JP2983305B2 - Chlorine injection control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chlorine injection calculator for a chlorine injection facility for injecting gaseous chlorine into treated water using a chlorine injector.

[0002]

2. Description of the Related Art Generally, chlorine injection in a water purification plant is widely performed to oxidize and disinfect substances contained in raw water. Chlorine injection control is an important operation in the water treatment plant to protect the sedimentation basin and Maki Pond, which are the water treatment processes, and to prevent the deterioration of treated water quality and the waste of chemicals due to excessive chlorine injection. Has become.

A conventional chlorine injection control device will be described with reference to FIG. In FIG. 4, raw water taken from a water source (not shown) flows into the landing well 1. A flocculant and a neutralizing agent are injected into the treated water flowing out of the landing well 1 and chlorine is injected from the chlorine injector 9. The treated water is mixed in the mixing pond 2 and reaches the floc forming pond 3. Mix Pond 2
The treated water is taken by the water sampling pump 4 near the exit of
The residual chlorine concentration of the treated water is measured by a residual salt meter 5. This measurement signal is input to the chlorine injection rate calculator 6 and the PID
The chlorine injection rate is calculated by a control method or the like, and the chlorine injection machine 9 is controlled based on the calculation result. On the other hand, the liquid chlorine in the liquid chlorine storage tank 8 becomes almost pure gaseous chlorine by the chlorine vaporizer 7 and is sent to the chlorine injector 9 through the chlorine gas reservoir 19.

[0004]

By the way, when liquid chlorine is received from the tank lorry 20 into the liquid chlorine storage tank 8,
The compressed air is introduced into the tank lorry 20 to receive the compressed air. For this reason, near the end of reception, compressed air may enter the liquid chlorine storage tank 8, and the compressed air may enter the chlorine injection line during chlorine injection to dilute gaseous chlorine. The compressed air that has entered the chlorine injection line is injected into the treated water and discharged out of the system.

[0005] However, when compressed air enters the chlorine injection line, the concentration of gaseous chlorine becomes lower than that of pure gaseous chlorine. May be. The present invention has been made in view of such a point, and an object of the present invention is to provide a chlorine injection control device that can stably control chlorine injection even when liquid chlorine is received in a liquid chlorine storage tank. And

[0006]

SUMMARY OF THE INVENTION The present invention relates to a chlorine injection control device for a chlorine injection facility for evaporating liquid chlorine in a liquid chlorine storage tank and injecting gaseous chlorine into treated water by a chlorine injector. A chlorine injection rate calculator for calculating,
A second judging device for judging the end of the reception of liquid chlorine into the liquid chlorine storage tank by introducing compressed air;
A correction arithmetic unit for correcting the calculation result of the chlorine injection rate arithmetic unit so as to compensate for a decrease in the concentration of chlorine due to the introduction of compressed air immediately after the completion of liquid chlorine reception and outputting the result to the chlorine injecting device, based on a signal from the determination device And a chlorine injection control device.

[0007]

Immediately after the completion of the chlorine acceptance is determined by the second determination device, the calculation result of the chlorine injection rate calculation device is corrected by the correction calculation device so as to compensate for the decrease in chlorine concentration, and chlorine injection is performed based on the corrected chlorine injection ratio. Inject gaseous chlorine into the treated water using a machine.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are views showing an embodiment of a chlorine injection control device according to the present invention. FIG. 1 is a schematic system diagram of the liquid chlorine facility. In FIG. 1, raw water taken from a water source (not shown) flows down to a mixing pond 2 via a landing well 1. Gaseous chlorine is injected into the treated water flowing out of the landing well 1 from the injector 9, and a flocculant and a neutralizer are injected into the treated water from another injector (not shown), and the treated water is mixed in the mixing pond 2. Is done. The treated water flowing out of the mixing pond 2 further flows down to the floc formation pond 3. The treated water in the vicinity of the outlet of the mixing pond 2 is taken by the water sampling pump 4 and led to the residual salt meter 5 for measuring the residual chlorine concentration. Then, the signal R _c of Zanshiokei 5 is input to the chlorinator computing device.

