MURTY, V.G.K., UPADHYAY, R., AND ASOKAN, S. Recovery of zircon from Sattankulam deposit in India—problems and prospects. The 6th
International Heavy Minerals Conference ‘Back to Basics’, The Southern African Institute of Mining and Metallurgy, 2007.
Recovery of zircon from Sattankulam deposit in India—
problems and prospects
CH. V.G.K. MURTY*, R. UPADHYAY*, and S. ASOKAN*
Titania Business Unit, Tata Steel, Chennai, India
Zircon (ZrSiO4) is the most frequently found zirconium ore occurring in heavy mineral sands,
from which it is extracted as a co-product in the production of ilmenite and rutile. Estimated world
reserves of zircon are 124 million tonnes, highest in Australia (around 56 million tonnes),
followed by Mozambique (15 million tonnes), India (12.6 million tonnes) and South Africa (12
million tonnes).
Zircon finds its application in ceramics (54%) and refractory industries (14%), which account
for 68% of zircon’s total world consumption of 1.20 million tonnes. The rest (32%) is consumed
in foundry, TV glass, zirconia chemicals and other applications.
It is a long recognized feature of the zircon industry that supply is totally dependent upon the
concurrent production of titanium minerals. But in recent years, several new developments such as
the discovery of zircon-rich mineral sands in Australia, the continuing trend of higher prices of
zircon and increase in trade of lower quality zircon have changed the scenario. These factors have
prompted more intensive efforts to increase the recovery of zircon, particularly in the process for
separating zircon from alumino-silicate minerals.
Tata Steel’s proposed heavy mineral sands deposit contains on an average 10% heavy mineral
content and 15% slimes of the size below 63 micron. Mineral assemblages of the resource contain
65–70% ilmenite, 4–6% rutile, 4% zircon, 16% sillimanite and other minor minerals. Wide size
range and tenacious iron oxide coating are the inherent characteristics of this deposit.
High concentration of sillimanite among the non-magnetic heavy minerals and heavy surface
coatings on the minerals are challenges for high recoveries and production of premium grade
zircon. This paper outlines various process steps that were taken at pilot plant stage to produce
zircon of premium grade and subsequently develop the appropriate flow-sheet.
Introduction
Zircon (ZrSiO4) is the most frequently occurring mineral
for the element, zirconium (Zr). It is a common accessory
mineral in granitic rocks and pegmatites and, because it is
highly resistant to mechanical and chemical disintegration,
it most commonly occurs as a detrital mineral in river and
beach sands1.
While zircon is a common accessory mineral, it is
generally not found in high concentrations other than in
placer and dune deposits, where it has been deposited along
with other heavy minerals such as ilmenite, rutile,
monazite, garnet, staurolite and kyanite. Such deposits have
been sorted and concentrated over geological time by the
action of tides, waves and wind to form concentrated
deposits of heavy minerals along old coastlines and in river
beds and deltas. It is these secondary concentrations of
zircon in placer deposits that provide the only commercial
sources of zircon. Consequently, zircon is always found in
association with principal titanium minerals, ilmenite and
rutile. The proportion of zircon in such heavy mineral
deposits varies widely, depending upon the original
concentration of zircon in the source rocks.
Zircon is by far the most common source of zirconium,
but the element also occurs in a number of other minerals,
either as an oxide or as a silicate. The most common
zirconium-containing minerals are shown in Table I. Apart
from zircon, the only zirconium mineral currently of
commercial significance is baddeleyite, which contains
predominantly zirconia (ZrO 2 ) with some associated
hafnium and is produced from a single source at Kovdaor,
Russia.
