Cement and Energy

extent by adopting cogeneration systems. At present, a major portion o f the grid power received by cement plants comprises power generated at the rmal power stations with lot ofgas emissions containing a high pe rcent of C02 leading to g lobal warmi ng. FUither, the poor quality of power has forced the plants to instaUcaptive DG sets . Cogeneration of power will not only help reduce environmental pollution but also reduce strain on the economy because of reduction in consumption of diesel oil. The present scenario therefore not onl y favours but warrants adoption of cogeneration systems in the Indian cement industry to make them more economical and to ensure cleaner environment. Cogeneration systems are already in use in some cement plants in J apan and USA. However, in India, these schemes have not ye t been imp leme nted owing to th e following constraints : • • Non-availability of technology indigenously suiting Indian cond itions. Jso•c 2,25.000 Nml/hr gases ranges from 180 to 250 kcal!kg clinker at a temperature range of 300 to 400oC. In addition, 80 to I30 kcal/kg cl inker heat is lost at a temperature range of 150 to 300oC from the ex it gases of grate coole r. Based on the experience of large scale cement plants ope rating in Japan and USA, it has been estimated that about 20 to 30% o f the total electrical power requireme nt of a pl ant ca n be met t hroug h vari o us cogeneration schemes. Studies carried out by the National Council for Cement and Building Materials (NCB) have indicated that in a cement plant of capacity 3000 tonnes per day of cement production, a potential o f 4.5 MW exists for cogeneration of power with waste heat boiler and steam turbine (Fig 1). LEGEND 1 COAL FIRING 2 ECOtiOHISER 3 WASTE HEAT BOILER 4 SHAH TURBINE 5 GENERATOR 6 CONDENSER 7 ~1AKE UP WATER Lack of operating experience resulting in Jack of confidence level for its adoption. KILNIJOOOTPO) • • • • • • • Frequent stoppages of kilns leading to their unstable operation. Unattractive economic viability till recently. Lack of thrust and fiscal incentives. Large capital requirement and fi nancial constraints. However, some of the constraints mentioned above have unde rgone favourable changes recentl y. Waste heat availability and cogeneration potential In the case of dry-process plants, nearly 40% of the total heat input is lost as waste heat from I he exhaust gases of preheater and coole r. The quantity of heal lost from preheater exit FIG. 1 WA STE HEAT BOILER WITH SH AH TURBINE The cogeneration potential can be further increased through supplementary fu·ing system . The investment on various cogeneration schemes ranges from Rs. 3.5 to 5.0 crore per MW depending on the plant capacity and the type of scheme adopted . Although installation of cogeneration system in a cement plant will not directl y result in the reduction of greenho use gas emissio n at source, yet the power generated through cogene ration will relieve the national g rid to that extent and will result in saving ofcoal in thermal power plants the reby reducing greenhouse gas emission. Keeping the above in view, efforts are being made by NCB for installation o f a cogene ration system in a cement p lant to 3