Dust collecting filter cloth, bag filter, and dust collector

Abstract

To provide a dust collecting filter cloth which has non-combustibility in addition to heat resistance, durability and flexibility and achieves low pressure loss and high dust collection efficiency and a bag filter, and to provide a dust collector including the bag filter.SOLUTION: A dust collecting filter cloth is provided that includes: a base fabric layer formed by an inorganic fiber cloth containing a stainless steel wire; and heat-resistant inorganic fiber layers disposed on both surfaces of the base fabric layer. The base fabric layer and the heat-resistant inorganic fiber layers are integrated by needling. The heat-resistant inorganic fiber layer comprises 100% inorganic fibers as a constituent fiber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a dust collection filter cloth, a bag filter using the dust collection filter cloth, and a dust collector including the bag filter. [Background technology]

[0002] A bag filter, which is made by sewing a dust-collecting filter cloth into a cylindrical shape, is installed in a dust collector, for example, while covering a cylindrical retainer. Dust-containing exhaust gas generated from a steel mill or the like is sent into the dust collector and passes through the dust-collecting filter cloth that constitutes the bag filter from the upstream side (outside) to the downstream side (inside), and the purified exhaust gas is released into the atmosphere. If the filter cloth continuously collects dust in the exhaust gas, the filter cloth becomes clogged and its dust-collecting capacity decreases. To regenerate the dust-collecting capacity of the dust-collecting filter cloth, for example, compressed air or the like is blown from the downstream side (inside) of the dust-collecting filter cloth to the upstream side (outside) at regular intervals to remove the dust collected on the filter cloth, a process known as "backwashing."

[0003] Heat resistance is required for bag filters used in sites where high-temperature gas containing dust is emitted, such as steelworks. Methods for treating high-temperature exhaust gas include installing cooling equipment before the dust collector to cool the high-temperature exhaust gas, and then treating the exhaust gas with a room-temperature bag filter made of organic fiber, or directly treating the high-temperature exhaust gas using a bag filter made of heat-resistant metal material or ceramic molded material.

[0004] The former method requires cooling equipment and is therefore disadvantageous in terms of energy conservation. Therefore, for example, by using a bag filter made of a highly heat-resistant metal material such as stainless steel, it is possible to directly treat high-temperature exhaust gas. However, such bag filters have poor compatibility with bag filters used in existing dust collectors. Furthermore, such bag filters result in high pressure loss and high costs. Furthermore, such bag filters result in a decrease in dust collection efficiency due to issues with the workability of the material and the diameter of the stainless steel. Therefore, there is a demand for dust collecting filter cloths and bag filters that combine heat resistance, durability, and flexibility, while enabling low pressure loss and high dust collection efficiency.

[0005] Patent Document 1 describes a bag filter that uses a needle felt (dust-collecting filter fabric) made of a glass woven fabric base fabric consisting of threads in which metal wires are twisted into glass fibers, and a web containing glass fibers and heat-resistant organic fibers arranged on one or both sides of the base fabric, the base fabric and the web being integrated by needling. According to Patent Document 1, the above needle felt and bag filter were faced with the problem of a complete lack of materials that could withstand temperatures from 260°C to 400°C, and to solve this problem, a bag filter that can be used at high temperatures and has excellent mechanical properties was provided.

[0006] Patent Document 2 describes a dust collecting filter cloth and a bag filter using the same, which includes a base layer made of stainless steel wire-reinforced inorganic fiber cloth and a laminate layer containing organic fibers, inorganic fibers, or stainless steel metal fibers arranged on one or both sides of the base layer, the base layer and the laminate layer being integrated by needling and coated on both sides with a heat-resistant binder. According to Patent Document 2, the dust collecting filter cloth and bag filter combine heat resistance, durability, and flexibility, and also achieve low pressure loss and a high dust collection rate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-84554 [Patent Document 2] Japanese Patent Application Publication No. 2019-25422 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a dust collecting filter cloth and a bag filter that are heat resistant, durable, flexible, and non-flammable, and that combine low pressure loss with a high dust collection rate, and a dust collecting device equipped with this bag filter. [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided a dust-collecting filter cloth comprising a base fabric layer made of stainless steel wire-reinforced inorganic fiber cloth and heat-resistant inorganic fiber layers disposed on both sides of the base fabric layer. The base fabric layer and the heat-resistant inorganic fiber layer are integrated by needling. The heat-resistant inorganic fiber layer contains 100% inorganic fibers as its constituent fibers.

