Dilute vs. Dense Phase: Which is right for your material?

Choosing the right pneumatic conveying system is more than a technical decision; it’s an operational strategy that impacts your plant's uptime, energy bills, and maintenance cycles. For engineers and plant managers, the debate often narrows down to two primary contenders: Dilute Phase and Dense Phase.

While industry "common knowledge" often pigeonholes these systems into rigid categories—such as claiming that dilute phase can’t handle abrasives—the reality on the factory floor is much more nuanced. At Delta Ducon, we’ve spent over a century proving that with the right engineering, both phases have a seat at the table, even in the harshest environments.

What is Dilute Phase Conveying?

Dilute phase conveying is the "high-velocity" approach to material transport. In this system, material is suspended in a continuous airstream. Think of it like a dust storm inside a pipe: the air moves fast enough to keep the particles airborne, preventing them from settling at the bottom of the line.

Key Characteristics of Dilute Phase:

• High Velocity: Airspeeds typically range from 3,200 to 8,000 feet per minute (FPM).

• Low Pressure: Generally operates under 15 PSIG (pounds per square inch gauge).

• High Air-to-Material Ratio: Uses a large volume of air to move a relatively small amount of material.

  
  

The Abrasive Myth

A common misconception is that dilute phase is unsuitable for abrasive materials like fly ash, cement, or sand because high velocities lead to pipe wear.

However, dilute phase can handle high abrasives effectively when designed with specialized components. By utilizing PERMA/flo abrasion-resistant pipe and heavy-duty Extreme Duty Rotary Valves, you can run a dilute phase system that outlasts standard installations by years. The "secret sauce" isn't just the phase; it's the metallurgy and the precision of the system design.

What is Dense Phase Conveying?

If dilute phase is a "dust storm," dense phase is a "slug." In this regime, material is not suspended. Instead, it moves in concentrated waves, dunes, or solid plugs that fill the entire cross-section of the pipe.

Key Characteristics of Dense Phase:

• Low Velocity: Airspeeds are significantly lower, often between 600 and 2,500 FPM.

• High Pressure: Operates at much higher pressures, often exceeding 15 PSIG and reaching up to 100 PSIG.

• High Material-to-Air Ratio: Moves a large mass of material with a relatively small volume of air.

  
  

When Dense Phase is the Right Choice

The real advantage of dense phase isn't just about protecting the material; it’s about scale and distance.

• Long Distances: Because dense phase uses high-pressure air to "push" material rather than suspend it, it is the superior choice for conveying over distances exceeding 1,000 feet.

• Higher Tonnage: When your process requires moving 100, or 300 tons per hour, the efficiency of dense phase becomes undeniable. It delivers a much higher "payload" per cubic foot of air.

  
  

Comparison Table: Dilute vs. Dense Phase

Feature	Dilute Phase	Dense Phase
Velocity	High (3,200 - 8,000 FPM)	Low (600 - 2,500 FPM)
Pressure	Low (< 15 PSIG)	High (> 15 PSIG)
Material Handling	Suspended in Air	Slugs, Dunes, or Plugs
Best For...	General purpose, versatile layouts	Long distance, high tonnage
Abrasive Capability	Excellent (with Delta Ducon design)	Excellent (with Delta Ducon design)
Capital Cost	Generally Lower	Generally Higher

Making the Decision: A Material-First Approach

When deciding which system is right for your plant, we recommend looking at three primary variables:

1. The "Distance and Tonnage" Threshold

If you need to move material across a massive facility or between buildings (long distance) or if you are unloading railcars into high-capacity silos (high tonnage), Dense Phase is your workhorse. It offers better energy efficiency at these scales.

2. Space and Layout Constraints

Dilute phase systems are often easier to retrofit into existing plants because they use smaller, more flexible piping and don't require the large pressure vessels (transmitters) that dense phase systems rely on.

3. Material Characteristics

While both can handle abrasives, if your material is friable (easily broken), the lower velocities of dense phase are gentler. However, if your material is "sticky" or cohesive, a high-velocity dilute phase system might be necessary to keep the lines from plugging.

The Delta Ducon Difference: Engineering for the Extreme

At Delta Ducon, we don't believe in "one size fits all" solutions. We recognize that every plant has unique hurdles, whether it's the harsh climate of a Canadian winter or the relentless abrasion of a glass-batching facility.

Our Capabilities:

• Expertise in Both Phases: We don't push one technology over the other. We evaluate your specific tonnage and distance requirements to recommend the most cost-effective solution.

• Abrasion Specialists: We are the industry leaders in high-abrasive handling. Our PERMA/flo abrasion-resistant pipe  and specialized elbows are designed to handle the "unconveyable."

• The FLS FK Pump Alternative: If you are looking for a drop-in replacement or an upgrade to legacy cement pumps, our custom-engineered solutions provide higher reliability with lower maintenance.

Whether you are designing a brand-new facility or troubleshooting a system that’s blowing through elbows every three months, our team is ready to help you optimize your flow.

Ready to Optimize Your Conveying System?

Don't guess which phase is right for your material. Let the experts at Delta Ducon run the calculations for you.

Contact Delta Ducon Today to schedule a consultation with our engineering team and find the system that maximizes your tonnage while minimizing your downtime.