PH value control system applied to circulating water supplementing system

Abstract

The invention discloses a pH value control system applied to a circulating water supplementing system. The system comprises a first pH sensor, a first PID controller, a first selector, a second PID controller and a second selector, the first pH sensor is arranged on a pipeline connected between the second acid adding point and the circulating cooling water system; the second PID controller is used for calculating a second candidate frequency value according to a first current pH value collected by the first pH sensor and a target pH value when the second acid adding equipment is in a starting state, and outputting the second candidate frequency value to the second selector; the second selector is used for selecting the first preset frequency value as a second target frequency value if a water replenishing trigger signal of the boiler make-up water treatment system is received, otherwise, selecting the second candidate frequency value as the second target frequency value, and then outputting the second target frequency value to second acid adding equipment; the second acid adding equipment is used for adding the acid liquid according to the second target frequency value. The water quality of circulating water can be kept stable.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of circulating water makeup water, and more specifically, to a pH control system applied to a circulating water makeup water system. Background Art

[0002] The circulating water make-up water system of a thermal power plant is an important component to ensure the safe and economical operation of the power plant. Its core function is to provide a continuous, stable and water quality-compliant make-up water source for the circulating cooling water system to compensate for water loss (such as evaporation, wind, sewage, leakage, etc.) and water quality deterioration during the circulation process, maintain the water balance of the circulating cooling water system, ensure power generation efficiency and cooling capacity, and ensure efficient and safe operation of the units.

[0003] In addition to the circulating cooling water system, the circulating water make-up water system is also usually connected to other water use systems (such as the boiler feed water treatment system) to meet the water quality and water quantity requirements of different production links. The boiler feed water treatment system is a key link to ensure the safe and efficient operation of the boiler. Its main function is to remove impurities such as suspended matter, colloids, dissolved salts, organic matter, etc. in the raw water, so that the treated water quality meets the water quality standards of boiler feed water, thereby preventing boiler scaling, corrosion and steam quality degradation. Its water demand is an intermittent demand that is dynamically triggered according to the operating status of the boiler, steam consumption, and system water loss. Therefore, when the boiler feed water treatment system initiates a water demand, the flow rate may be instantly too large due to the surge in water demand, exacerbating pH fluctuations and affecting water quality stability. Summary of the Invention

[0004] In order to solve one or more of the above-mentioned technical problems, the present invention provides a pH control system for a circulating water make-up water system. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0005] A pH control system for a circulating water makeup water system, the circulating water makeup water system comprising a crystallization and granulation fluidized bed, a clarifier, a first acid addition device, and a second acid addition device; the crystallization and granulation fluidized bed is connected to a makeup water source and the clarifier, respectively, and the clarifier is connected to a circulating cooling water system and a boiler feed water treatment system, respectively; a first acid addition point is provided on a pipeline connecting the crystallization and granulation fluidized bed and the clarifier, and the first acid addition point is connected to the first acid addition device; a second acid addition point is provided on a pipeline connecting the clarifier and the circulating cooling water system, and the second acid addition point is connected to the second acid addition device; the first acid addition device and the second acid addition device serve as backup for each other;

[0006] The pH control system includes a first pH sensor, a first PID controller, a first selector, a second PID controller, and a second selector; the first pH sensor is provided on a pipe connecting the second acid addition point and the circulating cooling water system; the first PID controller is connected to the first pH sensor and the first selector, respectively, and the first selector is connected to the first acid addition device; the second PID controller is connected to the first pH sensor and the second selector, respectively, and the second selector is connected to the second acid addition device;

[0007] The first PID controller is configured to calculate a first candidate frequency value according to a first current pH value and a target pH value collected by the first pH sensor when the first acid adding device is in a startup state, and output the first candidate frequency value to the first selector;

[0008] The first selector is configured to select a first preset frequency value as a first target frequency value if a water replenishment trigger signal from the boiler feed water treatment system is received, and otherwise select the first candidate frequency value as the first target frequency value, and then output the first target frequency value to the first acid addition device, so that the first acid addition device adds acid according to the first target frequency value;

[0009] The second PID controller is configured to calculate a second candidate frequency value based on a first current pH value and a target pH value collected by the first pH sensor when the second acid addition device is in a startup state, and output the second candidate frequency value to the second selector;

[0010] The second selector is configured to select the first preset frequency value as the second target frequency value if a water replenishment trigger signal from the boiler feed water treatment system is received, otherwise select the second candidate frequency value as the second target frequency value, and then output the second target frequency value to the second acid adding device so that the second acid adding device adds acid according to the second target frequency value.

[0011] The system provided by the present invention forms a spatially distributed control between the first acid addition point (outlet of the crystallization and granulation fluidized bed) and the second acid addition point (outlet of the clarifier) ​​by setting a first acid addition point and a second acid addition point as backup for each other, thereby reducing the risk of system downtime due to failure of a single device, achieving uninterrupted operation of the system, and significantly improving the fault tolerance of the system. When a water replenishment trigger signal is received from the boiler feed water treatment system, a selector selects a preset frequency value as a target frequency value to cope with the impact that a large amount of water replenishment may have on the pH value of the circulating water, facilitating rapid adjustment of the acid dosage during the water replenishment process and maintaining the balance and stability of the circulating water quality. A first PID controller and a second PID controller respectively calculate candidate frequency values ​​based on the current pH value and the target pH value collected by the first pH sensor to accurately control the dosage frequencies of the first and second acid addition devices. The system can dynamically adjust the acid dosage based on real-time water quality data, can quickly respond to changes in water quality, and promptly adjust the acid dosage to keep the pH value of the circulating water within the target range, thereby improving the response speed and efficiency of the system.