On the other hand, the liquid chlorine in the liquid chlorine storage tank 8 is completely vaporized by the vaporizer 7 through the chlorine liquid salt line valve 23 and the liquid salt line 21 to become gaseous chlorine. Thereafter, the gaseous chlorine is sent to the chlorine injector 9 via the chlorine gas reservoir 19. The gaseous chlorine in the liquid chlorine storage tank 8 is sent directly to the chlorine injector 9 via the gas-liquid line valve 12 and the gas-liquid line 22. Also,
A tank lorry 20 is connected to the liquid chlorine storage tank 8 via a receiving line 25 having a liquid salt receiving valve 11, and compressed air is introduced into the tank lorry 20 via an introduction line 24. The compressed air is introduced into the liquid chlorine storage tank 8 via the introduction line 28. The liquid chlorine storage tank 8 is provided with a plurality of pressure gauges 26. The liquid salt receiving valve 11 and the gas-liquid line valve 12 are provided with limit switches 11a and 12a for detecting opening of the valves and transmitting the detection signal to the first determination device 13, respectively. The pressure signal from the pressure gauge 26 of the liquid chlorine storage tank 8 is transmitted to the second determination device 14
To be sent to

Further, the first determining device 13 and the second determining device 1
4 and the chlorine injection rate calculator 6 are connected to the correction calculator 15. The chlorine injection rate calculated by the chlorine injection rate calculation device 6 is corrected by the correction calculation device 15 and
To be sent to Further, the correction operation device 15
Is connected to the setting device 16.

Next, a chlorine injection control method will be described.
The chlorine injection rate calculating device 6 has a setting device 10 for setting a control target set value sv of the residual chlorine concentration. The chlorine injection rate calculating unit 6 based on the signal R _c of the control target value set value sv and Zanshio five, it calculates the chlorine injection rate by the following equation (1) to (3).

[0012] _{S n = S n-1 +} △ S ... (1) △ S = K P · (E n -E n-1) + K i · E n ... (2) E n = sv-R c ... ( in 3) (1) to (3), E _n is input deviation, K _P is a proportional gain of the input deviation, E _n-1 is the previous control period of the control period of this time, K _i is an integral gain, S _n Is the calculated value of chlorine injection rate when pure chlorine gas is injected in this control cycle, S
_n-1 is a calculated chlorine injection rate value when pure chlorine gas is injected in the previous control cycle. During normal operation, the chlorine sent from the liquid chlorine storage tank 8 to the chlorine injector 9 via the liquid salt line 21, the chlorine vaporizer 7 and the chlorine gas reservoir 19 is the chlorine injection rate determined by the chlorine injection rate controller 6. Injected into treated water based on

Next, when liquid chlorine is received, both the liquid salt receiving valve 11 and the gas-liquid line valve 12 are opened, and the detection signals from the limit switches 11a and 12a are input to the first determination device 13. Then, in the first determination device, a state in which the liquid salt receiving valve 11 and the gas-liquid line valve 12 are simultaneously opened is determined as a liquid chlorine receiving state.
At the same time, the compressed air introduced into the tank truck 20 via the introduction line 24 transfers the liquid chlorine in the tank truck 20 from the receiving line 25 into the liquid chlorine storage tank 8.

When the reception of liquid chlorine is about to be completed, the compressed air enters the liquid chlorine storage tank 8 together with the residual gas in the tank truck 20, and the pressure in the liquid chlorine storage tank 8 rapidly increases. This pressure increase is detected by the pressure gauge 26, and a detection signal is sent to the second determination device 26. In the second determination device 26, as shown in FIG. 2, when a peak is detected immediately after the pressure in the liquid chlorine storage tank 8 changes by pkg / cm ² or more for n minutes, it is determined that the liquid chlorine reception is completed.

