Success Experience of NLC in Implementing the Highly Mechanized
Continuous Mining Technology at Neyveli
National Workshop on
The Technology Development & Mechanization of Mines
for enhancing Coal Production & Productivity
at
New Delhi on 20.01.2015
“Mission 1 Billion tons”
The one day National Workshop on “The Technology Development &
Mechanization of Mines
for enhancing Coal Production & Productivity”
organized by the Indian National Committee of World Mining Congress with the
support of Ministry of Coal, Government of India is a very good initiative to fulfill
the “Mission 1 Billion tons”.
In the economic development, you all know that mining is a core industry
which has to be managed very well. The absence of due management results in
mineral wastage and environment pollution. This amplifies the real urge of
Seminars, Symposiums and Workshops like this and I am happy over the huge
response from the sponsors and great friends like you indeed.
Mining industry is going to play a pivotal role in meeting the ever
increasing demand of minerals and metals to sustain higher growth rate of
Indian economy. I would like to share some statistics with the eminent
personalities, on certain important issues pertaining to Mining industry.
India, for its sustainable growth, needs energy from diversified energy
sources. In the recent years, India’s energy consumption has been increasing at
one of the fastest rates in the world due to population growth and Industrial
development. It is sorry to mention that the Demand is outstripping supply. But
Energy is not easily available in the world market including India. As low cost
energy is not just available, growing demand for clean energy coupled with
reduction of carbon foot print is ever increasing.
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India’s energy supply comes from different sources - Coal, Hydro, Oil &
Gas, Nuclear and various forms of non-conventional energy sources. Coal is the
most important and abundant fossil fuel in India. It accounts for 55% of the
country's energy need. Commercial primary energy consumption in India has
grown
by about
700%
in the
last four decades. The current per
capita commercial primary energy consumption in India is about 350 kgoe/year
(Kilo gram oil equivalent / year) which is well below that of developed countries.
Driven by the rising population, expanding economy and a quest for improved
quality of life, energy usage in India is expected to rise. Considering the limited
reserve potentiality of petroleum & natural gas, eco-conservation restriction on
hydel project and geo-political perception of nuclear power, coal will continue to
occupy centre-stage of India 's energy scenario.
India is well-endowed with both exhaustible and renewable energy
resources. India has the fifth largest reserves of coal in the world (301.56 billion
tonnes). India now ranks third amongst the coal producing countries in the
world, producing about 565 million tonnes and imports about 168 million tonnes.
Being the major fossil fuel in India till date, Coal continues to be one of the most
important sources for meeting the domestic energy needs.
NLC is presently operating four open cast Lignite Mines (3 in Neyveli,
Tamilnadu and one at Barsingsar, Rajasthan)
with Overburden Removal
capacity of 165 Mm3 /Annum and a total mining capacity of 30.6 MTPA linked to
four pit head Thermal Power stations with Generation capacity of 2740 MW.
With the addition of 500 MW in Thermal Power Station-II Expansion, the total
Generation capacity would increase to 3240 MW.
NLC is executing the renewable energy projects like 10 MW Solar power
plant at Neyveli and 51 MW Wind power project at Tirunelveli District.
As part of its ambitious growth plan, NLC is venturing in New/Expansion
Projects. NLC is currently executing 2X500 MW, Coal based Power project at
Tuticorin, through a joint venture company NTPL (NLC with TNEB-TANGEDCO)
and 2x500 MW New Thermal Power Project (as a replacement of old 600MW
TPS) at Neyveli with expansion of Mine-IA from 3 MTPA to 7 MTPA.
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With this the power generation capacity of NLC would be 4640 MW in thermal
sector, 51 MW in Wind sector and 10 MW in Solar sector.
The following Projects are under formulation:
 250 MW TPS with 2.25 MTPA Lignite Mine at Bithnok,
 250 MW TPS as Barsingsar Thermal Power Plant Extension with 1.9 MTPA
Hadla and augmenting the present capacity of Barsingsar Lignite Mine,
 A Joint Venture Coal based 1980 MW Power Project in Uttar Pradesh by
NUPPL, between NLC and UPRVUNL,
 10 MW Solar Power Plant at Barsingsar, Rajasthan,
 4000 MW Coal based Coastal Power Project “Sirkali Thermal Power Project” in
Tamil Nadu.
