JPS5952449B2 - Filtration flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filtration flow rate control device in the filtration stage of a water purification plant, and more specifically, when the intake flow rate of raw water is changed or when a disturbance factor occurs,
The present invention relates to an appropriate method for determining a set value of how to change or correct the filtration flow rate set value in the control device.

FIG. 1 is a schematic diagram showing an overview of a water purification process and an embodiment of the present invention. First, problems of the prior art will be explained with reference to the overview of the water purification process in FIG.

Generally, in the water purification process, as shown in Figure 1, raw water taken from a river, etc. is led to a settling tank 1, where sediment, gravel, etc. that flow in with the water are removed by sedimentation, and then in a settling tank 2, suspended matter in the water is removed. , fine particles, etc. are precipitated, and then the water is temporarily stored in the filtration basin raw water conduit 3 and then sent to the filtration basin 4, where it is passed through a sediment layer and filtered, and then sent through the mixing basin 5 and the water purification basin 6. It is a long process that takes several hours from water intake to water delivery.

In water purification plants, an operation method is generally adopted in which the intake flow rate of raw water is changed at appropriate time periods depending on a certain water demand pattern or water intake amount restrictions. On the other hand, the flow rate of water sent from the water purification plant is controlled by controlling the flow rate of filtration from the filter basin 4. However, even if the raw water intake flow rate changes, there is a considerable time delay before the effect reaches the filtration basin 4, so it is not recommended to change the set value for filtration flow rate control at the same time as the water intake flow rate is changed. Can not.
When there is a change in water intake flow rate, determining the optimal filtration flow rate setting value should be determined from the standpoint of water purification brand maintenance by maintaining the water level in raw water culvert 3 within a certain range of fluctuation, and from the standpoint of stabilizing water quality. It is preferable to do this under conditions such as minimizing fluctuations in the filtration flow rate in the filtration pond, and varying the filtration flow rate to the maximum extent within the range of the filtration capacity to achieve a wide range of operability. Conventionally, as a method for determining the optimum filtration flow rate setting value as described above, the flow rate of raw water taken, the water level of the filtration pond raw water conduit and its fluctuations, the water level of the water purification pond and its fluctuations, etc. are monitored, and each of these is monitored. A method is known in which a predetermined calculation is performed based on data and the filtration flow rate set value is successively changed based on the calculation result.

However, such a conventional method has a complicated data calculation mechanism, the filtration flow rate setting value is changed sequentially, so the filtration flow rate has to be controlled frequently, and it is based on the premise of a continuous filtration process. There were problems such as difficulty in applying it when stopping and starting water intake. This invention was made in order to solve the problems of the prior art as described above, and therefore, the purpose of this invention is to simplify the necessary data calculation mechanism and reduce the amount of water taken per time. There is no need to sequentially change the setting value over and over again in response to changes.
Furthermore, the present invention provides a filtration flow rate control device that is applicable not only during normal operation but also when starting and stopping water intake, and is equipped with an optimal filtration flow rate setting value determination method that can cope with the occurrence of disturbance factors. There is a particular thing.

The main point of the configuration of this invention is that the set value is determined by a set inflow rate of raw water into the process and a certain setting of the water level of the raw water conduit where the raw water flowing into the filtration pond is temporarily stored beforehand. The point is that the determination is made depending on the relative level position with respect to the upper and lower limits of the water level and the change tendency of the water level in the raw water culvert.

Next, referring again to FIG. 1, one embodiment of the present invention will be described in detail.

Although it was not explained earlier when explaining the outline of the water purification process, between the filtration pond raw water conduit 3 and the mixing basin 5, there is not one filtration basin 4 but multiple filtration basins in parallel, and the process 7
7'' is normally provided, and the filtration flow rate of interest in this invention is the total filtration flow rate of all the filter basins.

In FIG. 1, a raw water flow rate set value generator 8, a raw water flow rate control device 9, a raw water flow meter 10, a raw water flow rate control valve 11
A raw water intake control system is constructed by the following.

In addition, a total filtration flow rate target value generator 12 including a loss flow rate generator 13 that generates a signal for the loss flow rate in the settling basin 1 and settling basin 2, a total filtration flow rate set value generator 14, and a filtration basin raw water conduit water level gauge. 15, a filtration flow rate control device 16, a filtration flow rate adjustment valve 17, a filtration flowmeter 18, a water purification valve 19,
A filtration flow rate adder 20 is connected as shown.
Next, the operation will be explained.

