Basic knowledge of press cloth

The basic type of filter cloth

Filter cloth is divided into machine fabric, nonwoven fabric and composite fabric.

1. Woven fabric

Because the warp and weft of woven fabric can be arranged in various ways, different weave structure figures can be obtained, plus they can be used

There are different types of yarns and processing techniques, so there is virtually no limit to how the fabric is organized. Woven fabric is pressed by warp and weft

The regularity of upper and lower interlacing is called the organization of woven fabric. Machine fabrics commonly used to organize plain, twill and satin weave

Three basic styles.

Plain weave refers to the weaving in which each warp and each weft intersect with each other. Plain weave cloth is the densest, so the filtering effect is the most

Ok, best stiffness.

Twill weaving is a process in which a weft passes above and below two or more warp threads and is arranged from one line to the next

Regular crosswise moving weaving. The weave produces diagonal diagonal diagonal twill lines, usually moving up from left to right along the surface of the cloth.

The advantage of twill weave is that it can fill up more weft thread on the cloth of unit length, so the fabric is bigger. Compared to plain cloth, sloping

The fabric is more flexible and can be fitted to a filter.

Satin weave, which further expands the concept of twill weave by using wide interlacing point spacing. This method can weave surface light

Silky cloth, but twill satin without diagonal lines is the softest. In addition to easy removal of filter cake, this cloth also reduces the particle inside the cloth

The possibility of being caught. The drawback of satin, however, is that it is frictionless.

1.1 precision machining of woven fabrics

Precision machining of woven fabrics has three main purposes: to ensure the stability of the cloth, to improve the surface characteristics of the cloth and to adjust the permeability of the cloth.

(1) heat finalization. In the whole production process, there is tension on the filter cloth, so the filter cloth needs to be stable. Otherwise the tension is removed

After that, the size of the cloth will change, which may cause the feed hole of the filter press not to align with the hole on the filter cloth. In order to avoid such problems, we should

The temperature and duration of heat treatment depend on the polymer material of the cloth. The filter cloth needs stability

Another reason is that there is tension pre-applied to the filter cloth, such as on the belt filter and on the vertical filter press

The tension ACTS on the filter cloth. In this case, carefully control the temperature to stretch the cloth. Pre – stretching can reduce the use of the press cloth

In addition to the further elongation during the period, it can also ensure that the filter cloth has a good track in operation and reduce running deviation.

(2) pressure light. Calender light is the most commonly used method to improve the surface properties of cloth. During operation, let the filter cloth pass between the hot pressure rollers and root

Select the temperature, pressure, and speed of the rollers according to the different cloth. The filter cloth is smooth and easy to remove

The permeability is adjusted and the filtration efficiency is improved.

(3) the singeing. Burnishing is a slightly burnt surface treatment of fine hairs on the surface of a cloth woven from a short fiber yarn. The short fiber fuzz on the cloth

To prevent the removal of filter cake, air frame or very hot metal narrow strip can be used to quickly contact the cloth surface and the fine hair can be burnt away.

(4) raising. Fleece is a soft pile of fine steel combed on one or both sides of a cloth. Fleece not only improves the filter cloth’s ability to catch fine particles,

And it also improves cloth’s ability to absorb dirt. The fleece is often used to treat the dust filter cloth.

(5) surface coating. Surface coating is a special surface treatment method for filter cloth. Microporous polymer coating can be applied to both woven and nonwoven fabrics

In addition, the filter precision is improved, and the condition of removing filter cake from cloth is improved. For example, teflon trimer, can form very on the surface

A strong coating layer, with many holes in it, with a diameter of 5 ~ 8 inches.

2. Nonwoven fabric

The preparation of nonwoven fabric requires six steps: fiber preparation, net forming, bonding reinforcement, drying, finishing and rolling. In these 6 steps

Among them, it is most important to strengthen them with net forming and bonding.

2.1 into the net

Network can be divided into dry network, wet network, polymer extrusion network.

(1) dry method to form a net. The dry method is divided into mechanical network and air flow network. The dry net is chemically, mechanically, solvents, or

After thermal bonding treatment, the size of the stable non-woven fabric.

(2) wet forming of net. The wet net is made of water, so that the short fiber is suspended uniformly in the water, and then the fiber is immersed by the action of water flow

A wet net is formed on a water-permeable curtain or perforated drum.

(3) the polymer is extruded into a net. The principle and equipment of polymer extrusion are used to compress the polymer into a net. Typical spinning methods are melting

Net spinning, dry spinning and wet spinning.

2.2 the carton

Reinforcement can be divided into mechanical reinforcement, chemical bonding and thermal bonding. They can be used separately or in combination.

2.2.1 mechanical reinforcement

Mechanical reinforcement does not require adhesives, solvents and other chemicals, nor does it require hot melt adhesion

To bind together, or reinforce a web with coils or yarns.

