Product Code Database
taking on fuel, or "bunkering"]] Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil (bunker fuel), marine fuel oil (MFO), furnace oil (FO), gas oil (gasoil), (such as home heating oil), diesel fuel, and others.
The term fuel oil generally includes any liquid fuel that is burned in a furnace or boiler to generate heat (), or used in an engine to generate power (as ). However, it does not usually include other liquid oils, such as those with a flash point of approximately , or oils burned in cotton- or wool-wick burners. In a stricter sense, fuel oil refers only to the heaviest commercial fuels that crude oil can yield, that is, those fuels heavier than gasoline (petrol) and naphtha.
Fuel oil consists of long-chain , particularly , , and . Small molecules, such as those in propane, naphtha, gasoline, and kerosene, have relatively low , and are removed at the start of the fractional distillation process. Heavier petroleum-derived oils like diesel fuel and lubricant are much less volatile and distill out more slowly.
Use of residual fuel oil was more common in the past. It powered , railroad , and . Locomotives, however, have become powered by diesel or electric power; steamships are not as common as they were previously due to their higher operating costs (most use steam plants, as "boil-off" gas emitted from the cargo can be used as a fuel source); and most boilers now use heating oil or natural gas. Some industrial boilers still use it and so do some old buildings, including in New York City. In 2011 New York City estimated that the 1% of its buildings that burned fuel oils No. 4 and No. 6 were responsible for 86% of the soot pollution generated by all buildings in the city. New York made the phase out of these fuel grades part of its environmental plan, PlaNYC, because of concerns for the health effects caused by fine particulates, and all buildings using fuel oil No. 6 had been converted to less polluting fuel by the end of 2015.
Residual fuel's use in electrical generation has also decreased. In 1973, residual fuel oil produced 16.8% of the electricity in the US. By 1983, it had fallen to 6.2%, and , electricity production from all forms of petroleum, including diesel and residual fuel, is only 3% of total production. The decline is the result of price competition with natural gas and environmental restrictions on emissions. For power plants, the costs of heating the oil, extra pollution control and additional maintenance required after burning it often outweigh the low cost of the fuel. Burning fuel oil, particularly residual fuel oil, produces uniformly higher carbon dioxide emissions than natural gas.
Heavy fuel oils continue to be used in the boiler "lighting up" facility in many coal-fired power plants. This use is approximately analogous to using kindling to start a fire. Without performing this act it is difficult to begin the large-scale combustion process.
The chief drawback to residual fuel oil is its high initial viscosity, particularly in the case of No. 6 oil, which requires a correctly engineered system for storage, pumping, and burning. Though it is still usually lighter than water (with a specific gravity usually ranging from 0.95 to 1.03) it is much heavier and more viscous than No. 2 oil, kerosene, or gasoline. No. 6 oil must, in fact, be stored at around heated to before it can be easily pumped, and in cooler temperatures it can congeal into a tarry semisolid. The flash point of most blends of No. 6 oil is, incidentally, about . Attempting to pump high-viscosity oil at low temperatures was a frequent cause of damage to fuel lines, furnaces, and related equipment which were often designed for lighter fuels.
For comparison, BS 2869 Class G heavy fuel oil behaves in similar fashion, requiring storage at , pumping at around and finalizing for burning at around .
Most of the facilities which historically burned No. 6 or other residual oils were industrial plants and similar facilities constructed in the early or mid 20th century, or which had switched from coal to oil fuel during the same time period. In either case, residual oil was seen as a good prospect because it was cheap and readily available. Most of these facilities have subsequently been closed and demolished, or have replaced their fuel supplies with a simpler one such as gas or No. 2 oil. The high sulfur content of No. 6 oil—up to 3% by weight in some extreme cases—had a corrosive effect on many heating systems (which were usually designed without adequate corrosion protection in mind), shortening their lifespans and increasing the polluting effects. This was particularly the case in furnaces that were regularly shut down and allowed to go cold, because the internal condensation produced sulfuric acid.
