JP2003181225A - Dry filter medium and bag filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dry filter medium which can be used at temperature as high as ≥400°C and which is strong enough against repeated vibration when deposited dust is blown off by the reversed flow of high pressure air and to provide a bag filter made of the above medium. <P>SOLUTION: The dry filter medium comprises a woven ceramic cloth (particularly a woven cloth of silica fibers) as the base cloth, an aggregated body of metal fibers (particularly, metal fibers of a heat-resistant stainless steel containing 15 to 25 wt.% of chromium and 3 to 10 wt.% of aluminum) produced by a cut method (particularly, a cut method for a coil material) and by entangling by needling to deposit into two-layer or three-layer structure on the base cloth. If necessary, a ceramic coating material is applied on the layers. The bag filter is manufactured by using the above dry filter medium. <P>COPYRIGHT: (C)2003,JPO

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 a high temperature region for collecting dust in a high temperature gas such as an incinerator and a boiler, and a bag filter using the same.

[0002]

2. Description of the Related Art Air pollution due to harmful substances and environmental pollution due to dioxins have become serious global environmental problems, and regulations have been tightened around the world. Dust collection in industrial combustion furnaces such as boilers and incinerators, as well as nitrogen oxides and sulfur oxidation. Removal of things is obligatory. In particular, dioxin is a highly toxic and carcinogenic toxic substance that is subject to strict worldwide regulations.As a designated substance based on the Air Pollution Control Law in Japan as well, it is applied with the regulation value according to the treatment capacity of the incinerator. The timely regulation came into effect on December 1, 1997. In particular, in order to comply with the environmental standards of the "Dioxins Countermeasures Special Measures Law" that will be applied in the future, it is obligatory to install an advanced exhaust gas dust collector regardless of whether it is a new installation or not. Cost reduction is required.

Dioxins are said to generate hydrocarbons and chlorine by the catalytic action of metal compounds during incomplete combustion at low combustion temperatures, and even if complete combustion is performed under strict control in the incinerator, exhaust gas is cooled. In the process, it is resynthesized from a very small amount of precursor using the metals in the fly ash as a catalyst. In the re-synthesis, the temperature in the subsequent equipment whose temperature was lower than that of the combustion chamber was 200
It is said to be particularly high at ~ 400 ° C, and therefore
Dioxin generation can be suppressed by collecting dust at a low temperature of 200 ° C. or lower or a high temperature of 400 ° C. or higher.

The mainstream of dust collecting equipment is a method using an electric dust collector and a method using a bag filter.
The facility cost is high, the maintainability is not good, and the operating temperature is often around 300 ° C., so there is a limit to the control of dioxin. Therefore, the bag filter method, which collects dust at a temperature of 200 ° C. or less, is now the mainstream.

The treatment at a temperature of 200 ° C. or lower can be performed with a bag filter using organic heat-resistant fibers as a filter material. The bag filter has a multilayer structure in which a fine non-woven fiber aggregate is laminated on a base fabric made of a woven fabric [JP-A-11-137930, JP-A 2001-1209].
26, JP 2001-149719 A, etc.]
The gas that collects the fine dust on the fiber and passes through the filter is discharged after removing acidic substances such as hydrogen chloride and sulfur oxides in the gas. This method has a small pressure loss and a very high dust collection efficiency, and is suitable for dry dust collection. However, in the process of lowering the temperature of high-temperature exhaust gas to 200 ° C or lower, it is in the dioxin formation temperature range of 200
The time in the range of up to 400 ° C must be suppressed for a short period of time, and for this reason forced cooling is required with cooling equipment such as cooling water. Further, there is a problem that water in the exhaust gas and an acidic substance in the gas corrode the metal parts of the related equipment and that the incineration ash tends to stick.

On the other hand, if the dust can be removed at a high temperature of 400 ° C. or more, the causative substance that produces dioxin is removed here, so that the gas after passing through the filter can be sufficiently cooled, which is advantageous in terms of energy. And
Furthermore, since the particles that generate acidic substances are also removed, the corrosion is greatly mitigated.

