What are the main steps in processing mined oil shale aboveground?

The aboveground processing of oil shale involves four primary steps to convert the raw ore into usable fuel:1

• Mining: The oil shale ore is extracted from the ground using either surface or underground mining techniques.1
• Crushing: The extracted ore is crushed into specific sizes—either lumps or fines—to ensure it can be effectively handled by the retort equipment.1
• Retorting: The crushed shale is heated in a retort to pyrolysis temperatures, typically between 480 and 550 °C (900–1,020 °F), in an oxygen-free environment. This process breaks the chemical bonds of the kerogen to release liquid and gaseous hydrocarbons.12
• Upgrading: Because the resulting shale oil often contains high levels of impurities like nitrogen, sulfur, and oxygen, it must be upgraded to remove particulates and stabilize the hydrocarbons. This step is essential for refining the oil into high-quality products such as diesel fuel or jet fuel.3