Since the late 1970s, first scanning radiation pyrometers [1, 2] and then thermal imaging systems have gained acceptance in the cement industry for temperature control of the walls of rotary kilns [3]. In the scan technique used, the sector of view spans lengthwise a section of the casing of a rotary kiln (Fig. 1) to record the infrared radiation emitted by the heated casing wall. Since the scan speed is much higher than the kiln rotation speed, it is assumed that the line of temperature monitoring on the casing wall remains parallel to the kiln axis. This makes it possible to form a line-to-line temperature image of a selected portion in the sector of view synchronized with the kiln rotation. Here the size of the image frame is determined by the circumferential length of the kiln cylinder.
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