Extrusion of An Effervescent Granulation with a Twin Screw Extruder,Baker Perkins MPF 50D. Determination of Mean Residence Time

Abstract

Anhydrous citric acid and sodium bicarbonate were granulated with ethanol in an extruder. A rough estimate of the dwell time was obtained by adding a small amount of colour in the inlet port and measuring the time until it reached the outlet. The mean residence time was calculated from results obtained when analyzing the colour content of the continuously sampled granulations after drying. There was a significant relationship between dwell time and mean residence time. After elimination of the abnormal values of three of the factor combinations, the degree of significance for the slope of the line increased from P=0.003(**) to P=0.0001(***). The mean residence time was significantly influenced by the process variables screw speed and powder flow rate. Higher levels of these two factors reduced the mean residence time.