Comparison of Adsorption Dynamics in Kinetic and Equilibrium Beds in Hydrogen Ternary System

Abstract

ABSTRACTThe adsorption dynamics of a ternary hydrogen mixture (H2/CH4/CO; 59.3/30.5/10.2 vol%) in a carbon molecular sieve (CMS) bed were compared experimentally and theoretically with fixed beds by using activated carbon, zeolite 5A, and oxidized CMS. The breakthrough experiments were performed in the range of 4–16kgf/cm2 adsorption pressure and 4.5–9.1 LSTP (liter at standard temperature and pressure)/min feed flow rate. In the CMS bed regenerated at high temperature (548 K), the adsorption dynamics were similar to those in the activated carbon bed in terms of both breakthrough curves and temperature excursions due to the pore enlargement of the CMS regenerated at high temperature. Therefore, the effect of kinetic separation on the adsorption dynamics was not observed. However, in the CMS bed regenerated at low temperature (423 K), CH4 showed a breakthrough earlier than CO, owing to the sieving effects on the CMS. and CO showed the wide mass transfer zone. To understand the adsorption characteristics and the thermal effects by the heat of adsorption, a nonisothermal dynamic model incorporating mass, energy, and momentum balances was applied to the adsorption dynamics in the kinetic and equilibrium separation beds. Moreover, the kinetic effects on the adsorption dynamics also were studied by using a constant or variable diffusivity model.