Identification of Coating Thickness in Cement Rotary Kiln

The cement industry is one of the major industries in every country. This industry is the driving force behind the development of a nation. The heart of this industry is the rotary kiln. One of the significant concerns about a rotary kiln is forming a cover of molten materials on the kiln's inner wall called coating. The low thickness of this coating cause burns to the wall refractory bricks and heavy damage to the kiln, while its high thickness reduces the production volume and quality of products. Currently, the kilns are checked by experienced technicians for empirical coating estimation. This paper aims to identify the thickness of the coating for the automatic control purpose of the kiln. The identification problem of coating thickness is based on thermal resistances in different layers of the kiln and heat transfer equations between these layers. For this purpose, the linear and nonlinear identification methods such as Ordinary Least Squares (OLS), Recursive Least Squares (RLS), global search method, and genetic algorithm are used. The coating can be identified in the proposed identification approach by having the kiln's ambient and internal solid temperature profiles. The raw data for the identification process has been extracted by Finite Element Analysis (FEA) for a given solid temperature profile along with the kiln and different kiln coating thicknesses. The modeling and simulations carried out in this paper show that the identification methods were able to determine the amount of coating with acceptable errors depending on the method.