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Due to its abundant resources and advantages in transportation and storage, methane fueled solid oxide fuel cells (SOFCs) are highly needed. In this work, an exceptional internal reforming catalyst comprising in-situ exsolved NiRu bimetallic nanoparticles and oxygen-deficient layered double perovskite LaBaMn 1.6 Ni 0.3 Ru 0.1 O 5+δ (r-LBMNR) was prepared. Compared to the cell with LaBaMn 1.6 Ni 0.4 O 5+δ (r-LBMN) catalyst, the cell with a Ru-doping r-LBMNR catalyst layer, exhibits superior peak power output of 336 mW cm−2 and better durability with a less decay rate of 0.014% per hour in CH 4 fuel. The enhanced electrochemical performance can be attributed to the high oxygen ion and electron conductivities of the catalyst and the coupling of Ni and Ru sites with the oxygen-deficient r-LBMNR matrix This coupling activates CH 4 and H 2 O, promotes the oxidation of C atoms in CH 4 molecules, and enables reversible hydrogen spillover, ultimately leading to the production syngas of CO(g) and H 2 (g). [Display omitted] • Trace Ru-doping facilitating the exsolution of nanoparticles. • LaBaMn 1.6 Ni 0.3 Ru 0.1 O 5+δ was modified with abundant O v and exsolved NiRu alloy. • Cell can operate stably over 220 h with a degradation rate of 0.014% h−1. [ABSTRACT FROM AUTHOR]

As a new type of energy, hydrogen-enriched methane mixed fuel has a high risk of deflagration in the application process. In order to better understand the deflagration and inhibition characteristics of hydrogen-enriched methane fuel, the effect of potassium salt modified dry water material (DW) on the deflagration characteristics of hydrogen-enriched methane fuel was studied by 20 L spherical explosive apparatus, combined with pyrolysis characteristics and kinetic model. The results show that when the addition of different modifier concentrations, it can be divided into three types: small curvature, medium curvature and large curvature according to the change of pressure rising rate. With the increase of the proportion of potassium salt modifiers, the number of areas with small curvature is gradually increasing, the number of large curvature is gradually decreasing, and the number of medium curvature is almost unchanged. When the proportion of potassium salt modifier is 15% and ϕ ≤ 0.7, all enter the area below the medium curvature. When the addition of different modifiers, 15%KCl-DW has the best inhibition effect on P max and (dP/dt) max , while CH 3 COOK-DW and K 2 CO 3 -DW have better inhibition effect on Δ t 2 and Δ t 2. In general, when the hydrogen addition ratio is less than 70%, the addition of inhibitors can significantly reduce the explosion intensity. In terms of inhibition mechanism, we established the decomposition model of potassium salt modified dry water and found that potassium salt modified dry water will produce a large amount of gaseous K and KOH in the explosion system. And gaseous K and KOH will catalyze each other and combine with H and OH to form stable H 2 O, which significantly reduces the mass fraction of H and OH radicals in the chain reaction. The results of this paper provide a theoretical basis for the safe use of hydrogen-enriched methane fuel and the research and development of explosion emergency prevention and control technology. • The explosion suppression of potassium salt modified dry water on H 2 /CH 4 was studied. • The hierarchical inhibition model of H 2 /CH 4 explosion by dry water was defined. • Particle swarm optimization is adopted to optimize the decomposition parameters of DW. • Suppression mechanism of potassium salt modified dry water was analyzed. [ABSTRACT FROM AUTHOR]

The present work utilizes a response surface optimization technique to optimize hydrogen-rich syngas production through the process of methane dry reforming (DRM). This optimization is achieved by employing a bimetallic Mn–Ni/La 2 O 3 catalyst. The study aimed to evaluate the impact of three key parameters, namely reaction temperature, time on stream (TOS), and gas hourly space velocity (GHSV), on the hydrogen to carbon monoxide (H 2 /CO) ratio in syngas during the DRM. The Mn–Ni/La 2 O 3 catalyst, synthesized using the sequential wet impregnation technique, exhibited suitable physicochemical properties necessary for DRM reaction, as evidenced by the obtained characterization data. Among the five models examined, it was found that the quadratic versus 2FI model substantially fit the experimental data, as evidenced by a p-value <0.05. The analysis of variance (ANOVA) conducted on the quadratic response surface model compared to the 2FI model demonstrated that both the reaction temperature and the TOS had a significant impact on the H 2 /CO ratio in the syngas. The only significant interaction factor was the relationship between the reaction temperature and the TOS. Under the specified optimal circumstances of 15 000 ml/g.h, 850 °C, and 258.15 min, an H 2 /CO ratio of 0.98 was achieved. The resulting H 2 /CO ratio of 0.98 is almost 1, indicating its suitability as a feedstock for methanol production in the Fischer-Tropsch synthesis (FTS). • The Mn–Ni/La 2 O 3 catalyst exhibited suitable properties necessary for DRM reaction. • Temperature and time had a substantial impact on the H 2 /CO ratio in the syngas. • The response surface quadratic model is statistically significant to fit the experimental data. • At optimized conditions H 2 /CO ratio of 0.98 was obtained for the syngas. [ABSTRACT FROM AUTHOR]

The first part of the current study highlights the importance of developing a clean hydrogen supply chain (CHSC) in Iran to enhance energy security and contribute to global efforts towards sustainable energy transition. Depending on whether the focus is on domestic consumption or export of hydrogen, the study provides valuable insights into the prioritization of CHSC development pathways via multi-criteria decision-making tools (AHP, AHOP-TOPSIS, and AHP-VIKOR). The results show that for domestic hydrogen consumption (internal scenario), the best path of the supply chain includes blue hydrogen from steam methane reforming coupled with carbon capture and storage, H 2 -carriers (ammonia and methanol), natural gas grid for transportation and distribution, and industry sector as the end user. In the external scenario, however, the best path of the CHSC consists of green hydrogen production based on solar energy, and the other parts of the path include liquid hydrogen as the storage method, ship as the distribution and transportation, and industrial sector as the end user. By identifying the most suitable methods and technologies for each stage of the supply chain, this paper offers a comprehensive analysis that can guide decision-making in CHSC development. [ABSTRACT FROM AUTHOR]

One strategy for utilizing ammonia as an energy vector is to replace conventional hydrocarbons with hydrogen-enriched ammonia in existing or retrofitted combustors. However, the strong differential diffusion effect of hydrogen can significantly alter the combustion properties and cause challenges in combustor operability. Therefore, this numerical study performs a systematic investigation on the effect of differential diffusion on fundamental combustion properties of ammonia/hydrogen fuel blends. The investigated combustion properties span from the initiation of combustion, i.e., ignition, to stretched flame propagation and ultimately to flame stabilization mechanisms. The objective is to evaluate the feasibility of hydrogen/ammonia/air mixtures as substitutes for methane/air particularly considering the implications of differential diffusion effects. To this end, four fuel blends with similar unstretched burning properties are selected: fuel lean ammonia/hydrogen (AH-L), fuel rich ammonia/hydrogen (AH-R), fuel lean methane (M-L) and fuel lean methane/hydrogen (MH-L). First, the forced ignition and stretched flame propagation are evaluated. It is found that the AH-L (AH-R) mixture has a large negative (positive) Markstein length, and thereby among the selected fuel blends, AH-L (AH-R) has the lowest (highest) minimum ignition energy. Then flame stabilization mechanisms are investigated. For a stable flame, AH-L (AH-R) has an intensified (weakened) flame base and a weak (strong) flame tip, which shows a higher flashback (blow-off) propensity. Based on the critical gradient theory, a novel stability regime diagram is proposed. With the regime diagram, the flame stabilization limits (central flashback, boundary layer flashback, stable, and blow-off) and flow conditions can be determined for burners of different sizes. [Display omitted] • Feasibility of H 2 /NH 3 as a substitute fuel for CH 4 was evaluated (4 blends with equal s L 0). • A systematic analysis on ignition, flame propagation and stabilization was performed. • The rich (lean) H 2 /NH 3 mixture is more difficult (easier) to ignite than CH 4 mixture. • The rich (lean) H 2 /NH 3 flame is more prone to blow-off (flashback) than CH 4 mixture. • A flame stability regime diagram based on critical gradient theory was proposed. [ABSTRACT FROM AUTHOR]

The purpose of this work is to investigate the effects of adding hydrogen to the fuel on the combustion induced vortex breakdown flashback phenomenon in a combustion chamber. An atmospheric research burner is selected for studies and the analysis is performed using numerical simulations. In order to model the turbulence-chemistry interactions, the EDC combustion model is utilized and the GRI 2.11 reaction mechanism is used to investigate the combustion process as carefully as possible. The present studies are performed keeping the exit temperature constant. To do this, by adding any amount of hydrogen to the premixed inlet flow, the methane is decreased by using the trial-and-error until the mass averaged exit temperature remains almost constant. The purpose of applying this limitation is to keep the cycle operational condition unchanged that is important for adding hydrogen to the existing combustion chambers especially from technological viewpoint. In addition, the thermal NO x production is controlled. In the following, the effect of hydrogen addition on the flame thickness and flame shape is investigated and finally, the effect of operating pressure on the flashback behavior is analyzed. • Effect of hydrogen addition to the fuel on the combustion induced vortex breakdown flashback is investigated. • The studies are performed keeping the exit temperature constant. • By adding hydrogen and reducing methane, the equivalence ratio decreases but the flame moves upstream. • Adding hydrogen reduces the flame thickness, but at higher hydrogen percentages, flame thickness will no longer depend on hydrogen addition. • It is illustrated that increasing the pressure moves the upstream in both pure methane and hydrogen-methane fuels. [ABSTRACT FROM AUTHOR]

