JP2020028855A - Filter aid addition device, filtration facility and filter aid addition method - Google Patents

Abstract

To provide a filter aid addition device capable of adequately controlling the addition amount of a filter aid even when the supply amount of a stock solution is small.SOLUTION: A filter aid addition device 1 comprises: a powder supplier 11 adding a powder filter aid to an addition tank 22 temporarily storing the stock solution before being supplied to a filter 25; a flow meter 12 measuring the flow rate of the stock solution supplied to the addition tank 22; and a control unit 13 controlling the operation of the powder supplier 11. The control unit 13 calculates the integrated flow rate of the stock solution to the addition tank 22 based on the measured value of the flow meter 12. The filter aid corresponding to the target amount of the stock solution is discharged by operating the powder supplier 11 in each target amount of the integrated flow rate and stopped. The average addition amount of the filter aid can be reduced by intermittently operating the powder supplier 11 and the addition amount of the filter aid can be adequately controlled even when the supply amount of the stock solution is small.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a filter aid addition device, a filtration facility, and a filter aid addition method. More specifically, the present invention relates to an apparatus for adding a filter aid to a stock solution to be filtered, a filtration facility provided with the apparatus, and a method for adding a filter aid to a stock solution to be filtered.

  When a stock solution is filtered by a filter, a filter aid may be added to the stock solution in advance (for example, Patent Document 1). By adding a filter aid to the stock solution, the filtration speed of the filter is improved, and the duration of filtration (the time until the filter medium is clogged and the predetermined filtration speed cannot be obtained) is extended.

JP-A-56-121604

  In order to add the filter aid to the stock solution as a powder, a powder feeder is used. By adjusting the discharge speed of the powder feeder, the addition speed of the filter aid to the stock solution can be adjusted. When the wastewater from a particular process is filtered as a stock solution, the amount of the stock solution generated depends on the process. Therefore, in some cases, the supply amount of the undiluted solution is reduced, and even when the discharge speed of the powder feeder is set to the lower limit, the filter aid may be excessively added.

In view of the above circumstances, the present invention provides a filter aid adding device capable of appropriately controlling the amount of a filter aid even when the supply amount of a stock solution is small, and a filtration facility provided with the filter aid adding device. The purpose is to do.
Another object of the present invention is to provide a method for adding a filter aid that can appropriately control the amount of the filter aid even when the supply amount of the stock solution is small.

A filter aid adding apparatus according to a first aspect of the present invention includes a powder feeder for adding a powdery filter aid to an addition tank in which a stock solution before being supplied to a filter is temporarily stored, A flow meter for measuring the flow rate of the undiluted solution, and a control device for controlling the operation of the powder feeder, wherein the control device, based on the measurement value of the flow meter, to the addition tank Obtaining the integrated flow rate of the stock solution, every time the integrated flow reaches the target amount, operating the powder feeder to discharge an amount of the filter aid corresponding to the target amount of the stock solution, and stopping. Features.
The filtration equipment of the second invention is characterized by comprising the filter aid addition device of the first invention, the addition tank, and the filter.
The filtration equipment of the third invention is characterized in that, in the second invention, a stirring tank for temporarily storing and stirring the stock solution discharged from the addition tank is provided.
The filter aid adding method of the fourth invention is a method of adding a powder filter aid to an addition tank in which a stock solution before being supplied to the filter is temporarily stored using a powder feeder. Every time the integrated flow rate of the stock solution to the addition tank reaches a target amount, operating the powder feeder to discharge an amount of the filter aid corresponding to the target amount of the stock solution and stop the process. It is characterized by.

  In the present specification, “flow rate” means the amount of fluid flowing per unit time. “Integrated flow rate” means the integrated amount of fluid flowing in a specific period. “Supply amount” means the flow rate of a fluid supplied to a specific location. "Addition rate" means the amount of substance added per unit time. “Addition amount” means an integrated amount of a substance added in a specific period. “Discharge rate” means the amount of a substance discharged from a specific location per unit time.

