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Numerical modeling is a main part within all research activities of “plasma” group: gas phase synthesis, reforming,...
A particular effort has been devoted to model the thermal decomposition of hydrocarbons by thermal plasma processes in the frame of two successive thesis: B. Ravary, 1998 and I. Dème, 2002. Numerical modeling appears as a major tool for reactor characterization and optimization as well as the up scaling to an industrial pilot.
One of the aims is the development of simple models capable to achieve the objectives of process optimization and pilot dimensioning within reasonable reduced calculation times.
Some research topics :
1. Burning arcs in a three–phase system
The
arc region is particularly important cause of energy is supplied in this zone.
Three-phase arc plasma in an Argon atmosphere.
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Contrary to three-phase arcs commonly found in metallurgical applications, there is not a neutral point in the developed system. Thus the arcs move freely interacting mutually by electromagnetic forces. This electromagnetic interaction leads to a global motion in the centrifugal direction.
An original approach consists in to consider that the arc region is described as a volume in which two source terms are defined. corresponding to the energy and the momentum. The linear momentum is estimated from the time average of the Lorentz forces. These are calculated by using simple geometries and applying some simplifying hypothesis.
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2. Hydrodynamics in the three-phase plasma reactor
The research deals the following objectives:
- Determination of the heat and mass transfers in the
reactor and the distribution of the different heat exchange
modes (conduction, convention and
radiation).
- Evaluation of the efficiency of hydrocarbon – plasma
gas mixing. It concerns a common problem in plasmas
which are characterized by a high viscosity.
- Evaluation and optimization of the thermal efficiency
of the process.
- Study of the different mechanisms of gas-phase synthesis
of carbon from simple reaction mechanisms. The
integration of kinetic mechanisms of solid carbon formation
allows to describe the thermal decomposition of the
hydrocarbon as an irreversible process. the kinetic constants
are obtained from the data available in the literature as well
as experimentally measured.
- Plasma / particles interaction: Study of carbon particle
effects on mass and heat (mainly radiative heat) transfers in
the reactor. It concerns in the determination of radiative
absorption and scattering coefficients as a fraction of the
volume fraction of the solid carbon. This study also involves
the determination of mass and heat transfers between the
particles and the plasma surrounded them taking into account
the Knudsen effect as well as the phenomena related to the
evaporation and the condensation.
Perspectives
Research in the described subjects will carry on in the future and it will involve particularly the next topics:
- Carbon gas-phase synthesis.
- Radiative models concerning carbon particles : Size distribution effects, agglomeration,...
- Chemical kinetics of systems C – H – O.
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Plasma Conversion Processes
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