JPS6283091A - Chlorine injection apparatus - Google Patents

Abstract

PURPOSE:To keep a predetermined chlorine injection state, by mounting a chlorine gas change-over means, an operation means for calculating the injection ratio of chlorine gas and an operation means for calculating a corrected injection ratio. CONSTITUTION:Specimen water is sampled in the vicinity of the outlet of a mixing basin 2 by a specimen water pump 3 and guided to a residual chlorine meter 4. The signal Rc of the residual chlorine meter 4 is inputted to a first operation means 5 to calculate a chlorine injection ratio objective value. The change-over state signal of a chlorine gas change-over means 10 is inputted to a second operation means 13 and, on the basis of the state signal from the chlorine gas change-over means 10, it is automatically judged whether gaseous chlorine diluted by air is injected. When it is judged that the injection of gaseous chlorine diluted by air is performed, the chlorine injection ratio objective value outputted from the first operation means 5 is corrected. By this method, the control of chlorine injection is well performed.

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 uses chlorine as an oxidizing agent or disinfectant.

[Technical background of the invention and its problems]

In addition to oxidizing and disinfecting raw water, chlorine injection at water treatment plants is important for protecting sedimentation tanks and filtration during the water treatment process, as well as reducing the quality of treated water and wasting chemical costs due to excessive chlorine injection. This is an important operation for water treatment plants to prevent water leakage.

FIG. 4 shows an example of the conventional method. The raw water taken from a water intake source (not shown) flows into the landing well (11), and then chlorine is injected together with a flocculant and a medium phase agent from other injectors (not shown), and mixed in the mixing pond (2). Water is detected by a water test pump 3 near the outlet of the mixing tank 1 leading to the floc formation pond 8, and the residual chlorine concentration of the test water is measured by a residual chlorine meter 4. In the conventional chlorine injection control for liquid chlorine, in which this measurement (t4 is input to the first multiplication stage 5 and the chlorine injection rate is calculated by a PID control force formula), the liquid chlorine is purified by the chlorine vaporizer 6. This was applied when the liquid chlorine gas was converted into chlorine gas and injected into the water to be treated.However, recently, in order to save chlorine, when receiving liquid chlorine into the liquid chlorine tank 7, a tank 7 is used to store liquid chlorine in the upper part of the liquid chlorine tank. Chlorine gas diluted with the air that is inevitably generated may be injected into the water to be treated.

Conventionally, such chlorine gas was disposed of in a neutralization facility1, but as mentioned above, the chlorine gas diluted with air mixed in the liquid chlorine tank 7 was disposed of without passing through the chlorine vaporizer 6. When injecting directly into the water to be treated, since the concentration of chlorine gas is lower than that of pure chlorine gas, the residual chlorine in the mixing pond 2 has the disadvantage that it becomes unstable and cannot be controlled.

[Purpose of the invention]

The object of the present invention is to be able to cope with this disturbance even if the injection is changed from vaporized pure liquid chlorine to injection of gaseous chlorine diluted with air, and to maintain the prescribed chlorine injection rate. [Summary of the Invention] The present invention provides a chlorine injection device for a water treatment plant that injects chlorine gas into water to be treated at a predetermined injection rate. , a chlorine gas switching means for simultaneously supplying pure chlorine gas obtained by gasifying liquid chlorine in a vaporizer, adult chlorine, and gaseous chlorine diluted with air in a tank to the water to be treated; a calculation means for determining the injection rate of pure chlorine gas based on the difference between the measured value of a residual chlorine meter installed downstream of the gas injection point and the scheduled setting value; and the chlorine gas switching means. If the switching state is input and the switching is made to the gaseous chlorine supply side diluted with air, the second step calculates the injection rate corrected by the planned correction factor based on the injection rate obtained by the first calculating means. When switching from pure chlorine d gas to gaseous chlorine diluted with air, it is equipped with a calculation means that corrects it using a planned correction factor based on the value determined as the injection rate of pure 1-line gas. Determine the added injection rate and use this to calculate the amount of air diluted (
By injecting body chlorine, it is possible to prevent the residual chlorine from changing due to the A phase.

[Example of actual invention]

Hereinafter, an embodiment in which the present invention is applied to pre-chlorine injection control at a water treatment plant is shown in Fig. , FOO20 flows downstream.

During this process, chlorine is injected with an injector 12, and is added to the mixing pond 2 along with a flocculant and a neutralizing agent from other injectors (not shown).
The water to be treated that flows out of the mixing basin 2 and the mixing basin 2 further flows down to the floc forming basin 8. Test water is taken by a water test pump 3 near the outlet of the mixing basin 2, and a residual salt meter 4 is used to measure residual chlorine.