[0012] In a possible implementation, a first handheld operator is connected between the first PID controller and the first selector;

[0013] The first handheld operator is configured to receive the first candidate frequency value output by the first PID controller; select the third candidate frequency value as the first frequency value to be output if a first manual switching trigger signal for instructing to switch from the automatic mode to the manual mode is received, and otherwise select the first candidate frequency value as the first frequency value to be output; and output the first frequency value to be output to the first selector;

[0014] The first PID controller is further configured to receive a state value of an operating mode output by the first handheld operator; track the first candidate frequency value when the first handheld operator switches from the automatic mode to the manual mode; and track the third candidate frequency value when the first handheld operator switches from the manual mode to the automatic mode; and / or

[0015] A second handheld operator is connected between the second PID controller and the second selector;

[0016] The second handheld operator is configured to receive the second candidate frequency value output by the second PID controller; select the fourth candidate frequency value as the second frequency value to be output if a second manual switching trigger signal for instructing to switch the automatic mode to the manual mode is received, and otherwise select the second candidate frequency value as the second frequency value to be output; and output the second frequency value to be output to the second selector;

[0017] The second PID controller is also used to receive the status value of the working mode output by the second handheld operator; when the second handheld operator is switched from the automatic mode to the manual mode, track the second candidate frequency value; and when the second handheld operator is switched from the manual mode to the automatic mode, track the fourth candidate frequency value.

[0018] In a possible implementation, the pH control system further includes a first manual switching module connected to the first hand operator;

[0019] The first manual switching module is configured to output the first manual switching trigger signal to the first handheld operator when at least one of a first manual switching condition, a second manual switching condition, a third manual switching condition, and a fourth manual switching condition is met;

[0020] Wherein, the first manual switching condition is that the absolute value of the error between the first feedback frequency value returned by the first acid adding device and the first target frequency value is greater than a first preset value;

[0021] The second manual switching condition is that the first acid adding equipment protection trips;

[0022] The third manual switching condition is that the first acid adding device is in a stopped state;

[0023] The fourth manual switching condition is that the first handheld operator is in the manual mode and the water supply valve between the clarifier and the boiler feed water treatment system is in an open state; and / or,

[0024] The pH control system further includes a second manual switching module connected to the second hand operator;

[0025] The second manual switching module is configured to output the second manual switching trigger signal to the first handheld operator when at least one of a fifth manual switching condition, a sixth manual switching condition, a seventh manual switching condition, and an eighth manual switching condition is met;

[0026] The fifth manual switching condition is that the absolute value of the error between the second feedback frequency value returned by the second acid adding device and the second target frequency value is greater than a second preset value;

[0027] The sixth manual switching condition is that the second acid adding equipment protection trips;

[0028] The seventh manual switching condition is that the second acid adding device is in a stopped state;

[0029] The eighth manual switching condition is that the second hand operator is in manual mode and the water supply valve between the clarifier and the boiler feed water treatment system is in an open state.

[0030] In a possible implementation, the pH control system further includes a water replenishment trigger module; the water replenishment trigger module includes:

[0031] a demand submodule, configured to receive the operating mode status values ​​output by the first hand operator and the second hand operator; and output a water supply demand signal when the first hand operator or the second hand operator is in the manual mode and the water supply valve between the clarifier and the boiler feed water treatment system is in the open state;

[0032] The delay submodule is configured to output the water replenishment trigger signal to the first selector or the second selector if the water replenishment demand signal output by the demand submodule meets a preset delay condition.

[0033] In a possible implementation, the pH control system further includes a first delay module connected to the first pH sensor and the first PID controller respectively;

[0034] The first delay module is used to delay the input first current pH value for a first preset period and output it to the first PID controller; and / or,

[0035] The pH control system further comprises a second delay module connected to the first pH sensor and the second PID controller respectively;

[0036] The second delay module is used to delay the input first current pH value for a second preset period and output it to the second PID controller.

[0037] In a possible implementation, the circulating water make-up water system further includes a main alkali adding device and a backup alkali adding device for adding alkali solution to the crystallization granulation fluidized bed; the pH value control system further includes a second pH sensor provided at the crystallization granulation fluidized bed and a third PID controller connected to the second pH sensor;

[0038] The third PID controller is used to calculate a standby frequency value based on the second current pH value collected by the second pH sensor and the target pH value when the standby alkali adding equipment is in the startup state, and use the standby frequency value as the third target frequency value, and output the third target frequency value to the standby alkali adding equipment, so that the standby alkali adding equipment adds alkali solution according to the third target frequency value.

[0039] In a possible implementation, a third handheld operator is connected between the third PID controller and the standby alkali adding device;

[0040] The third handheld operator is configured to receive the standby frequency value output by the third PID controller; if a third manual switching trigger signal for instructing to switch from the automatic mode to the manual mode is received, select the set frequency value as the third target frequency value; otherwise, select the standby frequency value as the third target frequency value; and output the third target frequency value to the standby alkali adding device;

[0041] The third PID controller is also used to receive the status value of the working mode output by the third hand operator; when the third hand operator is switched from the automatic mode to the manual mode, track the standby frequency value; and when the third hand operator is switched from the manual mode to the automatic mode, track the set frequency value.

[0042] In a possible implementation, the third hand operator is further configured to switch the automatic mode to the manual mode when the standby alkali adding device is in a stopped state.

[0043] In a possible implementation, the pH control system further includes a third delay module connected to the second pH sensor and the third PID controller respectively;

[0044] The third delay module is used to delay the second current pH value collected by the second pH sensor for a third preset period and output it to the third PID controller.

[0045] In a possible implementation, the clarification tank includes a coagulation tank, a flocculation tank, and an inclined tube clarification zone connected in sequence. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an illustrative and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0047] Figure 1 This is a structural block diagram of a circulating water make-up water system according to an embodiment of the present invention;

[0048] Figure 2 This is a structural block diagram of a pH control system according to an embodiment of the present invention;

[0049] Figure 3 This is a logic control block diagram of a pH value control system with a first handheld operator added according to an embodiment of the present invention;

[0050] Figure 4 This is a logic control block diagram of a pH control system with a second handheld controller added according to an embodiment of the present invention;

[0051] Figure 5 This is a DCS logic control diagram of the water replenishment trigger module according to an embodiment of the present invention;

[0052] Figure 6 This is a structural block diagram of another circulating water make-up water system according to an embodiment of the present invention;

[0053] Figure 7 This is a structural block diagram of another pH control system according to an embodiment of the present invention;

[0054] Figure 8 This is a logic control block diagram of a pH value control system with a third handheld operator added according to an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The following will be combined with the accompanying drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the embodiments described are part of the embodiments of the present disclosure, not all of them. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present disclosure.