A kinetic theory, known as the Langmuir–Hinshelwood–Hougen–Watson adsorption model, is applied to describe the steam methane reforming (SMR) in a 500 kW scale micro chemically recuperated gas turbine (CRGT) cycle. The response surface models of important performance parameters, including the methane conversion, carbon monoxide selectivity, and chemically recuperated heat as a function of the temperature, pressure, steam-to-carbon ratio, and contact time are numerically obtained based on the cases selected by the central composite design. The factors affecting the SMR performance are analyzed, and the reformer performance is optimized using both the desirability function combined with the response surface methodology and the second generation non-dominated sorting genetic algorithm. Finally, performance of the optimized reformer and electrical efficiency of the micro CRGT cycle with the reformer are evaluated. Results reveal that the efficiency of the micro CRGT is 40.70%, which is much higher than the typical high-efficiency micro gas trubine without reformer. [Display omitted] • Steam methane reforming kinetics in micro chemically recuperated gas turbine. • Analyses of factors affecting reforming performance using response surface method. • Reformer optimizing by desirability function combined with response surface method. • Reformer optimizing by a second generation non-dominated sorting genetic algorithm. • Micro gas turbine cycle with the optimized reformer has an efficiency of 40.70%. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFCs) are considered the most efficient technology for the direct conversion of hydrocarbons to electrical energy. Although the commonly used Ni/YSZ cermet materials in SOFCs show excellent electrocatalytic properties in H 2 fuel, they suffer from carbon deposition problem when hydrocarbon fuels are used. In this work, we study the use of Ni 0 · 05 Ru 0.05 -Mo 2 C with a porous nanorod-shaped morphology as an internal reforming catalyst layer for methane-fueled SOFCs to solve the degradation of cell performance due to carbon deposition. The electrochemical performance and coking tolerance of two types of cells with and without the catalyst layer were systematically studied using methane and hydrogen as fuels. With the catalyst layer, the single cell using methane as fuel exhibits an improvement in peak power density by 24%, increasing from 297 to 367 mW cm−2 and there was no diffusion barrier for fuel gases within the cell. Furthermore, the cell can stably run for 100 h in methane at 700 °C. The improvement of electrochemical performance is attributed to the synergistic effect of Ni and Ru sites anchored on the porous Mo 2 C nanorods catalyst based on strong metal-support interactions, promoting the effective catalytic conversion of CH 4 to CO and H 2. This study demonstrates that the integration of a catalyst layer for internal reforming is an effective strategy for the direct use of methane in SOFCs. • Porous Mo 2 C nanorods loaded with Ni and Ru bimetal nanoparticles were prepared. • The NiRu–Mo 2 C nanorods were used as an internal reforming catalyst layer for SOFCs. • The NiRu–Mo 2 C nanorod catalyst layer improves the cell performance in CH 4. • The cell with the catalyst layer shows excellent long-term stability. [ABSTRACT FROM AUTHOR]

New materials that can efficiently store hydrogen and methane at high gravimetric and volumetric densities are crucial for the widespread adoption of hydrogen vehicles as an eco-friendly alternative to fossil-fueled vehicles. Metal-Organic Frameworks (MOFs) have emerged as promising candidates to meet the Department of Energy (DOE) targets for both hydrogen and methane storage. Performing Grand Canonical Monte Carlo (GCMC) simulations, the usable hydrogen and methane gravimetric and volumetric storage capacities of two recently synthesized Jilin University (JLU) MOFs have been investigated. These capacities have been compared to those of other specifically selected MOFs with similar metal compositions, with other MOF from the JLU family, as well as classical and well-established MOFs like IRMOF-15 and IRMOF-20 (IRMOF: Isoreticular Metal-Organic Framework). The two newly synthesized JLU MOFs have exhibited high usable gravimetric and volumetric storage capacities for both hydrogen and methane, at room temperature and moderate pressures ranging from 25 to 35 MPa. These capacities are comparable to or even higher than those of classical MOFs and selected MOFs with similar metal compositions. • Hydrogen storage capacities of two JLU MOFs. • Methane storage capacities of two JLU MOFs. • Storage capacities comparable to capacities of best classical MOFs. • Storage capacities comparable to capacities of best In-Bi-P-Sb-Al-based MOFs. [ABSTRACT FROM AUTHOR]

This study evaluated the biomethane and biohydrogen production capacity of an anaerobic sludge collected from a rice parboiling industry. Three main parameters were assess from an experimental batch with varying substrate-inoculum ratios (S/I): the final mass production, the maximum generation rate, and the reactors' biomethane and biohydrogen yield. From the analysis of the final production and the maximum generation rate, the best S/I ratios found for the methanogenic and hydrogenic reactors were, respectively, 1.4 and 3.8 gCOD/gVSS. These proportions produced 102.65 mgCH 4 /gVSS and 27.96 mgH 2 /gVSS, reaching the following maximum generation rates: 32.91 mgCOD CH 4 /gVSS.h and 12.63 mgCOD H 2 /gVSS.h. In contrast to the methanogenic microorganisms of the studied sludge, the acetogenics allow the use of higher organic loads in the systems. However, the lowest S/I ratio (0.1 gCOD/gVSS) resulted in both the best biomethane and biohydrogen production yield, around 2.33 mol CH 4 /mol glucose and 2.46 mol H 2 /mol glucose. Compared to the maximum theoretical yields, whereas the sludge produced biohydrogen more effectively under high S/I ratios, biomethane was generated more efficiently in low S/I ratios. Finally, the anaerobic sludge can be employed as a satisfactory inoculum in anaerobic digestion and dark fermentation processes designed for biomethane and biohydrogen production. • Specific Methanogenic and Hydrogenic Activity. • Production of 27.96 mgH 2 /gVSS. • Satisfactory inoculum in anaerobic digestion and dark fermentation processes. [ABSTRACT FROM AUTHOR]

To enhance ammonia's flammability, blending methane with ammonia is a viable strategy to improve the laminar burning velocity of ammonia combustion. We conducted three-dimensional numerical simulations to investigate the thermal performance, the 2nd thermodynamic law efficiency, and NO emissions of a micro-combustor fuelled by ammonia/methane. Three key parameters are identified and examined. They include: 1) the inlet volume flow rate, 2) the CH4 mole blended ratio, 3) the N 2 dilution rate. It is found that increasing the inlet volume rate give rise to an increase of the combustor outer wall temperature, and so the thermodynamic second-law efficiency, but a reduction of NO emissions. For example, when the inlet volume flow rate is set to 14.4 mL/s, the wall temperature and 2nd law efficiency are increased by 36 % and 21 % respectively, but the NO emission is reduced by 15 %, in comparison with those in the presence of 7.2 mL/s inlet flow. While an increase of the CH 4 blended ratio (molar fraction) is shown to have limited impact on the thermal performances. This variation of such blended ratio is found to be associated with a notable 22 % reduction of NO emissions. Additionally, injecting N 2 as a dilution gas is shown to be not beneficial to the thermal performance. However, NO emissions are reduced. When the N 2 dilution rate is set to 0.6, the wall temperature is found to be reduced by 173 K. However, 47 % more NO reduction is observed in comparison with those in the presence of the N_2 dilution rate being set to 0.3. • 3D numerical investigation of a micro-combustor fuelled by methane/ammonia is conducted. • Entropy generation analyses of the ammonia/methane-fuelled micro-combustor are performed. • Examining the effect of blending methane with ammonia on thermodynamic performances is conducted. • NO emissions from the ammonia/methane-fuelled micro-combustor are evaluated. • A reduced chemical reaction mechanism of ammonia-methane combustion is proposed. [ABSTRACT FROM AUTHOR]

Hydrogen, a sustainable energy source, has potential to address climate change. However, traditional steam reforming processes produce CO 2. Alternative fuels like bio-alcohols, biogas, and LPG are being adopted for steam reforming processes. This study presents a thermodynamic comparative examination of steam reforming processes employing different fuels, including methane, methanol, ethanol, propane, glycerol, and biogas. The analysis focuses on the hydrogen yield, environmental impact, and energy requirements of these processes and a comparison with experimental results. The analyses were conducted using AspenPlus® software, minimizing the Gibbs free energy under specified conditions (T = 25–1000 °C, n = 1–10, P = 1–40 bar). Among the fuels examined, methanol, biogas, and methane exhibited the highest hydrogen yields, reaching maximum values of 96.10 %, 95.86 %, and 95.26 % respectively at 600 °C, 1 bar, and a water-to-fuel ratio of 10. Ethanol, glycerol, and propane achieved yields of 89.66 %, 86.55 %, and 84.03 % respectively at 700 °C and the same pressure and water-to-fuel ratio. [Display omitted] • Thermodynamics of methane, bio-alcohols, glycerol, and propane steam reforming. • Non-monotonic trend of hydrogen yield vs temperature due to rWGS. • Maximum H 2 yield (96.10 %) at fixed water-to-C ratio achieved by methanol at 600 °C. • CO 2 emissions and energy demand evaluation in typical operative conditions. • Largest CO 2 emissions are due to biogas and glycerol (∼20 KgrCO 2 /KmolH 2). [ABSTRACT FROM AUTHOR]

Metal-Organic Frameworks (MOFs) are a significant and promising category of solid that have garnered substantial attention for their potential in storing hydrogen and methane. Grand Canonical Monte Carlo (GCMC) simulations of the usable hydrogen and methane storage capacities of five DUT MOFs (Dresden University of Technology), based on tritopic ligands and copper, have been carried out at room temperature and pressures between 0.5 and 35 MPa. These DUT MOFs exhibit high usable hydrogen and methane storage capacities, comparable or higher than the storage capacities of the best classical MOFs and the best Cu-based MOFs. The usable methane gravimetric storage capacities at 35 MPa and room temperature of these DUTs reach the Department of Energy (DOE) methane gravimetric target and their usable volumetric capacities are close to the DOE methane volumetric target. [Display omitted] • Hydrogen Storage Capacities of five DUT MOFs. • Methane Storage Capacities of five DUT MOFs. • Storage Capacities comparable to Capacities of Best Classical MOFs. • Storage Capacities comparable to Capacities of Best Cu-based MOFs. [ABSTRACT FROM AUTHOR]

