Calcium salt dosing control method and system based on pH value feedback

Abstract

The invention discloses a calcium salt dosing control method and system based on pH value feedback, and belongs to the technical field of water treatment. The method comprises the following steps: calculating a lime dosing concentration based on an inflow fluoride concentration, a lime dissolving concentration and an effective component content; combining the water inlet flow to obtain a basic dosing flow and converting the basic dosing flow into a first dosing pump frequency; the pH value and the change trend of effluent of the reaction tank are obtained in real time, and the frequency of a second dosing pump is determined based on a preset strategy; calculating basic dosing adjustment buffer time and linkage dosing adjustment interval time; and fusing the parameters to obtain a third dosing pump frequency, triggering update and correction according to time parameters, outputting to a frequency converter to execute dosing, and simultaneously realizing alarm through flow comparison. According to the invention, the problems of excessive medicament, unstable effluent and dependence on manpower in traditional calcium salt dosing are solved, accurate control of dosing is realized, the defluorination efficiency is improved, the medicament cost is reduced, and the method is suitable for a fluorine-containing wastewater treatment scene.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, and in particular to a calcium salt dosing control method and system based on pH value feedback. BACKGROUND

[0002] In fluorine-containing wastewater treatment, calcium salt precipitation method is a commonly used defluorination process, which is based on the principle of removing fluoride ions by adding calcium salt (such as lime) to react with fluoride in water to generate calcium fluoride precipitate. However, the traditional calcium salt precipitation defluorination process has the following defects: Medicament waste and secondary pollution: the traditional process uses manual control of calcium salt overdosing (such as using a 1.5 times safety factor), which results in excessive calcium salt dosing, not only increasing the cost of medicaments, but also causing environmental hazards due to the increase of residual calcium ions in water.

[0003] Unstable effluent quality: when the influent fluoride concentration and flow fluctuate, the fixed dosing mode cannot dynamically respond, resulting in large fluctuations in effluent fluoride concentration (10-50 mg / L), which is difficult to meet the stringent discharge standards; at the same time, the pH value fluctuates greatly during the reaction process (H + Inhibits the formation of precipitate; when pH>8, Ca(OH)2 precipitate competes with CaF2 for calcium ions), which indirectly affects the defluorination effect.

[0004] Dependence on human experience: the dosing amount needs to be manually detected and adjusted, which is time-consuming and has large errors, and cannot be optimized in real time. SUMMARY

[0005] To solve the technical problems in the background art, the present application proposes a calcium salt dosing control method and system based on pH value feedback.

[0006] The calcium salt dosing control method based on pH value feedback proposed by the present application comprises: Based on the obtained influent fluoride concentration, lime dissolving agent concentration and lime effective component content, the lime dosing concentration is calculated; Obtain the influent flow, calculate the basic dosing flow based on the lime dosing concentration and the influent flow, and convert the basic dosing flow to the first dosing pump frequency; Real-time acquisition of the pH value of the effluent of the reaction tank, determination of the second dosing pump frequency based on the pH value, the pH value change trend and the preset correction strategy; According to the structure volume from the influent fluoride monitoring point to the dosing point, the influent flow and the water quality detection time, the basic dosing adjustment buffer time is calculated, and according to the structure volume from the dosing point to the pH monitoring point and the influent flow, the linkage dosing adjustment interval time is calculated; According to the first dosing pump frequency, the second dosing pump frequency, the basic dosing adjustment buffer time and the linkage dosing adjustment interval time, the third dosing pump frequency is calculated, the dosing parameter is updated according to the basic dosing adjustment buffer time, the dosing correction is performed according to the linkage dosing adjustment interval time, and the third dosing pump frequency is output to the dosing pump frequency converter to perform calcium salt dosing.

[0007] Preferably, the formula for calculating the lime dosing concentration is: ; Wherein, is the lime dosing concentration; is the lime dissolving concentration; is the effective component content of lime; K is the safety factor; is the influent fluoride concentration; 19 is the relative atomic mass of fluorine element; 2 is the ratio of fluorine element to calcium element in CaF2 molecule; 74 is the relative molecular mass of Ca(OH)2.

