JP6790874B2 - Pre-coated vacuum filtration device and filtration method - Google Patents

Description

The present invention relates to a pre-coated vacuum filtration device including a filter drum and a scraper, and a filtration method using the device.

As a means for obtaining a high-purity filtrate (treated water), for example, a precoat type vacuum filtration device provided with a stock solution tank, a filter drum, and a scraper means as shown in Patent Document 1 is known. This device can continuously perform high-purity filtration, but since the precoat layer formed on the filter drum must be peeled off little by little when processing the undiluted solution, precoating increases as the amount of undiluted solution processed increases. The amount of material used increases proportionally. An increase in the amount of precoat material used not only increases costs but also increases the amount of waste discharged. Therefore, it has been required to devise ways to reduce the amount of precoat material used.

Patent Document 2 describes the contents by a top feed method in which the undiluted solution is supplied from above the filter drum of the precoat type vacuum filtration device to perform the filtration process. In this method, even if the undiluted solution is pretreated to increase the flocs, filtration and adsorption can be performed. Therefore, the processing efficiency can be improved by increasing the concentration ratio and increasing the flocs. However, since the filtration stock solution is continuously poured in the axial direction on the upper surface of the filter drum, the flocs may adhere to the filter drum in a mottled manner depending on the size of the flocs, and the dehydrated cake layer may form a uniform thickness. This was not possible, and the effect of reducing the amount of precoat material used was not achieved.

JP-A-2010-234325 Japanese Unexamined Patent Publication No. 8-38818

An object of the present invention is a precoat type vacuum filtration device provided with a filter drum and a scraper, which can reduce the amount of precoat material used and the amount of waste discharged by efficiently filtering the undiluted solution. It is to provide a formal vacuum filtration apparatus and a filtration method.

The precoat type vacuum filtration device in the present invention is a precoat type vacuum filtration device provided with a filter drum and a scraper, and a top feed unit for supplying the undiluted solution to the filter drum is provided above the filter drum to provide a top feed. The unit is characterized in that the sealing member is in contact with the precoat layer or the cake layer formed on the filter drum.

Since the sealing member of the top feed unit is in contact with the precoat layer or the cake layer formed on the filter drum, the undiluted solution can be formed as the cake layer in a uniform state on the surface of the precoat layer.

Preferably, the pre-coated vacuum filtration device of the present invention is characterized in that a liquid pool portion is formed between the sealing member and the pre-coated layer or the cake layer.

By forming a liquid pool portion between the sealing member and the precoat layer or the cake layer, it is possible to form the cake layer on the surface of the precoat layer in a more uniform state and to make the cake layer thicker. Become.

Further, preferably, in the precoat type vacuum filtration device of the present invention, the top feed unit is provided with a movable member so that the top feed unit can be brought into contact with the thickness of the precoat layer or the cake layer. It is a feature.

Since the precoat layer formed on the filter drum and the cake layer obtained by dehydrating the undiluted solution are scraped off by the scraper, the thickness of the layer becomes thinner as the precoat type vacuum filtration device operates. By moving the top feed unit according to the thickness of the precoat layer or the cake layer, the seal member of the top feed unit can always be in contact with the precoat layer or the cake layer.

The precoat type vacuum filtration method in the present invention includes a coagulation step in which the stock solution is reacted with a polymer flocculant, a precipitation separation step in which the supernatant is separated into a supernatant liquid and a sedimentation part liquid in a settling tank after the coagulation step, and a precoat type of the supernatant. The first filtration step in which vacuum filtration is performed by the precoat type vacuum filtration device after supplying to the processing tank of the vacuum filtration device, and vacuum by the precoat type vacuum filtration device after supplying the settling part liquid to the top feed unit of the precoat type vacuum filtration device. It is characterized in that the undiluted solution is treated by a second filtration step of filtering.

By separately vacuum-filtering the supernatant liquid and the sedimentation part liquid generated in the precipitation separation step with a precoat type vacuum filtration device, it is possible to perform efficient filtration processing while suppressing the amount of precoat material used. Become.

Preferably, the pre-coated vacuum filtration method of the present invention is characterized in that vacuum filtration is performed in the first filtration step without operating the scraper.

In the first filtration step, the supernatant liquid is filtered, so that the cake layer becomes thin. If the scraper is operated in this state, the precoat layer is scraped by the scraper even though the precoat layer has the filtering ability, which causes waste. In the present invention, when the precoat layer has a filtration capacity, vacuum filtration is performed without operating the scraper, so that it is possible to perform a filtration process in which the amount of the precoat material used is further reduced.

Further, preferably, the precoat type vacuum filtration method in the present invention is characterized in that the first filtration step and the second filtration step are alternately performed.