The signal rtc from the residual salt meter 4 is input manually to the first calculation means 5. The first calculation means 5 has a setting device 9 for setting the standard set value SV of the control 11 for residual chlorine, calculates the feedback correction position w S Y of the chlorine injection rate based on the following formula, and from this value When injecting pure chlorine gas obtained by vaporizing chlorine, the target value of chlorine injection rate S, f is 4 in total.

FiN=SV-几.・・・ ・・・・・・ tl
)MuS=, (gN-gN')+, -EN Song/listening (2) Here, BN is the input deviation of the current control cycle, EN'
is the input deviation of the previous control cycle, K is the proportional gain, K,
is the integral gain.

Chlorine injection rate target value S when injecting pure chlorine gas for the current control cycle. is calculated based on the following formula.

8 m = 8 m −s + /ΔS ・・・・・・・・・
(3) Here, S, -1 is the target value of the chlorine injection rate when pure chlorine gas in the previous control cycle is injected by ε.

On the other hand, chlorine is supplied from the liquid chlorine tank 7 to the chlorine gas switching means l.
If this is on the terminal (a) side, it passes through the chlorine vaporizer 6 and becomes pure chlorine gas, which is then sent to the chlorine gas reservoir 11. On the other hand, when the chlorine gas switch JILO is set to terminal (b), gaseous chlorine diluted with air in the liquid chlorine tank is directly supplied to the chlorine gas reservoir 11. And these are chlorinator I2
is injected into the water to be treated. The switching state signal of the chlorine gas switching means lO is input to the second calculation means 13.

The second calculation means 13 automatically determines whether gaseous chlorine diluted with air is being injected or whether pure chlorine gas is being injected, based on the status signal from the chlorine gas switch 1210. 1. If it is determined that gaseous chlorine diluted with air is injected 7.
The chlorine injection rate target value S outputted from the first calculation means 5 is corrected using the following equation. .

s; =8.・f(t) = (4) Here, B,
l is the corrected chlorine injection rate target value.

f(t) is a correction factor consisting of the onset of time, starting from the start of diluted gaseous chlorine injection ( f(t) ≧
1). In this embodiment.

f(t) = + input S sum αt + B sum βt ・・・・・・・・・
...(5) and is defined for the second calculation means 13. Here, K, A, B, α, and β are constants unique to the plant, and can be easily determined by analyzing plant operation data.

The second calculation means 13 calculates the chlorine injection rate target value B.
FIG. 2 shows the process of calculating BI.

The second calculation means 13 has a setting device 14 that can manually set A, B, α, and β as plant-specific constants, and it is also possible to modify the values based on the operator's judgment. It is.

The chlorine injection control device S,,′ modified as described above is
The water to be treated is transported to the chlorine injector 12, and chlorine is injected into the water to be treated. In FIG. What is the change in salt distilled chlorine when switching to injecting chlorine?
show. In the case of the conventional method in U (a), when the injection is switched to gaseous chlorine diluted with air, the residual chlorine concentration in the mixing pond decreases and even reaches the control target value! Since it takes too long to reach A, it is impossible to control. On the other hand, in the method according to the present invention shown in FIG. 6(b), the residual chlorine concentration in the mixing pond does not decrease, and chlorine injection control is performed well.

〔Effect of the invention〕

If salt: A is injected using the chlorine injection device of the present invention as described above, conventional methods could not handle it. It becomes possible to automatically inject chlorine when gaseous chlorine diluted with air is injected, making it possible to supply hygienic, stable, and quality drinking water1.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of a chlorine injection control device according to Akira Motomoto, Fig. 2 is a flowchart showing the flow of calculation of a control table that can withstand an embodiment of the present invention, and Fig. 3 is a Figure 4 shows the change state when switching chlorine gas compared to the conventional one.
The figure shows a conventional device. 4... Residual chlorine meter 5... First calculation means 7...
・Chlorine vaporizer 8...Liquid chlorine tank [0...Chlorine gas switching means 11...Chlorine gas reservoir 12...Chlorine injector 13...Second calculation means agent Patent attorney Rules Near Evil Yudo Hirofumi Mitsumata Figure 2 1 2 Intercostals (h) (Hon 4 bis day 1 - Yorofon f,) Figure 3

Claims (1)

[Claims] In a chlorine injection device for a water treatment plant that injects chlorine gas into water to be treated at a predetermined injection rate, pure chlorine gas obtained by gasifying liquid chlorine in a vaporizer and a liquid chlorine tank are provided. chlorine gas switching means that selectively supplies gaseous chlorine diluted with air to the water to be treated, and the difference between the measured value of the residual chlorine meter installed downstream of the chlorine gas injection point and the planned setting value. a first calculating means for calculating the injection rate of the pure chlorine gas based on the input rate of the pure chlorine gas; A chlorine injection device comprising: second calculation means for determining an injection rate corrected by a predetermined correction factor based on the injection rate determined by the calculation means.