Deep defluorination sludge backflow method and defluorination agent preparation method

Abstract

The invention discloses a deep defluorination sludge backflow method and a defluorination agent preparation method, and particularly relates to the technical field of sewage treatment.The deep defluorination sludge backflow method comprises the following steps that fluorine-containing waste water is introduced into a mixing cavity through flow regulation for a continuous flow defluorination reaction, polyaluminum chloride, anhydrous calcium chloride and sodium chloride serve as the defluorination agents, the water inflow amount is added, and the defluorination reaction is completed; and reducing the pH value in the wastewater to a set threshold value. The sludge reflux rate is predicted through the effluent fluorine concentration and the sludge concentration, when the effluent fluorine concentration exceeds the set threshold value, the reflux rate is increased to ensure the fluorine ion removal efficiency, and when the sludge concentration exceeds the set threshold value, the reflux amount is reduced, and the situation that excessive sludge in the reaction tank affects the action of a medicament is avoided; the method has the advantages that the fluorine ions in the wastewater can be effectively removed and the wastewater can reach the emission standard by accurately calculating the chemical dosage, dynamically feeding back and adjusting and controlling the sludge backflow rate through real-time monitoring data and dynamically adjusting a regression model.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and more specifically, to a deep defluorination sludge reflow method and a defluorination agent preparation method. Background Art

[0002] Fluoride-containing wastewater mainly comes from the electronics, electroplating, metal processing, chemical and other industries. Excessive fluoride ion emissions will cause serious harm to the environment and human health. Therefore, it is very important to effectively remove fluoride ions in wastewater. At present, common defluoridation methods include chemical precipitation, adsorption, ion exchange, etc., but these methods have certain limitations in practical applications. For example, the defluoridation effect of chemical precipitation is affected by many factors, and the removal of fluoride ions may not be complete; the adsorption method and ion exchange method have the problems of difficulty in regenerating adsorbents or ion exchange resins and high costs. At the same time, in the defluoridation process, precise control of the dosage of the agent and reasonable adjustment of the sludge reflow rate are also key factors in improving the defluoridation efficiency and reducing costs. However, the existing technology lacks effective dynamic control means in this regard, and it is difficult to optimize the treatment process in real time according to changes in wastewater quality, thereby affecting the overall defluoridation effect and treatment cost.

[0003] Some fluoride removal methods, such as chemical precipitation, are restricted by many factors and it is difficult to completely remove fluoride ions. There is a lack of effective methods to dynamically adjust the dosage of chemicals according to the wastewater quality, resulting in waste of chemicals or poor fluoride removal effect. It is difficult to achieve precise dosing to improve treatment efficiency. There is a lack of reasonable dynamic control strategy for the regulation of sludge return rate, and sludge return cannot be optimized according to actual conditions, affecting the system's fluoride removal effect and operational stability. Summary of the invention

[0004] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present invention provide a deep defluorination sludge reflow method and a defluorination agent preparation method. By controlling the fluorine concentration of the effluent and the sludge concentration, the sludge reflow rate is predicted. When the fluorine concentration of the effluent exceeds the set threshold, the reflow rate is increased to ensure the fluoride ion removal efficiency. When the sludge concentration exceeds the set threshold, the reflow rate is reduced to avoid excessive sludge in the reaction tank and affect the effect of the agent. Accurate agent dosage calculation, dynamic feedback adjustment and sludge reflow rate control are performed. Through real-time monitoring data and dynamic adjustment of the regression model, it is ensured that fluoride ions in the wastewater are effectively removed to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a deep defluorination sludge reflow method, comprising the following steps:

[0006] Fluoride-containing wastewater is introduced into the mixing chamber for continuous flow defluorination reaction by flow regulation;

[0007] By using polyaluminium chloride, anhydrous calcium chloride and sodium chloride as defluoridants, adding water volume to the influent, the pH value in the wastewater is reduced to the set threshold, and the reaction is promoted by stirring;

[0008] Monitor the fluoride ion concentration of wastewater. When the concentration drops to the set fluoride ion concentration threshold, adjust the dosage of defluoridation agent or start sludge return;

[0009] In the solid-liquid separation stage, when the sludge content drops to the set sludge content threshold, it enters the circulation mode and continues the reaction;

[0010] The fluoride ion concentration, pH value and defluoridation agent dosage of the wastewater are monitored by a fluoride ion monitor, a flow meter, a pH sensor and a chemical dosing device, and a monitoring data set is generated. The effluent fluoride ion concentration and the inlet fluoride ion concentration of the monitoring data set are used as the output values ​​of the feedback adjustment model. The output of the chemical pump is dynamically adjusted according to the dosage of the defluoridation agent and the fluoride ion removal threshold. The monitoring data set is used as the output value of the regression model. The model is trained according to the fluoride ion concentration, pH value, inlet flow rate and defluoridation agent dosage. The required defluoridation agent dosage is dynamically predicted by the linear regression coefficient. The accuracy of the model is verified by cross-validation and adjustment of the regularization parameter. The chemical dosage is dynamically adjusted through regression model monitoring and prediction, and the sludge return volume is dynamically adjusted according to the excessive threshold of fluoride concentration in the wastewater.

