Intelligent regulation and control system and method for adding phosphate into boiler water

Abstract

The invention discloses an intelligent regulation and control system and method for adding phosphate into boiler water, the system comprises a data acquisition / conversion unit and an intelligent regulation and control early warning unit connected with the data acquisition / conversion unit, and the intelligent regulation and control early warning unit comprises a storage calculation module, an intelligent control module, a report statistics module and an alarm diagnosis module; the storage calculation module is used for calculating a boiler water pH theoretical calculation value according to a boiler water pH theoretical calculation model, calculating a boiler water PO4 < 3-> concentration prediction value according to a boiler water PO4 < 3-> regression prediction model, comparing the boiler water pH theoretical calculation value and the boiler water PO4 < 3-> concentration prediction value with a control target value, sending a feedback instruction to a frequency converter of a dosing pump, and remotely regulating and controlling the frequency of the dosing pump to change the dosage. The precision and intelligent level of boiler water phosphate dosing control is improved, the measurement influence, human intervention and agent waste are reduced, and it is guaranteed that the water quality of subcritical unit boiler water is stable and qualified for a long time under the working condition of deep peak regulation.

Description

Technical Field

[0001] The invention belongs to the technical field of boiler water treatment for subcritical drum boiler units in thermal power industry, and specifically relates to an intelligent control system and method for adding phosphate to boiler water. Background Art

[0002] According to statistics, subcritical drum boiler units still account for a relatively high proportion of coal-fired power generation units. The quality control of drum boiler water is directly related to the corrosion and scaling of the unit's thermal equipment, and will have an important impact on its safe and economical operation. Since boiler water is the water sample with the most complex water quality components in the entire unit's water and steam system, boiler water quality control is a key link in ensuring the safe operation of the boiler, involving boiler water pH value, conductivity (Sc), silicon dioxide (SiO2), phosphate (PO4 3- ) and other indicators; among which boiler water pH value, PO4 3- Concentration is the most important monitoring indicator and an important basis for dosing adjustment. Domestically, drum boiler water is generally treated with low phosphate (Na3PO4) and low phosphate-low sodium hydroxide (NaOH) to remove calcium and magnesium ions from the boiler water, control the hardness of the boiler water, and improve the corrosion resistance of the boiler tubes and prevent boiler scaling.

[0003] At present, most subcritical drum boilers have realized the automation of adding phosphate to boiler water. The boiler water phosphate dosing system changes the amount of reagent added by adjusting the dosing pump frequency. Its technical principle is based on the traditional PID control of measurement parameters such as pH electrode, conductivity meter and phosphorus meter, which is prone to slow dosing response or over-adjustment. The existing boiler water phosphate dosing system is limited by the boiler water pH, PO4 3- The accuracy of monitoring and the lag of dosing make it difficult to adapt to the peak load and variable load conditions of the unit, and it often relies on manual operation and adjustment. In addition, the sampling pipeline of boiler water is long, the instrument analysis also requires a certain amount of time, and the measurement error and other factors interfere, resulting in nonlinearity, time-varying, lag, and uncertainty in the control object, making it difficult to accurately control the dosing of boiler water. Once the quality of the unit's boiler water is not well controlled, it is necessary to frequently discharge the boiler to ensure the water quality, which will result in a loss of heat energy and waste of reagents; and the dosing of boiler water cannot be continuously controlled, which will also cause large-scale fluctuations in indicators such as the pH value and conductivity of the boiler water, affecting the effect of the phosphate treatment of the boiler water, and there will be safety hazards such as corrosion and over-temperature explosion of the boiler tube. Therefore, it is necessary to optimize and improve the existing automatic dosing method of boiler water phosphate. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art, provide a system and method for intelligently controlling the addition of phosphate to boiler water, and establish a multivariate regression model to accurately predict the PO4 3-concentration, based on the theoretical calculated pH value under different water treatment conditions and the respective control target values, the phosphate dosage is automatically adjusted to ensure the pH value and PO4 3- When the concentration is within the qualified range of the standards, no human intervention is required, and the dosing operation can be carried out with few people on duty. The measurement errors of the online pH meter and online phosphorus meter of the boiler water are alarmed in real time, and faults such as insufficient output of the dosing pump, overpressure and leakage of the dosing pipeline are intelligently diagnosed.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a boiler water phosphate adding intelligent control system, including a data acquisition / conversion unit, an intelligent control early warning unit connected to the data acquisition / conversion unit, a boiler feed water flow meter, a drum blowdown flow meter, a boiler water online conductivity meter, a feed water online conductivity meter, a phosphate dosing box and a dosing pump; the boiler feed water flow meter is used to monitor the boiler feed water flow Q1; the drum blowdown flow meter is installed on the boiler drum blowdown pipeline to monitor the drum blowdown flow Q2; through the boiler water sampling point The online conductivity meter installed after monitoring the conductivity S1 of the boiler water, the online conductivity meter installed after the water sampling point monitors the conductivity S2 of the feed water, the data acquisition / conversion unit collects the liquid level L of the phosphate dosing box through the liquid level sensor, and the data acquisition / conversion unit controls the dosing pump through the frequency converter and collects the frequency f; the intelligent control and early warning unit includes a storage and calculation module, an intelligent control module, a report statistics module and an alarm diagnosis module; the storage and calculation module calculates the theoretical calculation value pH of the boiler water pH according to the theoretical calculation model of the boiler water pH js , according to boiler water PO4 3- Calculation of boiler water PO4 using regression prediction model 3- Concentration prediction value C x ; The intelligent control module sets the target control value of boiler water pH to pH mb 、Boiler water PO4 3- Concentration target control value C xmb , the boiler water PO4 3- Concentration prediction value C x , Theoretical calculated pH value of boiler water js As the actual output value, it is compared with the control target value, and a feedback instruction is issued to the frequency converter of the dosing pump to remotely control the frequency of the dosing pump to change the amount of dosing.

