Abstract
The deposition velocity is an important operation parameter in hydraulic transport of solid particles in pipelines. It represents flow velocity at which transported particles start to settle out at the bottom of the pipe and are no longer transported. A number of predictive models has been developed to determine this threshold velocity for slurry flows of different solids fractions (fractions of different grain size and density). Most of the models consider flow in a horizontal pipe only, modelling approaches for inclined flows are extremely scarce due partially to a lack of experimental information about the effect of pipe inclination on the slurry flow pattern and behaviour. We survey different approaches to modelling of particle deposition in flowing slurry and discuss mechanisms on which deposition-limit models are based. Furthermore, we analyse possibilities to incorporate the effect of flow inclination into the predictive models and select the most appropriate ones based on their ability to modify the modelled deposition mechanisms to conditions associated with the flow inclination. A usefulness of the selected modelling approaches and their modifications are demonstrated by comparing model predictions with experimental results for inclined slurry flows from our own laboratory and from the literature.
Highlights
One of the most important and yet one of the most difficult problems associated with the design and operation of a pipeline system transporting settling slurries is a prediction of the deposition limit velocity of the flowing slurry
The term “critical velocity” is often used to determine a threshold below which the flow of slurry should not drop in a pipe in order to avoid operational problems
An estimation of deposition limit velocity has been subject of numerous studies over last 60 years with pioneer works dating to early 1950s
Summary
One of the most important and yet one of the most difficult problems associated with the design and operation of a pipeline system transporting settling slurries is a prediction of the deposition limit velocity of the flowing slurry. Coarse settling slurries are transported at very different conditions (pipe size and geometry, solids contents in slurry etc) and exhibit very different properties (slurry density, degree of stratification etc). They are often transported in pipelines containing sections that are inclined from the horizontal. Examples include in-plant transfer lines, tailings disposal operations, dredging, deep sea mining, and long-distance pipelining [1]
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