Design and evaluation of novel spray drying atomization methods for in-line mixing and particle size control

Luna Alanis, Luis Gerardo

Permalink

https://hdl.handle.net/2142/120406 Copy

Description

Title

Design and evaluation of novel spray drying atomization methods for in-line mixing and particle size control

Author(s)

Luna Alanis, Luis Gerardo

Issue Date

2023-04-27

Director of Research (if dissertation) or Advisor (if thesis)

Lee, Youngsoo

Doctoral Committee Chair(s)

Feng, Hao

Committee Member(s)

• Schmidt, Shelly J
• Wang, Yi-Cheng

Department of Study

Food Science & Human Nutrition

Discipline

Food Science & Human Nutrition

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Spray drying
• Atomization
• 3-fluid nozzle
• ultrasound atomization
• in-line mixing
• particle size control

Abstract

Most food powders are produced using spray drying. Spray drying process is popular because it has a one-step continuous processing operation divided into three stages: atomization, droplet-to-particle conversion, and particle collection. Even though this technology has been around for approximately 100 years, there are still some limitations to spray drying that, to this day, have not been addressed. Continuous processing of feeds that require mixing before spray drying and controlling powders' particle size and distribution on an industrial scale are still considered relevant limitations that need to be solved. The atomization process determines the energy required to form the spray, the trajectory of liquid particles, their speed, particle size, and distribution. Because atomization is so critical in spray drying, changes in the nozzle design can help solve the challenges mentioned before. This research aims to design and evaluate novel atomization methods in spray drying that allow for the continuous processing of mixtures and the control of particle size and distribution of powders. The outcome of this research can be used to expand the options available for in-line mixing for pneumatic atomization and control particle size and distribution for pneumatic and ultrasound atomization. The three-fluid pneumatic nozzle (3FN) was used to tackle the challenge of continuous processing that requires mixing of feed before spray drying. Maltodextrin DE10 (MD10) and fructooligosaccharides (FOS) were used as materials to model the mixing of low molecular carbohydrates (FOS) with drying aids (MD10). The environmental stability of the mixture of the two materials was compared between batch and in-line mixing. The batch mixing was done for a two-fluid nozzle (2FN) and the in-line mixing was evaluated using a 3FN. Both types of mixing improved the thermal and moisture sorption stability compared to FOS and no significant difference in thermal and moisture sorption was observed between both types of mixing. This technology can be applied to eliminate a batch mixing step in drying operations and the composition of the powder can be readily controlled. An ultrasound nozzle (UN) was designed to house a vibrating mesh transducer to control particle size and particle size distribution. The mesh sizes were 8, 20 and 30μm. The 8μm mesh with the area diameter of 4 mm and 7 mm were used in a lab scale spray dryer and the results were compared to a 2FN housed in the same dryer (2FL). On the other hand, the 20 and 30μm ii meshes with the mesh area diameter of 7 mm were used and compared to a 2FN in a pilot-plant spray drier (2FP). Maltodextrin DE18 (MD18) was used at 10 and 20% concentrations. The 8μm 4 mm, 20 μm 7 mm, and 30 μm 7 mm produced significantly larger D50 particle sizes than the other nozzles, resulting in the lowest spans ranging from 0.77-0.86. The other nozzles produced powders with a span range of 2.1-2.5, indicating a significantly wider size distribution than the smaller span. The MD18 concentration affected the particle size, producing larger particles at higher, 20%, concentration in most of the nozzles tested. However, the concentration overall did not affect the particle size distribution (PSD) span. The vibrating mesh technology produced a narrower PSD span than pneumatic atomization in both lab and pilot-scale spray driers. Lastly, a 3FN was explored for particle size control using two independent gas inlets in the outer and innermost channels and a liquid feed in the intermediate channel. Two nozzle tips with 0.7 (ST) and 2.0 mm (LT) inner diameters (ID) were used, and inside (IM) and outside mixing (OM) were evaluated in the 3FN. The smallest particle size was 2.4 μm from the 3FN ST IM at the lowest MD18 concentration, and the largest size was 7μm for 3FN LT IM at the highest MD18 concentration. The particle size decreased with increasing the air flow in volume. Also, the particle sizes from the 3FN were smaller than their 2FN counterparts. The particle size increased with increasing MD18 concentration in feed. No significant difference in the span values were observed between the nozzle configurations. This technology can be used to achieve smaller particle sizes with higher viscous feeds in pneumatic atomization.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Luis Gerardo Luna Alanis

Owning Collections