Sharif Digital Repository

Supercritical fluid extraction (SFE) is a relatively new separation technique that has received much attention in recent years. This process is an alternative to distillation or liquid extraction. Its main advantage over the conventional ones is that the dissolved extract may be completely separated from the supercritical fluid simply by decreasing the pressure. In recent years considerable effort has been devoted to the measurement of equilibrium solubility data for solids in supercritical fluids. A coal tar distillate, anthracene oil, which contains 34.46 mass-% phenanthrene, 33.8 mass-% anthracene, 13.89 mass-% carbazole and other impurities, was used as the model mixture. In this study,... 

A new generalized and non-group contribution method has been developed to predict critical temperature (Tc), critical pressure (Pc), critical volume (Vc) and acentric factor (ω) for pure substances and petroleum fractions based on two types of input parameters. This method can take either refractive index and molecular weight or refractive index and normal boiling point as its input. Since refractive index cannot be obtained for an unknown mixture (petroleum fraction), in order to apply the proposed method for petroleum fractions, refractive index is converted to mass density at 293K using the one-third rule. Moreover, the proposed correlation is capable of predicting the properties using... 

A large variety of modifications have been presented for the temperature dependent function (α) existing in the attractive term of cubic equations of state (CEOS). Most of α-functions attempted to modify the vapor pressure prediction of polar components while other modifications have focused on both polar and non-polar compounds and other relations have considered an expansion of polynomials in the acentric factor (ω) and reduced temperature (Tr) to predict vapor pressure more accurately. In most cases such as Soave and Peng-Robinson equations of state, the suggested α-functions do not show a limiting behavior when temperature increases infinitely. In addition, the incompetency of many... 

In this work, PC-SAFT, an equation of state based on perturbation theory, is applied to predict the reservoir fluids phase behavior. PC-SAFT parameters for pure components have previously been assessed, but they cannot be determined for petroleum fractions with unspecified components and composition. In order to remove this difficulty and making use of PC-SAFT model in the reservoir fluids simulations, a new approach is studied which leads to appearing generalized correlations for the estimation of PC-SAFT parameters for petroleum cuts and plus fractions using only their molecular weight and specific gravity, without the essential need for the characterization of petroleum fractions in... 

This paper experimentally investigates the influence of hydrogen enrichment on the combustion and emission characteristics of a diesel HCCI engine using a modified Cooperative Fuel Research (CFR) engine. Three fuels, n-heptane and two middle distillates with cetane numbers of 46.6 and 36.6, are studied. The results show that hydrogen enrichment retards the combustion phasing and reduces the combustion duration of a diesel HCCI engine. Besides, hydrogen enrichment increases the power output and fuel conversion efficiency, and improves the combustion stability. However, hydrogen enrichment may narrow the operational compression ratio range and increase the knocking tendency. Both the overall...