Strong brine zero-discharge circulating cooling water high-salt operation method and system

Abstract

The invention provides a strong brine zero-discharge circulating cooling water high-salt operation method and system. The method comprises the following steps: S1, pretreating high-efficiency membrane softening produced water and controlling a shunting dynamic ratio; s2, variable parameter closed-loop control and energy consumption optimization of the water supplementing system; s3, multi-variable cooperative regulation and evaporation efficiency improvement of the circulating water system; s4, dynamically adding the high-salt scale and corrosion inhibitor and controlling the uniformity of a concentration field; s5, multi-dimensional data fusion and intelligent decision making of the online detection system; s6, carrying out dynamic flow regulation and energy recovery on the sewage discharge system; s7, carrying out self-adaptive backwashing and efficiency monitoring on the sewage filtering system; s8, double-circulation temperature difference matching and anti-scaling control of the closed cooling system are carried out; s9, simulating multi-working-condition corrosion monitoring and data inversion of the heat exchanger; s10, carrying out the digital twinborn modeling and parameter optimization of the whole system; the method has the advantages of remarkable water-saving effect, energy conservation, consumption reduction, stable operation and good economical efficiency.

Description

Technical Field

[0001] This invention specifically relates to a method and system for high-salt operation of circulating cooling water with zero discharge of concentrated brine. Background Technology

[0002] Traditional circulating water systems often employ open-type counter-flow cooling towers. While open towers offer good cooling performance, their cooling method primarily relies on water evaporation. This makes circulating water systems a major water consumer in enterprise operations, accounting for up to 60% of water usage. To save energy and reduce water consumption, a comparative study of various existing circulating water saving technologies was conducted. These technologies include: closed-circuit cooling towers, anti-fogging cooling towers, electrochemical technology, microbial control technology, and novel chemical agent technology. Through technical exchanges and on-site investigations, the novel chemical agent method was found to require less investment and offer greater flexibility compared to other technologies. On-site investigations revealed that the concentration ratio of the novel chemical agent method is significantly higher than that of traditional control systems, resulting in substantial water savings. Furthermore, corrosion control and scaling / clogging of the equipment are kept within manageable limits.

[0003] In summary, traditional circulating water control systems have low concentration ratios and limited water-saving effects. Furthermore, the low-concentration brine discharged from the circulating water system consumes a large amount of steam when entering the evaporator. Simultaneously, existing circulating water systems often use intermittent chemical dosing, resulting in unstable chemical concentration control, which easily leads to equipment corrosion, scaling, and clogging, affecting the stable operation of the system. Therefore, there is an urgent need for a circulating cooling water operation technology that can improve the concentration ratio, reduce water and steam consumption, and stably control corrosion and scaling. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for operating high-salinity circulating cooling water with zero discharge of concentrated brine, which can effectively solve the aforementioned problems.

[0005] To achieve the above requirements, the technical solution adopted by the present invention is: to provide a method for high-salinity operation of concentrated brine circulating cooling water with zero discharge, the method comprising the following steps:

[0006] S1: The steps for pretreatment of high-efficiency membrane softening permeate and dynamic proportioning control of diversion are as follows: 48 hours before the start of the test, the permeate from the high-efficiency membrane softening filter is continuously monitored for 24 hours, and the fluctuation curves of total hardness, calcium ions, and total alkalinity are recorded. The optimal mixing ratio of permeate before and after acid addition is calculated by PID algorithm. A dynamic proportioning model is established based on the water quality fluctuation curve. Real-time adjustment is achieved by linkage of electromagnetic flowmeter with an accuracy of ±0.5% and electric regulating valve with a response time of less than 1 second. An online turbidity meter and pH sensor are installed in the water tank. When the turbidity of the mixed water is greater than 3 NTU, the drain valve at the bottom of the water tank is opened for 10 minutes to drain the water. When the pH value deviates from the range of 8.5-9.0, compensation is made by the bypass fine-tuning valve of the mixer in the acid addition pipeline to ensure that the fluctuation range of the water quality entering the water tank is controlled within ±5%, which lays the foundation for the stability of subsequent water replenishment.

[0007] S2: Steps for variable parameter closed-loop control and energy consumption optimization of the water replenishment system. When the water level in the newly added water replenishment tank reaches 80% and the water quality meets the standards, the water replenishment system is started. A variable parameter algorithm based on model predictive control is used to adjust the operation of the water replenishment pump. The water level, conductivity, and ambient temperature of the circulating water tank are used as input variables. The water replenishment demand for the next hour is predicted based on historical data. When the ambient temperature is greater than 30℃ in summer, the frequency of the water replenishment pump is increased to 45Hz 15 minutes in advance. When the temperature is less than 5℃ in winter, the water replenishment is delayed until the water level drops to 1.6m. A pressure-flow composite sensor is installed at the outlet of the water replenishment pump to collect data in real time and substitute it into the energy consumption formula.

[0008] ;

[0009] Where E is energy consumption in kWh, Q is flow rate in m³ / h, H is head in m, ρ is water density of 1000 kg / m³, t is time, and η is pump efficiency of 65-80%. When the unit water replenishment energy consumption is greater than 0.3 kWh / m³, the system automatically switches to standby pump B to ensure that the water replenishment system meets the water demand while minimizing energy consumption. This step depends on the stable water quality after the previous pretreatment, and its output water replenishment parameters provide input conditions for the initial operation of the circulating water system.

[0010] S3: Steps for multivariate coordinated control and evaporation efficiency improvement of the circulating water system. After the water replenishment system has been running stably for 30 minutes, the circulating water system is started. A ternary regression model of circulating flow rate, cooling tower inlet water temperature, and fan speed is established using a multivariate coordinated control algorithm of flow rate, temperature, and fan speed.

[0011] ;

[0012] Where T_drop is the temperature drop in °C, Q is the circulation flow rate in m³ / h, V is the wind speed in m / s, and T_in is the inlet water temperature in °C. The system is equipped with an ultrasonic flow meter and an infrared thermometer, which collect data every 5 seconds and compare it with the model prediction value. When the deviation is >0.5℃, the model parameters are automatically corrected to ensure that the circulating water can maintain an actual temperature difference of 7-8℃ in different seasons, providing a stable evaporation rate for subsequent high-salt concentration.

[0013] S4: Steps for dynamic dosing and concentration field uniformity control of high-salt scale and corrosion inhibitors. After the circulating water system has been running continuously for 1 hour and the parameters have stabilized, the automatic dosing system is started. The dosing strategy is optimized by concentration field simulation based on computational fluid dynamics. The turbulence intensity distribution in the circulating water return pipe network is simulated by CFD. The agent dosing port is set in the pipe section with turbulence intensity >15m² / s². The dosing amount calculation formula introduces a multi-factor correction term: ;

[0014] Where Q is the flow rate of the dosing pump; C target is the target concentration of the agent in the circulating water; V circulation is the total volume of the circulating water system; K safety is the safety factor; ΔT is the temperature difference of the circulating water; ΔCl⁻ is the chloride ion deviation; τ is the time variable; the integral term is the agent decay correction, considering the accelerated decay under high salinity conditions; the quadratic term τ² is the nonlinear decay coefficient; t is the single dosing time; ρ agent is the agent density; and η is the effective utilization rate of the agent.

[0015] S5: Steps for multi-dimensional data fusion and intelligent decision-making in the online detection system. After the dosing system is running stably, the online detection unit enters closed-loop control mode. Multi-sensor data fusion technology is used to improve detection reliability. Three detection points are arranged at the inlet, middle, and outlet of the circulating water return network. Each point is equipped with a four-parameter sensor for pH, conductivity, ORP, and turbidity. The data from the three points are fused using DS evidence theory. When the deviation between the single-point data and the fused result is >5%, it is automatically marked as abnormal and backup sensor data is activated. A multi-parameter correction model is introduced for the concentration factor calculation.