GOI has recently allotted 2 Coal Blocks to NLC. One is an underground
block named Jilga-Barpali, Mand Coal Fields in Chhattisgarh as a linkage to the
proposed 4000 MW Sirkali Thermal Power Project and the other one is
Pachwara South Coal Block located in Dumka district, Jharkhand State to feed
Coal to the proposed (1980 MW Ghatampur Thermal Power Project at U.P.
As regard to Coal reserves, currently India’s estimated Coal resources
stand at 301 billion tonnes of which about 125 billion tonnes or 40% are proved
reserves. Similarly, Lignite reserves estimated at 42 billion tonnes of which
about 6 billion tonnes or 14% are proved reserves. Efforts are required to bring
more reserves to “proved category” to increase the confidence level of the
Investors.
Further, vast Coal & Lignite resources are at deeper depth (>200m).
Commercial Potential for development of these blocks which are not amenable
to Conventional methods requires to be analyzed.
In this context it requires to look into alternate technologies to address
the environmental issues, up gradation of Gross Calorific value, exploration of
deep seated deposits etc.
Clean Coal Technologies (CCTs like CBM, CMM, UCG, etc) are of
paramount important to fulfill the energy demand of the Nation. Few foreign
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countries proclaim that they have successfully implemented Clean Coal
Technologies for exploration of deep seated deposits, up-gradation of Gross
Calorific value of low rank Coals/Lignite, minimize CO2 emission etc. However,
the above technologies require to be tested for Indian condition.
NLC is contemplating to exploit the deep seated Lignite deposits of
Ramnad in Tamilnadu by Underground Gasification Technology.
NLC has developed a Bio-fertilizer namely Humic acid as a by-product
from Lignite and obtained Patent rights in the year 2006. NLC is initiating steps
to commercialize the product through National Research Development
organization (NRD).
NLC has executed an R&D project Utilizing Bottom ash of Thermal Power
Plants for Construction Activities as substitute of Fine Aggregates (Sand) in
collaboration with Vellore Institute of Technology (VIT) at a cost of Rs. 45.46
Lakhs. An experimental building of 920 SFT has been constructed by Utilizing
Bottom ash as substitute of Fine Aggregates (sand).
NLC is the first company having the expertise both in mining of lignite and
power generation. Neyveli Lignite Mines play a major role in meeting the energy
needs of several states of South India. Due to its excellence in performance,
expansion activities and achievements, NLC is conferred with “Navratna” status
under the Administrative control of MOC. NLC is identified as Nodal Agency for
exploration of Lignite in the country.
NLC has made significant contributions, not only in the area of Production
like Mines and Thermal, but also in the field of Environmental protection and
Ecological balance. By carefully planning the projects, implementing pollution
control measures, monitoring the effects of mining and rehabilitating mined
areas, the impact of the mines on the Ecology & Environment of the neighboring
Ecosystem is minimized. NLC does not hesitate to walk the extra mile, when it
comes to the needs and priorities of the society.
The lignite seam was first exposed in August 1961 in NLC and regular
mining of lignite commenced in May 1962.
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German excavation technology in open cast mining, using Bucket Wheel
Excavators, Conveyors and Spreaders (SME Technology) were used for the first
time in the country in Neyveli Mine-I. It is worth to mention here that the
Hambach, the largest Lignite opencast Mine in Germany (located in North
Rhine-Westphalia) is fore-runner of the state of art of Bucket wheel Excavator
technology. The first BWE was commissioned in 1933 in this mine. At present it
is claimed that Hambach mine is deploying the world’s biggest Excavator
capable of extracting 2.4 LT of lignite/day or 2.4 LCM of OB per day. The mine
capacity is 40 to 45 MTPA with OB removal of 240 to 260 Mm 3/A . They are
deploying 5 nos. of BWEs of capacity 2.4 LCM/day, 2 nos. of BWEs of capacity
2.0 LCM/day and 1 no. of BWE of capacity 1.1 LCM/day. The overburden strata
in this mine are loose and it does not require any blasting.
