Hydrocarbons flash point estimation

A further approach to estimating flash points of mixed hydrocarbons is to sum volume fraction weighted flashing indexes which are calculated directly from the flash points of the individual components (5). Blend flash points estimated by the latter two methods generally agreed with experimental values within the limits of reproducibility of experimental data. 

The measurement of the vapor pressure and flash point of crude oils enables the light hydrocarbon content to be estimated. 

An early approach to predicting TCC flash points for hydrocarbon mixtures used this concept by estimating flash point as the temperature at which mixture vapor pressure reached about 10 mm Hg (3). Other workers (4) have found both the product of vapor pressure at the flash point and molecular weight to be constant for a number of hydrocarbon fractions. The TCC flash point for hydrocarbon blends was predicted as the temperature at which... 

When handling solvent-laden air, as is common in activated charcoal recovery plants, it is normal to operate with a flammable solvent content in the range of 25-40% of LEL. If information on the flash point of a mixture is not available the great majority of solvents have an LEL of 10,000 ppm (1%) with a few In the range of 7000-10,000 ppm. The flash point of straight run hydrocarbon solvents (e.g. white spirit) can be estimated from their initial boiling point (IBP)... 

For hydrocarbon solvents such as white spirit (mineral spirits), which are not single pure materials, the flash point can be estimated from the initial boiling point (IBP) temperature ... 

Feed analyses in terms of component concentrations are usually not available for complex hydrocarbon mixtures with a final normal boihng point above about 38°C (100°F) (/i-pentane). One method of haudhug such a feed is to break it down into pseudo components (narrow-boihng fractions) and then estimate the mole fraction and value for each such component. Edmister [2nd. Eng. Chem., 47,1685 (1955)] and Maxwell (Data Book on Hydrocarbons, Van Nostrand, Princeton, N.J., 1958) give charts that are useful for this estimation. Once values are available, the calculation proceeds as described above for multicomponent mixtures. Another approach to complex mixtures is to obtain an American Society for Testing and Materials (ASTM) or true-boihng point (TBP) cui ve for the mixture and then use empirical correlations to con-strucl the atmospheric-pressure eqiiihbrium-flash cui ve (EF 0, which can then be corrected to the desired operating pressure. A discussion of this method and the necessary charts are presented in a later subsection entitled Tetroleum and Complex-Mixture Distillation. ... 

Now, the ways in which one can define yields and, hence, the overall material balance are to be considered. It should be remembered that, to this point, the hydrocarbon vapor leaving the flash zone and the overflash have been calculated. Thus, the total distillate yield is known. In discussing the various ways for estimating yields, the following terminology will be used. F ure 2 r4 illustrates the physical significance of these terms. 

Since this draw tray is a chimney tray and performs no fractionation, the temperature of the condensed liquid leaving the tray is estimated as being the dew point of the hydrocarbon vapor from the flash zone at the hydrocarbon partial pressure above the draw tray, the leakage air and the bottoms ste being defined as inerts. The temperature at this pressure is read from the vacuum region EFV curves. The vapor temperature leaving the grid is estimated in the same way but referred to the total pressure at that point. 

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