JP2768810B2 - Water injection plant chemical injection control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a chemical injection control device for a water purification plant having a self-cleaning filter pond.

(Prior Art) Conventionally, a chemical injection device shown in Fig. 9 is known as a chemical injection device for a water purification plant. In this conventional example, a post-chlorination injection control device for a water purification plant equipped with a self-cleaning filter pond is used. Is shown.

Generally, in a water treatment plant equipped with a self-cleaning filtration pond, raw water is first stored in the sedimentation basin 1 where the impure filth is precipitated.
The sediment water is guided to the filtration pond 3 through the sewer 2, where impurities are further filtered, and the filtered water is sent to the water purifier 5 through the filtration sewer 4. A total filtration flow meter 6 for measuring a total filtration flow rate is provided in a pipeline between the filtration culvert 4 and the water purification pond 5. Further, the self-cleaning water 7 flows backward from the filtration culvert 4 to the respective filtration ponds 3 and is discharged to the drainage ponds 8.

Further, the control system of this conventional example includes a post-chlorine injection control device 9.
And a chlorine injector 10.

The post-chlorine injection control device 9 calculates the injection amount target value qref from the injection rate target value γ1 set by the manual operation of the operator.
Is calculated using the first equation, and is output to the chlorine injector 10.

qref = γ1 × Q1 Equation 1 In the chlorine injector 10, the chlorine injection amount is ideally controlled such that q1 = qref Equation 2.

In the second equation, q1 represents the chlorine injection amount on the outlet side of the injector.

Here, assuming that the transport time of the chlorine water from the outlet of the injector to the rear chlorine injection point P is L [hour], the chlorine injection amount q2 at the rear chlorine injection point changes with a delay of L [hour] from q1. q1, q
If 2 is expressed as a function of time t, q2 (t) = q1 (tL)...

Now, it is assumed that the chlorine injection rate target value γ1 is constant with time t as shown in FIG. 10 (a).

At this time, it is assumed that washing of the filtration pond has occurred at the timing shown in FIG. 10 (b). At this time, as described above, in the self-cleaning type filter pond, the filter wash water 7 flows from the filter culvert 4 to the drain pond 8 through the filter pond 3 being washed.
The total filtration flow Q1 changes as shown in FIG. 10 (c).

Since the conventional post-chlorination control device outputs the control target value shown in equation (1), the chlorine injection amount q1 on the outlet side of the chlorine injector is calculated by equation (2) as shown in FIG. Filtration flow rate Q1
It changes according to.

Since the transport time of L [time] is required from the exit side of the chlorine injector to the post-chlorine injection point P, the chlorine injection amount q2 at the post-chlorine injection point P is shown in FIG. To change.

As a result, the effective injection rate γ2 at the chlorine injection point is changed as shown in FIG. 10 (f) because γ2 = q2 / Q1 ... Equation 4 (Problem to be Solved by the Invention) As shown in the figure, when the conventional post-chlorination control apparatus is used, even if the chlorine injection rate target value γ1 is constant, the effective injection rate γ2 at the chlorine injection point P is not constant, It will change every time the filter is washed.

In general, the washing of filter ponds occurs once every few hours, so the effective injection rate fluctuates with each washing, and the quality of the purified water produced also fluctuates in proportion to this. Was.

The present invention provides a chemical injection control device capable of minimizing fluctuations in the effective injection rate and maintaining stable water quality even in the event of filtration tank cleaning, in a water purification treatment facility equipped with a self-cleaning filter pond. It is in the thing.

[Constitution of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a self-cleaning filter, and a total filter for measuring the total filtration flow rate of the filtered water filtered by the filter. Filtration flow rate measuring means, during the washing of the filtration pond, washing consumption measuring means for measuring the amount of filtered water consumed by washing based on the change of the total filtration flow rate measurement value, and the total filtration flow rate measurement value Injection target flow rate calculating means for calculating the injection target flow rate of the chemical from the measured washing consumption amount and the cleaning interval time of the filtration pond, and the filtered water is calculated from the set chemical injection rate target value and the injection target flow rate calculation value. Injection amount calculating means for calculating a target value of a drug injection amount for a drug injection machine for injecting a drug into the device.

