On-Line Measurement of Powder Size and Velocity in the Water Atomization Process

The on-line control of the water atomization process, an appropriate way to achieve an improved efficiency and reduced costs in molten metal spraying, has to include measurements of the produced powder particles mean diameters. In this contribution, an optical measurement technique, extended phase/Doppler anemometry (PDA), capable of distinguishing on-line between melt and water droplets utilizing the different scattering mechanisms of both fluids, is described. The present investigations were performed using a modified commercial PDA system adapted to a specifically prepared atomization unit, yielding the required optical access to the region of interest below the water nozzles. Preliminary tests showed the capability of the measurement system in monitoring on-line the production process of CuCo5 powders. The PDA results show deviations of 10 to 20%, respectively, from the results of conventional sieving of the entire powder produced. Finally, the set up of a control loop for powder p roduction by water atomization is discussed.