Cement and Energy

MINERALISED CEMENT REDUCES ENERGY CONSUMPTION Mineralised cement is becoming a hot issue among cement people. F.L. Smidth-Fuller Engineering, working with FLS-associated Aalborg Portland and other cement producers, has developed methods and procedures based on mineralised clinker that comiderably cut energy consumption and reduce pollution of the enviro11ment. It has been known for several decades that impurities of foreign atoms in the crystal structure of alite (C 3 S) and belite (C 2 S) - the two main constituents of portland cement clinker - may modify the properties of the cement and increase the strength development rate. In the mid 1970's Blue Circle Cement found that a certain combination of sulphate (from gypsum) and fluoride (from fluorspar) in the kiln feed would lower burning zone temperatures and improve cement strengths. The company performed industrial scale trials, using a wet kiln, a grate preheater kiln and a 4-stage SP kiln. The tests confirmed the excellent results attained in the laboratory, although problems did occur in the cyclone preheater kiln due to serious blockings in the preheater. After Blue Circle had acquired 50% of Aalborg Portland, these two companies plus Lohja, a Finnish cement producer, decided to perform a comprehensive study of various clinker types and filJers. They found that a unique combination of mineralised clinker produced at Aalborg, according to the Blue Circle patents and using electrostatic precipitator dust as a filler, yielded the best results. Indeed, the results were so promising that Aalborg Photomicrograph ofmineralised clinker Portland decided to apply for a patent and to further develop this combination. For more than two years, Aalborg Portland worked on the new concept carrying out numerous experiments to overcome cyclone blocking and dust circulation between cooler and kiln. 12