Mass Transfer
Pick out the wrong statement pertaining to the rotary dryer.

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.
Recommended peripherial speed of a rotary drier is in the range of 10 to 30 metres/minute
Rotary dryer is suitable for drying sticky material

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Mass Transfer
The rate of solid-liquid extraction is limited by the

Diffusion of the solute through the solvent in the pores to the outside of the particle
Phase change of the solute as it dissolves in the solvent
Diffusion of the solute from the solution in contact with the particle to the main bulk of the solution
All of these

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Mass Transfer
McCabe-Thiele method

Is more accurate than Ponchan-Savarit method
Uses molal units for material and energy balance
Can use any type of units
Uses weight fractions to express liquid and vapour composition

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