Eco-Efficient Gravity Separation Solutions in India

XXV International Mineral Processing Congress (IMPC 2010)

Eco-Efficient Gravity Separation Solutions in India

Carlos A. Pena

Reference Number: 441 Contact Author: Full name Carlos A. Pena Position title Business Development Manager Organisation Name Mineral Technologies Address 11 Elysium Rd, Carrara, Qld, 4211 Phone 07 5569 1317 Fax 07 5525 3810 Mobile 0448 417 786 Email [email protected]

Eco-Efficient Gravity Separation Solutions in India

Carlos Pena1

1. Business Development Manager, Mineral Technologies, 11 Elysium Road, Carrara QLD 4216, [email protected]

ABSTRACT Sustainable development and social responsibility issues are a principal aspect of mineral

processing operations around the world. With the need for more environmentally effective

technologies, some gravity separation systems have provided eco-efficient mineral processing

solutions in places where it is not otherwise viable because of lack of fresh water or for other

environmental reasons. Advanced spiral separation technologies developed in Australia offer a

cost effective and environmentally viable way to process minerals. In particular, we review recent

case studies of spiral plants commissioned in India where environmentally sustainable solutions

to design problems included the use of spirals operated with sea water and the use of high

capacity (HC) spirals to provide low consumption of energy and materials and a reduced plant

footprint. This paper evaluates the performance of various spiral plants in India and how critical

environmental issues which affect the overall viability of wet concentrating processes where

resolved.

Keywords: Spiral separators, Gravity Concentration, Sea water mineral processing

INTRODUCTION India is home to a myriad of metals and minerals. Globally, the country is the largest producer of

sheet mica, the third largest producer of coal, the fourth largest producer of iron ore, the fifth

largest producer of bauxite and one of the largest producers of mineral sands in the world.

India’s mining industry continues to grow in economic importance. A report from Business Monitor

International, noted that India has significant amounts of natural resources, which should allow it

to develop a world-class mining industry.

The country clearly has massive potential but at present there are a host of problems to

overcome, including poor levels of resource recovery, sluggish geological exploration and

environmental damage from mining and mineral processing.

India having 18% of the world's population on 2.4% of world's total area has greatly increased the

pressure on its natural resources. Water shortages, soil exhaustion and erosion, deforestation, air

and water pollution afflicts many areas. In fact, India is at risk of severe environmental problems.

Many of its rivers are heavily polluted and fresh water sources limited, raising questions about the

sustainability of the mining sectors rapid growth.

In February 2009, the 20th National Convention of Mining Engineers in India emphasized the

importance of clean mining technologies, to help decrease the environmental effects of mining.

With the need for more environmentally effective and clean mining technologies, some gravity

separation systems have provided eco-efficient mineral processing solutions in places where it is

not otherwise viable in India because of lack of fresh water or for other environmental reason.

Advanced spiral separation technologies have offered a cost effective and environmentally viable

way to process minerals in India. Recent projects to process mineral sands in the state of Tamil

Nadu India have been viable thanks to the use of spiral separators processes using sea water.

This paper explores some recent projects where these technologies made the projects

environmentally viable.

Most of the metallurgical data and findings contained in this paper come from working closely with

V.V. Mineral, one of our main clients in the state of Tamil Nadu, and India's largest miner,

manufacturer and exporter of Garnet & Ilmenite. For a number of years, Mineral Technologies

has closely worked with VV Minerals to provide mineral processing solutions at their different

facilities located in Tamil Nadu India.

Water issues for mining in India Water shortages are a serious problem for mining companies in India. In a recent survey of

India’s water situation, Fred Pearce reported that the 21 million wells drilled in recent years are

lowering water tables in most parts of the country. From 1947 to 2002, average annual per capita

water availability declined by almost 70% to 1,822 cubic meters.

Tamil Nadu, located in the southeast tip of India and where we have focused the findings for this

paper, is a water-scarce state with a vast mining potential. In addition to mineral sands, the state

has diverse potential of minerals such as limestone, lignite, granite, clay, gypsum, feldspar,

graphite, and iron. Small quantities of gold, copper, kaolin, bauxite, and asbestos are also

available.

Even though Tamil Nadu has 33 river basins, the rivers are short, and carry water seasonally

making most of these mining projects unviable.

