MINE DETAIL'S
Asia's largest open mine
The Mine-I was established in 1957 with a production capacity of 3.50 MTPA. Later during 1978 the mine was expanded to 6.50 MTPA to sustain supply to Thermal Power Station –I [600 MW] and other downstream units. The first mine is demarcated over an area of 16.69 sq.km with a lignite reserve of 287 MT. Additional area of about 8.0 sq.km with lignite reserve of 78.0 MT is included to expand the first mine capacity to 10.50 MTPA to feed Thermal Power Station-I Expansion (420 MW). The lignite seam was first exposed in August 1961 and regular mining of lignite commenced in May 1962. German excavation technology in opencast mining usingBucket Wheel Excavator, Conveyor and Spreader was used in the mine for the first time in the country.
Continuous opencast mining technology is adopted in Neyveli mines [BWE, Conveyor & Spreader] for excavating huge quantities of overburden and lignite. The overburden thickness varies from 45m to 110m and lignite seam thickness varies from 8m to 26 m. Overburden is excavated in slices called Benches. Overburden is excavated in 4 benches and lignite is excavated in one bench. Excavated lignite is transported via conveyors to the surge bunker at surface and from there it is sent to downstream units.
A huge reservoir of ground water occurs below the entire lignite bed, exerting an upward pressure of 5 to 8 Kg/Cm2. By continuous pumping out of water round the clock through bore wells, the ground water pressure is controlled. For mining one tone of lignite about 13 tones of water has to be pumped out. The overburden to lignite ratio in this mine is 5.5 to 5 m3 (11 tones of overburden is to be removed for mining 1 tone of lignite).
Mine-IA is adjacent to the existing Mine-I block on the eastern side. In February 1998, Government of India approved the project and the project was commissioned in 2001. The selected mining area is about 8.36 sq.km and the total reserve in Mine-IA is 120 MT. Lignite was first exposed in March 2003 and the annual installed capacity of the mine is 3.0 Million Tones. The lignite excavated from this mine feeds a private power plant M/s. STCMS of 250 MW.
The various field investigations carried out so far revealed that the basin is a syncline with maximum thickness of 400 m. of water bearing sand in the central area and pinching to 50 m. in the west and east. The aquifer sands of the basin belong to upper Miocene age of Tertiary era.
The hydrology of this area is extremely complex. According to the classification, the aquifer system in the lignite field comprise of a] unconfined aquifer [water table], b] semi-confined aquifer above the lignite seam and c] confined aquifer below lignite seam.
MINE-I:-
LIGNITE DEPOSIT IN NEYVELI:
Lignite is the younger offspring of the coal family. It is a fossil fuel belonging to the Miocene age (25 million years). Popularly known as �Brown Coal�, lignite is tan brown in colour, light to handle and brittle in nature. This fuel is born from vegetable matter having undergone bio-chemical decay to the stage of peat (rotten wood) and then metamorphosed to lignite under the pressure of the soil above through floods, movements of the earth�s crust and dehydration when the pressure of the lignite, particularly the horizontal thrust is further increased, lignite is made more dense, less volumetric and becomes coal as such.
The lignite mined at Neyveli varies in colour from brown to dark brown and has a non-bonded granular structure. Microscopic studies of this sections prepared from bulk samples of lignite indicate that the fuel is composed of a wide variety of plant ingradients, mainly of coniferous nature.
Quality of Lignite:
Lignite contains 65-70% of carbon, 20-25% of oxygen, about 5% of hydrogen and small amounts of nitrogen and sulphur. The average calorific value of lignite is 2400 K.cal/Kg. It cannot be compared favourably with the high calorific value of pure coal. Yet lignite has an advantage of being free burning (non coking), of having low ash and of giving rapid and complete combustion. Since the volatile matter is usually high, lignite burns readily. Air dried lignite is quite suitable for direct burning. For high capacity boilers lignite can be burnt in the pulverized form.
Characteristics of Overburden and lignite
The lignite mined at Neyveli varies in colour from brown to dark brown and has a non-bonded granular structure. Microscopic studies of this sections prepared from bulk samples of lignite indicate that the fuel is composed of a wide variety of plant ingradients, mainly of coniferous nature.
Quality of Lignite:
Lignite contains 65-70% of carbon, 20-25% of oxygen, about 5% of hydrogen and small amounts of nitrogen and sulphur. The average calorific value of lignite is 2400 K.cal/Kg. It cannot be compared favourably with the high calorific value of pure coal. Yet lignite has an advantage of being free burning (non coking), of having low ash and of giving rapid and complete combustion. Since the volatile matter is usually high, lignite burns readily. Air dried lignite is quite suitable for direct burning. For high capacity boilers lignite can be burnt in the pulverized form.
