|
 |
|
 |
| |
PNEUMATIC CONVEYING SYSTEMS
The
pneumatic conveying system is a method of conveying
dry powdered material in a pipeline through air
without any moving parts. The pneumatic conveying
system can be routed conveniently above the working
area and can have bends and turns to reach the
destination point which gives pneumatic conveying
mode lot of flexibility. For conveying materials
such as powders, pellets and granules of sizes
from a few microns to about 25 mm, pneumatic conveying
is advantageous over any other conventional conveying
systems. Any pneumatic conveying system shall
have four basic components namely prime mover
which develops motive force (roots blower, compressor
or centrifugal fan), feeding device which introduces
product into conveying line (rotary valve, ventury,
pressure vessel),piping, bends diverters and product
to air separator (cyclone, bag filter) Typically
the systems are bifurcated in two main categories
- Pressure type & Vacuum type, each is sub
categorized in dense phase and dilute phase conveying
system
|
| |
Dilute
Phase Pressure Type Conveying System |
| |
Dilute
Phase Conveying
Dilute phase is a suspension flows
wherein the material to be conveyed
is introduced into a moving air
stream inside a pipeline. For the
material to remain in suspension
there is a minimum conveying velocity
which varies for different materials.
The quantity of material that is
fed into an air stream is also dependent
on material characteristics like
bulk density, particle size, sieve
analysis, frequency distribution
etc. Generally, the material to
air ratio varies between |
|
3
to 10 kg of material to kg. of air. Conveying
velocities are in the range of 18 to 28
m/sec depending on the product characteristics.The
dilute phase conveying system uses low-pressure
air at pressures less thanone bar in case
of pressure conveying and (-) 5000 mm
in case of vacuum convening, which is
generated by positive displacement type
roots blowers or by centrifugal blowers.
Dilute Phase
Pressure Conveying System
Pressure conveying systems are generally
used where the feeding point is one and
there are multiple discharge points. In
this system the prime mover is located
at the start of the conveying line and
product is fed to the system through either
rotary valve or ventury eductor or pressure
vessel. |
|
| |
Dense
Phase Pressure Type Conveying System |
| |
Dense
Phase Pressure Conveying
Dense phase conveying
is a widely known as plug flow systems
which is non-suspension flow. The
product is filled in a pressure
vessel, which is then pressurized
with the air or gas to be used for
conveying. Once a pre-set pressure
is reached inside the vessel, the
bottom discharge valve opens and
the material is conveyed to the
destination. The material to air
ratios is higher in dense phase
conveying in the range of 20 to
100 kg/kg of air. Dense phase conveying
uses compressed
|
|
air
and requires an air compressor. Dense
phase conveying is used for high capacity
and long distance conveying. Dense phase
conveying employs the pressure vessel
with valves and instrumentation which
is controlled through PLC based control
panel. |
|
|
| |
Dilute
Phase Vacuum Type Conveying System |
| |
Dilute
Phase Conveying
Dilute
phase is a suspension flows wherein
the material to be conveyed is
introduced into a moving air stream
inside a pipeline. For the material
to remain in suspension there
is a minimum conveying velocity
which varies for different materials.
The quantity of material that
is fed into an air stream is also
dependent on material characteristics
like bulk density, particle size,
sieve analysis, frequency distribution
etc. Generally, the material to
air ratio varies between
|
|
3
to 10 kg of material to kg. of air. Conveying
velocities are in the range of 18 to 28
m/sec depending on the product characteristics.The
dilute phase conveying system uses low-pressure
air at pressures less than one bar in
case of pressure conveying and (-) 5000
mm in case of vacuum convening, which
is generated by positive displacement
type roots blowers or by centrifugal blowers.
Dilute
Phase Vacuum Conveying System
These
systems are installed wherein multiple
feed points are involved. The advantage
of this system is any leakage is inward
due to which these systems are popular
for conveying of explosive or hazardous
products. As the system is operating
below the atmospheric pressure the conveying
velocities are generally higher than
the pressure conveying. These systems
are also popular for short distance
conveying in food and pharmaceutical
industries.
|
|
| |
Dense
Phase Vacuum Type Conveying System |
| |
Dense
Phase Vacuum Conveying
Dense phase
vacuum conveying systems are used
for very short distance of conveying
typically below 15 mtrs with 1
or 2 bends.The components are
specially designed suction nozzle
,conveying piping ,product separator
and airlock valve.These systems
are operating below (-) 5000 mm
of WG using roots blowers and
used for product conveying from
bags/drums or hoppers.
|
|
|
|
|
|
