JPH1121601A - Multilayer porous body and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a porous material capable of efficiently filtering fine particles such as dust generated from a refuse incinerator while suppressing pressure loss. The porous material comprises a porous metal sintered body having a controlled pore size as a base, and a relatively membrane having a controlled pore size made of metal, ceramic or a mixture thereof on the surface of the base. It has a multilayer structure in which a thin porous sprayed film is formed. By providing the sprayed film with a pore distribution having a pore diameter capable of filtering particles, the substrate (occupying most of the wall thickness) can have a pore distribution with a large pore diameter. A filtration process with low loss can be performed, and a backwash effect for recovering a decrease in filtration function due to clogging is also stably maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous material useful as a filter material for filtering out ultrafine particles such as dust generated from a refuse incinerator and a method for producing the same.

[0002]

2. Description of the Related Art Porous sintered bodies can be obtained by using metal powder as a raw material for sintering and adjusting the sintering conditions such as hot isostatic pressing. This porous metal sintered body is useful as a filter material or the like. The pore distribution can be controlled by the particle size of the sintering raw material powder, sintering conditions, etc., and by selecting the type of sintering raw material, it is possible to provide high-temperature heat resistance, corrosion resistance, etc. according to the application and use environment. (Japanese Patent Application Laid-Open Nos. 8-218102, 8-218103, 8-302404). By applying the above porous metal sintered body as a filter for removing dust from high-temperature exhaust gas from a refuse incinerator, for example, the drawbacks (lack of heat resistance, etc.) of a conventional bag filter made of a glass fiber filter cloth or the like are eliminated, and the durability is improved. It is possible to expect effects such as improvement of service life, improvement of maintenance, and improvement of dust removal efficiency.

[0003]

The soot particles in the exhaust gas generated from a refuse incinerator are extremely fine. The pore size and the like of the porous sintered body required for this dust removal treatment can be adjusted by the manufacturing conditions of the sintered body (particle size of raw material powder, sintering temperature and pressure, etc.). If so, the pressure loss in the dust removal process increases, and it becomes difficult to carry out the process efficiently. In addition, as the pore diameter becomes finer, the difficulty in recovering and regenerating the filtration function by backwashing increases. The present invention is intended to solve such a problem, and is useful as a filter material or the like capable of efficiently filtering fine particles while suppressing an increase in pressure loss accompanying finer pore diameters. Provided is a porous body and a method for producing the same.

[0004]

The porous body of the present invention comprises a porous metal sintered body having a controlled pore size as a base, and a controlled porous material made of metal, ceramics or a mixture thereof on the surface of the base. It has a multilayer structure in which a porous sprayed film having a pore diameter is formed.

[0005] The pore diameter and the like of the porous metal sintered body serving as a base are adjusted by sintering conditions (processing temperature, pressure, particle size of raw material powder, etc.) to cover the surface of the base (porous metal sintered body). The pore diameter of the porous sprayed film depends on the spraying conditions (injection gas pressure,
(Spraying distance, sprayed powder particle size, film thickness, etc.). By providing the sprayed film with a pore size corresponding to the particle size in the fluid to be filtered, filtration performance required as a filter material is imparted. The substrate (occupying most of the thickness of the filter material) may be a sintered body having a relatively coarse pore diameter, and by increasing the average pore diameter to be larger than that of the sprayed film, a filtration effect as a multilayer effect is obtained. A predetermined filtering effect can be ensured while suppressing and avoiding an increase in pressure loss in the treatment.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The multilayer porous body of the present invention forms a porous metal sintered body as a base material using metal powder as a sintering raw material, and then forms a porous sprayed film on the surface of the sintered body. It is manufactured by a process of forming a laminate. [Production of Porous Metal Sintered Body] It is preferable to apply hot isostatic pressing (HIP) to this sintering process. H
According to the IP treatment, a homogeneous porous sintered body can be obtained regardless of the shape or size. As the material type of the sintering raw material powder, carbon steel, a corrosion-resistant alloy, a heat-resistant alloy, and other various metal materials are appropriately selected according to the intended use of the intended multilayer porous body and required material properties. The particle size of the powder used is, for example, less than about 200 μm. The HIP process is successfully achieved by the low temperature low pressure HIP method or capsule free HIP method described below.

[0007] The low-temperature low-pressure HIP method is different from the usual HIP processing for producing a high-density sintered product, in that a sintered body is formed into a porous body (for example, porosity: about 20 to 40%,
(Pore size: about 200 μm or less). Preferably, temperature: 0.35 to 0.85 mpK [where mpK is the melting point of metal powder (absolute temperature)], pressure: 5 to 1
It is adjusted to 50 MPa. The obtained porous sintered body is subjected to a heat treatment (strengthening heat treatment) for strengthening the interparticle bonding, if desired. The processing temperature is suitably in the range of about 0.6 to 0.95 mpK, whereby the mechanical strength of the sintered body can be increased without impairing the porosity of the sintered body. The heat treatment can be performed in the HIP device in a state where the pressurizing action of the hydrostatic medium is released.

On the other hand, when the capsule-free HIP method is applied, the green compact is formed by uniaxial press molding, cold isostatic press molding (CIP molding) or the like, but CIP molding is preferred from the viewpoint of homogeneity. The relative density of the green compact for making the sintered body porous is about 95% or less, which is adjusted by the green compacting pressure or the like. The HIP processing temperature is about 0.7 to 0.
95mpK (mpK is the same as above), pressure is about 5 to 150MP
The range of a is appropriate. The processing conditions are almost the same as those of the normal HIP processing for producing a high-density sintered body, except that the pressure action of the hydrostatic medium acts on the surface of the green compact and at the same time, through the open pores. Also acts, and as an effect, it can be baked into a sintered body having high mechanical strength without losing the porosity.

