Uranium symposium covers state of the art (Part 5)

A number of presentations in the U2009 uranium symposium in Keystone, Colo., dealt with novel uranium recovery technologies.

Heap leaching has a successful track record in gold recovery, but the process is not usually associated with uranium mining. Enter Erik Hunter, a graduate student at the Colorado School of Mines, who presented a paper on improved methods of uranium leach and recovery, with special emphasis on heap leaching.

Hunter has identified an opportunity in the numerous dumps on old uranium mines in the Colorado Plateau. He suggests locating the heap near an existing disposal cell to reduce environmental impact. A mobile ion exchange unit can be used to recover the uranium from the leach solution.

The most troublesome aspect of uranium recovery was found to be the removal of iron during the uranium precipitation process. The problem was addressed by using various reagents.

Alan Miller of Dutch engineering contractor Bateman-Litwin described two case studies in a presentation on the development of solvent extraction processes in uranium recovery in Kazakhstan, as an alternative to using ion exchange. The main lesson that emerged during the tests was the need to use real solutions that came from the mines, since test results were different for each solution.

Furthermore, bench-scale tests in the laboratory were not sufficient, so Miller recommends tests in a pilot plant using real mine solutions.

In one case study, the results from the pilot-scale tests have indicated lower capital costs for a solvent extraction process than for an ion exchange process, and also lower processing costs per lb. of uranium.

In a second case study, Miller compared stripping the uranium in a conventional mixer-settler combination, with a process which strips the metal using solvent extraction, concluding that the solvent extraction process was superior because it makes it easier to avoid uranium precipitation.

Bryn Jones and James Davidson of Uranium Equities (UEQ-A) reported on a novel process for recovering uranium from phosphoric acid. According to Uranium 2007, a report prepared by the Nuclear Energy Agency, phosphates contain an estimated 7 to 22 million tonnes of uranium. Phosphates are a raw material for making phosphoric acid, so a process that could recover uranium from the acid could be a potentially large source of the metal.

Jones and Davidson reviewed the first two generations of processes developed to recover uranium from phosphoric acid. PhosEnergy, a subsidiary of Uranium Equities, is now developing a third generation process together with another company, Urtek.

The company has applied for patents for the new process. While sketchy on details, the speakers said that it is based on a novel pre-treatment combined with a robust extraction technology. They reported that the company had been operating a pilot plant since early 2009.

PhosEnergy has completed preliminary engineering for a demonstration plant, which it plans to have in operation later this year. It estimates capital expenditure at US$100-125 per lb. uranium oxide in annual production, and operating expenditure of US$20-30 per lb.

The company plans to complete a feasibility study in mid-2010, and have a commercial-scale plant running in 2013.

John Carr of Australian company Clean TeQ presented a paper which described how continuous resin technology can be used to improve uranium recovery from a leaching solution. Carr said that the use of elution and sorption technologies could potentially eliminate two stages in the traditional recovery process: the solid / liquid separation process, and the solvent extraction process.

Carr highlighted two sorption technologies: continuous resin in pulp, used for pulps, and resin in column, used for liquids. Continuous resin in pulp can operate with up to 50% solids, so its use can reduce or eliminate the need for solid / liquid separation.

Carr provided a detailed comparison among various flow sheet configurations. He concluded that continuous resin systems have a high reliability, and that they can both simplify and optimize the uranium recovery process.

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