JP7517282B2 - Filters for filter press type dehydrators - Google Patents

Description

The present invention relates to a filter that is placed between the filter plate and diaphragm plate of a filter press type dehydrator and has a liquid supply plate between two filter cloths, and in particular to a filter that can prevent blockage of the filtrate flow path of the liquid supply plate.

As waste liquid treatment equipment in waste liquid treatment plants of steelworks and the like, filter press type dehydrators such as those disclosed in Patent Document 1 are used. This filter press type dehydrator usually has many filter plates and many diaphragm plates arranged vertically and alternately, one by one. A filter is then placed between each of the opposing filter plates and diaphragm plates, and a hydraulic cylinder is used to sandwich two pieces of filter cloth as filters between the filter plates and diaphragm plates, with a liquid supply plate between them.

The filter press dehydrator then supplies waste liquid as filtrate between the two sandwiched filter cloths via a liquid supply plate. The diaphragm is then pressurized with pressurized water supplied between the diaphragm and the core plate of the diaphragm plate, and the diaphragm presses one of the filter cloths against the other filter cloth supported by the filter plate, filtering the waste liquid. The filtrate is then discharged from the discharge passages provided in the filter plate and diaphragm plate. The gap between the filter plate and diaphragm plate is then widened, and the filter is lowered to widen the gap between the two filter cloths, allowing the cake, which is the residue of waste liquid remaining between the filter cloths, to fall and be discharged.

For the purpose of extending the filter life, for example, Patent Document 2 discloses a filter in which a liquid supply plate has filtrate supply holes that align with the filtrate supply holes of the filter cloth and penetrate in the plate thickness direction, and a filtrate outlet path that extends from the filtrate supply hole to the lower end of the liquid supply plate, the liquid supply plate being formed from a deformable resin, and two thin lip portions that extend along the lower end are provided on both sides of the open end of the filtrate outlet path at the lower end of the liquid supply plate.

Japanese Patent Application Publication No. 09-000818 Japanese Patent Application Publication No. 2013-86035

In the conventional filters for the filter press type dehydrators, the liquid supply plate has an open end of a filtrate outlet channel that extends from a filtrate supply hole that penetrates the plate thickness direction to the lower end of the liquid supply plate.

For example, in the filter of Patent Document 2, the diameter of the filtrate outflow channel is not designed to take into consideration clogging caused by sludge in the waste liquid. Therefore, when waste liquid is supplied between two pieces of filter cloth sandwiched between a filter plate and a diaphragm plate, the sludge in the waste liquid that gushes out from the open end of the filtrate outflow channel clogs and blocks the filtrate outflow channel, which is a problem. If the filtrate outflow channel becomes clogged, the capacity of the filter press dehydrator decreases, making it necessary to clean the filtrate outflow channel periodically, which reduces the operating rate.

The present invention was made in consideration of the above circumstances, and its purpose is to provide a filter for a filter press type dehydrator that can prevent clogging of the filtrate outflow passage of the liquid supply plate.

The filter for a filter press type dehydrator according to the present invention, which was developed to solve the above problems and achieve the above objects, is a filter comprising two filter cloths arranged between the filter plate and diaphragm plate of a filter press type dehydrator, and a liquid supply plate located between the filter cloths, the liquid supply plate having a filtrate supply hole aligned with the filtrate supply hole of the filter cloth and penetrating in the plate thickness direction, and a filtrate outlet channel extending from the filtrate supply hole to the lower end of the liquid supply plate, the filtrate outlet channel of the liquid supply plate has a diameter that takes into account clogging due to sludge in the waste liquid, and a protective tube is installed in the filtrate outlet channel.

As explained above, in the filter for a filter press type dehydrator of the present invention, when filtrate is supplied between two filter cloths sandwiched between a filter plate and a diaphragm plate, the diameter of the filtrate outlet channel is sufficiently wide compared to the diameter of the sludge contained in the filtrate passing through the filtrate outlet channel of the liquid supply plate located between the filter cloths, so that blockage due to clogging can be prevented. Furthermore, in response to a decrease in the strength of the filtrate outlet channel wall of the liquid supply plate caused by widening the filtrate outlet channel diameter, the strength is reinforced by the protective tube, and deformation or damage to the filtrate outlet channel wall of the liquid supply plate can be prevented.

