Syngas Methanation Research Articles

Flame propagation dynamic characteristics and mechanisms of methane–syngas–air mixtures in a semi-enclosed duct

The composition of syngas is complex, often leading to the generation of methane, which impacts the explosive characteristics of syngas. The analysis focused on the kinetic characteristics and mechanisms of flame propagation in methane–syngas–air mixtures in a semi-enclosed duct under various equivalence ratios (φ = 0.8–1.4) and methane volume ratios (R = 0 %–70 %) under ambient temperature and pressure. The results indicated that the flame speed and pressure propagation of methane–syngas–air mixtures could be divided into three stages: a stable stage, an oscillatory increase stage, and an oscillatory decrease stage. In the stable stage, as the methane proportion in the premixed gas increased, the oscillations in the flame and pressure decreased. Turbulent flow of the mixed gas was observed due to restrictions and obstructions within the duct. This led to an increase in the peak pressure and flame speed of the mixed gas, thereby resulting in an oscillatory increase stage. Distorted tulip-shaped flames were also formed in the semi-enclosed duct. The flame of the pure syngas/air mixture exhibited a hemispherical shape and a finger-shaped and slope-shaped propagation structure. When 30 %, 50 %, or 70 % of the methane in the methane–syngas–air mixtures was added, the flame exhibited a propagation structure characterized by a hemispherical shape, finger shape, slope shape, flat shape, tulip shape, or distorted tulip shape. The flame front evolved with time from a linear growth stage to a nonlinear growth stage. The flame front speed of the methane–syngas–air mixtures was closely related to the pressure and flame structure. With the increase in the methane proportion in the methane–syngas–air mixtures, the concentration of key radicals and the rate of OH* generation and consumption gradually decreased. Sensitivity analysis revealed that with increasing methane proportion in the premixed gas, the most important reaction dominating OH* consumption changed from R15 (H + O2(+M) <=> HO2(+M)) to R138 (CH4 + OH <=> CH3 + H2O) and then to R112 (2CH3(+M) <=> C2H6(+M)); moreover, the most important reaction dominating OH* generation remained R1 (H + O2 <=> O + OH). The addition of methane interrupted the hydrogen–oxygen chain reaction of the methane–syngas–air explosion process.

Waste-derived char-supported Ni catalyst for syngas methanation: Ni recovery, performance evolution and its implications for assessing char support

Syngas methanation was studied using the regenerated Ni-based catalyst supported on municipal solid waste-derived char (Ni/MSWC). Catalysts were prepared by recovering Ni from the spent Ni/MSWC via an acid-assisted process and their performance evolution was analyzed by experiments and density functional theory (DFT) calculations. The regenerated catalysts showed similar methanation activity to the original with a CH4 yield of ∼90 % but repeated acid-assisted recovery carried the risk of deactivating the catalyst, due to the enrichment of acid-soluble minerals from the char carrier. The ash composition of char carriers quantified with an alkali-carbon index of ∼20 could be an indicator for assessing the char carriers. DFT insights proved defect-induced Ni particle adsorption on MSWC and the improved electronic structure of Ni particles induced by the active acid-soluble minerals. This research highlights the potential of utilizing MSWC and recovered Ni for sustainable methanation catalysts and provides implications for choosing qualified waste-derived char carriers.

Combustion Diagnosis in a Spark-Ignition Engine Fueled with Syngas at Different CO/H2 and Diluent Ratios

