Selection of viable ug technology

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SELECTION OF VIABLE TECHNOLOGY

FORUG COALMINES

U. Siva Sankaremail: [email protected]

Back ground• The underground production in SCCL

has come to the plateau at 12-13 Mt and any increase in quantum jump with present method of working and technology is looking bleak.

• Added to the above � Depth range is increasing – 350 to 600 m.� Geological disturbances, � Stress regime� Gradient - 1 in 3 to 1in4

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• Most important is the present cost of production with SDL and LHD is in the range of around Rs 2000 per Tonne, against the company average sales realization of around Rs 1423/ Tonne.

• The recent wage hike has totally dashed hopes of viability with SDL and LHD technology.

Back ground

COST OF PRODUCTION FOR 2009-10 IN Rs.

• LONGWALL - 1029.65• BLASTING GALLERY - 1416.53• CONTINUOUS MINER - 1543.04• SDL - 1790.03• LHD - 2068.45• HS - 3128.40• RH - 6723.61

• The major contribution of cost of production in existing Bord & Pillar with HS/LHD/SDL is Wage component.– HS -74%– LHD-60%– SDL-62%

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OBJECTIVE

• To design a suitable and viable “Method and Technology” for the available deposits keeping in view– Depth– Gradient – Geological disturbances– Low quality seams in upper horizons

ISSUES• Depth – Present B&P / Rhombus shaped pillars at more

than 350 m depth would not stand.• Requirement – long term stability (FoS-2)• Gradient –1 in 2.5 to 1in 4, there is limitation with

working of technologies like SDL,LHD, and CM etc.• Requirement - Negotiate /suitable cross gradient or

cutting the floor/ roof stone.• Geology – faults: Due to presence of faults Longwall

technology is becoming non viable in present coal blocks.

• Requirement- Viable LW technology (low cost) with shorter panels of length 500 -600 mtrs

• Low quality seams in upper horizons-(IRR)• Requirement- ,stowing for lower seams, coal washeries

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Technology selection Matrix

JJx or JJJJCM

JxxJxJSDL / LHD

JJx or JJJJBM

XJJJJJLongwall

Steeper than 1 in 4

Upto1 in 4/5

300-600Upto300

Geologicaldisturbances

CPTGradientDepth (m)Technology

x or J indicates both options may work when floor cutting is possible

INFERENCE• From the above, SDL / LHD deployment is not

viable for deep and steeply inclined deposits.• The alternative Technologies

– Longwall – The Low cost Longwalls, viable with even 500m to 600m length panels

– continuous miner / miner bolter- The technology should be able to cut stone roof/floor to overcome cross gradient problem.

• Alternative method:– As an alternative to the present Bord&Pillar / Rhombus

type of development, Block development with long headings and liquidating with Fenders for stability during development and safety during depillaring.

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Recommendations

• Keeping in view of above parameters we can set out� low cost Longwalls where, 600 to 1000m

panels can be formed �In other cases, where cut out distance

permits and frequent movement with out damaging the floor is possible a continuous miner otherwise bolter miner is a suitable option.

Technical Parameters

• Depth• Gradient• Cross Gradient• Floor Pressure or Ground Pressure• Cut out Distance• Number of Entries• Lead – Pillar Size• Angle between entries and crosscuts• Orientation of angled crosscuts

Operational and Technical Parameters Continuous Miner / Bolter miner

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• At present, the depth of working underground mines in SCCL is limited to 300m to 400m.

• Most of the Extractable Reserves are lying at a depth range of 300 to 600m

• Technology for faster extraction of coal seams is to be deployed to counter the problems of Ground control, Ventilation with increasing depths in order to ensure Safety and also to meet future energy requirements.

• If depth exceeds 400 m, Pillar stability is major hindrance for safety in Bord & Pillar method.

• To over come this, Instead of pillar formation, Block development with long headings and liquidating the same with Fenders.

Depth

Gradient� The limiting Gradient of Continuous Miner & Shuttle cars is 1 in 6

(91/20) & 1 in 8 (70) Respectively� Gradient of Coal seams vary from 1in 2.7 to 1in 8. � Maximum workable seam gradient is 1 in 4 with apparent dip limited to

1 in 6 due to limiting acute angle of Rhombus pillar

Cross Gradient� While working on apparent dip, if floor is not competent, wheels of

shuttle cars / LHDs move on different individual horizons. This leads to damage of suspensions and breakdown of equipment.

