Análise de um processo de recobrimento de comprimidos em um sistema vibro-jorrado bidimensional

Abstract

An experimental set up for the study of tablets coating in a two-dimensional spouted bed that uses vibration of the perforated base to enhance the circulation of the particles was developed. An acrylic rectangular upper section (4x32 cm) with fixed 4x4 cm draft plates was adjusted over 3 different convergent sections (inclination 50') with 4x4 cm, 4x6 cm or 4x8 cm bases and contained 800g, 1100g or 1300g of tablets, Air (0,8 to 1,6 m3/min) forced by a 7,5 cv blower, was cooled down to 55°C and spouted this bed. The lenticular tablets (0,12g; 0,25g., 0,44g) were coated with a polymeric aqueous solution (11% solids). A two-fluid atomizer (air pressure 82,7 1kPa) was used, inserted laterally, near the bed base, and showed no influence on the movement of the particles. The experimental characterization of the tablets circulation rates was emphasized, using a magnet (0,4062 g) that followed the particles, activating a bobbin located at the upper end of the draft plates. The electric pulses were processed by a data acquisition sistem and the cicle time distribution curves were adjusted by the Modified Spline fit technique. The mean of the cicle time distribution creased with are increase of the bed load and the size of the tablets in all comparative tests. The vibration (10 Hz, 8 mm amplitude) reduced the mean of the cicle time distribution by more than 10%, and also decreased its variance. The vibration also affected the maximum pressure drop (40% reduction) and the minimum spouting velocity. The vibro spouted bed showed higher- adhesion efficency (73 to 88%) than the non-vibrated spouted bed (66 to 79%) in all equivalent situations and the complete coating of the smaller tablets demanded less processing time due to higher surface area circulation rate.