Apparatus to convey pulverized material

A conveyor for pulverized material comprising the combination of a conduit, a. screw rotatably mounted within the conduit having a material inlet end and material discharge end, means for rotating the screw, means for supplying material to the screw at the material inlet end, whereby the material will be compacted as it is advanced by the screw to the material discharge end, means for admitting a gas under pressure to the compacted material at the material discharge end to render it fluent whereby the material will be conveyed through a conduit connected to the material discharge end of the screw by the pressure thus applied, wherein in a portion of the screw there a material seal is formed by the compacted material advanced by the screw thus preventing gas from traveling from the material discharge to the material inlet, and wherein in the material seal forming portion of the screw there are material pockets formed between adjacent screw flights, wherein the material pocket closest to the material inlet has the maximum volume of any material pocket, with the material pockets having the minimum volume being in the material seal forming portion of the screw nearest the material discharge end, and wherein there are at least two of such minimum volume pockets located in the material seal forming portion of the screw nearest the discharge end, with each pocket having a volume of about 50% to about 85% of the volume of the maximum size pocket.