RECTIFICATION WITH DIRECT

STEAM INJECTION

Stripping-Column Distillation

•Feed to be distilled is not supplied to the intermediate point in the column. •But it is added to the top of the stripping column. •The feed is usually a saturated liquid at the boiling point and no liquid returned to the tower. •The bottom products W, usually has high concentration of less volatile component B.

Fractional Distillation Using Enthalpy-

Concentration Method

Assumption made in McCabe-Thiele method:- (i) Latent heats are equal (ii)Sensible heat differences are negligible (iii)Constant molal overflow occurs in each

section of the tower

However the ENTHALPY-CONCENTRATION METHOD consider that the molal overflow rates are not necessarily constant.

The saturated liquid line enthalpy h (kJ/kg),

The saturated vapour line enthalpy H (kJ/kg),

Enthalpy balance,

Condenser duty, kJ/hr

Combining enthalpy balance and condenser duty,

Steps for enriching section,