[0006] Further preferably, it also includes an online pH meter for boiler water and an online phosphorus meter for boiler water, and the online pH value of the boiler water is monitored by the online pH meter for boiler water, and the online PO4 value of the boiler water is monitored by the online phosphorus meter for boiler water. 3- Concentration indication.

[0007] The present invention also provides a method for intelligently controlling the addition of phosphate to boiler water, which is specifically implemented based on the above-mentioned intelligent control system for adding phosphate to boiler water.

[0008] Control the pH of boiler water through intelligent control module. Control deviation δ1= pH mb -pH js , boiler water PO4 3- Control deviation of concentration δ2 = C xmb -C x ; When δ1 and δ2 are greater than 0, it means that there is a positive deviation in the control, and the frequency of the dosing pump should be increased; when δ1 and δ2 are less than 0, it means that there is a negative deviation in the control, and the frequency of the dosing pump should be reduced.

[0009] Further preferably, the report statistics module is used to statistically organize the phosphate dosage of boiler water, water quality indicators of boiler water, qualified rates and abnormal conditions under different unit loads, and automatically generate reports according to time span selection.

[0010] Further preferably, alarm thresholds for high and low liquid levels of the phosphate dosing box and measurement errors of the online boiler water pH meter and the online boiler water phosphorus meter are set in the alarm diagnosis module; data signals of the phosphate dosing box liquid level, the online boiler water pH meter and the online boiler water phosphorus meter measured by the data acquisition / conversion unit are received in real time, and the measurement errors of the online boiler water pH meter and the online boiler water phosphorus meter are calculated through comparison and analysis.

[0011] Further optimization was performed using a multiple regression model to establish the PO4 3- Concentration and boiler feed water flow rate Q1, drum blowdown flow rate Q2, boiler water conductivity S l , the quantitative relationship between the frequency f of the dosing pump and the boiler water PO4 3- Regression prediction model: ; Among them, A, B, C, and D correspond to the boiler feed water flow rate Q1, the drum blowdown flow rate Q2, and the boiler water conductivity S l , the regression coefficient of frequency f, and m is the intercept constant.

[0012] Further preferably, the NH3 concentration in the boiler water is C y The following relationship equation exists with the feed water conductivity S2: C y =0.7×(13.2 S2 2 +62.77 S2) / 17×10 -3 ; NH3 ionizes into OH in boiler water - The concentration of C z , based on the ionization equilibrium, the following equation is obtained: C z 2 +[(k+1) C x +K b ] C z -Kb C y =0 ; Where, k is the molar concentration ratio of NaOH to Na3PO4 when dispensing phosphate dosing box, K b is the ionization equilibrium constant of NH3 in water, K b =1.8×10 -5 , C x PO4 in boiler water 3- Concentration prediction value; The NH3 concentration in boiler water C y The following relationship equation is obtained with the feed water conductivity S2 to obtain the unique numerical solution: ; Total OH in boiler water - Concentration C1 = C z +C x +kC x , and obtain the theoretical calculation model of boiler water pH: pH js =14+lg[(C z +C x +kC x ) ×10 -3 ].

