Biogas purification on Na-X Zeolite: Experimental and numerical results

In the present paper, H2S adsorption from a synthetic biogas mixture in a laboratory–scale fixed bed adsorption column was studied and modelled. Na–X zeolite was used as bed material. Breakthrough and equilibrium data were obtained in a number of experiments carried out under typical operating conditions of industrial applications. Experimental results show that complete saturation of the bed could never be achieved, since outlet H2S concentration approaches an asymptotic value always lower than inlet one as a consequence of catalytic oxidation reactions of hydrogen sulphide. A one-dimensional coupled heat and mass transfer model, based on the “linear driving force” assumption and accounting for both H2S oxidation reaction and zeolite deactivation due to sulfur poisoning, was purposely developed and tailored to match experimental results. Consequently, the assessment of the effects of variation in H2S concentration, adsorption temperature and adsorbent age on the performances of the removal process was carried out.