This invention relates to a boiler (1) drying, igniting and combusting refuse and producing steam (2, 2a) by heat exchange with flue gases (3), said boiler defining a main flow direction (5) of gases, said boiler (1) comprising a separator element (4) and an end superheater (8), the separator element (4) being adapted for separating said flue gases (3) into streams of a less-corrosive gas flow (6) and a corrosive gas flow (7), said separator element (4) being located substantially in and along said main flow direction (5), said end superheater (8) being located in proximity to said separator element (4) and in the flow (6) of said less-corrosive gas. Said separator element (4) comprises a plate (4a) or a wall (4b), which in a number of said separator elements (4) forms a channel as another separator element. This provides for an increased lifetime of said superheater and makes the boiler provide a high and efficient electrical power output.