[0056] Figure 1 This is a structural block diagram of a circulating water replenishment system 100 provided in this embodiment. Figure 1 As shown, the circulating water make-up water system 100 includes a crystallization and granulation fluidized bed 101, a clarifier 102, a first acid addition device 103, and a second acid addition device 104. The water inlet of the crystallization and granulation fluidized bed 101 is connected to the water outlet of the make-up water source 300, and the water outlet of the crystallization and granulation fluidized bed 101 is connected to the water inlet of the clarifier 102; the clarifier 102 is connected to the circulating cooling water system 400 and the boiler feed water treatment system 500, respectively; a first acid addition point A is provided on the pipeline connecting the water outlet of the crystallization and granulation fluidized bed 101 and the water inlet of the clarifier 102, and the first acid addition point A is connected to the first acid addition device 103; a second acid addition point B is provided on the pipeline connecting the water outlet of the clarifier 102 and the water inlet of the circulating cooling water system 400, and the second acid addition point B is connected to the second acid addition device 104.

[0057] In this embodiment, the supplementary water source 300 can be selected by comprehensively considering water quality, cost, availability and environmental protection requirements. The supplementary water source 300 generally comes from urban tap water, surface water, groundwater, recycled water, rainwater, seawater, etc.

[0058] The circulating cooling water system 400 includes a cooling tower, a circulating water pump, a heat exchange device, a side filter and a dosing device, and the outlet of the clarifier 102 is connected to the water pool of the cooling tower.

[0059] Clarification tank 102 includes a coagulation tank, a flocculation tank, and an inclined tube clarification zone, which are connected in sequence. A coagulant is added to the coagulation tank to destabilize the colloidal particles, forming tiny flocs. A coagulant aid is added to the flocculation tank to further aggregate the tiny flocs, forming large, dense flocs that facilitate subsequent sedimentation or filtration. The synergistic effect of the coagulation and flocculation tanks achieves destabilization, aggregation, and sedimentation of the colloidal particles. The inclined tube clarification zone utilizes tilted tubular or plate-shaped components, utilizing the principle of shallow sedimentation to optimize the sedimentation process. This significantly improves water treatment efficiency by optimizing water flow and solid-liquid separation efficiency.

[0060] A portion of the clarified water from clarifier 102 flows by gravity into an underground clear water tank, where it is pumped to the boiler feed water treatment system 500's water tank and other system water points. The remaining portion flows by gravity to replenish the cooling tower tank of the circulating cooling water system 400. The sludge produced in clarifier 102 is partially returned to the flocculation tank via a sludge pump to maintain a high concentration of suspended solids in the flocculation zone and enhance flocculation efficiency. The remaining sludge is discharged into the existing sludge thickening tank. The concentrated sludge is then pumped to a sludge dewatering machine for dewatering and transported.

[0061] The filtrate water produced by the sludge dewatering machine is recycled to the newly built recycling water area recovery pool, and the backwash water of the PCF filter in the zero-discharge workshop and the backwash water of the ultrafiltration are recycled to the original recycling water pool of the workshop. The water in the recycling pools of the two workshops is pumped to the high-efficiency clarification tank 102 for circulating water make-up water for coagulation and clarification treatment, and then reused in the circulating cooling water system 400.

[0062] The circulating water make-up water system 100 and the circulating water sewage system can be arranged in the same area, and the repeated dosing and sludge storage and dehydration systems of the two systems can be designed and arranged together.

[0063] When the circulating water make-up water system 100 encounters abnormal operating conditions and the turbidity of the effluent from the high-efficiency clarifier 102 is greater than 5NTU, part of the effluent from the high-efficiency clarifier 102 (2100t / h) enters the filter of the bypass system for filtration, and the filtered water is mixed with the effluent from other high-efficiency clarifiers 102 (400t / h) to ensure that the turbidity index of the effluent from the entire circulating water make-up water system 100 meets 5NTU.

[0064] The first acid addition point A is located downstream of the crystallization granulation fluidized bed 101, and is generally designed on the water inlet pipe entering the clarification tank 102, so that the acid (such as sulfuric acid) and the inlet water are fully mixed in the pipe. By preferentially adjusting the surface chemical environment of the microcrystalline particles, the solid-liquid separation efficiency of the subsequent clarification tank 102 can be simultaneously improved, and the synergistic optimization of water softening and pH adjustment can be achieved. In addition, the scaling of high-hardness water in the clarification tank 102 can be reduced, thereby extending the life of the equipment.

[0065] The second acid addition point B is located downstream of the clarifier 102 and is generally designed on the water inlet pipe entering the cooling tower water pool. It can utilize the pH buffering capacity of the clarifier 102 to reduce the amount of acid used. It can also avoid the precipitation of scale such as calcium carbonate and calcium phosphate caused by excessively high pH (>9.0) and prevent the corrosion of metal pipes caused by excessively low pH (<7.0).

[0066] It should be noted that Figure 1 The arrow symbol in the figure represents the water pipeline, and the direction of the arrow represents the direction of water flow.

[0067] Figure 2 This embodiment provides an application for Figure 1 The structure block diagram of the pH value control system 200 of the circulating water replenishment water system 100 is shown. Figure 2 As shown, the pH control system 200 includes a first pH sensor 201, a first PID controller 202, a first selector 203, a second PID controller 204 and a second selector 205; the first pH sensor 201 is arranged on the pipeline connecting the second acid addition point B and the circulating cooling water system 400; the first PID controller 202 is connected to the first pH sensor 201 and the first selector 203 respectively, and the first selector 203 is connected to the first acid addition device 103; the second PID controller 204 is connected to the first pH sensor 201 and the second selector 205 respectively, and the second selector 205 is connected to the second acid addition device 104.

[0068] It should be noted that Figure 2 The circulating water makeup water system 100 shown retains only the first acid addition device 103 and the second acid addition device 104 , while omitting other devices.

[0069] In this embodiment, the first acid adding device 103 and the second acid adding device 104 are acid dosing pumps. The first acid adding device 103 and the second acid adding device 104 serve as backup for each other. That is, when the first acid adding device 103 is started, the second acid adding device 104 is stopped. When the second acid adding device 104 is started, the first computing device is stopped. If one of the acid adding devices fails, the other acid adding device is started.

