Search Results (233)

This work investigated the effect of experimental conditions of dry and wet torrefaction on the properties of olive leaves and olive pomace. Torrefaction improved the fuel properties of olive waste. According to Van Krevelen parameters (O/C and H/C ratios), torrefied biomass, tested as solid biofuel, achieved a similar quality threshold to lignite. For example, dry torrefaction conducted at 230 °C for 80 min reduced the O/C and H/C ratios of olive leaves from 0.51 and 1.51 for raw biomass to 0.25 and 1.17 for torrefied biomass, respectively. Under the same conditions, the O/C and H/C ratios of olive pomace were also reduced from 0.34 and 1.60 to 0.27 and 1.36, respectively. Calorific values of raw olive leaves and olive pomace amounted to 18.0 and 23.2 MJ/kg, respectively. Following dry torrefaction and biomass conversion into biochar, calorific values of olive leaves and olive pomace increased by 24% and 14% up to 22.2 and 26.3 MJ/kg through dry torrefaction, compared with 17% and 23% increments up to 21.1 and 28.5 MJ/kg through wet torrefaction, respectively. Interestingly, biomass processing through wet torrefaction performed in a fluidized bed powered by superheated steam could be completed 8- to 12-fold more rapidly than dry torrefaction. SEM analysis indicated a breakdown of the surface structure of olive waste following the torrefaction process. According to the Brunauer–Emmett–Teller (BET) method, total pore surface areas of biochar obtained from wet torrefaction of olive pomace and olive leaves amounted to 3.6 m²/g and 0.8 m²/g, with total pore volumes amounting to 0.0225 cm³/g and 0.0103 cm³/g, respectively. Maximal contents of 5-hydroxymethylfurfural and furfural in liquid by-products from dry torrefaction amounted to 1930 and 1880 mg/1 kg, respectively. Alternately, in liquid by-products from wet torrefaction, concentrations of these high-value compounds remained very low. Full article

The dry reforming of methane (DRM) and the combined steam–CO₂ reforming of methane (CSCRM) are promising routes for syngas production while simultaneously utilizing two major greenhouse gases—CO₂ and CH₄. In this study, a series of Ni/MgO-Al₂O₃ catalysts with varying Mg/Al molar ratios (Ni/MgAl(x), x = 0.5–0.9), along with Ni/MgO and Ni/Al₂O₃, were synthesized, characterized, and evaluated in both the DRM and CSCRM. Ni/MgO and Ni/Al₂O₃ exhibited a lower activity due to fewer active sites and a poor CH₄/CO₂ activation balance. In contrast, Ni/MgAl(0.6), Ni/MgAl(0.7), and Ni/MgAl(0.8) showed an enhanced activity, attributed to more abundant active sites and a more balanced activation of CH₄ and CO₂. Ni/MgAl(0.7) delivered the best DRM performance, whereas Ni/MgAl(0.8) was optimal for the CSCRM, likely due to its greater number of strong basic sites promoting CO₂ and H₂O adsorption. At 750 °C and 0.1 MPa over 100 h, Ni/MgAl(0.7) maintained a stable DRM performance (77% CH₄ and 86% CO₂ conversion; H₂/CO = 0.9) at 120 L/(g_cat·h), while Ni/MgAl(0.8) achieved a stable CSCRM performance (80% CH₄ and 62% CO₂ conversion; H₂/CO = 2.1) at 132 L/(g_cat·h). This study provides valuable insights into designing efficient Ni/MgO-Al₂O₃ catalysts for targeted syngas production. Full article

