With the progress of science and technology, the development of industry, solid-liquid separation has become more and more prominent. The filter is widely used in the fields of mineral processing, metallurgy, coal, petroleum, chemical industry, medicine, food, environmental protection and other fields. Industrial filter cloth is the heart of the filter, which often plays a decisive role in the success or failure of filtration. Therefore, understanding and understanding of filter cloths will help to properly select industrial filter cloths, which is beneficial to the successful application of good filter cloths. So, with everyone here to explore the filter cloth.
Filter cloth sub-textile filter cloth and non-woven filter cloth, the former belongs to the two-dimensional planar structure, which is the three-dimensional space structure.
⒈ textile filter cloth
Textile filter cloth is the largest variety, the most widely used filter cloth.
⒈ ⒈ textile filter cloth fiber types:
In order to adapt to the high filtration pressure, high pressure and high pressure of the role of washing pressure, textile filter cloth should meet the following conditions: ⑴ high probability of entrapment of solid particles; ⑵ less clogging of the gap, to maintain a stable filtration rate; ⑶ have a good filter Cake peelable; ⑷ higher tensile, resistance to swelling and corrosion resistance.
As the chemical fiber to meet the above conditions, but the price is relatively cheap, it is the main material to create filter cloth.
The types of textile filter cloths are shown in Table 1:
Table 1 textile filter cloth fiber types
fiber
Chemical Fiber
synthetic fiber
Polyamide system (nylon 6, nylon 66, nylon 11, aromatic nylon, etc.)
Polyvinyl alcohol system (vinylon)
PVC fork system (vinyl fork)
Polyvinyl chloride system
Polyester system (polyester)
Polypropylene clear system (propylene)
Polyethylene system
Polypropylene system (polypropylene)
Polyurethane system
other
Inorganic fibers
glass fiber
carbon fiber
Metal fiber
Rock fiber
Slag fiber
Natural fiber
Plant fiber (cotton, etc.)
Animal fibers (wool, rabbit fur, silk)
Mineral fiber (asbestos)
Synthetic fibers, polypropylene, polyester and nylon the most widely used.
Polypropylene fiber is the lightest, the only synthetic fiber that floats in water, and hardly ever
Moisturizing. Tensile strength is also high, comparable with nylon and polyester. Its excellent corrosion resistance, almost no erosion by strong acids and bases. Only slightly less heat resistance, the maximum temperature should not exceed 100 ℃. Fabric made of this fiber filter cloth, the surface is very smooth, easy to unload cake, is the most widely used in liquid filtration filter cloth.
The versatility of polyester fibers is very wide. It is characterized by high tensile strength, low elongation, dry and wet when the same intensity. Among the synthetic fibers, polyester fibers have the best heat resistance and hardly deteriorate below 150 ° C. Its excellent acid resistance, but poor alkali resistance.
Nylon has the highest tensile strength and wear resistance. Wet strength when the strength of 80% to 90% of the drying, which affects the stability of the size of the filter cloth, the common temperature does not exceed 110 ℃. Poor acid resistance, alkali resistance and resistance to other drug properties. In addition to benzoic acid, formic acid and glacial acetic acid, in other solvents more stable. Because the fiber surface is the most smooth and hygroscopic, it is easy to remove the cake. Abroad, Japan almost all use nylon 6, while Britain and the United States are mostly used nylon 66, the latter slightly better heat resistance than the former.
Polyvinyl chloride fiber is the most dense synthetic fiber with excellent corrosion resistance. It is not affected by other acids, including aqua regia, except for small amounts of concentrated sulfuric acid. Corrosion resistance to alkali and organic solvents. However, the strength is lower than the above three synthetic fibers, and the heat resistance does not exceed 70 ° C.
Due to the advent of synthetic fibers, cotton filter cloths are rarely used for industrial filtration, but cotton fibers are cloths that have a water-swellability and form the highest density. So far, oil dewaxing processes and varnish filtration processes are still being used. Cotton fiber strength of 27 ~ 48.02N / dm, elongation of 3% to 7%, when wet strength than the dryness of 2% to 10%, weak acid resistance, and strong alkali resistance.