[0070] When the first acid addition device 103 is in the startup state, the first PID controller 202 that controls the first acid addition device 103 operates. The first PID controller 202 calculates a first candidate frequency value based on the first current pH value and the target pH value collected by the first pH sensor 201, and outputs the first candidate frequency value to the first selector 203. If the first selector 203 receives a water replenishment trigger signal from the boiler feed water treatment system 500, the first preset frequency value is selected as the first target frequency value. Otherwise, the first candidate frequency value is selected as the first target frequency value, and the first target frequency value is then output to the first acid addition device 103, so that the first acid addition device 103 adds acid solution according to the first target frequency value.

[0071] When the second acid addition device 104 is in the startup state, the second PID controller 204 that controls the second acid addition device 104 operates. The second PID controller 204 calculates a second candidate frequency value based on the first current pH value and the target pH value collected by the first pH sensor 201, and outputs the second candidate frequency value to the second selector 205. If the second selector 205 receives a water replenishment trigger signal from the boiler feed water treatment system 500, the first preset frequency value is selected as the second target frequency value. Otherwise, the second candidate frequency value is selected as the second target frequency value, and the second target frequency value is then output to the second acid addition device 104, causing the second acid addition device 104 to add acid solution according to the second target frequency value.

[0072] By judging the water replenishment demand of the boiler feed water treatment system 500 in advance, the dosage of the acid adding equipment is adjusted in advance, the working frequency of the dosing pump is reduced, and the dosage is ensured not to be excessive. This not only ensures the stability and reliability of the water quality, but also controls the pH value within a reasonable range, reducing corrosion to the water supply pipeline.

[0073] When water quality suddenly changes (e.g., a sudden drop in raw water alkalinity caused by heavy rain) or when reagent dosage is abnormal (e.g., scale inhibitor mixed with acid), the PID parameters may not adapt quickly enough, causing automatic adjustment lag and prolonged pH deviation from the target value. Alternatively, when PID parameters (such as proportional gain and integral time) need to be regularly optimized, automatic control must be suspended during commissioning. Failure to do so can lead to system loss of control during the commissioning process.

[0074] Therefore, in addition to the automatic mode, a manual mode needs to be added, and the switching between the two operating modes needs to be controlled. Specifically, a first handheld operator 206 can be added between the first PID controller 202 and the first selector 203, and a second handheld operator 207 can be added between the second PID controller 204 and the second selector 205 to control the switching between the manual mode and the automatic mode.

[0075] Figure 3This is a logic control block diagram of the pH control system 200 with the first handheld controller 206 added to the embodiment. Figure 3 As shown, the first PID controller 202 uses the HSVPID module, and the first handheld operator 206 uses the HSVMAN module. When the first acid addition device 103 is in the startup state, the PV port of the first PID controller 202 is connected to the first pH sensor 201, inputting the first current pH value collected by the first pH sensor 201; the SP port is inputting the target pH value; and the AV port is connected to the IN port of the first handheld operator 206, which outputs the first candidate frequency value calculated based on the first current pH value and the target pH value to the IN port.

[0076] The PV port of the first handheld operator 206 is connected to the first pH sensor 201 to input a first current pH value. The FB port of the first handheld operator 206 is connected to the first acid addition device 103 to input a first feedback frequency value fed back by the first acid addition device 103. The first handheld operator 206 also provides a human-machine interface that displays the first current pH value and the first feedback frequency value.

[0077] The TM port of the first handheld operator 206 is used to receive a first manual switching trigger signal for instructing to switch from the automatic mode to the manual mode. If the first manual switching trigger signal is received, for example, TM=1, the first handheld operator 206 selects the third candidate frequency value as the first frequency value to be output; otherwise, the first handheld operator 206 selects the first candidate frequency value as the first frequency value to be output; the AV port of the first handheld operator 206 outputs the first frequency value to be output to the IN0 port of the first selector 203. The third candidate frequency value is the frequency value of the first acid adding device 103 in the manual mode pre-set by the staff.

[0078] The AV port of first selector 203 is connected to the TP port of first PID controller 202, inputting the first target frequency value into first PID controller 202. The TS port of first PID controller 202 is connected to the AM port of first handheld operator 206, receiving the manual mode status value output by first handheld operator 206. First PID controller 202 determines the switching state of first handheld operator 206 based on the manual mode status value. For example, TS = 1 indicates that first handheld operator 206 is in manual mode, and TS = 0 indicates that first handheld operator 206 is in automatic mode. In other words, the mode switching state of first handheld operator 206 can be determined by the change in the level of the TS port. When first handheld operator 206 switches from automatic mode to manual mode, first PID controller 202 tracks the first candidate frequency value. Furthermore, when first handheld operator 206 switches from manual mode to automatic mode, first PID controller 202 tracks the third candidate frequency value.

[0079] In this embodiment, the first target frequency value is transmitted as a tracking variable by the first handheld controller 206 to the TP port of the first PID controller 202. When switching from manual mode to automatic mode, the tracking variable received by the TS port of the first PID controller 202 is the third candidate frequency value in manual mode. At this time, the first PID controller 202 gradually adjusts the third candidate frequency value to the first candidate frequency value for output. After switching to automatic mode, the frequency value output by the AV port smoothly transitions to the first candidate frequency value. When switching from automatic mode to manual mode, the tracking variable received by the TS port of the first PID controller 202 is the first candidate frequency value in automatic mode. At this time, the first PID controller 202 gradually adjusts the first candidate frequency value to the third candidate frequency value for output. After switching to manual mode, the frequency value output by the AV port smoothly transitions to the first candidate frequency value.

[0080] In this way, the control mutation or fluctuation caused by mode switching can be reduced, and the continuity and stability of the control output can be ensured. The existence of the tracking quantity enables the first PID controller to achieve seamless switching between manual / automatic modes.

[0081] The IN1 port of the first selector 203 is used to input a first preset frequency value, and the S port is used to input a water replenishment trigger signal from the boiler feed water treatment system 500. If the S port receives the water replenishment trigger signal from the boiler feed water treatment system 500, the first preset frequency value is selected as the first target frequency value; otherwise, the first to-be-output frequency value is selected as the first target frequency value. The first target frequency value is then output to the first acid addition device 103 via the AV port, causing the first acid addition device 103 to add acid solution according to the first target frequency value.