[0011] In a preferred embodiment, fluorine-containing wastewater is introduced into a mixing chamber through a flow regulating device to perform a continuous flow defluorination reaction, the inlet flow is monitored online in real time, and the inlet conditions are dynamically evaluated in combination with the initial fluoride ion concentration and pH value of the wastewater. Polyaluminium chloride, anhydrous calcium chloride and sodium chloride are used as defluorinating agents, and the required dosage of the agent is calculated in real time according to a dynamic optimization prediction model. The dynamic optimization prediction model expression formula is:

[0012] A d =1(C in )+2(pH in )+3(Q in )

[0013] Among them, A d represents the dosage of the agent, 1, 2, 3 represent the dynamic control factors of the dosage of the agent, Q in Indicates the water inlet flow rate, which is monitored in real time by an online flow meter. in Indicates the initial concentration of fluoride ions in wastewater, detected by online fluoride ion monitor, pH in It indicates the initial pH value of the wastewater, which is obtained through the pH sensor. The introduction of wastewater requires precise control of the inlet flow rate to avoid excessively high or low flow rates affecting the residence time and reaction efficiency of the reactor. The initial parameter C in and pH inThe dynamic evaluation will directly affect the subsequent dosage calculation of the reagent, among which the fluoride ion concentration C in When the set threshold is exceeded, the dosage of the agent A d The more pH is needed to ensure effective removal of fluoride ions, the greater the in Affects the reaction rate of polyaluminium chloride and fluoride. Appropriate pH value is conducive to the formation of effective flocculants. Flow rate Q in When the set threshold is exceeded, the distribution of the reagent in the reaction pool per unit time may be more sparse, so the amount of reagent needs to be adjusted to compensate. The dynamic regulation of the reagent dosage is used and the reaction is promoted by stirring and mixing. The dynamic adjustment formula of the reagent dosage is:

[0014]

[0015] Where D(t) represents the dosage of the agent at time t. The dynamic output is calculated by the formula to ensure economy and efficiency. Q in It represents the water flow rate, D0 represents the basic dosage, which is usually the initial value set by experience, α, β, γ represent the adjustment coefficients, which are used to optimize the agent dosage curve, and T represents the adjustment cycle.

[0016] In a preferred embodiment, when the fluoride ion concentration does not drop to the set fluoride ion concentration threshold, the dosing strategy and the sludge return rate are adjusted through real-time monitoring and feedback regulation to ensure that the effluent fluoride concentration is stable within the discharge threshold and that the return concentration of the sludge flocs is high enough to support the long-term operation of the reactor. The dynamic feedback regulation formula is:

[0017] u adjust =k1·(C set -C out )+k2·(pH set -pH out )+k3·(S set -S sludge )

[0018] Among them, u adjust Represents a dynamic adjustment signal, used to determine the dosage or reflux rate of the reagent, C set Indicates target fluoride concentration, pH set Indicates the target pH value, S set represents the target sludge concentration, C out Indicates the fluoride concentration of the water, pH out Indicates pH value, S sludge represents sludge concentration, k1, k2, k3 represent feedback control coefficients.

[0019] In a preferred embodiment, dynamic adjustment is performed to ensure that the fluorine concentration in the effluent is stable within the discharge threshold, and the return concentration of the sludge flocs is high enough to support the long-term operation of the reactor. During the deep defluorination process, the sludge return is controlled to perform deep defluorination. The sludge return control formula is:

[0020] R sludge =ψ1(C out )+ψ2(S sludge )

[0021] Among them, R sludge represents the sludge return rate, ψ1 and ψ2 represent dynamic control factors, representing the influence weights of effluent fluoride concentration and sludge concentration on the return rate respectively.

[0022] In a preferred embodiment, the water inlet parameters, output parameters and control variable parameters are collected in real time, wherein the water inlet parameters include C in Fluoride ion concentration, pH in Wastewater pH, Q in Inlet flow, output parameters include C out Fluoride ion concentration in effluent, S sludge Sludge concentration, pH out The pH value of the outlet water, the control variable parameters include A d Dosage of reagent, R sludge The sludge return rate and influent data are collected in real time through online sensors and monitoring equipment as input data for the regression model. The data set includes C in Wastewater fluoride concentration, pH in pH value of wastewater, Q in Wastewater flow, C out Fluoride ion concentration in effluent, S sludge Effluent sludge concentration and A d The dosage of the agent is predicted by building a regression model through the data set. The regression model formula is:

[0023] A d =β0+β1C in +β2pH in +β3Q in

[0024] Among them, A d represents the predicted dosage of the reagent, β0 represents the bias term of the model, which is the initial fixed dosage, β1, β2, and β3 represent the weight coefficients of fluoride ion concentration, pH, and flow rate on the dosage demand of the reagent, respectively. In the regression model training, C in Fluoride ion concentration, pH in pH and Q in The flow rate is used as the independent variable, and the dosage of the reagent is Ad The dependent variable as output.

[0025] In a preferred embodiment, the coefficients β0, β1, β2, β3 are calculated by the least squares method using a linear regression method to optimize the dosage A of the agent. d The prediction of A d As the dependent variable, C in , pH in , Q in As an independent variable, the regression analysis was performed, and the data was divided into a training set and a test set using the cross-validation method. The accuracy of the regression model was evaluated, and the model performance was evaluated by calculating the mean square error. The regularization parameters were adjusted to avoid overfitting. After the model training was completed, C in Fluoride ion concentration, pH in pH and Q in Traffic to predict and adjust A d Dosage of reagent and R sludge Sludge return rate, real-time monitoring of C out When the fluoride ion concentration in the effluent is higher than the set threshold, the regression model will predict the need to increase the dosage of the reagent and make real-time adjustments through the feedback control system.

[0026] In a preferred embodiment, a defluorination agent preparation method is also included:

[0027] Step 1: Raw material preparation

[0028] Weigh the main ingredients: polyaluminium chloride, anhydrous calcium chloride and sodium chloride according to the amount of water;

[0029] Step 2: Preparation process

[0030] Add solid polyaluminium chloride into water and stir until dissolved to form a solution, dissolve anhydrous calcium chloride and sodium chloride in water and stir until completely dissolved;

[0031] Step 3: Prediction and calculation of dosage of reagents

[0032] According to the real-time monitoring data of influent fluoride concentration, pH value and influent flow rate, the required dosage of the reagent is predicted through the regression model. If the fluoride ion concentration is higher than the threshold, the dosage of the reagent needs to be increased accordingly to ensure sufficient reaction. The pH value affects the reaction effect of the reagent. When the pH value is higher or lower than the threshold, the dosage of the reagent needs to be adjusted. If the flow rate is higher than the threshold, the dosage of the reagent needs to be increased to ensure uniform distribution of the reagent in the wastewater.

