Zircon substitution: myth or reality?

By
Published: Thursday, 28 April 2011

In just over six months prices for zircon sand have doubled. Alister MacDonald evaluates global supply and markets, and outlines why zircon substitution is little more than a myth


Soaring prices for zircon are causing end users
to evaluate cheaper substitutes for a range of
applications, including foundries (pictured) where
chromite sand can replace its costlier counterpart


The world market for zircon and downstream zirconium materials represents a $3.5bn industry, which has witnessed dramatic changes in demand and supply during the past few years. The future forecast shortage in zircon supply has been brought forward due to strong demand in China, and has caught many people by surprise as they adjust to the reality of the current situation. Across all applications worldwide, the issue now is how to allocate approximately 1.3m. tpa of zircon when demand exceeds supply by more than 100,000 tpa in 2011.

Though the immediate concern is zircon supply in 2011, supply in future years is even more uncertain. TZ Minerals International Pty Ltd (TZMI) is forecasting that zircon supply will stay at current levels for the next several years (Figure 1).


Figure 1: Zircon supply outlook to 2020



Source: TZ Minerals International


New zircon production capacity will only offset falling production from existing mining operations. To make matters worse, the poor financial returns of recent years have deterred any new investment in mineral sands operations. Higher production costs and unfavourable currency exchange rates have only added to the problem. It has only been the result of sharp increases in zircon prices that investment in new mining capacity is starting to look attractive in terms of domestic currencies such as the Australian dollar or South African Rand.

Yet even for new mining projects which have completed feasibility studies and have financing in place, output from these mines are not expected to contribute to zircon supply for another two or three years. Complicating the supply situation, these new mineral sands projects contain moderate to very low ratios of zircon to titania minerals, thus reducing their contribution to future zircon supply.

Beyond this, it typically takes 7-10 years from the time a new mineral sands deposit is discovered to it achieving full commercial production. In this category, new Eucla Basin type developments (South Australia) have been announced. But, by the time these mines are fully operational, output from existing mines will have declined and no net gain in world zircon supply will be achieved. This is why total world zircon supply is not likely to increase significantly from current levels for many years. So, zircon end users will continue in their struggle to secure adequate supply in the years to come.

The present response of mineral sands companies to the shortage has been to allocate zircon to customers based on their consumption in 2010 rather than forecast demand for 2011. This is an important distinction as forecast demand for 2011 is very different for mature markets in Europe and North America, compared to high growth economies in Asia and South America.

Various sources have estimated China’s zircon consumption was between 600,000 and 650,000 tonnes in 2010. With a zircon growth rate close to 20%, and China consuming about 50% of world output, China’s 2011 demand for zircon will increase by 120,000 to 130,000 tonnes.

China’s high growth rate is not a sudden phenomenon, as annual growth rates have been approximately twice the rate of growth in GDP for the past 20 years. The end uses in China with the highest growth have been ceramics, and this rate of growth has now slowed during the past two years. Growth has continued for zirconium chemicals and fused zirconia, as well as for glass and steelmaking refractories. This is directly related to the urbanisation of China, wherein all construction materials have experienced strong demand.

In addition, a significant percentage of zircon consumed in 2010 was supplied from stocks built up by mineral sands companies during the global financial crisis, or due to the drawdown of stocks by end users. Zircon supply is now coming from existing production, so supply in 2011 will be less than last year.

The relationship between mineral sands companies and end users has also become an important supply factor. The loyal, long term zircon customers recognise that, while prices are important, supply is more critical to maintaining operations. Consistent zircon quality is also important, and is also likely to come under pressure as miners seek to maximise output. Zircon specifications requiring low impurities, such as alumina, iron, or titania, may reduce zircon production yields by 10% or more.

The difference between premium and other grades of zircon sand is also an important distinction. Under prevailing conditions, true premium grade zircon will become very scarce ‘like gold’, but leading companies will find ways to utilise sub grades without compromising end product specifications and performance.

Traditionally, Australia and South Africa have supplied approximately 75% of zircon and titania minerals worldwide, but there is increasing recognition of the strategic significance of these minerals and the value adding opportunities. South Africa’s National Empowerment Fund has just announced plans to invest $2.2bn to set up a vertically integrated rare metals facility to transform minerals sands such as zircon and titania minerals into value added chemicals, pigments and metals to add value to natural resources and to create much needed employment.

Zircon, for example, can be processed into zirconium chemicals and powders, or all the way to zirconium metal for nuclear and industrial applications. China has done this for many years, with its rare earths industry being a prime example.

