JPS6345242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a precoat type filtration device for waste liquid purification treatment, and in particular, an automatic control function that optimizes the flow rate of the liquid to be filtered by measuring the differential pressure before and after the filter body. The present invention relates to a filtration device equipped with a filtration device.

A precoat type filtration device uses a filter aid such as diatomaceous earth or natural fiber to entangle itself with a filter aid holding structure, such as a Johnson screen, using the flow of the filtered liquid. , a filter is formed, and when the filter becomes contaminated, the flow of the filtered liquid is reversed to flush out the dirt trapped in the filter along with the filter aid, and the filter is configured to Instead of replacing the filter body, the operation of reforming the filter body is extremely simple and is therefore widely used today.

However, in such a precoat type filtration device, the pressure difference between the pressure of the filtrate before passing through the filter and the pressure of the filtrate after passing through the filter is one of the dominant factors in the purification effect. It is known. That is, in order to increase the purification processing speed, if the flow rate of the filtrate is increased and the differential pressure is made excessive, the rate at which the filth in the filtrate leaks into the filtrate increases; On the other hand, if the differential pressure is made too small in order to suppress the increase in the rate of leakage of the filth, the flow rate of the liquid to be filtered becomes too small, which lengthens the total period of the purification process, resulting in inefficiency.

Therefore, when operating a conventional precoat type filtration device, the flow rate of the filtrate is kept at a constant value until the above differential pressure reaches a limit value, which in a typical device example is about 1 kg/cm ² . , when the limit value is exceeded, the flow rate of the filtrate is gradually reduced by manual operation to suppress the sudden increase in the differential pressure.
There was a need to increase the amount of filth captured during the total period of purification work. The manual operation for adjusting the flow rate depends on the nature of the waste,
It was necessary to deal with the differential pressure that increases moment by moment while being controlled by the concentration, the performance of the filter aid, and the flow rate of the filtrate. had the disadvantage of requiring constant monitoring work.

The purpose of the present invention is to divide the period of the purification process into three stages, namely, the first control stage of the constant flow rate control mode and the constant flow rate control mode, in view of the problems such as the complexity of flow rate control based on the above-mentioned conventional technology. Divided into a second control stage in pressure control mode and a third control stage in constant flow mode,
By automatically controlling the flow rate of the filtrate at each control stage, and also automatically transitioning between each control stage, the above drawbacks can be eliminated, and complicated manual operations and operations can be avoided. It is an object of the present invention to provide an excellent precoat type filtration device that can eliminate the monitoring work and further reduce the frequency of precoating the filter body.

The configuration of the present invention in accordance with the above object is to measure the flow rate of the filtrate introduced into the filtrate chamber with a flow rate measuring means and obtain a flow rate signal representing the flow rate value.
Furthermore, the pressure difference between the pressure of the filtrate in the filtrate chamber and the pressure of the filtrate led out into the filtrate chamber via the filter body is measured using a differential pressure measuring means, and a difference representing the measured value is measured. When the pressure signal is obtained and the subsequent flow rate adjustment means receives a control mode signal representing the constant flow rate control mode and a flow rate target value signal representing the flow rate target value, the flow rate of the liquid to be filtered matches the flow rate target value. When performing constant flow control such as this and receiving a control mode signal representing the constant differential pressure mode and a differential pressure target value signal representing the differential pressure target value, the differential pressure between the filtrate and the filtrate is equal to the differential pressure target. When operating the filtration device, constant differential pressure control is performed to match the value, and when the filtration device is operated, after the start of operation, until the differential pressure measured by the differential pressure measuring means reaches the differential pressure target value, the control stage storage means is set. A first control stage is stored, and in response, the first control stage setting means sends a control mode signal representing a constant flow rate control mode and a first flow rate target value to the flow rate adjusting means. By supplying the flow rate target value signal, the adjusting means executes the control of the first control stage, and then, the first control means determines that the differential pressure measured by the differential pressure measuring means has increased to the differential pressure target value. When the control stage changing means also detects the second control stage, the second control stage is stored in the control stage storage means, and in response, the second control stage setting means sets the constant difference to the flow rate adjusting means. By supplying a control mode signal representing the pressure control mode and a differential pressure target value signal representing the differential pressure target value, the adjusting means is caused to perform the control of the second control stage, and then the flow rate measuring means performs the measurement. When the second control stage changing means detects that the flow rate reduced to the second flow rate target value, the third control stage is stored in the control stage storage means, and in response, the third control stage is changed. The control stage setting means supplies the flow rate adjustment means with a control mode signal representing the constant flow rate control mode and a flow rate target value signal representing the second flow rate target value, thereby setting the flow rate adjustment means to the second flow rate target value. The gist of this system is to execute three control stages of control.

