JPH04358596A - Chlorine injection controlling apparatus - Google Patents

Abstract

PURPOSE:To lessen the alteration of effective chlorine injection in the case that the total filtration flow rate changes by immediately taking out a new desired flow rate value as an input for computation of a desired chlorine injection amount and installing a desired value controlling part to alter the desired chlorine injection amount. CONSTITUTION:When the alteration of a desired flow rate value Q to a rapidly stirring pond is detected, a desired value controlling part 3b of the rapidly stirring pond is sent out a desired value alteration signal 31 to a pre-chlorine injection controlling part 3a. Corresponding to the desired value alteration signal 31, the pre-chlorine injection controlling part 3a switches the rapidly stirring flow rate measured value Q to the rapidly stirring desired flow rate value Q1 of the rapidly stirring pond sent out of the pre-chlorine injection controlling part 3a and computes and calculates the desired injection amount (qrefl) and immediately controls the pre-chlorine injection amount. Meanwhile, the desired value controlling part 3b of the rapidly stirring pond changes present Q0 of the rapidly stirring desired flow rate value to post-alteration Q1 after chlorine delay time t1 of an injection apparatus since the rapidly stirring desired value alteration and controls the flow rate through a rapidly stirring flow control valve.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chlorine injection control device used in a chlorine injection process at a water purification plant, which takes into account fluctuations in the flow rate of raw water.

0002

2. Description of the Related Art In general, pre-chlorine injection processes and intermediate chlorine injection processes are known as methods for controlling chlorine injection processes in water purification plants. The former pre-chlorine injection process control method is to control the chlorine injection ratio constant to the rapid stirring tank inflow flow rate (raw water inflow rate), and the latter intermediate chlorine injection process control method is to control the chlorine injection rate after removing sediment in the sedimentation tank. This is to control the chlorine injection ratio to be constant with respect to the total filtration flow rate (raw water inflow rate) flowing into the mixing basin. Both control methods involve injecting and stirring a set amount of chlorine to the inflow of raw water to control the residual chlorine concentration to a certain value, and are mainly used for disinfecting raw water in the preliminary stage. .

FIG. 4 is a system diagram showing an example of a conventional pre-chlorine injection control device, in which the pre-chlorine injection rate set value (target value) r
1 is set externally, for example, by manual setting by an operator. In the conventional pre-chlorine injection control device 3, the pre-chlorine injection control unit 3a measures the rapid stirring pond inflow flow rate Q, which is the target flow rate for pre-chlorine injection, and performs the pre-chlorine injection based on this flow rate Q and the pre-chlorine injection rate set value r1. Quantity target value qref1
is calculated using the following equation (1), and this is determined as the injection amount target value of the injection machine and output to the chlorine injection machine 6. qref1=r1×Q... (1) In the chlorine injection machine 6, the chlorine injection amount (measured value) q1 at the chlorine injection machine outlet is q1 = qref1 with respect to the previous chlorine injection target value qref1
...(2) Feedback control is executed so that the following is true. That is, in the conventional pre-chlorine injection amount control, injection ratio constant control is performed such that the chlorine injection amount q1 at the outlet of the chlorine injection machine becomes a set injection ratio with respect to the injection target flow rate.

However, in the conventional pre-chlorine injection process in which the amount of chlorine injection is calculated and determined, there is a problem in the transportation delay time from the chlorine injection machine outlet side to the pre-chlorine injection point. If this transportation delay time is τ1 [hours], the amount of chlorine injected q2 at the pre-chlorine injection point is the amount q1 injected at the outlet of the chlorine injection machine.
Since it changes with a delay of τ1 [time] from q1 and q2
As a function of time t, the following equation q2 (t) = q1 (t-τ1) ...(3)
holds true. Therefore, for the injection target flow rate Q, the actual injection amount is q2 (t), that is, q1 (t-τ1)
Therefore, when the injection target flow rate Q changes, the injection ratio changes due to the transport time delay τ1 [time].

