Abstract
Asphaltene aggregation and precipitation are one of the major issues for marine low-sulfur fuel oil used on board. Many research studies have been carried out to investigate the aggregation behavior of asphaltene under different conditions, but the mechanism of asphaltene aggregation in low-sulfur fuel oil at the molecular level is still unclear. In this work, molecular dynamics (MD) simulations were performed to calculate the solubility parameters, intermolecular interaction energies, and radial distribution function (RDF) curves of each component in marine low-sulfur fuel oil to examine their mutual compatibility. Simulation results indicate that the solubility parameter of resin gains the highest value and it is close to asphaltene. The solubility parameters of aromatic, hexadecane, and saturate decrease successively. The interaction energy between resin and asphaltene molecules is higher than that between the same kind of molecules, which means that resin can inhibit the aggregation of asphaltene molecules. Typically, a light distillate component (hexadecane) is added to heavy fuel oil to yield low-sulfur oil, and our calculations reveal that this has a negative effect on asphaltene aggregation. Specifically, asphaltene is more likely to self-aggregate, as shown by the increase in peak height in the radial distribution function of the asphaltene-asphaltene pair. The findings of this study will provide theoretical support for the production of marine low-sulfur fuel.
Highlights
With the increasingly stringent requirements on global environmental protection, many countries have imposed strict restrictions on the sulfur content of marine fuel oil
According to the latest requirements made by the International Maritime Organization (IMO), from the beginning of January 1, 2020, all ocean-going vessels that do not equip with desulfurization equipment must use low-sulfur fuel oil with a sulfur content of no more than 0.5% (w/w) [1,2,3,4]
A low-viscosity residue or light distillate oil is added to reduce the fuel oil viscosity and improve the combustion performance [27, 28]. erefore, hexadecane (C16) was used as a representative compound for the light distillate. e SARA molecules chosen are based on existing studies of the components of vacuum residue (VR) [3, 29], and molecular structures of the five compounds chosen to represent saturate, aromatic, and resin molecules are shown in Figure 2. e molecular models were built according to the protype developed by G&D [30]
Summary
With the increasingly stringent requirements on global environmental protection, many countries have imposed strict restrictions on the sulfur content of marine fuel oil. Rogel et al [19] studied the asphaltene aggregation behavior in the crude oil and calculated the solubility parameters of different asphaltene models by molecular dynamics simulations.
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