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Wiktionary
upgrader

n. 1 One who, or that which, upgrades. 2 A facility that upgrades bitumen into synthetic crude oil.

Wikipedia
Upgrader

An upgrader is a facility that upgrades bitumen (extra heavy oil) into synthetic crude oil. Upgrader plants are typically located close to oil sands production, for example, the Athabasca oil sands in Alberta, Canada or the Orinoco tar sands in Venezuela.