NOVELTY - Direct flow from the biomass and heat carrier material feeds to the pyrolysis gas discharge (13) is prevented. A mechanical mixer (18) is used to mix the incoming flows of biomass material (5) and heat carrier material (12). The maximum average velocity of the gas downstream of the mixer is as great as the terminal falling velocity.    USE - For pyrolyzing biomass.    ADVANTAGE - Any clogging and blocking can be effectively prevented from occurring, despite the carbon and other solid material being of a tacky nature. Carbon, non-converted fibers and heat carrier material are discharged only via the solid material discharge and the pyrolysis discharge discharges only pyrolysis gas. All solid particles are separated from the pyrolysis gas in one part of the reactor where the mechanical mixer is situated. The separation between the discharge flows of pyrolysis gas and solid material takes place only under gravity since the average velocity of the gas and the entrained solid material has a low value downstream of the mixer. The device does not comprise a cyclone.    DETAILED DESCRIPTION - An apparatus for the pyrolysis of biomass comprises: a reactor (6) with a housing (7); a first feed (10) for biomass material or other organic material connected to the upper zone (9) of the reactor space; a second feed (11) for preheated heat carrier material, e.g. sand, connected to the upper side (20) of the reactor space; a first discharge for pyrolysis gas (14) connected to the upper zone of the reactor space at a distance from the first feed; and a second discharge (16) for solid material, e.g. carbon and heat carrier material, connected to the underside of the reactor space. The design of the reactor space prevents direct flow from the first and second feeds to the first discharge. A mechanical mixer (18) is present in the reactor space for mixing the incoming flow of biomass material with the incoming flow of preheated heat carrier material. The maximum average velocity of the gas and entrained material in the reactor space downstream of the mixer at a temperature of ca. 400-550 degrees C is about as great as the terminal falling velocity, so that at least a substantial separation between the discharge flows of the pyrolysis gas and solid material takes place predominantly under the influence of gravity, in particular without the use of a cyclone.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a reactor.    Biomass material (5)    Reactor (6)    Housing (7)    Upper zone of reactor space (9)    Biomas feed (10)    Preheated heat carrier material feed (11)    Preheated heat carrier material (12)    Pyrolysis gas discharge (13)    Pyrolysis gas (14)    Solid material discharge (16)    Solid material (17)    Mechanical mixer (18)    Upper wall of reactor space (20)