JP3296879B2 - Filter material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter material for separating solid particles from a gas containing solid particles, and more particularly to collecting and removing dust and other particles contained in high-temperature exhaust gas generated from an incinerator or the like. In addition, the present invention relates to a filter medium suitable for taking out only purified air to the outside.

[0002]

2. Description of the Related Art Gas discharged from a production line of a factory, various devices, a dryer, or a high-temperature furnace such as an incinerator or a melting furnace contains dust and other solid particles. It cannot be disposed of as it is outside,
Using a dust collector, the particles are collected and removed, and only purified air is taken out.

As a dust collector, an electric dust collector, a scrubber, a cyclone, a bag filter and the like are generally used. Among them, the bag filter has a simple structure and a dust collection efficiency of 99.9% or more. It is used more widely than other dust collectors because it has an extremely high filtration capacity of 1 to 5 mg / m ³ N in the clean gas after filtration.

In this bag filter, exhaust gas is introduced into a housing containing a large number of cylindrical or envelope-shaped filter media, and solid particles in the exhaust gas are collected by an inner or outer surface of the filter media to be cleaned. This is to take out the air to the outside. Filter materials include natural fibers such as cotton and wool, polypropylene, polyester, polyacrylonitrile, polyphenylene sulfide, polyamide, polyimide, polyvinyl acetate, and polytetrafluoroethylene (PTFE).
Or various fibers of inorganic fibers such as glass fiber, etc., which are made of felt or woven fabric.

[0005] In the early stage of use, these cloth-like filtration materials first form a primary adhesion layer composed of solid particles such as dust collected near the surface. This primary adhesion layer is shown in FIG.
As shown in the figure, the solid particles 4 in the dust-containing gas 3 flowing from the left side in the figure entered into the gaps between the fibers 2 near the surface of the filter medium 1, and an apparent layer composed of the solid particles 4 was formed. Things. For this reason, the substantial opening of the filter medium 1 becomes smaller than the stitch spacing of the fibers, and it becomes possible to collect finer particles. Therefore, the solid particles 4 in the dust-containing gas 3 flowing in thereafter are substantially collected by the primary adhesion layer, and the purified gas 5 is extracted from the right side of the filter 1 in the drawing.

However, during exhaust gas purification, solid particles accumulate on the surface of the filter medium or penetrate into the interstices of the fibers inside the primary adhesion layer to cause clogging, thereby reducing filtration efficiency. There is a disadvantage that. For this reason, in the bag filter, the deposited particles are periodically peeled off from the surface of the filter medium by a shaking method, a headwind method, a pulse jet method or the like during operation. In order to facilitate this peeling, a filter material in which a fluororesin fiber chemically inactive and having low affinity for solid particles is braided, or a fiber is subjected to a surface treatment such as fluorine processing and braided in a cloth shape. Filter materials have also been put to practical use.

For the same purpose, a filter medium having no primary adhesion layer has been developed. For example, JP-A-3-68
No. 409 discloses that a porous expanded PT is added to PTFE felt.
There is disclosed a filter material in which an FE membrane is laminated. Similarly, as a filter material without a primary adhesion layer,
Japanese Patent Application Laid-Open Publication No. H11-157, discloses a filter material in which PTFE fine particles are filled on the surface of a filter material base material made of sintered polyethylene particles having a large particle diameter.

[0008] These filtration materials can be used more widely because they have excellent heat resistance and chemical resistance in addition to easy separation of solid particles.

[0009]

As described above, the bag filter has an extremely high filtration performance of a dust collection efficiency of 99.9% or more and a dust concentration of 1 to 5 mg / m ³ N in the clean gas after filtration. Although having a filter material consisting of only fibers, a so-called "blooming phenomenon" occurs when a primary adhesion layer is not formed due to its structure.
And an effective filtration function cannot be achieved. In particular, in the early stage of use, the primary adhesion layer is not formed at all, and a considerable time is required for its formation and stabilization. For this reason, it is necessary to precoat the surface of the filter medium with the same or another powder as the powder to be collected before use to form a primary adhesion layer in advance.

[0010] In addition to the problem of the primary adhesion layer at the initial stage of use, the action of the removing mechanism during the operation of the bag filter causes
In addition to the solid particles adhered and deposited on the surface of the filter medium, the solid particles constituting the primary adhesion layer may be peeled off. As a result, a blow-by state is temporarily established until the primary adhesion layer is formed again, and no filtration is performed. Even if the solid particles are prevented from adhering to and accumulating on the surface of the filter medium by the wiping mechanism, the solid particles can be deposited thickly on the surface of the filter medium over a long period of use, or the gaps between the fibers inside can be reduced. , And accumulate between fibers, so-called "clogging phenomenon" occurs. As a result of this clogging phenomenon, the pressure loss of the filter medium increases, the amount of processing gas decreases, and the filtration efficiency decreases.