⒈ 2. Textile filter cloth fiber shape:
Single fiber: Each fiber is made as long as the metal wire, with such a fiber braid filter cloth, the eye is not easy to plug, the cake is also easy to peel, which is suitable for access to the cake occasion.
Long fibers: The first few fine filaments together and then woven into a cloth, compared with the staple fiber filter cloth, the filter cake on the long fiber cloth easy to peel. The resulting filtrate clarity, between the single fiber filter cloth and short fiber filter cloth.
Short fibers: Short fibers made of short fibers such as cotton or wool capture fine particles, but the eyelets are easily clogged and the filter cake is not easily peeled off.
⒈ ⒊ textile filter cloth type:
Textile filter cloth is by the warp and weft according to a certain law, under the staggered and woven, a single layer of woven and double weave points, single-layer weaving plain weave, twill and satin three weave, as shown in Figure 1 As shown. Double weave with warp double weave, weft double weave, warp and weft double weave, no matter what kind of weave are based on plain, twill and satin and its evolution type, such as Guangdong Xinhui P750AB double woven cloth , The front is plain, the back is twill.
Plain weave by the warp and weft, up and down and woven into each other. The structure of the most compact, low porosity, to capture particles, the filtrate of good clarity. However, easy to plug the eye, the filter cake is also difficult to peel.
Twill is the weft crossed by two warps and made. The organization of high strength, eye is not easy to plug, liquid flow, so the most widely used.
Satin is a warp weaving over three wefts. Due to its concentrated configuration of the weft, it is good cake peelable, but poor particle capture, it is less used. However, due to its large eyelet, filtration resistance is small, it can be used for a large number of flocculation sludge treatment.
Now single-fiber woven cloth, twill can be retained as low as 6um particles, flat vine (plain, but the warp than the weft thick), can be retained 16um particles, through further refined addition (shrinkage and calendering) Grain retention rating as low as 1 um range.
⒈ ⒋ textile filter cloth finishing:
In order to improve the filter performance of textile filters, they can be finished. The most important finishing methods are the following three:
Calendering: The filter cloth is subjected to a hot roller pressure roller so that the filter cloth to reduce porosity and make the filter cloth surface smooth. After calendering, the retention of the filter cloth and the peelability of the filter cake all improved, but the strength was somewhat reduced.
Fine hair: is the use of fine teeth steel comb, the surface of the filter cloth to produce soft fine hair, in order to enhance the ability of the filter cloth to retain particulates.
Heat Treatment: Mainly used for synthetic fiber filter cloth, the purpose is to make the cloth stable, more suitable for high temperature.
⒈ ⒌ contraction of textile filter cloth:
Textile filter cloth in the course of use will have a certain degree of shrinkage, especially polyamide cloth, if not pay attention to the filtration operation will have serious problems. Therefore, cutting should be set aside before the shrinkage margin or pre-shrinkage of cloth, pre-shrinkage in the following two ways:
⑴ filter cloth in a relaxed state, pre-shrink with boiling water.
⑵ in the weft tension state, the filter cloth on the thermostat heating (to maintain porosity, permeability).
⒈ ⒍ chemical fiber filter cloth cutting and suture:
Chemical fiber filter cloth cutting, electric iron ironing the best (with 150W electric iron), to prevent the latitude and longitude lines loose. Sewing with the line must use the same line of performance.
⒉ non-woven filter cloth:
Non-woven filter cloth is by mechanical, thermal, chemical and a combination of methods, the fabric synthesis of cloth. The fiber intertwined with each other to form the gap, although irregular, but the distribution is more uniform, the porosity rate of about 80%, if the surface of the nonwoven special treatment, resulting in a variety of shapes and irregular arrangement of holes, it can be at low pressure Poor under the filter tiny particles, so at present some very small particle filtration used more, such as Benxi Iron and Steel Company with a permanent magnetic vacuum filter cartridge filter iron concentrate used in polypropylene needle felt.
Table 2 shows the classification of non-woven filter cloth.
