ENERGY AUDIT OF A CEMENT MANUFACTURING PROCESS: A CASE STUDY OF BUA CEMENT PLANT OBU, OKPELLA
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Abstract
Cement manufacturing is one of the most energy-intensive industrial processes, requiring substantial thermal and electrical energy, particularly during clinkerization and cement grinding. In Nigeria, rising fuel costs, unstable power supply, and inefficient energy utilization have significantly increased production costs and environmental impacts, making effective energy management essential. This study presents a comprehensive energy audit of the BUA Cement Plant, Obu-Okpella, Edo State, with the aim of evaluating plant-wide energy performance, identifying inefficiencies and energy losses, and proposing strategies for improving efficiency and reducing production costs.
A detailed energy audit was conducted across major production stages, including raw material preparation, clinker production, cement grinding, and packaging of the finished product. Data were obtained through on-site equipment inspections, Central Control Room records, and production logs, supported by equipment inventories and design capacity data. Energy performance was evaluated using specific energy consumption (SEC) indicators, as well as mass and heat balance analyses. The results were further benchmarked against international best-practice standards to assess the plant’s relative performance.
The results reveal significant opportunities for energy optimization within the plant. The specific thermal energy consumption of the kiln was approximately 3.5 GJ/t of clinker, slightly above global best practice values of 2.8–3.0 GJ/t, indicating potential for improvement. Heat balance analysis showed total heat input and output of 3333 kJ/kg and 3342 kJ/kg clinker, respectively, with a minimal deviation of 0.27%, confirming data reliability. Kiln and cooler heat losses were estimated at 9 kJ/kg and 8 kJ/kg clinker, respectively, while total heat loss due to radiation and convection was 0.15 MJ/kg. The annual electrical energy intensity was 88.74 kWh/t of cement, within the global benchmark range of 80–120 kWh/t, with cement and raw mills identified as the largest electrical energy consumers. Furthermore, approximately 15.6% of total energy input in the 6000 t/day dry-process kiln system could be recovered through improved waste heat recovery and enhanced clinker cooler efficiency. The study concludes that while the plant operates within acceptable energy performance ranges, significant opportunities exist for further optimization. Implementation of improved kiln insulation, enhanced waste heat recovery systems, optimized process control, and structured energy management practices is recommended to reduce operational costs, improve overall efficiency, and support sustainable cement production.
A detailed energy audit was conducted across major production stages, including raw material preparation, clinker production, cement grinding, and packaging of the finished product. Data were obtained through on-site equipment inspections, Central Control Room records, and production logs, supported by equipment inventories and design capacity data. Energy performance was evaluated using specific energy consumption (SEC) indicators, as well as mass and heat balance analyses. The results were further benchmarked against international best-practice standards to assess the plant’s relative performance.
The results reveal significant opportunities for energy optimization within the plant. The specific thermal energy consumption of the kiln was approximately 3.5 GJ/t of clinker, slightly above global best practice values of 2.8–3.0 GJ/t, indicating potential for improvement. Heat balance analysis showed total heat input and output of 3333 kJ/kg and 3342 kJ/kg clinker, respectively, with a minimal deviation of 0.27%, confirming data reliability. Kiln and cooler heat losses were estimated at 9 kJ/kg and 8 kJ/kg clinker, respectively, while total heat loss due to radiation and convection was 0.15 MJ/kg. The annual electrical energy intensity was 88.74 kWh/t of cement, within the global benchmark range of 80–120 kWh/t, with cement and raw mills identified as the largest electrical energy consumers. Furthermore, approximately 15.6% of total energy input in the 6000 t/day dry-process kiln system could be recovered through improved waste heat recovery and enhanced clinker cooler efficiency. The study concludes that while the plant operates within acceptable energy performance ranges, significant opportunities exist for further optimization. Implementation of improved kiln insulation, enhanced waste heat recovery systems, optimized process control, and structured energy management practices is recommended to reduce operational costs, improve overall efficiency, and support sustainable cement production.
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