According to the first invention, by operating the powder feeder intermittently, the average addition amount of the filter aid can be reduced, and even when the supply amount of the stock solution is small, the addition of the filter aid is performed. The amount can be controlled appropriately.
According to the second invention, since the amount of the filter aid added does not become excessive, the stock solution can be efficiently filtered.
According to the third invention, since the stock solution to which the filter aid has been added is again stirred in the stirring tank, even if the filter aid is intermittently added, the concentration of the filter aid in the stock solution supplied to the filter is made uniform. Can be.
According to the fourth aspect of the present invention, by operating the powder feeder intermittently, the average amount of the filter aid can be reduced. The amount can be controlled appropriately.

It is explanatory drawing of the filtration equipment which concerns on one Embodiment of this invention. It is the graph which showed the time change of the integrated flow rate of stock solution, and the addition timing of a filter aid.

Next, an embodiment of the present invention will be described with reference to the drawings.
(Filtration equipment)
As shown in FIG. 1, a filtration facility AA according to one embodiment of the present invention is a facility that filters a stock solution to obtain a filtrate and a residue. The undiluted liquid is a liquid to be filtered, and contains suspended substances removed by filtration. The undiluted solution is, for example, a drainage generated in a specific process. In this case, the supply amount of the undiluted solution to the filtration facility AA depends on the amount of drainage generated in the process.

  The stock solution is first temporarily stored in the storage tank 21. The storage tank 21 is connected to the addition tank 22 via a pipe 31. The undiluted solution is transferred from the storage tank 21 to the addition tank 22 by driving a pump 32 provided in the pipe 31.

  The stock solution is temporarily stored in the addition tank 22. The filter aid is added to the addition tank 22 by the filter aid adding device 1. The addition tank 22 is provided with a stirrer. The stock solution is stirred by the stirrer, and the filter aid is dispersed. The filter aid is not particularly limited, but diatomaceous earth, perlite and the like are used.

  Downstream of the addition tank 22, stirring tanks 23 and 24 are provided. The addition tank 22 and the stirring tanks 23 and 24 are connected in series. The stock solution discharged from the addition tank 22 is supplied to a first stirring tank 23, and the stock solution discharged from the first stirring tank 23 is supplied to a second stirring tank 24. The transfer of the stock solution is performed, for example, by overflow. The stirring tanks 23 and 24 are provided with a stirrer. The stirring tanks 23 and 24 temporarily store the stock solution containing the filter aid and stir to disperse the filter aid.

  In this embodiment, two stirring tanks 23 and 24 are provided. Therefore, three tanks including the addition tank 22 and the stirring tanks 23 and 24 are connected in series. As a result, the residence time of the stock solution becomes longer, and the filter aid can be dispersed uniformly. The number of the stirring tanks 23 and 24 is not particularly limited, and may be one or three or more. Further, the stirring tanks 23 and 24 need not be provided.

  The stirring tank 24 at the last stage is connected to a filter 25 via a pipe 33. The undiluted solution is transferred from the stirring tank 24 to the filter 25 by the drive of the pump 34 provided in the pipe 33. The stock solution is filtered by the filter 25. The filtrate and the residue are discharged from the filter 25. The type of the filter 25 is not particularly limited. As the filter 25, for example, a filter press is used.

  A stock solution containing a filter aid is supplied to the filter 25. The action of the filter aid improves the filtration speed of the filter 25 and extends the duration of filtration. The operation of filtering a stock solution in which a filter aid is dispersed in advance through a filter 25 is referred to as “body feed”. The filtration equipment AA of the present embodiment performs a body feed.

  Prior to the filtration of the undiluted solution, an operation of passing the clarified liquid in which the filter aid is dispersed through a filter 25 to form a layer of the filter aid on the surface of the filter medium is referred to as “precoating”. Pre-coating may be performed together with the body feed.

