KINETICS OF HYDROGEN SEPARATION FROM REFINERY OFF-GAS

Abstract

Adsorption and desorption kinetic curves for equimolar hydrogen – methane mixture on molecular sieve type 5A were experimentally obtained for pressure range 0.122 – 3.546 MPa.The linear driving force rate expression model was used to simulate the dynamic of adsorption and desorption in adiabatic fixed bed adsorber. The model takes into account the interference effects for non-linear isotherms and non-isothermal system. The equations were solved by backward finite difference method with a fixed gridding technique. The individual mass transfer parameters were obtained by matching the theoretical with the experimental data and found to be equal to 8.510 s-1 and 0.783 s-1 for hydrogen and methane, respectively.The predicted effluent histories were shown to be in close agreement with the experimental data for the system. The lowest relative capacity of the bed for methane was almost approximately 95% of that predicted equilibrium capacity. The predicted temperature profiles tracked the experimental temperature data points, but with higher values. Furthermore, the maximum temperature increasing was observed for the adsorption of methane onto 5A molecular sieve at 35 atmospheres and was recorded as 44 K.