Talc grinding in an opposed air jet mill: start-up, product quality and production rate optimization

We present a study of talc grinding in an Alpine 100 AFG opposed air jet mill with an inline laser granulometer. The conditions for steady state operation have been determined from continuous grinding experiments and show that overloading occurs above a critical value of feed rate classifier resulting in unstable product size distribution. For each rotation speed of the classifier, there is an optimum feed rate, which gives the finest product, thus fixing a maximum reduction ratio. A linear relation exists between this ratio and the rotation speed of the classifier. The use of liquid grinding aids have been studied and showed they can result in an increase in the production rate but can also lead to a coarser product.