[0033] Step 4: Dynamic Feedback Adjustment

[0034] During the treatment process, dynamic feedback control is used to correct the dosage of reagents. If the actual fluoride concentration of the effluent is higher than the threshold, the fluoride concentration can be reduced by increasing the dosage of reagents. If the pH value of the effluent exceeds the set threshold, it is necessary to adjust the dosage of reagents or add sodium hydroxide as a regulating agent to control the pH value. If the sludge concentration exceeds the threshold, it is necessary to adjust the sludge return rate to avoid excessive sludge affecting the reaction efficiency of the reagents.

[0035] Step 5: Prediction and adjustment of sludge return rate

[0036] The sludge return rate is predicted by the effluent fluoride concentration and sludge concentration. When the effluent fluoride concentration exceeds the set threshold, the return rate is increased to ensure the fluoride ion removal efficiency. When the sludge concentration exceeds the set threshold, the return volume is reduced to avoid excessive sludge in the reaction tank and affect the effect of the agent. Accurate calculation of agent dosage, dynamic feedback adjustment and sludge return rate control are carried out through real-time monitoring data and dynamic adjustment of the regression model to ensure that fluoride ions in the wastewater are effectively removed and meet the emission standards.

[0037] Technical effects and advantages of the present invention:

[0038] 1. The sludge return rate is predicted by the effluent fluoride concentration and sludge concentration. When the effluent fluoride concentration exceeds the set threshold, the return rate is increased to ensure the fluoride ion removal efficiency. When the sludge concentration exceeds the set threshold, the return volume is reduced to avoid excessive sludge in the reaction tank and affect the effect of the agent. Accurate agent dosage calculation, dynamic feedback adjustment and sludge return rate control are carried out. Through real-time monitoring data and dynamic adjustment of the regression model, it is ensured that the fluoride ions in the wastewater are effectively removed and meet the discharge standards;

[0039] 2. Through dynamic adjustment of the dosage of the reagent, the dosage of the reagent can be adapted to the wastewater with different contents. When the fluoride ions in the wastewater are mixed with polyaluminium chloride, they will form a water-insoluble sodium hexafluoroaluminate precipitate with Na+, which can remove the fluoride ions from the water. In addition, the calcium chloride in the self-prepared defluoridation agent may also have an impact on fluoride, such as the production of calcium fluoride, etc. These chemical substances play a certain auxiliary role in the removal of fluoride. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram showing the effect of the dosage of the defluorination agent of the present invention on the defluorination effect.

[0041] Figure 2 It is a schematic diagram of the correlation between the amount of fluoride ion removal and the amount of defluorination agent added in the present invention.

[0042] Figure 3 This is a schematic diagram of the effect of pH on fluoride removal during the reaction process of the present invention.

[0043] Figure 4This is a schematic diagram of the fluoride removal effect of sludge reflow in the present invention.

[0044] Figure 5 It is a schematic diagram of the operation process of the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Refer to the instruction manual Figure 1-5 A deep defluorination sludge reflow method according to an embodiment of the present invention comprises the following steps:

[0047] Fluoride-containing wastewater is introduced into the mixing chamber for continuous flow defluorination reaction by flow regulation;

[0048] By using polyaluminium chloride, anhydrous calcium chloride and sodium chloride as defluoridants, adding water volume to the influent, the pH value in the wastewater is reduced to the set threshold, and the reaction is promoted by stirring. The main component of the PAC solid used in the defluoridation agent is a water-soluble inorganic high molecular polymer, polyaluminium chloride, which has certain defluoridation performance, especially in sewage treatment. Although PAC itself cannot directly remove fluorine, under certain conditions, it can promote the precipitation and removal of fluoride. When the fluoride ions in the wastewater are mixed with polyaluminium chloride, they will form a water-insoluble sodium hexafluoroaluminate precipitate with Na+, which can remove fluoride ions from the water. In addition, calcium chloride in the self-prepared defluoridation agent may also have an impact on fluoride, such as the production of calcium fluoride, etc. These chemicals play a certain auxiliary role in the removal of fluoride. However, the removal effect of fluoride ions is affected by many factors, such as pH value and the amount of defluoridation agent added. Therefore, if fluoride needs to be completely removed from the wastewater, it needs to be optimized and adjusted according to the specific situation to improve the removal efficiency;

[0049] Monitor the fluoride ion concentration of wastewater. When the concentration drops to the set fluoride ion concentration threshold, adjust the dosage of defluoridation agent or start sludge return;

[0050] In the solid-liquid separation stage, when the sludge content drops to the set sludge content threshold, it enters the circulation mode and continues the reaction;

[0051] The fluoride ion concentration, pH value and defluoridation agent dosage of the wastewater are monitored by a fluoride ion monitor, a flow meter, a pH sensor and a chemical dosing device, and a monitoring data set is generated. The effluent fluoride ion concentration and the inlet fluoride ion concentration of the monitoring data set are used as the output values ​​of the feedback adjustment model. The output of the chemical pump is dynamically adjusted according to the dosage of the defluoridation agent and the fluoride ion removal threshold. The monitoring data set is used as the output value of the regression model. The model is trained according to the fluoride ion concentration, pH value, inlet flow rate and defluoridation agent dosage. The required defluoridation agent dosage is dynamically predicted by the linear regression coefficient. The accuracy of the model is verified by cross-validation and adjustment of the regularization parameter. The chemical dosage is dynamically adjusted through regression model monitoring and prediction, and the sludge return volume is dynamically adjusted according to the excessive threshold of fluoride concentration in the wastewater.