Solid oxide fuel cells (SOFCs) represent a pivotal technology in renewable energy due to their clean and efficient power generation capabilities. Their role in potential carbon mitigation enhances their viability. SOFCs can operate via a variety of alternative fuels, including hydrocarbons, alcohols, solid carbon, and ammonia. However, several solutions have been proposed to overcome various technical issues and to allow for stable operation in dry methane, without coking in the anode layer. To avoid coke formation thermodynamically, methane is typically reformed, contributing to an increased degradation rate through the addition of oxygen-containing gases into the fuel gas to increase the O/C ratio. The performance achieved by reforming catalytic materials, comprising active sites, supports, and electrochemical testing, significantly influences catalyst performance, showing relatively high open-circuit voltages and coking-resistance of the CH₄ reforming catalysts. In the next step, the operating principles and thermodynamics of methane reforming are explored, including their traditional catalyst materials and their accompanying challenges. This work explores the components and functions of SOFCs, particularly focusing on anode materials such as perovskites, Ruddlesden–Popper oxides, and spinels, along with their structure–property relationships, including their ionic and electronic conductivity, thermal expansion coefficients, and acidity/basicity. Mechanistic and kinetic studies of common reforming processes, including steam reforming, partial oxidation, CO₂ reforming, and the mixed steam and dry reforming of methane, are analyzed. Furthermore, this review examines catalyst deactivation mechanisms, specifically carbon and metal sulfide formation, and the performance of methane reforming and partial oxidation catalysts in SOFCs. Single-cell performance, including that of various perovskite and related oxides, activity/stability enhancement by infiltration, and the simulation and modeling of electrochemical performance, is discussed. This review also addresses research challenges in regards to methane reforming and partial oxidation within SOFCs, such as gas composition changes and large thermal gradients in stack systems. Finally, this review investigates the modeling of catalytic and non-catalytic processes using different dimension and segment simulations of steam methane reforming, presenting new engineering designs, material developments, and the latest knowledge to guide the development of and the driving force behind an oxygen concentration gradient through the external circuit to the cathode. Full article

In this work, Aspen Plus was used to simulate a sorption-enhanced steam methane reforming (SE-SMR) process in a fluidized bed reformer using a Ni-based catalyst and CaO as a sorbent for CO₂ removal from the reaction environment. The performances of the process in terms of the outlet gas hydrogen purity (y_H2), methane conversion (X_CH4), and hydrogen yield (η_H2) were investigated. The process was simulated by varying the following different reformer operating parameters: pressure, temperature, steam/methane (S/C) feed ratio, and CaO/CH₄ feed ratio. A clear sorption-enhanced effect occurred, where CaO was fed to the reformer, compared with traditional SMR, resulting in improvements of y_H2, X_CH4, and η_H2. This effect, in percentage terms, was more relevant, as expected, in conditions where the traditional process was unfavorable at higher pressures. The presence of CaO could only partially balance the negative effect of a pressure increase. This partial compensation of the negative pressure effect demonstrated that the intensification process has the potential to produce blue hydrogen while allowing for less severe operating conditions. Indeed, when moving traditional SMR from 1 to 10 bar, an average decrease of y_H2, X, and η by −16%, −44%, and −41%, respectively, was recorded, while when moving from 1 bar SMR to 10 bar SE-SMR, y_H2 showed an increase of +20%, while X_CH4 and η_H2 still showed a decrease of −14% and −4%. Full article

This work explores the effect of the incorporation of CeO₂ into Co/SBA-15 catalysts in hydrogen production through acetic acid oxidative steam reforming as a bio-oil aqueous phase model compound. CeO₂ was incorporated (5–30 wt.%) to improve the physicochemical properties of the catalyst. XRD analysis confirmed that the addition of CeO₂ resulted in smaller Co⁰ mean crystallite sizes, while H₂-TPR showed enhanced reducibility properties. The catalytic performance was evaluated in the 400–700 °C range, S/C molar ratio = 2, O₂/C molar ratio = 0.0375, WHSV = 30.2 h⁻¹, and P = 1 atm. Catalysts containing 10 and 20 wt.% of CeO₂ exhibited the best catalytic performance, achieving nearly complete conversions and H₂ yield values, approaching thermodynamic equilibrium at 550 °C. Both samples maintained an acetic acid conversion above 90% after 30 h of time-on-stream, with H₂ yields above 55% along the steam reforming tests. This agrees with their lower coke formation rates (7.2 and 12.0 mg_coke·g_cat⁻¹·h⁻¹ for Co/10CeO₂-SBA15 and Co/20CeO₂-SBA15, respectively). Full article

