A vertical mill for grinding material to be ground and a method for this are claimed, wherein the vertical mill has a grinding table and one or more grinding rollers. A ring duct with blade ring for a transport gas flow ascending around the grinding table is provided. An annular gap distance is present between a downwardly projecting oversize material cone and the upper region of the grinding rollers, through which annular gap distance a proportion of fine particles is also fed back in a recirculating manner to the grinding table.In order to overcome this disadvantage, a barrier gas flow flowing from inside to outwards is provided in the region of the gap distance, whereby the recirculation of grinding particles of a certain size can be prevented.