(Filter aid addition device)
Next, the configuration of the filter aid adding device 1 will be described.
The filter aid adding device 1 has a powder feeder 11. The powder feeder 11 is a device for cutting out and discharging the powder held inside. Although the configuration of the powder feeder 11 is not particularly limited, it generally includes a hopper for holding powder and a discharge unit provided below the hopper. The discharge unit includes a rotary valve, a screw conveyor, a flight conveyor, a table feeder, and the like. The discharge speed of the powder can be adjusted by adjusting the rotation speed of the electric motor that drives the discharge unit. The powder feeder 11 holds a powder filter aid. The powder feeder 11 adds the filter aid to the addition tank 22 as powder.

  The filter aid adding device 1 has a flow meter 12. The flow meter 12 measures the flow rate of the stock solution flowing through the pipe 31, that is, the flow rate of the stock solution supplied to the addition tank 22. The filter aid adding device 1 has a control device 13 for controlling the operation of the powder feeder 11. The measurement value of the flow meter 12 is input to the control device 13. The control device 13 controls the operation of the powder feeder 11 based on the measurement value of the flow meter 12. More specifically, the control device 13 adjusts the rotation speed of the electric motor that drives the discharge unit of the powder feeder 11 to adjust the discharge speed of the filter aid.

  Generally, a filter aid is added to a stock solution after it is dispersed in a clear solution. On the other hand, the filter aid adding device 1 of the present embodiment adds the filter aid to the stock solution as a powder. Therefore, equipment for dispersing the filter aid in the clarified liquid, that is, a tank, a stirrer or the like is not required. Therefore, the equipment cost of the filtration equipment AA can be reduced, and the space can be saved.

(How to add filter aid)
Next, a method of adding a filter aid by the filter aid adding apparatus 1 will be described.
The addition speed f of the filter aid is adjusted so that the concentration ρ of the stock filter aid becomes the target concentration ρ _t . Here, the target concentration ρ _t of the filter aid is set to an optimum value as the filter aid concentration ρ of the stock solution. The target concentration ρ _t of the filter aid is determined in advance by a test or the like. When the flow rate of the stock solution and i, the target addition speed f _t of the filter aid is represented by the formula (1). As can be seen from equation (1), the addition rate f of the filter aid may be increased or decreased in accordance with the increase or decrease in the flow rate i of the stock solution.
f _t = ρ _t · i (1)

However, when the flow rate i undiluted is too small, also the discharge rate of the powder feeder 11 is set to the lower limit, there is that the addition rate f of the filter aid is faster than the target addition speed f _t. In this case, a filter aid will be added excessively.

  In addition, when a clear liquid in which a filter aid is dispersed (hereinafter, referred to as a “filter aid dispersion”) is added to a stock solution, the above problem does not occur, as is generally performed. . In this case, in addition to being able to adjust the filter aid concentration of the filter aid dispersion, the addition rate of the filter aid dispersion can be adjusted by the discharge amount of the pump, so that the rate of addition of the filter aid to the stock solution can be adjusted. This is because the width is large.

The filter aid adding apparatus 1 of the present embodiment intermittently adds a filter aid to a continuously supplied stock solution. Thus, the time-average addition amount of the filter aid is reduced, and the filter aid concentration ρ of the stock solution is adjusted to the target concentration ρ _t . Specifically, the control described below is performed.

  The measured value of the flow meter 12 (the flow rate i of the undiluted solution) is input to the control device 13. The controller 13 obtains the integrated flow rate I of the stock solution into the addition tank 22 based on the measurement value i of the flow meter 12. Here, the integrated flow rate I is obtained by integrating the flow rate i of the stock solution with time.

As shown in the graph of FIG. 2, the integrated flow rate I increases over time. I _t In the graph of FIG. 2 is a target amount. Target amount I _t is set in advance controller 13. The control device 13 starts integration of the flow rate i from time t = 0 to obtain the integrated flow rate I. When the control device 13 integrated flow I reaches the target amount I _t, the value of the accumulated flow rate I returned to 0 to obtain the integrated flow I to start integrating again flow i.

