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The path to European climate neutrality by 2050 will require comprehensive changes in all areas of life. For large industries such as steelworks, this results in the need for climate-friendly technologies. However, the age structure of existing steelworks makes transitional solutions such as carbon capture, utilization and storage (CCUS) necessary as short-term measures. Hence, a purposeful option is the integration of technical syntheses such as methanation into the overall process. This work summarizes hydrogen-intensified methanation experiments with synthetic steel gases in the novel additively manufactured reactor 'ADDmeth1'. The studies include steady-state operating points at various reactor loads. Blast furnace gas (BFG), basic oxygen furnace gas (BOFG) and three mixtures of these two gases serve as carbon sources. The methanation achieved methane yields of 93.5% for BFG and 95.0% for BOFG in the one-stage once-through setup. The results suggest a kinetic limitation in the case of BFG methanation, while an equilibrium limitation is likely for BOFG. There is a smooth transition in all respects between the two extreme cases. The reaction channel inlet temperature ϑ i n showed a large influence on the reactor ignition behavior. By falling below the threshold value, a blow-off occurred during experimental operation. By means of a simulation model, practical operating maps were created which characterize permissible operating ranges for ϑ i n as a function of the gas composition and the reactor load. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CO 2 methanation framework on Ni and Cu doped metakaolin is summarized. • The effect of Ni and Cu on metakaolin is revealed via electron structure analysis. • The introduction of Ni and Cu greatly improves the metakaolin surface activity. • The active sites for CO 2 methanation are identified as the O atoms near Cu and Ni. • The key step in the CO 2 methanation reaction is the second dehydration reaction. In this study, the adsorption and methanation mechanisms of CO 2 on the Ni and Cu doped metakaolin surface are investigated by density functional theory (DFT). The results indicate that the presence of Ni and Cu changes the chemical environment of the metakaolin surface and enhances the reactivity. H 2 and CO 2 preferentially react with O atoms in the vicinity of the Cu and Ni atoms. A complete CO 2 methanation network is established, in which two COH-Paths have the lowest energy barriers and the key reaction steps are the second dehydration reaction (COH* + H* → CH* + H 2 O). This theoretical study clarifies the effects of Ni and Cu as active components on the metakaolin catalysts at the electronic level, identifies the special role of the Ni and Cu doped metakaolin in the methanation reaction, and further complements the detailed mechanism of CO 2 methanation. This work unveils the intrinsic CO 2 methanation mechanism over the modified metakaolin surface for the first time, provides important theoretical guidance for the development of highly efficient carbon capture adsorbents and carbon dioxide methanation catalysts, which is of positive significance for socio-economic development and environmental protection. [ABSTRACT FROM AUTHOR]

Power-to-X systems which convert electrical energy into stable chemical energy carriers are a promising solution to the long-term energy storage challenge posed by the increasing market penetration of intermittent renewable power sources. In this paper, a systematic and flexible method for optimizing the steady-state operating conditions of Power-to-Methane (PtM) plant concepts is showcased and applied to perform a comparative assessment of a multitude of PtM process chains. As opposed to existing studies, a large number of comprehensive PtM system models integrating multiple carbon capture technologies and Solid Oxide Electrolysis Cell (SOEC) stacks are optimized. Using detailed 3D SOEC stack simulations and interpolation-based model reduction, the performance of electrolyte-supported (ESC) and cathode-supported cells (CSC) integrated in a variety of PtM systems with air and pure oxygen sweep gas concepts is compared. A total of 20 plant concepts using different combinations of carbon capture (biomass gasification, amine gas treatment, direct air capture) and methanation (fixed-bed, slurry bubble column) technologies are investigated using the pinch method. The results demonstrate that thermal integration of the carbon capture process in PtM systems can raise the total efficiency of the process chains by up to 10.9% for direct air capture and 10.4% for amine gas treatment, with the plants reaching high heating value efficiencies of 70.2% and 84.6% respectively. Endothermic, high temperature operation of SOECs is shown to consistently yield the highest PtM efficiencies due to the minimization of cell overpotentials and power inverter losses. Conversely, exothermic operation of SOECs thermally integrated with energy-intensive carbon capture processes is shown to significantly lower capital expenditures (CAPEX) while incurring an efficiency loss lower than 1% compared to thermoneutral operation. [Display omitted] • 20 PtM plant concepts with carbon capture technologies are comparatively assessed. • SOEC stack performance maps used in system simulation through model reduction. • Integration of carbon capture in Power-to-Methane increases total process efficiency. • Exothermic SOECs coupled to direct air capture reduces CAPEX without efficiency loss. [ABSTRACT FROM AUTHOR]

