Rotary cement kiln coating estimator: Integrated modelling of kiln with shell temperature measurement

Abstract

Coating thickness protection in the burning zone of a rotary cement kiln during operation is important from the viewpoint of the kiln productivity. In this paper, an integrated model is presented to estimate the coating thickness in the burning zone of a rotary cement kiln by using measured process variables and scanned shell temperature. The model can simulate the variations of the system, thus the impact of different process variables and environmental conditions on the coating thickness can be analysed. The presented steady-state model derived from heat and mass balance equations uses a plug flame model for simulation of gas and/or fuel oil burning. Moreover, the heat transfer value from shell to the outside is improved by a quasi-dynamic method. Therefore, at first, the model predicts the inside temperature profile along the kiln, then by considering two resistant nodes between temperatures of the inside and outside, the latter measured by shell scanner, it estimates the formed coating thickness in the burning zone. The estimation of the model was studied for three measured data sets taken from a modern commercial cement kiln. The results confirm that the average absolute error for estimating the coating thickness for the cases 1, 2, and 3 are 3.26, 2.82, and 2.21 cm, respectively.La protection de l'épaisseur du revêtement dans la zone de combustion d'un séchoir rotatif pour cimenterie pendant le fonctionnement est importante du point de vue de la productivité du séchoir. Dans ce document, un modèle intégré est présenté pour estimer l'épaisseur du revêtement de la zone de combustion d'un séchoir rotatif pour cimenterie en utilisant des variables de fonctionnement et des mesures de la température de l'enveloppe. Le modèle peut simuler les variations du système; par conséquent, on peut analyser les conséquences des différentes variables de fonctionnement et conditions environnementales sur l'épaisseur du revêtement. Le modèle en régime permanent présenté, dérivé deséquations de bilan de masse et d'énergie, fait usage d'un modèle de flamme enécoulement piston pour la simulation de la combustion de gaz ou de mazout. De plus, le transfert de chaleur de l'enveloppeà l'extérieur est amélioré par une méthode quasi dynamique. Par conséquent, en premier lieu, le modèle prédit le profil de la température intérieure tout au long du séchoir, puis en considérant la différence entre les températures intérieures et extérieures, mesurées par balayeur, l'épaisseur du revêtement formé est estimée sur le plan local. La prédiction du modèle est examinée par trois ensembles de données qui proviennent d'un séchoir pour cimenterie commercial moderne. Les résultats confirment que l'erreur absolue moyenne pour estimer l'épaisseur de revêtement pour les cas 1, 2 et 3 sont 3,26, 2,82 et 2,21 cm, respectivement.

A two-dimensional discrete lumped model for a trickle-bed vacuum gas oil hydrocracking reactor

“…The model equations are coded in the ACM, and they are solved by using the kinetic parameters of 1D model [24] as initial values. Because all paths contribute in the reaction network (Fig.…”

“…In this approach, It is obvious that during hydrocracking and hydrotreating reactions, hydrogen molecules are absorbed in the hydrocarbon structure, but sulfur and nitrogen are removed. As shown in the previous work, this assumption can only impose 1% error in the mass balance which is ignorable [24]. To model this reactor, which works in the trickle-bed regime, it is assumed that the variations around the central axis are negligible.…”

“…In this research, the same data for developing a 1D combinedbed kinetic model is used [24]. The device, catalyst, feed and operating conditions were described completely in the previous work [25].…”

Energy consumption assessment in a cement production plant

“…After proper leveling of the kilns, the rotational speed increased to 1.8 rpm. Although in a direct fired kiln of large diameter the convection heat transfer from hot gas to solid bed provides less than one quarter of the total heat received by the solid charge, but according to previous studies, increasing the kiln rotational speed increases the convection heat transfer coefficient, slightly [13][14][15]. The amount of heat transfers from the gas to solid (Q gs ) can be calculated from Eq.…”

“…In which h gs is the convection heat transfer coefficient from the hot gas to solid which is about 30 W/m 2°C [15], A s is the solid charge surface, and (T g À T ss ) is the difference between the hot gas and solid charge surface temperature which is about 200°C along the kiln [14]. The h gs increases about 25% while the rotational speed increases from 1.1 to 1.8 rpm [15].…”