JP4126643B2 - Dry filter material and bag filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high temperature region filter material for collecting dust in a high temperature gas such as an incinerator and a boiler, and a bag filter using the same.
[0002]
[Prior art]
Air pollution caused by harmful substances and environmental pollution caused by dioxins have become serious global environmental problems, and regulations have been strengthened globally. It is obliged to collect dust and remove nitrogen oxides and sulfur oxides in industrial combustion furnaces such as boilers and incinerators. It has been. In particular, dioxin is a highly toxic and carcinogenic hazardous substance that has strict regulations worldwide. In Japan, as a designated substance based on the Air Pollution Control Law, regulation values and application in accordance with the treatment capacity of incinerators. Legislative regulations that set the timing came into effect on December 1, 1997. In particular, in order to comply with the environmental standards of the “Dioxin Countermeasures Measures Law” to be applied in the future, it is obliged to install an advanced exhaust gas dust collector regardless of whether it is newly installed. Cost reduction is required.
[0003]
Dioxins are said to be generated by the catalytic action of metal compounds during incomplete combustion at low combustion temperatures. Even if complete combustion is performed under strict control in an incineration chamber, dioxins fly in the exhaust gas cooling process. It is re-synthesized from a very small amount of precursor using metals in ash as a catalyst. Resynthesis is said to be particularly high at temperatures of 200 to 400 ° C in the subsequent equipment where the temperature is lower than that of the combustion chamber. Therefore, dioxins are generated by collecting dust at a low temperature of 200 ° C or lower, or at a high temperature of 400 ° C or higher. Can be suppressed.
[0004]
For dust collectors, the method using an electrostatic precipitator and the method using a bag filter are the mainstream. However, the electrostatic precipitator has a large equipment cost and is not easy to maintain, and its operating temperature is around 300 ° C. There are many limits to dioxin suppression. Therefore, a bag filter system that collects dust at a temperature of 200 ° C. or lower is now mainstream.
[0005]
The treatment at 200 ° C. or lower can be performed with a bag filter using an organic heat-resistant fiber as a filter material. The bag filter has a multilayer structure in which fine non-woven fiber aggregates are laminated on a base fabric made of woven fabric [JP-A-11-137930, JP-A-2001-120926, JP-A-2001-149719. The gas that has collected the fine dust on the fiber and passed through the filter is released after removing acidic substances such as hydrogen chloride and sulfur oxide in the gas. This method is suitable for dry dust collection with low pressure loss and very high dust collection efficiency. However, in the process of lowering the high-temperature exhaust gas to 200 ° C. or lower, the time in the range of 200 to 400 ° C. that is the dioxin generation temperature range must be kept short. Forced cooling is required. Furthermore, there was a problem of corroding the metal parts of the related equipment due to moisture in the exhaust gas and acidic substances in the gas, and incineration ash was likely to stick.
[0006]
On the other hand, if the dust can be removed at a high temperature of 400 ° C. or higher, the causative substance that generates dioxin is removed here, so that the gas after passing through the filter is sufficient for gradual cooling, which is advantageous in terms of energy, In addition, the particles that generate acidic substances are also removed, which greatly reduces corrosion.
[0007]
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 a high temperature have been proposed. However, the method using a porous ceramic molded body (JP-A-11-253722, JP-A-9-10527, etc.) has a great feature that it can withstand high temperatures, but the fine particles penetrate deep into the pores. There is a problem that the ventilation resistance of the dust collecting ceramic filter gradually increases as the cleaning operation is repeated and the dust resistance is accumulated and solidified on the dust collecting side. Narrowing the gas flow path and applying pressure to destroy the ceramic molded body, or spraying an air flow during backwashing causes the high temperature ceramic molded body to cool rapidly, resulting in failure to withstand thermal shock and damage There is a problem.
[0008]
Bag filters that can be used at high temperatures are proposed, for example, high-temperature dust collection layers based on stainless steel or carbon fibers, high-temperature strength layers based on stainless steel fibers, and filter dust collectors that combine retainers (supports). JP, 61-28415, A). Until now, metal fibers have been manufactured by a so-called “focused wire drawing method” in which a large number of steel wires are wrapped with an outer packaging material, the bundles are bundled and drawn, and then the outer packaging material is chemically removed. The steel materials that can be produced by this method are limited, and the usable temperature of metal fibers produced so far is limited to 500 ° C, and the fiber cross section is circular. There was a drawback that the fibers were slipping and the aggregate was easily broken, and the price was high.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide a dry filter material that can be used at a high temperature of 400 ° C. or higher and that is resistant to repeated vibrations when dust particles are removed by flowing high-pressure air in reverse, and a bag filter comprising the same. It is.
[0010]
[Means for Solving the Problems]
In order to achieve the above objective, a wide range of materials that can withstand high temperatures and that are convenient for use in bag filters have been studied and studied. As a result, a metal fiber assembly obtained by cutting is entangled on a ceramic woven fabric. As a result, it has been found that a bag filter that can withstand high temperatures can be obtained, and the present invention has been completed.
