EVALUATION OF SPRAY CHARACTERISTICS IN PHARMACEUTICAL TABLET COATING PROCESSES: THE INFLUENCES OF DRUM ROTATIONAL SPEED AND DRYING AIR FLOW RATE

摘要

In this study, drop size, velocity, and volume flux for sprays produced by a pharmaceutical nozzle (Spraying Systems 1/4-JAU-SUE15A-PA67288-45o-SS) were characterized using a Fiber-PDA system (Dantec). Spraying was performed in a 120 cm (24 in) diameter tablet pan-coater (Accela-Cota Model 10, Thomas Engineering, UK). The separate influences of drum rotational speed and drying air flow rate were studied by making measurements at four different pan-coater operating conditions: stationary drum with drying air turned on/off, and 8 rpm rotating drum with drying air turned on/off. For each case, four different spraying conditions (liquid supply rate and atomizing air pressure) were used. PDA scans were performed along the spray semi-major and semi-minor axes at two different axial distances (7.5 and 10 cm) from the atomizer tip. Results were as follows. When both the drying air and drum rotation were absent, increasing liquid supply rate while operating the atomizer at the lower of two atomizing air pressures decreased drop size. The opposite occurred when operating at the higher of the two atomizing air pressures. This suggests that the nozzle operated as a simplex pressure-swirl atomizer at lower levels of atomizing air pressure, but as an airassist atomizer at higher levels of atomizing air pressure. Regardless, liquid supply rate had no significant effect on drop velocity. In contrast, a decrease in atomizing air pressure or an increase in axial distance always led to an increase in drop size and a decrease in drop velocity.