Surrogate Generation and Evaluation for Biodiesel and Its Mixtures with Fossil Diesel

Abstract

In this paper a precedently developed surrogate optimization algorithm for fossil fuels, which originally allowed simultaneous fitting of the true boiling point (TBP) curve, the liquid density at 15 °C, and the cetane number, is refined toward its application to biodiesel and its mixtures with fossil diesel. For this purpose, the algorithm is extended (1) to also include fitting of the kinematic viscosity at 40 °C and (2) to account for peculiarities of biodiesel concerning its narrow boiling range and compensation of systematic errors of measured boiling curves. To illustrate these improvements, first, the algorithm is applied to property estimation and surrogate optimization of three different biodiesel fuels, for which surrogates consisting of one to three components are proposed. Second, a surrogate for a commercial European fossil diesel is calculated and produced in lab-scale. Finally, the algorithm is used for surrogate optimization and property estimation of mixtures of biodiesel and fossil diesel, considering fractions of biodiesel of 7% and 20% per volume. It is shown that the improved algorithm is capable of reliably optimizing surrogates for fuels containing both biogenic and fossil components.

Optimization of formulation for surrogate fuels for diesel–biodiesel mixtures

“…This property, as defined by ASTM D4052, is introduced into the objective function so that the density of the optimized surrogate is as close as possible to the density of the target fuel. The density of a liquid mixture of n components was estimated as follows [21]:…”

“…ASTM D445 is used to determine the kinematic viscosity at 40 °C. The kinematic viscosity was calculated as follows [21]:…”

“…Concerning the nature of the surrogate components, Reiter et al [21] proposed four alternative fuels to emulate fossil diesel properties, with eight to ten components and three components from the composition of our optimized surrogate were present in their surrogates: Isocetane, 1-methylnaphthalene and n-eicosane.…”

“…Several fuels have been successfully imitated: diesel, gasoline, jet fuel as well as biofuels [1,19,20] and their usual blends with fossil fuels, such as gasoline-bioethanol and diesel-biodiesel [19,21]. However, little work has focused on diesel-biodiesel blends over a wide range of blended percentages.…”

“…The chemical nature of surrogates also varied depending on the studied target fuel or studied blends and generally consists of n-alkane, isoalkanes, aromatics and cycloalkanes [18,22]. For the surrogates that emulate biofuels and their blends with fossil fuels, in addition to these hydrocarbons, esters and oxygenates have often been used [19,21] In order to reproduce a fossil diesel in mixtures at different proportions with biodiesel, which was prepared by a transesterification reaction of local cooking oil wastes, in this work it is proposed to optimize a surrogate fuel considering density, viscosity and cetane number as the target properties. It is aimed at reproducing as closely as possible these properties of diesel, biodiesel and mixtures of the two fuels considering a large range in molar biodiesel percentages, namely 5%, 10%, 20%, 50% and 80%.…”