REACTION-ENGINEERING SIMULATIONS OF OXIDATIVE COUPLING OF METHANE IN A CIRCULATING FLUIDIZED-BED REACTOR

Oxidative coupling of methane in a circulating fluidized bed (ID = 1 m , H = 20 m) was investigated by means of reaction engineering modeling and simulations. The hydrodynamics of the catalytic bed was described applying a two-phase (core and annulus) and two-zone (acceleration an d fully developed flow) model. Chemical reactions were described by tw o separate networks for the heterogeneous and homogeneous reactions. T he one for the heterogeneous steps was developed for a La2O3/CaO catal yst. Concentration profiles revealed that due to the high activity of the catalyst, almost complete conversion of oxygen was already obtaine d in the acceleration zone. Reactor performance was found to be strong ly influenced by mass transport limitation between the core and annulu s and by gas-phase reactions. The maximum C2+ yield of 13 % (T = 800 d egrees C, X-CH4 = 34.5 %, SC2+ = 37.5 %) was obtained at a high solids circulation rate (G(s) = 800 kg/m(2) s) and a low methane-to-oxygen r atio (CH4/O-2 = 3). The C2+ yields in the CFB are comparable to the on es predicted for an industrial-scale bubbling-bed reactor.