Transport properties for process scale-up measured using magnetic resonance imaging

Transcription

1 Transport properties for process scale-up measured using magnetic resonance imaging Emilio J. Tozzi 1, David M. Lavenson 2, Michael J. McCarthy 3 and Robert L.Powell 2 1 Food Science and Technology, 2 Chemical Engineering and Materials Science, 3 Biological and Agricultural Engineering University of California, Davis, Davis, CA CPAC Summer institute Jul Seattle WA

2 Introduction Lignocellulosic Biomass Pretreatment Cellulases Hemicellulases Hydrolysis Sugars (Hexoses, Pentoses) Fermentation Micro organism (wild or recombinant) Separation Main Product Alcohols Acids Amino acids Industrial chemicals By-products (Fuel for boiler, Animal feed, Industrial chemicals)

3 Advantages of High-solids operation Sassner et al., Biomass Bioener.,32 (2008)

4 Reduced conversion at high-solids operation Kristensen et al., Biotech. Biofuel.,2, (2009)

5 Importance of rheology Design/scale-up/optimization. Progress of hydrolysis / Enzyme optimization Shao et al., Bioprocess Biosyst Eng, 33, 2010 N. Szijártó et al., Bioresource Technology, vol. 102, no. 2, pp , Jan

6 Imaging System 1 Tesla permanent-magnet-based imaging spectrometer (Aspect Imaging, Israel). Velocity profiles & rheology Concentration distribution Monitoring progress of liquefaction Diffusion coefficient

7 Rheology of cellulosic substrates Challenges in conventional cellulosic rheometry Particle size vs. gap Heterogeneity Entanglement Depletion layers Settling

8 MRI flow imaging

9 Velocity and signal Intensity profiles Water Re=1014 Re=1625 Re= 2107 Re= 3004

10 Rheological parameters Yield stress Uncertainty Rotational MRI >15% 5-8 % Measurement time Rotational MRI min 1-2 min Lavenson et al., Biotechnology and Bioengineering, 108, Sample volume Rotational MRI ~1-100 ml >2 liters Can analyze multi-kg sample

11 Mass transport challenges in high-solids enzymatic hydrolysis Well-mixed condition needed to proceed at acceptable rates. Homogenization dominated by slow convective flow and diffusion. Designing energy efficient mixing processes requires quantitative information on the rheology and diffusion properties of the materials.

12 Industrial cellulose fibers studied C EZ 0.5 mm 0.5 mm Fiber type Length (LW) Length (NW) Width (LW) a) Solka Floc 200EZ mm mm 26.4 um b) Solka Floc C mm mm 31.7 um

13 One-dimensional diffusion At time T=0 bottom half of fiber bed contains MnCl 2 Effective diffusivity over length scales >> fiber length

14 Evolution of concentration profiles Effective diffusivity computed by matching numerical (1-D Diffusion) and experimental concentration profiles C t D eff 2 Z C 2 M. S. Olson, R. M. Ford, J. A. Smith, and E. J. Fernandez. Environ. Sci. Technol., 39: , 2005.

15 Simplified effective diffusivity model Effective diffusivity Porosity D eff D (1 0 R) Bulk diffusivity Tortuosity Adsorption constant P. B. Weisz. Trans. Faraday Soc., 63: , E. J. Tozzi, D. M. Lavenson, M. J. McCarthy, and R. L. Powell, AIChE Journal, DOI: /aic.12578, 2011.

16 Adsorption

17 Diffusivity Comparison Bulk Experiment [1] K ads (l/g) C EZ Simplified model

18 Mixing

19 Effect of Mixing on glucose yield

20 Some approaches to mixing at low Re Pure Shear Mixing Shear flow in Couette geometry Hold,P., Mixing of Polymers- An overview. part II, Adv. Polymer Tech. 2, ,(1982)

21 Some approaches to mixing at low Re Extensional Flow (Planar elongational) Van Der Hoeven et al., Polymer Eng. Sci., 41,

22 Some approaches to mix at low Re Striation Thickness vs. Time shear flow planar elongational flow

23 Split-and-Recombine (SAR) mixer Multiflux Multilamination Multilayer coextrusion Folding flow mixer R. Sluijters,US Pat , 1965 Schönfeld et al., Lab Chip, 4, 65-69, 2004.

24 Prototype SAR mixer Fluid 1: 0.5% (w/w) Carbopol NaOH Fluid 2: 0.5% (w/w) Carbopol NaOH + Red dye + MnCl 2

25 Signal / Signal of udoped Prototype SAR mixer % Doped

26 Summary MRI sensor can measure rheology, diffusion and mixing in challenging suspensions (opaque & concentrated) MRI vs Rotational rheometry: MRI fast & larger sample sizes Diffusion & Mixing: Spatially resolved concentration profiles available from MRI Data generated can be applied for new process design & scale up

27 Questions What information from a MRI sensor would be most useful for process scale up? Practical ways to present the information: rheograms? parameters of simple models? yield stress? Accuracy needed? What solid concentrations are of interest? What particle sizes are of interest?

28 Acknowledgments Aspect Imaging Shoham, Israel Undergraduate students: Jonathan Tung, Yifeng Hong Financial support: CPAC, Seattle, WA Chevron corporation University of California Davis