Pour point kerosene

The increase in fuel viscosity with temperature decrease is shown for several fuels in Figure 9. The departure from linearity as temperatures approach the pour point illustrates the non-Newtonian behavior created by wax matrices. The freezing point appears before the curves depart from linearity. It is apparent that the low temperature properties of fuel are closely related to its distillation range as well as to hydrocarbon composition. Wide-cut fuels have lower viscosities and freezing points than kerosenes, whereas heavier fuels used in ground turbines exhibit much higher viscosities and freezing points. 

Pour point ranges from 213 K (—80°F) for some kerosene-type jet fuels to 319 K (115°F) for waxy No. 6 fuel oils. Cloud point (which is not measured on opaque fuels) is typically 3 to 8 K higher than pour point unless the pour has been depressed by additives. Typical petroleum fuels are practically newtonian liqmds between the cloua point and the boiling point and at pressures below 6.9 MPa (1000 psia). 

Other important properties include Hash point, volatility, viscosity, specific gravity, cloud point, pour point, and smoke point. Most of these properties are related directly to the boiling range of the kerosene and are not independently variable. The flash point, an index of fire hazard, measures the readiness of a fuel to ignite when exposed to a flame. It is usually mandated by law or government regulation to be 120° or 130° F (48° or 72° C), Volatility, as measured... 

D low sulfur Very low pour point fuel for use in high-speed engines requiring low-sulfur fuel also, for low-sulfur kerosene applications... 

Kerosene can be utilized effectively to reduce the pour point of most distillate fuels. The dilution limits are often based upon whether kerosene dilution will negatively impact fuel properties such as the viscosity, distillation parameters, sulfur limit, or cetane number. 

As a general rule the pour point of a diesel fuel can usually be reduced by 5°F to 10°F (about 3°C to 5°C) for each 10% of kerosene added. The typical maximum blending volume of kerosene is about 30% by volume. 

The effect of kerosene dilution on the pour point of a typical low-sulfur 2 diesel fuel is demonstrated in FIGURE 4-6. 

FIGURE 4-6. Effect of Kerosene Blending on the Pour Point of Low-Sulfur... 

Lowering the cloud point and pour point values of a distillate fuel can be accomplished by blending the fuel with a low-wax-content distillate stream such as a kerosene or jet fuel. Also, additives are frequently used in conjunction with kerosene blending or as a substitute for kerosene blending to reduce the pour point of diesel fuel. Additives are not as frequently used to reduce the cloud point of diesel fuel. 

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. 

Commercial value of a petroleum liquid can be estimated quickly through measurement of the following physical characteristics . specific gravity, gasoline and kerosene content, sulfur content, asphalt content, pour point, and cloud point. 

Kerosene is the lightest straight fuel oil in the distillate category and has uses, which range from lamp oils, to light stove oils, and diesel fuels for use in Arctic service. Pour points of below —50°C are the attraction of kerosene for low temperature diesel fuel applications. A small addition of lubricating oil stocks is made to diesel fuel in this service. 

Residual Fuel. The residual fuel produced by both the pilot and refinery meets all government specifications for low sulfur, high pour point 6 fuel oil. The residual fuels are in fact very "clean" as shown in Table VIII by the high hydrogen and low sulfur, metals, carbon and asphaltenes content. This stock is better utilized as cat cracker feed than residual fuel, since higher value gasoline and kerosene fuel can be easily produced via catalytic processing. 

Jet fuel is kerosene-based aviation fuel. It is medium distillate used for aviation turbine power units and usually has the same distillation characteristics and flash point as kerosene. Jet fuels are manufactured predominately from straight-run kerosene or kerosene-naphtha blends in the case of wide cut fuels that are produced from the atmospheric distillation of crude oil. Jet fuels are similar in gross composition, with many of the differences in them attributable to additives designed to control some fuel parameters such as freeze and pour point characteristics. For example, the chromatogram (Figure 27.4) of a commercial jet fuel (Jet A) is dominated by GC-resolved n-alkanes in a narrow range of n-C-j to n-Cig with maximum being around n-Ci. The UCM is well dehned. 

The separation of linear and branched alkanes is also of importance in the process known as dewaxing, in which the removal of normal alkanes makes the product hydrocarbon less viscous and reduces the so-called pour point temperature. Such processes can be combined with catalytic isomerisations to optimise the value of oil fractions (Chapter 8). Linear paraffins are also separated using a zeolite-based process from kerosene fractions to give reactants for the synthesis of linear alkylbenzene sulfonate anionic surfactants, which are both cost effective and biodegradable. 

In most cases, the additive depresses the pour point, which delays agglomeration of the wax crystals, but usually has no significant effect on diesel engine performance. A preferred means of improving cold flow is to blend kerosene with the diesel fuel, which lowers the wax appearance point by about 10° C for each 10% increment of kerosene added. 

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