AQUALESCER - A NewApproach
to Aqueous Coalescing
The general concept of the new Aqualescer® technology is pre-treatment of organic in Solvent Extraction (SX) Plants for hydrometallurgy applications. Removing organic (liquid ion exchange + diluent) from a strong copper electrolyte solution, for example, decreases the levels of entrained organic and also coalesces the residual organic for recovery improvements in the electrolyte filters.
Since it is crucial that each solvent extraction plant consider electrolyte filters in the removal of the entrained organic from the principal stream, the design of the new Aqualescer, or "tank within a tank", offers an elegant solution (Fig.1). The technology can be used in new mining filter installations or as a stand-alone coalescer; it can apply to all hydrometallurgy markets and applications in oil fields, especially for desulfurization of diesel.
This low cost solution was developed by SpinTek to provide improved coalescence by adding pressurized air in the inlet feed line, increasing efficiencies. The efficient removal of entrained organic from aqueous streams minimizes plant operating costs and maximizes electrolyte quality. The unique Aqualescer process controls flow problems due to operational conditions by delivering a homogeneous flow.
There are no similar technologies in the marketplace; the system is unique - a low cost method of entrained organic removal either as a stand-alone system on raffinate or a pre-treatment to CoMatrix® polishing filters on electrolyte.
In the past, entrained organic recovery equipment has found limited commercial implementation due to extremely high flow rates compared to typical electrolyte flow rates and subsequently high capital costs. The goal was to produce a low cost but very high flow rate system that consistently achieves 75% or greater organic removal.
For the past 10 years, while improvements in solvent extraction processes have led to a reduction in the levels of entrained organic, the recovery of entrained organic has become more challenging. As an example, past levels of entrained organic in rich electrolyte could be 100 ppm; current values reach 20 ppm or even 10 ppm. Exponentially decreasing coalescing efficiencies are therefore common due to this significantly lower amount of entrained organic. Because of this, the Aqualescer is designed to not only reduce the levels of organic but is capable of coalescing the organic. The increased efficiency in the filters achieves outlets lower than 2 ppm in the electro-winning feed lines.
By stabilizing the organic level sent to electrolyte filters, the chance of overrunning these filters that send organic to the tank house is significantly reduced. The service cycle of the filters prior to backwash can thus be more accurately predicted and allow for fewer backwashes. The added benefit of fewer backwashes is that filters are on line for longer periods of time and the amount of water or lean electrolyte used for backwashing is minimized.
The direct feed from the coalescer to the CoMatrix Filter was done to minimize pumping issues and other operational conditions for the test units. The principal objective for this removal in series is to assure a minimum amount of organic in the outlet.
In actual implementation, the configuration would be varied with the electrolyte feeding a Matrix Tower Coalescer and then gravity fed to the electrolyte feed tank. The existing pumps would then feed the electrolyte from the feed tank to the CoMatrix filters.
As can be seen in Table 1, the results show low levels of organic in the total effluent with the vast majority of organic removed by the coalescer. Note that efficiency removals approached 95% during parts of the service run.
The coalescer performed well even with the presence of significant amounts of crud (organic + suspended solids) and the system was never out of service during the five (5) day test run.
The system consistently averaged 75% organic removal from the feed electrolyte.
When the organic present in the feed was greater than 20 ppm the efficiency rose to 88%. As the level of organic is even higher in the 30 ppm range removal efficiency rises to the 95% range.
The Aqualescer has the ability to significantly reduce the amount of organic in the electrolyte, which will extend the service run of CoMatrix or Dual-Media filters used to polish and filter the electrolyte. In this pilot test, the overall efficiency rose 90% considering the coalescer and CoMatrix Filter.
NEW INSTALLATION - Kazakhstan
The first installation of a production pilot plant Aqualescer is in copper mining SX plant in the Republic of Kazakhstan in Central Asia. This system includes a Solvent Extraction System and will be operational first quarter 2012.