NOVELTY - The apparatus has a dry drum (10) which generates a solid fuel by drying granulation sludge formed based on dried sludge and dewatered sludge using a dry gas. A combustion furnace (42) supplies a heat source for heat exchanger (41) to heat the dry gas. A drying-apparatus exit temperature detection unit (51) detects temperature of exit (11) of dry drum. A fluid nozzle (53) injects mist inside the dry drum. A control unit (54) controls the fluid nozzle based on temperature of exit so that the fluid nozzle injects the mist inside the dry drum.    USE - Sludge drying apparatus e.g. sludge dry granulation system for controlling temperature of drying apparatus e.g. dry drum.    ADVANTAGE - The sludge drying apparatus can control the temperature of the dry drum appropriately. The dry drum is temperature-controlled safely without damaging the bag filter while heating up the combustion furnace.    DETAILED DESCRIPTION - The heat exchanger heats the dry gas and supplies the dry gas after the heating to the dry drum. A bag filter (20) is arranged in the exit side of the dry drum. The control unit controls the fluid nozzle to inject the mist inside the dry drum when the temperature of the exit to be preset becomes more than one target temperature, and controls the fluid nozzle so that the temperature of exit turns into one target temperature and heating of combustion furnace is performed so that the temperature of exit becomes other target temperature. The two target temperatures are set in a range more than a bag filter dew condensation avoidance temperature in the dry drum, and below the allowable temperature limit of bag filter. The other target temperature is higher than the one target temperature. A furnace temperature detection unit (52) detects the furnace temperature of combustion furnace. The control unit performs other control until temperature rising of combustion furnace is started and furnace temperature results in the deodorizing start possible temperature in the combustion furnace. A biaxial mixer (32) forms the granulation sludge based on the dried sludge and the dewatered sludge. The control unit switches control after predetermined time progress and after the dried sludge and dewatered sludge are supplied into the mixer. The control unit is proportional to the temperature-rise value of the exit, and controls the fluid nozzle to increase quantity of mist injected by the fluid nozzle inside the dry drum. An INDEPENDENT CLAIM is included for sludge drying method.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the sludge dry granulation system.(Drawing includes non-English language text)    Dry drum (10)    Exit of dry drum (11)    Bag filter (20)    Biaxial mixer (32)    Heat exchanger (41)    Combustion furnace (42)    Drying-apparatus exit temperature detection unit (51)    Furnace temperature detection unit (52)    Fluid nozzle (53)    Control unit (54)