JPS61187991A - Chlorination control device for clean water plant - Google Patents

Abstract

PURPOSE:To control dosage adequately by estimating the residual chlorine concn. of the process on the down stream of the intake point of test water to a residual chlorine meter by using a simulation model and executing PI feedback control or impusive chlorination control from the change state thereof. CONSTITUTION:The residual chlorine concn. near an outlet is calculated by a calculator 8 using the simulation model from the detection values of the residual chlorine meter 7 and flow meter 4 on the upper stream near the outlet in a chlorination control device for a clean water plant which controls the residual chorine concn. near the outlet to a target value by controlling the chlorine dosage. The chlorine dosage is subjected to the PI control in the controller 9 in such a manner that the calculated residual chlorine concn. attains the target value; at the same time, the required jump dosage is selected from the calculated residual chlorine concn. and the change rate thereof with time and the jump chlorination control is executed by interrupting the above-mentioned PI control for the required time. As a result, the chlorination rate is adequately controlled as against disturbance and the excessive chlorination in particular is prevented.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to controlling the amount of chlorine injected into a water treatment plant 1 so that the residual chlorine concentration remains constant by taking into account the operating conditions indicated by the residual chlorine concentration and its rate of change over time. This is related to the chlorine injection control device C in a water treatment plant.

[Technical background of the invention and its problems] Chlorine injection in purified water *(-) involves chlorine injection before raw water is injected, and intermediate chlorine injection before filtration.

There is a post-chlorine injection which is injected after the filtration.

In pre-chlorine injection, there is a long delay time due to the time required for the flow from the chlorine injection point to the intake point of the test water where residual chlorine is measured, and the time required from the intake of the test water to the residual salt meter (n4!). In addition, the delay time of the collector system from setting the chlorine injection rate to actually executing chlorine injection point C2 is added, so the overall delay time is at least 30 minutes. In the case of a long time, e'i can reach as long as 90 minutes, making it difficult to achieve stable control using normal feedback control.

At Sara-yu and Water Treatment Plant-2, cleaning wastewater from filtration electricity,
Wastewater with different #i element requirements from reservoirs, rain tanks, etc. 0)
Subject to disturbance due to delay.

If the filtration filter is washed once and washed periodically, then the wastewater is sent back, mixed with raw water, and treated again, but since the washing wastewater contains residual chlorine, the chlorine demand of the raw water is reduced. ,
As a result, excessive chlorine injection occurs and the residual chlorine concentration rapidly increases. Feedback control of the rapidly rising residual chlorine concentration results in a long delay time. In addition to fluctuations in the amount of chlorine required for raw water, there are sudden changes in the concentration of residual chlorine due to the return of wastewater from cleaning wastewater, retarding ponds, and rainwater tanks as described above.

Conventionally, there was no automatic injection control method that was effective against such rapid disturbances and rapid drops in residual chlorine.
There is 24-hour monitoring of all operators and manual control of injection rates based on experience.

In other words, the injection rate was quickly increased after the residual chlorine concentration began to decrease due to disturbances, which often resulted in excessive chlorine injection.

[Purpose of the Invention] The present invention uses a simulation model to estimate the residual chlorine concentration in the process downstream from the water intake point to the residual salt meter that measures the residual chlorine concentration. , PI feedback control or pulsed injection control is selected and carried out. Therefore, this is a chlorine injection control for water treatment plants that appropriately controls the injection rate in response to disturbances and particularly prevents excessive injection of chlorine. The purpose is to provide equipment.

[Summary of the Invention] The present invention provides a chlorine injection control system for a water treatment plant that controls the amount of chlorine injection to control the residual chlorine concentration near the outlet to a target value.
2, there is a calculator that uses a simulation model to calculate the residual chlorine concentration near the outlet from the detected values of the residual salt meter and flow meter, which are split into two parts upstream of the outlet; PI control the chlorine injection amount so that (C) It is equipped with a controller that performs control, and is designed to maintain a stable residual chlorine concentration near the outlet even when there is a sudden disturbance due to C2, such as cleaning drainage or rainwater. [Embodiment of the Invention] An embodiment of the present invention is shown in FIG.

In Figure 1 ζ, raw water taken from a water intake source (not shown) passes through pipe A, flows into the landing well IC, and further (-
As shown in the figure, wastewater from the washing drainage pond, retarding pond, and rainwater tank flows into the landing well 11 through pipe B.Water to be treated 1 flows from the landing well 1 through pipe C to the mixing pond 2C. :Fi, in the middle of pipe C, chlorine from injection pipe 3 is mixed with flocculant and neutralizing agent from other injection pipes (not shown).
It is injected and mixed in the mixing basin 2.

The water to be treated that has flowed out of the mixing pond 2 flows down to the 70-piece formation pond 5ζ through a conduit in which a flow meter 4 is installed.

