Cement is a fine, soft, powdered substance, made from a mixture of elements that are found in natural materials such as limestone, clay, iron ore and sand. When cement is mixed with water, it can bind sand and turns into a hard, solid mass called concrete.
Raw Material Preparation
The key element – Limestone and clay are mined through blasting from rock quarries by setting off explosives. Limestone and clay contains calcium, silicon, aluminum and iron, which are the essential elements for cement manufacturing. Latest technology is used for blasting so as to ensuring vibration, dust, and noise emissions are kept at a minimum level. Blasting produces materials in a wide range of sizes from approximately 1.5 meters in diameter to smaller particles less than a few millimeters in diameter. Quarried material is the loaded into trucks or belts for transportation to the crushing plant. Through a series of crushers and screens, the Limestone is reduced to a size less than 100 mm and is stored until required.
Pre - Homogenization
In the dry process, each raw material is proportioned to meet a desired chemical composition and fed to a vertical steel mill. The raw materials are dried with waste process gases and grinded through the pressure exerted by three conical rollers in a rotary kiln. The rotary kiln is fired with an intense flame produced by burning coal, coke, oil, gas or waste fuels. The dry materials exiting the mill are called "kiln feed". The kiln feed is pneumatically blended to ensure the chemical composition is well homogenized and is then stored in separate silos until required.
Basic chemical reactions that take place in the kiln, at 1400 °C are: Evaporation of moisture, calcinations of the Limestone to produce free calcium oxide and reaction of the calcium oxide with other materials (sand, shale, clay, and iron). This results in a final, nodular, red-hot product known as "Clinker" which is 3 – 4 centimeters in diameter and can be stored for several months.
Finishing, Packaging and Distribution
The clinker is cooled and grinded into a fine grey powder. The grinding is done through different-size steel balls. A small amount of gypsum and other process are also added during the final grinding. The amount of gypsum and process added during the process varies in all of the final cement products. Each cement product is stored in an individual silo from where it is transported to packaging facility for either sack – packaging or bulk transportation. Bulk cement is distributed through bulkers or is shipped; depending on the customer's needs.