Search Results (122)

The synthesis of “green ammonia” from “green hydrogen” represents a critical pathway for renewable energy integration and industrial decarbonization. This study investigates the green ammonia synthesis process using an axial–radial fixed-bed reactor equipped with three catalyst layers. A simplified two-dimensional physical model was developed, and a multiscale simulation approach combining computational fluid dynamics (CFD) with physics-informed neural networks (PINNs) employed. The simulation results demonstrate that the majority of fluid flows axially through the catalyst beds, leading to significantly higher temperatures in the upper bed regions. The reactor exhibits excellent heat exchange performance, ensuring effective preheating of the feed gas. High-pressure zones are concentrated near the top and bottom gas outlets, while the ammonia mole fraction approaches 100% near the bottom outlet, confirming superior conversion efficiency. By integrating PINNs, the prediction accuracy was substantially improved, with flow field errors in the catalyst beds below 4.5% and ammonia concentration prediction accuracy above 97.2%. Key reaction kinetic parameters (pre-exponential factor k₀ and activation energy Ea) were successfully inverted with errors within 7%, while computational efficiency increased by 200 times compared to traditional CFD. The proposed CFD–PINN integrated framework provides a high-fidelity and computationally efficient simulation tool for green ammonia reactor design, particularly suitable for scenarios with fluctuating hydrogen supply. The reactor design reduces energy per unit ammonia and improves conversion efficiency. Its radial flow configuration enhances operational stability by damping feed fluctuations, thereby accelerating green hydrogen adoption. By reducing fossil fuel dependence, it promotes industrial decarbonization. Full article

Heuristic optimization is used to find sustainable cogeneration steam power plants with steam reheat and supercritical main steam parameters. Design solutions are analyzed for steam consumer (SC) pressures of 3.6 and 40 bar and a heat flow rate of 40% of the fuel heat flow rate. The objective functions consisted in simultaneous maximization of global and exergetic efficiencies, power-to-heat ratio in full cogeneration mode, and specific investment minimization. For 3.6 bar, the indicators improve with the increase in the ratio between reheating and main steam pressure. The increase in SC pressure worsens the performance indicators. For an SC steam pressure of 40 bar and 9 feed water preheaters, the ratio between reheating and main steam pressure should be over 0.186 for maximum exergetic efficiency and between 0.10 and 0.16 for maximizing both global efficiency and power-to-heat ratio in full cogeneration mode. The average global efficiency for an SC requiring steam at 3.6 bar is 4.4 percentage points higher than in the case with 40 bar, the average specific investment being 10% lower. The Pareto solutions found in this study are useful in the design of sustainable cogeneration supercritical power plants. Full article

This study evaluates the risk assessment and hazard identification of hydrothermal liquefaction (HTL)-derived bio-oil from the MARINES project, which converts military organic waste into fuel. The high oxygen content (35–50 wt%), acidic pH (2–4), and viscosity (10–1000 cP) of bio-oils pose unique challenges, including oxidative polymerization, corrosion, and micro-explosions during combustion. Key hazards include storage instability, particulate emissions (20–30% higher than diesel), and aquatic toxicity (LC50 < 10 mg/L for phenolics). Mitigation strategies such as inert gas blanketing, preheating, and spill containment are proposed. While offering renewable fuel potential, HTL bio-oil demands rigorous safety protocols for military/industrial deployment, warranting further experimental validation. Full article

The advantages of torrefaction preheating, including the production of a hydrophobic solid product, improved particle size distribution, enhanced fuel properties with fewer environmental issues, decreased moisture content, and reduced volatile content. In order to meet the technical requirements of biomass oriented value-added and energy saving and emission reduction, pine sawdust (PS) was taken as the research object, and the physicochemical properties of the PS samples preheated at a low temperature were analyzed by synchronous thermal analysis (TG-DSC), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and organic element analyzer (EA). The effect of preheating at a lower temperature on the physicochemical properties of PS was discussed. The results showed that, under the preheating condition of 200 °C, compared with PS, the water content of PS-200 decreased by 3.23%, the volatile content decreased by 3.69%, the fixed carbon increased by 6.81%, the calorific value increased by 6.90%, the equilibrium water content decreases from 7.06% to 4.46%, and the hydrophobicity increases. This research, based on the improvement of the quality of agricultural and forestry waste and the promotion of the strategy of converting waste into energy, has contributed to the advancement of sustainable energy production. Full article