Energy transition strongly leads researcher to find short-term alternative carbon-free fuels to be used in internal combustion engines. An interesting and transient solution can be the dual fuel (DF) technology. It can offer significant reduction of carbon dioxide and pollutant emissions. In this paper, DF operation was performed in an optically accessed research diesel engine running at a constant speed of 1500 rpm. Substitute fuels (methane or hydrogen) were injected in the intake manifold in front of the entrance of the tumble intake port. The objective was to compare the two DF modes using simultaneously Fast UV–Visible and Fast Infrared (IR) Imaging. We observed that IR camera was able to give deeper combustion information and allowed to grab the whole phenomenon for both DF hydrogen and methane, while identifying the combustion starting points. Also, IR acquisitions for premixed hydrogen evidenced an unpredictably behaviour of the mixture, demonstrating the necessity of a specific Diesel injection strategy to avoid hydrogen auto-ignition at higher engine load. Finally, a comparison of the measured emissions at the exhaust evidenced that in DF mode (both with CH 4 and H 2) a significant reduction of particulate matter is achieved with respect to conventional diesel operation. In addition, when hydrogen is used as primary fuel, a more efficient combustion is obtained drastically reducing HC and CO 2. • Dual fuel use for energetic transition. • Emission reduction. • E-fuel possibility use. • High potential for fast IR camera in engine studies. [ABSTRACT FROM AUTHOR]

In this study, three different gas fuels such as hydrogen, propane, methane and six different liquid fuels such as, benzene, gasoline, toluene, hexane, methanol and ethanol have been combined and combustion characteristics have been simulated for a spark ignition engine (SIE). Variation of in-cylinder temperature, in-cylinder pressure, CO, CO 2 and NO has been investigated. The gas fuel ratios in the mixtures were changed between 0 and 100% by mass. It was investigated that how the addition of gaseous fuels to liquid fuels at different ratios affects the combustion characteristics and emission formation. The gas fuel ratios considerably affected emission and combustion specifications of the engine. Increasing liquefied gas fuel ratio in the mixture leads to decrement in the temperature of charge. The maximum pressure first increases with increasing gas fuel ratio and then start to minimize after maximum pressure. The maximum peak pressure values are observed at 50% gasoline and 50% methane, 75% gasoline and 25% propane, 50% gasoline-50% hydrogen as 48.1 bar, 46 bar and 62.4 bar for different gas fuel mixtures. The minimum peak pressure value is displayed at 100% methanol as 44.06 bar. The maximum temperature value is observed at 100% benzene as 2582 K and its minimum value seems at 100% hydrogen as 2059 K. The maximum mass fractions of CO, CO 2 , NO are observed at 100% benzene as 0.0271, 0.161, 0.0076, the minimum mass fraction of CO 2 is observed at 100% methane as 0.095. The minimum mass fraction of CO is observed at 100% methanol as 0.01243. The minimum mass fraction of NO is observed at 100% hydrogen as 0.00085. The fuels are ranked using a multi-criteria decision-making algorithm called AHP after evaluating the values of all performance criteria and their respective sub-criteria, including in-cylinder pressure, in-cylinder temperature, NO, CO 2 and CO to get preference rank between fuels. • Performance analysis is performed for different mixtures of gas-liquid fuels. • Effects of different fuel mixtures on combustion characteristics are investigated. • Emission characteristics of a SIE fuelled with gas-liquid fuel mixtures are investigated. • Performance and emission characteristics are considerably affected by fuel kinds and mixture ratios. [ABSTRACT FROM AUTHOR]

This research addresses the influence of hydrogen addition on adiabatic flame temperature, and energy-based amounts of biogas combustion products. The evaluations were conducted with the developed solving scheme based on the chemical equilibrium approach for fuel blends of methane (CH 4) –carbon dioxide (CO 2), and hydrogen (H 2) structures. Thus, the biogases, composed of CH 4 and CO 2 , including different levels of CO 2 (10, 25 and 40% by volume) were evaluated by blending H 2 in the range of 0–40% with a 5% increment by volume. Besides, the analyses were carried out at different equivalence ratios (ϕ) varying from 0.6 to 1.4 to determine the H 2 effect in lean, stoichiometric and rich mixture conditions. The results show that the effect of H 2 on the adiabatic flame temperatures and the energy-based amounts of CO 2 , CO, and NO, change heavily depending on the CO 2 concentration of biogas and the equivalence ratios. By adding a 40% H 2 to biogas involving 40% CO 2 , the adiabatic flame temperatures enhanced by 55.8 K, 67.9 K, and 114.7 K at φ = 0.6, 1.0, and 1.4, respectively. The H 2 addition significantly contributes to decreasing the energy-based amount of CO 2. The maximum improvements in the CO 2 amounts were obtained as 25.36%, 26.86%, and 32.38% at φ = 0.8, 1.0, and 1.4, respectively, by 40% H 2 addition. The CO amounts are tendency to decrease with H 2 addition at φ = 1.0 to 1.4 corresponding to stoichiometric and rich mixtures. However, the H 2 addition slightly increased the CO amount at the lean mixtures in which the amounts of CO are already quietly low level. Regarding the energy-based amounts of NO, the H 2 addition gave rise to increasing the NO amounts. However, the effect of H 2 on the NO amount decreased at rich mixtures independent of CO 2 content in biogas. The maximum increase in the NO amount by 40% H 2 addition is about 0.3 g/MJ at the φ = 0.6 while 0.006 g/MJ at φ = 1.4. • Chemical equilibrium-based combustion model was developed for biogas-hydrogen blends. • The H 2 addition to biogas enhances the adiabatic flame temperatures. • The contribution of H 2 to biogas varies depending on the CO 2 content in biogas and the equivalence ratio. • The energy-based amount of CO 2 decreases by adding H 2 to biogas. • The energy-based amount of NO has a tendency to increase with the H 2 addition to biogas. [ABSTRACT FROM AUTHOR]

Fuel synthesis through CO 2 hydrogenation is receiving much attention to decarbonizing the transport sector of future energy systems. In this study, an integrated system is proposed and investigated from a thermo-economic point of view to produce power and synthetic methane and methanol. The proposed system includes an externally fired gas turbine, Rankine cycle, organic Rankine cycle, proton exchange membrane electrolyzer, molten carbonate fuel cell and methane and methanol synthesis units. CO 2 hydrogenated under three different scenarios to produce methane-only, methanol-only and dual-production assuming various operating loads of electrolyzer. The influence of the key parameters on the system performance is assessed via response surface method and finally, the system performance is optimized. Under the base conditions, overall exergy efficiency, levelized cost of electricity, methanol and methane is estimated to be 36.8 %, 37.6, 92.8 and 79.4 $/MWh, respectively. Under the optimized conditions for the methane-only scenario, the overall exergy efficiency, levelized cost of electricity and methane is found to be 34.8 %, 36.7 $/MWh and 77.3 $/MWh, respectively. • A biomass-driven system is investigated to produce power and synthetic fuel. • Captured CO 2 via molten carbonate fuel cell is hydrogenated to produce synthetic fuel. • Three different scenarios are evaluated: producing methane, methanol and both. • Multi-objective optimization is conducted. • Minimum cost of electricity and methane is 36.7 and 77.3 $/MWh, respectively. [ABSTRACT FROM AUTHOR]

Biohythane (a mixture of hydrogen and methane) may play a significant role in a future decarbonised energy system. The production of biohythane can be achieved by sequential dark hydrogen fermentation and anaerobic digestion. However, the technology readiness level of biohythane can be limited by many process constraints negatively affecting its commercial feasibility. Here, a pilot experiment on fermentative hythane production from cassava stillage residue (CSR) incorporating dilute acid pretreatment and enzymolysis was undertaken. The production of hydrogen and methane was 72.0 ± 10.7 and 295.4 ± 28.5 mL/g volatile solid, respectively. Different scenarios for techno-economic analysis were developed in terms of the dried/wet form of CSR and total solids content during fermentation. Results suggested that hythane from CSR was not economically feasible with a high production cost (1.39–2.33 €/m3). There was a trade-off relationship between the increase in methane yield through pretreatment and the associated cost. • Pilot-scale biohythane production from cassava stillage residue was studied. • Four scenarios for techno-economic analysis of hythane production were developed. • The production cost was not economically viable varying between 1.39 and 2.33 €/m3. • Profit was affected by total solid content, pretreatment and hydrogen production. [ABSTRACT FROM AUTHOR]

The assessment of anaerobic biotransformation in thermophilic mode (55 °C) of agricultural waste was carried out. It has been established that organic wastes (wheat distillery vinasse, cow manure and chicken manure) have a great potential for producing biogas with a high content of methane and carbon dioxide with a low content of impurities. Biogas can be recommended as a raw material for hydrogen production. With the ratio of components in the composition of the mixed substrate of distillery vinasse, cow manure and chicken manure - 6: 3: 1 for 21–29 days of anaerobic digestion, the best indicators of the efficiency of methanogenesis for methane (61–63%) and biogas (70–73%) were provided, the share of methane in composition of biogas was 61%. With the biotransformation of alone vinasse, the nitrogen mineralization efficiency (58–67%) was lower than when using a mixture of organic waste (63–69%). From the point of view of obtaining the maximum amount of biogas, it is advisable to add a carbonate buffer or limestone flour (9% wt.) to the substrate to shift the pH of the working solution towards slightly alkaline values. From the point of view of the accumulation of free phosphates in the final solution, the use of a carbonate buffer is more preferable. The anaerobically treated solid sludge remaining after biogas production, as well as liquid effluents (anaerobically treated effluents) can be considered as potential organic and biogenic fertilizers or their components. [ABSTRACT FROM AUTHOR]