The gasification of residues into syngas offers a versatile gaseous fuel that can be used to produce heat and power in various applications. However, the application of syngas in engines presents several challenges due to the changes in its composition. Such variations can significantly alter the optimal operational conditions of the engines that are fueled with syngas, resulting in combustion instability, high engine variability, and misfires. In this context, this work presents an experimental investigation conducted on a port-fuel injection spark-ignition optical research engine using three different syngas mixtures, with a particular focus on the effects of CO/H2 and diluent ratios. A comparative analysis is made against methane, considered as the baseline fuel. The in-cylinder pressure and related parameters are examined as indicators of combustion behavior. Additionally, 2D cycle-resolved digital visualization is employed to trace flame front propagation. Custom image processing techniques are applied to estimate flame speed, displacement, and morphological parameters. The engine runs at a constant speed (900 rpm) and with full throttle like stationary engine applications. The excess air–fuel ratios vary from 1.0 to 1.4 by adjusting the injection time and the spark timing according to the maximum brake torque of the baseline fuel. A thermodynamic analysis revealed notable trends in in-cylinder pressure traces, indicative of differences in combustion evolution and peak pressures among the syngas mixtures and methane. Moreover, the study quantified parameters such as the mass fraction burned, combustion stability (COVIMEP), and fuel conversion efficiency. The analysis provided insights into flame morphology, propagation speed, and distortion under varying conditions, shedding light on the influence of fuel composition and air dilution. Overall, the results contribute to advancing the understanding of syngas combustion behavior in SI engines and hold implications for optimizing engine performance and developing numerical models.

Advanced Rectisol wash equipment incorporating syngas liquefaction and methane recovery for enhanced energy management

The efficient removal of acid gases is crucial for the advancement of carbon capture, storage and utilization. However, the inherently high energy consumption restricts the improvement of overall energy efficiency. This research focused on syngas treatment obtained from a fixed-bed coal gasifier, aiming to identify the significant energy management potential. It was found that multi-step decarbonization could be achieved through syngas liquefaction and absorption, while the challenge is to explore appropriate strategies to strengthen energy management. Therefore, an advanced Rectisol wash equipment was proposed, maintaining the original methanol flowrate to avoid technical risks associated with parameter alterations. The proposed equipment was seamlessly integrated with syngas liquefaction system and methane recovery system. Specifically, methane recovery equipment was equipped to address the issue of methane loss during the liquefaction process. The results showed that the advanced Rectisol wash equipment leads to a substantial 10.0 % reduction in standard energy consumption and 9.0 % in indirect carbon emissions. Economic analysis revealed that the innovative equipment decreases the total operating cost by 6.8 %. This research offers an environmentally sustainable and economically affordable approach to syngas decarbonization, contributing to the prompt achievement of carbon neutrality goals.

Multi-objective optimization of straw-based bio-natural gas supply chains considering cost, CO2 emission, and safety

Bio-natural gas (BNG) has received recent interest as a renewable alternative to natural gas (NG). BNG supply chains (BSC), including production, transportation, and utilization, are compatible and can overlap with existing NG infrastructure. The goal is to develop a set of models that achieve the various trade-offs between economic, environmental and safety risks by combining life cycle assessment (LCA), mixed-integer linear programming (MILP) and fuzzy optimization, expanding the utilization of BSC while quantifying the risk of the whole process, so as to improve the safety awareness of the project operation. BNG technologies were considered: anaerobic digestion (AD), gasification, and syngas methanation. This model can analyze the changes in the different objectives of each module and the distribution of biomass mass flow by comparing different straw-based harvesting rates. Results indicate that AD technology possesses the lowest economic cost, and BNG as transportation fuel will generate the most benefits. The unit cost of BNG for different technologies ranges from 0.36 to 0.67 $/m³，the emission reduction is from 5.18 kg/m³ to 10.28 kg/m³，and the maximum safety risk value is 1.96. The proposed model was applied to a case study in China to illustrate the optimization of a regional straw-based BSC. The results illustrate how BNG supply chains can be systematically planned as part of an integrated decarbonization policy while mitigating safety risks that may occur from handling this fuel.

Methanation of syngas from biomass gasification: Small-scale plant design in Aspen Plus

The objective of this study is to investigate the upgrading of low-quality nitrogen-diluted syngas derived from biomass air gasification processes into a methane-rich gas stream. Both the thermodynamic and the kinetic aspects are addressed in the paper. Using the Aspen Plus software, a thermodynamic analysis was conducted; then, different plant designs are simulated and compared, including reactor sizing and performance. The results demonstrate that the upgrading of diluted syngas poses challenges which limit its application to small-scale decentralized systems. It was found that a system comprising of four adiabatic fixed-bed reactors, inter-cooling, and efficient water removal achieves a favorable balance between performance and cost. Operating the system at a pressure of 5 bar is deemed adequate as it reduces the required catalyst mass and prevents solid carbon deposition. Notably, this configuration achieved good results, including a 99.4 % CO conversion, 89.3 % CO2 conversion, and 95.6 % CH4 yield. The final methane molar content reached 26.4 %, with a calorific value of 8.62 MJ/Nm3(STP).

