System and process for refining lignocellulosic biomass material

System for refining lignocellulosic biomass material, said system comprising:

• a presteaming bin for presteaming said biomass material;
• a dewatering device for dewatering said presteamed biomass material;
• a preheater for preheating said dewatered biomass material;
• a defibrator comprising at least one refining zone wherein said preheated biomass material is refined and wherein steam is generated during the refining of said biomass material so that a pressure peak occurs in the refining zone;
• a blow pipe for conveying biomass material away from the refining zone;
• and
• a first steam flow path arranged to convey steam flowing away from the pressure peak against a biomass material transport direction from said refining zone to said presteaming bin;
• characterized in that said system comprises:
• a second steam flow path arranged to convey steam flowing away from the pressure peak in the biomass material transport direction from said refining zone to said presteaming bin;
• wherein said first and second steam flow paths are connected to the refining zone on opposite sides of the pressure peak in the biomass material transport direction;
• and
• wherein said first and second steam flow paths are separate from said blow pipe.