A U-SHAPED FIBER OPTIC PROBE TO STUDY THREE-PHASE FLUIDIZED BEDS

A novel U-shaped fiber optic recently developed for three-phase fluidized beds was applied in the present study for bubble characterization in a cylindrical bed. The static pressure profile along the fluidized bed was measured by a data acquisition system constituted by a pressure transducer, a scani-valve and a microprocessor. Air, water and 335µm glass beads were used as gas, liquid and solid phases respectively. Liquid was evenly distributed by a perforated plate and air was introduced above the distributing plate through four injectors. Single core silica fibers were used to guide the helium-neon laser beams into the fluidized bed. Five U-probes, whose design is based on the difference of refraction indices between the gas and the liquid phases, were used for bubble detection. The detecting probes were located on a measuring window at 53.3 cm from the grid. The design of the measuring window allowed the U-probes to be slid into the fluidized bed at different radial positions. Bubble characteristics such as axial bubble length and bubble velocity were investigated. The influence of fluidization conditions on the hold-ups of gas, solid and liquid was also studied.