[0016] ;

[0017] Where N is the concentration factor; σ is the actual conductivity of the circulating water; σ_makeup water is the conductivity of the makeup water; ORP is the oxidation-reduction potential; pH is the pH value of the circulating water; τ is the operating time; the integral term is the long-term operating correction; the cubic term τ³ is used to compensate for the nonlinear effects of salting out; and 0.05 is the temperature correction coefficient.

[0018] S6: The steps for dynamic flow regulation and energy recovery of the sewage discharge system are as follows: When the online detection system determines that sewage discharge is required, the dynamic regulation program of the sewage discharge unit is activated. The sewage discharge strategy is optimized by combining real-time evaporation data. The actual evaporation is calculated in real time using ultrasonic level gauges and steam flow meters installed in the cooling tower water collection tank.

[0019] ;

[0020] Where E is the actual evaporation rate; k is a coefficient; Q is the circulating water flow rate; Treturn is the cooling tower return water temperature; Tin is the cooling tower inlet water temperature; and r is the latent heat of vaporization of water. Substituting these values ​​into the wastewater discharge formula:

[0021] ;

[0022] Where B is the discharge volume; N is the concentration factor; σ is the actual conductivity of the circulating water, in μs / cm. When the conductivity is below 90,000, the discharge volume is reduced. The correction coefficient is a linear adjustment term. When the conductivity is below 90,000, the discharge volume is reduced. The discharge electric valve adopts frequency conversion control. In the initial stage of opening, the discharge volume is rapidly reduced at the maximum flow rate of 40 m³ / h. When the conductivity drops to 85,000 μs / cm, the control mode is switched to PID regulation mode. A small hydraulic turbine is installed in the discharge pipeline. The recovered energy is used to drive the fiber filter backwash pump. When the turbine output power is > 0.5 kW, the backwash power source is automatically switched to achieve energy cascade utilization.

[0023] S7: Steps for adaptive backwashing and performance monitoring of the wastewater filtration system. After the wastewater enters the fiber filter, the system activates the adaptive backwashing control algorithm, dynamically adjusting the backwashing cycle based on changes in filtration resistance and water quality, and establishing a model relating the filter inlet and outlet pressure difference to the filtration time.

[0024] ;

[0025] Where ΔP is the pressure difference between the filter inlet and outlet; t is the filtration time; the integral term is the cumulative turbidity; when ΔP > 0.1 MPa or the integral turbidity > 50 NTU·h, the backwashing procedure is triggered. The backwashing process consists of three stages: air washing, air-water mixed washing, and water washing. The backwashing water volume is precisely controlled by a flow meter. A turbidity meter is installed in the backwash drainage. When the drainage turbidity is < 10 NTU, the backwashing is terminated in advance. An online ion chromatograph is installed in the filtered water pipeline to monitor the concentrations of Na⁺, Ca²⁺, and Cl⁻ in real time. When the ion concentration fluctuation is > 10%, the flow data of the sewage system is automatically correlated to check for short-circuit flow and ensure the stability of the water quality entering the DTRO concentrate tank.

[0026] S8: Steps for performing dual-circulation temperature difference matching and anti-scaling control of the closed-loop cooling system. After the circulating water system and the sewage system are running stably, the closed-loop cooling unit starts temperature difference matching control to establish a balance model of equipment cooling demand. By adjusting the speed of the newly added circulating pump, the cold side outlet temperature of the plate heat exchanger is stabilized. When the pump return water temperature is >38℃, the bypass valve of the equipment cooling water pipeline is opened, and the hot side flow of the plate heat exchanger is increased. Dynamic balance is achieved through temperature-flow coupling control. The closed-loop cooling system uses primary water for makeup water. A conductivity meter is installed. When the conductivity is >300μs / cm, the sewage valve is opened for replacement. At the same time, a trace amount of scale inhibitor is added to prevent scaling of the plate heat exchanger. The heat source of the hot side of the system comes from the circulating water system. Its stable operation depends on the temperature and flow parameters of the circulating water to provide reliable cooling for the equipment.

[0027] S9: Steps for multi-condition corrosion monitoring and data inversion of the simulated heat exchanger: After the circulating water system has been running stably for 72 consecutive hours, the simulated heat exchanger enters the multi-condition test mode. An orthogonal experimental design is used to cover key parameter combinations, setting 4 temperature levels and 3 flow rate levels. Each condition is run for 24 hours. A correlation model is established between the corrosion amount of the fins and the corrosion current density monitored by the electrochemical workstation. ;

[0028] Where V is the corrosion rate; k is the conversion coefficient; Icorr is the corrosion current density; τ is the time variable; Cl⁻ is the chloride ion concentration; and t is the operating time. The specimens were analyzed using a combination of weight loss method and scanning electron microscopy. The weight loss data was substituted into the formula to calculate the average corrosion rate. SEM was used to observe the corrosion morphology to determine whether there was localized corrosion. After each operating condition, circulating water samples were collected from the inlet and outlet of the heat exchanger to detect the residual concentration of the reagent and the content of metal ions. The effectiveness of the previous dosing system was inverted. When the corrosion rate under a certain operating condition is >0.06mm / a, it is automatically marked as high risk and the reagent concentration is increased in a targeted manner in subsequent dosing.

[0029] S10: This step involves performing full-system digital twin modeling and parameter optimization. A digital twin model is built daily based on the operational data from each step, achieving real-time mapping between the physical system and the virtual model. The model includes three dimensions: equipment layer, parameter layer, and performance layer. Real-time data is collected via the OPC UA protocol. A Kalman filter algorithm is used to correct model biases, and a genetic algorithm is employed to optimize key parameters. The objective function is: ;

[0030] Where J is the comprehensive objective function; water replenishment cost is the water fee per unit of water replenishment; reagent cost is the cost per unit of reagent consumption; steam saving is the amount of steam reduction compared to the traditional system; corrosion risk index is the normalized index of corrosion rate relative to the standard value; the constraints are corrosion rate ≤ 0.075 mm / a and concentration factor ≤ 5.0. The optimization results generate an operation manual.

[0031] The advantages of this high-salt operation method with zero-discharge concentrated brine circulating cooling water are as follows:

[0032] Significant water-saving effect: Using high-efficiency membrane softening filter water as makeup water, combined with high-salt operation technology, the concentration ratio of circulating water is improved, and the water consumption of enterprises is greatly reduced.

[0033] Energy saving and consumption reduction: Reduce the water intake of the evaporator and reduce steam consumption costs based on the steam consumption per ton of water in the evaporator.

[0034] Stable operation: The automatic dosing system precisely controls the dosage of chemicals, and the online monitoring system monitors water quality in real time, ensuring that the equipment corrosion rate and fouling thermal resistance meet national standards under conditions of salt content of 60,000-90,000 mg / L and chloride ion content of 10,000-20,000 mg / L.

[0035] Good economic efficiency: Compared with closed cooling towers, electrochemical and other technologies, this invention adopts a new reagent method, which requires less investment, is more flexible in application, and reduces membrane treatment costs and fresh water costs, resulting in significant overall economic benefits. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, use the same reference numerals to denote the same or similar parts. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0037] Figure 1 A schematic diagram of a high-salt operation method for zero-discharge circulating cooling water of concentrated brine according to an embodiment of this application is shown.

[0038] Figure 2 A schematic diagram of the structure of a cooling tower used in a high-salt operation method for zero-discharge circulating cooling water according to an embodiment of this application is shown.

[0039] Figure 3 A schematic diagram of the water replenishment system used in a high-salt operation method for zero-discharge circulating cooling water according to an embodiment of this application is shown.

[0040] Figure 4A schematic diagram of the sewage system used in a high-salt operation method for zero-discharge circulating cooling water of concentrated brine according to an embodiment of this application is shown.

[0041] Figure 5 A schematic diagram of the structure of a simulated heat exchanger used in a high-salt operation method for zero-discharge circulating cooling water according to an embodiment of this application is shown. Detailed Implementation

[0042] To make the objectives, technical solutions and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments.

[0043] In the following description, references to "an embodiment," "an embodiment," "an example," "example," etc., indicate that the described embodiment or example may include a particular feature, structure, characteristic, property, element, or limitation, but not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element, or limitation. Furthermore, the repeated use of the phrase "an embodiment according to this application," while possibly referring to the same embodiment, does not necessarily refer to the same embodiment.

