Question

How to calculate minimum no of stages for a distuillation column?

Answer 1

Answer:

.

Explanation:

The number of theoretical stages depends on the reflux ratio R = L0/D. As R increases, the

products from the column will reduce. There will be fewer equilibrium stages needed since

the operating line will be further away from the equilibrium curve. The upper limit of the

reflux ratio is total reflux, or R = ∞. The rectifying operating line is given as

yn+1 =

1

R

R +

xn +

1

R +1

xD

When R = ∞, the slop of this line becomes 1 and the operating lines of both sections of the

column coincide with the 45o

line. In practice the total reflux condition can be achieved by

reducing the flow rates of all the feed and the products to zero. The number of trays required

for the specified separation is the minimum which can be obtained by stepping off the trays

from the distillate to the bottoms.