The methanation process is discussed as one way to chemically store renewable energy in a future energy system. An important criterion for its application is the availability of compact, low-cost reactor concepts with high conversion rates for decentralized use where the renewable energy is produced. Current research focuses on the maximization of the methane yield through improved temperature control of the exothermic reaction, which attempts to avoid both kinetic and thermodynamic limitations. In this context, traditional manufacturing methods limit the design options of the reactor and thus the temperature control possibilities. The use of additive manufacturing methods removes this restriction and creates new freedom in the design process. This paper formulates the requirements for a novel methanation reactor and presents their implementation to a highly innovative reactor concept called 'ADDmeth'. By using a conical reaction channel expanding from Ø 8 to 32 mm, three twisted, expanding heat pipes (Ø 8 mm in evaporation zone, Ø 12 mm in condenser zone) and a lattice structure for feed gas preheating and mechanical stabilization of the reactor, the design explicitly exploits the advantages of additive manufacturing. The reactor is very compact with a specific mass of 0.36 kg/kW and has a high share of functional volume of 52%. The reactor development was accompanied by tensile tests of additively manufactured samples with the used material 1.4404 (316 L), strength calculations for stability verification and feasibility studies on the printability of fine structures. Ultimate tensile strengths of up to 750 N/mm2 (at room temperature) and sufficiently high safety factors of the pressure-loaded structures against yielding were determined. Finally, the paper presents the manufactured bench-scale reactor ADDmeth1 and its implementation. [ABSTRACT FROM AUTHOR]

The methanation process is discussed as one way to chemically store renewable energy in a future energy system. An important criterion for its application is the availability of compact, low-cost reactor concepts with high conversion rates for decentralized use where the renewable energy is produced. Current research focuses on the maximization of the methane yield through improved temperature control of the exothermic reaction, which attempts to avoid both kinetic and thermodynamic limitations. In this context, traditional manufacturing methods limit the design options of the reactor and thus the temperature control possibilities. The use of additive manufacturing methods removes this restriction and creates new freedom in the design process. This paper formulates the requirements for a novel methanation reactor and presents their implementation to a highly innovative reactor concept called ‘ADDmeth’. By using a conical reaction channel expanding from Ø 8 to 32 mm, three twisted, expanding heat pipes (Ø 8 mm in evaporation zone, Ø 12 mm in condenser zone) and a lattice structure for feed gas preheating and mechanical stabilization of the reactor, the design explicitly exploits the advantages of additive manufacturing. The reactor is very compact with a specific mass of 0.36 kg/kW and has a high share of functional volume of 52%. The reactor development was accompanied by tensile tests of additively manufactured samples with the used material 1.4404 (316 L), strength calculations for stability verification and feasibility studies on the printability of fine structures. Ultimate tensile strengths of up to 750 N/mm2 (at room temperature) and sufficiently high safety factors of the pressure-loaded structures against yielding were determined. Finally, the paper presents the manufactured bench-scale reactor ADDmeth1 and its implementation.

The direct methanation of biogas using hydrogen from electrolysis is a promising pathway for seasonal storage of renewables in the natural gas network. It offers particular advantages over the methanation of carbon dioxide separated from biogas, as it eliminates a costly and unnecessary carbon dioxide separation step. The key implementation challenges facing direct methanation of biogas are reviewed here: 1) treatment of biogas impurities; 2) competing reactor concepts for methanation; and 3) competing process concepts for final upgrading. For each of these three aspects, the state of the art is reviewed, focusing especially on results which have been validated at a high Technology Readiness Level (TRL) at recent long-duration demonstrations. The different technology solutions have advantages and disadvantages which may fit best to different technical and economic boundary conditions, which are discussed. As a final outlook, TRL 8 demo plants will be necessary to show the full potential of these systems, and to obtain consistent operation data to allow a cost comparison.