In addition to this, the state has a population of more than 62 million people, wells have been

drying up at a rampant rate and falling water tables have dried up 95 per cent of the wells owned

by small farmers thus reducing the irrigated area in the state by half over the last decade. In

communities where underground water sources have dried up entirely, all agriculture is rain-fed

and drinking water is trucked in.

Mineral Sands deposits in Tamil Nadu - India

Heavy mineral sand deposits consist of sand accumulations that contain significant amounts of

heavy minerals (generally defined as minerals with a specific gravity greater than 2.8SG).

Contained heavy minerals occur as disseminated, associated or concentrated deposits within the

sands and often include titanium minerals, zircon, garnet and sillimanite.

In India, exploration for, and extraction and processing of heavy mineral sands has intensified in

recent years due to increasing use and demand for titanium oxides, metals and alloys. Zircon

formerly viewed as a by product has now been a target in light of strong markets, especially

China during the years of strong construction growth.

The coastal districts of Kanyakumari, Tirunelveli, Thoothukkudi, Nagapattinam and

Ramanathapuram in Tamil Nadu are endowed with high quality heavy mineral placers such as

Garnet, Ilmenite, Rutile, Leucoxene, Monazite and Zircon. They have wide use in pigment,

refractory, ceramic industries and nuclear industry world wide.

The Department of Geology and Mining of the Government of Tamil Nadu,estimates reserves of

these deposits at about 23 million tonnes of Garnet, 98 million tonnes of Ilmenite, 5 million

tonnes of Rutile, 2 million tonnes of Monazite and 8 million tonnes of Zircon. The major players

are the Indian Rare Earths (IRE), a Government of India Undertaking, V.V. Minerals, Beach

Mineral Company, Transworld Garnet and Indian Ocean Garnet Sand.

Mineral Sands processing with spirals in Tamil Nadu – India Gravity concentration of minerals in India has traditionally been recognized as a low cost and

environmentally friendly process for the separation of minerals. Spirals separators are simple, low

energy consuming devices that separate minerals based on their respective densities and have

proven to be metallurgically efficient and cost effective since their widespread commercial

introduction more than 60 years ago.

Mineral sands processing in Tamil Nadu usually consists of wet and dry processes to extract

mineral concentrates. A typical wet plant will consist of pumping, hydrocyclones for desliming,

surge bins, spirals, up current classifiers and wet magnetic separation (Figure 1)

Wet plants in India are usually fed with water directly sourced from the sea with pumps located

near the coast line (Figure 2).

Process water ponds which handle sea water are specially lined with concrete ensuring the sea

water doesn’t infiltrate the ground. Spiral tailings are treated through hydrocyclones and the

overflow water recovered and sent to tailing ponds. Only 5-10% of the process plant water

reports with the final HMC and tailings which are again handled in concrete lined ponds. Water

overflow is recovered and sent back to the process water ponds.

In the case of VV Mineral they operate 8 spiral separation plants (Figure 3) which stretch from

Kanyakumari to Tuticorin near the coastline of Tamil Nadu.

Total spiral plant processing capacity at VV Minerals operations is 1,180tph made up of eight

plants with feed rates varying from 40 tph to 500 tph as detailed below:

• Three 120 tonnes per hour feed plant

• One 40 tonne per hour feed plant





Sea water vs. fresh water spiral performance A series of tests to determine the variance in spiral performance when operated with either fresh

water or sea water were carried out at VV Minerals operations over a two month period. The

trials utilized MG6.3 and HG10 spiral separators.

A series of 8 tests were carried out on the two spiral models at feed rates varying between 1.2 to

2.1 tph. Pulp density fed to the spirals varied within the range of 35.7% and 41.7% solids (w/w).

As the tests were carried out in an operating plant environment there were inevitable variations in

the feed conditions throughout the tests. In some tests the spirals were operated at higher feed

rates on the salt water slurry. In the case of the HG10, the spiral was operated at 2.0 t/h on fresh

water whereas it was run at 2.4 t/h on salt water. This is a 20% increase, which is significant. In

the case of the MG6.3, the feed rate was 2.7 t/h on fresh water and 11% higher at 3.0 t/h on sea

water.

Overall there was no conclusive difference in performance between salt water and fresh water

processing on the MG6.3 and HG10 spirals (once variations in feed conditions were taken into

account) (figure 4). While this result is perhaps not surprising given that there is very little

difference in viscosity or specific gravity between salt water and fresh water it does further

reinforce the viability of using low quality water in spiral separation plants.

