Heavy fuel oil

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Heavy fuel oil
other names

Bunker oil, HFO, RFO, IFO, Bunker C, Bunker B, heating oil S (heavy), heating oil ES (extra heavy)

Trade names

Marine (Residual) Fuel Oil (MFO)

Brief description Diesel fuel for marine engines


Physical state very high viscosity liquid (20 ° C)
  • RME 180: max. 180 mm² / s (50 ° C)
  • RMG 380: max. 380 mm² / s (50 ° C)
  • RMK 700: max. 700 mm² / s (50 ° C)
  • RME 180: max. 0.991 kg / L (15 ° C)
  • RMG 380: max. 0.991 kg / L (15 ° C)
  • RMK 700: max. 1.010 kg / L (15 ° C)
Flash point

min. 60 ° C

safety instructions
GHS labeling of hazardous substances
07 - Warning 08 - Dangerous to health 09 - Dangerous for the environment


H and P phrases H: 332-350-361d-373-410
P: 201-260-273-281-308 + 313-501
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Heavy oil ( English Heavy Fuel Oil , HFO ) is a residue oil from distillation , or from cracking units of the petroleum processing . International trade name of such oil is Marine (residual) Fuel Oil ( MFO ; German  Marines residual oil ), sometimes the US designation Bunker C .

It is used (mixed with diesel oil ) as fuel for large diesel engines , for example to drive ships (see marine fuel) and as fuel for steam locomotives with main oil firing as well as for power plants for generating electricity and for generating process steam .


Heavy oils mainly remain as residues from petroleum processing . In this context, residue means that this component was created as a part (“sump”) that can no longer be evaporated from a petroleum-processing (mostly distillative) process. Technically, a distinction is made between atmospheric residue ( long residue , sump of the atmospheric column ), vacuum residue ( short residue , sump of the vacuum column ), Visbroken residue (sump from the atmospheric Visbreaker column) or flashed Visbroken residue (vacuum residue from the vacuum column of a Visbreaker) . Nowadays, cracked vacuum residues are mainly used for economic reasons . All of these components contain the “heaviest” constituents of petroleum, the so-called asphaltenes , highly condensed aromatic compounds , some of which are complexed with metals . These compounds are responsible for the black color of these heavy oils.

Such residues have high viscosities (300 to 30,000 mm² / s at 100 ° C), they are mixed back to the specification viscosity (to specification MFO) with so-called diluents (also called cutter stocks ). Such a mixture is called a blend (of individual components mixed to specification). However, MFO usually only consists of two to three components; In comparison, gasoline may consist of 10 or more components. Anything can be used as a thinner - from kerosene (0.1 mm² / s at 100 ° C) to "Visbreaker vacuum distillate" (Flashed Cracked Distillate, 6 mm² / s at 100 ° C). So-called Light Cycle Oil (LCO), Heavy Cycle Oil (HCO) or slurry from the FCC system are popular. Of course, other specifications - especially the flash point  - have to be taken into account. Therefore, in many cases kerosene fails as a diluent, although it is the best alternative economically (the best “viscosity effect”, therefore low demand for this diluent and - despite its relatively high price - the best economy). The sulfur content of the heavy oil produced is controlled by the choice of crude oil and, if necessary, adjusted by adding high-sulfur residue components.

When using Heavy Cycle Oil or slurry , the fuel can with so-called " Catalyst fines (finely ground" zeolite - Catalyst of FCC ) be contaminated. Fines may not be able to be completely eliminated during the treatment phase on board (old separator system or similar). They are responsible for the abrasion in the fuel transport system and in the engine.


Heavy oil sample, the viscosity required for the operation of engines is only achieved by heating.

The main components of the MFO are above all alkanes , alkenes , cycloalkanes and highly condensed aromatic hydrocarbons ( asphaltenes ) with about 20 to 70 carbon atoms per molecule and a boiling range between 300 ° C and ≈ 700 ° C (the end of boiling of 700 ° C is a calculated Size). In addition, aliphatic and heterocyclic nitrogen and sulfur compounds occur (nitrogen content: 0.5% and more / sulfur content: up to ≈ 6%). All metallic impurities in petroleum, such as nickel , vanadium , sodium and calcium, are concentrated in residual oils . All other properties are given by the specifications.


