Residence time distribution and material flow studies in a rotary kiln

Axial dispersion of solid particles in a continuous rotary kiln

“…Large segregation of rolling distances, represented by low values of the parameter a defined by Eq. 11, decreases significantly the Pe numbers (10' -lo3) that is, increases the axial dispersion to a level consistent with that observed experimentally (Groen et al, 1986;Sai et al, 1990). Increasing the solids fill level increases the axial dispersion.…”

“…The Pe numbers predicted by the model are of the order of magnitude of (lo4) and slightly decrease (by less than one order of magnitude) as the Froude number increases from 7X lop6 to 7 X lop3. These values exceed the experimental finding of Peclet numbers of the order of lo3 obtained by Groen et al (1986) and Sai et al (1990).…”

“…Experimental studies of the average residence time in rotating drums (Sullivan et al, 1927;Bayard, 1945;Varentsov and Yufa, 1961;Zablotny, 1965;Chatterjee et al, 1983a,b;Perron and Bui, 1990) yield empirical correlations, valid only for specific materials and operating conditions. Room temperature measurements of the residence time distribution (RTD) in rotating drums were done by tracer techniques, such as counting and weighing of dyed particles (Rutgers, 1965b;Abouzeid et al, 1974;Karra and Fuerstenau, 1977;Sai et al, 1990), or using atomic absorption spectroscopy to measure tracer concentration (Wes et al, 1976;Arlyuk and Shakhov, 1982). High temperature RTD measurements were done using radioactive tracers (Costa and Peterman, 1959;Groen et al, 1986).…”

“…High temperature RTD measurements were done using radioactive tracers (Costa and Peterman, 1959;Groen et al, 1986). The measured range of the Pe numbers varies from 10-100 for short mixing drums (Abouzeid et al, 1974;Wes et al, 1976), to lo3 for calcination kilns (Groen et al, 1986;Sai et al, 1990). Figure 2 is a schematic of rotary kiln.…”

“…Previous models described the flow in the kiln by a network of ideal flow systems, the parameters of which are adjusted to fit the experimental RTD data. Fan and Ahn (19611, Rutgers (1965a), Abouzeid et al (1974), Wes and Drinkenburg (19761, Karra and Fuersenau (1977), Hehl et al (1978) and Sai et al (1990) proposed the use of an axial dispersion model with an appropriate Pe number determined by experiments. Rutgers (1965a), Groen et al (1986) and Sai et al (1990) used the n tanks-in-series model to fit experimental RTD curves.…”