Kinetic study of calcite particle (powder) thermal decomposition: Part I

In the first step of the firing cycle used to manufacture white-firing wall tile bodies, the calcium carbonate that is added, as a source of CaO, to the clay raw materials mixture used to form these bodies needs to decompose. In order to study the kinetics of this process, a representative rate equation of the chemical reaction step of calcium carbonate thermal decomposition is needed.There is a disparity of opinions regarding the reaction order of this chemical reaction step. For this reason, it was decided to obtain a rate equation for this chemical decomposition step, using the same type and size calcite particles that are usually added to these clay mixtures in industrial practice.The present paper proposes a rate equation for this chemical reaction step. With this rate equation and the application of the “Uniform Conversion Model”, an expression has been derived that relates the fractional calcium carbonate conversion, in the studied calcite particles, to residence time and operating temperature. The equation satisfactorily fits the experimental results obtained under isothermal conditions in the studied temperature range for particles smaller than 100 μm.The calcite particles studied are highly porous aggregates (smaller than 1.1 mm) of very small single crystals (smaller than 20 μm). The experiments were conducted in the 850–950 °C temperature range.