[0052] Fluoride-containing wastewater is introduced into the mixing chamber through a flow regulating device to carry out a continuous flow defluorination reaction. The inlet flow is monitored online in real time, and the inlet conditions are dynamically evaluated in combination with the initial fluoride ion concentration and pH value of the wastewater. Polyaluminium chloride, anhydrous calcium chloride and sodium chloride are used as defluoridants. The required dosage of the agent is calculated in real time according to the dynamic optimization prediction model. The dynamic optimization prediction model expression formula is:

[0053] A d =1(C in )+2(pH in )+3(Q in )

[0054] Among them, A d represents the dosage of the agent, 1, 2, 3 represent the dynamic control factors of the dosage of the agent, Q in Indicates the water inlet flow rate, which is monitored in real time by an online flow meter. in Indicates the initial concentration of fluoride ions in wastewater, detected by online fluoride ion monitor, pH in It indicates the initial pH value of the wastewater, which is obtained through the pH sensor. The introduction of wastewater requires precise control of the inlet flow rate to avoid excessively high or low flow rates affecting the residence time and reaction efficiency of the reactor. The initial parameter C in and pH in The dynamic evaluation will directly affect the subsequent dosage calculation of the reagent, among which the fluoride ion concentration C in When the set threshold is exceeded, the dosage of the agent A d The more pH is needed to ensure effective removal of fluoride ions, the greater the in Affects the reaction rate of polyaluminium chloride and fluoride. Appropriate pH value is conducive to the formation of effective flocculants. Flow rate Q inWhen the set threshold is exceeded, the distribution of the reagent in the reaction pool per unit time may be more sparse, so it is necessary to adjust the dosage of the reagent to compensate for it. The pH of the wastewater is adjusted to the optimal range (such as 7.0-8.0) through regression model calibration. The dynamic regulation of the reagent dosage is used and the reaction is promoted by stirring and mixing. The dynamic adjustment formula of the reagent dosage is:

[0055]

[0056] Where D(t) represents the dosage of the agent at time t. The dynamic output is calculated by the formula to ensure economy and efficiency. Q in represents the water flow rate, D0 represents the basic dosage, which is usually the initial value set by experience, α, β, γ represent the adjustment coefficients, which are used to optimize the reagent dosage curve; exp(-γ·|C out (t)-T set |) represents the effluent concentration C out (t) and target concentration T set The exponential decay function of the deviation is used to reflect the dynamic response of the dosage of the reagent to the deviation. T represents the adjustment period. For low-concentration fluoride-containing wastewater with a raw water fluoride ion mass concentration of about 10 mg / L, it only relies on the addition of calcium salt to generate CaF2 precipitation to remove fluoride ions in the solution. Its removal effect is very limited. First, the solubility product of CaF2 limits its removal of fluoride ions, and second, the sedimentation rate of CaF2 is extremely slow; therefore, a certain amount of defluoridation agent is added during the chemical defluoridation process. The floccules produced by its polyaluminum chloride will adsorb tiny crystalline calcium fluoride and cause it to settle quickly, thereby obtaining a better defluoridation effect. In the experiment, under the condition of maintaining the influent fluoride ion content at 8.92 mg / L and the pH at 8.63, the effects of different defluoridation agent dosages on the defluoridation effect were investigated. The results are as follows: Figure 1 As shown;

[0057] like Figure 2 As shown in the figure, with the increase of the dosage of defluoridation agent, the residual fluoride ion concentration in the effluent gradually decreases. When the mass concentration of fluoride ions in the raw water is ≤10mg / L, there is a good correlation between the amount of fluoride ions removed and the dosage of defluoridation agent. When the dosage of defluoridation agent is 0.2%, the fluoride content is 4.61mg / L; when the dosage of defluoridation agent is 0.3%, the fluoride content is about 3.20mg / L; the fluoride content can be reduced to 1.51mg / L with the increase of the dosage of defluoridation agent;

[0058] In the process of precipitation reaction for defluorination, pH is an extremely important factor, which directly affects the removal effect of fluoride ions. Therefore, controlling the optimal pH in the reaction process according to the different components in the fluoride-containing wastewater is a key measure to improve the treatment effect and reduce the consumption of drugs. Two groups of wastewater with different components and fluoride ion mass concentration ≤10mg / L were tested for the effect of pH on the treatment effect. Under the condition of 0.5% defluoridation agent dosage, the defluorination effect at pH 6.5, 7.0, 7.5 and 8.0 was tested respectively; the experimental results show that with the different pH values, the defluorination efficiency of the system varies while maintaining other operating conditions unchanged;

[0059] like Figure 3 As shown, under the condition of maintaining the fluoride ion content of the inlet water at 10 mg / L and the pH at 8.0, when the reaction pH is between 7.5 and 8.0, the fluoride content of the outlet water is 1.69 mg / L; the reaction pH is between 7.0 and 7.5, the fluoride content of the outlet water is 1.34 mg / L; the reaction pH is between 6.5 and 7.0, the fluoride content of the outlet water is 1.01 mg / L. In another group of experiments, the influent contained 3.65 mg / L of fluoride ions and the pH was 3.65; when the reaction pH was between 7.5 and 8.0, the effluent fluoride content was 0.80 mg / L; when the reaction pH was between 7.0 and 7.5, the effluent fluoride content was 0.61 mg / L; when the reaction pH was between 6.5 and 7.0, the effluent fluoride content was 0.52 mg / L. During the reaction, the pH increased, the fluoride content increased, and the fluoride ion removal rate decreased. It can be seen that in the reaction process of polyaluminium chloride and fluoride, pH has an important influence on it. For low-fluoride wastewater with a mass concentration of ≤10 mg / L, controlling the reaction pH at 6.5 to 7.0 can achieve the best fluoride removal effect. In addition, since PAC is acidic, the self-prepared defluoridation agent is generally weakly acidic, which makes It is found that as the amount of defluoridation agent added increases, the pH of the mixed solution will be less than 6. The experiment considered adjusting the pH when adding the defluoridation agent to examine the effect on the removal of fluoride ions. The experimental results show that adding sodium hydroxide at the same time as adding the defluoridation agent to keep the reaction pH at 6.5-7.0 will have a better effect on the removal of fluoride ions than further adjusting the pH of the mixed solution after adding the defluoridation agent. PAM is a product of catalytic polymerization of acrylamide monomer. Its high relative molecular mass and linear molecular structure give it exclusive properties such as adsorption, bridging, and netting. Therefore, PAM is mostly used as a coagulant for coagulation and sedimentation. During the experiment, under the conditions of 0.5% defluoridation agent and 6.5-7.0 influent pH, adding a small amount of PAM is beneficial to the removal of fluoride ions. This is mainly due to the unique molecular structure of PAM, which enables it to have a strong adsorption and bridging effect on flocs and micro-flocs produced by coagulation, promotes the flocculation of flocs, and thus facilitates the removal of fluoride ions.

