JP2019188362A - Method for operating filter press - Google Patents

Abstract

To provide a method for operating a filter press that calculates solid quantities in a filtering chamber from concentrations of undiluted liquid supplied to a filter press and quantities of filtered liquid from the filtering chamber of the filter press and stops supply of the undiluted liquid to the filter press.SOLUTION: In a method for driving a filter press 1, in a dehydration step S1, the filter press 1, which supplies undiluted liquid to a filtering chamber, dehydrates the liquid and then exhausts a dehydrated cake, measures concentration of undiluted liquid to be supplied and quantities of filtered liquid exhausted from the filtering chamber, calculates a cake thickness T and a moisture content W of the cake corresponding to solid separated by solid-liquid separation in the filtering chamber, and when the calculated values reach a reference cake thickness T0 and a reference moisture content W0 of a cake, finishes dehydration, where the step is transferred to a cake exhausting step S2, a property of the dehydrated cake is stable and no trouble is caused in the cake exhausting step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of operating a filter press that calculates the solid content of a filtration chamber based on the concentration of the stock solution supplied to the filter press and the amount of filtrate discharged from the filter press and stops the supply of the stock solution to the filter press.

  When a stock solution containing a solid content and a liquid content is supplied to the filter press, the liquid is separated into solid and liquid by a filter cloth in a filtration chamber. The liquid content in the stock solution passes through the filter cloth and is discharged from the filtration chamber, and the solid content remains in the filtration chamber. In the initial stage of filtration, a large amount of filtrate is discharged, but as the filtration time elapses, a cake is generated on the filtration surface and the amount of filtrate discharged is reduced. Filling the filtration chamber with solids by press-fitting the stock solution and dehydrating it, and after securing a sufficient amount of solids for stripping the cake, stop supplying the stock solution and move to the pressing process using a diaphragm, or open the filter plate Then, the process proceeds to the dewatering cake discharging process.

As a method of detecting the completion of dehydration, the total amount of filtrate from the start of dehydration of the filter press is measured, and compared with the theoretical value calculated in advance, if the measured value and the theoretical value are substantially the same, it is detected that dehydration is complete. A detection method is disclosed in Patent Document 1.

JP 2009-61387 A

Generally, the dehydration process of the filter press is performed for a preset time. In order to eliminate waste of dehydration time, there are many techniques for detecting the completion of dehydration based on the amount of filtrate discharged from the filter press as in Patent Document 1. Patent Document 1 calculates the theoretical value of the filtrate amount by inputting the target dehydrated cake moisture content, the solid density in the raw slurry, the concentration of the raw slurry, and the amount of dehydrated cake processed by the dehydrator in advance. When the actual measured value becomes substantially the same, the dehydration is completed.

However, the properties of the stock solution supplied to the filter press are constantly changing depending on the season, time, weather, etc., and may deviate from the input values entered in advance. If the dehydration is completed based on the amount of the filtrate only in such a state, the thickness of the dehydrated cake in the filtration chamber may be insufficient and the moisture content of the dehydrated cake may be high. Such dehydrated cake has poor peelability from the filter cloth, and the equipment may stop in the cake discharging process or cause trouble in the next process. Therefore, it was necessary to periodically measure the stock solution properties and re-enter various data. The above tendency is particularly noticeable in prolonged dehydration.

  The present invention measures the concentration of the stock solution supplied to the filter press and the amount of filtrate from the filter chamber of the filter press, calculates the properties of the dehydrated cake accumulated in the filter chamber, Provided is a method of operating a filter press that stops supply of a stock solution to the press.

The present invention relates to a filter press operating method for discharging a dehydrated cake after supplying the stock solution to the filtration chamber and dehydrating it, and setting the standard cake thickness and the standard cake moisture content in advance, The amount of filtrate discharged from the chamber is measured, and the cake thickness and cake moisture content of solids separated in the filtration chamber are calculated from the stock solution concentration and filtrate amount, and the calculated values are the reference cake thickness and the reference cake moisture content. When the rate is reached, the dehydration is completed and the process proceeds to the cake discharging step. Therefore, the thickness and moisture content of the cake accumulated in the filtration chamber in real time can be calculated corresponding to the stock solution properties. In the long press-in type filter press, the dehydrated cake property is detected and the cake peeling process is performed in an optimal time, so that unnecessary press-fitting supply (dehydration process) is not performed.

