Coal Handling Plant, what it is?

1. COAL HANDLING PLANT
OBJECTIVE:
Coal Handling Plant is a plant which handles the coal from its receipt from
Coal mines to transporting it to Boiler and store in Bunkers. It also processes
the raw coal to make it suitable for Boiler operation
A typical coal handling plant in any power plant shall have the following
processes in sequence depending on the capacity of the plant.
1. Unloading process
2. Feeding Process
3. Screening Process
4. Crushing Process
5. Stacking Process
6. Reclaiming Process
7. Bunkering Process
These processes are explained in successive pages along with figures and
flow diagrams. Other important accessories in coal handling plant like
magnetic separators and suspended magnets are explained at the end.

2. Unloading process
Normally thermal power station receives the coal by three modes of
operation
 By Railway
 By Road
 By Arial ropeways
Aerial ropeway is available only to the power stations which are near
the coal mines.
Cost of coal transportation by road is much higher than that for rail
Transport and hence most of the coal requirement of the power
stations is fulfilled by railway transport by Wagon Tipplers or by
BOBR (Bottom Open Bottom Discharge) Wagons.

3. Wagon Tipplers
These are the giant machines having gear boxes and motor assembly
and are used to unload the coal wagons into coal hoppers in very less
time
(e.g.20 wagons/hr. or more)
 For coal handling plant, wagon tippler arrangement is provided in most
of the power plants where bottom discharge wagon are not feasible.
 Wagon tipplers are at present available to unload 20 tips per hour of
55 ton capacity wagons.
 A typical Wagon Tippler is shown in the next page.

5. Track Hopper
Track Hoppers are mainly used for coal storage & handling in power
plants. The coal is generally transported from coal mines either by BOBR
wagons (Bottom Open Bottom Discharge), or by Top open wagons & rarely
by trucks.
A standard Track hopper is approximately 210m long. This length of track
hopper can accommodate at least 15 BOBR wagons. Each BOBR wagon can
carry approximately 45Mt of coal. Hence each length of track hopper,
carrying 15 BOBR wagons can unload 675Mt of coal in approximately
30minutes.
An assembled Track Hopper is made from a large number of mechanical
items. To name a few items are as listed below:
(1) Reinforced cement concrete (RCC) hopper of 210m long and 8m wide
(2) Steel Gratings covering the RCC hopper
(3) Two parallel rail tracks running at the center of the hopper (210m
length).
(4) Paddle/Plough Feeder located at the discharge side of the RCC hopper
(5) Trough Conveyor located at the discharge of the paddle feeders.

6. RCC Hopper
These hoppers function as a storage arrangement for discharged coal.
Coal filled BOBR wagons are stationed above the 210m long RCC
hoppers.
BOBR wagons are fitted with a bottom opening mechanism which
operates on electrical power. The bottom doors automatically actuates
to discharge the coal into the hopper.
The coal is transferred from wagons to RCC hopper under gravity. For
safety reasons, galvanized steel gratings cover the entire top surface of
the RCC hopper. These gratings are removable in times of need.
Paddle/ Plough Feeders
After the material is discharged from the wagons, they got stored in the RCC
hoppers. Paddle /Plough feeder is a mechanism used for the evacuation of
coal from the bottom of RCC hoppers. As the name suggests, the feeder
ploughs the accumulated coal from the bottom of the hopper and feeds it
into a moving belt conveyor. Its construction is like fan with few blades,
mounted on a trolley.

7. Feeding Process
The feeding process involves continuous and control coal flow to meet the
requirement.
The efficient and economical storage, movement and control of large coal
handling installations, coal car unloading, storage & reclaim system depend
on the proper application of feeders.
Feeders
Various types of feeders are used for these processes. Feeders protect the
belt conveyors from damage by feeding the material onto the belt conveyors
from storage hoppers, at a controlled rate. These feeders are located below
hoppers for feeding of material at uniform rate to Belt Conveyors.
The feeders, which are mainly used in the CHP, are listed below.
1)Belt Feeder
2)Apron Feeder
3)Vibrating Feeder

8. Typical Belt Feeder
Typical Belt Feeder

9. Typical Apron Feeder

10. Typical Vibrating Feeder

11. Screening Process
There are three basic types of screening processes.
1)Scalping,
2)Fines removal
3)Grading.
Scalping
For scalping operations at the coarse end of particle distribution, very high
screening capacities can be achieved since most of the particles are much
smaller than the screen opening and pass through quite easily. Vibrating
Screens and Roller Screens are generally used in CHP. But now days roller
screen are used.
Vibrating Screens
Vibrating screens are of gravity feed type, being sloped downward from the
feed to discharge end. A high frequency low magnitude vibration is given to
the screen by an electric vibrator or other means. The purpose of vibration is
to keep the meshes clear of wedged particles and stratify the coal so that
fine particles come down in contact with the screen.

12. Roller Screen
The coal is feed on the rollers, which are continuously rotate. While rotating
these shaft, transfers the coal from feeding end to crushing process end. The
required size of coal is passed through gap of roller shafts. The remaining
coal is passed through rollers to crusher
Crushing Process
There are four basic processes to reduce the size of material.
1)Impact
2)Attrition,
3)Shear
4)Compression.
In CHP, crushing process is the combination of Impact and Attrition
Processes. Some process involves Compression crushing.

