Pneumatic Conveying

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

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, namely, "dilute phase" and "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).

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.


The Dense Phase Advantage

 

1. LOW ENERGY CONSUMPTION

By conveying material below the saltation velocity in slugs of material the energy used per lbs/kg of material to lbs/kg of air is very low compared to dilute or vacuum systems.

 

2. LOW MAINTENANCE

Due to very low velocity, pipeline life is extended, requiring little to no maintenance. In addition, most dense phase pneumatic conveying systems have few wearing parts, reducing the need for spare parts and maintenance. The combination of these factors contribute to minimal maintenance and down time.

 

3. LOW PIPE WEAR

As material is conveyed in a solid form, only a small percentage of particles conveyed are in contact with the pipe reducing pipe wear. This is important in conveying materials such as sand which is highly abrasive.

 

 

4. LOW MATERIAL DEGRADATION

A well designed dense phase pneumatic conveying system will have low slug velocity and high slug stability.  These two conditions combined produce very low rates of material degradation – often important when conveying very fragile materials.

 

 

5. MINIMAL SEGREGATION OF BLENDED MATERIALS

Many processes mix and blend two or more materials such as glass, food, and chemical processes. Once the blending process is complete, the material must be conveyed without separation of the ingredients. Often, there is considerable difference in the characteristics of the ingredients, e.g., particle size and particle density. If the conveying velocity is high, as is the case in a dilute phase system, the individual particles tend to convey at different velocities and separate as they are airborne.  The best regime for these applications is discontinuous dense phase.


The Denseveyor® from Macawber Engineering is a low velocity, dense phase pneumatic conveying transporter. It can easily convey thousands of materials, including difficult-to-handle powders, granules, and others, using gases such as compressed air and nitrogen. The system design is simple with just one moving part, the Dome Valve®, and offers a dust-free, fully enclosed conveying system that is economical and environmentally sustainable. The Denseveyor® operates automatically on an as-needed basis, as the machine rests when not signaled to operate. Advanced control options are available.

 


The key to efficient dense phase pneumatic conveying is sealing the top of the transporter while it is pressurized.  The common solutions, slide gates and butterfly valves, quickly fail to seal properly due to wear on the sealing surfaces.  The Macawber Dome Valve® is uniquely and specifically designed for dense phase conveying applications. The sealing surface of the valve rotates 90° allowing a full port flow of material. The gasket is located beneath the top cover plate protecting it from direct material impact. Once the valve closes and the inflatable gasket is energized, the durometer of the gasket is such that it is capable of sealing around any entrapped material. This valve has proven to be highly reliable and durable in harsh environments.