| The effects of extruder operating conditions (moisture content of the feed, die temperature, screw speed, and mass flow rate) on various responses of a twin screw laboratory size MPC/V-30 extruder at high moisture contents were investigated. Operating parameters varied between 175 and 275 rpm for the screw speed, 80;Extrusion under steady state conditions was extensively studied. It was shown that extrudate viscosity is reduced, as indicated by die pressure drop and torque, during extrusion at elevated moisture, screw speed, and die temperature. Elevated mass flow rate levels resulted in higher die pressure drop and torque. However, extrusion at elevated moisture content, die temperature, and mass flow rate resulted in decreases in SME while elevating the screw speed caused an increase in SME. The proposed semi-empirical rheological model considered power-law dependency of shear rate and exponential dependency of temperature, moisture content, and screw speed. The fit between the experimental results and model was shown to be good. Die temperature was found to be the most important parameter influencing the die pressure drop, motor torque, SME, and viscosity of rice starch during extrusion.;Dynamic responses of the lab-size twin screw extruder were studied. Die pressure and motor torque responses were obtained by introducing step changes in mass flow rate, screw speed and screw speed-feed rate simultaneously. Experimental results showed that die pressure and motor torque always responded in the same manner. The responses of die pressure and motor torque were modeled by a first-order transfer function for step changes in the mass flow rate. The same dynamic responses to step changes in screw speed and screw speed-mass flow rate simultaneously were modeled by an inverse response. |