Heavy oil is available in different qualities. MARPOL 73/78 Annex VI regulates the emission of sulfur combustion products in certain sea areas, which is why even low-sulfur qualities are produced - which deviate from the norm. According to the current version of 2005 for marine fuels, a distinction is made between "Marine Distillate Fuel Oil" (DMX, DMA / MGO = Marine Gasoil, DMB / MDO = Marine Diesel Oil, DMC) and "Marine Residual Fuel Oil" (see Table), whereby the “residual fuels” are heavy oils in the narrower sense (see above). The DMC variety represents a special position: Here, the specifications allow residual oil to be mixed in.

If the ordered specification is not complied with, the ship owner can object to the delivery and, under certain circumstances, have the tanks completely pumped out at the supplier's expense.

The most important specifications limit the density , viscosity , water content and flash point . Further quality characteristics result from the so-called micro carbon residue test (MCR, describes the tendency of the MFO to form coke deposits) and the total sediment potential (TSP) .

  • The density must not exceed the specification limit, otherwise the water separation (see below) no longer works. The limit used to be 0.991 kg / L; new separator technologies allow a density of the heavy oil of up to 1.010 kg / L (types RMK).
  • The viscosity is determined by the technical possibilities of the system (storage temperature, maximum pump viscosity, preheating temperature, eg injection nozzle viscosity). The number after the 3-letter abbreviation describes the viscosity at 50 ° C (for example RMG-380 has a maximum viscosity of 380 mm² / s at 50 ° C).
  • A high water content is economically undesirable and also puts a strain on the separators and the injection system.
  • The flash point is an important safety parameter (see below).
  • Too high an MCR leads to coke deposits on the injection nozzles and in the combustion chamber.
  • The TSP describes the potential of the MFO to form sediments (= deposits of flocculated asphaltenes ) (see processing ). Flocculation leads to stress on the separators and, in extreme cases, to blockage of the entire fuel system.
Marine (Residual) Fuel Oils
parameter unit limit RMA 25 RMB 30 RMD 80 RME 180 RMF 180 RMG 380 RMH 380 RMK 380 RMH 700 RMK 700
(Int. Identifier) IFO 180 IFO 180 IFO 380 IFO 380
Density (15 ° C) kg / L Max 0.960 0.975 0.980 0.991 0.991 0.991 0.991 1.010 0.991 1.010
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
sulfur % ( m / m ) Max 3.5 3.5 4.0 4.5 4.5 4.5 4.5 4.5 4.5 4.5
MCR % (m / m) Max 10 10 14th 15th 20th 18th 22nd 22nd 22nd 22nd
Aluminum + silicon mg / kg Max 25th 40 40 50 60 60 60 60 60 60
Flash point ° C Min 60 60 60 60 60 60 60 60 60 60
Pourpoint , summer ° C Max 6th 24 30th 30th 30th 30th 30th 30th 30th 30th
Pour point , winter ° C Max 0 24 30th 30th 30th 30th 30th 30th 30th 30th
Total Sediment Potential (TSP) % wt Max 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

Quality control

According to the MARPOL regulations (MARPOL 73/78 ANNEX VI), at least one sample (MARPOL sample) must be taken from each fuel delivery at the bunker manifold of the ship to be bunkered. Permissible sampling methods according to MARPOL are:

  1. Sampler adjustable by hand using a valve with continuous dripping,
  2. time-proportional automatic samplers,
  3. Automatic sampler proportional to the flow.

These samplers must work in such a way that a representative sample is produced over the entire bunker process. As a rule, a larger sample is drawn into a special vessel by means of a sampler and this (after the bunker process has been completed) is transferred to four special sample bottles, labeled and sealed by both parties. One of the samples is sent to a testing laboratory. Ideally, the consumption of the new fuel should only begin when the laboratory confirms that the fuel complies with the information on the delivery note (bunker delivery note) and thus with the standard. The fuel supplier receives a sample bottle. The MARPOL sample and the 4th sample, called the commercial sample, remain on board. The MARPOL sample must be kept on board until most of the fuel has been used, but at least 12 months. It is used for control by the authorities of the port states, for example to check the sulfur content. The labels on the sample bottles must always be signed by the lead engineer on board and the supplier. The fuel supplier usually hands over a sample taken from the bunker facility (bunker barge or onshore facility). This is also kept on board.

Processing and environmental aspects

Heavy oil is highly viscous at room temperature (20 ° C) (from about 1,500 to 10,000 mm² / s, depending on the type) with a density of up to 1.010 kg / L (at 15 ° C; thus slightly heavier than water at 4 ° C). In order to make heavy oil pumpable or to keep it pumpable, it must be heated to a storage or pumping temperature of 40 to around 50 ° C. For injection into the engine combustion chamber, MFO is heated to 130 to 140 ° C (corresponds to 8 to 15 mm² / s). Similar values ​​apply to auxiliary boiler operation and boiler operation on steam ships or steam locomotives .

