Intrinsic kinetics of oxidation of residual organic carbon in rapidly pyrolyzed oil shale

The intrinsic kinetics of reaction of oxygen with carbonaceous residue in rapidly pyrolyzed Colorado oil shale were determined by a series of isothermal fluidized-bed experiments in the temperature range of 384 to 474°C. The char was produced from 100 L/Mg (24 gal/ton) oil shale by rapid heating to 530°C and isothermal pyrolysis for 5 min. The oxidation rate, determined by mass spectrometer measurements of evolved CO and C02, has second-order dependence on the unreacted char. The activation energy is 19.4 kcal/mole and the pre-exponential factor is 1.33 s~ Pa"" , assuming first-order dependence on oxygen. Rate measurements at temperatures higher than approximately 475°C are precluded by interference of C02 that is evolved from carbonate capture of S0_. A lower heating rate during pyrolysis (i.e., a lower effective pyrolysis temperature) significantly decreases subsequent oxidation reactivity of char.