Pressure, torque, and energy responses of a twin screw extruder at high moisture contents

The effects of extruder operating conditions (moisture content of the feed, die temperature, screw speed, and mass flow rate) on the pressure drop along the die, motor torque, and specific mechanical energy (SME) for a high moisture rice starch system were studied. A laboratory size MPC/V-30 co-rotating twin screw extruder (APV) and a slit die/torque rheometer (Haake Buhler) combination were used to measure the die pressure drop and torque. Die pressure drop and torque decreased with increases in moisture, screw speed, and die temperature, and increased with an increase in mass flow rate. However, increasing the moisture content, die temperature, and mass flow rate resulted in a decrease in SME. Increasing the screw speed increased the SME. This was attributed to the higher shear rates at higher screw speeds. Die temperature was found to be the most significant parameter influencing the die pressure drop, torque, and SME. Copyright (C) 1996 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology