Kiln shell cooling by water evaporation, controlled by infrared temperature measurement

The increased demands for noise protection during the operation of rotary kilns close to residential areas and rising energy costs have raised the question as to whether the classical fans used for cooling kiln shells could be replaced by water cooling. Detailed examination of the thermal energy that is dissipated through the surface of the kiln shell during normal operation has shown that comparatively small quantities of water of about 1 l/s are sufficient to cool the entire kiln provided the water is completely evaporated. Flat fan nozzles, which spray a very narrow fan-shaped jet of water onto the rotating kiln, are positioned next to one another in the axial direction to control the application of this quantity of water to the kiln. The flow of water through each nozzle is controlled by an IR pyrometer so that the kiln shell temperature at the location of the nozzle maintains a predetermined target value over the entire circumference. Tests on a kiln have shown that this method does work and is also highly suitable for selective cooling of hot spots and reducing mechanical stresses in the kiln shell. Examination of the effect of the water and of limescale deposits on the hot kiln shell led to the finding that no significant detrimental effects can be expected over a period of one year. Operation of the initial prototypes and production models shows that a substantial reduction in noise emission and power consumption is achieved. Hot spots can be cooled very selectively by precise application of the water, which extends the kiln running time until repairs are carried out.