End users of zircon and zirconium materials are now seeking to substitute alternative materials, but are finding there are few options which provide equivalent or similar performance. In general, zircon (Zr) is irreplaceable due to its specific and unique chemical and physical properties in almost all applications. It is also likely that wider industrial applications of Zr are yet to be discovered and understood in years to come. Any assessment of the potential to substitute for zircon requires an analysis of the main end uses for zircon, and the main attributes needed for each application.

TZMI has compared the main end uses for zircon between 2000 and 2008, plus a forecast for 2012 as shown in Figure 2. Ceramics remains the largest end use at 56 % for zircon, followed by zirconia and zirconium chemicals which have doubled from 9% in 1990 to a forecast 18% in 2012, which would require about 250,000 tonnes of zircon.

There is often confusion in understanding which zirconium materials are being discussed due to the different names which are used across the industry to describe each of the main zirconium intermediates or end products. Table 1 describes the main forms of zirconium materials and alternative sources of zirconium.

At present, naturally occurring zirconia, or baddeleyite, is the only commercially available source of zirconium apart from zircon. However, total baddeleyite production is only 7,000-8,000 tpa and is a by-product of iron ore from Kovdor Mining on the Kola Peninsula in Russia.

Other sources of zirconium are found in complex polymetallic ore bodies, with major deposits discovered in Australia and Canada. The most advanced project of this type is the Dubbo zirconia project held by Alkane Resources Ltd, which is expected to produce 6,000-15,000 tpa of zirconium chemicals and powders, niobium, as well as light and heavy rare earths (see panel). This is a strategically significant project because the zirconium chemicals and powders are independent of both the zircon supply chain, and China’s zirconium chemicals industry, which supplies over 90% of world supply. Similarly, it provides a strategic alternative to China for rare earths.

Finding and defining an economic polymetallic resource with access to good infrastructure and services is the first step, but separating and recovering the valuable metals is the real challenge. This is because it is difficult to put the metals in solution without dissolving the host rock as well.

Alkane’s Dubbo project is one example where the separation into zirconium, niobium, plus light and heavy are earth streams has been successfully achieved by using a sulphuric acid roast and subsequent leach. The Dubbo ore body is also large and consistent throughout, which simplifies processing to ensure stable quality products to be produced.


Figure 2: Zircon usage by application



Source: TZ Minerals International


Zircon substitution

Analysis of the major end uses for zircon shows that there is no readily available substitute for zircon in over 80% of applications. Table 2 shows the potential to substitute zircon in the top four applications for zircon which account for 96% of total consumption.

Where substitution is possible, this is mainly due to the use of other zirconium-derived raw materials, such as naturally occurring zirconium dioxide, baddeleyite, or zirconium from complex polymetallic ores. Substitution in this discussion refers to alternatives to zircon.


Table 2: Potential to substitute for zircon in major applications

Market segment Market share Substitution potential
Ceramics 1 10%
Zirconia & chemicals 0 10%
Refractories 0 10%
Foundries/casting 0 50%


*2012 zircon market: 1.4m. tpa. No zircon substitutes for over 80% of demand.
Sources: TZ Minerals International & TCMS


Table 3: Zircon substitutes in ceramics

Acid Oxide Refractive indices Price US$/tonne World production m. tpa
Tin oxide SnO2 2 $19,000 0.33
Zirconia ZrO2 2 $6,000 0.11
Zircon ZrSiO4 2 $1,750 1.3
Alumina Al2O3 2 $400 81.6



Sources: Ceramic Glazes-Parmelee, LME, and USGS


Ceramics

The main use for zircon is in ceramics as an opacifier in floor tiles, sanitaryware, and tableware. Gres porcellanto tiles also consume significant quantities of zircon. In total, ceramics applications are responsible for over 50% of total zircon consumed. Finely milled or micronised zircon imparts a high degree of whiteness due to its high refractive index. Zircon also has a low solubility in silicate melts, and is commercially available in large volumes. Zircon has substituted for tin oxide in ceramics since the 1950s due to the favourable combination of properties, cheap price, and ready availability.

Some European opacifier producers threatened to stop using zircon as an opacifier as prices moved higher over the past two decades, but a rational analysis of the alternatives shows that this was a myth, driven by commercial considerations to maintain low prices. Table 3 lists the key properties for ceramic opacifiers and potential alternatives. Tin oxide is recognised as a superior opacifier to zircon, but world production is very limited and its price is nearly ten times that of zircon. Alumina is often quoted as an alternative to zircon due to its lower price, but has a lower refractive index and produces a matt glaze.

Thrifting of zircon has resulted in specific consumption halving during the past 20 years to the present level of about 80g/m2, so further gains appear to be limited. Sensitivity to the zircon price for ceramic tiles also remains low, with the cost of zircon opacifier being approximately $0.16/m2 compared to ceramic tile production costs of around $6/m2 in China. Even with higher zircon prices in 2011, the cost of zircon opacifier is less than 3% of the cost of a ceramic tile, so end users can continue to absorb price increases.