The raw water flow rate set value generator 8 outputs a raw water flow rate set value GS according to a pattern of a certain water intake plan. The raw water flow rate control device 9 controls the raw water flow rate control valve 11 so that the raw water flow rate GQ input from the raw water flow meter 10 and the raw water flow rate set value GS given from the raw water flow rate set value generator 8 are equal. . Further, the raw water flow rate control device 9 outputs the raw water flow rate set value GS in the automatic mode, and the raw water flow rate GQ in the manual mode to the total filtration flow rate target value generator 12 depending on the control mode. In the generator 12, the raw water flow rate set value GS or the raw water flow rate GQ, which is the output of the control device 9, is calculated by subtracting the loss flow rate in the settling basin 1 and the settling basin 2 (generated from the loss flow rate generator 13). It is given to the total filtration flow rate set value generator 14 as the total filtration flow rate target value RG. The generator 14 outputs the water level H from the filtration basin raw water conduit water level meter 15, the upper limit GH of the water level set value in the raw water conduit 3, the lower limit GL of the water level, and the total Based on the relationship with the filtration flow rate target value RG, the total filtration flow rate setting value RS is determined by calculation, and the filtration flow rate control device 1
Output for 6. In other words, H (water level of raw water channel 3)
At every monitoring period Δt, H is greater than GH and RG is RS
When larger than (H>GH.RG>RS), or H
is smaller than GL and RG is smaller than RS (H<G
L. RS (total filtration flow rate set value) is updated so that RG<RS) and RS=RG. In addition, raw water channel 3
If the water level at deviates from the predetermined water level fluctuation range (between the upper limit GH and lower limit GL) due to the occurrence of a disturbance factor, simply adopting the method of updating the total filtration flow rate set value RS as described above will not result in the total Since the filtration flow rate target value RG is constant, it is impossible to restore the water level in the raw water culvert 3.

Therefore, the present invention takes this point into consideration.
This will be explained in detail below. A disturbance factor that changes the water level of the raw water conduit 3 is the filling of the filter basin 4 with water after cleaning is completed.

As mentioned earlier, there are multiple filtration ponds 4, and each pond is cleaned in appropriate shifts, and after such cleaning is completed, the water level in the raw water culvert 3 is reduced by filling the pond with water. descend rapidly. Other disturbance factors include inappropriateness of various setting values. In other words, if the water level monitoring cycle △t, the upper and lower limit set values GH and GL, and the total filtration flow rate target value RG, etc. are inappropriate, the water level in the raw water channel will rise or fall and deviate from the predetermined fluctuation range, and the operator Due to a change in the filtration flow rate due to manual operation or the like, the water level may rise or fall and deviate from a predetermined fluctuation range. Therefore, in such a case,
In order to restore the water level, the total filtration flow rate set value generator 14 sets the value when RG is equal to or smaller than RS and H is following an upward trend (H
>GH. RGdH × RS, 1>0), add an increasing correction to RS) Dt.

In other words, RS(1+α) is set as a new RS. However, RS
(1+β)RG. Also, when H is smaller than GL, RG is equal to or larger than RS, and H is following a downward trend (H<GL.RG>
R.S. (W〈0)) ) Dt) Add correction to RS in the decreasing direction.

In other words, RS(1-α) is set as a new RS. However, RS>
(1β) Must be RG. Here α (1〉α
〉0) and β (1〉β〉0) are values related to the speed of water level restoration, and are determined by the capacity of the raw water conduit, the maximum filtration capacity, the area of the filter pond, etc. The filtration flow rate control device 16 allocates the filtration flow rate setting value to each of the plurality of filtration ponds 4, obtains the filtration flow rate setting value Rs for each pond, and calculates the filtration flow rate setting value Rs, which is the input from the filtration flow meter 18 (Rq (filtration flow rate) ) and Rs are equal to each other. It consists of a control loop that monitors the total filtration flow rate in the pond 4) and RS. Next, regarding the case where the set values are corrected according to the present invention in response to the occurrence of a disturbance factor, the temporal changes in the total filtration flow rate target value RG, the filtration pond raw water level H, the total filtration flow rate set value RS, and the total filtration flow rate RQ are as follows. Second
This will be explained with reference to FIGS. 5 to 5. In all the time periods common to FIGS. 2 to 5, the raw water flow rate is constant, and as a result, the total filtration flow rate target value RG (FIG. 2) shows a constant value.

Before time 1, the filtration pond raw water level (Fig. 3) is in a stable water level state, and therefore RG=RS. Assuming that the filtration pond has been filled with water due to the completion of filtration cleaning, the water level of the raw water channel H
decreases rapidly. At time t1, H is lower than GL, RG:RS, and H is on a downward trend, so the total filtration flow rate set value generator 14 reduces the correction of the total filtration flow rate set value RS to the filtration flow rate controller 16. Do it in the direction. That is, the set value RS(t1) at time t1 is set to (1-α) times the set value RS(TO) at time t.
Expressed as a formula, RS(t1)=RS(TO)・[1-
α] RG(TO)=RG(t1). At time T2, since the same conditions exist, the set value RS is corrected.
That is, RG(TO)・[1−β]〈RS(T2)=
RS(t1)・[1-α]=RS(TO)・[1-
α]2 RG (TO) = RG (t1) = RG (T2).
At time T3, H is lower than GL, and RS is also lower than RG.
Although it is smaller, H is on the rise (the water level is moving in the direction of restoration), so the set value RS is not corrected.
RS(T3)=RS(T2). The water level H gradually rises, and at time T4, H is higher than GH, and RG
is larger than RS [=RS(T2)=RS(t1)], so in the total filtration flow rate set value generator 14, RG=RS7
The set value RS is changed so that [=RG(TO)]. Next, when a normal operation method is adopted in which the raw water intake amount is changed every certain time period, the raw water flow rate setting value GS, raw water flow rate GQ, filtration flow rate target value ')RG, and water level H in the raw water channel are calculated. , the total filtration flow rate set value RS, and the total filtration flow rate RQ over time will be explained with reference to FIGS. 6 to 11.