(Operation) According to the above configuration, the amount of the filtered water consumed by washing the filtration pond (washing consumption) is measured based on the change in the measured value of the total filtration flow rate. A chemical injection target flow rate is calculated from the cleaning consumption, the total filtration flow rate measured value, and the cleaning interval time, and a chemical injection amount target value is calculated from the calculated value and the chemical injection rate target value.

As a result, the effective injection rate at the injection point becomes constant, and stable water quality can be maintained.

(Embodiment) FIG. 1 is a system diagram showing an embodiment (first embodiment) of the present invention.

The post-chlorination injection control device 9 according to the present embodiment calculates the effective injection rate γ2 at the post-chlorination injection point according to the injection rate target value γ1 set and input from the outside, for example, manually by an operator, γ2 = γ1. So that the target injection amount qref for the chlorine injector 10 is
Is output.

For this purpose, in the post-chlorination injection control device 9 of the present invention, the filter pond cleaning controller 11 outputs a signal S1 indicating that the filter pond 3 is being cleaned, and a filter pouring during the next filter pond from the start of filter pond cleaning. Enter the time interval T1 until the start of cleaning.

The post-chlorination injection control device 9 includes a cleaning consumption measuring unit 12, an injection target flow rate calculating unit 13, and an injection amount calculating unit 14.

The washing consumption measuring unit 12 measures a change in the total filtration flow during the washing of the filter pond from the signal S1 during the filter pond washing and the indicated value Q1 of the total filtration flow meter, and detects the amount of filtered water consumed in the filter pond washing:
That is, the cleaning consumption V is measured.

In the injection target flow rate calculation unit 13, the cleaning consumption V and the cleaning interval
The post-chlorine injection target amount Q2 is measured based on T1.

The injection amount calculation unit 14 multiplies the injection rate target value γ1 by the injection target flow rate Q2 to determine the injection amount target value qref. The injection amount target value qref is output to the chlorine injector 10.

The chlorine injector 10 injects only chlorine (Cl ₂ ) into the injection water (H ₂ O) to match the injection amount target value qref to produce chlorine water. Here, the amount of chlorine on the outlet side of the chlorine injector in the chlorine water produced by the chlorine injector 10 is defined as q1. The time required for the chlorine water to be transported from the outlet of the chlorine injector to the rear chlorine injection point P is L, and the amount of chlorine in the chlorine water at the rear chlorine injection point P is q2. As described above, q1 and q2 have the relationship shown in the third equation.

The filter pond controller 11 includes a filter control set value R.
As the filter cycle, a filter cycle and a reference value for determining that cleaning is necessary, for example, a filter resistance setting value and a maximum filtration duration setting value are input. In addition, the filtration pond cleaning controller 11
Includes a filter pond status signal (that is, a signal indicating the state of the filter pond such as a status signal of a valve or a siphon installed in the filter pond 3, a water level indicator, a water level contact state, or a control compressed air source pressure). ) S2 has been entered. A signal S3 for controlling the state of the filter pond 3 is sent from the filter pond cleaning controller 11.
Or has been output.

FIG. 2 shows the relationship between the total filtration flow rate Q1 and the time t, and the area of the hatched portion in the figure indicates the amount of filtered water consumed for washing the filter pond 3 during the washing of the filter pond. (unit:
m ³ ).

 Next, the operation of the present embodiment will be described.

The washing consumption measuring unit 12 takes in the indicated value Q1 of the total filtration flowmeter 6 and the signal S1 during the washing of the filter tank, and when the filter is not being washed as shown by the formula 6, Q = Q1 during the washing of the filter. Q = value of Q1 immediately before the start of cleaning.

Further, the washing consumption measuring unit 12 The integral of the seventh equation is performed, and the amount of filtered water consumed by washing the filter pond, that is, the washing consumption V is measured. If the unit of Q1 is [m ³ / h] and the unit of time t is [h], the unit of V is [m ³ ].

The injection target flow rate calculation unit 13 calculates the cleaning consumption V and the cleaning interval T1.
And the following processing is performed.

Δq = V / T1 Equation 8 Q2 = Q1−Δq Equation 9 The temporal change of the injection target flow rate Q2 is almost constant as shown by the broken line in FIG.