White tiles are the standard of the industry (like white is the standard colour for motor cars) and they may simply cost a little more. It is also worthwhile to consider the relationship between titanium dioxide pigment prices and opacifier prices; historically the latter has always followed the former.

Zircon is also used in the production of coloured zircon pigments, where approximately 40,000 tpa of zircon is converted into either fused zirconia or chemical zirconia to produce praseodymium yellows, vanadium blues, or iron reds. South African baddeleyite from Palabora was used extensively for zircon pigments until 2001 when the open cut mine went underground and production of baddeleyite as a by-product effectively ceased.

Russian baddeleyite has only met with limited success in zircon colours. Substitution of zircon from polymetallic sources is likely for zircon pigments where zirconium chemicals and powders are used, while their use in ceramic opacifiers is also a longer term opportunity.

Zirconium materials

Zirconium materials represent the next largest market for zircon, with TZMI forecasting this segment to consume 18% of total zircon by 2012, which has doubled during the past decade. Figure 3 shows the diverse end uses for zirconium, which are used in everyday items.

In most applications, the use of zirconium materials provides superior properties and performance in each application, with no alternative material to take its place. For most applications, the cost of the zirconium material is a very minor part of the total production cost as only a small percentage is used, or parts are very small. As highlighted in Table 1, the two alternatives to zircon for a source of zirconium are baddeleyite and complex polymetallic ores.

Most high purity zirconium chemicals and powders are based on the use of zirconium oxychloride (ZrOCl2.8H2O), commonly referred to as ‘ZOC’. With China producing over 90% of world output, the dearth of zircon has resulted in shortages of ZOC, as well as zirconium chemicals and chemical zirconia. This has resulted in downstream zirconium products increasing in price by more than twice the zircon increase.

Chinese ZOC prices have doubled from $1,400/tonne in mid-2010 to about $2,800/tonne, FOB China by the end of March 2011. During the same time, zircon prices have increased from around $900/tonne to $1,600-2,000/tonne, CIF China as end users scramble to purchase zircon from trading companies on the spot market.

Using $1,800/tonne as a reference price, there has been a $900/tonne increase in the price of zircon. As approximately 0.65 tonnes of zircon is needed to produce 1 tonne of ZOC (36% ZrO2), the additional ZOC price due to zircon is approximately $585/tonne. The additional profit of $815/tonne reflects the shortage of zircon, as well as increased chemical and environmental compliance costs.

The shortage of ZOC has also caused a reduction in the production of chemical zirconia powders in China, with prices increasing higher than the ZOC price increases. Chemical zirconia prices are now $10,000-14,000/tonne, FOB China. Reduced exports of ZOC are also having a significant impact on all zirconium chemicals users worldwide, where supply issues have become critical for many end users.


Figure 3: Applications for zirconium materials



Source: Alkane Resources


Refractories

Zircon was one of the key refractories raw materials used in steelmaking until the end of the 1980s when it was replaced by superior alumina-spinel compositions. Today, zircon refractories have been mostly replaced by fused zirconia refractory materials produced from zircon, which are used extensively for glassmaking and steelmaking refractories.

In glassmaking refractories, monoclinic fused zirconia is added with zircon to form alumina-zirconia-silica (AZS) refractories used to line glass tanks for flat glass manufacture. Most liquid crystal display (LCD) and plasma display panels (PDP) use high zirconia refractory blocks in the furnace linings where minimal impurities are desirable (see IM April 2011: Fused-cast for glass).

Steelmaking refractories also use monoclinic fused zirconia as the main raw material for producing stabilised zirconia refractory materials. Zirconia is stabilised by either calcia, magnesia, or yttria.

One of the main uses for stabilised zirconia is for flow control nozzles used in slide gates.

Some of the key performance requirements for zirconia refractories are shown in Table 4. It is estimated that approximately 100,000 tpa of zircon is used to produce fused zirconia products. Fused zirconia has traditionally been used in refractories due to its low cost compared to chemical zirconia materials. However, it is expected that increased zircon prices will allow zirconia derived from polymetallic ores to be competitive as an alternative to fused zirconia when new sources of production are available.

Foundries

The use of zircon in foundries, sand casting and investment casting applications is one of the oldest uses for zircon since it was first used in the 1930s. Zircon is unique in these applications as it is not consumed in the process. This allows zircon to be recycled to remove binders and separate other foundry sands.

Zircon possesses many favourable properties which make it the first material of choice for foundry applications, and a list of the main attributes are shown in Table 5. Approximately 150,000 tpa of zircon is consumed in foundry and metal casting applications, which has remained relatively constant during the past twenty years, despite large fluctuations in supply and availability.

