EVALUATION OF THE JET PENETRATION DEPTH IN GAS-FLUIDIZED BEDS BY PRESSURE SIGNAL ANALYSIS

The interaction between a single jet and a bed of fluidized solids was investigated with the aim of evaluating a characteristic height of th e jetting region corresponding to the distance from the nozzle at whic h the dispersion of jet momentum is practically complete. A new experi mental technique, based on simultaneous measurements of the static pre ssure at the bed side wall and on the jet axis and on their elaboratio n, was used. Various experimental configurations, based on the combina tion of two fluidization columns (0.35 and 0.20 m, i.d.) and four jet nozzles (6, 10, 19 and 25 mm, i.d.), were employed. Glass ballotini of 800-1200 mu m were used as bed material. The influence of the nozzle gas velocity, of the fluidization velocity, and of the nozzle and the column sizes on the characteristic height of the jet was investigated. This height increases as nozzle gas velocity and nozzle size increase . In contrast, the influence of the fluidization velocity appears more complex and, in particular, cannot be separated from that of the nozz le diameter. The effect of the column diameter was negligible. Experim ental results were compared with predictions of jet penetration length from literature correlations since the characteristic height shows up evident similarities with the jet penetration length based on momentu m dissipation. (C) 1997 Elsevier Science Ltd.