FIG. 9 is a system diagram showing an example of a conventional medium chlorine injection control device, in which the medium chlorine injection rate setting value r3
is set externally, for example, by manual setting by an operator. In the conventional medium chlorine injection control device 4, the medium chlorine injection control unit 4a measures the total filtration flow rate Q2, which is the flow rate to be injected with medium chlorine, and determines the target medium chlorine injection amount from this flow rate Q2 and the medium chlorine injection rate setting value r3. The value qref3 is calculated using the following equation (4), determined as the injection amount target value of the chlorine injection machine, and outputted to the chlorine injection machine 6.

[0006]qref3=r3×Q2...(4
) In the chlorine injection machine 6, the measured value q3 of the chlorine injection amount at the chlorine injection machine outlet is q3 =
Feedback control is performed so that qref3...(5). That is, in the conventional intermediate chlorine injection amount control, injection ratio constant control is performed such that the injection amount q3 at the outlet of the chlorine injection machine becomes a set injection ratio with respect to the injection target flow rate.

However, in the conventional medium chlorine injection process in which the amount of chlorine to be injected is determined by calculation, there is a problem in the transportation delay time from the chlorine injection machine outlet side to the medium chlorine injection point. If this transportation delay time is τ2 [hours], the amount of chlorine injected q4 at the medium chlorine injection point is the amount q3 injected at the outlet of the chlorine injection machine.
Since it changes with a delay of τ2 [time] from q3 and q4
As a function of time t, the following equation q4 (t) = q3 (t-τ2) ...(6)
holds true. Therefore, the flow rate to be injected (total filtration flow rate)
The actual injection amount for Q2 is q4 (t), that is, q
3 (t-τ2), and when the injection target flow rate Q2 changes, the injection ratio changes due to the transport time delay τ2 [time].

[0008]

[Problems to be Solved by the Invention] By the way, in the pre-chlorine injection system diagram shown in FIG. 4, FIG. 5 shows an example of temporal changes in each measured value of the pre-chlorine injection amount control device when the pre-chlorine target flow rate changes. show. The pre-chlorine injection rate target value (set value) r1 is constant with respect to time t as shown in graph (a), and the pre-chlorine injection target flow rate (rapid stirring pond inflow flow rate) Q is as shown in graph (a).
b) Assuming that the amount changes as shown in (1), in the conventional pre-chlorine injection amount control device, the control target value qre is determined by equation (1).
Since f1 is output, the amount of chlorine injected q1 at the outlet of the chlorine injection machine changes as shown in graph (c) according to equation (2) above. Here, since there is a transportation delay time of τ1 [hours] from the chlorine injection machine outlet side to the pre-chlorine injection point 8, the chlorine injection amount q2 at the pre-chlorine injection point 8 is calculated by the graph (
d) changes as shown in .

As a result, the effective injection rate r2 = q2 /Q (7) at the pre-chlorine injection point 8 changes as shown in graph (e). In other words, in the conventional pre-chlorine injection control device, even if the pre-chlorine injection rate set value r1 is constant, the actual pre-chlorine effective injection rate r2 at the pre-chlorine injection point 8 is not constant; The injection delay time τ1 changes as the inflow rate changes. As a result, the residual chlorine concentration in the settling tank fluctuates, causing disturbance in the purified water treatment process and affecting the purified water treatment process after the settling tank.
This poses a problem in that the quality of the purified water being produced fluctuates.

On the other hand, in the medium chlorine injection system diagram in FIG.
FIG. 10 shows an example of a temporal change in each measurement value of the medium chlorine injection amount control device when the medium chlorine target flow rate changes. The medium chlorine injection rate target value (set value) r3 was constant over time t as shown in graph (a), and the medium chlorine injection target flow rate (total filtration flow rate) Q changed as shown in graph (b). Then, since the conventional medium chlorine injection amount control device outputs the control target value qref3 according to equation (4), the medium chlorine injection amount q3 at the chlorine injection machine outlet side is calculated as shown in graph (c) according to equation (5). Changes to Here, since there is a transportation delay time of τ2 [hours] from the chlorine injection machine outlet side to the medium chlorine injection point 9, the chlorine injection amount q4 at the medium chlorine injection point 9 changes as shown in graph (d). do.

