Diesel fuel is the common term used for distillate fuel oil that is used in motor vehicles that use a compression ignition engine. Nearly all semi-trailer trucks, delivery vehicles, buses, trains, ships, boats, and barges use diesel engines. In 2015, diesel fuel accounted for about 21% of total petroleum consumed by the transportation sector. In order to make diesel, crude oil must be refined. In order to understand how petroleum is produced, it is important to understand the refinement process that turns crude oil into diesel.
Crude oil is a naturally occurring liquid that can be refined into various fuels and other petroleum-based products. At the molecular level, crude oil is made of various hydrocarbons (hydrogen and carbon). The hydrocarbon chains come in various lengths with the longer chains having a higher boiling point than the shorter ones. The process of distilling the oil using the different boiling points to separate the distillates from the crude oil.
How is Crude Oil Turned Into Diesel Fuel?
Crude oil turns into fuel through the process of distillation. The refining starts by heating the oil to over 400 degrees Celsius. This turns the liquid into vapor and the vapor then enters a fractional distillation tower. As the vapor rises, it cools. When ti reaches a certain temperature, the hydrocarbon chains return to a liquid state. Different levels of the tower yields a density of product through the use of distillation plates.
The Products of Distillation
The longest hydrocarbons have a boiling point over 400 degrees Celsius. When the chains enter the distillation tower, the longest hydrocarbons turn into liquid again. The emerging product is asphalt or bitumen. As the vapor rises, the shorter hydrocarbons begin to liquify as well. Fuel oil emerges when the vapor cools to below 370 degrees celsius. When the vapor cools to between 200 and 300 degrees celsius, diesel fuel begins to emerge. The collected vapor is then siphoned off into a diesel holding tank.
Other Methods of Creating Diesel Fuel
There are methods to creating diesel fuel other than the traditional method. The higher the vapor rises up the tower, the shorter the hydrocarbon chains. The chains at the top emerge as vaporous gas. Another option is to recombine some of the shorter hydrocarbon chains. Added together a specific proportions, the hydrocarbons combine to diesel fuel. The result is a diesel fuel that can have additives blended in.
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