Zircon is produced mainly from heavy mineral sands
mining operations, from which it is extracted as a coproduct in the production of ilmenite and rutile. Estimated
world reserves of zircon are 124 million tonnes, highest in
Australia (around 56 million tonnes), followed by
Mozambique (15 million tonnes), India (12.6 million
tonnes) and South Africa (12 million tonnes)1. Zircon finds
Table I
Minerals containing zirconium
Mineral
Baddeleyite
Catapleite
Elpidite
Eudialyte-eucolite
Polymignite
Rosenbuschite
Tazheranite
Wohlerite
Zircon
Zirkelite
Composition
ZrO2
(Na3Ca)ZrSiO3O9.2H2O
Na2(Zr,Ti)Si6O15.3H2O
(Ca,Na)5Zr5Si6(O,OH,Cl)20
(Ca,Fe,Y,Zr)(Nb,Ta,Ti)O4
(Ca,Na)3(Zr,Ti)Si2O8F
CaTiZrO8
NaCa2(Zr,Nb)Si2O8(O,OH,F)
ZrSiO4
(Ca,Fe)Zr,TiO5
RECOVERY OF ZIRCON FROM SATTANKULAM DEPOSIT IN INDIA—PROBLEMS AND PROSPECTS
ZrO2, weight %
100.00
31.00
20.00
2.50
28.90
19.80
61.90
16.60
67.00
50.50
69
its application in ceramics (54 %) and refractory industries
(14 %), which account for 68% of zircon’s total world
consumption of 1.20 million tonnes per annum. The rest
(32%) is consumed in foundry, TV glass, zirconia
chemicals and other applications.
Tata Steel’s proposed Titania project covers a part of the
inland and coastal deposit of Tamil Nadu state in India,
which expends over an area of about 200 sq. km along the
coast. Tata’s area of interest consists of two sand
concentrations that cover approximately 120 sq. km. along
the coast and inland, referred to locally as the Teri Lands.
Tata Steel has applied for mineral licences on these two
deposits, referred to as Sattankulam and Kuttam
respectively, as shown in Figure 1.
Outokumpu-PAH-L&T consortium acted as the
feasibility study consultants and M.N.Dastur & Company
as the infrastructure consultants for carrying out the
bankable feasibility study. TZ Minerals International was
appointed as the process and marketing consultant to ensure
the feasibility study progressed as per the intended
purposes.
The sand contains heavy minerals that include ilmenite,
rutile, zircon, sillimanite, monazite, magnetite and other
minor minerals. The average total heavy minerals (THM)
and slime (below 63 microns) content within the deposit is
10% and 15% respectively. Heavy minerals are
concentrated in the -250 +75 micron size fraction. Mineral
assemblages of the resource contain 65–70% ilmenite,
4–6% rutile, 4% zircon, 16% sillimanite and other minor
minerals.
After mining, the ore is subjected to beneficiation
process, which involves a wet primary concentration and a
dry mineral separation. The primary concentration plant
(PCP) upgrades the run of mine (ROM) ore by rejecting
light gangue materials such as quartz and shells to produce
a heavy mineral concentrate (HMC) containing >95% HM
with minimum losses of valuable heavy minerals (VHM)
such as ilmenite, rutile and zircon. After separation of
ilmenite and rutile through magnetic and high tension (HT)
separators, the rest of the HMC is subjected to zircon
recovery processes. Typical mineralogical analysis of feed
to the zircon circuit and that of HMC from a bulk sample is
shown in Table II.
Challenges in recovery of
premium grade zircon
There is a continuing challenge to achieve higher product
recoveries from ever more difficult mineral suites, with
more consistent and predictable product quality. There is a
particular focus at the present time on achieving higher
recovery of zircon to satisfy growing demand of 3.0% per
year1. This challenge becomes more compounded when the
endeavour is to produce premium grade zircon.
