Vanadium is produced in China and Russia from the reprocessing of steel smelter slag. Some other countries produce it either from magnetite directly, from smelter flue dust or as a by-product of uranium mining.

It is mainly used to produce higher strength steel alloys and is used in small quantities in steel reinforcing bar. The most important industrial vanadium compound, vanadium pentoxide, is used as a catalyst in the production of sulphuric acid.

The vanadium redox battery for energy storage may be an important application in the future.

Vanadium redox flow batteries are a competitive alternative to lithium ion batteries for energy storage, particularly for stationary applications. This type of battery is now able to be purchased for home use but is finding more purpose in large scale storage applications.

The batteries have a longer life than lithium batteries, extending to some 20 years, but are larger than an equivalent lithium alternative and rely on a vanadium sulphate electrolyte.

Vanadium has many valence states which allow charge to be added when power is available and then for it to be drawn down, with the electrolyte changing valence state.

The diagram below shows the principle operation of a vanadium redox battery.

If vanadium batteries are widely accepted, then there will be an increased demand for vanadium.

Already, vanadium companies are reporting a strong increase in price for vanadium, as shown in the price chart for 98% vanadium pentoxide (V2O5)per pound.  

How to Make the Electrolyte for a Vanadium Redox Flow Battery

The traditional use for vanadium has been ferro-vanadium additions for adding vanadium to steel. In this instance, vanadium is produced as a vanadium pentoxide (V2O5) and added to the electric arc smelting process when making ferrovanadium.

China has large reserves of vanadium in “stone coal” deposits. Production of vanadium pentoxide from these deposits consists of basic mineral processing techniques, such as gravity separation, followed by a salt bake with added sodium chloride at 750-850°C . This is followed by dilute sulphuric acid roasting, purification of the solution and chemical precipitation of ‘red vanadium’. This is purified in a number of processing stages to make 98% vanadium pentoxide.

Whilst this process may suit Chinese processing cost structures, the capital cost of the roasting stage is largely considered prohibitive for Western producers.

The main deposits of vanadium in a Western context are:

  • Vanadium-bearing magnetite (or vanadium titanomagnetites)
  • Vanadium-bearing oil shale

There are many instances of vanadium-bearing magnetites in Australia. Often these are associated within other volcanic rock structures. The advantage is that a simple crushing, screening and grinding operation followed by magnetic separation can produce a vanadium bearing magnetite concentrate. These concentrates rarely exceed 2.5% vanadium pentoxide, but for operations wanting a simple mineral processing operation, these concentrates are saleable.

The main issue for these concentrates is the titanium content. The magnetite can contain up to or exceeding 10% TiO2 content.

The titanium dioxide content is valuable in its own right, but is not helpful in the steelmaking processing. With this in mind, many vanadomagnetite processing operations also have to consider making a titanium product as well. One example of this is TNG Limited’s TiVAN process that has been developed for processing of the Mount Peake vanadium and titanium magnetite in the Northern Territory.

The processing of vanadium containing oil shale is more complex.

Oil shale is a misnomer as they do not contain oil, but a mineral called kerogen. Kerogen can be decomposed by heating to produce petrochemical products.

Companies such as Vecco Group and QEM are examining methods for production of vanadium from both oxidised and fresh oil shale from the Julia Creek region in Queensland.  Here the deposit contains remnants of sea floor calcium structures that need to be removed before vanadium extraction can begin.

To date, most processes for making electrolyte suitable for redox flow batteries start with vanadium pentoxide. However, the vanadium sulphate solution ideally has the vanadium in a V(III) or V(IV) valence state, not the V(V) state from the pentoxide as there is considerable re-processing required to reduce the solution to make it suitable for battery operation.

In recent time, focus has been diverted to develop a vanadium recovery process that produces an electrolyte suitable for battery use, without the need to process to V(V) valence state.

Work is on-going on a leach-solvent extraction process that would produce battery grade vanadium sulphate directly from the strip solution of the solvent extraction process. Engenium is assisting Australian junior mining companies to help develop this process.

An example for the potential use of vanadium redox flow batteries is the Rongke Power Development in Dalian, China, which utilises an 800 MWh battery containing almost 7000 tonnes of vanadium pentoxide.   For this one battery, this correlates to just under 4% of the world global demand. This system is due to come on line in 2020. The facility, pictured below, has a large bank of solar panels providing the energy to the batteries.

Australian Companies Working on Vanadium Extraction

Some of the Australian companies working in the vanadium extraction space are listed below for further reading:

Vanadium Redox Flow Battery Companies

 

Contributor:

Nigel Ricketts

Manager of Studies, Queensland - Engenium Pty Ltd