[0060] When the fluoride ion concentration does not drop to the set fluoride ion concentration threshold, the dosing strategy and sludge return rate are adjusted through real-time monitoring and feedback regulation to ensure that the effluent fluoride concentration is stable within the discharge threshold and that the return concentration of the sludge flocs is high enough to support the long-term operation of the reactor. The dynamic feedback regulation formula is:

[0061] u adjust =k1·(C set -C out )+k2·(pH set -pH out )+k3·(S set -S sludge )

[0062] Among them, u adjust Represents a dynamic adjustment signal, used to determine the dosage or reflux rate of the reagent, C set Indicates target fluoride concentration, pH set Indicates the target pH value, S set represents the target sludge concentration, C out Indicates the fluoride concentration of the water, pH out Indicates pH value, S sludge represents sludge concentration, k1, k2, k3 represent feedback control coefficients. The main purpose of real-time monitoring is to adjust the dosing strategy and sludge return rate through feedback signals during operation.

[0063] Through dynamic adjustment, the fluorine concentration in the effluent is ensured to be stable within the discharge threshold, and the return concentration of the sludge flocs is ensured to be high enough to support the long-term operation of the reactor. In the deep defluorination process, the sludge return is controlled to achieve deep defluorination. The sludge return control formula is:

[0064] R sludge =ψ1(C out )+ψ2(S sludge )

[0065] Among them, R sludgerepresents the sludge return rate, ψ1 and ψ2 represent dynamic control factors, which represent the weights of the influence of fluorine concentration in the effluent and sludge concentration on the return rate respectively. The returned sludge not only contains calcium fluoride precipitate generated by the reaction, but also retains some chemical substances that have not fully reacted, which can significantly improve the reagent utilization rate and operation efficiency of the system. First, the raw water inlet pH is between 1.0 and 6.0, and the fluoride ion mass concentration is between 10 and 30 mg / L. The fluoride-containing waste liquid is pumped into the reaction tank through pretreatment, and calcium hydroxide with a concentration of 30% is added through the reagent pump to adjust the pH value between 6.5 and 8.0, and the fluoride content in the effluent is controlled to be ≤10 mg / L. After solid-liquid separation, the pretreated effluent is pumped into the continuous flow defluorination reaction tank, and a defluoridation agent with a concentration of 0.4% of the inlet water and sodium hydroxide with a concentration of 30% are added to control the reaction pH at 6.5-7.0, and the reaction is continuously stirred; the defluorination reaction tank is detected by a fluoride ion online monitor When the fluoride content is ≤1mg / L, the outlet of the continuous flow defluorination reaction tank can be opened, and the treated effluent can be discharged into the sludge sedimentation tank for solid-liquid separation. The qualified supernatant can be discharged directly. If the defluoridation agent is added at 0.4% of the influent water volume, and the fluoride ion concentration is still greater than 1mg / L through the fluoride ion online monitor, the dosage of the agent pump can be adjusted to add 0.5% of the influent water volume. At the same time, a small amount of 30% sodium hydroxide needs to be added to control the reaction pH at 6.5-7.0; if the dosage needs to be further increased, the dosage of the agent pump can be increased by 0.1% each time until the fluoride content in the reaction tank is detected to be ≤1mg / L, and the treated effluent is discharged into the sludge sedimentation tank for solid-liquid separation. The qualified supernatant can be discharged directly. The defluoridation reaction tank is a continuous flow, and the dosage of the defluoridation agent can be adjusted according to the different concentrations of fluoride-containing influent water. The raw water inlet pH is between 6.0 and 8.0, and the fluoride ion mass concentration is between 1 and 10mg / L.

[0066] The fluoride-containing waste liquid is directly pumped into the continuous flow defluorination reaction tank, and 0.4% of the self-prepared defluoridation agent of the influent water volume is added through the agent pump to stir the reaction; when the fluoride content in the defluoridation reaction tank is detected by the fluoride ion online monitor to be ≤1mg / L, the treated water can be discharged into the sludge sedimentation tank for solid-liquid separation, and the qualified supernatant can be directly discharged. If the self-prepared defluoridation agent of 0.4% of the influent water volume is added for treatment, when the fluoride ion concentration is still greater than 1mg / L detected by the fluoride ion online monitor, the agent pump can be used to remove the fluoride. The dosage is adjusted to add 0.5% of the self-prepared defluoridation agent to the influent water; the steps of adjusting the dosage of the agent pump (it is recommended to increase the dosage by 0.1% each time) can be repeated until the fluoride content in the reaction pool is detected to be ≤1mg / L (Note: the water in the reaction pool needs to control the reaction pH at 6.5-7.0. If the pH is <6.5, a small amount of 30% sodium hydroxide should be added to control the reaction pH). The treated water is discharged into the sludge sedimentation tank for solid-liquid separation. The qualified supernatant can be discharged directly. Considering the cost, if after adding 0.4% of the self-prepared defluoridation agent to the influent water, if the fluoride ion concentration detected by the fluoride ion online monitor is still greater than 1mg / L, sludge return can be considered, and the return pump at the lower end of the sludge sedimentation tank can be turned on, and the ratio of sludge return flow to direct water inlet is 1:4; at the same time, the dosage of the agent pump can be adjusted to add 0.3% of the self-prepared defluoridation agent to the influent water, and the fluoride content of the effluent can be controlled below 1mg / L. When the effluent is discharged into the sludge sedimentation tank, a small amount of PAM liquid with a concentration of 5‰ can be added for slow stirring, which is conducive to the flocculation and sedimentation of the sludge; at the same time, a grid can be added near the water inlet of the sludge sedimentation tank to facilitate the solid-liquid separation of mud and water. Increasing sludge return can improve the fluoride removal effect of the system. The loading of sludge increases the effective contact collision, improves the effective utilization rate of sodium hydroxide and the fluoride ion removal rate. The experimental object is low-concentration fluoride-containing wastewater with a fluoride ion mass concentration of ≤10mg / L. During the experiment, a comparative experiment was conducted on the impact of sludge return, and the results are as follows Figure 4 As shown by Figure 4 It can be seen that when the water is directly fed, the greater the amount of defluoridation agent added, the lower the fluoride content in the effluent, and the less obvious the effect of sludge return. When the amount of defluoridation agent added is ≤0.4% and the fluoride content in the effluent is >1mg / L, the use of muddy water mixed sludge return can be considered. Considering that the amount of defluoridation agent added can obtain an economical and appropriate defluoridation effect, the amount of muddy water mixed sludge return and the direct water intake are 1:4, the amount of defluoridation agent added is 0.3%, and the fluoride content in the effluent is ≤1mg / L.