[0011]
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 and laminated in a two-layer structure. It is a feature.
[0012]
The invention of claim 2 is a dry filter material, characterized in that an aggregate of metal fibers obtained by a cutting method is entangled on both sides of a base fabric made of a ceramic woven fabric and laminated in a three-layer structure. It is said.
[0013]
The invention according to claim 3 is the dry filter material according to claim 1 or 2, wherein the metal fiber is a stainless heat-resistant steel containing 15 to 25% by weight of chromium and 3 to 10% by weight of aluminum. It is said.
[0014]
A fourth aspect of the present invention is the dry filter material according to the first or second aspect, wherein the metal fiber is produced from the stainless heat-resistant steel according to the third aspect by a coil material cutting method.
[0015]
A fifth aspect of the invention is the dry filter material according to the first or second aspect, wherein the ceramic woven fabric is made of silica fibers.
[0016]
A sixth aspect of the present invention is the dry filter material according to the first or second aspect, wherein the ceramic fiber coating is further coated on the laminated metal fiber aggregate.
[0017]
The invention of claim 7 is a bag filter, characterized in that the dry filter material according to any one of claims 1 to 6 is used.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
In the dry filter material of the present invention, a ceramic woven fabric is used as a base fabric, and an assembly of metal fibers obtained by a cutting method is laminated on the surface thereof and entangled and integrated by needling.
[0019]
The ceramic woven fabric used in the present invention is composed of one or more selected from silicon carbide, silicon nitride, alumina, silica, alumina silica, boron nitride, and the like, and is preferably a woven fabric composed of silica fibers. A multifilament having a fiber diameter of 5 to 15 μm is a satin weave or plain weave. The basis weight of the woven fabric is preferably 300 to 1400 g / m ² , more preferably 400 to 800 g / m ² .
[0020]
The metal fiber used for this invention is manufactured by the cutting method. In addition to the focused wire drawing method described above, a metal fiber is a wire in which a steel wire having a diameter of about 3 mm is wound around a pair of left and right rolls with guide grooves several tens of times, the material is supplied by rotating the roll, and cutting is performed with a tool. It is manufactured by a cutting method, a coil material cutting method in which a thin metal plate is wound in a coil shape, and the end surface is cut into a thin and long metal fiber. The metal fiber of the present invention may be manufactured by any of the wire cutting method and the coil material cutting method, but is preferably based on the coil material cutting method. The coil material cutting method was difficult to commercialize due to the welding phenomenon between thin plates, but a method was developed in which the separation membrane was coated and cut into fibers, and then the separation membrane was washed and removed. Since then, practicality has been improved in various stages (see Journal of Textile Machinery Society, 51 卷, No. 2, pages 106-112 (1998)). The cutting method, especially the coil material cutting method, has a wide selection range of steel grades that can be made into fibers, can be made into fibers of various diameters, and has a simple manufacturing facility, so it is less expensive than other methods. Metal fibers can be obtained with Furthermore, the fiber by the cutting method has a substantially rectangular cross-sectional shape, and when it is made into a fiber assembly, the fibers are entangled with each other, and the fibers do not slip easily.
[0021]
The material of the metal fiber in the present invention is preferably a stainless heat resistant steel containing 15 to 25% by weight of chromium, 3 to 10% by weight of aluminum, more preferably 18 to 21% by weight of chromium and 4 to 6% by weight of aluminum. It is. At this time, the components other than chromium and aluminum contained in the iron are general trace components contained in the steel and are not particularly limited. However, the total amount of trace components other than chromium and aluminum is usually 1 in the stainless heat resistant steel. % By weight or less. By using such a metal fiber from stainless heat resistant steel, it can be used stably even in a high temperature range of 700 to 1000 ° C., and acid resistance is improved. In stainless steel by the focused wire drawing method, for example, SUS316, the temperature that can be used is limited to 500 ° C., and deterioration is severe particularly in an acidic atmosphere, but the steel material used in the present invention can be used at a higher temperature than before, and is acidic There is little deterioration even in the atmosphere.
[0022]
The metal fiber has a converted diameter (diameter having the same cross-sectional area and a diameter of its cross section) of 25 to 100 μm, preferably 25 to 50 μm. This range is selected from the effect of collecting fine particles and the availability of metal fibers.
[0023]
In the production of the dry filter material, a ceramic woven fabric is used as a base fabric, and metal fibers whose fiber length is cut to about 50 to 100 mm are placed on the surface of the fabric, and they are entangled by needling and laminated to be integrated. The metal fiber assembly has a two-layer structure in which a ceramic woven fabric is placed on one side of the base fabric, or a three-layer structure in which a ceramic woven fabric is placed on both sides of the base fabric. When a bag filter is used, it is the metal fiber assembly 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, friction resistance, and alkali resistance, and is easily damaged by vibration caused by high pressure air, and the metal fiber aggregate layer compensates for this weakness. Therefore, there is a significance that the metal fiber assembly layer is placed on both sides of the ceramic woven fabric to form a three-layer structure. Therefore, the metal fibers on the dust collecting surface are preferably selected to have a small fiber diameter. However, the metal fibers used on the opposite side may have a larger diameter.
