Assessment of the energy dissipation parameters inside the draft tube of a liquid spout-fluid bed


Erbil A., Turan M.

ENVIRONMENTAL SCIENCE & TECHNOLOGY, cilt.39, ss.2898-2905, 2005 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 39 Konu: 8
  • Basım Tarihi: 2005
  • Doi Numarası: 10.1021/es049216h
  • Dergi Adı: ENVIRONMENTAL SCIENCE & TECHNOLOGY
  • Sayfa Sayıları: ss.2898-2905

Özet

Spouted beds are fluid-particle contactors in which the fluid is introduced centrally through a nozzle instead of a distributor plate, resulting in a regular particle circulation pattern. To assess the suitability of such sytems to environmental engineering applications such as filter backwashing and biofilm systems, a priori knowledge of the energy dissipation parameters is essential. A new model is developed for evaluating the energy dissipation parameters inside the draft tube of spout-fluid beds. The shear stress, velocity gradient, and turbulence fluctuation parameters in the draft tube of a liquid spout-fluid bed are calculated with the help of an energy equation for flows carrying suspensions and the experimentally determined pressure losses inside the draft tube and compared with results for particulately fluidized beds. A spout-fluid bed with a draft tube provides higher shear stress inside the draft tube than a fluidized bed. The mean velocity gradient in the draft tube is comparable to and higher than in a fluidized bed and increases with solids fraction. The turbulence dissipation coefficient decreases very slightly with increasing solids fraction for both systems. Consequently, according to the model calculations, a spout-fluid bed with a draft tube can be an alternative to the classical fluidized bed filter backwashing system.