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Froth pumping has long been a major engineering challenge for mine operators, and new flotation practices designed to enhance mineral reclamation in the face of declining ore grades are proving problematic in sub-optimally designed pumping setups. 

Hoppers without systems for actively removing excess air are increasingly causing circuit bottlenecks and requiring more frequent maintenance as they struggle to deal with tenacious froths. 

To manage these problems, it’s important to understand the factors contributing to froth composition and how froth handling equipment can be improved to prevent build-up and alleviate performance bottlenecks. 

How to prevent issues in your sump and hopper 

For many operators, the hoppers feeding into the pumps represent a persistent source of problems, with air bubbles and their valuable mineral product building up in the sump and interrupting the effective flow of the froth.  

Frequently, these issues stem from a hopper which adheres to standard slurry pumping designs, rather than one specifically built to transport froth.  A standard slurry pump seeks to prevent solid matter from settling in corners of the tank and keep in suspension through sufficient turbulence. However, that same turbulence prevents the air in froth from escaping the slurry, reducing pressure, and causing blockages.  

Effective tanks for froth pumping instead promote continuous circular movement, which pushes the solids and liquid to the outside of the sump while air is gathered in the centre via centrifugal force, where it can escape to atmosphere.  

Ideally, froth pumping hoppers should be conical, or round with a conical shape at the bottom, to promote the transfer of minerals and liquid down into the pump rather than building up. Slurry should be introduced from the top of the hopper at a tangential direction to promote the whirlpool action inside the tank.  

Promoting efficient transport between the tank and froth pump 

As in nearly all aspects of froth pumping, intake pipes should be as large as practical to facilitate the clean movement of air and prevent blockages. They should be sloping down towards the pump, to allow air that does escape from the slurry to travel back up the suction pipe and into the sump, where it can ultimately escape. Otherwise, air can linger in the pipe and interfere with the slurry’s flow through to the pump. 

The pipe should also be as short as practically possible, with just enough space for a maintenance spool and an isolation valve, alongside a water injection port to help flush any built-up solids out.  

Having a dump valve on the suction side of the pipe will further streamline maintenance by making it simple to disconnect the pump from the tank and remove any residual solids from the pump.