Iron (Fe 2 O 3 ) content is often the most limiting
specification in determining the suitability of a zircon
product for a particular application. In particular, low Fe2O3
content is often requested for ceramic opacifier
applications. Iron content is controlled principally through
grain surface cleaning and efficient mineral separation,
minimizing contamination by leucoxene and staurolite.1
Table II
Typical mineralogical analysis of HMC and feed to zircon circuit
Mineral
Ilmenite
Rutile
Zircon
Monazite
Sillimanite
Others
Total heavy minerals
Weight % in feed to
zircon circuit
0.13
2.75
38.70
8.80
29.10
12.17
91.70
Weight % in HMC
79.80
5.00
5.20
1.30
4.00
1.80
97.10
Figure 1. Location of Tata Steel’s titania project
70
HEAVY MINERALS 2007
The next limiting factor is Al2O3. High Al2O3 contents
are normally an indication of contamination by aluminosilicate minerals, typically kyanite or sillimanite. While
these minerals can be effectively separated from zircon
using wet or dry gravity separation techniques, the presence
of corundum would make the separation complicated.
The low radioactivity of the zircon is important to
zirconium/zirconia producers, who must deal with the
elevation of radiation in waste streams. The level of U+Th
in a zircon product may be influenced by particles of
monazite, which may be removed by magnetic separation
and wet and dry gravity separation process at the cost of
recoveries. However, in most clean zircon products, the
U+Th content is a function of the extent to which these
elements are present in the zircon crystal structure, and this
U+Th cannot be removed by physical processing methods.
Therefore, maintaining U+Th levels of below 500 ppm in
the zircon product without losing much in recoveries
normally pose serious challenges to zircon producers.
The presence of undesired minerals such as sillimanite,
kaolin, corundum and monazite coupled with iron oxide
coatings poses formidable challenges in the production of
zircon of premium grade for ceramic applications. The
critical quality parameters for premium grade zircon are
given in Table III.
In production of premium grade zircon, rejection of
sillimanite from the zircon stream has always been the
biggest challenge due to the small specific gravity
difference between zircon (4.6) and sillimanite (3.25) and
the stringent limit on alumina content, i.e., 0.45% in
premium grade zircon.
Microscopic images of original zircon in ROM sand and
pure zircon mineral produced from the Sattankulam deposit
are shown in Figure 2A and Figure 2B. From these
photographs, one can see how white transparent grains of
zircon are coated with heavy tenacious iron oxide coatings
(which are deep and hard to remove) and interstitial iron
staining. Without removal of these coatings, specifications
of premium grade zircon (with respect to iron oxide
content) cannot be met.
Such heavy iron oxide coatings and the presence of
sillimanite are major challenges in the production of
premium grade zircon from Sattankulam deposit and call
for detailed studies for arriving at the most efficient process
route to produce zircon of premium grade.
gravity circuit, sillimanite and quartz are removed from
zircon, thereby producing zircon concentrate. After drying
the zircon concentrate, it is subjected to HT and magnetic
separation to remove traces of magnetic and conducting
minerals. However, surface stained zircon concentrates are
cleaned in high energy input attrition cells using a neutral,
acid, or basic solution. While this approach is found to be
suitable for mildly stained grains, for more strenuous
coatings, special chemical processes are used for removing
coatings from the surface of zircon grains. These are the1:
• Hot acid leach (HAL) process, in which hot zircon is
treated with moderately concentrated sulphuric acid
and reacted in a kiln, after which the product is
attritioned, neutralized and dried. A variant of this
process employs a plug flow reactor in place of the
rotary kiln
• Zircon upgrading process (ZUP), which involves
heating the zircon to around 400°C, after which it is
quenched in dilute sulphuric acid.
