Process Efficiency And Energy Consumption During The Extrusion Of Lignocellulosic Materials

Lignocellulosic raw material is the main substrate used in agricultural biogas plants. They become usable after proper preliminary treatment, part of which is the extrusion-cooking process. The aim of this work was to determine the efficiency and energy intensity of the process of extrusion-cooking of lignocellulosic materials under varied barothermal treatment conditions. Generally available vegetable raw materials were used for the study: maize bran, maize straw, lignified grass hay, and wheat straw. The extrusion-cooking process was performed with the TS-40 single-screw extruder by Metalchem Gliwice equipped with a plasticizing system of L/D = 12. Four levels of moistening were applied for raw material mixes (20, 25, 30 and 35% of dry matter) and three rotational speeds for the extruder screw (70, 90 and 110 rpm). The level of moistening of the raw material and changes to the extruder screw speed had an appreciable impact on the course of raw material processing. The top process efficiency was recorded for maize bran (50.40 kg h(-1)) treated at the extruder screw speed of 110 rpm and 30% of the level of moisture, and the lowest (11.22 kg h(-1)) for grass hay with 20% of the level of moisture and the extruder speed of 70 rpm. The lowest energy intensity indicator (0.093 kWh kg(-1)) was reported for maize bran processed at the screw speed of 70 rpm and a moisture content of 30%. The highest energy intensity indicator of the extrusion-cooking process, i.e. 0.37 kWh kg(-1), was seen in maize straw and wheat straw at a moisture content of 20% and the screw speed of 110 rpm.