The objective of this work is to develop a milling model for a continuous self-classifying spiral air jet mill. Its foundation is a population balance model with selection and breakage distribution functions that have been related to a minimal number of mill-dependent and powder-dependent parameters. Initially, experimentation is required to determine the mill-dependent parameters for a specific mill, by milling a "base" powder at multiple operating conditions. Powderdependent parameters can be determined from either mill experiments or from material characterization measurements that require small amounts of powder (presented in Part 2). Ultimately, the milling model presented successfully predicts the product particle size using as inputs the feed particle-size distribution and mill operating conditions. Three crystalline powders, sodium bicarbonate, lactose monohydrate, and sucrose, have been used to test the proposed milling model.

The milling model described in Part 1 has been expanded to a three-level model with the addition of powder-dependent parameter function models with simple material characterization measurements as inputs. This allows the determination of these parameters with minimal consumption of powder. Specifically, the powder-dependent parameters are related to material hardness from microindentation or to a breakage measure from single-impact milling. Three crystalline powders, sodium bicarbonate, lactose monohydrate, and sucrose, have been used to test the described material characterization techniques and expanded milling model.Grinding pressure (GP) and pusher pressure (PP) are reported in psig and feed rate (FR) is given in g/s.