JPS60212201A - Chlorine injection control apparatus of water purification plant - Google Patents

Abstract

PURPOSE:To stably control the concn. of residual chlorine of a precipitation basin to a required value, by preliminarily correcting the estimation amount of quantity of solar radiation and feeding the corrected value forwardly to operate and set the objective chlorine concn. of floc water flowed into the precipitation basin. CONSTITUTION:A chlorine injection apparatus 2 performs chlorine injection operation according to the chlorine injection ratio MV to the lately control cycle calculated by a residual salt meter 17, an actinometer 19 and first - fifth operators 18, 20, 25, 27, 29. As a result, feedback control by the actual residual chlorine concn. of floc water and feedforward control by the preliminarily calculated quantity of solar radiation are performed and the concn. of residual chlorine of a precipitation basin can be stably controlled by both control operations.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a chlorine injection control device for a water treatment plant that controls the pre-chlorine injection amount in a water treatment plant by taking into consideration the decomposition of residual chlorine in a sedimentation tank due to solar radiation. be.

[Technical background of the invention and its problems] Figure 1 shows the general configuration of a water treatment plant.

In FIG. 1, raw water flows into a receiving well 1 through a water conduit A, where chlorine and sodium chloride are injected from a pre-chlorine injection device 2 and a pre-alkali injection device 3, respectively.

Next, in the rapid mixing pond 4, #: PAC (
polyaluminum chloride) is injected and rapidly mixed in a flash mixer 6.

Next (flocs are formed in the nifloc formation pond 7).

It is precipitated and removed in the settling tank 8.

The microscopic 7 micron particles that did not settle in the sedimentation tank 8 and overflowed with the sedimentation tank outflow water are transferred to the filtration tank 1 after chlorine and caustic soda are injected from the medium chlorine injection device 9 and the medium alkali injection device 10 in the water conduit B. ] The IP water that has passed through the filter pond 11 is further injected with chlorine and caustic soda from the post-chlorine injection device 12 and the post-alkali injection device 13 in the water conduit C, and is stored in the water purification pond 14. .

As a result, turbid substances and other impurities in the raw water are removed, and purified water that is sufficiently disinfected and has an appropriate pH value is supplied from the ftJ water pond 14 to Wi Yasuya.

In this case, it is necessary to control the pre-chlorine injection by considering not only the chlorine demand of the raw water but also the distribution of residual chlorine due to the amount of solar radiation and its scattering by the wind.

To deal with fluctuations in chlorine concentration, measure the residual chlorine concentration early after pre-chlorine injection (for example, when injecting chlorine at the receiving well, at 90°C, at the rapid mixing pond or at the floc formation pond). Stable control is possible by providing feedback.

However, since the decomposition of residual chlorine takes place slowly in sedimentation tanks with short residence times, it is difficult to use feedback control, so manual control is used based on the judgment of operators who have predicted solar radiation patterns. However, this method not only increases the burden on the operator, but also causes problems in that chlorine injection may be insufficient or excessive.

For this reason, feedforward control has been proposed to increase or decrease the amount of chlorine injection in proportion to the predicted amount of solar radiation, but due to the time lag in the settling basin, the amount of solar radiation due to insufficient injection decreases in the morning when the amount of solar radiation increases. There is a problem that excessive chlorine injection occurs in the afternoon, making it impossible to properly control chlorine injection.

[Object of the invention] The present invention corrects the predicted value of solar radiation in advance, feeds it forward, calculates and sets the target chlorine concentration of floc water flowing into the sedimentation tank, and thereby reduces residual chlorine in the sedimentation tank. The purpose is to provide a chlorine injection control device for water treatment plants that stably controls the concentration to a required value.

[Summary of the Invention] The present invention provides a chlorine injection control device for a water treatment plant that controls the residual chlorine concentration in a settling tank to a predetermined value by enshrining the chlorine injection rate. The residual salt meter that detects
A first computing unit that calculates a compensation amount for the chlorine injection rate by comparing the chlorine concentration of floc water with a variable target value, and a second computing unit that adjusts the amount of solar radiation in advance according to the elapsed time from sunrise time. And, from the 3rd division ν, the chlorine injection rate correction amount is set for the day IA, which was revised in advance. A fourth computing unit that calculates a variable target value for concentrated water chlorine absorption, and a 5I45 calculation that calculates the chlorine injection rate by inputting the compensation amount for the chlorine injection rate and the variable target value for floc water. Decomposition of chlorine by solar radiation. The residual chlorine concentration in the sedimentation tank can be stably controlled by extracting the chlorine appropriately.

[Embodiments of the invention] An embodiment of the present invention is shown in FIG.

The water purification system in FIG. 2 is the same as in FIG. It is obtained by measuring water with a residual salt meter 17.

The above Rc is input to the first arithmetic unit 18, and the fourth arithmetic unit 27
(1) below using the variable target value P■ given by

The calculation of equation (2) is performed, and the output △S is the fifth calculation unit 2.
9 to control the chlorine injection rate MY.

△S= Kp・(F'n' Bn-i) ”-・kn
--------(1) TI En= PV-RC-----(2
) Here, KP is the proportional gain, h is the control period, TI is the integration time, and En, B, and Hn-1 are the input deviations in the current and 011 control periods.

The sedimentation basin 8 is further equipped with a solar radiation meter 19, and the solar radiation amount RAD detected here is input to the second calculator 20.

