A new rapid on-line imaging method to determine particle size distribution of granules

Abstract

The purpose of this research was to study the feasibility of the new image analysis method in the particle size determination of the granules. The method is capable of forming a three-dimensional topographic image of a sample surface from a digital picture. In the method, a flat granule bed surface was illuminated from three different directions, using the three primary colors (red, green, and blue). One color picture was taken by a digital camera, after which a topographic image of the object surface was constructed. The particle size distribution was then calculated from the image data. The particle size analysis method was tested both off-line and on-line. Off-line particle size measurement results determined by the image analysis method corresponded quite well to those of sieve analysis in the size fraction range 250-1,000 microm. In on-line application, images were successfully retrieved and median granule size trend could be calculated and followed during fluid bed granulations.

Fig. 1

Measuring principle of SAY-3D

Fig. 2

Topographic view of granule bed a surface from above b–d projections of the surface from various angles

Fig. 3

Granule size determination from topographic data

Fig. 4

Imaging installation attached to a fluid bed chamber

Fig. 5

On-line sampler in the granulation chamber

Fig. 6

Comparison of off-line SAY-3D particle size results with sieve analysis (batch I). The dotted lines show the upper and lower limits for various sieve fractions

Fig. 7

Raw images of granules taken on-line from the fluid bed process. The image sizes are 20 × 15 mm (bar 1 mm)

Fig. 8

Example of slow and continuous granule growth (batch II). The squares represent individual on-line determinations and the continuous curve is a moving average of ten consecutive determinations

Fig. 9

Development of granule size during granulation and drying (batch III). The squares represent individual on-line determinations and the continuous curve is a moving average of ten consecutive determinations

Fig. 10

Preventing granule growth by granulation liquid feed pulsing (batch IV). The squares represent individual determinations and the continuous curve is a moving average of ten consecutive determinations