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) Constructed boiler water PO4 3- The concentration regression prediction model and pH theoretical calculation model have realized the prediction of boiler water PO4 3- , and pH value are accurately predicted and calculated in real time, and the two are used as the basis for adjusting the phosphate dosing in the boiler water, providing a new technical path for the phosphate dosing control of the drum boiler water.

[0014] (2) Compared with traditional PID control, the present invention can quickly adapt to changes in operating conditions and parameters such as unit load and boiler water quality, avoiding defects such as control lag caused by sampling and analysis delays, instrument measurement errors, and poor regulation performance.

[0015] (3) The present invention improves the precision and intelligence level of boiler water phosphate dosing control, reduces human intervention and reagent waste, reduces manual operation intensity and risk, and improves production efficiency.

[0016] (4) The present invention has stronger anti-interference ability, faster response speed, and more stable dosing operation control effect, which can quickly ensure that the boiler water quality is stable and qualified. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of an intelligent control system for adding phosphate to boiler water according to the present invention.

[0018] Figure 2 The present invention is a flow chart of an intelligent control method for adding phosphate to boiler water.

[0019] In the figure, 1-data acquisition / conversion unit, 2-intelligent control and early warning unit, 3-boiler feed water flow meter, 4-steam drum blowdown flow meter, 5-boiler water online conductivity meter, 6-boiler water online pH meter, 7-boiler water online phosphorus meter, 8-feed water online conductivity meter, 9-phosphate dosing box, 10-dosing pump, 11-economizer, 12-boiler, 13-frequency converter. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments of the present invention. It is obvious that the described embodiments are only a part of the present invention, not all embodiments, and are not intended to limit the scope of the present invention.

[0021] like Figure 1 As shown, a boiler water phosphate adding intelligent control system comprises a data acquisition / conversion unit 1, an intelligent control early warning unit 2, a boiler feed water flow meter 3, a drum blowdown flow meter 4, a boiler water online conductivity meter 5, a boiler water online pH meter 6, a boiler water online phosphorus meter 7, a feed water online conductivity meter 8, a phosphate dosing box 9, and a dosing pump 10; the data acquisition / conversion unit 1 is connected to the intelligent control early warning unit 2, the boiler feed water flow meter 3, the drum blowdown flow meter 4, the boiler water online conductivity meter 5, the boiler water online pH meter 6, the boiler water online phosphorus meter 7, the feed water online conductivity meter 8, the phosphorus acid salt dosing box 9 and dosing pump 10; boiler feed water flowmeter 3 is installed on the pipeline from economizer 11 to the drum water inlet of boiler 12, and is used to monitor boiler feed water flow rate Q1; drum blowdown flowmeter 4 is installed on the drum blowdown pipeline of boiler 12, and is used to monitor drum blowdown flow rate Q2; online conductivity meter 5 installed after boiler water sampling point monitors boiler water conductivity S1, online conductivity meter 8 installed after feed water sampling point monitors feed water conductivity S2, online pH meter 6 monitors boiler water online pH indication, and online phosphorus meter 7 monitors boiler water online PO4 3- Concentration indication; the data acquisition / conversion unit 1 collects the liquid level L of the phosphate dosing box 9 through the liquid level sensor, and the data acquisition / conversion unit 1 controls the dosing pump 10 through the frequency converter 13 and collects the frequency f of the dosing pump 10.

