GB2028229A - Filter cloth made of needle felt for bag filter type dust collector - Google Patents

Filter cloth made of needle felt for bag filter type dust collector Download PDF

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Publication number
GB2028229A
GB2028229A GB7926207A GB7926207A GB2028229A GB 2028229 A GB2028229 A GB 2028229A GB 7926207 A GB7926207 A GB 7926207A GB 7926207 A GB7926207 A GB 7926207A GB 2028229 A GB2028229 A GB 2028229A
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Prior art keywords
filter cloth
dust
filter
webs
woven fabric
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Granted
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GB7926207A
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GB2028229B (en
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JFE Engineering Corp
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Nippon Kokan Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/06—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer characterised by a fibrous or filamentary layer mechanically connected, e.g. by needling to another layer, e.g. of fibres, of paper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/08—Filter cloth, i.e. woven, knitted or interlaced material
    • B01D39/083—Filter cloth, i.e. woven, knitted or interlaced material of organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/02—Particle separators, e.g. dust precipitators, having hollow filters made of flexible material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/14—Layered products comprising a layer of metal next to a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/024—Woven fabric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/065—More than one layer present in the filtering material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/065—More than one layer present in the filtering material
    • B01D2239/0659—The layers being joined by needling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/1216—Pore size
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/1233—Fibre diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/1291—Other parameters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/20—All layers being fibrous or filamentary
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/40—Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/10—Inorganic fibres
    • B32B2262/103—Metal fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/54—Yield strength; Tensile strength
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/584—Scratch resistance
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/02—Open containers
    • B32B2439/06—Bags, sacks, sachets

Landscapes

  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Filtering Materials (AREA)
  • Filtering Of Dispersed Particles In Gases (AREA)

Abstract

A filter cloth 3 for a bag filter type dust collector comprising: a woven core fabric 1 and a web 2 of synthetic fiber arranged on each surface of the core fabric; the core fabric and the webs being closely entwined to form a filter cloth by needling; each of the webs comprising synthetic fiber filaments having a thickness of 0.5 to 1.5 denier; the webs being such as to provide a total weight of 350 to 450 g/m<2> for the core fabric and the webs; at least one of the surfaces of the filter cloth being subjected to a smoothing treatment; said filter cloth having, through said needling and said smoothing, a thickness of 0.8 to 1.2 mm, an average micro-pore diameter of 10 to 20 mu m, a void ratio of 70 to 80%, and a permeability of 10 to 15 cc/cm<2>/sec at a pressure difference of 12.7 mmAq. <IMAGE>

