Device for the transfer of energy and/or matter between a soluble solid and a liquid

Device for the transfer, between a solid matter and a liquid, of energy and/or matter dissolvable in the liquid, which device comprises an outer drum mounted in lying position, an inner drum which is provided with perforations and which is situated coaxially in the outer drum and is connected to this latter, means for commonly rotating the two drums, and means situated inside the inner drum for moving the solid matter from a supply at one extremity of said drum to an outlet at its other extremity, whereby in between the two drums a number of troughs are formed, each trough running in a longitudinal direction of the inner drum and having a rim at the leading edge of said trough in the rotational sense of the drum, said troughs, during the rotation of the drums, scooping up liquid from beneath between the drums and bringing the liquid upward and further up pouring out said liquid through the inner drum onto the solid matter inside the inner drum, wherein the inner drum, at a position along the rim of each trough, is provided with at least one drain opening which is larger than the perforations of the inner drum, whereby opposite to said drain opening, means are provided for preventing, when the drain opening is at the bottom of the drums during the rotation of the drums, the penetration of solid matter therethrough but, during the pouring of liquid off the trough at the top of the drums allows for the unhampered flow of the liquid therethrough, together with solid matter wherein said means for preventing the penetration of solid matter through said drain opening comprising a flap hinged towards the inside of the inner drum, which flap, in closing position, closes off the drain opening.