[0008] Preferably, the basic dosing flow is calculated according to the lime dosing concentration and the influent flow, specifically: ; Wherein, is the influent flow; is the basic dosing flow; is the lime dosing concentration.

[0009] Preferably, the formula for calculating the basic dosing adjustment buffer time is: ; Wherein, T1 is the basic dosing adjustment buffer time; V1 is the total effective volume of the structure from the influent fluoride monitoring point to the dosing point; is the influent flow; is the detection time of the influent fluoride monitoring equipment; when V1 / ≤ , T1 = 0.

[0010] Preferably, the formula for calculating the linkage dosing adjustment interval time is: ; Wherein, T2 is the linkage dosing adjustment interval time; V2 is the total effective volume of the structure from the dosing point to the pH monitoring point of the effluent of the reaction tank; is the influent flow.

[0011] Preferably, the preset correction strategy specifically includes: When the interval of pH value is 6.5 < pH value ≤ 7, and the pH value change trend is rising, the value of the second dosing pump frequency is reduced by 1 Hz; When the interval of the pH value is 6.5 < pH value≤ 7, and the pH value change trend is a downward trend, the value of the second dosing pump frequency is increased by 1 Hz; When the interval of the pH value is 7 < pH value≤ 7.5, and the pH value change trend is a downward trend, the value of the second dosing pump frequency is increased by 1 Hz; When the interval of the pH value is 7 < pH value≤ 7.5, and the pH value change trend is an upward trend, the value of the second dosing pump frequency is decreased by 1 Hz; When the interval of the pH value is 7.5 < pH value≤ 8, the value of the second dosing pump frequency is decreased by 1 Hz; When the interval of the pH value is pH value > 8, the value of the second dosing pump frequency is decreased by 2 Hz; When the interval of the pH value is 6 < pH value≤ 6.5, the value of the second dosing pump frequency is increased by 1 Hz; When the interval of the pH value is pH value≤ 6, the value of the second dosing pump frequency is increased by 2 Hz.

[0012] Preferably, the buffer time triggering dosing parameter updating is adjusted according to the base dosing, in particular: The first dosing pump frequency is recalculated based on the real-time collected influent fluoride concentration and influent flow rate, wherein the influent fluoride concentration is adjusted and updated every interval of the base dosing adjustment buffer time.

[0013] Preferably, the dosing correction is performed every interval of the linkage dosing adjustment interval time, in particular: The second dosing pump frequency is recalculated based on the real-time collected pH value and change trend every interval of the linkage dosing adjustment interval time, and the third dosing pump frequency is updated.

[0014] Preferably, it further comprises: When the error between the actual flow rate measured by the dosing pipeline flow meter and the theoretical flow rate calculated by the system exceeds the preset threshold, an alarm is triggered.

[0015] The calcium salt dosing control system based on pH value feedback provided by the application comprises: A first processing module is used to calculate the lime dosing concentration based on the obtained influent fluoride concentration, lime dosing concentration and lime effective component content; A second processing module is used to obtain the influent flow rate, calculate the base dosing flow rate according to the lime dosing concentration and the influent flow rate, and convert the base dosing flow rate into the first dosing pump frequency; A third processing module is used to obtain the pH value of the effluent of the reaction tank in real time, determine the second dosing pump frequency based on the pH value, the pH value change trend and the preset correction strategy; The fourth processing module is configured to calculate a basic dosing adjustment buffer time according to a structure volume from a water inlet fluoride monitoring point to a dosing point, a water inlet flow rate, and a water quality detection time length, and to calculate a linkage dosing adjustment interval time according to a structure volume from the dosing point to a pH monitoring point and the water inlet flow rate; The execution module is configured to calculate a third dosing pump frequency according to the first dosing pump frequency, the second dosing pump frequency, the basic dosing adjustment buffer time, and the linkage dosing adjustment interval time, trigger dosing parameter updating according to the basic dosing adjustment buffer time, perform dosing correction according to the linkage dosing adjustment interval time, and output the third dosing pump frequency to a dosing pump frequency converter to perform calcium salt dosing.

