Workshop proceeding - final.pdf - Faculty of Information and ...
Workshop proceeding - final.pdf - Faculty of Information and ...
Workshop proceeding - final.pdf - Faculty of Information and ...
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Dual mode roll-up effect in a multicomponent near adiabatic adsorption<br />
process<br />
Gang Li, 1 * Dong Xu, 1,2 Penny Xiao, 1 Paul A Webley 1<br />
* Presenter<br />
1. Cooperative Research Centre for Greenhouse Gas Technologies, Department <strong>of</strong> Chemical<br />
Engineering, Monash University, Wellington Road, Clayton, Victoria 3800, Australia<br />
2. School <strong>of</strong> Materials & Metallurgy, Northeastern University, Shenyang 110004, P.R. China<br />
Adsorption technologies have been widely used in laboratorial analysis/separations, e.g.<br />
chromatography <strong>and</strong> portable life support systems, <strong>and</strong> also in industrial process, e.g. air<br />
separation <strong>and</strong> carbon capture. A common phenomenon in multi-component adsorption in a<br />
fixed bed is that the effluent concentration <strong>of</strong> some components may exceed their steady inlet<br />
values. This effect, <strong>of</strong>ten referred to as roll-up, is attributed to the displacement <strong>of</strong> the more<br />
weakly adsorbed component by the slower moving more strongly adsorbed component,<br />
according to the conventional explanation in the literature. This has also been applied to some<br />
practical operations in liquid chromatography <strong>and</strong> some large-scale chromatographic<br />
separations to desorb the pre-loaded components from a column by introducing a desorbent,<br />
which is more strongly adsorbed than any other component in the system. Many published<br />
works reported that in a system containing two adsorbed species, one could easily see a single<br />
roll-up <strong>of</strong> the weak component during the breakthrough process. However, our recent study<br />
showed that more than one roll-up could occur, in such a system using CO 2 <strong>and</strong> H 2 O vapour<br />
as the weakly <strong>and</strong> strongly adsorbed components respectively in double zeolite 3A/13X <strong>and</strong><br />
activated alumina/13X layered columns. It has also been found that a pure thermal wave was<br />
generated by H 2 O adsorption <strong>and</strong> it moved ahead <strong>of</strong> the H 2 O mass transfer zone, <strong>and</strong> the first<br />
roll-up coincided with the propagation <strong>of</strong> the thermal front to the 3A/13X layer interface<br />
while the second roll-up happened when H 2 O concentration front reached the 13X layer. In<br />
theory, enthalpy can be regarded as a direct equivalence to an extra adsorbed component so<br />
that temperature front will sweep <strong>of</strong>f the column before the propagation <strong>of</strong> the strongly<br />
adsorbed component (H 2 O in this case), but it only signifies under adiabatic or near adiabatic<br />
conditions. The interval <strong>of</strong> the two roll-ups reduces with the decrease <strong>of</strong> the length <strong>of</strong> 3A layer,<br />
<strong>and</strong> eventually they merge into a single pronounced roll-up. The results were further verified<br />
by computer simulations. Therefore, to the best <strong>of</strong> our knowledge, this is the first affirmative<br />
report about this unique dual mode roll-up effect, which will be essential in the design <strong>of</strong> near<br />
adiabatic adsorption/chromatography units.<br />
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