Thermal and hydraulic effects of coke deposit in hydrocarbon pyrolysis process

Nicolas Gascoin (1) , Grégory Abraham (1) , Philippe Gillard (1)

1 PRISME - Laboratoire Pluridisciplinaire de Recherche en Ingénierie des Systèmes, Mécanique et Energétique

Fuel pyrolysis can be of benefit for regenerative cooling techniques due to its endothermic effect in ensuring the thermal resistance of hypersonic vehicles and structures. Among pyrolysis species production, there is that of coke formation. A numerical code is used in this paper to investigate the related phenomena, based on two experiments using Titanium (Ti) and Stainless Steel (SS) reactors, which present different pyrolysis rates under similar operating conditions.. The absence of effect of the reactor's physical properties on the pyrolysis is demonstrated. The thermal insulation effect by coke deposit is proved to have a negligible impact on the system. The clogging of the reactor found experimentally is confirmed numerically at the same time. The carbon deposit thickness reaches the value of the reactor's inner radius: 2.175 mm. The corresponding reduction of flow cross-section modifies the Reynolds number, the residence time (decreased by a factor of 4) and the absorbed energy (reduction by a factor of 3). This last point is responsible for the discrepancies observed experimentally. The coke sticks to the SS reactor and not to the Ti reactor. Consequently, pyrolysis is lower for the SS case than for the Ti case under similar furnace temperature setups.

Domaines: Chimie analytique

Nicolas Gascoin, Grégory Abraham, Philippe Gillard. Thermal and hydraulic effects of coke deposit in hydrocarbon pyrolysis process. Journal of Thermophysics and Heat Transfer, 2012, 26 (1), pp.57-65. ⟨hal-00868686⟩