Environmental cleanups at such facilities are frequently complicated by the use of asbestos insulation on the fuel feed lines. No. 6 oil is very persistent, and does not degrade rapidly. Its viscosity and stickiness also make remediation of underground contamination very difficult, since these properties reduce the effectiveness of methods such as air stripping.
When released into water, such as a river or ocean, residual oil tends to break up into patches or tarballs – mixtures of oil and particulate matter such as silt and floating organic matter – rather than form a single slick. An average of about 5-10% of the material will evaporate within hours of the release, primarily the lighter hydrocarbon fractions. The remainder will then often sink to the bottom of the water column.
Even after the introduction of cleaner fuel rules in 2020, shipping air pollution is still estimated to account for around 250,000 deaths each year, and around 6.4 million childhood asthma cases each year.
The hardest hit countries by air pollution from ships are China, Japan, the UK, Indonesia, and Germany. In 2015, shipping air pollution killed an estimated 20,520 people in China, 4,019 people in Japan, and 3,192 people in the UK.
According to an ICCT study, countries located on major shipping lanes are particularly exposed, and can see shipping account for a high percentage of overall deaths from transport sector air pollution. In Taiwan, shipping accounts for 70% of all transport-attributable air pollution deaths in 2015, followed by Morocco at 51%, Malaysia and Japan both at 41%, Vietnam at 39%, and the UK at 38%.
As well as commercial shipping, cruise ships also emit large amounts of air pollution, damaging people's health. Up to 2019, it was reported that the ships of the single largest cruise company, Carnival Corporation & plc, emitted ten times more sulfur dioxide than all of Europe's cars combined.
Number 1 fuel oil is a volatile distillate oil intended for vaporizing pot-type burners and high-performance/clean diesel engines.Perry, Robert H., Chilton, Cecil H. and Kirkpatrick, Sidney D. Perry's Chemical Engineers' Handbook 4th edition (1963) McGraw Hill p.9-6 It is the kerosene refinery cut that boils off immediately after the heavy naphtha cut used for gasoline. This fuel is commonly known as diesel fuel, kerosene, and jet fuel. Former names include: coal oil, stove oil, and range oil.
Number 2 fuel oil is a distillate home heating oil. 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. The name gasoil 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 carbureted water gas manufactured gas.
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.
Number 4 fuel oil is a commercial heating oil for burner installations not equipped with preheaters. It may be obtained from the heavy gas oil cut. This fuel is sometimes known by the Navy specification of Bunker A.
Number 5 fuel oil is a residual-type industrial heating oil requiring preheating to for proper atomization at the burners. It may be obtained from the heavy gas oil cut, or it may be a blend of residual oil with enough number 2 oil to adjust viscosity until it can be pumped without preheating. This fuel is sometimes known by the Navy specification of Bunker B.
Number 6 fuel oil is a high-viscosity residual oil requiring preheating to . 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% water and 0.5% mineral oil. 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.
| + Fuel oil classes per BS 2869 | ||||||
| C1 | Distillate | — | — | 43 °C | 0.040 % (m/m) | Paraffin |
| C2 | Distillate | 1.000 mm2/s at 40 °C | 2.000 mm2/s at 40 °C | 38 °C | 0.100 % (m/m) | Kerosene, 28-second oil |
| A2 | Distillate | 2.000 mm2/s at 40 °C | 5.000 mm2/s at 40 °C | > 55 °C | 0.001 % (m/m) | low-sulfur gas oil, ULSD |
| D | Distillate | 2.000 mm2/s at 40 °C | 5.000 mm2/s at 40 °C | > 55 °C | 0.100 % (m/m) | Gas oil, red diesel, 35-second oil |
| E | Residual | — | 8.200 mm2/s at 100 °C | 66 °C | 1.000 % (m/m) | Light fuel oil, LFO, 250-second oil |
| F | Residual | 8.201 mm2/s at 100 °C | 20.000 mm2/s at 100 °C | 66 °C | 1.000 % (m/m) | Medium fuel oil, MFO, 1000-second oil |
| G | Residual | 20.010 mm2/s at 100 °C | 40.000 mm2/s at 100 °C | 66 °C | 1.000 % (m/m) | Heavy fuel oil, HFO, 3500-second oil |
| H | Residual | 40.010 mm2/s at 100 °C | 56.000 mm2/s at 100 °C | 66 °C | 1.000 % (m/m) | — |
Class C1 and C2 fuels are kerosene-type fuels. C1 is for use in flueless appliances (e.g. kerosene lamp). C2 is for vaporizing or atomizing burners in appliances connected to flues.
