JPH078718A - Filtering dehydrator - Google Patents

Abstract

PURPOSE:To enhance dehydration efficiency while preventing the back flow of a filtrate in a filter cloth direction by forming blind tube parts opened in a rotary shaft direction but not opened in a filtering surface direction to a filtering passage. CONSTITUTION:The interior of a rotary body 1 is divided into a plurality of sections and the interiors of the respective sections are depressurized or pressurized and the filtrate separated in a filtering dehydration process is collected. At this time, a back flow preventing filtrate sump 15 preventing the filtrate from again returning to filter cloth and a solid area is formed to the pipeline i.e., filtrate passage 14 guiding the filtrate to a filtrate receiving tank 8 through a filtrate discharge pipe. This filtrate sump 15 is opened to the filtrate passage 14 in a rotary shaft direction but not opened in a filtrate direction. Especially, the filtrate once passed through filter cloth is prevented from returning to the solid area at the time of the release of a bonded cake due to pressure purging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary filtration dehydrator for an aqueous suspension, and more particularly to a filtrate for separating a filtrate separated by filtration / dehydration and introducing the filtrate into a filtrate discharge pipe. The present invention relates to a filtration dehydrator capable of improving the dehydration efficiency by preventing backflow of the filtrate so that the solid content attached to the filtration surface does not absorb water again.

[0002]

BACKGROUND OF THE INVENTION The present inventors have replaced the centrifugal dehydrator widely used in dehydration of an aqueous suspension (hereinafter abbreviated as "suspension"), particularly a vinyl chloride polymer slurry. , For example, using a filter dehydrator with a rotating body,
It has been found that the water content of the polymer after the dehydration treatment can be remarkably lowered by setting the thickness of the solid content adhering to the filtration surface of the rotating body within a specific range, and a patent application has been filed. (Japanese Patent Application No. 3-2
(01782) In the rotary filtration dehydrator used in the application, the rotary body is divided into a plurality of sections, each of which is composed of sections capable of independently depressurizing and pressurizing, and the section and the rotary shaft. A pipe line for connecting the filtrate discharge pipe and the compressed air introduction pipe, which are arranged in the vicinity, via an automatic valve serves both as a filtrate passage and a compressed air passage. Therefore, the filtrate remaining on the inner wall of the pipe for this connection (hereinafter abbreviated as "filtrate passage") returns to the solid content adhering to the filter cloth due to its own weight or purging with compressed air and returns to the solid content. May absorb water again, and thus the desired dehydration efficiency may not be obtained.

[0003]

In view of the above points, the inventors of the present invention have investigated a method for ensuring the dehydration efficiency of a filtration dehydrator, and have openings in the filtrate passage in the direction of the rotation axis and openings in the direction of the filtration surface. By providing a blind pipe part (hereinafter abbreviated as “filtrate reservoir”) that is not provided to prevent the reverse flow of the filtrate toward the filter cloth, it is possible to improve the dehydration efficiency without hindering the discharge of air or the filtrate. Heading out, the present invention was reached.

That is, the gist of the present invention is to immerse the filtration surface in the suspension and suction the solid content of the suspension to the filtration surface by the negative pressure in the rotating body. Three steps are sequentially performed: a dehydration step of vacuum dehydration / aeration drying by negative pressure inside the rotating body outside the suspension, and a peeling step of separating adhered solids from the filtration surface by the purge pressure inside the rotating body. In a rotary filtration dehydrator, the rotating body is divided into a plurality of sections in the circumferential direction, and each of them is composed of sections that can be independently depressurized / pressurized, and these sections are arranged in the vicinity of the rotation axis. In the pipeline for connecting the filtrate discharge pipe and the compressed air introduction pipe via an automatic valve, there is a blind pipe portion that is opened in the rotation axis direction and is not opened in the filtration surface direction. Rotary filtration dehydrator,
Exist in.

The present invention will be described in more detail below. As the rotary filtration dehydrator used in the method of the present invention, a rotary dehydrator having a plurality of compartments capable of being depressurized or pressurized is used as the rotary filter dehydrator, and the rotary rotor is continuously rotated as the rotary body rotates. Which has a rotary drum called an Oliver type filter (for example, see “Chemical Engineering Handbook, 3rd edition, revised edition” p955 (1968, Maruzen Co., Ltd.)) Alternatively, a rotating disk sector type, etc., as described in JP-A-62-193609, can be used. In these rotary filtration dehydrators, the negative pressure inside the rotating body causes the solid content in the suspension to adhere to the filtering surface of the rotating body in the portion of the rotating body that is in suspension (filtering process). In the part where the body is above the liquid surface, the water content in the adhered solids is vacuum dehydrated and aerated by the negative pressure inside the rotor (dehydration process), and then compressed gas such as compressed air in the rotor. Is supplied to remove and collect the adhered cake (peeling step). The suspension can be supplied to the filtration / dehydration apparatus continuously or intermittently depending on the type of the filtration / dehydration machine.

