Surface deposit formation of sulfur compounds in both air-saturated and oxygen-free aviation fuels

Abstract

Trace sulfur compounds in aviation fuel play a key role in the surface deposit formation by aviation fuel. The effects of sulfide and disulfide on the surface deposition of aviation fuel in a horizontal heat exchange tube at temperatures from 20 to 420 °C were studied by adding a certain amount of methyl phenyl sulfide and dibenzyl disulfide (DBDS) to a baseline aviation fuel. The deposition characteristics of each fuel under both air-saturated and oxygen-free conditions were compared to analyze the relationship between sulfur compounds and the oxidation reaction in the formation of deposits. The distribution of the carbon deposition rate in the heat exchange tube was measured, and the morphology and sulfur: carbon ratio of the deposits were obtained using scanning electron microscopy and energy dispersive spectrometry, respectively. The experimental results show that the added sulfur compounds promote oxidative deposition, but sulfur is not transformed into deposits. The high-sulfur deposits appear after the bulk temperature exceeds 250 °C. This indicated that sulfur compounds dominate the deposition pathway in the high-temperature region. A large amount of sulfur-containing deposits is observed in the high-temperature region under both air-saturated and oxygen-free conditions after the DBDS with weak SS and SC bonds is added to the fuel. The presence of a fuel autoxidation reaction can inhibit the formation of sulfur deposits. Sulfur-containing deposits increase significantly after the deoxygenation of fuel.