Modeling of product variability in fluidized bed coating equipment.

摘要

Particle coating in fluidized bed equipment is common practice for improving the properties of solid products, particularly in the pharmaceutical, food and agricultural industries. In this thesis, the application of particle coating to pharmaceutical products utilizing the Wurster-column coating process is addressed. This technique is extensively used in the pharmaceutical industry for precision drug coating and modified release coating of tablets and pellets.;The simulation of particle movement in fluidized beds has been successfully developed using Monte Carlo simulation. Raw velocity and voidage data for each region of a semicircular fluidized bed, obtained by Subramanian (2001), are used in the simulation. The average velocities in the x- and y-directions, the average voidage, and the standard deviations of the velocities in each region were calculated and used as input data for the model. Random numbers generated from a unit normal distribution were used to determine the starting position of the particle as well as the movement of the particles within the bed. The simulation results show that the pattern of particle movement is similar to the velocity profile of the original data and voidage profile agrees with the original data.;A simple experiment in an empty (without particles) fluidizing bed shows that the spray material moves vertically through the draft tube and out of the top of the bed. In addition, the spray material was found to vary radially from the spray nozzle and form a non-symmetric spray distribution. The simulation results, which are verified with pulse test experiments, show that the spray distribution and the spray shape at the bottom of the bed varied with different bed conditions, particularly with and without the presence of a particle deflector. Comparison of simulated results with pulse test experiments showed that the distribution of spray material and shape of the spray play important roles in the prediction of the mass coating distributions per-tablet-per-pass through the spray zone.