Abstract: An apparatus for separating fine dust particles from coarse dust particles, such as are present in hot filling powders for pit furnaces for the production of electrodes by aluminium fusion electrolysis, comprises a first separator with an adjustable separation gap, arranged inside a bin on an intermediate bottom, which is preferably slanted, dividing the bin into an upper chamber and a lower chamber. The air flow is sustained by a fan connected with its discharge side to the lower chamber. The suction side of the fan is connected to the upper chamber through a further separator for the fine particles and through respective pipes. Preferably the suction return path through the pipes and the further separator leads through a further collector.