Mass Transfer
The surface renewal frequency in Danckwerts model of mass transfer is given by (KL: mass transfer co-efficient)

√(KL².DA)
KL².DA
KL²/DA
KL/DA²

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Mass Transfer
Priming in a distillation column

Reduces the overall pressure drop
Results from very low gas velocity
Is characterised by the presence of foam throughout the space between trays
Is desirable from point efficiency consideration

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Mass Transfer
Bollman extractor

Is used for extraction of oil from oilseed
Is a centrifugal extractor
Employs only counter-current extraction
Is a static bed leaching equipment

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