(308d) Interplay of Reaction and Transport within Biomass Particle during Fast Pyrolysis: Development of Reaction and Transport Models and Their Non-Dimensionalization

Pyrolysis of biomass and waste converts it to bio-oil, which can be further upgraded to fuels and chemicals.¹ Decomposition of the biomass/waste feed particle, within the pyrolysis reactor, governs the product distribution, and hence the yield and the composition of bio-oil. Complex and often unknown decomposition chemistry, high temperatures and short residence times of the particle in the reactor and an interplay between kinetics and heat and mass transport effects within the particle make it extremely difficult to understand the particle level decomposition of biomass. In the present work, we present a particle level model comprising of energy and reactant and products species mass conservation equations, as heat and mass transport occurs simultaneously along with pyrolysis reactions, considering the entire particle as a control volume. Conservation equations consist of generation, convective and diffusive transport and accumulation terms. Unlike using lumped models for the pyrolysis reactions^2-5, component specific kinetic models which are fitted using transport limitation free experimental data, are incorporated into the mass conservation equations. Changes in particle porosity and thermal conductivity and shrinkage of the particle during the pyrolysis process are also taken into account. Further, the model equations and boundary conditions are non-dimensionalized to group difficult to measure variables/properties/parameters into non-dimensional numbers like Biot, Pyrolysis, Peclet, Damkohler and Sherwood numbers that represent characteristic reaction and transport timescales. The non-dimensionalization would provide an independent platform to compare various pyrolysis experiments performed under different operating conditions.

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