[0022] The intelligent control and early warning unit is the central unit of the system, including a storage and calculation module, an intelligent control module, a report statistics module and an alarm diagnosis module; The storage and calculation module is used to store all operation and calculation data of the boiler water phosphate intelligent control system, and calculate the theoretical calculation value of the boiler water pH according to the boiler water pH theoretical calculation model.js , according to boiler water PO4 3- Calculation of boiler water PO4 using regression prediction model 3- Concentration prediction value C x ; The intelligent control module sets the boiler water pH target control value to pH mb 、Boiler water PO4 3- Concentration target control value C xmb , the boiler water PO4 3- Concentration prediction value, boiler water pH theoretical calculation value pH js As the actual output value, and compared with the control target value, a feedback instruction is issued to the frequency converter 13 of the dosing pump 10, and the frequency f of the dosing pump 10 is remotely controlled to change the amount of dosing; the pH control deviation of boiler water δ1 = pH mb -pH js , boiler water PO4 3- Control deviation of concentration δ2 = C xmb -C x ; When δ1 and δ2 are greater than 0, it indicates that a positive deviation occurs in the control, and the frequency f of the dosing pump 10 should be increased; when δ1 and δ2 are less than 0, it indicates that a negative deviation occurs in the control, and the frequency f of the dosing pump 10 should be reduced; The intelligent control module can automatically update the calculated control deviations δ1 and δ2, and gradually adjust the frequency f of the dosing pump 10 at a certain interval each time, so that the control deviations δ1 and δ2 gradually tend to 0, ensuring that the pH and PO4 of the boiler water are stable. 3- The concentration quickly reaches the control target range.

[0023] The report statistics module is used to compile statistics on the phosphate dosage of boiler water, water quality indicators, qualified rates and abnormal conditions under different unit loads, and can automatically generate reports according to time spans.

[0024] The alarm diagnosis module sets the alarm thresholds of the high and low liquid levels of the phosphate dosing box 9 and the measurement error ξ1 of the boiler water online pH meter 6 and the measurement error ξ2 of the boiler water online phosphorus meter 7 by input; receives the data signals of the liquid level of the phosphate dosing box 9, the boiler water online pH meter 6 and the boiler water online phosphorus meter 7 collected by the data acquisition / conversion unit 1 in real time, and calculates the measurement errors ξ1 and ξ2 of the boiler water online pH meter 6 and the boiler water online phosphorus meter 7 through comparison and analysis; the alarm diagnosis module is embedded with logic judgment, fault diagnosis and other programs, and stores a related fault case library; it can automatically identify and accurately diagnose the liquid level over-limit alarm, abnormal faults, etc. that may occur in the phosphate dosing process, and finally realize the intelligent dosing of the boiler water of the unit.

[0025] The measurement error calculation formula of the boiler water online pH meter 6 is ξ1= pH zx -pH js , pHzx is the boiler water online pH value measured by the boiler water online pH meter 6, and the calculation formula for the measurement error of the boiler water online phosphorus meter 7 is ξ2= (C zx - C x ) / C x ×100%,C zx Boiler water online PO4 measured by boiler water online phosphorus table 7 3- Concentration indication: the error control range of ξ1 and ξ2 can be set in the alarm diagnosis module.

[0026] Using multiple regression model to establish PO4 3- Concentration and boiler feed water flow rate Q1, drum blowdown flow rate Q2, boiler water conductivity S l , the quantitative relationship between the dosing pump frequency f, and the boiler water PO4 3- Regression prediction model: ; Among them, A, B, C, and D correspond to the boiler feed water flow rate Q1, the drum blowdown flow rate Q2, and the boiler water conductivity S l , the regression coefficient of frequency f, m is the intercept constant, obtained from historical operation data, combined with mathematical statistics analysis and multivariate regression fitting, boiler water PO4 3- The prediction accuracy of the regression prediction model should meet the requirements of fast and stable dosing control.

[0027] Collect boiler feed water flow, drum blowdown flowmeter, boiler water online conductivity meter, dosing pump frequency and other data in real time, and use them as boiler water PO4 3- The input of the regression prediction model is introduced into the intelligent control module, and then the boiler water PO4 at this moment is predicted and calculated. 3- Concentration prediction value C x , no need to rely on boiler water PO4 3- Online measurement.

[0028] Taking into account the influence of various impurities in boiler water on its pH, based on hydrolysis equilibrium, charge balance and assumption deduction, the theoretical calculation model of boiler water pH under given water treatment conditions was obtained, and the theoretical calculation value of boiler water pH was established. js With boiler water PO4 3- Concentration prediction value C x , the relationship equation of water supply conductivity S2.

[0029] Consider the three alkalizing agents ammonia (NH3), NaOH, and Na3PO4 in boiler water that dissociate into OH - As for the contribution to pH, the hydrolysis and ionization of the three interact with each other.

