(390f) CFD Investigation of Autothermal Biomass Pyrolizers
The performance of autothermal pyrolizers may be affected by several design choices and by the composition of the biomass feed stream. The geometric configuration of the pyrolyzer and the location of the biomass feed may affect mixing of the biomass in the pyrolizer, impacting the residence time of the biomass and the product yield.
In order to investigate these effects, we have formulated a computational model to describe biomass fast pyrolysis. The model is based on the Euler-Euler multi-fluid model [4,5] with kinetic theory closures for polydisperse granular phases [6,7], supplemented by a comprehensive chemical kinetic mechanism [8â18] accounting for devolatilization, char combustion and gas-phase reactions. Results demonstrating the predictive capabilities of the computational models in comparison to experimental data of pyrolysis product yield will be presented.
The model was then used to study mixing of biomass and sand in a fluidized bed pyrolizer to understand the level of mixing obtained in the fluidized bed with different injection location
of the biomass. To this purpose, a mixing index insensitive to the spatial discretization of the computational domain was formulated, in order to systematically quantify the quality of the mixing of the granular mixture. Numerical experiments were first performed considering a cold flow in a laboratory scale fluidized bed with sand and biomass without accounting for the effect of eventual effects of the temperature distribution and of the chemical reactions.
The effects of heat transfer and chemical reaction are then introduced to investigate the impact of the location of the injection point of the biomass on the products in realistic operating conditions.
 J.P. Polin, C.A. Peterson, L.E. Whitmer, R.G. Smith, R.C. Brown, Process intensification of biomass fast pyrolysis through autothermal operation of a fluidized bed reactor, Appl. Energy. 249 (2019) 276â285. doi:10.1016/j.apenergy.2019.04.154.
 J. ProanoâAviles, J.K. Lindstrom, P.A. Johnston, R.C. Brown, Heat and Mass Transfer Effects in a Furnace-Based Micropyrolyzer, Energy Technol. 5 (2017) 189â195. doi:10.1002/ente.201600279.
 K.H. Kim, X. Bai, M. Rover, R.C. Brown, The effect of low-concentration oxygen in sweep gas during pyrolysis of red oak using a fluidized bed reactor, Fuel. 124 (2014) 49â56. doi:10.1016/j.fuel.2014.01.086.
 D.A. Drew, Averaged equations for two-phase flows, Stud. Appl. Math. L (1971) 205 â 231.
 D.A. Drew, Continuum Modeling of Two-Phase Flows, in: R. Meyer (Ed.), Theory Dispersed Multiph. Flow, Academic Press, 1983: pp. 173 â 190.
 J.T. Jenkins, S.B. Savage, A theory of the rapid flow of identical, smooth, nearly elastic spherical particles, J. Fluid Mech. (1983) 187 â 202.
 J.T. Jenkins, F. Mancini, Balance Laws and Constitutive Relations for Plane Flows of a Dense, Binary Mixture of Smooth, Nearly Elastic, Circular Disks, J. Appl. Mech. 54 (1987) 27â34. doi:10.1115/1.3172990.
 M. Calonaci, R. Grana, E. Barker Hemings, G. Bozzano, M. Dente, E. Ranzi, Comprehensive Kinetic Modeling Study of Bio-oil Formation from Fast Pyrolysis of Biomass, Energy Fuels. 24 (2010) 5727â5734. doi:10.1021/ef1008902.
 M. Corbetta, A. Frassoldati, H. Bennadji, K. Smith, M.J. Serapiglia, G. Gauthier, T. Melkior, E. Ranzi, E.M. Fisher, Pyrolysis of Centimeter-Scale Woody Biomass Particles: Kinetic Modeling and Experimental Validation, Energy Fuels. 28 (2014) 3884â3898. doi:10.1021/ef500525v.
 E. Ranzi, P.E.A. Debiagi, A. Frassoldati, Mathematical Modeling of Fast Biomass Pyrolysis and Bio-Oil Formation. Note I: Kinetic Mechanism of Biomass Pyrolysis, ACS Sustain. Chem. Eng. 5 (2017) 2867â2881. doi:10.1021/acssuschemeng.6b03096.
 R.S. Miller, J. Bellan, A generalized biomass pyrolysis model based on superimposed cellulose, hemicellulose and lignin kinetics, Combust. Sci. Technol. 126 (1997) 97â137. doi:10.1080/00102209708935670.
 C. Di Blasi, Heat, momentum and mass transport through a shrinking biomass particle exposed to thermal radiation, Chem. Eng. Sci. 51 (1996) 1121â1132. doi:10.1016/S0009-2509(96)80011-X.
 R. Radmanesh, Y. Courbariaux, J. Chaouki, C. Guy, A unified lumped approach in kinetic modeling of biomass pyrolysis, Fuel. 85 (2006) 1211â1220. doi:10.1016/j.fuel.2005.11.021.
 M.R. Rover, P.A. Johnston, L.E. Whitmer, R.G. Smith, R.C. Brown, The effect of pyrolysis temperature on recovery of bio-oil as distinctive stage fractions, J. Anal. Appl. Pyrolysis. 105 (2014) 262â268. doi:10.1016/j.jaap.2013.11.012.
 A. Williams, M. Pourkashanian, J.M. Jones, Combustion of pulverised coal and biomass, Prog. Energy Combust. Sci. 27 (2001) 587â610. doi:10.1016/S0360-1285(01)00004-1.
 R. Barranco, A. Rojas, J. Barraza, E. Lester, A new char combustion kinetic model 1. Formulation, Fuel. 88 (2009) 2335â2339. doi:10.1016/j.fuel.2009.02.005.
 C. Di Blasi, Combustion and gasification rates of lignocellulosic chars, Prog. Energy Combust. Sci. 35 (2009) 121â140. doi:10.1016/j.pecs.2008.08.001.
 G. Perkins, Underground coal gasification â Part II: Fundamental phenomena and modeling, Prog. Energy Combust. Sci. 67 (2018) 234â274. doi:10.1016/j.pecs.2018.03.002.