JP3824056B2 - Filtration method and filter apparatus for filter press - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a filter press suitable for the treatment of clean water sludge, sewage sludge, industrial wastewater sludge and the like, and in particular, after a precoat layer is formed with a filter aid in a filter chamber formed between filter plates, The present invention relates to a filtration method of a filter press in which a filter is pressed and dewatered, and an improvement of the filtration device.
[0002]
[Prior art]
Conventionally, a filter press in which a filtration chamber is formed between a large number of filter plates arranged in an openable / closable manner, and the stock solution is press-fitted into the filtration chamber to perform filtration and dehydration is well known. Incompressible cakes are more advantageous and are widely used as solid-liquid separators. For example, Japanese Patent No. 2640960 discloses an operation technique for producing a precoat layer with diatomaceous earth on a filter cloth suspended in a filter chamber of a filter press, accumulating sludge in the stock solution, and clarifying and filtering extracts such as pharmaceuticals. Known as described. Further, instead of a filter press filter cloth, a filter plate in which a metal mesh is stretched on a filter bed as a filter medium has been proposed by the applicant of the present invention as described in, for example, Japanese Utility Model Laid-Open No. 5-13506. .
[0003]
[Problems to be solved by the invention]
In the case of using a filter cloth in the above conventional filter press, even if the filter cloth is washed, fine particles are fixed to the eyes of the filter cloth, crystals are deposited repeatedly, and the filtration capacity is reduced due to clogging. Was. Moreover, the filter cloth suspended in the filtration chamber by the injection of the stock solution was not restored due to shrinkage and shape, and the filter cloth had to be replaced. And in the filter press that coats diatomaceous earth on the filter cloth surface, it is possible to perform clarification filtration of extract extract etc. in the stock solution, but there is a risk that the discarded cake will be increased with expensive diatomaceous earth and become an environmental problem was there. In addition, filter media using metal mesh are less clogged and have better durability compared to filter cloth, but when the cake pressure density increases, the cake bites into the filter media and the peelability of the cake. There was a risk of getting worse. This invention does not use costly diatomaceous earth, etc., and recycles wastes such as dehydrated cakes and other types of cakes generated in the dehydration system to be used as a pre-coating material. A press is provided.
[0004]
[Means for Solving the Problems]
The gist of the present invention is that a filtration chamber is formed between a large number of filter plates arranged in parallel to be openable and closable, a precoat layer is generated with a filter aid on the filter medium surface of the filtration chamber, and then the stock solution is supplied to the filtration chamber for filtration. In a filter press that performs dehydration, a stock solution containing suspended solids is dehydrated by a dehydrator, and the dehydrated cake A is heated, and the dried cake is separated by a 250-500 mesh sieve, and is in the form of a powdery dried cake or baked cake Of the cake press is supplied to the filter chamber of the filter press to form a pre-coat layer of fine particles on the surface of the filter media, and then the stock solution is supplied to the filter chamber to perform filter dehydration. This is a filtration method, in which fine particles of a dry cake can be used as a precoat material. Therefore, the dehydrated cake is recycled into a precoat material that is inexpensive and suitable for the environment, and there is no increase in the amount of cake that is discharged.
[0005]
Specifically, the dehydrated cake is indirectly heated with steam at 120 to 150 ° C., the dehydrated cake is dried, and the fine particles of the dried cake whose particle size is adjusted are mixed with water, and the filtration area is added to the filtration chamber. A precoat layer having a fine pore size of 0.2 to 1.5 kg / m @ 2 is produced on the filter medium surface, and a dry cake having a particle diameter larger than the filter medium pore diameter is used to form a precoat layer having a small pore diameter in the filtration chamber. Since it can be made, a clear filtrate can be secured and the filter medium surface is not clogged. And since a particle | grain larger than the hole diameter of a filter medium surface is coated on a filter medium surface as a precoat layer, there is no biting into a filter medium surface and a cake can be peeled easily. In place of the indirect heating, the dehydrated cake may be directly heated with hot air of 100 to 1000 ° C. to obtain a dried cake. Moreover, if the dehydrated cake is directly heated with hot air of 300 to 1200 ° C. to burn or carbonize the organic matter in the solid material to obtain a baked cake, the water permeability of the precoat layer is improved and the strength is increased. is there. And when there are few fine powdery dried cakes or baked cakes generate | occur | produced at the time of heat drying, after crushing the said dewatering cake and adjusting a particle size, it is good also as a dried cake or a baked cake.