Therefore, according to the filter for a filter press type dehydrator of the present invention, the clogging of the filtrate flow path of the liquid supply plate can be effectively prevented, so that the cleaning interval of the liquid supply plate of the filter for a filter press type dehydrator can be extended more than before. Furthermore, when replacing the liquid supply plate, it is possible to limit the replacement to only the protective tube, rather than the entire liquid supply plate, which is expected to reduce costs.

The material of the protective tube to be inserted into the filtrate outflow passage of the liquid supply plate of the filter for the filter press type dehydrator of the present invention is preferably selected according to the properties of the filtrate, such as the pH value and liquid temperature.

This prevents corrosion and deformation caused by the nature of the filtrate flowing from the filtrate supply hole to the lower end of the supply plate, and extends the life of the protective tube.

Furthermore, it is preferable to use a protective tube with slits or a protective tube with a brim on the filtrate supply hole side.

This prevents the protective tube from coming loose due to the flow of filtrate from the filtrate supply hole to the lower end of the supply plate.

1A and 1B are a front view and a side view showing a typical filter press dehydrator to which an embodiment of the filter for a filter press dehydrator of the present invention is applied. 4A and 4B are a front view and a side view showing a filter plate of the filter press dehydrator. 4A and 4B are a front view and a side view showing a diaphragm plate of the filter press dehydrator. 3A and 3B are a front view and a side view showing the filter for a filter press type dehydrator according to the embodiment. FIG. 1A, 1B and 1C are a front view, a side view and a bottom view, respectively, showing the liquid supply plate of the filter for a filter press type dehydrator according to the embodiment. 1A, 1B, and 1C are respectively a front view, a side view, and a bottom view of a protective tube to be inserted into the liquid supply plate of a filter for a filter press type dehydrator of the above embodiment, (d), (e), and (f) are respectively a bottom view before insertion into a filtrate outflow path, and a bottom view and a side view when inserted into the filtrate outflow path of a slitted protective tube of another embodiment, and (g) is a front view of a flanged protective tube of another embodiment. 1A and 1B are explanatory diagrams showing the filter press dehydrator in a pressed position with a filter sandwiched between a filter plate and a diaphragm plate (viewed from A-A in FIG. 1), and in an open position in which the gap between the filter plate and the diaphragm plate is widened to open the filter. FIG. 1(a) is an explanatory diagram showing a state in which filtrate is supplied between the filter cloths sandwiched between a filter plate and a diaphragm plate; FIG. 1(b) is a state in which the diaphragm is pushed with pressurized water to press the filter cloths; FIG. 1(c) is a state in which the gap between the filter plate and the diaphragm plate is widened to open the filter; and FIG. 1(d) is a diagram showing a state in which the open filter is moved downward while widening the gap between the two filter cloths to allow the cake to fall.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Here, Figs. 1(a) and (b) are respectively a front view and a side view of a normal filter press type dehydrator to which one embodiment of the present invention is applied. Also, Figs. 2(a) and (b) are respectively a front view and a side view of a filter plate of the filter press type dehydrator. Also, Figs. 3(a) and (b) are respectively a front view and a side view of a diaphragm plate of the filter press type dehydrator.

As shown in FIG. 1, this filter press dehydrator is equipped with a number of filter plates 1 and a number of diaphragm plates 2 arranged vertically and alternately, a number of filters 3 arranged between the filter plates 1 and diaphragm plates 2, rails 4 that support the filter plates 1 and diaphragm plates 2 so that they can move horizontally toward and away from each other, hydraulic cylinders 5 that move the filter plates 1 and diaphragm plates 2 along the rails 4 between a press position where the filter plates 1 and diaphragm plates 2 overlap each other liquid-tightly via the filters 3 and an open position where they are separated from each other, and a filter lifting mechanism 6 that simultaneously lowers and raises all of the filters 3 when the filter plates 1 and diaphragm plates 2 are in the open position.

