Pneumatic Conveying Explained

Pneumatic Conveying

Pneumatic conveying is a process of transferring bulk materials from one location to another in a pipeline by means of gas such as compressed air or nitrogen.

Pneumatic Conveying was developed as an alternative to mechanical systems such as belt conveyors, screw conveyors, drag conveyors etc., and offers such advantages as:

  • Lower maintenance costs
  • Environmentally friendly and clean due to being a completely enclosed system eliminating dust and spillage of material
  • Smaller foot print and adaptability; pipeline can easily be moved and expanded
There are two primary pneumatic conveying methods:

*Dilute phase
*Dense phase

Each method takes a different approach to transferring dry bulk powders. Both dilute phase and dense phase regimes can be either positive or negative pressure (vacuum).

In the dilute phase of conveying, the material in the pipeline travels at a high velocity in a homogeneous mixture with the air. The dense phase, on the other hand, is a high pressure, low-velocity regime where material flows in a bed flow regime (continuous flow), controlled series of slugs (discontinuous flow), or the pipeline is filled with material (solid flow).

1. Dilute phase systems keep material air-suspended by high velocity, low pressure, and low material to air ratio.

dilute phase

2. Dense phase introduces a pulse of compressed gas to move a slug of material along the pipeline and is characterized by low velocity, high pressure, and high material to air ratio. Depending on the application, the material can be conveyed in various conveying regimes. The common regime is the continuous convey regime where material moves in slug flow. More on dense phase convey regimes can be found here.

dune phase Slug pipe