Which is the more popular process for manufacturing of cement: Wet/Dry? , Why?
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.