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.

Hydrogen Sulfide Adsorption by Iron Oxides and Their Polymer Composites: A Case-Study Application to Biogas Purification

“…The production of pellets is essential for a simpler execution of the industrial operations in real plants, where the recovery of the sorbent and its further regeneration are at a premium [ 34 ]. A first attempt consisted of realizing a pellet comprising a polybutadiene spherical core coated by a layer of sorbent located only at the surface of such an organic matrix.…”

“…In this regard, some authors tested the use of composites made of polymers as binders for the solid active matrix. In some cases, the resulting pellet was not subject to calcination [ 34 ], while in others the binder underwent thermal dissociation at moderate temperatures in order to reach a good trade-off between mechanical properties and microporosity [ 35 ].…”

Synergic Adsorption of H2S Using High Surface Area Iron Oxide–Carbon Composites at Room Temperature

“…It has been before that Fe 3 O 4 has a better H 2 S uptake performance relative to Fe 2 O 3 , 59 and iron has also been proposed to be used as a successful H 2 S sorbent. 60,61 No iron signal was seen in the XRD pattern of sample CM5 after H 2 S uptake, which also points toward the high reactivity of iron formed in the composite. We see this positive synergy, where the net composite effect is higher than the sum of the individual effects, happen in a relatively short range of iron content on OPC, which happens to be where samples CM4 and CM5 lie.…”

Improving the Quantity and Quality of Biogas Production in Tehran Anaerobic Digestion Power Plant by Application of Materials Recirculation Technique

“…This method showed unsuccessful in this project as it could not lower H2S below 5000ppm so even though this method showed a good result in CH4 content it was rejected from the list of feasible methods for biogas improvement at this large-scale plant. The raise in methane content could be attributed to the influential effect of iron ions on AD process (Park,2013;Wellinger et al, 2013) The 3 rd method is suitable for the treatment of low volumes of biogas with low H2S content as well (Janetaisong et al, 2017). An iron-oxide packed bed reactor was employed as a downstream unit operation for qualitative biogas improvement and showed almost the same performance as the method 2 hence, it was concluded to ignore it for this AD plant.…”