[0006]
A device that performs the above filtration method forms a filtration chamber between a number of filter plates arranged in parallel to be openable and closable, and after generating a precoat layer with a filter aid on the filter medium surface of this filtration chamber, the stock solution is supplied to the filtration chamber In a filter press that performs filtration and dehydration, a dehydrator that dehydrates suspended substances in the stock solution, a dryer that heats and dehydrates the dehydrated cake, and a 250 to 500 mesh sieving machine that separates the generated powdery dry cake And a mixing tank for mixing the separated powdery dry cake with water, and connecting this mixing tank to a feed pipe for a stock solution of a filter press to supply mixed water of the dry cake from the mixing tank to the filtration chamber. This is a filtration device that generates a pre-coat layer of fine particles of 0.2 to 1.5 kg / m @ 2 per filtration area on the filter medium surface, and then supplies the stock solution from the sludge storage tank to the filtration chamber for filtration and dehydration. A crusher for crushing the dehydrated cake may be provided, and after adjusting the particle size of the dehydrated cake, the crushed dehydrated cake may be supplied to a dryer and heated.
[0007]
If the filter medium in the filtration chamber for pre-coating the crushed cake is a metal filter medium stretched on the filter bed of the filter plate, the life of the filter medium will be prolonged, and the discarded filter medium can be recycled. Further, if the filter medium is a filter cloth suspended between the filter plates, SS is less likely to accumulate on the filter cloth due to the precoat layer, and the life of the filter cloth can be kept long. Then, if the filter medium is a wedge wire stretched on the filter bed of the filter plate, and the slit side of the wedge wire is the filter medium surface and the slit is arranged in the vertical direction, the slit surface is difficult to clog, and the peelability of the cake In other words, there is no deformation or shrinkage and the dimensional stability is excellent. In the case of a stock solution containing a large amount of organic matter, a vibration device may be provided above the filter plate on which the filter cloth is suspended, and the filter plate may be opened to vibrate the support bar of the filter cloth. In addition, a scraper that can be raised and lowered is arranged above the parallel filter plates, and the dewatered cake generated on the filter medium surface of the filter chamber by sliding the scraper against the filter medium surface of the filter medium and the filter medium surface of the filter plate is formed. It may be discharged.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The filtering method and apparatus of the filter press according to the present invention are configured as described above, and a flocculant is added to purified water sludge, sewage sludge, or industrial wastewater as necessary, and the stock solution is converted into a metal. When filtered through a filter medium or filter cloth, viscous particles and organic matter are dehydrated into solid form. Cakes with a high water content that have been filtered with a vacuum filtration pressure such as a vacuum filter or belt filter will return to slurry when soaked in water, but dried cakes that have been dried even with soft dehydrated cakes, or baked baked cakes The cake shrinks to increase the binding force, and the hydrophobicity is further increased. Even if the fine particles in the plastic state are immersed in water for a considerable period of time, they will return to a slurry state and will not deliquesce. If the dried cake or baked cake fine particles are used as a pre-coat material for a filter press, the fine particles become hydrophobic and strong, and even if the supplied stock solution is pressed under high pressure, the pre-coat layer will eat into the filter media. With no exfoliation. And by interposing between a filter medium and a dewatering cake, it also plays the role which helps the support material and water permeability of filtration, and can achieve the same peeling improvement effect as diatomaceous earth.
