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Dense Phase vs Dilute Phase Pneumatic Conveying
Efficient material handling plays a vital role in modern manufacturing and processing industries. Pneumatic conveying/transfer systems provide a clean, enclosed method for moving dry bulk materials such as powders and granules through pipelines using air pressure or vacuum.
The two primary types, dense phase and dilute phase, each offer distinct benefits. Understanding the differences between them is key to selecting the most suitable system for your specific application.
What is Pneumatic Conveying?
Pneumatic conveying is a method of moving dry bulk materials through pipelines using a flow of air or gas. Unlike mechanical conveying systems that use belts or chains, pneumatic systems rely on airflow to transport materials in a continuous or batch process. They are widely used in industries such as plastics, food and beverage, chemicals, pharmaceuticals and minerals.
The benefits of pneumatic conveying include dust-free operation, reduced contamination, flexibility in system layout and the ability to move materials vertically, horizontally or around obstacles. Choosing the correct type of pneumatic conveying system (dense phase or dilute phase) depends on the properties of the material and the specific requirements of the application.
What is Dilute Phase Conveying?
Dilute phase conveying (also known as lean phase conveying) is a high-velocity, low-pressure method in which materials are suspended in the airstream and transported through the pipeline. The particles are fully entrained and remain dispersed throughout the conveying process.
How Dilute Phase Conveying Works
Air is introduced at high velocity, typically between 15 to 35 m/s, with low system pressure (below 1 bar). This creates a fast-moving airstream that carries lightweight, non-abrasive materials over long distances. The air-to-material ratio is high, meaning more air is used relative to the volume of conveyed product.
Ideal Materials and Industries
Dilute phase conveying is suitable for a wide range of dry, free-flowing bulk materials that are lightweight and non-abrasive. This makes it well-suited to operations that demand rapid, consistent material movement to support high-throughput production.
Common materials conveyed in dilute phase systems include:
- Granulated sugar
- Plastic pellets
- Starch
- Flour
- Coffee beans
- Powdered milk
- Fine salt
- Dry cereal grains
Key Benefits:
- Lower initial system cost
- Simple design and straightforward operation
- Ideal for continuous conveying of lightweight materials
- Fast material transfer over longer distances
- Easy to clean and maintain
What is Dense Phase Conveying?
Dense phase conveying is a low-velocity, high-pressure system where materials move in a plug or slug form along the bottom of the pipeline. Instead of being fully suspended, materials are pushed in a more compact flow, often with the help of air injection points or air boosters along the pipeline to assist movement and reduce friction.
How Dense Phase Conveying Works
Dense phase systems operate at slower speeds, typically between 3 to 10 m/s, but at much higher pressures often above 1 bar and up to several bars depending on the application. The system moves material in discrete pulses or continuous slugs, using a controlled air supply to maintain consistent pressure and flow.
Ideal Materials and Industries
Dense phase conveying is well-suited to bulk materials that are fragile, abrasive, or prone to compacting. These include fine powders, granular solids, and materials that require careful handling to maintain product integrity. The system is particularly useful where dust control and minimised material degradation are priorities.
Common materials conveyed in dense phase systems include:
- Cement
- Fly ash
- Carbon black
- Silica sand
- Detergent powders
- Alumina
- Zinc oxide
- Soda ash
Key Benefits
- Gentle handling of fragile or abrasive materials
- Reduced material degradation and particle breakdown
- Lower air consumption over time
- Minimised wear on pipes and system components
- Better control over material flow and delivery
Dense Phase vs Dilute Phase: Key Differences
Understanding the operational differences between these two conveying methods is essential for selecting the right solution for your process.
| Dilute Phase | Dense Phase | |
|---|---|---|
| Flow Rate | High flow rate due to continuous suspension of material | Lower flow rate with controlled, batch-based delivery |
| Pressure | Operates under low pressure with high air velocity | Operates under high pressure with low air velocity |
| Material Suitability | Best for lightweight, non-abrasive, free-flowing materials | Suited to abrasive, fragile, or cohesive materials |
| System Complexity/Cost | Simpler system with generally lower capital cost | More complex system, higher initial cost, long-term efficiency |
How to Choose the Right System
Choosing between dense phase and dilute phase pneumatic conveying depends on a number of factors:
- Material characteristics: Is your product fragile, abrasive, hygroscopic or prone to segregation?
- Distance and layout: Will the material be conveyed over long distances, vertical lifts, tight bends or challenging facility layouts?
- Flow rate requirements: Do you need fast, continuous conveying or slower, controlled batch transfer?
- Energy efficiency and maintenance: Consider long-term operational costs, including air consumption, component wear and downtime for servicing.
At Summit Systems, we work closely with clients to design pneumatic conveying systems tailored to their materials, operations and facility layout. Whether you need a high-speed dilute phase solution for continuous manufacturing or a precision dense phase system for fragile bulk handling, our engineers ensure optimal performance, reliability and efficiency.
We also offer full integration with existing plant control systems, as well as design services that include simulation, testing and commissioning to guarantee the solution fits your exact needs.