Effect of lifter shape and operating parameters on the flow of materials in a pilot rotary kiln: Part II. Experimental hold-up and mean residence time modeling

Abstract

International audienceExperiments were carried out on a pilot scale rotary kiln equipped with lifters at room temperature to investigate the effects of the kiln slope, rotational speed, mass flow rate of materials, and exit dam height on the hold-up and the mean residence time (MRT). The MRT was determined from the residence time distribution measurements as detailed in Part I of this work. Two granular solids having different properties were used: sand and broken rice. Furthermore, two shapes of lifters were compared to determine the influence of lifter geometry: straight lifters (SL) and rectangular lifters (RL). A new model to predict the MRT was established by means of a dimensional analysis. The correlation not only gave good agreement with the experimental data from the present study, but also demonstrated good predictive performances when applied to published experimental data of other kilns; the model is applicable for inclined kilns that process materials in cascading (tumbling) motion, whether or not equipped with lifters or fitted with dams at the outlet end

Effect of lifter shape and operating parameters on the flow of materials in a pilot rotary kiln: Part III. Up-scaling considerations and segregation analysis

“…A comparison with the rotary kiln used in [1,2] shows that the two pilot-scale rotary kilns share a very similar length-to-diameter ratio. However, looking at their dimension ratio, there is a factor about two.…”

“…The focus of this study, initiated in [1,2], is the characterization of solids transport within flighted rotary kilns. If there have been several studies in that field up-to-date, most of these studies have generally focused on the bare kiln [3][4][5][6] to model through empirical or mechanistic correlations some of the main solids transport variables such as the hold-up, mean residence time or the bed depth profile.…”

Effect of lifter shape and operating parameters on the flow of materials in a pilot rotary kiln: Part I. Experimental RTD and axial dispersion study

“…These two methods are considered in the coming section to evaluate the Peclet numbers and resulting axial dispersion coecients for varying experimental conditions. 9 (2) the mean residence time of the distribution which is discussed elsewhere separately [47], (3) the variance of residence time, (4) the validity of the axial dispersion model, (5) the Peclet number and axial dispersion coecient.…”

Wall-to-solid heat transfer coefficient in flighted rotary kilns: Experimental determination and modeling

“…The influence of the operating parameters, namely the mass flow rate, the exit dam height and the lifter hold-up capacity on the w-t-s heat transfer coefficient were analyzed with the use of the filling degree, as the filling degree has been found to increase with these operating parameters [49,50,51]. Figure 10 shows the variation of the w-t-s heat transfer coefficient with the filling degree following a variation of the mass flow rate, the exit dam height and the lifter hold-up capacity.…”