Process Technology
The main objectives pursued by process technology research are to optimise energy consumption and manpower requirement in cement manufacture, to improve cement quality and homogeneity, and to reduce emissions without compromising economic efficiency. Process technology research is primarily concerned with the fields of thermal and mechanical research.
Thermal process technologyIn the past years, secondary fuel use and its impact on burner operation and the environment was one major focus of investigation. The share of secondary fuels in the total energy requirement of the German cement industry was increased to more than 50% over that period. In other words, many kilns are run at high substitution rates that exceed 60% in some cases. Since the BSE crisis in 2000, the German cement industry has also been burning meat and bone meal. The Research Institute has given close scrutiny to the effects that meat and bone meal utilisation has on product quality, kiln operation and emissions. From a plant technology perspective, the effects on recirculating chlorine systems and phosphate behaviour inside the kiln system were of central interest. From an emission point of view, interest primarily concentrated on possible impacts on NOx emissions. The work of a VDZ working group that intensely studied the effects of precalcining technology and secondary fuel use on the wear and tear and the stability of refractory materials also relates to secondary fuel utilisation. The endeavours to set up a computer model of the clinker burning process and to make use of simulation calculations to optimise kiln systems or investigate scientific questions, respectively, also form the subject of research. The process model of the entire clinker burning process that is available at the Research Institute has been extended to include the external cycle and the option to simulate the behaviour of chlorine and sulphur as well as recirculating alkali systems. Following corresponding validation on the basis of experimental results, the model can now be used to design or optimise bypass systems, for example. |
Mechanical process technology
Cement properties are primarily determined by the reactivity and the particle size distribution of the main constituents. For that reason, the influence that the fineness and particle size distribution of the cement has on its properties has been investigated thoroughly over the past decades.
The mill types chiefly employed in cement grinding are ball mills, vertical roller mills and high-pressure grinding rolls. The production of cement in different grinding systems usually yields different particle size distributions. The mathematical modelling of the grinding circuit allowed us to demonstrate that the particle size distribution of cement is substantially influenced by the fineness and the particle size distribution of the classifier feed.
Comminution processes in cement manufacture are very energy-intensive. Raw meal, coal and cement in particular account for more than 65% of the overall electrical power requirement in cement manufacture. Investigations on industrial and semi-industrial grinding and classifying plants mainly served to determine the influences of different grinding systems on energy efficiency and product properties.