Description

SPECIFICATION Filter cloth made of needle felt for bag filter type dust collector The present invention relates to a filter cloth made of a needle felt for a bag filler type dust collector, which gives a high filtration velocity of a dust-laden gas, is little susceptible to clogging and excellent in dust collection efficiency, and permits easy dust removal with a low-pressure counter air blowing because deposited dust can be easily peeled off.
A bag filter type dust collector is a device which collects dust by filtering a dust-laden gas through a filter cloth, sewn up into a cylindrical or envelope-like shape, hung under an appropriate tension in a dust collecting chamber (a filter cloth sewn up in a cylindrical or envelope-like shape in this manner being hereinafter referred to as a "filter bag").When a bag filter type dust collector is operated continuously for some period of time, the filter cloth is clogged with dust accumulated therein and dust is deposited on the surface of the filter cloth into a thick layer (when applying) a method comprising filtering a dust-laden gas from inside to outside the filter bag, dust is deposited onto the inner surface of the filter bag, whereas, when applying a method comprising filtering a dust-laden gas from outside to inside the filter bag, dust is deposited onto the outer surface of the filter bag). This leads to an increased pressure loss which in turn results in a lower filtration velocity of dust-laden gas. It is therefore necessary to remove from time to time dust from the interior and the surface of the filter cloth.In a bag filter type dust collector, dust collection from a dust-laden gas is continued for a long period of time by repeating dust collection and dust removal in this manner.
Afilter cloth for a bag filter type dust collector is therefore required t6 have in general the following performances: (a) A satisfactory dust collection efficiency; (b) A small pressure loss; (c) Possibility of high-speed filtration of a dust-laden gas, i.e. a high permeability; (d) To be little susceptible to clogging; (e) To cause deposited dust to be easily peeled off, i.e., to permit easy removal of deposited dust; (f) To be high in abrasion resistance and tensile strength; and (g) To be less expensive.
Conventionally used filter cloths for a bag filter type dust collector are broadly classified into a woven fabric and a non-woven fabric such as a pressed felt, a needle felt or a spun bond felt.
A pressed felt is manufactured by applying water and heat to a fiber layer (known as a "lap") formed with an animal hair such as wool and then applying a frictional force by vibration under pressure. A needle felt is usually manufactured by picking a synthetic fiber layer of uniform density and thickness (known as a "web") and a roughly woven core woven fabric or a web alone with a large number of needles having thorns to cause fibers and/or fibers and the core woven fabric to twine together (known as a "needling"). To increase tensile strength, a needle felt is often manufactured by using a core woven fabric, arranging webs on the both surfaces of said core woven fabric, and applying the needling treatment from the both sides. A spun bond felt is manufactured by bonding long synthetic fibers together.
A filter bag obtained by sewing up a woven fabric or a non-woven fabric into a cylindrical or envelope-like shape is hung under an appropriate tension in a dust collecting chamber of a dust collector to collect dust from a dust-laden gas. To remove dust deposited onto a filter bag, the shaking method or the counter air blowing method under a low pressure of up to 500 mmAq is usually applied when using a woven fabric filter cloth. When employing a non-woven fabric filter cloth, it is the usual practice to apply the counter air blowing or pulsating counter air blowing method under a medium or high pressure of over 500 mmAq, or the combination of counter air blowing and shaking methods under a low pressure.
When using a conventional woven fabric as the filter cloth, dust collecting operation is usually carried out at a filtration velocity of from 0.5 to 1.5 miminute with a pressure loss of from 100 to 300 mmAq. Since a woven fabric is high in longitudinal strength, it is possible to make a large-sized filter cloth therefrom, and hence to build a large-capacity dust collector. Also because of the thin thickness and the softness, a woven fabric permits dust removal by the low-pressure counter air blowing method. Another advantage is a low manufacturing cost of a woven fabric. In contrast to these advantages, a woven fabric filter cloth has the following defects: (1) A higher filtration velocity of dust-laden gas causes clogging of the filter cloth.
(2) There is a large pressure loss.
(3) Weave-loosening is liable to occur, thus leading to a lower dust collection efficiency.
(4) The service life is short. When dust collecting operation is conducted, for example, at a filtration velocity of about 1 miminute with a pressure loss of about 150 mmAq, it has usually a service life of from one to two years.
On the other hand, when using a conventional needle felt as the filter cloth from among non-woven fabrics, dust collecting operation is generally effected at a filtration velocity of from 1.0 to 2.5 miminute with a pressure loss of from 150 to 200 mmAq. Since a non-woven fabric such as a needle felt not only gives a satisfactory dust collection efficiency and has an excellent abrasion resistance, but also a smaller pressure loss as compared with a woven fabric, it is possible to use a high filtration velocity of a dust-laden gas.A non-woven fabric leads to a smaller pressure loss because, in a non-woven fabric, numerous micro-pores which are formed by numerous filaments obtained by unraveling a bundle of fibers are uniformly distributed, and it has a far larger void ratio of from 70 to 80 % that that of a woven fabric of from 30 to 40 %.
While a non-woven fabric has the advantages as mentioned above, it suffers from the following drawbacks: (1) There is a considerable elongation, and this makes it impossible to manufacture a large-sized filter cloth.
(2) It is susceptible to clogging.
(3) Deposited dust is hard to remove.
(4) It requires a higher manufacturing cost than a woven fabric.
As described above, a woven fabric and a non-woven fabric have respective merits and demerits as a filter cloth. In a bag filter type dust collector using a woven fabric as the filter cloth, therefore, while dust removal by the low-pressure counter air blowing method should be applicable, it is necessary to carry out operations at a low filtration velocity to avoid such inconveniences as clogging taking place in high-speed filtration of a dust-laden gas.