Water is taken in near the outlet of the mixing basin 2 by a detection pump 6, and then a residual salt meter 7 is introduced to measure the residual chlorine concentration.

The detection signal Q1 of the flowmeter 4 and the detection signal Re of the residual salt meter 7 are calculated by a calculation unit 8 (with a built-in simulation model) for calculating the residual chlorine concentration Rcf at the outlet of the floc formation pond 5.
will be transmitted.

The residual chlorine concentration Rcf calculated by the calculator 8 is calculated by the controller 9.
Therefore, the set value 8n of the chlorine injection rate is calculated by two people, and the chlorine injection rate Sn set by the setting device 10 (0) is the chlorine injection rate Sn of the chlorine injection flow rate. The set value is converted into chlorine injection machine 1 IC-sent,
This is how chlorine is injected.

Next, calculations performed by the C unit 8 (one will be explained below).

The simulation model built into the computing unit 8 expresses the flow state in the pipe line and the floc formation pond No. 5 in terms of dels for each mixing.
A complete mixture model of flocculation pond (:Fi5 Cypress) is used.

11. Formation of 70 ponds from pipe construction using an extrusion model.
+-th--residual chlorine concentration Rc at time t of outflow, (t
) is given by the following equation (1).

Here, Va is the volume of the pipe, Q(t) is the indicated value of the flow meter 4 in the time mill, Va/Q (is the residence time of the treated water in the pipe, Re is is the time) This is the indicated value of the residual salt meter 7 at t.

Further C:, the volume of each of the 5 tanks of the floc formation pond is Vb.
If Hbc@vd, ve, ■f, the respective residual chlorine concentrations Rcb(t) and Rcc(t
), Rcd(t), Rce(t).

Rcf(t)t:i are given by equations (2) to (6), respectively.

Here is the calculation cycle of the hH simulation model,
For example, it is set to 4 minutes C2.

In this manner, the calculator 8 calculates the indicated value Q1 of the flowmeter 4.
Using the above equations (1) to (6) from the indicated value RC of the residual salt meter, the residual chlorine concentration Rc corresponding to the outlet of the floc formation pond is calculated.
f (t) is calculated and output to the controller 9.

FIG. 2 is a block diagram showing the functional configuration of the controller 9 in FIG. 1.

In FIG. 2C, 12 is a PI calculation circuit, 13 is a difference calculation circuit, 14 is a state determination circuit, a 1stj jump generation circuit, and 16 is an output correction circuit.

The residual chlorine concentration Rcf at the outlet of the floc formation pond, which is output from the calculator 8 in FIG. At the same time, a calculation cycle of 4 minutes is input to the C2 difference calculation circuit 135.

The PI calculation circuit 12 has a control target value Sv of the residual salt level Rcf.
is set, and the following (power, (8) formula C: Therefore, the output deviation ΔS of the chlorine injection rate is calculated, and the output correction circuit 161:, transmitted O B, = 8V −Rcf −−−−−−− ---
−−−−−−1−−−(7) Δ8 = Kp−(En−
Bn-1)+-・Bn --------(8) TI Here, Kpilt proportional gain, In, In-In are the input deviations of the current control cycle and the previous control cycle, respectively.
h is the control period (8 minutes), TI is the integral time, and the proportional gain Kp and the integral time Ti fl are preset values.

Furthermore, in the difference calculation circuit 131, the following equation (9) (:
Therefore, the time rate of change I)rc of the residual salt concentration Rcf is calculated.
is the residual salt concentration in the current calculation cycle and the previous calculation cycle,
The unit of the time change rate Drc (hereinafter referred to as residual salt change rate) of the residual salt concentration is fl (t/rl/Hr).

In the state determination circuit 14, the residual salt concentration Rcf and the residual salt change rate I)
rc is read every control cycle, and it is determined which of the divided classes the current Rcf belongs to, based on the preset upper limit and multiple lower limit values of the number of morsels for the Rc day and two. Then, at the same time, the preset Dr.
c Which of the nine classes is divided by a plurality of upper limit values and a plurality of lower limit values for C (residual salt change rate I of the current control cycle)?
) Determine whether re belongs to the class number Yj and I of Rcf.
) The class number Xj of rc is output to the jump generation circuit 15.

In the jump generation circuit 15, a two-dimensional matrix M(Y,, The rate jump width is set,
Using the output values Yj and Xj of the state judgment path 14, the jump width ΔSJ is selected as follows and transmitted to the output correction circuit 161.