Researchers have tended to blend isopropanol (IPA) with other fuels in diesel engines to reduce emissions and improve performance. However, low-reactivity controlled compression ignition via port injection at a low cetane number results in a well-mixed charge of low-reactivity fuel, air, and recirculated exhaust gas (EGR). This study’s novel approach combines critical elements, such as the mass fraction of port-injected IPA, EGR ratio, and charge temperature, to improve combustion characteristics and lessen emissions from a diesel engine. The results demonstrated that the injection of IPA and the installation of EGR at the inlet reduced NO_x, smoke, and PM_2.5. On the contrary, HC and CO increased with the port-injection of IPA and EGR. Preheating air at the inlet can suppress the emissions of HC and CO. Under 1500 rpm and 60% load, when compared to diesel at the same EGR ratio and charge temperature, the maximum smoke decrease rate (26%) and PM_2.5 decrease rate (21%) occur at 35% IPA, 45 °C, and 10% EGR, while the maximum NO_x decrease rate (24%) occurs at 35% IPA, 60 °C, and 20% EGR. These findings support the novelty of the research. Conversely, it modestly increased CO and HC emissions. However, port-injecting IPA increased thermal efficiency by up to 24% at 60 °C, 1500 rpm, and 60% load with EGR. Full article

This study evaluates the feasibility of integrating pulsed electric field (PEF) technology with heat recovery for fruit juice pasteurization, comparing it to conventional high-temperature short-time (HTST) pasteurization. Three preheating temperature conditions (35 °C, 45 °C, and 55 °C) and varying heat recovery efficiencies have been assessed to analyze energy consumption, economic feasibility, and environmental impact. The results indicate that, while PEF pasteurization requires a higher initial investment, it improves energy efficiency, leading to significant reductions in utility costs. Across the tested configurations, PEF technology achieved reductions in electricity consumption by up to 20%, fuel gas usage by over 60%, greenhouse gas emissions by approximately 30%, and water consumption by 25%, compared to HTST. The optimal configuration of the PEF process, featuring a 35% waste heat recovery efficiency and a pre-heating temperature of 55 °C, has been identified as the most energy-efficient and sustainable solution, effectively reducing both water consumption and CO₂ emissions. A life cycle assessment has confirmed these environmental benefits, demonstrating reductions in global warming potential, fossil fuel consumption, and other impact categories. This study suggests that PEF technology can significantly contribute to more sustainable food processing by reducing environmental impacts, optimizing resource usage, and enhancing energy efficiency. Full article

Polymer electrolyte membrane fuel cells (PEMFCs) are emerging as the next-generation powertrain for unmanned aerial vehicles (UAVs) due to their high energy density and long operating duration. PEMFCs are subject to icing and performance degradation problems at sub-zero temperatures, especially at high altitudes. Therefore, an effective preheating system is required to ensure stable PEMFC operation in high-altitude environments. This study aimed to mathematically model a shell-and-tube heat exchanger that utilizes waste heat recovery to prevent internal and external PEMFC damage in cold, high-altitude conditions. The waste heat from the PEMFC is estimated based on the thrust of the MQ-9 Reaper, and the proposed heat exchanger must be capable of heating air to −5 °C. As the heat exchanger utilizes only waste heat, the primary energy consumption arises from the coolant pumping process. Calculation results indicated that the proposed heat exchanger design improved the overall system efficiency by up to 15.7%, demonstrating its effectiveness in utilizing waste heat under aviation conditions. Full article

Solid oxide fuel cell (SOFC) systems often employ metallic cathode air pre-heaters (CAPHs), frequently made from alloys with high chromium (Cr) content, to recover thermal energy from exhaust gases and pre-heat incoming air and fuel. Cr evaporation from metallic CAPHs can poison SOFC cathodes, reducing their durability. To mitigate this, we investigated controlled pre-oxidation of a FeCrAl alloy (alloy 318) to form a protective alumina scale by self-growing, assessing its impact on and oxidation resistance and Cr retention capability for CAPH applications. The effects of pre-oxidation were investigated across a temperature range of 800 to 1100 °C and dwelling times of 0.5 to 4 h. The formed oxide scales were characterised using gravimetry in combination with advanced analytic techniques, such as SEM/EDX, STEM/EDX, TEM, and XRD. Subsequently, the pre-oxidised FeCrAl alloys were characterised with respect to the oxidation rate and Cr₂O₃ evaporation in a tubular furnace at 850 °C, with 6.0 L/min air flow and 3 vol% H₂O to simulate the SOFC cathode environment. TEM analysis confirmed that the FeCrAl alloys formed alumina scales with 10 nm and 34 nm thickness after 1 h of pre-oxidation at 900 and 1100 °C, respectively. The corrosion and Cr₂O₃ evaporation rates of the FeCrAl alloy at 850 °C in humidified air were shown to be dramatically decreased by pre-oxidation. It was found that the mechanisms of oxidation and Cr₂O₃ evaporation were found to be controlled by the formation of different alumina phases during the pre-oxidation. Measurements of Cr₂O₃ evaporation and weight gain revealed that the alloy 318 pre-treated at 1100 °C for 1 h will form an α-Al₂O₃ scale, leading to a 98% reduction of the oxidation rate and 90% reduction of Cr₂O₃ evaporation compared to the non-oxidised alloy 318 under simulated SOFC cathode conditions. Full article