[0044] For simplicity, certain technical features known to those skilled in the art are omitted in the following description.

[0045] According to one embodiment of this application, a method for high-salt operation of concentrated brine circulating cooling water with zero discharge is provided, comprising the following steps:

[0046] S1: Steps for high-efficiency membrane softening permeate pretreatment and dynamic ratio control. Forty-eight hours before the experiment, continuous 24-hour water quality monitoring was conducted on the permeate from the high-efficiency membrane softening filter, recording the fluctuation curves of key indicators such as total hardness (13.0-50.0 mg / L), calcium ions (13.0-30.0 mg / L), and total alkalinity (114.4-200.0 mg / L). The optimal mixing ratio of permeate before and after acid addition was calculated using a PID algorithm. A dynamic ratio model was established based on the water quality fluctuation curves. When the alkalinity of the permeate before acid addition was greater than 180 mg / L, its ratio was automatically reduced to 2:1 before acid addition; conversely, it was increased to 4:1. Real-time adjustment was achieved through the linkage of an electromagnetic flowmeter with an accuracy of ±0.5% and an electric regulating valve with a response time of less than 1 second. An online turbidity meter (0-10 NTU) and a pH sensor were installed in the makeup water tank. When the turbidity of the mixed water was greater than 3 NTU... When the water tank is in a certain condition, open the drain valve (DN25) at the bottom of the water tank for 10 minutes to drain the water. When the pH value deviates from the range of 8.5-9.0, compensate through the bypass fine-tuning valve (DN15) of the acid addition pipeline mixer to ensure that the fluctuation range of the water quality entering the water tank is controlled within ±5%, which lays the foundation for the stability of subsequent water replenishment. This step completes the water quality baseline measurement and valve calibration, which is a prerequisite for the start-up of the subsequent water replenishment unit.

[0047] S2: Steps for variable parameter closed-loop control and energy consumption optimization of the water replenishment system. When the newly added water replenishment tank reaches 80% capacity and the water quality meets standards, the water replenishment system is started. A variable parameter algorithm based on model predictive control (MPC) is used to adjust the operation of the water replenishment pump. The circulating water tank level (1.5-2.5m), conductivity (70000-90000μs / cm), and ambient temperature (-10-40℃) are used as input variables. A neural network model trained on historical data predicts the water replenishment demand for the next hour. In summer, when the ambient temperature is above 30℃, the water replenishment pump frequency is increased to 45Hz 15 minutes in advance (pre-replenishment). In winter, when the temperature is below 5℃, water replenishment is delayed until the water level drops to 1.6m. A pressure-flow composite sensor is installed at the water replenishment pump outlet to collect data in real time and input it into the energy consumption formula.

[0048] ;

[0049] Where E is energy consumption in kWh, Q is flow rate in m³ / h, H is head in m, ρ is water density of 1000 kg / m³, t is time, and η is pump efficiency of 65-80%. When the unit water replenishment energy consumption is greater than 0.3 kWh / m³, the system automatically switches to standby pump B to ensure that the water replenishment system meets the water demand while minimizing energy consumption. This step depends on the stable water quality after the previous pretreatment, and its output water replenishment parameters provide input conditions for the initial operation of the circulating water system.

[0050] S3: Steps for multivariate coordinated control and evaporation efficiency improvement of the circulating water system. After the water replenishment system has been running stably for 30 minutes, start the circulating water system and use a multivariate coordinated control algorithm of "flow rate-temperature-wind speed" to establish a ternary regression model of circulating flow rate (1000-1200 m³ / h), cooling tower inlet water temperature (32-37℃), and fan wind speed (10-15 m / s):

[0051] ;

[0052] Where Tdrop is the temperature drop (°C), Q is the circulation flow rate (m³ / h), V is the wind speed (m / s), and Tin is the inlet water temperature (°C), the PLC solves the model in real time and outputs control commands. In summer, when Tdrop is less than 8°C, the fan frequency is preferentially increased to 50Hz (maximum wind speed 15m / s). If this is still insufficient, the circulating water pump speed is increased (maximum flow rate 1200m³ / h). In winter, when Tdrop is greater than 9°C, the fan frequency is reduced to 25Hz (minimum wind speed 10m / s), and the cooling tower inlet and outlet temperature difference regulating valve (DN300) is opened to reduce heat dissipation by bypassing 30% of the circulating water. The system is equipped with an ultrasonic flow meter (accuracy ±1%) and an infrared thermometer (resolution 0.1°C). Data is collected every 5 seconds and compared with the model prediction. When the deviation is >0.5°C, the model parameters are automatically corrected to ensure that the circulating water can maintain an actual temperature difference of 7-8°C in different seasons, providing a stable evaporation rate for subsequent high-salt concentration.

[0053] S4: Steps for dynamic dosing and concentration field uniformity control of high-salt scale and corrosion inhibitors. After the circulating water system has been running continuously for 1 hour and the parameters have stabilized, the automatic dosing system is started. The dosing strategy is optimized by concentration field simulation based on computational fluid dynamics (CFD). The turbulence intensity distribution (Reynolds number 50,000-80,000) in the circulating water return pipe network is simulated by CFD. The agent dosing port is set in the pipe section with turbulence intensity >15m² / s² (1.5D from the elbow, where D is the pipe diameter of 300mm). The dosing amount calculation formula introduces a multi-factor correction term: ;

[0054] Where Q is the flow rate of the dosing pump (L / h); C target is the target concentration of the agent in the circulating water (50mg / L); V circulation is the total volume of the circulating water system (665.28m³); K safety is the safety factor (1.2); ΔT is the temperature difference of the circulating water (°C, deviation from the design value of 8°C); ΔCl⁻ is the chloride ion deviation (mg / L, deviation from 20000mg / L); τ is the time variable (h); the integral term is the agent decay correction (considering the accelerated decay under high salinity, the quadratic term τ² is the nonlinear decay coefficient); t is the single dosing time (2h); ρ agent is the agent density (1.1g / cm³); η is the effective utilization rate of the agent (90%).

[0055] The quadratic term τ² is used to correct for the accelerated decay of the reagent in a high-salt environment. The integration interval is t=2h. A static mixer (SX type, mixing uniformity >95%) is installed in the dosing pipeline, and a sampling point is set at 5D downstream. The reagent concentration is detected every 15 minutes. The concentration accuracy of ±1mg / L is achieved by controlling the pulse width modulation (PWM) of the dosing pump. When the flow rate fluctuation of the circulating water system is >10%, the concentration field is automatically re-simulated, and the frequency of the dosing pump is adjusted to compensate for the flow rate change, ensuring that the standard deviation of the reagent concentration distribution in the pipeline network is <3mg / L. This step requires stable flow rate and temperature difference data of the preceding circulating water system, and its output reagent concentration field provides a monitoring benchmark for the online detection system.

[0056] S5: Steps for multi-dimensional data fusion and intelligent decision-making in the online monitoring system. After the dosing system is running stably, the online monitoring unit enters closed-loop control mode. Multi-sensor data fusion technology is used to improve monitoring reliability. Three monitoring points are arranged at the inlet, middle, and outlet of the circulating water return network. Each point is equipped with a four-parameter sensor for pH (accuracy ±0.01), conductivity (±1% FS), ORP (±5mV), and turbidity (±2%). The three-point data are fused using DS evidence theory. When the deviation between a single-point data point and the fused result is >5%, it is automatically marked as abnormal and backup sensor data is activated. A multi-parameter correction model is introduced for concentration factor calculation.