An embodiment of the present invention will be described below based on FIGS. 1 to 7.

FIG. 1 is a block diagram showing the hardware configuration. The filtration device 1 includes a filtrate chamber 1a into which a filtrate is introduced, a filtrate chamber 1b from which a filtrate is taken out, and a filtrate chamber 1b from which a filtrate is taken out. It has a filter body 1c interposed between 1a and 1b, and the filter body 1c is formed of a filter aid 1c'' entwined with a Johnson screen 1c' as a net-like body. 1
In a, a waste liquid pipe 2 extends from a waste liquid tank (not shown), and a waste liquid pump 3, a three-way valve 4, and a flow rate regulator 5 are inserted into the waste liquid pipe in this order from the waste liquid tank side. A conduit 11 extends from the filtrate chamber 1b toward a purification device for the next process (not shown), such as a demineralization tower, and a flow rate measuring section 6 is inserted into the conduit, and a flow rate signal is received from the flow rate measuring section. An output terminal for outputting is connected to the flow rate adjustment section 5. Further, pressure impulse pipes 7 and 8 extend from each of the filtrate chamber 1a and the filtrate chamber 1b and are connected to a differential pressure measuring section 9, and an output terminal for outputting a differential pressure signal from the differential pressure measuring section is connected to a flow rate. It is connected to the adjustment section 5. The arithmetic processing unit 10 includes a microprocessor and has four input ports and three output ports.

Among the above input ports, port 1 is for the ready-to-operate state signal _S1 , and is connected to the power supply through a resistor 10a, and is also connected to the power supply through a switch _SW1 ' linked to the ready-to-operate setting switch _SW1 . Grounded. Port 2 is for the operating state signal S ₂ and is connected to the power supply through the resistor 10b, as well as the operating state setting switch SW ₁
Switch SW ₁ ″ and operation changeover switch linked to
It is grounded through each of the switches SW ₂ ' that are linked to SW ₂ . The port 3 is for the flow rate signal _S5 and is connected to the output terminal of the flow rate measurement section 6. Port 4 is for differential pressure signal S ₆ and is connected to the output terminal of differential pressure measuring section 9 .

Further, among the output ports, port 5, port 6, and port 7 respectively output a flow rate target value signal S ₄ representing the first and second flow rate target values, a differential pressure target value signal S ₇ representing the differential pressure target value, and They are for the control mode signal _S3 , and are connected to the input terminals of the flow rate adjustment section 5, respectively.

On the other hand, conduits 12 and 13 branched from the conduit 11 extending to the purification device in the next step return to the filtrate chamber 1a to form a holding loop, and a holding pump 14 is inserted into the conduit 13.

Further, a conduit 16 branched from the conduit 12 via a pot 15 is connected to a precoat tank 17 as an inlet pipe, and a conduit 18 as an outlet pipe from the tank returns to the three-way valve 4 in the waste liquid pipe 2. A precoat pump 19 is inserted into the conduit 18 forming a precoat loop.

The a-side fixed contact of the operation changeover switch SW ₂ is connected to the electric motor 3' connected to the waste liquid pump 3, and the b-side fixed contact of the switch SW ₂ is connected to the electric motor 14' connected to the holding pump 14. , the movable contact of the switch SW ₂ is connected to a power source (not shown) through the operable state setting switch SW ₁ . Further, an electric motor 19' connected to the precoat pump 19 is connected to a power source (not shown) through a precoat switch _SW3 .