On the other hand, a bag filter type dust collector using a non-woven fabric as the filter cloth, while permitting high-speed filtration of a dust-laden gas, is easily susceptible to clogging and liable to have dust deposit which is difficult to peel off. Consequently, pressure loss increases gradually during operation, thus resulting in a lower filtration velocity of a dust-laden gas. Therefore, when using a non-woven fabric, dust removal by the high-pressure counter air blowing method is generally applied. However, when adopting the dust collecting method comprising filtering a dust-laden gas from outside to inside a filter bag made by sewing a non-woven fabric, it is necessary to provide several ring-shaped reinforcements in the inside of the filter bag so as to prevent the filter bag from being crushed flat toward inside under the external pressure of the dust-laden gas.As a result, the filter cloth is constantly pushed and rubbed against the reinforcements by the pressure of the dust-laden gas during dust collecting operation. The resultant wear of the portion of the filter cloth in contact with the reinforcements easily causes breakage of the filter cloth during dust collection or dust removal, leading to a shorter service life of the filter cloth.
In a filter bag made of a non-woven fabric, a primary dust deposit layer is formed on the surface of the filter bag in the initial stage of dust collecting operation. More specifically, in the case of a method comprising filtering a dust-laden gas from inside to outside the filter bag (called the "outward filtration"), a primary dust deposit layer is formed on the inner surface of the filter bag, whereas, in the case of a method comprising filtering a dust-laden gas from outside to inside the filter bag (called the "inward filtration"), a primary dust deposit layer is formed on the outer surface of the filter bag. The dust collection efficiency of the filter bag is remarkably improved by the formation of the above described primary dust deposit layer. In a filter bag made of a non-woven fabric, in general, the high-pressure counter air blowing method is adopted for dust removal.When removing dust, therefore, not only dust caught on the primary dust deposit layer but also the primary dust deposit layer are removed at the same time. As a result, during the initial stage of dust collecting operation after a dust removal, part of dust contained in a dust-laden gas passes through the filter cloth without being caught (known as "blowing leakage of dust"), and the dust collecting efficiency temporarily decreases seriously. In a large-sized filter bag, furthermore, it is difficult to ensure a counter air blow of a high pressure uniformly over the entire surface of the filter bag during dust removal, so that dust removal may be non-uniform and may cause local blowing leakage.
An object of the present invention is therefore to provide a filter cloth made of a needle felt for a bag filter type dust collector which is capable of filtering a dust-laden gas at a filtration velocity of at least 1.5 m/minute, excellent in dust collection efficiency, not susceptible to clogging, and applicable not only to a small-capacity dust collector but also to a large-capacity dust collector.
A principal object of the present invention is to provide a filter cloth made of a needle felt for a bag filter type dust collector which permits removal of dust by the counter air blowing method under a low pressure of up to 500 mmAq.
In accordance with one of the features of the present invention, there is provided a filter cloth made of a needle felt for a bag filter type dust collector, which comprises: A core woven fabric and two webs of a synthetic fiber arranged each on each of the both surfaces of said core woven fabric; said core woven fabric and said two webs closely twining together integrally to form a single filter cloth by a needling treatment; and at least one of the surfaces of said filter cloth being subjected to a smoothing treatment; said filter cloth being characterized in that: said core woven fabric is woven with synthetic fiber threads having a thickness of from 200 to 500 denier at a rate of from 25 to 40 treads per 2.54 cm; each of said two webs comprises synthetic fiber filaments having a thickness of from 0.5 to 1.5 denier, and said two webs are arranged on the both surfaces of said core woven fabric at a rate of from 350 to 450 g/m2 including the weight of said core woven fabric in total for the two webs; ; at least one of the surfaces of said filter cloth is subjected to a smoothing treatment comprising a singeing step and a roll compressing step at a roll surface temperature of from 150 to 2100C under a pressure offrom 6 to 11 kg/cm2; and said filter cloth is provided, through said needling treatment and said smoothing treatment, with a thickness of from 0.8 to 1.2 mm, an average micropore diameter of from 10 to 20#m, a void ratio of from 70 to 80%, and a permeability of from 10 to 15cc/cm2/sec at a pressure difference of 12.7 mmAq.
Figure 1 is a schematic sectional view illustrating the structure of the filter cloth of the present invention; Figure 2 is a front view illustrating an embodiment of a cylindrical filter bag formed with the filter cloth of the present invention; Figure 3 is a schematic sectional view illustrating a state in which a cylindrical filter bag formed with the filter cloth of the present invention is hung under an appropriate tension in the duct collecting chamber of a dust collector; and Figure 4 is a schematic sectional view illustrating the structure of a closed suction type dust collector incorporating a cylindrical filter bag formed with the filter cloth of the present invention.
With the above-mentioned merits and demerits of a woven fabric and a non-woven fabric as a filter cloth in view, we carried out extensive studies with a view to achieving a filter cloth for a bag filter type dust collector, which is excellent in dust collection efficiency, permits high-speed filtration of a dust-laden gas, is little susceptible to clogging, allows removal of deposited dust by low-pressure counter air blowing, and is applicable not only to a small-capacity dust collector but also to a large-capacity dust collector.
As a result, we found that it is possible to obtain a filter cloth made of a needle felt for a bag filter type dust collector, which are provided with all the advantages mentioned above, by causing, by a needling treatment, a core woven fabric and two webs of a synthetic fiber arranged each on each of the both surfaces of said core woven fabric to closely twine together integrally into a single filter cloth; weaving said core woven fabric with synthetic fiber threads having a thickness of 200 to 500 denier at a rate of from 25 to 40 threads per 2.54 cm; arranging said two webs comprising synthetic fiber filaments having a thickness of from 0.5 to 1.5 denier on the both surfaces of said core woven fabric at a rate of from 350 to 450 kg/m2 including the weight of said core woven fabric in total for the two webs; subjecting at least one of the surfaces of said filter cloth to a smoothing treatment comprising a singeing step and a roll compressing step at a roll surface temperature of from 150 to 2100C under a pressure of from 6 to 11 kg/cm2; and providing said filter cloth, through said needling treatment and said smoothing treatment, with a thickness of from 0.8 to 1.2 mm, an average micro-pore diameter of from 10 to 20 um, a void ratio of from 70 to 80%, and a permeability of from 10 to 15 cc/cm2/sec at a pressure difference of 12.7 mmAq.
