Assembly for processing viscous material comprising: • a process duct extending along a longitudinal axis (A) 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 (D); • 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 (B) substantially parallel to the longitudinal axis (A) 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 (B) . • a process duct extending along a longitudinal axis (A) 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 (D); • 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 (B) substantially parallel to the longitudinal axis (A) 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 (B) substantially parallel to the longitudinal axis (A) 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 (B) . <EOS>