From the initial capacity of 6.5 MTPA, NLC has grown in multifold to a
production capacity of 30.6 MTPA with OB removal of 165 Mm3/A in a span of 5
decades. The adoption of Bucket Wheel Excavator technology at Neyveli was a
landmark event and it has helped for the multifold growth. Now it has been
planned to increase this capacity to 49.0 MTPA of Lignite during 2020-21.
The total SMEs deployed presently at NLC Mines viz. Mine-I, Mine-IA
and Mine-II at Neyveli area are summarized:
1) 1400 L BWEs
: 13 Nos
2) 700 L BWEs
: 16 Nos
3) 20000 TPH Spreader
: 4 Nos
4) 11000 TPH Spreader
: 7 Nos.
5) 5000 TPH Spreader
: 4 Nos
6) 2400 mm Conveyor
: 27.34 Km
7) 2000 mm Conveyor
: 61.80 Km
8) 2400 mm Conveyor
: 27.34 Km
9) 1500/1600/1800 mm Conveyor
: 34.08 Km
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The configuration of SME equipments deployed in our Mine-II of 15.0
MTPA capacity with an Overburden removal capacity of 78.0 Mm3/A is depicted
for your better understanding.
EQUIPMENT CONFIGURATION – OVERBURDEN & LIGNITE ( MINE-II)
SYSTEM
New Surface
Bench
Capacity
# 21.15 Mm3/A
Surface Bench
Capacity
# 21.15 Mm3/A
Bench
Height
25 m
25 m
Top Bench
Capacity
# 19.575 Mm3/A
25 m
Middle Bench
Capacity
9.0 Mm3/A
25 m
Bottom Bench
Capacity
# 7.125 Mm3/A
18 m
SME EQUIPMENTS
Equivalent CME
equipments reqd.
Remarks
26 Numbers shovels of
10 to 12 M3 size with
combination of 230
Nos. of 100 T Dump
Trucks are required for
removal of 78.0 Mm3
over burden.
# Capacity of one
1400 L BWE is
9.0Mm3 for 4000
working hours. By
deploying
additional
BWE
during overhaul,
working hours of
system
is
increased to 4700
hours and thereby
getting increased
capacity.
2* 1400L Bridge Type BWEs
2400mm Conveyor (11.58
Km)
1* 20,000 TPH Spreader.
2* 1400 L Bridge Type
BWEs,
2400 mm Conveyor (9.64
Km),
1* 20,000 TPH Spreader.
2* 1400 L BWE,
2000 mm Conveyor (7.49
Km),
1* 20,000 TPH Spreader.
1* 1400 L BWE,
2000 mm Conveyor (7.46
Km),
1* 11,000 TPH Spreader.
2* 700 L BWEs,
2000 mm Conveyor (7.64
Km),
1* 11,000 TPH Spreader.
Overburden
Total capacity
78.0 Mm3/A
Lignite System
Capacity
15.0 MTPA
4* 700 L BWEs,
5 Numbers shovels of
3
2000 mm conveyor (9.50 10 to 12 M size with
combination of 40 Nos.
Km).
of 100 T Dump Trucks.
#
18 m
The capacity of a 1400 lit. excavator for 4000 working hrs., works out to 9.0
Mm3. By deploying an additional BWE as substitute during major overhaul and
repairs, the effective working hours of the system could be increased to 4700
hrs. The additional excavator capacity of 9.0 Mm 3 was distributed on need
based among the overburden systems viz. New Surface Bench System by
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3.125 Mm3, Surface Bench System by 3.125 Mm 3, Top Bench system by 1.575
Mm3 and Bottom Bench System by 1.125 Mm3.
In order to visualize equipment configuration required in CME for a similar
production capacity, I would like to take 10 to 12 cum shovel and 100 T dump
trucks as a bench mark.