Now, the filter cloth made of a needle felt for a bag filter type dust collector of the present invention (hereinafter simply referred to as the "filter cloth of the present invention") is described with reference to the drawings.
Figure 1 is a schematic sectional view illustrating the structure of the filter cloth of the present invention. In Figure 1, 1 is a core woven, 2 are webs of a synthetic fiber, arranged each on each of the both surfaces of said core woven fabric, and 3 is the filter cloth of the present invention formed by said core woven fabric 1 and said webs 2. The core woven fabric 1 is woven, like a conventional core woven fabric, with threads of a synthetic fiber such as polyester, polyamide or polypropyrene. The synthetic fiber thread preferably has a thickness of from 200 to 500 denier and the number of threads is preferably from 25 to 40 per 2.54 cm. One denier, as used herein, is defined as the unit of thickness of a fiber weighing 1 g as mentioned at a length of 9,000 m.With a thickness of the thread of the core woven fabric 1 of under 200 denier and a number of threads of under 25 per 2.54 cm, the low tensile strength may cause breakage of the filter cloth during a dust collecting operation at a filtration velocity of from 1.5 to 2.5 mlminute and a dust removing operation by counter air blowing under a low pressure of the order of 500 mmAq, in the case of a filter cloth of longer than 10 m. Under the operating conditions mentioned above, on the other hand, it is not necessary to increase tensile strength of the filter cloth with a thickness of the thread of over 500 denier and a number of threads of over 40 per 2.54 cm.
The webs 2 comprise, like a conventional web, synthetic fiber filaments such as polyester, polyamide or polypropylene. The core woven fabric 1 and the webs 2 arranged on the both surfaces of the core woven fabric 1 are subjected on the sides thereof, at least twice for each side, to a needling treatment by a conventional needling machine equipped with a large number of needles having thorns. The needling treatment causes filaments of webs 2 to twine together in a three-dimensional manner (i.e., in three directions), and also causes the core woven fabric 1 and the two webs 2 to closely twine together integrally to form a single filter cloth. In other words, the filter cloth of the present invention is composed of a needle felt.
It is necessary that the filaments forming the webs 2 should have a thickness of from 0.5 to 1.5 denier and the quantity of the arranged webs 2 should be within the range of from 350 and 450 glum2 in total including the weight of the core woven fabric 1. With a thickness of filament of under 0.5 denier, not only it becomes difficult to apply a needling operation, but also it is not easy to manufacture such fine filaments. On the other hand, with a thickness of filament of over 1.5 denier, the average micro-pore diameter of the filter cloth 3 exceeds the prescribed range described later, and dust in a dust-laden gas penetrates into the filter cloth 3, thus causing clogging. With a quantity of arranged webs 2 of under 350 g/m2, the average micropore diameter and permeability of the filter cloth 3 exceed the prescribed ranges described later, leading to a lower dust collection efficiency. With a quantity of arranged webs 2 of over 450 g/m2, on the other hand, permeability of the filter cloth 3 becomes smaller than the prescribed range described later, leading to a larger pressure loss. This not only makes it difficult to ensure high-speed filtration of a dust-laden gas, but also results in a thickness of the filter cloth 3 exceeding the prescribed range described later, impairing flexibility of the filter cloth 3 and making it difficult to remove dust by low-pressure counter air blowing.
In a filter cloth made of a needle felt, in general, a smoothing treatment is often applied to the surface of the filter cloth facing incoming dust-laden gas, i.e., the surface onto which dust is deposited (hereinafter referred to as the "filtration-side surface"), with a view to catching dust in a dust-laden gas on the surface of the filter cloth without allowing dust to penetrate into the filter cloth as far as possible, and making it easy to peel off a dust deposit layer on the surface. In the present invention, also, the filtration-side surface of the filter cloth formed as mentioned above is subjected to a smoothing treatment. More particularly, a nap on the filtration-side surface of the filter cloth 3 is fused through singeing with a burner or a red-hot roll.Then, the filter cloth 3 is compressed between rolls at a roll surface temperature of from 150 to 21 0"C under a pressure of from 6 to 11 kg/cm2. With a roll surface temperature of under 1500C and a pressure of under 6 kg/cm2, the average micropore diameter of the filter cloth 3 exceeds the prescribed range described later and dust in a dust-laden gas penetrates into the filter cloth 3, thus causing clogging. On the other hand, with a roll surface temperature of over 21 00C and a pressure of over 11 kg/cm2, the average micropore diameter and permeability of the filter cloth 3 becomes smaller than the prescribed ranges described later, resulting in a larger pressure loss, and hence making it difficult to conduct a high-speed filtration of a dust-laden gas.
Therefore, the roll surface temperature should be within the range of from 150 to 21 00C, and the pressure, within the range of from 6 to 11 kg/cm2.
In the present invention, by limiting the thickness of filaments of the webs 2, the quantity of the arranged webs 2, the needling treatment conditions and the smoothing treatment conditions within the aforementioned ranges, the following characteristic values are imparted to the filter cloth 3.
Thickness: from 0.8 to 1.2 mm, Micro-pore diameter: from 10 to 20 urn Void ratio: from 70 to 80 %, and Permeability at a pressure difference of 12.7 mmAq: from 10 to 15 cc/cm2/sec.
The characteristic values of the filter cloth of the present invention are limited as mentioned above for the following reasons: (1) Thickness: With a thickness of the filter cloth of under 0.8 mm, not only it is difficult to conduct a needling treatment satisfactorily, but also the average micro-pore diameter and permeability of the filter cloth exceed the prescribed ranges. As a result, while the filtration velocity of a dust-laden gas becomes higher, the dust collection efficiency worsens and clogging is caused. On the other hand, with a thickness of the filter cloth of over 1.2 mm, the average micro-pore diameter and permeability of the filter cloth becomes smaller than the prescribed ranges.As a result, in spite of an improved dust collection efficiency, the filtration velocity of a dust-laden gas becomes lower, making it difficult to conduct a high-speed filtration at a velocity of 1.5 m/minute or higher. In addition, since flexibility of the filter cloth is lost, it is impossible to apply dust removal by low-pressure counter air blowing. Therefore, the thickness of the filter cloth should be within the range of from 0.8 to 1.2 mm.
