Thanks to today’s highly efficient precalcination systems, significantly smaller rotary kilns can now be installed, even though the throughput rates are usually higher than in the past.
This has the effect of reducing the capital cost. The actually required kiln dimensions essentially depend on the employed raw materials and fuels, the plant configuration, the quality of the cement clinker and the production rate itself. Due to the increasing use of high-ignition-point fuels and secondary fuels, modern calciner kilns usually have a length-to-diameter ratio of between 13 and 15.
This L:D ratio cannot be achieved with a classical two-support kiln. However, the POLRO kiln, which has two supports and directly driven supporting rollers, can be employed, enabling the advantages of the two-support kiln to be combined with the required retention time of modern kiln lines.
The POLRO rotary kiln has a statically determined support configuration on only two roller stations and has a direct drive system. The kiln shell with its splined tyres rotates on self-aligning rollers, which automatically adjust themselves to the momentary running conditions.
The kiln is directly driven via the rollers of the inlet-end roller station. The POLRO is rounded off by pneumatic inlet and outlet seals, hydraulic axial thrust system and air-cooled inlet trough.
Thanks to the statically determined support configuration, this kiln design is characterised by high operating reliability, minimal maintenance and inspection requirements and therefore very low operating costs.