To reduce the initial operation cost, maintenance cost and chemical cost, and thus the total operation cost for drying a sludge slurry, by utilizing the subject direct drying facility having a concentrator, a mixing granulator, dryer, a cogeneration electric power gas turbine and a classifier but having no dehydrator.

A direct drying facility of a sludge slurry utilizing waste heat of a cogeneration gas turbine has a concentrator 11 for concentrating high moisture slurry of sludge such as cleaned water or sewage, a mixing granulator 12 for mixing the concn. sludge slurry with dry sludge to form a sludge cake, a dryer 13 for drying the sludge cake, a cogeneration electric power gas turbine 14 sending waste heat to the dryer in order to utilize the same as a heat source and a classifier for classifying the dry sludge from the dryer into a necessary circulating amt. of the dry sludge to the mixing granulator and a dry product.