A 10 to 12 cum shovel will have an annual productivity of 3.0 Mm3/A. It
will be required to deploy about 26 nos. of 10 to 12 cum shovels with
combination of 230 Nos. of 100 T dumpers for the prevailing leads in Mine-II for
an annual productivity of 78 Mm3/A of OB. For Lignite excavation, 5 nos. of 10 to
12 cum shovels with combination of 40 Nos. of 100 T dumpers are required to
be deployed for the annual capacity of 15.0 MT. This will amplify the magnitude
of OB removal with huge fleet of equipments involved in the mining operations.
However the height of each bench and surplus productivity of Shovels may have
to be balanced by prudential utilization / placement of Shovels and Dumpers in
each system.
SME technology is a continuous mining system. It involves excavating
the formation in benches of (approximately) 20 to 25m height in slices of 4 to 6
m using the Bucket Wheel Excavators, transporting the excavated solid waste
through Conveyor belts and dumping the material in the dump yard and back
filling in the void area generated after advancement of mine.
The lignite mining at Neyveli has twin challenges of handling of
Overburden with a tune of 6 Cu. M per tonne of Lignite and adverse hydrological
conditions requiring pumping of 8 to 10 Cu. M of water. The lignite is underlined
by powerful artisan aquifer which extends around 400 mts below lignite with an
upward thrust of 5 to 8 Kg/cm2. The aquifer is made up of alternate layers of
sand and clay. Depressurization of aquifer is being done to control the upward
pressure for safe mining of lignite. The challenges posed by nature on lignite
mining were aptly handled in the Neyveli mines by adopting SME technology and
by continuously optimizing the Ground water pumping pattern.
The SME technology is well suited for mining conditions prevailed at
German Lignite Mines. Initially in adopting the technology at Neyveli, NLC
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encountered major teething problems. The successful deployment of BWEs was
made possible by adopting suitable modifications in the design of the buckets,
teeth and structural parts to tackle the hard and abrasive nature of the Neyveli
Overburden strata consisting of Cuddalore Sandstone / ferruginous stone which
is hard compared to the strata of German Lignite Mines.
Modification in the Bucket Teeth:
Bucket Wheel Excavators are severely strained due to the hard nature of
the sandstone, resulting in reduced teeth life, damages to differential & other
gears, the slewing mechanism and the structures with consequent reduction in
efficiency of operation. Yet another factor is the reduction in the hourly output of
production which varies inversely as the square of the hardness of the strata.
A large scale experimenting on teeth design & finally providing Tungsten
Carbide tips with hard-faced sides on the teeth and modifications on the
structural side of the bucket wheel excavators, the strain on the machine got
reduced to certain extent.
Modification in the Bucket:
The overburden soil in the top most bench, due to its sticky nature got
stuck up with the bucket and thereby reduced the bucket volume and hence
reduced the production rate. This problem was overcome by fixing chain mate on
the backside of all the buckets.
Blasting:
Even after these modifications to improve the productivity, it is thought of
loosening the hard strata akin to the looseness of OB in the German mines.
Blasting of the overburden to loosen the strata for efficient handling by bucket
wheel excavators has made a remarkable improvement in production. Loosening
the hard strata has become beneficial to the bucket wheel excavator by reducing
strain on it and thereby increasing the rate of output.
In the past, Cartridge Explosives were the main type of explosives used in
NLC. Presently around 70% is Site Mixed Emulsion (SME) type explosives and
the balance 30% is met out with Cartridge explosives due to
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a) Superior bore hole coupling result in better utilization of explosive energy.
b) Highly safe as it is Non explosive until it is mixed at site.
c) Eliminates the manual loading, unloading and threat of pilferage.
d) Operation Cost of Manpower and Explosive van is lowered.
Around 7,300 tons of Explosive/annum is being consumed in Neyveli.
Latest systems available in the market like Electronic Detonators and Gas bags
are being regularly used in the sensitive areas.
Implementation of VVVF Drives:
This improvisation is helpful in optimizing power consumption.
 VVVF (Variable Voltage & Variable Frequency) drives are fully digital using
proven technology based on pulse encoder feedback technology for individual
motors.
