Mechanisms and mitigation of agglomeration during fluidized bed combustion of biomass: A review

Solids motion and holdup profiles in liquid fluidized beds

A new wavelet-threshold criterion was developed to distinguish the cluster and the void phases from the transient solids holdup/concentration fluctuation signals when measured in a 108 mm-i.d. × 5.75 m-high circulating fluidized bed with FCC particles (dp = 78 μm, ρp = 1,880 kg/m3). An appropriate level of approximation subsignal was systematically specified as a threshold for cluster identification, based on multiresolution analysis (MRA) of wavelet transformation. By the established threshold, the dynamic properties of clusters including the appearance time fraction of clusters Fcl, average cluster duration time τcl, cluster frequency fcl, and local average solids holdup in clusters esc, at different radial and axial positions were determined under the turbulent, transition and fast fluidization flow regimes. The results also describe the dynamic properties of clusters and flow patterns in the splash zone along with the dense bottom region of the circulating fluidized beds. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Multiresolution analysis on identification and dynamics of clusters in a circulating fluidized bed

Data interpretation techniques for inferring bubble size distribution from probe signals in fluidized systems

The proper design and control of an indirect coal liquefaction process plant require an accurate knowledge of bubble sizes and size distribution. Of particular importance regarding proper design is the understanding of the complicated dependence of bubble dynamics on bubble column geometry, and of the nature of the solid-liquid phases. The nature of the products and their relative proportions, on the other hand, are seriously influenced by the bubbling characteristics of the reactor because the mass transfer behavior and mixing are dependent on the bubble size and velocity distributions. This report reviews experimental techniques that have been employed to measure bubble sizes in multiphase reactors. The methods, which fall in three different categories, namely, the photographic method, the optical probe, and the electrical conductivity (resistivity) probe, are described in a historical sequence; and in each case, their unique features and design details are discussed. A general methodology of data analy...

Hitoshi Tanaka

Papers

An optical probe to detect both bubbles and suspended particles in a three-phase fluidized bed.