� Joy Mining is offering individual suspension shuttle cars in new versions on optional basis.

� To overcome this, stone floor is to be cut on the rise side of the gallery to make it level.

� Stone cutting will lead to coal degradation during development.� The limiting Cross Gradient of Continuous Miner & Shuttle cars is 1 in

11.5 (50)

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Continuous miner development

Cutting into Floor and Roof

Floor cutting for rectangular roadways

Roof cutting for rectangular roadways

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Gradient & Cross Gradient

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Ground pressure parameter is considered

1. For with standing partition between two contiguo us seams,

2. For with standing of floor coal when working on cross gradient subjects to frequent movement of machinery.

� The compressive strength of the coal can be taken a s a least value of 2.8 MPa (406 Psi) ( I seam of KTK – 5 Incli ne, NIRM Report) and maximum of 22.5 MPa.

� Tensile strength of the coal can be taken as minimu m 0.28 MPa and 2.25 Mpa as maximum for our coal seams.

� Where Parting thickness between working sections is less than 1/5th of the Gallery width, failure is usually in t ension.

� The ground pressure of Continuous Miner varies from 0.11 MPa (16 Psi) to 0.22 MPa (32 Psi)

� Shuttle car ground pressure varies from 0.834 MPa ( 121 Psi) to 1.09 MPa (158 Psi)

Technical Parameters - Ground Pressure

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3.80 –4.50

3.0 –4.5

1.80 –3.0* & 2.10 –3.70

1.37 –2.70

1.80 -3.60

1.17 –3.1

Cutting height(m)

1159762.307539/44*60Weight(Tonnes)

0.220.220.17- --0.11* /0.12

0.158Ground Pressure (MPa)

6.60/7.204.20/6.04.724.702.703.50Cutting Width (m)

MB 750MB 670MB430*MB450

MB250ACM10/ MC 250MC255*

MC 350

CM or MB

SPECIFICATIONS OF MINER BOLTER(MB), CONTINUOUS MINER(CM)

20161414118Capacity(Tonnes)

1.090.961.00.940.970.85Ground Pressure (MPa)

29.5027.202522.7020.4818.1Weight(Tonnes)

654321Shuttle car

1,2,3 : Low to Medium height Seams , others : Medium to high seams

SPECIFICATIONS OF SHUTTLE CARS

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Technical Parameters -Cut out Distance or Length of a cut

Cut out Distance (m)CMRI RMRMine

1562VK7 Incline (Non- Caving)

1248GDK 11A Incline(Caving)

The maximum unsupported span of the gallery which can be cut with Cutting machine safely with out an y failure of immediate roof, which may or may not be supported later

It plays vital role in the selection of Continuous miner or Bolter miner for particular geo mining condition

Beniawski RMR & Bartons Q – System Approach

VK-7

GDK-11

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Basic Geometry of Room & Pillar Workings

Twin Entry Development Layout for Longwall

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Sequence of cutting in Development

Entry Mechanized Room & Pillar Layout

15-25m0m

Main1 Left 1 Right 2 Right

2 Left

Continuous

Miner

Shuttle

Cars

Feeder

Breaker Electrical

Equipment(Load

Center)

Twin Boom

Roofbolter

“Load-Haul-

Dumper” (LHD)

Machine

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�When the number of entries are less, there are only a few available working faces results in delays because cyclical mi ning (including continuous mining).

�When there are many working faces available, an act ivity can be shifted to another location without any interruptio n.

�More entries facilitates machines to maneuver easil y and quicklyand shuttle cars will have different routes for loa ded and emptycars, thereby reducing travel times.

�The more the entries, less is the air resistance. H owever, with too many entries, section ventilation may be difficult and prone to leakages.

�One disadvantage of many entries is that it slows d own development and therefore, pillaring. Hence, cash f low may be small for a long time.

�Generally 5 entries Panels are being preferred due to Less shifting of feeder breaker optimized Lead , Product ion. (since any less number of entries causes congestion with bridg e conveyors)

Number of Entries

Lead

�Production & productivity increases with reducing lead and Vice versa.

� Lead mainly depends up on pillar size, so pillar si ze should be optimized considering Ground control as well as techno-economic analysis.

� It impacts the haulage cycle times (shuttle or ram car) since when one car is in an entry, others have to w ait until the entry is cleared.

� For larger pillars, such idle waiting times can be long.

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Angle between entries and crosscuts

�The angle between crosscuts and entries depends on the machinery.