To quantify performance of various surface cleaning
techniques on primary zircon concentrates, tests conducted
elsewhere revealed that conventional attritioning was able
to reduce ferric oxide level from 1.02% to 0.92–0.94%,
whereas by using HAL it can be reduced to a level of
0.29 %.2
Zircon
Figure 2A. Coated zircon in ROM sand
Industry practice for zircon recovery
Traditionally in the mineral sands industry, after removal of
magnetic and conducting minerals, viz., ilmenite, rutile,
monazite and garnet, HMC now rich in non-conducting and
non-magnetic minerals, is fed to the zircon circuit. In
general, for simple deposits without any coatings, the wet
gravity circuit is followed by the dry mill. In the wet
Zircon
Table III
Quality specification of premium grade zircon
Constituent
Weight %
ZrO2+HfO2
TiO2
Al2O3
Fe2O3
SiO2
U+Th (ppm)
Min. 66
Max. 0.15
Max. 0.45
Max. 0.10
32.80
Max. 500
Figure 2B. Pure zircon mineral
RECOVERY OF ZIRCON FROM SATTANKULAM DEPOSIT IN INDIA—PROBLEMS AND PROSPECTS
71
Floatex density separator for classification prior to the
Wilfley table. The Wilfley table was used instead of spirals
due to the limited sample size at this stage of the flowsheet.
The concentrates from the Wilfley tables were combined
and scrubbed to remove any surface coatings.
As for the choice of reagent for attrition scrubbing,
sulphuric acid has been found most effective for primary
scrubbing and for secondary scrubbing; both acidic and
alkaline reagents were found to work quite similarly. The
zircon circuit being at the end of the MSP process, it was
decided to do an alkaline scrub rather than an acid scrub in
view of possible oil and carbon contamination. Therefore,
slaked lime was used for scrubbing.
The list of major zircon producers is given in Table IV.
From the same, it is evident that major zircon producers
have hot acid leaching facilities in their zircon circuit. It is
observed that deposits with a higher proportion of slimes
have coatings problems and, hence, require hot acid
leaching facilities.
Pilot plant test work for zircon recovery4
During the feasibility study for Tata Steel’s Titania project,
the non-conductors and non-mags from the rutile separation
process were used as feed to the zircon circuit for the pilot
plant test work. The flowsheet of pilot plant for zircon
circuit is shown in Figure 3. The feed first reports to a
Table IV
List of major zircon producers3 and the acid leaching facilities
Producer
Bemax Resources NL
Consolidated Rutile Limited
Doral Mineral Sand Pty Ltd
EI Dupont de Nemours & Co Inc
Iluka Resources Limited
Indian Rare Earths
Industrias Nucleares do Brasil
Millennium Chemicals do Brasil
Minerals and Trading Company (MITRACO)
Namakwa Sands
Richards Bay Minerals
Ticor
Corridor Sands (proposed)
Moma (Proposed)
Tiwest Joint Venture
Vilnohrisk State Mining and Metallurgical Plant
Country
Hot acid leaching facility
Zircon production in’2005 (’000 tonnes)
Australia
Australia
Australia
USA
Australia/USA
India
Brasil
Brasil
Vietnam
South Africa
South Africa
South Africa
Mozambique
Mozambique
Australia
Ukraine
No
No
No
Calcining only
Yes
No
No
No
No
Yes
Yes (calcining)
Yes
Yes
Yes
No
No
20
53
16
65
365
22
5
20
8
129
235
47
30
60
70
30
Non-cond product
feed to zircon cicuit
Underflow
Floatex density
separator
Overflow
Wilfley
shaking table
Wilfley
shaking table
NaOH Scrub
Non-cond
eForce
HTR
Cond
Non-cond
Non-cond
5-P ES Plate
eForce
HTR
Con to
rutile
Cond
Mag
RER
Non-mag
zircon
Non-mag
Mag
RER
eForce
HTR
Cond
Non--cond
zircon
Figure 3. Zircon pilot plant flowsheet
72
HEAVY MINERALS 2007
Table V
Chemical analysis of zircon products before scrubbing
Product
Feed
No. 1 zircon
No. 2 zircon
No. 3 zircon
Total zircon
Conductor to rutile circuit
Sillimanite feed
Tails from table
Weight %
%TiO2
%ZrO2
Dist. TiO2
6.95
2.09
0.81
0.09
2.99
0.47
1.20
1.49
6.36
0.08
0.19
0.28
46.78
66.69
66.71
66.38
49.34
1.17
11.87
34.90
0.34
33.72
5.10
0.03
0.03
0.00
0.06
2.68
0.20
2.10
After scrubbing, desliming and drying, the material was
subjected to HT separation. The conductors from the initial
stage were scavenged on an additional stage of high tension
roll (HTR) separator. The non-conductors from the
scavenging stage were combined with the middlings from
the initial HTR stage and treated on an ES plate separator.
