Uncertainty in metallurgical coke supplies has prompted development of form coke from low quality coals and fines. Reaction rates have been measured and mechanisms identified that control carbonaceous briquette reaction rate in CO2. Three briquette formulations were prepared, characterized and coked in an inert atmosphere at high temperature. A given weight of each formulation was then reacted in a packed bed with CO2 at 1373 K for 0.5-2 h. Partially reacted briquettes contained a solid core with some internal reaction surrounded by a loosely adhering layer of carbon-containing ash. The reaction rate of briquettes with CO2 was affected by diffusion of CO2 through the bulk gas and the ash-carbon layer to the core surface, as well as CO2-carbon reaction. Key variables governing briquette reaction rate included CO2 mole fraction and briquette void fraction. (c) 2007 Elsevier Ltd. All rights reserved.