Reactor simulations can reduce the effort when designing fixed‐bed reactors for methanation processes. Several microkinetic models were developed under a variety of operating conditions. However, most production‐scale fixed‐bed methanation processes exceed the temperature range in which these kinetic models were obtained. In addition, heat and mass transport limitations strongly influence the reaction kinetics. In this work, microkinetic rate equations for CO and CO2 methanation were analyzed with respect to their suitability for high‐temperature, pseudohomogeneous reactor modeling. The best‐suited kinetic model was fitted to the operating conditions and validated by means of CFD simulations. It is shown that the simulations match the experimental data for various operating conditions. [ABSTRACT FROM AUTHOR]

The by-product gases from the blast furnace and converter of an integrated steelworks highly contribute to today’s global CO2 emissions. Therefore, the steel industry is working on solutions to utilise these gases as a carbon source for product synthesis in order to reduce the amount of CO2 that is released into the environment. One possibility is the conversion of CO2 and CO to synthetic natural gas through methanation. This process is currently extensively researched, as the synthetic natural gas can be directly utilised in the integrated steelworks again, substituting for natural gas. This work addresses the in situ methanation of real steelworks gases in a lab-scaled, three-stage reactor setup, whereby the by-product gases are directly bottled at an integrated steel plant during normal operation, and are not further treated, i.e., by a CO2 separation step. Therefore, high shares of nitrogen are present in the feed gas for the methanation. Furthermore, due to the catalyst poisons present in the only pre-cleaned steelworks gases, an additional gas-cleaning step based on CuO-coated activated carbon is implemented to prevent an instant catalyst deactivation. Results show that, with the filter included, the steady state methanation of real blast furnace and converter gases can be performed without any noticeable deactivation in the catalyst performance.

The energy supply in Austria is significantly based on fossil natural gas. Due to the necessary decarbonization of the heat and energy sector, a switch to a green substitute is necessary to limit CO2 emissions. Especially innovative concepts such as power-to-gas establish the connection between the storage of volatile renewable energy and its conversion into green gases. In this paper, different methanation strategies are applied on syngas from biomass gasification. The investigated syngas compositions range from traditional steam gasification, sorption-enhanced reforming to the innovative CO2 gasification. As the producer gases show different compositions regarding the H2/COx ratio, three possible methanation strategies (direct, sub-stoichiometric and over-stoichiometric methanation) are defined and assessed with technological evaluation tools for possible future large-scale set-ups consisting of a gasification, an electrolysis and a methanation unit. Due to its relative high share of hydrogen and the high technical maturity of this gasification mode, syngas from steam gasification represents the most promising gas composition for downstream methanation. Sub-stoichiometric operation of this syngas with limited H2 dosage represents an attractive methanation strategy since the hydrogen utilization is optimized. The overall efficiency of the sub-stoichiometric methanation lies at 59.9%. Determined by laboratory methanation experiments, a share of nearly 17 mol.% of CO2 needs to be separated to make injection into the natural gas grid possible. A technical feasible alternative, avoiding possible carbon formation in the methanation reactor, is the direct methanation of sorption-enhanced reforming syngas, with an overall process efficiency in large-scale applications of 55.9%.

Power to gas is a way to convert surplus electricity available on the grid (that might come from renewable sources like solar or wind) and store it as methane. It is also a way to valorize carbon dioxide and reduce CO2 emissions into the atmosphere. At the heart of the process, the methanation reaction has to achieve high-performance conversion in a completely dynamic mode of operation. This mode of operation—linked to the fluctuations of available power on the grid, and the possible thermal runaway of the reactor due to the exothermic nature of the methanation reaction—means that special care is needed in the design of the reactor as well as its control. The reactor, which might be catalytic fixed-bed, should also restart quickly after an idle period. Start-up requires the reactor temperature to be sufficiently high to ignite the reaction. In this paper, the intermittent operation of a fixed-bed methanation reactor is studied. A mathematical model is developed in order to simulate successive gas shutdowns and reinjections. It is examined as well if the reactor is able to restart spontaneously (i.e. with no external heating, but utilizing thermal inertia and the exothermicity of the reaction), when reactants are reinjected after an idle phase. A relation is found between the respective durations of spontaneous restart and idle phase, which can be used to evaluate whether using an external heat source is preferable to relying on spontaneous restart. [ABSTRACT FROM AUTHOR]