The use of sea water, or highly saline water, will naturally increase the potential for corrosion in

and around the processing plant and may reduce the life of the plant if a high level of corrosion

protection is not maintained. Spiral separators however are manufactured from fibreglass with a

highly resistant polyurethane surface and are far less susceptible to corrosive attack in such

environments.

Fresh water savings in the spiral plants at VV Mineral The average water requirement for a spiral plant is between 0.15 – 0.18 tph of water per tonne of

solids feed. The total spiral plant capacity at VV Mineral is 1,180 tph for the 8 plants currently in

operation. Taking this into consideration and with the use of sea water in their process, fresh

water savings at VV Minerals run in the order of 4,248,000 litres per day.

According to the Stockholm International Water Institute, 100 litres a day is the minimum per

capita water requirement for India’s basic domestic needs. With this in mind VV Mineral’s fresh

water savings provide an availability of fresh water per day for 42,480 people in the Tamil Nadu

State.

In addition to this, the use of sea water in these plants has allowed for the viability of these

projects that generate employment for local workers in the order of 3,400 direct employments

High Capacity spirals (HC Spirals) Ongoing research and development efforts have improved separation efficiencies of spiral

models over the years. Improvements in materials of manufacture have reduced weight and

enhanced operational capabilities.

The concept of a high capacity, small footprint processing plant has now been successfully

commercialized in recent mineral sands and iron ore projects. In some cases a small footprint,

high capacity plant was necessary to make projects viable.

Modern high capacity spiral models can process up to 35 tph per quad start spiral. In some cases

both the rougher and scavenger processing stages are incorporated into the same spiral.

Conventional spiral separators can process up to 9 tph per triple start spiral.

Combining rougher and scavenger stages of separation into one unit obviates the need for

intermediary equipment including feed sumps, pumps and motors, electrics, laundering and feed

distribution systems. The introduction of two stage high capacity spirals into the industry has

allowed the reduction of plant foot prints to just 40% of the area of plants designed based on

conventional (i.e.: low capacity) spiral technology (Figure 5).

This provides substantial environmental and capital cost savings in the plant construction costs

and Results in an efficient, non-polluting and low energy solution for concentrating heavy

minerals.

CONCLUSIONS With the need for more environmentally effective mining technologies, spiral separation

technologies have been shown to provide eco-efficient mineral processing solutions in India and

places where wet processing is not otherwise viable because of a lack of fresh water.

Tests carried out in operations in Tamil Nadu, India, show no substantial difference in

metallurgical performance of spiral separators when treating slurries based on either salt water or

fresh water. This has allowed for the viability of these projects that generate not only employment

for local workers (3,400 direct employments) but vast fresh water savings for communities in this

water scarce region (savings in excess of 4 million litres of water per day).

The focus in spiral plant design in recent years has been to not only improve separation

efficiencies, but to significantly increase feed capacities and look more broadly at ways of

optimizing the overall process design rather than just individual separation stages. A recent

success of this focus is the concept of a high capacity, low footprint spiral processing plants that

enable plants to be constructed and operated using less steel and pumping power than

previously possible.

ACKNOWLEDGEMENTS I will like to acknowledge the assistance of VV Minerals in India that allowed testing of spiral

equipment in their Tamil Nadu operations and to the staff at Mineral Technologies for their

valuable guidance and assistance with a special thanks to Mark Palmer. I also thank the

management of Mineral Technologies for permission to publish this paper.

REFERENCES

Business Monitor International, 2009, India Mining Report Q3 2009 including 5-year industry

forecasts. Mermaid House London, UK

Government of Tamil Nadu, Department of Geology and Mining. An overview of mineral reserves

(2006). Available from: http://www.tnmine.tn.nic.in/ [Accessed: 03/October/2009].

Lester Brown, 2007, Earth Policy Institute, Water shortages in India Report, Washington USA

Pearce, F, 2007 When the Rivers Run Dry: Water--The Defining Crisis of the Twenty-first

Century p 122-125 Beacon Press, Boston MA USA

The Stockholm International Water Institute (2006) Statistics http://www.siwi.org/ [Accessed:

03/October/2009]

Mark Palmer, 2007, High Capacity Gravity Separation Solutions, Industrial Minerals a Metals Bulletin Publication . London UK

FIGURE CAPTIONS Fig 1 - Typical wet plant with spiral circuit in mineral sands operations

