This document discusses filtration and the use of fibres and fabrics for filtration. It begins by defining filtration as the separation of solids from fluids using a medium that allows only the fluid to pass. It then discusses the principles of filtration, including factors that impact efficiency like porosity and permeability. Finally, it provides examples of applications for textile filtration in areas like vacuum cleaners, medical uses, power stations, sewage disposal, water filtration and geotextiles.

1. FIBRES AND FABRICS FOR
FILTRATION
SILAJIT NASKAR
JFT 02
8TH SEMESTER
D.J.F.T., C.U
EMAIL ID- silajitnaskar90@gmail.com

2. FILTRATION
Filtration is a mechanical or physical operation, which is used for the
separation of solids from fluids (liquids or gases) by interposing a medium
through which only the fluid can pass. Oversize solids in the fluid are
retained, but the separation is not complete; solids will be contaminated
with some fluid and filtrate will contain fine particles (depending on the
pore size and filter thickness).
Filtration is used to separate particles and fluid in a suspension, where the
fluid can be a liquid, a gas or a supercritical fluid. Depending on the
application, either one or both of the components may be isolated.

3. PRINCIPLES OF FILTRATION
 Objective 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

4. FILTRATION AND TEXTILES
The separation of solids from liquids or gases by textile filter media is an
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.

5. FABRIC CONSTRUCTION
Three basic types of construction are found in Filter fabrics, viz., woven
fabrics, needlefelts 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.

6. VARIOUS APPLICTIONS OF TEXTILES IN
FILTRATION
 In vaccum cleaners - The bag used in
vaccum cleaners is the typical method to
capture the debris vacuumed up. It
involves a paper or fabric bag that
allows air to pass through, but attempts
to trap all dust and debris in the bag.
The bag may be disposable, or designed
to be cleaned and re-used.
 In medical uses – Woven filters set the
standard for safe and efficient filtration
solutions in medical devices. Precision
woven fabrics is a critical component
for medical filter devices, blood
filtration : precision woven fabrics set
the standard for safe and efficient
filtration.

7.  In Power Stations- A baghouse (BH, B/H)
or fabric filter (FF) is an air pollution control
device that removes particulates out of air or
gas released from commercial processes or
combustion for electricity generation. Power
plants, steel mills, pharmaceutical producers,
food manufacturers, chemical producers and
other industrial companies often use
baghouses to control emission of air
pollutants. Baghouses came into widespread
use in the late 1970s after the invention of
high-temperature fabrics (for use in the filter
media) capable of withstanding temperatures
over 350°F.
 In Sewage disposal-A non-woven fabric
filter was experimentally evaluated for solid-
liquid separation in an activated sludge
reactor as an alternative membrane. A
polypropylene fabric filter (70, 50 and 35
g/m2) was used.

8.  Water filtration- This type of filter is a
common solution to the problem of
obtaining clean water in many parts of the
world, especially rural parts of developing
nations. It is a fairly simple process that
involves only materials that are available in
most parts of the world.
 In Geo-textiles- The non-woven geo-textile
fabric is a common choice for areas looking
to stabilize, separate or filter materials. All
non-woven fabrics come with a needle-
punched exterior that allows thin water
particles to filter through the fabric while
keeping soil from filtering through. This
geo-textile filter fabric helps to retain fine
particles when water passes from fine to
coarse-grained soil layers.

9. CONCLUSION
The separation of solids from liquids or gases by textile filter media is an 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.
The final products of processes which involve filtration by textile filter media may
ultimately find their way into our everyday lives.
In addition to assisting in the refinement of products for our general everyday use,
textile filter media are also engaged in the purification of both industrial and domestic
effluents, thereby contributing to a cleaner environment.

10. REFERENCES:
 TEXTILES IN FILTRATION BY Edwin Hardman
Madison Filters (formerly Scapa Filtration), Haslingden,
Rossendale, Lancashire, UK
 A HANDBOOK OF TECHNICAL TEXTILES edited by A.R. HORROCKS & S.C. ANAND
 WIKIPEDIA AND GOOGLE SITES
THANK YOU