100 years of successful rotary kiln operation - a comparison of cement production past and present

The first functional rotary kiln was commissioned 100 years ago, in 1899. I n. spite of all attempts it has not yet been possible to replace the rotary kiln as the sintering machine for clinker burning. As a two-support kiln f orming part of a modern precalciner production system its dimensions have b een reduced during the past 100 years, and at the same time its specific vo lume loading has been substantially increased. One of the most important mi lestones in the historical development of the burning process was the inven tion of the Lepol grate in 1928. The introduction of the cyclone preheater in the 50s transferred the preheating of the raw meal to a static system, w hich greatly accelerated the development of produc tion units for large thr oughputs. 100 years ago the clinker leaving the kiln was still cooled in th e air but nowadays the grate cooler has become accepted at the most efficie nt clinker cooler In the majority of cases raw meal is now produced in vert ical mills. By using high-pressure grinding rolls for cement grinding it is possible to achieve energy savings of up to 50% when compared to conventio nal arrangements using ball mills. The most dynamic developments are unmist akably to be found in the automation sector. Automated laboratories carry o ut the quality control, and the entire production process can be controlled and managed reliably with the aid of modern control systems. The specific heat consumption for clinker burning 100 years ago was 8 000 kJ/kg but now it is often below 2900 kJ/kg clinker The throughputs, relative to the produ ction unit, have increased by 70 to 80 times and so, inevitably, has the pr oductivity of the cement production process, which has risen from 700-800 t per head to the productivity level of 20 000 t per head. The great progres s made in reducing dust and gas emissions should not be overlooked. The ope rating permit for an entire production, plant can depend on complying with the limits.