Raw material blending silo, preheater tower and rotary kiln at National Cement Company of Alabama, Ragland.
Production of Types I-V portland cement entails pyroprocessing of finely ground limestone, clay and other mineral sources selected to yield the basic chemistry of calcium, alumina, silica and iron. Clinker, the product of the raw materials agglomerating at high temperature in a rotary kiln, is ground to various fineness levels to meet the ASTM International C 150 standard. The carbon dioxide emissions associated with portland cement are concentrated in the a) kiln or calcining phase, where coal or alternative fuels are consumed to generate heat up to 1,450°C; and, b) grinding or finishing phase, an energy-intensive process.
Portland Cement Association, Skokie, Illinois
Cement Association of Canada, Ottawa