A feasibility evaluation of the addition of fumed silica (SiO2) into an agitated dryer to aid spray-dried solid dispersion intermediate (SDSDi) flow during secondary drying and discharge is described. The quantity of SiO2 to enhance the flow character of SDSDi was assessed by measuring particle size distribution, bulk density, and flow-through-an-orifice. Results indicate that the addition of the SiO2 did not alter the drying kinetics and did not impact the bulk particle size distribution of the SDSDi. While bulk density of SDSDi increased with the addition of SiO2, the flow, and thus the recovery of the SDSDi-SiO2 batch from the secondary dryer, was significantly higher than that for the intermediate alone. Imaging indicated uniform distribution of SiO2 in the bulk powder and coating on intermediate particles. Premixing and co-sieving of the SiO2 with a portion of pre-dry SDSDi promotes the uniform distribution of SiO2 within the bulk powder bed.
Keywords: agitation dryer; powder flow; secondary drying; spray drying.