As described above, according to the present invention, in the precoat type vacuum filtration device provided with the filter drum and the scraper, the undiluted solution is efficiently filtered to reduce the amount of the precoat material used and the amount of waste discharged. be able to.

It is a front view of the precoat type vacuum filtration apparatus used in this invention. It is a partial cross-sectional front view of the precoat type vacuum filtration apparatus used in this invention. It is an enlarged view of the top feed unit part in FIG. It is a perspective view of the top feed unit used in this invention. It is a front view of the top feed unit used in this invention. It is a perspective view of another form of the top feed unit used in this invention. It is a front view of the precoat type vacuum filtration apparatus by the top feed unit of FIG. It is a partial cross-sectional front view of the precoat type vacuum filtration apparatus by the top feed unit of FIG. It is an overall view which shows an example of the filtration system using the precoat type vacuum filtration apparatus of this invention.

The pre-coated vacuum filtration device used in the present invention will be described with reference to FIGS. 1 to 3. The basic configuration is that the processing tank 13 is arranged on the lower side of the filter drum 12 and the scraper 14 is arranged on the side surface of the filter drum 12, as in the conventional precoated vacuum filtration device. The top feed unit 15 used in the present invention is arranged above the filter drum 12.

The filter drum 12 has a cylindrical shape, and a precoat layer 21 acting as a filtration filter is formed on the outer peripheral surface of the filter drum 12, and then the undiluted solution is filtered. Since the inside of the filter drum 12 is decompressed by a vacuum pump, filtration by solid-liquid separation is possible on the surface of the precoat layer. The precoat material for forming the precoat layer is not particularly limited, but for example, diatomaceous earth, pearlite, or the like can be used.

As described in Patent Document 1 of the prior art document, the treatment tank 13 is a tank for introducing a precoat liquid for forming a precoat layer on the outer peripheral surface of the filter drum 12, and is a coagulation precipitate. It is also a tank for introducing the supernatant liquid separated by the tank and performing filtration treatment. In the present invention, when the undiluted solution is filtered by the top feed unit, the inside of the treatment tank 13 is emptied. The amount of liquid in the treatment tank 13 is controlled by a level switch so as not to overflow.

The top feed unit 15 is a unit for introducing the undiluted solution into the filter drum 12. The mounting position of the top feed unit 15 is above the horizontal line passing through the rotation axis at the center of the filter drum 12. However, the larger the size of the flocs produced by agglomerating the undiluted solution, the higher the processing efficiency. Therefore, the flocs should be located as high as possible above the filter drum so that filtration and adsorption can be performed even if the flocs are large. Is preferable.

The top feed unit 15 will be described with reference to FIGS. 3 to 5. The top feed unit 15 is basically composed of a feed box 34 and a sealing member 32 for receiving the supply of the undiluted solution and sending it to the filter drum. The seal member 32 is arranged so as to be parallel to the axial direction of the filter drum 12 and in contact with the outer peripheral surface of the filter drum 12. The shape of the seal member 32 is preferably a round bar, but is not particularly limited, and may be a sheet shape such as a flat plate. Although metal can be used as the material, rubber is preferable because it is advantageous in terms of adhesion. Further, the surface of the metal may be covered with rubber. It is preferable that the end face of the feed box 34 through which the undiluted solution flows is provided with a weir 35 for uniformly supplying the undiluted solution to the filter drum.

The top feed unit moves by its own weight so that the seal member 32 of the top feed unit can come into contact with the thickness of the precoat layer or the cake layer formed on the outer peripheral surface of the filter drum 12. It is preferable to include the movable member 31. The movable member 31 may be movable with as little resistance as possible by providing a bearing in the movable member so as to be in contact with the precoat layer or the cake layer on the filter drum 12 due to its own weight. If there is, there is no particular limitation. For example, the movable member 31 of the top feed unit may be brought into contact with the thickness of the precoat layer or the cake layer formed on the outer peripheral surface of the filter drum 12 by the rotational movement with the axis as the fulcrum. The movable member 31 shown in FIG. 3 is provided at the lower part of the feed box 34, and a round bar is inserted into each of the two holes, and the round bar slides in the direction of the filter drum while rotating due to the weight of the top feed unit. It can be moved while.

Next, the liquid pool portion 51 formed between the seal member of the top feed unit and the precoat layer or the cake layer will be described with reference to FIG. The liquid pool portion 51 is formed by collecting the stock liquid between the seal member 32 and the precoat layer 21 or the cake layer 22 when the stock liquid flows from the feed box 34 of the top feed unit to the seal member 32. .. The formation of the liquid pool makes it possible to form a more uniform and thick cake layer.