However, in order to remove dust at a high temperature of 400 ° C. or higher, a filter that can be used at that temperature is required,
For this purpose, a porous ceramic molded body filter and a bag filter that can be used at high temperatures have been proposed. But,
Method using porous ceramic compact [Japanese Patent Laid-Open No. 11-2
No. 53722, JP-A-9-10527, etc.]
Has a great feature of withstanding high temperatures, but it cannot be completely blown off by backwashing during cleaning because the fine particles penetrate deep into the pores, and the ventilation resistance of the ceramic filter for dust collection increases as the cleaning work is repeated. Is gradually rising, and soot dust accumulates and solidifies on the dust collecting side, narrowing the gas flow passage and applying pressure to destroy the ceramic molded body, or when the air flow is injected during backwashing, the temperature becomes high. There is a problem that a certain ceramic molded body cannot be endured against thermal shock and is damaged because it is rapidly cooled.

Bag filters that can be used at high temperatures include, for example, a high temperature dust collecting layer based on stainless fiber or carbon fiber and a high temperature strength layer based on stainless fiber,
Further, a filter dust collecting device in which a retainer (supporter) is combined has been proposed (Japanese Patent Laid-Open No. 61-28415). Up to now, metal fibers have been produced by a so-called "focused wire drawing method" in which a large number of steel wires are wrapped in a sheathing material, which are bundled and drawn, and then the sheathing material is chemically removed. The steel materials that can be manufactured by this method are limited, and the usable temperature of the metal fibers manufactured up to now is 500 ° C., and since the fiber cross section is circular, metal fibers are used when forming a fiber aggregate. The fibers are slippery and the aggregate is easily broken, and the cost is high.

[0009]

The object of the present invention is 40
(EN) It is possible to provide a dry filter material which can be used at a high temperature of 0 ° C or more and is resistant to repeated vibration when the accumulated dust is blown off by flowing high pressure air in the reverse direction, and a bag filter made of the dry filter material.

[0010]

[Means for Solving the Problems] In order to achieve the above object,
As a result of extensively seeking and investigating a wide range of materials that can withstand high temperatures and that are convenient for using bag filters, a bag that withstands high temperatures by forming a structure in which metal fiber aggregates obtained by the cutting method are entangled on a ceramic woven fabric. The inventors have found that a filter can be made and have completed the present invention.

That is, the invention of claim 1 is a dry filter material, wherein a metal fiber aggregate obtained by a cutting method is needling and entangled on the surface of a base fabric made of a ceramic woven fabric to be laminated in a two-layer structure. It is characterized by having done.

The invention of claim 2 is a dry filter material, wherein a metal fiber aggregate obtained by a cutting method is needling and entwined on both sides of a base fabric made of a ceramic woven fabric and laminated in a three-layer structure. It is characterized by that.

The invention of claim 3 is the dry filter material according to claim 1 or 2, wherein the material of the metal fiber is stainless heat resistant steel containing 15 to 25% by weight of chromium and 3 to 10% by weight of aluminum. It is characterized by that.

The invention according to claim 4 is the dry filter material according to claim 1 or 2, wherein the metal fiber is produced from the stainless heat-resistant steel according to claim 3 by a coil material cutting method. There is.

The invention of claim 5 is the dry filter material according to claim 1 or 2, wherein the ceramic woven fabric is made of silica fiber.

A sixth aspect of the present invention is the dry filter material according to the first or second aspect, characterized in that the aggregate of metal fibers is laminated and further coated with a ceramic paint.

The invention of claim 7 is a bag filter,
The dry filter material according to any one of claims 1 to 6 is used.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The dry filter material of the present invention comprises a ceramic woven fabric as a base fabric, and an aggregate of metal fibers obtained by a cutting method is laminated on the surface thereof and entwined and integrated by needling. .

The ceramic woven fabric used in the present invention is a woven fabric composed of at least one selected from silicon carbide, silicon nitride, alumina, silica, alumina silica, boron nitride, etc., and preferably composed of silica fibers. ,
Usually, a multifilament with a fiber diameter of 5 to 15 μm
Satin weave or plain weave, preferably with a basis weight of 30
0 to 1400 g / m ² , more preferably 400 to 80
It is 0 g / m ² .