Under the strategic objectives of carbon peaking and carbon neutrality, it is inevitable for large-scale integration of renewable energy into thermal power units. Nevertheless, improving the capacity of these units for flexible peak shaving is necessary on account of the intermittent and instability of renewable energy. As a novel combustion technology, self-preheating combustion technology offers enormous merits in this aspect, with increasing combustion efficiency (η) and controlling NO_x emissions simultaneously. Considering production and operation cost, installation difficulty and environmental pollution, this study innovatively proposed a compact fluidized modification device (FMD) on the basis of this technology and explored the influences of buffer tank and operation load on operation stability, fuel modification, combustion characteristics and NO_x emissions on an MW grade pilot-scale test platform. Afterwards, the comparative analysis on performance disparities was further launched between FMD and traditional self-preheating burner (TSB). Adding the buffer tank enhanced operation stability of FMD and improved its modification conditions, and thus promoted NO_x emission control. Optimal modification efficiency was realized at medium and high loads, respectively, for high-volatile and low-volatile coals. As load increased, η increased for high-volatile coal, but with NO_x emissions increasing. In comparison, this condition reduced NO_x emissions with high η for low-volatile coal. Compared to TSB, FMD demonstrated more conspicuous advantages in stable operation and fuel modification. Simultaneously, FMD was more conducive to realizing clean and efficient combustion at high temperatures. In industrial applications, appropriate FMD or TSB should be picked out grounded in diverse application requirements. By optimizing burner structure and operational parameters, original NO_x emissions decreased to a minimum of 77.93 mg/m³ with high η of 98.59% at low load of 30%. Full article

This paper presents a theoretical and experimental investigation into improving the energy efficiency of electrically heated systems through thermal energy recovery. Enhancing efficiency in such systems can significantly reduce energy consumption, operating costs, and greenhouse gas emissions, particularly when electricity is generated from fossil fuels. Commercial dishwashers are inherently energy-intensive due to the need for rapid and effective cleaning. Regulatory and market pressures increasingly encourage manufacturers to develop energy-efficient technologies. This study aimed to design, develop, and incorporate a miniaturized heat exchanger to recover waste thermal energy and reduce the overall energy consumption in a commercial dishwasher. In collaboration with Norris Industries, the University of Newcastle trialed a retrofitted internal heat exchanger in representative commercial dishwasher models. The device was designed to transfer heat from discharged wash water to preheat incoming freshwater. The heat exchanger was developed based on a theoretical thermal analysis and engineered for practical integration. Experimental testing demonstrated that the system achieved up to a 50% reduction in energy use without compromising the cleaning performance or increasing the manufacturing complexity. This approach offers a scalable and effective solution for enhancing energy efficiency in commercial dishwashing. Its broader implementation could substantially reduce the energy demand and greenhouse gas emissions across the sector. Full article

The combustion of ammonia with oxygen presents a promising pathway for global energy transformation using carbon dioxide-neutral energy solutions and carbon capture. Ammonia, a carbon-free fuel, offers several benefits, owing to its non-explosive nature, high octane rating, and ease of storage and distribution. However, challenges such as low flammability and excessive nitrogen oxide (NO_x) emissions must be addressed. This paper explores the recent advances in ammonia oxy-combustion and highlights recent experimental and numerical research on NO_x emission traits, combustion, and flame propagation across various applications, including gas furnaces, internal combustion engines, and boilers. Furthermore, this review discusses the diverse approaches to overcoming the challenges of ammonia combustion, including oxygen enrichment, fuel blending, plasma assistance, preheating, multiple injections, and burner design modifications. By summarizing the advancements in ammonia oxy-combustion investigation, this paper aims to provide valuable insights that can serve as reference information for prospective ammonia oxy-combustion research and applications toward the transition to sustainable energy. Full article

