Thickener feedwell internal trough slurry distribution method

Abstract

This paper presents a numerical and experimental investigation of an innovation in thickener feedwell technology. A feedwell plays a leading role in the robust operation of a thickener. Its multifunctional duties include slurry feed momentum dissipation, solids and liquor mass fraction preparation, flocculation, and symmetrical aggregate delivery to the tank. The testing of new concepts in the pursuit of developing a next generation feedwell presented an opportunity to create an improvement in process performance. An alternative method of using a feedwell trough, populated by a multitude of vertically directed nozzles, is adopted. These deliver slurry into a flocculation chamber before dispersing through an exit gap into the thickener tank. The trough most innovatively ensures flash mixing, and highly uniform solids dispersion inside the aggregate growth chamber. Initial examination adopted a multiphase Eulerian mathematical model to explore geometric configurations under various process scenarios. Numerical modelling indicated that when quantitatively compared to an equivalently sized diluting Vane Feedwell TM the design provides a large improvement in solids hold-up, mixing, exit distribution, and more. Modelling advanced to onsite testing of a non-diluting small 2 m diameter prototype in an industrial mineral processing plant. The retrofitted feed system improved thickener performance when compared to the pre-existing feedwell and at a newly higher throughput duty. The first occurrence of a networked bed was observed, underflow densities improved by 6.5% w/w, flocculant consumption reduced by 5%, and overflow clarity largely improved. Underpinned by this positive result, modelling has shown even greater benefits may be found in application of the new technology to self-diluting feedwells.