Coal Transportation and Handling

7/30/2019 Coal Transportation and Handling

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24 December 2012 PMI Revision 00 1

OFF - SITE FACILITIES

Coal Transportation &

Handling

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Grade Useful Heat Value(UHV) (Kcal/Kg)

Corresponding Ash%+ Moisture % at(60% RH & 40O C)

Gross Calorific ValueGCV (Kcal/ Kg) (at 5%moisture level)

A Exceeding 6200 Not exceeding 19.5 Exceeding 6454

B Exceeding 5600 but notexceeding 6200

19.6 to 23.8 Exceeding 6049 butnot exceeding 6454

C Exceeding 4940 but notexceeding 5600

23.9 to 28.6 Exceeding 5597 butnot exceeding. 6049

D Exceeding 4200 but notexceeding 4940

28.7 to 34.0 Exceeding 5089 butnot Exceeding 5597

E Exceeding 3360 but not

exceeding 4200

34.1 to 40.0 Exceeding 4324 but

not exceeding 5089

F Exceeding 2400 but notexceeding 3360

40.1 to 47.0 Exceeding 3865 butnot exceeding. 4324

G Exceeding 1300 but notexceeding 2400

47.1 to 55.0 Exceeding 3113 butnot exceeding 3865

Grades of Coal


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Daily on an average around 30,000 Tone of Coal is

required for a typical 2000 MW Station.

Each super Thermal Power Project has been linked to aparticular coal mine to meet its coal requirements

The required coal is supplied through Rail wagon. If thepower station is away from coal mines then it is fedthrough Indian Railway system other wise for pit headstation it is done through Merry Go Round railwaysystem


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Merry Go Round (MGR) system is a private, full fledgedRailway system of NTPC used for hauling the requiredCoal from Mines to its Thermal power plants.

Each coal rake consists of Bottom open Broad Gauge

wagons (BOBR) hauled by one/two locomotive.

Modern Multi Aspect Colour Light Signalling (MACLS)system with panel Interlocking is provided for the

safety of the rake movement.


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Main feature of MGR Loading System

This system calls for high-speed load- outstation at the mines

It consists of one or two loading silos depending upon the coal requirement

of the linked power stationThe capacity of the silos for the NTPC project varies between 2400 ton/4000

ton.

The silos are cylindrical and fed by twin belt conveyors.

For accurate weighing of coal to each wagon, Load cells are provided with

silos.

A sampling unit suitable size coal is provided at the feed point of the loading

silo to collect samples for quality analysis

The loading operation of the coal rake takes place while it is moving under

the silo at a speed of 0.8 k.m. per hr.

Wagons are provided with bottom discharge hoppers fitted with

pneumatically operated automatic door actuating mechanism.Line side equipment is installed by the track hopper for initiating the opening

of doors in groups of 10-14 wagons. The unloading operation of 60 tonne per

load wagon takes about 20/30 seconds.


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At NTPC end, Coal is unloaded in the Track hoppers.

Track Hopper, normally of 200-250m length. After placing the wagons on the hopper, electrical pulse is

given to the pneumatic device for opening the bottomdoors.

Coal rushes down due to its own weight. When the track hopper is empty, it takes only 20 seconds

for unloading one wagon i.e. 60 Tons.

This coal falls on a T table, over which a paddle feeder

runs and pushes the coal on to a conveyor.


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Coal handling system is the arrangement for transferring ofcoal from coal-wagons to coal-bunker or coal stock yard.

It also provide arrangement for separation of material

impurities, crushing of coals, Coal sampling etc.

In the coal handling system of NTPC stations, three coal paths are

normally available

Path A - direct conveying of coal from track hopper to boiler bunkers.

Path B - from track hopper to stockyardPath C - from stockyard to boiler bunkers.

The storage facilities at the stockyards have been provided only for

crushed coal.


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The coal handling system is designed to provide

100% standby for all the equipment and conveyors.

