Cement Energy and Environment

Energy Conservation Measures Adopted by the Plant Electrical Energy • Arresting of false air infiltration • Optimum capacity utilisation of equipment • Installation of belt bucket elevator in silo feeding and kiln feeding systems Thermal Energy • Regular monitoring of thermal energy consumption through heat and gas balance studies • Use of clean hot air from cooler ESP fan as primary air • Installation of Rotaflame multi-channel burner UTILISATION OF LIME SLUDGE AND FLY ASH FOR VALUE ADDED PRODUCTS AND PRODUCTIVITY ENHANCEMENT OF LIME KILNS N ational Council for Cement and Building Materials (NCB), New Delhi and Central Pulp & Paper Research Institute (CPPRI), Saharanpur (UP) have jointly taken up a project for the utilisation of lime sludge and fly ash for value added products, such as lime, cement, lime-fly-ash bricks/blocks; and for improving the productivity and energy efficiency of the lime sludge reburning rotary kilns. At present more than 400 paper mills including big and small are in operation in India. Their total installed capacity is estimated at 4 million tonnes and production around 3 million tonnes. The present generation of lime sludge, cinder and fly ash from the paper mills is reported to be 0.8 million tonne per annum (MTPA), 0.6 MTPA and 0.105 MTPA respectively. Around 10 million tonnes of lime sludge and 7 million tonnes of cinder are reported to have so far accumulated. Dumping of these wastes on land has not only made land unfertile but causes environmental problems and hazards too. A few plants have put up rotary kilns for burning of the lime sludge to manufacture lime. Reburning of the lime sludge in rotary kilns converts lime sludge (CaC0 3 ) back into quick lime (CaO) for reuse. The process involves drying the lime sludge followed by heating to the calcining temperature of around 800° C. The calcined powder is further heated to 1000 - 1100° C to achieve sintering of the resulting nodules. Owing to the very high energy requirement for calcination (1600 - 1800 kcal/kg lime), fuel cost and energy efficiency of the units are critical for their economic operation. However high sludge moisture, low dryness of the output from drum washer and high silica content in the lime sludge, besides a number of process and operational problems, act as constraints in achieving a high energy efficiency of rotary lime reburning kilns operating in the country. In this background, the NCB– CPPRI joint project will examine the constraints through detailed investigation and systematic studies. 12 ..