Highlights • Catalytic metals, in combination with alkaline adsorbents and various carriers were evaluated for CO 2 capture and conversion to CH 4. • Ru,"NaO"/Al 2 O 3 is the best combination for capturing CO 2 from an O 2 -containng flue gas followed hydrogenation to CH 4. • Formation of inactive NiO, from the O 2 -containing flue gas capture step, does not form CH 4 during hydrogenation. Abstract Dual Function Materials (DFM) capture CO 2 from flue gas followed by catalytic conversion to methane all at 320 °C using renewable H 2. DFM is composed of a catalytic metal intimately in contact with alkaline metal oxides supported on high surface area carriers. The catalyst is required to methanate the adsorbed CO 2 after the capture step is carried out in an O 2 -and steam-containing flue gas. Ruthenium, Rhodium and Nickel are known CO 2 methanation catalysts provided they are in the reduced state. Ni is a preferred methanation catalyst based on price and activity, however, its inability to be reduced to its active state during the DFM process (capture and hydrogenation at 320 °C) was compared with Ru and Rh as methanation candidates. The performance of a variety of alkaline adsorbents was also studied and the strengths and weaknesses of candidate catalysts and adsorbents were evaluated. All samples were tested in a fixed bed reactor to quantify the extent and rate of methane generation. Complementing fixed bed testing, thermogravimetric analysis (TGA) was used to evaluate the extent of CO 2 adsorption and rate of catalytic methanation. Pre-reduced (at 650 °C) Ni-containing DFM is highly active for CO 2 methanation. However, the hydrogenation with 15% H 2 /N 2 is completely inactive after exposure to O 2 and steam, in a flue gas simulation, during the CO 2 capture step at 320 °C. Rh and Ru DFMs were effective methanation catalysts with Ru being superior based on capture capacity, hydrogenation rate and price. In contrast to Ni – containing DFM, Ru remained active towards methanation even after exposure to flue gas simulation. Alkaline adsorbents ("Na 2 O", CaO, "K 2 O" and MgO) in combination with reduced Ru were tested for adsorption and methanation. Ru – "Na 2 O"/Al 2 O 3 DFMs showed the highest rates for methanation although CaO is also a reasonable candidate. To date, we have demonstrated that γ-Al 2 O 3 is the most suitable carrier for DFM application relative to other materials studied. [ABSTRACT FROM AUTHOR]

• Catalytic direct methanation of biogas was demonstrated with real biogas. • Stable operation of the fluidised bed methanation for over 1100 h. • Biomethane with an average methane yield of 96% was injected into the gas grid. • Slow deactivation by organic sulphur compounds was identified and solved. • Experimental results were in accordance with results from a rate-based model. The catalytic direct methanation of biogas to produce biomethane was conducted in a pilot plant with real biogas from a biogas plant in Zurich. Stable operation of the methanation system including a bubbling fluidised bed could be demonstrated for over 1100 h of regular operation with subsequent injection into the gas grid. An average methane yield of 96% was reached. During the long-duration experiment, the slow deactivation process was monitored and found to be only moderate. Organic sulphur compounds could be identified as the main source of deactivation. However, deactivation from coking could not be fully excluded. With appropriate measures in the gas cleaning unit, so that no sulphur compounds were measured subsequently (limit of detection: <0.05 ppm of relevant components), the yield reduction went close to zero. Additionally, experimental results were compared to simulation results from a rate-based model presented elsewhere. Model predictions and experimental results are in accordance. The kinetics used in the rate-based model allowed a correct prediction of the optimum reaction temperature found by experimental results. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Literature review on recent demonstration projects concerning structured and micro-structured reactors. • Novel and innovative integration of heat pipes in a structured reactor for methanation. • Extensive experimental work and proof-of-concept. • Grid-injectable SNG in lab-scale two-stage experimental setup. Abstract Establishing the power-to-gas process as a suitable energy storage in future energy systems requires process simplification in order to make it competitive. An intensified methanation reactor concept could contribute to this overall goal. The present work suggests a new catalytic methanation reactor with heat pipe integration into a structured reactor. This approach benefits from the highly industrial maturity of the methanation process and simultaneously addresses the requirements of new applications in power-to-gas processes. The concept comprises a metallic body, which is perforated by channels for internal gas preheating, reaction channels and spaces for the incorporation of heat pipes. Calculation of the radial temperature profiles provided the limits for the channel geometry. Three layers of internal manifolds at different heights distribute, collect and divert the gas. Heating cartridges integrated at the bottom of the reactor enable rapid start up from cold conditions. The metallic block structure facilitates the sealing of the pressurized reaction space and the scaling. First experiments with a 5 kW prototype prove that the maximum temperature is kept more than 100 K below calculated adiabatic synthesis temperatures. Furthermore, the integration in a lab-scale two-stage test rig with intermediate water removal demonstrates the Substitute Natural Gas (SNG) production with grid-injectable quality. [ABSTRACT FROM AUTHOR]