Among biomass gasification syngas cleaning methods, non-catalytic reforming emerges as a sustainable and high-efficiency alternative. This study employed integrated experimental analysis and kinetic modeling to examine non-catalytic reforming processes of biomass-derived producer gas utilizing a synthetic tar mixture containing representative model compounds: naphthalene (C₁₀H₈), toluene (C₇H₈), benzene (C₆H₆), and phenol (C₆H₅OH). The experiments were conducted using a high-temperature fixed-bed reactor under varying temperatures (1100–1500 °C) and equivalence ratios (ERs, 0.10–0.30). The results obtained from the experiment, namely the measured mole concentration of H₂, CO, CH₄, CO₂, H₂O, soot, and tar suggested that both reactor temperature and O₂ content had an important effect. Increasing the temperature significantly promotes the formation of H₂ and CO. At 1500 °C and a residence time of 0.01 s, the product gas achieved CO and H₂ concentrations of 28.02% and 34.35%, respectively, while CH₄, tar, and soot were almost entirely converted. Conversely, the addition of O₂ reduces the concentrations of H₂ and CO. Increasing ER from 0.10 to 0.20 could reduce CO from 22.25% to 16.11%, and H₂ from 13.81% to 10.54%, respectively. Experimental results were used to derive a kinetic model to accurately describe the non-catalytic reforming of producer gas. Furthermore, the maximum of the Root Mean Square Error (RMSE) and the Relative Root Mean Square Error (RRMSE) between the model predictions and experimental data are 2.42% and 11.01%, respectively. In particular, according to the kinetic model, the temperature increases predominantly accelerated endothermic reactions, including the Boudouard reaction, water gas reaction, and CH₄ steam reforming, thereby significantly enhancing CO and H₂ production. Simultaneously, O₂ content primarily influenced carbon monoxide oxidation, hydrogen oxidation, and partial carbon oxidation. Full article

This study employed a two-stage fixed-bed pyrolysis-reforming reactor to investigate H₂ production behaviors from municipal solid waste (MSW) and biomass with their self-derived catalysts under different operating parameters. The self-derived catalysts are prepared by mechanically mixing pyrolysis-derived chars with CaO and iron powders. The main results are as follows: (1) The higher oxygen content in biomass facilitates oxidative dehydrogenation reactions, enabling in situ generation of H₂O, which results in a higher H₂/CO ratio for biomass compared to MSW under steam-free conditions. (2) There are optimal values for the reforming temperature and steam-to-feedstock ratio (S/F) to achieve best performance. In the presence of steam, MSW generally exhibits superior H₂ and syngas production performance to biomass; (3) Both MSW char (MSWC)- and biomass char (BC)-based catalysts showed satisfied H₂ production and tar cracking performance at 850–900 °C, and the MSWC-based catalyst demonstrated better catalytic activity than the BC-based catalyst due to its higher contents of several active metals. In addition, the iron powder can be recycled easily, proving the effectiveness of the self-derived convenient and cheap catalysts. Full article

Biogas is a crucial renewable energy source for green hydrogen (H₂) production, reducing greenhouse gas emissions and serving as a carbon-free energy carrier with higher specific energy than traditional fuels. Currently, methane reforming dominates H₂ production to meet growing global demand, with biogas/landfill gas (LFG) reform offering a promising alternative. This study provides a comprehensive simulation-based evaluation of Steam Methane Reforming (SMR) and Dry Methane Reforming (DMR) of biogas/LFG, using Aspen Plus. Simulations were conducted under varying operating conditions, including steam-to-carbon (S/C) for SMR and steam-to-carbon monoxide (S/CO) ratios for DMR, reforming temperatures, pressures, and LFG compositions, to optimize H₂ yield and process efficiency. The comparative study showed that SMR attains higher specific H₂ yields (0.14–0.19 kgH₂/Nm³), with specific energy consumption between 0.048 and 0.075 MWh/kg of H₂, especially at increased S/C ratios. DMR produces less H₂ than SMR (0.104–0.136 kg H₂/Nm³) and requires higher energy inputs (0.072–0.079 MWh/kg H₂), making it less efficient. Both processes require an additional 1.4–2.1 Nm³ of biogas/LFG per Nm³ of feed for energy. These findings provide key insights for improving biogas-based H₂ production for sustainable energy, with future work focusing on techno–economic and environmental assessments to evaluate its feasibility, scalability, and industrial application. Full article