The metal fiber used in the present invention is manufactured by a cutting method. In addition to the above-mentioned focused wire drawing method, the metal fiber is a wire in which a steel wire with a diameter of about 3 mm is wound around a pair of left and right rolls with guide grooves several tens of times, the raw material is supplied by the rotation of the rolls, and cutting is performed by a tool It is manufactured by a cutting method, a coil material winding method in which a thin metal plate is wound in a coil shape, and an end face thereof is cut to form a thin metal fiber having a small diameter. The metal fiber of the present invention may be manufactured by any of a wire cutting method and a coil material cutting method, but is preferably a coil material cutting method. The coil material cutting method was difficult to put into practical use commercially because of the welding phenomenon between thin plates, but a method was developed to coat and cut the separation membrane into fibers, and then wash and remove the separation membrane. Since then, the practicality has improved significantly [Journal of the Textile Machinery Society, 51
No. 2, No. 2, pp. 106-112 (1998)]. The cutting method, especially the coil material cutting method, has a wide selection range of steel materials that can be made into fibers, can make fibers of various diameters, and since the manufacturing equipment is simple, it is cheaper than other methods. Metal fibers can be obtained with. Further, the fibers formed by the cutting method have a substantially rectangular cross-sectional shape, and when formed into a fiber aggregate, the fibers are easily entangled with each other, which is convenient because the fibers do not easily slip.

The material of the metal fiber in the present invention is preferably 15 to 25% by weight of chromium and 3 to 1 of aluminum.
It is a stainless heat resistant steel containing 0% by weight, more preferably 18 to 21% by weight of chromium and 4 to 6% by weight of aluminum. At this time, the components other than chromium and aluminum contained in iron are general trace components contained in iron and steel and are not particularly limited, but usually the total of trace components other than chromium and aluminum is 1 in the stainless heat-resistant steel. weight%
It is the following. By using the metal fiber made of such stainless heat-resistant steel, it can be stably used even in a high temperature range of 700 to 1000 ° C. and the acid resistance is improved. The usable temperature of the stainless steel by the focused wire drawing method, for example, SUS316, is 500 ° C. and the deterioration is severe especially in an acidic atmosphere. However, the steel material used in the present invention can be used at a higher temperature than before, Little deterioration even in the atmosphere.

The metal fibers are selected to have a reduced diameter (diameter of the cross section of a circle having the same cross-sectional area) of 25 to 100 μm, preferably 25 to 50 μm. This range is selected from the effect of collecting fine particles and the availability as metal fibers.

The dry filter material is manufactured by using a ceramic woven fabric as a base fabric, and arranging metal fibers whose fiber length is cut to about 50 to 100 mm on the surface thereof as an aggregate, entwining them by a needling and laminating them to be integrated. To do. The metal fiber aggregate has a two-layer structure in which a ceramic woven fabric is placed on one side of a base fabric, or a three-layer structure in which a ceramic woven fabric is placed on both sides of the base fabric. When made into a bag filter, it is the metal fiber aggregate layer that collects dust, and a two-layer structure is sufficient for this purpose. However, as will be described later, the ceramic woven fabric is inferior in bending stress, abrasion resistance, and alkali resistance, and is particularly apt to be damaged by the vibration of the high-pressure air blown off, so that the metal fiber aggregate layer compensates for this weakness. Therefore, it is significant to place the metal fiber aggregate layer on both sides of the ceramic woven fabric to form a three-layer structure. Therefore, the metal fibers on the surface to collect dust are preferably selected to have a small fiber diameter to enhance the dust collection effect, but the metal fibers used on the opposite side may have a larger diameter.

According to the present invention, the metal fiber aggregate can be fixed by applying a ceramic coating to the metal fiber aggregate to prevent the metal fibers from falling off, if necessary. The ceramic paint is not particularly limited as long as it forms a heat resistant coating on the metal surface, but for example, silicates, which are generally marketed as heat resistant paints for steel materials, siloxane resins, etc. are used as binders and silica. There are compositions containing inorganic fillers such as alumina, mica, and titanium oxide. The adhered amount of the ceramic paint is 50% by weight or less with respect to the metal fiber, and is practically 5 to 30%. If the adhered amount is more than 50% by weight, the air permeability will be reduced and the function as a filter will be impaired. On the contrary, if the adhered amount is less than 5% by weight, the significance of applying the ceramic coating may not be fully exerted.

