How Lites-Out™ Flat Bottom Classifiers Work
In a typical Lites-Out™ system, the Flat Bottom Classifier is fed by a Hydrocyclone to provide a controlled, dense and deslimed feed. This slurry enters the top of the unit via a central feed well, while water is injected via a plenum chamber through specialised nozzles to create an upward rising current. This establishes a zone of suspended, or teetered, solids. The solids in suspension are of a size fraction at the point of separation (better described as the cut point), suspended as neither coarser nor finer than the cut desired. Fine/light particulates don’t penetrate this dense fluidised bed and are carried up by the rising water current over the weir as overflow at the top of the unit. Coarser/heavier particles are able to penetrate the teetering bed and, by gravity, pass through the water injection zone to be collected and discharged through an underflow valve.
The McLanahan Lites-Out™ maintains separation automatically through a simple PID control loop. Operators can set the water injection rate and the desired operating density. The unit requires minimal supervision, as the Lites-Out™ control monitors the classification environment and opens/closes the dart valves at the bottom of the separation chamber. The unit automatically compensates for changes in feed rate, and the only moving parts are the underflow valves.
A manual globe valve and a flow meter is supplied with every unit so teeter water can be adjusted easily. For additional cost, the teeter water volume can also be automatically set and maintained using a separate PID loop control utilising an air-operated control valve.
Where the Lites-Out™ units are being used for organics removal such as in soils washing or lignite removal, the overflow will contain larger organics with the finer sand (equivalent weight particulates); in this case, an interstage screen is used to separate the larger organics from the finer sands.
Typically, in construction aggregates, the screen throughs will be recombined with the coarse Underflow and fed to either Screws, Hydrocyclones and/or Dewatering Screens to produce a stackable product. Screws and Hydrocyclones assist in further removal of the finest lightweight materials.
The organics are either disposed of with plant effluent, collected for use for site restoration or sent to high temperature destruction in the case of contaminated soils projects.