JP2023076973A - Air blow method of filter press - Google Patents

Abstract

To provide an air blow method of a filter press that can efficiently decreases water content ratios of dehydrated cake, while preventing air consumptions required in air blow from being increased unnecessarily.SOLUTION: In an air blow method of a filter press, in which undiluted liquid is supplied to a filtration chamber 9 formed of a plurality of filter plates 5 and is compressed and dehydrated in a diaphragm 10 annexed to the filtration chamber 9, and air is introduced into the filtration chamber 9 so as to perform air blow, a reference value at which a pressure in a diaphragm chamber 11 is preliminarily increased and a pressure boosting value at which the pressure in the diaphragm chamber 11 is gradually boosted by a predetermined pressure are set, a measured value is compared with the reference value in an air-blow step, the air blow step is continued in a same condition, when the measured value is in a range of the reference value, and a holding pressure in the diaphragm chamber 11 is boosted by the pressure boosting value, when the measured value is out of the range of the reference value, and then the air blow step is continued, which can block voids in dehydrated cake and can perform the air blow efficiently.SELECTED DRAWING: Figure 3

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air blow for a filter press, and more particularly to an air blow method for a filter press that increases holding pressure in a diaphragm chamber during air blow.

Conventionally, in a filter press that compresses the dehydrated cake by expanding the diaphragm, as a means of removing moisture between cake particles that is difficult to push out with mechanical compression pressure, air compressed to a high pressure state is introduced into the filter chamber. There is an air blow method to send it into the cake.

Patent Literature 1 discloses a technique of detecting the flow rate of filtrate discharged by an air blow process in which compressed air is introduced into a filter chamber, and sequentially increasing the flow rate or pressure of the compressed air according to the detected flow rate.

JP-A-61-15715

In the conventional air blowing method, voids (air passages) are generated inside the cake as the moisture in the cake is discharged, and the air sent into the filtration chamber preferentially passes through the voids with low passage resistance (short pass). there was a problem with As a result, the amount of air supplied to lower the moisture content of the cake was increased. Furthermore, if the amount of air supplied is increased, cracks will occur in the dehydrated cake, causing uneven dehydration of the dehydrated cake and troublesome post-processes, making efficient air blowing difficult.

The technique of Patent Document 1 can slightly decrease the moisture content of the cake by gradually increasing the flow rate or pressure of the compressed air used for the air blow, but it promotes the action of expanding the voids inside the cake by the air blow. Since the voids generated at the initial stage of air blowing are further expanded as the flow rate or pressure increases, the short-pass tendency of the compressed air is accelerated, and the moisture content of the cake cannot be uniformly lowered. In addition, if it is attempted to reduce the moisture content of the cake from this state, there is a problem that the consumption of compressed air becomes enormous.

To provide an air blowing method for a filter press that prevents a wasteful increase in air consumption due to cracks in a dewatered cake and voids between cake particles that occur during air blowing, and performs efficient air blowing.

In the air blowing method of a filter press in which the undiluted solution is supplied to a filtration chamber formed by a plurality of filter plates, dehydrated by compression with a diaphragm attached to the filtration chamber, and air is blown by introducing air into the filtration chamber, the diaphragm chamber is preliminarily A reference value for increasing the pressure of the diaphragm chamber and a pressure increasing value for increasing the diaphragm chamber by a predetermined pressure are set, and the measured value and the standard value are compared during the air blow process. Continue the air blow process under the same conditions, and if the measured value is out of the range of the standard value, increase the holding pressure in the diaphragm chamber by the boost value and continue the air blow process. Eliminates the air gap, and can perform an efficient air blow.

The reference value for pressurizing the diaphragm chamber is the flow rate of air supplied to the filtration chamber, the flow rate of air discharged from the filtration chamber, the pressure of air supplied to the filtration chamber, the flow rate of filtrate discharged from the filtration chamber, and the start of the air blow process. By setting at least one of the elapsed times from time, it is possible to accurately detect the moment when voids are generated in the dehydrated cake.

When the holding pressure in the diaphragm chamber is increased by the boost value, the moisture content can be reduced without applying a sudden force to the dehydrated cake by increasing the amount of air supplied to the filtration chamber by a specified amount. .

The filter press air blowing method according to the present invention can prevent cracks and voids from occurring in the dehydrated cake, and air does not short pass. Since the air can be uniformly fed into the dehydrated cake, the air can be supplied with high efficiency, and the moisture content of the dehydrated cake can be further reduced.

1 is a conceptual diagram of a filter press according to the present invention; FIG. Similarly, it is a partial longitudinal perspective view of the parallel filter plate. Similarly, it is a partial conceptual diagram of a filter chamber formed by closing parallel filter plates.

