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. In. 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 forming part of a modern precalciner production system its dimensions have been reduced during the past 100 years, and at the same time its specific volume loading has been substantially increased. One of the most important milestones in the historical development of the burning process was the invention 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, which greatly accelerated the development of produc tion units for large throughputs. 100 years ago the clinker leaving the kiln was still cooled in the air but nowadays the grate cooler has become accepted at the most efficient clinker cooler In the majority of cases raw meal is now produced in vertical mills. By using high-pressure grinding rolls for cement grinding it is possible to achieve energy savings of up to 50% when compared to conventional arrangements using ball mills. The most dynamic developments are unmistakably to be found in the automation sector. Automated laboratories carry out 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 production unit, have increased by 70 to 80 times and so, inevitably, has the productivity 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 progress made in reducing dust and gas emissions should not be overlooked. The operating permit for an entire production, plant can depend on complying with the limits.