may be for example a screw conveyor optionally a second feeder part or chute which forms a passage which is at least partially vertical and through which the torrefied material may drop down due to gravity to through a rotary lock feeder 4 b to the mill 5 it should be understood that the feeder system 4 a 4 b could also be designed in other ways for example the feeder system 4 a 4 b may be formed by a single screw conveyor in the figure the preferred feeder system 4 a 4 b provides for a gas phase lock between the inert gas phase of the roaster 3 and the mill 5 where cooling water is added thus preventing water vapour from entering the roaster with reference to fig2 it can be seen that an inlet conduit 6 is connected to both the first feeder part 4 a and to the mill 5 immediately before as shown the mill or in the mill itself not shown this inlet conduit 6 is arranged to introduce a cooling liquid at least in one position either directly into the mill 5 and or into a part of the first feeder part 4 a that is arranged to convey torrefied material to the mill 5 cooling liquid can thus be added to at least one of the first feeder part 4 and the mill 5 in fig2 the inlet conduit 6 is shown as having one branch that leads to the first feeder part 4 a and one branch that leads directly into the mill 5.