�Bridge conveyors and ram cars, require oblique angl es, while shuttle cars require perpendicular angles.

�In case of FCT, spillage is high when the direction of flow takes a sharp turn

� Therefore, oblique angles are to be planned whereve r the conveyor flow direction is expected to change.

Fig. Spillage at Transfer Points

�Angled crosscuts should be aligned with Major Horizontal stress direction for ensuring the stability of Trunk road ways or panel galleries.

Orientation of angled crosscuts

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Operational Parameters

• Floor Condition• Watery condition• Cables handling & Equipment Rerouting• Damage of Cables & Tyres• Bolter & Miner Compatibility• Side spalling• Floor Heaving• Fire problem• Ventilation• Quality• Roadway Maintenance• Extraction of Developed Pillars

Floor condition & watery Condition

� The floor coal gets crushed due to frequent movement of Machinery and lead to formation of ditches, which in further leads to heightening of galleries. The Minimum required compressive strength of floor coal is 15 Mpa for movement of machinery ..

� With presence of water used for dust suppression (≈30 GPM) or seepage water causes slushy conditions results in skidding of shuttle cars even on stone floors.

� To overcome the above problems1. Routing cars in different routes & placement of

feeder breaker to facilitate unloading in three directions

2. Dinting floor on dip side to collect and divert water

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Cables Handling & Equipment Rerouting

• In case of electrically operated machinery, cables handling is cumbersome at the time of operation & equipment rerouting

• Continuous miner cable to be handled manually & cables need to be lifted at junctions through which shuttle cars travel.

Damage of Cables & Tyres

• cumbersome cable handling and slushy floor conditions leading to damage of cables & tyres of shuttle cars

• Foam filled tyres instead of air filled and also chains engulf to tyres to prevent the damage of tyres

Bolter & Miner Compatibility• With Quadra bolter the distance between two side booms

is fixed and it is not possible to use all the booms simultaneously for bolting, if the spacing between bolts is to be varied.

• Bottom row of side bolting could not be done with the dual boom bolter (above 1.5 m from floor)

• Mismatch of Bolter & miner leading to idling of Miner during development and also during widening of developed pillars

Ventilation

• For development, 1200 cu.m /min air quantity is required to facilitate comfortable working conditions.

• Automatic methane monitoring system is incorporated in CM to cut off power incase of exceeding limits.

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• To overcome the gradient problem, Floor stone/coal to be made level by cutting stone in thin seams.

• For cutting stone floor, Design requirement for cutting drum is different and only sandvik is offering to cut the stone up to 35 Mpa compressive strength.

• This will results in to coal contamination, varies from 6% to 16% depends on seam gradient.

Ground Control Problem• The success of any extraction method is depends on

Cavability.• Induced blasting to be adopted where caving is not

regular• Jumbo drill to be included in the CM/BM package for

Induced Blasting wherever required.

QUALITY

• Continuous miner/ Miner Bolter feasibility depends on the Geo mining parameters.

• Its success depends on suitable mechanized environment at the mine.

• Facilities like man riding, Good ventilation system, spares management, availability- utilization and overall maintenance adds to achieve improved performance.

As a final point

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ADVANTAGES OF CM/ BMADVANTAGES OF CM/ BMADVANTAGES OF CM/ BMADVANTAGES OF CM/ BM

• The Continuous Miner/BM can extract the coal to full seam

thickness of 4.5m to 5.0m in a single lift.

• Strata control problems can be minimized by avoiding blasting

operations as the depth is increasing 350m and more.

• It gives higher production rates.

• Remote operation leads to safety.

• Risk of spontaneous heating can be reduced due to faster rate of

extraction.

• Moderate Capital cost when compared to Longwall.

Continuous miner Vs Bolter miner

Simultaneous cutting and supporting possible

Immediate supporting is not possible

Strata management

Eliminates the problem of cut out distance

Limits the applicability and performanceWhere cut out distance is more, it gives high production

Cut out distance

�Cutting is done by Hydraulic Sumping

Better floor condition

�Cutting is done by tractive force�Frequent plying to facilitate boltingMore floor damage

Floor degradation

BMCM

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SOLUTION• Quality Geo-tech Information. As depths

are increasing huge investments on technology, energy activity like supports , ventilation etc becomes expensive.– For a viable design quality geological

information is required.

• Technology suggested:– Longwall – Low cost Longwalls to work

shorter panels and still viable.– Bolter miner: Bolter miner instead of

continuous miner in view of cutout distance.