JPH0790133B2 - Cylindrical filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a filter material for a filter for removing impurity fine particles from a slurry containing fine impurity particles, and more particularly, a process for producing an organic or inorganic pigment, for example, Microfiltration of titanium black liquor (slurry obtained by digesting titanium-containing ores such as ilmenite with sulfuric acid and containing undigested residue) in the titanium dioxide pigment manufacturing process using the sulfuric acid method, filtration of metatitanic acid or titanium dioxide The present invention relates to a filter material for a filter, which is useful for cleaning.

(Prior Art) In the manufacturing process of a sulfuric acid method titanium dioxide pigment, a filter commonly used as a titanium black liquor precision filter has a filter aid layer such as diatomaceous earth attached to the filter surface of a carbon tube as a filter medium. This is a so-called tube filter. The carbon tube is a porous cylindrical tube formed by molding carbon with a binder, and has been used for many years in this field because it has excellent pressure resistance and chemical resistance.

(Problems to be Solved by the Invention) On the other hand, when the titanium black liquor is pressure-filtered using the carbon tube filter, the advantages are recognized. On the other hand, in continuous operation for a long time, pickling is performed while the filtration is repeated. There is a defect that the so-called clogging phenomenon occurs, in which fine particles of a poorly soluble acid that cannot be removed even close the pores of the carbon tube. Under the present circumstances, the clogged tube is forced to be discarded and replaced with a new carbon tube, which causes a high cost. Moreover, since the weight of the carbon tube itself is heavy, it is not always easy to replace and handle it.

(Means for Solving the Problem) The inventors of the present invention have conducted research on filtering agents of various materials to solve the above-mentioned defects of the carbon tube, and have used general-purpose resins such as commercially available vinyl chloride resin pipes. Even in the case of a pipe, the porosity of the surface of the pipe is appropriately adjusted, and two or more layers of synthetic resin nets having a mesh of a specific size are provided between the pipe and the filter cloth covering the pipe. The patent application was previously filed based on the knowledge that a layered product can be a filter material having high strength that will not be damaged by ordinary filtration pressure even when continuously operated for a long time. (Japanese Patent Application No. 60-173714) After that, as a result of further research, a filter medium having a structure in which three or more layers of a synthetic resin net having a specific size of mesh are laminated around a resin pipe is
It has been found that the use of a filter cloth is unnecessary by using it in combination with a filter aid, and it is stable without clogging even during continuous operation for a longer time.

That is, the present invention is a cylindrical filter medium having a structure in which at least three layers of synthetic resin nets are laminated around a cylindrical tube having a surface porosity of 0.1 to 1%.

The present invention will be described below with reference to the drawings.

FIG. 3 shows an example of a general filter in which the filter medium of the present invention is disposed, 1 is a filtering container, and 2 is a filter medium. The filtration container is
Stainless steel, carbon steel, or steel with rubber or FRP interior has been commonly used until now. The filter medium is vertically attached to the partition plate 3 in the container.

FIG. 2 shows a cylindrical tube 4 which is the core of the filter medium of the present invention, and this tube is provided with pores 5 so that the open area ratio per total surface area is 0.1 to 1%. Generally, if the porosity is increased, the filtration resistance is reduced, which is advantageous in this respect, but on the contrary, the strength of the filter medium is reduced. If the opening ratio is reduced when the filter cloth is simply attached to the cylindrical tube or only one net is installed between them, the filtration resistance increases sharply as shown in Fig. 4, limiting the selection of the cylindrical tube material. Join.

According to the present invention, by laminating three or more layers of synthetic resin nets around the cylindrical tube, the outermost layer of filter cloth is not required, and even if the opening ratio is 1% or less, the filtration resistance is rapidly increased. There is no. Therefore, in the present invention, since a cylindrical tube that serves as a filter core can be made of a general-purpose and inexpensive material, there is a great advantage in practical use.

