The air distributor plays a key role in circulating fluidized-bed (CFB) boilers providing an even gas distribution in the cross section of the furnace. In most cases, this task under real conditions is very difficult to implement due to the destruction of the tuyeres. For this reason, the air distributors of many CFB boilers operate under conditions deviating from the design recommendations, which has a direct impact on the hydrodynamics of the fluidized bed and heat transfer conditions. This work reports studies on the performance of a tuyere-type air distributor utilized in a CFB boiler and working under non-reference operating conditions. Based on the results of simulation calculations, practical equations for a distributor pressure drop calculation have been derived taking into account a different degree of tuyere destruction.