Main objective of the present work is the experimental investigation of parameters affecting limestone desulphurization capability in fluidized bed coal combustion. A set of experiments was carried out in a lab-scale Atmospheric Bubbling Fluidized Bed Combustor using Polish coal as fuel and limestone from the region of Kozani –Greece as additive. Experiments were carried out by batch addition of specific limestone quantities at various steady states (constant fluidization velocities, temperatures etc), and by monitoring SO2, N2O and NO levels as the sulphation of limestone proceeded. Bed samples were collected and studied with SEM/EDS