Note that a backwash valve 21 is provided in the backwash pipe 20 from the filtrate chamber 1a.

FIG. 2 is a claim correspondence diagram showing the connection relationship between the function realizing means corresponding to each of the plurality of functions performed by the microprocessor in the arithmetic processing unit 10 in FIG. 1 and the hardware components.

In the figure, the function realizing means in the arithmetic processing unit 10 are a control stage storage means 10A and a storage means 1.
A first control stage setting means 10B following 0A via a first control stage information line ₁ , and a first control stage changing means _10C preceding the storage means 10A via a first control stage change information line 2. , a second control stage setting means 10D following the storage means 10A via a second control stage information line ₃ , and a second control stage setting means 10D preceding the storage means 10A via a second control stage change information line ₄ . comprising a control stage changing means 10E and a third control stage setting means 10F following the storage means 10A via a third control stage information line ₅ ;
A constant flow rate control mode information line ₆ and a first flow rate target value information line _{7 extend from the first control stage setting means 10B to the flow rate adjusting section 5, and from the second control stage setting means 10D, a constant flow rate control mode information line 6} and a first flow rate target value information line 7 extend A differential pressure control mode information line ₈ and a differential pressure target value information line ₉ extend to the flow rate adjusting section 5, and the third control stage setting means 10
From F, a constant flow control mode information line ₁₀ and second flow target information I ₁₁ extend to the flow rate adjustment section 5 .

The first and second control stage changing means 1
The input terminals 0C and 10E are connected to the differential pressure measuring section 9 and the flow rate measuring section 6, respectively. Note that other hardware components are the same as those indicated by the same reference numerals in FIG.

The operation of the above configuration is also shown in FIGS. 3 to 6, which are flowcharts of the arithmetic processing unit 10, and FIG. 7, which is a time chart of the differential pressure between the filtered liquid and the filtrate, the flow rate of the filtered liquid, etc. The following is an explanation with reference to it.

First, prior to the start of operation of the filtration device, preparatory work for re-forming the filter body 1c in the filtration device 1 is performed. To do this, the backwash valve 21 in the backwash pipe 20 is opened to allow the filtrate in the filtrate chamber 1b to flow back into the filtrate chamber 1a, thereby reducing the amount of filter aid on the Johnson screen 1c'. 1c'' together with the captured material and flow out of the filter device 1 through the backwash pipe 20.

Next, close the backwash valve 21 to return the filtrate chamber 1a and filtrate chamber 1b to full water state, then open the three-way valve 4 between the conduit 18 and the waste liquid pipe 2, and then open the pot 15. Then, when the pre-coat switch SW ₃ is closed and power is supplied to the motor 19' to drive the pre-coat pump 19, the unused filter aid stored in the pre-coat tank 17 is pumped into the conduit 18-- along with water as a carrier. The unused filter aid 1 is forced into the filtrate chamber 1a through a part of the precoat loop including the three-way valve 4, the waste liquid pipe 2, and the flow rate adjustment section 5.
C'' is entwined with the bare Johnson screen 1c' to form a new filter body 1c, and the water as a carrier is connected from the filtrate chamber 1b to the conduit 11 - flow rate measuring section 6 - conduit 12 - Kotoku 15 - Passes through the remainder of the precoat loop, including conduit 16, and is collected in precoat tank 17.

When the backwash processing work and the precoat processing work are completed, the precoat switch SW ₃ is opened, the three-way valve 4 is opened between the waste liquid pipes 2 and 2, and the pot 15 is closed, and then the state is ready for operation. The setting switch SW ₁ is closed, and furthermore, at this time, the movable contact of the operation changeover switch SW ₂ is connected to the a-side fixed contact, and the states of both switches SW ₁ and SW ₂ are mechanically maintained. Then, electric power is supplied to the electric motor 3', the waste liquid pump 3 is started, and the filtration device 1 is put into operation. That is, the waste liquid from the waste liquid tank is sent to the waste liquid pump 3.
The waste liquid is fed under pressure through the waste liquid pipe 2, passes through the flow rate adjustment section 5, reaches the filtered liquid chamber 1a, and further passes through the filter body 1c formed on the Johnson screen 1c'. The filtrate is removed and led out to the filtrate chamber 1b, and then sent through the conduit 11 and the flow rate measuring section 6 to the next process device.

