Thermogravimetric Analysis of Huadian Oil Shale Combustion at Different Oxygen Concentrations

As the simplest conversion route, combustion is extensively applied to oil shale utilization. To improve oil shale conversion techniques, we used non-isothermal thermogravimetric analysis to explore the combustion reactivity and kinetics of Huadian oil shale at various oxygen concentrations (10, 20, 30, 50, 65, and 80 vol %) and heating rates (5, 10, and 20 °C min–1). With an increase in oxygen concentration, the combustion performances of oil shale could be significantly improved; the volatile-releasing temperature, ignition temperature, and burnout temperature decreased; the mass loss rate increased; and the integrated combustion characteristics of oil shale were enhanced. These improvements were attenuated when the oxygen concentration exceeded 50 vol %. When the oxygen concentration increased from 10 to 80 vol %, the average activation energy in the second combustion stage increased from 46.85 to 117.98 kJ mol–1 by the Kissinger–Akahira–Sunose method, from 46.85 to 117.98 kJ mol–1 by the Starink method, from 59.08 to 129.17 kJ mol–1 by the Friedman method, and from 36.34 to 57.58 kJ mol–1 by the Coats–Redfern method at a heating rate of 20 °C min–1. Results indicated oxygen enrichments beyond which additional enrichment yields significantly less enhancement to the combustion process.