The capacity of the coal handling system for super

thermal stations varies from 1200 to 2000 t/h,normally, for a stage of 1000 MW,


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plough feeder/ paddle feeder vibrating screen

crushers,

Conveyor belt,

Idlers, Pulleys,

Drive Unit,

Take-ups,

Skirt board, Scrapper,

Stacker-cum-reclaimer,

Magnetic separators,

Motorized tripper.


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Below track hopperpaddle feeder arrangement isprovided to unload coal to coal conveyors.

The 200mm coal as received at the track hopper is

fed to the crusher house through 1A & 1B

conveyors.


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Vibrating Screen :The function of the vibratingscreen is: -

To send the coal having size of less than 20mm to

belt feeder through the bypass chute bypassing thecrusher and

To send the coal of more than 20mm size to the

crusher.


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CRUSHERS

To crush the coal from 200mmto 20mm size received

from vibrating screenCrusher hammer are made of MAGNEESE STEEL .

Hammer row -4(stage 1)

(a)Row-1 & 2 =18 hammer each

(b)Row-3&4=20 hammers each

No of hammer in each Crusher-

stage-1 = 76 hammers

stage-2 = 92 hammersWeight of each hammer=18.5kg

Crushing motor rating -740kw/3.3kv

Life of hammer =4 lac MT of coal

Normal capacity=600 tons/hr


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Normally these crushers have a capacity of around 600

tons per hour.


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CONVEYOR BELTS

Made of diff. Layers or piles of fabric duck with rubber

protected by a rubber cover on both sides & edges.Fabric duck are designed to withstand tension created in

carrying the load .

Nylon rubber cover protect the fabric duck.

Material =fire resistant grade.

Belt Width=1600 mm.

Strength= 1000/1250 kN.

Belt speed=3.2-3 m/s.Belt length=20km.


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IDLERS

Idlers consists essentially of rolls made out of seamlesssteel tubes enclosed fully at each end fitted with

stationary shaft, antifriction bearing and laybrith sealing.

TYPES

TROUGHING IDLERS- shape the belt to support a

moving load without spillage or damage to the belt.

IMPACT IDLERS - absorb the shock of falling material

at loading and transfer points to protect belt from damage.


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POSITIVE ACTION TROUGHING TRAINERS

automatically maintain troughing side alignment inone-way conveyors. A center pivot frame and offset

neutral guide rolls provide the troughing action.

RETURN IDLERS support the empty belt during the return run.

POSITIVE ACTION RETURN TRAINERS

automatically maintain return belt alignment on one-way

conveyors.


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PULLEYS

Made of mild steel.

Rubber coating is used to increase friction

factor between belt & pulley (rubber lagging

Shell dia-500mm.

Shaft dia-1400mm.

Pulley length-1800mm.

Shaft length-2350mm(bearing centre to

centre)


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DRIVE UNIT

Motors coupled to reduction gear with the help

of flexible/fluid coupling on the high speed shaft of theGear box

Flexible coupling on the input side

TAKE UPSTake up pulley to facilitates

Necessary tension for the drive to operate the belt

Sag at a point where requires horse power will be

at a minimum and load will move with least

disturbance over idlers


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SKIRT BOARD

Used with chutes at trail end.

Guides material centrally on the belt while loading

until it has settle down on the belt

SCRAPPERS

Placed at discharge pulley in order to clean the

carrying side of belt.It avoids the wear of return idlers due to build up

material.


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Pull Chord

Belt Sway

Zero Speed

Chute block


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This is used for stacking and reclaiming the coal fromstock yard. Generally two stacker claimers have beenprovided at each of the NTPC's projects. Their normalcapacity is 200 tons per hour and maximum design

capacity is 450 tons per hour. The stacker reclaimer generally consists of (a) bucket

wheel or digging wheel (b) boom conveyor. While thebelt conveyor carrying the coal for the stock yard is in thesame direction but the direction of the boom conveyor

with respect to stacking and reclaiming is opposite. Digging Wheel The digging wheel is use for cutting and

lifting the coal from the stock yard to the belt used fortransfering coal from the yard. The above transfer takes

place in case of reclaiming the coal only.


