Abstract: This particulate solids pump is of the screw conveyor type for transmitting particulate solids from a hopper through a barrel when the screw conveyor is rotated and in which a flowstream of gas is supplied for facilitating the movement and suspension of the particulate solids after exiting the barrel. A sealing chamber formed by termination of the screw conveyor short of the exit end of the barrel provides an accumulation of particulate solids therebetween and a spring biased flapper valve to form a blow-back pressure seal. A flapper valve at the exit end of the barrel operates to loft the particulate solids exiting from the barrel into the flowstream of gas. A sealing apparatus provides lateral and axial sealing of the rotating shaft of the screw conveyor.