The first part of this study was dedicated to quantifying the variation of the level of IPFs by temperature in a gas-solid fluidized bed. To this end, the variation of minimum fluidization velocity (Umf) with temperature for 225-micron silica sand and 83-micron FCC particles, as well as 67-micron glass beads was studied. It was shown that the difference between the magnitude of IPFs at a given temperature and that at ambient conditions is proportional to the deviation of the experimental Umf from the prediction of an appropriate correlation. The correlation must be capable of adequately accounting for the effect of gas properties on Umf, while matching the experimental data at ambient conditions. The difference between the experimental and predicted Umf was then translated into the force that the fluidizing gas is required to exert on the particles to overcome thermally induced IPFs.
The second approach was established on the overshoot in the bed pressure drop profile at Umf due to the difference between the minimum fluidization voidage (Îµmf) and the loose bulk voidage (Îµ0). The Îµmf and Îµ0 were measured in beds of 83-micron FCC particles and 67-micron glass beads at temperatures ranging from ambient up to 600ËC. It was shown that the ratio of Îµmf/Îµ0, which was called the âdynamic Hausner ratioâ, increases as the level of IPFs grows. A model was, hence, proposed to quantify the magnitude of IPFs as a function of the dynamic Hausner ratio.
The magnitudes of IPFs quantified by the above approaches were in the same order as the particleâs weight for 67-micron glass beads and 83-micron FCC particles, which is analogous to the findings reported in the literature for similar powders. In addition, the results of both approaches were in accordance with the temperature variation of the normalized peak area, i.e., the area under the overshoot between the pressure drop profiles in the increasing and decreasing velocity passes at a given temperature divided by that at ambient conditions, as a qualitative indication of the magnitude of IPFs.