A method is described to evaluate the reaction rate coefficients, pore diffusivity and thermal conductivity of the lime layer in the decomposition of limestone by linearization of conversion curves, based on the shrinking core model. Spherical and long cylindrical samples with diameters in the range of 20-50 mm were prepared and thermally decomposed in a chamber furnace at constant temperature and CO2 pressure. By weighing and simultaneous measuring of the internal temperature, the decomposition behavior of these samples was studied. The reaction rate coefficients thus obtained vary from 0.003 to 0.012 m s(-1) with a factor of 4, depending upon the origin of the limestone. The reaction coefficients measured by other authors based on limestone powder lie within this range. (c) 2006 Elsevier B.V. All rights reserved.