Computational Fluid Dynamic Analysis of Reduction Gas Emissions Level inTurbine Combustor

in this paper, (CFD) Computational Fluid Dynamics was used for a detailed burner design by the software Fluent (ANSYS). However, a number of numerical simulations were performed on a generic swirl burner and turbulence flow selection of a non-premixed which using syngas.However, non-premixed flames which characterized by relatively high temperatures, high NOx concentrations, and emission indices. The results showed that the presence of methane in syngas increases the peak flame temperature and the thermal NOx, significantly.Therefore, Investigation showed that effecting of H2, CO, and N2 contents in the fuel mixture level NOx emissions, thus the present compositions for pure methane are respectively influenced on syngas1 by (10% CH4, 45% H2, 45% CO) , syngas2 by (50% CH4, 10% H2, 40%N2) and syngas3 (60% CH4, 20% H2, 20%N2).

Coffee Pulp Gasification for Syngas Obtention and Methane Production Simulation Using Ni Catalysts Supported on Al2O3 and ZrO2 in a Packed Bed Reactor.

The methanation of CO2 is of great interest in power-to-gas systems and contributes to the mitigation of climate change through carbon dioxide capture and the subsequent production of high-added-value products. This study investigated CO2 methanation with three Ni catalysts supported on Al2O3 and ZrO2, which were simulated using a mathematical model of a packed bed reactor designed based on their chemical kinetics reported in the literature. The simulated reactive system was fed with syngas obtained from residual coffee pulp obtained after a solvent phytochemical extraction process under several gasification conditions. The results reflect a high degree of influence of the catalyst support, preparation method, and syngas composition on CO2 and H2 conversions and CH4 selectivity. For all the syngas compositions, the Ni/ZrO2 catalysts showed the best values for CO2 conversion and H2 conversion for the Ni/Al2O3 catalyst except in gasification at 700 °C and using the Ni/ZrO2p catalyst.

Power-to-methane via co-electrolysis of H2O and CO2: Reactor operation and system simulation

The traditional pathway of electrolysis based power-to-methane systems consists of water (liquid or vapor) electrolysis followed by CO2 methanation. The use of solid-oxide electrolysers allows an alternative pathway, i.e., steam and CO2 electrolysis followed by syngas methanation which can be more efficient than the traditional pathway but requires additional considerations related to cost and operation. The operation of an evaporating water-cooled CO2 methanation reactor in syngas methanation is first validated: (1) H2 concentrations between 10.3 and 21.0 % are measured with the lowest concentration occurring at higher reactant pressure and cooling water pressure and lowest reactant flow rate. (2) Increasing the CO concentration in the reactant, while supplying the stochiometric ratio of H2 and a ratio of H2O to CO of 1, increases the measured hot spot temperature but it remains under 700 °C. However, the changes in H2 concentration at the outlet are within the error of the injected reactant.Furthermore, an idealized power-to-methane system is analyzed, using various system layouts, to identify the impact of the steam production’s energy source, as well as the additional steam requirement for syngas methanation, on the system’s heating value efficiency and on the key operating variables. Restricting the internal steam production to the cooling system of the reactor causes a decrease in maximum efficiency from 94.1% to 91.1%. Directly compressing the humid mixture to be injected into the reactor as it exits the solid-oxide electrolyzer partially alleviates the stress of restricting the evaporation process to reach a maximum efficiency of 92.4%. When including heat losses in the reactor, avoiding the condensation offered a gain of up to 1.2% compared to condensing the water before the compression step.

