Calculation method and system for residual chlorine distribution of clean water tank

Abstract

The invention relates to a calculation method and system for residual chlorine distribution of a clean water tank, and belongs to the technical field of drinking water chlorination and disinfection. Firstly, a residual chlorine attenuation curve of a water sample is obtained through fitting, then a clean water tank is gridded through fluid mechanics simulation software, and a clean water tank water inlet and outlet quantity prediction model is established; predicting the water inlet and outlet amount of the clean water tank in a certain time period by using the clean water tank water inlet and outlet amount prediction model, and simulating the flow distribution of each grid in the clean water tank by using fluid mechanics simulation software; and calculating the hydraulic retention time of each grid unit and the total accumulated hydraulic retention time from the inlet of the clean water tank to each grid unit along the water flow horizontal direction, calculating the residual chlorine concentration of the chlorinated raw water passing through each grid of the clean water tank through a residual chlorine attenuation curve, and setting a time step length to update the residual chlorine concentration of each grid unit in real time. The residual chlorine distribution from the inlet to the outlet of the clean water tank can be accurately predicted and managed, so that the water quality safety is ensured, and a basis is provided for improving the use efficiency of a disinfectant.

Description

Technical Field

[0001] The invention relates to a calculation method and system for residual chlorine distribution in a clear water tank, belonging to the technical field of chlorination disinfection of drinking water. Background Art

[0002] Residual chlorine is a key chemical used in water treatment to ensure the safety of water quality in the water supply system, but the residual chlorine will gradually decay during storage and transportation. The clean water tank is an important part of the water treatment system. Its function is to store and treat the treated clean water to ensure that the water quality meets the standards. After the filtered water is chlorinated, the water will pass through the water pipe and the clean water tank in turn. The time passing through the clean water tank is the longest, and the consumption of residual chlorine is greater. Therefore, it is particularly important to calculate and predict the decay of residual chlorine in the clean water tank.

[0003] Traditional residual chlorine attenuation calculation methods often use empirical values ​​for estimation, but their accuracy and applicability are limited under complex hydraulic conditions. This method ignores the spatial variability of water in the clear water tank due to flow, mixing and reaction processes, as well as the changes in the water inflow and outflow of the clear water tank at different time periods. This leads to deviations between the calculation results and the actual situation, and cannot accurately guide water quality management and residual chlorine control. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a method for calculating the residual chlorine distribution in a clear water tank. The method takes into account the spatial distribution and flow characteristics of water flow in the tank, and can simulate the attenuation process of residual chlorine in each grid unit in detail, thereby improving the accuracy of residual chlorine attenuation prediction.

[0005] The technical solution adopted by the present invention is:

[0006] A method for calculating residual chlorine distribution in a clear water tank comprises the following steps:

[0007] S1. Take water samples near the water inlet in the clean water tank, record the residual chlorine concentration at different time points, and fit the data using the parallel first-order reaction model of residual chlorine to obtain the residual chlorine attenuation curve of the water sample;

[0008] S2. Using fluid mechanics simulation software to grid the clean water tank according to its geometric shape and internal structure, divide it into a plurality of cubic grid units, and record the position of each grid unit;

[0009] S3. Based on the historical data of the changes in the inflow and outflow of the clean water tank over time, a conventional deep learning algorithm is used to train the model and establish a prediction model for the inflow and outflow of the clean water tank;

[0010] S4. Use the clean water tank inflow and outflow prediction model to predict the inflow and outflow of the clean water tank within a certain period of time, and use fluid mechanics simulation software to simulate the flow distribution of each grid inside the clean water tank according to the geometric shape, internal structure, grid size, and inflow and outflow of the clean water tank;

[0011] S5. Calculate the hydraulic retention time HRT for each grid cell x and the total accumulated hydraulic retention time HRT from the clean water tank inlet to each grid unit along the horizontal direction of the water flow n总 , the hydraulic retention time HRT of each grid cell x for:

[0012]

[0013] Where V is the volume of each grid cell, Q x is the flow through that grid cell;

