9.1 Coal Weighing System in Cement Plant
Thermal energy is one of major raw material along with electrical energy for
cement plant. The coal is mostly used to get thermal energy in a cement plant.
The quality and consumption of coal, directly impacts to per ton cost of clinker
produced. The performance of cement plant depends upon per unit cost of power
and coal consumption. The coal booking becomes a big problem if the power
plant is integrated with cement plant and the input coal yard is common for the
both.
The coal consumption booking is directly measured from raw coal feeder and fine
coal feeder. The calorific value of coal along with moisture percentage is measured
from laboratory test. Thermal energy is calculated on per ton clinker production.
This also helps in measurement of KILN efficiency.
The accurate coal consumption gives information about operational efficiency
of the Kiln or quality of purchased coal. A small improvement in the quality of coal
purchased or operational efficiency may results saving of lacs of rupees per annum
for the organization.
We are herewith illustrating an effective and efficient method of coal measurement
system in thermal power plant which may help out for correct coal consumption
as well as may confirm the quality of coal purchased at certain parameters.
Process of coal feeding and coal consumption measurement in the cement plant
can be followed as under:
- Coal is stored in common coal storage pile (for cement and power plant) after
crushing by primary crusher which is installed in cement plant. The size of stor
age coal is less than 75 mm. - The coal (-) 75 mm is reclaimed from storage pile by re-claimer (150 tph).
There is belt weighing system after re-claimer belt which will measure the on line
feed rate of coal conveying to raw coal hopper. Feed to raw coal hopper of
coal mill which is mounted on three active load cells capable to measure coal
storage quantity at >=0.5% accuracy. - The accuracy of belt weigher can be ±0.25% with four live load cells which can
be calibrated inline by hopper weighing system. Similarly, hopper weighing
system can be calibrated with extraction weigh feeder and belt weigher in
stalled as above. - The raw coal is fed to coal mill with help of coal weigh feeder which has better
than 0.5% accuracy which can be calibrated with help of coal bunker periodically. - The fine coal is fed to coal bin which is also mounted on three active load cells.
There is coal feeder (Pfister Rota scale) below the fine coal bin which is used
for coal firing in the kiln. The Pfister has accuracy of ±0.5% and it can be rechecked
/ calibrated with help of weighing system installed the fine coal bin.