(397f) Effects of Mill Designs and Process Parameters In Milling of Alumina-Magnesia Extrudates

Milling process is one of the most common processes involved in solids processing industries. Generally selection a mill for a given application is based on its capacity, and its ability to produce the desired particle size. Choice mill and the necessary operating parameters is often made based on heuristic information. In solids processing plants, the capacity of manufacturing is subjected to change which leads to changes in the throughput and also the material properties of incoming material to the mill, and it is necessary to adjust the operating parameters (e.g. Rotor Speed and Flow rate) to maintain the intermediate material/product specifications under desired limits. In such cases, it is beneficial to have a predictive understanding of the particle size distribution (PSD) as a function of operating parameters. The work presented in this paper focuses on optimization of a milling process involved in manufacture of ceramic (Alumina-Magnesia) supports. The main objectives of this work were to increase the capacity of the milling process while maintaining a tighter particle size distribution in an industrial application.

A set of mills (Jaw crusher, co-mill, hammer-mill, knife-mill and reciprocating mill) exhibiting different milling mechanisms under a range operating conditions (different screens and rotor speeds) were examined. Two types of initial materials in the form extrudate pallets of alumina-magnesia, differing in the content of dry matter were used for the milling experiments. Material response to the milling conditions over the entire PSD range was examined. The relationships between various statistical parameters such as (d10 vs. d50) and (d90 vs. d50) were assessed for all possible experimental conditions to understand capability of a given mill produce more/less fines (d10) or coarse particles (d90) at a desired particle size (d50). The scaling behavior of the PSD was also analyzed by computing its poly-dispersity index (d90-d10)/d50 and assessing its behavior over the entire operating space.

This work enhances the predictive understand of the milling process of ceramic materials, it also offers quantitative methodologies to compare the milling performance of industrial mills.