Additionally, it is a normal practice to insert a period of holding operation, which will be described later, prior to the start of such purification work.
The explanation will be omitted here.

On the other hand, during this time, when a reset signal is sent to the microprocessor in the arithmetic processing unit 10 to start it, the arithmetic processing unit 10 executes the program whose flowchart is shown in FIGS. 3 to 6. do.

First, the arithmetic processing unit 1 started (Fig. 3a)
0 reads the ready state signal _S1 from port 1 into the D register (Figure 3b).

By the way, as mentioned above, during the period of backwashing processing work and precoating processing work, the operation ready state setting switch SW ₁ is opened, and in conjunction with this, the switch SW ₁ ' is closed. , the operable state signal S ₁ is "0" (FIG. 7B, a), but as mentioned above, when starting the purification process, the operable state setting switch SW ₁ is closed; Since the switch SW ₁ ' is opened in conjunction with this, the signal S ₁ is inverted to "1" (FIGS. 7B and b).

Therefore, the arithmetic processing unit 10 determines whether the contents of the D register, that is, the operable state signal _S1 , is "0" or not (FIG. 3c), and when the determination result is YES, that is, the reverse During the period of washing treatment work and pre-coat treatment work, return to the process shown in Fig. 3b,
While repeating the subsequent processing (FIGS. 3b to 3c), wait until the signal _S1 becomes "1". When the judgment result (Fig. 3 c) is NO, that is, when the device is in the operable state, the E register is cleared (Fig. 3 d), and then, from port 1, it is again in the operable state. Read the signal S ₁ into the D register (Fig. 3 e), determine whether it is "0" (Fig. 3 f),
If the determination result is YES, the process returns to the step in FIG. 3b and waits until the signal _S1 becomes "1" while repeating the subsequent processes (FIG. 3b to f). If the judgment result (Fig. 3 f) is NO, then
The operating status signal _S2 is read from port 2 to the accumulator (Fig. 3g).

By the way, as mentioned above, during the purification process after the start of operation, the movable contact of the operation changeover switch SW ₂ is connected to the a-side fixed contact, so the switch SW ₂ ' is opened in conjunction with this. However, the operating state signal _S2 becomes "1" (FIG. 7C, c).

Therefore, the processing unit 10 determines whether or not the signal _S2 is "1" (Fig. 3h), and if the determination result is NO, that is, it performs the holding operation described later. If it is, return to the step in Figure 3e and repeat the subsequent processes (Figure 3e to h) until both the operable state signal _S1 and the operating state signal _S2 become "1". wait. When the determination result (FIG. 3 f, h) becomes NO or YES, respectively, it is then determined whether the E register is "0" (FIG. 3 i). At the initial stage of the purification process, the E register remains cleared in the process shown in Figure 3 d, so the determination result (Figure 3 i) is
YES.

Therefore, the processing device 10 stores the first control step (third control step) in the control step storage means (FIG. 2 10A).
d), the following flow is executed in response to the first control stage information supplied from the storage means 10A via the first control stage information line (FIG. 2, ₁ ).

That is, the processing unit 10 outputs the control mode signal _S3 of "0" representing the constant flow control mode from the port 7 (FIG. 4j), and then outputs the first flow rate target value F from address 8000. ₁ (Fig. 4, k), and outputs a flow rate target value signal _S4 representing this from port 5 (Fig. 4, l).

Through the above processing (FIG. 4 j to l), the first control stage setting means (FIG. 2 10B) sends the constant flow control mode information line (FIG. 2 ₆ ) and the first flow rate target value information line (second
Constant flow rate control mode information and first flow rate target value information are supplied via (FIG. ₇ ).

