Industrial practice of energy-saving cement production of extremely coarse-ground raw meal

Extremely coarse-ground raw cement meal can increase the amount of the melt and reduce the melting temperature to 1100°C. The higher reactivity of the extremely coarse-ground raw meal can increase its saturation factor and the silicate module. The thermal treatment of the extremely coarse-ground material in preparatory zones of the furnace is improved due to its good overturning capacity. The heat loss is significantly reduced due to a lower temperature of the off-gases, better heat transfer in the preparatory zones of the kiln, lower temperature of the kiln shell and lower dust discharge from the kiln. This can cut the fuel consumption by 15% and increase the capacity of the kiln up to 30%.
With extremely coarse grinding the raw mill performance increases 3.0-4.5 times, with the specific power consumption reduced 3.0-4.5 times over, the specific consumption of grinding media - 3-4 times, the noise level of raw mills – by 60-70%, the moisture content of the raw slurry with the same spreadability of 50-60 mm – by 4-8%. The raw slurry density increases from 1650 to 1700-1935 g/l, thereby increasing the capacity of vertical and horizontal slurry tanks. With the same spreadability the water separation from the extremely coarse-ground raw slurry after 24 hours of storage is lower than that of the regular finely ground raw slurry. The raw slurry can retain limestone particles up to 5 mm for a long time. Thus, the maximum slurry grain size can be easily increased from 0.5 mm for the finely ground raw slurry to 1.3-2.0 mm for the extremely coarse-ground raw slurry, with a substantial margin. The results of the slurry grinding chart analysis in the raw mill sized Ø 3 × 14 m show that the approach to calculating the range of grinding media for extremely coarse grinding was chosen correctly.

Author: P. Loerke, A.N. Chukmarev, P.F. Korobkov

Section: Equipment and technology

Keywords: sludge, raw mill, grinding, burning