Impacts of oxygenated compounds concentration on sooting propensities and soot oxidative reactivity: Application to Diesel and Biodiesel surrogates

Abstract

The aim of this paper is to evaluate the effect of the oxygenated compounds concentration on sooting propensities of Diesel and Biodiesel surrogates and to investigate the oxidative reactivity of soot obtained by combustion of these surrogates using an atmospheric axisymmetric co-flow diffusion flame burner. Methyl decanoate (MD) concentrations from 3 to 30 % (in mole %) are added to a Diesel surrogate made up of a binary mixture of 70 % of n-decane and 30 % of α-methylnaphthalene (α-MN). The sooting propensities of these mixtures are estimated through the Yield Sooting Indices (YSIs) in methane diffusion flames doped with 35,000 ppm of surrogate vapors. The characteristics of the soot volume fraction are extracted using the light extinction method (LEM). Additionally, soot generated from the combustion of the model Diesel and Biodiesel fuels were collected, sampled and characterized using physico-chemical techniques. MD addition is found to reduce sooting tendencies. This decrease is more pronounced when the concentration of oxygenate additives increases. On another side, the oxidative reactivity of soot generated from the diffusion flame burner is found to decrease when the Biodiesel percentage increases. Furthermore, soot generated from the combustion of Diesel and Biodiesel surrogates exhibited different behaviors. Biodiesel-derived soot particles were smaller and less reactive than Diesel-derived ones, the latter displaying less ordered graphite-like structures and higher amorphous carbon concentration.

Potassium and soot interaction in fast biomass pyrolysis at high temperatures

“…All soot samples based on the A D1 /A G ratios exhibited a common structure of amorphous carbon and nano-crystalline graphite, as discussed by Ferrari and Robertson [35]. In addition, the alfalfa straw soot contained a higher fraction of distorted small PAH clusters within the amorphous carbon than other soot samples, as observed experimentally by Abboud et al [36]. The average extensions of graphene stacks (L a ) from the Raman bands in beechwood, wheat straw, alfalfa straw and leached wheat straw soot were lower than those of pinewood and washed soot from wheat straw.…”

Effects of Camphor Oil Addition to Diesel on the Nanostructures and Oxidative Reactivity of Combustion-Generated Soot

“…The activation energies for soot and carbon black are found in the range of 130-200 kJ/mol in the literature [55]. For commonly used palm oil-derived biodiesel blended fuels, which contain two oxygen atoms per molecule of methyl ester, (i.e., a high concentration of fuel-bound oxygen), the activation energy for soot oxidation is reported to be relatively lower in the range of 100-150 kJ/mol [54,56]. Such oxygen-rich fuel blends are reported to produce soots with high O/C ratio, and the subsequent decomposition of strongly bound oxygenated functional groups on soot to CO and CO2 (especially above 400 oC) is known to enhance the soot oxidation rate [57,58].…”

Experimental and numerical study on soot formation in laminar diffusion flames of biodiesels and methyl esters

“…Abboud et al [5] evaluated the soot reduction effect of the addition of methyl decanoate (MD), a biodiesel surrogatem to diesel in coflow diffusion flames. A similar method was used by Gao et al [6] to investigate the chemical mechanism and soot reduction effects of dibutyl ether (DBE) in addition to MD.…”

“…These studies have expanded the understanding of soot formation and properties in pre-vapourised diffusion flames with biodiesel and MEs. In all previous studies cited above, the fuel was diluted with N 2 [6][7][8][9][10] or argon [5] to improve flame stability during experiments. However, the dilution effect itself may affect the soot formation and yield in these types of flames [11].…”