Thus, the flow rate adjustment section 5 operates in a constant flow rate control mode, receives the flow rate signal _S5 representing the actual flow rate of the waste liquid, that is, the liquid to be filtered, from the flow rate measurement section 6, and adjusts the flow rate to the first flow rate target value. Automatically control the flow rate to match F ₁ . As a result, during the period of the first control stage, the flow rate F of the liquid to be filtered is maintained at a constant value of the first flow rate target value _F1 (FIG. 7D,
d). During that time, the filter body 1c in the filtration device 1 is affected by the adhesion and accumulation of captured dirt in the filtrate chamber 1.
The pressure difference P between the pressure of the liquid to be filtered in a and the pressure of the filtrate in the filtrate chamber 1b gradually increases over time (FIGS. 7A and 7e).

On the other hand, during the period of the first control stage, the arithmetic processing unit 10 reads the differential pressure target value P ₁ from address 8002 (Fig. 4m), and transfers it from the first control stage to the second control stage. It is stored in the L register as a reference value for determining the switching point (FIG. 4n). Subsequently, the processing section 10 receives a differential pressure signal _S6 representing the actual differential pressure between the filtrate and the filtrate from the differential pressure measuring section 9, reads it from the port 4 (see Fig. 4 o). ) and stored in the C register (Fig. 4 p), and then whether the contents of the C register are greater than the contents of the L register,
That is, it is determined whether the actual differential pressure P has exceeded the target differential pressure value _P1 (FIG. 4q).

If the determination result is NO, read the operating status signal _S2 again from port 2 (Fig. 4r) and check whether the signal _S2 is "1" or not.
In other words, the holding operation described below does not start,
It is determined whether the purification work is continuing (FIG. 4s). At this time, the judgment results (Fig. 4q,
If s) is NO or YES, respectively, return to the step o in Figure 4 and repeat the subsequent processes (o to s in Figure 4) until the actual differential pressure P reaches the target differential pressure _P1. wait until During this time, when the holding operation, which will be described later, starts, the judgment result shown in Fig. 4 s is displayed.
Since the result is NO, go back to the step in Figure 3e and repeat the subsequent processes (Figure 3e to h) until both the operable state signal _S1 and the operating state signal _S2 become "1". wait.

Meanwhile, during this period, the actual differential pressure gradually increases and eventually reaches the differential pressure target value P ₁ (Fig. 7A,
f), the judgment result in Figure 4q is YES, so E
Store "1" in the register (FIG. 4, t).

Through the above processing (o to s in FIG. 4), the first control step change information line is sent from the first control step change means (FIG. 2 10C) to the control step storage means (FIG. 2 10A). The first control stage change information is sent via (FIG. ₂ ).

Therefore, the arithmetic processing unit 10 stores the second control stage (the fourth
t), the following flow is executed in response to the second control stage information supplied from the storage means via the second control stage information line (FIG. 2, ₃ ).

That is, the processing section 10 outputs the control mode signal _S3 of "1" representing the constant differential pressure control mode from the port 7 (Fig. 5 u), and then outputs the differential pressure target value _P1 from the L register. A differential pressure target value signal _S7 representing this is output from port 6 (FIG. 5v).

Through the above processing (Fig. 5 u to v), the constant differential pressure control mode information line (second Figure ₈ ) and differential pressure target value information line (Figure 2 ₉ )
Constant differential pressure control mode information and differential pressure target value information are provided via.

Thus, the flow rate adjustment section 5 operates in the constant differential pressure control mode, receives the differential pressure signal _S6 representing the actual differential pressure between the filtrate and the filtrate from the differential pressure measuring section 9, and detects the differential pressure. The flow rate is automatically controlled to match the pressure target value _P1 . As a result, during the period of the second control stage, the differential pressure P between the liquid to be filtered and the filtrate is equal to the target differential pressure value.
P is maintained at a constant value of ₁ (Fig. 7A, g). During this time, the captured dirt continues to adhere and accumulate on the filter body 1c, so the flow rate F of the liquid to be filtered gradually decreases over time (FIG. 7D, h).

On the other hand, during the period of the second control stage, the arithmetic processing unit 10 reads out the second flow rate target value _F2 from address 8001 (Fig. 5 w), and transfers it from the second control stage to the third control stage. This value is stored in the H register as a reference value for determining the switching point (FIG. 5x).