The non-conductors from both stages were combined and
reported to a three-stage rare earth roll (RER) magnetic
separator with the non-magnetic product from this stage
being the primary zircon product. The magnetic product
was then subjected to a scavenging stage on another threepass RER to recover any remaining zircon. The nonmagnetic product was then cleaned on an HTR separator. In
order to further increase the recovery of zircon, the
magnetic reject from the scavenger magnet was again
treated on another three-stage RER and the non-magnetic
product so derived as a secondary product contained
slightly higher TiO2 values.
Within the zircon process flowsheet, three different
zircon products were produced ranging from a high grade
zircon to zircon of lower grades. Chemical analysis and the
proportion of products are given in Table V.
Table V shows that a total of 65.81% of the total zircon
was recovered in three separate products of various grades
with the majority (47.96%) recovered as the No.1 zircon
product. Of the losses, the single largest stream was the
tailing stream from tables accounting for 15.76% of the
zircon or 69.9% of the losses. The material was coarse,
because the zircon was treated on wet tables. Wet tables
inherently recover fine material in preference to coarse
mineral. This material was treated on a Kelsey jig to
improve zircon recovery. Analysis of Kelsey jig
concentrate5 revealed that it contains 1.51% alumina (Table
VI), which is higher than the specification. To reduce it
further, Kelsey jig concentrate was treated on wet tables.
Detailed analysis of zircon recovered from different
process routes revealed Fe2O3 content of more than 0.16%
Dist ZrO2
47.96
15.95
1.90
65.81
5.36
0.20
15.76
Table VI
Analysis of Kelsey jig test
Concentrate assays
Constituent
Weight %
ZrO2+HfO2
TiO2
Fe2O3
Al2O3
53.50
13.10
0.81
1.51
which is well beyond specification of 0.10% for premium
grade zircon. It showed that even the treatment with slaked
lime was not able to keep Fe2O3 within limits and therefore,
required hot acid leaching.
Having realized that hot acid leaching is essential to
reduce iron oxide to an acceptable level, the question
remained about the ideal location of hot acid leaching in the
flowsheet. The various locations of hot acid leaching in the
rutile/zircon circuit were anticipated to affect differently the
recovery as well as the quality of rutile and zircon products,
besides operating and capital costs. Hence, the following
four options were tested to decide the best option
(Table VII). The determination was based on single pass
HT separation efficiency.
Since the presence of quartz was expected to interfere
with the operation of HT separation, it necessitated going
for wet gravity concentration (WGC) prior to HAL/HT.
This will not only improve separation efficiency of HT
separators but also reduce the quantity of material to be
redried. The combination of Floatex and wet gravity circuit
vis-à-vis the use of the Kelsey jig ahead of the HT circuit
was also studied for efficient recovery of zircon and rutile.
Therefore it was decided to test only options 3 and 4.
For hot acid leaching, the material was heated to 150°C,
then moistened with 40% H 2 SO 4 solution and left for
digestion in a refractory lined vessel for 30 minutes. After
digestion, zircon was quenched in water, counter currently
washed, dewatered and dried.
Table VII
Hot acid leaching–various location options in zircon flowsheet
Sl. No.
Option
Advantage
Disadvantage
1
HAL-HT-Gravity
Dry feed, 100% chances to recover in
HT, highest recovery
Higher costs since 100% through acid leach
2
HAL-WGC-HT
Drying of zircon once
Potential loss of leucoxene.
