The Effect of Chemical Composition of Coal-Based Jet Fuels on the Deposit Tendency and Morphology

Abstract

The formation of carbonaceous deposits on metal surfaces in fuel systems is a major concern for the development of advanced aircraft. This study examines the thermal stability behavior and carbon deposition and morphology of carbon deposits of thermally stressed coal-based jet fuels. These materials consisted of hydrotreated 1:1, 2:1, and 3:1 blends of refined chemical oil (RCO) with light cycle oil (LCO). Reactions were carried out in a thermal stressing reactor on an Inconel 718 surface at a 470 °C fuel temperature. Chemical compositions of jet fuel samples were determined using gas chromatography−mass spectrometry. In this work, it was found that jet fuels containing low amounts of sulfur and nitrogen and higher amounts of decalins and saturated cyclics gave lower carbon depositions at 470 °C. The quantity of carbon deposits formed was found to be independent of the RCO/LCO ratio. The morphology of carbon deposits and chemical composition were also examined. The RCO/LCO ratio in the blend changed the deposit nature and deposit surface coverage. It was also observed that, if two fuels have very similar chemical compositions but different sulfur and nitrogen concentrations, the carbon deposit surface coverage or deposit growth was different.

Effect of the Reaction Temperature and Fuel Treatment on the Deposit Formation of Jet Fuels

“…Inconel 718 was obtained from Goodfellow Metals Ltd. (Cambridge, U.K.). The nominal composition of Inconel 718 alloy has been reported . Strips were cut and rinsed in acetone prior to use.…”

“…The total amount of carbon deposit on Inconel strips was determined using a LECO RC-412 multiphase carbon analyzer. Conventionally, the LECO RC-412 instrument has been used to measure the amount of deposition on metal surfaces. ,, In the carbon analyzer, carbon in the deposit was oxidized to carbon dioxide by the reaction with ultra high purity (UHP) O 2 over a CuO catalyst bed. The product CO 2 was quantitatively measured by a calibrated infrared detector as a function of the temperature in the furnace.…”

“…The mechanistic understanding of these thermal reactions at the molecular level is made very difficult because of the complex structure of fuels. Naphthene-rich coal-based jet fuels have been shown to be more thermally stable than their petroleum-derived counterparts. , Studies involving model compounds, mixtures of model compounds, and authentic fuels have shown that the desired stability can be provided from high concentrations of cycloalkanes, which have excellent resistance to pyrolytic degradation, and hydroaromatics, which interrupt the degradation process by capping nascent free radicals. – Many studies have been carried out with light hydrocarbons – and real coal-based jet fuel ,– candidates to understand the mechanism of carbon formation on metals or to understand the relationship between chemical composition and carbon deposit.…”

Thermal stability and decomposition of diesel fuel under subcritical and supercritical conditions

“…Other studies have reported the effects of trace amounts of sulfur and nitrogen compounds and other contaminants such as metals [35,36], because these elements were found in large concentrations in deposits compared to fresh fuels [25]. A recent study reported that nitrogen and sulfur compounds were presented only in the liquid-phase product, but not in the solid phase deposits, and indicated that they did not aggregate during solid formation [34].…”

A review of upgrading heavy oils with supercritical fluids

“…Additionally, the present upgrading processes in industry mainly aim at the cracking of a certain range of boiling points of heavy oils and the processes have to be carried out in a set of complex and expensive multi-stage reactors. [6][7][8] Therefore, several new technologies should be developed to convert the heavy and extraheavy oils into light products efficiently and environmentally.…”