Method and system for continuously treating biomass material

A system for continuous hydrothermal steam treatment of biomass material, said system comprising:

• a substantially vertically arranged pressurized vessel;
• a discharge device configured to discharge the biomass material from a bottom portion of the pressurized vessel;
• a conduit connecting a top portion of the pressurized vessel with said discharge device, said conduit comprising a control valve for controlling a flow of vapor from said top portion to said discharge device;
• a pressure measurement device configured to measure differential pressure between said top portion of the pressurized vessel and said discharge device,
• at least one steam injection nozzle configured to inject steam into said pressurized vessel, each injection nozzle comprising a corresponding valve to control the steam flow, wherein at least one of said at least one steam injection nozzle is arranged at a lower portion of said pressurized vessel, and
• a control unit configured to control said control valve in response to differential pressure measurement data from said pressure measurement device, the control unit further being configured to determine a minimum flow of steam needed to heat the biomass material in the pressurized vessel to a predetermined temperature, and to control each valve of the at least one steam injection nozzle such that the total flow of steam into the pressurized vessel is higher than said minimum flow.