2. Experiments and methodologies

2.1. Material characterization

In the current study, the standard cylindrical hardwood pellets and spherical LDPE particles, both belonging to the Geldart D type, have been used as the test material. The characterization has been conducted following the procedures established in Tucker et al .26. Briefly, the particle size and shape statistics of the spherical LDPE have been obtained using a SympaTEC - QICPIC® particle analyzer which is compliant with the ISO 13322-1/2 Standard. The principle of QICPIC® operation is based on the analysis of dynamic particle images obtained from backlighting a thin sheet of passing particle samples. Calculation of the minimum superficial gas velocity has been performed.
An in-house small-scale fluidization test has been performed to determine the minimum superficial gas velocity (U mf ) of the LDPE particles by determining the pressure drop over the bed as a function of the superficial gas velocity. The resulting U mf is used to non-dimensionalize the superficial gas velocity for all test cases in the study. All wood pellets have been cut into the same length with aspect ratio, AR = L /D = 2, where L andD correspond to the length and diameter of the cylindrical wood pellets, respectively. The size of the wood pellet is too large for standard QICPIC® analysis, thus standard imaging is applied to measure the particle dimensions, to ensure the monodisperse nature of the prepared wood pellets. All related material properties have been summarized in Table 1.
Table 1. Properties of the cylindrical and spherical particles.