The Detection of the Thermal Processes’ Variations into Rotary Cement Kilns by Thermographic Imaging of the Kiln Outer Shell

The fabrication process of the cement in rotary cement kilns involves chemical, transport, combustion and thermodynamic interdependent processes. Monitoring and controlling these processes are essential for both the quality of the final product – the clinker - and for the energetic efficiency of the kiln. Modern rotary cement kilns are provided with infrared cameras for monitoring the burning processes inside the kiln and laser scanners for monitoring the outer shell of the kiln for the detection of faults at the outer shell. In this paper we propose using the images of the outer shell’s thermal spectrum provided by the laser scanner to extract information about the variations of the thermal processes inside the kiln. The method consists in the implementation of a second degree polynomial approximation of the 2D image of the scans - the analytical model, - and estimating the image of the differences between the observed image and its analytical model. The variations within the thermal processes inside the kiln reflect in both the model’s parameters, and mainly in the image of the differences. For the selection of the principal information regarding the variations within the thermal processes, we propose implementing the null hypothesis test of similarity between these images. The experimental results presented in this work prove that the proposed method identifies the variations of the thermal processes inside the kiln, in numerical values suitable for both faults detection and control of the kiln.