Study On Coke Inhibition Techinques In Pyrolysis Of Endothemic Fuels Under Supercritical Conditions

Carbon deposition from jet fuel on metal surfaces will create problems for the operation of future aircraft. A set of continuous flow reactor which simulates engine system in hypersonic aircraft was set up to evaluate coke formation from thermal cracking of jet fuel RP-3 under supercritical conditions and three methods suppressing deposits build up. Solid deposits collected on the substrates were examined by scanning electron microscopy(SEM), energy-dispersive X-ray spectroscopy(EDS), and temperature programmed oxidation(TPO) and cracking products was analyzed.There are three different species including chemisorbed carbon, amorphous carbon and filamentous coke in the solid deposits which forming from thermal cracking of RP-3 jet fuel; Beyond 90% of coke deposits are carried away by supercritical fluid which have highly capabilities of extraction for coke precursors and dissolution for coke deposits. Coke formation results carburetion on alloy.The coke inhibitor, dibenzyldiselenides, could suppress filamentous coke by forming thermal stable M2Se over the stainless steel surface at the higher temperature. It is found that with the addition of 100ppm dibenzyl diselenides the total coke deposits were reduced by 49.6%, and yields of gas was reduced by 20% without significant composition variation change. The passivation of metal surface could suppress filamentous coke by forming passivation film. Beyond 98% of coke deposits was decreased and influence of temperature to coke formation are weakened by surface passivation, which the ability of coke inhibition are durative; The distribution of gas products produced from passive reactor was not changed , but the 14.47% of gas yields was decreased by passive film. Hydrogen donors, BzOH was added into fuel while reactor metal surface was passived to suppress amorphous carbon and filamentous coke synchronously. Comparation to the passivation film, the addition of 0.5% BzOH could reduce the 15% of coke deposition amounts and the yields of gas was reduced by 16% without significant composition variation change. The three coke inhibition methods discussed above all suppressed the coke precursors forming.