Investigation of the shifting-parameter as a function of density in the fluidization of a packed bed
Original version
Rautenbach, C., Melaaen, M.C & Halvorsen, B.M. Investigation of the shifting-parameter as a function of density in the fluidization of a packed bed. Paper presented at the the 7th International Conference on Multiphase Flow (ICMF) in Tampa, Florida in May/June 2010.Abstract
Accurate predictions of pressure drops in fluidized beds are of great importance in the industry. Up to date no satisfactory correlation exists to predict the pressure drop in a fluidized bed as the bed is traversing from one regime to another. In the present study experiments have been performed in an experimental fluidized bed reactor. The experimental tower has been equipped with a set of nine pressure sensors located at different positions along the height of the tower. The tower has a diameter of 7.2 cm and a height of 1.5 m. A procedure providing a correlation for data in the transition region between asymptotic solutions or limiting correlations have been described by Churchill & Usagi (1947). This correlation can generally be expressed as ys{x} = ys o{x} + ys1{x}, where yo{x} and y1{x} represents the asymptotic solutions for large and small values of the independent variable x and s is the shifting parameter. Changing the value of s shifts the correlation given by y{x} closer to or away from the asymptotic solutions. This procedure has been proven to give good correlations in a wide range of applications. A series of different powders have been used to investigate the influence of a particular parameters on the shifting parameter, s. Up to date no expression has been stated for this shifting parameter to govern the transition from fixed to fluidized bed. Two powders have been used in the present study and they are Zirconium Oxide (ZrO) and spherical glass particles. The powders have the same size distributions but very different densities. The effect of different densities on the shifting parameter was investigated. Several different drag models were used to serve as a control for investigating the shifting parameter. The results are given in the form of pressure drop data versus superficial velocity data. Experimental data are presented with the drag model correlations and the investigated values of the shifting parameter, s. Some of the drag models that were used were the Syamlal O’ Brien drag model (Syamlal, Rogers & O’Brien (1993)) and the extended Hill-Koch-Ladd drag correlation (Benyahia, Syamlal & O’Brien (2006)). The results are evaluated and discussed.