Size matters: ABx enhances fluorine recovery

ABx Group is confident its subsidiary Alcore will achieve substantially-enhanced fluorine recovery after incorporating new equipment to deliver the ideal feed particle size for its reactor to handle.

The company is awaiting results from a fourth phase of testing after a ball mill and an ultrasonic vibrating screen were used to prepare a narrower range of particle sizes for feed material.

While ABx says an independent study on bath samples used in its new pilot fluorine reactor showed lower than expected fluorine recoveries of only 70 per cent in a third test run of Alcore’s reactor, it concluded that large and possibly inconsistent sample particle sizes were an issue.

The pending results on finer grind sizes will be the first from testwork using sample material produced by the new equipment. Improved fluorine recovery will give the company a stronger case for commercialisation.

ABx Group managing director and chief executive officer Dr Mark Cooksey said: “As we await results from the fourth test run, my confidence in the ALCORE process to produce hydrogen fluoride has not wavered. With newly-commissioned equipment to allow bath feed particle size to be controlled, I strongly believe that we will achieve a higher recovery of fluorine from upcoming test runs at pilot scale.”

Particle size is an important factor in almost all chemical processes. For any given sample weight, multiple smaller particles possess a greater total surface area than fewer bigger particles and the more surface area available, the faster and more completely reactions will occur.

Alcore says it realised it had to reduce particle size after conducting its previous testing using bath feed as received directly from aluminium smelters. The company says it had already ordered its ball mill and vibrating screen, but they had not been available for use until January, in time for the fourth phase of testwork.

ABx will now also need to establish the scalability of sizing because a feed size that works in a test or pilot-scale reactor may not be the same as that required for a commercial-scale reactor, due to mass heat sink and other considerations. Such considerations will ultimately influence the commercial plant design.

Bath is a fluorine-rich waste typically produced in excess by the industrial-scale process of aluminium smelting. Until now, it has been expensive to replace with new products and is labour and energy-intensive and often wasteful to reprocess to recover even some of the entrained fluorine for re-use.

Since the installation and commissioning of Abx’s custom-made reactor in September, Alcore has been evaluating the process of fluorine recovery from bath through the production of the highly-reactive and industrially-important chemical, hydrogen fluoride. The hydrogen fluoride can then be further processed commercially to yield aluminium fluoride, which is a critical additive necessary in the production of aluminium from alumina – an aluminium oxide which is universally produced from bauxitic ore.

Australia is the world’s biggest miner of bauxite, producing up to 100 million tonnes per annum and it is the fourth largest exporter of aluminium metal in various forms. The nation has until now been dependent on international supplies of aluminium fluoride, for which China is currently its main source.

In that context, Australia’s ability to guarantee continued aluminium production remains insecure.

ABx says it is encouraged by its progress and the pilot bath reactor is performing as designed, enabling the effects of varying process conditions to be determined as Alcore steadily increases reactor throughput.

With aluminium being recently included in Australia’s strategic materials list, ABx’s efforts to enable home-grown aluminium fluoride production represents a vital safety belt for the country’s aluminium industry.

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