Modelling and understanding deposit formation of hydrocarbon fuels from the coke characteristics

Abstract

Coking during the hydrocarbon fuel pyrolysis is a key problem that needs to be considered. To get more insights into coke, this work explored deposit formation of hydrocarbon fuels from the coke characteristics. Pyrolytic deposition experiments of n-decane and HF-01 were experimentally performed by using electric heating stainless steel and TiN-coated tubes to investigate the different growth pathway of coke. The morphology, graphitization degree and mass of coke produced under different experimental conditions were analyzed by means of scanning electron microscopy, Raman spectroscopy and carbon burn-off method, respectively. Results reveal that the differences in physical properties and reactivity of coke between different tubes are due to the different growth mechanism. The graphitization degree of coke can distinguish the main growth mechanism. It is also found that the low reactive filamentous carbon with ID/IG value below 2.7 produced by metal catalytic coking is the primary cause of pipeline blockage. TiN coating effectively inhibits the production of filamentous carbon, meanwhile, the coking inhibition efficiency can reach above 70%. The simplified coking kinetic models and semi-empirical coke combustion models are established to explore the coke formation and oxidation process. The models are performed to investigate the coke characteristics, for further exploring and understanding intrinsic hydrocarbon fuel pyrolysis coking mechanism.