According to the present invention, in the above filtration dehydrator, the filtrate separated from each compartment by filtration and dehydration is collected, and the filtrate discharge pipe (and the compressed air introduction pipe for purging) installed near the rotary shaft. A blind pipe part (filtrate reservoir) for preventing the reverse flow of the filtrate is provided in the filtrate passage for connecting to, so that the filtrate flows back to the filtration surface even when pressurized purging with compressed air or the like particularly in the cake peeling process. It is characterized by improving the dehydration efficiency by preventing the adhered solids from absorbing water again.

The present invention will be described with reference to the drawings using an Oliver type filter as an example. FIG. 1 is an explanatory view showing the outline of the filtration and dehydration apparatus of the present invention, and FIG.
FIG. 3 is an explanatory view illustrating each step of dehydration / separation, FIG. 3 is an explanatory view illustrating the structure and action of the filtrate reservoir, and FIGS. 4 and 5 are explanatory views illustrating cross-sectional views of the structure of the filtrate reservoir.

In the figure, reference numeral 1 is a rotating body of a filter dehydrator (hereinafter referred to as "vacuum drum"), a part of which is immersed in a suspension tank 2, and 3 is an endless filter wound around the vacuum drum 1. Cloth, 4
Is a stirrer for the suspension to be filtered, 5 is a scraper for scraping the cake, 6 is a cake receiver, 7 is a suspension supply pump, 8 is a filtrate receiving tank from the vacuum drum 1, 9
Is a vacuum pump, 10 is a filtrate extraction pump, 11 is an air compressor for producing compressed air for purging that is supplied to the vacuum drum in the cake stripping process, and 12 is filtrate discharge for transferring the filtrate from the vacuum drum to the filtrate receiving tank. A pipe, 13 is a pipe for introducing compressed air into a vacuum drum, and 14 is a pressure reducing or pressurizing inside of a plurality of divided compartments of the rotating body, and a filtrate separated in the filtering step and the dehydrating step is collected. A conduit for guiding the filtrate to the filtrate receiving tank 8 via the filtrate discharge pipe 12, that is, a filtrate passage, 15 is a filtrate backflow prevention for preventing the sucked filtrate from passing through the filter cloth and returning to the filter cloth and the solid content side again. Is a filtrate reservoir, 16 is an opening of the filtrate passage, and 17 is an opening for aeration and liquid passage.

Regarding the structure of the filtrate reservoir, when a funnel-shaped filtrate passage as shown in FIGS. 3 and 4, for example, is considered and divided into a liquid collecting part corresponding to the funnel head part and a liquid passing part corresponding to the funnel leg part, As a shape with a combination of similar funnels (but without legs) on the inside, and with a gap between the two funnels open only in the direction of the legs and the filter cloth side is closed. This gap may be used as the filtrate reservoir 13 (FIG. 4 is a cross-sectional view comparing the one without the filtrate reservoir with the one with the filtrate reservoir), or in a similar filtrate passage, as shown in FIG. , A blind tubular filtrate reservoir that is directly connected to the liquid passage part and is closed on the filter cloth side, and an opening for ventilation / liquid passage is provided near the side liquid passage part of the pipe (close to the leg part of the funnel). In addition, at least one of the openings has a shape that is at the base of this closed tube. Good.

The shape and size of the opening or the opening of the filtrate reservoir are not particularly limited so long as the surface tension of water prevents the trapped water from being discharged, that is, the so-called capillary effect does not occur. There is no limitation. The operation of the device of the present invention will be specifically described. In order to simplify the explanation, as described above, attention is paid to a part of the vacuum drum, which is a process that is actually performed at the same time depending on the part of the vacuum drum, and the part performs continuous processing as the drum rotates. Described as a state.

When the portion of interest of the vacuum drum enters the suspension tank 2 as the vacuum drum 1 rotates, the negative pressure in the vacuum drum 1 generated by the operation of the vacuum pump 9 causes the solid content in the suspension to be increased. Are attached to the filter cloth 3 on the filtering surface (filtering step). When the portion comes out of the suspension surface due to the rotation of the drum, the negative pressure inside the vacuum drum causes the moisture in the adhered solids to be vacuum dehydrated and dried by aeration (dehydration step). Next, compressed air is fed into the vacuum drum, and the adhered cake is peeled off by the compressed air and the scraping plate 5.
The cake is collected in the cake receiver 6 (peeling step). On the other hand, the filtrate that has passed through the filter cloth in the filtration / dehydration process (direction A → B in FIG. 3) is
The vacuum drum 1 is guided to the filtrate discharge pipe 12 through the filtrate passage.
And is stored in the filtrate receiving tank 8 and further transferred from the filtrate receiving tank to the outside of the system by the filtrate extracting pump 10. At this time, the filtrate remaining on the wall of the filtrate passage is
Due to its own weight and purging with compressed air during the cake peeling process, it tends to return to the solid content side (B → A direction) attached to the filter cloth. The returned filtrate is trapped in the backflow preventing filtrate reservoir 15 to prevent moisture absorption of the solid content. The captured filtrate is collected again in the filtrate receiving tank in the next filtration step or dehydration step.

