The Process of Manufacturing of Cement
Table of Contents
Cement is made from raw materials. These raw materials contain clay or shale and limestone CaO. They are extracted from the quarry and they are crushed into a fine powder. After that, it is mixed in a right proportion.
The materials that are blended in correct proportion is called “kiln feed” because it is feed to a rotatory kiln. The temperature in this rotatory kiln is 1450° C. The dimension of the rotatory kiln is about 200m long pipe and 6m dia. This raw material enters from the cool side and passes through the hot end. The material in the kiln is called clinker. It is temporarily stored in a clinker store. It may pass directly to the cement mill. At the cement mill, the clinker is further grinded into a very fine powder and then gypsum is added in a very small amount. The gypsum is used to control the initial and final setting time of cement.
Manufacturing of cement is a very critical process because there are more than 25 types of cement. It begins with mining, grinding of material, and then passes through the kiln at 1450° C which is very high temperature and then gypsum is added with it. Cement is used in different types of concrete, but the most commonly used cement is Portland cement which is used in normal constructions.
The detailed process of manufacturing of cement is given below:
Process of Manufacturing of Cement
There are mainly four stages in the process of manufacturing of cement which is given below:
- Crushing of Raw Material
- Blending the Material
Crushing of Raw Material
In the process of manufacturing cement, the first step is the crushing of raw materials. These raw materials contain limestone and clay or shale. Usually, the material is crushed in a tube mill. In the tube mill, there are steel balls. This process can be done in wet or dry conditions depending on the product in use but in dry process, the materials should be dried first before putting in tube mill.
Blending the Material
This is the second step in the manufacturing of cement. In blending, the first step is the manufacturing of particular chemical composition which is obtained by selective quarrying and control of raw material fed to the crushing plant. In the dry process, these materials will be stored in silos. While in the wet process, the slurry tanks are used.
The dry process is ensured by agitation and vigorous circulation induced by compressed air. In the wet process, the slurry contains 35 percent of water but sometimes the water is filtered and reduced up to 20%. This reduces fuel consumption in the burning process mentioned next.
This process is used for burning the raw material in the kiln. The dimension of this kiln is 200m and the diameter is 6m. However, the kiln used for the dry process may be smaller in dimensions. The temperature in this kiln is about 1400°–1500° C. The raw material is entered from the cool side of kiln and passes through the hot end. The fuel for combustion in the kiln is pulverized by coal, oil, or natural gas. In the semi-dry process, the raw material contains 15% of the water before passing to shorter rotatory kiln are put into a chain grate.
Nowadays modern cement plants are invented. In which raw material composition is calculated and control by computers. The largest rotatory kiln can process more than 5,500 tons per day.
The raw materials that enter from the cool side of the kiln and pass through the hot end are called clinker. Clinker is stored in clinker mill or stock mill for later use or it may pass directly to the cement mill.
In this process, the gypsum is added to the clinker in a horizontal mill similar to the grinding of the raw material. Sometimes a small amount of agent is grinding and added to the material. For air-entraining cements, the air-entraining agent is added.
In the end, when cement is prepared, it is passed to the silos where it is drawn for packing in bags or put in bulk containers.
You may also read:
- What is Cement and Types of Cement
- Applications & Uses of Cement
- Difference Between Cement, Mortar & Concrete