Design considerations for hydraulic backfilling with coal combustion products (CCPs) at high solids concentrations

摘要

The Theological characteristics for the complex hydro-mixture of coal combustion products (CCPs) such as fly ash and fly ash-bottom ash mixture slurry at high solids concentration in the range of 60-70% by weight were investigated. Based on the rheological data, a non-Newtonian pseudo-plastic power law head loss model was used to evaluate the head loss of ash slurry pipelines having nominal bores in the range of 100-300 mm. The results indicated that the addition of bottom ash fractions to fly ash slurry at a given solids concentration has a beneficial effect in reducing the pumping power requirement. A monogram (design chart) for the ash mixture slurry has been formulated indicating the variation of backfilling rate W_s with H/L ratio for a range of pipe sizes and transport velocities which may provide relevant pipe flow and operational conditions for hydraulic disposal of these coal combustion products for mine backfilling purpose.