The second arithmetic unit 20 is provided with a sunrise time T81 from a clock device.
1. Sunset time T88 and ratio measurement PKy are input through contacts 21 and 22.23, respectively, and are corrected to actual solar radiation sensing RAD power ZMfJ by the following calculation.

RAD""KRAD'RAD,,---------
-----1---(81 Here, t is the elapsed time from sunrise time T8R, and Figure 3 shows KRA when KY = 2.
It shows changes in the relationship between D and RAD' and RAD with respect to 11JJ t.

The above RAD' is input to the third arithmetic unit 25, and is separately connected to the contact 2.
Using the conversion coefficient KCL input via 4, the following <5
) is calculated, and the correction amount △ for the chlorine injection rate MV is calculated.
CL is i-1 father-in-law.

△CL=KCL・(RAD'RAD'')
---, (δ) where RAD'' is the RAD of the previous control cycle
'is.

The correction amount ΔCL is calculated by the following equation (6) together with the constant XSV inputted to the fourth calculator 27 and inputted through the one contact 26 and the Rc target value S■' of the previous control cycle.
The l(C target value Sv of the current control cycle is calculated, and this is input to the first arithmetic unit 18 described above.

SV = 8V' + Key ・△C1, ---"-
--------(6) The above △CL is also input to the fifth calculator 29, and the constant KMV inputted manually from the first calculator 18 via the △S1 contact 28 is stored, and the next and previous The following equation (7) is calculated using the chlorine injection rate MY',
As a result, the chlorine injection rate MY for the current control cycle is p, OMV = MY'+△8 + KMV ・ΔCL −-
-------1-(7) Since the pre-chlorine injection device 2 performs the chlorine injection operation according to the above MV, feedback control based on the actual degree of residual chlorine in the floc water and feedforward control based on the amount of solar radiation brought forward are performed. 71
This makes it possible to stably control the residual chlorine concentration in the settling tank.

Figure 4 shows the case where the chlorine concentration of floc water is controlled to be constant using the conventional method, Figure 5 shows the case where the amount of solar radiation is fed forward as it is, and Figure 6 shows the case where the amount of solar radiation is fed forward and fed forward using the present invention. These are simulation results showing changes in residual chlorine concentration in each settling tank over a period of one day (24 hours).

In Figure 4, the residual chlorine level in the settling tank reaches its lowest level in the afternoon due to solar radiation, and is expected to drop to below 0.5 ppm, which is necessary for protection against f overcharge.

In the fifth step, it is expected that the residual chlorine concentration in the settling tank will be lower than the required value in the morning, and will rise significantly more than the required value in the afternoon.

Figure 6 shows a case where the amount of solar radiation is corrected in advance and feedforward is carried out according to the present invention, and the chlorine concentration in the floc water rises in advance, thereby controlling the residual chlorine concentration in the settling tank to the required value. It is shown that.

[Effects of the Invention] As explained above, according to the present invention, the daily solar radiation is corrected ahead of time with respect to the passage of time, and this is fed forward as a correction factor, and the chlorine quality of the actual floc water is fed back. This provides a rational chlorine injection control device for a water treatment plant that controls the amount of pre-chlorine injection, thereby stably controlling the residual chlorine concentration in the settling tank to a required value.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the general configuration of a water purification plant, Fig. 2 is a system diagram showing an embodiment of the present invention, Fig. 3 is a characteristic diagram showing the method of correcting the amount of solar radiation in the present invention, and Fig. 4 5 and 5 are diagrams showing the simulation results in the conventional method, respectively, and FIG. 6 is a diagram showing the SiminiLesion tea supply in the present invention. l...Water landing well 2...Pre-chlorine injection device 4...Rapid mixing tank 7...Floc formation tank 8...Sedimentation tank 15
...Sedimentation current inlet 16...Water sampling pump 17...
Residual salt meter 19... Solar radiation 1 meter 18.20.25.27.
29...Arithmetic unit agent Patent attorney Yoshiaki Inomata (1 person) Figure 3 D 4-8 tZ /mu 2001. HR Figure 5 Figure 6 Figure 04 δtZ t(:, πDI, HF:

Claims (1)

[Claims] In the chlorine injection control device at a water treatment plant, which adjusts the pre-chlorine injection amount to control the residual chlorine concentration in the settling tank to the required value,
A residual salt meter detects the chlorine concentration of the floc water flowing into the pond, a solar radiation mIt measures the amount of solar radiation in the sedimentation tank, and chlorine injection is performed by comparing the chlorine setting of the floc water with a variable target value. The first speech and device that calculates the amount of compensation for the rate, the second operation profit that adjusts the above solar radiation amount earlier according to the elapsed time rti from the sunrise time, and the above) solar radiation amount that was revised earlier than 7iJ. a third computing unit that calculates a correction amount for the chlorine injection rate from the chlorine injection rate correction amount; and a third computing unit that calculates the variable target value for chlorination of the floc water corresponding to the required value of the residual chlorine concentration in the settling tank from the chlorine injection rate correction amount. It is equipped with a fourth calculator and a fifth calculator which inputs the compensation amount of the chlorine injection rate and the variable target value of the floc water and sums the chlorine injection rate. A chlorine injection control device for a water treatment plant that is characterized by adjusting the amount of chlorine injection.