[0082] Furthermore, for obtaining the first manual switching trigger signal, the pH control system 200 further includes a first manual switching module connected to the first hand operator 206 .

[0083] When at least one of the first manual switching condition, the second manual switching condition, the third manual switching condition and the fourth manual switching condition is met, the first manual switching module outputs a first manual switching trigger signal to the first hand operator 206 to switch the first hand operator 206 to manual mode.

[0084] Among them, the first manual switching condition is that the absolute value of the error between the first feedback frequency value returned by the first acid adding equipment 103 and the first target frequency value is greater than the first preset value; the second manual switching condition is that the first acid adding equipment 103 protection trips; the third manual switching condition is that the first acid adding equipment 103 is in a stopped state; the fourth manual switching condition is that the first hand operator 206 is in manual mode and the water supply valve between the clarifier 102 and the boiler feed water treatment system 500 is in an open state.

[0085] Figure 4 This is a structural block diagram of the pH control system 200 with the second handheld controller 207 added to the embodiment. Figure 4 As shown, the second PID controller 204 uses the HSVPID module, and the second handheld operator 207 uses the HSVMAN module. When the second acid addition device 104 is in the startup state, the PV port of the second PID controller 204 is connected to the first pH sensor 201, and the first current pH value collected by the first pH sensor 201 is input; the SP port is connected to the SP port of the second handheld operator 207, and the target pH value is input; the AV port is connected to the IN port of the second handheld operator 207, and the second candidate frequency value calculated based on the first current pH value and the target pH value is output to the IN port.

[0086] The PV port of the second handheld operator 207 is connected to the first pH sensor 201 to input the first current pH value. The FB port of the second handheld operator 207 is connected to the second acid addition device 104 to input the second feedback frequency value fed back by the second acid addition device 104. The second handheld operator 207 also provides a human-machine interface that displays the first current pH value and the second feedback frequency value.

[0087] The TM port of the second handheld operator 207 is used to receive a second manual switching trigger signal. If the second manual switching trigger signal indicating switching from the automatic mode to the manual mode is received, for example, TM=1, the second handheld operator 207 selects the fourth candidate frequency value as the second frequency value to be output. Otherwise, the second handheld operator 207 selects the second candidate frequency value as the second frequency value to be output. The AV port of the second handheld operator 207 outputs the second frequency value to be output to the IN0 port of the second selector 205. The fourth candidate frequency value is the frequency value of the second acid-adding device 104 in the manual mode pre-set by the operator.

[0088] The AV port of second selector 205 is connected to the TP port of second PID controller 204, inputting the second target frequency value into second PID controller 204. The TS port of second PID controller 204 is connected to the AM port of second handheld operator 207, receiving the manual mode status value output by second handheld operator 207. Second PID controller 204 determines the switching state of second handheld operator 207 based on the manual mode status value. For example, TS = 1 indicates that second handheld operator 207 is in manual mode, while TS = 0 indicates that second handheld operator 207 is in automatic mode. In other words, the mode switching state of second handheld operator 207 can be determined by changes in the level of the TS port. When second handheld operator 207 switches from automatic mode to manual mode, second PID controller 204 tracks the second candidate frequency value. Furthermore, when second handheld operator 207 switches from manual mode to automatic mode, second PID controller 204 tracks the fourth candidate frequency value.

[0089] In this embodiment, the second target frequency value is transmitted as a tracking variable by the second handheld controller 207 to the TP port of the second PID controller 204. When switching from manual mode to automatic mode, the tracking variable received by the TS port of the second PID controller 204 is the fourth candidate frequency value in manual mode. At this time, the second PID controller 204 gradually adjusts the fourth candidate frequency value to the second candidate frequency value for output. After switching to automatic mode, the frequency value output by the AV port smoothly transitions to the second candidate frequency value. When switching from automatic mode to manual mode, the tracking variable received by the TS port of the second PID controller 204 is the second candidate frequency value in automatic mode. At this time, the second PID controller 204 gradually adjusts the second candidate frequency value to the fourth candidate frequency value for output. After switching to manual mode, the frequency value output by the AV port smoothly transitions to the second candidate frequency value.

[0090] In this way, the control mutation or fluctuation caused by mode switching can be reduced, and the continuity and stability of the control output can be ensured. The existence of the tracking variable enables the second PID controller 204 to achieve seamless switching between manual / automatic modes.

[0091] The second selector 205's IN1 port is used to input the second preset frequency value, and the S port is used to input the water replenishment trigger signal from the boiler feed water treatment system 500. If the S port receives the water replenishment trigger signal from the boiler feed water treatment system 500, the second preset frequency value is selected as the second target frequency value; otherwise, the second to-be-output frequency value is selected as the second target frequency value. The second target frequency value is then output to the second acid addition device 104 via the AV port, causing the second acid addition device 104 to add acid according to the second target frequency value.

[0092] Furthermore, to obtain the second manual switching trigger signal, the pH control system 200 further includes a second manual switching module connected to the second handheld operator 207. When at least one of the fifth manual switching condition, the sixth manual switching condition, the seventh manual switching condition, and the eighth manual switching condition is satisfied, the second manual switching module outputs the second manual switching trigger signal to the first handheld operator 206, causing the first handheld operator 206 to switch to manual mode.

[0093] Among them, the fifth manual switching condition is that the absolute value of the error between the second feedback frequency value returned by the second acid adding equipment 104 and the second target frequency value is greater than the second preset value; the sixth manual switching condition is that the second acid adding equipment 104 protection trips; the seventh manual switching condition is that the second acid adding equipment 104 is in a stopped state; the eighth manual switching condition is that the second hand operator 207 is in manual mode and the water supply valve between the clarifier 102 and the boiler feed water treatment system 500 is in an open state.

[0094] In some optional embodiments, such as Figure 3 As shown, the pH control system 200 further includes a first delay module 208 connected to the first pH sensor 201 and the first PID controller 202 respectively; the first delay module 208 is used to delay the input first current pH value by a first preset period and output it to the first PID controller 202.

