Hydrocarbon Engineering - March 2017

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March 2017 75 HYDROCARBON
ENGINEERING
R efiners have always sought to boost their
profitability by improving their crude diet
flexibility. Such flexibility allows refiners to control
how much of a discounted, opportunity crude to
include in their feed slate, after weighing the financial
benefits of running the crude against the processing
problems it is likely to create. As crude oil quality declines
globally and refiners face additional pressure to boost
margins, they will have to process greater volumes of
opportunity crudes on a more frequent basis if they are to
remain profitable and, ultimately, operational.
Processing problems can begin as soon as the
opportunity crude enters the crude unit’s desalter and are
often exacerbated by uncontrolled desalter pH. The pH of
the brine in desalters can vary widely, ranging from 5 to as
high as 10. For most desalters, controlling brine pH at the
lower end of this range benefits the overall refining process
by improving oil/water separation; lowering salt, basic
sediment, and water in the crude; and reducing oil
undercarry, which decreases chemical oxygen demand
(COD) of the brine sent to the wastewater treatment plant.
Additionally, managing brine pH also offers other
significant advantages when processing challenging crudes.
Crude oils are often treated with H2S scavengers prior to
transportation. The most common scavengers produce
sizeable quantities of undesirable amine that remain in the
crude oil. Amines can also be re-introduced through the
desalter wash water stream or in slop oils that are
A
FLEXIBLE
DIET
Ralph Navarrete and George Duggan, Baker Hughes Inc., USA,
explain how desalter pH management can help to increase crude
diet flexibility.