NUMERICAL MODELING OF TITANIUM CARBIDE SYNTHESIS IN THERMAL PLASMA REACTORS

Titanium carbide powders synthesized in thermal plasma reactors are vi rtually always contaminated by soot. Equilibrium modeling predicts a v iable process window without soot formation; however, this has not bee n achieved in practice. A numerical model incorporating chemical kinet ics, nucleation and growth, and soot formation mechanisms has been dev eloped to investigate this process. The chemical kinetic scheme was ba sed on ethylene pyrolysis and methane combustion with additional react ions to account for titanium-based molecules and the free carbon speci es found at plasma temperatures. Nucleation and soot formation were ba sed on simple kinetic models. The governing equations were integrated through time using typical temperature-time histories found by computa tional fluid dynamic (CFD) modeling of a radiofrequency plasma torch. The results indicate that the synthesis is governed by interactions be tween several parallel processes and that there is a delicate balance between reactant stoichiometry, system pressure, cooling rate, product formation, and soot formation. This balance may be a limiting feature of ceramic carbide production in thermal plasma reactors.