[0067] By collecting the inlet parameters, output parameters and control variable parameters in real time, the inlet parameters include C in Fluoride ion concentration, pH in Wastewater pH, Q in Inlet flow, output parameters include C out Fluoride ion concentration in effluent, S sludge Sludge concentration, pHout The pH value of the outlet water, the control variable parameters include A d Dosage of reagent, R sludge Sludge return rate, among these parameters, the influent data is collected in real time through online sensors and monitoring equipment as the input data of the regression model, and records under multiple different conditions are collected in the historical operating conditions. The data set includes C in Wastewater fluoride concentration, pH in pH value of wastewater, Q in Wastewater flow, C out Fluoride ion concentration in effluent, S sludge Effluent sludge concentration and A d The dosage of the agent is predicted by building a regression model through the data set. The regression model formula is:

[0068] A d =β0+β1C in +β2pH in +β3Q in

[0069] Among them, A d represents the predicted dosage of the reagent, β0 represents the bias term of the model, which is the initial fixed dosage, β1, β2, and β3 represent the weight coefficients of fluoride ion concentration, pH, and flow rate on the dosage demand of the reagent, respectively. In the regression model training, C in Fluoride ion concentration, pH in pH and Q in The flow rate is used as the independent variable, and the dosage of the reagent is A d The dependent variable as output.

[0070] The coefficients β0, β1, β2, and β3 were calculated by the least squares method using the linear regression method to optimize the dosage of the agent A. d The prediction of A d As the dependent variable, C in , pH in , Q in As the independent variable, regression analysis is performed to obtain the best regression coefficient. The data is divided into training set and test set using cross-validation method to evaluate the accuracy of the regression model. The model performance is evaluated by calculating the mean square error. The regularization parameters are adjusted to avoid overfitting and increase the generalization ability of the model. After the model training is completed, the C in Fluoride ion concentration, pH in pH and Q in Traffic to predict and adjust A d Dosage of reagent and R sludge The sludge return rate, if monitored in real time, is outWhen the fluoride ion concentration in the effluent is higher than the set threshold, the regression model will predict the need to increase the dosage of the reagent and make real-time adjustments through the feedback control system.

[0071] In addition, a method for preparing a defluorination agent:

[0072] Step 1: Raw material preparation

[0073] Weigh the main ingredients: polyaluminium chloride, anhydrous calcium chloride and sodium chloride according to the amount of water;

[0074] Step 2: Preparation process

[0075] Add solid polyaluminium chloride into water and stir until dissolved to form a solution, dissolve anhydrous calcium chloride and sodium chloride in water and stir until completely dissolved;

[0076] Step 3: Prediction and calculation of dosage of reagents

[0077] According to the real-time monitoring data of influent fluoride concentration, pH value and influent flow rate, the required dosage of the reagent is predicted through the regression model. If the fluoride ion concentration is higher than the threshold, the dosage of the reagent needs to be increased accordingly to ensure sufficient reaction. The pH value affects the reaction effect of the reagent. When the pH value is higher or lower than the threshold, the dosage of the reagent needs to be adjusted. If the flow rate is higher than the threshold, the dosage of the reagent needs to be increased to ensure uniform distribution of the reagent in the wastewater.

[0078] Step 4: Dynamic Feedback Adjustment

[0079] During the treatment process, dynamic feedback control is used to correct the dosage of reagents. If the actual fluoride concentration of the effluent is higher than the threshold, the fluoride concentration can be reduced by increasing the dosage of reagents. If the pH value of the effluent exceeds the set threshold, it is necessary to adjust the dosage of reagents or add sodium hydroxide as a regulating agent to control the pH value. If the sludge concentration exceeds the threshold, it is necessary to adjust the sludge return rate to avoid excessive sludge affecting the reaction efficiency of the reagents.

[0080] Step 5: Prediction and adjustment of sludge return rate

[0081] The sludge return rate is predicted by the effluent fluoride concentration and sludge concentration. When the effluent fluoride concentration exceeds the set threshold, the return rate is increased to ensure the fluoride ion removal efficiency. When the sludge concentration exceeds the set threshold, the return volume is reduced to avoid excessive sludge in the reaction tank and affect the effect of the agent. Accurate agent dosage calculation, dynamic feedback adjustment and sludge return rate control are carried out. Through real-time monitoring data and dynamic adjustment of the regression model, it is ensured that the fluoride ions in the wastewater are effectively removed and meet the discharge standards;

