An apparatus wherein the gas enters from an opening 4 located in a part of a compaction chamber 3 and is dragged through a granulator 5, a fractioning device 12, a special cyclone 11 and a filter system 8A to a suction fan, which creates a gas stream. In such apparatus the bulk to be compacted 1, the fine particles to be compacted again and the compacted bulk have the same flow direction than the carrier gas. Due to its complete or partial impermeability, the structure of the apparatus makes also possible the use of a gas different from normal air. This is important when the bulk is sensible to oxygen.