Fluidization in small-scale gas-solid 3D-printed fluidized beds

Abstract

Additive manufacturing could be used to facilitate the rapid fabrication and testing of small-scale fluidized beds for use in screening applications, such as adsorbent screening for carbon capture. In this work, experiments were performed in order to map the different flow regimes produced in small-scale (Dh = 3–15 mm) gas-solid fluidized beds that were fabricated using additive manufacturing using the stereolithography approach. Here, the effects of bed hydraulic diameter (Dh), static particle height (Hs), and particle type/size (Dp and ρp) were considered. Pressure drop data and high speed camera images were used to develop simple flow regime maps for these printed beds showing the operating windows for packed bed, bubbling, slugging and turbulence applicable to a wide range of bed size to particle diameter ratios (Dh/Dp = 20–200) and gas velocities (Ug = 1–400 mm/s) in both ‘2D’ and ‘3D’ bed aspect ratios. Fast Fourier transforms of the pressure drop signals were also used to study the evolution of bubbling/slugging behaviour as the gas velocity was increased by creating 2D colour maps of the frequency spectra. These allowed a new quantitative method to be proposed for the identification of slugging – the point where the dominant frequency in the power spectrum becomes constant as the gas velocity increases. It is concluded in this study that the rougher surfaces generated by additive manufacturing do not influence the fluidization characteristics nor modify the wall effects of small-scale beds. Macro-scale fluidization could also be achieved at smaller Dh/Dp ratios in these 3D printed beds compared to more conventional Plexiglas beds (Dh/Dp = 75 compared to Dh/Dp = 300).