The two basic methods to produce cement are the wet and dry manufacturing processes. The main difference between wet and dry process is the mix preparation method prior to burning clinker in the kiln.
In the wet process water is added to the raw materials to form a raw thick slurry whereas the dry process is based on the preparation of a fine powdered raw meal by raw materials grinding and drying.
The choice of the process is mainly based on the nature of the available raw materials. When the moisture content in raw materials is more than 20% (and up to 45%), the wet method is preferred to the dry method.
In the past, the wet process was mostly preferred because the homogenization of wet raw materials was easier than that of dry powders. The wet process also enables an easier control of the chemical composition of the raw mix. However, the wet process is more energy intensive and expensive than the dry process as it requires the wet slurry to be evaporated before calcination.
The total heat requirement with new dry precalciner kiln systems ranges from 850 to 900 kcal/kg which is approximately 56 to 66% of the energy requirement of old wet process kilns (1300-1600 kcal/kg).
For saving energy and reducing costs, if dry raw materials are available as a basic input, traditional wet process plants are usually converted into dry process plants at the occasions of equipment renewal.