Process design for carbon black size and morphology

Abstract

The structure (size and morphology) of carbon black (CB) largely determines its performance in tires, inks, batteries etc. Here, the impact of CB process synthesis variables, i.e. temperature, T, precursor (i.e. acetylene) flow rate, Q, and volume fraction, fv, on CB structure is elucidated by discrete element modeling (DEM) and compared to experimental data in the literature. The CB structure is quantified by the mobility, dm, and spherule or primary particle, dp, diameters, effective density, ρeff, and fractal dimension, Df. Decreasing Q or T enhances the CB yield, surface growth and agglomeration. This increases the mean dm and dp, consistent with experimental data from laminar flow ethylene pyrolysis reactors. The CB made at high Q or T is less compact than that made at low Q and T, having up to 50% smaller ρeff and 30% smaller Df, in excellent agreement with experimental data also. Increasing the fv (e.g. by increasing the precursor flow rate) results in CB aggregates (covalently-bonded CB primary particles) and increases the mean dm and dp, explaining commercial furnace black data. These CB aggregates are quite compact having up to 45% larger Df and larger ρeff than those of ethylene black. So process design diagrams generated by the present DEM simulations can be used to guide design and optimization of CB for various applications from first principles.