Validation of and Simulations using a High-Temperature Electrolysis Model

Efforts for increasing the share of renewable power generation are dramatically boosted since electrical power from fossil fuels has been used as weapon [1]. Therefore, efficient conversion systems are of great importance to conserve most of the delivered power by nature. High-temperature electrolysis is such an efficient type of energy conversion system compared to similar technologies [2-4]. To bridge the gap to an industrial scale application, the electrochemical and chemical processes have to be understood in detail which is enlightened by some publications from our group [5-8]. In this contribution, a multiphysics model for three types of electrolysis processes (steam, CO2 and co-electrolysis) is presented and evaluated. Relevant parameters like the exchange current density or the anodic / cathodic transfer coefficient including parameter variations for the inlet gas stream, flow rate of the gas, temperature and applied current are investigated. For the microscale properties in the functional layer, Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) is used with the “Slice and View” technique [9,10]. Extracting information like the Triple Phase Boundary Length (TPBL), the fraction of electronic and ionic phase in mixed ionic-electronic conducting (MIEC) materials or the porosity and tortuosity of the (La,Sr)CoO3-δ (LSC) air electrode and the Ni / 8 mol% yttria stabilized zirconia (Ni-8YSZ) fuel electrode help in enhancing the modeling quality of high-temperature SOC model. A conversion from the TPBL (s. Figure 1) to an active area to volume ratio for the computation is needed.Calculated iV-characteristics and experimental curves are compared and serve as a validation for (I,V) data points at higher currents. Depending on the degree of agreement, the (missing) main contributions to loss mechanisms can be identified and initiate a feedback loop for material optimization. Sensitivity analyses are carried out for parameters that are difficult to vary in experiments (e.g. porosity). Porosity and tortuosity parametrize the porous structure for a homogeneously distributed property assumption across the material layers. The ratio between electronic and ionic phase fine-tunes the positioning of iV-characteristics within the potential regime of Ohmic and polarization losses. Calculated electrochemical impedance spectra (EIS) enhance the insight into the theoretical system and may be compared to experimental spectroscopy data via Equivalent Circuit Models (ECM). Calculated data from the model are acquired as in the used experimental setup. As an example, calculated EIS data from steam electrolysis show good agreement with a R-(RQ)4 ECM which as well describes most of the corresponding experimental data in our group. Effects of degradation are envisioned to be incorporated into the model as well.[1] Hosp, G.; Höltschi, R.; Keusch, N.; Schürpf, T.: https://www.nzz.ch/wirtschaft/rohstoffe-als-waffen-die-neusten-entwicklungen-ld.1681268 (28th October 2022, 2.13 pm)[2] Foit, S.R.; Dittrich, L.; Duyster, T.; Vinke, I.; Eichel, R.-A.; de Haart, L.G.J. (2020): Direct Solid Oxide Electrolysis of Carbon Dioxide: Analysis of Performance and Processes. In: Processes 8 (11), 1390[3] Foit, S.R.; Vinke, I.C.; de Haart, L.G.J.; Eichel, R.-A. (2017): Power-to-Syngas: An Enabling Technology for the Transition of the Energy System? In: Angew. Chem. Int. Edit. 56 (20), 5402–5411[4] Tanaka, Y.; Hoerlein, M.P.; Schiller, G. (2016): Numerical simulation of steam electrolysis with a solid oxide cell for proper evaluation of cell performances. In: Int. J. Hydrogen Energ. 41, 752–763[5] Wolf, S.E.; Dittrich, L.; Nohl, M.; Duyster, T.; Vinke, I.C.; Eichel, R.-A.; de Haart, L.G.J. (2022): Boundary Investigation of High-Temperature Co-Electrolysis Towards Direct CO2 Electrolysis. In: J. Electrochem. Soc. 169, 034531[6] Unachukwu, I.D.; Vibhu, V.; Vinke, I.C.; Eichel, R.-A.; de Haart, L.G.J. (2022): Sr Substituted La2-xSrxNi0.8Co0.2O4+ d (0 ≤ x ≤ 0.8): Impact on Oxygen Stoichiometry and Electrochemical Properties.In: Energies 15, 2136[7] Mebrahtu, C.+; Nohl, M.+; Dittrich, L.; Foit, S.R.; de Haart, L.G.J.; Eichel, R.-A.; Palkovits, R. (2021): Integrated Co-Electrolysis and Syngas Methanation for the Direct Production of Synthetic Natural Gas from CO2 and H2O. In: ChemSusChem 14, 2295 – 2302[8] Dittrich, L.; Nohl, M.; Jaekel, E.E.; Foit, S.R.; de Haart, L.G.J. (Bert), Eichel, R.-A. (2019): High-Temperature Co-Electrolysis: A Versatile Method to Sustainably Produce Tailored Syngas Compositions. In: J. Electrochem. Soc. 166 (13), F971 – F975[9] Wilson, J.R.; Kobsiriphat, W.; Mendoza, R.; Chen, H.; Hiller, J.M.; Miller, D.J.; Thornton, K.; Voorhees, P.W.; Adler, S.B.; Barnett, S.A. (2006): Three-dimensional reconstruction of a solid-oxide fuel-cell anode. In: Nat. Mater. 5, 541–544[10] Gostovic, D.; Smith, J.R.; Kundinger, D.P.; Jones, K.S.; Wachsman, E.D. (2007): Three-Dimensional Reconstruction of Porous LSCF Cathodes. In: Electrochem. Solid St. 10 (12), B214–B217Figure 1: Histogram of the TPBL from a 400 image sample set of a FIB-SEM cut of a Ni-8YSZ electrode. Figure 1

