Manufacture of cement

Manufacture of cement

There are generally two processes adopted for manufacturing cement in Bangladesh namely.

1.Wet process.

2.Dry process.

Wet process : The manufacture of cement by this process is divided into three stages:

1. Prepaeation of cement slurry.

2.TO obtain cement clinkers.

3.To prepare cement.

In the first, the raw materials are mixed together. Generally 3 volumes of calcareous materials are mixed with 1 volume of argillaceous materials. After mixing the materials are crushed in a crushing machine.

The crushed materials are put into a wash will where they are finely grounded with addition of requisite quantity of water. The quantity of water used in the wet process is round about 45 present. The grinding of the materials in the wash mail should be such that about 80 to 85 present should pass through no 200 sieve. The mixture now exists a complete homogeneous condition of suspension in water. Such an intimate mixture is termed as slurry. This slurry is sufficiently liquid to pass through pipes and to admit of being handled by pumps. The slurry  is then pumped into correcting silos where it is corrected for its composition.

In the second stage 2 the slurry is  fed into a rotary kiln at the top. A rotary kiln is a long inclined steel cylinder lined with refractories. It is inclined  steel about ½’’ to a foot, and is about  8 to 12 ft in diameter and  200 to 400 ft in length. The fuel to be used  for the purpose may be either coal, oil or gas. If coal is to be used ,it should be in thoroughly grounded form. The col dust is blown in the rotary kiln under pressure from the lower end together with sufficient amount if air to be utilized during the progess of combustion. The  kiln revolves  at a speed of about 2-3 revolution per minute, depending  upon the nature of the materials and the time taken by the materials to reach the lower end of kiln.