[Formation of a Porous Thermal Sprayed Film] The porous metal sintered body is uniformly sprayed after the surface is uniformly processed and subjected to an appropriate surface cleaning treatment (eg, degreasing cleaning). In the thermal spraying, a metal, ceramics, a mixture thereof, or the like is used as a raw material, and is sprayed as a heated droplet by a thermal spray gun onto the surface of an object to be processed, thereby forming a film as an adhesion deposition layer. Thermal spray material is made of various metals or
Alloy or ceramic powder (oxide such as alumina, chromium _carbide, carbide-based carbide titanium, silicon _nitride,
A nitride based material such as boron nitride) is appropriately used. As the thermal spraying method, a known thermal spraying method such as flame thermal spraying, arc thermal spraying, or plasma thermal spraying is applied according to the kind of the thermal spraying material.

[0010] The pore diameter and porosity of the sprayed film are determined by the injection pressure,
The temperature of the droplet, the spray distance, the supply speed of the spray material, and the like can be controlled by adjusting the height, and the film thickness can be easily adjusted.
In general, the higher the injection pressure, the denser the film formed,
Although the porosity is reduced, it depends on the spraying distance, the droplet temperature, the film thickness, and the like, and also differs depending on the powder particle size when powder is used as the spraying material. Therefore, the thermal spraying conditions are specifically set according to the pore distribution of the thermal spray coating required for the target multilayer porous body.

[0011]

〔Example〕

[1] Production of substrate (porous metal sintered body) Mild steel capsule [Slurry of silica powder (average particle size: 10 μm) is applied to the inner surface of the capsule in advance and dried to a layer thickness of about 3 mm.
A silica powder layer is formed), stainless steel SU
S 316L powder (particle size 200μm or less) is sealed and HIPed [Temperature: 650 ° C (0.56mpk), Pressure: 100MPa, Processing time: 2Hr
). The silica powder layer on the inner surface of the capsule is HIP
It has the role of preventing diffusion bonding at the interface between the sintering raw material and the capsule during the treatment process and facilitating removal of the sintered body from the capsule.

After the HIP treatment, the pressurizing action of the hydrostatic pressurizing medium is released, and a heat treatment (temperature: 1150 ° C. (0.86 mpk), treatment time: 4 hr) is performed in the same apparatus. After the heat treatment, the porous sintered body is taken out of the capsule, and the silica powder remaining on the outer peripheral surface is removed with a brush. Sintered body size: outer diameter 114 mm, wall thickness: 1 mm, tube length 300 m
m. Pore distribution: porosity 25%, pore size 200μm or less (average pore size 70μm)

[2] Formation of Thermal Sprayed Film As the thermal spraying material, (A) stainless steel SUS 316L powder (average particle size: 90 μm) or alumina ceramic powder (average particle size: 70 μm) is used, and the porous sintered material is used. Body (porosity 2
Plasma spraying is applied to the outer peripheral surface (5%, pore size 200 μm or less) to obtain multilayer porous bodies (A) and (B).

[0014]

Comparative Example Porous metal sintered body (without sprayed film) Shape: outer diameter 114, wall thickness 1, tube length 300 (mm) (multilayer porous body A,
(Same as the substrate of B) Porosity: 15%, Average pore diameter: 20 μm (equivalent to the sprayed film of the multilayer porous body A)

[3] Permeation test Pressurized air is passed from the outside of the test sample pipe to the hollow hole side. The pressure loss (mm Aq) when passing air at a ventilation speed of 1.0 m / min was measured, and the results shown in Table 1 were obtained. The invention example is based on the sprayed film formed on the surface,
It has the same filtering effect of fine particles as the porous metal sintered body of the comparative example (without the sprayed film), and the pressure loss is lower than that of the porous metal sintered body, so that the filtering effect can be enhanced.

[0017]

Table 1 Test material Pressure loss (mm Aq) Multi-layer porous body A (Invention example) 20 Multi-layer porous body B (Invention example) 35 Porous metal sintered body (Comparative example) 50

[0018]

According to the multilayer porous body of the present invention, fine particles can be trapped and filtered off while suppressing an increase in pressure loss by the effect of the multilayer structure. For example, it is generated from a refuse incinerator. It is useful as a filter material for exhaust gas soot filtration. The distribution of fine pores is only the sprayed film on the surface, and the substrate has a pore distribution with a relatively large pore size.Therefore, the backwashing efficiency for recovering the decrease in filtration function due to clogging is maintained at a high level, and repeated repetition is performed. It is easy to use and can perform efficient filtration for a long period of time.

Continued on the front page (72) Atsushi Funakoshi 1-1-1, Nakamiya Oike, Hirakata City, Osaka Prefecture Inside Kubota Hirakata Plant Co., Ltd. (72) Ryutaro Motoki 1-1-1, Nakamiya Oike, Hirakata City, Osaka Prefecture Kubota Corporation Hirakata Factory

Claims (3)

[Claims] 1. A porous metal sintered body having a controlled pore diameter is used as a base, and a porous sprayed film having a controlled pore diameter made of metal, ceramics or a mixture thereof is formed on the surface of the base. A multi-layered porous body. 2. The filter material according to claim 1, wherein the pores of the porous sprayed film have a pore size for filtering particles in the fluid to be treated, and the substrate has an average pore size larger than the sprayed film. 2. The multilayer porous body according to 1. 3. A porous metal sintered body having a controlled pore diameter, which is a hot isostatic pressing sintered body, is used as a base, and metal, ceramics, or a mixture thereof is sprayed on the surface of the base. And forming a sprayed film having a controlled pore diameter.