The control device 13 each time the accumulated flow I reaches the target amount I _t, the powder feeder 11 is operated, the addition of a filter aid addition tank 22. In this case, the powder feeder 11 is an amount commensurate with the stock solution of the target quantity I _t (hereinafter, referred to as "the target addition amount F _t".) Is added a filtration aid. Here, the target amount F _t of the filter aid is that amount which filter aid concentration of the stock solution of the target quantity I _t [rho is the target density [rho _t. Target addition amount F _t of the filter aid is represented by the formula (2).
F _t = ρ _t · I _t (2)

Controller 13, the integrated each time the flow I reaches the target amount I _t, from the powder feeder 11 is discharged filter aid target addition amount F _t, is stopped. Here, the discharge speed of the powder feeder 11 may be set to the lower limit or may not be the lower limit. Operating time of the powder feeder 11 is determined from the discharge speed and the target amount F _t.

  As described above, the filter aid adding device 1 operates the powder feeder 11 intermittently. Thereby, the average addition amount of the filter aid can be reduced. Therefore, even when the supply amount of the stock solution is small, the addition amount of the filter aid can be appropriately controlled. Since the addition amount of the filter aid does not become excessive, the stock solution can be efficiently filtered.

By the way, if the filter aid is intermittently added to the stock solution, the concentration of the filter aid in the stock solution may fluctuate with time. If the time interval for adding the filter aid is sufficiently shorter than the residence time of the stock solution in the addition tank 22, fluctuations in the concentration of the filter aid in the stock solution can be suppressed. Time interval for adding a filter aid can be adjusted by the target quantity I _t. It is preferred that less than half of the effective volume of the addition tank 22 the target quantity I _t. By doing so, the time interval for adding the filter aid can be made equal to or less than の of the average residence time of the stock solution in the addition tank 22, and fluctuations in the filter aid concentration of the stock solution can be suppressed.

  Further, in the filtration equipment AA of the present embodiment, stirring tanks 23 and 24 are connected downstream of the addition tank 22. Since the stock solution to which the filter aid has been added is again stirred in the stirring tanks 23 and 24, even if the filter aid is intermittently added, the concentration of the stock solution supplied to the filter 25 can be made uniform. .

[Other embodiments]
In the above-described embodiment, the control device 13 automatically controls the operation of the powder feeder 11, but instead, the operator may control the operation of the powder feeder 11. In this case, the operator intermittently operates the powder feeder 11 at an appropriate timing based on the measurement value of the flow meter 12.

AA filtration equipment 1 filtration aid addition device 11 powder supply device 12 flow meter 13 control device 21 storage tank 22 addition tank 23 stirring tank 24 stirring tank 25 filtration machine

Claims (4)

A powder feeder for adding a powder filter aid to an addition tank in which the stock solution before being supplied to the filter is temporarily stored,
A flow meter for measuring the flow rate of the stock solution supplied to the addition tank,
A control device for controlling the operation of the powder feeder,
The control device includes:
Based on the measurement value of the flow meter, determine the integrated flow rate of the stock solution to the addition tank,
Each time the integrated flow rate reaches a target amount, a filter aid adding device that operates the powder feeder to discharge an amount of the filter aid corresponding to the target amount of the stock solution, and stops the filter aid. . A filter aid adding device according to claim 1,
Said addition tank,
And a filtration device. 3. The filtration equipment according to claim 2, further comprising a stirring tank for temporarily storing and stirring the stock solution discharged from the addition tank. Using a powder feeder, a method of adding a powder filter aid to an addition tank in which the stock solution before being supplied to the filter is temporarily stored,
Each time the integrated flow rate of the stock solution to the addition tank reaches a target amount, the powder feeder is operated to discharge an amount of the filter aid corresponding to the target amount of the stock solution, and to stop. Method of adding a filter aid.

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