Novel materials capable of storing hydrogen or/and methane at high gravimetric and volumetric densities are required for hydrogen vehicles to be widely employed as a clean alternative to fossil-based vehicles. Metal-Organic Frameworks (MOFs) are considered as promising candidates to achieve the Department Of Energy (DOE) targets for both, hydrogen and methane storage. Using Grand Canonical Monte Carlo (GCMC) simulations, the hydrogen and methane gravimetric and volumetric storage capacities of two recently synthesized Al-nia MOFs have been studied. Their storage capacities have been compared with the storage capacities of other Al-based MOFs and classical and well-known MOFs, such as IRMOF-5. The two novel Al-nia MOFs have shown high hydrogen and methane gravimetric and volumetric storage capacities at room temperature and moderate pressures, 25–35 MPa, comparable or higher than the storage capacities of classical and Al-based MOFs. • Hydrogen Storage Capacities of two Novel Al-nia MOFs. • Methane Storage Capacities of two Novel Al-nia MOFs. • Storage Capacities comparable to Capacities of Best Classical MOFs. • Storage Capacities comparable to Capacities of Best Al-based MOFs. [ABSTRACT FROM AUTHOR]

Hydrogen Fuel Cell Electric Vehicles (HFCEVs) and Natural Gas Vehicles (NGVs) are cleaner alternatives to present oil-based vehicles. The main problem of these technologies is the on-board storage. Metal-organic frameworks (MOFs) is one of the main groups of solid porous materials that can be used to store hydrogen or methane on-board these vehicles at room temperature and low or moderate pressures. The synthesis of these materials is usually expensive. Recently a group of eleven new BUT MOFs (BUT: Beijing University of Technology) has been synthesized using cheap organic precursors. Grand Canonical Monte Carlo simulations (GCMC) of the hydrogen and methane storage capacities and isosteric heats of these BUTs have been carried out and analyzed at 298.15 K and at pressures in the range 0.5–50 MPa. The correlations between the storage capacities and the porosity, the density, the pore size and the isosteric heat of the MOFs are analyzed. According to the simulations, three of the newly developed BUTs demonstrated high storage capacities for both hydrogen and methane. BUT-104 and 105 exhibited useable hydrogen volumetric and gravimetric capacities of approximately 0.023–0.027 kg/L and 4 wt % at 50 MPa. Additionally, they showcased useable methane volumetric and gravimetric capacities of 0.16–0.21 kg/L and 25 wt % at 25–35 MPa. Moreover, BUT-107 achieved the U.S. Department of Energy (DOE) hydrogen target for 2025, with a useable hydrogen gravimetric capacity of 5.5 wt % at 27 MPa. Furthermore, BUT-107 met the corresponding DOE methane targets, with useable methane volumetric and gravimetric capacities of 0.25 kg/L and 33.33 wt % at 50 MPa. • Hydrogen Storage Capacities of Novel BUT MOFs. • Methane Storage Capacities of Novel BUT MOFs. • Volumetric capacities highly correlated with product porosity and isosteric heat. • Three BUTs have high hydrogen gravimetric storage capacities. • One BUT MOF, BUT-107, reaches the methane DOE targets. [ABSTRACT FROM AUTHOR]

Due to the increasing demand for low carbon fuels, ammonia is considered a viable option. Considering the problems associated with the combustion of ammonia, such as its narrow flammability range, it has been suggested to use it together with other fuels, such as methane. Following previous studies, which mainly focus on the emission of this fuel mixture in burners and simplified chambers, this research attempts to conduct an experimental and numerical study with a greater emphasis on performance parameters and pollution in an actual microturbine combustion chamber. The study investigates the effect of a mixture of ammonia with methane and its fraction on the combustion performance of the combustor and its emissions (NOx, CO) in two different thermal powers. The results showed that flame temperature decreased as the fraction of ammonia in the fuel increased, and the flame moves away from the injector. It also appeared that adding ammonia to the fuel increased the amount of NOx produced in the combustor without reducing CO significantly. Also, the combustor outlet temperature remained almost unchanged, but the combustion efficiency of the combustor decreased as the ammonia fraction increased. • Investigated performance and emissions of microturbine combustor with ammonia/methane fuel mixture. • Stable combustion achieved up to 50% mixing ratio, without altering combustor configuration. • Lowering reaction rate delays ignition and hampers chamber performance. • Ammonia in methane reaction reduces complete combustion, causing elevated CO and NOx emissions. • Higher ammonia ratio reduces combustor efficiency, raises pattern factor, with constant output temperature. [ABSTRACT FROM AUTHOR]

A continuous process for producing hydrogen from the gasification of ethanol with supercritical water (SCWG) is investigated, which involves a fixed bed steam methane reforming (SMR) reactor downstream of the SCWG reactor. Increasing temperature and decreasing space velocity in the SMR reactor resulted in increased hydrogen concentration and methane conversion. The catalyst activity was more affected at low than high pressures, presumably due to the kinetics of the SMR reaction. The significant increase in total hydrogen yield based on ethanol in the feed showed the importance of installing the reformer after gasification. The excessive steam from the SCWG reactor helped to prevent carbon formation, but it might have resulted in the sintering of the active metal. A long-time experiment proved the stability of the catalyst up to 49 h of time on stream (TOS) with a minor decrease in methane conversion from 84% to 78%. [Display omitted] • Ethanol supercritical water gasification followed by steam reforming of product gas. • Increasing temperature, decreasing space velocity increased H 2 yield and CH 4 conversion. • CH 4 conversion was decreased more at low (1–20 bar) than high (20–40 bar) pressures. • Excessive steam prevented carbon formation but caused sintering of the active metal. • Integration of steam reforming reactor increased significantly the total hydrogen yield. [ABSTRACT FROM AUTHOR]

Estimates on the costs of renewable energy supply by hydrogen and hydrogen-based derivatives such as ammonia or organic compounds (e.g., synthetic methane, methanol, Fischer-Tropsch fuels) vary substantially among current publications. Hence, comprehensive analyses of each stage of the renewable energy supply chain are necessary, with ship transportation as the focus of this work. Shipping cost projections for various hydrogen-based derivatives from a wide range of recent international publications are compared, identifying uncertainties and research gaps in the shipping of Power-to-X energy carriers. While transportation costs in literature reveal a consistent picture for liquid ammonia, projections for liquid hydrogen, LOHCs, and, surprisingly, also for methanol, Fischer-Tropsch fuels and liquid methane differ significantly. Technological and economic assumptions contributing to the discrepancies are discussed. A sensitivity analysis is provided to quantify the effects of divergent assumptions for different parameters on shipping costs. • Projections of future ammonia shipping costs are quite consistent. • Cost projections for hydrogen diverge as large-scale shipping is not established. • Cost projections for hydrocarbon energy carriers reveal significant inconsistencies. • Discrepancies mainly attribute to ship's speed, lifetime and CAPEX assumptions. [ABSTRACT FROM AUTHOR]

As conventional fossil fuel is depleting, ammonia has attracted extensive attention as a renewable fuel, which could be made from water, air, and sun. There is current interest in burning ammonia in macro, meso, and micro-combustors. The present work is concerned with the numerical investigations of the entropy production, thermodynamic exergy performance from ammonia/methane-fueled micro-combustors with a single-channel inlet and double-channel outlet (SIDO) in the presence and absence of a porous media (PM). For this, a 3D time-domain model is developed. With the model being validated with experimental data available in the literature, it is then applied to examine the effects of 1) equivalence ratio (Φ), 2) inlet velocity (V in), 3) blending/mixing ratio (Φ b) between the methane and ammonia, and 4) PM porosity (σ). In comparison with the combustion system without PM, the application of PM is found to lead to a significant improvement on thermal performances, as V in is varied. It is found that there is a substantial 37.5% reduction in the standard deviation of the combustor outer wall temperature S T,W at V in = 2.0 m/s. The optimal thermal performance is achieved, as Φ = 0.9. However, nitrogen oxide emission is shown to be decreased, as Φ is increased. As the entropy production is concerned, the σ of PM is shown to exhibit a notable influence. A higher porosity gives rise to a lower entropy production within the PM. The lowest entropy production resulting from heat conduction is shown to be achieved, when σ = 0.8. By implementing PM, the exergy efficiency (η exergy) is found to be increased by 23.9% at V in = 2.0 m/s. In general, the present investigation shed physical insights on the entropy production and thermodynamic exergy performances of ammonia/methane-fueled micro-combustion systems with and without PM. • Simulation of double channel outlet combustor with porous medium is conducted. • Ammonia combustion mixed with methane can lead to an increase in the wall temperature. • The pollutants can be reduced by the appropriate equivalence ratio. • The entropy production can be reduced by higher porosity of porous medium. • The exergy efficiency can be boosted by inserting porous medium. [ABSTRACT FROM AUTHOR]

This study experimentally examines the effect of the addition of mixed gas (C 2 H 6 + C 2 H 4): (CO + H 2) = 1:5 on the explosion characteristics of methane (volume fractions of 7%, 9.5%, and 11%) The explosion pressure, rate of increase in explosion pressure and time to reach the maximum explosion pressure are monitored. The mole fraction of radicals, sensitivity of CH 4 , and rate of production (ROP) are then calculated. The results show that the addition of mixed gas has the greatest impact on the explosion characteristics of the 7% methane mixture. For methane mixture of 7%, 9.5% and 11%, R1, R107 and R104, respectively, have the greatest impact on the methane sensitivity. The impact on the methane sensitivity in descending order is 7% > 9.5% > 11%. R1 (H + O 2 = O + OH) was the most promoting and primary reaction for the consumption of O 2 and the production of OH. • Adding a mixed gas has the greatest impact on the explosive reaction of a 7% methane mixture. • When the volume fraction of CH 4 is 7%, the O· radical molar fraction peaked at 1.6% mixed gas. • The order of the impact on the sensitivity to the CH 4 volume is 7% > 9.5% > 11%. • R1 (H + O 2 =O + OH) is the most effective in promoting and inhibiting the ROPs of O 2 and OH. [ABSTRACT FROM AUTHOR]