[0030] The NH3 in the boiler water comes from the addition of ammonia to the boiler feed water, and the free NaOH and Na3PO4 in the boiler water come from the reagents added to the boiler water.

[0031] The hydrolysis balance and charge balance process: NaOH = Na + +OH - (Complete ionization), Na3PO4=3Na + + PO4 3- (Complete ionization), NH3+H2O=NH4 + +OH - (Partial ionization, ionization equilibrium constant K b =1.8×10 -5 ), PO4 3- +H2O=HPO4 2- +OH - (First-order hydrolysis, first-order hydrolysis equilibrium constant K h1 =2.27×10 -2 ), HPO4 2- +H2O=H2PO4 - + OH - (Secondary hydrolysis, secondary hydrolysis equilibrium constant K h2 =1.59×10 -7 ), H2PO4 - +H2O=H3PO4+ OH - (Third-order hydrolysis, third-order hydrolysis equilibrium constant K h3 =1.32×10 -12 ).

[0032] According to the analysis of boiler water composition, phosphate only undergoes primary hydrolysis, and secondary and tertiary hydrolysis can be ignored. Therefore, PO4 3- Concentration prediction value C x That is, the OH contributed by it - Concentration, if low NaOH and low Na3PO4 reagents are added at the same time, set k as the molar concentration ratio of NaOH to Na3PO4 when the phosphate dosing box is dispensed, which is a fixed value, and the NaOH concentration in the boiler water is kC x , that is, the OH contributed to it - Concentration: if there is no NaOH, k=0; combined with experience and practical verification, the NH3 concentration in boiler water is generally 70% of the NH3 concentration in feed water.

[0033] The pH value of boiler water depends on the total OH in the boiler water. - content, which is the OH produced by adding NH3 ionization - , add NaOH to generate OH - , add Na3PO4 to generate OH - The sum of the three.

[0034] 1) NH3 concentration in boiler water C y The following relationship equation exists with the feed water conductivity S2: C y =0.7×(13.2 S2 2 +62.77 S2) / 17×10 -3 ; The NH3 concentration C in boiler water can be calculated by the above formula y Since NaOH and Na3PO4 in the boiler water will affect the ionization of NH3, OH is ionized from NH3 in the boiler water. - The concentration of C z ; According to NH3+H2O=NH4 + +OH - (K b =1.8×10 -5 ) ionization equilibrium, derive the equation: C z 2 +[(k+1) C x +K b ] C z -K b C y =0 ; Where, k is the molar concentration ratio of NaOH to Na3PO4 when dispensing phosphate dosing box, K b is the ionization equilibrium constant of NH3 in water, K b =1.8×10 -5 , C x PO4 in boiler water 3- Concentration prediction value, it should be noted that the predicted value is used here, and the boiler water online PO4 measured by boiler water online phosphorus table 7 3- Concentration indication is also possible.

[0035] The NH3 concentration in boiler water C y The following relationship equation is obtained with the feed water conductivity S2 to obtain the unique numerical solution: ; 2) Total OH in boiler water - Concentration C1 = C z +C x +kC x , and obtain the theoretical calculation model of boiler water pH: pH js =14+lg[(C z +C x +kC x ) ×10 -3 ] .

[0036] The applicable conditions of the boiler water pH theoretical calculation model are that the boiler water is treated with low phosphate (PO4 3- concentration is controlled at 0.3~1 mg / L), or low phosphate-low sodium hydroxide treatment (NaOH, PO4 3- The concentrations were all controlled to be less than 1 mg / L); the calculated data were all converted values ​​after the sample water temperature was compensated to 25°C.

[0037] The feed water flow Q1 is linearly correlated with the unit load P, and can directly reflect the change of the unit load; drum blowdown is an important way to quickly adjust the boiler water quality, including fixed discharge and continuous discharge. Whether to perform blowdown operation is determined according to the salt content and alkalinity of the boiler water, and the blowdown flow rate is changed by adjusting the opening of the blowdown door during operation; the boiler water conductivity S1 is directly used to characterize the salt content of the boiler water. It is measured by a conductivity electrode, which can respond to changes in the impurity composition and concentration in the boiler water in a timely manner. The measurement accuracy is generally high and the service life is long.

