BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:—
FIG. 1 is a longitudinal cross-section through a fluidising apparatus;
FIG. 2 is a cross-section on line AA in FIG. 1;
FIG. 3 is a Computational Fluid Dynamics (CFD) image of the pressure profile of the fluidising apparatus of FIG. 1;
FIG. 4 is a CFD image of the inverted vortex flow from fluidising apparatus of FIG. 1;
FIG. 5 is a schematic diagram of a typical precious metal recovery plant; and
FIG. 6 is a schematic diagram of a mixing apparatus using a magnetic unit.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
FIGS. 1 and 2 illustrate a fluidising unit comprising a flow chamber 102 having a fluid inlet 104 and a fluid outlet 106. The flow chamber 102 comprises a housing in the form of a cap 108 having a side wall 110 and a top 112 which in the region 114 is generally in the shape of a cone with a concave side wall. The underside of the top 112 is provided with an annular recess 116 in which is located a cylindrical flow guide 118. As best shown in FIG. (2), the upper portion 120 of the flow guide 118 is provided with a series of tangential slots 122a to 122f. The lower portion 124 of the flow guide 118 has an external thread which cooperates with an internal thread formed in an annular flange 126.
A fluid outlet 106 is defined between the side wall 110 of the cap 108 and the flange 126 and an annular flow passage 128 is defined between the side wall 110 of the cap 108 and the upper portion 120 of the flow guide 118. The annular flow passage 128 is continuous with the fluid outlet 106, so that the fluid inlet 104 communicates with the fluid outlet 106 by means of the tangential slots 122a to 122f and the flow passage 128. Directly above the flow chamber 102 is located a discharge pipe 130.
In use of the “HydroTrans” fluidising unit illustrated in FIGS. 1 and 2, fluid under pressure enters the fluidising unit through the fluid inlet 104, passes down the flow guide 118 and exits the flow guide tangentially via the slots 122a to 122f (as the open end of the flow guide 118 is closed by the cap 108). The cap 108 also acts as a swirl enhancer and is positioned such that its side wall 110 forms one side of the said annular flow passage 128 around the tangential slots 122a to 122f. The cap 108 is longer than the slots 122a to 122f, such that it overlaps the slots by an amount ‘d’ and defines the fluid outlet 106 by which the concentrated swirling fluid exits the flow chamber 10 The profiled region 114 of the cap 108 is shaped in order to encourage a stable fluid regime above the flow chamber 102.
FIG. 3 shows the pressure profile of the HydroTrans fluidising unit, with a solvent feed pressure of 20 psig. The pressure profile is created by Computational Fluid Dynamics (CFD).
FIG. 4 shows that the swirling exiting fluid (solvent) from the HydroTrans head produces an inverted vortex at the entry to the discharge pipe, which is considered to be fairly stable under normal velocity flow conditions, resulting in enhanced mobilisation of solids surrounding the HydroTrans head. The vortex generally has a low pressure core or zone compared to that of the rotating liquid around it (see FIG. 3). This can create a boundary layer of liquid rotating around this core where the core's pressure may be close to the vapour pressure of the liquid (solvent) being used thus allowing the water at this point to become excited leading potentially to cold boiling. For example, water, whilst still below its natural boiling temperature, can behave as boiling water (water surface tension reduces, and may even affect the water's natural capilliary force) which may approach endothermic conditions at certain temperatures which could increase the solubility of the solute in question.
The dissolving, leaching (see FIG. 5) or oxidising process using the fluidising unit can be carried out below atmospheric pressure until it is discharged into an open tank or vessel. The dissolving, leaching or oxidising process in the fluidising unit can also be carried out in a pressurised environment, although the vortex zone of influence created by the fluidising unit will normally show evidence of a lower pressure zone to the surrounding liquid pressures. The vortex low pressure zone/core can only exist within the vortex itself and virtually instantaneously reverts back to the surrounding pressure when discharged from the pressure vessel. This rapid fluctuation in pressure zones can in some instances assist in keeping the solutions in a saturated or super-saturated state.
The process may be further improved by passing the feed fluid and/or slurry/solution discharge through a magnetic field to magnetise for example the feed water (solution), see (see FIG. 6) prior to the formation of the vortex to enhance the cold boiling effect. The process may be further enhanced due to the particle interaction and attrition created within the aforementioned reasonably stable vortex. The ability of the fluidising unit to control solids (solute) discharge concentration also effects and helps to control the dissolving rate of the solids (solute).
The process can be described as a high throughput low size reactor within the confines of a large vessel which can subject each particle in the zone of influence of the vortex to the reaction described above prior to discharging the solids and saturated solution from the vessel. This maybe due to the mass transfer happening within the vortex and the fluidising unit creating the vortex, which is also in close proximity to the discharge pipe exiting the vessel, where the greatest Delta P will be evident.
The process described above can be used in the metals recovery industry (see FIG. 5) to achieve rapid leaching, and has the benefit of increasing recovery levels of metals whilst reducing solvent and chemical demands. This increases the efficiency and economic viability, whilst reducing volumes of waste streams to the environment. For example, if the process is used for leaching copper with an acid from ore in a pressurised system as opposed to a heap stack process, the environmental benefit is substantial.
The process allows the use of continuous metal recovery systems which can have several treatment stages using different solvents, acidic or alkaline; to seek out and recover particular metals in the recovery process as may be required, see (FIG. 5).
Patent Application
20080064766
