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.
Thermal Behavior of Activated Carbon Cloths Heated by Joule Effect
Activated carbon cloths (ACC) are promising adsorbents for the treatment of air loaded with volatile organic compounds (VOC). Their characteristics and properties allow them particularly high adsorption capacities and useful handling. Moreover, the Joule effect regeneration of these media may be used as a regeneration process. These peculiarities make it possible to design and size ACC filters for a wide range of industrial applications: low VOC concentration and flow for indoor air quality as well as high concentration and flow in some industrial effluents. Hence, innovating reactors could be equipped with such an adsorption-desorption process which permit us to recover the condensed compounds. The heating of ACC by Joule effect (between 20 and 250°C) is generally highly homogeneous, and the spatial distribution of the temperatures is directly connected to the activation level distribution in the material. A characterization method and a modeling approach are proposed to describe the ACC thermal behavior and to compare and select the best media in term of regeneration process. This allows sizing of future industrial processes.
Mathematical Modeling of Scour and Deposition
Electronic computers are opening up the field of sedimentation engineering by permitting the analysis of problems which heretofore have required too much time and effort. Movable stream bed profiles are being calculated in addition to water surface profiles. The initial gradation of sediment material in the stream bed may be prescribed to facilitate the calculation of an armor layer. This gradation is continually changed by the computer program in response to sediment particles being deposited on the stream bed and material on the stream bed being removed to satisfy transport capacity. Hydraulic sorting of sediment by grain size is accomodated. The stream bed does not have to be represented by a single grain size. Retardance of motion because of armor layer is calculated.