(2) Average micro-pore diameter and permeability: With an average micro-pore diameter of the filter cloth of under 10 urn and a permeability at a pressure difference of 12.7 mmAq of under 10 cc/cm2/sec, the dust collection efficiency is improved, whereas the increased pressure loss results in a lower filtration velocity of a dust-laden gas, and it becomes difficult to conduct a high-speed filtration at a velocity of 1.5 m/minute or higher. On the other hand, with an average micro-pore diameter of over 20 urn and a permeability of over 15 cc/cm2/sec, while the filtration velocity of a dust-laden gas becomes higher, the dust collection efficiency becomes lower and clogging occurs.
Therefore, the average micro-pore diameter of the filter cloth should be within the range of from 10 to 20 urn, and permeability, within the range of from 10 to 15 cc/cm2/sec.
(3) Void ratio: The void ratio of the filter cloth of the present invention is substantially the same as that of the conventional filter cloth made of a needle felt. A void ratio of under 70 % results in a larger pressure loss, making it difficult to conduct a high-speed filtration of a dust-laden gas. On the other hand, a void ratio of over 80 % leads to a lower dust collection efficiency. The void ratio of the filter cloth should therefore be within the range of from 70 to 80 %.
In the conventional filter cloth made of a needle felt (hereinafter referred to as the "conventional filter cloth"), filaments of webs arranged on the both surfaces of a core woven fabric have a thickness of at least 3 denier, which is far larger than that of filaments of the webs of the filter cloth of the present invention. In the conventional filter cloth, needling is usually applied three times or so, and roll compression in the smoothing treatment is applied under a relatively low pressure as from about 1 to about 5 kg/cm2.Consequently, the average micro-pore diameter in the conventional filter cloth of from 20 to 50 urn is more than two times as large as the average micro-pore diameter in the present invention of from 10 to 20 urn. Therefore, the conventional filter cloth is easily susceptible to clogging and inferior in the dust collection efficiency as compared with the filter cloth of the present invention.Furthermore, the conventional filter cloth has a thickness of from 1.0 to 1.7 mm in the case of a quantity of arranged webs of from 300 to 450 g/m2 including the weight of the core woven fabric, and has a permeability of from 20 to 40 cc/cm2/sec at a pressure difference of 12.7 mm, whereas the filter cloth of the present invention has a thickness of from 0.8 to 1.2 mm in the case of a quantity of arranged webs of from 350 to 450 g/m2 and has a permeability of from 10 to 15 cc/cm2/sec. In spite of almost the same quantities of arranged webs as described above, the conventional filter cloth has a larger thickness and a higher permeability than the filter cloth of the present invention. This is partly because of the difference in the conditions of the needling treatment and the smoothing treatment, but chiefly attributable to the difference in the thickness of filaments of the webs.The conventional filter cloth, being slightly superior to the filter cloth of the present invention in the filtration velocity of a dust-laden gas, is inferior in the dust collection efficiency to the latter. In addition, the conventional filter cloth not only is easily susceptible to clogging but also requires dust removal by high-pressure counter air blowing to cope with the larger thickness and the lack of flexibility. The filter cloth of the present invention is, in contrast, little susceptible to clogging, thin and flexible, and dust removal is easily applicable by low-pressure counter air blowing.
As has already been proposed, incorporation of metal fibers in an amount of at least 0.1 wt. % in the core woven fabric 1 and/or webs 2 of the filter cloth 3 of the present invention not only permits prevention of a maintenance personnel from being struck by electricity at the time of maintaining the filter cloth through prevention of occurrence of static electricity, but also improves exfoliation property of deposited dust.
Figure 2 is a front view illustrating an embodiment of a cylindrical filter bag formed with the filter cloth of the present invention. In Figure 2,3' is a filter bag formed by sewing the filter cloth of the present invention, and 17 are a plurality of reinforcing rings attached outside the filter bag 3' at appropriate intervals. The filter bag 3' shown in Figure 2 is used in a dust collector of the outward filtration type in which a dust-laden gas is filtered from inside to outside the filter bag. The filter bag 3' is therefore formed so that the surface of the filter cloth having been subjected to the smoothing treatment becomes inside. Dust is therefore caught by being deposited in a layer onto the inner surface of the filter bag 3'. As has been defined previously, the surface onto which dust is deposited is referred to as the filtration-side surface.Counter air is blown from outside toward inside the filter bag 3' to remove the dust layer deposited onto the inner surface of the filter bag 3', i.e., the filtration-side surface. During this counter air blowing, the filter bag 3', being supported by the plurality of reinforcing rings 17, is never crushed flat toward inside. It is needless to mention that, in a filter bag used in a dust collector of the inward filtration type in which a dust-laden gas is filtered from outside to inside the filter bag, inversely to the above description, the filter bag is formed so that the surface of the filter cloth having been subjected to the smoothing treatment, i.e., the filtration-side surface becomes outside, and it is necessary to provide a plurality of reinforcing rings inside the filter bag.
Figure 3 is a schematic sectional view illustrating a state in which a cylindrical filter bag formed with the filter cloth of the present invention, described above with reference to Figures 1 and 2, is hung under an appropriate tension in the dust collecting chamber of a dust collector. In Figure 3, 3' is a filter bag formed with the filter cloth of the present invention, and 17 are a plurality of reinforcing rings attached outside the filter bag 3' at appropriate intervals. The lower end 3a of the filter bag 3' is tightened by a lower band 6 against a thimble 5 fixed to the upper surface 4a of a hopper 4 of the dust collector. A cap 7 provided with an eyebolt 9 is tightened by an upper band 8 against the upper end 3b of the filter bag 3'.The bag filter 3' is hung from a suspension rack 10 of the dust collecting chamber under an appropriate tension by a hook 11 connected to the eyebolt 9. A dust-laden gas is introduced through the opening at the lowermost end of the filter bag 3' into the interior of the filter bag 3' as shown by an arrow, subjected to dust catching on the inner surface of the filter bag 3', i.e., on the filtration-side surface to become a clean gas, and passes through the filter bag 3' to be released to outside.
