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Packed Column Internals . Packed Column. Factors Favoring P acked C olumns. Vacuum systems: Low pressure drop Small diameter column Corrosive system Foaming Lower liquid hold-up Batch distillation. Objectives of Packing D esign.
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Factors Favoring Packed Columns • Vacuum systems: Low pressure drop • Small diameter column • Corrosive system • Foaming • Lower liquid hold-up • Batch distillation
Objectives of Packing Design • To attain maximum mass transfer and capacity with minimum pressure drop by improving • Aerodynamic properties • Liquid distribution • Gas/liquid contact
Properties of Packing • High surface area per volume • Hood wettabilityand good resistance to the pressure (high strength). • Pressure drop should be desirably low. When the size increases, both mass transfer and pressure drop decrease. The optimal size and shape is the one which compromise both factors.
Materials Nowadays metal and plastic packing have replaced the ceramic • Ceramic elements are still used when corrosive chemicals are involved and good wettability is required • Metal elements provide good wettability with the advantage of having higher strength • Plastic, usually polypropylene, is largely used because of low cost but they fail in case of high temperature. Besides they have poor wettabiity.
Packing Types • Random or dumped packing • Structured packing: layers of wire mesh/corrugated sheets • Grids: open lattice structure