The filter plate 1 and diaphragm plate 2 here are normal, and as shown in Figures 2 and 3, each filter plate 1 has recesses 1a on both sides to define the filtration chamber, and filtrate supply holes 1b formed as through-holes. Each diaphragm plate 2 has a core plate 2b with recesses 2a on both sides to define the filtration chamber, and two diaphragms (not shown) stretched over both sides of the core plate 2b, each fixed liquid-tightly around the recesses 2a of the core plate 2b, and has filtrate supply holes 2c formed as through-holes. In addition, two rollers 1c and 2d are provided on the lower ends of the filter plate 1 and diaphragm plate 2, respectively.

Figures 4(a) and (b) are a plan view and a side view showing the filter for a filter press type dehydrator of the above embodiment. Figures 5(a), (b), and (c) are a front view, a side view, and a bottom view showing the liquid supply plate of the filter for a filter press type dehydrator of the above embodiment. Also, Figures 6(a), (b), and (c) are a front view, a side view, and a bottom view showing the protective tube of the liquid supply plate of the filter for a filter press type dehydrator of the above embodiment. Each filter 3 of this embodiment is formed by folding back a rectangular filter cloth at the center in the longitudinal direction, with the folded back portion as the upper end 7a and the original ends as the lower end 7b, and has a double-layered filter cloth 7 with a filtrate supply hole 7c formed in the center in the width direction near the upper end 7a. It also has a filtrate supply hole 8a consisting of a through hole aligned with the filtrate supply hole 7c near the upper end 7a of the filter cloth 7, and two filtrate outlet paths 8c, for example with an oval or rounded rectangular cross section, extending downward from the filtrate supply hole 8a to the lower end 8b, and is disposed between the double-layered filter cloth 7, and has a liquid supply plate 8 fixed on both sides to the double-layered filter cloth 7.

The liquid supply plate 8 here is made of a resin that has a certain degree of elasticity and can be deformed, such as polypropylene, and on both sides of the open end of the filtrate outflow passage 8c at the lower end 8b of the liquid supply plate 8, two thin lip portions 8d extending in the left-right direction in FIG. 4(a) are formed integrally with the lower end 8b along the lower end 8b. Here, of the two lip portions 8d, the lip portion 8d closer to the filter plate 1 is shorter than the lip portion 8d closer to the diaphragm plate 2. In addition, a protective tube 8e made of general structural rolled steel is attached to the filtrate outflow passage 8c.

Figure 7(a) shows the filter press dehydrator in a pressed position with the filter 3 sandwiched between the filter plate 1 and the diaphragm plate 2 (as viewed from A-A in Figure 1), and Figure 7(b) is an explanatory diagram showing the filter press dehydrator in an open position with the filter 3 opened by widening the gap between the filter plate 1 and the diaphragm plate 2. Figure 8(a) shows the state in which filtrate is supplied between the filter cloth 7 of the filter 3 sandwiched between the filter plate 1 and the diaphragm plate 2, Figure 8(b) shows the state in which the diaphragm is pressed with pressurized water to press the filter cloth 7 of the filter 3, Figure 8(c) shows the state in which the filter 3 is opened by widening the gap between the filter plate 1 and the diaphragm plate 2, and Figure 8(d) is an explanatory diagram showing the state in which the open filter 3 is moved downward to widen the gap between the two filter cloths 7 and drop the cake. However, to simplify the illustration, the filters 3 located on the outside of the filter plate 1 and diaphragm plate 2 have been omitted here.

In the filter press dehydrator installed in the waste liquid treatment plant of a steelworks, when the hydraulic cylinder 5 presses the numerous filter plates 1 and numerous diaphragm plates 2 to the press position shown in FIG. 7(a), where they overlap liquid-tightly with the filter 3 interposed therebetween, the recesses 1a, 2a of the overlapping filter plates 1 and diaphragm plates face each other to define a filtration chamber, and the filtrate supply holes 1b, 2c formed in the overlapping filter plates 1 and diaphragm plates 2, respectively, are aligned with the filtrate supply holes 7c, 8a of the filter 3 to define a filtrate supply path. As shown in FIG. 8(a), the waste liquid as filtrate is pressure-fed to each filter 3 through the filtrate supply path, passes through the inside of the protective tube 8e of the filtrate outflow path 8c from the filtrate supply hole 8a of the liquid supply plate 8, and is supplied between the intermediate parts of the two filter cloths 7 located within the filtration chamber. The supplied waste liquid passes through the filter cloth 7 under the pressure of the waste liquid supplied later, becoming filtered liquid, and is discharged through the filtered liquid passages formed in each filter plate 1 and diaphragm plate 2.

Next, as shown in FIG. 8(b), pressurized water is supplied between the core plate 2b of each diaphragm plate 2 and the diaphragms on both sides of it. The diaphragm pressed by this pressurized water presses one of the two filter cloths 7 in the filtration chamber, which is closer to the diaphragm, toward the other filter cloth 7 supported by the filter plate 1, which is closer to the filter plate 1. As a result, the waste liquid supplied between the two filter cloths in the filtration chamber is pressed, and the water in the waste liquid passes through the filter cloth 7 to become filtered liquid, and the remaining solids solidify into a thick plate shape, becoming the so-called cake 9.

Then, the hydraulic cylinder 5 pulls the many filter plates 1 and the many diaphragm plates 2 to the open position shown in FIG. 7(b), separating them from each other. The filter lifting mechanism 6 connects both ends to the upper end 7a and the lower end 7b of the filter cloth 7 of all the filters 3, respectively, and simultaneously moves the many chains attached to the many sprockets on a common drive shaft, so that the upper end 7a of the filter cloth 7 of all the filters 3 is simultaneously lowered between the filter plate 1 and the diaphragm plate 2, as shown in FIG. 8(d), and at the same time, the lower end 7b of the filter cloth 7, which is wound around the rollers 1c and 2d, two of which are provided at the lower end of the filter plate 1 and the diaphragm plate 2, is simultaneously raised, and the cake 9 sandwiched between the two filter cloths 7 is peeled off from the filter cloths 7 and dropped downward.

Then, the filter lifting mechanism 6 operates in the reverse manner to simultaneously raise the upper ends 7a of the filter cloths 7 of all filters 3 between the filter plate 1 and the diaphragm plate 2, and simultaneously lower the lower ends 7b of those filter cloths 7, so that the middle parts of the filter cloths 7 are returned to between the filter plate 1 and the diaphragm plate 2 while being spray-cleaned, and the hydraulic cylinder 5 presses the many filter plates 1 and many diaphragm plates 2 to position them in the initial press position shown in Figure 7(a).

During the operation of the filter press dehydrator, in the filter 3 of this embodiment, when waste liquid containing sludge as filtrate passes through the inside of the protective tube 8e of the filtrate outlet passage 8c of the liquid supply plate 8 located between the two filter cloths 7 sandwiched between the filter plate 1 and the diaphragm plate 2, the filtrate outlet passage diameter is sufficiently larger than the sludge diameter, so that it does not become clogged and blocked. In addition, in order to make the filtrate outlet passage diameter sufficiently larger than the sludge diameter, the wall thickness of the filtrate outlet passage 8c part of the liquid supply plate 8 becomes thin, but the strength is maintained by the protective tube 8e, preventing deformation and damage of the liquid supply plate 8 body. The filtrate outlet passage diameter is the short diameter, and is preferably three times or more the sludge diameter, and is preferably 7 mm or less due to equipment constraints. Here, the sludge diameter is the sphere equivalent diameter, and is the value when 50% of the volume standard passes through.

Therefore, according to the filter 3 for a filter press type dehydrator of this embodiment, the blockage of the filtrate flow path 8c of the liquid supply plate 8 can be effectively prevented, so that the cleaning of the liquid supply plate 8c of the filter for a filter press type dehydrator can be extended more than before.

In addition, the protective tube 8e can prevent damage to the filtrate flow path 8c of the liquid supply plate 8 caused by the flow of waste liquid containing sludge, so the replacement range of the liquid supply plate 8 can be limited to only the protective tube 8e, reducing costs.

