PALE IRON ORE Mine

PALE IRON ORE MINE of M/S Chowgule & Company Limited 
(Ponds for managing tailings waste from mining dumps

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PALE IRON ORE MINE

The Pale iron ore mine of M/S Chowgule & Company Limited is situated in Bicholim Taluka of North Goa district. Pale mine is a large mechanized mine. It was inaugurated by honorable Sri Manubhai Saha, Minister of Commerce, Government of India on 21st November 1964. The ore deposit of Pale iron ore mine is a part of Velguem-Pale deposite of north Goa.

It consists of two mining lease covering an area of 153 Ha. In addition to above 123 Ha private land adjoining to lease has been acquired for the use of mining related activities. Out of the total area mine pit covers an area of 81 Ha. Dump covers an area of 63 Ha. Infrastructure covers an area of 31 Ha.

In views of difficulty of working independently because of small and contiguous nature of both the leases are worked together with a common infrastructure. The method of mining is by conventional open pit system and fully mechanised. Mining operation is done by the Shovel-Dumper combination with Ripper-Dozer (eliminated drilling & blasting).

The annual production is around 1.5 million tonnes. The mine management is very much concerned about the optimum utilization of the mineral resources (sustainable mining). Mine management also takes all type of environment protection measure like dust suppression arrangement, afforestation programe, proper drainage of mine water, consolidation of dumps etc.

CUT OFF GRADE:

The cut off grade in any mine is dependent on the market value of the product as well as the operating philosophy of the management. The cut off grade is the grade of the weakest miner utilization than minimal at a profit. The cut off grade of Pale mine is 1:3.5 for the iron ore.

GEOGRAPHICAL SETTING

LOCATION AND ACCESSIBILITY: Pale mine is about 50 Km from the capital Panjim (Panaji) and falls under North Goa district. The railway line from Mumbai to Madgaon passes through Thivim. The area is easily accessible from Thivim and Madgaon.

ALTITUDE: The peak level of Pale mines of 175 (MSL) adheres, as valley level is 10 (MSL).

CLIMATE: Climate of this place is wet. Monsoon reaches here first and it causes
heavy rainfall. It is a cool place surrounded by large no trees. The summer temperature ranges from 240C to 330C while it varies from 210C to 320C in winter. Humidity 70% to 85%.

SOIL: The whole area is covered at the top by Laterite bed which makes the top
soil reddish brown in colour.

THE SEASONS: From June to September the land is bathed by the southwest monsoon,
which is worth watching and appreciating.

GEOLOGY: The loose areas covers the south western slopes of north westerly trending
Pale- Velguem hill (Dongar) extending over the whole length of area with a moderate slope towards west.

The ore deposits of Pale iron ore mine from apart of Pale-Velguem ore deposit and extended over a length of 1600m along the strike with width ranging from 300 to 450 meter. The ore body is an anticline and having a strike of N300W to S300E and plunges towards the south. The highest existing elevation in the lease area is 172m (MSL) and the lowest leve 11m(MSL) in opened up pit. The main drainage system of the lease area is from northeast to southwest. The handling wall formation is of ferregenous clay with Dhyllite whereas footwall formation is of phyllitic clay locally magniferrous.

METHOD OF WORKING:

The method of working is the conventional mechanised opencast mining for a hilly iron ore deposit. Shovel-dumper (loading & transporting) combination with ripper-dozer (excavation) is used for the mining operation.

EXCAVATION PROCESS:

In mine the practical results obtained with Seismograph were as follows: Seismic velocity in overburden (practically laterite) is 600 to 1200 m/s and in ore area it is 1050 to 1500 m/s. So for better safety and efficiencycompany introduce ripper-dozer and eliminate drilling and blasting fully.

BENCH DESIGN:

Considering the safety parameters the height of the benches are kept 6 to 8 m with variable width of 12 to 15 m. Trenching arrangements are done inside of every bench for proper drainage system. Now about 25 working benches are active in Pale. The slope angle is maintained in between 400 to 450.

HAUL ROAD:

The average width of the haul road is 12 meter and generally 1 in 16 gradient is maintained.
No specific turning radius is maintained. Trenching arrangements are done beside every haul road for proper drainage system. Regular water spraying is done by water tank of 9 to 10 KL for dust suppression. Maintenance of Haul roads is done regularly for decreasing the cycle time of the trippers.

