Charge characteristics of adsorbed natural gas storage system based on MAXSORB III

The present work deals with Natural gas (methane) adsorption onto super activated carbon (MAXSORB III) and graphite mixture in order to establish the reliability of this phenomenon as a valuable storage technique of natural gas. The objective of the subject work is to optimize different design and operating parameters of the adsorbed natural gas (ANG) system subjected to variable charge and the boundary conditions. The model duly considers the real gas properties of methane and variation of adsorbed phase properties as well as the heat of adsorption with adsorbate uptake. The storage capacities, storage efficiency as well as the filling time of activated carbon bed are studied for both constant inlet flow and constant inlet pressure charging conditions. The possibility of controlling length to width ratio (L/D ratio ranging from 0.35 to 7.8) is presented which will enable to optimize the geometry of storage tank for optimal storage efficiency. The effects of variation in inlet flow rates and variation in boundary conditions (natural convection, adiabatic wall, forced convection and constant wall temperature) on storage capacity as a function of other design and operating parameters are presented. From the study it is found that for suitable L/D ratio and external heat transfer coefficient it is possible to achieve a storage capacity of 150 V/V for constant pressure charging condition within 200 s. Addition of graphite powder for thermal enhancement of system resulted in 22%-27% (for different L/D ratios) rise in storage efficiency for model subjected to constant pressure charging and forced convection whereas 41.8%-50.4% rise in storage efficiency for model subjected to constant inlet flow and forced convection.