Transcript Slide 1

EQUIPMENT FOR FILTRATION OFAIR
PRESENTED BY
SWAPNA.M
M. Pharm
2nd semester
Department of pharmaceutics
University College of Pharmaceutical Sciences,
Kakatiya University, Warangal-506009.
CONTENTS
INTRODUCTION
 PRINCIPLES OF AIR FILTRATION
 AIR FILTERS
 CONCLUSION
 REFERENCES
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INTRODUCTION
 The purpose of air filtration is to remove
contaminants from the air.
 The removal of airborne particulate from an air
stream is called air filtration and is accomplished
through mechanical, and electrostatic
phenomenon.
 The first step in selecting an air filtration system
is to understand the contamination – what it is
and how it is harmful.
PRINCIPLES OF AIR FILTRATION
There are four basic principles of operation
which apply to the various types of air filtration
systems.
 Inertial Separation
 Impingement
 Diffusion
 Electrostatic
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Inertial Separation:
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In inertial separators, particles are collected
by centrifugal forces arising from a rapid
deflection of the airflow such that the dust
particles, having mass and kinetic energy, are
unable to follow the path of the gas
molecules and, proceed in a different path to
the main air stream.
Viscous Impingement:
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The term “viscous” is in front of the impingement
principle of operation because the air filter media is
oiled with a sticky adhesive and, therefore, operates
as a “viscous” filter.
Viscous impingement filter media is made up of
synthetic fibers, glass fibers, or expanded metal foil
mesh in a pad, or mat, in multi layers or pleated
forms.
DIFFUSION:
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In the case of aerosols moving through a filter, Brownian
motion causes erratic motion of the particles about the
steady aerodynamic path.
This motion would not of itself result in additional collection
of particles by fibers if the particle concentration were
everywhere identical.
But since the motion is totally random, the transfer of
particles across any surface near a fiber will be proportional
to the concentration on opposite sides of that surface.
It can be shown that there is a net transfer of particles across
a surface and that this transfer is in the direction of the fiber
surface itself. The rate at which such transfer takes place is
proportional to a diffusion coefficient
Electrostatic filtration:
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Electrostatic filtration is an extremely effective
method for removing dust, smoke, and other small
particles from air over a particle size range from
about 10 to 0.01 microns.
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The principle involved is that of passing the air
through an ionizer screen where electrons colliding
with air molecules generate positive ions which
adhere to dust and other small particles present,
giving them a positive charge.
AIR FILTERS
 Historically, packed towers were the first air
filters used by the industry for air purification.
 Different air filters include
 Packed towers
 Membrane filter cartridges
 Bag filters
 HEPA filters
DESCRIPTION OF PACKED TOWERS:
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Packed towers used to filter fermentation air are
comprised of beds which can be constructed of pad
of paper, cotton wool, glass wool.
The diameter of fibrous material is typically between
0.5 and 15 micro meters and the space between the
fibers can be many times this range.
The filter consists of a steel container or housing
filled with loose fibrous packing.
The air inlet is on the bottom and the outlet is on the
top of the filter.
MEMBRANE FILTER CARTRIDGES:
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Cartridge filters are easily handled, and
consists of high surface area and tight particle
capture specifications.
Membrane filters can have absolute or
normal ratings.
A normal rating is an arbitary micron value
assigned by the manufacturer, based up on
the removal of some percentage of all
particles of a given size or larger.
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An absolute pore rating can be defined as the
diameter of the largest spherical particle that will
pass through a filter under specified conditions. It is
an indication of the largest available pore opening in
the filter elements.
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Membrane filter cartridges are available as either pre
filter or sterilizing filter configurations.
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Pre filters are used for particulate removal and
sterilizing filters are used for removal of bacterial
contaminates.
BAG FILTERS:
Recovery of particulate matter from exhaust gas is vital for any
industry from two aspects
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To avoid pollution problems
Recovery of finished product-increasing the plant yield
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For recovering particulate matter different options available are –
Cyclones, Venturi, scrubbers, bag filters, electrostatic precipitators
etc. Out of these bag filter becomes the best choice if following are
dominant selection criteria’s:
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Material is expensive and hence high collection efficiency is desired.
Particulate size is very fine.
Material recovery in powder form is desirable & not in solution form.
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WORKING PRINCIPLE OF BAG FILTER:
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The dust-laden air enters the bag filter bustle.
The air is uniformly distributed avoiding channeling.
Initially a coat of material forms on the bags. Subsequently,
the coat acts as the filtering medium.
The dust is accumulated on filter elements while the air
passes thorough the filter bags from outside to inside.
The accumulated powder is dislodged from the bags by
reverse pulse-jet air intermittently.
The dislodged powder falls on bottom cone and is
discharged through powder discharge valves.
The dust free air is sucked by induced draft fan and is
exhausted to atmosphere.
Knockers are provided on conical portion especially for
sticky/hygroscopic materials
FEATURES OF BAG FILTERS
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Better performance.
Easy in maintenance and long life.
HEPA FILTERS:
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HEPA filters, by definition, remove at least 99.97% of
airborne particles 0.3 micrometers (µm) in diameter.
HEPA filters are composed of a mat of randomly arranged
fibres. The fibres are typical composed of fiberglass and
possess diameters between 0.5 and 2.0 micron. Key metrics
affecting function are fibre diameter, filter thickness, and face
velocity.
The common assumption is that, a HEPA filter acts like a
sieve where particles smaller than the largest opening can pass
through is incorrect. Unlike membrane filters, where particles
as wide as the largest opening or distance between fibres
cannot pass in between them at all, HEPA filters are designed
to target much smaller pollutants and particles.
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These particles are trapped (they stick to a fibre)
through a combination of the following three
mechanisms:
Interception, where particles following a line of flow in the air
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Impaction, where larger particles are unable to avoid fibres by
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Diffusion, an enhancing mechanism is a result of the collision
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stream come within one radius of a fibre and adhere to it.
following the curving contours of the air stream and are
forced to embed in one of them directly; this effect increases
with diminishing fibre separation and higher air flow velocity.
with gas molecules by the smallest particles, especially those
below 0.1 µm in diameter, which are thereby impeded and
delayed in their path through the filter.
Conclusion
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The level of sophistication of air filtration
equipment is dependent on the service of the air
and the environment conditions of the rotating
machinery`s locatiion.
Thus, we can ensure that filtration equipments
for air is very necessary in the pharmaceutical
industry.
References
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James Swarbrick , Encyclopedia of
Pharmaceutical Technology , vol-6 ,pg no 51
Theodore H. Meltzer , Maik W. Jornitz ,
Filtration in the Bio pharmaceutical Industry
Sarfaraz Niazi , Handbook of Pharmaceutical
Manufacturing Formulations:Sterile….,vol-6
James Swarbrick , Encyclopedia of
Pharmaceutical Technology , vol-3 ,pg no-1748
www.wikipedia.org
www.thomasnet.com
Thank You