In addition, the dehydration process is a stock solution press-in process and a press process, and the cake thickness is calculated at the time of the stock solution press-in process, and when the calculated value reaches the standard cake thickness, the process moves to the press process, and the moisture content of the cake is set at the press process. When the calculated value reaches the standard cake moisture content, the process moves to the cake discharging process, and therefore, it is possible to cope with a filter press of a type that is squeezed with a diaphragm or the like.

When the amount of filtrate discharged from a part of the filtration chamber is measured, a small measuring device can be used, and the cost is reduced without being limited to the installation space.

The operation method of the filter press according to the present invention measures the concentration of the stock solution and the amount of the filtrate in real time, and detects the completion of dehydration when the solid content (cake) in the filtration chamber is in an optimum state. Processing is possible with press-fitting and pressing time. After detection, since the thickness and moisture content of the dehydrated cake are in an optimal state, the peelability is good and there is no trouble. In addition, since the properties of the dehydrated cake are stable, it does not take time in the post-process of processing or using the dehydrated cake.

It is a schematic side view of the filter press concerning this invention. Similarly, it is a partial cross-sectional view of the filtration chamber. Similarly, it is a partial cross-sectional view of a filtration chamber of another embodiment.

FIG. 1 is a schematic side view of a filter press according to the present invention.
In the filter press 1, a large number of filter plates 5 are movably supported on a pair of guide rails 4 and 4 bridged between the front and rear frames 2 and 3. A number of filter plates 5 are moved in the axial direction by an opening / closing device 6 provided on one frame 3. A concave filter bed 7 is formed on the filter plate 5, and a filter cloth 8 is stretched over the filter bed 7, and a filter chamber 9 is formed between adjacent filter plates 5 and 5.

A stock solution supply pipe 10 communicating with the filtration chamber 9 is connected to the filter plate 5, and the stock solution stored in the storage tank 12 is supplied to the filtration chamber 9 via the stock solution supply pump 11. The storage tank 12 is provided with a concentration meter 13 for measuring the stock solution concentration.

Alternatively, the compressed water supply pipe 14 may be connected to the filter plate 5, and the raw solution may be supplied from a supply source (not shown) to the filtration chamber 9 via the compressed water pump 15, and then the dehydration may be performed with the diaphragm 16 or the like.

The filtrate is collected in the filtrate discharge passage 21 in the filter plate 5 and discharged through the filtrate discharge pipe 17 connected from the outside. The filtrate discharge path 21a of some of the filtration chambers 9 is independently provided with a flow meter 18, connected to the filtrate discharge pipe 17, and discharged together with other filtrates.

The concentration meter 13 and the flow meter 18 transmit data to the control device 19, and determine the operation / stop of the stock solution supply pump 11 and the squeezed water pump 15 based on the result calculated by the control device 19.

FIG. 2 is a partial cross-sectional view of the filtration chamber.
A filtration chamber 9 is configured by closing the filter plates 5 and 5 each having a concave filtration bed 7 and 7. The raw solution sludge is pressed into the filtration chamber 9 from a raw solution supply path (not shown), and solid-liquid separation is performed with the filter cloth 8. After injecting the stock solution, the diaphragm 16 is expanded to squeeze the cake in the filtration chamber, and further promote solid-liquid separation. The separated filtrate is discharged to the filtration beds 7 and 7 of the filter plates 5 and 5, extracted from the filtrate discharge holes 20 and 20 provided at the lower ends of the filter plates 5 and 5, and the filtrate passing through the filter plate 5. It discharges to the discharge path 21.

The filtrate discharge path 21 of the present embodiment penetrates the filter plate 5, and the filtrate discharge path 21 communicates when the filter plates 5 are arranged in parallel, and is discharged to the outside through the filtrate discharge pipe 17.
The filtrate discharge path 21 may be configured by separately providing a pipe material outside the filter plate 5.

Some of the filtration chambers 9a are connected to a filtrate discharge path 21a in which a discharge hole 20a is independently formed, and the filtrate is discharged to the outside separately through the filtrate discharge path 21a. The flow rate 18 is provided in the independent filtrate discharge path 21a, and the amount of the filtrate discharged | emitted from the specific filtration chamber 9a can be measured. The filtrate discharged from the other filtration chambers 9... Downstream of the filtrate discharge passage 21 a is joined to the filtrate discharge pipe 17 for discharging and discharged.

In this embodiment, a filtrate discharge passage 21a is connected to the filter plate 5 on the front frame 2 side from outside, and only the amount of filtrate discharged from the filtration chamber 9a on the front frame 2 side is measured. However, for example, as shown by a broken line, the filtrate may be discharged from the discharge holes 20a of the plurality of filtration chambers 9a to the filtrate discharge path 21a and measured collectively.

