Effects of endothermic hydrocarbon fuel composition on the pyrolysis and anti-coking performance under supercritical conditions

N-dodecane (C-12) and decahydronaphthalene (DHN) were considered as the model compounds of alkanes and cycloalkanes, respectively. Pyrolysis of C-12, DHN and C-12-DHN binary fuels with different mass ratios of C-12/DHN was performed on a supercritical cracking experimental apparatus equipped with a tubular reactor under supercritical conditions (3.5 MPa and 700 degrees C). The coke amount deposited on the inner surface of the tubular reactor was determined by weight method using an electronic analytical balance with a high measurement precision. Effects of EHF composition on the pyrolysis and anti-coking performance were studied. It was observed that there were reciprocal inhibition and competition effects during the co-pyrolysis of C-12 and DHN. The increasing ratio of C-12/DHN exerted a positive effect on gas yields of EHFs, but hardly on selectivities of H-2 and alkenes (<= C-4). Heat sink of EHFs depended largely on the gas yields representing thermal cracking level. C-12/DHN ratio greatly affected the coke amount and morphologies of EHFs. Proper ratios of alkanes/cycloalkanes for advanced EHFs should not be less than 3/7 in terms of anti-coking performance. Inherent consistency could be obtained among carbon deposition, coking precursors, elements distribution and morphologies of coke. The results could provide a significant guidance on the design and development of advanced EHFs.