A rotary filtration dehydrator having a filtrate reservoir of the present invention is used to suspend vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable therewith in an aqueous medium using an oil-soluble polymerization initiator. The average particle size obtained by polymerization is 70 to 25.
When used for dehydration of a vinyl chloride polymer slurry having a range of 0 μm, the dehydration efficiency is good, the power consumption can be reduced as compared with the conventional centrifugal dehydrator, and vinyl chloride remaining after dehydration is used. It is particularly effective because it can reduce the amount of the monomer.

When the vinyl chloride polymer slurry is dehydrated by the filter dehydrator of the present invention, the solid content of the slurry is generally in the range of 20 to 40% by weight, and the temperature of the slurry is It is usually in the range of 10 to 80 ° C. When the vinyl chloride polymer slurry is dehydrated by the rotary filtration dehydrator of the present invention, it is preferable to operate so that the thickness of the attached cake on the surface of the filter cloth installed on the vacuum drum is 5 to 20 mm. If the thickness of the attached cake exceeds 25 mm, for example, the water content of the cake tends to increase. This thickness can be adjusted by selecting the slurry concentration, the type of filter cloth, the operating pressure in the filtration step, the residence time, and the like. Further, as described above, the filter dehydrator of the present invention may be of a disc type or a belt type other than the exemplified drum type.

[0014]

EFFECTS OF THE INVENTION When vacuum-filtering a suspension using a filtration dehydrator having a filtrate reservoir for preventing filtrate backflow of the present invention, particularly when peeling the adhered cake by pressure purging with compressed air or the like in the peeling step, The filtrate that has once passed through the filter cloth can be prevented from returning to the solid content, and the dehydration efficiency can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view illustrating the outline of a vacuum filtration dehydrator of the present invention.

FIG. 2 is an explanatory diagram illustrating each step of filtration, dehydration, and separation in the apparatus shown in FIG.

FIG. 3 is an explanatory diagram illustrating a structural example and an action of a filtrate reservoir for preventing filtrate backflow.

FIG. 4 is a cross-sectional view comparing the one without a filtrate reservoir and the one with a filtrate reservoir.

FIG. 5 is an explanatory diagram illustrating an example of the structure of a filtrate reservoir for preventing filtrate backflow.

[Explanation of symbols]

 1 Filter dehydrator 2 Suspension tank 3 Filter cloth 4 Suspended liquid stirrer 5 Scraper (scraping plate) 8 Filtrate receiving tank 9 Vacuum pump 11 Air compressor 12 Filtrate discharge pipe 13 Compressed air introduction pipe 14 Filtrate passage 15 Filtration backflow prevention Filtrate reservoir 16 Opening of filtrate passage 17 Opening for ventilation / liquid passage

Front page continuation (72) Inventor Masayuki Okazaki 3-10, Shiodo, Kurashiki-shi, Okayama Mitsubishi Kasei Vinyl Co., Ltd. Mizushima Plant (72) Inventor Akira Nishinaka 3--10, Shiodo, Kurashiki, Okayama Mitsubishi Kasei Engineering Inside the China office

Claims (2)

[Claims] 1. A filtering step of immersing a filtering surface in a suspension and sucking and adhering the solid content in the suspension to the filtering surface by negative pressure inside the rotating body, and the adhering solid content outside the suspension in the rotating body. In the rotary filtration / dehydration machine, which sequentially goes through three steps, a dehydration step of vacuum dehydration / aeration drying by negative pressure of, and a separation step of separating adhered solids from the filtration surface by the purge pressure in the rotating body, The body is divided into multiple parts in the circumferential direction,
In addition, each of them is composed of independently depressurizable / pressurizable compartments, and these compartments are connected to the filtrate discharge pipe and compressed air introduction pipe arranged near the rotary shaft via an automatic valve. A rotary filtration / dehydration machine having a blind pipe portion, which is opened in a rotation axis direction and is not opened in a filtration surface direction, in a pipe line. 2. A slurry of a vinyl chloride polymer obtained by suspension polymerization of vinyl chloride or a monomer having vinyl chloride as a main component in an aqueous medium is dehydrated by the rotary filtration dehydrator according to claim 1. A method for dehydrating a vinyl chloride-based polymer, comprising: