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1

WELCOME TO OUR PRESENTATION

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2 Presentation Topic-

Textile Filtration

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3 FILTRATION Filtration is a process of separating dispersed particles from a dispersing fluid by means

of porous media. The dispersing medium can be a gas (or gas mixture) or a liquid

Upstream

Dispersing fluid

Dispersed particles

Filter thickness

Face of the filter with „filter cake“ of deposited particles

Downstream

Particles deposited inside the filter

Filter

Channel wall

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4 Types of filtration

Flat filtration

Deep filtration

Pleated filters

Pocket filters

Cartridge filters

Drum filters

Bag filters, pulse-jet filters

Disc filters

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5Flat filtration

All particles which are bigger than pores are captured on the flat filter surface. It is typical for example for fabric or spunbond filters. Thus for these filters the pores distribution and permeability are important properties. Flat filtration is common for liquid filtration. Flat filters are described in subject „High funcional textiles“

Direction of flow

Textile filter expressed as a set of cylinders placed in parallel

Captured particles

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6 Deep filtration

Depth filter are able to capture particles that are too small to be sieved out as in flat filtration. Particles, which can be a lot of smaller than the distances between the fibers penetrate into the fiber structure. Filtered particles are captured in terms of the filtration mechanisms. This type of the filtration process is importatn for the most of filter applications.

Direction of flow

Textile filter expressed as a set of cylinders placed in parallel

Captured particles

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7 Pleated filters

It is suitable for high efficient filters. Pleating process leads to bigger filter surface and consequently to smaller pressure drop. It is possible to pleat flat materials, which stiffness and elongation is similar to paper. It is necessary to hold textile pleats by rigid frame. Filter thickness is usually from 1 to 3 cm.

Polluted air

Clean air

Rigid frame

Filter

Air flow direction

Filter thickness

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8Examples of pleated filters

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9 Pocket filters

Principle is similar to pleated filters, only filter thickness is similar to other filter dimensions. Generally it is possible to use nearly all textile fabrics. At first are stitched or bonded each pockets and then it put into the frame.

Polluted air

Clean air

Filter

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10 Cartridge filters

Flat (bulky) filter or pleated filter is wrapped around the perfored tube. The advantage is smaler dimension of filter with regard to acting surface.

Variants of cartridge filter cross-section

Flat (bulky) filter Pleated filterFilter

Perforated tube

Polluted air

Clean air

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11 Examples of cartridge filters

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12Drum filters

1.The rotating drum is actually a frame withmounted filter panels. The filter panels use apolyester or stainless steel filter cloth that isof a specific micron porosity.2. Waterborne solid waste particles enter theDrum Filter from the inside of the rotating drum.3. Solid waste particles (larger than the micronporosity rating of the filter screens) areocaptured n the filter screens.

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Examples of Drum filters

Bag filters, pulse-jet filtersPrinciple is similar as cartridge filters however bag length is much bigger than diameter and usually filter is cleanable by reverse pressure pulse. Commonly many bag filters are used for one application (hundreds). Most of the dust is collected on the surface of filters. When the increasing pressure drop reached a set value, the filters are cleaned by a short burst of compressed air moving in reverse direction. Typical maximum pressure drop is 1000 – 2000 Pa, typical pressure pulse is in range 0,5 – 1 MPa and cleanig time 0,1 - 100 sec.

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15Examples of pulse-jet filters

Steel frames

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16 Disc filters

A disc filter is a type of water filter used primarily in irrigation, similar to a screen filter, except that the filter cartridge is made of a number of discs stacked on top of each other like a pile of poker chips. The water passes through the small grooves in between and the impurities are trapped behind

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17Example of Disc filters

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18 Filtration variables

Filtration variables are divided onto three groups:

1. Variables of filter material

2. Variables of filtered particles

3. Variables of filtration process

Variables of filter material:

•Filtration area

•Filter thickness

•Density and surface density of filter

•Uniformity of fibrous material

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19 Variables of filtered particles•Particle size

•Concentration of particles

•Shape and surface of particles

•Electrical properties

Variable of filtration process•Face velocity (speed of filtered particles in front of filter)

•Viscosity of the flow

•Temperature, pressure, humidity

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20 PRINCIPLES OF FILTRATIONObjective of filter medium is to maximize the possibility of collision and the subsequent retention of the suspended particles with fibrous structures while minimizing the energy loss of the system. The efficiency of filtration in industrial fabrics are affected by there porosity. Knowledge of air permeability is also important for suitability for use. Permeability is capacity of porous materials to transmit the fluids. Liquid and gas permeability increases with the increase in porosity of the fabric. The type of finish also affects the permeability. When Porosity increases pressure drop tends to decrease. When flow rate increases, pressure drop increases.

