ABSTRACT
In recent years, the density and sulfur contents of crude oils charged to U.S. refineries have been increasing, and consequently a higher percentage of the crude oils are in the 1050
+
°F (566
+
°C) boiling range. In the past, this resid has been sold as asphalt (if the qualities of the crude permit) or as heavy fuel oil (No. 6 or bunker fuel oil). Stricter environmental emission standards have made it much more difficult and costly to use these heavy oils for fuels, and more of these must be converted in the refinery to feedstocks for refining processes that will convert them to transportation fuel blending stocks.