[0038] The alarm diagnosis module is used to alarm and judge the liquid level changes of the phosphate dosing box, the measurement accuracy of the online pH meter and the online phosphorus meter. If the normal liquid level range of the phosphate dosing box is set to 30~90mm, the module will automatically send out an alarm signal if a high liquid level (greater than 90mm) or a low liquid level (less than 30mm) appears; similarly, the measurement error ξ1 of the online pH meter 6 of the boiler water should be less than 0.05, and the measurement error ξ2 of the online phosphorus meter 7 of the boiler water should be less than ±10%. If the measurement errors ξ1 and ξ2 are not within the above range, the system will automatically identify the alarm and remind that the measurement errors of the online phosphorus meter 7 and the online pH meter 6 of the boiler water are too large.

[0039] In the attached Figure 2 In the embodiment, the specific application process of the present invention is given.

[0040] Take the subcritical drum boiler 300MW unit as an example. In the boiler water phosphate intelligent control system, the pH control range of the boiler water is set to 9.0~9.7, PO4 3- The concentration control range is 0.3~1 mg / L.

[0041] When the unit load is 145MW, the boiler feed water flow is 471 t / h, the continuous drum blowdown is 1.5 t / h; 1 dosing pump is put into operation, the frequency f is 20Hz; the feed water conductivity S2 is 3.08 μS / cm; the boiler water online pH is 9.08, the boiler water conductivity S l The value is 9.16 μS / cm, and the online phosphorus table 7 of boiler water shows 0.62 mg / L. The boiler water PO4 predicted by regression 3-The predicted concentration value is 0.59 mg / L, and the calculated theoretical value of boiler water pH is 9.06; the measurement error ξ1 of the boiler water online pH meter 6 is 0.02, which is within the error control range (less than 0.05); the measurement error ξ2 of the boiler water online phosphorus meter 7 is 5.08%, which is also within the error control range (less than ±10%). Therefore, it is considered that the online meters such as the boiler water online pH meter 6 and the boiler water online phosphorus meter 7 are qualified.

[0042] When the unit load increases rapidly to 280MW, the boiler feed water flow rate increases to 901 t / h, the amount of ammonia added to the feed water increases by 1 time, and the feed water conductivity is controlled to be around 3.0 μS / cm; the continuous blowdown of the drum remains unchanged at 1.5 t / h. At this time, the boiler water PO4 3- The predicted concentration value is 0.28 mg / L, but the theoretical calculated value of boiler water pH is only 8.92. Therefore, the intelligent control module will feedback and regulate the inverter 13 of the dosing pump 10 according to the control deviations δ1 and δ2 to adjust the dosing amount, set the dosing point and the sampling point, and monitor through the boiler water online phosphorus meter 7 and the boiler water online pH meter 6. The frequency of the dosing pump 10 will be increased by 2Hz every 1min until the frequency f of the dosing pump 10 is adjusted to 32Hz. The boiler water phosphate intelligent control system performs online monitoring data collection and calculates the theoretical calculated value of boiler water pH according to the theoretical calculation model of boiler water pH. js , according to boiler water PO4 3- Calculation of boiler water PO4 using regression prediction model 3- Concentration prediction value C x , the boiler water PO4 in this experiment 3- The predicted concentration value is 0.53 mg / L, and the theoretical calculated value of boiler water pH is 9.02. In addition, if the measurement error ξ1 of the boiler water online pH meter 6 and the measurement error ξ2 of the boiler water online phosphorus meter 7 exceed the set range, a real-time alarm will be issued and fault diagnosis will be performed.

