An automatic control system for circulating water quality of a power plant

Abstract

The application relates to the technical field of circulating water of power plants, in particular to an automatic control system for circulating water quality of a power plant. The system comprises a water supplement unit for controlling the water supplement amount of a circulating water pool, a central control unit for generating a water supplement instruction according to a preset water supplement node and setting the working parameters of the water supplement unit according to the water supplement instruction, the central control unit is further used for establishing a salt content rate model and generating the circulating water salt content rate of each water supplement node, the central control unit judges whether to generate a blowdown instruction according to the circulating water salt content rate, a monitoring unit is used for collecting the operation parameters of the circulating water, and a blowdown unit sets the blowdown amount of the circulating water pool according to the blowdown instruction. The circulating water pool is periodically supplemented with water through the setting of multiple water supplement nodes, the salt content rate of the circulating water is gradually increased, the water-saving purpose is achieved, the circulating water salt content rate model is established, whether blowdown is performed is judged according to the real-time salt content rate of each water supplement node, and therefore the salt content rate in the circulating water is ensured to be within a safe range.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of circulating water of power plants, in particular to an automatic control system for circulating water quality of a power plant. BACKGROUND

[0002] The circulating cooling water system of a power plant mainly comprises a cooling tower, a cooling pool, a circulating water pump, a condenser and circulating water pipelines. The process flow is that the cooling water is sent into the condenser by the circulating water pump to perform heat exchange, the cooled water is cooled by the cooling tower, and then is sent back to the condenser by the circulating water pump for recycling.

[0003] In this process, the circulating water is heated, and the circulating water is sprayed in the cooling tower to contact with air, evaporates, releases latent heat of vaporization, and achieves the process of cooling the circulating water. In engineering, part of the water evaporates, and new water is added to keep the water volume unchanged. However, the salt and impurities cannot be evaporated, which causes the circulating water to be gradually concentrated, the concentration ratio of operation is increased, the purpose of water saving is achieved, but with the increase of the concentration ratio, the dissolved salt in the circulating water is concentrated, the concentration of scale forming substances is increased, and the corrosion phenomenon is increased. SUMMARY

[0004] The purpose of the application is to solve the above technical problems, and the application provides an automatic control system for circulating water quality of a power plant, which can ensure that the salt content of the circulating water is in a safe range, achieve water saving, and avoid scaling and corrosion.

[0005] In some embodiments of the application, multiple water supplement nodes are arranged to periodically supplement the circulating water pool, gradually increase the salt content of the circulating water, and achieve the purpose of water saving. The circulating water salt content model is established, and whether the water is discharged is determined according to the real-time salt content of each water supplement node, so as to ensure that the salt content of the circulating water is in a safe range.

[0006] In some embodiments of the application, the water is discharged first and then supplemented, the overall water consumption is reduced, the operation and maintenance cost of the circulating water system is reduced, a blowdown pump and a blowdown pipeline are additionally arranged in the circulating water pool, a control valve and a flow measuring device are correspondingly added, the blowdown flow regulating valve is dynamically adjusted according to the real-time blowdown amount, and the circulating water quality is stably maintained in a safe range.

[0007] In some embodiments of the application, an automatic control system for circulating water quality of a power plant is provided, which comprises:

[0008] The water supplement unit is used for controlling the water supplement amount of the circulating water pool.

[0009] The central control unit is used for generating a water supplement instruction according to the preset water supplement node, and setting the working parameters of the water supplement unit according to the water supplement instruction.

[0010] The central control unit is further configured to establish a salt content rate model and generate the circulating water salt content rate of each water replenishment node;

[0011] The central control unit determines whether to generate a blowdown instruction according to the circulating water salt content rate;

[0012] The monitoring unit is configured to collect the operating parameters of the circulating water;

[0013] The blowdown unit is configured to set the blowdown amount of the circulating water pool according to the blowdown instruction.