By measuring only the filtrate discharged from some of the filtration chambers 9a, it is possible to use a small-sized measuring device, and the cost is reduced without being limited to the installation space.

FIG. 3 is a partial cross-sectional view of a filtration chamber of another embodiment.
The filter plates 5 having the diaphragm 16 and the filter plates 5 not having the diaphragm 16 are alternately connected to each other, and the discharge holes 20 are communicated between the adjacent filtration chambers 9, 9. , 9 collectively discharge the filtrate discharged from one side. The discharge hole 20 is discharged to a filtrate discharge pipe 21 that passes through the filter plate.

Some filtration chambers 9a are connected to a filtrate discharge path 21a in which a discharge path 20a is formed independently, and the filtrate is separately discharged to the outside through the filtrate discharge path 21a.

As in the embodiment of FIG. 2, for example, the filtrate may be discharged from the discharge holes 20a of the plurality of filtration chambers 9a to the filtrate discharge path 21a as shown by broken lines and measured in a lump.

In the present invention, the solid content of the filtration chamber 9 is calculated based on the concentration of the stock solution supplied to the filter press 1 and the amount of the filtrate discharged from the filter press 1 in the above configuration, and the filter press 1 is dehydrated at an optimal time. In this operation method, the process S1 is stopped and the process proceeds to the discharge process S2.

From the concentration of the stock solution supplied to the filtration chamber 9 and the amount of filtrate discharged from the filtration chamber 9, the solid content (cake thickness T) and cake moisture content W remaining in the filtration chamber 9 are calculated by the controller 19, and the calculated value As a result of comparing the reference cake thickness T0 and the reference cake moisture content W0, the operation of the stock solution supply pump 11 or the squeezed water pump 15 is stopped and discharged when it is determined that the calculated value has reached the reference value. The process proceeds to step S2.

The cake thickness and cake moisture content can be calculated using the following equations.
Cake thickness = wet cake mass / wet cake specific gravity / filtration area cake moisture content = 100− (SS dry weight / wet cake mass) × 100

Here, the specific gravity of the wet cake and the dry amount of SS can be calculated using the following equations.
Wet cake specific gravity = wet cake mass / (water mass in cake + SS dry weight / true specific gravity)
Wet cake mass = SS dry weight / (100-cake water content prediction) × 100
SS dry volume = SS concentration × (filtration chamber volume + pressed filtrate volume) × coefficient water volume = filtration chamber volume−pressed filtrate volume−SS volume
Note that the above equation may be multiplied by a coefficient calculated in advance through experiments or the like as necessary.

<SS concentration>
The SS concentration is a stock solution concentration, and is measured by a densitometer 13 provided in a storage tank 12 temporarily stored for supplying the stock solution to the filter press 1. In order to make the concentration of the storage tank 12 uniform, a stirring device may be provided. The densitometer 12 may be a known one, and may be provided in the stock solution supply pipe 10.

<Filtration area / filtration chamber volume>
The filtration area and the filtration chamber volume are known from the model of the filter press 1, and each value is input to the control device 19 in advance.

<Press-fit filtrate volume / pressed filtrate volume>
The amount of press-fit filtrate and the amount of pressed filtrate are measured by the flow meter 18 provided in the filtrate drainage channel 21a. In the present embodiment, since the filtrate is discharged from one filtration chamber 9a, a small flow meter 18 is used. The control device 19 calculates the total amount (cumulative amount) of the filtrate transmitted from the flow meter 18 and substitutes it into the previous equation.
The flow meter 18 may be a known device such as one that is directly attached to the pipe, one that is attached to the outside of the pipe, a storage type, and an overflow type.

First, the filtration chamber volume and filtration area, the standard cake thickness, and the standard cake water content determined from the type of the filter press 1 are determined in advance and input to the control device.

<Undiluted solution press-fitting step S11>
In the dehydration step S1, a stock solution press-fitting step S11 is performed in which the filter plates 5 are closed and the stock solution is press-fitted from the storage tank 12 into the filtration chamber 9 by the stock solution supply pump 11.
At this time, the measured value of the SS concentration measured by the concentration meter 13 installed in the storage tank 12 is transmitted to the control device 19. Further, the flow rate of the press-fit filtrate that is separated and discharged in the filtration chamber 9 is measured by the flow meter 18 and transmitted to the control device 19. It is measured and transmitted to the control device 19 every predetermined time.

