In the 1960s, the world’s leading aerospace engineers at Lockheed’s Skunk Works facility faced an extraordinarily difficult engineering challenge: how to design a successor to the U-2 spy aircraft, which had proven increasingly vulnerable to advanced Soviet anti-aircraft systems. Among other capabilities, the next-generation aircraft they were to design required an ability to cruise at a sustained speed of Mach 3+, operate at altitudes exceeding 80,000 feet, and feature as low a radar cross section as possible. Given the technologies of the day – slide rules were still used by engineers for most calculations – it was a daunting task.
One of the key hurdles was designing and machining components of the jet’s outer skin such that it could handle temperatures from aerodynamic friction and continuous engine operation as high as 1,050 °F. The answer: titanium-based alloys that contained the metal vanadium. When added to titanium, vanadium helps to create alloys with the best strength-to-weight ratio of any engineered material on earth.
Half a century later, there remains no acceptable substitute for vanadium in aerospace titanium alloys. Vanadium-containing alloys of titanium and aluminum are deployed in virtually every jet aircraft flying today, from jet engine components to high-speed airframes.
What Is Vanadium and Where is it Produced?
A hard, silvery gray, ductile, and malleable transition metal with atomic number 23, vanadium (V) is the 22d most abundant element in Earth’s crust. It is a major constituent (>10 weight percent) in more than 150 different minerals. Several diverse mineral deposit types contain vanadium-bearing minerals, and vanadium deposits are globally distributed. In general, these minerals comprise four principal deposit types: vanadiferous titanomagnetite (VTM), sandstone-hosted vanadium (SSV), shale-hosted vanadium, and vanadate deposits. Additionally, significant amounts of vanadium are available for commercial use as a byproduct of petroleum refining. Processing of coal, tar sands, and oil shales may be important future sources.
The majority of the world’s supply of vanadium (approximately 80 to 85 percent) is derived from mined ore that comes either directly from deposits or from steelmaking slags produced by processing the ores mined from VTM deposits. The remaining 15 to 20 percent of the world’s supply of vanadium comes from (a) spent catalysts that collected vanadium during the refining of crude oils; (b) residues from the production of alumina, uranium, and some hydrocarbons; and (c) ash derived from burning high-vanadium-content coal or petroleum.
World vanadium resources in 2012 were estimated to be 63 million metric tons of vanadium. Reserves were estimated to be 14 million metric tons. The majority of vanadium supply in 2019 is from China (61 percent), Russia (14 percent), and South Africa (8 percent) (Figure 1).
Vanadium’s Many Uses
Vanadium is used principally in the production of metal alloys, and its consumption trends are heavily influenced by trends in steel production.
Vanadium is used in steel to impart strength, toughness, and wear resistance. The formation of vanadium-rich carbides and nitrides imparts the strength to steel; the addition of less than 0.1% vanadium per ton of steel can result in increased strength of the steel by as much as 50-100 percent. Apart from its strengthening characteristic, vanadium also inhibits corrosion and oxidation.
The high-strength, low-alloy (HSLA) steels containing vanadium are widely used for the construction of auto parts, buildings, bridges, cranes, pipelines, rail cars, ships, and truck bodies, including armor plating for military vehicles. Such HSLA steels are increasingly being used in the oil and gas industry to meet demand for pipelines with higher strength and higher low-temperature toughness.
Vanadium is used in tool steels in various combinations with chromium, niobium (columbium), manganese, molybdenum, titanium, and tungsten. Only a limited degree of substitution is possible among these metals, however. Replacement of vanadium with other mineral commodities requires significant technical adjustments to the steel production process to ensure that product specifications and quality are not compromised. For example, use of vanadium generally requires less energy consumption during production than does niobium to give equivalent steel properties. Therefore, substitution for vanadium is normally not considered for short-term changes in market conditions because of the considerable effort involved in implementing the change.
Non-metallurgical applications of vanadium include catalysts, ceramics, electronics, and vanadium chemicals. For catalytic uses, platinum and nickel can replace vanadium compounds in some chemical processes. Vanadium dioxide is used in the production of glass coatings that block infrared radiation and in special optical glasses for night vision. Vanadium also is becoming more widely used in green technology applications, especially in battery technology.
Vanadium and Renewable Energy Systems
The emerging need for large-scale electricity storage makes vanadium redox-flow batteries (VRBs) a major potential future use of vanadium. Because of their large-scale storage capacity, development of VRBs could prompt increases in the use of wind, solar, and other renewable, intermittent power sources. Lithium-vanadium-phosphate batteries produce high voltages and high energy-to-weight ratios, which make them ideal for use in electric cars.