FIG. 1 is a conceptual diagram of a filter press according to the present invention.
A filter press 1 has a large number of filter plates 5 movably supported on guide rails 4 bridged between front and rear frames 2 and 3 . A clamping cylinder 6 provided on one frame 3 is used to move a large number of filter plates 5 in the axial direction.

FIG. 2 is a partial longitudinal perspective view of filter plates arranged in parallel.
A concave filter bed 7 is formed on each filter plate 5 , and a filter cloth 8 is suspended from the filter bed 7 to form a filter chamber 9 between adjacent filter plates 5 , 5 . A diaphragm 10 is stretched on one filter bed 7 to form a diaphragm chamber 11 inside the filter chamber 9 .

FIG. 3 is a partial conceptual diagram of a filtration chamber formed by closing parallel filter plates.
A stock solution supply port 12 is provided on the upper portion of the filter plate 5 , and a stock solution is pressurized into the filtration chamber 9 from a stock solution supply pipe (not shown) and solid-liquid separated by the filter cloth 8 . The separated filtrate is extracted from the filtrate discharge holes 13 provided at the lower ends of the filter beds 7, 7 of the filter plates 5, 5 and discharged to the filtrate pipes 14a, 14b. The filtrates discharged to the filtrate pipes 14a and 14b are collected by the discharge pipe 15 and discharged to the outside of the apparatus.

A pressure fluid supply pipe 16 communicating with the diaphragm chamber 11 is connected to the filter plate 5 on which the diaphragm 10 is stretched. The pressure fluid supply pipe 16 is branched and connected to the pressure fluid supply hole 19 of each filter plate 5 so as to supply the pressure fluid to all the diaphragm chambers 11. A fluid is supplied to each diaphragm chamber 11 from a pressure fluid supply pipe 16 through a pressure fluid supply hole 19 . The diaphragm chamber 11 to which the pressurized fluid is supplied expands toward the filter chamber 9 side, and compresses and dehydrates the dehydrated cake formed in the filter chamber 9 .

A pressure gauge 20 is provided in the pressure fluid supply pipe 16, and the holding pressure of the diaphragm chamber 11 when the pressure fluid is supplied to the diaphragm chamber 11 can be measured in real time. A measured value is transmitted from the pressure gauge 20 to the control device 21 .

The holding pressure of the expanded diaphragm chamber 11 increases, and the holding pressure of the diaphragm chamber 11 can be kept constant by closing the valve V1 arranged in the pressure fluid supply pipe 16 .

The pressurized fluid used in this embodiment may be liquid (eg, water) or gas, and is not particularly limited. When gas is used, a known air tank or the like is provided instead of the water supply tank 17 .

The diaphragm 10 may be stretched on both sides of the filtration bed 7 constituting the filtration chamber 9, or may be stretched on only one side. When the diaphragms 10 are stretched on both sides of the filter bed 7, the dehydrated cake is squeezed from both sides, so that the water content of the dehydrated cake is further reduced. When the diaphragm 10 is stretched only on one side of the filter bed 7, the filter plate 5 stretched with the diaphragm 10 on both sides and the filter plate 5 without the diaphragm 10 stretched on both sides are alternately arranged in parallel, or the diaphragm is placed only on one side. It is possible to configure such that the filter plates 5 on which the filter plates 10 are stretched are arranged in parallel.

An air supply pipe 22 is connected to one of the filtrate pipes 14a communicating with the filtration chamber 9, and the air, which is in a high pressure state at the supply source 23, is supplied from the air supply pipe 22 to the filtration chamber via the filtrate pipe 14a. Air blow is performed by making it flow into 9. The air that has flowed into the filtration chamber 9 passes through the dehydrated cake and is discharged from the other filtrate pipe 14b together with the moisture in the dehydrated cake.

When air is supplied to the filtration chamber 9, the valve V2 arranged in the air supply pipe 22 is opened and the valve V3 arranged in each filtrate pipe 14a is closed, so that the air passes through the filtration chamber 9. It is possible to prevent the liquid from flowing out from the discharge pipe 15 without During the press-fitting/squeezing step, the valve V2 is closed and the valves V3 are opened in order to convey the filtrate from both the filtrate pipes 14a and 14b to the discharge pipe 15.

The air supply pipe 22 is provided with a flow meter 24, which measures in real time the amount of air supplied from the supply source 23 during the air blow. The measured value is transmitted from the flow meter 24 to the control device 21 . For the supply source 23 that generates high-pressure air, a known technology such as a compressor is used.

