Verification of Scaling Laws for Spouting Beds

The internal friction angle is also important for slugging beds (Zenz and Othmer, 1960). DiFelice et al. (1992 a, b) did not report their values it could be that the disagreement they found in their slugging bed tests was due to mismatches of the internal friction angle. 

Glicksman and Farrell (1995) constructed a scale model of the Tidd 70 MWe pressurized fluidized bed combustor. The scale model was fluidized with air at atmospheric pressure and temperature. They used the simplified set of scaling relationships to construct a one-quarter length scale model of a section of the Tidd combustor shown in Fig. 34. Based on the results of Glicksman and McAndrews (1985), the bubble characteristics within a bank of horizontal tubes should be independent of wall effects at locations at least three to five bubble diameters away from the wall. Low density polyurethane beads were used to obtain a close fit with the solid-to-gas density ratio for the combustor as well as the particle sphericity and particle size distribution (Table 6). 

Differential pressure measurements were made between several vertical elevations within the bed. The probability density function of the cold model and combustor gave very close agreement (Fig. 35). The solid fraction profiles were obtained from the vertical pressure profile with a hydrostatic assumption. The cold model solid fraction profile showed very close agreement with data taken from pressure taps in two different locations within the combustor (Fig. 36). The solid fraction shows a 

Figu re 34. Tidd boiler enclosure with scaled section designated. (From Glicksman and Farrell, 1995.) 

A substantial number of experimental demonstrations of the validity of scaling has increased awareness of the concept and confidence in its application. Although applications to commercial designs have been undertaken, unfortunately only a modest number have been documented in the open literature. 

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