The critical consequence of climate change resulting from global warming is the increase in temperature. In combined cycle power plants (CCPPs), the Electric Power Output (PE) is affected by changes in both Ambient Temperature (AT) and Sea Surface Temperature (SST), particularly in plants utilizing seawater cooling systems. As AT increases, air density decreases, leading to a reduction in the mass of air absorbed by the gas turbine. This change alters the fuel–air mixture in the combustion chamber, resulting in decreased turbine power. Similarly, as SST increases, cooling efficiency declines, causing a loss of vacuum in the condenser. A lower vacuum reduces the steam expansion ratio, thereby decreasing the Steam Turbine Power Output. In this study, the effects of increases in these two parameters (AT and SST) due to global warming on the PE of CCPPs are investigated using various regression analysis techniques, Artificial Neural Networks (ANNs) and a hybrid model. The target variables are condenser vacuum (V), Steam Turbine Power Output (ST Power Output), and PE. The relationship of V with three input variables—SST, AT, and ST Power Output—was examined. ST Power Output was analyzed with four input variables: V, SST, AT, and relative humidity (RH). PE was analyzed with five input variables: V, SST, AT, RH, and atmospheric pressure (AP) using regression methods on an hourly basis. These models were compared based on the Coefficient of Determination (R²), Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Mean Square Error (MSE), and Root Mean Square Error (RMSE). The best results for V, ST Power Output, and PE were obtained using the hybrid (LightGBM + DNN) model, with MAE values of 0.00051, 1.0490, and 2.1942, respectively. As a result, a 1 °C increase in AT leads to a decrease of 4.04681 MWh in the total electricity production of the plant. Furthermore, it was determined that a 1 °C increase in SST leads to a vacuum loss of up to 0.001836 bar_a. Due to this vacuum loss, the steam turbine experiences a power loss of 0.6426 MWh. Considering other associated losses (such as generator efficiency loss due to cooling), the decreases in ST Power Output and PE are calculated as 0.7269 MWh and 0.7642 MWh, respectively. Consequently, the combined effect of a 1 °C increase in both AT and SST results in a 4.8110 MWh production loss in the CCPP. As a result of a 1 °C increase in both AT and SST due to global warming, if the lost energy is to be compensated by an average-efficiency natural gas power plant, an imported coal power plant, or a lignite power plant, then an additional 610 tCO₂e, 11,184 tCO₂e, and 19,913 tCO₂e of greenhouse gases, respectively, would be released into the atmosphere. Full article

To address the insufficient early strength development of steel-fiber-reinforced high-performance concrete (SF-HPC) under subzero temperatures, this study proposes an electric-induced heating curing method for SF-HPC fabrication at −20 °C. The effects of mix parameters, including steel fiber content, water-to-binder ratio, silica fume dosage, and fine aggregate gradation, on the curing temperature and mechanical properties of SF-HPC were systematically investigated. The optimal mix proportion was identified through the curing temperature and compressive strength development for the specimens. Results revealed that compressive strength initially increased and then decreased with higher silica fume content and fine aggregate replacement ratios, while increased water-to-binder ratios positively influenced curing efficiency and strength development. The optimal mix comprised 2.0 vol% steel fibers, a water-to-binder ratio of 0.22, 20% silica fume, and 60% fine aggregate replacement. Further, comparative analyses of electric-induced heating curing, room-temperature curing, and high-temperature steam curing revealed that electric-induced heating curing can promote the strength formation of SF-HPC in a negative-temperature environment. Microstructural characterization via BET analysis demonstrated that electric-induced heating curing refined the pore structure of SF-HPC. These findings highlight the benefits of electric-induced heating as an efficient strategy for fabricating SF-HPC in cold climates, providing theoretical and practical insights for winter construction. Full article