The co-combustion of traditional methane gas and alternative fuels importance to reduce emissions in combustion has increased in recent years. The literature proves the successful operations of ammonia and hydrogen as diesel engine fuels. However, there is not sufficient information about the combustion of methane along with ammonia and hydrogen. In this study, the effects of the combustion of methane-hydrogen and methane-ammonia-hydrogen fuel mixture on system performance and emissions are numerically investigated. Firstly, the effects of methane and 5%, 10%, and 15% hydrogen mixture are investigated. Then, methane and 5% fixed hydrogen ratio with 5% ammonia, 10% ammonia, and 15% ammonia mixtures are examined. The numerical model is validated against the literature data using the Sandia D model with a difference of 5.9% at x/d = 0.5. As a result of the study, 15% hydrogen addition to methane increased the maximum combustion chamber temperature by 100 K. However, with the addition of 15% of ammonia, the temperature is dropped by 200 K and the peak temperature location is slightly shifted away from the injection point. A 10% enhancement of hydrogen content rate will cause a 28% increase in thermal NO X emission and a 10% increment in the ammonia content of the fuel blend has caused to 3000 ppm enhancement in NO X emission. With the addition of %5, 10%, and %15 ammonia mass fraction to methane and hydrogen blend fuel at the axial location of x/d = 0.444, the NOx emission production rate has been increased by 1970, 3010, and 3790 ppm, respectively. In addition, the 15% hydrogen addition to methane (85% methane/15% hydrogen) and 5% hydrogen plus 15% ammonia addition to methane (80% methane/5% hydrogen/15% ammonia) reduced the CO 2 emission by 30.7% and 14% compared to neat methane (100% methane) combustion. To sum up, this study shows that the use of methane-ammonia-hydrogen as a diesel engine fuel reduces combustion emissions. • One-dimensional Methane/Hydrogen and Ammonia combustion model has been established. • The use of carbon free alternative fuels reduced CO 2 emission by about 30.7%. • Hydrogen addition increased combustion chamber temperature and NOx emissions. • Flame formation was investigated for different blend rates of hydrogen and ammonia. • The effects of CH 4 /H 2 /NH 3 blends on emissions and performance were evaluated. [ABSTRACT FROM AUTHOR]

Coking is still a major cause of catalyst deactivation in catalytic methane reforming processes. In this work, doping the support of Ni/γ-Al 2 O 3 catalysts with iron to provide redox functionality was found to significantly enhance coking resistance in methane partial oxidation. Catalysts with well-dispersed Fe3+ in the support, with Fe mass% in the range of 1.1–15.2 were prepared and tested in reactions at 700 °C. The catalyst with 3.2% Fe in the support showed negligible crystalline carbon at a coking rate of 9.0 × 10−6 g c g−1 catalyst h−1 compared with its Fe-free counterpart that showed a coking rate of 7.7 × 10−4 g c g−1 catalyst h−1. On the other hand, ≥10% Fe resulted in the formation of FeAl 2 O 4 and Fe0 that promoted considerable coking. The unique influence of iron was referred to the role of the dispersed Fe2+, which is dominant upon reduction, in promoting a redox cycle that allow the oxidation and removal of carbon. [Display omitted] • Fe molar concentrations up to 5% gave well-dispersed Fe2+ in reduced alumina. • Molar concentrations of Fe ≤ 5% in the support showed significant coking resistance. • High Fe contents resulted in FeAl 2 O 4 and Fe0 that considerably enhanced coking. • Redox functionality of Fe2+ in the support promoted carbon oxidation and removal. [ABSTRACT FROM AUTHOR]

To get a general understanding of hydrogen fuel usage in a real-condition high-pressure industrial gas turbine burner operating at 15 atm pressure, the effects of hydrogen addition to methane fuel are studied numerically. Methane-hydrogen premixed fuel-lean flame is investigated while hydrogen is substituted for methane at a fixed fuel and air mass flow rate at the burner inlet. Steady-state reacting and swirling flow equations (RANS) are solved using the standard k − ε model as the turbulence model. A detailed methane combustion mechanism GRI 2.11 is used to simulate methane-hydrogen combustion with Finite Rate formulation more accurately. Temperature and axial velocity variation and important pollutant species emissions such as CO, CO 2 , and NOx were investigated at the combustion chamber exit. Flame shape, flow pattern, and flame location variation with hydrogen addition were studied due to hydrogen flashback limits. The hydrogen addition leads to higher temperatures inside the burner and the hot zone inside the combustion chamber extends and moves toward the fuel inlet. Flow structure including recirculation zones change with hydrogen addition. CO emission increases by hydrogen addition to the fuel mixture near the burner exit while CO 2 mass fraction is reduced. A significant increase in NO mass fraction with hydrogen addition was observed near the burner exit due to higher temperature. • Hot zone inside the combustion chamber extends and moves towards fuel inlet by hydrogen addition. • Recirculation zones move to downstream by hydrogen addition to the fuel. • CO emission increases by addition of hydrogen to the fuel mixture. • CO 2 mass fraction is reduced by hydrogen addition to the fuel mixture. • Significant increase in NO mass fraction with hydrogen addition was observed. [ABSTRACT FROM AUTHOR]

The purpose of this work is to evaluate the characteristics of hydrogen-blend methane explosion. The explosion characteristics without initial turbulence or with initial turbulence are firstly explored. Then the factors affecting laminar burning velocity and turbulent flame regime are revealed. Finally, the different prediction models are developed to evaluate peak explosion pressure of hydrogen-blended methane fuel. The results indicated that the MFFV, PEP, PRPR and laminar burning velocity of MR = 10% and MR = 30% continue to increase with the increase of ER, the peak value of MFFV, PEP, PRPR and laminar burning velocity of other MRs is arrived at ER = 1.0. The MFFV, PEP and PRPR increase gradually with increasing root-mean-square velocity. Regardless of initial turbulence, the MFFV, PEP and PRPR continue to decrease with increasing MR, the PEP and PRPR decrease obviously with increasing distance from ignition location. The turbulent flame regime is highly sensitive to MR, not root-mean-square velocity. The predicted value of laminar model, wrinkled model and turbulent model is relatively conservative, maximum wrinkling coefficient induced by flame instabilities and flame front itself needs to accurately evaluated. • Characteristics of hydrogen-blended methane explosion are explored. • Laminar burning velocity and turbulent flame regime are revealed. • Different theoretical models of predicting PEP are established. [ABSTRACT FROM AUTHOR]

For a hydrogen-based economy, safe and efficient hydrogen storage is essential. Compared to other chemical hydrogen storage technologies, such as ammonia or methanol, liquid organic hydrogen carrier (LOHC) systems allow for a reversible storage of hydrogen while being easy to handle in a diesel-like manner. In our contribution, we describe for the first time the successful utilization of the exhaust gas enthalpy of a porous media burner to directly supply the dehydrogenation heat for a kW-scale dehydrogenation of the hydrogen-rich LOHC compound perhydro dibenzyltoluene (H18-DBT). Our setup demonstrates the dynamics of the dehydrogenation unit at a realized maximum hydrogen power of 3.9 kW th , based on the lower heating value of the released hydrogen. For the intended applications with fluctuating hydrogen demand, e.g. a hydrogen refueling station (HRS) or stationary heating in buildings, a dynamic hydrogen supply from LOHC is important. Methane, e.g. from a biogas plant, is utilized in our scenario as a fuel source for the burner. Hydrogen is released within 30 min after cold start of the system. The dehydrogenation unit exhibits a power density relative to the reactor volume of about 0.5 kW therm l−1 based on the lower heating value of the hydrogen and a catalyst productivity of up to 0.65 g H2 g Pt −1 min−1 for hydrogen release from H18-DBT. An analysis of the by-products and reaction intermediates shows low by-product formation (e.g. maximum 0.6 wt.-% for high boilers and 0.9 wt.- % for low boilers) and uniform distribution of intermediates after the reaction. Thus, a relatively homogeneous temperature distribution and a uniform LOHC flow in the reaction zone can be assumed. Our findings illustrate the dynamics (heating rates of about 10 K min−1) and performance of direct heating of a release unit with a burner and represent a significant step towards LOHC-based hydrogen provisioning systems at technically relevant scales. • Direct heating of a dehydrogenation unit using the exhaust gas enthalpy of a burner. • Dynamic dehydrogenation of a LOHC at a realized hydrogen power of 3.9 kW th. • Catalyst productivity of 0.65 g H2 min−1 g Pt −1 for 54% degree of dehydrogenation. • Low by-product formation and uniform distribution of intermediates after the reaction. [ABSTRACT FROM AUTHOR]

Renewable power-to-fuel (PtF) is a key technology for the transition towards fossil-free energy systems. The production of carbon neutral synthetic fuels is primarily driven by the need to decouple the energy sector from fossil fuels dependance which are the main source of environmental issues. Hydrogen (H 2) produced from water electrolysis powered by renewable electricity and direct carbon dioxide (CO 2) captured from the flue gas generated by power plants, industry, transportation, and biogas production from anaerobic digestion, are used to convert electricity into carbon-neutral synthetic fuels. These fuels function as effective energy carriers that can be stored, transported, and used in other energy sectors (transport and industry). In addition, the PtF concept is an energy transformation that is capable of providing services for the balancing of the electricity grid thanks to its adaptable operation and long-term storage capacities for renewable energy surplus. As a consequence, it helps to potentially decarbonize the energy sector by reducing the carbon footprint and GHG emissions. This paper gives an overview on recent advances of renewable PtF technology for the e-production of three main hydrogen-based synthetic fuels that could substitute fossil fuels such as power-to-methane (PtCH 4), power-to-methanol (PtCH 3 OH) and power-to-ammonia (PtNH 3). The first objective is to thoroughly define in a clear manner the framework which includes the PtF technologies. Attention is given to green H 2 production by water electrolysis, carbon capture & storage (CCS), CO 2 hydrogenation, Sabatier, and Haber Bosch processes. The second objective is to gather and classify some existing projects which deal with this technology depending on the e-fuel produced (energy input, conversion process, efficiency, fuel produced, and application). Furthermore, the challenges and future prospects of achieving sustainable large-scale PtF applications are discussed. • An overview on recent advances of renewable power to fuel technologies. • Power-to-methane (PtCH4), power-to-methanol (PtCH3OH) and power-to-ammonia (PtNH3). • Green hydrogen production, carbon capture and storage, and CO 2 hydrogenation. • Energy input, conversion process, efficiency, fuel produced, and application. • Role of power to fuel technologies for the decarbonization of energy sector. [ABSTRACT FROM AUTHOR]

