Measurement of the residence time distribution of a cohesive powder in a flighted rotary kiln

Ingrid J. Paredes, Bereket Yohannes, Heather Emady, Fernando J. Muzzio, Al Maglio, William G. Borghard, Benjamin J. Glasser, Alberto M. Cuitiño

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


The rotary kiln is an essential device in chemical and metallurgical industries, with applications in a wide range of solids manufacturing processes. In particular, in the preparation of industrial chemical catalysts, the kiln has become a popular reactor for continuous calcination of catalysts ranging from millimeter-sized extrudates to micron-sized powders. As granular and powder flow behaviors are difficult to characterize, the design and scale-up of rotary calcination processes are often performed empirically. The goal of this research is to improve the fundamental understanding of powder flow in rotary kilns to aid in optimization of the continuous calcination process. For successful calcination to occur, the residence time of the particles must exceed the time required for heating and subsequent treatment. For uniform treatment of the feed, the particles must also exhibit low axial dispersion. In this work, the mean residence time and axial dispersion coefficient for a cohesive fluid catalytic cracking powder were determined in a pilot plant kiln by measuring the residence time distribution. This study utilized a pulse test developed by Danckwerts. Results were fit to the Taylor solution of the axial dispersion model and compared to the Sullivan prediction for mean residence time. It was found that the mean residence time decreases as the feed rate, kiln incline, and rotation rate increase. It was also found that the axial dispersion coefficient increases with speed of rotation and angle of incline. However, the axial dispersion coefficient decreases as the feed rate is increased.

Original languageEnglish (US)
Pages (from-to)56-66
Number of pages11
JournalChemical Engineering Science
StatePublished - Dec 14 2018


  • Axial dispersion coefficient
  • Calcination
  • Particle technology
  • Powder flow
  • Rotary kilns

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Industrial and Manufacturing Engineering


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