NOVELTY - The method comprises supplying a biomass by a conveying device (3) to a reactor (5), in which the biomass is dehydrated and carbonized, and removing a carbon sludge from the reactor. The reactor comprises a carbonation chamber (14) and a dehydration chamber (15). The biomass is: supplied to the carbonation chamber; and converted in the carbonation chamber to a process intermediate product, which is transferred from the carbonation chamber into the dehydration chamber. The intermediate product is converted in the dehydration chamber to a carbon particle containing process end product.    USE - The method is useful for the hydrothermal carbonization of biomass in the passage (claimed), where: the biomass is animal biomass and plant biomass such as green waste, wood chips, plants and plant residues, straw, silage, residues from agriculture, paper and sewage sludge; and the hydrothermal carbonization is an exothermic reaction.    ADVANTAGE - The method allows rapid hydrothermal carbonization of the biomass with high efficiency and less consumption of heat.    DETAILED DESCRIPTION - The method comprises supplying a biomass by a conveying device (3) to a reactor (5), in which the biomass is dehydrated and carbonized, and removing a carbon sludge from the reactor. The reactor comprises a carbonation chamber (14) and a dehydration chamber (15). The biomass is: supplied to the carbonation chamber; and converted in the carbonation chamber to a process intermediate product, which is transferred from the carbonation chamber into the dehydration chamber. The intermediate product is converted in the dehydration chamber to a carbon particle containing process end product. The carbonation chamber is separated from the dehydration chamber by a separating device. The step of transferring the intermediate product from the carbonation chamber to the dehydration chamber is carried out by a gravitational force and by a discharge opening in the separating device. A gravitational slipping of the intermediate product is produced into the dehydration chamber by the separating device. Flows between the carbonation chamber and the dehydration chamber are reduced or suppressed by the separating device. Water and/or gas contained in the dehydration chamber is transferred by the discharge opening provided in the separating device and in the carbonation chamber. The reactor is temperature-stabilized by a passage of gases or vapors. The gases are flue gases obtained from a combustion process or a water vapor. The gases or vapors are conducted through a heat exchanger (6) provided in the reactor. The biomass is heated using a preheating device before introducing the biomass into the reactor. The step of heating the biomass takes place via removal of dehydrated water in the fluid state of the reactor originating from dehydration, via immediate supply of the dehydrated water for the preheating device and via mixing the dehydrated water with the biomass in the preheating device. An INDEPENDENT CLAIM is included for a device for the hydrothermal carbonization of biomass in the passage.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a device for the hydrothermal carbonization of biomass in the passage.    Conveying device (3)    Reactor (5)    Heat exchanger (6)    Carbonation chamber (14)    Dehydration chamber. (15)