Impact of loss of leucoxene on zircon quality
3
WGC-HAL-HT
Lower HAL tonnages, HT advantage
2 times drying
4
Crude zircon product-HAL
(WGC-HT-HAL)
Lowest volume through HAL,
least likely to mobilize radio nuclides from monazite
May not clean up grains enough to get best HT
and mag. sep results for rutile and leucoxene recovery
RECOVERY OF ZIRCON FROM SATTANKULAM DEPOSIT IN INDIA—PROBLEMS AND PROSPECTS
73
Though HT separation efficiency (Table VIII) in the case
of option 3 (WGC-HAL-HT) was higher than that in option
4 (WGC-HT-HAL), the difference was only marginal and
within analytical errors. Finally, option 4 was selected as it
will also give a cost advantage.
Based on the decision to subject the crude zircon product
from the HT separation to hot acid leaching, zircon product
produced from pilot plant was hot acid leached. Analysis of
zircon product before and after HAL treatment (Table IX)
revealed that hot acid leaching of zircon product is effective
in reducing the iron oxide content to below 0.07 % resulting
in a premium grade zircon.
Microphotographs of zircon in non-mag and the zircon
product after hot acid leaching (Figure 4) clearly indicate
the significant drop in iron oxide level6. The brownish
colour of zircon particles (Figure 4A) is due to heavy
coatings of iron oxide and the same is conspicuous by its
absence in the final product (Figure 4B).
Coating
on
Zircon
(a) Zircon in Non Mag.— Reflected light
Zircon
Conclusion
Zircon is the most frequently found zirconium ore and is
produced mainly from heavy mineral sands mining
operations, from which it is extracted as a co-product in the
production of ilmenite and rutile. A high proportion of
sillimanite among the non-magnetic heavy minerals, heavy
iron oxide surface coatings on the zircon mineral and the
presence of monazite are major constraints for high
recoveries and production of premium grade zircon in the
case of the Sattankulam deposit in India.
The combination of a conventional wet gravity circuit
and dry separation employing electrostatic and magnetic
separators is not able to produce premium grade zircon,
necessitating the introduction of a hot acid leaching facility
in the circuit. Various permutations and combinations were
tried to decide on the location of the hot acid leaching
circuit, and hot acid leaching of crude zircon concentrate
was found to be the best among all the options tried for
producing premium grade zircon economically.
(b)Washed zircon—Reflected light
Figure 4. Microphotographs of zircon particles in non-mag and in
final zircon product
Acknowledgements
encouragement and support provided. The authors also
would like to express their gratitude to Mr D.S. Rao of the
National Metallurgical Laboratory, Chennai, India for his
assistance in preparing microphotographs of various
products.
The authors would like to express their thanks to their
colleagues in the Titania Business Unit for their help in
preparing the paper and Tata Steel for the constant
References
Table VIII
Comparison of HT separation efficiency with and w/o HAL
Options
Separation efficiency(TiO2/ZrO2) %
WGC+HAL+HT (3)
WGC+HT+HAL (4)
89.4
88.5
1. TZ MINERALS INTERNATIONAL PTY. LTD., The
Global Zircon Industry, New era—new dynamics,
2005. pp. 39–154.
2. LAYVENDER, M.D. and JAMES, D.G. Production
of high quality zircon using the H.A.L.process, 10th
Industrial Minerals International Congress.
3. TZ MINERALS INTERNATIONAL PTY LTD.,
Mineral Sands Annual Review 2006. pp. 144–222.
Table IX
Analysis of zircon products before and after HAL
Compound
Feed to zircon circuit,
weight%
ZrO2+HfO2
TiO2
Al2O3
Fe2O3
16.01
38.79
8.95
6.3
74
Zircon product, weight%
Before HAL
After HAL
66.23
0.05
0.39
0.161
66.69
0.081
0.291
0.065
4. OUTOKUMPU TECHNOLOGY, Feasibility Study
Test Results. Private Communication, 2006.
5. ROCHE (MT), Kelsey Jig Test Report, Private
communication, 2006.
6. OUTOKUMPU TECHNOLOGY, Mineralogical
analysis. Private communication, 2004.
HEAVY MINERALS 2007