[0016] In the present application, the calcium salt dosing control method and system based on pH value feedback realize the organic integration of feedforward and feedback control, improve the accuracy and robustness of dosing control through basic dosing calculation and linkage feedback adjustment, avoid calcium salt overdosing, reduce reagent cost, and reduce secondary pollution. The time lag compensation algorithm ensures that dosing adjustment is synchronized with water quality changes, avoids over-regulation or under-regulation, and ensures the stability of the effluent water quality. The self-diagnosis alarm mechanism ensures the stable operation of the system and improves the reliability of the process. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The calcium salt dosing control method based on pH value feedback proposed in the present application is a work flow chart; Figure 2 The calcium salt dosing control method based on pH value feedback proposed in the present application is a work flow chart; Figure 3 The calcium salt dosing control method based on pH value feedback proposed in the present application is a work flow chart; Figure 1 ; Figure 4 The calcium salt dosing control method based on pH value feedback proposed in the present application is a work flow chart; Figure 2 ; Figure 5 The calcium salt dosing control method based on pH value feedback proposed in the present application is a work flow chart; Figure 1 ; Figure 6 The calcium salt dosing control method based on pH value feedback proposed in the present application is a work flow chart; Figure 2 ; Figure 7The system architecture schematic diagram of the calcium salt dosing control system based on pH value feedback provided by the application. DETAILED DESCRIPTION

[0018] REFERENCE Figures 1-6 The calcium salt dosing control method based on pH value feedback provided by the application comprises the following steps: S1, calculating the lime dosing concentration based on the obtained influent fluoride concentration, lime dissolving concentration and lime active ingredient content.

[0019] In the embodiment, the calculation formula of the lime dosing concentration is: ; Among them, the lime dosing concentration (mL / L); the lime dissolving concentration (%); the lime active ingredient content (%); K is the safety factor; the influent fluoride concentration (mg / L); 19 is the relative atomic mass of fluorine element; 2 is the ratio of fluorine element to calcium element in CaF2 molecule; 74 is the relative molecular mass of Ca(OH)2.

[0020] S2, obtaining the influent flow rate, calculating the basic dosing flow rate according to the lime dosing concentration and the influent flow rate, and converting the basic dosing flow rate into the first dosing pump frequency.

[0021] In the embodiment, the basic dosing flow rate is calculated according to the lime dosing concentration and the influent flow rate, specifically: ; Among them, the influent flow rate (m 3 / h); the basic dosing flow rate (L / h); the lime dosing concentration.

[0022] In the embodiment, the intelligent joint control coupling of the basic dosing amount, the basic dosing flow rate is not only associated with the influent fluoride, but also directly multiplied by the real-time influent flow rate, so as to realize the dynamic calculation of the dosing concentration flow rate. The calculated basic dosing flow rate is directly converted into the first dosing pump frequency output through the relationship between the lime dosing flow rate=the first dosing pump frequency coefficient a+coefficient b, realizing the real-time control of the pump, and constructing the complete closed loop basic layer of “detection-calculation-execution”, wherein the coefficients a and b are obtained through the linear relationship between the dosing pump running frequency and the corresponding dosing flow rate meter data.

[0023] S3, real-time acquisition of the pH value of the effluent of the reaction tank, determination of the frequency of the second dosing pump based on the pH value, the pH value change trend and a preset correction strategy.