[0014] In some embodiments of the present application, the central control unit comprises:

[0015] The first processing module is configured to generate a circulating water loss evaluation value according to the historical operating parameters of the circulating water and set a time interval t between adjacent water replenishment nodes according to the condensate water loss evaluation value;

[0016] The second processing module is configured to establish a salt content rate model and generate the circulating water salt content rate k of the water replenishment node according to the operating parameters of the circulating water;

[0017] The third processing module is configured to preset a first salt content rate threshold K1;

[0018] If the circulating water salt content rate k of the current water replenishment node is greater than K1, the third processing module establishes a plurality of feedback time nodes between the current water replenishment node and the next water replenishment node and generates the circulating water salt content rate k' of each feedback time node;

[0019] The fourth processing module is configured to establish a blowdown amount model;

[0020] The fourth processing module is further configured to preset a second circulating water salt content rate threshold K2, and K2>K1;

[0021] When the circulating water salt content rate k' of the feedback time node is greater than K2, the fourth processing module generates the blowdown amount g according to the blowdown amount model and the operating parameters of the circulating water, and generates the blowdown instruction according to the blowdown amount g.

[0022] In some embodiments of the present application, the second processing module is further configured to:

[0023] establish a first salt content rate model k=(q1*m1+q2*m2) / (q1-q3+q2);

[0024] wherein q1 is the circulating water amount of the previous water replenishment node, m1 is the circulating water salt content rate of the previous water replenishment node, q2 is the water replenishment amount, m2 is the water replenishment salt content rate, and q3 is the circulating water evaporation amount from the previous water replenishment node to the current water replenishment node;

[0025] generate the circulating water salt content rate k of each water replenishment node according to the first salt content rate model.

[0026] In some embodiments of the present application, the third processing module is further configured to:

[0027] establish a second salt content model k'=(q1*m1) / (q1-q4);

[0028] wherein q1 is the circulating water volume of the previous water replenishment node, m1 is the circulating water salt content of the previous water replenishment node, and q4 is the circulating water evaporation volume between the current feedback time node and the previous water replenishment node;

[0029] generate the circulating water salt content k' between each feedback time node according to the second salt content model.

[0030] In some embodiments of the present application, when the blowdown amount model is established, the method comprises:

[0031] a=(Q1*k'+Q2*M2+Q3*k'-Q1*M4) / k';

[0032] wherein a is the blowdown amount, Q1 is the circulating water volume of the current feedback time node, k' is the circulating water salt content of the current feedback time node, Q2 is the water replenishment amount after blowdown, M2 is the water replenishment salt content, Q3 is the total circulating water evaporation volume between the current feedback time node and the previous blowdown node, and M4 is the expected circulating water salt content after water replenishment.

[0033] In some embodiments of the present application, the blowdown unit comprises:

[0034] a blowdown pump configured to control the blowdown speed;

[0035] a blowdown pipeline configured to connect the blowdown pump and the clean water pool;

[0036] a clean water pool configured to purify the blowdown water in the circulating water pool

[0037] a first control module configured to obtain a blowdown instruction and set the blowdown flow speed v according to the blowdown amount a.

[0038] In some embodiments of the present application, the first control module is further configured to:

[0039] preset a first blowdown amount interval (A1, A2), a second blowdown amount interval (A2, A3), and a third blowdown amount interval (A3, A4);

[0040] if the blowdown amount a is in the preset first blowdown amount interval, set the blowdown speed v as a preset first blowdown speed V1, i.e., v=V1;

[0041] if the blowdown amount a is in the preset second blowdown amount interval, set the blowdown speed v as a preset second blowdown speed V2, i.e., v=V2;

[0042] If the pollution amount a is in a preset third pollution amount interval, a pollution speed v is set as a preset third pollution speed V3, i.e., v=V3; and V1<V2<V3.

[0043] In some embodiments of the present application, the first processing module is further configured to:

[0044] generate a circulating water historical evaporation rate and a circulating water standard operation amount according to the circulating water historical operation parameters;

[0045] generate a first reference evaluation value H1 according to the circulating water historical evaporation rate;

[0046] generate a first reference evaluation value H2 according to the circulating water standard operation amount;

[0047] generate a circulating water loss evaluation value b according to the first reference evaluation value H1 and the second reference evaluation value H2;

[0048] b=e1*H1+e2*H2, wherein e1 is a preset first weight coefficient, and e2 is a second weight coefficient.

[0049] In some embodiments of the present application, the first processing module is further configured to:

[0050] preset a first circulating water loss evaluation value interval (B1, B2), a second circulating water loss evaluation value interval (H2, H3), and a third circulating water evaluation value interval (B3, B4)

[0051] If the circulating water evaluation value b is in the preset first circulating water evaluation value interval, a time interval t is set as a preset first time interval T1, i.e., t=T1;

[0052] If the circulating water evaluation value b is in the preset second circulating water evaluation value interval, the time interval t is set as a preset second time interval T2, i.e., t=T2;

[0053] If the circulating water evaluation value b is in the preset third circulating water evaluation value interval, the time interval t is set as a preset third time interval T3, i.e., t=T3; and T1>T2>T3.

[0054] In some embodiments of the present application, the third processing module is further configured to:

[0055] obtain a circulating water evaporation speed g between a current water replenishment node and a previous water replenishment node;

[0056] set a feedback cycle duration j according to the circulating water evaporation speed g;

[0057] preset a first circulating water evaporation speed interval (G1, G2), a second circulating water evaporation speed interval (G2, G3), and a third circulating water evaporation speed interval (G3, G4)

[0058] If the circulating water evaporation speed g is in the preset first circulating water evaporation speed interval, the feedback cycle length j is set as the preset first feedback cycle length J1, that is, j = J1;

[0059] If the circulating water evaporation speed g is in the preset second circulating water evaporation speed interval, the feedback cycle length j is set as the preset second feedback cycle length J2, that is, j = J2;

[0060] If the circulating water evaporation speed g is in the preset third circulating water evaporation speed interval, the feedback cycle length j is set as the preset third feedback cycle length J3, that is, j = J3; and J1 > J2 > J3;

[0061] A plurality of feedback time nodes are set according to the feedback cycle length j.

[0062] Compared with the prior art, the power plant circulating water quality automatic control system has the beneficial effects that:

[0063] By setting a plurality of water replenishment nodes, the circulating water tank is periodically replenished with water, the salt content of the circulating water is gradually increased, the purpose of water saving is achieved, by establishing a circulating water salt content model, whether to discharge sewage is determined according to the real-time salt content of each water replenishment node, so that the salt content of the circulating water is kept in a safe range.

[0064] By the method of discharging sewage first and then replenishing water, the overall water consumption is reduced, thereby reducing the operation and maintenance cost of the circulating water system, and a sewage pump and a sewage pipeline are additionally installed in the circulating water tank, a control valve and a flow measuring device are correspondingly added, the sewage flow regulating valve is dynamically adjusted according to the real-time sewage discharge amount, and the circulating water quality is stably maintained in a safe range. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 is a structural schematic diagram of a power plant circulating water quality automatic control system in a preferred embodiment of the present application. DETAILED DESCRIPTION

[0066] The specific embodiments of the present application will be further described in detail below in combination with the drawings and examples. The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0067] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0068] The terms "first", "second", "third", etc. are used only for descriptive purposes and do not connote or imply relative importance or an ordering between or among the indicated technical features. Thus, a feature defined with "first", "second", etc. can include one or more of the features implicitly or explicitly.

[0069] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be direct connection, can also be indirect connection through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0070] As shown in the preferred embodiment of the present application, a circulating water quality automatic control system of a power plant comprises: Figure 1

[0071] A water replenishment unit is configured to control the replenishment amount of the circulating water pool;

[0072] A central control unit is configured to generate a replenishment instruction according to a preset replenishment node, and to set the working parameters of the water replenishment unit according to the replenishment instruction;

[0073] The central control unit is further configured to establish a salt content rate model, and to generate the circulating water salt content rate of each replenishment node;

[0074] The central control unit is configured to determine whether to generate a blowdown instruction according to the circulating water salt content rate;

[0075] A monitoring unit is configured to collect the operating parameters of the circulating water;

[0076] A blowdown unit is configured to set the blowdown amount of the circulating water pool according to the blowdown instruction.

[0077] Specifically, the monitoring unit comprises a parameter collector configured to collect the evaporation speed of the circulating water, the initial salt content rate of the circulating water, etc.

[0078] Specifically, the central control unit comprises:

[0079] A first processing module is configured to generate a circulating water loss evaluation value according to the historical operating parameters of the circulating water, and to set the time interval t between adjacent replenishment nodes according to the condensate loss evaluation value;

[0080] A second processing module is configured to establish a salt content rate model, and to generate the circulating water salt content rate k of the replenishment node according to the operating parameters of the circulating water; ​

[0081] a third processing module configured to preset a first salt content threshold K1;

[0082] If the circulating water salt content k of the current water replenishment node is greater than K1, the third processing module establishes a plurality of feedback time nodes between the current water replenishment node and the next water replenishment node, and generates the circulating water salt content k' of each feedback time node.

