Viscosity of fuel oil

Mild (880-920°F) heating at 50-200 psig Reduce viscosity of fuel oil Low conversion (10%) to 430°F Heated coil or drum Delayed coking... 

Purpose to reduce viscosity of fuel oil to acceptable levels Conversion is not a prime purpose... 

FIGURE 6.26 Approximate viscosity of fuel oil at various temperatures. 

Liquid viscosity is usually measured by the amount of time it takes for a given volume of liquid to flow through an orifice. The Saybolt universal viscometer is the most widely used device in the United States for the determination of the viscosity of fuel oils and liquids. It should be stressed that Saybolt viscosities, which are expressed in Saybolt seconds SSU), are not even approximately proportional to absolute viscosities except in the range above 200 SSU hence, converting units fiom Saybolt seconds to other units requires the use of special conversion tables. As the... 

Applied to vacuum residue, its purpose is to reduce the viscosity of the feedstock to a maximum so as to minimize the addition of light diluents for production of fuel-oil for industrial uses. 

Poor vaporization of the fuel will also produce oil dilution. Generally, this fuel will be driven off when the engine becomes warm and is mnning at optimum conditions. However, severe dilution of the oil by fuel could have serious results, as the viscosity of the oil will be reduced to an unacceptable level. 

Residual fuel oils, such as fuel oil no. 4, are manufactured by the addition of blending stocks to distillation residues in order to meet viscosity specifications set by ASTM (LARC 1989). No data were located for the manufacturing process of fuel oil UNSP. 

Crude oil and high-boiling-point, high-viscosity petroleum fractions such as 6 fuel oil, atmospheric tower bottoms, and vacuum gas oil can contain wax which crystallizes at temperatures often above room temperature. It is not unusual for these oils to have base pour points of 100°F (37.8°C) or greater. In order to utilize these heavy oils, the pour point and viscosity of these oils must be reduced. One method which is used to accomplish this is to dilute the heavy oil with lower-viscosity components such as diesel fuel or kerosene. The oil then becomes pumpable at lower temperatures. 

In a diesel engine the contamination comes from the above and additional sources such as (a) soot as a normal by-product of diesel engine will increase the viscosity of the oil and become abrasive as its level increases in the oil (b) the fuel dilution will reduce the film strength of the oil to a point where accelerated wear occurs (c) the fuel dilution will reduce the flash-point of the oil (d) a diesel engine oil will also be exposed to the formation of acid from the sulfurized fuel max.5% a diesel engine will have a high TBN to assist it in combating the acid formation. 

However, conversion from light to heavy fuel cannot be accomplished without regard for the deleterious effect the use of a residual quality or coal-derived fuel oil would have on combustion eflBciency, pollutant emissions, and engine operational costs. That is, the extent of fuel atomization required for eflBcient combustion in gas turbine and similar combustion devices cannot be achieved if a high-viscosity heavy fuel oil is simply substituted for a lighter oil. Furthermore, the required atomization cannot be realized easily by modifying the configuration of the fuel injector because injectors compatible with current or currently... 

Diebold, J.P. and Czernik, S., Additives to Lower and Stabilize the Viscosity of Pyrolysis Oils during Storage, Energy Fuels, (1997), 11,1081-1091. 

Although the pour point test is still included in many specifications, it is not designated for high-boiling fuel oil (ASTM D 396). In fact, although the failure to flow at the pour point normally is attributed to the separation of wax from the fuel oil (in the case of waxy crude oil precursors), it also can be due to the effect of the viscosity of the fuel oil (in the case of naphthenic crude oil precursors). In addition, the pour point of fuel oil may be influenced by the previous thermal history of the fuel oil. Thus the usefulness of the pour point test in relation to fuel oil, especially residual fuel oil, may be open to question. 

Problems of handling and storage may also arise, particularly with higher-boiling fuel oil, because at ambient temperatures this type of fuel oil may be viscous and even approach a semisolid state. Although such fuel oil is usually stored in heated tanks, test methods to determine the low-temperature behavior of the fuel oil are necessary. In addition, because viscous or semisolid fuel oil should be preheated to obtain the correct injection (atomizing) conditions for efficient combustion, test methods that describe viscosity are also necessary. 

Types - There are two basic types of fuel oil distillate fuel oil (lighter, thinner, better for cold-start) and residual fuel oil (heavier, thicker, more powerful, better lubrication). Often, some distillate is added to residual fuel oil to get a desired viscosity. They are only used for industrial and marine applications because, although fuel oil is cheaper than diesel oil, it is more difficult to handle it must be settled, pre-heated and filtered, and leave a sludge at the bottom of the tanks. Notice that sometimes, particularly in the USA, the term "fuel oil" also includes diesel and kerosene. 

Two properties of fluids influence the way fluids behave. They are density and viscosity. Most gases have a relatively low density and low viscosities. On the other hand liquids can display a range of densities and viscosities, for instance the density and viscosity of light organic liquids are relatively low, but other liquids such as mercury have a high density and liquids with a high viscosity include fuel oils and treacle. 

Maximum lump size allowed (big lumps of rock phosphate will take more time/consume more power for crushing and grinding in fertiliser plant). Minimum pour points and maximum viscosity (for ease of storage and handling of fuel oils) shall not be beyond the specified values. This is required for smooth handling of the oils in the plant. 

Biodiesel has similar properties to the diesel fuel that is produced from petroleum, and it can be burned in any vehicle with a diesel engine or in furnaces that burn diesel fuel. It should be noted that vegetable oil can also be burned as a fuel, but because the viscosity of vegetable oil is somewhat greater than diesel fuel, engines must be modified in order to bum vegetable oil. 

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