JPS6197012A - Filter controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a filter control device that controls the timing of water flow operation and backwash operation.

Technical background of invention C] Generally when removing crud from waste fluids.

A filter is used. The waste liquid is transferred from the pretreatment equipment,
It is transferred to a post-processing device via a filter.

At this time, since the filter is equipped with a filter,
This filter removes crud from the waste liquid sent to it. Further, as waste liquid is processed, crud adheres to the filter and the filter becomes clogged, making it difficult to process the waste liquid. Therefore.

The state of filter clogging is identified by measuring the differential pressure between the inlet and outlet of the filter, and when the differential pressure exceeds a certain value, the flow of waste liquid is stopped, air is allowed to flow into the filter, and air is removed from the filter. The crud is removed, and the backwash water receiver begins backwashing operation in which the waste liquid floating in the crud is discharged into the tank. When this backwashing operation is completed, the operation of entering a water flow operation in which the waste liquid from the pretreatment device is filtered and transferred to the posttreatment device is repeated alternately.

However, even if backwashing is performed, the crud cannot be completely removed from the filter, so the initial value of the differential pressure when moving to one-flow operation gradually increases. Therefore, the operating time for one water flow is shortened, and the frequency of backwashing is extremely increased, resulting in a decrease in the operation of the filter and an increase in the amount of waste liquid generated in the plant due to the backwash water. Therefore, the operator monitors the operating state of the filter, and when such a state occurs, switches the set value of the differential pressure for shifting to backwashing to a set value higher than the above-mentioned constant value. As a result, water flow and backwashing are repeated at the high setting value for a while. Eventually, even if backwashing is performed, the differential pressure value will hardly drop below the set value. The operator replaces the filter when the water flow time becomes shorter and the frequency of backwashing increases.

[Problems in the background art] However, according to the conventional method described above, it is not possible to keep the time for one water flow (backwash frequency) constant. It was extremely difficult to create a water treatment operation plan that would be completed within a few days. In addition, operators constantly monitor the water flow time (backwash frequency) and perform backwashing to maximize the operating rate of the filter and to minimize the increase in waste liquid generation due to backwash water. There is the hassle of having to switch the set value of the differential pressure during the transition and to judge when to replace the filter.

[Objective of the invention] The present invention makes it easier to plan water treatment operations by controlling the water flow time almost constant when the turbidity of waste liquid is constant, and also eliminates the need for switching the differential pressure setting value for transitioning to backwashing. The purpose of the present invention is to provide a filter control device with extremely high operational efficiency.

[Summary of the Invention] For this reason, the present invention stores the differential pressure value of the filter at the start of water flow operation after completion of backwashing or immediately after filter replacement, and stores the value obtained by adding a fixed value to this stored value when the filter Set value for the differential pressure when moving from water flow to backwashing, keep the water flow operation time almost constant, and when the differential pressure during water flow reaches the differential pressure limit value.

A feature of this system is that it automatically notifies the operator of the need to replace the filter.

[Embodiment of the Invention] Fig. 1 shows a block diagram of a filter control device according to an embodiment of the present invention, which includes a pretreatment device 1, a valve 2, a filter 3, and a filter control device. Valve 4, after-treatment device 5, valves 6-9, backwash water receiver is tank 10. Differential pressure detector 11. Filter control circuit 12, filter 13. It consists of a valve 14.

When the waste liquid starts to be transferred from the pretreatment device 1 by the operator's operation, the filter control circuit 12 outputs the water flow signal as ONL, .
Valve 2 and valve 4 are fully opened to enter a water flow operation state. As a result, when the waste liquid is transferred from the pre-treatment device 1 to the post-treatment device 5 via the filter 3, crud is removed from the waste liquid by the filter 13 in the filter 3. By monitoring the differential pressure signal from the differential pressure detector 11, the control circuit 12 identifies that the removed crud has clogged the filter 13, making it difficult to process the waste liquid as described below. Then turn off the water signal.
L.

Turn the backwash signal ONL and shift to backwash operation.

Backwash operation is performed by switching valve 2. Valve 4 is fully open, and valve 6. When the valve 8 is fully opened, air is injected from the top of the filter 3 and the crud is removed from the filter. Then, valve 6 is fully closed.
Valve 7 is fully opened to perform bubbling, and further valve 9 is fully opened and valve 7. When the valve 8 is closed, the waste liquid in which the crud is suspended in the filter 3 is discharged to the tank 10 from the backwash water receiver. When the discharge is completed, valve 9 is fully opened, valve 14 is fully opened,
Condensate flows into the filter 3 to fill it with water. When filling with water is completed, the valve 14 is fully opened, backwashing is completed, the differential pressure in the filter 3 is reduced and the filter 13 is unclogged), and water flow operation begins again.

FIG. 2 shows a control block diagram when transitioning to backwashing in the filter control circuit 12. It consists of a counter 20, a memory 21, an arithmetic unit 22, comparators 23, 211, and a display 25. starts counting when the water flow signal is input, and resets the count value when the filter replacement signal or backwash signal is input. Then, it is output only when the count value is the set value n.

The memory 21 inputs and stores the differential pressure signal cip from the differential pressure detector 11 only when there is an output signal from the counter 20.

