Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H<sub>2</sub>S Oxidation Rate
Its relatively low cost and high surface area makes activated carbon an ideal adsorbent candidate for H<sub>2</sub>S removal. However, physical adsorption of H<sub>2</sub>S is not very effective; therefore, methods to facilitate reactive H<sub>2</sub>S oxidation o...
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doaj-f01aff00cd3b45c98f22d5a7b2d9557f2021-05-31T23:42:26ZengMDPI AGChemEngineering2305-70842021-05-015232310.3390/chemengineering5020023Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H<sub>2</sub>S Oxidation RateChristian Frilund0Ilkka Hiltunen1Pekka Simell2VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 Espoo, FinlandVTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 Espoo, FinlandVTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 Espoo, FinlandIts relatively low cost and high surface area makes activated carbon an ideal adsorbent candidate for H<sub>2</sub>S removal. However, physical adsorption of H<sub>2</sub>S is not very effective; therefore, methods to facilitate reactive H<sub>2</sub>S oxidation on carbons are of interest. The performance of H<sub>2</sub>S removal of non-impregnated, impregnated, and doped activated carbon in low-temperature syngas was evaluated in fixed-bed breakthrough tests. The importance of oxygen content and relative humidity was established for reactive H<sub>2</sub>S removal. Impregnates especially improved the adsorption rate compared to non-impregnated carbons. Non-impregnated carbons could however retain a high capture capacity with sufficient contact time. In a relative performance test, the best performance was achieved by doped activated carbon, 320 mg g<sup>−1</sup>. Ammonia in syngas was found to significantly improve the adsorption rate of non-impregnated activated carbon. A small quantity of ammonia was consumed by the carbon bed, suggesting that ammonia is a reactant. Finally, to validate ammonia-enhanced desulfurization, bench-scale experiments were performed in biomass-based gasification syngas. The results show that when the ammonia concentration in syngas was in the tens of ppm range, 40–160 ppm H<sub>2</sub>S oxidation proceeded rapidly. Ammonia-enhanced oxidation allows utilization of cheaper non-impregnated activated carbons by in situ improvement of the adsorption kinetics. Ammonia enhancement is therefore established as a viable method for achieving high-capacity H<sub>2</sub>S removal with unmodified activated carbons.https://www.mdpi.com/2305-7084/5/2/23syngas desulfurizationactivated carbonhydrogen sulfideH<sub>2</sub>S oxidationammonia |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Christian Frilund Ilkka Hiltunen Pekka Simell |
spellingShingle |
Christian Frilund Ilkka Hiltunen Pekka Simell Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H<sub>2</sub>S Oxidation Rate ChemEngineering syngas desulfurization activated carbon hydrogen sulfide H<sub>2</sub>S oxidation ammonia |
author_facet |
Christian Frilund Ilkka Hiltunen Pekka Simell |
author_sort |
Christian Frilund |
title |
Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H<sub>2</sub>S Oxidation Rate |
title_short |
Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H<sub>2</sub>S Oxidation Rate |
title_full |
Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H<sub>2</sub>S Oxidation Rate |
title_fullStr |
Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H<sub>2</sub>S Oxidation Rate |
title_full_unstemmed |
Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H<sub>2</sub>S Oxidation Rate |
title_sort |
activated carbons for syngas desulfurization: evaluating approaches for enhancing low-temperature h<sub>2</sub>s oxidation rate |
publisher |
MDPI AG |
series |
ChemEngineering |
issn |
2305-7084 |
publishDate |
2021-05-01 |
description |
Its relatively low cost and high surface area makes activated carbon an ideal adsorbent candidate for H<sub>2</sub>S removal. However, physical adsorption of H<sub>2</sub>S is not very effective; therefore, methods to facilitate reactive H<sub>2</sub>S oxidation on carbons are of interest. The performance of H<sub>2</sub>S removal of non-impregnated, impregnated, and doped activated carbon in low-temperature syngas was evaluated in fixed-bed breakthrough tests. The importance of oxygen content and relative humidity was established for reactive H<sub>2</sub>S removal. Impregnates especially improved the adsorption rate compared to non-impregnated carbons. Non-impregnated carbons could however retain a high capture capacity with sufficient contact time. In a relative performance test, the best performance was achieved by doped activated carbon, 320 mg g<sup>−1</sup>. Ammonia in syngas was found to significantly improve the adsorption rate of non-impregnated activated carbon. A small quantity of ammonia was consumed by the carbon bed, suggesting that ammonia is a reactant. Finally, to validate ammonia-enhanced desulfurization, bench-scale experiments were performed in biomass-based gasification syngas. The results show that when the ammonia concentration in syngas was in the tens of ppm range, 40–160 ppm H<sub>2</sub>S oxidation proceeded rapidly. Ammonia-enhanced oxidation allows utilization of cheaper non-impregnated activated carbons by in situ improvement of the adsorption kinetics. Ammonia enhancement is therefore established as a viable method for achieving high-capacity H<sub>2</sub>S removal with unmodified activated carbons. |
topic |
syngas desulfurization activated carbon hydrogen sulfide H<sub>2</sub>S oxidation ammonia |
url |
https://www.mdpi.com/2305-7084/5/2/23 |
work_keys_str_mv |
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1721416888980865024 |