[0095] The first delay module 208 adopts the HSFOP module. The IN port of the HSFOP module is connected to the first pH sensor 201 to input the first current pH value, the TC port inputs the first preset period (for example, 2 periods), and the AV port is connected to the PV port of the HSVPID module to delay the first preset period to output the first current pH value to the HSFOP module.

[0096] like Figure 4 As shown, the pH control system 200 may further include a second delay module 209 connected to the first pH sensor 201 and the second PID controller 204, respectively. The second delay module 209 is configured to delay the input first current pH value by a second preset period and output it to the second PID controller 204. Since the second delay module 209 has the same structure and function as the first delay module 208, a detailed description thereof will not be given.

[0097] During actual measurement, pH sensors are susceptible to various noises, such as electromagnetic interference and sensor-derived electronic noise. This noise can cause momentary fluctuations and inaccuracies in the collected pH value. The HSFOP module buffers the data for two cycles, effectively performing a simple filtering process on the collected data.

[0098] Even in the absence of significant noise interference, the pH value may fluctuate slightly due to flow, uneven mixing, etc. Buffering for two cycles can smooth these fluctuations and prevent the HSVPID module from making unnecessary control actions due to frequent data fluctuations.

[0099] Incorrect pH inputs to the HSVPID module due to noise or data fluctuations can cause system malfunctions, such as incorrectly starting or stopping dosing pumps or regulating valves. Using the HSFOP module to buffer the pH value by two cycles can reduce these malfunctions and improve system reliability.

[0100] In some optional embodiments, the pH control system 200 further includes a water replenishment trigger module; the water replenishment trigger module includes:

[0101] The demand submodule 2091 is configured to receive the operating mode status values ​​output by the first handheld operator 206 and the second handheld operator 207; and output a water supply demand signal when the first handheld operator 206 or the second handheld operator 207 is in manual mode and the water supply valve between the clarifier 102 and the boiler feed water treatment system 500 is open.

[0102] The delay submodule 2092 is configured to output a water replenishment trigger signal to the first selector 203 or the second selector 205 if the water replenishment demand signal output by the demand submodule meets a preset delay condition.

[0103] Taking two clarification tanks and two clear water tanks as an example, Figure 5 FIG. 1 shows the DCS logic control diagram of the water replenishment trigger module of this embodiment. Figure 5 As shown, the delay submodule 2092 adopts the HSTP module, and the RT port of the HSTP module inputs the preset delay condition, such as the valve opening delay setting time.

[0104] In addition to being equipped with an acid-adding device, the circulating water replenishment system 100 of this embodiment also needs to be equipped with an alkali-adding device to feed alkali solution (such as sodium hydroxide) into the crystallization and granulation fluidized bed 101. The crystallization and granulation fluidized bed 101 is provided with an alkali solution dosing port. By adding alkali solution, the hardness in the water can be deposited in the form of crystals on the filler grains in the bed to soften the incoming water. The crystallization and granulation fluidized bed 101 has no function of removing the turbidity of the incoming water. The effluent from the fluidized bed has a pH above 10 and enters the inlet channel of the clarification tank 102. Concentrated sulfuric acid is added to the pipe before entering the channel to adjust the pH to reduce the impact of pH on subsequent coagulation and clarification.

[0105] The number of alkali dosing devices is related to the number of crystallization and granulation fluidized beds 101. For example, there is a one-to-one correspondence between each crystallization and granulation fluidized bed 101 and each alkali dosing device. Furthermore, to meet equipment hot standby requirements and operational procedures, a backup alkali dosing device is provided, along with a corresponding switch button and PID automatic adjustment logic, ensuring that the backup alkali dosing device can serve as a backup pump.

[0106] In some optional embodiments, such as Figure 6 As shown, the circulating water make-up water system 100 further includes a main alkali adding device 105 and a standby alkali adding device 106 for adding alkali solution to the crystallization granulation fluidized bed 101; Figure 7 As shown, the pH control system 200 further includes a second pH sensor 210 disposed at the crystallization granulation fluidized bed 101 and a third PID controller 211 connected to the second pH sensor 210 .

[0107] The third PID controller 211 is used to calculate the standby frequency value based on the second current pH value and the target pH value collected by the second pH sensor 210 when the standby alkali adding equipment 106 is in the startup state, and use the standby frequency value as the third target frequency value, and output the third target frequency value to the standby alkali adding equipment 106, so that the standby alkali adding equipment 106 adds alkali solution according to the third target frequency value.

[0108] In this embodiment, the main alkali adding equipment 105 and the standby alkali adding equipment 106 use alkali solution dosing pumps.

[0109] In the early stage of system debugging, the operator manually starts the alkali dosing equipment and observes the pump's operating sound, vibration, outlet pressure and other parameters to determine whether the pump is operating normally; if the automatic control system fails, such as sensor damage, controller failure, etc., the alkali dosing pump will not be able to add drugs according to the automatic control requirements. The manual mode can be used as a backup control method to ensure that before the automatic control system is repaired, an appropriate amount of alkali can still be added to the circulating water to maintain the basic operation of the system; the circulating water quality may be affected by various factors and experience abnormal fluctuations, such as changes in water source quality, production process adjustments, system leakage, etc. At this time, the automatic control system may not be able to adjust the dosing amount in a timely and accurate manner. The manual mode allows the operator to respond quickly according to the actual situation and flexibly adjust the dosing amount to restore the circulating water quality as soon as possible.

[0110] Therefore, in addition to the automatic mode, a manual mode needs to be added and the switching between the two working modes needs to be controlled. Specifically, a third handheld controller 212 connected to the third PID controller 211 is added to switch between the manual mode and the automatic mode.

[0111] Figure 8 This is a structural block diagram of the pH control system 200 with the third handheld controller 212 added to the embodiment. Figure 8 As shown, a third handheld operator 212 is connected between the third PID controller 211 and the standby alkali-adding device 106; the third handheld operator 212 adopts an HSVMAN module, and the IN port of the third handheld operator 212 is connected to the AV port of the third PID controller 211 to receive the standby frequency value output by the third PID controller 211; the TM port of the third handheld operator 212 inputs the operating status value of the standby alkali-adding device 106. If the standby alkali-adding device 106 is in a stopped state, it is determined that a third manual switching trigger signal is received, the automatic mode is switched to the manual mode, and the set frequency value is selected as the third target frequency value. If the standby alkali-adding device is in a started state, the automatic mode is maintained, and the standby frequency value is selected as the third target frequency value; then, the third handheld operator 212 outputs the third target frequency value to the standby alkali-adding device 106 through the AV port.

