UNIFAC residual marine fuels stability prediction from NMR and elemental analysis of SARA components

Abstract

This paper focuses on the development of theoretical approaches to predict the stability of very low-sulfur residual marine fuel (VLSFO) and is based on molecular weight, CHNS-, SARA-, NMR analysis, and the UNIFAC model. The main issue of using the UNIFAC model is to determine the group composition of marine fuel components in the UNIFAC representation. According to the data obtained, we developed a method for calculating UNIFAC pseudo-components group composition for residual and distillate petroleum products. The hyperparameters used in this model were the asphaltenes’ heat of fusion and melting point. The melting point was successfully estimated using a regression formula that took into account the molecular weight and C/H ratio. The heat of fusion was calculated using the optimization method. The resulting model makes it possible to estimate the influence of the VLSFO component’s parameters on the shape and position of the metastability line in ternary systems. The reliability of the developed model was confirmed by comparing the calculated and experimental data on the example of the VLSFO sedimentation stability diagram in the system of hydrotreated diesel fuel - catalytic cracking light gasoil - visbreaking residue. Based on the developed model it is possible to predict the stability of the residual marine fuel of a given composition. The application of this model is intended to greatly simplify the development of the stable VLSFO composition that meets the requirements of ISO 8217:2017.