The main competitor to zircon is chromite, which has enjoyed a rapid growth in demand for foundry applications, and chromite consumption is estimated to be about 700,000 tpa. It is also estimated that chromite could substitute for zircon in up to 50% of foundry applications, and with zircon now costing four to five times more than chromite, there will be increased efforts to replace zircon.

Summary

The zircon shortage will force end users to critically review the need for its usage in each of the major applications. However, in most cases, there are no obvious alternatives to zircon. Therefore, substitution is largely a myth, while the zircon supply chain is virtually empty with no recovery in sight for the near to medium term.

Sensitivity to substitution is generally low, with other minerals or polymetallic ore bodies needed as a source of zirconium. The trend of increasing zircon prices is set to continue, with no significant zircon supply coming on stream for the immediate future. Supply of zircon and downstream products has become a significant strategic issue for many companies, with prices for downstream zirconium chemicals and powders increasing by much more than the zircon price alone. No immediate relief is in sight, however polymetallic ores offer a significant new source of material for the high growth rate zirconium chemicals and chemical zirconia segment from late 2013 onwards.

Contributor:
Alister MacDonald is the director of Technical Ceramic Marketing Services Pty Ltd, with over 25 years’ experience in zircon and zirconium materials. This article is adapted from the paper, “The myth of zircon substitution”, presented at the TZMI Asia in Focus Congress in Hong Kong, November 2010.



Table 1: Zirconium nomenclature and alternatives

Zircon (ZrSiO4):
zirconium silicate mineral from which most zirconia, and zirconium materials are derived.

Zirconia (ZrO2):
zirconium dioxide exists in three crystalline forms:

  • Monoclinic, tetragonal, and cubic;
  • Stabilised by rare earths such as yttria or ceria.

Alternative zirconium sources include natural zirconia, baddeleyite, or complex ores, but current supply is limited or is under development:

  • Russian baddeleyite: ~7-8,000 tpa;
  • Alkane’s Dubbo Zirconia Project: 6-15,000k tpa.

Zirconium metal (Zr): produced from zircon or zirconium intermediates.

Zirconium materials: including chemicals, oxides, and metals.

Source: TCMS



Spotlight: Dubbo zirconia project

The Dubbo zirconia project (DZP) in New South Wales, Australia, is one of the world’s most advanced developments for zirconium, niobium, yttrium and rare earth production and is based upon a world class resource. This large resource has over 100 years open minable life at a 1m. tpa production rate.

Mineral concentrations at the Toongi deposit

Toongi Deposit Tonnage ZrO2 HfO2 Nb2O5 Ta2O5 Y2O3 REO U3O8
(m. tonnes) (%) (%) (%) (%) (%) (%) (%)
Measured 36 1.96 0.04 0.46 0.03 0.14 0.75 0.014
Inferred 38 2-Jan 0.04 Jan-04 0.03 0.14 0.75 0.014
TOTAL 73 1.96 0.04 1-Jan 0.03 0.14 0.75 0.014

A demonstration pilot plant (DPP) at ANSTO (Australian Nuclear Science and Technology Organisation) has been operating continuously since 2008 and has proven the flow sheet for the DZP. Apart from zirconium, the DZP offers a new source for heavy rare earths, particularly yttrium, gadolinium, dysprosium and terbium.

Production output from the Dubbo zirconia project

Product* 400,000 tpa (Base Case) 1,000,000 tpa
ZBS, ZOH, ZBC, ZrO2 15,000 tpa (6,000 tpa ZrO2) 37,000 tpa (15,000 tpa ZrO2)
Nb -Ta concentrate  2,000 tpa (1,400 tpa Nb2O5) 5,000 tpa (3,500 tpa Nb2O5)
LREE concentrate 1,980 tpa (REOs) 4,950 tpa (REOs)
YHREE concentrate 600 tpa (REOs) 1,500 tpa (REOs)

*ZBS = zirconium basic sulphate; ZOH = zirconium hydroxide; ZBC = zirconium carbonate; ZrO2 = zirconia ; equivalent ~99% ZrO2 + HfO2 basis. Nb-Ta concentrate = ~70% Nb2O5; 1.0% Ta2O5 calcined basis.

LREE = lanthanum, cerium, neodymium and praseodymium. YHREE = yttrium, gadolinium, dysprosium and terbium. (70% rec)

A detailed feasibility study is to be completed in mid-2011, with construction expected to commence in early 2012. First production is expected late in 2013, with potential to expand beyond 1m. tpa annual production due to the large ore body which is open at depth.

Source: Alkane Resources