Subsequently, the processing unit 10 reads the flow rate signal _S5 from the port 3 into the B register (FIG. 5y), and determines whether the content of the B register is smaller than the content of the H register, that is, The actual flow rate F is the second flow rate target value
Determine whether it has become F ₂ or less (Fig. 5 z).
If the determination result is NO, the operating state signal _S2 is read (Fig. 5 a'), and it is determined whether the signal _S2 is "1" (Fig. 5 b'). ), when the judgment result is YES, return to the process in Figure 5 y, and conversely, when the judgment result is NO,
The process of returning to the step in FIG. 3e is as shown in FIG.
This is the same as the process in steps .

On the other hand, during this period, the actual flow rate gradually decreases and eventually reaches the second flow rate target value _F2 (Fig. 7 D, i), and the judgment result in Fig. 5 z becomes YES, so the E register is ``2'' is memorized (Fig. 5 c').

Through the above processing (Fig. 5 y to b'), the second control stage change information is sent from the second control stage change means (Fig. 2 10E) to the control stage storage means (Fig. 2 10A). A second control step change information is sent via the line (FIG. 2, ₄ ).

Therefore, the arithmetic processing unit 10 stores the third control stage (the fifth
c'), the following flow is executed in response to the third control stage information supplied from the storage means via the third control stage information line (FIG. 2, ₅ ).

That is, the processing unit 10 outputs the control mode signal _S3 of "0" representing the constant flow control mode from the port 7 (FIG. 6 d'), and then outputs the second flow rate target value F from the H register. ₂ and outputs the flow rate target value signal _S4 representing this from port 5 (Fig. 6).
e′).

Through the above processing (Fig. 6 d' to e'), the third control stage setting means (Fig. 2 10F) sends the constant flow control mode information line (Fig. The constant flow rate control _mode and the second flow rate target value information are supplied via the second flow rate target value information line (FIG. 2, ₁₀ ) and the second flow rate target value information line (FIG. 2, 11).

Thus, the flow rate adjustment section 5 operates in the constant flow rate control mode, and the flow rate of the liquid to be filtered reaches the second flow rate target value _F2.
The flow rate is automatically controlled to match the As a result, during the third control stage, the flow rate F of the liquid to be filtered is maintained at a constant value, which is the second flow rate target value F ₂ (FIG. 7D, j).

Then, the above series of processing (Fig. 3 e to Fig. 6
After executing _step e′), the arithmetic processing unit ₁₀ returns to the process shown in _{FIG .} The above series of processes (Fig. 3 e to Fig. 6 e') are repeated until one of them becomes "0", and when the operable state signal S ₁ becomes "0", the 3
Returning to the process in Figure b, the subsequent processing (Figure 3 b -
While repeating step c), wait for the signal S ₁ to become "1", and on the other hand, when the operating state signal S ₂ becomes "0", return to the step shown in FIG.
While repeating the steps in Figures e to h), the signal _S2 becomes "1".
It is something to wait for.

Next, the holding operation will be explained as follows.

When the operation ready state setting switch SW ₁ is closed, the movable contact of the operation changeover switch SW ₂ is closed.
When connected to the side fixed contact, the waste liquid pump 3 is stopped, and instead, the electric motor 14' is supplied with power and the holding pump 14 is started, so that the filtrate chamber 1
The water in b is transferred to the conduit 11, the flow rate measuring section 6, the conduit 12,
Tour the Holdein Group, which consists of 13 members.

This holding operation prevents the filter aid from falling off due to the release of the engagement force of the filter aid with the Jeonson Clean, since the flow rate of the liquid to be filtered becomes zero when the purification process is interrupted. It is necessary to do so.

Then, when the halluding movement is performed,
Switch in conjunction with operation selector switch SW ₂
Since SW ₂ ' is closed, the operation state signal S ₂ of "0" representing the holding operation is supplied to port 2 of the arithmetic processing unit 10 (FIG. 7C, k).