Characteristics of Overburden and lignite
| Overburden (Sandstone) |
Lignite
| ||
| Specific gravity | 2.5 | Bulk Density | 1.15 T/Cu.m |
| Bulk Density | 2.1 gm/cc | Fixed Carbon | 20% |
| Porosity | 27% | Ash content | 3.0% |
| Normal moisture content | 7% | Moisture | 53% |
| Main Mineral Constituent | Quartz 38% Feldspar 5.5% | Volatile matter | 24% |
| Cementing media | Clay 55% | Calorific value | 2400 K.cal/kg |
| Cutting resistance compressive | 20 to 60 Kg/cm | Grindability Index | 108 to 127 |
| Strength | 25 to 75 Kg/sq.cm | ||
Some of the unique characteristic features of the Neyveli Lignite Mine are:
Occurrent of Ground water Aquifer below lignite bed: Huge reservoir of ground water occurs below the entire lignite bed, exerting an upward pressure of 6 to 8 kg/cm2. Unless this water pressure is reduced before mining, it will burst the lignite seam and flood the Mines. The problem is solved by selective bore wells formation and pumping to depressurise the water pressure to the safe mining condition. The water is being used for the TPS water requirement. The water level is continuously monitored through observation wells for proper ground water management.
Hard overburden strata:
The highly consolidated strata consists mainly of Cuddalore strand stone which is hard and abrasive in nature. The Bucket wheel used for handling large volume of overburdens faced problems due to the hard strata and uses overcome by carrying out suitable modification in the bucket wheel teeth and by instituting a systematic drilling and shatter blasting programme.
MINE-I
Demarcated over an area of 26.69 sq.kms. with a reserve of 365 million tones. Mine-I is situated on the northern part of the field adjacent to the Neyveli Township. This mine has a production capacity of 10.5 million tones of lignite per annum and feeds lignite to the 600 MW capacity of First Thermal Power Station and 420MW Thermal Power Station � I Expansion.The lignite seam was first exposed in August 1961 and regular mining of lignite commenced in May 1962. German Excavation technology in opencast mining, using Bucket Wheel Excavators, Conveyors and Spreaders is used in this Mine for the first time in India. While overburden thickness varies from 50-95 metres, lignite thickness varies from 10 to 23 metres. The overburden to lignite ratio in this mine is 5.5 to 5 c.metre to one time (about 11 times of overburden is to be removed for mining one tonne of lignite).
Sl.No
|
Equipment
|
Capacity
|
Mine -I
|
1
| Bucket Wheel Excavator (BWE) Bridge Type | 1400 L |
3
|
2
| BWE (Normal Type) | 1400 L |
3
|
3
| BWE | ||
3.a.
| with deep cut facility | 700 L |
2
|
3.b.
| without deep cut facility | 700 L |
1
|
4
| BWE | 500 L |
1
|
5
| BWE | 350 L |
1
|
6
| Bucket Chain Excavator | 500 L |
1
|
7
| Mobile Transfer Conveyor | 11,000 tph |
3
|
8
| Spreader | 20,000 tph |
1
|
9
| Spreader | 11,000 tph |
3
|
10
| Spreader | 8,000 tph |
1
|
11
| Spreader | 4,700 tph |
3
|
12
| Tripper Car | 20, 000 tph |
1
|
13
| Tripper Car | 11, 000 tph |
3
|
14
| Tripper Car | 8, 000 tph |
1
|
15
| Stacker (Rail Mounted) |
1
| |
16
| Reclaimer | 2, 700 tph |
2
|
In addition NLC deploys conventional mining equipments, viz. dozers, shovels, dumpers, back hoes, pipe layers, Motor Graders, Cranes, etc. as supporting auxiliary equipment.
Conveyor Deployment in Mine-I& 1A as on 01-07-2006
Width
|
Type of Belt
|
Length in KM
|
No. of Conveyors
|
No. of drivers
|
Motor capacity
|
2400 mm
|
Steel cord
|
7.2724
|
7-36
|
25-101
|
1250 KW-630 KV
|
2000 mm
|
Steel cord
|
32.7021
|
1
|
2
|
1250 KV
|
1800 mm
|
Steel cord
|
2.0524
|
3
|
6
|
630 KW
|
1600 mm
|
Steel cord
|
11.6257
|
15-2
|
40-2
|
350-630 KW
|
1500 mm
|
Steel cord
|
6.1450
|
6
|
8
|
630 KW
|
1500 mm
|
Fabric
|
6.8740
|
19
|
72
|
78 KW
|
Total
|
66.6716
|
89
|
256
|
Storm Water Management:
Neyveli mines are located in predominantly monsoonic and cyclonic area where the average rainfall in a year is about 1200 mm and the wind velocity goes up to 160 km per hour Heavy rain flood the open pit bottoms and these difficulties are met by evacuating the flood water through float pump mounted on floating pontoons. Intermediate booster stations pump out the storm water to the surface level.
MINE-I A:-
To meet the fuel needs of the 250 MW Independent Power Project put up at Neyveli and additional requirements of NLC's Thermal Power Stations, NLC has developed a new mine, Mine-IA with a capacity of 3 million tonnes of lignite per annum. The tiny mine with a reserve of 120 million tonnes is spread over an area of 11.6 sq.kms. The excavation of overburden commenced on 30 th July 2001 and the lignite production commenced on 30 th March 2003. The Mine-IA project is one of the mega projects of NLC that has been completed without cost and time over run.
