NOVELTY - The screw conveyor reactor has a reactor shell (1) having an elongated shape, and ends which are provided opposite to each other. A shaftless screw (5) having a central axis is mounted to a drive unit at the first end of reactor shell to allow for the rotation about central axis. A heat transfer tube (4) is located concentrically inside the shaftless screw fixed to the second end of the reactor shell and connected to the source of a heat transfer medium. The reactor shell is provided with an inlet (2) and outlet (3) for fresh feed of a material to be processed in the reactor.    USE - Screw conveyor reactor used as conveyer, dryer and cooler and for performing conductive heating and thermochemical conversion processes of biomass, and to oil, char and gas in biomass torrefaction plant (all claimed).    ADVANTAGE - The efficiency of heat transfer is improved. The vibration of helical screws during operation is reduced. The high heat and mass transfer capability is achieved. The maintenance of the screw is facile and the wear is reduced, by constructing the instant kind metal to metal friction is minimized.    DETAILED DESCRIPTION - The inlet and outlet of the fresh feed is located adjacent to the second end of the reactor shell. The shaftless screw is capable of conveying material along the envelope surface of the heat transfer tube from first zone adjacent to the inlet to second zone adjacent to the outlet. An envelope surface of the heat transfer tube is formed with a heat transfer surface capable of transferring heat to or from the material to be processed in the reactor, and having a closed end next to the first end of the reactor shell. The clearance between the end of the first tube and the closed end of the second tube is set to allow for the flow of heat transfer media between the first tube to second tube or vice versa. The tubes are connected to the source of fresh heat transfer media. The envelope surface of the heat transfer tube is provided with the perforations to allow for flow of heat transfer media to or from the material processed in the reactor. The heat transfer tube is provided with a steam coil concentrically fitted inside the heat transfer tube, and several catalytic reaction zones capable of generating heat by combustion of gas. The heat transfer tube is exhibited with cylindrical zones having different diameters. The cylindrical zones are connected by conical collar zones to form a wedging zone between the inner surface of the reactor shell and the envelope surface of the heat transfer tube. The conical collar zones is formed with the inclined surfaces standing at an angle of 85-45 degrees against the central axis of the shaftless screw. ?The screws are provided with the pitches in different directions of thread turns. The two screws are connected to each other so that the second screw is made to support the main transport screw. The rifles or grooves are provided in the inner surface of the reactor shell. The angle of the thread turns of the first screw and of the rifles or grooves is less than 90 degrees with respect to the central axis of the screw. The drive-locks for the screw are opened with a hatch for screw change or reparation. The reactor shell is provided with wear-out elements changed, when the shells are opened. An INDEPENDENT CLAIM is included for a biomass torrefaction plant has a material that is merely torrefied. The screw conveyor reactors are separated such that the off- gases of the reactors are not mixed together.    DESCRIPTION OF DRAWING(S) - The drawing shows an explanatory view illustrating the construction of torrefaction plant.    Reactor shell (1)    Inlet (2)    Outlet (3)    Heat transfer tube (4)    Shaftless screw (5)