The stored differential pressure value dpm is output to the arithmetic unit 22 until a backwash signal or a filter replacement signal as a reset signal is input. Therefore, if the set value n of the counter is set to correspond to the time when the filter 3 starts water flow operation and enters steady operation, the memory 21 will be set as the initial value dpn+ of the differential pressure of the filter 3 during one water flow operation. can be memorized.

That is, in the transient state at the start of water flow operation.

The differential pressure of the filter 3 also fluctuates, making it impossible to obtain a normal value.

Therefore, it is necessary to measure the initial differential pressure dpi at the time when the water flow state becomes stable.The set value n is set to a value appropriate for that time, and the differential pressure value dpm at the start of water flow operation is retrieved from the memory 21. to be memorized.

In addition, since this stored value dpI11 is not reset even if the water flow through the filter is stopped, the memory 21 stores the initial value of the differential pressure of the filter 3 when the water flow operation is started immediately after backwashing or filter replacement. Continue to do so.

The calculator 22 inputs the stored value dpm and the current differential pressure value dP of the filter 3 from the differential pressure detector 11, so that
The computation dp −dpm = dpc is performed, and the computation result dpc is output to the comparator 23 .

Comparator 23 compares with dpct&gt (setting value), and dp
c: When it becomes >51, a backwash signal is output and filter 3
Shift from water flow operation to backwash operation. Note that the backwash signal is held until the backwash is completed.

The comparator 24 inputs the signal ctp from the differential pressure detector 11 and compares it with 52 (differential pressure limit set value). When -dp>s2, it outputs a filter replacement signal, which causes the display 25 to indicate Indicates the need for filter replacement.

With the above configuration, when water flow is started at time t1 as shown in FIG. 3, in the filter control circuit 12, when the counter 20 in FIG. 2 reaches n after a very short time has elapsed from that point, That is, the initial value dpm of the differential pressure when a stable water flow state is reached is stored in the memory 21.

Then, the computing unit 22 calculates the difference dpc between the differential pressure dpm at the start of water flow and the current differential pressure value ctp of the filter 3, and the comparator 23 compares the difference dpc with the set value s1. As a result, the water flow is continued until the differential pressure difference dpc exceeds the set value s1, and at the second point in time when the differential pressure difference dpc exceeds the set value s1, the backwashing operation is started. At this time, the counter 20. The value in memory 21 is reset.

After that, perform the backwash operation as described above to remove the crud attached to the filter of the filter 3, discharge the waste liquid with floating crud to the backwash water receiver tank 1o, and then fill the filter 3 with water. When the backwashing operation is completed, the water flow operation is started again.

In the process of repeating such water flow and backwash operations, if the turbidity of the waste liquid is constant, the increase in the differential pressure of the filter 3 during the water flow operation will be approximately constant. Therefore, the time from the start of water flow through the filter 3 to backwashing until the differential pressure of the filter 3 reaches the differential pressure limit set value s2 is 2-bl, (shia ta) + (t
s-us), tat, t, and tlo-s are approximately constant6. Furthermore, (tsta) represents the operation stop time.

On the other hand, the comparator 24 constantly compares the differential pressure value dp with the differential pressure limit set value s2, and when the differential pressure dp reaches the differential pressure limit set value s2, the water flow operation is stopped and a filter replacement signal is issued. Displayed on the display 25.

In this way, by keeping the water flow time (backwash frequency) constant, water treatment planning becomes easier, and operators can monitor the water flow time (backwash frequency) and perform backwash operations as usual. This eliminates the hassle of changing the differential pressure set value and determining when to replace the filter when transitioning to the new system, and the burden on the operator is greatly reduced.

[Effects of the Invention] As described above, according to the present invention, the water flow time becomes almost constant, making it easier to plan the water treatment operation, and there is no need to change the differential pressure setting value that is transferred to backwashing. It is possible to obtain a filter control device that is extremely efficient in operation and automatically notifies the time for filter replacement.

[Brief explanation of the drawing]

Fig. 1 is a system configuration diagram of a filter control device according to an embodiment of the present invention, Fig. 2 is a control block diagram in the filter control circuit of Fig. 1, and Fig. 3 explains the operation of Fig. 1. It is a filter differential pressure characteristic diagram for. 1... Pretreatment device, 2, 4, 6, 7, 8, 9.14
···valve. 3... Filter, 5... Post-processing device, 10... Backwash water receiver is tank, 11... Differential pressure detector, 12... Filter control circuit, 13... Filter, 20...Counter. 21...Memory, 22...Arithmetic unit, 23,24.
...Comparator. 25...Display device.

Claims (1)

[Claims] In a filter control device that monitors the differential pressure across the filter of the filter and controls the water flow operation or backwash operation of the filter,
a memory device that stores the differential pressure of the filter at the start of each water flow operation; and a calculator that calculates the deviation between the differential pressure of the filter at each point after the start of the water flow operation and the differential pressure at the start of the water flow operation; ,
A first comparator that detects that the calculation result of this calculator is equal to or higher than a predetermined value; and a second comparator for detecting that the filter has been replaced, and is characterized in that it shifts to backwash operation control every time the first comparator outputs, and notifies the filter replacement time using the second comparator outputs. filter control device.