Temperature measurement of coal fired flame in the cement kiln by raw image processing

This paper presents an experimental study on temperature measurement of coal fired flame in the cement kiln by raw image processing. Firstly the characterization of raw image was carefully examined on a calibration system, and then an improved ratio pyrometry based on raw image processing was proposed. The ratios of spectral color and exposure time in the raw image were calculated as the detection signals, in order to solve the temperatures from an implicit equation without making approximations of the filter profiles of CCD camera. The monochromatic emissivity detected by spectrometer was fitted with an exponential polynomial, and was utilized to correct the temperature solution. The experiments were conducted on a 5000 t/h cement rotary kiln, and the flame image temperatures and emissivity in different cases were detected on line. The results indicated that, the emissivity of coal fired flame in the cement kiln was slightly larger than that in the utility boiler. The temperatures measured by raw image processing were verified by an infrared pyrometer, and the errors were limited within 2%.