Feeding system and method for feeding comminuted cellulosic material to a high-pressure treatment zone

The invention relates to a system and a method for feeding comminuted cellulosic material from a lowpressure zone (PL) to a high-pressure zone (PE) with at least 1 bar higher pressure. The invention uses a screw feeder having a feeding screw (1) arranged in a feeding pipe (2)Excess air that may blow backwards from the high-pressure zone (PE) can be ventilated (Vent") in an intermediate part (Pc) of the feeding pipe (2)， and thus not reach the low-pressure zone.