Investigation on nozzle zone agglomeration during spray drying using response surface methodology
During spray drying, dry powder is circulated into the nozzle zone to force collisions, inducing agglomeration. This study systematically determined the effect of fine powder mass flowrate (varying from 7.1 ± 1.2–15.9 ± 0.5 kg∙h−1), drying air temperature (160–200 °C), and drying air mass flowrate (472.8 ± 6.2–590.8 ± 9.9 kg∙h−1) on agglomerate size and morphology using a central-composite trial design.
Agglomeration increases with a higher collision frequency in the nozzle zone
The dosing rate of fine powder impacted agglomeration the most
Higher drying rates reduced nozzle zone agglomeration
The onset of nozzle zone agglomeration can best be studied using image analysis
Agglomeration was quantified using an agglomeration index based on laser diffraction and by quantifying particle morphology using static image analysis. Response surface models were used to quantify factor effects. Increasing the fines mass flowrate had the largest positive effect on particle size enlargement and development of grape-like agglomerates. Increasing drying air temperature had a small negative effect on particle size enlargement and no significant effect on morphology. Increasing drying air mass flowrate had a small negative effect on particle size enlargement, but a positive effect on morphology. Finally, image analysis was found to be the preferred method to quantify the onset of agglomeration.
Maltodextrin DE 21 (MD21) was used as model system (Glucidex 21, Roquette Frères, France). The colorant ponceau red E124 was obtained from Natural Spices (the Netherlands). Regular tap water was used to prepared the feed.
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Anneloes P. van Boven, Santiago M. Calderon Novoa, Reinhard Kohlus, Maarten A.I. Schutyser, Investigation on nozzle zone agglomeration during spray drying using response surface methodology, Powder Technology, 2023, 118910, ISSN 0032-5910,