Position #3 – Macroscopic Modeling of Biomass Pyrolysis

Host institution
FR - CentraleSupélec
Lab or research department name
Mechanical Engineering
Sub-domain or keywords
Pyrolysis, wood, volume averaging, non-local thermal equilibrium, tomography
Type of mobility
Duration (months)
From 6 to 10 months

Rarefaction and price increase of fossil hydrocarbons, combined with more and more restrictive rules on Greenhouse Gas Emissions (GGE), involve a growing effort for research activities in the domain of new fuels. Using biomass, which is a renewable source with an almost neutral balance for GGE on its whole life cycle, is one of the most promising ways to achieve this objective. It is for example possible to convert, by means of a thermochemical way, raw materials coming from lignocellulosic plants (wood, straw, waste…) into a synthesis gas.

This gas is an energy vector that can later intervene in the production of pure hydrogen (directly usable as a fuel or in fuel cells) or hydrocarbons (via a Fischer-Tropsch-like process). Conversion can be realized in two steps:
– Pyrolysis, which is a thermal decomposition of biomass into a carbonaceous residue and gas,
– Gasification, which is a heterogeneous chemical reaction, i.e. interfacial, between the carbonaceous residue and a reactive gas (typically water vapor or carbon dioxide).
Modeling of these steps, from the scale of a biomass sample to the scale of an industrial reactor, will contribute to the development and optimization of this path of energy production.

The project that we propose comes within the scope of modeling the pyrolysis phase for a wood particle. The difference between the considered scales (pores, whole particle) and the complexity of microstructure make impossible a local representation of the transfer mechanisms at particle scale. A homogenized representation can then be obtained with the method of volume averaging, where the particle is represented by an equivalent continuous medium. The averaged conservation equations involve effective properties (permeability, conductivity…), which are determined by solving associated closure problems on elementary cells, representative of the local geometry.

During previous work, the conversion of wood was described at local scale by two parallel phase changes (wood into gas and wood into carbonaceous residue), which kinetics follow Arrhenius’ laws. The macroscopic modeling, relying on local thermal equilibrium and on the resolution of closure problems on schematic structures, led to a simplified description, without convection, of the evolution of mass with time.

The objectives of this project are now to propose a more “realistic” description of the process of biomass pyrolysis when the heat transfer description is obtained with a non-local thermal equilibrium, taking into account the main chemical species making up the gas and considering the evolution with time of the microstructure of a wood sample tomography. Close exchanges with a PhD student working on the effects of gas compressibility on the flow and heat
transfer are expected.

Researchers involved

Fabien Bellet (Assistant Professor at ECP / EM2C, (+33) 1 41 13 10 47, name.surname@ecp.fr)

Benoît Goyeau (Professor at ECP / EM2C, (+33) 1 41 13 10 58, name.surname@ecp.fr)

Dominique Gobin (Researcher at EM2C, (+33) 1 41 13 10 92, name.surname@ecp.fr)

Detailed description in PDF format at the following link

From January 2016
Maximum available positions
Researcher with a PhD level, having good knowledge in Fluid Mechanics, Transport in Porous Media, Numerical Simulation and possibly in Chemical Engineering. The candidate must be interested in modeling, image processing and visualization techniques.
Benoit Goyeau <benoit.goyeau@ecp.fr>