The dry filter material of the present invention is characterized in that the ceramic base cloth and the cut metal fiber aggregate are laminated and integrated. Ceramic woven cloth is very strong against heat and has sufficient strength even at 1000 ° C, but it is inferior in bending stress, abrasion resistance, and alkali resistance, and fine particles deposited on the filter are backwashed by high-pressure air to be wiped off. It is easy to be damaged by the vibration applied at the time of. On the other hand, the metal fiber aggregate plays the most important role as a filter for collecting fine particles in gas, and complements the disadvantages of the ceramic woven fabric inferior in bending stress, abrasion resistance, and alkali resistance. . Thus, by combining the ceramic base cloth and the metal fiber aggregate, it is possible to provide a bag filter that can withstand high temperatures and withstand vibrations during repeated particle removal.

[0026]

EXAMPLES Example-1: FIG. 1 shows a dry type filter of the present invention.
It is a schematic diagram of a luther material. Dry filter material 1 is ceramic
Randomly woven on the surface of the woven fabric 2 made of wool fibers
Place the metal fiber layer 3 by the above cutting method and knead from above.
Ring and integrated. Ceramic fiber woven cloth 2 is
620 g / m2 made of mosquito fiber^Two, Thickness 0.72m
m, 8 sheets of satin weave were used. The metal fiber layer 3 is made of chromium (C
r) 20 wt% and aluminum (Al) 5 wt% resistant
Cutting hot stainless steel [made by Nippon Steel Corporation] into coil material
By the method, it is made into fibers with a converted diameter of 35 μm and this is weighted 1
000g / m ^Two, 3.5mm thick, needle density 1
20 / cm^TwoNeedling and joining. Needle
Can be performed without breaking the needle and has a thickness of 4 mm,
Basis weight 1600 g / m^Two, Density 0.40 g / cm^ThreeDry type
The filter material 1 could be obtained. Also, dry fill
The tar material 1 has excellent durability without delamination,
The fiber layer 3 also provided cushioning properties. Ceramic fiber
700 ° C when only woven fabric 2 made of fiber is used as a filter
In the atmosphere, the sutures were damaged due to vibration.
The ceramic base cloth and cut metal fiber of the present invention
7 for dry filter 1 that is made by stacking and integrating aggregates
It could be used even in an atmosphere of 00 ° C.

Example-2: On the dry filter material 1 obtained in Example 1, a thermosetting silica coating material was diluted with a thinner and sprayed to apply the surface, followed by heat drying at 150 ° C., and filter weight. To 10%. This thermosetting silica-based coating material had heat resistance equivalent to that of the dry filter material 1 of the present invention, and it was possible to prevent the metal fibers, which had been partially divided by needling, from falling off and to promote integration.

[0028]

The dry filter material according to the present invention is
It is stable at a high temperature of 0 ° C. or higher, and is resistant to repeated vibrations caused by blowing back high pressure air when it is used as a bag filter, and is useful as a bag filter for high temperature region. Since it is possible to collect dust at a high temperature of 400 ° C or higher, dioxin-causing substances can be removed before dioxin is generated to eliminate environmental pollution, and particles that generate acidic substances are also removed, so corrosion is greatly reduced, Moreover, since the exhaust gas can be treated without forced cooling, it is advantageous in terms of energy.

[Brief description of drawings]

FIG. 1 is a schematic view of a dry filter material (two-layer structure) of the present invention.

[Explanation of symbols]

1: Heat resistant filter 2: Woven cloth (woven cloth made of ceramic fibers) 3: Metal fiber layer

Claims (7)

[Claims] 1. A surface of a base cloth made of ceramic woven cloth,
A dry filter material, characterized in that an aggregate of metal fibers obtained by a cutting method is needling, entwined and laminated in a two-layer structure. 2. A dry filter material, characterized in that an aggregate of metal fibers obtained by a cutting method is needling and entwined on both sides of a base fabric made of ceramic woven fabric and laminated in a three-layer structure. 3. The metal fiber is made of 15 to 15% chromium.
A stainless heat resistant steel containing 25% by weight and 3 to 10% by weight of aluminum.
Dry filter material described. 4. The dry filter material according to claim 1 or 2, wherein the metal fiber is produced from the stainless heat-resistant steel according to claim 3 by a coil material cutting method. 5. The dry filter material according to claim 1 or 2, wherein the ceramic woven fabric is made of silica fiber. 6. The ceramic coating is further coated on the metal fiber aggregates laminated together.
Alternatively, the dry filter material described in 2. 7. A bag filter using the dry filter material according to any one of claims 1 to 6.