Two-dimensional particle shape analysis from chord measurements to increase accuracy of particle shape determination

• Chord measurements can be used for the two-dimensional particle shape analysis.
• We define three new non-dimension parameters of chord distributions.
• The new parameters are connected with aspect ratio of the particle shape.
• Two examples show the applicability for coating processes of particles.
• The advantage is the simultaneous determination of size and shape.

Some in-process two-dimensional particle sizing methods can provide on-line information about the chord length distribution of a population of particles. The objective of this study is to use the chord measurement not only for the size determination but also for the determination of the particle shape. Main results are the non-dimensional aspect ratio or the roundness of the particle. The elongation values can be calculated by three non-dimensional parameters which are derived from the mean, mode or maximal chord length of the number and area based chord distributions. The application of these shape parameters is limited to narrow particle size and shape distributions. The application is demonstrated for coating of elliptical seed particles and spherical pellets (Cellets®1000). An optical probe system (IPP 70, Parsum GmbH, Germany) was used for the measurement of chord lengths during the coating processes. Results of an image analysis were in a good correlation with the results of the chord measurements. The advantage is the simultaneous use of the measured chord lengths for the characterization of the particle size and also the particle shape without any need for additional measurement equipment. Another advantage is the in-line determination of the particle shape without taking a powder sample.

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