[0057] ;

[0058] Where N is the concentration factor; σ is the actual conductivity of the circulating water (μs / cm); σmakeup water is the conductivity of the makeup water (μs / cm); ORP is the oxidation-reduction potential (mV, used to compensate for the influence of the oxidizing environment on conductivity); pH is the pH value of the circulating water (used to correct for alkalinity fluctuations); τ is the operating time (h); the integral term is the long-term operation correction (the cubic term τ³ is used to compensate for the nonlinear effect of salting out); 0.05 is the temperature correction coefficient. The cloud platform predicts the change in the concentration factor in the next 2 hours using an LSTM neural network. When the predicted value is >5.2, a sewage discharge warning is issued 30 minutes in advance. At the same time, a water quality-equipment status correlation model is established. When the turbidity is >8 NTU and ORP is <200 mV, it is judged as a risk of microbial growth, and the biocidal dosage is automatically increased (1.5 times the original dosage). This step integrates the water quality data after the previous dosing, and its decision directly triggers the subsequent sewage discharge procedure.

[0059] S6: The steps for dynamic flow regulation and energy recovery in the sewage discharge system are as follows: When the online monitoring system determines that sewage discharge is necessary, the dynamic regulation program of the sewage discharge unit is activated, and the sewage discharge strategy is optimized based on real-time evaporation data. The working principle is as follows: The actual evaporation rate is calculated in real time using an ultrasonic level gauge and a steam flow meter (evaporation device) installed in the cooling tower's water collection tank.

[0060] ;

[0061] Where E is the actual evaporation rate (m³ / h); k is a coefficient (0.001); Q is the circulating water flow rate (m³ / h); Treturn is the cooling tower return water temperature (°C); Tin is the cooling tower inlet water temperature (°C); and r is the latent heat of vaporization of water (2260 kJ / kg). Substituting these values ​​into the wastewater discharge formula:

[0062] ;

[0063] Where B is the discharge volume (m³ / h); N is the concentration factor; σ is the actual conductivity of the circulating water (μs / cm). When the conductivity is below 90000, discharge is reduced. The correction coefficient is a linear adjustment term. When the conductivity is below 90000, discharge is reduced. The discharge electric valve adopts frequency conversion control. In the initial stage of opening, it discharges quickly at the maximum flow rate of 40m³ / h. When the conductivity drops to 85000μs / cm, it switches to PID regulation mode (target flow rate 33m³ / h ± 1m³ / h). A small hydraulic turbine (efficiency > 70%) is installed in the discharge pipeline. The recovered energy is used to drive the fiber filter backwash pump. When the turbine output power > 0.5kW, the backwash power source is automatically switched to achieve energy cascade utilization. This step requires the preceding detection system to provide stable concentration factor and conductivity data. Its discharge flow rate parameters provide input conditions for subsequent filtration treatment.

[0064] S7: Steps for adaptive backwashing and performance monitoring of the wastewater filtration system. After the wastewater enters the fiber filter, the system activates the adaptive backwashing control algorithm, dynamically adjusting the backwashing cycle based on changes in filtration resistance and water quality. A model is established to model the relationship between the filter inlet / outlet pressure difference (ΔP) and filtration time (t).

[0065] ;

[0066] Where ΔP is the pressure difference between the filter inlet and outlet (MPa); t is the filtration time (h); the integral term is the cumulative turbidity (NTU·h, reflecting the long-term impact of suspended solids deposition); when ΔP > 0.1MPa or the integral turbidity > 50NTU·h, the backwashing procedure is triggered. The backwashing process consists of three stages: air wash (0.4MPa, 30 seconds) - air-water mixed wash (air 0.3MPa + water 0.2MPa, 60 seconds) - water wash (0.3MPa, 90 seconds). The backwash water volume is precisely controlled by a flow meter (5% of the filtered water volume). A turbidity meter is installed on the backwash drain. The backwashing is terminated early when the drain turbidity is < 10NTU. An online ion chromatograph (detection cycle of 5 minutes) is installed in the filtered water pipeline to monitor the concentrations of Na⁺, Ca²⁺, and Cl⁻ in real time. When the ion concentration fluctuates by more than 10%, it automatically correlates with the flow data of the sewage system to check for short-circuit flow and ensure the stability of the water quality entering the DTRO concentrate tank. This step depends on the stable flow of the preceding sewage system, and its output filtered water parameters provide feed conditions for the evaporation system.

[0067] S8: Steps for implementing closed-loop cooling system dual-circulation temperature difference matching and anti-scaling control. After the circulating water system and sewage system are running stably, the closed-loop cooling unit starts temperature difference matching control to establish the equipment cooling demand (Qcooling = 21 pumps × 5kW + 2 centrifuges × 20kW + 4 endoscopes × 1kW = 209kW) and the plate heat exchanger heat exchange capacity (Qexchange = K × A × ΔT, where K is the heat transfer coefficient 2000W / (m²・℃), A...). For a balance model with a heat exchange area of ​​11.7 m², the cold side outlet temperature of the plate heat exchanger is stabilized at 30 ± 1℃ by adjusting the speed of the newly added circulating pump (20 m³ / h). When the pump return water temperature is >38℃, the bypass valve (DN40) of the equipment cooling water pipeline is opened, and the flow rate of the hot side (circulating water) of the plate heat exchanger is increased (120% of the original flow rate). Dynamic balance is achieved through temperature-flow coupling control. The closed cooling system uses primary water for makeup water. A conductivity meter (0-500 μs / cm) is installed. When the conductivity is >300 μs / cm, the drain valve (DN15) is opened for replacement. At the same time, a trace amount of scale inhibitor (1 mg / L) is added to prevent scaling of the plate heat exchanger. The heat source of the hot side of the system comes from the circulating water system. Its stable operation depends on the temperature and flow parameters of the circulating water to provide reliable cooling for the equipment.

[0068] S9: Steps for multi-condition corrosion monitoring and data inversion of the simulated heat exchanger. After the circulating water system has been running stably for 72 consecutive hours, the simulated heat exchanger enters the multi-condition test mode. An orthogonal experimental design is used to cover key parameter combinations, setting four temperature levels (40℃, 45℃, 50℃, 55℃) and three flow rate levels (1m / s, 1.5m / s, 2m / s). Each condition is run for 24 hours. A correlation model is established between the corrosion amount of the fins and the corrosion current density (Icorr) monitored by the electrochemical workstation (measurement accuracy ±1%). ;

[0069] Where V is the corrosion rate (mm / a); k is the conversion coefficient (3.27×10⁻³mm・a⁻¹ / (μA・cm⁻²)); Icorr is the corrosion current density (μA / cm²); τ is the time variable (d); Cl⁻ is the chloride ion concentration (mg / L, with the correction term being the accelerating effect of chloride ions on corrosion); t is the operating time (24h). The specimens were analyzed using a combination of weight loss method and scanning electron microscopy (SEM). The weight loss data was substituted into the formula to calculate the average corrosion rate. SEM was used to observe the corrosion morphology to determine whether there was localized corrosion. After each operating condition, circulating water samples were collected from the inlet and outlet of the heat exchanger to detect the residual concentration of the reagent and the content of metal ions. The effectiveness of the preceding dosing system was inverted. When the corrosion rate under a certain operating condition was >0.06mm / a, it was automatically marked as high risk, and the reagent concentration was increased in a targeted manner in subsequent dosing. This step integrates the water quality parameters and dosing concentration data of the preceding circulating water system, and its output corrosion model provides a basis for the optimization of the entire system.

[0070] S10: The steps for performing full-system digital twin modeling and parameter optimization. A digital twin model is constructed daily based on the operational data from each step, achieving real-time mapping between the physical system and the virtual model. The model includes three dimensions: equipment layer (pumps, heat exchangers, etc.), parameter layer (flow rate, concentration, etc.), and performance layer (corrosion rate, energy consumption, etc.). Real-time data is collected via the OPC UA protocol (sampling frequency 1Hz). A Kalman filter algorithm is used to correct model bias (<3%). A genetic algorithm is used to optimize key parameters. The objective function is: ;

[0071] Wherein, J is the comprehensive objective function (dimensionless, with weighting coefficients determined based on cost and risk assessment); the water replenishment cost is the water fee per unit replenishment volume (yuan / m³); the chemical cost is the cost per unit chemical consumption (yuan / kg); the steam saving is the reduction in steam compared to the traditional system (t / a, converted to economic value); the corrosion risk index is the normalized index of the corrosion rate relative to the standard value (0.075mm / a) (>1 indicates high risk); the constraints are corrosion rate ≤0.075mm / a, concentration factor ≤5.0, etc. The optimization results generate operation instructions, such as recommending that the concentration factor be controlled at 4.8 in summer to balance water saving and corrosion risk, and increased to 5.0 in winter to reduce sewage discharge. Model verification is performed weekly. When the deviation between actual operating data and model prediction is >5%, the model parameters are retrained to ensure that the digital twin model can accurately guide actual operation. This step needs to integrate the operating data of all previous steps to form a closed-loop optimization mechanism, and its output optimization parameters are fed back into the control algorithms of each step.

