Towards Better Size Reduction Flowsheets: How the Application of Some Simple, yet Powerful Philosophies and Principles Can Improve both Process Operation and Product Quality

On the face of it, size reduction appears to be a relatively straightforward unit operation. Hit the desired material hard enough, use lots of energy, and make sure the device is sufficiently robust and we can make large stuff into small bits. Unfortunately, this is often not the case, resulting in poor grinding flowsheet performance and off-specification product. There are countless, complex articles in the literature which allow us to model in the most minute detail the selection function and daughter size fractions for various size reduction devices. However in many cases, it is simple, yet fundamental, concepts which can significantly improve both product quality and process operability. The most important concept is to look at the size reduction process holistically and understanding the connections between the various pieces of equipment and their limitations. For example, over grinding results not from inherently poor mill performance but rather poor selection of the screens associated with the mill. In addition, since many of the materials produced by comminution by chemical engineers are very high value-added products, we should divorce ourselves from the traditional fixation on energy use and conservation associated with size reduction processes. These are just a few ideas which we will examine and support with data from actual plant operations.