2 - Fluid-particle transport processes

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This chapter discusses the transport processes relating to particle conservation and flow. The formation and subsequent solid–liquid separation of particulate crystals from solution commonly involves alternate periods of suspension and sedimentation during which they experience relative fluid-particle motion. Similarly, solid matter may change phase from liquid to solid or vice versa. New particles may be generated or existing ones may be lost. They may be separated from fluids by flow through vessels, such as settlers, thickeners, or filters. Thus, the solid phase is subject to the physical laws of change: continuity—for conservation of both mass and particle— and flow—solid through liquids and liquid through particle arrays. These are collectively known as transport processes. The chapter provides a brief introduction to fluid-particle hydrodynamics that describes the motion of crystals suspended in liquors and enables solid–liquid separation equipment to be sized. The chapter also includes the momentum and population balances respectively, which describe the complex flows and mixing within crystallizers and, along with particulate crystal formation processes, enable particle size distributions from crystallizers to be analyzed and predicted.