Elimination Of Siloxanes By Adsorption ProcessAs A Way Of Upgrading Biogas
Biogas is increasingly being investigated as a source of renewable energy, however its utilisation requires an improvement of its quality. Certain biogases contain compounds called siloxanes; these compounds are the origin of some problems when using biogas. At high temperatures siloxanes are transformed to silicate oxides which can damage equipment (i.e. engines corrosion, the clogging of fuel cell membranes.). This paper provides details of the research done in the treatment of siloxane by adsorption process of adsorption. Different porous materials were studied in order to evaluate adsorption capacities. Influences of humidity and temperature on the mass transfer were evaluated. Moreover, reactors were filled with a mixture of methane and carbon dioxide (principal compounds on the biogas) in order to evaluate the impact of the gas composition in the adsorption capacities. Finally the capacity of adsorption is also evaluated in the presence of an organic volatile compound (VOC). Activated carbon cloth was chosen to continue with the experiences realised for the adsorption – desorption process. This porous material has shown good adsorption capacities. Furthermore, desorption process can be performed in situ and their implementation in industrial process is more easy. Adsorption-desorption cycles were performed and the possibilities of the material regeneration evaluated. Joule effect was employed in the desorption process in order to reduce the duration of regeneration. First cycles have been accomplished. Results are promising, even if the operational conditions of the process must be optimised.
Purification du biogaz pour sa valorisation énergétique : adsorption de siloxanes sur charbons actifs
Le biogaz issu de la degradation anaerobie de matieres organiques peut remplacer le gaz naturel dans plusieurs applications. Pour une meilleure valorisation energetique du biogaz, ce travail s’interesse a l’elimination des composes organiques volatils du silicium (siloxanes) dans biogaz par l’adsorption sur des materiaux poreux. Trois charbons actifs (CA) commerciaux ont ete utilises pour l’adsorption des siloxanes. Leurs proprietes physicochimiques sont caracterisees par plusieurs techniques. Un CA montre excellent capacite d’adsorption d’octamethylcyclotetrasiloxane (D4) ce qui est bien superieur que l’autre. En presence de la vapeur, les capacites d’adsorption des CA peuvent etre reduites plus ou moins fort dependant de degree d’humidite relative et la presence des sites hydrophiles sur la surface de CA. Ainsi, la capacite des echantillons possedant ces sites specifiques est reduite apres la thermodesorption a cause de la formation des especes non volatiles sur la surface de CA. Tests avec d’autres siloxanes ont montre que le phenomene de polymerisation s’est produit avec de reactivite et de mecanisme different, dependant de la nature du CA et de siloxane. La polymerisation est toujours plus importante pour le CA qui present plus de sites hydrophiles, conduisant egalement a sa plus faible regenerabilite
Numerical Simulation for Natural State of Two-Phase Liquid Dominated Geothermal Reservoir with Steam Cap Underlying Brine Reservoir
Hydrothermal reservoir which liquid-dominated hydrothermal reservoir is a type of geothermal reservoir that most widely used for power plant. The exploitation of mass and heat from the geothermal fluid will decrease the pressure in the reservoir over time. Therefore the pressure drop in the reservoir will have an impact on the formation of boiling zones or boiling will increase. The impacts are an increase in the fraction of steam, dryness, in the reservoir and with good vertical permeability will form a steam cap underlying the brine reservoir. The two- phase liquid dominated reservoir is sensitive to the porosity and difficult to assign average properties of the entire reservoir when there is boiling zone in some area of the reservoir. These paper showed successful development of two-phase liquid dominated geothermal reservoir and discussed the formation of steam cap above brine reservoir through numerical simulation for state natural conditions. The natural state modeling in steam cap shows a match with the conceptual model of the vapor-dominated developed. These paper also proofed the presence of transition zone, boiling zone, between steam cap and brine reservoir.