Crystallization Kinetics of Ammonium Perchlorate in an Agitated Vessel

Abstract

Overall crystal growth kinetics for ammonium perchlorate in laboratory scale batch agitated vessel crystallizer have been determined from batch experiments performed in an integral mode. The effects of temperature between 30-60ºC, seed size 0.07, 0.120 and 0.275 mm and stirrer speed 160, 340, and 480 rpm, on the kinetics of crystal growth were investigated. Two different methods, viz. polynomial fitting and initial derivative were used to predict the kinetics expression. In general both methods gave comparable results for growth kinetics estimation. The order of growth process is not more than two. The activation energy for crystal growth of ammonium perchlorate was determined and found to be equal to 5.8 kJ/ mole. Finally, the influence of the affecting parameters on the crystal growth rate gives general expression that had an obvious dependence of the growth rate on each variables of concern (temperature, seed size, and stirrer speed) . The general overall growth rate expression had shown that super saturation is the most significant variable. While the positive dependence of the stirrer speed demonstrates the importance of the diffusional step in the growth rate model. Moreover, the positive dependence of the seed size demonstrate the importance of the surface integration step in the growth rate model. All the studied variables tend to suggest that the growth rate characteristics of ammonium perchlorate from aqueous solution commenced in a batch crystallizer are diffusion kinetic controlled process.