When the conditions were compared for two months before and after applying the filter 3 of this embodiment to the filter press type dehydrator installed in the wastewater treatment plant of a steelworks, the percentage of clogged filters out of 50 filters was reduced from 20% to 0%.

Figures 6(d) to (f) show a slitted protective tube 8e as an example of another embodiment. Figure 6(d) is a bottom view showing the state before the slitted protective tube 8e is inserted into the filtrate outflow path 8c, with the slit 8f open. Figures 6(e) and (f) are bottom and side views showing the state after the slitted protective tube 8e is inserted into the filtrate outflow path 8c, with the slit 8f closed. At this time, the biasing force trying to open the slit 8f presses the long side surface of the protective tube 8e against the inner surface of the filtrate outflow path 8c. Figure 6(g) shows a front view of a flanged protective tube 8e as an example of another embodiment. The flange 8g is provided on the filtrate supply hole 8a side of the protective tube 8e, and protrudes so as to catch on the edge of the filtrate supply hole 8a of the liquid supply plate 8. In this way, it is possible to prevent the protective tube 8e from falling off due to the flow of filtrate flowing from the filtrate supply hole 8a to the lower end of the liquid supply plate 8.

The above explanation is based on the illustrated example, but the present invention is not limited to the above example. For example, the material of the protective tube 8e inserted into the filtrate outflow passage 8c does not have to be general structural rolled steel as long as it has enough strength to prevent deformation or damage to the wall thickness of the filtrate outflow passage 8c. It is sufficient if the material is at least stronger than the resin that forms the liquid supply plate 8. In addition, it is preferable to select a material that does not corrode or deform, such as stainless steel, or to apply a coating, taking into account the pH value and temperature of the filtrate.

In the above example, the liquid supply plate 8 is formed from a single resin plate, but the liquid supply plate 8 may be formed from two laminated thin plates, which are attached to the two filter cloths 7, respectively. In this way, each thin plate has a supply hole without an inverse shape, a groove portion that defines the filtrate outflow path, and one of the two lip portions, so that a molding die such as an injection mold that forms the thin plate having these from a resin material can be constructed simply and inexpensively. In addition, since it can be installed in a manner that sandwiches the protective tube, it becomes easy to attach and remove the protective tube.

Furthermore, the filter in the above example was applied to a filter press type dehydrator installed in a waste liquid treatment plant of a steelworks to treat waste liquid containing sludge, but the filter of the present invention is not limited to this and can also be applied to a filter press type dehydrator that treats other types of filtrate.

The present invention is suitable for use in devices where the flow path is clogged with deposits and it is difficult to install separate cleaning equipment.

REFERENCE SIGNS LIST 1 filter plate 1a recess 1b filtrate supply hole 1c roller 2 diaphragm plate 2a recess 2b core plate 2c filtrate supply hole 2d roller 3 filter 4 rail 5 hydraulic cylinder 6 filter lifting mechanism 7 filter cloth 7a upper end 7b lower end 7c filtrate supply hole 8 liquid supply plate 8a filtrate supply hole 8b lower end 8c filtrate outflow path 8d lip 8e filtrate outflow path protection tube 8f slit 8g flange 9 cake

Claims (3)

A filter comprising two filter cloths disposed between a filter plate and a diaphragm plate of a filter press type dehydrator, and a liquid supply plate disposed between the filter cloths, the liquid supply plate having filtrate supply holes aligned with the filtrate supply holes of the filter cloths and penetrating in a plate thickness direction, and a filtrate outlet path extending from the filtrate supply holes to a lower end of the liquid supply plate,
A filter for a filter press type dehydrator, characterized in that the filtrate outflow passage of the liquid supply plate has a diameter that takes into consideration clogging due to sludge in the waste liquid, and a protective tube with slits is installed in the filtrate outflow passage. The filter for a filter press type dehydrator according to claim 1, characterized in that the material of the protective tube is selected taking into consideration the physical properties of the filtrate. 3. The filter for a filter press type dehydrator according to claim 1 , wherein the protective tube has a flange on the side of a filtrate supply hole.

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