The introduction of other combustible gases to methane could change accident consequences. This work aimed to experimentally compare the effects of blended fuels (C 2 H 6 , C 2 H 4 , CO, and H 2 mix in different proportions) on the explosion pressure behavior of methane and blended fuels in air. The explosion pressure properties of the mixtures were tested. Principal component analysis was employed, and multiple regression models were developed to predict the influences of principal components on the maximum explosion pressure of CH 4. In addition, the software was used to analyze and compare the sensitivity analysis. For the fuel-lean CH 4 -air mixture(φ = 0.72), the results demonstrated that the value of P max and (d P/ d t) max of the mixed gases increased, as the volume fraction of the blended fuels increased. The effects of other gases followed the order C 2 H 6 >C 2 H 4 >H 2 >CO. For stoichiometric concentrations (φ = 1), the order of the influence degree was H 2 >CO > C 2 H 6 >C 2 H 4 , and the value of P max and (d P/ d t) max of the mixed gases tended to decrease slightly. As the volume fraction of the blended fuels was increased to 2%, the P max and (d P/ d t) max of CH 4 showed a decreasing trend for the fuel-rich CH 4 -air mixture. The effects of blended fuels on the equivalence ratio of φ = 1.1 followed the order C 2 H 4 >H 2 >CO > C 2 H 6. The sensitivity variation analysis and normalized sensitivity variation analysis indicated that the chain branching reaction 2CH 3 (+M)<=>C 2 H6(+M) was the most sensitive reaction under various conditions. However, it was not very susceptible to changes in the blended fuel ratio. Most reactions were susceptible to changes in the blended fuel ratio. The 10 most sensitive reactions were generally much more susceptible to changes in the blended fuel ratio in the 2% blended fuels than they were in the 0.4% blended fuels. • Different ratios of blended fuels have significant effects on the explosion characteristics parameters of CH 4. • Multiple regression models were developed to obtain which gas plays the main role in the explosion of the gas mixture. • Insight was gained into the chemical mechanisms at different gas ratios and methane concentrations. • The effects were analyzed based on reaction characteristics. [ABSTRACT FROM AUTHOR]

As a by-product of the coking industry, coke oven gas (COG) is often burned as fuel gas. However, COG contains a large amount of hydrogen. If hydrogen is recovered, the economic and environmental benefits of the coking industry can be improved. In this work, a novel automotive fuel cell hydrogen production process coupled with membrane separation (PRISM® Membrane Separator, polyimide hollow fiber membrane), pressure swing adsorption (PSA) and methane steam reforming (SMR) is proposed. The process uses membrane separation and PSA to produce high-purity hydrogen for fuel cells. The methane-rich membrane residue gas is used as the feed gas of the reforming reactor. The hydrogen-containing gas at the outlet of the reactor enters the membrane separator to further improve the hydrogen yield. In addition, based on the principle of temperature gradient utilization, the high-temperature gas at the outlet of the reactor is used as the heat source for the system. Through a synergy of separation and reaction, the process supports the low-cost and efficient production of fuel cell hydrogen from COG. The proposed process was established using UniSim Design. The key variables were determined by sensitivity analysis, and the response surface methodology based on Box–Behnken design (BBD) method was further used to optimize the key variables. The optimal operating variables are as follows: the area of the third hydrogen membrane (HM3) is 3000 m2, the reaction temperature is 917 K and the molar ratio of steam to methane (S/C) is 1.12. The cost of the hydrogen production process is 1.56 $/kg, which means it has good prospects for use in industrial applications. • A novel fuel cell hydrogen production process from coke oven gas is proposed. • The process is coupled with membrane separation, PSA and MSR. • The process is strictly simulated and optimized by the response surface methodology. • The cost of the hydrogen production process from coke oven gas is 1.56 $/kg. [ABSTRACT FROM AUTHOR]

This research aims to develop a better carbon resistant anode compared to conventional Ni-BCZY anode for methane fueled protonic ceramic fuel cell (PCFC). Solid-state reaction process is used to prepare alloy Ni 1-x Cu x -BCZY anode in PCFC. Ni is doped with Cu for better carbon resistance. Results show that, Ni 0·9 Cu 0.1 -BCZY anode calcined at 800 °C for 0.5 h exhibit an electrical conductivity of 2054 S/cm at 600 °C, which is 8.4% less than traditional Ni-BCZY anode. XPS, and Raman data show that Ni 0·9 Cu 0.1 -BCZY anode exhibit resistance to carbon deposition compared to traditional anode. The best carbon deposition resistance is observed for the Ni 0·7 Cu 0.3 -BCZY sample. This work demonstrates the suppression of carbon deposition and inhibition of anode deformation in methane fueled PCFC with Ni 1-x Cu x -BCZY anode. This work is helpful for development of carbon-resistant materials for energy generation with solid oxide fuel cells. • Cu is doped in Ni-BCZY anode for increasing carbon deposition resistance (CDR). • Effects of Cu content on CDR and conductivity of anode are investigated. • EDS, XPS, EA and Raman spectroscopy are used to characterize CDR. • Increasing Cu content increases CDR, but reduces conductivity. [ABSTRACT FROM AUTHOR]

Dry reforming of methane (DRM) is a promising alternative technology for the production of syngas with simultaneous utilization of two main greenhouse gases (CH 4 , CO 2). However, DRM technology is still an industrially immature process due to the lack of stable and active catalyst. Therefore, the search for new catalytic materials is of great research interest. Recently, MAX and MXenes materials are increasingly being tested as potential materials for catalytic processes including dry reforming of hydrocarbons. However, transition metal carbides may be deactivated under DRM conditions due to phase transition caused by an oxidation process. The combining of the MAX/MXene materials with nickel phase may be beneficial for to improve catalytic activity and stability. In this view, we report preparation and characterization of nickel-modified V 2 CTx/V 2 AlC materials. The Ni–V 2 CTx/V 2 AlC catalysts were prepared using HF-etching followed by impregnation/precipitation method. The effect of preparation route on morphology and catalytic activity was investigated. The properties of fresh and spent catalysts were evaluated using XRD, XPS, MP-AES, SEM, BET surface area, H 2 -TPR, CO 2 -TPD, TG/DTG and TEM techniques. Catalytic activity was investigated in the DRM process at 800 °C and 1 bar. It was found that the V 2 CT x /V 2 AlC- based materials undergo phase transition to vanadium oxide V 2 O 3 , vanadium carbide V 8 C 7 and aluminium oxide. The presence of nickel was crucial for the catalyst activity of V 2 CT x /V 2 AlC- based catalysis. The catalytic activity was different and related to the preparation procedure resulting in dissimilar nickel-phase morphology and intercalation of sodium ions. It was found that the distribution of nickel phase and presence of alkali ions determined catalysts' activity and stability. The highest activity and stability in DRM process was observed for Ni–V 2 CT x /V 2 AlC_IMP catalysts obtained using only impregnation method without precipitation agents. For the catalysts nickel phase was distributed uniformly forming needle-like structures. The CO 2 and CH 4 conversions during 20 h-test were in the range of 90–93% and 90-80%, respectively. The molar ration of H 2 to CO in outlet stream fluctuated from 1.05 in the first hour of the process to 0.95 after 20 h of the DRM. The activity and stability of Ni–V 2 CT x /V 2 AlC_IMP catalyst was higher compared to unmodified V 2 CT x /V 2 AlC, unetched V 2 AlC and Ni–SiO 2. • The nickel phase is crucial for effective DRM over MXene/MAX materials. • The method of nickel phase deposition was crucial for DRM efficiency. • The Ni–V 2 CT x /V 2 AlC-based catalysts were tested in DRM for the first time. • The Ni–V 2 CT x /V 2 AlC-based catalysts underwent phase change to Ni–V 2 O 3 –V 8 C 7. • The content of sodium ions retarder the activity of Ni–V 2 CT x /V 2 AlC-based catalysts. [ABSTRACT FROM AUTHOR]

International trade volumes have grown due to acceleration of marine transportation of goods between continents. However, there is a concomitant increase in fossil fuel consumption and adverse environmental impact. This paper presents a new design of marine engines comprising of gas Brayton cycle, solid oxide fuel cell, and two organic Rankine cycles to replace two-stroke internal combustion engines. Hydrogen, methane, dimethyl ether, ethanol, and methanol are potentially selected as green fuels. In addition, liquified natural gas is used for cooling processes. This integrated hybridized marine engine is thermodynamically analyzed using the Aspen Plus software to assess its performance energetically and exergetically. It is found that the engine's total power is boosted by 33% to an average of 15758 kW with average energetic and exergetic efficiencies of 38% and 46%, respectively. The maximum power is fulfilled using all sustainable fuel blends to reach 16087 kW with a maximum carbon emission reduction of 83% and minimum specific fuel consumption. The proposed engine has better performance and less environmental impact, which is a more convenient choice than traditional engines. [Display omitted] • Five alternative fuels are chosen with different concentrations. • Integrated hybrid marine engine produces a total power of 16087 kW by 33% increase. • Engine runs at a 38% energy efficiency and 46% exergetic efficiency. • Alternative fuels can reduce carbon emissions by more than 80%. • New engine fuel consumption is reduced by more than 55%. [ABSTRACT FROM AUTHOR]

