Pneumatic conveyors are conveyors that convey materials in an enclosed tube system using either vacuum or compressed air. Both vacuum systems and compressed air systems use the same principle that when differential air pressure is high enough so that air velocity is fast, solid particles are picked up by the conveyor’s airflow and transported through the pipe. Hence, conveyors are primarily used to convey granular and powdery materials.
Pneumatic conveyors are categorized into two; negative pressure systems that pull materials through a vacuum or positive pressure systems that use compressed air to push the materials. These two kinds of conveyors are defined based on the flow medium, the material’s properties, the pipe route shape, and the volumes of both the material and the flow medium.
Dilute phase conveying system
Also known as suspension flow conveying, this is characterized by a relatively small volume of material being obtained by large air volumes at high velocity and low pressure. It is suitable for light materials in low quantities.
Dense phase conveying system
A higher volume of material being transported by a smaller air volume is a significant feature of this phase. It requires high pressure, and the materials use slow transportation.
Advantages of Pneumatic conveyors
- Ease of Routing
Pneumatic systems can run vertically or horizontally and can cover long distances. They are also easy to design around obstructions like existing equipment. It offers a lot of flexibility concerning routing.
Pneumatic systems are easily adjustable to fit in with existing equipment, which means that there’s no need to start from scratch. They also do not take up space. And you can set up multiple pickups and discharge points, creating a flexible and efficient system.
- Construction Flexibility
Materials used to construct pneumatic conveying systems are lightweight, so they require little structural support. It removes many potential construction challenges and also saves money and space.
- Ease of Maintenance
Pneumatic systems only have a few significant parts: air compressor or pump, in-feed apparatus, tube or pipe, and a separator. You can repair each of those parts separately from the rest of the system. That makes maintenance quicker and downtime limited.
Pneumatic conveyors are built as closed systems, with few moving parts, which require less maintenance. It results in pneumatic conveyors presenting less danger to maintenance workers and operators.
Disadvantages of Pneumatic conveyors
- Less energy efficient
Pneumatic conveyors require more power to run compared to other types of conveyors.
- It requires an extensive dust collection system.
Pneumatic conveying systems need larger dust collection systems because they have to be separated from the conveying system’s airstream at the discharge point(s).
- Some materials are difficult to convey.
Pneumatic conveying systems are most suitable for lower density bulk powders like sugar, flour, or wheat, but not for substances with larger particle sizes or particles that are extremely sticky. For example, materials with high-fat content are more difficult to convey by air and can clog up in the pipeline.
- Suitable for combustible bulk solids.
Combustible bulk solids may leave explosive dust residue in the air because pneumatic conveyors use air to move materials. This combustible dust poses fire hazards, which means users must take special precautions.
Despite their limitations, Pneumatic conveyors are popular among industrial facilities because of their flexibility, reliability, efficiency, and easy cleaning. Pneumatic conveyors reduce dust and protect materials from being contaminated during transfer, making it one of the best means of conveying material. They are used in various industries, ranging from food processing to agriculture to chemical engineering and beyond.