Mass Transfer MCQs

Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it down through the current of hot air/gases. It extends from the wall to a distance which is about 8-12%

Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at any instant. The best performance for rotary drier is obtained, when the hold up is in the range of 0.

Rotary dryer is suitable for drying sticky material

Recommended peripherial speed of a rotary drier is in the range of 10 to 30 metres/minute

Employs only one solvent

Employs two solvents

Results in low interfacial tension

None of these

Azeotropes

High boiling substances from nonvolatile impurities

Heat sensitive materials

Mixtures of low relative volatility

Partial condenser

Total condenser

Reboiler

Both B and C

Raschig

Lessing

Cross-partition

Single spiral

Entrainment

Foaming

Weeping & dumping

All of the above

Distillation

Solvent extraction

Absorption

None of these

Bone charcoal

Wood charcoal

Silica gel

Activated clay

10-9 cm/sec

10-1 cm²/sec

10-3 sec/cm

10-4 cm²/seC₂

Added to alter the relative volatility of the mixture

Of high volatility

Present in overhead stream

Of high viscosity to give high tray efficiency