Reactor for the hydrothermal treatment of biomass

The present invention concerns a reactor and a process for the hydrothermal treatment of an aqueous mixture, such as watery biomass. The reactor according to the invention comprises (31) an inlet for receiving the aqueous mixture, (32) a tube-shaped reactor interior, which is inclined at an angle in the range of 1-45°; (33) a first zone in the reactor interior (32) comprising means (5) for heating the aqueous mixture; (34) a second zone in the reactor interior (32) for keeping the aqueous mixture at the predetermined temperature; (35) a third zone in the reactor interior (32) for cooling the aqueous mixture; (38) an outlet for discharging a hydrothermally treated aqueous mixture, and (43) an outlet for discharging gas, wherein inlet (31) and outlet (43) are positioned at the top part of the reactor and outlet (38) at the bottom part of the reactor. The inclined nature of the reactor ensures that all gases are efficiently removed from the liquid effluent, and the CO2 formed during the process is used to improved efficacy of the hydrothermal treatment.