Ultrafast Plug Flow Agglomeration—Exploiting Hydrophobic Interactions Via a Concentrated Water-In-Oil Emulsion Binder

Kim Van Netten,Kevin P Galvin,Daniel J Borrow

doi:10.3390/min10060506

Abstract

The selective agglomeration of a fine coal tailings stream using a high internal phase emulsion binder was investigated using a continuous steady-state plug flow through a high shear constriction. The emulsion binder effectively switches off the viscous resistance to particle–binder collision and adhesion, revealing the remarkable underlying speed of hydrophobic interactions. The emulsion binder is permeable, meaning the lubrication force between the particle and binder vanishes. The binder comprised a 95% aqueous solution dispersed within a 5% organic liquid (including the emulsifier). The agglomeration occurred within a high shear zone formed using a flow constriction within a 25 mm diameter pipe. The performance of the process was investigated at different flowrates in the range of 20–128 L/min, equating to extraordinarily high superficial flow velocities of up to 4.2 m/s and pressure drops in the range of 20–220 kPa. This rate greatly exceeds the nominal superficial feed velocity in flotation of order 0.01 m/s. Provided there was sufficient shear within the flow constriction, it was possible to process fine coal tailings with a feed ash of 50.1%, and generate a product ash of 8% at a combustible recovery of ~78%.

Highlights

Froth flotation has underpinned the continued economic production of coal and minerals since its discovery 100 years ago and, arguably, is the most important method of fine particle beneficiation today [1]
The plug flow approach appeared to perform significantly better than the previous high-speed blender
TheseThus, performance improvements appear istoimproved become marginal marginal the performance of the binder if the binder/particle suspension is subjected to a higher level of shear for a shorter period

Summary

Introduction

Froth flotation has underpinned the continued economic production of coal and minerals since its discovery 100 years ago and, arguably, is the most important method of fine particle beneficiation today [1]. The volume of the conventional mechanical cells has been increased progressively over the years to achieve sufficient economy of scale, reaching over 600 m3 in recent years. These large cells reflect the fact that flotation superficial velocities remain very low at only ~1 cm/s. As feed quality continues to decline there will be a need to consider using ever larger flotation cells, though in reality this may not be feasible. This means that new, innovative methods will be needed to address these challenges

Methods

Results

Conclusion