Predicting pneumatic conveyability and flowability of fly ash using bulk property characterization

Pneumatic fly ash conveying systems in thermal power plants are often not able to transport ash as per their expected duty due to either variability of ash characteristics and/or inadequate system sizing resulting in generation loss and reduced ash utilization. This paper results from an ongoing investigation into the relationship between the physical characteristics of ash to some of the important design criteria, such as ash conveyability and flowability. Based on a comprehensive test program including the pneumatic conveying (in a pilot plant) and flow property testing of 23 ash samples obtained from five different power stations, predictions for conveyability and flowability have been made using bulk property characterization. Of all the different particle and bulk parameters investigated, the angle of repose has been found to be the most significant parameter linking conveyability and flowability. A newly developed design tool based on the angle of repose is expected to assist designers and operational engineers to predict the flow condition and appropriately size equipment/system with suitable operating parameters.