The stainless-steel single screw feeder ensures carbon black is evenly extracted across the inlet from the hopper above, resulting in ‘uniform flow’. The manufacturer’s existing equipment provided mass flow, sufficient in most processes; however, in this application, any level of uneven residence time led to undesired variance in residence time and therefore powder temperature.
The screw feeder transfers carbon black powder, a challenging material to handle, as part of a cooling process. Commenting Eddie McGee, managing director, Ajax Equipment said, “The customer required good flow from a material that needs considered design. Ajax developed a feeder that provides the most even hopper residence time possible through progressive extraction geometry and a gentle extraction pattern. As a result, the feeder delivers a reliable supply of carbon black powder in a consistent and temperature.”
Continuing, Eddie said, “a further requirement was for the machine to have a maintenance-friendly construction. In response Ajax designed the feeder with a profiled clean-out door under the inlet, allowing easy access to the screw.”
Uniform Flow – Improving on Mass Flow
In most applications, mass flow, where all material moves together, provides a reliable supply of material in the condition required for further processing. However, although all the material moves, it does not flow entirely evenly. Uniform flow moves completely evenly.
In the case of process applications, such as heating or cooling, the differing rates at which regions of material pass through a hopper can result in undesired differences in material conditions, in this case, temperature. Uniform flow offers even drawdown and equal residence time, providing the all of material with the same opportunity to settle, resulting in a consistent condition. However, uniform flow is not easy to achieve and requires a very careful design of the hopper and equipment to extract the contents.