The scraper 14 shown in FIG. 1 is for scraping off the precoat layer 21 on the filter drum 12 and the cake layer 22 formed by filtering the stock solution. By this operation, the precoat layer 21 is constantly refreshed, and the undiluted solution can be filtered on the precoat layer without deteriorating the filtration performance. When the precoat layer is formed on the filter drum or when the supernatant liquid separated by the coagulation sedimentation tank is treated, the scraper can be retracted to a position where it does not come into contact with the precoat layer.

Next, the processing flow of the precoat type vacuum filtration device by the top feed unit will be described with reference to FIGS. 1 to 3. The inside of the processing tank 13 is emptied in advance, the inside of the filter drum 12 is decompressed, and the filter drum 12 is rotated clockwise in FIG. After that, when the undiluted solution is poured into the feed box 34 of the top feed unit 15 at the upper part of the precoat type vacuum filtration device by a pump, the undiluted solution flows from the feed box 34 over the weir 35 onto the filter drum. The undiluted solution that has flowed onto the filter drum comes into contact with the seal member 32 of the top feed unit, and the undiluted solution is uniformly distributed in the rotation axis direction on the filter drum. Here, when the liquid pool portion 51 is formed in the space between the filter drum and the seal member, a more uniform and thick cake layer is formed. In this state, the filter drum continues to rotate, but during that time, the cake layer on the filter drum is in a state where filtration is maintained, and the water content of the cake layer decreases with time. After that, at the scraper installation position, the cake layer and the precoat layer are scraped off to refresh the surface of the filter drum. By rotating the filter drum, the above operation can be repeated, and the undiluted solution can be continuously filtered. Compared with the method of Patent Document 1 of the prior art document, the vacuum filtration device using the top feed unit of the present invention has a filter drum in the direction of gravity of the stock solution, so that there is a large floc in the stock solution. However, the filtration process can be performed without any problem, and the cake layer is easily formed thick. Since the filtration efficiency is improved by using the top feed unit in this way, the amount of the precoat material used for forming the precoat layer can be suppressed, which makes it possible to reduce the amount of waste discharged.

FIG. 6 shows another form of the top feed unit. The components of the top feed unit 16 are the same as those of the top feed unit 15, but by slightly increasing the distance between the feed box 44 to which the undiluted solution is supplied and the sealing member 42, until the undiluted solution reaches the sealing member 42. Since the contact area with the filter drum is increased, the amount of undiluted solution processed can be increased. The end face of the feed box 44 through which the undiluted solution flows is preferably provided with a weir 45 that evenly supplies the undiluted solution to the filter drum. If the shape is sawtooth-shaped, even a large flock can be provided. The supply of the undiluted solution to the filter drum 12 is stable. The movable member 41 is provided at one end of the feed box 44, and in a simple structure, the top feed unit 16 can move up and down around the movable member 41 by passing thin rods through three holes. However, the movable member 41 may be on the side surface of the top feed unit as in the top feed unit 15.

The processing flow of the precoat type vacuum filtration device by the top feed unit 16 will be described with reference to FIGS. 7 and 8. The difference from the top feed unit 15 shown in FIG. 2 is that the rotation direction of the filter drum is opposite and the direction of the blade of the scraper with respect to the filter drum is opposite. The inside of the processing tank 13 is emptied in advance, the inside of the filter drum 12 is decompressed, and the filter drum 12 is rotated counterclockwise as shown in FIG. After that, when the undiluted solution is poured into the feed box 44 of the top feed unit 16 at the upper part of the precoat type vacuum filtration device by a pump, the undiluted solution flows from the feed box 44 over the weir 45 onto the filter drum. The undiluted solution that has flowed onto the filter drum comes into contact with the seal member 42 of the top feed unit, and the undiluted solution is uniformly distributed in the rotation axis direction on the filter drum. Here, when the liquid pool portion 51 is formed in the space between the filter drum and the seal member, a more uniform and thick cake layer is formed. In this state, the filter drum continues to rotate, but during that time, the cake layer on the filter drum is in a state where filtration is maintained, and the water content of the cake layer decreases with time. After that, at the scraper installation position, the cake layer and the precoat layer are scraped off to refresh the surface of the filter drum.

Next, the pre-coated vacuum filtration method of the present invention will be described with reference to FIG. First, in order to prepare for filtration of the precoat type vacuum filtration device 11, an operation of forming a precoat layer on the filter drum 12 is performed. As a procedure, a precoat liquid in which the precoat material is dispersed with water is prepared in the precoat tank 64, and the liquid is pumped from the precoat tank 64 to the treatment tank 13 provided in the lower part of the precoat type vacuum filtration device 11. Next, the inside of the filter drum 12 is depressurized by the vacuum pump 68 connected to the precoat type vacuum filtration device 11, and the filter drum 12 is rotated to form a precoat layer on the outer peripheral surface of the filter drum 12.

