Knowing the difference between depleted and dilute phase transport, especially in terms of fluid mechanics, enables precise design and calibration of pneumatic conveying systems. Calibrating speed and air pressure is very important in an air slide conveying system, and the accuracy of the calibration depends largely on the type of material being conveyed.

What is Dense Phase Conveying?

Dense phase conveying is a relatively new concept in air slide conveying. Dense phase conveying, as the name suggests, refers to the way of conveying bulk materials tightly in pipelines. In dense phase conveying, the product is not suspended in the air because the conveyed material is either too heavy or very abrasive, maintaining a high air velocity. This means that the product will be delivered in “waves”, “plugs” or “strands”, which create less wear and therefore dense phase delivery is more suitable for fragile products.

What is Dilute Phase Transport?

Dilute-phase conveying involves the conveying of large quantities of dispersed material, which are lighter and more abrasive. This means that material can be conveyed at a faster rate and with higher pressure than dense phase conveying. For example, talc is lighter and less abrasive than plastic particles, so it can be delivered at higher speeds and air pressures. In dilute phase conveying, a blower is used to convey the product into the system by airflow. The airflow just keeps the material flowing and prevents it from depositing on the bottom of the pipe.

The difference between dense phase conveying and dilute phase conveying

air slide conveyor

Some differences between dense-phase transport and dilute-phase transport are unavoidable because they are inherent properties of the bulk material itself—for example, dilute-phase transport often handles lighter particles. Here are some of the key differences between dense phase transport and dilute phase transport:

  1. Speed: The speed of dilute phase pneumatic conveying is usually faster than that of dense phase. Considering the abrasiveness of the particles carried, the conveying speed of dense phase is smaller.
  2. Wind pressure: The wind pressure in the air duct and pipeline of the dilute phase conveying system is lower than that of the dilute phase conveying or the dense phase pneumatic conveying. The pressure of the dilute phase is lower, and the pressure of the dense phase is higher.
  3. Abrasion: Abrasion refers to the breaking of powder. In dilute phase transport, losses can be very large due to the speed of particle motion. The opposite is true when it comes to dense phase conveying, as in these processes, the bulk material is usually conveyed at a lower velocity, keeping the material intact and less likely to break.
  4. Pipeline size: The pipe size of the dilute phase conveying system is often larger than that of the dense phase conveying system. The various components used in these pneumatic conveying systems also vary slightly in size, as their optimal performance depends on the particles they carry and their abrasiveness or sensitivity.
  5. Cost: The cost of building a dense phase conveying system is usually higher, mainly because of the specifications of the components, which are relatively stronger compared to dilute phase conveying systems.
  6. Load capacity or ratio: Dilute phase pneumatic conveying systems have a low solid to gas mass load ratio compared to very high solid to gas mass load ratios for dense phase systems.
  7. Distance: The maximum conveying distance of dense phase conveying and dilute phase conveying is also different: the conveying distance of the dilute phase system is longer, while the conveying distance of the dense phase system is generally shorter.