Development of a biogas production and purification process using promoted gas hydrate formation - A feasibility study

This work proves the feasibility of an integrated process chain, which combines a continuous biogas production unit and a pioneering gas hydrate separation technique to advance biogas utilization. First, a fermentation was launched and optimized to produce biogas. Therefore, a mixed microbiological culture from sewage sludge of a nearby waste water clarification plant was cultivated by feeding a nutrient solution based on saccharose. The second experimental series had the intention to find an optimal hydrate promoter system with a maximized separation factor. To guarantee moderate operating conditions and fast hydrate formation, thermodynamic and kinetic promoters were combined. Tetrahydrofuran was used as thermodynamic, sodium dodecyl sulfate as kinetic promoter. To effectuate higher separation factors, additional substances were tested. One approach deals with additional surfactants of varying HLB numbers. The alternative attempt takes advantage of the properties of physical absorbents. To find an optimal promoter and separation medium several systems were tested. Both experimental series were recombined in a continuous biogas production and upgrading process and separation efficiency was determined to show proof of concept. In a closing experimental series an adapted McCabe-Thiele-diagram was constructed to determine the necessary stage number with the aim to reach a purity within industrial specifications. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.