An assessment of energy cost saving a cement grinding plant case study

Abstract

The production of cement is an energy-intensive process. The cost of energy as part of the total production costs in the cement industry is significant and warrants attention to energy efficiency to improve the bottom line. As the cost of energy continues to rise, Bamburi Cement Limited has experienced higher cost of energy especially over the last five years. In 2008, the fuel cost had risen by 361% since 2003 and the cost of electricity had increased by 226% in the same period. The Nairobi Grinding Plant (NGP) of Bamburi Cement had a maximum electricity demand range of 7.7 MVA to 7.9MVA in period 2007 to 2008. The plant operates on a 24-hour basis with an equipment maintenance strategy and schedule in place. The plant has two grinding mills each using a 2800kW motor, and with their associated auxiliaries they consume about 90% of the plant’s electrical energy. The balance of the energy is consumed by fans, electric motors, and compressors and lighting. Electrical sub-metering is done for mills, mill auxiliaries, the separators, raw materials section, packing plant, general utilities and group information technology (IT) infrastructure. The grinding plant’s average monthly electricity consumption was 4,182 MWh in 2007 and 4,264 MWh in 2008 with recorded intensities of 47 kWh/ton and 41 kWh/ton respectively. In 2007 and 2008, electrical intensity varied up to 36 kWh/ton at high production rates of over 120,000 tons per month while it went up to 48kWh/ton at low production below 80,000 tons per month. The plant target is an intensity of 40 kWh/ton for an average production of 100,000 tons per month.