In order to suppress the progress of the clogging phenomenon, it is necessary to treat the exhaust gas at a relatively low flow rate of usually 0.5 to 1.5 m / min. In addition, solid particles that have once penetrated deeper into the filter medium cannot be removed by a normal drop-off mechanism, and careful cleaning with a chemical or water is required for their removal. However, since even the primary adhesion layer is removed with this cleaning, the same phenomenon as the blow-through occurs at the time of reuse, and it takes time until the filtration performance is stabilized, or after cleaning such as drying and precoating. Post-processing is required. In addition, the life of the filter material is shortened due to damage caused by contact between the fibers during cleaning and the cleaning jig, thermal deterioration of the fibers due to a drying process, and the like.

Further, in order to improve the releasability from solid particles and increase the mechanical strength and chemical strength, the fibers constituting the filter material are subjected to chemical treatment or film treatment by a chemical immersion step or drying. Various processes such as a process, a dispersion process, and a waste liquid treatment process are required. On the other hand, with respect to a filter material having a structure without a primary adhesion layer, a laminated filter material as described in JP-A-3-68409 requires a heating and pressing laminating apparatus for laminating. In addition to the problems related to the manufacture of the filter, the filter medium vibrates due to the dropping during filtration, the porous membrane on the surface peels off, the adhesive spreads in a film form to form a non-permeable membrane, There are structural problems such as blocking pores of the porous membrane and preventing exhaust gas from passing through the filtering material.

[0013] Further, in the filter medium described in JP-B-2-39926, in which PTFE fine particles are filled on the surface of a filter medium base material composed of sintered polyethylene particles having a large particle diameter,
Since the filter material base material is polyethylene, it cannot be used at high temperatures, and its use conditions are limited due to low resistance to moisture and chemical substances in exhaust gas. Accordingly, an object of the present invention is to provide a filtering material which is excellent in chemical and mechanical strength in addition to filtering performance, and is capable of treating high-temperature exhaust gas.

[0014]

Means for Solving the Problems The inventors of the present invention have made various improvements to solve the above-mentioned problems relating to the filter material, and as a result, have obtained a porous material made of a fluororesin sintered body such as PTFE having excellent chemical and mechanical strength. By filling the surface of a high quality base material sheet with a fine powder of fluororesin, the inventors have found that the filtration performance is excellent and that the treatment can be performed even with a high-temperature gas.

That is, the object is to contain solid particles.
A filter for separating the solid particles from the gas.
Te, becomes by sintering large-diameter fluororesin powder, our Keru pressure loss in filtration air velocity 0.5 to 2 m / min from 9.8 to 49
On the surface of a porous base material sheet having a ventilation resistance of 0 Pa ,
Coating with fine communication holes containing fluororesin fine powder
A fluorine-containing resin fine powder,
Between the large-diameter fluororesin powder on the surface of the material sheet
Rukoto filled in the cavity to be formed can be solved by filtering material, characterized in.

In order for the base material sheet to satisfy the above-mentioned airflow resistance, it depends on the particle size of the fluororesin and the thickness of the sheet. For example, if the average particle size of the resin is 20 to 50 μm and the thickness is 2
mm base material sheet, bulk density 1-2 g / c
If m ³ and the porosity are 30% or more, the above-described airflow resistance can be obtained. Such a base material sheet is filled with a fluororesin powder in a metal mold, and pressure-molded so that the volume ratio becomes 40 to 60% of the volume at the time of filling, and the sintering temperature of the resin, for example, 340 in case of PTFE. After sintering at ~ 360 ° C for several hours, it is obtained by processing the surface of the obtained sintered body into a thin skin by skiving.

Since the base material sheet is composed of particles having a large diameter of several tens of μm, unevenness of the same scale is formed on the surface thereof. The resin fine powder is filled. The coating agent is a suspension obtained by mixing a fluororesin fine powder having an average particle size of 10 μm or less, preferably 5 μm or less, and a binder made of a heat-resistant resin or a thermosetting resin-based adhesive in an alcohol solvent.

The kind of the fluororesin constituting the fluororesin fine powder is not particularly limited, and the same resin as the above-mentioned fluororesin constituting the base material sheet can be appropriately selected and used. The binder is not limited as long as it is alcohol-soluble and has a heat resistance temperature of 200 ° C. or higher. For example, a typical thermosetting resin such as a phenol resin, a melamine resin, and a resorcinol resin can be used. Among them, solid content 50-60
A wt% phenolic resin-based alcohol solution adhesive is preferred.

The solvent is a monohydric lower alcohol such as methanol, ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol and isobutyl alcohol, and ethyl alcohol is preferred in view of toxicity and viscosity. These mixing ratios of the coating material according to the present invention are as follows: fluororesin fine powder 10 to 50 wt%, binder 1 to 1
A range of 5 wt% and a solvent of 50 to 200 wt% is preferred.

The method for forming the coating layer on the surface of the base material sheet is not particularly limited, and the coating material may be sprayed or brushed to a film thickness of several tens μm, preferably 20 to 30 μm, using known means such as brushing. Is applied to a sheet so as to obtain a coating material, and heated to a curing temperature of a binder, and the coating material and the sheet are fixed by heat curing. As a result, a coating layer having fine communication holes having a hole diameter of several μm or less can be obtained.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a filter according to the present invention. However, the present invention is not limited to the embodiments described below, and various modifications are possible. A mold is filled with PTFE powder having an average particle size of 50 μm, compressed to a volume ratio of 60% of that at the time of filling, formed into a cylindrical shape, taken out of the mold, and left standing in a heating furnace to air. During,
Sintered at 340 ° C. for 4 hours. After sintering, allow to cool to room temperature,
A 0.5 mm thick fluororesin porous base material sheet was obtained by skiving. The bulk density of the obtained sheet is 1.3 g.
/ Cm ³ and about 50 Pa at a passing wind speed of 1 m / min.
Showed the airflow resistance.