Underexpanded, cryogenic hydrogen and methane jets were measured using laser Raman scattering diagnostic. The jets were released from 1 mm to 1.25 mm orifices for the stagnation pressure ranges of 2–6 bar and temperature ranges of 37–46 K (hydrogen) and 112–189 K (methane). Raman signals are inherently small, thus a denoising algorithm was developed to substantially reduce the noise hindering the statistical analysis of the data. The time-averaged concentration and temperature data were plotted to show a hyperbolic decay law along the jet centerline and a Gaussian distribution in the radial direction. The concentration fluctuations of the cryogenic jets are similar to those of warm jets, the centerline RMS mass fraction decays similarly to the mean mass fraction, and the highest radial concentration fluctuations appear in the shear layer. Thus, the self-similar characteristics of the cryogenic jets are comparable with room-temperature jets for the present test conditions. • Data denoising algorithm was developed for the cryogenic H 2 and CH 4 jets. • Time-averaged and fluctuating behaviors of the cryogenic jets were analyzed. • The self-similarity of the cryogenic jets was comparable with the warm jets. [ABSTRACT FROM AUTHOR]

This numerical study investigates the impact of four proposed porous burner designs, which are based on a diamond lattice structure similar to what could be obtained with additive manufacturing technology, on H 2 /CO syngas production. The performances of all the burners were compared, and the results showed that for a given porosity, the recirculation efficiency increased with increasing the pore density. Decreasing the porosity by a factor 2 increased the recirculation efficiency thanks to the presence of higher thermal inertia and local temperature, which allowed to achieve a 53% fuel conversion. Promising results were obtained with the new linearly varying pore diameter matrix, with an observed conversion efficiency of 63% and a reduction in the soot precursor production. This latter behavior itself resulted from an increase in the size of the reaction zone, where elevated temperatures led to high concentrations of H 2 and to the partial oxidation of C 2 species. • A 3D pore-resolved CFD model of a diamond lattice-based porous burner is proposed. • A new tailored graded geometry was tested and compared to isotropic matrices. • The energy recirculation efficiency was maximized with a higher specific surface. • The methane-to-syngas conversion ratio was maximized with the graded geometry. • The graded matrix led to low levels of soot precursors due to a longer oxidation zone. [ABSTRACT FROM AUTHOR]

Liquid organic hydrogen carrier (LOHC) systems offer a promising way to store and transport hydrogen in a safe and dense form at ambient conditions. Compared to other chemical hydrogen storage systems such as ammonia, formic acid, and methanol, LOHC systems enable reversible storage of hydrogen. For the endothermic hydrogen release reaction, heat and a suitable catalyst are needed. In this work for the first time, the exhaust gas enthalpy of a porous media burner is utilized to supply the heat for dehydrogenation of the LOHC compound perhydro dibenzyltoluene (H18-DBT). This approach significantly increases the system dynamics and the power density of the dehydrogenation unit compared to conventional heating via a heat transfer fluid. A dynamic hydrogen release is important to satisfy the fluctuating hydrogen demand, especially in hydrogen refuelling stations (HRS) or in stationary heating applications, e.g., for buildings. Our setup utilized methane as fuel source for the burner. The key challenge is the precise temperature control of the direct heating of the LOHC in the dehydrogenation unit. This is required as hot spots may result in thermal decomposition of the LOHC compounds, while cold spots limit the rate of the dehydrogenation reaction. With our laboratory-scale setup, we demonstrate a hydrogen release from H18-DBT of up to 450 ml N min−1 with 8.2 g of Pt on alumina catalyst (0.3 mass % Pt loading, i.e., 25 mg of Pt). Hydrogen is released within 10 min after a cold start of the entire system. The system exhibits a catalyst productivity of up to 1.5 g H2 g Pt −1 min−1 and a power density relative to the reactor volume of about 3.6 kW therm L−1 based on the lower heating value of hydrogen. Our findings show the strong potential of the direct heating concept in hydrogen release from LOHC systems and represent a significant step towards LOHC-based technical hydrogen provision systems. • Dehydrogenation of a LOHC using the exhaust gas enthalpy of a porous media burner. • LOHC heating rates in the dehydrogenation unit of about 60 K min−1. • Catalyst productivity of 1.5 g H2 min−1 g Pt −1 for 18% degree of dehydrogenation. • Power density of the dehydrogenation unit of about 3.6 kW therm L−1. [ABSTRACT FROM AUTHOR]

In this work, a hibonite-type Ni/La-hexaaluminate (Ni/LHA) synthesized from an industrial waste is used and compared as catalyst in the dry reforming of methane (DRM) at 973 K. The structure, catalytic behavior, and stability during a run time of at least 50 h of three Ni-catalysts obtained from two commercial supports and two preparation methods were used for comparison. An aluminum solution (9.40 g/L) obtained from an aluminum saline slag waste by acid extraction was used to synthesize the hexaaluminate by mixing with a stoichiometric amount of lanthanum nitrate and methanol/Peg400/PegMn400 under hydrothermal conditions at 493 K for 16 h. The Ni/LHA catalyst (10 wt% NiO) was obtained by impregnation of the synthesized support, calcined previously at 1473 K for 2 h. The resulting solids were characterized by several techniques as: X-ray diffraction (XRD), N 2 adsorption at 77 K, temperature-programmed reduction (TPR), scanning electron microscopy (SEM) and transmission electron microscopy (HR-TEM). In order to compare the catalytic behavior and properties of the Ni/LHA catalyst, three Ni catalysts obtained from two commercial supports (γ-Al 2 O 3 and SiO 2) and two preparation methods (wet impregnation (I) and precipitation-deposition (PD)) were synthesized. Analysis of the TPR patterns for the catalysts allowed the type of metal support interaction and NiO species to be determined, with a weak interaction with the support being observed in Ni/LHA and Ni–I/SiO 2. The NiO species observed, with crystallite sizes between 9.7 and 40.4 nm, confirm the X-ray structural analyses. The Ni/LHA catalyst was found to be active and very stable in the DRM reaction after 50 h. The catalytic behavior was evaluated from the CO 2 and CH 4 conversions, as well as the H 2 /CO selectivity, with values of 99% over almost all the time range evaluated. The behavior of this catalyst is comparable to that of Ni–I/Al 2 O 3 and Ni-PD/SiO 2. The results found indicating that the strong interaction of nickel with the support favors the stability of the catalysts in the DRM reaction. • Acid aluminum extracted was used in the synthesis of a La-hexaaluminate. • The solid was used as support for Ni catalyst for DRM. • Three Ni-catalysts from commercial supports were used for comparison. • The behavior of Ni/LHA is similar to the catalysts with high Ni-support interaction. [ABSTRACT FROM AUTHOR]

A green template-free method is proposed for the synthesis of mesoporous Ni–Cu/Al 2 O 4 catalyst in sub-kilogram scale. In the convenient synthetic method, an intermediate is formed via electrostatic forces and hydrogen bonding interactions between the aluminate ions and the metal ions and/or metal hydroxides under suitable pH conditions. The desired Ni–Cu/Al 2 O 4 composites, with Ni/Cu molar ratios of 10%, 20% and 30% of Cu at Cu/Al molar ratio of 10.0%, respectively, are then obtained from calcination. The nitrogen adsorption-desorption isotherms show that the Ni–Cu/Al 2 O 4 composites have specific surface areas of 136–170 m2g-1. The Ni–Cu/Al 2 O 4 products are used as catalyst materials in the methanol steam reforming (MSR) of hydrogen and are shown to have a high conversion efficiency (>99%), a low methane concentration, good stability, and a high hydrogen yield (H 2 /methanol molar ratio ≈ 3.0) at low reaction temperatures in the range of 200–300 °C. In addition, the coke formation on the catalyst surface is less than 1.0 wt% even after a reaction time of 30 h. Notably, the Ni–Cu/Al 2 O 4 catalyst can be regenerated by calcination at 800 °C and retains a high methanol conversion efficiency of close to >99% when reused in MSR. • A green method is proposed for the synthesis of Ni–Cu/Al 2 O 4 catalyst in sub-kilogram scale. • The Ni–Cu/Al 2 O 4 products have a high conversion efficiency (>99%) at 200 °C. • The Ni–Cu/Al 2 O 4 catalyst can be regenerated and retains a high methanol conversion rate. [ABSTRACT FROM AUTHOR]

Chemical-looping combustion (CLC) is recognized as a promising technique to efficiently and economically capture emitted carbon dioxide in common combustion processes. In this study, the bubbling fluidized bed (BFB) fuel reactor performance of the CLC system was examined through numerical simulation. The reduction reaction performance obtained from conventional BFB fuel reactor and BFB fuel reactor incorporated with internal particle circulation denoted as internal circulation bubbling fluidized bed reactor (ICBFB), were compared under the same fuel flow rate and operating conditions. By using CH 4 as fuel and ilmenite as the oxygen carrier, it was found the reduction reaction can be enhanced by using the ICBFB fuel reactor due to particle circulation. The particle circulation increased the mixing and contact time between fuel and oxygen carrier that produced reduction reaction enhancement. Moreover, the simulation results indicated that higher reduction reaction performance can be achieved by higher reduction reaction temperature and initial oxygen carrier volume fraction. • A CFD model was built to study fuel reduction in a chemical looping combustion system. • The bubbling fluidized bed with and without internal particle circulation was used as the fuel reactor. • Fuel reduction can be enhanced by particle circulation due to increased particle mixing. • Reaction temperature plays an important role in fuel reduction in fuel reactor. • Fuel reduction can be enhanced by using a higher initial volume fraction of oxygen carrier. [ABSTRACT FROM AUTHOR]

