Petroleum refining processes in the context of Fossil-fuel

A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geological formations. Reservoirs of such compound mixtures, such as coal, petroleum and natural gas, can be extracted and burnt as fuel for human consumption to provide energy for direct use (such as for cooking, heating or lighting), to power heat engines (such as steam or internal combustion engines) that can propel vehicles, or to generate electricity via steam turbine generators. Some fossil fuels are further refined into derivatives such as kerosene, gasoline and diesel, or converted into petrochemicals such as polyolefins (plastics), aromatics and synthetic resins.

The origin of fossil fuels is the anaerobic decomposition of buried dead organisms. The conversion from these organic materials to high-carbon fossil fuels is typically the result of a geological process of millions of years. Due to the length of time it takes for them to form, fossil fuels are considered non-renewable resources.

Petroleum naphtha is an intermediate hydrocarbon liquid stream derived from the refining of crude oil with CAS-no 64742-48-9. It is most usually desulfurized and then catalytically reformed, which rearranges or restructures the hydrocarbon molecules in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-octane component of gasoline (or petrol).

There are hundreds of different petroleum crude oil sources worldwide and each crude oil has its own unique composition or assay. There are also hundreds of petroleum refineries worldwide and each of them is designed to process either a specific crude oil or specific types of crude oils. Naphtha is a general term as each refinery produces its own naphthas with their own unique initial and final boiling points and other physical and compositional characteristics.

Heavy fuel oil (HFO) is a fuel oil of a tar-like consistency. Also known as bunker fuel, or residual fuel oil, HFO is the residual mixture leftover from the distillation and cracking of crude oil in oil refineries. Generally, it has a boiling temperature between 350 and 500 °C and a significantly increased viscosity compared to diesel. As it is created through the extraction of more valuable components of its petroleum precursor, HFO contains various undesirable compounds and elements, which includes aromatics, sulfur, nitrogen, vanadium, and others. These non-hydrocarbon contaminants significantly increase toxic gas and particulate emissions upon combustion, such as sulfur dioxide, carbon monoxide, and nitrogen oxides.

As the fuel is cheap, it is predominantly utilized for marine vessel propulsion in marine diesel engines due to its relatively low cost compared to cleaner fuel sources such as diesel fuel or distillates. The emission-heavy nature of the fuel also contributes to this method of usage; marine vessels, such as oil tankers and cruise ships, are generally distant from population centers, sailing in open seas and oceans for the majority of the time, minimizing the exposure of humans to harmful aerosols and gaseous emissions. Ships utilizing heavy fuel oil may switch to cleaner alternatives such as diesel when approaching land. The use and carrying of HFO in seafaring vessels presents several environmental concerns, such as accidental oil spills due to adverse weather or routine handling, which are common due to their universal and dominant usage in marine transportation.

Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation to fractionate. Generally the component parts have boiling points that differ by less than 25 °C (45 °F) from each other under a pressure of one atmosphere. If the difference in boiling points is greater than 25 °C, a simple distillation is typically used.

A crude oil distillation unit uses fractional distillation in the process of refining crude oil.