[0072] According to one embodiment of this application, the logical connection between the steps of the high-salt operation method of zero-discharge concentrated brine circulating cooling water is not a simple process progression, but a deep coupling based on the three-dimensional synergy of "water quality-energy-efficiency" in the high-salt circulating water system. Each step is a precise continuation and technical deepening of the previous output, ultimately forming a closed-loop optimized organic whole.

[0073] The core value of step S1 lies in establishing the system's "water quality baseline." In a high-salt environment, even minor fluctuations in water quality (such as alkalinity ±10mg / L, pH ±0.2) can be amplified by subsequent concentration processes, potentially leading to a sharp increase in the scaling tendency index (LSI) or a shift in corrosion potential. Dynamically adjusting the ratio of permeate before and after acidification using a PID algorithm essentially locks in key water quality parameters (total hardness ≤50mg / L, pH 8.5-9.0) at the source, providing a stable "raw material matrix" for all subsequent treatment stages. This baseline control is not isolated but lays the data foundation for the variable-parameter closed-loop control of the subsequent makeup water system. If water quality fluctuations exceed ±5%, the subsequent MPC prediction model will fail due to distorted input variables, resulting in a mismatch between makeup water volume and circulating water demand, directly affecting the system's salinity balance.

[0074] Step S2 is not simply a "water delivery" function, but rather a collaborative control of "water volume, energy consumption, and water quality" through a neural network model. After receiving the stable water quality data from step S1, it couples and analyzes the circulating water tank level, conductivity, and ambient temperature: the decision to pre-replenish water 15 minutes in summer is essentially based on the "slow response characteristics" of the high-salt water replenishment in the first step (high-salt solutions have large heat capacity and lag in temperature regulation), thus mitigating the risk of a surge in cooling tower evaporation; switching to the standby pump when unit energy consumption > 0.3 kWh / m³ is achieved through the "low frictional resistance" (few suspended solids) brought about by the stable water quality in the first step, enabling accurate judgment of pump unit operating efficiency. The stable flow and pressure parameters output by this control become the premise for the "multi-variable collaborative control" of the circulating water system in the third step. The adjustment of the circulating water pump head and cooling tower wind speed must be based on the water replenishment flow rate in the second step; otherwise, water imbalance will cause system pressure fluctuations, disrupting the stability of evaporation and concentration.

[0075] Step S3, the core of its ternary regression model, establishes the relationship between "evaporation intensity" and "water quality stability." Low-hardness makeup water reduces the scaling tendency of the circulating water, making it less likely for the cooling tower packing to lose heat dissipation efficiency due to calcium scale buildup. Stable makeup water flow ensures a constant circulating water volume Q, guaranteeing the linear relationship between "flow rate - wind speed - temperature drop" in the model. When the system maintains a stable temperature difference of 7-8℃, it essentially creates a "predictable concentration environment" for the fourth step of reagent addition. A stable temperature difference means a constant evaporation rate, and the circulating water salinity increases linearly over time. This makes the calculation of the reagent attenuation formula in step S4 more accurate, avoiding fluctuations in reagent concentration due to evaporation volatility.

[0076] Step S4, with its CFD simulation and pulse modulation control, is essentially a "chemical response" to the preceding water quality and circulation parameters. The low hardness characteristic of the first step reduces the ineffective reaction between the reagent and calcium and magnesium ions, ensuring that the effective utilization rate η of the reagent remains stable at 90%. The stable temperature difference dynamically compensates for the influence of temperature on reagent activity through the ΔT correction term (for every 1°C increase in temperature, the reagent half-life is shortened by 2%). More importantly, the uniform environment with a "concentration field standard deviation < 3 mg / L" constructed in this step provides a "benchmark truth value" for the online detection in step S5. If the reagent distribution is uneven, the ORP and conductivity data detected by multiple sensors will show irregular deviations, causing the DS evidence theory fusion to fail and making it impossible to accurately determine the concentration factor.

[0077] Step S5's core function is to convert the preceding physical parameters into control commands. Based on the uniform concentration field established in step S4, this step compensates for the impact of reagent oxidation loss on conductivity through an ORP correction term (1 + 0.005 × ORP), and balances the alkalinity fluctuations caused by the high-alkalinity water replenishment in the first step through a pH correction term (1 + 0.01 × (pH - 9.0)). The final output concentration factor N is not only a numerical value, but also a comprehensive representation of the system's "salinity-reagent-oxidation environment" balance. When N ≥ 5.0, wastewater discharge is triggered, essentially by using the "salinity safety threshold" (chloride ions ≤ 20000 mg / L) established by all preceding steps to prevent material corrosion.

[0078] Step S6, with its wastewater discharge formula (B=E / (N-1)×correction term), precisely controls the "salt balance" from the preceding steps. E (evaporation rate) comes from the temperature difference data in step three, N (concentration factor) comes from the detection results in step five, and the correction term (including 90000-σ actual) is related to the salinity of the makeup water in step one. If the conductivity of the product water in step one deviates from 13.85-21.60 ms / cm, the correction term will dynamically adjust the wastewater discharge to offset the initial salinity deviation. Simultaneously, the hydraulic turbine recovers energy to drive the backwash pump, essentially converting the "energy loss" of the preceding steps into "system benefit." This cascaded energy utilization depends on the stable wastewater discharge flow rate in step five (fluctuation ±1 m³ / h); otherwise, the turbine output power will be unstable, and the backwash process will be easily interrupted.

[0079] Step S7, with its ΔP model (including the cumulative turbidity integral), is a response to the preceding "suspended solids load." The stable wastewater discharge flow in step six ensures a constant total amount of suspended solids entering the filter, while the low-turbidity makeup water from the first pretreatment step (mixed water turbidity < 3 NTU) reduces the initial concentration of suspended solids, making the change in ΔP over time predictable. When the ion concentration fluctuation in the filtered water exceeds 10%, short-circuit flow is investigated. This essentially involves reverse-checking the filtration efficiency using the conductivity data from step five. If the conductivity of the circulating water is stable but the filtered water fluctuates significantly, it indicates an abnormality in the filtration system, requiring timely intervention to ensure stable feed to the subsequent evaporation unit.

[0080] Step S8's core principle is to utilize the "stable cold source" of the preceding system to protect the equipment. The circulating water temperature (24-37℃) is controlled by the cooling tower in step three, while the water quality (chemical concentration, hardness) is achieved through the synergistic effect of steps four and one. Together, these ensure that the hot side of the plate heat exchanger is less prone to scaling (chemical scale inhibition + low hardness) and the cold side is less prone to corrosion (closed system + trace scale inhibitor). When the pump return water temperature is >38℃, the plate heat exchanger flow rate is adjusted. This essentially uses clean circulating water filtered in step seven to prevent a decrease in heat exchange efficiency due to blockage by suspended solids, thus ensuring the cooling reliability of precision equipment (centrifuges, endoscopes).

[0081] Step S9, with its orthogonal experimental design, verifies the preceding "system limit state." The temperature level (40-55℃) corresponds to the possible extreme operating conditions of the cooling tower in step three, the flow rate level (1-2 m / s) is related to the fluctuation range of the makeup water volume in step two, and the Cl⁻ concentration correction term comes from the pretreatment control in step one (initial value of 2121 mg / L). Through the corrosion rate formula, not only can the actual effectiveness of the agent in step four under high-salt environment be verified, but the parameter redundancy of each preceding step can also be deduced. If the corrosion rate is >0.06 mm / a under a certain operating condition, it indicates that there is room for optimization in the hardness control of step one or the agent addition in step four under that operating condition, providing data for setting the system safety boundary.