For the cylindrical tube, one selected from vinyl chloride resin, polyethylene resin, acrylic resin, fluororesin and other hard synthetic resins, and various metals is used, but vinyl chloride resin is used. In this case, it is possible to use a large amount of PVC pipe that is commercially available at low cost, which is economical. The arrangement of the pores on the surface of the cylindrical tube is such that the intervals of the pores are all equal, the diameter of the pores is made as large as possible, and the number of pores is set so that the tube strength is not partially impaired. Although it is important to reduce the number as much as possible, the present invention has a great feature in making these possible.

FIG. 1 shows the structure of the filter medium of the present invention. The outermost layer of the cylindrical tube 4 is a synthetic resin net 8 having an air permeability of 200 cc / sec or less,
At least two layers of synthetic resin nets 6 and 7 are laminated between the pipe 4 and the synthetic resin net 8.

As the outermost synthetic resin net, synthetic resin fibers such as polyethylene, polypropylene, nylon, Teflon, and acrylic are used. Usually, synthetic resin having an air permeability of 20 to 100 cc / sec is used, but acrylic resin fiber is particularly preferable.

In the present invention, at least two layers of a synthetic resin net having a specific opening are laminated between the cylindrical tube 4 and the synthetic resin net 8. In this case, nets of the same kind and the same mesh may be laminated, but it is desirable to use different kinds of nets in order to enhance the efficiency of filtration. Especially, those having a lot of meshes on the side closer to the outermost net. That is, it is important to use the one with a small opening. Figure 1 shows nets 6 and 7
An example in which two layers are laminated is shown.
It is preferable to use 20 to 70 mesh as 7 for 20 mesh. As the material of the net, wire mesh can be used in addition to commercially available synthetic resin fibers such as polypropylene, polyethylene, nylon and polyester, as in the case of the outermost net.

When a filter provided with the filter material of the present invention is used, it is important to coat the surface of the outermost synthetic resin net with a commonly used filter aid such as diatomaceous earth, perlite or cellulose.

FIG. 5 shows a cylindrical filter medium (A) of the present invention in which three layers of synthetic resin nets are laminated around a cylindrical tube, and a filter cloth for the outermost net of the filter medium for comparison. 3 shows the transition of the filtration speed (fine filtration speed and the filtration speed difference during the period of use) when the titanium black liquor was microfiltered using the cylindrical filter material (B). Both filter media were used by coating the surface of the outermost layer thereof with a filter aid. From FIG. 5, the cylindrical filter medium (B) was clogged in about 5 months, and the operation had to be stopped, but the cylindrical filter medium (A) was not clogged even after about 10 months. It is not recognized, and it can be seen that the operation is continuing smoothly.

(Effect of the Invention) The cylindrical filter medium for a filter of the present invention is economical because it can be used as a general-purpose synthetic resin pipe as it is, and it is easy to handle and is very excellent in workability. .

[Brief description of drawings]

FIG. 1 shows an example of the structure of the filter medium of the present invention. FIG. 2 shows an example of a cylindrical tube that serves as the core of the filter medium. FIG. 3 shows an example of a general filter equipped with the filter material of the present invention. Fourth
The figure shows the relationship between porosity and filtration resistance. FIG. 5 shows the transition of the filtering speed when the filter medium of the present invention and the filter medium for comparison were used. 1 ... Filter container, 2 ... Filter material, 3 ... Partition plate, 4 ... Cylindrical tube, 5 ... Pores, 6,7,8 ... Net.

Claims (1)

[Claims] 1. A cylindrical filter medium for mounting in a pressure filter for precision filtration of titanium black liquor, the surface porosity of which is from 0.1 to 10.
A structure in which at least three layers of synthetic resin nets are laminated around a 1% vinyl chloride resin cylindrical tube, and the opening of the first net immediately above the cylindrical tube is 10 to 20 mesh,
A cylindrical filter medium characterized in that the mesh of the net of the second layer is 20 to 70 mesh and the mesh of the net of the outermost layer has an air permeability of 200 cc / sec or less.