[0083] a fourth processing module configured to establish a blowdown amount model;

[0084] The fourth processing module is further configured to preset a second circulating water salt content threshold K2, and K2>K1.

[0085] When the circulating water salt content k' of the feedback time node is greater than K2, the fourth processing module generates the blowdown amount g according to the blowdown amount model and the operating parameters of the circulating water, and generates the blowdown instruction according to the blowdown amount g.

[0086] Specifically, by setting a plurality of water replenishment nodes, the circulating water tank is periodically replenished, the salt content of the circulating water is gradually increased, the purpose of water saving is achieved, the circulating water salt content model is established, whether to blow down is determined according to the real-time salt content of each water replenishment node, so that the salt content in the circulating water is kept within a safe range.

[0087] Specifically, when blowdown is performed, the method of blowdown first and then water replenishment is adopted, the circulating water consumption is reduced, and thus the operating cost of the circulating water system is reduced.

[0088] Specifically, the first salt content threshold and the second salt content threshold can be set according to historical operating parameters. When the real-time salt content threshold exceeds the second salt content threshold, the scaling probability of the circulating water will greatly increase, and a part of the circulating water with poor water quality needs to be blown down in time.

[0089] In the preferred embodiment of the present application, the second processing module is further configured to:

[0090] establish a first salt content model k=(q1*m1+q2*m2) / (q1-q3+q2);

[0091] wherein q1 is the circulating water amount of the previous water replenishment node, m1 is the circulating water salt content of the previous water replenishment node; q2 is the water replenishment amount; m2 is the water replenishment salt content; and q3 is the circulating water evaporation amount from the previous water replenishment node to the current water replenishment node.

[0092] generate the circulating water salt content k of each water replenishment node according to the first salt content model.

[0093] Specifically, the first salt content model is used to calculate the circulating water salt content after water replenishment of the water replenishment node.

[0094] Specifically, the third processing module is further configured to:

[0095] A second salt content model k'=(q1*m1) / (q1-q4) is established.

[0096] Wherein, q1 is the circulating water volume of the previous water replenishment node, m1 is the circulating water salt content of the previous water replenishment node; q4 is the circulating water evaporation amount between the current feedback time node and the previous water replenishment node.

[0097] The circulating water salt content k' between each feedback time node is generated according to the second salt content model.

[0098] Specifically, the second salt content model can also calculate the circulating water salt content before the water replenishment node replenishes water.

[0099] In the preferred embodiment of the present application, when the blowdown amount model is established, it includes:

[0100] a=(Q1*k'+Q2*M2+Q3*k'-Q1*M4) / k';

[0101] Wherein, a is the blowdown amount, Q1 is the circulating water volume of the current feedback time node, k' is the circulating water salt content of the current feedback time node; Q2 is the water replenishment amount after blowdown; M2 is the water replenishment salt content; Q3 is the total circulating water evaporation amount between the current feedback time node and the previous blowdown node; M4 is the expected circulating water salt content after water replenishment.

[0102] Specifically, the blowdown unit includes:

[0103] A blowdown pump is used to control the sewage discharge speed.

[0104] A blowdown pipeline is used to connect the blowdown pump and the clean water pool.

[0105] A clean water pool is used to purify the sewage discharged from the circulating water pool.

[0106] A first control module is used to obtain a blowdown instruction and set the blowdown flow speed v according to the blowdown amount a.

