Cement and Energy

Cost-benefit anulysis The strategy has been successfully implemented in 33 cement grinding mi lls and 6 raw grinding mills in a number of cement plants in America and Canada. Tbe feedback received from the plants has shown increases in production and reduction in specific energy consumption. These improvements are usually of the order of 5 to 10% increase in the mill output and 3 to 5 % decrease in !he specific power consumption. Tn addition to the improvements in output and power consumption. consistency in quality and reduced wear and Lear of the grinding balls and liners are experienced by the plants due to stable running of the mills. The pay back period for a typical mill of I50 tlh OPC capacity consumi ng about 35 kWh/t cement is around 2 years based on specific power savings alone. However considering the production gains, the pay back period will he even lower. If the strategy is implemented in more than one mill in a si ngle plant then the pay back periods wil l be much lower for addi tional mills in view of the development charges not being required. Courtesy: Holtec Consulting Pvt. Ltd., New Delhi Approach/Mcthodolo~y The methodology for the implementation of the strategy is as given below: • • Obtaining base data from the plant regarding the mill and circuit equipment specifications, operational data and hardware/software details. Visit of the expert team to the plant for observing the operation of the mill and collection of additional operational and hardware/ software data, if required. • Designing of the mill load control strategy. • • • Identi fication of the requirement of transducers, cali bration ranges, etc, for the control strategy. .Installation, commissioning and primary tuning of the control strategy. Fine tuning of the control strategy after observation of the mill performance for 4 to 6 months operation . EFFECTIVE UTILISATION OF GUJARAT AND RAJASTHAN LIGNITE C oal i ~ predominantl y being used as fuel by Indian Cement Industry. The coal requirement of the cement industry is not fully met due to various constrai nts, such as inadequate coal production, infrastructure bottlenecks. shortfall in coal supply, transportat ion over long distances. These constraints, coupled wi th rising costs of inputs and declining margin in cement sector. have necessitated the search for ways and means 1\lr reduction in energy cost and hence cost or cemen t manufacture. The cement industry, a highly energy inten~ i ve industry, has always displayed in terest in energy recovery and usc of al ternati ve Juels. Lignite is considered on e ~uch promising fuel for the cement plants located far away !'rom coalli clds but ncar lignite deposits. The landed cost or lignite per unit heat hecomes much less than that of coal , resulting in a lower cost of energy input. Some states having no coal deposits, such as Tami l Nadu, Gujarat and Rajasthan are bestowed with lignite deposits. About 24 billion tonnes of lignite reserves have been assessed in the country. The lignite from Gujarat and Rajasthan have sulphur content up to JO%. Such lignites cause a number of operational problems including coating formation in the kiln system and hence can not be used as such. Due to thi s, the huge energy resources of lignite in these two states are lying unutilised for long. The sulphur content or these have, therefore, to be lowered down to a level where it can suitably be blended with coal and fired in the ki ln system with minimum operational problems. 3