Biomass processing system for treatment of biomass material

A biomass processing system for treatment of biomass material, wherein said biomass processing system is a biomass conversion system, said biomass processing system comprising:

• a first vessel configured to hold said biomass material under a first pressure during treatment of the biomass material;
• a second vessel configured to receive said biomass material and to hold said biomass material at a second pressure which is lower than the first pressure, wherein a difference between the first and second pressures is at least 10 bar;
• a blow line connecting an outlet of the first vessel with an inlet of the second vessel for transporting the biomass material from the first vessel to the second vessel;
• and
• a blow valve connected in said blow line and configured for controlling the flow of biomass material and fluid in the blow line and configured to control a steam explosion of the material occurring at the passage through the blow valve, wherein said blow valve comprises a shutter valve with a central opening of controllable size, said shutter valve comprising a number of valve plates which are disposed in an annular pattern surrounding the central opening of the shutter valve and wherein said valve plates are movable in relation to each other whereby the size of the central opening is controllable by moving the valve plates.