Flash distillation, differential distillation & steam distillation are all continuous distillation processes
In differential (simple) distillation, the vapour is removed as soon as it is formed without appreciable condensation
In flash (equilibrium) distillation, a definite fraction of liquid is vaporised in such a way that the evolved vapour & residual liquids are in equilibrium with each other
Distillation under vacuum is a substitute for steam distillation
Using split flow, radial flow or cascade flow for column diameter large than 4 ft
Decreasing the number of rows of caps through which the liquid flows or by decreasing the velocity of liquid flow past the caps or by reducing the distance along the tray through which the liquid must
Providing a higher skirt clearance or a higher weir