Correlation of carbon nanostructures yield with flue gas emissions in oxy-fuel diffusion flames

This paper investigates the relationship between yield of carbon nanostructures produced in flame environment and flue gas emissions for an axisymmetric co-flow diffusion flame. Simulation has been carried out at four different equivalence ratios to scrutinize the optimum ratio at which maximum carbon nanostructures can be obtained with minimum hazardous emissions. Numerical model solves the time-independent Navier-Stokes equation coupled with the equations for energy and species conservation to compute the temperature and species distributions inside the flame. A simple one-step soot model has been used to model the soot formation process. The computed species concentrations are compared with the experimental values and are found to show less than 10% variation. The results indicate that the level of emission of NO (X) decreases appreciably at higher equivalence ratios. The percentage emission of CO and CO2 however is not affected significantly. Furthermore, HRTEM and EDX analysis has been conducted on collected carbon material to determine its internal structure and elemental composition. HRTEM indicates the formation of spherical nanoparticles having an average diameter of 30 nm and EDX spectrum reveals that the synthesized sample consists of 99.35 weight% carbon.