Equipment deployed
Sl.No.
|
Equipment
|
Capacity
|
Mine-IA
|
1
|
BWE
| ||
2
|
a) without deep cut facility
|
700 L
|
4
|
3
|
BWE
|
500 L
|
1
|
4
|
BWE
|
350 L
|
1
|
5
|
Mobile Transfer Conveyor
|
4,700 tph
|
5
|
6
|
Spreader
|
4,700 tph
|
4
|
7
|
Stacker (Rail Mounted)
|
1
|
Conveyor Deployment in Mine-I& 1A as on 01-07-2006
Width
|
Type of Belt
|
Length in Km
|
No. of Conveyors
|
No. of drivers
|
Motor capacity
|
2400 mm
|
Steel cord
|
7.2724
|
7-36
|
25-101
|
1250 KW-630 KV
|
2000 mm
|
Steel cord
|
32.7021
|
1
|
2
|
1250 KV
|
1800 mm
|
Steel cord
|
2.0524
|
3
|
6
|
630 KW
|
1600 mm
|
Steel cord
|
11.6257
|
15-2
|
40-2
|
350-630 KW
|
1500 mm
|
Steel cord
|
6.1450
|
6
|
8
|
630 KW
|
1500 mm
|
Fabric
|
6.8740
|
19
|
72
|
78 KW
|
Total
|
66.6716
|
89
|
256
|
MINE-II:-
In February, 1978 Government of India sanctioned the Second Lignite Mine of capacity 4.7 MT of lignite per annum and in February 1983, Government of India sanctioned the expansion of Second Mine capacity from 4.7 Million Tonnes to 10.5 Million Tonnes. Further capacity expansion to 15 MT/A was sanctioned by Government of India in October 2004 and is presently under implementation.Unlike Mine-I, Mine-II had to face problems in the excavation of sticky clayey soil during initial stage. The method of mining and equipment used are similar to that of Mine-I.
This Mine is located 5 kms south of Mine-I, spread over an area of 26 sq.kms. with 390 million tonnes reserves. The initial mine cut was started in April 1981. The lignite seam was first exposed in September 1984 and regular lignite mining commenced from March 1985. The overburden thickness varies from 50-100 m and the lignite thickness varies from 8 to 22m. The average overburden to lignite ratio is 5m3 to a tonne. The lignite production in this mine meet the fuel requirements of Thermal Power Station-II. The method of mining and equipment used are similar to that of Mine-I. | |
The seam is the same as of Mine-I and is contiguous to it. The lignite seam in Mine-II was first exposed in September 1984 and the excavation of lignite commenced in March, 1985. The Last overburden system (surface bench system) under the expansion scheme was commissioned on 15.12.1991. The lignite excavated from Mine-II meets the fuel requirements of Thermal Power Station-II.
| |
| Mine II | |
| Selected Mining Area | 41.22 Sq.KM |
| Lignite Reserve | 624 M.T |
| Thickness Of Overburden | 45 to 103 Metres |
| Thickness Of Lignite | 8 to 22 Metres |
| Project Sanctioned | 22.02.1978 |
| Cost Of The Project | Rs. 278 Crores |
| Project Inaugurated | July 1979 |
| Project Commenced | 14.04.1981 |
| Initial Mine Cut Completed | 16.06.1985 |
| Lignite First Exposed On | 30.09.1984 |
| FIRST EXPANSION FROM 4.7 MTA to 10.5 MTA | |
| Project Sanctioned For 10.5 M.T Stage | February 1983 |
| Revised Cost Of Expansion | Rs.1065.40 Crores : (Feb.'91) |
| Project sanctioned for 15.0 M.T Stage | October 2004 |
Sl.No.
|
Equipment
|
Capacity
|
Mine-II
|
| 1 | Bucket Wheel Excavator (BWE) Bridge Type | 1400 L |
3
|
| 2 | BWE (Normal Type) | 1400 L |
2
|
| 3 | BWE | ||
| 3.a | a) with deep cut facility | 700 L |
2
|
| 3.b | b) without deep cut facility | 700 L |
4
|
| 4 | Mobile Transfer Conveyor | 11,000 tph |
2
|
| 5 | Mobile Transfer Conveyor | 4,700 tph |
2
|
| 6 | Spreader | 20, 000 tph |
2
|
| 7 | Spreader | 11, 000 tph |
2
|
| 8 | Tripper Car | 20, 000 tph |
2
|
| 9 | Tripper Car | 11, 000 tph |
2
|
| 10 | Stacker (Rail Mounted) |
1 (at TPS-II)
| |
| 11 | Reclaimer | 2, 700 tph |
2 (at TPS-II)
|
Conveyors in Mine - II
Width
|
Type of Belt
|
Length in Km
|
No. of drive heads
and total capacity |
| 1800 mm | Steel Cord | 4.86 | 4 Nos.(11 x 350 KW) |
| 2000 mm | Steel Cord | 20.41 | 29 Nos.(52 x 630 KW) |
| 2400 mm | Steel Cord | 20.56 | 14 Nos.(53 x 1250 KW) |
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