Apparatus for contacting solids with a liquid

An apparatus for contacting solids with a liquid, which comprises

• (a) a drum rotatable about a substantially horizontal axis in a direction of rotation and having a cylindrical side wall and two closed end walls, the drum walls defining an interior chamber, the solids being delivered into the interior chamber through one of the end walls and the liquid being delivered thereinto through the other end wall,
• (b) a screw conveyor arranged in the interior chamber for continuously conveying the solids from the one end wall towards the other end wall upon rotation of the drum while the liquid flows countercurrently thereto, the screw conveyor having helical turns affixed to the cylindrical side wall of the drum and defining a helical passageway for the solids between the helical conveyor turns,
• (c) means for raising the solids and for draining the solids during rotation of the drum, said means being spaced along the helical passageway and dividing the passageway into a series of compartments, each of the solids raising and draining means including
• (1) a grating receiving the solids and raising the received solids while liquid is drained through the grating and then permitting the drained solids to fall into a succeeding one of the compartments, and
• (2) an imperforate partition trailing the grating in the direction of rotation of the drum, the partition having an inner end adjacent the axis of the drum and defining a chamber receiving the liquid drained from the solids with the adjacent side wall of the drum and the helical screw turns, and
• (d) a passageway interconnecting each of said chambers with the compartment upstream of the chamber in the direction of movement of the solids from the one to the other end wall, the passageways extending along the side wall of the drum, and each passageway communicating with the upstream compartment it feeds through openings in a trailing part thereof in the direction of rotation of the drum and through orifices in a leading part thereof in the direction of drum rotation, the leading part adjoining the imperforate partition of the solids raising and draining means,
• (1) a perforate dike defining the orifices, the dike being arranged in the leading part and being disposed approximately in the median plane of the compartment and extending transversely to the axis of the drum.