Page 248 - Pressure Swing Adsorption

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224 PRESSURE SWING ADSORPTION PSA PROCESSES 225

.10- · BED LENG TH U6 m
BED DIAMETER 021 m
D9 ADSORBENT 2-';mm ACT. ALUM. 0 I I I I
'
ADSORBATE HzD (VAPOR) Q- iNL~Tw
OEWPO[NT
IMPRESSED GAS: AIR 0--
TEMPERATURE 294 ° K. 0-
5
PRESSURE ';.6'; X/0 Pa
\_ :a--
NEMA CYCLE 600 Sec.
"' .06 PURGE TIME 280 Sec. .a-
..._.az ADSORPTION TIME 300 Sec. 10---
.Q'; PURGE FLOWRATE 01)204 kg,s
e's - OUTL::T
...J FROSTPJ/NT
~
2 '/0-
--END OF ADSORPTION -~ I 1i
----END OF REGENERATION 20 ·~ 0 - "'") 10 1 - - - .
0P'c?.ATING TIME. HOUl'IS
.02
ff.ST DATA
.0/ Adsorbent: ALCOA F~zoo 3.2 mm Activated Alumina
Adsoroent per Chamoer: I t.B kg
e:. e:. Bed Size: 0.12065m Dia. x 1.27m Long
INLET OUTLET NE:MA Cycle: 600 Sec.
ADSORPHON BED LENGTH
Purge Time~ 270 sec. Adsorot1on Time 300 sec.
Figure 6.2 Expenmentai concentration profiles for a heatless a1r drier packed with Influent ~iowrore: 0.02211 kalsec
an activated alumma adsorbent. (From D. H. White,2 with perm1ss1on.) Inlet ?ressure: 6.533 x 1Q=i Pa
Inlet Temoerature: 294 ° K
P:.irge Ciowrate: 0. 007634_ kglse'.::.
P.Jrge ;:;ressure: /_ 413 :,; :o' :;,~
region by an mert solid with a high heat caoac1ty. Since the heat capacity of
!nler Water '✓apor Oewooint (Ava.J: zg,:; 35°K [at Pressurei
the mert solid can be higher than that of the adsorbent, a rectucllon m overall Outlet Water VafX}f Frosrpo1nt (Avg.i : 211. 93 ° K (at Pressurej
beet volume can be achieved. The reoutred bed length (typ1cally 1-2 m) is
Figure 6.3 Performance test data showing constancy of effluent dew pamt over a 25
normally determined from a classical heat transfer calcmlatlon, following the
hour penod for a "heatless drier" pac!eed with an activated alumina adsorbent. (From
method of Anzelius,4 although a full dynamic simulation of the nomsother- D. H: White, with permissmn.) -
2
mal PSA cycle, as described in Section 5.4, 1s preferable, since such an
approach provides more detailed and reliable information concernmg the
effects of the process vanables. not be satisfied and the mmsture front will siowly advance through the bed.
To allow · for the obvious deviation from the ideal equilibnum situation, a
margm of at ieast 15% over the theoretical mm1mulil purge 1s normally
6. 1.4 Purge Flow Rate desirable:
Under ideal equilibrmm conditions the partial pressure of moisture m the purge rate - is(,, 1· (Pc).
purge stream leavn1g the beet will be the same as that of the entermg feect. 1 ( 6 .I )
feed rate · /P PH
Conseouently, the stoichiometnc mimmum ourge volume (measured at ourge
pressure) 1s equal to the actual feed volume (measured at feed pressure). If where the flow rates are expressed on a moiar basis and t , iP refer to the
1
the purge flow 1s reduced beiow this level, the steacty-state mass balance will feed and purge times.