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Starting: We arrived at the factory after crossing a river by a ferry of their own use.
Before crossing the river we were given cards individually for the
identification as visitor. Then we reached the reception room by the transport
of the factory. After their cordial reception and short briefing we were
permitted to visit the factory.
Safety precautions of the
factory : At the very
beginning we became more aware of seeing
their highly safety precautions. It is compulsory to follow the safety roles
for all in the factory. In the boat and ferry they use life jacket. In the
vehicle they hardly use seat belts. In the laboratory they follow the necessary
safety precaution.
Observation:
We were divided into
two groups to visit the large factory. In the laboratory we observed various
sophisticated instruments. By using this standard instrument they ensure the
quality of the product.
Preparing cement: There
are generally two processes adopted for manufacturing cement namely wet process
and dry process.
Dry process: The
manufacture of cement by this process is divided into three stages
1. Preparation of
cement slurry
2. To obtain cement
clinkers
3. To prepare cement
In the fist stage the
raw materials (calcareous and argillaceous materials) are mixed together.
Generally 3 volumes of calcareous materials are mixed with 1 volume of
argillaceous materials. After mixing the materials are crushed in a crushing
machine.
After grinding the
materials are pumped into correcting silos where it is corrected for its
composition. In the second stage the slurry is fed into a rotary kiln at the
top.
A rotary kiln is a long
inclined steel cylinder lined with refractory. It is inclined
about ½ to 1 foot and is about 8 to 12ft in
diameter and 200 to 400 ft in length.
The kiln revolves at a
speed of about 2-3 revolution per minute depending upon the nature of the
material and the time taken by the
material to reach the lower end of the
kiln The fuel is use for this purpose is gas. In the first few feet length of
the kiln, a system of thick iron handing
chains is provided. The slurry dries and peel off in the form of flakes and
drops down at the bottom of the kiln. This section of the kiln is termed as
drying zone and has a temperature of about four hundred to six hundred degree
farenhide to remove water from the slurry. In the next section termed as
calcinations zone, takes place at a temperature of twelve hundred to sixteen
hundred farenhide and the entire moisture from the flakes removed.
The flakes gradually slide down to the third
and last section termed as clinker zone. In the clinker zone the temperature
ranges from 1600 to 3000F.In this zone the calcareous and argillaceous
materials enter into chemical reaction to form the cement compounds of
silicates, aluminates and ferried. These compounds come out as vitrified glassy
nodules of varying sizes from 3/8 to 1/4” downwards.