[0009]
Next, when the separated powdered dry cake or baked cake is mixed with the stock solution, filtrate, or tap water, and this mixed water is supplied to the filter chamber of the filter press, a hydrophobic cake with a metal filter medium or filter cloth is used. The fine particles are captured and a precoat layer is formed on the filter medium surface. This precoat layer can be made into a precoat layer having a smaller pore size by using a dry cake or a baked cake having a particle size larger than the pore size of the filter medium. Next, when the stock solution is pressed into the filter chamber of the filter press, the turbidity in the stock solution is captured by the precoat layer of fine particles generated on the filter medium surface of the metal filter medium or filter cloth, and clarification filtration is performed. The target stock solution is filtered through a precoat layer having a pore size smaller than the pore size of the filter medium, and the clarification is higher than that of direct filter medium filtration. The suspended particles do not pass through the precoat layer, and SS does not accumulate on the filter medium surface of the metal filter medium or filter cloth and the filtrate flow path of the filter plate, and the cake formed in the filtration chamber is formed by the fine particle precoat layer. Easy to peel off. In addition, in the case of using a wedge wire as a filter medium, the surface of the wedge wire is pre-coated with a fine particle pre-coating layer having a particle size larger than that of the slit, and hydrophobic fine particles are eaten into the wedge wire slit even at high pressure density. In other words, the peelability is maintained.
[0010]
【Example】
The filter device of the filter press according to the present invention will be described in detail with reference to the drawings. First, FIG. 1 is a flow chart of the filter device, and the filter press 1 for filtering and dehydrating the stock solution is supported on the front and rear frames 2 and 3. On the guide rail 4, the filter plates 5 are arranged in parallel so as to be freely opened and closed. In the embodiment of the filter plate shown in FIG. 2, a metal filter medium 6 is stretched on the filter bed 5 a of the filter plate 5, and a filtration chamber 7 is formed between the filter plates 5 and 5. As shown in FIG. 1, the sludge in the sludge storage tank 8 is press-fitted into the filtration chamber 7 of the filter press 1 by the press-fitting pump 9, and the stock solution press-fitted into the filtration chamber 7 from the stock solution supply path 10 of the filter plate 5 Solid-liquid separation is performed with the metal filter medium 6, and the filtrate is taken out from the filtrate hole 11 communicating with the filtration bed 5a. The dehydrated cake A captured by the metal filter medium 6 in the filtration chamber 7 is opened on the filter plate 5, discharged onto the conveyor 12, transported to the quantitative feeder 13, and while quantitatively supplying the dehydrated cake A with the quantitative feeder 13, The particle size is adjusted by crushing with a crusher 14. In addition, the metal filter medium 6 has good peelability of the cake, is durable, has a long life, and can be recycled at the time of disposal.
[0011]
The crushed cake is supplied to the dryer 16 with the supply feeder 15, and while the dehydrated cake A is indirectly heated with steam at 120 to 150 ° C., the stirring and rolling are repeated, and drying is performed while granulating and heat transfer heating. The granulated dry cake C is fractionated by a sieve separator 17 having an opening of about 250 mesh and the fine particles of the dry cake C are stored in the cake hopper 18. Also, instead of indirect heating, the dehydrated cake A is directly heated with hot air of 100 to 1000 ° C. to dry cake B, or the dehydrated cake A is directly heated with hot air of 300 to 1200 ° C. An organic substance in a solid material may be burned or carbonized to obtain a baked cake C. If the dehydrated cake A to be heated is a baked cake C, it becomes fine cake particles having a large porosity and strength. In addition, in the cake in which many fine particles are contained in the dried cake B and the baked cake C heated with the dryer, it is not necessary to adjust a particle size with the crusher 14. FIG.
[0012]
The fine particles of the dried cake B and the baked cake C are put into the mixing tank 19 and stirred and mixed with water, and the mixed water of fine particles 1.5 to 3.0 times the volume of the filtration chamber is the surface of the filter medium 7 It is the amount of liquid that can be coated on the whole. The supplied water can be tap water, filtrate, or stock solution. The powdery fine particles of the dried cake B and the baked cake C have a higher binding force due to shrinkage and become more hydrophobic, so that they do not return to a slurry or deliquesce even when immersed in water. A liquid supply pipe 20 of the mixing tank 19 is connected to a raw liquid supply pipe 21 of the filter press 1 through a supply pump 22, and mixed water containing cake fine particles is supplied from the mixing tank 19 to the filtration chamber 7. A precoat layer of fine particles of 0.2 to 1.5 kg / m 2 per area is formed on the filter medium surface of the metal filter medium 6. A cake with a particle size larger than the filter media pore size can be used to make a precoat layer with a smaller pore size.
