Page 261 - Pressure Swing Adsorption

238 PRESSURE SWING ADSORPTION PSA PROCESSES 239

signed to orovide local sources of high-ourity hydrogen. 18 23 Large-scale
-
These processes, which employ up to twelve beds with several pressure I Pressuri-
mult1ole-bed processes were cteveioped m the late 1970s, the first bemg the
24
41 MMSCFD plant at the Wintershall AG Lingen refinery m Germany.
rnlloJl
equalization steps, can achieve hydrogen recovenes in the 8S-90% range at l Lrne
99.99% nurity from a typical feed containing 75% l--1 • 25 28 '
-
2
Pre\11.1re
Eq1.1i!1za!\Oll
Lifle
6.5.1 The Four-Bed Process
The system for the ·four-bed orocess 1s essentially similar to the four-bed
oxygen process (Lindox) shown m Figures 3.9 and 3.10. A mixed adsorbent of
Ad~orp!ion
activated carbon and 5A zeolite is commonly used, although, smce the Bod
selectivity for most impurities relative to hydrogen is high, almost any
adsorbent can be employed. Production of a hydrogen product with 99.99%
purity at 'JS% recovery from a feed contaming 70-80% hydrogen is claimed
for the four-bed process with two pressure equalization steps. The process
Feed
~JPerates between 20-30 atmospheres and 1-2 ·atmospheres. The cycle is
(al

F 2 3 4 5 6 7 8 9 10 11 12 13 mm 20 sec.
30.B "

-
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f (b)
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2 3 4 5 6 7 8 9 10 11 12
Hydrogen Recovery (..-011, l Time (minutes)
Figure 6,13 Experimental recoverv-punty profile for four-bed H 2 PSA system. (cl
(From Tomita et al., 23 with oermisston.)
Figure 6.14 (a) Flowsheet, (b) pressure histol)', and (c} switching seouence for
polvbed (ten-bed) PSA hydrogen purification process. (Courtesv of Umon Carbide.)