Mitigating climate change for negative CO2 emission via syngas methanation: Techno-economic and life-cycle assessments of renewable methane production

Recently, electric fuels (E-fuel), which are the chemicals produced from the conversion of renewable-based hydrogen (H2), are actively being developed as a sustainable energy carrier. Renewable methane is particularly a promising alternative to fossil-based natural gas, which can be produced from CO2 or syngas methanation. In this work, techno-economic assessment (TEA) and life-cycle assessment (LCA) for renewable methane production are performed through syngas methanation, where CO2 is collected using direct air capture (DAC) and syngas is produced by solid oxide electrolysis (SOE) with renewable-based electricity. This research considers the different technical, economic, and environmental performances of the systems for renewable methane production. A favorable reduction in a maximum of 23.3% of CH4 production cost is observed by the scale-up effects of SOE system from 1 MW to 10 MW. TEA draws the conclusion that economic infeasibility is proved at the current level, but additional research and improvement of SOE system and a plunge in renewable electricity prices can lead to the economic equivalent of conventional natural gas. Furthermore, given that certain energy resources with low energy intensity (0.0394 kg CO2-eq MJ−1) are integrated with SOE system for methane production, the LCA results that renewable methane production at a large scale has a potential to access negative CO2 emissions and accelerate climate change mitigation. Consequently, it is concluded that syngas methanation with renewable-based energy systems and DAC can make a considerable opportunity for climate change mitigation under the assumption that SOE system and renewable energy are significantly improved.

Syngas methanation over a metal hydride catalyst: Technology performance, efficiency and economic profitability

In the last decade, biomass has been considered one of the main renewable energy sources to replace fossil fuels and consequently, biomass conversion technologies for the production of alternative fuels will play a specific role in the future energy as green biofuels for the transport sector or a power generation at small-scale distributed plants. During the thermal conversion - gasification, biomass is converted into more valuable products - syngases which could be used for biomethane production. Though, some challenges still exist related to the broad applicability of the thermal conversion of biomass to biomethane: costly short-life catalysts and a low conversion efficiency due to the high amount of carbon monoxide/dioxide in syngas.To overcome these challenges, an innovative biomethane production concept based on the plasma-assisted gasification and conversion of synthetic gases to biomethane was developed and tested, including research on the adaptability of two catalysts, magnesium nickel and magnesium nickel hydride, for raw syngas conversion. The performance of catalysts was investigated in a fixed bed type reactor using raw syngas obtained from plasma-assisted gasification.The results indicate the magnesium nickel hydride catalysts' good activity and functionality for converting carbon dioxide and carbon monoxide-containing syngas. A high conversion of 0.997 is reached. Determined that the surplus of hydrogen promotes the conversion of carbon oxides, though the volumetric concentration of methane (the maximum of 86.4 vol%) in product gas is reduced. Considering that the developed technology concept can be integrated into small combined heat and power plants, bio-waste generating plants, or decentralized areas as an additional source of renewable energy or biofuel production, the energy-mass balance and economic analysis for the optimization of 1 MWh bio-CH4 production concept was provided.

