Pelletization of Iron Oxide Based Sorbents for Hydrogen Sulfide Removal

Abstract:

Biogas derived from anaerobic digestion of biological wastes has been extensively used for heating purposes and/or electricity generation. Presence of hydrogen sulfide (H₂S) in biogas affects engine performance adversely, thus reducing H₂S content is a valuable part in practical application before utilizing biogas. Adsorptive separation is very appealing due to being an economical and effective method including the use of iron oxide based adsorbents. Pelletization of iron oxide adsorbents has never been reported among the adsorbents described to date. Therefore, H₂S capture in two iron oxides (ferric oxide (Fe₂O₃) and magnetite (Fe₃O₄)) was experimentally investigated to determine technical feasibility of shaping pellets based on active iron oxide sorbent in removing H₂S from a simulated gas stream (0.35 vol.% H₂S balanced in N₂). Many factors affecting the behavior of gas adsorption such as gas in-flow rate, adsorption temperature, binder loadings and textural characteristics were considered. The pellet strengths were also undertaken using a bulk crushing strength analyzer. The results indicated that higher temperature favors the diffusion of H₂S molecules from the surface into the bulk of iron oxides. The H₂S-sorption capacity of Fe₃O₄ sorbent was higher than that of Fe₂O₃ sorbent corresponding with the different pore volume and surface area in each adsorbent. With the same active Fe₃O₄, the extruded pellet produced with starch binder showed the excellent H₂S uptake and crushing resistance. The higher gas in-flow rate had positive impact to contacting efficiency and mass transfer of solid and gas phase. The adsorbed H₂S gas can be readily desorbed from the pellets with the desorption temperature below 60°C and the H₂S-sorption capacity was consistent over repeated cycles. The pellets can be reused several times for consecutive adsorption/desorption cycles, without loss of performance in a large-scale reactor and therefore represent serious candidates for use in commercial absorbers.

• Periodical: Key Engineering Materials (Volume 751)
• Pages: 449-454
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.751.449
• Online since: August 2017
• Authors: Pathompong Janetaisong, Viset Lailuck, Somsak Supasitmongkol*
• Keywords: Desulfurization, Hydrogen Sulfide, Iron Oxide, Pelletization

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