[0082] The pH value of the raw water inlet is between 1.0 and 6.0, and the mass concentration of fluoride ions is between 10 and 30 mg / L. Pretreatment: the fluoride-containing waste liquid is pumped into the reaction tank, and calcium hydroxide with a concentration of 30% is added through a reagent pump to adjust the pH value between 6.5 and 8.0, and the fluoride content of the effluent is controlled to be ≤10 mg / L. After solid-liquid separation, the pretreated effluent is pumped into the continuous flow defluorination reaction tank, and at the same time, 0.4% of the inlet water volume of the self-prepared defluoridation agent and 30% sodium hydroxide are added to control the reaction pH to 6.5-7.0, and the reaction is continuously stirred; when the fluoride content in the defluorination reaction tank is detected to be ≤1 mg / L by the fluoride ion online monitor, the continuous flow defluorination reaction can be The water outlet of the pool is opened, and the treated water is discharged into the sludge sedimentation tank for solid-liquid separation. The qualified supernatant can be discharged directly. If after adding 0.4% of the influent water volume of the self-prepared defluoridation agent, when the fluoride ion concentration detected by the fluoride ion online monitor is still greater than 1mg / L, the dosage of the chemical pump can be adjusted to add 0.5% of the influent water volume of the self-prepared defluoridation agent, and a small amount of 30% sodium hydroxide needs to be added to control the reaction pH at 6.5-7.0; if the dosage needs to be further increased, the dosage of the chemical pump can be increased by 0.1% each time until the fluoride content in the reaction pool is detected to be ≤1mg / L, and the treated water is discharged into the sludge sedimentation tank for solid-liquid separation, and the qualified supernatant can be discharged directly. Because the defluorination reaction tank of this process section is a continuous flow, the dosage of the self-prepared defluorination agent can be adjusted according to the different concentrations of fluoride-containing influent water. The pH of the raw water inlet is between 6.0 and 8.0, and the mass concentration of fluoride ions is between 1 and 10 mg / L. The fluoride-containing waste liquid is directly pumped into the continuous flow defluorination reaction tank, and 0.4% of the influent water volume of the self-prepared defluorination agent is added through the agent pump for stirring reaction; when the fluoride content in the defluorination reaction tank is detected by the fluoride ion online monitor to be ≤1 mg / L, the treated water can be discharged into the sludge sedimentation tank for solid-liquid separation, and the qualified supernatant can be discharged directly, such as adding 0.4% of the influent water volume. After being treated with the self-prepared defluoridation agent, if the fluoride ion concentration is still greater than 1mg / L as detected by the fluoride ion online monitor, the dosage of the agent pump can be adjusted to add 0.5% of the self-prepared defluoridation agent to the influent water; the dosage of the agent pump can be adjusted repeatedly, and the dosage can be increased by 0.1% each time until the fluoride content in the reaction pool is detected to be ≤1mg / L. The water in the reaction pool needs to control the reaction pH at 6.5-7.0. If the pH is less than 6.5, a small amount of 30% sodium hydroxide needs to be added at the same time to control the reaction pH. The treated water is discharged into the sludge sedimentation tank for solid-liquid separation, and the qualified supernatant can be discharged directly. Figure 5 shown.

[0083] From a comprehensive consideration, if after adding 0.4% of the self-prepared defluoridation agent to the influent water, if the fluoride ion concentration detected by the fluoride ion online monitor is still greater than 1mg / L, you can consider enabling sludge return and opening the reflux pump at the lower end of the sludge sedimentation tank. The ratio of sludge return flow to direct water inflow is 1:4; at the same time, the dosage of the chemical pump can be adjusted to add 0.3% of the self-prepared defluoridation agent to the influent water, and the fluoride content in the effluent can be controlled below 1mg / L.

[0084] When the treated water is discharged into the sludge sedimentation tank, a small amount of PAM liquid with a concentration of 5‰ can be added and slowly stirred to help the flocculation and sedimentation of the sludge; at the same time, a grid can be added near the water inlet of the sludge sedimentation tank to help the solid-liquid separation of the mud and water.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A deep defluorination sludge reflow method, characterized in that: The following steps are involved: Fluoride-containing wastewater is introduced into the mixing chamber for continuous flow defluorination reaction by flow regulation; By using polyaluminium chloride, anhydrous calcium chloride and sodium chloride as defluoridants, adding water volume to the influent, the pH value in the wastewater is reduced to the set threshold, and the reaction is promoted by stirring; Monitor the fluoride ion concentration of wastewater. When the concentration drops to the set fluoride ion concentration threshold, adjust the dosage of defluoridation agent or start sludge return; In the solid-liquid separation stage, when the sludge content drops to the set sludge content threshold, it enters the circulation mode and continues the reaction; The fluoride ion concentration, pH value and defluoridation agent dosage of the wastewater are monitored by a fluoride ion monitor, a flow meter, a pH sensor and a chemical dosing device, and a monitoring data set is generated. The effluent fluoride ion concentration and the inlet fluoride ion concentration of the monitoring data set are used as the output values ​​of the feedback adjustment model. The output of the chemical pump is dynamically adjusted according to the dosage of the defluoridation agent and the fluoride ion removal threshold. The monitoring data set is used as the output value of the regression model. The model is trained according to the fluoride ion concentration, pH value, inlet flow rate and defluoridation agent dosage. The required defluoridation agent dosage is dynamically predicted by the linear regression coefficient. The accuracy of the model is verified by cross-validation and adjustment of the regularization parameter. The chemical dosage is dynamically adjusted through regression model monitoring and prediction, and the sludge return volume is dynamically adjusted according to the excessive threshold of fluoride concentration in the wastewater.

2. A deep defluorination sludge reflow method according to claim 1, characterized in that: Fluoride-containing wastewater is introduced into the mixing chamber through a flow regulating device to carry out a continuous flow defluorination reaction. The inlet flow is monitored online in real time, and the inlet conditions are dynamically evaluated in combination with the initial fluoride ion concentration and pH value of the wastewater. Polyaluminium chloride, anhydrous calcium chloride and sodium chloride are used as defluoridants. The required dosage of the agent is calculated in real time according to the dynamic optimization prediction model. The dynamic optimization prediction model expression formula is: A d =1(C in )+2(pH in )+3(Q in ) Among them, A d represents the dosage of the agent, 1, 2, 3 represent the dynamic control factors of the dosage of the agent, Q in Indicates the water inlet flow rate, C in Indicates the initial concentration of fluoride ions in wastewater, pH in Indicates the initial pH value of the wastewater, initial parameter C in and pH in The dynamic evaluation will affect the subsequent calculation of the dosage of the reagent. The dynamic adjustment formula of the reagent dosage is: Where D(t) represents the dosage of the agent at time t; D0 represents the basic dosage; α, β, γ represent the adjustment coefficients used to optimize the agent dosage curve; T represents the adjustment period; exp(-γ·|C out (t)-T set |) represents the effluent concentration C out (t) and target concentration T set The exponential decay function of the deviation is used to reflect the dynamic response of the dosage of the reagent to the deviation.