As a result, the effective injection rate r4 = q4 /Q (8) at the intermediate chlorine injection point 9 changes as shown in graph (e). That is, in the conventional medium chlorine injection control device, even if the medium chlorine injection rate r3 is constant, the effective injection rate r4 at the actual medium chlorine injection point 9 is
is not constant, but varies by the injection delay time τ2 as the total filtration flow rate changes. As a result, the residual chlorine concentration in the filtration basin fluctuates, causing a disturbance in the purified water treatment process and affecting the water treatment process after the filtration basin, which in turn causes fluctuations in the quality of the purified water being produced. There's a problem.

The present invention was made in order to solve the problems that occur with the conventional pre-chlorine injection control device or intermediate chlorine injection control device described above, and it is possible to reduce the effective chlorine effect when the rapid agitation inflow flow rate or the total filtration flow rate changes. The object of the present invention is to provide a chlorine injection control device that reduces fluctuations in injection rate.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a flow rate control section that controls the flow rate of raw water to be chlorinated in accordance with a target value, and a chlorine injection machine that injects the raw water into the raw water. In a chlorine injection control device for a water treatment plant process, the chlorine injection control device for a water treatment plant process is equipped with a chlorine injection control unit that controls the injection amount of chlorine in accordance with a target injection amount calculated from the flow rate of the raw water and a predetermined injection ratio. detecting a change in the flow rate target value, outputting the new flow rate target value as the raw water flow target value after delaying the chlorine transport time from the chlorine injection machine to the raw water injection point, and outputting the new flow rate target value as the raw water target flow value. The present invention is characterized by comprising a target value control section that immediately outputs the chlorine injection amount target value as an input for calculation of the chlorine injection amount target value and immediately changes the chlorine injection amount target value. In pre-chlorine injection, where the raw water flowing into the rapid stirring pond is the subject of chlorine injection, the amount of chlorine injected into this raw water is adjusted to the injection amount target value calculated from the flow rate of the raw water and a predetermined injection ratio. It is equipped with a pre-chlorine injection control unit that controls the amount of chlorine injected into the raw water. The medium chlorine injection control unit controls the amount of chlorine according to a target injection amount calculated from the flow rate of the raw water and a predetermined injection ratio.

[0014]

Therefore, according to the present invention, it is possible to prevent fluctuations in the effective chlorine injection rate due to the chlorine transport delay time during chlorine injection, so that the quality of purified water can be made uniform.

[0015]

[Embodiment] An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a pre-chlorine injection control device which is an embodiment of the present invention. In the figure, the pre-chlorine injection control device 3 includes:
In addition to the same pre-chlorine injection control section 3a as in the conventional pre-chlorine injection control device shown in FIG. 4, a rapid stirring pond target value control section 3b is provided.

The rapid stirring pond target value control section 3b is always inputted with the rapid stirring pond inflow flow rate target value Q, and when a change in this target value Q is detected, the rapid stirring pond is first injected into the pre-chlorine injection control section 3b. An inflow flow rate target value change signal 31 is output. The pre-chlorine injection control section 3a outputs a rapid stirring inflow flow rate target value change signal 31.
According to the above equation (1), the measured value Q of the rapid agitation inflow flow rate
is switched to the rapid agitation inflow flow rate target value Q1 outputted from the rapid agitation basin target value control unit 3b, and the calculation of equation (1) is performed,
Immediately after calculating the injection amount target value qref1, the pre-chlorine injection amount is controlled.

On the other hand, the rapid stirring pond target value control section 3b controls the chlorine transport delay time τ1 of the injector from the time of changing the rapid stirring flow rate target value.
Q after changing the target value of rapid agitation inflow flow rate from the current Q0
1, and the flow rate is controlled via the rapid agitation inflow flow rate control valve.

Next, the rapid agitation inflow flow rate target value change signal 31 for the pre-chlorine injection control section 3a is reset, and the pre-chlorine injection control section 3a returns to normal control using the rapid agitation inflow flow rate measurement value Q1 as input. .

