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.
