Vapor pressures of liquids increase in the presence of excess high pressure gases. Recent papers on the phase behaviors of high pressure hydrogen and pure hydrocarbon systems were thoroughly investigated and it has been found that within the range of y<0.2, x>0.8 and
Tr<0.9, in other words in case when the assumptions of ideal gas and ideal solution are reasonably valid, the Poynting equation
1) may be used to estimate the vapor pressure of the liquid under high pressure,
Pπ.
Here x and y are the mole fraction of hydrocarbon in the liquid phase and in the gas phase respectively, and
Tr is the reduced temperature of hydrocarbon concerned. The new method of calculation of flash vaporization of petroleum oil in the presence of high pressure hydrogen has been developed.
Supposing that sp. gr. and A.S.T.M. distillation data are available,
1. At the first true boiling point curve of the sample oil is calculated by Edmister's method.
2. Using the normal boiling points and ρ/ω of the paraffin homologous members, the contents of the representative components are estimated.
3. The average molecular volume of each component under pressures between total pressure π and normal vapor pressure
Pn is calculated by Watson's method, using the density ρ and expansion factor ω of each component.
4. The value of
Pπ/Pn of each component is calculated by Poynting equation.
1)5. Solubility of hydrogen in the given sample oil under the given total pressure and at the given temp. is estimated from the literature.
6. Equilibrium flash vaporization constant of each component
Ki under given conditions is calculated by the following equation.
(9)
Here, n
0 is the mole fraction of oil in the liquid phase and can be calculated from the solubility data, and P
0 is the partial pressure of the oil vapor in the vapor phase.
7. Dry points and percentages of vaporization at various temp. can be calculated by equations (11), (12) and (13) (by trial and error method).
8. The results of calculation were plotted in Cox vapor pressure charts and vaporization line charts; Fig. 5 and 6 thus obtained serve well to explain the actual operation of the high pressure hydrogenation plant.
The authors believe that this method of calculation may find wide practical applications in the various high pressure vaporization processes.
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