The wet process of cement manufacturing involves adding water to finely crushed raw material, such as limestone, clay or iron ore, in a proportion of 35 to 50 percent water to 50 to 65 percent raw material to make a slurry that is fed into a cement kiln, whereas no water is added in the dry process. Instead, the raw material is fed into the kiln in its dry state.
Traditionally, the wet process was used in the absence of efficient mixing methods. Making a slurry offers better control over the chemistry of the mixture, resulting in a granular crumble that is best for heating in the kiln. The main disadvantage of this method is that evaporating the water from the slurry uses a large amount of fuel. This takes more time because the mix stays in the rotary kiln for two to three hours compared to 20 minutes with the more contemporary dry process, which uses compressed air to mix the dry material.
The wet process also calls for a bigger kiln to facilitate the evaporation of the slurry before heating occurs to produce the clinker, which resembles grey balls. The output clinker is cooled, ground finely and then mixed with gypsum and limestone to produce the finished cement.