[0014] S6. The total accumulated hydraulic retention time HRT from the clean water tank inlet to each grid unit n总 Substitute the residual chlorine attenuation curve of step S1, calculate the residual chlorine concentration of each grid of the clean water tank through the residual chlorine attenuation curve, and then calculate the residual chlorine concentration C of each grid in the clean water tank and the residual chlorine concentration C of the clean water tank outlet based on the real-time monitored residual chlorine amount C0 at the inlet of the clean water tank. 出 ;

[0015] S7. Set the time step Δt, and update the residual chlorine concentration of each grid cell in real time according to the inlet and outlet water flow of the clean water tank within the time Δt, so as to predict the attenuation and residual chlorine distribution in the clean water tank.

[0016] In the above method, the parallel first-order reaction model formula of residual chlorine used in step S1 is:

[0017]

[0018] In the formula, t represents the reaction time, x represents the percentage of the initial residual chlorine concentration participating in the fast reaction to the total initial residual chlorine concentration, C0 is the total initial residual chlorine concentration, k f is the residual chlorine fast reaction decay constant, k s is the residual chlorine slow reaction decay constant, C is the residual chlorine concentration;

[0019] The initial residual chlorine concentration participating in the fast reaction is the residual chlorine concentration participating in the reaction within 0-30 minutes, and x is the ratio of the initial residual chlorine concentration minus the residual chlorine concentration sampled at 30 minutes to the initial residual chlorine concentration. The calculation formula is as follows:

[0020] x=y(C0-C 30 ) / C0,

[0021] Where C0 is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration after 30 minutes, y is the adjustment coefficient, which is taken as 1.15.

[0022] The least squares method is used to fit k f and k s Two parameters, get k s and k f , we can get the functional relationship between residual chlorine concentration C and time t.

[0023] The fluid mechanics simulation software in step S2 includes but is not limited to FLOW-3D model software and CFX model software, which can support complex geometric modeling and meshing and can accurately simulate the flow distribution inside the clear water tank.

[0024] The HRT in step S5 n总 It is the sum of the hydraulic retention times of all grid cells in one direction from the entrance of the clean water tank to the nth grid cell in the horizontal direction of the water flow. Therefore, HRT n总 Contains the single hydraulic retention time HRT of all grid cells in the horizontal flow path direction x ,x=1,2,3…n, the formula is as follows:

[0025] HRT n总 =HRT1+HRT2+...+HRT(n-1)+HRTx.

[0026] Another object of the present invention is to provide a calculation system for residual chlorine distribution in a clean water tank, including a residual chlorine attenuation curve model building module, using the residual chlorine concentration of water samples near the water inlet in the clean water tank at different time points and the parallel first-order reaction model fitting data of the residual chlorine to obtain the residual chlorine attenuation curve of the water sample;

[0027] The fluid mechanics simulation software processing module uses the fluid mechanics simulation software to grid the clean water tank according to the geometric shape and internal structure of the clean water tank, divides it into multiple cubic grid units, records the position of each grid unit, and simulates the flow distribution of each grid inside the clean water tank according to the geometric shape, internal structure, grid size, and water inlet and outlet of the clean water tank;

[0028] The clean water tank inflow and outflow prediction model module uses conventional deep learning algorithms to train the model based on the historical data of the clean water tank inflow and outflow over time, and uses the clean water tank inflow and outflow prediction model to predict the clean water tank inflow and outflow within a certain period of time;

[0029] The hydraulic retention time calculation module is used to calculate the hydraulic retention time of each grid unit and the total accumulated hydraulic retention time HRT from the clean water tank inlet to each grid unit.n总 , the hydraulic retention time HRT of each grid cell x for:

[0030]

[0031] Where V is the volume of each grid cell, Q x is the flow through the grid cell,

[0032] HRT n总 Contains the single hydraulic retention time HRT of all grid cells in the horizontal flow path direction x ,x=1,2,3…n, the formula is as follows:

[0033] HRT n总 =HRT1+HRT2+...+HRT(n-1)+HRTx;

[0034] The residual chlorine concentration calculation module calculates the total accumulated hydraulic retention time HRT of each grid unit. n总 Substitute the residual chlorine attenuation curve into the calculation, and calculate the residual chlorine concentration of each grid of the clean water tank through the residual chlorine attenuation curve. Based on the residual chlorine amount at the inlet of the clean water tank monitored in real time, the residual chlorine concentration of each grid in the clean water tank and the residual chlorine concentration at the outlet of the clean water tank are obtained.

