Refiners processing heavy crudes can experience crude distillation problems

Refiners will process increasingly heavier crude slates during the next 10 years. A majority will originate from the Orinoco oil belt bitumen upgraders in Venezuela and the Athabasca tar sands region of northern Alberta. Even blended with lighter crudes, these lower-gravity blends will require crude-unit process flow scheme and equipment design changes to meet profitability objectives. This article addresses crude distillation unit (CDU) problem areas and identifies specific sections requiring investment to maintain profitability throughout a 4-5 year run length for refiners processing heavy crudes. Some heavy crudes are blends of 6-8° API bitumens combined with hydrotreated lighter products from bitumen upgraders. The blended lighter products that help produce synthetic crudes generally distill in the atmospheric column leaving a very heavy 6-8° API feed to the vacuum unit. CDUs must operate at increased severity to maintain product cut points and qualities. Heavy crudes are more difficult for the CDU to process. Historically, refiners processing heavier crudes have had problems maintaining: • Crude charge rate. • Product yield and quality. • Unit reliability.