Analysis of Fuel Concentration Effect Toward Carbon Nanotubes Growth in Methane Diffusion Flame Using CFD Simulations

The utilization of flame synthesis as a viable method for the large-scale production of carbon nanotubes (CNTs) holds great promise. Nevertheless, works related to the optimization of the synthesis process is still limited in this study, a computational fluid dynamics (CFD) model at the flame-scale has been developed to predict the growth of CNTs within a synthesis chamber placed on top of a diffusion burner using a growth rate model (GRM). The primary objective is to analyse the effects of fuel concentration on the length of CNTs synthesized in the synthesis chamber using methane as a fuel. Generally, the length of the diffusion flame above the burner is reduced as the concentration of methane decreases which leads to a reduction in temperature within the synthesis chamber. Interestingly, about a 60% increase in maximum CNT length is predicted for flame with a reduction of methane concentration from 100 to 97 vol% which can be attributed to the favourable thermochemical conditions within the synthesis chamber. However, further decreases in fuel concentration will result in a reduction in CNT length. The growth of CNTs is not feasible with fuel concentrations below 92 vol% due to the low temperature and minimal carbon concentration. Furthermore, the optimal temperature range for CNT growth is found to be between 875K and 905K which facilitates the formation of nanoparticle catalysts and the growth of CNTs with lengths ranging from approximately 2.6 to 4.7 μm.