Jean-Louis Dirion

Determination of a reaction scheme for cardboard thermal degradation using thermal gravimetric analysis

Abstract In this paper, we present new thermogravimetic analysis on cardboard material performed at different heating rates. Several reaction schemes are proposed to serve as an interpretation basis. Considering the experiments independently, it is found that the best fitted parameters are highly sensitive upon the heating rate. In order to avoid complicated and hazardous interpolation schemes, a simplest interpretation is proposed that does not involve a heating rate dependency on the kinetic parameters.

Determination of reaction parameters for cardboard thermal degradation using experimental data

This work is part of an ongoing research effort in which parameter estimation techniques have been utilized in recovering the kinetic parameters of a given reacting model using measurements collected from TGA devices. The goal of this research work is to develop a useful and universal estimation procedure to determine simultaneously the kinetic parameters involved in the chemical modelling under study such as combustion, pyrolysis, waste stabilization, etc . The present parameter estimation problem is solved with the Levenberg–Marquardt method of minimization of the least square norm representing the square difference between the measured mass variations during cardboard pyrolysis and the mass responses obtained with numerical solution of the model. An analysis of the linear dependency of the pyrolysis parameters needed to design a robust estimation tool is presented. In order to perform this analysis, the sensitivity coefficients and the sensitivity matrix determinant were examined. Experimental data obtained with TGA during the pyrolysis process of cardboard are analysed in this paper and the unknown parameters involved in the kinetic modelling are estimated.

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.

Calcination of Dredged Sediments : Investigation of the Behaviour of Heavy Metals and the Organic Compounds.

The deposit of sediment causes the silting of channels, rivers and lakes. This completely natural phenomenon is exacerbated by the introduction of industrial and urban wastes into the erosion and sedimentation process. Consecutively, other problems appear, such as flooding risks, decrease of biological purification capacity and associated loss of the biodiversity. The presence of toxic compounds (from industrial, household or agricultural origins) in the sediments worsens the situation, and requires curing to restore the natural environment and its function. This study assesses the technology to treat heavy metals from dredged sediments using phosphoric acid (The Novosol® process, developed by Solvay) with the goal of converting metals, mainly Pb, Cd, Zn and Cu to insoluble metallic phosphates, and engineering properties (by calcination) of the final residues for the beneficial use. The effectiveness of the treatment was evaluated by performing the chemical reaction, followed by convective drying and maturation of the treated sediment at ambient temperature and finally calcination (400°C-1000°C). This paper is focused on the investigation of the behaviour of the heavy metals and organic compounds during calcination of the phosphated dredged sediment. Afterwards, the structural change of the sediment during thermal treatment was investigated: particle size, specific surface area, density and the porosity changes of the treated sediment in relation with the vaporization of heavy metals.

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.

Modelling of the rheological behavior of mechanically dewatered sewage sludge in uniaxial cyclic compression

The rheological behavior of mechanically dewatered sewage sludges is complex but essential as it affects almost all treatment, utilization and disposal operations, such as storage, pumping, land-spreading, or drying. In this work, a specific methodology coupling experiments and modelling is developed to characterize the rheological and textural properties of highly concentrated sludge. The experimental part based on a uniaxial compression method has been presented in a previous paper (Liang etxa0al., 2017). This article is dedicated to the modelling part, which includes the behavior identification and the parameters optimization. Previous and additional mechanical tests allow the identification of a visco-elasto-plastic behavior. This behavior is then modelled with a Burgers-Ludwik model, with 7 rheological parameters. This model is able to simulate the viscoelastic behavior of sludge under the yield stress, and the visco-elasto-plastic hardening behavior over the yield stress. The optimization of model parameters is carried out in two steps and relies on the calculation of basins of attraction and confidence intervals with initial conditions estimated from the mechanical tests. Finally, the entire characterization methodology, from experimental mechanical tests to model parameter optimization, is applied to sludge samples at different operating conditions and structural states. The determination of the rheological properties of sludge is achieved with excellent matching between simulation and experimental results. Being able to take into account these impact factors, the rheological model can be used to predict the sludge behavior in various operating conditions.