[0024]
In the present invention, if necessary, a ceramic coating can be applied to the metal fiber assembly to prevent the metal fibers from falling off and to fix the metal fiber assembly. The ceramic paint is not particularly limited as long as it can form a heat-resistant coating on the metal surface. For example, silicates or siloxane resins that are generally marketed as heat-resistant paints for steel materials are used as a binder, and silica is used. There are compositions containing inorganic fillers such as alumina, mica and titanium oxide. The adhesion amount of the ceramic paint is 50% by weight or less with respect to the metal fiber, and is practically 5 to 30%. When the adhesion amount is more than 50% by weight, the air permeability is reduced and the function as a filter is impaired. On the other hand, when the adhesion amount is less than 5% by weight, the significance of applying the ceramic paint may not be fully exhibited.
[0025]
The dry filter material of the present invention is characterized in that a ceramic base fabric and a cut metal fiber assembly are laminated and integrated. Ceramic woven fabric is extremely resistant to heat and has sufficient strength even at 1000 ° C, but it is inferior in bending stress, friction resistance, and alkali resistance, and the fine particles deposited on the filter are made to flow backward by high pressure air. It is easy to be damaged by the vibration applied at the time. On the other hand, the metal fiber aggregate plays the most important role as a filter for collecting fine particles in the gas, and complements the disadvantages of the ceramic woven fabric that are inferior in bending stress, friction resistance and alkali resistance. . In this way, the combination of the ceramic base fabric and the metal fiber aggregate can provide a bag filter that can withstand high temperatures and can withstand vibration during repeated fine particle removal.
[0026]
【Example】
Example-1 FIG. 1 is a schematic view of a dry filter material of the present invention. In the dry filter material 1, a metal fiber layer 3 formed by a cutting method formed into a random web was placed on the surface of a woven fabric 2 made of ceramic fibers and integrated by needling from above. As the ceramic fiber woven fabric 2, a satin weave having a basis weight of 620 g / m ² , a thickness of 0.72 mm, and made of silica fibers was used. The metal fiber layer 3 is made of a heat-resistant stainless steel (produced by Nippon Steel Corporation) containing 20% by weight of chromium (Cr) and 5% by weight of aluminum (Al) by a coil material cutting method, and converted into a fiber having a converted diameter of 35 μm. They were accumulated at a basis weight of 1000 g / m ² and a thickness of 3.5 mm, and were joined by needling at a needle density of 120 needles / cm ² . Needling can be performed without breaking the needle, and the dry filter material 1 having a thickness of 4 mm, a basis weight of 1600 g / m ² , and a density of 0.40 g / cm ³ can be obtained. In addition, the dry filter material 1 was excellent in durability without delamination, and the metal fiber layer 3 provided cushioning properties. If only the woven fabric 2 made of ceramic fibers is used as a filter, the stitching part may be damaged due to vibration in an atmosphere at 700 ° C. However, the ceramic base fabric of the present invention and the cut metal fiber assembly are laminated and integrated. The dried dry filter 1 could be used in an atmosphere at 700 ° C.
[0027]
Example-2: The dry filter material 1 obtained in Example 1 was sprayed with a thermosetting silica-based paint diluted with a thinner and spray-coated, heat-dried at 150 ° C., and 10 times the weight of the filter. %. This thermosetting silica-based paint has a heat resistance equivalent to that of the dry filter material 1 of the present invention, and it was possible to prevent the metal fibers slightly cut off by needling from falling off and to promote integration.
[0028]
【The invention's effect】
The dry filter material according to the present invention is stable at a high temperature of 400 ° C. or higher, and is resistant to repeated vibration caused by the dust dust flow-off caused by the reverse flow of high-pressure air when used as a bag filter, and is useful as a bag filter for high temperature regions. It is. Since dust can be collected at a high temperature of 400 ° C or higher, dioxin-causing substances can be removed before dioxins are generated to eliminate environmental pollution, and particles that generate acidic substances are also removed, so corrosion is greatly reduced. In addition, the exhaust gas can be treated without forced cooling, which is advantageous in terms of energy.
[Brief description of the 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)

A dry filter material comprising a base fabric made of a ceramic woven fabric, a metal fiber aggregate obtained by a cutting method is needling and entangled to form a two-layer structure. A dry filter material characterized in that an aggregate of metal fibers obtained by a cutting method is entangled on both sides of a base fabric made of a ceramic woven fabric, and is laminated in a three-layer structure. 3. The dry filter material according to claim 1, wherein the metal fiber is a stainless heat resistant steel containing 15 to 25% by weight of chromium and 3 to 10% by weight of aluminum. 3. 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. The dry filter material according to claim 1 or 2, wherein the ceramic woven fabric is made of silica fibers. 3. The dry filter material according to claim 1, wherein a ceramic paint is further coated on the laminated metal fiber aggregate. A bag filter using the dry filter material according to claim 1.

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