Laurent Cassayre

Behavior of heavy metals during gasification of phytoextraction plants: thermochemical modelling

Waste such as contaminated biomass, which contain potentially high level of heavy metals, are widely available resources. One of the drawbacks of using this biomass in gasification processes is that some heavy metals might be transferred in the produced syngas, and requires then specific further cleaning steps. Thermodynamic equilibrium calculations are a relevant tool to estimate the behavior of those heavy metals to manage the syngas treatment. The calculations were made with the commercial software FactSage. Due to the several thousands of produced compounds, a specific methodology was set up to choose the stable compounds of the database for the simulations. As an illustrative example, the results of the thermodynamic equilibrium calculations of lead are presented in this paper.

On the relevance of thermodynamics to predict the behaviour of inorganics during CO2 gasification of willow wood

This work is a contribution to the understanding of the behavior of inorganic elements during the gasification process of biomass, with the help of a robust thermodynamic equilibrium calculation methodology. A specific procedure combined with a thorough investigation of available thermochemical databases was developed in order to calculate the behaviour of 23 inorganic elements during CO2 gasification. In parallel, the gasification of willow wood was performed in a laboratory fixed bed reactor, providing the chemical composition of solid residue and major gases. The specificity of the methodology consists in (i) considering an open system to simulate a gas flow in the system (ii) determining the amount of gasification agent added at each calculation step based on experimental measurements of CO2 and CO concentration profiles. One of the main conclusions is that the thermodynamic approach is a relevant and powerful tool since most of the inorganics behavior is correctly reproduced.

Experimental and thermodynamic study of Co-Fe and Mn-Fe based mixed metal oxides for thermochemical energy storage application

Metal oxides are potential materials for thermochemical heat storage, and among them, cobalt oxide and manganese oxide are attracting attention. Furthermore, studies on mixed oxides are ongoing, as the synthesis of mixed oxides could be a way to answer the drawbacks of pure metal oxides, such as slow reaction kinetics, loss-in-capacity over cycles or sintering, selected for thermochemical heat storage application. The addition of iron oxide is under investigation and the obtained results are presented. This work proposes a comparison of thermodynamic modelling with experimental data in order to identify the impact of iron oxide addition to cobalt oxide and manganese oxide. Fe addition decreased the redox activity and energy storage capacity of Co3O4, whereas the cycling stability of Mn2O3 was significantly improved with added Fe amounts above 20u2005mol% while the energy storage capacity was unchanged. The thermodynamic modelling method to predict the behavior of the Mn-Fe-O and Co-Fe-O systems was validated, and the possibility to identify other mixed oxides becomes conceivable, by enabling the selection of transition metals additives for metal oxides destined for thermochemical energy storage applications.

Modeling of a pyrolysis process for the elimination of epoxy resin from embedded nuclear fuels

This paper presents the modeling of a bench-scale reactor for the pyrolysis of epoxy resin containing nuclear fuel samples. Strict operating conditions must be met to avoid nuclear fuel oxidation and the final hydrogen content in the residual char must be close to zero. By using the finite element method software, COMSOL Multiphysics®, transport phenomena and reaction kinetics can be combined to obtain a representative model of the reactor in terms of the temperature and the concentration distribution of the representative chemical species. The numerical results have been found consistent with the temperature measurements in the reactor. The model is also able to predict the distribution of permanent gases in the reactor over time. The variation in the composition and concentration of the gas near the fuel sample can then be monitored to control the oxygen potential. We have calculated the in-vessel transfers of a representative species of gases, hydrogen. The comparison of simulated and experimental values for hydrogen shows good agreement.