Experimental study of oil yields and properties of light and medium Venezuelan crude oils under steam and steam-propane distillation

Abstract

Six experimental runs were carried out to study the yields for a light crude oil (34.2°API) and an intermediate crude oil (25.1°API) under steam distillation and steam-propane distillation. Yields, were measured at five temperatures, 110, 150, 200, 250, and 300°C at slightly superheated conditions. A propane:steam mass ratio of 5:100 was used for the steam-propane distillation runs. For the 34.2°API crude oil, weight yields are very similar for steam and steam-propane distillation, about 54% weight of original oil. However for the 25.1°API crude oil, weight yield for steam-propane distillation, 63%, is significantly higher than for steam distillation, 42% weight of original oil. The results indicate that propane has a stronger distillation effect on the intermediate oil than on the light oil. This is possibly due to the following reasons: (1) lesser amount of light fractions in the intermediate oil that enhance the separation of components in the oil caused by the concentration gradient, (2) the solvent effect of the propane on paraffinic fractions, these being more abundant in the intermediate than in the light oil, and (3) the propane is inducing a cracking of the oil at the higher temperatures and pressure. The positive effect of propane on distillation of the intermediate oil is also evident from the fact that the residual oil is highly viscous (due most likely to asphaltene precipitation), while lighter fractions have been distilled off.