FIG. 2 is a graph showing each measured value when pre-chlorine injection control according to the present invention is performed, and graph (a)
If the pre-chlorine injection rate setting value (target value) r1 is constant as shown in graph (b), the time t0 marked with ▽ in graph (b)
When the rapid agitation inflow flow rate target value is changed from Q0 to Q1, the rapid agitation inflow flow rate target value input to the pre-chlorine injection control section 3a in FIG. 1 is immediately switched from Q0 to Q1, and the pre-chlorine injection amount target The value qref1 corresponds to equation (1) above, and becomes qref1=r1 ×Q1 (9), so that the target value Q is achieved even though the actual flow rate is Q0.
1, and the pre-chlorine injection amount q1 is calculated using the graph (
c) It becomes like this.

The actual injection amount q2 at the injection point is delayed by the transport time delay τ1 time relative to the pre-chlorine injection amount q1 at the injection machine outlet, as shown in equation (3) above, and the graph (d
). In this case, at time t0 when the rapid stirring inflow target value is changed to Q1, the rapid stirring pond inflow flow Q is not changed yet, but is changed after a delay of time τ1 (dotted line in graph (b)). graph(
The effective pre-chlorine injection rate r2 determined from b) and graph (d) is a constant value as shown in graph (e). In other words, the actual rapid stirring pond inflow flow rate is changed to Q1 after the chlorine injection transport delay time τ1 from the time t0 when the rapid stirring inflow target value is changed, so that the actual rapid stirring pond inflow flow rate is changed to Q1.
The amount of chlorine injected immediately at the injection point is injected in a timely manner to the target flow rate Q1, and the injection amount q2 at the injection point shown in graph (d) and the target flow rate shown by the dotted line in graph (b) are By matching, the effective pre-chlorine injection rate r2
There is no fluctuation as shown in graph (e). Note that FIG. 3 is a functional configuration diagram showing in an easy-to-understand manner the functional configurations of the pre-chlorine injection control section 3a and the rapid stirring basin target value control section 3b, which have already been described.

FIG. 6 is a system diagram of a medium chlorine injection control device which is another embodiment of the present invention. In the figure, a medium chlorine injection control device 4 is provided with a total filtration flow rate target value control section 4b in addition to a medium chlorine injection control section 4a, which is the same as in the case of the conventional medium chlorine injection control device shown in FIG. 9, which has already been explained. It is being

The total filtration flow rate target value control unit 4b is always inputted with the total filtration flow rate target value Q, and when a change in this target value Q is detected, first the total filtration flow rate target value is set to the intermediate chlorine injection control unit 4a. A value change signal 41 is output. In response to the total filtration flow rate target value change signal 41, the medium chlorine injection control unit 4a converts the total filtration flow rate measurement value Q2 in the above equation (4) into the total filtration flow rate target value output from the total filtration flow rate target value control unit 4b. Q3 and calculates the formula (4) to calculate the injection amount target value qref3 and immediately control the medium chlorine injection amount.

On the other hand, the total filtration flow rate target value control unit 4b controls the chlorine transport delay time τ2 of the injector from the time of changing the total filtration flow rate target value.
After changing the total filtration flow rate target value from the current Q2
3, and the flow rate is controlled via the total filtration flow rate control valve. Next, the total filtration flow rate target value change signal 41 for the medium chlorine injection control section 4a is reset, and the medium chlorine injection machine control section 4a
returns to normal control using the total filtration flow rate measurement value Q3 as input.

FIG. 7 is a graph showing each measured value when medium chlorine injection control according to the present invention is performed, and graph (a)
If the medium chlorine injection rate set value (target value) r3 is constant as shown in graph (b), the time point t0 marked with ▽ in graph (b)
When the total filtration flow rate target value Q is changed from Q2 to Q3, the total filtration flow rate Q input to the medium chlorine injection control unit 4a in FIG. 6 is immediately switched from Q2 to Q3, and the medium chlorine injection amount target value qref3 is changed. Corresponding to the above calculation formula (4), qref3=r3×Q3...(10),
Target value Q3 even though the actual flow rate is Q2
The pre-chlorine injection amount q3 is calculated using graph (c)
become that way.

