ABSTRACT
The basic raw material for refineries is petroleum or crude oil, even though in some areas synthetic crude oils from other sources (Gilsonite, oil sands, etc.) and natural gas liquids are included in the refinery feedstocks. The chemical compositions of crude oils are surprisingly uniform even though their physical characteristics vary widely. Since 1980, crude oils charged to U.S. refineries have become heavier (lower °API, higher sp. gr.) and have higher sulfur contents. Both of these properties require more severe and more costly processing. In 1980, the average gravity was 33.8°API (sp. gr. 0.856) and the sulfur content, 0.89 wt%. By 2004, the gravity had decreased to 30.5°API (sp. gr. 0.874) and the sulfur content had increased to 1.42 wt% [1].