If the raw water flow rate set value GS is changed at current time T5, the raw water flow rate GQ follows it, and the filtration flow rate target value RG also follows, and RG (T5) is set.

The setting of RS is changed at time T6 when H becomes equal to or higher than GH as the raw water flow rate GQ increases.
Similarly, when the raw water flow rate is decreased at time T7, the setting of RS is changed because H changes to GL as the raw water flow rate decreases.
This is at time T8 when the value becomes lower. When the raw water flow rate is increased again at time T9, the setting of RS is changed at time TlO. In FIGS. 12 to 17, water intake stops at time Tll, and water intake stops at time Tll.
7, the progress until the filtration flow rate RQ becomes zero is shown in GS.7. GQ
．． R.G. H. It is a time change diagram shown about each of RS and RQ.

As explained above, according to the present invention, in determining the set value in the filtration flow rate control device, the calculation mechanism for this purpose is relatively simple, and the set value can be successively changed with respect to one change in water intake amount. In addition to the advantages that it does not require repeated changes and can be applied not only during normal operation but also when starting and stopping water intake, the raw water level may change due to disturbance or below the set water level. There is an advantage that even if the upper and lower limit set values and the water level monitoring cycle are inappropriate and deviate from the upper and lower limit set ranges, they can be restored.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an overview of the water purification process and an embodiment of the present invention, and Figs. 2 to 5 show the total filtration flow rate target value RG, the filtration pond raw water channel water level H, and the total filtration flow rate set value R, respectively.
S is a time chart correspondingly showing an example of a temporal change in the total filtration flow rate RQ, and FIGS. 6 to 11 similarly show the raw water flow rate set value GS, raw water flow rate (1), and RG. H
．． R.S. FIGS. 12 to 17 are time charts showing examples of respective temporal changes in RQ, and FIGS.
Similarly, G.S. GQ. R.G. H. 3 is a time chart correspondingly showing an example of temporal changes in RS and RQ. In the figure, 1 is a settling basin, 2 is a sedimentation basin, 3 is a filtration basin, 4 is a filtration basin, 5 is a mixing basin, 6 is a water purification basin, 7 is a block including the filtration basin 4, and 8 is a raw water flow rate setting value generation. 9 is a raw water flow rate control device, 10 is a raw water flow meter, 11 is a raw water flow rate control valve, 12 is a total filtration flow rate target value generator, 13 is a loss flow rate generator, 14 is a total filtration flow rate set value generator, 15 16 is a filtration pond raw water channel water level gauge, 16 is a filtration flow rate control device, 17 is a filtration flow rate adjustment valve, 18 is a filtration flowmeter, 19 is a water purification valve, and 20 is a filtration flow rate adder.

Claims (1)

[Claims] 1 In a filtration flow rate control device that controls the filtration flow rate in a filtration pond in a water purification process to be equal to a predetermined filtration flow rate setting value RS, the water level H of a raw water culvert that temporarily stores raw water flowing into the filtration pond before it is is higher than the set water level upper limit GH in the culvert, and the filtration flow rate target value RG, which depends on the set inflow rate of the process of raw water, is greater than the filtration flow rate set value RS, or the water level H is higher than the set water level GH in the raw water culvert. When the set water level lower limit value GL is lower than the set water level lower limit value GL, and the filtration flow rate target value RG is smaller than the set value RS, the set value RS is updated so that the filtration flow rate target value RG and the set value RS become equal. At the same time, regardless of whether the water level H is higher than the upper limit value GH, when the target value RG is equal to or smaller than the set value RS, and the water level H is in an upward trend, the set value RS increases in an increasing direction. Regardless of whether the water level H is lower than the lower limit value GL, if the target value RG is equal to or larger than the set value RS, and the water level H is on a downward trend, In such a manner that the set value RS is corrected in the decreasing direction, the set value RS is calculated based on the set inflow rate of raw water to the process and the water level of the raw water conduit in which the raw water flowing into the filtration pond is temporarily stored beforehand in the conduit. 1. A filtration flow rate control device, characterized in that the flow rate control device is determined depending on a level position relative to a set upper limit value and lower limit value of the water level, and a change tendency of the water level.