Fig 2 - Sea water pump for wet spiral concentration plants

Fig 3 - Sea water spirals at VV Mineral

Fig 4 - Sea water vs. fresh water spiral tests data and performance curves

Fig 5 - Reduce Plant Foot Print with HC Spirals

TK005

TK009TK008

Static Screen

TK010

TK011TK012

Non-Mags

TK012

TK013

TK014

From MUP

Primary Scavenger Middling Cleaner Re-Cleaner

Linear Screen

Primary WHIMS

Secondary WHIMS

Overflow Scavenger

Dewatering

Non-Mags Dewatering

LIMS

TK006 TK007

Non-Mags Mags

Non-Mags

Upstream Classifier

21

TK003

6

10 33 7690

90

79 98

96

81

97

86

96 28

8140

2

30 32

Stacker

Non-Mags Stockpile

90

30

Cyclone Banks

81

Key

Grade (%HM)

Fig 1 - Typical wet plant with spiral circuit in mineral sands operations

Fig 2 - Sea water pump for wet spiral concentration plants

Fig 3 - Sea water spirals at VV Mineral

Test 1, HG10, Sea Water , 1.58 t/h, 40.1% solids, 73.53% HMStream Flow rates Chemical Analysis Cumulative Separation

Solid Kg/hr Water Mass Shell HM LM HM Mass HM EfficiencyKg/hr Dist'n% Recovery Dist% recovery% %

0.0 0.0 0.0 0.0 0.0Con 720 78 45.6 2.16 89.31 8.53 55.4 45.6 55.4 37.0Mid 336 48 21.3 5.45 72.9 21.65 21.1 66.8 76.4 36.3 Tail 524 2234 33.2 9.49 52.24 38.27 23.6 100.0 100.0 0.0

calc. feed 1580 2360 100.0 5.29 73.53 21.18 100.0meas. Feed 1580 2360 100.0 4.54 77.84 17.62

Test 2, HG10, Fresh Water , 1.20 t/h, 37.8% solids, 71.13% HMStream Flow rates Chemical Analysis Cumulative Separation

Solid Water Mass Shell HM LM HM Mass HM EfficiencyKg/hr Kg/hr Dist'n% Recovery Dist% recovery% %

0.0 0.0 0.0 0.0 0.0 Con 563 46 47.0 1.81 90.43 7.76 59.8 47.0 59.8 44.2 Mid 256 29 21.4 6.45 61.12 32.43 18.4 68.4 78.2 33.8 Tail 378 1893 31.6 8.26 49.15 42.59 21.8 100.0 100.0 0.0


Test 3, MG6.3, Sea Water , 1.66 t/h, 35.7% solids, 21.08% HMStream Flow rates Chemical Analysis Cumulative Separation


0.0 0.0 0.0 0.0 0.0 Con 336 78 20.3 4.11 80.43 15.46 77.4 20.3 77.4 72.4 Mid 168 36 10.1 16.57 21.77 61.66 10.5 30.4 87.9 72.8 Tail 1152 2874 69.6 17.58 3.67 78.75 12.1 100.0 100.0 0.0


Test 4, MG6.3, Fresh Water , 1.48 t/h, 35.8% solids, 22.56% HMStream Flow rates Chemical Analysis Cumulative Separation


0.0 0.0 0.0 0.0 0.0 Con 336 26 22.7 3.77 81.11 15.12 81.5 22.7 81.5 76.0 Mid 136 14 9.2 15.18 22.23 62.59 9.0 31.8 90.5 75.8 Tail 1010 2621 68.2 15.45 3.13 81.42 9.5 100.0 100.0 0.0


Sea water vs. fresh water spiral tests 1 to 4

Spiral Tests - Fresh water versus Sea water

0

10

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0 10 20 30 40 50 60 70 80 90 100

Cumulative mass yield%

HM

Rec

over

y %

Test 1, HG10, Sea Water , 1.58 t/h, 40.1% solids, 73.53% HM

Test 2, HG10, Fresh Water , 1.20 t/h, 37.8% solids, 71.13% HM


0

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HM

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Test 1, HG10, Sea Water , 1.58 t/h, 40.1% solids, 73.53% HM

Test 2, HG10, Fresh Water , 1.20 t/h, 37.8% solids, 71.13% HM

Sea water vs. fresh water spiral tests 1 and 2 performance curves


0

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0 10 20 30 40 50 60 70 80 90 100


