Environmental Engineering Reference
In-Depth Information
Figure 6.28: Carbon removal from spent catalyst: 1: radiation heating; 2: in ozone; 3:
conventional burn-off [From ref. 422 . Reprinted with permission].
use of ozone for catalyst regeneration has been prevented because of its limited availability in
desirable concentrations and quantities.
6.3 Other Regeneration Methods
In this part, only the methods based on the solid-gas reactions are included. This includes
steam and CO 2 , as well as N 2 O, NO, and H 2 . The driving forces for these reactions expressed
as the log K values are shown in Fig. 6.29 [423] . Among those, the reactions of carbonaceous
solids with steam and CO 2 have been studied extensively as part of carbon gasification
research. In this case, the reference was made to such reactions as reductive carbon conversion
compared with the oxidative regeneration in O 2 . Thus, while carbon was partially oxidized
during these reactions, the other reactants, i.e., steam and CO 2 were reduced. Although they
might exhibit an adequate reactivity, N 2 O and NO have little chance to be used on an industrial
scale because of the limited availability in desirable concentrations. From this point of view,
the reductive regeneration of spent catalysts in H 2 yielding hydrocarbons has much more
potential to be used commercially than nitrogen containing oxides.
6.3.1 Regeneration in H 2 O and CO 2
The coke on catalyst surface can also be removed via its reaction with H 2 O and CO 2 , i.e.,
carbon gasification [424] . The products of these reactions include CO and H 2 . This ensures the
 
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