Residual fuel components

Residues may also be processed by removing carbon. These processes include deasphalting and coking, which produce usable liquid fuel components while rejecting a carbon-rich phase (asphalt or coke). 

The residuum from vacuum distillation became, and still is, the basic component of residual fuel oil. It contains the heaviest fraction of the crude, including all the ash and asphaltenes. It is extremely high in viscosity and must be diluted with light distillate flux (a low viscosity distillate or residual fraction which is blended with a high viscosity residual fraction to yield a fuel in the desired viscosity range) to reach residual fuel viscosity. The lowest value distillates, usually cracked stocks, are used as flux. In some cases the vacuum residuum is visbroken to reduce its viscosity so that it requires less distillate flux. 

Residual fuel oil is generally more complex than distillate fuels in composition and impurities. Limited data are available, but there are indications that the composition of No. 6 fuel oil includes (volume basis) aromatics (25%), paraffins (15%), naphthenes (45%), and nonhydrocarbon compounds (15%). Polynuclear aromatic hydrocarbons and their alkyl derivatives and metals are important hazardous and persistent components of No. 6 fuel oil. 

In naphtha and light distillate components, oxygen-containing compounds appear as carboxylic acids and phenols. Most of these compounds concentrate in the kerosene, fuel oil, and lighter lubricant fractions. Straight-run gasoline, heavy distillates, and residual fuels usually contain few acids. 

Marine residual fuels bunker fuel oil Grades ISO RMA through RML marine residual fuel and bunker fuel are blended from components such as atmospheric resid, vacuum resid, visbreaker resid, FCC bottoms, low-grade distillate, and cracked components. Bunker fuel has a maximum viscosity of 550 cSt 122°F (50°C), density of 0.990 g/cc, and sediment of 0.1 wt%. ISO marine fuel oil viscosities range from 10 to 55 cSt 212°F (100°C). These fuels are used in slow-speed diesel engines and boilers. 

Fuel asphaltenes, resins, and other heavy compounds can build up as residues on engine components after evaporation and burning away of the more volatile fuel components. These residues can accumulate as deposits which may interfere with heat transfer, lubrication, and efficient fuel combustion. 

Marine fuel sulfur can range from 1.5 wt% for DMA to as high as 5.0% for RME and higher-viscosity grades of marine residual fuel. Problems related to sulfur include high SOx emissions and the formation of sulfuric and other acids within the fuel combustion system. At low temperatures, the formation and condensation of acids within the combustion chamber can result in corrosion and wear of metal system components. 

Residual fuel oils and heavy marine fuels are composed of high-boiling-petroleum fractions, gas oils and cracked components. Residual and clarified oil streams from the FCC process can contain degraded alumina/silica catalyst fines. These 20- to 70-micron-diameter fines are known to contribute to a variety of problems in fuel injection and combustion systems. In marine engines, excessive injector pump wear, piston ring wear, and cylinder wall wear can all be due to the abrasive action of catalyst fines on these fuel system parts. 

The amount of carbon present in fuel components can be correlated with a tendency to form deposits in fuel systems. Although the use of various detergent and dispersant additives helps to minimize deposit formation, the carbon residue value is still quite useful. 

Prevent copper-catalyzed oxidation of fuel components. Copper ions can act as catalysts to initiate the rapid oxidation and degradation of fuel components. The result of this rapid oxidation will be a darkened, viscous fuel residue. 

During the processing of fuels and fuel components, solutions of sodium hydroxide or potassium hydroxide may be used. These caustic solutions can react with phenols, mercaptans, and naphthenic acids to form water-soluble salts. As a result, these undesirable components are removed from the fuel as the caustic separates from the fuel. Further water washing can be performed to clear the fuel of residual caustic and salts. 

An increase in the concentration of high-boiling-point components in fuel can enhance combustion chamber deposits high-end-point fuel high D-86 residue fuel... 

Increased problems of deposit formation and corrosion are encountered in industrial gas turbines such as those used in electric power generation and locomotives. Here, residual fuel oil must be used for economic reasons. Ash may deposit and tend to choke the gas turbine, thereby reducing volumetric efficiency. Moreover, vanadium and sodium, two common ash components, cause severe corrosion of super alloys at the high temperatures prevailing in gas turbines. Sulfur content is also significant, because the metal sulfates that form are much lower in melting point than the corresponding oxides and thereby contribute to deposit formation (17). 

Petroleum-derived butanol is currently used in food and cosmetic industries as an extractant (11), but there are concerns about its carcinogenic aspects associated with the residual petroleum components. Many new uses will occur in these fields as "green" butanol becomes available to the market. Other uses include current industrial applications in solvents, rubber monomers, and break fluids. Butanol has the propensity to solve some infrastructure problems associated with fuel cell use. Dispersed through existing pipelines and filling stations and then reformed onboard the fuel cell vehicle, butanol offers a safer fuel with more hydrogen. 

The residue from crude distillation in North America is usually processed to an asphalt product as much as possible, since as a component of residual fuel oils it generally fetches a lower price than as asphalt itself. The residual fuel oil market is quite competitive since ships and tankers can choose to load at centers, which offer the lowest cost fuels. Also the price of the heavier grades of bunker fuel used to supply power stations has to be comparable to coal to be competitive. 

Figure 13.15 shows Ogi for various aerosol chemical components. Elements present in the primary emissions include the metals, silicon, and black carbon (BC). Among the primary aerosol emission sources are automotive emissions and tire wear, residual fuel oil combustion, crustal materials, and the marine aerosol. Despite the variety of primary emission sources, values of a,- fell within a narrow band, 1.8.5 0.14. Similar results were obtained for data. sets at other Los Angeles sites. Thus variations in the ambient... 

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