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24 December 2012 PMI Revision 00 28Stacker Reclaimer


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During stocking operation, the coal from the crusherhouse is diverted towards the stockyard conveyor at atransfer point TP2/ TP3. The above conveyor dischargescoal to the boom conveyor through a discharge chute.The boom conveyor, running in the forward direction,

creates coal stacks. During reclaiming, coal from the stock yard falls on the

boom conveyor with the help of the bucket wheel and theboom conveyor, during this period, rotates in backwarddirection. The coal from central chute falls on the

conveyor belts used for transferring the coal from thestock yard. By this way, the coal moves on theunderground conveyor belts connected to the main belts.

A 6.6 KV motor is used for running the stacker-cum-reclaimer and has a cable reeling drum on which flexiblecable is wrapped.


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Coal to/from stock yard

Generally 2nos

Capacity ---200T/hr

Maximum---400T/hr

Bucket wheel

Boom conveyor


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RECLAIMER IN OPERATIONSTACKER IN OPERATION

Bucket wheel


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MAGNETIC SEPARATOR

Any ferrous material onthe conveyor will be liftedfrom the moving conveyor.

No Tripping involved.

MS is interlocked withConveyor start up.

When ferrous Metal is

picked up, the MS ismoved from the Conveyor,de-magnatised and themetal piece is removed.

METAL DETECTORAny Metal with an area

of 100 Sq Cm will be

detected.Conveyor is trippedafter detection.

MD is not having

interlock with start up.A sandbag is droppednear the Metal piecefor easy location


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TRIPPERS

To stack material at

desired bunker

Provided with wheels which moves on railsparallel to conveyor.

Three types

motorized tripper

Belt propelled manually operated tripper

Winch driven tripper


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WEATHERING OF COAL

WHEN COAL IS EXPOSED TO ATMOSPHERE - IT

REACTS WITH OXYGEN - PRODUCTION OF

HEAT - RISE IN TEMPERATURE - OXIDATION

REACTION IS ACCELERATED - NUMBER OF

CHANGES IN PHYSICAL AND CHEMICAL

PROPERTIES OF COAL TAKE PLACE - IT IS

CALLED WEATHERING OF COAL.


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IMPORTANT FACTORS FOR

STORAGE OF COAL

RANK OF COAL

SURFACE AREA

VENTILLATION

COMPACTION

AGE OF COAL

SIZE AND HEIGHT OF STOCK PILES

% LOSS I N CVSI ZE OF COAL

( MM) 1 YEAR 2 YEAR50 75 O. 11 0. 24

12 03 0. 5 1. 0

0. 3 0. 2 1. 0 2. 1


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PREDICTION OF SPONTANEOUS

COMBUSTION

B-M LIABILITY INDEX:

= 21.48M+ 0.98A- 0.62M2

-0.58MA+ 0.08A2

+ 10.2WHERE, M=% MOISTURE(AIR DRIED BASIS)

A=% ASH(AIR BASIS)

COALS HAVING B-M INDEX > 80 ARE HIGHLY

PRONE TO AUTO-OXIDATION.


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MANAGEMENT OF COAL STOCKYARD

Proper coal-air interaction to avoid auto- oxidation andspontaneous combustion.

Close monitoring during march-june.

Design should ensure that for maximum duration of the year, air

strikes the width of the stockpile and not the length.

Freshly mined coals should be stacked and old coal should be used.

Freshly mined coals should not be stacked over old coal.

Stacking of coal layer by layer, with compaction of each layer.


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MANAGEMENT OF COAL STOCKYARD (CONTD.)

Stacking in trapezoidal shape, not in conical shape.

Height of stockpile not more than 9-10m (indian coal).

Lumps and fines should be stacked together and compacted.

Before stacking coal should be visibly wet.

Segregation of stockpiles into various segments and relevent records

of period of stacking, quality of coal (cv) should be maintained.

Compaction of finer particles over the bigger particles.


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Documents

Coal Transportation and Handling