Study of the particle formation and morphology of single mannitol-water droplets depending on the drying conditions

Transcription

1 Engineering Conferences International ECI Digital Archives Design and Manufacture of Functional Microcapsules and Engineered Products Proceedings Study of the particle formation and morphology of single mannitol-water droplets depending on the drying conditions Thomas Hellwig, University of Hamburg, Germany, Matthias Griesing, University of Hamburg, Germany Hans-Ulrich Moritz, University of Hamburg, Germany Werner Pauer, University of Hamburg, Germany, Holger Großhans Interdisciplinary Center for Scientific Computing (IWR), University of Heidelberg, Germany See next page for additional authors Follow this and additional works at: Recommended Citation Thomas Hellwig, Matthias Griesing, Hans-Ulrich Moritz, Werner Pauer, Holger Großhans, and Eva Gutheil, "Study of the particle formation and morphology of single mannitol-water droplets depending on the drying conditions" in "Design and Manufacture of Functional Microcapsules and Engineered Products", Chair: Simon Biggs, University of Queensland (Aus) Co-Chairs: Olivier Cayre, University of Leeds, UK Orlin D. Velev, North Carolina State University, USA Eds, ECI Symposium Series, (2016). This Abstract and Presentation is brought to you for free and open access by the Proceedings at ECI Digital Archives. It has been accepted for inclusion in Design and Manufacture of Functional Microcapsules and Engineered Products by an authorized administrator of ECI Digital Archives. For more information, please contact

2 Authors Thomas Hellwig, Matthias Griesing, Hans-Ulrich Moritz, Werner Pauer, Holger Großhans, and Eva Gutheil This abstract and presentation is available at ECI Digital Archives:

3 Study of the Particle Formation and Morphology of Single Mannitol-Water Droplets Depending on the Drying Conditions Design and Manufacture of Functional Microcapsules T. Hellwig, M. Griesing, H. Grosshans, W. Pauer, E. Gutheil, H.-U. Moritz

4 Type of Substance: Mannitol Carrier for dry powder inhalators (DPI) Manufactured by spray process with various morphologies Challenging process design M. Mönckedieck et al., Influence of particle shape of spray-dried mannitol carriers on powder flow and aerodynamic properties, DDL 25, Edinburgh, 2014 Slide 2

5 Advantage of Spray Drying Process Aqueous solution Multiple operations Single stage process Process intensification Slide 3

6 Observing Single Droplet Using Acoustic Levitation s Spray process Acoustic levitation Educts Disproportional effort to monitor single droplet Acoustic levitation offers accessible analytics for single droplet Slide 4

7 Levitation Aq. Mannitol Droplets - Experimental Design droplet diameter / µm Design of Experiment Factors: Temperature ( C) Mass fraction (5-15 w%), Droplet size ( µm) 5 experiments for each condition Constant relative humidity (r.h.) 1 % Outcomes Drying kinetics Evaporation rate Solid layer formation Porosity Surface texture (morphology) w% 10 w% 15 w% temperature / C Slide 5

8 Numerical Simulation for Drying of Single Aq. Mannitol Droplets reduced surface (d/d 0 ) 2 / - droplet generation Experimental determined drying kinetic via shadowgraphy Numerical simulation procedure by H. Großhans, S.R. Gopireddy and E. Gutheil (IWR, University of Heidelberg) 1.0 Mass conservation 1 st drying step 2 nd drying step Simulation wi D12 2 wi 2 r t r r r Experiment time / s Energy conservation dt Q mh ( T ) mc m h T d l L d p,l * L d dt 1 Nu kg,f / (2 ks R ) Developed numerical simulation is able to describe 1 st drying step H. Grosshans et al., Int. J. Heat Mass Trans. 2016, 96, Slide 6

9 Solid Layer Formation of Single Aq. Mannitol Droplets (d/d 0 ) 2 / - droplet generation # of experiment st drying step 2 nd drying step Point of solid layer formation time / s T= 100 C, 10 w%, 350 µm T= 120 C, 5 w%, 350 µm time solid layer formation / s experiment simulation T= 80 C, 10 w%, 450 µm Numerical simulation can be used to determine point of solid layer formation Slide 7

10 initial droplet diameter / µm evaporation rate / s -1 initial droplet diameter / µm time until point of solid layer formation / s Influences on Drying Kinetic Evaporation rate Point of solid layer formation Y M0 = 5 % Y M0 = 10 % Y M0 = 15 % temperature / C temperature / C 40 Mass fraction x Temperature Starting droplet diameter Mass fraction Temperature Starting droplet diameter Slide 8

11 Porosity of Produced Single Mannitol Particles porosity / - Porosity calculated based on shadowgraphy data experiment simulation V V V Y with V end m d0 d0 m0 m Vend m d 0 = 450 µm, Y m0 = 10 % Higher deviation at higher temperatures: Simulation does not take inner pressure into account temperature / C The porosity is increased with increasing temperature at constant d 0 and Y m0 Slide 9

