An Investigation into the Flowability and Conveyability of Fly Ash

Abstract

This thesis presents the results of an ongoing investigation into the pneumatic fly ash conveying systems in thermal power plants that often cannot transport ash as per their expected duty due to either newlinevariability of ash characteristics and/or inadequate system sizing, resulting in generation loss and newlinereduced ash utilization. Based on a comprehensive test program, including the pneumatic conveying newline(in a pilot plant) and flow property testing of 23 ash samples obtained from five different power newlinestations, predictions for conveyability and flowability have been made using bulk property newlinecharacterization. Of all the different particle and bulk parameters investigated, the angle of repose is newlinethe significant bulk parameter linking conveyability and flowability. A newly developed design tool newlinebased on the angle of repose is expected to assist designers and operational engineers predict the flow newlinecondition and appropriate sizing of equipment/system with suitable operating parameters. newlineAccurately predicting the flow mode is essential for the design of reliable pneumatic conveying newlinesystems. The existing popular powder classification diagrams use particle or loose poured bulk density newlineand average particle diameter. An evaluation of powder characterization and conveying data of 59 newlinepowders reveals that all the existing classification diagrams have overlapping zones between fluidized newlinedense- and dilute-phase. Such uncertainty significantly limits the use of existing classification newlinediagrams. A novel classification diagram has been developed using the powder characterization and newlineconveying data of 59 powders for fluidized dense to dilute-phase regime using a modified particle newlineFroude number term (based on loose poured bulk density) and particle size distribution. The novelty newlineof this classification diagram is that it uses particle size distribution (instead of average particle size) and quantitatively marks the uncertain zone in the classification diagram, ensuring design reliability. newline