INDUSTRIAL ENGINEERING APPLICATION TO COAL HANDLING PLANT
INTRODUCTION
A
coal handling plant is a facility that washes coal of soil and rock,
preparing it for transport to market. It may also be called a “coal
preparation plant (CPP)”, “coal handling and preparation plant” (CHPP),
“prep plant,” “tipple,” or “wash plant”. Caiman coal handling plant can
handles the coal from its receipt to transporting it to Boiler and store
in Bunkers. It also processes the raw coal to make it suitable for
Boiler Operation. It Receipt of coal from coal mines, weighing of coal,
crushing it to required size and transferring the quanta of coal to
various coal mill bunkers. This is the responsibility and duty of the
coal handling plant and its staff.
Crushing and screening in coal handling processing
Crushing and screening are very important step in coal handling processing:
Crushing
Crushing
reduces the overall size of the ROM coal so that it can be more easily
handled and processed within the coal handling plant. Crushing
requirements are an important part of coal handling plant design and
there are a number of different types.
Screening
Screens
are used to group process particles into ranges by size. These size
ranges are also called grades. Dewatering screens are used to remove
water from the product. Screens can be static, or mechanically vibrated.
Screen decks can be made from different materials such as high tensile
steel, stainless steel, or polyethylene.
Equipment used in a coal handling plant
1. Pull chord switch
a
series of such switches are arranged in series at a 1m distance on the
side of conveyor belt. The power supply to rotor of the conveyor belt is
established only if all switches in series are connected.
2. Vibrating feeder
The coal stored in a huge hub is collected on the belt through vibrations created by the vibrating feeder.
3. Flap gates
These
are used to channelize the route of coal through another belt in case
the former is broken or unhealthy. The flap gates open let the coal pass
and if closed stop its movement.
4. Magnetic separator
these are used to separate the ferrous impurities from the coal.
5. Metal detector
These
are detect the presence of any ferrous and non-ferrous metal in the
coal and sends a signal to a relay which closes to seize the movement of
belt until the metal is removed. It basically consists of a transmitter
and a receiver.
The
transmitter consists of a high frequency oscillator, which produces a
oscillations of 1500 Hz at 15V. The receiver receives this frequency
signal. If there is any presence of metal in the coal. Then this
frequency is disturbed and a tripping signal is send to relay to stop
the conveyor belt.
6. Belt weightier
1. It is used to keep an account of the tension on the belt carrying coal and is moves accordingly to release tension on the belt.
7. Reclaim hopper
Reclaimation
is a process of taking coal from the dead storage for preparation or
further feeding to reclaim hoppers. This is accomplished by belt
conveyors
Availability of Coal in India.
It
is used for iron and steel industry and smelting. It is found in Jharia
coal mines. Ordinary coking coal is found in Raniganj and the western
part of Jharia, Bokaro, Ramgarh, northern Karanpura (Damodar Valley) and
in some mines of M.P
(2) Ordinary Coal.
Apart
from coking coal the ordinary variety of coal has reserve of 64 billion
tonnes. This type of coal is used in railway engines, steamships,
thermal electric plants, chemical industry and for domestic purposes.
This
type of coal is found in (i) Western Raniganj, (ii) Karanpura (Northern
and Southern part), (iii) Bokaro (iv) Rajmahal (Damodar Valley) (v)
Talcher (Mahanadi Valley) (vi) Singrauli, Korba, Sohagpura (vii) Sanhat
(Sone Valley) (viii) Kampatee (Maharashtra) (ix) Godavari Valley (A.P)India
being a large country its every state tries to get coal from the
nearest source in order to cut transport charges and its early supply.
As such:(i) The Northern states of India depend upon coal produced in Raniganj, Jharia, Bokaro, Karanpura, Rajmahal and Singrauli.(ii) The Southern Indian States meet their coal demand from coal of Godavari valley mines.(iii) The north-eastern states draw coal from Assam, Arunachal and Meghalaya states, situated close by.(3) Lignite Coal (Production).This
poor quality coal is extracted in various parts of the country like
Jammu and Kashmir, Rajasthan (Bikaner), Gujarat (Bharauch and Kutchch)
and Tamil Nadu (Neyveli). Transportation of coalThere are four ways of Transportation.• 1. Railways.
Problem Definiton
During
rainy season usually coal supplied to thermal power plants is wet.
During transfer of coal from different sources such as wagon tripler ,
Arial ropeway, road weigh & coal reclaimed from stack yard to
bunkering or to boiler, wet coal has to pass from the system of conveyor
belt, crusher, vibrating feeders and coal transfer guide i.e. chute
from one conveyor to another conveyor as shown in fig.- . In this
process of coal conveying when the coal is wet it starts accumulating to
the inside part of chute slowly & start blocking the coal transfer
guide. As the process goes on accumulation goes on increasing & at
one stage will completely block the chute. Even after this as there is
no automated provision for switching of the feeding conveyor belts motor
off process goes on & chute gets choke up completely till it was
recognized by the local operator, or motor will gets tripped on
overload. The system the need to be cleared by removing the choke up
manually by deploying manpower & till then the system will not be
available for the conveying usually it takes 02to 03 hours to clear the
choke up.
PROBLEM ANALYSIS
After
looking at the problem the main cause of the chut choke up was the
wetness of the coal which is not under our control and the next cause
is there is no alternate provision to turn off the motor when chute
choke up occurs. So it was necessary to make some provision for
automatic turn off the motor whenever there is a choke up situation.
DEVELOPING SOLUTIONS
We
decided to have some modification in electrical side to make the motor
turn off whenever chute choke up takes place. We made a provision of a
window with a gate opening sideways as shown in figure. The window hole
gate is connected in such a way that it will get open whenever coal
accumulation starts in the chute. We connected a levered limit switch
having normally closed contact and the switch having normally closed
contact opens when lever gets triggered by the opening of the gate.
Whenever chute choke up starts, coal starts accumulating in the hopper
and pushes the window door. This triggers the limit switch and operates
switch to open state from normally closed state which turns off the
motor prior to the chute choke up. Electrical connection is done from
local stop push button. Limit switch which has normally closed contact
is taken in series with local stop push button contact as shown in the
figure
IMPLEMENTATION
BENEFITS:
¢ Reliability of the coal handling system is increased.
¢ Down time of the system is reduced.
¢ Demurrage charged by Indian railways due to delay In unloading is reduced.
¢ Saves manpower required for cleaning and system restoration.
¢ Electrical power consumption is reduced as there is no overloading of motors.
¢ Life of conveyer belts, gearbox and motor is increased by reducing frequent overloading.
