Reactor assembly and method for treatment of biomass material

The invention relates to a discharge screw assembly (12) for discharging treated biomass material (A) received from a reactor vessel (2; 102)， which discharge screw assembly comprises an inner space (23) that extends along a longitudinal axis (X) from a first end (23a) to a second end (23b) and an outlet (15) for discharging said biomass material out of said inner space， which outlet is located at the second end， wherein the inner space accommodates a discharge screw (17) for conveying said biomass material to the outlet. The discharge screw assembly further comprises at least one transport steam injection orifice (19) arranged at the second end. The invention also relates to a reactor assembly (1; 101) comprising a discharge screw assembly as described above and a method for treatment of biomass material in such a reactor assembly.