DRAINAGE SYSTEM:

Trenching arrangements are done beside every bench of mine pit and waste dump. All the trenches are connected to the main drain. The trenches and drains are desilted regularly for proper drainage. The drains are connected with seven settling ponds in series. After settling the silt of the wash off water from mine, the clear water is supplied to near by villages for cultivation

OVERBURDEN DUMP:

Pale mines situated in hilly area and mining operation is going on for the past so many years.
So no topsoil is need to being handled. Overburden dumps are made in steps. The width and height of every step is not more than 30 m. Considering the safety parameters angle of repose is kept less than 350 in dry season and less than 250 in rainy season. Trench is present in the inner side of the every step for giving more safety as well as better drainage system. Laterite walls or pack walls are provided all along the periphery of the dumps at some distance from the toe. The height and width of such walls is kept asn 1.5 meter and at place even increased depending upon the flow, slopes and dump height. The silt from wash off is arrested in these arrestors. Additional laterite wall / arrestors are provided to maximize the effect of these arrestors.
In addition to this 1 to 1.5 meter deep trenches are provided where the arrested silt is regularly removed as a preventive measure.

ORE DESPATCH ARRANGEMENT:

First ores, collected from the face is loaded onto the trippers by shovel. Then ore filled trippers are directly sent to the processing plant. Processed ores are then dispatched to the loading point situated in KHAZAN. Then small vessels full with ores are sent to the harbour of Vasco-da-gama, where ships are waiting for filling up with ores.

MONSOON PREPARATION:

The main problem for an opencast mine is the production reduction in the time of monsoon.
For maintaining the production following preparatory steps are done in pale before the monsoon is come

1) Haul road soaling (at mines as well as dumps).

2) Trenching in the mines as well as dumps to rejects the water flow in a desired direction.

3) Making and maintaining of setting pond in single and in series.

4) Construction of arresters.

5) Construction of filter beds.

6) Safety ponds are constructed at the near of dumps (not far, the length equal to the height of the dumps) with overflow preparation.

PROCESSING PLANT

It is an essential part of the Metal industry as to take the crude ore and make it the purest form and according to the market demand. At Pale mine two dry screening and two wet washing plants are in operation .
The run of mine (R.O.M) ore from Pale mine as well as other sister concerns mines are treated at these mines.
Washing facilities including crushing screening classifier and hydro cyclones have been installed for fines and lamps recovery.

All the processing work is carried out and the ore is achieved in two forms:

1) +10 mm 40 mm lumps

2) -10 mm fine

10 mm fine is used to carry out sintering, nodulizing and peletising so that they can be used in the blast furnace fine below 10mm are not suitable for blast furnace as it obstruct the free passage of air containing O2 important for combustion and hence reduces the efficiency and output of blast furnace. So these fines are shed for different process so that they are suitable for blast furnace.

The material of size between +10mm and 10mm is the actual material of market demand as most of the furnaces have suitable in these criteria. So this size is used in blast furnace to get iron. Actually Beneficiation of ore is done to reduce the cost of production and hence make it more economical to use by the market in a convenient way.

The whole processing process involves crushing, screening and washing. In the process of washing about 350 liter/min water is consumed. This water contains many metal including iron which is avoided to send directly to the fertile land because this metal rich water reduce the fertility of land and continuous expose to this water may make the fertile land fully infertile. Many precautions are taken about this concern problem. The water, which is washing the material, is primarily passed through water cyclone classifier in which modified from of hydroclone classifier in which heavy media moves upward and collected from top. This is more effective than the hydroclone classifier. Water cyclone classifier is used so that denser particle are collected and only finer particle can flew through it.

The water containing the percentage of different mineral is recycled and rescued for the purpose of washing. About 60% of the total water is recycled. The rest 40% water rich in the mineral content is made thicker by special arrangement provided. So its clensity increases from 1.02 to 1.07. This water is stored in the tailing pond so that they do not reach in the fertile land and affect the fertile land.

In Pale mine tailing ponds are created in which the tailing material is disposed. Underground arrangement is provided o that the tailing is directly send to the tailing pond. Precautions are taken as that the pond should not overflows. At this time two tailing ponds are there for accommodating the whole tailing of the processing plant without affecting the fertility and the life of the surrounding.