[0107] Specifically, a clean water pool is arranged at the end of the blowdown pipeline as an intermediate storage of blowdown water, and the blowdown water is stored in the clean water pool for sedimentation. A clean water pump and an ultrafiltration device are arranged to filter the stored blowdown water, and then the filtered blowdown water is sent into a reverse osmosis membrane after being adjusted in pH value by adding hydrochloric acid and sodium hydroxide. After reverse osmosis, the blowdown water becomes high-quality desalted water, which can be used as make-up water of a heat supply network. The concentrated water with high salt content is stored in a concentrated water pool and used as water for ground washing, coal yard spraying and greening irrigation. When the insoluble substances accumulated in the clean water pool reach a certain amount, the insoluble substances are pressed into mud cakes by a filter press, and the mud cakes are dried and used as soil. The water pressed out by the filter press is recycled to the clean water pool for continuous treatment. The excess concentrated water that cannot be consumed is sprayed into a boiler flue through a pipeline for evaporation, and water vapor is discharged. The salt and impurities are precipitated and collected in a dust collector together with the boiler fly ash for treatment, and become building raw materials. The whole process realizes continuous and stable control of the water quality in the circulating water pool, and realizes zero discharge of blowdown water while blowdown.

[0108] Specifically, the first control module is further configured to:

[0109] a first blowdown amount interval (A1, A2), a second blowdown amount interval (A2, A3), and a third blowdown amount interval (A3, A4) are preset;

[0110] if the blowdown amount a is in the preset first blowdown amount interval, the blowdown speed v is set as a preset first blowdown speed V1, i.e. v=V1;

[0111] if the blowdown amount a is in the preset second blowdown amount interval, the blowdown speed v is set as a preset second blowdown speed V2, i.e. v=V2;

[0112] if the blowdown amount a is in the preset third blowdown amount interval, the blowdown speed v is set as a preset third blowdown speed V3, i.e. v=V3; and V1

[0113] Specifically, a blowdown pump and a blowdown water pipeline are added to the circulating water pool, and a control valve and a flow measurement device are correspondingly added. According to the real-time blowdown amount, the blowdown flow regulating valve is dynamically adjusted to control the real-time blowdown speed, so as to ensure that the circulating water quality is stably maintained in a safe range.

[0114] In the preferred embodiment of the present application, the first processing module is further configured to:

[0115] generate a circulating water historical evaporation rate and a circulating water standard operating amount according to historical operating parameters of the circulating water;

[0116] generate a first reference evaluation value H1 according to the circulating water historical evaporation rate;

[0117] generate a first reference evaluation value H2 according to the circulating water standard operating amount;

[0118] generate a circulating water loss evaluation value b according to the first reference evaluation value H1 and the second reference evaluation value H2;

[0119] b = e1*H1 + e2*H2, wherein e1 is a preset first weight coefficient, and e2 is a second weight coefficient.

[0120] Specifically, the first reference evaluation value and the second reference evaluation value have the same value range, the faster the circulating water historical evaporation speed is, the greater the first reference evaluation value is, the smaller the circulating water standard operating quantity is, the greater the second reference evaluation value is, and the greater the circulating water loss evaluation value is, indicating that the current circulating water salt content rate increases faster.

[0121] Specifically, the first processing module is further configured to:

[0122] a preset first circulating water loss evaluation value interval (B1, B2), a second circulating water loss evaluation value interval (H2, H3), and a third circulating water evaluation value interval (B3, B4)

[0123] If the circulating water evaluation value b is in the preset first circulating water evaluation value interval, the set time interval t is a preset first time interval T1, that is, t = T1.

[0124] If the circulating water evaluation value b is in the preset second circulating water evaluation value interval, the set time interval t is a preset second time interval T2, that is, t = T2.

[0125] If the circulating water evaluation value b is in the preset third circulating water evaluation value interval, the set time interval t is a preset third time interval T3, that is, t = T3; and T1 > T2 > T3.

[0126] Specifically, the circulating water loss evaluation value is dynamically adjusted to adjust the water replenishment time node, and the circulating water pool is periodically replenished, so as to maintain the dynamic balance of the circulating water quantity and ensure the overall stable operation of the system.

[0127] In the preferred embodiment of the present application, the third processing module is further configured to:

[0128] obtain a circulating water evaporation speed g between the current water replenishment node and the last water replenishment node;

[0129] set a feedback cycle length j according to the circulating water evaporation speed g;

[0130] a preset first circulating water evaporation speed interval (G1, G2), a second circulating water evaporation speed interval (G2, G3), and a third circulating water evaporation speed interval (G3, G4)

[0131] If the circulating water evaporation speed g is in the preset first circulating water evaporation speed interval, the set feedback cycle length j is a preset first feedback cycle length J1, that is, j = J1.

