In-line particle size measurement for control of jet milling

Jet milling is suitable for the production of very fine powders with a well -defined particle size distribution (PSD). The major disadvantage of the pr ocess is the poor energy efficiency. In practice jet mills have to be opera ted below their maximum capacity in order to avoid the production of off-sp ecification material, due to operation disturbances. Therefore, it is impor tant to automate operation with a realtime PSD instrument for quality contr ol. In this paper, a study for in-line particle size measurement using lase r diffraction is presented to improve operation control. This measurement s ystem uses a novel CMOS pixel array, which has a robust and flexible featur e for the application. It also includes an in-line cell system, where direc t measurement is implemented in the product particle stream coming from the mill and an air purge for the cell window allows continued operation. Expe riments were conducted on a 10-inch spiral jet mill pilot plant with alpha- AL(2)O(3) as test material. The milling process is investigated by varying the operational conditions. The measurement results are useful to build a g rinding model for control purpose.