Influence of liquid-phase hydrogen on dark fermentation by Thermotoga neapolitana. (September 2019)

• Record Type: Journal Article
• Authors: Dreschke, Gilbert; Papirio, Stefano; Lens, Piet N.L.; Esposito, Giovanni
• Is Part Of: Renewable energy. Volume 140(2019)
• Page Start: 354
• Page End: 360
• Publication Date: 2019-09
• Subjects: Thermotoga neapolitana -- Hyperthermophilic -- Dark fermentation -- Gas recirculation -- Hydrogen inhibition -- Supersaturation; Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.renene.2019.02.126
• Languages: English
• ISSNs: 0960-1481

Abstract

Abstract: Hydrogen is a strong inhibitor of dark fermentation. We aimed at directly correlating the hydrogen production by Thermotoga neapolitana with the supersaturation of hydrogen in the liquid phase (H2aq ), which is often disregarded. Different agitation speeds, biogas recirculation and bubble induction by AnoxK™ K1 carrier were tested to prevent the supersaturation of H2aq . At 100 rpm agitation, the H2aq was 29.7 (±1.4) mL/L, which is 3-times higher than 9.7 mL/L, i.e. the equilibrium concentration given by Henry's law. Increasing the agitation speed up to 600 rpm reduced the H2aq until 8.5 (±0.1) mL/L in 2 h and increased the hydrogen production rate (HPR) from 39 (±2) mL/L/h at 0 rpm to 198 (±4) mL/L/h at 600 rpm. Similar to 600 rpm, biogas recirculation and the presence of K1 carrier at 200 rpm maintained the H2aq below the equilibrium concentration. This study demonstrates the reciprocal influence of HPR and H2aq and revealed an inverse nonlinear correlation between the two parameters. Therefore, we conclude that an adequate gas-liquid mass transfer, efficiently provided by biogas recirculation or the presence of solid materials (e.g. a biomass carrier), is essential to remove H2 from the liquid phase and prevent H2 supersaturation. Highlights: An inverse nonlinear correlation was found between HPR and H2aq . The equilibrium between H2aq and HPR depends on the gas-liquid mass transfer. Agitation at 100 rpm resulted in a supersaturation of H2aq up to 29.7 (±1.4) mL/L. Gas recirculation and K1 carrier led to the lowest H2aq, i.e. 5.8 (±0.5) mL/L. K1 carrier induced H2 bubble formation reducing H2aq by about 50% in the first 15 h.