Experimental and modeling investigations have been performed on the co-combustion of a traditional fossil fuel and a tire residue. The experimental runs have been carried out using a pilot-scale vertical furnace (0.5 MW) with a burner for pulverized solid fuels. Different conditions have been set up for the co-combustion of a medium volatile bituminous coal and a tire residue. The scope was to test the feasibility of burning secondary fuels (biomasses and residues) with coals using a low NOx burner developed for pulverized coal in the ENEL Research Centre. A co-combustion model was developed for interpreting the results and extrapolating kinetic parameters to practical conditions. It considers the effect of the particle size distribution, the different reactivity, and, in general, the different combustion behavior of each fuel fed to the furnace. The kinetic scheme adopted is simple and the introduced assumptions allow easy coupling with computational reactive fluid dynamic codes. Fuel conversion, oxygen concentration and carbon-in-ash profiles have been computed and compared with the experimental results. Quite good agreement has been obtained, allowing kinetic information to be used in more comprehensive descriptions of full-scale systems.