Now, when a holding operation is performed during the first control stage, the flow rate F of the liquid to be filtered passing through the flow rate measuring section 6 at that point becomes the holding flow rate F ₀
(FIG. 7D, l), and correspondingly, the differential pressure P between the filtrate and the filtrate decreases to the holding differential pressure (FIG. 7A, m).

Note that this holding differential pressure is based on the holding flow rate of circulating water in the holding group.
It is caused by F ₀ and changes depending on the state of adhesion and accumulation of dirt on the filter body 1C at the time when the holding operation is performed.

On the other hand, the arithmetic processing unit 10 determines that the operating state signal S ₂ has become "0" (FIG. 4 s) during the processing of the first control stage (FIG. 4 o to s), and the third The process of returning to the step in Figure e is as described above, but when the purification process is restarted, the movable contact of the operation changeover switch SW ₂ is returned to the fixed contact on the a side, and the switch SW ₂ ' linked to this is opened. Then, when the operating status signal _S2 is inverted to "1", the judgment result in Fig. 3h becomes YES.
Therefore, it is subsequently determined whether the contents of the E register are "0" (FIG. 3i). At this time, since the E register stores the code "0" representing the control stage at the time when the holding operation is started, that is, the first control stage in the above operation example, the determination result (third YES in Figure i), the process proceeds to Figure 4J, and the purification work after the holding operation is continued in the control mode of the first control stage.

Next, if a holding operation is performed during the second control stage (n, o, p in Figure 7), the E register stores the code "1" representing the second control stage. Therefore, when restarting the purification process, the determination result in Figure 3 i becomes NO, and subsequently, when it is determined whether the contents of the E register are "1" (Figure 3 f'), the Judgment result is YES
becomes.

Then, the arithmetic processing section 10 measures the elapse of the set time T ₀ (Fig. 3 g') and proceeds to the step shown in Fig. 5 u, and the purification process after the holding operation is performed in the second control stage. continues in control mode. The timing of the elapse of the set time (Fig. 3 g') is carried out when restarting the purification work after the holding operation.
Before the flow rate of the filtered liquid rises sufficiently, the switching point judgment from the second control stage to the third control stage (fifth
This is necessary in order to eliminate the inconvenience of transitioning to the third control stage at the same time as the resumption of the purification process due to execution of FIG. z).

Subsequently, if a holding operation is performed during the third control stage (Fig. 7 q, r, s), the E register stores the code "2" representing the third control stage. Therefore, when restarting the purification process, both the determination results in FIG. 3 i and FIG. The purification process continues in the third control stage control mode.

As mentioned above, regarding the holding operation, the process of _FIG . When returning to purification work, the purification work is continued at the control stage at the start of the holding operation.On the other hand, when the operation is stopped for backwashing or pre-coating, , while repeating the processes in FIGS. 3b to 3c, waiting for the operable state signal _S1 to be inverted to "1", and when the signal is inverted, that is, at the start of the purification process,
By clearing the E register (FIG. 3d), the purification process of the first control stage is always performed.

As described above, according to the present invention, the period of the purification process is divided into the first stage of constant flow control, the second stage of constant differential pressure control, and the third stage of constant flow control, and each control By automatically controlling the flow rate of the filtrate at each stage and also automatically transitioning between each control stage, the flow rate control of the filtrate, which was previously required, has been improved. Since manual operation can be completely abolished, the driving operation becomes very simple and there is an excellent effect that constant monitoring work for the operation is no longer necessary.

Moreover, after determining that the differential pressure between the pressure of the filtered liquid and the pressure of the filtrate has reached a limit value from the perspective of the amount of waste leakage, etc., a constant flow rate is determined for a considerably small flow rate target value. By adopting a configuration in which the third control stage is extended, it is possible to significantly increase the amount of dirt captured during the total period from backwashing/precoat treatment to the next backwash/precoat treatment. There is also the effect that it can be done.

In addition, in the first control stage, which is not constrained by the differential pressure that has reached the above-mentioned limit value, the purification process is At the initial stage of work, high-speed purification processing is possible, which has the effect of shortening the purification processing time.

