Pierre-Xavier Thivel

Towards the modelling and control of NOx emission in a fluidized bed sludge combustor

Sludge incineration is a widely used technology because of its large volume reduction and complete organic destruction. However, incineration does encounter a number of drawbacks, among which are notably carbon monoxide (CO) and nitrogen oxides (NOx) emissions. Carbon monoxide emissions are efficiently avoided by oxygen regulation in the furnace. Nitrogen oxide (NOx) formation, however, is very complex and not well known. This paper proposes a dynamic model of sludge combustion in an industrial fluidized bed combustor mainly focused on NOx formation. The model is tuned with industrial data. A control strategy is proposed to improve on the current industrial regulation, simultaneously ensuring CO and NOx control, yet without decreasing the combustion efficiency. The results are sufficiently acceptable for this process to be carried out in a real incinerator plant.

Electrochemical Impedance and Acoustic Emission Survey of Water Desorption in Nafion Membranes

This study evaluates the acoustic emission (AE) technique for the detection of membrane dehydration in proton exchange membrane fuel cells during operation. The dehydration of the membrane owing to inefficient water management leads to drastic performance losses. Electrochemical impedance spectroscopy (EIS) and AE measurements were carried out during dehydration of Nafion samples. Results have shown that electrochemical parameters obtained from EIS yield monotonic exponential-like responses following the water loss. AE was shown to be sensitive enough to detect structural changes taking place at the last stages of dehydration.

Diagnosis and modelling of proton-exchange-membrane fuel cell via electrochemical-impedance-spectroscopy and Acoustic-Emission measurements

The diagnosis and modelling of flooding or drying is an important factor in improving the reliability and durability of PEMFCs. Indeed, flooding and drying lead to a reduction in the output voltage delivered by the fuel cell. Among the various techniques, electrochemical impedance spectroscopy (EIS) and Acoustic Emission (EA) are powerful tools. In this study, EIS and AE measurements were carried out respectively on a 500 W stack and on a 25 cm2 fuel cell. EIS measurements and its modelling by an electrical equivalent circuit model revealed that flooding mainly affects the transfer resistance and the cathodic Warburg impedance. AE measurements show that it is possible to follow the water content within the fuel cell. Coupling this two methods seem to be an interesting diagnosis tool.

Dynamic model of NOx emission for a fluidized bed sludge combustor

Abstract Abstract Sludge incineration in fluidized bed is a very complex process, producing gaseous pollutants (carbon monoxide (CO) and nitrogen oxides (NOx)). The legislative norms need to be respected in spite of variations of sludge in composition and in quantity. The NOx formation, due to lots of chemical reactions from sludge nitrogen, is partly unknown. This paper deals with the design of a dynamic model of NOx emissions for a fluidized bed sludge combustor to be used in control strategy. The model is validated with industrial data, and the simulation results validate the simplification hypotheses, but need the reconstruction of sludge composition.