[0082] Step S10, through genetic algorithm optimization, represents the ultimate extraction of the "data value" from the preceding steps. The "water replenishment cost" in the objective function is related to the pretreatment energy consumption in step one and the pump energy consumption in step two; the "chemical cost" is related to the dosage in step S4 and the corrosion data in step S9; and the "steam savings" are related to the wastewater discharge and water replenishment salinity in step six (higher salinity results in lower steam consumption in the evaporator). Through a digital twin model, the discrete parameters of the physical system are transformed into continuously optimizable variables. The final output parameters are fed back to each step, achieving a leap from "passive adaptation" to "active optimization." If the model shows a low risk of corrosion in winter, the alkalinity can be increased by raising the pre-acidification water ratio in step one, and the concentration factor can be relaxed to 5.0 in step five, maximizing water-saving benefits while ensuring safety.

[0083] According to one embodiment of this application, the specific parameters of the high-salt operation system for zero-discharge circulating cooling water of concentrated brine are as follows:

[0084] Circulation unit: Actual circulating water circulation rate is 1100 m³ / h; cooling tower model is GFNL-1600; fan diameter is φ6000 mm; air volume is 10×10⁻⁶ m³ / h. 5 m³ / h; The circulating water pump model is KPS35-300, Q=1000m³ / h, H=45m, the impeller is 1.4460 duplex stainless steel, and the pump casing is HT250;

[0085] Water replenishment unit: The new water replenishment tank is made of PE material with a volume of 20 cubic meters (the old ozone preparation room has a 15 cubic meter water tank). The new water replenishment pump has a head of 30 meters and a flow rate of 35 cubic meters. The material is 304 stainless steel (the old ozone preparation room has a 21 cubic meter water pump).

[0086] Sewage discharge unit: The fiber filter utilizes idle equipment in the membrane workshop, requiring no relocation, only modification of the inlet water, backwash drainage and backwash inlet water pipes;

[0087] Dosing unit: The dosing tank has a volume of 2.5 cubic meters (PE material), and the dosing pump is a diaphragm metering pump with a flow rate of 50L / H and a head of 40 meters;

[0088] Online detection unit: The online detection instruments include a pH meter (measurement range 0-14) and a conductivity meter (measurement range 0-100000μs / cm). The closed sampling flow cell is installed between the circulating water supply and return water pipes next to the dosing device on the first floor of the evaporator.

[0089] Closed-loop cooling unit: The new plate heat exchanger is model BR18BH-0.8-11.7, with plate material SS304; the new circulating pump has a head of 21 meters and a flow rate of 20 cubic meters, and is installed in the open space next to the 12-meter-high water tank.

[0090] During operation, the permeate water from the high-efficiency membrane softening filter (conductivity 13.85-21.60 mS / cm) is introduced into the newly added makeup water tank before and after acid addition, and then pumped into the circulating water pool. The circulating water is cooled in the cooling tower and then pumped to various cooling equipment. An automatic dosing device continuously adds high-salt scale and corrosion inhibitors, and online monitoring instruments monitor water quality in real time. When the conductivity reaches approximately 90,000 mg / L, a blowdown is initiated. The discharged wastewater is filtered through a fiber filter and then enters the evaporation system. The closed-loop cooling unit provides clean cooling water to pumps and other equipment to ensure their normal operation.

[0091] According to one embodiment of this application, the system includes a circulating water device, which mainly provides cooling water for the pumps, surface coolers, and built-in cameras of the zero-emission evaporator. The designed circulating water treatment capacity is 1600 m³ / h, with an actual operating circulation volume of 1100 m³ / h. The circulating water inlet pressure is 0.45 MPa, and the return water pressure is 0.30 MPa. In summer, the circulating water inlet temperature is 29℃ and the return water temperature is 37℃; in winter, the circulating water inlet temperature is 24℃ and the return water temperature is 32℃. The cooling tower structure is a steel structure counter-flow mechanical ventilation packed cooling tower. The tower frame is made of Q235B hot-dip galvanized steel, and the tower enclosure panels are made of flame-retardant fiberglass. The air duct is made of flame-retardant fiberglass (kinetic energy recovery type), with a service life of 30 years. Air duct connections and fasteners are made of S30408 ​​stainless steel. The water collection tank is a reinforced concrete tank with asphalt anti-corrosion coating on the concrete surface inside. The circulating water piping is made of carbon steel, and the circulating water pumps are Kenfulai double-suction single-stage centrifugal pumps with 2205 stainless steel impellers and cast iron pump casings and covers. The circulating water surface cooler shell side is made of Q345 steel, and the tube side end caps are made of 304 stainless steel. A portion of the low-hardness, high-salt water (conductivity approximately 21000 mg / L) treated by the high-efficiency membrane softening filter is sent to DTRO for concentration, while the remainder directly replaces the original recycled water as makeup water for the circulating cooling water system. Utilizing the evaporation of the circulating cooling water, high-salt water concentration and volume reduction are achieved, replacing traditional membrane concentration systems. To prevent corrosion and scaling in circulating water equipment, several patented technologies, including high-salt scale and corrosion inhibitors and intelligent monitoring and control, are employed in the circulating water system. Even under conditions of high salt concentrations (60,000-90,000 mg / L) and chloride ion concentrations (10,000-20,000 mg / L), the corrosion rate and fouling thermal resistance meet national standards (carbon steel ≤0.075 mm / a, stainless steel ≤0.005 mm / a, copper ≤0.005 mm / a), ensuring safe, stable, and long-term operation of the circulating water under high-salt conditions. Finally, the concentrated salt wastewater, after passing through a filter to remove suspended solids, directly enters the multi-effect evaporator, achieving water conservation and reduced energy consumption in high-salt operation. This treatment process eliminates the complex membrane treatment process, making operation simpler, more water-efficient, and more energy-efficient, significantly reducing water treatment costs.

[0092] According to one embodiment of this application, the parameters of the high-salt operation system for zero-discharge circulating cooling water with concentrated brine are as follows:

[0093] 1. High-efficiency membrane softening filter produces high-quality water.

[0094]

[0095] 2. Parameters of the circulating cooling water system

[0096]

[0097] 3. The makeup water volume, evaporation volume, and sewage discharge volume of the high-salt circulating water system.

[0098]

[0099] Based on the current operating temperature difference, the unit can save 149,000 cubic meters of make-up water (recycled water) per year, reduce the water intake of the evaporator by 111,000 cubic meters per year, and save 46,620 tons of low-pressure steam per year based on the current steam consumption per ton of water in the evaporator.

[0100] According to one embodiment of this application, the process of the high-salt operation method for zero-discharge circulating cooling water with concentrated brine includes: water produced by a high-efficiency membrane filter softener is led to the circulating water makeup tank from before and after acid addition, and then pumped into the circulating water pool. The water is concentrated by evaporation in the circulating water. After reaching the set concentration ratio, the circulating water begins to discharge wastewater. The discharged wastewater passes through a fiber filter and is then sent to the DTRO concentrate tank, where it enters the multi-effect evaporator through the original system. An automatic dosing device and pH adjustment equipment are added to the circulating water system, and online water quality monitoring is added to detect indicators such as conductivity, pH value, and turbidity. Analysis and recording are performed through an intelligent cloud platform for circulating water, allowing for timely adjustments to the water quality.