Direct methanation of biogas is a promising application of the Power-to-Gas concept, since up to 80% more methane can be produced in comparison to conventional biogas upgrading methods. Six different processes, in which a bubbling fluidized bed or a fixed bed technology serves as the main reactor, were designed, simulated in detail and evaluated in terms of technical feasibility and product gas quality. Both reactor types showed the same chemical performance, since they are both restricted by kinetic and thermodynamic effects. However, the cooled fixed bed reactor requires about three times more catalyst mass than the bubbling fluidized bed. Both methanation technologies did not reach Swiss or German high calorific gas grid requirements in one step. Further upgrading units are necessary which were often not considered in previous literature. Hence, the technological effort for biogas upgrading is higher than often stated in literature. With a subsequent second-stage fixed bed or a gas separation membrane, every process considered reaches the required product gas quality. It is more challenging to fall below the maximum limit of hydrogen (2 vol-%) than to reach the mandatory methane content for grid injection. The electrolysis clearly dominates the power consumption in all processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The tandem hydrotreatment process was initially proposed to produce biomethane. • Ni/NiAl 2 O 4 catalyst yielded 77.7% CH 4 with 97.8% selectivity from pine sawdust. • The tar and CO x intermediates were fully converted into CH 4. • The optimized temperatures: hydropyrolysis at 550 °C, hydrotreatment at 350 °C. • Increasing reaction pressure to 1.2 MPa shifted dominance to cycloalkanes. This study investigated hydropyrolysis and subsequent vapor-phase hydrotreatment over a NiAl 2 O 4 catalyst to produce biomethane (CH 4) from pine sawdust. The non-catalytic pressurized hydropyrolysis generated tar, CO 2 , and CO as the primary products. However, using a NiAl 2 O 4 catalyst in the second-stage reactor significantly increased the formation of CH 4 and reduced CO and CO 2 in gas products. The catalyst also fully converted tar intermediates to produce CH 4 , resulting in a maximum carbon yield of 77.7% with 97.8% selectivity. The temperature plays a crucial role in CH 4 generation, with both its yield and selectivity showing a positive correlation with the reaction temperature. Increasing the reaction pressure from 0.2 to 1.2 MPa notably inhibited the production of CH 4 , leading to a shift towards cycloalkanes due to a competitive reaction. This tandem approach shows great potential as an innovative technique for producing alternative fuels from biomass wastes. [ABSTRACT FROM AUTHOR]

Catalytic CO 2 methanation is devoted to both carbon-emission reduction and valuable-product generation. Ni-based catalyst is widely investigated for its effective CO 2 conversion and high CH 4 selectivity. However, seldom work reported resource substitution for production of Ni-based catalyst. In this work, Ni-Si catalysts are synthesized from Ni-rich and Si-rich electroplating sludges by a simple coprecipitation method, and applied in catalytic CO 2 methanation. As a result, CO 2 conversion and CH 4 selectivity of sludge-derived catalyst are both increased when the catalytic temperature is increased from 250 °C to 450 °C. The best catalyst converts 58.3% of CO 2 together with a high CH 4 selectivity of 88.6% at 450 °C. After detailed characterizations, the high performance is attributed to two mechanisms. On one hand, Ni0/Ni2+ couple in NiO contributes to electron and material transfers in low-temperature CO 2 methanation. On the other hand, an interface (NiSi 2) is formed between NiO and Si in the sludge-derived catalyst. Ni0/Ni2+, Si0/Sin+ (n = 3 and 4), and their combination in the interface play the main role in CO 2 methanation at high temperature. Therefore, this work is in favor of utilizing wastes (CO 2 and sludge) to produce cost-effective products (CH 4 and catalyst). [Display omitted] • CO 2 methanation catalysts are synthesized from Ni and Si sludges. • Best CO 2 conversion was 58.3% together with a high CH 4 selectivity of 88.6%. • The performance was comparable to that of pure-reagent-synthesized catalyst. • Enhanced electron transfers on Ni/Si interface determined the performance. • Electroplating sludges are potential resources for catalyst synthesis. [ABSTRACT FROM AUTHOR]

