Automation of an olive waste industrial rotary dryer Original Research Article

Orujo is a waste product of the olive oil mill industry that still has significant oil content. Before extracting the remaining oil with hexane, the moisture of the wet waste product has to be reduced from approximately 65% to about 8% (wet basis). The high water content of orujo and its stickiness make the drying process difficult. The most common solution adopted by the industry is to use two rotary dryers in serie. In the first one, a mix of fresh and dried orujo with a moisture content of approximately 52–57% (w.b.) is introduced and leaves the dryer with a 25–35% (w.b.). There the main issue is not to control the outlet solid moisture but to treat as much solid as possible and to overcome serious operational problems.