12 Investigation of Particle Morphology by SEM Temperature Morphology map by SEM 120 C Tailor-made particles Influences onto particle surface Mass fraction and temperature Starting droplet diameter x Mass fraction 100 C 80 C Slide 10

13 spherical diameter / µm Numerical Simulation of Temperature Profile temperature / C simulation r.h. 1 % experiment r.h. 1 % simulation r.h. 15 % experiment r.h. 15 % simulation r.h. 1 % experiment r.h. 1 % simulation r.h. 15 % experiment r.h. 15 % time / s Thermocouple type K, Ø= 150 µm, ± 0.8 C time / s Numerical simulation is able to describe whole droplet evolution at different rel. humidity Slide 11

14 Effect of Relative Humidity on Structure Formation Quenching of droplet 1 % r.h. 0 s 28 s 34 s 200 s T = 100 C 15 % r.h. T = 100 C, d 0 = 480 µm, dry, crystalline 0 s 70 s 200 s 20 µm Mannitol on heating plate 100 C 168 C 15 % r.h. T = 100 C, d 0 = 501 µm, remains liquid What is the difference between the dry crystalline particle and the remaining liquid? Slide 12

15 Raman Spectroscopy of Remaining Liquid and Molten Mannitol Melting-point or freezing-point depression should lead to indifferent spectra The remaining liquid is not molten mannitol Slide 13

16 (d/d 0 ) 2 / - Study of Evaporation and Crystallization via Raman-Spectroscopy mass fraction mannitol 15 w%; initial droplet diameter 0.7 mm 1.0 drying temperature 100 C 1 % r.h time / s Drying and evaporation can be monitored using Raman spectroscopy Slide 14

17 Analyzing the Spectra via Multivariate Curve Resolution (MCR) intensity / - MCR suggests 3 components within spectra: Aq. mannitol Water Solid mannitol drying temperature 100 C 1 % r.h. mass fraction mannitol 15 w% initial droplet diameter 0.7 mm How do the concentration profiles evolve? Cornel, J., Kidambi, P., Mazzotti, M., Ind. Eng. Chem. Res. 49, wavenumber / cm -1 Slide 15

18 Analyzing the Spectra via Multivariate Curve Resolution (MCR) intensity intensity / / MCR suggests 3 components within spectra: Aq. mannitol Water Solid mannitol drying temperature 100 C 1 % r.h. mass fraction mannitol 15 w% initial droplet diameter 0.7 mm 0.5 How do the concentration profiles evolve? Cornel, J., Kidambi, P., Mazzotti, M., Ind. Eng. Chem. Res. 49, wavenumber // cm -1-1 Slide 16

19 Analyzing the Spectra via Multivariate Curve Resolution (MCR) intensity / - MCR suggests 3 components within spectra: Aq. mannitol Water Solid mannitol drying temperature 100 C 1 % r.h. mass fraction mannitol 15 w% initial droplet diameter 0.7 mm How do the concentration profiles evolve? Cornel, J., Kidambi, P., Mazzotti, M., Ind. Eng. Chem. Res. 49, wavenumber / cm -1 Slide 17

20 Analyzing Components and Crystallization via MCR component quantity / - (d/d 0 ) 2 / - drying temperature 100 C, 1 % r.h., mass fraction mannitol 15 w%, initial droplet diameter 1 mm 1.0 aq. mannitol water solid mannitol droplet size time / s Qualitatively model for evaporation and crystallization accessible Slide 18

21 (d/d 0 ) 2 / - Using Raman Spectroscopy to Resolve liquid Mannitol mass fraction mannitol 15 w%; initial droplet diameter 1 mm drying temperature 100 C r.h. 15 % time / s Raman spectra reveal no crystallization Slide 19

22 Resolving liquid Mannitol out of Spectra via MCR MCR suggests 2 components within spectra: Aq. mannitol Water drying temperature 100 C 15 % r.h. mass fraction mannitol 15 w% initial droplet diameter 1 mm R.h. 15 % prevents crystallization Slide 20

23 Calculated Concentration Profile at Relative Humidity 15 % component quantity / - (d/d 0 ) 2 / drying temperature 100 C, r.h. 15 %, mass fraction mannitol 15 w%, initial droplet diameter 1 mm aq. mannitol water droplet size time / s Small amount of water prevents crystallization of mannitol Slide 21

24 Conclusion and Future Prospects Easy accessible Morphology Map Tailor-made particle structures Solid-layer formation Particle porosity Structure formation Numerical model in good agreement with experimental results Raman spectroscopy was utilized to monitor evaporation and crystallization At relative humidity above 15 % droplets consist of a oversaturated mannitol solution Remaining water prevents crystallization of mannitol Next step: validate results via spray process Slide 22

25 Thank you for your attention! Slide 23