Effect Of Comminuted Flint On Pumping Chalk Slurry In The 92-Kmkensworth?Rugby Pipeline

The effects were studied of the presence of comminuted flint on the rheological characteristics of chalk slurry pumped through a 92-km long pipeline from Kensworth Quarry to Rugby Cement Works in the UK, and their impact on the pipe flow conditions. Flow curves were measured for 63different chalk slurry samples; these were described by the Bingham plastic model. In addition to observing trends in the yield stress parameter and plastic viscosity in the model with variations in both flint concentration and dispersant additive, use was also made of slurry viscosity values at a reference shear rate of 60 s-1for the pipe flow. It was found that chalk slurry viscosity decreases with increasing flint content up to 10% by weight for a given additive concentration, and increases with increasing additive concentration from 0.7 to 1.0%, for a given flint content. The pipeline flow regimes were identified using the critical value of the Bingham Reynolds number for laminar flow breakdown. For Bench 11 (quarry bottom) chalk slurries, it was observed that all sections of the pipeline operate in the turbulent flow regime for the nine different formulations and for the three pipe diameters used along the pipeline. However, this was not always the case for Bench 1(quarry top) slurries. It was therefore recommended that chalk slurries prepared from Bench 1 should not be used because of the strong likelihood that laminar flow conditions will occur owing to the presence of higher clay concentrations within this bench. This, in turn, will lead to an unsafe operation of the pipeline because of the potential for coarse particle settling. Likewise, blending of chalk from Bench 1 with the lower benches such as Bench 11 could be problematic and this requires further experimentation.