Measurement of the reactivity of a solid fuel provides a foundation for predicting how the fuel burns. However, previous studies of the combustion kinetics of coal have been largely restricted to small sized particles (similar to those found in pulverised fuel), so that the combustion characteristics of large heterogeneous solid fuel “lumps” (typically 5 to 50mm in size) are not that well understood. The reactivity of these larger “lumps” cannot necessarily be determined from measurements on much smaller particles since adsorption and desorption are important controlling factors in the combustion process. This paper thus presents experimental data, measured by means of a specially designed thermobalance, for the reactivity of solid fuel briquettes under oxidising conditions. The results are analysed by modification of an existing model for the combustion kinetics of smaller solid fuel particles. The briquettes were composed of low volatile anthracite together with an inert binding agent. The addition of this binding agent further complicates the combustion process, but is necessary, as briquettes cannot be successfully produced from anthracite alone. The coal particle size can modify the briquette reactivity and the effects of this parameter are reported.