Now, the filter cloth of the present invention is described in more detail by means of an example with reference to the drawings.
Example Figure 4 is a schematic sectional view illustrating the structure of a closed suction type dust collector incorporating a cylindrical filter bag formed with the filter cloth of the present invention, described above with reference to Figures 1 to 3. In Figure 4,3' and 3" are bag filters formed with the filter cloth of the present invention, 12 and 12' are dust collecting chambers, and 4 and 4' are hoppers provided below the dust collecting chambers 12 and 12'. The bag filters 3' and 3" are hung under an appropriate tension respectively between the upper surface 4a of the hopper 4 and a suspension rack 10, and between the upper surface 4a' of the hopper 4' and a suspension rack 10'. The upper ends of the dust collecting chambers 12 and 12' communicate with an exit duct 14through switchover dampers 13a and 13a', and with an air inlet 15 through switchover dampers 13b and 13b'. In Figure 4, the filter bag 3, and the dust collecting chamber 12 are shown in the state during dust collection, and the filter bag 3" and the dust collecting chamber 12', in the state during dust removal.
When, in the dust collecting chamber 12, the swichover damper 13a on the exit duct 14 side is opened, and the switchover damper 13b on the air inlet 15 side is closed, and in the dust collecting chamber 12', on the other hand, the swichover damper 13a' on the exit duct 14 side is closed and the switchover damper 13b' on the air inlet 15 side is opened, and when a blower (not shown) provided in the exit duct 14 is driven to generate a suction force, a dust-laden gas flows into the filter bag 3, in the dust collecting chamber 12 from a dust-laden gas inlet 16 through the hopper 4. Dust contained in the dust-laden gas is caught on the inner surface of the filter bag 3', i.e., on the filtration-side surface and deposited in a layer on said surface.The dust-laden gas, thus converted into a clean gas, goes through the filter bag 3' and is discharged through the switchover damper 13a from the exit duct 14.
On the other hand, air is introduced from the air inlet 15 and blown through the switchover damper 13b' into the dust collecting chamber 12' at a low pressure of up to 500 mmAq. The blown air passes through the filter bag 3" from outside to inside, and in passing, removes the dust layer deposited on the inner surface of the filter bag 3", i.e., the filtration-side surface. The removed dust falls into the hopper 4' and is accumulated therein. The dust accumulated in the hopper 4' is discharged therefrom at an appropriate timing. Air having passed through the filter bag 3", on the other hand, flows through the hoppers 4' and 4 into the filter bag 3', in the dust collecting chamber 12, together with the dust-laden gas. Air for removing dust deposited on the filter bag 3' may be replaced by the clean gas obtained in the filter bag 3' or by a combination gas of air and clean gas.
When, while dust is collected by the filter bag 3', a thick dust layer is deposited onto the inner surface of the filter bag 3', i.e., onto the filtration-side surface, and thus the pressure loss for the filter bag 3' exceeds a prescribed value, dust may be removed from the filter bag 3' in the dust collecting chamber 12 and dust may be collected in the filter bag 3" in the dust collecting chamber 12' in a manner similar to that mentioned above, by automatically or manually switching over the switchover dampers 13a and 13a' on the exit duct 14 side and the switchover dampers 13b and 13b' on the air inlet 15 side. Thus, dust collecting operation in a bag filter type dust collector can be continued for a long period of time by repeating alternately dust collection and dust removal respectively in the filter bags 3' and 3".
For comparison purposes, a filter bag formed with the filter cloth of the present invention was hung in a dust collecting chamber of the dust collector shown in Figure 4, and another filter bag formed with the conventional filter cloth made of a needle felt was hung in the other dust collecting chamber, and the dust collector was operated continuously. The filter bag formed with the conventional filter cloth made of the needle felt had to be replaced 130 to 280 days after the start of operation because of the seriously increased pressure loss caused by clogging. The filter bag formed with the filter cloth of the present invention, in contrast, could be operated continuously even beyond 470 days after the start of operation because of the slightest increase in pressure loss since there was only very small clogging.
According to the present invention, as described above in detail, a filter cloth made of a needle felt for a bag filter type dust collector, which has the following excellent characteristics, is obtained, thus providing industrially useful effects: (1) The average micro-pore diameter is very small because filaments of webs have a very small thickness.
This leads to a high dust collection efficiency and prevents clogging.
(2) Because of the high void ratio of from 70 to 80 % and the little possibility of clogging, not only the pressure loss is small, but also there is only a small increase in pressure loss in a long-term service. It has therefore a filtration velocity almost equal to that of the conventional filter cloth made of a needle felt, and permits filtration of a dust-laden gas at a velocity of at least 1.5 m/minute over a long period of time.
(3) Because of the thin thickness, the high flexibility and the easy exfoliation of the deposited dust layer, dust may satisfactorily be removed by counter air blowing under a low pressure of up to 500 mmAq as in the conventional filter cloth made of a woven fabric.
(4) It has a long service life.
(5) Since appropriate manufacturing conditions are selected, including the thickness of the thread of the core woven fabric, the number of threads thereof, the thickness of filaments of the webs, the quantity of arranged webs, and conditions of the needling and smoothing treatments, it has a high tensile strength, and its tensile elongation is less than 0.75 % in the longitudinal direction and less than 1.25 % in the transverse direction. Therefore, it is possible to manufacture a large-sized filter cloth longer than 10 m as with a conventional filter cloth made of a woven fabric, thus permitting application not only to a small-capacity dust collector but also to a large-capacity dust collector.

