through a conduit 21 with air which has preferably been preheated by the exhaust gases which are formed and through a conduit 22 with fuel in the form of gas or fuel oil the combustion of the fuel or of recirculated coke with the aid of the air results in combustion gases which elevate the recirculated coke and at the same time heat it to a temperature of 760 u00b0 c the heated recirculated coke is separated from the combustion gases in the collecting bin 4 and is stored in the lower part of the collecting bin and refed to the mixer 1 at a metered rate the exhaust gases leave the collecting bin through a conduit 23 and are subjected to a mechanical dust collection in the conventional manner in a cyclone not shown and subsequently utilized to preheat the air to generate steam and preferably to dry coal before they are discharged into the open through a dust filter the gases and vapors which have been liberated from the coal which is subjected to dry distillation are subjected to a very thorough dust collection in the cyclone 5 and any succeeding second cyclone 6 and flow into the heavy tar scrubber 7 through which they flow from top to bottom concurrently with the sprayed recirculated tar which is also supplied at the top in this step the gases and vapors are cooled by the recirculated tar to the temperature which is required to ensure that the recirculated tar is at the desired softening point and the high boiling tar constituents are condensed at the same time whereas the fine residual dust entrained by the gases and vapors is removed by the recirculated tar.