<Calculation and comparison of cake thickness T>
The control device 19 calculates the cake thickness T from the measurement values transmitted from the concentration meter 13 and the flow meter 18. The calculated cake thickness T is compared with a predetermined reference cake thickness T0. If the cake thickness is smaller than the reference cake thickness T0, the stock solution press-fitting step S11 is continued, and if it is greater than the reference cake thickness T0, the stock solution supply pump 11 is stopped. Then, the compressed water pump 15 is operated to shift to the pressing step S12.
In addition, when there is no pressing process S12, calculation and comparison of the cake water content W are performed simultaneously.

<Pressing step S12>
If necessary, after the undiluted solution press-fitting step S11, a squeezing step S12 is performed in which the squeezed water pump 15 is operated to expand the diaphragm 16 with the squeezed water to squeeze the filtration chamber 9.
The amount of squeezed filtrate separated and discharged from the solid content by squeezing the filtration chamber 9 by the diaphragm 16 is measured by the flow meter 18 and transmitted to the control device 19. It is measured and transmitted to the control device 19 every predetermined time.

<Calculation and comparison of cake moisture content W>
The cake moisture content W is calculated from the measured value measured by the dehydration step S1 (raw solution press-fitting step S11 or pressing step S12). The calculated cake moisture content W is compared with a predetermined reference cake moisture content W0. If the calculated cake moisture content W is greater than the reference cake moisture content W0, the stock solution press-fitting step S11 or the squeezing step S12 is continued. When it is smaller than the cake water content W0, the stock solution supply pump 11 or the squeezed water pump 15 is stopped, and the process proceeds to the cake discharging step S2.
In addition, you may transfer to cake discharge | emission process S2, when the amount of filtrate discharged | emitted becomes zero.

<Cake discharge process S2>
When it is determined that the cake thickness T and the cake moisture content W in the filtration chamber have reached the reference cake thickness T0 and the reference cake moisture content W0, respectively, the filter plate 5 is opened and the dehydrated cake in the filtration chamber 9 is discharged. .

  Since not only the solid content (cake thickness T) accumulated in the filtration chamber 9 but also the solid water content (cake water content W) is judged and the process proceeds to the cake discharge step S2, poor peeling in the discharge step S2 In addition to reducing the error due to, there is no trouble in the subsequent process of processing the dehydrated cake.

The operation method of the filter press according to the present invention measures the fluctuation of the properties of the stock solution in real time, calculates the thickness and moisture content of the cake accumulated in the filtration chamber, and detects the end of the dehydration process with the optimal cake properties for discharge. it can. The time required for the dehydration process is not wasted, the peelability of the dehydrated cake is improved, and there is no adverse effect on the subsequent process.
In particular, the properties of dehydrated cakes are stable in machinery such as undiluted liquids whose properties frequently change, purified water that performs dehydration for a long period of time, and machines where cake properties are limited when processing dehydrated cake in the subsequent process. At the same time, there is no waste in processing time, which is a very useful technique.

DESCRIPTION OF SYMBOLS 1 Filter press 9 Filtration chamber S1 Dehydration process S11 Stock solution injection process S12 Squeeze process S2 Cake discharge process T0 Standard cake thickness T Cake thickness W0 Standard cake moisture content W Cake moisture content

Claims (3)

In the operation method of the filter press for discharging the dehydrated cake after supplying the stock solution to the filtration chamber (9) and dehydrating,
Set the standard cake thickness (T0) and the standard cake moisture content (W0) in advance,
The concentration of the stock solution supplied during the dehydration step (S1),
Measure the amount of filtrate discharged from the filtration chamber (9),
Calculate the cake thickness (T) and cake moisture content (W) of the solid content that is solid-liquid separated in the filtration chamber (9) from the stock solution concentration and the filtrate amount,
When the calculated value reaches the standard cake thickness (T0) and the standard cake moisture content (W0),
A method of operating a filter press, characterized in that dehydration is completed and the process proceeds to a cake discharging step (S2).
The dehydration step (S1) is a stock solution press-fitting step (S11) and a pressing step (S12),
When calculating the cake thickness (T) during the stock solution press-fitting step (S11) and the calculated value reaches the standard cake thickness (T0), the process proceeds to the pressing step (S12).
The cake moisture content (W) is calculated during the pressing step (S12), and when the calculated value reaches the reference cake moisture content (W0), the process proceeds to the cake discharging step (S2). The operation method of the filter press as described.
The method of operating a filter press according to claim 1 or 2, wherein the amount of filtrate discharged from a part of the filtration chamber (9) is measured.

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