Δ8J=M (Yj, Xj) --------
−−−−−−−−α [The output correction circuit 16 receives the information from the jump generation circuit, and if the jump width Δ8j has a positive or negative value, the output correction circuit 16 inputs the data from the output correction circuit 16 to the setter 10 from the next control cycle. It has a contact point for inputting the length of time during which the set output sn is temporarily stopped, that is, the holding time H1o, and when the jump width Δ8J is 0, the following υ formula C: Therefore, the setter lO
The set value sn to be output to is calculated O Bn = sc + ΔS ・----1---1-
−−−−−−αυHere, the injection machine 11 of ScH Figure 1
Pipe CC: is the actual injection rate of injected chlorine,
Injected by injection machine 11ζU, 1icI (f/H)
r) and the amount of treated water Q i (rr
l/Hr''] by a calculation circuit (not shown) using the following (1 force formula).

If the jump width Δ8j is positive or negative, a set value 8n is calculated by the following equation 0 and outputted to the setter lO(:), and at the same time, counting of the remaining time Ht of the (-holding time) is started.

8, == 8c+Δ8j −−−−−−−−
-----------(13 Count of remaining time H9, jump injection starts every control period (-) Calculation of the next a4 formula is performed, and continues until Hl (IC-).

Ht = Ht −1−−−−−−−−−−−−−−−
-------(14 Setting output 8 from the output correction circuit 16 to the setting device 10 at a control period in which the remaining time H1 decreases to 1 i''-
The holding operation that had temporarily stopped n is canceled, and the executed jump injection is returned to the pre-jump value (Y) and the preset return rate Kb (:, therefore, the same time (; again from the jump generation circuit 15). The control output sn is calculated from the value l of the jump width Δ8J.

In the control period in which the holding operation is canceled, the control output Sn when Δ5j=0 is given by the following equation a9.

8n: Se −Kl) −Δ81′ +Δ8 −−−−
--------(1!9 Also, when Δs3'-, o is 8n
is calculated using the following formula for α, jump injection is performed again, and the current holding operation is started.

sn = sc-Kl)-ΔSj' +ΔJ ・--
--------(161 above αS, (In the Le equation, ΔSj' is the jump width when the previous holding operation started.

Figure 3 is a 7I:I-chart showing the calculation procedure in the calculator 8 and the controller 9C. If the chlorine injection is calculated in this way and is controlled based on the 9 chlorine injection rate an, the filtration charge cleaning Water is returned to the residual salinity meter at a point as close as possible to the chlorine injection point downstream of the chlorine injection point, where the chlorine demand changes rapidly due to disturbances, such as wastewater and water from reservoirs and rainwater tanks. The computing unit smoothes the changes in the residual chlorine concentration at the water treatment plant that takes water, so it stabilizes the PI feedback control without causing it to run out of control. Since this compensates for chlorine, control followability is improved, under-injection and over-injection are prevented, and appropriate chlorine injection becomes possible.

Although the above embodiment deals with pre-chlorine injection, the present invention can also be applied to intermediate chlorine injection and post-chlorine injection.

[Effects of the Invention] As explained above, according to the present invention (Yu), the measured value of the residual chlorine concentration, which varies minutely, is processed and smoothed using a simulation model, and compared with the target value, and the deviation C: chlorine is injected accordingly. In addition to feedback controlling the heron, the jump C2 injection rate is changed when a disturbance that causes a sudden change in the residual chlorine concentration improves the followability of the control, allowing the water treatment plant to flow from the consumer C unit. It becomes possible to control the residual chlorine concentration of the supplied tap water to a desirable target value.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing an embodiment of the present invention.
FIG. 3 is a block diagram showing the functional configuration of the controller in the figure, and FIG. 3 is a flowchart showing the calculation operation in the present invention. Total 5...floc formation pond
6...Water test Bongua...Residual salt meter 8...
Arithmetic unit 9...controller lO...setter 11
- Injection machine agent Patent attorney Yoshiaki Inomata (and 1 other person) No. 3
1. Indication of the case Japanese Patent Application No. 60-28471 2. Name of the invention Chlorine injection control device for water purification plants 3. Person making the amendment Relationship with the case Patent applicant (307) Toshiba Corporation 4 , Agent Address: 1-9-10 Toranomon, Minato-ku, Tokyo 105 May 8, 1985 (Date of dispatch: May 28, 1985) 6. Column 7 of the title of the invention in the specification to be amended, Amendment On page 1, line 3 of the letter detailing the contents, the phrase ``Chlorine injection equipment for water treatment plants'' is corrected to [Chlorine injection control equipment for water treatment plants]. that's all

Claims (1)

[Claims] In a chlorine injection control device at a water treatment plant that controls the amount of chlorine injected to keep the residual chlorine concentration near the outlet to the target value, the above value is calculated from the detected values of the residual salt meter and flow meter installed upstream of the outlet area. A calculator that calculates the residual chlorine concentration near the outlet using a simulation model, a PI control of the chlorine injection amount so that the residual chlorine concentration calculated above becomes the target value, and a computer that calculates the residual chlorine concentration calculated above and its time change. A chlorine injection control device for a water purification plant, comprising a controller that selects a required jump injection amount from the ratio and performs jump injection control by interrupting the P1 control for a required time.