 It increases the power factor and hence there is a substantial energy saving.
 The drives facilitate smooth starting and thereby resulting in lesser downtime
of the machine.
 The VVVF drives are also introduced in conveyor drive heads also.
PLC Based Automation System for Lignite Bunker
An automated system in operating lignite bunker for smooth dispatch of
lignite to various downstream units was a long felt need at NLC Mines. To
accomplish this PLC based automation control including retrofitting of relay logic
with PLC networking, centralized control system, operation and monitoring with
two way industrial paging system and CCTV system was implemented during
2006
The latest generation of SMEs procured for NLC mines are of with PLC
and other advance controls. Hence, the working hours of these equipments are
touching nearly 6000 hours per year.
Wireless Based Centralized Monitoring Operation and Control System:
Wireless based automation control in Mine-IA consisting of one 700 L.
BWE, one 4420 cubic meter/hour of MTC, five 1600 mm Conveyor of total length
5000 meters (approximately) and one 4420 cubic meter/hour spreader including
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networking of existing programmable logical control stations for centralized
monitoring, operation and control. This would be very helpful for operation as
well as maintenance without much wastage of productive time.
Mining equipment maintenance management system (MEMMS) (SAP
based):
This system is to reduce the Breakdown, plan preventive maintenance,
reduces the stoppage duration and also to reduce the inventory. Equipment
details, maintenance task details, manpower, spare parts are computerized. For
the work either planned or Breakdown, Work order will be generated with all the
required information and tools to complete the work.
Condition Monitoring for SME Equipment:
Condition monitoring is being accepted as an effective method to assess
the requirements of maintenance and to increase the operating life of installed
plant and machines. Many parameters can be monitored for an effective health
condition of the equipment. Condition monitoring of SMEs are carried out using
the technique of “Vibration Analysis and Diagnostic Studies” in which vibration
analysis is being applied to pinpoint the health condition of the SME equipment.
Ground water management:
Observation wells at strategic locations are established to monitor the
ground water level and quality regularly. In addition, regional water level and
quality monitoring is being done in and around Neyveli area as a part of the
ground water management. Over the years, through continuous study and
implementation of new methods, the quantity of water pumped out has been
reduced considerably. The water pumped out from mines is gainfully utilized in
captive Thermal Power stations.
Storm Water:
Major portion of the storm water, collected in sumps is due to rain and
seepage from the Mines. This storm water is collected in sedimentation sumps.
Towards conserving water, a part of the clear water from Mine-I is pumped to a
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modern Water Treatment Plant of 8,000 GPM capacity and treated water is
supplied for domestic purpose to the Township.
Similar treatment plant of 15,000 GPM is under construction to treat the
storm water from Mine-II, for utilization in the Thermal Power Station-II and for
Thermal Power Station-II Expansion (2 x 250 MW). By utilizing the storm water
for drinking/industrial use, ground water pumping is reduced and thus resulting in
conserving valuable ground water.
Further, the clear storm water from Mines is supplied to surrounding
villages for agricultural activities, which helps in raising crops three times in a
year. This, in a great way helps in conserving the ground water in the region.
Adaptation of CME Technology in NLC:
In NLC Mines, CME equipments were mostly used for initial development
of mines, to carryout auxiliary supporting works like ramp formation, road
formation, second seam mining etc. In the year 2006, CME with outsourcing
option was introduced to tackle high ratio areas, exploiting the left out areas due
to land eviction problem. Based on the experience gained, for our Barsingsar
mine project, CME technology with outsourcing option was adopted for both OB
& Lignite production to have better cost effectiveness.
For the projects under formulation like Bithnok and Hadla, it is proposed to
adopt the CME technology with outsourcing option to tackle the multi seams
apart from having cost effectiveness.
Assessment of SME technology:
SME technology was introduced first time in India by NLC in its first
opencast mine during 1962. Since then, NLC has acquired considerable
experience, expertise besides indigenization of various parts and spares in India.
Now many Indian firms are capable of erecting SME equipments.
