|
The techniques of intimate mixing of raw material
in dry powder form were not available earlier. Thus wet process was
initially popular.
In
the wet process, the slurry contains 35-50% water whereas in
dry process materials are already in dry state. Thus, the obvious
disadvantage of wet process was that when the slurry was introduced into the
kiln, a large amount of extra fuel was used in evaporating the water.
In
a wet process, the material is in the kiln for 2 to 3 hours. This
time is reduced to 1
to 2 hours for a dry process. Some new heat exchanges only require 20
minutes. Thus the dry process requires significantly lesser fuel compared to
the wet process.
Quantity of coal required to produce 1 Ton of cement is only about 100 kg
in case of dry process compared to 350 kg for wet process.
Furthermore, in wet process larger kiln was needed for a
given clinker output, because much of the kiln's length was used up for the drying
process.
On the other hand, the wet
process had a number of advantages. Wet
grinding of hard minerals is usually much more efficient than dry grinding. When slurry is dried in
the kiln, it forms a granular crumble that is ideal for subsequent heating in
the kiln.
With
development of modern techniques for dry mixing of powdered material using
compressed air, the dry process has become more popular on account of lesser
fuel consumption & efficiency of grinding operation.
|
