Powder Characterization For Process Designers And Engineers

By Tim Freeman, Freeman Technology

For process designers specifying new plant, the goal is to engineer equipment that will process and handle powders consistently and efficiently, as defined by the design brief. In contrast, engineers working as part of the manufacturing team rarely have the option of changing out equipment, but strive to achieve acceptable operation using the existing plant. While these goals are somewhat different the two groups share a need for detailed process understanding, knowledge of the interplay between powder properties and process equipment and how, in combination, they deliver product with the intended properties and quality. For the particulate handling industries this can be a daunting challenge. To successfully design and operate powder processes, engineers need to determine the conditions to which a specific unit operation will subject the powder, and then measure the powder's response to each of these environmental conditions.

Consider the example of a blend flowing from a hopper into the feed shoe of a tablet press. Each time the powder level falls below a certain point, the hopper is refilled with a new batch of feed. With certain blends it is noticeable that a short time after this refill, discharge flow becomes erratic, resulting in a plant stoppage. When hopper flow is reinstated the blockage problem translates through to the shoe, with poor flow to the dies giving rise to inconsistent filling. However, not all blends exhibit this behavior.