SME technology is very much suitable for soft strata like sand, alluvium
etc. However, at Neyveli, the strata are bit harder resulting in reduced efficiency
of SME operation with low productivity. To improve the productivity after
analyzing the experience gained during the operation of SME over 5 decades,
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the imported technology was modified periodically to suit the indigenous
conditions prevailing at Neyveli Mines. This made the SME technology a perfect
match for the Geo-mining condition at Neyveli where lignite is associated with
unconsolidated sandstones and clays when compared with the sand stone, silt
stone and shale in coal deposits.
It is widely acclaimed that the SME technology is highly capital intensive
and the operating cost will be lower only when high capacity equipments are
deployed. However, for the Neyveli Mines the strata condition coupled with
depressurizing of confined aquifer preference was accorded to SME. Besides, at
Neyveli mines, for deploying the CME, it requires to prepare suitable haul roads
with road making materials to increase the bearing capacity of the floor to offer
trafficability for the dumpers. This makes CME operating cost to be higher side.
For production of Overburden of about 156 Mm3 per annum at the Mines
at Neyveli, within the available range of CME equipments, the capital cost
involved and operating cost including carpeting the working benches for CME
technology balances with the capital intensive SME technology.
NLC initially preferred for combination of SME and CME for its Barsingsar
project at Rajasthan mainly for utilizing the skilled manpower and in-house
expertise in O&M of SME with its high confidence level in achieving the higher
capacity utilization in the absence of confined aquifer at Rajasthan.
But the annual Overburden removal capacity of 9.0 Mm3 per annum after
offsetting OB removal at the bottom most slice over lignite with CME option due
to steep gradient and splits in the lignite formation, only lower capacity SMEs
was proposed. This resulted in 63% of OB handling by SME and the balance
37% by CME for Barsingsar project.
The economics for departmental operation favored for the combined
technology for SME & CME against complete operation by CME. But when
compared with outsourcing, CME technology was mainly preferred on account of
reduction of transfer price. As there is no suitable player for Outsourcing of SME
technology, a point to point comparison of both the technologies with the
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outsourcing of CME technology could not be made. However, a theoretical
evaluation could always be possible.
With the changed Global scenario, a techno commercial evaluation on
built own operate transfer (BOOT) basis for various combination of technologies
could be evaluated for different geo technical and various capacities of mines.
NLC for its Mine-III Lignite project of 9.0 MTPA at Neyveli, with 60 to 70
Mm3 of OB removal per annum and for the proposed Jayamkondam project of
suitable capacity (between 5.5 MTPA to 13.5 MTPA), actively considers looking
for techno economically viable option for either combination of SME & CME or
completely SME or CME deployment for attaining the above requirements.
Adaptation of NLC’s experience in other Opencast mines:
In pursuance of NLC’s high level of success in adopting an imported
technology of SME, I would like to suggest consideration of this technology in
large opencast mines on the following counts.
1)
Superior in environment friendliness:
As this technology fully uses electrical power, its carbon emissions are
negligible with low heat emissions compared with diesel operated equipments /
machineries.
2)
Higher annual production of OB:
Presently OC Coal mines are planned with high ratios, warranting higher
OB removal, it is suggested to carry out a techno-commercial evaluation of CME
and SME technology prior to freezing the technology. Soft strata associated with
trafficability difficulties in deploying CME equipments (suitable haul roads with
road making materials to increase the bearing capacity of the floor to offer
trafficability for the dumpers), this evaluation may be exercised mandatorily.
3)
Combination of Technology:
Presently coal mines are adopting combination of CME & Dragline, CME
& Surface Miners very advantageously. In line with the above, an attempt can be
made for combination of SME with any of the above technologies wherever the
strata condition is amenable to be excavated by BWEs. Besides, SCCL is
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adopting In-pit Crusher, Conveyor and Spreader with CME technology for which
NLC has provided consultancy services.
Thanking one and all for giving me this opportunity and with a hope it is
not the end but a beginning of a fruitful discussion for achieving the “Mission 1
Billion Tons”.
*****
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