Although various studies on nitrous oxide as a prospective green propellant have been recently explored, a polyethylene nitrous oxide catalytic decomposition hybrid thruster was barely demonstrated due to an inordinately high catalyst preheating time of a heater, which led to the destruction of components. Therefore, hydrogen peroxide was used as a preheatant, a substance to preheat, with a dual-catalyst bed. The thruster with polyethylene (PE) as a fuel, N₂O as an oxidizer, H₂O₂ as the preheatant, Ru/Al₂O₃ as a catalyst for the oxidizer, and Pt/Al₂O₃ as a catalyst for the preheatant was arranged. A preheatant supply time of 10 s with a maximum catalyst bed temperature of more than 500 °C and without combustion and an oxidizer supply time of 20 s with a burning time of approximately 15 s were decided. Because the catalyst bed upstream part for decomposing the preheatant was far from the post-combustion chamber, the post-combustion chamber pressure increased and the preheatant mass flow rate decreased after a hard start during the preheatant supply time. Moreover, because the catalyst bed upstream part primarily contributed to preheating, the maximum catalyst bed temperature was less than the decomposition temperature of the preheatant during the preheatant supply time. Additionally, because the catalyst bed downstream part for decomposing the oxidizer was far from the post-combustion chamber, the post-combustion chamber pressure decreased and then increased during a transient state in the oxidizer supply time. Full article

This paper reports studies on the thermal chemistry of the flash pyrolysis (heating rate of 20,000 °C/s up to 800 °C) of non-fossil fuel carbon (NFF-C) waste (or refuse-derived fuel, RDF) in the context of using this as an alternative reductant for blast furnace ironmaking. Gas chromatography–mass spectrometry (GCMS) analysis linked to the pyrolyser was used to simulate the thermal processes that take place during injection in the blast furnace raceway, where material experiences extreme temperature (ca. 1000 °C) over very short residence times (<300 ms). Species identification and qualitative analysis of evolved species generated are reported. Whilst the pyrolyser uses flash heating of a static sample, a drop tube furnace was also employed to study a sample moving rapidly through a pre-heated furnace held at 1000 °C to enable reductant burnout rates to be measured. The overarching aim of this piece of work is to study the suitability of replacing fossil fuel with non-recyclable plastic and paper as blast furnace reductants. Full article

This study focuses on the modeling, simulation, and optimization of an integrated biomass gasification and methanation process to produce bio-synthetic natural gas (Bio-SNG) as part of the AIRE project. The process was simulated using Aspen Plus^® software (V14), incorporating experimental results from pilot-scale gasification setups. Key steps involved syngas production in a dual fluidized bed gasifier and its subsequent conversion to Bio-SNG in a methanation section. Heat integration strategies were implemented to enhance system results demonstrate that optimized heat recovery, achieved by utilizing exothermic methanation reactions to preheat gasification inputs, eliminates the need for auxiliary fuel in the gasification process. The optimized system achieved a thermal recovery rate of 80%, a cold gas efficiency of 79%, a Bio-SNG production rate of 0.4 Nm³/kg_Biom, and a methane content of 85 vol.%. These optimizations reduced CO₂ emissions by 10% while increasing overall energy efficiency. This work highlights the potential of integrating biomass gasification and methanation processes with heat recovery for sustainable methane production. The findings provide a basis for scaling up the process and further exploring syngas utilization pathways to produce renewable energy carriers. Full article

Pre-heat trains (PHTs) significantly reduce refinery fuel consumption and carbon emissions. However, these benefits are diminished by fouling in heat exchangers (HEXs). Current methods for optimizing cleaning schedules often report high computation times due to the transient nature of the fouling process and do not consider shell-side fouling, which can be significant for some oil fractions. This paper addresses these issues by adding shell-side fouling to the model and by transforming cleaning time variables into integers, reducing the problem of optimizing cleaning schedules to an integer nonlinear programming (INLP) problem. The reformulated problem is solved using integer particle swarm optimization (PSO) coupled with a simple search strategy, where the number of cleaning actions is preset and their timing is optimized. The adopted approach achieved up to 84% lower computation times compared to previous ones. Additionally, the relationship between cleaning actions and PHT performance is nonlinear, with diminishing returns from additional cleaning, and optimal cleaning schedules are often asymmetric for different HEXs within the same PHT. The proposed approach effectively reduces operating costs and provides a framework for future optimization enhancements. Full article