The actual injection amount q4 at the injection point relative to the injection amount q3 at the injection machine outlet is delayed by the transport time delay τ2 time as shown in equation (6) above, and changes as shown in graph (d). . In this case, the total filtration flow rate target value is Q3
At the time t0 when the setting is changed to , the total filtration flow rate Q is still
2 is not changed and is changed after a delay of time τ2 (dotted line in graph (b)), so the effective medium chlorine injection rate r4 determined from graph (b) and graph (d) is shown in graph (e). As shown, it becomes a constant value. In other words, the actual total filtration flow rate will be Q
3, the amount of chlorine injected immediately at time t0 is injected in a timely manner for the target flow rate Q3, and the amount of chlorine injected at the injection point shown in graph (d) is q.
4 and the target flow rate shown by the dotted line in graph (b) match, and the effective medium chlorine injection rate r4 is as shown in graph (e).
No fluctuation occurs as shown in . In addition, FIG. 8 is a functional configuration diagram showing in an easy-to-understand manner the functional configurations of the medium chlorine injection control section 4a and the total filtration flow rate target value control section 4b in FIG. 6, which have already been described.

[0026]

As explained above, according to the chlorine injection control device of the present invention, the chlorine injection rate that occurs when the flow rate of chlorine injection target changes due to transport time delay in conventional chlorine injection machines can be reduced. Fluctuations in chlorine are prevented, and the effective injection rate of chlorine can be kept constant. Therefore, it is possible to eliminate the disturbance of fluctuations in the residual chlorine concentration due to fluctuations in the chlorine injection rate, which conventionally caused problems when changing the target flow rate for chlorine injection, making it possible to perform water purification treatment with stable water quality. It has this excellent effect.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a pre-chlorine injection control device that is an embodiment of the present invention.

FIG. 2 is a time chart showing the operation of the pre-chlorine injection control device according to the present invention.

FIG. 3 is a diagram showing the functional configuration of a pre-chlorination injection control device according to the present invention.

FIG. 4 is a system diagram showing an example of a conventional pre-chlorine injection control device.

FIG. 5 is a time chart showing the operation of a conventional pre-chlorine injection control device.

FIG. 6 is a system diagram of a medium chlorine injection control device which is another embodiment of the present invention.

FIG. 7 is a time chart showing the operation of the intermediate chlorine injection control device according to the present invention.

FIG. 8 is a diagram showing the functional configuration of a medium chlorine injection control device according to the present invention.

FIG. 9 is a system diagram showing an example of a conventional intermediate chlorine injection control device.

FIG. 10 is a time chart showing the operation of a conventional intermediate chlorine injection control device.

[Explanation of symbols]

3... Pre-chlorine injection control device, 3a... Pre-chlorine injection control section, 3
b... Target value control unit, 4... Medium chlorine injection control device, 4a... Medium chlorine injection control unit, 4b... Target value control unit, 6... Chlorine injection machine, 8... Pre-chlorine injection point, 9... Medium chlorine injection point, 31... Rapid stirring inflow target value change signal, 41... Total filtration flow rate target value change signal.

Claims (3)

[Claims] Claim 1: A flow rate control unit that controls the flow rate of raw water to be chlorinated in accordance with a target value, and a chlorine injection amount that is injected into the raw water from a chlorine injection machine according to the flow rate of the raw water and a predetermined injection ratio. In a chlorine injection control device for a water purification plant process, which is equipped with a chlorine injection control unit that performs control corresponding to an injection amount target value calculated from Delaying the chlorine transport time from the chlorine injection machine to the point of injection into the raw water and outputting it as a target flow rate value for the raw water, and immediately outputting the new target flow rate value as an input for calculation of the target value for the amount of chlorine injection; A chlorine injection control device comprising a target value control section that immediately changes a chlorine injection amount target value. [Claim 2] The raw water flowing into the rapid stirring pond is to be injected with chlorine, and the amount of chlorine injected into the raw water is determined in accordance with the target value of the amount of chlorine to be injected, which is calculated from the flow rate of the raw water and a predetermined injection ratio. The chlorine injection control device according to claim 1, further comprising a pre-chlorine injection control section for controlling the chlorine injection. [Claim 3] Raw water after sediment has been removed in a settling tank is to be injected with chlorine, and the amount of chlorine to be injected into this raw water is calculated from the flow rate of the raw water and a predetermined injection ratio. The chlorine injection control device according to claim 1, further comprising a medium chlorine injection control section that controls the chlorine injection in accordance with the above.