P3HB from CH4 using methanotrophs: aspects of bioreactor, fermentation process and modelling for cost-effective biopolymer production.

P3HB (poly-β-hydroxybutyrate), an energy-storage compound of several microorganisms, can be used as bioplastics material. P3HB is completely biodegradable under aerobic and aerobic conditions, also in the marine environment. The intracellular agglomeration of P3HB was examined employing a methanotrophic consortium. Supplanting fossil, non-degradable polymers by P3HB can significantly reduce the environmental impact of plastics. Utilizing inexpensive carbon sources like CH4 (natural gas, biogas) is a fundamental methodology to make P3HB production less costly, and to avoid the use of primary agricultural products such as sugar or starch. Biomass growth in polyhydroxyalkanoates (PHA) in general and in Poly (3-hydroxybutyrate) manufacture in specific could be a foremost point, so here the authors focus on natural gas as a proper carbon source and on the selection of bioreactors to produceP3HB, and in future further PHA, from that substrate. CH4 can also be obtained from biomass, e.g., biogas, syngas methanation or power-to-gas (synthetic natural gas, SNG). Simulation software can be utilized for examination, optimizing and scale-up of the process as shown in this paper. The fermentation systems continuously stirred tank reactor (CSTR), forced-liquid vertical loop bioreactor (VTLB), forced-liquid horizontal tubular loop bioreactor (HTLB), airlift (AL) fermenter and bubble column (BC) fermenter were compared for their methane conversion, kLa value, productivity, advantages and disadvantages. Methane is compared to methanol and other feedstocks. It was discovered that under optimum processing circumstances and using Methylocystis hirsuta, the cells accumulated 51.6% cell dry mass of P3HB in the VTLB setup.

Waste-derived chars as methanation catalyst support: Role of inorganics in the char and its guide to catalyst design

The municipal solid waste-derived biochar (MSWC) can be applied as a catalyst support for low-cost syngas methanation. However, the mechanism of the char support as a catalyst in methanation process remains unclear. Based on the similarity between the intrinsic inorganics present in the chars and the promoters used for methanation catalyst modification, the impacts of the inorganics in different waste-derived chars on the methanation reaction were investigated. The results showed that the acid-soluble inorganics in the MSWC significantly improved the methanation activity of the MSWC-supported Ni catalysts. The acid-soluble inorganics were proved to have the role of promoting the formation of suitable Ni/support interactions, improving the dispersion of the Ni species, and increasing the concentration of the basic sites on the catalyst’s surface. Compared with the MSWC, the biochar contained much more water-soluble alkali metal salts (up to 15–57% of ash), which may be detrimental to the methanation activity of the biochar-supported Ni catalysts by leading to increases in Ni particle size and the concentration of the strong basic sites on the catalyst’s surface, especially when existing alone. A new alkali–carbon index was created to evaluate the effect of the inorganics in the waste-derived char on the methanation activity of the char-supported catalyst. A higher alkali–carbon index reflects improved methanation activity. Thus, the findings of this study can provide quantitative guidance for designing suitable waste-derived char as methanation catalyst supports.