[0132] If the circulating water evaporation speed g is in the preset second circulating water evaporation speed interval, the feedback cycle length j is set as the preset second feedback cycle length J2, that is, j = J2;

[0133] If the circulating water evaporation speed g is in the preset third circulating water evaporation speed interval, the feedback cycle length j is set as the preset third feedback cycle length J3, that is, j = J3; and J1 > J2 > J3;

[0134] A plurality of feedback time nodes are set according to the feedback cycle length j.

[0135] Specifically, when the real-time salt content in the circulating water reaches the preset value, a plurality of feedback cycles are established. The faster the evaporation rate of the circulating water, the faster the rising rate of the salt content in the circulating water, and the shorter the corresponding feedback cycle. By establishing feedback time nodes, the salt content in the circulating water is obtained in time and it is determined whether to discharge sewage. A part of the circulating water with poor water quality is discharged in time to avoid continuous increase of the salt content in the circulating water and to avoid scaling and corrosion phenomena.

[0136] According to the first concept of the present application, the circulating water tank is periodically replenished by setting a plurality of water replenishment nodes, the salt content of the circulating water is gradually increased, the purpose of water saving is achieved, the circulating water salt content model is established, and it is determined whether to discharge sewage according to the real-time salt content of each water replenishment node, so as to ensure that the salt content in the circulating water is in a safe range.

[0137] According to the second concept of the present application, the overall water consumption is reduced by the method of discharging sewage first and then replenishing water, thereby reducing the operation and maintenance cost of the circulating water system. At the same time, a sewage pump and a sewage pipeline are installed in the circulating water tank, a control valve and a flow measuring device are correspondingly added, the sewage flow regulating valve is dynamically adjusted according to the real-time sewage discharge amount, and the circulating water quality is stably maintained in a safe range.

[0138] The above is only the preferred embodiment of the present application. It should be pointed out that for ordinary skilled persons in the technical field, several improvements and replacements can be made without departing from the technical principles of the present application, and these improvements and replacements should be regarded as the protection scope of the present application.

Claims

1. An automatic control system for the quality of circulating water in a power plant, characterized in that, The application relates to a circulating water replenishing and discharging control system. The application comprises: a replenishing unit for controlling the replenishing amount of a circulating water pool; a central control unit for generating a replenishing instruction according to a preset replenishing node and setting the working parameters of the replenishing unit according to the replenishing instruction; the central control unit is further used for establishing a salt content model and generating the circulating water salt content of each replenishing node; the central control unit judges whether to generate a discharging instruction according to the circulating water salt content; a monitoring unit for collecting the operating parameters of the circulating water; a discharging unit for setting the discharging amount of the circulating water pool according to the discharging instruction; the central control unit comprises: a first processing module for generating a circulating water loss evaluation value according to the historical operating parameters of the circulating water and setting the time interval t between adjacent replenishing nodes according to the circulating water loss evaluation value; a second processing module for establishing a salt content model and generating the circulating water salt content k of the replenishing node according to the operating parameters of the circulating water; a third processing module for presetting a first salt content threshold K1; if the circulating water salt content k of the current replenishing node is greater than K1, the third processing module establishes a plurality of feedback time nodes between the current replenishing node and the next replenishing node and generates the circulating water salt content k' of each feedback time node; a fourth processing module for establishing a discharging amount model; the fourth processing module is further used for presetting a second circulating water salt content threshold K2, and K2>K1; 2. The power plant circulating water quality automatic control system as claimed in claim 1, wherein, when the circulating water salt content k' of the feedback time node is greater than K2, the fourth processing module generates the discharging amount g according to the discharging amount model and the operating parameters of the circulating water and generates the discharging instruction according to the discharging amount g. the second processing module is further used for: establishing a first salt content model k=(q1*m1+q2*m2) / (q1-q3+q2); wherein q1 is the circulating water amount of the last replenishing node, m1 is the circulating water salt content of the last replenishing node, q2 is the replenishing amount, m2 is the replenishing salt content, and q3 is the circulating water evaporation amount between the last replenishing node and the current replenishing node; 3. The power plant circulating water quality automatic control system as claimed in claim 2, wherein, generating the circulating water salt content k of each replenishing node according to the first salt content model. the third processing module is further used for: establishing a second salt content model k'=(q1*m1) / (q1-q4); wherein q1 is the circulating water amount of the last replenishing node, m1 is the circulating water salt content of the last replenishing node, and q4 is the circulating water evaporation amount between the current feedback time node and the last replenishing node; 4. The power plant circulating water quality automatic control system as claimed in claim 3, wherein, generating the circulating water salt content k' between each feedback time node according to the second salt content model. when the discharging amount model is established, a=(Q1*k'+Q2*M2+Q3*k'-Q1*M4) / k'; wherein a is the discharging amount, Q1 is the circulating water amount of the current feedback time node, k' is the circulating water salt content of the current feedback time node, Q2 is the replenishing amount after discharging, M2 is the replenishing salt content, Q3 is the total circulating water evaporation amount between the current feedback time node and the last discharging node, and M4 is the expected circulating water salt content after replenishing.

