These compact, stackable units offer considerable savings for new installations and are ideal for expanding capacity in an existing plant.
A new high-capacity flotation technology, the StackCell, has been developed as an alternative to both conventional and column flotation machines. This technology makes use of a pre-aerated, high-shear feed canister that provides efficient bubble-particle contacting, thereby substantially shortening the residence time required for coal flotation. Other potential advantages of the process include low air pressure requirements, low capital and installation costs, and increased flexibility in plant retrofit applications.
Recent full-scale plant trials suggest that this low-profile technology can provide coal recoveries and product qualities comparable to column flotation systems. Two full-scale approaches were tested including a single unit rougher application as well as a 3-stage, in-series arrangement. In the rougher application, the StackCell was able to successfully offload an existing overloaded flotation circuit which resulted in an increase in combustible recovery in excess of 90%. For the 3-stage circuit, the metallurgical results show that the StackCells, when arranged in-series, are meeting the design requirements at an acceptable combustible recovery, product carrying capacity, and product ash content.
StackCell technology provides an alternate means to efficiently achieve column-like performance when plant space and/or capital is limited. In particular, the small size and low weight of this new technology makes it amenable to low-cost plant upgrades where a single unit can be placed into a currently overloaded flotation circuit with minimal retrofit costs.
During operation, feed slurry enters the separator through either a bottom-fed or side-fed feed nozzle at which point low pressure air is added. The slurry travels into an internal pre-aeration sparging device that provides significant shear and contacting prior to arrival into the separation chamber. In fact, all of the necessary bubble-particle contacting is conducted in an aeration chamber prior to injection into the primary tank which is used only for the phase separation between the pulp and the froth. A liquid slurry level is maintained inside the tank so as to provide a deep froth that can be washed, thereby providing a high-grade float product. Froth is then carried into the froth launder via mass action. These separators are specifically designed to have both a small footprint and gravity-driven feed system that allows cells to be easily “stacked” in-series or placed ahead of existing conventional or column flotation cells. As such, the StackCell successfully integrates key design characteristics of both traditional column flotation and conventional (mechanical) cells.
StackCell can be deployed in multiple circuit configurations. The above graphic shows three possible circuits.