The dynamic adsorption isotherms of CO2-EGR were measured by using a
Intelligent Gravimetric Analysis system.In the beginning stage of CO2
injection, all the injected CO2 enters into the adsorbent and the mole
fraction of CH4 (yCH4) keeps 1.0. The CH4 recovery factor (RCH4)
increases. The during of this stage (tcd) depends on the selectivity of
CO2 over CH4 ( SCO2/CH4). A adsorbent with large SCO2/CH4 has long tCD.
When SCO2/CH4 is greater than 1.0, CO2 reduces the fraction of CH4 in
the adsorbed phase (xCH4) and more CH4 is driven out. In the second
stage,the injected CO2 competes with CH4 for adsorption. The cumulative
RCH4 of this stage is much larger than that of the initial stage.
However, yCH4 decrease sharply. pCH4 in the whole CO2 injection is
always larger than that before CO2 injection, suggesting CH4 desorption
results from the displacement by CO2 rather than from pressure