To investigate the impact of varying steaming durations on the flavor characteristics of mutton and carrot stuffing, dynamic changes in volatile organic compounds (VOCs) and fatty acids were analyzed using solid-phase micro-extraction gas chromatography–mass spectrometry (SPME-GC-MS) and gas chromatography–ion mobility spectrometry (GC-IMS). The results revealed a total of 116 VOCs identified throughout the steaming process, with 73 detected by GC-MS and 44 by GC-IMS. Notably, VOC concentrations were significantly higher at 18–24 min compared to 8–16 min. Additionally, a GC-IMS fingerprint was developed to assess the distribution of VOCs during steaming. Orthogonal partial least squares discriminant analysis (OPLS-DA) indicated that 11 compounds, such as ethyl caprylate (B3), linalyl acetate (B6), and 1-nonanal (C1), significantly influenced the flavor characteristics of the mutton and carrot filling. Further analysis demonstrated that stearic acid content reached its lowest point at 20–22 min of steaming, while n-6 and n-3 series polyunsaturated fatty acids (PUFAs) and the ratio of polyunsaturated fatty acids to saturated fatty acids (P/S) peaked at this time. Full article

The LNG maritime industry started to anticipate offshore LNG production in tandem with increasing demand for FLNG platforms as offshore gas resources were developed further. The rapid expansion of FLNG deployment demands equipment and procedures that handle challenges associated with weight and space constraints. The chemical composition of LNG will result in slightly fewer CO₂ emissions. While not significant, another crucial aspect is that LNG predominantly comprises methane, which is acknowledged as a greenhouse gas and is more harmful than CO₂. This requires investigation into clean energy fuel supply for power generation systems, carbon emissions from the process, and thermodynamic analysis and optimisation. Focus on supplying fuel for FLNG power generation to reduce the essential management of boil-off fuel gas, which can be researched on the direct reforming method of hydrogen as a marine fuel gas to support the power generation system. The principal reason for choosing hydrogen over other energy sources is its exceptional energy-to-mass ratio (H/C ratio). The most effective method for hydrogen production is the methane reforming process, recognised for generating significant quantities of hydrogen. To optimise the small-scale plant with a carbon capture system (CCS) as integrated into the reforming process to produce blue hydrogen fuel with zero carbon emissions, this research selection focuses on two alternative processes: steam methane reforming (SMR) and autothermal reforming (ATR). Furthermore, the research article will contribute to other floating production platforms, such as FPSOs and FSRUs, and will be committed to clean energy policies that mandate the support of green alternatives in substitution of hydrocarbon fuel utilisation. Full article

Steam-assisted gravity drainage (SAGD) is a widely used thermal enhanced oil recovery (EOR) technique in North America, particularly in high-permeability oil sand reservoirs. While effective, its economic viability has declined due to low oil prices and high greenhouse gas (GHG) emissions from the steam generation. To improve cost-effectiveness and reduce emissions, solvent-assisted SAGD techniques have been explored. Expanding Solvent-SAGD (ES-SAGD) involves co-injecting light hydrocarbons like propane or butane with steam to enhance oil viscosity reduction. This approach lowers the steam–oil ratio by combining solvent dissolution effects with thermal effects. However, the high cost of solvents, particularly butane, challenges its commercial feasibility. Propane is cheaper but less effective, while butane improves performance but remains expensive. This research aims to optimize ES-SAGD by using a propane–butane mixture to achieve efficient performance at a lower cost than pure butane. A linear sand pack is used to evaluate different propane/butane compositions, maintaining constant operational conditions and a solvent concentration of 15 vol.%. Temperature monitoring provides insights into steam chamber growth. Results show that solvent injection significantly enhances ES-SAGD performance compared to conventional SAGD. Performance improves with increasing butane concentration, up to 80% butane in the C₃–C₄ mixture at the test pressure and ambient temperature. Propane alone results in the lowest system temperature, while conventional SAGD reaches the highest temperature. These findings highlight the potential of optimized solvent mixtures to improve ES-SAGD efficiency while reducing costs and GHG emissions. Full article

