Quantitative Analysis of Powder-Binder Agglomeration

Publication Reference: 
Author Last Name: 
Jim Litster
Report Type: 
FRR - Final Report
Research Area: 
Particle Formation
Publication Year: 
Publication Month: 

Executive Summary

This report summarises the work done over six years in IFPRI project 37 Quantitative Analysis of Powder-Binder Agglomeration. This is a large body of work undertaken by ten researchers and IFPRI funds were substantially leveraged with funds from other sources. The main focus of the report is the analysis, in turn, of each of the three classes of granulation rate processes that dictate the product granule attributes:

1. Wetting, binder dispersion and nucleation

2. Consolidation and growth

3. Wet granule breakage

We now know the key formulation properties and process parameters that control the rate processes of (1) nucleation and wetting, and (2) consolidation and growth. For both these rate processes, regime maps have been developed and validated based on the controlling dimensionless groups: a and tp for wetting and nucleation, Stv, Stdef, and s for growth and consolidation. This quantitative understanding of granulation rate processes is now at the point where it can be directly used in scaling granulation processes (eg. keeping dimensionless spray flux constant to maintain nucleation conditions) and characterising formulations for the their granulation behaviour (eg measuring the dynamic yield stress of a new formulation).

The report gives details of the development of characterisation tools, models and regime maps used to quantify the rate processes and experimental verification of models and regime maps. The impact of both process parameters and formulation properties on the granulation rate processes is studied in detail.

We are applying the same approach to quantify wet granule breakage, although this work will not be complete to till the end of 2004. We report an approach to characterize the mode of failure of the granule matrix (brittle crack propagation or plastic deformation) for different formulations using an Instron Dynamite testing rig and detail the design and methodology for studying wet granule breakage in a breakage only granulator (BOG).

The report also gives summaries of related research in two areas, not directly funded by IFPRI, but very relevant to our multiscale approach to granulation modeling:

• Using positron emission particle tracking (PEPT) to characterize powder flow fields in granulators and using this information in conjunction with rate process models to predict granulator performance; and

• Design and modeling of regime separated granulators for significant improvement in the control of granule attributes. Finally, a discussion of research and development gaps and opportunities in the field of granulation is presented.