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This paper presents a process model for the polygeneration of Synthetic Natural Gas (SNG), power and heat by catalytic hydrothermal gasification of biomass and biomass wastes in supercritical water. Following a systematic process design methodology, thermodynamic property models and thermoeconomic process models for hydrolysis, salt separation, gasification and the separation of CH 4 , CO 2 , H 2 and H 2 O at high pressure are developed and validated with experimental data. Different strategies for an integrated separation of the crude product, heat supply and energy recovery are elaborated and assembled in a general superstructure. The influence of the process design on the performance is discussed for some representative scenarios that highlight the key aspects of the design. Based on this work, a thermo-economic optimisation will allow for determining the most promising options for the polygeneration of fuel and power depending on the available technology, catalyst lifetime, substrate type and plant scale.

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In the present work, the influence of metal ions and oxidative degradation inhibitors on the stability of monoethanolamine solvents (MEA) is studied. 2 induces additional costs and impacts the environmental balance of the CO 2 capture process as well as its efficiency. The two main degradation pathways of MEA are studied under accelerated conditions: oxidative degradation with continuous gas feed and thermal degradation in batch reactors. It is confirmed that metal ions (resulting from solvent impurities and wall leaching) enhance the oxidative degradation of MEA, while they do not impact its thermal degradation.Moreover, different oxidative degradation inhibitors are tested with varying results according to the inhibitor. It appears that at the selected concentration, radical scavengers like Inhibitor A and DMTD (2,5-dimercapto-1,3,4-thiadiazole) are more efficient than chelating agents like HEDP(1-hydroxyethylidene diphosphonic acid) at inhibiting oxidative degradation. Furthermore, attention must be paid to the influence of oxidative degradation inhibitors on the thermal degradation of MEA. Indeed, some inhibitors like DMTD, DTPA (diethylenetriaminepentaacetic acid) and DTDP (3,3′-Dithiodipropionic acid) appeared to decrease the MEA thermal stability, which cannot be accepted in industrial applications. Finally, a further drawback of DTPA is its high affinity for metal ions leading to a more corrosive solution, so that its use is not recommended for CO 2 capture applications.