[0043] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. It should be noted that any equivalent replacement or change made by a person skilled in the art based on the technical solution or concept of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A boiler water phosphate adding intelligent control system, comprising a data acquisition / conversion unit, an intelligent control early warning unit connected to the data acquisition / conversion unit, a boiler feed water flow meter, a drum blowdown flow meter, a boiler water online conductivity meter, a feed water online conductivity meter, a phosphate dosing box and a dosing pump; the boiler feed water flow meter is used to monitor the boiler feed water flow Q1; the drum blowdown flow meter is installed on the boiler drum blowdown pipeline, and is used to monitor the drum blowdown flow Q2; the boiler water conductivity S1 is monitored by an online conductivity meter installed after the boiler water sampling point, and the feed water conductivity S2 is monitored by an online conductivity meter installed after the feed water sampling point, the data acquisition / conversion unit collects the liquid level L of the phosphate dosing box through a liquid level sensor, and the data acquisition / conversion unit controls the dosing pump through a frequency converter and collects the frequency f; it is characterized in that: The intelligent control and early warning unit includes a storage and calculation module, an intelligent control module, a report statistics module and an alarm diagnosis module; the storage and calculation module calculates the theoretical calculation value of the pH value of the boiler water according to the theoretical calculation model of the pH value of the boiler water. js , according to boiler water PO4 3- Calculation of boiler water PO4 using regression prediction model 3- Concentration predicted value C x ; The intelligent control module sets the target control value of boiler water pH to pH mb 、Boiler water PO4 3- Concentration target control value C xmb , the boiler water PO4 3- Concentration predicted value C x , Theoretical calculated value of boiler water pH js As the actual output value, it is compared with the control target value, and a feedback instruction is issued to the frequency converter of the dosing pump to remotely control the frequency of the dosing pump to change the amount of dosing.

2. The intelligent control system for adding phosphate to boiler water according to claim 1, characterized in that: It also includes an online pH meter for boiler water and an online phosphorus meter for boiler water. The online pH meter for boiler water monitors the online pH value of boiler water sampled from the boiler water, and the online phosphorus meter for boiler water monitors the online PO4 3- Concentration indication.

3. A method for intelligently controlling the addition of phosphate to boiler water, based on the intelligent control system for adding phosphate to boiler water according to claim 1, characterized in that: Control the pH of boiler water through intelligent control module. Control deviation δ1= pH mb -pH js , boiler water PO4 3- Control deviation of concentration δ2 = C xmb -C x ; When δ1 and δ2 are greater than 0, it indicates that a positive deviation occurs in the control, and the frequency of the dosing pump is increased; when δ1 and δ2 are less than 0, it indicates that a negative deviation occurs in the control, and the frequency of the dosing pump is reduced.

4. The intelligent control method for adding phosphate to boiler water according to claim 3, characterized in that: The report statistics module is used to collect statistics on the phosphate dosage of boiler water, water quality indicators, qualified rates and abnormal conditions under different unit loads, and automatically generate reports according to time span selection.

5. The intelligent control method for adding phosphate to boiler water according to claim 3, characterized in that: The alarm diagnosis module sets the alarm thresholds for the high and low liquid levels of the phosphate dosing box and the measurement errors of the boiler water online pH meter and the boiler water online phosphorus meter; receives in real time the data signals of the phosphate dosing box liquid level, boiler water online pH meter and boiler water online phosphorus meter measurements collected by the data acquisition / conversion unit, and calculates the measurement errors of the boiler water online pH meter and the boiler water online phosphorus meter through comparison and analysis.

6. The intelligent control method for adding phosphate to boiler water according to claim 3, characterized in that: Using multiple regression model to establish PO4 3- Concentration and boiler feed water flow rate Q1, drum blowdown flow rate Q2, boiler water conductivity S l , the quantitative relationship between the frequency f of the dosing pump and the boiler water PO4 3- Regression prediction model: ； Among them, A, B, C, and D correspond to the boiler feed water flow rate Q1, the drum blowdown flow rate Q2, and the boiler water conductivity S l , the regression coefficient of frequency f, and m is the intercept constant.

7. The intelligent control method for adding phosphate to boiler water according to claim 3, characterized in that: NH3 concentration in boiler water C y The following relationship equation exists with the feed water conductivity S2: C y =0.7×(13.2 S2 2 +62.77 S2) / 17×10 -3 ; NH3 ionizes into OH in boiler water - The concentration of C z , based on the ionization equilibrium, the following equation is obtained: C z 2 +[(k+1) C x +K b ] C z - K b C y =0 ; Where, k is the molar concentration ratio of NaOH to Na3PO4 when dispensing phosphate dosing box, K b is the ionization equilibrium constant of NH3 in water, K b =1.8×10 -5 , C x PO4 in boiler water 3- Concentration prediction value; The NH3 concentration in boiler water C y The following relationship equation is obtained with the feed water conductivity S2 to obtain the unique numerical solution: ； Total OH in boiler water - Concentration C1 = C z +C x +kC x , and obtain the theoretical calculation model of boiler water pH: pH js =14+lg[(C z +C x +kC x ) ×10 -3 ] 。

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