Crushed Glass Metering Bin
This is an example of a small metering hopper designed to handle crushed glass.
Why Conventional Equipment Often Suffer from Chronic Plugging and Inconsistent Discharge
Typical metering hoppers handling crushed glass use a pyramid hopper that converge to a small opening that is discharged using a screw feeder.
In summary, a pyramid hopper with a small opening is typically a poor choice of bin shape for handling difficult flowing materials. The bin shape promotes a funnel flow discharge pattern. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with large bins with large discharge outlets. However, when the discharge outlet is small, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.
In addition, the pyramid hopper is discharged by a feeder that preferentially withdraws material from the hopper outlet, which again, promotes a funnel flow discharge pattern.
The solution to a reliable crushed glass metering hopper has two parts.
The first half of the solution is to choose a conservative hopper shape. Kamengo prefers using a plane flow hopper with a wide and long discharge opening. A plane flow hopper only converges in one plane at a time, and is vertical in the opposite plane. The purpose of using a conservative bin shape with a long and wide discharge outlet is to employ a geometry where if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern.
The second half of the solution is to pair the plane flow hopper with a fully-effective feeder – that is a feeder that withdraws material evenly from its entire infeed opening. By definition, to achieve mass flow, where the stored material comes down as a single body, the feeder must withdraw material evenly from its entire opening. If the Feeder withdraws material selectively from the bin discharge outlet, sections of material in the bin will be stagnant and funnel flow will ensue.
A great example of a fully-effective feeder is the Kamengo Feeder. In addition to being fully-effective, the Feeder offers consistent metering, and can be made as wide as needed and as long as wanted. As a result, the Kamengo Feeder offers valuable advantages when designing for a difficult flowing material.
To learn more about the physics of storage bin and feeder design as well as the root causes of bin plugging, please download our white paper entitled: The Design of Reliable Storage Bins and Feeders for the Recycling Industry.