HM

Rec

over

y %

Test 3, MG6.3, Sea Water , 1.66 t/h, 35.7% solids, 21.08% HM

Test 4, MG6.3, Fresh Water , 1.48 t/h, 35.8% solids, 22.56% HM


0

10

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0 10 20 30 40 50 60 70 80 90 100


HM

Sep

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Effic

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y %

Test 3, MG6.3, Sea Water , 1.66 t/h, 35.7% solids, 21.08% HM

Test 4, MG6.3, Fresh Water , 1.48 t/h, 35.8% solids, 22.56% HM

Sea water vs. fresh water spiral tests 3 and 4 performance curves

Test B1, MG6.3, Fresh Water , 2.10 t/h, 39.8% solids, 34.68% HMStream Flow rates Chemical Analysis Cumulative Separation


0.0 0.0 0.0 0.0 0.0Con 528 44 25.2 2.96 94.83 2.21 68.9 25.2 68.9 66.9Mid 218 27 10.4 15.08 48.58 36.34 14.6 35.6 83.5 73.3 Tail 1349 3104 64.4 21.2 8.89 69.91 16.5 100.0 100.0 0.0

calc. feed 2095 3175 100.0 15.97 34.68 49.35 100.0

Test B2, MG6.3, Sea Water , 1.90 t/h, 40.3% solids, 34.55% HMStream Flow rates Chemical Analysis Cumulative Separation


0.0 0.0 0.0 0.0 0.0 Con 499 40 26.2 3.51 93.65 2.84 71.1 26.2 71.1 68.6 Mid 204 27 10.7 16.96 50.45 32.59 15.7 37.0 86.8 76.1 Tail 1199 2747 63.0 25.76 7.25 66.99 13.2 100.0 100.0 0.0

calc. feed 1902 2814 100.0 18.98 34.55 46.47 100.0

Test B3, HG10, Fresh Water , 1.99 t/h, 41.7% solids, 87.27% HMStream Flow rates Chemical Analysis Cumulative Separation


0.0 0.0 0.0 0.0 0.0 Con 1640 171 82.5 2.14 95.62 2.24 90.4 82.5 90.4 62.0 Mid 262 30 13.2 8.73 57.03 34.24 8.6 95.7 99.0 26.2 Tail 86 2575 4.3 22.45 20.09 57.46 1.0 100.0 100.0 0.0

calc. feed 1988 2776 100.0 3.89 87.27 8.85 100.0

Test B4, HG10, Sea Water , 2.11 t/h, 41.6% solids, 87.45% HMStream Flow rates Chemical Analysis Cumulative Separation


0.0 0.0 0.0 0.0 0.0 Con 1692 163 80.1 1.84 95.11 3.05 87.1 80.1 87.1 55.9 Mid 309 37 14.6 6.9 70.69 22.41 11.8 94.7 98.9 33.5 Tail 112 2762 5.3 22.01 18 59.99 1.1 100.0 100.0 0.0

calc. feed 2113 2962 100.0 3.65 87.45 8.90 100.0

Sea water vs. fresh water spiral tests 5 to 8


0

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0 10 20 30 40 50 60 70 80 90 100


HM

Rec

over

y %

Test B1, MG6.3, Fresh Water , 2.10 t/h, 39.8% solids, 34.68% HM

Test B2, MG6.3, Sea Water , 1.90 t/h, 40.3% solids, 34.55% HM


0

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HM

Sep

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Effic

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Test B1, MG6.3, Fresh Water , 2.10 t/h, 39.8% solids, 34.68% HM

Test B2, MG6.3, Sea Water , 1.90 t/h, 40.3% solids, 34.55% HM

Sea water vs. fresh water spiral tests B1 and B2 performance curves


0

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0 10 20 30 40 50 60 70 80 90 100


HM

Rec

over

y %

Test B3, HG10, Fresh Water , 1.99 t/h, 41.7% solids, 87.27% HM

Test B4, HG10, Sea Water , 2.11 t/h, 41.6% solids, 87.45% HM


0

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0 10 20 30 40 50 60 70 80 90 100


HM

Sep

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Effic

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Test B3, HG10, Fresh Water , 1.99 t/h, 41.7% solids, 87.27% HM

Test B4, HG10, Sea Water , 2.11 t/h, 41.6% solids, 87.45% HM

Sea water vs. fresh water spiral tests B3 and B4 performance curves Fig 4 - Sea water vs. fresh water spiral tests data and performance curves

Fig 5 - Reduce Plant Foot Print with HC Spirals

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Eco-Efficient Gravity Separation Solutions in India