Floating Membrane Bioreactors with High Gas Hold-Up for Syngas-to-Biomethane Conversion

Konstantinos Chandolias,Enise Pekgenc,Mohammad Taherzadeh

doi:10.3390/en12061046

Konstantinos Chandolias, Enise Pekgenc + Show 1 more

Open Access

https://doi.org/10.3390/en12061046

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Journal: Energies	Publication Date: Mar 18, 2019
Citations: 16	License type: CC BY 4.0

Affiliation: University of Borås, Istanbul Technical University

Abstract

The low gas-to-liquid mass transfer rate is one of the main challenges in syngas biomethanation. In this work, a new concept of the floating membrane system with high gas hold-up was introduced in order to enhance the mass transfer rate of the process. In addition, the effect of the inoculum-to-syngas ratio was investigated. The experiments were conducted at 55 °C with an anaerobic mixed culture in both batch and continuous modes. According to the results from the continuous experiments, the H2 and CO conversion rates in the floating membrane bioreactor were approximately 38% and 28% higher in comparison to the free (suspended) cell bioreactors. The doubling of the thickness of the membrane bed resulted in an increase of the conversion rates of H2 and CO by approximately 6% and 12%, respectively. The highest H2 and CO consumption rates and CH4 production rate recorded were approximately 22 mmol/(L·d), 50 mmol/(L·d), and 34.41 mmol/(L·d), respectively, obtained at the highest inoculum-to-syngas ratio of 0.2 g/mL. To conclude, the use of the floating membrane system enhanced the syngas biomethanation rates, while a thicker membrane bed resulted in even higher syngas conversion rates. Moreover, the increase of the inoculum-to-syngas ratio of up to 0.2 g/mL favored the syngas conversion.

Highlights

Gasification is a thermochemical process which converts biomass into a gaseous mixture, called syngas
A main challenge during syngas fermentation is the low gas-to-liquid mass transfer, which can improved by increasing the gas hold-up inside the liquid medium of bioreactors
The new concept of floating MBR was successfully applied during continuous syngas biomethanation with a mixed culture and thermophilic conditions

Summary

Introduction

Gasification is a thermochemical process which converts biomass into a gaseous mixture, called syngas (mostly CO, H2 , and CO2 ). This gas can be employed for the production of electricity, energy, and transport fuels. Approximately 50% of the generated syngas is converted into. Syngas is considered as a promising vector for heat and power generation [3]. Another promising application of syngas and other industrial off-gases is anaerobic fermentation and conversion into biofuels, alcohols, bioplastics, and value-added chemicals. In particular, is considered as a sustainable alternative to the applications mentioned above [4]

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