5. The power plant circulating water quality automatic control system as claimed in claim 4, wherein, the discharging unit comprises: a discharging pump for controlling the sewage discharging speed; a discharging pipeline for connecting the discharging pump and the clean water pool; a clean water pool for purifying the sewage discharged from the circulating water pool. The first control module is configured to obtain a blowdown instruction and set a blowdown flow rate v according to a blowdown amount a.

6. The power plant circulating water quality automatic control system as claimed in claim 5, wherein, The first control module is further configured to: preset a first blowdown amount interval (A1, A2), a second blowdown amount interval (A2, A3), and a third blowdown amount interval (A3, A4); if the blowdown amount a is in the preset first blowdown amount interval, set the blowdown speed v as a preset first blowdown speed V1, i.e., v = V1; if the blowdown amount a is in the preset second blowdown amount interval, set the blowdown speed v as a preset second blowdown speed V2, i.e., v = V2; if the blowdown amount a is in the preset third blowdown amount interval, set the blowdown speed v as a preset third blowdown speed V3, i.e., v = V3; and V1 < V2 < V3.

7. The power plant circulating water quality automatic control system as claimed in claim 1, wherein, The first processing module is further configured to: generate a circulating water historical evaporation rate and a circulating water standard operating amount according to a circulating water historical operating parameter; generate a first reference evaluation value H1 according to the circulating water historical evaporation rate; generate a second reference evaluation value H2 according to the circulating water standard operating amount; generate a circulating water loss evaluation value b according to the first reference evaluation value H1 and the second reference evaluation value H2; b = e1*H1 + e2*H2, wherein e1 is a preset first weight coefficient, and e2 is a second weight coefficient.

8. The power plant circulating water quality automatic control system as claimed in claim 6, wherein, The first processing module is further configured to: preset a first circulating water loss evaluation value interval (B1, B2), a second circulating water loss evaluation value interval (H2, H3), and a third circulating water evaluation value interval (B3, B4) if the circulating water evaluation value b is in the preset first circulating water evaluation value interval, set a time interval t as a preset first time interval T1, i.e., t = T1; if the circulating water evaluation value b is in the preset second circulating water evaluation value interval, set the time interval t as a preset second time interval T2, i.e., t = T2; if the circulating water evaluation value b is in the preset third circulating water evaluation value interval, set the time interval t as a preset third time interval T3, i.e., t = T3; and T1 > T2 > T3.

9. The power plant circulating water quality automatic control system as claimed in claim 8, wherein, The third processing module is further configured to: obtain a circulating water evaporation speed g between a current water replenishment node and a last water replenishment node; set a feedback cycle length j according to the circulating water evaporation speed g; preset a first circulating water evaporation speed interval (G1, G2), a second circulating water evaporation speed interval (G2, G3), and a third circulating water evaporation speed interval (G3, G4) if the circulating water evaporation speed g is in the preset first circulating water evaporation speed interval, set the feedback cycle length j as a preset first feedback cycle length J1, i.e., j = J1; if the circulating water evaporation speed g is in the preset second circulating water evaporation speed interval, set the feedback cycle length j as a preset second feedback cycle length J2, i.e., j = J2; if the circulating water evaporation speed g is in the preset third circulating water evaporation speed interval, set the feedback cycle length j as a preset third feedback cycle length J3, i.e., j = J3; and J1 > J2 > J3. set a plurality of feedback time nodes according to the feedback cycle length j.

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