Understanding and preventing agglomeration in a filter drying process

The occurrence of severe agglomeration during a filter drying process is a challenging issue in the pharmaceutical industry and has yet to be fully understood. Product degradation, extended drying times, additional equipment required for the elimination of lumps and downstream processing issues are some of the problems caused by this phenomenon and there is great interest among researchers from various industries to explore how the filtration/drying processing step impacts the agglomeration of powder. This paper investigates the effect of operating condition such as the drying temperature, agitation speed, fill volume and blow-down period on the formation of large agglomerates. In addition, other potential sources of agglomeration such as the dripping of condensates as well as surface tension of wash solvents were also explored. A series of systematic experimental work was carried out using sodium bicarbonate, calcium carbonate and an API intermediate which has high agglomeration tendency to understand behaviour of agglomeration among the different types of powder. It was found that similar trends may be observed in the formation of lumps for different types of powders but the underlying mechanisms of agglomeration were different. The unique behaviour of each powder suggested that a universal solution or mitigation method to eliminate the formation of agglomerate may not be possible. However, by identifying the specific agglomeration mechanisms present in a powder-solvent system, it is possible to carry out the mitigation in a more effective way to minimize the agglomeration.