18.08.2015   NUCLEAR CHEMICAL ENGINEERING

STAGE PROPERTIES

4.1 Terminology

The simplest type of separating unit or stage is one that receives one feed stream and produces one heads stream enriched in the desired component and one tails stream depleted in the desired component. Figure 12.9 shows such a stage, which is fed at rate Z with z fraction desired component and which produces a heads stream at rate M with у fraction desired component and a tails stream at rate N with x fraction desired component. Flow rate and composition should be on the same basis, e. g., weight, mole, or atom.

Because of overall material balance,

Z=M + N

(12.8)

Material balanced

on desired component leads to

Zz = My + Nx

(12.9)

Hence

M z —x Z ~y-x

(12.10)

and

N_y-2 Z y-x

(12.11)

The ratio of heads flow rate to feed rate is known as the cut в,

_yM ув r~zZ z

t *0-0) z

The fraction of a component appearing in the hepds stream is known as the recovery r of that component. The recovery of the desired component, for example, is

Weight, mole or atom fractionof Weight, desired mole or alom Flowrate isotope ratio

M у n

Tails*

Figure 12.9 Flow rates, composi­tions, and separation factors.