[0010] In the dust collecting filter cloth according to the first aspect of the present invention, the stainless steel wire-reinforced inorganic fiber cloth may contain glass fibers containing 60% or more of silicon dioxide, and the inorganic fibers contained in the heat-resistant inorganic fiber layer may contain glass fibers containing 60% or more of silicon dioxide.

[0011] According to a second aspect of the present invention, there is provided a bag filter in which the dust collecting filter cloth according to the first aspect is sewn.

[0012] According to a third aspect of the present invention, there is provided a dust collecting device including the bag filter according to the second aspect. [Effects of the Invention]

[0013] According to the present invention, there are provided a dust collecting filter cloth and a bag filter that are heat resistant, durable, flexible and non-flammable, and that also achieve low pressure loss and high dust collection efficiency, as well as a dust collecting device equipped with this bag filter. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a dust collecting filter cloth according to an embodiment of the present invention. [Figure 2] 1 is a partially cutaway perspective view schematically illustrating an example of a bag filter according to an embodiment of the present invention. [Figure 3] 1 is a cross-sectional view schematically illustrating an example of a dust collecting device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, components that perform the same or similar functions are designated by the same reference numerals, and redundant description will be omitted.

[0016] FIG. 1 is a cross-sectional view showing an example of a dust collecting filter cloth according to one embodiment of the present invention. The dust-collecting filter cloth 1 shown in Fig. 1 comprises a base fabric layer 2 and heat-resistant inorganic fiber layers 3 disposed on both sides of the base fabric layer 2. The base fabric layer 2 and the heat-resistant inorganic fiber layers 3 are integrated by needling.

[0017] The base fabric layer 2 is a layer made of plain woven or twill woven inorganic fiber cloth containing stainless steel wires (SUS wires). The inorganic fiber cloth containing stainless steel wires includes inorganic fiber cloth 4 and stainless steel wires 5 woven into the inorganic fiber cloth 4.

[0018] The material of the inorganic fibers constituting the inorganic fiber cloth 4 used in the fabric layer 2 is, for example, glass, crystallized glass (glass ceramics), or a mixture thereof, and does not include refractory ceramic fiber (RCF). Crystallized glass may contain, for example, silica (SiO2), alumina (Al2O3), and calcium oxide (CaO). The material of the inorganic fibers constituting the inorganic fiber cloth 4 is appropriately selected depending on the temperature range of the exhaust gas expected at the site. A specific example of the inorganic fiber cloth 4 is acid-resistant glass cloth. The fiber diameter of the inorganic fibers is, for example, 5 μm to 13 μm. The fiber length of the inorganic fibers is, for example, 30 mm to 100 mm. The basis weight of the inorganic fiber cloth 4 is, for example, 800 g / m 2 ~1250g / m 2 is.

[0019] The type of stainless steel wire 5 used in the fabric layer 2 is not particularly limited and can be appropriately selected in consideration of heat resistance and processability. The diameter of the stainless steel wire 5 is, for example, 50 μm to 300 μm, preferably 50 μm to 200 μm, and more preferably 100 μm to 180 μm. The stainless steel wire 5 is woven into the inorganic fiber cloth 4 by plain weave or twill weave. The weight of the stainless steel wire 5 is, for example, 90 g / m 2 ~130g / m 2 , preferably 100 g / m 2 ~120g / m 2 , more preferably 105 g / m 2 ~115g / m 2 is.

[0020] By weaving the stainless steel wires 5 into the inorganic fiber cloth 4, the strength of the base fabric layer 2 can be improved. Furthermore, by providing this base fabric layer 2, the strength of the entire filter cloth against the inflowing exhaust gas is improved. A bag filter in which the dust-collecting filter cloth is sewn into a cylindrical shape can be installed in a dust collector, for example, with a cylindrical retainer covered. By improving the strength of the filter cloth, friction with the retainer can be prevented. In other words, by providing the base fabric layer 2, the durability of the entire filter cloth can be improved. The basis weight of the base fabric layer 2 is, for example, 500 g / m 2~1500g / m 2 The thickness of the fabric layer 2 is, for example, 0.3 mm to 2.5 mm.

