A nonisothermal combustion model for a spherical anthracite briquette is developed and studied on the basis of the unreacted shrinking core model. The feasibility region, in which the solution must lie, is constructed and used for the prediction of the combustion characteristics. It turns out that the bounding curves of the feasibility region may be determined by analyzing the three limiting cases known as the single ash layer model and the double ash layer model. This treatment enables us to find the upper and lower bounds of the unreacted core surface temperature corresponding to various particle surface temperature. The solutions of the limiting cases provide expressions for the upper and lower bounds of the molar fluxes of the reactants and products as well as those of the energy flux at the particle surface. Also examined is the way how the feasibility region changes as the combustion proceeds. In the case of anthracite briquette combustion it is unlikely that multiple solutions may exist and it is deduced that the oxidation reacton of carbon monoxide in the ash layer may be neglectd when the particle surface temperature is sufficiently high.