Biogas (primarily biomethane), as a carbon-neutral renewable energy source, holds great potential to replace fossil fuels for sustainable hydrogen production. Conventional biogas reforming systems adopt strategies similar to industrial natural gas reforming, posing challenges such as high temperatures, high energy consumption, and high system complexity. In this study, we propose a novel multi-product sequential separation-enhanced reforming method for biogas-derived hydrogen production, which achieves high H₂ yield and CO₂ capture under mid-temperature conditions. The effects of reaction temperature, steam-to-methane ratio, and CO₂/CH₄ molar ratio on key performance metrics including biomethane conversion and hydrogen production are investigated. At a moderate reforming temperature of 425 °C and pressure of 0.1 MPa, the conversion rate of CH₄ in biogas reaches 97.1%, the high-purity hydrogen production attains 2.15 mol-H₂/mol-feed, and the hydrogen yield is 90.1%. Additionally, the first-law energy conversion efficiency from biogas to hydrogen reaches 65.6%, which is 11 percentage points higher than that of conventional biogas reforming methods. The yield of captured CO₂ reaches 1.88 kg-CO₂/m³-feed, effectively achieving near-complete recovery of green CO₂ from biogas. The mild reaction conditions allow for a flexible integration with industrial waste heat or a wide selection of other renewable energy sources (e.g., solar heat), facilitating distributed and carbon-negative hydrogen production. Full article

The construction waste of brick and concrete can be used to produce recycled powder and recycled sand, which can replace cement and natural sand, respectively, in concrete. This can reduce the cost of concrete, reutilize construction waste and decrease environmental pollution. The idea of producing UHPC incorporating both RP and RS by standard curing instead of steam curing is proposed in this study. The optimal mixture design of ultra-high-performance concrete (UHPC) with both recycled powder and recycled sand is investigated. Based on the revised Dinger–Funk model, the optimal mix proportions of green UHPC (GUHPC) with recycled powder and recycled sand were calculated on this basis, and the effects of the superplasticizer content, water–binder ratio, recycled powder and recycled sand replacement ratio on the workability and mechanical properties of GUHPC at different ages were investigated through the designed experimental program. The test results show that when the superplasticizer to cementitious material ratio was 0.8%, the flowability and the 28 d compressive strength were highest. When the water–binder ratio was 0.16, the flexural strength and compressive strength of the GUHPC at different ages were the largest. As the replacement ratio of the recycled powder increased, the workability of the GUHPC decreased. However, even when replacement ratio of recycled powder was 30%, the flowability was still higher than 180 mm. The flexural strength and the 28 d compressive strength increased first and then decreased. Compared with mixtures without RP, the 28 d compressive strength increased by 6.4% and reached the maximum value when the replacement ratio of the RP was 30%. The comprehensive contribution of recycled powder to the strength was analyzed. Recycled powder can enhance the contribution of cement to GUHPC strength, and the enhancement effect increases with increases in the recycled powder content and age. The optimal replacement ratio of recycled powder is 30%. As the replacement ratio of the recycled sand increased, the flowability of the GUHPC first increased and then decreased, and the flexural and compressive strength decreased. The toughness was analyzed by the flexural strength to compressive strength ratio (f:c). With increases in the recycled sand, the f:c at 3 d of age increased, the f:c at 7 d of age showed no significant change, and the f:c at 28 d of age first increased and then decreased. The f:c at 28 d of age reached a maximum value of 0.316 when the replacement ratio of recycled sand was 50%. Therefore, the replacement ratio of the recycled sand was selected to be 50%. The optimum mix proportions of GUHPC were obtained by considering the workability, mechanical properties and amount of recycled material. Full article