[0021] The heat-resistant inorganic fiber layer 3 is a web made of inorganic fibers. The heat-resistant inorganic fiber layer 3 contains 100% inorganic fibers as its constituent fibers and does not contain any organic materials as constituent materials of the web. This allows the dust collecting filter cloth 1 to be non-flammable. Therefore, the dust collecting filter cloth 1 will not burn even when exposed to sparks or ironwork. A layer containing less than 100% inorganic fibers as constituent fibers, for example, a layer containing a few percent organic fibers as constituent fibers, may exhibit flame retardancy but will not be non-flammable.

[0022] Compared to inorganic fibers, organic fibers have superior flex resistance. For example, bag filters using organic fibers are advantageous in terms of resistance to continuous pulses of compressed air during pulse-jet backwashing and dust removal performance. However, the inventors have discovered that even a dust collecting filter cloth 1 using a heat-resistant inorganic fiber layer 3 made entirely of inorganic fibers can fully exhibit the resistance to continuous pulses, dust removal performance, and flex resistance required of a bag filter. Therefore, the dust collecting filter cloth 1 and a bag filter using it combine heat resistance, durability, flexibility, and non-flammability, while also achieving low pressure loss and high dust collection efficiency.

[0023] Here, the heat-resistant inorganic fiber layer 3 containing 100% inorganic fibers as its constituent fibers means that the material forming the web that constitutes the heat-resistant inorganic fiber layer 3 is made up of inorganic fibers. For example, a small amount of organic fibers mixed between the fibers in an inorganic fiber web structure is not considered to be a constituent fiber. Note that a modifier containing an organic material may be used when forming the inorganic fiber web, but since this volatilizes at about 100°C to 300°C when the bag filter into which the dust collection filter cloth 1 is sewn is used, the non-flammability is not impaired by the modifier.

[0024] The material of the inorganic fibers used in the heat-resistant inorganic fiber layer 3 is, for example, glass, crystallized glass (glass ceramics), or a mixture thereof. The material of the inorganic fibers is appropriately selected depending on the temperature range of the exhaust gas expected at the site. A specific example of the inorganic fiber is heat-resistant glass fiber. The fiber diameter of the inorganic fibers used in the heat-resistant inorganic fiber layer 3 is 2 μm to 30 μm, preferably 4 μm to 15 μm, and more preferably 6 μm to 12 μm. The fiber length of the inorganic fibers is, for example, 50 mm to 150 mm. The heat-resistant inorganic fiber layer 3 may contain the inorganic fibers at a density of, for example, 200 g / m 2 ~1800g / m 2 , preferably 200 g / m 2 ~500g / m 2 , more preferably 300 g / m 2 ~450g / m 2 Includes basis weight.

[0025] For both the stainless steel wire-reinforced inorganic fiber cloth and the heat-resistant inorganic fiber layer 3, the inorganic fibers constituting the layer preferably contain glass fibers containing 60% or more silicon dioxide (SiO2) by mass. For example, E-glass, a glass fiber term specified in the Japanese Industrial Standard JIS R 3410:2006, has an SiO2 content of less than 60%, while C-glass, S-glass, and D-glass are glass fibers containing 60% or more SiO2. Fibers with a higher SiO2 content exhibit higher heat resistance and acid resistance. Basalt fiber is known as an inorganic fiber, but basalt contains approximately 50% SiO2 by mass. Therefore, it is preferable not to use basalt fiber as the inorganic fiber.

[0026] The inorganic fibers constituting the heat-resistant inorganic fiber layer 3 more preferably contain glass fibers containing SiO2 in a mass ratio of 64% or more.

[0027] The inorganic fibers may have a heat resistance temperature of, for example, 600°C as a fiber material. A dust collecting filter cloth 1 using such inorganic fibers can exhibit a heat resistance temperature of, for example, 350°C. As such, the heat resistance temperature of the fibers constituting the filter cloth is not directly reflected in the heat resistance temperature of the filter cloth. This is true not only for inorganic fibers but also for organic fibers. For example, aramid-based fibers using para-aramid resin can exhibit a heat resistance temperature of about 400°C, but the heat resistance temperature of a filter cloth composed solely of aramid-based fibers is limited to about 200°C at most. Furthermore, the heat resistance of fibers differs from the melting point (softening point) of the material forming the fibers. For example, the heat resistance of glass fibers with a melting point of 840°C can be 600°C.