As the air blow progresses, voids are generated in the dehydrated cake in the filtration chamber 9 and the capacity decreases. The dewatered cake formed in the filter chamber 9 can be pressed against the other filter bed 7 side. At this time, as the cake is compressed, the voids disappear, so by blowing air through the cake that has closed the voids, the short pass of the air is prevented and the increase in air consumption is suppressed, resulting in efficient moisture content in the cake. can be removed.

Therefore, in the air blow method of the present embodiment, a reference value for the flow rate of air to be supplied during air blow and a boost value for stepwise increasing the pressure of the diaphragm chamber 11 by a predetermined pressure are set in the controller 21 in advance. During the air blow process, the air flow rate introduced from the supply source 23 is measured by the flow meter 24 and transmitted to the control device 21 . The controller 21 compares the measured value with the reference value, and if the measured value exceeds the range of the reference value, the controller 21 sends an instruction to the water supply pump 18 . Based on the holding pressure of the diaphragm chamber 11 measured by the pressure gauge 20, the pressure of the diaphragm chamber 11 is increased by the pressure increase value. The time interval for measuring the air flow rate and the holding pressure of the diaphragm chamber 11 is appropriately set.

The air blowing method of the present invention will be described in detail below with reference to FIGS.
A reference value for the flow rate of air supplied from the supply source 23 to the air supply pipe 22 at the time of air blow and a boost value for increasing the pressure of the diaphragm chamber 11 stepwise by a predetermined pressure are set in the controller 21 in advance. The filter press 1 forms a filter chamber 9 by closing the filter plates 5, 5 in advance.

<Press-fitting process>
First, each valve V3 is opened and the valve V2 is closed. The open/close state of the valve V1 is not particularly limited. The undiluted liquid is supplied from the undiluted liquid supply port 12 to each filter chamber 9 to form a dehydrated cake. At this time, the filtrate discharged from the dehydrated cake by the pressurization pressure passes through the filter cloth 8 and is discharged from the filtrate pipes 14a and 14b through the discharge holes 13. FIG. Filtrates passing through the respective filtrate pipes 14a and 14b are collected in a discharge pipe 15 and discharged outside the machine.

<Compressing process>
The valve V1 is opened, and the pressure fluid pulled up from the water supply tank 17 by the water supply pump 18 is supplied from the pressure fluid supply pipe 16 to the diaphragm chamber 11 through the pressure fluid supply hole 19 . The diaphragm chamber 11 to which the pressurized fluid is supplied expands toward the filter chamber 9, and the dehydrated cake formed in the filter chamber 9 is compressed and dehydrated. The filtrate passes through the filter cloth 8 and is discharged from the filtrate pipes 14 a and 14 b to the discharge pipe 15 .

After the squeezing time has elapsed, the valve V1 is closed to keep the holding pressure of the diaphragm chamber 11 constant. The holding pressure of the diaphragm chamber 11 may be maintained by constantly activating the water supply pump 18 to continuously supply pressure fluid to the diaphragm chamber 11 at a constant pressure.

<Air blow process>
The air blowing process is started with the diaphragm 10 expanded in the preceding compression process. By opening the valve V2 and closing the valve V3, the conduit communicates from the air supply pipe 22 through one of the filtrate pipes 14a to the filtration chamber 9, and from the same filtration chamber 9 through the other filtrate pipe 14b. It is formed in one way so as to communicate with the discharge pipe 15 .

High-pressure air is supplied from a supply source 23 to the air supply pipe 22 . After that, air is supplied to each filter chamber 9 through the discharge hole 13 from each filtrate tube 14a. The air passes through the filter cloth 8 and collides with the dehydrated cake to remove moisture in the dehydrated cake. The removed moisture is accompanied by air, passes through the other filter cloth 8, and is discharged from the other discharge hole 13 communicating with the filtrate pipe 14b.

At this time, voids are generated in the dehydrated cake in the filtration chamber 9 due to the removed moisture, and the capacity of the dehydrated cake is reduced. If the air blow is continued in this state, the air will short pass through the voids in the dehydrated cake, resulting in an enormous amount of air consumption and a low moisture content.
Therefore, in the present embodiment, when the consumption of the air supplied at a constant rate exceeds a specified value, it is considered that a gap is generated in the dehydrated cake, and pressure fluid is supplied to the diaphragm chamber 11 to expand the diaphragm 10. By pressing the dehydrated cake, voids disappear.

The flow rate of air supplied from the supply source 23 to the air supply pipe 22 during the air blow is measured. As the air blow progresses, the air passes through the gaps formed in the dehydrated cake, so the air flow rate increases. The control device 21 compares the measured value with the reference value, and when the measured value exceeds the range of the reference value, pressure fluid is supplied to the diaphragm chamber 11 to inflate the diaphragm 10 .