After applying a coating agent having the compounding ratio shown in Table 1 to the surface of the base material sheet, the coating material was heated at 150 ° C. for 30 minutes in a heating furnace to cure the coating material, and the average value was applied on the base material sheet. A filter layer was obtained by forming a coating layer having a thickness of 30 μm.

[0023]

[Table 1]

The obtained filter medium has a passing air velocity of 1 m / min.
Showed a ventilation resistance of about 400 Pa. FIG. 1 shows an enlarged cross-sectional view of the obtained filter medium. As shown in the drawing, the filter medium 1 according to the present invention has a structure in which the PTFE fine particles 7 are filled in the irregularities on the surface of the base material sheet made of the PTFE sintered particles 6, and the dust-containing gas flowing from the left side in the figure The solid particles 4 in 3 are collected by the PTFE fine particles 7 and only the purified air 5 is taken out from the right side of the filter 1 in the drawing. At this time, the solid particles 4 are converted into PT
Cannot enter the inside of the base material sheet made of the FE sintered particles 6,
Collected on the filter media surface.

As shown in FIG. 2, the filter medium 1 is mounted on a support body 8 and mounted on a filter element 9 having a diameter of 117 mm and a height of 1000 mm, and a particle diameter of 0.5 to 10 mm.
2 containing solid particles at a concentration of 500 mg / m ³ N
The high-temperature dust-containing gas 3 at 50 ° C. was continuously filtered under the condition of a filtration wind speed of 2 m / min. The concentration of the solid particles contained in the purified gas 5 after filtration was 1 mg / m ³ N or less.

During filtration, the pressure loss of the filter was measured at predetermined intervals. FIG. 3 shows the measurement results. It can be seen that the filter material of the present invention shows little change in pressure loss (ΔP) with time and always shows stable filtration performance.

[0027]

As described above, in the filter material of the present invention, since the surface of the base material sheet is covered with the coating layer made of the fine powder of fluororesin, solid particles and moisture in the exhaust gas are trapped inside the base material sheet. Hard to penetrate, clogging and condensation,
The occurrence of dissolution precipitation and the like is suppressed, and stable filtration performance is maintained for a long time. Further, since the clogging phenomenon does not occur, the filtration flow rate can be increased, the processing time is shortened, and the filtration efficiency is significantly improved.

Since both the base material sheet and the coating layer are made of fluororesin, they are excellent in heat resistance and chemical resistance, and can treat exhaust gas containing various chemical substances such as high-temperature exhaust gas and household waste. In addition, because of low affinity for solid particles, water and oil contained in exhaust gas, the accumulation of solid particles on the surface of the filter material is suppressed, and washing is easy. It can be completely washed and removed, and can be used immediately after washing without going through a drying step.

Further, since the base material sheet is a sintered body of a fluororesin, the mechanical strength is superior to that of the fibrous base material sheet, and the fine particles of the fluororesin constituting the coating layer are also formed by the anchor effect. Because it is fixed to the surface, it has high resistance to shaking and impact during operation,
No risk of damage. Furthermore, since the structure does not have a primary adhesion layer, there is no problem of blow-by or pre-coating at the beginning of operation or at the time of reuse after washing.

Regarding the production method, in the present invention, it is only necessary to apply a coating agent containing a fine powder of fluororesin to the base material sheet and heat and cure it. Compared to the conventional case where the fluororesin film is laminated, the number of processes is smaller and special equipment
It can be manufactured at low cost, for example, without the need for equipment.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a filter medium according to the present invention.

FIG. 2 is a diagram showing a state in which a filter medium according to the present invention is mounted on a filter element.

FIG. 3 is a diagram showing a change over time in pressure loss of a filter medium according to the present invention.

FIG. 4 is an enlarged sectional view of a conventional filter medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filtration material 2 Fiber 3 Dust-containing gas 4 Solid particles 5 Purification gas 6 Fluororesin sintered particles (base material sheet) 7 Fluororesin fine particles (coating layer) 8 Support 9 Filter element

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-165599 (JP, A) European Patent Application Publication 450894 (EP, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 39/00-39/20

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein said solid is contained in a gas containing solid particles.
A filtering material for separating particles, which is obtained by sintering a large-diameter fluororesin powder and has a filtering air speed of 0.5
Contact Keru pressure loss in ~2m / min is 9.8~490Pa
The surface of a porous base material sheet having a low airflow resistance contains a fine powder of fluorocarbon resin and has a fine communication hole.
A fluorine-containing resin fine powder,
Between the large-diameter fluororesin powder on the surface of the material sheet
Filtering material, characterized that you have filled in the cavity to be formed.