[0013]
Next, the stock solution is supplied from the sludge storage tank 8 to the filtration chamber 7 where the precoat layer is generated, and the filter press 1 is subjected to filtration dewatering. Particles larger than the filter medium pore diameter of the metal filter medium 6 are used as the precoat layer. Since the surface is coated, clogging is eliminated because there is no biting into the metal filter medium, and the dewatered cake A can be easily peeled off. In actual filtration, the particle size distribution of the filter medium to be used and the particle size distribution of the filtrate stock solution is taken into consideration, and the particle size of the fine particles of the dried cake B and the baked cake C used for the pre-coating is determined. For example, if a filter medium having a pore size of 50 μm is precoated with an auxiliary agent of about 70 to 100 μm, assuming that the auxiliary agent is spherical, the precoat layer has a pore size of about 1/3 of the particle size, so that it is 25 to 30 μm. The pore diameter is about half that of the filter medium. V1 and V2 are open / close valves provided in the raw solution supply pipe 21 and the liquid supply pipe 20 from the mixing tank 19. The cake used as the precoat material may be the cake of the filter press itself that performs filtration and dewatering, but the cake of a filter press, screw press, or vacuum filter that treats the raw water of other drainage systems is used. You may do it. Further, the remaining dried cake B or baked cake C used as a coating material after being dried or baked is effectively used for gardening, adsorbent, construction material, or the like.
[0014]
When polyaluminum chloride or sulfuric acid band is added to water purification sludge, sewage sludge, or industrial wastewater as a flocculant, turbidity is agglomerated due to the adhesive strength of aluminum hydroxide and the positive charge of aluminum. The stock solution contains several percent of suspended matter. When this stock solution is dehydrated by the filter press 1, the hydrophilic layer of aluminum hydroxide is also destroyed, the charge of the particles is completely neutralized, and the hydrophilic force that attracts water to the outside is weakened and becomes hydrophobic. And if this dehydrated cake A is dried or made into a baked state, the cake shrinks to further increase the binding force, resulting in a dried cake B or baked cake C having a stronger hydrophobicity, and even if immersed in water for a long time. It will not dissolve. If these fine particles are used as a coating material, the fine particles of the dried cake B or the baked cake C can form a strong precoat layer on the filter medium surface of the filtration chamber 7.
[0015]
FIG. 3 shows another embodiment of the filter medium disposed on the filter plate. A spring 24 is inserted into the support rods 23, 23 erected on the shoulder of the filter plate 5, and a support bar 25 is inserted into the support rod 23. A filter cloth 26 is suspended from the support bar 25 so as to be swingable. As shown in FIG. 4, a vibrating device 27 is disposed along the parallel filter plates 5... And the vibrating device 27 is applied to the bottom of both ends of the support bar 25 on which the filter cloth 26 is suspended. The vibration shaft 28 includes a vibrator 29 attached to the vibration shaft 28. Then, the filter plate 5 is opened, the vibration shaft 28 is vibrated by the vibrator 29, the support bar 25 of the filter cloth 26 is vibrated, and the dewatered cake A sandwiched between the filter cloths 26 and 26 is peeled off. It is like that.
[0016]
FIG. 5 shows another embodiment of the filter medium stretched on the filter plate. A punching metal 30 is laid on the filter bed 5 a of the filter plate 5, and a wedge wire 31 is stretched on the upper surface of the punching metal 30. The slit side of the wedge wire 31 is used as a filter medium surface, the slit is arranged in the vertical direction, and the wedge-shaped tip of the wedge wire 31 is abutted against the filtration bed 5a of the filter plate 5, and the wedge wire 31 is expanded in the shape of a wedge toward the back surface, and the discharge of the filtrate becomes good. Further, fine particles of a dried cake or a baked cake having a particle size larger than that of the slit form a precoat layer, and even at a high pressure density, the crushed cake does not bite into the slit of the wedge wire, and the peelability can be maintained. The metal filter medium 6 may be a metal screen or a wire mesh in addition to the wedge wire 31.
