Study of Polycyclic Aromatic Hydrocarbon formation during acetylene pyrolysis in a jet-stirred-reactor and numerical investigations of residence time distribution using CFD simulations

Abstract

The aim of this study was to understand the formation of PAHs (Polycyclic Aromatic Hydrocarbons) during acetylene pyrolysis. Experiments were carried out with a jet-stirred-reactor in laboratory conditions similar to those used in industrial low-pressure gas carburizing processes (1173 K and 8 kPa). The influence of residence time was studied. At the outlet from the reaction zone, products of pyrolysis were analyzed by gas chromatography (mass detector). A detailed kinetic model was used to describe PAH formation and to validate experimental findings. Differences were found between the experiments and the kinetic model. Several explanations are presented such as a lack of mixing within the reactor. To explain why the reactor’s hydrodynamic characteristics deviate from the perfectly stirred assumption under several operating conditions, such as low-pressure and high temperature, CFD calculations were performed to determine the Residence Time Distribution (RTD) of the gas phase. This deviation is particularly linked to the pressure in the chamber which was not taken into account when constructing the jet-stirred-reactor over the last fifty years.