Claims (3)

1. A filter cloth for a bag filter type dust collector, which comprises: a woven core fabric and two webs of a synthetic fiber, arranged one on each surface of the core fabric; the core fabric and the two webs being closely entwined to form a single filter cloth by a needling treatment; and at least one of the surfaces of said filter cloth being subjected to a smoothing treatment; said filter cloth being characterized in that:: said core fabric is woven from synthetic fiber threads having a thickness of from 200 to 500 denier at a rate of from 25 to 40 threads per 2.54 cm; each of the two webs comprises synthetic fiber filaments having a thickness of from 0.5 to 1.5 denier, the webs being arranged on respective surfaces of the core fabric to provide a total weight of from 350 to 450 g/m2, including the weight of core woven fabric and the two webs; at least one of the surfaces of the filter cloth is subjected to a smoothing treatment comprising a singeing step and a roll-compressing step at a roll surface temperature of from 150 to 21 00C under a pressure of from 6 to 11 kg/cm2; and said filter cloth is provided, through said needling treatment and said smoothing treatment, with a thickness of from 0.8 to 1.2 mm, an average micro-pore diameter of from 10 to 20 urn, a void ratio of from 70 to 80%. and a permeability of from 10 to 15 cc/crn2/sec at a pressure difference of 12.7 mmAq.
2. A filter cloth as claimed in Claim 1,wherein at least 0.1 wt.% of a metal fiber is incorporated into at least one of said core woven fabric and the two webs.
3. A filter cloth as claimed in Claim 1 and substantially as herein before described with reference to the accompanying Drawings.
GB7926207A 1978-08-18 1979-07-27 Filter cloth made of needle felt for bag filter type dust collector Expired GB2028229B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP10079078A JPS5528707A (en) 1978-08-18 1978-08-18 Filter cloth for bag filter

