Lean Phase Pneumatic Conveying

Lean phase pneumatic conveying systems, also know as suspension flow, operate on the principle that the solids will be suspended in the conveying line air stream. This is accomplished by metering product into a moving air stream. Lean phase conveying velocities typically are greater than 3500 FPM and material to air ratios are less than 12 to 1. Individual particles in the air stream will have some separation by their suspension in the air stream.

Example of Vacuum Lean Phase Installation

Commonly Conveyed Products

Products commonly conveyed in dilute phase systems include flours, resins and compounds, specialty chemicals, ground feeds, and granular and pelletized products. In many cases, the product needs to be evaluated based on process needs and possibly lab tested prior to final system selection to ensure the desired results can be achieved. Lab testing will also allow the product properties to be evaluated.

System Design

Pressure, vacuum, combination vacuum/pressure and vacuum sequencing are the common types of dilute phase systems. The motive gas is typically generated by a positive displacement blower with pressure capability ranging from 2 – 15 PSIG. Pressure systems generally use a rotary airlock as a feed device. A vacuum system simply needs a product flow control device such as a probe box or screw feeder, although rotary airlocks are commonly used.