13. Typical Impact Crusher
The bottom of the Reversible Impactor is
open, allowing sized materials to pass
through almost instantaneously. Liberal
clearance between hammers and the breaker
blocks eliminates attrition. Crushing is by
impact only.
In crushing, impact is the sharp,
instantaneous impingement of one moving
object against another. Both objects may
be moving (a bat connecting with a ball), or
one object may be motionless (a golf ball
hit off a tee).
Typical Attrition Crusher
When a Non-Reversible Hammer mill is used
for reduction, material is broken first by impact
between hammers and material and then by shear
and a scrubbing action (attrition) of material
against screen bars.

14. Typical Shear Crusher
Shear is a trimming or cleaving action that is
usually combined with other methods: single-roll
crushers, for example, use shear, impact and
compression methods combined. Shear crushing
is usually called for under these circumstances:
When material is somewhat friable and has
relatively low silica content.
For primary crushing with a reduction ratio of 6
to 1.
Typical Compression Crusher
This crushes by compression without rubbing.
Hinged overhead and on the centerline of the
crushing zone, the swinging jaw meets the
material firmly and squarely. There is no
rubbing action to reduce capacity, to
generate fines or to cause excessive wear of
jaw plates.

15. Stacking & Reclaiming Process
Stacking:
In this process coal from unloading area shall be stored/stacked in a yard
for future use. This shall be done by using belt conveyor with telescopic
chute arrangement.
Reclaiming:
In this process the stacked coal shall be reclaimed for sending to boiler
bunkers. Reclaiming shall be done by bulldozer and grizzly hopper
arrangement.
Both the process shall be combined and executed by Stacker Reclaimers.
This equipment receives coal from a charge conveyor or discharge coal
from a yard to a discharging conveyor. It is operated by complete remote
control with a computer.
This shall be controlled by a PLC along with SCADA or by traditional joy
sticks.
Typical stacker recalimer photos are shown below.

18. Bunkering Process
This process involves feeding of bins/bunkers and maintaining the level of
these bins.
From the conveyor belt the coal is discharged into bunker or bins with the
help of trippers.
The tripper is provided with wheels, which moves on rails parallel to
conveyor on each side. It can be set in one position or made to travel slowly
backward or forward between stops; to discharge the quantity of coal at
desired location.
Motorized trippers are usually used where continuous and uniform
distribution of coal along the conveyor is required or where frequent forward
or reverse movement is required.
Trippers having rigid welded steel frame to resist shock and minimize
distortion. One way or two way discharge chutes are provided. The
bifurcating chute permits the flow and discharge of coal to the desired side.

19. Magnetic Separator and Suspended Magnet
There are more chances of ferrous metal pieces come along with coal from
mines. It is essential to remove these metal pieces, to safe guard the crusher
and belt conveyors from damage.
Inline Magnetic Separators are provided, for continuous and automatic
extraction and discharge of tramp magnetic pieces from coal being
discharged from conveyors as specified.
Suspended Magnetic Separator is provided for picking up tramp magnetic
pieces from moving coal over Conveyor.
Mounting height of 400 mm shall be taken between top of conveyor belt or
bottom of falling material trajectory and the surface of magnetic separator
belt.
The cross sections of magnet are suitably designed to provide sufficient
area for magnetizing the coil effectively, covering full cross section of the
discharge material.
The magnetic separator is located such that it picks-up tramp iron from coal
trajectory, after it has been discharged from head pulley

20. Magnetic Separator:

21. Suspension magnet:

22. Typical Coal Handling System Flow
To understand the coal flow staring from unloading area to coal bunker, let
us take Arasmeta Captive Power Company Private Limited phase 2, Coal
Handling System. The coal flow diagram is given in next page.
Details of the flow diagram are explained.
BCN – Belt Conveyor Number
BC – Belt Conveyor
BCN1 is the belt which starts from the coal unloading area which lies in
Lafarge cement plant premises and has approximately 1000 M length.
Coal from wagon tipplers are dropped in a chute at unloading area, and from
there it will be dropped in BCN1 which is up to junction tower number 1
From this junction tower, coal shall be taken by BCN2. This BCN2 has
movable tripper, for stacking purpose in phase 1 side coal storage yard.
Coal flow to bunker through various options are detailed in successive pages.

24. Sequence of coal flow from phase 1 secondary crusher to phase2 coal bunker
Coal from secondary crusher of phase1
↓
BC12
↓
BC13
↓
BC8
↓
BC9
↓
BC10
↓
BC11
↓
BC11A
For phase 2, coal from BCN2 shall be diverted by flap gate arrangement and
coal reaches BC2 through BC1. BC2 has movable tripper for stacking the coal
in coal yard for phase 2.

25. The sequence of coal flow to phase 2 coal bunker from phase 2 coal yard.
From reclaim hopper
↓
BC4
↓
Reversible belt feeder in Primary crusher
↓
If primary vibrating screen 1 is in line (OR) If PVS2 is in line
↓ ↓
BC5 BC6
↓ ↓
BC6 BC9
↓ ↓
BC9 BC10
↓ ↓
BC10 BC11
↓ ↓
BC11 BC11A
↓
BC11A

26. Coal flow from phase 1 secondary crusher and phase 2 coal yard to phase2 coal
bunker is explained in the previous page.
Similarly, from phase 2 secondary crusher, coal can be taken to phase 1 coal bunker.
Refer the coal flow diagram, in junction tower 4 there is a flap gate through which
phase 2 coal shall be taken to phase 1 coal bunker through BCN8 which is present in
phase 1 coal handling plant.

27. Thank You !