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Update your knowledge of modelling, optimizing and controlling slurry pipeline flows.
DEVELOPMENTS IN SLURRY-HANDLING technology (SHT) (1) continue to be applied across the process industries, particularly in the modeling of pipeline flow, and in the design and selection of pumps, agitated-slurry storage vessels and online instrumentation. Such developments are applicable to the design and operation of systems involving both in-plant slurry-transfer pipework, and long-distance slurry pipelines. This article focuses on advances in our understanding of the fundamental processes of slurry pipeflow, and how such flows can be better modelled, optimized and controlled.
Pipeflow of non-settling slurries
Pipeflow of settling slurries
Prevention of solids deposition in horizontal pipe, flow -- Much attention continues to be paid to the limit-deposit slurry velocity (sometimes referred to as the "critical" velocity) -- or, the minimum mean slurry velocity in the pipe below which particles begin to settle onto the pipe bottom and form a sliding bed. Regardless of whether the actual velocity is below or above this condition, heterogeneous flow conditions often occur, causing potential pipe blockage problems, excessive pipe wear, or a maldistribution of solids feeding certain unit operations, such as hydrocyclones.
Researchers at the Univ. of Nottingham (Nottingham, UK; www.nottingham.ac.uk) have been investigating the benefits of swirl-inducing pipe technology using computer-assisted modeling (32). The induced swirl causes rotational flow about the pipe axis, thereby lifting particles concentrated in the lower part of the pipe into the upper part, creating a more homogeneous flow pattern. Figure 6 shows the three-lobed design of a swirl-inducing pipe - a design that is very loosely based on an existing boiler tube. This design has been used for initial computational models and physical tests, and has shown advantages over several other geometries, such as a triangular cross-section with fillet radii in the vertices, and other polygonal shapes, in generating swirl for a given (delta)P.
In addition, designs for a new swirl-inducing pipe for particle-bearing liquids are nearing completion, and these are not constrained by factors in the original design (e.g., numbers of lobes, helix, etc.). Several new swirl-inducing pipe designs for particle-bearing liquids are nearing completion at the Univ. of Nottingham. Potential advantages are as follows:
* Settling particles in the carrier liquid can be kept in suspension at lower velocities...