Page 303 - Pressure Swing Adsorption

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280 PRESSURE SWING ADSORPTION EXTENSIONS OF THE PSA CONCEPT 281

PRODUCT
therefore be accounted for explicitly m any model. In general Darcy's Law 1s
'i used to relate the flow to the pressure drop through the bed;
I Kap
v= ---
&J.l az ' (7-5)
Both eouilibnum and kinetic models (LDF approx1mat1on) have been
I 7 .3.2 Expenmental Studies
p developed.
(a)

5
l Turnock and Kadlec studied the separation of a nitrogen-methane mixture
by RPSA over 5A zeolite. Representative purity-recovery data and equilibM
rium theory predictions from their study are shown m Figure 7.11. It 1s clear
l, that the mtrogen recovery was unacceptably low ( < 5% at 90% product
•
' I
t
FEED WASTE
CYCLING
(Consider bed as a sanes of vessels) FREQUENCY
(CPS}
0 o,
..
~
i. Pressunsat1on ~ • A 0.10
020
0
~
(b) "' 0 0.40
~
0
~
..
0
IE
- "'
2. Transoort of Oz ~
z
ennched gas to w
the next soct1on ,; 0 QC
~
z
~
z
- w 40
,J. Oepressur1sat1on w
..
0
QC
w
J
0
~
.o,
0
RATIO OF PRODUCT RATE TO FEED RATE
Figure 7.11 Purity of mtrogen product versus product-to-feed ratio for a RPSA
Figure 7.10 The rapid pressure swmg process showing _(a) pressure variation and process. (From Turnock and Kadlec,=:; with oermission.)
(b) the analogy with a ratchet. (From Kenney,' with perm1ss1on.)