[0017]
FIG. 6 shows another embodiment of the peeling apparatus, in which a cylinder 33 supported on a gantry 32 is suspended above parallel filter plates 5... And a spring 35 is attached to the tip of a piston rod 34 of the cylinder 33. A biased scraper 36 is provided. And it is made to fall between the filter plates 5 and 5 before and after opening, and it is made to slidably contact with the wedge wire 31 stretched around the filter plate 5, and the cake A of the filtration chamber 7 is peeled off. Further, a cleaning tube 37 hangs down from the gantry 32 so as to clean the slit surface of the wedge wire 31 from which the cake A has been peeled off. In addition, this peeling apparatus can be used also for the filter cloth 26 suspended between the filter plates 5 and 5 shown in FIG. Further, the vibration device 27 shown in FIG. 4 may be disposed on the filter plate 5 on which the metal filter medium 6 is stretched.
[0018]
【The invention's effect】
As described above, the filtering method of the filter press and the filtration device of the present invention do not use expensive diatomaceous earth or the like, and use wastes such as dehydrated cakes and other types of cakes generated in the dehydration system as a precoat material. It is a cheap and suitable filter press for the environment. That is, the filter cloth used in the conventional filter press has to be replaced by contraction or deformation of the filter cloth and a decrease in the filtration capacity. In addition, in the case where the filter cloth is coated with diatomaceous earth, the amount of cake to be discarded is increased with diatomaceous earth, which may cause an environmental problem. And in the case of using a metal filter medium, if the cake pressure density becomes high, the cake bites into the filter medium and the peelability deteriorates. After supplying mixed water to the filter chamber of the filter press and generating a pre-coat layer of fine particles on the filter medium surface, the stock solution is supplied to the filter chamber for filtration dehydration, so the filter medium surface of the filter chamber has a small pore size. A precoat layer can be formed, which also serves to support the filtration support material and water permeability, and can provide the same peeling improvement effect as diatomaceous earth.
[0019]
The fine particles of the cake forming the precoat layer can be obtained by heating the dehydrated cake with steam at 120 to 150 ° C. or hot air at 100 to 1000 ° C. to dry cake, or baking the dehydrated cake with hot air at 300 to 1200 ° C. Since the cake is made into a cake, even a soft dehydrated cake shrinks by drying or baking to increase the binding force, further increase the hydrophobicity, and the fine particles change to a plastic state to become a strong filter medium. In addition, since a precoat layer of fine particles of 0.2 to 1.5 Kg / m @ 2 per filtration area of the filtration chamber is generated on the filter medium surface, a clear filtrate can be secured and clogging of the filter medium is eliminated. And even if the undiluted | stock solution to supply is high-pressure press-fit, a precoat layer will not bite into the filter-medium surface of a filtration chamber, and a peelability will not be worsened.
[0020]
If the filter medium surface of the filter chamber is made of a metal filter medium stretched on the filter bed of the filter plate, the filter medium life becomes longer and the discarded filter medium can be recycled. Moreover, if the filter cloth has the filter medium surface suspended between the filter plates, SS is less likely to accumulate on the filter cloth due to the precoat layer, and the life of the filter cloth can be kept long. Then, if the filter medium surface is a wedge wire stretched over the filter bed of the filter plate, and the slit side of this wedge wire is the filter medium surface and the slit is arranged in the vertical direction, the slit surface is difficult to clog, and the cake The releasability is also improved, and there is no deformation or shrinkage and the dimensional stability is excellent.
[Brief description of the drawings]
FIG. 1 is a flowchart of a filter device for a filter press according to the present invention.
FIG. 2 is also a partially cut perspective view of a filtration chamber in which a metal filter medium is stretched on a filter plate.
FIG. 3 is a perspective view of a filter plate in which a filter cloth is suspended.
FIG. 4 is also a front view of a filter plate provided with a vibration device.
FIG. 5 is also a longitudinal side view of a filtration chamber in which a wedge wire is stretched on a filter plate.
