Desulfurization of Biomass Syngas Using ZnO-Based Adsorbents: Long-Term Hydrogen Sulfide Breakthrough Experiments

Abstract

Dry-bed adsorptive desulfurization of biomass-based syngas with low to medium sulfur content using ZnO was investigated as an alternative to the conventional wet scrubbing processes. The technical feasibility of ZnO-based desulfurization was studied in laboratory-scale H2S breakthrough experiments. The experiments were set up to utilize realistic H2S concentrations from gasification and therefore long breakthrough times. Experiments were performed in a steam-rich model biosyngas in varying conditions. The long-term breakthrough experiments showed apparent ZnO utilization rates between 10 and 50% in the tested conditions, indicating intraparticle mass-transfer resistances partly due to space velocity and particle size constraints as well as the most likely product-layer resistances as evidenced by the large spent adsorbent surface area decrease. An empirical deactivation model to estimate full breakthrough curves was fitted to the laboratory-scale experimental data. Breakthrough experiment in tar-rich syngas was also performed with the conclusion that ZnO performance is not significantly affected by hydrocarbons despite carbon deposition on the particle surfaces.

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

“…At room temperature, even the poorer performance offered by Fe 2 O 3 pellets prepared according to the method proposed in this study is greater than the ones obtainable by ZnO or SulfaTreat ® pellets in the same operating conditions. Concerning ZnO, a possible explanation could be given reminding that, in many previous investigations, ZnO proved to be kinetically active only at temperatures much higher than the ones here considered [ 42 ]. Another reason could stem from differences in surface area, estimated at 54 m 2 /g for Fe 2 O 3 versus 23 m 2 /g for ZnO pellets.…”

Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H2S Oxidation Rate

“…All of the options mentioned in Table 7 require an oxygen-containing atmosphere with moisture to facilitate the oxidation reaction for improved sulfur capture rate. The equilibrium capture capacity for activated carbons is assessed to be high on a mass-basis relative to other available adsorbents, but volume-based capacity suffers from their inherent low density [48,49]. The adsorption rates exhibited in this study show that H 2 S removal is feasible to high purity levels at industrially relevant conditions with ammonia-enhanced AC, IAC, and DAC.…”

Container-Sized CO2 to Methane: Design, Construction and Catalytic Tests Using Raw Biogas to Biomethane

“…The backup carbon filter could not remove all the bulk sulfur from the biogas to ppb levels required by the Ni catalyst. A potential future improvement could be a sacrificial ZnO adsorbent before the active Ni catalyst, which can reduce the sulfur level to ppb in case of such unforeseen conditions [35,36]. Still, it was surprising to see that the catalyst was active and showing more than 90% CO 2 conversion at all the time.…”