Identification of overheating of an industrial fluidized catalytic cracking regenerator

Highlights: • A new algorithm for identification of the crack dimensions in the refractory lining. • Heat transfer coefficient identification between FCC particles and regenerator walls. • Measured temperatures in the fluidized bed and on the outer regenerator surface. • A thermal and strength analysis to explain the outer surface overheating process. • The method accuracy is presented using the Gaussian error propagation rule. - Abstract: Considerable overheating can be observed on the outer surface of the fluidized catalytic cracking regenerator. The maximum temperature values and the location of overheating areas change over time. Considering the long times between overhauls (of up to 5 years), it is difficult to pinpoint the factors that cause overheating. An examination of the insulation layer during renovation works does not reveal any obvious damage that could have been responsible for the phenomenon. In order to explain the observed overheating process, a thermal and strength analysis of the fluid catalytic cracking regenerator was conducted. A new algorithm is formulated for identification of the refractory lining state and the heat transfer coefficient between the FCC zeolite catalyst particles and the regenerator walls. The heat transfer coefficient on the regenerator inner surface is estimated after its repair, when no overheating areas are visible. The heat transfer coefficients due to radiation and natural and forced convection are determined based on measured values of the regenerator shell and air temperatures, wind velocity and air pressure. The regenerator outer steel surface temperature is measured using an infrared camera. The presented numerical model of the catalytic cracking regenerator wall enables identification of the wall overheating process. The numerical simulation shows how cracks can open and close in the insulation layer depending on atmospheric conditions. This paper puts forward a new method of identifying heat transfer coefficients and cracks in the refractory lining. The unknown heat transfer coefficient on the regenerator inner surface and the crack dimensions will be calculated by means of the inverse method. A least squares objective function is defined to select parameters such that the computed temperatures will agree within certain limits with the temperature values measured experimentally. The information about the crack size can be used for an on-line assessment of the refractory lining, during the lining modification, and also to estimate the remnant life of steel pressure elements. The method accuracy is presented during real measurements performed by means of an infrared camera using the Gaussian error propagation rule.