The first thinking when processing heavy oils is not to use either a preflash drum or apreflash tower, as the amount of light hydrocarbons (combustible gas, LPG and lightnaphtha) tends to be very low. With this configuration it is necessary to preventvaporization along the preheating train and before the atmospheric furnace pass inletvalves. On the other hand, two aspects appear related to heavy oil processing. The firstone is that desalting is more difficult, requiring higher temperatures. Desalted crude watercontent is higher due to the effect of higher water solubility, higher content of surfactants,and higher conductivity among other effects that lower desalting efficiency. The second oneis that very high inlet atmospheric furnace temperature can be achieved due to greaterheavy products yields and the use of pinch technology to reduce energy consumption. Theresult of the combination of high temperature and higher salty water content in the desaltedcrude is a necessity of a very high operating pressure to prevent vaporization andsometimes a special metallurgy. In some cases it would be required even to changeequipment and piping to a more expensive pressure class. Thus, as a consequence, onesolution is to use a configuration with a preflash drum to allow the vaporization of the waterand some amount of light hydrocarbons, reducing the vapor pressure at the furnace inlet,and eliminating any aqueous phase at the preheating trains after desalters. In this paper, acase study of a grass-roots refinery design having a 16 °API gravity feedstock will bepresented. Some different oil and water mixtures had those vapor pressures studied usingprocess simulators and compared with PVT cell experimental results.
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