An Economic Assessment of Air Assisted Gravity Conveying as an Alternative to Pneumatic Pipeline Conveying

Air assisted gravity conveying is not a new technique and indeed it could be argued that it is the simplest of all forms of pneumatic conveying. For effective operation, the conveyor or airslide as they are commonly known, relies on the ability of the product being conveyed to take on liquid-like characteristics when conditioned with air so that the product will flow down a shallow inclined channel. In addition to the limitations in the products that can be conveyed, the need to have a conveying channel that slopes in the region of 1-10 degrees and the difficulty in achieving anything than conveying in straight lines, the application of such technology appears to be problematical. In its favour, compared with the pneumatic conveying through a pipeline, air assisted gravity conveying is very gentle to the product causing very little degradation even to very friable products and is not itself subjected to excessive wear with erosive materials. However, by far the greatest advantage is the extremely low air requirements and hence energy consumption as the air slide only requires air to condition the product and not to convey it. This paper examines the results of some airslide trials undertaken at the Wolfson Centre for Bulk Solids Handling Technology at the University of Greenwich, and correlates these with pneumatic pipeline trials for a particular material, thereby enabling a direct comparison of relative energy consumption to be made.