If one or both of the first and second determination devices 13 and 14 do not satisfy the above-described conditions, it is determined that the above-described normal operation is being performed, and the chlorine injection rate calculating means 6 is determined.
Is converted into a chlorine injection amount without correction and output to the chlorine injector 9 side. When both the first determination device 13 and the second determination device 14 satisfy the above-described condition, that is, when it is determined that the liquid chlorine reception has been completed after the liquid chlorine reception state, the correction calculation device 15 Correct the chlorine injection rate immediately. The correction calculating means 15 performs the following correction by the equation (4). _Sn ′ = a · S _n + b (4) In equation (4), a and b are parameters specific to the water purification plants, and are constants that are easily determined for each water purification plant. The parameters a and b are given by the setting device 16. S _n 'is a corrected chlorine injection rate calculation value. The corrected injection rate is immediately converted to a chlorine injection amount and output to the injector 9. Thereafter, normal feedback calculation is performed. That is,
In the present embodiment, correction is performed only for one control synchronization, and thereafter normal operation control is performed.

FIG. 3 is a graph showing the effect of the embodiment of the present invention. In this way, by correcting the disturbance at the time of receiving liquid chlorine immediately after detecting the disturbance, the residual chlorine concentration after the chlorine injection can be set to a target value, and the water quality of the treated water can be stabilized. be able to.
In the above-described embodiment, an example in which the calculation is performed in a feedback manner by the chlorine injection rate calculating device 6 has been described. it can. In addition, an example has been described in which the liquid chlorine receiving state determined by the first determination device 13 and the end of liquid chlorine reception determined by the second determination device 14 are set as correction conditions. Only the termination of the acceptance of liquid chlorine to be determined may be used as the condition for correction. Further, the liquid chlorine receiving state determined by the first determination device 13 may be determined by a liquid level signal of the liquid chlorine storage tank 8. Further, the control synchronization of the chlorine injection rate calculating device 6 is preferably set to a relatively short cycle of about 30 seconds to 5 minutes in order to correct the disturbance with good timing.

[0017]

As described above, according to the present invention,
Since the chlorine injection rate is corrected at the end of receiving liquid chlorine,
Even when gaseous chlorine is diluted by compressed air, the concentration of residual chlorine in the treated water after chlorine injection can be set to a target value, and chlorine injection can be stably controlled.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of a chlorine injection facility incorporating a chlorine injection control device according to the present invention.

FIG. 2 is a diagram showing a pressure change in a liquid chlorine storage tank when liquid chlorine is received.

FIG. 3 is a graph showing changes in chlorine injection rate and residual chlorine concentration.

FIG. 4 is a schematic system diagram of a chlorine injection facility in which a conventional chlorine injection control device is incorporated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Landing well 2 Mixing pond 3 Floc formation pond 4 Water sampling pump 5 Residual salt meter 6 Chlorine injection rate calculator 7 Chlorine vaporizer 8 Liquid chlorine storage tank 9 Injector 11 Liquid salt receiving valve 12 Steam salt line valve 13 First judgment device 14 Second judgment device 15 Correction operation device 16 Setting device 20 Tank lorry 26 Pressure gauge

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/00 C02F 1/00 DK 1/76 1/76 A

Claims (2)

(57) [Claims] A chlorine injection control device of a chlorine injection facility for evaporating liquid chlorine in a liquid chlorine storage tank and injecting gaseous chlorine into treated water by a chlorine injection device; A second judging device for judging the end of the liquid chlorine reception into the liquid chlorine storage tank, which is performed by introducing the compressed air; and, based on a signal from the second judging device, introducing the compressed air immediately after the end of the liquid chlorine receiving. And a correction calculation device for correcting the calculation result of the chlorine injection rate calculation device so as to compensate for the decrease in chlorine concentration caused by the above, and outputting the result to the chlorine injection device. 2. A method for judging a state of receiving liquid chlorine,
The chlorine injection control device according to claim 1, further comprising a first determination device that outputs a determination result to the correction operation device.