back pressure P0 was maintained within the allowable range only by adjusting the airflow of the air-cooled fan; when the ambient temperature T e ≥T s At that time, according to the ambient relative humidity (RH) e With humidity operating threshold RH low Humidity shutdown threshold RH high The relationship between the wastewater atomization device and its operating intensity determines whether it is permissible to put it into operation. Step 3, Collaborative optimization solution: Under the condition that the wastewater atomization device is allowed to be put into operation, based on the constraints of evaporation capacity, cooling demand and resource supply, the optimization algorithm with the goal of minimizing the total power of the air-cooled fan is used to solve for the high-salt wastewater injection rate and the air volume of the air-cooled fan. Step 4, Closed-loop verification and dynamic adjustment: Apply the high-salt wastewater injection rate and air-cooled fan volume obtained in Step 3 to the wastewater atomization device and the air-cooled fan, and detect the condenser back pressure P0 at this operating point. When the condenser back pressure P0 is within the allowable range, maintain this operating point; when the condenser back pressure P0 exceeds the allowable range, prioritize adjusting the high-salt wastewater injection rate and air-cooled fan volume through safety override control or efficiency optimization control, and perform the verification cyclically until the condenser back pressure P0 returns to the allowable range.

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