Main Results of Analysis

In this section, some of the main results obtained on the separate and combined effect of inhibition and polarization are presented and discussed. Further details concerning the validation of the analysis can be found elsewhere.  

In this section, the analysis is focussed on the direct effect that inhibition by CO and concentration polarization have on hydrogen permeance and transmembrane flux. To do that, the operating conditions reported in Table 14.4 are considered.As shown in the table, two mixtures are considered to separate the CO contribution to concentration polarization and inhibition. 

As regards the first case (horizontal dashed lines), it is possible to notice that the membrane permeance is constant. This is because it represents an intrinsic property of the material, which, thus, cannot be influenced by any external fluid-dynamic factor. 

When concentration polarization is taken into account, the permeance evaluated according to the bulk driving force (dashed-line named Bulk ) is significantly different with respect to the membrane one. This is due to the external mass transfer influence, whose resistance becomes higher as the composition of the other species progressively increases. 

In the latter case, both polarization and inhibition are considered. As stated before, the presence of these two phenomena at the same time makes the system analysis more complex, since they are mutually dependent on each other. Analyzing the profiles in the plot, for high hydrogen molar fraction (approximately higher than 0.9) no appreciable difference between inhibition alone and inhibition affeeted by polarization can be observed. This occurs because of the small eontent of the other species (CO and N2 for mixture 1 and CO for mixture 2), which do not provide significant polarization effects. 

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