Heavy oil contains up to 2.5% non-flammable components. Normally, the water and then the solid components (fines, sediments from asphaltenes) are removed (settling tank, first prior to combustion separators , filters ), and as waste, so-called mud (engl. Sludge collected) in the tank. Excessive amounts of sludge put a strain on the cleaning systems. In extreme cases, the capacity of the cleaning systems can become a bottleneck factor at high engine loads; this could affect the safety of the ship at sea.

Sludge (the contents of the sludge tanks) can be disposed of in ports for a fee. The remaining oil content contains a certain amount of energy. In the past, Sludge was also dumped at sea to save costs . Lumps of sludge washed up or driven onto beaches still pollute some stretches of beach today.

In 1973 the International Maritime Organization (IMO) put the International Convention for the Prevention of Marine Pollution from Ships (MARPOL) into effect. The convention was fundamentally expanded in 1978; it is commonly referred to as MARPOL 73/78. MARPOL 73/78 has six annexes ANNEX I to ANNEX VI, which regulate the handling of pollutants on ships.

MARPOL 73/78 Annex I regulates the handling of oil-like substances on board ships, in particular the keeping of an oil diary that documents the whereabouts of all oils. The flag states and the port states regularly check compliance with these regulations at short intervals.

The use of heavy fuel oil as a fuel for ship engines is denounced by environmental groups such as NABU . The criticism is directed against the dumping of Sludge and also against the high pollutant emissions in normal operation. The high soot emissions and the sulfur content of the heavy fuel oil are criticized (see table above). For comparison: standard heating oil has a maximum sulfur content of 1 ‰, low-sulfur heating oil a maximum of 0.05 ‰.


The prices for MFO are based in Europe on the Rotterdam market, internationally also on the market prices in Houston , Fujairah and Singapore . Various types are noted, for example BUNKER 380 CST (corresponds to RMG 380). The grades are traded in US dollars per 1000 kg (US $ / t). Various publications report (sometimes daily) on current trading prices and volumes, for example Platts and ICIS . The price is understood, at least in Rotterdam, as: "delivered in ship". A precise definition of the various quotations can be found at Platts. Seagoing ships use MFO as fuel for their main propulsion; the price rose from around US $ 200 / t in spring 2005 to over US $ 700 / t in July 2008. In Rotterdam on June 19, 2013, 1 t IFO380 $ 595, IFO $ 180 618, MGO $ 894. The high fuel prices and the weak demand for goods due to the global economic crisis meant that ships often travel at reduced speed in order to save fuel ( slow steaming ). A reduction in cruising speed from 25 to 20  knots, for example, can reduce consumption by around 50% (depending on the shape of the hull , the amount of fouling on the hull , trim of the ship, etc.).

supply and demand

Although the oil industry in Germany, for example , has significantly reduced the proportion of heavy fuel oil in the product portfolio thanks to modern refinery technologies ( e.g. delayed coker , flue gas desulphurization ), MFO is enjoying increased demand due to the sharp increase in international trade flows and the associated shipping. Also because of the strongly increasing demand of the People's Republic of China , a decrease in heavy oil combustion is not to be expected, but rather an increase. The supply can actually only be controlled via the choice of crude oil (processing of “heavier” crude oils).

Illegal admixtures are observed. For example, residues from plastics production or used oils can be added. This saves the perpetrators disposal costs and also earns money from the sale. The admixtures often lead to problems with the on-board fuel cleaning.

See also

Web links

Individual evidence

  1. a b c d e f g h i ExxonMobil Residual Marine Fuel Oil (RMFO), Product Description , accessed March 7, 2019.
  2. a b BP: MSDS Fuel Oil, residual
  3. epa.gov: In-Use Marine Diesel Fuel (EPA420-R-99-027, August 1999) (PDF; 66 kB).
  4. Note: Organic liquids expand significantly more than water. Oil with a density of 1.010 kg / L at 15 ° C can become lighter when heated than water at the same temperature. In addition, water can increase its density due to dissolved salt content.
  5. "Dino of the year 2011" for AIDA and TUI Cruises - Out of greed for profit, cruise ships use poisonous heavy fuel oil , press release of the Naturschutzbund dated December 28, 2011, accessed on January 2, 2012.
  6. nabu.de: I stink! - NABU campaign for clean cruise shipping , background paper from August 15, 2012 (pdf, 9 pages; 337 kB).
  7. ^ Price assessment methodologies. In: platts.com. Retrieved January 6, 2018 .