Patent ID: 8141801

Claim:
A method for a continuous dry milling operation using a vertical grinding machine having a vertical, closed milling container ( 1 ); a screw conveyor ( 2 ) which is arranged centrally in the milling container ( 1 ), the screw conveyor ( 2 ) including: a drive shaft ( 4 ) with a central axis ( 3 ) and at least one screw flight ( 5 ) which is arranged on the drive shaft ( 4 ), extends along a height hs up to an upper end ( 6 ) and covers the cross-section of the milling container ( 1 ) only partially; a package of grinding bodies ( 17 ), the package having an upper surface ( 39 ); a grinding stock inlet ( 19 ) which projects into the milling container ( 1 ) above the package of grinding bodies ( 17 ); a gas inlet ( 24 , 24 ′, 24 ″) which projects into the milling container ( 1 ) for introducing gas; a grinding stock outlet ( 11 ) which projects out of the milling container ( 1 ) and has a lower edge ( 18 ) and a height h 13 for discharging grinding stock ( 22 ) and gas; and a motor ( 7 ) for driving the screw conveyor ( 2 ) in a direction of rotation ( 8 ) where the at least one screw flight ( 5 ) conveys grinding bodies ( 17 ) upwards, said method comprising the steps of: adjusting the surface ( 39 ) of the package of grinding bodies ( 17 ) such that when the screw conveyor ( 2 ) is driven for rotation, the surface ( 39 ) obtains an approximately frustoconical shape which slopes radially outwards and ends radially outside in the region of the lower edge ( 18 ) of the grinding stock outlet ( 11 ); introducing the gas into the milling container ( 1 ) above the package of grinding bodies ( 17 ); and discharging the gas and grinding stock ( 22 ) from the milling container ( 1 ) in the region of the surface ( 39 ) of the package of grinding bodies ( 17 ) through the grinding stock outlet ( 11 ).