A two-phase reactor model has been developed using a system of ordinary differential equations in MATLAB to model the carbonation reaction and therefore determine the kinetics of calcium oxide in a pressurised fluidised bed reactor as part of the calcium looping cycle. The model assumes that the particulate and bubble phases are modelled as a CSTR and a PFR respectively. The random pore model developed by Bhatia and Perlmutter1 is incorporated into the system of equations to predict the rate of carbonation for pressures up to 5 bara total, and CO2 partial pressures up to 150 kPa. The surface rate constant and product layer diffusivity in the random pore model expression were obtained by fitting the model to experimental data for a range of pressures, CO2 concentrations and temperatures by minimization of the resid-ual sum of squares. The surface rate constants were found to be between 3.05 and 12.9 x 10-10 m4 mol-1 s-1 for a temper-ature range of 550 to 750 °C. The product layer diffusivities were found to be between 0.06 and 23.6 x 10-13 m2 s-1 for the same temperature range. The surface rate constant and product layer diffusivity activation energy were calculated using the Arrhenius e