Residence Time Distribution Determination Using On-Line Digital Image Processing

A less laborious, and non-destructive on-line digital image processing (DIP) technique was developed to measure the residence time distribution (RTD) in an extruder. The a* value of the L*a*b* color space coordinates was measured using DIP and compared to the value obtained by a colorimeter method. The R-2 values showed a high correlation (R-2 = 0.88) of a* values between both methods. The influence of screw configuration (compression and mixing screws) and barrel temperature (150 and 160 degrees C) on RTD were analyzed by the mean residence time (MRT) and variance for both methods. Mixing screws and lower temperature resulted in higher MRT and variance for both methods. The DIP method was faster and less subjected to human and experimental errors than traditional off-line measurements.