[0035] Residual chlorine concentration distribution display module, used to display the residual chlorine concentration distribution results;

[0036] The residual chlorine calculation and update module is used to update the calculation of the residual chlorine concentration of each grid cell in real time according to the inlet and outlet water flow of the clean water tank within the set time step.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The clean water tank is divided into fine areas through grid modeling. Combined with the real-time residual chlorine data, the residual chlorine attenuation curve is used to predict the residual chlorine change trend. The predicted water volume of the clean water tank inlet and outlet is integrated to achieve accurate prediction and management of the residual chlorine distribution from the inlet to the outlet of the clean water tank, thereby ensuring water quality safety and providing a basis for improving the efficiency of disinfectant use.

[0039] (2) Through gridding processing, the clean water tank is divided into multiple independent grid units, and each unit is calculated and simulated independently. The decay process of residual chlorine in each grid unit can be simulated in detail, thereby improving the accuracy of residual chlorine decay prediction.

[0040] (3) Through grid modeling and real-time monitoring technology, the distribution of residual chlorine in the clean water tank can be predicted, which improves the monitoring efficiency and accuracy. The amount of chlorine can be automatically adjusted according to the prediction results, achieving precise control of water quality safety. Compared with traditional chlorination methods, it reduces the waste of drugs and helps reduce the use of disinfectants, thereby reducing operating costs and achieving energy-saving and environmental protection effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The figure is a flow chart of the calculation method of the present invention. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0043] Example 1 A method for calculating the residual chlorine distribution in a clear water tank, such as Figure 1 , including the following steps:

[0044] S1. Take water samples near the water inlet in the clean water tank, record the residual chlorine concentration at different time points, and use the parallel first-order reaction model of residual chlorine to fit the data to obtain the residual chlorine attenuation curve of the water sample:

[0045] (1) Take a water sample from the clean water tank near the water inlet, add the water sample into a brown container, and place the brown container in a constant temperature box with the temperature kept constant at 13-19°C.

[0046] The purpose of controlling the temperature to be constant is to ensure that the residual chlorine decay can be carried out at the same temperature and the various measurement data are not affected by temperature changes.

[0047] Take the above water samples and measure the residual chlorine concentration C (mg / L) at different times. The different times refer to the 10th minute, 20th minute, 30th minute, 60th minute, 90th minute, 120th minute, 150th minute, 180th minute and 240th minute. Use the parallel first-order reaction model fitting data of the following formula:

[0048]

[0049] In the formula, t represents the reaction time, x represents the percentage of the initial residual chlorine concentration participating in the fast reaction to the total initial residual chlorine concentration, C0 is the total initial residual chlorine concentration, k f is the residual chlorine fast reaction decay constant, k s is the residual chlorine slow reaction decay constant, C is the residual chlorine concentration;

[0050] There are two types of residual chlorine decay in water of poor quality. One is a rapid reaction, which is generally completed within 0.5 hours and consumes 30%-60% of the residual chlorine. The residual chlorine rapid reaction decay constant k fCorresponding to this process; the other is a slow reaction, which generally takes 10 to 20 hours to complete. The residual chlorine slow reaction decay constant k s Corresponding to this process.

[0051] The least squares method is used to fit k f and k s Two parameters, get k s and k f , we can get the functional relationship between residual chlorine concentration C and time t.

[0052] The initial residual chlorine concentration participating in the fast reaction is the residual chlorine concentration participating in the reaction within 0-30 minutes. x is the ratio of the initial residual chlorine concentration minus the residual chlorine concentration sampled at 30 minutes to the initial residual chlorine concentration, and the calculation formula is as follows:

[0053] x=y(C0-C 30 ) / C0,

[0054] Where C0 is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration after 30 minutes, y is the adjustment coefficient, which is taken as 1.15.

[0055] The residual chlorine is Cl2, HClO and ClO - The sum of the concentrations.

[0056] S2. Use fluid mechanics simulation software to grid the clean water tank according to its geometric shape and internal structure, divide it into multiple cubic grid units, and record the position of each grid unit:

[0057] The volume of a grid cell is:

[0058] V = Δx*Δy*Δz,

[0059] Where: Δx, Δy, Δz are the dimensions (length, width and height) of the grid in the x, y and z directions.

[0060] S3. Based on the historical data of the changes in the inflow and outflow of the clean water tank over time, a conventional deep learning algorithm is used to train the model and establish a prediction model for the inflow and outflow of the clean water tank:

[0061] Obtain the inflow and outflow data of the clean water tank for each time period (such as every hour) within a year, check the missing values ​​in the data, and choose to fill (such as using the average, median, previous value, etc.) or delete the missing data points as appropriate. Divide the data set into a training set and a test set (for evaluating model performance). After building the model using regression analysis, use the test set data to evaluate the performance of the model. Calculate the error between the predicted value and the actual value, and perform continuous calibration and correction to achieve a higher prediction accuracy.

[0062] Finally, the inlet and outlet water flow of the clear water tank in each time step can be obtained.

[0063] Preferably, the time period of the calculation time step is 10 minutes.

[0064] S4. Use the clean water tank inflow and outflow prediction model to predict the inflow and outflow of the clean water tank within a certain period of time, and use fluid mechanics simulation software to simulate the flow distribution of each grid inside the clean water tank based on the geometric shape, internal structure, grid size, and inflow and outflow of the clean water tank.

[0065] S5. Calculate the hydraulic retention time HRT for each grid cell x and the total accumulated hydraulic retention time HRT from the clean water tank inlet to each grid unit along the horizontal direction of the water flow n总 , the hydraulic retention time HRT of each grid cell x for:

[0066]

[0067] Where V is the volume of each grid cell, Q x is the flow rate through that grid cell.

[0068] The HRT n总 It is the sum of the hydraulic retention times of all grid cells in one direction from the entrance of the clean water tank to the nth grid cell in the horizontal direction of the water flow. Therefore, HRT n总 Contains the single hydraulic retention time HRT of all grid cells in the horizontal flow path direction x ,x=1,2,3…n, the formula is as follows:

[0069] HRT n总 =HRT1+HRT2+...+HRT(n-1)+HRTx.

[0070] S6. Substitute the accumulated total hydraulic retention time from the clean water tank inlet to each grid unit into the residual chlorine decay curve of step S1, calculate the residual chlorine concentration of each grid of the clean water tank through the residual chlorine decay curve, and then calculate the residual chlorine concentration C of each grid part in the clean water tank and the residual chlorine concentration C of the clean water tank outlet based on the residual chlorine amount C0 at the clean water tank inlet monitored in real time. 出 , the calculation process is as follows:

[0071] (1) Calculate the total hydraulic retention time HRT of each grid cell n总 .

[0072] (2) The total hydraulic retention time HRT of each grid cell n总Substitute the residual chlorine attenuation curve of step S1, and based on the residual chlorine amount C0 of the clean water tank inlet water, obtain the residual chlorine amount C in each grid unit.

[0073] S7. Set the time step Δt, and update the residual chlorine concentration of each grid cell in real time according to the inflow and outflow of the clean water tank within the time Δt, so as to predict the attenuation and residual chlorine distribution in the clean water tank:

[0074] In each time step Δt, the residual chlorine concentration in each grid cell is updated: preferably, the time step Δt is 10 minutes.

[0075] For each grid, the residual chlorine concentration of each grid at any time is calculated based on the residual chlorine attenuation model and the water flow rate, geometric parameters and initial residual chlorine concentration in the grid.

[0076] Preferably, the residual chlorine concentration in each grid and the residual chlorine transfer amount between grids are summarized, and the calculation results are output as a residual chlorine concentration distribution map to obtain a residual chlorine concentration distribution map of the entire clear water tank, which intuitively displays the distribution of residual chlorine concentration in the clear water tank.