VRB systems consist of an assembly of power cells in which two vanadium-based electrolytes are separated by a proton exchange membrane. The main advantages of the VRBs are (a) their nearly unlimited capacity, which is made possible simply by using sequentially larger storage tanks; (b) their ability to be left completely discharged for long periods of time with no detrimental effects; (c) the ease of recharging them by replacing the electrolyte if no power source is available to charge it; and (d) their ability to withstand permanent damage if the electrolytes are accidentally mixed.
The Strategic Nature of Vanadium Today
On May 18, 2018 The Department of the Interior published a list of 35 mineral commodities considered critical to the economic and national security of the United States. This list will be the initial focus of a multi-agency strategy to implement President Donald J. Trump's Executive Order to break America's dependence on foreign minerals. Vanadium is included as one of the 35 critical commodities.
The Role of High-Purity Vanadium
Given that the majority of vanadium is used in steel production where the addition rate of vanadium is very low, vanadium in the steel industry is very much a commodity market. Due to the low addition levels, in most cases impurities present in the vanadium are of no consequence to the steel maker. As a result, the vast majority of the global vanadium capacity is designed to meet the quality requirements of the steel industry at the lowest possible cost.
Typically, commodity grade vanadium pentoxide has a purity of 98%.
However, in aerospace, energy storage, catalyst and other chemical applications, high-quality vanadium oxides or downstream alloys and chemicals are required. In the aerospace industry, it is critical to ensure that the quality of the vanadium oxide used in the production of master alloys for the titanium industry has high purity and is free from any potential high melting point contaminates. The critical application of vanadium bearing titanium alloys in rotating and other critical aerospace applications requires assurance of high purity and no defects.
High-Purity Vanadium Oxide Production in the U.S.
In Hot Springs, Arkansas, U.S. Vanadium produces the highest-purity vanadium oxides and downstream vanadium chemicals in the world. The Hot Springs facility recovers vanadium from secondary sources such as residues, ashes, and other materials resulting from the burning or refining of vanadium bearing oil. The Hot Springs plant also can recover vanadium from vanadium bearing slags generated at steel mills and other smelting operations where vanadium is present. The Hot Springs facility is shown in Figure 2 and the process for producing high purity vanadium oxides at the facility is depicted in Figure 3.
The materials are fed to the plant at Hot Springs and vanadium is leached into the aqueous phase. After separation of the solids, the pregnant liquor is fed to an ion exchange/solvent extraction process, which effectively removes any metal contaminates that may have come into solution during the leaching process. The clean pregnant liquor is then fed to multistage growth type crystallizers where relatively large orthorhombic crystals of ammonium metavanadate are precipitated. The crystals are washed, dried and decomposed to form either V2O5 or V2O3. The high purity oxides can be used for production of master alloys for the titanium and aerospace industries, or they can be converted into other downstream vanadium chemicals and alloys for various applications.
The Future of vanadium
Growth prospects for vanadium consumption, both in steelmaking and in high-purity chemical processes, look very attractive. Global growth in steel production, combined with growth in the use of high-strength, low-alloy vanadium steels to replace lower strength carbon manganese steels will continue to drive growth in commodity quality vanadium consumption. Growing commercial aerospace and defense demand for titanium alloys will mean growing use of high-purity vanadium in these applications.
Looking at newer applications, there is a tremendous potential for vanadium in energy storage applications, both in front and behind the meter. Other very interesting potential new uses for vanadium in the future could include dynamically switchable thermochromic fenestration coatings for architectural glass leading to massive energy savings, as a catalyst for water-splitting to support the future hydrogen-based economy, and the next generation (beyond lithium ion) of intercalation and solid state batteries for mobility applications (Figure 4).
Vanadium is irreplaceable for its role in aerospace applications, and its importance in supporting the development of commercial aviation and defense applications will continue to grow in the future. At the same time, the utilization of vanadium in the steel industry allows for the ongoing development of infrastructure in the developing world to support economic development in the most efficient manner possible by using high-strength, low-alloy vanadium steels to replace lower strength carbon manganese steels.
Potential new applications in energy storage, thermochromic fenestration and solar water splitting ensure that vanadium will grow in its importance to terms of supporting global economic development in the most efficient manner possible.
This article was written by Terry Perles, Member of the Board, US Vanadium Holding (Pittsburgh, PA). For more information, visit here .