If the unit of T1 is [h], the unit of Δq, Q2 is [m ³ / h].

The injection amount calculation unit 14 uses the injection rate target value γ1 and the injection target flow rate Q2 to output the injection amount target value to the chlorine injector 10.
qref is obtained by the following equation (10).

qref = γ1 × Q2 Expression 10 Here, the unit of γ1 is [ppm] or [g / m ³ ].
Then, the unit of qref is [g / h].

The chlorine injector 10 inflows and outputs a chlorine injection amount q1 that ideally satisfies q1 = qref.

Therefore, as can be seen from the waveforms of the conventional example shown in FIG. 10 and the present embodiment shown in FIG.
Takes a constant value (FIG. 3 (d)), and accordingly the chlorine injection amount q2 at the injection point P also takes a constant value (FIG. 3 (e)).
Thereby, the fluctuation of the effective inflow rate γ2 is greatly suppressed,
The quality of purified water can be maintained stably.

 FIG. 4 is a system diagram showing a second embodiment of the present invention.

In this embodiment, two chlorine injectors 10a and 10b are installed. The two chlorine injectors 10a and 10b have different injection capacities, one is a small injector 10a, and the other one is a large injector (select one with an injection capacity 2 to 6 times that of the small injector) It is 10b in general).

Injection amount target value qr output from post chlorine injection amount control device 9
ef is the right side according to its size,
Input to 10b or small injector 10a.

Further, an injector switching logic unit 15 is provided, and in the injector switching logic unit 15, the injection target value is input to the appropriate chlorine injector 10a or 10b according to the magnitude of the injection amount target value qref. As such, the injector switch 16 is switched, and the injector switch valve 17a or 17b installed on the outlet side of the chlorine injector 10a or 10b on the side where the injection amount target value is input is opened. Control so that The other configuration is the same as that of the first embodiment.

 Next, the operation of the present embodiment will be described.

In the present embodiment, in the cleaning consumption measuring unit 12, the values QN and QS obtained by the expression 6 ′ are used instead of the value Q of the expression 6.

 That is, when the filter pond is not being washed, a moving average of QN = Q1 for n minutes During the filter pond washing, QS = the average value of Q1 during the washing ... Values QN and QS as expressed by Equation 6 'are obtained.

Here, QN is a moving average value of the total filtration flow rate during non-washing for n minutes (n is about 10 minutes), and QS is an average value of the total filtration flow rate during cleaning.

Further, the filter pond cleaning time T [h] is measured by using the eleventh equation using the filter pond cleaning signal S1.

T = washing end time−washing start time Expression 11 Then, instead of Expression 7, using the following Expression 7 ′,
Filtration water consumption by filtration tank washing, that is, washing consumption V
Ask for. Note that Q = QS.

V = (Q−Q1) × T Expression 7 ′ The subsequent processing is the same as in the first embodiment. That is,
The injection target flow rate calculation unit 13 obtains the injection target flow rate Q2 from the cleaning consumption amount V and the cleaning interval T1 using the eighth and ninth formulas.

Δq = V / T1 Equation 8 Q2 = Q1−Δq Equation 9 The temporal change of the injection target flow rate Q2 is almost constant as shown by the broken line in FIG.

The injection amount calculation unit 14 outputs the target injection amount qr to the chlorine injector 10 using the injection rate target value γ1 and the injection target flow rate Q2.
ef is calculated by the following equation (10).

qref = γ1 × Q2 Equation 10 When the injection amount target value qref is obtained in this manner, the injector switching logic unit 15 injects the appropriate amount of chlorine into the chlorine injector 10a or 10b according to the magnitude of the injection amount target value qref. Quantity target value
The injector switch 16 is switched so that the qref is inputted, and the injector switch valve 17a or 17b provided on the outlet side of the chlorine injector 10a or 10b on the side to which the injection amount target value qref is inputted. Is controlled to be in the open state.

The chlorine injector 10a or 10b outputs a chlorine injection amount q1 that ideally satisfies q1 = qref.

As described above, according to the present embodiment, chlorine is injected by calculating the flow rate Q2 to be injected. Therefore, as shown in FIG. 3, even when the filter tank is washed, the fluctuation of Q2 is reduced, and As a result, the chlorine injection amount q1 at the chlorine injection machine outlet side and the chlorine injection amount q2 at the chlorine injection point are both smoothed.

