Modelling the pumping characteristics of power station ash in a dense phase hydraulic conveying system

This study examines the flow of dense phase fly ash slurries in horizontal pipes. It includes an evaluation of the previous work, a rigorous experimental investigation, a new and original model for determining pipeline pressure drop characteristics and a new method of characterising typically homogeneous fluid behaviour based on a particle size distribution, slope factor and a median particle size. The experimental investigation was undertaken to obtain data for modelling the flow of dense phase fly ash slurries. Tests were conducted using fly ashes from different power stations in a purposely built test facility. The test facility contained 50 mm and 80 mm bore internal pipeline viscometers in series. Slurry pump discharge pressure, differential pressure over 5 meters of a 80 mm pipe section, differential pressure over 5 meters of a 50 mm of pipe section, slurry temperature, slurry volumetric and mass flowrates were measured. Slurries settling were determined visually using an 80 mm glass pipe section. The particle size distribution and solids density of the fly ash were analysed and the solids concentration of the slurries were determined using the wet weight, drying and dry weight method. The experimental results were used to develop a new model to determine the pressure drop characteristics of dense phase fly ash slurry pumping systems and grout pumping plants, in order to develop a new description of what typical characteristics homogeneous fluid contain. The model indicated a polynomial relationship between pipeline differential pressure and solids concentration which has proven to be a much improved predictor of actual system performance. A software based design program has been produced that utilises power station physical and operational details to determine the pumping characteristics of dense phase ash slurries which will lead to better practical outcomes in the power industry.