3. A deep defluorination sludge reflow method according to claim 2, characterized in that: When the fluoride ion concentration does not drop to the set fluoride ion concentration threshold, the dosing strategy and sludge return rate are adjusted through real-time monitoring and feedback regulation to ensure that the fluoride concentration in the effluent is stable within the discharge threshold. The dynamic feedback regulation formula is: u adjust =k1·(C set -C out )+k2·(pH set -pH out )+k3·(S set -S sludge ) Among them, u adjust Represents a dynamic adjustment signal, used to determine the dosage or reflux rate of the reagent, C set Indicates target fluoride concentration, pH set Indicates the target pH value, S set represents the target sludge concentration, C out Indicates the fluoride concentration of the water, pH out Indicates pH value, S sludge represents sludge concentration, k1, k2, k3 represent feedback control coefficients.

4. A deep defluorination sludge reflow method according to claim 3, characterized in that: Through dynamic adjustment, the fluorine concentration in the effluent is ensured to be stable within the discharge threshold, and the return concentration of the sludge flocs is ensured to be high enough to support the long-term operation of the reactor. In the deep defluorination process, the sludge return is controlled to remove fluorine in depth. The sludge return control formula is: R sludge =ψ1(C out )+ψ2(S sludge ) Among them, R sludge represents the sludge return rate, ψ1 and ψ2 represent dynamic control factors.

5. A deep defluorination sludge reflow method according to claim 4, characterized in that: By collecting the inlet parameters, output parameters and control variable parameters in real time, the inlet parameters include C in Fluoride ion concentration, pH in Wastewater pH, Q in Inlet flow, output parameters include C out Fluoride ion concentration in effluent, S sludge Sludge concentration, pH out The pH value of the outlet water, the control variable parameters include A d Dosage of reagent, R sludge The sludge return rate and influent data are collected in real time through online sensors and monitoring equipment as input data for the regression model. The data set includes C in Wastewater fluoride concentration, pH in pH value of wastewater, Q in Wastewater flow, C out Fluoride ion concentration in effluent, S sludge Effluent sludge concentration and A d The dosage of the agent is predicted by building a regression model through the data set. The regression model formula is: A d =β0+β1C in +β2pH in +β3Q in Among them, A d represents the predicted dosage of the reagent, β0 represents the bias term of the model, which is the initial fixed dosage, β1, β2, and β3 represent the weight coefficients of fluoride ion concentration, pH, and flow rate on the dosage demand of the reagent, respectively. In the regression model training, C in Fluoride ion concentration, pH in pH and Q in The flow rate is used as the independent variable, and the dosage of the reagent is A d The dependent variable as output.

6. A deep defluorination sludge reflow method according to claim 5, characterized in that: The coefficients β0, β1, β2, and β3 were calculated by the least squares method using the linear regression method to optimize the dosage of the agent A. d The prediction of A d As the dependent variable, C in , pH in , Q in As an independent variable, the regression analysis was performed, and the data was divided into a training set and a test set using the cross-validation method. The accuracy of the regression model was evaluated, and the model performance was evaluated by calculating the mean square error. The regularization parameters were adjusted to avoid overfitting. After the model training was completed, C in Fluoride ion concentration, pH in pH and Q in Traffic to predict and adjust A d Dosage of reagent and R sludge Sludge return rate, real-time monitoring of C out When the fluoride ion concentration in the effluent is higher than the set threshold, the regression model will predict the need to increase the dosage of the reagent and make real-time adjustments through the feedback control system.

7. A deep defluorination sludge reflow method according to claim 6, characterized in that: Also included is a method for preparing a defluoridating agent: Raw material preparation; weigh the main ingredients: polyaluminium chloride, anhydrous calcium chloride and sodium chloride according to the amount of water; Preparation process; Add solid polyaluminium chloride into water and stir until dissolved to form a solution, dissolve anhydrous calcium chloride and sodium chloride in water and stir until completely dissolved; Prediction and calculation of reagent dosage; Based on the real-time monitoring data of influent fluoride concentration, pH value and influent flow rate, the required reagent dosage is predicted through regression model. If the fluoride ion concentration is higher than the threshold, the reagent dosage needs to be increased accordingly to ensure sufficient reaction. The pH value affects the reaction effect of the reagent. When the pH value is higher or lower than the threshold, the reagent dosage needs to be adjusted. If the flow rate is higher than the threshold, the dosage needs to be increased to ensure uniform distribution of the reagent in the wastewater. Dynamic feedback regulation: During the treatment process, dynamic feedback control is used to correct the dosage of reagents. If the actual effluent fluoride concentration is higher than the threshold, the fluoride concentration is reduced by increasing the dosage of reagents. If the pH value of the effluent exceeds the set threshold, it is necessary to adjust the dosage of reagents or add the regulating agent sodium hydroxide to control the pH value. If the sludge concentration exceeds the threshold, it is necessary to adjust the sludge return rate. Prediction and regulation of sludge return rate; The sludge return rate is predicted by the effluent fluoride concentration and sludge concentration. When the effluent fluoride concentration exceeds the set threshold, the return rate is increased to ensure the removal of fluoride ions. When the sludge concentration exceeds the set threshold, the return volume is reduced to avoid excessive sludge in the reaction tank and affect the effect of the agent. Accurate calculation of agent dosage, dynamic feedback adjustment and sludge return rate control are carried out through real-time monitoring data and dynamic adjustment of the regression model to ensure that fluoride ions in the wastewater are effectively removed and meet the emission standards.

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