(195g) Interfacial Phenomena during Biomass Pyrolysis

Saurabh Maduskar, Christoph Krumm, and Paul J. Dauenhauer

Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave. SE, 484 Amundson Hall, Minneapolis, MN 55455, USA.

Difficult to handle solid feedstock, heat transfer limitations and complexity of multi-phase products are the major design challenges of bio-reactors. During high temperature pyrolysis, biomass transforms into a liquid intermediate before depolymerizing and volatilizing into condensable bio-oil products for upgrading into fuels and chemicals. The interfacial heat and mass transport for lignocellulosic biomass particles during thermal processing at high temperature (>400°C) dramatically affects the yield and quality of renewable products. Therefore, it is important to understand solid-liquid and liquid-gas interfacial interaction during this transformation for efficient design of bio-reactors.

Crystalline cellulose particles were discovered to lift off heated surfaces by high speed photography similar to the Leidenfrost effect in hot, volatile liquids.^[1] Introduction of macroporosity to the heated surface was shown to completely inhibit the cellulose Leidenfrost effect, providing a tunable design parameter to control particle heat transfer rates in industrial bio-reactors.^[2] Additionally, cellulosic particles were shown to spontaneously move on a patterned metal surface of microstructured, asymmetric ratchets (100 by 400 µm) at reactor temperatures with limited resistance to flow. The spontaneous motion of particles orthogonal to ratchet wells was analyzed using high speed photography. The ability to controllably move organic solid particles and fibers within high temperature systems provides a simple alternative for transporting and processing difficult-to-handle solid feedstocks.

Inorganic content in biomass not only alters the pyrolysis chemistry, thereby degrading the bio-oil quality, but also affects the performance of downstream equipment due to corrosion and/or scaling. The mechanism of transfer of non-volatile inorganics from solid biomass to condensed bio-oil was unknown. By studying ablative pyrolysis of crystalline cellulose with and without doped calcium, the spontaneous ejection of aerosols through liquid-gas interface was found to be the probable pathway of transfer of inorganics to bio-oil.^[4]

(1) Teixeira, A. R.; Krumm, C.; Vinter, K. P.; Paulsen, A. D.; Zhu, C.; Maduskar, S.; Joseph, K. E.; Greco, K.; Stelatto, M.; Davis, E.; Vincent, B.; Hermann, R.; Suszynski, W.; Schmidt, L. D.; Fan, W.; Rothstein, J. P.; Dauenhauer, P. J. Sci. Rep. 2015, 5 (JUNE), 11238.

(2) Krumm, C.; Maduskar, S.; Paulsen, A. D.; Anderson, A. D.; Barberio, N. L.; Damen, J. N.; Beach, C. A.; Kumar, S.; Dauenhauer, P. J. Energy Environ. Sci. 2016.

(3) A. R. Teixeira, K. G. Mooney, J. S. Kruger, C. L. Williams, W. J. Suszynski, L. D. Schmidt, D. P. Schmidt, P. J. Dauenhauer, Energy Environ. Sci. 2011, 4, 4306 – 4321

(4) A.R. Teixeira, R. Gantt, K. Joseph, S. Maduskar, A.D. Paulsen, C. Krumm, C. Zhu, ChemSusChem 2016, 9(11), 1322-1328.