ReaxFF Reactive Molecular Dynamics Study on Methanation Reaction from Syngas

The side reactions The side reactions in the syngas methanation process can lead to carbon deposition and deactivation of Ni-based catalysts. The existing ReaxFF reaction force field parameters are not suitable for the present study system; thus, new force field parameters of Ni-C/H/O need to be developed for the syngas methanation process. The DFT method was used to calculate the adsorption energies and transition state energy barriers for elementary reactions, which were used as the training set of the force field. The transition state was searched by DFT and reaction force field methods, respectively, to narrow the gap between the two energy barriers under similar structures. The comparison of the results of DFT and ReaxFF indicates that the developed force field suits the system. Based on the developed force field, ReaxFF was used to study the transformation process of CHx (x = 0–3) species on the Ni surface. The results show that at high temperatures and low H coverage, CHx species are easily dissociated and eventually become C species on the Ni(111) surface. Increasing H coverage can significantly increase the hydrogenation of CHx species to methane and inhibit the dissociation of CHx species. The methanation activity on the Ni(211) surface is higher, but the carbon deposition phenomenon is more serious. The reaction rate equations of each species were given, and the kinetic parameters of the elementary reactions were solved. Finally, the best reaction conditions with a higher yield of CH4 and less carbon deposition were found.

Pre-Feasibility Study of a Multi-Product Biorefinery for the Production of Essential Oils and Biomethane

Rural areas can benefit from the development of biorefineries for the valorization of endogenous feedstocks. In this study, a pre-feasibility assessment of an integrated multi-product biorefinery to produce essential oils and biomethane is carried out considering current technical and economic conditions. The proposed concept is based on the steam distillation of forestry biomass for the extraction of essential oils (2900 L/y) followed by biomethane production via syngas methanation using the spent biomass as feedstock (30.4 kg/h). In parallel, the anaerobic treatment of WWTP sludge (5.3 kg/h) is used to produce additional biomethane for mobile applications. The results show that the intended multi-product biorefinery delivers attractive benefits for investors as described by the calculated financial indicators: NPV of EUR 4342.6, IRR of 18.1%, and PB of 6 years. Overall, the pre-feasibility analysis performed in this study demonstrates that the proposed biorefinery concept is promising and warrants further investment consideration via cost and benefit analysis, ultimately promoting the implementation of multi-product biorefineries across Europe.

Numerical Investigation of Heat/Flow Transfer and Thermal Stress in an Anode-Supported Planar SOFC

To elucidate the thermofluid reacting environment and thermal stress inside a solid oxide fuel cell (SOFC), a three-dimensional SOFC model is implemented by using the finite element method in the commercial software COMSOL Multiphysics®, which contains both a geometric model of the full-cell structure and a mathematical model. The mathematical model describes heat and mass transfer, electrochemical reactions, internal reforming reactions, and mechanical behaviors that occur within the cell. A parameter study is performed focusing on the inlet fuel composition, where humidified hydrogen and methane syngas (the steam-to-carbon ratio is 3) as well as the local distribution of temperature, velocity, gas concentrations, and thermal stress are predicted and presented. The simulated results show that the fuel inlet composition has a significant effect on the temperature and gas concentration distributions. The high-temperature zone of the hydrogen-fueled SOFC is located at the central part of units 5, 6, and 7, and the maximum value is about 44 K higher than that of methane syngas-fueled SOFC. The methane-reforming and electrochemical reactions in the anode active layer result in a significant concentration gradient between the anode support layer and the active layer of the methane syngas-fueled SOFC. It is also found that the thermal stress distributions of different fuel inlet compositions are rather different. The maximum stress variation gradient between electrode layers of hydrogen SOFC is larger (44.2 MPa) than that of methanol syngas SOFC (14.1 MPa), but the remaining components have a more uniform stress distribution. In addition, the electrode layer of each fuel SOFC produces a significant stress gradient in the y-axis direction, and stress extremes appear in the corner regions where adjacent assembly components are in contact.

