A process for producing solid detergent granular materials is presented involving (a) forming an aqueous surfactant paste of an anionic surfactant, an amphoteric surfactant or mixtures thereof, and (b) drying and granulating the aqueous paste in a horizontal thin-layer evaporator or dryer having rotating fittings, wherein the drying is carried out at a temperature of 120° C. to 130° C. The process produces granules having a bulk density greater than 600 grams/liter and a uniform particle size distribution.