Furthermore, a control stage storage means is provided to store the control stage at the time when the holding operation was performed, and when the purification work is restarted, the purification work is continued at the stored control stage. This configuration also has the effect that even if the purification process is interrupted, it is possible to maintain proper progress of the control stages without requiring any manual operation.

[Brief explanation of the drawing]

The figure relates to one embodiment of this invention,
Figure 1 is a block diagram showing its hardware configuration, Figure 2 is a block diagram showing its software function implementation means, and Figures 3, 4, 5, and 6 are arithmetic processing. Figure 7 is a flowchart of the program executed in the section.
This is a time chart showing a comparison of (A) the differential pressure between the filtrate and the filtrate, (B) the operable state signal, (C) the operating state signal, and (D) the flow rate of the filtrate. . 1... Filtration device, 1a... Filtered liquid chamber, 1b...
...Filtrate chamber, 3... Waste liquid pump, 5... Flow rate adjustment section, 6... Flow rate measurement section, 9... Differential pressure measurement section, 10
... Arithmetic processing unit, 10A ... Control stage storage means,
10B...First control stage setting means, 10C...First control stage changing means, 10D...Second control stage setting means, 10E...Second control stage changing means,
10F...Third control stage setting means, 14...Holding pump, 17...Precoat tank,
19... Precoat pump, SW ₁ ... Operation ready state setting switch, SW ₂ ... Operation selection switch.

Claims (1)

[Scope of Claims] 1. A filtrate chamber 1a into which a filtrate is introduced, a filtrate chamber 1b from which a filtrate is taken out, and an intervening device to isolate the filtrate chamber from the filtrate chamber. A liquid filtration device comprising a filter body 1c, which includes: a flow rate measuring means 6 for measuring the flow rate of the liquid to be filtered introduced into the liquid to be filtered chamber 1a and outputting a flow rate signal S5 representing the flow rate value; differential pressure measuring means 9 that measures the differential pressure between the pressure of the filtrate in the filtrate chamber 1a and the pressure of the filtrate in the filtrate chamber 1b and outputs a differential pressure signal S6 representing the differential pressure value; Control mode signal S3 representing constant flow control mode
In response to this, the constant flow rate control mode is entered, and the flow rate value of the filtrate introduced into the filtrate chamber 1a is made to match the flow rate target value represented by the flow rate target value signal S4. In addition to adjusting the flow rate of the filtrate, in response to the control mode signal S3 representing the constant differential pressure control mode, the mode shifts to the constant differential pressure control mode, and the differential pressure target value represented by the differential pressure target value signal S7 is adjusted. a flow rate adjusting means 5 for adjusting the flow rate of the filtrate so as to match the pressure difference between the pressure of the filtrate in the filtrate chamber 1a and the pressure of the filtrate in the filtrate chamber 1b; A control stage storage means 10A that stores any one of the first control stage, second control stage, and third control stage, and when the control stage storage means 10A stores the first control stage, constant flow control is performed. First control stage setting means 10B sends a control mode signal S3 representing the mode and a flow rate target value signal S4 representing the first flow rate target value F1 to the flow rate adjusting means 5 to set the first control stage in the adjusting means. and a first step of determining that the differential pressure value represented by the differential pressure signal S6 from the differential pressure measuring means 9 matches the differential pressure target value P1, and storing the second control step in the control step storage means 10A. Control stage changing means 10C
When the control stage storage means 10A stores the second control stage, the control mode signal S3 representing the constant differential pressure control mode and the differential pressure target value signal S7 representing the differential pressure target value P1 are sent to the flow rate adjusting means 5. a second control stage setting means 10D for setting the second control stage in the adjusting means 5; second control stage changing means 10 which determines this and stores the third control stage in the control stage storage means 10A;
E, and when the control stage storage means 10A stores the third control stage, the control mode signal S3 representing the constant flow rate control mode and the flow rate target value signal S4 representing the second flow rate target value F2 are sent to the flow rate adjusting means 5. A liquid filtration device characterized in that a third control stage setting means 10F is attached to the adjusting means 5 for setting a third control stage.