Integration of a water scrubbing technique and two-stage pressurized anaerobic digestion in one process

Two-stage pressurized anaerobic digestion is a promising technology. This technology integrates in one process biogas production with upgrading and pressure boosting for grid injection. To investigate whether the efficiency of this novel system could be further increased, a water scrubbing system was integrated into the methanogensis step. Therefore, six leach-bed reactors were used for hydrolysis/acidification and a 30-L pressurized anaerobic filter operated at 9 bar was adopted for acetogenesis/methanogenesis. The fermentation liquid of the pressurized anaerobic filter was circulated periodically via a flash tank, operating at atmospheric pressure. Due to the pressure drop, part of dissolved carbon dioxide was released from the liquid phase into the flash tank. The depressurized fermentation liquid was then recycled to the pressurized reactor. Three different flow rates (0 L·day$^{-1}$, 20 L·day$^{-1}$ and 40 L·day$^{-1}$) were tested with three repetitions. As the daily recycled flashed liquid flow was increased from 0 to 40 L, six times as much as the daily feeding, the methane content in the biogas increased from 75 molar percent (mol%) to 87 mol%. The pH value of the substrate in the methane reactor rose simultaneously from 6.5 to 6.7. The experimental data were verified by calculation

Modelingof Acetylene Pyrolysis under Steel Vacuum Carburizing Conditions in a Tubular Flow Reactor

In the present work, the pyrolysis of acetylene was studied under steel vacuumcarburizing conditions in a tubular flow reactor. The pyrolysis temperature ranged from650 °C to 1050 °C. The partial pressure of acetylene in the feed mixture was 10 and 20mbar, respectively, while the rest of the mixture consisted of nitrogen. The total pressureof the mixture was 1.6 bar. A kinetic mechanism which consists of seven species andnine reactions has been used in the commercial computational fluid dynamics (CFD)software Fluent. The species transport and reaction model of Fluent was used in thesimulations. A comparison of simulated and experimental results is presented in thispaper

Renewable Power-to-Gas: A technological and economic review

The Power-to-Gas (PtG) process chain could play a significant role in the future energy system. Renewable electric energy can be transformed into storable methane via electrolysis and subsequent methanation. This article compares the available electrolysis and methanation technologies with respect to the stringent requirements of the PtG chain such as low CAPEX, high efficiency, and high flexibility. Three water electrolysis technologies are considered: alkaline electrolysis, PEM electrolysis, and solid oxide electrolysis. Alkaline electrolysis is currently the cheapest technology; however, in the future PEM electrolysis could be better suited for the PtG process chain. Solid oxide electrolysis could also be an option in future, especially if heat sources are available. Several different reactor concepts can be used for the methanation reaction. For catalytic methanation, typically fixed-bed reactors are used; however, novel reactor concepts such as three-phase methanation and micro reactors are currently under development. Another approach is the biochemical conversion. The bioprocess takes place in aqueous solutions and close to ambient temperatures. Finally, the whole process chain is discussed. Critical aspects of the PtG process are the availability of CO₂ sources, the dynamic behaviour of the individual process steps, and especially the economics as well as the efficiency

Integration of a Water Scrubbing Technique and Two-Stage Pressurized Anaerobic Digestion in One Process

Two-stage pressurized anaerobic digestion is a promising technology. This technology integrates in one process biogas production with upgrading and pressure boosting for grid injection. To investigate whether the efficiency of this novel system could be further increased, a water scrubbing system was integrated into the methanogensis step. Therefore, six leach-bed reactors were used for hydrolysis/acidification and a 30-L pressurized anaerobic filter operated at 9 bar was adopted for acetogenesis/methanogenesis. The fermentation liquid of the pressurized anaerobic filter was circulated periodically via a flash tank, operating at atmospheric pressure. Due to the pressure drop, part of dissolved carbon dioxide was released from the liquid phase into the flash tank. The depressurized fermentation liquid was then recycled to the pressurized reactor. Three different flow rates (0 L·day−1, 20 L·day−1 and 40 L·day−1) were tested with three repetitions. As the daily recycled flashed liquid flow was increased from 0 to 40 L, six times as much as the daily feeding, the methane content in the biogas increased from 75 molar percent (mol%) to 87 mol%. The pH value of the substrate in the methane reactor rose simultaneously from 6.5 to 6.7. The experimental data were verified by calculation

Evaluation of Organic and Ionic Liquids for Three-Phase Methanation and Biogas Purification Processes

Three ionic liquids {butyl-trimethyl-ammonium bis­(trifluoromethylsulfonyl)­imide [N₁₁₁₄]­[BTA], 1-methyl-1-propyl-piperidinium bis­(trifluoromethylsulfonyl)­imide [PMPip]­[BTA], and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMIM]­[Tf]} and two heat-transfer oils [dibenzyltoluene (DBT) and polydimethylsiloxane (trade name X-BF)] were evaluated for use in the three-phase methanation and the biogas purification processes. The density, viscosity, and surface tension of these liquids were measured and modeled as a function of the temperature. The solubilities of H₂, CO, CO₂, and CH₄ in these five liquids were also obtained under different pressures and temperatures. Additionally, the criteria required for each of the two processes considered were identified: the three-phase methanation process requires a thermally stable liquid with a low vapor pressure and a high H₂, CO₂ and CO solubility, while the biogas purification process requires a highly selective CO₂ solubility liquid at ambient temperature. From the evaluation of both the experimental data and the process requirements, the most suitable liquid for each of the aforementioned processes was identified. For the three-phase methanation process, the two ionic liquids [N₁₁₁₄]­[BTA] and [PMPip]­[BTA] and the two heat-transfer oils DBT and X-BF met the minimum requirements, while [EMIM]­[Tf] showed promising potential for the biogas purification process