Dry-Stacked Tailings Filter Cake Truck Load-Out Bin
This is an example of a tall truck load-out bin designed specifically to handle difficult flowing cohesive, high-moisture content dry-stacked tailings filter cake.
Why Conventional Clam Shell Bins Suffer from Chronic Bridging and Inconsistent Discharge
Standard truck load-out bins use a clamshell or slide gates to meter discharge. Unfortunately, many of these systems suffer from chronic bridging and rat-holing.
In summary, these bins suffer from chronic plugging because when the clam shell or slide gate is only partially open it induces a funnel flow discharge pattern despite the fact that the geometry of the storage bin may be correct, where if the slide gate or clam shell were removed, the bin would self-empty in a mass flow or first-in, first-out discharge pattern. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with a very large discharge outlet. However, when the discharge outlet is constricted, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.
Ideally, a cohesive bulk solid such as a high-moisture content filter cake should be discharged in mass flow, or a first-in, first-out discharge pattern. The definition of mass flow is that during discharge, the entire mass of stored material comes down as a single body (single mass). To achieve this, material must discharge evenly from the entire discharge outlet of the storage bin. The tell-tale sign that you have mass flow is that material is sliding down the bin walls. In contrast, with funnel flow, material is stagnant along the hopper walls. When the clam shell or slide gate is only partially open, then material is not permitted to withdraw evenly from the entire discharge outlet of the storage bin because the slide gate has limited the “live” opening, causing some sections of material in the storage bin to be stagnant during discharge. The result is a funnel flow discharge pattern.
The solution to a reliable truck load-out storage bin for handling cohesive materials such as high-moisture content filter cake is simple. First, ensure the geometry of the storage bin is correct, such that if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern. Typically, Kamengo would recommend a plane flow hopper with a long and wide discharge opening, as this is among the most conservative bin shapes. Second, pair the storage bin 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 Mining Industry.