[0101] The following are the circulating water control indicators:

[0102]

[0103] According to one embodiment of this application, the cooling tower used in the high-salt operation method of zero-discharge circulating cooling water for concentrated brine is as follows: Figure 2 As shown, the existing pipelines for the pumps, centrifuges, and camera cooling water supply do not need to be added. However, the return water pipelines need to be completely re-routed. Since the elevated water tank is currently placed on a 12-meter platform, all newly added closed-loop pumps and plate heat exchangers will be installed in the open space next to the 12-meter elevated water tank. The system will use primary water for makeup water; the makeup water system is as follows... Figure 3 As shown, the makeup water source was changed to high-efficiency membrane softening permeate, reducing both recycle water consumption and the amount of low-concentration brine entering the evaporator. In this experiment, the alkalinity and pH of the circulating water were controlled at a relatively high level. To reduce investment in the modification of the dosing facilities and to facilitate management, the makeup water for the experimental circulating water was drawn from both before and after the high-efficiency membrane softening permeate acidification pipeline mixer and fed into the newly added makeup water tank. The newly added makeup water pump then used the original recycled water makeup water pipeline to replenish the circulating water pool. The sewage system is as follows: Figure 4 As shown, the TDS of the circulating water is planned to be increased to 90,000 mg / L. Therefore, the circulating water wastewater will not be concentrated and can be discharged to the evaporator for treatment. Considering that the experimental circulating water is from an open circulating water cooling tower, and that there is significant seasonal wind and sand, which may lead to a higher level of turbidity and impurities in the circulating water, to avoid impurities affecting the quality of the salt product, the circulating water wastewater will be filtered using an existing idle fiber filter in the membrane workshop before being sent to the evaporator. The simulated heat exchanger used is as follows: Figure 5 As shown, the heat exchange equipment in the evaporative circulating water system, apart from the pump cooling water, consists of only one stainless steel surface cooler. To facilitate observation of the corrosion of carbon steel materials by high-salt operation of circulating water under hot conditions, a carbon steel simulated heat exchanger is installed in the circulating water system. The simulated heat exchanger is made of Q345 steel, and the tube diameter is ∅19. In winter, the heat source for the heat exchanger is the exhaust gas from the pipe gallery heating. In summer, after the pipe gallery heating is stopped, the heat source utilizes the low-pressure steam condensate from the first effect. All the generated condensate is recycled to the condensate return pipe and sent to the recycled water tank.

[0104] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for zero-discharge circulating cooling water operation in high-salinity environments, characterized in that: Includes the following steps: S1: The steps for pretreatment and dynamic proportioning control of permeate water from high-efficiency membrane softening are as follows: 48 hours before the start of the experiment, the permeate water from the high-efficiency membrane softening filter is continuously monitored for 24 hours, and the fluctuation curves of total hardness, calcium ions, and total alkalinity are recorded. The optimal mixing ratio of permeate water before and after acid addition is calculated by PID algorithm. A dynamic proportioning model is established based on the water quality fluctuation curve. Real-time adjustment is achieved by linkage of electromagnetic flowmeter with an accuracy of ±0.5% and electric regulating valve with a response time of less than 1 second. An online turbidity meter and pH sensor are installed in the water tank. When the turbidity of the mixed water is greater than 3 NTU, the drain valve at the bottom of the water tank is opened for 10 minutes to drain the water. When the pH value deviates from the range of 8.5-9.0, compensation is made by the bypass fine-tuning valve of the mixer in the acid addition pipeline to ensure that the fluctuation range of the water quality entering the water tank is controlled within ±5%, which lays the foundation for the stability of subsequent water replenishment. S2: Steps for variable parameter closed-loop control and energy consumption optimization of the water replenishment system. When the level of the newly added water replenishment tank reaches 80% and the water quality meets the standards, the water replenishment system is started. A variable parameter algorithm based on model predictive control is used to adjust the operation of the water replenishment pump. The level of the circulating water tank, conductivity, and ambient temperature are used as input variables. The water replenishment demand for the next hour is predicted based on historical data. When the ambient temperature is greater than 30℃ in summer, the frequency of the water replenishment pump is increased to 45Hz 15 minutes in advance. When the temperature is less than 5℃ in winter, the water replenishment is delayed until the level drops to 1.6m. A pressure-flow composite sensor is installed at the outlet of the water replenishment pump to collect data in real time and substitute it into the energy consumption formula. ； Where E is energy consumption in kWh, Q is flow rate in m³ / h, H is head in m, ρ is water density of 1000 kg / m³, t is time, and η is pump efficiency of 65-80%. When the unit water replenishment energy consumption is greater than 0.3 kWh / m³, the system automatically switches to standby pump B to ensure that the water replenishment system meets the water demand while minimizing energy consumption. This step depends on the stable water quality after the previous pretreatment, and its output water replenishment parameters provide input conditions for the initial operation of the circulating water system. S3: Steps for multivariate coordinated control and evaporation efficiency improvement of the circulating water system. After the water replenishment system has been running stably for 30 minutes, the circulating water system is started. A ternary regression model of circulating flow rate, cooling tower inlet water temperature, and fan speed is established using a multivariate coordinated control algorithm of flow rate, temperature, and fan speed. ； Where T_drop is the temperature drop in °C, Q is the circulation flow rate in m³ / h, V is the wind speed in m / s, and T_in is the inlet water temperature in °C. The system is equipped with an ultrasonic flow meter and an infrared thermometer, which collect data every 5 seconds and compare it with the model prediction value. When the deviation is >0.5℃, the model parameters are automatically corrected to ensure that the circulating water can maintain an actual temperature difference of 7-8℃ in different seasons, providing a stable evaporation rate for subsequent high-salt concentration. S4: Steps for dynamic dosing and concentration field uniformity control of high-salt scale and corrosion inhibitors. After the circulating water system has been running continuously for 1 hour and the parameters have stabilized, the automatic dosing system is started. The dosing strategy is optimized by concentration field simulation based on computational fluid dynamics. The turbulence intensity distribution in the circulating water return pipe network is simulated by CFD. The agent dosing port is set in the pipe section with turbulence intensity >15m² / s². The dosing amount calculation formula introduces multi-factor correction terms: ; Where Q is the flow rate of the dosing pump; C target is the target concentration of the agent in the circulating water; V circulation is the total volume of the circulating water system; K safety is the safety factor; ΔT is the temperature difference of the circulating water; ΔCl⁻ is the chloride ion deviation; τ is the time variable; the integral term is the agent attenuation correction, considering the accelerated attenuation under high salinity conditions; the quadratic term τ² is the nonlinear attenuation coefficient; t is the single dosing time; ρ agent is the agent density; and η is the effective utilization rate of the agent. S5: Steps for multi-dimensional data fusion and intelligent decision-making in the online detection system. After the dosing system is running stably, the online detection unit enters closed-loop control mode. Multi-sensor data fusion technology is used to improve detection reliability. Three detection points are arranged at the inlet, middle, and outlet of the circulating water return network. Each point is equipped with a four-parameter sensor for pH, conductivity, ORP, and turbidity. The data from the three points are fused using DS evidence theory. When the deviation between the single-point data and the fused result is >5%, it is automatically marked as abnormal and backup sensor data is activated. A multi-parameter correction model is introduced for the concentration factor calculation. ； Where N is the concentration factor; σ is the conductivity of the circulating water; σ_makeup water is the conductivity of the makeup water; ORP is the oxidation-reduction potential; pH is the pH value of the circulating water; τ is the operating time; the integral term is the long-term operation correction; the cubic term τ³ is used to compensate for the nonlinear effect of salting out; and 0.05 is the temperature correction coefficient. S6: The steps for dynamic flow regulation and energy recovery of the sewage discharge system are as follows: When the online detection system determines that sewage discharge is required, the dynamic regulation program of the sewage discharge unit is activated. The sewage discharge strategy is optimized by combining real-time evaporation data. The actual evaporation is calculated in real time using ultrasonic level gauges and steam flow meters installed in the cooling tower water collection tank. ； Where E is the actual evaporation rate; k is a coefficient; Q is the circulating water flow rate; Treturn is the cooling tower return water temperature; Tin is the cooling tower inlet water temperature; and r is the latent heat of vaporization of water. Substituting these values ​​into the wastewater discharge formula: ； Where B is the sewage discharge volume; N is the concentration factor; σ is the actual conductivity of the circulating water, in μs / cm. When the conductivity is below 90,000, sewage discharge is reduced. The correction coefficient is a linear adjustment term. When the conductivity is below 90,000, sewage discharge is reduced. The sewage discharge electric valve adopts frequency conversion control. In the initial stage of opening, sewage is discharged quickly at the maximum flow rate of 40m³ / h. When the conductivity drops to 85,000μs / cm, it switches to PID regulation mode. A small hydraulic turbine is installed in the sewage discharge pipeline. The recovered energy is used to drive the fiber filter backwash pump. When the turbine output power is >0.5kW, the backwash power source is automatically switched to achieve energy cascade utilization. S7: Steps for adaptive backwashing and performance monitoring of the wastewater filtration system. After the wastewater enters the fiber filter, the system activates the adaptive backwashing control algorithm, dynamically adjusting the backwashing cycle based on changes in filtration resistance and water quality, and establishing a model relating the filter inlet and outlet pressure difference to the filtration time. ； Where ΔP is the pressure difference between the filter inlet and outlet; t is the filtration time; the integral term is the cumulative turbidity; when ΔP > 0.1 MPa or the integral turbidity > 50 NTU·h, the backwashing procedure is triggered. The backwashing process consists of three stages: air washing, air-water mixed washing, and water washing. The backwashing water volume is precisely controlled by a flow meter. A turbidity meter is installed in the backwash drainage. When the drainage turbidity is < 10 NTU, the backwashing is terminated early. An online ion chromatograph is installed in the filtered water pipeline to monitor the concentrations of Na⁺, Ca²⁺, and Cl⁻ in real time. When the ion concentration fluctuation is > 10%, the flow data of the sewage system is automatically correlated to check for short-circuit flow and ensure the stability of the water quality entering the DTRO concentrate tank. S8: Steps for performing dual-circulation temperature difference matching and anti-scaling control of the closed-loop cooling system. After the circulating water system and the sewage system are running stably, the closed-loop cooling unit starts temperature difference matching control to establish a balance model of equipment cooling demand. By adjusting the speed of the newly added circulating pump, the cold side outlet temperature of the plate heat exchanger is stabilized. When the pump return water temperature is >38℃, the bypass valve of the equipment cooling water pipeline is opened, and the hot side flow of the plate heat exchanger is increased. Dynamic balance is achieved through temperature-flow coupling control. The closed-loop cooling system uses primary water for makeup water. A conductivity meter is installed. When the conductivity is >300μs / cm, the sewage valve is opened for replacement. At the same time, a trace amount of scale inhibitor is added to prevent scaling of the plate heat exchanger. The heat source of the hot side of the system comes from the circulating water system. Its stable operation depends on the temperature and flow parameters of the circulating water to provide reliable cooling for the equipment. S9: Steps for multi-condition corrosion monitoring and data inversion of the simulated heat exchanger: After the circulating water system has been running stably for 72 consecutive hours, the simulated heat exchanger enters the multi-condition test mode. An orthogonal experimental design is used to cover key parameter combinations, setting 4 temperature levels and 3 flow rate levels. Each condition is run for 24 hours. A correlation model is established between the corrosion amount of the fins and the corrosion current density monitored by the electrochemical workstation. ; Where V is the corrosion rate; k is the conversion coefficient; Icorr is the corrosion current density; τ is the time variable; Cl⁻ is the chloride ion concentration; and t is the operating time. The specimens were analyzed using a combination of weight loss method and scanning electron microscopy. The weight loss data was substituted into the formula to calculate the average corrosion rate. SEM was used to observe the corrosion morphology to determine whether there was localized corrosion. After each operating condition, circulating water samples were collected from the inlet and outlet of the heat exchanger to detect the residual concentration of the reagent and the content of metal ions. The effectiveness of the previous dosing system was inverted. When the corrosion rate under a certain operating condition is >0.06mm / a, it is automatically marked as high risk and the reagent concentration is increased in a targeted manner in subsequent dosing. S10: This step involves performing full-system digital twin modeling and parameter optimization. A digital twin model is built daily based on the operational data from each step, achieving real-time mapping between the physical system and the virtual model. The model includes three dimensions: equipment layer, parameter layer, and performance layer. Real-time data is collected via the OPC UA protocol. A Kalman filter algorithm is used to correct model biases, and a genetic algorithm is employed to optimize key parameters. The objective function is: ; Where J is the comprehensive objective function; water replenishment cost is the water fee per unit of water replenishment; reagent cost is the cost per unit of reagent consumption; steam saving is the amount of steam reduction compared to the traditional system; corrosion risk index is the normalized index of corrosion rate relative to the standard value; the constraints are corrosion rate ≤ 0.075 mm / a and concentration factor ≤ 5.

