1. Pneumatic Transfer – A Natural Phenomenon
Transfer of Seeds and Pollens by Wind
AIR KINETICS

2. The Basic Scheme of Pneumatic Conveying
Generate the airflow into a closed pipe or duct
Introduction of bulk solid from source into air stream
Convey this material to the desired destination
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3. Saltation Velocity
When powder or granular material is introduced in the pipe
Particles will be either carried away by air current. Or
They will settle down at the bottom of the pipe.
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4. Saltation Velocity For different materials value of "Vc" is different.
Even for same material (Same Particle Density)
"Vc" will depend on particle size and shape.
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5. Pneumatic Conveying Systems
Dense Phase
Dilute Phase
Positive Pressure
Negative Pressure
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6. Positive Pressure & Negative Pressure System
Positive Pressure System
Higher Efficiency
To generate given pick up velocity lesser of air volume is required and hence blower size is smaller
In case of leakage in the conveying line this is easily detected.
Negative Pressure System
Lower Efficiency
To generate given pick up velocity higher volume of air is required and hence blower size is bigger.
In case of leakage in the conveying line this is not easily detected.
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7. Positive Pressure & Negative Pressure System Contd.
Preferred for conveying hygroscopic products
Rotary Air Locks should be of superior quality with smaller clearance between rotor blades and casing to limit leakage air or else loss of air can choke the conveying lines.
To be avoided for hygroscopic products.
Rotary air lock quality need not matter.
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8. Dilute Phase Conveying Systems
If conveying velocity is sufficient to carry away the particles in suspended state in air stream this is called dilute phase system.
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9. AIR KINETICS

10. Common Sources of Bulk Solids in the Industry.
1)Blenders
2)Storage Silos
3)Intermediate Silos
4)SFD Bag house
5)Blenders
6)Pulverizes
7)Jumbo Bags
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11. Common Destinations for Bulk Solids in the Industry.
1)Blenders
2)Storage silos
3)Packing Silos
4)Mixing Tanks
5)Reactors
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12. Properties of the Bulk Solids
1. Fluidizing Property
2. Bulk Density
3. particle Size Distribution
4. Wall Friction Angle
5. Moisture Content
6. Air Permeability
These properties matter in selection of pneumatic conveying system and storage silos
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13. Review of Dilute Phase & Dense Phase System
Advantages and Disadvantages of Dilute Phase System
Advantages and Disadvantages of Dense Phase System
Almost All Materials irrespective of fluidizing property can be conveyed.
Any System where conveying distance is maximum 200 mtrs can be operated by inexpensive air movers like fan blowers and roots blowers as conveying pressure drop can be maintained less than 1 bar
Only good fluidizing property bulk solids or good air permeability solids can be conveyed.
Any System of comparable conveying distance requires higher pressure drop and hence air mover required is expensive like screw compressor.
Energy efficiency is high but generally these systems are batch conveying processes and any continuous process dense phase system requires special rotary feeders.
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14. Review of Dilute Phase & Dense Phase System Contd.
Advantages and Disadvantages of Dilute Phase System
Advantages and Disadvantages of Dense Phase System
Though Initial capital cost is low, energy efficiency is less than dense phase conveying
For Abrasive Materials higher conveying velocities cause excessive wear to the pipes, bends and feeding devices.
Excessive Conveying Velocities cause particle degradation of friable materials.
Pipe line sizes for the given conveying rate are smaller but the conveying lines are prone to heavy vibrations and hence requires stronger supports and the distribution equipment like diverter valves need special strong holding locking system.
Because of Low conveying velocities wear and tear can be limited.
The particle degradation is least in dense phase conveying
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15. Building Blocks of Pneumatic Conveying Systems
Air Blower
Feeding Devices
Conveying Lines
Diverter Valves
Air Separation Unit or Bag Filter
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16. Air Mover
For dilute phase pneumatic conveying systems roots blowers or fan blower is used. If conveying distance is short and solid loading ratio is small fan can be used as maximum pressure drop can be limited to values less than
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17. Feeding Devices
Many different feeding devices are used but in general rotary air locks and ventury feeders are used in dilute phase systems and blow tanks are the most common feeding device in dense phase system.
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18. Conveying Lines
Conveying lines are of normal pipes with a good internal surface finish. As these lines carry solid particles mixed with air the bends used are long radius bends these can be 7D or 10D bends using shorter radius bends cause excessive pressure drop across bend hence long radius bends are used.
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19. Types of Diverter Valves
When conveying Line is intended to carry the material to different destinations diverter valves are used. There can be different types of diverters with different diversion angle. Also there are three main construction variants in diverters.
Types of Diverter Valves
Flap type diverter
Pipe Diverters
Plug Diverters
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20. Pipe Diverter
Plug Diverter
Flap
Diverter
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21. Air Separation Unit or Bag Filter
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22. Safety Devices on Pneumatic Conveying System
Pressure Safety Valve
Pressure Switch
Differential Pressure Switch
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23. Trouble Shooting Tripping of Overload Relay of roots blower motor
Insufficient conveying Rate
Insufficient conveying Rate in case of negative pressure system
Choking of conveying line
Frequent deposition of powder layers inside the pipe line