[0077] Embodiment 2: A calculation system for residual chlorine distribution in a clean water tank, which can implement the method described in Embodiment 1, includes a residual chlorine decay curve model construction module, and uses the residual chlorine concentration of the water sample at different time points and the parallel first-order reaction model of the residual chlorine to fit the data to obtain the residual chlorine decay curve of the water sample;

[0078] The fluid mechanics simulation software processing module uses the fluid mechanics simulation software to grid the clean water tank according to the geometric shape and internal structure of the clean water tank, divides it into multiple cubic grid units, records the position of each grid unit, and simulates the flow distribution of each grid inside the clean water tank according to the geometric shape, internal structure, grid size, and water inlet and outlet of the clean water tank;

[0079] The clean water tank inflow and outflow prediction model module uses conventional deep learning algorithms to train the model based on the historical data of the clean water tank inflow and outflow over time, and uses the clean water tank inflow and outflow to predict the clean water tank inflow and outflow within a certain period of time;

[0080] The hydraulic retention time calculation module is used to calculate the hydraulic retention time of each grid unit and the total accumulated hydraulic retention time HRT from the clean water tank inlet along the horizontal direction of the water flow to each grid unit. n总 , the hydraulic retention time HRT of each grid cell x for:

[0081]

[0082] Where V is the volume of each grid cell, Q xis the flow through that grid cell;

[0083] HRT n总 Contains the single hydraulic retention time HRT of all grid cells in the horizontal flow path direction x ,x=1,2,3…n, the formula is as follows:

[0084] HRT n总 =HRT1+HRT2+...+HRT(n-1)+HRTx.

[0085] The residual chlorine concentration calculation module substitutes the accumulated total hydraulic retention time of each grid unit into the residual chlorine attenuation curve, calculates the residual chlorine concentration of each grid of the clean water tank through the residual chlorine attenuation curve, and obtains the residual chlorine concentration of each grid in the clean water tank and the residual chlorine concentration at the clean water tank outlet based on the residual chlorine amount at the inlet of the clean water tank monitored in real time;

[0086] Residual chlorine concentration distribution display module, used to display the residual chlorine concentration distribution results;

[0087] The residual chlorine calculation and update module is used to calculate the inlet and outlet water flow of the clean water tank according to the set time step, and update the calculation of the residual chlorine concentration of each grid unit in real time.

[0088] The above description is only a specific implementation mode of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating residual chlorine distribution in a clear water tank, characterized in that: The steps include: S1. Take water samples near the water inlet in the clean water tank, record the residual chlorine concentration at different time points, and fit the data using the parallel first-order reaction model of residual chlorine to obtain the residual chlorine attenuation curve of the water sample; S2. Using fluid mechanics simulation software to grid the clean water tank according to its geometric shape and internal structure, divide it into a plurality of cubic grid units, and record the position of each grid unit; S3. Based on the historical data of the changes in the inflow and outflow of the clean water tank over time, a conventional deep learning algorithm is used to train the model and establish a prediction model for the inflow and outflow of the clean water tank; S4. Use the clean water tank inflow and outflow prediction model to predict the inflow and outflow of the clean water tank within a certain period of time, and use fluid mechanics simulation software to simulate the flow distribution of each grid inside the clean water tank according to the geometric shape, internal structure, grid size, and inflow and outflow of the clean water tank; S5. Calculate the hydraulic retention time HRT for each grid cell x and the total accumulated hydraulic retention time HRT from the clean water tank inlet to each grid unit along the horizontal direction of the water flow n总 , the hydraulic retention time HRT of each grid cell x for: Where V is the volume of each grid cell, Q x is the flow through that grid cell; S6. The total accumulated hydraulic retention time HRT from the clean water tank inlet to each grid unit n总 Substitute the residual chlorine attenuation curve of step S1, calculate the residual chlorine concentration of each grid of the clean water tank through the residual chlorine attenuation curve, and then calculate the residual chlorine concentration C of each grid in the clean water tank and the residual chlorine concentration C of the clean water tank outlet based on the real-time monitored residual chlorine amount C0 at the inlet of the clean water tank. 出 ; S7. Set the time step Δt, and update the residual chlorine concentration of each grid cell in real time according to the inlet and outlet water flow of the clean water tank within the time Δt, so as to predict the attenuation and residual chlorine distribution in the clean water tank.

