A pulp lifter for installation in a rotary grinding mill has a leading edge wall and a trailing edge wall with respect to rotation of the mill. The leading edge wall and the trailing edge wall define a pulp lifter chamber, and a grate allows slurry to pass to a radially outward collecting region of the pulp lifter chamber for removal from the mill by way of a radially inward discharge region of the pulp lifter chamber. In one embodiment, a gate is positioned between the collecting region and the discharge region, the gate being movable between an open position, in which the gate permits solid material to pass from the collecting region to the discharge region, and a closed position, in which the gate prevents return movement of solid material from the discharge region to the collecting region.