Next, the steps from flock formation of the stock solution to precipitation separation will be described. The undiluted solution is charged into the undiluted solution reaction tank 65, and is charged into the undiluted solution reaction tank 65 from the inorganic coagulant tank A61 in which the inorganic coagulant is dispersed and the inorganic coagulant tank B62, respectively. For example, an alkaline solution of slaked lime is stored in the inorganic coagulant tank A, and for example, a sulfate band, PAC, etc. are stored in the inorganic coagulant tank B. After the reaction in the stock solution reaction tank 65, the liquid is pumped from the stock solution reaction tank 65 to the polymer coagulation tank 66. In the polymer flocculant tank 66, the polymer flocculant is charged from the polymer flocculant tank 63, and large flocs are formed by stirring. After that, the liquid is sent from the polymer coagulation tank 66 to the coagulation sedimentation tank 67, and is separated into the supernatant liquid and the sedimentation portion liquid by natural sedimentation in the coagulation sedimentation tank 67.

Next, the process proceeds to the first filtration step by the precoat type vacuum filtration device 11. The first filtration step performs the following processing. The supernatant liquid in the coagulation sedimentation tank 67 is pumped to the treatment tank 13 of the precoat type vacuum filtration device 11. After that, the supernatant liquid in the processing tank 13 is filtered while rotating the filter drum 13. As a result, a cake layer is formed on the precoat layer. At this time, the cake layer including the precoat layer can be scraped off by the scraper 14, but due to the low SS concentration of the supernatant liquid, if the cake layer is thin in one rotation of the filter drum and still has filtration capacity, It is also possible to rotate the filter drum several times to increase the thickness of the cake layer. In this case, vacuum filtration is performed while rotating the filter drum without operating the scraper. By performing such an operation, it is not necessary to wastefully scrape off the precoat layer.

After the first filtration step, the process moves to the second filtration step. The second filtration step performs the following processing. The supernatant liquid in the treatment tank 13 is sent to the coagulation sedimentation tank 67 to empty the treatment tank 13. After that, the settling portion liquid in the coagulation settling tank 67 is transferred to the top feed unit 15 on the upper part of the precoat type vacuum filtration device 11 by a pump. When the sedimentation part liquid is poured into the top feed unit, the space between the top feed unit and the filter drum is in a state where the stock solution can be held, so that the stock solution collects here and forms a liquid pool part. When the filter drum is moved in this state, a cake layer formed by filtration of the settling portion liquid is formed on the precoat layer on the filter drum or the cake layer formed by filtering the supernatant liquid in the coagulation sedimentation tank 67. It is formed in a uniform state. Then, the cake layer and the precoat layer are scraped off at the place where the scraper is installed by the rotation of the filter drum, and the filtration surface of the filter drum is refreshed. After the second filtration step of filtering a certain amount of the settling part liquid, the supply of the settling part liquid to the top feed unit can be stopped, and the process proceeds to the first filtration step again to continue the filtration operation. .. Alternating the first filtration step and the second filtration step is the most efficient in terms of the amount of precoat material used. However, depending on the state of the stock solution, it is possible to perform filtration only in the second filtration step.

11 Pre-coated vacuum filtration device 12 Filter drum 13 Processing tank 14 Scraper 15, 16 Top feed unit 21 Pre-coated layer 22 Cake layer 31, 41 Movable members 32, 42 Sealing members 51 Liquid pool 61 Inorganic coagulant tank A
62 Inorganic coagulant tank B
63 Polymer coagulant tank 64 Precoat tank 65 Undiluted solution reaction tank 66 Polymer coagulant tank 67 Coagulation sedimentation tank 68 Vacuum pump

Claims (3)

A pre-coated vacuum filter equipped with a filter drum and a scraper.
A top feed unit for supplying the undiluted solution to the filter drum is provided above the filter drum at a position different from the scraper .
A pre-coated vacuum filtration device characterized in that the sealing member of the top feed unit is in contact with a pre-coated layer or a cake layer formed on the filter drum. The precoated vacuum filtration device according to claim 1, wherein a liquid pool portion is formed between the sealing member and the precoat layer or the cake layer. The first or second aspect of the invention, wherein the top feed unit is provided with a movable member so that the top feed unit can be brought into contact with the precoat layer or the cake layer according to the thickness of the cake layer. The precoated vacuum filtration device described.