2. The method for calculating residual chlorine distribution in a clear water tank according to claim 1, characterized in that: The parallel first-order reaction model formula of residual chlorine used in step S1 is: In the formula, t represents the reaction time, x represents the percentage of the initial residual chlorine concentration participating in the fast reaction to the total initial residual chlorine concentration, C0 is the total initial residual chlorine concentration, k f is the residual chlorine fast reaction decay constant, k s is the residual chlorine slow reaction decay constant, C is the residual chlorine concentration; The initial residual chlorine concentration participating in the fast reaction is the residual chlorine concentration participating in the reaction within 0-30 minutes, and x is the ratio of the initial residual chlorine concentration minus the residual chlorine concentration sampled at 30 minutes to the initial residual chlorine concentration. The calculation formula is as follows: x=y(C0-C 30 ) / C0, Where C0 is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration at 30 minutes, y is the adjustment coefficient, which is 1.15; The least squares method is used to fit k f and k s Two parameters, get k s and k f , we can get the functional relationship between residual chlorine concentration C and time t.

3. The method for calculating residual chlorine distribution in a clear water tank according to claim 1, characterized in that: The fluid dynamics simulation software in step S2 includes FLOW-3D model software and CFX model software.

4. The method for calculating residual chlorine distribution in a clear water tank according to claim 1, characterized in that: The HRT in step S5 n总 It is the sum of the hydraulic retention time of all grid cells in the horizontal direction of the water flow from the inlet of the clean water tank to the nth grid cell. n总 Contains the single hydraulic retention time HRT of all grid cells in the horizontal flow path direction x ,x=1,2,3…n, the formula is as follows: HRT n总 =HRT1+HRT2+...+HRT(n-1)+HRTx。 5. A calculation system for residual chlorine distribution in a clean water tank, characterized in that: It includes a residual chlorine decay curve model building module, which uses the residual chlorine concentration of water samples near the water inlet in the clean water tank at different time points and the parallel first-order reaction model fitting data of residual chlorine to obtain the residual chlorine decay curve of the water sample; The fluid mechanics simulation software processing module uses the fluid mechanics simulation software to grid the clean water tank according to the geometric shape and internal structure of the clean water tank, divides it into multiple cubic grid units, records the position of each grid unit, and simulates the flow distribution of each grid inside the clean water tank according to the geometric shape, internal structure, grid size, and water inlet and outlet of the clean water tank; The clean water tank inflow and outflow prediction model module uses conventional deep learning algorithms to train the model based on the historical data of the clean water tank inflow and outflow over time, and uses the clean water tank inflow and outflow prediction model to predict the clean water tank inflow and outflow within a certain period of time; The hydraulic retention time calculation module is used to calculate the hydraulic retention time of each grid unit and the total accumulated hydraulic retention time HRT from the clean water tank inlet to each grid unit. n总 , the hydraulic retention time HRT of each grid cell x for: Where V is the volume of each grid cell, Q x is the flow through the grid cell, HRT n总 Contains the single hydraulic retention time HRT of all grid cells in the horizontal flow path direction x ,x=1,2,3…n, the formula is as follows: HRT n总 =HRT1+HRT2+...+HRT(n-1)+HRTx; The residual chlorine concentration calculation module calculates the total accumulated hydraulic retention time HRT of each grid unit. n总 Substitute the residual chlorine attenuation curve into the calculation, and calculate the residual chlorine concentration of each grid of the clean water tank through the residual chlorine attenuation curve. Based on the residual chlorine amount at the inlet of the clean water tank monitored in real time, the residual chlorine concentration of each grid in the clean water tank and the residual chlorine concentration at the outlet of the clean water tank are obtained. Residual chlorine concentration distribution display module, used to display the residual chlorine concentration distribution results; The residual chlorine calculation and update module is used to update the calculation of the residual chlorine concentration of each grid cell in real time according to the inlet and outlet water flow of the clean water tank within the set time step.

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