![]() Table 1 lists commonly used categories of marine fuel oil and mixtures all mixtures including the low sulfur marine fuel oil are still considered HFO. Residual oils are often combined to various degrees with distillates to achieve desired properties for operational and/or environmental performance. In contrast to HFOs, distillates are the petroleum products created through refining crude oil and include diesel, kerosene, naphtha and gas. Marine vessels can use a variety of different fuels for the purpose of propulsion, which are divided into two broad categories: residual oils or distillates. Data available until 2011 for fuel oil sales to the international marine shipping sector reports 207.5 million tonnes total fuel oil sales with HFO accounting for 177.9 million tonnes. Data available until 2007 for global consumption of HFO at the international marine sector reports total fuel oil usages of 200 million tonnes, with HFO consumption accounting for 174 million tonnes. For these two reasons, HFO is the single most widely used engine fuel oil on-board ships. Since the middle of the 19th century, HFO has been used primarily by the shipping industry due to its low cost compared with all other fuel oils, being up to 30% less expensive, as well as the historically lax regulatory requirements for emissions of nitrogen oxides (NO x) and sulfur dioxide (SO 2) by the IMO. Resulting formation of nitric acid (HNO 3) a component of acid rain:ĤNO + 3 O 2 + 2 H 2O → 4HNO 3 Heavy fuel oil use and shipping Given HFO elevated sulfur contamination (maximum of 5% by mass), the combustion reaction results in the formation of sulfur dioxide SO 2 which will eventually lead to the formation of acid rain ( sulfuric acid or H 2SO 4) in the atmosphere. HFO is characterized by a maximum density of 1010 kg/m 3 at 15☌, and a maximum viscosity of 700 mm 2/s (cSt) at 50☌ according to ISO 8217. Being the final remnant of the cracking process, HFO also contains mixtures of the following compounds to various degrees: "paraffins, cycloparaffins, aromatics, olefins, and asphaltenes as well as molecules containing sulfur, oxygen, nitrogen and/or organometals". As a result of the wide compositional spectrum, HFO is defined by processing, physical and final use characteristics. HFOs are blended to achieve certain viscosity and flow characteristics for a given use. The chemical composition of HFO is highly variable due to the fact that HFO is often mixed or blended with cleaner fuels, blending streams can include carbon numbers from C 20 to greater than C 50. Thus, HFO is also commonly referred to as residual fuel oil. HFO consists of the remnants or residual of petroleum sources once the hydrocarbons of higher quality are extracted via processes such as thermal and catalytic cracking. For similar reasons, an HFO ban in Arctic waters is currently being considered. Presently, the use of HFOs is banned as a fuel source for ships travelling in the Antarctic as part of the International Maritime Organization's (IMO) International Code for Ships Operating in Polar Waters (Polar Code). The use and carriage of HFO on-board vessels presents several environmental concerns, namely the risk of oil spill and the emission of toxic compounds and particulates including black carbon. HFO is predominantly used as a fuel source for marine vessel propulsion using marine diesel engines due to its relatively low cost compared to cleaner fuel sources such as distillates. For this reason, HFO is contaminated with several different compounds including aromatics, sulfur, and nitrogen, making emissions upon combustion more polluting compared to other fuel oils. ![]() Also known as bunker fuel, or residual fuel oil, HFO is the result or remnant from the distillation and cracking process of petroleum. ![]() Heavy fuel oil (HFO) is a category of fuel oils of a tar-like consistency. Fuel oils of a tar-like consistency Tar-like consistency of heavy fuel oil ![]()
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