Assembly for processing viscous material comprising: • a process duct extending along a longitudinal axis between an inlet and an outlet; in use, the process duct being fed with viscous material, for example coming from a screw extruder; wherein, in use, the viscous material advances in the process duct in one advancing direction; • at least one pumping device provided with: - a stator comprising a cylindrical seat; - at least one cylindrical rotor, which is housed in the stator and is coupled to the stator with a sliding seal; wherein the rotor is configured to rotate around a rotating axis substantially parallel to the longitudinal axis and has an outer face with at least one groove, which forms with the inner surface of the stator at least one pumping channel; wherein the pumping device is configured so that the pumping channel extends between at least one input and at least one output; the input and the output being in fluid connection with the process duct, so that, in use, the viscous material advancing in the process duct is fed to the pumping channel through the input and is discharged in the process duct through the output; characterized in that the process duct has a first opening in connection with the input of the pumping channel and a second opening in connection with the output of the pumping channel; and in that the input and the output of the pumping channel are substantially arranged side by side along a direction orthogonal to the axis of rotation. • a process duct extending along a longitudinal axis between an inlet and an outlet; in use, the process duct being fed with viscous material, for example coming from a screw extruder; wherein, in use, the viscous material advances in the process duct in one advancing direction; • at least one pumping device provided with: - a stator comprising a cylindrical seat; - at least one cylindrical rotor, which is housed in the stator and is coupled to the stator with a sliding seal; wherein the rotor is configured to rotate around a rotating axis substantially parallel to the longitudinal axis and has an outer face with at least one groove, which forms with the inner surface of the stator at least one pumping channel; wherein the pumping device is configured so that the pumping channel extends between at least one input and at least one output; the input and the output being in fluid connection with the process duct, so that, in use, the viscous material advancing in the process duct is fed to the pumping channel through the input and is discharged in the process duct through the output; - a stator comprising a cylindrical seat; - at least one cylindrical rotor, which is housed in the stator and is coupled to the stator with a sliding seal; wherein the rotor is configured to rotate around a rotating axis substantially parallel to the longitudinal axis and has an outer face with at least one groove, which forms with the inner surface of the stator at least one pumping channel; the process duct has a first opening in connection with the input of the pumping channel and a second opening in connection with the output of the pumping channel; and in that the input and the output of the pumping channel are substantially arranged side by side along a direction orthogonal to the axis of rotation.