Experimental Bench-Scale Study of Residual Biomass Syngas Desulfurization Using ZnO-Based Adsorbents

Christian Frilund (Corresponding Author), Pekka Simell, Esa Kurkela, Patrik Eskelinen

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Dry-bed adsorptive desulfurization of biomass-based syngas with a low- to medium sulfur content using ZnO was
studied as an alternative to conventional wet-scrubbing processes for a small- to medium-scale biomass-to-liquid process concept.
Following laboratory-scale long-term H2S breakthrough experiments in a previous study, desulfurization tests were scaled-up to
bench-scale with actual bio-syngas to verify the lab-scale results under more realistic process conditions. A desulfurization unit was
constructed and connected to a steam-blown atmospheric pilot-scale fluidized bed gasifier. Two successful 70+ h test campaigns
were conducted with H2S removal below the breakthrough limit using full-sized ZnO adsorbent particles. Scanning electron
microscopy (SEM), energy-dispersive X-ray spectroscopy elemental analysis, and Brunauer−Emmett−Teller (BET) surface area
characterization of the fresh and spent adsorbent pellets were performed. SEM micrographs displayed the outward enlarging particle
size in the sulfided layer. Characterization showed significant core−shell sulfidation behavior with a few hundred micron-thick
sulfided layer leaving the majority of ZnO unutilized. Adsorbents lost most of their porosity in use, which was evident from BET
surface area results. Simultaneous COS removal was found possible by the hydrolysis reaction to H2S. Furthermore, evidence of
minor chlorine adsorption was found, thus highlighting the need for a dedicated HCl removal step upstream of desulfurization.
Original languageEnglish
Pages (from-to)3326–3335
JournalEnergy & Fuels
Volume34
Issue number3
DOIs
Publication statusPublished - 28 Feb 2020
MoE publication typeA1 Journal article-refereed

Keywords

  • desulfurization
  • biomass
  • gasification
  • zinc oxide
  • H2S

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