[0112] Furthermore, the AV port of the third handheld operator 212 is connected to the TP port of the third PID controller 211, outputting a third target frequency value to the third PID controller 211. The AM port of the third handheld operator 212 is connected to the TS port of the third PID controller 211, outputting the operating mode status value to the third PID controller 211. For example, if TS = 1, it indicates that the third handheld operator 212 has switched from automatic mode to manual mode, and the third PID controller 211 is tracking the backup frequency value. If TS = 0, it indicates that the third handheld operator 212 has switched from manual mode to automatic mode, and is now tracking the set frequency value. The specific principles are the same as those of the first handheld operator 206 and the second handheld operator 207, and will not be further described here.

[0113] In some optional embodiments, the pH control system 200 further includes a third delay module 213 connected to the second pH sensor 210 and the third PID controller 211 respectively; the third delay module 213 is used to delay the second current pH value collected by the second pH sensor 210 by a third preset period and output it to the third PID controller 211.

[0114] like Figure 8 As shown, the third delay module 213 adopts the HSFOP module, the IN port of the HSFOP module is connected to the second pH sensor 210, and the second current pH value is input, the TC port inputs the third preset period (for example, 2 periods), and the AV port is connected to the PV port of the HSVPID module, which is used to delay the third preset period to output the second current pH value to the HSFOP module.

[0115] It should be noted that each main alkali adding device 105 is provided with a second pH sensor 210 , so the staff can select the second current pH value collected by the second pH sensor 210 corresponding to any main alkali adding device 105 and input it into the third PID controller 211 . Figure 8 The control logic for selecting the second current pH values ​​collected by the second pH sensors 210 corresponding to the three main alkali adding devices 105 through the switching button is shown, and includes two selectors.

[0116] In addition, the PID automatic control strategy of the main alkali adding device 105 is the same as that of the standby alkali adding device 106, which will not be described in detail here.

[0117] Through comparative experiments, the following experimental data were obtained: #1 fluidized bed flow rate is about 450m 3 / h, #2 fluidized bed flow rate is about 800m 3 / h, the pH of the fluidized bed is 10.1-10.3, no acid is added at the first acid addition point, the pH of the second acid addition is 6.5-7.0, the dosage of polyferric is 11-13 mg / L, the dosage of PAM is 0.3-0.5 mg / L, the calcium hardness of the fluidized bed effluent is about 0.9-1.2 mmol / L (calcium hardness removal rate is about 40%-60%), the turbidity of the cooling tower feed water is about 2-3 NTU, the calcium hardness is 1.1-1.2 mmol / L (calcium hardness removal rate is about 40%-47%), and the alkalinity is about 1.0 mmol / L.

[0118] The fluidized bed is controlled at an optimized pH of 10.1-10.3, compared to the previous pH of 10.5-10.7. The alkali dosage is reduced from 232mg / L to 171mg / L, saving 26%. The alkali dosage cost per ton of water is reduced from 0.274 yuan to 0.202 yuan (based on the actual purchase price of 1,180 yuan per ton of alkali), reducing alkali consumption by approximately 360 tons annually (for an annual water treatment volume of 5.9 million tons), and reducing alkali dosage costs by approximately 420,000 yuan annually.

[0119] In the above description of this application, unless otherwise expressly specified or limited, terms such as "fixed," "mounted," "connected," or "connected" should be understood in a broad sense. For example, with respect to the term "connected," it can mean a fixed connection, a detachable connection, or an integral connection; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean internal communication between two elements or an interaction between two elements. Therefore, unless otherwise expressly specified in this application, those skilled in the art can understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0120] In addition, the terms "first" or "second" used in this application to refer to numbers or ordinal numbers are used for descriptive purposes only and should not be understood as explicitly or implicitly indicating relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this application, the meaning of "plurality" is at least two, such as two, three or more, etc., unless otherwise clearly and specifically defined.

[0121] Although a number of embodiments of the present invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art may devise numerous modifications, variations, and alternatives without departing from the concept and spirit of the present invention. It should be understood that in practicing the present invention, various alternatives to the embodiments of the present invention described herein may be employed. The appended claims are intended to define the scope of the present invention and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A pH control system used in a circulating water make-up water system, characterized in that: The circulating water make-up water system includes a crystallization and granulation fluidized bed, a clarifier, a first acid addition device and a second acid addition device; the crystallization and granulation fluidized bed is connected to the make-up water source and the clarifier, respectively, and the clarifier is connected to the circulating cooling water system and the boiler feed water treatment system, respectively; a first acid addition point is provided on the pipeline connecting the crystallization and granulation fluidized bed and the clarifier, and the first acid addition point is connected to the first acid addition device; a second acid addition point is provided on the pipeline connecting the clarifier and the circulating cooling water system, and the second acid addition point is connected to the second acid addition device; the first acid addition device and the second acid addition device serve as standby for each other; The pH control system includes a first pH sensor, a first PID controller, a first selector, a second PID controller, and a second selector; the first pH sensor is provided on a pipe connecting the second acid addition point and the circulating cooling water system; the first PID controller is connected to the first pH sensor and the first selector, respectively, and the first selector is connected to the first acid addition device; the second PID controller is connected to the first pH sensor and the second selector, respectively, and the second selector is connected to the second acid addition device; The first PID controller is configured to calculate a first candidate frequency value according to a first current pH value and a target pH value collected by the first pH sensor when the first acid adding device is in a startup state, and output the first candidate frequency value to the first selector; The first selector is configured to select a first preset frequency value as a first target frequency value if a water replenishment trigger signal from the boiler feed water treatment system is received, and otherwise select the first candidate frequency value as the first target frequency value, and then output the first target frequency value to the first acid addition device, so that the first acid addition device adds acid according to the first target frequency value; The second PID controller is configured to calculate a second candidate frequency value based on a first current pH value and a target pH value collected by the first pH sensor when the second acid addition device is in a startup state, and output the second candidate frequency value to the second selector; The second selector is configured to select the first preset frequency value as the second target frequency value if a water replenishment trigger signal from the boiler feed water treatment system is received, otherwise select the second candidate frequency value as the second target frequency value, and then output the second target frequency value to the second acid adding device so that the second acid adding device adds acid according to the second target frequency value.

