Pipeline Pulsing Flow of Slurries

Abstract

<p>This thesis presents the results of pulsing flow experiments on solid-liquid suspensions. Specifically, the hydraulic energy requirement in pulsing flows for a given slurry flowrate is compared with the steady state energy consumption for the same flowrate. It is also shown theoretically that, for the same time-averaged flowrate as in the steady state case, it is feasible to reduce the time-averaged pressure gradient and hence power requirement by pulsing.</p> <p>The following five different types of flow systems were the subject of study: water, bentonite clay water, fine sand water, fine sand bentonite clay water and coarse sand water.</p> <p>For the above five types of flow systems the following pertinent flow variables were studied: pulsation frequency, pulsation amplitude, average slurry velocity, solids volume concentration, mean particle size and the presence of a small amount of ultra fine particles in coarse solid liquid mixtures.</p> <p>The experimental results of pulsing flow of water alone indicated that the pulsing to steady state power ratio (Jᴘ/Js) was always greater than unity indicating that for a Newtonian fluid the hydraulic energy in pulsing flow is greater than the steady flow, the increase of energy being used to maintain pulsation.</p> <p>Results of pulsing flow experiments with bentonite slurry have indicated that the power ratio (Jᴘ/Js) was observed to be less than unity for certain combinations of frequency, amplitude and slurry velocity. The minimum value of (Jᴘ/Js) found was about 0.75 at a frequency of about 0.80 Hz, amplitude of 51 mm and velocity of 1.9 m/s.</p> <p>In the ranges investigated, results with sand-water slurries have indicated that the power ratio (Jᴘ/Js) was a function of the variables listed above. The minimum value of the power ratio (Jᴘ/Js) for sand water slurries was found to be about 0.50 at the following values of the variables: pulsation frequency 0.45 Hz, amplitude 32 mm, slurry average velocity 1.8 m/s, solids volumetric concentration 12.5% and particle size 0.47 mm.</p> <p>The reduction in the power ratio in the case of pulsing flow of sand water slurries is attributed to the formation of a particle free layer near the pipe wall while the bulk of the particles flow as a plug in the middle of the annulus of the lubricating particle free layer.</p> <p>In the case of bentonite clay water slurry the reduction in the power ratio is attributed to the formation of a low viscosity layer near the pipe wall. The bulk of the slurry flows as a plug in the middle of the annulus of the low viscosity layer.</p> <p>Results of this thesis indicate that power consumption for transport of slurries using pulsing flow is considerably less than power required to transport the same amount of slurry by a steady flow method.</p>