Developments in Petroleum Refining - Spent Hydroprocessing Catalysts - page 5

CHAPTER 2
Developments in Petroleum Refining
Decreasing supply of conventional crude on the world market, offset by the gradual increase in
the supply of medium heavy and heavy crude, resulted in the significant change in the
structure of refinery and refining strategy. In addition, petroleum refineries must respond to a
continuous change in the demand of transportation fuel in favor of increased demand for diesel
fuel relative to that of gasoline, as it is shown in Fig. 2.1 [24] . Moreover, the feed imbalance
( Fig. 2.2 ) further complicates the situation in petroleum refining. Simultaneously with theses
changes, fuel specifications have been continuously evolving, i.e., becoming more stringent.
This is illustrated in Fig. 2.3 using the continuous changes in specifications in Europe [25] .
These changes require a redesign of refining units and/or development of entirely new refining
concepts. Some of these requirements could only be met with an increased consumption of
hydrogen and catalysts. In any case, significant additional costs had to be incurred by
petroleum refining industry during the change from conventional refinery to the advanced
refinery capable of processing more difficult crude and at the same time to comply with all
environmental regulations.
It has been realized that the integration of refining operations with non-refining (e.g., utility,
incineration, etc.) improved the overall refining efficiency. Moreover, it provided a viable
mean for emissions control, particularly in the large size refineries. Indeed, general trends
around the world indicate the preference of large size refineries compared with small or
medium size refineries. In some situations, the operation of a small refinery was discontinued,
whereas in other, a small refinery has been gradually revamped and upgraded to a modern type
of refinery [26] .
Table 2.1 [27] shows the properties of several well-known crudes. The differences in
properties influence the extent of refining. A conventional refinery, requiring little
modification, may be suitable for processing light crudes such as Ekofisk and Arab Light. The
higher content of metals in Kuwait export and Arab Heavy crudes would require a redesign of
catalytic reactors in the case that further processing of distillation residues is considered.
Advanced refining schemes have to be capable of processing heavy crudes such as Maya,
Boscan and Cold Lake crudes. For such heavy feeds, the choice of the primary upgrading step,
i.e., hydrogen addition versus carbon rejection may be critical.
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