Fremgangsmate for utluting av faststoffer fra en slammasse

Leaching of solid matter from a sludge uses a tubular reactor which is equipped with a concentric central pipe and a double-action mixer. The mixer is located in the vicinity of the central pipe's lower edge. Leaching solid matter from a sludge with the aid of an oxygen-containing gas uses a tubular reactor. The reactor is equipped with a concentric central pipe (2), and a double-action mixer (5) in the vicinity of central pipe's lower edge (7). With the aid of the mixer, the sludge flows downward in the central pipe, and then turns upward outside the central pipe as the gas is fed at the same time into the sludge and dispersed into small bubbles. The mixer preferably has nearly rectangular straight lower blades which facilitate the dispersion of the gas and the turning of the discharge sludge into the upward flow. It has curved upper blades which facilitate the downward flow of the sludge in the central pipe. It is preferred that the cross-section area remaining between the mixer and the central pipe is adjusted to be less than half (preferably at most one third) of the flow cross-section area in the central pipe and the lower edge of the central pipe is at a height (measured form the reactor bottom) of 0.7-1.3 times that of the reactor diameter, preferably the same as the diameter. The cross-section ratio of the central pipe and its surrounding reactor casing is preferably below 0.1.