0. The optimization results generate an operation manual.

2. The method for zero-discharge circulating cooling water operation with concentrated brine according to claim 1, characterized in that, In step S1, when establishing a dynamic ratio model based on the water quality fluctuation curve, if the alkalinity of the produced water before acid addition is greater than 180 mg / L, its ratio is automatically reduced to 2:1 before acid addition and 4:1 after acid addition; otherwise, it is increased to 4:

1.

3. The method for zero-discharge circulating cooling water operation with concentrated brine according to claim 1, characterized in that, In step S3, the ternary regression model is solved in real time by the PLC and control commands are output. In summer, when the temperature drop is less than 8°C, the fan frequency is increased to 50Hz first. If it still does not meet the standard, the speed of the circulating water pump is increased.

4. The method for zero-discharge circulating cooling water operation with concentrated brine according to claim 1, characterized in that, In step S3, the ternary regression model is solved in real time by the PLC and control commands are output. When the temperature drop in winter is greater than 9°C, the fan frequency is reduced to 25Hz, and the temperature difference regulating valve at the inlet and outlet of the cooling tower is opened to reduce heat dissipation by bypassing 30% of the circulating water.

5. The method for zero-discharge circulating cooling water operation with concentrated brine according to claim 1, characterized in that... In step S4, the quadratic term τ² is used to correct for the accelerated decay of the agent in a high-salt environment. The integration interval is t=2h. A static mixer is installed in the dosing pipeline, and a sampling point is set at 5D downstream. The agent concentration is detected every 15 minutes. The concentration accuracy of ±1mg / L is achieved by controlling the pulse width modulation of the dosing pump. When the flow rate of the circulating water system fluctuates by more than 10%, the concentration field is automatically re-simulated, and the frequency of the dosing pump is adjusted to compensate for the flow rate change, ensuring that the standard deviation of the agent concentration distribution in the pipeline network is <3mg / L.

6. The method for zero-discharge circulating cooling water operation with concentrated brine according to claim 1, characterized in that, In step S5, the cloud platform uses an LSTM neural network to predict the concentration factor change in the next 2 hours. When the predicted value is >5.2, a sewage discharge warning is issued 30 minutes in advance. A water quality equipment status correlation model is established. When the turbidity is >8 NTU and the ORP is <200 mV, it is determined to be a risk of microbial growth, and the biocide dosage is automatically increased.

7. The method for zero-discharge circulating cooling water operation with concentrated brine according to claim 1, characterized in that, In step S8, the cold side outlet temperature of the plate heat exchanger is stabilized at 30±1℃.

8. The method for zero-discharge circulating cooling water operation with concentrated brine according to claim 1, characterized in that... In step S9, the four temperature levels are 40℃, 45℃, 50℃, and 55℃, and the three flow rate levels are 1m / s, 1.5m / s, and 2m / s.

9. The method for zero-discharge circulating cooling water operation with concentrated brine according to claim 1, characterized in that, The operating instructions in step S10 include the following: In summer, the concentration factor should be controlled at 4.8 to balance water conservation and corrosion risk, and in winter, it should be increased to 5.0 to reduce sewage discharge. The model should be validated weekly. When the deviation between the actual operating data and the model prediction is greater than 5%, the model parameters should be retrained to ensure that the digital twin model can accurately guide the actual operation.

10. A high-salinity circulating cooling water system with zero discharge of concentrated brine, characterized in that: The high-salt operation method of concentrated brine zero-discharge circulating cooling water as described in any one of claims 1 to 9 was used.

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