[0024] In this embodiment, the preset correction strategy specifically includes: when the interval of the pH value is 6.5 when the interval of the pH value is 6.5 when the interval of the pH value is 7 when the interval of the pH value is 7 when the interval of the pH value is 7.5 when the interval of the pH value is pH value>8, the value of the frequency of the second dosing pump is reduced by 2 Hz. when the interval of the pH value is 6 when the interval of the pH value is 6

[0025] S4, calculation of a basic dosing adjustment buffer time according to the structure volume from the influent fluoride monitoring point to the dosing point, the influent flow rate and the water quality detection time length, and calculation of a linkage dosing adjustment interval time according to the structure volume from the dosing point to the pH monitoring point and the influent flow rate.

[0026] In this embodiment, the calculation formula of the basic dosing adjustment buffer time is: ; wherein, T1 is the basic dosing adjustment buffer time; V1 is the total effective volume of the structure from the influent fluoride monitoring point to the dosing point (m 3 ); is the influent flow rate (m 3 / h); is the detection time length of the influent fluoride monitoring equipment (h); when V1 / ≤ , T1=0.

[0027] In this embodiment, the calculation formula of the linkage dosing adjustment interval time is: ; T2 is the linkage dosing adjustment interval time (h); V2 is the total effective volume of the structure from the dosing point to the pH monitoring point of the effluent of the reaction tank (m 3 ). is the influent flow rate (m 3 / h).

[0028] S5, according to the first dosing pump frequency, the second dosing pump frequency, the basic dosing adjustment buffer time and the linkage dosing adjustment interval time, the third dosing pump frequency is calculated, the dosing parameter update is triggered according to the basic dosing adjustment buffer time, the dosing correction is executed according to the linkage dosing adjustment interval time, and the third dosing pump frequency is output to the dosing pump frequency converter to execute calcium salt dosing.

[0029] In this embodiment, the dosing parameter update is triggered according to the basic dosing adjustment buffer time, specifically: The first dosing pump frequency is recalculated based on the real-time collected influent fluoride concentration and influent flow rate, wherein the influent fluoride concentration is adjusted and updated every interval of the basic dosing adjustment buffer time.

[0030] In this embodiment, the dosing correction is executed according to the linkage dosing adjustment interval time, specifically: Every interval of the linkage dosing adjustment interval time, the second dosing pump frequency is recalculated based on the real-time collected pH value and change trend, and the third dosing pump frequency is updated.

[0031] In this embodiment, it also includes: Compare the actual flow rate of the dosing pipeline flow meter with the system calculated theoretical flow rate, and trigger an alarm when the error exceeds the preset threshold.

[0032] Specifically, the dosing control mode is clearly divided into two layers of logic, namely basic dosing (real-time calculation based on influent fluoride and influent flow rate) and linkage dosing (real-time feedback adjustment based on effluent pH value of the reaction system), realizing the organic integration of feedforward control (based on load) and feedback control (based on effect), and improving the accuracy and robustness of control.

[0033] Example 1: The calcium salt dosing control system based on pH value feedback in this embodiment is applied to a calcium salt precipitation defluorination pilot project. The process of this project: the fluorine-containing wastewater passes through the reaction zone and the precipitation zone in turn, lime is added in the reaction zone, the lime reacts with the fluoride in the water to generate calcium fluoride precipitate, the mixture after sufficient reaction enters the precipitation zone for precipitation, the effluent of the precipitation zone is the system effluent, and the sludge goes to the sludge disposal system. The design water treatment capacity is 50m 3 / d, the design water quality standard is influent fluoride ≤1000mg / L, and effluent fluoride ≤20mg / L. The process flow chart of this embodiment is as follows: Figure 2As shown, the small test results of the original water before the embodiment debugging: when the calcium fluoride ratio is controlled at 0.6, the effluent fluoride can be controlled within 20 mg / L, wherein d represents day.

[0034] During the operation, the effluent pH of the reaction tank is controlled in the range of 6.3-7.8, as shown in Figure 3 , the average influent fluoride is 1169 mg / L, the average effluent fluoride is 12.16 mg / L, and is stably below 20 mg / L, as shown in Figure 4 , the average calcium fluoride ratio during the accounting operation is 0.59, which saves about 16.31% of the reagent compared with the embodiment.

