Temperature optimization in a gas reactor for the synthesis of carbon nanofibers: A numerical approach

Abstract

The synthesis of carbon nanofibers (CNF) in a gas reactor requires specific thermal conditions. The temperature at which the process is carried out determines the final structure of the CNF, being 600 °C (873.15 K) the optimal temperature. In this work we address the modeling and numerical simulation of flow and temperature for a mixture of gases in a 0.09 m of diameter and 1 m long reactor to optimize the temperature inside it. The study is focused on determining appropriate temperatures at the reactor shell, to assure optimal temperatures at the catalyst support device where the reaction of formation of CNF takes place. Different locations of the support device are considered: the position on the left is at 17 cm from the reactor entrance; the central position is in the middle of the reactor, at 44 cm from both, the entrance and the outlet of the reactor; and the position at the right is at 17 cm from the outlet. We show that the location on the left is not suitable as it requires an impracticable temperature at the reactor shell. Optimal temperatures at the reactor shell can be found when the support device is located at the center of the reactor or closer to the outlet, being the latter more convenient for energy efficiency, as it requires a lower temperature at the shell. Simulations are performed using COMSOL Multiphysics. Results are interesting for laboratory experiments in order to control the temperature required for the optimal formation of these important industrial nanomaterials.