Pneumatic conveying is a process that uses air to transport dry, granular materials through closed pipes. There are several types of pneumatic conveying systems depending on the air pressure used - low pressure, medium pressure, and high pressure systems. Low pressure systems include positive pressure systems, which use blowers to inject air into pipes to move materials up to 500 meters, negative pressure systems which use vacuum to suck materials into pipes, and combination systems that employ both positive and negative air pressure. Pneumatic conveying offers a flexible and low-cost material handling solution for transporting materials like coal, grain, and ashes within plants and between facilities.

1. Pneumatic conveying is the process of conveying
granular / powdered materials by floating the materials
in a gas, primarily air, and then allowing it to flow to the
destination through a closed pipe.
Definition

2.  Pneumatic conveying system is used for delivery of non-sticky, dry
materials via pipelines to various storage or process points which
are economically inaccessible by conventional conveyors.
 The operating principle common to all types of pneumatic
conveying is that motion is imparted to the material by a fast
moving stream of air.
 Thus any pneumatic conveyor consists of an air supply equipment
(blower or compressor), pipelines, product storages, air lock
feeders and dust filters.
About Pneumatic Conveying

3.  Materials can be picked from one or more points and can be
delivered to one or more points in a plant or even outside to a
different plant.
 The conveying of materials takes place through air tight piping and
auxiliary system and hence neither pollutes the environment nor the
materials get contaminated with foreign materials.
 It offers plant and operator safety in handling fine powdery materials
which may be toxic in nature or fire prone.
 If offers a flexible system. The conveying pipe lines can be routed and
rerouted with little efforts as per demand of the operations.
Advantages

4.  It makes possible unloading of materials from ships, barges,
transport vessels directly to storage bins.
 It is self-cleaning system, preventing accumulation of materials in
the conveying system. Because of this, the same installation may be
used for conveying different materials.
 If offers a low maintenance cost system. It also offers a lower cost
materials handling system compared to handling and storage of
bulk materials in bags or small containers.
 A pneumatic system can be operated automatically and can easily
be integrated into manufacturing processes as feeders.
Advantages(Contd.)

5.  The types of materials suitable for pneumatic conveying is limited to
materials which are dry, granulated, pulverized, crushed etc. and
essentially free flowing.
 Friable or too abrasive materials are not suitable to be transported
by pneumatic conveyors.
 The movement of transportation is fixed (uni-directional)
 Relatively high energy consumption per unit weight of materials
transported.
 The length of pneumatic conveyors is limited. Vacuum systems are
limited to 500 m while high pressure systems up to 2 kms or
marginally more
Disadvantages

6.  Cement
 Coal dust
 Grain
 Alumina
 Apatite concentrate
 Ashes
 Cotton
 Crushed coal
 Saw dust
 Catalyzers for cracking plants
Types of Material Conveyed

7.  Constructions work
 Rail and water transport
 Convey materials within shops and stores
 Convey materials from store to hopper
 Deliver materials from unloading areas of railway cars or ships to
the hoppers or silos of
 plants
 For unloading of railway cars and ships
 The unloading of pressurized containers
 For the controlled reclaiming of materials from silos and for many
similar purposes.
Applications

8. Pneumatic
Conveyor
Pipeline
Conveyor
Low Pressure
System
Positive
Pressure
System
Negative
Pressure
System
Combination
System
Medium
Pressure
System
Positive
Pressure
System
High
Pressure
System
Positive
Pressure
System
Air-activated
Gravity
Conveyor
Tube
Conveyor
Classification

9. Positive Pressure System:
A positive low pressure pipeline system is one in
which a positive air flow, created by a positive
displacement blower, effectively transport slow
flowing materials over a distance up to 500 meters.
The major characteristics of this system is that it can
pick up material from one source and discharge the
same to more than one points.
Pipeline Conveyor
Low Pressure System

10. Positive Pressure System

11. A positive displacement blower (lobe type or roots blower) sucks
air from the atmosphere through a suction filter and delivers
pressurized air into the conveyor pipe line.
Materials to be conveyed are introduced into the pipelines from
the feeding bin/hopper through different types of air lock feeder
at controlled rate.
The materials so introduced are immediately air laden and blown
to one or a number of receiving bins / silos through diverting
valves, also called change over valves.
Pipeline Conveyor
Positive Pressure System

12. The air, after the material get discharged at the
receiving hoppers, is made to pass through an
appropriate dust removal system, before it is allowed
to escape back to atmosphere.
Pipeline Conveyor
Positive Pressure System

13. Positive Pressure System

14. Negative Pressure System:
Easy flowing materials like cereals, grains, powdery materials
etc. are conveyed in suction conveyors.
Materials from multiple storage points may be collected and
transported to a single storage point.
Pipeline Conveyor
Low Pressure System

15. Negative Pressure System

16. A positive displacement blower creates a vacuum in the
conveyor pipe line, which causes the material to be sucked
through one or multiple nozzles and conveyed to a receiving
hopper.
The conveyed material is separated from the air stream and
collected in the hopper.
The air is generally made to pass through a dust collector to
be freed from remaining finer particles of materials and then
released to the atmosphere.
Pipeline Conveyor
Negative Pressure System

17. Negative Pressure System

18. Combined negative-positive pressure (or combination)
system:
In this system the principles of both positive pressure
system and suction system are employed.
This type of pneumatic conveyor is particularly
employed when materials from more than one points
have to be picked up and simultaneously delivered to
multiple delivery points.
Pipeline Conveyor
Low Pressure System

19. Combination System

20. Generally one positive delivery blower is used.
The suction side of the blower conveys material from the storage
points to an intermediate receiving station.
The suction air passes through this intermediate receiving station
and then through a cyclone separator and a further dust cleaner,
if required, and enters the blower.
The compressed air is then thrown into the pressure delivery pipe
line, into which the material from the intermediate storage is
discharged through necessary air lock feeder.
From there, material is conveyed to the multiple storage silos as
per a positive pressure system already discussed.
Pipeline Convey0r
Combination System

21. These systems are basically similar to a positive
pressure system in its operational principles. The
difference is the range of air pressure used.
Because of use of increased air pressure, the medium
and high pressure systems principally differ from a low
pressure system in two aspects:
Firstly, the type of air supply equipment will vary
according to the pressure selected.
Secondly, the feeding devices used will be different to
make the system leak-proof.
Pipeline Conveyor
Medium and high pressure systems

22. When small piece goods in standardized containers,
called carriers, are transported pneumatically over short
distance through pipe, it is called Tube conveyor. This
type of transportation of piece goods is used in
telegraph offices, banks, stores, newspaper offices and
also in industries. The pipes of these installations may
be round (up to 100 mm diameter) or elliptical. The
carriers are moved at speeds range of 6 to 12 mps.
Tube Conveyor

23. Dry powdered materials, when aerated acquire fluidity
and can move along a plane having a slope of only 4% to
5%. This principle is adopted in an air slide for short
distance movement of powdery materials at a fairly
controlled rate.
Air-activated Gravity Conveyors
(Air slide)

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