Cement, Energy and Environment

3 levels of 100-110 kWh/t of cement and 850-850 kcal/kg of clinker. The best value for specific electricity consumption in India and Japan is 68 kWh/t of cement, while the best specific heat consumption in India is marginally higher at 667 kcal/kg of clinker than 650 kcal/kg of clinker in Japan. Further energy conservation and environmental improvements are expected by achieving higher thermal substitution rate (TSR) in coal firing by alternative fuels as projected by CII in Fig. 3. The major obstacles in increasing the use of alternative fuels and raw materials are collection, processing, handling, storage, feeding and pollution control. Another potentially effective measure to reduce energy and, consequently, the CO 2 emission is to produce clinker with lower C 3 S content as its enthalpy of formation is 1848 kJ/kg clinker, while that of C 2 S formation is only 1337 kJ/kg. In order to realize this objective, quite extensive developmental efforts have been undertaken locally and globally to produce Reactive Belite Cement (RBC) and alternatively, Calcium Sulfo-Aluminate - Belite Cement (CŚA- BC). Although technically these products can be manufactured in the existing cement plants, little effort has been directed towards establishing their viability and consumer acceptance. More Cement with Less Clinker The step of producing more cement with less clinker involves the use of supplementary cementing materials (SCM) in substitution of clinker, and the proportion of clinker used in the resultant cement is known in general parlance as the ‘clinker factor’. The reduced quantum of clinker use corresponds to the reduction of CO 2 emission. The projected trend of reduction of clinker factor in the next few decades is given in Fig.4. The reduction of clinker use will be achieved obviously through the incorporation of SCMs, the estimated global availability of which is shown in Fig.5. The SCMs are broadly categorized as pozzolanic, cementitious, reactive fillers and inert fillers. Fig.3. Projected trend of TSR by alternative fuels Fig.4. Projected need for reduction in clinker factor in cement in future Fig.5. Global availability and use of SCMs to reduce the clinker factor