[0028] This dust collecting filter cloth 1 can be produced, for example, by the following method: Heat-resistant inorganic fiber layers 3 are superimposed on both the front and back sides of a base fabric layer 2, and these are integrated by needling. The laminate integrated by needling can be optionally subjected to compression processing to obtain the dust collecting filter cloth.

[0029] The above-described dust-collecting filter cloth 1 can be sewn to form a cylindrical bag, and used as a bag filter to be installed in a dust collector that treats high-temperature exhaust gas.

[0030] An example of a bag filter according to one embodiment of the present invention is shown in a partially cutaway view in Fig. 2. The bag filter 6 shown in Fig. 2 covers a cylindrical retainer 7.

[0031] The bag filter 6 can be obtained by sewing the overlapping portions of the dust collecting filter cloth 1 together using inorganic or metal fiber threads, either alone or in combination. For example, glass threads are used on both sides of the overlapping portion of the dust collecting filter cloth 1, and SUS thread is used in the center. By employing such a sewing method, the strength of the bag filter 6 can be improved.

[0032] The diameter of the glass yarn is, for example, 5 μm to 50 μm, preferably 7 μm to 20 μm, more preferably 8 μm to 15 μm, and is made by twisting single fibers into a yarn of 0.3 mm to 1.0 mm. The diameter of the SUS yarn is, for example, 20 μm to 70 μm, preferably 30 μm to 60 μm, more preferably 45 μm to 55 μm, and is made by twisting single fibers into a bundle of multiple fibers into a yarn of 0.3 mm to 1.0 mm.

[0033] This bag filter 6 is made of the above-mentioned dust collecting filter cloth 1, and therefore is heat resistant, durable, flexible and non-flammable, and is capable of achieving both low pressure loss and high dust collection efficiency.

[0034] An example of a dust collecting device according to one aspect of the present invention is shown in Fig. 3. Fig. 3 is a cross-sectional view showing an example of such a dust collecting device 10.

[0035] The dust collector 10 includes a housing 11 that defines a flow path for exhaust gas and has a bag filter 6 installed therein, and a hopper 12 that receives dust that is removed from the bag filter 6 by backwashing. The housing 11 is, for example, supported by supports 17 while being elevated above the ground, with the hopper 12 located between the housing 11 and the ground. An inlet duct 15 is provided upstream of the flow path defined by the housing 11, through which exhaust gas from a steel mill or the like is introduced into the housing 11. In FIG. 3, the retainer 7 is omitted, and only the bag filter 6 that covers it is shown. An outlet duct 16 is provided downstream of the flow path, through which exhaust gas from which dust captured by the bag filter 6 has been removed is discharged. A compressed air jetting device 13 is provided downstream of the flow path relative to the bag filter 6, and a nozzle 14 of the compressed air jetting device 13 is provided downstream of the bag filter 6. For example, as shown in the figure, a plurality of bag filters 6 may be installed within the dust collector 10, and one nozzle 14 may be disposed above the upper opening of each bag filter 6.

[0036] Dust-laden exhaust gas generated at a steel mill or other facility is sent as dust-laden airflow 20 through inlet duct 15 into dust collector 10. Dust-laden airflow 20 passes through the dust-collecting filter cloth constituting bag filter 6 from the upstream side (outside) to the downstream side (inside) and is purified. The purified exhaust gas is then released as clean airflow 21 through outlet duct 16, for example, into the atmosphere. Continuous collection of dust particles in the exhaust gas by the filter cloth leads to clogging of the filter cloth, reducing its dust-collecting capacity. To regenerate the dust-collecting capacity of the dust-collecting filter cloth, compressed air is continuously blown from nozzle 14 of compressed air blower 13 from the downstream side of the exhaust gas flow path toward the upper opening and inside of bag filter 6 at regular intervals. The dust collected by the dust-collecting filter cloth of bag filter 6 is then blown down into hopper 12. The dust accumulated in hopper 12 is periodically collected from the bottom of hopper 12 and disposed of.