2. The pH control system for a circulating water make-up water system according to claim 1, characterized in that: A first handheld operator is connected between the first PID controller and the first selector; The first handheld operator is configured to receive the first candidate frequency value output by the first PID controller; select the third candidate frequency value as the first frequency value to be output if a first manual switching trigger signal for instructing to switch from the automatic mode to the manual mode is received, and otherwise select the first candidate frequency value as the first frequency value to be output; and output the first frequency value to be output to the first selector; The first PID controller is further configured to receive a state value of an operating mode output by the first handheld operator; track the first candidate frequency value when the first handheld operator switches from the automatic mode to the manual mode; and track the third candidate frequency value when the first handheld operator switches from the manual mode to the automatic mode; and / or A second handheld operator is connected between the second PID controller and the second selector; The second handheld operator is configured to receive the second candidate frequency value output by the second PID controller; select the fourth candidate frequency value as the second frequency value to be output if a second manual switching trigger signal for instructing to switch the automatic mode to the manual mode is received, and otherwise select the second candidate frequency value as the second frequency value to be output; and output the second frequency value to be output to the second selector; The second PID controller is also used to receive the status value of the working mode output by the second handheld operator; when the second handheld operator is switched from the automatic mode to the manual mode, track the second candidate frequency value; and when the second handheld operator is switched from the manual mode to the automatic mode, track the fourth candidate frequency value.

3. The pH control system for a circulating water make-up water system according to claim 2, characterized in that: The pH control system further includes a first manual switching module connected to the first hand operator; The first manual switching module is configured to output the first manual switching trigger signal to the first handheld operator when at least one of a first manual switching condition, a second manual switching condition, a third manual switching condition, and a fourth manual switching condition is met; Wherein, the first manual switching condition is that the absolute value of the error between the first feedback frequency value returned by the first acid adding device and the first target frequency value is greater than a first preset value; The second manual switching condition is that the first acid adding equipment protection trips; The third manual switching condition is that the first acid adding device is in a stopped state; The fourth manual switching condition is that the first handheld operator is in the manual mode and the water supply valve between the clarifier and the boiler feed water treatment system is in an open state; and / or, The pH control system further includes a second manual switching module connected to the second hand operator; The second manual switching module is configured to output the second manual switching trigger signal to the first handheld operator when at least one of a fifth manual switching condition, a sixth manual switching condition, a seventh manual switching condition, and an eighth manual switching condition is met; The fifth manual switching condition is that the absolute value of the error between the second feedback frequency value returned by the second acid adding device and the second target frequency value is greater than a second preset value; The sixth manual switching condition is that the second acid adding equipment protection trips; The seventh manual switching condition is that the second acid adding device is in a stopped state; The eighth manual switching condition is that the second hand operator is in manual mode and the water supply valve between the clarifier and the boiler feed water treatment system is in an open state.

4. The pH control system for a circulating water make-up water system according to claim 2, characterized in that: The pH value control system further includes a water replenishment trigger module; the water replenishment trigger module includes: a demand submodule, configured to receive the operating mode status values ​​output by the first hand operator and the second hand operator; and output a water supply demand signal when the first hand operator or the second hand operator is in the manual mode and the water supply valve between the clarifier and the boiler feed water treatment system is in the open state; The delay submodule is configured to output the water replenishment trigger signal to the first selector or the second selector if the water replenishment demand signal output by the demand submodule meets a preset delay condition.

5. The pH control system for a circulating water make-up water system according to any one of claims 1 to 4, characterized in that: The pH control system further comprises a first delay module connected to the first pH sensor and the first PID controller respectively; The first delay module is used to delay the input first current pH value for a first preset period and output it to the first PID controller; and / or, The pH control system further comprises a second delay module connected to the first pH sensor and the second PID controller respectively; The second delay module is used to delay the input first current pH value for a second preset period and output it to the second PID controller.

6. The pH control system for a circulating water make-up water system according to any one of claims 1 to 4, characterized in that: The circulating water replenishment system further includes a main alkali adding device and a standby alkali adding device for adding alkali solution to the crystallization granulation fluidized bed; the pH value control system further includes a second pH sensor provided at the crystallization granulation fluidized bed and a third PID controller connected to the second pH sensor; The third PID controller is used to calculate a standby frequency value based on the second current pH value collected by the second pH sensor and the target pH value when the standby alkali adding equipment is in the startup state, and use the standby frequency value as the third target frequency value, and output the third target frequency value to the standby alkali adding equipment, so that the standby alkali adding equipment adds alkali solution according to the third target frequency value.

7. The pH control system for a circulating water make-up water system according to claim 6, characterized in that: A third handheld operator is connected between the third PID controller and the standby alkali adding device; The third handheld operator is configured to receive the standby frequency value output by the third PID controller; if a third manual switching trigger signal for instructing to switch from the automatic mode to the manual mode is received, select the set frequency value as the third target frequency value; otherwise, select the standby frequency value as the third target frequency value; and output the third target frequency value to the standby alkali adding device; The third PID controller is also used to receive the status value of the working mode output by the third hand operator; when the third hand operator is switched from the automatic mode to the manual mode, track the standby frequency value; and when the third hand operator is switched from the manual mode to the automatic mode, track the set frequency value.

8. The pH control system for a circulating water replenishment system according to claim 7, characterized in that: The third hand operator is further used to switch the automatic mode to the manual mode when the standby alkali adding equipment is in a stopped state.

9. The pH control system for a circulating water make-up water system according to claim 6, characterized in that: The pH control system further comprises a third delay module connected to the second pH sensor and the third PID controller respectively; The third delay module is used to delay the second current pH value collected by the second pH sensor for a third preset period and output it to the third PID controller.

10. The pH control system for a circulating water make-up water system according to any one of claims 1 to 4 and 7 to 9, characterized in that: The clarifier includes a coagulation tank, a flocculation tank and an inclined tube clarification area which are connected in sequence.

Images