Page 233 - Adsorption Technology & Design, Elsevier (1998)

212 Selected adsorption processes

Distillation

B+D
w

A
Adsorbing bed
Desorbing bed
preloaded with D
D
and with D being
w
replaced by A

A+D
Feed
A+B
~,T,) Distillation

Figure 7.11 Principle of a displacement purge cycle operation (source: Keller 1983).

containing branched chain and cyclic isomers, all with molecular masses
typical of hydrocarbons in the C10 to C18 range, make use of displacement
purge gas cycles. The Ensorb process of Exxon, in which ammonia is used as
the desorbent, is typical of these displacement purge cycles (Asher et al.
1969).

7.7 CONTINUOUS COUNTERCURRENT ADSORPTION
SEPARATIONS

Countercurrent operation of an adsorption column in which gaseous or
liquid feed is passed continuously through a bed of adsorbent countercur-
rent to a flow of solid adsorbent is, in principle, more efficient than the
previous descriptions of cyclic batch operations because countercurrent flow
maximizes the average driving force for mass transfer between fluid and
adsorbent. The saturated spent adsorbent emerging from the adsorber