Cement and Energy

CASE STUDIES ON USE OF MINERALIZERS FOR REDUCING ENERGY CONSUMPTION IN CLINKERISATION National Council for Cement and Building Materials (NCB), New Delhi I n the July 1997 issue of Cement and Energy, an article entitled "Mineralized cement reduces energy consumption" was publi shed. In th is issue we are reporting on one of the many plant-based case studies on use of mineralizers under Indian conditions, carried out by NCB and its subsequent successful adoption by the sponsoring plant. In vestigations have been carried out for a 3700 tpd dry process cement rotary kiln equipped wi th 5-stage preheater and a separate line FLS precalciner. The plant uses difficult-to-burn raw mixes using crystalli ne limestone having about 14% silica. Raw mix design optimised by using NCB's raw mix design software, resulted in lowering of free lime. Further improvements in the burnabi lity were achieved with the use of nuorspar as well as barite mineralizers (Fig. 1). Between the two mineralizers, barite was preferred as the mixes with lluorspar were found to be sensitive to temperature rise and therefore expected to be difficult to control. 1450 u !.. 1417 • w Q: 2 \~00 <t Q: w NMl K Q. 1391 --- I - - - - K~O'/, NO MIHERAUSER L· O.S'/,l M·W/, BARITEAS BaO N-)O'f. p· " 25 '/~ FLUORSPAR Q- ·15 •t.j w ,_ IJS0~~~~ .. -4 0·2 ·4 ·H ·75 1.0 1·2 H FREE LIME ('1.) FIG t EFFECTOF BARITE AND FLUORSPAR MlNERALISER ON BURNABILITY OF OPTIMISED RAW MX Barite of 95% purity was used as a minerali zer in the optimised raw mix with 0.72% addition by weight. It was found that use of 0.72% barite as mineralizer lowered the clinkeri ng temperature by 55°C. Considering the calorific value of coal as 4300 kcal/kg of coal, the saving on coal consumption per day worked out to be 47.3 tonnes. Due to reduction in coal consumption, there would be reduction in air required to combust the coal. Air requirement worked out on the basis of ultimate analysis of coal using standard formula reveals the estimated reduction in air requi rement to be 0.36 x 10 3 kg/day. Therefore there is a possibility of increasing the production of clinker by up to 7.0% approximately, subject to balancing of other process parameters. Optical microscopic studies of cli nker with and without barite showed improved crystal morphology and microstructure of cl inker wi th barite; in addition, cls content of the mineralized cli nker also increased from 46% to 51%. Optical micrographs of clinker without and with barite as mineralizer arc given in plates 1 and 2 respecti vely. The 28 day compressive strength of cement prepared from mineralized clin ker increased by 55 kg/cm 2 • Benefits The following benefits have resulted from the use of barite as minerali zer: • Reduction in clinkering temperature. • Reduction in fuel consumption and increase in production . • Improvement in morphology and microstructure of clinker. • Increase in C 3 S content. • Improvement in quality of cement. 3