Power-to-Methane is a technically feasible process that can store large amounts of electrical energy for a long time period. The produced gas of the process can be fed into the natural gas grid or used as fuel. An essential part of the process chain is the catalytic methanation of carbon dioxide. In the methanation process, carbon dioxide and hydrogen are converted into methane and water vapor. Carbon dioxide can be won from industrial processes, ambient air or biogas plants. In this paper, fundamentals and process developments of methanation of carbon dioxide are described. [ABSTRACT FROM AUTHOR]

Power to gas is an attractive option for storing excess energy from fluctuating renewable energy sources. In recent years, the concept has gained great interest. An essential part of the process chain of power to gas is the methanation of CO2. Within this work the catalytic methanation of pure CO2 and of biogas is modeled in a three-dimensional polytropic pseudo-homogeneous flow tube and numerically simulated at different loads. The results represent axial and radial quantitative information about the reaction behavior under the different boundary conditions. [ABSTRACT FROM AUTHOR]

Power-to-Methane (P2M) pathways are proposed as an innovative solution to utilize surplus renewable electricity for long-term and long-distance storage. This electricity can produce hydrogen using electrolysis and, with the input of CO 2 from biogas, be further used for the production of synthetic methane. The methanation reaction can be done with a biocatalyst or nickel catalyst, each with a different pathway of pre- and post-treatment steps. To date, only a limited number of studies have analysed the environmental impact of P2M pathways using life cycle assessment, and no study has directly compared the biological and catalytic P2M pathways. The goal of this research is to close this knowledge gap by quantifying the environmental impact of synthetic methane production and identifying differences between both pathways. Mass and heat balances of both pathways were simulated with AspenPlus and used as basis for a thorough life cycle inventory of the material and energy demand. The global warming potential per MWh synthetic CH 4 is similar for the biological and catalytic pathways, but the impact is differently distributed between the processes. The catalytic pathway requires more sulfur removal, compression power and cooling demand. In the biological pathway, the bioreactor has a large impact due to its electricity and nutrient demand, whereas the catalytic reactor's impact is almost negligible. [Display omitted] • First life cycle assessment comparison of biological & catalytic Power-to-Methane pathways. • Similar global warming potential of biological & catalytic Power-to-Methane pathways. • Main contributors to GWP in biological pathway: electrolysis, bioreactor, compressor, water removal. • Main contributors to GWP in catalytic pathway: electrolysis, compressor, sulfur removal, chilling. • Environmental impact can be reduced by using renewable energy & heat integration. [ABSTRACT FROM AUTHOR]

Methane production from syngas goes back to more than 100 years of research and process development. Early developments (1970–1980) using syngas from coal gasification plants primarily focused on fixed-bed and fluidized-bed methanation technologies. Temperature control and catalyst deactivation, e.g. caused by fouling and mechanical stress, were key issues of investigation. Due to the debate about a sustainable energy supply, research on methanation has been intensified during the last ten years. Novel reactor developments comprise e.g. micro reactors and three-phase reactors aiming at an advanced temperature control and a reduced complexity of future methanation plants. The developments are supported by detailed modeling and simulation work to optimize the design and dynamic behavior. To accompany and facilitate new methanation developments, the present work is aimed at giving researchers a comprehensive overview of methanation research conducted during the last century. On one hand, application-orientated research focusing on reactor developments, reactor modeling, and pilot plant investigation is reviewed. On the other hand, fundamentals such as reaction mechanisms and catalyst deactivation are presented. [ABSTRACT FROM AUTHOR]

A thermodynamic analysis of the methanation of CO 2 within biogas sets the limits to the achievable performances, directing process and catalyst development. Practical indications of thermodynamics are elaborated. The large presence of CH 4 in the biogas does not hinder the achievement of an almost complete CO 2 methanation, even with CH 4 /CO 2 = 3. The smaller the temperature, the higher the CH 4 concentration in the dry biomethane, and the lower the residual H 2. Results comply with some grid specification even operating at 1 bar, below 400 °C, where active commercial catalysts are available. CO in the product is never a concern, in this temperature range. There is no advantage in operating above approx. 400 °C. The H 2 slip can be further reduced increasing the pressure, but the improvement is most effective with a few bars; 15 bar is already quite good. H 2 in excess of the stoichiometric is not useful. The process can be completely autothermal, but adiabatic operation must be avoided. Significant improvements in biomethane purity can be achieved with two methanation steps, with steam condensation in between. Residual H 2 can be reduced from 7% (single stage, 1 bar, 300 °C), to 1.8% (two stages, at 300 °C, and 1 and 15bars, respectively). Partial steam condensation allows to limit coking in the second step, without a remarkable increase of residual H 2. The second step cannot be autothermal above 150 °C, but the first step provides heat in excess, at 300 °C, to support also the second step. • CO 2 can be effectively methanized within the biogas, without separation. • A 2-steps process produces CH 4 within the grid specification for H 2 and CO. • The process does not need external thermal support. • The grid-ready methane is obtained at T where commercial catalysts are active. • Pressure improves purity, but even low P allows CH 4 in specs. [ABSTRACT FROM AUTHOR]