Class A2 fuel is suitable for mobile, non-road engine that are required to use a sulfur-free fuel. Class D fuel is similar to Class A2 and is suitable for use in stationary applications, such as domestic, commercial, and industrial heating. The BS 2869 standard permits Class A2 and Class D fuel to contain up to 7% (V/V) biodiesel (fatty acid methyl ester, FAME), provided the FAME content meets the requirements of the BS EN 14214 standard.
Classes E to H are residual oils for atomizing burners serving boilers or, with the exception of Class H, certain types of larger combustion engines. Classes F to H invariably require heating prior to use; Class E fuel may require preheating, depending on ambient conditions.
Marine diesel oil contains some heavy fuel oil, unlike regular diesels.
The density is also an important parameter for fuel oils since marine fuels are purified before use to remove water and dirt from the oil. Since the purifiers use centrifugal force, the oil must have a density which is sufficiently different from water. Older purifiers work with a fuel having a maximum of 991 kg/m3; with modern purifiers it is also possible to purify oil with a density of 1010 kg/m3.
ISO8217:2017 The ISO standard describe four qualities of distillate fuels and 10 qualities of residual fuels. Over the years the standards have become stricter on environmentally important parameters such as sulfur content. The latest standard also banned the adding of used lubricating oil (ULO).
Some parameters of marine fuel oils according to ISO 8217 (3. ed 2005):
| Density at 15 °C | kg/m3 | Max | - | 890.0 | 900.0 | 920.0 |
| Viscosity at 40 °C | mm2/s | Max | 5.5 | 6.0 | 11.0 | 14.0 |
| mm2/s | Min | 1.4 | 1.5 | - | - | |
| Water | % V/V | Max | - | - | 0.3 | 0.3 |
| Sulfur1 | % (m/m) | Max | 1.0 | 1.5 | 2.0 | 2.0 |
| Aluminium + Silicon2 | mg/kg | Max | - | - | - | 25 |
| Flash point3 | °C | Min | 43 | 60 | 60 | 60 |
| Pour point, Summer | °C | Max | - | 0 | 6 | 6 |
| Pour point, Winter | °C | Max | - | -6 | 0 | 0 |
| Cloud point | °C | Max | -16 | - | - | - |
| Calculated Cetane Index | Min | 45 | 40 | 35 | - |
| Density at 15 °C | kg/m3 | Max | 960.0 | 975.0 | 980.0 | 991.0 | 991.0 | 991.0 | 991.0 | 1010.0 | 991.0 | 1010.0 |
| Viscosity at 50 °C | mm2/s | Max | 30.0 | 30.0 | 80.0 | 180.0 | 180.0 | 380.0 | 380.0 | 380.0 | 700.0 | 700.0 |
| Water | % V/V | Max | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 |
| Sulfur1 | % (m/m) | Max | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 |
| Aluminium + Silicon2 | mg/kg | Max | 80 | 80 | 80 | 80 | 80 | 80 | 80 | 80 | 80 | 80 |
| Flash point3 | °C | Min | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 60 |
| Pour point, Summer | °C | Max | 6 | 24 | 30 | 30 | 30 | 30 | 30 | 30 | 30 | 30 |
| Pour point, Winter | °C | Max | 0 | 24 | 30 | 30 | 30 | 30 | 30 | 30 | 30 | 30 |
Since the 1980s the International Organization for Standardization (ISO) has been the accepted standard for marine fuels (bunkers). The standard is listed under number 8217, with recent updates in 2010 and 2017. The latest edition of bunker fuel specification is ISO 8217: 2017. The standard divides fuels into residual and distillate fuels. The most common residual fuels in the shipping industry are RMG and RMK. The differences between the two are mainly the density and viscosity, with RMG generally being delivered at 380 centistokes or