Pneumatic conveying is a fast and efficient method of transporting small, bulk materials throughout a facility. It can be used in manufacturing processes, loading and unloading, and numerous other applications. Essentially, pneumatic conveying is achieved by creating a pressure differential along or within a sealed pipeline and using moving air to carry bulk materials toward the lower-pressure section of that pipeline. A vacuum can be used to “pull” the air (and, therefore, materials) through the pipeline tubes, or compressed air can be used to “push” the air and materials along.
A pneumatic conveyor system. Photo credit: stephenwanjau via Foter.com / CC BY-NC-SA
Whether it utilizes a vacuum inducer or compressed air, a pneumatic conveyor will be either a high pressure, or dense phase, system or a low pressure, or dilute phase, system. Apart from the obvious—pressure—what differences are there betwixt the two?
Dense Phase Pneumatic Conveying for Bulk Materials
When using high-pressure, dense-phase pneumatic conveying for bulk materials, a larger volume of material is moved by lower volumes of air (or other gas) at low velocity. That is, less air moves more material at a slower pace. The material is not suspended in the air as it moves but rather pushed along en masse, (relatively) slowly but surely. Dense-phase pneumatic conveying generally causes less wear and tear on the material and the conveying system. For most materials, there will be little to no degradation, making it ideal for materials that crumble or smear easily, as well as more abrasive products. Additionally, dense phase systems can be significantly more energy efficient than dilute phase systems, as lower velocity movement equates to less energy use.
Dilute Phase Pneumatic Conveying for Bulk Materials
Conversely, dilute phase pneumatic conveying uses greater volumes of air (or other gas) at lower pressure and higher velocity (generally between 5,000 and 8,000 feet per minute). Air moves quickly through these systems, generally keeping the conveyed materials suspended in the air as they move. These pneumatic conveyor systems move less material in a given volume of air but do so much faster. Nearly any material can be moved via dilute phase pneumatic conveying, and these systems are relatively easy and inexpensive to set up and maintain. However, because of the high-speed travel, materials may experience a great deal of degradation; depending on the material being moved, the pipeline itself can be damaged as well. Also, dilute-phase conveyor systems typically generate higher energy costs, due to the high volumes of air and the high speeds required.
