Pneumatic Conveying Definition
Pneumatic conveying by definition is the name for describing the bulk powder handling.
Heavy duty material is transported through an enclosed conveyor system from one place to another using the force of air-activated gravity. This allows the material to be transported across floors, or long distances in a more efficient way with less manpower required than using a labour based transportation system.
What is a Pneumatic Conveyor?
A pneumatic conveyor system is the configured transportation system used in bulk powder handling. The pneumatic conveyor efficiently transport heavy duty cargo (powders, grains, stone etc.) from one area to another.
Types of Pneumatic Conveyors
There are two types of bulk powder handling pneumatic conveyors. These are:
- Dilute Phase handling pneumatic conveyors
- Dense Phase handling pneumatic conveyors
Each type of phase has both pressure and vacuum conveying. Pressure pushes pulverized material, whereas vacuum sucks the bulk powder to it’s required destination.
Depending on the type of of bulk powder you are looking to transport, the type of pneumatic conveyor will vary. For example, a Dilute Phase pneumatic conveyor system will move small grain, plastic, wood chips and cement, but may also be used in pharmaceutical and food processing.
A Dense Phase pneumatic conveyor on the other hand, will be used where heavier materials are required to be moved in bulk, and a tendency for abrasion may happen.
Dilute Phase Pneumatic Conveyors
Dilute Phase pneumatic conveyor systems makes use of ‘pressures’ to move pulverized/fine materials through a tube system from one area to another.
Depending on the type of industry, or application you require, the Dilute Phase pneumatic conveyor makes use of both positive and negative energy.
Positive pressure conveyors use a single inlet and low amount of air pressure to move the powder material through the conveyor system to it’s required destination.
Conversely, negative pressure conveyors are most efficient when moving materials from multiple entry points to a required destination.
The system can be closed loop or open air depending on the industry the conveyor system services. For example, pharmaceutical, or chemical industries may require a closed loop system to ensure hazardous gases are not released from the conveyor system into the air.
Dense Phase Pneumatic Conveyors
Dense Phase pneumatic conveyors are used differently to Dilute Phase conveyor systems as a result of the pressure, speed and density of the material they’re transporting.
Due to the chances of abrasion from the material transported, Dense Phase pneumatic conveyors utilize compressors to generate higher volumes of air pressure, moving pulverized materials such as grain, stone, rock and sand at higher heights than Dilute Phase pneumatic conveyor systems.
Dense Phase pneumatic conveyors are traditionally enclosed systems with a ‘bottom-discharge’ design. This is due to how the material is transported through the conveyor system. Similarly to how fluid deposits at the bottom of a conveyor, so too does the pulverized material in the Dense Phase conveyor, and this is dragged through to the bottom using the air slide conveyor belt.
Components of Pneumatic Conveyors
A pneumatic conveyor that’s used for bulk powder handling may consist of an array of individual components that when configured together, make up the pneumatic conveyor belt system:
Fans are used to blow the pulverised material through the conveyor system and into the air chamber. Fan sizes vary depending on the amount of wheels required for the conveyor system. The larger the fan, the lower the tip speed, and higher the longevity of the fans lifespan. Furthermore, a larger fan will work at a lower noise level, improving noise pollution from the pneumatic conveyor.
Shredders are used to help the pulverization process, which takes the raw material (such as stone or granit) and pulverizes the material before it is transported through the enclosed loop system.
Filters (Dry and Wet)
Used wherever an exchange of air takes place air filtration is required. Filter bags are used to help avoid the transported product being contaminated with the environment.
Filters are also used to avoid ejection of dust in vented areas, which is a legal requirement, but also is a requirement for a safe working environment.
In pneumatic conveying, filters are used at the beginning and end of the cyclone filter points.
Finally, the filter must be dedusted at regular intervals to avoid blockage and maintain filter quality.
The separator cyclone is used in vacuum Dense Phase pneumatic conveying. They are part of the cyclone system where by the pulverized material is separated from the air flow in order to catch larger particles that might not be prone to dusting.
Electronic controls are used through the conveyor system to ensure that the correct pressure, air velocity and speed is being used to treat the movement of the bulk powder.
As with Electronic Controllers, Velocity Controllers are used to monitor the velocity of the cyclone and air pressure within the pneumatic conveyor system.
These are used to identify sparks or hot glowing particles. The system uses a built-in extinguisher to put out the hot particles without any disturbance to the production process.
Air Slide Conveyor Belts
Air Slide Conveyor Belts are part of the transportation process of the pulverized material during the pneumatic conveying process.
Air Slide conveyor belts are high in air permeability, which allows the air-activated gravity to push air through the conveyor belt and transport the bulk powder in a ‘liquid fashion’.
The Air Slide belting is usually woven, and made from polyester or other synthetic woven belt material. However, on some occasions, cotton conveyor belting may be used as a solution for air slide belts.
Unique Air Slide Belts for Pneumatic Conveying
Depending on the requirement for the pneumatic conveyor certain air slide belt manufacturers can create belts to bespoke requirements.
Specifically, elements that require transportation in high temperatures such as cement, would require a conveyor belt that can transport the material at extreme temperatures with minimal wear and tear. A perfect solution for this is glass fiber belting.