(1) acupuncture reinforcement. In dry nonwovens, needle-pricking nonwovens are the most widely used nonwovens and have been used in geotechnics

Fabrics, carpets, automotive upholstery materials, paper blankets, filtration materials, synthetic leather fabrics and high temperature resistant synthetic materials.

Nonwoven fabric made by needling has many uniform and irregular internal pores. So good air permeability, good retention of particles is also one

The big advantage. However, when the particles enter the interior of the nonwoven fabric, the pores will be blocked, and the plush on the surface of the cloth will also make the filter cake hard to be peeled. To solve the

The policy is to burn the cloth, pressure, surface coating resin. The needle-prick nonwovens treated in this way have both good particle retention and good quality

Good filter cake peeling. If a substrate is laid between the upper and lower webs of fibers, the nonwoven fabric is as strong as the woven fabric.

(2) water thorn reinforcement method. Compared with needling, water spines exert less force on the fiber, so the density of non-woven fabric is also less

Some, also softer.

(3) sewing. The appearance and properties of the fabric are similar to those of traditional woven or knitted fabrics.

2.2.2 chemical bonding reinforcement

Chemical reinforcement of nonwoven fabric is the longest and most widely used method in history. Chemical adhesives have adhesives

Adhesion and solvent adhesion.

2.2.3 thermal bonding reinforcement

2.3 after finishing

(1) heat finishing. The thermal shrinkage finishing method can be used to increase the compactness of nonwoven fabric, increase the strength, and improve dimensional stability.

(2) calendering. The purpose of this paper is to make the thickness of nonwoven fabric even and meet the requirement of certain thickness.

(3) wool finish. Gas is used to burn up the surface of the non-woven fabric surface of the floating fiber in order to get a smooth surface of the non-woven fabric.

(4) vacuum cleaning. The purpose of dust collection is to increase the dust adsorption capacity of nonwoven fabric. The key to dust cleaning is to use electrostatic resistors.

Dehumidifier, paraffin emulsion and so on, non – woven fabric soak treatment. The fibers of a filter material made of nonwoven cloth, which has been vacuumed, can be filtered

Dust is absorbed in the process.

(5) finish the coating. To improve the original function of nonwoven fabric, or to give it new function, the surface can be coated with a layer of chemical materials

Material. The strength and other properties of the polymer can be improved by using an appropriate coating polymer formula.

(6) laminated finishing. The principle of lamination is simple, that is, two or more layers of materials are superimposed together by means of adhesive to form composite materials.

3. Compound fabric

(1) coating. Coating a layer of chemical material on the surface of woven or nonwoven fabric can improve the retention of particles and the clarification of filtrate

Degree, improve the peeling of filter cake, improve corrosion resistance, improve service life.

(2) the lamination. The thick layer above plays the role of pre-filtration to trap larger particles, while the thin layer below is used to trap the larger particles

Small particles maximize the pollutant carrying capacity of the medium. Surface filter media, using the surface of the medium thin layer or film layer to collect particles, filtering effect

The rate depends entirely on the hole in the surface of the medium.

(3) layers. The upper layer of a multilayer medium is the thinnest, used for filtering, and the lower layers are thicker and stronger, providing mechanical stability to the entire medium

Sex.

Characteristics of filter cloth

1. The permeability of the press cloth

(1) permeability is an important parameter to determine the initial flow rate of fluid through the medium, while the initial flow rate affects the filter cake junction near the medium

Structure.

(2) permeability is a parameter that directly affects the pressure loss during filtering. When the permeability is high, the pressure loss is small and the filtration speed is fast.

(3) permeability is the key to the success of filter cake filtering.

(4) permeability determines the amount of particles trapped in the medium by rarefied filter slurry, which of course makes it difficult for the medium to reverse rinse and regenerate.

(5) permeability is an important parameter to determine the fan size or power of air filtration station.

2. A bridge over a filter hole

The pores of the filter cloth are larger than those of the filter cake above it. The larger the pores of the filter cloth, the less clogging the filter cloth, the easier it is to wash

Filter cloth with the largest possible porosity should be selected. The clogging of filter cloth is easily related to the bridge on the hole of filter cloth.

First, large particles form an arch bridge, and then small particles form a filter cake on the arch bridge. Small particles can be filtered out from the larger pores of the filter cloth

Zi, attributed to the bridge phenomenon.

3. Flow resistance of filter cloth

In most cases, the medium is used many times before it is abandoned due to wear and pore congestion. Even after each use

Cleaning media, but the capacity of the filter cloth through the fluid is still inevitably reduced, and the extent of reduction is related to the flow resistance of the media.

The initial filtration pressure and the concentration of solid particles significantly affect the initial resistance of the medium. If the filter pressure used exceeds a certain threshold, then

The filter cake filter the desired conditions will not appear. This is because under such filtering pressure, a stable bridge cannot be formed, and the bridge failed

Particles can clog pores in the medium. Similarly, if the slurry concentration is lower than a certain value, it will not form a bridge.


Post time: Jul-25-2018

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