Abstract: A boiler system includes an arrangement for drying fuel material to be combusted in the boiler system. A combustion chamber combusts fuel material, and generates ash and flue gases. An ash removal conduit connected to the combustion chamber leads ash out of the combustion chamber. A flue gas conduit connected to the combustion chamber leads Hue gases out of the combustion chamber. A flue gas heat recovery system, arranged to the flue gas conduit, recovers heat from the flue gases. A fuel dryer, provided with a first heat transfer device, transfers heat into the fuel to be dried. A second heat transfer device is arranged in connection with the flue gas conduit downstream of the flue gas heat recovery system. A third heat transfer device is arranged in connection with the ash removal conduit and a fourth heat transfer device is arranged in heat transfer connection with the fuel dryer.