Developments in Petroleum Refining - Spent Hydroprocessing Catalysts - page 13

Figure 2.9: Effect of inter-stage separation ( Fig. 2.8 ) on residue conversion [From ref. 39 .
Reprinted with permission].
confirmed that at high H 2 S/H 2 ratios, some catalytic sites were inhibited due to the excessive
adsorption of H 2 S [40] . It is believed that this phenomenon is responsible for the difference in
system performance indicated in Fig. 2.9 [39] .
It is evident that any form of revamping has a direct effect on catalyst performance, i.e., overall
utilization, activity and stability. Consequently, catalyst consumption, as well as the amount of
generated spent catalyst, is decreased. However, there might be limits beyond which any form
of revamping may not bring necessary benefits. In such circumstances, more advanced
processes have to be employed. The decision between revamping and employing a novel
process becomes more critical with increasing content of contaminants in the feed.
2.3 Advanced Refineries
Table 2.1 [27] indicates that for light crudes such as North Sea Ekofisk and Arab Light, the
yields of distillates (atmospheric and vacuum) exceed 80%. For little heavier crude, such as
Arab Heavy and Kuwait export, the yields are between 75 and 80%. On the other extreme,
only about 50% and less than 40% of the distillates can be obtained from Cold Lake and
Boscan crude, respectively, unless the residues (e.g., 50 and 64%, respectively) are subjected
to additional upgrading. This comparison shows that no conventional refinery would be ready
to undertake such tasks without significant modifications and/or revamping of existing units
combined with the entirely new systems added to the refining operation. Also, an integration
of refining operation with non-refining processes may be necessary to improve viability of the
former.