At this time, the diaphragm chamber 11 is boosted by a predetermined boost value. The holding pressure of the diaphragm chamber 11 is measured by a pressure gauge 20, and based on the measured value, the control device 21 controls the water supply pump 18 to set the diaphragm chamber 11 to an arbitrary holding pressure. Inflate 10.

By expanding the diaphragm 10, the gaps in the filtration chamber 9 are filled with the diaphragm 10, and the gaps in the dehydrated cake are also eliminated. Since the air blow is performed in this state, the air blow efficiency is improved and the moisture content can be further reduced. If the measured value of the air flow rate does not exceed the reference value, the air blow is continued.

By repeating the above control, the moisture content of the dehydrated cake can be lowered to an arbitrary level. By sequentially supplying the pressurized fluid to the diaphragm chamber 11 during the air blow, the diaphragm 10 can be expanded step by step, so that the dehydrated cake is not abruptly pressurized. Therefore, the dehydrated cake can be prevented from cracking, and the cake can be uniformly compressed. By squeezing the dehydrated cake sequentially, it is possible to prevent air from short-passing and reduce air consumption.

In this embodiment, initially set fixed values are used for the reference value and the boost value, but variable values that vary according to time or the holding pressure may be used.

The amount of air supplied may be increased each time the holding pressure in the diaphragm chamber 11 is raised. Since the dehydrated cake, which has become firmer due to the expansion of the diaphragm 10, has greater resistance during air blowing, when the holding pressure in the diaphragm chamber 11 is increased by the boost value, the amount of air supplied to the filtration chamber 9 is increased by a specified amount. By doing so, it is possible to remove more moisture from the dehydrated cake and to prevent the formation of voids in the dehydrated cake. Moreover, since the amount of air supply is not increased abruptly, the dehydrated cake is not cracked.

In this embodiment, it was determined whether or not voids were generated in the dehydrated cake by measuring the amount of air supplied to the filtration chamber 9. In addition, the flow rate of the air discharged from the filtration chamber 9, A reference value for increasing the pressure of the diaphragm chamber 11 may be set from any of the pressure of the air supplied to the chamber 9, the flow rate of the filtrate discharged from the filtration chamber 9, the elapsed time from the start of the air blow, etc. Reference values may be combined. In that case, a known measuring instrument or the like is used.

When the dehydrated cake in the filtering chamber 9 reaches a predetermined moisture content, the air blowing step is finished. Alternatively, only the control of the holding pressure of the diaphragm chamber 11 is finished, and the air blow is continued until an arbitrary moisture content is reached. In addition to the moisture content of the dehydrated cake, each control may be terminated depending on the flow rate of the filtrate discharged from the filtration chamber 9, the elapsed time from the start of the air blow process, and the like.

The air blowing method for the filter press according to the present invention can reduce the moisture content of the dehydrated cake while reducing air consumption by expanding the diaphragm while supplying air to the filtration chamber. If it is a filter plate with a diaphragm attached, it can be carried out without additional equipment, and by setting each value according to the sludge properties, it is possible to perform a highly efficient air blow. It will be a very useful technology for various production processes such as sludge treatment, chemical industry, pulp and paper industry.

5 Filter plate 9 Filter chamber 10 Diaphragm 11 Diaphragm chamber

Claims (3)

A stock solution is supplied to a filtration chamber (9) formed by a plurality of filter plates (5), dehydrated by compression with a diaphragm (10) attached to the filtration chamber (9), and air is introduced into the filtration chamber (9). In the air blow method of the filter press in which the air blow is performed by
A reference value for increasing the pressure of the diaphragm chamber (11) and a pressure increasing value for increasing the pressure of the diaphragm chamber (11) stepwise by a predetermined pressure are set in advance,
During the air blow process, compare the measured value with the reference value,
If the measured value is within the range of the standard value, continue the air blow process under the same conditions,
An air blowing method for a filter press, characterized in that, when the measured value is out of the range of the reference value, the holding pressure of the diaphragm chamber (11) is increased by the boost value and the air blowing process is continued. The reference value for increasing the pressure of the diaphragm chamber (11) is
Flow rate of air supplied to the filtration chamber (9), flow rate of air discharged from the filtration chamber (9), pressure of air supplied to the filtration chamber (9), flow rate of filtrate discharged from the filtration chamber (9), 2. The air blowing method for a filter press according to claim 1, wherein the air blowing method for a filter press according to claim 1, wherein the air blowing method is set from at least one of the elapsed time from the start of the air blowing process. 3. The filter press according to claim 1 or 2, wherein when the holding pressure of the diaphragm chamber (11) is increased by the boost value, the amount of air supplied to the filtration chamber (9) is increased by a specified amount. air blow method.

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