As a result, it is possible to prevent switching between the large injector 10b and the small injector 10a of the chlorine injector every time the filter pond is washed, so that the chlorine injectors 10a, 10b and the injector switching valves 17a, 1
The number of operations of 7b is reduced, and the effect of extending the life of the chlorine injectors 10a and 10b and the injector switching valves 17a and 17b can be expected.

The effective injection rate γ2 at the injection point is shown in FIG.
As shown in FIG. 10, the fluctuation becomes smaller as compared with FIG. 10 (f). As a result, there is an effect that the quality of the filtered water is stabilized.

Further, since the average value of the total filtration flow rate Q1 is used in the calculation of QN and QS in Equation 6 ', noise is superimposed on Q1 which is the value measured by the online sensor (total filtration flow meter 6). There is an effect that stable operation can be performed even when the

5 to 8 each show still another embodiment of the present invention, and these embodiments show an example in which the sedimentation filtration process of the water purification plant is composed of two or more systems.

In FIG. 5, the injection amount calculation for each system has the same configuration as the configuration of the post-chlorine injection control device of the present invention shown in FIG. In FIG. 5, the target injection amount qref calculated for each system is shown.
1 and qref2 are added to obtain the target injection amount for the chlorinator 10.
qref.

In FIG. 6, the average value of the 1-system washing interval T1 'outputted from the 1-system filtration pond washing controller 11a and the 2nd system washing interval T1 "outputted from the 2nd-system filtration pond washing controller 11b is calculated by the averaging section 18. This is calculated and input as the cleaning interval T1 to the injection target flow rate calculation unit 13. Similarly, the OR circuit 19 calculates the logical sum of the signal during washing of the system 1 filter tank and the signal during washing of the system 2 filter tank, and The signal S1 is during washing, and the sum of the total filtration flow Q1 'and the secondary filtration flow Q1 "is input to the total filtration flow Q1.

In FIG. 7, the injection target flow rate Q2 is separately calculated and added in the first system and the second system. That is, the first system injection target flow rate Q2 'and the second system injection target flow rate Q2 "are
Calculation is performed using the configuration shown in the figure, and the flow rate Q2 to be injected is obtained by Q2 = Q2 '+ Q2 ".

In Fig. 8, the cleaning consumption is measured independently for the first and second systems, and the sum of the first system cleaning consumption V 'and the second system cleaning consumption V "is defined as the cleaning consumption V. The flow rate to be cleaned is calculated. Is the same as in FIG.

As described above, in each embodiment, post-chlorine injection control has been described as an example. However, the present invention can also be applied to injection control of chemicals such as disinfectants and neutralizing agents.

[Effects of the Invention] As described above, according to the present invention, the effective injection rate at the injection point is stabilized, and the quality of filtered water is stabilized.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams of the operation of the embodiment, and FIGS. 4 to 8 are systems showing other embodiments of the present invention, respectively. FIG. 9 is a system diagram showing a conventional example, and FIG. 10 is an operation explanatory diagram of the conventional example. 3 Filtration pond 5 Purification pond 6 Total filtration flow meter 9 Chemical (post-chlorine) injection control device 10 Chlorine injection machine 11 Filtration pond cleaning controller 12 Cleaning consumption measurement unit 13 …… Injection target flow calculator 14 …… Injection amount calculator

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/50 540 C02F 1/50 540B 550 550L 560 560Z

Claims (1)

(57) [Claims] 1. A self-cleaning type filtration pond, a total filtration flow rate measuring means for measuring a total filtration flow rate of filtered water filtered by the filtration pond, and a change in a total filtration flow rate measurement value during washing of the filtration pond. A washing consumption measuring means for measuring an amount of filtered water consumed by washing based on the above, and calculating a chemical injection target flow rate from the total filtration flow rate measurement value, the washing consumption measurement value, and the cleaning interval time of the filter pond. An injection target flow amount calculating means, and an injection amount for calculating a chemical injection amount target value for a chemical injection machine for injecting a chemical into the filtered water from the set chemical injection ratio target value and the injection target flow amount calculation value. A chemical injection control device for a water purification plant, comprising: a calculating means.