Publications (2)

Publication Number Publication Date
GB2028229A true GB2028229A (en) 1980-03-05
GB2028229B GB2028229B (en) 1982-09-08

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JP (1) JPS5528707A (en)
DE (1) DE2933246C2 (en)
GB (1) GB2028229B (en)

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GB2145370A (en) * 1983-08-23 1985-03-27 Nat Res Dev Textile material
GB2211730A (en) * 1987-10-30 1989-07-12 Alan Sherick Curtain linings
EP0612551A2 (en) * 1993-01-22 1994-08-31 MONSANTO ENVIRO-CHEM SYSTEMS, Inc. Improved fiber beds for fiber bed mist eliminators
EP0620874A4 (en) * 1992-09-25 1995-02-08 Albany Int Corp Novel fabrics for high temperature pressing applications.
EP0645487A1 (en) * 1993-09-03 1995-03-29 Pall Corporation Method of preparing a support material for use with a filtration medium
DE19615022A1 (en) * 1996-04-17 1997-10-23 Mgf Gutsche & Co Gmbh Betriebs Filter medium
CN109910380A (en) * 2019-04-24 2019-06-21 苏州新誉卓新材料科技有限公司 A kind of three-dimensional low-resistance high-efficiency air filtering woven cloths
WO2021230838A1 (en) * 2020-05-12 2021-11-18 Ceksan Yol Supurme Araclari-Makina Sanayi Ve Ticaret Limited Sirketi Manually or automatically cleanable filter

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JPH0380877A (en) * 1989-08-24 1991-04-05 Miyota Seimitsu Kk Optical guidance pace maker unit
DE4211465C2 (en) * 1992-04-06 1996-03-28 Intensiv Filter Gmbh Method and device for the dry separation, recovery and processing of a mist of sticky paint particles from the exhaust air flow that occurs during spray painting
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JP5568826B2 (en) * 2010-10-26 2014-08-13 日本スピンドル製造株式会社 Filter material for dust collector and dust collector
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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2145370A (en) * 1983-08-23 1985-03-27 Nat Res Dev Textile material
GB2211730A (en) * 1987-10-30 1989-07-12 Alan Sherick Curtain linings
GB2211730B (en) * 1987-10-30 1991-04-24 Alan Sherick Improvements in curtains
EP0620874A4 (en) * 1992-09-25 1995-02-08 Albany Int Corp Novel fabrics for high temperature pressing applications.
EP0612551A2 (en) * 1993-01-22 1994-08-31 MONSANTO ENVIRO-CHEM SYSTEMS, Inc. Improved fiber beds for fiber bed mist eliminators
EP0612551A3 (en) * 1993-01-22 1995-02-01 Monsanto Enviro Chem Syst Improved fiber beds for fiber bed mist eliminators.
US5605748A (en) * 1993-01-22 1997-02-25 Monsanto Enviro-Chem Systems, Inc. Fiber beds for fiber bed mist eliminators
EP0645487A1 (en) * 1993-09-03 1995-03-29 Pall Corporation Method of preparing a support material for use with a filtration medium
US5614095A (en) * 1993-09-03 1997-03-25 Pall Corporation Filtration mediam support material and filter comprising same
DE19615022A1 (en) * 1996-04-17 1997-10-23 Mgf Gutsche & Co Gmbh Betriebs Filter medium
CN109910380A (en) * 2019-04-24 2019-06-21 苏州新誉卓新材料科技有限公司 A kind of three-dimensional low-resistance high-efficiency air filtering woven cloths
WO2021230838A1 (en) * 2020-05-12 2021-11-18 Ceksan Yol Supurme Araclari-Makina Sanayi Ve Ticaret Limited Sirketi Manually or automatically cleanable filter

Also Published As

Publication number Publication date
DE2933246A1 (en) 1980-02-21
GB2028229B (en) 1982-09-08
JPS5528707A (en) 1980-02-29
DE2933246C2 (en) 1982-11-18

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