[0037] By applying the above-described bag filter 6 to the dust collector 10, a high dust collection rate can be achieved with high efficiency. [Example]

[0038] A dust-collecting filter cloth was produced in which a base fabric layer made of inorganic fibers and metal fibers and heat-resistant inorganic fiber layers (100% by mass inorganic fiber) laminated on both sides of the base fabric layer and made of inorganic fibers were integrated by needling (Example).Also, a dust-collecting filter cloth was produced in which a base fabric layer made of polyester and heat-resistant inorganic fiber layers (about 20% by mass to 30% by mass para-aramid fiber) laminated on both sides of the base fabric layer and made of polyester and para-aramid were integrated by needling (Comparative Example).

[0039] For each of the Examples and Comparative Examples, a combustion test was conducted in accordance with JACA No. 11A-2003 "Guidelines for Combustion Test Methods for Filter Media for Air Purifiers" as defined by the Japan Air Cleaning Association (JACA). For the Examples, when a flame was applied to the test specimen with a burner for 60 seconds, no combustion was observed. Therefore, the Examples were rated as Class 3, the highest level. For the Comparative Examples, when a flame was applied to the test specimen with a burner for 60 seconds, partial burning was observed. The Comparative Examples were rated as Class 1.

[0040] More detailed test results for the Examples and Comparative Examples are shown in Tables 1 and 2 below. For both the Examples and Comparative Examples, each test specimen was pretreated by heating at 70±1°C for 168 hours. Table 3 shows the evaluation criteria for the tests.

[0041] [Table 1]

[0042] [Table 2]

[0043] [Table 3]

[0044] From the above results of the combustion tests for the Examples and Comparative Examples, it is clear that non-combustibility can be imparted by adopting a configuration of 100% inorganic fibers without using organic fibers.

[0045] The examples were evaluated for heat resistance, durability and flexibility against pulse jet backwashing, and pressure loss (pressure loss) as follows. A cylindrical bag filter measuring φ130 mm x 10,000 mm was fabricated using the dust collection filter fabric of the example. The bag filter sample was placed in a dust collector. An airflow containing dust was introduced from the upstream side (outside) of the bag filter, and a pulse jet of compressed air was introduced from the downstream side (inside) of the bag filter alternately. Gas at 400 to 500°C was introduced so that the gas temperature inside the dust collector was 300 to 350°C. Fly ash was used as the test dust, and the inlet dust content was 5 g / m 3 The filtration speed was set to 1.50 m / min. The pulse pressure was 0.2 MPa or less, and the injection time was 0.05 to 0.15 seconds. The test period was approximately one year, during which the total number of pulses was 50,000.

[0046] The pressure drop value remained stable over the test period at temperatures above 300°C, and the dust collection efficiency was above 99.9%. Thus, the dust collection filter cloth of the example demonstrated high heat resistance and low pressure drop. Furthermore, when the sample was inspected, no damage such as tears was found. The evaluation results show that even a dust collection filter cloth using a 100% inorganic fiber layer is heat resistant and durable (flexible) against continuous pulses, and can also demonstrate dust removal performance.

[0047] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention. [Explanation of symbols]

[0048] 1...dust collecting filter cloth, 2...base fabric layer, 3...heat resistant inorganic fiber layer, 4...inorganic fiber cloth, 5...stainless steel wire, 6...bag filter, 7...retainer, 10...dust collector, 11...housing, 12...hopper, 13...compressed air ejection device, 14...nozzle, 15...inlet duct, 16...outlet duct, 17...support, 20...dust-laden air flow, 21...clean air flow.

Claims

1. a base fabric layer made of inorganic fiber cloth containing stainless steel wire; and a heat-resistant inorganic fiber layer disposed on both sides of the fabric layer and containing 100% inorganic fibers as constituent fibers. The dust-collecting filter cloth is formed by integrating the base fabric layer and the heat-resistant inorganic fiber layer by needling.

2. 2. The dust collecting filter cloth according to claim 1, wherein the stainless steel wire-reinforced inorganic fiber cloth contains glass fibers containing 60% or more of silicon dioxide, and the inorganic fibers contained in the heat-resistant inorganic fiber layer contain glass fibers containing 60% or more of silicon dioxide.

3. A bag filter sewn with the dust-collecting filter cloth according to claim 1 or 2.

4. A dust collecting device comprising the bag filter according to claim 3.

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