Quantitative measurement of particle size distributions of carbonaceous nanoparticles during ethylene pyrolysis in a laminar flow reactor

Evolution of the particle size distributions (PSDs) for carbonaceous nanoparticles formed from ethylene pyrolysis in a laminar flow reactor was quantitatively measured by a scanning mobility particle sizer coupled with the small orifice sampling technique. The sampling dilution ratio was calibrated and determined to eliminate effects of particle loss in the sampling line. Investigation of various possible effects on the PSDs indicates that while the PSDs are very sensitive to the inlet flow rate, they are not much affected by the probe location and the sampling delay time within operating errors. The evolution of PSDs was determined by varying the inlet flow rates and compared for different ethylene concentrations (0.4 vol%, 0.6 vol%, and 0.8 vol%) and different tube temperatures (1573 K, 1673 K, and 1773 K). A distinct bimodal distribution was observed under fuel pyrolysis conditions. An increase of fuel concentration led to slightly earlier particle inception and a notable increase of particles yield, while temperature variation severely affected the rates of nucleation and mass growth. The particle induction delay times depended exponentially on the temperature, following the Arrhenius law.