NOVELTY - The heating- or cooling device comprises a heating- or cooling jacket surrounding a reactor tube (10) and having first- (23) and second chamber (24), which are thermally separated from each other by a third chamber (26) and are arranged parallel to a longitudinal axis of the reactor tube and symmetrical to a transverse axis (10') of the reactor tube. The first chamber is arranged for heating and the second chamber is arranged for cooling. Each of the chambers is arranged as a chamber receiving a thermal fluid. The first chamber is couplable with the second chamber.    USE - Heating- or cooling device for a cylindrically designed reactor tube, which is useful for carrying out a hydrothermal carbonization (claimed) of biomass.    ADVANTAGE - The heating- or cooling device is simple and easy to use, and efficiently avoids sediments on the inner wall of a reactor tube without mechanical assistance thus ensuring simple and highly-efficient production of carbonaceous products from biomass with less energy requirements without negative impact on the quality of the end product.    DETAILED DESCRIPTION - The heating- or cooling device comprises a heating- or cooling jacket surrounding a reactor tube (10) and having first- (23) and second chamber (24), which are thermally separated from each other by a third chamber (26) and are arranged parallel to a longitudinal axis of the reactor tube and symmetrical to a transverse axis (10') of the reactor tube. The first chamber is arranged for heating and the second chamber is arranged for cooling. Each of the chambers is arranged as a chamber receiving a thermal fluid. The first chamber is couplable with the second chamber, so that a part of the thermal fluid of the second chamber is supplyable to the first chamber.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of a heating- or cooling device.    Reactor tube (10)    Transverse axis of the reactor tube (10')    First chamber (23)    Second chamber (24)    Third chamber. (26)