[0035] The calcium salt precipitation defluorination pilot project process of the present comparative example is the same as that of the embodiment, the difference lies in that before using the pH feedback calcium salt dosing control method and system, the site operators manually control the dosing pump frequency to excessively add lime. During the operation, the effluent pH fluctuates greatly in the range of 6.8-9.7, as shown in Figure 5 ; the average influent fluoride is 1291 mg / L, the average effluent fluoride is 20.37 mg / L, as shown in Figure 6 ; the average calcium fluoride ratio during the accounting operation is 0.705.

[0036] Referring to Figures 1-7 , the calcium salt dosing control system based on pH value feedback provided by the present application comprises: A first processing module for calculating the lime dosing concentration based on the obtained influent fluoride concentration, lime dissolving concentration and lime effective component content; A second processing module for obtaining the influent flow, calculating the basic dosing flow based on the lime dosing concentration and the influent flow, and converting the basic dosing flow into the first dosing pump frequency; A third processing module for real-time obtaining the effluent pH of the reaction tank, determining the second dosing pump frequency based on the pH value, the pH value change trend and the preset correction strategy; A fourth processing module for calculating the basic dosing adjustment buffer time according to the structure volume from the influent fluoride monitoring point to the dosing point, the influent flow and the water quality detection time, and calculating the linkage dosing adjustment interval time according to the structure volume from the dosing point to the pH monitoring point and the influent flow; An execution module for calculating the third dosing pump frequency according to the first dosing pump frequency, the second dosing pump frequency, the basic dosing adjustment buffer time and the linkage dosing adjustment interval time, triggering the dosing parameter update according to the basic dosing adjustment buffer time, executing the dosing correction according to the linkage dosing adjustment interval time, and outputting the third dosing pump frequency to the dosing pump frequency converter to execute the calcium salt dosing.

[0037] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for controlling the addition of calcium salt based on pH feedback, characterized by, include: The lime dosing concentration is calculated based on the obtained influent fluoride concentration, lime solution concentration, and effective component content of lime. Obtain the influent flow rate, calculate the basic dosing flow rate based on the lime dosing concentration and the influent flow rate, and convert the basic dosing flow rate into the frequency of the first dosing pump; The pH value of the effluent from the reaction tank is acquired in real time, and the frequency of the second dosing pump is determined based on the pH value, the pH value change trend, and the preset correction strategy. Based on the volume of the structure from the influent fluoride monitoring point to the dosing point, the influent flow rate, and the water quality testing duration, calculate the basic dosing adjustment buffer time, and based on the volume of the structure from the dosing point to the pH monitoring point and the influent flow rate, calculate the linkage dosing adjustment interval time. Based on the frequency of the first dosing pump, the frequency of the second dosing pump, the basic dosing adjustment buffer time, and the linkage dosing adjustment interval time, the frequency of the third dosing pump is calculated. The dosing parameters are updated according to the basic dosing adjustment buffer time, the dosing correction is performed according to the linkage dosing adjustment interval time, and the frequency of the third dosing pump is output to the dosing pump inverter to perform calcium salt dosing.

2. The pH value feedback-based calcium salt dosing control method according to claim 1, characterized by, The formula for calculating the lime dosage concentration is as follows: ； wherein, is the lime dosage concentration; is the lime solution concentration; is the lime active ingredient content; is the safety factor; is the influent fluoride concentration; 19 is the relative atomic mass of fluorine; 2 is the ratio of the number of fluorine atoms to calcium atoms in a CaF2 molecule; and 74 is the relative molecular mass of Ca(OH)2.

3. The pH value feedback-based calcium salt dosing control method according to claim 1, characterized by, The basic dosing flow rate is calculated based on the lime dosing concentration and the influent flow rate, specifically as follows: ； wherein, is the influent flow rate; is the base chemical addition flow rate; is the lime chemical addition concentration.

