Fuel Oil A liquid or liquefiable petroleum product that is used to generate heat or power Any of the petroleum products which are less volatile than gasoline and are burned in furnaces, boilers, or other types of heaters. The two primary classes of fuel oils are distillate and residual. Distillate fuel oils are composed entirely of material which has been vaporized in a refinery distillation tower. Consequently, they are clean, free of sediment, relatively low in viscosity, and free of inorganic ash. Residual fuel oils contain fractions which cannot be vaporized by heating.
These fractions are black and viscous and include any inorganic ash components which are in the crude. In some cases, whole crude is used as a residual fuel. Distillate fuel oils are used primarily in applications where ease of handling and cleanliness of combustion are more important than fuel price. The most important use is for home heating. They are also used in certain industrial applications where low sulfur or freedom from ash is important. Increasing amounts of distillate fuel oils have been burned in gas turbines used for electricity generation Residual fuel oils are used where fuel cost is an important enough economic factor to justify additional investment to overcome the handling problems they pose.
They are particularly attractive where large volumes of fuel are used, as in electric power generation, industrial steam generation, process heating, and steamship operation Fuel oil is a fraction obtained from petroleum distillation, either as a distillate or a residue. Broadly speaking, fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power, except oils having a flash point of approximately 40 °C (104 °F) and oils burned in cotton or wool-wick burners. In this sense, diesel is a type of fuel oil.
Fuel oil is made of long hydrocarbon chains, particularly alkanes, cycloalkanes and aromatics. The term fuel oil is also used in a stricter sense to refer only to the heaviest commercial fuel that can be obtained from crude oil, heavier than gasoline and naphtha
Number 1 fuel oil is a volatile distillate oil intended for vaporizing pot-type burners.[1] It is the kerosene refinery cut that boils off right after the heavy naphtha cut used for gasoline. Older names include coal oil, stove oil and range oil.\
[2] Number 2 fuel oil is a distillate home heating oil.[1] Trucks and some cars use similar diesel fuel with a cetane number limit describing the ignition quality of the fuel. Both are typically obtained from the light gas oil cut. Gas oil refers to the original use of this fraction in the late 19th and early 20th centuries - the gas oil cut was used as an enriching agent for carburetted water gas manufacture.[2]
Number 3 fuel oil was a distillate oil for burners requiring low-viscosity fuel. ASTM merged this grade into the number 2 specification, and the term has been rarely used since the mid 20th century.[1]
Number 4 fuel oil is a commercial heating oil for burner installations not equipped with preheaters.[1] It may be obtained from the heavy gas oil cut.[2]
Number 5 fuel oil is a residual-type industrial heating oil requiring preheating to 170 - 220 °F (77 - 104 °C) for proper atomization at the burners.[1] This fuel is sometimes known as Bunker B. It may be obtained from the heavy gas oil cut,[2] or it may be a blend of residual oil with enough number 2 oil to adjust viscosity until it can be pumped without preheating.[1]
Number 6 fuel oil is a high-viscosity residual oil requiring preheating to 220 - 260 °F (104 - 127 °C). Residual means the material remaining after the more valuable cuts of crude oil have boiled off. The residue may contain various undesirable impurities including 2 percent water and one-half percent mineral soil. This fuel may be known as residual fuel oil (RFO), by the Navy specification of Bunker C, or by the Pacific Specification of PS-400.[1]