Energy analysis and environmental impact assessment of cement production: Tanzanian and South African case studies

The cement industry is a world-wide industry, consuming about 2% of annual global energy demand. Technical innovations have increased the exergetic efficiency of the production of clinker, the main ingredient of cement, over the last 50 years. Mixing of clinker with waste products like fly ash and blast furnace slag also increases energy efficiency. The major environmental impacts of cement production are resource depletion, mainly fossil fuels, and the greenhouse effect. Almost half of the CO₂ emissions from cement production are related to the dissociation of calcium carbonate, the main raw material. This study showed that there exist large opportunities, which are economically feasible, to improve the exergetic efficiency of cement kilns in developing countries like Tanzania and South Africa. Furthermore exergy analysis proved to be a useful tool in determining the part of the process with the largest exergy losses. A correlation between exergy efficiency and environmental impact of the kiln process in cement plants was also found.