In-situ biogas upgrading in thermophilic granular UASB reactor: key factors affecting the hydrogen mass transfer rate

Abstract

Biological biogas upgrading coupling CO with external H to form biomethane opens new avenues for sustainable biofuel production. For developing this technology, efficient H to liquid transfer is fundamental. This study proposes an innovative setup for in-situ biogas upgrading converting the CO in the biogas into CH, via hydrogenotrophic methanogenesis. The setup consisted of a granular reactor connected to a separate chamber, where H was injected. Different packing materials (rashig rings and alumina ceramic sponge) were tested to increase gas-liquid mass transfer. This aspect was optimized by liquid and gas recirculation and chamber configuration. It was shown that by distributing H through a metallic diffuser followed by ceramic sponge in a separate chamber, having a volume of 25% of the reactor, and by applying a mild gas recirculation, CO content in the biogas dropped from 42 to 10% and the final biogas was upgraded from 58 to 82% CH content.

Biogas upgrading and utilization: Current status and perspectives

“…Thus, the aqueous solubility of most gasses is rather low, which limits the gas-liquid mass transfer and hampers the performance of the bioreactor (Tirunehe and Norddahl, 2016). For that reason, the material and type of the module that is used to inject H 2 , the application of gas recirculation flows and the reactor designs are considered as fundamental elements for the implementation of sufficient in-situ biogas upgrading (Bassani et al, 2016). In batch experiments, it was found that the H 2 uptake rate decreased rapidly at CO 2 concentrations < 12% (Agneessens et al, 2017) and the maximum CH 4 content in biogas reached 89% (Mulat et al, 2017).…”

“…In another research performed in upflow anaerobic sludge blanket reactor, hollow fiber membrane was installed in an external degassing unit and the obtained efficiency of the in-situ biogas upgrading reached 94% (Luo et al, 2014). However, as the cost of such membranes has to be considered for full scale applications, other porous devices, such as ceramic sponges, have been proven to benefit the coupling of CO 2 and H 2 and their consequent transformation to CH 4 (Bassani et al, 2016). A comparison of different in-situ configurations is presented in Table 2. 2.2.1.2.…”

“…(3) (Martin et al, 2013) where r t is the H 2 gas-liquid mass transfer rate (L/(L Reactor .day), 22.4 is the corresponding volume that occupies 1 mol of gas at standard condition of temperature and pressure (L/mol), k L a is the gas transfer coefficient (day − 1 ), H 2g is the H 2 concentration in the gas phase (mol/ L), and finally H 2l expresses the dissolved H 2 in the liquid phase (mol/ L). Therefore, it is obvious the H 2 gas-liquid mass transfer rate is proportionally correlated with the k L a, which in turn is dependent on specific operational parameters such as the gas recirculation flow (Guiot et al, 2011;Kougias et al, 2017b), the reactor configuration (Bassani et al, 2016;Kougias et al, 2017b), the installed diffusion device (Bassani et al, 2017;Díaz et al, 2015;Luo and Angelidaki, 2013b) and the stirring intensity Angelidaki, 2013b, 2012). A number of research publications are proposing different novel concepts for increased biomethanation efficiencies.…”

Spatial Distribution and Diverse Metabolic Functions of Lignocellulose-Degrading Uncultured Bacteria as Revealed by Genome-Centric Metagenomics

“…The grass obtained after the separation of the liquid material was processed in order to recover the firmly attached microbes (i.e., sample denoted "FG"), as previously described (37). The grass was washed with basal anaerobic (BA) medium (38) to remove loosely attached microbial cells. After this step, the firmly attached microbes were stripped off by incubating the grass at 4°C in anaerobic conditions with BA medium containing 0.15% Tween 80 and, subsequently, by homogenizing the grass with a VDI-12 homogenizer (2 ϫ 2 min bursts; VWR, Radnor, PA).…”

Anaerobic Process

“…All the enhanced processes showed higher biogas yields and higher destruction of pathogens than conventional processes. Bassani et al (2016) proposed an innovative system for in-situ conversion of carbon dioxide in the biogas into methane. Through liquid and gas recirculation and chamber configuration, gas-liquid mass transfer was increased.…”