Limitations on the upgradation of biogas to biomethane in terms of cost effectiveness and technology maturity levels for stationary power generation purpose in rural applications have redirected the research focus towards possibilities for enhancement of biogas fuel quality by blending with superior quality fuels. In this work, the effect of hydrogen enrichment on performance, combustion and emission characteristics of a single-cylinder, four-stroke, water-cooled, biogas fuelled spark-ignition engine operated at the compression ratio of 10:1 and 1500 rpm has been evaluated using experimental and computational (CFD) studies. The percentage share of hydrogen in the inducted biogas fuel mixture was increased from 0 to 30%, and engine characteristics with pure methane fuel was considered as a baseline for comparative analysis. The CFD model is developed in Converge CFD software for a better understanding on combustion phenomenon and is validated with experimental data. In addition, the percentage share of hydrogen enrichment which would serve as a compromise between biogas upgradation cost and engine characteristics is also identified. The results of study indicated an enhancement in combustion characteristics (peak in-cylinder pressure increased; COV IMEP reduced from 9.87% to 1.66%; flame initiation and combustion durations reduced) and emission characteristics (hydrocarbon emissions reduced, and NOx emissions increased but still lower than pure methane) with increase in hydrogen share from 0 to 30% in biogas fuelled SI engine. Flame propagation speed increased and combustion duration reduced with hydrogen supplementation and the same was evident from the results of the CFD model. Performance of the engine increased with increase in hydrogen share up to 20% and further increment in hydrogen share degraded the performance, owing to heat losses and the enhancement in combustion characteristics were relatively small. Overall, it was found that 20% blending of hydrogen in the inducted biogas fuel mixture will be effective in enhancing the engine characteristics of biogas fuelled engines for stationary power generation applications and it holds a good compromise between biogas upgradation cost and engine performance. • Comparative study on characteristics of SI engine fuelled with methane, biogas and hydrogen enriched biogas. • Effect of hydrogen enrichment on characteristics of biogas fuelled engine. • Detailed analysis of in-cylinder combustion by computational approach (CONVERGE CFD). • 20% blending of hydrogen in biogas was observed to be effective. [ABSTRACT FROM AUTHOR]

In this work, gadolinium is used to modify nickel catalyst, which can improve the properties of nickel oxide particle and inhibit its sintering and grain growth. Interface contact between nickel catalyst and YSZ is significantly improved and fine anode microstructure can be obtained when gadolinium is used to modify Ni-YSZ anode. Fine interface contact of GdNi-YSZ anode can accelerate charge transfer process and steam formation process, which leads to high activity for electrochemical oxidation of hydrogen and low impedance resistance. The remarkable characteristic of GdNi-YSZ anode cell is that the cell performance for humidified methane fuel is greatly improved due to the high anode activity for methane reforming and electrochemical oxidation of hydrogen. The maximum power density of GdNi-YSZ anode cell with humidified methane as fuel can reach 1.59 W/cm2 at 800 °C and 0.46 W/cm2 at 650 °C. High performance of GdNi-YSZ anode cell with humidified methane as fuel leads to much H 2 O produced during the electrochemical oxidation process, which can depress carbon deposition and improve the cell stability for humidified methane fuel. [Display omitted] • Interface contact of Ni-YSZ anode is significantly improved by Gd modification. • Fine interface contact accelerates charge transfer and steam formation processes. • Gd modification can improve the anode activity and cell performance for CH 4 fuel. • High cell performance leads to much H 2 O produced and good stability for CH 4 fuel. [ABSTRACT FROM AUTHOR]

Hydrogen fuel production from methane cracking is a sustainable process compared to the ones currently in practice due to zero greenhouse gas emissions. Also, carbon black that is co-produced is valuable and can be marketed to other industries. As this is a high-temperature process, using solar energy can further improve its sustainability. An integrated solar methane cracking system is proposed where hydrogen and carbon products are sent to fuel cells to generate electricity. The CO 2 exhaust stream from the carbon fuel cell is captured and reacted with hydrogen in the CO 2 hydrogenation unit to produce liquid fuels – Methanol and dimethyl ether. The process is simulated in Aspen Plus®, and its energy and exergy efficiencies are evaluated by carrying out a detailed thermodynamic analysis. In addition, a sensitivity analysis is performed on various input parameters of the system. The overall energy efficiency of 41.9% and exergy efficiency of 52.3% were found. [Display omitted] • Energy and exergy analysis of an integrated methane cracking system. • Clean electricity generation using hydrogen and carbon black. • One-step DME synthesis using captured CO 2 for hydrogen carrier production. • Aspen Plus simulation of the overall process. • Overall energy and exergy efficiencies of 41.9% and 52.3%, respectively. [ABSTRACT FROM AUTHOR]

Combined with need of the carbon emissions, the feasibility of Moderate or Intense Low-oxygen Dilution (MILD) combustion fueled with hydrogen/methane blends needs to be investigated. This paper discusses the pollutant emissions, the stable operating range and the flame morphology for a jet-induced MILD model combustor. The hydrogen/methane volume ratios range 0:10 to 5:5. The NO x emissions are less than 5 ppm@15%O 2 when the hydrogen content is less than 50% by volume in the atmospheric conditions. The calculation using chemical reactor network (CRN) model demonstrates that the effect of heat loss on NO x emissions increases as the adiabatic combustion temperature increases, which is consistent with the experimental results. The maximum OH∗ signal intensity increased at higher hydrogen content, especially when the hydrogen content exceeds 30% by volume. Due to the increase in turbulent burning velocity and the enhancement in the reaction intensity, the reaction zones shrink with increasing hydrogen content. In addition, with increasing hydrogen content, the stable operation range of the combustor becomes narrower, and the stable combustion is not maintained when the hydrogen content exceeds 50% by volume. The findings of the paper help to further understand the effect of hydrogen content on the formation of MILD combustion in the jet-induced combustor. • NOx emissions are ultralow when the combustor outlet temperature is below 1800K fueled with hydrogen/methane blends. • Effect of heat loss on NO X emissions increases when the adiabatic combustion temperature increases. • The stable operation range of jet-induced MILD model combustor becomes narrower increasing hydrogen content. [ABSTRACT FROM AUTHOR]

Partial gasification of coal char was conducted with addition of metal oxides for co-production of fuel gas and methane decomposition catalysts. Effect of the metal composition (Ni, Co and Fe based mono- or bi-metals) was investigated on the fuel gas production and the resultant catalyst surface and textural properties, morphology and performance in catalytic methane decomposition (CMD). Besides H 2 -rich fuel gas production (the combustion energy up to 11.03–23.42 MJ/kg char) from the gasification, the gasification residue can directly serve as the effective and efficient catalyst for CMD. The Fe and Fe–Co composite oxides were found to be better among the mono- and bi-metallic oxides for the fuel gas production during the gasification, respectively. The Ni-based mono-/bi-metallic catalysts could display high and stable methane conversion (up to 80%) during the 600-min CMD test at 850 °C. Promotional role of the second metal in CMD was discussed on the carbon diffusion, metal mobility and reducibility, formation and growth of the deposited carbons. The formed carbon morphology after CMD was analyzed based on the Kirkendall effect and Tammann temperature and further correlated to the potential catalyst deactivation. [Display omitted] • Partial gasification of coal char (<39%) is studied with addition of metal oxides. • Co-production of H 2 -rich (>60%) fuel gas and CH 4 pyrolysis catalysts are achieved. • Effects of Ni, Co and Fe mono-/bi-metals are studied at the content of about 10%. • Kirkendall effect and Tammann temperature are used to analyze the formed carbons. [ABSTRACT FROM AUTHOR]

This study aims at investigating the combustion characteristics of methane and a hydrogen-rich fuel on distributed regime in a combustor with high internal recirculation as distributed regime can achieve with highly internal entrainment. The model validation was first taken place with the existing experimental results under non-reacting conditions, and it is demonstrated that the mean velocity profiles predicted are in satisfactorily good agreement with the existing data in the combustor. Then, the methane and the hydrogen-rich fuel were consumed at an equivalence ratio of 0.8 and a thermal power of 10 kW under distributed conditions which means that oxygen concentration in the oxidizer is reduced from 21% to 15% along with internal entrainment for each fuel used. The results showed that the velocity magnitudes increased in the combustor with decrease in oxygen concentration because of diluent introduction. Moreover, distributed regime enabled uniformly temperature field inside the combustor together with the ultra-low NO X values with introducing the diluent. In addition, one can say that the maximum temperature and the outlet NO X values (1800 K and 27.60 ppm at 21% O 2 – 1450 K and 0.05 ppm at 15% O 2 for methane, 2000 K and 32.47 ppm at 21% O 2 – 1700 K and 0.19 ppm at 15% O 2 for the hydrogen-rich fuel) were relatively higher while combusting the hydrogen-rich fuel compared to those of methane due to the presence of hydrogen. However, It is concluded that distributed regime provided uniformly temperature fields and ultra-low NO X levels even the hydrogen-rich fuel is used. • Colorless distributed combustion was investigated using a recirculative combustor. • External/internal recirculation zones were obtained in the combustor. • Velocity profiles were highly affected with highly internal recirculation. • More uniform thermal fields and ultra-low NO X emissions were achieved. [ABSTRACT FROM AUTHOR]

In order to study the influence of nitrogen on the deflagration characteristics of premixed hydrogen/methane, the explosion parameters of premixed hydrogen/methane within various volume ratios and different dilution ratios were studied by using a spherical flame method at room temperature and pressure. The results are as follows: The addition of nitrogen makes the upper limit of explosion of hydrogen/methane premixed gas drop, and the lower limit rises. For explosion hazard (F -number), hydrogen/methane premixed fuel with a hydrogen addition ratio of 10% has the lowest risk, and nitrogen has a greater impact on the dangerous degree of hydrogen and methane premixed gas whose hydrogen addition ratio does not exceed 30%. In terms of flame structure, the spherical flame was affected by buoyancy instability as the percentage of nitrogen dilution increased, but the buoyancy instability gradually decreased as the percentage of hydrogen addition increased. The addition of diluent gas reduces the spreading speed of the stretching flame and reduces the stretching rate in the initial stage of flame development. The laminar flame propagation velocity calculated by the experiment in this paper is consistent with the laminar flow velocity of the hydrogen/methane premixed gas calculated by GRI Mech 3.0. Considering the explosion parameters such as flammability limit, laminar combustion rate and deflagration index, when hydrogen is added to 70%, it is the turning point of hydrogen/methane premixed fuel. • Nitrogen lowers the upper explosion limit and raises the lower limit. • When φ = 0.1, the explosion risk of premixed fuel is the lowest. • Buoyancy instability is affected by the addition of nitrogen. • The more diluent gas, the lower the stretching rate in the initial stage. • φ = 0.7 is the turning point of the hydrogen/methane premixed fuel. [ABSTRACT FROM AUTHOR]