Table 2 non-woven filter cloth classification
Non-woven filter cloth
Adhesive type
Impregnation method non-woven filter cloth
Adhesive fiber method non-woven filter cloth
Mechanical joint type
Acupuncture law non-woven filter cloth (needle felt non-woven filter cloth)
Rolling non-woven filter cloth
Spinning type
Short fiber method non-woven filter cloth
Long fiber method non-woven filter cloth
Although non-woven filter cloth can be used as filter cloth, but made by acupuncture needle felt non-woven filter
Cloth (its structure shown in Figure 2) the best use of the effect, it pore density, pore by the small, micro
Hole distribution, with good filtering performance.
Acupuncture felt the main approach is: the carding layer made of woven fiber layer woven shop cloth (the density of the cloth is only equivalent to the general textile filter cloth 1/6 ~ 1/4, the resistance is minimal) , With acupuncture needle repeatedly, so that the fiber layer and the fabric firmly together to form a three-dimensional space structure. Acupuncture needle punched by hot pressing, singeing and coating or coating, shaping and a series of finishing processes, so that the shape and improve its filtering performance.
Most of the raw materials used in needle-felt are polyester, polypropylene or other staple fibers. Polypropylene needle felt is mainly used for flue gas temperature below 150 ℃ occasions. Acrylic needle felt is mainly used in the field of liquid-solid separation, and board frame filter press, vacuum filter and other supporting the use of filters. Microfiber needle felts are mainly used for the collection of fine dust, in order to improve the filtration accuracy and in the field of liquid-solid separation for the purification of sub-micron particles.
Needle felt compared with the general textile filter cloth, has the following advantages:
⑴ porosity, permeability is good, can reduce pressure loss and energy consumption.
⑵ catching dust, high efficiency, low concentration of gas emissions.
⑶ surface by hot pressing, singeing and coating or coating finishing, the surface smooth, easy to block, not easy to deformation.
⑷ chemical stability, high temperature.
But there are also the following disadvantages:
⑴ low tensile strength, easy to deformation with the filter room, so no box filter press application.
⑵ damaged after sewing is not easy to use, the cost is higher.
⑶ particles into a non-woven filter cloth, can plug the gap, easy to clean and reuse.
⒊ filter cloth choice:
The correct choice of filter cloth is not a breeze. The reason is a wide range of filter cloth, filter a variety of structures, the nature of the filter and filter conditions vary. In addition, the current filtering theory can not give us a specific selection guide. Precisely because of the above complex factors, making the choice of filter cloth is difficult. Therefore, what we can do now is to choose a reasonable compromise on the premise of fully understanding and recognizing various filter cloths and considering each filter as much as possible.
The choice of filter cloth can be in the following order:
⑴ selection of filter equipment in line with the type of filter cloth. For example, in the case of a drum filter, which has a low vacuum suction force, it is not advisable to use a thick filter cloth having an eyelet in order to avoid the filter resistance, and it is therefore difficult to obtain a filtrate of high clarity. On the contrary in the case of pressurized filter, the filter pressure of 0.1 ~ 2.0Mpa, so the choice of fine mesh eye cloth filter, in order to obtain a higher clarity of the filtrate.
⑵ selection of corrosion-resistant material. Chemical fibers have high corrosion resistance to almost any acid or alkali. But for special liquids and organic solvents, its corrosion resistance is poor.
⑶ selection of anti-filtration temperature of the material. General temperature filter cloth can be about 80 ℃.
⑷ roughly determine the thickness of the cloth eyelet hole. In order to obtain a clear filtrate, the eyelet of the filter cloth should of course be fine. However, in the case of cake filtration, since the bridging phenomenon exists, it is also possible that the eyelet of the filter cloth is slightly larger than the solid particles. For particles below 10um, if flocculation occurs, it is not considered a single particle.
⑸ decide the shape of the fiber and the type of weaving. Mainly based on the ability to capture solid particles, filter cake stripping and strength to decide.
进 appropriate price comparison.
初 use the primary filter cloth filter test, to provide the basis for the final determination.
浙江天台丰顿滤料有限公司是一家专业从事：液体过滤袋、工业滤布、滤布、滤袋、除尘袋生产销售的滤布厂家，多年来在液体过滤袋、滤袋、工业滤布、除尘袋生产上积累了丰富的经验和领先的技术。
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