Bed expansion and disengagement in corrugated-wall bubbling fluidized beds

Corrugated walls were installed in narrow gas–solid bubbling fluidized bed (CWBFB) enclosures to reduce bubble sizes, improve gas distribution and offer stable operation. Thorough analyses of bed expansion in flat- (FWBFB) and corrugated-wall bubbling fluidized beds were performed for a variety of wall declinations and operating conditions covering a range of corrugation angles, inter-wall clearances (C), initial rest bed heights (Hi) and ratios of gas superficial velocity to minimum bubbling velocity, Ug/Umb. Bed expansion was discriminated in terms of expansion bed height ratio (Hf/Hi) and transport disengagement height (TDH). A digital image analysis technique was employed to compare the behaviors of time-averaged Hf/Hi and TDH in FWBFB and CWBFB. For a given Ug/Umb, the former was barely affected by wall patterning whereas the latter underwent appreciable reduction in CWBFB compared to FWBFB. Regardless of wall shape, both Hf/Hi and TDH increased with increasing Ug/Umb and C and with decreasing Hi. Full 3-D transient Euler–Euler CFD simulations with kinetic theory of granular flow employed to simulate the solids volume fraction and granular temperature in FWBFB and CWBFB reached qualitative agreements with experimental findings.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (469 K)Download as PowerPoint slideHighlights► New concept of slim corrugated wall bubbling fluidized bed is proposed. ► Bed expansion ratio (ER) and transport disengagement height (TDH) analyzed. ► Corrugated beds slightly lowered ER than flat wall beds. ► TDH decreases in corrugated beds as compared to flat wall beds. ► CFD simulations in good agreement with visualization studies.