Patent ID: 7651565

Claim:
A process for the calcining of gypsum, in a gypsum dryer/calciner comprising: a calcining space; a first pipe having an inlet connected to a source of hot gas and an outlet emerging in the calcining space; a second pipe having an inlet connected to a source of gypsum and an outlet emerging in the calcining space, the second pipe being concentric with the first pipe; a force-feeding screw positioned at least partially in the second pipe, the screw carrying the gypsum along in the calcining space; the process comprising the stages of: (i) supplying hot gases to the inlet of a first pipe; (ii) supplying gypsum to the inlet of a second pipe concentric with the first pipe; (iii) carrying the gypsum along in the second pipe via a force-feeding screw; (iv) indirect heat exchange between the gypsum and the hot gases; and (v) calcining the gypsum to plaster.