FIG. 6 is a side view of the scraper disposed between the filter plates.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Filter press 5 Filter board 5a Filtration bed 6 Metal filter medium 7 Filtration room 8 Sludge storage tank 14 Crusher 16 Dryer 17 Sieving machine 19 Mixing tank 21 Supply pipe 22 Supply pump 25 Support bar 26 Filter cloth 27 Excitation device 31 Wedge wire 36 Scraper A Dehydrated cake B Dry cake C Baking cake

Claims (12)

A filtration chamber (7) is formed between a large number of filter plates (5 ...) that can be freely opened and closed, and a precoat layer is formed on the filter medium surface of the filtration chamber (7) with a filter aid, and then the filtration chamber (7). In a filter press in which the stock solution is supplied to the filter for dehydration, the stock solution containing suspended solids is dehydrated with a dehydrator, the dehydrated cake (A) is heated, and the dried cake (B) is 250 to 500 mesh. Powdered dry cake (B) or baked cake (C) separated by sieving is mixed with water, and the mixed water of this cake is supplied to the filter chamber (7) of the filter press (1), and fine particles are formed on the filter medium surface. A filter press filtration method, characterized by producing a precoat layer. The dehydrated cake (A) is indirectly heated with steam at 120 to 150 ° C. to dry the dehydrated cake (A), and the fine particles of the dried cake (B) whose particle size is adjusted are mixed with water, and the filtration chamber ( 7. The filtration method of a filter press according to claim 1, wherein a precoat layer of fine particles of 0.2 to 1.5 kg / m @ 2 is produced on the filter medium surface in 7).   The filtration method of a filter press according to claim 2, wherein instead of the indirect heating, the dehydrated cake (A) is directly heated with hot air of 100 to 1000 ° C to obtain a dried cake (B).   Instead of the indirect heating, the dehydrated cake (A) is directly heated with hot air of 300 to 1200 ° C. to burn or carbonize the organic matter in the solid to obtain a baked cake (C). Item 3. A filter press filtration method according to Item 2.   The filtration method of a filter press according to any one of claims 1 to 4, wherein the dehydrated cake (A) is crushed to adjust the particle size and then heated. A filtration chamber (7) is formed between a large number of filter plates (5 ...) that can be freely opened and closed, and a precoat layer is formed on the filter medium surface of the filtration chamber (7) with a filter aid, and then the filtration chamber (7). In a filter press where the stock solution is fed to the filter for dehydration, a dehydrator for dehydrating suspended substances in the stock solution, a dryer (16) for heating and drying the dehydrated cake (A), and the generated dry powder cake A 250-500 mesh sieving machine (17) for separating (B) and a mixing tank (19) for mixing the separated powdered dry cake (B) with water are provided, and this mixing tank (19) is used as a filter. It connects with the supply pipe | tube (21) of the undiluted | stock solution of a press (1), the mixed water of a dry cake (B) is supplied to a filtration chamber (7) from a mixing tank (19), and 0.2-1. A precoat layer of 5Kg / m2 fine particles is formed on the filter medium surface. After that, the filter apparatus of the filter press characterized by supplying a stock solution from the sludge storage tank (8) to the filtration chamber (7) and performing filtration dehydration.   The crusher (14) for crushing the dehydrated cake (A) is provided, and after adjusting the particle size of the dehydrated cake (A), the dehydrated cake (A) is supplied to the dryer (16) and heated. Filter press filtration device.   The filter device of the filter press according to claim 6 or 7, wherein the filter medium in the filtration chamber (7) is a metal filter medium (6) stretched on the filter bed (5a) of the filter plate (5). .   The filter device of the filter press according to claim 6 or 7, wherein the filter medium in the filtration chamber (7) is a filter cloth (26, 26) suspended between the filter plates (5, 5).   A vibration device (27) is provided above the filter plate (5) on which the filter cloth (26) is suspended, and the filter plate (5) is opened to vibrate the support bar (25) of the filter cloth (26). The filter apparatus of the filter press of Claim 9 characterized by the above-mentioned.   The filter medium in the filtration chamber (7) is composed of a wedge wire (31) stretched on the filter bed (5a) of the filter plate (5). The filter device for a filter press according to any one of claims 6 to 8, wherein the filter device is disposed in a direction.   A scraper (36) that can be raised and lowered is disposed above the parallel filter plates (5 ...), and the scraper (36) is brought into sliding contact with the filter medium surface of the opened filter plate (5). Item 12. The filter press of the filter press according to Item 8 or 11.

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