Abstract
The production of cement clinker is an energy consuming process. At about 50% of the energy is associated with grinding and milling of the raw meal, that normally is in the range 100% <200 μm with 90% <90 μm. Question: is it possible to use coarser components of the raw meal without reducing the clinker quality. With synthetic raw meals of various grain sizes the clinker formation was studied at static (1100 - 1450°C) and dynamic conditions (heating microscope). A routine to adjust the grain size of the components for industrial raw meals is developed. The fine fraction <90 μm should mainly contain the siliceous and argileous components, whereas the calcitic component can be milled separately to a grain size between 200-500 μm, resulting in lower energy consumption for milling. Considering the technical and economical realizability the relation fine/coarse should be roughly 1:1. The energy for milling can be reduced significantly, that in addition leads to the preservation of natural energy resources.
Highlights
Compared to other industries cement production is an energy intensive process
Concerning the question, is it possible by coarsening the raw meal for cement production to achieve a controlled phase formation and eventually partial melting of a silica rich melt resulting in a “lower melting” eutectic, synthetic raw meals composed from Calcite p.a. resp
For a so called “super coarse” mixture, where the total calcitic component was added as Warsteiner Kalk with a grain size 200 - 500 μm, the eutectic Wollastonite - Gehlenite - Anorthite with 1265°C was established
Summary
Compared to other industries cement production is an energy intensive process. Besides big energy reductions in the last years due to improvements in the preparation of raw materials, kiln development and heat recovery, a further reduction of energy by an extreme coarsening of the raw meal (up to 2000 μm grain size) is discussed. In the proposed process the energy consumption and operational costs shall be reduced by lowering the energy for milling, prolongation of the life time for the mills, lowering the sintering temperatures and shortening the reaction times in the rotary kiln, resulting in at least 30% energy reductions. It was supposed in a patent (Lörke, 2001 [1]), that the raw meal should be milled separated in a fine fraction of grain size < 80 μm (SiO2, Al2O3 rich) and a coarse fraction up to 2 mm (CaO rich) in a relation 1,5 : 1 up to 1.
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