The invention relates to a circulating mass dryer for drying wet sludge. According to the invention, the circulating mass dryer includes two adjacent circulating mass systems in heat exchange communication with one another, wherein the first circulating mass system is a sludge drying side and the second circulating mass system is a heat releasing side, and the first and the second circulating mass system each comprises at least one elongated riser (3, 16), and the riser (3) of the first circulating mass system and the riser (16) of the second circulating mass system are adjacent in such a way that a common heat exchange surface is formed therebetween. In addition, the invention relates to a corresponding method.