4. The pH value feedback-based calcium salt dosing control method according to claim 1, characterized by, The formula for calculating the basic dosing adjustment buffer time is as follows: ； Wherein, T1 is the basic dosing adjustment buffer time; V1 is the total effective volume of the structure from the water inlet fluoride monitoring point to the dosing point; is the water inlet flow rate; is the detection duration of the water inlet fluoride monitoring device; when T1=0. 5.The pH value feedback based calcium salt dosing control method and system of claim 1, wherein, The formula for calculating the adjustment interval time of the linkage dosing is: ； Wherein, T2 is linkage dosing adjustment interval time; V2 is total effective volume of structure from dosing point to pH monitoring point of effluent of reaction tank; is the influent flow rate.

6. The pH value feedback-based calcium salt dosing control method according to claim 1, characterized by, The preset correction strategy specifically includes: When the pH range is 6.5 < pH ≤ 7, and the pH trend is upward, the frequency of the second dosing pump is reduced by 1 Hz. When the pH range is 6.5 < pH ≤ 7, and the pH trend is downward, the frequency of the second dosing pump is increased by 1 Hz. When the pH range is 7 < pH ≤ 7.5 and the pH trend is downward, the frequency of the second dosing pump is increased by 1 Hz. When the pH range is 7 < pH ≤ 7.5 and the pH trend is upward, the frequency of the second dosing pump is reduced by 1 Hz. When the pH range is 7.5 < pH ≤ 8, the frequency of the second dosing pump is reduced by 1 Hz; When the pH value is greater than 8, the frequency of the second dosing pump is reduced by 2 Hz; When the pH range is 6 < pH ≤ 6.5, the frequency of the second dosing pump is increased by 1 Hz; When the pH range is pH ≤ 6, the frequency of the second dosing pump is increased by 2 Hz.

7. The pH value feedback-based calcium salt dosing control method according to claim 1, characterized by, The step of adjusting the buffer time according to the basic dosing to trigger the update of dosing parameters is as follows: The frequency of the first dosing pump is recalculated based on the real-time collected influent fluoride concentration and influent flow rate. The influent fluoride concentration is adjusted and updated every interval of the basic dosing adjustment buffer time. 8.The pH value feedback based calcium salt dosing control method and system of claim 1, wherein, The process of adjusting the dosing interval according to the aforementioned linkage dosing adjustment time specifically involves: The interval time for each dosing cycle is adjusted, and the frequency of the second dosing pump is recalculated based on the real-time collected pH value and its changing trend, and the frequency of the third dosing pump is updated. 9.The pH value feedback based calcium salt dosing control method and system of claim 1, wherein, Also includes: The system compares the measured flow rate of the dosing pipeline flow meter with the theoretical flow rate calculated by the system, and triggers an alarm when the error exceeds a preset threshold.

10. A calcium salt dosing control system based on pH feedback, characterized by, include: The first processing module is configured to calculate a lime dosing concentration based on the obtained influent fluoride concentration, lime dissolving agent concentration and lime active ingredient content; The second processing module is configured to obtain an influent flow rate, calculate a basic dosing flow rate based on the lime dosing concentration and the influent flow rate, and convert the basic dosing flow rate into a first dosing pump frequency; The third processing module is configured to obtain a real-time effluent pH value of the reaction tank, determine a second dosing pump frequency based on the pH value, pH value change trend and preset correction strategy; The fourth processing module is configured to calculate a basic dosing adjustment buffer time based on a structure volume from an influent fluoride monitoring point to a dosing point, influent flow rate and water quality detection time length, and calculate a linkage dosing adjustment interval time based on a structure volume from the dosing point to a pH monitoring point and the influent flow rate; The execution module is configured to calculate a third dosing pump frequency based on the first dosing pump frequency, the second dosing pump frequency, the basic dosing adjustment buffer time and the linkage dosing adjustment interval time, trigger dosing parameter updating according to the basic dosing adjustment buffer time, perform dosing correction according to the linkage dosing adjustment interval time, and output the third dosing pump frequency to a dosing pump frequency converter to perform calcium salt dosing.

Images