Dense Phase Pneumatic Conveying

The Gentle Way to Convey

Dense phase pneumatic conveying involves the transfer of powders, granules, and other dry bulk materials through an enclosed pipeline. In dense phase conveying, particles are not suspended in the conveying air and are transported at high pressure and low velocity. This results in a more gentle delivery process for the products being conveyed. Abrasive, blended or friable materials usually require dense phase conveying.

Nol-Tec’s Dense Phase Pneumatic Conveying – the Difference

Our exclusive air management system enhances efficiency, lowers overall resistance, decreases air pressure requirements and improves material flow by injecting air into the convey line via strategically placed Air Assists™. The unique design of the high-pressure Air Assist manifold prevents back-feeding, which can occur with low-pressure manifold systems.


• Gentle material handling
• Reduced product degradation & segregation
• Minimal component wear
• Decreased dusting
• Flexible routing


Dense Phase Pressure Conveying vs. Vacuum Conveying:

Why Choose Pressure Conveying

The system conveys materials at a relatively low speed to reduce material degradation, air consumption, and abrasion on pipeline, bend, and diverter contact surfaces.

Material conveyed by this method is loaded into a pressure vessel. When the vessel is full, compressed air is metered into the vessel. The compressed air extrudes the material from the pressure vessel into the conveying line and to the destination. Once the vessel and conveying line are empty, the compressed air is turned off and the vessel is reloaded. This cycle continues until all of the required materials have been transferred.

To overcome resistance in the conveying line, supplementary air injectors (also called air boosters or Air Assists™) can provide additional air to help maintain conveying velocity, transfer materials over long distances, and minimize line plugging. They can also be used to gently restart flow when materials are left in the line after the conveying cycle.

Fast Facts:

  • Dense phase pressure conveying is suitable for gently conveying fragile or abrasive materials (with particles ¾ inch and smaller) over long distances (typically more than 250 feet).
  • This system can stop or start with the conveying line full of material.
  • An air injector should be used with a high-pressure manifold to prevent back-feeding of material into the compressed air system.
  • Commonly handled materials include silica sand, feldspar, fly ash, glass cullet, alumina, glass batch mix, carbon black, sorbitol, dextrose, candies, resins, cocoa beans, hazelnuts, and puffed rice cereal.

Why Choose Vacuum Conveying

This system is typically used to transfer powder and granules at a low rate (25 tph or less) for truck and/or railcar unloading.

This system uses a pressure vessel with a fluidizing bottom so it can handle semi-abrasive powders and fluidizable powders that need aeration to discharge into the conveying line. This method is not the ideal choice for fragile materials or materials containing large and/or variable particle sizes.

Fast Facts:

  • Dense phase vacuum conveying is ideal for gently conveying fragile or abrasive materials short distances (typically 200 feet or less).
  • The largest particles handled by this method are approximately ¼ inch.

Dense Phase Pneumatic Conveying Case Studies

Starting from Scratch

Ohio / Carbon Black, Calcium Carbonate, Talc
Helping a rubber compound producer design a new processing facility.

It's OK to be a Little Dense When Conveying Salt

Midwest / Salt
A food manufacturer installs a dense-phase pressure conveying system to prevent problems while conveying salt.