There are five principles of filtration:

Interception

Inertial disposition

Random diffusion (Brownian motion)

Electrostatic disposition

Gravitational forces

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21 FILTRATION AND TEXTILES Essential part of countless industrial processes, contributing to purity of product,

savings in energy, improvements in process efficiency, recovery of precious materials and General improvements in pollution control. In the coming decades, fabric filtration will play a very critical role in day to day life, and there is no single type of fabric being used in all the process.

Filtration fabrics are used widely in:

Vacuum cleaners

Medical uses

Power stations

Petrochemical plants

Sewage disposal

Water filtration

Geotextiles etc

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22 FABRIC CONSTRUCTION Three basic types of construction are found in Filter fabrics, viz., woven fabrics, need lefelts and

knitted structures. The first two are produced in flat form and will require (i) slitting to appropriate width and (ii) converting into tubular sleeves, whereas knitted fabrics may be produced directly in tubular form.

The technologist has basically four types of yarn to choose from when designing a filter fabric, namely monofilament, multifilament, fibrillated tape and staple-fibre Yarns.

IMPORTANT CHARECTERISTICS OF FILTER FABRICS With the fabric warp and weft density increases, the filtration resistance of the filter cloth

increases gradually.

With the increase in the fabric warp, weft twist, the filtration resistance of the

filter cloth is reduced gradually

Fabric tissue filtration resistance: resistance of plain weave, twill path of least

resistance.

Porosity of the fabrics.

Air permeability of the fabrics

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23 VARIOUS APPLICTIONS OF TEXTILES IN FILTRATION

In vaccum cleaners - The bag used invaccum cleaners is the typical method tocapture the debris vacuumed up. Itinvolves a paper or fabric bag thatallows air to pass through, but attemptsto trap all dust and debris in the bag.The bag may be disposable, or designedto be cleaned and re-used.

In medical uses – Woven filters set thestandard for safe and efficient filtrationsolutions in medical devices. Precisionwoven fabrics is a critical componentfor medical filter devices, bloodfiltration : precision woven fabrics setthe standard for safe and efficientfiltration

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24 In Power Stations- A baghouse (BH, B/H)or fabric filter (FF) is an air pollution controldevice that removes particulates out of air orgas released from commercial processes orcombustion for electricity generation. Powerplants, steel mills, pharmaceutical producers,food manufacturers, chemical producers andother industrial companies often usebaghouses to control emission of airpollutants

Water filtration- This type of filter is acommon solution to the problem ofobtaining clean water in many parts of theworld, especially rural parts of developingnations. It is a fairly simple process thatinvolves only materials that are available inmost parts of the world.

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25In Geo-textiles- The non-woven geo-textilefabric is a common choice for areas lookingto stabilize, separate or filter materials. Allnon-woven fabrics come with a needle-punched exterior that allows thin waterparticles to filter through the fabric whilekeeping soil from filtering through. Thisgeo-textile filter fabric helps to retain fineparticles when water passes from fine tocoarse-grained soil layers

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26 Fibres and Polymers used in Filtration Media

Natural - fibres from vegetable matter such ascotton, flax, jute, wood cellulose- or fibres from animals such assilk, wool, fur, hair

Fibres from Vegetable matter

cotton Flax

jute

Wood cellulose

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27 Fibres from animals

silk wool hair

Fibres and Polymers used in Filtration MediaArtificial - fibres from natural resources such as glass, ceramic, carbon,metal, reconstituted cellulosesynthetic – fibres derived from oil such as thermoplastic polymers

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28Artificial fibres

reconstituted cellulosecarbonceramicglass

Out of these fibres Polyester and Polypropylene would be the most widely used

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