Non-catalytic partial oxidation of methane in biomass-derived syngas with high steam and hydrogen content optimal for subsequent synthesis process

Methane is present in biomass gasification syngas but cannot be directly utilized in the synthesis of fuels or chemicals. As a result, a method for converting methane into useable gases such as H2 and CO for synthesis processes is required. This study thus investigated the non-catalytic partial oxidation of methane in sorption enhanced gasification (SEG) environments composed mainly of steam and hydrogen at atmospheric pressure using a non-premixed burner system. The results indicated that the oxygen to fuel ratio had a strong impact on CH4 conversion, whereas the effects of preheating temperature and steam were insignificant. The highest CH4 conversion of 67% was achieved at the highest oxygen to fuel ratio of 0.77. Through the oxidation process, not only hydrocarbons but also H2 were reduced with increasing oxygen to fuel ratios. Nevertheless, the desired CO was improved in SEG environments with 60% steam. While CH4 and H2 concentrations decreased by 23% and 10%, respectively, CO concentration increased by 39% in relation to the inlet syngas at an oxygen to fuel ratio of 0.24. This condition allows for a target module M of roughly 2 for methanol synthesis. Taken together, the non-catalytic partial oxidation method could be used to upgrade methane in syngas for downstream synthesis applications. To attain complete hydrocarbon conversion, combining partial oxidation and catalytic reforming is suggested, with oxidation supplying heat for reforming reactions.

Experimental investigation on the methanation of hydrogen-rich syngas in a bubbling fluidized bed reactor utilizing an optimized catalyst

Catalytic methanation processes allow the production of natural gas substitutes on a sustainable and renewable basis. This study investigates the catalytic methanation of syngas from dual fluidized bed steam gasification of biomass in an innovative bubbling fluidized bed methanation reactor with an optimized catalyst. Syngas from conventional gasification and a novel combination with syngas from sorption enhanced reforming were investigated. The applied fluidized bed reactor allowed an almost isothermal operation with optimal reaction temperatures between 320 °C–360 °C. Simultaneously, no chemical deactivation or mechanical attrition during 200 h of operation indicates a high long-term stability of the catalyst. The methane concentration downstream the methanation reactor increased from 43 to 74 vol.-%db through the methanation of a hydrogen-rich syngas produced via sorption enhanced reforming. Simultaneously, the methane yield is doubled to 95% and the hydrogen, carbon monoxide and carbon dioxide conversions are improved. Furthermore, it could be shown that a CO2 content below 1 vol.-%db is feasible in the (raw) synthetic natural gas, allowing grid injection without CO2 separation. The results indicate that sorption enhanced reforming in combination with an optimized fluidized bed methanation can lead to technical and economic improvements in sustainable synthetic natural gas production.

Microbial community development during syngas methanation in a trickle bed reactor with various nutrient sources

Microbial community development within an anaerobic trickle bed reactor (TBR) during methanation of syngas (56% H2, 30% CO, 14% CO2) was investigated using three different nutrient media: defined nutrient medium (241 days), diluted digestate from a thermophilic co-digestion plant operating with food waste (200 days) and reject water from dewatered digested sewage sludge at a wastewater treatment plant (220 days). Different TBR operating periods showed slightly different performance that was not clearly linked to the nutrient medium, as all proved suitable for the methanation process. During operation, maximum syngas load was 5.33 L per L packed bed volume (pbv) & day and methane (CH4) production was 1.26 L CH4/Lpbv/d. Microbial community analysis with Illumina Miseq targeting 16S rDNA revealed high relative abundance (20–40%) of several potential syngas and acetate consumers within the genera Sporomusa, Spirochaetaceae, Rikenellaceae and Acetobacterium during the process. These were the dominant taxa except in a period with high flow rate of digestate from the food waste plant. The dominant methanogen in all periods was a member of the genus Methanobacterium, while Methanosarcina was also observed in the carrier community. As in reactor effluent, the dominant bacterial genus in the carrier was Sporomusa. These results show that syngas methanation in TBR can proceed well with different nutrient sources, including undefined medium of different origins. Moreover, the dominant syngas community remained the same over time even when non-sterilised digestates were used as nutrient medium.Key points•Independent of nutrient source, syngas methanation above 1 L/Lpbv/D was achieved.•Methanobacterium and Sporomusa were dominant genera throughout the process.•Acetate conversion proceeded via both methanogenesis and syntrophic acetate oxidation.Graphical abstract