The Gas-to-Particle Heat Transfer and Hydrodynamics in Spouted Bed Drying of Sawdust

Abstract This article presents experimental results for spouted bed drying of sawdust, carried out in a full-scale as well as in a laboratory-scale dryer using air as well as steam as drying media. The aim is to present design parameters for a spouted-bed sawdust dryer that can be used by the industry in designing full-scale dryers. A hydrodynamically stable spouted jet spouted bed was obtained. The heat transfer characteristics of the bed were represented in terms of a volumetric heat transfer coefficient (VHC). When sawdust is dried in a spouted bed, the mean VHC is increasing up to fiber saturation level (20–25% wb) from 40 to 110 W/m3 K. The VHC decreases with the residence time and with an increased static bed height. Gas temperature profiles are also presented for the bottom part of the drying chamber.

[1]  Roland Wimmerstedt,et al.  Recent advances in biofuel drying , 1999 .

[2]  A. Mujumdar,et al.  Drying of a Dilute Suspension in a Revolving Flow Fluidized Bed of Inert Particles , 2004 .

[3]  Jonas Berghel,et al.  USEFULNESS AND SIGNIFICANCE OF ENERGY AND MASS BALANCES OF A FLUIDIZED SUPERHEATED STEAM DRYER , 2001 .

[4]  A. S. Jensen.  Pressurized steam drying of sludge, bark and wood chips : Process offers full energy recovery and avoids air pollution , 1996 .

[5]  Arun S. Mujumdar,et al.  Fluidized bed drying , 2006 .

[6]  José Teixeira Freire,et al.  GAS-TO-PARTICLE HEAT TRANSFER IN THE DRAFT TUBE OF A SPOUTED BED , 2001 .

[7]  Jonas Berghel,et al.  Usefulness and significance of energy and mass balances of a superheated steam dryer , 2001 .

[8]  Arne Sloth Jensen.  Industrial Experience in Pressurized Steam Drying of Beet Pulp, Sewage Sludge and Wood Chips. , 1995 .

[9]  Anders Rasmuson,et al.  Some aspects of the modelling of wood chips drying in superheated steam , 1997 .

[10]  Jonas Berghel,et al.  DRYING OF SAWDUST IN AN ATMOSPHERIC PRESSURE SPOUTED BED STEAM DRYER , 2002 .

[11]  A. Mujumdar,et al.  GAS-TO-PARTICLE HEAT TRANSFER IN TWO-DIMENSIONAL SPOUTED BEDS , 1989 .

[12]  A. Mujumdar,et al.  Advanced drying technologies , 2001 .

[13]  John R. Grace,et al.  Spouting of Particulate Solids , 1997 .

[14]  J. T. Freire,et al.  HEAT TRANSFER IN SPOUTED BEDS , 1993 .

[15]  Jonas Berghel,et al.  Basic design criteria and corresponding results performance of a pilot-scale fluidized superheated atmospheric condition steam dryer , 2002 .

[16]  Javier Bilbao,et al.  Hydrodynamics of sawdust and mixtures of wood residues in conical spouted beds , 1994 .

[17]  Jonas Berghel,et al.  Controllability of Product Moisture Content When Nonscreened Sawdust Is Dried in a Spouted Bed , 2004 .

[18]  A. Kmieć.  Simultaneous heat and mass transfer in spouted beds , 1975 .

[19]  V. Vanec̆ĕk,et al.  Fluidized bed drying , 1966 .

[20]  Rogelio Moreno,et al.  SAWDUST FLUID-BED DRYING WITH HEATING TUBES , 1998 .

[21]  A. Rasmuson,et al.  The influence of the drying medium on high temperature convective drying of single wood chips , 1997 .