Applying Reaction Kinetics to Pseudohomogeneous Methanation Modeling in Fixed-Bed Reactors Keywords: Catalytic methanation; Fixed-bed reactors; Methanation kinetics; Reactor modeling EN Catalytic methanation Fixed-bed reactors Methanation kinetics Reactor modeling 991 991 1 04/22/22 20220501 NES 220501 Addendum Valentin Scharl, Felix Fischer, Stephan Herrmann, Sebastian Fendt, Hartmut Spliethoff, Applying Reaction Kinetics to Pseudohomogeneous Methanation Modeling in Fixed-Bed Reactors, I Chem. Eng. Technol i . Catalytic methanation, Reactor modeling, Fixed-bed reactors, Methanation kinetics. [Extracted from the article]

The by-product gases from the blast furnace and converter of an integrated steelworks highly contribute to today's global CO2 emissions. Therefore, the steel industry is working on solutions to utilise these gases as a carbon source for product synthesis in order to reduce the amount of CO2 that is released into the environment. One possibility is the conversion of CO2 and CO to synthetic natural gas through methanation. This process is currently extensively researched, as the synthetic natural gas can be directly utilised in the integrated steelworks again, substituting for natural gas. This work addresses the in situ methanation of real steelworks gases in a lab-scaled, three-stage reactor setup, whereby the by-product gases are directly bottled at an integrated steel plant during normal operation, and are not further treated, i.e., by a CO2 separation step. Therefore, high shares of nitrogen are present in the feed gas for the methanation. Furthermore, due to the catalyst poisons present in the only pre-cleaned steelworks gases, an additional gas-cleaning step based on CuO-coated activated carbon is implemented to prevent an instant catalyst deactivation. Results show that, with the filter included, the steady state methanation of real blast furnace and converter gases can be performed without any noticeable deactivation in the catalyst performance. [ABSTRACT FROM AUTHOR]

The energy supply in Austria is significantly based on fossil natural gas. Due to the necessary decarbonization of the heat and energy sector, a switch to a green substitute is necessary to limit CO2 emissions. Especially innovative concepts such as power-to-gas establish the connection between the storage of volatile renewable energy and its conversion into green gases. In this paper, different methanation strategies are applied on syngas from biomass gasification. The investigated syngas compositions range from traditional steam gasification, sorption-enhanced reforming to the innovative CO2 gasification. As the producer gases show different compositions regarding the H2/COx ratio, three possible methanation strategies (direct, sub-stoichiometric and over-stoichiometric methanation) are defined and assessed with technological evaluation tools for possible future large-scale set-ups consisting of a gasification, an electrolysis and a methanation unit. Due to its relative high share of hydrogen and the high technical maturity of this gasification mode, syngas from steam gasification represents the most promising gas composition for downstream methanation. Sub-stoichiometric operation of this syngas with limited H2 dosage represents an attractive methanation strategy since the hydrogen utilization is optimized. The overall efficiency of the sub-stoichiometric methanation lies at 59.9%. Determined by laboratory methanation experiments, a share of nearly 17 mol.% of CO2 needs to be separated to make injection into the natural gas grid possible. A technical feasible alternative, avoiding possible carbon formation in the methanation reactor, is the direct methanation of sorption-enhanced reforming syngas, with an overall process efficiency in large-scale applications of 55.9%. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 methanation tests were performed in a demonstration fluidized bed reactor. • Maximum possible conversions were achieved regardless of the operating conditions. • Different process chains were evaluated through process simulation. • SNG meeting the H natural gas European standards can be produced by this reactor. • This technology appears as an efficient and flexible solution for a PtM application. CO 2 methanation tests were carried out in a demonstration scale fluidized bed reactor (400 kW SNG capacity) to investigate its efficiency and flexibility towards operating conditions fluctuations associated with Power-to-Methane (PtM) production units. A wide range of operating conditions were explored: pressure (2–4 bara), reaction temperature (260−375 °C), H 2 /CO 2 inlet ratio (1.5–4.8), heat released by the reaction exothermicity (13.4–32.7 kW th), and U/U mf (2.2–7.2). Whatever the operating conditions, this technology (reactor and catalyst) reached the maximum possible conversion, i.e. the thermodynamic equilibrium, in only one step. These excellent performances resulted from efficient management of methanation exothermicity (temperature gradient in the fluidized bed is lower than 20 °C) and optimized catalyst activity (even at low temperature: 280 °C). In addition to its high flexibility towards operating conditions, short stabilization time (<30 min) was required for the process to reach permanent and stable regime when the operating condition setpoints were changed. Simulations were performed to investigate different process chains efficiency for producing SNG (Substitute Natural Gas) compliant with natural gas grid standards. A process chain composed of the fluidized bed reactor studied in this article followed by a condensation step, a partial recirculation stream to the reactor inlet, and a polishing reactor was proved to be an interesting solution to produce high quality SNG with reduced equipment and compression cost. The present reactor together with the specific metal-based catalyst developed in this study appear as a very efficient and flexible solution for PtM application. [ABSTRACT FROM AUTHOR]

