Sedimentation in Coal-Water Slurry Pipelining

Abstract

In this paper we present an overview of recent investigations on the problem of sedimentation related to the pipelining of a Coal-Water Slurry. The main aspects of the problem are both the determination of the sedimentation velocity, and the understanding and modelling of the dynamics of the sedimentation bed which accumulates on the bottom of the pipe. The analysis is carried out using a combination of suggestions dictated by experimental evidence and suitable mathematical techniques. The result is a model which appears to be both easily manageable and flexible. Predictions of the model are compared with experiments finding a remarkable agreement with the available data.

Dynamic settling of particles in shear flows of shear-thinning fluids

“…Examples include the transport of cuttings by drilling mud [1], proppant emplacement in hydraulic fracturing (e.g. [2], §6.2), the transport of coarse material such as sand and gravel in a fine-grained slurry [3,4] or debris flow [5,6] and the handling of two-phase materials in food processing [7]. Key questions for modelling such flows include the distance that particles can be transported before settling out, the time they take to do so, the geometry of the deposit, and the distribution of grain sizes within it.…”

“…Notable experimental contributions have included those of Merkak et al [17,18], who studied experimentally the flow and sedimentation of small particles suspended in a viscoplastic gel, and that of Ovarlez et al [19] has examined experimentally the shear-induced sedimentation of relatively small particles in yield stress fluids using MRI to determine the evolving concentration within a sheared Couette device. The most substantial modelling contribution has been that of Angelis and Mancini [20] (and see also the review by [4]), who used an empirical settling velocity correlation to calculate the trajectories of particles settling within a viscoplastic pipe flow and feeding a mobile dense layer at the bottom of the pipe, under which a static deposit grew.…”