A novel hydrophobic binder consisting of tightly-packed drops of aqueous salt solution, stabilized by thin films of oil, in the form of a high internal phase water-in-oil emulsion was used to agglomerate ultrafine hydrophobic particles in seconds to a size sufficient for their capture on a 150 micron screen. Almost complete recovery of the particles, extending from sizes of more than 100 microns to below 500 nanometers, was achieved. Examination of the process revealed that the agglomeration appears to be governed primarily by the length scale of the thin oil films, of order 30 nm, and their ability to efficiently deliver organic liquid to the particles quickly. Moreover, it appears that the hydrodynamic resistance that develops when a particle is 2 driven towards an interface is reduced due to the permeability of the films. Water permeation driven by osmosis also appears to assist the transport of the particles towards the interface.

Fine coal may be separated from an aqueous suspension of coal and mineral particles through the application of a pure oil. The pure oil preferentially wets and agglomerates only the coal, forming a high quality, granular product. However, the use of the pure oil also comes at a relatively high cost and this cost prohibits commercial implementation of this process. In this work a new, economic binder, was introduced. This binder consisted of a high internal phase water-in-oil emulsion which was 95 vol% water and 5 vol% organic. This type of binder was selected as it possessed the hydrophobic surface functionality of oil while the space filling functionality of the binder was primarily satisfied by the dispersed water droplets within the emulsion. The application of this emulsion in the agglomeration process led to a 10-fold reduction in the organic liquid dosage required to achieve agglomeration as compared a pure oil binder. It was also observed that the agglomeration time required when using the emulsion binder was one order of magnitude less than required when using a pure oil binder. This variation was considered to result from the five orders of magnitude difference in the viscosity of the two binders.

A high internal phase (HIP) water-in-oil emulsion was used as the binder in the selective agglomeration of fine coal from an aqueous suspension of coal and mineral particles. Traditionally, this agglomeration is achieved by a pure oil, hydrophobic, binder. However, the high cost associated with using pure oil makes the process economically unfeasible. Therefore, the emulsion binder introduced in this work was motivated by the economic need to reduce the amount of organic liquid required in the process. The effect of agitation time during the agglomeration process and the composition of the emulsion on its performance as a binder were investigated. The best result obtained was for a HIP emulsion made from 3 wt% aqueous NaCl and diesel oil with sorbitan monooleate as the emulsifier. This emulsion had a dispersed phase volume fraction of 0.94 and achieved a seven-and-a-half-fold reduction in the amount of organic liquid required to achieve agglomeration.

No abstract

The process of fine coal agglomeration is a beneficiation technique that uses an organic liquid, such as, diesel, to agglomerate fine coal from an aqueous suspension of coal and mineral particles. The organic binding liquid is dispersed in the aqueous suspension through the application of agitation and selectively wets and agglomerates the hydrophobic coal particles. The hydrophilic mineral particles remain finely dispersed and, thus, the product coal agglomerates can be easily retrieved by passing the suspension over a screen. Fine coal agglomeration can achieve high quality beneficiation and allows for more effective dewatering of a fine coal feed. Regardless of these excellent capabilities, however, there are no industrial applications of this process. This is because the high cost of the oil makes the process economically unfeasible. Therefore, in this study a modified fine coal agglomeration process has been investigated in which the aim is to reduce the amount of organic liquid required in the process. The modification involves the use of a water-in-oil (W/O) emulsion as the immiscible binding liquid, replacing the conventional pure oil approach. A high internal phase (HIP) emulsion is used as it provides the interfacial functionality of the oil, while the space filling functionality is provided by the stabilised internal water droplets. In this study, an investigation into the kinetics of agglomeration of the modified process was undertaken. It was found that complete agglomeration of the carbonaceous material in the feed could be achieved by the emulsion binder in one third of the time required for a pure diesel binder. In addition, the improved kinetics were achieved by the emulsion binder at an organic liquid dosage of five-times less than required by a pure diesel binder.