less, and RMK at 700 centistokes or less. Ships with more advanced engines can process heavier, more viscous, and thus cheaper, fuel. Governing bodies around the world, e.g., California, European Union, have established Emission Control Areas (ECA) that limit the maximum sulfur of fuels burned in their ports to limit pollution, reducing the percentage of sulfur and other particulates from 4.5% m/m to as little as 0.10% as of 2015 inside an ECA. As of 2013 3.5% continued to be permitted outside an ECA, but the International Maritime Organization has planned to lower the sulfur content requirement outside the ECAs to 0.5% m/m by 2020. This is where Marine Distillate Fuels and other alternatives to use of heavy bunker fuel come into play. They have similar properties to diesel #2, which is used as road diesel around the world. The most common grades used in shipping are DMA and DMB. Greenhouse gas emissions resulting from the use of international bunker fuels are currently included in national inventories.
| + Table of fuel oils | |||||||
| No. 1 fuel oil | No. 1 distillate | No. 1 diesel fuel | Kerosene | Jet fuel | Distillate | 9-16 | |
| No. 2 fuel oil | No. 2 distillate | No. 2 diesel fuel | Road diesel | Rail diesel | Marine gas oil | Distillate | 10-20 |
| No. 3 fuel oil | No. 3 distillate | No. 3 diesel fuel | Marine diesel oil | Distillate | |||
| No. 4 fuel oil | No. 4 distillate | No. 4 residual fuel oil | Bunker A | Intermediate fuel oil | Distillate/Residual | 12-70 | |
| No. 5 fuel oil | No. 5 residual fuel oil | Heavy fuel oil | Bunker B | Navy special fuel oil | Furnace fuel oil | Residual | 12-70 |
| No. 6 fuel oil | No. 6 residual fuel oil | Heavy fuel oil | Bunker C | Marine fuel oil | Furnace fuel oil | Residual | 20-70 |
Heavy fuel oil is still the primary fuel for , a tourism sector that is associated with a clean and friendly image. In stark contrast, the exhaust gas emissions - due to HFO's high sulfur content - result in an eco balance significantly worse than that for individual mobility.
Alternatively "bunkering" may apply to the shipboard logistics of loading fuel and distributing it among available bunkers (on-board fuel tanks).
Finally, in the context of the oil industry in Nigeria, bunkering has come to refer to the illegal diversion of crude oil (often subsequently refined in makeshift facilities into lighter transportation fuels) by the unauthorized cutting of holes into transport pipelines, often by very crude and hazardous means and causing spills.
As of 2018, some 300 million metric tons of fuel oil is used for ship bunkering. On January 1, 2020, regulations set by the International Marine Organization (IMO) all marine shipping vessels will require the use of very low sulfur fuel oil (0.5% Sulfur) or to install exhaust gas scrubber systems to remove the excess sulfur dioxide. The emissions from ships have generally been controlled by the following sulfur caps on any fuel oil used on board: 3.50% on and after 1 January 2012 and 0.50% on and after 1 January 2020. Further removal of sulfur translates to additional energy and capital costs and can impact fuel price and availability. If priced correctly the excess cheap yet dirty fuel would find its way into other markets, including displacing some onshore energy production in nations with low environmental protection .
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