International E-publication: Publish Projects, Dissertation, Theses, Books, Souvenir, Conference Proceeding with ISBN.  International E-Bulletin: Information/News regarding: Academics and Research

Drying Characteristics of Ragi using Circulating Fluidised Bed

Author Affiliations

  • 1Dept. of Chemical Engineering, Kongu Polytechnic College, Perundurai 638 052, Tamilnadu, INDIA
  • 2Dept. of Chemical Engineering, Kongu Engineering College, Perundurai 638 052, Tamilnadu, INDIA

Res.J.chem.sci., Volume 3, Issue (1), Pages 67-71, January,18 (2013)


A Circulating Fluidized Bed is a type of gas-solid reactor consisting of a riser in which a gas-solid suspension is transported vertically upwards and separated at the top by gas-solid separators. After separation, the suspension is recycled to the bottom via a stand pipe or down comer. The behavior of CFB differs from a conventional fluidized bed, because of absence of bubbles and entrained flow of solids. A CFB operates at much higher gas velocities than those used in conventional fluidized bed and lower than those used in pneumatic conveying. Circulating fluidized bed is finding increased industrial applications in recent years. One such application is extension of a CFB for granular materials drying. It is essentially a process of simultaneous heat and mass transfer and a very common process in many of the chemical process industries. In this article an attempt was made to study the hydrodynamic properties of ragi in Circulating Fluidized Bed. Experiments were conducted in a column of 0.05m internal diameter and 1.6m long covering a wide range of operating conditions. The transport velocity was estimated by emptying time technique, the effect of pressure drop with axial co-ordinate for different gas mass flux and solids circulation rate, the effect of voidage and the effect of solid circulation rate with pressure gradient. In the present work an attempt has been made to dry in the riser of the circulating fluidized bed covering a wide range of operating parameters. The effects of various operating parameters such as initial moisture content on exposure time, moisture content with drying rate and relative moisture content with exposure time with varying temperature of heating medium. The results obtained are quite satisfactory with literatures.


  1. Og Sin KIM, Dong Hyun LEE and Sang Done KIM,Drying characteristics of fine powders in an inert mediumcirculating fluidized bed, J. of Chem. Engg., 41(7), 705-709(2008)
  2. Qi Miao, Chu Wang, Chuangzhi Wu, Xiuli Yin and JesseZhu, Fluidization of saw dust in a cold model circulatingfluidized bed: Experimental study, Chem. Engg. J., 167,335-341 (2011)
  3. Balasubramanian N., Srinavasakannan C. and AhmedBasha C., Transition velocities in the riser of a circulatingfluidized bed, Adv. Pow. Tech., 16(3), 247-260 (2005)
  4. Balasubramanian N. and Srinavasakannan C., Drying ofgranular materials in circulating fluidized beds, Adv. Pow.Tech., 18(2), 135-142 (2007)
  5. Xiaobo Qi, Jesse Zhu and Weixing Huang, Hydrodynamicsimilarity in circulating fluidized bed risers, Chem. Engg.Sci., 63, 5613-5625 (2008)
  6. Van der Ham A.G.J., Prins W. and Van Swaaij W.P.M., Asmall scale regularly packed circulating fluidized bed PartI: Hydrodynamics, Pow. Tech., 79, 17-28 (1994)
  7. Balasubramanian N. and Srinivasakannan C., Slip velocitycharacteristics in the riser of circulating fluidized bed,Chem. Engg. Tech., 20, 1-4 (1997)
  8. Won Namkung, Sung Won Kim and Sang Done Kim, Flowregimes and axial profiles in a circulating fluidized bed,Chem. Engg. J., 72, 245-252 (1999)
  9. Balasubramanian N. and Srinavasakannan C.,Hydrodynamic aspects of a circulating fluidized bed withinternals, Ind. Engg. Chem. Res., 37, 2548-2552 (1998)
  10. Balasubramanian N., Srinavasakannan C. and AhmedBasha C., Drying kinetics in the riser of circulatingfluidized bed with internals, Dry. Tech., 25, 1-5 (2007)
  11. Arena U., Marzochella A., Massimilla L. and MalamdrinoA., Hydrodynamics of circulating fluidized beds with risersof different shape and size, Pow. Tech., 70, 237-247 (1992)