Steelworks' by-product gases contain significant amounts of carbonaceous species, which can serve as carbon source for Power-to-Gas processes. The CO x components from the by-product gases are converted into methane together with renewable hydrogen in a hydrogen-intensified synthesis reaction. Dynamic operation modes of the methanation are discussed to supersede large gas buffer capacities. This paper presents results from a two-stage methanation concept operated with by-product gases from steel industries. The first reactor is designed as heat pipe cooled structured fixed-bed reactor. Both the influence of the volume flow rate and the stoichiometric ratio are examined for different steady-state operating points as well as for dynamic operation modes with repetitive alteration of those two parameters. The two-stage methanation concept provides a consistent product gas quality over a wide syngas power range at slightly over-stoichiometric conditions for both steady-state and dynamic operating conditions. Full methane yield is achieved. The design of the heat pipe cooled structured reactor allows for step changes in syngas power up to 1.6 kW. Catalyst deactivation by coking took place in the first reactor stage during the performed experiments. This happened probably due to unfavourable operating conditions in the carbon formation regime while methanizing CO-rich gases. • Catalytic methanation in a bench-scale test rig comprising an innovative heat pipe cooled structured fixed-bed reactor. • Utilization of by-product gases from steel industries as carbon source in hydrogen-intensified synthesis. • Dynamic variation of volumetric flow rate and stoichiometric ratio. • Evaluation of catalyst deactivation in consequence of unconventional feed gases and dynamic operation mode. • Presentation of a refined heat pipe cooled structured reactor design dedicated for additive manufacturing. [ABSTRACT FROM AUTHOR]

• An adsorbent and catalyst captures CO 2 from flue gas (w/O 2) and methanates at 320 °C. • Ni will not methanate adsorbed CO 2 after exposure to O 2 during CO 2 capture. • Ru doping enables Ni reduction after O 2 exposure at 320 °C. • Ru-Ni enhances CO 2 adsorption and methane production. • Cyclic aging corroborates the stability of Ru-Ni dual function material (DFM). A study of a dual function material (DFM) for CO 2 capture from O 2 -containing flue gas with catalytic conversion to fuel is presented. The DFM is composed of an alkaline adsorbent in concert with a methanation catalyst supported on γ-Al 2 O 3. The process operates at 320 °C for both CO 2 capture and fuel generation upon the addition of renewable H 2. Ni alone will not methanate adsorbed CO 2 after exposure to O 2 in the flue gas during CO 2 capture since it oxidizes and cannot be reduced to Ni metal under DFM conditions (320 °C). We report that small amounts of precious metal (≤1% Pt, Pd or Ru) enhance the reduction and activation of Ni-containing DFM towards methanation even after O 2 exposure in a flue gas. While ruthenium is most effective, Pt and Pd all enhance reduction of oxidized Ni. In this study we attempt to replace some of the Ru in the DFM with less expensive Ni and demonstrate the advantages and disadvantages of this replacement. The main advantage of the presence of Ni is an increase in CO 2 adsorption and increase in methane produced, however, at the expense of a lower methanation rate. Extended cyclic aging studies corroborate the stable performance of 1% Ru, 10% Ni, 6.1% "Na 2 O"/Al 2 O 3. [ABSTRACT FROM AUTHOR]