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| Fig. 1: Schematic flow diagram of a Fluid Catalytic Cracker seen in crude oil distillation. (Source: Wikimedia Commons) |
According to the EIA's November 2017 Month Energy Review, the U.S. consumed 3.148 Quadrillion BTUs of Petroleum energy in August 2017, accounting for 38% of total energy consumption. [1] However, Let's take a look at the processes that convert oil extracted from the ground to the petroleum energy we consume, specifically in California.
The most popular method to extract oil is through wells throughout the world. California derives most of its crude oil from the state itself, Alaska, as well as oil producing countries such as Saudi Arabia and Ecuador. [2] When this crude oil is pumped from the ground, it is not functional for use, but must be refined for various uses. In order to determine its use, the crude oil is tested for two characteristics, density and sulfur content in order to determine quality and price. [2] The ideal form of crude oil is low density and low sulfur content, as higher density requires more refinement work, while high sulfur oil corrodes pipes and require more work in order to meet current low sulfur emissions standards.
The next step in the process is to transport the crude oil from the well to the refineries. Crude oil is generally transported through two ways, over land through pipelines or over water by oil tanker. [2]
During refinement, crude oil undergoes three density changing processes: distillation, conversion, and alkylation, in addition to de-sulfurization in order to produce a variety of petroleum based products. [2] Distillation uses heat to separate the crude oil into various different products based on various boiling temperatures, taking place within the crude and vacuum towers. In the crude tower, the petroleum is heated using a furnace. As the oil is heated, it separates with the lowest boiling components rising to the top of the furnace. As seen in Fig. 1, gasoline has a low boiling point at 150°C, Jet Fuel and Kerosene at 200°C, Diesel at 300°C, and asphalt at 400°C. When the boiling temperatures reach roughly 730°F to 850°F, the heavy components begin to "crack" and are sent to the vacuum tower where they can be broken down at lower boiling temperatures using lower pressure. [2] Next, the conversion process takes place. There are three core areas to conversion: the coker, the hydrocraker, and the Fluidized Catalytic Cracker (FCC). [2] The coker takes the heavy components from the vacuum tower and converts them into lighter components using high pressure and temperature while the hydrocraker breaks up the heaviest components using hydrogen and catalysts. [2] The FCC uses chemical catalysts to break up large molecules into smaller, more useful components. Alkylation combines heavier molecules with molecules that are too light for certain products. Lastly, different components from various areas of the refinery are brought together for blending. Typically, there are 3 to 8 components that are combined to create various grades of gasoline.
Gasoline is now shipped to refiner's terminal or to wholesalers, generally through pipeline. At the refiner terminals, additives are normally blended to the gasoline and the final product is tested to meet California regulations before being trucked and sold to companies which sell to consumers.
In conclusion, gasoline and diesel fuel was available at roughly 10,200 outlets throughout California, resulting in approximately 15.7 billion gallons of gasoline and 3 billion gallons of diesel fuel consumed in 2007.
© Daniel Cohn. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Monthly Energy Review - November 2017," U.S. Energy Information Administration, DOE/EIA-0035(2017/11), November 2017.
[2] "Oil to Car," California Energy Commission, CEC-180-2008-008, July 2008.
