Transfer across the Pulp Froth Interface

The bubble structure at the top of the pulp is shown for two-phase foams in Figure 12. It can be shown that the rate at which bubbles are required to cross through a volume at the top of the pulp, described by the surface area of the cell multiplied by one bubble diameter, is determined by the overall aeration rate to the cell and the bubble size produced by the agitator or sparger.

The free rise velocity of a single bubble of a typical size produced in this way has a residence time significantly smaller than that calculated by dividing the liquid volume in the cell by the aeration rate. The dispersed bubble hold-up in the pulp is thus considerably less than that the bubble hold-up in the close-packed foam structure, producing a sharp discontinuity in the bubble volumetric fraction at the pulp-froth interface.

If, at the bottom of the foam layer the bubbles remain spherical in a closest-packed rhombohedral

Figure 12 The structure of the interface between bubbles dispersed in water containing surfactant and the froth. No particles are present in this system.

structure, the volume fraction occupied by inter-bubble water will be s = 0.26.

This means that solids transfer from the pulp to the froth in two ways. In the first the valuable particles are selectively attached to the bubble surface, while in the second the particles will be non-selectively entrained in the inter-bubble water. This entrainment will adversely affect the selectivity of the separation, but will apparently improve the total particle recovery.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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