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Abstract
Spray drying is widely used to produce shelf-stable powders like food ingredients, valued for functional properties such as flowability, reconstitution behavior, bulk density, and mechanical stability. These properties arise from particle agglomeration. However, the process has a significant environmental impact due to high energy consumption and dust emissions. This thesis aims to develop knowledge-based guidelines for controlling particle structure formation, focusing on primary particle morphology and agglomeration.A literature review in Chapter 2 explored mechanisms influencing particle structure at various experimental scales. Single droplet drying (SDD) effectively studies primary particle morphology, while pilot-scale experiments capture nozzle-zone agglomeration dynamics. Computational fluid dynamics (CFD) modeling integrates findings across scales, despite computational limitations.Chapter 3 investigated how material properties and spray drying conditions affect particle morphology and functional properties. Using maltodextrins with different dextrose equivalents (DE) and varying drying air temperatures, the study linked morphology to skin rheological properties. Low-DE maltodextrins produced spherical particles with smooth dents, while higher-DE maltodextrins were more wrinkled. Higher drying temperatures yielded smaller, more wrinkled particles. Guidelines for bulk density were developed, emphasizing that low-DE and high temperatures reduce bulk density, whereas higher DE or lower temperatures increase it.Chapter 4 assessed the impact of spray dryer design on operability. Experiments and CFD simulations examined agglomeration and fouling for different nozzle positions and air swirl levels. Lowering the nozzle reduced fouling on the dryer roof. Air swirl had limited effects on fouling, allowing freedom in air distribution design to minimize fouling without compromising agglomeration.Chapter 5 analyzed how drying conditions influence agglomeration. Using maltodextrin DE21, fine powder mass flowrate, drying air temperature, and air flowrate were varied. Results showed that increasing fine powder flowrate enhanced agglomerate size and grape-structure agglomerates. Slightly lower drying air temperatures and higher air flowrates also favored grape-structure formation.Chapter 6 explored the effects of material properties on particle structure, particularly protein addition to maltodextrin DE38. Protein advanced the onset of the sticking regime, shifting collision outcomes from coalescence to sticking. Pea protein delayed the regime’s end compared to whey protein. Protein addition improved agglomeration yield at pilot scale, with dose-dependent effects up to 5% (db), beyond which viscosity changes impacted droplet size and drying behavior. Guidelines for product formulation were developed, balancing agglomeration and fouling.The main findings of Chapters 2-6 are discussed in Chapter 7. Overall, the pilot-scale dryer showed less agglomeration than industrial-scale dryers. Introducing a fluidized bed for multi-stage processing or a second atomizer lance could enhance industrial scalability. Guidelines were formulated for optimizing bulk density, agglomeration, and fouling based on material properties, drying conditions, and spray dryer configurations, supporting industry efforts to control particle structure development.
Original language | English |
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Qualification | Doctor of Philosophy |
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Award date | 31 Jan 2025 |
Place of Publication | Wageningen |
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DOIs | |
Publication status | Published - 31 Jan 2025 |
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Dive into the research topics of 'From mist to matter: Steering particle structure development during pilot-scale spray drying'. Together they form a unique fingerprint.Projects
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Steering particle agglomeration in spray drying at the pilot scale.
van Boven, A. (PhD candidate) & Schutyser, M. (Promotor)
1/10/20 → 31/01/25
Project: PhD