Cement

Cement is one of the most vital construction materials which acts as a binder for other materials through a chemical process known as hardening and stiffening. The cement industry in India stands as the second-largest producer in the world. Out of this production, 98% is contributed by the private sector. There has been an increased demand in the market because of government infrastructure development, especially in the construction sector, which uses over 65% of the cement. Limestone is a major raw material mainly extracted in some states such as Gujarat, Andhra Pradesh, and Madhya Pradesh. 

 

Cement Manufacturing Process 

Modern Portland cement, also known as Ordinary Portland Cement (OPC), is produced from a mixture of limestone, sand, and clay heated to a temperature of 1400-1500°C. The key stages of cement manufacturing are: 

  • Mining: Limestone, being the key raw material, is mined through drilling and blasting, followed by transporting it to crushers. 
  • Crushing, Stacking, and Reclaiming: Limestone is reduced to 80mm in size, which is then piled up and then reclaimed for pulverizing. 
  • Coal Crushing and Reclaiming: Coal is pulverized to fine coal for use in heating during the process of clinkerization. 
  • Grinding and Homogenization: Limestone is milled together with other materials and dried with hot gasses from clinker manufacturing before storing it in silos. 
  • Clinkerisation: The limestone powder is then burned at 1450°C to produce clinkers that are cooled, conveyed, and subjected to further milling. 
  • Cement Grinding: Clinkers and gypsum are ground and separated into fine and coarse products, and the fine product is stored for packing. 
  • Packaging: Cement is usually packed in 50-kg bags to facilitate its transport from one place to another. 

 

Boilers in cement production 

Energy costs constitute approximately 40% of the OF cement industries total costs. Waste Heat Recovery Boilers (WHRBs) are crucial equipment in the cement industry for conserving energy. They recover heat from the exhaust gasses of rotary kilns and produce steam through the turbines to provide approximately 20-30% of a plant's electricity requirement, helping in cutting expenses and increasing efficiency.