The Effect of Permeability on Lignite Fly Ash Pneumatic Conveying System Design

摘要

The aim of this experimental study was to evaluate the effect of permeability on the mode of flow that lignite fly ash will support in a pneumatic conveying pipeline. This research was initiated by recurring problems with the long distance and high capacity low grade lignite ash pneumatic conveying system at the 1200 MWe thermal power plant, such as clogging, unsteady flow mode, significant increase of velocity due to pressure drop and erosive wear of pipeline. Ash samples were taken during pneumatic conveying system clogging for further analysis. The experiment was limited to measuring parameters that provide data to determine minimum fluidizing velocity and permeability. The results showed very heterogeneous materials of group B by Geldart, what caused specific phenomenon during the experimental fluidization tests. Minimum fluidizing velocity for this kind of material is not authoritative for defining pneumatic conveying system, since extremely heterogeneous materials at this air speed will remain stationary or will convey very slow or with stoppage, and that required velocities are from 10 to 15 times higher than minimum fluidizing velocity. According to the results, this ash is the most suitable for dense phase pneumatic conveying.